CN101807975B - Channel coding method for enhancing transmission quality of fountain code on wireless channel - Google Patents

Abstract

The invention discloses a channel coding method for enhancing the transmission quality of a fountain code on a wireless channel, which comprises the following steps of: when coding an IBRC channel, sequentially displacing input code words firstly by an IBRC coder circularly through taking each element in two displacement vectors as the amplitude of the circular displacement of each time sequentially, then carrying out modular two addition on all the obtained code words after displacing circularly to obtain two code words totally, afterwards cascading the two code words to obtain coding code words, modulating by using BPSK and transmitting; when decoding the IBRC channel, dividing the received code words into a front section and a back section after carrying out BPSK demodulation on the received code words by an IBRC decoder, then carrying out modular two addition, afterwards carrying out reverse circular displacement, determining whether IBRC code words are erroneous in the transmission process or not on the basis of the code words obtained after displacing circularly, and outputting the code words directly if the IBRC code words are not erroneous; otherwise, setting an erroneous bit number sequentially within a certain range, decoding under the setting, and outputting a decoding result if the decoding is successful; and if the set erroneous bit number is still not decoded successfully after the set erroneous bit number samples all integers in the range, outputting all-zero code words by the IBRC decoder.

Description

Be used for promoting the channel coding method of fountain codes transmission quality on wireless channel

Technical field

The present invention relates to the channel coding method of fountain codes and wireless channel, belong to the Wireless Data Transmission field.

Background technology

After LT codes and Raptor codes are suggested and are studied as two kinds of ways of realization of fountain codes, fountain codes is proved to be a kind of data encoding mode that has the implementation procedure of outstanding transmission performance and low complex degree, therefore fountain codes also is counted as the desirable transmission means that realizes large-scale data broadcasting, and has been put into the relevant criterion as concrete 3GPP and DVB-H.The key of this technology is exactly the LT encoder by core, produced the coding codeword of the unlimited a plurality of LT of being called as codes by K source data packet, and the LT decoder of receiving terminal only needs therefrom correctly to receive N the LT codes that is a bit larger tham arbitrarily K, K source data packet about just can recovering.

Traditional data transmission technology need to be set up a channel (backhaul) and process data re-transmission request (ARQ) from receiving terminal between transmitting terminal and receiving terminal, and in multicast, broadcast service, transmitting terminal may need to process the ARQ for the different pieces of information bag from different receiving terminals, these processing procedures will seriously reduce the throughput of network, the performances such as time delay.And when carrying out transfer of data with fountain codes, if transmission channel is erasure channel, the packet that sends at this channel so or be dropped, correctly receive the receiving end, so when under the environment of erasure channel, using fountain codes to transmit, receiving terminal only needs the LT codes that transmits on the continuous receive channel, no matter in receiving course, there is what LT codes to be deleted by channel, successfully recovers K source data packet thereby receiving terminal finally must successfully receive N LT codes.Therefore after using fountain codes, transmitting terminal will no longer need to process the ARQ from receiving terminal, only need to send LT codes always, just can stop to have transmitted current data after receiving until all receiving terminals all feed back to finish.

Yet only in cable environment, mention before the lacking of fountain codes not necessarily has in the above superperformance of erasure channel, that is because wireless channel is not erasure channel but interference channel, thereby the LT codes that receiving terminal is received in wireless channel might comprise wrong.And according to the coded system of LT encoder, in case wrong LT codes enters the LT decoder, will cause a series of LT decoding error (error propagation) and cause the ultimate source packet correctly to be recovered fully.Although can come the LT codes that generates is done chnnel coding in the common forward error correction coder (FEC) of the LT of transmitting terminal encoder back cascade, then by receiving terminal the packet that is interfered that receives on the channel is carried out fec decoder, the LT decoder that reduces to a certain extent successively receiving terminal receives the possibility of wrong LT codes, but at channel conditions comparatively in the rugged environment, the limited error correcting capability of FEC can't be tackled the interference that noise or decline cause, the packet of receiving when receiving terminal has comprised too much can't correctly be recovered because of the mistake that channel disturbance causes the time, common fec decoder device will become this decoded packet data the LT code of a mistake, finally still can't effectively stop the LT codes of mistake to enter the LT decoder.In sum, even do auxiliary chnnel coding with common FEC, or can't bring enough liftings for the transmission performance of fountain codes on wireless channel, therefore need to search out the special channel coding method that the LT codes that can effectively stop mistake enters the LT decoder, guarantee that with this fountain codes can carry out reliable transfer of data at wireless channel.

Summary of the invention

The purpose of this invention is to provide a kind of channel coding method for promoting fountain codes transmission quality on wireless channel.

For achieving the above object, the present invention proposes new channel coding method, utilize IBRC(improvedbinary repetition code) the simple cataloged procedure of code and gathered the decode procedure of error detecting and error correcting function in one, contrast remaining conventional channel encoding scheme, reduce by a larger margin the possibility that wrong LT codes enters the LT decoder, reach it in the performance of wired erasure channel so that fountain codes can be similar in Packet Error Ratio (the per:packet loss rate) performance that the air interference channel reaches under lower SNR, thereby guarantee that successfully fountain codes also can have transmission performance good on the erasure channel in wireless network.

Specifically, the present invention realizes that the technical scheme that above-mentioned purpose is taked is: should be used for promoting fountain codes channel coding method of transmission quality on wireless channel and mainly comprise the steps:

Step (1): the code word that comprises in the source data with transmitting terminal forms unlimited many LT code words through the LT encoder;

Step (2): the IBRC encoder carries out cyclic shift to each element of one of them in two motion vectors of the LT code word to be encoded of inputting this IBRC encoder successively as the amplitude of each cyclic shift, and resulting all code words after the cyclic shift are carried out mould two additions;

Described two motion vectors are respectively suc as formula shown in (1) and the formula (2),

α ₁=(a ₁,a ₂,…a _K,a _K+1) （1）

α ₂=(a ₁,a ₂,…a _K) （2）

Wherein, motion vector α ₂Than motion vector α ₁Few element a _K+1, each the element a that comprises in the described motion vector ₁, a ₂... a _k, a _K+1Value different,

The length 4K+4 bit of described code word to be encoded, wherein, K is vectorial α in the formula (2) ₂The element number that comprises;

Step (3): the IBRC encoder carries out cyclic shift to the described LT code word to be encoded of step (2) another each element in described two motion vectors successively as the amplitude of each cyclic shift, and resulting all code words after the cyclic shift are carried out mould two additions;

Step (4): the IBRC encoder after with two additions of step (2) mould code word and the code word after two additions of step (3) mould carry out cascade, the code word of having been encoded;

Step (5): the code word that the IBRC encoder will have been encoded transfers to receiving terminal by wireless channel after modulating through BPSK;

Step (6): a) the IBRC decoder of receiving terminal receives the code word of having encoded through the BPSK modulation from wireless channel, and this reception code word is carried out the BPSK demodulation, obtains the IBRC code word after the demodulation;

Step (7): b) the IBRC code word of IBRC decoder after with demodulation is divided into the front and back two segment encode words of equal in length;

Step (8): c) the IBRC decoder carries out mould two additions with the front and back two segment encode words of described equal in length;

Step (9): the cyclic shift of opposite direction when d) code word of IBRC decoder after to two additions of step (8) mould carries out encoding with the IBRC encoder, the amplitude of this cyclic shift is motion vector α ₁In element a _K+1Value;

Step (10): the code word that e) step (9) is obtained by described step (2) to the order of step (4) by the IBRC decoder is carried out the IBRC coding;

Step (11): f) the IBRC code word after the IBRC code word behind the resulting coding of step (10) and the resulting demodulation of step (6) is compared, if both are identical, the code word after the cyclic shift that then step (9) is obtained is as result's output of IBRC decoder; If different, then the IBRC decoder carries out error correction to the code word after the resulting cyclic shift of step (9) according to the following steps:

I) to set the error bit number of the code word after the cyclic shift that step (9) obtains be n to the IBRC decoder, wherein 1≤n≤K;

Ii) in the code word of IBRC decoder after the cyclic shift that step (9) obtains, in [1, K], select arbitrarily n-1 element, this n-1 element is carried out the binary system negate;

Iii) at step I i) select arbitrarily again an element in the surplus element that is not chosen to, and this element is carried out the binary system negate;

Code word after the binary system negate that iv) step I is ii) obtained by described step (2) to step (4) by the IBRC decoder is carried out the IBRC coding;

V) with step I v) IBRC code word behind the resulting coding and the IBRC code word after the resulting demodulation of step (6) compare:

If Hamming distance between the two equals n, then the IBRC decoder is with step I i i) code word after the binary system negate that obtains exports as decoded result, and this moment, decoding finished;

If both Hamming distances are not equal to n, then at step I i) in the surplus element that is not chosen to carry out one by one the binary system negate; Carry out the IBRC coding by the IBRC decoder by described step (2) to the code word of step (4) after to the binary system negate again; Then the IBRC code word after resulting IBRC code word and the resulting demodulation of step (6) is compared:

If the situation that Hamming distance equals n occurs, then the code word after the current binary system negate that obtains of IBRC decoder output is decoded and is finished;

If the situation that Hamming distance all is not equal to n occurs, then the code word after the cyclic shift that successively step (9) obtained again of IBRC decoder is not repeatedly selected n-1 element, and this n-1 element of each selection is carried out the binary system negate; Then after n-1 element to each selection carries out the binary system negate, this non-selected surplus element carries out the binary system negate successively in the code word after the cyclic shift that again step (9) is obtained; Carry out the IBRC coding by the IBRC decoder by described step (2) to the code word of step (4) after to the binary system negate again; Then the IBRC code word after resulting IBRC code word and the resulting demodulation of step (6) is compared:

Equal the situation of n if there is Hamming distance, the code word after the current binary system negate that obtains of IBRC decoder output then, decoding finishes;

All be not equal to the situation of n if there is Hamming distance, then with n value again repeatedly not in the scope of [1, K], then at each repeated execution of steps ii after the value again) to step v); If the situation that Hamming distance equals n do not occur yet exhaust all values in [1, K] scope at n after, then the IBRC decoder is exported the all-zero code word, and the length of this all-zero code word is identical with the length of the code word to be encoded of step (2), finishes decoding this moment;

Step (12): the decoded result of IBRC decoder output is sent into the LT decoder carry out the LT decoding.

Compared with prior art, the invention has the beneficial effects as follows:

1) sends in the situation of the same number of LT codes at transmitting terminal, when receiving terminal recovers source data packet, Packet Error Ratio of the present invention (per) can be issued at lower channel signal to noise ratio (SNR) environment the Packet Error Ratio performance of fountain codes on the erasure channel, thereby promotes the transmission quality of fountain codes on wireless channel.Described Packet Error Ratio refers to compare the packet of the original transmission of transmitting terminal, the percentage of the misdata bag that comprises in the source data packet that receiving terminal LT decoder recovers.

2) under the identical environment of SNR, when receiving terminal recovered source data packet, the present invention can guarantee that the packet that transmitting terminal only need to send still less just can reach per performance same as the prior art, promotes the transmission quality of fountain codes on wireless channel thus.

Description of drawings

Fig. 1 is the structural representation block diagram that the present invention comprises the fountain codes transceiver system of IBRC;

Fig. 2 is the decoding process figure of IBRC code in one embodiment of the present invention;

Fig. 3 is the Packet Error Ratio curve chart of the IBRC code of one embodiment of the present invention.

Embodiment

Fig. 1 is the structural representation of the used fountain codes transceiver system that comprises IBRC of the present invention.Transmitting terminal comprises the IBRC encoder of LT encoder and afterwards cascade, and receiving terminal comprises the LT decoder of IBRC decoder and afterwards cascade.The source data of transmitting terminal comprises r code word X _j(j=1 ... r), these code words at first form unlimited many LT codes through the LT encoder, for each LT code(U _i), U _iCarry out chnnel coding through the IBRC encoder first, forming corresponding IBRC code word C _iAfter carry out again BPSK modulation, IBRC code word after last IBRC channel encoder is modulated BPSK mails to receiving terminal by awgn channel, receiving terminal carries out the BPSK demodulation after receiving code word, obtain may existing through noise jamming the IBRC code word C ' that has encoded of certain several bit mistake _i, the IBRC decoder is to C ' _iDecode, with the decoded result U ' that obtains _iSend into the LT decoder and carry out the LT decoding, therefrom obtain the source data code word X ' that receiving terminal recovers _j(j=1 ... r).If X _j(j=1 ... r) with X ' _j(j=1 ... r) have m code word different in, system's Packet Error Ratio (per) is exactly m/r so.

Channel coding method of the present invention comprises IBRC chnnel coding and IBRC channel-decoding two parts.

Wherein, the execution in step of IBRC chnnel coding part is:

1. determine that a pair of IBRC encoder is employed, length is respectively the Vector Groups of K and K+1, α ₁=(a ₁, a ₂... a _K, a _K+1) and α ₂=(a ₁, a ₂... a _K), α wherein ₁With α ₂Two conditions below must satisfying: 1) α ₁Only than α ₂Many element a _K+1, all the other elements are all identical, and the element in each vector is different, i.e. a ₁≠ a ₂≠ a ₃≠ a _K2) encoder uses α ₁With α ₂The code word C that obtains after encoding _iSmallest hamming distance d _Min=2K+1.

α ₁With α ₂In each element a of comprising _i(i=1 ... that value K+1) is indicated is U _iThe amplitude of each cyclic shift, described amplitude specifically refers to the bit number of cyclic shift, therefore for α ₁Arbitrary element a _i(i=1 ... K+1), U _iTo carry out a _iThe cyclic shift of bit.

The direction of the cyclic shift of acquiescence is to the right, namely for vectorial U _i=(u ₁, u ₂, u ₃... u _k), establish

Represent vectorial U _iBe a in the execution amplitude _iCyclic shift after the vector that obtains, so

Just can be expressed as $U_i^{a_i}=(U_{k-a_i+1}...,u_k,{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="HSA00000030373900011.png"\; state="\{\{state\}\}">u</figure-callout>}}_1,{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">u</figure-callout>}}_2...u_{k-a_i});$

More convenient in order to narrate, in content of the present invention, use α ₁=(0,3,7,10) and α ₂The vector that this group of=(0,3,7) satisfies condition is introduced cataloged procedure and the decode procedure of IBRC code, the code word U of input IBRC encoder _iThe length k of code word is according to α ₁With α ₂Length also to satisfy certain requirement (〉=4K+4=16); 2. order Expression U _iThe process amplitude is the resulting code word of ring shift right of j, and the value of j is Vector Groups α ₁=(a ₁, a ₂... a _K, a _K+1) and α ₂=(a ₁, a ₂... a _K) in the value of each element, a ₁, a ₂... a _K, a _K+1Set vectorial P ₁, P ₂Be respectively vectorial U to be encoded _iAccording to motion vector α ₁With α ₂In the value of each element all code words of carrying out successively obtaining after the cyclic shift carry out the new code word that mould two additions produce.Work as α ₁=(0,3,7,10), α ₂During=(0,3,7), mod ₂Binary addition, the IBRC encoder is at first according to α ₁In the value of each element (be U _iThe amplitude of each cyclic shift) to U _iCarry out cyclic shift, the code word after obtaining being shifted

Again these four code words are carried out mould two additions and obtain code word P ₁, namely ${\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HSA00000030373900011.png"\; state="\{\{state\}\}">P</figure-callout>}}_1={\mathrm{mod}}_2(U_i^0+U_i^3+U_i^7+U_i^{10});$

3.IBRC encoder is obtaining code word P ₁After again according to α ₂In the value of each element to U _iCarry out cyclic shift, the code word after obtaining being shifted Again these four code words are carried out mould two additions and obtain code word P ₂, namely ${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={\mathrm{mod}}_2({\mathrm{<figure-callout\; id="0"\; label="U\; i"\; filenames="HSA00000030373900021.png,HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+{\mathrm{<figure-callout\; id="3"\; label="U\; i"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+U_i^7);$

4. with P ₁, P ₂Cascade generates U _iCorresponding IBRC code word C _i=(P ₁| P ₂), C wherein _iLength be U _iTwice, i.e. 2k.

The IBRC code that the present invention uses have quite intuitively decode procedure and lower decoding complex degree, and receiving terminal only need to be known the employed motion vector α of transmitting terminal ₁With α ₂, just can carry out the IBRC decoding, and not need other any information relevant with this code word.

The IBRC decode procedure of IBRC decoder section is divided into the detected transmission mistake and corrects error of transmission two parts, in the detected transmission error procedure, the IBRC decoder determines whether the IBRC code word after the current demodulation of receiving exists error of transmission, if there is no error of transmission, the IBRC decoder will finish after the detected transmission error procedure is finished the decode procedure of code word; If the IBRC decoder is determined the IBRC code word after the current demodulation of receiving and has the error of transmission of some bits that the IBRC decoder will carry out error correction to this code word.In the process of error correction, only during the error bit number that comprises of the IBRC code word after the current demodulation that obtains≤K, this code word can be correctly decoded by the IBRC decoder, otherwise the IBRC decoder is at the error bit number of determining that code word comprises〉behind the K, the IBRC decoder will abandon this code word, output length is the full 0 code word of k, finishes the decoding to current code word, and the IBRC code word after the new demodulation that then the IBRC decoder is obtained is decoded.

The present invention will and correct the error of transmission process and narrate respectively the detected transmission error procedure in the IBRC codeword decoding process.

The detected transmission wrong step is:

1) decoder is with the C ' that receives _iBe divided into isometric front and back two segment encode word P ' ₁, P' ₂, C ' _iCan further be expressed as:

E wherein _1iWith e _2iRepresent respectively the code word P that generates in the transmitting terminal IBRC encoder ₁With P ₂The interference that in transmission course, is subject to respectively.

2) the IBRC decoder is with code word P ' ₁, P ' ₂Addition obtains code word P ' _i, P ' _iCan be expressed as:

$P_i^{\&prime;}={\mathrm{mod}}_2({\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HSA00000030373900011.png"\; state="\{\{state\}\}">P</figure-callout>}}_1^{\&prime;}+{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">P</figure-callout>}}_2^{\&prime;})$

$={\mathrm{mod}}_2({\mathrm{mod}}_2({\mathrm{mod}}_2({\mathrm{<figure-callout\; id="0"\; label="U\; i"\; filenames="HSA00000030373900021.png,HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+{\mathrm{<figure-callout\; id="3"\; label="U\; i"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+{\mathrm{<figure-callout\; id="7"\; label="U\; i"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+U_i^{10})+e_{1i})+{\mathrm{mod}}_2({\mathrm{mod}}_2({\mathrm{<figure-callout\; id="0"\; label="U\; i"\; filenames="HSA00000030373900021.png,HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+{\mathrm{<figure-callout\; id="3"\; label="U\; i"\; filenames="HSA00000030373900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_i^{}+U_i^7)+e_{2i}))(,$

$={\mathrm{mod}}_2(U_i^{10}+e_i^{\&prime;})$

3) the IBRC decoder is to code word P ' _iCarry out cyclic shift, the opposite direction of the cyclic shift that the direction of the cyclic shift that this moment is performed and IBRC encoder carry out when coding, namely the IBRC decoder is to code word P ' _iRing shift left; IBRC is to P ' _iThe ring shift left amplitude of carrying out is α ₁Compare α ₂That element value that has more, namely then 10 bits obtain P ' _iCode word behind the ring shift left

Can be expressed as

E wherein _iThat characterize is exactly LT code word U _iThe noise jamming that in awgn channel, is subject to.

4) right Carry out the IBRC coding one time, the motion vector that wherein uses is α ₁=(0,3,7,10), α ₂=(0,3,7), the IBRC decoder obtains

Corresponding IBRC code word C _s

5) with C _sThe IBRC code word C ' to be decoded that receives with the IBRC decoder _iCompare, if C ' _i=C _s, decoder is thought IBRC code word C _iIn transmission course, do not make mistakes,

Just as decoded result U ' _iOutputed to the LT decoder by the IBRC decoder and carry out the LT decoding, the IBRC decoder finishes current to code word C ' _iDecode procedure.If C ' _i=C _sBe false, the IBRC decoder is thought C ' _iComprise the error of transmission of some bits, need it to carry out error correction, IBRC decoder then enter the decode procedure of correcting error of transmission.

Confirm C ' at decoder _iAfter comprising error of transmission, because the motion vector that the IBRC encoder in this example uses is α ₁=(0,3,7,10), α ₂=(0,3,7), so K=3, IBRC code word smallest hamming distance is d _Min=2K+1=7, so the IBRC decoder can correctly be corrected at most the IBRC code word of the error of transmission that comprises 3 bits.

The IBRC decoder is according to this conclusion, to the vectorial U that obtains in the detected transmission error procedure _i ^fCarry out test decode 3 times, C ' when repeatedly not setting each test with order at random _iThe error bit number that comprises, each error bit scope of counting of setting is 1 bit to 3 bit, the IBRC decoder is just attempted under current setting the IBRC codeword decoding after the demodulation after having set the error bit number at every turn.At the most through three tests, after three kinds of error situations in the setting range all were completed, the IBRC decoder must obtain the decoded result of IBRC code word and with its output.

Correct the error bit number that the IBRC code word after the demodulation that the process of error of transmission will set when each test according to the IBRC decoder comprises, be 1 bit to setting the error bit number, 2 bits, the test process of 3 bits is by following paragraph 1), 2), 3) narrate respectively.

What decoding process shown in Figure 2 embodied is the error bit number that the IBRC code word is comprised when the IBRC decoder, according to 3 bits, and 1 bit, when 2 bit-order were set, decoder was to the test decode process of IBRC code word.The IBRC decoder is after having set at random the error bit number, just from following paragraph 1), 2), 3) in find the test process corresponding with the error bit number that sets, according to this test process the IBRC code word under the current setting is decoded:

1) as IBRC decoder setting code word C ' _iThe error bit number that comprises is 1 o'clock, and the IBRC decoder will be got an integer successively at random in the scope of [1, K], not repeatedly to multiselect K time, is m at the integer of choosing for the j time even _j, m so ₁≠ m ₂≠ m ₃... m _K-1≠ m _KThe IBRC decoder after having selected an integer, to code word at every turn Carry out the processing of following steps, finish the current IBRC code word C ' that sets with this _iTest decode process in the mistake 1 bit number situation that comprises:

A. establish the IBRC decoder and in the 1st time is selected, chosen the interior integer m of scope that is positioned at [1, K] ₁, decoder pair

M ₁Individual element

Negate, even

The IBRC decoder passes through code word after carrying out negate

Obtained a new code word

Namely $U_i^{f^{\&prime;}}=({u_1}^f,{u_2}^f,...{u_{m_1}}^{f^{\&prime;}}...{u_K}^f);$

B.IBRC decoder pair Carry out the IBRC coding one time by aforementioned coding step order, the motion vector that wherein uses in the cataloged procedure is employed that a pair of motion vector α of the IBRC encoder of transmitting terminal again ₁=(0,3,7,10), α ₂=(0,3,7), the IBRC decoder obtains code word Corresponding IBRC code word C _f

The c.IBRC decoder is C relatively _fWith C ' _iBetween Hamming distance d, if d=1, the IBRC decoder just will

As decoded result output, namely

Decoding finishes; If d=1 is false, decoder is confirmed

Comprise in the situation of mistake of 1 bit,

Be not that wrong bit, the IBRC decoder will be reset

In the scope of [1, K], carry out successively remaining K-1 unduplicated at random selection; The IBRC decoder for choose at every turn integer m _l, obtain according to the described method of step a)

Again to this Carry out IBRC coding and obtain code word C to correspondence _f, decoder compares C again _fWith C ' _iBetween Hamming distance d, if there is d=1, decoder is just with the code word after the corresponding binary system negate of the integer of current selection

As decoded result output, if the IBRC decoder after repeatedly not selecting at random K integer in the scope of [1, K], all code words that obtains

With and corresponding IBRC code word C _fAll can not be so that d=1 to set up, the IBRC decoder finishes the test of the situation of 1 bit mistake that the IBRC code word is comprised, and current setting is wrong, IBRC decoder then again set

The error bit number that comprises, and test accordingly.

2) as IBRC decoder setting IBRC code word C ' _iWhen comprising 2 bits wrong, the IBRC decoder will be got an integer successively at random in the scope of [1, K], not repeatedly to more options K time, be m at the integer of choosing for the j time even _j, m so ₁≠ m ₂≠ m ₃M _K-1≠ m _KThe IBRC decoder is being set IBRC code word C ' _iComprise in the situation of 2 bit mistakes, will be to code word

Carry out the processing of following steps, finish test decode process under the current setting with this:

A. establish the IBRC decoder and in the 1st time is selected, chosen the interior integer m of scope that is positioned at [1, K] ₁, decoder is to code word M ₁Individual element

Negate, even

The IBRC decoder passes through code word after finishing negate

Obtained a new code word

Wherein $U_i^{f^{\&prime;}}=({u_1}^f,{u_2}^f,...{u_{m_1}}^{f^{\&prime;}}...{u_K}^f).$

The b.IBRC decoder is selected one again and is different from m in the scope of [1, K] ₁Several n ₁, decoder is to code word N ₁Individual element

Negate, even The IBRC decoder passes through code word

Obtain new code word

Wherein $U_i^{f^{\&prime;\&prime;}}=({u_1}^f,{u_2}^f,...{u_{n_1}}^{f^{\&prime;}}...{u_{m_1}}^{f^{\&prime;}}...{u_K}^f)$ Perhaps $U_f^{\&prime;\&prime;}=(u_1^f,u_2^f...u_{m_1}^{f^{\&prime;}},...u_{n_1}^{f^{\&prime;}}...u_k^f);$

C.IBRC decoder pair

Carry out the IBRC coding one time, the motion vector that wherein uses is α ₁=(0,3,7,10), α ₂=(0,3,7), the IBRC decoder obtains code word

Corresponding IBRC code word C _f

The d.IBRC decoder is C relatively _fWith C ' _iBetween Hamming distance d, if d=2, decoder just will

As decoded result output, namely

Decoding finishes; If d=2 is false, the IBRC decoder will be reset In the scope of [1, K], select to be different from successively again m ₁And n ₁Integer, be again at the most K-2 time and unduplicatedly select at random; The IBRC decoder is for obtain different Integer n at every turn _l, according to the described method of step b), with corresponding with it

N _lThe position negate obtains code word $U_i^{f^{\&prime;\&prime;}}=({u_1}^f,{u_2}^f,...{u_{n_l}}^{f^{\&prime;}}...{u_{m_1}}^{f^{\&prime;}}...{u_K}^f),$ Again to this

Carry out the IBRC coding, obtain Corresponding IBRC code word C _f, decoder compares C again _fWith C ' _iBetween Hamming distance d, set up if there is d=2, decoder is just with the Integer n of current selection _lThe corresponding code word that negate obtains through binary system

As decoded result output, decoding finishes;

If repeatedly not selected K-2 time at random, the IBRC decoder is not different from m in the scope of [1, K] ₁And n ₁Integer after, all code words that obtains

With and corresponding IBRC code word C _fAll can not be so that d=2 to set up, the IBRC decoder will recover code word Then in the scope of [1, K], or else repeatedly select to be different from successively m ₁Integer, select K-1 time altogether;

Integer m for each selection _l, the IBRC decoder is to code word

M _lIndividual element

Negate, even

The IBRC decoder passes through code word Obtained a new code word

Wherein

At the current m that selected _lSituation under, the IBRC decoder is according to step b, repeatedly do not select to be different from successively again m in the scope of [1, K] _lInteger n _l,, obtain by current at the most K-1 time

And each Integer n of selecting _l, the IBRC decoder will successively obtain corresponding at the most K-1 The IBRC decoder is successively to obtain at every turn Carry out the IBRC coding, obtain corresponding IBRC code word C _f, the IBRC decoder is C relatively _fWith C ' _iBetween Hamming distance d, if there is d=2, decoder is just with current selected integer m _lWith n _lThe code word that obtains after the corresponding binary system negate

(namely respectively to U _i ^fIn two elements

Negate) as decoded result output, decoding finishes;

If the IBRC decoder is not repeatedly selected K time altogether integer m at random in the scope of [1, K] _lAfter, to all code words that obtains

Carried out the negate of step b, the described IBRC of step c coding and steps d are described all can't to be obtained by integer m after relatively _lWith n _lDetermined code word

So that d=2 sets up, the IBRC decoder finishes the test of the situation of 2 bit mistakes that the IBRC code word is comprised, and current setting is wrong, IBRC decoder then again set C ' _iThe error bit number that comprises, and test accordingly.

3) as IBRC decoder setting IBRC code word C ' _iWhen comprising 3 bits wrong, decoder will be got two unequal integers successively at random in the scope of [1, K], not repeatedly to multiselect K* (K-1)/2, even form integers to (m at two integers choosing for the j time _j, n _j), to select for these all K* (K-1)/2 times so, all integers that decoder obtains are at m _j≠ n _jThe time have (a m ₁, n ₁) ≠ (m ₂, n ₂) ≠ ... ≠ (m _{K* (K-3)/2}, n _{K* (K-3)/2}) ≠ (m _{K* (K-1)/2}, n _{K* (K-1)/2}).The IBRC decoder is being set IBRC code word C ' _iComprise in the situation of 3 bit mistakes; To code word

Carry out the processing of following steps, finish test decode process under the current setting with this:

A. establish the IBRC decoder and in the 1st time is selected, chosen integer in the scope that is positioned at [1, K] to (m ₁, n ₁), decoder is to code word M ₁Individual element

And n ₁Individual element Negate, even ${u_{m_1}}^{f^{\&prime;}}={\mathrm{mod}}_2({u_{m_1}}^f+1),$ ${u_{n_1}}^{f^{\&prime;}}={\mathrm{mod}}_2({u_{n_1}}^f+1);$ The IBRC decoder passes through code word

Obtained a new code word

Wherein $U_f^{\&prime;}=(u_1^f,u_2^f...u_{m_1}^{f^{\&prime;}},...u_{n_1}^{f^{\&prime;}}...u_k^f);$

The b.IBRC decoder is selected one again and is different from m in the scope of [1, K] ₁, n ₁Several r ₁, decoder is to code word

R ₁Individual element

Negate, even

The IBRC decoder passes through code word after carrying out negate Obtain new code word

C.IBRC decoder pair

Carry out the IBRC coding one time, the motion vector that wherein uses is α ₁=(0,3,7,10), α ₂=(0,3,7), the IBRC decoder obtains code word

Corresponding IBRC code word C _f

The d.IBRC decoder is C relatively _fWith C ' _iBetween Hamming distance d, if d=3, decoder just will As decoded result output, namely

Decoding finishes; If d=3 is false, the IBRC decoder will be reset ${U_i}^{f^{\&prime;}}=({u_1}^f,{u_2}^f,...{u_{n_l}}^{f^{\&prime;}}...{u_{m_1}}^{f^{\&prime;}}...{u_K}^f),$ In the scope of [1, K], repeatedly do not select to be different from random successively again m ₁, n ₁And r ₁Integer, to more options K-3 time; The IBRC decoder is for obtain different integer r at every turn _l, according to the described method of step b), with corresponding U _i ^f' r _lThe position negate obtains code word ${U_i}^{f^{\&prime;\&prime;}}=({u_1}^f,{u_2}^f,...{u_{n_l}}^{f^{\&prime;}}...{u_{m_1}}^{f^{\&prime;}}...{u_{r_l}}^{f^{\&prime;}}...{u_K}^f);$ Encoder is to this code word

Carry out the IBRC coding, obtain

Corresponding IBRC code word C _fDecoder compares C again _fWith C ' _iBetween Hamming distance d, set up if there is d=3, decoder is just with the Integer n of current selection _lCode word after the corresponding binary system negate

As decoded result output, decoding finishes;

If the IBRC decoder has not repeatedly selected K-3 time to be different from m altogether at random in the scope of [1, K] ₁, n ₁And r ₁Integer after, all code words that obtains

With and corresponding IBRC code word C _fAll can not be so that d=3 to set up, the IBRC decoder will recover code word

Then in the scope of [1, K], select successively to be different from integer to (m ₁, n ₁) all the other integers pair, selecting at the most number of times is K* (K-3)/2 again;

For the new integer of each selection to (m _l, n _l), the IBRC decoder is to code word

M _lIndividual element

And n _lIndividual element

Negate, even negate, even ${u_{m_1}}^{f^{\&prime;}}={\mathrm{mod}}_2({u_{m_1}}^f+1),$ ${u_{n_1}}^{f^{\&prime;}}={\mathrm{mod}}_2({u_{n_1}}^f+1),$ The IBRC decoder passes through code word Obtained a new code word

Wherein ${U_i}^{f^{\&prime;}}=({u_1}^f,{u_2}^f,...{u_{n_l}}^{f^{\&prime;}}...{u_{m_l}}^{f^{\&prime;}}...{u_K}^f);$ At the current integer of having selected to (m _l, n _l) situation under, the IBRC decoder is by repeatedly do not select to be different from random successively again m among the step b in the scope of [1, K] _lWith n _lInteger r _l, to more options K-2 time; Selecting r at every turn _lAfter, the IBRC decoder passes through current

R _lIndividual element negate obtains accordingly To what obtain at every turn

Carry out successively the IBRC coding and obtain corresponding IBRC code word C _fThe IBRC decoder is C relatively _fWith C ' _iBetween Hamming distance d, if there is d=3, decoder just with current selected integer to (m _l, n _l) and r _lIt is corresponding that to have passed through the binary system negate (namely right respectively

In three elements

Negate) resulting code word

As decoded result output, decoding finishes; If the IBRC decoder does not repeatedly select altogether K* (K-1)/2 time integer to (m in the scope of [1, K] at random _l, n _l) after, to all code word U that obtains _i ^f' carried out the successively negate of step b, the described IBRC coding of step c and steps d are described all can't to obtain integer to (m after relatively _l, n _l) and r _lCorresponding code word

So that d=3 sets up, the IBRC decoder finishes the test of the situation of 3 bit mistakes that the IBRC code word is comprised, and current setting is wrong, IBRC decoder then again set IBRC code word C ' _iThe error bit number that comprises, and test accordingly.

Receiving terminal IBRC decoder is deciphered processing by above process to the IBRC code word that receives, because K=3, so the IBRC decoder will repeatedly not set C ' in the scope of [1,3] _iThe error bit number.So the IBRC decoder at the most three tests that are over, has not repeatedly been set C ' at the most _iThe error bit number that comprises is 1 bit, and 2 bits or 3 bits, and after carrying out corresponding test decode according to above-mentioned process just can be determined the IBRC code word C ' after the demodulation _iThe scope of the error bit number that comprises; For the reception code word C ' of the mistake that comprises within 3 bits _i, decoder can be accomplished entirely true decoding; And for the code word of mistake greater than 3 bits, the IBRC decoder can't be correctly to C ' _iDecode,, decoder will directly be abandoned code word C ' _iDecoding, the all-zero code word that sends length and be the k bit is exported as decoded result, and finishes C ' _iDecoding.

Because the output of IBRC decoder is exactly the input of LT decoder, the LT code word that namely recovers at receiving terminal, and for the LT decode procedure, complete zero LT code word is to cause the LT decoding error, and wrong LT code word will cause a series of LT decoding error.Therefore the IBRC decoder can prevent effectively that by above-mentioned decode procedure the decoded result (LT code word) of wrong IBRC code is as the enter code word of LT decoder.So by using the IBRC code as chnnel coding, the enter code word of the LT decoder of receiving terminal or be correct, exactly the LT decode procedure do not had influential all-zero code word, thereby the scrambling characteristic of wireless channel has been approximated to the deletion characteristic of the wire message way of suitable fountain codes work, has stopped a series of decoding errors that receiving terminal LT decode procedure causes because enter code word comprises mistake.

Meanwhile, because fountain codes itself can produce the characteristics that numerous coding codeword transmits, after using the IBRC code as chnnel coding, receiving terminal only needs the IBRC code word that receives to be decoded according to the described process of content of the present invention always, with regard to a correct LT code word that decodes surely sufficient amount; Receiving terminal recovers the raw information of transmitting terminal again from a large amount of LT code word of IBRC decoder output by the LT decoder.Therefore the IBRC code by narrating among the present invention can improve the transmission performance of fountain codes on wireless channel effectively.

Three curves during Fig. 3 comprises are respectively the Packet Error Ratio curve of IBRC code word when awgn channel uses fountain codes transmission sources data that the present invention gives an example; The Packet Error Ratio curve of common FEC mode when identical awgn channel uses fountain codes transmission sources data; And the Packet Error Ratio curve of fountain codes when wired erasure channel transmitting data; Can find out that therefrom the IBRC code that the present invention narrates compares common FEC mode, give the data transmission performance of fountain codes at the AWGN wireless channel, be that the Packet Error Ratio performance is brought obvious lifting, so that fountain codes can be with lower error probability the transmission of data, and can be issued at lower signal to noise ratio environment the performance similar to the Packet Error Ratio of fountain codes on wire message way.Therefore the IBRC code narrated of the present invention is a kind of channel coding method that can the data transmission performance of Effective Raise fountain codes on wireless channel.

Claims (1)

1. a channel coding method that is used for promoting fountain codes transmission quality on wireless channel is characterized in that comprising the steps:

Step (1): the code word that comprises in the source data with transmitting terminal forms unlimited many LT code words through the LT encoder;

Step (2): the IBRC encoder carries out cyclic shift to each element of one of them in two motion vectors of the LT code word to be encoded of inputting this IBRC encoder successively as the amplitude of each cyclic shift, and resulting all code words after the cyclic shift are carried out mould two additions;

Described two motion vectors are respectively suc as formula shown in (1) and the formula (2),

α ₁=(a ₁,a ₂,…a _K,a _K+1)（1）

α ₂=(a ₁,a ₂,…a _K)（2）

Wherein, motion vector α ₂Than motion vector α ₁Few element a _K+1, each the element a that comprises in the described motion vector ₁, a ₂... a _k, a _K+1Value different,

The length 4K+4 bit of described code word to be encoded, wherein, K is vectorial α in the formula (2) ₂The element number that comprises;

Step (3): the IBRC encoder carries out cyclic shift to the described LT code word to be encoded of step (2) another each element in described two motion vectors successively as the amplitude of each cyclic shift, and resulting all code words after the cyclic shift are carried out mould two additions;

Step (4): the IBRC encoder after with two additions of step (2) mould code word and the code word after two additions of step (3) mould carry out cascade, the code word of having been encoded;

Step (5): the code word that the IBRC encoder will have been encoded transfers to receiving terminal by wireless channel after modulating through BPSK;

Step (6): a) the IBRC decoder of receiving terminal receives the code word of having encoded through the BPSK modulation from wireless channel, and this reception code word is carried out the BPSK demodulation, obtains the IBRC code word after the demodulation;

Step (7): b) the IBRC code word of IBRC decoder after with demodulation is divided into the front and back two segment encode words of equal in length;

Step (8): c) the IBRC decoder carries out mould two additions with the front and back two segment encode words of described equal in length;

Step (9): the cyclic shift of opposite direction when d) code word of IBRC decoder after to two additions of step (8) mould carries out encoding with the IBRC encoder, the amplitude of this cyclic shift is motion vector α ₁In element a _K+1Value;

Step (10): the code word that e) step (9) is obtained by described step (2) to the order of step (4) by the IBRC decoder is carried out the IBRC coding;

Step (11): f) the IBRC code word after the IBRC code word behind the resulting coding of step (10) and the resulting demodulation of step (6) is compared, if both are identical, the code word after the cyclic shift that then step (9) is obtained is as result's output of IBRC decoder; If different, then the IBRC decoder carries out error correction to the code word after the resulting cyclic shift of step (9) according to the following steps:

I) to set the error bit number of the code word after the cyclic shift that step (9) obtains be n to the IBRC decoder, wherein 1≤n≤K;

Ii) in the code word of IBRC decoder after the cyclic shift that step (9) obtains, in [1, K], select arbitrarily n-1 element, this n-1 element is carried out the binary system negate;

Iii) at step I i) select arbitrarily again an element in the surplus element that is not chosen to, and this element is carried out the binary system negate;

Code word after the binary system negate that iv) step I is ii) obtained by described step (2) to step (4) by the IBRC decoder is carried out the IBRC coding;

V) with step I v) IBRC code word behind the resulting coding and the IBRC code word after the resulting demodulation of step (6) compare:

If Hamming distance between the two equals n, then the code word after the binary system negate that step I is ii) obtained of IBRC decoder is exported as decoded result, and this moment, decoding finished;

If both Hamming distances are not equal to n, then at step I i) in the surplus element that is not chosen to carry out one by one the binary system negate; Carry out the IBRC coding by the IBRC decoder by described step (2) to the code word of step (4) after to the binary system negate again; Then the IBRC code word after resulting IBRC code word and the resulting demodulation of step (6) is compared:

If the situation that Hamming distance equals n occurs, then the code word after the current binary system negate that obtains of IBRC decoder output is decoded and is finished;

If the situation that Hamming distance all is not equal to n occurs, then the code word after the cyclic shift that successively step (9) obtained again of IBRC decoder is not repeatedly selected n-1 element, and this n-1 element of each selection is carried out the binary system negate; Then after n-1 element to each selection carries out the binary system negate, this non-selected surplus element carries out the binary system negate successively in the code word after the cyclic shift that again step (9) is obtained; Carry out the IBRC coding by the IBRC decoder by described step (2) to the code word of step (4) after to the binary system negate again; Then the IBRC code word after resulting IBRC code word and the resulting demodulation of step (6) is compared:

Equal the situation of n if there is Hamming distance, the code word after the current binary system negate that obtains of IBRC decoder output then, decoding finishes;

All be not equal to the situation of n if there is Hamming distance, then with n value again repeatedly not in the scope of [1, K], then at each repeated execution of steps ii after the value again) to step v); If the situation that Hamming distance equals n do not occur yet exhaust all values in [1, K] scope at n after, then the IBRC decoder is exported the all-zero code word, and the length of this all-zero code word is identical with the length of the code word to be encoded of step (2), finishes decoding this moment;

Step (12): the decoded result of IBRC decoder output is sent into the LT decoder carry out the LT decoding.

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