JP3110346B2 - Frame synchronization method for mobile communication base station - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of synchronizing a frame of a mobile communication base station, and more particularly to establishing a frame synchronization with a base station of another system in a TDMA type mobile communication system including a plurality of base stations. The present invention relates to a frame synchronization method for a mobile communication base station.

[0002]

2. Description of the Related Art TDM constituted by a plurality of base stations
In the mobile communication system of the A system, when frame synchronization is not established between base stations, transmission / reception timing between adjacent base stations collides and interference of a communication channel occurs,
The call channel cannot be used effectively, and the call channel utilization efficiency decreases.

For example, as shown in FIG. 7, when the frame timing of the base station A and the frame timing of the base station B are not synchronized, the base station A
When a call is being made using Ra2, the base station B
Slot Tb1, Rb1 and second slot Tb2, Rb
Since the interference is detected at b2 and recognized as being in use, the first slot is not used even though it is an empty slot.

[0004] For this reason, in an independent office system,
The line controller to which each base station of the business office system is connected transmits a frame synchronization signal to each base station, and each base station performs frame synchronization based on the frame synchronization signal transmitted from the line controller. I have to.

[0005]

However, there are base stations of other office systems or public systems that are not frame-synchronized adjacent to the base station of the above-mentioned office system, and the service areas overlap with each other. In such a state, conventionally, there is a problem in that frame synchronization cannot be established between these base stations, so that interference occurs and a communication channel cannot be used effectively.

An object of the present invention is to improve the communication channel utilization efficiency by establishing frame synchronization with a base station of another system.

[0007]

According to the present invention, there is provided a method for synchronizing a frame of a mobile communication base station, comprising the steps of:
The base station which generates frame timing based on the clock of the N network and transmits the control signal, and establishes the frame synchronization, receives the control signal of each system based on the clock of the ISDN network and synchronizes with the base station. , The broadcast signal included in the control signal is detected, the frame timing is corrected, and the frame synchronization is established. Specifically, control signal selection means for receiving and searching for the control signal based on the clock of the ISDN network to select a control signal of a base station to be synchronized, and a unique word (UW) included in the selected control signal Timing detecting means for detecting UW reception timing and detecting broadcast information included in the control signal, and correcting the UW reception timing based on the timing information included in the broadcast information to establish frame synchronization. Timing correction means. The control signal selecting means may include a unique word.
(UW) window width is set to the maximum
Receive control signal while delaying UW reception timing
And the source identification code (CS-ID) of the received control signal.
Detect and memorize the reception level and receive the
Selects a control signal that matches another code and has a high reception level
The timing detecting means corrects the caller identification code.
Check the UW window
UW reception by narrowing c width from maximum to minimum
Improve timing detection accuracy.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

Here, as shown in FIG. 6, adjacent to the base station 1A of the office system A, the base station 1 of the public system is located.
B and the base station 1C of the other office system C exists,
It is assumed that frame synchronization is not established between these base stations. The base stations 1A and 1C of the office system are connected to the line controllers 2A and 2C of each office system, respectively, and the line controllers 2A and 2C are connected to the ISDN 3 respectively.

By the way, if each base station of the business office system and the public system generates a frame timing based on the clock of the ISDN network and transmits the control signal, each base station will be based on the clock of the ISDN network. As a result, a control signal of the base station to be synchronized can be received, and frame synchronization can be established based on the received control signal. Therefore, each base station of the office system and each base station of the public system transmit a control signal in synchronization with the clock of the ISDN network.

A control signal transmitted from each base station is intermittently transmitted at a constant period of 100 ms in synchronization with a 192 kHz clock of the ISDN network, for example, as shown in FIG.
Within a period of 100 ms, there are 20 frames of 5 ms width, and each frame has a total of 8 625 μs transmission and reception slots. Each slot includes a unique word for synchronization (UW) and a caller identification code (CS-ID) indicating a source base station. The broadcast information is transmitted using any one slot in the frame. This broadcast information includes slot position information indicating which slot in the frame is transmitting.

The operation will be described with reference to the flowchart shown in FIG. 1 by taking as an example a case where the office system base station 1A receives the control signal of the public system base station 1B and establishes frame synchronization.

The base station 1A sets the reception frequency to the control channel frequency, receives control signals transmitted from the base stations 1B and 1C (step 101), and selects a synchronization target public system base station from these control signals. 1B control signal is selected. In this case, based on the 192 kHz clock of the ISDN network, the detection allowable range (window width) of the unique word (UW) is extended to the maximum so that the UW can be easily detected, and the UW reception timing is gradually set every 100 ms. A control signal is searched for by sequentially delaying (step 102).

For example, as shown in FIG. 2, when the window width of the unique word (UW) is expanded to ± 4 clocks, the search is performed while delaying the UW reception timing by 4 clocks every 100 ms. 6
By repeating 0 times, it is possible to search for all the timings of the control signal transmitted from each of the base stations 1B and 1C.

For the received control signal, a source identification code (CS-ID) indicating the source base station, a reception level, and a delay amount of UW reception timing are detected and stored (step 103). Thereafter, by reading out the stored calling identification code (CS-ID), the received level, and the amount of delay of the UW reception timing, by selecting the one that matches the calling identification code specified in advance and has a high receiving level, The control signal of the public system base station 1B to be synchronized is selected (step 104).

The UW reception timing is corrected based on the delay amount of the UW reception timing, and the window width of the unique word (UW) is received while receiving the control signal of the selected base station (public system base station 1B to be synchronized). Is narrowed down from the maximum to the minimum to improve the detection accuracy of the UW reception timing (step 105).

For example, as shown in FIG. 3A, if the window width is ± 4 clocks at the maximum expansion state at the UW reception timing t1, the UW reception timing is set to t2 and the window width is set to t2 as shown in FIG. 3B. Is reduced to ± 2 clocks to receive a control signal. Then, it is confirmed whether or not the calling identification code (CS-ID) has been correctly received. If the reception is successful, the window width is set to ± 3 with the UW reception timing as t3, as shown in FIG.
It is reduced to one clock, and it is confirmed whether or not the calling identification code (CS-ID) has been correctly received. Here, if the reception is successful, it is determined that the UW reception timing t3 is the correct UW reception timing of the slot. In FIG. 9B or 9C, the caller identification code (CS-I
If D) cannot be received correctly, the reception timing is adjusted to a position where it can be received correctly.

After detecting the UW reception timing in this way, the broadcast information transmitted in any one slot of the frame is detected, and the timing is corrected based on the slot position information included in the broadcast information. This establishes frame synchronization (step 10
6).

For example, the frame timing tentatively determined in the office system base station 1A is as shown in FIG. 4A, and the frame timing of the public system base station 1B to be synchronized is shown in FIG. b), and the broadcast information is transmitted from the base station 1B to the slot Tb.
3 is transmitted by the base station 1A.
B, the slot T1 of the base station 1B in the slot Ra1 at the tentatively determined frame timing.
The notification information is detected from b3.

The base station 1A uses the detected broadcast information to
The slot Ta3 of the provisionally determined frame timing is the base station 1
It detects that it corresponds to the frame start slot of B, and corrects the timing so that the slot Ta3 of the tentatively determined frame timing becomes the frame start slot. By this timing correction, frame synchronization with the public system base station 1B to be synchronized can be established.

[0021]

As described above, according to the present invention, each base station of a different system generates a frame timing based on the clock of the ISDN network and transmits a control signal, respectively, so that the frame synchronization is performed. The established base station receives and searches for the control signal of the synchronization target base station based on the clock of the ISDN network and establishes frame synchronization, thereby preventing interference due to frame synchronization deviation between base stations and enabling the communication channel. Available to

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining a control signal search operation.

FIG. 3 is a diagram for explaining a UW reception timing detection operation.

FIG. 4 is a diagram for explaining a timing correction operation.

FIG. 5 is a diagram illustrating a configuration example of a control signal transmitted from a mobile communication base station.

FIG. 6 is a diagram illustrating a configuration example of a mobile communication system.

FIG. 7 is a diagram illustrating an example of interference between base stations.

[Explanation of symbols]

 1A, 1C Base station of business office system 1B Base station of public system 101-106 Steps showing operation.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-93186 (JP, A) JP-A-7-312773 (JP, A) JP-A-2-79523 (JP, A) JP-A-5-93 235835 (JP, A) JP-A-7-255082 (JP, A) JP-A-7-193525 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/24-7 / 26 H04Q 7/04-7/38

Claims (2)

(57) [Claims] 1. Frame synchronization with a base station of another system
In the established frame synchronization method of the mobile communication base station, the base station of another system uses the clock of the ISDN network to perform the frame synchronization.
Generate frame timing and send control signal
In addition, the base station that establishes frame synchronization uses the IS
Receiving and searching for the control signal based on the clock of the DN network
Control signal selection procedure for selecting the control signal of the base station to be synchronized
Stages and unique words contained in the selected control signal
(UW) to detect UW reception timing
And a notification information included in the control signal.
UW reception timing is corrected based on the
Timing correction means for establishing synchronization,
The signal selection means is a unique word (UW) window
The width is set to the maximum, and the UW reception timing is set at the above-mentioned fixed period.
The control signal is received while delaying the
Detection code (CS-ID) and reception level
Stored in the memory, and matches with a predetermined caller identification code and
A high-level control signal, and the timing detection means reduces the UW window width from a maximum to a minimum while confirming whether or not the calling identification code has been correctly received, thereby improving the detection accuracy of the UW reception timing. frame synchronization method for mobile communications base station characterized by improved. 2. The timing correction means detects broadcast information transmitted by any one of a plurality of slots in a frame, and corrects the UW reception timing based on slot position information included in the broadcast information. frame synchronization method for a mobile communication base station according to claim 1, characterized in that to establish the frame synchronization.