What is the difference between Processing Gain and Coding Gain?
A. Interference removal technology digitally subtracts the interference signals. The amplitude that can be subtracted is called the Processing Gain. This is separate from the Coding Gain, which shows how much benefit you can get when you trade off throughput for interference or noise rejection. Coding Gain is like adding 3 bytes of forward error correction (FEC) to every 10 bytes of data. If you add another 1 to 3 bytes of FEC to the same amount of data, you have achieved Coding Gain. Cisco cable modem termination system (CMTS) products can remove between 2 or 3 dB of impairment (worst case, most complex signal possible in an hybrid fiber-coaxial (HFC) network, also known as Common Path Distortion [CPD]) and 25 to 29 dB of impairment (best case, single AM or FM modulated signal). One typically achieves a 5 to 15 dB Processing Gain on a real HFC network. In addition, one might see a 1 or 2 dB Processing Gain on some other CMTS, but that is offset by a 3.5 to 4.5 dB Implementation Loss.
