Optimal link scheduling for real-time traffic in wireless mesh networks in both per-flow and per-path frameworks

Abstract

In this paper we investigate link scheduling for Wireless Mesh Networks (WMNs) carrying real-time (i.e., delayconstrained) traffic. We show that the problem of computing a conflict-free link schedule with end-to-end delay constraints can be formulated as a mixed-integer non linear problem that can be optimally solved in reasonable time (i.e., minutes) for relatively large WMNs (up to 20-30 nodes). We use the above result to explore the schedulability region of a WMN with a given routing and input traffic, assessing whether and when aggregating flows which traverse the same path makes a given input flow set schedulable. Furthermore, we devise a heuristic solution strategy, which computes good suboptimal solutions within up to few seconds, thus being amenable for online admission control.

Optimal joint routing and link scheduling for real-time traffic in TDMA Wireless Mesh Networks

“…As queuing is a component (and often the dominant one) of the end-toend delay, especially with VBR traffic, there is no guarantee that such algorithms can actually find a delay-feasible schedule if there exists one. We showed this in [9], using [26] as a comparison. Within the second category, [25] considers both CBR (voice) and VBR (video) flows, however assuming that VBR sources can be described as stationary, ergodic and independent processes with known statistics, so as to characterize them as equivalent CBR sources.…”

“…In the latter, we use a capacitated multicommodity flow (CMF) routing, where each flow q requires a capacity equal to its rate q ρ , and the routing that minimizes the overall number of traversed links is chosen, keeping into account the capacity constraints. The CMF sets the q e t variables, and then the link scheduling is solved optimally given the routing, as in [9]. In the joint approach, we use LCS+r-DARS, with the latter solved through the Lagrangian heuristic.…”

“…While all the above goals are indeed important and worth pursuing, they are not enough to guarantee that pre-specified worst-case delays are enforced if it is actually possible to do so. For instance, we showed in [9] that minimizing the TDMA delay, as done in [26], yields schedules that largely violate pre-specified delay bounds, even though it is possible to find alternative, delayfeasible schedules. Our previous works [8]- [10] are actually the first to consider delay-constrained link scheduling in WMNs, also evaluating different architectural options for flow aggregation.…”

“…Our previous works [8]- [10] are actually the first to consider delay-constrained link scheduling in WMNs, also evaluating different architectural options for flow aggregation. However, routing is left outside the scope of these works, by assuming either a tree network topology, with a single possible path from each node to the network gateway ( [8], [10]), or an arbitrary but given routing plan, upon which a delay-feasible link schedule is computed ( [9]). Tackling the problem of routing and link scheduling separately (e.g., in a cascading approach) leads to a loss in effectiveness.…”

An optimization scheme for routing and scheduling of concurrent user requests in wireless mesh networks

“…An Overview Multiple pair paths (MPP) in WMNs may have node intersections as in real-time video communications [13]. For example, in Fig.…”