WO2010118576A1

WO2010118576A1 - Multicast method, device and system

Info

Publication number: WO2010118576A1
Application number: PCT/CN2009/071305
Authority: WO
Inventors: 陈大庚; 王艺
Original assignee: 华为技术有限公司
Priority date: 2009-04-16
Filing date: 2009-04-16
Publication date: 2010-10-21
Also published as: CN102282792B; CN102282792A

Abstract

A multicast method, device and system are disclosed. The method includes the following steps: When a sending device receives the same service requests sent by a plurality of receiving devices, a plurality of optimal degree distributions and coding modes corresponding to different code rates respectively are chosen. Multicast information is encoded using the chosen optimal degree distributions and coding modes corresponding to different code rates in turn, and then sent.

Description

Multicast method, device and system

The present invention relates to data transmission technologies, and in particular, to a multicast method, device and system.

Background technique

RC ( Rateless Code) is simple and high performance, and is used in P2P (Peer to Peer) communication and satellite communication. In the multicast/broadcast system, RC is mainly applied to the service level, and the object of processing is the data packet.

At present, the technique of transmitting information at the bit level is to transmit information by using a fixed code rate, and the adaptive is based on a fixed code rate mother code (such as Turbo code) to obtain a high code rate channel coding by puncturing, by repeating The method obtains a low code rate channel coding. Although, the mother code of a given code rate (such as the Turbo code with a given code rate of 1/3 in 3GPP) has very good performance, it can approach the capacity world, but it cannot guarantee that it is greater than 1 due to punching. At /3 code rate, the capacity can still be approximated. When the code rate is lower than the low code rate, the repeated coding does not have the coding gain. When the code rate is less than 1/3, the performance with the approximate capacity cannot be guaranteed. Therefore, the current coding scheme does not guarantee that the channel quality can be approximated at any desired code rate.

To this end, RC is applied to the bit level in the prior art. ARC (Accumulate Rateless Code) is a code that RC applies to the bit level and still has excellent performance. The object processed by ARC is a bit, and the encoding steps are as follows:

1. randomly select a degree dc in a predetermined degree distribution;

2. randomly selecting dc bits from the k raw data bits;

3. modulo-add or XOR the selected dc bits to generate a coded bit;

4. Differentially encode 6, and obtain the encoded output bit c,

, where Φ represents a modulo two plus or exclusive OR operation;

Repeat steps 1 - 4 to get N encoded bits.

The above encoding process of the ARC can be represented by the graph shown in FIG. Where 〇 represents the information bit, and the dv connected thereto indicates the number of times the information node is selected. Port indicates modulo two plus or exclusive OR operation, right The input bits are modulo-added or XORed, and dc represents the number of bits for the modulo-two or XOR operation. This coding method optimizes the degree distribution at a given code rate, and the optimal degree distribution can be obtained, so that the ARC has the capability of approaching capacity. However, for different code rates, the optimality distribution obtained at a given code rate cannot guarantee the performance of approximating capacity, which will affect the transmission efficiency of multicast.

Summary of the invention

The embodiments of the present invention provide a multicast method, device, and system, which can fully utilize channel differences of different receiving devices, adaptively match channels in a large range, and improve multicast transmission efficiency.

A multicast method provided by an embodiment of the present invention includes:

After receiving the same service request sent by multiple receiving devices, the sending device selects multiple optimality distributions and encoding modes corresponding to different code rates.

The multicast information is encoded and transmitted by using the optimal degree distribution and coding mode corresponding to each selected code rate.

A sending device provided by the embodiment of the present invention includes:

a receiving unit, configured to receive a service request of the receiving device;

a selecting unit, configured to: after the receiving unit receives the same service request from multiple receiving devices, select a plurality of optimality distributions and encoding modes respectively corresponding to different code rates;

And a sending unit, configured to sequentially encode the multicast information by using an optimality distribution and an encoding manner corresponding to each code rate selected by the selecting unit, and send the encoded multicast information to the plurality of receiving devices.

A multicast system according to an embodiment of the present invention includes a sending device and a plurality of receiving devices, where the sending device is configured to: after receiving the same service request of the multiple receiving devices, select multiple corresponding code rates respectively. Optimality distribution and coding mode; and sequentially encoding the multicast information by using the selected optimality distribution and coding mode corresponding to each code rate, and transmitting the encoded multicast information to the plurality of receiving devices;

The receiving device is configured to send an acknowledgement message to the sending device after receiving the multicast information sent by the sending device and decoding.

The multicast method, device and system provided by the embodiment of the present invention receive multiple receiving devices in the transmitting device After preparing the same service request, selecting multiple optimality distributions and coding modes corresponding to different code rates; sequentially encoding and transmitting the multicast information by using the optimal distribution and coding mode corresponding to each selected code rate, and The degree distribution is switched between the optimality distributions corresponding to different code rates by adding redundancy bits. Adaptive adjustment of the degree distribution at different bit rates based on ARC, so that it has different degrees of distribution at different code rates, thereby matching channel quality, thereby improving multicast transmission efficiency and improving the performance of the multicast system.

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DRAWINGS

1 is a schematic diagram of a coding process of an ARC used in the prior art;

2 is a flowchart of a multicast method according to an embodiment of the present invention;

3 is a schematic diagram of a moderate distribution adjustment according to an embodiment of the present invention;

4 is a specific implementation flowchart of a multicast method according to an embodiment of the present invention;

FIG. 5 is a flowchart of another specific implementation of a multicast method according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a multicast information transmitting apparatus according to an embodiment of the present invention.

detailed description

The embodiments of the present invention are further described in detail below with reference to the accompanying drawings and embodiments.

As shown in FIG. 2, it is a flowchart of the multicast method according to the embodiment of the present invention, which includes the following steps: Step 201: After receiving the same service request sent by multiple receiving devices, the sending device selects multiple corresponding code rates respectively. Optimality distribution and coding method;

When selecting a plurality of optimality distributions and coding modes respectively corresponding to different code rates, selecting, according to channel qualities of the plurality of receiving devices, a plurality of optimality distributions and coding modes respectively corresponding to different code rates; Selecting a plurality of optimality distributions and encoding modes corresponding to different code rates from the presets;

Step 202: Code and transmit the multicast information by using the optimal degree distribution and coding mode corresponding to each selected code rate.

In order to achieve convenience, the selected multiple code rates may be sorted from high to low, and then the optimal degree distribution and coding method corresponding to each code rate are sequentially used according to the multiple code rate orders. Broadcast information is encoded and sent;

When switching between optimality distributions corresponding to different code rates, the current optimal use can be used. On the basis of the degree distribution, adding redundant bits changes the current optimality distribution to an optimality distribution corresponding to the next code rate.

The process can be abstracted and can be represented by FIG. 3, which is a schematic diagram of the degree distribution adjustment in the embodiment of the present invention: It is assumed that the current optimality distribution function is δθ(χ), and ARC coding is performed with δθ(χ), if redundancy is needed. To reduce the code rate, use the next optimality distribution function δ, (χ) to obtain additional redundancy. As a whole, the degree distribution function changes from δθ(χ) to δ1(χ).

Specifically, when the optimality distribution is switched, there are various implementations, which will be described in detail later.

The multicast method of the embodiment of the present invention may be applied to various multicast systems. In the multicast system, the sending device may know the channel quality of multiple receiving devices, or may not know. Therefore, the foregoing step 201 is selected. When multiple optimal distributions and coding modes corresponding to different code rates are respectively selected, multiple optimality distributions and coding modes corresponding to different code rates may be selected according to channel quality of the plurality of receiving devices according to an actual application environment; Alternatively, a plurality of optimality distributions and coding modes respectively corresponding to different code rates may be selected from preset settings;

In a wireless communication system, usually the transmitting device can be a station, and the receiving device can be a terminal. Of course, the multicast method of the embodiment of the present invention is not limited to the wireless communication scenario.

The multicast method of the embodiment of the present invention will be further described in detail below by taking a wireless communication system as an example. As shown in FIG. 4, it is a specific implementation process of the multicast method in the embodiment of the present invention.

In this embodiment, it is assumed that the base station can learn the channel quality of multiple terminals, and the base station pre-stores a plurality of optimality distributions corresponding to different code rates and corresponding coding modes.

Step 401: The base station receives the same service request sent by multiple terminals, for example, the same service request of multiple terminals is watching a certain video information.

Step 402: The base station selects, according to different channel qualities of the multiple terminals, multiple optimality distributions and coding modes corresponding to different code rates.

The number of different code rates selected may be the same as or different from the number of terminals. For example, if there are five terminals whose channel quality is different, then five code rates corresponding to the five terminals are selected, and the optimality distribution and coding corresponding to the corresponding code rate are obtained according to the information pre-stored on the base station. For example, if there are 5 terminals, but two of the terminals have similar channel qualities, they can be grouped into one group, and only 4 code rates corresponding to different channel qualities are selected; Step 403: Sort the selected code rates according to the order of the channel quality from high to low. Step 404: sequentially select the optimality distribution and coding mode corresponding to each code rate to encode and transmit the multicast information.

Step 405, it is determined whether a confirmation message sent by the terminal corresponding to the code rate is received; if yes, step 406 is performed; otherwise, step 409 is performed;

Step 406, further determining whether an acknowledgment message sent by all terminals is received; if yes, executing step 407; otherwise, performing step 408;

Step 407, stopping encoding and transmitting the multicast information;

Step 408, adding redundant bits, adjusting the degree distribution to the optimal degree distribution corresponding to the next code rate; then returning to step 404;

Step 409, adding redundant bits but not changing the current optimality distribution; then returning to step 405. In this embodiment, after receiving the multicast information sent by the base station, each terminal sends an acknowledgment message to the base station if it can correctly decode, and the handover of the optimality distribution corresponding to the different code rate is sent by the base station to the corresponding terminal. After the confirmation message is made.

In order to further improve the transmission efficiency, the base station can also perform adaptive adjustment of the code rate in sequence without waiting for the confirmation message received by the terminal to be received.

As shown in FIG. 5, it is another specific implementation process of the multicast method in the embodiment of the present invention.

Step 501: The base station receives the same service request sent by multiple terminals, for example, the same service request of multiple terminals is watching a certain video information.

Step 502: The base station selects, according to different channel qualities of the multiple terminals, multiple optimality distributions and coding modes corresponding to different code rates.

Step 503: Sort the selected code rates according to the order of the channel quality from high to low. Step 504: sequentially select the optimality distribution and coding mode corresponding to each code rate to encode and transmit the multicast information.

Step 505: Determine whether an acknowledgment message sent by all terminals is received; if yes, perform step 506; if the acknowledgment message sent by any one of the terminals is not received, perform the step Step 506: Stop coding and transmitting the multicast information.

Step 507, adding redundant bits but not changing the current optimality distribution; then returning to step 505. In this embodiment, after receiving the multicast information sent by the base station, each terminal sends an acknowledgement message to the base station if it can correctly decode, and the handover of the optimality distribution corresponding to different code rates is received by the base station. Only after the confirmation message is sent.

In practical applications, there may be cases where the base station does not know the channel quality of the terminal, or the terminal channel quality cannot be utilized. In this case, multiple degrees of optimality distribution may be preset, and the degree distribution may be used for multicasting. Adaptive transmission of information. For the specific process, reference may be made to the descriptions in the foregoing embodiments, and details are not described herein again.

It can be seen that, in the multicast method of the embodiment of the present invention, after the transmitting device receives the same service request from multiple receiving devices, selecting a plurality of optimality distributions and encoding modes respectively corresponding to different code rates; sequentially selecting the selected code rates. The corresponding optimality distribution and coding mode encodes and transmits the multicast information, and the degree distribution is switched between the optimality distributions corresponding to different code rates by adding redundant bit manners. Based on ARC, adaptively adjust the degree distribution at different code rates to have different degrees of distribution at different code rates, so as to match channel quality, make full use of channel differences of different receiving devices, improve multicast transmission efficiency, and improve The performance of the multicast system.

It should be noted that the multicast method in the embodiment of the present invention can be applied not only to the information bits of the physical layer, but also to the encoding and transmission of the data blocks of the service layer, for example, using the fountain code and the Raptor code to adaptively change the redundant data. The degree distribution of the block, thereby changing the overall degree distribution.

A person skilled in the art can understand that all or part of the steps of implementing the above embodiments can be completed by a program to instruct related hardware, and the program can be stored in a computer readable storage medium, the storage. Media, such as: ROM/RAM, disk, CD, etc.

The embodiment of the present invention further provides a multicast information sending device, as shown in FIG. 6, which is a schematic structural diagram of the transmitting device.

In the sending device, including:

The receiving unit 601 is configured to receive a service request of the receiving device.

The selecting unit 602 is configured to select, after the receiving unit 601 receives the same service request of the multiple receiving devices, a plurality of optimality distributions and encoding modes respectively corresponding to different code rates;

The sending unit 603 is configured to sequentially select an optimal corresponding to each code rate selected by the selecting unit 602. The degree distribution and encoding method encodes the multicast information, and transmits the encoded multicast information to the plurality of receiving devices.

The selecting unit 602 may select, according to the channel quality of the multiple receiving devices, a plurality of optimality distributions and encoding modes respectively corresponding to different code rates; and may select multiple presets corresponding to different code rates from preset settings. Optimality distribution and coding method.

A preferred structure of the transmitting unit 603 includes: a sorting subunit 631, an encoding processing subunit 632, and a transmitting subunit 633. The sorting sub-unit 631 is configured to sort the selected multiple code rates from high to low. The encoding processing sub-unit 632 is configured to sequentially use each code according to the sequence of the multiple code rates. The rate corresponding to the optimality distribution and the encoding mode encodes the multicast information; the sending subunit 633 is configured to send the multicast information encoded by the encoding processing subunit 632.

Of course, in the embodiment of the present invention, the sending unit 603 is not limited to the above structure, and may have other configurations according to application requirements.

In another embodiment of the invention, the sending device may further include: switching between the optimal degree distributions of the switching unit rates. For example, when the degree distribution is switched, the current optimality distribution is first obtained, and then the redundant bits are added, and the current optimality distribution is changed to the optimal distribution corresponding to the next code rate.

After receiving the same service request from multiple receiving devices, the multicast information sending device of the embodiment of the present invention selects multiple optimality distributions and encoding modes corresponding to different code rates respectively; The optimality distribution and coding mode encodes and transmits the multicast information, and the degree distribution is switched between the optimality distributions corresponding to different code rates by adding redundant bits. Based on ARC, the adaptive adjustment degree distribution at different code rates has different degrees of distribution at different code rates, so as to match channel quality, make full use of channel differences of different receiving devices, improve multicast transmission efficiency, and improve The performance of the multicast system.

In order to further ensure that each receiving device can correctly decode the received multicast information, in another embodiment of the present invention, the receiving unit 601 is further configured to receive an acknowledgement message sent by the receiving device, where the switching unit 604 further And after the receiving unit 601 receives the acknowledgment message sent by the receiving device that is corresponding to the channel quality corresponding to the current code rate, and performs switching between the optimality distributions corresponding to different code rates; the receiving unit 601 does not receive To any receiving device that corresponds to the channel quality of the current code rate When receiving an acknowledgment message sent by the device, the redundant bits are added but the current optimality distribution is not changed.

It should be noted that, after the receiving unit 601 receives the confirmation message sent by all the multiple receiving devices, the sending unit 603 stops transmitting the multicast information.

The embodiment of the invention further provides a multicast system, where the multicast system comprises: a sending device and a plurality of receiving devices. among them:

The sending device is configured to: after receiving the same service request of the multiple receiving devices, select a plurality of optimality distributions and encoding modes respectively corresponding to different code rates; and sequentially select the most corresponding to each selected code rate The goodness distribution and the encoding method encode the multicast information and send the encoded multicast information to the plurality of receiving devices;

Further, the sending device is further configured to switch between the optimality distributions corresponding to different code rates after receiving the acknowledgement message sent by the receiving device that partially corresponds to the channel quality of the current code rate; When the current code rate corresponds to the acknowledgement message sent by any one of the receiving devices of the channel quality, the redundant bits are added but the current optimality distribution is not changed; after all the acknowledge messages sent by the plurality of receiving devices are received, Stop sending multicast information.

The specific structure of the sending device can be referred to FIG. 6 and the corresponding description, and details are not described herein again. The multicast system of the embodiment of the present invention may be applied to, but not limited to, a wireless communication environment. Specifically, in a wireless communication environment, the sending device may be a base station, and correspondingly, the receiving device is a terminal.

The multicast system according to the embodiment of the present invention may select an appropriate code rate to match the channel conditions of different receiving devices according to the channel condition of the receiving device, and increase the redundancy bit manner to distribute the degree distribution to the optimal degree distribution corresponding to different code rates. Switching between them can match different channel qualities, make full use of channel differences of different receiving devices, improve multicast transmission efficiency, and improve the performance of the multicast system.

The embodiments of the present invention have been described in detail above, and the present invention has been described with reference to the specific embodiments thereof. The description of the above embodiments is only for facilitating understanding of the method and device of the present invention. Meanwhile, for those skilled in the art, The present invention is not limited by the scope of the present invention.

Claims

Rights request

A multicast method, comprising:

2. The method according to claim 1, wherein the selecting the plurality of optimality distributions and coding modes respectively corresponding to different code rates comprises:

Selecting, according to channel qualities of the plurality of receiving devices, a plurality of optimality distributions and encoding modes respectively corresponding to different code rates; or

A plurality of optimality distributions and coding modes corresponding to different code rates are selected from the presets.

The method according to claim 1, wherein the encoding and transmitting the multicast information by using the optimal degree distribution and the encoding manner corresponding to each of the selected code rates are:

Sorting multiple code rates from high to low;

The multicast information is encoded and transmitted sequentially according to the order of the plurality of code rates by using an optimality distribution and an encoding method corresponding to each code rate.

The method according to claim 1, wherein the method further comprises: switching the degree distribution between the optimality distributions corresponding to different code rates by adding a redundant bit manner.

The method according to any one of claims 1 to 4, wherein the method further comprises:

If the sending device receives the acknowledgment message sent by the receiving device that corresponds to the channel quality corresponding to the current code rate, then the switching is performed between the optimality distributions corresponding to different code rates;

If the transmitting device does not receive an acknowledgment message sent by any of the receiving devices corresponding to the channel quality of the current code rate, the redundant bits are added but the current optimality distribution is not changed.

After receiving the acknowledgement message sent by all the multiple receiving devices, the transmitting device stops encoding and transmitting the multicast information.

7. A transmitting device, comprising: a receiving unit, configured to receive a service request of the receiving device;

The transmitting device according to claim 7, wherein the selecting unit is specifically configured to: according to the channel quality of the multiple receiving devices, after the receiving unit receives the same service request from multiple receiving devices Selecting a plurality of optimality distributions and coding modes respectively corresponding to different code rates; or selecting a plurality of optimality distributions and coding modes respectively corresponding to different code rates from preset settings.

The transmitting device according to claim 7, wherein the sending unit comprises: a sorting subunit, configured to sort the selected multiple code rates from high to low;

And an encoding processing sub-unit, configured to encode the multicast information by using an optimality distribution and an encoding manner corresponding to each code rate according to the sequence of the plurality of code rates;

And a sending subunit, configured to send the multicast information encoded by the encoding processing subunit.

10. The transmitting device according to claim 7, further comprising: switching between optimality distributions of different code rates.

11. The transmitting device according to claim 10, characterized in that

The receiving unit is further configured to receive a confirmation message sent by the receiving device;

The switching unit is further configured to switch between the optimality distributions corresponding to different code rates after the receiving unit receives the acknowledgment message sent by the receiving device that is corresponding to the channel quality of the current code rate; When the receiving unit does not receive the acknowledgment message sent by any one of the receiving devices corresponding to the channel quality of the current code rate, the redundant bits are added but the current optimality distribution is not changed.

A multicast system, comprising: a sending device and a plurality of receiving devices, wherein the sending device is configured to: after receiving the same service request of the multiple receiving devices, select multiple corresponding code rates respectively Optimality distribution and coding mode; and sequentially encoding the multicast information by using the selected optimality distribution and coding mode corresponding to each code rate, and transmitting the encoded multicast information to the plurality of receiving devices; The receiving device is configured to send an acknowledgement message to the sending device after receiving the multicast information sent by the sending device and decoding the multicast information.

13. The system of claim 12, wherein

The sending device is further configured to switch between the optimality distributions corresponding to different code rates after receiving the acknowledgment message sent by the receiving device that is corresponding to the channel quality of the current code rate; the current code rate is not received. When any one of the receiving devices corresponding to the channel quality receives the acknowledgment message sent by the device, the redundant bit is added but the current optimality distribution is not changed; after receiving the acknowledgment message sent by all the plurality of receiving devices, the pair is stopped. Broadcast information is sent.

The system according to claim 12 or 13, wherein the transmitting device is a base station, and the receiving device is a terminal.