Conectronica Revista Maganize industrial de electronica

With the techniques of compression of present video, neither symmetrical systems SHDSL nor the asymmetric ADSL can provide the necessary bandwidth for IPTV. 26 ADSL2+ to 50 Mbps and VDSL to Mbps offer major bandwidth, but counterpart of a reduced physical reach more. The subscribers need to be more near the Power station or the speeds that can be reached when the distance increases decrease strongly. Many operators find the possibility of offering IPTV on xDSL since attractive they already have existing and unfolded copper networks, and so the facility to give service is very great. Nevertheless, one of the main problems is the delivery of services of traditional television channels and new channels of high resolution on MPEG2. With MPEG2, the channels of high resolution they require approximately 20 Mbps by channel, compared with the 2.5 to 3.5 Mbps for the standard television channels. MPEG4 is the following stage in the compression techniques, similar to MPEG2 that mainly compresses digital data of audio and video (AV). Introduced at the end of 1998, MPEG4 designates a group of standard of codification of audio video and. The transmitted services using standard MPEG4 include video in the Web (Streaming), distribution of CDs, videotelephone, and broadcast of television. MPEG4 uses tools of MPEG1 and MPEG2, and adds new capacities like “Virtual Reality Modeling Language vrml” that supports rendering 3D. Other characteristics MPEG4 include direction to objects (including audio, video and objects vrml), it externally supports management of specified rights of author, and several types of interactivity like video on demand. Most of the characteristics and possibilities of MPEG4 are available for the developer, that is the one who decides she implements if them or no. This means that it is probable that are not complete implementations of everything what the standard can offer. This is resisted with concepts that the standard like “profiles” includes and “levels” that allow to specify kit of capacities or functionalities particular and to use it in specific applications. The new Standard Already ratified like part of standard MPEG-4 (MPEG4 Part 10) and the last standard of ITU videoconference, the H.264 standard is compulsory for the specifications of HD-DVD and Blu-Ray (both high resolution formats DVD) and also ratified in the last versions of standards DVB (Digital Video Broadcasters) and 3GPP (3rd Generation Partnership Project). Numerous companies of broadcast, cable, videoconference and manufacturers of electronics consider the H.264 standard like their option of codec for their new products and services. This adoption by so different variety from companies of an open standard posibilidta that any company in the world can create devices - mobile telephones, decoders, reproducers of DVD, etc - that will offer the new specifications of HDTV. An area where MPEG4 necessary Part 10 has settled down as is in the compression of audio video and making the transmission easier of the signal through different types of networks and mechanisms from broadcast (Table 1). Requirements of multiple channels of video simultaneously After investigating “drivers” of the necessity of multiple channels of video by subscriber, the results reflect that this necessity is not ligature to the number of televisions by home. At the moment 98.2% of the homes in the United States have some television, and 74.3% of the same have 2 or televisions more. (Source: Nielsen Average Research). Another statistical swide that 4 of each 5 sold televisions today are televisions preparations for high resolution (HDTV). (Source: Harvard Research). Table 2 shows the growth of high definition TVs by million homes (Source: The Yankee system Group).

Driver additional to push the standards of digital video it is the “anticipated analogical Blackout” for the 2010. Studying the tendencies of the television distributors, the idea would be not only to distribute digital video, but digital video of High resolution. Bandwidths PON and comparison with MPEG This section focuses in the support of IPTV that can realise several topologies PON, including BPON (Broadband PON) with 622/1.2 speeds of Gbps, GEPON (Gigabit Ethernet PON) with 1.2 ratios of Gps in Downstream, and GPON (Gigabit PON) with 2.4 ratios of Gbps. Being based on the shown calendar of Table 3, the unfolding strategies would have to take benefit from technologies like MPEG2 and BPON, but making sure a way evolution to technologies like GEPON and GPON, as well as to MPEG4.

The objective studying different topologies PON is to know if a particular implementation of PON can support the requirements of bandwidth. This is not only important in the final end of the subscriber, but also in the power station, where they must apply techniques of multi-casting. The capacity of network PON must guarantee a maximum use non-blocking of the video. Architecture PON must be designed to work with the habitual traffic, and to also assure the provision on watch during tips demand in the network. The capacity of network PON determines the maximum number of channels of video by subscriber. But capaciad to do multicasting is going to be critical to be able to handle the services of video that are going away to demand on network PON. As it is possible to be seen in Figure 2, the shipment of simultaneous channels to different subscribers, as well as the habitual use of the service of Video On Demand is going to condition the necessary bandwidth in the connection between OLT and final subscriber. Following the type on watch of Video On used Demand, techniques multicast can be used or only unicast.

Multicast is the capacity stops from a node of the network to send identical data to a variable number of end users. Multicast, in contrast to Unicast and Broadcast, consists of the transmission to different users from information using a single channel of shipment. In a typical transmission multicast IP the complication is added of which the users can at any time enter or leave the transmission group. Unicast is the transmission of a simple unit PDU (Protocol Data Unit) from a source to a single destiny. In the case of Unicast video, it is only the individualized transmission of a channel sent to an end user. A point-to-point transmission unicast require that is sent a copy individualized of the message to each end user. Using technical of multicast, network PON it can be able to distribute better the bandwidth and to assign it more efficiently. On the contrary, with a transmission completely and for all the users unicast, the connection between OLT and main network require demands much majors of bandwidth.

The bandwidth used of network PON is going to depend much on the type on watch that the final client uses. All the networks PON are not going away to find used to the 100% and with a 100% of services of video. As one is in figure 3 is going to have great differences of requirements of bandwidth following the service used by the final client. In figure 3, to calculate the occupied total bandwidth, two types of different packages have been offered on watch:

Premium service, that includes 3 channels standard of video and 2 channels of high resolution; and

Standard Service, in which 2 channels of standard video and 1 channel of high resolution video are offered. The video channels are codified being based on MPEG2, with the channels of video of high resolution codified to 19.2 Mbps and the codified channels of 3.5 standard video to Mbps.

In figure 4 4 groups of unfolding PON can be observed (I, II, III and IV) that give the same bandwidth by end user. In the part inferior the ratio of division of subscribers by port of the OLT can be seen. Effective capacity PON measures the number of different channels of video that can be given by end user. It measures the real capacity of the network combining the impact of the compression of video and the groups of unfolding. Cost Components of Cost of a network PON The cost of the components and interfaces of a network PON is going to be changing in the time without a doubt. At the moment a typical unfolding of a network BPON cost less than

The costs of head equipment PON are basically 3: the cost of the interface with the servers of video, terminal equipment OLT and the interface with the access network. The investigations show to a clear relation between the interface with the network of access and the cost of the solution. A greater ratio of divisón, a source with greater bandwidth and a new technology take to a greater cost of the interface. Since it has been described previously, BPON has quickly lowered of cost by the maturity of the technology and the high volumes. GPON nevertheless hopes that it has sharp and much more fast a reduction of costs. This goes away to having to the 64 subscribers by trunk and the inclusion of techniques like MPEG4.

At the time of comparing different unfoldings and architectures PON, face to a yield analysis, it agrees to consider some aspects:

1) it is an unfolding in a new zone, where I will be the unique supplier and therefore I can wait for a 100% of penetration.

2) I am re-building my present network, so that already I have clients of voice and data, and the unique additional income that I can hope are of video.

3) I am reconstructing my network to avoid that the competition considers to enter this zone. The services triple-play represent a very important source of income so that if I delay the construction I can be incurring a cost of important opportunity. Figure 7 shows as in 2005 the CAPEX spent in architectures PON exceeded the income (Source: Published Financial results of Verizon).

When the ratios of penetration of new services PON study, it is assumed that 40% of to the new will do it subscribers to the services of video, and that 64% of will do it to the subscribers to Internet of high speed, all this before the 2010. A 40% again service triple-play are translated in a 60% more of income or in 1,8 million dollars by residential unit of 2000 past homes. (Source: Forecasts of the Yankee system Group for 2006 - 2010).

Summary With the present techniques of compression, neither technologies VDSL nor the ADSL2+ provide the bandwidth requeriedo for the transport of multiple channels IPTV. Using technical of compression MPEG2 a channel of high deficinición require 19.2 Mbps whereas a standard channel of televisón require 3.5 Mbps. The change of a channel with the remote control in house even supposes that in techniques DSL it happens a latency, since indeed it is necessary to change the transmitted channel. This supposes a delay until with VDSL. Like alternative to XDSL, networks PON they offer a much greater bandwidth and major distances. Multiple clients can be served with a single fiber using optical splitters, and with great flexibility to make reconfigurations of the network. Following the version of unfolded network PON, the speeds in downstream can go from 622 Mbps to 2 ' 488 Gbps on a single fiber, with ratios of division from 1:16 to 1:128. A 488 network GPON giving 2 ' Gbps with a ratio of division 1:32 can offer 77.75 Mbps by client doing very attractive the possible supply on watch of video. Nevertheless, even with the bandwidth of GPON, the delivery of channels HDTV she is complicated but MPEG4 for the distribution is used.

Conclusions

- The traditional operator of telephony must change “mix” on watch one rendered and to focus much more in the video, mainly with the competition of the cable operators.

- The Video on Demand (VoD) and the high resolution (HDTV) are acquiring every day more push and their requirements of bandwidth do essential to construct a robust fiber infrastructure.

- The number of televisions by home is not the detonating in future of the necessary bandwidth by user, but it is it the capacity of channels in house and the requirements of high resolution.

- the ADSL2+ and the VDSL have served like handle to arrive quickly at the market with the new services, but the necessity to compete in video with a supply equivalent to the one of the cable operators, causes that the technology on copper has little competitiveness in means term.

- Architectures PON offer sufficient bandwidth to compete today with video using or nonMPEG4.

- The types of supplied bandwidths PON are determined by the line speed of cards, the ratio of division and the used compression of video, and not only to choose BPON, GEPON or GPON.

- The video supposes a very interesting percentage of the potential income of services triple and quadruple play.

- A cost of very important opportunity by the lack of action or delay in implementing new services Triple Play Can have on architectures PON.

Author:

José Luis González. Director Técnico ADC Krone Iberia