JPH05308319A - Radio sector selection system - Google Patents

Abstract

PURPOSE:To reduce interference between sectors by preferentially selecting a sector in the same base station with a sector where a mobile station presently belongs to when there are >=2 sectors under equal quality conditions. CONSTITUTION:When none of sectors 8, 9, and 10 where the mobile station 1 is present has no free channel and the channel of a peripheral sector is assigned, the mobile station 1 is informed of the frequencies of the monitor channels of the peripheral sectors through control channels 12, 13, and 14. Then the reception levels of the monitor channels are measured and reported. Consequently, when there are plural sectors having equal quality conditions among sectors which have reception levels higher than a specific threshold value and the highest level and can be connected, the sector in the base station is preferentially selected. Consequently, the interference with other sectors due to an increase in the output of the base station is reduced and the electric power is saved by increasing the output unnecessarily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio sector selection control of a mobile communication system in which the propagation characteristics of a radio wave emitted from an antenna having directivity are utilized to minimize interference with others. In particular, the present invention relates to a wireless sector selection system having a configuration suitable for a system having a simple control system.

[0002]

2. Description of the Related Art Since many conventional mobile communication systems employ a fixed channel allocation system in which channels are allocated to each sector, even if traffic is congested in a certain sector and no empty channel exists, There may be channels available in the surrounding sectors. Further, the sector, which is a communicable area, is not clearly separated by the boundary with the adjacent sector, and there is an overlap area connectable to both sectors.

Therefore, when allocating a radio channel to a mobile station existing in the overlap area, even if there is no free channel in one sector, a channel is selected from another communicable sector and connected. By making it possible (selecting another sector), effective use of the radio frequency due to the swarming effect is performed.

FIG. 4 shows a system configuration example of an implementation example of another sector selection performed by a conventional mobile communication system. In the figure, 51 is a mobile station, 52 and 53 are base stations, 54 is a line control station, 55, 56 and 57 are transmitters belonging to the base station 52, 58 is a transmitter belonging to the base station 53, 59, 60, 6
1 and 62 are sectors corresponding to the transmitters 55, 56, 57 and 58, 67 is a data line connecting the base stations 52 and 53, and 63, 64 and 65 are also monitoring channels of the base stations 52 and 53 and stand by. Represents a radio control channel through which information is sometimes passed. The operation from the stand-by of communication until the communication connection request is generated and the wireless channel is allocated will be described below with reference to FIG.

At the time of standby, the mobile station 51 determines that it is in the radio sector 59 and receives the control channel 63. The transmitter 55 transmits the mobile station 5 via the control channel 63.
In No. 1, the frequency of the monitoring channel of the peripheral sector to be monitored when the control information is not received is notified. In this example,
The mobile station 51 is notified of the frequencies of the control channels 64 and 65.
Periodically switches to the notified frequency and measures the reception level. When the reception level of the monitoring channel of the peripheral sector exceeds the reception level of the control channel of the sector in which it is located, it is judged that the sector has been moved and the control channel to be received is switched. The reception levels of the supervisory channels of a plurality of notified peripheral sectors are constantly measured.

When a communication connection request is made due to a call originating from a mobile station or a call arriving at a mobile station, the mobile station 51 uses the control channel of the serving sector to set the reception level of the monitoring channel of the peripheral sector to the base level. Report to station 52. The base station 52 including the transmitter of the serving sector 59 selects the wireless channel in response to the communication connection request.
If there is no available free channel in 9, the mobile station 51
It is determined whether or not the reception level of the supervisory channel reported by the above is equal to or higher than a predetermined threshold value and there is a free channel in another connectable sector having the highest level.

In this example, the mobile station 51 has sectors 59 and 60.
If the reception level from the sector 62 is the highest, it is determined that the sector 62 can be connected, and the base station 53 via the data line 67 has a radio channel available for the sector 62. Ask if it exists. When there are multiple connectable sectors,
Inquiries are continued until a usable wireless channel is found in descending order of reception level. For example, when there are available radio channels 68 in sector 62 of the figure,
The frequency of the wireless channel is specified for the mobile station 51, and the wireless channel is set.

[0008]

Based on FIG. 4, as described above,
Although the operation at the time of call origination has been described, other sector selection similar to that described above can be applied when switching channels during communication. for that reason,
Information is exchanged between the base station and the mobile station using the control channel during communication, and the mobile station measures the reception level of the monitoring channel during communication. The peripheral sector monitoring during communication of the mobile station is made possible by adopting the TDMA method and performing it during the idle time slot time.

However, the following problems can be considered in this example. The radio wave from the transmitter usually has a low reception level at some distance from the transmitter because it is attenuated by a building or the like. However, in some cases,
A certain level of reception may be obtained even in a place that is not normally considered due to line-of-sight propagation because there is no obstacle to radio wave propagation. However, even in such a case, the reception level is often lowered due to the influence of a shield or the like if a slight movement occurs. In the above cases, if the reception level happens to be high and that sector is selected, the transmitter must increase its output when the reception level decreases, and the range of the radio waves from that sector expands. There is a risk of interference with other sectors using the same frequency (for example, when the same frequency is used in the sector 61 and the sector 62 in the above example, the sector 62 is selected for the mobile station 51, and the sett 61 is interfered with. Is possible).

When a sector belonging to a base station other than the base station to which the first serving sector belongs is selected, information must be exchanged between a plurality of base stations (in this example, the sector 62 is If selected, information needs to be exchanged between the base stations 52 and 53), and control becomes complicated. Such a problem is largely due to the fact that the sector in the same base station as the serving sector and the base station did not distinguish between different sectors. The present invention has been made in view of the above problems and provides a sector selection control method in a mobile communication method that can reduce interference between sectors as compared with the conventional method and can be realized with simple control. Has a purpose.

[0011]

According to the invention, the above objects are achieved by the means recited in the claims. That is, according to the present invention, a plurality of base stations forming a small radio zone composed of a plurality of sectors communicating with a mobile station are distributed in a service area, and the base station has a plurality of channels used for communication with the mobile station. In the mobile communication system, which is allocated to each sector and a radio channel that satisfies the quality condition as a communication channel is selected and assigned when a communication connection request is generated, an empty channel is allocated to a sector in which the mobile station is located. If there are two or more sectors that are communicatively connectable under the same quality condition when the mobile station is connected to a peripheral communicatively connectable sector, the sector to which the mobile station is located belongs to the sector. This is a wireless sector selection method that controls so as to preferentially select a sector within the same base station as the base station.

[0012]

According to the present invention, a plurality of base stations forming a small radio zone composed of a plurality of sectors for communicating with a mobile station are installed in a service area, and the base station is used for communication with the mobile station. In a mobile communication system in which multiple channels are allocated to each sector and a wireless channel that satisfies the quality condition as a communication channel is selected and allocated when a communication connection request is generated, in a sector in which a mobile station is located, an empty channel is available. Instead, when allocating the channels of the peripheral sectors, the mobile station is informed of the frequencies of the monitoring channels of the peripheral sectors via the control channel, and the reception levels of the respective monitoring channels are measured and reported. If there are multiple sectors that have the same quality conditions among the above-mentioned connectable sectors with the highest level, select the sector in the same base station. Ahead basis to act as you choose.

According to the present invention, for example, the base station creates a table as shown in Table 1 described later based on the reception level of the monitoring channel from the mobile station, and allows the reception level to have a certain range to satisfy the quality condition. 3 is different from the prior art in that it has a function of detecting that they are equivalent to each other (see FIG. 3) and also has a function of considering whether or not a sector is in the same base station when selecting a sector. That is, the present invention realizes a sector priority selection method within its own zone, thereby reducing inter-sector interference and simplifying control related to channel selection, as compared with the conventional technique.

[0014]

FIG. 1 is a diagram for explaining an embodiment of the present invention, in which 1 is a mobile station, 2 and 3 are base stations, 4 is a line control station,
5, 6 are transmitters belonging to the base station 2, 7 are transmitters belonging to the base station 3, 8, 9, 10 are sectors corresponding to the transmitters 5, 6, 7 respectively, 11 is between the base stations 2 and 3. Data lines 12, 13, and 14 connecting to each other represent a radio control channel that also serves as a monitoring channel for the base stations 2 and 3 and that sends information during standby. FIG. 2 is a flowchart showing the control of the base station.

The operation from the standby time of communication of this embodiment to the request for communication connection and the allocation of the wireless channel will be described below with reference to FIGS. 1 and 2. During standby, the mobile station 1 determines that it is in the radio sector 8 and receives the control channel 12. Transmitter 5 has control channel 1
The mobile station 1 notifies the frequency of the monitoring channel of the peripheral sector to be monitored when the control information is not received via the mobile station 2.
In this embodiment, the frequencies of the control channels 13 and 14 are notified, the mobile station 1 periodically switches to the notified frequency, the reception level is measured, and the result is sent together with the reception level of the serving sector to the transmitter. 5 to the base station 2. The base station 2 creates a table as shown in Table 1 based on the data.

[0016]

[Table 1]

When the reception level of the monitoring channel of the peripheral sector exceeds the reception level of the control channel of the sector in which it is located (comparing the reception level of each sector based on the table), the sector is said to have been moved. The mobile station always determines the reception level of the serving sector and the reception levels of the monitoring channels of the multiple peripheral sectors notified by the control channel, and switches the control channel to be received. And the base station updates the table based on the data.

When a communication connection request is made due to a call originating from a mobile station or a call arriving at a mobile station, the mobile station 1 uses the control channel of the serving sector to determine the reception level of the monitoring channel of the peripheral sector as described above. Report to 2. The base station 2 including the transmitter of the serving sector 8 selects a wireless channel in response to the communication connection request, but if there is no available channel in the serving sector, the monitoring reported from the mobile station 1 is performed. It is determined whether there is another connectable sector having the highest reception level of the channel which is equal to or higher than a predetermined threshold value. Here, if there are two or more such sectors and they have the same quality condition, the sector in the same base station is given priority (whether or not they are in the same base station can be seen by looking at the base station flag). In this example, the mobile station 1 exists in the overlapping area of the sectors 8, 9, and 10, but the reception level from the mobile station is as shown in Table 1.

At this time, since there is no empty channel in sector 8 (which can be seen from the fact that 1 is set in the empty channel flag), the reception level of another sector is scanned. Although the reception level of the sectors 9 and 10 is higher than the reception level of 10, but the quality conditions are the same, the sector 9 in the same base station is preferentially selected, and whether or not a usable radio channel exists in the sector is determined. Find out. Whether or not the quality conditions are equivalent may be considered to be equivalent if the difference between the reception levels is within a certain range as shown by the letter A in FIG. 3 as shown in FIG. If there is no free channel in that sector and there are multiple sectors that can be connected, the inquiry will continue based on the reception level in the table to check if there is a free channel in that sector in descending order of reception level. , If there are multiple sectors having the same quality condition, the sector within the same base station as the serving sector is prioritized. When there is a usable wireless channel 15 in the sector 9 selected in this way, the frequency of the wireless channel 15 is designated to the mobile station 1 to set the wireless channel.

In the above description, the operation at the time of call initiation is described, but as in the conventional technique, the selection of another sector can be applied when switching the channel during communication. The base station uses directional antennas to divide the radio zone into sectors, but due to its characteristics, the reception level of radio waves from adjacent sectors in the same base station is Some value cannot be obtained unless the transmitter is approached.

Therefore, when a sector within the same base station is selected, the reception level does not suddenly drop even if the mobile station slightly moves, and therefore the base station increases its output and interferes with other sectors. The phenomenon to say becomes less. In addition, since the sectors within the same base station are selected preferentially, the channel allocation is often completed within one base station,
Information exchange with other base stations is reduced. As is apparent from this result, interference with other sectors is reduced as compared with the conventional technique, control is simplified, and the system efficiency is improved.

In the above description, for simplification of the description, an example of selecting another sector between two zones and three sectors at the time of call origination is shown, but the present invention limits the number of zones and the number of sectors. This makes it possible to select a wireless channel from all sectors that can be connected for communication without communication.

[0023]

As described above, according to the present invention, since the reception level sharply decreases and therefore the output of the base station is not unnecessarily increased, the sector selection system is used.
There is an advantage that interference with other sectors due to an increase in the output of the base station is reduced and the output is not unnecessarily increased to save power. Also, by preferentially selecting sectors within the same base station, the amount of information transfer between base stations is reduced, control is simplified, and various costs associated with communication between base stations and information processing are reduced. There is also the effect of leading to.

[Brief description of drawings]

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

FIG. 2 is a flow chart showing control of the base station of the present invention.

FIG. 3 is a diagram showing a concept of quality conditions in which reception levels are equivalent.

FIG. 4 is a diagram showing an example of a conventional car telephone system configuration.

[Explanation of symbols]

 1 mobile device 2,3 base station 4 line control station 5,6,7 transmitter 8,9,10 sector 11 data line 12,13,14 radio control channel 15 radio channel

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief explanation of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

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

FIG. 2 is a flow chart showing control of the base station of the present invention.

FIG. 3 is a diagram showing a concept of quality conditions in which reception levels are equivalent.

FIG. 4 is a diagram showing an example of a conventional car telephone system configuration.

[Explanation of Codes] 1 mobile station 2, 3 base station 4 line control station 5, 6, 7 transmitter 8, 9, 10 sector 11 data line 12, 13, 14 radio control channel 15 radio channel ────── ────────────────────────────────────────────────

[Procedure amendment]

[Submission date] August 5, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Explanation of code

[Correction method] Change

[Correction content]

[Explanation of Codes] 1 mobile station 2, 3 base station 4 line control station 5, 6, 7 transmitter 8, 9, 10 sector 11 data line 12, 13, 14 radio control channel 15 radio channel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Fujita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A plurality of base stations forming a small radio zone composed of a plurality of sectors communicating with a mobile station are distributed in a service area, and the base station has a plurality of channels used for communication with the mobile station. Has been deployed for each sector,
In a mobile communication system that selects and allocates a wireless channel that satisfies the quality condition as a communication path when a communication connection request is generated, there is no free channel in the sector in which the mobile station is located When there are two or more sectors that can be connected for communication under the same quality condition when connecting to a possible sector, the sector within the same base station as the sector to which the mobile station is located is prioritized. A wireless sector selection method characterized in that the control is performed so that the wireless sector is selected.