Improving end-to-end packet delivery ratio in high traffic multi-hop ad hoc networksSyed Rehan Afzal, Majid Nabi, Sander Stuijk, Twan BastenElectronic Systems Group (ES), Dept. of EE, Eindhoven University of Technology

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Context & Problem Statement

Limited Energy

Limited Tx Range

Unreliable

Discovery (d > Tx)

Connectionless Data

End-to-end QoS

Dynamic Qualities

Packet Delivery Ratio (PDR)

Bandwidth

Latency

Throughput

Connection with highest Packet Delivery? Grub

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• We present xDDR (eXpected Directional Delivery Ratio)– Based on ETX metric– Leverages on the reasons discovered during our

experiments accounting to ETX’s shortcomings– xDDR shows considerable gain in end-to-end PDR

xDDR – An Improved Packet Delivery Ratio Estimation Metric

End-to-end Packet Delivery Ratio Comparison

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Network Architecture• Type of qualities

– Link-level – Stream/connection level

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Proactive Beaconing & Routing ModuleGrubNode A √ √ X √ X X √ √ . . . . . . .

Node B √ X X √ √ √ X √ . . . . . . .

Node C √ √ X X √ X √ . . . . . . .

Pick best & Reply

Link-level PDR

Connection Discovery

Data Transmission

Proactive Beaconing

In-band Signaling

Connection 1?Connection 2?Connection 3?

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• Role of MAC Layer & the broadcast problem– Unicast communication improves with MAC retry Limit– While broadcast packets are oblivious to MAC Retry Limit– Do not employ RTS/CTS mechanism– Simulation Environment (Omnet++ with INETMANET)

Motivation - Problems with ETX

Data Delivery Ratio v/s ETX estimate

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• Role of broadcast discoveries on link ETX– Under high traffic circumstances excessive broadcast

discovery packets cause some nodes to wrongly under estimate link quality

Motivation - Problems with ETX

Link ETX estimates w.r.t. route discoveries

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xDDR (eXpected Directional Delivery Ratio) - Outline

• Broadcast only during initialization phase• Uses unicast as opposed to broadcast to cater RTS/CTS

support as well as MAC retry limit• Selects a subset of neighboring nodes as proactive

beaconing unicast recipients

= number of proactive beacons received = Directional level delivery ratio = WindowSize = Beaconing interval

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xDDR – Window Selection• xDDR uses xDDRWindow, double the size of ETXWindow• Each node attempts to estimate PDR by selecting a window

where there is no overlap with RREQ broadcast discovery packets

• This window is the xDDRmWindow

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Experimental Setup & Results10

End-to-end Packet Delivery Ratio Comparison

xDDR vs ETX Estimation

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xDDR packet overhead11

Grub

Ratio of packets transmitted by MAC layer of each node w.r.t. total UDP packets delivered

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― Proposed xDDR, an improved link-level delivery ratio estimation metric based on ETX

― In high traffic scenarios, selective unicast beaconing yields more accurate packet delivery ratio estimates (xDDR-I)

― xDDR-I coupled with xDDRWindowSelection avoids quality estimation during conflicting window slots

― Coupled with quality aware routing results in a higher end-to-end multi-hop data delivery

― This implies on average 3 times gain over Min. hop count, 1.94 times gain over ETX and 1.7 times gain over HETX

Conclusions

Thank You

S. Rehan Afzals.r.afzal@tue.nlElectronic Systems Group (ES), Dept. of EE, Eindhoven University of Technology, The Netherlands