US 5,835,857 A · Position determination for reducing unauthorized use of a communication system

Abstract

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.

Claims2

Dependent claims

In the operation of a wireless communications system, which system includes at least two cellular nodes as to establish at least two cells, and a plurality of user units, each said user unit including means for establishing selective communication between at least one node and the user unit, the improvement for reducing use of said system by an unauthorized user comprising:

a) establishing the geographical location of a selected user including;
i) providing a timing signal to the user unit from at least one node;
ii) providing a timing response signal from the user unit in response to the timing signal;
iii) receiving the timing response signal by at least two nodes;
iv) measuring the response times of the user unit to the timing signal based on receipt of the timing response signal by at least two nodes;
and
v) determining the position of the user unit based on the round trip time of transmission of the timing signal and receipt of the timing response signal by at least two nodes;
b) comparing the location of said selected user with the known locations of authorized users;
and
c) denying service to said selected user if said selected user's location does not correspond to one of said known locations.

7 more elements

Dependencies are inferred from the claim text.

Position determination for reducing unauthorized use of a communication system

Life of this patent

Position determination for reducing unauthorized use of a communication system

Life of this patent

Abstract

Claims2