JPH0666722B2 - Diversity reception method in mobile station - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a diversity reception system performed by a mobile station to reduce fading in mobile communication.

[Prior art and its problems]

FIG. 1 is a block diagram showing a conventional diversity reception system in a mobile station. The system shown in the figure is a diversity reception system based on a two-branch selective combining method. Such selective combining methods include before detection and after detection. In this case, the selective combination after detection is performed.

In FIG. 1, 1 is an antenna of a branch (1), 2 is a receiving unit of the branch (1), 3 is a reception level output signal of the branch (1), 4 is a demodulation signal of the branch (1), and 5 is a branch ( 2) antenna, 6 branch (2) receiver, 7 branch (2) reception level output signal, 8 branch (2) demodulation signal, 9 selective combining section, 10 diversity reception demodulation signal is there.

The signals received by antennas 1 and 5, respectively, are received by the receiver.
Demodulated by 2, 6 and demodulated signals 4, 8 are output. The selective combining unit 9 receives the level 3 of the signal received by the antenna 1 and the antenna 2
The level 7 of the signal received in is compared, and when the reception level 3 of the branch (1) is higher than the reception level 7 of the branch (2), the demodulation signal 4 of the branch (1) is output as the diversity reception demodulation signal 10. If the reception level 7 of the branch (2) is higher than the reception level 3 of the branch (1), the demodulation signal 8 of the branch (2) is output as the diversity reception demodulation signal 10.

When a mobile station receives a signal from a radio base station (not shown) by a diversity reception method based on a two-branch selective combining method as shown in FIG. 1, diversity reception is always performed regardless of the signal reception level at that time. It was For this reason, it is necessary to constantly supply power to the two receiving units 2 and 6, and although diversity reception shows an improvement effect in terms of signal transmission reliability, call quality, etc., power consumption of the mobile station device is large. However, there is a drawback that it causes an inconvenience.

FIG. 2 is a conceptual diagram showing a configuration of a wireless zone in mobile communication.

That is, for example, N radio base stations Ri are provided in one control zone as a service area for car telephone services.
(I = 1, 2, ..., N), and the control zone is constituted by a set of small radio zones belonging to each base station Ri. The radio base stations Ri are connected to the common radio control station 11 by fixed transmission lines.

The radio control station 11 is connected to a general telephone line network via a mobile station (automobile) switching station (not shown). Also, the size of the small radio zone belonging to each radio base station Ri is determined to be a size that enables sufficient communication between the mobile station and the radio base station due to the transmission power of the mobile station in the zone. Has been.

FIG. 2A is an explanatory diagram showing a signal structure of a control channel for calling a mobile station in mobile communication for one frame.

In the figure, the signal configuration is N radio base stations (R _{1 to} R _N ).
Are simultaneously transmitted by the wireless base station and N time slots Si (i = 1, 2,
, N) is defined as one frame, and such a frame is continuously repeated.

That is, in the time slot S, each base station simultaneously transmits a paging signal to the mobile station in order to know from the base station whether there is any mobile station in the control zone. When a mobile station is present in the control zone and the mobile station receives the paging signal, when the paging is for its own mobile station, it transmits a response signal to the base station. After that, control of call connection progresses, and communication is performed between the wireless base station and the mobile station.

As described above, when calling the mobile station, the time slot S
Then, since N radio base stations simultaneously transmit the paging signal, unlike the case in the other time slots S _{1 to} S _N ,
Since the return diversity effect is generated, the mobile station side can receive the ringing signal without necessarily performing the diversity reception by selectively combining the reception signals of the two branches, but conventionally, regardless of the time slot. , The mobile station was performing diversity reception.

Therefore, the conventional mobile station has a drawback that it also causes an increase in power consumption, which causes inconvenience.

[Object of the Invention]

The present invention has been made to eliminate the above-mentioned drawbacks of the prior art. Therefore, an object of the present invention is to provide an economical diversity receiving system in a mobile station that does not consume more power than necessary. To provide.

[Main points of the invention]

The point of the present invention is to reduce power consumption by stopping diversity reception and switching to single reception by one of the receiving systems when a signal can be received without using diversity reception in a mobile station diversity reception system in mobile communication. This is the point.

Example of Invention

 Next, an embodiment of the invention will be described with reference to the drawings.

When diversity reception is applied under Rayleigh fading propagation path, the characteristics are improved in terms of signal transmission reliability and speech quality compared to non-diversity reception. The amount of improvement depends on the correlation between branches and the evaluation parameters,
For example, if the bit error rate during non-diversity reception is P ₁ when the receiver input is x (dBμ), the receiver input that obtains the same bit error rate P ₁ during diversity reception is x-G.
(DBμ) (G> 0). This G is the amount of improvement due to diversity and is also called diversity gain. This situation is shown in a graph in FIG.

Now, assuming that the bit error rate P ₁ in FIG. 3 is a permissible limit value in system design, the receiver input may be at least x−G (dBμ) during diversity reception, and at least x (dBμ) during non-diversity reception. .

Therefore, even with a diversity receiver, it is not necessary to always perform diversity reception, and the receiver input is x (dB
μ) or more, the required bit error rate P ₁ or more can be satisfied even if switching to non-diversity reception. Also, with respect to the reception of voice and the like, if there is a reception level above a certain value, sufficient call quality can be obtained without diversity reception.

The above is the principle of the present invention.

FIG. 4 is a graph showing bit error rate characteristics for individual transmission-diversity reception, multi-station simultaneous transmission-diversity reception, individual transmission-non-diversity reception, and multi-station simultaneous transmission-non-diversity reception.

In the figure, G (dB) is the gain of diversity reception, A
Is the gain of multi-station simultaneous transmission. When the bit error rate P ₁ is set as the allowable limit in system design, multi-station simultaneous transmission −
Required receiver input for non-diversity reception is multi-station simultaneous transmission-Required receiver input for diversity reception x-G-A
X- which is the value obtained by subtracting the diversity gain G from (dBμ)
It is considered to be A (dBμ).

From this, the required bit error rate P ₁ even if switching to non-diversity reception if the receiver input is x-A (dBμ) or more even if diversity reception is not always performed in the time slot for simultaneous multi-station transmission by the diversity receiver. It is clear that the above is satisfied.

FIG. 5 is a block diagram showing an embodiment of the present invention based on the above-mentioned examination. In the figure, the first
The same parts as those in the figure are denoted by the same reference numerals. In addition, 13 is a time slot generation circuit, 14 is the same detection circuit,
Is.

At the mobile station side, it has been known in advance that the time slot of the calling signal repeatedly changes in the order of S, S _{1 to SN in} the frame structure shown in FIG. 2A, so the time slot generation circuit synchronized with this Preparing 13 is easy. The slot period S is detected from the output of this circuit 13 by the detection circuit 14, and only during this period the power supply circuit of the receiving unit 6 (or 2) is turned off to stop the diversity reception, and only one of the branches receives independently. Then, the power supply to the other branch is stopped to reduce the power consumption.

Referring again to FIG. 2A. The signal structure of the control channel shown in the figure is, as described above, the time slot S portion simultaneously transmitted by N radio base stations and the time slot individually transmitted by one radio base station. Slots S _{1 to} S _N
And part of. In the time slot S, there is a transmission diversity effect due to simultaneous transmission by a plurality of stations, and the reliability of signal transmission is higher than that in the time slot S _{1 to SN} portion of individual sequential transmission.

In the present embodiment, diversity reception is stopped simply by measuring the time slot in the period S without measuring the received power level in the mobile station one by one, but the received power level in the period of the time slot S is sufficient. Since it is known to be high, it will be clear that the present embodiment does not impair the reliability of signal reception.

〔The invention's effect〕

As described above, according to the present invention, there is an advantage that unnecessary power consumption can be reduced in the diversity receiving system of a mobile station in mobile communication.

It should be noted that the present invention, diversity reception of three or more branches,
Alternatively, diversity reception using a combining method such as a maximum ratio combining method or an equal gain combining method other than the selective combining method can be easily applied based on the same idea.

[Brief description of drawings]

FIG. 1 is a block diagram showing a conventional diversity reception system in a mobile station, FIG. 2 is a conceptual diagram showing a configuration of a radio zone in mobile communication, and FIG. 2A is a signal configuration of a control channel for calling a mobile station in mobile communication. FIG. 3 is a graph showing bit error rates in comparison between diversity reception and non-diversity reception, and FIG. 4 shows individual transmission and multi-station simultaneous transmission respectively. FIG. 5 is a graph showing the bit error rate separately for diversity reception, and FIG. 5 is a block diagram showing an embodiment of the present invention. Reference numeral 1 ... Branch (1) antenna, 2 ... Branch (1) receiving section, 3 ... Branch (1) reception level output signal, 4 ... Branch (1) demodulation signal, 5 ... Branch (2) antenna, 6 ... Branch (2) receiver, 7 ... Branch (2) reception level output signal, 8 ...
... Branch (2) demodulated signal, 9 ... Selective combining section, 10 ...
… Diversity reception demodulation signal, 11 …… Radio control station, 13…
… Time slot generation circuit, 14 …… Time slot detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kiyoto Nagata 1, 2356 Take, Yokosuka City, Kanagawa Pref., Yokosuka Telecommunications Research Institute, Nippon Telegraph and Telephone Public Corporation (72) Tadaaki Nakata 1, 2356 Take, Yokosuka City, Kanagawa Japan Toshiyuki Ikeda, Examiner, Yokosuka Electro-Communications Laboratory, Telegraph and Telephone Public Corporation

Claims (1)

[Claims] 1. A control zone having N (N is an integer of 1 or more) radio base stations in one control zone, and between a mobile station and a radio base station in any of the radio zones of each radio base station. In addition, one time slot (hereinafter referred to as a simultaneous transmission time slot) as a period in which the N radio base stations transmit at the same time in synchronization with each other, and subsequently, the radio base stations do not overlap each other. N individual timeslots as a set of time periods (hereinafter referred to as individual timeslots) to be transmitted independently by shifting in time,
A control channel for paging in which the frame structure consisting of is continuously repeated is set, and a transmission from the radio base station on the control channel is received by the mobile station having at least two sets of reception systems, In the diversity reception method in the mobile station, which is configured to selectively combine the received signals according to to receive as diversity reception, in the simultaneous transmission time slot in which all the radio base stations simultaneously transmit, diversity reception is stopped and either one of them is stopped. A diversity reception system in a mobile station, characterized in that the mobile station is provided with means for switching to single reception by the reception system and stopping power supply to the other reception system.