本文首先介绍了两种协作方式与OFDM框架，并结合OFDM技术进行了系统仿真，对比分析了OFDM系统与CRC编码OFDM系统与卷积码编码OFDM系统仿真性能。-two methods to realize cooperative diversity in OFDM systems are proposed simulations using OFDM techniques are performed and the performance of the CRC coding OFDM syst

参考3GPP相关标准并根据LTE技术特征和关键特性，对下行链路级进行设计，包含以下步骤：比特生成、CRC校验、码块分割、编码、速率匹配、码块级联、加扰、调制、层映射、预编码、资源映射、OFDM符号生成和天线映射。为模拟无线传输信道，还需仿真相应的信道模型。收端则是发端的严格逆过程，对接收信号进行一系列处理，得到代表原始发送的信息并判决。-References 3GPP LTE technology standards and in accordance with characteristics

Long-Term Evolution (LTE) is a new standard specied by 3GPP for fourth generation (4G) wireless communications. LTE provides high spectral eciency, high peak data rates, short round trip time, and frequency exibility. It relies on the follow