Published on June 20, 2007
Long Distance WiFi Trial Long Ermanno Pietrosemoli Distance WiFi Trial EsLaRed-ULA www.eslared.org.ve Ermanno Pietrosemoli Venezuela International Summit for EsLaRed-ULA Community Wireless Networks Venezuela Columbia, Md. May 18, 2007 Pico del Aguila
Motivation • For rural area, Wireless is the only economically feasible solution for achieving digital inclusion • WiFi is by far the less expensive technology available, and can provide voice and data • Interference is less severe in sparsely populated areas Pietrosemoli 2
WiFi LD Background • 70 km link operational in Merida since 2001 • Swedish space agency 300 km transmission towards a stratospheric balloon • Defcon contest in 2004 achieved 125 miles w/o amplifiers Pietrosemoli 3
WiFi LD Background • EHAS program for health maintenance support in rural areas • Berkeley’s TIER group activities in several countries • EsLaRed 279 km link with 100 mW transmitters and repurposed antennas in 2006 Pietrosemoli 4
Issues • MAC of WiFi designed for up to 100 m, extending the range two orders of magnitude requires modifications • CSMA/CA not well suited for Pt-Pt links • Established Telecom operators vested interests Pietrosemoli 5
279 km path Pietrosemoli 6
279 km path Pietrosemoli 7
Aerial view of El Aguila site Pietrosemoli 8
View from El Aguila site Pietrosemoli 9
El Baul Site Accounting for the declination, we aimed the antenna to a bearing of 277 degrees Pietrosemoli 10
TIER Wireless routers at Baul Pietrosemoli 11
We were able to establish a video and audio communication over the 279 km path: Iperf showed a solid throughput greater than 3 Mbps in both directions Pietrosemoli 12
With the Linksys WRT54 Pietrosemoli 13
With the Linksys WRT54 The measured throughput was above 65 kbps, enough to sustain an audio and video session: Pietrosemoli 14
Can we do better? Pietrosemoli 15
From Platillon: Pietrosemoli 16
Aguila-Platillon (382 km) • We tried at different power • The Iperf results for the 382 km settings and there was a link with TIER routers and considerable variation on the TDMA:merida2:~# ping results, 10.0.200.12PING 10.0.200.12 (10.0.200.12) from 10.0.200.12 : • So we concluded that although 56(84) bytes of data.64 bytes from communication over this path 10.0.200.12: icmp_seq=1 ttl=64 is feasible, further testing are time=0.745 ms64 bytes from required to ascertain the 10.0.200.12: icmp_seq=2 ttl=64 stability of this kind of links. time=0.399 ms64 bytes from 10.0.200.12: icmp_seq=3 ttl=64 time=0.399 ms--- 10.0.200.12 ping statistics ---3 packets transmitted, 3 received, 0% loss, time 2003msrtt min/avg/max/mdev = 0.399/0.514/0.745/0.164 Pietrosemoli 17
We then repeated the experiment over the 382 km path using two Linksys boxes, obtaining the following results: • --10.0.1.1 ping statistics ---58 packets transmitted, 57 received, 1% packet loss, time 57569 ms rtt • min/avg/max/mdev = 6.165/11.990/40.591/8.011 ms Pietrosemoli 18
Acknowledgements • This work was funded by ICA-IDRC • Dr. Eric Brewer from Berkeley University provided the wireless routers with the modified MAC for long distance, as well as enthusiastic support through his collaborator, Sonesh Surana • RedULA, CPTM, Dirección de Servicios ULA and Fundacite Mérida contributed to this trial • Roger Coudé, author of the free Radio Mobile Software, which has been so useful to the international wireless community Pietrosemoli 19
Members of the Team El Aguila Baúl and Platillón sites • Javier Triviño, EsLaRed • Leonardo González V., Dirección de Servicios – • José Torres M., CPTM- ULA ULA • Alejandro González, • Francisco Torres N., RedULA RedULA • Leonardo González G., EsLaRed • Ermanno Pietrosemoli, EsLaRed Pietrosemoli 20
Conclusions • WiFi is a viable and economic means for wireless links at distances of hundreds of kilometers when a good LOS is available. • TDMA over WiFi as implemented by the TIER group of UC Berkeley has shown a remarkable throughput greater than 3 Mbps over a 300 km on a Pt- to- Pt link. Pietrosemoli 21
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