Improving the delay performance of CSMA algorithms: A Virtual Multi-Channel approach

Abstract

Abstract-CSMA algorithms have recently received a significant amount of interest in the literature for designing efficient wireless control algorithms. CSMA algorithms are attractive because they incur low computation complexity and communication overhead, and can be shown to achieve the optimal capacity under certain assumptions. However, it has also been observed that CSMA algorithms suffer the starvation problem and incur large delay that may grow exponentially with the network size. In this paper, we propose a new algorithm, called Virtual-Multi-Channel (VMC-) CSMA, that can dramatically reduce delay without sacrificing the high capacity and low complexity of CSMA. The key idea of VMC-CSMA to avoid the starvation problem is to use multiple virtual channels to emulate a multi-channel system and compute a good set of feasible schedules simultaneously (without constantly switching/re-computing schedules). Under the protocol interference model and a single-hop utility-maximization setting, our proposed VMC-CSMA algorithm can approach arbitrarily close to the optimal total system utility, with both the number of virtual channels and the computation complexity increasing logarithmically with the network size. The VMC-CSMA algorithm inherits the distributed nature of CSMA algorithms. Further, once our algorithm converges to the steady-state, the expected packet delay for each link equals to the inverse of its long-term average rate, and the distribution of its head-of-line (HOL) waiting time can also be asymptotically bounded. Our simulation results confirm that the proposed VMC-CSMA algorithm indeed achieves both high throughput and low delay. Further, it can quickly adapt to network traffic changes.

Achieving Optimal Throughput Utility and Low Delay With CSMA-Like Algorithms: A Virtual Multichannel Approach

“…be the optimal solution of problem (1). Note that problem (1) is a cross-layer control problem [3] because it involves two control mechanisms.…”

“…This nice result is presented in the following proposition. Recall that R * ℓ is the optimal solution of link ℓ in problem (1).…”

“…is the optimal rate allocation of problem (1). By Caratheodory's Theorem [23], ⃗ R * can be represented as a convex combi-…”

“…It is well known that max-weight algorithms [2] can attain the largest capacity This work has been partially supported by the National Science Foundation through grant CNS-0643145, CNS-0721484, and CNS-0831999. Earlier version of this paper has appeared in IEEE INFOCOM'13 [1].…”

“…Recently, a class of CSMA (Carrier Sense Multiple Access) algorithms were studied in [5,6]. CSMA algorithms are attractive because they are fully distributed and have O (1) complexity that is independent of the network size. Further, CSMA algorithms can be shown to achieve the optimal capacity under certain assumptions.…”