Journal of Communication and Computer 9 (01) 141-143 D DAVID PUBLISHING Analysis of Different Parameters that Affect QoS/QoE for Offering Arianit Maraj 1 and Adrian Shehu 1. Faculty of Information Technology, Polytechnic University of Tirana, Prishtina 10 000, Republic of Kosova. Faculty of Information Technology, Polytechnic University of Tirana, Tirana, 1016, Republic of Albania Received: November 16, 01 / Accepted: November 16, 01/ Published: December 31, 01. Abstract: QoS (quality of service) and QoE (quality of experience) have become major criteria for implementing and delivering IPTV services. There are a lot of factors that affect directly to the QoS/QoE. QoS is seen today as one of the most important means for increasing subscribers loyalty and securing successful service growth. To satisfy QoS requirements for delivering IPTV services the authors should study parameters that affect directly to the QoS/QoE. Here they will measure in real network in TK (telecom of Kosova) the main parameters that affect in QoS/QoE, such as: delay factor, losses as well as PCR. In this paper the authors will study how many video channels can be transmitted simultaneously, while maintaining high QoS/QoE. These measurements and analysis the authors will make in headend part of IPTV technology implemented in TK. Key words: QoS, QoE, IPTV, headend, delay factor, media loss. 1. Introduction There are a number of techniques as to how QoS can be implemented in an operator s network: (1) over-provisioning; () integrated services (IntServ); (3) DiffServ (with or without MPLS). The IntServ model has its well-known scalability problems. Using only over provisioning technique, it is quite expensive and not appealing for some operators. In addition, without differentiated services it is difficult to use different over-provisioning ratios per service class. Selective prioritization of high priority traffic-class would make the over-provisioning factor only applicable for that class. The best solution is to combine over-provisioning of bandwidth to minimize the long-term average level of congestion, while also deploying DiffServ to address the requirements of delay, and jitter sensitive traffic during short-term Adrian Shehu, Ph.D., professor, research field: broadband communications. E-mail: adshehu@tcn.al. Corresponding author: Arianit Maraj, Ph.D. student, research field: QoS for offering video services. E-mail: arianit.maraj@ptkonline.com. periods of congestion. It is only by using a combination of technologies being able to support a portfolio of differentiated services on a large scale, with high QoS and at a reasonable cost. Service providers worldwide are looking for ways to deliver new broadband services. IPTV is one of the broadband services all operators tend to offer to the customers. IPTV is designed to send streams of video programming to each costumer [1-4]. Growing demands for IPTV services necessarily direct operators worldwide to implement new and intelligent technologies for offering these services. TK (telecom of Kosovo) is an incumbent fix telecommunications service provider. In its efforts to keep the leading position in Kosovo s competitive telecommunication market, TK has implemented IPTV platform. The trend toward increasing the number of customers and their requirements for IPTV services, very soon will overcome Gbps capacities in core network. While the authors have a competition for bandwidth, the video can suffer in aspect of quality.
Analysis of Different Parameters that Affect QoS/QoE for Offering 1413 Thus in a case where one household requires more than one video, the authors will have degradation of quality of service. So, one user from the same household can have good quality whereas the others may have bad quality. That is why it is needed to share fairly the bandwidth for having good quality. In this paper it is described IPTV technology, IPTV services [5], QoS requirements for IPTV services, network parameters and their effect in QoS. A special attention is paid for the main factors that affect in QoS/QoE. The paper is organized as follows: Section discusses IPTV technology and services; Section 3 explains IPTV technology implemented in TK; Section 4 discusses encoders in IPTV platform in TK; Section 5 introduces the role of ICC in QoS /QoE in TK. Section 6 introduces IPTV over ADSL technology in TK; Section 7 discusses the most common problems in TK for offering multi IPTV video channels; Section 8 presents testing methodology for QoS/QoE in IPTV platform; Section 9 presents testing platform and results in IPTV technology implemented in TK; Section 10 gives conclusions.. IPTV Technology and Services For offering IPTV services the network should be prepared for supporting some specific protocols for signal stream processing. The main reason for using these protocols is that the bandwidth demands are increasing from day to day. Bandwidth limiting is critical in copper lines. So, it is needed to use some intelligent compressed techniques that are specified by some international standards for telecommunication. The main techniques for video compression are MPEG [6] (moving pictures expert groups) techniques. Usually, for video compression is used MPEG- TS (for transport stream) and MPEG-4 (for aggregated streams). Also it is needed to use audio compression protocols such as MPEG-1 audio, DOULBY digital etc.. The equipment in access network must support IGMP [7] snooping. IPTV technology in general is comprised from these layers, as shown in Fig. 1: services (video head end, internet, voip etc.), edge/core and aggregation, access network and home network. Video head end receives content from different sources and transforms it into appropriate form for transmission through IP network. This content can be mix of national and local TV programs, advertisements, satellite content and interactive video services. Video head end encompass broad range of heterogeneous technologies. Internet and VoIP are not the scope of Fig. 1 General centralized IPTV platform.
1414 Analysis of Different Parameters that Affect QoS/QoE for Offering this paper. The video head end is comprised from: Satellite antenna farms which receives broadcast analog and digital TV content; Terrestrial antennas for receiving national content from different TV providers; Cable TV receivers which receive content from CATV providers and live TV content in different formats from studio. IPTV head end collects different formats of content from different sources and prepares it for transmitting in IP format. The equipments which convert different formats of content into IP format are: Video encoders-encode content in MPEG- and MPEG-4/H.64 and transmit it into IP network; Audio encoders-encode audio in multiple formats MPEG-1, Dolby Digital.0 Audio etc.. The edge/core and aggregation nodes are based on feature rich BSR (broadband service routers) and BSA (broadband service aggregator) supporting all standardized protocols for IP/MPLS/Ethernet networks, guaranteeing QoS and respecting data traffic security for offering triple play services. Access network: contains nodes which are BSAN (broadband multiservice access nodes). These nodes enable delivering of broadband services (IPTV, HIS, VoIP), with QoS guarantees through wireline (ADSL, FTTH) or wireless (WiMAX) connections. Home network: contains home equipments (STB, residential gateways, modems, TV set etc.). These equipments enable conversation of IP packet format into analog or digital TV signals. IPTV services: there are a lot of services that IPTV technology can offer: VoD content/movies: Video on demand [6] allows users to select and view to video on demand. VoD content that can be transmitted through IPTV platform includes a library with movie titles, music on demand etc.; Pay per view or subscribe VoD: service which offers consumers access to one or more VoD movies for a subscription; PVR (personal video recorded): The PVR must allow the end-user to record broadcast content. The service mimics recording of broadcast TV channels in VCR (video cassette recorders); Network PVR-Network recording: NPVR is a PVR service where content is recorded on service provider equipment (VoD servers). Service must be activated per subscriber, and must support quota to limit amount of recorded content; Teletext for SD live TV channels: contain embedded teletext information (VTI) picture- in- picture: The PIP (picture-in-picture) service enables the end-user to bring up an additional broadcast channel in an overlay window to create a picture-in-picture. 3. IPTV Technology Implemented in TK In this paper the authors have analyzed the concrete centralized IPTV architecture that is implemented in TK and also they have made measurements in this centralized architecture. This platform, which is depicted in Fig., comprises two mirrored locations with the following components: Antenna system; Headend with receivers and encoders; Service delivery platform (middleware); Data warehouse; Content encryption; Content on demand (VoD and recording); ICC system; Network equipment; CPE devices (STB); Management & monitoring system. The two locations are interconnected with redundant connections, thus providing redundancy for the application platform. It is assumed that TK provides Redundant optical connections between the two locations. The proposed system is modular and flexible and facilitates the pay-as-you-grow approach, i.e., PK can start with a small system supporting a smaller initial subscriber base, while the IPTV system can be easily
Analysis of Different Parameters that Affect QoS/QoE for Offering 1415 Fig. IPTV platform implemented in TK. and gradually upgraded to support the growing subscriber base in the future. IPTV service competes with traditional services offered by cable companies so the high number of attractive channels is a mandatory for the multiplay service providers. As today most of the content is available on the satellite, building an antenna system is one of the challenges service provider is facing with. Satellite antenna system is designed to receive and convert QPSK signals from the number of satellites defined by TK. In TK there are professional parabolic antenna systems with all converters needed for receiving of channels from designated satellites. The included mounting system enables mounting of antennas either on flat surface or on the mounting construction prepared by TK. 4. Encoders in IPTV Platform in TK In IPTV platform implemented in TK, there are MPEG-4 AVC encoders that encode the video signals. The encoding system implemented in TK is split into two parts, AVC standard and high definition, but the same encoder is used for both. For each channel, encoder will produce full resolution video. Each encoder has dual IP output to feed two networks for redundancy. The encoder system supports MPEG- and MPEG-4 plus SD and HD formats. Till now, this encoder system has fulfilled the user s expectation regarding to quality experience. But, now the users are always looking for another solution in order to use IPTV services also via different equipment with different processing power and different resolution formats. Thus, in order to fulfill these requirements, it is a need to use SVC coding instead of using MPEG-4 AVC. Since the authors have implemented the IPTV platform, they need just to replace the AVC encoders with SVC. The other parts of platform should not be changed. In the overall design of IPTV platform in TK, there are 7 regional sites each providing either or 4 channels. In total, there are 5 sites that provide channels and another that provide 4 channels. Each site has regular analogue receiver(s) which provide(s) analogue video/audio. This is converted to SDI using A/D converter which also embeds audio into SDI which feeds encoders. For each channel, AVC encoder will produce full resolution video with PIP. The AVC encoder is not field upgradable and is purchased as either SD or HD. It is assumed that the 5 DVB-T signals are already in MPEG-4 format and they are received at one regional headend. Two DVB-T interfaces are available for receiving and are sufficient for at least 5 SD channels (depends on CAMs). The encoders are connected in (1 + 1) redundant configuration. Output of the encoders connects to TK IP network for delivering the streams to central site.
1416 Analysis of Different Parameters that Affect QoS/QoE for Offering 5. The Role of ICC in QoS/QoE in TK QoS and QoE have become major criteria to evaluate IPTV products and services. Increasing quality of experience is seen today as one of the most important means for increasing subscribers loyalty and securing successful service growth. The majority of content delivery network deployments are designed with highly reliable components and numerous degrees of redundancy, yet it is impossible to completely eliminate all potential network-level failures. ICC system in TK is end-to-end IPTV solution which enhances user quality of experience by mitigating several video content delivery challenges such as slow channel change experience, network congestion effects and packet loss due to errors on access lines. ICC ensures end-user quality of experience which is one of the most important measures for increasing subscribers loyalty and securing successful service growth. In the TK solution only FCC (fast channel change) features are implemented. ICC enhances the subscriber s experience for live content by providing PLR (packet loss recovery) & FCC. Responsible for caching channels and serving end users, ICC server provides: Field proven caching & streaming technologies; High performance & high scalability, enable reaching high throughput from a single server and easy scaling by adding additional servers; Sharing innovative infrastructure to support redundancy, load-balancing & fail-over; Software appliance design requiring minimal management and maintenance from the operator. ICC main features: (1) Packet loss recovery ICC system implemented in TK has mechanism to ensure top quality video and audio reception by utilizing FEC (forward error correction) together with retransmission of missing packets: Supports variable packet loss lengths; Supports H.64 & MPEG-, both SD & HD; Supports both RTP & Raw UDP multicasts; Integrated with majority of CA vendors; () Fast channel change-fast & consistent channel change experience. Upon channel change, streaming unicast for a short period of time followed by smooth & seamlessly transition to normal multicast (IGMP join). unicast includes all MPEG information required in order to immediately initiate stream presentation, including: I-Frame, PAT, PMT, Sequence Headers (MPEG-), SPS/PPS (H.64) & ECM. Fast channel change is based on unique patent pending technology. By providing the SDK, ICC simplifies the requirements from STB vendors & ensures high quality end to end solution. 6. IPTV over ADSL Technology in TK IPTV over ADSL [8, 9] is a solution for transmitting high quality of service such as video services over broadband lines. Improving quality of ADSL broadband access is the main focus of all operators that use this technology. According to [10] seventy-five percent of IPTV households in all over the world receive IPTV via ADSL connections, according to Kendall s recent research. Reducing crosstalk across copper bonded pairs using the ITU-TG. vector standard (G.993.5), introducing software solutions to maximize network logistics, and using caching in the network are all solutions that are occurring right now, as Telco s position themselves to meet the rapidly growing consumer s OTT (over the top) demands. Even further, many operators are looking at deploying local CDS (content delivery servers) to keep their traffic local, reducing costs of bandwidth transit. Service providers which offer IPTV, need to engineer their network to fulfill the customer requests for streaming multiple video services. In TK fixed infrastructure, currently dominates access network which is based on copper cables. This access network is a limiting factor for achieving the objectives of penetration and for huge amount of multiple IPTV video services delivery. The technologies that are used for transmitting IPTV
Analysis of Different Parameters that Affect QoS/QoE for Offering 1417 services are ADSL and recently ADL+. In TK all customers receive IPTV services via ADSL technology. The trend toward increasing the number of customers and their requirements for IPTV services very soon will overcome Giga bit capacities in core network also, especially in centralized architecture that is implemented in TK. This is the reason why it is preferred to analyze this problem and to find a solution for better bandwidth usage for offering IPTV services with high quality. 7. The most Common Problems in TK for Offering Multi -IPTV Video Channels In the cases where the authors have more than one request for video within one household, they will have STB devices competing for bandwidth over the shared access link. This link is considered as bottleneck. This may cause unfair bandwidth share between users; one can have good quality, whereas the other can have bad quality. But, even if the bandwidth is shared equally between users, there also might be other problems that we should consider. One problem can come from the fact that we have different video services and one video can require more bit rates than the others. In this case they have to consider bandwidth allocation, but under conclusion that they have different bit rates for different video channels. Ex. sport channels require higher bit rate than news channels. Beside this, also the authors have bottleneck links in some of the backbone links in TK, from AN to edge routers. Whereas in the links between service routers and Ethernet service switches (edge routers) the authors have optical cable implemented, and they do not have any bandwidth constraint there. So, for solving bottleneck links, the authors have to consider two problems; when they have one bottleneck and the case when for two sets of bottlenecks. From the viewer s perspective, the most important quality criteria are image quality, service interruption security etc.. The challenge for quality increases even more with increasing user demands for different IPTV services, including here HDTV. In TK, since the access network is based on copper cable, there are some issues that should be considered for quality of experience and quality of service. QoE is translated into network quality, and the main factors that affect QoS in IPTV platform in TK, can be categorized as below: Link capacity; Delays; Jitter; Bandwidth stability etc.. In order to address IPTV quality issues in TK, first the authors have to know the source of degradation. One of the main issues for video quality can be bandwidth allocation between users. Some video signal degradations in TK IPTV technology are caused because problems that might be in the physical ADSL links. But also, the other degradations are caused using inappropriate parameters for audio and video compression in headend and from other elements that are involved in the end-to-end transmission. 8. Testing Methodology for QoS/QoE in IPTV Platform As methodology for measurement and for testing they have used MDI (media delivery index) technology. The media delivery index measurements are cumulative throughout the network and can be measured from any point between the video sources and STBs (set top boxes).the MDI is typically displayed as two numbers separated by a colon: the DF (delay factor) and the MLR (media loss rate). 8.1 Delay Factor In order to understand the delay factor component of the MDI [11], it is useful to revisit the relationship between jitter and buffering. Jitter is a change in end-to-end latency with respect to time. Packets arriving at a destination at a constant rate exhibit zero jitter.
1418 Analysis of Different Parameters that Affect QoS/QoE for Offering The DF component of the MDI is a time value indicating how many milliseconds worth of data the buffers must be able to contain in order to eliminate jitter. It is computed as packets arrive and is displayed to the user at regular intervals (typically one second). It is calculated as follows: (1) At every packet arrival, calculate the difference between the bytes received and the bytes drained. This is the MDI virtual buffer depth : _ _ (1) () Over a time interval, take the difference between the minimum and maximum values of and divide by the media rate (Eq. ()): () The most important think that the authors have to consider is that DF is limited between these values: 9-50 ms. So, the values higher than 50 ms, will directly indicate into the quality of experience and quality of service. 8. Media Loss Rate The media loss rate is simply defined as the number of lost or out-of-order media packets per second. Out-of-order packets are important because many devices make no attempt to reorder packets before presenting them to the decoder. Any packet loss represented as a non-zero MLR will adversely affect video quality and can introduce visual distortions or irregular, uneven video playback. MLR [11] is a convenient format for specifying SLAs (service level agreements) in terms of packet loss rates. So, taken in context with the previous DF component, a device with an MDI of 4:0.001 would indicate that the device has a delay factor of 4 ms and a media loss rate of 0.001 media packet per second. Thus, the authors have done measurements of DF (delay factor), media losses and PCR parameters. They have tried to transmit simultaneously multi video channels through one single ADSL line. Recommended maximum acceptable average MLRs is shown in the Table 1. 9. Testing Platform and Results in IPTV Technology Implemented in TK The authors have made some measurements and they have tried to transmit more than videos simultaneously, whereas as access link quality is based in ADSL+ technology. The case where the authors have tried this test has link capacity 8 Mbps. The testing platform and the point where they have made the necessary measurements are shown in the Fig. 3. The authors have made some measurements in the IPTV platform in TK, in: headend, access nodes (DSLAM) and in access lines that are based on ADSL technology. These measurements the authors have done with Ineoquest equipments. In order to have high QoS/QoE for offering IPTV services, it is important to have one overview regarding to the main parameters that affect directly to the QoS/QoE. 9.1 Program Clock Reference Analysis To enable a decoder to present synchronized content, such as audio tracks matching the associated video, at least once each 100 ms a Program Clock Reference, or PCR is transmitted in the adaptation field of an MPEG- transport stream packet. The value of the PCR, when properly used, is employed to generate a system timing clock in the decoder. The STC or system time clock decoder, when properly implemented, provides a highly accurate time base that is used to synchronize audio and video elementary streams. Timing in MPEG references this clock. For example, the PTS (presentation time stam) is intended to be relative to the PCR. The first 33 bits are based on a 90 khz clock. The last 9 are based on a 7 MHz clock. The maximum jitter permitted for the PCR is ±500 ns [1]. Table 1 Maximum acceptable average MLRs. Service (all codec s) Maximum acceptable average MLR SDTV 0.004 VOD 0.004 HDTV 0.0005
Analysis of Different Parameters that Affect QoS/QoE for Offering 1419 Fig. 3 Testbed for QoS/QoE analysis in TK IPTV. PCR is very important also to analyze because it also affect QoS/QoE. The authors have analyzed this parameter in the headend part, for different encoding rates: 0.5 Mbps, 1 Mbps and Mbps (Fig. 4). After this, the authors have made a comparison and they can clearly see that when the encoding rate is Mbps, the PCR parameter is higher compared to 1 Mbps and 0.5 Mbps. From here, the authors can conclude that the tolerance in jitter is much higher if the encoding rate is higher. Thus, if the tolerance in jitter is higher, the system will offer higher QoS and QoE. 9. PCR Analysis in Access Node-DSLAM Here in this section, the authors will analyze the PCR parameter in the access node. The comparison between cases when they have encoding rate 0.5 Mbps, 1 and Mbps, is depicted in Fig. 5. From Fig. 5, all can see that PCR has higher values when encoding rate is higher. This means that the tolerance in jitter is much higher when we have encoding rate Mbps, compared to 1 Mbps and 0.5 Mbps. 9.3 PCR Analysis in ADSL Line Analyses in ADSL lines are most important because in TK the authors have bottleneck exactly in these ADSL lines. In this part the authors will analyze the PCR parameter in the access line for different encoding rate and different number of streams transmitted.5 1.5 3 x 106 PCR Headend, enkodimi 0.5,1 dhe Mbps 1 PCR Headend Mbps PCR Headedn 1Mbps PCR Headedn 0.5Mbps 0.5 Number of measurements for different time intervals Fig. 4 PCR measured in TK, for different encoding parameters..6 x 106 PCR DSLAM, 0.5, 1 dhe Mbps.4. 1.8 1. 1 PCR DSLAM 0.5Mbps PCR DSLAM 1 Mbps PCR DSLAM Mbps 0.8 Fig. 5 PCR parameter in DSLAM.
140 Analysis of Different Parameters that Affect QoS/QoE for Offering.8 x 106 PCR-ADSL 1 stream.6.4. 1.8 1. 1 0.8 (a).3 x 106 PCR-ADSL 3 stream, Mbps..1 1.9 1.8 1.7 1.5 ADSL 1 stream, 0.5Mbps ADSL 1 stream, 1 Mbps ADSL 1 stream, Mbps ADSL 3 streams, Mbps 1.3 (c).3 x 106 PCR-ADSL 1 Mbps, 1 stream vs stream..1 1.9 1.8 1.7 ADSL 1Mbps, 1 stream ADSL 1Mbps, stream.8 x 106 PCR ADSL, stream, 0.5, 1 dhe Mbps.6.4. 1.8 1. 1 ADSL stream-0.5mbps ADSL stream-1 Mbps ADSL stream-mbps 0.8 1.5 1.3 1. 1.1 1 (b) 1.7 x 106 PCR-ADSL 0.5Mbps, 1 stream vs stream ADSL 1 stream 0.5Mbps ADSL stream 0.5Mbps 0.9 (d).8 x 106 PCR ADSL Mbps, 1 vs vs3 streams.6.4. 1.8 ADSL Mbps, 1 stream ADSL Mbps, streams ADSL Mbps, 3 streams 1.5 1. (e) (f) Fig. 6 (a) PCR parameter, stream; (b) PCR parameter, streams; (c) PCR parameter, 3 streams, ADSL line; (d) PCR parameter, 1 stream vs. stream, 0.5 Mbps; (e) PCR parameter, 1 stream vs. stream, 1 Mbps; (f) PCR parameter, 1 sream vs. vs 3 streams, Mbps.
Analysis of Different Parameters that Affect QoS/QoE for Offering 141 simultaneously (Fig. 6). These ADSL lines are based on copper cable. As all people can see from Fig. 6, PCR parameter in ADSL lines depends from encoding rate and from number of streams transmitted simultaneously via one ADSL line. 9.4 Analysis of DF in Headend Part of IPTV Platform Knowing the importance of DF parameter in QoS/QoE, in this section the authors have analyzed the DF in the headend; exactly they have measured the actual, mean and maximal values for DF in ms. These analysis are shown in the Fig. 7. In this figure the authors have represented the measurements values for 60 different time intervals, whereas the coding rate is Mbps. From Fig. 7 all can see that the actual value of DF is smaller than maximum value and bigger than minimum value. This means that in this point of analysis, the quality is very high. According to the DF values, the maximum value of DF should not exceed 50 ms, so the measured values are very small in this case. The results of transmitting videos simultaneously are not bed, but when the authors tried to transmit 3 or more videos, the results are very bad. Exactly, in this case, the delay factor is too high, and thus it will has a very bad video quality. Recommended maximum acceptable DF for having acceptable quality is 9-50 ms. From the Fig. 8, all can see that when trying to transmit one or two videos simultaneously, the DF is very low, but when we transmit 3 stream simultaneously, the DF is too high. In the Fig. 8 all will also see that it has much higher values for DF. These analyses are done with IQDVx application and IQ media monitor. Also, all can see from the Fig. 9 that in this case, the ML (media loss) is to high and affect directly video quality. From the figure, all readers can clearly see that 3 videos that are coded with bit rate Mbps can not be transmitted simultaneously, even in this case when it has bandwidth constraint 8 Mbps. Delay factor measured in ADSL line and in headend part of IPTV platform is seen in Fig. 10. In this figure all can see that the DF in ADSL line is bigger than in headend. This is because of the external noises caused in ADSL line based on copper cable. DF Fig. 7 300 50 00 150 100 7.4 7. 7 6.8 6.6 6.4 6. 6 5.8 Fig. 8 5.6 50 DF analyzed in headend. DF ADSL 1vsvs 3 stream DF for 1, and 3 streams simultaneously. Fig. 9 Media losses for transmitting 3 streams simultaneously. DF-Headend-Vlera aktuale Vlera mesatare Vlera maksimale DF-ADSL 3 Stream DF-ADSL stream DF-ADSL 1 stream 0
14 Analysis of Different Parameters that Affect QoS/QoE for Offering 16 14 1 10 8 6 DF-ADSL 1 stream DF-Headend 1 stream 4 Fig. 10 16 15 14 13 1 11 10 9 Fig. 11 s DF analyzed in headend vs. in ADSL line. s DF analyzed in ADSL line, 1 stream vs. streams. From the Fig. 10, all can see the DF analyzed in headend and in ADSL lines. As all can see, the DF in ADSL line is much higher than in headend. This comes because the transmission lines based on copper cables are far from perfect. Thus, noise is picked up during transmission. This results in a deformation of the video signal. Whereas, the analysis of DF in ADSL line for the cases where it has 1 and streams transmitting simultaneously, all will see in the Fig. 11. 10. Conclusions DF: ADSL 1 Stream vs Headend 1 stream DF-ADSL 1 stream DF-ADSL stream DF ADSL 1 stream vs stream 8 Since in TK the authors have exponential subscriber growth, it will be hard to assure quality among all users in near future. Also all people have to state that the bandwidth and processing resources are finite in IPTV TK and this may lead to the situation where more subscribers requesting IPTV video services, in this case the higher will be the threat for quality degradation. Another problem in IPTV TK network is also the dynamic subscriber behaviors. Every time the authors are facing with requests for multiple video services inside one household. All of the video services will compete for finite network bandwidth and equipment resources and the different traffic weights each requiring different bandwidth capacities. This would be the biggest challenge for TK, because this dynamic behavior can really jeopardize QoE. For transmitting multi-iptv video channels with high QoS/QoE, it is important to have one overview regarding to the main parameters that affect directly to the QoS/QoE. In this paper the authors have done some measurements in real IPTV platform which is implemented in telecom of Kosova. The authors have analyzed some of the main parameters that affect directly QoS and QoE. From analysis, they have seen that when they try to transmit 1 or videos simultaneously via one ADSL link, the results are very good. This means that the main factors that affect quality, are below the allowed level. For example, all people have seen that delay factor in this case is very low, under 50 ms. But, when the authors tried to transmit more than videos, they have seen that the quality is not good. To be more concrete, the delay factor when we tried to transmit 3 video channels simultaneously is about 300 ms. This value is much more than 50 ms and this value is clear indicator that shows that QoS and QoE are not satisfied. So, the authros can conclude that when they do not have multiple videos competing with each other for bandwidth, it will has high quality. But when concurrent video services are requested from within the same household, the bandwidth limitation of the home access link (the link from access node to household) become a bottleneck and put the clients into the
Analysis of Different Parameters that Affect QoS/QoE for Offering 143 competition. The existing approach in TK IPTV platform treats all video streams equally, without taking into consideration that some video channels require higher bit rates than the others to reach the same quality. This is the reason why it will have problems in quality if the authors try to transmit more than videos simultaneously. References [1] S. Rugova, A. Maraj, Traffic load and cost analysis for different IPTV architectures, in: 8th WSEAS International Conference on Telecommunications and Informatics (TELE-INFO '09), Turkey, 009. [] A. Shehu, A. Maraj, Analysis of Network Traffic Load for Offering IPTV Services in Telecom of Kosova, Scientist Bulletin of UPT, Tirana, 011. [3] A. Maraj, A. Shehu, R.M. Mitrushi, Studying of different parameters that affect QoS in IPTV systems, in: 9PthP WSEAS international Conference on Telecommunication and Informatics (TELE-INFO), Catania, Italy, 010. [4] A. Shehu, A. Maraj, Analysis of different parameters that affect QoS in different IPTV architectures, Journal of Communication and Computer, David Publishing company (ISSN: 1548-7709, USA), 011. [5] W. Simpson, H. Greenfield, IPTV and Internet Video, Focal Press Publisher, 007. [6] L. Harte, Introduction to MPEG, MPEG-1, MPEG- and MPEG-4 (006)18-7. [7] S. Schoaf, M. Bernstein, Introduction to IGMP for IPTV networks, Juniper Networks, 006. [8] C. Franklin, How DSL works, http://computer.howstuffworks.com/dsl1.htm (accessed May.08, 01). [9] Broadband Forum, marketing report, R-180 Achieving Quality IPTV over DSL Issue: 1 Issue Date: March 01 [10] A. Burger, Plan Accordingly for OTT Video Onslaught, 7/0/11, http://www.telecompetitor.com/plan-accordingly-for-ottvideo-onslaught/. [11] Agilent technologies IPTV QoE: Understanding and interpreting MDI values, white paper, http://cp.literature.agilent.com/litweb/pdf/5989-5088en.p df, Agilent Technologies, Inc. 008, Printed in USA September 30, 008. [1] http://en.wikipedia.org/wiki/mpeg_transport_stream.