Investigation of sub-carrier multiplexed fiber optic link supporting WLAN and WCDMA

In this thesis, an optical fiber based radio access architecture that simultaneously provides services of the wireless local area network (WLAN) and the third generation (3G) mobile communication system is investigated. The sub-carrier multiplexed (SCM) technique of the fiber optic system is considered. The SCM architecture does not require frequency conversion and plays an important role enabling the WLAN to complement the cellular mobile communication systems so that the user can have both services as needed. In the SCM architecture, the two mediums that signals propagate are the air interface and the radio over fiber (ROF) link. In the air interface, the signal experience path loss and multipath fading that have effect on the system performance. The ROF link introduces nonlinear distortions and optical noise. The uplink and downlink analysis are performed in this thesis considering all the impairments from the air interface and the ROF link. Thereafter, numerical results are generated for both the uplink and downlink to illustrate the performance of the SCM architecture. The analysis identifies the interdependent relationship of the WLAN and the WCDMA system. The numerical results graphically illustrate such interdependent relationship. In the downlink, a 5 km ROF link operating at optimal power can support a WCDMA system with 1 km radius of coverage that has 26 dB of signal to distortion and noise ratio (SDNR); and a WLAN system with 400 m radius of coverage that has 27 dB of SDNR. The throughput of IEEE 802.11 WLAN depends on the medium access control. Hence, the medium access control is investigated and the throughput expression is modified to adapt to the SCM architecture where signals travel extra distance in a fiber.