Key Algorithms Research Of LMDS Baseband Receiver

LMDS(Local Multi-point Distribution Service) is a newly developed millimeterwave band wireless broadband communication technique. With the advantages of highdata rate capacity and simple deployment, the market prospect of LMDS is verypromising. Due to the high bandwidth and data rate, QAM is usually used as themodulation mechanism in LMDS system. High-order QAM carries great amount ofinformation and is therefore vulnerable to channel condition, noises, time delay andISI(inter-symbol interference), which degrades the performance of baseband receiver.To ensure the reliability and effectiveness of information’s transmission, the basebandreceiver needs to be well designed. To improve the performance of QAM demodulationin low SNR and severe channel condition scenario is critical and difficult in QAMsystem design.The work of this paper based on the joint project of Ka band millimeter wavewireless LMDS communication system which is conducted by a certain domesticcommunication corporation and my laboratory. My team is responsible for basebandsubsystem and the research mainly focuses on baseband receiver, especially the designand implementation of channel equalization and carrier recovery. The theoreticalfundamental of certain algorithms including LMS in channel equalization andtimes-four square loop in carrier-recovery is given and Simulink is used to simulate andverify the validity and performance of related algorithms. Then a switch algorithmcombining LMS and CMA is devised and a new analog-digital hybrid carrier-recoveryalgorithm is proposed and evaluated by Simulink.After simulation, MCADAMA and hybrid carrier recovery algorithms are chosento be the system’s equalization and carrier recovery algorithms respectively, and thealgorithms are evaluated by fixed-point simulation. Also the baseband receiver link’sarchitecture is determined. The algorithms’ performance of baseband receiver is verifiedon FPGA platform by Verilog HDL code.