CN103200088A - Improved type MMRS fixed relay node selection signal transmission method based on fountain encoding - Google Patents

Abstract

The invention relates to an improved type MMRS fixed relay node selection signal transmission method, discloses the improved type MMRS fixed relay node selection signal transmission method based on fountain encoding, and aims at improving MMRS relay node selection transmission efficiency. Through the improved type MMRS fixed relay node selection signal transmission method, the fountain encoding is used on the basis of a traditional MMRS relay node selection method, original data to be transmitted at a base station end is subject to the fountain encoding to obtain an encoded data packet, and a base station selects a relay with the highest backhaul link SINR in odd-numbered time slots to carry out data transmission, and the relay which is selected decodes the received data packet and then stores the data packet in a register of the relay to be ready to forward the data packet at any time. In the following even numbered time slot, a user terminal selects a relay with a higher SINR from relay links which are adjacent to the user terminal for carrying out communications, receives information from the relay, carries out a demodulation process, a fountain code decoding process and other processes on the received data packet, and therefore the original data are restored. The improved type MMRS fixed relay node selection signal transmission method based on the fountain encoding is suitable for signal transmission.

Description

A kind of method for transmitting signals of selecting based on the modified model MMRS fixed relay node under the fountain coding

Technical field

The present invention relates to the method for transmitting signals that a kind of modified model MMRS fixed relay node is selected.

Background technology

For traditional MMRS trunk node selection method, be example to have only a base station S and a user terminal D, it has N half-duplex via node R ₁, R ₂..., R _N, each relaying has a memory, and transmission comprises two time slots, and the relaying that first time slot is chosen to receives data from source node and then data is deposited in the memory; The relaying that is selected for transmission in second time slot is passed to destination node with top data in the memory, and destination node receives data.Suppose that simultaneously source node can not directly link to each other with destination node, and suppose the form transmission with packet, channel parameter remains unchanged in the process that passes a packet, passes different data packet channel and keeps separate.Because each relaying has memory, so the information that relaying can the reception sources node transmits and need just not forwarding at next time slot, this just can realize selecting simultaneously best S-R link to be used for receiving and best R-D link is used for relaying transmission data at once.

To be people such as John Byers and Michael Luby proposed in 1998 fountain coding, is a kind of desirable solution that proposes at the application characteristic of large-scale data distribution and reliable broadcast.It has great advantage at data broadcaster mask, so fountain coding has become one of research focus that gets most of the attention.

In fact fountain coding is exactly initial data to be divided into the packet of some making a start, these packets are encoded, export a coded data packet stream, the encoded packets of sufficient amount can recover all raw data packets by decoder to receiving end in this stream as long as correctly receive, and what needn't consider to receive is which packet in the coded data packet stream and the reception order of these packets.The similar fountain owing to make a start, so its coding that adopts is called fountain coding.Why digital fountain scheme is called a kind of ideal solution and is because its initial proposition is for conclusion and refinement to the demand of the broadcasting of big data quantity and delivery applications fully, so that digital fountain scheme is when just proposing even do not meet the coding of its sending mode.Up to the appearance of practical fountain codings such as LT sign indicating number and Raptor sign indicating number, the realization of digital fountain scheme just becomes possibility.

Fig. 1 is the system link schematic diagram behind the introducing relaying, and wherein L1 is direct connected link (Direct link), and L2 is back haul link (Backhaul link), and L3 is access link (Access link).

Fig. 2 is the relay system schematic diagram that has buffer.

It is because thereby relaying is introduced register allows the information that relaying can the reception sources node transmits and need just not forward at next time slot for traditional MMRS trunk node selection algorithm at once, this also will cause very big delay, and must receive all at the receiving terminal place fully and send code words and can correctly recover original code word.Thereby restricted its application prospect.

Summary of the invention

The present invention is in order to improve MMRS trunk node selection efficiency of transmission, thereby a kind of modified model MMRS fixed relay node selecting method based on fountain coding is provided.

A kind of method for transmitting signals of selecting based on the modified model MMRS fixed relay node under the fountain coding, it is characterized in that: it is realized by following steps:

Step 1, carry out fountain coding for information sequence waiting for transmission { x (n) }, obtain coding result;

The described concrete grammar that carries out fountain coding for information sequence waiting for transmission { x (n) } is:

Steps A 1, information transmitted sequence { x (n) } is divided into k information block packet, k is the integer greater than 1; And with this k information block packet composition set Y={y ₁, y ₂... y _k;

Steps A 2, in 1 to k scope, by integer d of preset coding degree distribution picked at random _i, and with this integer d _iDegree as i encoded packets; The initial value of described i is 1;

Steps A 3, at steps A 1 described set Y={y ₁, y ₂... y _kIn even picked at random d _iIndividual information block packet, and the d to choosing _iIndividual information block packet carries out XOR, obtains a coded data packet s _i, and with this coded data packet s _iDeposit coding groups set s in;

Steps A 4, the value of i is added 1; And whether the value of judging i less than predetermined threshold value M, and described M is the integer greater than 1; If judged result is for being then to return execution in step A1; If judged result is not, then execution in step A5;

Steps A 5, coding groups set s that steps A 3 is obtained are as coding result;

Step 2, be under the 2*t+1 at time slot, the initial value of described t is 0; The base station is according to the Signal to Interference plus Noise Ratio of each receiving node back haul link, selects the link of Signal to Interference plus Noise Ratio maximum as communication link, with the reception via node of this communication link correspondence as optimal relay node R _BrThen, the base station is to via node R _BrThe coding result that forwarding step one obtains; Via node R _BrReceive this coding result and decode, deposit in then in the memory;

Step 3, be under the 2*t+2 at time slot; User side according to and each receiving node between the Signal to Interference plus Noise Ratio of link, select the link of Signal to Interference plus Noise Ratio maximum as communication link, with the reception via node of this communication link correspondence as optimal relay node R _BtThen, via node R _BtBe positioned in the memory with this node and send to user side after top data are modulated again;

Via node R in step 4, the user side receiving step three _BtData after the modulation that sends, and carry out demodulation, obtain data after demodulating;

Step 5, the value of t is added 1, and whether the value of judging t is less than preset value N; Described N is the integer greater than 1; If judged result is for being then to return execution in step two; If judged result is that then execution in step six;

Step 6, user side carry out fountain decoding with the data after demodulating that obtains under all time slots, obtain original information sequence { x (n) }, finish the signal transmission of selecting based on the modified model MMRS fixed relay node under the fountain coding;

The concrete grammar that user side carries out fountain decoding to the data after demodulating that obtains under each time slot is:

Step B1, the data after the demodulation are designated as: coding groups s '=s ' ₁, s ' ₂..., s ' _i... }, and the searching degree is 1 encoded packets in this coding groups, obtains Z degree and be 1 encoded packets, Z is integer; And whether the value of judging Z greater than zero, if judged result is for being, and execution in step B2 then; If judged result is not, then execution in step B4;

Step B2, each degree that step B1 is obtained are that 1 encoded packets copies, and obtain the unique information grouping that links to each other with this encoded packets, that is: be the information block packet in the initial data of base station end transmission;

The information block that step B3, each encoded packets that step B1 is obtained link to each other with this encoded packets is carried out the sheet exclusive disjunction, each obtains operation result, adopt this operation result pair and this operation result corresponding codes bag to upgrade, and delete contacting between this operation result and the information block that this operation result links to each other; And return execution in step B1;

Step B4, judge whether that all packets that receive each time all are resumed, if judged result, is then finished user side for being to the correct decoding of the data after demodulating that obtains under each time slot; If judged result is not for, decoding failure then, user side carries out the data decoding of next time slot.

Base station described in the step 2 receives the Signal to Interference plus Noise Ratio of via node back haul link according to each, selects the link of Signal to Interference plus Noise Ratio maximum as communication link, with the reception via node of this communication link correspondence as optimal relay node R _BrBe to pass through formula:

$\mathrm{br}=\arg \underset{i\∈\{1,...,N\}}{\max }{\mathrm{\γ}}_{g_i}$

Realize; In the formula: g _iRepresent base station S to the channel gain of via node,

Expression base station S is to the link Signal to Interference plus Noise Ratio of via node.

Be under the 2*t+2 at time slot described in the step 3, user side according to and each via node between the Signal to Interference plus Noise Ratio of link, select the link of Signal to Interference plus Noise Ratio maximum as communication link, the via node of this communication link correspondence is sent via node R as the best _BtBe to pass through formula:

$\mathrm{bt}=\arg \underset{i\∈\{1,...,N\}}{\max }{\mathrm{\γ}}_{h_i}$

Realize; In the formula: h _iExpression source via node is to the channel gain of user side,

Expression source via node is to the link Signal to Interference plus Noise Ratio of user side.

The present invention combines MMRS trunk node selection method and fountain coding and is applied in the relay system, the base station end is divided into initial data the packet of some, these packets are encoded, export a coded data packet stream, the packet that can correctly receive sufficient amount in this coded data packet at receiving terminal use MMRS trunk node selection method to select respectively to utilize that best link of channel quality carries out transfer of data in back haul link and the access link, as long as can recover all original transmission data by the fountain code decoder.The present invention has increased substantially MMRS trunk node selection efficiency of transmission.

Description of drawings

Fig. 1 is the system link schematic diagram behind the introducing relaying described in the background technology; Fig. 2 is the relay system schematic diagram that has buffer described in the background technology.

Embodiment

Embodiment one, a kind of method for transmitting signals of selecting based on the modified model MMRS fixed relay node under the fountain coding, realized by following steps:

Step 1, base station use the LT fountain coding to handle to original information sequence { x (n) }, suppose that being divided into k information block by initial data { x (n) } forms set Y={y ₁, y ₂... y _k, s={s ₁, s ₂..., s _i... } and be corresponding may be the coding groups of endless, each coding groups element s so _iDivide into groups with message the relation of Y} is as follows:

In 1～k scope, press integer d of a certain coding degree distribution picked at random _i, d _iThe degree that is called encoded packets; Even picked at random d in k packet of information block then _iIndividual different packet carries out the sheet exclusive disjunction to it and obtains a coded data packet s _iObtain coding groups set { s} at last by above-mentioned rule.

Step 2, in relay system as shown in Figure 2, when current time slots is 2*t+1, t=0 wherein, 1 ..., the base station is according to the Signal to Interference plus Noise Ratio of each back haul link, therefrom select that link of maximum SINR to communicate, namely be used for receiving the best relay R of base station transmission data in the back haul link _BrSystem of selection is:

$\mathrm{br}=\arg \underset{i\∈\{1,...,N\}}{\max }{\mathrm{\γ}}_{g_i}$

G wherein _iRepresent base station S to the channel gain of the Ri of relaying,

Expression base station S is to the Signal to Interference plus Noise Ratio of the Ri link of relaying, then to relaying R _BrSend data { s}, the relaying R that is chosen to _BrAfter the base station receives data, decode and data are deposited in the memory.

Step 3, at the 2*t+2 time slot, t=0,1 ..., user side selects that link of SINR maximum to communicate with it according to the Signal to Interference plus Noise Ratio of link between itself and each relaying, namely is used for the best relay R to user terminal to transmit data in the access link _BtSystem of selection is:

$\mathrm{bt}=\arg \underset{i\∈\{1,...,N\}}{\max }{\mathrm{\γ}}_{h_i}$

H wherein _iThe Ri of expression source relaying is to the channel gain of user terminal D, The Ri of expression source relaying is to the Signal to Interference plus Noise Ratio of user terminal D link.The relaying that is selected for transmission carries out coded modulation again with top data in its register and sends to this user side.

Step 4, user side carry out demodulation with the packet that receives and carry out LT fountain sign indicating number decode procedure then, and idiographic flow is as follows:

At first the coding groups s ' that receives=s ' ₁, s ' ₂..., s ' _i... } and in the searching degree be 1 grouping set, be 1 encoded packets s ' to any one degree wherein _iCopy and to recover the unique information block that is attached thereto, after this, decoder carries out XOR with each packet that translates respectively with all encoded packets that link to each other with it, and result of calculation replaces the original value of corresponding encoded packets, leaves out and the annexation between them after finishing.Repeat said process till presence is not 1 bag.If all packets all are resumed then are successfully decoded, otherwise decoding failure.

The present invention combines MMRS trunk node selection method and fountain coding and is applied in the relay system, the base station end is divided into initial data the packet of some, these packets are encoded, export a coded data packet stream, the packet that can correctly receive sufficient amount in this coded data packet at receiving terminal use MMRS trunk node selection method to select respectively to utilize that best link of channel quality carries out transfer of data in back haul link and the access link, as long as can recover all original transmission data by the fountain code decoder.Than traditional MMRS trunk node selection method, the present invention has following beneficial effect:

(1) correctly receives the situation that all transmission packets can be deciphered for the receiving terminal that needs that occurs in traditional MMRS trunk node selection method, this invention needn't consider that receiving terminal receives is which packet in the coded data packet stream and the reception order of these packets, does not also need to wait the packet of all transmissions all successfully to receive simultaneously.When a certain relaying not good when causing this relaying always can not transmit the packet that is sent by the base station end all the time because of the access link performance, user terminal if correct receive abundant packet just can correct decoding, recover initial data, thereby can reduce the time delay of relay system, improve the efficiency of transmission of system.

(2) owing to adopted the fountain sign indicating number, do not need receiving terminal to feed back, receiving end only need be received enough enough packets just can recover original transmission data, can avoid the round time-delay of signal like this, thereby has improved the efficient of system.

(3) owing to introduced register in the relaying, the information that makes relaying receive from the base station can not forward at once, the base station just can take full advantage of top-quality those chain road direction relaying transmission data of link in the back haul link like this, and same relaying can take full advantage of top-quality those chain road direction user terminal forwarding data of link in the access link.

(4) because fountain coding adopts the method for random coded, each encoded packets is all independent of one another, it can generate the encoded packets enormous amount, so the probability that generation repeats between the encoded packets is very low, reduces thereby can eliminate owing to the user receives the efficient that duplicate packages causes.

Claims (3)

1. method for transmitting signals of selecting based on the modified model MMRS fixed relay node under the fountain coding, it is characterized in that: it is realized by following steps:

Step 1, carry out fountain coding for information sequence waiting for transmission { x (n) }, obtain coding result;

The described concrete grammar that carries out fountain coding for information sequence waiting for transmission { x (n) } is:

Steps A 1, information transmitted sequence { x (n) } is divided into k information block packet, k is the integer greater than 1; And with this k information block packet composition set Y={y ₁, y ₂... y _k;

Steps A 2, in 1 to k scope, by integer d of preset coding degree distribution picked at random _i, and with this integer d _iDegree as i encoded packets; The initial value of described i is 1;

Steps A 3, at steps A 1 described set Y={y ₁, y ₂... y _kIn even picked at random d _iIndividual information block packet, and the d to choosing _iIndividual information block packet carries out XOR, obtains a coded data packet s _i, and with this coded data packet s _iDeposit coding groups set s in;

Steps A 4, the value of i is added 1; And whether the value of judging i less than predetermined threshold value M, and described M is the integer greater than 1; If judged result is for being then to return execution in step A1; If judged result is not, then execution in step A5;

Steps A 5, coding groups set s that steps A 3 is obtained are as coding result;

Step 2, be under the 2*t+1 at time slot, the initial value of described t is 0; The base station is according to the Signal to Interference plus Noise Ratio of each receiving node back haul link, selects the link of Signal to Interference plus Noise Ratio maximum as communication link, with the reception via node of this communication link correspondence as optimal relay node R _BrThen, the base station is to via node R _BrThe coding result that forwarding step one obtains; Via node R _BrReceive this coding result and decode, deposit in then in the memory;

Step 3, be under the 2*t+2 at time slot; User side according to and each receiving node between the Signal to Interference plus Noise Ratio of link, select the link of Signal to Interference plus Noise Ratio maximum as communication link, with the reception via node of this communication link correspondence as optimal relay node R _BtThen, via node R _BtBe positioned in the memory with this node and send to user side after top data are modulated again;

Via node R in step 4, the user side receiving step three _BtData after the modulation that sends, and carry out demodulation, obtain data after demodulating;

Step 5, the value of t is added 1, and whether the value of judging t is less than preset value N; Described N is the integer greater than 1; If judged result is for being then to return execution in step two; If judged result is that then execution in step six;

Step 6, user side carry out fountain decoding with the data after demodulating that obtains under all time slots, obtain original information sequence { x (n) }, finish the signal transmission of selecting based on the modified model MMRS fixed relay node under the fountain coding;

The concrete grammar that user side carries out fountain decoding to the data after demodulating that obtains under each time slot is:

Step B1, the data after the demodulation are designated as: coding groups s '=s ' ₁, s ' ₂..., s ' _i... }, and the searching degree is 1 encoded packets in this coding groups, obtains Z degree and be 1 encoded packets, Z is integer; And whether the value of judging Z greater than zero, if judged result is for being, and execution in step B2 then; If judged result is not, then execution in step B4;

Step B2, each degree that step B1 is obtained are that 1 encoded packets copies, and obtain the unique information grouping that links to each other with this encoded packets, that is: be the information block packet in the initial data of base station end transmission;

The information block that step B3, each encoded packets that step B1 is obtained link to each other with this encoded packets is carried out XOR, each obtains operation result, adopt this operation result pair and this operation result corresponding codes bag to upgrade, and delete contacting between this operation result and the information block that this operation result links to each other; And return execution in step B1;

Step B4, judge whether that all packets that receive each time all are resumed, if judged result, is then finished user side for being to the correct decoding of the data after demodulating that obtains under each time slot; If judged result is not for, decoding failure then, user side carries out the data decoding of next time slot.

2. a kind of method for transmitting signals of selecting based on the modified model MMRS fixed relay node under the fountain coding according to claim 1, it is characterized in that base station described in the step 2 receives the Signal to Interference plus Noise Ratio of via node back haul link according to each, select the link of Signal to Interference plus Noise Ratio maximum as communication link, with the reception via node of this communication link correspondence as optimal relay node R _BrBe to pass through formula:

$\mathrm{br}=\arg \underset{i\∈\{1,...,N\}}{\max }{\mathrm{\γ}}_{g_i}$

Realize; In the formula: g _iRepresent base station S to the channel gain of via node,

Expression base station S is to the link Signal to Interference plus Noise Ratio of via node.

3. a kind of method for transmitting signals of selecting based on the modified model MMRS fixed relay node under the fountain coding according to claim 1, it is characterized in that described in the step 3 at time slot being under the 2*t+2, the Signal to Interference plus Noise Ratio of link between user side basis and each via node, select the link of Signal to Interference plus Noise Ratio maximum as communication link, the via node of this communication link correspondence is sent via node R as the best _BtBe to pass through formula:

$\mathrm{bt}=\arg \underset{i\∈\{1,...,N\}}{\max }{\mathrm{\γ}}_{h_i}$

Realize; In the formula: h _iExpression source via node is to the channel gain of user side,

Expression source via node is to the link Signal to Interference plus Noise Ratio of user side.

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