A Request Cluster Allocation Method for DOCSIS CATV/HFC Networks

Tomoya SAITO  Kyoko KATO  Hiroshi INAI  

IEICE TRANSACTIONS on Communications   Vol.E87-B   No.2   pp.286-293
Publication Date: 2004/02/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Network
CATV/HFC networks,  access networks,  request cluster allocation,  random reservation,  

Full Text: PDF(701.4KB)>>
Buy this Article

As an access network to the Internet, CATV/HFC network has been widespread recently. Such a network employs a reservation access method under which reservation and data transmission periods appear by turns. Before data transmission, a station must send a request in a random access manner during the reservation period called a request cluster. If the cluster size is large, the probability of request collision occurrence becomes small. A large cluster size however increases the packet transmission delay. Moreover the throughput decreases since vacant duration of reservation period increases. DOCSIS, a de facto standard for the networks, employs the binary back-off method for request cluster allocation. Since that method normally allocates unnecessary large request cluster, the transmission delay increases under heavy load conditions. In this paper, we propose a request cluster allocation method which dynamically changes the cluster size according to the load conditions. In order to evaluate performance of the proposed method, we build a queuing model and execute computer simulation. Simulation result shows that the proposed method provides smaller delay than the binary back-off method.