WO2014124131A2 - Enabling secondary user coexistence on dynamic shared spectrum with primary user - Google Patents

Abstract

Systems, methods and instrumentalities are provided to implement a mechanism of a secondary user (SU) system coexisting with a primary user (PU) system. The SU system may gather information associated with the operation cycle(s) of the PU system of a shared channel. An operation cycle of the PU system may include a quiet phase and a pulse phase. For example the SU system may gather information associated with the operation cycle of the PU system. Such information may include pulse phase duration, pulse duty cycle, and/or allowed hopping sequences, etc. Based on information associated with the operation cycle of the PU system, the SU system may transmit or schedule transmission on the shared channel during the quiet phase of the PU operation cycle. The SU system may perform interference mitigation based on the timing of the pulse phase.

Description

ENABLING SECONDARY USER COEXISTENCE ON DYNAMIC SHARED

SPECTRUM WITH PRIMARY USER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional patent application no.

61/761,636, filed February 6, 2013, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] With regulations put in place, a number of bands, e.g., the 3550-3650 MHz band, currently being used by the United States government, its agencies, and/or the United States military navy radar systems may be made available to telecommunication operators. For example, small cell operators may utilize these bands. As such spectrums become available for sharing, there may be an opportunity to develop wireless technologies that may coexist with the available bands. Current wireless coexistence technologies may be inadequate, for example, for enabling secondary users to coexist with primary users on government held spectrum.

SUMMARY OF THE INVENTION

[0003] Systems, methods and instrumentalities are provided to implement a mechanism of a secondary user (SU) system coexisting with a primary user (PU) system. The SU system may gather information associated with the operation cycle(s) of the PU system of a shared channel. An operation cycle of the PU system may include a quiet phase and a pulse phase. For example, the SU system may gather information associated with the operation cycle of the PU system. Such information may include pulse phase duration, pulse duty cycle, and/or allowed hopping sequences, etc.

Based on information associated with the operation cycle of the PU system, the SU system may transmit or schedule transmission on the shared channel during the quiet phase of the PU operation cycle. The SU system may determine a SU and PU impact zone status, and based on the impact zone status, the SU system may apply an interference mitigation solution, including for example, a proactive solution or a reactive solution. The SU system may perform interference mitigation based on the timing of the pulse phase. For example, the SU system may schedule one or more blank frames during the pulse phase. For example, the SU system may schedule one or more almost blank subframes during the pulse phase. An almost blank subframe may include transmissions in specific reference symbols. For example, an almost blank subframe may include transmissions only in specific reference symbols. For example, the SU system may schedule one or more multicast broadcasts on a single frequency network (MBSFN) subframes during the pulse phase.

[0004] There may be multiple pulses in a pulse phase separated by inter-pulse periods.

The SU system may determine the timing and the duration of an inter-pulse period in the pulse phase, and schedule transmission on the shared channel during the inter-pulse period. The SU system may bias link adaptation based on the timing of the pulse phase such that rate suppression (e.g., caused by PU interference) may be lifted immediately after the PU pulse phase ends. The SU system may determine how long it may take to transmit a packet (e.g., a time period required for transmitting the packet), and schedule packet transmission time such that the packet can be transmitted before the pulse phase begins.

[0005] The SU system may gather information associated with the operation cycle of the

PU system from a spectrum access system or via a sensing mechanism. For example, the spectrum access system may receive declassified information associated with federal primary user system operations and provide spectrum availability information to the SU systems. For example, the spectrum access system may receive a request for accessing shared channel(s) at a geographic location, and may identify available shared channel(s) at the geographic location and the associated primary user(s) based on the declassified information. The spectrum access system may determine the information associated with the operation cycle(s) of the primary user system(s) based on the declassified information, and may send the available shared channels) arid the information associated with operation cycle(s) of the respective primary user system(s) to the requesting SU system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] A more detailed understanding may he had from the following description, given by way of example in conjunction with the accompanying drawings.

[0007] FIG. 1A is a system diagram of an example communications system in which one or more disclosed embodiments may be implemented.

[0008] FIG. IB is a system diagram of an example wireless transmit/receive unit

(WTRXJ) that may be used within the communications system illustrated in FIG. 1A.

[0009] FIG, 1 C is a system diagram of an example radio access network and an example core network that may be used within the communications system illustrated in FIG. 1 A.

[0010] FIG. ID is a system diagram of another example radio access network and another example core network that may be used within the communications system illustrated in FIG. 1A.

[001 1 ] FIG. IE is a system diagram of another example radio access network and another example core network that may be used within the communications system illustrated in FIG. 1A.

[0012] FIG, IF is a system diagram of an embodiment of the communications system

100.

[0013] FIG. 2 illustrates an example of a Federal spectrum access system (SAS).

[0014] FIG. 3 illustrates an example radar signal.

[0015] FIG, 4 illustrates examples of almost blank subframe (ABS) and Multicast

Broadcasts on a Single Frequency Network (MBSFN).

[0016] FIG. 5 illustrates an example solution space for a secondar user (SU) operating along a coastline.

[0017] FIG, 6 illustrates example pulse phases and quiet phases of radar pulse cycles,

[0018] FIG, 7 illustrates example macro or rotation cycles and micro or pulse cycles representing opportunities for SU operation.

[0019] FIG, 8 illustrates an example of query-enabled interference mitigation procedure.

[0020] FIG. 9 illustrates an example flow chart of SU operation, [0021] FIG. 10 illustrates an example SU operation where the SU may stop transmission during pulse phases.

[0022] FIG. 1 1 illustrates an example SU operation where a SU may hop frequencies to avoid using a shared channel during pulse phases of the PU system.

[0023] FIG. 12 illustrates various example military regions.

[0024] FIG. 13 illustrates example subdivisions of primary user exclusion zones.

[0025] FIG. 14 illustrates an example SU operation using on sensing-based interference mitigation.

[0026] FIG. 15 illustrates an example use of blank frame(s).

[0027] FIG. 16 illustrates an example of long term evolution (LTE) aggregating a radar channel with another channel.

[0028] FIGs. 17A and I 7B illustrate example effects of link adaptation bias.

[0029] FIG. 18 illustrates an example clear to send (CTS)-to-self mechanism.

[0030] FIG. 19 illustrates an example radar back off period mechanism.

[0031] FIG. 20 illustrates an example solution when staggered radar signals are detected.

[0032] FIG. 21 illustrates an example of an LTE system transmitting with added limitation of subframe timing.

[0033] FIG. 22 illustrates an example of an eNode B (eNB) scheduler that may avoid scheduling transmissions during radar pulses.

[0034] FIG. 23 illustrates an example of enhanced physical data control channel

(ePDCCH) in presence of a radar pulse.

DETAILED DESCRIPTION

[0035] A detailed description of illustrative embodiments will now be described with reference to the various figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

[0036] FIG, IA is a diagram of an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single- carrier FDMA (SC-FDMA), and the like.

[0037] As shown in FIG. 1 A, the communications system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, and/or 102d (which generally or collectively may be referred to as WTRU 102), a radio access network (RAN) 103/104/105, a core network 106/107/109, a public switched telephone network (PSTN) 108, the Internet 1 10, and other networks 1 12, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102 a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d may be configured to transmit and/or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, consumer electronics, and the like.

[0038] The communications systems 100 may also include a base station 1 14a and a base station 1 14b. Each of the base stations 1 14a, 1 14b may be any type of device configured to wireiessiy interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the core network 106/107/109, the Internet 1 10, and/or the networks 1 12. By way of example, the base stations 1 14a, 1 14b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a site controller, an access point (AP), a wireless router, and the like. While the base stations 1 14a, 1 14b are each depicted as a single element, it will be appreciated that the base stations 1 14a, 1 14b may include any number of interconnected base stations and/or network elements.

[0039] The base station 1 14a may be part of the RAN 103/104/105, which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 1 14a and/or the base station 1 14b may be configured to transmit and/or receive wireless signals within a particular geographic region, which may be referred to as a cell (not shown). The cell may further be divided into cell sectors. For example, the cell associated with the base station 1 14a may be divided into three sectors. Thus, in one embodiment, the base station 1 14a may include three transceivers, i.e., one for each sector of the cell. In another embodiment, the base station 1 14a may employ multiple-input multiple output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell

[0040] The base stations 1 14a, 1 14b may communicate with one or more of the WTRU s

102a, 102b, 102c, 102d over an air interface 1 15/1 16/1 17, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 1 15/116/1 17 may be established using any suitable radio access technology (RAT).

[0041] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 1 14a in the RAN 103/104/105 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 1 15/1 16/1 17 using wideband CDMA (WCDMA).

WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

[0042] In another embodiment, the base station 1 14a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 1 15/1 16/117 using Long Term Evolution (LTE) and/or LTE Advanced (LTE-A).

[0043] In other embodiments, the base station 1 14a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 IX, CDMA2000 EV-DO, Interim Standard 2000 (IS-2.000), Interim Standard 95 (lS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0044] The base station 1 14b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, and the like. In one embodiment, the base station 1 14b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.1 1 to establish a wireless local area network (WLAN). In another embodiment, the base station 1 14b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802. 5 to establish a wireless personal area network (WPAN). n yet another embodiment, the base station 1 14b and the WTRUs 102c, 102d may utilize a cellular- based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 1 14b may have a direct connection to the Internet 1 10. Thus, the base station 1 14b may not be required to access the Internet 1 10 via the core network 106/107/109.

[0045] The RAN 103/104/105 may be in communication with the core network

106/107/109, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. For example, the core network 106/107/109 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in FIG. 1 A, it will be appreciated that the RAN 103/104/105 and/or the core network 106/107/109 may be in direct or indirect communication with other RANs that employ the same RAT as the RA 103/104/105 or a different RAT. For example, in addition to being connected to the RAN 103/104/105, which may be utilizing an E-UTRA radio technology, the core network 106/107/109 may also be in communication with another RAN (not shown) employing a GSM radio technology.

[0046] The core network 106/107/109 may also serve as a gateway for the WTRUs 102a,

102b, 102c, 102d to access the PSTN 108, the Internet 1 10, and/or other networks 1 12. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 1 10 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and the internet protocol (IP) in the TCP/IP internet protocol suite. The networks 1 12 may include wired or wireless

communications networks owned and/or operated by other sendee providers. For example, the networks 1 12 may include another core network connected to one or more RANs, which may employ the same RAT as the RAN 103/104/105 or a different RAT.

[0047] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system

100 may include multi-mode capabilities, i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with the base station 1 14a, which may employ a cellular-based radio technology, and with the base station 1 14b, which may employ an IEEE 802 radio technology. [0048] FIG. IB is a system diagram of an example WTRU 102. As shown in FIG. IB, the WTRU 102 may include a processor 1 18, a transceiver 120, a transmit/receive element 122, a speaker/microphone 124, a keypad 126, a display/touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment. Also, embodiments contemplate that the base stations 1 14a and 1 14b, and/or the nodes that base stations 1 14a and 1 14b may represent, such as but not limited to transceiver station (BTS), a Node-B, a site controller, an access point (AP), a home node-B, an evolved home node-B (eNodeB), a home evolved node-B (FleNB), a home evolved node-B gateway, and proxy nodes, among others, may include some or all of the elements depicted in FIG. IB and described herein.

[0049] The processor 1 18 may be a general ur o e processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of

microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (1C), a state machine, and the like. The processor 1 18 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit/receive element 122. While FIG. IB depicts the processor 11 8 and the transceiver 120 as separate components, it will be appreciated that the processor 1 18 and the transceiver 120 may be integrated together in an electronic package or chip.

[0050] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 1 14a) over the air interface

1 15/1 16/1 17. For example, in one embodiment, the transmit/receive element 122 may be an antenna configured to transmit and/or receive RF signals. In another embodiment, the transmit/receive element 122 may be an emitter/ detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element 122 may be configured to transmit and receive both RF and light signals. It will be appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

[0051] In addition, although the transmit/receive element 122. is depicted in FIG. IB as a single element, the WTRU 102 may include any number of transmit/receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 1 15/1 16/1 17.

[0052] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, for example.

[0053] The processor 1 18 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 1 18 may also output user data to the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128. In addition, the processor 1 1 8 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and/or the removable memory 132. The non-removable memory 130 may include random- access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0054] The processor 11 8 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZii), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like,

[0055] The processor 11 8 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current locaiion of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 1 15/1 16/1 17 from a base station (e.g., base stations 1 14a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire locaiion information by way of any suitable location-determination method while remaining consistent with an embodiment. [0056] The processor 1 18 may further be coupled to other peripherals 138, which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth© module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like.

[0057] FIG. I C is a system diagram of the RAN 103 and the core network 106 according to an embodiment. As noted above, the RAN 103 may employ a UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 1 15. The RAN 103 may also be in communication with the core network 106. As shown in FIG. IC, ihe RAN 103 may include Node-Bs 140a, 140b, 140c, which may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 1 15. The Node-Bs 140a, 140b, 140c may each be associated with a particular cell (not shown) within the RAN 103. The RAN 103 may also include RNCs 142a, 142b. It will be appreciated that the RAN 103 may include any number of Node-Bs and RNCs while remaining consistent with an embodiment.

[0058] As shown in FIG. IC, the Node-Bs 140a, 140b may be in communication with the

RNC 142a. Additionally, the Node-B 140c may be in communication with the RNC 142b, The Node-Bs 140a, 140b, 140c may communicate with the respective RNCs 142a, 142b via an Tub interface. The RNCs 142a, 142b may be in communication with one another via an lur interface. Each of the RNCs 142a, I42b may be configured to control the respective Node-Bs 140a, 140b, 140c to which it is connected. In addition, each of the RNCs 142a, 142b may be configured to cany out or support other functionality, such as outer loop power control, load control, admission control, packet scheduling, handover control, macrodiversity, security functions, data encryption, and the like,

[0059] The core network 106 shown in FIG. IC may include a media gateway (MGW)

144, a mobile switching center (MSC) 146, a serving GPRS support node (SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each of the foregoing elements are depicted as part of the core network 106, it will be appreciated that any one of these elements may be o wned and/or operated by an entity other than the core network operator.

[0060] The RNC 142a in the RAN 103 may be connected to the MSC 146 in the core network 106 via an IuCS interface. The MSC 146 may be connected to ihe MGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102a, 102b, 102c with access to eireuit- switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices,

[0061] The R C 142a in the RAN 103 may also be connected to the SGSN 148 in the core network 106 via an luPS interface. The SGSN 148 may be connected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 1 10, to facilitate communications between and the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0062] As noted above, the core network 106 may also be connected to the networks 1 12, which may include other wired or wireless networks that are owned and/or operated by other service providers.

[0063] FIG. ID is a system diagram of the RAN 104 and the core network 107 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 1 16, The RAN 104 may also be in communication with the core network 107.

[0064] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 1 16. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 102a.

[0065] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell

(not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and the like. As shown in FIG. ID, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0066] The core network 107 shown, in FIG. ID may include a mobility management gateway (MME) 162, a serving gateway 164, and a packet data network (PDN) gateway 166. While each of the foregoing elements are depicted as part of the core network 107, it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator.

[0067] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, 160c in the

RAN 104 via an S 1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer

activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 02c, and the like. The MME 162 may also provide a control plane fimction for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA.

[0068] The serv ing gateway 164 may be connected to each of the eNode-Bs 160a, 160b,

160c in the RAN 104 via the S I interface. The serving gateway 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 164 may also perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when downlink data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like,

[0069] The serving gateway 164 may also be connected to the PDN gateway 166, which may provide the WTRUs 102a, 102b, 102c with access to packet- switched networks, such as the Internet 1 10, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0070] The core network 107 may facilitate communications with other networks. For example, the core network 107 may provide the WTRUs 102a, 102b, 102c with access to circuit- switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land- line communications devices. For example, the core network 107 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the core network 107 and the PSTN 108. In addition, the core network 107 may provide the WTRUs 102a, 102b, 102c with access to the networks 1 12, which may include other wired or wireless networks that are owned and or operated by other service pro viders,

[0071] FIG. IE is a system diagram of the RAN 105 and the core network 109 according to an embodiment The RAN 105 may be an access service network (ASM) that employs IEEE 802.16 radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 1 17. As will be further discussed below, the communication links between the different functional entities of the WTRUs 102a, 102b, 102c, the RAN 105, and the core network 109 may be defined as reference points.

[0072] As shown in FIG, IE, the RAN 105 may include base stations 180a, 180b, 180c, and an A.SN gateway 182, though it will be appreciated that the RAN 105 may include any number of base stations and ASN gateways while remaining consistent with an embodiment. The base stations 180a, 180b, 180c may each be associated with a particular cell (not shown) in the RAN 105 and may each include one or more transceivers for communicating with the WTRU s 102a, 102b, 102c over the air interface 117. In one embodiment, the base stations 180a, 180b, 1 80c may implement MIMO technology. Thus, the base station 1 80a, for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 02a. The base stations 180a, 180b, 180c may also provide mobility management functions, such as handoff triggering, tunnel establishment, radio resource management, traffic classification, quality of service (QoS) policy enforcement, and the like. The ASN gateway 182 may serve as a traffic aggregation point and may be responsible for paging, caching of subscriber profiles, routing to the core network 109, and the like.

[0073] The air interface 1 17 between the WTRUs 102a, 102b, 102c and the RAN 105 may be defined as an Rl reference point that implements the IEEE 802.16 specification, in addition, each of the WTRUs 102 a, i02b, 102c may establish a logical interface (not shown) with the core network 109, The logical interface between the WTRUs 102a, 102b, 102c and the core network 109 may be defined as an R2 reference point, which may be used for

authentication, authorization, IP host configuration management, and/or mobility management.

[0074] The communication link between each of the base stations 180a, 180b, 180c may be defined as an R8 reference point that includes protocols for facilitating WTRU handovers and the transfer of data between base stations. The communication link between the base stations 180a, 180b, 180c and the ASN gateway 182 may be defined as an R6 reference point. The R6 reference point may include protocols for facilitating mobility management based on mobility events associated with each of the WTRUs 102a, 102b, 102c,

[0075] As shown in FIG. IE, the RAN 105 may be connected to the core network 109.

The communication link between the RAN 105 and the core network 109 may defined as an R3 reference point that includes protocols for facilitating data transfer and mobility management capabilities, for example. The core network 109 may include a mobile IP home agent (MIP-HA) 184, an authentication, authorization, accounting (AAA) server 186, and a gateway 188. While each of the foregoing elements are depicted as part of the core network 109, it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator.

[0076] The MIP-HA may be responsible for IP address management, and may enable the

WTRUs 102a, 102b, 102c to roam between different ASNs and/or different core networks. The MIP-HA 184 may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 1 10, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The AAA server 186 may be responsible for user authentication and for supporting user services. The gateway 188 may facilitate interworking with other networks. For example, the gateway 188 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. In addition, the gateway 188 may provide the WTRUs 102a, 102b, 102c with access to the networks 1 12, which may include other wired or wireless networks that are owned and/or operated by other service providers.

[0077] Although not shown in FIG. IE, it will be appreciated that the RAN 105 may be connected to other ASNs and the core network 109 may be connected to other core networks. The communication link between the RAN 105 the other ASNs may be defined as an R4 reference point, which may include protocols for coordinating the mobility of the WTRUs 102a, 102b, 102c between the RAN 105 and the other ASNs. The communication link between the core network 109 and the other core networks may be defined as an R5 reference, which may include protocols for facilitating interworking between home core networks and visited core networks.

[0078] FIG. IF is a system diagram of an embodiment of the communications system

100, A WLAN in infrastructure basic service set (IBSS) mode may have an access point (AP) 180 for the basic service set (BSS) and one or more stations (STAs) 190 associated with the AP as illustrated by example in FIG. IF. The AP 180 may have access or interface to a Distribution System (DS) or another type of wired/wireless network that may carr traffic in and out of the BSS. Traffic to STAs may originate from outside the BSS, may arrive through the AP and may be delivered to the STAs. The traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to the respective destinations. Traffic between STAs within the BSS may be sent through the AP where the source STA may sends traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be peer-to-peer traffic. Such peer-to-peer traffic may be sent directly between the source and destination STAs, e.g., with a direct link setup (DLS) using an IEEE 802.1 le DLS or an IEEE 802.1 Iz tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may have no APs, and the STAs 190 may communicate directly with each other. This mode of

communication may be an ad-hoc mode.

[0079] Using the IEEE 802.1 1 infrastructure mode of operation, the AP 180 may transmit a beacon on a fixed channel, usually the primary channel. This channel may be 20 MHz wide, and may be the operating channel of the BSS. This channel may also be used by the STAs to establish a connection with the AP 180. The channel access in an IEEE 802.11 system may be Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). In this mode of operation, the STAs 190, including the AP 180, may sense the primary channel. If the channel is detected to be busy, the STA 190 may back off. One STA. 1 0 may transmit at any given time in a given BSS.

[0080] In IEEE 802.1 1 n, High Throughput (HT) STAs may use a 40 MHz wide channel for communication. This may be achieved, for example, by combining (he primary 20 MHz channel, with an adjacent 2.0 MHz channel to form a 40 MHz wide contiguous channel.

[0081 ] In IEEE 802.1 1 ac, very high throughput (VHT) STAs may support, e.g., 20MHz,

40 MHz, 80 MHz, and/or 160 MHz wide channels. The 40 MHz, and 80 MHz, channels may be formed, e.g., by combining contiguous 20 MHz channels. A160 MHz channel may be formed, for example, by combining eight contiguous 20 MHz channels, or by combining two noncontiguous 80 MHz channels (e.g., referred to as an 80+80 configuration). For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser (hat may divide it into two streams. Inverse fast Fourier transform (IFFT), and time domain, processing may be done on each stream separately. The streams may be mapped on to the two channels, and the data may be transmitted. At the receiver, this mechanism may be reversed, and the combined data may be sent to the MAC.

[0082] IEEE 802.1 1 af and IEEE 802.1 1 ah may support sub 1 GHz modes of operation.

For these specifications the channel operating bandwidths may be reduced relative to those used in IEEE 802.1 In, and IEEE 802.1 lac. IEEE 802, 1 laf may support 5 MHz, 10 MHz and/or 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and IEEE 802.1 lah may support 1 MHz, 2 MHz, 4 MHz, 8 MHz, and/or 16 MHz bandwidths, e.g., using non-TVWS spectrum. IEEE 802.11 ah may support Meter Type Control (MTC) devices in a macro coverage area. MTC devices may have capabilities including, for example, support for limited bandwidths, and a requirement for a very long battery life.

[0083] In WLA.N systems that may support multiple channels, and channel widths, e.g.,

IEEE 802.1 In, IEEE 802.1 lac, IEEE 802.1 laf, and/or IEEE 802.1 lah, may include a channel which may be designated as the primary channel. The primary channel may have a bandwidth that may be equal to the largest common operating bandwidth supported by the STAs in the BSS. The bandwidth of the primary channel may be limited by the STA 190, of the STAs such as STAs 190A, 190B, 190C in operating in a BSS, which may support the smallest bandwidth operating mode. For example, in IEEE 802.1 1 ah, the primary channel may be 1 MHz wide, if there may be STAs 190 (e.g., MTC type devices) that may support a 1 MHz mode even if the AP 180, and other STAs 190 in the BSS, may support a 2 MHz, 4 MHz, 8 MHz, 16 MHz, or other channel bandwidth operating modes. The carrier sensing, and NA V settings, may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA 190 supporting a 1 MHz operating mode transmitting to the AP 180, the available frequency bands may be considered even though majority of it may stay idle and available.

[0084] In the United States, for example, the available frequency bands that may be used by IEEE 802.1 lah may be from 902 MHz io 928 MHz, In Korea, for example, it may be from 917.5 MHz to 923.5 MHz. In Japan, for example, it may be from 916.5 MHz to 92.7.5 MHz. The total bandwidth available for IEEE 802.1 lah may be 6 MHz to 26 MHz may depend on the country code.

[0085] FIG. 2 illustrates an example spectrum access system (SAS) such as federal spectrum access system. As shown, the SAS may include a database, such as a spectrum database that may store spectrum availability information. Spectrum availability information may include, but not limited to, sensing information, policy information, pricing information, restrictions and legacy requirements. The spectrum database may store information about what spectrum may be occupied by a primary (e.g. federal system) or secondary user for a given location and time; the parameters of the signal, such as power and bandwidth; constraints for specific locations, such as no transmission in blasting zones or along international boarders; and the price for accessing the spectrum. The SAS may include a Radio Access Coordination and Management and Optimization function that may provide frequency assignments and authorizations. The function may optimize overall spectrum efficiency over a given region, and may ensure that legacy Federal systems retain priority access to spectrum.

[0086] Using the SAS, the primary users of a spectrum may share their spectrum with general access users, e.g., Wi-Fi or femto cell users. The primary users may provide dynamic licenses, for example, a rent or a lease of the spectrum. The secondary users may send access requests to the S AS, and the SAS may allocate spectrum for the secondary users to use. When using the shared spectrum, the secondary users such as devices and their base station may communicate with the SAS periodically.

[0087] The bands that may become available in the USA may include the 3550-3650

MHz band. The 3550-3650 MHz band may be shared outside of specified exclusion zones, the size of which may vary depending on the power levels and antenna heights of the secondary and tertiary users. The SAS may have an interface that may be used to query data about available shared spectrum and operating parameters, and manage secondary spectrum lease agreements, etc.

[0088] Radar systems may operate with high po wered pulses on the order of megawatts.

A. typical system may feature a 9GdBm pulse with a large antenna gains of the order of 40dB for an E1RP of I30dBm. FIG, 3 illustrates an example radar signal. As shown, the signal is characterized by a high powered pulse period for a duration of pulse width 310 followed by a much longer quiet period before the next pulse period. The pulse width 310 and/or the pulse repetition period 320 may vary based on the desired range, resolution, accuracy, modulation type, or the like. Pulse period and pulse phase may be used interchangeably herein, and quiei period and quiet phase may be used interchangeably herein. The pulse width and the quiet period may vary from one pulse repetition period to another, as electronic antenna steering can modify the pulse width. The frequency used from one pulse repetition period to another can change for anti-jamming purpose. Randomness on the radar pulse duration or periodicity can be introduced for anti-jamming purpose. A pulse period may include a period where the PU operates on the shared channel, for example, pointing the radar at the SU system's location.

[0089] A radar signal may interfere with communicator^) on the channel it operates on, and/or the channels that are adjacent to the operating channel. Due to the high power of the radar signal, side lobe may cause interference as, for example, the interference in case on mobile services in the 2.6GHz mobile band by the 2.8GHz radar band.

[0090] Due to national security considerations, the details of military radars may be classified. The specifics of the classified radar signals may be unavailable. Many military types of radars may be designed to avoid detection. To avoid detection, the radar systems may change, for example, randomly or pseudo -randomly, their modulation type, pulse repetition period and/or pulse width, and/or employ frequency hopping, etc. However, some basic coexistence information may be made available, if a spectrum in frequency bands, e.g., the 3. l-3.7GHz frequency band, is made available for shared use, the government may choose to make additional information public via the SAS on a more dynamic basis.

[0091] Spectrum sharing may be allowed in the 5GHz Band. Dynamic frequency selection is performed. An unlicensed device, before transmitting, may perform sensing to determine ihai ihe Radar is below -64dBm. The 3.5GHz band may be lightly licensed allowing RATs such as long term evolution (LTE) to have guaranteed QoS. The development of 5 GHz Wi-Fi technologies may allow for solutions combining database queries and geo-location.

Advances in listen-before-talk technologies may shorten the inter- frame spacing to the order of tens of micro-seconds.

[0092] FIG. 4 illustrates example multicast broadcasts on a single frequency network

(MBSFN) and almost blank subframes (ABS). MBSFN and/or ABS may allow an eNB to avoid data transmission in a given subframe. The MBSFN may be combined with ABS subframes to further reduce transmissions in a given subframe. An eNB may send MBSFN subframes or ABS subframes during the time instances when radar transmissions are expected to occur for avoiding interference to/from the radar signal,

[0093] A New Carrier Type (NCT) may include non-backward compatible carriers including, e.g., extensions carriers. Such carriers may include the ability to have completely blank subframes. The NCT may use the enhanced Physical Downlink Control Channel

(ePDCCH) that may allow control space sent over the space being used for data avoiding OFDM symbols dedicated to the control space. A set of Physical Resource Blocks (PRBs) in this space may be set aside for ePDCCH transmission in each subframe and the remaining PRBs may be used for physical downlink shared channel (PDSCH). An eNB may operate NCT in a band or channel where radar transmissions are expected. Specific PRBs that occur at the frequency location of the radar signal can be blanked out in order to a void interference between the LTE control information and the radar signal.

[0094] Regulatory changes may present opportunities for small cell dynamic shared spectrum to use including up to 100MHz of federal spectrum in the 3.5GHz band being used by military applications, such as naval radar.

[0095] Radars may operate with very high powered pulses and large antenna gains that may reach peak powers as high as 130dBm, and may interfere with secondary systems or general access users by, for example, saturating the receiver's low-noise amplifier (LNA). The high power levels may result in interference on the adjacent bands and at large distances.

[0096] Primar '' user radar systems may employ a mechanical antenna system that may rotate a focused beam of RF energy to scan the horizon. Radar may employ an electronic antenna steering system where directivity can be electronically changed. The electronic antenna steering system may be coupled with a mechanical steering system. Systems of interest may rotate anywhere from 1- 100 rpm. Secondary licensed or general access systems may be allowed to operate on Primary User (PU) frequencies if they do not interfere with the radar PUs receivers. A. secondary system may operate if the system is sufficiently far away from the radar PU or if the system employs mechanisms to avoid interference such as not transmitting when radar's beam is pointing towards it.

[0097] When dynamic spectrum sharing (DSS) small cells operate on a radar spectrum, there may be issues with real time service. For example, the radar interference may be present for tens of milliseconds at a time, which may cause noticeable disruptions in real time applications such as voice over internet protocol (VOIP), creating an unacceptable user experience. The disruption may vary from one pulse period to another to introduce randomness to the radar signal. [0098] Methods, systems and instrumentalities are provided herein that may allow DSS small cell secondaiy users (SUs) to coexist with a radar system in shared spectrum bands, such as US military naval radars in the 3.5GHz bands. A SU may be a tier 2 or tier 3 user, or may be a licensed or an unlicensed user that may be affected by the PU system,

[0099] FIG. 5 illustrates an example of solution space for a secondary user (SU) along a coastline. An SU or an SU system may include a WTRU and/or a base station (e.g., eNB) as described herein. An SU system may include a communication system as described herein with respect to FIGs. 1 A, 1 C, ID, IE and IF. SU and SU system may be used interchangeably herein. PU and PU system may be used interchangeably herein.

[0100] The solution space may include a SU impacted region, where an SU may contact the SAS and be allowed to transmit. The SU impacted region may include PU potentially affected region 520 and SU potentially affected region 530. In the PU potentially affected region 520, the radar PU 510 may experience interference from the SU s, The radar PU may not experience interference from the SUs if the SU operate in the SU potentially affected region 530. In ihe SU potentially affected region 530, as well as the PU potentially affected region 520, the SUs may be affected by interference from the radar PU 510. Reactive solutions and proactive solutions may be used in the SU potentially affected region 530, and proactive solutions may be used in the PU potentially affected region 520. A DSS small cell may operate during the quiet phase of the radar's interference cycle, e.g., when the rotating radar points away (electronically or mechanically) from the DSS small cell. Such an arrangement may be referred to as the macro or rotation cycle solution (e.g., as illustrated by example in FIG. 7).

[0101] FIG. 6 illustrates example pulse phases and quiet phases of radar pulse cycles. As shown, pulse phases 610A, 610B and 610C may be separated by quiet phases 620A and 620B. Quiet phases such as quiet phases 620A and 620B may provide opportunities for SUs to use the spectrum band.

[0102] FIG. 7 illustrates example macro or rotation cycles and micro or pulse cycles representing opportunities for SU operation. As shown, from a macro cycle's perspective, a SU may experience interference from the PU during pulse phases 71 OA, 71GB and 710C. A DSS small cell may use the spectrum during quiet phases of a radar signal, such as quiet phases between pulse phases 71 OA, 710B and 7 IOC. During quiet phases, the SU may not experience interference from the PU. The DSS small cell may use the spectrum during the pulse phase when the Radar's beam is pointing towards it. Such an arrangement may be referred to as the micro or pulse cycle solution. As shown in FIG. 7, from a micro cycle's perspective, there may be opportunities for the SU to use the spectrum within a pulse phase. For example, within pulse phase 71 OA, there may be multiple pulses, such as pulses 730A, 73GB, 730C and 730D. The DSS small cell may use the spectrum during inter-pulse periods such as inter-pulse periods 720A, 72.0B and 720C. The micro or pulse cycle solutions may be used to avoid or reduce buffering data during pulse phase, allowing real time applications such as VOIP.

[0103] Methods, systems and instrumentalities are provided herein for a SU radio access network to acquire declassified information about radar PU operation parameters and to adapt to the interference conditions. This information may be acquired via a database query. The SU radio access network may query the SAS or a shared spectrum database, for example, via the internet, a backhaul link or the like. The PU may have an interface with the shared spectrum database such that it may post usage information about the Radar PU spectrum (e.g., operation cycle information) for the SU system to query. The operating information may be acquired through sensing mechanisms by the SU system. This information may be used by the SU devices to manage the impact of radar interference on the SU system.

[0104] FIG. 8 illustrates by example a query enabled interference mitigation procedure.

At 810, the SU may contact the SAS. At 820, it may be determined whether the SU is in a SU impacted zone. The determination may be made at the SAS, or it may be made at the SU based on information sent by the SAS. The SU may determine whether it is in a SU impacted zone by inquiring the SAS. For example, the SU may send its geographic location information to the SAS. The SAS may determine, based on the information stored therein, whether the SU in a SU impacted zone, and send the information to the SU. The SAS may send information associated with potential radar systems in and/or near the location of the SU to the SU. The SU may determine, based on the information from the SAS, whether the SU in a SU impacted zone, if the SU falls outside of the SU impacted zone, at 830, the SU may use the channel.

[0105] Tf it is determined that the SU is in a SU impacted zone, at 835, it may be determined whether the SU is in a PU impacted zone. The determination may be made at the SAS, or it may be made at the SU based on information sent by the SAS. For example, the SU may send its geographic location information to the SAS. The SAS may determine, based on the information stored therein, whether the SU in a PU impacted zone, and send the information to the SU. The SAS may send information associated with potential radar systems in and/or near the location of the SU to the SU. The SAS may determine, based on the information stored therein, whether the SU in a PU impacted zone, and send the information to the SU. The SU may determine, based on the information from the SAS, whether the SU in a PU impacted zone. [0106] If it is determined that the SU is not in a PU impacted zone, at 840, proactive or reactive interference mitigation may be applied. For example, reactive SU solutions, as described herein, may adapt to PU interference, and proactive SU techniques that may avoid muasal interference with the PU. If it is determined that the SU is in a PU impacted zone, at 850, the advanced proactive solutions may be used. Application of these solutions for specific RATs, for example, LTE or Wi-Fi, described herein.

[0107] A SU may operate between the pulse phases. The SU may obtain information about the macro or rotation cycle of the radar PU. The SU may obtain such information from the SAS. The SU may sense the received RF signal while not transmitting and may derive the pulse repetition period, the pulse width and the start of the quiet period. The SU may obtain information about individual pulse timing(s) from the SAS or from RF sensing techniques as described herein. An opportunity may exist to operate between the individual radar pulses of a pulse phase, resulting in added throughput and QoS that may span the entire macro or rotation cycle. The SU may transmit during the radar operation, and may mitigate interference using biased link adaptation and/or scheduling during the radar operation period. The SU may not use the biased link adaptation and/or scheduling between the pulse phases.

[0108] FIG. 9 illustrates an example flow chart of SU operation, including, for example, the macro and micro solutions. As shown, at 910, the SU may determine whether information associated with PU radar systems is available. In radar coexistence, a SAS (e.g., spectrum broker system, or spectrum database), may gather information about a channel. For example, the SU may determine whether a database providing such information is accessible, or whether the database contains such information. If it is determined that information associated with PU radar systems is available, at 920, the SU may gather information about the radar PU from the database, and/or using sensing techniques to gather information about the channel and/or the PU of the channel. If it is determined that information associated with PU radar system is unavailable, at 930, the SU may gather information about the channel and/or the radar PU of the channel using sensing techniques.

[0109] The SU may apply an appropriate solution based on the gathered information about the channel availability zones and radar macro and/or micro cycles. After the SU gathers data about the radar PU of the shared channel, it may choose a solution. At 940, the SU may det ermine whether the channel is associated with a P U. If the channel is free of primar users (or, e.g., potentially secondary license users), the channel may be acceptable for full use. At 980, the S may use the channel. If the channel is associated with a PU, at 950, it may be determined whether information associated with the macro or rotation cycle of the PU is available. If the SU has knowledge of the macro or rotation cycle, at 960, it may determine whether information associated with the micro or pulse cycle of the PU. If the SU may gather information about the micro or pulse cy cle of the radar PU, at 982, the SU may apply coexistence solutions for micro cycles (e.g., in addition to coexistence solution for macro cycles). If the information about the micro or pulse cycle of the radar PU is not available to the SU, at 985, the SU may use coexistence solution for macro cycles. For example, the SU may use coexistence solution for macro cycles only.

[01 10] If information associated with the macro or rotation cycle of the PU is not available to the SU, at 970, whether the SU operation may interfere with the PU operation may be determined. This may be determined based on information about whether the SU is in the SU potentially affected region or in the PU potentially affected region, for instance. If it is determined that the SU operation may not interfere with the PU operation, reactive solutions, as described herein may be applied at 987. The reactive solutions may not provide mechanisms to protect radar PUs. if it is determined that the SU operation may interfere with the PU operation, proactive solution may be applied at 990. For example, the proactive solution as described herein may be applied to SU-impacted and PU- impacted zones. The reactive solutions may not be applied in PU impacted zones.

[01 1 1] A SU system may use the shared channel when a radar PU's beam is focused away from the SU's location such that interference may be kept below a threshold. The timing of the radar pulse phase may be determined, interference may be avoided by buffering data, switching channels, and/or using an interference mitigation mechanism. The SU may determine the characteristics of the radar pulses through database assisted techniques, or via sensing and/or a combination of database and sensing techniques,

[01 12] FIG. 10 illustrates an example SU operation where the SU that may stop transmitting during PU pulse phases (e.g., radar pulse phases). As illustrated by example in FIG. 10, in a proactive solution the SU may use the channel during a period outside of the pulse phases. For example, the SU may not transmit during the pulse cycle of the macro or rotation phase. There may be a period before and/or after the pulse phase where transmissions may be avoided. The SU may gather information on radar operation cycle(s) via a database and'Or via sensing.

[01 13] FIG. 1 1 illustrates an example SU operation. The SU may the determine radar pulse phase timing, and'Or the change of frequencies. As shown in FIG. 1 1, at 1 1 10, the S U may use a channel during a quiet phase of the channel's PU system. The SU base station may inform its associated TRUs of the alternate channef(s) that the base station may hop to when the pulse phase begins. At 1120, the SU may use the alternate channel during the pulse phase of the PU system 1 140. The SU system may remain on the alternate channel, or may hop back to the first shared channel at 1 130,

[01 14] The information about the radar PU may be gathered through an infrastructure link. The SU system may have access to a spectrum database, for example, via a SAS as described with reference to FIG. 2.

[01 15] Military PUs may not publicly disclose the location of its signal sources. The military may wish to dynamically control the regions that may be used for SU use, including, for example, potential decoy regions. FIG. 12 illustrates an example of various military regions including, for example, available region, military training region, and/or decoy region. PUs ma make use of a de-classification interface to the SAS to provide this information. Based on the information in the SAS, the SUs may determine whether a region is allowed or disallowed for SU access. The disallowed regions may be larger than the operating range of the PU radar, for example, to allow for maneuverability of a PU vessel. The PU may define such regions as "fuzzy" regions or decoy regions. The PU may define the regions along the coast, specifying the depth of radar penetration into land. The coastal regions may be defined as "worst case" regions.

[01 16] FIG. 13 illustrates an example of subdivisions of primary user exclusion zones.

As shown, the regions may be subdivided to include PU potentially affected regions, and/or SU potentially affected regions. The PU may designate the activity regions as worst case (e.g., when a vessel is close to the shore). When the ship is farther from shore, the designation of the activity region may depend on the amount of flexibility the PU may require or the amount of information the PU may make publicly available.

[01 17] A spectrum access system may allow a classified database to provide data to a civil database and inform secondary and/or general access users. A ship entering a navy area

"#n" may be defined as a coast line area of "y" miles along the coast line by "x" miles depth. A classified database and associated shared spectrum management (SSM) may inform of this event.

The classified database information may be mapped to publicly disclosed information using a public disclosure function that may, for example, alter the classified information for civil use, and/or add decoys, etc. The information may be sent to an SAS such as a civil SSM or a spectrum database. The SAS may request DSS users operating in a PU potentially affected region of navy area "#n" to cease operation. The SAS may inform tier 2 and tier 3 users

- '? Ί - operating in the SU potentially affected region of "declassified" radar characteristics to assist users in mitigating the PU signals.

[01 18] Upon receiving an indication of the information, the SU may operate in accordance with the radar characteristics of the PU . The SU may use an interface to gather information to coexist with radar PU systems. Information elements may he provided by the radar PU over the interface and used to assist coexistence. The spectrum database may include information elements listed in Table 1 or a subset thereof.

[01 19] The SU may query the spectrum database for at least one of the SU parameters as listed in Table 1. For example, the SU may send location information (e.g., longitude and latitude) regarding the current location of the SU. Based on the location information, the spectmm database may provide information of the PU sy stem associated with the location. The information may be used for micro cycle solutions and/or macro cycle solutions.

Table I

Receiver Adjacent Channel { 50dB 5MHz from center frequency, 40dB 2MHz from center Selectivity Guarantee frequency, ... , }

{Microsecond: Millisecond: :Second: :Minute: :Day : :Month: :Year

Synchronization Time

Synchronization Time

Accuracy (Coarse (5ms), Fine (lOQus), ... , }

Synchronization Phase { degrees from east, }

Synchronization Phase

Accuracy { Coarse , Fine }

{ Yes Radar can detect stationary devices , No Radar is Doppler

Doppler Cancellation Ability agnostic, , .. , }

Doppler Velocity Threshold { 50km/hour , 300km/hour, ... , }

[0120] An SU may avoid mutual interference with a PU system based on the information acquired from the SAS. For example, the SU system may avoid interference from, and/or, avoid interfering, a radar PU by hopping channels, by scheduling transmissions around known pulse periods, and'or by using the Doppler cancellation ability of a radar system below a velocity threshold.

[0121] Federal users may assign specific operation directives through a declassification interface to ihe SAS (e.g., the shared spectrum manager). The information in ihe spectrum database may reflect these directives. The SUs may discover these directives through database queries. The SUs may follow these directives in order to gain access to the channel.

[0122] For example, the SAS may provide frequency, frequency hopping sequences and frame timings that the SUs may use. The SAS may provide such information in the Allowed Hopping Sequences information element (IE). The PUs may operate at other times or may adjust their own receivers in order to cancel interference from civilian users using the specified hopping sequences. The SAS may provide the SU frequency hopping options. For example, the SU may receive a choice among a number of frequency hopping sequences possibly with different sequence phases allowed. The SU may select a hopping sequence, and perform frequency hopping accordingly. A hopping sequence may be allocated to an SU device or multiple SU devices that may share a hopping sequence at a given location,

[012.3] The PU may switch to another channel than the present shared channel prior to the pulse phase. For example, the eNB of the SU system may inform its associated SU WTRUs of the channel switch using a SIB block, MAC CE or RRC message prior to the channel change.

[0124] A PU, e.g., a military PU, may pseudo-randomfy alter its pulse periodicity (e.g., to avoid jamming), the hopping sequence may apply in a just-in-time fashion. The PU may make available, via the de-cl assification interface, a set of time sequences in which SUs may be allowed to transmit. For example, the hopping synchronization IE may be used to achieve synchronization. The SU may use the hopping synchronization information to determine the exact time in which a number of shared spectrum channels may be available based on the hopping sequence and timing information that may be sent in the hopping synchronization IE. The SU may use this timing to select the channel to operate on at a given time and the timing of channel switches in such a way to avoid the primary user. A federal user may direct the SU to avoid certain timeslots to allow the PU to transmit, including, e.g., the decoy time slots. The available shared channel information may include decoy information.

[0125] The SU may use the pulse information elements acquired from the database to set its timers for macro cycle solutions. For example, the SU may use synchronization information such as the Synchronization Phase, Synchronization Time, Rotation Speed lEs as well as Pulse Duty Cycle lEs to determine which franie(s), beacon period(s) and/or oiher unit(s) of iime may^¬ be impacted by radar interference. The S Us may adjust its timers and/or schedulers to adapt to the interference. The SU may apply its coexistence solutions during this period. For example, the SU may determine the timing of the pulse period of the PU with respect to the geographic location of the SU, and/or may determine the timing of the pulses with respect to the geographic location of the SU.

[0126] The SU may transmit based on the Doppler cancellation ability of radar for coexistence. If a SU queries the SAS (e.g., a designated spectrum database), and the Doppler Detection Ability IE indicates that the radars on the band are equipped with Doppler cancellation ability, the SU may operate on the channel under certain velocity restrictions as the Doppler effects may be detected above certain threshold.

[0127] In reactive solutions, the SU may avoid PU interference based on PU operation information such as one or more IBs described in Table 1 or based on sensing results. The SU may determine the PU radar cycle by gathering statistics about re-transmissions or burst errors. The SU may detect patterns characteristic of radar PUs, for example, the rotation period, to help determine the macro characteristics. Based on these determinations, the SU may employ link adaptation biasing techniques. The scheduler may avoid sending data or changing frequencies to avoid interference.

[0128] Sensing results may be used to select a channel and/or gain additional information to substitute, enhance or be used in conjunction with database information. For example, sensing techniques may be combined with database information to determine the PU radar's phase information. The SO may select a shared channel based on a sensing-information based algorithm.

[0129] For example, information associated with the macro or rotation cycle may be determined via sensing. Military radars may employ techniques that may make it difficult to sense. Energy detection may be used to detect the military radar PUs. For macro cycle solutions, such detection may be sufficient to determine the pulse phase timing. If the PU uses frequency hopping in a pseudo-random manner, the SU may modify its usage of the potential frequencies. An example sensing technique may include monitoring the operating channel and performing energy detection over a long period. For example, a periodic activity pattern such as high energy level followed by silent period (e.g., low energy level), may be detected. The periodic activity pattern may be used to determine information associated with the macro or rotation cycle of the PU. Additional post-processing such as filtering within the operating channel can be used to determine the radar bandwidth used, as radar might occupy a smaller bandwidth than the communicati on system. The bandwidth of the presumed PU signal may be an indication that the signal received is a radar as the SAS could provide this information. The detected characteristics of the radar may be sent back to the SAS. The SAS may share such information with the other SUs in proximity.

[0 30] The SU system may use a channel during quiet periods of the PU system. Before the micro cycle begins, the SU ma switch to an alternate channel or use a finer micro phase algorithm to transmit in between the pulses. If the SU leaves the channel, it may return to the original channel when the pulse phase ends.

[0 31] As compared to the military radars, the civilian radar sources such as weather radar and/or radio navigation may be more deterministic. Sensing of the civilian radars may provide the exact period and repetition period of the individual pulses, and the micro or pulse cycle timing enabling micro cycle solutions.

[0132] To synchronize the solution with the PU operation, the SU radio may detect the frame and/or sub-frame number(s) or beacon period(s) or other unit(s) of time that may be impacted by the radar PU. The SU may report the frame and/or sub frame numbers to a software entity in the SU that may use the periodicity to determine the next frame number or beacon period that may be affected. The prediction meihod may be applied io micro cycle solutions,

[0133] As illustrated by example in FIG. 14, the SU may determine a suitable channel based on sensing. For example, the SU may determine whether it is located in in PU impacted areas, and if so, the SU may not to operate on a radar channel . The SU may determine whether it is located in in an SU impacted region, if so, the SU may perform sensing to determine a channel to operate on.

[0134] As shown in FIG, 14, at 1410, the SU may perform quick sensing on a channel.

For example, the SU may sense the channel for a period of time (e.g., 10 milliseconds, or 8- 12 milliseconds) to assess if there is PU interference on the channel (e.g., whether the PU is using the shared channel). At 1420, whether potential interference from the PU to the SU is tolerable may be determined. Upon determining that potential interference from the PU is not tolerable, the SU may perform quick sensing on a next channel at 1410. Upon determining that potential interference from the PU is tolerable, the SU may perform long sensing on the channel at 1430, If the level of activity is tolerable, the SU may scan for an extended period of time to detect the presence of a radar PU. The mechanical rotation of radars may be on the order of 10 seconds per rotation. The sensing period may be 10 to 60 seconds per channel. For example, the SU may perform sensing on the channel for longer than 8 seconds, longer than 10 seconds, longer than 12. seconds, or the like. If a radar PU is detected, the SU may assess whether operating on the channel will cause interference to the PU at 1450. Upon determining that operating on the channel will cause interference to the PU, the SU may perform quick sensing on a next channel at 1410. Upon determining that operating on the channel may not cause interference to the PU, the SU may assess whether the PU interference to the SU is tolerable at 1460. If the PU interference to the SU is not tolerabie, the SU may perform quick sensing on a next channel at 1410. If the PU interference to the SU is tolerabie, the SU may determine whether more spectrum is needed at 1470.

[0135] If at 1440, a radar PU is not detected based on long sensing, the SU may determine whether more spectrum is needed at 1470. If more spectrum is needed, the SU may start using the channel and update the available channel list at 1480. The SU may use macro and/or micro coexistence solutions. If more spectrum is not needed, the SU may update the available channel list at 1490 and perform quick sensing on a next channel at 1410.

[0136] If a radar PU is detected, the S U may not cause interference, and the PU interference to the SU is tolerable, the SU may start using the channel and may use macro and/or micro coexistence solutions. For example, if the SU has enough sensing resolution to accurately predict the radar macro cycle, the SU may transmit during the quiet phase, avoiding the mutual interference. [0 37] A base station (e.g., an eNB or Wi-Fi access point) may perform sensing and collect data on an operating radar PU. If the SU system operates on the channel, it may inform its associated WTRUs without interfering with the radar PU. The base station may broadcast at specific times when a WTRU may attempt to access the channel. The broadcast may be performed, e.g., using system information broadcast (SIB) and/or a beacon signal. After initial access sensing, the base station may send the results or operation parameters may to its associated WTRUs.

[0138] In long term evolution (LTE) networks, an eNB may broadcast the allowed frame numbers and/or the disallowed frame numbers for channel access due to radar PUs. Such information may be sent in a SIB message. When the WTRU is in a connected mode, the eNB may send detailed sensing information or operating parameters using a MAC CE or RRC configuration signals. If during an operation, a PU is detected, the base station may inform its associated WTRUs of their respective channel evacuation time(s).

[0139] A blank frame (e.g., a transparent frame) may be used to avoid interfering with radar transmissions. For example, an eNB may schedule blank frame(s) based on the timing of the radar PU's pulse phase. If the pulse phase overlaps with more than a single blank frame, multiple consecutive blank frames may be scheduled. FIG. 15 illustrates an example of use of blank frame(s) for avoiding interfering with a radar PU.

[0140] As illustrated by example in FIG. 15, the eNB may schedule a blank frame or multiple blank frames during the pulse phase of the radar PU. The blank frame may be completely blank so that mutual interference mitigation between the PU and SU may be achieved. The blank frame solution may be used in the SU impacted and/or the PU impacted zones. Blank frames may be scheduled to cover the pulse phase. The timing of operations at the eNB and UE may be frozen during a blank frame.

[0141 ] For example, at the beginning of a frame (10ms) or at end of a frame, a base station may listen to the operating channel for a small duration of time (e.g., less than a subframe). The base station may determine whether a radar pulse is observed. If a radar pulse is detected, the base station may not use the operating channel in the LTE frame.

[0142] Carrier aggregation may be performed. FIG. 16 illustrates an example LTE aggregating a channel on a radar band with another channel. As shown, a licensed primary carrier may be used in combination with a secondary carrier using the radar band. The eNB may not schedule transmissions on the secondary carrier during the pulse phase of the radar PU. The system may maintain QoS during the pulse phase of the radar signal, and mutual interference between the SU and PU may be achieved.

[0143] In a reactive solution, almost blank subframe(s) (ABS) may be scheduled based on the pulse phase of the radar PU. For example, the SU system may transmit ABS subframes during radar pulse periods, in an embodiment, the SU system may transmit ABS subframe(s) on a condition that the SU system may not cause interference to the radar PU. An ABS subframe may carry reference symbols and may not carry data. There may not be any excessive retransm ssions, and the radar pulses may fall within the data space between the reference symbols. The eNB may notify associated WTRUs to avoid taking reference signal (RS) measurements during the radar pulse periods as they may be affected by interference due to the high powered radar pulses. Signaling may be sent via an RRC message or a MAC message, indicating the identification of the ABS subframe.

[0144] The SU system may reactively remain on the same channel and modify its operation to coexist with the PU system. For example, the SU may determine the macro cycle timing of the PU system. The SU system may bias the link adaptation based on the timing of the pulse phase. For example, before a pulse phase begins, right after a pulse phase ends, and/or during the pulse phase of the PU system, the Modulation and Coding Scheme (MCS) may be biased such that a more robust scheme may be selected. For example, error correction coding may be performed to recover from symbols that may be affected by the individual pulses. When the pulse phase ends, or after a predetermined time period lapses after the pulse phase, the bias may be removed so that the system may transition back to the MCS that was used before the pulse phase.

[0145] FIGs. 17 A and 17B illustrate an example link adaptation mechanism. The SU system, such as the base station, may determine link adaptation (e.g., MCS) based on a moving average. FIG. 17A illustrates an example link adaptation before link adaptation bias is employed. As shown in FIG. 17A, if link adaptation bias is not employed, link adaptation may suppress transmission rate at 1720 due to the interference from the PU pulse phase 171 OA. FIG. Γ7Β illustrates an example link adaptation with link adaptation bias. As shown, at 1730, link adaptation bias may be performed. Link adaptation bias may be imposed such that rate suppression (e.g., caused by PU interference) may be lifted when the PU pulse period ends. For example, as shown in FIG. 17B, after the PU radar pulse phase 1710B, rate suppression may be lifted. A less robust MCS may be selected after the PU radar pulse phase, and the transmission rate may be increased such that the SU system may resume its normal operation. The timing of the pulse phase may be signalled, from the base station to the WTRU, ahead of time. The WTRU may be aware of what MCS scheme to use at the appropriate time. This may avoid delay in decreasing and/or increasing the rate, and may significantly improve the real-time

performance during this phase.

[0146] The channels may be switched prior to the radar pulse burst. The eNB may inform the WTRUs of the channel switch using a SIB block, MAC CE or RRC message prior io the channel change.

[0147] In a Wi-Fi system, several methods may be used to avoid transmissions during radar pulse periods. For example, the Wi-Fi access point (AP) may signal the PU 's macro cycle timing information to the stations (STAs). The STA and/or the AP may include a scheduler that may schedule packet transmission time. The scheduler may avoid scheduling any packets that would o verlap with the PU pulse period.

[0148] For example, the scheduler may schedule packet transmission such that a packet may be transmitted prior io the beginning of the PU's pulse period. For example, if a buffered packet takes, e.g., X microseconds to transmit, the STA may avoid accessing the channel at time, e.g., equal to P - X microseconds, where, e.g., P may be the time of the beginning of the pulse period. The AP may obtain the PU's macro cycle timing information via database or sensing or some hybrid technique. The AP may signal the pulse phase timing to the STAs using a beacon or an individually sent management frame.

[0149] FIG. 18 illustrates an example management frame mechanism such as a clear to send (CTS)-to-self mechanism. The CTS-to-self mechanism may be used to block the STAs from transmitting during the PU pulse period. The AP may enforce a silence period with a CTS- to-self message. As shown, the Wi-Fi system may carry out normal operation at 1810. At 1820, the AP may send a CTS-to-self message before, e.g., immediately before, a PU pulse period 1830. The CTS-to-self message may not be addressed to anyone. The CTS-to-self message may- have the address of the AP itself. The CTS-to-self message may be associated with an extended back-off duration whereby other ST As may not transmit. The CTS-to-self message may indicate a silence period. The silence period may include the PU's radar pulse period. As shown, the silence period may begin prior to the PU's radar pulse period and may last until after the pulse period. At 1840, the Wi-Fi system may resume normal operation,

[0150] The Wi-Fi system may operate on a radar channel during radar micro cycles. For example, the scheduler may schedule transmission between individual pulses of the PU sy stem based on the timing of the PU's micro cycles. The AP and/or the S^'T^'A may reduce packet sizes such that the packets may be sent in between individual pulses of the PU system. For example, the timing and the duration of an inter-pulse period of the pulse phase may be determined, and the packet size of a packet to be transmitted may be determined based on (he timing and the duration of the inter-pulse period time such that the transmission of the packet can be completed prior to a next pulse.

[0151] The AP may send a CTS-to-self message to indicate a silence period covering the duration of the individual radar pulse. The silence period include an extra back off period to account for radar propagation time.

[0152] Extra throughput and QoS may be gained by using the time periods between individual radar pulses during the pulse phase. An SU device may gather statistics about the radar pulses via sensing, or via packet loss statistics, from the spectrum database or a combination thereof to determine patterns in the radar's micro cycle behaviour.

[0153] Based on the PU's micro pattern, the SU may transmit between the pulses. For example, the SU may avoid scheduling any packets when the pulse is expected to take place. If sensing is performed at the base station, the base station may send a message to its associated WTRUs before transmitting during a micro cycle.

[0154] FIG. 19 illustrates an example radar back off period mechanism. The SU may operate on the channel between the individual pulses. If operating in the PU impacted zone, the SU may wait a back off period Tba koff to allow the radar pulse to propagate across its range of operation. For example, the back-off period may be of the order of 1ms, if the PU radar has a range of 150 km.

[0155] As shown in FIG. 19, the PU system may have a pulse at 191 OA, 1910B and

1910C during a pulse phase. At 1920, the SU device may enter the channel and may perform sensing for one or more radar cycles. The SU device may detect pulse 1910B, and may set the back off timer. At 1930, the back off timer may expire after a back off period Tbackoff and the SU device may transmit on the channel during 1940. The SU device may detect pulse 19I0C, and may stop transmission on the channel. The SU device may set the back off timer. Upon expiry of the back off timer at 1950, the SU device may use the channel at 1960.

[0156] The SU device may operate on a channel with multiple PU radar systems. FIG.

20 illustrates a case where a SU coexists with multiple radars on a channel using the back off period mechanism. As shown, a first PU radar may pulse at 201 OA, 2010B and 20 IOC, and a second PU radar may pulse at 2020A, 2020B and 202.0C, At 2030, the SU device may enter the channel and may perform sensing for one or more full radar cycles. The SU device may detect pulse 201 OB and 2020B. For each radar system, the SU may keep track of the radar pulses to avoid transmitting during these pulses. For example, the SU may determine a back off period for each PU radar, such as ΤΪ backoff for the first PU radar and Τ2¾κ&ο« for the second PU radar. At 2040, the SU device may transmit on the channel. The SU device may set the back off timer upon detecting pulse 20 I OC. At 2050, the SU system may wait the longer/longest of the radar cy cles of the multiple PU radars. The back off timer may be set to expire after the longer of bac_ko_ff afl T2bac_{k ff} back off periods. The SU device may use the channel upon expiry of the back off timer.

[0157] An LTE system may coexist with radar PUs by adapting to the individual radar pulses. Coarse macro cycle synchronization may be assumed for LTE micro cycle solutions, whereby coarse synchronization ma allow for some drift.

[0158] For example, a small cell LTE system operating on a radar band may proactively avoid transmitting during subframes that may coincide with radar pulses plus their back-off time. FIG. 21 illustrates an example of a LTE system transmitting with added limitation of subframe timing. As shown in FIG. 21 , the LTE system may stop transmitting on the radar channel at 2120, slightly before an expected PU pulse 21 10A to allow for drift. The LTE system may wait for a back off time period 2130 before using the channel again at 2140. As shown, the LTE system may be limited by its subframe timing and may transmit during subframes that may fully overlap with an available transmit. For example, the LTE system may skip subframe 2170, e.g., the LTE system may not transmit on the radar channel during subframe 2170. After the back off time period ends, the LTE system may transmit in subframe 2180 until slightly before a next expected PU pulse 21 10B. The LTE system may wait for a back off time period 2150 before using the channel again at 2160. For example, the LTE system may skip subframe 2190, and after the back off time period ends, the LTE system may transmit in subframe 2195. The LTE system may skip individual subframes without disrupting HARQ processes, missing SI elements, etc.

[0159] The eNB scheduler may avoid scheduling any transmissions, including UL and

DL, on subframes that may be determined to likely to contain a radar pulse. FIG. 22 illustrates an example of how an eNB may avoid scheduling transmission on known radar pulse subframes.

[01 60] The eNB may schedule an ABS and/or MBSF subframe when there may be a radar pulse. This may prevent any re-transmissions and associated throughput loss. The solution may be useful when there are asymmetric UL/DL configurations, since grouped ACKs may occur such that a radar pulse may cause the loss of multiple subframes worth of data to be retransmitted.

[0161] The LTE New Carrier Type (NCT) for standalone small cells may be used to allow blank subframes to be scheduled. The eNB may schedule one blank subframe during expecied radar pulses or two blank subirames, if the back-off time reaches past the original blank subframe. NCT may require control signalling during subframes 0 and 5. This may improve the performance of such a system, if the frame timing may be modified to include subframes 0 and 5 during non-radar pulse subframes. If the Radar pulse period is not a multiple of 10ms, a pulse may land on subframe 0 or 5, and the eNB may send a signal to the associated UEs that special frame(s) may occur with a mod fied timing. For the speci l frame(s), the control signals may be moved to a different subframe such as subframes 2 and 7. The eNB may return to its normal timing after ihe special frame(s) are transmitted.

[0162] If the LTE system is not concerned with its operation interfering with the radar

PUs, it may be flexible in handling ihe interference. The proactive solutions may be used to improve performance.

[0163] An ABS subframe may be scheduled to coincide with PU pulse(s). Data may not be transmitted in the ABS subframe. By not transmitting data during the ABS subframe, throughput loss due to retransmissions may be avoided. ABS subframes may continue to transmit reference symbols that may be interfered with by radar signals. MBSFN subirames may be scheduled any time a radar pulse may occur. MBSFN subframes may be compatible with, for example, release 8 LTE devices. MBSFN and ABS may be combined in MBSFN ABS subframes and may provide the ideal subframe to use during radar subframes as fewest symbols may be interfered with.

[0164] The LTE New Carrier Type (NCT) for standalone small cells may contain an ePDCCTI control channel and the ability to leave some subframes empty. FIG. 23 illustrates an example of ePDCCH resource blocks (RBs) that may be interfered by a radar pulse. As shown, the PU radar system's pulses 231 OA and 2310B may block certain resource block (RBs) of the

LTE signalling. For example, the radar pulse 2310A may block RB(s) that may be allocated to the PDCCFL An enhanced PDCCH control channel, such as an ePDCCH control channel may spread in frequency and/or in time. As shown in FIG. 23, distributed ePDCCH may be allocated in RBs 2320. The distributed ePDCCH may provide frequency spreading and/or time spreading to avoid radar pulses. This solution may be combined with link adaptation, [0165] The mapping of data may be dynamically modified for subframes where OFDM symbols may be impacted. Since the duration of a radar pulse may be short (e.g., two microseconds), one to two OFDM symbols may be impacted. When a radar pulse is expected, the eNB may temporarily change ihe mapping of the data elements to avoid interference with the high powered radar pulse.

[0166] There may be a control element within the ePDCCH for example, to indicate the position of the next radar pulse. When the ePDCCH is spread in time, there may be a chance that the WTRU may miss this indication due to another radar pulse as compared to the regular PDCCH, where a radar pulse may cormpt the entire PDCCH. A MAC CE signal may be used to indicate future radar timings before the pulse period. An RjRC message may be used to indicate future radar timings before the pulse period.

[0167] A Wi-Fi system may operate under micro cycles of the PU system. The carrier sense multiple access with collision avoidance (C8MA-CA) system may allow operation within the space between radar pulses. The AP may inform a station (STA) of the macro timing via a beacon or individual management frame as described in the macro cycle solutions herein.

[0168] Before the pulse cycle, an indication may be sent via, for example, the medium access control (MAC) layer in a Wi-Fi device, such as a STA/WTRU to signal a modified MAC behaviour for the duration of this period. When the packet size may be longer than the pulse duration, the MAC layer may schedule packets of a reduced size as to avoid collisions with the next radar pulse. The maximum size of packets during the pulse phase may be determined based on the PU radar pulse information. For example, the packet size may be calculated upon receiving the information from a SAS (e.g., a spectrum database). The maximum packet size may be communicated via, for example, a beacon or an individual message sent to each STA. The MAC layer may segment a frame into smaller frames to fit into the reduced transmit opportunity.

[0169] During the pulse period, the Wi-Fi system may use a modified medium access scheme whereby the STA or the AP may listen for a radar pulse before trying to access the medium. In PU impacted regions, the Wi-Fi system may wait a back-off time corresponding to the propagation time of the radar through the air before accessing the channel For example, a

STA wishing to access the channel to send an ACK may listen for the radar pulse. Upon detecting the pulse, the STA may wait for a back off time Tb. The STA may wait for a time

SIFS (e.g., Short InterFrame Space from 802.1 1 standard). If the medium is free, the STA may send the ACK. If there is still sufficient time before the next radar pulse, another STA or the AP may try to access the channel and send another message. The packet size may be small enough to not overlap with the next radar pulse.

[0170] An AP may send a priority management frame immediately after a radar pulse is detected, which may indicate modified operation. Such an operation may be used, for example, in operation of pseudo-random military radars, and where a reactive solution may be needed.

[0171] A CTS-to-self mechanism may be used by the AP to coordinate the STAs. The

AP may determine whether the spacing between the pulses is large prior to coordinate the STAs. The CTS-to-self message may indicate a silence period covering the duration of the individual radar pulse, and may include an extra back off period to account for radar propagation time. The STAs may be made aware of the pulse phase so that they may use the reduced packet size.

[0172] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer- readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer- readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

CLAIMS What Is Claimed:

1. A method of using a shared channel associated with a primary user, the method comprising:

gathering information associated with an operation cycle of the primary user of the shared channel, wherein the operation cycle comprises a quiet phase and a pulse phase;

scheduling transmission on the shared channel during the quiet phase; and

performing inference mitigation based on a timing of the pulse phase.

2. The method of claim 1 , wherein performing inference mitigation further comprises: scheduling at least one blank frame during the pulse phase.

3. The method of claim 1, wherein performing inference mitigation further comprises: scheduling at least one almost blank subframe during the pulse phase, wherein an almost blank subframe is for transmission of certain reference symbols.

4. The method of claim 1 , wherein performing inference mitigation further comprises: determining a timing and a duration of an inter-pulse period in the pulse phase; and scheduling transmission on the shared channel during the inter-pulse period.

5. The method of claim 1, wherein performing inference mitigation further comprises: biasing fink adaptation during the pulse phase.

6. The method of claim 1 , wherein scheduling transmissio on the shared channel during the quiet phase further comprises:

determining a time period for transmitting a packet; and

scheduling a packet transmission time such that the packet is transmiited prior to the beginning of the pulse phase.

7. The method of claim 1 , wherein gathering information associated with an operation cycle of the primary user of the shared channel further comprises:

sending an indicator of a geographic location to a spectrum access system; and receiving information associated with the operation cycle of the primary user associated with the geographic location.

8. The method of claim 7, wherein the information associated with the operation cycle of the primary user associated with the geographic location comprises synchronization information of the primary user and pulse cycle information of the primary user, and the method further comprising:

determining the timing of the pulse phase of the primary user with respect to the geographic location based on the received information associated with the operation cycle of the primary user associated with the geographic location.

9. The method of claim 7, wherein the information associated with the operation cycle of the primary user associated with the geographic location comprises synchronization information of the primary user and pulse cycle information of the primary user, and the method further comprising:

determining a timing of at least one pulse of the pulse phase with respect to the geographic location based on the received information associated with the operation cycle of the primary user associated with the geographic location; and

sending the timing of the pulse phase to an associated wireless transmit and receive unit.

10. A base station for providing access to a shared channel associated with a primary user, the base station comprising:

a processor configured to:

gather information associated with an operation cycle of the primary user of the shared channel, wherein the operation cycle comprising a quiet phase and a pulse phase; schedule transmission on the shared channel during the quiet phase; and perform interference mitigation based on a timing of the pulse phase.

1 1. The base station of claim 10, wherein the processor is further configured to perform at least one of:

schedule at least one blank frame during the pulse phase;

schedule at least one almost blank subframe during the pulse phase, wherein an almost blank subframe is for transmission of only certain reference symbols; or schedule at least one multicast broadcasts on a single frequency network (MBSFN) subframe during the pulse phase.

12. The base station of claim 10, wherein the processor is further configured to:

receive a hopping sequence indicating information for performing frequency hopping when the shared channel is unavailable;

receive hopping synchronization information indicating a timing associated with the hopping sequence; and

select a second shared channel for operation when the shared channel is unavailable based on the hopping sequence and the hopping synchronization information.

13. The base station of claim 10, wherein the processor is further configured to:

determine a timing and a duration of an inter-pulse period in the pulse phase; and schedule transmission on the shared channel during the inter-pulse period based on the timing and the duration of the inter-pulse period.

14. The base station of claim 10, wherein the processor is further configured to:

bias link adaptation during the pulse phase.

15. The base station of claim 10, wherein the processor is further configured to:

determine a time period needed for transmitting a packet; and

schedule a packet transmission time such that the packet can be transmitted on the shared channel prior to the beginning of the pulse phase.

16. The base station of claim 10, wherein the processor is further configured to:

send an indicator of a geographic location to a spectrum access system; and

receive information associated with the operation cycle of the primary user associated with the geographic location.

17. The base station of claim 16, wherein the information associated with the operation cycle of the primary user associated with the geographic location comprises synchronization information of the primary user and pulse cycle information of the primary user, and the processor is further configured to: determine the timing of the pulse phase of the primary user with respect to the geographic location based on the received information associated with the operation cycle of the primar '- user associated with the geographic location.

18. The base station of claim 17, wherein the information associated with the operation cycle of the primary user associated with the geographic location comprises synchronization information of the primary user and pulse cycle information of the primary user, and the processor is further configured to:

determine a timing of at least one pulse of the pulse phase with respect to the geographic location based on the received information associated with the operation cycle of the primary user associated with the geographic location; and

send the timing of the pulse phase to an associated wireless transmit and receive unit.

19. A spectrum access system for providing spectrum availability information, the spectrum access system comprising:

a processor configured to:

receive declassified information associated with federal primary user system operations;

receive a request for accessing a shared channel at a geographic location;

identify an available shared channel at the geographic location and a primary user of the available shared channel based on the declassified information;

determine the information associated with an operation cycle of the primary user based on the declassified information, wherein the operation cycle comprises a quiet phase and a pulse phase; and

send information indicative of the available shared channel and the information associated with an operation cycle of the primary user.

20. The spectrum access system of claim 19, wherein the information associated with the operation cy cle of the primary- user of the shared channel comprises at lea st one of:

status informatio of the shared channel;

transmission power of the primary user;

antenna gain of the primary user;

beamwidth of the primary user;

a safety margin associated with the primary user; rotation speed of the primary user;

a pulse duration minimum;

a pulse duration maximum;

a pulse cycle minimum;

a pulse cycle maximum;

a modulation type of the primary user;

range of the primary user;

a center frequency of the primary user;

a bandwidth of the primary user;

Doppler cancellation ability of the primary user; or

a Doppler velocity threshold.

21. The spectrum access system of claim 19, wherein the processor is configured to:

allocate a frequency and an access time for a secondary user system to use when the shared channel is unavailable to the secondary user system; and

send information indicative of the allocated frequency and access time to the secondary- user.

22. The spectrum access system of claim 19, wherein the processor is configured to: determine a sequence of frequencies and associated access times for a secondary user system to use when the shared channel is unavailable to the secondary user system, wherein the information associated with the operation cycle of the primar user of the shared channel comprises:

a frequency hopping sequence indicating the determined sequence of frequencies and associated access times; and

hopping synchronization information indicating a timing associated with the hopping sequence.

23. The spectrum access system of claim 19, wherein the information associated with the operation cycle of the primary user of the shared channel comprises decoy information.

24. A wireless transmit and receive unit (WTRU) for accessing a shared channel associated with a primary user, the WTRU comprises:

a processor configured to: receive infomiation associated with an operation cycle of the primary user of the shared channel, wherein the operation cycle comprising a quiet phase and a pulse phase; send data on the shared channel during the quiet phase; and

perform interference mitigation during the pulse phase,

25. The WTRIJ of claim 24, wherein the processor is further configured to:

identify a timing and a duration of an inter-pulse period in the pulse phase; and determine a packet size of packet to he transmitted during the inter-pulse period, wherein the determination is based on the timing and the duration of the inter-pulse period time such that the transmission of the packet can be completed prior to a next pulse.

26. An access point for providing access to a shared channel associated with a primary user, the access point comprising:

a processor configured to:

gather information associated with an operation cycle of the primary user of the shared channel, wherein the operation cycle comprises a quiet phase and a pulse phase; send information associated with the operation cy cle of the primary user to a plurality of wireless transmit and receive units (WTRUs) associated with the access point; and

schedule transmission on the shared channel during the quiet phase; and perform interference mitigation based on a timing of the pulse phase.

2.7. The access point of claim 2.6, wherein the processor is further configured to:

perform interference mitigation based on a timing of the pulse phase at least in part by: sending a clear to send (CTS) -to-self message with a back- off duration that coincides with the pulse phase.

28. The access point of claim 27, wherein the CTS-to-self message is sent immediately before the pulse phase.