An investigation into HFC MAC protocols: Mechanisms, implementation, and research issues

This study comprehensively reviews two HFC MAC protocols: Data-Over-Cable Service Interface Specifications (DOCSIS) and IEEE 802.14a. DOCSIS was approved by the ITU as a standard and is supported by many vendors. However, IEEE 802.14a remains a draft due to the delayed standardization process. After briefly introducing the features of HFC networks, the basic operations and mechanisms of these two MAC protocols are then examined. Both standards view an upstream channel as a stream of minislots and have similar mechanisms for upstream bandwidth management, virtual queue, downstream in MPEG-2 format, data-linklayer security, and ranging. However, the standards adopt different mechanisms for upstream access modes, QoS support, and collision resolution. Moreover, the implementation issues over hardware and software design for DOCSIS networks are investigated. This work also identifies the research issues in HFC MAC protocols, particularly allocation and scheduling issues.