Telecommunications carriers and service providers are currently planning and deploying access network upgrades to enable delivery of IPTV and other advanced services. In choosing which technologies to use, carriers must consider the growing trend toward user-created content. As consumer-level digital media technology evolves, a new generation of "producer-consumers" has been created, and these users increasingly wish to share their photos and video programs via web sites such as Shutterfly, Yahoo!, ClipShack, Vimeo, YouTube, Snapfish and Blip.tv.
While the most visionary and forward-looking service providers have understood the importance of providing high upstream bandwidth, others
have focused primarily on upgrading the downstream bandwidth of their networks, mainly to enable video delivery. However, these carriers should also consider how to increase upstream bandwidth to serve their producer-consumer customers. In this article, we will examine the emerging producer-consumer trend and the challenges it creates for access networks, compare ADSL2+ and VDSL2 technologies as approaches to upgrading networks, and look at how these technologies impact carrier service offerings.
Carrier Upgrade
Plans
Virtually every telecommunications carrier worldwide is beginning or planning to upgrade its access network bandwidth to deliver IPTV and offer increased upstream speed. Carriers are rushing to offer video services to stave off competition from cable operators (who are luring customers with bundled video, voice, and data services) and wireless operators (who are stealing away wireline voice customers).
Carriers are pursuing several different upgrade strategies, including Verizon's fiber to the premises (FTTP) initiative, BellSouth's fiber to the curb (FTTC) initiative, and SBC/AT&T's Project Lightspeed initiative of deploying fiber-fed nodes (FTTN). Among these approaches, FTTN and FTTC offer distinct advantages in terms of cost and time--to-market because they require no major network upgrades or deployment of fiber optic cables to individual homes. In many cases, the upgrade consists of installing new line cards in existing nodes or remote terminals to support VDSL2.
Carriers who choose an FTTN model are typically upgrading their networks to support roughly 25 Mbps of downstream bandwidth to customers located within a mile of the remote terminal or central office (approximately 85 percent of subscribers). This level of bandwidth will be sufficient to support two HDTV and one or two SDTV video streams (using MPEG-4/AVC encoding) plus high-speed network access and IP voice traffic (see Figure 1).
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Service
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Downstream (Mbps)
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HDTV
(2 per household)
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7-9
(per TV channel)
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SDTV
(1 or 2 per household)
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2
(per TV channel)
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High
speed Internet
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5-10
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IP
Voice
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.25
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Figure 1. Downstream bandwidth budget for triple play
services
The Rise of the
Consumer-Producer
While carrier network upgrade cycles can take five to ten years, consumer technology and service demands evolve more rapidly. Who could have predicted the success of the iPod just five years ago? As carriers have been planning to upgrade downstream bandwidth to the consumer, consumers have been increasing their needs for upstream bandwidth.
This trend accelerated five years ago with the emergence of file-sharing services like Napster and Kazaa. Suddenly, a significant number of home computers became music file servers as well. Given that one song file can easily be 5-10MB or larger (depending on the encoding quality), file sharing caused significant performance headaches when users attempted to get songs from a home computer/server linked to the Internet by a "standard" 256Kbps or 384Kbps upstream ADSL connection. At this level of connectivity, it would take 30-60 minutes to upload just ten songs.
While most file-sharing services have stopped operation due to legal issues, there is still growing demand for consumers to share self-created music, photos, and video files. Since the early part of this decade, an explosion in the availability of low-cost digital media technologies has accelerated the producer-consumer trend. A $200 digital camera can produce individual photos that are 1-2 megabytes in size. Consumers wish to upload dozens or even hundreds of such photos to public sites like Yahoo! Photos, Shutterfly, or Snapfish so their friends can view them.
More recently, video-sharing sites like YouTube and ClipShack allow consumers to share their home video files.
According to a recent article in the San Jose Mercury News, "YouTube, a leading site, had more than 3 million visitors in December, nearly tripling its visitation in November, according to Nielsen/NetRatings. YouTube says its users have been sharing 20,000 new videos a day and watching some 10 million daily."
A 30-second video file,
however, can easily run well over 10MB in size. Using a digital camcorder in DV format, a 30 second video file (at 720x480 pixel resolution) can be in the 100MB range. Converting the same file to DVD quality MPEG2 format will still take up 18-35MB of storage. Although advances in video compression technology will reduce file sizes for a given resolution and quality, the emergence of higher quality High Definition camcorders may further increase video file sizes. Uploading such files over standard ADSL connections can be quite a painful process: even at 10MB file size, it could take over 5 minutes to upload a 30 second video file.
As generating high quality digital content has become easier, cheaper, and more prevalent, the limited upstream bandwidth of traditional ADSL connections for sharing such content has not kept pace with the ability of "home producers" to create it. While carriers are now offering as much as 5 Mbps of downstream bandwidth with "premium" ADSL services, they have not done much to upgrade bandwidth in the upstream direction. At most, premium ADSL consumers are offered 1 Mbps upstream, and many get 512 Kbps or less.
ADSL2+ versus VDSL2 for Upstream Bandwidth Upgrades
Carriers pursuing the FTTN approach are upgrading existing ADSL access services to support a minimum of 25 Mbps of downstream bandwidth. As carriers weigh ADSL2+ and VDSL2 for their FTTN and FTTC network upgrades, they must also consider the growing demand for upstream bandwidth.
At a recent IP Trends Summit held in San Francisco (December 2005), a presentation by one of the world's largest DSL equipment manufacturers pointed out that the reach of 22-25Mbps ADSL2+ over a single pair of copper wire is very limited and, therefore, HDTV and IPTV cannot be effectively offered using ADSL2+. The same presentation pointed out that VDSL2, on the other hand, enables complete triple play over a single pair of copper wire.
When we compare upstream bandwidths, we also find that VDSL2 is superior to ADSL2+. ADSL2+ bandwidth in the upstream direction is limited to a maximum of 1.1Mbps (and is nominally around 512kbps), even on very short loops using the most commonly-accepted ADSL2+ Annex A standard. VDSL2, on the other hand, can deliver up to 5 Mbps of upstream bandwidth to consumers at distances of 5,000 feet from the remote terminal or central office. When upstream consumer needs are considered, VDSL2's nominal 3Mbps is clearly a better solution. Figure 2 compares nominal upload speeds of ADSL2+ and VDSL2 for popular consumer services.
|
Upstream Bandwidth
|
Time
to Upload 20 digital photos
(1-2 MB each)
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Time to upload 30 digital songs
(5-10 MB each)
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Time to upload 1-minute
video clip (20 MB)
|
|
ADSL2+
at 512Kbps
|
10
minutes
|
75
minutes
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6.5
minutes
|
|
VDSL2
at 3Mbps
|
1.5
minutes
|
12.5
minutes
|
1
minutes
|
Figure 2. Upload speeds for
ADSL2+- and VDSL2- based services
In short loop deployment models, VDSL2 offers significantly more bandwidth and flexibility for tiered services than ADSL2+. In distances of up to 1000 feet, for example, VDSL2 can deliver 50 to 100 Mbps of symmetrical bandwidth, allowing service providers to offer higher-level services to some customers. For FTTC applications where the loops are shorter than 500 feet and are connected directly to the remote terminal, VDSL2 can offer a staggering 100Mbps symmetric bandwidth. This bandwidth provides an enormous amount of flexibility and opportunity for service providers to offer value-added, multi-tiered, revenue-generating services to their customers.
Carriers vs. the Internet
As carriers contemplate significant expenditures on network upgrades to enable IPTV delivery, they likely wonder whether their investments will pay off, particularly given the emergence of Internet-based video offerings from major TV networks including downloadable videos from Apple, Google, and TiVO, and plans by major studios to offer downloadable movies. Some carriers are concerned that their networks will be used to access content that competes with their own IPTV offerings.
Rather than seeing this as a threat, carriers should use network bandwidth to their advantage and deliver new, communications-oriented services that are compelling to their customers. At the IP Trends Summit, several speakers (carrier representatives, analysts, and network equipment vendors) pointed out that competitive IPTV services must go well beyond simple video distribution. Rather than mirroring broadcast TV's one-to-many video distribution model, IPTV must enable a many-to-many communications model. Paraphrasing many of the speakers, "IPTV is really about service convergence. The definition of IPTV is your TV being integrated into your broadband networked home, and video will be just one of many applications in the home."
In addition to a rapid and cost-effective upgrade for video services, VDSL2's high, bi-directional bandwidth enables other revenue-generating services that carriers are uniquely positioned to offer. For example, real-time home videoconferencing could yield additional per-call revenues. Ongoing video surveillance or environmental (fire, flood) monitoring by security firms, interactive gaming, and premium upload speeds to photo, video, and music sites are all examples of additional revenue-generating services
It is not clear what new applications will arise in the next few years. Ten years ago, no one could have predicted that SMS (Short Message Service), MMS (Multimedia Message Service), downloadable ring tones, wallpapers, and other content would provide significant revenue-generating opportunities for cellular phone service providers. Rather than creating a barrier, today's technology choices must enable future service delivery opportunities.
We know that carriers need significant access network upgrades to deliver advanced services to effectively differentiate from cable or satellite competition. We also know that the downstream and upstream bandwidth provided by ADSL2+ will be far from adequate. Upgrading bandwidth in both upstream and downstream directions can enable a platform with which carriers can out-maneuver their competitors.
IP service creation will continue unabated. By making the right technology choices, carriers can maximize growth of service revenues and ensure customer satisfaction and retention. By leveraging the combination of optical fiber and VDSL2 over existing copper infrastructure, carriers can deliver high upstream and downstream bandwidth and attain the flexibility to support compelling revenue-generating services.
About
the Author
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Alex Aali is Senior
Marketing Manager at Ikanos Communications
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About Ikanos
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Ikanos
Communications develops silicon solutions that are focused on delivering
fiber-fast broadband access over existing copper lines. Ikanos has
created highly integrated silicon solutions that are programmable in the
field, compliant with international standards, and support both ATM and
Ethernet network connectivity. In addition, the Ikanos solutions offer
best in class performance, with the most granular bandwidth scalability
and industry leading aggregate throughput of up to 150 Mbps over a
single copper line.
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