Abstract: A multiple subscriber unit (MSU) (600) is co-located with a mobile vehicle (110) and is coupled to multiple communication units (620) which can be used by MSU users to establish communication links between the MSU users and other terminals. The MSU (600) and a method for operating the MSU perform selective registration (200-210, 300-322) for the MSU users. In order to reduce unnecessary registration traffic, only after the MSU determines (202, 303) that a particular MSU user desires to receive incoming calls will the MSU register (208, 320) the particular MSU user with a communication system. If an MSU user does not desire to receive incoming calls, the MSU will not register (204, 304) the MSU user with the communication system.

Abstract: A communication system (100) includes satellites (102,104) and a mobile exchange unit (MXU) (120) for exchanging communication information with users. A satellite (102) generates synchronous timing frames requiring users operating through an MXU (120) to anticipate timing and frequency requirements to participate in communications. An MXU (120) must advance transmissions to a satellite (102) to insure transmissions arrive at satellite (102) within the proper synchronous receive window. Such advanced transmissions by MXU (120) interfere with reception of a ring alert/page transmission (130) which contains the location of broadcast channels (86) designating an incoming call or page data transmissions. The MXU (120) alternatively extracts a broadcast channel location from a candidate hand-off list being transmitted by a satellite (102) to in-use transceivers (310). The MXU 120 then distributes the location of the broadcast channel to those transceivers (310) presently not in-use.

Abstract: A communication system includes base communication units (105, 155) facilitating a communication link with portable communication units (110) in motion relative to base communication units. The relative motion between base communication units (105, 155) and portable communication units (110) introduces Doppler frequencies into communication links (115, 165). When portable communication units (110) travel in a predictable direction (119), frequency offsets for Doppler compensation are generally predictable. However, when portable communication units (110) move erratically in relationship to a base communication unit (105, 155), frequency offsets for Doppler compensation are not easily calculated. Incorporation of velocity vector data into the frequency offset calculation for Doppler compensation provides reliable tracking and Doppler frequency compensation for erratic motion of portable communication units (110).