Synchronization between wireless devices while saving power

• US 20080031208A1
• Filed: 09/29/2006
• Published: 02/07/2008
• Est. Priority Date: 08/04/2006
• Status: Abandoned Application

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Shen, Hui, Abhishek, Abhishek
• Application Number:
  US11/529,880
• Publication Number:
  US 20080031208A1
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0225 using monitoring of external events, e.g. the presence of a signal
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: H04W 84/20 Master-slave selection or change arrangements
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A wireless device in an ad hoc network detects other wireless devices within radio range and establishes synchronization with the detected wireless devices. The wireless device operates in a power save mode and wakes up, or turns on, periodically or on demand to implement discoverability. A received probe request packet or beacon packet contains information which allows the receiving wireless device to discover the transmitting wireless device. The wireless device may operate in a discoverable mode or in an active discovery mode.

Claims

1. A method to operate a wireless device in an ad hoc network, comprising:

operating the wireless device in a discoverable mode to enable discovery by neighbor wireless devices and to discover neighbor wireless devices passively; and

operating the wireless device in an active discovery mode to actively discover neighbor wireless devices which are in the active discovery mode or the discoverable mode.

2. A method as defined in claim 1, further comprising:

operating the wireless device in the discoverable mode during a discovery window of a periodic discovery interval; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

3. A method as defined in claim 1, wherein operating the wireless device in the discoverable mode comprises:

turning on a radio of the wireless device for a discovery window of a periodic discovery interval;

listening for probe request packets during the discovery window;

if a received probe request packet is verified and no probe response packet has been sent in a current discovery window, sending a probe response packet containing identifying information;

otherwise, not sending a probe response packet; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

4. A method as defined in claim 1, wherein operating the wireless device in the active discovery mode comprises:

turning on a radio of the wireless device for an active discovery period, in response to activation of the active discovery mode, the active discovery period being at least as long as a periodic discovery interval utilized by discoverable wireless devices;

sending a probe request packet for each active probe interval of the active discovery period if no other wireless device has sent a probe request packet earlier in a current probe interval, the active probe interval being shorter than a discovery window of the discoverable wireless devices;

listening for received probe response packets received during the active discovery period;

saving information contained in each of the received probe response packets; and

returning to the discoverable mode when the active discovery period expires.

5. A method as defined in claim 1, further comprising:

turning on a radio of the wireless device in response to activation of wireless operation;

listening for a beacon packet for a specified time;

if a beacon packet is received in the specified time, adjusting timing of a discovery window in accordance with parameters received in the beacon packet; and

if a beacon packet is not received in the specified time, sending a beacon packet.

6. A method as defined in claim 1, wherein operating the wireless device in the discoverable mode comprises:

turning on a radio of the wireless device during a discovery window of a periodic discovery interval, in response to activation of the discoverable mode;

listening for a beacon packet for a random back-off time;

if a beacon packet is received within the random back-off time, adjusting timing of the discovery window in accordance with parameters in the received beacon packet;

if a beacon packet is not received within the random back-off time, sending a beacon packet;

listening for a probe request packet during the discovery window;

saving information relating to received probe request packets;

sending a probe response packet if the wireless device has not sent a probe response packet or a beacon packet in the current discovery window; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

7. A method as defined in claim 1, wherein operating the wireless device in the active discovery mode comprises:

turning on a radio of the wireless device during a discovery window of a periodic discovery interval, in response to activation of the active discovery mode;

sending a broadcast request packet during the discovery window;

saving information contained in response packets sent by other wireless devices in response to the broadcast request packet; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

8. A wireless device comprising:

a computing device;

a radio; and

a wireless module logically connected to the computing device and to the radio, the wireless module comprising a processor programmed with instructions for;

operating the wireless device in a discoverable mode to enable discovery by neighbor wireless devices and to discover neighbor wireless devices passively; and

operating the wireless device in an active discovery mode to actively discover neighbor wireless devices which are in the active discovery mode or the discoverable mode.

9. A wireless device as defined in claim 8, wherein the instructions further include instructions for:

operating the wireless device in the discoverable mode during a discovery window of a periodic discovery interval; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

10. A wireless device as defined in claim 8, wherein the instructions for operating the wireless device in the discoverable mode include instructions for:

turning on the radio for a discovery window of a periodic discovery interval;

listening for probe request packets during the discovery window;

if a received probe request packet is verified and no probe response packet has been sent in a current discovery window, sending a probe response packet containing identifying information;

otherwise, not sending a probe response packet; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

11. A wireless device as defined in claim 8, wherein the instructions for operating the wireless device in the active discovery mode include instructions for:

turning on the radio for an active discovery period, in response to activation of the active discovery mode, the active discovery period being at least as long as a periodic discovery interval utilized by discoverable wireless devices;

sending a probe request packet for each active probe interval of the active discovery period if no other wireless device has sent a probe request packet earlier in a current probe interval, the active probe interval being shorter than a discovery window of the discoverable wireless devices;

listening for received probe response packets received during the active discovery period;

saving information contained in each of the received probe response packets; and

returning to the discoverable mode when the active discovery period expires.

12. A wireless device as defined in claim 8, wherein the instructions further include instructions for:

turning on the radio in response to activation of wireless operation;

listening for a beacon packet for a specified time;

if a beacon packet is received in the specified time, adjusting timing of a discovery window in accordance with parameters received in the beacon packet; and

if a beacon packet is not received in the specified time, sending a beacon packet.

13. A wireless device as defined in claim 8, wherein the instructions for operating the wireless device in the discoverable mode include instructions for:

turning on the radio during a discovery window of a periodic discovery interval, in response to activation of the discoverable mode;

listening for a beacon packet for a random back-off time;

if a beacon packet is received within the random back-off time, adjusting timing of the discovery window in accordance with parameters in the received beacon packet;

if a beacon packet is not received within the random back-off time, sending a beacon packet;

listening for a probe request packet during the discovery window;

saving information relating to received probe request packets;

sending a probe response packet if the wireless device has not sent a probe response packet or a beacon packet in the current discovery window; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

14. A wireless device as defined in claim 8, wherein the instructions for operating the wireless device in the active discovery mode include instructions for:

turning on the radio during a discovery window of a periodic discovery interval, in response to activation of the active discovery mode;

sending a broadcast request packet during the discovery window;

saving information contained in response packets sent by other wireless devices in response to the broadcast request packet; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

15. A computer-readable medium programmed with instructions for executing a method to operate a wireless device in an ad hoc network, comprising:

operating the wireless device in a discoverable mode to enable discovery by neighbor wireless devices and to discover neighbor wireless devices passively; and

operating the wireless device in an active discovery mode to actively discover neighbor wireless devices which are in the active discovery mode or the discoverable mode.

16. A computer-readable medium as defined in claim 15, wherein operating the wireless device in the discoverable mode comprises:

turning on a radio of the wireless device for a discovery window of a periodic discovery interval;

listening for probe request packets during the discovery window;

if a received probe request packet is verified and no probe response packet has been sent in a current discovery window, sending a probe response packet containing identifying information;

otherwise, not sending a probe response packet; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

17. A computer-readable medium as defined in claim 15, wherein operating the wireless device in the active discovery mode comprises:

turning on a radio of the wireless device for an active discovery period, in response to activation of the active discovery mode, the active discovery period being at least as long as a periodic discovery interval utilized by discoverable wireless devices;

sending a probe request packet for each active probe interval of the active discovery period if no other wireless device has sent a probe request packet earlier in a current probe interval, the active probe interval being shorter than a discovery window of the discoverable wireless devices;

listening for received probe response packets received during the active discovery period;

saving information contained in each of the received probe response packets; and

returning to the discoverable mode when the active discovery period expires.

18. A computer-readable medium as defined in claim 15, wherein the method further comprises:

turning on a radio of the wireless device in response to activation of wireless operation;

listening for a beacon packet for a specified time;

if a beacon packet is received in the specified time, adjusting timing of a discovery window in accordance with parameters received in the beacon packet; and

if a beacon packet is not received in the specified time, sending a beacon packet.

19. A computer-readable medium as defined in claim 15, wherein operating the wireless device in the discoverable mode comprises:

turning on a radio of the wireless device during a discovery window of a periodic discovery interval, in response to activation of the discoverable mode;

listening for a beacon packet for a random back-off time;

if a beacon packet is received within the random back-off time, adjusting timing of the discovery window in accordance with parameters in the received beacon packet;

if a beacon packet is not received within the random back-off time, sending a beacon packet;

listening for a probe request packet during the discovery window;

saving information relating to received probe request packets;

sending a probe response packet if the wireless device has not sent a probe response packet or a beacon packet in the current discovery window; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.

20. A computer-readable medium as defined in claim 15, wherein operating the wireless device in the active discovery mode comprises:

turning on a radio of the wireless device during a discovery window of a periodic discovery interval, in response to activation of the active discovery mode;

sending a broadcast request packet during the discovery window;

saving information contained in response packets sent by other wireless devices in response to the broadcast request packet; and

operating the wireless device in a power save mode during an inactive portion of the periodic discovery interval.