AWGN信道中二维扩展频谱系统的误码率分析

首先对时域、频域二维扩展频谱系统作了简要介绍，与传统的DS-CDMA系统相比，其主要区别是将经时域扩频后的信号复制成多个并行分支，在频域用一组正交的扩频码进行第二次扩频。该系统能更有效地利用传输带宽．实现频率分集，并且由于是二维扩频，所以该系统有更强的多址能力。然后，本文对多载波二维码分多址系统的接收机和发射机进行了较为详细的数学分析，给出了二维扩展频谱系统的工作原理，并且在假设系统完全同步的情况下，推导出了在加性白高斯噪声(AWGN)信道中二维扩展频谱系统的误码率表达式，并给出了相应的误码率特性曲线。

Bit Error Performance of Two-Dimensional Spread Spectrum System for AWGN Channels

Two-dimensional spread spectrum system is simply introduced first. Compared with traditional DS-CDMA systems, the system copies the time-domain spread signals to form several parallel branches and spreads them with an orthogonal code in the frequency-domain. So it uses the frequency bands more efficient and can realize frequency diversity. Because of two-dimensional spread spectrum, the system can contain more users in the whole system. Then this paper provides a detailed discussion of the transmitter and receiver in a multi-carrier two-dimensional CDMA system and the system integrates this technology. From the mathematical deduction, this paper knows how this system works and why it is better than the existing systems. Based on the previous analysis, with perfect synchronization, finally the bit error rate of the two-dimensional spread spectrum system for AWGN channel is presented and the graph is shown. Mathematical result and the corresponding graph show that the system has a low bit error rate. Therefore this new technology is feasible under the situations provided in this paper.