Implementation of QoS for Adaptive Multimedia in Wireless / Mobile Network-A Review 1

Most of the data communications depend on these emerging technologies. Mobile computing systems have nonfunctional properties that differ from fixed distributed systems due to the radio and mobile terminal characteristics. The term mobile computing system is used when considering a system consists of: application, middleware, operating system (OS), mobile terminal, and mobile communication system. End-to-end quality of service (QoS) in mobile computing systems is therefore the combination of QoS characteristics and QoS mechanisms across the system. INTRODUCTION In today’s environment, the need, uses and applications of the mobile networks are increasing. Most of the data communications depend on these emerging technologies. Mobile computing systems have non-functional properties that differ from fixed distributed systems due to the radio and mobile terminal characteristics. The term mobile computing system is used when considering a system consists of: application, middleware, operating system (OS), mobile terminal, and mobile communication system. End-to-end quality of service (QoS) in mobile computing systems is therefore the combination of QoS characteristics and QoS mechanisms across the system [1]. Reliable message transfer with error control and notification of non-delivery is common in many modern communication systems. However, it is only recently that much thought has been given to the ability to specify timeliness, and the perceived quality of the data arriving, particularly where more complex (multi-) media are being used. The underlying concepts of bandwidth, throughput, timeliness (including jitter), reliability, perceived quality and cost are the foundations of what is known as Quality of Service (QoS). In designing the applications over mobile networks, one must focus on quality of service (QoS). It is often required where a fixed bit rate is provided and the application are delay sensitive, and in those networks where the capacity is a limited resource, for example in mobile data communication. Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. [1][2][3]. QoS provides the following benefits [4]:  Gives administrators control over network resources and allows them to manage the network from a business, rather than a technical, perspective.  Ensures that time-sensitive and mission-critical applications have the resources they require, while allowing other applications access to the network.  Improves user experience.  Reduces costs by using existing resources efficiently, thereby delaying or reducing the need for expansion or upgrades. Modeling is a necessary activity while designing a system or application. It aims to express the essentials of some aspect of the system being designed, without unnecessary detail. It is often represented by visually by one or more diagrams [5]. QoS requirements are identified already at design-time. For modeling a system, we need adequate modeling languages. There are many modeling languages according to the area of applications. For modeling the QoS of any system, a specialized QoS Modeling Language (QML) has also been developed. Therefore, the QML can be applied to specify QoS properties like reliability and performance [6]. QUALITY OF SERVICE (QoS) Many multimedia and real-time applications entail the concept of QoS, where there may be a scale of performance which is acceptable, and the boundary between success and failure of the system may be blurred or varying [BLAIR 97b]. For instance, a video may still be acceptable if presented with a lower frame rate, or reduced resolution, but be unacceptable for viewing if there are pauses or gaps in the film. The results of a search on data potentially returning many fields may still be acceptable if only the first few results are given initially, as long as this is done within a time limit, when appearance of efficiency is needed in front of customers, or where connection time waiting for results incurs cost. Management of QoS includes various aspects, relating to the nature of perceived quality. This section Journal of Computing Technologies (2278 – 3814) / # 62 / Volume 5 Issue 1 © 2015 JCT. All Rights Reserved 62 provides an overview of these, and the treatment they have been given in the literature. The topics covered are: i) Definitions Fundamental to QoS management; ii) Techniques for the static management of QoS; iii) Techniques for the dynamic management of QoS; iv) QoS issues relating to multiple stream systems, common in multimedia applications; v) QoS issues relating to managing faults and availability; vi) A brief overview of the work described in the literature relating to formal specifications, standards and practical investigations where the previously described techniques are applied. Definitions and Categories of QoS The ISO/IEC recommendation X.901-5, Open Distributed Processing Reference Model (RMODP) provides a de-jure definition of QoS. This subsection presents an overview of the most critical parts of what QoS is, and what it entails, based on [BLAIR 97b, HUTCHISON 94,STOREY 96], whose treatment is primarily concerned with multimedia. QoS in Mobile Computing System There has been much recent research on the provision of Quality of Service (QoS) guarantees in mobile computing environment. The critical design issues for mobile system include Quality-of-Service (QoS) guarantees, high service accessibility, reliable data transfer, and high communication performance [1] [10]. These all parameters affected by mobility, both during and between connections. One of the aims of QoS is to manage the service response provided to low-speed devices such as mobile wireless devices. The QoS can be ensured only when the achieved / actual performance is greater than or equal to the desired performance [11] [12][13]. QML To facilitate QoS specification, a general Quality of Service Modeling Language has been introduced for defining multicategory QoS. QML is designed to support QoS in general QoS category such as reliability, performance, security, and timing [14]. QML has been developed at HP Software Technology Laboratory [15][16]. QML is similar to interface definition language that describes the functional prosperities of software component. It also allows specification at a fine-grained level for operations, operation arguments, and attributes. QML is designed for a good fit with object-oriented distribution architecture [6] [17]. OVERVIEW OF MOBILE ADHOC NETWORKS The increased demands for mobility and flexibility in our daily life are demand that lead the development from wired LANs to wireless LANs (WLANs). Today a wired LAN can offer users high bit rates to meet the requirements of bandwidth consuming services like video conferences, streaming video etc. With this in mind a user of a WLAN will have high demands on the system and will not accept too much degradation in performance to achieve mobility and flexibility. This will in turn put high demands on the design of WLANs of the future. During the last few years Wireless mesh networking has become increasingly ubiquitous and the preferred mechanism to provide coverage to campuses, small towns, etc. In Wireless mesh networks a subset of the wireless nodes are connected to the wired backbone and provide connectivity to the other nodes in the network through multi hopping over the wireless links. As a natural extension to WLANs, the medium access mechanism of choice for these networks is the CSMA/CA based IEEE 802.11 distributed MAC protocol [1]. While IEEE 802.11 MAC protocol was designed for and provides a reasonable performance in a single hop network, it results in severe performance degradation in a multi-hop setting. In a single hop 802.11 network, all nodes contend for the channel with equal opportunity and act as greedy as possible to increase their one hop throughput which directly results in increase of the network aggregate throughput. In a multi-hop network, however, the greedy behavior of the nodes may result in service degradation as the packets transmitted by a source might not reach their final destination due to network congestion. In a congested network packets might be dropped in an intermediate node. Such a behavior will result in waste of the system resources used to deliver the packets to the intermediate node [2]. Reliable message transfer with error control and notification of non-delivery is common in many modern communication systems. However, it is only recently that much thought has been given to the ability to specify timeliness, and the perceived quality of the data arriving, particularly where more complex (multi-) media are being used. The underlying concepts of bandwidth, throughput, timeliness (including jitter), reliability, perceived quality and cost are the foundations of what is known as Quality of Service (QoS). STATE OF ART Chalmers, D. Sloman, M. [1] presented the specification and management of Quality of Service (QoS) is important in networks and distributed computing systems, particularly to support multimedia applications. This paper is a survey of QoS concepts and techniques for mobile distributed computing