High-quality Multimedia Services Research Articles

A Generalized Analytical Framework for SMPT in a Multicode CDMA Wireless System

Simultaneous MAC Packet Transmission (SMPT) has recently been proposed for stabilizing the throughput over wireless links, which is one of the key challenges in providing high-quality wireless multimedia services. SMPT stabilizes the wireless link by transmitting multiple packets on multiple CDMA channels in parallel in response to packet drops due to wireless link errors. These parallel packet transmissions stabilize the link layer throughput, but they also increase the interference level in a given cell of a cellular network or cluster of an ad-hoc network, which in turn reduces the number of traffic flows that can be simultaneously supported in a cell/cluster. We have recently developed an analytical framework for the class of SMPT mechanisms for a simple Bernoulli packet generation process, which does not reflect the oftentimes bursty packet generation processes encountered in real networks. In this paper we develop a generalized analytical framework for SMPT, which accommodates bursty packet traffic (and also non-bursty Bernoulli traffic). This framework expresses the system dynamics in transition probabilities for a Markov chain and calculates the effects of the interference through an iterative approach. The numerical results from our analytical framework and verifying simulations indicate that SMPT provides a significant reduction in packet loss and buffer occupancies (and delay), especially for persistent traffic bursts, in exchange for a reduced number of supported flows. Our analytical framework quantifies these system trade-offs with good accuracy and can thus be employed for resource management.

Dynamic spectrum allocation in composite reconfigurable wireless networks

Future wireless systems are expected to be characterized by increasing convergence between networks and further development of reconfigurable radio systems. In parallel with this, demand for radio spectrum from these systems will increase, as users take advantage of high quality multimedia services. This article aims to investigate and review the possibilities for the dynamic allocation of spectrum to different radio networks operating in a composite reconfigurable wireless system. The article first looks into the current interest of regulators in this area, before describing some possible schemes to implement dynamic spectrum allocation and showing some example performance results. Following this, the technical requirements that a DSA system would have, in terms of reconfigurable system implementation, are discussed.

High capacity and reliability techniques for digital audio broadcasting system

Multiple transmitting and receiving antennas can be used in DAB systems to attain high-rate transmission and to offer better quality. In the MIMO-DAB systems, the transmission rate is efficiently increased by the number of antennas. In this paper, we introduce a new channel estimation method using the window function and evaluate the BER performance according to the number of antennas in MIMO-DAB systems. Also an effect of receiver diversity on the performance of MIMO-DAB system is investigated and the achievable receiver diversity gain for a Rayleigh fading environment is evaluated. For effective signal detection, a new detection scheme using interference nulling and cancellation operation is proposed in MIMO-DAB systems. And also we have been shown that the MIMO-DAB system with combining detection can achieve the high-rate transmission for high quality multimedia services.

Analytical Framework for Simultaneous MAC Packet Transmission (SMPT) in a Multicode CDMA Wireless System

Stabilizing the throughput over wireless links is one of the key challenges in providing high-quality wireless multimedia services. Wireless links are typically stabilized by a combination of link-layer automatic repeat request (ARQ) mechanisms in conjunction with forward error correction and other physical layer techniques. In this paper, we focus on the ARQ component and study a novel class of ARQ mechanisms, referred to as simultaneous MAC packet transmission (SMPT). In contrast to the conventional ARQ mechanisms that transmit one packet at a time over the wireless air interface, SMPT exploits the parallel code channels provided by multicode code-division multiple access. SMPT stabilizes the wireless link by transmitting multiple packets in parallel in response to packet drops due to wireless link errors. While these parallel packet transmissions stabilize the link layer throughput, they also increase the interference level in a given cell of a cellular network or cluster of an ad hoc network. This increased interference reduces the number of traffic flows that can be simultaneously supported in a cell/cluster. We develop an analytical framework for the class of SMPT mechanisms and analyze the link-layer buffer occupancy and the code usage in a wireless system running some form of SMPT. Our analysis quantifies the tradeoff between increased link-layer quality of service and reduced number of supported flows in SMPT with good accuracy, as verified by simulations. In a typical scenario, SMPT reduces the probability of link-layer buffer overflow by over two orders of magnitude (thus enabling high-quality multimedia services, such as real-time video streaming) while supporting roughly 20% fewer flows than conventional ARQ. Our analytical framework provides a basis for resource management in wireless systems running some form of SMPT and optimizing SMPT mechanisms.

Convergence of Broadcast and New Telecom Networks

The demand of the new telecom industry for cost efficient provision of mobile multimedia services is faced with the reality of scarce radio resources. The requirement of spectrum efficiency has driven the development of various digital radio technologies that have been optimized for specific services, namely for broadcast or for mobile communication. However, existing and emerging multimedia services exhibit challenging requirements in terms of asymmetry, interactivity, real-time, and multicast communication. This paper describes an IP based multi-radio infrastructure that enables the co-operation of existing radio networks to combine their capabilities to ensure a spectrum efficient provision of high-quality mobile multimedia services. Further the need for a dynamic allocation of spectrum to radio services is motivated. The basic functionality and the architecture of a multi-radio system is outlined, with a special emphasis on the cooperation between different radio systems. Further an evolution path for the convergence of broadcast and new telecom is desribed, starting from today's systems and leading to a fully coordinated system.

Tomas-inter-trial testbed of mobile applications for satellite communications project overview

The evolving third generation of mobile communication, Universal Mobile Telecommunication System (UMTS), foresees global provision of a broad variety of services with data rates of up to 2 Mbit/s, seamlessly integrated in different mobile and fixed networks. In addition to terrestrial networks, satellite systems (S-UMTS) are expected to ensure global coverage. Within the time schedule of UMTS no satellite system will be able to provide 2 Mbit/s rates for mobile phones. However, the evolving new LEO and MEO type satellite systems are expected to provide voice and low data rate (below 64 kbit/s) services to multimode terminals by the end of the century. An integration of these systems into UMTS seems feasible and is evaluated by different EU-ACTS projects (INSURED, SINUS). The TOMAS project in contrast focuses on high quality multimedia services and other high bit rate applications, which can be provided by geostationary satellites in the global cell of the UMTS. The terminals will not be handheld mobile phones but highly portable notebook-sized satellite terminals, but the services should be compatible with UMTS. The TOMAS main objectives are to demonstrate and evaluate applications and components of S-UMTS requiring higher bit rates (on a global platform). The emphasis is, however, on the end user's perspective. Therefore within TOMAS an 'Inter-Trial Testbed' will be set up, which will enable TOMAS and other ACTS and non-ACTS projects to test components and applications in real end-user trials, using existing ESA/EMS and Inmarsat geostationary satellites with data rates up to 2 Mbit/s.

Satellite‐ATM networking and call performance evaluation for multimedia broadband services

Currently, there is a huge increase in the demand for satellite communications operating at the Ka-frequency bands; several different systems have been proposed and are under development worldwide. In this paper, we investigate the design issues for the satellite protocol architecture that best satisfies the interconnection to the Broadband Integrated Services Digital Network (B-ISDN). The latest developments in broadband satellite communications aim to support a wide range of applications. These systems are designed to provide high quality multimedia services to remote user terminals. Furthermore, the mechanism that needs to be implemented in order to satisfy certain Grade Of Service (GoS) and Quality Of Service (QoS) criteria is discussed. A new methodology for the call performance evaluation of the Available Bit Rate (ABR) service class in a satellite Asynchronous Transfer Mode (ATM) network is proposed. Results at call level for different mix of service classes are presented using both analytical and simulation models. The simulation model was developed using OPNET modeller and it was used to record statistics that cannot be easily obtained by analysis. Copyright © 1999 John Wiley & Sons, Ltd.

Satellite-ATM networking and call performance evaluation for multimedia broadband services

Currently, there is a huge increase in the demand for satellite communications operating at the Ka-frequency bands; several different systems have been proposed and are under development worldwide. In this paper, we investigate the design issues for the satellite protocol architecture that best satisfies the interconnection to the Broadband Integrated Services Digital Network (B-ISDN). The latest developments in broadband satellite communications aim to support a wide range of applications. These systems are designed to provide high quality multimedia services to remote user terminals. Furthermore, the mechanism that needs to be implemented in order to satisfy certain Grade Of Service' (GoS) and Quality Of Service (QoS) criteria is discussed. A new methodology for the call performance evaluation of the Available Bit Rate (ABR) service class in a satellite Asynchronous Transfer Mode (ATM) network is proposed. Results at call level for different mix of service classes are presented using both analytical and simulation models. The simulation model was developed using OPNET modeller and it was used to record statistics that cannot be easily obtained by analysis.