By Jan Ariesen, Technetix Inc
The introduction of DOCSIS® 3.1 means that higher modulation schemes, higher levels and higher bandwidth increase the load on the cable network.
The downstream increases from several QAM channels used in DOCSIS 3.0 in spectrum carrying up to 862 MHz with the addition of a couple of OFDM channels in spectrum expanding up to 1.2 GHz. All these changes greatly increase the load on the equipment used in the network.
However, this is nothing compared to what happens in the upstream. The big change is the bandwidth from the current low split of 42/54 MHz in the USA or 65/85 MHz in Europe to mid-split in the USA 85-105MHz and high-split in Europe 204/258 MHz. In the USA, the bandwidth has grown by 216% and in Europe by 331%. In addition to the phenomenal bandwidth growth, increased loss in the cables is a reality and as a result, DOCSIS 3.1 increases the maximum level of the upstream carriers by 6dB to 57dBmV per 4 channels.
This growth in level and bandwidth creates four main challenges:
- Passive intermodulation (PIM) in in-home splitters
- 2nd order distortion in in-home amplifiers
- Overloading of the upstream amplifier in access amplifiers
- The downstream reducing the quality of the upstream in the access amplifiers
This White Paper summarizes the four challenges detailed and describes what to do to prevent possible problems.