PMAC: An adaptive energy-efficient MAC protocol for WSNs Tao Zheng, Sridhar Radhakrishnan and Venkatesh Sarangan School of Computer Science University of Oklahoma IEEE International Workshop on Algorithms for Wireless, Mobile, Ad Hoc and Sensor Networks, (IEEE WMAN 05), held along with IPDPS 2005

Agenda Introduction Overview of PMAC Protocol details Qualitative discussion Experimental results Conclusions

Introduction A MAC protocol is required in sensor networks to coordinate the sensor nodes’ access to the shared medium. Power efficient prolong the lifetime of the network. Latency Throughput

Introduction A new MAC protocol Pattern-MAC (PMAC) for sensor networks is proposed Adaptively determines the sleep-wake up schedules for a node Based on its own traffic and the traffic patterns of its neighbors.

Overview of PMAC Idle listening is one of the main sources of energy wastage. Energy saving MAC protocols try to minimize the length of the idle listening period. PMAC tries to save more power than SMAC and TMAC, without compromising on the throughput.

Overview of PMAC Sleep-wakeup pattern String of bits indicating the tentative sleep-wakeup plan for a sensor node over several slot times Bit 1: the node intends to stay awake during a slot time Bit 0: the node intends to sleep. A sleep-wakeup schedule for a sensor node is a string of bits indicating the actual sleep-wakeup itinerary derived from its own pattern and, the patterns of its neighboring nodes

Protocol details-Pattern Generation Pj be the binary string representing the pattern of a node j. In N time slots Example: Pj = 01 N =5 ->01010 In PMAC, we restrict a pattern to be 0m1,where m = 0,1,…N-1 Large m indicates the traffic load is light Small m (even a 0) indicates the traffic load is heavy.

Protocol details-Pattern Generation Pji: the working pattern of node j during period i Pji can be different from Pj i+1 Depending upon the node j’s traffic conditions observed during period i. Pji,n ,n = 0,1,…, xi, be the nth new pattern obtained in the sequence of updates. xi :the number of pattern updates during period i

Protocol details-Pattern Generation j Period 1 Period 2 N=9 Pj 1=01 1 Pj 2=001 1 1 1

Protocol details-Pattern Generation Predefined threshold d the number of 0 bits 0 < m<=d/2 0 < m<=d/2 Pj i,0=1 Pj i,1=01 Pj i,2=001 Pj i,3=00001 Pj i,k=00m1 Pj i,k+1=002m1 Pj i,k+2=002m+11 0 < m<=d/2 d<2m<N-1 2m+1=N-1 Pj i,k+3=002m+11 Pj i,k+4=1

Protocol details-Pattern Exchange Pattern Exchange Time Frame super time frames Pattern Repeat Time Frame

Protocol details-Pattern Exchange Pattern Repeat Time Frame Pattern Exchange Time Frame super time frames

Protocol details-Pattern Exchange Let d= 4 and N = 6 PAi,0 =001 PAi,1 =00001 PAi,2 =000001 last updated pattern

Protocol details-Schedule Generation Pattern bit at node j Packet to send Pattern bit at the receiving node Schedule at node j 1 1- *

Experimental results Simulated both PMAC and SMAC ns-2. mesh topology with different sizes constant bit rate traffic source with different time intervals UDP as the transport layer protocol. simulation time is set to 1500 seconds.

Experimental results PMAC SMAC TR =258ms TE = 104ms Number of time slots in PRTF is 64 Number of time slots in PETF is 4 SMAC duty cycle=10

Experimental results Various network size under heavy traffic load. 100bytes/s

Experimental results Various network size under heavy traffic load. 100bytes/s

Experimental results Different traffic loads.

Experimental results Different traffic loads

Conclusions This paper proposes a new MAC protocol, called PMAC sleep-wakeup times of the sensor nodes are adaptively determined. Achieves more power savings under light loads, and higher throughput under heavier traffic loads.