INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS Int. J. Commun. Syst. 2002; 15:325–340 (DOI: 10.1002/dac.538) Using a multiple priority reservation MAC to support differentiated services over HFC systems z J. D. Angelopoulos* ,y , N. Leligou, Th. Orphanoudakis and G. Pikrammenos Telecom Lab, National Technical University of Athens, Polytechniopolis Zographou, GR15753, Athens, Greece SUMMARY The successful commercial deployment of Hybrid Fibre/Coaxial (HFC) access networks in the residential market has so far been driven by demand for faster Internet access and the prospects of a host of new services based on real-time voice and video. To sustain their growth rates and compete with alternative approaches, such as ADSL, they must be enhanced with the capability to efficiently handle quality- intensive real-time services. The new multi-service paradigm mandates isolation of traffic classes, conditioning of entering traffic and preventive control in addition to traditional closed-loop control. The differentiated services (DiffServ) architecture with its relevant traffic control tools and the bundling of behaviour aggregates is particularly suited to the H/W-based MAC of HFC systems. It constitutes a suitable framework enabling the support of proliferating real-time voice- and video-based services while aligning the system to the emerging Internet strategy of scalable service differentiation. The implementation of such a solution in the ACTS 327AROMA research project is presented in this paper. The performance of the system is evaluated using computer simulation. Copyright # 2002 John Wiley & Sons, Ltd. KEY WORDS: HFC; MAC protocols; differentiated services; tree topology; access networks; cable modems; residential services; QoS 1. INTRODUCTION Tree-shaped topologies, a natural choice for distributive services, still offer attractive cost advantages for bi-directional broadband access networks by allowing many customers to share the expensive head-end equipment and the feeder section. Retrofitted with fibre feeders and enhanced with a return channel they possess the significant advantage as broadband access platforms of exploiting the legacy copper last drops to the homes, at least during the crucial introductory phase and probably for many years to come. Re-use of the existing infrastructure greatly reduces the initial investment outlay and provides a graceful upgrade path in step with Received 1 July 2000 Published online 7 February 2002 Revised 1 June 2001 Copyright # 2002 John Wiley & Sons, Ltd. Accepted 1 November 2001 *Correspondence to: John Angelopoulos, Electrical and Computer Engineering Department, National Technical University of Athens, 15773 Polytechniopolis Zographou, Athens, Greece. y E-mail: jangel@cs.ntua.gr z A preliminary version of this work was presented in the Globecom’99 Conference on December 7. Contract/grant sponsor: EU ACTS