JPH1032868A - Adaptive sector control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adaptive sector control method which does not degrade communication quality when there is unevenness in distribution of calls that occur in a cell in a mobile radio communication system, where a base station controls the transmitting power for each mobile station and performs communication by a sector cell structure. SOLUTION: A base station adaptively changes an area covering a corresponding sector so as to narrow it when communication quality in one of plural sectors is poor and also, to widen it when communication quality in one of the plural sectors in excessive (31 to 3M and 4), in response to unevenness in distribution of calls which occurs in a cell (1 and 2) and adaptively controls communication quality of an entire cell, so that the communication quality may be equalized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for adaptively controlling the directivity of a base station antenna corresponding to each sector in a mobile radio communication system using a sector cell configuration.

[0002]

2. Description of the Related Art In a cell system in which a service area is configured by arranging a large number of base stations having a communication range of a cell, a sector cell in which a base station of each cell divides a cell into a plurality of sectors using a directional antenna. There is a mobile radio communication system that uses a configuration and controls the transmission power of all mobile stations under intra-cell management so that the reception power from the mobile station at the base station becomes a predetermined desired reception power value.

[0003] As a known document on a mobile radio communication system using such a sector cell configuration, for example, there are the following documents. Literature: IEICE Journal, Vol. 78, No. 2, 1995.2, Masaharu Hata, “Cell Configuration Technology”, pp. 133-137. , A fixed directional antenna is used to realize a sector cell configuration, and a cell is equally divided into a plurality of sectors according to the number of divisions. In this case, each sector has the same center angle and the same coverage area (covering area).

[0004]

However, in the above method, the distribution of calls generated in a cell is biased.
When there is a bias in the number of calls in each sector, in a mobile radio communication system using a code division multiple access system, signals of other users performing simultaneous communication become interference signals. While the communication quality becomes poor, the communication quality becomes excessive in a sector where the number of calls generated is sparse. As described above, the uneven distribution of calls in the cell causes variations in communication quality, and there is a problem in that communication efficiency deteriorates as a whole system.

[0005]

In the adaptive sector control method according to the present invention, the base station of each cell of the cell system uses a directional antenna to divide the cell into a plurality of sectors, so that the base station can control each mobile station. In a method for adaptively controlling a coverage area of each of the plurality of sectors in a mobile radio communication system that performs communication by controlling transmission power of a station, the base station responds to a bias of a distribution of calls occurring in a cell. When the communication quality in one of the plurality of sectors is poor, the coverage area of the sector is narrowed. When the communication quality in the certain sector of the plurality is excessive, the corresponding sector is Is adaptively changed so as to widen the coverage area, and adaptively controlled so as to equalize the communication quality of the entire cell. Therefore, by applying the present invention,
Each base station can control the communication quality between the sectors by controlling all boundaries according to the number of calls generated in each sector of all the sectors in the cell even when the distribution of calls generated in the cell is uneven. Variations can be suppressed and communication efficiency of the entire system can be improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a cell system in which a service area is formed by arranging a large number of base stations having a communication range of a cell. Using a sector cell configuration divided into sectors
In a mobile radio communication system in which the base station controls the transmission power of all the mobile stations under cell management so that the reception power from the mobile station becomes a predetermined desired reception power value, execution is performed at each base station. That's how it works. First, the operation principle of the present invention will be described, and then means and devices for realizing this will be described.

FIG. 2 is a diagram for explaining the operation principle of the present invention. First, in order to explain a sector control method in a cell, a small sector obtained by equally dividing each sector in a cell into two is virtually introduced. As shown in FIG. 2, two sectors adjacent to the sector boundary are defined as a sector S1 and a sector S2, respectively. The sector center angle of the sector S1 and the number of calls generated within the sector are denoted by θ1, N1, respectively, and the sector center angle of the sector S2 and the number of calls generated within the sector are denoted by θ2, N2, respectively. Sector S
1 is equally divided into two small sectors having the same cover area area at the sector center angle θ1 / 2. Of the two equally divided small sectors, the small sector on the side in contact with the target boundary is the small sector S11 and the small sector on the non-contact side is the small sector S12, and the distribution of calls in the sector S1 before division is uniform. Assuming that there are two, the number of calls generated in two equally divided small sectors is N1 / 2. Similarly, the sector S2 is equally divided into two small sectors having the same coverage area at the sector center angle θ2 / 2, and the small sector on the side in contact with the target boundary among the two small sectors is not in contact with the small sector S21. If the small sector on the side is a small sector S22, assuming the same as above, the number of calls generated in the small sector of the small sector S21 and the small sector S22 is both N2 / 2.

Using the small sectors obtained by the above-mentioned sector division, for each of all the sector boundaries in the cell, the target sector boundary is determined from the small sectors S11 and S21 adjacent on both sides of the sector boundary. Determine the direction and width of the displacement. The sector boundary bisects the sum of the internally generated call counts of two adjacent small sectors (small sector S11 and small sector S21) on the assumption that the distribution of calls within the small sector is uniform. Position. The direction of the shift of the sector boundary position is on the side where the number of calls generated inside the small sector is large, and the width of the shift is based on the number of calls generated inside the small sector on the side where the number of calls generated inside the small sector is large. The value obtained by subtracting the average value of the number of calls internally generated in the sector is divided by the value of the number of internally generated small sectors per unit angle of the small sector having a larger number of internally generated calls in the small sector. This is shown as follows.

If N1> N2, the direction of the transition is on the side of the small sector S11, and the width of the transition (sector boundary movement amount) Δθ
Is that the number of internally generated small-sector calls of the small sector having the larger number of internally generated small-sector calls is N1 / 2, and the average number of internally generated calls of two small sectors is (N1 / 2 + N1 / 2) / 2.
Since the number of small sector internal calls per unit angle of the small sector on the side where the number of small sector internal calls is large is N1 / θ1, it is calculated by the following equation (1). Δθ = {N1 / 2− (N1 / 2 + N1 / 2) / 2} / (N1 / θ1) = (N1−N2) × θ1 / (4 × N1) (1) Also, if N1 <N2, the transition is performed. Direction is small sector S21
, The change width (the amount of movement of the sector boundary) Δθ is such that the number of small-sector internal calls of the small sector with the larger number of small-sector internal calls is N2 / 2, and the number of intra-sector calls of two small sectors. The average value of the number is (N1 / 2 + N1 / 2) / 2, and the number of small sector internal calls per unit angle of the small sector with the larger number of small sector internal calls is N2 / θ2. )
It is calculated by an expression. Δθ = {N2 / 2- (N1 / 2 + N1 / 2) / 2} / (N2 / θ2) = (N2-N1) × θ2 / (4 × N2) (2)

In this manner, the direction and width of the displacement of the sector boundary position can be determined. However, if the width of the displacement is too large in the sector control, the control may become unstable. (1A), (2)
The value is adjusted according to the expression A). Δθ = α × (N1-N2) × θ1 / (4 × N1), (where N1> N2) (1A) Δθ = α × (N2-N1) × θ2 / (4 × N2), where N1 < N2)... (2A) The combination of the sector boundary described above and two small sectors adjacent to both ends thereof can be combined independently without overlapping any other sector boundaries and small sectors in the cell. It is. Therefore, the direction and width of the displacement of each sector boundary position can also be determined independently. This is because, for all sectors in a cell, the number of calls generated inside the sector and the communication quality is inferior are improved for the sectors with poor communication quality, and the number of managed calls is reduced to improve the communication quality. An excess sector indicates that the operation of increasing the number of managed calls and suppressing the communication quality can be performed in parallel. By the adaptive sector control described above, it is possible to improve the communication efficiency of the entire system by suppressing the variation in the communication quality between the sectors.

FIG. 1 is a diagram showing a configuration of an adaptive sector control device according to the present invention. In FIG. 1, reference numeral 1 denotes an intra-sector total received power observation unit, 2 denotes an intra-sector generated call number calculation unit, 31 denotes a first sector boundary movement amount calculation unit, 32 denotes a second sector boundary movement amount calculation unit,. The M sector boundary movement amount calculation unit and 4 are antenna directivity control units. Here, M is the number of boundaries in the cell and is equal to the number of sectors. The intra-sector total received power output from the intra-sector total received power observation unit 1 is input to the intra-sector generated call count calculation unit 2. The number of calls generated within the sector of each sector, which is the output of the number-of-sector-generated calls calculation unit 2, is the first sector boundary movement amount calculation unit 31, the second sector boundary movement amount calculation unit 32,. Arithmetic unit 3
M, respectively. The first sector boundary movement amount and movement direction output from the first sector boundary movement amount calculation unit 31, the second sector boundary movement amount and movement direction output from the second sector boundary movement amount calculation unit 32, and the third sector boundary. Moving amount calculator 3
The third sector boundary movement amount and movement direction which are the outputs of 3... Mth sector boundary movement amount and movement direction which are the outputs of the Mth sector boundary movement amount calculation unit 3M are all input to the antenna directivity control unit 4. .

The operation of FIG. 1 will be described. All the operations in FIG. 1 are performed at discrete times at predetermined fixed time intervals T.
In the following example, it is assumed that the number of sectors M in a cell is 3, and an operation at a certain discrete time T0 will be described. It is also assumed that the transmission power of the mobile station is controlled such that the reception power from the mobile station at the base station becomes a predetermined desired reception power value. The intra-sector total received power observing section 1 observes all signal powers received by the directional antennas corresponding to the # 1 to # 3 sectors S1 to S3, respectively. Output as P3. The intra-sector generated call number calculation unit 2 divides the # 1 sector total received power P1 by the desired received power value to obtain the # 1 sector S1 generated call number N1 in the # 1 sector total received power P2. Is divided by the desired received power value to divide the number of calls N2 generated in the sector in the sector # 2 in the sector # 2, and the total received power P3 in the sector # 3 is divided by the desired received power value to obtain the number of calls in the sector # 3 in the sector S3. The number of generated calls N3 is calculated and output.

The first sector boundary movement vector calculation unit 31 calculates the number of calls generated in the sector with respect to the boundary F1 between the # 1 sector S1 having a center angle of θ1 and the # 2 sector S2 having a sector center angle of θ2. Of the number of calls N1 generated within the sector at # 1 sector S1, the number N2 of calls generated within the sector at sector # 2, and the number of calls N3 generated at sector # 3 at sector S3, N1 is calculated as N1. When N2> N2 and α is a predetermined positive constant equal to or less than 1 and N1> N2, the direction in which the boundary F1 moves is defined as the direction in which the cover area of the sector S1 becomes narrower. From the equation, the sector boundary movement amount Δθ1 = α × (N1−N2) × θ1 /
(4 × N1), and if N1 <N2,
The direction in which the boundary F1 moves is defined as the direction in which the cover area of the sector S2 becomes narrower, and the sector boundary movement amount Δθ1 = α × (N2-N1) × θ2 / (4 ×
N2) to calculate the moving direction of the boundary F1 and the boundary F
1 is determined as the sector boundary movement width Δθ1 which is the size of movement of the sector boundary.

The second sector boundary movement vector calculation unit 32 calculates the number of calls generated in the sector with respect to the boundary F2 between the # 2 sector S2 having a center angle of θ2 and the # 3 sector S3 having a sector center angle of θ3. Of the number of calls N1 and # 2 generated in the sector at # 1 sector S1 calculated by the part 2, the number of calls N2 generated within the sector at sector S2 and the number of calls generated within the sector N3 at # 3 sector S3, N2 When N2> N3 and α is a predetermined positive constant equal to or less than 1, the moving direction of the boundary F2 is defined as the direction in which the cover area of the sector S2 becomes narrower, and the above (1A )
Sector boundary movement amount Δθ2 = α × (N2-N3) × θ2 /
(4 × N2), and if N2 <N3,
The direction in which the boundary F2 moves is defined as the direction in which the cover area of the sector S3 becomes narrower, and the sector boundary movement amount Δθ2 = α × (N3-N2) × θ3 / (4) based on the equation (2A).
XN3) to determine the direction in which the boundary F2 moves and the sector boundary movement width Δθ2, which is the size of the movement of the boundary F2.

The third sector boundary movement vector calculator 3 calculates the number of calls generated in the sector for the boundary F3 between the # 3 sector S3 having the center angle θ3 and the # 1 sector S1 having the sector center angle θ1. N3 and N1 in the number of calls N1 generated in the sector in # 1 sector S1, the number of calls N2 generated in the sector in # 2 sector S2, and the number of calls generated in the sector N3 in # 3 sector S3 calculated in S2. And α is a positive constant equal to or less than 1 in advance, and if N3> N1, the boundary F
3 is defined as a direction in which the cover area of the sector S3 becomes narrower, and based on the above formula (1A), the sector boundary movement amount Δθ3 = α × (N3-N1) × θ3 / (4 × N
3), and if N3 <N1, the boundary F3
Is defined as the direction in which the cover area of the sector S1 becomes narrower, and the sector boundary movement amount Δθ3 = α × (N1−N3) × θ1 / (4 × N1) based on the equation (2A).
Is calculated to determine the moving direction of the boundary F3 and the sector boundary moving width Δθ3 which is the size of the moving of the boundary F3.

In the antenna directivity control section 4, the second sector boundary movement vector calculation section for the boundary F2 is provided in the direction determined by the first sector boundary movement vector calculation section 31 by the angle given by the sector boundary movement amount Δθ1. 32 is changed by the angle given by the sector boundary movement amount Δθ2 in the direction defined by the sector 32 and the angle given by the sector boundary movement amount Δθ3 in the direction defined by the third sector boundary movement vector calculation unit 33 with respect to the boundary F3. A new inter-sector boundary is determined, and the directivity of the base station directivity antenna corresponding to each sector is changed to satisfy this. As a method of controlling the antenna directivity, for example, when a base station antenna is configured by an array antenna, there is a method of adjusting a delay time and a weight coefficient corresponding to each antenna element. Due to the above directivity control of the base station antenna, the number of calls generated in the sector and the communication quality is inferior for a sector having a poor communication quality are shifted in the direction in which the coverage area is reduced, and the number of calls to be managed is reduced. In the sector where the number of calls generated inside the sector is small and the communication quality is excessive, the boundary moves in the direction of increasing the coverage area, the communication quality is suppressed by increasing the number of managed calls, and the communication quality is suppressed for a certain period of time. By the repetitive control for each interval T, the variation in the communication quality between sectors is gradually suppressed, and the communication efficiency of the entire system is improved.

[0017]

As described above, according to the present invention, the base station of each cell of the cell system uses a directional antenna to divide the cell into a plurality of sectors, so that the base station can transmit power of each mobile station. In the method for adaptively controlling the coverage area of each of the plurality of sectors in a mobile radio communication system that performs communication by controlling the base station, the base station, depending on the bias of the distribution of calls occurring in the cell, If the communication quality in a certain sector is poor, the coverage area of the corresponding sector is reduced.If the communication quality in a certain sector of the plurality is excessive, the coverage area of the corresponding sector is reduced. Since the adaptive control is performed so that the communication quality of the entire cell is equalized by adaptively changing the base station to be wider, each base station has:
Even when there is a bias in the distribution of calls generated in the cell, the system controls all boundaries according to the number of calls generated in each sector of all sectors in the cell, thereby suppressing variations in communication quality between the sectors and improving the system. There is an effect that the communication efficiency as a whole can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an adaptive sector control device according to the present invention.

FIG. 2 is a diagram illustrating the operation principle of the present invention.

[Explanation of symbols]

 1 Total received power observation unit within sector 2 Number of calls generated within sector calculation unit 31 First sector boundary movement vector calculation unit 32 Second sector boundary movement vector calculation unit 33 Third sector boundary movement vector calculation unit 3M Mth sector boundary movement vector Arithmetic unit 4 Antenna directivity control unit

Claims (2)

[Claims] A mobile radio communication system in which a base station of each cell of a cell system uses a directional antenna to divide a cell into a plurality of sectors, and the base station controls transmission power of each mobile station to perform communication. In the method for adaptively controlling the coverage area of each of the plurality of sectors in a system, the base station may adjust communication quality in a sector among the plurality of sectors according to a bias of distribution of calls occurring in a cell. When the communication quality in one of the plurality of sectors is excessive, the coverage area of the corresponding sector is adaptively changed so that the coverage area of the corresponding sector is widened when the communication quality in the certain sector is excessive. Adaptive control so as to equalize the communication quality of the entire cell. 2. The base station of each cell of the cell system uses a directional antenna to divide the cell into a plurality of sectors, so that the base station can adjust the received power from each mobile station to a desired power. In a method for adaptively controlling the coverage area of each of the plurality of sectors in a mobile radio communication system that performs communication by controlling the transmission power of a station, the base station is provided at every predetermined time. The total received power of the received signal is measured for each of the directional antennas corresponding to the plurality of sectors. Next, the total received power in each sector is divided by the desired power to obtain the number of calls generated in the sector. For each of the sector boundaries in the cell, two sectors adjacent to the sector boundary are defined as sectors S1 and S2, respectively, and the sector center angles of the sectors S1 and S2 and the number of calls generated in the sector. Each θ1, N1 and θ
2, N2, and α is a predetermined positive constant equal to or less than 1. When N1 is larger than N2, the sector boundary moving direction is set to a direction in which the coverage area of the sector S1 becomes narrower, and the sector boundary moving amount is set. Let Δθ be Δθ = α × (N1−N2) × θ
1 / (4 × N1), and when N1 is smaller than N2, the sector boundary moving direction is set to the sector S
2, and the sector boundary movement amount Δ
θ is defined as Δθ = α × (N2−N1) × θ2 / (4 × N2)
Next, for all the sector boundaries in the cell, the antenna directivity of the base station is controlled by an angle given by the calculated sector boundary moving direction and the sector boundary moving amount to move the inter-sector boundary. An adaptive sector control method characterized by: