CN103873187B - Deinterleaving method and device in ofdm system - Google Patents

Abstract

The invention discloses an interleaving method and device in an OFDM system. The method includes: S1. Dividing a complex symbol sequence to be transmitted into a real part and an imaginary part, that is, an in-phase and an orthogonal symbol sequence; S2. Keep the in-phase or orthogonal path symbol sequence unchanged, and divide the other path symbol sequence into multiple groups in turn, and perform intragroup interleaving in each group; S3. Combine the non-interleaved in-phase or orthogonal path symbols in step S2 with the interleaved The symbols of another path are recombined into a new complex symbol sequence, which is called the first complex symbol sequence; S4, performing symbol interleaving on the first complex symbol sequence to obtain a second complex symbol sequence; S5, performing symbol interleaving on the second complex symbol sequence; The sequence is modulated by Orthogonal Frequency Division Multiplexing. The invention improves the time, frequency and signal space diversity gain of the orthogonal frequency division multiplexing system, while maintaining high throughput rate and low implementation complexity.

Description

Interleaving method and device in OFDM system

technical field

The invention relates to the technical field of digital information transmission, in particular to an interleaving method and device capable of improving time, frequency, and signal space diversity gains in an Orthogonal Frequency Division Multiplexing (OFDM) system.

Background technique

In communication and broadcasting systems, actual channels usually have certain correlations in the time and frequency domains. From the time domain, the channel time domain impulse response (CIR) in adjacent time periods does not change much; from the frequency domain, the channel frequency domain impulse response (CFR) in adjacent frequencies is also almost the same; that is, the channel has memory characteristics . The memorization of channel response in the time/frequency domain can easily lead to burst errors, and the possibility that adjacent data in the instant/frequency domain are in deep fading at the same time is extremely high, especially for terrestrial wireless communication and broadcasting systems. However, the currently researched channel coding with excellent performance is usually designed for discrete memoryless channels. In order to obtain the memoryless channel required by channel coding, ideal interleaving is an effective way to convert the actual memory channel into a discrete memoryless channel. Because of this, the current communication system block diagram basically adopts the following structure: the transmitting end first undergoes channel coding, and then transmits it through interleaving; while the receiving end undergoes deinterleaving on the contrary, and then sends it to channel decoding. In this way, after ideal interleaving and deinterleaving, the equivalent channel after channel encoding and before channel decoding can be considered as memoryless.

However, due to various factors such as interleaving depth, delay, throughput rate, and processing complexity, the actual interleaving is far from ideal. Taking block interleaving in an Orthogonal Frequency Division Multiplexing (OFDM) system as an example, assuming that the number of subcarriers of OFDM is 4096, the block interleaver for constellation symbols before OFDM modulation contains 240 rows and 4096 columns. Row-write and column-read are used for interleaving, and column-write and row-read are used for deinterleaving. It is not difficult to find that after deinterleaving, although each row contains 4096 symbols, these 4096 symbols only come from 256 different subcarriers. When the 4096 or part of them (more than 256) symbols are sent to the decoder for decoding, the frequency diversity gain order obtained by the decoder is only 256.

On the other hand, the signal space diversity (signal space diversity) technology can further improve the diversity gain by transmitting two-dimensional or high-dimensional signals to be transmitted in different time and frequency, see J.Boutros and E.Viterbo, "Signal space diversity : A power-and bandwidth-efficient diversity technique for the Rayleigh fading channel,” IEEE Trans. Inform. Theory, vol.44, no.4, pp.1453–1467, July 1998. In order to realize the transmission of two-dimensional or high-dimensional signals in different time and frequency, it is necessary to split, interleave, and recombine the dimensions of the signal, the core of which is interleaving.

In order to obtain greater diversity gain than traditional block interleaving, many improved interleavers have been proposed. For example, the document (Yohei Murakami, "OFDM Transmitter, OFDM Receiver and Interleaving Method," Chinese Invention Patent, Application No. 200880100831.9) uses a random number generation method to achieve interleaving; or the document (Jap van der Bi Ke, Branislav M. Popovich, "Interleaving Method for Orthogonal Frequency Division Multiplexing Communication," Chinese Invention Patent, Publication No. CN1742450A) Divide the OFDM frequency band into several sub-bands and perform interleaving deal with.

Contents of the invention

(1) Technical problems to be solved

The technical problem to be solved by the present invention is to design an interleaving method and device in an OFDM system, so that the system can obtain higher time, frequency, and signal space diversity gains, while maintaining higher data throughput and lower implementation complexity. Spend.

(2) Technical solutions

In order to solve the above problems, the invention provides a method for interleaving in an OFDM system, the method comprising the following steps:

S1. Divide the complex symbol sequence to be transmitted into a real part and an imaginary part, that is, in-phase and quadrature two-way symbol sequences;

S2. Keeping the symbol sequence of the in-phase or quadrature path unchanged, divide the symbol sequence of the other path into multiple groups in turn, and perform intra-group interleaving in each group;

S3. Recombining the uninterleaved in-phase or orthogonal symbol sequence in step S2 and another symbol sequence after interleaving into a new complex symbol sequence, which is called the first complex symbol sequence;

S4. Perform symbol interleaving on the first complex symbol sequence to obtain a second complex symbol sequence;

S5. Perform OFDM modulation on the second complex symbol sequence.

Preferably, in the step S2, the number of symbols in each group is the same, and the interleaving within the group adopts the same interleaving pattern.

Preferably, if the number of symbols in each group is an even number, namely 2m, then the interleaving pattern is [x _m , x _m+1 ,..., x _2m , x ₁ , x ₂ ,..., x _m-1 ]; when When the number of symbols in each group is 4, the interleaving pattern is [2,4,1,3], that is, if the symbol group before interleaving is x ₁ , x ₂ , x ₃ , x ₄ , then the symbol after interleaving The groups are x ₂ , x ₄ , x ₁ , x ₃ ; when the number of symbols in each group is 6, the interleaving pattern is [3,5,6,2,3,1], that is, if the symbols before interleaving The groups are x ₁ , x ₂ , x ₃ , x ₄ , x ₅ , x ₆ , then the interleaved symbol groups are x ₃ , x ₅ , x ₆ , x ₂ , x ₁ , x ₄ .

Preferably, the symbol interleaving in the step S4 adopts block interleaving or block interleaving with block-by-row cyclic shift.

Further, the block interleaving of the block row cyclic shift includes the following steps:

S001. Write the sequence x to be interleaved into the symbol interleaver row by row to obtain the symbol sequence X in matrix form;

S002. Divide the symbol sequence X into a plurality of sub-blocks equally by column, wherein each sub-block performs row cyclic shift with different offsets to obtain a symbol sequence after row cyclic shift

S003, from the above symbol sequence Read the symbols column by column to get the interleaved symbol sequence

Preferably, in the step S002, each sub-block contains an integer number of OFDM symbols, and the offset address of each sub-block follows an arithmetic difference sequence.

Preferably, the step S003 is specifically: read down from the offset row, read the first row after reading the last row, and read until the previous row of the offset row to obtain the interleaved symbol sequence

Preferably, the row cyclic shift offset f _s in the step S002 is set to an arithmetic sequence of s, that is, f _s =δ·s, where δ is a positive integer, 0≤s<S, and S is a sub-block the number of .

Preferably, in the short interleaving mode: the number of symbol interleaver rows is 240, the number of columns is 4096, when the number of OFDM subcarriers is 4096, the row cyclic shift offset f _s =2s, 0≤ s<S, where S=16 represents the number of sub-blocks; when the number of OFDM subcarriers is 8192, f _s =4s, 0≤s<S, where the number of sub-blocks S=8; When the number of multiplexed subcarriers is 32768, f _s =8s, 0≤s<S, S=2;

In the long interleaving mode: the number of symbol interleaver rows is 480, and the number of columns is 4096. When the number of OFDM subcarriers is 4096, the row cyclic shift offset f _s =2s, 0≤s<S , where the number of sub-blocks S=32; when the number of OFDM subcarriers is 8192, f _s =4s, 0≤s<S, S=16; when the number of OFDM subcarriers is 32768 , f _s =8s, 0≤s<S, S=4.

The present invention also provides an interleaving device in an OFDM system, the device comprising:

An in-phase/orthogonal signal separator, which is used to divide the complex symbol sequence to be transmitted into in-phase and quadrature two-way symbol sequences;

A single-path symbol sequence block interleaver, connected to the in-phase/orthogonal signal separator, is used to divide the above-mentioned in-phase or orthogonal single-path symbol sequences into multiple groups in turn, and each group is interleaved within the group;

A signal combiner, connected to the single-way symbol sequence block interleaver, used to recombine the non-interleaved in-phase or orthogonal symbol sequence and another interleaved symbol sequence into a new complex symbol sequence;

A symbol interleaver, connected to the signal combiner, is used to perform symbol interleaving on the above recombined new complex symbol sequence.

(3) Beneficial effects

The invention improves the time, frequency, and signal space diversity gain of the OFDM system, while maintaining high throughput and low implementation complexity.

Description of drawings

Fig. 1 is a flow chart of the inventive method;

Fig. 2 is a typical OFDM system transmitter block diagram;

Fig. 3 is the overall flowchart of an embodiment of the present invention;

Fig. 4 is an IQ interleaving flow diagram of a group of preferred 4 symbols of the present invention;

Fig. 5 is a structural diagram of the interleaving device of the present invention.

detailed description

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Fig. 1 is the flowchart of the inventive method, and the present invention provides a kind of interleaving method in the OFDM system, and its steps are as follows:

S1. Divide the complex symbol sequence to be transmitted into a real part and an imaginary part, that is, in-phase and quadrature two-way symbol sequences;

S2. Keeping the symbol sequence of the in-phase or quadrature path unchanged, divide the symbol sequence of the other path into multiple groups in turn, and perform intra-group interleaving in each group;

S3. Recombining the uninterleaved in-phase or orthogonal symbol sequence in step S2 and another symbol sequence after interleaving into a new complex symbol sequence, which is called the first complex symbol sequence;

S4. Perform symbol interleaving on the first complex symbol sequence to obtain a second complex symbol sequence;

S5. Perform OFDM modulation on the second complex symbol sequence.

Preferably, in the step S2, the number of symbols in each group is the same, and the interleaving within the group adopts the same interleaving pattern.

Preferably, if the number of symbols in each group is an even number, namely 2m, then the interleaving pattern is [x _m , x _m+1 ,..., x _2m , x ₁ , x ₂ ,..., x _m-1 ]; especially , when the number of symbols in each group is 4, the interleaving pattern is [2,4,1,3], that is, if the symbol group before interleaving is x ₁ , x ₂ , x ₃ , x ₄ , then the interleaving The following symbol groups are x ₂ , x ₄ , x ₁ , x ₃ ; when the number of symbols in each group is 6, the interleaving pattern is [3,5,6,2,3,1], that is, if the interleaving The symbol group before is x ₁ , x ₂ , x ₃ , x ₄ , x ₅ , x ₆ , and the symbol group after interleaving is x ₃ , x ₅ , x ₆ , x ₂ , x ₁ , x ₄ .

Preferably, the symbol interleaving in the step S4 adopts block interleaving or block interleaving with block-by-row cyclic shift.

Further, the block interleaving of the block row cyclic shift includes the following steps:

S001. Write the sequence x to be interleaved into the symbol interleaver row by row to obtain the symbol sequence X in matrix form;

S002. Divide the symbol sequence X into a plurality of sub-blocks equally by column, wherein each sub-block performs row cyclic shift with different offsets to obtain a symbol sequence after row cyclic shift

S003, from the above symbol sequence Read the symbols column by column to get the interleaved symbol sequence

Preferably, in the step S002, each sub-block contains an integer number of OFDM symbols, and the offset address of each sub-block follows an arithmetic difference sequence.

Preferably, the step S003 is specifically: read down from the offset row, read the first row after reading the last row, and read until the previous row of the offset row to obtain the interleaved symbol sequence

Preferably, the row cyclic shift offset f _s in the step S002 is set to an arithmetic sequence of s, that is, f _s =δ·s, where δ is a positive integer, 0≤s<S, and S is a sub-block the number of .

Preferably, in the short interleaving mode: the number of symbol interleaver rows is 240, the number of columns is 4096, when the number of OFDM subcarriers is 4096, the row cyclic shift offset f _s =2s, 0≤ s<S, where S=16 represents the number of sub-blocks; when the number of OFDM subcarriers is 8192, f _s =4s, 0≤s<S, where the number of sub-blocks S=8; When the number of multiplexed subcarriers is 32768, f _s =8s, 0≤s<S, S=2;

In the long interleaving mode: the number of symbol interleaver rows is 480, and the number of columns is 4096. When the number of OFDM subcarriers is 4096, the row cyclic shift offset f _s =2s, 0≤s<S , where the number of sub-blocks S=32; when the number of OFDM subcarriers is 8192, f _s =4s, 0≤s<S, S=16; when the number of OFDM subcarriers is 32768 , f _s =8s, 0≤s<S, S=4.

The present invention is set forth below with specific embodiment:

As shown in Figure 2, a typical OFDM system includes: the information bits to be transmitted form a symbol stream after channel coding, bit interleaving, and constellation mapping. go out. Symbol interleaving and symbol deinterleaving at the receiving end play an important role in an OFDM system, which is responsible for breaking the time/frequency block fading into random fading in the OFDM system, creating the required discrete memory-free conditions for channel coding, and increasing the time / frequency diversity gain. The present invention adopts the signal space diversity technology at the same time. Compared with the traditional symbol interleaving, the separation, interleaving and recombination of the I/Q signal after the constellation mapping are newly added, and the purpose is to further break up the I/Q signal and increase signal space diversity gain. As shown in Figure 3, the overall process of an embodiment of the present invention is as follows:

S1. IQ separation step: divide the complex symbol sequence to be transmitted into a real part and an imaginary part, that is, in-phase (I) and quadrature (Q) two-way symbol sequences;

S2. Group interleaving step of single-way symbol sequence: keep the I (or Q) way symbol sequence unchanged, divide the Q (or I) way symbol sequence into several groups in turn, and perform intra-group interleaving in each group;

S3. IQ merging step: recombining the uninterleaved I (or Q) channel symbols and the interleaved Q (or I) channel signals in step S2 into a new complex symbol sequence, which is called the first complex symbol sequence;

S4, complex symbol sequence interleaving step: performing symbol interleaving on the first complex symbol sequence obtained in step S3 to obtain a second complex symbol sequence;

S5. Perform OFDM modulation on the second complex symbol sequence.

Wherein, in step S2, the number of symbols in each group is the same, and the same interleaving pattern is used for intra-group interleaving.

Among them, when the number of symbols in each group is 4, the interleaving pattern is [2,4,1,3], that is, if the I (or Q) path symbol group before interleaving is x ₁ , x ₂ , x ₃ , x ₄ , then the interleaved symbol groups are x ₂ , x ₄ , x ₁ , x ₃ . Figure 3 shows the effect before and after its IQ interleaving. The symbol stream after constellation mapping is divided into groups of four, let a certain group of signals be s=(s ₁ , s ₂ , s ₃ , s ₄ ), and separate s into I/Q two-way signals, namely with Keeping the signal of channel I unchanged, the signal of channel Q is interleaved according to the pattern [2, 4, 1, 3] to obtain I channel signal and the interleaved Q-channel signal recombine into Used for subsequent symbol interleaving.

Generally, if the number of symbols in each group of IQ interleaving is an even number, set to 2m, the preferred interleaving pattern is [x _m , x _m+1 ,..., x _2m , x ₁ , x ₂ ,..., x _m-1 ] .

The symbol interleaving in step S4 adopts block interleaving or block interleaving of block row cyclic shift; the block interleaving of block row cyclic shift includes the following steps:

S001, row-by-row writing step: write the pre-interleaved sequence x into the symbol interleaver row by row to obtain the symbol sequence X in matrix form;

Let the interleaved sequence of input symbols be x=(x ₀ , x ₁ ,...,x _M×N-1 ), write row by row, and obtain matrix form X={X _{i, j} }, where X _{i, j} represent the matrix The elements of the i-th row and j-column of X, 0≤i<M, 0≤j<N, so Xi _{, j} = x _i×N+j ; M represents the number of rows of the symbol interleaver, and N represents the number of symbol interleaver number of columns.

S002, block row cyclic shift step: divide X into several sub-blocks by column, each sub-block performs row cyclic shift with different offsets, and obtains the symbol sequence after row cyclic shift

Let the least common multiple of M and N _OFDM be G, and M×G ₁ =N _OFDM ×G ₂ =G, wherein G ₁ is a factor of N, G ₂ is a factor of T and N/G ₁ =T/G ₂ = S, N _OFDM represents the number of effective subcarriers of OFDM; the matrix X is divided into a sub-matrix by every G ₁ column, and there are S sub-matrix blocks in total, which are denoted as X=[X ⁽⁰⁾ , ..., X ^{(S-1 )} ], where X ^{(s) is} called a sub-block, 0≤s<S; the sub-block X ^(s) is cyclically shifted by row, that is, is a row vector of length G ₁ , representing the i-th row of X ^(s) , 0≤i<M, and X ^(s) is cyclically shifted downward by f _s to get which is Where j=mod(i+Mf _s , M), 0≤i<M, express In the i-th line, mod(a, b) means taking the remainder of a modulo b; get the matrix after the sub-block cyclic shift Wherein the cyclic shift offset f _s , 0≤s<S is a preset value.

S003, read step by column: sequentially from Read out column by column to get the interleaved symbol sequence

by column from Read N _OFDM symbols sequentially in order for OFDM modulation.

Wherein, in step S002, each sub-block includes an integer number of OFDM symbols.

Wherein, the offset f _s is usually set as an arithmetic sequence of s, that is, f _s =δ·s, where δ is a positive integer.

In the short interleaving mode: the number of symbol interleaver rows is 240, and the number of columns is 4096. When the number of OFDM subcarriers is 4096, the row cyclic shift offset f _s =2s, 0≤s<S , where S=16 represents the number of sub-blocks; when the number of OFDM subcarriers is 8192, f _s =4s, 0≤s<S, where the number of sub-blocks S=8; when OFDM When the number of subcarriers is 32768, f _s =8s, 0≤s<S, S=2;

In the long interleaving mode: the number of symbol interleaver rows is 480, and the number of columns is 4096. When the number of OFDM subcarriers is 4096, the row cyclic shift offset f _s =2s, 0≤s<S , where the number of sub-blocks S=32; when the number of OFDM subcarriers is 8192, f _s =4s, 0≤s<S, S=16; when the number of OFDM subcarriers is 32768 , f _s =8s, 0≤s<S, S=4.

Fig. 5 is a structural diagram of the interleaving device of the present invention, and the present invention also provides an interleaving device in an OFDM system, the device comprising:

An in-phase/orthogonal signal separator, which is used to divide the complex symbol sequence to be transmitted into in-phase and quadrature two-way symbol sequences;

A single-path symbol sequence block interleaver, connected to the in-phase/orthogonal signal separator, is used to divide the above-mentioned in-phase or orthogonal single-path symbol sequences into multiple groups in turn, and each group is interleaved within the group;

A signal combiner, connected to the single-way symbol sequence block interleaver, used to recombine the non-interleaved in-phase or orthogonal symbol sequence and another interleaved symbol sequence into a new complex symbol sequence;

A symbol interleaver, connected to the signal combiner, is used to perform symbol interleaving on the above recombined new complex symbol sequence.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and replacements can also be made, these improvements and replacements It should also be regarded as the protection scope of the present invention.

Claims (8)

1. the deinterleaving method in a kind of ofdm system, it is characterised in that comprise the following steps：

S1, complex symbol series to be transmitted are divided into real part and imaginary part, i.e., same to phase, orthogonal two-way symbol sebolic addressing；

S2, holding are described constant with phase or positive cross-channel symbol sebolic addressing, and another road symbol sebolic addressing is divided into multigroup successively, and every group is carried out Interweave in group；

S3, the same phase not interweaved in step S2 or orthogonal symbols sequence are reassembled into another road symbol sebolic addressing after interweaving New complex symbol series, claim the first complex symbol series；

S4, symbol interleaving is carried out to first complex symbol series, obtain the second complex symbol series；

S5, OFDM modulation is carried out to second complex symbol series；

Symbol interleaving in the step S4 uses the block interleaving of piecemeal row cyclic shift；

The block interleaving of the piecemeal row cyclic shift is comprised the steps of：

S001, will treat that interleaved sequence x is write in symbol interleaver line by line, obtain the symbol sebolic addressing X of matrix form；

S002, the symbol sebolic addressing X is divided into multiple sub-blocks by row, wherein each sub-block carries out the row circulation of different side-play amounts Displacement, obtains the symbol sebolic addressing after row cyclic shift

S003, from above-mentioned symbol sebolic addressingIn read symbol by column, the symbol sebolic addressing after being interweaved

2. the method for claim 1, it is characterised in that identical per group code number in the step S2, in described group Interweave and use identical intertexture pattern.

3. method as claimed in claim 2, it is characterised in that it is even number, i.e. 2m per group code number to make described, then intersection chart Sample is [x_m, x_m+1..., x_2m, x₁, x₂..., x_m-1]；When every group code number is 4, intertexture pattern is [2,4,1,3], i.e., If the set of symbols before order interweaves is x₁, x₂, x₃, x₄, then the set of symbols after interweaving is x₂, x₄, x₁, x₃；When described per group code number For 6 when, intertexture pattern be [3,5,6,2,3,1], even order interweave before set of symbols be x₁, x₂, x₃, x₄, x₅, x₆, then after interweaving Set of symbols be x₃,x₅,x₆,x₂,x₃,x₁。

4. the method for claim 1, it is characterised in that in the step S002, each sub-block is orthogonal comprising integer Frequency division multiplexing symbol, the offset address of each sub-block obeys arithmetic sequence.

5. the method for claim 1, it is characterised in that the step S003 is specially：Down read since offset row, The first row is read again after reading last column, and reads the previous row of offset row always, the symbol sebolic addressing after being interweaved

6. the method for claim 1, it is characterised in that the row cyclic shift amount f in the step S002_sSet It is the arithmetic progression of s, i.e. f_s=δ s, wherein δ are positive integer, and 0≤s≤S, S are the number of sub-block.

7. method as claimed in claim 6, it is characterised in that in short delivery knits pattern：Symbol interleaver line number is 240, row Number is 4096, when OFDM sub-carrier number is 4096, row cyclic shift amount f_s=2s, 0≤s ＜ S, wherein S =16 represent sub-block number；When OFDM sub-carrier number is 8192, f_s=4s, 0≤s ＜ S, wherein sub-block number S=8； When OFDM sub-carrier number is 32768, f_s=8s, 0≤s ＜ S, S=2；

In intertexture pattern long：Symbol interleaver line number is 480, and columns is 4096, when OFDM sub-carrier number is When 4096, row cyclic shift amount f_s=2s, 0≤s ＜ S, wherein sub-block number S=32；When OFDM sub-carrier number For 8192 when, f_s=4s, 0≤s ＜ S, S=16；When OFDM sub-carrier number is 32768, f_s=8s, 0≤s ＜ S, S =4.

8. the interlaced device in a kind of ofdm system, it is characterised in that the device includes：

Inphase/orthogonal demultiplexer, for complex symbol series to be transmitted to be divided into same phase, orthogonal two-way symbol sebolic addressing；

Single channel symbol sebolic addressing Block Interleaver, is connected with the inphase/orthogonal demultiplexer, for will it is above-mentioned with mutually or it is orthogonal Single channel symbol sebolic addressing is divided into multigroup successively, and every group interweave in group；

Signal combiner, is connected with the single channel symbol sebolic addressing Block Interleaver, for by the same phase or orthogonal symbols that do not interweave Sequence is reassembled into new complex symbol series with another road symbol sebolic addressing after interweaving；

Symbol interleaver, is connected with the signal combiner, for entering to the above-mentioned new complex symbol series being reassembled into Row symbol interleaving；

The symbol interleaving uses the block interleaving of piecemeal row cyclic shift；

The block interleaving of the piecemeal row cyclic shift is comprised the steps of：

S001, will treat that interleaved sequence x is write in symbol interleaver line by line, obtain the symbol sebolic addressing X of matrix form；

S002, the symbol sebolic addressing X is divided into multiple sub-blocks by row, wherein each sub-block carries out the row circulation of different side-play amounts Displacement, obtains the symbol sebolic addressing after row cyclic shift

S003, from above-mentioned symbol sebolic addressingIn read symbol by column, the symbol sebolic addressing after being interweaved