Synchronization of distributed networks

• US 8,284,755 B2
• Filed: 02/21/2007
• Issued: 10/09/2012
• Est. Priority Date: 02/23/2006
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Challapali, Kiran S., Cordeiro, Carlos M.
• Primary Examiner(s): Yao, Kwang B
• Assistant Examiner(s): Tran, Tung Q
• Application Number:
  US12/280,226
• Publication Number:
  US 20090041003A1
• Time in Patent Office: 2,057 Days
• Field of Search: 370/310.1, 370/310.2, 370/314, 370/324, 370/328, 370/350, 370/395.62, 370503-520, 455/13.2, 455/502, 455/208, 455/265
• US Class Current: 370/350
• CPC Class Codes: H04B 7/2696 Over the air autonomous synchronisation, e.g. by monitoring network activity H04B7/2693 takes precedence
• CPC Class Codes: H04J 3/0679 by determining clock distribution path in a network

Abstract

A system (400), apparatus (300), and method (100) are provided to synchronize distributed (otherwise uncoordinated) networks (400) of independent nodes (401_i). Such synchronization can be used in a number of different ways. In the context of cognitive radios, such synchronization can be used to synchronize quiet periods. Quiet periods are times when all cognitive radios (that are otherwise uncoordinated) become quiet so that incumbent users can be detected reliably. The technique of the present invention converges quickly and scales well.

Claims

1. A synchronization system for wireless networks, comprising:

a plurality of uncoordinated wireless devices j configured to transmit a beacon in a beacon period having a beacon period start time BPST_j and receive a beacon in a beacon period having a beacon period start time BPST_i for all devices i, where devices i are not the same as devices j; and

a beacon alignment apparatus for aligning BPST_j to BPST_i by performing an adjustment procedure by setting BPST_j to BPST_i if BPST_j∈

1^st half of BPST_i if BPST_j∈

1^st half of BPST_i, incrementing a counter unique to the device i and trying to perform the adjustment procedure again;

wherein if the counter reaches a predetermined maximum number of times without aligning BPST_j to BPST_i setting BPST_j to a random number,

wherein the beacon alignment apparatus is used by the device j whenever the device j receives a beacon from another device i of said plurality of uncoordinated wireless devices j and BPST_j is not the same as BPST_i.

2. The system of claim 1, wherein the beacon period occurs at a beginning of a superframe.

3. The system of claim 1, wherein each device of said plurality is further configured to include an own beacon alignment apparatus.

4. The system of claim 3, wherein the beacon alignment apparatus is configured to include a synchronizer module to perform the adjustment procedure.

5. The system of claim 4, wherein the beacon period occurs at a beginning of a superframe.

6. A beacon alignment apparatus, comprising:

an antenna to transmit a beacon in a beacon period having a beacon period start time BPST_j and receive a beacon of another wireless device i in another beacon period having a beacon period start time BPST_i;

a synchronization memory to store said received beacon;

a synchronizer module operably connected to said antenna to accept said received beacon therefrom and operably connected to said synchronization memory to store said accepted received beacon therein;

the synchronizer module aligning BPST_j to BPST_i by performing an adjustment procedure by setting BPST_j to BPST_i if BPST_j∈

1^st half of BPST_j;

if BPST_i∈

1^st half of BPST_i, incrementing a counter unique to the device i and trying to perform the adjustment procedure again;

wherein if the counter reaches a predetermined maximum number of times without aligning BPST_j to BPST_i, setting BPST_j to a random number.

7. The apparatus of claim 6, wherein the beacon period occurs at a beginning of a superframe.

8. A method for synchronizing a plurality of uncoordinated wireless devices, comprising:

receiving a beacon in a beacon period having a beacon period start time BPST_i from an uncoordinated wireless device i by another uncoordinated wireless device j that transmits an own beacon in a beacon period having a beacon period start time BPST_j, where device j is not the same as device i;

performing an adjustment by setting BPST_j to BPST_i if BPST_j∈

1^st half of BPST_i;

if BPST_j∈

1^st half of BPST_i, incrementing a counter unique to the device i and trying to perform the adjustment procedure again;

wherein if the counter reaches a predetermined maximum number of times without aligning BPST_j to BPST_i, setting BPST_j to a random number; and

transmitting an own beacon by device j in the beacon period having the beacon period start time BPST_j.

9. The method of claim 8, wherein the beacon period occurs at a beginning of a superframe.