This paper addresses the problem of multiuser Orthogonal Frequency Division Multiplexing (OFDM) with adaptive sub-carrier, bit, and power allocation to minimize overall transmit power in a frequency selective fading environment. The authors propose an algorithm that assigns sub-carriers to users based on their instantaneous channel gains and determines the number of bits and transmit power level for each sub-carrier. The performance of the proposed algorithm is evaluated in a multiuser frequency selective fading environment, showing significant improvement over static TDMA or FDMA systems. The improvement is quantified in terms of overall transmit power, average bit error rate, and area of coverage for a given outage probability. The paper also discusses the implementation details of the algorithm and compares it with other static sub-carrier allocation schemes through Monte Carlo simulations. The results demonstrate that the proposed algorithm can reduce transmit power by 5-10 dB compared to conventional OFDM systems and by 3-5 dB compared to systems with adaptive modulation and bit allocation but without adaptive sub-carrier allocation. Additionally, the algorithm shows better performance in terms of bit error rate and coverage area.This paper addresses the problem of multiuser Orthogonal Frequency Division Multiplexing (OFDM) with adaptive sub-carrier, bit, and power allocation to minimize overall transmit power in a frequency selective fading environment. The authors propose an algorithm that assigns sub-carriers to users based on their instantaneous channel gains and determines the number of bits and transmit power level for each sub-carrier. The performance of the proposed algorithm is evaluated in a multiuser frequency selective fading environment, showing significant improvement over static TDMA or FDMA systems. The improvement is quantified in terms of overall transmit power, average bit error rate, and area of coverage for a given outage probability. The paper also discusses the implementation details of the algorithm and compares it with other static sub-carrier allocation schemes through Monte Carlo simulations. The results demonstrate that the proposed algorithm can reduce transmit power by 5-10 dB compared to conventional OFDM systems and by 3-5 dB compared to systems with adaptive modulation and bit allocation but without adaptive sub-carrier allocation. Additionally, the algorithm shows better performance in terms of bit error rate and coverage area.