Method and System for Improved WLAN Location

• US 20090017841A1
• Filed: 07/08/2008
• Published: 01/15/2009
• Est. Priority Date: 10/06/2003
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Lewis, Thomas P., Barr, Russell A.
• Granted Patent: US 8,121,612 B2
• Time in Patent Office: Days
• US Class Current: 455/456.500
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Mobile units within an area are located using a wireless local area network. Reference signal transmitters are provided at selected fixed locations within the area. Reference signals are transmitted using the reference signal transmitters using a first selected channel of the wireless local area network. A computer is provided having a database relating signal characteristics of signals transmitted by the reference signal transmitters to location within the area At least one access point is coupled to the computer and provides wireless data communications between the computer and the mobile unit using one or more channels of the wireless data communications system that are different from the first data communications channel. A selected plurality of the reference signals are received at the mobile unit, signal characteristics of the received reference signals are determined and data representing the received reference signal characteristics is transmitted to the computer via the access point using the one or more data communications channels. The data representing reference signal characteristics is received at the computer and position of the mobile unit is determined using the database.

Claims

1-20. -20. (canceled)

21. A computing device, comprising:

a memory storage storing a database, the database relating signal strength characteristics of signals transmitted by reference signal transmitters to locations within an area within which at least one mobile unit is disposed; and

a processing unit determining a position of the at least one mobile unit within the area based on at least one signal received at the computing device, the at least one signal representing at least one reference signal strength characteristic determined by the at least one mobile unit based on the signals transmitted from the reference signal transmitters,

wherein the position is determined using the database.

22. The computing device of claim 21, wherein the area is covered by a wireless communication network, and wherein the at least one reference signal strength characteristic includes an RSSI value at the at least one mobile unit.

23. The computing device of claim 21, further comprising:

an arrangement receiving via an access point the at least one signal representing at least one reference signal characteristic.

24. The computing device of claim 21, wherein the computing device is a microcomputer.

25. The computing device of claim 21, wherein the computing device is a digital signal processor.

26. The computing device of claim 21, wherein the processing unit determines the position based on a signal strength ratio computation.

27. The computing device of claim 21, wherein the processing unit determines the position based on an absolute signal strength computation.

28. A computer storage medium containing instructions that when executed results in

a performance of:

determining a position of a mobile unit within an area based on at least one signal provided by the mobile unit, the at least one signal representing at least one reference signal strength characteristic determined by the at least one mobile unit based on the signals transmitted from reference signal transmitters, wherein the position is determined using a database relating signal strength characteristics of signals transmitted by reference signal transmitters to locations within an area within which mobile units are disposed.

29. The computer storage medium of claim 28, wherein the area is covered by a wireless communication network, and the at least one reference signal strength characteristic includes an RSSI value at the at least one mobile unit.

30. The computer storage medium of claim 28, wherein the at least one signal representing at least one reference signal strength characteristic is provided via an access point to a computing device executing the instructions of the computer storage medium.

31. The computer storage medium of claim 28, wherein the instructions are executed on a microcomputer.

32. The computer storage medium of claim 28, wherein the instructions are executed by a digital signal processor.

33. The computer storage medium of claim 28, wherein the determining is based on a signal strength ratio computation.

34. The computer storage medium of claim 28, wherein the determining is based on an absolute signal strength computation.

35. A mobile unite, comprising:

a radio unit receiving reference signals using a first selected channel, and transmitting and receiving data signals using at least one data communications channel that is different from the first data communications channel; and

a processor arranged determining received signal characteristics of the reference signals received on the first selected channel, generating data representing the received signal characteristics and controlling the radio unit to transmit a data message having the generated data.

36. A mobile unit of claim 35, wherein the processor is further arranged to control the radio unit to receive the reference beacon signals only during selected periodic location time intervals having a selected duration.

37. A mobile unit of claim 35, wherein the mobile unit is arranged to transmit request signals using the first selected channel and receive the reference signals in response to the request signals.

38. A mobile unit, comprising:

a radio unit receiving reference signals using only first selected channel; and

a processor powering up the radio unit at selected time intervals, determining received signal characteristics of the reference signals received on the first selected channel, generating and storing data representing the received signal characteristics and thereafter powering down the radio unit.

39. A mobile unit, comprising:

a radio unit receiving reference signals using only a first selected channel; and

a processor communicating with a database, the processor powering up the radio unit at selected time intervals, determining received signal strengths of the reference signals received on the first selected channel, generating data representing the received signal strengths, determining location data by comparing the signal strength data to the database, storing the location data and thereafter powering down the radio unit.

40. A mobile unit, comprising:

a radio unit receiving reference signals using only a first selected channel and transmitting data using at least one other data communications channel different from the first selected channel; and

a processor communication with a database, the processor powering up the radio unit at selected time intervals, determining received signal strengths of the reference signals received on the first selected channel, generating data representing the received signal strengths, determining location data by comparing the signal strength data to the database, transmitting the location data using the communications channel and thereafter powering down the radio unit.