Synchronous transmission has been exploited recently for accelerating fundamental operations of wireless sensor networks like data dissemination, data collection, and network-wide agreement by an order of magnitude. Although these protocols (e.g., Glossy) have shown to be highly reliable for small packet sizes, the use of large packet sizes coupled with an excessive number of simultaneous transmissions can reduce reliability significantly. Our work is motivated by the observation that capture effect can improve the reliability of synchronous transmission. We experimentally study the effect of physical layer capture and identify guidelines in which it can be exploited to enhance reliability. Based on these observations, we propose Syncast, a data dissemination protocol that improves over Glossy by exploiting capture effect over multichannels. The evaluation shows that Syncast provides a robust, reliable, and scalable data dissemination of large packets with lower end-to-end delay and up to 92% reduced radio-on-time.

In this paper, we present a dual-radio framework for implementing MAC protocols in wireless sensor networks. The framework is based on the observation that MAC operations can be categorized into time-dependent and bandwidth-dependent. Unlike existing dual-radio systems, we do not propose a new MAC protocol. Instead, we show how a given MAC protocol can be re-implemented using a dual-radio framework resulting in substantial energy savings. Our approach is generic. Different categories of MAC protocols can be re-implemented using dual radios, including synchronous (e.g., SMAC), asynchronous (e.g., BMAC) and hybrid (e.g., SCP-MAC). The proposed framework is easy-to-implement. We have been able to re-implement SMAC, BMAC and SCP-MAC in TinyOS to dual-radio implementations using a combination of mica2 and micaZ motes. Extensive evaluation shows that a reduction of up to 5 times in energy consumption can be attained.

A large percentage of links in low-power wireless sensor networks are of intermediate quality. To the best of our knowledge, opportunistic exploitation is currently the only way to use these links. However, such exploitation requires overhearing which consumes a significant amount of energy. In this paper, we propose a new approach to exploit intermediate quality (IQ) links through channel diversity with a new protocol, called IQ Link Transformation Protocol (ILTP), that does not require overhearing. ILTP transforms IQ links into good links thus allowing us to exploit such links continuously rather than using them only opportunistically. Our key insight is that the packet reception ratios (PRR) across different channels on IQ links are not correlated and it is common on such links to find channels that change in quality on the time scale of a few minutes. Consequently, when the link quality of a channel is bad, it is highly likely that a good channel can be found and its quality will remain good for at least a few minutes. Our evaluations on three large-scale test beds demonstrate that ILTP is able to consistently transform the IQ links into good links. We observe that even a poor link with a PRR of 0.05 can be transformed into a good link with a PRR greater than 0.9. When ILTP is integrated with CTP, the default collection tree protocol for TinyOS, the average number of transmissions per end-to-end packet delivery is reduced by 24% to 58%.