A simple mapping from C/I to FER and BER for a GSM type of air-interface

Abstract

To evaluate the performance of a mobile radio system, both network and link quality aspects have to be evaluated. A network simulator is often used to find the influence of different system parameters, such as DTX, frequency hopping and power control. To complete the evaluation, a link simulator has to be integrated in the network simulator, so that each radio link can be simulated. An obvious method to integrate the radio link quality aspects with the network simulator is to use the output of the network part of the simulator as input for an integrated link simulator. This will however lead to time consuming simulations, In this paper a simpler method is presented, which leads to a shorter simulation time. The output of the network part of the simulator, expressed in signal to interference (C/I) values, is used as input for look-up tables, which lead to a BER and a frame erasure rate (FER) for each radio link. These look-up tables are depending on the hopping pattern and channel profile and they are also receiver dependent. The results of the mapping method are good, except for a few situations, where the prediction of the BER goes wrong. This happens when sequential hopping with a few frequencies is used and the speed of the mobile user is low. In general the presented predictions are within 1 dB (FER) and within 0.2 dB (BER).