JPH05259950A - Diversity system for mobile communication-frequency mutual communication system - Google Patents

Abstract

PURPOSE:To reduce the influence of the frequency selective fading caused by a reflecting object by providing plural antenna groups consisting of plural antennas of different pointing directions and performing the reception/transmission diversity after selection of an antenna that has the best receiving quality. CONSTITUTION:The respective antenna groups A and B consist of K units of antennas having the different pointing directions. That is, the group A includes the antennas a-1-a-k and the group B includes the antennas b-1-b-k respectively. These antennas are connected to the receivers 13a and 13b via the high frequency switches 11a/11b and 12a/12b respectively. In such a constitution, the antennas are sequentially switched in such sets of antennas a-1/b-1, a-k/b-k, etc., and then selected based on the deciding results of receiving quality. Then the reception diversity is carried out and then the transmission diversity is carried out via the antenna that is connected to the receiver of the highest receiving quality.

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 which the base station performs reception diversity and transmission diversity for communication. The present invention relates to a diversity method in a one-frequency alternating communication method for mobile communication, which improves 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 includes a plurality of (two in this case) transmitting / receiving antennas 42a for diversity.
42b, one transmitter and two receivers. The mobile station 43 has one transmitting / receiving antenna 44, one transmitter, and one receiver.

The signal of the carrier frequency f transmitted from the antennas 42a and 42b of the base station 41 is received by the antenna 44 of the mobile station 43. In addition, the antenna 44 of the mobile station 43
The signal of the carrier frequency f transmitted from is received by the antennas 42a and 42b of the base station 41. Base station 41
Then, among the signals received by the plurality of antennas, selection diversity is performed to demodulate the received signal from the antenna having the best reception quality.

A mobile communication system in which the base station 41 and the mobile station 43 perform bidirectional communication at a single frequency is as shown in FIG.
This is press talk communication in which data is alternately transmitted 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 upstream signal 51, and the signal from the base station 41 to the mobile station 43 is referred to as a downstream 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 structure will be described. The frame length of the upstream signal and the downstream signal is T, and the transmission time is equal to the frame length T.

FIG. 6 is a block diagram showing the construction of a base station, and FIG. 7 is a block diagram showing the construction of a mobile station. In FIG. 6, the transmitter 66 and the receivers 62a and 62b of the base station are controlled by a switch control circuit 68 to control a high frequency switch 61.
The antennas 60a, 6 are connected via the contact points a, b of a, 61b.
0b.

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 which is switch-controlled by a switch control circuit 74. The high frequency switches 61a and 61b shown in FIG.
In response to the transmission / reception switching signal from the switch control circuit 68, the antenna contact is switched to the b side for transmission, and the antenna contact is switched to the a side for reception.

Here, within the transmission time T of the upstream signal transmitted by the mobile station, the high frequency switch 71 of the mobile station is transmitted 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 point a. Further, within 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.
Switched to the side.

At the base station, the receiver 6 is received during the upstream signal reception period.
Reception quality detection circuits 63a, 6 connected to 2a, 62b
The reception quality is detected in 3b, a receiver having a good reception quality is determined, and the result is input to the switch control circuit 68 as an antenna switching control signal. When the reception quality of the receiver 62a is better than the reception quality of the receiver 62b, it is connected to the contact a of the changeover switch 65 to extract the reception data signal of the receiver 62a and receive it. When the reception quality of the receiver 62b is better than that of the receiver 62a, the switch 62 is connected to the contact b side to take out the reception data signal of the receiver 62b.

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

Further, the reception quality of the receiver 62b is the same as that of the receiver 6.
If it is better than the reception quality of 2a, it is transmitted from the antenna 60b. A horizontal plane directivity pattern of the antennas 60a and 60b is shown in FIG. As a conventional antenna, an omnidirectional antenna pattern is used as shown in FIG. In the figure, 80a shows the directivity pattern in the horizontal plane of the antenna 60a in FIG. 6, and 80b shows the directivity pattern in the horizontal plane of the antenna 60b.

The transmission diversity utilizes reversibility of the propagation path under the condition that the fluctuation of fading is slow for the downlink signal following the uplink signal, and the transmission diversity of the uplink signal received by the base station is better. It utilizes the property that the reception quality of a downlink signal transmitted from an antenna at a mobile station is better than that when transmitted from another antenna. In this way, the base station performs reception diversity for upstream signals and transmission diversity for downstream signals.

[0013]

When performing narrow band signal transmission in land mobile communication, deterioration of transmission quality due to frequency selective fading can be improved by receiving diversity and transmitting 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 conventional diversity cannot be expected to have a sufficient improvement effect.

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

This indicates that the effect of frequency selective fading appears in the transmission diversity because the transmission diversity is performed corresponding to the reception diversity. This effect is particularly noticeable when receiving with an omnidirectional antenna.

An object of the present invention is to provide a diversity system capable of improving the reception quality of an upstream signal at a base station and the reception quality of a mobile station when receiving a downlink signal under frequency selective fading. ..

[0017]

According to the present invention, a signal of a single frequency is alternated at a predetermined cycle between a base station having a plurality of antennas for both transmission and reception and a mobile station having a single antenna for both transmission and reception. The base station performs reception diversity using the antenna having the best reception quality among the plurality of antennas, and also performs transmission diversity transmitting to the mobile station using the antenna having the best reception quality. In the one-frequency alternating communication system for mobile communication, 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 the respective antenna groups and respective receivers are provided. The reception quality inspecting section that inspects the reception quality of the signal received at and outputs the result, and compares the above inspection result of the reception quality. A comparison unit that outputs a signal indicating which receiver has good reception quality and one transmitter are provided, and when receiving at the base station, the antennas in the antenna group corresponding to each receiver are sequentially arranged. Switch and receive, each time, by comparing the inspection results of the reception quality, select the antenna with the best reception quality (use reception level or bit error rate etc. as the reception quality) in each antenna group, Next, a reception diversity means for selecting a receiver having the best reception quality by examining the reception quality of each receiver to which the best reception quality antenna in the corresponding antenna group is connected, At the time of transmission from the base station, a diver equipped with transmission diversity means for performing transmission using the antenna with the best reception quality immediately before the start of transmission A switch system.

[0018]

According to the present invention, a base station is provided with a plurality of antenna groups each consisting of a plurality of antennas having different directivity directions, and the antenna having the best reception quality is selected from the respective antenna groups, and then reception diversity and transmission diversity are selected. Therefore, it is possible to reduce the influence of delay caused by reflected waves from buildings and improve communication quality.

[0019]

1 is a block diagram showing the configuration of a base station according to an 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
Each of B and B is composed of K antennas having different directivity directions. The antenna group A includes antennas a-1, a
,-, AK, and the antenna group B is composed of antennas b-1, b-2, ..., b-K.

FIG. 2 is a diagram for explaining the structure 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. In the horizontal plane, and 2a-K represent the horizontal pattern in the horizontal plane of the antenna a-K.

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

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

In FIG. 1, each antenna a-1 to a-
K and b-1 to b-K are high frequency switches 11a,
11b and high-frequency switches 12a and 12b for switching between transmission and reception, which are connected to the receivers 13a and 13b, respectively. Also, the high frequency switches 12a, 12
The transmitter 17 is connected via b and the high frequency switch 18. Each high-frequency switch 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 reception data signals output from the receivers 13a and 13b is selected by the change-over switch 16 according to the result of comparison 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 last reception quality judgment result at the time of reception, and transmission is performed from one antenna of the antenna group A or B. To do.

In the present embodiment, antennas having different directivity directions are called, for example, antenna a-1 and antenna b-1, antenna a-2 and antenna b-2, antenna a-K and antenna b-K. After switching sequentially in combination, an antenna is selected according to the reception quality judgment result, then reception diversity is performed, and transmission diversity is performed in which the antenna connected to the receiver having the best reception quality is used for transmission.

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

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

As a method for selecting antennas, the reception quality is compared for each corresponding antenna direction, such as antenna a-1 of antenna group A and antenna b-1 of antenna group B. However, this does not necessarily have to take such a combination, and a method of comparing the two may be adopted as an arbitrary combination.

[0029]

As described above, the present invention provides a plurality of antenna groups each composed of a plurality of antennas having different directivity directions, and selects the antenna with the best reception quality from each antenna group. Since the antenna with the best reception quality is selected from the antennas of each group, there is an advantage that the influence of frequency selective fading due to the delayed wave generated by the reflector can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing 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 showing a frame structure of an upstream signal.

FIG. 4 is a diagram illustrating a mobile communication system in which a single frequency signal is alternately transmitted and received between a base station and a mobile station.

FIG. 5 is a diagram illustrating a signal configuration.

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

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

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

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

[Explanation of symbols]

a-1 to aK, b-1 to b-K antennas 2a-1 to 2a-K, 2b-1 to 2b-K antenna horizontal pattern 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

Claims (1)

[Claims] 1. 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 alternately transmit and receive a signal of a single frequency at a predetermined cycle, and the base station , One-frequency alternating communication for mobile communication, which performs reception diversity using the antenna having the best reception quality among the plurality of antennas and performs transmission diversity which transmits to the mobile station using the antenna having the best reception quality In the system, the base station is provided with multiple antenna groups each consisting of multiple antennas with different directivity directions, and multiple receivers corresponding to each antenna group and signals received by each receiver are received. The reception quality inspection unit that inspects the quality and outputs the result is compared with the reception quality inspection result above, and the reception quality of any receiver is compared. A comparison unit that outputs a signal indicating whether or not the quality is good, and one transmitter are provided, and when receiving at the base station, each receiver sequentially switches the antennas in the corresponding antenna group to receive, By comparing the reception quality inspection results each time, the antenna with the best reception quality in each antenna group is selected, and then the antenna with the best reception quality in the corresponding antenna group is connected. The receiver diversity means that selects the receiver with the best reception quality by checking the reception quality of the receiver, and when transmitting from the base station, use the antenna with the best reception quality immediately before the start of transmission. A diversity method in a one-frequency alternating communication method for mobile communication, characterized by comprising: a transmission diversity means for performing.