JP3212732B2 - Receiver and communication system including the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a convolutional code as an error correction code and a differential phase shift keying (PSK) as a modulation method.
The present invention relates to a communication system using ft Keying modulation and a receiver applied to the communication system.

[0002]

2. Description of the Related Art For a receiver applied to a communication system using a conventional convolutional code and differential PSK modulation, see, for example, the document "Study of Soft Decision Viterbi Decoding in π / 4 Shift QPSK Baseband Differential Detection" (Bi Hosatsu, Matsuoka, Yamamoto, Onishi, Makimoto, 1991 IEICE Autumn Conference, B-235). Less than,
The prior art will be described with reference to the drawings.

FIG. 19 shows a conventional convolutional code and differential PS.
1 is a configuration diagram showing a configuration of a communication system using K modulation, in which 100 is a transmitter, 110 is a convolutional encoder, 120 is an assignment circuit, 130 is a differential encoder, and 140 is a differential encoder.
Is a phase modulator, 200 is a receiver, 210 is a phase delay detector, 220 is a phase soft decision circuit, and 230 is a Viterbi decoder.

Next, the operation will be described. Transmitter 100
, The transmission data sequence {a _i } (a _i ∈ ｛0,
1｝; i is a natural number that increases every symbol period) is convolutionally encoded by the convolutional encoder 110. Now, the convolutional encoder 110 performs coding at a coding rate R = １ ／,
For the i-th transmission data a _i , p _i , q _i (p _i ,
and outputs an q _i ∈ {0,1}) becomes 2 bits of convolutional encoded data. The output convolutionally encoded data (p _i , q _i ) is input to assignment circuit 120. The convolutional encoded data (p _i , q _i ) from the assignment circuit 120
, A transmission differential phase Δθ _i is output. Here, it is assumed that differential four-phase PSK modulation is used as a modulation method, and correspondence between convolutionally encoded data (p _i , q _i ) and transmission differential phase Δθ _i is as shown in Table 1 below. I do.

[0005]

[Table 1]

The transmission differential phase Δθ _i output from the assignment circuit 120 is input to a differential encoder 130. Differential encoder 130 differentially encodes transmission differential phase [Delta] [theta] _i according to the following equation, and outputs the transmission signal phase theta _i. Note that the initial value θ ₀ of the transmission signal phase is θ ₀ = π / 4.

[0007]

(Equation 1)

The transmission signal phase θ _i output from the differential encoder 130 is input to the phase modulator 140 and the transmission signal s _i = Aexp (−jθ _i ) (A>), which is a differential PSK signal.
0) is output.

On the other hand, in the receiver 200, the received signal
r _i

[0010]

(Equation 2)

Is input to a phase delay detector 210, and a phase delay detection signal θ _{(1) i} is output. Here, θ _{(1) i} is given by the following equation.

[0012]

(Equation 3)

That is, the phase delay detection signal θ _{(1) i} is obtained by subtracting the reception signal phase θ _{(0) i-1} one symbol period before from the phase θ _{(0) i} of the current reception signal r _i. . The phase delay detection signal θ _{(1) i} is input to the phase soft decision circuit 220,
₍₁₎ phase soft decision data x _i according to the value of _i, y _i is output. Here, x _i and y _i are phase soft decision data corresponding to the convolutionally encoded data p _i and q _i , respectively. Also,
Here, it is assumed that for 8-valued soft decision phase delay detection signal θ _{(1) i} and the phase soft decision data (x _i, y _i) corresponding to the assumed that as shown in the following Table 2.

[0014]

[Table 2]

The phase soft decision data (x _i , y _i ) outputted from the phase soft decision circuit 220 is inputted to the Viterbi decoder 230. Viterbi decoder 230 decodes the phase soft decision data (x _i, y _i) by the Viterbi decoding method is a convolutional code decoding method using the Viterbi algorithm, corresponding to the transmission data a _i

[0016]

(Equation 4)

Is output. Since the Viterbi decoding method is described in, for example, the document “Code Theory” (Imai, IEICE, 1990), the detailed description is omitted.

[0018]

As described above, in the conventional communication system using the convolutional code and the differential PSK modulation, the receiver 200 obtains only one kind of the phase delay detection signal θ _{(1) i.} Phase soft decision data (x _i , y
_i ) only

[0019]

(Equation 5)

Has been determined. For this reason, the error correction capability of the convolutional code cannot be fully utilized due to the occurrence of an error peculiar to the differential detection scheme. Therefore, the bit error rate of the receiver 200 (hereinafter abbreviated as BER; Bit Error)
r Rate) is inferior, and it is difficult to perform highly reliable communication.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a receiver which can effectively utilize the error correction capability of a convolutional code and can realize a good BER characteristic. It is another object of the present invention to provide a communication system using a convolutional code and differential PSK modulation that can perform highly reliable communication by including the receiver.

[0022]

A communication system according to the present invention comprises a convolutional coding means for performing convolutional coding on transmission data, and a convolutional coding data output from the convolutional coding means. Allocating means for converting to a dynamic phase, differential encoding means for differentially encoding a transmission differential phase output from the allocating means, and outputting the result as a transmission signal phase, and transmission output from the differential encoding means A transmitter having phase modulation means for generating and outputting a transmission signal which is a differential phase shift keying modulation signal based on the signal phase, and a current reception signal and 1, 2, ..., N (N is 2 or more) , N, which is a phase difference from the received signal before the symbol period, and a multi-delay detection means for generating a N-symbol delayed detection signal, and a phase trellis diagram based on a change in the transmission differential phase. The multiple delay detection circuit And a sequence estimation means for generating a branch metric from the output 1, 2,..., N symbol differential detection signal, estimating transmission data by a Viterbi algorithm, and outputting an estimation result as reception data. It is like that.

Also, convolutional encoding means for convolutionally encoding transmission data, allocating means for converting convolutionally encoded data output from the convolutional encoding means to transmission differential phase, and allocating means A differential encoding means for differentially encoding a transmission differential phase output from the differential encoding means and outputting the modulated differential phase as a modulation phase, and rearranging the order of the modulation phase output from the differential encoding means based on a predetermined rule, A transmitter including interleaving means for outputting as a phase, and phase modulation means for generating and outputting a transmission signal that is a differential phase shift keying modulation signal based on a transmission signal phase output from the interleaving means; and Phase detecting means for detecting and outputting the phase of the signal; and rearranging the order of the received signal output from the phase detecting means based on a predetermined rule, and outputting as a detection phase. .., N (where N is an integer equal to or greater than 2) and a 1, 2,..., N-symbol delayed detection signal that is a difference between the current detection phase and the detection phase before the symbol period. Using a multi-delay detection means and a phase trellis diagram based on a change in a transmission differential phase, branch metrics are generated from 1, 2,..., N-symbol differential detection signals output from the multi-delay detection circuit, and a Viterbi algorithm And a sequence estimating means for estimating transmission data according to the above and outputting the estimation result as reception data.

[0024]

In the receiver of the communication system according to the present invention,
The multiple delay detection means generates 1, 2,..., N symbol differential detection signals, and the sequence estimating means determines received data using N types of differential detection signals output from the multiple delay detection means. By doing so, the BE of the conventional communication system which determines the reception data using only the phase soft decision data obtained from only one kind of differential detection signal is BE
The R characteristic is improved.

In the transmitter of the communication system according to the present invention, the interleaving means rearranges the order of the modulation phase outputted from the differential encoding means and outputs the result to the phase modulation means. The received signal output from the phase detector is rearranged in order and output to the multiplexed delay detector. By doing this,
When interleaving is not performed, it is possible to perform suitable interleaving for preserving the relationship established between 1, 2,..., N symbol differential detection signals output from the multiple differential detection means, and to perform burst error communication such as a fading communication path. The BER characteristics on the road are improved.

[0026]

[Embodiment 1] The first embodiment will be described below with reference to the drawings. FIG.
FIG. 2 is a configuration diagram illustrating an example of a configuration of a transmitter in the communication system according to the first embodiment. In the diagram, 132 is an adder modulo 2π, and 134 is a delay element having a delay time equal to one symbol period (hereinafter, “1”). A symbol delay element). Note that the same or corresponding parts as those in FIG. 19 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 2 shows the transmitter 10
FIG. 3 is a configuration diagram showing an example of the configuration of a convolutional encoder 110 within 0, in which 112 and 114 are one-symbol delay elements, and 116 and 118 are adders modulo 2.

FIG. 3 is a configuration diagram showing an example of the configuration of a receiver in the communication system according to the first embodiment. In FIG. 3, reference numeral 300 denotes a receiver, 310 denotes a multiplex delay detection circuit, and 320 denotes one-symbol delay detection. 321 is a one symbol delay element, 322 is a phase comparator, 331 and 332 are 1
The symbol delay elements 335 and 336 are adders modulo 2π, and 340 is a sequence estimator. FIG.
FIG. 3 is a configuration diagram showing an example of the configuration of a sequence estimator 340 within 0, where 342 is a branch metric generation circuit, and 344 is addition, comparison, and selection (hereinafter abbreviated as ACS; Add-Comp).
are-select) circuit 346 is a path memory.

Next, the operation will be described. First, the operation of the transmitter 100 will be described with reference to FIGS. In transmitter 100 shown in FIG. 1, transmission data sequence {a _i }
(A _i {0, 1}; i is a natural number) is the convolutional encoder 11
0 is convolutionally coded. In the present embodiment, as shown in FIG.
It is assumed that the convolutional encoder is composed of adders 116 and 118 modulo 12, 114 and 2, and has a constraint length K = 3 and a coding rate R = 1/2. Here, assuming that the coded data output from the adders 116 and 118 when the i-th transmission data a _i is input to the convolutional encoder 110 are p _i and q _i , respectively, p _i , generator polynomial G _{1 of} q _i
(X) and G ₂ (x) are given by the following equations, respectively.

[0029]

(Equation 6)

The convolutionally encoded data (p _i , q _i ) output from convolutional encoder 110 is input to assignment circuit 120. Assignment circuit 120 outputs transmission differential phase Δθ _i according to the value of convolutionally encoded data (p _i , q _i ). Here, it is assumed that the differential four-phase PSK modulation is used as the modulation method, and the correspondence between the convolutionally encoded data (p _i , q _i ) and the transmission differential phase Δθ _i is as shown in Table 3 below. I do.

[0031]

[Table 3]

The transmission differential phase Δθ _i output from the assignment circuit 120 is input to the differential encoder 130. The differential encoder 130 includes an adder 132 modulo 2π and a one-symbol delay element 134, performs differential encoding represented by the following equation, and outputs a transmission signal phase θ _i .

[0033]

(Equation 7)

The transmission signal phase θ _i output from the differential encoder 130 is input to the phase modulator 140, and the differential four-phase PS
Transmission signal s _i = Aexp (−jθ _i ) which is a K signal
(A> 0) is output.

Next, the receiver 30 will be described with reference to FIGS.
The operation of 0 will be described. In the receiver 300 shown in FIG. 3, the received signal r _i

[0036]

(Equation 8)

Is input to a one-symbol differential detector 320 in the multiple differential detector 310. In the present embodiment, the one-symbol delay detector 320 includes a one-symbol delay element 321 and a phase comparator 322. The phase comparator 322 compares the phase θ _{(0) i} of the current reception signal r _i with the reception signal r one symbol period earlier output from the one-symbol delay element 321.
Compared _i-1 of the phase theta and _{(0) i-1,} and outputs the result as one symbol differential detection signal theta _{(1) i.} That is, θ _{(1) i} is given by the following equation.

[0038]

(Equation 9)

Next, using the one-symbol delayed detection signal θ _{(1) i} , which is the phase difference between the current received signal output from the one-symbol delayed detector 320 and the received signal one symbol period earlier, the current received signal is used. Received signal and 2, ..., N (N is an integer of 2 or more)
2,..., N, which is the phase difference from the received signal before the symbol period
Generate a symbol differential detection signal. Hereinafter, the generation procedure will be described using mathematical expressions. Since the n (n is an integer of 2 or more) symbol differential detection signal θ _{(n) i} is a phase difference between the current reception signal and the reception signal n symbol periods before, it is expressed by the following equation.

[0040]

(Equation 10)

From equation [7] and equation [6], the following equation is established.

[0042]

[Equation 11]

Accordingly, the following recurrence formula that gives the n-symbol differential detection signal θ _{(n) i} holds.

[0044]

(Equation 12)

That is, by sequentially adding the one-symbol differential detection signals, 2,..., N-symbol differential detection signals can be generated. The number N of differential detection signals generated in the present invention is hereinafter referred to as the “maximum number of delayed symbols”. In the present embodiment, the maximum number of delayed symbols N = 3. Now, assuming that the one-symbol delay detector 320 outputs the one-symbol delay detection signal θ _{(1) i} , the one-symbol delay element 331 outputs θ _{(1) i−1} . Therefore, from the adder 335 modulo 2π, θ _{(1) i} + θ
_{(1) i-1} = θ _{(2) i} , that is, a two-symbol differential detection signal is output. Similarly, one-symbol delay element 332 outputs θ
_{(1) Since i-2} is output, an adder 336 modulo 2π
Output a θ _{(2) i} + θ _{(1) i−2} = θ _{(3) i} , that is, a three-symbol differential detection signal.

As described above, the phase difference symbols Θ _i = (θ _{(1) i} , θ _{(2) i} ,... ₎ Composed of the 1, 2,..., N symbol differential detection signals generated by the multiple delay detection circuit 310. θ
_{(N) i} ) is input to the sequence estimator 340. Sequence estimator 3
40 estimates a transmission data sequence {a _i } from the phase difference symbol sequence { _i }, and

[0047]

(Equation 13)

Is output.

[0049] Hereinafter, the method of estimating the transmitted data sequence {a _i} from the phase difference symbol sequence {theta _i} will be described with reference to FIG. A trellis diagram showing the transition of the internal state of the convolutional encoder 110 of FIG. 2 is shown in FIG. In FIG. 5, the state on the left side of the figure transits to the state on the right side.
For example, the state (0,0) and the state (1,0) transit to the state (0,0) and the state (0,1). The numbers attached to the branches indicating the state transition indicate the transmission data a _i input to the convolutional encoder 110 and the convolutional encoded data p _i , q _i output respectively. For example,
“0/11” added to the branch that transitions from the state (1, 0) to the state (0, 0) indicates the transmission data a _i and the convolutionally encoded data p _i , q _i when this state transition occurs. Is the value of
It shows that a _i = 0, p _i = 1, and q _i = 1, respectively.

By the way, in the transmitter 100, the convolutional encoded data p output from the convolutional encoder 110 is output.
_i , q _i and the transmission differential phase Δθ _i output from the assignment circuit 120 have a one-to-one correspondence.
It is represented by Therefore, a specific transmission differential phase Δθ _i corresponds to a state transition of the convolutional encoder 110. FIG. 6 shows a trellis diagram representing this correspondence. In FIG. 6, the numbers attached to the respective branches indicating the state transitions are the transmission data a _i input to the convolutional encoder 110 and the assignment circuit 1
20 shows a transmission differential phase Δθ _i output from the reference numeral 20.
For example, “0, π” added to the branch that transitions from state (1,0) to state (0,0) indicates the value of the transmission data a _i and the transmission differential phase Δθ _i when this state transition occurs. Indicate that a _i = 0 and Δθ _i = π, respectively.

Here, as shown in FIG. 7, the state (0,
0) and state (1,0) via state (0,0), and again via state (0,0), then state (0,0)
And state transition to state (0, 1). With this state transition, the value of the transmission differential phase Δθ _i output from the assignment circuit 120 changes from “0” and “π” to “0”, and then changes to “0” and “π”. 7
It is more obvious. Accordingly, if the combination of two temporally continuous transmission differential phases (Δθ _i−1 , Δθ _i ) is regarded as one state, FIG. 7 shows a state (0, 0) and a state (π, 0). Can be interpreted as representing a state transition from state to state (0, 0) and state (0, π).

At this time, the transition to the state (0, 0) corresponds to the transmission data a _i = 0, and the transition to the state (0, π) corresponds to the transmission data a _i = 1. Accordingly, FIG. 7 shows the state (Δθ _i−1 , Δθ _i ) when transmission data a _i is input.
_i ) It can be transformed into a trellis diagram showing the transition. FIG. 8 shows the result of such deformation. In FIG. 8, the numbers attached to the respective branches indicating the state transitions are the transmission data a _i input to the convolutional encoder 110 and the assignment circuit 1
20 shows a transmission differential phase Δθ _i output from the reference numeral 20.
For example, “1, π” added to the branch that transitions from the state (π, 0) to the state (0, π) is the value of the transmission data a _i and the transmission differential phase Δθ _i when this state transition occurs. Indicate that a _i = 1 and Δθ _i = π, respectively.

Similarly, focusing on the relationship between the transmission data a _i input to the convolutional encoder 110 and the transmission differential phase Δθ _i output from the assignment circuit 120, the state (Δθ _i
FIG. 9 is obtained as a trellis diagram showing all the transitions of _i−1 , Δθ _i ). In FIG. 9, the number attached to each branch indicating the state transition indicates the value of the transmission data a _i when the state transition occurs. Therefore, if the trellis diagram of FIG. 9 is used, the state (Δ
By estimating the transition of θ _i−1 , Δθ _i ), the value of the transmission data a _i can also be estimated.

It is assumed that a transition has occurred from the state (Δθ _i-2 , Δθ _i-1 ) to the state (Δθ _i-1 , Δθ _i ).
In this case, noise is not present in the communication path (i.e. the received signal r _i is equal to the transmission signal _{s i, θ (0) i} = θ i is satisfied), then the transmission differential phase [Delta] [theta] _i and 1 symbol differential detection The values of the signals θ _{(1) i} are equal. Therefore, in this case, the transmission differential phase and the 1, 2, or 3 symbol differential detection signals θ _{(1) i} , θ
_{(2) i} and θ _{(3) i} hold the following relationship.

[0055]

[Equation 14]

By utilizing this relationship, 1, 2, 2,
Phase difference symbol Θ _i = 3 symbol differential detection signal
(Θ _{(1) i} , θ _{(2) i} , θ _{(3) i} ) based on the state (Δθ
_i-2, the state from _{Δθ i-1) (Δθ i} -1, the transition to the [Delta] [theta] _i), thus estimating the value of the transmission data a _i.

In the present embodiment, sequence estimator 340 estimates transmission data sequence {a _i } from phase difference symbol sequence { _i } using the Viterbi algorithm based on the trellis diagram of FIG. To the received data sequence {a _i }
Output as The sequence estimator 340 of the present embodiment corresponds to the Viterbi decoder 230 of the conventional example in that the received data sequence {a _i } is output using the Viterbi algorithm. However, the conventional Viterbi decoder 230 receives only the phase soft decision data (x _i , y _i ) obtained from only one kind of phase delay detection signal, and uses the trellis diagram of the convolutional encoder 110 as well. Fig. 5 showing transition of internal state
It is. In contrast, the sequence estimator 34 in the present embodiment
0 is 1, 2, 2 output from the multiple delay detection circuit 310.
.., A phase difference symbol composed of N symbol differential detection signals
_i = (θ _{(1) i} , θ _{(2) i} ,..., θ _{(N) i} ), and the trellis diagram to be used is FIG. 9 showing a state transition in which the transmission differential phase Δθ _i is combined. Yes, completely different.

The operation of sequence estimator 340 will be described below. However, the sequence estimation method using the Viterbi algorithm is described in detail in the above-mentioned document “Code Theory” and the like, and will be briefly described here. As shown in FIG. 4, the sequence estimator 340 includes a branch metric generation circuit 342, an ACS circuit 344, and a path memory 346. The phase difference symbol Θ _i = output from the multiple delay detection circuit 310
(Θ _{(1) i} , θ _{(2) i} ,..., Θ _{(N) i} ) are input to the branch metric generation circuit 342 in the sequence estimator 340. Branch metric generating circuit 342 by using the phase difference symbol theta _i 9
Is generated for all the branches representing the state transitions shown in the trellis diagram of FIG. That is, when the phase difference symbol Θ _i = (θ _{(1) i} , θ _{(2) i} ,..., Θ _{(N) i} ) is input, the branch metric generation circuit 342 sets the arbitrary state Φ
_{From i-1} = (φi _{-N + 1} , φi _{-N + 2} , ..., φi _-1 ), the state Φ
λ (Φ given by the following equation as a branch metric for a branch transitioning to _i = (φ _{i−N + 2} , φ _{i−N + 3} ,..., φ _i )
_i−1 , Φ _i | Θ _i ).

[0059]

(Equation 15)

The branch metric output from the branch metric generation circuit 342 is input to the ACS circuit 344. AC
The S circuit 344 adds the branch metric of the branch transitioning from the state to the path metric of the surviving path to each state, compares the addition results of the paths transitioning to the same state, and determines the path having the smallest value of the addition result. A path is selected as a new surviving path, an ACS operation is performed with the minimum addition result as a new path metric, and the path metric is sequentially updated. The ACS circuit 344 outputs information indicating the branch selected in the ACS operation and the value of the transmission data a _i corresponding to the selected branch to the path memory 346. The path memory 346 stores the input value and stores the storage contents corresponding to the surviving path having the minimum path metric.

[0061]

(Equation 16)

Is output.

As described above

[0064]

[Equation 17]

By determining the above, the receiver 300 of the communication system according to the present invention exhibits better BER characteristics than the receiver 200 of the conventional example. This is shown by computer simulation results. FIG. 10 is a characteristic diagram showing BER characteristics of the receiver 300 of the communication system according to the present invention and the receiver 200 of the conventional example by computer simulation.
FIG. 10 shows that the BER characteristic of the present invention is 1d higher than the conventional example.
It is evident that B or more is improved. As described above, the receiver 300 of the communication system according to the present invention generates the 1, 2,..., N-symbol differential detection signal by the multiple delay detection circuit 310 and the multiple delay detection circuit by the sequence estimation unit 340.
Since the received data is determined using the N types of differential detection signals output from 310, the reception of the conventional communication system that determines the reception data using only the phase soft decision data obtained from only one type of differential detection signal is performed. BER from machine 200
The characteristics are improved.

As described above, in this embodiment, the convolutional coding means for convolutionally coding the transmission data, and the convolutional coding data output from the convolutional coding means are converted into the transmission differential phase. Allocating means, differential encoding means for differentially encoding a transmission differential phase output from the allocating means, and a differential encoding means for outputting as a transmission signal phase, based on a transmission signal phase output from the differential encoding means. A transmitter including phase modulation means for generating and outputting a transmission signal that is a differential phase shift keying modulation signal;
.., N (N is an integer of 2 or more) a multiplexed delay detection means for generating a 1, 2,... A branch metric is generated from the 1, 2,..., N-symbol differential detection signal output from the multiple delay detection circuit using a phase trellis diagram based on the above, and transmission data is estimated by a Viterbi algorithm, and the estimation result is used as reception data A receiver provided with a sequence estimating means for outputting.

Embodiment 2 FIG. In the first embodiment, the one-symbol delay detector 321 and the phase comparator 32
2, the configuration may be made up of a phase detector 326, a one-symbol delay element 327, and a subtractor 328 modulo 2π, as shown in FIG. 11, the phase detector 326 is the received signal r _i phase θ _{(0) i}
Is added with a constant δ of 0 or more and less than 2π modulo 2π. That is, the value of the output of the phase detector 326 is
_{Assuming i} , the following equation holds.

[0068]

(Equation 18)

The output ω _i of the phase detector 326 is input to one-symbol delay elements 327 and a subtracter 328 modulo 2π. Also, the output of the one symbol delay element 327 is 2π
Is input to a subtractor 328 modulo. Therefore, in the subtractor 328 modulo 2π, the current phase detector 32
From the output omega _i of 6 output from the 1-symbol delay element 321 one symbol period output omega _i-1 of the previous phase detector 326
Is subtracted. This subtraction result is obtained by the above equation [14].
Is expressed by the following equation.

[0070]

[Equation 19]

This value is nothing more than the one-symbol differential detection signal θ _{(1) i} which is the phase difference between the current reception signal given by the equation [6] and the reception signal one symbol period before. That is, the one-symbol differential detection signal θ _{(1) i} is output from the subtractor 328 modulo 2π.

Embodiment 3 FIG. Further, in the first embodiment, the maximum number N of delay symbols, that is, the number of differential detection signals generated by the multiple delay detection circuit 310 is N = 3, but the maximum number N of delay symbols is another value, for example, N = 4 or N = 5. In general, when the maximum number of delay symbols is N, a state in which (N-1) successively transmitted transmission differential phases are combined (Δθ _{i−N + 2} , Δθ _{i−N + 3} ,...) , Δθ _i ) can be estimated. This is obtained by the equation [8]
This is because the following equation holds as the relationship between the one-symbol differential detection signal θ _{(1) i} and the n-symbol differential detection signal θ _{(n) i} .

[0073]

(Equation 20)

[0074] As described above, if the noise in the communication channel does not exist, 1 symbol differential detection signal theta ₍₁₎ the value of _i is equal to the transmission differential phase [Delta] [theta] _i. That is, the n-symbol differential detection signal θ _{(n) i} is composed of n transmission differential phases ｛Δ
Equation [16] indicates that information about θ _{i−N + 1} , Δθ _{i−N + 2} ,..., Δθ _i } is included. Therefore, when the maximum number of delay symbols is N, the state (Δθ _{i−N + 1} ) in which (N−1) transmission differential phases that are continuous in time are combined in the same manner as in the first embodiment. , Δθ _{i-N + 2} ,…,
Δθ _i-1 ) to state (Δθ _{i-N + 2} , Δθ _{i-N + 3} , ..., Δ
θ _i ) can be estimated.

FIG. 12 shows an example of the configuration of receiver 300 when the maximum number of delayed symbols N = 4. In FIG. 12, a one-symbol delay detector 333 and an adder 337 modulo 2π are added to the multiple delay detector 310. With such a configuration, the one-symbol delay element 333 outputs the one-symbol delayed detection signal θ _{(1) i-3} three symbol periods earlier, so that the adder 337 modulo 2π outputs θ _{(3) i} + θ _{(1) i-3} = θ _{(4) i} , that is, a 4-symbol differential detection signal is output. Accordingly, the multiplexed delay detection circuit 310 outputs a phase difference symbol Θ _i = (θ _{(1) i} , θ ₎ composed of 1, 2, 3, and 4 symbol differential detection signals.
_{(2) i} , θ _{(3) i} , θ _{(4) i} ) are output. As described above, by setting the maximum number of delay symbols N = 4, a state in which three temporally continuous transmission differential phases are combined (Δθ
_i−2 , Δθ _i−1 , Δθ _i ) can be estimated. FIG. 13 shows a trellis diagram used in sequence estimator 340 in this case. By increasing the maximum number N of delay symbols, the BER characteristic of the receiver 300 is further improved. This is shown by computer simulation results. FIG. 14 is a characteristic diagram showing BER characteristics by computer simulation when the maximum number of delay symbols N = 4. As shown in FIG. 14, the BER characteristic is further increased by increasing the maximum number of delay symbols from N = 3 to N = 4.
It is clear that the gain is improved by about 4 dB.

Embodiment 4 FIG. Further, in the first embodiment, the convolutional encoder 110 has the constraint length K = 3 and the coding rate R = 1/2, but the constraint length K and the coding rate R are other values. For example, K = 4, K = 5, etc., and R = 2/3, R = 3/4, etc. Further, in the first embodiment, the modulation scheme using the differential four-phase PSK modulation is described. However, the modulation scheme may be another differential PSK modulation. Differential 8-phase PSK modulation may be used. As an example, a convolutional encoder having a constraint length K = 3 and a coding rate R = 2/3 composed of adders 118a modulating one-symbol delay elements 112a, 114a and 2 shown in FIG. FIG. 16 shows BER characteristics when the modulator 110 is used and differential 8-phase PSK modulation is used as a modulation method. However, FIG. 16 shows the result of computer simulation, and the correspondence between the convolutional encoded data (a _i , p _i , q _i ) and the transmission differential phase Δθ _i in the assignment circuit 120 is shown in Table 4 below. It is assumed to be as follows.

[0077]

[Table 4]

FIG. 16 clearly shows that the BER characteristics of the present invention are improved by about 2 dB as compared with the conventional example. As described above, even when the configuration and the modulation scheme of the convolutional encoder 110 are different, the present invention provides a better BE than the conventional example.
It is possible to realize the R characteristic.

Embodiment 5 FIG. Next, a configuration for performing interleaving in the present embodiment will be described. In a burst error channel such as a fading channel, a long burst error exceeding the error correction capability of an error correction code may occur.
For this reason, in such a burst error communication channel, even when error correction coding is performed, the BER characteristic is greatly deteriorated. In order to improve the BER characteristic, such a long burst error may be dispersed into short errors that the error correction code can correct. Interleaving is one of the techniques for dispersing such burst errors, and is usually performed by the following procedure. First, the transmitter rearranges the error-correction-coded data sequence according to a certain rule. This reordering operation is called interleaving, and the reordering device is called an interleaver. The interleaved error correction coded data is transmitted as a transmission signal by the modulator and transmitted. On the other hand, the receiver rearranges the demodulated data obtained by demodulating the received signal in a procedure reverse to the interleaving. This reverse reordering operation is called deinterleaving, and a reordering device is called a deinterleaver. Burst errors included in demodulated data are dispersed by the deinterleaving. Note that if only burst errors are to be dispersed, rearrangement may be performed only at the receiver, but in order to decode an error correction code, the data sequence input to the decoder must be transmitted at the transmitter. It must be in the same arrangement as the error correction coded data sequence before being interleaved. Therefore, by performing interleaving in the transmitter in advance, the deinterleaved demodulated data sequence returns to the correct arrangement in which error correction decoding can be performed at the same time as burst errors are dispersed. By decoding the deinterleaved demodulated data sequence by the decoder, the influence of burst errors is reduced and good BER characteristics are realized.

The interleaving is performed according to the above procedure. Therefore, in the conventional example, the interleaver is composed of the convolutional encoder 110 in the transmitter 100 and the assignment circuit 120.
, And the deinterleaver is inserted between the phase soft decision circuit 220 and the Viterbi decoder 230 in the receiver 200. When such a normal interleaving method is applied to the present invention, a deinterleaver is inserted between the multiple differential detection circuit 310 in the receiver 300 and the sequence estimator 340. However, when a deinterleaver is inserted at this position, the phase difference symbols Θ _i = (θ _{(1) i} , θ _{(2) i} ,..., Θ _{(N) i} ) output from the multiple delay detection circuit 310 are rearranged. And input to the sequence estimator 340. Due to this rearrangement, in the sequence estimator 340, Expression [16], which is a relational expression between the one-symbol differential detection signal θ _{(1) i} and the n-symbol differential detection signal θ _{(n) i} , does not hold. As described above, Expression [16] is a precondition for estimating a state transition of a state combining temporally continuous transmission differential phases. If Expression [16] does not hold, correct estimation of the state transition is performed. Becomes impossible. Therefore, when a normal interleaving method is applied to the present invention and a deinterleaver is inserted between multiple delay detection circuit 310 and sequence estimator 340, estimation of transmission data sequence {a _i } by sequence estimator 340 is incorrect. And the BER characteristic is rather deteriorated.

In this embodiment, such a problem does not occur, that is, even in the sequence estimator 340, the equation [16]
Is provided. Hereinafter, a fifth embodiment will be described with reference to the drawings. FIG.
7 is a configuration diagram illustrating an example of a configuration of a transmitter in the communication system according to the fifth embodiment. In the drawing, reference numeral 410 denotes an interleaver. FIG. 18 is a configuration diagram illustrating an example of a configuration of a receiver in the communication system according to the fifth embodiment. In the drawing, reference numeral 310a denotes a multiple delay detection circuit;
0 is a phase detector, 430 is a deinterleaver, and 440 is 1
The symbol delay element 450 is an adder modulo 2π. 17 and FIG. 18, FIG. 3, FIG.
The same or corresponding parts as those in FIG. 19 are denoted by the same reference numerals, and description thereof will be omitted.

Next, the operation will be described. First, FIG.
The operation of the transmitter 100 will be described with reference to FIG. In transmitter 100 shown in FIG. 17, transmission data sequence {a _i } (a _i
{0, 1}; i is a natural number) is convolutionally encoded by the convolutional encoder 110. Now, the convolutional encoder 110
In the same manner as in Example 1 constraint length K = 3, convolutional encoder with a coding rate R = 1/2, p against the i-th transmission data a _i
i , q _i (p _i , q _i ∈ {0, 1}), and outputs 2-bit convolutionally encoded data. The output convolutionally encoded data (p _i , q _i ) is input to assignment circuit 120. Allocation circuit 120 outputs the transmission differential phase [Delta] [theta] _i based on the value of the convolutional coded data (p _i, q _i). The output transmission differential phase Δθ _i is
Input to 0. Differential encoder 130 differentially encodes transmission differential phase [Delta] [theta] _i according to the following equation, and outputs the modulation phase theta _i. Note that the initial value θ ₀ of the modulation phase is the transmission differential phase Δθ _i
Is one of the possible values of

[0083]

(Equation 21)

The modulation phase θ _i output from differential encoder 130 is input to interleaver 410. Interleaver 410 rearranges the order of modulation phase sequence {θ _i } based on a predetermined rule, and sets transmission signal phase sequence { _k } (k is 0
Integer). Here, the sorting rule is represented by a function F [•]. That is, the modulation phase sequence {θ _i ｝
Of the transmission signal phase sequence { _k }
Is located at the F [m] -th position. Therefore, the following relationship is established.

[0085]

(Equation 22)

The transmission signal phase ψ _k output from interleaver 410 is input to phase modulator 140, and differential PSK
Transmission signal s _k = Aexp (−jψ _k ) (A
> 0) is output.

Next, the operation of the receiver 300 will be described with reference to FIG.
Will be described. In the receiver 300 shown in FIG.
Signal r _k

[0088]

(Equation 23)

Is input to the phase detector 420. Phase detection
Can 420 a 2π modulo the phase ψ _{(0) k} of the received signal r _k
And outputs a value obtained by adding a constant δ of 0 to less than 2π. sand
KazuSatoshi, when the value of the output of the phase detector 420 and xi] _k, the following
The equation holds.

[0090]

(Equation 24)

The output ξ _k of the phase detector 420 is input to the deinterleaver 430. The deinterleaver 430 rearranges the order of the output sequence { _k } of the phase detector 420 in the reverse procedure to that of the interleaver 410, and detects the detection phase sequence {ω
Convert to _i ｝ and output. Here, the interleaver 410
The inverse function of the function F [•] that represents the sorting rule of
[•]. That is, the following equation is satisfied.

[0092]

(Equation 25)

At this time, it is clear that the rule for rearranging the deinterleaver 430 is represented by the function G [•]. Therefore, the following relationship is established.

[0094]

(Equation 26)

The detection phase ω _i output from the deinterleaver 430 is input to the multiple delay detection circuit 310a.
In the multiplex delay detection circuit 310a, the detection phase ω _i is calculated by the one-symbol delay elements 440 and the subtracter 45 modulo 2π.
Input to 0. The output of the one-symbol delay element 440 is also input to a subtractor 450 modulo 2π. Accordingly, the subtractor 450 modulo 2π subtracts the detection phase ω _i−1 one symbol period before output from the one-symbol delay element 321 from the current detection phase ω _i .
The subtractor 450 modulo 2π outputs the result of the subtraction as a one-symbol differential detection signal θ _{(1) i} . Therefore, the following equation is established.

[0096]

[Equation 27]

[0097] Now, the noise is not in the communication path, i.e. consider the case where the received signal r _k is equal to the transmission signal s _k.
This time is clearly _{ψ (0) k = ψ k} , therefore, the following relationship from equation [21] is satisfied.

[0098]

[Equation 28]

In the equation [23], if k = F [i], the following equation is established from the equation [20].

[0100]

(Equation 29)

The following equation is obtained by substituting equation [18] into equation [24].

[0102]

[Equation 30]

The following equation is obtained from Equations [22] and [25].

[0104]

(Equation 31)

Further, the following expression is obtained from Expressions [17] and [26].

[0106]

(Equation 32)

[0107] That is, similarly as in Example 1 in the present embodiment, when the noise in the communication channel does not exist, 1 symbol differential detection signal theta _{(1) i} is equal to the transmission differential phase [Delta] [theta] _i.

From the 1-symbol delayed detection signal θ _{(1) i} output from the subtractor 450 modulo 2π, in the same manner as in the first embodiment, adders modulo 1-symbol delay elements 331, 332 and 2π With 335 and 336, a two-symbol differential detection signal θ _{(2) i} and a three-symbol differential detection signal θ _{(3) i} are generated. The phase difference symbol Θ _i = (θ _{(1) i} , θ _{(2) i} , θ _{(3) i} ) composed of the 1, 2, and 3 symbol differential detection signals generated by the multiplex differential detection circuit 310a in this manner.
Is input to the sequence estimator 340. Sequence estimator 340
Is calculated from the phase difference symbol sequence { _i } based on the Viterbi algorithm in the same manner as in the first embodiment.
_i推定 is estimated, and the estimation result is represented by a received data sequence {a _i } (a
_i {0, 1}).

As described above, in the present embodiment, the transmitter 100 is configured to include the interleaver 410 between the differential encoder 130 and the phase modulator 140, and correspondingly, the receiver 300 is provided with the phase detector 420 And multiple delay detection circuit 31
0a, a deinterleaver 430 is provided. With such a configuration, unlike the case where a normal interleaving method is applied, sequence estimator 340
, A suitable interleave that satisfies Expression [16], which is a relational expression between the one-symbol differential detection signal θ _{(1) i} and the n-symbol differential detection signal θ _{(n) i} , can be performed.
Good BER characteristics can be realized even in burst error communication paths such as fading communication paths.

As described above, in this embodiment, the convolution coding means for convolutionally coding the transmission data and the convolution coding data output from the convolution coding means are converted into the transmission differential phase. Allocating means for performing differential encoding of a transmission differential phase output from the allocating means and outputting the modulated differential phase as a modulation phase, and a predetermined order of the modulation phase output from the differential encoding means. Interleaving means for rearranging according to the rule of, and outputting as a transmission signal phase, and phase modulation means for generating and outputting a transmission signal that is a differential phase shift keying modulation signal based on the transmission signal phase output from the interleaving means. A transmitter and a phase detector that detects and outputs the phase of the received signal, and rearranges the order of the received signal phase output from the phase detector based on a predetermined rule, A deinterleaving means for outputting as a wave phase current detection phase and 1, 2, which is the difference between N (N is an integer of 2 or more) symbol periods previous detection phase 1,
2,..., N symbol using a multi-delay detection means for generating a differential detection signal and a phase trellis diagram based on a change in a transmission differential phase, the output of the multi-delay detection circuit being 1, 2, 2,
.., A branch metric is generated from the N-symbol differential detection signal, transmission data is estimated by a Viterbi algorithm, and a sequence estimation means for outputting an estimation result as reception data is provided.

Embodiment 6 FIG. In the fifth embodiment, the maximum number N of delay symbols, that is, the number of differential detection signals generated by the multiple delay detection circuit 310a is N = 3, but the maximum number N of delay symbols is another value, for example, N = 4 or N = 5. In the fifth embodiment, the convolutional encoder 1
Although the constraint length K = 3 and the coding rate R = 1/2 are shown as 10, the constraint length K and the coding rate R may be other values, for example, K = 4 or K = 5. , R = 2/3 or R =
3/4 may be used. Further, in the fifth embodiment, the modulation scheme using differential four-phase PSK modulation is described. However, the modulation scheme may be another differential PSK modulation, such as differential two-phase PSK modulation or Differential 8-phase PSK modulation may be used.

[0112]

As described above, according to the present invention, the receiver can effectively utilize the error correction capability of the convolutional code to obtain a good B signal.
A communication system using a convolutional code and differential PSK modulation that can realize ER characteristics and can perform highly reliable communication can be obtained.

Further, according to the present invention, suitable interleaving can be performed, and the BER characteristic of the receiver in a burst error channel such as a fading channel is improved. A communication system using a convolutional code capable of performing communication and differential PSK modulation can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of a configuration of a transmitter 100 in a communication system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an example of a configuration of a convolutional encoder 110 in the transmitter 100 in the communication system according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram illustrating an example of a configuration of a receiver 300 in the communication system according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a configuration of a sequence estimator 340 in the receiver 300 in the communication system according to the first embodiment of the present invention.

FIG. 5 is a trellis diagram illustrating an example of a trellis structure of a convolutional code in the communication system according to the first embodiment of the present invention.

FIG. 6 is a trellis diagram illustrating an example of a case where a value of a transmission differential phase is reflected in a trellis structure of a convolutional code in the communication system according to the first embodiment of the present invention.

FIG. 7 is a state transition diagram illustrating an example of state transition of a convolutional code and a transmission differential phase in the communication system according to the first embodiment of the present invention.

FIG. 8 is a state transition diagram illustrating an example of a state transition of a state obtained by combining transmission differential phases in the communication system according to the first embodiment of the present invention.

FIG. 9 shows a correspondence relationship between state transition of a state obtained by combining transmission differential phases and transmission data applied to sequence estimator 340 in receiver 300 in the communication system according to the first embodiment of the present invention. It is a trellis diagram which shows an example of a trellis structure.

FIG. 10 is a characteristic diagram illustrating an example of a BER characteristic of the receiver 300 in the communication system according to the first embodiment of the present invention.

FIG. 11 is a configuration diagram showing another configuration example of the one-symbol differential detector 320 in the receiver 300 in the communication system according to the second embodiment of the present invention.

FIG. 12 is a configuration diagram illustrating another configuration example of the receiver 300 in the communication system according to the third embodiment of the present invention.

FIG. 13 is another example of a trellis structure applied to the sequence estimator 340 in the receiver 300 in the communication system according to the third embodiment of the present invention and representing a state transition relation of a state obtained by combining transmission differential phases. FIG.

FIG. 14 is a characteristic diagram illustrating another example of the BER characteristic of the receiver 300 in the communication system according to the third embodiment of the present invention.

FIG. 15 is a configuration diagram illustrating another configuration example of the convolutional encoder 110 in the transmitter 100 in the communication system according to the fourth embodiment of the present invention.

FIG. 16 is a characteristic diagram illustrating another example of the BER characteristic of the receiver 300 in the communication system according to the fourth embodiment of the present invention.

FIG. 17 is a configuration diagram illustrating an example of a configuration of a transmitter 100 in a communication system according to a fifth embodiment of the present invention.

FIG. 18 is a configuration diagram illustrating an example of a configuration of a receiver 300 in a communication system according to Embodiment 5 of the present invention.

FIG. 19 is a configuration diagram showing a configuration of a conventional communication system.

[Explanation of symbols]

 Reference Signs List 100 transmitter 110 convolutional encoder 120 assignment circuit 130 differential encoder 140 phase modulator 300 receiver 310, 310a multiple delay detection circuit 320 one symbol delay detector 321 one symbol delay element 322 phase comparator 326 phase detector 327 1-symbol delay element 328 Subtractors 332 2π modulo 331 332 1-symbol delay elements 335, 336 Adders modulo 340 340 Sequence estimator 410 Interleaver 420 Phase detector 430 Deinterleaver 440 1-symbol delay element 450 2π Adder

Continuation of the front page (56) References JP-A-4-170129 (JP, A) JP-A-4-208740 (JP, A) JP-A-6-177928 (JP, A) JP-A-58-145265 (JP) , A) “Delay detection using maximum likelihood sequence estimation for phase information”, Proc. Examination of Characteristics in Environment-", IEICE Transactions, Vol. J81-B-II, No. 9, pp 846-854 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/00-27/38 H03M 13/12 H03M 13/41

Claims (6)

(57) [Claims] 1. A receiver for receiving, as a reception signal, a transmission signal obtained by subjecting convolutionally encoded transmission data to differential phase shift keying modulation to obtain reception data corresponding to the transmission data. 1, 2, ..., N (N is an integer of 2 or more)
1, 2, 2, which is the phase difference from the received signal before the symbol period
, N-symbol differential detection signal generating means for generating N-symbol differential detection signals, and 1, 2,. And sequence estimation means for estimating transmission data from the received data and outputting the estimation result as received data , wherein the sequence estimation means is limited by convolutional coding.
Using the phase trellis diagram representing the phase transition,
, N symbol delay detection output of the delay detection means
Generates branch metrics from wave signals and uses the Viterbi algorithm
A receiver characterized by estimating transmission data by: Wherein said multiple differential detection means, the current reception signal and one symbol period prior to the reception signal and the phase of
One symbol that generates the one-symbol differential detection signal that is the difference
Delay detecting means, and a one-symbol delay output from the one-symbol delay detecting means.
Add 2, 3, ..., N symbols consecutively to the delayed detection signal
To generate a 2,..., N symbol differential detection signal.
2. The receiver according to claim 1, wherein: 3. The one-symbol delay detection means compares a phase of a reception signal with a signal output from the delay means with a delay means for delaying a reception signal by one symbol period.
And a phase comparing means for comparing
3. The receiver according to claim 2, wherein 4. The one-symbol delay detection means detects a phase of a received signal and outputs the detected signal , and a delay means for delaying the output of the phase detection means by one symbol period.
Stage and subtracting the output of the delay means from the output of the phase detection means
Claims characterized by comprising:
3. The receiver according to claim 2. 5. A convolutional code for convolutionally encoding transmission data.
Encoding means and convolutionally encoded data output from the convolutional encoding means
Means for converting the transmission differential phase into a transmission differential phase, and differentially encoding the transmission differential phase output from the allocation means .
And a differential encoding means for outputting as a transmission signal phase, based on the transmission signal phase output from the differential encoding means
Generates a transmission signal that is a differential phase shift keying modulation signal.
A transmitter having phase modulation means for generating and outputting
Beauty, current received signal and the 1, 2, ..., N (N is an integer of 2 or more)
1, 2, 2, which is the phase difference from the received signal before the symbol period
... Multiple differential detector for generating N-symbol differential detection signal
Stage, and using the phase state transition of the differential phase of the transmission signal,
1, 2,..., N symbol delays output from the delay detection means
Estimates the transmission data from the detected signal and returns the estimation result to the reception data.
And a sequence estimation means for outputting as a data
Communication system, wherein the sequence estimation means is limited by the convolutional coding.
Using a phase trellis diagram showing phase transitions
.., N symbols which are the outputs of the heavy delay detection means
Generate a branch metric from the delayed detection signal and use the Viterbi algorithm
Communication characterized by estimating transmission data by the mechanism
system. 6. A convolutional code for convolutionally encoding transmission data.
Encoding means and convolutionally encoded data output from the convolutional encoding means
Means for converting the transmission differential phase into a transmission differential phase, and differentially encoding the transmission differential phase output from the allocation means .
The differential encoding means for outputting as a modulation phase, and the order of the modulation phase output from the differential encoding means are determined in a predetermined manner.
Rearranged according to the rules of the above and output as the transmission signal phase
Interleaving means, and a transmission signal phase output from the interleaving means.
Transmission signal, which is a differential phase shift keying modulation signal
A transmitter having phase modulation means for generating and outputting; and
And a phase detecting means for detecting and outputting the phase of the received signal, and an order of the phase of the received signal output from the phase detecting means.
The data is rearranged based on the fixed rules and output as the detection phase.
Interleave means, current detection phase, 1, 2, ..., N (N is an integer of 2 or more)
1, 2,..., N, which are the differences from the detection phase before the symbol period
And multiple differential detection means for generating a symbol differential detection signals, a transition of the phase states of the differential phase of the transmission signal, the multiple
1, 2,..., N symbol delays output from the delay detection means
Estimates the transmission data from the detected signal and returns the estimation result to the reception data.
And a sequence estimation means for outputting as a data
Communication system, wherein the sequence estimation means is limited by the convolutional coding.
Using a phase trellis diagram showing phase transitions
.., N symbols which are the outputs of the heavy delay detection means
Generate a branch metric from the delayed detection signal and use the Viterbi algorithm
Communication characterized by estimating transmission data by the mechanism
system.