Determining an operation domain of a base station in a cellular network

0001The present invention relates generally to the field of the determination if a first cell of a wireless cellular network managed by a first base station is neighbour of a second cell of the wireless cellular network managed by a second base station.

0002Current wireless cellular networks are based on a centralised architecture. A base station controller controls multiple base stations, which in turn aim at covering given cells. When a cellular wireless mobile network operator wishes to add a cell in its network, it usually achieves the following operations. First, it installs the base station on the site and connects it physically to its serving base station controller. Then, it configures the base station controller so that base station controller configures the base station with its operation domain such as the frequency or time slots or codes used for its operation.

0003In addition, the base station controller handles the handover procedures of mobile terminals from/to newly added cell to/from existing neighbouring cells, so that mobile terminals wandering in an area served by such cells can continue their communications seamlessly while moving from one cell to another.

0004In order to enable handover procedure, the base station controller has to be aware of neighbouring conditions between the newly added cell and existing cells. Usually, such determination of neighbouring conditions is defined according to radio network planning techniques.

0005Radio network planning is classically determined by simulation methods. Prior to installing a base station on a given site, the cells that would be the neighbouring cells of this newly introduced cell are determined. Such simulation methods usually require a fine knowledge of antenna type, position and steering used to operate each cell, as well as information related to radio wave propagation in the vicinity of the cell.

0006Such techniques are adapted for centralized wireless cellular networks or to wireless cellular networks which doesn't evolve a lot in the time. If the number of base stations which have to be added is rather important, or if one or several base stations need to be moved from one location to another one or if some base stations are powered off periodically, as for maintenance purpose, such techniques are not efficient.

0007<patcit id="pcit0001" dnum="US5864764A"><text>US5864764</text></patcit> discloses a method for enabling, by a server, the determination, by a first base station managing a first cell, if the first cell is neighbour of a second cell managed by a second base station. The server receives from the first base station information related to the location of the first base station, determines a second base station which is located in the vicinity of the first base station and transfers to the first base station information identifying the second base station.

0008The present invention aims to propose a base station which allows to determine, in a distributed wireless cellular network, the cell operation domain of a cell or cells managed by a base station.

0009The invention is defined in the independent claim. Preferred embodiments are defined in the dependent claims.

0010The characteristics of the invention will emerge more clearly from a reading of the following description of an example embodiment, the said description being produced with reference to the accompanying drawings, among which : <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a diagram representing the architecture of the wireless cellular network according to the present invention ;</li><li><figref idref="f0002">Fig. 2</figref> is a diagram representing the architecture of a server according to the present invention;</li><li><figref idref="f0002">Fig. 3</figref> is a diagram representing the architecture of a base station according to the present invention;</li><li><figref idref="f0003">Fig. 4</figref> is an algorithm executed by a base station when it is installed in the wireless cellular network according to the present invention ;</li><li><figref idref="f0004">Fig. 5</figref> is an algorithm executed by the server when a base station is installed in the wireless cellular network according to the present invention ;</li><li><figref idref="f0005">Fig. 6</figref> is algorithm executed by a neighbouring base station of a base station installed in the wireless cellular network according to the present invention.</li></ul>

0011<figref idref="f0001"><b>Fig. 1</b></figref> is a diagram representing the architecture of the wireless cellular network according to the present invention.

0012In the wireless cellular network of the <figref idref="f0001">Fig. 1</figref>, several base stations 10a, 10b, 10c and 10d are linked each other through a telecommunication network 50. The base stations 10a to 10d access through the same telecommunication network 50 to services provided by a server 20.

0013Each base station 10a to 10d is in charge of at least one cell 15 wherein mobile terminals 30 which are located within that cell 15 can detect a pilot signal and establish or receive some communications through the base stations 10 which manage the cells 15.

0014In the <figref idref="f0001">Fig. 1</figref>, only one cell 15a, 15b and 15d is shown respectively for each of the base stations 10a, 10b and 10d, but we can understand that a more important number of cells are managed by a base station 10 in the present invention.

0015A cell 15 may be defined as a set of geographical locations to which a given base station 10 provides the best quality of received pilot signals by the mobile terminals 30 comprised in that cell 15 among pilot signals of other neighbouring cells 15.

0016For the sake of simplicity, the cell managed by the base station 10c is not shown in the <figref idref="f0001">Fig. 1</figref>.

0017In the <figref idref="f0001">Fig. 1</figref>, only four base stations 10a to 10d are shown, but we can understand that a more important number of base stations 10 can be used in the present invention. On a similar way, only one server 20 is shown, but we can understand that a more important number of servers can be used in the present invention.

0018The server 20 stores information about all the base stations 10a to 10d which are linked to the telecommunication network 50. These information are information representative of the geographical location of the different base stations 10a to 10d, the International Base Subscriber Identifier of each of the base station 10. With such information, the server 20 is able to determine which given base station 10 of the base stations 10a to 10d is geographically neighbour to a given base station 10.

0019The telecommunication network 50 is a dedicated wired network or a public network like a public switched network or an IP based network or a wireless network or a combination of above cited networks.

0020The telecommunication network 50 connects the base stations 10 and the server 20 together and allows the transfer of messages between the base stations 10 and between each base station 10 and the server 20 according to the present invention.

0021Each base station 10 is connected to the telecommunication network 50 through at least one link. Preferably, each base station 10 is connected to the telecommunication network 50 through at least two links.

0022Such links are more preferably physical or logical access ports. An access port allows the transfer of information between two base stations 10a to 10b.

0023The base station 10a has two access ports noted P10a1 and P10a2, the base station 10b has two access ports noted P10b1 and P10b2, the base station 10c has two access ports noted P10c1 and P10c2 and the base station 10d has two access ports noted P10d1 and P10d2.

0024For the sake of simplicity, only two access ports are shown in the <figref idref="f0001">Fig. 1</figref> for each of the base stations 10a to 10d, but we can understand that a more important number of access ports are used in the present invention.

0025The general principal of the present invention is that the wireless telecommunication network is built from interconnected base stations 10, which can individually serve multiple cells 15. When a new base station 10, as example the base station 10b is added to the wireless telecommunication network, such base station 10b connects itself to the server 20 and declares to the server 20 the list of access ports P10b1 and P10b2 to be used for further communication with the other base stations 10.

0026For such newly added base station 10b, the server 20 determines a large list of neighbouring base stations 10 that are assumed, according to a first criterion, to be neighbours to the base station 10b. Such first criterion is as example based on the distance which separates the base stations 10. More precisely, a base station 10 is neighbour of another base station 10 if the distance which separates the base stations 10 is below a predetermined distance. When two base stations 10 are neighbours, the cells 15 they are managing respectively can be considered as potential neighbouring cells.

0027Such list of neighbouring base stations 10 is transmitted back to the base station 10b, together with the address and at least an access port identifier of each the neighbouring base station 10.

0028The server 20 transmits a list comprising the address and access ports number of the neighbour base stations 10a and 10d according to the first criterion to the base station 10b.

0029Then, the base station 10b establishes some permanent physical or logical connection with its neighbour base stations 10a and 10d.

0030The connection between the base stations 10a and 10b is noted Co1 in the <figref idref="f0001">Fig. 1</figref> and is made through the links P10a1 and P10b1.

0031The connection between the base stations 10b and 10c is noted Co2 in the <figref idref="f0001">Fig. 1</figref> and is made through the links P10b2 and P10d2.

0032Once the inter-base station 10 connection is ready, the base station 10b retrieves some information related to the operation domain used by the involved neighbour cells managed by neighbour base stations 10 such as frequency, time slot, codes....

0033From this information, the base station 10b decides on its own, of an acceptable operation domain for its own cell 15b and then informs its neighbouring base stations 10a and 10d that it starts operation of its radio cell 15b on the selected operation domain. The base stations 10a and 10d then add the new cell 15b in their individual neighbouring cells lists for broadcasting, so that the mobiles terminals 30 served by their respective cells 15a and 15d can now measure the signals of the newly added cell 15b in order to proceed, if necessary, to handover procedure with the newly added cell 15b. On its side, the base station 10b starts to broadcast in its cell 15b, for the same reason, the neighbouring cells list of cell 15b.

0034After some given time, the base station 10b checks whether or not the cells 15a, 15d of its neighbouring base stations 10a and 10d are neighbours of its cell 15b according to a second criteria, which is different from the first one. Such second criteria is, as example, representative of the quantity of information transferred through each of the connections Co1 and Co2 used for establishing handovers between its cells 15b and the potential neighbours cells 15a or 15d.

0035The base station 10b decides that a given cell 15a is no longer a neighbour to its cell 15b, when it determines that the quantity of information in relation to handover across cells 15a and 15b, as observed across connection Co1, is marginal with respect to its own activity. In such case, the base station 10b reconfigures the neighbouring cells list broadcasted in cell 15b, so that mobile terminals 30 located in cell 15b no longer make measurements on cell 15a in order to prepare handover.

0036Similarly, under such occasion, the base station 10a may decide autonomously to remove any cell 15b from the neighbouring cells list of any of its cell 15a.

0037The base station 10b initiates a base station disconnection procedure with one of its neighbouring base stations 10a and 10d, when it determines that the activity of the connection with a base station 10 is marginal with respect to its own activity. In such case, the base station 10b stops the connection with the base station 10. If that base station 10 is the base station 10d, the connection Co2 is then released and the associated access ports becomes available at both base stations 10b and 10d for further connection to some other base stations 10. To that end, the releasing base station 10b informs the server 20 that its access port P10b2 is now available, and that it is no longer connected to the base station 10d via the access port P10d2.

0038The neighbouring cells lists for the cells of base station 10b and 10d are updated accordingly.

0039Then, the neighbouring cells lists converge to a restricted number of neighbours.

0040In case of handover procedure, the communication contexts of the mobile terminals 30 are then exchanged across base stations 10a and 10b, 10b and 10d via the connections Co1 and Co2.

0041It has to be noted here that, the general principle of the present invention is disclosed in an example wherein each base station 10 manages one cell 15. When a base station 10 manages plural cells 15, the same process is executed for each of the cells 15 managed by the base station 10.

0042<figref idref="f0002"><b>Fig. 2</b></figref> is a diagram representing the architecture of a server according to the present invention.

0043The server 20 has, for example, an architecture based on components connected together by a bus 201 and a processor 200 controlled by programs as disclosed in the <figref idref="f0004">Fig. 5</figref>.

0044The bus 201 links the processor 200 to a read only memory ROM 202, a random access memory RAM 203, a telecommunication network interface 206 and a data base 204.

0045The memory 203 contains registers intended to receive variables and the instructions of the programs related to the algorithm as disclosed in the <figref idref="f0004">Fig. 5</figref>.

0046The processor 200 executes the algorithm as disclosed in the <figref idref="f0004">Fig. 5</figref>.

0047The read only memory 202 contains instructions of the programs related to the algorithm as disclosed in the <figref idref="f0004">Fig. 5</figref> which are transferred, when the server 20 is powered on to the random access memory 203.

0048The server 20 is connected to the telecommunication network 50 through the network interface 206. As example, the network interface 206 is a DSL (Digital Subscriber Line) modem, or an ISDN (Integrated Services Digital Network) interface, or PLC (Power Line Communication) interface, or a wireless interface, etc. Through such interface, the server 20 transfers information to the base stations 10 as it will be disclosed in reference to the <figref idref="f0004">Fig. 5</figref>.

0049The database 204 comprises all information related to the bases stations 10 like information representative of their geographical location, the International Base Subscriber Identifier of each of the base station 10, the available access ports of the base stations 10.

0050<figref idref="f0002"><b>Fig. 3</b></figref> is a diagram representing the architecture of a base station according to the present invention.

0051The base station 10 has, for example, an architecture based on components connected together by a bus 301 and a processor 300 controlled by programs as disclosed in the <figref idref="f0003">Figs. 4</figref> and <figref idref="f0005">6</figref>.

0052The bus 301 links the processor 300 to a read only memory ROM 302, a random access memory RAM 303, a network interface 304 and a wireless interface 306.

0053The memory 303 contains registers intended to receive variables, the list of neighbouring base stations, the neighbouring cells list of its cell 15, the operation domain of each of the neighbouring cells 15 and the instructions of the programs related to the algorithms as disclosed in the <figref idref="f0003">Figs. 4</figref> and <figref idref="f0005">6</figref>.

0054The processor 300 controls the operation of the network interface 304 and the wireless interface 306.

0055The read only memory 302, contains instructions of the programs related to the algorithms as disclosed in the <figref idref="f0003">Figs. 4</figref> and <figref idref="f0005">6</figref> which are transferred, when the base station 10 is powered on to the random access memory 303.

0056A base station 10 is connected to the telecommunication network 50 through the network interface 304. As example, the network interface 304 is a DSL (Digital Subscriber Line) modem, or an ISDN (Integrated Services Digital Network) interface, or PLC (Power Line Communication) interface, or a wireless interface, etc. Through such interface, the base station 10 exchanges information which the server 20 and the neighbour base stations 10 which manage potential neighbouring cells 15.

0057The network interface 304 comprises several access ports. Each access port is used for a dedicated connection with a base station 10 which manages at least one neighbouring cell 15. It has to be noted here that one common access port can be dedicated for the negotiation with unknown base stations of a given access port which will be used latter for the connection. Another specific access port can be dedicated for the signalling with the server 20.

0058The wireless interface 306 allows to communicate with the mobile terminals 30 which are in the cells 15 of the base station 10. The wireless interface 306 contains one radio antenna or multiple radio antennas, each radio antenna serving a given cell 15 of base station 10.

0059<figref idref="f0003"><b>Fig. 4</b></figref> is an algorithm executed by a base station when it is installed in the wireless cellular network according to the present invention.

0060Such algorithm is, as example, executed by the processor 300 of a base station 10 when it is installed and connected to the telecommunication network 50 or when it is powered on or when it is moved from one location to another one.

0061At step S400, the processor 300 obtains information representative of the location of the base station 10. Such information is obtained, as example and in a non limitative way, from the person who installs the base station 10 through a man machine interface not shown in the <figref idref="f0002">Fig. 3</figref> or through a Global Positioning System (GPS) device included within the base station 10 or connected to it. As example and in a non limitative way, the information representative of the location of the base station 10 is the post address of the building wherein the base station 10 is located, the phone number allocated to a telephone line within the building wherein the base station 10 is located or any other network address which permits to retrieve the post address of the building wherein the base station 10b is located, or the GPS coordinates of the base station 10 or the latitude, longitude and altitude of the position of the base station 10.

0062The information representative of the location of the base station 10 can be also the amplitude of signals and identifiers of base stations 10 comprised in that signals, which are transmitted by some base stations 10 in their respective cells 15 and received by the base station 10 or by a device connected to the base station 10.

0063At step S401, the processor 300 commands the transfer of a registration message to the server 20. The registration message comprises the information representative of the location of the base station 10 previously obtained, the telecommunication network address of the base station 10 and the identifier of each of its access ports. As example, if the base station 10 is the base station 10b, the processor 300 commands the transfer of the network address of the base station 10b and the identifiers of the access ports P10b1 and P10b2 of the base station 10b. In a variant of realization, the base station 10b transfers only the identifier of an access port P10b1 or P10b2 which has to be used for the negotiation of further connections or for the initialization of further connections with some other base stations 10. In another variant of realization, the base station 10b also transfers the identifier of one access port P10b1 or P10b2 which is dedicated to communication with the server 20.

0064At next step S402, the processor 300 receives a response message from the server 20 through the telecommunication network 50. The response message comprises the list of neighbouring base stations 10 determined by the server 20 according to the first criterion. The list of neighbouring base stations 10 comprises the addresses, within the telecommunication network 50, of the base stations 10 which are neighbours of the base station 10b according to the first criterion. According to the example of the <figref idref="f0001">Fig. 1</figref> the list comprises the addresses of the base station 10a and 10d.

0065More precisely, the list of neighbouring base stations 10 comprises also, for each of the base stations 10a and 10d which are neighbours of the base station 10b, the identifier of at least one access port available for future connection.

0066At next step S403, the processor 300 establishes connections with at least some of the base stations 10 which are comprised in the list of neighbouring base stations.

0067More precisely, if the number of available access ports of the base station 10b is smaller than the number of the base stations 10 comprised in the list of neighbouring base stations, the processor 300 establishes connections with a subset of its neighbouring base stations 10 and memorizes the remaining part in the RAM memory 303.

0068A connection is established through the telecommunication network 50 between two bases stations 10 by reserving an access port of each of the base station 10 through which, a permanent signalling logical connection is established between the two base stations 10. Such access port reservation can be made, in a variant, during a negotiation phase through a common access port, dedicated to the negotiation of access ports. Preferably, no more than one connection is established between two base stations 10, even though these base stations 10 may involve neighbouring conditions between more than two of their cells 15.

0069The logical connection can be as example and in a non limitative way, compatible with the TCP (Transmission Control Protocol) or the UDP ( User Datagram Protocol) protocol, to be used on top of IP signalling.

0070Each base station 10 allocates a unique identifier to each connection. Such identifier is the identifier of the access port or the access port number. The combination of an access port number and the IP address of a base station 10 form then a unique socket. The IP address is used to identify a base station 10, and the access port number identifies the connection itself.

0071So, when the base station 10b establishes a bi-directional signalling connection with another base station 10, as example the base station 10a, it sends its messages together with its IP address, the IP address of the base station 10a, the identifier of the access port it has reserved for that connection and with an identifier of an access port that is still available at the base station 10a. Similarly, the base station 10a addresses the base station 10b with the IP address of the base station 10b and with the access port identifier received from the base station 10b.

0072In another implementation mode of the invention, all the base stations 10 use the same single fixed access port for the purpose of common signalling between base stations 10. The signals exchanged between the base stations 10 over that access port carry the identification of the emitting base station 10 but later, a connection is established through negotiated access port.

0073A first connection noted Co1 is then established between the base station 10b and the base station 10a through their respective access ports P10b1 and P10a1. A second connection noted Co2 is then established between the base station 10b and the base station 10d through their respective access ports P10b2 and P10d2.

0074At the same step, the processor 300 transfers a message to the server 20 informing it that the access port of each successful connection is now unavailable.

0075Through the respective established connections Co1 and Co2, at step S404, the processor 300 obtains and stores in RAM memory 303 the list of cells 15a and 15d managed by its neighbouring base station 10a and 10d and the operation domain of cells 15a and 15d managed by its neighbouring base station 10a and 10d.

0076The operation domain of a cell 15 managed by a base station 10 comprises, as example and in a non limitative way, the frequencies used by the base station 10 in its cell 15 and/or the time slots used by the base station 10 in its cell 15 and/or the codes used by the base station 10 in its cell 15.

0077Each neighbouring base station 10 transfers through the established connection with the base station 10b, the operation domain of its cell 15.

0078At step S405, the processor 300 determines the operation domain of its cell 15b.

0079For that, the processor 300 builds an occurrence table of usage among cells 15 of neighbouring base stations 10 stored in RAM memory 303 at step S404 of the operation domains it has received and stored in RAM memory 303 at step S404.

0080The processor 300 selects for its cell 15b the operation domain among those of smallest occurrence observed among the cells 15 of its neighbouring base stations 10. When the base station 10b controls more than one cell 15b, the table also includes the operation domain of its cells 15b. Each time an operation domain is chosen for one cell 15b, the table of usage of the operation domains is updated. Then, the operation domain of subsequent cells 15b is selected among those of smallest occurrence and not yet being selected for other cells 15b.

0081Preferably, the processor 300 selects for its cell 15b the operation domain among those of smallest occurrence observed among only the cells 15 of its neighbouring base stations 10 that are neighbour to cell 15b.

0082In another yet preferred embodiment, the probability of selection of an operation domain of a neighbouring cell 15a of the cell 15b is a decaying function of the monitored information quantifying the neighbourhood relationship between the cell 15a and the cell 15b, that is collected in step S407.

0083At next step S406, the processor 300 transfers the operation domains of the cell 15b back to its neighbouring base stations 10a and 10d through the respective connections Co1 and Co2, so that they can maintain their own occurrence table of usage of the operation domains.

0084At next step S407, the processor 300 activates the monitoring of the information transferred through the connections Co1 and Co2 established at step S403.

0085The information monitored are, as example, the messages transferred to and/or received from a neighbouring base station 10a which are related to handover procedures of mobiles terminals 30 comprised in their respective cells 15.

0086A handover procedure occurs when a mobile terminal 30 is in communication with another telecommunication device through a given base station 10b in an initial cell 15b and moves to a cell 15a of a neighbouring base station 10a. During the handover procedure, the given base station 10b has to stop to serve the mobile terminal 30 and the neighbouring base station 10a has to start to serve the mobile terminal 30 enabling the continuation of the communication. During a soft handover procedure, the neighbouring base station 10a has to start to serve the mobile terminal 30, while the given base station 10b keeps serving the mobile terminal 30, enabling macro-diversity, and the simultaneous continuation of the communication over multiple cells.

0087If an handover procedure is engaged by a mobile terminal 30, it means that the mobile terminal 30 receives pilot signals from the cell 15a with a higher power strength than the one of the pilot signals of the cell 15b while still being located in the initial cell 15b, and that the cell 15a is an effective neighbouring cell of the cell 15b of the base station 10b. When a handover procedure between two base stations 10 is realised, some specific signalling messages are exchanged between the two base stations 10.

0088Using these information over numerous consecutive or parallel handover procedures involving more than one mobile terminal 30, it is possible, for the base station 10b to determine which are, among the cells 15 of its neighbouring base stations 10, the neighbouring cells of each of its cell 15b.

0089As example, and in a non limitative way, each time a message related to a handover procedure from/to cell 15b to/from cell 15a managed by base station 10a is transferred through the connection Co1, the processor 300 increments a counter associated to the neighbourhood between cell 15b and cell 15a of base station 10a. Each time a message related to a handover procedure from/to cell 15b to/from cell 15d managed by base station 10d is transferred through the connection Co2, the processor 300 increments a counter associated to the neighbourhood between cell 15b and cell 15d of base station 10a and 10d.

0090As another example, each time a message related to a handover procedure is transferred trough the connection Co1, the processor 300 increments a counter associated to the connection Co1. Each time a message related to a handover procedure is transferred trough the connection Co2, the processor 300 increments a counter associated to the connection Co2.

0091At next step S408, the processor 300 determines if whether or not it has to check if the cells 15 of its neighbouring base stations 10 are or not neighbouring cells of its cells according to the second criterion.

0092As example and in a non limitative way, the processor 300 determines that it has to check if the cells 15 of its neighbouring base stations 10 are neighbouring cells of its cells according to the second criterion, after a predetermined time of operation of the base station 10b and/or periodically and/or when the amount of information transferred through the connections Co1 and Co2 reaches a predetermined quantity.

0093If the processor 300 has to check if the cells 15 of its neighbouring base stations 10 are neighbouring cells of its cells according to the second criterion, the processor 300 moves to step S409. In the opposite, the processor 300 moves to the step S420.

0094At step S420, the processor 300 checks whether or not it has received a message from a neighbouring base station 10 informing it that the neighbouring base station 10 suppresses the connection with it.

0095If no message is received, the processor 300 returns to step S408.

0096If such message is received, the processor 300 moves to step S421.

0097At step S421, the processor 300 removes from the list of neighbouring base stations, the base station 10 which sent message. The processor 300 also removes from the neighbouring cells list of its served cell 15b, the cell or cells 15 served by the base station 10 which sent the message, and removes the operation domain of the cell or cell 15 served by that base station 10 from the table of usage of the operation domains.

0098At next step S422, the processor 300 transfers a message to the server 20 informing it that the connection between the base station 10b and the other base station 10 which sent the message at step S408, is broken and that the access port of that connection is now available for further access.

0099The processor 300 returns then to the step S405 in order to define a new operation domain for its cell 15. As far as the operation domain of a cell is defined according to the operation domains of the neighbouring cells and/or according to the monitored information collected at step S407, it is interesting to conduct a new determination of an operation domain for its cell.

0100It has to be noted here that, if the processor 300 has established at step S403 connections with a subset of its neighbouring base stations 10, the processor 300 moves to step S403, considers a base station 10 of the remaining part of base stations 10 memorized and in the RAM memory 303 and continue the present algorithm.

0101At step S409, the processor 300 considers the first connection with one of its potential neighbouring base stations 10. As example, the processor 300 considers the connection Co1.

0102At next step S410, the processor 300 checks whether or not, there is some activity on that connection, and updates the cell neighbouring conditions according to the monitored information.

0103For that, in one realisation mode of the invention, the processor 300 reads the value of the counter associated to the connection under process. If the value of the counter is upper than a predetermined threshold, the processor 300 decides that there is some activity on that connection and moves to step S411. On the contrary, the processor 300 moves to step S413.

0104It has to be noted here that in a variant of realization, the processor 300 calculates the sum of the values of each of the counters associated to the connections Co1 and Co2, divides the value of the counter associated to the connection under process by the calculated sum and compare it to a predetermined threshold.

0105In another realisation mode of the invention, the processor 300 reads the value of the counter associated to the neighbourhood between each cell 15b of the base station 10b and the each cell 15a of the distant base station 10a. If the value of the counter is upper than a first predetermined threshold, and that cell 15a is not yet part of the neighbouring cells list of cell 15b, the cell 15a is added to the neighbouring cells list of cell 15b. If the value of the counter is below a second predetermined threshold, and that cell 15a is part of the neighbouring cells list of cell 15b, the cell 15a is removed from the neighbouring cells list of cell 15b. When this is done for all cells 15b and 15a, the processor 300 informs the wireless interface 306 to start to broadcast the updated neighbouring cells list of the cell 15b.

0106It has to be noted here that in a variant of realization, the processor 300 calculates the sum of the values of each of the counters, divides the value of each of the counters associated to the connection under process by the calculated sum and compare it to a predetermined threshold.

0107At step S411, the processor 300 checks whether or not there are some other connections for which the activity has not been checked.

0108If there is at least one connection for which the activity has not been checked, the processor 300 moves to step S412, considers another connection and returns to step S410.

0109If there is no more connection for which the activity has not been checked, the processor 300 returns to step S408.

0110At step S413, the processor 300 removes from the list of neighbouring base stations, the base station 10 through which it is connected through the connection under process. The processor 300 also removes from the neighbouring cells list of its served cell 15, the cell served by the base station 10 which it is connected through the connection under process and removes the operation domain of the cell served by that base station 10 from the table of usage of the operation domains.

0111As far as the amount of handovers between the cells of two base stations is limited or null, it means that, despite the base stations 10 are neighbours, their respective cells 15 can not be considered as neighbours according to the second criterion.

0112At next step S414, the processor 300 sends a message to the base station 10 it is linked through the connection under process, informing it that the connection is suppressed and releases the access port of that connection.

0113At next step S415, the processor 300 transfers a message to the server 20 informing it that the access port of that connection is now available. Preferably, The processor 300 informs also the server that the access port of the neighbour base station 10 used for that connection is now available.

0114The processor 300 then returns to the step S405 in order to define a new operation domain for its cell 15.

0115It has to be noted here that, if the processor 300 has established at step S403 connections with a subset of its potentials neighbouring base stations 10, the processor 300 moves to step S403, considers a base station 10 of the remaining part of base stations memorized and in the RAM memory 303 and executes the algorithm as already been explained.

0116<figref idref="f0004"><b>Fig. 5</b></figref> is an algorithm executed by the server when a base station is installed in the wireless cellular network according to the present invention.

0117The present algorithm is executed by the processor 200 of the server 20.

0118At step S500, the processor 200 checks whether or not a message is received from the network interface 206. As far as no message is received, the processor 200 executes the loop constituted by the step S500.

0119If a message is received from the network interface 206, the processor 200 stores the contents of the message in the RAM memory 203 and moves to step S503.

0120At step S503, the processor 200 checks whether or not the base station 10 which sent the message has already accessed to the server 20. For that, the processor 200 checks whether or not a list of neighbouring base stations has been created for the base station 10 or if the database 204 comprises the list of the available access ports of the base station 10.

0121If the base station 10 which sent the message has already accessed to the server 20, the processor 200 moves to step S504. On the contrary, the processor 200 moves to step S507.

0122At step S507, the processor 200 determines, according to a first criterion, the neighbouring base stations 10 of the base station 10 which sent the message.

0123The first criterion, is preferably the distance between the base stations geographical locations.

0124From information representative of the geographical location of the base station 10 which was comprised in the received message, that was stored in RAM 203 at step S500, the processor 200 consults the database 204 and determines the set of base stations 10 that are in the vicinity of that location, with a predetermined distance criterion or a distance criterion chosen so as to find a given number of neighbouring base stations 10.

0125If the information representative of the location of the base station 10 which sent the message is the post address of the building wherein the base station 10 is located, the processor 200 determines from the post address, the latitude, longitude and altitude of the base station 10 and determines the set of base stations 10 that are in the vicinity of that location.

0126If the information representative of the location of the base station 10 which sent the message is the phone number allocated to a telephone line within the building wherein the base station 10 is located, the processor 200 determines from the phone number, a post address, and then the latitude, longitude and altitude of the base station 10b and determines the set of base stations 10 that are in the vicinity of that location.

0127If the information representative of the location of the base station 10 which sent the message are the GPS coordinates of the base station 10 or the latitude, longitude and altitude of the position of the base station 10, the processor 200 determines the set of base stations 10 that are in the vicinity of that location.

0128If the information representative of the location of the base station 10 are the amplitude of the signals and identifiers measured by the base station 10 which sent the message, the processor 200 determines from such identified signals an estimation of the latitude, longitude and altitude of the base station 10 and determines the set of base stations 10 that are neighbour to that estimated location.

0129At next step S508, the processor 200 retrieves from the database 204, for each base station 10 which is in the vicinity of the base station 10 which sent the message, its address within the telecommunication network 50 and the identifier of at least one available access port. The processor 200 then adds in the database 204, the information representative of the geographical location of the base station 10, which was comprised in the received message, the determined list of neighbouring base station 10, with their address and the selected available access port for each base station 10 comprised in the determined list. At next step S509, the processor 200 commands the transfer, through the telecommunication network 50, to the base station 10 which sent the message, of a response message which comprises the list of neighbouring base stations 10.

0130The list of neighbouring base stations 10 contains the address of base station 10 which sent the message, the address of each the base station 10 which is in the vicinity of the base station 10 which sent the message, the identifier of an available access port of each base station 10 which is in the vicinity of the base station 10 which sent the message.

0131Once the message is transferred, the processor 200 returns to the step S500 and waits the reception of a new message to be processed.

0132If at step S503, the processor 20 determines that the base station 10 which sent the message has already accessed to the server 20, the processor 200 moves to step S504.

0133At that step, the processor 200 checks whether or not the received message, stored in RAM 203 at step S500 is representative of the availability status of an access port of a base station 10. Such message is as the one transferred at steps S415 or S422 of the algorithm of the <figref idref="f0003">Fig. 4</figref>.

0134If the received message is representative of the availability status of an access port of a base station 10, the processor 200 moves to step S505 and updates in the database 204, the access port status in the list of access ports of the base station 10 which sent the message by marking it as available if the availability status indicates that the port is available, or by marking it as unavailable if the availability status indicates that the port is unavailable. If an access port is marked as unavailable, the processor 200 removes the base station 10 which was connected, through that link, to the base station which sent the message, from the list of neighbour base stations of the base station 10 which sent the message.

0135The processor 200 returns to the step S500 and waits the reception of a new message to be processed.

0136If the received message is not representative of the availability status of an access port of a base station 10, the processor 200 moves to step S507 already described and continue the process of the message.

0137<figref idref="f0005">Fig. 6</figref> is algorithm executed by a neighbouring base station of a base station installed in the wireless cellular network according to the present invention.

0138At step S600, the processor 300 of the base station 10a, as example, checks whether or not a message is received from the network interface 304. As far as no message is received, the processor 300 executes the loop constituted by the step S600.

0139If a message is received from the network interface 304, as example from the base station 10b, the processor 300 stores the message in the RAM 203 and moves to step S603.

0140At step S603, the processor 300 checks whether or not the base station 10 which sent the message is known or not by the processor 300. For that, the processor 300 checks whether or not the message has been received from an already established connection.

0141If the base station 10 which sent the message is known, the processor 300 moves to step S606. On the contrary, the processor 300 moves to step S604.

0142At the step S604, the processor 300 proceeds to a connection establishment in response to the one as disclosed at step S403 of the <figref idref="f0003">Fig. 4</figref>.

0143At the same step and in a variant of realisation, the processor 300 transfers a message to the server 20 informing it that the access port of that connection is now unavailable.

0144At next step S605, the processor 300 transfers the operation domains of its cells 15 to the base station 10 which sent the message. Then processor 300 then returns to step S600.

0145At step S606, the processor 300 checks if the received message is a message informing the base station 10 that the connection between the base station 10 and the base station 10 which sent the message is released.

0146If the message is not a connection release message, the message stored in the RAM 203 at step S600 comprises the operation domain of the cell or cells of the base station 10 which sent the message. The processor 300 moves then to the step S607 and updates its occurrence table of usage of the operation domains of the cells 15 of its neighbouring base stations 10.

0147After that, the processor 300 moves to step S611 which will be disclosed latter.

0148If the message is a connection release message, the processor 300 moves to step S608.

0149At that step S608, the processor 300 removes from the list of neighbouring base stations, the base station 10 which sent the message, removes from the occurrence table of usage of operation domains the cells served by the base station 10 which sent the message, removes the operation domain of the cell of that base station 10 from the table of usage of the operation domains and removes that cell from the neighbouring cells lists. For each cell being served by the base station 10, the processor 300 indicates to the wireless interface 306 to start broadcasting an updated neighbouring cells list.

0150At step S609, the processor 300 releases the connection with the base station 10 which sent the message.

0151In a variant of realisation, the processor 300 transfers at step S610 a message to the server 20 informing it that the access port used for the released connection is now available. The processor 300 then moves to step S611.

0152At next step S611, the processor 300 determines the operation domain of its cell 15 using the modified table of usage of the operation domains.

0153The processor 300 selects for its cell 15 the operation domain among those of smallest occurrence observed among the cells of its neighbouring base stations 10. When the base station 10 controls more than one cell, the table also includes the operation domain of all of its cells 15. Each time an operation domain is chosen for one cell 15, the table of usage of the operation domain is updated. Then, the operation domain of subsequent cells 15 is selected among those of smallest occurrence and not yet being selected for other cells 15.

0154In a preferred embodiment, the processor 300 selects for the cell 15 of its base station 10, the operation domain among those of smallest occurrence observed among only the cells 15 of its neighbouring base stations 10 that are neighbour to the cell 15 of its base station 10.

0155At next step S612, the processor 300 transfers the determined operation domains of its cell 15 to all its neighbouring base stations 10 through the respective connections. Then, the processor 300 returns back to step S600.

0156Naturally, many modifications can be made to the embodiments of the invention described above without departing from the scope of the present invention.