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008 030926s2002 th u m rtt 00| a1eng d
035 _a.b11900234
099 9 _aAIT Thesis no.TC-02-10
100 1 _aWasantha, Muthuthanthrige Kumudu
245 1 0 _aAdaptive modulation techniques for OFDM-CDMA based 4G mobile networks
260 _aBangkok :
_bAsian Institute of Technology,
_c2002
300 _a65 leaves
490 1 _aThesis ;
_vno. TC-02-10
500 _aA thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology
502 _aThesis (M.Eng.) - Asian Institute of Technology, 2002
520 _aEver 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.
650 0 _aModulation theory
650 0 _aCode division multiple access
700 1 _aFernando, W.A.C.,
_eChairperson
700 1 _aAhmed, Kazi Mohiuddin,
_eExamination Committee
700 1 _aErke, Tapio J.,
_eExamination Committee
710 2 _aSonera Corporation, Finland,
_eScholarship donor
810 2 _aAsian Institute of Technology.
_tThesis ;
_vno. TC-02-10
856 _3Full-Text
_uhttp://203.159.5.9/ait-thesis/detail.php?q=B07561
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