Wireless data communication system having radio frequency devices, and related operating methods for disabling a transmit mode

• US 7,880,616 B2
• Filed: 06/25/2008
• Issued: 02/01/2011
• Est. Priority Date: 06/25/2008
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Kanagala, Sameer, Malik, Ajay
• Primary Examiner(s): Nguyen; Hung T.
• Application Number:
  US12/146,298
• Publication Number:
  US 20090322488A1
• Time in Patent Office: 951 Days
• Field of Search: 340/572.1, 340/572.4, 340/539.1, 340/825.69, 340/10.1, 340/10.3, 340/10.33, 340/10.34, 235/375, 235/376, 235/380, 235/381, 235/487, 235/492
• US Class Current: 340/572.1
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 76/25 Maintenance of established connections
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A wireless system suitable for use as a radio frequency (RF) locationing or presence detection system includes at least one wireless access device and at least wireless device, such as an active RF tag, corresponding to an item or asset of interest. A method of managing RF transmissions by the wireless devices is provided. The method involves the wireless device receiving keep-alive beacons during a first period of time. During this first period of time, the wireless device is operated in a transmit mode. During a second period of time that follows the first period of time, the wireless device receives no keep-alive beacons. During this second period of time, the wireless device is operated in a standby mode such that RF transmissions are disabled.

Claims

1. A method of managing transmissions in a wireless system having a wireless device and at least one wireless access device, the method comprising:

the wireless device receiving keep-alive beacons during a first period of time;

operating the wireless device in a transmit mode during the first period of time;

measuring, during the first period of time, a time interval initiated in response to receiving a last keep-alive beacon;

comparing the time interval to a threshold value;

switching the wireless device to a standby mode if the time interval exceeds the threshold value;

the wireless device receiving no keep-alive beacons during a second period of time that follows the first period of time; and

operating the wireless device in a standby mode during the second period of time.

2. The method of claim 1, wherein operating the wireless device in the standby mode comprises preventing transmissions by the wireless device.

3. The method of claim 1, wherein the keep-alive beacons originate from the at least one wireless access device.

4. The method of claim 1, wherein during the first period of time the wireless device receives keep-alive beacons in designated time slots.

5. The method of claim 4, further comprising switching to the standby mode if the wireless device fails to receive a keep-alive beacon in a designated time slot.

6. The method of claim 4, further comprising switching to the standby mode if the wireless device fails to receive keep-alive beacons in a predetermined consecutive number of designated time slots.

7. The method of claim 1, further comprising:

the wireless device receiving keep-alive beacons during a third period of time that follows the second period of time; and

operating the wireless device in the transmit mode during the third period of time.

8. A wireless data communication system comprising:

one or more wireless access devices, each configured to transmit keep-alive beacons to support operation of the wireless data communication system in a transmit mode; and

a radio frequency (RF) device configured to support operation of the wireless data communication system in the transmit mode for as long as it receives keep-alive beacons from any of the one or more wireless access devices, and to support operation of the wireless data communication system in a standby mode if it no longer receives any keep-alive beacons, wherein the RF device is configured to;

measure, while operating in the transmit mode, a time interval initiated in response to receiving a last keep-alive beacon;

compare the time interval to a threshold value;

switch to the standby mode if the time interval exceeds the threshold value; and

disable its wireless transmissions while operating in the standby mode.

9. The system of claim 8, wherein the one or more wireless access devices are onboard aircraft devices.

10. The system of claim 9, further comprising an aircraft control unit coupled to the one or more wireless access devices, and configured to initiate powering down of the one or more wireless access devices for the standby mode.

11. The system of claim 8, wherein the RF device is an active RF tag.

12. The system of claim 8, wherein the RF device is configured to:

receive, while operating in the transmit mode, keep-alive beacons in designated time slots;

switch to the standby mode if it fails to receive a keep-alive beacon in a designated time slot; and

disable its wireless transmissions while operating in the standby mode.