Dual QoS loading algorithms for DMT systems offering CBR and VBR services

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, dual loading algorithms for both finite and infinite granularity cases, specifically for DMT systems simultaneously offering CBR and VBR services with different QoS. These methods are based on a novel tone selection procedure that offers significant reduction in complexity but still achieves near optimal performance. We present simulation results of these loading algorithms applied to frequency selective Rayleigh fading channels with additive white Gaussian noise and to asymmetric digital subscriber lines (ADSL) service