The per sector or per cell downlink capacity in a spread spectrum wireless network is determined using a single test mobile that is operating within a background of simulated co-channel interference being broadcast in each sector by all cell sites in the network whose capacity is of interest. From all sectors, an Orthogonal Channel Noise Simulator (OCNS) generates a multiple number of calibrated test signals, which are aggregated and broadcast downlink, where each transmitted test signal simulates the downlink power transmitted to a live mobile. Each component test signal in the aggregated OCNS output transmitted in each sector is a sample of a stochastic process with a set mean and standard deviation that are determined from the mean and standard deviation of the power of a real signal transmitted downlink to the test mobile as it is moved around the network's coverage area. The capacity of the sector is determined by increasing the number of test signals in each aggregated OCNS output until measurable performance is compromised.