Reference Broadcast Synchronization (RBS) is a

synchronization Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

method in which the receiver uses the

physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip. The ...

broadcasts for comparing the clocks. This is slightly different from traditional methods which synchronize the sender's with the receiver's clock. RBS allows nodes to synchronize their clocks to the resolution necessary for example for wireless sensor network applications. Rather than broadcasting a

timestamp A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolut ...

in a synchronization packet as in protocols such as

Network Time Protocol The Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable- latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in c ...

, RBS allows the nodes receiving the synchronization packets to use the packet's time of arrival as a reference point for clock synchronization. Because most of the non-deterministic propagation time involved in transmitting a packet over a wireless channel lies between the construction of the packet and the sender's transmitter (e.g., sender's queue delay, MAC contention delay, etc.), by timestamping only at the receiver, RBS removes most delay uncertainty involved in typical time synchronization protocols. For single-hop networks, the RBS algorithm is very simple. First, a transmitter broadcasts some number M as reference broadcasts. Each receiver that receives these broadcasts exchanges the time that each reference broadcast was received locally with its neighbors. Nodes then calculate phase shifts relative to each other as the average of the difference of the timestamps of the node's local clocks for the M reference broadcasts. In multihop networks, time synchronization can be performed hop by hop between two nodes as long as the nodes on each link along the path have a common node whose reference broadcasts they can synchronize to.J. Elson, L. Girod, and D. Estrin. "Fine-grained network time synchronization using reference broadcasts". ACM SIGOPS Operating Systems Review - OSDI '02: Proceedings of the 5th symposium on Operating systems design and implementation. Volume 36 Issue SI, Winter 2002. Pages 147-163.

References

Time {{time-stub

See also

References