17890167
A Parallelism Analyzer for Conservative Parallel Simulation
Most small-scale simulation applications are implemented by sequential simulation techniques. As the problem size increases, however, sequential techniques may be unable to manage the time complexity of the simulation applications adequately. It is natural to consider re-implementing the corresponding large-scale simulations using parallel techniques, which have been reported to be successful in reducing the time complexity for several examples. However, parallel simulation may not be effective for every application. Since the implementation of parallel simulation for an application is usually very expensive, it is required to investigate the performance of parallel simulation for a particular application before re-implementing the simulation. The Chandy-Misra parallel, discrete-event simulation paradigm has been utilized in many large-scale simulation experiments, and several significant extensions have been based on it. Hence the Chandy-Misra protocol is adopted here as a basic model of parallel simulation to which our performance prediction techniques are applied. For an existing sequential simulation program based on the process interaction model, this paper proposes a technique for evaluating Chandy-Misra parallel simulation without actually implementing the parallel program. The idea is to insert parallelism analysis code into the sequential simulation program. When the modified sequential program is executed, the time complexity of the parallel simulation based on the Chandy-Misra protocol is computed. Our technique has been used to determine whether a giant Signaling System 7 simulation (sequential implementation) should be re-implemented using the parallel simulation approach. >
2805042
A new random walk model for PCS networks
This paper proposes a new approach to simplify the two-dimensional random walk models capturing the movement of mobile users in personal communications services (PCS) networks. Analytical models are proposed for the new random walks. For a PCS network with hexagonal configuration, our approach reduces the states of the two-dimensional random walk from (3n/sup 2/+3n-5) to n(n+1)/2, where n is the layers of a cluster. For a mesh configuration, our approach reduces the states from (2n2-2n+1) to (n/sup 2/+2n+4)/4 if n is even and to (n/sup 2/+2n+5)/4 if n is odd. Simulation experiments are conducted to validate the analytical models. The results indicate that the errors between the analytical and simulation models are within 1%. Three applications (i.e., microcell/macrocell configuration, distance-based location update, and GPRS mobility management for data routing) are used to show how our new model can be used to investigate the performance of PCS networks.
15619003
A Graphical User Interface Design for Network Simulation
Abstract This article describes a prototyping effort of a flexible graphical user interface (GUI) for a simulation tool called COPS. The GUI is designed to allow parameter setup for all modules in simulation model, and can be easily replaced by new GUIs implemented in different languages/graphical tools. This article provides design guidelines and implementation details of the flexible GUI.
16848330
A flexible graphical user interface for performance modeling
We identify three goals for the graphical user interface (GUI) of a network simulation environment: user friendliness, model re-usability, and application extensibility. We address the user friendliness issue by proposing a simple yet efficient approach to setup parameters for the simulation models. We address the application extensibility issue by a two-layer GUI architecture. The two layers are loosely-coupled, and the first layer can be easily replaced (without affecting the other components of the simulation environment). We address the model re-usability issue by subnetworks. Unlike most existing simulation packages where subnetwork is simply a method to group the nodes, the subnetwork construct in our approach is an integral part of the simulation environment (i.e., all operations for a basic node also apply to a subnetwork). The port concept is used to explicitly define the I/O relationship between a subnetwork and the outside world. Parameter dialog boxes are used to set up the parameters for a subnetwork conveniently. Finally, a simple stack mechanism is proposed to measure subnetwork-wide output statistics.<<ETX>>
5110930
A comparison study of the two-tier and the single-tier personal communications services systems
A two-tier PCS system integrates the high tier PCS system and the low tier PCS systems into a single system to provide the advantages of both tiers. Such a system is expected to provide better service (more available and more cost effective to the users) at the expense of the extra tier switching management. We compare the performance of the two-tier PCS system and the single low tier system in two aspects: the registration traffic and the service availability. Because of the tier management, the two-tier system generates more registration traffic than the single low tier system. Under the range of the input parameters in our study, we show that the two-tier system generates less than 10% extra registration traffic than the single low tier system in most cases and generates less than 20% registration traffic in the worst cases. It is clear that for the service availability, the two-tier system is better than the single one tier system. We also study the probability that a call is forced terminated in the single low tier system because the low tier becomes unavailable during the call (such a call can be continued in the two-tier system).
16744149
Performance Analysis for Dual Band PCS Networks
In a dual band personal communications services (PCS) network, heavy traffic areas are covered by microcells which overlay macrocells. In such a network, microcells and macrocells utilize different frequency bands. We propose an analytic model to study the performance of a dual band PCS architecture. Our model assumes that a PCS subscriber has a general residence time distribution in a microcell and the macrocell residence time distribution is derived from the microcell residence time distribution. An iterative algorithm is used to compute the overflow traffic from a microcell to its overlaid macrocell. Then, the call incompletion probability is computed by a macrocell model based on the overflow traffic. Our study indicates that the variance of the microcell residence time distribution and the number of microcells covered by a macrocell have significant effects on the call incompletion probability.
10756003
A 3-step approach for performance-driven whole-chip routing
We propose a 3-step approach for whole-chip detail routing. In the first step, we construct a performance-driven Steiner tree for each net ignoring the existence of other nets. In the second step, we optimally assign significant wire segments of all trees to the tracks of a two-dimensional, two-layer grid under the design rule constraint. Finally, in the third step, we complete the remaining local short connection between net terminals and those assigned wire segments and resolve any violations or congestion. We have incorporated this approach into an industrial VDSM design flow. Experimental results on large benchmark circuits implemented in a TSMC 0.18um CMOS process have demonstrated the effectiveness of the proposed approach. We achieve more than 14% improvement over a state-of-art commercial performance-driven router in a critical path delay. Our tool can be viewed as a preprocessor for a router. Users do not have to change their existing design flow. Only a small time-efficient step is needed to achieve the performance gain.
13450793
On IEEE 802.14 medium access control protocol
In this article we present a comprehensive survey on the architecture, protocol issues, and standard of the hybrid fiber coaxial (HFC) networks which are evolving from the existing residential CATV networks. We first describe the HFC architecture and discuss the problems in providing two-way communication. Then, we identify three important medium access control (MAC) issues in designing the IEEE 802.14 standard; namely, synchronization, upstream channel access modes, and collision resolution. Resolutions adopted by the IEEE 802.14 Committee are illustrated after giving a protocol overview. Key resolutions include compensating round trip correction (RTC), interleaving minislots of data and request concurrently, and resolving collisions by multiple collision resolution engines, using the n-ary tree plus p-persistence algorithm with a first transmission rule. A comparative summary of some draft proposals that lead to the standard is given. Finally, we pinpoint two headend algorithms, minislot allocation and request scheduling, which are left open in the standard. They do not affect interoperability but may have a critical impact on performance.
32397104
On 3-cutwidth critical graphs
The cutwidth of a graph G is the minimum congestion (the number of overlap edges) when G is embedded into a path. The cutwidth problem has been motivated from both applied and theoretical points of view. The characterization of forbidden subgraphs or critical graphs is always interesting in the study of a graph-theoretic parameter. In this paper we characterize the set of 3-cutwidth critical graphs by five specified elements.
5123114
Bayesian Regularization and Nonnegative Deconvolution for Time Delay Estimation
Bayesian Regularization and Nonnegative Deconvolution (BRAND) is proposed for estimating time delays of acoustic signals in reverberant environments. Sparsity of the nonnegative filter coefficients is enforced using an L1-norm regularization. A probabilistic generative model is used to simultaneously estimate the regularization parameters and filter coefficients from the signal data. Iterative update rules are derived under a Bayesian framework using the Expectation-Maximization procedure. The resulting time delay estimation algorithm is demonstrated on noisy acoustic data.
27475892
SILK: a simulated evolution router
The authors present a rip-up-and-rerouter based on a matrix representation scheme and simulated evolution technique for solving detailed routing problems in VLSI layout. The status of the routing region is represented as a matrix. Rip-up and reroute operations are emulated as matrix subtractions and additions, respectively. The quality of a routing result can be measured by a few simple matrix operations on the matrix. A rip-up and reroute switch-box/channel router, called SILK, using a simulated evolution technique has been implemented based on this representation alone. Experimental results showed that SILK, when solving all the benchmarks from the literature, outperformed WEAVER, the most successful switch-box router to date, in both quality and speed aspects. >