Channel-gain matched macrodiversity in the forward link of CDMA systems

The orthogonality factor was used to simplify the expression of the E_b/N₀ of a mobile station communicating with a single base station in the forward link of CDMA systems. This paper extends the orthogonality factor to express the E_b/N₀ of a mobile station communicating with multiple base stations by using the channel-gain matched combination approach. A simplified expression of the E_b/N₀ is derived by averaging over fast fading and using average orthogonality factor. This new expression of E_b/N₀ simplifies the capacity and outage calculations of the CDMA systems in the forward link. The relationship between the average E_b/N₀ in practical CDMA systems and that obtained using the simplified model is discussed. The analysis shows that averaging over fast fading leads to a conservative evaluation of the CDMA system performance.