In this paper, we introduce QMR/PR, a flexible QoS-sensitive routing framework for mobile ad hoc networks, which addresses the problems caused by mobility-induced route failures. QMR/PR combines packet-interleaving using multipath routing and packet-level forward error correction. A particularly promising feature is its ability to significantly reduce both random and correlated packet losses, a critical issue for real-time applications. To provide accurate and reliable performance evaluation results, we have integrated QMR/PR into the QualNet simulation software, allowing us to conduct an extensive performance evaluation in a realistic networking architecture including all layers of the protocol stack. Simulation results demonstrate the effectiveness of the proposed framework and show that, compared to single-path routing, QMR/PR can reduce packet loss by 42-84 percent depending on the networking environment (e.g, node mobility, frequency of path failures), while simultaneously reducing routing overhead.

We propose an adaptive QoS routing scheme based on the prediction of the local performance in ad hoc networks. It is implemented by a link performance prediction strategy. Integrated QoS performance in each local area is estimated based on translating the effects of the lower layer parameters into the link state information. Corresponding to the prediction approach, several mechanisms are built to complete the location information management process (i.e., information monitoring, collecting and updating functions). The node movement is characterized by the probabilities of the link state and the prediction of local QoS performance. The QoS routing proposed is adaptive to its node's mobility, and also scalable due to the distributed structure. Theoretical computation and simulation results are presented and discussed.

Mobile ad hoc networks (MANETs) are an emerging class of network architectures that are characterized by their highly dynamic topology, limited resources (i.e., bandwidth and power), and lack of fixed infrastructure. The primary motivation for such networks is increased flexibility and mobility. Random node mobility along with various other factors such as network size and traffic intensity may be very dynamic, resulting in unpredictable variations in the overall network performance. This study centers on investigating and quantifying the effects of various factors and their two-way interactions on the overall performance of ad hoc networks. This study contributes to the modeling and development of adaptive ad hoc protocols (routing, medium access control, scheduling and buffer management). Using 2/sup k/r factorial experimental design, we isolate and quantify the effects of five factors: node speed, pause-time, network size, number of traffic sources, and type of routing (source versus distributed), that affect the performance of ad hoc networks. Specifically, this paper evaluates the impact of these factors on the following performance metrics: throughput, average routing overhead, and power consumption. Our study was conducted using a library-based simulator for sequential and parallel simulation of wireless networks.

Abstract The general field of mobile ad hoc networking is still in its infancy. Particularly, the challenge of providing Quality‐of‐Service (QoS) support for ad hoc networks is an open problem and remains relatively uncharted territory. Providing a complete QoS solution for the ad hoc networking environment requires the interaction and cooperation of several components. These components include: (1) a QoS routing protocol, (2) a resource reservation scheme and (3) a QoS capable medium access control (MAC) layer. In this paper, we present a survey of the current research that has addressed each of these components in the context of ad hoc networks. This work is intended to provide a broad and comprehensive view of the various components and protocols required to provide QoS support in computer networks, focusing primarily on ad hoc networks. First, we introduce the unique characteristics of mobile ad hoc networks, which distinguishing this new network architecture from traditional infrastructured wired and wireless networks (i.e. cellular‐based networks). We also discuss the impact of these characteristics on QoS provisioning. Next, we describe the first QoS model proposed for mobile ad hoc networks and its relationship to QoS models proposed for the Internet. We then present a review of the proposed algorithms for each QoS component (e.g. QoS routing, resource reservation and the MAC layer). Copyright © 2002 John Wiley & Sons, Ltd.

This paper studies the statistical model of MPEG video over wireless networks. A real-time MPEG video traffic workload was generated and transmitted over a wireless network. The model parameters of I, B and P frames were measured before and after wireless transmission. The results we got were very interesting. Intuitively, larger frames are more sensitive to network errors. The parameters associated with the statistical model should change after transmission. However, the results of the experiments showed that the statistical models of all I, B and P frames remain almost unchanged after transmission. We repeated the experiment under different wireless link layer error rates and got the same results. To simulate errors, we designed a controllable wireless link layer error model by modifying the WaveLAN device driver which is a Linux kernel module.

Preserving ATM cell sequencing is an important issue in the future wireless ATM network. Out-of-sequence ATM cells will cause entire data frame to be discarded and causes either data retransmission or quality of service degradation. Currently there is no connection handoff scheme providing a schematic method to preserve ATM cell sequencing. In this paper, we investigate the issue of preserving ATM cell sequencing during connection handoff sessions. A proposed VP-based hierarchical network infrastructure and a handoff mechanism are used to support connection handoffs and preserve cell sequencing for both uplink and downlink handoffs in the wireless ATM network.

This paper presents call admission control issues for an ATM-based wireless network with mobile hosts. Such wireless ATM networks are motivated by both an increasing demand for mobile capability for future broadband networks and broadband multimedia services for mobile systems. An ATM compatible wireless network capable of supporting a mix of broadband ISDN services is discussed. We present a conceptual view of a wireless ATM architecture with distributed call admission functions. Related issues of call admission control caused by these characteristics are discussed, and new trends toward call admission control in future wireless ATM network are identified.

Traffic measurements taken from real data are highly desirable for validating traffic models, designing congestion control and flow control algorithms, implementing communication protocols, and developing switch architectures. This paper investigates the traffic characteristics of several applications in an ATM network with the goal of studying bursty traffic behavior and realizing the multiplexing effects of variable bit rate (VBR) traffic. Specifically, three types of traffic (ftp, voice, and video) are obtained from an ATM testbed. These applications are reported to be important applications that tend to dominate the wide-area networks. The multiplexing effects of FTP traffic are studied to identify empirical bandwidth requirements. The characteristics of the multiplexing effects can be applied to develop an efficient call admission algorithm based on the measured data. These experimental results designed to investigate traffic characteristics provide insights to bursty traffic behavior and performance requirements of practical real-time loads.

Compression of digital video is the only viable means to transport real-time full-motion video over BISDN/ATM networks. Traffic streams generated by video compressors exhibit complicated patterns which vary from one compression scheme to another. In this paper we investigate the traffic characteristics of video streams which are compressed based on the MPEG standard. Our study is based on 23 minutes of video obtained from an entertainment movie. A particular significance of our data is that it contains all types of coded frames, namely: Intra-coded (I), Prediction (P), and Bidirectional (B) MPEG frames. We describe the statistical behavior of the VBR stream using histograms and autocorrelation functions. A procedure is developed to determine the instants of a scene change based on the changes in the size of successive I frames. It is found that the length of a scene can be modeled by a geometric distribution.A model for an MPEG traffic source is developed in which frames are generated according to the compression pattern of the captured video stream. For each frame type, the number of cells per frame is fitted by a lognormal distribution whose parameters are determined by the frame type. The appropriateness and limitations of the model are examined by studying the multiplexing performance of MPEG streams. Simulations of an ATM multiplexer are conducted, in which traffic sources are derived from the measured VBR trace as well as the proposed model. The queueing performance in both cases is found to be relatively close.

An algorithmic language interpreter is presented which provides users of various technical backgrounds a convenient way to describe algorithms and simultaneously focus on problem-solving concepts: problem analysis, algorithm development, and the computer implementation of the algorithm. The interpreter permits the use of decision tables as a means of expressing complex logic.