DOCSIS® 3.1 (D3.1) offers exceptional capabilities for broadband service providers to enhance capacity and throughput both in the downstream (DS) and upstream (US) directions. While there has already been considerable activity in deploying D3.1 in the downstream, operators are in the early phases of rolling out D3.1 in the upstream.
While sharing many similarities with DOCSIS®3.0 (D3.0), D3.1 standards differ in important aspects –OFDMA operation, higher orders of modulation, increased flexibility in channel width, and most notably in burst upstream operation. There are many new things to consider in D3.1 including basic parameters such as Cyclic Prefix (CP), Roll-off Period (RP), OFDMA FFT size, minimum performance requirements, and encompassed spectrum. While D3.1 allows for a large encompassed spectrum affording significantly increased capacity, it also allows for very small mini-slots thus leading to a rather large dynamic range of RF inputs to existing RFoG ONUs. It is therefore an appropriate time to understand the capability of currently deployed RFoG plant and endeavor to jointly optimize D3.1 and RFoG parameters to ensure robust throughput in the downstream and the upstream.
In this paper, we describe relevant D3.1 parameters and link them to physical characteristics of an RFoG network. We examine performance of individual ONUs using stand-alone D3.1 test equipment as well as analyze D3.1 initial range and register protocols in a realistic D3.1 CMTS environment. We next consider a complete multi-ONU RFoG environment with multiple simultaneously transmitting cable modems and ONUs and introduce a new way for analyzing ranges of error free operation windows of D3.1 upstream systems. We conclude with a discussion of real world application of analysis presented in this paper for legacy deployed RFoG systems and offer practical suggestions for green-field D3.1 RFoG deployments.