Stringent QoS Research Articles

Adaptive tabu search-based core selection algorithm in heterogeneous network

Nowadays, several networks like mobile ad hoc networks (MANETs), wireless sensor networks (WSNs), satellite networks, etc. are attached to the backbone internet through gateways. When a group of people work in a cooperative way, there is a stringent quality of service (QoS) requirement on delay and delay variation. This problem is called delay and delay variation multicast tree (DVBMT) problem. The main problem concerning the construction of shared multicast tree is to efficiently select the core point that is the root of the multicast tree. In this paper, we propose an adaptive tabu search-based core selection (ATS-CS) algorithm for multicast routing. The algorithm aims to minimise the delay variation subject to an end-to-end delay bound. The proposed algorithm is evaluated through simulation. It is observed that the proposed algorithm gives better and consistent performance than the existing algorithms. The actual execution time of the proposed algorithm is comparable to the existing algorithm.

A New QoS Management Scheme for VoIP Application over Wireless Ad Hoc Networks

Nowadays, mobile ad hoc networks (MANETs) have to support new applications including VoIP (voice over IP) that impose stringent QoS (quality of service) constraints and requirements. However, VoIP applications make a very inefficient use of the MANET resources. Our work represents a first step toward improving aspects at the network layer by addressing issues from the standpoint of adaptation, claiming that effective adaptation of routing parameters can enhance VoIP quality. The most important contribution is the adaptive OLSR-VA algorithm which provides an integrated environment where VoIP activity is constantly detected and routing parameters are adapted in order to meet the application requirements. To investigate the performance advantage achieved by such algorithm, a number of realistic simulations (MANET scenarios) are performed under different conditions. The most important observation is that performance is satisfactory in terms of the perceived voice quality.

A multiple-metric QoS-aware implementation of the optimised link state routing protocol

The optimised link state routing OLSR protocol is one of the most promising for mobile ad hoc networks MANETs. Despite numerous proposals for quality of service in MANET, there is a lack of OLSR implementations that efficiently support applications with stringent QoS constraints like VoIP or videoconference. In this paper, we present a QoS-OLSR implementation based on a multiple-metric approach. We first describe how QoS metrics values are estimated and disseminated. Then we show how the multipoint relays MPR can be selected using the QoS metrics as criteria, while keeping low the number of MPR in order to ensure flooding optimisation. The underlying problem is formally presented as a multicriteria problem. Finally, a heuristic is proposed in order to find quickly a satisfying solution to this latter. The evaluations carried out using OPNET show that, despite the additional traffic introduced by the dissemination of QoS information, QoS-OLSR achieves better performance than native OLSR for best-effort applications as well as for applications that are subject to QoS constraints.

A Near-Optimal Distributed QoS Constrained Routing Algorithm for Multichannel Wireless Sensor Networks

One of the important applications in Wireless Sensor Networks (WSNs) is video surveillance that includes the tasks of video data processing and transmission. Processing and transmission of image and video data in WSNs has attracted a lot of attention in recent years. This is known as Wireless Visual Sensor Networks (WVSNs). WVSNs are distributed intelligent systems for collecting image or video data with unique performance, complexity, and quality of service challenges. WVSNs consist of a large number of battery-powered and resource constrained camera nodes. End-to-end delay is a very important Quality of Service (QoS) metric for video surveillance application in WVSNs. How to meet the stringent delay QoS in resource constrained WVSNs is a challenging issue that requires novel distributed and collaborative routing strategies. This paper proposes a Near-Optimal Distributed QoS Constrained (NODQC) routing algorithm to achieve an end-to-end route with lower delay and higher throughput. A Lagrangian Relaxation (LR)-based routing metric that considers the “system perspective” and “user perspective” is proposed to determine the near-optimal routing paths that satisfy end-to-end delay constraints with high system throughput. The empirical results show that the NODQC routing algorithm outperforms others in terms of higher system throughput with lower average end-to-end delay and delay jitter. In this paper, for the first time, the algorithm shows how to meet the delay QoS and at the same time how to achieve higher system throughput in stringently resource constrained WVSNs.

RECOG: A Sensing-Based Cognitive Radio System with Real-Time Application Support

While conventional cognitive radio (CR) system is striving at providing best possible protections for the usage of primary users (PU), little attention has been given to ensure the quality of service (QoS) of applications of secondary users (SU). When loading real-time applications over such a CR system, we have found that existing spectrum sensing schemes create a major hurdle for real-time traffic delivery of SU. For example, energy detection based sensing, a widely used technique, requires possibly more than 100 ms to detect a PU with weak signals. The delay is intolerable for real-time applications with stringent QoS requirements, such as voice over internet protocol (VoIP) or live video chat. This delay, along with other delays caused by backup channel searching, channel switching, and possible buffer overflow due to the insertion of sensing periods, makes supporting real-time applications over CR system very difficult if not impossible. In this paper, we present the design and implementation of a sensing-based CR system - RECOG, which is able to support realtime communications among SUs. We first redesign the conventional sensing scheme. Without increasing the complexity or trading off the detection performance, we break down a long sensing period into a series of shorter blocks, turning a disruptive long delay into negligible short delays. To enhance the sensing capability as well as better protect the QoS of SU traffic, we also incorporate an on-demand sensing scheme based on MAC layer information. In addition, to ensure a fast and reliable switching when PU returns, we integrate an efficient backup channel scanning and searching component in our system. Finally, to overcome a potential buffer overflow, we propose a CR-aware QoS manager. Our extensive experimental evaluations validate that RECOG can not only support realtime traffic among SUs with high quality, but also improve protections for PUs.

QoS routing algorithm with multi-dimensions for overlay networks

Overlay networks have emerged as a useful approach to providing a general framework for new applications and services that are to be implemented without significantly changing the IP-layer network infrastructure. Overlay routing has been used as an alternative to the default best effort Internet routing for the absence of end-to-end Quality of Service (QoS). While the former has recently been investigated, the conflict of QoS restraints and resource optimization remains unsolved. Recent studies have shown that overlay paths can give better latency, loss rate and TCP throughput. In this paper, a multi-dimensional QoS objective model based on the analysis of multiple QoS constraints has been presented, and a routing algorithm to optimise the overlay resource of its nodes and links is then proposed. In fact, the algorithm obtained multiple QoS values using probability theory to achieve the routing according to the multi-dimensional QoS objective vector of the QoS objective model. Simulation results reveals that the algorithm works better than other existing algorithms in balancing the network resources, and applications with stringent QoS requirements could be run.

Toward Wireless Backhaul Using Circuit Emulation Over Optical Packet-Switched Metro WDM Ring Network

Optical WDM metro-ring networks have been considered to be promising solutions for wireless backhaul. In this paper, we propose an integrated traffic control scheme (ITCS), which facilitates circuit emulation service (CES) for wireless backhaul over a previously proposed experimental optical packet-switched WDM metro-ring network, HOPSMAN. The ITCS seamlessly integrates variable-bit-rate (VBR) CES wireless with connection-less best-effort data, satisfying stringent QoS requirements and retaining maximal network throughput. The ITCS ensures efficient setup of CES connections by employing a simple mean-rate-based distributed admission control followed by a novel slot-marking reservation. The total connection setup delay is comprised of the setup queueing delay and slot-marking delay. While the slot-marking delay is nearly a ring time, the mean setup queueing delay is formally computed through an accurate approximation based on an M/G/m queueing analysis. We show simulation results to demonstrate that the ITCS accommodates remarkably high CES traffic loads while satisfying a wide range of delay requirements for wireless backhaul. Taking the background best-effort traffic into account, ITCS achieves exceedingly low delay, jitter, and delay bound for CES under various traffic loads and burstiness.

QoS‐driven jointly optimal subcarrier pairing and power allocation for OFDM amplify‐and‐forward relay systems

SUMMARYIn this paper, we investigate the quality‐of‐service (QoS) driven subcarrier pairing and power allocation for two‐hop amplify‐and‐forward OFDM relay systems. By integrating the concept of effective capacity, our goal is to maximize the system throughput subject to a given delay QoS constraint. We propose a jointly optimal subcarrier pairing and power allocation scheme, which can be implemented with two separate steps. First, pair the subcarriers over the source‐relay channel and relay‐destination channel by the descending order of the subcarriers’ channel gains. Second, by making use of the derived equivalent end‐to‐end channel gains of the subcarrier pairs, optimally allocate power over the subcarrier pairs, and then optimally partition the power of the subcarrier pairs between the source and the relay. The simulation results show that our proposed scheme can efficiently provide different levels of delay QoS guarantees, even if under stringent delay QoS constraints. The simulation results also verify that our proposed scheme shows significant superiorities over the other existing schemes. Copyright © 2013 John Wiley & Sons, Ltd.

Spectrum sharing optimization with QoS guarantee in cognitive radio networks

In this paper, we propose an optimized spectrum sharing scheme based on the Hungarian Algorithm to guarantee the quality of service (QoS) for individual cognitive radio (CR) users belonging to different CR cells. The proposed scheme is most favorable for overlapping cells where the users are demanding channels for heterogeneous applications such as chatting, web browsing, or voice and video streaming. The spectrum sharing optimization with the QoS guarantee (SSO-QG) is an optimal scheme that can operate in throughput enhancement mode, high reliability mode and collision avoidance mode based on the weight assigned to the corresponding QoS parameters in accordance with the demands of different applications. Simulation results show that the proposed scheme outperforms the existing schemes in terms of forming the optimal sharing pattern and meeting the stringent QoS requirements fairly enough according to the demands of the cell. Moreover, it reduces collisions with primary users.

A Guarantee Mechanism of QoS Diversity Based on Error Control Aware and ARQ Block Importance in WiMAX Networks

The dynamic characteristics of WiMAX networks and stringent QoS requirements identify significant challenges for providing diversity of QoS guarantees in such wireless environment. In this paper, a QoS guaranteeing mechanism is proposed, which is based on error control aware and the importance of ARQ Block with IEEE 802.16e protocol. The mathematical analysis and simulation results show that the proposed mechanism achieves better performance, in terms of communication reliability and system throughput in WiMAX networks. In addition, the quality of real-time multimedia is improved significantly, in terms of decodable frame ratio, delay and packet error rate, etc. The destination and contribution of this work is to provide an effective, robust and reliable selection strategy of error control protocols to support QoS for WiMAX networks.

On collaborative anonymous communications in lossy networks

ABSTRACTMessage encryption does not prevent eavesdroppers from unveiling who is communicating with whom, when, or how frequently, a privacy risk wireless networks are particularly vulnerable to. The Crowds protocol, a well‐established anonymous communication system, capitalizes on user collaboration to enforce sender anonymity. This work formulates a mathematical model of a Crowd‐like protocol for anonymous communication in a lossy network, establishes quantifiable metrics of anonymity and quality of service (QoS), and theoretically characterizes the trade‐off between them. The anonymity metric chosen follows the principle of measuring privacy as an attacker's estimation error. By introducing losses, we extend the applicability of the protocol beyond its original proposal. We quantify the intuition that anonymity comes at the expense of both delay and end‐to‐end losses. Aside from introducing losses in our model, another main difference with respect to the traditional Crowds is the focus on networks with stringent QoS requirements, for best effort anonymity, and the consequent elimination of the initial forwarding step. Beyond the mathematical solution, we illustrate a systematic methodology in our analysis of the protocol. This methodology includes a series of formal steps, from the establishment of quantifiable metrics all the way to the theoretical study of the privacy QoS trade‐off. Copyright © 2013 John Wiley & Sons, Ltd.

Characterizing per-application network traffic using entropy

The Internet has been evolving into a more heterogeneous internetwork with diverse new applications imposing more stringent bandwidth and QoS requirements. Already new applications such as YouTube, Hulu, and Netflix are consuming a large fraction of the total bandwidth. We argue that, in order to engineer future internets such that they can adequately cater to their increasingly diverse and complex set of applications while using resources efficiently, it is critical to be able to characterize the load that emerging and future applications place on the underlying network. In this article, we investigate entropy as a metric for characterizing per-flow network traffic complexity. While previous work has analyzed aggregated network traffic, we focus on studying isolated traffic flows. Per-application flow characterization caters to the need of network control functions such as traffic scheduling and admission control at the edges of the network. Such control functions necessitate differentiating network traffic on a per-application basis. The “entropy fingerprints” that we get from our entropy estimator summarize many characteristics of each application's network traffic. Not only can we compare applications on the basis of peak entropy, but we can also categorize them based on a number of other properties of the fingerprints.

QoS Challenges in Wireless Sensor Networked Robotics

Wireless sensor networks and mobile robotics are two hot research topics. Integrating them leads to a wide range of new applications in many different environments such as terrestrial, underwater, underground and aerial. Where sensor networks are mainly used for large-scale monitoring and control, mobile robotics are used for performing fine-scale actions and automation. Network heterogeneity together with stringent Quality of Service (QoS) demands from applications such as voice and video make QoS support very challenging. Therefore, this paper investigates the QoS challenges in wireless sensor networked robotics and presents a novel QoS framework as solution to cope with these challenges.

Elastic ONU-class-based idle time elimination algorithm for Ethernet passive optical networks

To fully exploit the upstream bandwidth in Ethernet passive optical networks (EPONs), dynamic bandwidth allocation (DBA) algorithms need to collect the report messages from all the optical network units (ONUs), incurring an idle time comprising the DBA computation time and the round trip time. Some studies have addressed the problem by using the data transmissions of some or all ONUs (ONU-based) to eliminate the idle time. To satisfy the stringent quality of service (QoS) requirements, for example, to improve the packet delay and jitter for delay sensitive applications without degrading QoS support for other types of applications, some studies have proposed to separate the transmission of higher-class and lower-class traffic within one scheduling cycle. Existing studies on the separable scheduling scenario use the class-based concept, that is, use either the higher-class transmission or the lower-class transmission to eliminate the idle time. By contrast, in this paper, an elastic ONU-class-based idle time elimination algorithm (EOCA) is proposed in which the idle time is eliminated using both the higher-class and lower-class transmissions. The proposed mechanism is elastic in the sense that the lower-class transmission is first considered, and then if insufficient lower-class transmissions exist to eliminate the idle time, the OLT pre-allocates the higher-class transmissions in the following cycle to test whether or not the idle time is eliminated. If the idle time is still not eliminated, the OLT reallocates the bandwidth corresponding to the uneliminated idle time to either the last ONU (uneven method) or all of the ONUs (even method) such that the ONU(s) can early transmit any lower-class packets which arrive during the waiting time. Compared to existing class-based or ONU-based idle time elimination algorithms, the proposed EOCA algorithm performs better. The validity of the proposed EOCA algorithm is demonstrated via detailed simulation experiments.

Effective capacity of delay quality-of-service constrained spectrum sharing cognitive radio with outdated channel feedback

In this paper, we consider a spectrum sharing cognitive radio network coexisting with a primary network. Particularly, the channel state information (CSI) between the secondary transmitter and the primary receiver is assumed to be outdated due to channel feedback latency. The secondary user (SU) is assumed to satisfy a given delay quality-of-service (QoS) constraint as well as the average interference power constraint. We aim to derive the maximum arrival rate of the SU under aforementioned constraints with the outdated CSI. In this respect, we derive the optimal power allocation to achieve the maximum effective capacity, and further derive the effective capacity. The closed-form expressions for the lower and upper bounds on the effective capacity are also derived. In addition, we obtain the effective capacities under two widely adopted adaptive transmission schemes, i.e., optimal power and rate allocation (OPRA) and truncated channel inversion with fixed rate (TIFR). Numerical results are conducted to corroborate our studies. It is shown that the effective capacities of the SU under various transmission schemes are insensitive to the channel correlation coefficient especially under low channel correlation coefficient. It is also shown that the lower and upper bounds on the effective capacity are significantly tight under stringent delay QoS constraint.

Signal Strength based Scanning Considering Free Capacity for Handover Execution in WiMAX Networks

In mobile networks handover is initiated when there is change in network Quality of Service (QoS) parameters such as signal strength, signal to interference noise ratio (SINR), bit error rate (BER) etc. Handover considering signal strength is a basic scheme in mobile networks. Considering only signal strength is not ideal for WiMAX networks, which has stringent QoS requirements. Signal strength along with hysteresis and threshold serves as an accurate handover mechanism in WiMAX network. But it is not necessary that selected target base station have enough capacity to handle the data of mobile station. In this paper we propose a multiple trigger initiated handover execution which considers the signal strength along with hysteresis and threshold during scanning phase and the estimation of free capacity during handover execution phase. We evaluate our proposed scheme in Opnet Modeler simulator and its performance is verified.

Simulation Design and Performance Analysis for VoIP in Cognitive Radio Networks

Increasing popularity of VoIP systems has witnessed applications in emerging technologies like Cognitive Radio Networks (CRN). The stringent QoS requirements in VoIP coupled with complexities in CRN have initiated intensive research in the field of performance analysis and optimizations guided by simulation results. However, in the absence of any standard model of VoIP over CRN, accuracy and credibility of the simulation output are strongly dependent on proper design of the simulation model that must have a strong mathematical foundation. The objective of this paper is to build standard models for VoIP in CRN and successfully implement VoIP applications over CRN domain, which will serve as initial point for development with respect to all future simulation studies in VoIP over CRN category. Initially, models of VoIP in CRN are developed using OPNET Modeler 16.0.A following distributed architecture in single-channel and multi-channel scenarios and further in Visual C++ adhering to the principles of centralized architecture. The models are validated by comparison of simulation results obtained in both platforms. The underlying mathematical model behind the design is established and the critical factors pertaining to both VoIP and CRN domain are extensively analyzed.

Peer-to-Peer Multicasting Inspired by Huffman Coding

Stringent QoS requirements of video streaming are not addressed by the delay characteristics of highly dynamic peer-to-peer (P2P) networks. To solve this problem, a novel locality-aware method for choosing optimal neighbors in live streaming multicast P2P overlays is presented in this paper. To create the appropriate multicast tree topology, a round-trip-time (RTT) value is used as a parameter distinguishing peers capabilities. The multicast tree construction is based on the Huffman source coding algorithm. First, a centrally managed version is presented, and then an effective use of a distributed paradigm is shown. Performance evaluation results prove that the proposed approach considerably improves the overlay efficiency from the viewpoint of end-users and content providers. Moreover, the proposed technique ensures a high level of resilience against gateway-link failures and adaptively reorganizes the overlay topology in case of dynamic, transient network fluctuations.

On the Influence of Network Impairments on YouTube Video Streaming

Video sharing services like YouTube have become very popular which consequently results in a drastic shift of the Internet traffic statistic. When transmitting video content over packet based networks, stringent quality of service (QoS) constraints must be met in order to provide the comparable level of quality to a traditional broadcast television. However, the packet transmission is influenced by delays and losses of data packets which can have devastating influence on the perceived quality of the video. Therefore, we conducted an experimental evaluation of HTTP based video transmission focusing on how they react to packet delay and loss. Through this analysis we investigated how long video playback is stalled and how often re-buffering events take place. Our analysis revealed threshold levels for the packet delay, packet losses and network throughput which should not be exceeded in order to preserve smooth video transmission.

Resource allocation for OFDM relay systems with statistical QoS guarantees

SUMMARYBy integrating the concept of effective capacity, we propose the resource allocation schemes for subcarrier‐pair based OFDM decode‐and‐forward and amplify‐and‐forward relay systems for quality‐of‐service (QoS) guarantees. The objective is to maximize the system throughput subject to a given statistical delay QoS constraint. First, we pair the subcarriers over the source‐relay channel and the relay‐destination channel by the descending order of the subcarriers' channel gains. Second, by making use of the derived equivalent end‐to‐end channel gains of the subcarrier pairs, we apply joint water‐filling power allocation over the subcarrier pairs and then partition the power of the subcarrier pairs between the source and the relay. We prove that as the equivalent end‐to‐end channel gains of the subcarrier pairs are given, the combination of sorted subcarrier pairing and joint water‐filling power allocation is jointly optimal to maximize the effective capacity. The simulation results show that our proposed schemes achieve the highest effective capacity for OFDM decode‐and‐forward and amplify‐and‐forward relay systems as compared with other existing schemes. The results also verify that our proposed schemes can efficiently provide different levels of delay QoS guarantees, even if under the stringent delay QoS constraints. Copyright © 2012 John Wiley & Sons, Ltd.