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Power saving for
extending session lifetime is an important research subject in wireless
sensor networks (WSNs). Recognizing the fact that Quality of Service can
be deteriorated by insufficient transmit power, this work studies how
to minimize power consumption while achieve a satisfactory QoS of data
streams in WSNs. A crosslayer routing scheme is proposed to maximize
session lifetime by adjusting individual transmit power on intermediate
nodes. The thesis is divided into two major parts for analyzing our proposition.
In the first part, we propose an efficient routing scheme with optimal
power management and ondemand quality control for WSNs. When source node
issues a QoS provision for route discovery, an adjustment of transmit
power is computed for each passby node by taking into its individual
wireless link account. Then, an optimal route associated with lowest power
consumption and consistent QoS can be selected among all of the candidate
routes.
In the second part, by following the definition of QoS criterion in the first part, we further consider the problem of how to balance the needs on constraining endtoend quality and prolonging lifetime in an established route. The problem can be interpreted as a nonlinear optimization paradigm, which is then shown to be a maxmin composite formulation. To solve the problem, we propose two methods, (1) routeassociated power management (RAPM), and (2) linkassociated power management (LAPM). Considering computationrestricted sensor nodes, the RAPM scheme is twofold simplification; not only it can reduce power computation, but it also quickly determines the longest lifetime and proper transmit power for nodes. On the other hand, if computational cost is not a major concern in a sink node, the LAPM algorithm is more suitable than RAPM to solve the lifetime maximization problem, in terms of accuracy. Finally, we analyze the performance of these two methods. The results demonstrate that the LAPM scheme is very comparable to a heuristic approach.

Publication List
Publication List:
Journal Paper:
1. YiJen Lu and TsangLing
Sheu, "Lifetime Maximization Schemes under EndtoEnd FrameError Constraints
in Wireless Multimedia Sensor Networks," in Wireless Communications &
Mobile Computing, Mar. 2009. (SCIE, 2007 Impact Factor = 1.225)
2. YiJen Lu and TsangLing
Sheu, "An Efficient Routing Scheme with Optimal Power Control in Wireless
Multihop Sensor Networks," Computer Communications, Vol. 30, No. 1415,
pp. 27352743, Oct. 2007. (SCIE, 2006 Impact Factor = 0.444)
Conference Paper:
1. YiJen Lu, ChiJen Huang,
and TsangLing Sheu, "Threecolor Marking with MLCN for Crosslayer TCP
Congestion Control in Multihop Mobile Ad Hoc Networks," Int'l Conference
on New Technologies, Mobility and Security (NTMS), Paris, France, May
2007.
2. TsangLing Sheu
and YiJen Lu, "Effective Power Control for Multimedia Streaming with
QoS Constraints in Heterogeneous Networks," IEEE Wireless Communications
and Networking Conference (WCNC), Hong Kong, Mar. 2007.
3. TsangLing Sheu
and YiJen Lu, "Power Minimization with EndtoEnd Frame Error Constraints
in Wireless Multihop Sensor Networks," IEEE/ACM Int'l Wireless Communications
and Mobile Computing (IWCMC) Conference, Vancouver, Canada, Jul. 2006.
