Hi,
I am looking to find a CMTS that can send a very narrow downlink. We would like to send RF on 430-432Mhz down and 50.0 - 50.2 Uplink for Amateur Radio Data and voice system.
I see C2000WL-Fixed Wireless base station based on DOCSIS over Air (DoA)
Downstream features supported: QAM256, QAM64, QAM16 and QPSK
Bandwidth supported: 6MHz to 3.5MHz (to accommodate wireless channels)
Programmable symbol rates Downstream features supported:
• QAM256, QAM64, QAM16 and QPSK
Downstream per channel bit rate 10, 20, 27 and 38 Mbps
However I would like:
2MHz wide = 1.7M sym per sec (though we could run faster, creates higher noise outside allocation)
16 QAM = 4 bits per sym
= 6.8Mbps
FEC = 1/9 so 6.12Mbps downlink
Uplink
200kbps approx 170ksym/s
QPSK = 2 bits per sym = 340kbps
An 8Mhz or 6MHz modem will work on 2MHz, as long as no interfering signal. Most modems work 1.5Msym/s to more than 8Msym/s (1.6MHz to > 8MHz). Bits per symbol 2 (QPSK) to 10 (1024QAM!).
If it's a modem with an IF 44MHz (Arris rather than Thomson), then a 2nd IF can be added with switch for 8MHz / 2MHz operation.
So is there any CMTS that can operate at very low downstream bit-rate or is there a setting in any CMTS that allows very low bit rates? How can I get this to work?