Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-12-22
2004-06-01
Gary, Erika (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S437000, C455S438000, C455S440000
Reexamination Certificate
active
06745034
ABSTRACT:
The present invention relates, generally to a manner by which to facilitate selection of handoff of communications with a mobile station by a serving communication station to a target communication station, such as the serving and target base transceiver stations of a cellular communication system. More particularly, the present invention relates to apparatus, and an associated method, by which adaptively to select the threshold at which the handoff of communication is requested. Because of the adaptive selection of the threshold at which the request is initiated, an appropriate threshold is selectable irrespective of the communication characteristics of the cells or other geographical areas defined by the serving and target communication stations.
BACKGROUND OF THE INVENTION
A communication system is formed, at a minimum, of a sending station and a receiving station interconnected by way of a communication channel. The communication channel provides a communication path by which information originated at the sending station is communicated to the receiving station. Communication systems have been developed, and implemented, to communicate a wide variety of types of information between a large variety of types of sending and receiving stations.
Advancements in communication technologies have permitted new types of communication systems to be developed and implemented. A radio communication system is exemplary of a type of communication system. In a radio communication system, the sending station, a radio transmitter, transmits information upon a radio communication channel to a receiving station formed of a radio receiver. The radio communication channel is defined upon a radio link formed between the radio transmitter and receiver. The conventional need for a wireline connection to interconnect the sending and receiving stations is obviated due to the formation of the radio communication channel upon a radio link. A radio communication system permits, as a result, increased communication mobility. Sending and receiving stations of a radio communication system are operable to send and to receive information, respectively, at positions in which communications by a conventional wireline system would be impractical or impermissible.
A cellular communication system is a type of radio communication system which provides multiple numbers of users concurrently to communicate therethrough. Generally, such a communication system is referred to as a cellular communication system as the geographical area over which the cellular communication system is installed is divided into regions, referred to as cells. The cells are each defined by a fixed-site transceiver, referred to as a base transceiver station. The base transceiver stations are positioned at locations such that the cells defined thereby encompass the geographical area in which the cellular communication system is to be operable.
Radio communications are effectuable with a mobile station positioned at any location within the area encompassed by the cellular communication system. Generally, a mobile station communicates with the base transceiver station which defines the cell in which the mobile station is positioned. If the mobile station moves to be repositioned at another cell, a procedure, referred to as a handoff, is effectuated. Handoffs of communications are sometimes also effectuated due to channel traffic conditions or channel communication conditions irrespective of the repositioning of the mobile station.
In a handoff procedure, communications of the mobile station, initially with a first base transceiver station, referred to as the serving station, are transferred to another base transceiver station, referred to as a target station. Once the transfer is completed, subsequent communications of the mobile station are carried out with the target base transceiver station. Successive handoffs, from one base transceiver station to another, can occur as the mobile station travels through successive cells.
Handoff of communications from a serving base station to a target base station permits communications by a mobile station to continue even though the mobile station travels out of communication range with the base station which initially forms the serving base station. When in an active communication session, uninterrupted communications are generally possible with a mobile station as a handoff is effectuated from a serving base station to a target base station. And, the handoff occurs both without the active intervention of a user of the mobile station as well as, generally, also without the knowledge of the user that a handoff has occurred.
In different cellular communication systems, different manners are utilized by which to select when to effectuate handoff of communications with a mobile station from a serving base station to a target base station. In some systems, determination of when to initiate handoff of communications is performed entirely at the network infrastructure portion of the communication system. In other systems, at least some of the information utilized in the determination of when to initiate handoff of communication is determined at, or otherwise provided by, the mobile station. In some cellular communication systems, a procedure referred to as MAHO (mobile-assisted handoff) is utilized in the determinations of when to initiate handoff of communications.
In an exemplary MAHO procedure, measurement is made at selected intervals, by a mobile station of signal indicia of signals transmitted by the serving base station and one, or more, potential target base stations. The signal indicia is formed, for instance of signal strength measurements of the signals. Responsive to such measurements a report is made by the mobile station to the network infrastructure to request, when appropriate, a handoff of communications from the serving base station to a selected target base station. Thereafter, handoff of communications is selectably effectuated.
Communication characteristics might differ, however, in differing ones of the cells. In some cells, for instance, relatively low levels of fading are exhibited. In other cells, conversely, relatively high levels of fading might be exhibited.
Conventionally, uniform thresholds are utilized in the handoff procedures irrespective of the communication characteristics of the cells defined by serving and potential target base stations. However, due to the different communication characteristics of the different cells, the uniform thresholds might cause selection of initiation of a handoff of communications when a handoff is not necessary. And, also, selection might be made not to initiate handoff of communications when a handoff is necessary. If a manner could be provided by which adaptively to select the thresholds, responsive to communication characteristics, used in handoff procedures, improved communications in a cellular communication system would be possible.
It is in light of this background information related to handoff procedures in a radio communication system that the significant improvements of the present invention have evolved.
SUMMARY OF THE INVENTION
The present invention, accordingly, advantageously provides apparatus, and an associated method, by which to facilitate selection of handoff of communications with a mobile station by a serving communication station to a target communication station.
Through operation of an embodiment of the present invention, a manner is provided by which adaptively to select the threshold at which the handoff of communications is requested. An appropriate threshold is selectable irrespective of the communication characteristics of the geographical area in which the mobile station is positioned. Selection of the threshold to be used in the handoff procedures is responsive, in part, to the communication characteristics of the geographical area is defined by the serving and target communication stations. By adaptively selecting the threshold at which the request is initiated, an appropriate threshold is determined thereby to e
Green Marilynn
Wang Shu-Shaw
Davis Temica M.
Fraccaroli Federico
Gary Erika
Nokia Corporation
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