CN105812096A - Method for improving decoding precision of physical layer of receiver by using check information of data link layer - Google Patents

Abstract

The invention relates to a method for improving the decoding accuracy by using the verification information of the data link layer at the physical layer of the receiver, and improving the decoding performance of the physical layer by using the verification information of the link layer PDU packet. The method includes: after the physical layer receives the demodulated signal from the radio frequency end, it performs likelihood decoding in units of frames, and errors may occur in frame decoding; CRC (Cyclic Redundancy Check) check obtained. If there is no error information, submit the PDU to the upper layer; if there is an error, use the known correct PDU package in the frame as additional information for decoding the physical layer of the frame to perform the second likelihood decoding. The advantage of this method is that it makes full use of potential accurate redundant information between layers, does not increase additional transmission resource overhead, reduces the amount of retransmission information, and has a small system delay.

Description

A method for improving decoding accuracy by using data link layer verification information at the receiver physical layer

technical field

The invention belongs to the wireless communication technology, and relates to performing secondary decoding on a PDU (ProtocolDataUnit, protocol data unit) that is verified correctly at the link layer at the physical layer, and specifically relates to a receiver physical layer that utilizes data link layer verification information to upgrade Method for decoding precision.

Background technique

ARQ (Automatic Repeat Request, Automatic Repeat Request) and HARQ (Hybrid Automatic Repeat Request, Hybrid Automatic Repeat Request) are currently two major packet error processing technologies. In the traditional ARQ mechanism, once the link layer finds an erroneous packet, it discards it, and then requires the packet to be retransmitted in the next frame. Since ARQ is an adaptive system, the number of retransmissions of its feedback is closely related to channel interference. When the bit error rate of the channel is high, too frequent retransmissions will cause excessive system overhead and even cause congestion. HARQ is the current mainstream technology, especially in 3G technology and LTE, HARQ is widely used. In HARQ, depending on the partial retransmission of the physical frame to obtain additional redundant information, the overhead of the system is still relatively large, and the system delay is also relatively large.

Through research, it is found that among the various existing technologies, there is no technology that feeds back the information of the link layer to the physical layer as additional redundant information for error correction and decoding.

Through the observation of error correction decoding, it is found that when the receiving end performs likelihood decoding on the received front and back related sequences, because the probability judgment is used, the uncertainty in the decoding will be transmitted and accumulated step by step; if With additional redundant information to reduce this uncertainty, the decoding accuracy can be improved. Taking the likelihood decoding of the convolutional code with the structure (n,k,K) as an example, the constraint length of the convolutional code is n*K (or K), that is, the interrelated symbols in the encoding result are n*K In the process of decoding, this internal correlation law is used to correct errors and decode. However, in the decoding process, due to the existence of this association, when the previous bit decoding is wrong, this error information will be used as the prior information for the next bit decoding, which may lead to wrong judgment of the next bit. , and the impact depth of this error is n*K. Therefore, if the accuracy rate of prior bits can be improved, the performance of decoding will be effectively improved.

Contents of the invention

The purpose of the present invention is to overcome the problems and shortcomings of the above-mentioned prior art, and provide a method for the physical layer of the receiver to use the verification information of the data link layer to improve the decoding accuracy. The PDU packet is used as additional information to perform secondary decoding. When this method handles wrong PDU packets, it does not retransmit first, but uses the decoded correct PDU information to reduce the uncertainty of decoding, and then corrects and decodes errors again, effectively reducing the number of retransmissions and reducing system overhead. Improve system throughput.

The method that the physical layer of the receiver utilizes the check information of the data link layer to improve the decoding accuracy is characterized in that it comprises the following steps:

(1) After the physical layer receives a physical frame containing multiple PDU data, it decodes in units of frames, and submits the decoding result to the link layer;

(2) The link layer extracts each PDU, and identifies correct and incorrect PDUs through the packet check information;

(3) The correct PDU is used as additional information, and the initial frame received by the physical layer in step (1) is jointly decoded, that is, secondary decoding;

(4) Submit the decoding result to the link layer again, and check whether the PDU of the second decoding is correct through the PDU check information;

(5) Start a HARQ retransmission mechanism for still incorrect data packets.

The decoding steps after a frame of data is transmitted through the channel and received are as follows:

A1. Assume that each PDU packet has Mbit data, LbitCRC check information, there are n PDU packets in one frame, the channel coding adopts (3, 1, 2) convolutional code, and the CRC generator polynomial g(x)=x ⁴ + x+1; get M=10, L=4, n=20 here;

A2. A frame of data is encoded by a convolutional code in the physical layer of the sending end, and the generation matrix of the convolutional code is G=[100; 101; 111];

A3. Perform BPSK modulation on the encoded frame, the channel is an additive Gaussian channel, the mean value is 0, the variance is N, and the modulated data is sent;

A4. The receiving end receives and demodulates the data, saves the demodulated data, and then decodes the data for the first time;

A5. The link layer of the receiving end splits the first decoding result into packets, restores each PDU packet, and numbers each PDU packet;

A6. Through the CRC check information of each PDU, identify the correct and wrong packets of decoding;

A7. Use the information of the packets that have been correctly decoded to reduce the decoding uncertainty, and perform second decoding on step A4.

The specific strategy for the second decoding is as follows:

One. Obtain and store the index of the wrong PDU package in step A6;

Two. extract an index value, have obtained the numbering of all PDU packets after decoding for the first time in step A5, find the PDU packet corresponding to this index value, and carry out likelihood decoding to the correct data before and after utilization of this packet;

3. Replace the information of the corresponding error PDU packet with the re-decoded result of step 2;

4. For the secondary decoding of PDU packets with errors, repeat steps 2 and 3.

The present invention is inspired by the ARQ/HARQ idea and the likelihood decoding idea, but is not limited to obtaining additional redundant information only through retransmission, but feeds back the link layer information to the physical layer as additional information for secondary decoding, The invention overcomes the defect that in the existing likelihood decoding process, the step-by-step transmission and accumulation of uncertainty leads to the increase of the possibility of error. In order to reduce the uncertainty of decoding, in the second decoding, the correct PDU information of the first decoding verification is fully utilized as additional information for decoding, which improves the decoding accuracy and reduces the retransmission overhead.

The characteristics of the present invention are: using the link layer packet check information to identify the correct PDU, using the data contained in the correct PDU as additional information for secondary decoding, reducing the uncertainty of prior information in the physical frame decoding process performance, thereby effectively reducing the number of retransmissions, reducing system overhead, and reducing delay.

Description of drawings

Fig. 1 is a flow chart of a specific example of the present invention.

Fig. 2 is a flowchart of the secondary decoding core of the present invention.

Fig. 3 is a schematic diagram of simulation results of packet error rates under different signal-to-noise ratios according to the present invention.

FIG. 4 is a schematic diagram of simulation results of bit error rates under different signal-to-noise ratios according to the present invention.

detailed description

Consider the decoding and secondary decoding after a frame of data is transmitted through the channel and received. As shown in Figure 1:

A1. Assume that each PDU packet has Mbit data, LbitCRC check information, there are n PDU packets in one frame, the channel coding adopts (3, 1, 2) convolutional code, and the CRC generator polynomial g(x)=x ⁴ + x+1; get M=10, L=4, n=20 here;

A2. A frame of data is encoded by a convolutional code in the physical layer of the sending end, and the generation matrix of the convolutional code is G=[100; 101; 111];

A3. Perform BPSK modulation on the encoded frame, the channel is an additive Gaussian channel, the mean value is 0, the variance is N, and the modulated data is sent;

A4. The receiving end receives and demodulates the data, saves the demodulated data, and then decodes the data for the first time;

A5. The link layer of the receiving end splits the first decoding result into packets, restores each PDU packet, and numbers each PDU packet;

A6. Through the CRC check information of each PDU, identify the correct and wrong packets of decoding;

A7. Use the information of the correctly decoded package to reduce the decoding uncertainty, and perform secondary decoding on A4. The core process of the secondary decoding is shown in Figure 2: the correctly identified PDU package provides additional redundant information , the channel coding module combines the redundant information and the demodulation information stored in A4 to decode the initially received frame again, that is, the second decoding.

For secondary decoding the following strategies can be used:

1. Obtain and store the index of the wrong PDU package in step A6;

2. extract an index value, have obtained the numbering of all PDU packets after decoding for the first time in step A5, find the PDU packet corresponding to this index value, and carry out likelihood decoding (such as The maximum likelihood method can be used to iteratively replace the wrong PDU package, and the combination with the minimum Hamming distance can be selected as the expected decoding result; or a Viterbi-like method can be used);

3. Replace the information corresponding to the wrong PDU packet with the re-decoded result in step 2;

4. For the secondary decoding of other wrong PDU packets, repeat steps 2 and 3.

Fig. 3 and Fig. 4 have provided the emulation result of this concrete example, and Fig. 3 represents the comparison of the packet error rate under different signal-to-noise ratios (SNR), namely the packet error rate after decoding for the first time in A4 (and in A7 The comparison of the packet error rate after the secondary decoding.Fig. 4 shows the comparison of the bit error rate under different signal-to-noise ratios (SNR), namely the bit error rate after the first decoding in A4 and the secondary decoding in A7 The comparison of the bit error rate after.As can be seen from the two figures, secondary decoding can significantly improve the performance of the system without retransmission overhead.The advantage of the present invention is that the decoding error correction can be obtained without retransmission The additional redundant information required improves the packet error rate and BER, effectively reduces retransmission overhead, and reduces delay.

Claims (3)

1. receiver physical layer utilizes the method that data link layer checks information promotes decoding precision, it is characterised in that comprise the following steps:

(1) after physical layer receives the physical frame containing multiple PDU data, decoding in units of frame, decoding result is committed to link layer；

(2) link layer extracts each PDU, by the PDU that packet check information identification is correct and wrong；

(3) using correct PDU as extraneous information, and the initial frame that in step (1), physical layer receives carries out joint decoding, i.e. secondary decoding；

(4) again decoding result is committed to link layer, is checked by PDU check information the PDU of secondary decoding whether correct；

(5) still incorrect packet is started HARQ retransmission mechanism.

2. receiver physical layer according to claim 1 utilizes the method that data link layer checks information promotes decoding precision, it is characterised in that a frame data channel transmission and by the decoding procedure after receiving particularly as follows:

A1. assuming that each PDU is surrounded by Mbit data, LbitCRC check information, have n PDU bag in a frame, chnnel coding adopts (3,1,2) convolutional code, CRC generator polynomial g (x)=x⁴+x+1；Here M=10, L=4, n=20 are taken；

A2. frame data are encoded by convolutional code in transmitting terminal physical layer, and the generator matrix of convolutional code is G=[100；101；111]；

A3. the frame of coding being carried out BPSK modulation, channel is additive Gaussian channel, and average is 0, and variance is N, and the data after modulation are sent；

A4. receiving terminal receives data and demodulates, and preserves the data after demodulation, and then data carry out first time decoding；

A5. first time decoding result is carried out bag fractionation by receiving end link layer, and reduction obtains each PDU bag again, and to each PDU packet number；

A6. by the CRC check information of each PDU, the bag that decoding is correct and wrong is identified；

A7. the information utilizing the bag of correct decoding reduces decoding uncertainty, and step A4 is carried out secondary decoding.

3. receiver physical layer according to claim 2 utilizes the method that data link layer checks information promotes decoding precision, it is characterised in that: secondary decoding specific strategy is:

One. obtain and the index of the PDU bag of mistake in storing step A6；

Two. extracting an index value, obtained the numbering of all PDU bags after first time decoding, find the PDU bag that this index value is corresponding in step A5, before and after this bag is utilized, correct data carry out likelihood decoding；

Three. the result after again decoding by step 2 replaces the information of corresponding mistake PDU bag；

Four. the secondary for also vicious PDU bag decodes, repeat step 2, three.