WO2017027059A1 - Prach design for unlicensed channels - Google Patents

Prach design for unlicensed channels Download PDF

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Publication number
WO2017027059A1
WO2017027059A1 PCT/US2015/067475 US2015067475W WO2017027059A1 WO 2017027059 A1 WO2017027059 A1 WO 2017027059A1 US 2015067475 W US2015067475 W US 2015067475W WO 2017027059 A1 WO2017027059 A1 WO 2017027059A1
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WIPO (PCT)
Prior art keywords
prach
preamble
unlicensed channel
enb
circuitry
Prior art date
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PCT/US2015/067475
Other languages
French (fr)
Inventor
Christian Ibars Casas
Abhijeet Bhorkar
Seunghee Han
Hwan-Joon Kwon
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Intel IP Corporation
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Publication of WO2017027059A1 publication Critical patent/WO2017027059A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/14—Spectrum sharing arrangements between different networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J13/0055—ZCZ [zero correlation zone]
    • H04J13/0059—CAZAC [constant-amplitude and zero auto-correlation]
    • H04J13/0062—Zadoff-Chu
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0006—Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H04L27/26132—Structure of the reference signals using repetition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
    • H04L5/001—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT the frequencies being arranged in component carriers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0833—Random access procedures, e.g. with 4-step access
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]

Definitions

  • Embodiments pertain to systems, methods, and component devices for wireless communications, and particularly physical random access channel (PRACH) design for use with long term evolution (LTE), LTE-advanced, and other similar wireless communication systems that operate with license assisted access (LAA), LTE-uniicensed (LTE-U), or other similar communication systems which use channels in unlicensed frequency bands.
  • PRACH physical random access channel
  • LTE and LTE-advanced are standards for wireless communication of high-speed data for user equipment (UE) such as mobile telephones.
  • UE user equipment
  • carrier aggregation is a technology where multiple earner signals operating on different frequencies may be used to carry communications for a single UE, thus increasing the bandwidth available to a single device.
  • Carrier aggregation may be used where one or more component carriers operate on unlicensed frequencies.
  • FIG. 1 is a block diagram of a system including an evolved node B (eNB) and a user equipment (UE) that may operate according to some embodiments described herein.
  • eNB evolved node B
  • UE user equipment
  • FIG. 2 is a block diagram showing a system including a UE communicating with a cell on an unlicensed frequency according to some embodiments described he ein.
  • FIG. 3 is a block diagram showing a system including a UE communicating with two cells, including one cell on a licensed frequency and another cell on an unlicensed frequency according to some embodiments described herein.
  • FIG. 4 illustrates aspects of a physical random access channel (PRACH) preamble.
  • PRACH physical random access channel
  • FIG. 5A illustrates a PRACH preamble with repeated PRACH preamble sequences according to some embodiments.
  • FIG. 5B illustrates a PRACH preamble with a reservation signal according to some embodiments described herein.
  • FIG. 6 illustrates aspects of generating a PRACH preamble according to some embodiments described herein.
  • FIG. 7 illustrates aspects of generating a PRACH preamble according to some embodiments described herein.
  • FIG. 8 illustrates aspects of generating a PRACH preamble according to some embodiments described herein.
  • FIG. 9 illustrates aspects of generating a PRACH preamble according to some embodiments described herein .
  • FIG. 10 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
  • FIG. 11 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
  • FIG. 12 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
  • FIG. 13 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
  • FIG. 14 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
  • FIG. 15 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
  • FIG. 16 illustrates aspects of system operation and alignment of propagation delays according to some embodiments.
  • FIG. 17 illustrates aspects of PRACH preamble detection according to some example embodiments.
  • FIG. 19 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
  • FIG. 20 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
  • FIG. 21 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
  • FIG. 22 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
  • FIG. 23 is a method for PRACH preamble use according to some embodiments described herein.
  • FIG. 24 is a method for PRACH preamble use according to some embodiments described herein.
  • FIG. 25 illustrates aspects of a computing machine, according to some example embodiments.
  • FIG. 26 illustrates aspects of a UE, in accordance with some example embodiments.
  • FIG. 27 is a block diagram illustrating an example computer system machine which may be used in association with various embodiments described herein.
  • FIG. 28 is a block diagram illustrating an example user equipment including aspects of wireless communication systems, which may be used in association with various embodiments described herein.
  • Embodiments relate to systems, devices, apparatus, assemblies, methods, and computer readable media to enhance wireless communications, and particularly to communication systems that operate with carrier aggregation with at least some carriers operating on unlicensed channels where coexistence operations are used.
  • the following description and the drawings illustrate specific embodiments to enable those skilled in the art to practice them.
  • Other embodiments can incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments can be included in, or substituted for, those of other embodiments, and are intended to cover all available equivalents of the elements described.
  • FIG. 1 illustrates aspects of a wireless network system. 100, in accordance with some embodiments.
  • the wireless network system 100 includes a UE 101 and an eNB 150 connected via an air interface 190.
  • UE 101 and eNB 150 communicate using a system that supports carrier aggregation and the use of unlicensed frequency bands, such that the air interface 190 supports multiple frequency carriers and licensed as well as unlicensed bands.
  • a component carrier 180 and a component carrier 185 are illustrated. Although two component carrie s are illustrated, various embodiments may include any numbe of two or more component carriers. Various embodiments may function with any number of licensed channels and one or more unlicensed channels.
  • At least one of the component earners 180, 185 of the air interface 190 comprises a carrier operating in an unlicensed frequency, referred to herein as an unlicensed carrier.
  • An "unlicensed carrier” or ' unlicensed frequency” refers to a range of radio frequencies that are not exclusively set aside for the use of the system. Some frequency ranges, for example, may be used by communication systems operating under different communication standards, such as a frequency band that is used by both Institute of Electronic and Electrical Engineers (IEEE) 802.11 standards (e.g., "WiFi") and third generation partnership (3GPP) standards.
  • IEEE Institute of Electronic and Electrical Engineers
  • 3GPP third generation partnership
  • Some embodiments may implement license assisted access (LAA) communications where primary channels with control signals are sent on licensed channels.
  • FIG. 2 illustrates an embodiment that may implement LAA, with UE communicating on licensed channels using communications 203 with cell 202, and unlicensed channel communications including physical random access channel (PRACH) 210 and timing advance 209 with cell 204.
  • PRACH physical random access channel
  • Other embodiments may implement long term evolution or similar systems where only unlicensed channels are used for some communications, or other similar systems using unlicensed channels.
  • Other embodiments may include any system implemented using an eNB to communicate using unlicensed channels.
  • LTE may also be operated via dual connectivity or the standalone LTE mode which may use limited assistance from the licensed spectram.
  • LAA license assisted access
  • 3GPP third generation partnership project
  • LTEfire an LTE based technology "MuLTEfire” has been under consideration, requiring no assistance from the licensed spectrum to enable a leaner, self-contained network architecture that is suitable for neutral deployments where any deployment can service any device .
  • the operation of LTE on the unlicensed spectrum without any assistance from licensed carrier will be referred to as standalone LTE unlicensed (LTE-U) herein.
  • FIG. 3 illustrates a simple embodiment with UE 306 communicating with cell 302 on unlicensed channels, including PRACH initial access communication 304.
  • Cell 302 of FIG. 3 and cells 202 and 204 of FIG. 2 will all be associated with eNB systems as part of a larger communication network to enable network access to UEs such as UE 206 and UE 306.
  • FIG. 2 particularly shows the use of PRACH 210 and FIG. 3 shows PRACH initial access 304 communications.
  • the PRACH or physical random access channel as men tioned above, is used for a number of functions, including managing initial access, handover between cells, and timing advance correction.
  • PRACH enables random access procedures to enable UE devices to synchronize with the network .
  • a UE wants to access a network via a cell of an eNB (e.g. a device including antenna(s) and various circuitry as described herein)
  • the UE will attempt to attach or synchronize with the network.
  • the PRACH is provided for such processes.
  • a UE such as UE 206 or 306 powers on or moves to a new area, the UE will search for a network for the frequencies available to the UE. If a network is available, an initial synchronization occurs usmg primary and secondary synchronization signals (PSS and SSS) broadcast by an eNB.
  • PSS and SSS primary and secondary synchronization signals
  • the UE reads system information such as system information block 1 and system information block 2, and then the UE begins a random access procedure, using communications such as PRACH initial access communication 304 or PRACH 210.
  • PRACH communications may include a preamble sequence selected from a limited set of preamble sequences that may be used for the initial identification of the UE by the eNB.
  • the eNB scans for PRACH communications including one of the preselected PRACH preamble sequences, and uses this to identify the presence of the UE requesting a connection. A response from the appropriate cell of an eNB may then lead to a connection between the UE and the eNB.
  • PRACH signals may be used for this purpose.
  • a primary carrier is transmitted on a licensed band and secondary earners are transmitted over unlicensed bands.
  • the PRACH is normally sent over the primary carrier.
  • a primary channel is sent over a cell 202 and secondary channels use a separate cell 204 and the cell 202 and cell 204 are not co-located, propagation delay between the UE and the ceils 202, 204 are different. Therefore, primary and secondary carriers may use different timing advance values.
  • a PRACH procedure for timing advance correction may be carried out over secondary carriers to properly synchronize the UE and secondary cells.
  • a group of secondary carriers may be configured with common timing advance values as a secondary timing alignment group. Timing advances can also be obtained by means of eNB initiated random procedures, where upon request, the UE transmits a
  • PRACH communication including a PRACH preamble sequence to the cell for which the request is intended.
  • the communication including the PRACH preamble sequence may then be used to manage the timing advance differences between ceils that are in different locations, such a cells 202 and 204, where an eNB may know a timing advance from a primary channel PRACH procedure using communications 203 between cell 202 and UE 206.
  • the eNB may then initiate a timing advance operation for cell 204 which is not co-located with cell 202.
  • UE 206 may send PRACH 210 to cell 204, and may receive a timing advance 209 communicat on.
  • the timing advance may be handled in communications between cell 204 and other control circuitry of the eNB communicating with the UE using cell 202 and cell 204.
  • LTE cellular communications may, for example, operate with a centrally managed system designed to operate in a licensed spectrum for efficient resource usage. Operating with such centrally managed use within unlicensed channels where systems not centrally controlled that use different channel access mechanisms than legacy LTE may be present carries significant risk of direct interference. Coexistence mechanisms described herein enable LTE, LTE-advanced, and communications systems building on or similar to LTE systems to coexist with other technologies such as WiFi in shared unlicensed frequency bands (e.g., unlicensed channels.)
  • Embodiments described herein for coexistence may operate within the wireless network system 100.
  • the UE 101 and any other UE in the system may be, for example, laptop computers, smartphones, tablet computers, printers, machine-type devices such as smart meters or specialized devices for healthcare monitoring, remote security surveillance systems, intelligent transportation systems, or any other wireless devices with or without a user interface.
  • the eNB 150 provides the UE 101 network connectivity to a broader network (not shown). This UE 101 connectivity is provided via the air interface 190 in an eNB service area provided by the eNB 150.
  • a broader network may be a wide area network operated by a cellular network provider, or may be the Internet.
  • Each eNB service area associated with the eNB 150 is supported by antennas integrated with the eNB 150.
  • the se dee areas are divided into a number of sectors associated with certain antennas. Such sectors may be physically associated with fixed antennas or may be assigned to a physical area, with tunable antennas or antenna settings adjustable in a beamforming process used to direct a signal to a particular sector.
  • One embodiment of the eNB 150 for example, includes three sectors each covering a 120 degree area with an array of antennas directed to each sector to provide 360 degree coverage around the eNB 150.
  • the UE 101 includes control circuitry 105 coupled with transmit circuitry HO and receive circuitry 1 15.
  • the transmit circuitry 110 and receive circuitry 115 may each be coupled with one or more antennas.
  • the control circuitry 105 may be adapted to perform operations associated with wireless communications using carrier aggregation.
  • the transmit circuitry 1 10 and receive circuitry 1 15 may be adapted to transmit and receive data, respectively.
  • the control circuitiy 105 may be adapted or configured to perform various operations such as those described elsewhere in this disclosure related to a UE.
  • the transmit circuitry 110 may transmit a plurality of multiplexed uplink physical channels.
  • the plurality of uplink physical channels may be multiplexed according to time division multiplexing (TDM) or frequency division multiplexing (FDM) along with carrier aggregation.
  • the transmit circuitry 110 may be configured to receive block data from the control circuitry 105 for transmission across the air interface 190.
  • the receive circuitry 1 15 may receive a plurality of multiplexed downlink phy sical channels from the air interface 190 and relay the physical channels to the control circuitry 105.
  • the uplink and downlink physical channels may be multiplexed according to FDM.
  • the transmit circuitiy 110 and the receive circuitiy 115 may transmit and receive both control data and content data (e.g., messages, images, video, et cetera) structured within data blocks that are carried by the physical channels.
  • FIG. 1 also illustrates the eNB 150, in accordance with various embodiments.
  • Hie eNB 150 circuitiy may include control circuitiy 155 coupled with transmit circuitry 160 and receive circuitiy 165.
  • the transmit circuitry 160 and receive circuitr ' 165 may each be coupled with one or more antennas that may be used to enable communications via the air interface 190.
  • transmit circuitry 160 and receive circuitiy 165 may be structured with multiple cells which may be coupled to the core eNB circuitiy via wired or wireless connections. This enables cells with varying frequency support or other characteristics, and antennas for an eNB to be located in different areas. Cells communicating with a UE for a single eNB may thus be sufficiently far apart to generate timing issues such as those described above.
  • the control circuitiy 155 may be adapted to perform operations for managing channels and component carriers used with various UEs.
  • the transmit circuitiy 160 and receive circuitry 165 may be adapted to transmit and receive data, respectively, to and from any UE connected to the eNB 150.
  • the transmit circuitiy 160 may transmit downlink physical channels comprised of a plurality of downlink subframes.
  • the receive circuitry 165 may receive a plurality of uplink physical channels from various UEs including the UE 101.
  • the plurality of uplink physical channels may be multiplexed according to FDM in addition to the use of earner aggregation.
  • the communications across the air interface 190 may use carrier aggregation, where multiple different component carriers 180, 185 can be aggregated to carry information between the UE 101 and the eNB 150.
  • Such component earners 180, 185 may have different bandwidths, and may ⁇ be used for uplink communications from the UE 101 to the eNB 150, downlink communications from the eNB 150 to the UE 101, or both.
  • Such component carriers 180, 185 may cover similar areas, or may cover different but overlapping sectors.
  • the radio resource control (RRC) connection is handled by only one of the component carrier cells, which may be referred to as the primary component carrier, with the other component carriers referred to as secondary component carriers.
  • the primary component carrier may be operating in a licensed band to provide efficient and conflict-free
  • This primary' channel may be used for scheduling other channels including unlicensed channels as described below.
  • the PRACH is used for initial access and timing advance acquisition . It occupies 6 physical resource blocks (PRB) in one or up to three consecutive uplink subframes, depending on the format.
  • the PRACH preamble length for frequency- division duplex ranges from 1ms to 3ms, depending on the fonnat used.
  • FIG. 4 illustrates LTE PRACH preamble format 0, shown as PRACH preamble 400 which may be modified according to certain embodiments described herein to generate new PRACH preamble formats.
  • a PRACH preamble is a communication including at least one PRACH preamble sequence in addition to other elements.
  • the PRACH preamble 400 consists of a Zadoff- Chu sequence of length 839 bits shown as PRACH preamble sequence 410, transmitted using a sub-carrier spacing of 1.25 KHz. This results in symbol length of 800us.
  • PRACH format 0 the CP and GT are inserted resulting in a total length of lms, such that PRACH preamble 400 fits within one sub-frame 406. Given that the UE does not know its timing advance, the PRACH preamble 400 will arrive at the e B within a delay window equal to the round trip propagation delay. Therefore, the GT 412 length should be at least as large as the delay window plus the channel delay spread.
  • PRACH preamble 400 of FIG. 4 illustrates an example PRACH preamble fonnat.
  • Fonnat 0 that exists within LTE and related systems
  • other PRACH formats are also defined, and may be considered within the context of the example PRACH preamble 400 of FIG. 4.
  • a PRACH format 4 is defined with sub-carrier spacing of 7.5 kHz and preamble duration of 133us.
  • a Zadoff-Chu sequence of length 139 is used, and the overall preamble length is 142.7 microseconds.
  • the unmodified format 0 and format 4 LTE PRACH design is not adequate for systems using unlicensed channels, including LAA and LTE-U systems, for at least the following reasons.
  • PRACH transmission may not satisfy the minimum bandwidth occupancy criteria imposed in some regulator ⁇ 7 domains.
  • a threshold amount of a channel bandwidth is set for users of the unlicensed channel.
  • PRACH preamble transmission occupies the channel for an unnecessarily long period of time ( lms). Because the channel is shared, and other users wait for the channel to be free (e.g.
  • a communication process that uses a small amount of channel bandwidth for a long period of time is not efficient.
  • the supported ceil size e.g. 1.4km for format 4
  • Such cell sizes as matched to PRACH preamble formats and associated system power thresholds to make sure that the initial communications used to establish a connection between an eNB and a UE are consistently detectible.
  • using a small bandwidth for PRACH transmission will significantly reduce the range and detection performance of the PRACH preamble, since not all transmitter power may be used.
  • Some embodiments described herein thus modify the formats discussed above, including particular modified versions of LTE PRACH Format 4 to make it suitable for use in unlicensed bands, both for LAA and standalone LTE- U.
  • a PRACH preamble is generated from a modified format
  • other embodiments comprises new PRACH formats not generated from the above discussed LTE PRACH formats.
  • Some embodiments discussed belo then include options for transmission of the PRACH preambles, either in standalone fashion or embedded in uplink or downlink subframes.
  • Embodiments described herein thus include PRACH preambles where the LTE PRACH format is modified in order to fulfill the criteria of unlicensed bands and reduce overhead.
  • Various embodiments include a modified version of LIE PRACH Format which satisfies the bandwidth occupancy criteria of an unlicensed channel.
  • Other embodiments include a new PRACH design optimized for unlicensed bands, which has reduced duration with respect to current LTE PRACH formats, allowing the medium to be freed for other systems sooner and thus improving coexistence. Some embodiments occupy the full transmission bandwidth or an amount of bandwidth above a channel threshold, thereby satisfying a minimum bandwidth channel occupancy criteria. In some embodiments where a power spectral density constraint is observed, the proposed preamble allows additional transmit power beyond existing systems (e.g. up to 12 dB), providing much better coverage and detection performance. Some embodiments provide low overhead for small cells (e.g. cells with a smaller expected coverage area and lower transmission powers) and also support for larger cell sizes (e.g. cells with a larger expected coverage areas and
  • FIGs. 5 A and 5B illustrate examples of PRACH communications including PRACH preambles as described herein .
  • PRACH preambles use LTE PRACH Formats such as PRACH format 4 for unlicensed bands.
  • the disclosure describes some embodiments based on PRACH Format 4 for convenience.
  • the bandwidth occupancy of PRACH Format 4 is only 1.08 MHz, the embodiments of FIGs. 5A and 5B include the following modifications to satisfy the minimum BW occupancy.
  • FIG. 5 A describes repetition of a PRACH preamble format 4 structure shown as PRACH format 4 preamble sequence 502 to generate a new PRACH preamble 500.
  • the PRACH preamble 500 includes replication the PRACH preamble sequence from PRACH format 4 preamble sequence 502 in the frequency domain. 3 repetitions are shown in as part of PRACH preamble 500. In other embodiments, the number of repetitions may depend on the unlicensed channel bandwidth 530. In some embodiments, for example, with channel bandwidth 530 having a value of 20MHz, thus using 100 PRBs to fill the entire channel, a number of repetitions for PRACH format 4 preamble structures 502 may be selected based on occupancy criteria and the receiver of the eNB that is attempting to detect the PRACH preamble 500. Each of the PRACH format 4 preamble structures 502 includes a sequence selected from a set of system sequences, as well as CP and GT elements. After transmission of the PRACH preamble 500, other LAA transmissions 540 may be sent during the available time on the unlicensed channel before the channel must be released for use by other devices.
  • FIG. 5B shows a system where only a single PRACH format 4 preamble structure 552 is used.
  • Such embodiments transmit a reservation signal outside the bandwidth occupied by the LTE PRACH preamble format to generate a PRACH preamble 550 that meets occupancy criteria. Instead of meeting a bandwidth occupancy threshold associated with unlicensed channel bandwidth 570 with repetitions of structure 552, the bandwidth criteria is met using reservation signal 554.
  • reservation signal 554 In some embodiments, reservation signal
  • reservation signal 554 may include information or data for the eNB.
  • reservation signal 554 is only used to inform other devices that the unlicensed channel is in use.
  • the channel is then available for other LAA transmissions by a UE until the unlicensed channel must be relinquished according to coexistence (e.g. fair use) criteria.
  • Some such embodiments may be used with clustered frequency division multiple access (SC-FDMA) solutions already specified in 3GPP release 10 (SP-52 June 8, 2011) the uplink.
  • SC-FDMA clustered frequency division multiple access
  • Such embodiments may use modified PRACH preambles such as PRACH preamble 500 or PRACH preamble 550 for random access procedures on unlicensed channels.
  • each PRACH repetition e.g. each repetition of PRACH format 4 preamble structures 502 may be phase-modulated in order to facilitate transmitter implementation.
  • FIGs 6 and 7 then illustrate embodiments where a PRACH sequence generated in a time domain is applied by discrete Fourier transform (DFT) precoding and then the preceded sequence is divided into multiple chunks (e.g. elements).
  • the divided multiple chunks are mapped on the frequency domain in distributed manner.
  • each chuck has the same size and the chunks are mapped on frequency domain with equal distances each other.
  • This equal sized distributed manner may reduce PAPR (Peak to Average Power Ratio) / CM (Cubic Metric) which would reduce power back-off in transmission among different types of chunk-based transmission.
  • the transmit PRACH preamble is based on constant amplitude zero autocorrelation (CAZAC) sequences (e.g. Zadoff-Chu sequence)
  • CAZAC constant amplitude zero autocorrelation
  • FIG. 6 begins with a time domain PRACH preamble sequence in operation 602.
  • a DFT process is applied in operation 604 to generate a PRACH preamble in operation 606 after DFT.
  • the PRACH preamble sequence is then divided into elements 609-614 (e.g. chunks), which are separated into separate elements 616-622 and separately mapped onto different parts of the transmission format for transmission 626 following an inverse DFT operation 624.
  • the different elements 716-722 may then be transmitted as part of a PRACH preamble, with the different elements of the PRACH preamble sequence distributed across the channel bandwidth as needed to meet occupancy criteria for the unlicensed channel.
  • PRACH preamble sequence of operation 706 is a CAZAC sequence, and so the initial DFT process is not used.
  • the PRACH preamble sequence is divided into elements 709-714 which are separated as elements 716- 722 for transmissions 726 following IDFT operation 724.
  • Figure 4 and Figure 5, respectively, show the illustrations with DFT and without DFT operation.
  • FIGs. 6 and 7 show sequences divided into four elements, but in different embodiments, different numbers of elements may be created from the PRACH preamble sequence.
  • FIGs. 8 and 9 show additional aspects for transmission of PRACH preambles.
  • a PRACH preamble sequence generated in operation 802 is subject to DFT in operation 804 to generate a modified sequence in operation 806.
  • the sequence of operation 806 following DFT is divided into N elements shown as elements 808-818, and these are separated from each other to create N individual elements 820-828.
  • These N individual elements 820-828 are processed with IDFT 830 mapped fully distributed in a subcarrier level in frequency domain across unlicensed channel bandwidth 899 so the single carrier property (i.e. low CM) can be maintained for transmission 840.
  • the unlicensed channel bandwidth 899 can be also a certain bandwidth which is smaller than unlicensed channel bandwidth.
  • the certain bandwidth can be 5MHz which is a specified nominal bandwidth according to the regulation.
  • the unlicensed channel bandwidth 899 may be set to values smaller than the available unlicensed channel bandw idth. If the available channel bandwidth is 20MHz, the unlicensed channel bandwidth 899 may be structured to use less than the full 20MHz as the unlicensed channel bandwidth 899. In one embodiment, 2400 subcarriers may be used with the bandwidth 899, In this embodiment, the DFT size is smaller than an inverse fast Fourier transform (IFFT) size or an IDFT size corresponding to used bandwidth. In some embodiments, a prime number of carriers smaller than the maximum number of subcarriers may be used with channel bandwidth 899 and use less than the maximum available bandwidth.
  • IFFT inverse fast Fourier transform
  • FIG. 9 shows a corresponding embodiment with a CAZAC PRACH preamble sequence generated in operation 906, the DFT operation can be omitted, and the sequence is divided into elements 909-919 and separated into elements 920-929 before IDFT 930 and transmission 940.
  • the DFT size is less than IDFT size, and the sequence elements after DFT are distributed in equal distance across entire unlicensed channel bandwidth 999 for the system (e.g. across used subcarriers) in the frequency domain.
  • the unlicensed channel bandwidth 999 can be also a certain bandwidth which is smaller than unlicensed channel bandwidth.
  • the certain bandwidth can be 5MHz which is a specified nominal bandwidth according to the regulation.
  • the unlicensed channel bandwidth 999 may thus be less than the maximum, available bandwidth for the channel.
  • the mapping in any embodiment above may be equi -distance mapping according to the embodiments with DFT and without DFT, respectively. In some
  • repetitions of a PRACH sequence may be interleaved in the frequency domain.
  • the preamble sequences discussed above may be replaced with multiple preamble sequences or preamble sequence repetitions, with the elements generated from multiple sequences
  • each individual element of the sequence is repeated N times, with N for example 16, and loaded into consecutive sub- carriers for transmission.
  • a generated sequence for a PRACH preamble sequence length can be equal or the largest prime number smaller than the length corresponding to used bandwidth. So, in this particular example,
  • N 2399 (the largest prime number smaller than 2400 subcarriers).
  • a basic PRACH format is defined consisting of a longer sequence than specified in LTE Format 4.
  • One embodiment may use a sub-carrier spacing of 15 kHz, resulting in a minimum preamble length of 66.7 microseconds.
  • the PRACH may occupy one or more symbols and up to 100 PRB (e.g. 1200 sub-carriers).
  • a Zadoff Chu sequence of a prime length or odd length may be used, considering a desirable correlation property.
  • phase modulation SC-FDMA are possible implementations as described above. Additional details of some embodiments are described below in table 1.
  • the preamble sequence is based on Zadoff Chu sequences of length 293, which can be transmitted in one symbol using 25 PRB, fitting a 5 MHz carrier. Other prime sequence lengths are also possible.
  • a single repetition is used.
  • system BW 10MHz and 20MHz two and four repetitions are used.
  • FIG. 10 illustrates an embodiment with a repeated PRACH preamble sequence shown with four repetitions 1002A-D in a system with unlicensed channel bandwidth 1010 having a 20MHz value.
  • FIG. 11 illustrates an embodiment with a PRACH preamble having a single PRACH sequence 1102 taking up the entire unlicensed channel bandwidth 11 10.
  • any structure in accordance with Table 1 above may be used.
  • the number of repetitions may be further configurable by the eNB or an eNB may dynamically determine a preferred structure when requesting PRACH signaling for timing adjustments or other such PRACH signaling.
  • a transmit power gain can be obtained (e.g. 12 dB).
  • PRACH formats are defined and illustrated in FIGs. 12-14.
  • a single orthogonal frequency division multiplexing (OFDM) symbol is used.
  • the CP length is reduced to accommodate for the GT.
  • an example embodiments with symbol 1204 is shown including CP 1209 and GT 1212 around PRACH preamble sequence 1210.
  • a GT of 2 microseconds is defined, supporting a cell radius up to 300m with a symbol length 1214 of 71.3 to 71.0 microseconds.
  • the format includes 25 PRBs 1216 as part of the structure.
  • a second format is shown with respect to FIG. 13.
  • two symbols 1320 and 1316 are used to transmit a PRACH preamble sequence 131 1 with a 25 PRE 1324 bandwidth.
  • sequence 131 1 has a length of 66.7 microseconds. The remaining time is split between CP 131 1 and GT 1319 for a PRACH preamble length 1322. In one embodiment, this length is 142.6microseconds. As an example, for a GT 1319 of 40 microseconds a cell radius up to 6km can be supported.
  • a third format is shown with respect to FIG. 14.
  • the format of FIG. 14 three symbols are used, shown as symbol 1404, 1409, and 1416.
  • the format has a length 1414 (e.g. 214 microseconds in some embodiments with 25 PRE associated with a 5 MHz channel bandwidth.)
  • the format is used to transmit two repetitions of the PRACH preamble sequence, a first sequence 1410 and a second sequence 1412. The remaining time is split between CP1406 and GT 1419. With this format, additional coverage is possible since the PRACH preamble sequence contains more energy. Similar cell sizes as in standard LTE Format 2 can be supported.
  • additional formats occupying more symbols may be defined.
  • the additional length e.g. length 1414 can be extended in some embodiments
  • PRACH preamble duration can be reduced from a minimum of 2 symbols to 1 symbol, thanks to increased sub-carrier spacing. Therefore, PRACH overhead can be cut in half for small cells.
  • PRACH formats provide large cell support. In some embodiments, a smaller FFT size can be used, since sub-carrier spacing may be set to 15 kHz and FFT size may be the same as for all other physical channels to standardize operation of the PRACH.
  • FIG. 15 illustrates aspects of concurrent transmission of multiple PRACH preambles.
  • the PRACH preamble design allows proper detection of multiple PRACH preambles simultaneously, by using zero autocorrelation shifts of a ZC sequence. Moreo ver, CP and GT are designed such that zero autocorrelation property holds for the largest possible timing misalignment between two UE.
  • LBT listen before talk procedure
  • embodiments may operate as follows.
  • a PRACH preamble 1516 is modified and a second GT 1506 in addition to GT 1512 is added before the CP 1509 and the PRACH preamble sequence 1510, of length exceeding the maximum timing misalignment between two UE in the cell. Since no signal is transmitted during the GTs 1506 and 1512 for a particular eNB, all UEs operating with an eNB can sense the channel available and transmit PRACH preambles simultaneously.
  • FIG. 16 illustrates two PRACH processes for two separate UEs, having a propagation delay 1602 (e.g. based on a different distance between each UE and the eNB/ceil).
  • a first UE performs LBT 1604 prior to a PRACH preamble including GT 1612, CP 1614, preamble sequence 1616, and GT 1620.
  • a second UE performs LBT 1606 prior to a PRACH preamble including GT 1609, CP 1610, preamble sequence 1619, and GT 1622.
  • a UE stops channel sensing early and does not sense for the last n microseconds, where n is calculated according to the maximum timing misalignment for a UE. Guard time 1609 thus prevents LBT 1604 from sensing CP 1610 and/or preamble sequence 1619.
  • LBT 1604 may determine that the channel is in use, and may refrain from transmitting on the unlicensed channel.
  • the additional guard time allows both random access communications, with the eNB able to detect the communications from both UEs based on the differences in the preamble sequences 1616 and 1619.
  • FIG. 17 then describes eNB detection of PRACH signals.
  • PRACH detection for embodiments described herein can be performed similarly to the current LTE PRACH, by performing a frequency domain correlation between the received signal and the configured PRACH preamble. Multiple repetitions will enhance the detection capability of PRACH, since more energy is being transmitted. A longer sequence will also enhance detectability.
  • FIG. 17 illustrates multiple PRACH preamble format repetitions, shown as first repetition 1704 and Nth repetition 1710. A one or two symbol period is used to take the FFT in operation 1714. For example, 2 symbols may be used for LTE Format 4 or one symbol for the newly proposed format.
  • the output of FFT 1714 to demapping 1716 contains multiple PRACH repetitions in the frequency domain.
  • a separate correlator is used for each PRACH repetition, shown as correlators 1719-1720 for correlators 1 through N, and the output is then combined in operation 1722.
  • An IFFT is then taken in operation 1724, followed by peak detection in operations 1726 and 1729.
  • An alternative approach consists in performing independent FFT and squaring operation for each preamble, then combining, and then perform peak detection.
  • PRACH location is specified by the eNB during an initial configuration phase. Since transmission over unlicensed bands must be preceded by LBT, it is likely that PRACH may not be transmitted at the specified time, since the channel may be occupied by another transmission.
  • Embodiments may thus include a time window (e.g. PRACH TX windows 1802,
  • the eNB can expect the reception of PRACH at any time during the time window, or at specified
  • Periodicity and length of the PRACH time window can be configurable, including the option where the PRACH can be sent at any time (e.g. in order to reduce latency).
  • the UE will attempt to transmit a PRACH preamble at the specified locations, using LBT.
  • LBT Low-power Bluetooth
  • PRACH transmission window 1822 occurs, and is shown as including PRACH 1824 with corresponding LBT 1820. This may be associated with a third UE different than the UE form PRACH 1806, 1807, or may again be the same UE.
  • the PRACH preamble in addition to falling within the PRACH transmission window, may be chosen to be transmitted at fixed symbol locations within the LTE sub-frame timing, or at any given symbol. In various embodiments, the tradeoff between PRACH latency and eN B capability is used to determine the PRACH operation structure.
  • FIGs. 19-21 then describe options for PRACH transmission in the context of other communications and system structures.
  • FIG. 19 illustrates a first embodiment, where a UE performs LBT and sends a PRACH preamble at the time specified by the configured PRACH.
  • the eNB does not schedule any concurrent transmission in the subframes containing
  • the PRACH preamble may follow the same LBT procedure used for data transmission (e.g. LBT I , 1909, 1916), or a short version resulting in faster channel access (e.g. LBT2 1904, 1920).
  • LBT I LBT I
  • LBT2 1904 1920
  • a PRACH 1906 follows a shortened LBT2 1904 during PRACH transmission window 1902 and LBT2 1920 during PRACH transmission window 1922.
  • LAA download hurst transmission 1910 and 1919 each performs a longer standard LBT1 1909, 1916 respectively.
  • another system or device may transmit WIFI communication 1914 using the unlicensed channel, and data communications for LA A uplink hurst 1919 may also use the channel after a coexistence criteria LBT1 process 1916 following WIFI communication 1914.
  • FIG. 20 illustrates another embodiment, where PRACH
  • PRACH 2006 occurs during PRACH transmission window 2004, but does not have an independent LBT coexistence operation. Instead, LAA downlink burst 2002 and a corresponding LBT (not shown) is used for channel access for the PRACH that occurs at the end of the LAA downlink burst.
  • LAA downlink burst 2002 and a corresponding LBT (not shown) is used for channel access for the PRACH that occurs at the end of the LAA downlink burst.
  • other transmission such as WIFI 2009 and LAA uplink burst 2014 with an associated LBT1 2012 operation occur.
  • LBT1 2016 for LAA downlink burst 2019 occurs before PRACH transmission window 2020.
  • LAA downlink burst 2002 and 2019 include an indication or data value indicating that PRACH 2006 and 2022 may rely on the corresponding listen before talk processes.
  • the PRACH communications may occur automatically without data in the corresponding downlink bursts.
  • a PRACH sequence may be considered embedded with the LAA downlink burst and is communicated from the UE to the eNB just following the downlink burst from the eNB to the UE.
  • the PRACH may be embedded in either the uplink or downlink LAA frame.
  • PRACH may be located in the first symbols of an LAA uplink frame.
  • the eNB concurrently schedules the PRACH with physical uplink shared channel (PUSCH) transmissions.
  • PUSCH physical uplink shared channel
  • PRACH may start transmission immediately, while UE scheduled in the may PUSCH defer transmission until the PRACH allocation has completed. In some embodiments, during some or all of the PRACH communications, du ring the PRACH symbols, a UE may not transmit, or may transmit a reservation signal.
  • the reservation signal for a UE is a reserved PRACH preamble. Since valid PRACH preambles are cyclic shifts of the preamble sequence and have zero correlation among them, PRACH detection will not be affected by transmission of the reservation signal by a UE implementing a PRACH communication. As an example, if one of the PRACH configurations in 3GPP TS36.211, Table 5.7.2-3 is adopted, then all preambles, including the one sent by PUSCH UE, will conform to the cyclic shift value specified therein. One PRACH preamble (e.g. a specific cyclic shift) would be reserved as reservation signal for UE performing a PRACH operation and would not be used by any other UE performing a PRACH operation.
  • PRACH preamble e.g. a specific cyclic shift
  • FIG . 21 then illustrates another embodiment of a PRACH transmission operation using an unlicensed channel.
  • a PRACH preamble is embedded with the uplink LAA frame.
  • a PRACH may be located in the initial symbols of an LAA uplink frame.
  • PRACH transmission ends within the given subframe period, and the next subframe may be used for LAA uplink.
  • a common downlink control (DCI) message can be defined to indicate the presence of PRACH, As shown in FIG , 21 , PRACH 2110 and PRACH 2124 each occur before a corresponding LAA uplink burst 2106, 2126 and following a corresponding LBTl 2102, 2120 performed for data transmissions.
  • DCI downlink control
  • PRACH communications occur during PRACH transmission windows 2104 and 2119 spaced apart by PRACH periodicity 2114, with other communications LAA downlink burst 2112 and VVIFI 2116 and LET operations (e.g. LBTl 2109) using the channel as well.
  • LAA downlink burst 2112 and VVIFI 2116 and LET operations e.g. LBTl 2109
  • an eNB transmitting a downlink data burst during the PRACH transmission window may reserve the last symbol(s) for PRACH; and may therefore use the embodiment of FIG. 21 to transmit PRACH.
  • An eNB scheduling an uplink data burst during the PRACH transmission window may reserve the initial symbol(s) for PRACH; and any UE will use the embodiment of FIG. 20 to transmit PRACH communications following this eNB scheduling.
  • UE may scan to detect such scheduling from an eNB. If a UE is set for a PRACH process, and does not detect a scheduling from an eNB, the UE may use the embodiment of FIG. 19 to transmit PRACH preambles during a PRACH transmission window independent of any other transmission and using an independent (e.g. a standard LBT1 or shortened LBT2) coexistence process to gain access to the unlicensed channel.
  • an independent e.g. a standard LBT1 or shortened LBT2
  • FIG. 22 then illustrates an asynchronous PRACH design for PRACH processes according to some embodiments.
  • one design option is that there is no pre-configuration of which subframes are downlink (DL) and which subframes are uplink (UL), (e.g. a subframe can be either DL subframe or UL subframe.)
  • DL downlink
  • UL uplink
  • the system may coexist with other networks (e.g., a Wi- Fi network) and every DL or UL transmission is subject to LBT coexistence processes.
  • one possible embodiment operates where it is not pre-configured which set of time/frequency resources are reserved (or exclusively used) for PRACH transmission. Rather, a UE can transmit PRACH at any time independent of any PRACH transmission window limitations so Song as coexistence criteria are met (e.g.
  • a UE performing PRACH transmission does not take into account the subframe boundary in the way subframe boundaries are considered for the embodiments of FIGs. 19-2.1 and therefore can be referred to as asynchronous PRACH transmission.
  • WIFI transmission 2230, PRACH transmission 2232, eNB transmission 2234, and PRACH transmission 2236 are each independent transmissions competing for access to the unlicensed channel, with corresponding LBT processes 2220, 2222, 2224, and 2226 that complete before the device performing the transmission uses the channel.
  • sequence elements e.g. as described
  • a PRACH transmission can consist of PRACH preamble and payload.
  • the preamble can be used for detection of the signal and time/frequency synchronization at the receiver.
  • the payload can include eNB identifiers (ID), UE IDs, buffer status (e.g., amount of data in the buffer, possibly separately for different quality of service (QoS) classes), or other such information.
  • ID eNB identifiers
  • UE IDs e.g., UE IDs
  • buffer status e.g., amount of data in the buffer, possibly separately for different quality of service (QoS) classes
  • FIG. 23 then illustrates on method 2300 performed by a user equipment (UE) for communications with an evolved node B (eNB).
  • the method may be implemented by circuitry of a UE or by an apparatus that is a portion of a UE, such as an integrated circuity of a UE.
  • the method may be a method described by instructions stored in memory, such that the instructions configure a UE to perform the method when the instructions are executed by circuitry of the UE.
  • Method 600 involves operation 2305 to receive, from the eNB, a set of system information associated with the eNB.
  • the UE then generates, using baseband circuitry of the UE, a physical random access channel (PRACH) preamble structured to meet one or more occupancy criteria for a first unlicensed channel as part of operation 2310.
  • PRACH physical random access channel
  • This preamble may be generated according to any embodiment of a PRACH preamble structure described herein, or scheduled using embodiments for PRACH transmission described herein.
  • the PRACH preamble is then transmitted using radio frequency (RF) circuitry of the UE, the PRACH preamble on the first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel in operation 2315.
  • RF radio frequency
  • this may involve LBT procedures identical to those used for data communications, may involve a shortened LBT procedure, particularly when the PRACH transmission is below a channel time use threshold (e.g. the PRACH transmission uses the unlicensed channel for a small/below threshold period of time.) This may also involve scheduling so that a PRACH
  • transmission occurs within a PRACH transmission window and/or in conjunction with another data transmission where the PRACH transmission shares a LBT operation with the data transmission.
  • FIG. 24 describes an example method 2400 performed by an eNB or an apparatus of an eNB, which may involve instructions in memory or circuitry of the eNB, or any device described herein that may be used to implement an eNB.
  • Method 2400 includes operation 2405 to transmit, to a first UE, a set of system, information associated with the eNB. In some embodiments, this may be a general broadcast not specifically directed to the first UE. In other embodiments, this may be a particular command such as a timing assessment or handoff command directed specifically to the UE (e.g.
  • the eNB receives, from the first UE, a first physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel in operation 2410.
  • PRACH physical random access channel
  • This PRACH preamble may using any embodiment of a PRACH preamble, PRACH preamble sequence or sequences, PRACH format including additional guard times, or any other such PRACH structure described herein.
  • Operation 2415 then involves processing the first PRACH preamble.
  • the eNB may then use the information from processing the first PRACH preamble (e.g. timing alignment information) to manage further communications with the first UE.
  • the eNB may receive, from the first UE, a second PRACH preamble on a second channel; and process the first PRACH preamble and the second PRACH preamble to synchronize the first unlicensed channel and the second channel.
  • inventions may include UEs such as phones, tablets, mobile computers, or oilier such devices. Some embodiments may be integrated circuit components of such devices, such as circuits implementing various processing in integrated circuitry. In some embodiments, functionality may be on a single chip or multiple chips in an apparatus. Some such embodiments may further include
  • Example 1 is a computer readable medium comprising instructions that, when executed by one or more processors, configure a user equipment (UE) for communications with an evolved node B (eNB), the instructions to configure the UE to: receive, from the eNB, a set of system information associated with the eNB; generate, using baseband circuitry of the UE, a physical random, access channel (PRACH) preamble structured to meet one or more occupancy criteria for a first unlicensed channel; and transmit, using radio frequency (RF) circuitry of the UE, the PRACH preamble on the first unlicensed channei according to a set of coexistence criteria for the first unlicensed channel.
  • PRACH physical random, access channel
  • RF radio frequency
  • Example 2 the subject matter of Example 1 optionally includes wherein the instructions configure the PRACH preamble for transmission by the UE on the first unl icensed channel immediately following receipt by the UE of a downlink subframe from the eNB,
  • Example 3 the subject matter of any one or more of Examples 1-2 optionally include wherein the instructions configure the PRACH preamble for transmission on the first imlicensed channel by the UE as part of an initial portion of an uplink subframe.
  • Example 4 the subject matter of any one or more of Examples
  • the set of coexistence criteria comprises a set of listen before talk (LBT) timing criteria, and wherein the PRACH preamble is transmitted on the first unlicensed channel following a LBT procedure performed by the UE.
  • LBT listen before talk
  • Example 5 the subject matter of Example 4 optionally includes wherein the instructions configure the PRACH preamble for transmission without additional frame-boundary alignment following the LBT procedure.
  • Example 6 the subject matter of any one or more of Examples
  • 1-5 optionally include-5 wherein the one or more occupancy criteria comprise a bandwidth occupancy threshold.
  • Example 7 the subject matter of any one or more of Examples
  • 1-6 optionally include-6 wherem the one or more occupancy criteria comprises a power spectral density threshold
  • Example 8 the subject matter of any one or more of Examples 1-7 optionally include-7 wherein the one or more occupancy criteria comprises an upper time limit threshold for use of the first unlicensed channel associated with transmission of the PRACH preamble.
  • Example 9 the subject matter of any one or more of Examples
  • the PRACH preamble comprises a 1.08 megahertz (MHz) preamble signal and a reservation signal configured such that a total bandwidth of the 1.08 MHz signal and the reservation signal meet the one or more occupancy criteria for the first unlicensed channel.
  • MHz 1.08 megahertz
  • Example 10 the subject matter of any one or more of
  • Examples 1-9 optionally include-8 wherein the PRACH preamble comprises a plurality of 1.08 MHz preamble signals repeated within the PRACH preamble to meet the one or more occupancy criteria for the first unlicensed channel.
  • Example 11 the subject matter of any one or more of
  • Examples 9-1 optionally include- 10 wherein the instructions configure each 1.08MHz preamble signal for phase modulated prior to transmission.
  • Example 12 the subject matter of any one or more of
  • Examples 9-11 optionally include- 1 1 wherein the instructions configure each 1.08 MHz preamble signal to be: generated as a time domain signal; transformed using discrete Fourier Transform (DFT) preceding to generate a precoded preamble sequence; and divided into a plurality of preceded preamble sequence elements; wherein the pluralit 7 of precoded preamble sequence elements are mapped to a portion of a bandwidth of the first unlicensed channel to reduce peak to average power ration divided by cubic metric ( APR/CM) values.
  • DFT discrete Fourier Transform
  • Example 13 the subject matter of any one or more of
  • Examples 1-12 optionally include- 1 1 wherein the PRACH preamble comprises a constant amplitude zero autocorrelation (CAZAC) sequence.
  • CAZAC constant amplitude zero autocorrelation
  • Example 14 the subject matter of Example 13 optionally includes wherein instructions configure the CAZAC sequence to be transmitted as part of the PRACH preamble with the CAZAC sequence divided into a
  • Example 15 the subject matter of any one or more of
  • Examples 12-14 optionally include and 14 wherein the plurality of precoded preamble sequence elements are mapped as fully distributed at a frequency domain subcarrier level to maintain a single carrier property.
  • Example 16 the subject matter of Example 15 optionally includes where each element of the plurality of precoded preamble sequence elements are distributed at equal distances across the bandwidth of the first unlicensed channel.
  • Example 17 the subject matter of any one or more of
  • Examples 1- 16 optionally include-8 wherein the PRACH preamble comprises a plurality of repetitions of a PRA CH sequence, wherein each PRA CH sequence is interleaved in the frequency domain prior to transmission on the first unlicensed channel .
  • Example 18 the subject matter of any one or more of
  • Examples 1-17 optionally include-8 wherein the PRACH preamble comprises a PRACH sequence with a generated sequence length equal to the largest prime number smaller than a number of symbols corresponding to a bandwidth of the first unlicensed channel.
  • Example 19 the subject matter of any one or more of
  • Examples 1-18 optionally include-8 or 13-18 wherem the PRACH preamble comprises a PRACH format with a sub-carrier spacing of 15 kilohertz (kHz).
  • Example 20 the subject matter of Example 19 optionally includes wherein the PRACH preamble further comprises a PRACH sequence comprising a Zadoff-Chu sequence of length 293.
  • Example 21 the subject matter of Example 20 optionally includes wherein the instructions configure the PRACH preamble to be transmitted in one symbol on the first unlicensed channel using 25 physical resource blocks, the first unlicensed channel having a 5 MHz bandwidth.
  • Example 22 the subject matter of any one or more of
  • Examples 20-21 optionally include wherein the PRACH preamble comprises
  • the first unlicensed channel having a 10 MHz bandwidth.
  • Example 23 the subject matter of any one or more of
  • Examples 20-22 optionally include wherein the PRACH preamble comprises four of the PRACH sequences, the first unlicensed channel having a 20 MHz bandwidth.
  • Example 24 the subject matter of any one or more of
  • Examples 19-23 optionally include wherein the PRACH preamble comprises one or more PRACH sequences each comprising a Zadoff-Chu sequences, wherein a number of PRACH sequences and a sequence length for each of the PRACH sequences is configured by the eNB.
  • Example 25 the subject matter of any one or more of
  • Examples 1-24 optionally include -24 wherein the instructions configure the PRACH preamble to be transmitted with a cyclic prefix and a guard time using one symbol of the first unlicensed channel .
  • Example 26 the subject matter of any one or more of
  • Examples 1-25 optionally include-24 wherein the instructions configure the PRACH preamble to be transmitted with a cyclic prefix and a guard time using two symbols of the first unlicensed channel.
  • Example 27 the subject matter of any one or more of
  • Examples 1-26 optionally include-24 wherein the instructions configure the PRACH preamble with two or more PRACH preamble sequences to be transmitted se uentially on the first unlicensed channel with a shared cyclic prefix and a shared guard time for the two or more PRACH preamble sequences.
  • Example 28 the subject matter of any one or more of
  • Examples 1-27 optionally include-27 wherein the PRACH preamble is transmitted from the UE to the eNB as part of a license assisted access (LAA) system, communication.
  • LAA license assisted access
  • Example 29 the subject matter of any one or more of
  • Examples 1-28 optionally include-27 wherein the PRACH preamble is transmitted from the UE to the eNB as part of a long term evolution unlicensed (LTE-U) system communication without transmission of an associated licensed channel communication.
  • Example 30 is an apparatus of a user equipment (UE) for license assisted access (LAA) or long term evolution unlicensed (LTE-U)
  • the apparatus comprising: radio frequency circuitry configured to: receive, from the eNB, a set of system information associated with the eNB; and transmit, to the eNB, a physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel; and baseband circuitry configured to generate the PRACH preamble to meet one or more occupancy criteria for a first unlicensed channel.
  • radio frequency circuitry configured to: receive, from the eNB, a set of system information associated with the eNB; and transmit, to the eNB, a physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel
  • PRACH physical random access channel
  • Example 31 the subject matter of Example 31 optionally includes further comprising: one or more antennas; and front end module (FEM) circuitry coupled to the one or more antennas and the baseband circuitry, the FEM circuitry configured to filter received and transmitted radio frequency signals as part of communications using the one or more antennas.
  • FEM front end module
  • Example 32 is an apparatus of an evolved node B (eNB) for license assisted access (LAA) or long term evolution unlicensed (LTE-U) communications with user equipment (UE), the apparatus comprising: radio frequency circuitry configured to: transmit, to a first UE, a set of system information associated with the eNB; receive, from the first UE, a first physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel; and control circuitry configured to process the first PRACH preamble and manage communications for the first UE.
  • eNB evolved node B
  • LAA license assisted access
  • LTE-U long term evolution unlicensed
  • Example 32A is an apparatus of claim 32 wherein the control circuitry- is further configured to process a second PRACH preamble received on a second channel to synchronize the first unlicensed channel and the second channel.
  • Example 33 the subject matter of Example 32 optionally includes wherein the set of coexistence criteria comprises a set of listen before talk (LBT) timing criteria, and wherein the PRACH preamble is received on the first unlicensed channel following a LBT procedure performed by the UE; and wherein the one or more occupancy criteria comprise a bandwidth occupancy threshold, a power spectral density threshold, and an upper time limit threshold
  • LBT listen before talk
  • Example 34 is a method for timing alignment for LTE Licensed
  • Example 35 is a method for initial access, timing alignment, and random access procedure for standalone operation of LTE over unlicensed bands.
  • Example 36 is a method as specified in claims 34-35, consisting in the transmission of a PRACH preamble signal.
  • Example 37 is a method as specified in claim 36, wherein the
  • PRACH preamble is preceded by a listen before talk procedure.
  • Example 38 is a method as specified in claim 36, wherein the preamble is an enhancement from the current LTE preamble as specified in tins disclosure.
  • Example 39 is a method as specified in claim 36, wherein a predefined transmission window is specified for the transmission of the PRACH preamble.
  • Example 40 is a method as specified in claim 36, wherein one or multiple PRACH preambles are transmitted by UE(s) after completion of an LBT procedure.
  • Example 41 is a method as specified in claim 36, wherein one or multiple PRACH preambles are transmitted by UE(s) immediately following a downlink subframe.
  • Example 42 is a method as specified in claim 36, wherein one or multiple PRACH preambles are transmitted by UE(s) during the initial symbol(s) of an uplink subframe.
  • Example 43 is a method as specified in claim 36, wherein the PRACH can be transmitted at any time after an LBT procedure, without need to further align with the frame boundary.
  • Example 44 is a method as specified in claim 36, wherein the
  • PRACH may contain a payload as specified in this IDF.
  • Example 45 is a method as specified in claim 36, where UE transmitting PUSCH subframes transmit a predetermined CAZAC sequence (e.g. Zadoff-Chu sequence) during the symbols allocated to PRACH.
  • a predetermined CAZAC sequence e.g. Zadoff-Chu sequence
  • Example 46 the subject matter of Example 46 optionally includes wherein the control circuitry is further configured to: process a second PRACH preamble received on a second channel to synchronize the first unlicensed channel and the second channel.
  • any of the examples detailing further implementations of an element of an apparatus or medium may be applied to any other corresponding apparatus or medium, or may be implemented in conjunction with another apparatus or medium.
  • Tims, each example above may be combined with each other example in various ways both as implementations in a system and as combinations of elements to generate an embodiment from the combination of each example or group of examples.
  • any embodiment above describing a transmitting device will have an embodiment that receives the transmission, even if such an embodiment is not specifically detailed.
  • methods, apparatus examples, and computer readable medium examples may each have a corresponding example of the other type even if such examples for every embodiment are not specifically detailed.
  • FIG. 25 illustrates aspects of a computing machine according to some example embodiments. Embodiments described herein may be implemented into a system 2500 using any suitably configured hardware and/or software.
  • FIG. 25 illustrates, for some embodiments, an example system 2500 comprising radio frequency (RF) circuitry 2535, baseband circuitry 2530, application circuitry 2525, memory/storage 2540, a display 2505, a camera 2520, a sensor 2515, and an input/output (I/O) interface 251 , coupled with each other at least as shown.
  • RF radio frequency
  • the application circuitry 2525 may include circuitry such as, but not limited to, one or more single-core or multi-core processors.
  • the processor(s) may include any combination of general -purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.).
  • the processors may be coupled with the memoi /storage 2540 and configured to execute instructions stored in tlie memory /storage 2540 to enable various applications and/or operating systems running on the system 2500,
  • the baseband circuitry 2530 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. Tlie processor(s) may include a baseband processor.
  • the baseband circuitry 2530 may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 2535. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, and the like.
  • the baseband circuitry 2530 may provide for communication compatible with one or more radio technologies.
  • the baseband circuitry 2530 may support communication with an evolved universal terrestrial radio access network (EUTRAN), other wireless metropolitan area networks (WMANs), a wireless local area network (WLAN), or a wireless personal area network
  • EUTRAN evolved universal terrestrial radio access network
  • WMANs wireless metropolitan area networks
  • WLAN wireless local area network
  • wireless personal area network wireless personal area network
  • Embodiments in which the baseband circuitry 2530 is configured to support radio communication s of more than one wireless protocol may be referred to as multi-mode baseband circuitry.
  • the baseband circuitry 2530 may include circuitry to operate with signals that are not strictly considered as being in a baseband frequency.
  • the baseband circuitry 2530 may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.
  • the RF circuitry 2535 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium.
  • the RF circuitry 2535 may include switches, filters, amplifiers, and the like to facilitate tlie communication with tlie wireless network.
  • the RF circuitry 2535 may include circuitry to operate with signals that are not strictly considered as being in a radio frequency.
  • the RF circuitry 2535 may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.
  • the transmitter circuitry or receiver circuitry discussed above with respect to the UE 271 or the eNB 150 may be embodied in whole or in part in one or more of the RP circuitry 2535, the baseband circuitry 2530, and/or the application circuitr ' 2525.
  • a baseband processor may be used to implement aspects of any embodiment described herein. Such embodiments may be implemented by the baseband circuitry 2530, the application circuitry 2525, and/or the memor /storage 2540 implemented together on a system on a chip (SOC).
  • SOC system on a chip
  • the memory/storage 2540 may be used to load and store data and/or instructions, for example, for the system 2500.
  • the memory/storage 2540 may include any combination of suitable volatile memory (e.g., dynamic random access memory (DRAM)) and/or non-volatile memory (e.g., flash memory).
  • suitable volatile memory e.g., dynamic random access memory (DRAM)
  • non-volatile memory e.g., flash memory
  • the I/O interface 2510 may include one or more user interfaces designed to enable user interaction with the system 2500 and/or peripheral component interfaces designed to enable peripheral component interaction with the system 2500.
  • User interfaces may include, but are not limited to, a physical keyboard or keypad, a touchpad, a speaker, a microphone, and so forth.
  • Peripheral component interfaces may include, but are not limited to, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, and a power supply interface.
  • USB universal serial bus
  • the senor 2515 may include one or more sensing devices to determine environmental conditions and/or location information related to the system 2500.
  • the sensors 25 15 may include, but are not limited to, a gyro sensor, an acceierometer, a proximity- sensor, an ambient light sensor, and a positioning unit.
  • the positioning unit may also be part of, or interact with, the baseband circuitry 2530 and/or RF circuitry 2535 to communicate with components of a positioning network (e.g., a global positioning system (GPS) satellite).
  • the display 2505 may include a display (e.g., a liquid crystal display, a touch screen display, etc.).
  • the system 2500 may be a mobile computing device such as, but not limited to, a laptop computing device, a tablet computing device, a netbook, an ultrabook, a smartphone, and the like.
  • the system 2500 may have more or fewer components, and/or different architectures,
  • FIG. 26 shows an example UE, illustrated as a UE 2600.
  • the UE 2600 may be an implementation of the UE 271, or any device described herein.
  • the UE 2600 can include one or more antennas 2608 configured to communicate with a transmission station, such as a base station (BS), an eNB, or another type of wireless wide area network (WWAN) access point.
  • the UE 2600 can be configured to communicate using at least one wireless communication standard including 3 GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi .
  • the UE 2600 can communicate using separate antennas for each wireless communication standard or shared antennas for multiple wireless communication standards.
  • the UE 2600 can communicate in a WEAN, a WPAN, and/or a WWAN,
  • FIG. 26 also shows a microphone 2620 and one or more speakers 2612 that can be used for audio input and output to and from the UE 2600.
  • a display screen 2604 can be a liquid crystal display (LCD) screen, or another type of display screen such as an organic light emitting diode (OLED) display.
  • the display screen 2604 can be configured as a touch screen.
  • the touch screen can use capacitive, resistive, or another type of touch screen technology.
  • An application processor 2614 and a graphics processor 2618 can be coupled to an internal memory- 2616 to provide processing and display capabilities.
  • a nonvolatile memory port 2610 can also be used to provide data I/O options to a user.
  • the non-volatile memory port 2610 can also be used to expand the memory capabilities of the UE 2600.
  • a keyboard 2606 can be integrated with the UE
  • a virtual keyboard can also be provided using the touch screen.
  • a camera 2622 located on the front (display screen) side or the rear side of the UE 2600 can also be integrated into a housing 2602 of the UE 2600.
  • FIG. 27 is a block diagram illustrating an example computer system machine 2700 upon which any one or more of the methodologies herein discussed can be run, and which may be used to implement the eNB 150, the UE
  • the machine operates as a standalone device or can be connected (e.g., networked) to other machines.
  • the machine can operate in the capacity of either a server or a client machine in server-client network environments, or it can act as a peer machine in peer-to-peer (or distributed) network environments.
  • the machine can be a personal computer (PC) that may or may not be portable (e.g., a notebook or a netbook), a tablet, a set-top box (STB), a gaming console, a Personal Digital Assistant (PDA), a mobile telephone or smartphone, a web appliance, a network router, switch, or bridge, or any machine capable of executing instructions (sequential or othenvise) that specify actions to be taken by that machine.
  • PC personal computer
  • PDA Personal Digital Assistant
  • the example computer system machine 2700 includes a processor
  • the computer system machine 2700 can further include a video display device 2710, an alphanumeric input device 2712 (e.g., a keyboard), and a user interface (Ul) navigation device 2714 (e.g., a mouse).
  • the video display unit 2710, alphanumeric input device 2712, and UI navigation device 2714 are a touch screen display.
  • the computer system machine 2700 can additionally include a mass storage device 2716 (e.g., a drive unit), a signal generation device 2718 (e.g., a speaker), an output controller 2732, a power management controller 2734, a network interface device 2720 (which can include or operably
  • sensors 2728 such as a GPS sensor, compass, location sensor, accelerometer, or other sensor.
  • the mass storage device 2716 includes a machine-readable medium 2722 on which is stored one or more sets of data structures and instructions 2724 (e.g., software) embodying or utilized by any one or more of the methodologies or functions described herein.
  • the instructions 2724 can also reside, completely or ai least partially, within the main memory 2704, static memory 2706, and/or processor 2702 during execution thereof by the computer system machine 2700, with the main memory 2704, the static memory 2706, and the processor 2702 also constituting machine-readable media,
  • machine-readable medium 2722 is illustrated in an example embodiment to be a single medium, the term ' " machine-readable medium” can include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more instructions 2724.
  • the term “machine-readable medium” shall also be taken to include any tangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present disclosure, or thai is capable of storing, encoding, or carrying data structures utilized by or associated with such instructions.
  • the instructions 2724 can further be transmitted or received over a communications network 2726 using a transmission medium via the network interface device 2720 utilizing any one of a number of well-known transfer protocols (e.g., hypertext transfer protocol (HTTP)),
  • HTTP hypertext transfer protocol
  • the term "transmission medium” shall be taken to include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine, and includes digital or analog communications signals or other intangible media to facilitate communication of such software.
  • Various techniques may take the form of program code (i.e., instractions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, computer readable storage media, or any other machine -readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the various techniques.
  • the computing device may include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device.
  • the volatile and non-volatile memory and/or storage elements may be a RAM, Erasable Programmable Read-Only Memory (EPROM), flash drive, optical drive, magnetic hard drive, or other medium for storing electronic data.
  • the base station and mobile station or eNB and UE may also include a transceiver module, a counter module, a processing module, and/or a clock module or timer module.
  • One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.
  • Various embodiments may use 3GPP LTE/LTE-A, Institute of Electrical and Electronic Engineers (IEEE) 2702.11, and Bluetooth
  • Tliese standards include, but are not limited to, other standards from 3 GPP (e.g., HSPA+, UMTS), IEEE 2702.16 (e.g., 2702.16p), or Bluetooth (e.g., Bluetooth 26.0, or like standards defined by the Bluetooth Special Interest Group) standards families.
  • 3 GPP e.g., HSPA+, UMTS
  • IEEE 2702.16 e.g., 2702.16p
  • Bluetooth e.g., Bluetooth 26.0, or like standards defined by the Bluetooth Special Interest Group
  • Other applicable network configurations can be included within the scope of the presently described communication networks. It will be understood that communications on such communication networks can be facilitated using any number of PANs, LANs, and WANs, using any combination of wired or wireless transmission mediums.
  • FIG. 28 illustrates, for one embodiment, example components of a UE 2800 in accordance with some embodiments.
  • the UE 2800 may include application circuitry 2802, baseband circuitry 2804, Radio Frequency (RF) circuitry 2806, front-end module (FEM) circuitry 2808, and one or more antennas 2810, coupled together at least as shown.
  • RF Radio Frequency
  • FEM front-end module
  • the UE 2800 may include additional elements such as, for example, memory/storage, a display, a camera, a sensor, and/or an input/output (I/O) interface.
  • additional elements such as, for example, memory/storage, a display, a camera, a sensor, and/or an input/output (I/O) interface.
  • the application circuitry 2802 may include one or more application processors.
  • the application circuitry 2802 may include circuitry such as, but not limited to, one or more single-core or multi-core processors.
  • the processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.).
  • the processors may be coupled with and/or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the UE 2800.
  • the baseband circuits" ⁇ ' 2804 may include circuity such as, but not limited to, one or more single-core or multi-core processors.
  • the baseband circuitry 2804 may include one or more baseband processors and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 2806 and to generate baseband signals for a transmit signal path of the RF circuitry 2806.
  • the baseband circuity 2804 may interface with the application circuitry 2802 for generation and processing of the baseband signals and for controlling operations of the RF circuity 2806.
  • the baseband circuitry 2804 may include a second generation (2G) baseband processor 2804a, third generation (3G) baseband processor 2804b, fourth generation (4G) baseband processor 2804c, and/or other baseband processor(s) 2804d for other existing generations, generations in development, or generations to be developed in the future (e.g., fifth generation (5G), 6G, etc.).
  • the baseband circuitry 2804 e.g., one or more of the baseband processors
  • the radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc.
  • modulation/demodulation circuitry of the baseband circuitry 2804 may include Fast-Fourier Transform (FFT), preceding, and/or constellation
  • encoding/decoding circuitry of the baseband circuitry 2804 may include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality.
  • LDPC Low Density Parity Check
  • the baseband circuitry 2804 may include elements of a protocol stack such as, for example, elements of an EUTRAN protocol including., for example, physical (PHY), media access control. (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or RRC elements.
  • a central processing unit (CPU) 2804e of the baseband circuitry 2804 may be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP, and/or RRC layers.
  • the baseband circuitry 2804 may include one or more audio digital signal processor(s) (DSP) 2804f.
  • DSP audio digital signal processor
  • the audio DSP(s) 2804f may include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments.
  • Components of the baseband circuitry 2804 may be suitably combined in a single chip or a single chipset, or disposed on a same circuit board in some embodiments.
  • some or ail of the constituent components of the baseband circuitry 2.804 and the application circuitry 2802 may be implemented together, such as, for example, on a system on a chip (SOC).
  • SOC system on a chip
  • the baseband circuitry 2804 may provide for communication compatible with one or more radio technologies.
  • the baseband circuitry 2804 may support communication with an EUTRAN and/or a WMAN, a WLAN, or a WPAN.
  • the baseband circuitry 2804 is configured to support radio
  • multi- mode baseband circuitry communications of more than one wireless protocol may be referred to as multi- mode baseband circuitry.
  • the RF circuitry 2806 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium.
  • the RF circuitry 2806 may include switches, filters, amplifiers, et cetera to facilitate the communication with the wireless network.
  • the RF circuitry 2.806 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 2808 and provide baseband signals to the baseband circuitry 2804.
  • the RF circuitry 2806 may also include a transmit signal path which may include circuitry- to up-convert baseband signals provided by the baseband circuitry 2804 and provide RF output signals to the FEM circuitry 2808 for transmission.
  • the RF circuitry 2806 may include a receive signal path and a transmit signal path.
  • the recei ve signal path of the RF circuitry 2806 may include mixer circuitry 2806a, amplifier circuitry 2806b, and filter Circuitry 2806c.
  • the transmit signal path of the RF circuitry 2806 may include the filter circuitry 2806c and the mixer circuitry 2806a.
  • the RF circuitry 2806 may also include synthesizer circuitry 2806d for synthesizing a frequency for use by the mixer circuitry 2806a of the receive signal path and the transmit signal path.
  • the mixer circuitry 2806a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 2808 based on the synthesized frequency provided by the synthesizer circuitry 2806d.
  • the amplifier circuitry 2806b may be configured to amplify the down- converted signals
  • the filter circuitry 2806c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down- converted signals to generate output baseband signals.
  • Output baseband signals may be provided to the baseband circuitry 2804 for further processing.
  • the output baseband signals may be zero-frequency baseband signals.
  • the mixer circuitry 2806a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.
  • the mixer circuitry 2806a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 2806d to generate RF output signals for the FEM circuitry 2808.
  • the baseband signals may be provided by the baseband circuitry 2804 and may be filtered by the filter circuitry 2806c.
  • the filter circuitry 2806c may include an LPF, although the scope of the embodiments is not limited in this respect.
  • the mixer circuitry 2806a of the recei ve signal path and the mixer circuitry 2806a of the transmit signal path may include two or more mixers and may be arranged for quadrature down conversion and/or up conversion respectively.
  • the mixer circuitry 2806a of the receive signal path and the mixer circuitry 2806a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g.,
  • the mixer circuitry 2806a of the transmit signal path may be arranged for direct down conversion and/or direct up conversion, respectively.
  • the mixer circuitry 2806a of the receive signal path and the mixer circuitry 2806a of the transmit signal path may be configured for super-heterodyne operation.
  • the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect.
  • the output baseband signals and the input baseband signals may be digital baseband signals.
  • the RF circuitry 2806 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 2804 may include a digital baseband interface to communicate with the RF circuitry 2806.
  • ADC analog-to-digital converter
  • DAC digital-to-analog converter
  • a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.
  • the synthesizer circuitry 2806d may be a fractional-N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect, as other types of frequency synthesizers may be suitable.
  • the synthesizer circuitry 2806d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.
  • the synthesizer circuitry 2806d may be configured to synthesize an output frequency for use by the mixer circuitry 2806a of the RF circuitry 2806 based on a frequency input and a divider control input.
  • the synthesizer circuitry 2806d may be a fractional N/N+l synthesizer.
  • frequency input may be provided by a voltage controlled oscillator (VCO). In other embodiments, other means may be used to provide the frequency input.
  • VCO voltage controlled oscillator
  • Divider control input may be provided by either the baseband circuitry 2804 or the application circuitry 2802 depending on the desired output frequency.
  • a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the application circuitry 2802.
  • the synthesizer circuitry 2806d of the F circuitry 2806 may include a divider, a delay-locked loop (DLL), a multiplexer, and a phase accumulator.
  • the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A), in some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio.
  • the DLL may include a set of cascaded, tunable delay elements, a phase detector, a charge pump, and a D-type flip-flop.
  • the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line.
  • Nd is the number of delay elements in the delay line.
  • the synthesizer circuitry 2806d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other.
  • the output frequency may be a LO frequency (fLQ).
  • the RF circuitry 2806 may include an IQ/polar converter.
  • the FEM circuitry 2808 may include a receive signal path which may include circuitry configured to operate on RF signals received from the one or more antennas 2810, amplify the received signals, and provide the amplified versions of the received signals to the RF circuitry 2806 for further processing.
  • the FEM circuitry 2808 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 2806 for transmission by one or more of the one or more antennas 2810.
  • the FEM circuitry 2808 may include a TX/RX switch to switch between transmit mode and receive mode operation.
  • the FEM circuitry 2808 may include a receive signal path and a transmit signal path.
  • the receive signal path of the FEM circuitry 2808 may include a low-noise amplifier
  • the transmit signal path of the FEM circuitry 2808 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by the RF circuitry- 2806), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 2810).
  • PA power amplifier
  • the UE 2800 comprises a plurality of power saving mechanisms. If the UE 2800 is in an RRC Connected state, where it is still connected to the eNB as it expects to receive traffic shortly , then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the UE 2800 may power down for brief intervals of time and thus save power.
  • DRX Discontinuous Reception Mode
  • the UE 2800 may transition to an RRCJEdie state, where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc.
  • the UE 2800 goes into a very low-power state and performs paging, wherein it periodically wakes up to listen to the network and then powers down again.
  • the UE 2800 cannot receive data in this state, and in order to receive data, it transitions back to the RRC Connected state.
  • An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to die network and may power down completely. Any data sent during this time incurs a large delay, and it is assumed that the delay is acceptable.
  • semiconductor memory devices e.g., EPROM, Electrically Erasable
  • EEPROM Electrically Programmable Read-Only Memory
  • machine such as a computer or networking device, the machine becomes an apparatus for practicing the various techniques.
  • VLSI virtual logic integration
  • a component or module can also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like.
  • Components or modules can also be implemented in software for execution by various types of processors.
  • An identified component or module of executable code can, for instance, comprise one or more physical or logical blocks of computer instructions, which can, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified component or module are not necessarily physically located together, but can comprise disparate instructions stored in different locations which, when joined logically together, comprise the component or module and achieve the stated purpose for the component or module.
  • a component or module of executable code can be a single instruction, or many instructions, and can even be distributed over several different code segments, among different programs, and across several memory devices.
  • operational data can be identified and illustrated herein within components or modules, and can be embodied in any suitable fonn and organized within any suitable type of data structure. Hie operational data can be collected as a single data set, or can be distributed over different locations including over different storage devices, and can exist, at least partially, merely as electronic signals on a system or network.
  • the components or modules can be passive or active, including agents operable to perform desired functions.

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Abstract

Devices, methods, storage media, instructions, and apparatus for communications between a user equipment (UE) and an evolved node B (eNB) on unlicensed channels are described. In one embodiment, a receives, from an eNB, a set of system information associated with the eNB, generates a physical random access channel (PRACH) preamble structured to meet one or more occupancy criteria for a first unlicensed channel, and transmits, using radio frequency (RF) circuitry of the UE, the PRACH preamble on the first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel. In various embodiments, the PRACH preamble unlicensed channel use are structure to meet occupancy and coexistence criteria for the unlicensed channels in different ways.

Description

PRACH DESIGN FOR UNLICENSED CHANNELS
PRIORITY CLAIM
[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 62/204,682, filed on August 13, 2015, and entitled "PRACH DESIGN FOR LICENSED ASSISTED ACCESS AND
STANDALONE LTE-UNLICENSED", which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] Embodiments pertain to systems, methods, and component devices for wireless communications, and particularly physical random access channel (PRACH) design for use with long term evolution (LTE), LTE-advanced, and other similar wireless communication systems that operate with license assisted access (LAA), LTE-uniicensed (LTE-U), or other similar communication systems which use channels in unlicensed frequency bands..
BACKGROUND
[0003] LTE and LTE-advanced are standards for wireless communication of high-speed data for user equipment (UE) such as mobile telephones. In LTE- advanced and various wireless systems, carrier aggregation is a technology where multiple earner signals operating on different frequencies may be used to carry communications for a single UE, thus increasing the bandwidth available to a single device. Carrier aggregation may be used where one or more component carriers operate on unlicensed frequencies. BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a block diagram of a system including an evolved node B (eNB) and a user equipment (UE) that may operate according to some embodiments described herein.
[0005] FIG. 2 is a block diagram showing a system including a UE communicating with a cell on an unlicensed frequency according to some embodiments described he ein.
[0006] FIG. 3 is a block diagram showing a system including a UE communicating with two cells, including one cell on a licensed frequency and another cell on an unlicensed frequency according to some embodiments described herein.
[0007] FIG. 4 illustrates aspects of a physical random access channel (PRACH) preamble.
[0008] FIG. 5A illustrates a PRACH preamble with repeated PRACH preamble sequences according to some embodiments.
[0009] FIG. 5B illustrates a PRACH preamble with a reservation signal according to some embodiments described herein.
[0010] FIG. 6 illustrates aspects of generating a PRACH preamble according to some embodiments described herein.
[0011] FIG. 7 illustrates aspects of generating a PRACH preamble according to some embodiments described herein.
[0012] FIG. 8 illustrates aspects of generating a PRACH preamble according to some embodiments described herein.
[0013] FIG. 9 illustrates aspects of generating a PRACH preamble according to some embodiments described herein .
[0014] FIG. 10 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
[0015] FIG. 11 illustrates another embodiment of a PRACH preamble according to some implementations described herein. [0016] FIG. 12 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
[0017] FIG. 13 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
[0018] FIG. 14 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
[0019] FIG. 15 illustrates another embodiment of a PRACH preamble according to some implementations described herein.
[0020] FIG. 16 illustrates aspects of system operation and alignment of propagation delays according to some embodiments.
[0021] FIG. 17 illustrates aspects of PRACH preamble detection according to some example embodiments.
[0022] FIG. 19 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
[0023] FIG. 20 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
[0024] FIG. 21 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
[0025] FIG. 22 illustrates aspects of channel usage with PRACH preamble transmission according to some example embodiments.
[0026] FIG. 23 is a method for PRACH preamble use according to some embodiments described herein.
[0027] FIG. 24 is a method for PRACH preamble use according to some embodiments described herein.
[0028] FIG. 25 illustrates aspects of a computing machine, according to some example embodiments.
[0029] FIG. 26 illustrates aspects of a UE, in accordance with some example embodiments.
[0030] FIG. 27 is a block diagram illustrating an example computer system machine which may be used in association with various embodiments described herein. [0031] FIG. 28 is a block diagram illustrating an example user equipment including aspects of wireless communication systems, which may be used in association with various embodiments described herein.
DETAILED DESCRIPTION
[0032] Embodiments relate to systems, devices, apparatus, assemblies, methods, and computer readable media to enhance wireless communications, and particularly to communication systems that operate with carrier aggregation with at least some carriers operating on unlicensed channels where coexistence operations are used. The following description and the drawings illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments can incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments can be included in, or substituted for, those of other embodiments, and are intended to cover all available equivalents of the elements described.
[0033] FIG. 1 illustrates aspects of a wireless network system. 100, in accordance with some embodiments. The wireless network system 100 includes a UE 101 and an eNB 150 connected via an air interface 190. UE 101 and eNB 150 communicate using a system that supports carrier aggregation and the use of unlicensed frequency bands, such that the air interface 190 supports multiple frequency carriers and licensed as well as unlicensed bands. A component carrier 180 and a component carrier 185 are illustrated. Although two component carrie s are illustrated, various embodiments may include any numbe of two or more component carriers. Various embodiments may function with any number of licensed channels and one or more unlicensed channels.
[0034] In various embodiments described herein, at least one of the component earners 180, 185 of the air interface 190 comprises a carrier operating in an unlicensed frequency, referred to herein as an unlicensed carrier. An "unlicensed carrier" or ' unlicensed frequency" refers to a range of radio frequencies that are not exclusively set aside for the use of the system. Some frequency ranges, for example, may be used by communication systems operating under different communication standards, such as a frequency band that is used by both Institute of Electronic and Electrical Engineers (IEEE) 802.11 standards (e.g., "WiFi") and third generation partnership (3GPP) standards. By contrast, a licensed channel or licensed spectrum operates under a particular standard, with limited concern that other unexpected signals operating on different standards will be present.
[0035] Some embodiments may implement license assisted access (LAA) communications where primary channels with control signals are sent on licensed channels. FIG. 2 illustrates an embodiment that may implement LAA, with UE communicating on licensed channels using communications 203 with cell 202, and unlicensed channel communications including physical random access channel (PRACH) 210 and timing advance 209 with cell 204. Other embodiments may implement long term evolution or similar systems where only unlicensed channels are used for some communications, or other similar systems using unlicensed channels. Other embodiments may include any system implemented using an eNB to communicate using unlicensed channels. Apart from the license assisted access (LAA) operation considered in Release 13 of the third generation partnership project (3GPP) standard (3GPP release 13, open of September 30, 2012), LTE may also be operated via dual connectivity or the standalone LTE mode which may use limited assistance from the licensed spectram.. For example an LTE based technology "MuLTEfire" has been under consideration, requiring no assistance from the licensed spectrum to enable a leaner, self-contained network architecture that is suitable for neutral deployments where any deployment can service any device . The operation of LTE on the unlicensed spectrum without any assistance from licensed carrier will be referred to as standalone LTE unlicensed (LTE-U) herein. FIG. 3 illustrates a simple embodiment with UE 306 communicating with cell 302 on unlicensed channels, including PRACH initial access communication 304. Cell 302 of FIG. 3 and cells 202 and 204 of FIG. 2 will all be associated with eNB systems as part of a larger communication network to enable network access to UEs such as UE 206 and UE 306.
[0036] Communication systems such as those described above in FIGs. 1-3, in addition to usins unlicensed channels, use certain communication channel structures. FIG. 2 particularly shows the use of PRACH 210 and FIG. 3 shows PRACH initial access 304 communications. In LTE and similar systems for embodiments described herein, the PRACH, or physical random access channel as men tioned above, is used for a number of functions, including managing initial access, handover between cells, and timing advance correction. The
PRACH enables random access procedures to enable UE devices to synchronize with the network . When a UE wants to access a network via a cell of an eNB (e.g. a device including antenna(s) and various circuitry as described herein), the UE will attempt to attach or synchronize with the network. The PRACH is provided for such processes. When a UE such as UE 206 or 306 powers on or moves to a new area, the UE will search for a network for the frequencies available to the UE. If a network is available, an initial synchronization occurs usmg primary and secondary synchronization signals (PSS and SSS) broadcast by an eNB. The UE reads system information such as system information block 1 and system information block 2, and then the UE begins a random access procedure, using communications such as PRACH initial access communication 304 or PRACH 210. These PRACH communications may include a preamble sequence selected from a limited set of preamble sequences that may be used for the initial identification of the UE by the eNB. The eNB scans for PRACH communications including one of the preselected PRACH preamble sequences, and uses this to identify the presence of the UE requesting a connection. A response from the appropriate cell of an eNB may then lead to a connection between the UE and the eNB. Similarly, when a handover occurs or a UE is performing a timing advance correction, PRACH signals may be used for this purpose.
[0037] In LAA systems, as mentioned above, a primary carrier is transmitted on a licensed band and secondary earners are transmitted over unlicensed bands. In carrier aggregation, the PRACH is normally sent over the primary carrier. In systems such as that shown in FIG. 2 where a primary channel is sent over a cell 202 and secondary channels use a separate cell 204 and the cell 202 and cell 204 are not co-located, propagation delay between the UE and the ceils 202, 204 are different. Therefore, primary and secondary carriers may use different timing advance values. In this situation, a PRACH procedure for timing advance correction may be carried out over secondary carriers to properly synchronize the UE and secondary cells. In earner aggregation, a group of secondary carriers may be configured with common timing advance values as a secondary timing alignment group. Timing advances can also be obtained by means of eNB initiated random procedures, where upon request, the UE transmits a
PRACH communication including a PRACH preamble sequence to the cell for which the request is intended. The communication including the PRACH preamble sequence may then be used to manage the timing advance differences between ceils that are in different locations, such a cells 202 and 204, where an eNB may know a timing advance from a primary channel PRACH procedure using communications 203 between cell 202 and UE 206. The eNB may then initiate a timing advance operation for cell 204 which is not co-located with cell 202. As part of such a timing advance, UE 206 may send PRACH 210 to cell 204, and may receive a timing advance 209 communicat on. In other embodiments, the timing advance may be handled in communications between cell 204 and other control circuitry of the eNB communicating with the UE using cell 202 and cell 204.
[0038] In addition to the timing advance use for PRACH communications in LAA systems as described for FIG. 2, in embodiments such as the LTE-U system of FIG. 3, where only unlicensed channels are available, the handoff and initial attach PRACH operations are also handled using PRACH transmissions with PRACH preamble sequences over unlicensed channels.
[0039] When a system operates in an unlicensed spectrum, rules and operations for verifying that the unlicensed channels are available provide additional overhead and system operational elements that are not present in licensed channels. The sharing of a channel may be referred to as "fair coexistence", where different systems operate to use an unlicensed or shared channel while limiting both interference and direct integration with the other systems operating on different standards. When UE 306 and cell 302 transmit on an unlicensed channel as part of PRACH initial access 304 communications, coexistence rales that do not apply for licensed channels are used.
[0040] LTE cellular communications may, for example, operate with a centrally managed system designed to operate in a licensed spectrum for efficient resource usage. Operating with such centrally managed use within unlicensed channels where systems not centrally controlled that use different channel access mechanisms than legacy LTE may be present carries significant risk of direct interference. Coexistence mechanisms described herein enable LTE, LTE-advanced, and communications systems building on or similar to LTE systems to coexist with other technologies such as WiFi in shared unlicensed frequency bands (e.g., unlicensed channels.)
[0041] Embodiments described herein for coexistence may operate within the wireless network system 100. In the wireless network system 100, the UE 101 and any other UE in the system may be, for example, laptop computers, smartphones, tablet computers, printers, machine-type devices such as smart meters or specialized devices for healthcare monitoring, remote security surveillance systems, intelligent transportation systems, or any other wireless devices with or without a user interface. The eNB 150 provides the UE 101 network connectivity to a broader network (not shown). This UE 101 connectivity is provided via the air interface 190 in an eNB service area provided by the eNB 150. In some embodiments, such a broader network may be a wide area network operated by a cellular network provider, or may be the Internet. Each eNB service area associated with the eNB 150 is supported by antennas integrated with the eNB 150. The se dee areas are divided into a number of sectors associated with certain antennas. Such sectors may be physically associated with fixed antennas or may be assigned to a physical area, with tunable antennas or antenna settings adjustable in a beamforming process used to direct a signal to a particular sector. One embodiment of the eNB 150, for example, includes three sectors each covering a 120 degree area with an array of antennas directed to each sector to provide 360 degree coverage around the eNB 150.
[0042] The UE 101 includes control circuitry 105 coupled with transmit circuitry HO and receive circuitry 1 15. The transmit circuitry 110 and receive circuitry 115 may each be coupled with one or more antennas. The control circuitry 105 may be adapted to perform operations associated with wireless communications using carrier aggregation. The transmit circuitry 1 10 and receive circuitry 1 15 may be adapted to transmit and receive data, respectively. The control circuitiy 105 may be adapted or configured to perform various operations such as those described elsewhere in this disclosure related to a UE. The transmit circuitry 110 may transmit a plurality of multiplexed uplink physical channels. The plurality of uplink physical channels may be multiplexed according to time division multiplexing (TDM) or frequency division multiplexing (FDM) along with carrier aggregation. The transmit circuitry 110 may be configured to receive block data from the control circuitry 105 for transmission across the air interface 190. Similarly, the receive circuitry 1 15 may receive a plurality of multiplexed downlink phy sical channels from the air interface 190 and relay the physical channels to the control circuitry 105. The uplink and downlink physical channels may be multiplexed according to FDM. The transmit circuitiy 110 and the receive circuitiy 115 may transmit and receive both control data and content data (e.g., messages, images, video, et cetera) structured within data blocks that are carried by the physical channels.
[0043] FIG. 1 also illustrates the eNB 150, in accordance with various embodiments. Hie eNB 150 circuitiy may include control circuitiy 155 coupled with transmit circuitry 160 and receive circuitiy 165. The transmit circuitry 160 and receive circuitr ' 165 may each be coupled with one or more antennas that may be used to enable communications via the air interface 190. In some embodiments, transmit circuitry 160 and receive circuitiy 165 may be structured with multiple cells which may be coupled to the core eNB circuitiy via wired or wireless connections. This enables cells with varying frequency support or other characteristics, and antennas for an eNB to be located in different areas. Cells communicating with a UE for a single eNB may thus be sufficiently far apart to generate timing issues such as those described above.
[0044] The control circuitiy 155 may be adapted to perform operations for managing channels and component carriers used with various UEs. The transmit circuitiy 160 and receive circuitry 165 may be adapted to transmit and receive data, respectively, to and from any UE connected to the eNB 150. The transmit circuitiy 160 may transmit downlink physical channels comprised of a plurality of downlink subframes. The receive circuitry 165 may receive a plurality of uplink physical channels from various UEs including the UE 101. The plurality of uplink physical channels may be multiplexed according to FDM in addition to the use of earner aggregation.
[0045] As mentioned above, the communications across the air interface 190 may use carrier aggregation, where multiple different component carriers 180, 185 can be aggregated to carry information between the UE 101 and the eNB 150. Such component earners 180, 185 may have different bandwidths, and may¬ be used for uplink communications from the UE 101 to the eNB 150, downlink communications from the eNB 150 to the UE 101, or both. Such component carriers 180, 185 may cover similar areas, or may cover different but overlapping sectors. The radio resource control (RRC) connection is handled by only one of the component carrier cells, which may be referred to as the primary component carrier, with the other component carriers referred to as secondary component carriers. In some embodiments, the primary component carrier may be operating in a licensed band to provide efficient and conflict-free
communications. This primary' channel may be used for scheduling other channels including unlicensed channels as described below.
[0046] As mentioned above, in standard in LTE communication systems, the PRACH is used for initial access and timing advance acquisition . It occupies 6 physical resource blocks (PRB) in one or up to three consecutive uplink subframes, depending on the format. The PRACH preamble length for frequency- division duplex ranges from 1ms to 3ms, depending on the fonnat used. FIG. 4 illustrates LTE PRACH preamble format 0, shown as PRACH preamble 400 which may be modified according to certain embodiments described herein to generate new PRACH preamble formats. As described herein, a PRACH preamble is a communication including at least one PRACH preamble sequence in addition to other elements. The PRACH preamble 400 of FIG . 4 consists of a cyclic prefix (CP) 404, a PRACH preamble sequence 410, and a guard time (GT) 412. In other various embodiments described herein various combinations of different PRACH preamble sequences, CPs, and GTs may be included in different PRACH preambles. The PRACH preamble 400 consists of a Zadoff- Chu sequence of length 839 bits shown as PRACH preamble sequence 410, transmitted using a sub-carrier spacing of 1.25 KHz. This results in symbol length of 800us. In PRACH format 0, the CP and GT are inserted resulting in a total length of lms, such that PRACH preamble 400 fits within one sub-frame 406. Given that the UE does not know its timing advance, the PRACH preamble 400 will arrive at the e B within a delay window equal to the round trip propagation delay. Therefore, the GT 412 length should be at least as large as the delay window plus the channel delay spread.
[0047J PRACH preamble 400 of FIG. 4 illustrates an example PRACH preamble fonnat. In addition to Fonnat 0 that exists within LTE and related systems, other PRACH formats are also defined, and may be considered within the context of the example PRACH preamble 400 of FIG. 4. For time domain duplex systems, a PRACH format 4 is defined with sub-carrier spacing of 7.5 kHz and preamble duration of 133us. In this fonnat, a Zadoff-Chu sequence of length 139 is used, and the overall preamble length is 142.7 microseconds. The unmodified format 0 and format 4 LTE PRACH design is not adequate for systems using unlicensed channels, including LAA and LTE-U systems, for at least the following reasons. By using only 6 PRB, or 1.08 MHz, PRACH transmission may not satisfy the minimum bandwidth occupancy criteria imposed in some regulator}7 domains. In other words, in order to both effectively use a shared unlicensed channel and provide other users with an adequate ability to detect that a channel is in use, a threshold amount of a channel bandwidth is set for users of the unlicensed channel. Additionally, in LTE formats 1-3, by using a full subframe (e.g. sub-frame 406), PRACH preamble transmission occupies the channel for an unnecessarily long period of time ( lms). Because the channel is shared, and other users wait for the channel to be free (e.g. using listen before talk processes), a communication process that uses a small amount of channel bandwidth for a long period of time is not efficient. In some existing PRACH preamble formats, such as fonnat 4, the supported ceil size (e.g. 1.4km for format 4) may not be sufficient in some cases. Such cell sizes as matched to PRACH preamble formats and associated system power thresholds to make sure that the initial communications used to establish a connection between an eNB and a UE are consistently detectible. In regulatory domains where the power spectral density is limited, using a small bandwidth for PRACH transmission will significantly reduce the range and detection performance of the PRACH preamble, since not all transmitter power may be used.
[0048] Some embodiments described herein thus modify the formats discussed above, including particular modified versions of LTE PRACH Format 4 to make it suitable for use in unlicensed bands, both for LAA and standalone LTE- U. In addition to embodiments where a PRACH preamble is generated from a modified format, other embodiments comprises new PRACH formats not generated from the above discussed LTE PRACH formats. Some embodiments discussed belo then include options for transmission of the PRACH preambles, either in standalone fashion or embedded in uplink or downlink subframes.
[0049] Embodiments described herein thus include PRACH preambles where the LTE PRACH format is modified in order to fulfill the criteria of unlicensed bands and reduce overhead. Various embodiments include a modified version of LIE PRACH Format which satisfies the bandwidth occupancy criteria of an unlicensed channel.
[0050] Other embodiments include a new PRACH design optimized for unlicensed bands, which has reduced duration with respect to current LTE PRACH formats, allowing the medium to be freed for other systems sooner and thus improving coexistence. Some embodiments occupy the full transmission bandwidth or an amount of bandwidth above a channel threshold, thereby satisfying a minimum bandwidth channel occupancy criteria. In some embodiments where a power spectral density constraint is observed, the proposed preamble allows additional transmit power beyond existing systems (e.g. up to 12 dB), providing much better coverage and detection performance. Some embodiments provide low overhead for small cells (e.g. cells with a smaller expected coverage area and lower transmission powers) and also support for larger cell sizes (e.g. cells with a larger expected coverage areas and
corresponding adjustments in transmission and receive circuitry operation.) [0051] In addition, as discussed below with respect to FIGs. 1 8-22, different system operations with different channel use structures and transmission mechanisms for PRACH are described, including standalone PRACH use, after performing LBT; PRACH preambles occupying the first symbols of an uplink subframe, performing LBT simultaneously with other uplink users; and PRACH preambles occupying the last symbols of a downlink subframe, without using LET.
[0052] FIGs. 5 A and 5B illustrate examples of PRACH communications including PRACH preambles as described herein . Such embodiments use LTE PRACH Formats such as PRACH format 4 for unlicensed bands. Among the PRACH preamble formats, the disclosure describes some embodiments based on PRACH Format 4 for convenience. However, since the bandwidth occupancy of PRACH Format 4 is only 1.08 MHz, the embodiments of FIGs. 5A and 5B include the following modifications to satisfy the minimum BW occupancy. FIG. 5 A describes repetition of a PRACH preamble format 4 structure shown as PRACH format 4 preamble sequence 502 to generate a new PRACH preamble 500. The PRACH preamble 500 includes replication the PRACH preamble sequence from PRACH format 4 preamble sequence 502 in the frequency domain. 3 repetitions are shown in as part of PRACH preamble 500. In other embodiments, the number of repetitions may depend on the unlicensed channel bandwidth 530. In some embodiments, for example, with channel bandwidth 530 having a value of 20MHz, thus using 100 PRBs to fill the entire channel, a number of repetitions for PRACH format 4 preamble structures 502 may be selected based on occupancy criteria and the receiver of the eNB that is attempting to detect the PRACH preamble 500. Each of the PRACH format 4 preamble structures 502 includes a sequence selected from a set of system sequences, as well as CP and GT elements. After transmission of the PRACH preamble 500, other LAA transmissions 540 may be sent during the available time on the unlicensed channel before the channel must be released for use by other devices.
[0053] FIG. 5B, by contrast, shows a system where only a single PRACH format 4 preamble structure 552 is used. Such embodiments transmit a reservation signal outside the bandwidth occupied by the LTE PRACH preamble format to generate a PRACH preamble 550 that meets occupancy criteria. Instead of meeting a bandwidth occupancy threshold associated with unlicensed channel bandwidth 570 with repetitions of structure 552, the bandwidth criteria is met using reservation signal 554. In some embodiments, reservation signal
554 may include information or data for the eNB. In other embodiments, reservation signal 554 is only used to inform other devices that the unlicensed channel is in use. Just as above, after the PRACH preamble including PRACH format 4 preamble structures 552 and reservation signal 554, ends, the channel is then available for other LAA transmissions by a UE until the unlicensed channel must be relinquished according to coexistence (e.g. fair use) criteria.
[0054J Some such embodiments may be used with clustered frequency division multiple access (SC-FDMA) solutions already specified in 3GPP release 10 (SP-52 June 8, 2011) the uplink. Such embodiments may use modified PRACH preambles such as PRACH preamble 500 or PRACH preamble 550 for random access procedures on unlicensed channels. In addition, such embodiments each PRACH repetition (e.g. each repetition of PRACH format 4 preamble structures 502) may be phase-modulated in order to facilitate transmitter implementation.
[0055] FIGs 6 and 7 then illustrate embodiments where a PRACH sequence generated in a time domain is applied by discrete Fourier transform (DFT) precoding and then the preceded sequence is divided into multiple chunks (e.g. elements). The divided multiple chunks are mapped on the frequency domain in distributed manner. One specific further example is that each chuck has the same size and the chunks are mapped on frequency domain with equal distances each other. This equal sized distributed manner may reduce PAPR (Peak to Average Power Ratio) / CM (Cubic Metric) which would reduce power back-off in transmission among different types of chunk-based transmission. In some embodiments, if the transmit PRACH preamble is based on constant amplitude zero autocorrelation (CAZAC) sequences (e.g. Zadoff-Chu sequence), DFT operation can be omitted and the generated sequence can be directly divided into multiple chunks.
[0056J FIG. 6 begins with a time domain PRACH preamble sequence in operation 602. A DFT process is applied in operation 604 to generate a PRACH preamble in operation 606 after DFT. The PRACH preamble sequence is then divided into elements 609-614 (e.g. chunks), which are separated into separate elements 616-622 and separately mapped onto different parts of the transmission format for transmission 626 following an inverse DFT operation 624. In various embodiments, the different elements 716-722 may then be transmitted as part of a PRACH preamble, with the different elements of the PRACH preamble sequence distributed across the channel bandwidth as needed to meet occupancy criteria for the unlicensed channel.
[0057] In FIG. 7, PRACH preamble sequence of operation 706 is a CAZAC sequence, and so the initial DFT process is not used. The PRACH preamble sequence is divided into elements 709-714 which are separated as elements 716- 722 for transmissions 726 following IDFT operation 724. Figure 4 and Figure 5, respectively, show the illustrations with DFT and without DFT operation. FIGs. 6 and 7 show sequences divided into four elements, but in different embodiments, different numbers of elements may be created from the PRACH preamble sequence.
[0058] FIGs. 8 and 9 show additional aspects for transmission of PRACH preambles. In the embodiments of FIG. 8, a PRACH preamble sequence generated in operation 802, is subject to DFT in operation 804 to generate a modified sequence in operation 806. Just as in FIG. 6, the sequence of operation 806 following DFT is divided into N elements shown as elements 808-818, and these are separated from each other to create N individual elements 820-828. These N individual elements 820-828 are processed with IDFT 830 mapped fully distributed in a subcarrier level in frequency domain across unlicensed channel bandwidth 899 so the single carrier property (i.e. low CM) can be maintained for transmission 840. Throughout the disclosure, the unlicensed channel bandwidth 899 can be also a certain bandwidth which is smaller than unlicensed channel bandwidth. For instance, the certain bandwidth can be 5MHz which is a specified nominal bandwidth according to the regulation. In various
embodiments, the unlicensed channel bandwidth 899 may be set to values smaller than the available unlicensed channel bandw idth. If the available channel bandwidth is 20MHz, the unlicensed channel bandwidth 899 may be structured to use less than the full 20MHz as the unlicensed channel bandwidth 899. In one embodiment, 2400 subcarriers may be used with the bandwidth 899, In this embodiment, the DFT size is smaller than an inverse fast Fourier transform (IFFT) size or an IDFT size corresponding to used bandwidth. In some embodiments, a prime number of carriers smaller than the maximum number of subcarriers may be used with channel bandwidth 899 and use less than the maximum available bandwidth.
[0059] FIG. 9 shows a corresponding embodiment with a CAZAC PRACH preamble sequence generated in operation 906, the DFT operation can be omitted, and the sequence is divided into elements 909-919 and separated into elements 920-929 before IDFT 930 and transmission 940. Just as described above for FIG. 8, the DFT size is less than IDFT size, and the sequence elements after DFT are distributed in equal distance across entire unlicensed channel bandwidth 999 for the system (e.g. across used subcarriers) in the frequency domain. Throughout the disclosure, the unlicensed channel bandwidth 999 can be also a certain bandwidth which is smaller than unlicensed channel bandwidth. For instance, the certain bandwidth can be 5MHz which is a specified nominal bandwidth according to the regulation. The unlicensed channel bandwidth 999 may thus be less than the maximum, available bandwidth for the channel. The mapping in any embodiment above may be equi -distance mapping according to the embodiments with DFT and without DFT, respectively. In some
embodiments, the subcarrier spacing is 17 with N=139 (e.g. 2400
subcarriers/ 139), but it is noted that any distance should be okay in terms of CM thanks to the sampling property (e.g. could be 20 with N=139), as long as the distributed sequences can be fitted into the used bandwidth.
[0060] In other embodiments, repetitions of a PRACH sequence may be interleaved in the frequency domain. In such embodiments, the preamble sequences discussed above may be replaced with multiple preamble sequences or preamble sequence repetitions, with the elements generated from multiple sequences In some embodiments, each individual element of the sequence is repeated N times, with N for example 16, and loaded into consecutive sub- carriers for transmission.
[0061] In still further embodiments, a generated sequence for a PRACH preamble sequence length can be equal or the largest prime number smaller than the length corresponding to used bandwidth. So, in this particular example,
N=2399 (the largest prime number smaller than 2400 subcarriers).
[0062] In another embodiment, a basic PRACH format is defined consisting of a longer sequence than specified in LTE Format 4. One embodiment may use a sub-carrier spacing of 15 kHz, resulting in a minimum preamble length of 66.7 microseconds. In such an embodiment, the PRACH may occupy one or more symbols and up to 100 PRB (e.g. 1200 sub-carriers). In the preamble, a Zadoff Chu sequence of a prime length or odd length may be used, considering a desirable correlation property. In some embodiments, it is possible to repeat use a single sequence without repetition or to use a shorter sequence and repeat it in the frequency domain. For sequence repetition, phase modulation SC-FDMA are possible implementations as described above. Additional details of some embodiments are described below in table 1.
Figure imgf000019_0001
TABLE 1
[0063] In some embodiments, the preamble sequence is based on Zadoff Chu sequences of length 293, which can be transmitted in one symbol using 25 PRB, fitting a 5 MHz carrier. Other prime sequence lengths are also possible. For system BW of 5 MHz, a single repetition is used. For system BW 10MHz and 20MHz, two and four repetitions are used. FIG. 10 illustrates an embodiment with a repeated PRACH preamble sequence shown with four repetitions 1002A-D in a system with unlicensed channel bandwidth 1010 having a 20MHz value. FIG. 11 illustrates an embodiment with a PRACH preamble having a single PRACH sequence 1102 taking up the entire unlicensed channel bandwidth 11 10. In various other embodiments, any structure in accordance with Table 1 above may be used. In some embodiments, the number of repetitions may be further configurable by the eNB or an eNB may dynamically determine a preferred structure when requesting PRACH signaling for timing adjustments or other such PRACH signaling.
[0064] In some embodiments, if a power spectral density constraint must be observed, by using the entire bandwidth or a large portion of the unlicensed channel bandwidth (e.g. 1 8 MHz) as opposed to the current LTE standard
17-1 PRACH bandwidth of 1.08 MHz, a transmit power gain can be obtained (e.g. 12 dB).
[0065] In embodiments structured according to table I above, or any PRACH preamble sequences structured using similar new formats, for any chosen sequence length and repetition factor, following PRACH formats are defined and illustrated in FIGs. 12-14. In a first format described with respect to FIG. 12, a single orthogonal frequency division multiplexing (OFDM) symbol is used. The CP length is reduced to accommodate for the GT. In FIG. 12, an example embodiments with symbol 1204 is shown including CP 1209 and GT 1212 around PRACH preamble sequence 1210. As an example, a GT of 2 microseconds is defined, supporting a cell radius up to 300m with a symbol length 1214 of 71.3 to 71.0 microseconds. The format includes 25 PRBs 1216 as part of the structure.
[0066] A second format is shown with respect to FIG. 13. In the format of FIG. 13, two symbols 1320 and 1316 are used to transmit a PRACH preamble sequence 131 1 with a 25 PRE 1324 bandwidth. In one embodiment, sequence 131 1 has a length of 66.7 microseconds. The remaining time is split between CP 131 1 and GT 1319 for a PRACH preamble length 1322. In one embodiment, this length is 142.6microseconds. As an example, for a GT 1319 of 40 microseconds a cell radius up to 6km can be supported.
[0067] A third format is shown with respect to FIG. 14. In the format of FIG. 14, three symbols are used, shown as symbol 1404, 1409, and 1416. The format has a length 1414 (e.g. 214 microseconds in some embodiments with 25 PRE associated with a 5 MHz channel bandwidth.) The format is used to transmit two repetitions of the PRACH preamble sequence, a first sequence 1410 and a second sequence 1412. The remaining time is split between CP1406 and GT 1419. With this format, additional coverage is possible since the PRACH preamble sequence contains more energy. Similar cell sizes as in standard LTE Format 2 can be supported.
[0068] In some embodiments, additional formats occupying more symbols may be defined. The additional length (e.g. length 1414 can be extended in some embodiments) can be used to obtain longer GT and/or increased coverage with more preamble repetitions. These newly defined preamble formats have the
18 following advantages with respect to reusing LIE Format 4. Such embodiments enable longer PRACH sequences to be used. A longer sequence provides higher gain at the correlator and better detection performance. PRACH preamble duration can be reduced from a minimum of 2 symbols to 1 symbol, thanks to increased sub-carrier spacing. Therefore, PRACH overhead can be cut in half for small cells. Additional embodiment PRACH formats provide large cell support. In some embodiments, a smaller FFT size can be used, since sub-carrier spacing may be set to 15 kHz and FFT size may be the same as for all other physical channels to standardize operation of the PRACH.
[0069] FIG. 15 illustrates aspects of concurrent transmission of multiple PRACH preambles. In embodiments described herein, the PRACH preamble design allows proper detection of multiple PRACH preambles simultaneously, by using zero autocorrelation shifts of a ZC sequence. Moreo ver, CP and GT are designed such that zero autocorrelation property holds for the largest possible timing misalignment between two UE. In LAA there is an additional structure related to the listen before talk procedure (LBT)(e.g. coexistence criteria). It may happen that two misaligned UE start transmitting the PRACH preamble at different time instants, and if the delayed UE has not finished its channel sensing procedure (e.g. coexistence procedure), it may sense the channel as occupied and refrain from transmitting. In order to avoid this situation, embodiments may operate as follows.
[0070] As illustrated in FIG. 15, a PRACH preamble 1516 is modified and a second GT 1506 in addition to GT 1512 is added before the CP 1509 and the PRACH preamble sequence 1510, of length exceeding the maximum timing misalignment between two UE in the cell. Since no signal is transmitted during the GTs 1506 and 1512 for a particular eNB, all UEs operating with an eNB can sense the channel available and transmit PRACH preambles simultaneously. FIG. 16 illustrates two PRACH processes for two separate UEs, having a propagation delay 1602 (e.g. based on a different distance between each UE and the eNB/ceil). A first UE performs LBT 1604 prior to a PRACH preamble including GT 1612, CP 1614, preamble sequence 1616, and GT 1620. A second UE performs LBT 1606 prior to a PRACH preamble including GT 1609, CP 1610, preamble sequence 1619, and GT 1622. While performing LBT prior to PRACH preamble transmission, a UE stops channel sensing early and does not sense for the last n microseconds, where n is calculated according to the maximum timing misalignment for a UE. Guard time 1609 thus prevents LBT 1604 from sensing CP 1610 and/or preamble sequence 1619. Without the guard time 1609, LBT 1604 may determine that the channel is in use, and may refrain from transmitting on the unlicensed channel. The additional guard time allows both random access communications, with the eNB able to detect the communications from both UEs based on the differences in the preamble sequences 1616 and 1619.
[0071] FIG. 17 then describes eNB detection of PRACH signals. PRACH detection for embodiments described herein can be performed similarly to the current LTE PRACH, by performing a frequency domain correlation between the received signal and the configured PRACH preamble. Multiple repetitions will enhance the detection capability of PRACH, since more energy is being transmitted. A longer sequence will also enhance detectability. FIG. 17 illustrates multiple PRACH preamble format repetitions, shown as first repetition 1704 and Nth repetition 1710. A one or two symbol period is used to take the FFT in operation 1714. For example, 2 symbols may be used for LTE Format 4 or one symbol for the newly proposed format. The output of FFT 1714 to demapping 1716 contains multiple PRACH repetitions in the frequency domain. After demapping, a separate correlator is used for each PRACH repetition, shown as correlators 1719-1720 for correlators 1 through N, and the output is then combined in operation 1722. An IFFT is then taken in operation 1724, followed by peak detection in operations 1726 and 1729. An alternative approach consists in performing independent FFT and squaring operation for each preamble, then combining, and then perform peak detection.
[0072J During detection, PRACH location is specified by the eNB during an initial configuration phase. Since transmission over unlicensed bands must be preceded by LBT, it is likely that PRACH may not be transmitted at the specified time, since the channel may be occupied by another transmission.
Embodiments may thus include a time window (e.g. PRACH TX windows 1802,
1822) for the transmission of PRACH, as shown in FIG. 18. The eNB can expect the reception of PRACH at any time during the time window, or at specified
20 time instants during the time window. Periodicity and length of the PRACH time window can be configurable, including the option where the PRACH can be sent at any time (e.g. in order to reduce latency). The UE will attempt to transmit a PRACH preamble at the specified locations, using LBT. In order to maximize the efficiency of medium occupancy, we now propose several options for PRACH transmission. By specifying the length of PRACH TX window and periodicity we must consider the tradeoff existing between reducing PRACH latency and the computational power and energy consumption at the eNB, which must monitor the channel for PRACH. This is illustrated by FIG. 18, which shows two PRACH transmission windows 1802 and 1822. During the first window 1802, two PRACH communications, shown as PRACH 1806 and 1807 occur. These may be from the same UE or may be from different UEs. Each PRACH is associated with a different LBT operation as part of system conformance with coexistence criteria. PRACH periodicity 1812 also provides coexistence benefits, where PRACH operation is limited and separated by PRACH periodicity 1812. After a delay following PRACH transmission window- 1802 where other devices or operations may use the unlicensed channel, PRACH transmission window 1822 occurs, and is shown as including PRACH 1824 with corresponding LBT 1820. This may be associated with a third UE different than the UE form PRACH 1806, 1807, or may again be the same UE.
[0073] In some embodiments, in addition to falling within the PRACH transmission window, the PRACH preamble may be chosen to be transmitted at fixed symbol locations within the LTE sub-frame timing, or at any given symbol. In various embodiments, the tradeoff between PRACH latency and eN B capability is used to determine the PRACH operation structure.
[0074] FIGs. 19-21 then describe options for PRACH transmission in the context of other communications and system structures. FIG. 19 illustrates a first embodiment, where a UE performs LBT and sends a PRACH preamble at the time specified by the configured PRACH. In such embodiments, the eNB does not schedule any concurrent transmission in the subframes containing
PRACH. The PRACH preamble may follow the same LBT procedure used for data transmission (e.g. LBT I , 1909, 1916), or a short version resulting in faster channel access (e.g. LBT2 1904, 1920). In the embodiment of FIG. 19 a PRACH 1906 follows a shortened LBT2 1904 during PRACH transmission window 1902 and LBT2 1920 during PRACH transmission window 1922. LAA download hurst transmission 1910 and 1919 each performs a longer standard LBT1 1909, 1916 respectively. During the portion of PRACH periodicity 1912 where PRACH communications are not allowed, another system or device may transmit WIFI communication 1914 using the unlicensed channel, and data communications for LA A uplink hurst 1919 may also use the channel after a coexistence criteria LBT1 process 1916 following WIFI communication 1914.
[0075] FIG. 20 illustrates another embodiment, where PRACH
communications are embedded in the time period for downlink LAA and use the coexistence criteria for LAA frames. In the embodiment of FIG. 20, PRACH 2006 occurs during PRACH transmission window 2004, but does not have an independent LBT coexistence operation. Instead, LAA downlink burst 2002 and a corresponding LBT (not shown) is used for channel access for the PRACH that occurs at the end of the LAA downlink burst. In the barred period of PRACH periodicity 2010 following PRACH transmission window 2004, other transmission such as WIFI 2009 and LAA uplink burst 2014 with an associated LBT1 2012 operation occur. Then, before PRACH transmission window 2020, LBT1 2016 for LAA downlink burst 2019 occurs. PRACH 2022
communication relies on LBT1 2016 and placement with LAA downlink burst 2019 to meet coexistence criteria for use of the unlicensed channel. In some embodiments, LAA downlink burst 2002 and 2019 include an indication or data value indicating that PRACH 2006 and 2022 may rely on the corresponding listen before talk processes. In other embodiments, the PRACH communications may occur automatically without data in the corresponding downlink bursts. In any such embodiments for FIG. 20, a PRACH sequence may be considered embedded with the LAA downlink burst and is communicated from the UE to the eNB just following the downlink burst from the eNB to the UE.
[0076] In various embodiments, the PRACH may be embedded in either the uplink or downlink LAA frame. PRACH may be located in the first symbols of an LAA uplink frame. In such embodiments, the eNB concurrently schedules the PRACH with physical uplink shared channel (PUSCH) transmissions. After simultaneously ending the coexistence criteria (e.g. LBT) period, a UE sending
I/.. PRACH may start transmission immediately, while UE scheduled in the may PUSCH defer transmission until the PRACH allocation has completed. In some embodiments, during some or all of the PRACH communications, du ring the PRACH symbols, a UE may not transmit, or may transmit a reservation signal.
[0077] In one embodiment of this disclosure, in order to avoid interference with PRACH preambles, the reservation signal for a UE is a reserved PRACH preamble. Since valid PRACH preambles are cyclic shifts of the preamble sequence and have zero correlation among them, PRACH detection will not be affected by transmission of the reservation signal by a UE implementing a PRACH communication. As an example, if one of the PRACH configurations in 3GPP TS36.211, Table 5.7.2-3 is adopted, then all preambles, including the one sent by PUSCH UE, will conform to the cyclic shift value specified therein. One PRACH preamble (e.g. a specific cyclic shift) would be reserved as reservation signal for UE performing a PRACH operation and would not be used by any other UE performing a PRACH operation.
[0078] FIG . 21 then illustrates another embodiment of a PRACH transmission operation using an unlicensed channel. In FIG. 21, a PRACH preamble is embedded with the uplink LAA frame. A PRACH may be located in the initial symbols of an LAA uplink frame. PRACH transmission ends within the given subframe period, and the next subframe may be used for LAA uplink. A common downlink control (DCI) message can be defined to indicate the presence of PRACH, As shown in FIG , 21 , PRACH 2110 and PRACH 2124 each occur before a corresponding LAA uplink burst 2106, 2126 and following a corresponding LBTl 2102, 2120 performed for data transmissions. These PRACH communications occur during PRACH transmission windows 2104 and 2119 spaced apart by PRACH periodicity 2114, with other communications LAA downlink burst 2112 and VVIFI 2116 and LET operations (e.g. LBTl 2109) using the channel as well.
[0079] In addition to the individual embodiments of FIGs. 19-21, in order to optimize PRACH transmission, some embodiments may use combinations of these embodiments. For example, an eNB transmitting a downlink data burst during the PRACH transmission window may reserve the last symbol(s) for PRACH; and may therefore use the embodiment of FIG. 21 to transmit PRACH. An eNB scheduling an uplink data burst during the PRACH transmission window may reserve the initial symbol(s) for PRACH; and any UE will use the embodiment of FIG. 20 to transmit PRACH communications following this eNB scheduling.
[0080] In such embodiments UE may scan to detect such scheduling from an eNB. If a UE is set for a PRACH process, and does not detect a scheduling from an eNB, the UE may use the embodiment of FIG. 19 to transmit PRACH preambles during a PRACH transmission window independent of any other transmission and using an independent (e.g. a standard LBT1 or shortened LBT2) coexistence process to gain access to the unlicensed channel.
[0081] FIG. 22 then illustrates an asynchronous PRACH design for PRACH processes according to some embodiments.
[0082 ] In LAA and LTE-U standalone, one design option is that there is no pre-configuration of which subframes are downlink (DL) and which subframes are uplink (UL), (e.g. a subframe can be either DL subframe or UL subframe.) This is mainly because the system may coexist with other networks (e.g., a Wi- Fi network) and every DL or UL transmission is subject to LBT coexistence processes. In such a system, one possible embodiment operates where it is not pre-configured which set of time/frequency resources are reserved (or exclusively used) for PRACH transmission. Rather, a UE can transmit PRACH at any time independent of any PRACH transmission window limitations so Song as coexistence criteria are met (e.g. the channel is deemed to be idle using LBT). In such embodiments, a UE performing PRACH transmission does not take into account the subframe boundary in the way subframe boundaries are considered for the embodiments of FIGs. 19-2.1 and therefore can be referred to as asynchronous PRACH transmission. In the embodiment of FIG. 22, WIFI transmission 2230, PRACH transmission 2232, eNB transmission 2234, and PRACH transmission 2236 are each independent transmissions competing for access to the unlicensed channel, with corresponding LBT processes 2220, 2222, 2224, and 2226 that complete before the device performing the transmission uses the channel.
[0083] In addition to the PRACH preamble structure described above with one or more PRACH preamble sequences, sequence elements (e.g. as described
24 in FIGs. 6-9), CP, and GT, a PRACH transmission can consist of PRACH preamble and payload. The preamble can be used for detection of the signal and time/frequency synchronization at the receiver. The payload can include eNB identifiers (ID), UE IDs, buffer status (e.g., amount of data in the buffer, possibly separately for different quality of service (QoS) classes), or other such information.
[0084] FIG. 23 then illustrates on method 2300 performed by a user equipment (UE) for communications with an evolved node B (eNB). In various embodiments, the method may be implemented by circuitry of a UE or by an apparatus that is a portion of a UE, such as an integrated circuity of a UE. In other embodiments, the method may be a method described by instructions stored in memory, such that the instructions configure a UE to perform the method when the instructions are executed by circuitry of the UE. Method 600 involves operation 2305 to receive, from the eNB, a set of system information associated with the eNB. This may, for example, by system information blocks received via synchronization signal transmissions, and these may provide the UE with information in initiating random, access transmissions to the UE. In other embodiments, the system information may be a command to perform a handoff procedure to a new eNB, or a timing alignment procedure. The UE then generates, using baseband circuitry of the UE, a physical random access channel (PRACH) preamble structured to meet one or more occupancy criteria for a first unlicensed channel as part of operation 2310. This preamble may be generated according to any embodiment of a PRACH preamble structure described herein, or scheduled using embodiments for PRACH transmission described herein. The PRACH preamble is then transmitted using radio frequency (RF) circuitry of the UE, the PRACH preamble on the first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel in operation 2315. As described above, this may involve LBT procedures identical to those used for data communications, may involve a shortened LBT procedure, particularly when the PRACH transmission is below a channel time use threshold (e.g. the PRACH transmission uses the unlicensed channel for a small/below threshold period of time.) This may also involve scheduling so that a PRACH
transmission occurs within a PRACH transmission window and/or in conjunction with another data transmission where the PRACH transmission shares a LBT operation with the data transmission.
[0085] FIG. 24 describes an example method 2400 performed by an eNB or an apparatus of an eNB, which may involve instructions in memory or circuitry of the eNB, or any device described herein that may be used to implement an eNB. Method 2400 includes operation 2405 to transmit, to a first UE, a set of system, information associated with the eNB. In some embodiments, this may be a general broadcast not specifically directed to the first UE. In other embodiments, this may be a particular command such as a timing assessment or handoff command directed specifically to the UE (e.g. using an identifier for the UE.) The eNB receives, from the first UE, a first physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel in operation 2410. This PRACH preamble may using any embodiment of a PRACH preamble, PRACH preamble sequence or sequences, PRACH format including additional guard times, or any other such PRACH structure described herein. Operation 2415 then involves processing the first PRACH preamble. The eNB may then use the information from processing the first PRACH preamble (e.g. timing alignment information) to manage further communications with the first UE. In some embodiments, the eNB may receive, from the first UE, a second PRACH preamble on a second channel; and process the first PRACH preamble and the second PRACH preamble to synchronize the first unlicensed channel and the second channel.
EXAMPLES
[0086] In various embodiments, methods, apparatus, media, computer program products, or oilier implementations may be presented as example embodiments in accordance with the descriptions provided above. Certain embodiments may include UEs such as phones, tablets, mobile computers, or oilier such devices. Some embodiments may be integrated circuit components of such devices, such as circuits implementing various processing in integrated circuitry. In some embodiments, functionality may be on a single chip or multiple chips in an apparatus. Some such embodiments may further include
26 transmit and receive circuitry on integrated or separate circuits, with antennas that are similarly integrated or separate structures of a device. Any such components or circuit elements may similarly apply to evolved node B embodiments described herein.
[0087] Example 1 is a computer readable medium comprising instructions that, when executed by one or more processors, configure a user equipment (UE) for communications with an evolved node B (eNB), the instructions to configure the UE to: receive, from the eNB, a set of system information associated with the eNB; generate, using baseband circuitry of the UE, a physical random, access channel (PRACH) preamble structured to meet one or more occupancy criteria for a first unlicensed channel; and transmit, using radio frequency (RF) circuitry of the UE, the PRACH preamble on the first unlicensed channei according to a set of coexistence criteria for the first unlicensed channel.
[0088] In Example 2, the subject matter of Example 1 optionally includes wherein the instructions configure the PRACH preamble for transmission by the UE on the first unl icensed channel immediately following receipt by the UE of a downlink subframe from the eNB,
[0089] In Example 3, the subject matter of any one or more of Examples 1-2 optionally include wherein the instructions configure the PRACH preamble for transmission on the first imlicensed channel by the UE as part of an initial portion of an uplink subframe.
[0090] In Example 4, the subject matter of any one or more of Examples
1-3 optionally include wherein the set of coexistence criteria comprises a set of listen before talk (LBT) timing criteria, and wherein the PRACH preamble is transmitted on the first unlicensed channel following a LBT procedure performed by the UE.
[0091] In Example 5, the subject matter of Example 4 optionally includes wherein the instructions configure the PRACH preamble for transmission without additional frame-boundary alignment following the LBT procedure.
[0092] In Example 6, the subject matter of any one or more of Examples
1-5 optionally include-5 wherein the one or more occupancy criteria comprise a bandwidth occupancy threshold.
27 [0093] In Example 7, the subject matter of any one or more of Examples
1-6 optionally include-6 wherem the one or more occupancy criteria comprises a power spectral density threshold,
[0094] In Example 8, the subject matter of any one or more of Examples 1-7 optionally include-7 wherein the one or more occupancy criteria comprises an upper time limit threshold for use of the first unlicensed channel associated with transmission of the PRACH preamble.
[0095] In Example 9, the subject matter of any one or more of Examples
1-8 optionally mciude-8 wherem the PRACH preamble comprises a 1.08 megahertz (MHz) preamble signal and a reservation signal configured such that a total bandwidth of the 1.08 MHz signal and the reservation signal meet the one or more occupancy criteria for the first unlicensed channel.
[0096 J In Example 10, the subject matter of any one or more of
Examples 1-9 optionally include-8 wherein the PRACH preamble comprises a plurality of 1.08 MHz preamble signals repeated within the PRACH preamble to meet the one or more occupancy criteria for the first unlicensed channel.
[0097] In Example 11, the subject matter of any one or more of
Examples 9-1 optionally include- 10 wherein the instructions configure each 1.08MHz preamble signal for phase modulated prior to transmission.
[0098] In Example 12, the subject matter of any one or more of
Examples 9-11 optionally include- 1 1 wherein the instructions configure each 1.08 MHz preamble signal to be: generated as a time domain signal; transformed using discrete Fourier Transform (DFT) preceding to generate a precoded preamble sequence; and divided into a plurality of preceded preamble sequence elements; wherein the pluralit 7 of precoded preamble sequence elements are mapped to a portion of a bandwidth of the first unlicensed channel to reduce peak to average power ration divided by cubic metric ( APR/CM) values.
[0099] In Example 13, the subject matter of any one or more of
Examples 1-12 optionally include- 1 1 wherein the PRACH preamble comprises a constant amplitude zero autocorrelation (CAZAC) sequence.
[00100] In Example 14, the subject matter of Example 13 optionally includes wherein instructions configure the CAZAC sequence to be transmitted as part of the PRACH preamble with the CAZAC sequence divided into a
28 plurality of precoded preamble sequence elements; and wherein the plurality of preceded preamble sequence elements of the CAZAC sequence is mapped to a portion of a bandwidth of the first unlicensed channel.
[00101] In Example 15, the subject matter of any one or more of
Examples 12-14 optionally include and 14 wherein the plurality of precoded preamble sequence elements are mapped as fully distributed at a frequency domain subcarrier level to maintain a single carrier property.
[00102] In Example 16, the subject matter of Example 15 optionally includes where each element of the plurality of precoded preamble sequence elements are distributed at equal distances across the bandwidth of the first unlicensed channel.
[00103] In Example 17, the subject matter of any one or more of
Examples 1- 16 optionally include-8 wherein the PRACH preamble comprises a plurality of repetitions of a PRA CH sequence, wherein each PRA CH sequence is interleaved in the frequency domain prior to transmission on the first unlicensed channel .
[00104] In Example 18, the subject matter of any one or more of
Examples 1-17 optionally include-8 wherein the PRACH preamble comprises a PRACH sequence with a generated sequence length equal to the largest prime number smaller than a number of symbols corresponding to a bandwidth of the first unlicensed channel.
[00105] In Example 19, the subject matter of any one or more of
Examples 1-18 optionally include-8 or 13-18 wherem the PRACH preamble comprises a PRACH format with a sub-carrier spacing of 15 kilohertz (kHz).
[00106] In Example 20, the subject matter of Example 19 optionally includes wherein the PRACH preamble further comprises a PRACH sequence comprising a Zadoff-Chu sequence of length 293.
[00107] In Example 21 , the subject matter of Example 20 optionally includes wherein the instructions configure the PRACH preamble to be transmitted in one symbol on the first unlicensed channel using 25 physical resource blocks, the first unlicensed channel having a 5 MHz bandwidth.
[00108] In Example 22, the subject matter of any one or more of
Examples 20-21 optionally include wherein the PRACH preamble comprises
29 two of the PRACH sequences, the first unlicensed channel having a 10 MHz bandwidth.
[00109] In Example 23, the subject matter of any one or more of
Examples 20-22 optionally include wherein the PRACH preamble comprises four of the PRACH sequences, the first unlicensed channel having a 20 MHz bandwidth.
[00110] In Example 24, the subject matter of any one or more of
Examples 19-23 optionally include wherein the PRACH preamble comprises one or more PRACH sequences each comprising a Zadoff-Chu sequences, wherein a number of PRACH sequences and a sequence length for each of the PRACH sequences is configured by the eNB.
[00111] In Example 25, the subject matter of any one or more of
Examples 1-24 optionally include -24 wherein the instructions configure the PRACH preamble to be transmitted with a cyclic prefix and a guard time using one symbol of the first unlicensed channel .
[00112] In Example 26, the subject matter of any one or more of
Examples 1-25 optionally include-24 wherein the instructions configure the PRACH preamble to be transmitted with a cyclic prefix and a guard time using two symbols of the first unlicensed channel.
[00113] In Example 27, the subject matter of any one or more of
Examples 1-26 optionally include-24 wherein the instructions configure the PRACH preamble with two or more PRACH preamble sequences to be transmitted se uentially on the first unlicensed channel with a shared cyclic prefix and a shared guard time for the two or more PRACH preamble sequences.
[00114] In Example 28, the subject matter of any one or more of
Examples 1-27 optionally include-27 wherein the PRACH preamble is transmitted from the UE to the eNB as part of a license assisted access (LAA) system, communication.
[00115] In Example 29, the subject matter of any one or more of
Examples 1-28 optionally include-27 wherein the PRACH preamble is transmitted from the UE to the eNB as part of a long term evolution unlicensed (LTE-U) system communication without transmission of an associated licensed channel communication. [00116] Example 30 is an apparatus of a user equipment (UE) for license assisted access (LAA) or long term evolution unlicensed (LTE-U)
communications with an evolved node B (eNB), the apparatus comprising: radio frequency circuitry configured to: receive, from the eNB, a set of system information associated with the eNB; and transmit, to the eNB, a physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel; and baseband circuitry configured to generate the PRACH preamble to meet one or more occupancy criteria for a first unlicensed channel.
[00117] In Example 31, the subject matter of Example 31 optionally includes further comprising: one or more antennas; and front end module (FEM) circuitry coupled to the one or more antennas and the baseband circuitry, the FEM circuitry configured to filter received and transmitted radio frequency signals as part of communications using the one or more antennas.
[00118] Example 32 is an apparatus of an evolved node B (eNB) for license assisted access (LAA) or long term evolution unlicensed (LTE-U) communications with user equipment (UE), the apparatus comprising: radio frequency circuitry configured to: transmit, to a first UE, a set of system information associated with the eNB; receive, from the first UE, a first physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel; and control circuitry configured to process the first PRACH preamble and manage communications for the first UE.
[00119] Example 32A is an apparatus of claim 32 wherein the control circuitry- is further configured to process a second PRACH preamble received on a second channel to synchronize the first unlicensed channel and the second channel.
[00120] In Example 33, the subject matter of Example 32 optionally includes wherein the set of coexistence criteria comprises a set of listen before talk (LBT) timing criteria, and wherein the PRACH preamble is received on the first unlicensed channel following a LBT procedure performed by the UE; and wherein the one or more occupancy criteria comprise a bandwidth occupancy threshold, a power spectral density threshold, and an upper time limit threshold
31 for use of the first unlicensed channel associated with transmission of the PRACH preamble.
[00121] Example 34 is a method for timing alignment for LTE Licensed
Assisted Access.
[00122] Example 35 is a method for initial access, timing alignment, and random access procedure for standalone operation of LTE over unlicensed bands.
[00123] Example 36 is a method as specified in claims 34-35, consisting in the transmission of a PRACH preamble signal.
[00124] Example 37 is a method as specified in claim 36, wherein the
PRACH preamble is preceded by a listen before talk procedure.
[00125] Example 38 is a method as specified in claim 36, wherein the preamble is an enhancement from the current LTE preamble as specified in tins disclosure.
[00126] Example 39 is a method as specified in claim 36, wherein a predefined transmission window is specified for the transmission of the PRACH preamble.
[00127] Example 40 is a method as specified in claim 36, wherein one or multiple PRACH preambles are transmitted by UE(s) after completion of an LBT procedure.
[00128] Example 41 is a method as specified in claim 36, wherein one or multiple PRACH preambles are transmitted by UE(s) immediately following a downlink subframe.
[00129] Example 42 is a method as specified in claim 36, wherein one or multiple PRACH preambles are transmitted by UE(s) during the initial symbol(s) of an uplink subframe.
[00130] Example 43 is a method as specified in claim 36, wherein the PRACH can be transmitted at any time after an LBT procedure, without need to further align with the frame boundary.
[00131] Example 44 is a method as specified in claim 36, wherein the
PRACH may contain a payload as specified in this IDF. [00132] Example 45 is a method as specified in claim 36, where UE transmitting PUSCH subframes transmit a predetermined CAZAC sequence (e.g. Zadoff-Chu sequence) during the symbols allocated to PRACH.
[00133] In Example 46, the subject matter of Example 46 optionally includes wherein the control circuitry is further configured to: process a second PRACH preamble received on a second channel to synchronize the first unlicensed channel and the second channel.
[00134] Further, in addition to the specific combinations of examples described above, any of the examples detailing further implementations of an element of an apparatus or medium may be applied to any other corresponding apparatus or medium, or may be implemented in conjunction with another apparatus or medium. Tims, each example above may be combined with each other example in various ways both as implementations in a system and as combinations of elements to generate an embodiment from the combination of each example or group of examples. For example, any embodiment above describing a transmitting device will have an embodiment that receives the transmission, even if such an embodiment is not specifically detailed. Similarly, methods, apparatus examples, and computer readable medium examples may each have a corresponding example of the other type even if such examples for every embodiment are not specifically detailed.
EXAMPLE SYSTEMS AND DEVICES
[00135] FIG. 25 illustrates aspects of a computing machine according to some example embodiments. Embodiments described herein may be implemented into a system 2500 using any suitably configured hardware and/or software. FIG. 25 illustrates, for some embodiments, an example system 2500 comprising radio frequency (RF) circuitry 2535, baseband circuitry 2530, application circuitry 2525, memory/storage 2540, a display 2505, a camera 2520, a sensor 2515, and an input/output (I/O) interface 251 , coupled with each other at least as shown.
[00136] The application circuitry 2525 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general -purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with the memoi /storage 2540 and configured to execute instructions stored in tlie memory /storage 2540 to enable various applications and/or operating systems running on the system 2500,
[00137] The baseband circuitry 2530 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. Tlie processor(s) may include a baseband processor. The baseband circuitry 2530 may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 2535. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, and the like. In some embodiments, the baseband circuitry 2530 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 2530 may support communication with an evolved universal terrestrial radio access network (EUTRAN), other wireless metropolitan area networks (WMANs), a wireless local area network (WLAN), or a wireless personal area network
(WPAN). Embodiments in which the baseband circuitry 2530 is configured to support radio communication s of more than one wireless protocol may be referred to as multi-mode baseband circuitry.
[00138] In various embodiments, the baseband circuitry 2530 may include circuitry to operate with signals that are not strictly considered as being in a baseband frequency. For example, in some embodiments, the baseband circuitry 2530 may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.
[00139] The RF circuitry 2535 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 2535 may include switches, filters, amplifiers, and the like to facilitate tlie communication with tlie wireless network.
[00140] In various embodiments, the RF circuitry 2535 may include circuitry to operate with signals that are not strictly considered as being in a radio frequency. For example, in some embodiments, the RF circuitry 2535 may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.
34 [00141] In various embodiments, the transmitter circuitry or receiver circuitry discussed above with respect to the UE 271 or the eNB 150 may be embodied in whole or in part in one or more of the RP circuitry 2535, the baseband circuitry 2530, and/or the application circuitr ' 2525.
[00142] In some embodiments, some or all of the constituent components of a baseband processor may be used to implement aspects of any embodiment described herein. Such embodiments may be implemented by the baseband circuitry 2530, the application circuitry 2525, and/or the memor /storage 2540 implemented together on a system on a chip (SOC).
[00143] The memory/storage 2540 may be used to load and store data and/or instructions, for example, for the system 2500. The memory/storage 2540, in one embodiment, may include any combination of suitable volatile memory (e.g., dynamic random access memory (DRAM)) and/or non-volatile memory (e.g., flash memory).
[00144] In various embodiments, the I/O interface 2510 may include one or more user interfaces designed to enable user interaction with the system 2500 and/or peripheral component interfaces designed to enable peripheral component interaction with the system 2500. User interfaces may include, but are not limited to, a physical keyboard or keypad, a touchpad, a speaker, a microphone, and so forth. Peripheral component interfaces may include, but are not limited to, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, and a power supply interface.
[00145] In various embodiments, the sensor 2515 may include one or more sensing devices to determine environmental conditions and/or location information related to the system 2500. In some embodiments, the sensors 25 15 may include, but are not limited to, a gyro sensor, an acceierometer, a proximity- sensor, an ambient light sensor, and a positioning unit. The positioning unit may also be part of, or interact with, the baseband circuitry 2530 and/or RF circuitry 2535 to communicate with components of a positioning network (e.g., a global positioning system (GPS) satellite). In various embodiments, the display 2505 may include a display (e.g., a liquid crystal display, a touch screen display, etc.).
[00146] In various embodiments, the system 2500 may be a mobile computing device such as, but not limited to, a laptop computing device, a tablet computing device, a netbook, an ultrabook, a smartphone, and the like. In various embodiments, the system 2500 may have more or fewer components, and/or different architectures,
[00147] FIG. 26 shows an example UE, illustrated as a UE 2600. The UE 2600 may be an implementation of the UE 271, or any device described herein. The UE 2600 can include one or more antennas 2608 configured to communicate with a transmission station, such as a base station (BS), an eNB, or another type of wireless wide area network (WWAN) access point. The UE 2600 can be configured to communicate using at least one wireless communication standard including 3 GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi . The UE 2600 can communicate using separate antennas for each wireless communication standard or shared antennas for multiple wireless communication standards. The UE 2600 can communicate in a WEAN, a WPAN, and/or a WWAN,
[00148] FIG. 26 also shows a microphone 2620 and one or more speakers 2612 that can be used for audio input and output to and from the UE 2600. A display screen 2604 can be a liquid crystal display (LCD) screen, or another type of display screen such as an organic light emitting diode (OLED) display. The display screen 2604 can be configured as a touch screen. The touch screen can use capacitive, resistive, or another type of touch screen technology. An application processor 2614 and a graphics processor 2618 can be coupled to an internal memory- 2616 to provide processing and display capabilities. A nonvolatile memory port 2610 can also be used to provide data I/O options to a user. The non-volatile memory port 2610 can also be used to expand the memory capabilities of the UE 2600. A keyboard 2606 can be integrated with the UE
2600 or wirelessly connected to the UE 2600 to provide additional user input. A virtual keyboard can also be provided using the touch screen. A camera 2622 located on the front (display screen) side or the rear side of the UE 2600 can also be integrated into a housing 2602 of the UE 2600.
[00149] FIG. 27 is a block diagram illustrating an example computer system machine 2700 upon which any one or more of the methodologies herein discussed can be run, and which may be used to implement the eNB 150, the UE
271, or any other device described herein. In various alternative embodiments,
36 the machine operates as a standalone device or can be connected (e.g., networked) to other machines. In a networked deployment, the machine can operate in the capacity of either a server or a client machine in server-client network environments, or it can act as a peer machine in peer-to-peer (or distributed) network environments. The machine can be a personal computer (PC) that may or may not be portable (e.g., a notebook or a netbook), a tablet, a set-top box (STB), a gaming console, a Personal Digital Assistant (PDA), a mobile telephone or smartphone, a web appliance, a network router, switch, or bridge, or any machine capable of executing instructions (sequential or othenvise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein.
[00150] The example computer system machine 2700 includes a processor
2702 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), or both), a main memory 2704, and a static memory 2706, which communicate with each other via an interconnect 2708 (e.g., a link, a bus, etc.). The computer system machine 2700 can further include a video display device 2710, an alphanumeric input device 2712 (e.g., a keyboard), and a user interface (Ul) navigation device 2714 (e.g., a mouse). In one embodiment, the video display unit 2710, alphanumeric input device 2712, and UI navigation device 2714 are a touch screen display. The computer system machine 2700 can additionally include a mass storage device 2716 (e.g., a drive unit), a signal generation device 2718 (e.g., a speaker), an output controller 2732, a power management controller 2734, a network interface device 2720 (which can include or operably
communicate with one or more antennas 2730, transceivers, or other wireless communications hardware), and one or more sensors 2728, such as a GPS sensor, compass, location sensor, accelerometer, or other sensor.
[00151] The mass storage device 2716 includes a machine-readable medium 2722 on which is stored one or more sets of data structures and instructions 2724 (e.g., software) embodying or utilized by any one or more of the methodologies or functions described herein. The instructions 2724 can also reside, completely or ai least partially, within the main memory 2704, static memory 2706, and/or processor 2702 during execution thereof by the computer system machine 2700, with the main memory 2704, the static memory 2706, and the processor 2702 also constituting machine-readable media,
[00152] While the machine-readable medium 2722 is illustrated in an example embodiment to be a single medium, the term '"machine-readable medium" can include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more instructions 2724. The term "machine-readable medium" shall also be taken to include any tangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present disclosure, or thai is capable of storing, encoding, or carrying data structures utilized by or associated with such instructions.
[00153] The instructions 2724 can further be transmitted or received over a communications network 2726 using a transmission medium via the network interface device 2720 utilizing any one of a number of well-known transfer protocols (e.g., hypertext transfer protocol (HTTP)), The term "transmission medium" shall be taken to include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine, and includes digital or analog communications signals or other intangible media to facilitate communication of such software.
[00154] Various techniques, or certain aspects or portions thereof, may take the form of program code (i.e., instractions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, computer readable storage media, or any other machine -readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the various techniques. In the case of program code execution on programmable computers, the computing device may include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. The volatile and non-volatile memory and/or storage elements may be a RAM, Erasable Programmable Read-Only Memory (EPROM), flash drive, optical drive, magnetic hard drive, or other medium for storing electronic data. The base station and mobile station or eNB and UE may also include a transceiver module, a counter module, a processing module, and/or a clock module or timer module. One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.
[00155] Various embodiments may use 3GPP LTE/LTE-A, Institute of Electrical and Electronic Engineers (IEEE) 2702.11, and Bluetooth
communication standards. Various alternative embodiments may use a variety of other WW AN, WLAN, and WPAN protocols and standards in connection with the techniques described herein. Tliese standards include, but are not limited to, other standards from 3 GPP (e.g., HSPA+, UMTS), IEEE 2702.16 (e.g., 2702.16p), or Bluetooth (e.g., Bluetooth 26.0, or like standards defined by the Bluetooth Special Interest Group) standards families. Other applicable network configurations can be included within the scope of the presently described communication networks. It will be understood that communications on such communication networks can be facilitated using any number of PANs, LANs, and WANs, using any combination of wired or wireless transmission mediums.
[00156] FIG. 28 illustrates, for one embodiment, example components of a UE 2800 in accordance with some embodiments. In some embodiments, the UE 2800 may include application circuitry 2802, baseband circuitry 2804, Radio Frequency (RF) circuitry 2806, front-end module (FEM) circuitry 2808, and one or more antennas 2810, coupled together at least as shown. In some
embodiments, the UE 2800 may include additional elements such as, for example, memory/storage, a display, a camera, a sensor, and/or an input/output (I/O) interface.
[00157] The application circuitry 2802 may include one or more application processors. For example, the application circuitry 2802 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with and/or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the UE 2800.
[00158] The baseband circuits"}' 2804 may include circuity such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 2804 may include one or more baseband processors and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 2806 and to generate baseband signals for a transmit signal path of the RF circuitry 2806. The baseband circuity 2804 may interface with the application circuitry 2802 for generation and processing of the baseband signals and for controlling operations of the RF circuity 2806. For example, in some embodiments, the baseband circuitry 2804 may include a second generation (2G) baseband processor 2804a, third generation (3G) baseband processor 2804b, fourth generation (4G) baseband processor 2804c, and/or other baseband processor(s) 2804d for other existing generations, generations in development, or generations to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 2804 (e.g., one or more of the baseband processors
2804a-d) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 2806. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 2804 may include Fast-Fourier Transform (FFT), preceding, and/or constellation
mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 2804 may include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.
40 [00159] In some embodiments, the baseband circuitry 2804 may include elements of a protocol stack such as, for example, elements of an EUTRAN protocol including., for example, physical (PHY), media access control. (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or RRC elements. A central processing unit (CPU) 2804e of the baseband circuitry 2804 may be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP, and/or RRC layers. In some embodiments, the baseband circuitry 2804 may include one or more audio digital signal processor(s) (DSP) 2804f. The audio DSP(s) 2804f may include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry 2804 may be suitably combined in a single chip or a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or ail of the constituent components of the baseband circuitry 2.804 and the application circuitry 2802 may be implemented together, such as, for example, on a system on a chip (SOC).
[00160] In some embodiments, the baseband circuitry 2804 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 2804 may support communication with an EUTRAN and/or a WMAN, a WLAN, or a WPAN. Embodiments in which the baseband circuitry 2804 is configured to support radio
communications of more than one wireless protocol may be referred to as multi- mode baseband circuitry.
[00161] The RF circuitry 2806 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 2806 may include switches, filters, amplifiers, et cetera to facilitate the communication with the wireless network. The RF circuitry 2.806 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 2808 and provide baseband signals to the baseband circuitry 2804. The RF circuitry 2806 may also include a transmit signal path which may include circuitry- to up-convert baseband signals provided by the baseband circuitry 2804 and provide RF output signals to the FEM circuitry 2808 for transmission.
41 [00162] In some embodiments, the RF circuitry 2806 may include a receive signal path and a transmit signal path. The recei ve signal path of the RF circuitry 2806 may include mixer circuitry 2806a, amplifier circuitry 2806b, and filter Circuitry 2806c. The transmit signal path of the RF circuitry 2806 may include the filter circuitry 2806c and the mixer circuitry 2806a. The RF circuitry 2806 may also include synthesizer circuitry 2806d for synthesizing a frequency for use by the mixer circuitry 2806a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 2806a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 2808 based on the synthesized frequency provided by the synthesizer circuitry 2806d. The amplifier circuitry 2806b may be configured to amplify the down- converted signals, and the filter circuitry 2806c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down- converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 2804 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals. In some embodiments, the mixer circuitry 2806a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.
[00163] In some embodiments, the mixer circuitry 2806a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 2806d to generate RF output signals for the FEM circuitry 2808. The baseband signals may be provided by the baseband circuitry 2804 and may be filtered by the filter circuitry 2806c. The filter circuitry 2806c may include an LPF, although the scope of the embodiments is not limited in this respect.
[00164] In some embodiments, the mixer circuitry 2806a of the recei ve signal path and the mixer circuitry 2806a of the transmit signal path may include two or more mixers and may be arranged for quadrature down conversion and/or up conversion respectively. In some embodiments, the mixer circuitry 2806a of the receive signal path and the mixer circuitry 2806a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g.,
Hartley image rejection). In some embodiments, the mixer circuitry 2806a of the
42 receive signal path and the mixer circuitry 2806a of the transmit signal path may be arranged for direct down conversion and/or direct up conversion, respectively. In some embodiments, the mixer circuitry 2806a of the receive signal path and the mixer circuitry 2806a of the transmit signal path may be configured for super-heterodyne operation.
[00165] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 2806 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 2804 may include a digital baseband interface to communicate with the RF circuitry 2806.
[00166] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.
[00167] In some embodiments, the synthesizer circuitry 2806d may be a fractional-N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect, as other types of frequency synthesizers may be suitable. For example, the synthesizer circuitry 2806d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.
[00168] The synthesizer circuitry 2806d may be configured to synthesize an output frequency for use by the mixer circuitry 2806a of the RF circuitry 2806 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 2806d may be a fractional N/N+l synthesizer.
[00169] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO). In other embodiments, other means may be used to provide the frequency input. Divider control input may be provided by either the baseband circuitry 2804 or the application circuitry 2802 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the application circuitry 2802.
43 [00170] The synthesizer circuitry 2806d of the F circuitry 2806 may include a divider, a delay-locked loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A), in some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable delay elements, a phase detector, a charge pump, and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.
[00171] In some embodiments, the synthesizer circuitry 2806d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLQ). In some embodiments, the RF circuitry 2806 may include an IQ/polar converter.
[00172] The FEM circuitry 2808 may include a receive signal path which may include circuitry configured to operate on RF signals received from the one or more antennas 2810, amplify the received signals, and provide the amplified versions of the received signals to the RF circuitry 2806 for further processing. The FEM circuitry 2808 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 2806 for transmission by one or more of the one or more antennas 2810.
[00173] In some embodiments, the FEM circuitry 2808 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry 2808 may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry 2808 may include a low-noise amplifier
44 (LNA) to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 2806). The transmit signal path of the FEM circuitry 2808 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by the RF circuitry- 2806), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 2810).
[00174] In some embodiments, the UE 2800 comprises a plurality of power saving mechanisms. If the UE 2800 is in an RRC Connected state, where it is still connected to the eNB as it expects to receive traffic shortly , then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the UE 2800 may power down for brief intervals of time and thus save power.
[00175] If there is no data traffic activity for an extended period of time, then the UE 2800 may transition to an RRCJEdie state, where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc. The UE 2800 goes into a very low-power state and performs paging, wherein it periodically wakes up to listen to the network and then powers down again. The UE 2800 cannot receive data in this state, and in order to receive data, it transitions back to the RRC Connected state.
[00176] An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to die network and may power down completely. Any data sent during this time incurs a large delay, and it is assumed that the delay is acceptable.
[00177] The embodiments described above can be implemented in one or a combination of hardware, firmware, and software. Various methods or techniques, or certain aspects or portions thereof, can take the form of program code (i.e., instractions) embodied in tangible media, such as flash memory, hard drives, portable storage devices, read-only memor ' (ROM), RAM,
semiconductor memory devices (e.g., EPROM, Electrically Erasable
Programmable Read-Only Memory (EEPROM)), magnetic disk storage media, optical storage media, and any other machine-readable storage medium or storage device wherein, when the program code is loaded into and executed by a
45 machine, such as a computer or networking device, the machine becomes an apparatus for practicing the various techniques.
[00178] It should be understood that the functional units or capabilities described in this specification may have been referred to or labeled as components or modules in order to more particularly emphasize their implementation independence. For example, a component or module can be implemented as a hardware circuit comprising custom very-large-scale
integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A component or module can also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. Components or modules can also be implemented in software for execution by various types of processors. An identified component or module of executable code can, for instance, comprise one or more physical or logical blocks of computer instructions, which can, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified component or module are not necessarily physically located together, but can comprise disparate instructions stored in different locations which, when joined logically together, comprise the component or module and achieve the stated purpose for the component or module.
[00179] indeed, a component or module of executable code can be a single instruction, or many instructions, and can even be distributed over several different code segments, among different programs, and across several memory devices. Similarly , operational data can be identified and illustrated herein within components or modules, and can be embodied in any suitable fonn and organized within any suitable type of data structure. Hie operational data can be collected as a single data set, or can be distributed over different locations including over different storage devices, and can exist, at least partially, merely as electronic signals on a system or network. The components or modules can be passive or active, including agents operable to perform desired functions.
46

Claims

CLAIMS What is claimed is:
1. A computer readable medium comprising instructions that, when executed by one or more processors, configure a user equipment (UE) for communications with an evolved node B (eNB), the instructions to configure the UE to:
receive, from the eNB, a set of system information associated with the eNB;
generate, using baseband circuitry of the UE, a physical random access channel (PRACH) preamble structured to meet one or more occupancy criteria for a first unlicensed channel; and
transmit, using radio frequency (RF) circuitry of the UE, the PRACH preamble on the first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel.
2. The computer readable medium of claim 1 wherein the instructions configure the PRACH preamble for transmission by the UE on the first unlicensed channel immediately following receipt by the UE of a downlink subframe from the eNB .
3. The computer readable medium of claim 1 wherein the instructions configure the PRACH preamble for transmission on the first unlicensed channel by the UE as part of an initial portion of an uplink subframe.
4. The computer readable medium of claim 1 wherein the set of coexistence criteria comprises a set of listen before talk (LBT) timing criteria, and wherein the PRACH preamble is transmitted on the first unlicensed channel following a LBT procedure performed by the UE.
5. The computer readable medium of claim 4 wherein the instructions configure the PRACH preamble for transmission without additional frame- boundary alignment following the LBT procedure.
47
6. The computer readable medium of claims 1-5 wherein the one or more occupancy criteria comprise a bandwidth occupancy threshold.
7. The computer readable medium of claims 1-6 wherein the one or more occupancy criteria comprises a power spectral density threshold.
8. The computer readable medium of claims 1-7 wherein the one or more occupancy criteria comprises an upper time limit threshold for use of the first unlicensed channel associated with transmission of the PRACH preamble.
9. The computer readable medium of claims 1-8 wherein the PRACH preamble comprises a 1.08 megahertz (MHz) preamble signal and a reservation signal configured such that a total bandwidth of the 1.08 MHz signal and the reservation signal meet the one or more occupancy criteria for the first unlicensed channel.
10. The computer readable medium of claims 1-8 wherein the PRACH preamble comprises a plurality of 1.08 MHz preamble signals repeated within the PRACH preamble to meet the one or more occupancy criteria for the first unlicensed channel.
1 1. The computer readable medium of claims 9-10 wherein the instructions configure each 1.08MHz preamble signal for phase modulated prior to transmission.
12. The computer readable medium of claims 9-11 wherein the instructions configure each 1.08 MHz preamble signal to be:
generated as a time domain signal;
transformed using discrete Fourier Transform (DFT) precoding to generate a preceded preamble sequence; and
divided into a plurality of precoded preamble sequence elements;
48 wherein the plurality of precoded preamble sequence elements are mapped to a portion of a bandwidth of the first unlicensed channel to reduce peak to average power ration divided by cubic metric (P APR/CM) values.
13. The computer readable medium of claims 1-1 1 wherein the PRACH preamble comprises a constant amplitude zero autocorrelation (CAZAC) sequence.
14. The computer readable medium of claim 13 wherein instructions configure the CAZA C sequence to be transmitted as part of the PRACH preamble with the CAZAC sequence divided into a plurality of precoded preamble sequence elements; and
wherein the plurality of precoded preamble sequence elements of the CAZAC sequence is mapped to a portion of a bandwidth of the first unlicensed channel .
15. The computer readable medium of claims 12 and 14 wherein the plurality of precoded preamble sequence elements are mapped as fully- distributed at a frequency domain subcarrier level to maintain a single carrier property.
16. The computer readable medium of claim 15 where each element of the plurality of precoded preamble sequence elements are distributed at equal distances across the bandwidth of the first unlicensed channel.
17. The computer readable medium of claims 1-8 wherein the PRACH preamble comprises a plurality of repetitions of a PRACH sequence, wherein each PRACH sequence is interleaved in the frequency domain prior to transmission on the first unlicensed channel.
18. The computer readable medium of claims 1-8 wherein the PRACH preamble comprises a PRACH sequence with a generated sequence length equal
49 to tlie largest prime number smaller than a number of symbols corresponding to a bandwidth of the first unlicensed channel.
19. The computer readable medium of claims 1-8 or 13-18 wherein the PRACH preamble comprises a PRACH format with a sub-carrier spacing of 15 kilohertz (kHz); and
wherein the PRACH preamble further comprises a PRACH sequence comprising a Zadoff-Chu sequence of length 293.
20. The computer readable medium of claim 19 wherein the instructions configure the PRACH preamble to be transmitted in one symbol on the first unlicensed channel using 25 physical resource blocks, the first unlicensed channel having a 5 MHz bandwidth.
21. The computer readable medium of claims 1-20 wherein the instructions configure the PRACH preamble to be transmitted with a cyclic prefix and a guard time using one symbol of the first unlicensed channel.
22. An apparatus of a user equipment (UE) for license assisted access (LAA) or long term evolution unlicensed (LTE-U) communications with an evolved node B (eNB), the apparatus comprising:
radio frequency circuitry configured to:
receive, from the eNB, a set of system information associated with the eNB; and
transmit, to the eNB, a physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel; and
baseband circuitry configured to generate the PRACH preamble to meet one or more occupancy criteria for a first unlicensed channel .
23. The apparatus of claim 22 further comprising:
one or more antennas; and front end module (FEM) circuitry coupled to the one or more antennas and the baseband circuitry, the FEM circuitry configured to filter received and transmitted radio frequency signals as part of communications using the one or more antennas,
24. An apparatus of an evolved node B (eNB) for license assisted access (LAA) or Song term evolution unlicensed (LTE-U) communications with user equipment (UE), the apparatus comprising:
radio frequency circuitry configured to:
transmit, to a first UE, a set of system, information associated with the eNB;
receive, from the first UE, a first physical random access channel (PRACH) preamble on a first unlicensed channel according to a set of coexistence criteria for the first unlicensed channel; and
receive, from the first UE, a second PRACH preamble on a second channel; and
control circuitry configured to process the first PRACH preamble and the second PRACH preamble to synchronize the first unlicensed channel and the second channel.
25. The eNB of claim 24 wherein the set of coexistence criteria comprises a set of listen before talk (LBT) timing criteria, and wherein the PRACH preamble is received on the first unlicensed channel following a LBT procedure performed by the UE; and
wherein the one or more occupancy criteria comprise a bandwidth occupancy threshold, a power spectral density threshold, and an upper time limit threshold for use of the first unlicensed channel associated with transmission of the PRACH preamble.
51
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