JP2616675B2 - Handover processing circuit - Google Patents

Abstract

PURPOSE:To reduce the hit time of voice in the handover processing in a digital mobile communication system adopting the narrow band TDMA system for a radio block. CONSTITUTION:A voice signal before handover is path-connected to input output terminals A, a, a voice signal after handover is path-connected to input output terminals B, b, and a voice signal of an opposite party of communication is path-connected to input output terminals C, c. A synchronization detection circuit 9 discriminates a coding type of the voice signal, and uses code conversion circuits 1, 3, 6 when the type is a code type 1 and uses code conversion circuits 2, 4, 7 when the type is a code type 2. The pre-stage conversion circuits 1, 3 or 2, 4 convert the signal into a linear code, an adder circuit 5 adds the voice signals before and after the handover to the converted signal, the post- stage code conversion circuit 6 or 7 restores the signal into the original code type and the resulting signal is fed to the output terminal C in any code type. The voice signal from the opposite party of communication is sent to the output terminals a, b via a timing adjustment circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handover processing circuit used in a communication channel switching process during communication in a digital mobile communication system.

[0002]

2. Description of the Related Art A digital mobile communication system generally comprises mobile stations 201 and 202 and base stations 203 and 2 as shown in FIG.
04, 205 and the mobile communication switching center 206.
During a call between the mobile station 201 and the mobile station 202, the mobile communication exchange 206 connects the communication paths 207 and 208. When the mobile station 201 moves from the service area of the base station 203 to the service area of the base station 204 during a call, the mobile communication switching station 206 receives the report of the establishment of the radio communication channel with the mobile station 201 from the base station 204. , Call path 2
07 is switched to the communication path 209 , and the handover process ends.

On the other hand, while the mobile station 201 is in a call with a general public subscriber, the mobile switching center 206 has a call path 2 as shown in FIG.
10 are connected. As described above, when the mobile station 201 moves, the mobile switching center 206 assigns the radio communication channels of the mobile station 201 and the base station 204, and at the same time,
Once the call paths 212 and 2 with the three-way call trunk 211
13 and 214. Thereafter, after receiving a report of establishing a wireless communication channel with the mobile station 201 from the base station 204, the mobile station switches to the communication path 215 and ends the handover process.

[0004] In this case, even in a transient state until the mobile switching center receives a new radio communication channel establishment report,
Since the voice before and after the handover of the mobile station 201 reaches the mobile station 202 by the three-way call trunk 211, the instantaneous interruption time is minimized.

[0005]

As described above, the conventional three-party call trunk can be used in a handover process during a call between a mobile station and a general public subscriber by using a narrow band TDMA method in a radio section. The mobile station may call the A-law or μ at the base station to talk to the general public.
This is because conversion is performed to 64 [kbps] serial transmission based on the PCM coding rule. However, in general, in a call between mobile stations, a conventional three-party call trunk is not used because the base station puts the data into fixed-length data and forms a frame structure together with a synchronization pattern as shown in FIG. There was a problem that it could not be used.

[0006]

According to the handover processing circuit of the present invention, the first code type to be encoded or the first code type to compress and encode information in order to lower the transmission rate in accordance with the A-law or the μ-law. A first, a second, and a third input terminal for inputting a digital signal having a code type of 2, a first, a second, and a third output terminal for outputting the digital signal; and a first input terminal. And the first signal
A first code conversion circuit that converts a code type of the second code into a linear code; and a second code conversion circuit that receives a signal from the first input terminal as an input.
A second code conversion circuit for converting the code type of the second code type into a linear code, and a signal from the first input terminal as an input, the signal of the second code type being included in fixed-length data, and a frame together with a synchronization pattern. A synchronization detection circuit for detecting a synchronization pattern when serial transmission is periodically performed in frame units by forming a structure and determining a code type of an input signal; and a signal from the second input terminal as an input. The first
A third code conversion circuit for converting the code type of the second code into a linear code;
A fourth code conversion circuit that converts the code type of the code into a linear code, and the synchronization detection circuit according to an external control signal;
A control circuit for instructing an operation of a delay circuit described later;
A first selection circuit which receives an output signal of the second code conversion circuit as an input, selects and outputs an input signal according to a synchronization pattern detection state of the synchronization detection circuit, and the third and fourth code conversion circuits And a second selection circuit for selecting and outputting an input signal according to the synchronization pattern detection state of the synchronization detection circuit, and adding a linear code output from the first and second selection circuits. And a fifth code conversion circuit for converting a signal from the linear code into the first code type, and a signal from the addition circuit as an input. A sixth code conversion circuit for converting into a code type of 2, a delay circuit for outputting a signal from the control circuit for a fixed time, a signal from the first input terminal and the fifth and sixth code conversion circuits The output signal of A third selection circuit that selects and outputs an input signal according to a synchronization pattern detection state of a detection circuit and an output signal of the delay circuit, and adjusts an output timing of the output signal of the third selection circuit to an external device. A first timing adjustment circuit that outputs the signal to the third output terminal, and an output timing of a signal from the third input terminal to an external device, and outputs the signal to the first and second output terminals. A second timing adjustment circuit.

[0007]

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

FIG. 1 is a block diagram showing an embodiment of a handover processing circuit according to the present invention. The code type of the digital signal input / output to / from the circuit of the present invention is a normal A law or μ.
There are two types, a code type 1 that complies with the PCM coding rule of the law and a code type 2 that performs information compression and encoding to reduce the transmission speed. Code type 1 is serially transmitted at normal 64 [kbps], and code type 2 is contained in fixed-length data as shown in FIG. 5, forms a frame structure together with a synchronization pattern, and is serially transmitted synchronously in frame units. These signals are input / output via three sets of input / output terminals A and a, B and b, and C and c. The interface between these three sets of input / output terminals and mobile switching center 206 is similar to a conventional three-way trunk.

The code conversion circuit 1 is connected to an input terminal A ,
The code type 1 is converted into a linear code, the code conversion circuit 2 is connected to the input terminal A, converts the code type 2 into a linear code, and outputs the result to the selection circuit 10 together. Code conversion circuit 3
Is connected to the input terminal B to convert the code type 1 into a linear code, and the code conversion circuit 4 is connected to the input terminal B and
Is converted to a linear code, and the result is output to the selection circuit 11. Control signal receiving circuit 8, the circuit used in the present invention
An instruction as to whether or not it is in the middle is received via the control input terminal D. You
In other words, if this circuit is used in handover processing,
Receiving a signal of an in-use instruction from the mobile switching center 206.
It is. The synchronization detection circuit 9 is connected to the input terminal A, detects the synchronization pattern of the code type 2 signal while the output signal from the control signal reception circuit 8 indicates that the circuit is in use, and inputs the signal. And outputs the result as a selection signal to selection circuits 10, 11, and 12 (described later). The selection circuits 10 and 11 select the output signals of the code conversion circuits 2 and 4 when the synchronization detection circuit 9 detects the synchronization pattern, and select the output signals of the code conversion circuits 1 and 3 when the synchronization pattern is not detected. And outputs it to the addition circuit 5. The addition circuit 5 adds the two linear codes to each other, and outputs the result to the code conversion circuits 6 and 7. The code conversion circuit 6 converts the linear code into the code type 1, and the code conversion circuit 7 converts the linear code into the code type 2, and outputs the result to the selection circuit 12. The signal from the input terminal A is also input to the selection circuit 12 as shown. The delay circuit 13 is a control signal receiving circuit 8
Is output to the selection circuit 12 for a certain period of time. This signal is a selection signal of the selection circuit 12 as shown in FIG. This is the time set by the delay circuit 13 from the time when the circuit receives the use instruction,
In the present embodiment, the signal from the input terminal A is selected until 40 [ms] elapses, and the output of the code conversion circuit 6 is selected if no synchronization pattern is detected within this set time . The timing adjustment circuit 14 adjusts the output timing when the output signal of the selection circuit 12 is put on the time slot on the transmission highway, and sends the signal to the output terminal c . The timing adjustment circuit 15 a signal from the input terminal C
The output timing at the time of loading on the time slot on the transmission highway is adjusted, and the signal is transmitted to the output terminals a and b.

The operation when a handover process is performed using the circuit of the present invention during a call between mobile stations will be described below. FIG. 2 shows a path connection at the time of handover. During a call between the mobile station 201 and the mobile station 202, the mobile station 20
1 moves from the service area of the base station 203 to the service area of the base station 204,
Is used to assign a radio communication channel between the mobile station 201 and the base station 204 and to simultaneously execute the handover processing circuit 1 of the present invention.
The call path is switched to 00. In this case, the mobile communication station 2
06, those in the control input terminal D of the handover processing circuit
At the same time as instructing the use of the circuit, the base station 203 and the input / output terminals A and a before handover are connected via the communication path 216.
The handover destination base station 204 is connected to the input / output terminals B and b by the communication path 217 and the base station 205 used by the mobile station 202 for communication with the input / output terminals C and c by the communication path 218. As described above, a signal of code type 2 is transmitted during a call between mobile stations. However, the continuation of the call is ensured immediately after switching until the synchronization detection circuit 9 detects a synchronization pattern.
For this reason, the selection circuit 12 selects the signal from the input terminal A by the delay circuit 13 and sends the signal to the output terminal C until the code type of the signal at the input terminal A can be reliably determined.

When the synchronization detection circuit 9 detects a synchronization pattern, the selection circuit 10 outputs the output signal of the code conversion circuit 2, the selection circuit 11 outputs the output signal of the code conversion circuit 4,
Selects the output signal of the code conversion circuit 7. At this time, the signal from the base station 203 is converted into a linear code by the code conversion circuit 2 and input to the addition circuit 5 via the selection circuit 10.
The signal from the base station 204 is converted into a linear code by the code conversion circuit 4 and input to the addition circuit 5 via the selection circuit 11. The signal added by the adding circuit 5 is converted into code type 2 by the code converting circuit 7 and reaches the mobile station 202 via the selecting circuit 12 , the timing adjusting circuit 14, the output terminal c , the communication path 218, and the base station 205. During the handover process, an idle signal equivalent to silence is output from the base station to which the mobile station has not established a radio communication channel, and the mobile station 20
The voice of No. 1 is input to the input terminal A via the base station 203 and the communication path 216 until immediately before the wireless communication channel switching, and immediately after the switching, the base station 204 and the communication path 217
Is input to the input terminal B via the. Therefore, the mobile station 201
There happens is only a short break it while switching the channel.

On the other hand, the voice of the mobile station 202 is transmitted to the base station 20.
5. The signal is input to the input terminal C via the communication path 218.
The signal input to the timing adjustment circuit 15 is output to the output terminals a and b.
No matter which base station 204 has established a wireless communication channel, the mobile station 201 is reached. Thereafter, after receiving the wireless communication channel establishment report from the base station 204, the mobile communication switching center 206 switches to the communication paths 219 and 220,
The busy instruction of the handover processing circuit is released, and the handover processing ends.

When the mobile station 201 moves as described above during a call with a general public subscriber, the general public subscriber is connected to the input / output terminals C and c, and the base stations 203 and 2 are connected.
Since the signal transmitted between the mobile communication switching center 204 and the mobile communication switching center 206 is of code type 1, the only difference is that the operation is performed so as to use the output signals of the code conversion circuits 1, 3, and 6.

[0014]

As described above, the handover processing circuit of the present invention converts a signal of code type 2 transmitted to the mobile communication switching center into a linear code at the time of communication between mobile stations by adding the signal to the linear code. Therefore, the same function as that of the conventional three-way trunk used in the handover process between the mobile station and the general public subscriber can be realized, and the instantaneous interruption time at the time of handover can be reduced.

In the conventional handover process, it is necessary to be aware of whether the other party communicating with the mobile station to be handed over is a mobile station or a general public subscriber. If an over-processing circuit is used, there is no need to be conscious at all.

[0016]

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram showing an embodiment of path connection at the time of handover.

FIG. 3 is a block diagram showing a first example of a conventional path connection at the time of handover.

FIG. 4 is a block diagram showing a second example of the conventional path connection at the time of handover.

FIG. 5 is a diagram showing a transmission mode between a base station and a mobile communication switching center.

[Explanation of symbols]

 1-4 code conversion circuit 5 addition circuit 8 control signal reception circuit 9 synchronization detection circuit 10-12 selection circuit 13 delay circuit 14,15 timing adjustment circuit 100 handover processing circuit 201,202 mobile station 203-205 base station 206 mobile communication Exchange 207-210, 212-220 Call path 211 Three-way call trunk

Claims (1)

(57) [Claims] A digital signal comprising a first code type to be encoded or a second code type to be encoded by compressing information in order to reduce the transmission rate according to the A-law or the μ-law. , Second and third input terminals, first, second, and third output terminals for outputting the digital signal, and a signal from the first input terminal as an input and the first code type being linear. A first code conversion circuit that converts a signal from the first input terminal into a code, a second code conversion circuit that converts the second code type into a linear code, and a first input terminal From the input, the signal of the second code type is put into fixed-length data to form a frame structure together with the synchronization pattern, and detects a synchronization pattern when serially transmitted periodically in frame units, Sign of input signal A synchronization detection circuit for determining a type, a third code conversion circuit that receives a signal from the second input terminal and converts the first code type to a linear code, and a signal from the second input terminal. A fourth code conversion circuit that converts the second code type into a linear code by using an input as a input, the synchronization detection circuit according to a control signal from the outside, a control circuit that instructs operation of a delay circuit described below, The output signals of the first and second code conversion circuits are input,
A first selection circuit that selects and outputs an input signal according to a synchronization pattern detection state of the synchronization detection circuit, and an output signal of the third and fourth code conversion circuits as inputs,
A second selection circuit that selects and outputs an input signal according to a synchronization pattern detection state of the synchronization detection circuit; an addition circuit that adds linear codes output from the first and second selection circuits; A fifth code conversion circuit that receives a signal from the circuit as an input and converts a linear code into the first code type, and converts a signal from the addition circuit as an input and converts the linear code into the second code type A sixth code conversion circuit, a delay circuit that outputs a signal from the control circuit for a fixed time , and a signal from the first input terminal and an output signal of the fifth and sixth code conversion circuits as inputs. A third selection circuit that selects and outputs an input signal according to a synchronization pattern detection state of the synchronization detection circuit and an output signal of the delay circuit, and an output timing of an output signal of the third selection circuit to an external device. Adjust and said A first timing adjustment circuit for outputting to the third output terminal; and a second timing adjustment circuit for adjusting the output timing of the signal from the third input terminal to the external device and outputting to the first and second output terminals. A handover processing circuit comprising: a timing adjustment circuit;