GoBackTV’s solution for IPTV-over-Cable
IPTV-over-Cable is supposed to be a big market opportunity. Equipment vendors expect it to be as big as telco deployed IPTV. While the latter might have an edge in terms of interactive services, Cable companies have responded by utilizing the IP bearer channel for VoD and other interactive services.
There are two broad approaches for handling IPTV-over-Cable from a technical standpoint. Casa, Cisco, and Arris being CMTS vendors advocate using the traditional architecture i.e. treating IPTV like ordinary data, and sending it through the CMTS core. Motorola (also a CMTS vendor) has proposed a related architecture (DIBA). BigBand and Harmonic are QAM modulator vendors, and have designed systems to leverage an existing DOCSIS 3.0 system. It is unclear whether they can gain maximal efficiency without the cooperation of the CMTS.
GoBackTV product is a CMTS-bypass solution for IPTV-over-Cable. CMTS-bypass continues to use the basic DOCSIS infrastructure, but allows the video traffic to bypass the CMTS core, and go directly to the edgeQAM. The edgeQAM is responsible for encapsulating the IP(TV) stream in DOCSIS headers, and packetizing it for QAM modulation. At the subscriber's home, a standard cable modem demodulates the signal, strips off the DOCSIS headers, and passes on the IP(TV) stream on its Ethernet port.
The reason for doing this is that video is much higher bandwidth than traditional internet data, but does not require any of the packet-processing features since video comes from trusted sources, has its own conditional access/scrambling, and must receive the highest qos priority. A DOCSIS core is an order of magnitude more expensive than a downstream QAM, and has a limited throughput. So, if you send video through a CMTS core, you quickly eat up its throughput capacity, but leave it underutilized in terms of packet processing, upstream handling, and cable modem management. If you let the video bypass the DOCSIS core, you need fewer cores to handle the system's worth of video.
That is a lot of technology on one blog.
