Discrete dual QoS loading algorithms for multicarrier systems

We derive the optimal bit and energy allocation for a discrete multitone (DMT) modulation system simultaneously providing two services with different quality of services (QoS), and show that it is NP-hard. Thus, we propose three novel, fast, discrete dual loading algorithms. These methods apply Campello´s (see IEEE International Symposium on Info. Theory, MIT, p.193, 1998) discrete loading algorithms and are based on a novel tone selection procedure that offers significant reduction in complexity but still achieves near optimal performance. Simulation results support our tone selection procedure by indicating the convergence in performance of these loading algorithms to the optimum with increasing N, N being the number of subchannels or tones