JP2591240B2 - Diversity receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention efficiently removes intersymbol interference and improves data transmission characteristics when performing data transmission via a communication path in which intersymbol interference occurs. The present invention relates to a diversity receiver.

(Prior Art) A method of improving reception characteristics by combining a diversity method and an equalization method is known. As such a technique, using a decision feedback equalization method as an equalization method, providing a matched filter or a forward equalizer in each diversity branch, synthesizing the outputs thereof, and inputting them to a decision feedback equalizer ( For example, Watanabe,
"Adaptive Receiving Method on Multipath Channel", IEICE, CS78-203, pp.57-64, P. Monsen, "Adaptive Equalization of the Slow Fading Channel", IEE, Transaction of Communications, Vol.COM-22, No. 8, Aug. 1974) is known.

As a technique using a maximum likelihood sequence estimation method known as an optimal equalization method as an equalization method, the quality of a received signal (spread of intersymbol interference, SN ratio, etc.) in each diversity branch is estimated. A method of selecting based on the estimated quality has been proposed (eg, Okanoue, Furuya, “Selection Diversity after Immersion Detection Suitable for MLSE”, 19
1989 IEICE Autumn National Convention, B-502).

(Problems to be Solved by the Invention) Diversity receiving techniques can be roughly divided into a method of combining received signals in each branch and a method of selecting received signals. In the combining type, the received signal power in each branch can be used effectively, so that the receiving characteristics are superior to the selective type. Therefore, it is considered that the reception characteristics can be greatly improved by using a combination of the combination type diversity and the maximum likelihood sequence estimation method.

Also, a method using a Vita algorithm to realize maximum likelihood sequence estimation is known (for example, haze,
“Xaviterbi Algorithm Applied Toe Digital Data Transmission”, IEE, Communication Society, 1975, No.1
3, pp. 15-20). In this method, a constant uniquely determined by the output of the matched filter and the communication path (branch metric constant part: Xaviterbi algorithm Applied toe digital data transmission ”, IEE
EE, Communication Society, 1975,
The branch metric of the received signal at each reception time point is obtained by adding the No. 13 pp. 18 equation 8b), the second and third terms on the right side. Further, the obtained branch metric is input to an ACS (Add, Compare and Select) circuit, and the path memory is controlled by the output from the ACS circuit, thereby realizing the maximum likelihood sequence estimation. When this method is applied to the combined diversity receiving method, the branch metric can be obtained from the signal obtained by combining the received signals in each diversity branch as shown in FIG. However, since the branch metric obtained by this method is obtained from a signal in which noise is also synthesized at the same time as a signal in each diversity branch, improvement in reception characteristics cannot be expected much.

(Means for Solving the Problems) (1) A diversity receiver according to the present invention, which uses a plurality of (L) antennas to simultaneously receive signals with each antenna, receives a reception signal of L diversity antennas as an input. , The channel impulse response (i) from the transmission point to the L diversity antennas (i = 0, 1,
.. L-1) are estimated and output, and the outputs of the L channel impulse response estimation circuits are input to set the internal state, and the L number of channels are set. L matched filter groups for inputting the received signal of the diversity antenna, and the output of the L matched filter group and the output of the L channel impulse response estimating circuit group as inputs, the branch metric of the received signal at each time point , An ACS (Add, Compare and Select) circuit that receives an output of the branch metric operation circuit as an input, and a path memory controlled by the ACS circuit.

(2) The branch metric calculation circuit in the diversity receiver according to the first item is the i-th (i = 0, 1,..., L−1) of the L channel impulse response estimation circuits according to the first item. And an L number of branch metric constant part operation circuits for calculating a constant (branch metric constant part) uniquely determined by the input communication path; I-th (i = 0,1,..., L-1) output among outputs;
2. An L adder group for adding an i-th (i = 0, 1,..., L-1) output among the outputs of the L matched filter groups according to claim 1; And an adder for adding the outputs and outputting the result as a branch metric of the received signal at each time point.

(3) The branch metric calculation circuit in the diversity receiver according to item 1, receives the outputs of the L channel impulse response estimation circuits according to item 1, and
A vector adder that adds each input signal (i) (i = 0, 1,..., L−1) in a vector manner and outputs = Σ (i), and inputs an output from the vector adder And
And a branch metric constant section operation circuit for calculating a constant (branch metric constant section) uniquely determined by the communication path, and a second circuit for adding L outputs from the L matched filters described in the first item. 1 adder, and a second adder that adds the output of the first adder and the output of the branch metric constant section operation circuit and outputs the result as the branch metric of the received signal at each time point. Have.

(Operation) According to the present invention, a received signal in each diversity branch is filtered by a matched filter.
Matched filters are commonly used as filters that maximize the signal-to-noise ratio (translated by JJ Jones, S. Stein, Hideo Seki, “Modern Communication Line Output Theory”, Morikita Publishing, 1970
Year). The branch metric is given by the sum of the output of the matched filter and the branch metric constant part uniquely determined by the channel impulse response as described in the section of the related art. For this reason, the influence of noise is reduced by obtaining a branch metric using the signal obtained by performing the matched filtering in each diversity branch and obtaining the maximum SN ratio and the channel impulse response information to each diversity branch. be able to.

According to claim 2 of the present invention, a branch metric is obtained independently for each diversity branch. Therefore, the branch metric obtained from each diversity branch is obtained with the maximum SN ratio in each diversity branch. At this time, AC
The branch metric input to the S circuit is given by the sum of the branch metrics obtained in each diversity branch, so that the influence of noise can be reduced.

According to the third aspect of the present invention, the same effect as that of the second aspect can be obtained. At this time, if the channel impulse response at the i-th diversity antenna is (i), Is obtained as a channel impulse response of a diversity-combined signal, a branch metric constant part can be obtained. Here, L is the number of diversity branches. For this reason, in the present invention, the number of multiplications when obtaining the branch metric constant part can be reduced to 1 / L.

(Embodiment) FIG. 1 is a system diagram showing an embodiment in which the diversity receiving apparatus according to the first aspect of the present invention is applied to a receiver having L diversity branches. In the figure, 1000 is an L diversity branch group, and 1001 is an L diversity branch group.
1002, L communication channel impulse response estimation circuits, 1003, a branch metric operation circuit, 1004, an ACS circuit, 1005, a bus memory, and 1006, an output terminal.

The received signals received by the diversity branch group 1000 are respectively the channel impulse response estimation circuit group.
1001 and the channel impulse response from the transmission point to each diversity branch is estimated. The channel impulse response estimated for each diversity branch is input to a matched filter group 1002 connected to each diversity branch, and the internal state of each is set. The matched filter group 1002 receives a signal from each diversity branch 1000, performs filtering, and performs a branch metric operation circuit.
Output to 1003. The channel impulse response estimated by the channel impulse response estimation circuit group 1001 is also input to the branch metric operation circuit 1003. The branch metric calculation circuit 1003 obtains a branch metric obtained by combining diversity branches at each reception time point from the input group of estimated values of the channel impulse response and the group of matched filter outputs.
The part composed of the ACS circuit 1004 and the path memory 1005 has the same configuration as that of a normal soft-decision Viterbi decoder.

FIG. 2 is a system diagram showing an embodiment in which the diversity receiving apparatus according to the second aspect of the present invention is applied to a receiver having two diversity branches. In the figure, 100 and 101 are diversity antennas, 102 and 103 are matched filters, 104 and 105 are communication channel impulse response estimating circuits, 106 and 107 are branch metric constant part operation circuits, 108 is an ACS circuit, 109 is a path memory, 110 to 112 are adders, 113 Is an output terminal.

The received signals received by the diversity antennas 100 and 101 are respectively transmitted by a channel impulse response estimation circuit.
The signals are input to 104 and 105, and the channel impulse response from the transmission point to each diversity antenna is estimated.
The channel impulse response estimated for each diversity antenna is input to matched filters 102 and 103 connected to diversity antennas 100 and 101, and the internal states of matched filters 102 and 103 are set.
Matching filters 102 and 103 receive signals from diversity antennas 100 and 101, respectively, filter and output the signals.

In addition, the estimated channel impulse response is also input to branch metric constant section operation circuits 106 and 107. In the branch metric constant part operation circuits 106 and 107,
From the estimated value of the input channel impulse response,
Find the branch metric constant part. Further, the obtained branch metric constant parts are respectively added to the adders 110,
The output from the matched filters 102 and 103 is added by 111,
Obtain a branch metric for each diversity branch. The outputs of the adders 110 and 111 are added by the adder 112 to obtain a branch metric considering the entire diversity branch. ACS circuit 108, path memory 109
Is the same as that of a normal soft-decision Viterbi decoder. The output from the adder 112 is input as a branch metric, and the demodulation result is output to an output terminal 113.

FIG. 3 is a system diagram showing an embodiment in which the diversity receiving apparatus according to the third aspect of the present invention is applied to a receiver having two diversity branches. In the figure, 200 and 201 are diversity antennas, 202 and 203 are matched filters, 204 and 205 are communication channel impulse response estimation circuits, 206 is a vector adder, 207 is a branch metric constant part calculation circuit, 208 and 209 are adders, 210 is an ACS circuit, and 211 is an ACS circuit.
Is a path memory, and 212 is an output terminal.

The received signals received by the diversity antennas 200 and 201 are respectively transmitted by the channel impulse response estimation circuit.
Communication channel impulse responses h (0), h input from 204 and 205 and transmitted from the transmission point to each diversity antenna
(1) is estimated. The channel impulse response estimated for each diversity antenna is
Input to matched filters 202 and 23 connected to diversity antennas 200 and 201, the internal states of matched filters 202 and 203 are set. Matching filters 202 and 203 receive signals from diversity antennas 200 and 201, respectively, and filter and output the input signals. The outputs of the matched filters 202 and 203 are added by an adder 208.

The estimated channel impulse responses (0) and (1) are also input to the vector adder 206. In the vector adder 206, = (0) + (1) is obtained, and is input to the branch metric constant part operation circuit 207 as a communication channel impulse response in consideration of the entire diversity antenna. The branch metric constant part calculation circuit 207 obtains a branch metric constant part based on the, and outputs it to the adder 209. Adder 2
In step 09, the branch metric considering the entire diversity branch is output by adding the output of the branch metric constant section operation circuit 207 and the output of the adder 208. The part composed of the ACS circuit 210 and the path memory 211 is the same as the configuration of a normal soft-decision Viterbi decoder, and inputs the output from the adder 209 as a branch metric,
The demodulation result is output to output terminal 212.

(Effect of the Invention) According to the present invention, via a communication path in which intersymbol interference occurs,
When performing data transmission, efficiently remove intersymbol interference,
Data transmission characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment in which the diversity receiver according to the first aspect of the present invention is applied to a receiver having L diversity branches. In the figure,
1000 is an L diversity branch group, 1001 is an L matched filter group, 1002 is an L channel impulse response estimation circuit, 1003 is a branch metric operation circuit, 1004
Is an ACS circuit, 1005 is a path memory, and 1006 is an output terminal. FIG. 2 is a system diagram showing an embodiment in which the diversity receiving apparatus according to the second aspect of the present invention is applied to a receiver having two diversity branches. In the figure, 100 and 101 are diversity antennas, 102 and 103 are matched filters, 104 and 105 are communication channel impulse response estimating circuits, 106 and 107 are branch metric constant part operation circuits, and 1
08 is an ACS circuit, 109 is a path memory, 110 to 112 are adders, 11
3 is an output terminal. FIG. 3 is a system diagram showing an embodiment in which the diversity receiving apparatus according to the third aspect of the present invention is applied to a receiver having two diversity branches. In this figure, 200 and 201 are diversity antennas, 202 and 203 are matched filters, 204 and 205 are communication channel impulse response estimation circuits, 206 is a vector adder, 207 is a branch metric constant part calculation circuit 208 and 209 are adders, 210 is an ACS circuit, and 211 is a path. A memory 212 is an output terminal. FIG. 4 is a system diagram of an example in the case of using a signal obtained by combining signals from the diversity branches. In the figure, 300 and 301 are diversity antennas, 301 is an adder,
302 is a communication channel impulse response estimation circuit, 303 is a matched filter, 304 is a branch metric constant part arithmetic circuit, 3
05 is an adder, 306 is an ACS circuit, and 307 is a path memory.

Claims (3)

(57) [Claims] 1. A diversity receiving apparatus for receiving signals simultaneously at each antenna using a plurality of (L) antennas, comprising: a) receiving signals of L diversity antennas as inputs and transmitting said L diversity signals from a transmission point; Channel impulse response to the antenna (i) (i = 0, 1,...)
L-1) a set of L channel impulse response estimating circuits for estimating and outputting L-1), and b) an output of the set of L channel impulse response estimating circuits is input to set an internal state, and L) matched filter groups for inputting the received signals of the diversity antenna of (c), and c) receiving signals at each point in time by using the outputs of the L matched filter groups and the outputs of the L channel impulse response estimation circuits as inputs. A) a branch metric calculation circuit that calculates the branch metric of the above, d) an ACS (Add, Compare and Select) circuit that receives an output of the branch metric calculation circuit, and e) a bus memory controlled by the ACS circuit. A diversity receiver. 2. The branch metric calculation circuit includes: a) an i-th (i = 0, 1,..., L-1) output of the L channel impulse response estimation circuits; B) a branch metric constant section operation circuit group for calculating a constant (branch metric constant section) uniquely determined by the communication path; and b) an i-th output of the L branch metric constant section operation circuit groups ( i = 0,1,
.., L−1) outputs and L adders for adding the i-th (i = 0, 1,..., L−1) output of the L matched filters of claim 1. 2. The diversity receiver according to claim 1, further comprising: c) an adder for adding outputs of the L adders and outputting the result as a branch metric of a received signal at each time point. . 3. The branch metric calculation circuit: a) receives the outputs of the L communication channel impulse response estimation circuits, and outputs respective input signals (i) (i = 0, 1,..., L
A) a vector adder that adds -1) as a vector and outputs = Σ (i); and b) a constant uniquely determined by a communication channel based on the input of the output from the vector adder. A branch metric constant section arithmetic circuit for calculating a branch metric constant section); c) a first adder for adding L outputs from the L matched filters; and d) an output of the first adder. 2. The diversity receiving apparatus according to claim 1, further comprising: a second adder that adds the output of the branch metric constant section arithmetic circuit and outputs the result as a branch metric of the received signal at each time point. .