Multi-cell WLANs Research Articles

WLAN Channel Assignment Based on Minimizing the Worst-Case Interference

An optimization model for solving the channel assignment problem in multi-cell WLANs which is based on minimizing the maximum interference at access points in the network is proposed. The channel assignment problem is formulated as a mixed integer linear program. The main advantage of the proposed model is that it guarantees that the worst access point interference is minimized. Simulation results show that the proposed model provides both the least worst access point interference and the best fairness, compared to the pick-first greedy algorithm, the optimum model and the maxmin model.

Low Complexity Channel Assignment for IEEE 802.11b/g Multi-Cell WLANs

Low Complexity Channel Assignment for IEEE 802.11b/g Multi-Cell WLANs

A maxmin approach for channel assignment in multi-cell WLANs

A maxmin approach for channel assignment in multi-cell WLANs

TCP performance optimization in multi-cell WLANs

Though significant attention has been given to understanding the performance of a single-cell WLAN, performance evaluation of a group of interfering basic service sets (BSSs) within an extended service set (ESS) is still an open area. In this paper, we first demonstrate that a severe throughput imbalance occurs between downlink TCP flows even in the simplest of multi-cell WLANs via simulation and real world experiments; then, to solve this unfairness problem, we derive an analytical model that describes the interaction between TCP flows at the MAC layer, and formulate a throughput allocation problem as a nonlinear optimization problem subject to certain fairness requirements. Our formulation considers real world complexity such as hidden terminals, packet transmission retry limit, and the unique characteristics of TCP traffic. Solving our optimization problem yields the optimal MAC layer contention window settings that can lead each TCP flow to its target end-to-end throughput without the need for any per-flow queuing nor modification of the TCP sender. Simulation results show that our approach can achieve a fair allocation on the end-to-end throughput and attest to the accuracy of our proposed method.

Traffic capacity of multi-cell WLANS

Performance of WLANs has been extensively studied during the past few years. While the focus has mostly been on isolated cells, the coverage of WLANs is in practice most often realised through several cells. Cells using the same frequency channel typically interact through the exclusion region enforced by the RTS/CTS mechanism prior to the transmission of any packet. In this paper, we investigate the impact of this interaction on the overall network capacity under realistic dynamic traffic conditions. Specifically, we represent each cell as a queue and derive the stability condition of the corresponding coupled queuing system. This condition is then used to calculate the network capacity. To gain insight into the particular nature of interference in multi-cell WLANs, we apply our model to a number of simple network topologies and explicitly derive the capacity in several cases. The results notably show that the capacity gain obtained by using M frequency channels can grow significantly faster than M, the rate one might intuitively expect. In addition to stability results, we present an approximate model to derive the impact of network load on the mean transfer rate seen by the users.