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EM-MAC: A Dynamic Multichannel Energy-Efficient MACProtocol for Wireless Sensor Networks
2014. 11. 11
Bonhyun Koo
Lei Tang*, Yanjun Sun†, Omer Gurewitz‡, and David B. Johnson*
*Department of Computer Science, Rice University, Houston, TX, USA†Systems and Applications R&D Center, Texas Instruments, Dallas, TX, USA
‡Department of Communication Systems Engineering, Ben Gurion University, Israel
MobiHoc’11
Contents
1. Introduction (Goal and Contributions)
2. Related Works
3. EM-MAC Protocol Design
- Design Overview
- Dynamic Channel Selection
- Precise and Quick Multichannel Ren-
dezvous
4. Performance Evaluation
- Multichannel Rendezvous
- Multihop Networks
- Wireless Interference
5. Conclusion
1. Goal and Contributions
Problem1) Traffic Loads (Energy Efficient Operation and Robust Support for varying)2) Wireless Interference (Example. Jamming Attacks)
Purpose
- Introduction of novel mechanism (EM-MAC) for adaptive receiver-initiated multichannel rendezvous and predictive wake-up scheduling
- A predictive and asynchronous duty-cycling MAC protocol (no control channel, dynamic channel selection)
Validation The lowest Sender and Receiver duty cycles and packet delivery latency 100% packet delivery ratio (PDR)
2. Related Works
- Comparison with previous MAC Protocols
Channel Type Protocols Problems
Single Radio Channel S-MAC, B-MAC, RI-MAC,PW-MAC, DW-MAC
Limitation of Network Throughput
Multiple Orthogonal Radio Channel
Y-MAC, A-MAC, MMAC, CAM-MAC
(Dedicated) Control Channel(interference, jamming attack)
Multiple Channel
MMSN, TMMAC (Assuming) Precise Time Synchronization
MuChMACFixed Channel Set
(without adapting to Channel Conditions)
3. EM-MAC (Design Overview)
Sender S, Receiver R Only three of the channels (i, j, and k) At the time of R’s second beacon, no node has a packet waiting to send to R.
Protocol Example
MICAz motesNch = 16, TmaxInterval =1500ms (500~1500ms)
• EM-MAC is a receiver-initiated MAC protocol • A node sends a wake-up beacon to notify potential senders (awake and ready to receive data packets)
3.1 EM-MAC Protocol Design• EM-MAC uses a pseudorandom function (LCG : Linear Congruential Generator) • Applied to (1) Channel and (2) Wake-up Time
Xn+1 = (aXn + c) mod m
m > 0 is the modulus,
a : multiplierc : incrementXn : current seed
Xn+1 becomes the next seed
m =7, a=3, c=0, X0=6
Example)
X1 = (3x6 + 0) mod 7 = 4
X2 = (3x4 + 0) mod 7 = 5
X7 = (3x2 + 0) mod 7 = 6
:
6,4,5,1,3,2, 6,4,5…
period : m-1(6)
Xn+1 = (aXn + c) mod m
Xn
Xn+2 = (aXn+1 + c) mod m
Xk = (aXk-1 + c) mod m
:
Node’s MAC address
3.1 EM-MAC Protocol Design• (Sender) Prediction Mechanism - Predicts the wake-up times and channels of a receiver based on ‘prediction state’
: Sender
(S)
Receiver(R) :
• Nch = 16• TmaxInterval =1500 ms• Tblack = 100 s
1
2
3
4
16
1
2
3
4
16
Ch.
Ch.
Waiting Tblack + 2 x Nch x TmaxInterval
DATA
I want to
send m
y DATA!
B
B
DATA B
DATA B
set a flag (in Header)
prediction state information(a, c, Xn, timestamp)
Channelnext : (300x10+300) mod16 = 4
Intervalnext : (300x60+300) mod500= 100 (ms)
Example: (300, 300, {10,60} , timestamp)
B DATA B
B DATA B
3.2 Dynamic Channel Selection
1) Detecting Channel Conditions
2) Multichannel Rendezvous with Blacklisted Channels
- Nodes maintains for each channel “badness” metric.
Ch. badness
1 5
2 1
: :
16 2
- Every Nodes maintains its own channel blacklist
Reset after Tblack Time (1000 ms)(badness = 0)
Assignment 2 bytes to Header
3.3 Precise and Quick Multichannel Rendezvous1) Adaptive Time Modeling
2) Sender Wake-up Time & Exponential Chase Algorithm
y = kx + b k=1 case, it doesn’t need additional clock sync. y1 = kx1+b
y2 = kx2+b
DATA B
DATA B
set a flag (in Header)
timestamp
y : the current time of Rx : the current time of Sk : clock rate differenceb : initial clock difference
Sender(S)
Receiver(R) B B
#1 #2
wake-upadvance time Fail
reset wake-up advance time
>Tgiveup
Decisionpowered offorout of range
4. Evaluation on MICAz MOTES
1) Performance on Multichannel Rendezvous
Experimental Environments
(S) (R)
R’s clock rate was Increased(until the sender failed)
Node wake-up interval : 1 sWake-up adv. Time : 20 ms30 times (repeat)
R’s clock rate was accelerated by 3000ppm