Research Of Rake Receiver In The Wireless Sensor Network On Fading Channel

Wireless sensor network(WSN) is a quite popular research field now, have a good application prospect, it laid a large number of sensor nodes in an monitored area,these nodes made up a network through the self-organizing way. Because of the special working mode, WSN needs their nodes have lower energy consumptions, smaller volumes and cheaper costs. The application environment of WSN is very complex, and the multipath fading affects communication quality greatly. Rake receiver is an effective means of anti-multipath fading, which makes use of PN codes, gives the multipath signals separations, corrections and weighted combinations and lets the multipath signals turn to useful signals.The aim of this paper is according to the specialty of WSN, do some performance researches and improvement for Rake receivers. First of all, the principle of operation and characteristic of WSN were introduced briefly, the paper's background and meaning were explained, and transfer characteristics of WSN's signals and multipath fading channel model were analyzed. And then the components of the WSN communication simulation model were introduced, the principle and related technologies of Rake receiver were an important part. Through the performance analysis of maximal ratio combining (MRC) Rake receiver, the shortage of MRC-Rake receiver was pointed, and an improved LMS-Rake receiver structure was adopted. This structure calculated the optimum weight with an simple iterative formula, improved the receiver's performance. No additional sending training sequences, the complexity of the equipment was reduced. At the same time, the original weight and step were improved through the result of channel estimation; the algorithm's accuracy and convergence speed were advanced. Theoretical analysis and computer simulations illustrate that the improved LMS-Rake receiver can give significant improvement when compared with the conventional MRC-Rake receiver, and have a simple structure, a lower complicated calculation and easy to implement. Finally, the key modules of improved Rake receiver's structure were designed and simulated by Verilog HDL language; the result proved the practicability and provided foundation for actual application.