Opportunistic scheduling policies for improved throughput guarantees in wireless networks

Abstract

Offering throughput guarantees for cellular wireless networks, carrying real-time traffic, is of interest to both the network operators and the customers. In this article, we formulate an optimization problem which aims at maximizing the throughput that can be guaranteed to the mobile users. By building on results obtained by Borst and Whiting and by assuming that the distributions of the users' carrier-to-noise ratios are known, we find the solution to this problem for users with different channel quality distributions, for both the scenario where all the users have the same throughput guarantees, and the scenario where all the users have different throughput guarantees. Based on these solutions, we also propose two simple and low complexity adaptive scheduling algorithms that perform significantly better than other well-known scheduling algorithms. We further develop an expression for the approximate throughput guarantee violation probability for users in time-slotted networks with the given cumulants of the distribution of bit-rate in a time-slot, and a given distribution for the number of timeslots allocated within a time-window.

Maximizing Minimum Throughput Guarantees: The Small Violation Probability Region

“…PFS handles the guaranteed throughput violation event in a better way. However, it is evident that our scheme outperforms all the schemes including the scheme proposed in [5]. Specifically, the gain in small violation probability region is substantial.…”

“…1(b) we observe the behaviour of the schemes when we decrease the ratio K/L W at fixed K = 10. We compare the schemes for the window size 80 and 235 (as suggested by the European Winner I project for future mobile systems [5]). We observe that increase in window size closes the gap between the schemes and all the schemes converge to a long term average behaviour.…”

“…Reference [4] provides approximate expressions for the violation probability for some of the existing schedulers under finite windows. The work in [5] uses a similar approach to compute the violation probability and proposes a heuristic scheme to provide throughput guarantees in finite windows. This work keeps the users out of contention whose throughput is above the target throughput.…”

Secondary User Scheduling under Throughput Guarantees for the Primary Network

“…Secondly, the time scale for averaging the throughput for a primary user is of the order of few tens (e.g. 16 for WIMAX [8]) since averaging of throughput over infinite time gives misleading results sometimes as shown in [1]. We characterize the tradeoff between gain in average throughput of the SN against a (small) loss in terms of violation probability at a guaranteed throughput (per user) for the PN.…”

“…References [7], [8] address specifically violation probability for a given minimum throughput guarantee in the finite window case. Similar problems have been addressed in CR domain as well.…”