On the Feasibility of the Link Abstraction in Wireless Mesh Networks

Outdoor community mesh networks based on IEEE 802.11 have seen tremendous growth in the recent past. The current understanding is that wireless link performance in these settings is inherently unpredictable, due to multipath delay spread. Consequently, researchers have focused on developing intelligent routing techniques to achieve the best possible performance. In this paper, we are specifically interested in mesh networks in rural locations. We first present detailed measurements to show that the PHY layer in these settings is indeed stable and predictable. There is a strong correlation between the error rate and the received signal strength. We show that interference, and not multipath fading, is the primary cause of unpredictable performance. This is in sharp contrast with current widespread knowledge from prior studies. Furthermore, we corroborate our view with a fresh analysis of data presented in these prior studies. While our initial measurements focus on 802.11b, we then use two different PRY technologies as well, operating in the 2.4-GHz ISM band: 802.11g and 802.15.4. These show similar results too. Based on our results, we argue that outdoor rural mesh networks can indeed be built with the link abstraction being valid. This has several design implications, including at the MAC and routing layers, and opens up a fresh perspective on a wide range of technical issues in this domain

To mesh or not to mesh: flexible wireless indoor communication among mobile robots in industrial environments

Mobile robots such as automated guided vehicles become increasingly important in industry as they can greatly increase efficiency. For their operation such robots must rely on wireless communication, typically realized by connecting them to an existing enterprise network. In this paper we motivate that such an approach is not always economically viable or might result in performance issues. Therefore we propose a flexible and configurable mixed architecture that leverages on mesh capabilities whenever appropriate. Through experiments on a wireless testbed for a variety of scenarios, we analyse the impact of roaming, mobility and traffic separation and demonstrate the potential of our approach

Generic sensor network architecture for wireless automation (GENSEN)

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Implementation and evaluation of the sensornet protocol for Contiki

Sensornet Protocol (SP) is a link abstraction layer between the network layer and the link layer for sensor networks. SP was proposed as the core of a future-oriented sensor node architecture that allows flexible and optimized combination between multiple coexisting protocols. This thesis implements the SP sensornet protocol on the Contiki operating system in order to: evaluate the effectiveness of the original SP services; explore further requirements and implementation trade-offs uncovered by the original proposal. We analyze the original SP design and the TinyOS implementation of SP to design the Contiki port. We implement the data sending and receiving part of SP using Contiki processes, and the neighbor management part as a group of global routines. The evaluation consists of a single-hop traffic throughput test and a multihop convergecast test. Both tests are conducted using both simulation and experimentation. We conclude from the evaluation results that SP's link-level abstraction effectively improves modularity in protocol construction without sacrificing performance, and our SP implementation on Contiki lays a good foundation for future protocol innovations in wireless sensor networks