Simulation of BCCH Channel of GSM/PCN Base Station with Signal Generator SME

Propagation measurements are indispensable in the planning of digital, cellular mobile radio net-works. To find the optimum sites for the base stations, a mobile test transmitter system simulating the base station is operated from a number of possible locations. The test receiver system is accommodated in a vehicle, which is driven along a test route to perform measurements. The parameters measured, such as level, bit error rate or channel impulse response, provide information on the coverage within the cell. The main problem is to minimize interference caused by multipath propagation in the reception area.
The SME offered by Rohde & Schwarz is a universal test generator that can be used as the core of a test transmitter system. The SME generates the GMSK-modulated signals required for GSM propagation measurements in line with the rele-vant standards. Thanks to its low weight of 17 kg it can be carried even to remote sites. Fitted with the new optional DM Memory Extension (SME-B12, in the following referred to as XMEM), the SME is able to store data sequences of up to 8 Mbit which are long enough for receiver measurements with test mobile stations.
A suitable test receiver system is for instance a test mobile station for measuring level and bit error rate and the Impulse Response Analyzer PCS from Rohde & Schwarz for measuring the channel impulse response.
The present Application Note describes how the XMEM can be loaded with suitable data (test sequence) by the GSM Radiocommunication Test Set CRTP from Rohde & Schwarz and how the SME has to be adjusted for GMSK modulation of these data.
First, however, an overview is given of all functions of the XMEM and their operation supplementary to the Operating Manual.
Finally, it is explained how the XMEM data can be transferred between PC and SME via the IEEE-488 or RS-232 interface.