Push Less and Pull the Current Highest Demanded Data Item to Decrease the Waiting Time in Asymmetric Communication Environments

In these days, the world experiences an unprecedented demand for data and data services, driven mainly by the popularity of the Web services and by the evolution of the Internet towards an information super-highway. We introduce a hybrid scheduling that effectively combines broadcasting for very popular data (push data) and dissemination upon-request for less popular data (pull data) in asymmetric communication environments. In our solution, the server continuously broadcasts one push item and disseminates one pull item. The clients send their requests to the server, which queues-up them for the pull items. At any instant of time, the item to be broadcast is designated applying a purepush scheduling, while the item to be pulled is the one stored in the pull-queue, which has accumulated, so far, the highest number of pending requests. The value of the average expected waiting time spent by a client in the hybrid system, denoted by Texp-hyb, is evaluated analytically, and the cut-off point between push and pull items is chosen in such a way that Texp-hyb is minimized. We find out that by doing so we can drop the cut off point to a value, which is much less than the total number of items present in the system, improving upon the average waiting time spent by a client in a pure push system and also on that spent in some of the hybrid systems already proposed in literature.