In the great broadband wars of '05, as cable companies and telephone companies battled to win the hearts of Internet surfers, casual and serious, many facts and figures were bandied about, notably price and bandwidth. Often missing in those discussions, however, was any mention of one element of both DSL and cable modem service that often gets overlooked: the upstream channel. Although both cable and telco Internet offerings are inherently asymmetric — delivering far more bandwidth per second downstream than upstream — the growing consumer interest in digital content such as photos and pictures, the boom in telecommuting of all types, the popularity of online games and even the advent of IPTV and other forms of video entertainment are generating interest in what goes upstream and how fast it travels.

“A lot of carriers and a lot of manufacturers recognize the need for upstream bandwidth already, with a lot of peer-to-peer networking,” said Michael Howard, principal analyst and co-founder of Infonetics Research. “When cable and DSL providers advertise a higher downstream, it comes with a higher upstream. It's just a matter of time before we see one of them start to advertise that fact.”

In Asian markets, where higher-bandwidth services are widely available in high-density areas, there is already a competitive battle raging over which company can deliver faster upstream as well as downstream bandwidth, he added.

“If you look in Asia, there are two sides to this — one is perceived need, and the other is actual need,” Howard said. “It doesn't matter that it is just perceived. Many people want to have the highest possible bandwidth in their apartment building versus their neighbors', whether they use it or not.”

The burst of home video, in particular, could spur demand for greater upstream bandwidth, particularly if that video is an always-on application such as a nanny-cam or home security service, said Marcus Weldon, chief technology officer of broadband access at Lucent Technologies.

Here in the U.S., cable providers and telcos are engaged in a battle of leapfrog when it comes to technological advantages, Howard said, and that is likely to continue as the cable industry looks forward to CableLabs' DOCSIS 3.0 standard and telephone companies deploy fiber optics to the premises or prepare for VDSL 2.

Initially, cable networks weren't well prepared for upstream traffic demand, and that caused early problems when peer-to-peer traffic suddenly took off, said Jay Rolls, vice president of telephone and data engineering for Cox Communications.

“We were much skimpier on upstream bandwidth — it wasn't tailored to early demand,” he said.

Part of the problem is that the upstream part of a cable network is in a noisy part of the spectrum, the 5 MHz to 40 MHz band, said John Mattson, director of Cisco Systems' broadband edge and midrange routing cable marketing group.

“There is a lot of other electrical interference — garage-door openers, blenders, vacuum cleaners, radar, ham radio — and it's traditionally limited by the fact that the plant itself had limitations,” Mattson said.

The cable industry began addressing those with DOCSIS 2.0 and with network changes.

“We did a bunch of things, like de-combining nodes on the upstream channel and using a larger channel size, going from 1.6 MHz to 3.2 MHz,” Rolls said. “We've also upped the modulation. But we have a lot of other levers we can still pull — we have not invoked any of the top modulation schemes within DOCSIS 2.0.”

Initially, Cox and many of its cable brethren used what Rolls termed a “vanilla” modulation known as QPSK or quadraphase-shift keying, but it has now stepped up to 16 QAM, or quadrature amplitude modulation, which boosts upstream capacity (see chart on page 30).

“They introduced a lot of fancy ingress cancellation, and with DOCSIS 2.0, they can crank up the volume of upstream transmitters,” Mattson said. “With that technology, you quadruple the upstream to QPSK from 16 QAM. The max used to be 2.5 Meg, and that has been turned up to 10 Meg. Plus, more spectrum is available so they can operate in more channels, and that multiplied the upstream bandwidth by 10.”

The upgrade is neither complex nor capital intensive.

“It can be done in software,” Cisco's Mattson said. “Download new software in the [cable modem termination system] and away they go. We have 75% to 80% of installed base of CMTS and about 50% have gone to 16 QAM. There is some operational stuff you have to do. You have to change a parameter in the CMTS, which tells the modems to change their operating mode. But it's done with one command.”

In addition, Rolls said, there is still room for further improvement, by moving to 64 QAM, if traffic patterns indicate the need.

“We watch all the traffic pretty carefully, and we have tools, on a dashboard, that flag the tell-tale early signs of congestion issues,” he said. “In addition, we are always going to smaller node sizes, and those bring relief as well.”

Even further benefit is available from using software — also part of the DOCSIS 2.0 spec — that increases available bandwidth even further, Mattson said. Advanced TDMA (ATDMA) and synchronous CDMA (SCDMA) technology can be deployed to double or triple the capacity again, he said.

“Less than 5% of our cable customers have turned on ATDMA or SCDMA,” Mattson said. “They still have a lot of growing room.”

Not that far down the road is DOCSIS 3.0, the next generation of technology, which incorporates wideband or channel-bonding technology. That allows bonding of channels to create a fat pipe — up to 100 Mb/s, Howard said. In addition, statistical muxing creates the possibility for “the whole to be greater than the sum of the parts,” Mattson said.

The other advantage for cable companies, he added, is that these newer technologies can be added on a node-by-node basis, enabling the cable companies to respond to competition as it arises.

“Where a telephone company is deploying fiber optics to the home, the cable company is in a position to respond directly to that,” Mattson said. “The cable companies are in a much better position to respond competitively than they have been in the past.”

Verizon is the telephone company most actively engaged in deploying fiber to the premises, and one of the driving forces behind the multi-billion dollar investment is the realization that higher volumes of traffic will be going in both directions, said Greg Evans, vice president of services and access technologies in Verizon's national technology group.

“We believe customers are going to use this bandwidth in a lot of different ways — like sharing videos of their kids at the beach,” he said. “Plus we see all sorts of ways for people who want to work at home to have an extension of their office environment, either casually or more formally. They want to be able to send, as well as receive, e-mail files with heavy attachments. They are moving presentations that are multiple megabits in size back and forth. With FiOS, they can do their own Web hosting.”

In a recent column, Wall Street Journal Personal Technology writer Walter Mossberg, a recent FiOS subscriber, noted that it took him just over 8 minutes to upload five digital photos, totaling 10.2 Mb in size, to an online photo service on FiOS, while his Comcast cable modem service required 1 hour and 22 minutes to do the same job.

Verizon offers 2 Mb/s upstream channels on both its 5 Mb/s and 15 Mb/s FiOS services. The high-end offering, at $200 per month, is 30 Mb/s downstream and 5 Mb/s upstream.

“We believe you can't have this asymmetrical view of the world because the service isn't just about Internet access, browsing the Web and downloading e-mail,” Evans said. “There's a lot of interactivity and other applications.”

But most of Verizon's network, as well as that of other telcos, remains copper-based, and that means continuing to push the limits of what DSL can offer.

Current service offers are based on G.DMT, which has a theoretical upstream limit of 768 kb/s, said Jay Fausch, senior director of marketing for the fixed communications group of Alcatel, the global leader in providing DSL technology to service providers.

Today, the top speed DSL offerings from major telcos are 3 Mb/s downstream and 768 kb/s upstream, with the more mainline offerings coming in at 1.5 Mb/s and 256 kb/s, he added.

“If you conjure up a model where you have a lot more always-on kinds of experiences being consumed by the users on the network — such as video components in the downstream or upstream — then the existing networks start to show strain,” Fausch said. “And the models that are used to authenticate users and manage the service flows and the queue begins to affect the quality of the time-sensitive service offerings, like voice and video.”

At that point, service providers must distribute intelligence for authentication and other key tasks closer to the user, he said.

“Some operators are moving in that direction already — SBC's Project Lightspeed is using distributed intelligence in the model,” Fausch said.

The network architecture also can determine how efficiently the bandwidth is used, said Geoff Burke, video solutions marketing director for equipment vendor Calix. Efficiently handling traffic to reduce the number of “hops” a signal has to make reduces latency, a factor that can be critical for interactive applications such as gaming.

Like cable companies, the telcos have a number of upgrade options to DSL that can add power to the upstream channel. Within the ADSL 2 technology, which is now being deployed, Annex M is designed to allow up to 3 Mb/s upstream, said Calix' Burke, whose company is delivering ADSL 2 today in its broadband loop carrier systems.

“We see that primarily aimed at business users — there aren't a lot of consumer applications today,” he said.

The VDSL 2 standard was finalized in the spring, and commercial gear could appear on the market as early as mid-to late 2006, although analyst Howard doesn't expect general availability before 2007. Depending on the loop length, VDSL 2 can deliver 50 Mb/s or 100 Mb/s upstream, in addition to the 100 Mb/s downstream signal.

There is also dynamic spectrum management, Lucent's Weldon said.

“It takes reconfiguration of modem from training time to show time, which is when you are running DSL connection,” he said. “Modifications to the power and the noise margins and the number of bits that you put in each tone can be made in such a way that you could support different grades of service, one of which is upstream.”

Service providers can dynamically allocate upstream bandwidth for a specific service, such as videoconferencing, Weldon said.

DOCSIS Bandwidth versus Bit Rate

Downstream	Standard: Channel Size:	DOCSIS 6MHz	Euro-DOCSIS 8MkHz
	64QAM 1.0/1.1/2.0	30 Mb/s	42 Mb/s
	256QAM 1.0/1.1/2.0	43Mb/s	56 Mb/s

Upstream	Symbol Rate: Channel Size:	160ksym 200kHz	320 ksym 400 kHz	640ksym 800 kHz	1.28Msym 1.6 MHz	2.56Msym 3.2 MHz	~6 Mhz
	QPSK DOCSIS 1.0/1.1/2.0	320 kb/s	640 kb/s	1.28 Mb/s	2.56 Mb/s	5.12 Mb/s
	16QAM DOCSIS 1.0/1.1/2.0	640 kb/s	1.28 Mb/s	2.56 Mb/s	5.12 Mb/s	10.2 Mb/s
	64QAM DOCSIS 2.0	960 kb/s	1.92 Mb/s	3.84 Mbps	7.68 Mb/s	15.36 Mb/s	30.7 Mb/s

Source: Cox

Residential DSL Service — a speed comparison

(All speeds listed are considered best-effort services)
(downstream/upstream)

BellSouth	• 56 kb/s/56 kb/s	• 256 kb/s/128 kb/s
	• 1.5 Mb/s/256 kb/s	• 3 Mb/s/384kb/s
Qwest	• 256 kb/s/256 kb/s	• 1.5 mbps/896 kb/s	• 3-5 Mb/s/896 kb/s
SBC	• 416 kb/s/416 kb/s	• 1.5 Mb/s/384 kb/s	• 3 Mb/s//512 kb/s
Verizon	• 768 kb/s/128 kb/s	• 3 Mb/s/768 kb/s