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Unformatted text preview: Reliability for our wireless networks was our key selling point. On the net- work side this translated into sizable investments in infrastructure substitu- tion, such as backup power, and attention to details such as crimping and cabling. The most ordinary reasons for a single customer to lose connectivity were cabling or crimping issues. Radio failures were essentially unheard of. A key competitive advantage of our customer installation process is that we pushed contractors to adhere to tight speci f cations. It was common for well- managed customer sites to remain connected for hundreds of days with zero unscheduled downtime. We controlled as much of our infrastructure as pos- sible (i.e building rooftops). As attractive as potential alliances with cellular providers seem, in our experi- ence they raise more problems than they solve. In East Africa, Internet busi- nesses generate a fraction of the revenue of mobile telephony, and so are mar- ginal to the cellular companies. Trying to run a network on top of infrastructure that doesn ¡ t belong to you and is, from the point of view of the cellular provider, a goodwill gesture, will make it impossible to meet service commitments. Implementing fully redundant networks, with fail-over or hotswap capability is an expensive proposition in Africa. Nonetheless the core routers and VPN hardware at our central point of presence were fully redundant, con f gured for seamless fail-over, and routinely tested. For base stations we took the deci- sion not to install dual routers, but kept spare routers in stock. We judged that the 2-3 hours of downtime in the worst case (failure at 1AM Sunday morning in the rain) would be acceptable to clients. Similarly weekend staff members had access to an emergency cupboard containing spare customer premises equipment, such as radios and power supplies. Flexibility was engineered into both the logical and RF designs of the net- work. The point-to-point VPN tunnel architecture rolled out in Nairobi was extraordinarily F exible in service of client or network needs. Client connec- tions could be set to burst during off-peak hours to enable offsite backup, as a single example. We could also sell multiple links to separate destinations, increasing the return on our network investments while opening up new serv- ices (such remote monitoring of CCTV cameras) to clients. On the RF side we had enough spectrum to plan for expansion, as well as cook up an alternative radio network design in case of interference. With the growing number of base stations, probably 80% of our customer sites had two possible base station radios in sight so that if a base station were de- stroyed we could restore service rapidly....
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Wireless+Networking+in+the+Developing+World_Part18 -...

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