Energy efficiency on real time transmission in multiuser OFDM downlink

It has been shown that energy efficiency can be significantly improved by adaptive multicarrier transmission. When the water-filling strategy is employed, different rates are allocated to subcarriers. However, a large signalling overhead is induced, when the employed allocation scheme must be sent to receivers via signalling. In this paper, to enhance energy efficiency, we propose that a dynamic and symmetric rate is allocated to subcarriers of each user. Thereby, fewer bits are required to express each allocation scheme. The asymptotic limit of induced performance loss is given compared to the water-filling strategy. Furthermore, the proposed strategy brings convenience for heuristic design. Simulations demonstrate that the proposed method achieves higher energy efficiency than the water-filling strategy as allocation schemes are frequently updated in fast time-varying environments.