Comparing IEEE 802.14 and MCNS Standards for Hybrid Fiber Coaxial Networks

Abstract

In this paper, we present a comprehensive review of two standards, IEEE 802.14 and MCNS, developed for the Hybrid Fiber Coax (HFC) CATV networks. After a brief introduction to the physical layer of the HFC networks, three major MAC protocol issues, including synchronization, collision resolution, and bandwidth allocation and scheduling, are identified. We then compare these two standards by illustration their similarities and differences. Both standards offer data-link-laver security, upstream as a stream of minis lots, downstream in MPEG-2 format, virtual queue, upstream bandwidth management, and request piggyback. But they have quite different mechanisms for ranging, upstream access, and collision resolution. Among them, IEEE 802.14 has reservation and isochronous access modes, while MCNS has reservation and immediate access modes. For collision resolution, IEEE 802.14 exercises a fairly complicated combination of priority control, n-ary tree walk, and multiple collision resolution engines, while MCNS uses a simple binary exponential back off algorithm. The space left open by the standards, especially the allocation and scheduling issues, are also identified.