High definition television (HDTV), real-time online gaming and videoblogging are just a handful of the new applications that are testingthe limits of service providers' network infrastructure. Consumers havean ever-expanding need for greater bandwidth ” both upstream anddownstream. And this demand is causing service providers to reassesstheir technology choices for last mile access.
Service providers can choose from a variety of alternative accessnetwork technologies to deliver the broadband applications thatconsumers desire today, and support development of newbandwidth-intensive services into the future. These technologies rangefrom copper-based solutions (VDSL2 and ADSL2+ )and fiber to cable and fixed wireless (WiMax).
Consumers are becoming more reliant on broadband access forentertainment, education and work at home. But, as these newapplications entrench themselves in everyday life, the need for largeamounts of bandwidth to the digital home grows exponentially.
Table 1 below shows thebandwidth required to deliver some of today's most popularapplications. HDTV and high speed Internet require large amounts ofreliable, always on downstream bandwidth to ensure customersatisfaction. On the other hand, high speed Internet requires thelargest amount of upstream bandwidth as consumers are increasinglyuploading terabytes of data ” from photos destined for grandparents tovideos for YouTube.
|Table1 ” Bandwidth Requirements for Digital Home Applications|
Delivering the Goods
The means by which service providers choose to deliver broadbandservices to their customers is determined by a number of factors,including:
* time to market;
* cost to deploy;
* performance; and
* geographic location of customers.
Fiber, for instance, is capable of delivering extremely highbandwidth and offers more flexibility and scalability for futureapplications. However, fiber builds are costly and time consuming.Service providers need to bury fiber and deploy completely newinfrastructure to every household.
Because it is the most advanced infrastructure available today,fiber is capable of delivering extremely high bandwidth. R&Defforts underway now are likely to result in new ways to utilize theoptical signals even more effectively, enabling greater bandwidth withlittle additional investment.
Service providers that are deploying fiber are taking a long-termview of their infrastructure upgrades. Verizon in the United States andNTT in Japan are just two examples of service providers that areupgrading most of their infrastructure to fiber.
They are pushing fiber as close to their customers as possible inorder to future-proof their network and guarantee its ability togenerate meaningful revenue long into the future. In neighborhoods,Verizon and NTT are deploying fiber directly to single family homes.
However, the initiative is expensive. Verizon reported in anewsletter detailing third quarter 2006 financial results that its fiber to the home (FTTH) build out costs $1,745 per home ” $845 to pass a premise with fiber andanother $900 to connect fiber to the home.
NTT's costs are slightly lower in Japan, where incremental FTTHinvestment per user was approximately 130,000 yen, or about US$1,070,the company said in its fiscal year 2006 report. The high price tag offiber deployment requires patience on the part of service providersseeking a return on their investment.
Most of the world's service providers, however, have opted for usingexisting copper in their networks. By using VDSL2 or ADSL2+, serviceproviders can maximize their existing assets by increasing broadbandcapabilities of their copper network infrastructure to deliver voice,data and video services.
Because they are not undertaking a complete overhaul of their accessnetwork, these service providers can quickly and cost-effectively beginoffering revenue-enhancing triple play and video services.
VDSL2 is the preferred choice for many telcos because it can offer ahigher symmetrical data rates than the various flavors of ADSL atshorter distances and the same performance as ADSLx at longerdistances.
For instance, VDSL2 can deliver up to 100 Mbps in the downstream andupstream directions, while ADSL2+ maxes out at 25 Mbps downstream and2-3 Mbps upstream.. However, VDSL2 and ADSLx are both similar in thatthe performance of each is dependent on the distance between the fibertermination point and the customer, as well as the electrical crosstalkthat is present between lines.
AT&T Inc. is one of many service providers that are making themost of their existing copper infrastructure. For its U-Versedeployment, AT&T is building out fiber to the node (FTTN) and using VDSL2 to increase bandwidth capabilities of copper loopsentering homes. AT&T estimates that by taking the FTTN approach,they are spending only about $360 per user to deploy advanced services” a cost that is significantly less than an all-fiber buildout.
NTT, KT and many other service providers in Europe, North America,and Asia, are using VDSL2 in a hybrid approach to deliver broadbandservices to multiple dwelling units (MDUs), such as apartment complexesor condominiums. In these types of buildings, riser space is limited,not leaving enough room to deploy new fiber.
Additionally, making fiber available to consumers on each floor ofthe building will complicate the installation process. With VDSL2,service providers can capitalize on the existing copper infrastructurein the buildings and offer the same types of services they aredelivering via fiber to the home.
Cable companies use a hybrid fiber coax (HFC)architecture to deliver advanced broadband and triple play services totheir customers. Much like the FTTN scenario with DSL, the typical HFCnetwork utilizes fiber from the cable head end to the serving nodelocated in the neighborhood, then coaxial cable is run from the node toindividual homes.
Most cable companies have had established HFC networks for more thana decade for their television offerings, making it easy to upgrade thearchitecture to support new broadband applications such as voicetelephony, high speed Internet access and video on demand. In theUnited States, cable companies are able to offer broadband access of 5Mbps or greater to more than 90 percent of all households, according tothe National Cable & Television Association.
WiMax ” short for Worldwide Interoperability for Microwave Access “has suffered from slow adoption because, while initially lacking astandard for interoperability, its equipment is more costly than massmarket technologies, such as DSL and cable. However, WiMax has smalldeployments in proprietary networks in more than 125 countriesworldwide, including many that didn't have existing wiredcommunications infrastructure.
With WiMax standards in place, it is expected that WiMax equipmentand access prices will, sometime in the future, offer consumers acomparable price point and broadband connectivity to DSL, cable andfiber Internet services.
WiMax can be quickly deployed to provide broadband services toconsumers in rural locations or other areas where it may be difficultto deploy a landline offering, which is a significant differentiator toany of the wired technologies.
However, distributing high-quality triple play video over a wirelesswide-area or local-area network has yet to be proven in high volumes,and pre-cursors to WiMax (MMDS, LMDS) have had significantline-of-sight issues. Thus, WiMax, while certainly a promisingtechnology today, will need to overcome the perceived shortcomings ofdistributing video over wireless and develop significant deploymentmomentum, to be considered a success in the future.
Table 2 below shows thebenefits of each broadband access method, with regard to price,performance, reach and time to market.
|Table2 ” Benefits of Access Methods|
A Worldview of Broadband Delivery
Around the world, service providers are undertaking a variety ofbroadband access strategies. These strategies take into account theirexisting network infrastructure, the geographic diversity of theirservice area and the regulatory environment.
DSL remains the most popular access technology, according toresearch done by Point Topic for the DSL Forum. More than 200 million “or about 66 percent – of the world's total 313 million broadbandsubscribers use DSL. Cable ranked second, with about 22 percent of allbroadband subscribers, while fiber accounted for almost 11 percent.
According to the DSL Forum's report, the United States boasts thelargest total of broadband subscribers (seeTable 3, below ), with more than 63.4 million. In the UnitedStates, cable subscribers exceed DSL by a slight margin (32.9 millionvs. 27.6 million).
Fiber-based broadband is growing as Verizon makes progress on itsFiOS network. The company recently announced that it has already signedup 500,000 customers and as of the second quarter, was addingapproximately 2,600 new customers per business day.
|Table3 ” A Breakdown of Broadband Access Technologies in the Top 10Countries by Number of Broadband Subscribers as of 30 June 2007|
In Asia, China, Japan and South Korea are among the top 10 countriesbased on broadband subscribers. China has more than 59 millionsubscribers, with the majority receiving broadband services over DSLnetworks. The majority of broadband subscribers in Japan and SouthKorea also use DSL.
In fact, many of the carriers there are adopting VDSL2 as a means todeliver greater bandwidth ” up to 100 Mbps symmetrical ” to support newservices, such as Internet protocol televisions (IPTV).
Germany, the United Kingdom and France are among the leadingEuropean countries with regard to broadband deployment. In thosecountries ” as well as Italy and Belgium ” DSL is the prominentbroadband access technology.
Judging from service providers' deployment plans, demand for consumerbroadband services is experiencing enormous growth. To capitalize onthis demand, service providers need to consider the types of servicesthey want to deliver now and well into the future, and how the varioustechnology options available to them best fit their needs.
While fiber clearly offers the best long-term strategy, copper-basedsolutions such as VDSL2 give service providers the bandwidth they needto quickly deliver services consumers desire today as well as amigration path for future network development.
Piyush Sevalia is the vice president of marketing for the AccessProducts Group at Ikanos Communications.Sevalia earned a B.E. in electrical engineering from the University ofBombay in India, an M.S. in electrical engineering from the Universityof Michigan, Ann Arbor, and an MBA from the University of California,Berkeley. He holds four patents, has authored several technology andbusiness articles, and frequently speaks at industry conferences.