WO2017196096A1

WO2017196096A1 - Method, device of transmitting and receiving signals in communications system

Info

Publication number: WO2017196096A1
Application number: PCT/KR2017/004875
Authority: WO
Inventors: Qi XIONG; Bin Yu; Chen QIAN; Chenxi HAO; Jingxing Fu
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2016-05-11
Filing date: 2017-05-11
Publication date: 2017-11-16
Also published as: CN107370702A; CN107370702B

Abstract

The present disclosure relates to a pre-5^th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4^th-Generation (4G) communication system such as Long Term Evolution (LTE). The present disclosure discloses a signal transmission method in a communication system. The method includes: a: a transmitter sequentially applies channel encoding, modulation and grid mapping to an information bit sequence which is to be transmitted; b: inserts a preamble sequence or a cyclic prefix into a symbol sequence generated after the grid mapping, applies baseband-to-RF processing to the symbol sequence in which the preamble sequence or the cyclic prefix has been inserted and transmits the sequence obtained after the baseband-to-RF processing. During the process, the preamble sequence is periodically inserted, and the cyclic prefix is inserted into the symbol sequence in which the preamble sequence has not been inserted. The present disclosure can solve the high peak-average power ratio (PAPR) problem at the transmitting end, and can increase the power amplifier (PA) efficiency.

Description

METHOD, DEVICE OF TRANSMITTING AND RECEIVING SIGNALS IN COMMUNICATIONS SYSTEM

The present disclosure relates to wireless communications, and particularly, to a method and a device of transmitting and receiving signals in a communications system.

To meet the demand for wireless data traffic having increased since deployment of 4^th generation (4G) communication systems, efforts have been made to develop an improved 5^th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution (LTE) System’.

The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.

In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

The present disclosure provides a method and a device of transmitting and receiving signals in a communications system, to solve the problem of high PAPR at transmitting terminals and improve the efficiency of PA.

To attain the above objective, the present disclosure provides the following technical mechanisms.

A signal transmission method in a communications system includes:

a: applying, by a transmitter, channel encoding, modulation and grid mapping sequentially to an information bit sequence which is to be transmitted;

b: inserting a preamble sequence or a cyclic prefix into a symbol sequence generated from the grid mapping, applying baseband-to-RF processing to the symbol sequence after the preamble sequence or the cyclic prefix is inserted, and transmitting the symbol sequence after the baseband-to-RF processing; wherein the preamble sequence is periodically inserted into the symbol sequence, the cyclic prefix is inserted into the symbol sequence in which the preamble sequence has not been inserted.

Preferably, the method includes: after the channel encoding and before the modulation, applying interleaving to a result of the channel encoding; wherein in the interleaving, a sequence has the same length before and after the interleaving.

Preferably, if the preamble sequence is periodically inserted into the symbol sequence generated from the grid mapping, preamble sequences of different users transmitting signals using the same time-frequency resources are different and orthogonal to each other.

Preferably, different users are distinguished from each other by interleaving patterns and/or grid patterns and/or preamble sequences, interleaving patterns are for the interleaving, and the grid patterns are for the grid mapping.

Preferably, the method may include: before the channel encoding, receiving preamble sequence configuration information, interleaving pattern information and grid mapping pattern information sent by a network side, determining the preamble sequence according to the preamble configuration information, determining an interleaving pattern for the interleaving according to the interleaving pattern information, and determining a grid mapping pattern for the grid mapping according to the grid mapping pattern information.

Preferably, the interleaving pattern for the interleaving comprises:

using an interleaving pattern included in the interleaving pattern information as the interleaving pattern for the interleaving; or using the interleaving pattern included in the interleaving pattern information as an interleaving pattern of a mother interleaver, cyclic shifting the interleaving pattern of the mother interleaver according to a pre-determined rule to obtain the interleaving pattern for the interleaving.

Preferably, a periodicity of inserting the preamble sequence is pre-determined or included in the preamble sequence configuration information.

Preferably, if the periodicity of inserting the preamble sequence is included in the preamble sequence information, the periodicity is determined by the network side according to changes in channel, and the faster the channel changes, the shorter the periodicity is.

Preferably, the method includes: before the preamble sequence is inserted, requesting, by the transmitter, the network side to temporarily adjust the periodicity of inserting the preamble sequence according to channel state information measured by the transmitter, and temporarily adjusting, by the transmitter after receiving confirmation information from the network side, the periodicity according to a pre-determined modification rule or according to an instruction from the network side, and executing the inserting the preamble sequence according to the temporarily adjusted periodicity;

inserting, by the transmitter, the pre-amble sequence according to newly received preamble configuration information if the newly received preamble sequence configuration information is received after the periodicity has been temporarily adjusted.

Preferably, the method includes: determining, by the network side, a manner of differentiating different users according to network load.

Preferably, different users are distinguished by interleaving patterns, grid mapping patterns, or preamble sequence if the network load ≤ a pre-determined first threshold γ₁; and/or,

different users are distinguished by a combination of any two of: interleaving patterns, grid mapping patterns, or preamble sequence if γ₁ <the network load ≤ a pre-determined second threshold γ₂; and/or

different users are distinguished by a combination of interleaving patterns, grid mapping patterns and preamble sequence if the network load>γ₂.

Preferably, if the information bit sequence to be transmitted is information bit sequences of a plurality of data flows,

applying channel encoding, modulation and grid mapping sequentially to the information bit sequence includes: for each data flow, applying channel encoding, interleaving, modulation and grid mapping sequentially to an information bit sequence of the data flow;

for each data flow, applying phase and power adjustment to a symbol sequence generated from the grid mapping of the data flow before the preamble sequence or the cyclic prefix is inserted; performing the inserting the preamble sequence or the cyclic prefix and performing the baseband-to-RF processing for the symbol sequence of each data flow after the phase adjustment and the power adjustment, and superimposing data of data flows after the processing and transmitting the superimposed data; or for each data flow, applying phase and power adjustment to a symbol sequence generated from the grid mappings before the preamble sequence or the cyclic prefix is inserted; superimposing symbol sequences of data flows after the phase and power adjustment, and performing the inserting the preamble sequence or the cyclic prefix and performing the baseband-to-RF processing for the symbol sequence after the superimposing;

when applying the phase and power adjustment to the symbol sequence of each data flow, the symbol sequences corresponding to different data flows are kept not overlapping with or being canceled by each other.

Preferably, regarding the preamble sequence assigned to users by the network side: preamble sequences of different users are different from each other and orthogonal to each other, if the preamble sequence or the cyclic prefix is inserted into the symbol sequence generated from the grid mapping before symbol sequences of a plurality of data flows are superimposed, the preamble sequence of different data flows of the same user are different from each other and orthogonal to each other.

Preferably, if the preamble sequence or the cyclic prefix is inserted into the symbol sequence generated from the grid mapping before symbol sequences of a plurality of data flows are superimposed, different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns, and different interleaving patterns or different grid mapping patterns are used to differentiate the different data flows of the different users; or different users are assigned with different interleaving patterns, and different data flows of the same user are assigned with the same interleaving pattern and different grid mapping patterns, different users are differentiated by interleaving patterns, and different data flows of the same user are differentiated using grid mapping patterns or preamble sequence or combinations of grid mapping patterns and preamble sequences; or different users are assigned with different grid mapping patterns, different data flows of the same user are assigned with the same grid mapping pattern and different interleaving patterns, different users are differentiated by grid mapping patterns, and different data flows of the same user are differentiated by interleaving patterns or preamble sequence or combinations of interleaving patterns and preamble sequences; or different data flows of the same user are assigned with different grid mapping patterns or different interleaving patterns or different combinations of grid mapping patterns and interleaving patterns, different users are differentiated by preamble sequences, and different data flows of the same user are differentiated by grid mapping patterns or interleaving patterns or combinations of grid mapping patterns and interleaving patterns; or different users are assigned with different combinations of interleaving patterns and grid mapping patterns, different users are differentiated by combinations of interleaving patterns and grid mapping patterns, and different data flows of the same user are differentiated by preamble sequences; or different users are assigned with different combinations of interleaving patterns and preamble sequences, and different data flows of the same user are assigned with different grid mapping patterns, different users are differentiated by combinations of interleaving patterns and preamble sequences, and different data flows of the same users are differentiated by grid mapping patterns; or different users are assigned with different combinations of grid mapping patterns and preamble sequences, and different data flows of the same user are assigned with different interleaving patterns, different users are differentiated by combinations of grid mapping patterns and preamble sequences, and different data flows of the same user are differentiated by interleaving patterns; and / or

if the preamble sequence or the cyclic prefix is inserted into the symbol sequence after the symbol sequence generated from the grid mapping is superimposed with a plurality of data flows, different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns, and different data flows of different users are differentiated by interleaving patterns or grid mapping patterns; or different users are assigned with different interleaving patterns, and different data flows of the same user are assigned with the same interleaving pattern and different grid mapping patterns, different users are differentiated by interleaving patterns, and different data flows of the same user are differentiated by grid mapping patterns; or different users are assigned with different grid mapping patterns, different data flows of the same user are assigned with the same grid mapping pattern and different interleaving patterns, different users are differentiated by the grid mapping patterns, and different data flows of the same user are differentiated using the interleaving patterns; or different data flows of the same user are assigned with different grid mapping patterns or different interleaving patterns or different combinations of grid mapping patterns and interleaving patterns, different users are differentiated by preamble sequences, and different data flows of the same user are differentiated by grid mapping patterns or interleaving patterns or combinations of grid mapping patterns and interleaving patterns; or different users are assigned with different combinations of interleaving patterns and preamble sequences, and different data flows of the same user are assigned with different grid mapping patterns, different users are differentiated by combinations of interleaving patterns and preamble sequences, and different data flows of the same user are differentiated by grid mapping patterns; or different users are assigned with different combinations of grid mapping patterns and preamble sequences, and different data flows of the same user are assigned with different interleaving patterns, different users are differentiated by combinations of grid mapping patterns and preamble sequences, and different data flows of the same user are differentiated by interleaving patterns.

Preferably, if K which is the number of data flows actually transmitted by the transmitter is smaller than K_max which is the maximum number of flows supported by a receiver,

transmitting, by the transmitter, K data flows after processing the K data flows, sending to the network side a flow number indication which specifies K which is the number of actually transmitted data flows; or

transmitting, by the transmitter, K_max data flows after processing the K_max data flows, wherein an information bit sequence of the K data flows is determined to be the information to be transmitted, and information bit sequences of the remaining K_max-K data flows are all zero and all zero information bit sequences indicate that the data flows corresponding to the all zero information bit sequences are not used for transmitting valid information bit sequences.

Preferably, if the transmitter comprises a plurality of transmit antennas, if the information bit sequence to be transmitted is a data flow A, or if the information bit sequence to be transmitted is a plurality of data flows, for a data flow A of the plurality of data flows, the step a comprises: applying channel encoding, interleaving, modulation, and grid mapping sequentially to an information bit sequence of the data flow A; the method comprises: between step a and step b, applying serial-to-parallel conversion or layer mapping to a symbol sequence generated from the grid mapping of the data flow A;

performing the inserting the preamble sequence or the cyclic prefix of step b for each of data flows generated from the serial-to-parallel conversion or layer mapping, applying pre-determined pre-processing to all of data flows after the preamble sequence or the cyclic prefix is inserted, and performing the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; or if the cyclic prefix is inserted, performing the inserting the cyclic prefix of step b for each of data flows generated from the serial-to-parallel conversion or layer mapping, applying pre-determined pre-processing for all of data flows after the cyclic prefix is inserted, and performing the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; if the preamble sequence is inserted, applying pre-determined pre-processing to all of data flows generated from the serial-to-parallel conversion or layer mapping, performing the inserting the preamble sequence for each preprocessed data flow, and performing the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; and/or

if the transmitter comprises a plurality of transmit antennas, if an information bit sequence to be transmitted is a plurality of data flows, the step a performed for an information bit sequence of some or each of the data flows comprises: applying the channel encoding, the interleaving, the modulation, and the grid mapping sequentially to an information bit sequence of each of some or all of the data flows one after another in unit of data flow; the method comprises: between step a and step b, applying layer mapping to a symbol sequence generated from the grid mapping of each data flow of some or all of the data flows;

performing the inserting the preamble sequence or the cyclic prefix of step b for each of data flows generated from the layer mapping, applying pre-determined pre-processing to all of data flows after the preamble sequence or the cyclic prefix is inserted, and applying the baseband-to-RF processing and the transmitting for each preprocessed data flow individually; or if the cyclic prefix is inserted, performing the inserting the cyclic prefix of step b for each of data flows generated from the layer mapping, applying pre-determined pre-processing for all of data flows after the cyclic prefix is inserted, and applying the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; if the preamble sequence is inserted, applying pre-determined pre-processing to all of data flows generated from the layer mapping, performing the inserting the preamble sequence, the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; and/or

if the transmitter comprises a plurality of transmit antennas, if an information bit sequence to be transmitted is a plurality of data flows, the step a performed for an information bit sequence of some or each of the data flows comprises: applying the channel encoding, the interleaving, the modulation, and the grid mapping sequentially for an information bit sequence of each of some or all of the data flows one after another in unit of data flow; the method comprises: between step a and step b, applying phase and power adjustment to a symbol sequence generated from the grid mapping of each of some or all of data flows, superimposing symbol sequences of all of the data flows after the adjustment, and performing serial-to-parallel conversion or layer mapping;

performing the inserting the preamble sequence or the cyclic prefix of step b individually for each of data flows generated from the serial-to-parallel conversion or layer mapping, performing pre-determined pre-processing for all of data flows after the preamble sequence or the cyclic prefix is inserted, and performing the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; or if the cyclic prefix is inserted, performing the inserting the cyclic prefix of step b for each of data flows generated from the serial-to-parallel conversion or layer mapping, applying pre-determined pre-processing to all of data flows after the cyclic prefix is inserted, and performing the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually; if the preamble sequence is inserted, applying pre-determined pre-processing to all of data flows generated from the serial-to-parallel conversion or layer mapping, performing the inserting the preamble sequence, the baseband-to-RF processing and the transmitting of step b for each preprocessed data flow individually.

Preferably, regarding preamble sequence assigned to users by the network side: preamble sequences of different users are different from and orthogonal to each other, and the preamble sequences of different data flows after the serial-to-parallel conversion or layer mapping are different from and orthogonal to each other and are for estimating a channel state of an equivalent channel from each transmitting antenna to the receiving antenna including the pre-processing.

Preferably, regarding interleaving patterns and grid mapping patterns assigned to users by the network side:

different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns, and different data flows of different users are differentiated by interleaving patterns or grid mapping patterns or preamble sequences; or different users are assigned with different interleaving patterns, different data flows of the same user are assigned with the same interleaving pattern and different grid mapping patterns, different users are differentiated by the interleaving patterns, and different data flows of the same user are differentiated by the grid mapping patterns or preamble sequence or combinations of grid mapping patterns and preamble sequences; or different users are assigned with different grid mapping patterns, different data flows of the same user are assigned with the same grid mapping pattern and different interleaving patterns, different users are differentiated by grid mapping patterns, and different data flows of the same user are differentiated by interleaving patterns or preamble sequence or combinations of interleaving patterns and preamble sequences; or different data flows of the same user are assigned with different grid mapping patterns or different interleaving patterns or different combinations of grid mapping patterns and interleaving patterns, different users are differentiated by preamble sequences, and different data flows of the same user are differentiated by grid mapping patterns or interleaving patterns or combinations of grid mapping patterns and interleaving patterns; or different users are assigned with different combinations of interleaving patterns and grid mapping patterns, different users are differentiated by combinations of interleaving patterns and grid mapping patterns, and different data flows of the same user are differentiated by preamble sequences; or different users are assigned with different combinations of interleaving patterns and preamble sequences, and different data flows of the same user are assigned with different grid mapping patterns, different users are differentiated by combinations of interleaving patterns and preamble sequences, and different data flows of the same user are differentiated by grid mapping patterns; or different user are assigned with different combinations of grid mapping patterns and preamble sequences, and different data flows of the same user are assigned with different interleaving patterns, different users are differentiated by the combinations of grid mapping patterns and preamble sequences, and different data flows of the same users are differentiated by interleaving patterns.

A method of receiving signals in a communications system may include:

applying, by a receiver, RF-to-baseband processing to a received signal to obtain a baseband receiving signal, removing a cyclic prefix or estimating channel information of channels from different users to the receiver using a preamble sequence which was periodically inserted into the received signal and removing the preamble sequence; and

applying multi-user iterative detection to the baseband receiving signal after the preamble sequence or the cyclic prefix is removed to determine information bit sequences sent by different users; wherein the multi-user iterative detection comprises grid de-mapping using a grid mapping manner used by a transmitter.

Preferably, signals of different users are differentiated by interleaving patterns, and/or grid mapping patterns and/or preamble sequences; wherein the interleaving patterns are used in de-interleaving, the grid mapping patterns are used in grid de-mapping.

Preferably, the method comprises: before receiving the signal, transmitting preamble sequence configuration information, interleaving pattern information and grid mapping pattern information of a transmitter to the transmitter.

Preferably, if a transmitter transmits data of a plurality of data flows, the receiver determines information bit sequences of different data flows transmitted by different users after performing the multi-user iterative detection.

Preferably, if a transmitter comprises a plurality of transmitting antennas,

estimating channel information of channels from different transmitters to the receiver comprises: estimating equivalent channel information of channels including preprocessing from different users to the receiver using a preamble sequence which was periodically inserted into the received signal; the multi-user detection is multi-antenna multi-user detection; or

estimating channel information of channels from different transmitters to the receiver comprises: estimating channel information of channels from different users to the receiver using a preamble sequence which was periodically inserted into the received signal; before the multi-user detection, using pre-processing information used by a transmitter to de-preprocess the baseband receiving signal from which the preamble is removed.

A transmitter in a communication system may include: a baseband processing unit, an inserting unit, an RF processing unit and a transmitting unit;

the baseband processing unit is configured for applying channel encoding, modulation and grid mapping sequentially to an information bit sequence to be transmitted;

the inserting unit is configured for inserting a preamble sequence or a cyclic prefix into a symbol sequence generated from the grid mapping; wherein the preamble sequence is periodically inserted, the cyclic prefix is inserted into the symbol sequence in which the preamble has not been inserted;

the radio frequency processing unit is configured for applying baseband-to-RF processing to the symbol sequence after the preamble sequence or the cyclic prefix is inserted; and

the transmitting unit is configured for transmitting a signal generated from the baseband-to-RF processing.

A receiver in a communication system may include: a radio frequency (RF) processing unit, a channel estimation unit, and an iterative detection unit;

the RF processing unit is configured for applying RF-to-baseband processing to a received signal to obtain a baseband receiving signal;

the channel estimation unit is configured for removing a cyclic prefix or estimating channel information of channels from different transmitters to the receiver using a preamble sequence periodically inserted into the received signal and removing the preamble sequence; and

the iterative detection unit is configured for applying multi-user iterative detection to the baseband receiving signal after the preamble sequence or the cyclic prefix is removed to determine information bit sequences sent by different users; wherein the multi-user iterative detection comprises grid de-mapping using a grid mapping manner used by a transmitter.

According to the above technical mechanism, the present disclosure applies channel encoding, modulation and grid mapping sequentially to an information bit sequence which is to be transmitted; inserts a preamble sequence or a cyclic prefix into a symbol sequence generated from the grid mapping and transmitting a sequence obtained after the insertion of the preamble sequence or the cyclic prefix and the baseband-to-RF processing; the preamble sequence is periodically inserted, the cyclic prefix is inserted into the symbol sequence in which the preamble has not been inserted. Through the above processing, single carrier modulation and non-orthogonal multiple access are combined to solve the problem of high PAPR at the transmitting end and improve PA efficiency.

FIG. 1 is a schematic diagram illustrating the principle of a transmitter in accordance with the present disclosure;

FIG. 2 is a flowchart illustrating a method of transmitting a signal in accordance with the present disclosure;

FIGS. 3A and 3B are a block diagram illustrating a principle of multiple access in accordance with the present disclosure;

FIG. 4 is a schematic diagram illustrating a receiving method in accordance with the present disclosure;

FIG. 5 is a schematic diagram illustrating another receiving method in accordance with the present disclosure;

FIG. 6 is a schematic diagram illustrating RF-to-baseband processing;

FIG. 7 is a schematic diagram illustrating differentiating different users using different preamble sequences;

FIG. 8 is a schematic diagram illustrating changing the periodicity of transmitting a preamble sequence according to changes in channel condition in accordance with an example;

FIG. 9 is a schematic diagram illustrating a process of requesting adjustment of the periodicity of transmitting preamble;

FIG. 10 is a schematic diagram illustrating a signal structure for temporarily shortening the periodicity of transmitting a preamble sequence;

FIG. 11 is a schematic diagram illustrating the structure of a transmitter which combines superimposed data flows with multiple access;

FIG. 12 is a schematic diagram illustrating a method of combining transmission of a single data flow with multiple antennas;

FIG. 13 is a schematic diagram illustrating the structure of a receiver which combines transmission of a single data flow with multiple antennas;

FIG. 14 is a schematic diagram illustrating a method of combining multiple antennas which are mapped individually with transmission of multiple data flows;

FIG. 15 is a schematic diagram illustrating a manner of combining multiple antennas with superimposed data flows;

FIG. 16 is a schematic diagram illustrating the basic structure of a transmitter in accordance with the present disclosure; and

FIG. 17 is a schematic diagram illustrating the basic structure of a receiver in accordance with the present disclosure.

In order to make the objectives, technical schemes and merits of the present invention clearer, a detailed description of the present disclosure is hereinafter given with reference to specific embodiments.

The present disclosure provides a method of transmitting signals based on single carrier modulation and a corresponding transmitter, and provides a non-orthogonal multiple access method based on the transmitter and the transmitting method. Compared with conventional code division multiple access (CDMA), the multiple access method of the present disclosure distinguishes users by using different preamble sequence and/or grid mapping patterns, thus multiple access is not restricted by orthogonal code resources. Alternatively, processing at the transmitter may also include interleaving, and users may also be differentiated using interleaving patterns. Further, since grid mapping is used, it is possible to flexibly configure users' data rate by configuring different grid mapping patterns. Grid mapping can also map data symbol sequences onto all or some of assigned time-frequency resources, which facilitates reusing the same time-frequency resources by multiple users, increases the number of served users, and helps to combat interference and fading. At the same time, single-carrier modulation is used in the present disclosure to help reduce the peak-to-average ratio and improve energy efficiency at the transmitter side.

With the rapid development in the information industry, especially the rapid growth of demand for mobile Internet and the Internet of Things (IoT), future mobile communications technology is faced with unprecedented challenges. According to a report of ITU, ITU-R M.[IMT.BEYOND 2020.TRAFFIC], the mobile traffic volume in 2020 is estimated to be almost 1000 times of that in 2010 (which is in the 4G era), and the number of connected user terminals may exceed 17 billion. The number of connected devices will see more drastic growth if a mass of IoT devices are gradually connected to the mobile communication network. In view of the challenge, the fifth generation mobile communication technology (5G) for the 2020 era is being widely studied by the communication industry and the academia. The ITU report ITU-R M.[IMT.VISION] discusses the framework and overall target of 5G, detailing the prospect of demands for 5G, application scenarios, and key parameters. The ITU report ITU-R M.[IMT.FUTURE TECHNOLOGY TRENDS] provides information regarding future trends of the 5G technology, aiming at remarkably increasing system throughput, providing uniform user experiences, improving extensibility to support IoT, reducing time delay, increasing power efficiency, reducing costs, increasing network flexibility, supporting emerging services, improving flexibility in utilizing the spectrum resources and the like.

Facing the more diversified business scenarios in 5G, flexible multiple access techniques are needed to support different scenarios and business requirements. For example, under the business scenario of massive connection, it is the key problem to be solved by 5G multiple access techniques that how to serve more users with the limited resources. Conventional 4G LTE networks mainly adopts Orthogonal Frequency Division Multiplexing (OFDM)-based multiple access techniques. However, conventional orthogonality-based access techniques cannot meet the requirements of 5G for 5 to 15 times increase in spectral efficiency and area and millions of connected user per square kilometer. Non-orthogonal multiple access (NoMA) technology enables multiple users to reuse the same resources, thus can greatly increase the maximum number of allowed user connections. Since users are given more access opportunities, the overall throughput and spectrum efficiency of the network can be remarkably increased. In addition, considering the cost and implementation complexity of terminals, the scenario of massive machine type communication (mMTC) may require a multiple access technique that is simple to use, handle and process. In low-latency or low-power consumption scenarios, non-orthogonal multiple access (NoMA) can enable contention-based access without scheduling, low-latency communication, and reduce switch-on time and power consumption.

Non-orthogonal multiple access techniques currently being studied include: Multiple User Shared Access (MUSA), Non-Orthogonal Multiple Access (NOMA), Pattern Division Multiple Access (PDMA), Sparse Code Multiple Access (SCMA), Interleave Division Multiple Access (IDMA). MUSA identifies users using code words, SCMA identifies users using code books, NOMA identifies users using power, PDMA identifies users using different characteristic patterns, and IDMA identifies users using interleaving sequences. Details of IDMA can be found in an earlier document: “Interleave Division Multiple Access” by Li Ping, Lihai Liu, Keying Wu and W. K. Leung, IEEE Transactions on Wireless Communication, Vol. 5, No.4, pp. 938-947, Apr. 2006.

At present, a scheme which combines multicarrier modulation (such as OFDM carrier modulation) and non-orthogonal multiple access (e.g., SCMA, IDMA, etc.) has been proposed. However, under the scheme, the transmitting terminal may encounter high peak-average power ratio (PAPR) which may result in low efficiency of power amplifier (PA) and low power efficiency of the whole system, and the difficulty in implementing components of devices is also increased. This has become a drawback in enabling a large number of low-cost devices to access the network in 5G mMTC scenarios, and makes it hard to meet the demand of keeping the battery life of devices up to 10-15 years.

FIG. 1 is a block diagram illustrating the principle of a novel transmitter of the present disclosure. FIG. 2 is a flowchart illustrating a basic method of transmitting a signal in accordance with the present disclosure. The method as shown in FIG. 2 may be implemented by a transmitter as shown in FIG. 1. The transmitting method and the transmitter of the present disclosure will be briefly described below with reference to FIG. 1 and FIG. 2. As shown in FIG. 2, the transmitting method may include the following procedures.

In step 201, channel encoding is applied to an information bit sequence which is to be transmitted.

Firstly, an information bit sequence d_k={d_k(m),m=0, ... ,M-1} (M is the length of the information bit sequence) is processed through channel encoding. The channel encoding may use a code composed of a component code with a code rate of R₁, or a code composed of a plurality of component codes. The component code may be Turbo code, low density parity check (LDPC) code, repetition code (RC), or the like. For example, the code may be generated by combining a Turbo code whose code rate is R₁ with a repetition spreading code whose code rate is R₂ to generate a lower code rate of R₃=R₂R₁, or may be a Turbo code with a code rate of R₃. The information bit sequence d_k may be channel encoded to obtain a coded sequence c_k={c_k(n),n=0, ... ,N-1} (N is the length of the sequence after the channel encoding).

In step 202, the coding sequence after the channel encoding is interleaved, and the sequence after the interleaving is modulated.

The coded sequence c_k is interleaved by interleaver α_k to obtain an interleaved sequence x_k={x_k(n),n=0, ... ,N-1}. α_k represents a bit (chip) level interleaving pattern, the length of the interleaved sequence is identical to the length of the sequence fed into the interleaver. The interleaving reduces correlation of neighboring chips, facilitates detection by chip at the receiver. The interleaving pattern α_k may be formed by digits in {0,1, ... ... ,N} arranged in a random order. Digits from 0 to N represent positions of data.

The interleaved sequence obtained is processed through bit-to-symbol modulation to generate a symbol sequence S_k={S_k(l),l=0, ... ,L-1}. L is the length of the symbol sequence, and is related with the modulation scheme and the length of the interleaved sequence. The modulation scheme may be a constellation-based modulation scheme (e.g., quadrature amplitude modulation (QAM), phase-shift keying, or the like), or may be a waveform modulation scheme (e.g., frequency-shift keying (FSK), or the like).

The above interleaving process is a preferable process. The transmitter may omit the interleaving process, i.e., and the modulation operation may be performed immediately after the channel coding. In the following description of the present disclosure, the interleaving process is included in all of the following described examples.

In step 203, grid mapping is applied to the symbol sequence after the modulation.

The symbol sequence S_k is processed through grid mapping to generate a mapped symbol sequence. The grid mapping pattern used in the grid mapping is denoted by β_k. The grid mapping can map symbols carrying user information onto all or some of assigned time-frequency resources, thus can help combating interference and fading. Meanwhile, if different users use different grid mapping patterns, the system can serve more users with the same time-frequency resources.

In step 204, a preamble sequence or a cyclic prefix is inserted into the symbol sequence generated from the grid mapping.

The preamble sequence is periodically inserted, thus some symbol sequences may have the preamble sequence inserted and some other symbol sequences may not have the preamble sequence inserted. When the preamble sequence is not inserted, a cyclic prefix is inserted into the symbol sequence. When the preamble sequence is inserted, no cyclic prefix is inserted. If the preamble sequence is inserted, preamble sequences assigned to different users are different from and orthogonal to each other. That is, different users who are transmitting signals on the same time-frequency resources have different preamble sequence and the preamble sequence are orthogonal to each other. As such, the receiver can estimate the channel of each user, which facilitates frequency domain equalization. If the cyclic prefix is inserted, data at the tail of the signal is copied to the head of the signal to serve as the cyclic prefix.

In step 205, a symbol sequence in which the preamble sequence or the cyclic prefix has been inserted is processed through baseband-to-RF processing and then transmitted.

The data sequence obtained after the processing of step 204 is processed through baseband-to-RF processing or the like, and is transmitted finally. The single-carrier modulation enables the transmitter to achieve a lower peak-to-average ratio, thus energy efficiency can be increased and the transmitter can be put to commercial use.

Hence, the basic signal transmitting method of the present disclosure is completed.

Based on the above-mentioned transmitter as shown in FIG. 1 and the transmitting method as shown in FIG. 2, the present disclosure provides a new multiple access method in which different users are differentiated with each other by preamble sequences, interleaving patterns and/or grid mapping patterns. For facilitating description, the transmitting method and the receiving method based on multiple access are described together. As shown in FIGS. 3A and 3B, K transmitters obtain respective interleaving information, grid mapping information, and/or preamble sequence configuration information from the network side. The method of obtaining the above information from the network side may include: the transmitter receives the information from the network side via a physical broadcast channel, a physical downlink control channel, or a physical downlink shared channel. The interleaving pattern information and the grid mapping information specify an interleaving pattern and a grid mapping pattern which may be identified by looking up a table or the like. The network side may directly configure the detailed information of the interleaving pattern, that is, the interleaving pattern included in the interleaving pattern information may be directly used as the interleaving pattern used in the interleaving process. Alternatively, the transmitter may configure a mother interleaver and generate an interleaver according to a certain generation rule. That is, the interleaving pattern included in the interleaving pattern information is used as the interleaving pattern of the mother interleaver, and the interleaving used in the interleaving process can be generated by cyclically shifting the interleaving pattern of the mother interleaver according to a pre-determined rule. The interleaving pattern and the grid mapping information may be used by a receiver as identities for distinguishing different users. The preamble configuration information specifies the preamble sequence used by the user. The periodicity of inserting the preamble sequence may be predetermined, e.g., defined in a protocol, or included in the preamble configuration information. According to the above, different transmitters corresponding to different users obtain respective interleaving information, grid mapping information and preamble sequence configuration information for distinguishing different users, and the transmitter performs signal transmission according to the method as shown in FIG. 2.

As in the above, signals transmitted by K transmitters according to the transmission method as shown in FIG. 2 pass through respective channels, then converge at the receiver with impact of noise. Then, the detection of the user signal at the receiver is described.

The receiver uses multi-user iterative detection. As shown in FIGS. 3A and 3B, the receiver first applies RF-to-baseband processing to the received mixed signal to obtain a time-domain signal as a baseband receiving signal. Then, if it is a preamble sequence that was inserted by the transmitter, the receiver estimates the channel information of each user using the preamble sequence of the users which are orthogonal to each other, and feeds the baseband signal after removal of the preamble sequence into a multi-user detector; If it is a cyclic prefix that was inserted at the transmitter, the receiver removes the cyclic prefix and feeds the signal after removal of the cyclic prefix into a multi-user detector. The multi-user detector calculates posterior probability of each bit or each symbol using the baseband receiving signal from which the preamble sequence or the cyclic prefix has been removed, estimated channel information of each user and the prior probability information of each bit of each user obtained from the previous iteration process, and calculates extrinsic information A using prior probability information inputted into the detector. The extrinsic information A outputted by the detector is processed through grid de-mapping according to the grid mapping pattern β_k of each user. A soft information sequence recovered is deinterleaved using the interleaving pattern corresponding to the user. Soft information B after the de-interleaving is inputted into a decoder. In the decoder, decoding is performed using a component code used by the transmitter, and user data is obtained after a decision is made. For the next iteration detection, the decoder encodes the decoded soft information again using the same channel encoding with that in the transmitter, and the de-interleaved soft information B is subtracted from the prior probability information C which is channel encoded and outputted by the decoder to obtain extrinsic information D. The obtained extrinsic information D is interleaved again using the interleaving pattern α_k, and processed through grid mapping again using the grid mapping pattern. The sequence generated from the grid mapping is inputted into the multi-user detector as prior probability information. Hence, an iteration of detection is complete. The above procedures can be repeated as the next iteration of detection and decoding. In the above process, information passed down in the iterative detection and decoding is always probability information indicating the probability of the bit being 0 or 1 or the probability of a symbol being a value. This kind of information is referred to as soft information. The logarithmic likelihood or logarithmic probability can be used to represent the soft information to simplify the implementation. In the first iteration, there is no prior probability information, thus prior probabilities inputted into the multi-user detector are equally distributed probabilities; a subsequent iteration uses the prior probability information updated in the previous iteration. If the number of iterations reaches a pre-determined maximum value, the decoder performs a hard decision to obtain a final result regarding user data. The above multi-user signal detector may use an elementary signal estimator (ESE), or a detector based on message passing algorithm (MPA), or a detector based on serial interference cancellation (SIC), or the like.

Based on the above receiving method, it is also possible to apply frequency domain equalization to the signal of each user and perform iterative detection and decoding through IFFT conversion and FFT conversion, or to apply time-domain equalization to the signal of each user and perform iterative multi-user detection to improve detection performance. This can be done as follows:

The receiver may first perform RF-to-baseband processing on the received mixed signal, then process the obtained time-domain signal as a baseband reception signal via FFT processing to convert the time-domain signal into a frequency-domain signal. The obtained frequency-domain signal is processed through frequency domain equalization. Then a signal obtained after the equalization is converted into a time-domain signal using IFFT processing, and the time-domain signal is inputted into the multi-user detector. Subsequent operations are similar with those of the above method. The receiver may be as illustrated in FIG. 4.

In another example, the receiver may first perform RF-to-baseband processing on the received mixed signal, then process the obtained time-domain signal as a baseband reception signal via FFT processing to convert the time-domain signal into a frequency-domain signal. The obtained signal is inputted into the multi-user detector after a preamble sequence or a cyclic prefix is removed from the signal. Subsequent operations are similar with those of the above method except that data of each user are first processed through IFFT to be converted into a time-domain signal before grid de-mapping, and the time-domain signal is then processed through grid de-mapping. After being updated by the decoder and processed through the grid mapping, the extrinsic information may be first processed through an FFT operation, and then sent to the multi-user detector for the next iteration or for the iterative detection decoding for the next user. The receiver may be as illustrated in FIG. 5.

The receiver may first process the received mixed signal through RF-to-baseband processing, remove a preamble sequence or a cyclic shift from the obtained time-domain signal, and then send the signal to the multi-user detector for time domain equalization. The other operations are similar to those of the first method. In view of the foregoing, the signal receiving method of the present disclosure includes: a receiver processes a received signal through radio frequency to baseband processing to obtain a baseband receiving signal, removes a cyclic prefix or estimates channel information from different transmitters to a receiver using a preamble sequence which was periodically inserted into the received signal and removes the preamble sequence. The receiver processes the baseband receiving signal through iterative detection after the preamble sequence or the cyclic prefix is removed from the baseband signal to determine information bit sequences sent by different users. In multi-user iterative detection, grid de-mapping is performed according to a grid mapping manner used by the transmitter, and may be performed according to a conventional method. The multi-user iterative detection using the outer information as shown in FIGS. 3A and 3B are merely an example, not for limiting the iterative detection of the present disclosure. The detection method of FIGS. 3A and 3B are performed based on an example where a transmitter performs interleaving. In the iterative detection as shown in FIGS. 3A and 3B, any iteration includes: applying multi-user detection to the baseband receiving signal from which the preamble or the cyclic prefix has been removed using the prior probability information of the information bits of each user and the estimated channel information of each user generated in the previous iteration to obtain the posterior probability information of each bit or each symbol of each user, subtracting the prior probability information from the posterior probability information to obtain the outer information; applying grid de-mapping and de-interleaving to the outer information, and applying channel decoding and data decision to the outer information after the de-interleaving to obtain soft information of data of each use; the prior probability information is bit information obtained by processing the decoded soft information through the same channel encoding as performed at the transmitter and processing the channel encoded soft information through the same interleaving and grid mapping process as performed at the transmitter after the de-interleaved soft information is subtracted from the channel encoded soft information. If the transmitter does not perform an interleaving process, the de-interleaving process is not included in the iteration process described above. The following descriptions of the receiving method are all based on an example where a transmitter performs interleaving, and the example is not for limiting the receiving method of the present disclosure.

Embodiment one:

In this embodiment, a working process in a transmitter is described with reference to a set of system configurations (e.g., channel encoding parameters, design parameters of an interleaving device and grid mapping, assigning of preamble sequences).

FIGS. 3A and 3B are a block diagram illustrating a system. Transmitters obtain respective interleaving pattern information, grid mapping information and configuration of preamble sequence from a physical broadcast channel, a physical downlink control channel or a physical downlink shared channel. The configuration of preamble sequence specifies the preamble sequence of a user and the periodicity of inserting the preamble. The interleaver and the grid mapping information specify an interleaving pattern and a grid mapping pattern which may be identified by looking up a table or the like. The system may directly configure specific information of the interleaver, or may make the transmitters generate respective interleavers according to a mother interleaver and a certain generation rule, e.g., generating an interleaver using a mother interleaver configured based on a rule that the k’th transmitter uses a k-bit cyclic shifting of the mother interleaver. The interleaving pattern α_k may be generated using {0,1, ... ... ,N} which is randomly scrambled. The values from 0 to N denotes the order of the position taken by each data. For example, in this embodiment, α_k={4,503, ... ... ,52}, and it can be obtained that x_k(0)=c_k(4),x_k(1)=c_k(503), ... ... ,x_k(503)=c_k(52).

It is assumed that a transmitter has an information bit sequence d_k={d_k(m),m=0, ... ,M-1} with a length of M=126, i.e., the transmitter has 126 information bits. The information bit sequence is processed through channel encoding. The channel encoding uses a combination of an LTE Turbo code whose code rate is R₁=1/2 and a repetitive spread spectrum code whose length is 2 (equivalent code rate R₂=1/2), thus the code rate generated by the whole channel encoding is R₃=R₂R₁=1/4. The channel encoding may also use a Turbo code or another component code with a code rate of 1/4. The information bit sequence d_k may be channel encoded to obtain a coded sequence c_k={c_k(n),n=0, ... ,N-1} (N is the length of the sequence after the channel encoding, N=M/R₃=126*4=504). The coded sequence c_k is then interleaved using interleaving pattern α_k to obtain an interleaved sequence x_k={x_k(n),n=0, ... ,N-1}. The interleaving pattern α_k is a bit (chip) level interleaver, and the length of the interleaved sequence is identical to the length of the sequence fed into the interleaver. The interleaving reduces correlation between neighboring bits (chips), thus facilitates detection by bit (chip) at the receiver.

The interleaved sequence x_k obtained is processed through bit-to-symbol modulation to generate a symbol sequence S_k={S_k(l),l=0, ... ,L-1} (L is the length of the symbol sequence, and is related with the modulation scheme and the length of the interleaved sequence). The modulation scheme used in this example is QPSK, the modulation rank M_s=2, i.e., two code words (bits) are mapped to a symbol. Thus, the length of the symbol sequence

. The symbol sequence S_k is then processed through grid mapping to generate a symbol sequence S'_k={S'_k(l'),l=0, ... ,L'-1} (L' is the length of the sequence after the grid mapping). The present disclosure uses single carrier modulation, thus the grid mapping are applied to time-domain symbols. The grid mapping may be implemented in various manners, e.g., zero-filling before interleaving, direct zero-insertion, zero-insertion after interleaving, interleaving mapping, and direct mapping. The purpose of grid mapping is to map the symbols carrying user information to all or part of the assigned time-frequency resources, to facilitate anti-interference and anti-fading, and to support more users on the same time-frequency resources. Detailed process of the grid mapping can be found in Chinese application 201610082443.9 filed on February 5, 2016 by the present applicant. In addition, it is worth noting that if the signal is mapped to part of the resources, the overall equivalent code rate of the transmitter R can be further reduced with respect to the encoding rate R₃. The amount of the decrease depends on the density of the grid mapping pattern. In this embodiment, the length of the symbol sequence is increased by one time, the equivalent code rate of the transmitter is reduced by half, i.e.,

. Then, according to the configuration information of the preamble sequence, a cyclic prefix or an assigned preamble sequence is added to the front of the symbol sequence S'_k, and the preamble sequence of the users are different from each other and are orthogonal to each other. Then the signal is processed through D/A conversion, up conversion and the remaining baseband-to-RF processing, and the signal is sent out finally.

At the receiver, a combination of signals from multiple transmitters, suffered from the interference of noise, is received. In this embodiment, the receiver uses multi-user iterative detection in decoding. The received mixed signal is first processed through RF-to-baseband processing, as shown in FIG. 6.

The obtained signal is processed to remove a cyclic prefix or a preamble sequence, and preamble sequence assigned to users are used to estimate respective channels of the users. The signal is then fed into a multi-user detector. In the first iteration, a pre-determined prior probability of user signal and channel information estimated for each user are used by the multi-user detector to calculate posterior probability information of each user signal, and the posterior probability information and the prior probability are used for calculating an extrinsic information sequence A. Grid de-mapping is performed using the grid mapping pattern of each user. A soft information sequence obtained from the grid de-mapping is fed into the interleaving pattern α_k corresponding to the user to be deinterleaved. Soft information B after the de-interleaving is inputted into a decoder. The decoder decodes the information using a component code used at the transmitter. In this embodiment, a repetitive spread spectrum decoding is first performed, and Turbo decoding is then performed, and a decision is made to obtain user data. The prior probability information of a user signal is updated for the next iteration and detection. Thus the soft information obtained from the decoding is processed through the same channel encoding with that performed at the transmitter to obtain a prior probability information C, i.e., using the same component code or the same combination of component codes as used in the transmitter. In this embodiment, the soft information is processed using a Turbo with a code rate of R₁=1/2 and a repetitive spread spectrum code with a length of 2. The soft information B obtained from the previous interleaving is subtracted from the prior probability information C after the channel encoding to obtain extrinsic information D. The obtained extrinsic information D is interleaved again using the interleaving pattern α_k, and processed through grid re-mapping again using the grid mapping pattern. The sequence obtained after the grid re-mapping is fed into the multi-user detector as the prior probability sequence to serve as the input of the next iteration of detection. Hence, an iteration of detection is completed. The above procedures can be repeated as the next iteration of detection and decoding. If the number of iterations reaches a pre-determined maximum value, the decoder performs a hard decision to obtain a final result of user data. Because the first iteration does not have prior probability information, the prior probability inputted into the multi-user detector is equally distributed probabilities. Subsequent iterations use the prior probability information updated in respective preceding iterations. The above multi-user signal detector may use an elementary signal estimator (ESE), or a detector based on message passing algorithm (MPA), or a detector based on serial interference cancellation (SIC), or the like. As in embodiment one, the receiving processing may also include frequency-domain equalization for the signal of each user, and iterative detection and decoding using IFFT/FFT transformation. Alternatively, the receiving processing may also include time-domain equalization of user signal. Various embodiments are not elaborated herein.

Example two

A novel transmitter and a method of multi-user iterative detection and decoding are introduced in embodiment one. Based on those, this embodiment introduces a multiple access method of the transmitter.

FIGS. 3A and 3B are a schematic diagram of a transmitter and a receiver in a system. Transmitters obtain respective interleaving pattern information, grid mapping information and configuration of preamble sequence from a physical broadcast channel, a physical downlink control channel or a physical downlink shared channel. The configuration of preamble sequence specifies the preamble sequence of a user and the periodicity of inserting the preamble. The interleaver and the grid mapping information specify an interleaving pattern and a grid mapping pattern which may be identified by looking up a table or the like. The system may directly configure specific information of the interleaver, or may make the transmitters generate respective interleavers according to a mother interleaver and a certain generation rule, e.g., generating an interleaver using a mother interleaver configured based on a rule that the k’th transmitter uses a k-bit cyclic shifting of the mother interleaver. The interleaving pattern α_k may be generated using {0,1, ... ... ,N} which is randomly scrambled. The values from 0 to N denotes the order of the position taken by each data. For example, in this embodiment, α_k={4,503, ... ... ,52}, and it can be obtained that x_k(0)=c_k(4),x_k(1)=c_k(503), ... ... ,x_k(503)=c_k(52).

It is assumed that the system has K=4 transmitters, and each transmitter uses the transmitting method of embodiment one. It is assumed that a transmitter has an information bit sequence d_k={d_k(m),m=0, ... ,M-1} with a length of M=126, i.e., the transmitter has 126 information bits. The information bit sequence is processed through channel encoding. The channel encoding uses a combination of an LTE Turbo code whose code rate is R₁=1/2 and a repetitive spread spectrum code whose length is 2 (equivalent code rate R₂=1/2), thus the code rate generated by the whole channel encoding is R₃=R₂R₁=1/4. The channel encoding may also use a Turbo code or another component code with a code rate of 1/4. The information bit sequence d_k may be channel encoded to obtain a coded sequence c_k={c_k(n),n=0, ..., N-1} (N is the length of the sequence after the channel encoding, N=M/R₃=126*4=504). The coded sequence c_k is then interleaved using interleaving pattern α_k to obtain an interleaved sequence x_k={x_k(n),n=0, ... ,N-1}.

The interleaving pattern α_k is a bit (chip) level interleaver, and the length of the interleaved sequence is identical to the length of the sequence fed into the interleaver. The interleaving reduces correlation between neighboring bits (chips), thus facilitates detection by bit (chip) at the receiver.

The interleaved sequence x_k obtained is processed through bit-to-symbol modulation to generate a symbol sequence S_k={S_k(l),l=0, ... , L-1} (L is the length of the symbol sequence, and is related with the modulation scheme and the length of the interleaved sequence). The modulation scheme used in this example is QPSK, the modulation rank M_s=2, i.e., two code words (bits) are mapped to a symbol. Thus, the length of the symbol sequence

. The symbol sequence S_k is then processed through grid mapping to generate a symbol sequence S'_k={S'_k(l'),l=0, ... , L'-1} (L' is the length of the sequence after the grid mapping). The grid mapping may be implemented in various manners, e.g., zero-filling, direct zero-insertion, zero-insertion after interleaving, interleaving mapping, and direct mapping. The grid mapping pattern is denoted by β_k. The purpose of grid mapping is to map the symbols carrying user information to all or part of the assigned time-frequency resources, to facilitate anti-interference and anti-fading, and to support more users on the same time-frequency resources. In addition, it is worth noting that if the signal is mapped to part of the resources, the overall equivalent code rate of the transmitter R can be further reduced with respect to the encoding rate R₃. The amount of the decrease depends on the density of the grid mapping pattern. In this embodiment, the length of the symbol sequence is increased twofold, the equivalent code rate of the transmitter is reduced by half, i.e.,

. Then, according to the configuration information of the preamble sequence, a cyclic prefix or an assigned preamble sequence is added to the front of the symbol sequence S'_k, and the preamble sequence of the users are different from each other and are orthogonal to each other.

This embodiment differentiates users using any one or any combination of interleaving patterns, grid mapping patterns, preamble sequences. Specifically, users may be differentiated with each other by:

1. different interleaving patterns;

2. different grid mapping patterns;

3. different combinations of interleaving patterns and grid mapping patterns;

4. different preamble sequences, as shown in FIG. 7;

5. different combinations of preamble sequence and interleaving patterns;

6. different combinations of preamble sequence and grid mapping patterns;

7. different combinations of preamble sequence and interleaving patterns.

Since different preamble sequence may be used to differentiate channels of different users at the receiver, the above manners 4 to 7 may directly use preamble sequence to differentiate different user data, or differentiate users using the preamble sequence together with other information (e.g., interleaving patterns and/or grid mapping patterns).

The system may decide which manner is used for differentiating users according to network load γ, as in Table 1. In table 1, γ₁<γ₂.

When the network load is smaller than or equal to a pre-determined threshold 1, i.e., γ₁, the network uses preamble sequence or interleaving patterns or grid mapping patterns to differentiate users;

When the network load is smaller than or equal to a pre-determined threshold 2, i.e., γ₂, and is larger than the pre-determined threshold 1, i.e., γ₁, the network uses combinations of preamble sequence and interleaving patterns, or combinations of preamble sequence and grid mapping patterns, or combinations of interleaving patterns and grid mapping patterns to differentiate users;

When the network load is larger than or equal to the pre-determined threshold 2, i.e., γ₂, the network uses combinations of preamble sequences, interleaving patterns and grid mapping patterns to differentiate users.

According to the above mechanism of differentiating users, the larger the network load is, the more the number of combinations for differentiating user is, thus the system can support more users. In addition, if the processing at the transmitter does not include interleaving, the above manners of differentiating users do not include those using interleaving patterns or combinations including interleaving patterns.

At the receiver, a combination of signals from multiple transmitters, suffered from the interference of noise, is received. In this embodiment, the receiver uses multi-user iterative detection and decoding. The received mixed signal is first processed through RF-to-baseband processing. The obtained signal is processed to remove a cyclic prefix or a preamble sequence, and preamble sequence assigned to users are used to estimate respective channels of the users. The signal is then fed into a multi-user detector. In the first iteration, a pre-determined prior probability of user signal and channel information estimated for each user are used by the multi-user detector to calculate posterior probability information of each user signal, and the posterior probability information and the prior probability are used for calculating an extrinsic information sequence A. Grid de-mapping is performed using the grid mapping pattern of each user. A soft information sequence obtained from the grid de-mapping is fed into the interleaving pattern α_k corresponding to the user to be de-interleaved. Soft information B after the de-interleaving is inputted into a decoder. The decoder decodes the information using a component code used at the transmitter. In this embodiment, a repetitive spread spectrum decoding is first performed, and Turbo decoding is then performed, and a decision is made to obtain user data. The prior probability information of a user signal is updated for the next iteration and detection. Thus the soft information obtained from the decoding is processed through the same channel encoding with that performed at the transmitter to obtain a prior probability information C, i.e., using the same component code or the same combination of component codes as used in the transmitter. In this embodiment, the soft information is processed using a Turbo with a code rate of R₁=1/2 and a repetitive spread spectrum code with a length of 2. The soft information B obtained from the previous interleaving is subtracted from the prior probability information C after the channel encoding to obtain extrinsic information D. The obtained extrinsic information D is interleaved again using the interleaving pattern α_k, and processed through grid mapping again using the grid mapping pattern. The sequence obtained after the grid re-mapping is fed into the multi-user detector as the prior probability sequence to serve as the input of the next iteration of detection. Hence, an iteration of detection is completed. The above procedures can be repeated as the next iteration of detection and decoding. If the number of iterations reaches a pre-determined maximum value, the decoder performs a hard decision to obtain a final result of user data. Because the first iteration does not have prior probability information, the prior probability inputted into the multi-user detector is equally distributed probabilities. Subsequent iterations use the prior probability information updated in respective preceding iterations. The above multi-user signal detector may use an elementary signal estimator (ESE), or a detector based on message passing algorithm (MPA), or a detector based on serial interference cancellation (SIC), or the like. As in embodiment one, the receiving processing may also include frequency-domain equalization for the signal of each user, and iterative detection and decoding using IFFT/FFT transformation. Alternatively, the receiving processing may also include time-domain equalization of user signal. Various embodiments are not elaborated herein. If the number of iterations reaches a pre-determined maximum value, the decoder performs a hard decision to obtain a final result of user data. Data of users can be obtained according to the manner of differentiating users being used.

Example three

Embodiment one introduces a working process in a transmitter with reference to a set of system configurations (e.g., channel encoding parameters, design parameters of an interleaving device and grid mapping, assigning of preamble sequences). As described above, the periodicity of inserting the preamble sequence can be pre-determined, e.g., defined in a protocol, or can be determined by the network side of the system and included in preamble sequence configuration information. This embodiment provides a transmitting method for situations where the periodicity of transmitting preamble sequence at a transmitter is decided by the system.

FIGS. 3A and 3B are a block diagram illustrating a system. It is assumed that a transmitter has an information bit sequence d_k={d_k(m),m=0, ... ,M-1} with a length of M=126, i.e., the transmitter has 126 information bits. The information bit sequence is processed through channel encoding. The channel encoding uses a combination of an LTE Turbo code whose code rate is R₁=1/2 and a repetitive spread spectrum code whose length is 2 (equivalent code rate R₂=1/2), thus the code rate generated by the whole channel encoding is R₃=R₂R₁=1/4. The channel encoding may also use a Turbo code with a code rate of 1/4 or another component code. The information bit sequence d_k may be channel encoded to obtain a coded sequence c_k={c_k(n),n=0, ... ,N-1} (N is the length of the sequence after the channel encoding, N=M/R₃=126*4=504). The coded sequence c_k is then interleaved using interleaving pattern α_k to obtain an interleaved sequence x_k={x_k(n),n=0, ... ,N-1}. The interleaving pattern α_k is a bit (chip) level interleaver, and the length of the interleaved sequence is identical to the length of the sequence fed into the interleaver. The interleaving reduces correlation between neighboring bits (chips), thus facilitates detection by bit (chip) at the receiver. Transmitters obtain respective interleaving pattern information, grid mapping information and configuration of preamble sequence from a physical broadcast channel, a physical downlink control channel or a physical downlink shared channel. The configuration of preamble sequence specifies the preamble sequence of a user and the periodicity of inserting the preamble. The network side may determine the periodicity of inserting a preamble sequence at a transmitter according to “channel change”. For example, it may be determined that preamble sequence are transmitted according to a larger periodicity (i.e., less frequently) or a smaller periodicity (i.e., more frequently). Table 2 is an example of determining the periodicity of inserting preamble sequences.

As shown in FIG. 8, the system may add the determined periodicity of transmitting preamble sequence into preamble sequence configuration information, and transmit the information to transmitters via downlink broadcast channels, downlink control channel, or downlink shared channels. The interleaver and the grid mapping information specify an interleaving pattern and a grid mapping pattern which may be identified by looking up a table or the like. The system may directly configure specific information of the interleaver, or may make the transmitters generate respective interleavers according to a mother interleaver and a certain generation rule, e.g., generating an interleaver using a mother interleaver configured based on a rule that the k’th transmitter uses a k-bit cyclic shifting of the mother interleaver. The interleaving pattern α_k may be generated using {0,1, ... ... ,N} which is randomly scrambled. The values from 0 to N denotes the order of the position taken by each data. For example, in this embodiment, α_k={4,503, ... ... ,52}, and it can be obtained that x_k(0)=c_k(4),x_k(1)=c_k(503), ... ... ,x_k(503)=c_k(52).

. The symbol sequence S_k is then processed through grid mapping to generate a symbol sequence S'_k={S'_k(l'),l=0, ... ,L'-1} (L' is the length of the sequence after the grid mapping). The grid mapping may be implemented in various manners, e.g., zero-filling before interleaving, direct zero-insertion, zero-insertion after interleaving, interleaving mapping, and direct mapping. The purpose of grid mapping is to map the symbols carrying user information to all or part of the assigned time-frequency resources, to facilitate anti-interference and anti-fading, and to support more users on the same time-frequency resources. In addition, it is worth noting that if the signal is mapped to part of the resources, the overall equivalent code rate of the transmitter R can be further reduced with respect to the encoding rate R₃. The amount of the decrease depends on the density of the grid mapping pattern. In this embodiment, the length of the symbol sequence is increased twofold, the equivalent code rate of the transmitter is reduced by half, i.e.,

Embodiment four

Embodiment three provides a transmitting method for situations where the periodicity of a transmitter transmitting preamble sequence is decided by the system. This embodiment provides a transmitting method for situations where the periodicity of transmitting preamble sequence at a transmitter is decided by the transmitter.

FIGS. 3A and 3B are a block diagram illustrating a system. It is assumed that a transmitter has an information bit sequence M=126 with a length of d_k={d_k(m),m=0, ... ,M-1}, i.e., the transmitter has 126 information bits. The information bit sequence is processed through channel encoding. The channel encoding uses a combination of an LTE Turbo code whose code rate is R₁=1/2 and a repetitive spread spectrum code whose length is 2 (equivalent code rate R₂=1/2), thus the code rate generated by the whole channel encoding is R₃=R₂R₁=1/4. The channel encoding may also use a Turbo code with a code rate of 1/4 or another component code. The information bit sequence d_k may be channel encoded to obtain a coded sequence c_k={c_k(n),n=0, ... ,N-1} (N is the length of the sequence after the channel encoding, N=M/R₃=126*4=504). The coded sequence c_k is then interleaved using interleaving pattern α_k to obtain an interleaved sequence x_k={x_k(n),n=0, ... ,N-1}. The interleaving pattern α_k is a bit (chip) level interleaver, and the length of the interleaved sequence is identical to the length of the sequence fed into the interleaver. The interleaving reduces correlation between neighboring bits (chips), thus facilitates detection by bit (chip) at the receiver. Transmitters obtain respective interleaving pattern information, grid mapping information and configuration of preamble sequence from a physical broadcast channel, a physical downlink control channel or a physical downlink shared channel. The configuration of preamble sequence specifies the preamble sequence of a user and the periodicity of inserting the preamble.

As described in embodiment three, the network side may decide the preamble sequence transmitting periodicity that is to be notified to the users according to received channel state feedback or channel state information measured at the network side. In this embodiment, the transmitter may decide whether to request temporarily adjusting preamble sequence transmitting periodicity according to channel state information measured by the transmitter. For example, when the channel measurement information reflects a rapid change in channel, the transmitter request reducing preamble sequence transmitting periodicity by sending an uplink control channel, or an uplink shared channel to the network side, as shown in FIG. 9.

When the transmitter receives a response from the network side after sending the request of temporary adjusting preamble sequences, there may be two processing manners: one is the transmitter temporarily adjusts the periodicity of inserting preamble sequence according to a pre-determined rule, e.g., increasing the frequency or reducing the periodicity of transmitting preamble sequences; the other is the network side transmits a temporary adjustment instruction specifying a temporarily adjusted inserting periodicity, e.g., notifying users of a higher preamble sequence transmitting frequency. After the inserting periodicity is temporarily adjusted according to any of the above two manners, the preamble sequence transmitting periodicity in the next notification sent by the network side specifying preamble sequence configuration information recovers to a periodicity decided according to measurements at the network side. The signal structure as shown in FIG. 10 is a signal structure used when the temporarily shortened preamble sequence transmitting periodicity is 1 (e.g., the preamble sequence is transmitted in every frame).

The interleaver and the grid mapping information specify an interleaving pattern and a grid mapping pattern which may be identified by looking up a table or the like. The system may directly configure specific information of the interleaver, or may make the transmitters generate respective interleavers according to a mother interleaver and a certain generation rule, e.g., generating an interleaver using a mother interleaver configured based on a rule that the k’th transmitter uses a k-bit cyclic shifting of the mother interleaver. The interleaving pattern α_k may be generated using {0,1, ... ... ,N} which is randomly scrambled. The values from 0 to N denotes the order of the position taken by each data. For example, in this embodiment, α_k={4,503, ... ... ,52}, and it can be obtained that x_k(0)=c_k(4),x_k(1)=c_k(503), ... ... ,x_k(503)=c_k(52).

. The symbol sequence S_k is then processed through grid mapping to generate a symbol sequence S'_k={S'_k(l'),l=0, ... , L'-1} (L' is the length of the sequence after the grid mapping). The grid mapping may be implemented in various manners, e.g., zero-filling before interleaving, direct zero-insertion, zero-insertion after interleaving, interleaving mapping, and direct mapping. The purpose of grid mapping is to map the symbols carrying user information to all or part of the assigned time-frequency resources, to facilitate anti-interference and anti-fading, and to support more users on the same time-frequency resources. In addition, it is worth noting that if the signal is mapped to part of the resources, the overall equivalent code rate of the transmitter R can be further reduced with respect to the encoding rate R₃. The amount of the decrease depends on the density of the grid mapping pattern. In this embodiment, the length of the symbol sequence is increased twofold, the equivalent code rate of the transmitter is reduced by half, i.e.,

At the receiver, a combination of signals from multiple transmitters with the interference of noise is received. In this embodiment, the receiver uses multi-user iterative detection and decoding. The received mixed signal is first processed through RF-to-baseband processing. The obtained signal is processed to remove a cyclic prefix or a preamble sequence, and preamble sequences assigned to users are used to estimate respective channels of the users. The signal is then fed into a multi-user detector. In the first iteration, a pre-determined prior probability of user signal and channel information estimated for each user are used by the multi-user detector to calculate posterior probability information of each user signal, and the posterior probability information and the prior probability are used for calculating an extrinsic information sequence A. Grid de-mapping is performed using the grid mapping pattern of each user. A soft information sequence obtained from the grid de-mapping is fed into the interleaving pattern α_k corresponding to the user to be de-interleaved. Soft information B after the de-interleaving is inputted into a decoder. The decoder decodes the information using a component code used at the transmitter. In this embodiment, a repetitive spread spectrum decoding is first performed, and Turbo decoding is then performed, and a decision is made to obtain user data. The prior probability information of a user signal is updated for the next iteration and detection. Thus the soft information obtained from the decoding is processed through the same channel encoding with that performed at the transmitter to obtain a prior probability information C, i.e., using the same component code or the same combination of component codes as used in the transmitter. In this embodiment, the soft information is processed using a Turbo with a code rate of R₁=1/2 and a repetitive spread spectrum code with a length of 2. The soft information B obtained from the previous interleaving is subtracted from the prior probability information C after the channel encoding to obtain extrinsic information D. The obtained extrinsic information D is interleaved again using the interleaving pattern α_k, and processed through grid mapping again using the grid mapping pattern. The sequence obtained after the grid re-mapping is fed into the multi-user detector as the prior probability sequence to serve as the input of the next iteration of detection. Hence, an iteration of detection is completed. The above procedures can be repeated as the next iteration of detection and decoding. If the number of iterations reaches a pre-determined maximum value, the decoder performs a hard decision to obtain a final result of user data. In the first iteration, there is no prior probability information, thus prior probabilities inputted into the multi-user detector are equally distributed probabilities; a subsequent iteration uses the prior probability information updated in the previous iteration. The above multi-user signal detector may use an elementary signal estimator (ESE), or a detector based on message passing algorithm (MPA), or a detector based on serial interference cancellation (SIC), or the like. As in embodiment one, the receiving processing may also include frequency-domain equalization for the signal of each user, and iterative detection and decoding using IFFT/FFT transformation. Alternatively, the receiving processing may also include time-domain equalization of user signal. Various embodiments are not elaborated herein. If the number of iterations reaches a pre-determined maximum value, the decoder performs a hard decision to obtain a final result of user data. Data of users can be obtained according to the manner of differentiating users being used.

Embodiment five

The above embodiment introduces a novel transmitting method based on single carrier modulation. The single carrier-based method may restrict the data rate of users to a certain extent. This embodiment introduces a mechanism of improving single-user data rate by superimposing multiple transmission flows. The system is as shown in embodiment one. K transmitters adopts the transmitter structure of the present embodiment, and the receiver uses the multi-user combined iterative detection receiver as shown in FIGS. 3A and 3B to perform detection of data of K users.

In order to increase the transmission data rate of each single user, multiple data flows are transmitted at the same time at the same frequency at the transmitter after the multiple flows are superimposed. Modules of the transmitter are as shown in FIG. 11.

In FIG. 11, data flow 1 to data flow M are data flows of single users, and may be branches obtained by splitting a data flow generated by one data source, or may be respectively generated by M individual data sources. In another example, the data flows 1 to M may include some data flows obtained from splitting a data flow generated by one data source, and some data flows respectively generated by individual data sources. Data from each data flow is processed through channel encoding, interleaving, modulation and grid mapping, and a symbol flow obtained is processed through phase and power adjustment and then superimposed. The superimposed flow then has a cyclic prefix or a preamble sequence inserted, and then is processed through baseband-to-RF conversion before being transmitted. It should be noted that the cyclic prefix or the preamble sequence may also be inserted before the data flows are superimposed. When the data flows are superimposed before the cyclic prefix or the preamble sequence is inserted, different data flows of the same user have the same cyclic prefix or the same preamble sequence inserted. When the data flows are superimposed after the cyclic prefix or the preamble sequence is inserted, different data flows of the same user may have different cyclic prefix or different preamble sequences inserted.

The structure of the receiver for performing detection and decoding is similar to that as shown in FIGS. 3A and 3B. The multi-user detection performs symbol detection according to the phase and power adjustment applied to modulated symbols of each data flow of each user, and then performs subsequent iterative detection and decoding procedures. The iterative detection and decoding device outputs all of data flow information of each user, and the receiver performs identification and differentiation of user data according to interleaving patterns and/or grid mapping patterns and/or preamble sequences.

When the data flows are superimposed after the cyclic prefix or the preamble sequence is inserted, different data flows of different users may be assigned with different preamble sequences, and may be differentiated with each other according to assigning scheme of interleaving patterns and grid mapping patterns. The different data flows of different users include different data flows of the same user and data flows belonging to different users. The assigning scheme may be one of the following:

different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns; the receiver differentiates different data flows of different users by interleaving patterns or grid mapping patterns or preamble sequences;

different users are assigned with different interleaving patterns, and different data flows of the same user are assigned with the same interleaving pattern and different grid mapping patterns; the receiver differentiates different users by interleaving patterns, and differentiates different data flows of the same user by grid mapping patterns or preamble sequences or combinations of grid mapping patterns and preamble sequences;

different users are assigned with different grid mapping patterns, and different data flows of the same user are assigned with the same grid mapping pattern and different interleaving patterns; the receiver differentiates different users by grid mapping patterns, and differentiates different data flows of the same user by interleaving patterns or preamble sequences or combinations of interleaving patterns and preamble sequences;

different data flows of the same user are assigned with different grid mapping patterns or different interleaving patterns or different combinations of grid mapping patterns and interleaving patterns; the receiver differentiates different users by preamble sequences and differentiates different data flows of the same user by grid mapping patterns or interleaving patterns or combinations of grid mapping patterns and interleaving patterns;

different users are assigned with different combinations of interleaving patterns and grid mapping patterns, the receiver differentiates different users by combinations of interleaving patterns and grid mapping patterns, and differentiates different data flows of the same user by preamble sequences;

different users are assigned with different combinations of interleaving patterns and preamble sequences, different data flows of the same user are assigned with different grid mapping patterns; the receiver differentiates different users by combinations of interleaving patterns and preamble sequences, and differentiates different data flows of the same user by grid mapping patterns;

different users are assigned with different combinations of grid mapping patterns and preamble sequences, different data flows of the same user are assigned with different interleaving patterns; the receiver differentiates different users by combinations of grid mapping patterns and preamble sequences, and differentiates different data flows of the same user by interleaving patterns.

When data flows are superimposed before the cyclic prefix or the preamble sequence is inserted, different data flows of the same user are assigned with the same preamble sequence. Preamble sequences are used only in differentiate different users, and not used in differentiating different data flows of the same user. Different data flows of the same user are differentiated based on an assigning scheme of interleaving patterns and/or grid mapping patterns. Here, different data flows of different users include different data flows of the same user and data flows belonging to different users. The assigning scheme may be one of the following:

different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns; the receiver differentiates different data flows of different users by interleaving patterns or grid mapping patterns;

different users are assigned with different interleaving patterns, and different data flows of the same user are assigned with the same interleaving pattern and different grid mapping patterns; the receiver differentiates different users by interleaving patterns, and differentiates different data flows of the same user by grid mapping patterns;

different users are assigned with different grid mapping patterns, and different data flows of the same user are assigned with the same grid mapping pattern and different interleaving patterns; the receiver differentiates different users by grid mapping patterns, and differentiates different data flows of the same user by interleaving patterns;

The above description of the manners of differentiating different data flows of different users is based on an example where a transmitter performs interleaving. When the transmitter does not perform interleaving, manners using interleaving patterns or combinations including interleaving patterns may be excluded from the above manners.

The phase and power adjustment of different data flows is required to satisfy a criteria: ensuring symbols from different data flows of the same user do not overlap or cancel each other during the superimposing procedure. A preferred criteria for constellation points-based modulation is: while meeting the power restriction requirement, the criteria of phase and power adjustment of data flows through a lower rank modulation is designed according to the constellation of a higher rank modulation, i.e., the criteria is adjusted according to a modulation constellation of a modulation rank higher than the current modulation rank. Table 3 illustrates factors of phase and power adjustment of each flow for an example where BPSK modulation is used and a transmitter transmits 8 flows.

When the phase adjustment factor of the k‘th data flow is θ_k, the power adjustment factor is a_k, where θ_k and a_k are determined according to Table 3 and the symbol of the transmission constellation point is x_k, the actual transmitted symbol of the k‘th data flow is

. After the phase and power adjustment according to Table 3, the superimposed signal transmitted by the transmitter is a constellation similar to 16QAM modulation, and transmission symbols of the flows are not overlap with nor cancel each other during the superimposing procedure.

In order to serve multiple users using the same time-frequency resources, the receiver may send interleaving patterns, grid mapping patterns, preamble sequences for differentiating users, phase and power adjustment factors and the maximum supported flows through a table for lookup in a physical broadcast channel, a physical downlink control channel or a physical downlink shared channel. The transmitter determines the number of flows to be superimposed and the interleaving pattern, the grid mapping patter, the preamble sequence and phase and power adjustment factors assigned to each flow according to the number of data flows to be transmitted and the maximum number of flows supported.

If the number K of actually transmitted flows is smaller than the maximum number K_max of supported flows of the receiver, the transmitter may perform transmission according to the following schemes:

Only K data flows are transmitted, and the number of flows transmitted by the receiver is reported in a physical uplink control channel or a physical uplink shared channel. That is, a flow number indicator is transmitted, and the number of flows to be received is reported to the receiver by looking up a table.

Alternatively, K_max data flows are transmitted, among which K data flows are used for transmitting data and K_max-K data flows are all zero. Since all zero sequences is a code word allowed to be used in channel encoding, the receiver may determine the flow is not used for transmitting data when a detected sequence is all zero or almost all zero. That is, after the iterative detection and decoding, the number of zeros in the decoded sequence is calculated. When the number of zeros exceeds a pr-determined threshold, it is determined the flow is used for transmitting valid data; when the number of zeros does not exceed the threshold, it is determined the flow is not used for transmitting a valid sequence.

By superimposing multiple flows, the mechanism of this embodiment can support more users using the same time-frequency resources while increasing single-user transmission data rate and maintaining relatively high reliability.

Embodiment six

The embodiment introduces a mechanism which combines the transmitting method with multi-antenna technique. The system is as shown in embodiment one. K transmitters adopt the single-carrier based transmitting method of the present disclosure, have N_T transmitting antennas, and transmit data using a multi-antenna method. The receiver adopts the iterative detection and decoding method as shown in FIGS. 3A and 3B to detect and estimate a transmitted bit flow. The receiver is equipped with N_R receiving antennas.

The transmitter may perform transmission using multi-antenna technique according to one of the following methods.

As shown in FIG. 12, when the transmitter only transmits one data flow, the data flow is processed through channel encoding, interleaving, modulation and grid mapping, and then through serial-to-parallel conversion to convert one data flow into multiple data flows. Alternatively, a layer mapping similar to that in LTE may be performed to convert one data flow into multiple data flows. In order to estimate channel state information, the transmitter inserts preamble sequences or cyclic prefixes that are orthogonal to each other into each link after the serial to parallel conversion (or layer mapping). Preamble sequences used by different transmitters are also orthogonal to each other. The method of inserting the preamble sequences or the cyclic prefixes is the same with that in the above embodiments. The preamble sequences are periodically inserted. The cyclic prefixes are inserted when the preamble sequences are not inserted. Several subsequent processing are the same, and are not elaborated herein. The data flows in which the preamble sequences or the cyclic prefixes have been inserted are processed through preprocessing and baseband-to-RF processing to obtain multi-antenna data flows to be transmitted. The preprocessing may include space-time precoding, e.g., multiply with a precoding matrix, or be processed through space-time encoding, or the like. The receiver estimates preprocessed equivalent channel state information according to the preamble sequences. The receiver still adopts the iterative detection and decoding structure as shown in FIGS. 3A and 3B, which is as shown in FIG. 13. The received signals are processed through RF-to-baseband processing, equivalent channel estimation is performed using the preamble sequences or the cyclic prefixes are removed. Estimation of each transmission link signal is obtained after the signals are processed by the multi-antenna multi-user detector. The signals are processed through parallel-to-serial conversion (or layer demapping) to obtain a data flow from one transmitter. The data flow is processed through grid demapping, de-interleaving and channel decoding to obtain an estimation of data transmitted by the transmitter. The estimated data is used as prior probability information and processed through interleaving, grid mapping and serial-to-parallel conversion (or layer mapping), and is then inputted into the multi-antenna multi-user detector as the prior probability information of the next iteration.

In order to differentiate data from different transmitters, besides using different and orthogonal preamble sequences, different transmitters may also use different interleaving patterns and/or grid mapping patterns. Assigning of interleaving patterns may be similar to that of the above embodiments, and is not repeated herein.

As shown in FIG. 14, when a transmitter is to transmit M data flows, each data flow is processed through channel encoding, interleaving, modulation and grid mapping. In FIG. 14, the function of generating data in the modules related with grid mapping is the processing of data flow through the channel encoding, interleaving, modulation and grid mapping as shown in FIG. 1. The processed data flows are processed through layer mapping, and then orthogonal preamble sequences or cyclic prefixes are added. Different transmitters also use orthogonal preamble sequences. Then the data flows are preprocessed, and the preprocessed data flows are respectively processed through baseband-to-RF processing and transmitted through multiple antennas. With respect to the layer mapping and preprocessing, a possible method of performing layer mapping and preprocessing is using identity matrices as the layer mapping equivalent matrix and preprocessing equivalent matrix, i.e., the processed data flows are corresponding to the transmitting antenna links in a one-to-one manner. In this manner, orthogonal preamble sequences are inserted into each data link for channel estimation of each data link. At the receiver, each link is regarded as different transmitters using a single antenna. The receiver performs detection of data bit flows using the iterative detection and decoding structure as shown in FIGS. 3A and 3B, and differentiates data flows of different users using interleaving patterns and grid mapping patterns.

The transmitters are notified of assigning of interleaving patterns and the grid mapping patterns via a table for lookup which is transmitted in a physical broadcast channel, a physical downlink control channel or a physical downlink shared channel. Different data flows of different users are assigned with different preamble sequences. Different data flows of different users may be differentiated by interleaving patterns and/or grid mapping patterns and/or preamble sequences. The method may be the same with that in embodiment five.

As shown in FIG. 15, when a transmitter is to transmit M data flows, each data flow is processed through channel encoding, interleaving, modulation and grid mapping. In FIG. 15, the function of generating data in the modules related with grid mapping is the processing of data flow through the channel encoding, interleaving, modulation and grid mapping as shown in FIG. 1. Then, multiple data flows transmitted by the same transmitter are processed through phase and power adjustment and then superimposed with each other. The superimposed data flow is processed through serial-to-parallel (or layer mapping), then preamble sequences or cyclic prefixes are inserted into the obtained data flows. In order to estimate equivalent channel state information of each link, different and orthogonal preamble sequences are assigned to the links for estimating the equivalent channel including the preprocessing at the receiver. The sequences after the preamble sequences or cyclic prefixes have been inserted are processed through preprocessing and baseband-to-RF processing, and then transmitted via multiple transmitting antennas. In order to differentiate different data flows from different transmitters, the data flows are assigned with interleaving patterns and grid mapping patterns. The assigning method may be the similar to that of embodiment five. The transmitters are notified through a physical broadcast channel, a physical downlink control channel and a physical downlink shared channel. Phase/power adjustment aims at ensuring data flows of the same transmitter do not overlap with or cancel each other. The adjustment method is similar to that in embodiment five. After phase/power adjustment, the receiver may detect received signals according to the method as shown in FIG. 13, and differentiate different data flows from different transmitters using interleaving patterns and/or grid mapping patterns and/or preamble sequences. The differentiating method may be similar to that of embodiment five.

In the above three methods, cyclic prefixes or preamble sequences are inserted before preprocessing to obtain equivalent channel estimation including preprocessing. In fact, the cyclic prefixes needs to be inserted before preprocessing, but preamble sequences may be inserted before preprocessing or after preprocessing. When a transmitter inserts preamble sequences after preprocessing, the channel characteristics estimated by the receiver according to the preamble sequences during detection and decoding do not include channel characteristics of the preprocessing. After channel estimation results are obtained, symbol sequences from which preamble sequences have been removed are processed through de-preprocessing using preprocessing information used at the transmitter, then the processed sequences are inputted into the multi-antenna multi-user detector.

Combinations of any two of the above three methods may be used. For example, some links are mapped using manner 2, and some links are processed through serial-to-parallel conversion and layer mapping according to manner 3.

It should be noted that in the above manners, manner 2 is more suitable for increasing transmission data rates, i.e., increasing transmission data rates by transmitting different data flows on different links. The manner 1 is more suitable for improving transmission reliability, i.e., using space-time encoding including space-time block encoding, space-frequency block encoding or the like to obtain space diversity to improve transmission reliability. The manner 3 can improve reliability and increase data rate at the same time, i.e., using space-time encoding, e.g., space-time block encoding, space-frequency block encoding or the like, to obtain space diversity while superimposing multiple data flows to increase the data rate. The manner four can be regarded as a compromise between reliability and data rate.

When a transmitter can obtain channel state information of transmission channels through measures such as channel estimation or feedback or the like, precoding (e.g., zero-forcing precoding) may be used to eliminate interference between different links of the same transmitter, which can greatly simplify processing at the receiver. The above manners may also be used for increasing transmission data rates.

FIG. 16 illustrates a basic structure of a transmitter provided by the present disclosure. The transmitter in a communication system includes: a baseband processing unit, an inserting unit, an RF processing unit and a transmitting unit.

The baseband processing unit is configured for applying channel encoding, modulation and grid mapping sequentially to an information bit sequence to be transmitted. The inserting unit is configured for inserting a preamble sequence or a cyclic prefix into a symbol sequence generated from the grid mapping. The preamble sequence is periodically inserted, the cyclic prefix is inserted into the symbol sequence in which the preamble has not been inserted. The radio frequency processing unit is configured for applying baseband-to-RF processing to the symbol sequence after the preamble sequence or the cyclic prefix is inserted. The transmitting unit is configured for transmitting a signal generated from the baseband-to-RF processing.

FIG. 17 illustrates a basic structure of a receiver provided by the present disclosure. The receiver includes: an RF processing unit, a channel estimating unit and an iterative detection unit.

The RF processing unit is configured for applying RF-to-baseband processing to a received signal to obtain a baseband receiving signal. The channel estimating unit is configured for estimating channel information of channels from different transmitters to the receiver using preamble sequences which are periodically inserted, or removing cyclic prefixes. The iterative detection unit is configured for applying multi-user iterative detection to the baseband receiving signal after the preamble sequence or the cyclic prefix is removed to determine information bit sequences sent by different users. The multi-user iterative detection includes grid de-mapping using a grid mapping manner used by a transmitter.

In multi-user iterative detection using extrinsic information when transmitters perform interleaving, any iteration of the iterative detection includes: applying multi-user detection to a baseband receiving signal from which a preamble sequence or a cyclic prefix has been removed according to prior probability information of information bits generated in a preceding iteration to obtain posterior probability information of each bit or each symbol, subtracting the prior probability information from the posterior probability information to obtain the extrinsic information; the prior probability information is bit information obtained by processing the decoded soft information through the same channel encoding as performed at the transmitter and processing the channel encoded soft information through the same interleaving and grid mapping process as performed at the transmitter after the de-interleaved soft information is subtracted from the channel encoded soft information.

In view of the foregoing, the present disclosure provides a transmitting method using single carrier modulation and a multiple access method and apparatus, avoid the problem of high peak average ratio in multi-carrier modulation, thus the mechanism is more suitable for mMTC scenarios in 5G for providing low cost and access of mass amount of devices. By incorporating non-orthogonal multiple access, multiple users can be multiplexed on the same time-frequency resources, which can increase the number of accessible users. In addition, insertion of preamble sequences is introduced in single carrier modulation, which increases the dimensions for differentiating users. The flexible preamble sequence transmitting periodicity can adapt to the transmission environment with unstable channel state.

The foregoing are only preferred examples of the present disclosure and are not for use in limiting the protection scope thereof. All modifications, equivalent replacements or improvements in accordance with the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

A signal transmission method in a communication system, the method comprising:

applying, by a transmitter, channel encoding, modulation and grid mapping sequentially an information bit sequence which is to be transmitted; and

inserting a preamble sequence or a cyclic prefix into a symbol sequence generated after the grid mapping, applying baseband-to-radio frequency (RF) processing to the symbol sequence in which the preamble sequence or the cyclic prefix has been inserted, and transmitting a sequence obtained after the baseband-to-RF processing; wherein the preamble sequence is inserted periodically, and the cyclic prefix is inserted into the symbol sequence in which the preamble sequence has not been inserted.
The method of claim 1, further comprising: between the channel encoding and the modulation, interleaving a result of the channel encoding; wherein a sequence has the same length before and after the interleaving.
The method of claim 1 or 2, wherein if the preamble sequence is inserted into the symbol sequence generated from the grid mapping, preamble sequences of different users transmitted on the same time-frequency resources are different from and orthogonal to each other.
The method of claim 2, wherein different users are differentiated by interleaving patterns and/or grid mapping patterns and/or preamble sequences; wherein the interleaving patterns are used in the interleaving, and the grid mapping patterns are used in the grid mapping.
The method of any of claims 1 to 4, further comprising: before the channel encoding, receiving preamble sequence configuration information, interleaving pattern information and grid mapping pattern information sent from a network side, identifying the preamble sequence according to the preamble sequence configuration information, identifying an interleaving pattern used in the interleaving according to the interleaving pattern information, and identifying a grid mapping pattern used in the grid mapping according to the grid mapping pattern information.
The method of claim 5, wherein identifying the interleaving pattern used in the interleaving comprises:

using an interleaving pattern included in the interleaving pattern information as the interleaving pattern used in the interleaving; or taking the interleaving pattern included in the interleaving pattern information as an interleaving pattern of a mother interleaver, and cyclic shifting the interleaving pattern of the mother interleaver according to a pre-determined rule to obtain the interleaving pattern used in the interleaving.
The method of any of claims 1 to 5, wherein a periodicity of inserting the preamble sequence is pre-determined or included in the preamble sequence configuration information.
The method of claim 7, wherein if the periodicity of inserting the preamble sequence is included in the preamble sequence configuration information, the periodicity is determined by a network side according to changes of a channel, and the more rapidly the channel changes, the shorter the periodicity is.
The method of claim 8, further comprising: before inserting the preamble sequence, requesting, by the transmitter before inserting the preamble sequence, the network side to temporarily adjust the periodicity of inserting the preamble sequence according to channel state information measured by the transmitter, temporarily adjusting the periodicity according to a pre-determined rule after receiving a confirmation from the network side, or temporarily adjusting the periodicity according to an instruction sent by the network side, and performing the inserting the preamble sequence according to the temporarily adjusted periodicity; and

inserting, by the transmitter, the preamble sequence according to newly received preamble sequence configuration information if the newly received preamble sequence configuration information is received after the periodicity is temporarily adjusted.
The method of claim 4, further comprising: determining, by a network side, a method of differentiating different users according to network load.
The method of claim 10, wherein if the network load ≤ a pre-determined first threshold γ₁, different users are differentiated by interleaving patterns, grid mapping patterns or preamble sequences; and/or

if γ₁ < the network load ≤ a pre-determined second threshold γ₂, different users are differentiated using a combination of any two of: interleaving patterns, grid mapping patterns, preamble sequences; and/or

if the network load >γ₂, different users are differentiated using a combination of: interleaving patterns, grid mapping patterns, preamble sequences.
The method of claims 1, 2, 4 or 5, wherein if the information bit sequence includes information bit sequences of a plurality of data flows,

the applying the channel encoding, the interleaving, the modulation and the grid mapping sequentially to the information bit sequence which is to be transmitted comprises: applying the channel encoding, the interleaving, the modulation and the grid mapping sequentially to an information bit sequence of the data flow for each of the data flows individually;

before inserting the preamble sequence or the cyclic prefix, applying phase and power adjustment to a symbol sequence generated from the grid mapping of each of the data flows; for each of the data flows, applying the inserting the preamble sequence or the cyclic prefix procedure and the baseband-to-RF processing procedure to a symbol sequence of the data flow after the phase and power adjustment, and superimposing processed data of the data flows and transmitting the superimposed data; or, before inserting the preamble sequence or the cyclic prefix, applying phase and power adjustment to a symbol sequence of each of the data flows after the grid mapping, superimposing symbol sequences of the data flows after the phase and power adjustment, applying the inserting the preamble sequence or the cyclic prefix procedure and the baseband-to-RF processing procedure to a symbol sequence generated from the superimposing, and transmitting the symbol sequence after the inserting and the baseband-to-RF processing;

wherein when superimposed with each other, symbol sequences of different data flows are processed through the phase and power adjustment in a manner that makes the symbol sequences do not overlap with one another or negate one another.
The method of claim 12, wherein if the preamble sequence of users are assigned by a network side, the preamble sequences of different users are different from and orthogonal to each other; if the symbols sequences of the data flows are superimposed after the preamble sequence or the cyclic prefix is inserted into the symbol sequences generated by the grid mapping, preamble sequences of different data flows of a same user are different from and orthogonal to each other.
The method of claim 12 or 13, wherein

if the symbol sequences of data flows are superimposed after the preamble sequence or the cyclic prefix is inserted into the symbol sequences generated by the grid mapping, different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns, and different interleaving patterns or different grid mapping patterns are used to differentiate the different data flows of the different users; or different user are assigned with different interleaving patterns, different data flows of a same user are assigned with a same interleaving pattern and different grid mapping patterns, different users are differentiated by interleaving patterns, and different data flows of a same user are differentiated by grid mapping patterns or preamble sequence or combinations of grid mapping patterns and preamble sequences; or different user are assigned with different grid mapping patterns, different data flows of a same user are assigned with a same grid mapping pattern and different interleaving patterns, different users are differentiated by grid mapping patterns, and different data flows of the same users are differentiated by interleaving patterns or preamble sequence or combinations of interleaving patterns and preamble sequences; or different data flows of a same user are assigned with different grid mapping patterns or different interleaving patterns or different combinations of grid mapping patterns and interleaving patterns, different users are differentiated by preamble sequences, and different data flows of a same user are differentiated by grid mapping patterns or interleaving patterns or combinations of grid mapping patterns and interleaving patterns; or different users are assigned with different combinations of interleaving patterns and grid mapping patterns, different users are differentiated by combinations of interleaving patterns and grid mapping patterns, and different data flows of a same user are differentiated by preamble sequences; or different users are assigned with different combinations of interleaving patterns and preamble sequences, and different data flows of a same user are assigned with different grid mapping patterns, different users are differentiated by combinations of interleaving patterns and preamble sequences, and different data flows of a same user are differentiated by grid mapping patterns; or different user are assigned with different combinations of grid mapping patterns and preamble sequences, and different data flows of a same user are assigned with different interleaving patterns, different users are differentiated by combinations of grid mapping patterns and preamble sequences, and different data flows of a same users are differentiated by interleaving patterns; and / or

if the preamble sequence or the cyclic prefix is inserted into a symbol sequence obtained by superimposing the symbol sequences of the data flows generated from the grid mapping, different data flows of different users are assigned with different interleaving patterns or different grid mapping patterns, and different data flows of different users are differentiated by interleaving patterns or grid mapping patterns; or different user are assigned with different interleaving patterns, and different data flows of a same user are assigned with a same interleaving pattern and different grid mapping patterns, different users are differentiated by interleaving patterns, and different data flows of different users are differentiated by grid mapping patterns; or different user are assigned with different grid mapping patterns, different data flows of a same user are assigned with a same grid mapping pattern and different interleaving patterns, different users are differentiated by grid mapping patterns, and different data flows of a same users are differentiated by interleaving patterns; or different data flows of a same user are assigned with different grid mapping patterns or different interleaving patterns or different combinations of grid mapping patterns and interleaving patterns, different users are differentiated by preamble sequences, and different data flows of a same user are differentiated by grid mapping patterns or interleaving patterns or combinations of grid mapping patterns and interleaving patterns; or different users are assigned with different combinations of interleaving patterns and preamble sequences, and different data flows of a same user are assigned with different grid mapping patterns, different users are differentiated by combinations of interleaving patterns and preamble sequences, and different data flows of a same user are differentiated by grid mapping patterns; or different users are assigned with different combinations of grid mapping patterns and preamble sequences, and different data flows of a same user are assigned with different interleaving patterns, different users are differentiated by combinations of grid mapping patterns and preamble sequences, and different data flows of a same user are differentiated by interleaving patterns.
The method of claim 12, wherein when K which is the number of data flows actually transmitted by the transmitter is smaller than K_max which is the maximum number of data flows supported by the transmitter,

processing and transmitting, by the transmitter, K data flows, sending a flow number indication to a network side, the flow number indication specifies K which is the number of actually transmitted data flows; or

processing and transmitting, by the transmitter, K_max data flows, wherein information bit sequences of K data flows in the K_max data flows are data to be transmitted, and information bit sequences of the remaining K_max-K data flows are all zero, an information bit sequence set to be all zero indicates a data flow corresponding to the information bit sequence is not for transmitting a valid information bit sequence.