Does Packet Replication Along Multipath Really Help ? Swades DE Chunming QIAO EE Department CSE...
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Transcript of Does Packet Replication Along Multipath Really Help ? Swades DE Chunming QIAO EE Department CSE...
Does Packet Replication Along Multipath Really Help ?
Swades DE Chunming QIAO EE Department CSE Department
State University of New York at Buffalo
Buffalo, NY 14260
{swadesd,qiao}@cse.buffalo.edu
Presentation Outline
Introduction Motivation for improved routing in wireless networks Cost issues with packet replication and selective forwarding Performance studies Results Summary and conclusion
Introduction
Possible features of ad hoc wireless networksNo centralized control
Nodes act as communicating entities as well as routersMultihop source-destination routesWide usage: required highly affordable cost required
Nodes may have limited memory and processing power Nodes may have limited mobility (e.g., in mobile ad hoc
networks)Nodes could be unattended: highly failure-prone nodes (e.g.,
in fiend sensor networks) Robust routing technique necessary
Battery operated: limited battery resource Energy-efficient routing required
Motivations for Improved Routing Existing multihop wireless routing techniques Packet replication (PR) along multiple routes (noted in [Kulik’99,
Ganesan’01]) simple but could be energy-intensive
Traffic splitting along multiple disjoint routes (D-MPR) [Lee’01,Tsirigos’01]
End node controlled – no routing flexibility at an intermediate stage
The preferred (primary) route is used, secondary routes are kept standby [Nasipuri’99, Ganesan’01] Additional energy for route maintenance Little traffic load balancing – may lead to quicker network partition
End-to-end ACK/NACK [Chen’99], or adjacent node NACK[Ganesan’01,Wan’02], or promiscuous listening [Johnson’96] based retransmission Involved flow-control mechanism, additional buffer space, transmit/receive
changeover delay, and receive power
Summary of Multipath Routing Approaches
Multipath routing approaches Disjoint multipath (D-MPR) Meshed multipath (M-MPR) [ WCNC’03]
Packet forwarding approaches Packet replication (PR) (or limited flooding) Selective forwarding [our proposed approach] Preferential routing (primary/secondary routes)
Throughput Performance Evaluation
Assumptions made in the analysis Equal length routes Regular mesh Additive white gaussian channel noise Equal failure probability of nodes (routers) For PR along meshed route, only one of possible multiple correct reception is
forwarded
An example disjoint multipath route
Meshed multipath routes considered for analysis
even odd, even odd, oddH H 2H H 2
H
Throughput Performance Evaluation (..contd.)
• 500 nodes randomly uniformly distributed in 500 m sq. area• Coverage range of each node 40 m• Gaussian channel with SNR at the receiver 14 dB Node failure probability: varied Packet size 50 Bytes 1000 data blocks (packets) per message Simulation results are within 95% confidence interval
Simulation parameters
Let
PR vs. SF: Equivalent Resource Usage
T be the the packet throughput (obtained for D-MPR and M-MPR, with PR and SF, respectively
D be the message size in packets (blocks)be the # of error correcting blocks required (using FEC coding)
for successful message receptionC
Then, minimum # error correcting blocks required is: [by Ayanoglu’93]
T
TDC
)1(
Equivalent energy usage Number of transmit-receive operations, i.e.,
)( RxTxNENCD )(
Likewise, equivalent channel resource usage Number of transmit operations, i.e.,
TxCDCh )(
Summary and Conclusion There have been numerous proposals that suggest packet replication (limited
flooding) along multipath as a potential routing approach in multihop wireless networks
Our original analytic studies supported by simulations show that: Packet replication approach has has higher per-packet throughput compared to
the selective forwarding approach along disjoint multipath as well as meshed multipath
However, overall performance of selective forwarding approach, when resource usage is taken into account, is superior in either multipath routing approaches.
This observation throws potential insight in routing protocol design for energy-constrained applications, such as sensor networks.
Our meshed multipath routing approach (WCNC’03) along with the observations in this paper will appear in Elsevier Computer Networks, special issue on Sensor Networks.