Link-level Link-level Measurements from Measurements from an 802.11b Mesh an 802.11b Mesh NetworkNetwork

Dainel Aguyo, John Dainel Aguyo, John Bicket,Sanjit Biswas, Glenn Bicket,Sanjit Biswas, Glenn

Judd, Robert MorrisJudd, Robert MorrisM.I.T , CMUM.I.T , CMU

AbstractAbstract Roofnet Roofnet を使用して、実際にを使用して、実際に MANETMANET

を構築を構築 ロスの解析を行なうロスの解析を行なう

Roofnet Roofnet

RoofnetRoofnet

Distribution of Delivery Distribution of Delivery ProbabilitiesProbabilities

Links with intermediate loss rates Links with intermediate loss rates are common, with no sharp are common, with no sharp transition between high and low transition between high and low packet loss rates.packet loss rates.

Spatial Distribution of Loss RateSpatial Distribution of Loss Rate Inter-node distance is not strongly Inter-node distance is not strongly

correlated with whether nodes can correlated with whether nodes can communicates.communicates.

Time Variation of Loss RateTime Variation of Loss Rate Most links have non-bursty loss Most links have non-bursty loss

patterns.patterns.

Effect of Signal-to-Noise RatioEffect of Signal-to-Noise Ratio Links with very high signal Links with very high signal

strengths are likely to have low strengths are likely to have low loss rates, but in general signal loss rates, but in general signal strength has little predictive value.strength has little predictive value.

Effect of Transmit Bit-rateEffect of Transmit Bit-rate A link isA link is likely to have a significant likely to have a significant

loss rate at its optimum 802.11b loss rate at its optimum 802.11b bit-rate.bit-rate.

Effect of Multi-pathEffect of Multi-path Mutil-path fading greatly affects Mutil-path fading greatly affects

outdoor links and helps explain outdoor links and helps explain intermediate loss ratesintermediate loss rates

Comparison of Routing Comparison of Routing Metrics for Static Multi-Metrics for Static Multi-Hop Wireless NetworksHop Wireless Networks

Richard Draves, Richard Draves, Jitendra Padhy, Brian Jitendra Padhy, Brian

ZillZillMicrosoft ResearchMicrosoft Research

AbstractAbstract DSR like DSR like のの MANETMANET プロトコルを実プロトコルを実

装して、装して、 Path Metric Path Metric の違いによる、の違いによる、性能評価を行なう。性能評価を行なう。

Metric – ETX, Per-hop RTT, per-hop Metric – ETX, Per-hop RTT, per-hop packet pair, minimum-hoppacket pair, minimum-hop

Link Quality MetricsLink Quality Metrics Hop Count: shortest-path routingHop Count: shortest-path routing RTT: round-trip time latencyRTT: round-trip time latency PktPair: packet-pair latencyPktPair: packet-pair latency ETX: expected transmission countETX: expected transmission count

Ad Hoc Routing ArchitectureAd Hoc Routing Architecture DSR + support link quality metricDSR + support link quality metric

（（ Link-Quality Source Routing)Link-Quality Source Routing) Supports IPv4, IPv6 etc Supports IPv4, IPv6 etc unmodifiedunmodified Supports multiple link technologiesSupports multiple link technologies

Ethernet 802.11 802.16

Mesh Connectivity Layer (with LQSR)

IPv4 IPv6 IPX

Impact of Long Lived TCP FlowsImpact of Long Lived TCP Flows Route Flapping Route Flapping のため、のため、 RTTRTT ・・

PktPairPktPair は性能が良くないは性能が良くない

Impact of Path LengthImpact of Path Length EXTEXT は は shortest hop shortest hop より、より、 hophop 数数

の多い経路を使用しているの多い経路を使用している

Impact of Path Length(Cont.)Impact of Path Length(Cont.)

Multiple Simultaneous TCP Multiple Simultaneous TCP TransferTransfer

pktpair pktpair は ホップ数が増えるほど低下は ホップ数が増えるほど低下

Web-like TCP TransfersWeb-like TCP Transfers Hop Hop 数が長いと、数が長いと、 ETXETX のほうがのほうが HOPHOP

に比べ性能がよいに比べ性能がよい

A Mobile ScenarioA Mobile Scenario ETX ETX ではノードの移動による経路品質ではノードの移動による経路品質

の変化に対し、適応できないの変化に対し、適応できない