Development of Indoor Wideband Digital Radio MODEM using a Multi-Carrier Modulation Technique

在本研究中，我们开发了一种新的多载波调制系统，用于宽带室内通信。首先，我们提出了一个最佳的符号定时，符号周期和频偏估计器，这是所需的多载波调制接收机。由于所提出的估计器不需要已知的导频符号，更带宽的有效传输将被实现。计算机仿真结果表明，在加性白色高斯噪声环境下，该方案仅用10个符号就能实现符号和频率同步。在此基础上，我们制作了一个多载波调制系统，该系统包括一个数字多载波调制器、一个模拟室内传播环境的多径衰落模拟器和一个采用该估计器的多载波调制接收机。在室内无线电环境下，该系统的工作速率可达8 Mb/s。在发射机和接收机处，使用数字信号处理技术来调制和解调多载波调制信号。采用分组传输来实现需要宽带宽范围的多媒体传输。最后，我们对所开发的多载波调制系统的传输性能进行了实验评估。通过实验得到了以下结果。(1)该估计器应用于多载波接收机中，在加性白色高斯噪声信道中，可以在10个符号内建立符号和频率同步，在多径衰落信道中，可以在50个符号内建立符号和频率同步。(2)在加性白色高斯噪声信道和多径衰落信道中，系统的误比特率性能均符合理论界。这意味着多载波调制技术可以用作支持多媒体传输的室内宽带数字通信系统。

In this study, we have developed a new multi-carrier modulation system for wide-band indoor communications. First, we have proposed an optimum symbol timing, symbol period and frequency offset estimator which is required for the multi-carrier modulation receiver. Since the proposed estimator requires no known pilot symbol, more band-width efficient transmission would be achieved. Computer simulation results show the proposed scheme can establish the symbol and frequency synchronization with only about 10 symbols in an additive white Gaussian noise environment. Then we have made the multi-carrier modulation system which contains a digital multi-carrier modulator, a multi-path fading simulator which simulate indoor propagation environment and a multi-carrier modulation receiver with the proposed estimator. The developed system can operate at about 8Mb/s in indoor radio environment. At the transmitter and the receiver, digital signal processing techniques are used to modulate and to demodulate the multi-carrier modulation signal. Packet transmission is employed to achieve a multi-media transmission which requires wide ranges of band-width. Finally, we have experimentally evaluated the transmission performances the developed multi-carrier modulation system. The following results are obtained by the experiment.(1) The proposed estimator, which is employed to the multi-carrier receiver, can establish symbol and frequency synchronization within 10 symbols in an additive white Gaussian noise channel and within 50 symbols in a multi-path fading channel.(2) The bit error rate performance of the developed system agrees well with the theoretical bound in both the additive white Gaussian noise channel and the multi-path fading channel. This means that the multi-carrier modulation technique can be employed as an indoor wide-band digital communication system which support multi-media transmission.