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Proactive or time-driven sensor networks are devoted to the continuous reporting of environmental data to a sink or base station. An important issue associated with these networks is the management of a potentially large number of packets that are regularly generated by the set of nodes. A common solution at the MAC level is to use scheduled TDMA-based protocols, which minimize the communication duty cycle. However, TDMA schemes have strong synchronization requirements and exhibit low adaptability to changing traffic conditions. Thus, this paper proposes an alternative MAC protocol that overcomes the limitations of TDMA-based protocols while still approaching their performance in terms of lifetime. Essentially, this proposed solution combines randomization of the sensing and transmission process with a mechanism based on transmission announcements between adjacent nodes. The result is a lightweight protocol, called Randomized Data-Gathering (RDG), which exhibits desirable characteristics with respect to energy efficiency, synchronization avoidance, performance, scalability and adaptability to traffic changes in both time and space. The role of the randomization distribution is considered in detail, and an effective randomization scheme is selected. Both analytical and simulation methods are applied. |
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