CN101414898A

CN101414898A - Receive coalition method, system and equipment

Info

Publication number: CN101414898A
Application number: CNA2007101632653A
Authority: CN
Inventors: 吴涛; 朱胡飞; 赵印伟; 司宏杰; 葛绍伟
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2007-10-19
Filing date: 2007-10-19
Publication date: 2009-04-22
Also published as: WO2009052736A1

Abstract

The invention relates to the technical field of mobile communication, in particular to a receiving and combining technology. The embodiment of the invention provides a receiving and combining method, a system and a device thereof, which improve the system performance effectively. The receiving and combining method based on data retransmission comprises the following steps: the data symbols which carry out at least twice emitting to one group of data are received and buffered; after interference cancellation and symbol combination are carried out to the data symbols, the data symbols are demodulated and decoded, thus obtaining the combined receiving data. The receiving and combining system based on data retransmission comprises an emitting device and a receiving device. The embodiment of the invention provides an emitting device and a receiving device, and the embodiment of the invention also provides a receiving and combining method based on transmit diversity and a system thereof.

Description

Receiving and combining method, system and equipment

Technical Field

The invention relates to the technical field of mobile communication, in particular to a receiving and combining technology.

Background

The third Generation Mobile Communication system (3G) and the future fourth Generation Mobile Communication system (4G) have significantly improved reliability requirements while transmitting high-speed data, and especially have to meet high reliability requirements in severe natural environments. Under the background, a hybrid Automatic Repeat Request (HARQ) technology has become one of the key technologies for improving reliability, and the HARQ technology is based on an ARQ (Automatic Repeat Request) technology and a Forward Error Correction (FEC) technology, and if a receiving end verifies that received data has an Error through Cyclic Redundancy Check (CRC), the receiving end requests to retransmit the data, thereby improving the reliability of correctly receiving the data.

The HARQ technology performs data retransmission based on feedback from the receiving end, which essentially achieves the effect of the time diversity technology. The diversity technique is also an effective way to improve the system performance, and the diversity technique is to transmit a set of data separately over at least two transmit diversity at the transmitting end, and to receive and combine the data symbols transmitted separately over at least two transmit diversity at the receiving end. There are several transmit diversity schemes, including: time diversity, which refers to transmitting the same data symbols or suitable combinations thereof at different times; cell diversity, which means that the same data symbols or their appropriate combinations are transmitted in different cells; polarization diversity, which means transmitting the same data symbols or their appropriate combinations in different polarization directions of the same antenna; frequency diversity, which refers to transmitting the same data symbols or their appropriate combinations in different frequency bands; spatial diversity, which refers to transmitting the same data symbols or suitable combinations thereof on different antennas; code diversity, which means that different spreading codes are used to modulate and transmit the same data symbols or the appropriate combination thereof; relay (Relay) diversity refers to transmitting different data symbols or their appropriate combinations between different Relay Stations (RSs) or between an RS and a Base Station (BS).

As shown in fig. 1, which is a block diagram of a receiving and combining system based on HARQ technology in the prior art, at a transmitting end, a group of data added with CRC check codes at a MAC layer is sent to a physical layer for transmission; the information bits after FEC coding are modulated into constellation point modulation symbols through constellation mapping, and in order to improve the spectrum utilization rate of a system, high-order modulation is generally adopted; the constellation point modulation symbols are called data symbols when being transmitted, and a plurality of data symbols are sent into a channel through a transmitting unit in the form of data packets. At a receiving end, a receiving unit receives a data packet transmitted through a channel, demodulates data symbols in the data packet after interference elimination, buffers demodulated Log Likelihood information (Log likehood Ratio, LLR), which is also called soft bit information, and finally performs FEC decoding on the soft bit information. Performing CRC on the decoded data to check the correctness of the receiving, if the receiving end checks that the data is received correctly through the CRC, clearing the cached soft bit information, and informing the transmitting end of transmitting the next group of data through feedback; if the receiving end checks out the data receiving error through the CRC, the transmitting end is informed to retransmit the group data through feedback.

For at least two transmissions of a group of data, the receiving end needs to carry out CRC check on the received data after receiving and combining. In the receiving and combining method in the prior art, data symbols in a retransmitted data packet are demodulated after interference cancellation, demodulated soft bit information is cached, and is combined with the previously cached demodulated soft bit information of the group of data, and the combining method mainly includes two methods: chase Combining (CC) combining and MRC (Maximum Ratio combining, MRC) combining, and further FEC decoding after soft bit information combining. Performing CRC on the decoded data to check the correctness of the receiving, if the receiving end checks that the data is received correctly through the CRC, clearing the cached soft bit information, and informing the transmitting end of transmitting the next group of data through feedback; if the receiving end checks out the data receiving error through the CRC, the transmitting end is informed to retransmit the group data through feedback. And ending the transmission of the group of data until the CRC verifies that the data is received correctly or the maximum retransmission times is reached.

The high-order modulated constellation diagram can be formed by properly combining the low-order modulated constellation diagrams, and each low-order constellation diagram needs to be multiplied by a corresponding coefficient in the combining process, and each coefficient is referred to as a modulation factor. When a group of data is transmitted, because the transmitting end adopts high-order modulation, the high-order constellation point modulation symbol is formed by combining a plurality of low-order constellation point modulation symbols and different modulation factors, and the different modulation factors cause the difference of the decoding reliability of the receiving end, the performance of the error correcting code is difficult to achieve the optimum. Due to the fact thatTherefore, in the prior art, a constellation rearrangement method is proposed, which changes the constellation mapping rule of information bits during each data retransmission, so that the soft bit information combined by the receiving end obtains more average decoding reliability. Examples of constellation rearrangement methods used in the prior art are given, for example, at time t₁Transmitting information bits as b₀b₁b₂b₃Wherein b is₀b₁Mapping to modulation symbol x of low-order constellation point, b₂b₃And the high-order constellation point modulation symbol is formed by combining the low-order constellation point modulation symbols x and y and different modulation factors alpha and beta, and the constellation mapping mode adopted in the combination is that z is alpha x + beta y, namely the transmitted data symbol is z is alpha x + beta y. Due to the adoption of constellation recombination technology, the information bit b is subjected to₀b₁b₂b₃In the case of row retransmission, the data symbol transmitted after constellation mapping modulation may be any one of z ═ α x + β y, z ═ β 1x- β 0y, z ═ β 3x + β 2y, z ═ β 5x- β 4y, z ═ β x + α y, z ═ β x- α y, z ═ β x + α y, and z ═ β x- α y.

It can be seen that in the prior art, data retransmission is performed based on the HARQ technology, when a group of data is transmitted at least twice by using a constellation rearrangement method and then received and combined at a receiving end, soft bit information demodulated from received data symbols is combined, bit-level-based combining makes system performance improvement more limited, and the constellation rearrangement method has little effect on improving system performance by using bit-level reception and combination, and still has room for further improvement. Meanwhile, the receiving and combining method based on the transmit diversity is similar to the receiving and combining method based on the data retransmission, and the same technical problem is also solved.

Disclosure of Invention

The embodiment of the invention provides a receiving and combining method, a receiving and combining system and receiving and combining equipment, which are used for improving the performance of a system.

The embodiment of the invention provides a receiving and combining method based on data retransmission, which comprises the following steps:

receiving and buffering data symbols transmitted at least twice for a group of data;

and after the data symbols are subjected to interference elimination and symbol combination, demodulating and decoding to obtain combined received data.

The embodiment of the invention also provides a receiving and combining system for data retransmission, which comprises:

the transmitting device: for transmitting data symbols, which are respectively modulated on a group of data, at least twice;

the receiving device: and the data symbol receiving and buffering unit is used for receiving and buffering the data symbol transmitted by the transmitting equipment, demodulating and decoding the data symbol after interference elimination and symbol combination to obtain combined received data.

An embodiment of the present invention provides a transmitting device, including:

an encoding unit: the device comprises a decoder, a decoder and a decoder, wherein the decoder is used for performing coding operation on a group of data to obtain information bits;

a modulation unit: the modulation factors used for modulating the information bits output by the coding unit into data symbols and respectively modulating and distributing the same information bits in a group of data are different when the group of data is transmitted for at least two times;

a transmitting unit: for transmitting the data symbols output by the modulation unit.

An embodiment of the present invention provides a receiving device, including:

a receiving unit: for receiving data symbols;

a cache unit: the buffer is used for buffering the data symbols received by the receiving unit;

an interference cancellation unit: the data symbol buffer unit is used for carrying out interference elimination and symbol combination on the data symbol buffered by the buffer unit to obtain a data symbol subjected to interference elimination and combination;

a demodulation unit: the data symbol is used for demodulating the data symbol output by the interference elimination unit to obtain information;

a decoding unit: for decoding the information output by the demodulation unit to obtain the combined received data.

The embodiment of the invention also provides a receiving and combining method based on the transmit diversity, which comprises the following steps:

receiving and caching data symbols transmitted after a group of data is respectively modulated on at least two transmit diversity branches;

The embodiment of the invention also provides a receiving and combining system based on the transmit diversity, which comprises the following steps:

the transmitting device: the data transmission device is used for transmitting data symbols obtained by modulating a group of data on at least two transmission diversity branches respectively;

the receiving device: and the data symbol is used for receiving and buffering the data symbol transmitted by the transmitting equipment, and after the data symbol is subjected to interference elimination, the data symbol is demodulated and decoded to obtain combined received data.

The receiving and combining method, the receiving and combining system and the receiving and combining equipment based on data retransmission provided by the embodiment of the invention transmit the received data symbols at least twice through the buffer memory on a group of data, demodulate and decode the buffered data symbols after interference elimination and symbol combination, realize symbol-level receiving and combining on the data, effectively improve the system performance, reduce the frame error rate and the bit error rate, and improve the channel capacity and the spectrum utilization rate of the system.

The receiving and combining method and the receiving and combining system based on the transmit diversity provided by the embodiment of the invention realize the receiving and combining of the symbol level for the data by caching the received data symbols on at least two transmit diversity branches, and demodulating and decoding after eliminating the interference and combining the symbols, thereby effectively improving the system performance, reducing the frame error rate and the bit error rate, and improving the channel capacity and the spectrum utilization rate of the system.

Drawings

Fig. 1 is a block diagram of a receiving and combining system based on HARQ technology in the prior art;

FIG. 2 is a block diagram of a system for combining and receiving data based on retransmission according to an embodiment of the present invention;

FIG. 3 is a flow chart of a receiving and combining method based on data retransmission according to an embodiment of the present invention;

fig. 4 is a schematic diagram of 16QAM data symbols formed by superimposing two QPSK data symbols according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating transmission of a dual-transmission and dual-reception system according to an embodiment of the present invention;

FIG. 6 is a diagram illustrating a combination pattern of constellation mapping when dual antennas transmit according to an embodiment of the present invention;

fig. 7 is a schematic diagram illustrating a comparison between the embodiment of the present invention and a receiving and combining method based on data retransmission in the prior art for improving system performance;

fig. 8 is a flow chart of a receive combining method based on transmit diversity according to an embodiment of the present invention.

Detailed Description

In the receiving and combining method based on data retransmission adopted in the current mobile communication system, for at least two transmissions of a group of data, the data symbols transmitted through a channel are respectively and independently subjected to interference elimination at a receiving end, then demodulated, and the demodulated soft bit information is subjected to CC combining or MRC combining and then decoded to obtain the received data. The method improves the system performance relatively low, and the inventor considers that if the data symbols transmitted at least twice through the channel are processed comprehensively by the receiving end through the interference elimination technology, the symbol-level combination can be realized, and the combined data symbols are demodulated and decoded to obtain the combined received data, so the system performance can be improved greatly. Further, the embodiment of the present invention further provides, based on the existing constellation rearrangement method: when a group of data is transmitted at least twice at a transmitting end, the modulation factors distributed to the same information bit in the group of data are different, so that after the receiving end receives and combines the data symbols transmitted at least twice, the overall balance of the decoding reliability of each information bit is realized, which is called as an optimized constellation recombination strategy.

Based on the above analysis, an embodiment of the present invention provides a receiving and combining system based on data retransmission, as shown in fig. 2, the system includes a transmitting device 201 and a receiving device 202, where:

the transmitting apparatus 201: for transmitting data symbols, which are respectively modulated on a group of data, at least twice;

the reception apparatus 202: for receiving and buffering the data symbols transmitted by the transmitting device 201, performing interference cancellation and symbol combination on the data symbols, and then performing demodulation and decoding to obtain combined received data.

According to the optimized constellation rearrangement strategy, when the transmitting equipment transmits a group of data at least twice, the modulation factors for respectively modulating and distributing the same information bit in the group of data are different.

The receiving device 202 is further configured to verify the received data, and if it is verified that the data is received correctly, clear the buffered data symbols and instruct transmission of the next set of data; if the data receiving error is checked out, indicating to retransmit the group of data;

the transmitting device 201 transmits the next set of data after receiving the indication of transmitting the next set of data fed back by the receiving device 202; the group data is retransmitted after receiving an indication to retransmit the group data fed back by the receiving device 202.

An embodiment of the present invention provides a transmitting device 201, including:

the encoding unit 2011: the device comprises a decoder, a decoder and a decoder, wherein the decoder is used for performing coding operation on a group of data to obtain information bits;

the modulation unit 2012: the modulation factors used for modulating the information bits output by the encoding unit 2011 into data symbols and further performing modulation and allocation on the same information bit in a group of data at least twice according to an optimized constellation rearrangement strategy are different;

a transmitting unit 2013: for transmitting the data symbols output by the modulation unit 2012.

An embodiment of the present invention provides a receiving apparatus 202, including:

reception section 2021: for receiving data symbols;

the buffer unit 2022: for buffering the data symbols received by the receiving unit 2021;

interference cancellation unit 2023: the data symbol buffer unit 2022 is configured to perform interference cancellation and symbol combination on the buffered data symbol to obtain an interference-cancelled and combined data symbol;

demodulation section 2024: the information is obtained by demodulating the data symbols output by the interference cancellation unit 2023, and is generally log-likelihood information;

the decoding unit 2025: for decoding the information output by the demodulation unit 2024 to obtain the combined received data.

Receiving section 2021, buffering section 2022, interference canceling section 2023, demodulating section 2024, and decoding section 2025 have realized reception combining of data by the receiving end, and receiving apparatus 202 further includes:

the verification unit 2026: for checking the received data output by the decoding unit 2025, and if it is checked that the data is received correctly, clearing the buffered data symbols and instructing to transmit the next set of data; and if the data receiving error is checked out, indicating to retransmit the group of data.

Each unit in the transmitting device and the receiving device provided by the embodiment of the present invention may be located on one physical entity, or may be located on different physical entities.

The embodiment of the invention also provides a receiving and combining method based on data retransmission, which comprises the following steps as shown in fig. 3:

s301, receiving and caching data symbols which are transmitted for at least two times for a group of data;

s302, after the data symbols are subjected to interference elimination and symbol combination, demodulation and decoding are carried out to obtain combined received data.

If the optimal constellation rearrangement strategy is based, when a group of data is transmitted at least twice, the modulation factors distributed to the same information bit in the group of data are different.

S303, checking the received data, and if the data is checked to be correctly received, clearing the cached data symbols and indicating the sending end to send the next group of data; and if the data receiving error is checked out, the sending end is instructed to retransmit the group of data.

The receiving and combining system and the method based on data retransmission provided by the embodiment of the invention can realize symbol-level combination of the received data, and meanwhile, if the transmitting terminal adopts an optimized constellation recombination strategy, the decoding reliability of each information bit corresponding to the receiving terminal can be balanced, thereby greatly improving the system performance.

The following describes in detail the receiving and combining method and system based on data retransmission provided in the embodiments of the present invention, and a specific application scenario is a Single Input Single Output (SISO) system based on an HARQ technology, and certainly, the method and system may also be based on an ARQ technology, where the difference between the two technologies is that the HARQ technology is a physical layer retransmission technology, the ARQ technology is a high-layer retransmission technology above a physical layer, and whether the HARQ technology or the ARQ technology is used has no influence on implementation of the present solution.

In the embodiment of the present invention, a SISO system based on HARQ technology is taken as an example for detailed description, and a high-order modulation technology, such as M-PSK, M-QAM, and log, is applied to a group of data transmitted at a transmitting end₂(M)>And 2, checking the correctness of the group of data reception by CRC at the receiving end. If the receiving end checks out the data receiving error through the CRC, the transmitting end is informed to retransmit the group of data through feedback, namely, data retransmission is generated. For a group of data transmitted at least once, before CRC check is performed at a receiving end, receiving and combining are required. Commonly used Interference Cancellation receivers include Zero-Forcing (ZF), Minimum Mean-Squared Error (L-MMSE), Maximum Likelihood (ML), Successive Interference Cancellation (SIC), Parallel Interference Cancellation (PIC), and possibly a combination of multiple Interference Cancellation techniques. The interference elimination receiver is connected with a buffer unit, and the buffer unit buffers the data symbols received by the receiving unit after the group of data is transmitted at least once. The data symbols buffered in the buffer unit pass through the interference elimination receiver at the same time, so that the receiving end can perform symbol level combination on the group of data transmitted at least once, the data symbols output after the combination of the interference elimination receiver are sent into the demodulation unit and the decoding unit again to obtain combined received data, and finally the received data are sent into the check unit to perform CRC check.

The embodiment of the invention provides a receiving and combining method, which comprises the following steps:

a1, assume at t₁A group of data is transmitted at a time, and information bits after FEC coding are b₀b₁b₂b₃，b₀b₁Mapping to QPSK constellation point modulation symbol x, b₂b₃Mapping to QPSK constellation point modulation symbol y, the modulation factors of x and y are alpha and beta respectively, and information bit b₀b₁b₂b₃The constellation mapping mode adopted when the modulation is changed into a 16QAM constellation point modulation symbol is that z is alpha x + beta y;

a2, the receiving end receives and buffers the data symbol transmitted by the channel, and the data symbol received at the receiving end after the data symbol is transmitted by the channel is assumed to be r₁After demodulation and FEC decoding, CRC check is carried out on the decoded received data, if the reception is correct and the transmission of the group of data is successfully completed, the buffered data symbols r are cleared₁And informing the sending end to transmit the next group of data through feedback; if the CRC check finds t₁If the data transmitted at the moment is received incorrectly, the HARQ request sending end retransmits the group of data, and the process continues to be a 3;

a3 if at t₂Retransmitting the group of data, i.e. information bit b, at a time₀b₁b₂b₃；

When the group of data is transmitted again, constellation reconstruction mapping can be carried out on the group of data according to the prior art, and the data is transmitted after modulation;

further, in order to ensure that the same information bit of the same group of data has different modulation factors allocated in two or more transmissions, an embodiment of the present invention further provides an optimized constellation rearrangement scheme, which specifically includes:

suppose that at a certain time, the information bit of the data added with the CRC code in the MAC layer after the data is FEC coded is b₀b₁b₂b₃，b₀b₁Mapping to QPSK constellation point modulation symbol x, b₂b₃Mapping to QPSK constellation point modulation symbol y, however, other grouping methods may be used to map the information bits, e.g. b₀b₂Mapping onto constellation symbol x, b₁b₃Mapping to constellation symbol y, no longer enumerating one by one, multiplying x and y by corresponding modulation factors α and β, and superimposing them to transmit a 16QAM constellation point modulation symbol, because there are two modulation factors, the modulation order can be said to be 2, and the process is shown in fig. 4. The 16QAM constellation point modulation symbols are formed by superimposing two QPSK constellation point modulation symbols, and there are 8 different constellation mapping manners, namely z ═ β 1x + β 0y, z ═ β 3x- β 2y, z ═ β 5x + β 4y, z ═ β 7x- β 6y, z ═ β 9x + β 8y, z ═ α 1x- α y, z ═ α 2x + α 0y, and z ═ α 4x- α 3 y. The embodiment of the present invention provides an optimized constellation rearrangement strategy, when α 5 and α 6 are real numbers, if a constellation mapping manner adopted by a first transmission is z ═ α 7x + α 8y, then a constellation mapping manner that can be adopted by a second transmission is any one of z ═ β x + α 9y, z ═ β x- α y, z ═ β x + α y, and z ═ β x- α y, so that it can be ensured that modulation factors allocated to the same information bit of the same group of data in two transmissions are different, and thus a first optimized constellation rearrangement scheme can be obtained according to the optimized constellation rearrangement strategy and the modulation order of 2: the two transmissions can be any one of the following combinations, such as formula [ 1]]As shown, the order of the two constellation mapping schemes provided in each combination used for the two transmissions may be switched, preferably, combination 3 or combination 4 is used.

Combination 1:

and (3) combination 2:

and (3) combination:

and (4) combination:

the first optimized constellation rearrangement scheme is proposed based on that both alpha and beta are real numbers, and both beta 0 and beta 1 are real numbers and are determined by a traditional constellation mapping mode. In the 3GPP2 standard, during high-order modulation (high-order modulation), a conventional constellation mapping manner is adjusted, where modulation factors α and β in a transmitted data symbol z ═ α x + β 2y may be complex numbers, and for a case where α and β are complex numbers, according to an optimized constellation rearrangement strategy, if a constellation mapping manner adopted in a first transmission is z ═ α x + β y, then a constellation mapping manner that can be adopted in a second transmission is z ═ β y^*x-α^*y、z＝-β^*x+α^*y、z＝β^*x+α^*y、z＝-β^*x-α^*y, wherein ()^*Representing conjugation. Thereby, a second optimized constellation rearrangement scheme is proposed: the two time transmit diversity uses any one of the following combinations, e.g. equation [ 2]]As shown, the order of the two constellation mapping schemes provided in each combination used for the two transmissions may be switched, preferably, combination 3 or combination 4 is used.

Combination 1:

and (3) combination 2:

and (3) combination:

and (4) combination:

for the case where α and β are complex numbers, according to the optimized constellation rearrangement strategy, if the constellation mapping manner adopted by the first transmission is z ═ α x + β y, then the constellation mapping manner that can be adopted by the second transmission is z ═ β x^*-αy^*、z＝-βx^*+αy^*、z＝βx^*+αy^*、z＝-βx^*-αy^*Any one of them. A third optimized constellation rearrangement scheme is thus proposed: the two time transmit diversity uses any one of the following combinations, e.g. equation [ 3]]As shown, the order of the two constellation mapping schemes provided in each combination used for the two transmissions may be switched, preferably, combination 3 or combination 4 is used.

Combination 1:

and (3) combination 2:

and (3) combination:

and (4) combination:

a corresponding optimized constellation rearrangement scheme provided in the embodiments of the present invention may be selected according to whether α and β are real numbers or imaginary numbers, and if α and β are real numbers, according to the first optimized constellation rearrangement scheme, after being modulated in a constellation mapping manner, a transmitted data symbol is z ═ β x + α y, or z ═ β x- α y, z ═ β x + α y, or z ═ β x- α y;

a4, the receiving end receives and buffers the retransmitted data symbol, and the data symbol received at the receiving end after the retransmitted data group is transmitted through the channel is assumed to be r₂The receiving end will r₁And r₂Simultaneously, detecting signals through an interference elimination receiver to eliminate the interference of related channels and carry out symbol combination, and further demodulating and FEC decoding the data symbols after the interference elimination and the symbol combination;

a5, making CRC check on the decoded received data, if the reception is correct, indicating that the transmission of the group data is successfully completed, clearing the buffered data symbolNumber r₁And r₂And informing the sending end to transmit the next group of data through feedback; if t is found by CRC check₂If the group data transmitted at the moment is received wrongly, the sending end is requested to resend the group data through the HARQ;

and the rest is done until the CRC checks that the data reception is correct or the configured maximum retransmission times are reached.

The following is a description of the reception principle by which an interference cancellation receiver can implement symbol-level combining. Preferably, the interference cancellation receiver adopted in the embodiment of the present invention is an LMMSE receiver or a ZF receiver, and the example is described in which the transmitting end adopts an optimized constellation rearrangement scheme to transmit the same group of data twice, specifically, t is the above-mentioned t₁And t₂Time of day information bit b₀b₁b₂b₃Two transmissions are performed. When both α and β are real numbers, for example, in the first optimized constellation rearrangement scheme provided in the embodiment of the present invention, combination 1 is used, and a data symbol transmitted through a channel received by a receiving end after transmitting the same group of data twice may be represented by formula [4]]Shown in the figure:

wherein, in combination with the existing noise theory model, assume n₁、n₂Is Gaussian noise with an average value of 0, and

E {{| n_{1} |}^{2}} = E {{| n_{2} |}^{2}} = \frac{N_{0}}{2},

E{^*means for^*The mathematical expected value of (a) is,

representing the noise power; h is₁、h₂Respectively representing channel response parameters when data are transmitted twice; x and y are QPSK data symbols with amplitude 1, | x | ═ y | ═ 1, and the x and y modulation factors are α and β, respectively, assuming that

From equation [4], equation [5] can be derived:

wherein

For a virtual antenna transmission matrix, the parameter h can be derived from the pilot signal₁、h₂Thus, the specific value of the matrix is determined, and the x and y added with the influence of the channel noise can be solved after the interference elimination receiver, thereby realizing the symbol-level combination of the received data and further carrying out demodulation and decoding.

The x and y added noise contribution, e.g. obtained by a ZF receiver, can be expressed as equation [6 ]:

for matrix H, there may also be cases where there is no inverse matrix, then equation [6]]H in (1)^-1Is prepared from (H)^*H)^-1H^*In place of, wherein H^*And the matrix is a conjugate transpose matrix of the matrix H, x and y with noise influence added can be obtained, and the effect is equivalent.

Similarly, x and y obtained by the L-MMSE receiver to add noise contribution are expressed as equation [7 ]:

wherein W is (H)^*H+σ²I)^-1H^*Wherein

σ²Representing the variance of the noise, P_sRepresenting the power of the transmitted signal, σ²I represents the noise power of the received signal and is a2 × 2 identity matrix.

When both α and β are complex numbers, for example, in the second optimized constellation rearrangement scheme provided in the embodiment of the present invention, combination 1 is used, and a data symbol transmitted through a channel received by a receiving end after transmitting the same group of data twice may be represented by formula [8]]Shown, suppose

From equation [8], equation [9] can be derived:

wherein

The parameter h can also be obtained by a pilot signal for a virtual antenna transmission matrix₁、h₂Thus, the specific value of the matrix is determined, and the x and y added with the channel noise influence can be solved after the interference elimination receiver.

The x and y added noise contribution, e.g. obtained by a ZF receiver, can be expressed as equation [10 ]:

if matrix H has no inverse matrix, same H^-1May also be used (H)^*H)^-1H^*The form and effect of (1) are equivalent.

Similarly, let W ═ H^*H+σ²I)^-1H^*Wherein

σ²Representing the variance of the noise, P_sRepresenting the transmit signal power, x and y, obtained by the L-MMSE receiver, to which the noise contribution is added, can be expressed as equation [11]：

When both α and β are complex numbers, for example, in the third optimized constellation rearrangement scheme 1 provided in the embodiment of the present invention, the data symbol transmitted through the channel received by the receiving end after transmitting the same group of data twice may be as shown in formula [12]]Shown, suppose

At this time, x and y cannot be solved directly, and equation [12] needs to be deformed in an identical manner to obtain equation [13 ]:

from equation [13], equation [14] can be derived:

wherein

The x and y added noise contribution, e.g. obtained by a zero-forcing receiver, can be expressed as equation [15 ]:

Likewise, let

Wherein

σ²Representing the variance of the noise, P_sRepresenting the transmit signal power, the x and y added noise contribution obtained by the L-MMSE receiver can be expressed as equation [16 ]]：

After the data symbols transmitted twice are respectively received and buffered, the x and y added with the influence of channel noise can be solved through the interference elimination receiver, thereby realizing the symbol level combination of the receiving end, and further carrying out demodulation and decoding to obtain the received data.

In a 3G/4G mobile communication system, in order to enhance system performance, a Multiple Input Multiple Output (MIMO) technology is introduced, which is a spatial diversity technology, and utilizes Multiple inputs and Multiple outputs of one channel, thereby greatly improving the spectrum utilization rate of the system and the coverage of a base station. Now, a dual-transmitting and dual-receiving system is taken as an example for explanation, and fig. 5 is a schematic diagram of transmitting and receiving of a transmitting unit and a receiving unit both being dual antennas. In the MIMO system, the embodiment of the present invention assumes that at a certain time, after data to which a CRC check code is added in the MAC layer is FEC-encoded, information bits to be transmitted in the antenna #1 and the antenna #2 are b respectively₀b₁b₂b₃And b₄b₅b₆b₇Wherein b is₀b₁And b₄b₅Respectively mapping to QPSK constellation point modulation symbol x₁And x₂，b₂b₃And b₆b₇Respectively mapping to QPSK constellation point modulation symbol y₁And y₂The above step (1); x is the number of₁、y₁The modulation factors are respectively alpha and beta, and are superposed into a 16QAM constellation point modulation symbol which is transmitted on an antenna #1, and x₂、y₂The modulation factors of (1) are respectively alpha, beta, of course, x₂、y₂The modulation factor may also be a set of modulation factors reselected according to a constellation rearrangement strategy in the prior art or a set of modulation factors reselected according to an optimized constellation rearrangement strategy proposed by the embodiment of the present invention, and the selected modulation factors are superposed to form a 16QAM constellation pointThe modulation symbols are transmitted on antenna #2, but may be x₁、y₁Transmitting at antenna #2, x₂、y₂Transmitting at antenna # 1. A set of data respectively transmitted on the antenna #1 and the antenna #2 may be modulated according to respective constellation mapping manners, if the constellation mapping manners respectively adopted by the antenna #1 and the antenna #2 in the 1 st time diversity are mode 1, according to an optimized constellation rearrangement strategy, please refer to fig. 6, modes 2 to 19 are all the modes of the constellation mapping manners that can be respectively adopted by the antenna #1 and the antenna #2 in the 2 nd time diversity, and modes 2 to 10 are x in the 2 nd time diversity₁、y₁Still transmitting at antenna #1 and x₂、y₂Still given the antenna #2 transmission, patterns 11 through 19 are x at 2 nd time diversity₁、y₁Transmit at antenna #2 and x₂、y₂Given at antenna # 1. Modes 2 to 19 are based on that both α and β are real numbers, and the embodiment of the present invention provides a first optimized constellation rearrangement scheme when both α and β are real numbers: the constellation mapping mode adopted by the 1 st time diversity antenna #1 and the antenna #2 is mode 1, the constellation mapping mode adopted by the 2 nd time diversity antenna #1 and the antenna #2 is any one of modes 2 to 19, and the order of the two modes adopted by the two transmissions can be exchanged.

When both α and β are complex, the second proposed optimized constellation rearrangement scheme, as in the SISO system, is: the constellation mapping mode adopted by the 1 st time diversity antenna #1 and the antenna #2 is mode 1, and the constellation mapping mode adopted by the 2 nd time diversity antenna #1 and the antenna #2 is any mode obtained by conjugating each alpha and beta in modes 2 to 19; similarly, the third optimized constellation rearrangement scheme is: the constellation mapping method adopted by the 1 st time diversity antenna #1 and the antenna #2 is the mode 1, and the constellation mapping method adopted by the 2 nd time diversity antenna #1 and the antenna #2 is the x in the modes 2 to 19₁、y₁、x₂、y₂And taking an arbitrary mode after conjugation. Preferably, the constellation mapping manner adopted by the antenna #1 and the antenna #2 in the 2 nd time diversity can select any one of the modes 2 to 5 and the modes 11 to 14, and this wayThe 8 modes not only ensure that the modulation factors of the same information bit are different on different time diversities, but also ensure that the signs of the same information bit are different, thereby ensuring that the decoding reliability of the soft bit information after the receiving end demodulates is more balanced.

The embodiment of the invention provides a receiving and combining method based on data retransmission of an optimized constellation recombination strategy, which comprises the following steps:

b1, assume at t₁A group of data is transmitted at a time, and information bits to be transmitted of an antenna #1 and an antenna #2 after FEC coding are respectively b₀b₁b₂b₃And b₄b₅b₆b₇Wherein b is₀b₁And b₄b₅Respectively mapping to QPSK constellation point modulation symbol x₁、x₂，b₂b₃And b₆b₇Respectively mapping to QPSK constellation point modulation symbol y₁、y₂The above step (1); x is the number of₁、y₁Respectively alpha and beta, information bit b₀b₁b₂b₃The constellation mapping mode adopted when the modulation is changed into a 16QAM constellation point modulation symbol is z₁＝αx₁+βy₁，x₂、y₂The modulation factors of (a) and (b) may be different, and the information bit b₄b₅b₆b₇The constellation mapping mode adopted when the modulation is changed into a 16QAM constellation point modulation symbol is z₂＝αx₂+βy₂；

b2, the receiving end receives and buffers the data symbol transmitted by the channel, and the data symbol received by the receiving end after the data symbol is transmitted by the channel is assumed to be r₁₁、r₂₁After demodulation and FEC decoding, CRC check is carried out on the decoded received data, if the reception is correct and the transmission of the group of data is successfully completed, the buffered data symbols r are cleared₁₁、r₂₁And informing the sending end to transmit the next group of data through feedback; if the CRC check finds t₁The data transmitted at the moment is received in errorThe HARQ requests the sending end to retransmit the group of data, and b3 is continued;

b3 if at t₂Retransmitting the group of data, i.e. information bit b, at a time₀b₁b₂b₃And b₄b₅b₆b₇Selecting a corresponding optimized constellation reconstruction scheme according to whether alpha and beta are real numbers or imaginary numbers, and if alpha and beta are real numbers, modulating the first optimized constellation reconstruction scheme in a constellation mapping mode according to the first optimized constellation reconstruction scheme, wherein the sent data symbol is any one of modes 2 to 19;

b4, the receiving end receives and buffers the retransmitted data symbol, and the data symbol received at the receiving end is assumed to be r after the retransmitted data group is transmitted through the channel₂₁、r₂₂The receiving end will r₁₁、r₂₁And r₂₁、r₂₂Simultaneously, detecting signals through an interference elimination receiver to eliminate the interference of related channels, and further demodulating and FEC decoding after the interference is eliminated;

b5, making CRC check to the decoded received data, if the reception is correct, indicating the transmission of the group of data is completed successfully, clearing the buffered data symbol r₁₁、r₂₁And r₂₁、r₂₂And informing the sending end to transmit the next group of data through feedback; if t is found by CRC check₂If the group data transmitted at the moment is received wrongly, the sending end is requested to resend the group data through the HARQ;

and retransmitting the group of data until the CRC checks that the data is received correctly or the configured maximum retransmission times are reached.

The following is a description of the reception principle by which an interference cancellation receiver in a MIMO system can achieve symbol level combining. Preferably, the interference cancellation receiver employed is an LMMSE or ZF receiver. When the interference cancellation technique is adopted at the receiving end in the MIMO system, the following two processing schemes can be adopted, and the following implementation principles are introduced respectively. First, processing scheme one is introduced for t₁On two antennas at the momentIf the transmitted data packet adopts the mode 1, the two data symbols received by the receiving end can be represented as:

assuming n in combination with the existing noise theory model₁、n₂Is a mean of 0 Gaussian noise, and

E {{| n_{1} |}^{2}} = E {{| n_{2} |}^{2}} = \frac{N_{0}}{2},

wherein, E^*Means for^*The mathematical expected value of (a) is,

representing the noise power;

representing the channel transfer function of the ith transmitting antenna to the jth receiving antenna on the nth transmission diversity; x and y are QPSK modulation symbols with amplitude of 1: 1, | x | ═ y |;

the modulation factors of x and y are alpha,β, α and β may be real numbers or complex numbers, and when α and β are real numbers, a first optimized constellation rearrangement scheme may be used, and when α and β are complex numbers, a second optimized constellation rearrangement scheme may be used. Since mathematically, real numbers are only one particular form of complex numbers, e.g.

When theta is₁And theta₂When k pi is obtained, k belongs to z, alpha and beta are real numbers, and the conjugation of the real numbers is the real numbers. Herein too, to

The receiving principle using the first two optimized constellation rearrangement schemes is described as an example.

According to the receiving principle in the SISO system, after the two data symbols of the formula [17] are subjected to the interference cancellation operation, the following formula [18] can be obtained:

wherein f is_N(n₁，n₂..) (N ═ 1, 2) for N₁And n₂And other relevant parameters, e.g. x₁、y₁、x₂、y₂And the like.

For t₂For a data packet transmitted on two antennas at the time, if the mode 12 is adopted, the data symbol received by the receiving end can be represented as:

if α and β are real numbers, then α ═ α^*，β＝β^*Assuming n in combination with the existing noise theory model₃、n₄Is a mean of 0 Gaussian noise, and

E {{| n_{3} |}^{2}} = E {{| n_{4} |}^{2}} = \frac{N_{0}}{2} .

after the data symbols of equation [19] are subjected to the interference cancellation operation, the data symbols are obtained as shown in equation [20 ]:

wherein, f_N(n₃，n₄..) (N ═ 3, 4) for N₃And n₄And other relevant parameters, e.g. x₁、y₁、x₂、y₂And the like.

From equations [19] and [20], the following two equations can be derived:

for the formula [21]And [22 ]]Separately performing interference cancellation can solve for x₁、y₁、x₂And y₂。

Next, the second processing scheme is described, and the receiving principles of the first optimized constellation rearrangement scheme and the second optimized constellation rearrangement scheme are also described. For t₁And t₂At the moment, if the first transmission adopts the mode 1 and the second transmission adopts the mode 12, the data symbol received by the receiving end can be used as four paths of data symbols of one transmission, such as the formula [23]]Shown in the figure:

from equation [23], equation [24] can be derived:

for the formula [24]X for solving the influence of noise added to channel by interference elimination₁、y₁、x₂、y₂。

When α and β are complex numbers, a third optimized constellation rearrangement scheme can be used, and the receiving principle thereof will be described below. In the scheme, the constellation mapping mode adopted by the antenna #1 and the antenna #2 on the 1 st time diversity is mode 1, and the constellation mapping mode adopted by the antenna #1 and the antenna #2 on the 2 nd time diversity is x in the modes from 2 to 19₁、y₁、x₂、y₂Taking any mode after conjugation, the description will be made by taking the mode 12 as an example.

For processing scheme one, for t₁The data packets transmitted on the two antennas at the moment adopt the mode 1, and then two paths of data symbols received by the receiving end can be expressed as the formula [17]]E.g. of

After the two paths of data symbols of the formula [17] are subjected to interference cancellation operation, the two paths of data symbols are obtained as shown in the formula [18 ]:

E.g. for t₂Data packets transmitted on two antennas at the moment, if each x in pattern 12 is used₁、y₁、x₂、y₂Taking the conjugated mode, the data symbol received by the receiving end can be expressed as formula [25 ]]：

To realize the post-pair x by the interference eliminator₁、y₁、x₂、y₂Solving, can be for equation [25]Is subjected to constant deformation to obtain the following formula [26]：

The data symbols of equation [26] undergo interference cancellation operation to obtain the data symbols as shown in equation [27 ]:

wherein,

f_{N} (n_{3}^{*}, n_{4}^{*} . .) (N = 3,4)

represent aboutAnd

and other relevant parameters, e.g. x₁、y₁、x₂、y₂And the like.

From equations [18] and [27], equations [28] and [29] can be derived:

for the formula [28]And [29]]Separate interference cancellation can solve the effect of added channel noise₁、y₁、x₂、y₂。

The second processing scheme is described below, which shows that t is the target of₁And t₂In a data packet transmitted on two antennas at a time, a data symbol received by a receiving end can be used as a four-way data symbol transmitted at one time, as shown in a formula [30 ]]Shown in the figure:

to realize the post-pair x by the interference eliminator₁、y₁、x₂、y₂Solving, can be for equation [30 ]]Performing an identity transformation to obtain the formula [31]：

From equation [31], equation [32] can be derived:

for the formula [32]X for solving the influence of noise added to channel by interference elimination₁、y₁、x₂、y₂。

After the data symbols transmitted twice are respectively received and buffered, the x added with the influence of channel noise can be solved by the interference elimination receiver₁、y₁、x₂、y₂Therefore, symbol-level combination of the receiving end is realized, and further demodulation and decoding are carried out to obtain received data.

All the three optimized constellation reconstruction schemes are realized based on 16QAM, namely the specific realization that the modulation order is 2, and the optimized constellation reconstruction strategy provided by the embodiment of the invention is also suitable for other modulation modes such as 8PSK, 8APSK, 64QAM, 128QAM and the like. Taking 64QAM with modulation order of 3 as an example, six information bits b₀b₁b₂b₃b₄b₅Mapped to constellation point s of 64QAM, and can be decomposed into the following form: where α, β, γ are modulation factors, may be real or complex, and x, y, and z are QPSK constellations mapped by 2 information bits, respectivelyThe symbols are point modulated. Then, a combination manner in the optimized constellation rearrangement scheme can be obtained according to the optimized constellation rearrangement strategy and the modulation order, if the data symbol transmitted at the 1 st time is s₁Then the data symbol transmitted at the 2 nd transmission may be s₂＝β⁽²⁾x⁽²⁾+γ⁽²⁾y⁽²⁾+α⁽²⁾z⁽²⁾The data symbol transmitted at the 3rd time may be s₃＝γ⁽³⁾x⁽³⁾+α⁽³⁾y⁽³⁾+β⁽³⁾z⁽³⁾. There are also many combination ways that meet the optimized constellation rearrangement strategy, and they are not listed one by one. The data symbols transmitted at least once are combined by the receiving and combining method provided by the embodiment of the invention to obtain the received data, so that the system performance can be improved.

Referring to fig. 7, a schematic diagram illustrating a comparison between the receiving and combining method based on data retransmission and the receiving and combining method in the prior art for improving system performance according to the embodiment of the present invention is obtained through computer simulation, which shows that the frame error rate and the bit error rate are reduced, and the channel capacity and the spectrum utilization rate of the system are improved.

The receiving and combining method based on data retransmission provided by the embodiment of the invention is applied to at least one data transmission at different time by adopting the HARQ technology, and can also transmit a group of data on at least two transmit diversity branches such as different time, different cells, different antennas, different polarization directions, different frequency bands, different spreading codes, different relay base stations and the like based on the transmit diversity technology, and the data needs to be received and combined at a receiving end. An embodiment of the present invention provides a receiving and combining method and system based on transmit diversity, and as shown in fig. 8, the receiving and combining method based on transmit diversity provided by the embodiment of the present invention includes:

s801, receiving and caching data symbols transmitted after a group of data is respectively modulated on at least two transmit diversity branches;

preferably, when a group of data is modulated on at least two transmit diversity branches, the modulation factors allocated to the same information bit in the group of data are different;

s802, after carrying out interference elimination and symbol combination on the data symbols on at least two transmitting diversity branches, demodulating and decoding to obtain combined received data.

the receiving device: the receiving and buffering device is used for receiving and buffering the data symbols transmitted by the transmitting device, demodulating and decoding the data symbols after interference elimination and symbol combination to obtain combined received data.

Preferably, when the transmitting device modulates a group of data on at least two transmit diversity branches, the modulation factors allocated to the same information bit in the group of data are different.

The receiving and combining method and the receiving and combining system based on the transmitting diversity effectively improve the system performance, reduce the frame error rate and the bit error rate, and improve the channel capacity and the spectrum utilization rate of the system.

The receiving and combining method based on data retransmission and other transmit diversity provided by the embodiment of the invention can be used in a system at the same time, and a specific application scene is an MIMO system based on HARQ technology. Assuming that the MIMO system is a dual transmission and dual reception system, the information bits to be transmitted at the antenna #1 and the antenna #2 are both b₀b₁b₂b₃The method comprises the following steps:

c1、t₁the group of data b is transmitted at time on two spatial transmit diversity branches, antenna #1 and antenna #2, respectively₀b₁b₂b₃；

Preferably, when the group of data is modulated on the two space transmit diversity branches, the modulation factors allocated to the same information bit in the group of data are different;

c2, the receiving end receives and buffers the data symbols transmitted by the two space transmit diversity branches, and demodulates and decodes the data symbols after interference elimination and symbol combination to obtain the combined received data;

c3, carrying out CRC check on the received data, if the data reception is correct through the CRC check, indicating that the group of data transmission is successfully completed, clearing the buffered data symbols and indicating to transmit the next group of data; if the CRC checks that the data is received in error, indicating to retransmit the group of data, and continuing to execute c 4;

c4、t₂retransmitting the group of data b at two spatial transmit diversity branches, antenna #1 and antenna #2, at a time instant₀b₁b₂b₃；

c5, the receiving end receives and buffers the data symbols re-transmitted on the two space transmit diversity branches, and demodulates and decodes the data symbols respectively transmitted on the two space transmit diversity branches after interference elimination and symbol combination to obtain the combined received data;

c6, carrying out CRC check on the received data, if the received data is correct, indicating that the transmission of the group of data is successfully completed, clearing the buffered data symbols and indicating to transmit the next group of data; if the CRC checks that the data is received wrongly, indicating to retransmit the group of data;

and so on until the data reception is verified to be correct or the configured maximum retransmission times are reached.

And preferably, for a set of data b₀b₁b₂b₃Is carried out t₁And t₂In the two transmissions, the same information bit in the group of data is allocated with different modulation factors.

In general, for high order modulation with a modulation order of M, α is assumed₁，...，α_MFor the modulation factor, it can be real or complex, x₁，...，x_MIs a low-order constellation point modulation symbol mapped by information bits; suppose z₁，z₂，...，z_KData symbols transmitted separately for different transmission times or data symbols transmitted separately on different transmit diversity branches, where transmit diversity includes different time instants/different frequency bands/different antennas/different polarization directions/different cells/different relay base stations/different spreading code modulations and combinations of the above, e.g. at different time instants, different antennas, etc.;

an optimized constellation rearrangement scheme can be made according to the optimized constellation rearrangement strategy and the modulation order, for example, the data symbol on the 1 st transmission or the 1 st transmission diversity is represented as z₁＝α₁x₁+α₂x₂+…α_Mx_MThen, for α, on the 2 nd to Kth transmission or the 2 nd to Kth transmission diversity₁，...，α_MAnd x₁，...，x_MThe data symbols transformed by suitable combination are denoted as z₂，...，z_KThe method accords with an optimized constellation reconstruction strategy, and the combined transformation comprises addition, subtraction, multiplication, division, conjugation and the like;

for the above K transmissions or data symbols z in K transmission diversity₁，z₂，...，z_KThe data merging method on each diversity branch adopts interference elimination technologies such as ZF, L-MMSE, ML, SIC, PIC and the like to detect signals;

k and M may be equal or different, and the constellation mapping modes adopted in different transmit diversity may be used in turn according to a certain mode.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A receiving and combining method based on data retransmission is characterized by comprising the following steps:

2. The method of claim 1, wherein the same information bit in a group of data is separately assigned different modulation factors for at least two transmissions of the group of data.

3. The method of claim 1, further comprising:

checking the received data, if the data reception is checked to be correct, clearing the cached data symbols and indicating to transmit the next group of data; and if the data receiving error is verified, indicating to retransmit the group of data until the data receiving is verified to be correct or the configured maximum retransmission times are reached.

4. The method of claim 2, wherein said separately modulating the same information bit in the group of data comprises:

determining a modulation factor distributed when the same information bit is modulated in at least two transmissions of a group of data according to a modulation order;

and respectively modulating the same information bit in the group of data in at least two transmissions according to the determined modulation factor.

5. A system for combining data retransmissions, comprising:

6. The system of claim 5, wherein the transmitting device is configured to transmit a group of data at least twice with different modulation factors for respective modulation bit assignments for the same information in the group of data.

7. The system of claim 6, wherein the receiving device is further configured to verify the received data, clear the buffered data symbols if correct data reception is verified, and direct transmission of a next set of data; and if the data receiving error is checked out, indicating to retransmit the group of data.

8. The system of claim 7, wherein the transmitting device further transmits a next set of data upon receiving an indication to transmit the next set of data; the group of data is retransmitted upon receiving an indication to retransmit the group of data.

9. A receiving device, comprising:

a receiving unit: for receiving data symbols;

10. The receiving device of claim 9, further comprising:

a checking unit: the data receiving unit is used for receiving the received data and sending the received data to the decoding unit; and if the data receiving error is checked out, indicating to retransmit the group of data.

11. A transmitting device, comprising:

12. The transmitting apparatus as claimed in claim 11, wherein the modulating unit further modulates the information bits output by the encoding unit on at least two transmit diversity branches to obtain data symbols, and when a group of data is modulated on at least two transmit diversity branches, the modulation factors allocated to the same information bit in the group of data are different.

13. A receive combining method based on transmit diversity, comprising:

14. The method of claim 13, wherein a group of data is modulated on at least two transmit diversity branches respectively, and a modulation factor assigned to a same information bit in the group of data is different.

15. The method of claim 14, wherein separately modulating a set of data over at least two transmit diversity branches comprises:

determining modulation factors distributed when the same information bit in a group of data is respectively modulated on at least two transmit diversity branches according to the modulation order;

and respectively modulating the group of data on the transmit diversity branches according to the determined modulation factors.

16. The method of claim 13, further comprising:

17. The method of claim 15, wherein the same information bit in a group of data is separately assigned different modulation factors for at least two transmissions of the group of data.

18. A receive combining system based on transmit diversity, comprising:

the receiving device: and the data symbol is used for receiving and buffering the data symbol transmitted by the transmitting equipment, and the data symbol is demodulated and decoded after interference elimination to obtain combined received data.

19. The system of claim 18, wherein the transmitting device assigns different modulation factors to the same information bit in a group of data when modulating the group of data over at least two transmit diversity branches, respectively.

20. The system of claim 19, wherein the receiving device further checks the received data, clears the buffered data symbols if correct data reception is verified, and instructs transmission of a next set of data; and if the data receiving error is checked out, indicating to retransmit the group of data.

21. The system of claim 20, wherein the transmitting device transmits a next set of data over the at least two transmit diversity branches upon receiving an indication to transmit the next set of data;

and after receiving the indication of retransmitting the group of data, the transmitting equipment retransmits the group of data on the at least two transmit diversity branches.

22. The system of claim 21, wherein the transmitting device is configured to transmit a group of data at least twice with different modulation factors assigned to modulation of the same information bit in the group of data.