A novel probabilistic algorithm for low duty-cycle dynamic (mobile sensors) wireless sensor networks (WSNs) is proposed. The rapid development of smart phones and mobile sensors had fostered a demand for opportunistic encounter-based networking to support mobile social networking and proximity-based gaming. However, the performance of such applications was restricted by a lack of specialised neighbour discovery algorithms. For existing algorithms, even though the probabilistic algorithms have good performance in average discovery latency, when working with a low duty-cycle, the performance is not so encouraging. Deterministic algorithms can provide bound time for the worst discovery latency, but they sacrificed the average discovery latency. In response, a novel prime-set-based neighbour discovery algorithm (PSBA) is proposed. The PSBA is a probabilistic algorithm tailored to low duty-cycle dynamic WSNs. Leveraging on the certainty of the deterministic algorithm and the randomness of the probabilistic algorithm, the inherent long tail of the probabilistic algorithm can be improved. Also, the average discovery latency of the PSBA can be drastically reduced compared to existing algorithms, which precisely meets the requirements in low duty-cycle dynamic WSNs.Introduction: In dynamic WSNs, the encounter of two sensors is not predictable, and so is how soon they will leave each other. Therefore, how to make a sensor discover its transient neighbours as soon as possible is a primary concern. As far as we know, existing neighbour discovery algorithms fall into two categories, namely group-based approaches [1, 2] and pairwise approaches. Typically, pairwise approaches can be further divided into two categories, i.e., the probabilistic algorithm and the deterministic algorithm.Deterministic algorithms can provide bound time for the worst discovery latency. The most well-known algorithms of this kind are SearchLight [3], Disco [4] and U-Connect [5], of which Disco is most relevant to the PSBA. However, such algorithms perform worse than probabilistic algorithms when it comes to average discovery latency, which makes them unsuitable for applications in dynamic WSNs.Most popular among the probabilistic algorithms is the Birthday [6] protocol. The probabilistic nature of such an algorithm makes it perform better on average discovery latency, which precisely satisfies the requirements of dynamic WSNs. However, the average discovery latency of the existing probabilistic algorithms is not so encouraging when working with a low duty-cycle. Hence, a better trade-off solution for low duty-cycle dynamic WSNs is desirable.In response to the above, in this Letter we propose a novel prime-set based probabilistic neighbour discovery algorithm tailored to low dutycycle dynamic WSNs. By leveraging on the advantages of both probabilistic and deterministic algorithms, the PSBA can achieve lower average discovery latency compared to existing algorithms. Also, the inherent long tail of the probabilistic algorithm is improved. Moreover, we op...

A novel distributed range-free localisation algorithm, named polygonal overlapped possible area (POPA), is proposed to accurately localise an unknown node. First, for an unknown node, to theoretically define its possible localisation area (PLA), virtual radiation regions of its nth-hop anchor neighbours are introduced. Then an effective area-splitting algorithm is employed to simplify and speed up the computation of the possible localisation area. Simulation shows localisation error can be controlled within 20% with off-the-shelf devices.

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For real-time applications in mobile low-duty-cycle (DC) wireless sensor networks (WSNs), discovering neighbours needs to be achieved in both short average latency and high fraction of discoveries (FDs) with low energy consumption. A novel asynchronous probabilistic method is proposed, in which a node randomly chooses a prime, e.g. p, from a pre-configured prime set and wakes up only at the first slot during every p continuous slot which is for a hyper-cycle length, i.e. a fixed number continuous slots, determined by the prime sets, and then selects another prime for the next hyper cycle. For low-DCs, especially <2%, one can flexibly configure different prime sets for the given DC, and the more the primes in the sets, the lower the average discovery latency (ADL) that is achieved. Simulations show that the proposed method can not only achieve a shorter ADL than SearchLight, but also obtain a shorter and smaller tail on FDs than Birthday.