JPH07245577A - Diversity communication equipment - Google Patents

Abstract

PURPOSE:To obtain low power consumption and high line quality by the use of a simple equipment by providing plural antennas and selecting 'any of the antennas to send a transmission signal when the detected reception quality is lower than a threshold quality. CONSTITUTION:A comparator 308 in a mobile station 300 having antennas 301, 302 compares a signal strength detected by a reception signal strength detector 307, that is, a detection result of a reception signal with a threshold level received externally in advance. When the signal strength is smaller than the threshold level, the comparator 308 switches the setting of a switch 309 so as to select the opposite antenna to be connected. Thus, the reception signal received by a receiver 303 is demodulated by a demodulator 305 and outputted. When an externally inputted signal is modulated by a modulator 306 in the transmission of an incoming signal from the mobile station 300 and the modulated signal becomes a transmission signal by a transmitter 304 and sent through either of the antennas 301, 302 selected by the switch 309 after via the switch 310.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity communication device used in digital mobile communication, and particularly in a low speed fading line, TDD (time division duplex: TDD).
The present invention relates to a diversity communication device suitable for a time division bidirectional communication system.

[0002]

2. Description of the Related Art In mobile communication and the like, in order to improve the deterioration of signal transmission characteristics due to multipath fading, a space diversity receiving system in which a plurality of independent antennas are used for reception is widely used. Further, in a communication system using the TDD method, it is used that a reception signal from a communication partner station and a transmission signal to a communication partner station are adjacently propagated in a propagation path at short time intervals, and the propagation path between them is used. There is known a transmission diversity scheme that can improve the reception quality of a communication partner station by transmitting using an antenna having a good reception quality as a method that can ignore the state change of. In a mobile communication system, a reception and transmission diversity method is applied to a base station device from the viewpoint of simplification of the mobile station device, and the uplink and base station from the mobile station to the base station are increased without increasing the device size of the mobile station. A general method is to improve the quality of both downlinks from the mobile station to the mobile station.

FIG. 2 is a block diagram showing an implementation example of a mobile communication device using a conventional TDD system. Here, an example is shown in which base station 100 performs space diversity with the number of antennas “2”. FIG. 3 shows a signal format when bidirectional communication is performed by the TDD method using this type of device. As shown in the figure, the base station and the mobile station perform bidirectional communication by alternately transmitting and receiving upstream signals and downstream signals in time.

In FIG. 2, the antenna 1 of the base station 100
The upstream signals received by 01 and 102 are input to the corresponding switches 103 and 104, respectively. Each of the switches 103 and 104 is a switch that switches the connection destination of the antenna during reception and during transmission in TDD communication. When receiving the upstream signal, the received signal is
Receivers 10 corresponding to the switches 103 and 104, respectively
5, 106 are input. The received signals output from the receivers 105 and 106 are input to the corresponding received signal strength detectors 109 and 110, respectively, and also the demodulator 1
It is also input to 07 and 108, respectively. Then, the reception signal strengths detected by the reception signal strength detectors 109 and 110, that is, the detection results of the reception qualities, are obtained by the comparator 1
11 are input respectively. The comparator 111 compares the signal strengths detected by the respective received signal strength detectors, and sets the switch 112 so that the demodulated signal obtained from the demodulator corresponding to the antenna having a high signal strength is output. The comparator 111 makes the same setting for the switch 115 and fixes this setting immediately before the end of the upstream signal. By fixing the settings in this way, when transmitting downlink signals,
The switch 115 is connected to the antenna side having a high received signal strength.

Next, when transmitting a downlink signal from the base station 100, a signal inputted from the outside is modulated by the modulator 113 and further becomes a transmission signal by the transmitter 114. The output of the transmitter 114 is connected to the switch 103 or 104 side fixed by the switch 115 as described above, and is transmitted from the corresponding antenna 101 or 102.

On the other hand, in mobile station 200, a downlink signal is received by antenna 201 and output to switch 202. The switch 202 is the switch 103, 10 in the base station.
Similar to 4, the connection destination is switched during transmission / reception. The received signal is input to the receiver 203 when the downlink signal is received.
The received signal output from the receiver 203 is the demodulator 205.
Are demodulated by and output. A signal input from the outside at the time of transmitting an upstream signal from the mobile station is modulated by the modulator 206 and further becomes a transmission signal by the transmitter 204, which is transmitted from the antenna 201 via the switch 202.

[0007]

However, the apparatus shown in FIG. 2 may not obtain sufficient line quality. That is, when the received electric field strength is lowered due to the distance between the base station and the mobile station being long, the line quality is deteriorated. In order to extend the communicable distance with the device shown in FIG. 2, it was necessary to increase the number of antennas in the base station to increase the diversity gain, or to increase the transmission power of both stations. The former method has a problem that the device scale of the base station becomes large, and the latter method increases power consumption, which is a problem especially in the mobile station.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a diversity communication apparatus which has low power consumption and can obtain high line quality by a simple apparatus. .

[0009]

In order to solve the above problems, in the invention described in claim 1, a first transceiver having a plurality of antennas, and a second transceiver for transmitting and receiving with the first transceiver. And a first reception quality detecting means for individually detecting reception quality received by each of the antennas, and the diversity communication device including: First receiving means for individually demodulating the received signals, demodulated signal combining means for selecting or weighting and combining the output signals of the receiving means according to the detection result of the reception quality, and the detection result of the reception quality is the best. In the diversity communication device including the first transmitting means for transmitting a transmission signal from the antenna, the second transceiver has two antennas and an antenna for selecting one of the two antennas. Tena switching means, second receiving means for demodulating a signal received via the antenna switching means, and second reception quality detecting means for detecting the quality of the signal received via the antenna switching means. Switching means for comparing the quality detected by the second reception quality detecting means with a preset threshold value and for switching the selection of the antenna switching means when the detected quality is lower than the threshold value. A second transmitting means for transmitting a transmission signal via the antenna switching means.

Further, in the invention according to claim 2,
In the invention according to claim 1, the first and second transceivers perform time-division bidirectional communication, and the switching means transmits from the first transceiver to the second transceiver. The feature is that switching is performed at the end timing.

According to a third aspect of the invention, the invention according to the first aspect is characterized by further comprising setting means for variably setting the threshold value. According to the invention described in claim 4, in the invention described in claim 1, at least two or more of the second transceivers are provided for the first transceiver.

[0012]

According to the first aspect of the invention, the two antennas and the switching means for the two antennas are provided also on the mobile station side, and transmission / reception is possible from any of them, so that the base station and the mobile station are Communication is possible via independent propagation paths of the number of antennas of the base station × 2). That is, according to this configuration, the number of antennas of the base station is 2 in the conventional device configuration.
Diversity gain that is almost the same as when doubled is obtained.
Further, the increase in the device scale in the mobile station is simple due to the changeover switch and the like, and the power consumption is small. Claim 2
According to the invention described in (1), since the antennas are not switched during reception, noise generation due to switching can be prevented, and the second transceiver following the transmission from the first transceiver to the second transceiver can be prevented. From the transmission to the first transceiver, good line quality is secured.

According to the third aspect of the invention, the switching of the antenna in the second transceiver can be adjusted by the operator. According to the invention of claim 4, a plurality of operators carry the second transceivers, respectively,
It becomes possible to communicate with the first transceiver.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In this embodiment, similar to the apparatus shown in FIG. 2, the signal format shown in FIG. 3 is used, and the base station 100 shows an example of performing space diversity with the number of antennas “2”. And mobile station 300
Two-way communication with.

In FIG. 1, the antenna 1 of the base station 100
The upstream signals received by 01 and 102 are input to the corresponding switches 103 and 104, respectively. Each of the switches 103 and 104 is a switch that switches the connection destination of the antenna during reception and during transmission in TDD communication. When receiving the upstream signal, the received signal is
Receivers 10 corresponding to the switches 103 and 104, respectively
5, 106 are input. The received signals output from the receivers 105 and 106 are input to the corresponding received signal strength detectors 109 and 110, respectively, and also the demodulator 1
It is also input to 07 and 108, respectively. Then, the received signal strengths detected by the received signal strength detectors 109 and 110 are input to the comparator 111, respectively. The comparator 111 compares the signal strengths detected by the respective received signal strength detectors, and sets the switch 112 so that the demodulated signal obtained from the demodulator corresponding to the antenna having a high signal strength is output. The comparator 111 makes the same setting for the switch 115 and fixes this setting immediately before the end of the upstream signal. By fixing the setting like this,
At the time of transmitting the downlink signal, the switch 115 is connected to the antenna side having a high received signal strength.

Next, when transmitting a downlink signal from the base station 100, a signal inputted from the outside is modulated by the modulator 113 and further becomes a transmission signal by the transmitter 114. The output of the transmitter 114 is connected to the switch 103 or 104 side fixed by the switch 115 as described above, and is transmitted from the corresponding antenna 101 or 102. As described above, the configuration and operation of the base station 100 are the same as those shown in FIG.

On the other hand, in the mobile station 300, the downlink signals are received by the antennas 301 and 302, respectively, and the switch 309 is received.
Is output to. The switch 309 has a function of switching the connection between the antennas 301 and 302 and the subsequent device according to the comparison result of the comparator 308. The output of the switch 309 is input to the switch 310. The switch 310 is
Similar to the switches 103 and 104 in the base station, the connection destination is switched during transmission / reception. When the downlink signal is received, the received signal is input to the receiver 303 and the received signal strength detector 307.

The signal strength detected by the received signal strength detector 307, that is, the detection result of the received signal is the comparator 308.
Is compared with a threshold value input in advance from the outside. The threshold value is set to a desired value by an operator who operates the mobile station 300 by a setting means (not shown). Comparator 3
08 is a switch 309 so that the connected antenna is on the opposite side when the signal strength is smaller than the threshold value.
Switch the setting of. However, in order to prevent generation of noise due to switching, the switch 309 is switched only immediately before the end of the downlink signal and is fixed at other times. By such switching, the probability of receiving via the antenna on the side where the signal strength is below the threshold and the line quality has deteriorated is reduced, and at the time of uplink signal transmission following downlink signal reception, similarly good line quality is achieved. Quality is obtained. Further, by adjusting the setting of the threshold value, it becomes possible for the operator to set the reception signal strength at which the antenna is switched, and the usability for the operator is also improved. Although an antenna, a switch, a comparator and a received signal strength detector are required as compared with the conventional device shown in FIG. 2, all of them are small and consume low power.

The received signal input to the receiver 303 is demodulated by the demodulator 305 and output. When transmitting an uplink signal from a mobile station, the signal input from the outside is modulated by the modulator 3
06, and further becomes a transmission signal by the transmitter 304, and after passing through the switch 310, the antenna 30
Switch 3 out of 1, 302 set as described above
09 is transmitted from the connecting side.

According to this embodiment, since both the base station and the mobile station perform transmission and reception via the antenna having high received signal strength, high line quality can be obtained and the device scale is small. .

Here, the code error rate characteristics by computer simulation in the embodiment shown in FIG. 1 are shown in FIGS. FIG. 4 shows downlink bit error rate characteristics, and FIG. 5 shows uplink bit error rate characteristics. In addition,
In this simulation, it is assumed that the transmission rate is 384 kbps, the modulation / demodulation method is π / 4 shift QPSK-delay detection method, the communication method is 4 ch TDMA-TDD with a frame period of 5 ms, the fading is a fading frequency of 15 Hz, and the delay time difference is 500 ns. . From FIG. 4 and FIG. 5, it can be seen that this embodiment can improve the diversity gain of 4 dB to 5 dB at the point that the code error rate becomes 10 ⁻³ .

In the above embodiment, the received signal strength detector is used as the received quality detecting means.
Instead of this, a code error rate detector or a frame error rate detector may be used. Further, in the embodiment shown in FIG. 1, the number of mobile stations 300 with respect to the base station 100 is set to “1” for convenience of description, but the present application is not limited to this.
That is, the number of mobile stations 300 may be “2” or more. In this case, a plurality of operators respectively operate the mobile station 300.
By carrying the mobile phone, it becomes possible to communicate with the base station 100.

[0023]

The present invention described above has the following effects. It is possible to obtain high line quality with a device that is small, simple, and has low power consumption (claim 1). Good line quality can be ensured even in the transmission from the second transceiver to the first transceiver following the transmission from the first transceiver to the second transceiver (claim 2). The usability of the operator who uses the second transceiver can be improved (claim 3). Multiple operators
By carrying each second transceiver,
It becomes possible to communicate with the transceiver of the above (Claim 4).

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional device.

FIG. 3 is an explanatory diagram showing a signal format of TDD communication.

FIG. 4 is a characteristic diagram showing a downlink bit error rate according to the embodiment of the present invention.

FIG. 5 is a characteristic diagram showing an uplink code error rate according to the embodiment of the present invention.

[Explanation of symbols]

100 ... First transceiver (base station) 101, 102 ... Antenna 105, 106 ... Receiver (first receiving means) 109, 110 ... Received signal strength detector (first reception quality detecting means) ) 112 ... switch (demodulated signal synthesizing means) 114 ... transmitter (first transmitting means) 300 ... second transceiver (mobile station) 301, 302 ... antenna 303 ... receiver (second receiver) Receiving means 304 ... Transmitter (second transmitting means) 307 ... Received signal strength detector (second receiving quality detecting means) 309 ... Switch (switching means)

Claims (4)

[Claims] 1. A diversity communication apparatus comprising a first transceiver having a plurality of antennas and a second transceiver for transmitting and receiving the first transceiver, wherein the first transceiver includes each of the above First reception quality detection means for individually detecting reception quality received for each antenna, first reception means for individually demodulating received signals from the respective antennas, and reception signals for output signals of the reception means In the diversity communication device, the demodulation signal combining means for selecting or weighting combining according to the quality detection result and the first transmitting means for transmitting the transmission signal from the antenna having the best reception quality detection result, The transmitter / receiver has two antennas, an antenna switching unit that selects one of the two antennas, and a signal that is received via the antenna switching unit is demodulated. Second receiving means, second receiving quality detecting means for detecting the quality of a signal received via the antenna switching means, and quality detected by the second receiving quality detecting means are preset. Switching means for switching the selection of the antenna switching means when the detected quality is lower than the threshold value as compared with a threshold value, and transmitting a transmission signal through the antenna switching means
And a transmitting means for transmitting the diversity communication device. 2. The first and second transceivers perform time-division bidirectional communication, and the switching means switches at a transmission end timing from the first transceiver to the second transceiver. The diversity communication device according to claim 1, wherein 3. The diversity communication device according to claim 1, further comprising setting means for variably setting the threshold value. 4. The diversity communication device according to claim 1, wherein at least two or more second transceivers are provided for the first transceiver.