The Hybrid Mobile Wireless Sensor Networks for Data Gathering Biao Ren, Jian Ma, Canfeng Chen Proceeding of the 2006 international conference on Communications and mobile computing IWCMC '06 July 2006
Traditional wireless sensor networks extension based on pure ad-hoc networks ,where the dense distribution of sensor nodes and multi-hop transmission over the whole network are their outstanding characteristics.
Some disadvantages still exist, such as poor scalability, weak energy balance, as well as low network lifetime.
Hybrid wireless sensor network is usually comprised of some kinds of heterogeneous devices, which mainly act as sinks responsible for gathering and forwarding data from sensor nodes.
Some of them are energy-rich or rechargeable, some are capable of communication with better capability and some are mobility enabled. These features can not only improve the network performance, but also extend the potential applications and make commercial implementation easy.
The paper investigates the impacts of the number, velocity, transmission radius and gathering mode of mobile sinks on large-scale and sparse wireless sensor networks.
Each of the total m mobile sinks pick a direction uniformly at random from (0, 2π ] and moves in that direction for a distance d at speed v , where d is a exponentially distribution.
If the sink hits the boundary of the sink, it is reflected at the boundary (The positions of mobile nodes are independent of each other). The direction of the mobile node is also uniformly distributed in (0, 2π ] all the time.
In dense sensor network, data gathered from environment is forwarded to sink node in multi-hops fashion. Although it can provide low data delivery delay, the energy consumption per bit is much higher due to the multi-hop forwarding of one packet.
We adopt the limited k-hop scheme for data gathering from sensor nodes. That is, the data transmission of a sensor node will not happen until at least one mobile sink approach to it within at most k-hop distance.
Theorem Given a sensor node S . Let m denotes the number of mobile sinks, r is the range of transmission and v is the velocity of mobile sinks. With high probability, the average duration D until which a mobile sink first enters the field of sensor node S is
High velocity can increase the probability for the sensor and mobile sink meet with each other, but mobile sinks passing through the effective region of a sensor node so fast that there is no adequate time to perform continuous transmission.
Increasing velocity will increase the service probability whereas decrease the service duration of each time.
Choosing appropriate number, transmission range, velocity as well as gathering fashion of mobile sinks can significantly guarantee lower end-to-end data delivery delay and achieve better energy conservation.
A promising direction for future work is to explore the use of cooperative mobility, find an effective data dissemination protocol, and improve the throughput capacity of hybrid sensor network.