By Richard S. Prodan, Ph.D. Engineering Fellow Comcast Cable
This paper explores the optimization of upstream capacity from an information theoretic viewpoint. A profile management application (PMA) is derived from the well-known Shannon channel capacity theorem. The maximization of the sum rate of all upstream channels using Shannon’s formula employs a well-known optimization solution known as “water-filling”. Novel methods tailoring this solution to the DOCSIS protocol are derived with examples of the increase in available capacity achievable in currently deployed cable systems.
It should be noted that both DOCSIS 4.0 full-duplex (FDX) and extended spectrum (ESD) DOCSIS specifications can benefit from this approach as the upstream spectrum using orthogonal frequency division multiple access (OFDMA) transmission are the same. Also note that a similar power allocation optimization has been suggested in several 5G wireless radio orthogonal frequency-division multiplexing (OFDM) implementations (references in [2]).