Traffic load and cost analysis for different IPTV architectures SKENDER RUGOVA, ARIANIT MARAJ Post and Telecommunication of Kosova-PTK Dardania, p.nr., Prishtina, Republic of Kosova Skender.rugova@ptkonline.com, arianit.maraj@ptkonline.com, www.ptkonline.com Abstract: - 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. This paper presents a detailed comparison between different architectures supporting IPTV services. There are a lot of architectures offering IPTV, but two of the most important architectures taken into consideration in this paper are: centralized and distributed architecture. It is well known that bandwidth requirements are very low for voice and data services, but for delivering Broadcast TV and Video on Demand (VoD) a high bandwidth is required. The more attractive service for the customer is VoD which requires highest volume of bandwidth because it is unicast. The main objective of this paper is to address the core network design in support of IPTV services, considering the traffic load and cost analysis for both abovementioned architectures offering voice, data, broadcast TV and VoD services. Key-Words: - Broadband services; IPTV; broadcast TV; Video on Demand 1 Introduction IPTV is used to transmit digital television via broadband connections using Internet Protocols. IPTV is designed to send streams of video programming to each costumer. These streams are continuous each customer can select the stream they want to view. This process is functionally identical to the programming delivered by local broadcasters. [1]. IPTV service is transmitted through telephone lines and this is the reason why telephone companies are in the first position for offering IPTV to the customers. Preserving video quality in IPTV networks that rely in copper access lines is a big challenge for operators. Service providers need intelligent mechanisms in core and in distribution networks to offer IPTV services. IPTV service providers receive content in different formats and from different sources. Through IPTV technology all of these formats should be converted in IP format in order to be transmitted to customers as service with high quality in the same IP network. In this paper is described IPTV technology, IPTV services [2], service nodes, possible access networks for offering IPTV and bandwidth requirements. Usually service providers use two architectures for delivering IPTV services to customers: distributed and centralized architecture. In this paper we have analyzed both of these architectures in aspect of core network traffic load and implementation cost. Also here are explained the advantages and disadvantages of centralized and distributed architectures. 2 IPTV technology 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 [3] (moving pictures expert groups) techniques. Usually, for video compression is used MPEG-2 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 [4] snooping. IPTV technology is based in 4 main layers (see Figure 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 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. ISSN: 1790-5117 163 ISBN: 978-960-474-084-0
Figure 1. General architecture for offering triple play services 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-2 and MPEG-4/H.264 and transmit it into IP network. - Audio encoders-encode audio in multiple formats MPEG-1, Dolby Digital 2.0 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: contain nodes which are broadband multiservice access nodes (BSAN). 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. 2.1. IPTV services There are a lot of services that IPTV technology can offer: VoD content/movies: Video on demand [5] 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. [6] 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 personal video recorded (PVR) must allow the end-user to record broadcast content. The service mimics recording of broadcast TV channels in video cassette recorders (VCR). 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 Picture-in-Picture (PIP) ISSN: 1790-5117 164 ISBN: 978-960-474-084-0
service enables the end-user to bring up an additional broadcast channel in an overlay window to create a picture-in-picture. 2.2. IPTV service nodes In service nodes are located servers which are the main components in technology for providing IPTV services. Video servers perform a lot of functions including here storage, processing and delivery of IPTV services. There are many types of video servers but the most commonly used are: live streaming servers, VOD (video on demand) servers and advertising servers. Live streaming servers: are characterized with low storage capacity and high processing possibilities. This server supports IPTV broadcast in IP network. This is achieved through one mechanism which has the possibilities to replicate unicast stream into more copy of streams delivering throughout multiple users. Live streaming servers also must have the processing power for channel changing information. VOD servers: are characterized with high storage and processing capacity. Three main parameters for defining VOD server performances are: content capacity in hours in server library, nominal bit rate of video content and the number of simultaneous streams which support this server. Content in VOD server commonly is stored in well known compressing formats also must support transrating. In the cases when content arrives in other formats, the server has the mechanism to convert in the adequate format. VOD servers must perform four main functions: - Storage of content - Network interface and Interface for offering multiple simultaneous streams - Interactive users support which enables a viewer to pause, rewind and fast-forward video content. - Catalog and ordering support Advertising servers: The advertising server s job is to insert advertisements into video streams at specially indicated times called avails. The result is a video stream delivered to a viewer with specialized advertising inserted [1]. Main characteristics of Advertising server are: handle multiple channels simultaneously, the storage capacity is low, the cost is low etc. They must be flexible in changing of advertises and in receiving of video content from different sources. Also they must support advertiser billing. Digital right management-drm Digital rights management (DRM) is a set of software and hardware technologies designed to protect ownership rights of a content provider [1]. DRM System must support Content Protection. This means the protection of content stored in local devices of the user. Content protection must enforce viewing policy of content by defining expiry criteria such as number of plays and expiry date. STB-Set up box STB is user equipment which offers access in IPTV services and in network. From network side has Ethernet interface whereas from user side has a number of TV interfaces. STB must to decrypt incoming signals. It must have chipset in order to run decryption, also must have the opportunity to receive IP packets which contain MPEG-4 TS encapsulation and to convert them in video signal which can be displayed in the TV set. STB supports middleware functions. Middleware supports user interface and possibility for navigation of EPG, searching new channels, VoD etc. 3 ACCESS NETWORKS AND BANDWIDTH REQUIREMENTS FOR OFFERING IPTV SERVICES Operators must deliver broadband services (IPTV, VoIP, HIS-High speed Internet) to any user at any time in the most efficient and cost effective way. To achieve this, operators must use a variety of access technologies including [7]: - FTTx technology - DSL technology - Carrier Ethernet - WiMAX technology Bandwidth requirements for offering one TV channel with MPEG-2 compression method are: MPEG-2 SD 4 Mbps MPEG-2 HD 18-24 Mbps Whereas, bandwidth requirements for offering one TV channel with MPEG-4 compression methods are: MPEG-4 SD 2 Mbps MPEG-4 HD 8 Mbps These requirements for broadband dictate the needs for using broadband access technology. The best case is using FTTH (or FTTU-Fiber to the User). In rural areas this wireline technology is very expensive, so in these areas it is more appropriate to use wireless access broadband technology such as WiMAX. 4 APPROPRIATE ARCHITECTURES FOR OFFERING IPTV SERVICES Usually service providers have two different philosophies for distribution of servers in network. Two most common architectures are centralized and distributed. Each of them has the advantages and disadvantages. Centralized architecture include server farm installed in central location called super headend. These are servers with high capacity which serve directly to customers. ISSN: 1790-5117 165 ISBN: 978-960-474-084-0
Figure 2. General centralized architecture for offering IPTV services Figure 3- General distributed architecture for offering IPTV services Is attractive architecture for little and middle service providers in small geographical area. Centralized network architecture has advantages in aspect of reducing number of servers that have to be installed, reduces cost for transport, aggregation and management of redundant streams towards multiple locations. The main disadvantages for this architecture are: very high link capacity required in core network especially in a case of delivering VoD services which are unicast, the servers should be with high capacity and high quality and thus there are very expensive etc. In Figure 2 it is presented in detail access part of ISSN: 1790-5117 166 ISBN: 978-960-474-084-0
network architecture which is critical in aspect of bandwidth for offering IPTV services. Distributed network architecture (see Figure 3) is very appropriate for reducing the need for high capacities, especially in case of delivering VoD services, which is very expensive service. The servers are with lower capacities compared with servers used in centralized architecture, thus the cost is lower. As disadvantage we can mention the number of servers located through network, the management is very difficult, also operation and maintenance is more difficult, as well as the cost is higher than in centralized architecture. Above mentioned network architectures are applicable but implementation of each one depends from different factors such as customer distribution through one geographical area, terrain configuration etc. for both types of architectures. The situation changes when it is required to deliver VoD services which are unicast. It is well known that from total number of users (25 000), usually 5% of users use simultaneously this service (5% of 25000 =1250). Usually content stream from VoD server is transmitted with 4 Mbps. According to this, in peak load traffic (80% of VoD users use this service simultaneously) network bandwidth requirements are approximately 4 Gbps. VoD services are going to be very attractive to consumers. As unicast services these are critical for network bandwidth requirements, especially in centralized architecture, because VoD servers are centralized. In this case each user that requires a certain service should communicate directly with super head end (SHE). Here is also considered the traffic used for intercommunication between STB and SHE (Figure 5). 5 CORE NETWORK TRAFFIC LOAD AND COST ANALYSIS FOR CENTRALIZED AND DISTRIBUTED IPTV ARCHITECTURE In this paper we analyzed one case study that explains the impact of delivering IPTV services in one concrete network with its own specifics with 25 000 subscribers. This analysis is made for 2 types of architectures: centralized and distributed, in aspect of cost and core network utilization. A standard triple play service for one user has bandwidth requirements as in figure below (Figure 4): 1 HDTV channel 8 Mbps 1 SDTV channel 2 Mbps HSI 2 Mbps Voice 64 kbps 1 VoD channel 4 Mbps Figure 5- Core network traffic load for Centralized architecture Video = 10 Mbps Video + Data + Voice + VoD=16 Mbps Data+Voice= 2 Mbps Figure 4- Bandwidth requirements Based on these bandwidth requirements for a user, it is calculated the network load for a certain number of users for two types of architectures. Example: Analysis of IPTV service Integration in one existing IP/MPLS network Delivering 100 BTV channels from which 10 HD channels, 10 national/local and 80 SD (standard definition), require 280 Mbps bandwidth. Since this service is multicast the core network will be permanently loaded with this service but also with data and voice traffic, as will be shown in the diagram below The trend toward increasing the number of customers and their requirements for VoD services very soon will overcome Giga bit capacities in core network, especially in centralized architectures. According to this, traffic load is mostly affected from VoD services. This is the reason why it is preferred to distribute VoD servers in farthest and most populated locations. In this paper we analyzed the distribution of servers in three farthest regions and most populated locations. As example it is taken the distribution of users in three different zones: 9000 users in zone 1, 8000 users in zone 2 and 8000 users in zone 3. Based on the rule that 5% of total number of users use VoD services simultaneously, there are: 450 users in zone 1, 400 users in zone 2 and 400 users in zone 3. ISSN: 1790-5117 167 ISBN: 978-960-474-084-0
aspect of traffic analysis this architecture requires lower network resources. Therefore, even if we have double number of customers there is no need for new network resources. Figure 6- Core network traffic load for distributed architecture Since the service in this case is distributed in different regions then traffic load in core network is also distributed uniformly all over the core network. Numerical values show that core network in this case is loaded with 1.3 Gbps. It is presented in Figure 6. Cost Analysis Here we made cost analyses for two types of IPTV network architectures. Main cost parameters are: overall cost of IPTV platform for both types of architectures and the cost for increasing network resources. This analysis is made for 5 year time period. Figure 7 Cost analysis for centralized and distributed network architectures Implementing cost for IPTV platform with centralized architecture at the beginning is lower. According to traffic analysis (see Figure 5) this architecture requires higher network resources. The number of customers and requirements for new services are increasing very fast. This is a reason why it is needed to increase the core network capacity that affects directly in the common cost. Implementing cost for IPTV platform with distributed architecture at the beginning is higher. In 6 CONCLUSION In this paper we analyzed two main philosophies of architectures for server distribution in core network offering IPTV services. This paper is based in a case study for core network designing with respect to traffic load and cost effectiveness. Here we analyzed two types of core network architectures: centralized and distributed architectures. These analyses are important for existing service providers who want to offer IPTV services. The analyses show that centralized architecture has some advantages over distributed architecture such as: less number of equipments for operation and maintenance, network management, user management and low implementation cost. It is more appropriate to offer multicast IPTV. The disadvantage of centralized architecture is in offering VoD service-unicast, which overloads core network. In this case it is better to implement distributed architecture, which is better for network utilization. The high demand for the expansion of network capacities is costly, therefore distributed architecture, as time goes by makes this implementation cost reasonable, even though in the beginning its implementation cost is very high as compared to centralized architecture. Regarding centralized architecture, with the increase of service requirements, network investments are necessary and costly at the same time. REFERENCES [1] IPTV and internet Video-Copyright 2007, Elsevier Inc.- ISBN 13: 978-0-240-80954-0 [2] The state of IPTV 2006, new millennium research council, June 2006 [3] Introduction to MPEG; MPEG-1, MPEG-2 and MPEG-4 by Lawrence Harte (Paperback - Aug 21, 2006) [4] Introduction to IGMP for IPTV Networks- Understanding IGMP Processing in the Broadband Access Network - White Paper - Juniper Networks, Inc. 1194 North Mathilda Avenue, Part Number: 200188-003 Oct 2007 [5] Whitepaper IPTV/VoD: "The IPTV/VoD Challenge - Upcoming Business Models" By Jochen Altgeld1 and John D. (J.D.) Zeeman2- IBM Paper for the International Engineering Consortium (IEC) [6] Next generation IPTV services and technologies- Copyright # 2008 by John Wiley & Sons, Inc. New Jersey. [7] Architecture of Mobile IPTV over the IEEE 802.16e Mobile WiMAX Network: A Survey Gary K. W. Wong,- TECHNICAL REPORTS, HKUST, JANUARY 2008 1 ISSN: 1790-5117 168 ISBN: 978-960-474-084-0