Position determination for reducing unauthorized use of a communication system

• US 5,835,857 A
• Filed: 11/18/1996
• Issued: 11/10/1998
• Est. Priority Date: 03/19/1990
• Status: Expired due to Fees

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: Celsat America, Inc.
• Inventors: Otten, David D.
• Primary Examiner(s): Bost, Dwayne D.
• Assistant Examiner(s): LEGREE, TRACY MICHELLE
• Application Number:
  US08/751,651
• Time in Patent Office: 722 Days
• Field of Search: 455/410, 455/456, 455/411, 455/403, 342/357, 342/47, 342/88, 342/125, 342/450, 342/458, 342/457, 342/387
• US Class Current: 455/410
• CPC Class Codes: H04B 7/18517 Transmission equipment in earth stations
• CPC Class Codes: H04B 7/18532 Arrangements for managing transmission, i.e. for transporting data or a signalling message
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04B 7/18558 Arrangements for managing communications, i.e. for setting up, maintaining or releasing a call between stations
• CPC Class Codes: H04B 7/18567 Arrangements for providing additional services to the basic mobile satellite telephony service
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0042 Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 1/0047 Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 5/02 Channels characterised by the type of signal
• CPC Class Codes: H04W 12/084 using delegated authorisation, e.g. open authorisation [OAuth] protocol
• CPC Class Codes: H04W 12/126 Anti-theft arrangements, e.g. protection against subscriber identity module [SIM] cloning
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/225 Calculation of statistics, e.g. average, variance
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 92/02 : Inter-networking arrangements

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.

Claims

1. 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.

2. In a communication system having a plurality of user units and at least two cellular nodes so as to establish at least two cells, the improved cellular communication system comprising:

a) position determination means for establishing the geographical location of a selected user, said position determination means including;

i) timing signal means for providing a timing signal to the user unit from at least one cellular node;

ii) timing response signal means for providing a timing response signal from the user unit to at least two nodes in response to said timing response signal;

iii) timing measurement means for measuring the response times of the user unit to each timing signal received by at least two nodes; and

b) logic means for comparing the location of said selected user with the known locations of authorized users; and

c) fraudulent detection means for determining whether said selected user is a fraudulent user of the communication system.