JP3290338B2 - Spatial diversity transceiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception apparatus using space diversity used for data transmission of digital car telephones, portable telephones and the like.

[0002]

2. Description of the Related Art In data transmission, a multiple access system is a line connection system in which a plurality of stations simultaneously communicate in the same frequency band. Code division multiple access (CD
MA: Code Division Multiple Access (MA) means that multiple access is performed by spread spectrum communication in which an information signal is multiplied by a different spreading code for each channel, and the original information signal is spread over a band sufficiently larger than the bandwidth and transmitted. It is a technique to perform. A plurality of channel signals are simultaneously superimposed on the same frequency band and transmitted, and the signal of each channel is separated on the receiving side by a different spreading code for each channel. CDM
A is a time division multiple access system (TDMA: Time Divisio)
n Multiple Access) or frequency division multiple access (F
DMA: Frequency Division Multiple Access)
As a high frequency use efficiency can be expected compared to
This is one of the leading multiple access schemes in the next-generation world land mobile communication system (FPLMTS).

[0003] TDD (Time Division Duplex) is a time-division bi-directional multiplexing method, also called a ping-pong method, in which the same frequency band is time-divided into an uplink line and a downlink line to alternately communicate. is there. As an advantage of the TDD scheme, it is known that transmission diversity can be easily applied to a base station, so that spatial diversity is not required in a mobile station, and miniaturization can be achieved.

[0004] A received wave that has passed through a moving propagation path is subject to a change called fading, which is a cause of deterioration of a transmission system. In order to realize high quality transmission, there is a diversity technique as a technique for reducing the influence of the fading. The space diversity will be described below with reference to a base station.

[0005] Reception space diversity is one of diversity reception techniques for receiving signals using two or more reception antennas.
One. By arranging the antennas sufficiently far from each other, the fading received by the reception wave of each antenna can be regarded as an independent fluctuation. Fading fluctuation can be reduced by selecting and switching an antenna having a good reception state from a plurality of received waves having independent fading fluctuations, or by combining the received waves of each antenna while aligning them. . In contrast,
Transmission space diversity is a diversity technique for transmitting using two or more transmission antennas. By selecting an antenna having a good transmission path of a communication circuit with the mobile station from a plurality of transmission antennas and switching the antenna for transmission, it is possible to reduce fading fluctuation of a received wave in the mobile station.

In general, the fading fluctuation due to multipath varies depending on the frequency. In the case of the TDD scheme, since the frequency bands of the uplink and the downlink are the same, the correlation between the fading fluctuations of the uplink and the downlink is high. It is easy to estimate the state of the transmission path between each antenna and the mobile station from the reception state of the line.

FIG. 8 shows a configuration example of a base station of a mobile communication device in a conventional example. This is an example when the number of antennas is 2 and the number of channels is 2. In FIG. 8, 101 is a first antenna, and 201 is a second antenna. 10
2 is a transmission / reception switch for the antenna 101, 20
2 is a transmission / reception switch for the antenna 201, 10
Reference numeral 3 denotes a wireless receiving unit for the antenna 101, and reference numeral 203 denotes a wireless receiving unit for the antenna 201. Reference numeral 301 denotes a despreading circuit for channel 1, which comprises a despreading circuit 301A for the reception signal of the antenna 101 and a despreading circuit 301B for the reception signal of the antenna 201. Reference numeral 401 denotes a despreading circuit for channel 2, which includes a despreading circuit 401A for the received signal of the antenna 101 and a despreading circuit 401B for the received signal of the antenna 201. 302 is a combining circuit for combining the two despread signals obtained in the despreading circuit 301;
Reference numeral 402 denotes a combining circuit that combines the two despread signals obtained by the despreading circuit 401. 303 is a synthesis circuit 3
Reference numeral 403 denotes a channel 1 error correction decoding circuit for decoding the received signal synthesized by the synthesis circuit 402, and reference numeral 403 denotes a channel 2 error correction decoding circuit for decoding the reception signal synthesized by the synthesis circuit 402.

Reference numeral 304 denotes an error correction coding circuit for performing error correction coding on transmission data of channel 1;
Is an error correction coding circuit that performs error correction coding on the transmission data. Reference numeral 305 denotes transmission data of channel 1 on channel 1
A spreading circuit for spreading by a spreading code assigned to
Reference numeral 05 denotes a spreading circuit that spreads transmission data of channel 2 using a spreading code assigned to channel 2. 306
Is an antenna switch for switching from which antenna the spread channel 1 transmission signal is transmitted, 406
Is an antenna switch for switching from which antenna the spread channel 2 transmission signal is transmitted.
104 is an addition circuit for adding the spread signal transmitted from the antenna 101, and 204 is an addition circuit for adding the spread signal transmitted from the antenna 201. 105 is the antenna 10
Reference numeral 205 denotes a wireless transmission unit for the antenna 201.

The base station thus configured alternately repeats transmission and reception according to transmission / reception switching signal 501. A period during which transmission is performed is referred to as a transmission time slot, and a period during reception is referred to as a reception time slot. The selection of which of the antennas 101 and 201 to use is made by the antenna selection signal 502 from the combining circuits 302 and 402.

In the reception time slot, both transmission / reception switches 102 and 202 are switched to the reception side, and the reception signals received by antennas 101 and 201 are input to radio reception sections 103 and 203, respectively. Radio receiving sections 103 and 203 perform primary demodulation on the signals received by antennas 101 and 201, respectively, and output the signals to both despreading circuits 301 and 401. The despreading circuit 301 despreads the signals from the radio receiving units 103 and 203 using the spreading code assigned to channel 1 and outputs two despread signals to the combining circuit 302. Similarly, in the despreading circuit 401, the radio receiving sections 103 and 203
And outputs two despread signals to the synthesis circuit 402. Synthesis circuits 302 and 402
Then, the two input signals are switched and selected, or the phases are adjusted, weighted and combined, and output to the error correction decoding circuits 303 and 403, respectively. At this time, the combining circuits 302 and 402 determine the transmission antenna in the next transmission time slot from the selection switching and the weighting coefficient of the combination, and output the antenna selection signal 502 to the antenna switches 306 and 406, respectively. The error correction decoding circuits 303 and 403 perform error correction decoding from the respective input signals and output received data of channels 1 and 2, respectively.

In the transmission time slot, transmission data of channel 1 and channel 2 are input to respective error correction coding circuits 304 and 404, subjected to error correction coding, and output to spreading circuits 305 and 405, respectively. The spreading circuit 305 spreads the error-correction-coded transmission data of the channel 1 with the spreading code assigned to the channel 1 and outputs the spread data to the antenna switch 306. Spreading circuit 405 spreads the error-correction coded transmission data of channel 2 with the spreading code assigned to channel 2 and outputs the spread data to antenna switch 406. In the antenna switches 306 and 406, the spreading circuit 30
5, the input signal from 405 is switched by the antenna selection signal 502 determined in the immediately preceding reception time slot,
Output to the adding circuit 104 or 204. Adder circuit 10
4 and 204, the spread signals transmitted from the antennas 101 and 201 are added and synthesized, and
Output to 05. Radio transmitting sections 105 and 205 modulate the added spread signal, limit the band, and output the result. In the transmission time slot, the transmission / reception switches 102 and 202
Since both are switched to the transmission side by the transmission / reception selection signal 501, the outputs of the wireless transmission units 105 and 205 are transmitted from the antennas 101 and 201, respectively.

[0012]

However, in the above-mentioned conventional example, the selection of the transmission antenna in the transmission time slot is determined by the magnitude of the power, and information on the certainty at the time of error correction decoding is not used. Therefore, even if a large error occurs due to fading,
If the received power is large, the antenna is selected, and there is a problem that it cannot be said that the best antenna estimated from the entire received signal including the certainty at the time of error correction decoding is selected. Was.

The present invention solves such a conventional problem, and makes the selection of the transmission antenna branch more accurate by linking it with the certainty of the error correction decoding. It is an object of the present invention to provide a spatial diversity transmitting / receiving apparatus capable of reducing interference, improving communication quality and increasing subscriber capacity.

[0014]

According to the present invention, in order to achieve the above object, not only the output from the synthesizing circuit but also the output of the despreading circuit before synthesis is input to the error correction decoding circuit. The error correction decoding is performed from the signal, and the antenna selection signal is output not from the combining circuit but from the error correction circuit.

[0015]

Therefore, according to the present invention, it is possible to more reliably select an antenna to which a signal of each channel is to be transmitted in a transmission time slot as compared with the conventional art. Is smaller than before, and interference due to cross-correlation of spreading codes between channels can be reduced as compared with the conventional case. Therefore, it is possible to improve the bit error rate characteristics and enhance the quality transmission, and also to increase the capacity of simultaneous subscribers and increase the frequency use efficiency.

[0016]

【Example】

(Embodiment 1) FIG. 1 shows a configuration example of a base station of a mobile communication apparatus according to a first embodiment of the present invention, in which the number of antennas is two and the number of channels is two. The same elements as those in the conventional example shown in FIG. 8 are denoted by the same reference numerals.
In FIG. 1, reference numeral 101 denotes a first antenna, and 201 denotes a second antenna.
Antenna. Reference numeral 102 denotes a transmission / reception changeover switch for the antenna 101, 202 denotes a transmission / reception changeover switch for the antenna 201, 103 denotes a radio reception unit for the antenna 101, and 203 denotes a radio reception unit for the antenna 201.
Reference numeral 301 denotes a despreading circuit for channel 1, which comprises a despreading circuit 301A for the reception signal of the antenna 101 and a despreading circuit 301B for the reception signal of the antenna 201. 4
Reference numeral 01 denotes a despreading circuit for channel 2, which is a despreading circuit 401A for the reception signal of the antenna 101 and an antenna 2
01 comprises a despreading circuit 401B for the received signal No. 01. 30
Reference numeral 2 denotes a combining circuit that combines the two despread signals obtained by the despreading circuit 301, and reference numeral 402 denotes a combining circuit that combines the two despread signals obtained by the despreading circuit 401. Reference numeral 303 denotes an error correction decoding circuit of channel 1 for performing error correction decoding on the two signals obtained by the despreading circuit 301 and the synthesized signal synthesized by the synthesizing circuit 302. Reference numeral 403 denotes two error correction decoding circuits obtained by the despreading circuit 401. This is an error correction decoding circuit of channel 2 that performs error correction decoding on the signal and the synthesized signal synthesized by the synthesis circuit 402.

Reference numeral 304 denotes an error correction coding circuit for performing error correction coding on transmission data of channel 1;
Is an error correction coding circuit that performs error correction coding on the transmission data. Reference numeral 305 denotes transmission data of channel 1 on channel 1
A spreading circuit for spreading by a spreading code assigned to
Reference numeral 05 denotes a spreading circuit that spreads transmission data of channel 2 using a spreading code assigned to channel 2. 306
Is an antenna switch for switching from which antenna the spread channel 1 transmission signal is transmitted, 406
Is an antenna switch for switching from which antenna the spread channel 2 transmission signal is transmitted.
104 is an addition circuit for adding the spread signal transmitted from the antenna 101, and 204 is an addition circuit for adding the spread signal transmitted from the antenna 201. 105 is the antenna 10
Reference numeral 205 denotes a wireless transmission unit for the antenna 201.

The base station thus configured alternately repeats the transmission operation and the reception operation in accordance with the transmission / reception switching signal 501. A period during which the transmission process is performed is referred to as a transmission time slot, and a period during which the reception process is performed is referred to as a reception time slot. The selection of which of the antennas 101 and 201 to use is made by the error correction decoding circuits 303 and 4.
This is performed by the antenna selection signal 502 from the receiver 03.

In the reception time slot, both transmission / reception switches 102 and 202 are switched to the reception side, and the reception signals received by antennas 101 and 201 are input to radio reception sections 103 and 203, respectively. Radio receiving sections 103 and 203 perform primary demodulation on the signals received by antennas 101 and 201, respectively, and output the signals to both despreading circuits 301 and 401. The despreading circuit 301 despreads the signals from the radio receiving units 103 and 203 using the spreading code assigned to channel 1 and outputs two despread signals to the combining circuit 302. Similarly, in the despreading circuit 401, the radio receiving sections 103 and 203
And outputs two despread signals to the synthesis circuit 402. Synthesis circuits 302 and 402
Then, the two input signals are switched and selected, or the phases are adjusted, weighted and combined, and output to the error correction decoding circuits 303 and 403, respectively. The error correction decoding circuits 303 and 403 are composed of combining circuits 302 and 40, respectively.
Error correction decoding is performed using both the signal synthesized in step 2 and the despread signal before synthesis as input, and the received data of channels 1 and 2 are output, respectively. At this time, the error correction decoding circuit 3
03 and 403 determine the transmission antenna in the next transmission time slot from the likelihood of the input signal in the error correction decoding process, and output the antenna selection signal 502 to the antenna switches 306 and 406, respectively.

In the transmission time slot, the transmission data of channel 1 and channel 2 are input to respective error correction coding circuits 304 and 404, subjected to error correction coding, and output to spreading circuits 305 and 405, respectively. The spreading circuit 305 spreads the error-correction-coded transmission data of the channel 1 with the spreading code assigned to the channel 1 and outputs the spread data to the antenna switch 306. Spreading circuit 405 spreads the error-correction coded transmission data of channel 2 with the spreading code assigned to channel 2 and outputs the spread data to antenna switch 406. The antenna switches 306 and 406 switch to the immediately preceding reception time slot with the antenna selection signal 502 determined by the error correction decoding circuits 303 and 403, and output the input signals from the spreading circuits 305 and 405 to the addition circuit 104 or 204, respectively. I do. The adders 104 and 204 add and combine the spread signals transmitted from the antennas 101 and 201, respectively, and output the combined signals to the wireless transmitters 105 and 205. Radio transmitting sections 105 and 205 modulate the added spread signal, limit the band, and output the result. In the transmission time slot, both the transmission / reception switches 102 and 202 are switched to the transmission side by the transmission / reception selection signal 501, so that the outputs of the wireless transmission units 105 and 205 are output from the antennas 101 and 2 respectively.
Sent from 01.

Here, error correction decoding circuits 303 and 403
Will be described in more detail. First, convolutional codes and Viterbi decoding (maximum likelihood decoding) will be described. FIG. 2 shows an example of a very simple convolutional coding circuit. D denotes a delay circuit, a state that the holding at the time t _n and S _n. X indicates an integrating circuit. At time t _n to the input I _n the (+1) or (-1), the output 01 _n, 02 _n) is
(+ 1, + 1), (+ 1, -1), (-1, + 1),
(-1, -1). FIG. 3 shows the state S held.
_n-1 and the input I _n, representing the output 01 _n, 02 _n, and updated relation between state S _n.

FIG. 4 is a trellis diagram showing the state transition.
You. Initial state S₀Is (+1), (-1) or
(+1) 3-bit input data string I₁, I_Two, I_Threeof
Finally tail I_Four4 bits added = (+1)
This is an example in the case of force. Bold arrow indicates input I_nIs (+
In the case of 1), the thin arrow indicates the input I_nIs (-1)
Is shown. The + and-signs attached to the arrows
Output 01_n, 02_nIs (+1) or
(-1). Input I_Four= (+ 1)
So state S_FourIs always (+1). On the sending side,
Output data string 01 _n, 02_n(01₁, 02₁, 01
_Two, 02_Two, ..., 01_Four, 02_Four) Are sequentially transmitted. arrow
A mark is called a branch, and a series of arrows is called a path.

[0023] On the receiving side, the received data sequence of the transmitted signal _{R1 n, R2 n (R1 1} , R2 1, ..., R1 4, R2
₄ ) get. The state transition of the encoding circuit on the transmission side is estimated based on the received data sequence. A measure of the likelihood of the estimation is called a metric (likelihood) M. Here, the metric up to time t _n is defined as follows. _{M n = (R1 1 -01 1} ) 2 + (R2 1 -02 1) 2 +
_{... + (R1 n -01 n)} 2 + (R2 n -02 n) 2

In this case, the smaller the metric, the more certain
It can be said that. State S₀From state S _FourAll paths (through
Metric) and calculate the most
The path with the smallest
The input corresponding to the_n(D₁, D_Two,
…, D_Four) Is the output of the decoding circuit.

In this example, states _Sn are (+1) and (−)
Since there are only 2) and the number of state transitions is only 4 times, it is not difficult to obtain a metric for all paths, but generally the calculation is enormous. Therefore, a method for finding the most probable path and reducing the calculation amount is the Viterbi decoding method.

Only the most probable path is required. When the least metrics small paths of several paths merging the same state at time t _n to P _M, the path P ₀ otherwise, rather than the path P _M to the exact same state transition to the time after The metric cannot be small. Thus, a path that has a higher metric than another path that joins the same state is not likely to be the ultimately most likely path. Such a path can be deleted at each time, so that only one path remains at the final time, and this path becomes the most likely path (small metric). .

(R1₁, R2₁, R1_Two, R2_Two) =
Explaining the case of (+ 1,0, + 1,0) as an example,
t₁The metric M of the path in each state₁| (S = +
1), M _Two| (S = -1) is M₁| (S = + 1) = {(+ 1)-(+ 1)}^Two+ $ 0
− (+ 1)｝^Two= 1 M¹| (S = -1) = {(+ 1)-(+ 1)}^Two+ $ 0
− (-1)｝^Two= 1. Time t_TwoThen, (S₀= + 1, S₁= + 1, S
_Two= +1)₁And (S₀= + 1, S₁=
-1, S_Two= +1)_TwoMerge. This
When, the metric of each path is M_Two| (P₁) = M₁| (S₁= + 1) + ｛(+ 1)-
(+1)｝^Two+ {0-(+ 1)}^Two= 2 M_Two| (P_Two) = M₁| (S₁= -1) + ｛(-1)-
(+1)｝^Two+ {0-(+ 1)}^Two= 6. Therefore, S_Two= Branch to transition to +1
And S₁= Transition from branch (P₁Bu
Lunch) survived, S₁= Bras that transition from -1
(P_TwoBranch) is deleted. Similarly, S_Two=
The path that transitions to -1 is S₁==-1
The coming branch survives, S₁= Transition from +1
The branch is deleted. In this way, each state in time order
Survive one of several transitioning branches
Delete the branches left as branches. Time t
_FourAt state S_FourThe branch that transitions to = + 1 is also 1
Only books survive. Time out the surviving branches
As you go back and follow, time t₀State S in₀=
Only one path up to +1 is selected.

The error correction decoding circuit 3 operating as described above
03 and 403, the following operation is further added. FIG.
FIG. 11 shows an example of a trellis diagram for correction decoding in the present embodiment. In the conventional example of FIG. 4, the branch of each state transition, which was one (solid line) in the conventional example, is divided into three branches (solid line, broken line, dotted line), and the metric is the inverse of the signal received by the antenna 101, respectively. It is calculated from the spread signal and the despread signal of the signal received by the antenna 201.

The selection of the surviving path is determined by comparing only the path (branch) indicated by the solid line, and finally one state transition path is finally selected in the same manner as in the prior art, and decoding is performed according to the selection result. A path indicated by a broken line following the same path as this path (a path for calculating a metric from a despread signal of a signal received by the antenna 101, a series of branches indicated by a broken line)
And a dashed path (a path for calculating a metric from a despread signal of the received signal at the antenna 201, a series of dashed branches), and the antenna corresponding to the path with the smaller metric is transmitted to the next transmission. The antenna is selected as the transmitting antenna in the time slot and the antenna selection signal 50 is selected.
Output as 2. If the metric of the dashed path is smaller, the antenna 101 is selected, and if the metric of the dotted path is smaller, the antenna 201 is selected.

In selecting a transmitting antenna, a branch indicated by a broken line (a branch for calculating a metric from a despread signal of a signal received by the antenna 101) and a branch indicated by a dotted line are used for each branch on the state transition path that has finally survived. The metric is compared (a branch for calculating a metric from a despread signal of the received signal at the antenna 201). An antenna corresponding to a path having more branches with smaller metrics is selected as a transmission antenna in the next transmission time slot and output as an antenna selection signal 502. At this time, the antenna 101 is selected when the metric of the dashed branch is often smaller, and the antenna 201 is selected when the metric of the metric of the dotted branch is smaller.

In this way, in selecting a transmission antenna, selection is made by taking into account the certainty (metric) in error correction decoding, as compared with the conventional selection by comparing reception powers in a combining circuit. More accurate antenna selection becomes possible.

(Embodiment 2) FIG. 6 shows an example of the configuration of a base station of a mobile communication apparatus according to a second embodiment of the present invention, in which the number of antennas is two and the number of channels is two. is there. The same elements as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals. In FIG. 6, reference numeral 101 denotes a first antenna, and 201 denotes a second antenna. Reference numeral 102 denotes a transmission / reception changeover switch for the antenna 101, 202 denotes a transmission / reception changeover switch for the antenna 201, 103 denotes a radio reception unit for the antenna 101, and 203 denotes a radio reception unit for the antenna 201. Reference numeral 301 denotes a despreading circuit for channel 1, which includes a despreading circuit 301 A for the received signal of the antenna 101 and a despreading circuit 3 for the received signal of the antenna 201.
01B. Reference numeral 401 denotes a despreading circuit for channel 2, which is a despreading circuit 4 for a received signal of the antenna 101.
01A and the despreading circuit 40 for the reception signal of the antenna 201
1B. 303 is the 2 obtained by the despreading circuit 301
An error correction decoding circuit of channel 1 that performs error correction decoding from two signals, and 403 is an error correction decoding circuit of channel 2 that performs error correction decoding from two signals obtained by the despreading circuit 401.

Reference numeral 304 denotes an error correction coding circuit for performing error correction coding on transmission data of channel 1;
Is an error correction coding circuit that performs error correction coding on the transmission data. Reference numeral 305 denotes transmission data of channel 1 on channel 1
A spreading circuit for spreading by a spreading code assigned to
Reference numeral 05 denotes a spreading circuit that spreads transmission data of channel 2 using a spreading code assigned to channel 2. 306
Is an antenna switch for switching from which antenna the spread channel 1 transmission signal is transmitted, 406
Is an antenna switch for switching from which antenna the spread channel 2 transmission signal is transmitted.
104 is an addition circuit for adding the spread signal transmitted from the antenna 101, and 204 is an addition circuit for adding the spread signal transmitted from the antenna 201. 105 is the antenna 10
Reference numeral 205 denotes a wireless transmission unit for the antenna 201.

The base station thus configured alternately repeats the transmission operation and the reception operation in accordance with the transmission / reception switching signal 501. A period during which the transmission process is performed is referred to as a transmission time slot, and a period during which the reception process is performed is referred to as a reception time slot. The selection of which of the antennas 101 and 201 to use is made by the error correction decoding circuits 303 and 4.
This is performed by the antenna selection signal 502 from the receiver 03.

In the reception time slot, both transmission / reception switches 102 and 202 are switched to the reception side, and the reception signals received by antennas 101 and 201 are input to radio reception sections 103 and 203, respectively. Radio receiving sections 103 and 203 perform primary demodulation on the signals received by antennas 101 and 201, respectively, and output the signals to both despreading circuits 301 and 401. The despreading circuit 301 performs despreading processing on the signals from the radio receiving units 103 and 203 using the spreading code assigned to the channel 1 to convert the two despread signals into the error correction decoding circuit 30.
Output to 3. Similarly, in the despreading circuit 401, the radio receiving unit 10
Signals 3 and 203 are respectively despread, and two despread signals are output to error correction decoding circuit 403. The error correction circuits 303 and 403 perform error correction decoding using the respective two despread signals as input, and output received data of channels 1 and 2, respectively. At this time, the error correction decoding circuits 303 and 403 determine the transmission antenna in the next transmission time slot from the certainty of the input signal in the error correction decoding process, and transmit the antenna selection signal 502 to the antenna switches 306 and 406, respectively. Output.

In the transmission time slot, transmission data of channel 1 and channel 2 are input to respective error correction coding circuits 304 and 404, subjected to error correction coding, and output to spreading circuits 305 and 405, respectively. The spreading circuit 305 spreads the error-correction-coded transmission data of the channel 1 with the spreading code assigned to the channel 1 and outputs the spread data to the antenna switch 306. Spreading circuit 405 spreads the error-correction coded transmission data of channel 2 with the spreading code assigned to channel 2 and outputs the spread data to antenna switch 406. The antenna switches 306 and 406 switch to the immediately preceding reception time slot with the antenna selection signal 502 determined by the error correction decoding circuits 303 and 403, and output the input signals from the spreading circuits 305 and 405 to the addition circuit 104 or 204, respectively. I do. The adders 104 and 204 add and combine the spread signals transmitted from the antennas 101 and 201, respectively, and output the combined signals to the wireless transmitters 105 and 205. Radio transmitting sections 105 and 205 modulate the added spread signal, limit the band, and output the result. In the transmission time slot, both the transmission / reception switches 102 and 202 are switched to the transmission side by the transmission / reception selection signal 501, so that the outputs of the wireless transmission units 105 and 205 are output from the antennas 101 and 2 respectively.
Sent from 01.

FIG. 7 shows an example of a trellis diagram for error correction decoding in this embodiment. In the conventional example of FIG. 4, one (solid line)
Each state transition branch is divided into two branches (dashed line and dotted line), and the metrics are respectively the despread signal of the received signal at the antenna 101 and the antenna 201
From the despread signal of the received signal at.

The metric is compared not only with the path that transitions from another state and merges, but also with the path that calculates the metric from the despread signal of the signal received by another antenna that makes the same transition from the same state, as in the prior art. And select a survivor path. As in the conventional case, one state transition path is finally selected, and decoding is performed according to the selection result. And
A broken-line path (antenna 1) following the same path as this path
01, a path for calculating a metric from the despread signal of the received signal, a series of dashed branches) and a dotted path (a path for calculating a metric from the despread signal of the received signal at the antenna 201, a series of dotted branches) , The antenna corresponding to the path with the smaller metric is selected as the transmitting antenna in the next transmission time slot, and is output as the antenna selection signal 502.
If the metric of the dashed path is smaller, the antenna 10
1 is selected, and if the metric of the dotted path is smaller, the antenna 201 is selected.

In selecting a transmitting antenna, a branch indicated by a broken line (a branch for calculating a metric from a despread signal of a signal received by the antenna 101) and a branch indicated by a dotted line are used for each branch on the state transition path that has finally survived. The metric is compared (a branch for calculating a metric from a despread signal of the received signal at the antenna 201). An antenna corresponding to a path having more branches with smaller metrics is selected as a transmission antenna in the next transmission time slot and output as an antenna selection signal 502. At this time, the antenna 101 is selected when the metric of the dashed branch is often smaller, and the antenna 201 is selected when the metric of the metric of the dotted branch is smaller.

As a result, even if there is no conventional combining circuit for combining the despread signals, the effect of substantially combining two despread signals in the error correction decoding process can be obtained. No longer needed. Further, by selecting the transmission antenna from the certainty (metric) in the error correction decoding, it is possible to more accurately select the antenna.

(Embodiment 3) The configuration and operation of this embodiment are the same as those of Embodiments 1 and 2. However, when the transmitting antenna is selected, the path for calculating the metric from the despread signal of the received signal at the antenna 101 shown by the broken line or the metric of the branch and the dotted line are shown for the entire state transition path that finally survived. Antenna 201
Instead of comparing the metric of the path or the branch for calculating the metric from the despread signal of the received signal at, the comparison is made for some branches of the state transition path that has finally survived.

In the case of transmission using an error correction code, generally, in order to enhance the error correction capability, the transmission side replaces the output data of the encoding circuit in accordance with a predetermined rule and transmits the data in accordance with a predetermined rule. The side often performs processing called interleaving and deinterleaving, respectively, in which the original sequence is returned to the original order (by performing the reverse operation) and input to the decoding circuit.

Therefore, the temporal order on the radio transmission path is often different from the temporal order in the decoding circuit. By comparing the metric of the above-mentioned dashed path or branch and the dashed path or branch of the branch corresponding to the signal transmitted later in time on the radio transmission path, the radio transmission It is possible to increase the specific gravity of a branch that has been subjected to fading (fluctuations in the state of the transmission line in wireless transmission) at a time later on the road, that is, near the next transmission time slot.

As a result, in selecting a transmission antenna, the specific gravity of a signal received at a time closer to the time of actual transmission becomes higher, and it is possible to cope with fading whose fluctuation period is fast.

Also, in the convolutional code / Viterbi decoding, the error correction capability at the beginning or end at the time of decoding is higher than at the middle. That is, in the case of the first or last branch, the probability that a wrong branch is erroneously selected and survives is lower than that of the middle branch. Therefore, it is also possible to obtain a weighted metric by increasing the specific gravity of the branches in these sections, and compare the antennas to select a transmission antenna.

[0046]

According to the present invention, as is apparent from the above embodiment, the error correction decoding and the selection of the transmission antenna are performed separately by combining the error correction decoding of the reception signal and the selection of the transmission antenna. Compared to the conventional method, error correction decoding improves the error correction capability by decoding based on more information, and considers a measure of the likelihood of error correction decoding when selecting a transmission antenna. By doing so, antenna selection can be performed more accurately.
That is, since the propagation state of each channel can be improved, interference with multiple channels can be relatively reduced, and the error correction capability can be increased, so that high quality communication can be achieved. In communication by code division multiple access,
Reducing interference with multiple channels has the effect of increasing subscriber capacity.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a base station according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a convolutional encoding circuit.

FIG. 3 is a list showing a relationship between an internal state of the convolutional encoding circuit and input / output;

FIG. 4 is a schematic diagram showing an example of a trellis diagram.

FIG. 5 is a schematic diagram illustrating an example of a trellis diagram of the Viterbi decoding circuit according to the first embodiment;

FIG. 6 is a block diagram illustrating a configuration of a base station according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating an example of a trellis diagram of a Viterbi decoding circuit according to a second embodiment.

FIG. 8 is a block diagram showing a configuration of a conventional base station.

[Explanation of symbols]

 101, 201 Antenna 102, 202 Transmission Switch 103, 203 Radio Reception Unit 104, 204 Addition Circuit 105, 205 Radio Transmission Unit 301, 401 Despreading Circuit 302, 402 Synthesis Circuit 303, 403 Error Correction Decoding Circuit 304, 404 Error Correcting Code Circuit 305, 405 Spreading circuit 306, 406 Antenna switch 501 Transmission / reception selection signal 502 Antenna selection signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-1131395 (JP, A) JP-A-2-279029 (JP, A) JP-A-5-48511 (JP, A) JP-A-6-131 90227 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/04 H04B 1/707 H04B 7/26

Claims (7)

(57) [Claims] 1. A plurality of antennas, a plurality of transmission / reception switches respectively connected to the plurality of antennas, for switching operation between transmission and reception by time division, and connection to each of the plurality of antennas via the transmission / reception switches A plurality of wireless receiving units and a plurality of wireless transmitting units, and a despreading circuit connected to each of the plurality of wireless receiving units and performing despreading with a spreading code assigned to each of the plurality of wireless channels, A plurality of combining circuits connected to the plurality of despreading circuits, respectively, for combining a plurality of despread signals; and a signal connected to the despreading circuit and the combining circuit, respectively, and combined by the combining circuit. Performs error correction decoding and outputs received data, and outputs an antenna selection signal for selecting a transmission antenna. Signal circuits, a plurality of error correction coding circuits for convolutionally coding transmission data of a plurality of radio channels, respectively, and a spreading code assigned to each radio channel connected to each of the plurality of error correction coding circuits. A plurality of spreading circuits for performing band spreading in, a plurality of antenna switches respectively connected to the plurality of spreading circuits, and a plurality of antenna switches for switching an antenna to be connected by an antenna selection signal from the error correction decoding circuit, and each of the plurality of antenna switches And a plurality of adding circuits for adding spread signals transmitted from the antenna selected by the antenna selection signal and outputting the added signals to the corresponding wireless transmission units, thereby performing wireless communication by code division multiple access. Spatial diversity transmitter / receiver. 2. A plurality of error correction decoding circuits perform Viterbi decoding on a signal synthesized by a synthesis circuit to generate received data of a wireless channel, and generate a received data of a radio channel on a maximum likelihood state transition path obtained in a decoding process. 2. The spatial diversity transmitting / receiving apparatus according to claim 1, wherein likelihoods of the despread signals corresponding to the plurality of antennas are compared, and an antenna selection signal for selecting an antenna having a high likelihood as a transmission antenna is output. 3. A plurality of error correction decoding circuits perform Viterbi decoding on a signal synthesized by the synthesis circuit to generate received data of a wireless channel, and each of the error correction decoding circuits on a maximum likelihood state transition path obtained in a decoding process. 2. The spatial diversity transmission / reception according to claim 1, wherein the likelihoods of the despread signals corresponding to the plurality of antennas are compared for the respective branches, and an antenna selection signal for selecting an antenna having many branches with high likelihood as a transmission antenna is output. apparatus. 4. A plurality of antennas, a plurality of transmission / reception switches respectively connected to the plurality of antennas, for switching between transmission and reception by time division, and a connection to each of the plurality of antennas via the transmission / reception switches. A plurality of wireless receiving units and a plurality of wireless transmitting units, and a despreading circuit connected to each of the plurality of wireless receiving units and performing despreading with a spreading code assigned to each of the plurality of wireless channels, A plurality of error correction decoding circuits respectively connected to the plurality of despreading circuits, performing error correction decoding from the plurality of despread signals, outputting received data, and outputting an antenna selection signal for selecting a transmission antenna; A plurality of error correction coding circuits for convolutionally coding transmission data of a plurality of radio channels, respectively; A plurality of spreading circuits respectively connected to an encoding circuit and performing band spreading with a spreading code assigned to each wireless channel; and an antenna selection signal from the error correction decoding circuit connected to each of the plurality of spreading circuits. A plurality of antenna switches for switching the antennas to be connected, and a spread signal transmitted from the antenna selected by the antenna selection signal, which is connected to each of the plurality of antenna switches, to the respective corresponding wireless transmission units A space diversity transmitting / receiving apparatus for performing wireless communication by code division multiple access, comprising a plurality of adding circuits for outputting. 5. A plurality of error correction decoding circuits perform Viterbi decoding using a plurality of despread signals as separate branches to generate received data of a wireless channel, and generate a received data of a radio channel, and perform a process on a maximum likelihood state transition path obtained in a decoding process. 5. The spatial diversity transmitting / receiving apparatus according to claim 4, wherein the likelihood when only the respective despread signals are traced is compared, and an antenna selection signal for selecting an antenna having a high likelihood as a transmission antenna is output. 6. A plurality of error correction decoding circuits perform Viterbi decoding by using a plurality of despread signals as separate branches to generate received data of a wireless channel, and generate a received data of a radio channel, and execute the decoding on a maximum likelihood state transition path obtained in a decoding process. 5. The spatial diversity transmission / reception apparatus according to claim 4, wherein the likelihood of each despread signal is compared for each of the branches, and an antenna selection signal for selecting an antenna having many antennas with high likelihood as a transmission antenna is output. 7. The part of the maximum likelihood state transition path obtained in the decoding process, which is temporally later in the order of wireless transmission, instead of on the maximum likelihood state transition path obtained in the decoding process. The space diversity transmitting / receiving apparatus according to any one of claims 1 to 6, wherein: