Abstract: A radio for determining the occupancy of a variable width channel for secondary use, the variable width channel with a bandwidth equal to an integer multiple of the bandwidth of a plurality of narrowband channels in an RF frequency band. The radio decides whether the variable width channel in the RF band is occupied by whether classifying each of the narrowband channels corresponding to the variable width channel and each of a plurality of sub-bands with bandwidths of narrowband channels but center frequencies shifted by one-half of the bandwidth of the narrowband channel and overlap with the bandwidth of the variable width channel as containing signal or noise based on measured energy levels.

Abstract: A radio for determining the occupancy of a variable width channel for secondary use, the variable width channel with a bandwidth equal to an integer multiple of the bandwidth of a plurality of narrowband channels in an RF frequency band. The radio decides whether the variable width channel in the RF band is occupied by whether classifying each of the narrowband channels corresponding to the variable width channel and each of a plurality of sub-bands with bandwidths of narrowband channels but center frequencies shifted by one-half of the bandwidth of the narrowband channel and overlap with the bandwidth of the variable width channel as containing signal or noise based on measured energy levels.

Abstract: A method for facilitating the more efficient opportunistic use of one or more frequency division multiplexed (FDM) channels in a frequency band by a group of two or more secondary users (SU) that have formed a point-to-multipoint, centralized ad hoc network, with one SU acting as a central node and the remaining SU acting as remote nodes. Each SU adheres to a predetermined protocol utilizing synchronized time slots in each of the channels being used by the network, each time slot having at least one data transmission period and at least one primary user detection period during which no SU transmits. The central SU node determines channel availability. Remote SU nodes may listen for primary user transmissions in a channel and inform the central SU node of detected activity. Remote nodes contend for transmission during a data transmission period of a time slot unless the channel has been reserved by a remote node after successful transmission in the data transmission period of a preceding time slot.

Abstract: A method for reducing co-channel or cross-channel interference between cells of a cell network in a frequency division multiple access (FDMA) communications system is disclosed. The method comprises the steps of: dividing the cells of the cell network into a first subset of cells and a second subset of cells; dividing the available bandwidth for the system into a first set of sub-bands, each of which has a sub-band bandwidth and a second set of sub-bands, each of which has a sub-band bandwidth, the second set of sub-bands being offset in frequency from the first set of sub-bands; assigning the first set of sub-bands to the first subset of cells and the second set of sub-bands to the second subset of cells.