The Meraka Indoor wireless mesh test The Meraka Indoor wireless mesh test bed bed A new multi hop routing benchmarking tool A new multi hop routing benchmarking tool David Johnson Senior Researcher Wireless Africa Programme Meraka CSIR
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The Meraka Indoor wireless mesh test bedThe Meraka Indoor wireless mesh test bedA new multi hop routing benchmarking toolA new multi hop routing benchmarking tool
David Johnson
Senior Researcher
Wireless Africa Programme
Meraka
CSIR
450 million rural people in Africa areisolated from the rest of the world
Connect them all by 2017
Sound crazy?
How do these sound?
7 trillion wireless devices serving 7 billion people by 2017 …Wireless World Research Forum
Affordable mobile communications for half the world's population by 2015 …Nokia
Half the world have Internet access by 2015 …AMD 50x15
Creates cognitive dissonance
Here’s how it could be done
Turn the “first mile” into an open bazaar of community networks
As easy to setup as a TV
Telcos just provide backhaul
Income stays in the communities
Modernized without being urbanized
Ubuntu = community networks = mesh networks
• Plenty of research problems to address– Routing protocols and routing metrics– Gateway selection for multiple gateways– Power efficiency– Auto channel allocation– Distributed services– Multimedia over mesh– Clustering optimization– Smart antennas for mesh– Business models for village entrepreneurs– Security over mesh– Vulnerability of first time exposure to the internet– Building technical skills in developing regions– Logistics
Why build a test bed?
Mathematical models good enough for rules of thumb but no tractable solution for a real network
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Simulation models good for early protocol development and testing but still far from reality
Real outdoor wireless = reality but difficult to build and manage
Indoor test beds provide controlled environment and expose theoretical simplifications
Construction of the meraka wireless grid
Construction of the meraka wireless grid
Construction of the meraka wireless grid
Construction of the meraka wireless grid
Construction of the meraka wireless grid
Challenges when building experiments
Challenges when building experiments
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rssi
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Challenges when building experiments
• Which combination of mode/rate/txpower to use• Experiments are time consuming ... 52 hours to test 4
routing protocols using all combinations of 49 nodes in the grid with 20 second test time
Electromagnetic modelling of the grid
Done with WIPL-D modelling software
Electromagnetic modelling of the grid
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distance between nodes, m
meas: 11bDS1Mbps-5ch8model: ant1_box_7x7model: wire_model_7x7
Results – 49 node multi hop chain
Results – 49 node multi hop chain
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Results – 49 node multi hop chain
• After 4 hops – Gupta best = 50%– Gupta worst = 42.47%– Gupta indoor measurements = 9.74%– Meraka lab = 25.7%
Choosing routing protocols to benchmark
Results – hop count distribution
Results –Routing traffic overhead
Results –Routing traffic overhead
Results – throughput, packet loss, delayString of 7 nodes
Forward HOP count Route changes Packet loss Delay Delay(stddev) TP No link
AODV 1.33 0.43 11.19 37.24 116.64 2723.36 1DYMO 1.52 0 9.52 3.65 2.37 2907.67 0OLSR_ETX 1.43 0.1 8.57 27.56 101.91 2730.69 0OLSR_RFC 1.67 0.76 2.14 5.35 5.35 2923.64 0
Results – throughput, packet loss, delayFull 7x7 grid
Forward HOP count Route changes Packet loss Delay Delay(stddev) TP No link
AODV 1.36 0.53 71.22 117.87 317.35 773.33 1425DYMO 2.2 0.11 32.81 64.72 150.2 1165.66 413OLSR_ETX 1.84 0.25 24.05 68.84 247.78 1187.57 453OLSR_RFC 2.28 2.34 22.22 67.44 132.49 1330.05 381
Comparison of throughput to baseline
Conclusions
• Proved that multi hop wireless networks possible on scaled test beds (up to 5 hops were achieved in a space of 7Mx7M)
• Complexity in the grid is high and produces a worst case scenario for routing algorithms.
• The AODV protocol showed the weakest performance but had the lowest routing overhead.
• DYMO showed good results for its low routing overhead with the least amount of delay for the full 7x7
• The RFC version of OLSR had the best overall performance the full 7x7 grid.
• OLSR with the ETX extension performed better in medium size networks of about 21 nodes.
Future improvements to the mesh lab
• Compare results to NS2 simulations
• Add a lab sandbox• Add a lab scheduler to make it
simple for multiple interested parties to run experiments
• Build a measurement framework to simplify setting up experiments
• Test virtual mobility and install a roaming robot
• Experiment with parameters beyond the RFC values for routing protocols
• Add support for power measurements
• Add support for control of smart antennas
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