Ripple flooding in wireless sensor networks

Abstract

Flooding is a fundamental operation to support route discovery and time synchronization in wireless sensor networks. A simple flooding causes the broadcast storm problem and leads to long latency to complete the broadcast. This paper presents the Ripple flooding scheme (RFS) for wireless sensor networks (WSNs). The proposed scheme improves the convergence speed of flooding by using a synchronized packet rebroadcasting instead of using a CSMA (Carrier Sense Multiple Access) MAC based packet rebroadcasting. We analyse the multipath delay spread feasibility on a receiver for the packets from multiple senders. The theoretical upper bound of packet loss rate (PLR) is less than 13%. The experimental result shows the same as the PLR of the theoretical analysis. We implement the RFS on the sensor node with the MSP430 microcontroller and the CC2420 transceiver and evaluate the major performance metrics including the convergence time and the reliability in various network scales and densities. The convergence time is at least 3.5 times faster than the CSMA MAC based flooding in the dense network environments. The transmission reliability of the RFS is slightly better than the reliability of the CSMA MAC based flooding because of the implicit overhearing scheme provided by the RFS.

Precise time synchronization based on ripple flooding in wireless sensor networks

“…The reference node uses the MAC layer time-stamping scheme to distribute periodically its global time in a sync message to neighbor nodes which are located in RF range of the reference node. The level-1 nodes, which are the receivers of the sync message flooded from the reference node, save their local time and the global time to make their observation set and rebroadcast the same message that they received except a slot number [1] after the guard interval D in Fig. 1.…”

“…In this letter, we propose a time synchronization algorithm RFTS based on the ripple flooding [1], which is our previous work. By using a synchronized packet broadcasting of multiple nodes instead of a CSMA-CA MAC based broadcasting, convergence time of the ripple flooding is faster than the simple flooding by a factor of 3.5.…”