05835857 is referenced by 232 patents and cites 8 patents.

Methods for operating a wireless communications system provided for reducing the use of the system by unauthorized users by establishing the geographical location of selected user, comparing this location with the known locations of authorized users and denying service to the selected user if the selected user's location does not correspond to the known location of authorized users. Seamless hand-over of a user between nodes of the communication system is effected by periodically recomputing a algorithm which determines a preferred node for communication with the user. When the algorithm indicates that another node is preferred, a call initiation handshake is established between the user and the preferred node, while still maintaining communication with the original node. Communication between the user and the first node is not interrupted until the user establishes a communication "lock" with the second node. Passive intermodulation interference of signals transmitted and received by nodes of a multi-satellite node system is eliminated by using certain of the satellite nodes for transmit-only and other of the satellite nodes for receive-only operation. In another embodiment PIM interference is eliminated by time duplexing the signals transmitted and received by a satellite's antenna. PIM interference is also reduced by assigning unique portions of each transmitter subband and each receiver subband to each of the satellite nodes.

Position determination for reducing unauthorized use of a communication system
Application Number
Publication Number
Application Date
November 18, 1996
Publication Date
November 10, 1998
David D Otten
Redondo Beach
Drummond & Duckworth
Celsat America
H04Q 7/00
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