Opportunistic scheduling for streaming users in high-speed downlink packet access (HSDPA)

High-speed downlink packet access (HSDPA) achieves high data rates and high spectral efficiency by using adaptive modulation and coding (AMC) schemes and employing multi-code operation of CDMA. In this paper we present opportunistic algorithms for scheduling HSDPA users and selecting modulation and coding schemes that exploit channel variations to increase the probability of an uninterrupted media play-out. First we introduce a discrete event model for HSDPA system to transform the scheduling problem for providing an uninterrupted play-out to a feasibility problem that considers short term and long term quality of service (QoS) constraints. A methodology for obtaining a feasible solution is then proposed by starting with a so called stable algorithm that satisfies the long term QoS constraints (if possible with any scheduling policy). Next, we present stochastic approximation algorithms that adapt the parameters of the stable algorithm in a way that a feasible point for the short term QoS is reached within the feasibility region of the long term QoS.