Interference mitigation in mobile units having location transmitters

• US 20050243781A1
• Filed: 04/30/2004
• Published: 11/03/2005
• Est. Priority Date: 04/30/2004
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Vesuna, Sarosh, Zegelin, Chris
• Granted Patent: US 8,169,991 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A mobile device for data communications has a radio circuit for data communications with a wireless network access point and a radio tag for transmitting location-identifying radio signals. The radio circuit and the radio tag are co-located on a circuit board or are commonly powered. The operation of the radio circuit and the radio tag are segregated in time to avoid interference. Standard wireless network interface protocol functions are exploited to identify time intervals in which the radio circuit is inactive for data communications. These time intervals are used to operate the radio tag to transmit the location-identifying radio signals

Claims

1. A method for wireless data communications between a network of wireless access points and a mobile device, wherein the mobile device comprises a first radio circuit for bi-directional wireless communication with an associated access point and a second radio circuit for transmitting identification signals for the purpose of revealing at least one of mobile unit'"'"'s identification and location, the method comprising the steps of:

(1) identifying a time interval during which the first radio circuit is inactive in wireless communication with the associated access point; and

(2) operating the second radio circuit to transmit the identification signals during the time interval that is identified at step (1).

2. The method of claim 1 wherein the wireless network access points and the mobile device interface through a protocol layer having functions for managing the flow of wireless communications between the wireless network access points and the mobile device, and wherein step (1) further comprises using a function of the protocol layer to identify a time interval during which the first circuit is inactive in wireless communication with the associated access point.

3. The method of claim 2 wherein the protocol layer is a medium access control layer selected from the group of IEEE 802.11, IEEE 802.16, IEEE 802.20, and industry Standard wireless medium access control layers.

4. The method of claim 2 wherein the protocol layer has a power save mode that may be activated by a user of the mobile device to indicate that no data transmissions are intended for a time period, and wherein in response the associated access point buffers data intended for the mobile unit, the method further comprising shutting down power to the first radio circuit and operating the second radio circuit to transmit the location and identification signals while power to the first radio circuit is shut down.

5. The method of claim 4, further comprising periodically re-activating the first radio circuit to receive beacon transmissions from the access point according to a regular polling schedule and scheduling operation of the second radio circuit according to the polling schedule.

6. The method of claim 2 wherein the protocol layer has a request-to send/clear-to-send function, and wherein step (1) comprises:

sending a request-to-send frame from the mobile device to the associated access point;

receiving a clear-to-send duration value from the associated access point;

reserving a time interval within the duration value exclusively for transmitting identification signals from the mobile device.

7. An arrangement for data communications between a network of wireless access points and a mobile device, wherein the mobile device comprises a first radio circuit for bi-directional wireless communication with an associated access point and a second radio circuit for transmitting identification signals for the purpose of revealing the mobile device'"'"'s location, wherein the arrangement comprises:

a first provision for identifying a time interval during which the first radio circuit is inactive in wireless communication with the associated access point; and

a second provision for operating the second radio circuit to transmit the identification signals during the time interval that is identified by the first provision.

8. The arrangement of claim 7 wherein the wireless network access points and the mobile device interface through a protocol layer having functions for managing the flow of wireless communications between the wireless network access points and the mobile device, and wherein the first provision comprises use of a function of the protocol layer to identify the time interval during which the first radio circuit is inactive in wireless communication with the associated access point.

9. The arrangement of claim 8 wherein the protocol layer is a medium access control layer selected from the group of IEEE 802.11, IEEE 802.16, IEEE 802.20, and industry Standard wireless medium access control layers.

10. The arrangement of claim 8 wherein the protocol layer has a power save mode that may be activated by a user of the mobile device to indicate that no data transmissions are intended for a time period, wherein in response the associated access point buffers data intended for the mobile device, and wherein the first and second provisions comprising provisions for shutting down power to the first radio circuit and operating the second radio circuit to transmit the identification signals while power to the first circuit is shut down.

11. The arrangement of claim 8, further comprising provisions for periodically re-activating the first circuit to receive beacon transmissions from the access points according to a regular polling schedule and scheduling the operation of the second radio circuit according to the polling schedule.

12. The arrangement of claim 7 wherein the protocol layer has a request-to send/clear-to-send function, and wherein the first provision comprises provisions for:

sending a request-to-send frame from the mobile device to the associated access point;

receiving a clear-to-send duration value from the associated access point; and

reserving a time interval within the duration value exclusively for transmitting location &

identification signals from the mobile device.