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Abstract

A method and system are disclosed for coordinating RF use in primary and adjunct wireless systems which are overlapped or layered in a common geographic area and which share the same the same RF spectrum. The adjunct system includes adjunct base stations defining respective adjunct wireless cells and serving adjunct mobile stations located within the respective adjunct cell. The primary system includes primary base stations defining respective primary wireless cells and serving primary mobile stations located within the primary wireless cell. The adjunct base stations monitor all RF channels and partition them into two sets, a set of channels likely to be interference-free and a set of noisy channels. Once control channels have been assigned to the base stations, the adjunct mobile stations may also participate in the monitoring step by employing the MAHO/MACA features of the IS 136 or GSM Air Interface Standard. The adjunct system forms a pool of interference-free channels for use by all adjunct base stations and mobiles. Channels are assigned to the adjunct base stations from the interference-free set. The interference-free channels left unassigned serve as back-up channels for period replacement of the assigned channels and in case the assigned channels become noisy. A channel not being used by the adjunct system is an nonassigned channel. The spectrum monitoring procedure by the adjunct base stations for nonassigned channels measures received signal strength. If a channel has a strong signal above a predetermined threshold, then it is deemed noisy. If a channel has a weak signal strength, then the adjunct base stations must deduce the likelihood of future interference caused by activity in nearby cells in the primary system. During the operation phase, each adjunct base station, in conjunction with mobile units in its respective adjunct cell, continually monitor the channels and their classification is updated if there is a change in the background noise or in the interference signal strength indicating a change spectrum use by the primary system.

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First Claim