By Saifur Rahman Distinguished Engineer, Access Networks Comcast Cable Marc Morrissette Sr. Principal Engineer, Access Networks Comcast Cable
In this paper we will look at an often-overlooked method to add US capacity via optimally setting and dynamically adjusting the return levels of a DOCSIS system. The return level set point (RLSP) is an indirect method of controlling the modem transmitter (TX). DOCSIS systems have been historically set statically to achieve a flat radio frequency (RF) level at the input of the receiver, whether this is in a Remote PHY architecture or an Integrated-CCAP architecture. This results in the TX being adjusted by the CMTS via DOCSIS ranging1 until its RLSP is achieved. In addition, operators have not dynamically adjusted the RLSP and have set this uniformly across all US Ports based on plant design. This paper will explore why flipping the paradigm by having the modem TX at or near its maximum power by letting the CMTS vary the RLSP dynamically, can provide capacity benefits. All of this can be done without any work being done on the HFC plant.