Pull vs. Hybrid: Comparing Scheduling Algorithms for Asymmetric Time-Constrained Environments

Data broadcasting has been recognized as a very effective data delivery mechanism in mobile computing environments with an unlimited number of users and changing demand patterns. A fundamental server design issue is the scheduling algorithm needed for the construction of the broadcast program. In most situations, users require information before a certain time, and therefore the server scheduling algorithm should consider the existence of timing constraints. In this paper we analyse the theoretical lower bound for deadlines missed in strong server overload conditions. Considering the results of the theoretical analysis, this paper compares two recent scheduling algorithms, pull-based SINα and hybrid (push-pull) AHB, both proved to perform efficiently in asymmetric time-constrained communication environments in which the user access distribution is dynamic. Performance is evaluated by simulation.