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

Abstract

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.

HSDPA Performance in a Mixed Traffic Network

“…The residual intracell interference (after Rake processing), arriving at the receiver from the serving base station, is given by [6],…”

“…O →Ō and L m,i →L m . The orthogonality factor, α, can be calculated in a simple way as described in [6],…”

System level performance evaluation of MIMO and SISO OFDM-based WLANs

“…Figure 2 illustrates the considered system, modeling a MIMO OFDM system incorporating closed loop power allocation algorithms. Equation 15 can be reordered to express the input-output relation as a set of P matrices that involve only one sub-carrier each:…”

“…Other methodologies can be found in [14] based on PER-prediction indicator, in [15] based on Variable Orthogonality Factor, in [16] based on SINR estimation and [17] based on postdetection SNR. A different approach is described in [18] where a link-to-system interface is developed based on an information theoretic metric and specifically, channel capacity.…”

“…Among the above challenges, the development of efficient link-to-system interfaces has attracted significant research and various methodologies have been proposed [7][8][9][10][11][12][13][14][15][16][17][18]. However, to the best of our knowledge, there is no previous work that applies such an interface to system level studies of MIMO WLANs.…”