www.enablence.com

MULTIDWELLING

UNIT SERVICE USING ENABLENCE

PONS

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INTRODUCTION

Multidwelling units, MDUs, are important service locations for telecommunications service providers, but they present some unique challenges. Not the least of these challenges is the fact that no two MDUs are the same, making it hard to generalize a solution. This paper in intended to help you sort through the issues in order to choose the best solution for every situation. Feel free to contact Enablence Technologies for any questions that are not answered here.

Note that we cannot address legal issues that may get in the way of some of the technical solutions we will show. Every situation in every jurisdiction is different legally and contractually in terms of access to common areas or individual apart- ments, and in terms of your ability to use existing wiring. We shall show a number of options, not all of which will apply in each case for these reasons.

Before we begin describing the options, we shall take a page or so to review modern PON standards. We also need to ac- quaint you with Enablence’s wide range of products for the market. Then we shall use these products to describe solutions to various MDU installation issues.

A BRIEF REVIEW OF MODERN PONS

Passive Optical Networks, PONs, are another name for the most common form of fiber-to-the-home (FTTH) installations. A PON is characterized by outside plant that consists of nothing more than fiber optic cable and passive optical splitters (and, of course, the usual installation materials used with them). This is opposed to active networks such as cable TV HFC (hybrid fiber-coax) or telephone DSLAM (digital subscriber line access multiplexer) architectures, which place power-consuming devices in the field. Compared with them, PONs offer much, much lower operating expense, better reliability, higher quality, and higher bandwidth.

There are two standards that modern PONs follow, as outlined below. Enablence Technologies offers both standards, so you can choose the best for your situation. Both standards utilize downstream data transmission on 1490 nm, with upstream data transmission on 1310 nm. Both use 1550 nm for the transmission of downstream broadcast video (analog and digital). Both are commonly used with 32-way splits, though 16- and 64-way splits are possible. Both are specified to 20 km in all-passive configurations. GPON has an option for up to 60 km operation, but with the restriction that the difference in distance of the nearest and farthest ONTs cannot exceed 20 km, and an active intermediate device is required.

EPON Ethernet PON, or EPON, is a standard developed by the Institute of Electrical and Electronic Engineers, the IEEE, under the auspices of their 802.3 Subcommittee, the group responsible for the Ethernet standard. EPON has been incorporated into the Ethernet standard document.1 It is also known as 802.3ah (after the designation of the working group that developed the standard, EFM, Ethernet in the First Mile, or GE-PON, Gigabit Ethernet PON.

Today’s EPON operates at a wire speed, the actual data speed you would measure if you observed the fiber transmission di- rectly, of 1.25 Gb/s in each direction. Because of the 8b/10b encoding used, the data rate is actually 1 Gb/s in both direc- tions. The next version of EPON will operate at 10 Gb/s downstream, and either 1 or 10 Gb/s upstream. This standard is being developed by the 802.3av Working Group, of which Enablence Technologies is an active member.

GPON The Gigabit PON, or GPON, standard is promulgated by the International Telecommunications Union, the ITU. It is the lat- est in a series of ITU PON standards, the earlier of which are APON and BPON. It features a downstream speed of 2.488 Gb/s and an upstream speed of 1.244 Gb/s. The next generation of GPON is just now starting to be defined, but will likely operate at 10 Gb/s, the same as the EPON standard. There is a move to harmonize the two standards at some level, but the outcome of this effort is not finalized as of this writing.

1 http://standards.ieee.org/getieee802/802.3.html

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EMERGING AND NEXT GENERATION PONS EPON and GPON are by far the most prevalent PONs being installed today, and Enablence Technologies is the only com- pany that has a comprehensive array of OLTs and ONTs for both standards. Emerging standards include the SCTE RFoG (RF over Glass) standard, and the 10 Gb/s standards, 10 GE-PON (IEEE) and 10 Gb/s GPON (ITU). Enablence is active in the development of these standards, and will provide product as the standards mature to the point that it is feasible to provide cost-effective PONs conforming to those standards. You can turn to Enablence Technologies regardless of your PON needs.

POINT-TO-POINT While not a PON by definition, point-to-point (P2P) networks have been deployed, some for residential applications, but more for business. These are also known as active Ethernet networks. A fiber is extended from the central office (or a re- mote switch) all the way to the subscriber’s premise. At the central office, a switch concentrates the data.

ENABLENCE’S FIRSTS

Enablence Technologies’ FTTx division has been pioneering innovative solutions since 2000, predating the EPON and GPON standards by several years. Firsts include:

- First multidwelling ONTs, featuring individual control over each and every port via the element management system (EMS)

- First implementation of broadcast overlay with no interaction with the data wavelength

- First choice of field- or CO (headend) rack-mountable, temperature stabilized OLT

- First mitigation of SRS effects in EPON and GPON

- First RF return, to support standard cable TV set tops

- First digital RF return support, eliminating the cost, limitations, and difficulty of analog returns

- First easy-to-use graphical interface EMS

- First management-compatible layer 2 switch for in-apartment use

OPTICAL LINE TERMINALS

Enablence Technologies offers a high-density OLT, the Trident7, and a low-density OLT, the COLT, for EPON, GPON, and point-to-point (P2P) systems. The Trident7 can mix and match either standard EPON, GPON, or P2P Ethernet, with a com- mon management platform. In addition, we offer a wide variety of ONTs for every purpose. Our line of ONTs is available for any of the standards, so we shall not distinguish between them throughout most of this paper. All of our OLTs and our ONTs support IGMP snooping, so IPTV multicast is extremely efficient: when more than one subscriber is watching the same program, that program only occupies bandwidth once. All Enablence OLTs and ONTs are compatible with an optional broadcast tier on 1550 nm. ONTs which do not themselves support broadcast, include a filter for the broadcast wavelength, so that they can be used in systems that also have broadcast video. Data sheets are available at www.enablence.com .

HIGH DENSITY SOLUTIONS – THE T7 Figure 1 shows the Enablence Technologies Trident7 (T7) OLT chassis at an actual customer location. At the top (above the technician’s right hand) is the power and alarm panel, with the fan tray just under it. The fan tray may be removed for clean- ing or service while the Trident7 is operating. Under the fan tray are the blades that define the Trident7. At the extreme left (not visible in the picture) is a management module, which serves the entire chassis and any COLTs subtending it (see be- low). In the center are two switch modules, the PSMs (orange fiber cables connect to one of them in the picture). Each switch module provides either five ports of Gigabit Ethernet connectivity to your network, or four 10 Gigabit Ethernet con- nections. All connections are on industry-standard SFP modules, so you may choose the physical interface you need, either electrical or optical.

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Figure 1. Enablence Trident7 OLT Chassis

The two switch modules may be used together to increase network capacity into the Trident7, and they may be used for redundancy. You can configure them to provide more bandwidth during normal operation, and if you experience a failure, such as due to a fiber cut, the chassis will continue to operate, using the remaining data connec- tions.

The remaining 18 module slots accept PON cards that are specific to the standard used, EPON, GPON, or point-to-point Ethernet (P2P). The EPON cards fit into a single slot, and feature four PON inter- faces, each of which usually serve 32 ONTs, but which can serve up to 64. In addition, an extra Gigabit Ethernet connector is provided. This may be used to provide additional bandwidth for the PONs, or it can be used as a mirror port, or for any other need.

GPON cards are double wide and feature 8 PON ports, as well as two extra 10 Gb/s Ethernet port on the network side. As with EPON, these ports may be used to enable more bandwidth, may be used as a mirror, or for any other use. One use of these ports can be to support CALEA (Communications Assistance for Law Enforcement Act), by mirroring any communication specified by court order. See En- ablence’s white paper, Implementing Lawful Intercept (CALEA) Re- quirements with Enablence PONs, available at www.enablence.com . LOW DENSITY SOLUTIONS – THE COLT Figure 2 illustrates the Enablence Technologies COLT chassis. The primary application is connection of a remote group of subscribers, and it is sometimes used within MDUs where fiber connections are made to each residence. In this application, the COLT may be lo- cated in a common wiring closet, and facilitates maximum service to

each dwelling. The COLT uses the same PON blades as does the Trident7, with one blade per COLT chassis. This makes it easy to train personnel, and reduces your need for sparing. The chassis fea- tures 4 Gb/s of network interconnectivity via SFF plug-in transceiv- ers supporting long or short distance Ethernet electrical or optical connections. In addition, you have the ports on the PON blade de- scribed above, which can be used for more bandwidth or for other applications. The COLT is two rack units high, and operates from - 48 Vdc. It is managed using the same EMS as is used for the Tri- dent7 and the entire line of ONTs. In order to minimize the cost of deploying it, the COLT is temperature-hardened and only requires protection from the weather.

Figure 2. Enablence Technologies Compact

OLT, the COLT

OPTICAL NETWORK TERMINALS FOR MDU APPLICATIONS

Enablence Technologies features a wide range of ONTs for MDU applications. Some of them are also used in single family applications. We shall show many configurations suitable for various MDU needs. Since each MDU applications is unique, though, if you don’t see something here that fits your needs, please contact your sales representative. It may be that we can use yet some other combination of elements to meet your needs. We are continuously developing solutions to unique needs, and we can solve your requirements too.

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1 outlet 280 feet 85 meters 2 outlets 220 feet 67 meters 4 outlets 165 feet 50 meters

Figure 3 illustrates the model numbering convention used with Enablence ONTs. The prefix indicates PON ONT) or an electri- cal input (ENT), described below. Next is a G for GPON or an E for EPON if the ONT has the optical input. Point-to-point (P2P) ONTs are the same as EPON ONTs with a different software load.

If present, number of GBE outputs (omit if none)

ONT -G1321i

ONT=optical input

Number of analog voice (POTS) ports i=indoor RTN=includes

RF return

If the ONT includes a Gigabit Ethernet port, there will be four digits, or there will be three digits if no such port is provided. The second digit is the number of 10/100Base-T ports, and this is followed by the number of analog voice (POTS) ports. En- ablence ONTs support either SIP or MGCP (NCS) protocols, and

ENT=Ethernet electrical input

G=GPON E=EPON

Number of RF (broadcast) ports

Number of 10/100Base-T ports

interoperation has been verified with most switches on the mar- ket. Note that there are no specific VoIP ports, as VoIP phones can be connected to any Ethernet port.

Figure 3. Enablence ONT Model Numbering System

The final digit indicates the number of RF (broadcast) ports. Frequency response is 54 to 1,002 MHz, in order to afford you as much bandwidth as is available from the most advanced cable TV systems. The RF port is optional on all models that provide for one. Enough output level is provided to directly drive at least four TVs, with a generous allowance for cable loss. If the letters RTN appear after the digits in the model number, then RF return is included. Several different RF return stan- dards are used in the industry. Each ONT can support up to two standards. The standard(s) supported can be downloaded from the EMS, and are supplied per-order from the factory. The letter i indicates that the ONT is not weatherproof and should be used in a protected (indoor) environment.

E/G-888

Figure 4. ONT-E/G888 ONT in available weatherproof, secure housing

Figure 4 illustrates the 888 ONT (available for either EPON or GPON), in its optional secure steel housing. This product is the workhorse product for triple play MDUs in many countries. The housing provides both weather and intrusion protection, and since the ONT is temperature-hardened, it may be mounted out-of-doors. The power supply is 48 Vdc, and may include standby battery backup. The 888 is available with and without broadcast video (will be model 880 without broadcast). Each port, including broadcast, can be switched on and off independently from the EMS. This can be a major cost saver in MDU applications where churn is a big issue. You can turn off service when one tenant moves out, and turn it back on when the next moves in, all without ever rolling a truck! You will not affect the service to any other subscribers in the process. When a tenant leaves, you can leave phone service connected, possibly al- lowing only emergency calls and calls to your office, with RF turned off. The data port can be placed in a walled garden that only gets to your order entry site. That way, when the next tenant moves in, you can, if you wish, allow him to call or go on-line for service, and never have to roll a truck.

The 888 RF output level is +19 dBmV

nominal, +17 dBmV minimum, with some uptilt to compensate for the frequency-dependent loss of coaxial cable. This is adequate to supply sig- nals directly to the number of TVs shown, over the approximate distances shown in Figure 5. In constructing this table, we assume standard RG-6 coax and high-quality splitters. Alas, such are not to be found in all MDU applications. If wiring is substandard you may have to modify what you

Figure 5. Approximate length of RG-6 coax that can be used with

the 888

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do. This table is only intended to be a guide. For more information about in-home wiring, please consult Enablence Tech- nologies’ white paper #990-00003 entitled In-Home Wiring, available at www.enablence.com If longer distances or more splits are needed, you can use larger coaxial cable, such as RG-11, or you can add an amplifier. Note that not all amplifiers are created equal, so you have to use one with appropriate specifications. Please consult your Enablence sales professional for more information. Also see the appendix for more information on RF distribution.

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In most MDU applications, we find that providing an equal number of broadcast, voice, and data ports is optimum. Data ports may be isolated from each other so that one subscriber cannot see another subscriber’s computer(s). In some cases you may find that you need to provide more service than this arrangement allows. If so, you can supply fewer apartments from the 888, or you can use an external data switch located in an apartment.

Figure 6 illustrates the 888 installed without the housing. This con- figuration is appropriate when the ONT can be installed in a secure utility location. The cost is lower since you don’t have to buy the housing, and it is generally easier to wire this configuration. The restriction, of course, is that you must have a secure, protected loca- tion. The module shown is identical to the module in the housing shown above, so it is still outdoor temperature rated, but of course it is not weatherproof, and not secure.

The RF portion includes a jumper, which carries RF before the split- ter and service disconnect switches. This may be used to inject local video at an MDU complex. Example applications include front door cameras, pool cameras, or other video intended only for residents of the MDU. The signals thus injected must either be on a channel not

Figure 6. 888 ONT Mounted in Secure Wiring Closet

used as part of the normal video feed, or the normal video feed on the channel must be removed using a special-purpose notch filter. Con- sult Enablence if you need to remove an incoming channel and are not sure how to do it.

E/G-1800I Figure 7 illustrates the Enablence Technologies 1800i ONT. This indoor-only device is intended for data-only applications, which may include IPTV. If voice is needed, external adaptors, often called in- tegrated access devices, or IADs, can be used. This unit is intended to be used in data centers and similar applications. While it does not receive the 1550 nm broadcast overlay, it includes a 1550 nm filter, so may be used in systems that have broadcast signals on the same fiber. The unit is normally supplied with a wall-plug transformer (often called a wall-wart). Backup power, if provided, may be sup- plied via any uninterruptible power supply. Fiber management is under a removable top cover. Each port may be isolated from other ports.

Ways to use the 1800i in MDU applications are shown below. The 1800i is available for EPON, for GPON, and with an electrical input (ENT-1800i) for switching applications, as shown below. (Part of the FTTx division of Enablence Technologies was previously Wave7 Optics, hence the name on pictures of certain equipment.)

Figure 7. ONT/ENT-E/G1800i ONT top view

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ENT-1800I

Figure 8. E/G/ENT-1800i ONT rear view

The ENT-1800i was developed as a companion to the ONT- E/G1800i. They are the same product, except that the ENT-1800i has no optical input. It is useful for wiring large MDUs, as we shall see below. Any suitably-managed switch could be used for these applications, but the ENT-1800i is uniquely manageable from the same EMS that manages the rest of the Enablence Technologies system. All of the management features of the E/G-1800i are available on the ENT-1800i. On a per-service and per-port basis, you can manage the data rate a customer receives in both direc- tions, and you can establish VLANs for various services. Higher- priority VLANs can be established for higher-priority traffic such

as telephone and IPTV, with lower-priority for web surfing and email. As customers enter and leave your system, and as they change service levels, you can update their service from your element management system.

E/G-1321I

Figure 9. 1321i ONT

Figure 9 illustrates the ONT-E/G1321i ONT. This product was ini- tially developed for single family units (SFUs), but may find applica- tion in some MDU applications too. Electrically it is identical to the outdoor ONT-E/G1321. It is powered by 12 Vdc, usually from a battery-backed power supply. If battery-backup is not needed, it may be powered from a wall-mount supply.

This product can be supplied with or without the RF overlay, and the version with overlay can be supplied with RF return support for cable TV set top boxes. It comes with one Gigabit Ethernet port, and with

three 10/100Base-T ports. It or its cousin, the outdoor model, is sometimes used in MDU applications with an external data switch (such as an ENT-1800i), and for broadcast an external RF amplifier may be used. Of course, when you use the 1321 for broadcast delivery to multiple housing units, you do not have individual control of service to each apartment through the EMS. Sometimes individual control is needed and sometimes it is not.

IN-BUILDING WIRING OPTIONS

This section covers briefly some of the issues and opportunities you may encounter in wiring MDUs or in taking over the existing wiring in an MDU. You should also consult the white paper entitled In-Home Wiring, #990-00003, available at www.enablence.com It contains additional information, primarily written around SFUs, though much of the material is applicable to MDUs as well. It shows structured wiring techniques, the preferred way to do low voltage wiring in new con- struction. Unfortunately, there is a lot of construction that doesn’t follow these guidelines.

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TWISTED PAIR Twisted pair, or telephone wiring, is ubiquitous almost everywhere in the world. The problem is that the quality and wiring method may not be known. Most modern wiring is done using the same category 5 (cat5) cable as is used for data. Older wiring used cat3 cable, four conductors in a less-controlled impedance environment.

While it is a violation of modern structured wiring rules, much telephone wiring is looped-through, or daisy-chained from one phone outlet to the next. While this works for voice, it is not feasible to use looped-through wiring for Ethernet data. If you must use existing looped-through phone wiring, you could consider either using a local DSL loop (see case study #5 be- low), or using the phone line version of HPNA. While DSL modems can be lower in cost than are HPNA devices, the cost of a local DSLAM for the DSL system may make it more expensive than HPNA, depending on the number of subscribers.

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COAXIAL CABLE We consider coaxial cable to be the most likely no-new-wires option at this time, due to near ubiquity of coax and the capac- ity of that coax. There are two standards that are being used today for Ethernet over coax (EoC). Both standards as a practi- cal matter can deliver over 100 Mb/s of throughput, though obviously limited to 100 Mb/s over any one Ethernet connection. Both have a roadmap for higher bandwidth in the future, and both can be used for in-home networking in addition to deliver- ing data from an ONT to the MDU. The In-Home Wiring paper referenced above contains a lot of information about these standards.

- MoCA stands for Multimedia over Coax Alliance. It uses frequencies 1 GHz and above on the coax.

- HPNA started as the Home Phone Networking Alliance, but has changed its name to HPNA, as much of the application is over coax now. Three frequency bands are used, all below 50 MHz. The most popular band at this time seems to be 12-28 MHz. HPNA applied to the coax network is sometimes called HCNA, presumably for Home Coax Network Alliance.

- Enablence also offers a very cost-effective passive EoC solution, described below. It has more limited performance, but also costs less, and is suitable for some applications.

Figure 10. Wiring using Ethernet-over-coax

Much of our discussion below of options for getting data into MDUs is based on using existing coax wiring. Figure 10 shows the basic idea. It is drawn more for a large single family unit rather than for an MDU, but it illustrates the principle. In some cases, the best solution will be to construct a network as shown for each dwelling in the MDU. The ONT originates both RF broadcast video (when used), voice, IPTV, and other data. An Ethernet-to-coax converter is mounted in the ONT. The coaxial cable shown transports both data and broadcast video. It goes to a normal coaxial splitter in the home, which is used to divide the RF signal to multiple locations. The splitter is a symmetrical device, operating in both directions. Signals at the four (illustrated) outputs are nominally isolated one from another, and signals flowing upstream (to the ONT) nomi- nally don’t go to other outputs of the splitter. However, some signal will leak from one output to another, and later we shall take advantage of that leakage. Here we show the signal going to four locations. At the top is a digital broadcast set top con- nected to a TV. The digital set top can also receive analog broadcast signals.

To the lower left we show an analog TV, receiving only analog broadcast signals over the coax. No data is consumed at this location. In the lower center we show a computer receiving data from the ONT over the Ethernet-to-coax converter. This

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emphasizes that the Ethernet-to-coax converter operates in both directions. Finally, the lower right portion illustrates an IPTV set top receiving IPTV delivered as Ethernet-over-coax.

The splitter divides the incoming signal power into four different outputs in this case. Since no power is added at the splitter, the law of conservation of energy dictates that the total output power at the four connections must equal the input power at the one input on the left. In practice, the power will be less than this by the loss of the splitter. Each time the power is split two ways, the power available at each output is one half the input to that splitting stage, which is a drop of 3 dB. When you add the loss of the splitter, the total loss is about 3.5 dB per two-way split. Since the four-way splitter shown consists of a cascade of two-way slitters, the total loss from the input to each port is about 7 dB. The splitter is a bi-directional device, so signals being combined in it (i.e., going right to left) are also attenuated by 7 dB for the four-way splitter.

The current practice is to use a type of coax known generically as RG-6. The RG might stand for Radio Grade, but no one knows for sure – the terminology dates back to World War 2, and the meaning seems to have been lost (though theories abound). The best coax has four layers of shielding, and is referred to as quad shield. Triple shielding is probably good enough in most cases, and dual shielding may be marginally OK if installed properly, and if there are no major sources of interference close by. Unfortunately there is some real junk out there, and since it is cheaper, some installers have used it. Knowing what you have is difficult without removing the outer jacket and inspecting the shielding.

Coax wiring installed before the early to mid 90s may be smaller diameter RG-59 coax. It has more loss than does RG-6, and so cannot be used for as long runs. All coaxial cable has loss that increases with frequency, so if your maximum frequency is lower, you can go further on the coax. On the other hand, you will have the capacity to offer fewer video channels.

At least as important as the shielding is the quality of the connectors, and the quality of the installation of those connectors. The industry has evolved a number of connectors over the years. Good connectors are out there, but so are bad ones, unfor- tunately. One fairly good, but not perfect, test for existing wiring is to screw the coax onto something you can pull against. If you can pull the coax out of the connector with your bare hands, the connection was not good to begin with.

Good coax can be turned into bad coax by bending it too tightly or by driving a fastener through it, or even by hammering a wiring staple down too tightly on the coax. Unfortunately it is not always possible to inspect all coax in a building to know if it has these problems. If in doubt, you may have to sweep the coax plant, measuring its attenuation at different frequencies, in order to really know the quality. And just because one cable run tests good does not mean another will. Sweeping coax requires specialized test equipment and skill. If you don’t have the skill set internally, you may be better off hiring a consult- ant who knows how to do the work, and who has the equipment. Normally, sweeping tends to be a trouble-shooting tool, invoked when you don’t deliver satisfactory service to a subscriber.

The type and quality of splitters used is important, too. Splitters have evolved over the years, with high frequency cut-off going from 300 MHz to above 1,000 MHz (1 GHz). The low frequency performance of the splitters can be of concern too, though this is less likely a problem than is high frequency performance. One caution is that you need to avoid splitters de- signed for satellite service. The satellite band is higher, and these splitters may not pass the frequencies you need.

WIFI After about 10 years of use, we understand that the term WiFi is being accepted into the Oxford English Dictionary, so it must be a legitimate word now. WiFi is the common terminology for the IEEE 802.11 series of wireless protocols. All the wireless hot spots use WiFi. 802.11b/g is most common today, running at wire speeds (really, air speeds) up to 54 Mb/s. The next generation, 802.11n, is in the final stages of approval as this is written, and pre-802.11n equipment has been on the market for some time. There are several improvements in –n, including higher speed and smart antenna technology that ef- fectively steers the antenna beam to put energy and pickup sensitivity where it is needed. (WiFi is not to be confused with WiMAX, a newer standard, IEEE 802.16, which is intended for wider-area wireless communications.)

There is no question that WiFi is a useful service and is here to stay. However, using it as a solution for not putting new wires in an apartment complex is highly questionable for several reasons. First, there are the perils of the radio path: while radiated signals work, sometimes they don’t go where you think they should go, and sometimes there are bad (or worse, changing) reflections that make reception problematic. And of course, interference is a way of life. Microwave ovens, among other things, use the frequency band adjacent to the most commonly used WiFi band, for example, and some cordless

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phones share the band with WiFi. So reliability is not 100%, and if you get a path working, there is no guarantee that it will still be working in a year. But when it works, which is often, it is convenient.

There is, of course, a real security problem with WiFi: put it in one subscriber’s apartment and what’s to keep him from shar- ing the connection with his neighbor? You can invoke the security built into the standard, but you either have to maintain security information on each of the subscriber’s computers as he changes machines (a service and record-keeping problem for you), or you have to tell him how to do it. In the latter case, he can simply tell his neighbor and you don’t sell data service to the neighbor. Of course, there is nothing you can do, nor do you want to do anything, to keep the subscriber from buying his own wireless access point and sharing with his neighbor. But you probably don’t want to be an accessory to reducing your own sales of data services.

Using WiFi for IPTV is a whole different and much more complex issue. We can state with certainty that 802.11b/g is not up to handling entertainment-grade IPTV. Of course it can handle over-the-top video from YouTube and the many other dis- tributors of such material. But the data rate required for entertainment-grade video, particularly in high definition, is much higher, and we are not aware of anyone claiming to operate a successful business transmitting entertainment-grade video over WiFi. It is claimed that 802.11n has the capability to do entertainment-grade video, and this may be true to a certain extent. However, we have yet to see proof that multiple HD channels can be transmitted over 801.11n without causing any problems. Given the well-known fact that actual throughput in a wireless environment is a small fraction of the claimed speed (which has all sorts of optimism and overhead built in), we are not sure you could safely run IPTV over 802.11n in an MDU applica- tion.

DATA OVER POWER LINE There are at least two bodies with standards for transporting data over power wiring. It clearly works for low-speed data, such as for device control. However, the likelihood of it being widely deployed for high speed data or IPTV is, we think, low. But there are those who will argue with us. MDUs are particularly problematic due to long power lines and different wiring techniques. If the data origination point and an apartment taking that data are wired from different transformers (likely in large installations), then the probability of successful service is extremely low.

MULTIMODE FIBER This is not a “no new wires” option, but we are seeing some attractive options for multimode fiber in residential settings now. You may already be familiar with the multimode technology, which is used for fiber audio interconnection in some consumer audio equipment, much sold for the home theater market. We are looking at some Ethernet to multimode fiber media con- verters that hold a lot of promise for low cost, high speed, and interference immunity, along with low installed cost. Typi- cally one fiber carries data in each direction. The wavelength used is about 700 nm, visible red light. The fiber is easy to install. Termination consists of cutting the fiber with diagonal cutters, pushing the ends into a receptacle and closing a lock – much easier than terminating a cat5 cable or a coax cable. The fiber used is also referred to as plastic optical fiber, POF.

BEND-INSENSITIVE SINGLE MODE FIBER This is not a “no new wires” option either, but is a very important technology when you need to bring fiber into an MDU. Traditional fiber cable has fairly severe restrictions on how tight a bend you can put in the fiber. Bending the fiber more than this can cause excessive signal loss, and can reduce the life of the fiber. In recent years, a new class of fiber optic cable has been defined, “bend-insensitive” fiber.2 3 It is not really completely insensitive to bend radius, but it will tolerate much tighter bends without increased signal loss or limiting the fiber life.

The International Telecommunications Union, the ITU, has standardized the performance of fiber optic cable. Their standard G.652 covers conventional single mode fiber (the type of fiber used in outside plant construction). It is specified to have a

2 See, for example, http://lw.pennnet.com/articles/article_display.cfm?ARTICLE_ID=339718&p=13&section=ARTCL&subsection=none&c=no ne&page=1 3 John George, Understanding and Optimizing MDU Optical Cabling Systems, Paper T-404G, presented at the 2008 FTTH Conference.

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maximum loss of 0.2 dB (at 1550 nm) loss for a single turn of fiber on a 15-30 mm radius, and 0.5 dB per turn at 1625 nm. Contrast this to the newer G.657 specification for bend-insensitive fiber. Two loss budgets have been defined to date, with more definitions on the way. G.657A specifies a loss per turn of 0.75 dB and 1.5 dB (respectively 1550 and 1625 nm) with a 10 mm radius, and G.657B specifies 0.75 and 1 dB per turn on a radius of 7.5 mm. The longest wavelength used in current PON standards is 1560 (stated as 1550) nm, though longer wavelengths are proposed for next-generation networks.

These new fibers make indoor wiring much easier and less failure-prone. You can make much sharper bends in the fiber without causing problems. This means that if you must run fiber in a public area, you can make it more nearly conform to corners than you could with traditional G.652 fiber. You have less to worry about if someone tries to turn the fiber too tightly around a stud or other attachment point, or is someone pulls a small cable too tightly.

MORE ON ETHERNET OVER COAX

Many of the examples we shall show later are built around these options for using existing coax wiring (Ethernet-over-coax, or EoC). While they work somewhat differently, HPNA and MoCA do pretty much the same thing, in that they are active devices that put data over the coax using complex RF modulation in order to achieve high data rates. Currently there is some variation in the feature set available from different manufacturers, and different products may be optimum for different appli- cations. Enablence Technologies FTTx Division is ready to help you choose the optimum solution for each requirement.

HPNA OR MOCA

Figure 11. HPNA or MoCA Ethernet-over-coax architecture

Figure 11 illustrates either an HPNA or a MoCA environment. The ONT has an RF output (when broadcast video is used), and a data output used with the EoC solution. The master unit is located at or close to the ONT, and receives data from it. As shown, the data on coax is combined externally with the RF, but this function may be performed in the EoC module. If the module does the combining internally it will have two F connectors, which are not interchangeable. (The master shown actually has the combining function built in, but we have shown it externally to emphasize what is happening to the RF inside the master. The combining may be done in a directional coupler as shown, or it could be a diplex filter.)

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The coax runs to a splitter, which has enough ports to serve all places that need signals from the coax. The splitter is a pas- sive device that works in both directions. A photo of a two-way splitter is shown in the lower part of Figure 11. The splitter may be a single device as implied in the figure, or it may be distributed at several places in the coax network. Care must be taken with splitting, as it is possible to loose too much signal level going to an endpoint. Every time you split the signal two ways, half the signal power goes one way and half the other. This means that the signal at each output is lower than the sig- nal at the input, by a theoretical 3 dB (half signal power). In practice, there is usually about an extra half decibel of signal loss for every two-way split. For analog video, too low a signal level will usually result in a snowy picture. For digital sig- nals, either the error rate will be high or, more likely, nothing will get through.

The top output of the splitter in Figure 11 is shown connected to a EoC client (or slave) device, which in turn is connected to both a computer and to an IPTV set top (the set top or the TV may also receive RF broadcast). The next splitter output is connected to a computer. Both computers may receive internet data from the ONT, and, if permitted, they may network with each other through the EoC devices. This networking takes advantage of the limited isolation between output ports on the splitter, so that some signal passes from one output port to another. When not enough signal passes, it is possible to place a reflective trap in the system to improve the amount of signal (that is, the isolation between ports, which ideally is infinite, is intentionally degraded over a certain frequency band in order to allow networking as shown). If this is necessary, consult Enablence Technologies for assistance in selecting the filter and placing it in the network properly.

We also show a set top box connected directly to the coax. This is appropriate for either a broadcast set top box or an IPTV box with the EoC client built in. Several manufacturers have incorporated EoC technology, either internal to the set top or as part of a docking station used with the set top. In addition, we show an older analog TV connected directly to the coax for reception of legacy analog services only. All services can be delivered on the same coax in the home or running to an apart- ment.

PASSIVE ETHERNET OVER COAX In addition to the active (HPNA and MoCA) options shown above, Enablence Technologies offers a passive EoC adaptor for situations in which the limitations of the device are acceptable. The advantage is that the cost is very low, and the EoC de- vice does not have to be powered. We do not recommend trying to use this for IPTV service, and data service will be limited to less than 10 Mb/s. It is only useful where you have an individual coax to each apartment.

Figure 12 illustrates use of this passive adapter. Two identical devices are used, one at the ONT and one at the apartment. An RF output of the ONT is connected to the cable TV port of one passive EoC de- vice, and an Ethernet cable is connected to the Ethernet port on the device. Coax from the common port goes to the apartment, terminating in the common port of a second EoC device. The cable TV port connects digital and analog broadcast to the TV, and the Ethernet port connects data to the com- puter.

The EoC device contains a balun (balanced Figure 12. Passive EoC solution to unbalanced transformer) to convert the

balanced Ethernet signals to unbalanced for transmission on the coax, and a low pass filter to prevent the data spectrum from spilling over into the broadcast spectrum, where it would create interference. The system is limited to half duplex operation at 10Base-T. It may be necessary to con- figure the computer to operate in this mode. Thus, the data rate is limited to well under 10 Mb/s and IPTV is not feasible, but the cost to get data to the apartment is very low. The spectrum used by the data overlaps that used by RF return from set top boxes, so this feature cannot be used with RF return.

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MDU CASE STUDIES

In this section we shall present a number of case studies we have delivered for customers installing FTTH in MDUs in a number of different countries. We shall draw on the components introduced above. While these are representative real- world examples, they are by no means exhaustive. Other configurations may be more appropriate for other applications. Feel free to discuss your needs with us. We can put together a lot different combinations of products to solve any problem.

CASE STUDY 1: SERVE UP TO 8 RESIDENCES WITH FULL SERVICE, FROM ONE ONT This first case study illustrates the basic concept of a triple play MDU service. Up to 8 subscribers can be served from one E/G888 ONT. This counts as only one endpoint on your PON, so if you have a PON serving all MDU subscribers in a 32- way split, you can serve 32 time 8, or 256 subscribers on one PON. Each subscriber in this scenario can be provided the same service levels as can a single family resident. In nearly a decade of providing FTTH systems, we have found that 8 data, voice, and video (optional) ports is the “sweet spot” in MDU service, allowing you to efficiently service the highest percentages of units with the minimum inventory. Along with the other products introduced in this paper, you will be able to service all sorts of MDU applications.

Figure 13. Cast Study 1: Basic triple play MDU service

Figure 13 illustrates this basic installation. An Enablence 888 MDU ONT (either GPON or EPON, your choice) can be mounted on an exterior wall in the available security box as shown, or it can be mounted in a secure closet without the secu- rity box, as shown in Figure 6. The 888 features eight individual RF outputs with enough level to drive a long coax into the apartment, without any need of amplification. The RF signal level is held constant regardless of the incoming optical level, the type of modulation on the RF carriers, and even the number of carriers. Each port, RF, data, and voice, may be shut off individually through the element management system (EMS). This means that if you’re in a high-churn area, with a lot of subscribers moving in and out, you do not need to roll a truck every time someone moves in or out. When you get a service disconnect, simply enter it in the computer. When a new subscriber moves in, tell him to connect his TV, enter the order in the computer, and you’re through.

A jumper between two additional RF connectors allows you to insert local video if desired. For example, the apartment com- plex may provide one or more security cameras on the entrance, the front door, and/or the pool. Video from these may be inserted here before the RF is split, minimizing the complexity of adding local video.

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As with all Enablence ONTs that carry video, digital RF return is available as an option. It supports all common return for- mats. Enablence’s patented RF return system is all-digital for higher accuracy and easier installation and maintenance. You can locate your set top control system wherever it is most convenient. And no need to worry about level control as you must do with analog returns – the level is set by design at the ONT and at the headend, and nothing in between will affect it.

The data ports in the 888 are all 10/100Base-T autosensing ports to make it easy to connect to either a single computer or a home network. Enablence provides a wide range of management tools to allow you to tailor the data service to each sub- scriber. Each subscriber is served on his own VLAN(s) as needed, with a rich set of quality of service (QoS) features con- trolled from a highly intuitive graphical user interface (GUI) on the EMS. The ports may be isolated from one another in order to protect one subscriber from seeing the network of another subscriber. Data is encrypted over the network to further ensure the privacy of each subscriber’s data. The Ethernet over coax(EoC) options shown elsewhere in this paper can be used to get data into each apartment without having to install data cable. Wireless or phone line data transmission is also possible, with appropriate caveats as shown elsewhere in this paper.

IPTV can be provided with no problems. You can create an IPTV VLAN to each port, along with a data VLAN and any other VLANs needed. The video VLAN is assigned adequate bandwidth to service all subscribers. The VLANs are nor- mally stripped off as the downstream data exits the ONT and added to upstream data. If a data switch is used inside the resi- dence, it will be accepting data from the ONT. This data has already been prioritized and rate-shaped to afford IPTV the quality of service (QoS) it needs, and this quality can be preserved in an in-home switch. However, if the user is networking data inside his apartment, the switch must have suitable QoS features so as to not delay IPTV data if the switch experiences congestion. Many consumer-grade switches do not have either the bandwidth or the QoS needed to perform properly with IPTV in the presence of other data transfers. We offer Enablence’s ENT-1800 switch, designed with this need in mind.

Enablence has many years of experience making POTS ports work with the wide range of telephones, answering machines, and other equipment in the hands of subscribers. We support all of the popular VoIP protocols, MGCP and its cousin NCS, and SIP. We have interoperated with most of the IPTV solutions on the market. QoS parameters ensure that voice signals always get through during periods of network congestion. Because voice takes such a miniscule fraction of the bandwidth of the PON, there is no need to compress it, and as a consequence of that and other design features, our mean opinion scores (MOS) consistently rank better than those of incumbent telephone companies who transport the voice signal a significant distance before digitizing it. Each voice port is terminated in a standard RJ-11 outlet in order to provide network demarca- tion, and standard connection blocks are provided to interface with normal telephone wiring practice.

CASE STUDY 2: BASIC TV AND DATA OVER COAX (LOWEST COST) This case involves a customer who needed to deliver basic analog video service, along with reasonable data service but no phone service, to a number of apartment buildings, each having a large number of apartments per floor. He had access to a riser, which afforded him access to a utility closet on each floor, but from the utility closet, only coax was available to each apartment. Advanced video services were not needed, and cost was a major constraint.

Figure 14 illustrates the solution for a building with up to 32 apartments, expandable to larger buildings. A single ONT, in this case a Model 1321i, serves the entire building. Only one of the 32 endpoints on the PON is taken by the entire building. The one RF output from the ONT is split four ways in a passive splitter, and one output from the splitter is taken to each floor. The 1321i ONT has four data ports: three 10/100Base-T (also called fast Ethernet, or FE) and one Gigabit Ethernet port. The Gigabit port is not needed in this application, but it may be used as a connection to the ENT-1800i. Alternatively, the Gigabit port can serve businesses on the base floor of the building, and the FE ports can serve residential floors. Each data port is taken to the utility closet on one floor. In the utility closet we located an ENT-1800i switch, using the Gigabit Ethernet connection to connect to the 1321i ONT data port, and the eight 10/100Base-T ports to connect to eight apartments, via the passive EoC solution of Figure 12. Of course, it is not necessary that the eight apartments be on one floor; buildings with four apartments per floor could be accommodated by grouping together the apartments on two floors. We do recom- mend that you respect the Ethernet limit of 100 meters in the length of the Ethernet runs when using the passive EoC adap- tors.

If voice service is offered, some voice ports are available on the ONT, depending on which ONT is chosen. Of course, you must provide voice wiring to the apartment using it. If more ports of voice service are needed, you can use an IAD (inte- grated access device) either at the ONT or in an individual apartment, to provide the voice lines.

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Figure 14. Case study 2: Basic video and data

The one RF output from the 1321i ONT is split four ways in an unamplified RF splitter, with one of the four outputs being taken to each floor on RG-6 coax (if the runs are longer, RG-11 coax can be used, or an amplified splitter could be used). The high RF level from the ONT minimizes the need for amplification. At the floor, we needed to use an amplified splitter, since the signal level was getting too low to serve the apartment. The eight outputs from the amplified splitter on the floor were supplied to the cable TV ports of each of eight passive EoC adaptors. The EoC adaptor common port was connected into the apartment using existing coax. Inside the apartment, another passive EoC adaptor was used to connect the TV and the computer.

This very low-cost solution worked in this case, because the data speeds offered (well under 10 Mb/s, limited by the passive EoC adaptors) was deemed adequate, and there were no upstream services associate with video (RF return) demanded. Fur- thermore, it was not considered important to disconnect service remotely. Had there been more than 32 apartments in the building, the job could have been handled by locating an ENT-1800i switch with the 1321i ONT, or by using an ONT with more outputs, such as an 888. Depending on the size of the building, different techniques might be needed in designing the RF section.

An alternative configuration, if broadcast video is not used, is to use a single E/G1800i ONT and ENT1800 switches to serve up to 72 apartments with data, from one ONT. Another alternative configuration is to use an E/G1800i ONT with each port connected to an E/G1320 ONT located in each apartment and used as an Ethernet device only. This will give you three 10/100 ports and two voice ports per apartment. (For this latter configuration, you would be limited if you try to use the pas- sive EoC devices for data transport into the apartment, but you could use all the features with either HPNA or MoCA to get data into the apartment.) This illustrates the wide variety of approaches that can be taken to wire apartments.

CASE STUDY 3: INDIVIDUAL VIDEO SERVICE, DATA OVER COAX Individual control of video to the apartment was needed, as was telephone service and Ethernet-over-coax, to avoid adding data wiring. An Enablence 888 ONT serves up to 8 apartments, and can provide up to 100 Mb/s per apartment (limited by the Ethernet connection), as well as voice and video, which can be disconnected individually. The video level is high enough

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that in most cases you will not need to amplify it. Support for RF return is available. This will let you use standard cable TV set tops, taking advantage of the economy of scale and the maturity of the technology, with all the features that have been developed.

Figure 15. Case 3: Individual video service, data on coax

Figure 15 illustrates an 888 ONT used with individual apartment EoC boxes (an HPNA box is illustrated). One of the RF outputs from the ONT is connected to the TV connector on the EoC adaptor. One of the Ethernet connectors on the 888 is connected to one of the Ethernet connectors on the EoC adaptor. The other Ethernet connector may be used for additional services if desired. A coaxial cable runs from the HCNA (same as HPNA) port on the EoC adaptor into the apartment. Once in the apartment, the cabling can follow the principles of Figure 11 above, where we showed the EoC connection serving a home or apartment with broadcast video, IPTV, and data, all over the coaxial cable.

Normally, an EoC master unit is put somewhere in the system, logically but not necessarily at the ONT. The master manages bandwidth for the EoC network, handling bandwidth requests from other EoC adaptors (slaves, or clients) and apportioning bandwidth to them. With some products the master is identified by a mechanical switch on the EoC devices, and with other products the EoC system itself will automatically appoint a master, a process that is invisible to the user. If there is a switch on the EoC adapters, then one of the adapters must be designated as the master. Failure to do so will result in very slow data transfer.

In this configuration, a data VLAN is usually established for the individual subscriber, and can run to the user’s port on the ONT. It is stripped off at that point. A management VLAN for all of the EoC devices is established to the EoC adaptor at the ONT. The EoC adaptor strips it off so that the user doesn’t see it. This VLAN may be used with the EoC’s management tools to manage it from the network operations center. Normally management of the EoC network is not necessary, but the facility is there if you need it. (Note that not all EoC adaptors have the same management capabilities. The description ap- plies to those HPNA EoC adaptors sold by Enablence. MoCA adaptors may not have the same capabilities as offered in HPNA adaptors. Since this field is very fluid, talk to us before making a decision – things may have changed.)

In this configuration, there is an HCNA device for each subscriber located at the ONT, with at least one complementary HCNA device in the apartment. The resident may also use the HCNA devices to establish a home network. Data will not cross to other apartments due to the use of individual VLANs that stop at the ONT. Certain HCNA devices may be config- ured with proper QoS parameters to ensure that any data being sent around the apartment will not delay VoIP or IPTV pack- ets, the delivery of which is time-critical.

Each broadcast video output from the 888 is at a very high RF level, so you can run a long distance to each apartment, the actual distance depending on how many times you must split the video signal in the apartment. Figure 5 gives you a rough idea of how far you can go, but several things affect this number, so be sure to talk to Enablence if your distances are “push-

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ing” these numbers. As with all Enablence RF ports, you can turn the RF port on and off independently of any other service. Turning off the RF port will not affect data flow through the EoC adaptor, so you can leave data on even while you turn video off. Of course, you can also turn off data and/or phone from your network operations center. You can also get inte- grated support for set top RF return in the 888, permitting you to use set top boxes designed for the cable TV industry, allow- ing you to take advantage of the maturity and features found in that market.

Note that you can use this same configuration without broadcast video if you wish, by substituting an 880 ONT, which is the same as an 888 without broadcast video. It is possible to provide IPTV in this configuration, and you will likely want to use the quality of service features of some HPNA EoC adaptors (such as those sold by Enablence). The need for QoS arises be- cause the customer can establish communications links in his apartment that are independent of IPTV and other data you are sending to him. Figure 11 illustrates such a client-to-client data flow simultaneously with delivering data from the PON. If the internal network gets congested, then you want to make sure that IPTV packets are delivered first, and any client-to-client packets are delayed. Otherwise, TV picture freezes or blocking will occur, resulting in a customer complaint even if the problem was caused by his internal network.

CASE STUDY 4: COMMON RF FEED WITH FASTER DATA Case 4 is similar to case 2 above, except that rather than use the passive EoC adaptor of Figure 14, an HPNA (HCNA) adap- tor is used. This give an advantage that you can connect directly to any computer’s Ethernet adaptor without the worry about configuring anything, and the data rate is better than that achievable in case 1. As in case 1, individual control of the on/off function in each apartment is not required. Cost is a factor, but a higher level of data performance is also required.

Figure 16. Case 4: Broadcast video, voice, and data over coax

Figure 16 shows an E/G1321, as used in Figure 14. Here the RF output is amplified as required – the amount of amplifica- tion and even the requirement for amplification will depend on the number of splits to come later. The output of the RF am- plifier is supplied to a new product we have not introduced before, an HPNA (HCNA) MDU Master unit (a somewhat unfor- tunate term, not to be confused with the master EoC device used with an EoC-based home network). The input connection used is the TV/Antenna input. Note that the RF connectors on the HPNA units are not interchangeable. This unit is intended to provide isolated service to each residence. A data connection between the ONT and the HPNA Master provides data ser- vice to each subscriber. The HCNA RF output of the MDU Master is split according to the number of units to be served by this MDU Master, and goes to the individual apartment. At the apartment, an HCNA EoC adapter identical to that which

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might be used in Figure 15, separates the data and the RF video. The RF video goes to the TV(s) and the data to a computer or a home network gateway.

Differing from Figure 15, the EoC adaptors in this case are prohibited from talking to each other, under control of the MDU Master. You would not want communications between the apartment-side EoC adaptors in this case, because allowing that would allow one resident to probe another resident’s computer if it was accidently enabled for sharing. Not allowing the HCNA units to talk to each other does preclude making this the basis for a home network, though. In order to build a home network, you will have to come out of the data port on the EoC adaptor and go into a residential gateway of some sort. More sophisticated subscribers will likely do this on their own anyway.

When using the HCNA MDU Master, you establish a VLAN for each subscriber, which terminates on the EoC adaptor in his apartment. For upstream data, the VLAN tag is added upon data ingress. The data VLAN exists from the EoC adaptor to the OLT. A second, common, VLAN is used for management. It terminates on the HCNA MDU Master, so the subscribers cannot see it. Through this VLAN, you can open a management channel to the MDU Master, which in turn can manage the individual EoC Adaptors.

As to the data rate you can achieve to each apartment, you are limited by the 10/100Base-T connector on the MDU Master, to 100 Mb/s shared across all users. The HPNA standard will allow up to 32 users on one Master, but if you put this many on, your average data rate per subscriber will be only about 3 Mb/s, though any one subscriber could peak to nearly 100 Mb/s. This is not as bad as you might imagine, since almost all residential data usage is occasional use, and statistically not all sub- scribers will be using the data at the same time. For example, suppose five people are surfing the web. Typically, each will pull in a web page then will spend some time adsorbing what is on that page. While he is adsorbing his page, other users can be pulling down their own web pages and no one will know the others are even present. The cable TV industry has found that it can offer around 5 Mb/s service to subscribers, on a network with an average speed of 10-30 kb/s per subscriber, and everyone will be happy. (The problem is that the cable TV industry keeps loading too many subscribers on one link, and when you go too far, bad things do happen. Also, as the service mix on the Internet changes, the old ratios may not work as well.) IPTV does require a different way of looking at data capacity, where you make assumptions regarding the number of people watching different channels and common channels simultaneously.

Most Internet video is delivered at a rate on the order of 1 Mb/s. This is for over-the-top, OTT, video, not for a true IPTV service. Examples include YouTube, Joost, Hulu, and all the many other purveyors of IP video today. The video looks good on a computer monitor, but if you put it on a big screen TV and compare it with entertainment video, you would not be happy. Even if some subscribers are downloading OTT video, all will be well. For entertainment-grade video, you will need 2-4 Mb/s for standard definition and 8-15 Mb/s for high definition, depending on a few things we can’t go into here. These tend to be continuous data rates, so you add the number of subscribers simultaneously watching TV to figure out what your IPTV bandwidth is. Of course, not all subscribers are watching TV all the time. At peak viewing hours, maybe 1/3 of all TVs will be on simultaneously.

The bottom line, and the reason for this digression, is to figure out how many subscribers you can put on one MDU Master. If you are not carrying IPTV, you can likely get away with putting a lot of subscribers on. Each one will be capable of burst- ing to tens of Mb/s if you so allow, and the average data rate will be much, much higher than what the cable TV industry pro- vides. You’ll still be more than competitive. On the other hand, if you are providing IPTV, you may need to be more modest in the number of subscribers you put on one MDU Master, because the ones watching TV will be pulling pretty constant bandwidth. Enablence Technologies will be happy to talk to you further about data capacity – it’s a complex and dynamic issue.

At this time, the features of the HCNA MDU Master are only available using HPNA technology. At some point they may appear in MoCA technology too. Again, talk to us as you are planning your in-home networking, and we can discuss what may have come on the market after this was written.

CASE STUDY 5: LARGE MDU, VOICE AND DATA OVER EXISTING PHONE LINE This is a large apartment complex where voice and data had to be delivered over existing phone lines. Broadcast video is not used, but could be added if desired by changing the ONT model. This configuration is also useful for serving one medium business or several small businesses, such as in a strip shopping mall.

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Figure 17. Voice and data to larger MDU

Figure 17 illustrates provision of voice and data service to either a larger MDU or a business (or businesses). An Enablence BAS 100 (voice only), 210 (DSL only) or 300 (voice and DSL) Broadband Access Switch (BAS) is teamed with, in this case, an Enablence ONT-E/G1800 ONT. The gigabit Ethernet port of the ONT connects to the BAS. The BAS 300 shown pro- vides either 24 or 48 ADSL2+ data and analog voice lines. Other models provide either DSL only or voice only interfaces. The analog voice circuits are internally interfaced to either MGCP or SIP VoIP circuits, though this is invisible to the sub- scriber. Within an apartment building the analog phone lines are going to be short, and in most cases the wiring should be of good quality, so the data rates achieved in the DSL circuits should approach and likely equal ADSL2+’s theoretical speed of 24 Mb/s downstream and 1.4 Mb/s upstream.

The 1800 ONT has an additional 8 10/100Base-T ports, which may be used for any application where such ports are needed. If broadcast video is needed, then the 1800 ONT could be replaced with the 1321i for one video port. This ONT will add two additional voice lines.

REDUNDANCY

When serving some MDUs, and certainly when serving commercial customers, you may have to provide for redundancy to protect against a cable break (“backhoe fade”) or other catastrophic event that would take down communications. This pro- tection usually extends to data and voice service, but usually not to video (except IPTV, which rides the data path). We shall show two redundancy solutions that you can implement with off-the-shelf Enablence PON equipment. The first protects one PON to the point of the splitter, and involves nothing more than a second port on the OLT. The second solution provides protection to a unique customer, but involves using two PONs and an extra ONT. Both solutions assume that you run fibers on redundant paths, so that a break in one cable will not destroy both paths; running both fibers along the same path defeats the purpose of redundancy, since any event that breaks one fiber is likely to break the other.

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REDUNDANCY TO THE SPLITTER

Figure 18. Redundancy to PON Splitter

Figure 18 illustrates providing redundancy to the PON splitter. This is a suitable redundancy solution when you want to pro- tect all subscribers connected to the PON and you have a significant distance between the OLT and the splitter. A second port on the OLT is required, as is of course the redundant fiber. Otherwise no additional facilities are required. The splitter used has two inputs, not the normal one. Such splitters are readily available. The redundant fiber, the backup path, is con- nected from a second port on the OLT to the second input on the splitter. This fiber must be routed along a different physical path from the primary path fiber if meaningful redundancy is to be provided. No protection is afforded beyond the splitter, but all users on the PON are protected.

If the primary path is interrupted, such as from a cable cut (a “backhoe fade”), the OLT detects the loss of upstream data and switches to the backup path. Switching is not instantaneous, but will automatically restore service while the fault is being repaired. During normal operation, the backup port on the OLT monitors upstream traffic in order to ensure integrity of the backup path.

Broadcast video may be provided on the primary path only. You cannot put broadcast video on the backup path because the difference in fiber lengths will create intolerable interference. Generally this is not a problem, though, since redundant video supply is usually not a requirement.

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REDUNDANCY TO ONE CUSTOMER

Figure 19. Redundancy to One Customer

You can provide redundancy all the way to a customer if you are able to route fibers from two different PONs to that cus- tomer location. Again, the fibers need to follow different physical routes all the way from the OLT to the ONT in order to provide meaningful redundancy.

Figure 19 illustrates the solution. Drops from two separate PONs connected to the same OLT are brought to the customer needing (and paying for) redundancy. Two ONTs, not necessarily the same model, are placed at the customer’s location. In Figure 19, PON 2 is the primary path, and is provisioned normally. PON 1 provides the backup path, and may serve other subscribers with or without redundancy. A reserved VLAN is established from one of the data ports on the primary ONT, to the backup ONT, and from there to the OLT.

Software in the primary ONT monitors for loss of downstream data, usually by monitoring for loss of optical signal. If the optical signal goes away, data is routed to the backup VLAN, and continues flowing between the primary ONT and the OLT through that backup path. Since the backup VLAN is already established, switchover is very fast, well within the magical 50 ms expectation. Both PONs may serve other customers, mixed between backed-up customers and non backed-up customers. In order to ensure the integrity of the backup path, the primary ONT periodically transmits a heartbeat signal over the reserve VLAN to the OLT. If the OLT doesn’t get this heartbeat, it generates an alarm to the EMS.

CONCLUSION

Each multidwelling unit is different. Enablence Technologies offers a wide range of products that make it easy to install FTTH to a multidwelling unit no matter what the challenges. We offer both inside and outside units, along with a managed switch designed for MDU applications, and an array of Ethernet over coax solutions to ease installation issues. We have shown the product suite, and by case study have shown some representative configurations. Many other configurations are possible. We will be glad to work with you on unique situations.

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APPENDIX: MORE ON RF DISTRIBUTION IN A BUILDING

RF amplification must be designed for the particular job at hand, and cannot really be relegated to just a table of splits vs. distance (as we did in Figure 5 above), though the table can give you a rough idea of what you can do without amplification. The signal level at a TV or set top must fall within a certain range: too high a level and the TV or set top will overload, ren- dering a degraded analog picture or no digital picture. Too low a level and the signal will be too close to the noise floor of the TV, resulting in a snowy analog picture and no digital picture.

The maximum level we can provide from the ONT is constrained by several factors: the amplifier used in the ONT has a maximum signal limit, over which it will distort the signal, similar to the way a TV can overload. This limit is determined by amplifier technology, and the power the amplifier consumes. If the level coming out of the ONT is too high, then if you go from the ONT into just one TV, that can overload the TV.

The RF level that the ONT supplies is affected by the modulation of the 1550 nm RF optical transmitter at the headend, though the variation due to modulation is rather small. Within reasonable limits, the output is not affected by the received optical level at the input to the ONT. Enablence uses an automatic gain control (AGC) technique in which the optical signal level is measured, and the RF output level is corrected based on this measurement. The alternative AGC method used by some vendors measures the output level of the RF and corrects the gain to hold that constant. While that is a common tech- nique in RF receivers and cable TV amplifiers, it falls short in this application by making the output level depend on whether the modulation is analog or digital, the number of RF signals being carried, and, when analog modulation is used, the picture content.

Given a fixed level out of the ONT, the level at the TV is affected by several things:

- The coax used to connect the ONT to the TV has a loss that depends on frequency, length of the coax, and the type of coax

- Each splitter has loss associated with it, both a laws-of-physics loss due to splitting the power, plus some additional loss due to use of real components.

- Any other devices the signal passes through, such as the EoC adaptors shown, will have some minimal loss associated with them.

Any amplifiers used must be suitable for the purpose. Any real amplifier has the potential to degrade the signal in any of several ways:

- If the input signal level to the amplifier is too low, the amplifier will add too much noise. The noise will show up as snow in analog channels, and possibly as failure to receive a digital channel reliably. Of course, if the signal is this low, it will not look good on any TV either – once you get too close to the noise level, there is nothing you can do to recover a good signal.

- If the input signal level to the amplifier is too high, the amplifier may add distortion to the signal, usually measured as composite second order distortion (CSO) and composite triple beat (CTB), and sometimes as cross modulation (XMOD).

Enablence Technologies has extensive experience working with these issues, and if needed, can assist in designing an RF distribution system that delivers good signals to all TVs. A number of consultants with experience in the RF distribution field can also assist. A spreadsheet is available to our customers to aid in designing the RF network. More information is contained in Enablence Technologies’ white paper entitled In-Home Wiring, #990-00003, available at www.enablence.com While you are there, be sure to grab copy of paper #990-00004, Introduction to Video. As for books on the subject of RF design, we can recommend Ciciora et. al., Modern Cable Television Technology: Video, Voice and Data Communications,

.

2nd ed., 2004. The transmission portion of this book has been updated and issued as Large et. al., Broadband Cable Access Networks, 2009. (For full disclosure, one of the authors of this white paper is also a co-author of both of these books.)

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For more information visit www.enablence.com ©2010 Enablence Technologies Inc. The information presented is subject to change without notice. Enablence Technologies Inc. assumes no responsibility for changes or inaccuracies contained herein. Copyright © 2010 Enablence Technologies Inc. All rights reserved.