基于无线传感网扩频通信的跨层CSMA多用户接入

无线传感网是一个应用于恶劣传输环境下的异步通信系统，且对于节点的体积功耗具有较高要求。本文对异步扩频通信系统中的载波侦听多址接入（CSMA）碰撞机制进行改进，通过建立协议层和物理层的联系来减小碰撞概率，实现多用户基本同时的信息交互。其基本思想是通过侦听到的信号的相位调整发送信号的相位，使不同信息发送节点到达同一接收节点的扩频码相位不同，从而使接收节点可实现多用户分辨接收，并通过接收端的长时间相关峰值平方和来进行捕获确认，短时间相关峰值来进行解扩处理。从而使系统在对单信道接收系统复杂程度增加不大的情况下，具有多用户接入能力。

The Multi-User Access Based on Cross-Layer CSMA of Wireless Sensor Network Spreading Communication System

Wireless sensor network (WSN) is an asynchronous communication network based on limited energy nodes working in a bad communication circumstance. This paper discusses an improved CSMA in a spread communication WSN system, analyses the possibility of connecting MAC layer and physical layer to reduce system collision and realize multi-user access with little increase of system complexity. The main idea is adjusting the phase of sending signal according to the phase of listened signal so that the received signal of different user has different phase which can be used to distinguish them out.