Hybrid Approach to Integrated QoS Capable Protocols for Wireless LANs

802.11 WLAN technology has been widely used recently to transmit heterogeneous data. The transmission of multimedia data has its quality of service (QoS) requirements. Hybrid Coordination Function (HCF) is proposed to provide service differentiation to support real-time transmission by 802.11e working group. HCF is composed of connection-based Enhanced Distributed Coordination Access (EDCA) and contention-free control-based HCF Controlled Channel Access (HCCA). The simple scheduler in HCCA proposed by 802.11e working group generates constant bit rate service, which is not efficient for the multimedia data with variable bit rates. An efficient scheduling scheme for the 802.11e wireless LAN is proposed in this paper. The allocation of the transmission opportunity to each wireless station is based on the optimization performance index and uses the queue length of the wireless station as feedback information. Simulation results demonstrate that the proposed scheduling can achieve a better QoS for different traffic class under heavy traffic load.

The relationship between the user perceived Quality of Experience (QoE) with Internet applications and the Quality of Service (QoS) of the underlying network and applications is complex. Unveiling statistical relations between QoE and QoS can boost the prediction and diagnosis of QoE. In this paper, we shed light on the relationship between QoE and QoS for a popular application: YouTube video streaming. We conducted a controlled study where we asked users to rate their perceived quality of YouTube videos under different network conditions. During this experiments, we also captured network QoS and application QoS. We then analyze the resulting dataset with SES, a feature selection algorithm that identifies multiple, minimal-size, statistically-equivalent signatures with maximal predictive power for a target variable (e.g., QoE). We found that we can build optimal QoE predictors using a minimal signature of only three features from application or network QoS metrics compared to four when we consider features from both layers.

IEEE 802.11e Medium Access Control (MAC) is a supplement to the IEEE 802.11 Wireless Network (WLAN) standard to support Quality of Service (QoS). The 802.11e MAC defines a new coordination function, namely Hybrid Coordination Function (HCF), which takes the QoS requirements of flows into account and allocates Transmission Opportunity (TXOP) to stations. On the basis of mean sending rate, delay of Variable Bit Rate (VBR) traffic cannot be bounded with the reference HCF scheduling algorithm proposed in this supplement. In this paper, we propose a new Connection Admission Control (CAC) and a scheduling algorithm that utilize the token bucket and a modified Latency-Rate (LR) scheduling algorithm to guarantee a bounded delay for HCF Controlled Channel Access (HCCA). The new Service Interval (SI) is calculated to optimize the number of stations accommodated and takes into account delay bound and token bucket parameters. We show that it is possible to obtain worst-case performance guarantees on delay. First, we analyze the behavior of the new scheduler with a loss free wireless channel model and after this, with a burst loss model and we explain how it is possible to extend this scheduler for a multi-rate scheme. Properties of the proposal are investigated both theoretically and using ns-2 simulations. We present a set of simulations with both Constant Bit Rate (CBR) and VBR flows and performance comparisons with HCF scheduling algorithm. The results show that the delay upper bound can be achieved for a large range of networks load with bandwidth optimization.

The medium access control of IEEE 802.11e defines a novel coordination function, namely hybrid coordination function (HCF), which allocates transmission opportunity (TXOP) to stations taking their quality of service (QoS) requirements into account. However, the reference TXOP allocation scheme of HCF controlled channel access, a contention-free channel access function of HCF, is only suitable for constant bit rate traffic. For variable bit rate (VBR) traffic, serious packet loss may occur. In this article, we generalize the reference design with an efficient TXOP allocation algorithm, a multiplexing mechanism, and an associated admission control unit to guarantee QoS for VBR flows with different delay bound and packet loss probability requirements. We define equivalent flows and aggregate packet loss probability to take advantage of both intra-flow and inter-flow multiplexing gains so that high bandwidth efficiency can be achieved. Moreover, the concept of weighted-loss fair service scheduling is adopted to allocate the aggregate TXOP to individual flows. From numerical results obtained by computer simulations, we found that our proposed scheme meets QoS requirements and results in much higher bandwidth efficiency than previous algorithms.

The distributed resource controller (DRC) technology described in this paper provides a novel approach to interfacing applications with emerging network mechanisms to deliver quality of service (QoS) and controlling network resource utilization. DRC aims to unify network services (e.g., Diffserv, Intserv, and ATM) and application QoS provisioning by introducing a middleware system and a set of generic interfaces. DRC middleware is the core part that translates application requests for QoS delivery into respective access to underlying network systems in a manner that optimizes resource utilization and shelters applications from such a complexity. Applications can request QoS to the DRC middleware in two ways: either on-line using the DRC QoS API or off-line via the DRC utility. Application QoS requirements are specified in terms of two categories of parameters: traffic profile (quantitative) and user expectation (qualitative). DRC currently uses the CORBA-based object-oriented technology to develop a CORBA-based resource controller (CRC). The working CRC prototype built to manage the integrated services is also presented.

The IEEE 802.11n supports high data rate transmissions due its physical layer Multiple Input ‎Multiple Output (MIMO) advanced antenna system and MAC layer enhancement features (frame ‎aggregation and block acknowledgement). As a result this standard is very suitable for multimedia ‎services through its Enhanced Distributed Channel Access (EDCA). This paper focuses on ‎evaluating the Quality of Service (QoS) application on the performance of the IEEE 802.11n ‎random topology WLAN. Three different number of nodes (3, 9 and 18) random topology with one ‎access point are modeled and simulated by using the Riverbed OPNET 17.5 Modular to ‎investigate the Wireless Local Area Network (WLAN) performance for different spatial streams. ‎The result clarified the impact of QoS application and showed that its effect is best at the 18 node ‎number topology. For a 4x4 MIMO, when QoS is applied and with respect to the no QoS ‎application case, simulation results show a maximum improvement of 86.4%, 33.9%, 52.2% and ‎‎68.9% for throughput, delay, data drop and retransmission attempts, respectively. ‎

Software-Defined Networking (SDN) is a new efficiently idea of programmable networks that separates the control plane from data plane of all network devices. Internet service provider is responsible for all the control decisions and communication among the forwarding elements from centralized controller. SDN provides the various optimized services. Quality of service (QoS) routing is a path computation method that is suitable for the different traffics generated by several applications, while utilization of network resources has increased. This agreement of service is defined by QoS requirements such as throughput, delay, jitter and packet loss etc. Multimedia applications often require assured from multi QoS constrained, causing the NP-complete problem which cannot be simply solved in polynomial time and high management complexity in the transition network. SDN is able to reduce complexity and it is used to efficiently implement traffic, hence SDN significantly values to development QoS routing. In this paper, we propose QoS routing algorithm called Quantized Level Balance (QLB) for SDN that considers one or many QoS parameters relating to the network application. To satisfy the requirements, QLB selects QoS parameters depending to the level of appropriate application service quality. We have replicated our algorithm on simulate topology with Scalable Video-streaming Evaluation Framework (SVEF). We measure the Peak Signal-to-Noise Ratio (PSNR) and Mean Opinion Score (MOS) of Scalable Video Coding (SVC) at the receiver. Our propose algorithm is improved than single-metric approach that may choose poor QoS parameter paths.

In this paper an efficient scheduling mechanism for wireless local area networks (WLAN) is proposed. This innovative scheme, named hybrid HCCA-EDCA centralised scheme (HHE-CS), is based on the hybrid coordination function (HCF) protocol introduced by the IEEE 802.11e standard. The HHE-CS aims at satisfying the user quality of service (QoS) demands for real time (RT) services with variable bit rate while maximising the throughput of best effort users. This paper proves conclusively that an adequate allocation of downlink and uplink traffic between EDCA and HCCA increases system performance as compared with more traditional schemes in which all best effort traffic is exclusively delivered by a distributed mechanism like EDCA.

The idea behind the proposition of Networks-on-Chip (NoCs) for modern and future systems on chip capitalizes on the fact that busses do not scale well when shared by a large number of cores. Even if NoC research is a relatively young field, the literature abounds with propositions of NoC architectures. Several of these propositions claim providing quality of service (QoS) guarantees, which is essential for real time and multimedia applications. The most widespread approach to attain some degree of QoS guarantee relies on a two-step process. The first step is to characterize application performance through traffic modeling and simulation. The second step consists in tuning a given network template to achieve some degree of QoS guarantee. These QoS targeted NoC templates usually provide specialized structures to allow either the creation of connections (circuit switching) or the assignment of priorities to connectionless flows. It is possible to identify three drawbacks in this two-step process approach. First, it is not possible to guarantee QoS for new applications expected to run on the system, if those are defined after the network design phase. Second, even with end-to-end delay guarantees, connectionless approaches may introduce jitter. Third, to model traffic precisely for a complex application is a very hard task. If this problem is tackled by oversimplifying the modeling phase, errors may arise, leading to NoC parameterization that is poorly adapted to achieve the required QoS. This Chapter has two main objectives. The first one is to evaluate the area-performance trade-off and the limitations of circuit switching and priority scheduling to meet QoS. This evaluation will show where such implementations are really suited for QoS, and when more elaborate mechanisms to meet QoS are needed. The second objective comprises proposing a method, called rate-based scheduling, to approach QoS requirements considering the execution time state of the NoC. The evaluation of circuit switching and priority scheduling show that: (i) circuit switching can guarantee QoS only to a small number of flows; the technique do not scale well, and can potentially waste significant bandwidth; (ii) priority-based approaches may display best-effort behavior and, in worst-case situations, may lead to unacceptable latency for low priority flows, besides being subject to jitter. In face of these limitations, rate-based scheduling arises as an option to improve the performance of QoS flows when varying traffic scenarios are used.

As the market for wireless local area networks (WLANs) based on IEEE 802.11 addresses no longer only the business market but also the home user, new demands for WLANs emerge. Multimedia applications require support for quality of service (QoS), which is addressed by the upcoming IEEE 802.11. For the satisfaction of the home user these wireless ad hoc networks must support multihop communication. The centralized prioritizing mechanism of the hybrid coordination function (HCF) relies on an infrastructure of hybrid coordinators (HCs) which may not be available in the home environment. Thus we provide a new decentralized reservation scheme to prioritize data in 802.11 and present simulation results.

Performance evaluation on IEEE 802.11e considering emergency calls in congested situation

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.

Analysis and adaptive optimization of vehicular safety message communications at intersections

It is crucial to achieve Quality of Service (QoS) on IEEE802.11 in order to provide stable and reliable communication for real time and multimedia applications. Most of the recent QoS techniques for Ad Hoc Networks rely on basic QoS classifications such as Enhanced Distributed Channel Access (EDCA) and Hybrid Coordination Function Channel Access (HCCA) with stationary backoff range for specific services, without considering overall resource consumption and the external correlation among terminals. In this paper, a novel contention window adjustment QoS scheme, as a special case of QoS classification, is proposed for achieving QoS-fairness on Ad Hoc Networks. It applies dynamic automatic QoS assignment with low complexity by considering the restriction among various terminal requirements. Throughput estimation with a proportional relation between throughput and backoff parameters is discussed based on a Markov chain model of a saturated Ad Hoc Networks. We measure the performance of different QoS algorithms theoretically and verify improvements of our algorithm on QoS-fairness with detailed simulations.

Network slicing is a technology that virtualizes a single infrastructure into multiple logical networks (called slices) where resources or virtualized functions can be flexibly configured by demands of applications to satisfy their quality of service (QoS) requirements. Generally, to provide the guaranteed QoS in applications, resources of slices are isolated. In wired networks, this resource isolation is enabled by allocating dedicated data bandwidths to slices. However, in wireless networks, resource isolation may be challenging because the interference between links affects the actual bandwidths of slices and degrades their QoS. In this paper, we propose a slice management scheme that mitigates the interference imposed on each slice according to their priorities by determining routes of flows with a different routing policy. Traffic flows in the slice with the highest priority are routed into shortest paths. In each lower-priority slice, the routing of traffic flows is conducted while minimizing a weighted summation of interference to other slices. Since higher-priority slices have higher interference weights, they receive lower interference from other slices. As a result, the QoS of slices is differentiated according to their priorities while the interference imposed on slices is reduced. We compared the proposed slice management scheme with a naïve slice management (NSM) method that differentiates QoS among slices by priority queuing. We conducted some simulations and the simulation results show that our proposed management scheme not only differentiates the QoS of slices according to their priorities but also enhances the average throughput and delay performance of slices remarkably compared to that of the NSM method. The simulations were conducted in grid network topologies with 16 and 100 nodes and a random network topology with 200 nodes. Simulation results indicate that the proposed slice management increased the average throughput of slices up to 6%, 13%, and 7% and reduced the average delay of slices up to 14%, 15%, and 11% in comparison with the NSM method.