Recommendations on nodes with more than four channel bonding should be lowered on the high end to a maximum transmit power of 47 dBmV.įigure 1. If more than four channels are bonded in the upstream, a cable modem’s max transmit may be limited to 48 dBmV if it does not include the extended transmit ECN. The maximum transmit power per channel of 50 dBmV allows for 1 dB of additional headroom. The upper limit of 50 dBmV assumes four-channel bonding. The lower limit of 40 dBmV elevates the modem’s signal out of the noise floor in the HFC plant. This ideal spot has typically been between 40-50 dBmV. Next, to achieve the optimal signal quality or receive modulation error ratio (RxMER), the HFC network should be configured to force the cable modem to transmit its signal above the noise floor while leaving headroom to transmit more power when needed.

Frequently, failure to have enough transmit power to communicate with the CMTS is a key reason that modems are unable to register with the CMTS or the root cause for modems to frequently drop offline and re-register (often called flapping modems). Having too little or too much attenuation between the modem and CMTS will exceed the minimum or maximum transmit power of the cable modem, which will cause the modem to fail to communicate with the CMTS. First, every modem has a minimum and maximum transmit power. Transmit power per channel of a DOCSIS 3.1 cable modem is important for several reasons. Transmit power per channel is defined as the average RF (radio frequency) power in the occupied bandwidth (channel width). Why is DOCSIS 3.1 cable modem transmit power important? A DOCSIS 3.1 cable modem’s transmit power introduces some new considerations which are discussed in this article. It not only determines if the cable modem will be able to come online and register with the CMTS (cable modem termination system) but obtaining the optimal transmit power will make or break the subscriber’s quality of experience (QoE). A cable modem’s transmit power is extremely important.

Tc4400 docsis 3.1