JPH01238329A - In-busy channel switching method for mobile communication system - Google Patents

Abstract

PURPOSE:To eliminate hitting time attended with a busy channel switching by applying time division multiplex to plural speech channels so as to synchronize with each other in each carrier frequency and assigning the channel such that the timewise consecutive speech channel group is not used in adjacent radio zones. CONSTITUTION:In order to synchronize carrier frequencies f1, f2...fn respectively, 12 speech channels are subject to time division multiplex to constitute speech channel groups T1-T12 a by the speech channels in the same timing. The speech channel groups T1-T12 are assigned to each radio base station so that the timewise consecutive speech channel group is not adjacent radio base stations. If the mobile terminal equipment in a BS-A using the speech channel of the speech channel group T1 is moved to the radio zone of the adjacent radio base station, the speech channel group assigned newly has a time difference of one time slot or over, the speech test is conducted by selecting the speech channel group assigned newly while the communication is being made by the speech channel T1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for switching a call/medium channel in a mobile communication system, and particularly relates to a method for switching a call/intermediate channel in a mobile communication system in a small zone system (cellular system). .

[Conventional technology]

The small zone system (cellular system) is a system that divides the service area into many wireless zones and reuses the same frequency in separate wireless zones to increase the number of frequency units accommodated, and is used in car phone systems. has been done. However, the potential demand for car telephones far exceeds the capacity of the current system, and there is a need to realize a system with a larger capacity. One possible method for increasing capacity in a limited frequency band is to minimize the wireless zone.For example, if the radius of the wireless zone is reduced to 1/10, the frequency utilization rate will be increased by 100 times.

When the wireless zones are minimized in this way, the frequency of channel switching during a call increases because the mobile station moves from one wireless zone to another during a call.

Regarding the method of switching channels during a call in the conventional car phone system of Nippon Telegraph and Telephone Corporation, as described in Car Phone (Supervised by Moriji Kurihara) published by Institute of Electronics and Communication Engineers, pages 197 to 200, The mobile station that has been designated a new communication channel interrupts the current call, switches to the new communication channel, performs a call test, and then resumes the call on the new communication channel.

[Problem to be solved by the invention]

In the above-mentioned method of switching channels during a call in the conventional mobile communication system, a call cannot be made during a call test, so 0.
There is a drawback that the call is interrupted momentarily for 7 to 0.8 seconds, and as the frequency of switching increases with the miniaturization of the zone, the call quality deteriorates significantly.

SUMMARY OF THE INVENTION An object of the present invention is to realize a method for switching channels during a call without degrading call quality.

Means for Solving the Problem] In the mobile communication system of the present invention, the channel switching method during a call is such that each radio base station has at least one time division multiple access (hereinafter referred to as TDMA) and distribution radio, and the TDMA radio While communicating with a specific radio base station, the mobile terminal transmits and receives data from the specific wireless base station (the transmission and reception timings are the same within the same radio base station), and is separated by at least l time slots between adjacent radio base stations. Conduct a call test with the base station and the adjacent wireless base station.

In the conventional car telephone system, since analog modulation is performed, one communication channel is assigned to one carrier frequency.
er-Carrier+hereinafter referred to as 5CPC) is generally adopted. In the 5cpc method, the mobile station during a call is always in the transmitting/receiving state, so in order to perform a call test while continuing the call, the mobile station must have two transmitters and receivers.
A stand is required.

On the other hand, if digital modulation is performed, N communication channels can be assigned to one carrier frequency by time division multiplexing. In this case, the time the valley mobile station is in the transmitting state and the receiving state is only 1/N of the total time, and the remaining time is in the standby state. At this time, if the timing difference between the current call channel and the new call channel is longer than the time required for channel switching, the standby mode uses the time in the state to test the new call channel without interrupting the current call. This can be done with one transceiver.

Therefore, in the present invention, a plurality of communication channels are time-division multiplexed so as to be synchronized with each other on each carrier frequency, and a communication channel group'(i
- Construct and allocate this communication channel group as a unit to each wireless zone so that temporally consecutive communication channel groups are not used in adjacent wireless zones. If you do this, there will be a timing difference of more than -call channel between the current call channel and the new call channel in the adjacent wireless zone, so you can make a new call while continuing the call on the current call channel. It is possible to perform a channel call test, and it is possible to eliminate instantaneous interruption time associated with channel switching during a call.

〔Example〕

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

FIG. 1 is a diagram showing an example of the configuration of a digital mobile communication system in which a method for switching channels during a call according to an embodiment of the present invention is used.

In FIG. 1, the digital mobile communication system in this application example is composed of a switching center 10, a radio base station 20, and a mobile terminal 30. They each have

A mobile terminal 30 located within the wireless zone of the base station 20 (hereinafter referred to as BS-A) sets up a communication channel with the BS-A and is connected to the wired network via the switching center 10t. . During communication, the mobile terminal 30 confirms that a new communication channel can be set between the wireless zone of BS-A and an adjacent wireless base station, and then transfers the communication channel that was set between the mobile terminal 30 and BS-A. Switch to BS-B to continue full communication.

FIG. 2(at) and FIG. 2(b) are the first embodiment of the present invention, respectively.
FIG. 2 is a time-division diagram of carrier frequencies and a space-division diagram of communication channels into wireless zones based on the time-division carrier frequencies; FIG.

In Fig. 2 (a) and (o), the carrier frequencies to be used are fl, f, f...fn, and the carrier frequencies fs*T2*T3...fn are respectively Twelve communication channels are time-division multiplexed so as to be synchronized with each other, and communication channel groups T1 to T1. Configure. The communication channel groups T-T, . . . are allocated to each radio base station so that temporally continuous communication channel groups are not used by adjacent radio base stations, as shown in FIG. In this case, the number of zones in which the same frequency is repeated is 12.

Since the communication channel group T1 is assigned to BS-A,
Mobile terminals within the wireless zone of BS-A perform transmission and reception only at timing T on each carrier frequency f1 to fn, like this! Then, for example, if a mobile terminal in BS-A using a communication channel of communication channel group T1 is in the wireless zone of an adjacent wireless base station (any wireless base station of BS-B-BS-G). When the mobile terminal moves, the communication channels that may be newly assigned to this mobile terminal are T4 and T s
T7, Tg, TI. , T'tt. Since all of these call channel groups have a time difference of one time slot or more from the call channel group T1 that has been used up until now, a newly allocated call can be made in a free time while a call is being made in the call channel group TI. Call tests can be performed by switching to a channel group.

FIG. 3 is a diagram showing an example of the method for switching channels during a call according to the first embodiment.

In the first embodiment, a mobile terminal using a communication channel of frequency f in the communication channel group T□ of BS-A [hereinafter referred to as communication channel (Tl, fx)] A case in which the user moves to the wireless zone of B5-H will be explained. When this mobile terminal moves into the wireless zone of BS-B, the exchange detects the conflict, selects an empty communication channel in the wireless zone of the movement destination, for example (T,,fl), as a new communication channel, and sets this as the communication channel. (T,,l
, ) is used to designate the mobile terminal. The detection method using this switch is well known in the industry as described in the above-mentioned literature, and its explanation will be omitted here. The switchboard was B
Let S-B transmit a test signal on the traffic channel (T,f,). *A mobile terminal to which a small communication channel (T,,fl) is specified will switch to the communication channel (T,,fl) when the time slot of the communication channel (T, f,) ends.
Wait for the test signal gold on. If the test signal is confirmed, the confirmation signal is returned on the communication channel (T % fl ), and the communication channel (T1, fl ) is returned to continue for all nine conversations. In Figure 5g3, the communication test t is performed over two frames, but even if the communication test result t'' is completed in one frame, it will not be purchased even if the communication test is performed over three frames or more.B5 -H communication channel (T S
The exchange that receives the confirmation signal via the communication channel (fl) instructs the mobile terminal to switch using the signal in the communication channel (T1, f,), and also switches the communication path from BS A to BS-B. The mobile terminal that has been instructed to switch will
Change the communication channel from (T S f,) to (T,, fl
) Switch to! By performing a call test while continuing a call in this way, it is possible to reduce the time required for momentary interruptions caused by channel switching during a call.

FIG. 4(a) and FIG. 4(b) are respectively the second embodiment of the present invention.
FIG. 2 is a time-division diagram of carrier frequencies and a space-division diagram of communication channels into wireless zones based on the time-division carrier frequencies; FIG.

In Figure 4 (a) and 2), the carrier frequency to be used is set to fll·'1! ef13echit, f***'s
s ”...” f kt (an integer of L≦ and ≦n, t=1
．． 2.3)...Fn19fn, Ifn3, call channel group Tl*T2...
... T18, and the communication channel Ti (1≦i
≦12 integer) is the same time slot as S 1 + R
For example, S is the carrier frequency f18.
．． . . fk, . . . fnm are time-divided in the same time slot as the communication channel T3.

In this way, communication channel groups T, ~T12, S1~S, , R1-R are created by communication channels at the same timing.
1, and this communication channel group T1, ~T18,
S1-S18, R1-R13, 4th d(b)
Assign to each wireless zone as shown in . In this case,
This means that three clusters of size 120 are combined to form a cluster of size 36, and the number of repetition zones of the same frequency is 36. Similarly, the multiplicity of the call channel is set to 1.
It is possible to keep the value 2 and repeat the number of zones tS.

〔Effect of the invention〕

As explained above, the invention is such that the transmission timing of TDMA radio equipment is the same within the same unrelated base station, and by separating adjacent radio base stations by at least one time slot, even if a call test is performed during a call. This has the advantage of being able to provide a method for switching channels during a call in a digital mobile communication system in which there is almost no instantaneous interruption time associated with channel switching during a call.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a digital mobile communication system in which a mid-call channel switching method according to an embodiment of the present invention is used, and FIG. 2(a) and FIG. FIG. 3 is a time-division diagram of carrier frequencies and a spatial division diagram of communication channels into wireless zones based on the time-division carrier frequencies, showing an example of the channel switching method during a call in the first embodiment. Figure 4(a)
and FIG. 4(b) are a time-division diagram of carrier frequencies and a space-division diagram of communication channels into radio zones based on the time-division carrier frequencies, respectively, showing the second embodiment of the present invention. 10... Switching station, 20... Wireless base station (BS-A to BS-G), 30... Backward terminal. f, ~f n----Carrier frequency, flm"1
lf13~fn3...Carrier frequency, T1~
Tn...Telephone channel, S1~Sn...
- Call channel, R, ~Rn... Call channel. Agent: Susumu Uchihara, patent attorney Time foil Z plate α

Claims (1)

[Claims] Each radio base station has at least one time division multiple access radio, and the transmission and reception timing of the time division multiple access radio is the same within the same radio base station, and is one time slot or more between adjacent radio base stations. A method for switching channels during a call in a mobile communication system, characterized in that the mobile terminal performs a call test with a radio base station adjacent to the specific radio base station while communicating with the specific radio base station.