In this paper we identify important characteristics of a fading/shadowing fading channel and present the work of measurement-based channel modeling for packet-level network queueing analysis. Our integration of wireless channel modeling and data queueing analysis at the packetlevel provides a unique approach to study the effect of various channel dynamics on high layer network performance, which otherwise cannot be captured through the traditional bit-level physical-layer channel modeling. In our study, the channel statistics are decomposed into three frequency regions (i.e., low, mid and high); the statistics in each frequency region is found to have significantly different impact on the queueing performance. While the high-frequency statistics can be largely ignored in channel modeling due to its negligible impact on queueing performance, the low-frequency statistics plays the most important role in channel modeling because of its substantial impact on queueing performance....

The multipath fading channel modeling traditionally focuses on physical-level dynamics such as signal strength and bit error rate. In this paper we characterize multipath fading channel dynamics at the packet-level and analyze the corresponding data queueing performance in various environments. The integration of wireless channel modeling and data queueing analysis provides us a unique way to capture important channel statistics with respect to various wireless network factors such as channel bandwidth, mobile speed and channel coding. The second order channel statistics, i.e., channel power spectrum, is found to play an important role in the modeling of multipath fading channels. The data queueing performance is largely dependent on the interaction between the channel power spectrum and the data arrival power spectrum; whichever has more low frequency power will have more impact on queueing performance. Note that the data arrival power spectrum provides a measure of burstine...

We present procedures and tools for the analysis of network traffic measurements. The tools consist of stand-alone modules that implement advanced statistical analysis procedures and a flexible web-based interface through which a user can create, modify, save, and execute experiments using the statistical analysis modules. The tools do not assume a specific source traffic model, but rather process actual measurements of network traffic. Indeed, the theory that the tools are based on can identify the time-scales that affect a link's performance, hence suggest the appropriate time granularity of traffic measurements. We present and discuss case studies that demonstrate the application of the tools for answering questions related to network management and dimensioning, such as the maximum link utilization when some quality of service is guaranteed, how this utilization is affected by the link buffer and traffic shaping, the acceptance region and the effects of the scheduling discipline, and the token (or leaky) bucket parameters of a traffic stream. The case studies involve actual traffic measurements obtained by a high performance measurement platform that we have deployed at the University of Crete network. 2002 Elsevier Science B.V. All rights reserved.

Abstract. With the scalability and flexibility of the MPEG-4 and the emergence of the broadband wireless network, wireless multimedia services are foreseen to become deployed in the near future. Transporting MPEG-4 video over the broadband wireless network is expected to be an important component of many emerging multimedia applications. One of the critical issues for multimedia applications is to ensure that the quality-of-service (QoS) requirement to be maintained at an acceptable level. This is further challenged in that such a service guarantee must be achieved under unreliable and time-varying wireless channels. In this paper we study the link level performance of MPEG-4 video transmission over the uplink of an unreliable wireless channel. We introduce the discrete time batch Markovian arrival process (DBMAP) with two types of arrivals to model the MPEG-4 video source, which takes into account the inherent nature of the adaptiveness of the video traffic. We prove that in a hidden Markov modeled (HMM) wireless channel with probabilistic transmission, the service time for an arbitrary radio link control (RLC) burst follows phase type (PH-type) distribution. We show that the link level performance of a wireless video transmission system can be modeled by a DBMAP/PH/1 priority queue, and present computation algorithm and numerical results for the queueing model. Extensive simulations are carried out on the queueing behavior of the video transmission buffer, as well as on the packet level error behavior of the video data. The results demonstrate that video quality can be substantially improved by preserving the high priority video data during the transmission. Keywords: DBMAP with marked transitions, HMM channel, PH-type distribution, DBMAP/PH/1 priority queue 1.

Understanding the end-to-end packet delay dynamics of the Internet is of crucial importance since it directly affects the QoS (Quality of Services) of realtime services, and it enables us to design an efficient congestion control mechanism. In this paper, we measure the round-trip time, and build a mathematical model representing its dynamics using system identification. We first measure, as the input and output data for system identification, the packet inter-departure time from a source host and the corresponding round-trip time measured by the source host.