Ip Video to the Home Using an Ethernet Passive Optical Network T
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IP VIDEO TO THE HOME USING AN ETHERNET PASSIVE OPTICAL NETWORK T. Neel, Alloptic One of the key challenges to Internet discusses the benefits, features, and protocol (IP) video in the past has been technological foundation of EPON, in the large amount of bandwidth needed to comparison with APON, as the best deploy it. Optical fiber is recognized as alternative end-to-end architecture for the most effective means for transporting IP video. voice, video, and data traffic; however, it is expensive to deploy and manage The Case for IP Video Services point-to-point (PP) fiber connections between every subscriber location and Video Delivery Options the central office. Ethernet passive Over the past few years, digital-cable optical network (EPON) is an emerging and digital broadcast satellites (DBS) broadband fiber infrastructure that have created a new business revenue addresses the high cost of PP fiber model for the television (TV) industry. solutions. Gigabit EPONs were also Similarly, IP multicast has the ability to developed to address the shortcomings generate new revenue models for the of asynchronous transfer mode passive Internet. There are many ways to deliver optical networks (APON), which are video to the home. Video delivery inappropriate for the local loop as they options to the home include the are complex and expensive and lack following: cable TV (CATV) over sufficient video capabilities and hybrid fiber/coax (HFC), DBS, digital bandwidth capacity. EPONs provide cable over HFC with a set-top box, greater service capabilities and higher multi-channel multipoint distribution bandwidth at reduced costs. Though service (MMDS), IP video over digital EPONs are in the early stages of subscriber line (DSL), analog video development, they figure to become the overlay over fiber, and IP video over primary means for delivering converged optical EPONs. Despite this plethora of video, voice, and data over a single choices, the trend is toward convergence optical access system. This paper on two different layers (see Figure 1). Figure 1: Convergence of all Services over One Network In the first layer of convergence, three IP, there is convergence to a single networks are converged into a single infrastructure on a single protocol. IP is optical-fiber network. The second layer thus the ubiquitous protocol for network of convergence occurs in the IP layer. convergence (see Figure 2). With the introduction of new services to The optical last data IP Traffic mile network IP data needs to carry this IP video IP voice Optical Access deployments need to be Source: www.caida.org optimized for today IP delivery voice Figure 2: IP Traffic Will Dominate the Last Mile Because of the increase in IP traffic on definition TV (HDTV). New services in networks, service providers must be able the buffered video space include to offer different types of services, such personal videocassette recorders (VCR), as video, data, or voice. Optical access time-shifted TV, and full-screen deployments need to be optimized for IP streaming video. Viewers can now enjoy delivery, and Ethernet is just that—a interactive features of video, Web-based packet-based network, optimized to video, and services that allow them to carry IP traffic. watch programs at their convenience. The market for personal VCRs is growing at the moment because of TiVo Services Enabled by IP Video boxes, which act locally or remotely in IP video enables a growing number of an IP video head-end. As this technology services. Existing services for real-time matures, more enablers will become video include broadcast and pay-per- available. Service providers benefit from view TV, and streaming video is an IP video services, as it is easier to example of buffered video on the manage a converged single network for Internet. The simple act of adding voice, data, and video. IP video services bandwidth enables new video services. create multiple revenue streams, New services for real-time video include improved competitiveness, and a interactive TV, on-demand TV, simplified network at reduced cost that is videoconference, integrated Web easy to manage, administer, and content, digital TV (DTV), and high- customize. IP video is in the process of becoming an incremental investment services for the end user include more over data and voice, which are already in video services, better picture quality, IP format, and it allows service providers bundled service packages, Web-enabled to amortize the cost of broadband services, and ultra-fast Internet access. In buildout over multiple services. IP video addition, end users can choose from a reduces provisioning costs for the large team of service providers to service provider, as interactive media provide any service at any time. allows the subscriber to perform self- provisioning relatively easily. Converged EPON Primer networks minimize equipment and network management costs and There are three primary ways to run fiber eliminate the need to train a large to a home. The first option is to establish number of technicians to maintain the PP links (see Figure 3). network. The benefits of IP video 32 homes 64 transceivers 64 trunk fibers CO 66 transceivers 2 trunk fibers CO 33 transceivers 1 trunk fiber CO Figure 3: PONa Natural Step in Access Evolution In Figure 3, each of the 32 homes uses that they require power, which creates a two fibers, which correspond to 64 separate network with power needs. transceivers and 64 trunk fibers. Using a curb switch reduces the number Convergence to a single fiber reduces the of trunk fibers; however, the number of number of fibers and transceivers to 32 optical transceivers is not diminished. and 64 respectively. Because it is a fiber- The cost of curbside switch boxes is rich infrastructure, companies have dominated by the cost of the optical begun to install curb switches, such as transceivers. Therefore, the most logical Ethernet switches, in the network. A solution would be to replace this box potential problem with these switches is with an optical splitter to serve as a passive directional coupler. The optical between metro-network capacity and the splitter reduces the number of end user’s needs, separated by this last- transceivers needed by nearly 50 percent mile bottleneck. PONs respond to this and conserves fiber in the trunk, on the last mile of the communications order of 1 to 64. PON is therefore a infrastructure between the service- natural step in access evolution, as it provider central office, head-end, and simplifies the infrastructure and requires customer locations. PONs are point-to- little maintenance. multi-point (PMP) networks, which have the capacity to downstream broadcast PON Architectures media to residential homes. The Bandwidth is increasing on long-haul following figure illustrates PON networks through wavelength division architecture (see Figure 4). multiplexing (WDM) and other technologies. However, there is a gap Figure 4: PON Architecture There are some benefits to using PONs conversion is required for Ethernet. for video overlay. Although there is a APON has been the traditional choice, cost to install an amplifier, which is especially the optical carrier (OC)−3, shared by multiple locations, PONs are which has a bandwidth of 155 megabits passive and eliminate all power in the per second (Mbps). In APONs, data is field. The two primary types of PON transmitted in fixed-length, 53-byte cells technology are APON and EPON. with a 48-byte payload. At the time that APON was developed, ATM was APON considered best suited for multiple APONs were developed in the mid- protocols, and PON appeared to be the 1990s through the work of the full- most economical broadband optical service access network (FSAN) initiative solution. in the interest of extending high-speed services, such as IP data, video, and EPON Ethernet over fiber, to homes and EPON was developed in 2000 and 2001 businesses. In APONs, protocol through the Ethernet in the First Mile (EFM) initiative, the standardization number of lasers required at the central effort of the Institute of Electrical and office. Unlike PP fiber-optic technology Electronics Engineers (IEEE). EPON optimized for metro and long-haul was developed because the APON applications, EPONs respond to the standard proved to be an inadequate needs of the access network in a simpler solution for the local loop. EPON has a and more cost-effective manner. EPONs gigabit-per-second (Gbps) bandwidth allow service providers to run fiber into and yields eight times more bandwidth the last mile at lower cost in order to than APON. While EPON offers greater provide an efficient, highly scalable, bandwidth and broader service end-to-end fiber-optic network that is capabilities at reduced costs than APON, easy to manage. Ethernet has evolved it has a similar fiber infrastructure. It is significantly in the past 15 years, and most effective to transport data, video, everything about it has changed except and voice traffic via fiber. However, the frame. Figure 5 illustrates how EPON has a point-to-multipoint (PMP) Ethernet has evolved for metropolitan- architecture, which eliminates the need area-network (MAN) and wide-area- for regenerators, amplifiers, and lasers network (WAN) applications. from an outside plant and minimizes the Figure 5: Ethernet Has Evolved for MAN and WAN Applications In EPONs, data is transmitted in conversion. An important industry variable-length packets of up to 1,522 objective is full-service fiber to the home bytes per packet in a 1,500-byte payload (FTTH) for delivering data, video, and (according to the IEEE 802.3 protocol voice over a single platform. The first for Ethernet), distinguishing it from instances of broadband in the home APONs. Ten-gigabit Ethernet (10 GbE) appeared with the advent of DSL and products had begun to appear in the cable modems.