Physical Layer Design for a Spread Spectrum Wireless LAN

(ABSTRACT) A wireless local area network (LAN) system is proposed to provide mobility for existing data communication services. This thesis presents a physical layer design for a direct sequence spread spectrum ISM band radio LAN system. This radio system employs spread spectrum communication technology and a differential binary phase shift keying/quadrature phase shift keying (BPSK/QPSK) non-coherent receiver to overcome the adverse indoor wireless environment. Moreover, a variable data rate transmission technique is used to dynamically configure the spread spectrum system according to channel performance. This physical layer incorporates the Zilog Z2000 Evaluation Board performing direct sequence spread spectrum processing, a Grayson 900 MHz radio receiver and a transmitter module which was designed and built at Virginia Tech. The transmitted spectrum occupies a 4 MHz bandwidth in the 900 MHz ISM band and this system supports a data rate of up to 363 Kbits/sec. The spread spectrum system design along with detailed descriptions of hardware and control software development are presented. ACKNOWLEDGEMENTS I would like to express my deep appreciation to my advisor, Professor Dennis G. Sweeney for his introducing me to spread spectrum communications and hardware design. Without his guidance, suggestions and encouragement, I could not have completed this work. I am also very grateful for his patience in correcting and commenting on my thesis. My sincere thanks also go to my committee members: Professor Scott F. Midkiff and Professor Brian D. Woerner for their ideas, suggestions on my work and their comments on this thesis. I want to thank Barry Mullins for his terminal program support and also Todd Fleming for their advice on the software development. It is also a pleasure to acknowledge Gunadi Gunawan who sponsored me for further study in United States and has always encouraged me during these past two years. I would also like to thank MingZhi Yao for her spiritual support from the beginning of this research work. Finally, I wish to thank my parents and my brothers for their understanding, encouragement and love during my life.