Mobile Relay Configuration in Data-Intensive Wireless Sensor Networks

Mobile Relay Configuration in Data-Intensive Wireless Sensor Networks



Wireless Sensor Networks (WSNs) are increasingly used in data-intensive applications such as microclimate monitoring, precision agriculture, and audio/video surveillance. A key challenge faced by data-intensive WSNs is to transmit all the data generated within an application’s lifetime to the base station despite the fact that sensor nodes have limited power supplies. We propose using lowcost disposable mobile relays to reduce the energy consumption of data-intensive WSNs. Our approach differs from previous work in two main aspects. First, it does not require complex motion planning of mobile nodes, so it can be implemented on a number of low-cost mobile sensor platforms. Second, we integrate the energy consumption due to both mobility and wireless transmissions into a holistic optimization framework. Our framework consists of three main algorithms. The first algorithm computes an optimal routing tree assuming no nodes can move. The second algorithm improves the topology of the routing tree by greedily adding new nodes exploiting mobility of the newly added nodes. The third algorithm improves the routing tree by relocating its nodes without changing its topology. This iterative algorithm converges on the optimal position for each node given the constraint that the routing tree topology does not change. We present efficient distributed implementations for each algorithm that require only limited, localized synchronization. Because we do not necessarily compute an optimal topology, our final routing tree is not necessarily optimal. However, our simulation results show that our algorithms significantly outperform the best existing solutions.

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A key challenge faced by data-intensive WSNs is to minimize the energy consumption of sensor nodes so that all the data generated within the lifetime of the application can be transmitted to the base station. Several different approaches have been proposed to significantly reduce the energy cost of WSNs by using the mobility of nodes. A robotic unit may move around the network and collect data from static nodes through one-hop or multihop transmissions. The mobile node may serve as the base station or a “data mule” that transports data between static nodes and the base station. Mobile nodes may also be used as relays that forward data from source nodes to the base station. Several movement strategies for mobile relays have been studied.


ØFirst, the movement cost of mobile nodes is not accounted for in the total network energy consumption. Instead, mobile nodes are often assumed to have replenishable energy supplies which are not always feasible due to the constraints of the physical environment.

ØSecond, complex motion planning of mobile nodes is often assumed in existing solutions which introduces significant design complexity and manufacturing costs.

ØIn mobile nodes need to repeatedly compute optimal motion paths and change their location, their orientation and/or speed of movement. Such capabilities are usually not supported by existing low-cost mobile sensor platforms.



In this paper, we use low-cost disposable mobile relays to reduce the total energy consumption of data-intensive WSNs. Different from mobile base station or data mules, mobile relays do not transport data; instead, they move to different locations and then remain stationary to forward data along the paths from the sources to the base station. Thus, the communication delays can be significantly reduced compared with using mobile sinks or data mules. Moreover, each mobile node performs a single relocation unlike other approaches which require repeated relocations.


ØOur approach takes advantage of this capability by assuming that we have a large number of mobile relay nodes.

ØOn the other hand, due to low manufacturing cost, existing mobile sensor platforms are typically powered by batteries and only capable of limited mobility.

ØConsistent with this constraint, our approach only requires one-shot relocation to designated positions after deployment. Compared with our approach, existing mobility approaches typically assume a small number of powerful mobile nodes, which does not exploit the availability of many low-cost mobile nodes




üProcessor                     Pentium –IV

üSpeed                                     1.1 Ghz

üRAM                            256 MB(min)

üHard Disk                    20 GB

üKey Board                    Standard Windows Keyboard

üMouse                          Two or Three Button Mouse

üMonitor                        SVGA




üOperating System                    : Windows XP

üProgramming Language           : JAVA

üJava Version                           : JDK 1.6 & above.

üDatabase                                 : MYSQL



Fatme El-Moukaddem, Eric Torng, and Guoliang Xing,Member, IEEE “Mobile Relay Configuration in Data-Intensive Wireless Sensor Networks”- IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 12, NO. 2, FEBRUARY 2013.

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