WO2010048748A1

WO2010048748A1 - Distributed retransmission method based on superposition coded modulation in multihop relay network

Info

Publication number: WO2010048748A1
Application number: PCT/CN2008/001832
Authority: WO
Inventors: 陈继明; 刘继民; 王伟
Original assignee: 上海贝尔阿尔卡特股份有限公司; 阿尔卡特朗讯
Priority date: 2008-10-31
Filing date: 2008-10-31
Publication date: 2010-05-06
Also published as: CN102119496B; CN102119496A

Abstract

A distributed retransmission method is proposed in present invention. The method includes the following steps: Base Station (BS) broadcasts Superposition Coded Modulation (SCM) data bursts to Relay Station (RS) and the first Mobile Station (MS), wherein the SCM data bursts are composed of the superposition of the first coded modulation data bursts which can be supported by transmission channel from BS to the first MS and the second coded modulation data bursts which can be supported by transmission channel from BS to RS, wherein the destination of the second coded modulation data bursts may be the first MS or the second MS in multi-user transmission mode; RS judges whether the first MS has correctly decoded the first coded modulation data bursts, and also judges the channel condition between RS and the first MS, then determines RS retransmission scheme according to the judgments. The retransmission scheme based on SCM proposed in present invention enables the retransmission time delay to be decreased and the cell throughput and capacity to be increased.

Description

More ^ » Relay network

Distributed retransmission method based on overlapping code modulation

The present invention relates to a retransmission scheme for use in a wireless communication network, and more particularly to a distributed retransmission method based on Overlap Code Modulation (SCM) in a multi-hop relay network. Background technique

In order to improve the reliability of wireless links, retransmission schemes are widely used in current wireless systems. In general, these schemes assume that the erroneous data block (burs t) in the cell (i.e., the data block that was not correctly received at the mobile station (MS)) must be retransmitted from the corresponding base station (BS) based on the retransmission scheme. In this case, the MS with poor channel conditions will experience a large delay in order to correctly receive the data block.

Traditionally, there are three retransmission schemes in a multi-hop relay network.

1 is a schematic diagram showing a first type of retransmission scheme, that is, a conventional point-to-point retransmission scheme.

As shown in Fig. 1, the first scheme is designed for a point-to-point link in which the scheme is implemented between a BS and an MS (e.g., a conventional cellular system), and the relay station (RS) does not have an additional retransmission function. Since the resources of the BS are retransmitted, the transmission delay of the cell increases, and the throughput of the cell is wasted.

2 is a schematic diagram showing a second retransmission scheme, that is, a dual link retransmission scheme. ,

As shown in FIG. 2, the second scheme is a dual-link retransmission scheme in which a relay link (ie, a link between a BS and an access RS) and an access link (ie, an access RS and an MS) The retransmission scheme is performed on the link between). For the access link, when the received data block is decoded incorrectly (for example, the RS receives a negative acknowledgement (NAK) from a certain MS), a retransmission function is performed between the access RS and the MS, and the retransmission is initiated by the BS. For the relay link, a retransmission scheme is performed between the BS and the access RS, and the retransmission is initiated by the RS.

FIG. 3 is a schematic diagram showing a third retransmission scheme, that is, a local retransmission scheme. As shown in FIG. 3, the third mode is a local retransmission scheme, wherein it is assumed that the relay link has a higher signal to noise ratio (SNR) due to reasonable placement of RSs in the cell. Therefore, even if the data block is decoded incorrectly at the destination MS, the probability that the RS can correctly receive the data block is still high. Basically, the RS can correctly receive data blocks that are forwarded by the RS to MSs within its service range. For example, in the first phase, the BS broadcast transmission destination is a data block of the MS, at which time both the RS and the MS will receive the data block, and the RS can correctly receive the data block. When the MS cannot correctly receive the data block, then in the second phase, the BS commands a particular RS to initiate and perform the local required retransmission.

According to the second and third retransmission schemes, the RS performs retransmission to reduce the cell delay. However, regardless of whether the MS can correctly decode the data block, 'no RS can be used to transmit new data blocks to improve cell throughput and capacity.

In a multi-hop relay network, the use of the relay not only realizes retransmission of data from the BS, but also retransmits data locally from the RS, such as the second and third schemes described above, wherein the RS performs data in the first phase. Decoding, and retransmitting data that was not received correctly by employing the second phase of the downlink subframe. Since the retransmission function can be supported by the relay, the transmission delay of the cell will be reduced. However, these retransmission schemes will consume the total traffic, so the total throughput and spectral efficiency in the cell will be reduced. .

The Overlap Coded Modulation (SCM) scheme (see Reference [1]) is a multiplexing method that is widely used in wireless 'communication systems to increase the total data rate of the downlink and achieve higher throughput. The basic principle is that it will be different. The traffic of the code rate and modulation order is superimposed and broadcasted to a specific user. In the SCM scheme, in order to correctly decode each stream, it is necessary to appropriately select the user, the transmission code rate, the modulation order, and the transmission power.

In a multi-hop relay network, the BS-to-MS direct link is divided into two or more short-distance high-quality links due to the reasonable placement of RSs in the cell. At the same time, the "far-and-far" effect caused by the large difference between the distance from BS to RS and the distance from BS to MS makes the path loss greatly different. By utilizing these advantages, the present invention proposes a SCM-based distributed retransmission method for reducing the cell transmission delay and increasing the throughput and capacity of the cell.

Spring literature list

[1] A. Seeger, "Broadcas t Communication on Fading Channel s Us ing Hierarchical Coded Modulation, " in Proc. GLOBECOM' 00, Vol. 1, Dec. 2000, pp. 92-97. Summary of the Invention

The distributed retransmission method in the multi-hop relay network proposed by the present invention adopts overlapping code modulation (SCM) technology to improve the existing retransmission scheme:

1) separately modulating and encoding two traffic streams into HCM (High Code Rate High Modulation Order) data block and LCM (Low Code Rate Low Modulation Order) data block;

2) The BS simultaneously transmits the SCM data block to the RS and the MS, and the SCM data block is a superposition of the HCM data block and the LCM data block having different transmission powers;

3) The RS can correctly decode the LCM data block and the HCM data block, and the MS can only receive the LCM data block;

4) In the case of an error in the reception of the MS, the RS first determines the channel condition between the RS and the MS:

4. 1) If the channel conditions between the RS and the MS are poor, the RS uses an incremental redundancy (IR) or Chase combining (CC) retransmission scheme to perform retransmission operations on the LCM data.

4. 2) Otherwise, if the channel conditions between the RS and the MS are good, the RS encodes and modulates the HCM data and the LCM data using a higher order modulation and coding scheme (MCS) supported on the RS-MS link, where the LCM is The data can be retransmitted using an IR or CC retransmission scheme and then transmitted.

5) In case the MS receives correctly, the RS transmits the HCM data to the MS using the MCS that can be supported on the RS-MS link.

More generally, the present invention proposes a distributed retransmission method, the method comprising: a base station broadcasting an overlap coded modulated data block to a relay station and a first mobile station, wherein the overlap coded modulated data block is transmitted by the base station to the first mobile station The first coded modulated data block that the channel can support and the second coded modulated data block that the base station to the transport channel of the relay station can support are superimposed, wherein the destination of the second coded modulated data block may be the first mobile station or the multi-user transmission mode. a second mobile station; the relay station determines whether the first mobile station successfully decodes the first coded modulated data block according to the information fed back by the first mobile station; if the first mobile station correctly decodes the first coded modulated data block , the relay station modulates the destination of the data block according to the second code to be the first A mobile station or a second mobile station transmits the second coded modulated data block to the first mobile station or the second mobile station.

Preferably, the distributed retransmission method according to the present invention further comprises: in a case where the first mobile station does not correctly decode the first coded modulated data block, the relay station determines a channel condition of the relay station to the first mobile station;

If it is determined that the channel condition is good, and the destination of the second coded modulated data block is the first mobile station, the relay station retransmits the overlap coded modulated data block to the first mobile station;

The first mobile station recovers the first coded modulated data block based on the signals received from the base station and the relay station;

The first mobile station decodes the second coded modulated data block.

More preferably, the distributed retransmission method according to the present invention further includes:

If it is determined that the channel condition is poor or the destination of the second coded modulated data block is the second mobile station, the first coded modulated data block is first retransmitted to the first mobile station;

The first mobile station recovers the first coded modulated data block based on the signals received from the base station and the relay station.

If the first mobile station fails to correctly decode the second coded modulated data block, the relay station retransmits the second coded modulated data block to the first mobile station.

Preferably, the relay station initiated retransmission is terminated when the first mobile station correctly decodes the first or second coded modulated data block or reaches a predetermined maximum number of retransmissions.

Preferably, the link between the relay station and the first or second mobile station can support higher order modulation and coding scheme to perform transmission or overlap a second block coded modulation code modulation and retransmission of data blocks ₀

Preferably, the retransmission of the first coded modulated data block is performed using an incremental redundancy retransmission scheme or a Chase combining retransmission scheme. Accordingly, the first mobile station recovers the first code modulated data block using the incremental redundancy retransmission scheme or the Chase combining retransmission scheme for the signals transmitted from the base station and the relay station.

Preferably, the weight of the second coded modulated data block is performed using a higher order modulation coding scheme Pass.

Preferably, the distributed retransmission method according to the present invention further comprises: if the second mobile station does not correctly decode the second coded modulated data block, the relay station retransmits the second coded modulated data block to the second mobile station. More preferably, the relay-initiated retransmission is terminated when the second mobile station correctly decodes the second coded modulated data block or reaches a predetermined maximum number of retransmissions.

Preferably, the channel conditions required to correctly decode the second coded modulated data block are better than the channel conditions required to correctly decode the first coded modulated data block. Preferably, the second coded modulation block is a block of data generated by high code rate and/or higher order modulation, and the first coded block of modulated data is a block of data produced by low bit rate and/or low order modulation.

Preferably, the channel condition is represented by a signal to noise ratio on the channel, and if the signal to noise ratio on the channel is equal to or higher than a predetermined threshold, the channel condition is determined to be good; otherwise, if the signal to noise ratio on the channel is 4, at a predetermined threshold, then Determine the channel condition difference.

Preferably, the distributed retransmission method according to the present invention further comprises: if the first or second mobile station correctly decodes or restores the first or second coded modulated data block, the first or second mobile station to the relay station 4 The advertisement acknowledges the answer), and after receiving the acknowledgement, the relay station determines that the first or second mobile station successfully decodes the first or second coded modulated data block.

Preferably, the distributed retransmission method according to the present invention further comprises: if the first or second mobile station fails to correctly decode or recover the first or second coded modulated data block, the first or second mobile station to the relay station A negative acknowledgement (ΝΑΚ) is reported, and after receiving the negative acknowledgement, the relay station determines that the first or second mobile station failed to correctly decode the first or second coded modulated data block.

Preferably, the higher order modulation coding scheme is the same as the modulation coding scheme used to generate the second coded modulated data block.

Preferably, the distributed retransmission method according to the present invention is applicable to a multi-hop relay network.

The SCM-based retransmission scheme proposed by the present invention can reduce retransmission delay and improve cell throughput and capacity.

Advantages of the Invention ' From a technical point of view, the following values exist:

1. Two data streams using an IR or CC retransmission scheme experience two separate channels, so a diversity gain can be obtained;

2. Since LCM theory can be used to transmit services with low latency requirements, 'use HCM The theory is to transmit services with high bandwidth requirements, so flexible scheduling algorithms can be used in the retransmission scheme of the present invention to meet performance requirements;

3. Due to the overlapping scheme of two traffic flows, the multiplexing gain can be obtained;

4. The retransmission scheme adapts the channel conditions on the access link in the relay network, so that higher throughput and capacity can be obtained;

5. The proposed solution is easy to extend to multi-user scenarios.

Compared with the prior art solutions, the invention also has the following advantages:

1. Since the low-rate and low-latency required traffic is transmitted over the direct link and the retransmission is initiated at the RS, the transmission delay of the delay-sensitive service is reduced;

2. Using the SCM scheme, simultaneously transmitting two service flows with different MSCs to the MS and the RS, and initiating retransmission at the RS, so that the throughput of the system can be effectively improved when the link quality between the RS and the MS is good. Quantity and capacity;

3. The present invention can be flexibly extended to a multi-user relay network, i.e., the destinations (MS) of two traffic streams transmitted by the BS and the RS can be different users. DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from

1 is a schematic diagram showing a first conventional retransmission scheme (point-to-point retransmission scheme); 'Fig. 2 is a diagram showing a second conventional retransmission scheme (dual-link retransmission scheme); A schematic diagram of a third conventional retransmission scheme (local retransmission scheme) is shown; Figure 4 illustrates a two-hop relay network in which a destination (i.e., MS) can receive signals from a source via two paths, The path is a two-hop relay link and a single-hop direct link;

Figure 5 shows an example of an overlap coding modulation scheme that can be used in the present invention;

Figure 6 is a timing diagram showing the retransmission process proposed in accordance with the present invention;

7 is a schematic diagram showing a multi-user scenario in which the present invention is equally applicable;

Figure 8 is a timing diagram showing a retransmission process that can be used for multiple users in accordance with the present invention;

Figure 9 is a diagram showing simulation results, particularly showing the throughput of different transmission schemes. detailed description

Hereinafter, the present invention will be described with reference to the accompanying drawings. In the following description, some specific embodiments are merely illustrative, and should not be construed as limiting the invention. Descriptions of conventional structures or configurations are omitted as they may obscure the present invention.

In a multi-hop relay network, the introduction of a relay divides the direct link into two or more high-quality links, forming a multi-hop path between the base station and the user terminal, which overcomes the shadow and path loss. The problem of coverage blind spots and low data rates.

Figure 4 shows a two-hop relay network in which a destination (i.e., MS) can receive signals from a source via two paths: a two-hop relay link and a single-hop direct link. In a two-hop relay link, the physical channel between the BS and the RS is called a relay link, and the physical channel between the RS and the MS is called an access link.

In most cases, the reasonable placement of the RS in the cell will cause a "far-and-far" effect, that is, the difference between the distance from the BS to the RS and the distance from the BS to the MS is large, so that the path loss of the two links is very different. For example, in a typical mobile environment, the path loss exponent is 4, and the path loss difference is 12 dB in the scenario where the distance between the MS and the RS is 2 km and the distance between the RS and the BS is l n . Therefore, the relay link between the BS and the RS has a higher SNR due to lower path loss, and the direct path between the BS and the MS has a lower SNR due to the longer distance. Different path losses can be used for retransmissions in multi-hop relay networks to further increase capacity and achieve higher spectral efficiency. In general, the channel conditions of the relay link are better than the channel conditions of the direct link, where the channel conditions can be reflected by the SNR or other known parameters on the channel.

As shown in FIG. 4, according to the overlap coding modulation scheme, the BS simultaneously transmits the superimposed signals of the HCM data and the LCM data for the BS to the RS and the BS to the MS by correctly allocating the code rate, the modulation order, and the power. It is assumed that the powers allocated to the HCM data and the LCM data are P1 and P2, respectively, and in the case where the total transmission power of the BS is P, then Pl+P2-P. For example, as shown in FIG. 5, the HCM data uses a coded modulation scheme of a 3/4 code rate 16QAM (Quadrature Amplitude Modulation) constellation, and the LCM data uses a code modulation of a 1/2 code rate QPSK (Quadrature Phase Shift Keying) constellation. the way. However, the present invention is not limited to specific code rates and modulation schemes for HCM data and LCM data, except that HCM data is a high bit rate and/or high order modulation pair source signal supported by a link with better channel conditions. Generated by encoding and/or modulation, while LCM data is passed through poor channel conditions The low bit rate and/or low order modulation supported by the link is generated by encoding and/or modulating the source signal. Essentially, the present invention only requires simultaneous provision of the channel conditions required to properly decode the HCM data and the channel conditions required to properly decode the LCM data.

Since the relative noise levels of the HCM data and the LCM data are different and the transmission power is different, the constellation received in the RS and MS has different ambiguities. Because MS has a large path loss, the signal received by the MS is weak and the relative noise level is high. Therefore, the constellation is very ambiguous and it is difficult to recover the HCM data. However, the MS still recognizes the LCM data, that is, the low code rate and the modulated constellation, and the HCM data is regarded as interference. For RS, the relative noise level is low, so the received constellation is only slightly blurred. Both LCM data and HCM data are identifiable. Therefore, the RS first recovers the LCM data (while treating the HCM data as interference:) and then subtracts the recovered LCM data from the received signal. At this point, the remaining signal of the RS consists of two parts: HCM data and noise. As long as the information rate of the HCM data does not exceed the capacity of the relay channel without any interference, the RS can recover the information of the HCM data. Therefore, the MS can only get the LCM data, and the RS can get the HCM data and the LCM data. ■ Due to the reasonable placement of RSs in the cell, line-of-sight (L0S) propagation conditions and high-profile wireless relay links can be easily obtained between the BS and the RS, so the RS can correctly decode the overlapping signals completely. However, due to high path loss and NL0S (non-line-of-sight) propagation conditions, long-distance links between BS and MS will increase the probability of MS error detection LCM data. In order to improve the reliability of the direct link in the multi-hop relay network, a retransmission scheme is adopted for the MS. Since the RS can simultaneously detect the information data of the HCM data and the LCM data, the RS can complete the retransmission scheme. Although the path loss between RS and MS is lower and the channel quality is higher than the path loss between BS and MS and channel quality, the complex wireless environment of MS will affect the RS retransmission strategy. Figure 6 is a timing diagram showing the retransmission process proposed in accordance with the present invention, briefly described as follows:

1. In the first phase, the BS broadcasts SCM data blocks to the RS and MS broadcasts, which is a superposition of HCM data and LCM data. Since the SNR of the link between the BS and the RS is high, the RS can correctly recover the SCM data block and then send the acknowledgement CK to the BS, and since the SNR of the link between the BS and the MS is low, the MS can only The LCM data from the BS is correctly decoded.

2. When the MS is unable to correctly decode the LCM data in the first phase, the MS will send the RS to the RS. Send NAK. Based on the previously measured channel conditions between the BS and the MS, there are two kinds of retransmissions. a) If the channel condition between the BS and the MS is good, in the second stage, the RS utilizes a higher order supported by the RS-MS. The Modulation and Coding Scheme (MSC) encodes the modulated HCM data and the LCM data, wherein the LCM data may use an IR or CC retransmission scheme, and then transmit the new data block to complete the retransmission operation. The MS will combine the data streams of the two independent channels (ie BS to MS direct channel and RS to MS access channel) obtained by the IR or CC retransmission scheme to recover the LCM data while decoding the HCM data.

b) If the channel quality between the RS and the MS is poor, the RS transmits the LCM data to the MS only using the IR or CC retransmission scheme until the MS merges the LCM data from the two phases (or two independent channels) Correctly decode the data or the system reaches the maximum number of retransmissions.

3. If the MS successfully decodes the LCM data in the first phase, the MS will send the ACK information to the RS, then the RS will transmit in the second phase using the higher order modulation and coding scheme (MCS) supported on the RS-MS. HCM data. If the MS fails to correctly decode the HCM data, the RS will receive another NAK information, and the RS will also retransmit the HCM data by the IR or CC retransmission scheme until the MS correctly receives the HCM data or the system reaches the maximum weight. The number of passes.

In the above description, the first phase and the second phase can be defined throughout the process. The first phase represents the time period from the BS to the RS and MS broadcast SCM data block to the time when the MS reports AC or NAK information to the RS. The first stage represents the time period from when the RS transmits the SCM data block to the MS, the HCM number selection or the LCM data starts until the MS reports the ACK information to the RS or the system reaches the maximum number of retransmissions. Regarding the criteria for determining whether channel conditions are good or bad, SNR can be used as an example of a metric. In this case, if the SNR is equal to or greater than a predetermined threshold, it is determined that the channel condition is a good channel condition; otherwise, if the SNR is less than the predetermined threshold, it is determined that the channel condition is a bad channel condition. The higher order modulation coding scheme used by the RS in its transmission or retransmission can be the same as the scheme used to generate the HCM data. But this is not a special limitation, they can also be different from each other.

Since the retransmission process is initiated and performed by the RS, and two traffic flows are transmitted simultaneously in two phases, instead of transmitting only one data block in two phases as in the prior art, the weight is reduced. Delays are transmitted and the throughput and capacity of the cell are increased.

• Similarly, the proposed invention can be extended to multi-user scenarios. As shown in Figure 7, one MS (MS1) is served by the BS and RS, while the other MS (MS2) is served only by the RS. Therefore, two traffic flows from the BS to MS1 and MS2 can be simultaneously transmitted to the MS and RS using the SCM scheme. • Figure 8 shows the retransmission scheme. In the first phase, the SCM data is broadcast to the MS1 and the RS, the SCM data being an overlap of the LCM traffic flow from the BS to the MS1 and the HCM traffic flow from the BS to the MS2; similarly, the RS decodes the HCM data and the LCM data, and the MS1 Receive LCM data. If the MS1 fails to recover the LCM data correctly, the RS will retransmit the LCM data to the MS1 using the IR or CC retransmission scheme in the second phase; otherwise, the RS transmits using the higher order MCS supported on the RS-MS2 link. HCM data to MS2. Since the distributed retransmission scheme is run by the RS, the retransmission delay can still be reduced and the cell throughput and capacity can be increased.

Using the above assumptions, the throughput performance of the SCM-based retransmission scheme is simulated based on the IEEE 802.16e downlink PUSC (Partially Used Subchannel) mode, and for comparison, the RS for the two modulation coding schemes is also simulated. Skip HARQ (Hybrid Automatic Repeat Request). Table 1 shows the simulation, where 16QAM-1/2 for RS hop-by-hop HARQ is the highest-order modulation coding scheme applicable to BS-MS, and 64QAM-2/3 scheme is transportable and based. The SCM retransmission scheme has the same information bit scheme.

Table 1: Simulation parameters

Figure 9 shows the throughput of retransmissions. As we expected, the SCM-based retransmission method can significantly improve throughput compared to the RS hop-by-hop HARQ scheme using the other two modulation coding methods.

In summary, the path loss between the BS to RS path and the BS to MS path The difference and proper power allocation, the proposed SCM-based retransmission scheme can maintain reliable communication at the lowest rate, such as low bit rate and low order modulation. Utilizing the SNR (Signal to Noise Ratio) gain of the L0S channel of the relay link and the access link, the inventive scheme can further increase the total data rate of the downlink. The above description is only a preferred embodiment of the invention, and is not intended to limit the invention. Therefore, any modifications, substitutions and improvements made within the spirit and scope of the invention are included in the scope of the invention.

Claims

Claim

A distributed retransmission method, comprising:

The base station broadcasts the overlap coded modulated data block to the relay station and the first mobile station, wherein the overlapped coded modulated data block can be supported by the first coded modulated data block and the base station to the relay station's transport channel supported by the base station to the first mobile station's transport channel. a second coded modulated data block superimposed, wherein the destination of the second coded modulated data block may be the first mobile station or the second mobile station in the multi-user transmission mode;

The relay station will determine, based on the information fed back by the first mobile station, whether the first mobile station correctly decoded the first coded modulated data block;

In a case where the first mobile station correctly decodes the first coded modulated data block, the relay station transmits the second coded modulated data block to the first mobile station or the second mobile station according to whether the destination of the second coded modulated data block is the first mobile station or the second mobile station The first mobile station or the second mobile station.

2. The distributed retransmission method according to claim 1, further comprising: in a case where the first mobile station fails to correctly decode the first coded modulated data block, the relay station determines a channel condition of the relay station to the first mobile station;

The first mobile station decodes the second coded modulated data block.

3. The distributed retransmission method according to claim 2, further comprising:

4. The distributed retransmission method according to claim 2, further comprising:

If the first mobile station fails to correctly decode the second coded modulated data block, the relay station will The second coded modulated data block is retransmitted to the first mobile station.

The distributed retransmission method according to any one of claims 2 to 4, wherein the relay station initiates when the first mobile station correctly decodes the first or second coded modulated data block or reaches a predetermined maximum number of retransmissions The retransmission is terminated.

The distributed retransmission method according to any one of claims 2 to 5, wherein the overlap coding modulation is performed by a higher order modulation coding scheme supported by the link between the relay station and the first or second mobile station Transmission and retransmission of data blocks or second coded modulated data blocks.

The distributed retransmission method according to any one of claims 2 to 6, wherein the retransmission of the first coded modulated data block is performed using an incremental redundancy retransmission scheme or a Chase combining retransmission scheme.

8. The distributed retransmission method according to claim 7, wherein the first mobile station recovers the first code modulation by using an incremental redundancy retransmission scheme or a Chase merge retransmission scheme for signals transmitted from the base station and the relay station. data block.

9. The distributed retransmission method according to claim 1, wherein the retransmission of the second coded modulated data block is performed using a higher order modulation coding scheme.

The distributed retransmission method according to claim 1, further comprising:

If the second mobile station fails to correctly decode the second coded modulated data block, the relay station retransmits the second coded modulated data block to the second mobile station.

The distributed retransmission method according to claim 10, wherein the relay-initiated retransmission is terminated when the second mobile station correctly decodes the second coded modulated data block or reaches a predetermined maximum number of retransmissions.

12. The distributed retransmission method according to any one of claims 1 to 11, wherein a channel condition required for correctly decoding the second coded modulated data block is better than a channel condition required for correctly decoding the first coded modulated data block .

The distributed retransmission method according to claim 12, wherein the second coded modulated data block is a data block generated by high code rate and/or high order modulation, and the first coded modulated data block is low coded. Data blocks generated by rate and/or low-order modulation.

14. The distributed retransmission method according to any one of claims 1 to 13, wherein the channel condition is represented by a signal to noise ratio on the channel, and if the signal to noise ratio on the channel is equal to or higher than a predetermined threshold, determining the channel Good condition; otherwise, if the signal to noise ratio on the channel is less than a predetermined threshold, then determine The channel conditions are poor.

The distributed retransmission method according to any one of claims 1 to 14, further comprising: if the first or second mobile station correctly decodes or restores the first or second coded modulated data block, the first or The second mobile station reports a positive response to the relay station.

The relay station determines that the first or second mobile station successfully decodes the first or second coded modulated data block after receiving the acknowledgement.

16. The distributed retransmission method according to any one of claims 1 to 15, further comprising: if the first or second mobile station fails to correctly decode or recover the first or second coded modulated data block, the first Or the second mobile station reports a negative response to the relay station,

The relay station determines that the first or second mobile station fails to correctly decode the first or second coded modulated data block after receiving the negative acknowledgement.

17. The distributed retransmission method according to claim 6 or 9, wherein the higher order modulation coding scheme is the same as the modulation coding scheme used to generate the second coded modulation data block.

The distributed retransmission method according to any one of claims 1 to 17, wherein the method is applicable to a multi-hop relay network.