## 2 Related Work  
The energy consumption model in [5] established that the energy consumed by transmitting a unit of data is the same for each node, whereas energy performance is still hard to evaluate based on elusory communication distance measurements. In [6] the problem of maintaining the distance measurement of the best- and worst-case coverage of a network was studied. For any given \(\varepsilon\), \(\varepsilon>0\), the algorithm could maintain a \((1+\varepsilon)\) approximation on the best-case coverage distance and a \((\sqrt{2}+\varepsilon)\)approximation on the worst-case coverage distance of a sensor network. To find an optimal sensor deployment, the search space should contain not only the Delaunay triangulation of sensors but also the edges formed by any two sensors. Our solution finds the best locations for new sensors in polynomial time so that the placement of new sensors can optimally improve the best-case coverage of a sensor network. The thought behind the algorithm is based on computational geometry and graph theory, including Voronoi diagrams, Delaunay triangulation, and graph search algorithms for coverage calculation. Regarding the use of MS, [8] proposed a dual-sink protocol which shows that when it scales up, the network using Dual-Sink enjoys steady lifetime improvement and energy saving from sink mobility, whereas the network with only one MS performs no better than the network with a single SS. [7] designed a movement circle trajectory for MS, all the sensed data are forwarded into the annularity area and then be collected by the MS. The proposed MA (Movement in an Annulus) was proven to be efficient compared with RM (Random Movement), PM (Peripheral Movement) and SM (Static-based Model) [8]. In [9] a sink mobility supported route protocol for environment monitoring called Patrol Grid Protocol (PGP) was proposed, that was proven to be better than TWO-Tier Data Dissemination (TTDD) [10] in terms of less overhead and delay rate. PGP is more suitable for urgent events and query-driven mode. The authors in [11] proposed a novel cooperative forwarding process and presented a novel cooperative contention-based forwarding (CCBF) that extends the scope of cooperation and attains the full potential of cooperative forwarding at the expense of sending one additional control message on demand. CCBF employed a retransmission mechanism to significantly decrease the end-to-end hop counts and energy efficiency and latency as well as the packet loss ratio. In [12] the use of two mobile sinks in the event-driven WSN was proposed. It prolongs the network lifetime and reduces the data delay in a different mobility patterns. In [13] an algorithm called EMOSEN that introduced a multi-radio enabled mobile into WSN to investigate the heterogeneity, sensor mobility and capacity gain was proposed. In [14] an efficient Query-based data collection scheme (QBDCS) that considers a moving mobile sink queries a specific area or a point of interest for data collection is proposed. Due to the mobility of the mobile sink, the Query and Response should be in different routes. QBDCS chooses the optimal timing to send the query packet and tailors the routing mechanism for partial sensor nodes forwarding packets with minimum energy consumption and delivery latency. In [15] the authors investigated the impacts of different features and behavior of mobile sinks on hybrid wireless sensor networks. Analysis and simulation results showed that, instead of deploying as many mobile sinks as possible, choosing appropriate number, transmission range, velocity and gathering mode of the sink nodes can significantly decrease the average end-to-end data delivery delay and improve the energy conservation. In [16] a cluster based data dissemination (CBDD) scheme was proposed to divide the communication between mobile sinks and source sensors into inter-cluster and intra-cluster communication phases and limit the disruption of the data disseminationpath within a cluster which does not require any location algorithms.