Motorola Corporation

Steven H Moritz

Theresa C Wang

Peter J Armbruster

Raymond Joseph Leopold

Steven Paul Sawyer

Ralph C Gregg, Jr

Methods (100) assign a subscriber unit (30) to be served by a gateway (40) based on such factors as the location of the subscriber unit (30), whether the call is to be intercepted and whether the serving gateway (40) is capable of servicing the connection request. The method (100) does not drop a call because the visited gateway initially assigned by the home gateway (40) is unable to service the connection request; but instead routes the call around disabled or congested gateways to an alternate visited gateway that is capable of servicing the connection request.

Methods for assigning subscriber units to visited gateways

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.

Cellular communications with scheduled handoffs

A communication network keeps track of the locations of mobile units which utilize the network. On powering up, the mobile units determine their current locations using signals broadcast, for example, by overhead satellites. They then send data communication messages to the network describing their locations. The network saves the locations and returns data messages that describe borders which surround the mobile units' locations. The mobile units repetitively determine their current locations on a regular schedule. When their current locations are outside of their prescribed borders, they send other location data messages to the network to update the location data being maintained by the network and to receive a definition of a new border.

Mobile unit tracking system

A distributed communication network includes switching offices (SOs), moving-orbit satellites, and subscriber information managers (SIMs). A population of mobile units (MUs) communicates through the network. A MU automatically determines its location and communicates with the network so that this information is kept current at a SO serving the MU and at a home SIM for the MU. The terrestrial nodes of the network have information showing which MUs are logged on at any given time. This knowledge is used to block calls to MUs known to be logged off. Calls are setup through cooperation between SOs. When calls are being setup to MUs, call-originating SOs determine appropriate SIMs and obtains the current location of the MUs from those SIMs. This current location corresponds to a call-destination SO with which the originating SO may cooperate in setting up a call.

Call setup method for use with a network having mobile end users

A communications network includes satellites, which serve as switching nodes and move in orbits about the earth. The network additionally includes stationary switching offices. Mobile communication units communicate with the network through the satellites using TDMA data packets and network control messages. The switching offices couple to PSTNs. Each mobile unit is managed by a nearby switching office that assigns a logical channel identification (LCID) value to the unit. The unit and network use the LCID value to identify the unit in network communications so that network resources are conserved. The network insures that LCID values assigned to opposing parties in a call are included in all TDMA data packets transported to the opposing parties. Satellites and switching offices use these LCID values as logical channel assignments which do not change throughout the duration of the call, in spite of movement by satellites.

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Phoenix, AZ, United States of America

Steven H Moritz