04884nas|a2200469 i 4500 20260817161527.0 030926s2002 th u m rtt 00| a1eng d .b11900234 AIT Thesis no.TC-02-10 Wasantha, Muthuthanthrige Kumudu Adaptive modulation techniques for OFDM-CDMA based 4G mobile networks Bangkok : Asian Institute of Technology, 2002 65 leaves Thesis ; no. TC-02-10 A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology Thesis (M.Eng.) - Asian Institute of Technology, 2002 Ever increasing demand for high speed data transmission with mobility due to the quantum advancement in multimedia applications used in this information era day to day life has created a huge burden on the limited radio frequency bandwidth available for wireless communication. OFDM - CDMA (Orthogonal Frequency Division Multiplexing - Code Division Multiple Access) with adaptive modulation techniques is one of the most promising technologies for high speed data transmission over wireless channels due to its favourable properties to overcome many channel impairments. Quadrature Amplitude Modulation (QAM), Phase Shift Keying (PSK) and Multi-h Continuous Phase Modulation schemes are investigated in this study as adaptive modulation techniques. A pilot symbol assisted channel estimation method is used to estimate the channel quality and to decide the suitable modulation format to meet the targeted Bit Error Rate (BER) of 1 o-04 or better. BER performance of M-ary QAM (M=2, 4, 16), M-ary PSK (M=2, 4, 8) and M-ary MHPM (M=2, 4) modulation schemes in OFDM-CDMA system under different channel conditions and with different number of CDMA users has been investigated and presented in this thesis. In general higher order modulation schemes can accommodate only few number of CDMA users and more noise resilient lower order modulation schemes can support more number of CDMA users. Based on the results of the OFDM-CDMA system with fixed modulation schemes and the corresponding estimated channel CNR, OFDM-CDMA systems with adaptive modulation schemes were simulated. The simulation results show that an adaptive modulation based system can use the available spectrum more efficiently than fixed modulation based system under varying channel conditions while maintaining a targeted BER performance criterion. Further simulation results show that irrespective of modulation scheme i.e., whether QAM, PSK or MHPM, any higher order modulation format need better channel condition than a lower order format to maintain the same BER performance. In poor channel conditions all adaptive systems end up with the lowest order modulation scheme available in the system. There is no specific advantage in terms of BER performance in limiting modulations formats to one category in adaptive systems such as adaptive PSK, adaptive QAM etc., but in terms of hardware and software it is easier to implement such a system than an adaptive system having many different modulation schemes such as QAM, PSK and MHPM. Modulation theory Code division multiple access Fernando, W.A.C., Chairperson Ahmed, Kazi Mohiuddin, Examination Committee Erke, Tapio J., Examination Committee Sonera Corporation, Finland, Scholarship donor Asian Institute of Technology. Thesis ; no. TC-02-10 Full-Text http://203.159.5.9/ait-thesis/detail.php?q=B07561 .b11900234 mnait u 240710 0 030926 m a u 0 mnait mnait mnarc mnarc mnarc 20 40 Barcode : 30050120810006 CREATED : 2002-04-29 RECORD # : i12356542 LPATRON : 1015831 LCHKIN : 2003-08-09 # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 6 TOT RENEW : 14 Barcode : 30050120809990 CREATED : 2002-04-29 RECORD # : i12356554 LPATRON : 1024121 LCHKIN : 2013-11-10 # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 10 TOT RENEW : 18 Barcode : 30050160045000 CREATED : 2016-03-03 RECORD # : i12888941 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 Barcode : 30050211033492 CREATED : 2021-04-30 RECORD # : i13341388 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 Barcode : 30050211032403 CREATED : 2021-05-05 RECORD # : i13344778 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 1615 1615 0 0 0 0 MAIN MAIN mnait 2026-08-17 50.00 0 AIT Thesis no.TC-02-10 30050120810006 2026-08-17 16:15:27 1 2026-08-17 20 0 0 0 0 MAIN MAIN mnait 2026-08-17 50.00 0 AIT Thesis no.TC-02-10 30050120809990 2026-08-17 16:15:27 2 2026-08-17 20 0 0 0 0 MAIN MAIN mnarc 2026-08-17 0 AIT Thesis no.TC-02-10 30050160045000 2026-08-17 16:15:27 2026-08-17 40 0 0 0 0 MAIN MAIN mnarc 2026-08-17 50.00 0 AIT Thesis no.TC-02-10 30050211033492 2026-08-17 16:15:27 3 2026-08-17 20 0 0 0 0 MAIN MAIN mnarc 2026-08-17 50.00 0 AIT Thesis no.TC-02-10 30050211032403 2026-08-17 16:15:27 4 2026-08-17 20