JPH08195704A - Mobile communication system - Google Patents

Abstract

PURPOSE: To apply a space diversity communication system to the mobile communication system with a simple hardware by executing the changeover of antennas regardless of a reception state of a transmission reception antenna of a changeover destination when an error in excess of a threshold level is found in information received by a receiver of a mobile station. CONSTITUTION: A receiver 3 of a mobile station uses a CRC detection circuit 5 to monitor occurrence of error in a received signal. Upon the detection of an error in excess of a threshold level, a switch control circuit 8 executes changeover of an antenna I1 or I2 regardless of the reception state of the antenna I1 or I2 being a changeover destination. In this transmission diversity, a frame error is regarded as a reduction in a reception level of an outgoing signal and the signal is sent while selecting either the antenna I1 or I2 , then it is regarded that a reception power versus noise power ratio of the signal received by a base station is a maximum. Thus, the space diversity effect is improved by 2 or 3dB in comparison with the case of the reception diversity by the base station only.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used in a two-way mobile communication system. INDUSTRIAL APPLICABILITY The present invention is used in a mobile communication system in which the same frequency is used for bidirectional communication in a time division manner. The present invention relates to improvement of space diversity in which an antenna having a plurality of antennas and having a good reception state is selected and used for reception and transmission.

[0002]

2. Description of the Related Art A conventional mobile communication system will be described with reference to FIG. FIG. 6 is a conceptual diagram illustrating a conventional one-frequency alternating communication system for mobile communication, in which signals of a single frequency are alternately transmitted and received between a base station and a mobile station. In FIG. 6, a plurality of base stations 10 are provided for diversity (here, 2
The present invention has antennas 9 ₁ and 9 _{2 for} both transmission and reception, two receivers 17 ₁ and 17 ₂ and one transmitter 22. The mobile station 12 has one antenna 1 for both transmission and reception, one receiver 3, and one transmitter 6 for downsizing.

A radio signal having a carrier frequency f transmitted from the antenna 9 ₁ or 9 _{2 of the} base station 10 is transmitted to the mobile station 12
It is received by the antenna 1. In addition, the signal of the carrier frequency f transmitted from the antenna 1 of the mobile station 12 is
0 antennas 9 ₁ and 9 ₂ are received, and one of them is selected. That is, the base station 10 has a plurality of antennas 9
_{In the} configuration, spatial diversity is performed in which the reception signal from the antenna 9 ₁ or 9 ₂ that maximizes it among the reception levels ₁ and 9 ₂ is performed.

As shown in FIG. 7, the one-frequency alternating communication system in which the base station 10 and the mobile station 12 perform bidirectional communication at a single frequency is press talk communication in which transmission is performed alternately at a predetermined transmission time T, as shown in FIG. is there. FIG. 7 is a diagram showing allocation of transmission timings for press talk communication. Here, the signal from the mobile station 12 to the base station 10 is used as an uplink signal, and the base station 10
From the mobile station 12 to the downlink signal.

FIG. 9 is a block diagram showing a main configuration of the base station 10 and the mobile station 12 in the conventional example. 9A shows a base station and FIG. 9B shows a mobile station.
Referring to FIG. 9, in the base station 10, the transmitter 22 to which the encoder 23 is connected has high-frequency switches 16 ₁ , 16 ₂ and 16 ₄ which are switch-controlled by a switch control circuit 21 _2.
The antennas 9 ₁ and 9 ₂ are connected via the. Further, the decoder 20 is connected via the high frequency switch 16 ₃ which is switch-controlled by the switch control circuit 21 ₁ . Receiver 17
_1, 17 is _2, the antenna 9 _1, 9 ₂ are connected via the high-frequency switch 16 _1, 16 ₂ are switched controlled by the switch control circuit 21 _2. In the mobile station 12, the encoder 7
An antenna 1 is connected to a transmitter 6 to which is connected and a receiver 3 to which a decoder 4 is connected via a high frequency switch 2 which is switch-controlled by a switch control circuit 8. The high frequency switches 16 ₁ , 16 ₂ and 2 are switched according to the transmission / reception switching control signal, and the high frequency switch 1
6 ₃ and 16 ₄ are switched according to the antenna switching control signal.

Here, within the transmission time T of the upstream signal transmitted by the mobile station 12, the high frequency switch 2 of the mobile station 12 is located on the transmitter 6 side and the high frequency switches 16 ₁ , 16 of the base station 10 are arranged.
₂ is switched to the receivers 17 ₁ and 17 ₂ side, respectively. Further, within the transmission time T of the downlink signal transmitted by the base station 10, the high frequency switches 16 ₁ and 16 ₂ of the base station 10 are on the transmitter 22 side, and the high frequency switch 2 of the mobile station 12 is on the receiver 3 side.
Switched to the side. Further, the high frequency switch 16 ₃ of the base station 10 is switched to a higher receiving level of the signals received by the antennas 9 ₁ and 9 ₂ .

The switching operation of the high frequency switch 16 ₃ will be described below. FIG. 8 is a diagram showing a frame structure of an upstream signal and a downstream signal transmitted / received in one signal section. The signal lengths of the upstream signal and the downstream signal correspond to the transmission time T, and are composed of a preamble signal, an information signal and a CRC signal. Note that the preamble signal and CR
The C signal does not include the information signal.

[0008] In the base station 10, in the reception time T of the uplink signal, the high frequency switch 16 _1, 16 ₂ via the antenna 9 _1, 9 ₂ connected to the receiver 17 _1, 17 ₂ each received uplink in The reception levels of the signals are detected by the reception level detection circuits 18 ₁ and 18 ₂ , and the reception levels of the respective signals are compared by the comparator 19, and as a result, the antenna 9 ₁ or 9 ₂ and the receiver 17 having the higher reception level are received. ₁ or 17
Receive diversity is selected to select ₂ .

On the other hand, since the mobile station 12 has only one antenna 1, the base station 10 side has a suitable antenna 9 ₁ or 9 _2.
The transmission diversity for selecting is performed. That is, in the base station 10, within the reception time T of the upstream signal, the comparator 19
Switch control circuit 2 based on the comparison result of reception level at
1 ₁ uses the high-frequency switch 16 ₃ to successively receive the antenna 9 ₁ or 9 ₂ and the receiver 17 ₁ or 17 having a large reception level.
₂ is selected, and within the transmission time T of the next downlink signal, the switch 22 is connected to the last selected antenna 9 ₁ or 9 ₂ within the reception time T of the previous uplink signal. 21 ₂ performs transmission diversity for controlling the high frequency switch 16 ₄ . It should be noted that this transmission diversity is received by the base station 10 by utilizing the reversibility of the propagation path in which the correlation of the propagation path is sufficiently high under the condition that the fluctuation of the fading is slow for the downlink signal following the uplink signal. It is considered that the downlink signal transmitted from the antenna 9 ₁ or 9 _{2 having the} highest reception level detected last within the reception time T of the uplink signal has a high reception level at the mobile station 12.

As described above, the base station 10 performs reception diversity by using the comparison result of the reception levels of the upstream signals received by the plurality of antennas 9 ₁ or 9 ₂ , and receives the last signal within the reception time T of the upstream signals. Transmission diversity for the transmission time T of the next downlink signal is performed using the comparison result of the reception levels.

[0011]

In the conventional one-frequency alternating communication system for mobile communication, in which a single-frequency signal is alternately transmitted and received between a base station and a mobile station, the size and power consumption are reduced. Therefore, the mobile station does not perform diversity, and the base station performs reception diversity and transmission diversity using the diversity circuit described above.

However, in practice, the effect of receiving diversity only on the base station side is small, and more particularly in the mobile communication system in which the transmission power of the mobile station cannot be increased to reduce the power consumption. It is required to apply a diversity communication system with a large number.

However, when the diversity circuit in the base station described above is used in the mobile station, the communication quality is improved, but the circuit configuration of the mobile station becomes large and the power consumption accompanying it increases. Increasing is inevitable.

The present invention has been made against such a background, and an object thereof is to provide a mobile communication system to which a space diversity communication system having a great effect can be applied. An object of the present invention is to provide a mobile communication system that can apply the space diversity communication system with simple hardware. It is an object of the present invention to provide a mobile communication system that can be applied to a mobile station with a space diversity communication system that is small and consumes less power.

[0015]

The present invention realizes a space diversity communication system applicable to a mobile station which is required to be small in size and low in power consumption, and monitors an error occurrence in a received signal. As a result, the antenna is switched regardless of the reception state of the transmission / reception antenna of the switching destination. As a result, it is possible to realize an effective space diversity communication system with simple hardware while satisfying the requirements of small size and low power consumption.

That is, a first aspect of the present invention comprises a base station and a mobile station connected to the base station by a radio line, and the mobile station and the base station are radio signals of the same frequency. Is a mobile communication system that includes a transmitter and a receiver that alternately transmit and receive at predetermined intervals to communicate information signals.

Here, the feature of the present invention is that the mobile station comprises a plurality of transmitting / receiving antennas and means for switchingly connecting the plurality of transmitting / receiving antennas to a transmitter and a receiver, and the mobile station receives signals. A unit for detecting an error in the received information signal, and when an error exceeding a threshold value is detected by the detecting unit, switching of the plurality of transmission / reception antennas is executed regardless of the reception state of the transmission / reception antenna of the switching destination. It is equipped with means.

The means for detecting the error is C of the received signal.
It is desirable to detect RC.

A second aspect of the present invention is a mobile station device used in this mobile communication system. Since the means for detecting an error in the information signal is generally hardware conventionally provided in a mobile station, by adding the plurality of transmitting / receiving antennas and the means for executing the switching, The mobile station device of the present invention can be realized.

[0020]

[Operation] In the space diversity communication system of the mobile station,
An error of the information signal received by one of the plurality of antennas is detected by using a cyclic redundancy code (CRC) or other error detection code.

When an error is detected, at the transmission timing for the next base station, one of the plurality of antennas, which is different from the antenna used at the reception timing when the error is detected, transmits a radio signal.

At this time, since it suffices to perform switching regardless of the reception state of the switching destination antenna, the hardware for realizing this can be realized with a simple configuration. Furthermore, an effective space diversity communication system can be realized by combining with the reception diversity of the base station.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of an embodiment of the present invention. FIG. 2 is a block diagram of the mobile station device. FIG. 3 is a more specific block configuration diagram of the mobile station apparatus.

The present invention relates to a base station 10 and this base station 10
And a mobile station 12 connected by a wireless line. The mobile station 12 and the base station 10 have the same carrier frequency f.
Transmitters and 22 and receivers 3 and 17 ₁ , which alternately transmit and receive wireless signals of the above in a predetermined cycle to communicate information signals,
17 ₂ is a mobile communication system provided with each.

Here, the feature of the present invention is that the mobile station 12 switches and connects _two antennas 1 ₁ and 1 ₂ and the antennas 1 ₁ and 1 ₂ to the transmitter 3 and the receiver 6. A diversity control unit 50 as means, a CRC detection circuit 5 as means for detecting an error in a received information signal in the receiver 3 of the mobile station 12, and an error exceeding a threshold value is detected by the CRC detection circuit 5. is located at the place and a switch control circuit 8 as a means for performing the switching of the antenna 1 ₁ or 1 ₂ regardless reception state of the antenna 1 ₁ or 1 ₂ of the switching destination when the.

Next, the operation of the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a time chart showing the operation of the embodiment of the present invention. In FIG. 3, between the two transmitting / receiving antennas 1 ₁ and 1 ₂ and the receiver 3 to which the decoder 4 is connected and the transmitter 6 to which the encoder 7 is connected, an antenna for selecting an antenna is provided. A high-frequency switch 2 ₁ and a high-frequency switch 2 ₂ that switches alternately at a predetermined transmission / reception cycle are inserted.

The switch control circuit 8 alternately switches the high frequency switch 2 ₂ according to a predetermined transmission / reception cycle, and based on the CRC detection result 14 ₁ of the CRC detection circuit 5 connected to the decoder 4, the high frequency switch 2 Switch ₁ Note that FIG. 3 shows the state of the mobile station at the time of receiving the downlink signal.

As shown in FIG. 3, assuming that the high frequency switch 2 ₁ is selected on the antenna 1 ₁ side and the high frequency switch 2 ₂ is selected on the receiver 3 side, the antenna 1 ₁ and the receiver 3 are selected. The received downlink received signal is decoded by the decoder 4. CRC detection circuit 5 connected to the decoder 4
Then, as shown in FIG. 4, a frame error (whether or not the information signal is erroneous by at least 1 bit) of the information signal of the downlink reception signal from the CRC signal decoded by the decoder 1
4 ₃ is detected and the CRC detection result 14 ₁ is transmitted to the switch control circuit 8. In the switch control circuit 8, if there is a frame error 14 ₃ due to the CRC detection result 14 ₁ ,
At the time of transmission to the next base station, the high frequency switch 2 ₂ is switched to the transmitter 6 side in synchronization with a predetermined transmission / reception cycle, and the antenna 1 which used the high frequency switch 2 ₁ in the previous reception period by the antenna switching signal 14 ₂ . ₁ performs transmission diversity by switching to another antenna 1 ₂ is a. Incidentally, this transmission diversity, similarly to the conventional, for the upstream signal subsequent to the downlink signal, utilizing the reversibility of the propagation path correlation of the propagation path is sufficiently high under the condition that the fluctuation of the fading is slow, and, This utilizes the correlation between the _two antennas 1 ₁ and 1 _{2 of the} mobile station 12 for both transmission and reception. That is, if the correlation between the _two antennas 1 ₁ and 1 ₂ is sufficiently low by considering the frame error as a decrease in the reception level of the downlink signal, it is used during the reception period in which the frame error is detected when transmitting to the base station 10. an antenna 1 ₁ or 1 ₂ another antenna 1 ₁ or 1 and
If the signal is transmitted from _2, the reception power to noise power ratio (CNR) when received by the base station 10 is considered to be the maximum.

The effects of the embodiment of the present invention will be described with reference to FIG. FIG. 5 is a diagram showing the result of computer simulation, in which the horizontal axis represents the average received power to noise power ratio and the vertical axis represents the average bit error rate. This is a simulation for an upstream signal and the fading frequency is 10H.
z. As a result, the fading frequency is 10 Hz
When the average bit error rate is 10 ⁻³ under the above condition, the mobile station 12 performs the transmission diversity according to the present invention, and the base station 1
The spatial diversity effect in the case of performing the receive diversity at 0 is improved by 2.3 dB as compared with the spatial diversity effect in the case of performing only the receive diversity in the base station 10.

[0030]

As described above, according to the present invention,
It is possible to realize a mobile communication system to which a space diversity communication system having a great effect can be applied. Also,
According to the present invention, the space diversity communication method can be applied with simple hardware. This allows
A compact and low power consumption space diversity communication system can be applied to a mobile station.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a mobile station device.

FIG. 3 is a more specific block configuration diagram of a mobile station device.

FIG. 4 is a time chart showing the operation of the embodiment of the present invention.

FIG. 5 is a diagram showing a result of computer simulation.

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

FIG. 7 is a diagram showing allocation of transmission timing of press talk communication.

FIG. 8 is a diagram showing frame configurations of an upstream signal and a downstream signal.

FIG. 9 is a block configuration diagram showing main configurations of a base station and a mobile station in a conventional example.

[Explanation of symbols]

1, 1 ₁ , 1 ₂ , 9 ₁ , 9 ₂ Antenna 2, 2 ₁ , 2 ₂ , 16 ₁ , 16 ₂ , 16 ₃ , 16 ₄ High frequency switch 3, 17 ₁ , 17 ₂ Receiver 4 Decoder 5 CRC detection Circuit 6, 22 Transmitter 7 Encoder 8 Switch control circuit 10 Base station 12 Mobile station 14 ₁ CRC detection result 14 ₂ Antenna switching signal 14 ₃ Frame error 18 ₁ , 18 ₂ Reception level detection circuit 19 Comparator 20 Decoder 21 ₁ , 21 ₂ Switch control circuit 23 Encoder 30 Receiver 40, 50 Diversity controller 60 Transmitter

Claims (3)

[Claims] 1. A base station and a mobile station connected to the base station by a radio line, wherein the mobile station and the base station alternately transmit and receive radio signals of the same frequency at a predetermined cycle. In a mobile communication system that includes a transmitter and a receiver that perform communication, the mobile station includes a plurality of transmission / reception antennas and means for switching and connecting the plurality of transmission / reception antennas to the transmitter and the receiver. The receiver of the station detects the error of the received information signal, and when the detecting unit detects an error exceeding the threshold, switches the plurality of transmitting / receiving antennas regardless of the receiving state of the transmitting / receiving antenna of the switching destination. And a means for executing the mobile communication method. 2. The mobile communication system according to claim 1, wherein said error detecting means detects a CRC of a received signal. 3. A mobile station apparatus used in the mobile communication system according to claim 1.