Adaptive Modulation Schemes In 3G UMTS/WCDMA Wireless Technology

The term Adaptive modulation denotes to the selection of modulation schemes according to the wireless channel condition.Nowadays adaptive modulation scheme is widely used in wireless communication system due to limited bandwidth.The adaptive modulation scheme uses the available bandwidth efficiently to increase throughput of the system.The main aim of adaptive modulation scheme is to improve BER and throughput of wireless communication system.In this thesis,adaptive modulation scheme is used in 3G UMTS/WCDMA wireless technology.The purpose of adaptive modulation in 3G UMTS/WCDMA is to improve BER,throughput,Quality of service of a signal by changing modulation schemes according to the SNR of wireless communication channel.Adaptive modulatio n is used for long coverage area.For changing modulation schemes according to the SNR,the SNR of different modulation schemes like BPSK,QPSK,16 QAM,64QAM has estimated.The simulation results of SNR estimation show that the effect of noise on high modulation scheme is high and give low SNR as compared to low modulation scheme.The BER of the described modulation schemes are measured individually and combine on the basis of that estimated SNR.The simulation results of combi ne modulation schemes of BER vs SNR measurement show that high modulation schemes like 16 QAM,64QAM have high BER at low SNR values as compared low modulation schemes like BPSK,QPSK.A large error occurs in transmission of high-modulated signal as compared low modulation scheme in low SNR value.The high modulation schemes 16 QAM,64 QAM has low BER and small error occur in high-modulated signal at high SNR value as compared low modulation schemes like BPSK,QPSK.The simulation results show that the performance of combine modulat ion schemes,which are also,called adaptive modulation scheme is better than one type of higher modulation scheme like 64 QAM in overall value of SNR in wireless communication system.The SNR vs Distance relation of adaptive modulation scheme is used in Single B.S,Two B.S and Six Base station simulated environment having same coverage area of transmitted signal.The simulation results show that the mobile user in Six B.S simulated environment gets high received power from Six B.S and produces high SNR due to which high modulation schemes like 64 QAM,16 QAM is used in whole coverage area as compared to Single and Two B.S simulated environment.In Six B.S,high spectral efficiency achieves as compared Single and Two B.S simulated environment.