On-line algorithm for optimizing throughput performance of wireless LANs

Throughput improvement of the wireless LANs has been a constant area of research. Most of the work in this area focuses on designing throughput optimal schemes for fully connected networks (no hidden nodes). The schemes are optimal in a sense that they maximize the sum throughput subject to giving equal channel access opportunity to each user. But, we demonstrate that the optimal schemes proposed in the literature, though perform optimally in fully connected network, achieve significantly lesser throughput even than that of standard IEEE 802.11 in a network with hidden nodes. This motivates designing schemes that provide near optimal performance even when hidden nodes are present. This problem is particularly challenging as mathematical models for networks with hidden nodes do not exist. Here, we consider the weighted fair throughput allocation policy that maximizes system throughput while guaranteeing that every user achieves a throughput that is proportional to their weights. We prove the optimality of the proposed scheme in a fully connected network. However, the specialty of the algorithm, as observed in the simulation study, is that it can provide the optimal throughput even in networks with hidden terminals. Unlike existing techniques, which use the mathematical model to derive invariant features, we attempt to maximize the throughput directly using stochastic approximation techniques, and hence does not require the estimation of any system parameters which can result in inaccurate predictions. Simulations show that our proposed policies perform better than the standard IEEE 802.11 protocol without or with hidden nodes present. Moreover, our proposed schemes outperform existing schemes when the network is not fully connected.