Multi-carrier Modulation Technology Research And Applications

The Discrete Multi-Tone modulation technology was been proved that it can make the best of the frequency band to optimize the transmission performance as early as 1964, it hasn't been adopted as it's realization is complicated. In 1990s,it turns into realization as the appearance of DSP with high speed and high performance.As the typical application of the DMT, in this paper the following studies on the application of this technology in ADSL real-time communication system. Firstly, the transmission characteristic and noise characteristic of copper wire, the technology and architecture characteristic of ADSL system are discussed in this paper. And it introduces the theory knowledge of the Multi-Tone modulation technology detailedly. Secondly, the hardware construct of the ADSL real time communication system which is realized by using DMT modulation with DSP chip, especially, the design process and flowchart of system software are discussed in detail. Finally, we homely discuss the arithmetic on bit distributing, channel discrimination technology and synchronization technology, analysis the existent problem and the aspect could be optimized, and bring forward new arithmetic on bit distributing and combine arithmetic on channel discrimination technology and synchronization technology. From the simulate date it is testified that the improved arithmetic on bit distributing can reduce the calculation quantity in great range and the system performance depress few. The channel discrimination and symbol synchronization have a mutual precondition connection. The existing method adopts an approximate way to do the symbol synchronization, then make the channel discrimination. But the approximate of symbol synchronization bring the performance losing unavoidably. The improved arithmetic can get the firmly result of the channel discrimination as get the best position of symbol synchronization well and truly. It is proved from the test date that the improved arithmetic can amend the geometry SNR average more than lOdB as compare to the existing arithmetic. This system has passed the company's normal test on performance and function. It is proved that it's all function satisfied requirements and passed the company's test.All the theory analyse and arithmetic in this paper can be used in the digital communication system more widely.