Motorola is promoting a DOCSIS feature for cutting down noise in the spectrum range typically used for upstream transmission -- which the vendor claims can boost bandwidth up to 50% -- before cable operators start employing upstream-channel bonding to boost speeds.
The feature, synchronous code-division multiple access (S-CDMA), was developed by Terayon Communications Systems, which Motorola acquired in 2007. S-CDMA was incorporated into the DOCSIS 2.0 specification and is supported in DOCSIS 3.0.
Floyd Wagoner, director of marketing and communications for Motorola's Access Networks division, said S-CDMA represents the first step toward increasing upstream utilization in the 5-42 MHz range before moving to DOCSIS 3.0 channel-bonding on the upstream side. (Motorola's BSR 64000 cable-modem termination system does not currently support upstream channel bonding.)
The modulation schema is aimed at reducing impulse noise particularly between 5 and 15 MHz, and can increase overall bandwidth available in the 5-42 MHz range to from 100 Mbps to 150 Mbps, according to Motorola.
"This is ‘barren land' that is today not usable," Wagoner said, adding that there may be some remediation necessary on the physical plant to enable S-CDMA.
Other vendors, however, believe operators are looking to increase upstream speeds using DOCSIS 3.0 channel-bonding in high frequency ranges. Todd Kessler, Arris's vice president of CMTS product management, said S-CDMA has not been widely deployed by MSOs because it did not provide as much improvement as a different modulation scheme for the upstream, advanced time division multiple access (ATDMA).
Arris is offering upstream channel-bonding with the current release of its DOCSIS 3.0 CMTS platform, but does not yet support S-CDMA, a feature slated for a future release.
Still, analysts believe S-CDMA can in fact deliver bandwidth gains without an enormous amount of capital spending.
"In today's economy, it's smart to try to wring as much usable bandwidth out of your cable TV infrastructure as you can," In-Stat analyst Gerry Kaufhold said. "Motorola's approach is an excellent way to get more from an existing DOCSIS 2.0 cable plant, and can be upgraded to support a DOCSIS 3.0 channel-bonded approach later on." (In-Stat and Multichannel News are both owned by Reed Business Information.)
For an operator that is near the upstream limit with DOCSIS 2.0, "the S-CDMA approach can save some money this year and still permit you to continue improving your service offerings," Kaufhold added.
According to Wagoner, one Motorola customer experienced an increase in the average sustained upstream rates of 17% from 2007 to 2008. Meanwhile, the average peak across usage for 12 months increased 24%.
"What we're saying is, there's real evidence that the upstream bandwidth is increasing," he said
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