WLC03-2: Capacity Analysis of Downlink CDMA Systems with Quasi-Orthogonal Sequences

We analyze the user capacity of downlink CDMA systems with quasi-orthogonal sequences (QOSs) considering various system parameters, such as user activity, spreading factor, the amount of transmission symbol energy allocated to common control channels, the amount of outer-cell interference, and sectorization factor. We also consider a power control mechanism with geometric factors such as propagation loss and shadowing effect. This user capacity analysis gives us the pole capacity of the system, which is the user capacity when all BSs transmit signals with unlimited power. Numerical examples show that the introduction of QOSs makes it possible to overcome the code limitation. We discuss how much the user capacity is increased according to various system parameters. For example, in an omni-cell environment with minimum outer-cell interference, if the mean channel activity and the required (E_b/I₀) value are set to 0.2 and 2.0 [dB] respectively, the user capacity is 194 which is much higher than the code limitation.