Energy-feedback tradeoff in the best-M OFDMA systems

Feedback is required to design energy efficient schemes in order to adapt the transmitter processing to the channel characteristics and to boost the system performance, but the feedback load is an important parameter with a large impact on the system performance. Its signalling load represents a main challenge for multi-carrier and multiuser systems, where its optimization is required. Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-carrier technique currently under consideration in several commercial standards, where the feedback over each one of its subcarriers induces a non-acceptable signalling load in the system. A tradeoff is obtained between the two conflicting objectives, where this paper studies the feedback effect and how it induces additional energy consumption in the system. Closed form expressions are obtained for the amount of wasted energy where the effect of all the involved parameters is shown.