(19) Europäisches Patentamt European Patent Office Office européen des brevets (12) EUROPEAN PATENT SPECIFICATION (11) EP 1 327 373 B1 (4) Date of publication and mention of the grant of the patent: 13.09.06 Bulletin 06/37 (21) Application number: 0197909.1 (22) Date of filing: 04..01 (1) Int Cl.: H04Q 7/38 (06.01) (86) International application number: PCT/CA01/0016 (87) International publication number: WO 02/03216 (18.04.02 Gazette 02/16) (4) NETWORK DRIVEN CELL SWITCHING AND HANDOFF WITH LOAD BALANCING FOR WIRELESS SYSTEMS NETZGESTEUERTE ZELLUMSCHALTUNG UND -WEITERLEITUNG MIT LASTAUSGLEICH FÜR DRAHTLOSE SYSTEME COMMUTATION CELLULAIRE COMMANDEE PAR UNE ENTITE RESEAU ET TRANSFERT AVEC EQUILIBRAGE DE CHARGE POUR SYSTEMES SANS FIL (84) Designated Contracting States: DE FR GB () Priority: 13..00 US 68738 (43) Date of publication of application: 16.07.03 Bulletin 03/29 (73) Proprietor: Nortel Networks Limited St.Laurent, Quebec H4S 2A9 (CA) (72) Inventors: HUANG, Wei Nepean, Ontario K2G Y8 (CA) ZHANG, Hang Ottawa, Ontario K2C 0S1 (CA) FONG, Mo-Han L Original, Ontario K0B 1K0 (CA) (74) Representative: Coyle, Philip Aidan et al F. R. KELLY & CO. 27 Clyde Road Ballsbridge Dublin 4 (IE) (6) References cited: WO-A-00/3226 WO-A-99/14972 WO-A-99/2 US-A- 6 041 23 EP 1 327 373 B1 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, 7001 PARIS (FR)
Description BACKGROUND OF THE INVENTION 1 2 3 [0001] The present invention is directed to communication via a wireless connection and, more particularly, to wireless communication capable of carrying voice and/or data signals at high data rates. [0002] Recent wireless communication systems, such as cellular systems that use code division multiple access (CDMA) technology, often employ a "soft handoff" where, at any given time, a mobile station communicates with the network via more than one base transceiver station (BTS). The soft handoff ensures that the mobile station communicates continuously with the network while the mobile station moves across cell regions covered by respective BTSs. [0003] Soft handoff systems, however, are prone to having the transmissions from one BTS interfere with those from another BTS. Also, when such systems are used to transfer data packets, complex scheduling of the routing of the packets is required which often delays the movement of the packets. [0004] To reduce interference and improve the packet transfer speed, cell switching may be employed instead of a soft handoff. In cell switching, only the BTS having the best transmission channel quality is selected to transmit to the mobile station. The mobile station periodically measures the channel quality of each BTS in its active set, typically by measuring the carrier to interference ratio (C/I) of each BTS. When a mobile station that is receiving forward link transmissions from one BTS enters a region where it can receive transmissions from more than one BTS, or when the mobile station that is receiving forward link transmissions from the BTS experiences a reduction in forward link transmission quality because of fading, shadowing or signal path loss, the mobile station then determines which BTS is transmitting at the highest channel quality and sends an indication of the desired BTS, namely the BTS transmitting at the highest channel quality, to each BTS in the active set [000] Because the switching from one BTS to another is based solely on the channel quality, a mobile station may be switched from one BTS to another BTS in its active set that is already heavily loaded. As a result, the traffic load is unevenly distributed among the BTSs which results in traffic congestion and transmission delays that degrade the quality of service for some or all of the mobile stations that are served by the heavily loaded BTS. [0006] WO 99/2 discloses a method of selecting one of a plurality of base stations for communicating with a respective remote station, said method comprising the steps of: receiving transmission channel quality information associated with at least two of said plurality of base stations; receiving loading information associated with said at least two base stations; selecting a respective one of said at least two base stations as a function of said quality information and said loading information; and sending, to said respective remote station, an indication that said respective remote station is to commence communication with said selected one of said at least two base stations. The selection algorithm is performed by a control unit (eg. BSC) on the network side. [0007] It is desirable that the mobile stations be switched from one BTS to another in a manner that more evenly distributes the loading of the BTSs. It is further desirable that the switching be driven by a network-side entity so that the loading of the BTSs is centrally controlled. [0008] The present invention provides a method of selecting one of a plurality of base stations for communicating with a respective remote station characterised by: said receiving steps being performed at respective pre-defined intervals; and said selecting step including selecting said respective one of said at least two base stations having a greatest k value, wherein said k value is defined by the relation: 4 0 wherein i is a respective index associated with a particular one of said at least two base stations, f 1 and f 2 are functions, (C/I) i is a carrier to interference ratio (C/I) of a forward link transmission channel associated with said particular base station, and L i is a function of number of packets that are stored in a buffer of said particular base station. [0009] The present invention provides for fast switching from one BTS to another that is network driven and that is based on the loading conditions of the BTSs that are in the active set as well as being based on the transmission channel quality of the BTSs. [00] The invention will now be described in greater detail in the following detailed description with reference to the drawings in which: Figure 1 is a block diagram showing an example of a wireless communication arrangement in which a remote station communicates with one of a plurality of base transceiver stations under the control of a mobile control point. Figure 2 is a flow chart illustrating a sequence of operations for selecting one of a plurality of base transceiver 2
stations in accordance with the invention. DETAILED DESCRIPTION OF THE INVENTION 1 2 3 [0011] Figure 1 illustrates an example of a cellular, wireless communication arrangement for providing voice and/or data services, such as packet data services, to a remote station. A plurality of base transceiver stations (BTS) 1, 1, 1,... are each assigned to respective geographic regions, known as cells. [0012] A remote station 1 communicates with one of the BTS 1 of its active set, i.e. the set of nearby BTSs whose forward link transmissions could be received by the remote station. The remote station may be a mobile station (MS), such as cellular telephone or other wireless telephone, a personal digital assistant (PDA) or other handheld or pocket device, or another wireless device. Alternatively, the remote station may be a fixed location wireless device. [0013] A mobile control point (MCP) 0 or other network-side control device directs each voice and/or data connection to a respective BTS via a cable connection. The BTS, in turn, provides a wireless link for the voice and/or data connection to the remote station. The MCP may also send control information to the remote station and receive control information from the remote station via the BTS using, for example, inband signaling. [0014] When a remote station is located within the transmission range of more than one BTS, namely when the remote station is situated in a region where two or more cells overlap, the MCP may determine which of the BTSs communicates with the remote station. [001] Figure 2 illustrates an example of a method, according to the invention, by which the MCP selects which BTS is to communicate with a remote station. As step 0 shows, each remote station periodically measures the channel quality of one or more of the BTSs in its active set. The remote station periodically transmits the channel quality information to the BTS that is presently receiving its signal which, in turn, delivers the information to the MCP. [0016] Typically, the transmission channel quality of each BTS is determined by the carrier to interference ratio (C/I) of the forward link transmission channel as received at the remote station. The C/I is defined as the ratio of the energy of the modulation carrier signal received from the BTS, integrated over time, to the energy of all other received signals that are on the same frequency band, integrated over time. However, other indications of the transmission channel quality may alternatively be used. [0017] The C/I of the BTS may be based on a single value determined by integrating over the duration of one or more time slots that are each of a duration of, typically, 1.2 ms. Alternatively, the C/I may be based on plural values that are each determined by integrating over the duration of one or more time slots and then averaging the values and/or eliminating anomalous values. The choice of method may be based on the conditions at the locations of the BTSs. [0018] Each BTS also periodically determines its forward link loading condition L and delivers the loading condition information to the MCP, as step 2 shows. The forward link loading condition L of the BTS is typically determined by the number of packets that are stored in its buffer and that are awaiting transmission, though other loading indicators may be used. The forward link loading condition L may be determined with every time slot or at intervals of two or more time slots. [0019] Then, as shown at step 4, the MCP periodically determines a value K for each BTS that is a function of both the C/I and the forward link loading condition L. The value K for each BTS is typically based on the relation: 4 0 where i is the index of a respective BTS, and f 1 and f 2 are functions. [00] The MCP then selects the BTS having the greatest K value, as step 6 shows, and signals the remote station, such as by using inband signaling, to terminate communication with its current BTS, if any, and initiate communication with the selected BTS at a specific time slot. The MCP also informs the current BTS and the selected BTS of the switch, typically using inter-bts signaling. [0021] Thus, the MCP determines which BTS is to communicate with the remote station not only based on the channel quality of the BTS but also based on the loading condition of the BTS. As a result, the remote station is less likely to be switched to a heavily loaded cell, thereby reducing network congestion and signal delay and avoiding degradation of the quality of service. [0022] Also, the switching from one BTS to another is driven by the MCP so that the control of the loading of the BTSs is centralized in a network-side entity, rather than being distributed among the remote stations. [0023] Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses may become apparent to those skilled in the art. It is preferred, therefore, 3
that the present invention be limited not by this specific disclosure herein, but only by the appended claims. 1 Claims 1. A method of selecting one of a plurality of base stations (1, 1, 1) for communicating with a respective remote station (1), said method comprising the steps of: receiving (0) transmission channel quality information associated with at least two of said plurality of base stations; receiving (2) loading information associated with said at least two base stations; selecting (6) a respective one of said at least two base stations as a function of said quality information and said loading information; and sending, to said respective remote station, an indication that said respective remote station is to commence communication with said selected one of said at least two base stations, characterised by said receiving steps (0,2) being performed at respective pre-defined intervals; and said selecting step including selecting said respective one of said at least two base stations having a greatest k value, wherein said k value is defined by the relation: 2 3 wherein i is a respective index associated with a particular one of said at least two base stations, f 1 and f 2 are functions, (C/I) i is a carrier to interference ratio (C/I) of a forward link transmission channel associated with said particular base station, and L i is a function of number of packets that are stored in a buffer of said particular base station. 2. The method of claim 1 wherein said receiving transmission channel quality information step includes receiving said transmission channel quality information from said remote station. 3. The method of claim 2 wherein said remote station comprises at least one of a mobile station and a stationary wireless station. 4. The method of claim 3 wherein said mobile station comprises at least one of: a cellular telephone, a wireless telephone, a personal digital assistant, PDA, a handheld wireless communication device, and a pocket sized wireless communication device.. The method of claim 1 wherein said predefined intervals each comprise at least one time slot interval. 6. The method of claim 1 wherein said receiving loading information step includes receiving said loading information from said at least two base transceiver stations, BTS. 4 7. The method of claim 1 wherein said further predefined intervals each comprise at least one time slot interval. 8. The method of claim 1 wherein said functions f 1 and f 2 are linear functions. 0 9. The method of claim 1 wherein said sending step includes sending, to said respective remote station, an indication that said respective remote station is to terminate communication with a further one of said at least two base stations that is currently communicating with said respective remote station.. The method of claim 1 further comprising the step of sending, to a further one of said at least two base stations that is currently communicating with said respective remote station, an indication that said further base station is to terminate communication with said respective remote station. 11. An apparatus (0) for selecting one of a plurality of base stations (1, 1, 1) for communicating with a respective remote station (1), said apparatus comprising: 4
means for receiving (0) transmission channel quality information associated with at least two of said plurality of base stations; means for receiving (2) loading information associated with said at least two base stations; means for selecting (6) a respective one of said at least two base stations as a function of said quality information and said loading information; and means for sending, to said respective remote station, an indication that said respective remote station is to commence communication with said selected one of said at least two base stations, characterised by: said receiving means being arranged to receive information at respective pre-defined intervals; and said selecting means including means for selecting said respective one of said at least two base stations having a greatest k value, wherein said k value is defined by the relation: 1 wherein i is a respective index associated with a particular one of said at least two base stations, f 1 and f 2 are functions, (ClI) i is a carrier to interference ratio (C/I) of a forward link transmission channel associated with said particular base station, and L i is a function of number of packets that are stored in a buffer of said particular base station. 2 12. The apparatus of claim 11 wherein said receiving transmission channel quality information means includes means for receiving said transmission channel quality information from said remote station. 13. The apparatus of claim 12 wherein said remote station comprises at least one of: a mobile station and a stationary wireless station. 14. The apparatus of claim 13 wherein said mobile station comprises at least one of: a cellular telephone, a wireless telephone, a personal digital assistant, PDA, a handheld wireless communication device, and a pocket sized wireless communication device. 1. The apparatus of claim 11 wherein said predefined intervals each comprise at least one time slot interval. 3 16. The apparatus of claim 11 wherein said receiving loading information means includes means for receiving said loading information from said at least two base transceiver stations, BTS. 17. The apparatus of claim 11 wherein said further predefined intervals each comprise at least one time slot interval. 4 18. The apparatus of claim 11 wherein said functions f 1 and f 2 are linear functions. 19. The apparatus of claim 11 wherein said sending means includes means for sending, to said respective remote station, an indication that said respective remote station is to terminate communication with a further one of said at least two base stations that is currently communicating with said respective remote station.. The apparatus of claim 11 further comprising means for sending, to a further one of said at least two base stations that is currently communicating with said respective remote station, an indication that said further base station is to terminate communication with said respective remote station. 0 Patentansprüche 1. Verfahren zur Auswahl einer einer Anzahl von Basisstationen (1, 1, 1) zur Kommunikation mit einer jeweiligen entfernt angeordneten Station (1), wobei das Verfahren die folgenden Schritte umfasst: Empfangen (0) von Übertragungskanal-Qualitätsinformation, die zumindest zwei der Anzahl von Basisstationen zugeordnet ist; Empfangen (2) von Lastinformation, die den zumindest zwei Basisstationen zugeordnet ist;
Auswahl (6) einer jeweiligen einen der zumindest zwei Basisstationen als eine Funktion der Qualitätsinformation und der Lastinformation; und Senden einer Anzeige an die jeweilige entfernt angeordnete Station, dass die jeweilige entfernt angeordnete Station die Kommunikation mit der ausgewählten einen der zumindest zwei Basisstationen beginnen soll, dadurch gekennzeichnet, dass: die Schritte des Empfangens (0, 2) unter jeweiligen vordefinierten Zeitintervallen ausgeführt werden; und der Schritt der Auswahl die Auswahl der jeweiligen einen der zumindest zwei Basisstationen einschließt, die einen größten k-wert hat, wobei der k-wert durch die Beziehung: 1 2 definiert ist, worin i ein jeweiliger Index, der einer bestimmten einen der zumindest zwei Basisstationen zugeordnet ist, f 1 und f 2 Funktionen sind, (C/I) i ein Träger-zu-Störverhältnis (C/l) eines Vorwärts-Verbindungsstrecken-Übertragungskanals ist, der der bestimmten Basisstation zugeordnet ist, und L eine Funktion der Anzahl von Paketen ist, die in einem Puffer der bestimmten Basisstation gespeichert sind. 2. Verfahren nach Anspruch 1, bei dem der Schritt des Empfangens der Übertragungskanal-Qualitätsinformation den Empfang der Übertragungskanal-Qualitätsinformation von der entfernt angeordneten Station einschließt. 3. Verfahren nach Anspruch 2, bei dem die entfernt angeordnete Station zumindest eine von Folgenden umfasst: eine Mobilstation und eine stationäre drahtlose Station. 3 4 0 4. Verfahren nach Anspruch 3, bei dem die mobile Station zumindest eines von Folgendem umfasst: ein Zellulartelefon, ein drahtloses Telefon, einen persönlichen digitalen Assistenten, PDA, ein Hand-gehaltenes drahtloses Kommunikationsgerät, und ein drahtloses Kommunikationsgerät mit Taschengröße.. Verfahren nach Anspruch 1, bei dem die vordefinierten Intervalle jeweils zumindest ein Zeitschlitz-Intervall umfassen. 6. Verfahren nach Anspruch 1, bei dem der Schritt des Empfangens der Lastinformation den Empfang der Lastinformation von den zumindest zwei Basis-Sendeempfänger-Stationen, BTS, einschließt. 7. Verfahren nach Anspruch 1, bei dem die weiteren vordefinierten Intervalle jeweils zumindest ein Zeitschlitz-Intervall umfassen. 8. Verfahren nach Anspruch 1, bei dem die Funktionen f 1 und f 2 lineare Funktionen sind. 9. Verfahren nach Anspruch 1, bei dem der Schritt des Sendens das Senden einer Anzeige an die jeweilige entfernt angeordnete Station dafür einschließt, das die jeweilige entfernt angeordnete Station die Kommunikation mit einer weiteren einen der zumindest zwei Basisstationen beenden soll, die derzeit mit der jeweiligen entfernt angeordneten Station kommuniziert.. Verfahren nach Anspruch 1, das weiterhin den Schritt des Sendens einer Anzeige an eine weitere der zumindest zwei derzeit mit der jeweiligen entfernt angeordneten Station kommunizierenden Basisstationen dafür umfasst, dass die weitere Basisstation die Kommunikation mit der jeweiligen entfernt angeordneten Station beenden soll, 11. Vorrichtung (0) zur Auswahl einer einer Anzahl von Basisstationen (1, 1, 1) zur Kommunikation mit einer jeweiligen entfernt angeordneten Station (1), wobei die Vorrichtung Folgendes umfasst: Einrichtungen zum Empfang (0) von Übertragungskanal-Qualitätsinformation, die zumindest zwei der Anzahl von Basisstationen zugeordnet ist; Einrichtungen zum Empfang (2) von Lastinformation, die den zumindest zwei Basisstationen zugeordnet ist; Einrichtungen zur Auswahl (2) einer jeweiligen einen der zumindest zwei Basisstationen als eine Funktion der Qualitätsinformation und der Lastinformation; und Einrichtungen zum Senden einer Anzeige an die jeweilige entfernt angeordnete Station dafür, dass die jeweilige 6
entfernt angeordnete Station die Kommunikation mit der ausgewählten einen der zumindest zwei Basisstationen beginnen soll, dadurch gekennzeichnet, dass: die Empfangseinrichtungen so angeordnet sind, dass sie Information zu jeweiligen vordefinierten Intervallen empfangen; und die Auswahleinrichtungen Einrichtungen zum Auswählen der jeweiligen einen der zumindest zwei Basisstationen einschließt, die einen größten k-wert hat, wobei der k-wert durch die Gleichung 1 definiert ist, worin i ein jeweiliger Index ist, der einer bestimmten einen der zumindest zwei Basisstationen zugeordnet ist, f 1 und f 2 Funktionen sind, (C/I) i ein Träger-zu-Störverhältnis (C/I) eines Vorwärts-Verbindungsstrecken-Übertragungskanals ist, der der bestimmten Basisstation zugeordnet ist, und L eine Funktion einer Anzahl von Paketen ist, die in einem Puffer der bestimmten Basisstation gespeichert sind. 12. Vorrichtung nach Anspruch 11, bei der die Empfangseinrichtungen für die Übertragungskanal-Qualitätsinformation Einrichtungen zum Empfang der Übertragungskanal-Qualitätsinformation von der entfernt angeordneten Station einschließen. 2 3 4 13. Vorrichtung nach Anspruch 12, bei der die entfernt angeordnete Station zumindest eine von Folgenden umfasst: eine Mobilstation und eine stationäre drahtlose Station. 14. Vorrichtung nach Anspruch 13, bei der die Mobilstation zumindest eines von Folgendem umfasst: ein Zellulartelefon, ein drahtloses Telefon, einen persönlichen digitalen Assistenten, PDA, ein Hand-gehaltenes drahtlose Kommunikationsgerät und ein drahtloses Kommunikationsgerät mit Taschengröße. 1. Vorrichtung nach Anspruch 11, bei der die vordefinierten Intervalle jeweils zumindest ein Zeitschlitz-Intervall umfassen. 16. Vorrichtung nach Anspruch 11, bei der die Empfangseinrichtung für die Lastinformation Einrichtungen zum Empfang der Lastinformation von den zumindest zwei Basis-Sendeempfänger-Stationen, BTS, einschließt. 17. Vorrichtung nach Anspruch 11, bei der die weiteren vordefinierten Intervalle jeweils zumindest ein Zeitschlitz-Intervall umfassen. 18. Vorrichtung nach Anspruch 11, bei der Funktionen f 1 und f 2 lineare Funktionen sind. 19. Vorrichtung nach Anspruch 11, bei der die Sendeeinrichtung Einrichtungen zum Senden einer Anzeige an die jeweilige entfernt angeordnete Station dafür einschließt, dass die jeweilige entfernt angeordnete Station die Kommunikation mit einer weiteren einen der zumindest zwei Basisstationen beenden soll, die derzeit mit der jeweiligen entfernt angeordneten Station kommuniziert.. Vorrichtung nach Anspruch 11, die weiterhin Einrichtungen zum Senden einer Anzeige an eine weitere eine der zumindest zwei derzeit mit der jeweiligen entfernt angeordneten Station kommunizierenden Basisstationen dafür umfasst, dass die weitere Basisstation die Kommunikation mit der entfernt angeordneten Station beenden soll. 0 Revendications 1. Un procédé de sélection d une parmi une multiplicité de stations de base (1, 1, 1) pour communiquer avec une station distante (1) respective, ce procédé comprenant les étapes consistant à : recevoir (0) une information de qualité de canal de transmission associée à au moins deux de la multiplicité de stations de base; recevoir (2) une information de charge associée aux au moins deux stations de base; 7
sélectionner (6) l une respective des au moins deux stations de base en fonction de l information de qualité et de l information de charge; et envoyer, à la station distante respective, une indication du fait que la station distante respective doit commencer la communication avec la station sélectionnée parmi les au moins deux stations de base, caractérisé en ce que les étapes de réception (0, 2) sont accomplies à des intervalles prédéfinis respectifs, et l étape de sélection comprend la sélection de la station respective parmi les au moins deux stations de base ayant une plus grande valeur k, la valeur k étant définie par la relation : 1 dans laquelle i est un index respectif associé à l une particulière des au moins deux stations de base, f 1 et f 2 sont des fonctions, (C/I) i est un rapport porteur à brouillage (C/I) d un canal de transmission de liaison d ailer associé à la station de base particulière, et L i est une fonction du nombre de paquets qui sont stockés dans un tampon pour la station de base particulière. 2. Le procédé de la revendication 1, dans lequel l étape de réception d information de qualité de canal de transmission comprend la réception de l information de qualité de canal de transmission à partir de la station distante. 3. Le procédé de la revendication 2, dans lequel la station distante comprend une au moins de : une station mobile et une station sans fil fixe. 2 4. Le procédé de la revendication 3, dans lequel la station mobile comprend au moins un de : un téléphone cellulaire, un téléphone sans fil, un assistant numérique personnel ou PDA, un dispositif de communication sans fil tenu à la main, et un dispositif de communication sans fil de poche.. Le procédé de la revendication 1, dans lequel chacun des intervalles prédéfinis comprend au moins un intervalle de créneau temporel. 3 4 0 6. Le procédé de la revendication 1, dans lequel l étape de réception d information de charge comprend la réception de l information de charge à partir des au moins deux stations d émetteur - récepteur de base ou BTS (Base Transceiver Station). 7. Le procédé de la revendication 1, dans lequel chacun des intervalles prédéfinis supplémentaires comprend au moins un intervalle de créneau temporel. 8. Le procédé de la revendication 1, dans lequel les fonctions f 1 et f 2 sont des fonctions linéaires. 9. Le procédé de la revendication 1, dans lequel l étape d envoi comprend l envoi, à la station distante respective, d une indication du fait que cette station distante respective doit mettre fin à la communication avec une station supplémentaire parmi les au moins deux stations de base qui est en cours de communication avec la station distante respective.. Le procédé de la revendication 1, comprenant en outre l étape consistant à envoyer, à une station supplémentaire parmi les au moins deux stations de base qui est en cours de communication avec la station distante respective, une indication du fait que la station de base supplémentaire doit mettre fin à la communication avec la station distante respective. 11. Un appareil (0) pour sélectionner l une d une multiplicité de stations de base (1. 1, 1) pour communiquer avec une station distante (1) respective, cet appareil comprenant : un moyen pour recevoir (0) une information de qualité de canal de transmission associée à au moins deux de la multiplicité de stations de base; un moyen pour recevoir (2) une information de charge associée aux au moins deux stations de base; un moyen pour sélectionner (6) l une respective des au moins deux stations de base en fonction de l information de qualité et de l information de charge; et 8
un moyen pour envoyer, à la station distante respective une indication du fait que la station distante respective doit commencer la communication avec la station sélectionnée parmi les au moins deux stations de base, caractérisé en ce que le moyen de réception est agencé pour recevoir de l information à des intervalles prédéfinis respectifs; et le moyen de sélection comprend un moyen pour sélectionner la station respective parmi les au moins deux stations de base ayant une plus grande valeur k, la valeur k étant définie par la relation : 1 dans laquelle i est un index respectif associé à l une particulière des au moins deux stations de base, f 1 et f 2 sont des fonctions, (C/I) i est un rapport porteur à brouillage (C/I) d un canal de transmission de liaison d aller associé à la station de base particulière, et L i est une fonction du nombre de paquets qui sont stockés dans un tampon pour la station de base particulière. 12. L appareil de la revendication 11, dans lequel le moyen de réception d information de qualité de canal de transmission comprend un moyen pour recevoir l information de qualité de canal de transmission à partir de la station distante. 2 13. L appareil de la revendication 12, dans lequel la station distante comprend une au moins de : une station mobile et une station sans fil fixe. 14. L appareil de la revendication 13, dans lequel la station mobile comprend au moins un de : un téléphone cellulaire, un téléphone sans fil, un assistant numérique personnel ou PDA, un dispositif de communication sans fil tenu à la main, et un dispositif de communication sans fil de poche. 1. L appareil de la revendication 11, dans lequel chacun des intervalles prédéfinis comprend au moins un intervalle de créneau temporel. 3 16. L appareil de la revendication 11, dans lequel le moyen de réception d information de charge comprend un moyen pour recevoir l information de charge à partir des au moins deux stations d émetteur - récepteur de base ou BTS (Base Transceiver Station). 17. L appareil de la revendication 11, dans lequel chacun des intervalles prédéfinis supplémentaires comprend au moins un intervalle de créneau temporel. 18. L appareil de la revendication 11, dans lequel les fonctions f 1 et f 2 sont des fonctions linéaires. 19. L appareil de la revendication 11, dans lequel le moyen d envoi comprend un moyen pour envoyer, à la station distante respective, une indication du fait que la station distante respective doit mettre fin à la communication avec une station supplémentaire parmi les au moins deux stations de base qui est en cours de communication avec la station distante respective. 4. L appareil de la revendication 11, comprenant en outre un moyen pour envoyer, à une station supplémentaire parmi les au moins deux stations de base qui est en cours de communication avec la station distante respective, une indication du fait que la station de base supplémentaire doit mettre fin à la communication avec la station distante respective. 0 9
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