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Case study: Dharamsala Community Wireless Mesh Network
The Dharamsala Wireless-Mesh Community Network came to life in Febru- ary 2005, following the deregulation of WiFi for outdoor use in India. By the end of February 2005, the mesh had already connected 8 campuses.
Extensive testing during February of 2005 showed that the hard mountainous terrain is most suitable for mesh networking, as conventional point-to- multipoint networks, cannot overcome the line-of-sight limitations presented by the mountains. mesh topology also offered much larger area coverage, while the “self healing” nature of mesh routing, proved to be essential in places where electricity supply is very erratic at best.
The mesh backbone includes over 30 nodes, all sharing a single radio channel. Broadband Internet services are provided to all mesh members. The total up- stream Internet bandwidth available is 6 Mbps. There are over 2,000 computers connected to the mesh, The broadband internet connection is putting the mesh under great load. At present, the system seems to handle the load without any increase in latency or packet-loss. It is clear that scalability will become an issue if we continue to use a single radio channel. To solve this problem, new mesh routers with multiple radio channel support are being developed and tested in Dharamsala, with an emphasis on products that meet our technical require- ments and our economically viable. The initial results are very promising.
The mesh network is based on recurring deployments of a hardware device, which is designed and built locally – known as the Himalayan-Mesh-Router
332 Chapter 11: Case Studies
(http://drupal.airjaldi.com/node/9). The same mesh-routers are installed at every location, with only different antennas, depending on the geographical locations and needs. We use a wide range of antennas, from 8 - 11 dBi om- nidirectional, to 12 - 24 dBi directional antennas and occasionally some high- gain (and cost) sector antennas.
The mesh is primarily used for:
• Internet access • File-sharing applications • Off-site backups • Playback of high quality video from remote archives.
A central VoIP, software-based PBX is installed (Asterisk) and it provides ad- vanced telephony services to members. The Asterisk PBX is also interfacing the PSTN telephone network. However, due to legal issues it is presently used only for incoming calls into the mesh. Subscribers use a large variety of software-phones, as well as numerous ATAs (Analog Telephone Adaptors) and full-featured IP phones.
The encrypted mesh back-bone does not allow access to roaming mobile devices (notebooks and PDAs), so we have placed multiple 802.11b access- points at many of the same locations where mesh-routers are installed. The mesh provides the backbone infrastructure while these APs provide access to mobile roaming devices, where needed.
Access to the mesh back-bone is only possible by mesh-routers. Simple wireless clients lack the intelligence needed to “speak” the mesh routing pro- tocols and strict access policies. The mesh channel is therefore encrypted (WPA), and also “hidden” to prevent mobile devices from nding it or attempt- ing to access it. Allowing access to the mesh only by mesh-routers allows for strict access control policies and limitations to be enforced at the CPE (Client Premises Equipment) which is a crucial element needed to achieve end-to- end security, trafc-shaping, and quality-of-service.
Power consumption of the mesh-Router is less than 4 Watts. This makes them ideal for using with solar panels. Many of the Dharamsala Mesh routers are powered solely by small solar panels. The use of solar power in combina- tion with small antennas and low power routers is ideally suitable for disaster areas, as it very likely to survive when all other communication infrastructure is damaged.
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