In this paper, real-time video transmission with quality of service (QoS) assurance over orthogonal frequency division multiplexing (OFDM) wireless systems is studied. Three quasi-optimal subcarrier allocation schemes, namely regular, delay tolerant and adaptive, are proposed. In the proposed schemes, effective throughput per subcarrier employing adaptive forward error correction (FEC) coding in a Rayleigh fading channel is evaluated, and a capacity matrix that governs all active users and all assignable subcarriers is formulated. The Munkres algorithm is used in the schemes to achieve optimal subcarrier assignment. Performance analyses in terms of spectral efficiency and packet loss probability are presented. Multi-user multichannel diversity is investigated to exploit the innate capacity gain in terms of fading variation and delay tolerance. The proposed schemes are scalable to both single-cell and multi-cell circumstances. Numerical results demonstrate that the proposed schemes can effectively achieve quasi-optimal spectral utilization and significantly improve system throughput.

In this paper, transmitting the real-time video with QoS provisioning over orthogonal frequency division multiplexing (OFDM) wireless channels is studied. Efficient subcarrier allocation schemes, namely regular, delay tolerant and adaptive, are proposed for real-time video streaming with QoS satisfaction to achieve near-maximal frequency efficiency. The Munkres algorithm is properly applied to the schemes to assure the optimality of subcarrier assignment. Multiuser multichannel diversity is investigated to exploit the innate multiplexing gain from fading variation and delay tolerance.

In this paper, the capacity of an orthogonal variable spreading factor code division multiple access (OVSF-CDMA) system supporting convergent variable rate video and data services is studied. An analytical approach for evaluating the system outage probability based on interference analysis is introduced. An optimization model to achieve maximum video and data throughput with QoS assurance and satisfactory outage probability is proposed. Numerical results demonstrate the effectiveness of the proposed approaches.

In this paper, adaptive transmission of scalable multi-layered video with quality of service (QoS) assurance over wireless channels is studied. By properly formulating the channel fading as a finite state Markov channel (FSMC) model, three rate adaptation schemes, namely, assured-rate-allocation, neighbor- interleaving, and swing-loaded schemes, are proposed to exploit the inherent multiplexing gain. An analytical model for QoS performance evaluation of video transmission over time-varying erroneous channels is derived. The accuracy of the analytical model is validated by simulations. Analytical and simulation results demonstrate that the proposed rate adaptation schemes can effectively improve the channel utilization and the system throughput.

In this paper, efficient rate adaptation schemes for scalable multi-layered video transmission over wireless links with quality of service (QoS) assurance are proposed. An analytical model for QoS performance evaluation on video transmission over time-varying erroneous channels is derived. The accuracy of the analytical model is validated by simulations. Analytical and simulation results show that the proposed rate adaptation schemes can effectively improve the channel utilization and the system throughput.

In this paper, the utilization of real-time video service in the downlink of an orthogonal variable spreading factor code division multiple access (OVSF-CDMA) system is studied. By modeling the video traffic and wireless channel as a joint Markov modulated process, and properly partitioning the states of the Markov process, an adaptive rate allocation scheme is proposed for real-time video transmission with quality of service provisioning while achieving high channel utilization. The scheme is applicable for packet switching and frame-by-frame real-time video transmission, and incorporates both the physical layer and network layer characteristics. For QoS provisions, the closed form expressions of packet delay and loss probability are derived based on the Markov model. Analytical and simulation results demonstrate that the proposed scheme can significantly improve the channel utilization over the commonly used effective bandwidth approach

The paper studies downlink channel utilization for real-time video traffic transmission in an orthogonal variable spreading factor code division multiple access (OVSF-CDMA) system. By modeling video traffic as a Markov modulated process and properly partitioning the states of the Markov process, an adaptive rate allocation scheme is proposed for real-time video transmission with quality of service (QoS) satisfaction while achieving high channel utilization. The scheme is applicable for packet switching and frame-by-frame real-time video transmission, and incorporates both physical layer and network layer characteristics. The QoS requirements include stringent packet delay and packet loss rate. Analytical and simulation results demonstrate that the proposed scheme can significantly improve the channel utilization over the commonly used effective bandwidth approach.

In this paper, a self-organizing map (SOM) scheme for mobile location estimation in a direct-sequence code division multiple access (DS-CDMA) system is proposed. As a feedforward neural network with unsupervised or supervised and competitive learning algorithm, the proposed scheme generates a number of virtual neurons over the area covered by the corresponding base stations (BSs) and performs non-linear mapping between the measured pilot signal strengths from nearby BSs and the user's location. After the training is finished, the location estimation procedure searches for the virtual sensor which has the minimum distance in the signal space with the estimated mobile user. Analytical results on accuracy and measurement reliability show that the proposed scheme has the advantages of robustness and scalability, and is easy for training and implementation. In addition, the scheme exhibits superior performance in the non-line-of-sight (NLOS) situation. Numerical results under various terrestrial environments are presented to demonstrate the feasibility of the proposed SOM scheme. Copyright © 2006 John Wiley & Sons, Ltd.