Influence of Slow Frequency Hopping and Antenna Diversity Techniques in European GSM System
Antenna Diversity (AD) and Slow Frequency Hopping (SFH) are used in GSM cellular system to improve significantly the transmission quality. The former technique combats multipath fading and shadowing while the latter additionally averages the effects of co-channel interference. The aim of this paper is to identify the optimum use of SFN and AD techniques in urban environment with cells of radius less than 1 km and with mobiles moving at a speed of 50 km/h and below.
In the first part, the simulation tool is described and optimum parameters for each method (choice of frequency in SFH, correlation of receiving signals in AD etc.) are proposed. Then improvements introduced by these different techniques are compared. The simulation results presented assess the efficiency domains of each of these techniques depending on the mobile velocity. Finally, assessment of the performance achieved when both techniques are used simultaneously is presented.
The simulation results show that in urban environment both techniques allow to have a system working with a lower co-channel interference level. However SFH is more efficient than AD for mobiles whose velocity is below 20 km/h. Moreover C/1 versus BER curves reveal that the best performance is obtained with a system using SFH and AD simultaneously and that improvements obtained by each technique are additive.
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