Quality of Service of Voice over Internet Protocol - Coursework Example

Quality of Service of Voice over Internet Protocol Technology has brought about many changes in almost all spheres of life. Information technology in particular has proved to be a great influence towards transforming the way we communicate, listen to radio broadcasts, watch television broadcasts, impart education, search for information, track the movement of processes and services etc. The digital revolution starting off from analog to digital conversion has provided plenty of opportunities to the communication and broadcasting industry with the development of Internet Protocol (IP). Services like IPTV, Voice over IP (VoIP), Video on Demand services etc. are providing opportunities to retailers in the industry to take on the traditional broadcasters and telecommunication companies. Companies like Cisco and Alcatel in close cooperation with ISPs like AT&T, Verizon and Comcast, took a lead in coming out with state of art internet telephony gadgets. The convergence of video, voice and data on next generation networks has resulted into integration of many services. As a result the all important digital pipe is stated to provide telephone service, television channels, radio channels, internet connections and data services all bundles in one connection. Theoretically such services can work wonders for an individual or a limited number of consumers. But as the number of online consumers increase substantially, the quality of digital services deteriorates. For example, mobile operators are already offering audio and video streaming services to their customers on 2.5G and 3G networks (Eastwood, 2007). But the problem starts when large numbers of people start using the digital pipe to communicate with each other or when millions of radio listeners hook on to the radio network to listen the weekly radio broadcast of President of America. This causes traffic congestion in the Internet line, thus severely affecting the quality of the service over the Internet Protocol. A debate has therefore started over the effectiveness of such technological advancements in replacing the traditional copper or fiber cables for telephony, terrestrial or cable television broadcasts or radio transmissions. This study is an effort towards analyzing the developments in information technology in general and telephony and communication technologies in particular. An effort would also be made to study how the perception of user has changed over the years towards accepting these changes and how smooth this transition has proved to be. Introduction As internet is gradually maturing and presenting a paradigm shift in its very ideation, the infrastructure has acquired a business character, a transcontinental personality and a vending framework of wide-ranging, business, educational, scientific and personal data. These very services have popularized the use of internet in all corners of the globe. Now we often make use of internet for real time conferencing between remote locations, real time telephony services etc. These are the applications of internet protocol services. But we often observe that the audio as well the video quality often appears quite broken and patchy during such IP conferencing. Such distractions put a question mark on the effectiveness of the services being provided by IP. The ‘voice quality’ or ‘quality of service’ is measured by the clarity and understandability of the voice being transmitted over the network. During VoIP transmissions the sound is actually in digital format over the network. And digital quality is considered far superior to its analog counterpart. But the fact that the VoIP services are not considered as much qualitatively perfect as their traditional counterparts, mandates it on the part of VoIP service provider to have a relook on the quality of service aspect. The convergence era has started in right earnest, but now it seems there are some serious challenges towards effectively integrating the services in all spheres of life. Different aspects like security over the network, reliability of transmissions, privacy of transmissions, connectivity, user-friendliness, flexibility, extendibility etc. are now being discussed and debated in context with the quality of services over the internet protocol. In a market driven and consumerist society, providing best quality is considered a competitive edge, which implies that a service that suffers qualitatively cannot be attractive for users. Background of the study The dilemma in which internet services have found themselves in can be aptly summed up by a report in ‘the Economist’ (2007). The report, while predicting the shape technology will take in coming year/s, stated that, “The internet is not about to grind to a halt, but as more and more users clamber aboard to download music, video clips and games while communicating incessantly by e-mail, chat and instant messaging, the information superhighway sometimes crawls with bumper-to-bumper traffic.” The internet services and the broadband services are indeed making inroads into many billion homes around the world. This gives rise to expectations of the IT industry that it might be able to cater to these consumers with many more value added services as well. The penetration of cable broadband services across some of the developed markets in Western Europe and North America has come out with some interesting statistics. Amongst some of the highest levels of percentages, while Canada has about 23 percent households with such services, it is 22 percent and 21 percent respectively in case of the Netherlands and the USA (Eastwood, 2007a). Such statistics while giving hope for a digital tomorrow, also lead to introspection about the limitations of internet being used as a platform for delivering a variety of services to users. On the one hand while companies have started entering into strategic tie-ups with companies in order to enrich the products and services, innovative marketing techniques and competitive rivalries have also come out with promises of never before services and qualities. Gradually, devices like web-enabled cellular phones, palm pilots, PDAs etc. have also become darlings of consumer from businessman to students alike (Shih an Shim, 2002). A range of services are already on offer over the net, including voice transmissions. But somehow the problems being faced by the users in making fullest use of the potential of the technological drivers like internet protocol have so far resulted in limited use of IP services in general. This process is still in evolutionary stages and a number of issues like the legal framework are being decided the world-over. Therefore it is an appropriate topic to carry out a study. I’ll therefore be studying the quality of services aspect of IP services in general with an emphasis on VoIP in particular. Literature Review The penetration of internet services in general with wireless services providing additional support has done brought about revolutionary changes in the way we communicate now a days. Users are now being provided with services by integrating contents, voice and text communications. Convergence of multimedia technologies has made ‘global information networks’ a reality (Das et al, 2003). Making use of the existing IP infrastructure for carrying over the internet provides a very low cost alternative to the telephony network. In general the VoIP application services work in following steps; Step-1: The voice signal is sampled, digitized and encoded using an algorithm or coder. Step-2: The encoded data i.e. the frames are converted into packets and transmitted using RTP or UDP or IP. Step-3: At the receiver end, the data is converted back from packet form and forwarded to playout buffer, for smoothing out the delay incurred in the network. Step-4: The data thus received is then decoded and the voice signal is reconstructed for the receiver. The switching and routing technologies of the core networks evolve around packet-based transmissions like IP (Internet Protocol), ATM (Asynchronous Transfer Mode), Frame Relay, and optical routing (Das et al, 2003). Benefits being offered by such benefits offered by unified end-to-end IP network solution are; Cost reduction: voice and data convergence results in improved network efficiency and thus reduction in operation costs. Simplification: If the service provider is able to provide a range of services on one platform, that will allow more standardization and a common platform. Advanced Applications: Though telephone is considered the basic application for VoIP networks, but in the long run services like multimedia and multiservice applications can also be integrated into it. Consolidation: The costing system in general has different elements in it. User group is stated to be one of the significant cost elements for a network and service provider. Once the services are integrated it provides the company a better control over operations which helps in minimizing the points of failure. But these advantages prove short-lived once the number of users starts increasing. The effect on performance can be gauged by comparing the performance metrics of the ‘carrier grade’ plain old telephone system (POTS) with VoIP. For example, the International Telecommunications Union’s (ITU-T) recommendation G.114 specifies that one-way delays should not exceed 150 milliseconds (Melvin and Murphy, 2002). The POTS easily meets these limits presenting minimum end-to-end delays. It is worthwhile here to mention that propagation time forms a significant and consistent proportion of the total time. The internet on the other hand offers much higher and inconsistent delays due to congestion. These delays arise out mainly out of; Operating system delays: The computer system requires operating system, which takes its time. Similarly, the application requires its own set of driving software. Host hardware input/output delays: This includes packet conversion delays depending upon the type of codec used. Possible look-ahead delay: During transmission the packet looks ahead for a clear route and compares two or more routes. Network delays: This is combined effect of fixed propagation delay; transmission delay (set up by the interface speed; Variable queuing delays at intermediate routers or switches Application delay: This delay is introduced by the receiver to allow for the variance in inter-packet arrival times, or jitter. The queuing delays which are the manifestation of best effort services quite often prove detrimental for the quality of the transmissions over the internet. Besides the channel related congestion and losses the packets suffers delay depending on the congestion at the intermediate routers. Both the loss and delay of packets adversely affects the quality of VoIP calls, which is generally expressed in terms of R-score (Sengupta et al, 2008). In the traditional telephone networks a mechanism is in place to control the queuing delays. The mechanism known as call admission control (CAC) mechanism limits the number of attempts for one particular call (Wang et al, 2006). When the number of call attempts exceeds the capacity of links, the CAC rejects any new request for setting up the calls, while the existing calls continue unaffected. Most of the current IP networks do not have any CAC, which do not have any mechanism for limiting the overload, and thus the network can only offer best-effort services. This in effect implies that new traffic will keep entering the network even beyond the network capacity limit, thus causing both the existing and the new flows to suffer packet loss and/or significant delays (Wang et al, 2006). Combinations like Site-Utilization-Based Call Admission Control (SU-CAC) and the Link-Utilization-Based Call Admission Control (LU-CAC) have been tried on VoIP systems, but none of these mechanisms have been able to provide comprehensive service guarantees like the traditional CAC, owing to a number of reasons. For example, the SU-CAC mechanism performs admission control based on the pre-allocated resource to the sites, but the existing systems like Cisco’s VoIP system are not able come out with a systematic plan for such an approach. Similarly, the LU-CAC mechanism requires utilization of the individual link bandwidth. This mechanism needs resource reservation on individual links in a network, which in turn results in introduction of overheads and thus affecting the network performance. Similar delays are observed in other applications of IP like IPTVs. But, such shortcomings have not stopped researchers from coming out newer applications for IP based services. For example the IP multimedia subsystems (IMS) are being developed for providing mobile and fixed multimedia services with the help of next-generation networks (NGN). Similarly, WiMax is envisioned as a solution to the outdoor broadband wireless access in order to deliver high-speed streaming data. Conclusion: Internet Protocol applications have indeed provided a cost effective and convenient way of telephony. While on the one this alternative has helped in exploring a new technology for our communication needs. But, many people feel disappointed with the way internet telephony has progressed so far. It could not live up to the hype and the expectations have proved to be unrealistic so far. In the initial years the cost-effectiveness part of the VoIP was given more prominence than the technical aspect of it. Subsequently when the internet congestion started showing signs of overload, the present infrastructure proved to be a misfit for internet telephony. If the available trends are an indication, in the coming days, surfing on the web will be more like travelling on the highways on weekends or holidays, when everybody appears to be leaving the city for some good time with family and friends. This results in enormous traffic congestion and manifold increase in our travelling time. This indicates further problems for VoIP services, which are already plagued by the delays and losses, until something substantial is done to improve the quality of services. Establishment of minimum standards of performance to ensure the productivity of VoIP services in the industry is essential to advance the VoIP position. Unless the quality of VoIP reaches a quality level suitable as an enterprise product, the demand for VoIP will not be fully realized. References: 1. Das, Sajal K.; Enoch Lee; Enoch Lee and Sanjoy K. Sen (2003). Performance Optimization of VoIP Calls over Wireless Links Using H.323 Protocol. IEEE Transactions on Computers, VOL. 52, NO. 6, June 2003 2. Eastwood, Gary (2007). The Future of TV-The evolving landscape of HDTV, IPTV and mobile TV. Business Insights Ltd. 3. Eastwood, Gary (2007a). The Future Digital Home-New technologies, growth strategies and customer uptake. Business Insights Ltd. 4. Economist (2007). Tech. View - Technology in 2008-Three fearless predictions. The Economist, Dec 23rd 2007 5. Melvin, Hugh and Murphy, Liam (2002). Time Synchronization for VoIP Quality of Service. IEEE Internet Computing, 1089-7801/02/. IEEE 6. Sengupta, Shamik; Chatterjee, Mainak and Ganguly, Samrat (2008). Improving Quality of VoIP Streams over WiMax. IEEE Transactions on Computers, Vol. 57, No. 2, February 2008 7. Shih, Gary and Shim, Simon S.Y (2002). A Service Management Framework for M-commerce applications. Mobile Networks and Applications, Vol. 7. 8. Wang, Shengquan; Mai, Zhibin; Xuan, Dong; Zhao, Wei (2006). Design and Implementation of QoS-Provisioning System for Voice over IP. IEEE Transactions on Parallel and Distributed Systems, Vol. 17, No. 3, March 2006. Read More