By Michael Cooper, Cox Communications; David Job, Cox Communications; Alan Skinner, Cox Communications
HFC cable technology has provided a robust and flexible architecture that has allowed the industry to continue to evolve their networks to meet expanding capacity demands and higher product speed offerings for nearly three decades. The DOCSIS® 4.0 specifications, and in particular, the FDD (Frequency Division Duplex) option of DOCSIS 4.0, is just another example of that continued evolution capable of targeting in excess of 10 Gbps of downstream network capacity. While much is understood about operating a cable network in a FDD mode below 1 GHz, the expanded 1.8 GHz downstream frequency range provides for this incredible leap forward in capacity. HFC architectures commonly encompass nodes with amplifier cascade depths of 4 amplifiers or more. The amplifier cascade depth directly impacts signal quality and modulation levels achievable within the network and thus, network capacity. Cox has developed detailed models to aid in predicting performance within these cascades; however, it is critical that actual field testing be conducted to validate those expectations. In this paper, Cox will present results from a field test conducted with DOCSIS 4.0 downstream RF signals between 804 and 1764 MHz on a 20+ year old plant within Cox’s production network with a cascade depth of N+4 (5 amplifiers). The testing validates our assumptions and provides confidence in our ability to deliver the promise of 10Gbps.