CN112673599B

CN112673599B - Modulation symbol spreading

Info

Publication number: CN112673599B
Application number: CN201880094870.6A
Authority: CN
Inventors: 张元涛; K·帕朱科斯基; 姚春海
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2018-06-22
Filing date: 2018-06-22
Publication date: 2022-07-01
Anticipated expiration: 2038-06-22
Also published as: CN112673599A; WO2019242006A1

Abstract

Embodiments of the present disclosure relate to a method, apparatus, and computer-readable storage medium for modulation symbol spreading. In an example embodiment, a network device determines a set of spreading sequences for modulation symbols for a terminal device. One spreading sequence in the set corresponds to one of the modulation symbols. The correspondence of the set of spreading sequences between modulation symbols is at least partly different from the correspondence of the further set of spreading sequences between other modulation symbols of a further terminal device in communication with the network device. Then, the network device transmits the information of the spreading sequence set to the terminal device. In this way, the peak-to-average power ratio (PAPR) can be efficiently and effectively reduced.

Description

Modulation symbol spreading

Technical Field

Embodiments of the present disclosure relate generally to the field of communications, and, in particular, to a method, apparatus, and computer-readable storage medium for modulation symbol spreading.

Background

The basic multiple access scheme for the New Radio (NR) is orthogonal for downlink and uplink data transmission, which means that the time and frequency physical resources of different users do not overlap or the signals can be distinguished from the orthogonal space/code domain. On the other hand, non-orthogonal multiple access (NOMA) schemes have recently attracted a great deal of interest, leading to an initial research project for NR in which many NOMA schemes are proposed and evaluated and are now under investigation. For NOMA, signals from multiple User Equipments (UEs) are transmitted simultaneously in the same resource (e.g., time domain resource and frequency domain resource). Thus, there will be interference between transmissions. This non-orthogonal characteristic is more pronounced as the system load increases. To combat interference between non-orthogonal transmissions, transmitter-side schemes such as spreading (linear or non-linear, with or without sparsity) and interleaving are often employed to improve performance and reduce the burden on advanced receivers.

The NOMA scheme is beneficial for unlicensed transmissions due to the availability of a large number of NOMA signatures and a correspondingly low MA signature collision rate for unlicensed transmissions. In general, benefits may cover various use cases or deployment scenarios, including enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), large-scale machine type communication (mtc), and so on. Saving signaling also saves power consumption of the UE, reduces latency and increases system capacity. However, conventional NOMA schemes typically have a high peak-to-average power ratio (PAPR), result in undesirable non-linear regions, and are difficult to achieve a desired Adjacent Channel Leakage Ratio (ACLR).

Disclosure of Invention

In general, example embodiments of the present disclosure provide a method, apparatus, and computer-readable storage medium for modulation symbol spreading.

In a first aspect, a method at a network device is provided. A set of spreading sequences for modulation symbols for the terminal device is determined. One spreading sequence in the set corresponds to one of the modulation symbols. The correspondence between the set of spreading sequences and the modulation symbols is at least partly different from the correspondence between the set of further spreading sequences and other modulation symbols of a further terminal device, which is in communication with the network device. Information of the set of spreading sequences is transmitted to the terminal device.

In a second aspect, there is provided a network device comprising: at least one processor, and a memory coupled to the at least one processor. The memory stores instructions therein that, when executed by the at least one processor, cause the network device to perform acts comprising: determining a set of spreading sequences for a modulation symbol of a terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between a further set of spreading sequences and other modulation symbols of a further terminal device, the further terminal device being in communication with a network device; and transmitting information of the set of spreading sequences to the terminal device.

In a third aspect, a method at a terminal device is provided. Information of a set of spreading sequences for modulation symbols of a terminal device is received from a network device. One spreading sequence in the set corresponds to one of the modulation symbols. The correspondence between the set of spreading sequences and the modulation symbols is at least partly different from the correspondence between the set of further spreading sequences and other modulation symbols of a further terminal device, which is in communication with the network device. Based on the received information, a set of spreading sequences is determined. The modulation symbols are spread based on a set of spreading sequences. Transmitting a signal including the spread modulation symbols to a network device.

In a fourth aspect, there is provided a terminal device comprising: at least one processor and a memory coupled to the at least one processor. The memory stores therein instructions that, when executed by the at least one processor, cause the network device to perform acts comprising: receiving, from a network device, a set of spreading sequences for a modulation symbol of a terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between a further set of spreading sequences and other modulation symbols of a further terminal device, the further terminal device being in communication with the network device; determining a set of spreading sequences based on the received information; spreading the modulation symbols based on the set of spreading sequences; and transmitting a signal including the spread modulation symbols to a network device.

In a fifth aspect, a computer-readable storage medium having a computer program stored thereon is provided. The computer program, when executed by a processor, causes the processor to perform the method according to the first aspect.

In a sixth aspect, a computer-readable storage medium having a computer program stored thereon is provided. The computer program, when executed by the processor, causes the processor to perform the method according to the third aspect.

It will be understood that this summary section is not intended to identify key or essential features of the embodiments of the disclosure, nor is it intended to be used to limit the scope of the disclosure. Other features of the present disclosure will become readily apparent from the following description.

Drawings

Some example embodiments will now be described with reference to the accompanying drawings, in which:

FIG. 1 illustrates a communication network in which embodiments of the present disclosure may be implemented;

fig. 2 illustrates a diagram of signal processing at a transmitter, in accordance with some embodiments of the present disclosure;

FIG. 3 illustrates a flow diagram of a method according to some embodiments of the present disclosure;

FIG. 4 illustrates a flow diagram of a method according to some embodiments of the present disclosure;

fig. 5 illustrates a diagram of modulation symbol mapping in accordance with some embodiments of the present disclosure;

fig. 6 illustrates a diagram of spreading sequence allocation in accordance with some embodiments of the present disclosure;

fig. 7 illustrates a flow diagram of a method according to some embodiments of the present disclosure;

fig. 8 illustrates a graph comparing PAPR performance of an Orthogonal Frequency Division Multiplexing (OFDM) scheme and a conventional NOMA scheme;

fig. 9 illustrates a comparison graph of PAPR performance of the proposed NOMA scheme, OFDM scheme, and conventional NOMA scheme; and

FIG. 10 illustrates a simplified block diagram of a device suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numbers refer to the same or similar elements.

Detailed Description

The principles of the present disclosure will now be described with reference to a few exemplary embodiments. It is to be understood that these embodiments are described for illustrative purposes only and are intended to aid those skilled in the art in understanding and practicing the present disclosure without placing any limitation on the scope of the present disclosure. The disclosure described herein may be implemented in various ways other than those described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard or protocol, such as Long Term Evolution (LTE), LTE-advanced (LTE-a), and 5G NR, and employs any suitable communication technology, including, for example, multiple-input multiple-output (MIMO), OFDM, Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), Code Division Multiplexing (CDM), bluetooth, ZigBee, Machine Type Communication (MTC), eMBB, MTC, and urrllc technologies. For purposes of discussion, in some embodiments, an LTE network, an LTE-a network, a 5G NR network, or any combination thereof are examples of communication networks.

As used herein, the term "network device" refers to any suitable device on the network side of a communication network. The network device may comprise any suitable device in an access network of a communication network, including for example a Base Station (BS), a relay, an Access Point (AP), a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a gigabit NodeB (gnb), a remote radio module (RRU), a Radio Header (RH), a Remote Radio Head (RRH), a low power node (such as femto, pico, etc.). For discussion purposes, in some embodiments, an eNB is taken as an example of a network device.

The network devices may also include any suitable devices in the core network, including, for example, multi-standard radio (MSR) radios such as MSR BSs, network controllers such as Radio Network Controllers (RNCs) or Base Station Controllers (BSCs), multi-cell/Multicast Coordination Entities (MCEs), Mobile Switching Centers (MSCs) and MMEs, operations and management (O & M) nodes, Operations Support Systems (OSS) nodes, self-organizing network (SON) nodes, positioning nodes such as enhanced serving mobile location centers (E-SMLCs), and/or Mobile Data Terminals (MDTs).

As used herein, the term "terminal device" refers to a device capable, configured for, arranged for and/or operable to communicate with a network device or a further terminal device in a communication network. The communication may involve the transmission and/or reception of wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for communicating information over the air. In some embodiments, the terminal device may be configured to transmit and/or receive information without direct human interaction. For example, the terminal device may transmit information to the network device on a predetermined schedule when triggered by an internal event or an external event or in response to a request from the network side.

Examples of end devices include, but are not limited to, User Equipment (UE) such as a smart phone, a wireless-enabled tablet computer, a Laptop Embedded Equipment (LEE), a laptop installation equipment (LME), and/or a wireless Customer Premises Equipment (CPE). For discussion purposes, some embodiments will be described below with reference to a UE as an example of a terminal device, and the terms "terminal device" and "user equipment" (UE) may be used interchangeably in the context of the present disclosure.

As used herein, the term "cell" refers to an area covered by radio signals transmitted by network equipment. Terminal devices within a cell may be served by a network device and access a communication network via the network device.

As used herein, the term "circuitry" may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry); and

(b) a combination of hardware circuitry and software, such as (if applicable): (i) a combination of analog and/or digital hardware circuit(s) and software/firmware; and (ii) any portion of hardware processor(s) with software (including digital signal processor(s), software, and memory(s) that work together to cause a device such as a mobile phone or server to perform various functions) and

(c) hardware circuit(s) and/or processor(s), such as microprocessor(s) or portions of microprocessor(s), require software (e.g., firmware) for operation, but may not be present when operation is not required.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As yet another example, as used in this application, the term circuitry is also intended to cover an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. For example, and if applicable to the particular claim element, the term circuitry would also cover a baseband integrated circuit or processor integrated circuit for a mobile device or similar integrated circuit in a server, a cellular network device, or other computing or network device.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "including" and variations thereof is to be understood as an open-ended term meaning "including, but not limited to. The term "based on" is to be understood as "based at least in part on". The terms "one embodiment" and "an embodiment" should be understood as "at least one embodiment". The term "another embodiment" should be understood as "at least one other embodiment". Other definitions (explicit and implicit) may be included below.

Fig. 1 illustrates a communication network 100 in which embodiments of the present disclosure may be implemented. The communication network 100 may conform to any suitable protocol or standard that already exists or will be developed in the future. In some embodiments, the communication network 100 may be an LTE (or LTE-a) network, an NR network, or a combination thereof.

Communication network 100 includes network device 110. The network device 110 serves two terminal devices (including a first terminal device 120 and a second terminal device 130) in the cell 111. It is to be understood that the number of network devices and terminal devices is shown for illustrative purposes only and no limitation is set forth. Communication network 100 may include any suitable number of network devices and terminal devices.

First terminal device 120 and second terminal device 130 may communicate with network device 110 or with each other via network device 110. The communication may utilize any suitable technology that already exists or will be developed in the future.

When operating as a transmitter, the first terminal device 120 or the second terminal device 130 performs signal processing before transmission. Fig. 2 illustrates a diagram 200 of data processing at a transmitter.

As shown, data from a terminal device (e.g., first terminal device 120) may be encoded, e.g., by channel coding 210, and then modulated 220. Thus, the modulation symbols of the terminal device can be obtained. The modulation symbols are mapped onto a single OFDM symbol physical resource. The modulation symbols are then spread 230 with spreading sequence(s). The spread modulation symbols are scrambled 240, precoded 250, and then mapped 260 to the allocated resources (e.g., Resource Elements (REs)). Thus, a signal comprising the spread modulation symbols may be obtained and then transmitted to a receiver, such as network device 110.

Conventionally, the NOMA schemes based on spread spectrum differ mainly in the construction of the spreading sequence, the spreading length, and the like. On the other hand, they have a transmitter-side structure similar to the higher layer, in which each modulation symbol is spread by a sequence and then mapped to a resource element.

As a result, the symbols in the frequency domain are not independently and identically distributed in each OFDM symbol, but correlation is introduced due to the single spreading sequence used, which results in a higher PAPR than with Orthogonal Multiple Access (OMA). This is shown in fig. 8, and fig. 8 illustrates a graph comparing PAPR performance of OFDM and a conventional NOMA scheme. In fig. 8, a curve 810 represents PAPR performance of an OFDM scheme, and a curve 820 represents PAPR performance of a conventional NOMA scheme, in which a Spreading Factor (SF) is 6. It can be seen that the conventional NOMA scheme generally has a higher PAPR than the OFDM scheme.

In general, a higher PAPR means that on average the operating point of the PA must be lower to avoid the non-linear region and achieve the required ACLR. This results in a reduction in efficiency. Therefore, reducing PAPR is very important for spread spectrum based schemes.

Additionally, the conventional NOMA scheme is sensitive to other cell interference. This is because a small Spreading Factor (SF), e.g., 6, results in too few sequences to be fully reused between cells.

Embodiments of the present disclosure provide a new scheme for spreading a signal. In each OFDM symbol, it is proposed to use a different spreading sequence on a per modulation symbol basis. Different terminal devices are configured with different spreading sequences for spreading modulation symbols having the same index in the frequency domain. Thus, sequence collisions for all other modulation symbols can be avoided. In this way, PAPR may be reduced and inter-cell randomization may be provided for spread spectrum based NOMA schemes.

More details will be discussed below in connection with the embodiments of fig. 3-10. Fig. 3 illustrates a flow diagram of a method 300 according to some embodiments of the present disclosure. Method 300 may be implemented at network device 110 shown in fig. 1. For discussion purposes, the method 300 will be described with reference to fig. 1.

At 310, network device 110 determines a set of spreading sequences for modulation symbols for the terminal device. The terminal device may be

terminal device

120 or 130 shown in fig. 1, or may be other suitable terminal device that communicates with network device 110 but is not shown in fig. 1. For purposes of discussion, in some embodiments, terminal device 120 is discussed in conjunction with the discussion of the terminal device. It is to be understood that this is for discussion purposes and not a limitation.

One spreading sequence corresponds to one of the modulation symbols in the set of spreading sequences. The set of spreading sequences is at least partially different from a further set of spreading sequences used by a further terminal device communicating with the network device. In the above example where the terminal device is terminal device 120, the further terminal device may be, for example, terminal device 130.

The set of spreading sequences may be determined in various ways. In some embodiments, all available spreading sequences may be divided into a plurality of groups (also referred to as "sequence groups" in embodiments of the present disclosure). The number of sequences within each group (also referred to as "sequence number" in embodiments of the present disclosure) is equal to the number of modulation symbols that can be transmitted in each OFDM symbol. Network device 110 may determine a set of spreading sequences based on the groups.

In some embodiments, the number of sequences within each group may be determined from the allocated frequency domain resources and the spreading factor. The terminal device 120 is assigned (or selected) with one group index x and one sequence index y within the group for the 1 st modulation symbol. Then, for the nth modulation symbol in the same OFDM symbol, the principle may be that the spreading sequence is in the same sequence group as the spreading sequence for the 1 st OFDM symbol, and the sequence index is implicitly decided from (Y + n-1) mod Y, where Y is the number of sequences in the same group.

Spreading sequences within the same sequence group have low cross-correlation and better correlation properties than inter-group sequences, which helps network device 110 to control interference to terminal devices served by network device 110. In some embodiments, if the number of terminal devices is less than a predetermined number, such as where only

terminal devices

120 and 130 are served by network device 110, network device 110 may assign sequences in the same sequence group to

terminal devices

120 and 130 to have lower inter-UE interference.

In some embodiments, if terminal device 120 is allocated N Physical Resource Blocks (PRBs), it may be determined that there are N x Z REs in the frequency domain, where Z indicates the number of REs per PRB, e.g., 12. In this case, the network device 110 may determine the number of sequences by dividing the number of resource elements by a Spreading Factor (SF) denoted as "K". For example, the number of sequences (denoted "Y") may be calculated as:

Y＝N*Z/K. (1)

it should be noted that Y is also the number of modulation symbols transmitted in an OFDM symbol.

In an embodiment, assuming that the number of available spreading sequences is M, the M spreading sequences may be divided into X groups, wherein

X＝floor(M/Y)＝floor(M/(N*Z/K)). (2)

Terminal device 120 may be assigned (or self-select) a spreading sequence with a group index (x) and a sequence index (y), which may be represented as a two-dimensional index (x, y). In one embodiment, (x1, y1) is configured for the first modulation symbol, which indicates that the spreading sequence for the first modulation symbol is the y 1-th spreading sequence in sequence set x 1. In this case, for the nth modulation symbol, the index of the spreading sequence may be determined as (x1, (Y1+ n-1) mod Y), where 1< ═ n < ═ Y. This means that the spreading sequence of the nth modulation symbol is the ((Y1+ n-1) mod Y) th spreading sequence in the same sequence group x 1. It is to be understood that these modulation symbols refer to modulation symbols mapped on the same OFDM symbol.

In some embodiments, to further randomize the spreading sequences from different physical resources (e.g., first symbol, second symbol.) in the time domain, the starting spreading sequence may be changed according to the number of symbols mapped. For example, there may be an offset between the sequences for the first modulation symbol for different OFDM symbols.

In addition, to randomize inter-cell interference, a spreading sequence different from cell to cell may be allocated within each group. For example, the group index may be determined by a cell Identification (ID). Alternatively, a sequence index different from cell to cell may be employed.

It is to be understood that the above-described embodiments for determining a set of spreading sequences are described for purposes of discussion, and are not intended to suggest any limitation. Further embodiments of determining a set of spreading sequences will be discussed below with reference to fig. 4.

At 320, network device 110 transmits information of the set of spreading sequences (e.g., spreading sequence group indices) to terminal device 120. In some embodiments, network device 110 may transmit information of the set of spreading sequences to terminal device 120 via a downlink control channel (e.g., a Physical Downlink Control Channel (PDCCH)). Alternatively, in some embodiments, the information of the set of spreading sequences may be transmitted via higher layer signaling, such as Radio Resource Control (RRC) signaling or Medium Access Control (MAC) signaling. The network device also transmits information of the sequence indexes within the sequence group to the terminal device. Similarly, the information may be sent via PDCCH or RRC signaling or MAC signaling. In some embodiments, the terminal device may automatically select a group and a sequence in the group as the spreading sequence for the first modulation symbol. For other modulation symbols, the spreading sequence is from the same sequence group and is determined based on the modulation symbol index. In another embodiment, the sequence in each group may be different for different terminal devices and is determined by the terminal device ID.

In some embodiments, network device 110 may transmit an index of the spreading sequences in the set. The indexes indicate those sequence groups from which the spreading sequences are selected and the positions of the spreading sequences in the respective sequence groups. For example, if there are 6 spreading sequences in the set, their indices may be two-dimensional indices such as (x1, y1), (x2, y2), (x3, y3), (x4, y4), (x5, y5), and (x6, y 6). In this case, x1, x 2.., x6 are group indexes, and y1, y 2.., y6 are sequence indexes. The group index indicates a sequence group from which the spreading sequence is selected. The sequence index indicates the position of the spreading sequence in the corresponding sequence group.

Alternatively, in some embodiments, network device 110 may transmit the index of the spreading sequences in the set, grouping information, and sequence information. The index indicates a sequence group from which a spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group. The grouping information indicates division of sequence groups, and the sequence information indicates spreading sequences in each sequence group. In this case, after receiving such information, terminal device 120 may determine that the set of spreading sequences is to be used directly without having to determine the grouping information and the sequence information itself.

In some embodiments, after receiving the information, terminal device 120 may understand the set of spreading sequences assigned for the modulation symbol and may spread the modulation symbol by applying a corresponding spreading sequence of the set of spreading sequences to one modulation symbol. More specifically, the terminal device spreads the first modulation symbol in each OFDM symbol using the indicated sequence within the indicated sequence group. For other modulation symbols, the spreading sequence is from the same sequence group and is determined based on the modulation symbol index. Terminal device 120 may then transmit a signal including the spread modulation symbols to network device 110. In this case, the network device 110 may receive a signal from the terminal device 120. Since the signal comprises modulation symbols that have been spread by a set of spreading sequences that is at least partly different from a further set of spreading sequences used by a further terminal device communicating with the network device, a spread randomization of modulation symbols of different terminal devices may be achieved. In this way, the PAPR of the proposed NOMA scheme can be reduced effectively and efficiently.

Fig. 4 illustrates a flow diagram of a method 400 for determining a set of spreading sequences, in accordance with some embodiments of the present disclosure. Method 400 may be performed, for example, at network device 110 or other suitable device.

At 410, network device 110 determines a number of sequences for the sequence group based on a bandwidth allocated to terminal device 120 and a spreading factor used by terminal device 120. The number of sequences indicates the number of spreading sequences to be included in the sequence set.

In some embodiments, network device 110 may determine the number of Resource Elements (REs) in the uplink symbol allocated to the terminal device. For example, if terminal device 120 is allocated N Physical Resource Blocks (PRBs), it may be determined that there are N x Z REs in the frequency domain, where Z indicates the number of REs per PRB, e.g., 12. Network device 110 may then determine the number of sequences by dividing the number of resource elements by a Spreading Factor (SF). For example, assuming SF-K, the number of sequences (denoted as "Y") may be calculated as: y is N X Z/K.

At 420, network device 110 determines a plurality of sequence groups from a predefined sequence pool. The number of spreading sequences in each sequence group is equal to the number of sequences. The sequence pool may include a plurality of spreading sequences. The set of spreading sequences for the modulation symbols for terminal device 120 may be determined from the available spreading sequences included in the sequence pool.

The sequence pool may be predefined or implemented in various ways. In some embodiments, the sequence pool may include a plurality of spreading sequences constructed by Quadrature Phase Shift Keying (QPSK) constellations. Table 1 shows an example of a sequence pool.

Table 1: for SF 6

Table 1 includes the construction of spreading sequences, which are expressed as follows

Where u denotes the root for the spreading sequence and SF indicates the spreading factor.

In the example shown with respect to table 1, there are P (e.g., P ═ 30) roots and, for each root, there are Q available cyclic shifts (e.g., Q ═ 6), e.g., the sequence corresponding to the first cyclic shift is

And the sequence corresponding to the second cyclic shift is

And so on. Thus, a total of P × Q sequences are available for spreading. In this example, there are 30 × 6 ═ 180 available spreading sequences.

In some embodiments, network device 110 may determine the total number of available spreading sequences in a predefined pool of sequences. Network device 110 may also determine the number of groups based on the total number of available spreading sequences and the number of sequences of the sequence group. Network device 110 may then divide the available spreading sequences into sequence groups based on the number of groups.

Fig. 5 illustrates a diagram 500 of a mapping between NOMA resource allocations and modulation symbols, in accordance with some embodiments of the present disclosure. As shown in fig. 5, N PRBs 510 allocated to terminal device 120 in an uplink symbol are illustrated as 560, where N ═ 6. The

N PRBs

510 and 560 are respectively indexed 1 to 6. Assuming that there are 12 modulation symbols for each OFDM symbol, symbol indexes of the 12 modulation symbols are shown as 1 to 12, respectively. Assuming that the spreading factor is K (e.g., K-6), the number of sequences in a group (i.e., the number of sequences) will be Y-12/K-12/6-12, corresponding to 12 modulation symbols. The total number of sequences available is P × Q/Y180/12 — 15. In this case, the sequences for 2 roots are placed in the same group. Sequences in the same group with low cross-correlation are selected.

It is to be understood that the above examples of specific values are described for purposes of discussion and not limitation. In other embodiments of the present disclosure, any suitable value may be applied.

Still referring to fig. 4, at 430, network device 110 selects one of the sequence sets of modulation symbols for the terminal device. In some embodiments, network device 110 may select a first spreading sequence for a first one of the modulation symbols within the selected set of sequences. For example, the selection may be performed based on an identity of the terminal device. Network device 110 may then determine remaining spreading sequences in the selected sequence group for remaining ones of the modulation symbols.

In some embodiments, the spreading sequences in the determined sequence group are ordered in a predetermined order. Thus, the remaining spreading sequences may be assigned to the remaining modulation symbols by cyclic shifts according to a predetermined order. This will be further discussed with respect to the embodiment shown in fig. 6.

Fig. 6 illustrates a diagram 600 of spreading sequence assignments, in accordance with some embodiments of the present disclosure. As shown, there are 12 spreading sequences S1, S2, S11, S12 in one sequence group 610. Based on the available groups and the sequences within the groups, terminal device 120 may be configured with one group and one spreading sequence within the group for the first modulation symbol in each OFDM symbol. For subsequent modulation symbols, terminal device 120 may determine the spreading sequences sequentially in the same group according to the modulation symbol index. As an example, if network device 110 configured spreading sequence S9 for first modulation symbol 621 of terminal device 120 from sequence group 610, network device 110 may use spreading sequence S6 for modulation symbol 626, and so on. Thus, network device 110 may determine a set of spreading sequences { S9, S10, S11, S12, S1, S2, S3, S4, S5, S6, S7, S8} for the modulation symbols (denoted b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, and b12, respectively) for terminal device 120. The correspondence between the set of spreading sequences and the modulation symbols is shown in table 2.

TABLE 2

Spreading sequences	Modulation symbol
		S9	b1
S10	b2
		S11	b3
S12	b4
		S1	b5
S2	b6
		S3	b7
S4	b8
		S5	b9
S6	b10
		S7	b11
S8	b12

According to an embodiment of the present disclosure, for terminal device 130, the correspondence between the set of spreading sequences and the modulation symbols is at least partially different from the correspondence of terminal device 120. In the above embodiments, network device 110 may determine a set of spreading sequences { S11, S12, S1, S2, S3, S4, S5, S6, S7, S8, S9, S10} for the modulation symbols (denoted c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, and c12, respectively) for terminal device 120. The correspondence between the set of spreading sequences and the modulation symbols is shown in table 3.

TABLE 3

Spreading sequences	Modulation symbol
		S11	c1
S12	c2
		S1	c3
S2	c4
		S3	c5
S4	c6
		S5	c7
S6	c8
		S7	c9
S8	c10
		S9	c11
S10	c12

Comparing tables 2 and 3, it can be seen that the spreading sequence is determined as S9 for the first modulation symbol b 1of terminal device 120 and S11 for the first modulation symbol c 1of terminal device 130. With respect to the second modulation symbol b2 of terminal device 120, the spreading sequence is determined as S10, and with respect to the first modulation symbol c2 of terminal device 130, the spreading sequence is determined as S12. Thus, the correspondence between the set of spreading sequences and the modulation symbols for different terminal devices is at least partially different. As a result, spread spectrum randomization of the modulation symbols of different terminal devices can be achieved.

With embodiments of the present disclosure, network device 110 may configure different terminal devices with different spreading sequences for spreading the same modulation symbol (e.g., the first modulation symbol or a modulation symbol with a particular index) in the frequency domain. In this way, sequence collisions will not occur for all other modulation symbols.

In some embodiments, network device 110 may factor the terminal device's identification (UE-ID) as another determining factor if terminal device 120 selects the sequence group and sequence index itself, such that sequence collisions may occur for only a portion of the modulation symbols.

Additionally or alternatively, in some embodiments, the long sequence may be defined in terms of an allocated Bandwidth (BW), and the spreading sequence is part of the long sequence. For example, in the case of 12 PRB allocation with SF-6, the length of the long sequence is 144(12x12) and the length of the spreading sequence is 6. The first modulation symbol may be spread by a cyclic shift of the first 6 elements of the long sequence, and the second symbol may be spread by a cyclic shift of the last 6 elements of the long sequence. It is to be understood that the above examples of specific values are described for purposes of discussion and not limitation. In other embodiments of the present disclosure, any suitable value may be applied.

Fig. 7 illustrates a flow diagram of a method 700 in accordance with some embodiments of the present disclosure. Method 700 may be implemented at

terminal device

120 or 130 shown in fig. 1. For discussion purposes, the method 700 will be described with reference to fig. 1.

At 710, the terminal device 120 receives information from the network device for a set of spreading sequences for a modulation symbol of the terminal device 120. One spreading sequence in the set corresponds to one of the modulation symbols. The correspondence between the set of spreading sequences and the modulation symbols is at least partially different from the correspondence between the set of further spreading sequences and other modulation symbols of a further terminal device (e.g. terminal device 130) communicating with the network device 110.

In some embodiments, the terminal device 120 may receive information of the set of spreading sequences via a downlink control channel (e.g., PDCCH). Alternatively, in some embodiments, terminal device 120 may receive the information of the set of spreading sequences via higher layer signaling, such as RRC signaling or MAC signaling.

In 720, the terminal device 120 determines a set of spreading sequences based on the received information.

In some embodiments, the terminal device 120 may receive 710 the index of the spreading sequences in the set. The index indicates a sequence group from which a spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group. In this case, in 720, the terminal device may determine the number of sequences of the sequence group based on the bandwidth allocated to the terminal device and the spreading factor used by the terminal device. The number of sequences indicates the number of spreading sequences to be included in the sequence group. The terminal device 120 may also determine sequence groups from a pool of predefined sequences, each sequence group comprising a sequence number of spreading sequences. Terminal device 120 may then determine a set of spreading sequences from the sequence group based on the index.

Alternatively, in some embodiments, terminal device 120 may receive the index of the spreading sequences in the set, grouping information, and sequence information at 710. The index indicates a sequence group from which a spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group. The grouping information indicates division of sequence groups, and the sequence information indicates spreading sequences in each sequence group. In this case, at 720, terminal device 120 may determine a sequence group based on the grouping information and the sequence information, and determine a set of spreading sequences from the sequence group based on the index.

At 730, the terminal device 120 spreads the modulation symbols based on the set of spreading sequences, e.g., by applying a corresponding spreading sequence of the set of spreading sequences to one of the modulation symbols.

At 740, terminal device 120 transmits a signal including the spread modulation symbols to network device 110. For example, terminal device 120 may transmit the signal via a Physical Uplink Shared Channel (PUSCH).

Since the signal comprises modulation symbols that have been spread by a set of spreading sequences, and the set of spreading sequences is at least partly different from the set of spreading sequences used by the further terminal device 130, a spread randomization of the modulation symbols of the different

terminal devices

120 and 130 may be achieved. In this way, the PAPR of the proposed NOMA scheme can be reduced effectively and efficiently.

Fig. 9 illustrates a graph comparing PAPR performance of the proposed NOMA, OFDM, and conventional NOMA schemes. In fig. 9, a curve 910 represents PAPR performance of an OFDM scheme, a curve 920 represents PAPR performance of a conventional NOMA scheme (SF ═ 6), and a curve 930 represents PAPR performance of the proposed NOMA scheme. By evaluating the performance as shown in fig. 9, the proposed NOMA scheme achieves a better PAPR performance than the OFDM scheme and a much lower PAPR than the conventional NOMA scheme. Thus, the proposed NOMA scheme advantageously reduces PAPR and thus improves efficiency of the communication network 100, compared to a conventional NOMA scheme using the same spreading sequence for all modulation symbols in each OFDM symbol.

In some embodiments, an apparatus capable of performing methods 300 and/or 400 (e.g., at network device 110) may include means for performing the respective steps of methods 300 and/or 400. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some embodiments, the apparatus comprises: means for determining, at the network device, a set of spreading sequences for modulation symbols for the terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between a further set of spreading sequences and other modulation symbols of a further terminal device, the further terminal device being in communication with the network device; and means for transmitting information of the set of spreading sequences to the terminal device.

In some embodiments, the means for determining a set of spreading sequences for a modulation symbol may comprise: means for determining a number of sequences of the sequence group based on a bandwidth allocated to the terminal device and a spreading factor used by the terminal device, the number of sequences indicating a number of spreading sequences to be included in the sequence group; means for determining a plurality of sequence groups from a predefined sequence pool, each sequence group comprising a sequence number of spreading sequences; and means for selecting a sequence group of modulation symbols for the terminal device from the plurality of sequence groups.

In some embodiments, the means for determining the number of sequences for the sequence group may comprise: means for determining a number of resource elements in an uplink symbol allocated to a terminal device; and means for determining a number of sequences by dividing the number of resource elements by a spreading factor.

In some embodiments, the means for determining the plurality of sequence groups from the predefined sequence pool may comprise: means for determining a total number of available spreading sequences in a predefined sequence pool; means for determining a number of groups based on a total number of available spreading sequences and a number of sequences of a sequence group; and means for dividing the available spreading sequences into sequence group based on the number of groups.

In some embodiments, the means for selecting one of the sequence sets of modulation symbols for the terminal device may comprise: means for selecting a first spreading sequence for a first one of the modulation symbols within the selected set of sequences; and means for determining remaining spreading sequences in the selected set of sequences for remaining ones of the modulation symbols.

In some embodiments, the spreading sequences in the determined sequence group are ordered in a predetermined order, and the remaining spreading sequences are assigned to the remaining modulation symbols by cyclic shifts according to the predetermined order.

In some embodiments, the means for selecting the first spreading sequence may comprise: means for selecting a first spreading sequence from available spreading sequences in a predefined sequence pool based on an identification of the terminal device.

In some embodiments, the means for transmitting information of the set of spreading sequences may comprise: means for transmitting an index of a spreading sequence in the set, the index indicating a sequence group in which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group; or means for transmitting an index of a spreading sequence in the set, the index indicating a sequence group in which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group, grouping information indicating division of the sequence groups, and sequence information indicating the spreading sequence in each sequence group.

In some embodiments, the apparatus may further include means for receiving a signal from a terminal device, the signal comprising modulation symbols that have been spread by a set of spreading sequences.

In some embodiments, an apparatus capable of performing method 700 (e.g., at terminal device 120 or 130) may include means for performing the respective steps of method 700. The component may be implemented in any suitable form. For example, the components may be implemented in circuitry or software modules.

In some embodiments, the apparatus comprises: means for receiving, at a terminal device from a network device, information for a set of spreading sequences for a modulation symbol of the terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between a set of further spreading sequences and other modulation symbols of a further terminal device in communication with the network device; means for determining a set of spreading sequences based on the received information; means for spreading the modulation symbols based on a set of spreading sequences; and means for transmitting a signal comprising the spread modulation symbols to a network device.

In some embodiments, the means for receiving information of a set of spreading sequences may comprise: means for receiving an index of a spreading sequence in the set, the index indicating a sequence group in which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group.

In some embodiments, the means for determining the set of spreading sequences based on the received information comprises: means for determining a number of sequences of the sequence group based on a bandwidth allocated to the terminal device and a spreading factor used by the terminal device, the number of sequences indicating a number of spreading sequences to be included in the sequence group; means for determining sequence groups from a pool of predefined sequences, each sequence group comprising a sequence number of spreading sequences; and means for determining a set of spreading sequences from the set of sequences based on the index.

In some embodiments, the means for receiving information of a set of spreading sequences may comprise: means for receiving an index of a spreading sequence in a set, grouping information, and sequence information, the index indicating a sequence group in which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group, the grouping information indicating division of the sequence group, and the sequence information indicating the spreading sequence in each sequence group.

In some embodiments, the means for determining the set of spreading sequences based on the received information comprises: means for determining a sequence group based on the grouping information and the sequence information; and means for determining a set of spreading sequences from the set of sequences based on the index.

Fig. 10 is a simplified block diagram of a device 1000 suitable for implementing embodiments of the present disclosure. Device 1000 may be implemented at or as at least a portion of network device 110 or

terminal devices

120 or 130 shown in fig. 1.

As shown, the device 1000 includes a processor 1010, a memory 1020 coupled to the processor 1010, a communication module 1040 coupled to the processor 1010, and a communication interface (not shown) coupled to the communication module 1040. The memory 1010 stores at least a program 1030. The communication module 1040 is used for bidirectional communication. The communication interface may represent any interface required for communication with other network elements, such as an X2 interface for bidirectional communication between enbs, an S1 interface for communication between a Mobility Management Entity (MME)/serving gateway (S-GW) and an eNB, a Un interface for communication between an eNB and a Relay Node (RN), or a Uu interface for communication between an eNB and a UE.

Programs 1030 are assumed to include program instructions that, when executed by an associated processor 1010, enable device 1000 to operate in accordance with embodiments of the present disclosure, as discussed herein with reference to fig. 3-4 or 7. Embodiments herein may be implemented by computer software executable by the processor 1010 or hardware of the device 1000, or a combination of software and hardware. The processor 1010 may be configured to implement various embodiments of the present disclosure.

The memory 1010 may be of any type suitable to a local technology network and may be implemented using any suitable data storage technology, such as non-transitory computer-readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. Although only one memory 1010 is shown in device 1000, there may be several physically distinct memory modules in device 1000. The processor 1010 may be of any type suitable to the local technology network, and may include one or more of general purpose computers, special purpose computers, microprocessors, Digital Signal Processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. Device 1000 may have multiple processors, such as application specific integrated circuit chips that are time dependent from a clock synchronized to the main processor.

In general, the various embodiments of the disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of the embodiments of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer-executable instructions, such as those included in program modules executed in devices on target real or virtual processors, to perform the

methods

300, 400 or 700 described above with reference to fig. 3-4 or 7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions of program modules may be executed within local or distributed devices. In a distributed facility, program modules may be located in both local and remote memory storage media.

Program code for performing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, computer program code or related data may be carried by any suitable carrier for enabling a device, apparatus or processor to perform the various processes and operations described above. Examples of the carrier include a signal, computer readable medium.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer-readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Likewise, although the above discussion contains several specific implementation details, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A method of communication, comprising:

determining, at a network device, a set of spreading sequences for a modulation symbol of a terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between another set of spreading sequences and other modulation symbols of another terminal device, the other terminal device being in communication with the network device; and

and transmitting the information of the spreading sequence set to the terminal equipment.

2. The method of claim 1, wherein determining the set of spreading sequences for a modulation symbol comprises:

determining a number of sequences for a sequence group based on a bandwidth allocated to the terminal device and a spreading factor used by the terminal device, the number of sequences indicating a number of the spreading sequences to be included in the sequence group;

determining a plurality of sequence groups from a predefined sequence pool, each sequence group comprising the spreading sequences of the number of sequences; and

selecting the sequence group of modulation symbols for the terminal device from the plurality of sequence groups.

3. The method of claim 2, wherein determining the number of sequences for the group of sequences comprises:

determining a number of resource elements in an uplink symbol allocated to the terminal device; and

determining the number of sequences by dividing the number of resource elements by the spreading factor.

4. The method of claim 2, wherein determining the plurality of sequence groups from the predefined sequence pool comprises:

determining a total number of available spreading sequences in the predefined pool of sequences;

determining a group number based on the total number of the available spreading sequences and the number of sequences for a group of sequences; and

based on the number of groups, dividing the available spreading sequences into the sequence groups.

5. The method of claim 2, wherein selecting the set of sequences of the modulation symbols for the terminal device comprises:

selecting a first spreading sequence for a first one of the modulation symbols within the selected set of sequences; and

determining remaining spreading sequences in the selected set of sequences for remaining ones of the modulation symbols.

6. The method according to claim 5, wherein the determined spreading sequences in the sequence group are ordered in a predetermined order, and wherein the remaining spreading sequences are assigned to the remaining modulation symbols by cyclic shifts according to the predetermined order.

7. The method of claim 5, wherein selecting the first spreading sequence comprises:

selecting the first spreading sequence from available spreading sequences in the predefined sequence pool based on the identity of the terminal device.

8. The method of claim 1, wherein transmitting the information of the set of spreading sequences comprises one of:

transmitting an index of a spreading sequence in the set, the index indicating a sequence group from which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group; and

transmitting an index of a spreading sequence in the set, packet information, and sequence information, the index indicating a sequence group from which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group, the packet information indicating division of the sequence groups, and the sequence information indicating a spreading sequence in each sequence group.

9. The method of any of claims 1 to 8, further comprising:

receiving a signal from the terminal device, the signal comprising the modulation symbols that have been spread by the set of spreading sequences.

10. A method of communication, comprising:

receiving, at a terminal device from a network device, information for a set of spreading sequences for a modulation symbol of the terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between another set of spreading sequences and other modulation symbols of another terminal device, the another terminal device being in communication with the network device;

determining the set of spreading sequences based on the received information;

spreading the modulation symbols based on the set of spreading sequences; and

transmitting a signal including the spread modulation symbols to the network device.

11. The method of claim 10, wherein receiving the information of the set of spreading sequences comprises:

receiving an index of a spreading sequence in the set, the index indicating a sequence group from which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group.

12. The method of claim 11, wherein determining the set of spreading sequences based on the received information comprises:

determining sequence groups from a predefined sequence pool, each sequence group comprising a spreading sequence of the number of sequences; and

determining the set of spreading sequences from the sequence group based on the index.

13. The method of any of claims 10-12, wherein receiving the information of the set of spreading sequences comprises:

receiving an index of a spreading sequence in the set, grouping information and sequence information, the index indicating a sequence group from which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group, the grouping information indicating division of the sequence groups, and the sequence information indicating a spreading sequence in each sequence group.

14. The method of claim 13, wherein determining the set of spreading sequences based on the received information comprises:

determining the sequence group based on the grouping information and the sequence information; and

15. A network device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory storing instructions therein, which when executed by the at least one processor, cause the network device to perform acts comprising:

determining a set of spreading sequences of modulation symbols for a terminal device, one spreading sequence of the set corresponding to one of the modulation symbols, a correspondence between the set of spreading sequences and the modulation symbol being at least partially different from a correspondence between another set of spreading sequences and other modulation symbols of another terminal device, the other terminal device being in communication with the network device; and

16. The network device of claim 15, wherein determining the set of spreading sequences for a modulation symbol comprises:

17. The network device of claim 16, wherein determining the number of sequences for the set of sequences comprises:

18. The network device of claim 16, wherein determining the plurality of sequence groups from the predefined sequence pool comprises:

19. The network device of claim 16, wherein selecting the sequence group of the modulation symbols for the terminal device comprises:

20. The network device of claim 19, wherein the determined spreading sequences in the sequence group are ordered in a predetermined order, and wherein the remaining spreading sequences are assigned to the remaining modulation symbols by cyclic shifts according to the predetermined order.

21. The network device of claim 19, wherein selecting the first spreading sequence comprises:

22. The network device of claim 15, wherein transmitting the information of the set of spreading sequences comprises one of:

transmitting an index of a spreading sequence in the set, the index indicating a sequence group from which the spreading sequence is selected and a position of the spreading sequence in the corresponding sequence group, grouping information indicating division of the sequence groups, and sequence information indicating a spreading sequence in each sequence group.

23. The network device of any of claims 15-22, wherein the actions further comprise:

24. A terminal device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory having instructions stored therein that, when executed by the at least one processor, cause the terminal device to perform acts comprising:

determining the set of spreading sequences based on the received information;

spreading the modulation symbols based on the set of spreading sequences; and

25. The terminal device of claim 24, wherein receiving the information of the set of spreading sequences comprises:

26. The terminal device of claim 25, wherein determining the set of spreading sequences based on the received information comprises:

27. The terminal device of any of claims 24 to 26, wherein receiving the information of the set of spreading sequences comprises:

28. The terminal device of claim 27, wherein determining the set of spreading sequences based on the received information comprises:

29. A computer-readable storage medium, on which a computer program is stored, which, when executed by a processor, causes the processor to carry out the method according to any one of claims 1 to 9.

30. A computer-readable storage medium, on which a computer program is stored, which, when executed by a processor, causes the processor to carry out the method according to any one of claims 10 to 14.