This paper presents a multiuser Orthogonal Frequency Division Multiplexing (OFDM) system with adaptive sub-carrier, bit, and power allocation. The goal is to minimize the total transmit power by assigning sub-carriers to users and determining the number of bits and transmit power level for each sub-carrier based on instantaneous channel conditions. The proposed algorithm outperforms static TDMA or FDMA techniques in multiuser frequency selective fading environments. The results show that the proposed algorithm improves overall transmit power, bit error rate, and coverage area for a given outage probability. The system model considers K users with known channel gains and aims to minimize transmit power while meeting data rate requirements. The paper also presents a bit allocation algorithm for single-user channels and a multiuser sub-carrier and bit allocation algorithm. The results demonstrate that the proposed algorithm achieves significant improvements over static allocation schemes, with the MAO scheme outperforming others by up to 3-5dB in transmit power reduction. The algorithm is shown to be effective in reducing required bit SNR and improving coverage area for a given outage probability. The paper also discusses the impact of channel estimation errors on the performance of the proposed MAO scheme.This paper presents a multiuser Orthogonal Frequency Division Multiplexing (OFDM) system with adaptive sub-carrier, bit, and power allocation. The goal is to minimize the total transmit power by assigning sub-carriers to users and determining the number of bits and transmit power level for each sub-carrier based on instantaneous channel conditions. The proposed algorithm outperforms static TDMA or FDMA techniques in multiuser frequency selective fading environments. The results show that the proposed algorithm improves overall transmit power, bit error rate, and coverage area for a given outage probability. The system model considers K users with known channel gains and aims to minimize transmit power while meeting data rate requirements. The paper also presents a bit allocation algorithm for single-user channels and a multiuser sub-carrier and bit allocation algorithm. The results demonstrate that the proposed algorithm achieves significant improvements over static allocation schemes, with the MAO scheme outperforming others by up to 3-5dB in transmit power reduction. The algorithm is shown to be effective in reducing required bit SNR and improving coverage area for a given outage probability. The paper also discusses the impact of channel estimation errors on the performance of the proposed MAO scheme.