I will cover your questions in much more detail later, but here are some quick answers:
1) Yes, DOCSIS 3.0 does provide different modulations on different bonded upstream and downstream channels. So you can have one downstream bonded channel in 64-QAM and the next one in 256-QAM. Similarly in upstream channel bonding, one upstream channel can be operating in 16-QAM and the next in 64-QAM, which may be necessary depending upon frequency dependent upstream impairments.
2) No, DOCSIS really does not provide for real-time bonding changes on a per cable modem basis. However a cable modem does have the ability to use all bonded channels or to fall back into a DOCSIS 2.0 mode and use just one bonded channel if it is having problems with the bonded channels. This is a fall-back measure put in place to keep modems online in the case of impairments and/or compatibility issues.

-Brady

Thanks for your detailed tutorials. I have few questions on channnel bonding feature supported by docsis 3. I appreciate your help in understanding.

1.) Does Docsis 3 standard supports different modulations on different frequencies that are bonded? If so the modulations on each frequency is decided by CMTS based on available bandwidth?

2.) Does CMTS provide different number of channels to be bonded for different Cable modems (may be based on priority or real time bandwidth availability) or is it fixed for all cable modems connected to a given CMTS.

Thank you.

The obvious issue that I would see is that if you are transporting voice off of the GSM/3G network over DOCSIS you will want to implement a QoS on the DOCSIS for the voice traffic. DOCSIS specifications starting at 1.1 and up all support QoS so this is a matter of implementing it either at the CMTS or more ideally through PacketCable at a media access device that will know the voice traffic is coming and appropriately handle the transition from the 3G network to the DOCSIS network and setup the QoS flow. There is also the likely potential that you will have one CODEC on the 3G side and will find a more efficient CODEC to use on the DOCSIS side which does not over utilize a DOCSIS CMTS, in terms of packets per second (pps). So again, you will want a PacketCable media manager to handle this. There are a number of products on the market to handle this. One vendor I know off of the top of my head to recommend might be CedarPoint Communications.

Regards,
-Brady

We plan to inject GSM/3G signals onto the existing MATV distribution system. At certain junctions these signals will be extracted using link filter and off to the GSM antennas while the rest of the MATV system right to the Cable TV topbox.

All went well so far. However there is a plan to implement DOCSiS onto the same system. The end result: the distributions system will have cable TV services, DOCSiS and GSM/3G system running thru it.

Do you see any issues? We are about to start the trial next month. Look forward to your expert opinion so that we could manage the expectation on this project. Thanks.

You mention laser clipping in this post. I’m very curious about upstream laser clipping, specially about FP vs DFB when doing higher bandwidths and multiple upstreams in the return plant.

Do you have any good pointers for finding out more about this? I have seen some slides mentioning this but I’m having some problems grasping this.

Also, is there a good method for evaluating laser performance with normal field equipment such as spectrum analyzers?

// Philip

I read the draft RFC describing all this, and it basically told me everything I was wanted to know: http://tools.ietf.org/html/draft-mule-cablelabs-docsis3-ipv6-00

I notice that DOCSIS 3.0 adds support for IPv6, but what exactly does that mean? Why wouldn’t DOCSIS 2.0 for instance, be able to carry IPv6 packets in its payload?

Is it perhaps the addition of multicast support, needed by the IPv6 ND/RD process?

Or does “support” just mean that equipment like the CMTS, modems, etc, simply need proto stack support added to route IPv6, have IPv6 NICs and/or management addresses, etc?

Always good to hear from you. Yes, what I have termed “Adaptive Signal Cancellation” is the ingress cancellation referred to by Cisco. I have intentionally tried to avoid any trade-marked terminology to stay vendor agnostic. As for S-CDMA, yes, there are some minor challenges with it, which is why I believe it was never widely adopted when Terayon was pushing it heavily. However it is being successfully used by a number of North American operators specifically in the cases I mentioned in my blog – i.e. for business applications in the lower portion of the RF spectrum.

Regards,
-Brady

Thanks for another well explained lesson on DOCSIS and SCMDA!

Cheers,

Brian

cheers