JP2901165B2 - Diversity system in one-frequency alternate communication system for mobile communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system for alternately transmitting and receiving a signal of a single frequency between a base station and a mobile station. In the mobile communication system, the base station implements reception diversity and transmission diversity to perform communication. The present invention relates to a diversity scheme in a one-frequency alternate communication scheme for mobile communication for improving quality.

[0002]

2. Description of the Related Art FIG. 4 is a diagram for explaining a mobile communication system for alternately transmitting and receiving a signal of a single frequency between a base station and a mobile station. In the figure, a base station 41 has a plurality of (here, two) antennas 42a for transmission and reception for diversity.
42b, one transmitter and two receivers. The mobile station 43 has one transmitting / receiving antenna 44, one transmitter, and one receiver.

[0003] A signal of the carrier frequency f transmitted from the antennas 42 a and 42 b of the base station 41 is received by the antenna 44 of the mobile station 43. Also, the antenna 44 of the mobile station 43
Are transmitted by the antennas 42a and 42b of the base station 41. Base station 41
In, selection diversity for demodulating a signal received from an antenna having the best reception quality among signals received by the plurality of antennas is performed.

A mobile communication system in which a base station 41 and a mobile station 43 perform bidirectional communication at a single frequency, as shown in FIG.
This is a press talk communication in which transmission is performed alternately at a predetermined time.
Here, the signal from the mobile station 43 to the base station 41 in FIG. 4 is referred to as an uplink signal 51, and the signal from the base station 41 to the mobile station 43 is referred to as a downlink signal 52.

FIG. 5 shows a case of N-channel multiplexing, and the first to N-th (# 1 to #N) frame configurations are the same. As an example, the n-th frame configuration will be described. The frame length of the uplink signal and the downlink signal is T, and the transmission time is equal to the frame length T.

FIG. 6 is a block diagram specifically showing a configuration of a base station, and FIG. 7 is a block diagram specifically showing a configuration of a mobile station. In FIG. 6, a transmitter 66 and receivers 62a and 62b of the base station are switched by a switch control circuit 68.
antennas 60a, 60b via respective contacts a, b of the antennas 60a, 61b.
0b.

[0007] An antenna 70 is connected to a transmitter 72 and a receiver 73 of the mobile station shown in FIG. 7 via a high-frequency switch 71 that is switched and controlled by a switch control circuit 74. The high-frequency switches 61a and 61b shown in FIG.
Switches the antenna contact to the b-side in the case of transmission and switches the antenna contact to the a-side in the case of reception by a transmission / reception switching signal from the switch control circuit 68.

Here, during the transmission time T of the uplink signal transmitted by the mobile station, the high-frequency switch 71 of the mobile station transmits the signal to the transmitter 72 via the contact b and the high-frequency switch 61a of the base station.
61b is connected to the receivers 62a and 62b via the contact a. Also, during the transmission time T of the downlink signal transmitted by the base station, the high-frequency switches 61a and 61b of the base station are connected to the contact b
Side.

In the base station, the receiver 6
Reception quality detection circuits 63a and 63 connected to 2a and 62b
3b, the reception quality is detected, a receiver having good reception quality is determined, and the result is input to the switch control circuit 68 as an antenna switching control signal. The changeover switch 65 is switched by the output signal of the comparison circuit, and when the reception quality of the receiver 62a is better than the reception quality of the receiver 62b, it is connected to the contact point a of the changeover switch 65 to take out the reception data signal of the receiver 62a and receive. When the reception quality of the receiver 62b is better than that of the receiver 62a, the receiver 62b is connected to the contact b of the changeover switch 65 to extract the reception data signal of the receiver 62b.

On the downlink from the base station, transmission diversity is performed by antenna switching. That is, in the base station, if the quality of the receiver 62a is better than the receiver 62b based on the signal from the switch control circuit 68 based on the result of the last reception quality determination of the uplink signal, the contact 66 of the high frequency switch 67 is High frequency switch 61a11-1
The signal is transmitted from the antenna 60a via the contact b.

The reception quality of the receiver 62b is
If the reception quality is better than 2a, the signal is transmitted from the antenna 60b. FIG. 8 shows the horizontal directivity patterns of the antennas 60a and 60b. As the conventional antenna, an omnidirectional antenna pattern is used as shown in FIG. 6, reference numeral 80a denotes a directivity pattern of the antenna 60a in FIG. 6 in a horizontal plane, and reference numeral 80b denotes a directivity pattern of the antenna 60b in a horizontal plane.

[0012] Transmission diversity utilizes the reversibility of the propagation path under the condition that the fading variation of the downstream signal following the upstream signal is slow, and the transmission quality of the upstream signal received by the base station is better. Utilizing the property that the reception quality of a downlink signal transmitted from an antenna at a mobile station is better than the case of transmission from another antenna. As described above, the base station performs reception diversity for uplink signals and performs transmission diversity for downlink signals.

[0013]

In land mobile communication, when performing narrowband signal transmission, deterioration of transmission quality due to frequency selective fading can be improved by reception diversity and transmission diversity. However, in the case of wideband signal transmission, a floor error that is difficult to reduce occurs due to the influence of waveform distortion caused by frequency selective fading, and a sufficient improvement effect cannot be expected with conventional diversity.

The reason for this is that when the incoming waves having different propagation delay times are combined and received, the frequency characteristics of the received signal are distorted, and as a result, intersymbol interference occurs in the demodulated signal. FIG. 9 is a diagram illustrating a difference in the spectrum of a received signal depending on the presence or absence of distortion due to frequency selective fading. In the figure, 90 is the case where there is no distortion, 9 is
1 indicates a case where there is distortion. From this figure, it can be seen that when there is distortion, the effect of diversity cannot be sufficiently obtained.

This indicates that, since transmission diversity is performed in response to reception diversity, the effect of frequency selective fading also appears on transmission diversity. In particular, when the signal is received by an omnidirectional antenna, this effect becomes significant.

It is an object of the present invention to provide a diversity system capable of improving the reception quality of an uplink signal in a base station and the reception quality of a downlink signal in a mobile station under frequency selective fading. .

[0017]

According to the present invention, the above-mentioned object is attained by the means described in the claims. That is, the present invention alternately transmits and receives a signal of a single frequency at a predetermined cycle between a base station having a plurality of antennas for both transmission and reception and a mobile station having one antenna for both transmission and reception. Performs frequency diversity for reception using the antenna with the best reception quality among the plurality of antennas, and performs frequency diversity for mobile communication to perform transmission diversity for transmission to the mobile station using the antenna with the best reception quality. In the communication system, a base station is provided with a plurality of antenna groups each composed of a plurality of antennas having different directional directions, and a plurality of receivers respectively corresponding to each antenna group, and a signal received by each receiver. a reception quality inspection unit which output the result by checking the reception quality by comparing the test results of the reception quality, any receiver A comparison unit reception quality is a signal indicating a good, and one transmitter provided,
At the time of reception at the base station, each receiver sequentially receives and switches antennas in the corresponding antenna group, and each time,
By comparing the test results of the reception quality, best reception selecting good antenna quality, then each received connecting a good antenna of highest reception quality in the antenna group corresponding to each of the in each antenna group Receiving diversity means for selecting a receiver having the best reception quality by comparing the reception quality of the base station, and transmitting from the base station using the antenna having the highest reception quality immediately before the start of transmission. This is a diversity system in a one-frequency alternate communication system for mobile communication, which includes transmission diversity means for performing the transmission.

[0018]

According to the present invention, in a base station, a plurality of antenna groups each including a plurality of antennas having different directivity directions are provided, and an antenna having the best reception quality among the antenna groups is selected, and then reception diversity and transmission diversity are selected. Therefore, the effect of delay caused by reflected waves from buildings and the like can be reduced, and communication quality can be improved.

[0019]

FIG. 1 is a block diagram showing the configuration of a base station according to one embodiment of the present invention. The mobile station has the same configuration as the conventional configuration shown in FIG. In this embodiment, the case where the base station has two antenna groups is shown. Antenna group A
And B are each composed of K antennas having different directivity directions. Antenna group A includes antennas a-1, a
,..., AK, and the antenna group B includes antennas b-1, b-2,.

FIG. 2 is a diagram for explaining the configuration of the antenna group. 2a-1 is a directivity pattern in the horizontal plane of the antenna a-1 of the antenna group A shown in FIG. 1, and 2a-2 is an antenna a-2. 2a-K represent the directivity pattern in the horizontal plane of the antenna a-K.

In the figure, the antenna (a) next to the antenna a-2 (a
For the antennas from -3) to before the antenna a-K, the drawing of the directivity patterns in the horizontal plane is omitted.

Similarly, 2b-1 is the directivity pattern of the antenna b-1 in the horizontal plane, 2b-2 is the directivity pattern of the antenna b-2 in the horizontal plane, and 2b-K is the directivity pattern of the antenna bK in the horizontal plane. The drawing of the directivity patterns in the horizontal plane is omitted for the antennas from the antenna next to the antenna b-2 to the antenna before the antenna b-K.

In FIG. 1, each of the antennas a-1 to a-
K and b-1 to bK are high frequency switches 11a,
11b and high frequency switches 12a and 12b for switching between transmission and reception, and are connected to receivers 13a and 13b, respectively. In addition, the high frequency switches 12a, 12
b, and the transmitter 17 is connected via the high-frequency switch 18. Each of the high frequency switches 12a, 12b, 18 is switched according to a transmission antenna switching signal output from the switch control circuit 19 or a transmission / reception switching signal.

One of the received data signals output from the receivers 13a and 13b is selected by the changeover switch 16 according to the comparison result of the output signals of the reception quality detection circuits 14a and 14b. At the time of transmission, the contact of the high-frequency switch 18 is switched by a transmission antenna switching signal from the switch control circuit 19 based on the result of the last reception quality determination at the time of reception, and transmission is performed from one antenna of the antenna group A or B. I do.

In this embodiment, antennas having different directivity directions are referred to as, for example, antenna a-1 and antenna b-1, antenna a-2 and antenna b-2, and antenna aK and antenna bK. Switching and receiving in combination
You. The received signal is received by the reception quality detection circuits 63a and 63b.
The reception quality is checked and the result is
It is held in the reception quality detection circuit. At this time, the antenna group
In A, antennas a-1 to aK are sequentially switched to
Each time, the reception that already holds the reception quality
The better reception quality compared to the quality corresponds to the antenna number
It is kept attached. In this way, the antenna
As a result of switching all of the
Is selected by the contact of the high-frequency switch 11a.
Connected to the antenna. The same applies to antenna B.
By operation, the contact of the high-frequency switch 11b
Is also connected to an antenna with good reception quality. Next, the receiver
13a and 13b each use the selected antenna
Diversity reception is performed, and the reception quality of the output is
Are compared by the comparison circuit 15, and
Which system is selected. Then, transmission diversity for transmitting from the antenna connected to the receiver having the best reception quality is performed.

FIG. 3 is a diagram showing a frame structure of an upstream signal used in the present invention. The frame configuration shown here corresponds to the signal for one channel of the upstream signal shown in FIG.
This frame includes preamble signals # 1 to # 3 as shown in FIG.
It is composed of a preamble signal 31 composed of #K and an information signal 32. Here, K corresponds to the number of antennas constituting each antenna group. When receiving at the base station,
As described above, in the preamble signal # 1, the antenna a
-1, b-1 are connected, and the reception quality of each receiver when the antennas a-2, b-2 are connected is determined in the preamble signal # 2. In the following, the reception quality of a signal received using a corresponding antenna in each preamble signal is determined. A combination of antennas having the best reception quality is selected based on the determination result of the reception quality, and the high-frequency switches 11a and 11
The contact b is connected to the antenna having the best reception quality.

The operations of the reception diversity and the transmission diversity after the selection of the antenna are the same as in the case of the prior art, so that the description will be omitted. In the above description, the case where two antenna groups are provided is described, but the present invention is not limited to this, and three or more antenna groups may be provided.

As a method for selecting an antenna, the reception quality is determined for each of the antennas corresponding to the directional directions, such as the antenna a-1 of the antenna group A and the antenna b-1 of the antenna group B. However, it is not always necessary to take such a combination, and a method of determining both as an arbitrary combination may be adopted.

[0029]

As described above, according to the present invention, a plurality of antenna groups each including a plurality of antennas having different directivity directions are provided, and the antenna having the best reception quality is selected from each antenna group. Since the antenna having the best reception quality is selected from the antennas of each group, there is an advantage that the effect of frequency selective fading due to the delay wave caused by the reflector can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a configuration of an antenna group.

FIG. 3 is a diagram illustrating a frame configuration of an uplink signal.

FIG. 4 is a diagram illustrating a mobile communication system for alternately transmitting and receiving a signal of a single frequency between a base station and a mobile station.

FIG. 5 is a diagram illustrating a signal configuration.

FIG. 6 is a diagram illustrating an example of a configuration of a conventional base station.

FIG. 7 is a diagram illustrating an example of a configuration of a mobile station.

FIG. 8 is a diagram illustrating a horizontal directivity pattern of an antenna.

FIG. 9 is a diagram illustrating a spectrum of a received signal.

[Explanation of symbols]

a-1 to aK, b-1 to bK Antennas 2a-1 to 2a-K, 2b-1 to 2b-K Directivity Patterns in Horizontal Plane of Antennas 11a, 11b, 12a, 12b, 18 High-frequency Switch 13a , 13b Receivers 14a, 14b Reception quality detection circuit 15 Comparison circuit 16 Changeover switch 17 Transmitter 19 Switch control circuit 31 Preamble signal 32 Information signal

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) H04B 7/00 H04B 7/02-7/12 H04L 1/02-1/06

Claims (1)

(57) [Claims] A single frequency signal is alternately transmitted and received at a predetermined cycle between a base station having a plurality of antennas for both transmission and reception and a mobile station having one antenna for both transmission and reception. One frequency alternate communication for mobile communication, wherein reception diversity is performed by using the antenna having the best reception quality among the plurality of antennas, and transmission diversity is performed by transmitting to the mobile station using the antenna having the best reception quality. In the system, a base station is provided with a plurality of antenna groups each composed of a plurality of antennas having different directivity directions, and a plurality of receivers corresponding to each antenna group, and reception of signals received by each receiver. a reception quality inspection unit which output the result to inspect the quality, by comparing the test results of the reception quality, receiving either the receiver A comparison unit that outputs a signal indicating whether the quality is good, and one transmitter are provided. Upon reception at the base station, each receiver sequentially switches antennas in a corresponding antenna group and receives the signals. each time by comparing the test results of the reception quality, select the best receiving good antenna quality in each antenna group, and then connect the highest reception good antenna quality in the antenna group corresponding to each Reception diversity means for selecting the receiver having the best reception quality by comparing the reception quality of each receiver, and using the antenna with the best reception quality immediately before the start of transmission when transmitting from the base station. A diversity system in a one-frequency alternating communication system for mobile communication, comprising a transmission diversity unit for performing transmission.