JaldiMAC: taking the distance further

Abstract

WiFi has been promoted as an affordable technology that can provide broadband Internet connectivity to poor and sparsely populated regions. A growing number of deployments, some of substantial scale, are making use of WiFi to extend connectivity into rural areas. However, the vast majority of the 3.5 billion people living in rural villages [1] are still unserved. To reach these people, new technology must be developed to make small rural wireless Internet service providers (WISPs) profitable. We have identified radio towers as the largest expense for WISPs; to reduce or eliminate this barrier to entry, we propose a novel point-to-multipoint deployment topology that takes advantage of "natural towers" such as hills and mountains to provide connectivity even over great distances. We make this design practical with a new TDMA MAC protocol called JaldiMAC that (i) enables and is optimized for point-to-multipoint deployments, (ii) adapts to the asymmetry of Internet traffic, and (iii) provides loose quality of service guarantees for latency sensitive traffic without compromising fairness. To our knowledge, JaldiMAC is the first integrated solution that combines all of these elements. Our evaluation of JaldiMAC suggests that it fulfills its design goals. Our scheduler is able to provide a 71% decrease in jitter and superior latency characteristics in exchange for a 5% increase in average RX/TX switches, as compared to a stride scheduler. Overall, we find that JaldiMAC performs surprisingly well at this early stage.