JPH0613951A - Diversity system in mobile communication using single-frequency alternate communication system - Google Patents

Abstract

PURPOSE:To improve communication quality by correcting adaptively a deviation in a level detection circuit caused by a reception sensitivity deviation when transmission reception diversity is implemented in the case of communication between a base station and a mobile station. CONSTITUTION:An intermediate frequency signal from receivers 40-1, 40-2 connecting to antennas 1, 2 is inputted to level detection circuits 41-1, 41-2, in which an instantaneous reception level is detected. An output signal of the level detection circuits is divided into two, the one signal is inputted to median detection circuits 42-1, 42-2 and the other is inputted to a comparator 45 respectively. The median detection circuits 42-1, 42-2 obtain the median of accumulated instantaneous reception levels and output its output signal to a differential amplifier circuit 43, in which the reception sensitivity of the receiver is extracted. The difference output is fed to an adder circuit 44, the level detection characteristic is independent of the deviation in the reception sensitivity but always made coincident, the level comparison result is inputted to the comparator 45 and its output selects a changeover switch 46.

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 in which a single frequency signal is alternately transmitted and received between a base station and a mobile station, and the base station performs reception diversity and transmission diversity to improve communication quality. The present invention relates to a diversity transmission / reception system in mobile communication.

[0002]

2. Description of the Related Art FIG. 6 is a diagram for explaining a mobile communication system in which signals of a single frequency are alternately transmitted and received between a base station and a mobile station. In the figure, a base station 1 has a plurality of (two in this case) transmitting / receiving antennas 2-1 and 2 for diversity.
-2, one transmitter and two receivers. Mobile station 3
Has one transmitting / receiving antenna 4, one transmitter and one receiver. Antenna 2-1 or 2 of base station 1
The signal of the carrier frequency f transmitted from -2 is received by the antenna 4 of the mobile station 3.

The signal of the carrier frequency f transmitted from the antenna 4 of the mobile station 3 is the antenna 2-1 of the base station 1.
The receiver received at 2-2 and connected to one antenna is selected. The base station 1 demodulates the received signal from the antenna having the highest reception level among the signals received by the plurality of antennas. That is, selection diversity is performed.

As shown in FIG. 7, the mobile communication system in which the base station 1 and the mobile station 3 perform bidirectional communication at a single frequency is press talk communication in which transmission is performed alternately at a predetermined time. Here, the signal from the mobile station 3 to the base station 1 is an upstream signal, and the signal from the base station 1 to the mobile station 3 is a downstream signal. In the figure, the case of N-channel multiplexing is shown.
The No. to Nth 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.

8 and 9 are block diagrams specifically showing the configurations of a base station and a mobile station. FIG. 8 shows the base station,
FIG. 9 shows a mobile station. In these figures, the transmitter 16 and the receivers 12-1 and 12-2 of the base station are connected via the contacts a and b of the high frequency switches 11-1 and 11-2 which are switched and controlled by the switch control circuit 18. It is connected to the antennas 10-1 and 10-2. Mobile station transmitter 2
The antenna 20 is connected to the receiver 2 and the receiver 23 via a high frequency switch 21 which is switch-controlled by a switch control circuit 24. The high frequency switches 11-1 and 1
1-2, when transmitting by a transmission / reception switching signal from the switch control circuit 18, switches the antenna contact to the b side,
When receiving, the ANTES contact is switched to the a side.

Here, within the transmission time T of the upstream signal transmitted by the mobile station, the high frequency switch 21 of the mobile station is connected to the transmitter 22 side via the contact b and is connected to the high frequency switch 11- of the base station.
1, 11-2 are receivers 12-1, 12- via contact point a.
Connected to 2. Further, within the transmission time T of the downlink signal transmitted by the base station, the high frequency switch 21 of the mobile station has the contact
In addition, the high frequency switches 11-1 and 11-2 of the base station are switched to the contact b.

At the base station, the receiver 1
The level detection circuits 13-1 and 13-2 in the level detection unit 13 connected to 2-1 and 12-2 detect the reception level, sequentially determine the receivers with high reception levels, and compare the results with the comparison circuit. The signal is output from 14 as an antenna switching control signal and input to the switch control circuit 18. When the reception level of the receiver 12-1 is higher than the reception level of the receiver 12-2, it is connected to the contact a to connect the reception data signal of the receiver 12-1 with the output signal of the comparison circuit 14. On the other hand, when the reception level of the receiver 12-2 is higher than that of the receiver 12-1, it is connected to the contact b and the reception data signal of the receiver 12-2 is extracted.

For transmission (downlink) from the base station to the mobile station, transmission diversity is performed by switching antennas.
That is, in the base station, the receiver 12-1
Is higher than the receiver 12-2, the transmitter 1
6, the contact b of the high frequency switch 17 and the high frequency switch 1
The signal is transmitted from the antenna 10-1 via the contact point b of 1-1.
If the reception level of the receiver 12-2 is higher than that of 12-1, the signal is transmitted from the antenna 10-2.

The transmission diversity utilizes the 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 antenna having the higher reception level of the uplink signal received by the base station is used. This utilizes the property that the reception level of the downlink signal transmitted from the mobile station is higher than that when transmitted from other antennas. In this way, the base station performs reception diversity for upstream signals and transmission diversity for downstream signals.

[0010]

FIG. 8 is a block diagram of the base station.
The receivers 12-1 and 12-2 have different receiving sensitivities.
At this time, level detection by the level detection circuits 13-1 and 13-2
The characteristics are different. That is, the receiving sensitivity of the receiver 12-2 is
If L (dB) is larger than the receiving sensitivity of the receiver 12-1,
Bell detection characteristic is L (dB) shifted as shown in Fig. 10 (a).
It becomes a characteristic. Here, the input of the level detection circuit is x, and the output is
Let y be the level detection characteristic of the level detection circuit 13-1.
The sex is y = Ln (b₁x), the level detection circuit 13-2 is y
= Ln (b ₂x). Here, the level detection circuit 13
-1 input x₁, The input of the level detection circuit 13-2 is x
₂Then x₂-L (dB) <x₁<X₂The relationship of
When y₂<Y₁And the level judgment result is reversed
It

Therefore, the antenna 10- of FIG.
1 reception level waveform r ₁ (t), while the switching waveform of the reception level waveform r ₂ (t) of the antenna 10-2 so that if the ideal level selection is performed indicated by the bold line in FIG. As described above, when x ₂ > x ₁ , y ₂ <y ₁ is switched, which causes a switching waveform, which results in a selection waveform as shown by the dotted line in the figure, which reduces the diversity effect.

The present invention provides a diversity system in a one-frequency alternating communication system for mobile communication, which can improve the reception quality of an uplink signal at a base station and the reception quality of a mobile station at the time of transmitting a downlink signal at a mobile station. The purpose is to do.

[0013]

According to the present invention, the above problems can be solved by the means described in the claims. That is, the invention of claim 1 alternately transmits and receives a signal of a single frequency in 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, In the one-frequency alternating communication method for mobile communication, the station performs reception diversity using the antenna with the highest reception level and also performs transmission diversity using the antenna with the highest reception level to transmit to the mobile station. , A plurality of receivers, level detection circuits corresponding to the plurality of receivers, and one comparison circuit for comparing output signals of the level detection circuits,
The receiver of each receiver compares the output of the median value detection circuit with the median value detection circuit for detecting the median value of the cumulative value of the reception level (50% of the accumulated value of the reception level) from the output of the level detection circuit. Corresponding to the plurality of antennas, a circuit for obtaining the sensitivity deviation, an adding circuit for adding the difference of the receiving sensitivity deviation to the output signal of the level detection circuit which becomes a comparator input corresponding to the receiving sensitivity deviation of the receiver. One transmitter, and a reception diversity control means for sequentially selecting the receiver having the highest level of the signal received by each antenna, and a transmission diversity control means for transmitting using the antenna having the highest level. It is a diversity system in the one-frequency alternating communication system for mobile communication.

According to a second aspect of the present invention, in the above means, only one set of the level detection circuit and one set of the median value detection circuit for detecting the median value are provided, and these are switched in a time division manner to correspond to a plurality of antennas. It is configured to detect the reception levels of a plurality of receivers.

[0015]

According to the present invention, a plurality of receivers are provided in a base station, a level detection circuit corresponding to the plurality of receivers, a median value detection circuit for detecting a median value of the cumulative value of reception levels, and reception of each receiver. A circuit for extracting the sensitivity deviation, an adding circuit for adding the difference to the output of the level detection circuit, a reception diversity control means for correcting the deviation when the reception sensitivity deviation occurs and selecting a receiver with a high reception level, It comprises one transmitter corresponding to a plurality of antennas, and transmission diversity control means for transmitting using the antenna having the highest reception level.

When performing transmission / reception diversity in the communication between the base station and the mobile station, the deviation of the level detection circuit caused by the deviation of the receiving sensitivity of the receiver is adaptively corrected, so that the correct antenna selection can be made. Therefore, it is possible to reduce deterioration of diversity characteristics due to reception sensitivity deviation and improve communication quality.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a base station according to the method of the present invention. In FIG. 8, among the components shown in FIG.
The same components as in the case of are attached with the same numeral symbols. In the present invention, since the level detection unit 30 is different from the conventional technique,
This part will be described in detail below. The operations themselves of the reception diversity and the transmission diversity are the same as those in the prior art.

FIG. 2 is a diagram showing an embodiment of the level detecting section 30 of the present invention. In the figure, the intermediate frequency signals from the receivers 40-1 and 40-2 connected to the antenna 1 and the antenna 2 are input to the level detection circuits 41-1 and 41-2, and the instantaneous reception level is detected. The output signal of this level detection circuit is divided into two, one of which is the median value detection circuit 42-
1, 42-2, and the other is input to the comparator 45. The median value detection circuit is a circuit for calculating the median value of the cumulative value of the instantaneous reception levels.

FIG. 3 shows an example of the specific configuration. Figure 3
In the figure, 50, 52 and 55 are resistors, 51 and 54 are operational amplifiers, and 53 is a capacitor. The output of the integrating circuit composed of the capacitor 53 and the operational amplifier 54 is fed back to the operational amplifier 51, compared with the instantaneous level of the output of the level detection circuit, and the comparison signal is input to the operational amplifier 54 and taken out as a median value. The output signals of the median value detection circuits 42-1 and 42-2 are input to the differential amplifier circuit 43 to extract the reception sensitivity deviation of the receiver.

This corresponds to Ln (b ₁ /
This corresponds to taking out b ₂ ). By adding this difference to the adder circuit 44, the level detection characteristics match as shown in FIG. 4A, although there is a reception sensitivity deviation. This can always be matched regardless of the value of the reception sensitivity deviation. The level-corrected result is input to the comparator 45, and the contact of the change-over switch 46 is switched according to the level comparison result.
In the switching operation, the ideal operation indicated by the thick line and the operation of the present invention indicated by the dotted line coincide with each other, and no switching error occurs.

FIG. 5 is a diagram showing another embodiment of the level detecting unit. One level detecting circuit and one median value are provided in order to eliminate the deviation of the individual characteristics of the level detector and the median value detecting circuit. An example is shown in which the detection circuit is shared by a plurality of receivers. In the figure, receivers 60-1, 60-2
The intermediate frequency signal of is input to the switch 61, and the contact point of the switch 61 is alternately switched by the sample signal from the signal generation circuit 62. The alternately switched intermediate frequency signal is input to the switches 65 and 66 via the level detection circuit 63 and the median value detection circuit 64. The switches 65 and 66 are interlocked with the switch 61, and when the contact of the switch 61 is connected to a, the contact of the switch 65 and 66 is also connected to a, and the contact of the switch 61 is connected to b. When it is connected to the contact b.

The output signals of the switches 65 and 66 are passed through low pass filters 67, 68, 69 and 70 to remove high frequency components. The differential amplification circuit 72 detects the reception sensitivity deviation from the output signals of the low-pass filters 69 and 70, and inputs the difference to the addition circuit 71. The output signal of the low-pass filter 67 is corrected for the difference via the adder circuit 71, and the output signal of the low-pass filter 68 is input to the comparator 13. The comparison circuit 73 compares the levels, and the selector switch 74 switches the receiver output signal.

[0023]

As described above, according to the present invention, the receiver sensitivity deviation of the receiver is adaptively corrected so that the level detection characteristics are always matched. Therefore, the level determination for diversity reception is performed. Can be done correctly. Therefore, there is an advantage that it is possible to prevent deterioration of communication quality due to an antenna switching error during diversity transmission / reception.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a base station according to the present invention.

FIG. 2 is a diagram showing an embodiment of a level detection unit of the present invention.

FIG. 3 is a diagram showing an example of a configuration of a median value detection circuit.

FIG. 4 is a diagram for explaining level detection and received signal switching operation according to the present invention.

FIG. 5 is a diagram showing another embodiment of the level detection unit of the present invention.

FIG. 6 is a diagram illustrating a one-frequency alternating communication system for mobile communication.

FIG. 7 is a diagram showing a frame structure of a signal.

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

FIG. 9 is a block diagram showing a main configuration of a conventional mobile station.

FIG. 10 is a diagram illustrating conventional level detection and received signal switching operations.

[Explanation of symbols]

10-1, 10-2 antenna 11-1, 11-2, 17 high frequency switch 12-1, 12-2, 40-1, 40-2, 60-1,
60-2 Receiver 13-1, 13-2, 41-1, 41-2, 63 Level detection circuit 14, 45, 73 Comparison circuit 15, 46, 74 Changeover switch 16 Transmitter 18 Switch control circuit 30 Level detection section 42-1, 42-2, 64 Median value detection circuit 43, 72 Differential amplification circuit 44, 71 Adder circuit 50, 52, 55 Resistor 51, 54 Operational amplifier 53 Capacitor 61, 65, 66 Switch 62 Signal generation circuit 67 ~ 70 low pass filter 73

Claims (2)

[Claims] 1. A signal of a single frequency 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 a single antenna for both transmission and reception,
The base station uses the antenna with the highest reception level to perform reception diversity, and the antenna with the highest reception level to transmit diversity to the mobile station. A plurality of receivers, a level detection circuit corresponding to the plurality of receivers, one comparison circuit for comparing the output signals of the level detection circuits, and a center of the cumulative value of the reception levels from the output of the level detection circuit. A median value detection circuit for detecting a value, a circuit for comparing the outputs of the median value detection circuit to obtain the reception sensitivity deviation of each receiver, and the comparator input corresponding to the reception sensitivity deviation of the receiver An adder circuit for adding the difference of the reception sensitivity deviation to the output signal of the level detection circuit, one transmitter corresponding to the plurality of antennas, and a signal received by each antenna. One-frequency alternating communication system for mobile communication, characterized by further comprising: reception diversity control means for sequentially selecting the receiver having the highest level, and transmission diversity control means for transmitting using the antenna having the highest level. Diversity method in. 2. A level detection circuit and a median value detection circuit for detecting one median value are time-divisionally switched to detect the reception levels of a plurality of receivers corresponding to a plurality of antennas. 1. A diversity method in the one-frequency alternating communication method for mobile communication according to 1.