CN1630206A - Complementary convolution code construction method adapted for frequency diversity transmission - Google Patents

Abstract

A complementary convolution code construction method for frequency diversity transmission contains (1), selectively deleting matrix P1 in transmission end to construct deleting type convolution code with b/V(V0<=V) code rate, (2), constructing b number different equivalence convolution code according to b number equivalence deleting matrix in transmission end, (3), selecting P number complementary convolution code word from b number different convolution code in transmission end, (4), transmitting P number complementary convolution code in transmission end, (5), adaptively controlling received complementary word in receiving end according to known complementary deleting matrix, sending it to Viterbi decoder for simplifying decoding and error correcting.

Description

Complementary convolutional code construction method suitable for frequency diversity transmission

Technical Field

The present invention relates to a complementary convolutional code construction method for diversity transmission, and more particularly, to a complementary convolutional code construction method suitable for frequency diversity transmission.

Background

Digital Audio Broadcasting (DAB) is a full digital multi-carrier wireless transmission system, which adopts advanced digital processing new technology to realize wireless channel signal transmission. Compared with the traditional analog broadcasting, DAB has the outstanding advantages of strong multipath fading inhibition capability, advanced error correction performance, Compact Disc (CD) like tone quality, large system capacity, wide coverage range and the like. Because broadcasting only occupies limited frequency resources, different occupation modes of DAB to the frequency resources result in different systems of DAB: a dedicated frequency system represented by european Eureka-147 DAB and an in-band co-channel (IBOC) system represented by U.S. IBOC DAB.

Eureka-147 DAB originated in the end of the 80's 20 th century and was officially put into use in the uk and sweden in the fall in 1995 after standardization by the European Telecommunications Standards Institute (ETSI). The price of the Eureka-147 DAB receiver is always high and is incompatible with the existing AM and FM analog broadcasting, so that the popularization of the Eureka-147 DAB is very difficult.

IBOC DAB uses the same carrier frequency as the currently used analog broadcasting station, and simulcasts both analog and digital programs depending on frequency separation and modulation. The frequency band used for FM broadcasting is an ideal frequency band for implementing DAB. The FM IBOC DAB system places the digital audio signal in the same frequency band as the analog signal to realize a Hybrid simulcast mode (Hybrid mode) of the analog signal and the digital signal of the same FM broadcast program, and fig. 1 shows a power spectrum of a certain FM Hybrid IBOC signal.

Extensive simulation and analysis have shown that digital sideband DAB signals in FM IBOC DAB operating in Hybrid mode have minimal impact on the analog host FM performance when located between 129kHz and 197kHz from the analog host FM center frequency. However, interference between adjacent channels is always present. Fig. 2 shows the interference situation of the first adjacent channel to the main FM channel based on the system of channel spacing of 200kHz, in which the dashed triangle completely covers the upper digital sideband part of the main FM (in fact, the interference is mutual: the solid triangle in the main FM also covers the lower digital sideband of the dashed line), and it can be seen that the interference of the first adjacent channel to the digital sideband of the main FM channel is destructive.

Studies have shown that if channel splitting and geographical layout optimization of the stations is guaranteed, simultaneous first neighbor interference of 200KHz is not possible, which guarantees that at least one sideband of the frequency diversity transmission is not interfered with.

If a coding combination scheme that redundant frequency diversity transmission technologies (such as digital double sidebands) are adopted to respectively transmit the same code words is adopted, the optimal high-code-rate code word of each sideband can be constructed under the condition of no complementary deletion constraint; but practice has shown that, at least in the range we are studying, frequency diversity transmission using convolutional codes of complementary structure has significant advantages. Although the transmission of identical codewords results in the best single sideband codewords having a relatively low average information bit error weight, the free distance of the codewords in the dual sideband combination is severely compromised. While a coded combination of the same codeword can result in twice the effective free distance of a single sideband codeword, the free distance of a full bandwidth codeword is larger with complementary erasures.

Disclosure of Invention

The invention aims to provide a convolutional coding construction method based on a complementary structure, which adopts frequency diversity combined transmission of the complementary convolutional code, can effectively overcome the problems of transmission data damage or loss and the like caused by channel interference and obtain higher asymptotic coding gain. Simulation results and analysis show that compared with the coding combination transmission based on the same convolutional code pair, the complementary convolutional code joint transmission can obtain 1-2 dB progressive coding gain. Moreover, the encoder (transmitter) and decoder (receiver) hardware complexity increases very little.

The invention relates to a complementary convolutional code construction method suitable for frequency diversity transmission, which is implemented at a sending end by taking a code rate as 1/V₀As mother code, selects a specific erasure matrix P₁Deleting to construct a bit rate of b/V, wherein V₀A deletion type convolutional code of < V; according to P₁B equivalent deletion matrixes are constructed, b different equivalent convolutional codes are constructed according to the b equivalent deletion matrixes, and equivalent code words have the same distance characteristic and the same error correction performance; selecting p complementary convolutional code words from b different equivalent convolutional codes according to the definition of the complementary structure convolutional codes; then using frequency diversity transmission, receptionThe terminal properly controls the received complementary deleting code word according to the specific complementary deleting matrix and sends the complementary deleting code word to the Viterbi decoder for simplified decoding, and the method is characterized by comprising the following steps:

s01: sending end selects deleting matrix P₁Constructing a deletion type convolutional code with the code rate of b/V;

s02: the sending end constructs b different equivalent convolutional codes according to the b equivalent deletion matrixes;

s03: the sending end selects p complementary convolution code words from b different equivalent convolution codes;

s04: the transmitting end transmits p complementary convolution code words by adopting frequency diversity;

s05: the receiving end properly controls the received complementary code words according to the known complementary deletion matrix, and sends the complementary code words to the Viterbi decoder for simplified decoding and error correction.

Wherein the code rate of the sending end is 1/V₀As mother code, selects a specific erasure matrix P₁Deleting to construct a deletion type convolutional code with the code rate of b/V;

wherein according to P₁B equivalent deletion matrices are constructed, from which b different equivalent convolutional codes are constructed.

Wherein p complementary convolutional codewords are selected from b different equivalent convolutional codes according to the definition of the complementary structure convolutional code.

Wherein the transmitting end transmits p complementary convolution code words by adopting frequency diversity.

The receiving end controls the received complementary code word properly according to the known complementary deleting matrix, and sends the complementary code word into the Viterbi decoder for simplified decoding and error correction.

The performance of the complementary convolutional code constructed by the transmitting end depends on the set parameters: convolutional code storage depth m, deletion matrix P₁The equivalence deletion matrix P_i，(i＝1，2，…，b) Digital modulation modes such as BPSK and QPSK; the same convolution mother code sets different convolution code storage depth m and deletion matrix P₁The equivalence deletion matrix P_iWhen the digital modulation scheme such as (i) 1, 2, …, b), BPSK, QPSK, or the like is used, the asymptotic coding gain varies.

Drawings

To further illustrate the technical content of the present invention, the following detailed description is made in conjunction with the embodiment of FM IBOC DAB complementary convolutional code construction and the accompanying drawings (table), wherein:

FIG. 1 is a power spectrum of a certain FM Hybrid IBOC signal. Where the triangle indicated by the dashed line is the spectrum of the analog FM signal and the solid line rectangles on both sides of the FM indicate the DAB first digital sideband.

FIG. 2 shows the interference situation for the main FM channel (solid line) based on the first adjacent channel (at +200kHz from the main FM center frequency, dotted line) in the system with channel spacing of 200 kHz;

FIG. 3 is (n)₀-1)/n₀Code rate deletion type convolutional codes and Viterbi decoding block diagrams thereof;

FIG. 4 is 1/V₀The code rate mother code constructs a family of complementary deletion type convolution code word algorithm flow chart with the code rate of b/V;

fig. 5 is a BER simulation curve of three 2/5-rate full-bandwidth convolutional codes based on monte carlo simulation.

Detailed Description

Referring to fig. 3 and 4, the present invention relates to a complementary convolutional code construction method suitable for frequency diversity transmission. At the transmitting end, the code rate is 1/V₀Selects a specific rule (erasure matrix P) as the mother code₁) Deleting (dividing) to construct the code rate as b/V (V)₀< V) erasure-type convolutional codes; according to P₁Constructing b equivalent deletion matrices based thereonB different equivalent convolutional codes are constructed, and equivalent code words have the same distance characteristic and the same error correction performance; selecting p complementary convolutional code words from b different equivalent convolutional codes according to the definition of the complementary structure convolutional codes; and then transmitted using frequency diversity (e.g., digital double sideband technology). The receiving end properly controls the received complementary deleting code word according to the specific complementary deleting matrix and sends the complementary deleting code word to the Viterbi decoder for simplified decoding. The method is characterized by comprising the following steps:

s01: sending end selects deleting matrix P₁Constructing the code rate as b/V (V)₀< V) erasure-type convolutional codes;

s02: the sending end constructs b different equivalent convolutional codes according to the b equivalent deletion matrixes;

s03: the sending end selects p complementary convolution code words from b different equivalent convolution codes;

s04: the transmitting end transmits p complementary convolution code words by adopting frequency diversity;

s05: the receiving end properly controls the received complementary code word according to the known complementary deleting matrix, and sends the complementary code word into the Viterbi decoder for simplified decoding and error correction.

In VB decoding, the complexity of the decoder is 2^k0mThe code rate is low because the code rate is generally low due to exponential growth of the code (2, 1, m). In order to increase the code rate without increasing the complexity of the decoder, the (2, 1, m) code is often erased (pruned) according to a certain rule. The erasure rule can be defined by an erasure matrix with a code rate of 1/V₀The code rate can be constructed as b/V (V) by using the convolutional code as a mother code₀< V) of the erasure type convolutional code. The deletion matrix has V₀Rows and b columns, each row and code rate being 1/V₀Of a convolutional encoder V₀One bit in each output mother code corresponds to one coding period. The elements in the matrix are composed of 1 or 0, and "1" represents a code rate of 1/V₀The convolutional encoder outputs the corresponding bit symbol transmission in the mother code, and a "0" indicates the bit symbol transmissionThe bit symbols are deleted. E.g. according to the deletion matrix P as given in (1)₀The erasure-type convolutional code of (8, 7, 6) can be generated from the mother code of (2, 1, 6):

$P_0=\left[\begin{array}{ccccccc}1& 1& 1& 1& 0& 1& 0\\ 1& 0& 0& 0& 1& 0& 1\end{array}\right]---\left(1\right)Q_1=\left[\begin{array}{ccccccc}2& 1& 1& 2& 1& 1& 1\\ 1& 1& 1& 1& 2& 1& 1\end{array}\right]---\left(2\right)$

FIG. 3 is (n)₀-1)/n₀A flow chart for rate-erasure convolutional code generation and Viterbi decoding thereof. FIG. 3(a) includes (2, 1, 6) a convolutional encoder, a complementary erasure matrix, and associated control and timing elements; after the decoder in fig. 3(b) receives the codeword, a specific dummy symbol is inserted at the corresponding deleted codeword position according to the known deletion rule, and then the (2, 1, 6) code VB decoder is entered for decoding (the measurement calculation of the inserted dummy symbol is prohibited during decoding).

Similarly, the code rate can be 1/V₀According to the mother codeA certain repetition rule is used for constructing a code rate of b/(bV)₀+1) Repetition (Repetition) type convolutional codes, where l ≧ 1. The repetition rule is represented by a repetition matrix which has V in common₀And b columns. Unlike the erasure matrix, each element of the repetition matrix is greater than or equal to 1, indicating the number of repetitions of the corresponding bit in the mother code output. According to the repetition matrix Q as given in (2)₁A repeated convolutional code having a code rate R of 7/17 can be constructed from (2, 1, 6) convolutional codes having a code rate of 1/2.

Defining: is provided with C₁And C₂The two code words are 1/V of the original code rate₀If the b column in the deletion or repetition matrix corresponding to a certain code word is generated by circularly left-shifting (or right-shifting) the b column in the deletion or repetition matrix corresponding to another code word, the code is called C₁And C₂Are equivalent. The code rate 5/6 resulting from the 3 erasure matrices as in (3) is equivalent:

$P_1=\left[\begin{array}{ccccc}1& 1& 1& 0& 0\\ 1& 0& 0& 1& 1\end{array}\right],P_2=\left[\begin{array}{ccccc}0& 1& 1& 1& 0\\ 1& 1& 0& 0& 1\end{array}\right],P_3=\left[\begin{array}{ccccc}0& 0& 1& 1& 1\\ 1& 1& 1& 0& 0\end{array}\right]---\left(3\right)$

equivalent convolutional codes have the same distance characteristics and the same error correction performance. An erasure matrix or repetition matrix with b columns can construct at most b different equivalent codewords.

Defining: let C_i(i-1, 2, …, p) is determined by the original code rate being 1/V₀P b/V code rate equivalent codes generated by the mother code,let P_iRepresents a codeword C_iThe corresponding deletion matrix is then used to delete the deletion matrix,

order: <math> <mrow> <mi>P</mi> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>p</mi> </munderover> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>.</mo> </mrow> </math> if each element in the P matrix is greater than or equal to 1, the P code words C are called_iAre complementary. The mutual-complementing codes are equivalent in distance characteristic, and the mutual-complementing code joint transmission code rate at least comprises the original code rate 1/V in construction₀. When V is₀When the crystal is equal to V, the crystal can be obtained,the code rate in joint transmission is b/bV₀＝1/V₀Exactly the original code rate.

At 1/V₀The steps of constructing a family of complementary deletion type convolution code words with the code rate b/V by the code rate mother code are shown in the algorithm flow chart shown in figure 4. To ensure that the matrix P can be deleted from the initial in the algorithm flowchart₁In the cyclic shift operation of (1), P complementary deletion matrices are generated, then P₁The following requirements must be met:P₁the number of 1 s in each row is at least equal toThe conditions are not so critical that the conditions are,

a number of eligible complementary erasure convolutional codes can be constructed accordingly.

For FM IBOC DAB system, we take Additive White Gaussian Noise (AWGN) channel and coherent BPSK modulation as examples, construct a complementary convolutional code (referred to as half-bandwidth convolutional code) with a code rate of 4/5, and perform joint transmission through digital double sidebands respectively to obtain a convolutional code (referred to as full-bandwidth convolutional code) with a code rate of 2/5.

Two methods can be used to search for good complementary convolutional codes: one is a Top-down method, which firstly searches a full-bandwidth convolutional code and then generates a corresponding half-bandwidth complementary code according to a certain complementary deletion rule; the other method is a Bottom-up method, which directly searches half-bandwidth complementary convolutional codes and then jointly transmits the codes to form the full-bandwidth convolutional codes.

Two standard parameters are specified for selecting the optimal code: maximum worst free distance and minimum worst information error weight, worst free distance d_f，worstIs the minimum value of the free distance in the code pair, the worst information error weight c_worstIs the maximum value of the information error weight in the worst free distance path in the code pair.

Calculating free distances and information error weights for pairs of non-malignant error-propagation complementary codes constituting a 2/5-rate full-bandwidth code, those (c) in the pair having the largest worst free distance_worst/P) is the optimal complementary code pair. In calculating the free distance and the information error weight, a Viterbi algorithm of the extended metric may be employed.

Table 1 shows the constructed 2/5-rate full-bandwidth codes, and for convenience of comparison, the 2/5-rate Hagenauer full-bandwidth codes and Kroeger full-bandwidth codes corresponding to the second row and the third row in the table are introduced from the relevant documents, and based on this, complementary code pairs with a code rate of 4/5 are constructed by a Top-down method according to a complementary deletion rule, as shown in table 2; the fourth and fifth rows are 2/5 rate full bandwidth codes constructed based on the (3, 1, 6) Clark _ Cain mother code and the (3, 1, 8) Ottosson mother code, respectively.

TABLE 1

Codes and the like	Type of mother code	Deletion matrix (2 system)	df	cdf/P
					Hagenauer	Hagenauer	(1111，1111，1100)	11	1.00
Kroeger	Hagenauer	(1111，1111，1010)	11	2.00
					f-yyh-CC	Clark-Cain	(1010，1111，1111)	11	1.50
f-yyh-Ott	Ottosson	(1111，1100，1111)	14	7.00

TABLE 2

4/5 code rate half bandwidth code	Deleting matrices	df	cdf/P	Complementary deletion matrices	df	cdf/P
							h-yyh-CC half-bandwidth code	(1011，0100，1000)	4	8	(0100，1011，0100)	4	2.75
(1000，0011，1100)	4	9.5	(0111，1100，0000)	4	6.25
						h-yyh-Ott half-bandwidth code		(0110，1001，0010)	4	2.5	(1001，0110，1000)	4	2.5
(0110，1001，1000)	4	12	(1001，0110，0010)	4	12

FIG. 5 is a plot of Bit Error Rate (BER) obtained by performing respective Monte Carlo simulations based on Kroeger (Kro), f-yyh-CC (CC), and f-yyh-Ott (Ott)2/5 rate full-bandwidth convolutional codes in Table 1. Wherein,

representing the ratio of energy per dimension to noise power spectral density,

andand

the relationship between them is as follows: <math> <mrow> <mfrac> <msub> <mi>E</mi> <mi>b</mi> </msub> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>=</mo> <mfrac> <mn>1</mn> <mi>R</mi> </mfrac> <mo>&CenterDot;</mo> <mfrac> <msub> <mi>E</mi> <mi>d</mi> </msub> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>,</mo> <mfrac> <msub> <mi>E</mi> <mi>s</mi> </msub> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>=</mo> <msub> <mi>N</mi> <mi>d</mi> </msub> <mo>&CenterDot;</mo> <mfrac> <msub> <mi>E</mi> <mi>d</mi> </msub> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>,</mo> </mrow> </math> r is code rate, N_dDimension representing each symbol (N in BPSK modulation)_d1, QPSK modulation_d2). From the simulation results, it can be seen that the f-yyh-Ott (Ott) code with a memory depth of 8 performs significantly better than the other two codes with a memory depth of 6. Meanwhile, although the average information bit error weight of the f-yyh-CC (CC) code is less than that of the Kroeger (Kro) code, the bit error rate performance is still slightly worse in the low SNR channel.

Table 3 compares the free distance performance of the single-sideband code and the double-sideband code, and it can be seen that, for the storage depth m equal to 6, in the AWGN channel, the 2/5 code rate complementary deletion has a progressive coding gain of 10 · 1g (11/8) equal to 1.38dB for the full-bandwidth code transmission scheme relative to the code combination transmission of the same codeword; when m is 8, the progressive coding gain is 10 · 1g (14/10) ═ 1.46 dB.

TABLE 3

4/5 code rate half bandwidth code	Deleting matrices	df	cdf/P	Corresponding 2/5 code rate full bandwidth code pattern	df	cdf/P
							h-yyh-CC half-bandwidth code (m ═ 6)	(1000，0110，1001)	4	1.50	f-yyh-CC(m＝6)(1010，1111，1111)	11	1.50
(0010，1001，0110)	4	1.50
			h-yyh-Ott half-bandwidth code (m ═ 8)	(0101，1000，0110)	5	14		f-yyh-Ott(m＝8)(1111，1100，1111)	14	7.00
(1010， 0100，1001)	5	14

Claims (7)

1. A complementary convolution code construction method suitable for frequency diversity transmission is disclosed, wherein at the transmitting end, the code rate is 1/V₀As mother code, selects a specific erasure matrix P₁Deleting to construct a bit rate of b/V, wherein V₀A deletion type convolutional code of < V; according to P₁B equivalent deletion matrixes are constructed, b different equivalent convolutional codes are constructed according to the b equivalent deletion matrixes, and equivalent code words have the same distance characteristic and the same error correction performance; selecting p complementary convolutional code words from b different equivalent convolutional codes according to the definition of the complementary structure convolutional codes; then using the frequencyDiversity transmission, the receiving end controls the received complementary deleting code word properly according to the specific complementary deleting matrix, and sends it to the Viterbi decoder for simplified decoding, it is characterized in that, it includes the following steps:

s01: sending end selects deleting matrix P₁Constructing a deletion type convolutional code with the code rate of b/V;

s02: the sending end constructs b different equivalent convolutional codes according to the b equivalent deletion matrixes;

s03: the sending end selects p complementary convolution code words from b different equivalent convolution codes;

s04: the transmitting end transmits p complementary convolution code words by adopting frequency diversity;

s05: the receiving end properly controls the received complementary code words according to the known complementary deletion matrix, and sends the complementary code words to the Viterbi decoder for simplified decoding and error correction.

2. The method of claim 1, wherein the transmitter side uses a code rate of 1/V to construct the complementary convolutional codes for frequency diversity transmission₀As mother code, selects a specific erasure matrix P₁Deleting to construct a deletion type convolutional code with the code rate of b/V;

3. the method of claim 1, wherein the complementary convolutional code construction is based on P₁B equivalent deletion matrices are constructed, from which b different equivalent convolutional codes are constructed.

4. The method of claim 1, wherein p complementary convolutional code words are selected from b different equivalent convolutional codes according to the definition of the complementary convolutional code.

5. The method of claim 1, wherein the transmitting end transmits p complementary convolutional codewords using frequency diversity.

6. The method of claim 1, wherein the receiving end performs proper control on the received complementary code words according to the known complementary erasure matrix, and sends the complementary code words to the viterbi decoder for simplified decoding and error correction.

7. The method as claimed in claim 1 or 5, wherein the performance of the complementary convolutional code constructed by the transmitting end depends on the setting parameters: convolutional code storage depth m, deletion matrix P₁The equivalence deletion matrix P_i(i ═ 1, 2, …, b), BPSK, QPSK, or other digital modulation schemes; the same convolution mother code sets different convolution code storage depth m and deletion matrix P₁The equivalence deletion matrix P_iWhen the digital modulation scheme such as (i) 1, 2, …, b), BPSK, QPSK, or the like is used, the asymptotic coding gain varies.

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