Performance analysis and optimisation of the digital video broadcasting/Digital Audio Visual Council cable modem protocol for the delivery of isochronous streams

摘要

This paper presents a performance analysis of the European cable communications standard ETSI EN 200 800, developed by the digital video broadcasting (DVB) project in collaboration with the Digital Audio Visual Council (DAVIC) organization. The performance is based on the medium access control (MAC) protocol of the DVB/DAVIC standard. This protocol uses, by default, a limited reservation-access mechanism for the transmission of reservation requests. It was not optimised for the delivery of isochronous streams (timing critical interactive services), as is evident from the increased risk of collision with reservation requests among stations. Optimisation of this application is becoming more significant since alternative technologies, e.g. ADSL, are becoming popular. Therefore, five enhanced reservation request mechanisms are evaluated and analysed, each of which improves significantly overall system performance for the support of timing critical interactive services such as voice over IP and streaming video. The novel application of enhanced mechanisms presented here reduces (and/or avoids) collisions. Also, a new mechanism, the unsolicited grant slot, developed by the authors, is presented. It perfectly matches the requirements of constant bit rate (CBR) components.