Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1997-04-10
2001-04-10
Bost, Dwayne D. (Department: 2744)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S515000, C455S453000
Reexamination Certificate
active
06216009
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to wireless communications, and more particularly to a method and apparatus for providing access in a cellular communication system.
Wireless mobile telecommunications systems utilize radio signals to exchange information between base transceiver stations and mobile subscribers. Each base transceiver station transmits from an antenna throughout a predetermined area referred to as a cell. In order to provide service to mobile subscribers over a particular geographic region, many cells are positioned over the region or coverage area.
The service area of a cellular communication system is usually divided into cells of various sizes. Within each cell, a plurality of frequencies are allocated to communicate with a mobile subscriber. Each cell usually operates on a different subset of frequencies than neighboring cells to minimize the density of the used spectrum in a particular geographic area.
Because the frequency band allocated for telecommunications is limited, cellular systems may reuse the same frequencies at other cells. Reuse of the same frequencies may cause a mobile subscriber to access the cellular system at a number of cells having the same channel and digital color code. When a mobile subscriber accesses multiple cells, the call may be rejected or the mobile subscriber may receive a busy signal. Furthermore, multiple accesses usually result in resources being unnecessarily allocated to support “phantom” calls.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method for resolving multiple call accesses in a cellular system. The present invention prevents a mobile subscriber from accessing the system at multiple cells. In one aspect of the invention, a base transceiver station is provided. The base transceiver station has a signal strength receiver and is capable of transmitting a directed retry signal. A processor connects to the signal strength receiver and compares a received signal strength to a predefined threshold. The processor causes the base transceiver station to send the directed retry signal if the received signal strength is less than the predefined threshold.
In another aspect of the invention, a characteristic of a signal received at a base transceiver station is measured and compared to a predefined threshold. A directed retry is sent if the signal characteristic is less than the predefined threshold, and a communication channel is established if a response to the directed retry is received at the base transceiver station.
In another aspect of the invention, a cellular system capable of resolving multiple cell access requests is provided, comprising at least a first and second base transceiver station. Each base transceiver station has a signal strength receiver and a base station controller. The base station controllers have received signal strength thresholds. A first request for access signal is received at both base transceiver stations. The base transceiver stations both measure the signal strength of the first request for access signal and the signal strength at the first base transceiver station is below the received signal strength threshold for that base transceiver station. The first base transceiver station sends a directed retry signal. A communication channel with the first base transceiver station is established if a response to the directed retry is received by the first base transceiver station.
In yet another aspect of the invention, a first request for access signal is received at both a first and second base transceiver station. The first base transceiver station transmits a directed retry signal if the first signal strength of the first request for access is below a first received signal strength threshold, and the second base transceiver station establishes a communication channel if the second signal strength of the first request for access is above a second received signal strength threshold.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The invention, together with further objects and attendant advantages, will best be understood by reference to the following detailed description of the presently preferred embodiment of the invention, taken in conjunction with the accompanying drawings.
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Bost Dwayne D.
Hughes Electronics Corporation
Sales Michael W.
Vuong Quochien
Whelan John T.
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