What is the difference between ATDMA and SCDMA?
A. ATDMA is a direct evolution of DOCSIS 1.x physical layer (PHY), which uses TDMA multiplexing. DOCSIS 1.x upstream PHY uses a frequency division multiple access (FDMA)/TDMA burst multiplexing technique. FDMA accommodates simultaneous operation of multiple radio frequency (RF) channels on different frequencies. TDMA allows multiple cable modems to share the same individual RF channel, because it allocates each cable modem its own time slot in which to transmit. TDMA is carried over in DOCSIS 2.0, with numerous enhancements. SCDMA is a different approach, in which up to 128 symbols are transmitted simultaneously via 128 orthogonal codes. SCDMA multiplexing allows multiple modems to transmit in the same time slot. Both ATDMA and SCDMA provide the same maximum data throughput, although one might perform better than the other under specific operating conditions.
