On the Optimization and Comparative Evaluation of a Reliable and Efficient Caching-based WSN Transport Protocol

Introduction Related work Proposed Mechanisms Performance Evaluation Conclusion

On the Optimization and Comparative

Evaluation of a Reliable and Efficient

Caching-Based WSN Transport Protocol

Nestor M. C. Tiglao, António M. Grilo

INESC-ID/Instituto Superior TécnicoLisbon, Portugal

6 March 2013DRCN 2013, Budapest, Hungary


Outline

1 Introduction

2 Related workCaching-based WSN TransportDTSN

3 Proposed MechanismsNACK RepairAdaptive MAC RetryTransmission Window Optimization

4 Performance Evaluation

5 Conclusion


Wireless Sensor Network

Composed of small, resource-constrained wireless devices

Multi-hop operation

Transport protocol: reliability, congestion control,energy-efficiency


Motivation

Develop simple mechanisms that can be implemented inconstrained devices (i.e., O(1) complexity)

Explore novel approaches in the transport layer

Leverage on intermediate caching to improve performance


Caching-based Transport Protocols

Pump Slowly, Fetch Quickly (PSFQ, 2002)

sink-to-sensor, hop-by-hop reliability, designed for codeupdate, uses broadcast

Reliable Multi-Segment Transport (RSMT, 2003)

end-to-end reliability, uses NACKs, timer-driver lossdetection

Distributed TCP Caching (DTC, 2004)

caching TCP segments and retransmitting segmentslocal in case of packet loss

TCP Support for Sensor Networks (TSS, 2007)

not forward a cached TCP segment until the next-hophas received all previous segments (backpressure)

Distributed Transport for Sensor Networks (DTSN, 2007)


DTSN

Basic DTSN

Enhanced DTSN


Cross-Layer Approach


Enhanced NACK Repair Mechanism

RNACK Procedure

procedure pkt_recv(pkt)...if (!rpending_ && seqno! =next_) then

repseqno_ ← seqno

rpending_ ← 1 ⊲ raise Repair PendingSend RNACK (seqno)

else

do nothingend if

if (rpending_ && seqno==repseqno_) then

rpending_ ← 0 ⊲ clear Repair Pendingnext_ ← maxseen_ + 1 ⊲ update next_

end if

if (seqno > maxseen_) then

maxseen_ ← seqno ⊲ update maxseen_

end if

...end procedure

Example of the Enhanced NACKRepair Mechanism


Adaptive MAC Retry Limit

r ← max

{

3, ⌊log Π− log p

log p⌋

}

R = 1−Π

Π is the Frame Error Rate(FER)p is the physical layer frame error rater is the MAC retry limitR is the desired MAC layer reliability

0 0.2 0.4 0.6 0.8 10

10

20

30

40

50

60

FER

r

Π=0.8

Π=0.9

Π=0.95

MAC retry limit value, r , forvarious MAC reliability levels

R FER≤0.3 FER=0.5 FER=0.7

80% 3 3 490% 3 3 695% 3 4 8


Transmission Window Optimization

Dynamic Window

Additive Increase Multiplicative, Decrease (AIMD)algorithm (cwnd in TCP)inefficient in wireless networks

Fixed Window

based on the bandwidth-delay product, i.e., W =n4

where n = number of hopsHow about caching-based protocols?


Setup

Simulation Parameters

Parameter Value

Network topology Linear chainPacket size 500 bytesNumber of packets(pktno) 500DTSN EAR interval 200 msecRouting protocol StaticMAC protocol 802.11bMAC retry limit (default) 3 (default)PHY error model Binary Symmetric ChannelMax. simulation time 2,000 secondsSimulator ns-2.31

Assumptions:Routing topology is stable

Cross-layer information isavailable

Scenario 1: Global Hotspot

Scenario 2: Localized Hotspot


DTSN Transmission Window OptimizationGoodput

AWopt = [CS , CS + ∆], ∆ = 10

2 8 10 20 30 40 500

20

40

60

80

100

120

140

Acknowledgment Window (AW) (in packets)

Goo

dput

(in

pac

kets

/sec

)

FER=0 FER=0.1 FER=0.3 FER=0.5 FER=0.7

(a) CS=10

2 8 10 20 30 40 500

20

40

60

80

100

120

140


Goo

dput

(in

pac

kets

/sec

)


(b) CS=20

Scenario 1 – Goodput, as a function of AW


DTSN Transmission Window OptimizationTransmission Cost

tx_cost =Ndata + Nack + Nnack + Nmack

pktno

2 8 10 20 30 40 500

50

100

150

200

250


Tra

nsm

issi

on C

ost


(a) CS=10

2 8 10 20 30 40 500

50

100

150

200

250


Tra

nsm

issi

on C

ost


(b) CS=20

Scenario 1 – Transmission Cost, as a function of AW


Performance Analysis

Protocols considered:

DTPA – The DTPA protocol, W = BDP(n) + 3

DTPA-CWL – The DTPA protocol, W = BDP(n)

DTSN+ – The DTSN protocol with the proposedenhanced NACK repair and adaptive MAC retry limitmechanisms

TCP− – The TCP protocol without the RTO exponentialbackoff


Performance AnalysisGoodput

Scenario 1

0 0.10 0.30 0.50 0.700

20

40

60

80

100

120

140

Frame Error Rate

Goo

dput

(in

pac

kets

/sec

)

DTPA−BDPDTPATCP−

DTSN+

Performance Gain of DTSN+

FER DTPA-CWL DTPA TCP−

0 96% 129% 88%0.10 51% 138% 59%0.30 71% 75% 137%0.50 720% 723% 1221%0.70 ∞ ∞ ∞

Scenario 2

0 0.10 0.30 0.50 0.700

20

40

60

80

100

120

140

Frame Error Rate

Goo

dput

(in

pac

kets

/sec

)


DTSN+



0 96% 129% 88%0.10 87% 135% 81%0.30 67% 123% 69%0.50 100% 92% 239%0.70 346% 266% 883%


Performance AnalysisTransmission Cost

Scenario 1

0 0.10 0.30 0.50 0.700

20

40

60

80

100

120

140

160

Frame Error Rate

Tra

nsm

issi

on C

ost


DTSN+



0 29% 58% 29%0.10 20% 65% 21%0.30 19% 54% 19%0.50 39% 54% 49%0.70 ∞ ∞ ∞

Scenario 2

0 0.10 0.30 0.50 0.700

20

40

60

80

100

120

140

160

Frame Error Rate

Tra

nsm

issi

on C

ost


DTSN+



0 29% 58% 29%0.10 28% 60% 28%0.30 23% 63% 22%0.50 25% 57% 25%0.70 31% 48% 49%


Performance AnalysisTCP cwnd Evolution

100 110 120 1300

2

4

6

8

10FER=0

Time (in sec)cw

nd (

in p

kt)

100 110 120 1300

2

4

6

8

10FER=0.1

Time (in sec)

cwnd

(in

pkt

)

100 110 120 1300

2

4

6

8

10FER=0.3

Time (in sec)

cwnd

(in

pkt

)

100 110 120 1300

2

4

6

8

10FER=0.5

Time (in sec)

cwnd

(in

pkt

)

100 110 120 1300

2

4

6

8

10FER=0.7

Time (in sec)

cwnd

(in

pkt

)

Scenario 1 – Evolution of TCP cwnd


Performance AnalysisPacket Reception

100 102 104 106 108 1100

50

100

150

200

250

300

350

400

450

500

Time (in seconds)

Seq

uenc

e N

umbe

r

DTPA−CWLDTPATCP−

DTSN+

(a) FER=0

100 105 110 1150

50

100

150

200

250

300

350

400

450

500

Time (in seconds)

Seq

uenc

e N

umbe

r


DTSN+

(b) FER=0.1

100 105 110 115 120 125 1300

50

100

150

200

250

300

350

400

450

500

Time (in seconds)

Seq

uenc

e N

umbe

r


DTSN+

(c) FER=0.3

100 150 200 250 300 3500

50

100

150

200

250

300

350

400

450

500

Time (in seconds)

Seq

uenc

e N

umbe

r


DTSN+

(d) FER=0.5

Scenario 1 – Packet Reception


Conclusion

Transmission window and loss recovery semantics forcaching-based transport mechanisms need to be optimized

We have proposed the following mechanisms

enhanced NACK recoveryadaptive MAC retry limitoptimal DTSN transmission window

DTSN+ significantly outperforms TCP and DTPA interms of goodput and energy-efficiency

Future work

consider more complex and dynamic network scenariosstudy performance in presence of network congestion


References

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11 N. M. C. Tiglao and A. M. Grilo, "An analytical model for transport layer caching in wireless sensornetworks," Performance Evaluation, vol. 69, no. 5, pp. 227-245, 2012.

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On the Optimization and Comparative Evaluation of a Reliable and Efficient Caching-based WSN Transport Protocol