A base station system study for LTE, UMTS and GSM/EDGE

Abstract

Communication systems evolve day after day at a very fast pace. People not only have high expectations in regard of the conversation quality, but they also need more data download speeds and better coverage. The industry tries to come and fill in this expectation by developing state-of-the art systems that are cost-effective and that ensure good profits. Telecommunication operators require from vendors top class, cheap and reliable equipments for their sites. Vendors on the other hand try to cut down costs by simulating and then developing products. The aim of this project is to simulate three important wireless systems LTE, UMTS and GSM/EDGE (at physical layer level) for base stations, according to the implementations mentioned in the 3GPP standards. The most demanding requirements have been derived in this work for each of the transceiver systems and a realistic system description has been implemented in MatLab 2008b. The tolerance to RF imperfections (DC offset, I-Q amplitude and phase mismatch, cubic nonlinearity, frequency offset, phase noise, etc.) are taken into consideration. Also implementation specific RF imperfection, like the delay and amplitude misalignment in outphasing transmitters has been considered. The RF imperfections have been considered in equal measures for both the transmitter and the receiver. The resulting study ensured a perfect calibration of the BER curves with the theoretical curves using the uncoded bits. The final system comparison in this thesis has been made only for the communication standard LTE, considering classical IQ Tx configuration, a pure outphasing transmitter and an improved efficiency outphasing Tx. This in order to investigate which concept is more tolerant to RF impairments. The parameters used in the simulations to check the system performances are: EVM, ACPR, scatter plots and BER. In conclusion, this study offers some suggestions for future research activities, related to topics like estimation, equalization, Rayleigh channels and Doppler affected Rayleigh channels.