文档介绍：摘要
GMSK由于具有优良的频谱效率和功率效率等特性,因而作为一种主要的调制技术被广泛地应用于多种现行的无线标准之中(GSM, DECT, CDPD )。本文以综述的形式给出了相干解调和非相干解调技术的比较。本文在保留非相干差分解调方案拥有的快速同步,以及硬件实现简单等优点的同时,利用判决反馈均衡(DFE)、非冗余纠错(NEC)等技术来提升常规差分解调器的性能,并且利用几种技术的结合提出了多种新的解调方案。
本文详细阐明了无线通信中衰落产生的原因。借助衰落性道的统计模型对无线信道进行建模。利用计算机仿真解调方案在热噪声、多径衰落、多谱勒频移以及同信道干扰等多种通信环境下的误码性能。
短波跳频通信具有较强的抗干扰能力和任意选址等优点而在军事通信领域得到了广泛的应用。现代跳频系统需要传输大量数据信息,传统调制方式由于频谱利用率不高而不适合跳频系统的高速数据传输。因而,研究适合于跳频通信特点的具有高效频谱利用率的调制方式具有重要的意义。
本文拟将GMSK调制技术引入到短波跳频系统中,以实现高速数据传输。
关键词:GMSK,差分解调,判决反馈,非冗余纠错,短波跳频
ABSTRACT
GMSK is a digital modulation scheme for sending binary information, with perfect spectrum efficient, energy efficient and other desirable characteristics. It is and presides as the most prominent modulation type among the munications standards (GSM, DECT,CDPD).The dissertation includes an overview of the coherent demodulation technology and the noncoherent technology. Differential demodulation technology do not require knowledge of the reference phase,has the fast synchronization characterize. It is generally more robust, less expensive and easier to build than coherent techniques. We hold these merits of the differential demodulation, and use the bining. Decision Feed Back Equalization (DFE) and Nonredundance Error Correction (NEC) technologys to enhance the performance of the conventional differential demodulation. In the thesis we give several new structures and new variations on conventional demodulators.
This paper demonstrates that the cause of the formation of the fading in the munication, and the type of the fading depends on the nature of the transmitted signal with respect to the characteristics of the channel. We use statistics model to model the wireless fading channel. The investigation focuses on the BER performance of the new schemes used in channels typically found in wireless environments, and analysis the impact from the thermal noise, multipath fading, Doppler shifts and Co-channel interfere to their performance.
With the advantages of good spectrum uti