SE515898C2 - A method for cell load distribution in a cellular mobile radio communication system - Google Patents

Abstract

In a method of load sharing between a first cell (C4) and its neighbouring cells (C1, C2, C3, C5, C6, C7) in a cellular mobile radio system, wherein each cell serves a number of mobile stations (1, A, B, C, D), it is determined if the traffic load of said first cell (C4) is higher than a first load threshold (201, 202), and if so, it is determined if the traffic load of the neighbouring cells (C1, C2, C3, C5, C6, C7) is lower than a second load threshold (203). If it is lower, at least a neighbouring cell (C5) having the highest number of mobile stations, associated with said first cell (C4), with a signal strength above a signal strength threshold (204) is selected from the neighbouring cells (C2, C5, C7). The cell coverage of said neighbouring cell (C5) is increased towards said first cell (C4) (205), and the cell coverage of said first cell (C4) is decreased a corresponding amount in a direction from said neighbouring cell (C5) (206).

Description

If the system becomes overloaded, the system determines if there are any unloaded neighboring cells and which of the cells is least loaded. If such a cell is present, the signal strength threshold of the overloaded cell is increased in the direction of the neighboring cell and / or the signal strength threshold of the neighboring cell is decreased in the direction of the overloaded cell. By dynamically varying the thresholds, the effective areas of the cells are either increased or decreased and the cell shapes change. The effective area of the overloaded cell is reduced to a point so that fewer mobile stations are handled in the overloaded cell and a higher number of mobile stations are handled in the neighboring cells.

According to US-A-5 241 685, the movement of cell boundaries towards at least one of the neighboring cells to the gangs is performed to ensure small changes in the cell size. However, the effect of this movement is not predicted and the method can cause a movement of the boundaries of several neighboring cells before a sufficient number of mobile stations have moved out of the cell with the high traffic load.

In addition, the cell boundary is moved only a small predetermined step each time to avoid a larger number of transfers.

The algorithm is relatively slow and there is an imminent risk that the cell load distribution method will be activated late and consequently have a short time to provide a marginal effect.

The Invention It is an object of the present invention to provide an improved method of cell load distribution in a cellular mobile radio communication system which handles temporary load peaks in cells without adding additional cell resources, while maintaining the quality of service in the system. This object is achieved by a method of load distribution according to the present invention between a first cell and its neighboring cells in a cellular mobile radio system, each cell serving a number of mobile stations. It is determined whether the traffic load of a first cell is higher than a first load threshold. If so, it is determined if the traffic load of the neighboring cell is lower than a second load threshold, if so, at least one neighboring cell with the highest number of mobile stations connected to the first cell, with a signal strength above a signal strength threshold, is selected from the neighboring cells with a traffic load lower than the second load threshold. The cell coverage of at least one neighboring cell is increased towards the first cell and the cell coverage of the first cell decreases correspondingly in a direction from at least one neighboring cell.

In another embodiment of the invention, the position of mobile stations is determined for the distribution of the traffic load of mobile stations located in the border region between adjacent cells in the communication system. It is determined whether the traffic load of the first cell is higher than the first threshold. If so, it is determined if the traffic load of the neighboring cell is lower than the second load threshold, if so, at least one neighboring cell with the highest number of mobile stations connected to the first cell is selected, within a distance threshold from a cell boundary between the first cell and the second cell, from the neighboring cells with a traffic load lower than the second load threshold.

The cell coverage of the neighboring cell is increased towards the first cell and the cell coverage of the first cell decreases correspondingly in a direction from the neighboring cell. According to another aspect of the invention, it is determined how much the cell coverage of each cell is to be changed to reduce the traffic load of the first cell to be lower than the first load threshold. An advantage of the present invention is the efficient handling of fluctuations in the traffic load, whereby the cell coverage of each cell is changed in steps small enough to prevent oscillation and large enough to be fast.

Brief Description of the Drawings In order to explain the invention in more detail and the advantages and features of the invention, reference is made in the following detailed description of the preferred embodiment to the accompanying drawings, in which Fig. 1 is an illustrative view of a part of a cellular network, and Fig. 2 is a flow chart illustrating a first embodiment of the method of the present invention.

Detailed Description of the Invention A cell load sharing method (CLS) according to the present invention provides increased network capacity by distributing the traffic load between neighboring cells at temporary local load peaks. The invention relates to the field of cellular mobile radio communication systems and is exemplified by a TDMA (Time Division Multiple Access) based system, specifically GSM. However, it is applicable to other systems such as the PDC standard etc.

Referring to Fig. 1, a cellular network is illustrated, comprising 7 cells C1-C7, each cell serving a number of mobile stations (MS) 1, A, B, C, D. The mobile station interface to the cellular network is a base station ( BS), which is usually located in the center of each cell. To establish and maintain a call between two subscribers in a cellular network, the mobile station must be in contact with the base station. Since each cell has a limited area, the mobile station 1 must be in contact with different base stations if it is moved from one cell surface to another. A A mobile service switching center (MSC) is a switching node that controls a number of base stations. Depending on the configuration and size of the network, one or more MSCs are required.

Of course, a cellular network such as GSM (global system for mobile communications) includes additional equipment to function well. However, it is well known to those skilled in the art and will not be described in detail.

Thus, in the following description, a number of specific details, such as the number of cells, etc., are provided in detail to give a more thorough description of the present invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Some well-known units such as base stations, mobile service switching centers and other system units are not described in detail so that the invention will not become obscure.

In a digital system such as GSM, a mobile station continuously monitors the received power levels of the neighboring cells. Each base station transmits a list of base stations or channels to be measured to the mobile station. The mobile station continuously performs measurements of the quality of the transfer to / from and the power of the serving cell and the neighboring cells. The results are placed in a measurement report, which is periodically sent back to the base station. Based on the measurements, the decision and the thresholds for the signal strength, limitations and / or other information parameters associated with the transfer can then be adjusted according to the change in load or other operating conditions.

W U 20 25 30 35 515 898 In general, the MS continuously measures and reports the signal strength from the cell within which it is located, and from its neighboring cells. If the MS receives a better signal strength from a neighboring cell than from the current serving cell, a handover takes place.

Thus, it is possible to determine the position of a particular MS between a serving cell BS and the BS of each neighboring cell by using the signal strength measurements. The higher the signal strength from the neighboring cell, the closer the MS is to the cell boundary between the serving cell and the neighboring cell. In order to identify the spread of MSs in a cell, it is determined to which neighboring cells each MS adjoins. In addition, an MS may be close to more than one neighboring cell.

An operating cell BS receives the signal strength measurement from each MS and stores the result in an MS report list, which is a global system list. Each cell receives data from the MS report list to an MS distribution list, which does not take into account the identity of each MS. Data in the MS distribution list are used to calculate the relative position of each MS in a cell.

In the preferred embodiment of the invention, already performed measurements are used in the method, which avoids changes in the air interface.

In accordance with what has been stated above, an MS in busy state continuously measures the signal strength from the serving cell and the signal strength from a number of neighboring cells (perch frequencies), which are audible from the current MS, state report. Consequently, there is no need to change the sender of information to the BS in an existing condition report or modify MSs.

When the condition report is received in the coordination no- as a base station monitor (BSC = Base Station or an MSC, to map perch frequencies to their corresponding cells and the, Controller) the neighboring cells are identified by the message divided and stored in the global MS -report- list.

When the condition report is received in the BS, all entries in the MS report list for the specific MS are cleared, and the new values are stored. When an MS call is terminated, all records for that MS are also removed from the MS report list, as there will be no status reports sent from that MS. This helps to maintain the MS report list consistent with the MS distribution in the network.

If the signal strength is above a certain threshold, it is entered in the MS report list for the current cell. The threshold specifies when the mobile station is close enough to a neighboring cell to provide sufficient speech quality with its BS.

This list is continuously updated by the information reported by the MS. The list does not have to be sorted.

Each item in the list contains the following: the identity of the MS that performed the measurements, the identity of the neighboring cell for which the signal strength measurement was made, the current measured signal strength, and the serving cell identity.

For each cell there is an MS distribution list, which contains the identity of the neighboring cell, for which the signal strength measurements have been made, and the current measured signal strength.

For each cell controlled by the coordination node, a periodic update of the MS distribution list is performed, whereby the value of the neighboring cell designation and the signal strength are retrieved from the MS report list.

The MS distribution list is stored according to the neighboring cell number and within each neighboring cell according to the measured signal strength.

Before an update of a cell is performed, the MS distribution data for the specific cell is deleted. Since the data in the N U 20 25 515 898 8 MS report list is consistent, the MS distribution list will also be consistent with the MS distribution in the network.

Table 1 shows an MS distribution list for cell C4 in FIG. 1. However, the mobile stations A-D in Table 1 are for illustrative purposes only and are not necessary for the operation of the invention.

Table 1 MS distribution list (Cell C4) NCELL MS SS C% _ A 115 dB C5 B 120 dB C5 C 90 dB C7 C 100 dB C7 D 80 dB According to the measurement presented in table 1, MS B has reported the strongest signal strength with 120 dB from the BS in cell C5 and MS A have reported a signal strength of 115 dB from the BS in cell C2. MS C: 90 dB from the BS in C5 and 100 dB from the BS in C7. Finally, MS D has reported a signal strength measurement of 80 dB from the BS in C7.

In the method according to the invention, a pad is also provided. The deviation parameter thus defines a parallel adjustment of a logical boundary, ie a cell-to-cell signal-strength relationship. This is used in a cell selection (TCH) operation, as a means of adjusting the sufficient signaling algorithm for traffic channel assignment and plaque strength value between two neighboring cells.

The number of free traffic channels in all cells, where CLS- Its level function is activated, is monitored by the system. 10 15 20 25 30 35 .I 5_1E_5_ 898 is continuously compared with two other system parameters, namely two predetermined traffic channel occupancy levels_ The first load threshold is the traffic load in a cell, above which level CLS is initiated, which indicates few free TCHs.

The second load threshold is the traffic load in a cell, above which level CLS is accepted, which indicates the available capacity.

The main steps of the method according to an embodiment of the present invention are illustrated by the flow chart in FIG.

The traffic load of an operating cell, C4 in the embodiment, is measured in step 201. If a cell has a high traffic load, higher than the first load threshold, it is determined in step 202 and, if so, the boundary of the cell shall be moved inwards by changing the deviation parameter, ie the cell coverage must be reduced.

However, in order to reduce the coverage of the serving cell C4, it is required that at least one of the neighboring cells has low traffic. Therefore, in step 203, it is determined whether the traffic load of one neighboring cell or cells of the serving cell C4 is lower than the other load threshold. If no such low load cell is available, the method proceeds to step 207.

From the neighboring cells with low traffic, which indicates the possibility of receiving MSs with maintained service quality, a neighboring cell with the highest number of signal strength measurements is selected in step 204. According to Table 1, it is the neighboring cell C5. However, if there are two or more cells, C5 and C7 in this example, with the "highest" number of signal strength measurements, the first is represented, which is represented in ie cell 5. ring form, the cell with the most free traffic channels is selected, ie cell C7.

Thus, the cell coverage of the neighboring cell C5 should increase the list of these cells. This is achieved by changing the deviation.

To find out how many MSs are to be moved from the serving cell to a neighboring cell, the MS distribution list for the current cell is reviewed. For each neighboring cell, the number of measurements with sufficient signal strength is calculated.

In this embodiment, the neighboring cell which has the highest number of signal strength measurements, i.e. the highest for the current cell C4 to move its cell boundary towards, since the largest discharge number of MSs near the cell boundary, the power effect is achieved there, is selected.

It is determined how much the cell boundary should be adjusted to move a sufficient number of MSs from the serving cell to the selected neighbor cell.

MSs, which are close to the neighboring cell, are sorted according to signal strength in the MS distribution list. This means that the MS, the list and the MS, which is closest to the neighboring cell boundary, are placed first in which has the longest distance to the cell boundary, placed last in the list.

The distance is measured in dB and since a change in the cell boundary can be calculated in dB, the system can predict that a change in the cell boundary in X dB will affect the number of MSs.

This means that if the system wants to move Y number of MSs from the serving cell to the neighboring cell, the system knows how many dB the cell boundary and thus the deviation must be changed.

In the example illustrated in FIG. 1, it is determined that the occupancy level in cell C4 is to be reduced by two TCHs and, as a result, the cell coverage of the neighboring cell C5 is increased by moving a first boundary extending between a point 2 and a point 3. towards the serving cell C4 in step 205, the boundary then extending between another point pair 2 'and 3', and the cell coverage of the serving cell C4 is correspondingly reduced in a direction from the neighboring cell in step 206. MS B and C are thus moved over and are served by the neighboring cell C5.

In another situation, also illustrated in FIG. 1, it is determined that the occupancy level in cell C4 should be reduced by three TCHs. According to the measurements presented in Table 1, it is most adequate to move two cell boundaries of cell C4, both relative to cell C5, in the list of the highest number of signal strength measurements, which is the first cell and cell C7, which is the second cell in the list with the same maximum number of signal strength measurements. Accordingly, the cell coverage of the neighboring cell C5 is increased by moving the boundary between point 2 and point 3 toward the serving cell C4, and the cell coverage of the neighboring cell C7 is increased by moving a second boundary extending between a point 4 and a point S toward the neighboring cell C4 in step 205. As a result, the first boundary then extends between points 2 'and 3', and the second boundary extends between yet another pair of points 4 'and 5'. The cell coverage of the serving cell C4 is correspondingly reduced in the respective direction from the neighboring cells C5 and C7 in step 206. This is thus achieved by changing the deviation between the cells C4 and C5 and C4 and C7, respectively, whereby MS B and C are served by the neighboring cell C5 and MS D is served by cell C7. In addition, a check is made if all cells have been treated in step 207. If there are any cells not yet treated by the CLS method according to the invention, the next cell is selected in step 208 and the same procedure as for cell C4 is performed. However, if all cells have been processed, the method waits a time delay CLSDelay in step 209 before proceeding to the next cell, i.e. cell C1 of the set of cells C1-C7 connected to the coordination node.

In another embodiment of the invention, a check is made as to whether the neighboring cell, which is determined to be the receiving cell (and C7), has sufficient free traffic channels to receive the spirit cell or cells, C5 in this example , the required number of mobile stations to be transferred from the serving cell C4. This check is necessary to prevent the neighboring cell from becoming overloaded. There are four alternative embodiments to solve this problem.

According to the first alternative, the neighboring cell has a limit, which allows it to receive a number of mobile stations up to its first threshold value. The second alternative involves transfers of mobile stations until the current serving cell and the receiving neighboring cell are equally load-balanced. The third alternative involves transfers to achieve a load in the neighboring cell below its first load threshold but above its second load threshold. According to the fourth alternative, a maximum number of mobile stations are moved over, but do not cause the serving cell to go below its second load threshold at the same time as the neighboring cell C5 exceeds its second load threshold. Again, reference is made to step 202. If the current cell does not have high traffic, it is checked in step 210 whether the traffic load for the cell in question is low, ie lower than the second load threshold. If the traffic is not low, it is assumed to be normal and the method proceeds to step 207. If not all cells have been handled, the next cell in the row of cells in step 208 is selected and processed according to the CLS method. However, if the traffic load is considered low in step 210, it is determined in step 211 whether the coverage of the first cell has changed in at least one direction from a neighboring cell, i.e. the deviation and thus the cell boundaries have changed earlier with respect to CLS, the original cell boundaries of the current cell is reset in step 212.

The coverage of the neighboring cell or cells, which has previously changed in connection with the current serving cell, is thus reduced in a corresponding manner. On the other hand, if the coverage of the first cell has not changed, the method proceeds to step 207.

If the cell coverage has changed for a long time, longer than a predetermined time, the cellular network is not planned properly due to, for example, a change in traffic load in the area. Thus, a reorganization of cell planning is needed. In an alternative embodiment of the invention, a timer means is provided which indicates when it is time to reorganize the cell planning. For example, when calls involving MS B, C and D are terminated, the occupancy level of cell C4 is lower than the first load threshold, whereby the cell coverage of C4, C5 and C7 can then be restored. The deviation parameters and consequently the cell boundaries of cell 4 are thus moved, both in relation to cell C5 and cell C7. Accordingly, the cell coverage of the serving cell C4 is increased in step 212 and the cell coverage of the neighboring cell C5 is reduced by moving the boundary extending between point 2 'and point 3' from the serving cell C4, and the cell coverage of the neighboring cell C7 is reduced by move the second boundary, which extends between point 4 'and point 5', from the serving cell C4 in step 213. As a result, the first boundary extends between the original points 2 and 3, and the second boundary extends between the other original points 4 and 5. In the current system this is achieved by changing the deviation between cells C4 and C5 and C4 and C7 respectively.

In a second embodiment of the invention, instead of using the signal strength, the position of the mobile stations in relation to the cell boundaries is determined. This is done by means of a stand-alone positioning system such as ex- (GPS) for example Timing Advance, for example the Global Positioning System or with mobile system measurements, (TA). When the position of the MS is calculated by the MS itself, data can be transmitted via MSc / Bsc or via Unstructured Supplementary Service Data to the system via Short Message Service (SMS) (USSD).

Based on the current deviation, position data and (C4) c7), the cell boundary position is predicted based on known wave propagation transmitted power of the serving cell base station and the neighboring cell base stations (C1, C2, C3, C5, C6, ning models. The distance from each MS to each cell boundary To calculate the "amount" of cell boundary displacements, the distance is converted to a deviation change calculated in dB, again using known wave propagation models. Although the invention has been described by specific embodiments, it It is apparent that the present invention provides a method and system for cell load distribution in a cellular mobile radio communication system which fully meets the objects and advantages set forth above, and alternatives, modifications and variations will be apparent to those skilled in the art.

In relation to known techniques, the invention provides a faster and consequently more efficient method for distributing traffic load between cells. The method describes against which adjacent cells the boundary is to be moved and how much the boundary is to be moved. This is achieved while maintaining good properties of known technologies, for example stability against commuting.

The air interface between MS and BS will not change, which means that no change of MS is needed.

The problem should be applicable to other cellular systems, for example WCDMA, still within the inventive concept of the present invention.

Claims (23)

10 U 20 25 30 35 515 898 15 PATENT REQUIREMENTS Method for load distribution between a first cell (C1, C2, C3, C5, C6, C7) learned mobile radio system, each cell serving a number (1, A, B, c, D), determining whether the traffic load of the first cell (201, 202); (C4) and its neighboring cells in a cellular mobile station characterized by the steps of: (C4) being higher than a first load threshold case, determining the traffic load of the neighboring cells (c1, c2, c3, c5, c6, c7) (2o3); if so, if it is lower than a second load threshold from neighboring cells (C2, C5, C7), with a traffic load lower than the second load threshold, select at least one neighboring cell (B, C) connected to the first cell ( C4), with a signal strength (C5; C7) with the highest number of mobile stations higher than a signal strength threshold (204); increasing the cell coverage of at least one of the neighboring cells (C5; C7) towards the first cell (C4) (205); and reducing the cell coverage of the first cell (C4) to a corresponding degree in a direction from at least one of the neighboring cells (C5; C7) (206). Method according to claim 1, characterized in that, before the step of increasing the cell coverage of at least one of the neighboring cell (C5; C7) (C4), the step of: towards the first cell the further (C5, C7) the highest number mobile stations connected to the first if there are two or more neighboring cells with the cell (C4), with a signal strength higher than the signal strength threshold (204), select at least one neighboring cell starting from the first neighboring cell (C5), stored in an MS - report list of the first cell (C4). W U 20 25 30 35 515 898 16 Method according to claim 1, characterized in that the cell boundary towards at least one of the neighboring cells (C5; C7) is increased to: towards the first cell (C4), the further step if there are two or more neighboring cells (C5; C7) with the highest number of signal strength measurements, select at least one neighboring cell in order starting from the cell (C7) with the highest number of free traffic channels. Method according to any one of the preceding claims, characterized in that, before the step of increasing the cell coverage of at least- (c5; c7) the further step of: stone a neighboring cell against the first cell (C4), determining how much the cell coverage of each cell (C4, C5, C7) of the first cell shall be changed to reduce the traffic load (C4) to be lower than the first load threshold. Method according to claim 4, characterized in that the change of the cell coverage is measured in dB, wherein a special increase / decrease of the cell coverage of the first cell (C4) is a number of dB and a corresponding decrease / increase of the cell coverage of at least one of the neighboring cells (C5; C7), causes the transfer of a specific number of mobile stations between the first cell (C4) and the neighboring cell (C5; C7). Method according to claim 4 or 5, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) (C4) (205) for receiving at the neighboring cell a number of mobile stations is increased towards the first cell (C5; C7) to a maximum level of its first load threshold. Method according to claim 4 or 5, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) is increased towards the first cell (C4) (205) in order to in NH the neighboring cell (C5; C7) causes the first cell and the receiving neighboring cell (C5; C7) to receive a number of mobile stations, which are evenly load balanced. Method according to claim 4 or 5, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) (C4) (205), in order to receive a number of mobile stations at the neighboring cell, is increased towards the first cell (C5; C7) at a load is obtained in the neighboring cell (C5; C7), which is below its first load threshold but above its second load threshold. Method according to claim 4 or 5, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) (C4) (205) for receiving a number of mobile stations at the neighboring cell is not increased towards the first cell (C5; C7) causes the neighbor cell (C4) to go below its second load SOIT1 threshold while the neighbor cell (C5; C7) will exceed its second load threshold. Method according to one of the preceding claims, characterized in that, prior to the step of determining the traffic load (C1, C2, C3, C5, C6, C7), the further steps of: determining the traffic load (203), determining the traffic load of the first cell is lower than a second load threshold (C4) is lower than the second load threshold (210); if so, determine if the coverage of the first cell (C4) has changed relative to at least one neighboring cell (C5; C7) (211); if so, increase the coverage of the first cell against at least one of the neighboring cells (C5; C7) (212); and correspondingly reduce the coverage of at least one of the neighboring cells (C5; C7) (213). N Ü 20 25 30 515 898 18 Method according to one of the preceding claims, characterized in that the cell coverage of a cell is changed by modifying the signal strength ratio between a first cell (C4) and a second cell (C5). Method according to one of the preceding claims, characterized by the further steps of: checking whether the cell coverage has changed for a predetermined period of time, and if so, generating a signal indicating that a restructuring of the cell planning is required. Method for load distribution between a first cell (C4) (C1, C2, C3, C5, C6, C7) learned mobile radio system, each cell serving a number (1, A, B, C, D), characterized and its neighboring cells in a cellular mobile station of the steps of: determining whether the traffic load of the first cell (C4) is higher than a first load threshold (201,202); if so, determine the traffic load of the neighboring cells (C1, C2, C3, C5, C6, C7) (203); if so, is lower than a second load threshold (C2, C5, C7) lower than the second load threshold, select at least one neighbor from the neighboring cells with a traffic load cell (C5; C7) with the highest number of mobile stations (B, C) connected to the first cell (C4), within a distance threshold from a cell boundary between the first cell (C4) and at least one of the neighboring cells (C5; C7) (204); increasing the cell coverage of at least one of the neighboring cells (C5; C7) towards the first cell (C4) (205); reduce the cell coverage of the first cell (C4) and to a corresponding degree in a direction from at least one of the neighboring cells (C5; C7) (206). 10 U 20 25 30 35 515 898 19 Method according to claim 13, characterized in that, before the step of increasing the cell coverage of at least one of the neighboring (C5; C7) (C4), the further step of: the cells towards the first cell if there are two or more neighboring cells ( C5; C7) the highest number of mobile stations connected to the first cell (C4) with within the distance threshold (204) select at least one neighboring cell in order starting from the first neighboring cell (CS), (C4). stored in an MS report list of the first cell Method according to claim 13, characterized in that, before the step of increasing the cell coverage of at least one of the neighboring cells (C5; C7) towards the first cell (C4) (205), the further step of: if there are two or more neighboring cells (C5; C7) with the highest number of mobile stations within the distance threshold, select at least one neighboring cell in order starting from the cell (C7) with the highest number of free traffic channels. Method according to any one of claims 13-15, characterized in that, before the step of increasing the cell coverage of at least one of (C5; C7) towards the first cell (C4) (205), the further step of: the neighboring cells determining how much the cell coverage of each cell (c4, c5, c7) of the first cell (C4) must be moved to reduce the traffic load to be lower than the first load threshold. Method according to claim 16, characterized in that the change of the cell coverage is measured in a unit of length, wherein a special increase / decrease of the cell coverage of the first cell (C4) a special distance and a corresponding decrease / increase of the cell coverage of at least one of the neighboring cells (C5; C7) entails the transfer of a special number of mobile stations between the first cell (C4) (C5; C7). and the neighboring cell Method according to claim 16 or 17, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) is increased towards the first cell (C4) (205) to receive at (C5; C7) a number of mobile stations up to a maximum level of its first load threshold. the neighboring cells Method according to claim 16 or 17, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) (205) for receiving at the neighboring cell (C5; C7) a number of mobile stations, (G4) is evenly balanced. increases towards the first cell (C4) which causes the first cell (C5; C7) and the receiving neighboring cell Method according to claim 16 or 17, characterized in that the cell coverage of at least one of the neighboring cells (C5; C7) is increased towards the first cell (C4) (205 ') to receive at (C5; C7) a number of mobile stations, a load in the neighboring cell (C5; C7) load threshold but above its second load threshold. the neighboring cell as during its first A method according to claim 16 or 17, (C5; C7) for increasing in the neighboring cell characterized by towards the first cell (C5; C7) an receive which does not cause the serving cell to one of the neighboring cells (C4) (205) number mobile stations, len (C4) goes below its second load threshold while the neighboring cell (C5; C7) exceeds its second load threshold. Method according to any one of claims 13-21, characterized in that, before the step of determining whether the traffic load of the neighboring cells (C1, C2, C3, C5, C6, C7) load threshold (203) is lower than a second, the further steps of: WH 515 898 21 determine if the traffic load of the first cell (C4) is lower than its second load threshold (210); if so, determine if the coverage of the first cell (C4) has changed relative to at least one neighboring cell (C5; C7) (211); if so, increase the coverage of the first cell towards at least (212): correspondingly decrease the coverage of at least (C5; C7) (213). one of the neighboring cells (C5; C7) and one of the neighboring cells Method according to any one of claims 13-22, characterized by the further step of: checking whether the cell coverage has changed for a predetermined period of time, and if so, generating a signal indicating that a restructuring of the cell planning is required.