Fuquan Zhang

Design and Implementation of AMI System Using Binary CDMA for Smart Grid

To solve the energy problem and find new growth engines, the smart grid is getting more and more attention these days. AMI is the key component that should be preferentially constructed for smart grid. To establish a PLC-based AMI system with the existing conventional power supply network can save cost in construction of communication lines. However, the infrastructure is not ideal for communication because of signal attenuation and noise due to its harsh and noisy transmission medium, regulations and admission, and isolated place. In this paper, we analyze the requirements for building AMI system with Binary CDMA technology, and design a Binary CDMA-based AMI system. The performance evaluation results show that the Binary CDMA-based AMI system can be used together with the conventional PLC-based AMI system, or used alone.

Distributed Optimal Maximum Rate Allocation based on Data Aggregation in Rechargeable Wireless Sensor Networks

In Rechargeable Wireless Sensor Networks(R-WSNs), it is critical for data collection because a sensor has to operate in a very low and dynamic duty cycle owing to sporadic availability of energy. In this work, we propose a distribute maximum rate allocation based on data aggregation to compute an upper data generation rate by maximizing it as a linear programming problem. Subsequently, a dual problem by introducing Lagrange multipliers is constructed, and subgradient algorithms are used to solve it in a distributed manner. The resulting algorithms are guaranteed to converge to an optimal value with low computational complexity. Through extensive simulation and experiments, we demonstrate our algorithm is efficient to maximize data collection rate in rechargeable wireless sensor networks.

A Tier-Based Duty-Cycling Scheme for Forest Monitoring

Wireless sensor networks for forest monitoring are typically deployed in fields in which manual intervention cannot be easily accessed. An interesting approach to extending the lifetime of sensor nodes is the use of energy harvested from the environment. Design constraints are application-dependent and based on the monitored environment in which the energy harvesting takes place. To reduce energy consumption, we designed a power management scheme that combines dynamic duty cycle scheduling at the network layer to plan node duty time. The dynamic duty cycle scheduling is realized based on a tier structure in which the network is concentrically organized around the sink node. In addition, the multi-paths preserved in the tier structure can be used to deliver residual packets when a path failure occurs. Experimental results show that the proposed method has a better performance.

A cross-layer scheme to improve TCP performance in wireless multi-hop networks

TCP optimization problem in wireless multi-hop networks can be solved effectively by utilizing feedback from various layers. Since hop-count and round trip time are the critical factors that seriously affect TCP performance on end-to-end connection, we derive analytically the relation between these factors and TCP mechanism. The analytical result is facilitated to propose a cross-layer TCP congestion control scheme. The behavior of resulting scheme is analytically tractable. We show that our simple strategy significantly improves TCP performance in different topologies and flow patterns, in terms of throughput and delay.