In this paper, we first propose a redundant radix based number (RBN) representation for encoding the data to be transmitted in a wireless network. This RBN encoding uses three possible values - 0, 1 and @math , for each digit to be transmitted. We then propose to use silent periods (zero energy transmission) for transmitting the 0's in the RBN encoded data thus obtained. This is in contrast to most conventional communication strategies that utilize energy based transmission (EbT) schemes, where energy expenditure occurs for transmitting both 0 and 1 bit values. The binary to RBN conversion algorithm presented here offers a significant reduction in the number of non-zero bits in the resulting RBN encoded data. As a result, it provides a highly energy-efficient technique for data transmission with silent periods for transmitting 0's. We simulated our proposed technique with ideal radio device characteristics and also with parameters of various commercially available radio devices. Experimental results on various benchmark suites show that with ideal as well as some commercial device characteristics, our proposed transmission scheme requires 69 less energy on an average, compared to the energy based transmission schemes. This makes it very attractive for application scenarios where the devices are highly energy constrained. Finally, based on this transmission strategy, we have designed a MAC protocol that would support the communication of such RBN encoded data frames.
Recent research efforts on reducing energy consumption have mainly been focussed on the MAC layer design @cite_3 , optimizing data transmissions by reducing collisions and retransmissions @cite_1 and through intelligent selection of paths or special architectures for sending data @cite_4 . A survey of routing protocols in wireless sensor networks can be found in @cite_3 . In all such schemes, the underlying communication strategy of sending a string of binary bits is energy based transmissions (EbT) @cite_9 @cite_6 , which implies that the communication of any information between two nodes involves the expenditure of energy for the transmission of data bits. In @cite_9 , a new communication strategy called Communication through Silence (CtS) has been proposed that involves the use of silent periods as opposed to energy based transmissions. CtS, however, suffers from the disadvantage of being exponential in time. An alternative strategy, called Variable-base tacit communication (VarBaTaC) has been proposed in @cite_6 that uses a variable radix-based information coding coupled with CtS for communication.
@cite_4 @cite_9 @cite_1 @cite_6 @cite_3
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Energy conservation is a major concern in wireless sensor networking. Conventionally in wireless communications, each bit transmitted by a node consumes one unit of energy. Some recent advances, however, explore silent time intervals between signal transmissions to convey information (Zhu and Sivakumar [1]). Such a scheme of Communication through Silence (CtS), while reducing energy consumption for sensor nodes, introduces long delay. In this paper, we propose Variable-Base Tacit Communication (VarBaTaC) to mitigate the delay introduced by CtS. We also develop three MAC protocols based on VarBaTaC for different environments. We then outline experiment designs for further investigations and point out some interesting future research directions. Accurate analytical expressions of delay and packet reception probabilities, and energy consumption of duty-cycled wireless sensor networks with random medium access control (MAC) are instrumental for the efficient design and optimization of these resource-constrained networks. Given a clustered network topology with unslotted IEEE 802.15.4 and preamble sampling MAC, a novel approach to the modeling of the delay, reliability, and energy consumption is proposed. The challenging part in such a modeling is the random MAC and sleep policy of the receivers, which prevents to establish the exact time of data packet transmission. The analysis gives expressions as function of sleep time, listening time, traffic rate and MAC parameters. The analytical results are then used to optimize the duty cycle of the nodes and MAC protocol parameters. The approach provides a significant reduction of the energy consumption compared to existing solutions in the literature. Monte Carlo simulations by ns2 assess the validity of the analysis. This work addresses the problem of balancing the trade-off between the energy cost due to communication and the accuracy of the tracking-based trajectories’ detection and representation in Wireless Sensor Networks (WSNs) settings. We consider some of the approaches used by the Moving Objects Databases (MOD) and Computational Geometry (CG) communities, and we demonstrate that with appropriate adaptation, they can yield significant benefits in terms of energy savings and, consequently, lifetime of a given WSN. Towards that, we developed distributed variations of three approaches for spatio-temporal data reduction – two heuristics (Dead-Reckoning and the Douglas-Peuker algorithm), and a variant of a CG-based optimal algorithm for polyline reduction. In addition, we examine different policies for managing the buffer used by the individual tracking nodes for storing the partial trajectory data. Lastly, we investigated the potential benefits of combining the different data-reduction approaches into ”hybrid” ones during tracking of a particular object’s trajectory. Our experiments demonstrate that the proposed methodologies can significantly reduce the network-wide energy expenses due to communication and increase the network lifetime. Wireless sensor networks (WSNs) are typically characterized by a limited energy supply at sensor nodes. Hence, energy efficiency is an important issue in the system design and operation of WSNs. In this paper, we introduce a novel communication paradigm that enables energy-efficient information delivery in wireless sensor networks. Compared with traditional communication strategies, the proposed scheme explores a new dimension - time, to deliver information efficiently. We refer to the strategy as Communication through Silence (CtS). We identify a key drawback of CtS - energy - throughput trade-off, and explore optimization mechanisms that can alleviate the trade-off. We then present several challenges that need to be overcome, primarily at the medium access control layer of the network protocol stack, in order to realize CtS effectively.