International Journal of Advanced Science and Technology Vol.119 (2018), pp.111-122 http://dx.doi.org/10.14257/ijast.2018.119.10 ISSN: 2005-4238 IJAST Copyright ⓒ 2018 SERSC Australia Bit-Map-Assisted Energy-Efficient MAC protocol for Wireless Sensor Networks 1 Kumar Debasis 1 and Maheshwari Prasad Singh 2 1,2 Department of Computer Science and Engineering National Institute of Technology Patna, Bihar, India 800005 1 debasis.cse14@nitp.ac.in, 2 mps@nitp.ac.in Abstract Time Division Multiple Access (TDMA) based Medium Access Control (MAC) protocols allocate one or more time slots to each sensor node. A node transmits its data during these slot(s) and keeps its radio OFF during all other slots. This inherently reduces idle listening, overhearing, and collision which are the major energy consuming factors. Some MAC protocols include a control period within each time frame. A node that has data for its Cluster Head (CH), books one or more slots by sending a data request (inside a control packet) during the control period. In response to the requests received, the CH sets up and broadcasts a schedule for the source nodes. Each source node transmits in its own slot(s) and keeps its radio OFF during the rest of the data transmission period. In the proposed MAC protocol named Bit-Map-Assisted Energy-Efficient MAC (BEE-MAC), the schedule is broadcasted only once in a round, and is followed throughout the duration of the round. This saves the energy which would have been consumed otherwise, in sending and receiving schedules, multiple times in a single round. The energy consumption in BEE-MAC is compared with the energy consumption in an existing MAC protocol. The results, which have been derived through mathematical calculations, show that BEE-MAC can save a considerable amount of energy by allowing the CH to broadcast the schedule only once in a round. Keywords: TDMA, radio, CH, control period, schedule, announcement period 1. Introduction A Wireless Sensor Network (WSN) is a collection of small autonomous devices which monitor their surroundings and cooperate with each other to forward the collected data to a Base Station (BS) [1, 2]. The BS is a device that connects the WSN to the outside world. The autonomous devices, also called sensor nodes, operate on batteries and communicate wirelessly. The battery is a very limited source of energy, and therefore should be used efficiently. Moreover, recharging or replacing the battery may not be easy, due to the climatic conditions and/or terrain features of the deployment area. The radio of a sensor node consumes the maximum amount of energy as compared to all its other components. The sensor node loses a considerable amount of energy even when its radio is ON, but neither transmitting nor receiving anything. This is called the IDLE state. MAC protocols designed for WSNs, control when the radio is switched ON or OFF [3, 4]. An efficient MAC protocol can reduce the amount of time a node stays in the IDLE state. To this end, TDMA MAC protocols allocate one or more time slots to each sensor node in the network. Each node can transmit/receive to/from other nodes only during its own time slot(s). This inherently minimizes energy consuming factors like overhearing, idle listening and collision. Some MAC protocols partition the network into separate Received (May 10, 2018), Review Result (July 23, 2018), Accepted (August 11, 2018)