1. 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

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

3. 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

4. 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.

5. 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.

6. 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

7. 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.

8. 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

9. Protocol details-Pattern Generationj
Period 1
Period 2
N=9
Pj 1=01 1
Pj 2=001 1 1 1

10. 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

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

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

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

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

15. 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.

16. 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

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

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

20. Experimental results
Different traffic loads.

21. Experimental results
Different traffic loads

22. 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.