| US 7,567,544 B2 | ||
| Method and apparatus for clock synchronization in a wireless network | ||
| Andrew F. Myles, St. Ives (Australia); David S. Goodall, Randwick (Australia); and Alex C. K. Lam, Chatswood (Australia) | ||
| Assigned to Cisco Technology, Inc., San Jose, Calif. (US) | ||
| Filed on Nov. 08, 2006, as Appl. No. 11/557,588. | ||
| Application 11/557588 is a division of application No. 10/112220, filed on Mar. 29, 2002, granted, now 7,151,945. | ||
| Prior Publication US 2007/0091934 A1, Apr. 26, 2007 | ||
| Int. Cl. H04B 1/16 (2006.01); H04B 7/212 (2006.01); H04B 7/00 (2006.01) | ||
| U.S. Cl. 370—338 [370/324; 455/208; 455/502] | 24 Claims |
| 1. A medium access control (MAC) controller for a wireless node of a wireless network to operate according to a MAC protocol,
the MAC protocol including periodic transmission in the network of a data unit that includes synchronization information,
the MAC controller comprising:
a MAC administrator coupled to a data link layer interface;
receive hardware coupled to the physical layer interface and to the MAC administrator, the receive hardware being to receive
one or more data units including a first data unit containing synchronization information and to provide the first received
data unit to the MAC administrator; and
a free-running clock coupled to the receive hardware and to the MAC administrator to provide a copy of the free running clock
value to the receive hardware and to the MAC administrator,
wherein the receive hardware accepts the value of the free running clock value at a known reference point in time relative
to the time the first data unit was received to form a local timestamp and provides the local timestamp to the MAC administrator;
wherein the MAC administrator is to extract the synchronization information from the provided received first data unit to
form an extracted timestamp, and to determine an offset to the free running clock value using the extracted timestamp and
the local timestamp,
such that the sum of the determined offset and the value of the free-running clock provides a local clock value that is approximately
synchronized in time.
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