Abstract: A communication system (10), having dynamic nodes such as satellites (12), require narrow-tolerance communication parameters such as timing and frequency. A voice subscriber unit (26) establishes a traffic channel (17) by negotiating communication parameters. A user of voice subscriber unit (26) generates inherent voice pauses in communications. A data subscriber unit (31) possess a datagram for delivery through communication system (10). Instead of negotiating a dedicated traffic channel for delivery of the datagram, data subscriber unit (31) monitors an active voice subscriber unit (26) and determines if the communication parameters used by voice subscriber unit (26) are compatible for data subscriber unit (31). Data subscriber unit (31), upon detecting a voice pause by voice subscriber unit (26), transmits the datagram to satellite (12) using the negotiated communication parameters of voice subscriber unit (26).

Abstract: To obtain service from a satellite communication system, a mobile subscriber unit must acquire a TDMA communication channel. Because the satellites move with respect to the surface of the earth, propagation delays and Doppler shift affect the timing and frequency of received signals. A mobile subscriber unit synchronizes to the frequency and timing windows of a satellite communication station by receiving frequency and timing corrections during channel acquisition. The satellite initially estimates correction factors during initial acquisition requests and further estimates correction factors from synchronization bursts from the subscriber unit.

Abstract: A cellular communications network includes satellites which project cells toward the earth. The satellites and cells move relative to the earth. When a call is being set up to a subscriber unit, data describing the subscriber unit's location are sent to a switching office of the network. The switching office generates a schedule which forecasts when movement of the cells will cause the subscriber unit to cross cell boundaries. During an ongoing call, the subscriber unit 5 determines when scheduled boundary crossings occur. So long as an adequate signal is present in a scheduled cell and network capacity exists in the scheduled cell to handle the call, the call will be handed off to the scheduled cell. The subscriber unit also monitors signal strengths to determine when a traffic channel's signal is getting weak and when an alternate cell's signal is stronger.

Abstract: Audio frequency Doppler signals output from a radar are encoded and presented to left and right speakers of a headset. The Doppler signals are encoded so that the auditory effect produced by sounds emanating from the left and right speakers are perceived by an operator as originating from a particular location in space. In a preferred embodiment in-phase and quadrature Doppler signal outputs from a coherent radar couple through an optional phase shift to the left and right speakers. Sounds having phase differences dependent upon whether a target is approaching or receding result. The operator hears these sounds and perceives the sounds as being located toward the left or right.