Abstract: A position system and method utilizes a plurality of range transceivers located at known fixed locations and which are adapted to transmit approximately synchronized digital range signals for receipt by both a primary receiver and a supplemental receiver, the former disposed at a known location and the latter disposed at an unknown location. The range transceivers are adapted to transmit pulse sequences which include an error portion corresponding to the approximate synchronization error of each range signal. This error portion is constantly updated in accordance with the last determined synchronization errors of the corresponding range signals received by a secondary transceiver. In an alternative embodiment employing Code Division Multiple Access (CDMA) technology, the range transceiver time stamp on transmitted range signals may be adjusted to account for the measured timing error for a given range transceiver.

Abstract: The present invention relates to method and apparatus for substantially reducing the effects of interference at a receiver between concurrently received first and second digital signals which use the same frequency spectrum. Interference between signals is effectively reduced by transmitting the first digital signal in an uncoded form while concurrently transmitting the second digital signal with both reduced capacity when compared with the first signal and in coded form using a forward error correcting code such as, for example, a block or convolutional code. At the receiver intercepting both digital signals, a suitable detection process is performed to decode the second signal and separate both signals. The present invention is applicable to the simultaneous satellite transmission of an area coverage beam and a plurality of spot coverage beams or to increase capacity on a radio channel.

Abstract: The present invention relates to method and apparatus for substantially cancelling interference between signals using the same frequency spectrum which are received via overlapping area coverage and spot coverage antenna beams. At the transmitter where the overlapping area and spot coverage beams are concurrently transmitted, a predetermined portion of the area coverage signal is coupled into each of the spot beam signals which will be overlapped at the associated spot beam receiver area by the area coverage beam. The predetermined portion coupled into each spot beam signal will have a magnitude and phase to substantially cancel the area coverage signal at the associated spot beam receiver area.