I have two independent (separate) channels inside microwave link with bandwidth near 27MHz and planing to build 34Mbit/s data link with ethernet interfaces.
Is possible to tune or change the DOCSIS 2.0 cable modem firmware to make possible them to work like point-to-point model without central modulator? Generaly speaking is the QPSK output steam from cable modem the same structure as it receive it from central modulator?
Of course I will need to swap and fit streams from one modem to other to fit RX-TX and TX to RX. Of course exist many solutions from brand manufactures but cost ~5000USD or more and have the E3 interface.
Cable modem have all parts inside and cost 50 USD.
oles this forum has no relation to the technologies you speak of. this is a MikroTik product forum, and mikrotik doesn’t work with these devices that you describe.
Like Normis said, this is the wrong place, but since you are here, I can answer your question, as I was just recently working as a broadband engineer(that has an EE degree ), and have installed many CMTS routers…
According to the DOCSIS specification, which calls for a certain amount of backward-compatability, the modulation type used can be set in firmware. Assuming that the upstream modulator of the cable modem on one end could be tuned to a frequency above the standard 50-60MHz ceiling, and the downstream demodulator would tune down below 50MHz(since the transmit and receive bands must be separate and divided by a diplex filter), you would be able to get a radio link if you set the modulation scheme properly. The usefulness of doing any of this, though, escapes me. For data to be reliably transmitted over long distances, the RF has to be band-split using more diplex filters, and the upstream and downstream reamplified with separate upstream and downstream amplifiers about every 1000’, when using 1/2 inch cable. Using standard coax without the special amplifiers would yield you no more distance than you could get using standard Cat5 cable. You should also note that the single modulator and demodulator contained in the standard cable modem would not be able to communicate with more than one RF peer by design, so using a standard cable modem in place of a CMTS would be out of the question. You might be able to use several cable modems in place of a CMTS, though, using combiner/splitters, but each cable modem would only be able to connect to one other cable modem. If you had the idea of setting up point to point links using the cable company’s infrastructure, you should know that the company’s CMTS would quickly identify the additional RF activity on that “card”, and would report it immediately to the administrator. If you had the idea of using the modems for wireless links, it would be difficult to do, and even then only at short ranges without massive amounts of power, considering the very low frequencies used by the modems. And of course, these frequency ranges are strictly licensed and restricted from being used for free-air broadcast. Then, “the straw that broke the camel’s back”, is the fact that you would have to completely recode the firmware of the device, almost rewriting it from scratch. This would be a daunting task, but might be made easier by using one of the more “open” cable modems, such as some of the units made by Cisco…
If you have any more questions, or still want to persue this, please email me at “clint*xceltechnical.com”. Normis, or mods, if you want to delete or move this, feel free…
), and have installed many CMTS routers…