Enhanced Wireless Hotspot Downlink Supporting IEEE802.11 and WCDMA

Dual mode handsets that support both cellular and wireless local area network (WLAN) interfaces have been recently introduced by manufacturers like Nokia. Wireless hotspots also better to be enhanced to support both these services. Simultaneous subcarrier multiplexed transmission of both WLAN and cellular radio signals over a single radio-over-fiber (ROF) link is possible for hotspot enhancement. However, link design in this multi-system scenario is a complex task. There are number of quality measures such as signal to noise, distortion and interference ratios involved both in the optical link and in the air interface. These are functions of several parameters such as the fiber length, system bandwidth, modulation depth, radio cell size and relative RF power. The scenario is quite challenging when two RF systems are involved. In this paper we analyze such a dual system downlink and show how to decide the cumulative optical modulation index (mu) and the RF power ratio (T) that will yield the best performance for both systems