Bulk Synchronous Medium Access ( BSMA ) for Mote - based Sensor Networks

1. Research overview Energy efficiency is the chief concern in sensor networks as they have limited power and it often requires tradeoffs with throughput and latency when designing a medium access control (MAC) protocol. The goal of this research is to maximize energy savings based on sleep mode operation and Transmit Power Control (TPC) to save power in Mote-based sensor networks. Two key objectives are (i) to review and evaluate existing MAC protocols developed for Mote such as USC) based on IEEE 802.11 concept with sleep/wake and (ii) to develop an energy efficient MAC solution, called Bulk Synchronous Medium Access (BSMA). Planned future work include expanding BSMA protocol based on TPC (using PA_POW register) and RSSI (received signal strength). Common methods for MAC protocols in sensor networks are random access and TDMA. Prominent sources for energy inefficiency at medium access control (MAC) are collisions, idle listening, overhearing, and control packet overhead [1]. Collisions: the packets involved and control overhead needs to be retransmitted Idle listening: the radio is in listening mode in anticipation of being solicited instead of being in sleep mode. Overhearing: the radio listens promiscuously on the channel receiving packets addressed to other nodes when it could be in sleep mode. Control packet overhead: the headers for the packets and acknowledgement packet, which is used by most MAC schemes, contribute to the overhead. They are quite common in random access MAC protocols proposed for ad hoc networks. Control overhead is the only significant factor in TDMA-based MAC schemes, as it requires setting up and maintaining schedules. TDMA works best when there is no severe variation in traffic intensity. Also, packets may be delayed until the node's turn to transmit to the receiver comes up. Since energy efficiency is crucial for sensor networks, the main approach is to maintain a very low duty cycle with less control overhead. According to IEEE 802.11 standard [10], there are two modes of operation depending on the existence of an AP. They are referred to as the Distribution Coordination Function (DCF) and the Point Coordination Function (PCF). The DCF uses a contention algorithm to provide access to all traffic based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and delay known as InterFrame Space (IFS). The PCF is an optional access method implemented on top of the DCF and provides a contention-free service coordinated by an AP. In the PCF, the …