Why Not WiMax?
Vendor execs familiar with both Docsis and WiMax note that a combination of the platforms should be viewed as a technology fusion rather than as a violent collision of the wireless and wired worlds of broadband.
"Ultimately, there are striking similarities in some respects. I believe they can coexist quite well," says Mark Tubinis, the chief technology officer of Cedar Point Communications Inc. , a VOIP equipment player whose WiMax-enabled Safari C3 Multimedia Switching System packs several PacketCable network elements into one device. (See Cedar Point Plugs In WiMax .)
That WiMax and Docsis both carry TCP/IP traffic could be the most important part of the comparison, adds Dave Park, VP of product marketing for BelAir Networks Inc. , a firm that makes WiFi and WiMax equipment with some hooks for Docsis environments. "WiMax and WiFi are IP-centric networks, so they do fall very nicely into the cable companies' architecture. "
WiMax also owes much of its MAC (Media Access Control) heritage to Docsis. Further down in that layer, WiMax includes the Docsis scheduler, used by the radio to decide who on the network gets to transmit data at any given time.
Such scheduling isn't overly important in a "best effort" world for applications such as email, but it's critical for latency-sensitive IP apps, such as voice, and would be even more so should wireless video enter cable's WiMax picture.
The WiMax Forum, is still considering whether to adopt elements of PacketCable Multimedia (PCMM), a platform that injects dynamic quality of service (DQOS) into a wide set of IP services and applications, including video and voice, says Randy Fuller, the VP of business development at policy server specialist Camiant Inc.
Until a common standard is finalized, WiMax vendors are implementing DQOS on an "ad hoc" basis, though cable is "advocating pretty strongly" that the WiMax Forum take a good look at PCMM, Tubinis says. Officials for the WiMax Forum were not available for comment.
However it shakes out, the similarities between Docsis and WiMax from a radio frequency and shared capacity standpoint should give cable operators a jump start on how to engineer WiMax networks and couple them to the hardwired plant.
"But ultimately, the fact is it's also a relatively inexpensive way for them to get [wireless] spectrum," Fuller says.
Cable's experience in the field with WiMax so far has been limited.
Grupo TVCable of Ecuador and two yet-to-be-named cable ops in Northern Africa are using Cedar Point's WiMax-powered gear to extend the cable plant wirelessly.
BelAir, which formed a cable technical advisory committee in 2006, claims to have wireless deployments with ten of the top 12 U.S. cable operators, but the only one to be made public is with Bresnan Communications LLC in Billings, Mont. And that one is based on WiFi. (See Bresnan Whips Up Wireless Strategy .)
Still, several of BelAir's cable deployments involve Docsis-enabled microcells with both WiFi and WiMax radios on board. In those situations, WiFi is serving as the onramp, with WiMax handling the backhaul. "Because it's a common IP packet, there are no expensive mediation layers or conversion layers," Park says, noting that WiMax onramps will come into play once mobile WiMax devices, such as phones, enter the market.
— Jeff Baumgartner, Site Editor, Cable Digital News