INTERNET OVER DIGITAL VIDEO BROADCAST: PERFORMANCE ISSUES Hakan Yılmaz TÜBİTAK Marmara Research Center Information Technologies Research Institute Kocaeli, Turkey hy@btae.mam.gov.tr Bülent Sankur Boğaziçi University Department of Electrical and Electronics Engr. Istanbul, Turkey sankur@boun.edu.tr Abstract Digital Video Broadcasting (DVB) defines the carriage of multimedia information to clients by means of MPEG-2 Transport Streams (TS). Within MPEG-2 transport stream, it is also possible to carry defined data containers that can be used to realize new data services or to carry IP datagrams. In this paper, we analyze this for carrying best-effort IP traffic within the prioritized video traffic. We investigate the statistical properties of the traffic under different network resource configurations, i.e., bottleneck bandwidth, buffer size, and different traffic characteristics, i.e., self- similarity (Hurst parameter). Keywords: Self-similar traffic, Hurst parameter, IP over DVB, throughput, delay, drop rate 1. INTRODUCTION In this work we investigate the potential of a Digital Video Broadcast (DVB) [1] system, which is normally used for television programs, as an alternative Internet access scheme. In this scenario the consumer uses his set-top box and TV screen interactively both to decode and watch TV programs and/or to be connected to the Internet. The DVB system is based on the cell-oriented packet transmission system, where the MPEG-2 Systems Standard provides the means of multiplexing several types of multimedia information into one Transport Stream (TS). The variable-bit-rate (VBR) video compression causes a bursty traffic [2,3], which requires allocation of considerably larger bandwidth to satisfy delay and bit-error-rate (BER) requirements of DVB. MPEG-2 TS also allows for data containers in addition to the audio and video data containers, on which new data services can be implemented or simply IP datagrams can be carried. An important feature of video traffic at the packet level, which has significant impact on performance, is its temporal correlation or its self-similar characteristics [2,3]. Specifically, “bursts of data” generated by VBR compressed video is the main cause of long-range dependence in time and hence of the self-similar traffic [4]. Such self-similar traffic is encountered in both LAN and WAN environments, for http traffic [5] and can persist across several protocol layers. The studies on the impact of self-similarity on network performance [6] have shown that network performance degrades gradually with increased heavy-tailedness while queuing delay and response time deteriorate more drastically. To mitigate performance losses one can adjust the network resources, such as increasing link bandwidth and buffer capacity, which tend to improve the performance in a superlinear (i.e., logarithmic) fashion. This is an indication that optimal resource allocation plays an important role in achieving the desired Quality of Service (QoS).