Mohsin Iftikhar

Multiclass G/M/1 queueing system with self-similar input and non-preemptive priority

The Internet domains are tied together by service level agreements which are based on various QoS parameters such as delay, jitter, packet-loss rate, throughput and availability. To offer tighter and more comprehensive service level agreements, accurate modeling of IP traffic and its queuing behavior over the entire network domain is necessary. We present a novel analytical model of a single router which takes into account multiple classes of self-similar traffic based on G=M=1 queueing system with non-preemptive priority. Our long-range dependent traffic model is generated by infinitely many sources governed by a Poisson random measure. We derive exact expressions for the transition probabilities of the embedded Markov chain of G=M=1 by first deriving the interarrival distribution of the incoming traffic. Closed form expressions for the expected waiting time of multiple classes have been derived. The queuing system is evaluated numerically for a typical router to show the effect of the Hurst parameter on several performance measures. Such work forms a basis for modeling the behavior of self-similar traffic accurately through heterogenous network domains, eventually leading to the formation of realistic service level agreements. (Less)

Service level agreements (SLAs) parameter negotiation between heterogeneous 4G wireless network operators

Abstract We are currently witnessing a growing interest of network operators to migrate their existing 2G/3G networks to 4G technologies such as long-term evolution (LTE) to enhance the user experience and service opportunities in terms of providing multi-megabit bandwidth, more efficient use of radio networks, latency reduction, and improved mobility. Along with this, there is a strong deployment of packet data networks such as those based on IEEE 802.11 and 802.16 standards. Mobile devices are having increased capabilities to access many of these wireless networks types at the same time. Reinforcing quality of service (QoS) in 4G wireless networks will be a major challenge because of varying bit rates, channel characteristics, bandwidth allocation and global roaming support among heterogeneous wireless networks. As a mobile user moves across access networks, to the issue of mapping resource reservations between different networks to maintain QoS behavior becomes crucial. To support global roaming and interoperability across heterogeneous wireless networks, it is important for wireless network operators to negotiate service level agreement (SLA) contracts relevant to the QoS requirements. Wireless IP traffic modeling (in terms of providing assured QoS) is still immature because the majority of the existing work is merely based on the characterization of wireless IP traffic without investigating the behavior of queueing systems for such traffic. To overcome such limitations, we investigate SLA parameter negotiation among heterogeneous wireless network operators by focusing on traffic engineering and QoS together for 4G wireless networks. We present a novel mechanism that achieves service continuity through SLA parameter negotiation by using a translation matrix, which maps QoS parameters between different access networks. The SLA matrix composition is modeled analytically based on the G/M/1 queueing system. We evaluate the model using two different scheduling schemes and we derive closed form expressions for different QoS parameters for performance metrics such as packet delay and packet loss rate. We also develop a discrete event simulator and conduct a series of simulation experiments in order to understand the QoS behavior of corresponding traffic classes.

Towards the formation of comprehensive SLAs between heterogeneous wireless DiffServ domains

Traffic patterns generated by multimedia services are different from traditional Poisson traffic. It has been shown in numerous studies that multimedia network traffic exhibits self-similarity and burstiness over a large range of time-scales. The area of wireless IP traffic modeling for the purpose of providing assured QoS to the end-user is still immature and the majority of existing work is based on characterization of wireless IP traffic without any coupling of the behaviour of queueing systems under such traffic conditions. Work in this area has either been limited to simplified models of FIFO queueing systems which do not accurately reflect likely queueing system implementations or the results have been limited to simplified numerical analysis studies. In this paper, we advance the knowledge of queueing systems by example of traffic engineering of different UMTS service classes. Specifically, we examine QoS mapping using three common queueing disciplines; Priority Queuing (PQ), Low Latency Queuing (LLQ) and Custom Queueing (CQ), which are likely to be used in future all-IP based packet transport networks. The present study is based on a long-range dependent traffic model, which is second order self-similar. We consider three different classes of self-similar traffic fed into a G/M/1 queueing system and construct analytical models on the basis of non-preemptive priority, low-latency queueing and custom queueing respectively. In each case, expressions are derived for the expected waiting times and packet loss rates of different traffic classes. We have developed a comprehensive discrete-event simulator for a G/M/1 queueing system in order to understand and evaluate the QoS behaviour of self-similar traffic and carried out performance evaluations of multiple classes of input traffic in terms of expected queue length, packet delay and packet loss rate. Furthermore, we have developed a traffic generator based on the self-similar traffic model and fed the generated traffic through a CISCO router-based test bed. The results obtained from the three different queueing schemes (PQ, CQ and LLQ) are then compared with the simulation results in order to validate our analytical models.

Analysis of the Behavior of Self-Similar Traffic in a QoS-Aware Architecture for Integrating WiMAX and GEPON

The access network has remained the bottleneck in efforts to deliver bandwidth-intensive new-generation applications and services to subscribers. In the wired access network, the gigabit Ethernet passive optical network (GEPON) is a promising technology for relieving this bottleneck, while its counterpart in the wireless access network is worldwide interoperability for microwave access (WiMAX). A converged quadruplet-service-enabled (video, voice, data, and mobility) network, which takes full advantage of the strengths and weaknesses of each of these promising technologies, has been proposed. Besides, research and Internet measurements have revealed that actual Ethernet and wireless data traffic are self-similar and long-range dependent. Therefore, we review the quality of service (QoS) architecture for integrating WiMAX and GEPON access networks that we proposed in previous work. Then, we present an analysis of the queuing behavior of the QoS architecture under self-similar and long-range-dependent data traffic conditions and derive closed-form expressions of the expected waiting time in queue (queuing delay) and the packet loss rate per QoS traffic class. This work brings novelty in terms of presenting performance analysis of the proposed QoS-aware integrated architecture under realistic load conditions and facilitates the provisioning of tightly bound QoS parameters to end users of the converged access network.

An analytical model based on G/M/1 with self-similar input to provide end-to-end QoS in 3G networks

The dramatic increase in demand for wireless Internet access has lead to the introduction of new wireless architectures and systems including 3G, Wi-Fi and WiMAX. 3G systems such as UMTS and CDMA2000 are leaning towards an all-IP architecture for transporting IP multimedia services, mainly due to its scalability and promising capability of inter-working heterogeneous wireless access networks. During the last ten years, substantial work has been done to understand the nature of wired IP traffic and it has been proven that IP traffic exhibits self-similar properties and burstiness over a large range of time scales. Recently, because of the large deployment of new wireless architectures, researchers have focused their attention towards understanding the nature of traffic carried by different wireless architecture and early studies have shown that wireless data traffic also exhibits strong long-range dependency. Thus, the classical tele-traffic theory based on a simple Markovian process cannot be used to evaluate the performance of wireless networks. Unfortunately, the area of understanding and modeling of different kinds of wireless traffic is still immature which constitutes a problem since it is crucial to guarantee tight bound QoS parameters to heterogeneous end users of the mobile Internet. In this paper, we make several contributions to the accurate modeling of wireless IP traffic by presenting a novel analytical model that takes into account four different classes of self-similar traffic. The model consists of four queues and is based on a G/M/1 queueing system. We analyze it on the basis of priority with no preemption and find exact packet delays. To date, no closed form expressions have been presented for G/M/1 with priority.

Providing QoS guarantees to multiple classes of traffic in wireless sensor networks

Recent advances in miniaturization and low power design have led to a flurry of activity in wireless sensor networks. However, the introduction of real time communication has created additional challenges in this area. The sensor node spends most of its life in routing packets from one node to another until the packet reaches the sink In other words, we can say that it is functioning as a small router most of the time. Since sensor networks deal with time-critical applications, it is often necessary for communication to meet real time constraints. However, research dealing with providing QoS guarantees for real time traffic in sensor networks is still in its infancy. In this paper, an analytical model for implementing Priority Queueing (PQ) in a sensor node to calculate the queueing delay is presented. The model is based on M/D/l queueing system (a special class of M/G/l queueing systems). Here, two different classes of traffic are considered. The exact packet delay for corresponding classes is calculated. Further, the analytical results are validated through an extensive simulation study.

Performance Analysis of Priority Queuing Model for Low Power Wireless Body Area Networks (WBANs)

Abstract Wireless Body Area Network (WBAN) has been an active area of research over the past few years due to its tremendous benefits particularly related to healthcare systems. Through WBAN, the physicians can get real time updates for a long period of time in an inexpensive way about their patients who are suffering from different kinds of chronic diseases such as diabetes, asthma and myocardial infarction etc. A number of issues need to be addressed in the area of WBAN. There is a very strong need to develop scalable and low power MAC protocols. Further, novel and sophisticated queuing models are also needed to develop in order to provide guaranteed QoS to different classes of traffic generating from different types of events in WBAN. This paper focuses to analyze a three queues priority model for low power WBAN, which enables to provide guaranteed QoS to different types of traffic generated from different events. We extract closed form expressions of various QoS parameters such as queue length, queuing delay, throughput and packet loss rate. We also simulate the behaviour of traffic in WBAN to further evaluate the proposed analytical framework.

Traffic engineering and QoS control between wireless diffserv domains using PQ and LLQ

Numerous recent studies have proven that traffic patterns generated by multimedia services are different from traditional Poisson traffic. It has been shown that multimedia network traffic exhibits long-range dependency (LRD) and self-similar characteristics. The area of wireless IP traffic modeling in terms of providing assured QoS to the end-user is still immature and the majority of existing work is merely based on characterization of the wireless IP traffic without investigating the behavior of queueing systems under such traffic conditions. Work done in this area has been limited to simplified models of FIFO queueing systems which do not accurately reflect likely queueing system implementations or the results have been limited to simplified numerical analysis studies. In this paper, we contribute towards the solution of this problem by focusing on traffic engineering of different UMTS service classes by providing efficient QoS mapping using two common queueing disciplines; Priority Queueing (PQ) and Low Latency Queueing (LLQ), which are likely to be used in future all-IP based packet transport networks.The present study is based on a realistic traffic model which is long-range dependent and self-similar. We consider three different classes of self-similar traffic being fed to a queueing model of three queues based on a G/M/1 queueing system. We first make an analysis on the basis of non-preemptive priority and then on the basis of low-latency queuing and find closed form expressions of expected waiting times and packet loss rates of different traffic classes. In order to validate our models we conduct a series of experiments. We have developed a comprehensive discrete-event simulator for a G/M/1 queueing system in order to understand and evaluate the QoS behavior of self-similar traffic and carry out performance evaluations of multiple classes of input traffic in terms of expected queue length, packet delay and packet loss rate. Furthermore, we have developed a traffic generator to realize our self-similar traffic model and use it to feed traffic through a CISCO router-based test bed. The results obtained from the two different queueing schemes (PQ and LLQ) are then compared with the simulation results to ascertain the accuracy of our model.

A novel analytical model for provisioning QoS in body area sensor networks

Abstract Wireless Body Area Network (WBAN) has been an active area of research over the past few years due to its tremendous benefits particularly related to healthcare systems. The available research to evolve the QoS in WBAN is immature due to lack of sufficient methodology for modeling the behaviour of different kinds of traffic being generated from different kinds of events. It has been clearly demonstrated that traffic found in multimedia sensor nodes being used in WBAN is having bursty nature and cannot be modeled by using Poisson traffic distributions. However, most of the current available literature of traffic modeling related to Multimedia Wireless Sensor Networks (MWSNs) is based on Poisson distributions. To eliminate these kinds of performance evaluation limitations in MWSNs especially in time critical applications, this study proposes a novel analytical framework that relies on a traffic model resembling to an ON/OFF process. Proposed model exhibit self-similar behaviour and is capable to handle long range dependent traffic patterns. For providing enhanced QoS, proposed model deals with various traffic classes that has been judged in the current study through G/M/1 queuing system with a distinct scheduling strategy called as Low Latency Queuing (LLQ) to extract QoS performance metrics such as delay, queue length, throughput and packet loss rate (PLR). We also simulate the behaviour of traffic to further validate the proposed analytical framework.

On the provisioning of guaranteed QoS in wireless sensor networks through limited service polling models

Data gathering in a timely and reliable fashion has been a key concern in wireless sensor networks particularly related to military applications. The introduction of real time communication has created additional challenges in this area with different communication constraints. Since sensor networks represent a new generation of time-critical applications, it is often necessary for communication to meet real time constraints. However, research dealing with providing QoS guarantees for real time traffic in sensor networks is still immature. To provide guaranteed QoS in WSN, this paper presents a novel analytical model based on limited service polling discipline. The proposed model implements two queues in a sensor node which are being served according to round robin service. The model is based on M/D/l queueing system (a special class of M/G/l queueing systems), which takes into account two different classes of traffic in a sensor node. The exact queueing delay in a sensor node for corresponding classes is calculated. Further, the analytical results are validated through an extensive simulation study.