Post on 08-Jan-2016
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Energy-efficient collision-free medium access control for wireless
sensor networksVenkatesh RajendranKatia ObraczkaGarcia-Luna-Aceves
Department of Computer Engineering University of California, Santa Cruz
ACM SenSys’03 Speaker: Yung-Lin Yu
Outline• Introduction
• TRAMA– NP(Neighbor Protocol)– SEP(Schedule Exchange Protocol)– AEA(Adaptive Election Algorithm)
• Experimental setup
• Simulation results
• Conclusion
Introduction• The deployment of sensor network usually
done in ad-hoc manner– Self-organize into a multi-hop wireless network
• Nodes may be difficult to recharge
• Nodes recharging may not be cost effective
• Major challenge– Self adaptive to changes in traffic– Prolongs the battery life
TRAMA• Overview
– TRAMA consists of three components• NP (Neighbor Protocol)
• SEP (Schedule Exchange Protocol)
• AEA (Adaptive Election Algorithm)
NP• Nodes can only join during random access
periods– Main function of random access periods is node
additions and deletions– All nodes must be transmit or receive state– The most energy consumption
NP (cont.)• Using signaling packets to gather
neighborhood information– During the random access period
• Updates about its one-hop neighborhood– Added or deleted– Keep-alive– Time out a neighbor
SEP• SEP establishes and maintains schedule info
rmation
• The information is periodically broadcast
• Each node has a SCHEDULE_INTERVAL
• Winning slots– Node computes in the interval [t,t+ SCHEDUL
E_INTERVAL]• Last winning slot reserved for broadcasting the no
de’s schedule for the next interval
SEP (cont.)• Schedule packets
– Nodes announce their schedule via Schedule packets
• Using bitmap to transmit schedule packets– The length of bitmap is the number of one-hop
neighbors– Eg.
• A node has 4 one-hop neighbors with identities 14,7,5,4
• If broadcast , bitmap : 1111
• If multicast to 14 and 5, bitmap: 1010
SEP (cont.)• ChangeOver slot
– The slot after which all the winning slots go unused
• The maximum sleep periods– ChangeOver slot to l
ast winning slot
SEP (cont.)
• A summary of a node’s schedule– Sent with every data packet– Summary help minimize the effects of packet lo
ss– In order not to excessive overhead, the schedule
summary is 6 bytes
AEA• Purpose
– To Decide node’s state (TX, RX, SL)– Re-use slots
AEA (cont.)
CB
D
100
95 79
200
tx
A lost
ASK
Inconsistency problem
AEA (cont.)• Node u is tx(u)
– u wants to transmit• Let u.state = TX
• Let u.receiver = u.reported.rxId
– u gave up transmit• Call HandleNeedTransmissions
• tx(u) belongs to N1(u)– tx(u).announcedReceiver = u
• Let u.state = RX
– Else u.state = SL
AEA (cont.)• atx(u) hidden from tx(u)
– atx(u).announcedReceiver = u• Let u.state = RX
– Else u.state = SL
• HandleNeedTransmissions– ntx(u) = u
• Let u.state = TX• Let u.receiver = u.reported.rxId
– atx(u).announcedReceiver = u• Let u.state = RX
– Else u.state = SL
Experimental setup• Simulation platform
– Qualnet
• Physical layer model– TR1000
• 50 nodes are uniformly distributed over a 500m x 500m area
• 6 one-hop neighbors on average• 17 two-hop neighbors on average• 2 different types of traffic load
– Synthetic data generation– Data gathering application
Simulation results• Synthetic traffic
Average packet delivery ratio for synthetic traffic
Average queuing delay for synthetic traffic
Simulation results (cont.)
Simulation results (cont.)• Data gathering application
Simulation results (cont.)
Simulation results (cont.)
Conclusion• TRAMA achieves
– Energy-savings comparable to S-MAC– Delivery guarantees comparable to NAME
• TRAMA has higher delay– It Suited for
• Not delay sensitive
• High delivery guarantees
• Energy efficiency