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Engineering & Design – options abound

There are several distribution alternatives in the multiple dwelling unit (MDU) marketplace -- each with unique strengths and weaknesses.

July 1, 2001  

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From the moment that multichannel television programming became available from alternatives to the cable television operators (e.g. satellite, “wireless cable”), some multiple dwelling unit (MDU) tenants and building owners have thirsted for the opportunity to displace the cable service. The growth of interest in the Internet has added to the allure of regenerating the “smart building” concept in a more advanced, cyber-enhanced form.

It seems timely then to take a look at the current status of distribution alternatives in the MDU marketplace, uncover where the strengths and weaknesses lie and examine the likely importance of economics in the competitive scenario.


The Canadian Radio-television and Telecommunications Commission (CRTC) regulates all Broadcasting Distribution Undertakings (BDUs) in Canada — a category which includes cable television systems, Multipoint Distribution Systems (often called “wireless cable”), competitive multichannel television distribution systems in multiple dwelling units and even standalone Master Antenna Television (MATV) systems. The basic objectives of current CRTC regulation are to ensure that the appropriate local and regional signals are provided in multiple dwelling unit situations, approximating the offerings of any licensed cable television systems operating in the same city, and to foster competition between existing cable television operator service packages and any new multichannel television service offerings to apartment dwellers.

Since virtually all new apartment buildings (and many of the older ones) manifest existing coaxial cable distribution systems that were installed by the cable television operators, use of these wiring systems has become a major battleground between the established CATV operator and new service providers.

Current CRTC policy states that the inside wiring linking individual apartments with a central distribution point should be made available to other service providers, who would then lease use of that cabling from the CATV operator. The backbone, or riser, networks that deliver cable and high-speed data services to multi-tap distribution points clustered at various locations in the building, would continue to be owned by the cable television operators. New service providers would be required to install their own riser networks. At the distribution terminal locations, the inside wiring service drops running to individual apartments could be attached to either the cable television service or to that of the alternative service operator.

There are impediments to the implementation of competitive broadband service offerings in many apartment buildings, particularly those that feature older “loop-type” coaxial distribution systems. While loop systems can utilize addressable tap technology, pioneered in Canada by several firms during the 1970s, to control access within individual apartment units, loop distribution generally lends itself most affordably to bulk account service arrangements. In a bulk account arrangement, one operator serves all of the apartments within the building; this is usually done for a discounted rate that may be included in the apartment rental cost. In this type of situation, the only means of providing competitive access is to overwire the entire building with an alternative broadband distribution facility — either coaxial cable or unshielded twisted pair (UTP).

Old loop distribution systems or the more modern “home run” configurations, (which feature the dedicated distribution drop cable between each apartment and the central distribution point), can be classified as MATV systems and find exemption from CRTC’s BDU regulations. This can happen if they use wiring that is not connected to a BDU and the programming is consistent with that offered by cable television operators in the city of interest.

It is most likely that MATV opportunities will exist in situations where the building owner retains ownership of all of the distribution cabling, and where there are enough apartments to offset the costs of head end equipment required to receive off-air, satellite and perhaps locally originated signals for distribution to tenants.


1. Analogue MATV

Given that household televisions, FM receivers and VCRs utilize analogue input signals, the most cost-effective approach to delivering multichannel television and FM broadcast services is to employ analogue transmission on the distribution system. However, many of the desired programming services are now carried in digital video compressed (DVC) formats on DTH/DBS satellites — Bell ExpressVu and Star Choice / Cancom.

In an analogue MATV system, Integrated Receiver Decoders (IRDs) are required for each desired program service, whether analogue or DVC. The analogue IRD receives the downlinked signal from the satellite, decodes it (if is encrypted) and applies the baseband signals to an RF modulator for distribution on the wiring system. While analogue signals use frequency modulation (FM), with a single program occupying an entire satellite transponder, the DVC signal is modulated using Offset Quadrature Phase Shift Keying (O-QPSK), with an aggregate transponder bitstream being demodulated (which typically includes about six program sources). A digital IRD outputs a single program from the aggregate bitstream, removing any encryption and providing baseband audio and video for RF modulator addition to the wiring system.

Given the cost of individual channel IRDs, modulators, FM band strip amplifiers, combining networks and the high dynamic range broadband amplifiers required to drive the multichannel signal package through the apartment building distribution network, the number of channels that can be provided is generally limited by economics.

2. Digital MATV

Digital MATV offerings generally attempt to match those of the local cable television operator in both quality and quantity. With major market cable systems now offering at least 75 analogue channels, and digital packages that increase capacity to well over 100 program services, competition with cable must match these capacities, yet retain viable economics.

To obviate the requirement for multiple IRDs and RF modulators, direct distribution of DVC satellite signals using a transcoder approach can support substantial increases in the number of programming services at affordable costs. Transcoding preserves the “multi-program per transponder” satellite format throughout the MDU distribution into each apartment. A transcoder is capable of taking an entire satellite transponder, generally carrying from five to 10 channels of programming, converting it from O-QPSK modulation to 64 level Quadrature Amplitude Modulation (64 QAM) without the need for individual program channel demodulation, decoding and remodulation. Of prime importance is the compatibility of 64 QAM with existing cable television technology — it occupies a 6 MHz channel bandwidth, whereas the satellite bandwidth requirement in O-QPSK is nominally 27 to 30 MHz.

Several firms manufacture relatively low-cost multi-transponder transcoders geared to the MATV and MDU BDU marketplaces. A digital Set Top Box (STB) is required at each television receiver and VCR to recover the analogue format and remove encryption.

3. Digital MDS

Several regions of Canada have licensed BDUs providing what is generally called “wireless cable” service to both urban and rural areas. These systems utilize microwave transmission in the 2.5 GHz Multipoint Distribution System (MDS) band. LOOK Communications Inc. operates MDS systems in major populated portions of Quebec and southern Ontario, while similar digital MDS systems operate in southern Manitoba (SkyCable), Saskatchewan (Image Wireless) and have been licensed for regions in British Columbia.

Digital MDS systems typically provide at least sixty channels of programming, often more than 100, depending on the modulation scheme utilized. (While SkyCable is currently limited to about sixty channels through use of 16 QAM modulation, the newer systems using 64
QAM are capable of the higher channel capacities). Digital MDS operations deliver DVC programming in a 6 MHz channel format, fully compatible with existing MDU wiring systems.

A simple receiving antenna and downconverter on the roof of an apartment complex provides the entire MDS program package for distribution on an existing coaxial cable system, using just fifteen 6 MHz channels from 222 MHz to 318 MHz. The television bandwidth from 54 MHz to 222 MHz, and above 318 MHz, is then available for distribution of off-air or locally originated signals, such as door and garage cameras. This type of MDU service package can be more flexible than cable television for a property owner, but requires a digital STB to be used at each receiver/VCR.

The compatibility of digital MDS, in terms of frequency spectrum requirements, makes it an ideal competitive alternative to cable television in existing buildings wired for cable service.

4. Digital Satellite Distribution

Given that the satellite offerings from SRDU licencees, Bell ExpressVu and Star Choice, both provide over 100 channels of programming, they represent a competitive alternative to modern cable systems in terms of both quantity and signal quality. However, satellite carriage is not directly compatible with frequency spectrum and channel bandwidths utilized on existing MDU distribution cabling, and there is a varying degree of difficulty involved in implementing digital satellite service as a replacement for, or alternative to, cable television.

A DVC satellite typically utilizes 27 to 30 MHz transponder bandwidths, with two polarities of signal downlinked from the satellite. Each polarity carries half of the total satellite transponder complement in a “half-transponder frequency offset” arrangement. Early distribution systems utilized separate cables, one for each of the polarities, with the viewer switching between cables at each reception location. More recently, frequency stacking techniques are used at the receiving antenna to downconvert transponders from one polarity into the range of 950-1450 MHz, with the second polarity placed above 1450 MHz with an upper frequency limit of about 2050 MHz.

Frequencies of 950 MHz and higher involve substantial signal attenuation on the types of coaxial cable used in apartment block distribution systems. Cable services are generally restricted to carriage below where the cable attenuations are workable with state-of-the-art linear technology. The direct distribution of satellite signals at frequencies above 950 MHz requires substantially more system gain and elevated signal output levels, which would destroy standard 6 MHz analogue television quality due to intermodulation. However, given that the DVC signals utilize constant envelope O-QPSK modulation, they can be driven through amplifiers at levels that are close to saturation, while supporting acceptable reception.

A satellite receiver is required at each TV/VCR location with this signal delivery alternative. The dual riser/transferable subscriber drop distribution concept is applicable, supporting competition between the digital satellite and existing cable television services.

MDU Corporation, of Richmond, BC has been offering the digital satellite signal delivery alternative to major cities across Canada for several years.

5. “The Second Cable Operator”

In Montreal, VDN Inc. is providing significant competition for incumbent cable television operator, Videotron, using essentially the same technology and architectural infrastructure — supporting a cable equivalent package of services at monthly rates that are significantly lower than those of Videotron. VDN, which has now attained over 8,000 subscribers in apartment buildings, has its own centralized head end. It employs satellite TVRO, off-air antennas and local origination to compose a programming package which is rapidly approaching 100 channels of analogue services.

VDN, which holds a Class 1 BDU licence from the CRTC, utilizes Hybrid Fiber Coax (HFC) architecture to deliver its analogue signals via fiber optic trunk cables from its master head end to distribution nodes located at each apartment building. At the nodes, the AM optical signals are converted to standard cable television frequencies in a 6 MHz analogue NTSC format. An 870 MHz bi-directional distribution system, utilizing a scrambling technique called interdiction, is employed by VDN at each apartment building.

The interdiction technology uses jamming carriers, addressably-controlled from VDN’s head end, to deny reception of unauthorized video signals to apartments that have not purchased these services. Conversely, each apartment receives all of its authorized signals at every television receiver outlet without the requirement for an STB. The interdiction technique therefore supports maximum flexibility in the use of multiple receivers, VCRs and simultaneous recording/viewing.

6. Ethernet IP Distribution

Boardwalk Equities of Calgary, an MDU property owner in a number of cities, has implemented the latest broadband LAN architecture to suites in two of its Calgary properties and a condominium to afford both multichannel television and high-speed Internet services on a competitive basis to Shaw’s cable offerings. Boardwalk holds a Class 1 BDU licence from CRTC and links a state-of-the-art head end to MDUs using Gigabit Ethernet trunking for provision of television, data and voice (coming this fall) services on a fully integrated basis. Off-air and selected analogue and digital satellite programming is digitally encoded at a

4-Mb/s rate, using the MPEG-2 standard. Streaming technology is then employed for IP encapsulation and delivery at 1,000 Mb/s, along with Internet and future voice services, to Ethernet switches located at each apartment complex. A fully cable-competitive “100 plus” video program package sits at each Ethernet switch.

Within the apartment buildings, which are already wired for cable television service, twin UTP cables (CAT-5) have been installed to each apartment, providing a total per-suite capacity of 200 Mb/s. The in-place telephone pairs will be used this September for the implementation of competitive telephony service, with the analogue voice signals converted to TDMA at the Ethernet switch location, and IP transmission used, with appropriate Quality of Service (QoS), to Boardwalk’s Calgary DMS 500 switch. Conversion from IP back to TDMA will take place at the switch. Apartments can elect to retain existing telephone service or go with Boardwalk’s alternative offering. A significant “back office” equipment complement (e.g. proxy server) is required at each switch.

In each apartment, small hubs are used to develop outlets for computers, VCRs and television receivers. Each video device requires the use of a 10 Mb/s Ethernet STB to extract and reconstitute analogue video for display on standard television receivers. Only those video signals required in each apartment are extracted from the switch in the basement, with 200 Mb/s capacity affording simultaneous access to a number of video channels, as well as fast Ethernet.

7. DSL IP Service Provision

Elysium Broadband Inc., of Richmond Hill, has been working since 1996 on the development of a proprietary digital multichannel video, data and voice solution which utilizes telephone pairs for transmission to MDU suites. Simultaneous access to as many as five television channels in each apartment is afforded through the use of a Broadband Service Unit, located at a wall-plate under the control of a Master Control Unit (a server/processor centrally located in the building).

While Elysium’s system is proprietary, it appears to use a variant of Very High Data Rate Digital Subscriber Line (VDSL) technology, for its transport over paired wire.

It is interesting to compare Elysium’s technology with that of Boardwalk. Elysium’s VDSL is likely a derivative of paired-wire technology used by the telephone industry — ADSL for fast Internet access, SDSL for business high speed data/video and VDSL itself for higher bandwidth broadband. Boardwalk’s technology is drawn from the busin
ess LAN environment and the growth of Ethernet technology into a broader telecommunications perspective. While VDSL is currently viewed as a relatively niche market telecommunications technology that is almost prohibitively expensive, the Gigabit and Fast Ethernet explosion is largely fuelled by the cost economies associated with the widespread use of Ethernet throughout the information technology universe.


Given the cable operator’s ability to provide fast Internet access using its existing infrastructure and consumer-priced cable modems, a successful competitive thrust must provide relatively high bit rate data connectivity with each MDU entity, particularly those supporting SOHO enterprises.

Standalone interactive data systems in MATV configurations are likely not affordable, given the requirement for either separate UTP wiring or the use of cable modems with a Cable Modem Termination System (CMTS) or Ethernet switch and high speed trunking to an ISP.

The digital MDS service, while offering the potential for two-way wireless service to the building via MCS microwave frequencies (LOOK and SkyCable have MCS band licences), has no easy solution for multi-tenant Media Access Control (MAC) and presents the same economic challenges as the MATV model.

VDN can implement cable modem services using a shared, centralized CMTS approach and the placement of nodes in apartment buildings to support Internet traffic requirements. Frequency stacking is another technique that cable operators and Montreal’s VDN may utilize to handle growth of data traffic on a cost-effective basis.

MDU Corporation utilizes 3Com’s VCN technology to provide data and voice services. VCN uses VDSL technology on the existing telephone wiring, with a VCN Access Terminal required in connected suits and a concentrator located in proximity to the central telephone punch-down blocks. The concentrator separates telephony from Internet access, providing connectivity with an ISP via an Ethernet switch.

The Gigabit-Ethernet architecture employed by Boardwalk utilizes the Ethernet switch and servers in each MDU edifice to integrate data with video in the Gig-E trunks for transport back to the head end.

Some may look to wireless solutions within the MDU structures for high-speed data service. Using distributed antenna/transceiver systems meeting the IEEE 802.1(b) standard (11 Mb/s) and/or the emerging 802.11(a) standard (55 Mb/s) may afford some advantages in certain situations; however, that is an area to carefully consider.


While this specialized competitive marketplace now demonstrates all of the latest telecommunications technology — VDSL and 10/100/1000 Mb/s Ethernet with appropriate switches, routers and servers — the in-place coaxial cable plant of the incumbent cable television operator remains a valuable asset.

Technology aside, competing with an incumbent offering approximately six dozen quality television services, FM broadcast to all VCRs and TV receivers without need for an STB, dozens more digital video services by adding an STB, and fast Internet access via consumer-priced cable modems — all supported by an experienced 7/24 service infrastructure — is a tough challenge. Time will quickly tell if the new technology will deliver performance and, more importantly, economic viability to the new MDU service providers.CS

William E. (Bill) Evans, P.Eng., has spent close to 35 years in technical and senior management roles in private and telephone industry cable television, broadcast engineering, business telecom and microcomputer networking. He formed E B Systems Ltd. in 1989, a Winnipeg, Manitoba-based company that provides engineering consulting, system design, project management and implementation of broadband projects worldwide. Mr. Evans is a member of the IEEE, SMPTE, SCTE, SCTE (UK), CABC and the Cable Television Pioneers Club of Canada.

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