Service Differentiation Scheme Research Articles

A Geometric Backoff Time Distribution of IEEE 802.11 DCF: An Analytical Study

Today’s networks, including WLANs, transportdifferent classes of service. A service differentiation is thenessential to provide QoS. However, IEEE 802.11 for WLANs wasprimarily designed for best effort traffic and did not provide QoSspecifications. IEEE 802.11e MAC has been then described tosupport QoS in WLAN. In this paper, we propose a new schemefor service differentiation which is based on the 802.11 standardand requires minor modifications. In fact, we act on DCF whichuses the backoff procedure to solve contention in WLANs.For this scheme, we use, instead of the uniform distribution,a geometric distribution for random backoff time selection.Using a multi-class system, we propose three parametrizationsof the geometric distribution which imply different dynamicdifferentiation modes and we provide an analytical study, usinga Markov chain model, to compare our differentiation modes.We discuss our numerical results which give the performancesevaluation of the proposed mechanism in term of throughputand delay.

Restricted Access Window-Based Novel Service Differentiation Scheme for Group-Synchronized DCF

Group-synchronized distributed coordination function (GS-DCF) is a group-based medium access mechanism introduced in the IEEE 802.11ah draft standard. GS-DCF implements a novel channel access mechanism called restricted access window (RAW) which splits the channel time into various slots, devices into several groups, and assigns each slot to a group of devices. The Internet of Things is an ideal platform that captures the process and handles a large amount of data from the various heterogeneous applications with different channel access requirements. In this letter, we propose a novel RAW-based service differentiation scheme for GS-DCF. We propose a technique to allocate RAW slots to different applications based on their service requirements with minimal additional overhead. Analytical and simulation results show that the proposed scheme can effectively provide differentiated services in terms of throughput to the group of devices in GS-DCF.

Design and Analysis of Weighted Frequency-Domain Contention in Wireless LANs

The time to frequency protocol is the first frequency-domain contention protocol in wireless LANs, and has attracted a great deal of attention, since it can improve channel efficiency significantly. However, this protocol mainly provides a uniform service by letting each user conduct channel contention over the same frequency-domain range. In this paper, we first propose a novel weighted frequency-domain contention (WFC) scheme for service differentiation. In WFC, different frequency-domain ranges are assigned to different users to achieve weighted channel access opportunity, and a signature-assisted method is employed to completely exclude collisions. We then develop a theoretical framework to study the performance of WFC. With this framework, we can evaluate system throughput, optimize system parameter settings, and achieve proportional fairness. Extensive simulations verify that our theoretical model is very accurate.

Maximum-weight scheduling with hierarchical modulation for lower delay

In this paper, hierarchical modulation is used in conjunction with maximum-weight scheduling to achieve lower transmission delays. Via hierarchical modulation, the scheduled user has the option to transmit to two users simultaneously. In order to reflect service differentiation schemes used in upper layers, a scenario in which each user generates packets with different priority levels is considered. It is assumed that as long as there are high priority packets waiting in the scheduled user’s queue, lower priority packets cannot be transmitted. It is shown that, using hierarchical modulation in the presence of packet prioritization, average delay of low priority traffic can be reduced while achieving higher throughput. In the absence of packet prioritization, using hierarchical modulation lowers packet transmission delays without any loss in throughput. The effect of multiple access interference is also investigated. It is shown that both single and two-layer schemes have similar average spatial reuse factors.

Power consumption analysis of priority-based service differentiation scheme for LR-WPANs

ABSTRACTIn this paper, we investigate the effect of service differentiation on the power consumption in contention period of IEEE 802.15.4 sensor networks. Power consumption is analysed for two different service differentiation schemes under non-saturation condition. The two service differentiation schemes are the differentiation by the backoff exponent (BED) and differentiation by the contention window (CWD), which provide multilevel differentiated services in beacon-enabled mode with slotted carrier sense multiple access/collision avoidance (CSMA/CA) algorithm. The analysis is based on the stationary probabilities of a discrete-time Markov chain, which is a model of CSMA/CA describing the state of a head packet of a device. Numerical results show that CWD uses the power more efficiently and performs better in terms of throughput, while BED more differentiates the service.

Delay-Aware Medium Access Schemes for WSN-Based Partial Discharge Measurement

Wireless sensor networks (WSNs) are widely preferred measurement and monitoring tools for a large variety of industrial and environmental applications thanks to their low-cost, energy-efficiency, flexibility, and ease of deployment. However, the use of WSNs for measuring and monitoring industrial applications generating data at high rates, such as online monitoring of partial discharge activities in high voltage equipment in the power grid, presents a significant challenge for the system operators. In such applications, packet arrival rates could increase rapidly due to the occurrence of cascaded faults in the monitored environment. The WSNs with multihop topologies could experience excessive delays and an increase in packet drop of vital data due to the overwhelming increase in the packet arrival rates. Therefore, there should be an optimum operating point of the network where high packet arrival rates and low latency can be maintained at the same time. Thus, there is an immediate need for carefully designed quality of service (QoS) differentiation schemes that can guarantee the delivery of critical data with minimum latency and least loss. In this paper, we present a QoS differentiation scheme for high priority data in multihop WSNs based on an optimization scheme. Analytical and simulation results show that our proposed scheme significantly reduces the delay while maintaining high data delivery ratios and energy efficiency of the network.

IMPROVING QUALITY OF SERVICE IN IP NETWORKS FOR MULTIMEDIA APPLICATIONS WITH OPTIMAL FRAGMENTATION

The tremendous increase of Internet users and the w ide ranging need to support both multimedia traffic and other traffic leads to service differentiation sche mes. Multimedia applications have uncompromising and strict deadlines and the packets are worthless if t hey arrive late than their associated deadlines. Th e aim of the proposed system is to improve the quality of se rvice by increasing the number of multimedia packet s that reaches the destination before their associate d deadline without affecting the fairness of other data. The proposed algorithm estimates the optimal packet siz e for transmission and puts forward a Service Differentiation scheme that drops the packets based on the size and deadline of the packets. Packet lo ss percentage is observed to be reduced in the propose d system.

Exploiting Context Severity to Achieve Opportunistic Service Differentiation in Vehicular Ad hoc Networks

Wireless Access in Vehicular Environment (WAVE) dictates primitives for intelligent transportation system (ITS) applications and services. The medium access control (MAC) layer in WAVE facilitates service differentiation. This offers quality of service (QoS) by prioritizing traffic through different access categories (ACs), which are based on application-requested priorities. However, it is oblivious to network load, to delay requirements for ITS safety applications, and to the “severity” of vehicles. In this paper, we propose a novel opportunistic service differentiation (OSD) scheme as an enhancement to WAVE. We define a fuzzy inference system (FIS) to deduce a context severity metric (CSM) that relates the driving behavior of a vehicle to its environment. Our OSD traffic distribution heuristic prioritizes vehicle traffic, with respect to CSM, and accounts for network load and link layer bounds. Furthermore, the OSD scheme guarantees that ACs do not exceed maximum allowable delay for ITS applications. Our methodology entails defining and designing a linear programming (LP) model for verification and validation of the OSD scheme. We perform a comparative study of OSD-enhanced WAVE and classical WAVE analytically and in a vehicular ad hoc network (VANET) simulator. We show that both simulation and analytical results substantiate our claim of improvement in performance of OSD-enhanced WAVE over classical WAVE.

광 버스트 스위칭 네트워크에서 버퍼 기반의 서비스 차별화 방식

ABSTRACT In this paper, service differentiation scheme using optical buffer that is reduced in size with slow-light technology in optical burst switching networks is presented. In suggested scheme, each outport has buffer to store high-class burst only in case that all its wavelengths are occupied. When all wavelengths are being used, a new arriving high-class burst goes into the buffer and waits until a burst is serviced. As soon as a burst is serviced with a wavelength, the high-class burst at buffer is allocated to the free wavelength. In case that low-class burst is arriving under the same situation, it is not stored at the buffer but discarded. An analytical model is derived to analyze the performance of the suggested scheme and compare its performance with the conventional scheme such as preemption and deflection as well as no service differentiations. 키워드 : 서비스 차별화, 버퍼, 선취권, 우회경로, 광 버스트 스위치 Key word : Service Differentiation, Buffer, Preemption, Deflection Routing, Optical Burst SwitchJournal of the Korea Institute of Information andCommunication Engineering

A Geometric Backoff Time Distribution of IEEE 802.11 DCF: An Analytical Study

Today’s networks, including WLANs, transport different classes of service. A service differentiation is then essential to provide QoS. However, IEEE 802.11 for WLANs was primarily designed for best effort traffic and did not provide QoS specifications. IEEE 802.11e MAC has been then described to support QoS in WLAN. In this paper, we propose a new scheme for service differentiation which is based on the 802.11 standard and requires minor modifications. In fact, we act on DCF which uses the backoff procedure to solve contention in WLANs. For this scheme, we use, instead of the uniform distribution, a geometric distribution for random backoff time selection. Using a multi-class system, we propose three parametrizations of the geometric distribution which imply different dynamic differentiation modes and we provide an analytical study, using a Markov chain model, to compare our differentiation modes. We discuss our numerical results which give the performances evaluation of the proposed mechanism in term of throughput and delay.

Dynamic allocation and admission policies for QoS-aware provisioning systems

We present an architecture of a hosting system consisting of a set of hosted web services subject to QoS constraints, and a certain number of servers used to run user’s demand. The traffic is session-based, while provider and users agree on SLAs specifying the expected level of service performance such that the service provider is liable to compensate his/her customers if the level of performance is not satisfactory. The system is driven by a utility function which tries to optimise the average earned revenue per unit time. The middleware collects demand and performance statistics, and estimates traffic parameters in order to make dynamic decisions concerning server allocation and admission control. We empirically evaluate the effects of admission policies, resource allocation and service differentiation schemes on the achieved revenues, and we find that our system is robust enough to successfully deal with session-based traffic under different conditions.

A cross-layer TCP enhancement in QoS-aware mobile ad hoc networks

With the increase of multimedia traffic over the Internet, current network protocols are largely concerned with the QoS requirements of delay-sensitive applications. In Mobile Ad-hoc Networks (MANETs), the majority of protocols developed to date provide QoS mechanisms by assigning high priority to delay-sensitive applications. While today’s Internet traffic is still dominated by TCP-based applications, the negative effects of the IEEE 802.11e service differentiation scheme on TCP performance in the presence of high priority traffic have not been adequately addressed in the literature. In this paper we first evaluate the performance of TCP in 802.11e MANETs when competing with high priority VoIP traffic. We then propose a novel TCP-friendly scheme, called IEDCA, to improve IEEE 802.11e EDCA mechanism. Our simulation-based performance study demonstrates that our proposed scheme IEDCA not only improves the performance of TCP significantly, it also facilitates the voice traffic transmission.

A Service/Device Differentiation Scheme for Contention-Tone-Based Wireless LAN Protocol

A contention-tone-based wireless local area network (WLAN) protocol uses out-of-band signaling for contention resolution to achieve efficient medium access. It is shown that such a protocol can operate at near-optimal channel utilization in the medium access control (MAC) layer. This paper addresses the service differentiation design aspect of a contention-tone-based WLAN protocol. In particular, service and device differentiation schemes are proposed to fulfill a particular quality of service (QoS) for data packet transmissions for contention-tone-based WLANs. Our analysis shows that our design not only provides bandwidth differentiation that matches that specified in the IEEE 802.11e standard but operates at near-optimal channel utilization as well. Our design also incorporates device differentiation to eliminate the access-point bottleneck problem in WLANs. Analytical and simulation results confirm the performance advantages of our design.

Performance analysis of the TXOP burst transmission scheme in single-hop ad hoc networks with unbalanced stations

Transmission Opportunity (TXOP) is a promising burst transmission scheme defined in the IEEE 802.11e Medium Access Control (MAC) protocol to achieve differentiated Quality-of-Service (QoS) and improve the utilization of the scarce wireless bandwidth. Although performance modelling of the TXOP scheme has attracted tremendous research efforts from both the academia and industry, most existing analytical models have been developed under the unrealistic assumption that stations in wireless networks generate identical traffic loads. However, this assumption fails to capture the behaviour of wireless stations under the realistic working environment. To fill this gap, this paper proposes a new analytical model for the TXOP service differentiation scheme in single-hop ad hoc networks in the presence of unbalanced stations with different traffic loads. The QoS performance metrics including throughput, end-to-end delay, frame dropping probability, and energy consumption are derived. Extensive NS-2 simulation experiments are conducted to validate the accuracy of the developed model. The analytical results demonstrate the efficiency of the TXOP scheme for QoS differentiation and performance enhancement. Moreover, the analytical model is adopted as a cost-effective tool to investigate the impact of the buffer size and the number of stations on the performance of the TXOP scheme. The performance results show that the desirable throughput differentiation for different stations can be achieved by setting the appropriate TXOP limits.

Topology-aware wavelength partitioning for DWDM OBS networks: A novel approach for absolute QoS provisioning

Optical Burst Switching (OBS) is a promising switching technology for the next generation all-optical networks. An OBS network without wavelength converters and fiber delay lines can be implemented simply and cost-effectively using the existing technology. However, this kind of networks suffers from a relatively high burst loss probability at the OBS core nodes. To overcome this issue and consolidate OBS networks with QoS provisioning capabilities, we propose a wavelength partitioning approach, called Optimization-based Topology-aware Wavelength Partitioning approach (OTWP). OTWP formulates the wavelength partitioning problem, based on the topology of the network, as an Integer Linear Programming (ILP) model and uses a tabu search algorithm (TS) to resolve large instances efficiently. We use OTWP to develop an absolute QoS differentiation scheme, called Absolute Fair Quality of service Differentiation scheme (AFQD). AFQD is the first absolute QoS provisioning scheme that guarantees loss-free transmission for high priority traffic, inside the OBS network, regardless of its topology. Also, we use OTWP to develop a wavelength assignment scheme, called Best Effort Traffic Wavelength Assignment scheme (BETWA). BETWA aims to reduce loss probability for best effort traffic. To make AFQD adaptive to non-uniform traffic, we develop a wavelength borrowing protocol, called Wavelength Borrowing Protocol (WBP). Numerical results show the effectiveness of the proposed tabu search algorithm to resolve large instances of the partitioning problem. Also, simulation results, using ns-2, show that: (a) AFQD provides an excellent quality of service differentiation; (b) BETWA substantially decreases the loss probability of best effort traffic to a remarkably low level for the OBS network under study; and (c) WBP makes AFQD adaptive to non-uniform traffic by reducing efficiently blocking probability for high priority traffic.

Introducing size-oriented dropping policies as QoS-supportive functions

The continuous increase of Internet users worldwide, as well as the extensive need to support real-time traffic and bulk data transfers simultaneously, has directed research towards service differentiation schemes. These schemes either propose techniques that provide users with the necessary quality guarantees or follow a "better-than-best-effort" approach to satisfy broadly the varying needs of different applications. We depart from our new service principle called Less Impact Better Service (LIBS) and propose a novel service differentiation method, namely size-oriented dropping policies, which uses packet size to categorize time-sensitive from delay-tolerant flows and prioritize packet dropping probability, accordingly. Unlike existing proposals, the distinction of flows is dynamic and the notion of packet size is abstract and comparative; a packet size is judged as a unit within a dynamic sample space, that is, current queue occupancy. We evaluate size-oriented dropping policies both analytically and experimentally; we observe a significant increase on the perceived quality of real-time applications. Delaysensitive flows increase their bandwidth share, to reach a state of system fairness, regulating the dominant behavior of bulk-data flows.

A performance comparison of OPS with variable-size packets and OBS

This article presents a comparative study between Optical Burst Switching (OBS) and Optical Packet Switching (OPS) with variable-size packets on mono-service and multi-service network with Quality of Service (QoS) support. In terms of performance criteria, loss rate in byte and access delay are considered. A 2-state Markov Modulated Poisson Process (MMPP) traffic generator is used. A 14-nodes mesh network topology illustrating NSFNET and a ring topology are designed as the testbed. NS2 Network Simulation tool is used for our tests. According to the simulation results, we have seen that in both mono-service and multi-service networks, OPS is better than OBS under low traffic loads. However, OBS performs better than OPS in mono-service networks and low priority service classes under high traffic loads. In this study, we have shown that choosing one of these two switching technologies (OPS or OBS) in the future depends on the traffic load and the topology of network, together with the considered service differentiation scheme.

QoS‐aware fair packet scheduling in IEEE 802.16 wireless mesh networks

AbstractIn this paper, we address the problem of heterogeneous quality‐of‐service (QoS) provisioning in IEEE 802.16‐based wireless mesh networks. Our objective is to provide a novel service differentiation scheme based on distributed scheduling in the IEEE 802.16‐based mesh mode, thereby offering QoS guarantees. We first devise a novel scheme for the traffic class differentiation, which can be implemented at the medium access control layer. We then present a QoS‐aware fair packet scheduling (QFPS) algorithm to fulfill the QoS provisioning. With QFPS, a traffic flow with urgent QoS demand is guaranteed to be given priority in wireless resource allocation over those ones with mild QoS requirements. A shorter end‐to‐end delay is therefore expected to be offered for the traffic flows with time‐urgent requirements. Moreover, we propose a new fairness model among different traffic flows traversing the same node. All traffic flows passing through a node are served by the Deficit Round‐Robin scheduling algorithm to achieve fairness within the same priority group. The experimental results of the QFPS demonstrate that various traffic flows are provided with a differentiated service that offers QoS guarantees. Copyright © 2009 John Wiley & Sons, Ltd.

A contribution-based service differentiation scheme for peer-to-peer systems

Trust is required in a file sharing peer-to-peer system to achieve better cooperation among peers. In reputation-based peer-to-peer systems, reputation is used to build trust among peers. In these systems, highly reputable peers will usually be selected to upload requested files, decreasing significantly malicious uploads in the system. However, these peers need to be motivated by increasing the benefits that they receive from the system. In addition, it is necessary to motivate free riders to contribute to the system by sharing files. Malicious peers should be also motivated to contribute positively by uploading authentic files instead of malicious ones. Service differentiation is required to motivate peers to get involved by sharing and uploading the requested files. To provide the right incentives for peers to contribute to the system, the new concept of Contribution Behavior is introduced for partially decentralized peer-to-peer systems. In this paper, the Contribution Behavior of the peer is used as a guideline for service differentiation instead of peer’s reputation. Both Availability and Involvement of the peer are used to assess its Contribution Behavior. Performance evaluations confirm the ability of the proposed scheme to effectively identify both free riders and malicious peers and reduce the level of service provided to them. On the other hand, good peers receive better service. Simulation results also confirm that based on a Rational Behavior, peers are motivated to increase their contribution to receive services. Moreover, using our scheme, peers must continuously participate, reducing significantly the milking phenomenon.

A Payment-Based Incentive and Service Differentiation Scheme for Peer-to-Peer Streaming Broadcast

We propose a novel payment-based incentive scheme for peer-to-peer (P2P) live media streaming. Using this approach, peers earn points by forwarding data to others. The data streaming is divided into fixed-length periods; during each of these periods, peers compete with each other for good parents (data suppliers) for the next period in a first-price-auction-like procedure using their points. We design a distributed algorithm to regulate peer competitions and consider various individual strategies for parent selection from a game-theoretic perspective. We then discuss possible strategies that can be used to maximize a peer's expected media quality by planning different bids for its substreams. Finally, in order to encourage off-session users to remain online and continue contributing to the network, we develop an optimal data forwarding strategy that allows peers to accumulate points that can be used in future services. Simulation results show that the proposed methods effectively differentiate the media qualities received by peers making different contributions (which originate from, for example, different forwarding bandwidths or servicing times) and at the same time maintain high overall system performance.