JP2639840B2 - Digital mobile communication system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for digital mobile communication having a small zone configuration, and in particular, a digital mobile communication system in which a method for synchronizing frame transmission timing between base stations is improved. About.

[Conventional technology]

In a digital mobile communication system of a small zone configuration represented by a mobile telephone system, in order to transmit the same signal at the same frequency from a plurality of base stations, and when channel switching is performed between base stations between zones. As a technique for synchronizing the transmission timing between base stations for the purpose of reducing the time of instantaneous interruption, etc., the base station is provided with a dedicated receiver for receiving a signal transmitted from an adjacent base station, and the reception timing A method for establishing synchronization between base stations on the basis of the above has been developed.

[Problems to be solved by the invention]

This conventional method has a disadvantage that wireless communication is difficult and synchronization cannot be established when there is no line of sight between base stations. In order to ensure visibility, constraints on the locations of base stations and antennas are increased, and the system is extremely poor in applicability to a system with a minimum zone to increase subscriber capacity, and a system with a low antenna height, and Even after the system is introduced, it is affected by changes in surrounding buildings. Further, since a dedicated receiver for inter-station synchronization is required in the base station, there is a disadvantage that it is economically disadvantageous.

The object of the present invention is to eliminate the disadvantages mentioned above,
It is an object of the present invention to provide a digital mobile communication system which enables frame synchronization between stations even when there is no view between base stations, and does not require a dedicated receiver.

[Means for solving the problem]

The present invention provides a small zone configuration including an exchange, a plurality of base stations respectively connected to the exchange by a communication line, and a plurality of mobile stations communicating in a wireless zone formed by the base station. In the digital mobile communication system, the exchange includes timing information transfer means for adding or transferring timing information to the communication line, and the base station includes a delay adjustment buffer for adjusting a delay amount of the communication line. And detecting the reception timing of the uplink from the mobile station transmitting at the timing of communicating with another base station, and performing the delay adjustment based on the detection result and the reception timing of the timing information from the exchange. And delay adjustment control means for controlling the amount of delay of the buffer.

[Action]

According to the present invention, in a switching center, common timing information is added to a plurality of lines or transferred in parallel by a timing information transfer unit, and in a base station, a timing for communicating with another base station is controlled by a delay adjustment control unit. And the detection result of the reception timing of the uplink signal from the mobile station transmitting in
The inter-station synchronization is established by adjusting the delay amount of the delay adjusting buffer of the base station based on the reception timing of the timing information from the exchange.

Therefore, even when there is no line of sight between base stations, it is possible to establish frame synchronization between stations without requiring a dedicated receiver.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention,
FIG. 2 is a block diagram showing details of the delay adjustment control means.

In the first embodiment, an exchange 1 and three base stations 11, 12, and 13 connected to the exchange 1 by a communication line 70, respectively.
And four mobile stations 21 and 2 that communicate on the wireless channel 80 in the wireless zone constituted by the base stations 11, 12 and 13, respectively.
In the digital mobile communication system having a small zone configuration including 2, 23 and 24, the exchange 1 transfers the timing information 62 to the communication line in parallel with the input information 61, which is a feature of the present invention. The base stations 11, 12 and 13 include, as representatively represented by the base station 11, the delay of the communication line 70, which is a feature of the present invention, in addition to the transmitting / receiving device 33. The delay adjustment buffers (DB) 31 and 32 for adjusting the amount and the reception timing of the uplink from the mobile station transmitting at the timing of communicating with another base station are detected, and the detection result and the exchange 1 And a delay adjustment control means 40 for controlling the delay amount of the delay adjustment buffer 32 based on the reception timing of the timing information.

According to FIG. 2, the delay adjustment control means 40 is connected to the input of the delay adjustment buffer 32 to detect the timing of the downlink, and receives the output of the timing detection circuit 41 and , A timing detection circuit 42 that is connected to the output of the delay adjustment buffer 32 and detects the timing of the downlink that has been delayed by the delay adjustment buffer 32, and a timing detection circuit 42 A phase comparison circuit 47 for inputting the timing and the downlink reference timing 53 output from the reference timing generation circuit 46 and comparing the two phases.
And a timing detection circuit 43 connected to an uplink indicated by a dotted line in FIG. 2 by receiving a signal from another station (adjacent station) and detecting its timing, and the timing detected by the timing detection circuit 43 and the output from the reference timing generation circuit 46 The input of the uplink reference timing 52 and the phase comparison circuit 48 for comparing the phases of the two, and the outputs of the phase comparison circuits 47 and 48 are input, the amount of correction of the downlink delay buffer and the reference timing is calculated, and the delay is calculated. And a delay adjustment amount calculation circuit 51 for outputting the amount control signal 54 and the reference timing control signal 55, and furthermore, timing detection circuits 44 and 45 for detecting the downlink and uplink timings of the delay adjustment buffer 31.
And its phase comparison circuits 49 and 50.

In the first embodiment, the delay adjustment buffer
The figure shows a case in which a signal of another station (adjacent station) is received through a communication line passing through 32, and a case in which a signal of another station is received through a communication line passing through the delay adjustment buffer 31 can be similarly configured.

 Next, the operation of the first embodiment will be described.

In the exchange 1, the timing information transfer means 1a transfers the information to the base station 11 in parallel with the timing information 62 on the communication line 70. The mobile station 22 is communicating through the base station 12, and the timing is synchronized with the base station 12. When the mobile station 22 moves toward the base station 11 and a request for performing channel switching between zones is generated, the base station 11 receives a signal from the mobile station 22 (FIGS. 1 and 2). , A dotted line indicates reception of a signal from another station (adjacent station).) Based on the detection result of the frame synchronization timing and the timing information from the exchange 1, the delay buffer 31 and the
By controlling 32, frame synchronization between stations is achieved.

As shown in FIG. 2, the base station 11 generates a reference timing in a reference timing generation circuit 46 for controlling the delay amount. The reference timing is a timing obtained by detecting timing information 62 of a certain downlink by the timing detection circuit 41 and delaying the timing information by a certain amount. In the timing detection circuit 43 for detecting the timing of the uplink (signal reception timing from the mobile station), when receiving the signal from the adjacent base station, the phase is compared by the phase comparison circuit 48.
Control the reference timing. At the same time, the difference between the detection result of the downlink timing information and the reference timing is compared by the phase comparison circuit 47, and the amount of the downlink delay buffer and the correction amount of the reference timing are calculated based on the result and the comparison result by the comparison circuit 48. And outputs a delay amount control signal 54 and a reference timing control signal 55, and outputs the delay adjustment buffer 32
And the reference timing of the reference timing generation circuit 46 is controlled.

In the first embodiment, since the transceiver before use for communication is used, there is an advantage that a dedicated receiver for inter-station synchronization is not required. Another advantage is that synchronization can be established even when there is no perspective between base stations. In digital mobile communication, by compressing the time axis, forming an empty slot on the time axis, and switching the frequency of the mobile station at the timing of this empty slot when the mobile station changes zones, to continue communication, The present invention is particularly effective for inter-station frame synchronization for the purpose of performing channel switching without losing information bits. That is, at the time of channel switching between zones, the mobile station usually has a reception level at which it can communicate with the two base stations before and after the switching, so that the applicability of the present invention is guaranteed.

In general, in a system in which frequencies are geographically reused, communication with a base station to be switched to is difficult due to interference when performing communication at a frequency before switching even if a sufficient reception level is obtained. However, in the present invention, instead of controlling the amount of delay based only on the delay time difference information obtained at the time of one channel switching, an averaging process of a plurality of communication channels accommodated by the base station, In addition, since it is possible to set the reference timing by performing averaging processing in terms of time, it is possible to take measures against this interference. Since there is little temporal change in the delay time difference of the downlink wired line, a method of averaging over time is effective.

From the phase comparison circuits 47 and 48, it is obtained that the timing of the mobile station before switching is remarkably shifted, and it is impossible to perform channel switching without instantaneous interruption if the timing is adjusted to the reference timing of the switching destination base station. If it can be determined from the delay time difference information obtained, it is also possible to adjust the timing of the channel only before switching.

Reception of a signal of a mobile station belonging to an adjacent base station is performed immediately before channel switching between zones as described above, and when there is a transceiver that is not used for communication at the base station, communication with an adjacent zone is performed. By searching for an uplink channel and controlling the reference timing based on the reception when the channel is successfully received, the delay can be adjusted more accurately.

If there are few mobile stations in communication and there are no mobile stations that can be received by two base stations, delay control cannot be performed. However, in the case where inter-station synchronization is performed for the purpose of instantaneous interruption of channel switching between zones, channel switching does not occur in such a state, and thus synchronization is not required. Conversely, as the frequency of channel switching between zones is higher and the instantaneous interruption of channel switching is required, the number of times of delay control can be increased, so that accurate synchronization can be established.

When it is desired to perform control even when the number of mobile stations in communication is small, a method of virtually calling the mobile station without a ringing tone and forcibly setting the mobile station in primary communication can be applied. In order to perform control without relying on the user's mobile station in a zone with little traffic or the like, a method of specially installing a mobile station for delay adjustment may be adopted. There is also a method of partially applying the conventional technique of installing a dedicated receiver in a base station (only to necessary base stations).

FIG. 3 is a block diagram showing a second embodiment of the present invention, in which the present invention is applied to an area extending over a plurality of exchanges. In FIG. 3, 1, 2 and 3 are exchanges, 11, 12, 13 and 14 are base stations, 21, 22, 23 and 24.
Is a mobile station.

Exchange 2 is the master of frame synchronization, and exchanges 1 and 3 are subordinately synchronized. A fixed reference delay amount is set for one channel of the base station 13 connected by a direct line from the exchange 2, and the other channel is assigned to this channel the time position of the timing information additionally transferred on the downlink. Control the amount of delay to match. As described with reference to FIGS. 1 and 2, the base station 12 adjusts the delay in synchronization with the base station 13 via the mobile station 22. The same delay control is performed for the base stations 11 and 14. As described above, the present invention can be applied to an area extending over a plurality of exchanges.

〔The invention's effect〕

As described above, the present invention uses the transceiver before use for communication, and thus has the effect of not requiring a dedicated receiver for inter-station synchronization. In addition, there is an effect that synchronization can be established even when there is no perspective between base stations. That is, there is an effect that there are almost no restrictions on the positions of the base station and the antenna for securing the line of sight, and the system is extremely highly applicable to a system in which a minimum zone is used to increase the subscriber capacity and a system having a low antenna height. . Also,
Even after the introduction of the system, there is an effect of not being affected by changes in surrounding buildings.

Furthermore, in digital mobile communication, the time axis is compressed, an empty slot is formed on the time axis, and when the mobile station changes zones, communication is continued by switching the frequency of the mobile station at the timing of this empty slot. This is effective for performing channel switching without losing information bits. In other words, by establishing inter-station frame synchronization and using the frame timing information added to the downlink wired line for the frame configuration of the wireless section, the two base stations can recognize and transmit common information, so there is no instantaneous interruption. There is an effect that the channel can be switched. Instead of controlling the amount of delay based only on the delay time difference information obtained at the time of one channel switching, the average processing is performed on the communication channels including the base station, and the time is also averaged. Since the reference timing can be set, there is an effect that it is possible to cope with a case where adjustment via the mobile station may be difficult due to interference or the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 2 is a block diagram showing details of the delay adjustment control means. FIG. 3 is a block diagram showing a second embodiment of the present invention. 1, 2, 3 ... switching office, 11-14 ... base station, 21-24 ...
Mobile station, 31, 32 ... Buffer (DB) for delay adjustment, 33 ...
Transmitter / receiver, 40 ... Delay adjustment control means, 41-45 ... Timing detection circuit, 46 ... Reference timing generation circuit, 47-
50 …… Phase comparison circuit, 51 …… Operation circuit for delay adjustment, 52…
... uplink reference timing, 53 ... downlink reference timing, 54 ... delay amount control signal, 55 ... reference timing control signal, 61 ... information, 62 ... timing information, 70 ... communication line, 80 ... Radio channel.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akihiro Maehara Nippon Telegraph and Telephone Corporation, 1-6-1, Uchisaiwai-cho, Chiyoda-ku, Tokyo (56) References JP-A-2-164140 (JP, A)

Claims (1)

(57) [Claims] 1. A small zone configuration comprising an exchange, a plurality of base stations respectively connected to the exchange by a communication line, and a plurality of mobile stations communicating within a radio zone formed by the base station. In the digital mobile communication system, the exchange includes timing information transfer means for adding or transferring timing information to the communication line, and the base station adjusts a delay amount of the communication line. A buffer, and detects the uplink reception timing from the mobile station transmitting at the timing of communicating with another base station, and adjusts the delay based on the detection result and the reception timing of the timing information from the exchange. And a delay adjustment control means for controlling a delay amount of a buffer for use.