Time-of-flight echo techniques have been proposed to estimate the distance between a local and a target station over regular WiFi radio devices. Their current main shortcoming is that they are affected by severe noise components at both stations. Our aim in this work is to quantify the noise level introduced by the target in order to derive practical limits of the ranging accuracy achievable using off-the-shelf devices. For this purpose, we develop a low-noise experimental platform which allows us to measure the echo-reply delay with very high accuracy. Our preliminary results with two popular chipsets from different manufacturers show that the median echo-reply delay at the target is never equal to the nominal SIFS value, and it deviates by approximately 10−20 ns over time, suggesting a practical ranging accuracy limit of 3 m.
Mobile technology is already playing an important role in the economic and social empowerment of rural communities in developing regions. However, rural areas often suffer from slow and unreliable network infrastructures. This limits access to content and services that may promote economic development. Focusing on under-served areas in rural developing regions, we aim to explore how ICT systems for collective intelligence can be used to foster economic and social empowerment of rural communities. In our model, microentrepreneurs equipped with low-complexity cinema-in-a-backpack systems can deliver educational and entertainment content in remote villages. The content is distributed to microentrepreneurs by means of opportunistic (delay-tolerant) networks. In such networks, mobile infostations mounted on public transportation vehicles deliver content without the support of telecom operators or any other dedicated network infrastructure. The delay tolerance of opportunistic networks makes them ideally suited to environments with under-developed ICT infrastructures. We discuss the technical challenges behind distributing digital content with a low-cost delivery mechanism and opportunistic networks. We also establish the case for DTN as a socially-grounded approach to mobile empowerment in the context of rural development. Toward this end, we present our work in an ongoing project that provides communities in rural South Africa with cinema experience by training microentrepreneurs in the operation of a DTN-enabled microfranchise.
Wireless communication offers access to information even to users living in areas where little to no access to affordable communication channels is available. Delay Tolerant Networks (DTNs) enable content distribution in such areas, using mobility of devices and avoiding the need for traditional network infrastructure. In DTNs, data is passed from mobile device to mobile device, whenever possible, in an intelligent way. DTNs have the potential to reach out to under-served regions where cellular Internet access (3G, LTE, and beyond) might be expensive or unavailable. We are interested in DTNs for distributing media from cities to under-served rural areas. The content is distributed to the target destinations, using either public transportation or commuting vehicles such as taxis, equipped with wireless DTN-enabled devices. At each target destination, a micro-entrepreneur business is established with the help of our network: Microentrepreneurs use DTN-enabled projectors (also referred to as cinemas-in-a-backpack) to deliver entertainment content at low cost, and exploit the opportunity to create a microbusiness around the show events. In this paper, we introduce the DTN system setup, present performance results of laboratory tests and test with a local commuter train of periodic and predictable mobility. Further, we present the target scenario and specific technical challenges. We aim to explore opportunities for a rural, under-served region in the north of Pretoria, South Africa.
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