JPH08223638A - Mobile communication channel allocation method - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a mobile communication speech channel allocation method capable of suppressing a rise in traffic in some areas and reducing a call loss rate. [Configuration] When the number of channels used in the base station exceeds the specified value, the timing of transmitting the control signal is advanced under the condition that the interference wave level is below the specified value, or the number of channels used in the base station is less than the specified value. When the number decreases, the timing of transmitting the control signal is delayed under the condition that the interference wave level becomes equal to or lower than the specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in which a plurality of base stations share the same frequency and transmit control signals in a time division manner. The present invention relates to a mobile communication call channel allocation method for selecting a station and setting a call channel with the base station.

[0002]

2. Description of the Related Art FIG. 7 shows a basic configuration of a mobile communication system. In the figure, a plurality of base stations 11 each form a wireless zone 12 in which a predetermined communication quality is obtained. The wireless zones 12 of the adjacent base stations 11 overlap each other, and for example, the mobile station located in the area B is the base station 11-1.
Alternatively, it can communicate with the base station 11-2. Each base station 11 and the mobile station perform bidirectional communication by the TDMA (Time Division Multiple Access) method.

The mobile station selects a base station to be received at a high level when the power switch is turned on or when the reception level of the control signal transmitted by the base station which has been selected so far becomes low. When performing the base station selection, the mobile station selects the base station that first receives the control signal of the specified level or higher. Here, a method of selecting a base station with which the mobile station communicates will be described with reference to FIG. The base stations 11-1 and 11-2 transmit the control signal at the same frequency with a time shift. The height of the control signal corresponds to the reception level at the mobile station 13.
The control signal transmitted from the base station 11-3 is below the specified level, and the mobile station 13 ignores the control signal. T is one cycle of the control signal, t ₁ is a range in which the base station 11-1 is selected when the mobile station 13 starts the base station selection, and t ₂ is a base station when the mobile station 13 starts the base station selection. 11-2
Is the range to select. Therefore, when the mobile station 13 starts the base station selection at the timing shown in the figure, the control signal of the base station 11-2 is first received, and the mobile station 13 and the base station 11
-2, a call channel is assigned to the -2.

[0004]

In the conventional speech channel allocation method, the corresponding base station is selected by the control signal that the mobile station first receives. However, since the traffic of the selected base station is not taken into consideration at this time, the communication channel is not always set up with the selected base station. That is, a call may not be made due to the lack of a call channel of the base station, resulting in a call loss.

An object of the present invention is to provide a mobile communication speech channel allocation method capable of suppressing an increase in traffic in some areas and reducing a call loss rate.

[0006]

When the number of channels used in the base station exceeds a specified value, the timing of transmitting the control signal is advanced under the condition that the interference wave level becomes equal to or lower than the specified value (claim 1). When the number of channels used in the base station becomes less than the specified value, the timing of transmitting the control signal is delayed under the condition that the interference wave level becomes equal to or less than the specified value (claim 2).

Further, in the above mobile communication speech channel allocation method, the number of channels used in the base station is classified into a plurality of groups, and the transmission timing of the control signal is adjusted by a predetermined phase shift amount as a function of the number of channels used in each group. Advance or delay (Claim 3). Further, in the above mobile communication call channel allocating method, after performing control for advancing or delaying the transmission timing of the control signal, the control shifts to the next transmission timing control after a predetermined waiting time (claim 4).

[0008]

In the mobile communication call channel allocation method of the present invention,
By changing the transmission timing of the control signal according to the availability of the communication channel, it is possible to change the probability that a mobile station that may newly use the base station selects that base station. That is, when there are few empty channels (Claim 1), the transmission timing of the control signal is advanced to reduce the probability of being selected by the mobile station, and when there are many empty channels (Claim 2), the transmission timing of the control signal is increased. By increasing the probability of being selected by the mobile station by delaying the call, it is possible to prevent a large amount of traffic from concentrating on a specific base station and increasing the call loss rate.

Further, the traffic adjustment can be efficiently performed by setting the change amount of the transmission timing of the control signal according to the number of used channels (claim 3). Further, by providing the waiting time for each transmission timing control, it is possible to avoid the situation where the mobile station cannot follow the change in the transmission timing or the stability of the system control is lowered (claim 4). .

[0010]

1 shows the basic principle of a mobile communication speech channel allocation method according to the present invention. The wireless zone configuration is assumed to be in the situation shown in FIG. In the figure, the base station 11-
Reference numerals 1 and 11-2 transmit control signals at the same frequency with a time shift. The height of the control signal corresponds to the reception level at the mobile station 13, and control signals below the specified level are ignored. T is one cycle of the control signal, t ₁ is a range in which the mobile station 13 selects the base station 11-1 when the base station selection is started, and t ₂ is the mobile station 13.
Is a range in which the base station 11-2 is selected when the base station selection is started.

A feature of the present invention is that the timing (phase) at which the base station transmits the control signal is changed according to the traffic. In the example shown in FIG. 1, since the traffic of the base station 11-2 is high, the transmission timing of the control signal is advanced to relatively widen the range t ₁ for selecting the base station 11-1. It should be noted that the base stations are randomly selected and the probability of occurrence is uniformly distributed.
By widening the range t ₁ for selecting one, the mobile station 13
Can reduce the probability of selecting the base station 11-2 with high traffic. As a result, it is possible to prevent a large number of traffic from concentrating on a specific base station and increasing the call loss rate.

FIG. 3 shows a first embodiment of the mobile communication speech channel allocation method of the present invention. In the figure, first, the phase shift coefficient is initially set (i = 0) (S1), and the number of used channels is determined (S2). Here, when the number of used channels becomes N or more, 1 is added to the phase shift coefficient i (S3), and the phase shift amount p (=
2π / m · i) is calculated (S4). Note that m is a constant that determines the phase shift step. Next, the interference wave level Li of the phase p radian before the phase of the current control signal is measured (S5), and it is determined whether or not it exceeds a specified value (S6). If the interference wave level Li is greater than or equal to the specified value, then S
Return to 3 to further advance the phase. If the interference wave level Li is smaller than the specified value, the control signal is transmitted at that phase (phase shift amount p) (S7).

FIG. 4 shows a second embodiment of the mobile communication speech channel allocation method of the present invention. In the figure, first, the phase shift coefficient is initially set (i = 0) (S1), and the number of used channels is determined (S8). Here, when the number of used channels becomes less than N, 1 is subtracted from the phase shift coefficient i (S9), and the phase shift amount p (= 2π / m · i) is calculated (S4). Note that p has a negative value. Next, from the current phase of the control signal, | p |
The interference wave level Li of the phase after radian is measured (S1
0), it is determined whether or not it exceeds the specified value (S
6). If the interference wave level Li is not less than the specified value, the process returns to S9 to further delay the phase. If the interference wave level Li is smaller than the specified value, the control signal is transmitted at that phase (phase shift amount p) (S11).

FIG. 5 shows a third embodiment of the mobile communication call channel allocating method of the present invention. In the figure, first, the phase shift coefficient is initially set (i = 0) (S1), and the number of used channels is determined (S2). When the number of used channels becomes N or more, [the number of used channels / M] is added to the phase shift coefficient (S
12), the phase shift amount p (= 2π / m · i) is calculated (S
4). In addition, M is an integer, [the number of channels used / M]
Is the maximum integer that does not exceed the number of used channels / M. Thereby, the amount of phase shift corresponding to the number of used channels (the number of free channels) can be set first. Next, the interference wave level L of the phase p radian before the phase of the current control signal
i is measured (S5), and it is determined whether it exceeds a specified value (S6). If the interference wave level Li is not less than the specified value, 1 is added to the phase shift coefficient i (S3), and the process returns to S4 to further advance the phase. If the interference wave level Li is smaller than the specified value, the control signal is transmitted at that phase (phase shift amount p) (S7).

Since the present embodiment uses the value obtained by dividing the number of used channels by M as the phase shift coefficient i, it is effective when the number of used channels (the number of empty channels) monotonically increases (monotonically decreases). is there. Further, although this embodiment is applied to the first embodiment, it can be similarly applied to the second embodiment.
In each of the above embodiments, the phase of the control signal is adjusted according to the number of used channels, and then the number of used channels is determined again (S
2, S8) and the same control is repeated. Therefore,
In a situation where the traffic changes abruptly, the phase of the control signal changes at high speed, and the mobile station may not be able to follow the change or the stability of system control may deteriorate. As a method of coping with this, the phase of the control signal is adjusted according to the number of used channels, and a predetermined time (x seconds) is waited before returning to the determination of the number of used channels again. A flowchart corresponding to the first embodiment is shown in FIG. 6, but the same applies to other embodiments. The same applies to the number of free channels in the above embodiments.

As shown in FIG. 7, when the radio zone overlap of each base station is set to 50% and the traffic of the central base station 11-3 is set to 2.5 times the traffic of other base stations, the present invention is realized. Figure 2 shows the results obtained by computer simulation of the blocking loss reduction effect obtained when ideally realized.
Shown in The solid line shows the call loss rate in the base station 11-3, and the broken line shows the average call loss rate of the five base stations 11-1 to 11-5.

A is the result of the control according to the prior art, and is the call loss rate when the base stations to communicate are selected with equal probability. It can be seen that the call loss rate in the base station 11-3 is extremely high. On the other hand, B is based on the method of the present invention that dynamically changes the base station that communicates according to the fluctuation of the traffic of each base station, and both the call loss rate in the base station 11-3 and the average call loss rate of all the base stations are small. I understand.

[0018]

As described above, in the mobile communication speech channel allocation method of the present invention, an algorithm for adjusting the transmission timing of control signals is added to a base station using TDMA, and a radio zone formed by the base station is added. Only by overlapping, it is possible to suppress the traffic increase of some base stations and reduce the call loss rate.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the basic principle of a mobile communication call channel allocation method of the present invention.

FIG. 2 is a diagram for explaining the effect of the present invention.

FIG. 3 is a first method of assigning a mobile communication call channel according to the present invention.
The flowchart which shows an Example.

FIG. 4 is a second method of assigning a mobile communication call channel according to the present invention.
The flowchart which shows an Example.

FIG. 5 is a third mobile communication call channel allocation method according to the present invention;
The flowchart which shows an Example.

FIG. 6 is a fourth example of the mobile communication call channel allocation method according to the present invention.
The flowchart which shows an Example.

FIG. 7 is a diagram showing a basic configuration of a mobile communication system.

FIG. 8 is a diagram for explaining the basic principle of a conventional mobile communication call channel allocation method.

[Explanation of symbols]

 11 base station 12 wireless zone 13 mobile station

Claims (4)

[Claims] 1. A system capable of communicating between a mobile station and two or more base stations by overlapping a part of wireless zones formed by adjacent base stations, wherein each of the plurality of base stations has a control signal at a predetermined timing. In the mobile communication call channel allocation method, wherein the mobile station selects a base station corresponding to a control signal that the mobile station first received at a specified level or higher, and sets a call channel between the base station and the base station. A mobile communication speech channel allocation method, characterized in that when the number of used channels exceeds a prescribed value, the timing of transmitting the control signal is advanced under the condition that the interference wave level becomes equal to or lower than the prescribed value. 2. A system capable of communicating between a mobile station and two or more base stations by overlapping a part of radio zones formed by adjacent base stations, wherein a plurality of base stations control signals at predetermined timings. In the mobile communication call channel allocation method, wherein the mobile station selects a base station corresponding to a control signal that the mobile station first received at a specified level or higher, and sets a call channel between the base station and the base station. A mobile communication speech channel allocation method, characterized in that, when the number of used channels becomes smaller than a prescribed value, the timing of transmitting the control signal is delayed under the condition that the interference wave level becomes equal to or lower than the prescribed value. 3. The mobile communication channel allocation method according to claim 1, wherein the number of channels used in the base station is classified into a plurality of groups, and a predetermined phase shift is performed for each group as a function of the number of channels used. A mobile communication call channel allocation method characterized by advancing or delaying the transmission timing of a control signal by an amount. 4. The mobile communication call channel allocating method according to any one of claims 1 to 3, wherein after the control for advancing or delaying the transmission timing of the control signal is performed, a next waiting time is passed. A mobile communication call channel allocating method characterized by shifting to transmission timing control.