International Journal of Computer Applications (0975 – 8887) Volume 23– No.6, June 2011 38 A New Technique for Removing Jitter in Network Multimedia Communication to Achieve Guaranteed QoS over Packet Network Shyamalendu Kandar Assistant Professor, Computer Sc. & Engineering Haldia Institute of Technology Haldia, West Bengal, India C.T.Bhunia Director, Bengal Institute of Technology & Management, Bolpur, West Bengal India A.Chaudhuri Professor Computer Sc. & Engineering Jadavpur University, West Bengal, India ABSTRACT: Multimedia data are sensed by human. These types of data are delay intolerable but error tolerable to some extend. Two important parameters that degrade the quality of service (QoS) of multimedia services are Skew and Jitter. Achieving guaranteed Quality of Service (QoS) of multimedia service is a great research challenge. Different researchers proposed different techniques for removing jittering and skew to achieve guaranteed Qos. Accelerating and De accelerating technique, Buffer size estimation technique and Clock time synchronization between sender and receiver are some suitable techniques. But all of the techniques have some advantages and disadvantages. In this current work of the drawbacks of the available techniques for removing jitter is described and new techniques for removing jitter is proposed. A comparison of the available techniques with the proposed technique is made to show the superiority of the proposed technique than the already available techniques. KEYWORDS Jitter, QoS, Protocol, Clock Synchronization 1. INTRODUCTION Multimedia data are integration of one or multiple media components like Text, Graphics, Audio, Video and Animation.[1][2]. Multimedia services are made of two distinct services: Time dependent services and Time independent services, respectively often known as constant bit rate (CBR) services and variable bit rate (VBR) services.[3] In CBR services, in order to achieve some guaranteed QoS, two issues that are paramount importance are: jitter and skew[4][5]. Jitter refers to variable delays caused during transportation through network between packets of a particular service and skew refers to the variable delay between the two (or more) corresponding packets of two (or more) services during transportation in the network. Jitter occurs due to the variable phase delay among the packets of a particular service (May be Audio or Video) from source to destination. The phase lag between packets differs from the source end to the destination end because the total transfer delay varies from packet to packet. This phase delay occurs due to Propagation Delay, Transmission Delay, Queing Delay or Node processing delay at the time of transmission of packets in the network. [6][7] Among these first one is constant and the next three are variable. Due to jittering problem, a sending voice “ I shall go home” may be received as “ I shallgo home”. to the transmitter, the phase delay between “i” and “shall” has increased and that between “shall” and “go” has reduced to zero at the receiver. In the above given figure the phase lag between P 1 and P 2 and P 2 and P 3 are X at the transmitter side. At the receiver side, due to the delay in network, the phase lag becomes X 1 and X 2 respectively. If X 1 X and /or X 2 X, then jitter occurs. Jitter can be of positive or negative. If Jitter is zero then there is no jitter. The jitter is calculated at the receiver side. It is not a suitable technique to calculate the jitter between each two packets, but at the receiver side mean jitter is calculated after a certain interval. The mean jitter calculated, could be limited by increasing the bit rate capacities of the link and by adopting efficient routing technique among others. Yet it is seen that jittering effect can not be solved so simply. Jittering can be minimized in the receiver side but can not be totally removed. Section 2 describes and finds merits and demerits of the existing techniques for minimizing jitter. Section 3 describes the basic idea of the new protocol. Section 4 elaborately discusses the new protocol for minimizing jitter. Section 5 describes the experiment process for the implementation of the new protocol. Section 6 gives the results and Section 7 draws the conclusion and Section 8 points out on the future scope. 2. ALREADY EXISTING TECHNIQUES 2.1. Accelerating -De accelerating Technique There are several techniques to reduce the affect of the problem of jitter. One such technique is known as accelerating and de P 1 P 2 P 3 P 1 P 2 P 3 Time Time X X X 1 X 2 Fig 1: Occurrence of Jitter