Research On Cross-Layer Optimization Model For Data Transmission In UWB Wireless Sensor Networks

Ultra Wide Band(UWB)is a kind of wireless communication technique with very large bandwidth(from a few Hz to several GHz)and very low power impulse. There are many significant benefits of UWB for wireless communications,such as large bandwidth,huge transmission rate,extremely low power spectral density and large processing gain in the presence of interference.The U.S.Federal Communications Commission(FCC)approval of military use of UWB inspired a flourish of research and development efforts in both academia and industry. UWB-based wireless sensor networks is one of the research focus in wireless communication field.The large scale nature of wireless sensor network,however, introduces some unique challenges.Specifically,due to interference from neighboring links,a change of power level on one link will produce a change in capacity of all neighboring links.As a result,the capacity-based routing problem at the network layer is closely related to link layer problems such as scheduling and power control.An optimal solution to a network level problem thus must be pursued via a cross-layer approach.Scholars at home and abroad have done enormous researches on cross-layer design of wireless sensor networks in recent years,however,there still exist many unresolved problems.Based on studying and analysis of current research contributions,this dissertation makes extensive and thorough research on cross-layer optimization model for data transmission in UWB-based wireless sensor networks. The main reaserch work and innovation are as follows:(1)Building a cross-layer optimization model for data transmission in UWB wireless sensor networks.Cross-layer design is a promising approach to promote the performance of wireless sensor networks.This paper studies an UWB-based wireless sensor networks and builds a cross-layer optimization model with joint consideration of MAC layer scheduling,PHY layer power control and routing of network layer.The optimization model takes advantage of unique properties of UWB technology,such as huge bandwidth,extremely low power spectral density and large processing gain in the presence of interference and intends to achieve the maximal data rate of whole network.Simulation results show the optimal solution of optimization model can increase the data rate of network obviously and demonstrate it is effective to deal the cross-layer issues with building and resolving the optimization model.(2)Proposing an UWB-based nodes positioning algorithm.For the speciality of cross-layer optimization model(NLP model),we implement the solution procedure at base-station.It means the base-station must know the topology of whole network.In order to satisfy this demand,we proposed a novel distributed node positioning algorithm(DPNA)based on the accurate ranging capability of UWB technology.The proposed algorithm uses local information to build some Base-node Coordinates Systems(BCSs)at first.DPNA then builds a Network Coordinates System(NCS)through implementing coordinates transformation between BCSs,and each node within network can obtain its unique coordinates.The simulation results show that DNPA can get the physical topology of networks and is especially desirable for sensor networks or Ad Hoe networks that consist of nodes with less movement.In addition,the algorithm makes it possible to implement some basic networks functions effectively,such as routing,networks management.(3)Suggesting a solution for data transmission in large-scale UWB wireless sensor networks.The proposed solution is based on the simulation results of cross-layer optimization model for data transmission in small-scale sensor networks and detail analysis of impact of constraints to optimal solution.It has three steps as fellow:â‘ get the physical topology of whole networks through node positioning algorithm (DNPA);â‘¡when something special occurs in network,select appropriate node in detection region as base-node,build and execute cross layer optimal model for detection region;â‘¢adjust constraints of optimal model to reduce the amount of constraints and variables,and execute cross layer model of whole networks.If we can get feasible solution after each step,we can make conclusion that the data rate from source nodes can be relayed to the base station successfully.Using above approach increases the times of solving optimal model,but it reduces the constraints and variables of model and obviously.This approach reduces the computational complexity of model and makes full use of research results of optimal model of small- scale networks.And in hence,avoid repetitive development for both optimal model and execute procedure.(4)Studying and verificating the maximal data rate received by base-station. Through simulation we analyze the impact of relative position between base-station and its one-hop neighbors to object value of model,and make primary conclusion as fellow:â‘ the capacity of base-station has close connection with the amount and position of its one-hop neighbors;â‘¡for a given amount of one-hop neighbors,the position of these nodes have import influence to optimal value of model.Suggested by above results,we study the maximal data rate received by base-station thoroughly and demonstrate the correctness of it through simulations.The dissertation studies thoroughly on cross-layer optimal model for data transmission in UWB wireless sensor networks and makes effective proposals in terms of data transmission in large-scale networks which hope to contribute improving the research on UWB wireless sensor networks.