Reputation Based Access Point Selection in 802.11 Network

Mobile edge computing (MEC) is an innovative computing paradigm to enhance the computing capacity of mobile devices (MDs) by offloading computation‐intensive tasks to MEC servers. With the widespread deployment of wireless local area networks, each MD can offload computation task to server via multiple wireless access points (WAPs). However, computation offloading can bring a higher system cost if all users select the same access points to offload their tasks. This study proposes a computation offloading strategy and resource allocation optimisation scheme in a multiple wireless access points network with MEC, which aims to minimise the system cost by providing the optimal computation offloading strategy, transmission power allocation, bandwidth assignment, and computation resource scheduling. The proposed scheme decouples the optimisation problem into subproblems of offloading strategy and resource allocation since the problem is NP‐hard. The offloading strategy involves the optimal access point selection, which is analysed by the potential game. The resource allocation is obtained using Lagrange multiplier. The authors' analysis and simulation results verify the convergence performance of the proposed scheme, and the proposed scheme outperforms the simple resource allocation scheme and the offloading strategy optimisation scheme in terms of the system cost.

ABSTRACTUnderstanding the potential role of Smartphones and other portable wireless devices as relay nodes in message dissemination and content delivery in Delay Tolerant and Opportunistic networks depend on the knowledge about patterns and the number of encounter events among mobile nodes. One of the main challenges for extracting encounters is overlapping in the radio coverage areas of nearby access points (APs). Data about the usage of Wi-Fi networks can be used to perform an analysis of encounters among mobile devices. A realistic estimation of the number of encounters among mobile nodes is now a big challenge. In this paper, the effects of overlapping of radio coverage area among multiple APs for extracting realistic encounters among mobile devices has been discussed, and also an analytical approach has been proposed for extracting realistic encounters from overlapping in the coverage areas of multiple nearby APs. A significant difference was observed between the number of encounters by considering and ignoring overlapping. Our study finds that Wi-Fi datasets are not reliable source to estimate the number of encounters when there are overlapping in radio coverage areas of multiple APs.

PurposeWireless local area networks (WLANs) are the predominant option for broadband wireless access network, and multiple access points (APs) will be much more available for wireless stations (WSTAs). Call admission control (CAC) on AP selection problem over 802.11 WLAN is a critical issue. In the existing architecture, strongest‐signal‐first is the default AP selection mechanism in 802.11 WLAN which uses the single criterion, received signal strength indicator, to select AP. However, this method suffers from bandwidth deficiency and unbalanced load among APs due to the uneven distribution of user load, thus degrading the system throughput. Instead, the purpose of this paper is to propose a multi‐criteria CAC on AP selection algorithms.Design/methodology/approachThe distributed multi‐criteria considered in order are RSSI, minimum required bandwidth of WSTA, estimated effective bandwidth (EEB) and AP‐WSTA distance. A semiMarkov model considering both packet retransmission limit, packet error rate and collision effect is proposed to predict the system throughput and validated through simulation results. Two multi‐criteria AP selection algorithms after EEB is evaluated are proposed and compared based on this analytical model.FindingsThe proposed algorithms outperform the traditional SSF algorithm in terms of the balance index for AP and the average system throughput.Originality/valveThe paper presents performance analysis for multi‐criteria CAC for distributed access point selection in WLANs.

As the demand for high-throughput communications in wireless LANs increases, the need for expanding channel bandwidth also increases. However, the use of wider band channels results in the decrease of the number of channels available. Therefore, if multiple access points (APs) are in proximity and the cells overlap, it is difficult for each AP to use an orthogonal channel, and competitions thus increase between the APs using the same channel. To cope with this problem, this paper proposes coordinating APs to increase throughputs at Nash equilibria. A centralized controller coordinates the APs, which jointly select multibandwidth channels. To clarify the effect of coordinating APs, we assume a simple scenario where the cells of three APs overlap, and each AP can select multibandwidth channels. In this scenario, we consider two packet length assumptions. In the first case, the data bit amount of each packet is assumed to be the same. Thus, the packet length changes depending on a data rate. The other case assumes that the packet length is the same regardless of the data rate. Through game-theoretic analysis, it can be clarified that the coordinated APs are able to select channels more effectively than if each AP independently selects channels and that the total throughput of the coordinated APs at Nash equilibria is improved by at most 80 % in two packet length assumptions.

Wireless multicast has been exploited to bridge the gap between the limited wireless bandwidth and the rapidly increasing mobile video traffic demand. Multicast of videos to a set of heterogeneous users over multiple wireless access points, however, is challenging because of the trade-offs between high transmission rate, load balancing, and multicast opportunities. In this paper, we present JurCast, a joint user and rate allocation scheme for video multicast over multiple APs. Our approach balances the trade-off between these factors by determining user to Access Points (APs) association, the video resolution version (quality) to be delivered for each session, and the transmission link rate for each video version. The aim of our solution is to maximize the overall received video quality over all users. We have implemented and evaluated our solution on a WiFi testbed as well as the simulation of a large scale deployment. The results indicate that our method considerably outperforms the baseline schemes and achieves up to 3dB and 55% improvements in terms of peak signal-to-noise ratio (PSNR) and goodput, respectively.

Wireless LANs have been widely deployed, and multiple access points (APs) will be much more likely to be available there for STAs, which can roam from one AP to another by some rule. We here focus on an efficient and fair way to use the wireless access resources provided by multiple APs. In particular, our major concern is to develop a decentralized way to enable each of STAs to select an appropriate one of available APs independently. A straightforward way is to select an AP with strongest signal, which will be, however, shown to need further improvement. Hence, we propose decentralized AP selection strategies to achieve an efficient and fair share of wireless access resources, and evaluate them by simulations. Through our results, the proposed strategies can attain an excellent throughput performance by use of the number of active STAs sharing each AP even if STAs employ the strategies only when entering the wireless LAN. In addition, if STAs roam from one AP to another in response to changing situation, the total throughput and fairness can be further improved very much. keyword

The purpose of this study is to examine the impact of information placement within the confines of the online classroom architecture. Also reviewed was the impact of other variables such as course design, teaching presence and student patterns in looking for information. The sample population included students from a major online university in their first year course sequence. Students were tasked with completing a survey at the end of the course, indicating their preference for accessing information within the online classroom. The qualitative data indicated that student preference is to receive information from multiple access points and sources within the online classroom architecture. Students also expressed a desire to have information delivered through the usage of technology such as email and text messaging. In addition to receiving information from multiple sources, the qualitative data indicated students were satisfied overall, with the current ways in which they received and accessed information within the online classroom setting. Major findings suggest that instructors teaching within the online classroom should have multiple data access points within the classroom architecture. Furthermore, instructors should use a variety of communication venues to enhance the ability for students to access and receive information pertinent to the course.

In this paper, we present a framework for providing fair service and supporting quality of service (QoS) requirements in IEEE 802.11 networks with multiple access points (APs). These issues becomes critical as IEEE 802.11 wireless LAN are widely deployed in nationwide networks, linking tens of thousands of "hot-spots" for providing both real-time (voice) and non real-time (data) services to a large population of mobile users. However, both fairness and QoS guarantees cannot be supported in the current 802.11 standard. Our system, termed MiFi, relies on centralized coordination of the APs. During any given time of the "contention-free" period only a set of non-interfering APs is activated while the others are silenced. Moreover, the amount of service granted to an AP is proportional to its load and the system's performance is optimized by employing efficient scheduling algorithms. We show that such a system can be implemented without requiring any modification of the underlying MAC protocol standard or the behavior of the mobile stations. Our scheme is complementary to the emerging 802.11e standard for QoS and guarantees to overcome the hidden node and the overlapping cell problems. Our simulations establish that the system supports fairness and hence can provide QoS guarantees for real-time traffic, while maintaining a relative high throughput

In wireless local area networks (WLANs) made up of Extended Service Sets, access point (AP) selection is a key issue to improve the network performance and balance the traffic load. WLANs operating in the shared Industrial, Scientific and Medical band can benefit from the use of cognitive radio (CR) techniques to enable dynamic access to spectrum holes that are free from interference. In this paper, we propose an optimal Green AP Selection (GAPS) scheme, in which AP selection is optimized to maximize the system throughput while minimizing the energy consumption, for multi-rate WLANs enhanced by CRs. Different from most existing AP selection schemes, GAPS takes into account of the state transition tendency of APs and the influence of Automatic Rate Fallback mechanism in the Distributed Coordination Function. The AP selection problem is formulated as a restless bandit problem and solved by the primal-dual index heuristic algorithm based on first order relaxation to yield the GAPS scheme with the "indexability" property and hence a low complexity. GAPS is further divided into offline computation, which accounts for the bulk of the computations, and online selection, with a low complexity to facilitate implementation. Extensive simulation results illustrate the significant performance improvements of GAPS compared with existing AP selection schemes in different scenarios.

Sensor network with mobile access (SENMA) is an architecture in which randomly deployed low-power sensors are orchestrated by a few powerful mobile access points. This paper considers SENMA from energy-efficiency and information-theoretic perspectives. By allowing sensors to propagate data directly to mobile access points over multiaccess channels and relieving sensors from energy-consuming network functions, SENMA has the potential of offering orders of magnitude of improvement in energy efficiency over the multihop ad hoc architecture, as demonstrated by our analysis on scalability. Optimization configurations of SENMA such as the altitude, the trajectory, and the coverage of access points are considered next, using the sum-rate as the performance metric. Optimal strategies for single and multiple access points are determined. For multiple access points, the possibility of and the gain due to cooperation (i.e., joint decoding of signals received at different access points) are investigated.

Consider a wireless networking architecture, where multiple infrastructure access points (AP) dynamically offer (bid) service deals (modes) to a mobile over time. Akin to a market offer, each service deal is comprised of service/quality attributes (e.g, AP, rate) for a price (cost). The mobile dynamically selects the desirable deal at each time, so as to efficiently trade long term latency/quality for cumulative price. Offered service modes depend on the randomly fluctuating congestion state of the AP infrastructure. Dynamically switching from one service mode/deal to another, the mobile encounters `friction' (e.g. bandwidth loss, disconnection risk) and, hence, has an incentive to stick with the current deal for as long as this is significantly competitive. A model of this architecture is first developed, which allows for the formulation and computation of the optimal control for the mobile to accept an offered deal amongst many and switch into the corresponding service mode. A suite of low-complexity heuristic controls for mode switching is also discussed. The performance of the optimal and heuristic controls is probed via simulation. Finally, the `switching curve' structure of the optimal control is demonstrated on a simple system where the curves can be plotted.

Driven by the rapidly increasing popularity of Internet-connected phones, tablets and wearable devices, new wireless technologies and standards are emerging at an unprecedented pace. The evolution of wireless networking opens a myriad of possible mobile applications, which have greatly transformed the way we access information, entertain and connect with others. A critical question is how to satisfy the quality of service (QoS) requirements for various applications by delivering the data to users reliably and efficiently under different networking conditions. While many protocols have been proposed for better QoS, they usually requires modification to the networking core or heavy interaction between the layers of the networking stack. Therefore, the goal of dissertation is to develop lightweight, scalable and end-to-end transport solutions to bridge the long-standing gap between the increasing diversity of the mobile applications and the constant evolving wireless technologies. We first focus on studying how to tweak the logic and functionality of traditional TCP protocol given a new wireless networks with different link properties in the context of cognitive radio (CR) network. We start with an extensive ns-3 simulation study of three different classical end-to-end TCP flavors. We conclude that the main adverse impact to the TCP connection in a CR network is the interruption during the transmission period caused by spectrum sensing or primary user arrival events. Based on this insight, we propose TCP C^2, a method that greatly improves the flow responsiveness to abrupt variation of underlying layer spectrum availability in cellular CR architectures. We show that C^2 achieves 2x better throughput compared to TCP NewReno and TCP Westwood+, and approximately 20% improvement in throughput while also incurring 4X shorter queuing delay against Cubic (default implementation in Linux). Our second contribution is Janus, a new transport-layer framework that automatically selects among existing congestion control variants to optimize traffic in accordance with application demands. Janus solves the problem of how to select the right protocol to optimize the QoS for different applications given a large collection of existing TCP variants. We implement Janus in the Linux kernel and extensively evaluate its performance with both emulated and real Internet traffic. Our results show that Janus can significantly improve user-perceived performance according to QoE metrics, with up to 5X fewer interruptions for video streaming applications and 2X faster page loading for web-browsing applications. Finally, we seek to answer the question of how to increase the robustness of data delivery in mmWave networks with densely deployed access points (AP). We conduct real-world experiments with off- the-shelf 60GHz devices and show that naively connecting to any available AP, or even multiple APs, may not fully realize the promise of efficiently utilizing the extremely large bandwidths available in this band. To tackle this problem, we propose Multi-AP Association Protocol (MAP). MAP is a cross-layer connection management mechanism that runs only at the client-side and does not need centralized support from the APs, thus avoiding overheads of added control signaling. We show that MAP can substantially increase the QoS for videostreaming applications for mmWave networks with testbed evaluation and large-scale simulation.

Overlaid cellular technology has been considered as a promising candidate to enhance the capacity and extend the coverage of cellular networks, particularly indoors. The deployment of small cells (e.g. femtocells and/or picocells) in an overlaid setup is expected to reduce the operational power and to function satisfactorily with the existing cellular architecture. Among the possible deployments of small-cell access points is to manage many of them to serve specific spatial locations, while reusing the available spectrum universally. This contribution considers the aforementioned scenario with the objective to serve as many active users as possible when the available downlink spectrum is overloaded. The case study is motivated by the importance of realizing universal resource sharing in overlaid networks, while reducing the load of distributing available resources, satisfying downlink multi-channel assignment, controlling the aggregate level of interference, and maintaining desired design/operation requirements. These objectives need to be achieved in distributed manner in each spatial space with as low processing load as possible when the feedback links are capacity-limited, multiple small-cell access points can be shared, and data exchange between access points can not be coordinated. This contribution is summarized as follows. An adaptive downlink multi-channel assignment scheme when multiple co-channel and shared small-cell access points are allocated to serve active users is proposed. It is assumed that the deployed access points employ isotropic antenna arrays of arbitrary sizes, operate using the open-access strategy, and transmit on shared physical channels simultaneously. Moreover, each active user can be served by a single transmit channel per each access point at a time, and can sense the concurrent interference level associated with each transmit antenna channel non-coherently. The proposed scheme aims to identify a suitable subset of transmit channels in operating access points such that certain limits on the aggregate interference or number of serving access points are satisfied, while reducing the load of processing. The applicability of the results for some scenarios, including the identification of interference-free channels in operating access points is explained. Numerical and simulations results are shown to clarify achieved gains with the use of the proposed scheme under various operating conditions.

Currently, Internet of Things (IoT) has become common in various applications, including smart factories, smart cities, and smart homes. In them, wireless local-area networks (WLANs) are widely used due to their high-speed data transfer, flexible coverage ranges, and low costs. To enhance the performance, the WLAN configuration should be optimized in dense WLAN environments where multiple access points (APs) and hosts exist. Previously, we have studied the active AP configuration algorithm for dual interfaces using IEEE802.11n and 11ac protocols at each AP under non-channel bonding (non-CB). In this paper, we study the algorithm considering the channel bonding (CB) to enhance its capacity by bonding two channels together. To improve the throughput estimation accuracy of the algorithm, the reduction factor is introduced at contending hosts for the same AP. For evaluations, we conducted extensive experiments using the WIMENT simulator and the testbed system using Raspberry Pi 4B APs. The results show that the estimated throughput is well matched with the measured one, and the proposal achieves the higher throughput with a smaller number of active APs than the previous configurations.

With the increased deployment of wireless local area networks (WLAN) in many popular locations with multiple access points (AP), the limited number of usable radio channels provided by the IEEE 802.11 standard has resulted in a worse than expected network performance, such as very low throughput. The existing static radio channel allocation (RCA) schemes can only partially solve the problem in the initial planning of APs, but cannot adapt to environment changes and dynamic traffic conditions afterwards. We propose a new dynamic RCA scheme that aims to improve network performance by explicitly minimizing the cochannel interference among the neighboring APs that share a radio channel. Simulation results have demonstrated that the proposed scheme has not only significantly increased the overall network throughput, but also greatly reduced the cochannel interference among the APs