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UBC Theses and Dissertations

Spectrum efficiency optimization in cellular packet data communication Chong, Peter H. J.


In most studies on the effect of co-channel interferers, the interference is assumed to be Gaussian. In this thesis, a more realistic simulation model of multiple co-channel interferers in a cellular packet data communication system using non-coherent frequency shift keying modulation is developed for a non-fading and a fading environment. The performance of the packet data traffic as the number of co-channel interferers increases is investigated in terms of BER and BKER results obtained from the simulation. Other parameters studied are block length, propagation loss exponent, fading rate and background noise level. It is found that as the number of interferers increases, error rates increase except for the BER in slow Rayleigh fading which tends to be independent of the number of interferers. Eventually, the effect of the interference signal can be regarded as similar to that of Gaussian noise. The spectrum efficiency with different system configurations and parameters is obtained by assuming that the mobile is located near the cell boundary. The influence of the cluster size on spectrum efficiency is investigated. The optimal value, Kopt, of the cluster size is found. In an interference-limited environment, the spectrum efficiency tends to increase with the propagation loss exponent because of the improved SIR value. It is found that the optimal spectrum efficiency can be greatly increased with the use of directional antennas. In most non-fading and very slow fading cases considered, Kopt is typically less than 7. However, Kopt increases with the fading rate. Generally, measures such as FEC taken to counteract the effects of the interference result in a smaller value of Kopt. However, FEC does not necessarily improve the spectrum efficiency.

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