WO2019157618A1

WO2019157618A1 - Techniques and apparatuses for papr and inter-cell interference reduction for non-orthogonal multiple access

Info

Publication number: WO2019157618A1
Application number: PCT/CN2018/076613
Authority: WO
Inventors: Jing LEI; Renqiu Wang; Tingfang Ji; Joseph Binamira Soriaga; Yiqing Cao; Seyong PARK; Naga Bhushan; Wanshi Chen
Original assignee: Qualcomm Incorporated
Priority date: 2018-02-13
Filing date: 2018-02-13
Publication date: 2019-08-22

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment may process a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or precode a block of the data stream using a cell-specific precoding sequence; and transmit the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence. Numerous other aspects are provided.

Description

TECHNIQUES AND APPARATUSES FOR PAPR AND INTER-CELL INTERFERENCE REDUCTION FOR NON-ORTHOGONAL MULTIPLE ACCESS

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication, and more particularly to techniques and apparatuses for peak-to-average power ratio (PAPR) and inter-cell interference reduction for non-orthogonal multiple access (NOMA) .

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, etc. ) . 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-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs) . A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP) , a radio head, a transmit receive point (TRP) , a new radio (NR) BS, a 5G Node B, and/or the like.

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New radio (NR) , which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP) . NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL) , using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM) ) on the uplink (UL) , as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and NR technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ these technologies.

SUMMARY

In some aspects, a method for wireless communication may include processing a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or precoding a block of the data stream using a cell-specific precoding sequence; and transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.

In some aspects, a user equipment for wireless communication may include one or more processors configured to process a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or precode a block of the data stream using a cell-specific precoding sequence; and transmit the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a user equipment, may cause the one or more processors to process a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or precode a block of the data stream using a cell-specific precoding sequence; and transmit the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.

In some aspects, an apparatus for wireless communication may include means for processing a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or means for precoding a block of the data stream using a cell-specific precoding sequence; and means for transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, wireless communication device, and processing system as substantially described herein with reference to and as illustrated by the accompanying drawings and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 2 is a block diagram conceptually illustrating an example of a base station in communication with a user equipment (UE) in a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 3 is a diagram illustrating an example of processing a data stream using a cell-specific mask sequence to reduce PAPR for NOMA, in accordance with various aspects of the present disclosure.

Fig. 4 is a diagram illustrating an example of processing a data stream using a cell-specific precoding sequence to reduce PAPR for NOMA, in accordance with various aspects of the present disclosure.

Fig. 5 is a diagram illustrating an example process performed, for example, by a user equipment, in accordance with various aspects of the present disclosure.

Figs. 6A-6C are diagrams illustrating examples of performance improvements associated with use of a cell-specific mask sequence or a cell-specific precoding sequence, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

In 5G/NR, some communications may use CP-OFDM with non-orthogonal multiple access (NOMA) . NOMA refers to transmission/reception schemes characterized by non-orthogonal, inter-UE resource allocation (e.g. time, frequency, code, space, etc. ) . One technique for achieving NOMA is resource spread multiple access (RSMA) . In general, NOMA can use a variety of waveforms, including CP-OFDM and DFT-s-OFDM, which may work on the uplink. CP-OFDM with NOMA may be used for both DL and UL transmission.

For a NOMA UE using CP-OFDM, a data tone transmission of the UE may be orthogonalized using OFDM. That is, the data tones belonging to a single UE will not interference with each other. Among multiple NOMA UEs belonging to the same cell, resource allocations of the multiple NOMA UEs are non-orthogonal. That is, data tones/spreading codes/time slots/spatial beams of the UEs will interfere with each other. This mutual interference may be controlled or configured by the NOMA codebook. At the receiver side, by invoking advanced algorithms for multi-user detection, such controlled interference can be mitigated. As a result, the sum rate of NOMA can be enhanced.

However, some NOMA techniques, such as RSMA, may increase a peak-to-average power ratio (PAPR) of the waveform. This may be exacerbated as an overloading ratio of the waveform (e.g., a number of NOMA UEs divided by a spreading factor of the waveform) increases. A high PAPR is undesirable because an amplifier requires a higher backoff than for a low PAPR. In addition, due to the non-orthogonality of the signal, inter-cell interference may have a more destructive effect than for other (e.g., orthogonal) approaches.

Some techniques and apparatuses described herein provide for precoding or processing techniques to reduce PAPR. For example, some techniques and apparatuses described herein may provide for reduction of PAPR using a single-stage RSMA technique or a two-stage RSMA technique. This reduction may be achieved using a cell-specific sequence, such as a cell-specific mask sequence and/or a cell-specific precoding sequence. Thus, the PAPR of a NOMA signal may be reduced while preserving a low-cross-correlation property of the NOMA signal. Furthermore, these cell-specific sequences may be configured to reduce inter-cell interference of the NOMA UEs, thereby improving radio performance of the NOMA UEs.

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques 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.

It is noted that while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

Fig. 1 is a diagram illustrating a network 100 in which aspects of the present disclosure may be practiced. The network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. Wireless network 100 may include a number of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, a NR BS, a Node B, a gNB, a 5G node B (NB) , an access point, a transmit receive point (TRP) , and/or the like. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG) ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in Fig. 1, a BS 110a may be a macro BS for a macro cell 102a, a BS 110b may be a pico BS for a pico cell 102b, and a BS 110c may be a femto BS for a femto cell 102c. A BS may support one or multiple (e.g., three) cells. The terms “eNB” , “base station” , “NR BS” , “gNB” , “TRP” , “AP” , “node B” , “5G NB” , and “cell” may be used interchangeably herein.

In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the access network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network.

Wireless network 100 may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS) . A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in Fig. 1, a relay station 110d may communicate with macro BS 110a and a UE 120d in order to facilitate communication between BS 110a and UE 120d. A relay station may also be referred to as a relay BS, a relay base station, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in wireless network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts) .

A network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., 120a, 120b, 120c) may be dispersed throughout wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, etc. A UE may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet) ) , an entertainment device (e.g., a music or video device, or a satellite radio) , a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, such as sensors, meters, monitors, location tags, etc., that may communicate with a base station, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as may be implemented as NB-IoT (narrowband internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE) . UE 120 may be included inside a housing that houses components of UE 120, such as processor components, memory components, and/or the like.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a frequency channel, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed. In such a case, the RAT may use a NOMA configuration for radio access of UEs covered by the RAT.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within the scheduling entity’s service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. This scheduling may be non-orthogonal in some cases (e.g., when using RSMA or another NOMA technique) .

Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs) . In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access to time–frequency resources and having a cellular configuration, a P2P configuration, and a mesh configuration, a scheduling entity and one or more subordinate entities may communicate utilizing the scheduled resources.

In some aspects, two or more UEs 120 (e.g., shown as UE 120a and UE 120e) may communicate directly using one or more sidelink channels (e.g., without using a BS 110 as an intermediary to communicate with one another) . For example, the UEs 120 may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, and/or the like) , a mesh network, and/or the like. In this case, the UE 120 may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the BS 110.

As indicated above, Fig. 1 is provided merely as an example. Other examples are possible and may differ from what was described with regard to Fig. 1.

Fig. 2 shows a block diagram of a design 200 of BS 110 and UE 120, which may be one of the base stations and one of the UEs in Fig. 1. BS 110 may be equipped with T antennas 234a through 234t, and UE 120 may be equipped with R antennas 252a through 252r, where in general T ≥ 1 and R ≥ 1.

At BS 110, a transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS (s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI) , etc. ) and control information (e.g., CQI requests, grants, upper layer signaling, etc. ) and provide overhead symbols and control symbols. Transmit processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS) ) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively. According to various aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information.

At UE 120, antennas 252a through 252r may receive the downlink signals from BS 110 and/or other base stations and may provide received signals to demodulators (DEMODs) 254a through 254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all R demodulators 254a through 254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to a data sink 260, and provide decoded control information and system information to a controller/processor 280. A channel processor may determine reference signal received power (RSRP) , received signal strength indicator (RSSI) , reference signal received quality (RSRQ) , channel quality indicator (CQI) , etc.

On the uplink, at UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, etc. ) from controller/processor 280. Transmit processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, etc. ) , and transmitted to BS 110. In some aspects, the transmit processor 264, the TX MIMO processor 266, and/or modulator 254 may encode or process the data based at least in part on a cell-specific sequence described herein, such as a cell-specific mask sequence or a cell-specific precoding sequence.

At BS 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to controller/processor 240. BS 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller/processor 290, and memory 292.

In some aspects, one or more components of UE 120 may be included in a housing. Controller/processor 240 of BS 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with PAPR and inter-cell interference reduction for NOMA, as described in more detail elsewhere herein. For example, controller/processor 240 of BS 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 500 of Fig. 5 and/or other processes as described herein.

Memories

242 and 282 may store data and program codes for BS 110 and UE 120, respectively. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

The stored program codes, when executed by controller/processor 280 and/or other processors and modules at UE 120, may cause the UE 120 to perform operations described with respect to process 500 of Fig. 5. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, UE 120 may include means for processing a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell- specific mask sequence; means for precoding a block of the data stream using a cell-specific precoding sequence; means for transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence; and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2.

While blocks in Fig. 2 are illustrated as distinct components, the functions described above with respect to the blocks may be implemented in a single hardware, software, or combination component or in various combinations of components. For example, the functions described with respect to the transmit processor 264, the receive processor 258, and/or the TX MIMO processor 266 may be performed by or under the control of controller/processor 280.

As indicated above, Fig. 2 is provided merely as an example. Other examples are possible and may differ from what was described with regard to Fig. 2.

Fig. 3 is a diagram illustrating an example 300 of processing a data stream using a cell-specific mask sequence to reduce PAPR for NOMA, in accordance with various aspects of the present disclosure.

As shown in Fig. 3, the block diagram shown by reference numbers 305-325 may relate to a single-stage spreading technique, whereas the block diagram shown by reference numbers 330-355 may relate to a two-stage spreading technique. As shown by reference number 305, a UE 120 may obtain (e.g., receive, generate, determine, etc. ) a data stream. As shown by reference number 310, the UE 120 may perform spreading of the data stream using a short sequence. For example, the UE 120 may be associated with a codebook of short sequences. The short sequences may be configured to achieve NOMA (e.g., based at least in part on resource spread multiple access or another technique) . By spreading the data stream using the short sequence, NOMA may be achieved.

As a more particular example, the codebook may be represented by a matrix

of size N by K:

wherein

identifies a short sequence used by UE n. In the above matrix, K is a spreading factor/resource size and N is a number of UEs. For NOMA transmissions, N > K.

As shown by reference number 315, the UE 120 may multiply the short sequence codewords by a cell-specific mask sequence. For example, the cell-specific mask sequence may be a function of a cell identifier of a cell associated with the UE 120. In some aspects, the cell-specific mask sequence may include a constant-amplitude zero autocorrelation (CAZAC) sequence, a chirp sequence, a discrete Fourier transform sequence, and/or the like. For example, the cell-specific mask sequence may be configured to reduce PAPR and inter-cell interference of the UE 120 when combined with the codewords. By multiplying the codewords of the codebook by the cell-specific mask sequence, PAPR and inter-cell interference may be reduced.

As a more particular example, for a cell-specific mask sequence represented by W _q,

wherein q is a function of the cell identifier. The modified short sequence used by UE 120 (e.g., after multiplication by W _q) may be represented by

In other words, the UE 120 may replace codebook

by

as shown here:

The above operations may improve PAPR based at least in part on increasing systematic randomness of the NOMA signal. For example, the legacy NOMA codebook described in connection with reference number 310 may have good correlation properties but poor PAPR, since PAPR was not the controlled variable when creating the codebook. The cell-specific mask sequence (and the cell-specific precoding sequence described in connection with Fig. 4, below) modify the codebook so that the correlation properties are preserved while reducing the PAPR of NOMA signals generated using the codebook. Furthermore, since the sequences are cell-specific based at least in part on a cell identifier, inter-cell interference may be reduced.

As shown by reference number 320, the UE 120 may perform a serialization to parallelization operation with regard to the processed data stream. As shown by reference number 325, the UE 120 may perform OFDM modulation of the processed data stream. In this way, the UE 120 reduces PAPR of the NOMA waveform, and reduces inter-cell interference of the NOMA waveform, while preserving the correlation properties of the NOMA waveform.

As shown by reference number 330, for the two-stage spreading technique, the UE 120 may obtain a data stream. As shown by reference number 335, the UE 120 may perform spreading using the codebook of the short sequence, as described in more detail above. As shown by reference number 340, the UE 120 may use the cell-specific mask sequence to generate the codebook, as described in more detail above. This reduces PAPR of a signal generated using the two-stage spreading technique while preserving correlation of the signal, and reduces inter-cell interference.

As shown by reference number 345, the UE 120 may perform scrambling of the processed data stream using segments of a long sequence. For example, the long sequence may be a Gold sequence, a PN sequence, a chirp sequence, and/or the like. The combination of spreading and scrambling may be termed a two-stage spreading technique. The two-stage spreading technique may have better PAPR performance than the one-stage spreading technique. However, by processing the data stream using the cell-specific mask sequence, the PAPR may be further improved.

In some aspects, parameters for W _q and

can be dynamically signaled, or semi-persistently configured by BS 110. For example, the parameters may be configured using downlink control information, radio resource configuration (RRC) messaging, and/or the like.

As shown by reference number 350, the UE 120 may perform a serialization to parallelization operation with regard to the processed data stream. As shown by reference number 355, the UE 120 may perform OFDM modulation of the processed data stream.

As indicated above, Fig. 3 is provided as an example. Other examples are possible and may differ from what was described with respect to Fig. 3.

Fig. 4 is a diagram illustrating an example 400 of processing a data stream using a cell-specific precoding sequence to reduce PAPR for NOMA, in accordance with various aspects of the present disclosure. Fig. 4 shows examples using a single-stage spreading technique (reference numbers 405-425) and a two-stage spreading technique (reference number 430) .

As shown in Fig. 4, and by reference number 405, the UE 120 may obtain a data stream. As shown by reference number 410, the UE 120 may perform spreading of the data stream using a short sequence. For example, the UE 120 may perform spreading as described above in connection with reference number 310 of Fig. 3. In some aspects, the UE 120 may perform the spreading based at least in part on a codebook that is multiplied by a cell-specific mask sequence, as described in connection with reference number 315 of Fig. 3, above. In other words, the operations described in Figs. 3 and 4 can be performed with regard to the same data stream, thereby further improving PAPR and reducing inter-cell interference. As shown by reference number 415, the UE 120 may perform a serialization to parallelization operation with regard to the data stream.

As shown by reference number 420, the UE 120 may precode a block of the data stream using a cell-specific precoding sequence. For example, the UE 120 may precode the block of the data stream (e.g., a concatenation or repetition of a spreading sequence for the block) in the frequency domain. The cell-specific precoding sequence may reduce inter-cell interference based at least in part on being cell-specific (e.g., based at least in part on being a function of a cell identifier) . Furthermore, the cell-specific precoding sequence may be configured to reduce PAPR of the data stream while preserving the correlation properties of the data stream. In this way, an amplifier of the UE 120 may use a lower backoff value, thereby improving range and throughput of the UE 120.

As a more particular example, the cell-specific precoding sequence may be a cell-specific sequence

where q may be a function of a cell identifier, L is a size of a resource element allocated for UE 120, r is a root index, and L and r are relatively prime. Examples of such a sequence include a CAZAC sequence with length K, a DFT sequence with length K, or a chirp sequence with length K. In some aspects, parameters of

may be broadcast by the BS 110 to UEs covered by the BS 110 before starting the NOMA transmission. As above, parameters for

can be dynamically signaled, or semi-persistently configured by the BS 110 (e.g., using downlink control information, RRC messaging, and/or the like) . As shown by reference number 425, the UE 120 may perform OFDM modulation on the precoded data stream.

As shown by reference number 430, the two-stage spreading case may be similar. For example, the precoding may be performed before OFDM modulation is performed on the precoded data stream. Notably, performing the precoding using the cell-specific precoding sequence (in the two-stage spreading case and the single stage spreading case) may provide PAPR performance that surpasses a baseline PAPR performance without spreading or with legacy RSMA, as described in more detail in connection with Figs. 6A-6C.

As indicated above, Fig. 4 is provided as an example. Other examples are possible and may differ from what was described with respect to Fig. 4.

Fig. 5 is a diagram illustrating an example process 500 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 500 is an example where a UE (e.g., UE 120) performs PAPR and inter-cell interference reduction for NOMA. In some aspects, process 500 may be performed by a device other than a UE, such as a BS (e.g., BS 110) and/or the like.

As shown in Fig. 5, in some aspects, process 500 may include processing a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence (block 510) . For example, the UE may process (e.g., using controller/processor 280, transmit processor 264, the TX MIMO processor 266, modulator 254, and/or the like) a data stream. The data stream may be associated with NOMA with resource spreading (e.g., using RSMA or a different resource spreading technique) . The UE may process the data stream based at least in part on a codebook of spreading sequences. The codebook of spreading sequences may be conditioned using (e.g., multiplied by) a cell-specific mask sequence.

As shown in Fig. 5, in some aspects, process 500 may include precoding a block of the data stream using a cell-specific precoding sequence (block 520) . For example, the UE may precode (e.g., using controller/processor 280, transmit processor 264, the TX MIMO processor 266, modulator 254, and/or the like) a block of the data stream using a cell-specific precoding sequence. In some aspects, the UE 120 may perform blocks 510 and 520 for the same data stream. In some aspects, the UE 120 may perform only one of block 510 or 520 for a data stream.

As shown in Fig. 5, in some aspects, process 500 may include transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence (block 530) . For example, the UE may transmit (e.g., using controller/processor 280, transmit processor 264, TX MIMO processor 266, MOD 254, antenna 252, and/or the like) the data stream. In some aspects, the UE may transmit the data stream after processing the data stream using the codebook that is conditioned using the cell-specific mask sequence. Additionally, or alternatively, the UE may transmit the data stream after precoding a block of the data stream using the cell-specific precoding sequence.

Process 500 may include additional aspects, such as any single aspect or any combination of aspects described below.

In some aspects, the codebook identifies short spreading sequences for non-orthogonal resource spreading of the data stream. In some aspects, the cell-specific mask sequence is based at least in part on a cell identifier associated with the UE. In some aspects, the cell-specific mask sequence is based at least in part on a constant amplitude zero autocorrection (CAZAC) sequence, a chirp sequence, or a discrete Fourier transform sequence. In some aspects, the cell-specific mask sequence is configured to reduce peak to power average ratio (PAPR) and inter-cell interference, without modifying the correlation properties of intra-cell UEs performing non-orthogonal multiple access.

In some aspects, parameters for the codebook or the cell-specific mask sequence are signaled dynamically. In some aspects, parameters for the codebook or the cell-specific mask sequence are configured semi-persistently. In some aspects, processing the data stream is performed before scrambling the data stream using a long sequence. In some aspects, the cell-specific precoding sequence comprises a chirp sequence or a constant amplitude zero autocorrection (CAZAC) sequence. In some aspects, the cell-specific precoding sequence is configured to reduce peak to power average ratio (PAPR) and inter-cell interference. In some aspects, parameters relating to the codebook or the cell-specific precoding sequence are received by the UE before the data stream is transmitted by the UE. In some aspects, parameters relating to the codebook or the cell-specific precoding sequence are dynamically signaled to the UE. In some aspects, parameters relating to the codebook or the cell-specific precoding sequence are configured semi-persistently. In some aspects, precoding the data stream is performed after resource spreading and/or scrambling of the data stream. In some aspects, the precoding is performed in the frequency domain.

Although Fig. 5 shows example blocks of process 500, in some aspects, process 500 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 5. Additionally, or alternatively, two or more of the blocks of process 500 may be performed in parallel.

Fig. 6A shows an example 605 of PAPR performance without using the cell-specific mask sequence to condition the codebook. As can be seen, in the single-stage spreading case, the PAPR increases as the overloading ratio of the cell increases.

Fig. 6B shows an example 610 of PAPR performance while using the cell-specific mask sequence to condition the codebook. As can be seen, in comparison to Fig. 6A, PAPR performance is improved, particularly as the overloading ratio increases.

Fig. 6C shows an example 615 of PAPR performance using a cell-specific precoding sequence. The baseline performance for legacy RSMA using a long code only, and for quadrature phase shift keying (QPSK) without spreading, are shown by reference numbers 620 (for two-stage spreading) and 625 (for single stage spreading) . As shown by reference number 630, the cell-specific precoding sequence may provide better PAPR performance for two-stage spreading than legacy RSMA or QPSK without spreading. As shown by reference number 635, the cell-specific precoding sequence may provide better PAPR performance for single-stage spreading than legacy RSMA or QPSK without spreading. This PAPR performance increase may be more significant as the overloading factor increases.

As indicated above, Figs. 6A-6C are provided as examples. Other examples are possible and may differ from what was described with respect to Figs. 6A-6C.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term component is intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software.

Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.

It will be apparent that systems and/or methods, described herein, may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code-it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of possible aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of possible aspects includes each dependent claim in combination with every other claim in the claim set. 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) .

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc. ) , and may be used interchangeably with “one or more. ” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.

Claims

A method of wireless communication performed by a user equipment (UE) , comprising:

processing a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or

precoding a block of the data stream using a cell-specific precoding sequence; and

transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.
The method of claim 1, wherein the codebook identifies short spreading sequences for non-orthogonal resource spreading of the data stream.
The method of claim 1, wherein the cell-specific mask sequence is based at least in part on a cell identifier associated with the UE.
The method of claim 1, wherein the cell-specific mask sequence is based at least in part on a constant amplitude zero autocorrection (CAZAC) sequence, a chirp sequence, or a discrete Fourier transform sequence.
The method of claim 1, wherein the cell-specific mask sequence is configured to reduce peak to power average ratio (PAPR) and inter-cell interference, and to preserve the low correlation property of intra-cell UEs performing non-orthogonal multiple access.
The method of claim 1, wherein parameters for the codebook or the cell-specific mask sequence are signaled dynamically.
The method of claim 1, wherein parameters for the codebook or the cell-specific mask sequence are configured semi-persistently.
The method of claim 1, wherein processing the data stream is performed before scrambling the data stream using a long sequence.
The method of claim 1, wherein the cell-specific precoding sequence comprises a chirp sequence or a constant amplitude zero autocorrection (CAZAC) sequence.
The method of claim 1, wherein the cell-specific precoding sequence is configured to reduce peak to power average ratio (PAPR) and inter-cell interference.
The method of claim 1, wherein parameters relating to the codebook or the cell-specific precoding sequence are received by the UE before the data stream is transmitted by the UE.
The method of claim 1, wherein parameters relating to the codebook or the cell-specific precoding sequence are dynamically signaled to the UE.
The method of claim 1, wherein parameters relating to the codebook or the cell-specific precoding sequence are configured semi-persistently.
The method of claim 1, wherein precoding the data stream is performed after resource spreading and/or scrambling of the data stream.
The method of claim 1, wherein the precoding is performed in the frequency domain.
The method of claim 1, wherein processing the data stream, precoding the block of the data stream, and transmitting the data stream comprise:

processing the data stream based at least in part on the codebook of spreading sequences that is conditioned using the cell-specific mask sequence;

precoding the block of the data stream using the cell-specific precoding sequence; and

transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, and after precoding the block of the data stream using the cell-specific precoding sequence.
A user equipment for wireless communication, comprising:

a memory; and

one or more processors operatively coupled to the memory, the memory and the one or more processors configured to:

process a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or

precode a block of the data stream using a cell-specific precoding sequence; and

transmit the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.
A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising:

one or more instructions that, when executed by one or more processors of a user equipment, cause the one or more processors to:

process a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or

precode a block of the data stream using a cell-specific precoding sequence; and

transmit the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.
An apparatus for wireless communication, comprising:

means for processing a data stream, which is associated with non-orthogonal multiple access with resource spreading, based at least in part on a codebook of spreading sequences that is conditioned using a cell-specific mask sequence; or

means for precoding a block of the data stream using a cell-specific precoding sequence; and

means for transmitting the data stream after processing the data stream based at least in part on the codebook that is conditioned using the cell-specific mask sequence, or after precoding the block of the data stream using the cell-specific precoding sequence.