Lmds Wireless Broadband Access Technology

Local Multipoint Distribute Service ( LMDS) is newly developing fixed broadband wireless access technology. Because of the large amount of spectrum available at the frequencies millimeter wave technology operates, it has the capability of providing "fiber-like" speeds and offering bi-directional voice, data and video service.This paper introduces the system architecture, which pays emphasis on the key technology that used in the system. The whole paper consists of five chapters:In chapter 1, the definition and category of broadband access system are briefly introduced. Also, it details the advantages and disadvantages of all kinds broadband access systems.In chapter 2, the LMDS architecture and network design are briefly described. Based on the terrain of Hunan University and variation in the bandwidth that each department required, one solution of Hunan University LMDS wireless broadband access system is proposed and the consideration during system design is summarized.In chapter 3, the main LMDS standards are introduced systematically, such as DAVIC standard, ETSI standard and IEEE802.16 standard.In chapter 4,the coding and modulation for LMDS system are discussed, which pays emphasis on the pragmatic TCM coding and modulation scheme. Also, the general modulation schemes are thoroughly analyzed, such as MPSK, 16APSK, 16APM and 16QAM.In chapter 5, the main channel impairments, such as Rain Attenuation, Clear Air Absorption and Distortion Due to the HPA, are covered and approaches to overcome them are suggested.In the conclusion, the issues that to be solved in the system design are summarize, finally the prospect and the challenges to the LMDS technology are predicted.