CN101420291A - Combined decoding method for network and channel code in relay system - Google Patents

Abstract

The technology provided by the present invention is used in a mobile communication relay system. At the receiving end, the two-way direct arrival signal and the signal transmitted through the relay node after network coding are jointly iteratively decoded. In this process, the The diversity gain brought by the relay system can be obtained, and the network coding can also assist the channel coding through the exchange of soft information in the decoding process to improve the decoding reliability. The present invention combines the network in the relay transmission system with the decoding process of channel coding, realizes the exchange of soft information in it by introducing check nodes, thereby improving the decoding reliability of the relay system and system transmission performance.

Description

The combined decoding method of network and chnnel coding in the relay system

Technical field

The present invention relates to the combined decoding method of network and chnnel coding in a kind of relay system, by the data aggregate iterative decoding behind the network code of carrying out that the data that directly sent by transmitting terminal and via node is sent at receiving terminal, obtain the raising of the soft information exchange associating decoding data reliability that iterative decoding brought between the diversity gain of relay system and each decoder, and then improve the system transmissions performance.The present invention can be applied to the multiple access relay system and similarly have communication system of via node or the like with it.

Background technology

In recent years, network coding technique becomes the focus of the communications field gradually, mainly be because network coding technique can be good at improving the throughput performance of system, and be applied to bring diversity gain in the relay system, meanwhile do not increase the complexity of system, can reduce the processing complexity at the via node place on the contrary by certain processing method than traditional trunking plan.In traditional wireless channel transmission, certain channel coding schemes is necessary, relay system is no exception, chnnel coding and network code are all independently operated generally speaking, introduce the reliability that certain redundant information improves system transmissions by channel coding schemes, improve the throughput of system or introduce certain diversity gain by the network code scheme.Some simple federal solutions also just carry out at the via node place to reduce the processing complexity of via node, and the lifting that does not bring too many systematic function aspect is such as the error rate and throughput performance or the like.

Summary of the invention

The reliability that validity of being brought for the better utilization network code and chnnel coding are brought the present invention proposes the method for a kind of network and channel combined iterative decoding.Its basic principle is to utilize the decoding characteristic of chnnel coding soft inputting and soft output, in conjunction with the particularity of information that network code transmits, realizes the iterative decoding process that both soft information exchange mutually.At the via node place data of several (might as well be made as N) input sources being carried out network code handles, form a circuit-switched data and send, the N circuit-switched data information and one tunnel of direct transmission is together handled through the data message of via node network code at receiving terminal.Data message in the process that realizes behind primary data information (pdi) and the network code sends after all through chnnel coding, and what need the channel decoding employing is the decoded mode of the soft inputting and soft output of iteration, carry out primary decoding respectively at receiving terminal, the soft information that to decipher output then is input to check node and carries out a series of calculating, thereby draw the soft information of respectively making a fresh start, be sent to after merging with original external information and carry out secondary iterative decoding in the Initial Decoding device.Repeat this process, up to the iterations that reaches setting.The concrete performing step of the present invention is:

Step 1: at the via node place, input data in N road are carried out channel decoding, network code, chnnel coding handle, the data that generate after one tunnel combination send.

Step 2: the N circuit-switched data and a tunnel of direct transmission is carried out channel decoding operation, i.e. single treatment N+1 circuit-switched data respectively one time through the data message behind the via node network code at receiving terminal.The soft information value that obtains after each decoder deciphered for the first time is sent to check node and carries out a series of computing, promptly utilize wherein the soft information in any N road to generate one tunnel new and the independently soft mutually information of raw information, thereby obtain the new soft information value in N+1 road.

Step 3: the soft information that the N+1 road is new and self decoder are deciphered the external information addition that obtains for the first time and are merged, and are sent to the decoder input again as the prior information of deciphering for the second time.

Step 4: repeating step 2, step 3, till reaching predefined iterations.

Step 5: after reaching specific iterations, stop iteration, the N road is directly transmitted the soft information of data decoder output and carry out hard decision, thereby obtain the data message of original transmission.

Description of drawings

In conjunction with the following drawings and instantiation will be convenient to understand principle, step, the characteristics of invention to the detailed description done of invention, in the accompanying drawing:

Fig. 1 is that expression the present invention inserts the mode in the relay system example on the N road;

Fig. 2 is the data handling procedure schematic diagram of via node among expression the present invention, producing combined data structure behind the N circuit-switched data network code, and then is sent by via node;

Fig. 3 is the disposition schematic diagram of expression the present invention at receiving terminal, and the N+1 circuit-switched data is handled simultaneously, has comprised the exchange process of soft information between iterative decoding and the check-node.

Fig. 4 is a wherein circuit-switched data bit error rate, the frame error rate performance schematic diagram that expression is handled through the joint decoding process of network among the present invention and chnnel coding, and the resulting data bit error rate of relay system, the frame error rate schematic diagram of process network and chnnel coding separating treatment, therefrom the performance comparison of the two concerns that what wherein abscissa was represented is the signal to noise ratio of receiving terminal as can be seen.

Embodiment

Exist the transport model scope of via node more extensive in the radio communication, for the ease of understanding, use a kind of representational example to set forth the associating interative encode method of network and chnnel coding among the present invention at this, promptly two-way inserts the wireless transmission model that relay system adopts Turbo chnnel coding and XOR network coding technique down.The present invention generally is suitable for for the transmission system that all have this exemplary characteristics, promptly is equally applicable to the relay transmission system that multichannel inserts, multi-channel network is encoded and adopted the channel coding method of other iterative decodings.

Setting two-way transmission data at this and be respectively A road and B road, is the C road through the data behind the via node network code, and when sending, A and B circuit-switched data are modulated respectively, Turbo directly sends to receiving terminal after encoding, and also send to the via node place simultaneously.To A, B two paths of data demodulation respectively, Turbo decoding, carry out xor operation at the via node place again, thereby modulate again at last, the Turbo encoding operation obtains the C circuit-switched data, sends to receiving terminal then.That is to say that the C circuit-switched data is that A, B two paths of data are carried out the information that obtains after the XOR network code operation, thus the data message after receiving terminal obtains three road Turbo chnnel codings.

At first A, B, C three circuit-switched data are carried out the Turbo decoded operation of a demodulation and an iteration respectively at receiving terminal, promptly once decipher the external information that back second member's decoder obtain and do not transfer back to the input of first member's decoder at once, but the posterior probability log-likelihood ratio information (LLR) that No. three decoders obtain is delivered to a check node.Be respectively LLR in this posterior probability log-likelihood ratio information of setting each road _a, LLR _b, LLR _c, the corresponding bit in each circuit-switched data is got 1 probability and is respectively P _a, P _b, P _c, then get 0 probability and just be respectively 1-P _a, 1-P _b, 1-P _cWherein the relation of LLR and P is as follows:

$\ln \frac{P_i}{1-P_i}={\mathrm{LLR}}_i---\left(1\right)$

$P_i=\frac{e^{{\mathrm{LLR}}_i}}{1+e^{{\mathrm{LLR}}_i}},$ I ∈ (a, b, c) (2) wherein

At check node, can convert probable value earlier to according to the LLR value that top formula is exported each road decoder.Next because the C circuit-switched data is the XOR of A, B two paths of data information bit, that is to say that three's information bit satisfies:

A+B+C=0, what relate to is that the mould 2 of bit-level adds computing (3) herein

Can utilize the probable value of any two-way information to try to achieve the Third Road information bit in conjunction with this formula and get 1 probable value.Setting is respectively P by calculating the new probable value of each road information _a_ new, P _b_ new, P _c_ new.Can obtain:

$P_{a\_\mathrm{new}}=\frac{1}{2}+\frac{1}{2}(1-2P_b)(1-2P_c)---\left(4\right)$

$P_{b\_\mathrm{new}}=\frac{1}{2}+\frac{1}{2}(1-2P_a)(1-2P_c)---\left(5\right)$

$P_{c\_\mathrm{new}}=\frac{1}{2}+\frac{1}{2}(1-2P_a)(1-2P_b)---\left(6\right)$

Then can calculate each the road information bit that makes new advances according to the LLR value of input validation node and get 1 probable value in conjunction with (2), (4), (5), (6) formula.According to (1) formula probable value is converted into new LLR value---LLR again _{I_}New, wherein i ∈ (a, b, c).And then each road LLR value that will newly obtain carries back in each decoder, and is sent in first member's decoder prior information as the next round iterative decoding with external information addition that self second member's decoder is produced.

Take turns second and to repeat said process in the iterative decoding process, till reaching predefined iterations.Last is taken turns the LLR value that two-way is directly transmitted after the iteration data decoder output and carries out hard decision, thereby obtains the data message of original transmission.

Can find out that the combined decoding method for network in the relay system and chnnel coding proposed by the invention has following features more than comprehensive:

Combination by network and channel decoding can change simple being used for of traditional network code improve system effectiveness and For relay system brings the limitation of certain diversity gain, can utilize the particularity of network code institute transmission of information to be channel Coding provides more reliability of decode, and then improves the system transmissions performance.

In the process of joint decoding by the calculating of check-node, realize the mutual transmission of soft information between each decoder, advance And reach the effect of iterative decoding.

3. at check node, can obtain and the complete incoherent soft information of self decoder by certain calculating, with this new getting To the external information that produces with self decoder of the soft information iteration of carrying out next time as prior information after merging translate Code obtains more fully diversity gain with this.

4. insensitive to concrete implementation, for having Adoption Network coding and soft inputting and soft in via node and the transmission course The system of output iterative channel coding and decoding can adopt the method.

In a word, the present invention is the joint decoding scheme of a kind of flexibly and effectively network and chnnel coding, its objective is with simple knot Structure and the method that easily realizes improve the reliability of transfer of data in the relay system.

Claims (8)

1. A joint decoding method for network and channel coding in a mobile communication relay system. In order to make better use of the effectiveness brought by the network coding processing of relay nodes and the reliability brought by channel coding, the decoding characteristics of channel coding soft input and soft output are used at the receiving end, combined with the information transmitted by network coding Particularity, at the same time, several (represented by N) data directly transmitted by the sender and network encoded data forwarded by a route relay node are processed at the same time, and the first decoding is performed at the receiving end, and then the decoded output is The soft information is input to the check node for a series of calculations to obtain their own new soft information, which is combined with the original external information and sent to the initial decoder as a priori information for the second iteration Decoding, after reaching a certain number of iterations, hard judgment is made on the soft information output by the decoder, so as to obtain the original sent data. The specific implementation steps of this method are: Step 1: At the relay node, perform channel decoding, network coding, and channel coding processing on N channels of input data, and generate one channel of combined data and send it out. Step 2: At the receiving end, perform a channel decoding operation on the directly transmitted N channels of data and one channel of data information encoded by the relay node network, that is, process N+1 channels of data at a time. Send the soft information value obtained after the first decoding of each decoder to the check node for a series of calculations, that is, use any N soft information in it to generate a new soft information independent of the original information , so as to obtain N+1 new soft information values. Step 3: Add and combine the N+1 new soft information with the external information obtained by the first decoding by its own decoder, and then send it to the input terminal of the decoder as the prior information for the second decoding. Step 4: Repeat steps 2 and 3 until the preset number of iterations is reached. Step 5: After reaching a specific number of iterations, stop the iteration, and make a hard decision on the soft information output by the N-channel direct transmission data decoder, so as to obtain the original transmitted data information. 2. The joint decoding method for network and channel coding in the relay system as claimed in claim 1, characterized in that: at the relay node, network coding operations are performed on several paths of data at the same time, thereby generating one path The network encoded data is sent to the receiver. 3. The joint decoding method for network and channel coding in the relay system as claimed in claim 1, wherein at the receiving end, the data information after N+1 channel coding is jointly processed, including N channels Directly transmit data information and data information after network coding operation all the way. 4. the joint decoding method that is used for the network and channel coding in the relay system as described in claim 1, wherein at the receiving end, carry out the channel decoding for the first time to N+1 road data earlier, the output The soft information is input to the check node for calculation, and the calculation method is to use any N-way data information to calculate a new soft information independent of the original information. 5. The joint decoding method for network and channel coding in a relay system as claimed in claim 1, for the soft information after the check node operation and the external information generated by the first decoding of the decoder They are added and combined, and then sent back to the input end of the decoder as a priori information for the second decoding. 6. the joint decoding method that is used for the network in the relay system and channel coding as described in claim 1, repeats the step described in claim 4 and claim 5, realizes N+1 way decoder soft An iterative decoding method after information is exchanged. 7. the joint decoding method that is used for the network and channel coding in the relay system as described in claim 1, after reaching certain number of iterations, stop iteration, to the output soft information of N direct transmission data decoders Directly perform hard judgments to obtain original data information. 8. the joint decoding method that is used for the network in the relay system and channel coding as described in claim 1 is characterized in that its basic realization step is: Step 1: At the relay node, perform channel decoding, network coding, and channel coding processing on N channels of input data, and generate one channel of combined data and send it out. Step 2: At the receiving end, perform a channel decoding operation on the directly transmitted N channels of data and one channel of data information encoded by the relay node network, that is, process N+1 channels of data at a time. Send the soft information value obtained after the first decoding of each decoder to the check node for a series of calculations, that is, use any N soft information in it to generate a new soft information independent of the original information , so as to obtain N+1 new soft information values. Step 3: Add and combine the N+1 new soft information with the external information obtained by the first decoding by its own decoder, and then send it to the input terminal of the decoder as the prior information for the second decoding. Step 4: Repeat steps 2 and 3 until the preset number of iterations is reached. Step 5: After reaching a specific number of iterations, stop the iteration, and make a hard decision on the soft information output by the N-channel direct transmission data decoder, so as to obtain the original transmitted data information.

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