By Dr. Robert Howald, Comcast; John Ulm, CommScope; Saif Rahman, Comcast; Dr. Zoran Maricevic, CommScope
The promise of 10G is emerging, as Full Duplex DOCSIS (FDX) and Extended Spectrum DOCSIS (ESD) solutions make their way through laboratory testing to field trials towards first market launches. DOCSIS 4.0 consists of these two complementary technologies aimed at dramatically increasing upstream capacity and, correspondingly, upload speeds that customers will enjoy.
The FDX option for DOCSIS 4.0 is based on use of spectrum in the 108 MHz-684 MHz band (or subset of the band) for both downstream and upstream. Intuitively, signals overlapping in frequency and time interfere with one another. However, FDX has two key innovations that prevent this. Echo Cancellation (EC) technology removes potential interference where possible. Interference that cannot be removed by EC is avoided by controlling transmission timing within the DOCSIS scheduler. FDX sizes up the network and creates groups of users – “Interference Groups”(IG) – that should not access the same chunk of spectrum at the same time. This knowledge is incorporated into algorithms for allocating downstream and upstream resources.