- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Neighbor Discovery (ND) plays an important role in the initialization phase of wireless sensor networks. In real deployments, sensor nodes may not always be awake due to limited power supply, which forms low-duty-cycle networks. Existing researches on the problem of ND in low-duty-cycle networks are all based on the assumption that a receiver can receive only one packet successfully at a time. k-Multipacket Reception (MPR) techniques (i.e., k (k ≥ 2) packets can be successfully received at a time) have shown their significance in improving packet transmission. However, how MPR can benefit the problem of ND is still unknown. In this paper, we are the first to discuss the problem of ND in low-duty-cycle networks with MPR. Specifically, we first present a novel ALOHA-like protocol, and show that the expected time to discover all n−1 neighbors is View the MathML source by reducing the problem to a generalized form of the classic K Coupon Collector’s Problem . Second, we show that when there is a feedback mechanism to inform a node whether its transmission is successful or not, ND can be finished in time View the MathML source. Third, we point out that lacking of knowledge of n results in a factor of two slowdown in the two protocols proposed. We also discuss some extensions related to the protocol’s design and different MPR models. Finally, we evaluate the ND protocols introduced in this paper, and compare their performance with the analysis results.
7. Conclusion and future work
In this paper, we have analyzed the neighbor discovery problem in low-duty-cycle WSNs, and have derived the time complexity for two protocols respectively. For the ALOHA-like protocol, the expected time to finish ND is O( n log n log log n k ) with k-MPR. Furthermore, if afeedback mechanism is introduced into the system, the expected time is O( n log log n k ). In addition, the lack of knowledge of n results in a factor of two slowdown in comparison with the n-known case. Discussions are presented to solve the issues in real implementations. Furthermore, we have presented another MPR model, i.e., multi-channel MPR model, and pointed out the time complexity of ALOHA-like protocols under this model. Our theoretical results are verified by extensive simulations. In the future, we would like to evaluate these protocols by doing test-bed experiments. Also we would like to extend the protocols to some more realistic situations, e.g. nodes with different clocks, nodes with different duty cycles and more realistic radio models.