Dynamic tracking of mobile stations in wireless networks

• US 5,390,234 A
• Filed: 04/20/1992
• Issued: 02/14/1995
• Est. Priority Date: 04/20/1992
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kessler, Ilan, Bar-Noy, Amotz
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Shankar, Vijay
• Application Number:
  US07/871,253
• Time in Patent Office: 1,030 Days
• Field of Search: 379/58, 379/59, 379/60, 455/33.1, 455/33.2, 455/33.4, 455/54.1, 455/54.2, 455/56.1
• US Class Current: 455/456.1
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
• CPC Class Codes: H04W 68/04 multi-step notification using statistical or historical mobility data

Abstract

A method of tracking mobile stations in a cellular network. A mobile station will report to a base station only when the mobile station is turned on and only after having made a minimum number of intercellular movements. When communications with a mobile station is desired, the mobile station is searched for only in the neighborhood of the most recent current cell, which is the last cell from which the mobile station reported to the base station.

Claims

1. A method of tracking a mobile station u of a cellular network, comprising:

(a) reporting a first cell in which said mobile station is located to a base station of said network;

(b) determining the number of intercellular movements made by said mobile station after having reported its arrival in said first cell in step (a);

(c) repeating steps (a) and (b) each time after said mobile station makes an additional N(u)+1 intercellular movements after having last reported its cell location as in step (a) but from the cell in which said mobile unit is in each time an additional N(u)+1 intercellular movements are made, where N(u) is a predetermined number for said mobile unit u; and

(d) when communications with said mobile station is desired, searching for said mobile station in a L-neighborhood of a current cell, said current cell being the last cell from which said mobile unit last reported its location as in step (c), with said neighborhood being a set of all cells reachable by said mobile station travelling from said current cell along any path of length ≦

L, where L=N(u)≧

1, where the length of said path is the number of intercellular movements made as one travels from one end of said path to another end of said path.

2. A method as recited in claim 1, wherein N(u) is determined by selecting the value of N(u) for which C(u) is a minimum, where C(u)=a(u) M(u)+b(u) F(u), where a(u) is the cost of sending an update message by said mobile station u, b(u) is the cost incurred by searching for said mobile station u in a cell, M(u) is the number of update messages sent by mobile station u during a time interval T, and where F(u) is the number of cells in which said mobile station u was searched for in a time interval T.

3. A method as recited in claim 1, wherein the number of intercellular movements of said mobile station calculated by increasing the value of a counter for each intercellular movement of said mobile station.

4. An apparatus for tracking a mobile station in a cellular network comprising:

(a) means for reporting a first cell in which said mobile station is located to a base station of said network;

(b) means for determining the number of intercellular movements of said mobile station after having reported its arrival in said first cell in step (a);

(c) means for repeating steps (a) and (b) each time after said mobile station makes N(u)+1 intercellular movements after having last reported its cell location as in step (a) but from the cell in which said mobile unit is in each time an additional N(u)+1 intercellular movements are made, where N(u) is a predetermined number for said mobile unit u; and

(d) means for, when communications with said mobile station is desired, searching for said mobile station in a L-neighborhood of said current cell, said current cell being the last cell from which said mobile unit reported its location as in step (c) with said neighborhood being a set of all cells reachable by said mobile station by travelling from said current cell along any path of length ≦

L, where L=N(u)≧

1, where the length of said path is the number of intercellular movements made as one travels from one end of said path to another end of said path.