Variable orthogonality factor: a simple interface between link and system level simulation for high speed downlink packet access

Detailed simulations of the full physical layer operation of a cellular network are usually performed in two stages, link level and system level. Emergence of new link adaptation and radio resource management techniques together with need for higher modeling accuracy are blurring the line separating these stages. In this paper we address the issue of performing a link level/system level separation and defining the interface between them for simulating high speed downlink packet access (HSDPA), a part of WCDMA standard. The main challenge is to model frequency selective fading on the system level, while retaining the Rake receiver on the link level. We present available strategies and propose a novel interface based on variable orthogonality factor (OF), which serves as a compact description of the momentary channel impulse response. Finally, we present HSDPA simulation results demonstrating the high accuracy of our approach.