Abstract: A highway/railroad crossing detection and warning system which uses sets of Doppler radar transmitters and receivers to detect the approach of a train coming from either direction toward a highway crossing. The Doppler radar sets are located an extended distance from the crossing with each set detecting movement toward and away from its location. Presence detectors are located at the crossing and sense moving or stationary trains. All detector devices transmit signals to warning equipment to provide aural and visual indications to approaching motorists or work crews.

Abstract: A cellular communication system (10) includes any number of land stations (12), each of which controls a cell (14). When channels are assigned to cells (14), a figure of merit which predicts potential voice quality, such as C/I, is determined (34) for each channel/cell assignment. The assigned channels and associated figures of merit are distributed to corresponding land stations (14) to make channel-to-cell assignments. When a call arises in a cell (14) a channel is selected for assignment to the call. The channel is selected from channels assigned during the channel-to-cell assignment phase. A channel assignment algorithm (68) ensures that potentially lower quality channels (20) are the least used channels at the cell (14). When potentially lower quality channels (20) are assigned to calls, the calls are handed off to potentially higher quality channels (18) as soon as potentially higher quality channels (18) become available.