Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-04-28
2002-02-19
Urban, Edward F. (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S560000, C455S442000, C455S434000, C455S515000, C370S332000
Reexamination Certificate
active
06349208
ABSTRACT:
The present invention relates generally to cell reselection in a cellular, or other radio, communication system. More particularly, the present invention relates to apparatus, and an associated method, for selectively permitting initiation of effectuation of cellular reselection, such as a communication handover, or other control-channel-intensive event, of a mobile station operable in the communication system. A prediction is made of the likelihood that the cell reselection shall be successful. If the predicted likelihood is less than a minimum threshold, a request is made to increase the diversity, e.g., the coding rate, of control signals used in the cell reselection process. Cell reselection is permitted only when the likelihood of success is predicted to be high. Thereby, the possibility of loss of communications during the cell reselection is reduced.
BACKGROUND OF THE INVENTION
Advancements in communication technologies have permitted the implementation, and widespread usage, of multi-user radio communication systems. A cellular communication system is exemplary of such a radio communication system. Information signals generated during operation of the radio communication system are transmitted upon radio communication channels defined upon portions of the electromagnetic spectrum. Regulatory bodies allocate portions of the electromagnetic spectrum for communications in the various communication systems.
A cellular communication system includes network infrastructure which is installed throughout a geographical area which is to be encompassed by the system. The network infrastructure includes a plurality of spaced-apart radio base stations located at spaced positions throughout the geographical area. Groups of the radio base stations are coupled to a base station controller which operates to control various functions of the radio base stations. And, groups of base station controllers are coupled to mobile switching centers which perform switching operations to permit the performance of communication operations.
Each of the radio base stations defines a cell. A cell is a portion of the geographical area encompassed by the cellular communication system and positioned proximate to a radio base station. Generally, a mobile station positioned in a cell defined by a radio base station is able to communicate with such radio base station.
Cellular communication systems efficiently utilize the frequency bandwidth allocated for communications therein. Because of the positioning of the radio base stations at spaced positions throughout a geographical area, only relatively low-power signals need to be generated by the mobile station and also the radio base station to effectuate communications therebetween. The same channels can be reused throughout the cellular communication system according to a cell reuse plan. Because of such reuse of the same channels, the same channels can be concurrently used in different ones of the cells defined by the communication system.
However, because only relatively low-power signals are generated, as a mobile station travels throughout the geographical area encompassed by the cellular communication system, the mobile station cannot continue communicating with the same radio base station. That is to say, as a mobile station passes from cell-to-cell, the mobile station must communicate with successive ones of the radio base stations. Thereby, communications with the mobile station can continue as the mobile station passes through the successive cells.
In some cellular systems, the transfer of communications with the mobile station from one radio base station to another base station is referred to as a hand-off, or handover, of communications. The radio base station with which the mobile station has ongoing communications is sometimes referred to as a serving-cell and the radio base station with which a hand-off of communications is to be effectuated is sometimes referred to as a target cell. Handover of communications, or more generally, cell reselection, is a fairly complex process requiring, variously, a determination that the handover should occur, requests for, and allocation of, channel capacity at the target cell to continue communications, and, thereafter, effectuation of the handover of communications. Other control-channel-intensive events are analogously carried out as a mobile station passes from one cell to another.
In various cellular communication systems, the mobile station must be retuned from channels used at the serving-cell to channels used by the target-cell, requiring, thereby, action by both the network infrastructure and the mobile station to effectuate the handover. And, in various other systems, such as a CDMA (code-division, multiple-access) communication system, such as that defined in the IS-95 specification promulgated by the EIA/TIA, a process referred to as a soft handover is effectuated. In a soft handover, handover of communications from a serving-cell to a target-cell is effectuated without the need of the mobile station to retune to a different channel.
In other types of communication systems, analogous procedures are performed. For instance, in GPRS (general packet radio service) communications defined in a GSM (global system for mobile communications), a cell reselection procedure is effectuated in which communications between the mobile station and the serving-cell are terminated, and, thereafter, communications are restarted with the target-cell.
Handover of communications from a serving-cell to a target-cell are intended to be transparent to the use of a mobile station. That is to say, effectuation of handover of communications occurs without detection by a user. But, because a handover procedure is a relatively complex procedure, errors which might occur during the effectuation of such procedure might result in a “dropped call” or other disturbance which interferes with ongoing communications.
A manner by which to reduce the possibility that an error occurring during a control-channel-intensive event, such as handover of communications, or other cell reselection, from a serving-cell to a target-cell which might result in disruption of ongoing communications would advantageously improve operation of, and a user's perception of, communications in the radio communication system.
It is in light of this background information related to cell reselection 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, for selectively initiating effectuation of cell reselection, or other control-channel-intensive event, in a radio communication system. Cell reselection is permitted only if an acceptable likelihood of success of effectuation of the cell reselection is predicted. By permitting effectuation of cell reselection only if there is an acceptable likelihood that the effectuation of the cell reselection shall be successful, the possibility of a dropped call, or other undesired termination of communication, is reduced.
In one implementation, prediction is made of the likelihood of successful effectuation of the cell reselection, such as a communication handover, of a mobile station operable in a cellular communication system. If the predicted likelihood is less than a minimum threshold, effectuation of the cell reselection is not permitted. Instead, a request is made to increase the diversity of control signals transmitted between network infrastructure of the cellular communication system and the mobile station and used during cell reselection procedures. By increasing the diversity of the control signals, the likelihood that such control signals shall be accurately detected and acted upon is increased. Thereby, subsequent cell reselection is more likely to be effectuated successfully.
In one implementation, predictions are made dynamically, that is to say, subsequent to increasing the diversity of the control signals, and prediction is again mad
Pirhonen Riku P.
Sexton Thomas A.
Fraccaroli Federico
Nokia Corporation
Perez-Guierrez Rafael
Urban Edward F.
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