CN108123903B

CN108123903B - Signal processing method and device in communication system

Info

Publication number: CN108123903B
Application number: CN201611073505.6A
Authority: CN
Inventors: 骆喆; 陶涛; 刘建国; 沈钢; 孟艳
Original assignee: Nokia Shanghai Bell Co Ltd
Current assignee: Nokia Communications (Shanghai) Co., Ltd.
Priority date: 2016-11-29
Filing date: 2016-11-29
Publication date: 2021-12-14
Anticipated expiration: 2036-11-29
Also published as: WO2018100428A1; CN108123903A

Abstract

The present disclosure relates to a signal processing method and apparatus in a communication system. The present disclosure utilizes orthogonal and quasi-orthogonal spreading sequences and spatial channels to differentiate data for terminal devices. Since the spreading sequences used by the data of the same terminal equipment are orthogonal, the user's own interference is eliminated. The spreading sequences used by different terminal devices are quasi-orthogonal, and the interference between users is suppressed by the spatial channel. Compared with other non-orthogonal multi-user access schemes, the present disclosure can increase the supported overload factor through the combination of orthogonal spreading sequences and spatial channels.

Description

Signal processing method and apparatus in communication system

Technical Field

The present disclosure relates generally to the field of communications, and more particularly, to a signal processing method and apparatus in a communication system.

Background

A fifth generation (5G) mobile communication system needs to support a large-scale machine type communication mtc scenario. In a diversified mtc scenario, short packet traffic on the uplink is widespread. Since the grant-free contention based uplink transmission for the short packet can reduce signaling overhead and transmission delay, the grant-free contention based uplink transmission for the short packet plays an important role.

In a conventional mobile communication system, when a terminal device in an idle state needs to transmit some short packets upstream, the terminal device needs to connect to a network device (e.g., a base station device such as an eNB or a NodeB) and acquire an uplink transmission permission before transmitting data. At this time, the mobile communication system needs to face high signaling overhead and large connection delay for short packet transmission. And the uplink transmission without the authorization contention can realize one-step uplink transmission. In other words, the terminal device transmits data using the contention-based uplink, and the base station can recover the data.

In contention-based uplink transmission, there is a possibility that data signals for different active terminal devices collide because the network device does not allocate resources for the data. It is therefore desirable to design the form of the signal to reduce the probability of collisions. On the other hand, the transmission capacity for each terminal device and the maximum number of active terminal devices that the system can simultaneously support are important measures of signal design goodness and badness.

Disclosure of Invention

According to a first aspect of the present disclosure, a signal processing method is disclosed. The method comprises modulating a signal to be transmitted in a frequency domain; spreading the modulated signal with an orthogonal spreading sequence, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence; and transforming the spread signal from the frequency domain to the time domain.

According to a second aspect of the present disclosure, a signal processing method is disclosed. The method includes obtaining information related to a plurality of terminal devices, the information including an orthogonal spreading sequence specific to the terminal devices and a channel response for the terminal devices, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence; receiving a signal to be processed; transforming the received signal from the time domain to the frequency domain; and despreading the transformed signal based at least in part on the information.

According to a third aspect of the present disclosure, a terminal device is disclosed. The terminal device includes a controller and a memory including instructions. The instructions, when executed by the controller, cause the terminal device to perform actions. The actions include: modulating a signal to be transmitted in a frequency domain; spreading the modulated signal with an orthogonal spreading sequence, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence; and transforming the spread signal from the frequency domain to the time domain.

According to a fourth aspect of the present disclosure, a network device is disclosed. The network device includes a controller and a memory including instructions. The instructions, when executed by the controller, cause the network device to perform actions. The actions include obtaining information related to a plurality of terminal devices, the information including an orthogonal spreading sequence specific to the terminal device and a channel response for the terminal device, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence; receiving a signal to be processed; transforming the received signal from the time domain to the frequency domain; and despreading the transformed signal based at least in part on the information.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings. In exemplary embodiments of the present disclosure, like reference numerals generally represent like parts.

Fig. 1 shows an architectural block diagram of a communication system according to an embodiment of the present disclosure;

fig. 2 shows a flow diagram of a signal processing method according to a first aspect of an embodiment of the present disclosure;

fig. 3 shows a flow chart of a signal processing method according to a second aspect of an embodiment of the present disclosure;

fig. 4 shows a block diagram of an apparatus according to a third aspect of an embodiment of the disclosure;

fig. 5 shows a block diagram of an apparatus according to a fourth aspect of an embodiment of the disclosure;

fig. 6 illustrates a block diagram of an apparatus in accordance with certain embodiments of the present disclosure.

Fig. 7 shows a signal processing performance versus graph according to an embodiment of the present disclosure.

Detailed Description

The principles and spirit of the present disclosure will be described with reference to a number of exemplary embodiments shown in the drawings. It is understood that these specific embodiments are described merely to enable those skilled in the art to better understand and implement the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

The term "network device" as used herein refers to a base station or other entity or node having a particular function in a communication network. A "base station" (BS) may represent a node B (NodeB or NB), an evolved node B (eNodeB or eNB), a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), a relay, or a low power node such as a pico base station, a femto base station, or the like. In the context of the present disclosure, the terms "network device" and "base station" may be used interchangeably for purposes of discussion convenience, and may primarily be referred to as an eNB as an example of a network device.

The term "terminal equipment" or "user equipment" (UE) as used herein refers to any terminal equipment capable of wireless communication with a base station or with each other. As an example, the terminal device may include a Mobile Terminal (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), a Mobile Station (MS), or an Access Terminal (AT), and the above-described devices in a vehicle. In the context of the present disclosure, the terms "terminal device" and "user equipment" may be used interchangeably for purposes of discussion convenience.

To date, many non-orthogonal multi-user access (NOMA) schemes have been proposed, such as sparse multiple access SCMA, resource-extended multiple access RSMA, etc. However, these NOMA schemes do not provide a detailed approach to support spatial multiplexing of multiple antennas without precoding. In unlicensed uplink transmission, precoding is difficult to implement due to lack of channel response. In fact, some NOMA schemes have difficulty supporting spatial multiplexing without precoding. For example, sparse multiple access SCMA and pattern division multiple access PDMA schemes are derived based on observations of the sum of multiple terminal device data in each orthogonal resource, namely:

wherein, y_kDenotes an observation for a resource k, x_mRepresents data of terminal device m, and h_m,kRepresenting the channel response for terminal device m at resource k.

For the case of multiple receive antennas, the observation can then be expressed as:

(y_k,1,...,y_k,N)^T＝(h_k,1x,...,h_k,Nx)^T＝Hx (2)

where N is an integer representing the number of receive antennas. In the case of using spatial multiplexing, the number of terminal devices is much larger than the number of receiving antennas. Therefore, it becomes difficult to separate out a small amount of data for each terminal device. In other words, the matrix H cannot be transformed by the receiver into a block diagonal matrix. This means that Message Passing Algorithm (MPA) based receivers do not work efficiently.

In a 5G mobile communication system, the base station is equipped with a large number of antennas and supporting spatial multiplexing will significantly increase the transmission capacity for each active terminal device and the maximum number of simultaneously active terminal devices. However, for unlicensed uplink transmissions, precoding cannot be achieved, and thus spatial multiplexing with precoding is not supported. Therefore, in order to support spatial multiplexing in the case of precoding, data signals tend to be densely spread.

Most of the dense spreading based NOMA schemes use specially designed short spreading sequences, such as Zadoff-chu (zc) sequences. Note that due to the quasi-synchronicity for unlicensed transmission, the subcarriers of the OFDM symbol will be affected by random linear phase deflection. Therefore, a new spreading sequence needs to be designed.

The methods of the present disclosure consider the scenario of uplink transmissions, where each terminal device has a single transmit antenna and each network device (e.g., eNB) has a large number of receive antennas. For the case where the terminal device has a plurality of antennas, the terminal device can be regarded as a plurality of virtual terminal devices each having a single antenna. By using orthogonal spreading sequences and spatial multiplexing, the method of the present disclosure can distinguish different data of different terminal devices. In an example scenario, a large number of terminal devices transmit data in the same resource, i.e. with a high overload factor. The eNB uses spatial channels to distinguish data of different terminal devices. The method of the present disclosure is based on a long random orthogonal spreading sequence, which can be used to demodulate data of the same terminal device. Since the terminal device has a single transmission antenna, data of the same terminal device cannot be distinguished through a spatial channel.

Fig. 1 shows a block diagram of a communication system 100 according to an embodiment of the present disclosure. The communication system 100 includes a sender 110, a channel 120, and a receiver 130. According to the embodiment of the present disclosure, the sender 110 may be a terminal device, and the receiver 130 may be a base station device such as an eNB or a NodeB.

According to the embodiment of the present disclosure, when transmitting data, the transmitter 110 first modulates a signal to be transmitted in a frequency domain, then spreads the modulated signal with an orthogonal spreading sequence, which is a non-constant amplitude sequence generated randomly, and then transforms the spread signal from the frequency domain to a time domain. Accordingly, when receiving data, the receiving side 130 first acquires information related to a plurality of terminal devices, the information including an orthogonal spreading sequence specific to the terminal device and a channel response for the terminal device, the orthogonal spreading sequence being a non-constant amplitude sequence generated randomly; then receives the signal to be processed from the channel 120; transforming the received signal from the time domain to the frequency domain; and despreading the transformed signal based at least in part on the information.

Fig. 2 shows a flowchart of a method 200 for processing a signal by the sender 110 in a communication system according to an embodiment of the disclosure. In some embodiments, method 200 may be implemented by sender 110, for example. It should be understood that method 200 may also include additional acts not shown and/or may omit acts shown. The scope of the schemes described herein is not limited in this respect.

At 210, a signal to be transmitted is modulated in the frequency domain. In some embodiments, the manner of modulation may include Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and the like. In some embodiments, using QPSK or QAM modulation includes the need for serial-to-parallel conversion and symbol mapping of the signal to be transmitted. For example, the QAM modulation in the present disclosure may employ various orders of modulation, such as 64 QAM. It should be understood, however, that the modulation scheme in the embodiments of the present disclosure is not limiting. Various modulation modes can be adopted to modulate the signal to be transmitted.

At 220, the modulated signal is spread with an orthogonal spreading sequence, which is a randomly generated non-constant amplitude sequence. In some embodiments, spreading of the modulated signal by the sender 110 may be accomplished as such. A unitary matrix specific to the terminal device can be generated based on the random matrix and the modulated signal can be spread with the unitary matrix. It should be understood that unitary matrices are only one form of random orthogonal matrices and the present disclosure is illustrative only using unitary matrices. In some embodiments, the orthogonal spreading sequence may be selected from a unitary matrix for a data symbol of the terminal device, or may be directly determined for the data symbol using the data symbol of the terminal device, and the orthogonal spreading sequence is in the unitary matrix.

In certain embodiments, the baseband signal is generated by the orthogonal spreading sequences selected by the present disclosure. The baseband signal may be an OFDM symbol. The data signals occupy contiguous or non-contiguous subcarriers of one or more OFDM symbols. Multiple terminal devices may transmit their respective baseband signals on the same time-frequency resource, which may be a Physical Resource Block (PRB), or resource region. The process of expansion is described here as a non-limiting example. E.g. based on spreading sequences

Modulated signal x₁Will be expanded in the frequency domain

Where N represents the extension length for OFDM. In some embodiments, it is desirable to allocate multiple spread signals onto orthogonal frequency division multiplexing subcarriers. For the selected spreading sequence

K is 1, 2, … …, K, the value of subcarrier i is

Where K denotes the number of constellation symbols, x_kRepresenting a modulated signal. In some embodiments, the spreading sequence may be split into multiple portions, and each portion is transmitted over one OFDM symbol. For example, spreading sequences

Can be divided into

And

two parts, where N is an even number and the spreading sequence length for an OFDM symbol is N/2.

In some embodiments, in order to generate the random orthogonal matrix, the identification and/or transmission parameters of the terminal device need to be obtained as a seed. A random matrix is then generated using a pseudo-random algorithm based on the obtained seeds. In certain embodiments, the unitary matrix is generated by performing Singular Value Decomposition (SVD) on a random matrix.

In some embodiments, the identity of the terminal device comprises an international mobile subscriber identity, IMEI, and the transmission parameter comprises an orthogonal frequency division multiplexing symbol number or a subframe number. In some embodiments, the identification of the end device may also include a user name. Alternatively, an identifier that identifies the terminal device by another party may also be used as a seed for generating the random matrix. When orthogonal frequency division multiplexing symbol numbering is utilized, since the obtained orthogonal spreading sequence is unique to the symbol, the orthogonal spreading sequence for the symbol number can be directly obtained without a selection process.

In some embodiments, the orthogonal spreading sequences may be non-constant amplitude sequences. In such embodiments, the orthogonal spreading sequence is different from a constant amplitude Zadoff-chu (zc) sequence. In other words, the orthogonal spreading sequence is not required in this disclosure to be a constant amplitude sequence, i.e., the terms in the sequence are not required to have normalized absolute values. Thus, the flexibility of generating orthogonal spreading sequences can be improved, and the limitation of system design can be reduced.

By orthogonally spreading the signals, it is possible to effectively distinguish the received signals at the receiving side 130 and avoid collisions between different signals of the same terminal device or corresponding signals of different terminal devices. It should be understood that the orthogonal spreading sequences employed between different signals of the same terminal device are mutually orthogonal, and thus can be effectively distinguished at the receiving side 130. The spreading sequences employed between different terminal devices are not necessarily orthogonal, i.e., signals of different terminal devices cannot be distinguished at the receiving side 130 by means of only the spreading sequences, but are further distinguished by means of spatial channels, and thus the method employed by the present disclosure may also be referred to as a semi-orthogonal spreading sequence method.

At 230, the spread signal is transformed from the frequency domain to the time domain. In some embodiments, transforming the spread signal from the frequency domain to the time domain may be accomplished using an Inverse Fast Fourier Transform (IFFT). Of course, this is not limiting and any frequency domain to time domain transform methods now known or developed in the future may be used in conjunction with embodiments of the present disclosure.

Fig. 3 shows a flow chart of a method 300 of processing a signal by a receiving side in a communication system according to an embodiment of the disclosure. In some embodiments, the method 300 may be implemented by the recipient 130, for example. It should be understood that the method 300 may also include additional steps not shown and/or may omit the steps shown. The scope of the subject matter described herein is not limited in this respect.

At 310, information relating to a plurality of terminal devices is obtained. In some embodiments, the obtained correlation information comprises a terminal device specific orthogonal spreading sequence and a channel response for the terminal device, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence. In some embodiments, obtaining information related to a plurality of terminal devices includes detecting a pilot signal for the terminal device and obtaining an orthogonal spreading sequence and a channel response using the pilot signal. For a plurality of terminal devices for which information needs to be acquired, an orthogonal spreading sequence specific to each of the plurality of terminal devices and a channel response for the each terminal device need to be acquired.

At 320, a signal to be processed is received. In some embodiments, the signals may be received separately, for example, using multiple antennas. The received signal may be pre-processed, for example by passing the received signal through a filter. Pre-processing the signal may provide a signal that is more suitable for subsequent processing, e.g. amplifying the signal may reduce the sensitivity requirements for subsequent signal processing modules.

At 330, the received signal is transformed from the time domain to the frequency domain. In some embodiments, transforming the signal from the time domain to the frequency domain may be accomplished using a Fast Fourier Transform (FFT). Of course, this is not limiting and any time-domain to frequency-domain transform methods now known or later developed in the future may be used in conjunction with embodiments of the present disclosure.

At 340, the transformed signal is despread based at least in part on the acquired information. The input used for despreading can be viewed as a matrix. Each row in the matrix is a modulated spreading sequence with data information and the channel response of the antenna. Each column represents the values for multiple antennas received on the same subcarrier. For example, the input matrix may be written as:

where R denotes the number of receiving antennas, N denotes the length of the spreading sequence, M denotes the number of active terminal devices, h_i,j,mRepresenting the channel response from terminal device m to receiving antenna i at subcarrier j, r_i,jRepresenting the input matrix element, K, for antenna i at subcarrier j_mRepresenting the number of constellation symbols, x, for terminal device m_m,kRepresents the kth constellation symbol for terminal device m, and

a spreading sequence representing the kth constellation symbol for terminal device m.

Estimated constellation symbol x_m,kThe value of (d) may be calculated or despread to:

the asterisk (#) in equation (4) represents the conjugate of the complex number, using k, m and k ', m' to distinguishDifferent elements are denoted using the same reference numerals. The rightmost first term in equation (4)

Has high energy because both the spreading sequence and the channel response have high autocorrelation. The rightmost second term in equation (4)

Has low energy because the spreading sequences for the same terminal device are orthogonal. The third rightmost term in equation (4)

Has low energy because both the spreading sequence and the channel response for different terminal devices have low autocorrelation.

In some embodiments, the signal is processed using a successive interference cancellation receiver. In each iteration, the data of the terminal device with the strongest energy is demodulated. The demodulated data can be checked and recovered by forward error correction FEC to improve performance. The FEC decoded signal may then be output to the next processing device.

Fig. 4 shows a block diagram of an apparatus 400 according to a third aspect of an embodiment of the disclosure. It is understood that the apparatus 400 may be implemented as a terminal device. The apparatus 400 includes a modulation unit 410, a spreading unit 420, and a frequency-time conversion unit 430. The modulation unit 410 is configured to modulate a signal to be transmitted in a frequency domain; spreading unit 420 is configured to spread the modulated signal with an orthogonal spreading sequence, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence; the frequency-time transform unit 430 is configured to transform the spread signal from the frequency domain to the time domain.

In some embodiments, spreading unit 420 may include a random orthogonal matrix generation subunit configured to generate a random orthogonal matrix specific to the terminal device based on the random matrix and a random orthogonal matrix spreading subunit configured to spread the modulated signal with the random orthogonal matrix.

In some embodiments, the random orthogonal matrix generating subunit includes an acquiring subunit configured to acquire the identification and/or transmission parameters of the terminal device and a random orthogonal matrix generating subunit configured to generate the random orthogonal matrix based on the acquired identification and/or transmission parameters of the terminal device and using a pseudo-random algorithm.

In some embodiments, the identity of the terminal device comprises an international mobile subscriber identity, and wherein the transmission parameter comprises an orthogonal frequency division multiplexing symbol number or a subframe number.

In some embodiments, the random orthogonal matrix is a unitary matrix, and the random orthogonal matrix generating subunit includes a singular value decomposition subunit configured to generate the unitary matrix by performing singular value decomposition on the random matrix.

In some embodiments, the apparatus 400 further comprises a resource allocation unit configured to place the plurality of modulated signals of the terminal device on the same physical resource for transmission.

In some embodiments, the apparatus 400 further comprises a splitting unit configured to split the orthogonal spreading sequence into at least one portion, each of the at least one portion being transmitted on one orthogonal frequency division multiplexing symbol.

In some embodiments, the apparatus 400 further comprises an allocation unit configured to allocate the spread signal onto orthogonal frequency division multiplexing subcarriers.

Fig. 5 shows a block diagram of an apparatus 500 according to a fourth aspect of an embodiment of the disclosure. It is to be appreciated that apparatus 500 may be implemented as a network device. The apparatus 500 includes an information obtaining unit 510, a receiving unit 520, a time-frequency transforming unit 530, and a despreading unit 540. The information acquisition unit 510 is configured to acquire terminal device-related information including a terminal device-specific orthogonal spreading sequence that is a randomly generated non-constant amplitude sequence and a channel response for the terminal device. The receiving unit 520 is configured to receive a signal to be processed. The time-frequency transform unit is configured 530 to transform the received signal from the time domain to the frequency domain. The despreading unit 540 is configured to despread the transformed signal based at least in part on the orthogonal spreading sequences. In some embodiments, the orthogonal spreading sequence used by the despreading unit 540 to despread the signal is a non-constant amplitude sequence.

In some embodiments, the information acquisition unit 510 further includes a pilot detection subunit configured to detect a pilot signal for the terminal device and a pilot processing subunit to acquire the orthogonal spreading sequence and channel response using the pilot signal.

In some embodiments, the apparatus 500 further comprises a successive interference cancellation receiver. The successive interference cancellation receiver is configured to process the transformed signal.

For clarity, certain optional elements of apparatus 400 and apparatus 500 are not shown in fig. 4 and 5. However, it should be understood that the various features described above with reference to fig. 1-5 apply equally to the apparatus 400 and the apparatus 500. Furthermore, each unit of the apparatus 400 and the apparatus 500 may be a hardware unit or a software unit. For example, in some embodiments, apparatus 400 and apparatus 500 may be implemented in part or in whole using software and/or firmware, e.g., as a computer program product embodied on a computer-readable medium. Alternatively or additionally, the apparatus 400 and the apparatus 500 may be partly or entirely implemented on hardware basis, e.g. as Integrated Circuits (ICs), Application Specific Integrated Circuits (ASICs), system-on-a-chip (SOCs), Field Programmable Gate Arrays (FPGAs), etc. The scope of the present disclosure is not limited in this respect.

Fig. 6 illustrates a block diagram of a device 600 suitable for implementing embodiments of the present disclosure. Device 600 may be used to implement a network device and/or to implement a terminal device. As shown, the device 600 includes a controller 610. The controller 610 controls the operation and functions of the device 600. For example, in some embodiments, controller 610 may perform various operations by way of instructions 630 stored in memory 620 coupled thereto. The memory 620 may be of any suitable type suitable to the local technical environment and may be implemented using any suitable data storage technology, including but not limited to semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems. Although only one memory unit is shown in FIG. 6, there may be multiple physically distinct memory units within device 600.

The controller 610 may be of any suitable type suitable to the local technical environment and may include, but is not limited to, one or more of general purpose computers, special purpose computers, microcontrollers, digital signal controllers (DSPs), and controller-based multi-core controller architectures. The device 600 may also include a plurality of controllers 610. The controller 610 is coupled to a transceiver 640, which transceiver 640 may enable the reception and transmission of information by way of one or more antennas 650 and/or other components.

When the device 600 is acting as a terminal device, the controller 610 and the transceiver 640 may operate in conjunction to implement the method 200 described above with reference to fig. 2. When the device 600 is acting as a network device, the controller 610 and the transceiver 640 may operate in conjunction to implement the method 300 described above with reference to fig. 3. All of the features described above with reference to fig. 2 and 3 apply to the apparatus 600 and are not described in detail herein.

Fig. 7 shows a signal processing performance versus graph according to an embodiment of the present disclosure. According to one example, assuming that the terminal device is to transmit 24 bits in one OFDM symbol by QPSK modulation, which may result in 12 constellation symbols, the spreading sequence length N is 72. Two methods are used to generate the spreading sequence. The first method is the "random" method according to the present disclosure, where the vectors from the unitary matrix, which can be obtained by singular value decomposition, are chosen as the spreading sequence for the terminal device m. The second method is a method according to a "ZC" sequence, which has a length of 71, uses a cyclic shift without stop as a spreading sequence for a terminal device, and different roots are used to generate a semi-orthogonal spreading sequence. The modulated spreading sequence is mapped onto 6 consecutive physical resource blocks, where one physical resource block has 6 x 12 subcarriers. For conventional uplink transmission, 6 terminal devices may operate with these resources.

The bit error rate BER without forward error correction FEC is shown in fig. 7. Specifically designed ZC-based spreading sequences and orthogonal spreading sequences proposed by the present disclosure are compared in fig. 7, where different numbers of receive antennas and different overload factors are employed. In the simulation, the signal-to-noise ratio SNR for each spreading sequence ranged from-5 dB to 5dB, and the maximum time difference between the received signals of different terminal devices was 66.7 μ s. Note that each terminal device has a single antenna and the eNB has multiple receive antennas. The number of receiving antennas is shown as the value on the horizontal axis. As can be seen from the simulation results of fig. 7, the signal waveforms of the orthogonal spreading sequences of the present disclosure can support a larger overload factor, for example, up to 1600%, with the help of a large number of receive antennas, while the overload factor of the NOMA scheme without spatial multiplexing can typically reach 150% -400%. In addition, the randomly generated spreading sequence has better performance than a specially designed ZC spreading sequence.

Certain embodiments of the present disclosure utilize spreading sequences and spatial channels to distinguish data of terminal devices. The combination of spreading sequences and spatial channels can significantly increase the supported overload factor compared to the NOMA scheme. The spreading sequence in this disclosure is a vector of a randomly generated unitary matrix. The spreading sequence is complex and has non-uniform absolute values. Since the sub-carriers of an OFDM symbol are affected by random linear phase deflection, the orthogonality of specially designed short spreading sequences is affected accordingly. Moreover, since the number of potential spreading sequences is large enough to produce randomly generated spreading sequences, the probability of collision of spreading sequences becomes correspondingly small. The spreading sequences used by the different terminal devices are non-orthogonal and the interference between users is suppressed by the spatial channels. The spreading sequences used for the data of the same terminal equipment are orthogonal, so that the interference of the user is eliminated. Multiple terminal devices may transmit different sizes of data to the eNB.

In describing embodiments of the present disclosure, the terms "include" and its derivatives should be interpreted as being open-ended, i.e., "including but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment".

It should be noted that the embodiments of the present disclosure can be realized by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such code being provided, for example, in programmable memory or on a data carrier such as an optical or electronic signal carrier.

Further, while the operations of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions. It should also be noted that the features and functions of two or more devices according to the present disclosure may be embodied in one device. Conversely, the features and functions of one apparatus described above may be further divided into embodiments by a plurality of apparatuses.

While the present disclosure has been described with reference to several particular embodiments, it is to be understood that the disclosure is not limited to the particular embodiments disclosed. The disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A signal processing method, comprising:

modulating a signal to be transmitted in a frequency domain;

spreading the modulated signal with an orthogonal spreading sequence, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence, wherein spreading the modulated signal comprises: acquiring an identifier and/or a transmission parameter of the terminal equipment; generating a random orthogonal matrix by using a pseudo-random algorithm based on the acquired identification and/or transmission parameters of the terminal equipment, wherein the random orthogonal matrix is a unitary matrix generated by performing singular value decomposition on the random matrix; obtaining the orthogonal spreading sequence by using the random orthogonal matrix; and

the spread signal is transformed from the frequency domain to the time domain,

the orthogonal spreading sequences adopted among different signals of the terminal equipment are mutually orthogonal, and the spreading sequences adopted among the terminal equipment and other terminal equipment are non-orthogonal.

2. The method of claim 1, wherein the identity of the terminal device comprises an international mobile subscriber identity, and wherein the transmission parameter comprises an orthogonal frequency division multiplexing symbol number or a subframe number.

3. The method of claim 1, further comprising:

and placing a plurality of modulated signals of the terminal equipment on the same physical resource for transmission.

4. The method of claim 1, the orthogonal spreading sequence may be partitioned into at least one portion, and each of the at least one portion is transmitted on one orthogonal frequency division multiplexing symbol.

5. The method of claim 1, further comprising:

the spread signals are allocated onto orthogonal frequency division multiplexing subcarriers.

6. A signal processing method, comprising:

obtaining information relating to a plurality of terminal devices, the information comprising a terminal device specific orthogonal spreading sequence and a channel response for the terminal device, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence, wherein spreading the modulated signal comprises: acquiring the identification and/or transmission parameters of the terminal equipment; generating a random orthogonal matrix by using a pseudo-random algorithm based on the acquired identification and/or transmission parameters of the terminal equipment, wherein the random orthogonal matrix is a unitary matrix generated by performing singular value decomposition on the random matrix; obtaining the orthogonal spreading sequence by using the random orthogonal matrix;

receiving a signal to be processed;

transforming the received signal from the time domain to the frequency domain; and

despreading the transformed signal based at least in part on the information,

the orthogonal spreading sequences adopted among different signals of the same terminal equipment are mutually orthogonal, and the spreading sequences adopted among different terminal equipments are non-orthogonal.

7. The method of claim 6, obtaining information related to a plurality of terminal devices comprises:

detecting a pilot signal for the terminal device; and

and acquiring the orthogonal spreading sequence and the channel response by using the pilot signal.

8. The method of claim 6, further comprising:

the signal is processed using a successive interference cancellation receiver.

9. A terminal device, comprising:

a controller;

a memory comprising instructions that, when executed by the controller, cause the terminal device to perform acts comprising:

modulating a signal to be transmitted in a frequency domain;

spreading the modulated signal with an orthogonal spreading sequence, the orthogonal spreading sequence being a randomly generated non-constant amplitude sequence, wherein an identity and/or transmission parameter of the terminal device is obtained; generating a random orthogonal matrix by using a pseudo-random algorithm based on the acquired identification and/or transmission parameters of the terminal equipment, wherein the random orthogonal matrix is a unitary matrix generated by performing singular value decomposition on the random matrix; obtaining the orthogonal spreading sequence by using the random orthogonal matrix; and

the spread signal is transformed from the frequency domain to the time domain,

10. The terminal device of claim 9, wherein the identity of the terminal device comprises an international mobile subscriber identity, and wherein the transmission parameter comprises an orthogonal frequency division multiplexing symbol number or a subframe number.

11. The terminal device of claim 9, the acts further comprising:

12. The terminal device of claim 9, the orthogonal spreading sequence may be partitioned into at least one portion, and each of the at least one portion is transmitted on one orthogonal frequency division multiplexing symbol.

13. The terminal device of claim 9, the acts further comprising:

14. A network device, comprising:

a controller;

a memory comprising instructions that, when executed by the controller, cause the network device to perform acts comprising:

obtaining information related to a plurality of terminal devices, the information comprising terminal device specific orthogonal spreading sequences and channel responses for the terminal devices, the orthogonal spreading sequences being randomly generated non-constant amplitude sequences, wherein identification and/or transmission parameters of the terminal devices are obtained; generating a random orthogonal matrix by using a pseudo-random algorithm based on the acquired identification and/or transmission parameters of the terminal equipment, wherein the random orthogonal matrix is a unitary matrix generated by performing singular value decomposition on the random matrix; obtaining the orthogonal spreading sequence by using the random orthogonal matrix;

receiving a signal to be processed;

despreading the transformed signal based at least in part on the information,

15. The network device of claim 14, the acts further comprising:

detecting a pilot signal for the terminal device; and

16. The network device of claim 14, the acts further comprising:

the signal is processed using a successive interference cancellation receiver.