A Successive Times Based Scheduling for VoIP Services over HFC Networks

Bih-Hwang LEE  Jhih-Ming CHEN  

IEICE TRANSACTIONS on Communications   Vol.E87-B   No.11   pp.3343-3351
Publication Date: 2004/11/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Multimedia Systems for Communications" Multimedia Systems for Communications
VoIP,  HFC,  DOCSIS,  UGS/AD,  CMTS,  scheduling algorithm,  

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Voice over Internet protocol (VoIP) is to transfer voice packets over IP networks, while voice signal is processed by using digital signal processing technology before being transmitted. VoIP quality cannot be expected, because it is hard to predict the influence of delay, packet loss rate, packet error, etc. It is difficult to rebuild the voice wave form, if a large amount of voice packets are lost. This paper mainly studies on how to maintain a better voice quality over hybrid fiber/coaxial (HFC) networks, if it is inevitable to drop packets. We particularly consider the data over cable service interface specification (DOCSIS) version 1.1 with the unsolicited grant service with activity detection (UGS/AD) for VoIP services. We propose a smallest successive times first (SSTF) scheduling algorithm to schedule VoIP packets for cable modem termination system (CMTS), which can support fair transmission and long-term transmission continuity for VoIP connections. We analyze voice quality about continuity of the transmitted VoIP packets, consecutive clipping times, and VoIP packet drop rate for all connections. Performance measurement shows excellent results for the proposed algorithm by simulation experiments and objective evaluation.