WO2017079971A1

WO2017079971A1 - Methods and apparatus for decoding system information

Info

Publication number: WO2017079971A1
Application number: PCT/CN2015/094571
Authority: WO
Inventors: Daowei LIN; Xiaochen Chen; Jie Mao; Jun Deng; Ang Li; Hongwei Zhao; Jin Tao HOU; Tom Chin; Tim Tynghuei Liou; Ta-Yan Siu; Bhavan Shah; Muhammad Arif Munif; Muralidharan Murugan; Kuo-Chun Lee
Original assignee: Qualcomm Incorporated
Priority date: 2015-11-13
Filing date: 2015-11-13
Publication date: 2017-05-18

Abstract

Certain aspects of the present disclosure relate to methods and apparatus for decoding system information when one or more System Information (SI) windows for receiving at least one SI Block (SIB) overlap with at least one measurement gap used for measuring signals from one or more neighboring cells.

Description

METHODS AND APPARATUS FOR DECODING SYSTEM INFORMATION

Field

The present disclosure relates generally to wireless communication, and more particularly, to methods and apparatus for decoding system information in wireless communication systems.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP) . It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL) , SC-FDMA on the uplink (UL) , and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

Certain aspects of the present disclosure provide a method for wireless communications by a User Equipment (UE) . The method generally includes determining that one or more System Information (SI) windows for receiving at least one SI Block (SIB) overlap with at least one measurement gap used for measuring signals from one or more neighboring cells, and disabling measurement during one or more portions of the at least one measurement gap in response to the determination

Aspects generally include methods, apparatus, systems, computer program products, computer-readable medium, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings. “LTE” refers generally to LTE, LTE-Advanced (LTE-A) , LTE in an unlicensed spectrum (LTE-whitespace) , etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture.

FIG. 2 is a diagram illustrating an example of an access network.

FIG. 3 is a diagram illustrating an example of a DL frame structure in LTE.

FIG. 4 is a diagram illustrating an example of an UL frame structure in LTE.

FIG. 5 is a diagram illustrating an example of a radio protocol architecture for the user and control plane.

FIG. 6 is a diagram illustrating an example of an evolved Node B and user equipment in an access network, in accordance with certain aspects of the disclosure.

FIG. 7 illustrates example overlapping of SI windows and measurement gaps, in accordance with certain aspects of the present disclosure.

FIGs. 8a-c illustrate three different example scenarios when overlapping SI windows and measurement GAPs has been frequently observed, in accordance with certain aspects of the present disclosure.

FIG. 9 illustrates example operations, performed by a UE, for decoding system information received during SI windows overlapping measurement GAPs, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

Communicating LTE system information is one of the key aspects of the air interface. Certain System Information Blocks (SIBs) are carried by System Information (SI) messages. An SI message can include one or several SIBs. The SI messages are transmitted within periodically occurring time domain windows (e.g., referred to as SI-windows) using dynamic scheduling.

In LTE, measurement GAPs are provided, which are periods where a UE switches off its transmissions and reception in the serving cell and listens to transmissions in one or more neighboring cells. In current LTE systems, eNB configures measurement GAPs independent of and without considering scheduling of SI transmission windows. This may cause one or more SI windows to overlap measurement GAPs.

In accordance with current LTE specification, a UE should stop SI decoding during a measurement GAP period, and may resume SI decoding after expiration of the GAP period. Thus, if a SI window overlaps a measurement gap, the UE may not receive system information transmitted by the serving cell, since it may be tuned away from the serving cell during the measurement gap period. Since current LTE specification does not guarantee SI re-transmission, SI decode failure may happen frequently on the UE side in this scenario. Further, if the periodicities of the SI windows and GAPs are the same, the UE may be unable to decode SI until configuration of SI windows or the GAPs changes.

Aspects of the present disclosure discuss techniques and apparatus for successfully decoding system information when one or more SI windows overlap measurement GAPs. A UE may determine that one or more SI windows for receiving at least one SIB overlap with at least one measurement GAP used for measuring signals from one or more neighboring cells. The UE may disable measurement during one or more portions of the at least one measurement GAP in response to the determination, in an attempt to decode the at least one SIB.

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented with a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs) , field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, firmware, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, or combinations thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, PCM (phase change memory) , flash memory, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

FIG. 1 is a diagram illustrating an LTE network architecture 100 in which aspects of the present disclosure may be practiced.

For example, a UE (e.g., UE 102) may determine that one or more SI windows for receiving at least one SIB overlap with at least one measurement GAP used for measuring signals from one or more neighboring cells. The UE may disable measurement during one or more portions of the at least one measurement GAP in response to the determination, in an attempt to decode the at least one SIB.

The LTE network architecture 100 may be referred to as an Evolved Packet System (EPS) 100. The EPS 100 may include one or more user equipment (UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS) 120, and an Operator’s IP Services 122. The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. Exemplary other access networks may include an IP Multimedia Subsystem (IMS) PDN, Internet PDN, Administrative PDN (e.g., Provisioning PDN) , carrier-specific PDN, operator-specific PDN, and/or GPS PDN. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108. The eNB 106 provides user and control plane protocol terminations toward the UE 102. The eNB 106 may be connected to the other eNBs 108 via an X2 interface (e.g., backhaul) . The eNB 106 may also be referred to as a base station, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , an access point, or some other suitable terminology. The eNB 106 may provide an access point to the EPC 110 for a UE 102. Examples of UEs 102 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA) , a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player) , a camera, a game console, a tablet, a netbook, a smart book, an ultrabook, a drone, a robot, a sensor, a monitor, a meter, or any other similar functioning device. The UE 102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

The eNB 106 is connected by an S1 interface to the EPC 110. The EPC 110 includes a Mobility Management Entity (MME) 112, other MMEs 114, a Serving Gateway 116, and a Packet Data Network (PDN) Gateway 118. The MME 112 is the control node that processes the signaling between the UE 102 and the EPC 110. Generally, the MME 112 provides bearer and connection management. All user IP packets are transferred through the Serving Gateway 116, which itself is connected to the PDN Gateway 118. The PDN Gateway 118 provides UE IP address allocation as well as other functions. The PDN Gateway 118 is connected to the Operator’s IP Services 122. The Operator’s IP Services 122 may include, for example, the Internet, the Intranet, an IP Multimedia Subsystem (IMS) , and a PS (packet-switched) Streaming Service (PSS) . In this manner, the UE102 may be coupled to the PDN through the LTE network.

FIG. 2 is a diagram illustrating an example of an access network 200 in an LTE network architecture in which aspects of the present disclosure may be practiced. For example, UEs 206 may be configured to implement techniques for decoding system information when one or more SI windows for receiving at least one SIB overlap with at least one measurement GAP used for measuring signals from neighboring cells.

In this example, the access network 200 is divided into a number of cellular regions (cells) 202. One or more lower power class eNBs 208 may have cellular regions 210 that overlap with one or more of the cells 202. A lower power class eNB 208 may be referred to as a remote radio head (RRH) . The lower power class eNB 208 may be a femto cell (e.g., home eNB (HeNB) ) , pico cell, or micro cell. The macro eNBs 204 are each assigned to a respective cell 202 and are configured to provide an access point to the EPC 110 for all the UEs 206 in the cells 202. There is no centralized controller in this example of an access network 200, but a centralized controller may be used in alternative configurations. The eNBs 204 are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway 116. The network 200 may also include one or more relays (not shown) . According to one application, a UE may serve as a relay.

The modulation and multiple access scheme employed by the access network 200 may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM is used on the DL and SC-FDMA is used on the UL to support both frequency division duplexing (FDD) and time division duplexing (TDD) . As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB) . EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA； Global System for Mobile Communications (GSM) employing TDMA； and Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNBs 204 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data streams may be transmitted to a single UE 206 to increase the data rate or to multiple UEs 206 to increase the overall system capacity. This is achieved by spatially precoding each data stream (e.g., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL. The spatially precoded data streams arrive at the UE (s) 206 with different spatial signatures, which enables each of the UE (s) 206 to recover the one or more data streams destined for that UE 206. On the UL, each UE 206 transmits a spatially precoded data stream, which enables the eNB 204 to identify the source of each spatially precoded data stream.

Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.

In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The UL may use SC- FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR) .

FIG. 3 is a diagram 300 illustrating an example of a DL frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames with indices of 0 through 9. Each sub-frame may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, as indicated as R 302, R 304, include DL reference signals (DL-RS) . The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS) 304. UE-RS 304 are transmitted only on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.

In LTE, an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB. The primary and secondary synchronization signals may be sent in

symbol periods

6 and 5, respectively, in each of

subframes

0 and 5 of each radio frame with the normal cyclic prefix (CP) . The synchronization signals may be used by UEs for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe. The PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to 1, 2 or 3 and may change from subframe to subframe. M may also be equal to 4 for a small system bandwidth, e.g., with less than 10 resource blocks. The eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe. The PHICH may carry information to support hybrid automatic repeat request (HARQ) . The PDCCH may carry information on resource allocation for UEs and control information for downlink channels. The eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data for UEs scheduled for data transmission on the downlink.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of the system bandwidth used by the eNB. The eNB may send the PCFICH and PHICH across the entire system bandwidth in each symbol period in which these channels are sent. The eNB may send the PDCCH to groups of UEs in certain portions of the system bandwidth. The eNB may send the PDSCH to specific UEs in specific portions of the system bandwidth. The eNB may send the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to all UEs, may send the PDCCH in a unicast manner to specific UEs, and may also send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period. Each resource element (RE) may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs) . Each REG may include four resource elements in one symbol period. The PCFICH may occupy four REGs, which may be spaced approximately equally across frequency, in symbol period 0. The PHICH may occupy three REGs, which may be spread across frequency, in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong in symbol period 0 or may be spread in

symbol periods

0, 1, and 2. The PDCCH may occupy 9, 18, 36, or 72 REGs, which may be selected from the available REGs, in the first M symbol periods, for example. Only certain combinations of REGs may be allowed for the PDCCH. In aspects of the present methods and apparatus, a subframe may include more than one PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. The UE may search different combinations of REGs for the PDCCH. The number of combinations to search is typically less than the number of allowed combinations for the PDCCH. An eNB may send the PDCCH to the UE in any of the combinations that the UE will search.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structure in LTE. The available resource blocks for the UL may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.

A UE may be assigned

resource blocks

410a, 410b in the control section to transmit control information to an eNB. The UE may also be assigned

resource blocks

420a, 420b in the data section to transmit data to the eNB. The UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may span both slots of a subframe and may hop across frequency.

A set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH) 430. The PRACH 430 carries a random sequence and cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (10 ms) .

FIG. 5 is a diagram 500 illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer 506. Layer 2 (L2 layer) 508 is above the physical layer 506 and is responsible for the link between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control (MAC) sublayer 510, a radio link control (RLC) sublayer 512, and a packet data convergence protocol (PDCP) 514 sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer 508 including a network layer (e.g., IP layer) that is terminated at the PDN gateway 118 on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc. ) .

The PDCP sublayer 514 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer 512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) . The MAC sublayer 510 provides multiplexing between logical and transport channels. The MAC sublayer 510 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 506 and the L2 layer 508 with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer 516 in Layer 3 (L3 layer) . The RRC sublayer 516 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650 in an access network, in which aspects of the present disclosure may be practiced.

For example, a UE 650 may determine that one or more SI windows for receiving at lest one SIB overlap with at least one measurement GAP used for measuring signal from neighboring cells. The UE 650 may disable measurement during one or more portions of the at least one measurement GAP in response to the determination, in an attempt to decode the at least one SIB.

It may be noted that the UE noted above for implementing the techniques for decoding system information in accordance with certain aspects of the present disclosure may be implemented by a combination of one or more of the controller 659, the RX processor 656 and receiver 654 at the UE 650.

In the DL, upper layer packets from the core network are provided to a controller/processor 675. The controller/processor 675 implements the functionality of the L2 layer. In the DL, the controller/processor 675 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE 650 based on various priority metrics. The controller/processor 675 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 650.

The TX processor 616 implements various signal processing functions for the L1 layer (i.e., physical layer) . The signal processing functions includes coding and interleaving to facilitate forward error correction (FEC) at the UE 650 and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 674 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 650. Each spatial stream is then provided to a different antenna 620 via a separate transmitter 618TX. Each transmitter 618TX modulates an RF carrier with a respective spatial stream for transmission.

At the UE 650, each receiver 654RX receives a signal through its respective antenna 652. Each receiver 654RX recovers information modulated onto an RF carrier and provides the information to the receiver (RX) processor 656. The RX processor 656 implements various signal processing functions of the L1 layer. The RX processor 656 performs spatial processing on the information to recover any spatial streams destined for the UE 650. If multiple spatial streams are destined for the UE 650, they may be combined by the RX processor 656 into a single OFDM symbol stream. The RX processor 656 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 610. These soft decisions may be based on channel estimates computed by the channel estimator 658. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 610 on the physical channel. The data and control signals are then provided to the controller/processor 659.

The controller/processor 659 implements the L2 layer. The controller/processor can be associated with a memory 660 that stores program codes and data. The memory 660 may be referred to as a computer-readable medium. In the UL, the controller/processor 659 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink 662, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink 662 for L3 processing. The controller/processor 659 is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets to the controller/processor 659. The data source 667 represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission by the eNB 610, the controller/processor 659 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB 610. The controller/processor 659 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a reference signal or feedback transmitted by the eNB 610 may be used by the TX processor 668 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 668 are provided to different antenna 652 via separate transmitters 654TX. Each transmitter 654TX modulates an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar to that described in connection with the receiver function at the UE 650. Each receiver 618RX receives a signal through its respective antenna 620. Each receiver 618RX recovers information modulated onto an RF carrier and provides the information to a RX processor 670. The RX processor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. The controller/processor 675 can be associated with a memory 676 that stores program codes and data. The memory 676 may be referred to as a computer-readable medium. In the UL, the control/processor 675 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 650. Upper layer packets from the controller/processor 675 may be provided to the core network. The controller/processor 675 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. The controllers/

processors

675, 659 may direct the operations at the eNB 610 and the UE 650, respectively.

The controller/processor 659 and/or other processors, components and/or modules at the UE 650 may perform or direct operations, for example, operations 900 in FIG 9, and/or other processes for the techniques described herein for decoding system information. In certain aspects, one or more of any of the components shown in FIG. 6 may be employed to perform example operations 900 and/or other processes for the techniques described herein. The

memories

660 and 676 may store data and program codes for the UE 650 and eNB 610 respectively, accessible and executable by one or more other components of the UE 650 and the eNB 610.

EXAMPLE TECHNIQUES FOR DECODING SYSTEM INFORMATION

As noted above, communicating LTE system information is one of the key aspects of the air interface. System information is divided into the MasterInformationBlock (MIB) and a number of SystemInformationBlocks (SIBs) . The MIB includes a limited number of most essential and most frequently transmitted parameters that are needed to acquire other information from the cell, and is transmitted on Physical Broadcast Channel (PBCH) . SIBs may be sent on the Physical Downlink Shared Channel (PDSCH) through Radio Resource Control (RRC) messages. SIB1 is carried by "SystemInformationBlockType1" message. SIB2 and other SIBs are carried by "System Information (SI) " messages. An SI message can include one or several SIBs.

Mapping of SIBs to SI messages is flexibly configurable by schedulingInfoList included in SystemInformationBlockType1 message, with certain restrictions including that each SIB is included only in a single SI message, and at most once in that message, only SIBs having the same scheduling requirement (e.g., periodicity) can be mapped to the same SI message, and that SystemInformationBlockType2 is always mapped to the SI message that corresponds to the first entry in the list of SI messages in schedulingInfoList. There may be multiple SI messages transmitted with the same periodicity. SystemInformationBlockType1 and all SI messages are transmitted on Downlink Shared Channel (DL-SCH) .

The SI messages are transmitted within periodically occurring time domain windows (e.g., referred to as SI-windows) using dynamic scheduling. Each SI message is associated with a SI-window and the SI-windows of different SI messages do not overlap. That is, within one SI-window only the corresponding SI is transmitted. The length of the SI-window is common for all SI messages, and is configurable. Within the SI-window, the corresponding SI message can be transmitted a number of times in any subframe other than MBSFN subframes, uplink subframes in TDD, and subframe #5 of radio frames for which SFN mod 2 ＝ 0. The UE acquires the detailed time-domain scheduling (and other information, e.g. frequency-domain scheduling, used transport format) from decoding SI-RNTI on PDCCH (see TS 36.321) . A single SI-RNTI is used to address SystemInformationBlockType1 as well as all SI messages. SystemInformationBlockType1 configures the SI-window length and the transmission periodicity for the SI messages.

The UE may be configured to apply the system information acquisition procedure upon selecting (e.g. upon power on) and upon re-selecting a cell, after handover completion, after entering E-UTRA from another RAT, upon return from out of coverage, upon receiving a notification that the system information has changed, upon receiving an indication about the presence of an ETWS notification, upon receiving an indication about the presence of a CMAS notification, upon receiving a notification that the EAB parameters have changed, upon receiving a request from CDMA2000 upper layers and/or upon exceeding the maximum validity duration, for example. Unless explicitly stated otherwise in the procedural specification, the system information acquisition procedure overwrites any stored system information, e.g. delta configuration is not applicable for system information and the UE discontinues using a field if it is absent in system information unless explicitly specified otherwise. The UE continues using the previously received system information until the new system information has been acquired.

In LTE, measurement GAPs are provided, which are periods where a UE switches off its transmissions and reception in the serving cell and listens to transmissions in one or more neighboring cells. The measurement GAP period has to be in sync with the eNB because the eNB should know when the UE will enter the gap state. To configure the GAP period for a UE, the eNB uses measGapConfig IE which is included in RRCConnectionReconfiguration message. Typically, measurement GAP configuration carried by the measGapConfig IE includes GAP configuration information indicating a measurement GAP length and a measurement GAP periodicity (e.g., 40ms, 80ms, etc. ) .

In the active state, the eNB provides measurement GAPs in the scheduling of the UE where no downlink or uplink scheduling occurs. Ultimately the network makes the decision, but the GAP generally provides the UE sufficient time to change frequency, make a measurement, and switch back to the active channel. This may normally occur in a few TTIs.

In current LTE systems, eNB configures measurement GAPs independent of and without considering scheduling of SI transmission windows. This may cause one or more SI windows to overlap measurement GAPs.

FIG. 7 illustrates example overlapping of SI windows and measurement gaps, in accordance with certain aspects of the present disclosure. As shown in FIG. 7, SI windows 702 a-c overlap measurement GAPs 704 a-c. FIG. 7 shows a special scenario where the periodicity of the SI windows is same as the periodicity of the GAPs. Thus, in this case one or more portions of every SI windows 702 may overlap with one or more portions of a corresponding measurement GAP 704 at least until periodicity of either the SI windows or the GAPs changes.

In accordance with current LTE specification, a UE may be configured to stop SI decoding during a measurement GAP period, and may resume SI decoding after expiration of the GAP period. Thus, if a SI window overlaps a measurement gap, the UE may not receive system information transmitted by the serving cell, since it may be tuned away from the serving cell during the measurement gap period. Since current LTE specification does not guarantee SI re-transmission within an SI window, SI decode failure may happen frequently on the UE side in this scenario. Further, if the periodicities of the SI windows and GAPs are the same, the UE may be unable to decode SI until configuration of SI windows or the GAPs changes. Thus, SI decode may fail at the UE when measurement GAPs and SI windows overlap consistently.

In certain aspects, the UE being unable to acquire system information for a certain period of time, for example due to one or more SI windows overlapping measurement GAPs, may lead to call drops.

FIGs. 8a-c illustrate three different example scenarios when overlapping SI windows and measurement GAPs has been frequently observed, in accordance with certain aspects of the present disclosure. FIG. s8a-c show signaling among an eNB 850, an RRC layer 852 of a UE and a L1 (Physical) layer 854 of the UE (not shown) .

FIG. 8a illustrates signaling in a handover scenario when the UE is in RRC connected state. At 802, eNB 850 signals RRC_Connection_Reconfiguration message to the UE to handover the UE to a new cell. At 804 the UE has completed handover to the new cell and is camped on to the new cell. At 806, the RRC layer 852 at the UE sends SIB_Collection_REQ to the L1 layer 854 to start receiving and decoding system information including mandatory SIBs and other SIBs. Before the UE has completed decoding SIBs, the RRC layer 852 receives RRC_Connection_Reconfiguration message configuring (e.g., or enabling) GAP periods overlapping one or more SI windows. At 810, the RRC layer 852 sends GAP_Config_REQ to the L1 layer 854, to implement the configured GAPs. In this scenario, since the overlapping measurement GAPs are enabled before the UE has completed SI decoding, the UE may be unable to decode system information.

FIG. 8b illustrates signaling when the UE (e.g., in RRC Connected state) receives updated SI configuration. At 812, the UE receives RRC_Connection_Reconfiguration message from the eNB 850 configuring (e.g., or enabling) measurement GAP periods for listening to signals of one or more neighboring cells. At 814, the RRC layer 852 at the UE sends GAP_Config_REQ to the L1 layer 854, to implement the configured GAPs. At 816, the UE receives PAGE_Notification (e.g., SI update page) from the eNB 850, to modify SI configuration. At 818, the RRC layer 852 sends SIB_Collection_REQ to the L1 layer 854 to start receiving and decoding updated system information including mandatory SIBs and other SIBs. In this case, if one or more SI windows, according to the updated SI configuration, overlap the already configured and enabled GAP periods, the UE may be unable to decode SI. On the other hand, if the UE receives the SI update page from the network first, and before the UE could finish decoding the updated SIBs, it receives the Reconfiguration message configuring GAPs overlapping the updated SI windows, the UE may be unable to finish decoding the SIBs.

FIG. 8c illustrates signaling for updating system information when SIB modification boundary is crossed while the UE is in RRC Connected state. At 822, the UE receives RRC_Connection_Reconfiguration message from the eNB 850 configuring (e.g., or enabling) measurement GAP periods for listening to signals of one or more neighboring cells. At 824, the RRC layer 852 at the UE sends GAP_Config_REQ to the L1 layer 854, to implement the configured GAPs. At 826, the UE detects that an SIB modification boundary is crossed. As a result, the RRC layer 852 sends SIB_Collection_REQ to the L1 layer 854 to start receiving and decoding system information including mandatory SIBs and other SIBs. In this case, if one or more SI windows overlap the already configured and enabled GAP periods, the UE may be unable to decode SI. On the other hand, if the UE detects that the SIB modification boundary is crossed, and before the UE could finish decoding the SIBs, it receives the Reconfiguration message configuring GAPs overlapping the SI windows, the UE may be unable to finish decoding the SIBs.

Aspects of the present disclosure discuss techniques and apparatus for successfully decoding system information when one or more SI windows overlap measurement GAPs.

FIG. 9 illustrates example operations 900, performed by a UE, for decoding system information received during SI windows overlapping measurement GAPs, in accordance with certain aspects of the present disclosure. Operations 900 begin, at 902, by determining that one or more SI windows for receiving at least one SIB overlap with at least one measurement GAP used for measuring signal from one or more neighboring cells. At 904, the UE disables measurement during one or more portions of the at least one measurement GAP in response to the determination, in an attempt to decode the at least one SIB.

In certain aspects, the UE may determine or identify one or more SIBs that have a higher priority than one or more other SIBs. For example, one or more mandatory SIBs may be defined at the RRC layer, for example, in accordance with LTE specification (e.g., TS 36.331) . The RRC layer may indicate the defined mandatory SIBs to the physical layer. In an aspect, the physical layer stores information relating to the mandatory SIBs (e.g. in a local database) , and temporarily disables measurement in one or more portions of one or more measurement GAPs that overlap SI windows carrying one or more mandatory SIBs. In an aspect, the physical layer may disable measuremnt in the GAPs overlapping SI windows carrying mandatory SIBs, until the one or more mandatory SIBs are successfully decoded. For example, if the periodicity of the SI windows carrying one or more mandatory SIBs is same as the periodicity of measurement GAPs, the physical layer at the UE may disable measurement in every GAP overlapping the SI windows (e.g., carrying the mandatory SIBs) until the mandatory SIBs are successfully decoded. Once the mandatory SIBs have been decoded, the physical layer may enable measurement in the GAPs (e.g., enable measurement during one or more subsequent portions of the at least one measurement gap after the determination that the at least one SIB has been successfully decoded) . In an aspect, the RRC layer indicates to the physical layer which mandatory SIBs are successfully decoded. The physical layer may clear stored information relating to one or more mandatory SIBs upon receiving an indication from the RRC layer that the one or more SIBs are successfully decoded. In aspects, disabling measurement in one or more portions of one or more measurement GAPs includes the RRC layer 852 at the UE refraining from or avoiding sending GAP_Config_REQ to the L1 layer 854, to implement the configured GAPs.

In an aspect, the mandatory SIBs are configured by the network； and information regarding the configured mandatory SIBs is signaled to the UE. For example, information regarding the configured mandatory SIBs may be signaled between the L3 and L1 layers within the UE.

In certain aspects, a maximum number of consecutive overlaps between measurement GAPs and SI windows may be defined for each SIB based, for example, at least on the type of the SIB. The UE may disable measurement in at least one measurement GAP after detecting that the maximum number of consecutive overlaps of SI windows carrying a SIB and GAPs has occurred, in an attempt to decode the SIB. For example, the UE physical layer may prioritize SI decode once every X number of overlaps between SI windows and GAPs to make sure that the UE does not miss out on SI updates. In an aspect, X is dynamic depending on what system information (e.g., SIB type) is to be decoded and how the SI decode is progressing.

In an aspect, X＝2 sets equal priority for SI decode and GAPs. This means that legacy behavior will be followed. X＝NA may be set when no SI decodes are pending. In an aspect, for mandatory/essential SI (e.g., MIB, SIB1, SIB2, SIB8 etc. ) , X is set to 3. This means that SI decode is prioritized (e.g. by disabling measurement GAP measurements) for every 3 overlaps. In certain aspects, if SI decode does not succeed for a predetermined time T, X may be decremented, for example, by 1. In an aspect, the time T is set based on SIB schedule) .

In an aspect, for critical SIBs (e.g.,

SIBs

10, 11, and 12) carrying emergency notifications, X is set to 1, to always prioritize SI decode over gaps.

In certain aspects, for other non-essential and non-critical SIBs, X may start at a higher number (e.g., 5 overlaps) , and may be decremented by 1 if SI decode does not succeed for predetermined time T. In an aspect, non-essential SIBs, X is decremented at most to 3, so that SI decode priority never equals the priority of GAPs.

It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or. ” That is, unless specified otherwise, or clear from the context, the phrase, for example, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, for example the phrase “X employs A or B” is satisfied by any of the following instances: X employs A； X employs B； or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) ..

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

Claims

A method for wireless communication by a User Equipment (UE) , comprising:

determining that one or more System Information (SI) windows for receiving at least one SI Block (SIB) overlap with at least one measurement gap used for measuring signals from one or more neighboring cells； and

disabling measurement during one or more portions of the at least one measurement gap in response to the determination.
The method of claim 1, further comprising determining that the at least one SIB has a higher priority than one or more other SIBs.
The method of claim 2, further comprising receiving an indication that the at least one SIB has a higher priority than the one or more other SIBs.
The method of claim 2, further comprising:

storing information indicating that the at least one SIB has a higher priority over the one or more other SIBs； and

subsequently deleting the stored information in response to determining that the at least one SIB has been successfully decoded.
The method of claim 1, wherein the disabling comprises disabling the measurement during the one or more portions of the at least one measurement gap temporarily until the at least one SIB is successfully decoded.
The method of claim 1, wherein the one or more SI windows and the at least one measurement gap are scheduled at the same periodicity such that each of the one or more SI windows overlaps with one of the at least one measurement gap, and

wherein the disabling measurement during one or more portions of the at least one measurement gap comprises disabling measurement during one or more portions of each of the at least one measurement gap.
The method of claim 6, further comprising:

determining that the at least one SIB has been successfully decoded； and

enabling measurement during one or more subsequent portions of the at least one measurement gap after the determination that the at least one SIB has been successfully decoded.
The method of claim 1, further comprising:

detecting a number of consecutive overlaps between measurement gaps and SI windows used for receiving the at least one SIB, and

wherein the disabling comprises disabling measurement during at least one of the measurement gaps, after the detection.
The method of claim 8, wherein the number of overlaps is set based at least on a type of the at least one SIB.
The method of claim 9, wherein the type of the SIB comprises a mandatory SIB, a critical SIB, or a non-mandatory and non-critical SIB.
The method of claim 8, further comprising:

reducing the number of overlaps in response to determining that the SIB has not been successfully decoded for a period of time.
The method of claim 11, wherein the period is determined based on an SIB schedule.