32529879
Performance comparison of control schemes for ABR service in ATM LANs
The ATM Forum has defined a new service category, called the available bit rate service (ABR), which is intended for applications requiring tightly constrained cell loss but no bound on the delay or delay variation. Appropriate traffic control schemes are necessary for ABR service to achieve very low cell loss and maximize the network resource utilization by taking advantage of the available bandwidth remaining after CBR/VBR services have been supported. This paper compares the performance of a burst-level traffic control scheme and a rate-based feedback control scheme, through simulation in an ATM LAN environment. Our results indicate that the burst-level control scheme is more suitable for loss-sensitive but delay-insensitive applications such as ABR service, because it requires nearly zero buffers to achieve zero cell loss and potentially high network resource utilization, at the cost of an acceptable burst transfer delay.
45698420
An Approximate Solution for Queuing Network Models of a Burst-Level Traffic Control Scheme in ATM WAN
Abstract This paper proposes a closed queuing network model for a burst-level traffic control scheme in ATM WAN environments, and explores solution techniques for this model. An approximate solution technique is developed to solve the closed queuing networks with multiple chains, chain-dependent service times, MSFIFO (multiple servers first-in first-out) queues, and simultaneous resource possession. Results of this study show that, with respect to the subnetwork algorithm of Souza e Silva and Muntz [Approximate solution for a class of non-product form queuing network models, Performance Evaluation (7) (1987) 221–242], our algorithm is advantageous, because (1) it is applicable to queuing network models with nested first-allocated/first-released passive resources; (2) it greatly reduces the complexity of the subnetwork algorithm by not decomposing the network and representing the complements; (3) it achieves higher accuracy and provides more reliable conservative estimates; and (4) it is easy to understand due to its straightforward interpretation.
15434765
A Dynamic Sub-vector Weighting Scheme for Image Retrieval with Relevance Feedback
In image retrieval with relevance feedback, feature components obtained from low-level descriptors are often weighted to reflect the high-level concepts and a user’s subjective perception embodied in the images labelled by the user in the feedback. However, the number of the labelled images is often small and an optimal weighting cannot be achieved in practice because of the singularity of the covariance matrix needed for weighting. To solve this problem, a dynamic sub-vector weighting scheme is proposed in this paper. In this scheme, a multi-dimensional feature vector is partitioned into multiple sub-vectors whose dimensions are dynamically adjusted to match the small number of available labelled images. Because of the lower dimensionality of the sub-vectors, the optimal weighting can be performed based on these sub-vectors, respectively. The multiple similarity scores obtained from sub-vector comparisons are then combined, as the final score, to rank the database images and determine the retrieval result. Experimental results demonstrated better performance of the proposed weighting scheme than some existing weighting schemes.
3919925
Calculation of Loss Probability in a Finite Size Partitioned Buffer for Quantitative Assured Service
This paper proposes an approximate yet accurate approach to calculate the loss probabilities in a finite size partitioned buffer system for the achievement of a quantitative assured service in differentiated services networks. The input is modeled as a fractional Brownian motion (FBM) process including J classes of traffic with different packet loss requirements. A first-in first- out buffer partitioned with J-1 thresholds is used to provide J loss priorities. Heuristic expressions of the loss probabilities for all the J classes are derived, and validated by computer simulations. The proposed loss calculation technique is then extended to a general input process by using the recently proposed traffic substitution technique, where both long-range dependent and short-range dependent input sources are equivalent to a properly parameterized FBM. We also apply the loss calculation to admission control, where the partition thresholds are optimally configured for quality of service guarantee and maximal resource utilization. Computer simulation results demonstrate that resource allocation based on the accurate finite buffer loss analysis results in much more efficient resource utilization than that based on the classic large-buffer overflow approximation.
28547446
Low-Complex Equalization for Single Carrier Systems Employing Cyclic Prefix over Time-Variant Channels
A simplified equalization method based on the band structure of the frequency domain channel matrix is proposed for the single carrier systems employing cyclic prefix (SC-CP) over time-varying wireless channels. Using both theoretical analysis and computer simulation, it is shown that the complexity of this method is proportional to the number of symbols in one SC-CP block and is less than that of traditional block equalization methods. We also show that they have similar performance.
3921961
Call admission control for integrated on/off voice and best-effort data services in mobile cellular communications
This paper proposes a call admission control (CAC) policy for a cellular system supporting voice and data services, and providing a higher priority to handoff calls than to new calls. A procedure for searching the optimal admission region is given. The traffic flow is characterized by a three-dimensional (3-D) birth-death model, which captures the complex interaction between the on/off voice and best-effort data traffic sharing the total resources without partition. To reduce complexity, the 3-D model is simplified to an exact (approximate) 2-D model for voice (data). The mathematical expressions are then derived for the performance measures and for the minimal amount of resources required for quality-of-service (QoS) provisioning. Numerical results demonstrate that: 1) the proposed CAC policy performs well in terms of QoS satisfaction and resource utilization; 2) the approximate 2-D model for data traffic can achieve a high accuracy in the traffic flow characterization; and 3) the admission regions obtained by the proposed search method agree very well with those obtained by numerically solving the mathematical equations. Furthermore, computer simulation results demonstrate that the impact of lognormal distributed data file size is not significant, and may be compensated by conservatively applying the Markovian analysis results.
10512188
An immune neural network used for classification
Based on an analysis of immune phenomena in nature and utilizing performances of ANN, a novel network mode, i.e., an immune neural network (INN), is proposed which integrates the immune mechanism and the function of neural information processing. The learning algorithm of an INN selects an excitation function and adaptive algorithm of the network. This model makes it easy for a user to utilize directly the characteristic information of a problem and to simplify the original structure by adjusting the excitation function with prior knowledge, improving the working efficiency and searching accuracy. A theoretical analysis and a simulation test for the twin-spiral problem show that, compared with an artificial neural network, INN is not only effective but also feasible. INN can simplify the structure of the existent model and show good working performance.