JPH0555990A - Mobile communication system - Google Patents

Abstract

PURPOSE:To realize the control method for same channel allocation attended with spatial and timewise change in a call unit. CONSTITUTION:In this mobile communication system provided with plural base stations 43, 44 forming a radio zone for communication connection with mobile stations 45-48 being distributed in its service area and with a communication frequency channel group used for the communication between the base stations 43, 44 and the mobile stations 45-48 and selecting one channel and allocating it when a communication connection request takes place, if communication connection request calls are concentrated timewise and spatially resulting in increasing the traffic, the required value of a desired wave versus interference wave power ratio is changed in response to the traffic volume.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system having a small zone structure, and more particularly to a control system for adaptively allocating the same channel according to a change in communication connection call volume in repeated use of the same frequency. is there.

[0002]

2. Description of the Related Art The purpose of a small zone mobile communication system is to
By using the same frequency spatially and repeatedly within one service area, it is possible to effectively use the limited frequency.

In the small-zone system, a typical channel allocation technique that has been put to practical use or studied so far is a fixed channel allocation method and a dynamic channel allocation method.

A mobile communication system using these methods will be described below.

Fixed channel allocation seeks to maximize the effect of effective frequency utilization by sub-zoning by a simple method.

FIG. 2 shows the relationship between zones and the radio channel groups assigned to each zone when fixed channel assignment is used.

FIG. 2 shows a case where 7-zone repetitive channels are allocated to a zone configuration of a two-dimensional regular hexagonal zone arrangement, 11 is a radio zone, 12 is a radio base station, and 13 is a radio base station.
Is a mobile station around the zone, 14 is a mobile station in the center of the zone,
[1] to [7] respectively represent channel group numbers fixedly assigned to each zone 11.

Generally, in the wireless channel design of the fixed channel allocation system, it is designed so that communication can be performed with sufficient quality against thermal noise and interference noise even in the zone periphery.

For example, the channel of channel group number [1] used in the mobile station 13 can be used anywhere within the zone of the same group number [1].
On the contrary, since the channel group arranged in the zone is fixed, the other channels cannot be used. Therefore, in fixed channel allocation, a fixed number of repeating zones is always maintained.

Further, in fixed channel allocation, the zone in which the same channel is arranged is fixed,
Repeated use in closer zones is not allowed.

In other words, in fixed channel allocation, the number of repeating zones is fixedly set so as to guarantee the quality of the entire zone including the worst point of the propagation condition. It cannot be said that the optimum frequency is repeatedly used in the communication usage situation. This tendency is due to a system in which the variation in propagation within the zone due to fading etc. becomes relatively large, a system in which the zone has become extremely small, and a system in which a mobile phone exists in which the variation in the median short-range greatly affects the reception level. Become noticeable in.

On the other hand, dynamic channel allocation is
As a means to eliminate the division loss caused by dividing and holding the channels owned by the system, which has been mentioned as one of the problems of fixed channel allocation in the past,
Consideration has been advanced. Rather than dividing all channels into groups and assigning them to each zone like fixed channel assignment, all channels are held together in the entire system, and when a communication connection request occurs, a channel that satisfies a certain repeating condition from them. Assign

Therefore, since it is possible to select all channels in each zone, a large grouping effect can be expected. However, this effect has a large number of channels per zone even in fixed channel allocation when the total number of channels is large, and since it has a large grouping effect by itself, it is not possible to expect a larger grouping effect in dynamic channel allocation, therefore, There is a drawback that the effect will fade.

Therefore, a method of adaptive reuse of frequencies that is possible in dynamic channel allocation has also been proposed. This is shown in FIG. In FIG. 3, reference numeral 21 is a wireless zone, 22 is a wireless base station, 23 is a small zone equivalent to the channel used by the mobile station 27, 24 and 25 are mobile stations around the zone, and 26 and 27 are central zones of the zone. Is a mobile station of the department.

In the fixed channel assignment, the same frequency is assigned so that the same frequency can be used around the zone like the mobile stations 24 and 25 in FIG. However, when the mobile station is near each base station 22 as shown by reference numerals 26 and 27, the same desired wave-to-interference wave power ratio can be obtained even in a short distance such as the mobile stations 26 and 27. Therefore, the mobile stations 26, 27 can be used in dynamic channel allocation in which there is no channel allocation restriction for each zone.
Even in such a state, if the desired wave-to-interference wave power ratio satisfies the required value, the same channel can be allocated. This method does not depend on the large swarming effect, so that the effect is expected even when the number of channels is large.

[0016]

However, in this case, since the required value of the desired wave-to-interference power ratio, which is a reference for allocating channels, is predetermined, it is possible to cope with spatial and temporal changes in call volume. If you don't do it, you have the disadvantage that if you exceed the allowable amount, the call will be lost.

It is an object of the present invention to solve the call loss in the above-mentioned "method of adaptive reuse of possible frequencies in dynamic channel allocation" by spatially controlling call volume,
It is to provide a control method of co-channel allocation with time change.

[0018]

In order to achieve the above-mentioned object, the present invention provides a plurality of base stations forming a wireless zone distributed in a service area to establish a communication connection with a mobile station, and the base station and the mobile station. In the mobile communication system, which is equipped with a communication frequency channel group used for communication between terminals, and which selects and allocates one channel when a communication connection request occurs,
When communication connection request calls are concentrated in time and traffic is increased, the required value of the desired wave-to-interference wave power ratio is changed according to the amount of traffic.

Compared with the conventional “method of adaptive reuse of possible frequencies in dynamic channel allocation” in which the required value of the desired wave-to-interference wave power ratio is fixed, when the same channel does not reach the required value, , The communication connection request call was not able to be connected and caused a call loss.

However, in the present invention, by lowering the required value, the communication connection request call can be connected but the call loss does not occur although the quality is somewhat deteriorated. Also, when there are few communication connection request calls at that time,
Conversely, by raising the required value, it becomes possible to provide high-quality communication services.

To explain the above with reference to FIG. 4 (a), the broken line C represents the conventional method in which the required value is fixed, and the solid line D shows the required value which decreases as the call volume increases. Fig. 4 represents the relationship when using the method of the invention. Solid line D
Is determined by conditions such as zone arrangement.

From the figure, when the call volume is smaller than the amount at the intersection with the broken line C, the required value is selected large, so that the quality is improved by the amount of the area A, and when the call volume is large, the required value is increased. It is shown that the call loss is reduced by the amount of the area B by selecting a small value.

Further, referring to FIG. 1, when the connection request is generated from the mobile stations 45 and 46, when the desired wave-to-interference wave power ratio is viewed as the ratio of the mobile station distances, r1 / R2> = (desired Required value of wave-to-interference power ratio)> r1 / R1, r2 /
When there is a relationship of R2> r2 / R1, conventionally, the mobile station 45 is replaced by the mobile station 48.
It was not possible to allocate a channel to the mobile station 46 that has already been connected. However, in the present invention, the required value is set to r1 / R2> r1 / R1, r2 / R2> = (required value of desired wave-to-interference wave power ratio)> r2 / R1 to move to the mobile station 45. The connected channel of the station 47 and the connected channel of the mobile station 48 can be assigned to the mobile station 46.

[0024]

According to the present invention, when the traffic volume of the base station or the plurality of base stations including the base station is small, the required value of the desired wave to interference wave power ratio is set to a large value, and as the traffic volume increases, The required value of the desired wave to interference wave power ratio is set smaller.

[0025]

1 shows an example of the configuration of a system for carrying out the present invention, in which 41 is a control station of the system,
42 is a wired transmission line between the control station 41 and the base station, and 43 and 4
4 is a base station, 45, 46, 47 and 48 are mobile stations, r1, r2,
R1 and R2 are distances from the base station 43 in each mobile station.

Generally, in a mobile communication system, there are a communication channel actually used for subscriber communication and a control channel used for connection control. However, in this embodiment, both channels are provided and a connection request is made. On the other hand, before the actual communication, information is exchanged using the control channel.

In the embodiment shown in FIG. 1, the flow of control until a communication channel is assigned to a connection request will be described.
5 and 6 showing the control algorithm performed by the control station 41.
Will be described below. 5 and 6, B43 and B44 are base stations 43, 44, M45 and M4.
7, M48 is a general term for mobile stations 45, 47, 48, and Mco is an already connected mobile station in the base station 44.

When there is a connection request from the mobile station 45 (S
1) The reception level of the base station 43 and the mobile station 45 is measured using the control channel, and the measured value is received by the control station 41 through the wired transmission path 42. In the control station 41, the desired wave level of upstream and downstream in the actual communication from the level, that is, the desired wave level V of M45 (M45 → B43), B43.
Of the desired wave level V (B43 → M45) is measured (S
2).

On the other hand, the mobile stations Mco are sequentially changed (S
3), the interference wave level V (Mc of the mobile station 45 and the base station 43)
o → B43) and V (B44 → M45) are measured (S
4) Estimate V of interference wave level between mobile station Mco and base station 44 when mobile station 45 and base station 43 are connected (M43 →
Mco) = V (Mco → B43), V (M45 → B4)
4) = V (B44 → M45) is performed (S5).

Further, the mobile stations Mco are sequentially changed to obtain desired wave levels V (B44 → Mco) and V (Mco →
B44) is measured (S6).

Next, based on the measured values and estimated values in steps S2, S5 and S6, the mobile station 45 and the base station 4
Desired wave to interference wave ratio D / U of 3, that is, D / U of M45
[V (B45 → M45) -V (B44 → M45)], B
43 D / U [V (M45 → B43) -V (Mco → B
43)] and the desired wave-to-interference wave ratio D / U between the mobile station Mco and the base station 44, that is, D / U [V (B44 →
Mco) -V (B43 → Mco)], D / U of B44
[V (Mco → B44) −V (M45 → B44)] are calculated (S7).

In this way, 4 for each mobile station Mco
One D / U is stored (S8), and all D's of the mobile station Mco are stored.
It is determined whether or not / U has been stored (S9), Y
If es, the process proceeds to step S10, and if No, the processes after step S3 are repeated. Step S1
At 0, it is determined whether or not there is a mobile station Mco that satisfies all four D / Us with respect to the required D / U. If Yes, the same channel as the mobile station Mco has already been used in the area of the base station 43. It is determined whether or not (S11), Yes
In the case of, the same channel as the mobile station Mco that satisfies the required D / U is assigned to the mobile station 45 (S12).

If No in steps S10 and S11, the required D / U is changed to the D / U at the time of traffic increase (S13), and the mobile station Mco satisfying all four D / Us with respect to the required D / U. It is determined whether or not there is (S1
4) If Yes, it is determined whether the same channel as the mobile station Mco is already used in the area of the base station 43 (S15). If Yes, the process proceeds to step S12, and if No, the same. It is determined whether or not the already connected channel can be changed to another channel (S16). If Yes, the already connected channel is changed to another channel (S1).
7) and proceeds to step S12. Steps S14 and S
In the case of No in 16, connection is impossible (S18).

The above process is repeated each time a communication connection request call is generated.

The present invention can be applied to the case where another desired wave-to-interference wave power ratio measuring method or a means for estimating is adopted, and the desired wave-to-interference wave power ratio according to the call volume shown in FIG. The variation in the required value of (solid line D in FIG. 4) does not have to be continuous as shown in FIG. 4 (d).

[0036]

As described above, according to the present invention, when the same channel is allocated by repeatedly shortening the use interval for the communication connection request call in the mobile communication system having the small zone structure, the desired wave pair interference occurs. By changing the required value of the wave power ratio according to the amount of traffic, it is possible to reduce the call loss and, in some cases, to provide communication of higher quality than the conventional method.

In the future, in fixed channel allocation and dynamic channel allocation in the conventional system in which the zones are made smaller in accordance with the increase in the demand for mobile communication, the frequency is changed with respect to the traffic volume which varies greatly spatially and temporally. The application of the present invention to such a system is particularly effective because it is expected to be insufficient for effective use of the call, and eventually for call loss.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a system in which fixed channels are assigned to a zone configuration of a two-dimensional regular hexagonal zone arrangement.

FIG. 3 is a diagram for explaining the principle of a conventional “method of adaptive reuse of frequencies possible in dynamic channel allocation”.

FIG. 4 is a diagram in which the present invention and the conventional method are compared in terms of call volume and required value of desired wave to interference wave power ratio.

FIG. 5 is a diagram of a control algorithm executed by a control station according to an embodiment of the present invention.

FIG. 6 is a diagram of a control algorithm executed by a control station according to an embodiment of the present invention.

[Explanation of symbols]

11 ... Radio zone, 12 ... Radio base station, 13 ... Mobile station around zone, 14 ... Mobile station in central zone of the zone, 21 ... Radio zone, 22 ... Radio base station, 24, 25 ... Mobile station around zone, 26 , 27 ... mobile stations in the center of the zone, 23 ... equivalent small zones of channels used by the mobile station 27,
41 ... Control station, 42 ... Wired transmission path, 43, 44 ... Base station

Claims (1)

[Claims] 1. A plurality of base stations that are distributed in a service area to form a wireless zone for communication connection with a mobile station, and a communication frequency channel group used for communication between the base station and the mobile station. , When a communication connection request is generated, the base station in the radio zone in which the mobile station is located selects and allocates one channel with a desired wave-to-interference wave power ratio of the required value or more from all channels In a mobile communication system for communicating with a base station or a plurality of base stations including the base station, when the traffic volume is small, the required value of the desired wave to interference wave power ratio is set to a large value, and the traffic volume increases. Accordingly, a mobile communication system characterized in that the required value of the desired wave to interference wave power ratio is set small.