On minimum time span scheduling of non-real-time data in uplink of DS-CDMA systems

The focus of this paper is on the non-real-time service such as the background best effort service in UMTS. In case of non-real-time data, the latency requirement is not that strict as in the case of conversational and streaming type of real-time data. This increases the degree of freedom in the radio resource management by allowing packet scheduling. In this paper, we consider the problem of finding the shortest uplink schedule that is able to empty the transmission buffer of all the users. This problem was originally suggested in [R. Jantti et al., May 2001]. However, the paper only discussed the case, in which the relation between the signal-to-interference + noise ratio (SIR) and the transmission bit rate is linear. In this paper, we extend the results to the case of discrete set of rates. The minimum packet scheduling problem turns out to be NP complete and thus difficult to solve exactly. Based on the optimal minimum time schedules we derive simple heuristic rules for packet scheduling that achieves close to optimal performance.