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Proceedings ArticleDOI

Optimal Mapping of Stations to Access Points in Enterprise Wireless Local Area Networks

21 Nov 2017-pp 9-18
TL;DR: This work proposes to move the AP association decision to a periodically-running central controller which aims to maximize the proportionally-fair network throughput, and devise several heuristics requiring various degrees of knowledge, e.g., pairwise user-AP link rates, throughput demand of each user.
Abstract: Efficient resource allocation in enterprise wireless local area networks(WLAN) has become more paramount with the shift of traffic toward WLANs and increasing share of the video traffic. Unfortunately, current practise of client-driven association to APs has several shortcomings, e.g., sticky client problem. As a remedy, we propose to move the AP association decision to a periodically-running central controller which aims to maximize the proportionally-fair network throughput. After formulating the optimal mapping problem, we devise several heuristics requiring various degrees of knowledge, e.g., pairwise user-AP link rates, throughput demand of each user. Our analysis via simulations on realistic scenarios (conference, office, and shopping mall) shows the superior performance of our proposals in terms of aggregate logarithmic throughput. While the utility gain over the conventional client-driven approach is modest, up to 18%, the resulting increase in the weakest user's throughput is significant (71-120%) as well as that of AP load balance and fairness of user throughputs. Moreover, our evaluations reveal a very small optimality gap (between 0.1-5%). The highest gain is observed in the conference setting where the users are unevenly distributed in the network and hence there is a huge load imbalance among the APs. While schemes requiring more knowledge, i.e., on handover-cost and traffic demands, perform the best, a naive approach which runs periodically and assigns each user to the AP providing the highest signal level to that user maintains up to 41% gain in the weakest user's throughput over the client-driven handover approach.
Citations
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Proceedings Article
25 Jan 1995
TL;DR: In EFI XF 3.0, load balancing is not an officially supported feature and can only be achieved by manual ticket editing as mentioned in this paper, which is only recommended for experienced users.
Abstract: Load balancing is a standard feature of EFI XF 3.1 and later and is described in the manual provided with the product. However, in EFI XF 3.0, load balancing is not an officially supported feature and can only be achieved by manual ticket editing. Manual ticket editing is only recommended for experienced users. This document describes the steps necessary to achieve load balancing in EFI XF 3.0. NOTE: This method of load balancing cannot be applied to versions of EFI XF prior to 3.0.

110 citations

Journal ArticleDOI
TL;DR: ABRAHAM is introduced, a machine learning backed, proactive, handover algorithm that uses multiple metrics to predict the future state of the network and optimize the load to ensure the preservation of QoS.
Abstract: An important aspect of managing multi access point (AP) IEEE 802.11 networks is the support for mobility management by controlling the handover process. Most handover algorithms, residing on the client station (STA), are reactive and take a long time to converge, and thus severely impact Quality of Service (QoS) and Quality of Experience (QoE). Centralized approaches to mobility and handover management are mostly proprietary, reactive and require changes to the client STA. In this paper, we first created an Software-Defined Networking (SDN) modular handover management framework called HuMOR, which can create, validate and evaluate handover algorithms that preserve QoS. Relying on the capabilities of HuMOR, we introduce ABRAHAM, a machine learning backed, proactive, handover algorithm that uses multiple metrics to predict the future state of the network and optimize the load to ensure the preservation of QoS. We compare ABRAHAM to a number of alternative handover algorithms in a comprehensive QoS study, and demonstrate that it outperforms them with an average throughput improvement of up to 139%, while statistical analysis shows that there is significant statistical difference between ABRAHAM and the rest of the algorithms.

27 citations


Cites background from "Optimal Mapping of Stations to Acce..."

  • ...Similarly, Bayhan and Zubow [16] present an approach that uses a centralized controller and aims to maximize the overall throughput using different metrics such as AP-STA link rates, throughput demands of STAs, etc. Aldhaibani et al. [17] use several metrics such as bandwidth, jitter, delay and SINR, while Broustis et al. and Ahmed et al. consider power control and STA association information as metrics for AP selection and handover procedure....

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  • ...Similarly, Bayhan and Zubow [16] present an approach that uses a centralized controller and aims to maximize the overall throughput using different metrics such as AP-STA link rates, throughput demands of STAs, etc....

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Proceedings Article
01 Nov 2018
TL;DR: This paper uses virtualization and softwarization to shift the traditional mobile node-driven handovers to the access point, while maintaining compliance with legacy devices, and develops a proactive handover algorithm ADNA, which combines network state, traffic load and node mobility information.
Abstract: In large and densely deployed IEEE 802.11 networks, a fast and seamless handover scheme is an important aspect in order to provide reliable connectivity for mobile users. However, IEEE 802.11 only supports decentralized, reactive and mobile node-driven handovers resulting in long handover times, packet loss due to interrupted connectivity and sub-optimal access point selection. Recently, centralized approaches have been developed that try to solve many of the challenges but these are mostly proprietary, reactive and require changes to mobile node stacks. In this paper, we propose a novel handover solution based on the principle of Software Defined Networking, that addresses the aforementioned challenges. Using virtualization and softwarization, we shift the traditional mobile node-driven handovers to the access point, while maintaining compliance with legacy devices. Moreover, we develop a proactive handover algorithm ADNA, which combines network state, traffic load and node mobility information. We evaluate our approach extensively in a testbed, showing that it outperforms existing approaches by improving the overall throughput by 116% while reducing the number of handovers by 44% on average.

11 citations


Cites methods from "Optimal Mapping of Stations to Acce..."

  • ...[17] presented a similar approach of using a centralized controller and aiming to maximize the overall throughput using different metrics such as AP-STA link rates, throughput demands of STAs, etc....

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  • ...11 standard handover algorithm and to a state of the art proactive, centralized one called MAX RSSI, described in [5], [17], [12], which hands over a STA to the AP with the highest RSSI, regardless of perceived mobility....

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Journal ArticleDOI
TL;DR: This paper uses software-defined networking (SDN) to propose a user association solution for WLANs aiming to mitigate such inefficiencies, thus improving resource utilization and considering user-AP association jointly with multicast delivery leads to a significant performance increase over the default client-driven approach.
Abstract: Despite the planned operation of enterprise wireless local area networks (WLANs), they still experience unsatisfactory performance due to several inefficiencies. One of the major issues is the so-called sticky user problem, in which users remain connected to an access point (AP) until the signal quality becomes too weak. In this paper, we leverage software-defined networking (SDN) to propose a user association solution for WLANs aiming to mitigate such inefficiencies, thus improving resource utilization. As it is a computationally hard problem, we also design various low-complexity user-AP association schemes that consider not only signal quality but also AP loads and minimum quality requirements for user traffic. Moreover, to provide simultaneous content distribution in a sustainable mode, we propose exploiting link-layer multicasting to decide on user-AP associations. Our analysis via simulations and experimentation on an open-source testbed shows that considering user-AP association jointly with multicast delivery leads to a significant performance increase over the default client-driven approach: the median throughput is $11\times$ higher when all users request the same content and the achieved improvement decreases to 68% for 100 contents. Moreover, due to more efficient use of the airtime, unicast users achieve higher throughput if multicast delivery is exploited.

9 citations


Cites background or methods from "Optimal Mapping of Stations to Acce..."

  • ...Several key considerations in AP selection can be listed as: signal quality, AP bandwidth [11], [37], traffic requirements, load balance [38], heterogeneity of users [21], and handover cost [14], [20]....

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  • ..., [2], [10], [14], [23], [27], [33], have gained popularity with the increasing adoption of SDN in WLANs [5]....

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  • ...After solving a graphcolouring problem, we find the bandwidth per AP based on the total number of frequencies needed for this network to avoid inter-AP interference [14]....

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  • ..., for highly mobile settings, shorter periods should be preferred for the controller to react promptly to changes in user locations [14]....

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  • ...[14] ILP formulation Network utility Users-AP airtime SNR of probe requests 7 3 3 7 Shared or different 7 7...

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References
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Book
01 Jan 2009

936 citations


"Optimal Mapping of Stations to Acce..." refers methods in this paper

  • ...Our scenarios are similar to indoor scenario defined in IMT guidelines [12], e....

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Journal ArticleDOI
TL;DR: This paper presents a new load balancing technique by controlling the size of WLAN cells (i.e., AP's coverage range), which is conceptually similar to cell breathing in cellular networks, and develops a set of polynomial time algorithms that find the optimal beacon power settings which minimize the load of the most congested AP.
Abstract: Maximizing network throughput while providing fairness is one of the key challenges in wireless LANs (WLANs). This goal is typically achieved when the load of access points (APs) is balanced. Recent studies on operational WLANs, however, have shown that AP load is often substantially uneven. To alleviate such imbalance of load, several load balancing schemes have been proposed. These schemes commonly require proprietary software or hardware at the user side for controlling the user-AP association. In this paper we present a new load balancing technique by controlling the size of WLAN cells (i.e., AP's coverage range), which is conceptually similar to cell breathing in cellular networks. The proposed scheme does not require any modification to the users neither the IEEE 802.11 standard. It only requires the ability of dynamically changing the transmission power of the AP beacon messages. We develop a set of polynomial time algorithms that find the optimal beacon power settings which minimize the load of the most congested AP. We also consider the problem of network-wide min-max load balancing. Simulation results show that the performance of the proposed method is comparable with or superior to the best existing association-based methods.

215 citations

Journal ArticleDOI
TL;DR: A survey on the state of the art channel assignment schemes in IEEE 802.11-based WLANs is presented and a qualitative comparison among different schemes in terms of algorithm execution behaviors, complexity, and scalability is provided.
Abstract: Efficient channel assignment is crucial for successful deployment and operation of IEEE 802.11-based WLANs. In this article we present a survey on the state of the art channel assignment schemes in IEEE 802.11-based WLANs. After detailing out all the schemes, we provide a qualitative comparison among different schemes in terms of algorithm execution behaviors, complexity, and scalability. We then conclude the survey with several research issues open for further investigation.

203 citations


"Optimal Mapping of Stations to Acce..." refers background in this paper

  • ...2 pausing probability at each time slot and user speed ≈ [1, 5] m/s....

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  • ...2 s while a time slot = 1 s, minimum rate requirements ≈ [5, 15] Mbps considering the video rates reported by Skype and Netflix....

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  • ...Note that an efficient channel assignment scheme should guarantee minimal interference among co-channel APs [5]....

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Journal ArticleDOI
TL;DR: A handover decision method based on the prediction of traveling distance within an IEEE 802.11 wireless local area network (WLAN) cell that successfully keeps the number of failed or unnecessary handovers low is proposed.
Abstract: We propose a handover decision method based on the prediction of traveling distance within an IEEE 802.11 wireless local area network (WLAN) cell. The method uses two thresholds which are calculated by the mobile terminal (MT) as it enters the WLAN cell. The predicted traveling distance is compared against these thresholds to make a handover decision in order to minimize the probability of handover failures or unnecessary handovers from a cellular network to a WLAN. Our analysis shows that the proposed method successfully keeps the number of failed or unnecessary handovers low.

176 citations


"Optimal Mapping of Stations to Acce..." refers background in this paper

  • ...2 s while a time slot = 1 s, minimum rate requirements ≈ [5, 15] Mbps considering the video rates reported by Skype and Netflix....

    [...]

Proceedings ArticleDOI
01 Apr 2006
TL;DR: This paper presents a new load balancing technique by controlling the size of WLAN cells (i.e., AP's coverage range), which is conceptually similar to cell breathing in cellular networks, and develops a set of polynomial time algorithms that find the optimal beacon power settings which minimize the load of the most congested AP.
Abstract: Maximizing network throughput while providing fairness is one of the key challenges in wireless LANs (WLANs). This goal is typically achieved when the load of access points (APs) is balanced. Recent studies on operational WLANs, however, have shown that AP load is often substantially uneven. To alleviate such imbalance of load, several load balancing schemes have been proposed. These schemes commonly require proprietary software or hardware at the user side for controlling the user-AP association. In this paper we present a new load balancing technique by controlling the size of WLAN cells (i.e., AP’s coverage range), which is conceptually similar to cell breathing in cellular networks. The proposed scheme does not require any modification to the users neither the IEEE 802.11 standard. It only requires the ability of dynamically changing the transmission power of the AP beacon messages. We develop a set of polynomial time algorithms that find the optimal beacon power settings which minimize the load of the most congested AP. We also consider the problem of network-wide min-max load balancing. Simulation results show that the performance of the proposed method is comparable with or superior to the best existing association-based methods.

116 citations


"Optimal Mapping of Stations to Acce..." refers background in this paper

  • ..., balancing the network loads on APs [4, 10, 16], managing user mobility [17] or interference by hidden nodes....

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  • ...To tackle with the a potential load imbalance, [4] proposes to dynamically adjust the signal power of AP beacons in a way similar to cell breathing in cellular networks....

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  • ...Another line of related research is on load balancing among APs [4, 10, 14, 16]....

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