Mobile Multi-hop Data Gathering Mechanisms in WSN Networks Essay

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In some existing work, the transmission range of an omnidi-rectional antenna was simply assumed to be a disk-shaped area around the transceiver. Based on this assumption, given a point in the plane, the neighbor set of this point consists of all sensors within the disk-shaped area around this point. However, due to the uncertainties of a wireless environment, such as signal fading, reflection from walls and obstacles, and interference, it is hard to estimate the boundary of the transmission range without real measurement [42], [43]. Therefore, in practice, it is almost impossible to obtain the neighbor set of an unknown point, unless the M-collector has moved to this point and tested wireless links between it and its one-hop neighbors, or…show more content…
Thus, all wireless links between sensors and the M-collector at the candidate polling points are bidirectionally tested. In addition, each sensor can also discover its one-hop neighbors by broadcasting the “Hello” messages during the neighbor discovering phase. After the sensor reports the IDs of its one-hop neighbors to the M-collector by including the information into the “ACK” message, the position of the sensor can also become a candidate polling point. In Fig. 1, we illustrate the definition of polling points, neighbor set, and candidate polling point set by an example, where there are four sensors s1, s2, s3, and s4 deployed at positions l1, l2, l3, and l4, respectively. During the exploration phase, the M-collector discovers the neighbor sets of l5 and l6 by broadcasting “Hello” messages at these points. Thus, l5 and l6 can be added into the candidate polling point set. Since sensors s1, s2, s3, and s4 also report their one-hop neighbors to the M-collector by sending “ACK” to the M-collector, l1, l2, l3, and l4 also become candi-date polling points. In Fig. 1, if there is a wireless link between sensor si and position lj , we say that si belongs to the neighbor set of lj , where si ∈ {s1, s2, s3, s4} and lj ∈ {l1, l2, . . . , l6}. Thus, candidate polling point set L = {l1, l2, . . . , l6}; neighbor sets of
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