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...ile sinks in physical worlds usually have limited speed. On the other hand, underlay applications like the real-time surveillance demand a delay upper bound. Therefore, it is natural to take delay issue into consideration. Basagni et al. jointly considered the sink mobility and delay issue in [8]. But they assumed that the routes are predetermined. Wang et al. used multiple controllable sinks to travel among event locations to efficiently gather data. They considered issues like the mobile distance of a sink and time delay [9]. However, only one-hop routing has been used. Recently, Yun et al. [10] jointly considered the multi-hop routing, sink mobility and delay bound to improve the energy efficacy. However, the network model is totally different with ours. They still used the fast mobility assumption [13], so the delay is caused by nodes holding their transmissions until the location of the sink is most favorable for energy saving, not by the movement of the sink. In this paper, we study delay-bounded sink mobility problem (DeSM) in WSNs. We assume that WSNs are deployed to monitor the surrounding environment and the data generation rate of sensors can be estimated accurately. We cons...

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...connected or disconnected networks. In some practical applications, however, the trajectory for the mobile sink is fixed and the locations for the sink to pick up data are pre-arranged. Yun et al. in =-=[4]-=- assume that there are a set of possible locations for the mobile sink to stop. The sink is supposed to collect data from all sensors by visiting a partial, or all, of these possible locations. In our...

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...stent and continuous energy supply is lacking. Therefore, the main objective of WSN designsis to prolong network lifetime by balanced and effective energy consumption. In the literature,sWSN lifetime =-=[4]-=- has often been defined as the time for the first node to die in the course ofsrouting due to battery exhaustion. Network topology, as the important foundation of upper layersprotocols, not only impro...

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...ing nodes. This phenomenon is called “energy hole problem”[15] [16] [29] or “crowded center effect”[23]. There are many papers lengthen WSNs lifetime by addressing the “energy hole problem” [23] [15] =-=[32]-=- [16] [29]. In [15] [16], they propose a formal mathematical model for analysing “energy hole problem” in WSNs. Some other approach [23] replaces shortest path routing to curveball routing to mitigate...

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...In literature, a considerable number of works advocate for using a single or multiple mobile sinks [2, 3, 4, 23, 12, 14, 16, 29, 5, 19, 27, 28, 6, 24, 9]. The majority of these deal with single sinks =-=[2, 12, 16, 29, 17, 27, 24, 30, 9]-=- and all of them focus on prolonging lifetimes. The effects on information transfer delay are either completely neglected or simply observed without taking actions to establish delay as an objective o...

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...ng traffic load among nodes to ensure that the average energy expenditure in all nodes is the same [24, 45]. In GRP, there are two common energy balance routing techniques: route level energy balance =-=[46,47]-=- and region level energy balance [23,28,48]. 2.4.1 Route level energy balance Route level energy balance is aiming to prolong the network lifetime by optimizing the energy usage in the senor nodes tha...

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...lized approaches in [45], [46].s2.5.2 Distributed Algorithms in Delay-TolerancesDelay-tolerance is another important issue among the research topics in WSNssregarding the application requirements. In =-=[47]-=- the authors propose a framework thatsimplements the mobile sink approach taking into account the delay tolerancesrequirements. This model permits certain level of delay in data delivery and guarantee...

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...lculated with (3)sand (4).smi jj n n = =∑1 1( )Ds(3)ss mi j ij n n = − − =∑1 1 21( )Ds(4)sWhere n is the total of sensor nodes in the cluster.sStandardize the data set to obtain {X1,X2,….Xj,……Xnswith =-=(5)-=-.sX1= ((D1-μi)/σi),… Xj=((Dj-μi)/σi),…Xn=((Dn-μi)/σi (5)sIf X TLi ≥ , then the measurement of ith sensor issconsidered as primary data and the remaining data aressecondary data. TL is threshold limit ...