npr - NonpipelinedRelayImprovesThroughput...

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1 Non-pipelined  Relay Improves Throughput  Performance of Wireless Ad-hoc Networks
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2 Ad-hoc Networks Infrastructure-less  wireless networks dynamically  formed using only mobile hosts (no routers) Mobile hosts themselves double up as routers Multi-hop  paths … Highly  resource constrained  -   limited wireless  bandwidth and high interference Network topology dynamic as all hosts are  mobile
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3 Outline Pipelined and Non-pipelined relay models Performance comparisons Idealized conditions Practical conditions Distributed Forwarding Protocol (DFP) Summary
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4 Pipelined Relay (PR) Source node transmits packets into the  network with the objective of keeping the pipe  full between the destination and itself Source pumps packets at a rate sustainable  by the end-to-end path If the hop-length of a flow  f i  is  h ,  then at  steady state the flow will have  h i   mini-flows  contending in the network
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5 PR Illustration Time I 1 I 3 D S Packet 1 Packet 1 Packet 1 Packet 1 Packet 2 Packet 2 Packet 2 Packet 3 Packet 3 Packet 3 Packet 4 Packet 2 Packet 5 Packet 4 S S S I 3 I 3 I 3 D D D I 1 I 1 I 1 I 2 I 2 I 2 D I 3 I 2 I 1 S I 2
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6 Non-Pipelined Packet Relay  (nPR) Source does not perform pipelining of data  packets Source transmits a packet into the network only  when the preceding packet arrives at the  destination Each flow has exactly  one   mini-flow in the  network at any given time-instant
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7 nPR Illustration I 1 I 2 I 3 D S Time Bundle 1 Bundle 1 Bundle 1 Bundle 1 Bundle 2 S S S S I 1 I 1 I 1 I 1 I 2 I 2 I 2 I 2 I 3 I 3 I 3 I 3 D D D D
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8 Comparison – Idealized  Conditions Throughput Capacity Fairness Network Capacity
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9 Model Network topology : 3-D sphere of unit surface  area nodes randomly distributed in the network Every node is a source : total of n flows in the  network Nodes use constant transmission range to keep  network minimally connected [Model adopted from Gupta & Kumar, 2001]
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10 Notations W : capacity of the channel (or contention region) M : Total number of contention regions in the  network l av :  Average hop-length of flows p h ( k ) : number of flows with hop-length  k
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11 Throughput Capacity Sum of the e2e throughputs of all flows in the  network nPR  provides more throughput to shorter hop  flows than longer hop ones Every unit of throughput that a longer hop flow  sacrifices increases the throughput of  l av  single  hop flows Thus the average throughput achieved by the  flows in the network is increased
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12 Throughput capacity (contd.) Contention level : Number of mini-flows contending for a 
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This note was uploaded on 12/14/2009 for the course ECE 6610 taught by Professor Staff during the Fall '08 term at Georgia Institute of Technology.

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npr - NonpipelinedRelayImprovesThroughput...

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