By Noam Geri, Itay Lusky,Texas Instruments, Broadband Communications Group
A new generation of data over cable service interface specification (DOCSIS) 2.0 cable modem and cable modem termination systems (CMTS) offer cable operators the promise of increased upstream capacity and greater robustness to common channel impairments such as ingress and impulse noise. It is already clear that the many tools in the new DOCSIS 2.0 standard that allow for efficient use of the upstream spectrum and mitigation of impairments also make the task of optimizing transmission parameters increasingly difficult. In fact, the performance of a DOCSIS 2.0 based CMTS will greatly depend on its ability to dynamically assess upstream channel conditions and set the transmission parameters accordingly. In this paper we present digital upstream channel analyzer (DUCA) – a set of functions running on a DOCSIS 2.0 CMTS that implements algorithms for optimal channel allocation and selection of transmission parameters. DUCA analyzes the entire upstream spectrum, measures and records noise and impairment conditions, and sets the parameters of the various noise mitigating tools in DOCSIS 2.0 optimally for maximum upstream throughput. We will show how proper selection of parameters, using DUCA, ensures that operators will benefit significantly from the new improved upstream PHY.