Resource allocation in OFDMA system by low complexity algorithm using M-QAM modulation:- In this the resource allocation of downlink of mobile communication in OFDMA system is efficiently done by the use of low complexity algorithm and the type of modulation used is M-QAM (in this the result are shown for M=4,16). By implementing these new modulation and algorithm to the system the throughput performance is increased as compared to previous technologies tested.