【文章內(nèi)容簡介】 ined the rapid development. In 80, the integrated circuit to be a breakthrough, realize largescale integrated circuit to make the fast Fu Liye transform and fast Fu Liye transform is not insurmountable obstacles, some other difficulties of implementation have been solved, since orthogonal frequency division multiplexing on the munication stage, gradually moving towards high speed digital mobile munication field. Enter 90 age, the realization of the technology, application of orthogonal frequency division multiplexing involves the use of mobile FM and single sideband channel high speed data munication, mobile munication, high speed digital subscriber loop, asymmetric digital subscriber loop, highdefinition digital TV and land mobile radio munication system. In 1999, the International Association of electrical and electronic engineers through the wireless LAN standard one, the orthogonal frequency division multiplexing modulation technique is adopted as the standard of physical layer, the transmission rate can be up to 54Mbps. In this way, Ether wireless frame structure of wireless ATM interface and 10Mbps interface provides 25Mbps, and support for voice, data, video service. This rate can satisfy the various applications of indoor, outdoor. LAN standard HiperiLAN2 broadband radio access work European Telemunications Organization of the orthogonal frequency division multiplexing for physical layer modulation technology it. Orthogonal frequency division multiplexing many key technology. (1) the time domain and frequency domain synchronization. Orthogonal frequency division multiplexing system is sensitive to the timing and frequency offset, in particular may be used in actual application bined with FDMA, TDMA and CDMA, FDMA, time and frequency synchronization is very important. As with other digital munication systems, synchronization is divided into two stages to capture and track. In the downlink, base station to each mobile terminal to broadcast type synchronous signal, therefore, the downlink synchronization is relatively simple, is easy to realize. In the uplink, signals from different mobile terminal must be synchronized to the base station, in order to ensure the orthogonality between subcarriers. The base station according to the extraction of each mobile terminal to the sub carrier to carry the information of the time domain and frequency domain synchronization information, then the base station transmitted back to the mobile terminal, so 通信工程專業(yè)畢業(yè)設(shè)計外文資料翻譯 第 7 頁 that the mobile terminal synchronization. Concrete implementation, synchronization will be divided into synchronous time synchronization and frequency domain, time domain and frequency domain at the same time synchronization can also be. (2) Channel estimation. In orthogonal frequency division multiplexing system, the design of channel estimator has two main problems: one is the selection of pilot information. Since the wireless channel is often a fading channel, need to continue to track the channel, the pilot information must also be continuous conveyor. The two is to design both the channel estimator with low plexity and good pilot tracking capability. In practical design, the design of pilot information selection and optimal estimator is usually related to each other, because the transmission performance and pilot information estimator of. (3) Channel coding and interleaving. In order to improve the performance of digital munication system, channel coding and interleaving is a monly used method. For fading random errors in the channel, the channel coding for fading。 burst error channel, can the interleaving. In practical application, usually at the same time, channel coding and