In this paper, we present a generic plug-and-play controller that ensures fair and efficient operation of IEEE 802.11 infrastructure wireless local area networks with multiple co-channel access points, without any change to hardware firmware of the network devices. Our controller addresses performance issues of TCP transfers in multi-AP WLANs, by overlaying a coarse time-slicing scheduler on top of a cascaded fair queuing scheduler. The time slices and queue weights, used in our controller, are obtained from the solution of a constrained utility optimization formulation. A study of the impact of coarse time-slicing on TCP is also presented in this paper. We present an improved algorithm for adaptation of the service rate of the fair queuing scheduler and provide experimental results to illustrate its efficacy. We also present the changes that need to be incorporated to the proposed approach, to handle short-lived and interactive TCP flows. Finally, we report the results of experiments performed on a real testbed, demonstrating the efficacy of our controller.
SMARTA @cite_1 is a centralized controller that sets and dynamically adjusts the operating parameters of enterprise WLAN Access Points (e.g., channel frequency and power allocation) to optimize a predefined objective. In @cite_1 , the authors describe several simple tests to estimate the interference environment and obtain a . Based on this conflict-graph, the controller executes channel assignment and power control algorithms that aim to minimize the number of conflicting transmissions. We note that SMARTA focuses on system configuration, and that there are no mechanisms for controlling the rate of traffic on the links. Also, SMARTA does not incorporate the capacity of the wide-area-network (WAN)-WLAN links into its design. Therefore, SMARTA may not perform efficiently in networks with WAN-WLAN traffic. Further, we would like to note that SMARTA is evaluated via simulations and not on a real testbed.
@cite_1
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Optimally choosing operating parameters for access points in an enterprise wireless LAN environment is a difficult and well-studied problem. Unlike past work, the SMARTA self-managing wireless LAN architecture dynamically adjusts both access point channel assignments and power levels in response to measured changes in the wireless environment to optimize arbitrary objective functions, while taking into account the irregular nature of RF propagation, and working with unmodified legacy clients. We evaluate the SMARTA architecture through simulation and show that our solution is not only feasible, but also provides significant improvements over existing approaches. For example, in a realistic scenario, SMARTA can provide 50 more throughput and 40 lower mean per-packet delay than a hand-optimized configuration. Moreover, SMARTA can automatically reconfigure channels and power levels in response to both small and large changes in the RF environment due to client movement. With the development of information technology those years, big data and cloud computing technology has been widely used. Those new communication scenarios require the network with very powerful computing power and real-time business processing capabilities. But limited by the number of channels that can be used in 802.11b g, there are a lot of channel interferences in WLAN system. In this paper, firstly we propose a hierarchical WLAN architecture suiting for big data communication environment, which can ensure the transmission of important information and enhance the central control capability of the system. And then we give a channel allocation algorithm RCE for typical and hierarchical WLAN architectures. Especially, the algorithm can make use of all 14 channels by introducing channel interference factors. A large number of experiments show that our channel allocation algorithm has better result in reducing overall system interference and improving channel utilization, and can be applied to different network structures preferably. In wireless cellular networks and wireless local area networks, nonlinear network utility maximization need to be conducted over both user rates and transmit powers. For each of the three cases considered in this paper, we present an algorithm that converges to the jointly optimal pair of rate vector and power vector. For the simple case when data rates are not limited by interferences, for example in single-cell downlink transmissions, we propose algorithm 1, which is an iterative bidding mechanism between the base station and mobile users, where knowledge about channel conditions and individual user utility functions is only needed locally at each user but not needed at the base station. In the case when data rates are limited by interferences, the utility maximization problem is complicated both by nonlinear coupling between powers and rates, and by interference among powers. Through centralized iterative steps, we propose algorithm 2, which converges to a joint and global optimum over the solution space of rates and powers. We then consider end-to-end transmissions in cellular networks, which traverse both wireless fading channels and many hops of wired links shared by other traffic. There is a tradeoff between attaining air-interface capacity in the wireless hop and controlling congestion in the wired backbone wide area network. We formulate this end-to-end resource allocation problem in such hybrid networks, and present a solution to obtain the Pareto optimal tradeoff between attaining wireless multi-access fading channel capacity and maximizing global network utility. Bulk transfer on the wide-area network (WAN) is a fundamental service to many globally-distributed applications. It is challenging to efficiently utilize expensive WAN bandwidth to achieve short transfer completion time and meet mission-critical deadlines. Advancements in software-defined networking (SDN) and optical hardware make it feasible and beneficial to quickly reconfigure optical devices in the optical layer, which brings a new opportunity for traffic management on the WAN. We present Owan, a novel traffic management system that optimizes wide-area bulk transfers with centralized joint control of the optical and network layers. can dynamically change the network-layer topology by reconfiguring the optical devices. We develop efficient algorithms to jointly optimize optical circuit setup, routing and rate allocation, and dynamically adapt them to traffic demand changes. We have built a prototype of Owan with commodity optical and electrical hardware. Testbed experiments and large-scale simulations on two ISP topologies and one inter-DC topology show that completes transfers up to 4.45x faster on average, and up to 1.36x more transfers meet their deadlines, as compared to prior methods that only control the network layer.