A Density-Based General Greedy Channel Routing Algorithm in VLSI Design Automation.

One of the most important forms of routing strategies is called channel routing . This approach allows us to reduce the extremely difficult VLSI layout problem to a collection of simpler subproblems. For channel routing problems, most frequently mentioned heuristic algorithms use parameters derived from experiments to approach the routing solution without carefully considering the effect of each selected wire segment to the final routing solution. In this dissertation, we propose a new channel routing algorithm in the two-layer restricted-Manhattan routing model (2-RM) in detail. There are three phases involved in developing the new routing algorithm. In the first phase, we distinguish one type of wire from the others using some optimality criteria, which makes the selection of a set of best horizontal wire segments for a track more effective so that good performance of the generated routing solutions can be achieved. In the second phase, we develop a theoretical framework related to two major data structures, column density and vertical constraint graph, which effectively improves search efficiency and routing performance. Finally in the third phase, we develop an efficient powerful heuristic channel routing algorithm based on the concepts shown in phase one and the theoretical framework proposed in phase two. We highlight the application of our algorithm to the channel routing problems in the three-layer restricted-Manhattan overlap (3-RM-O) and three-layer Manhattan overlay (3-M-O) routing models. On many tests we have conducted on the examples known in the literature, our algorithm has performed as well or better than the existing algorithms in both 2-RM and 3-M-O routing models. Our experiments show that our approach has the potential to outperform other algorithms in other routing models

Crossing-aware channel routing for photonic waveguides

pre-printAbstract-Silicon photonics technology is progressing at a rapid pace. Despite greatly expanded manufacturing capability, physical design of integrated optical circuits currently lacks the level of automation found in VLSI design. A key component of integrated optic design is waveguide routing; however, unlike VLSI, where signal nets are routed with metal layers and vias, photonic waveguides are fabricated in planar substrates. For many applications, our studies show that the waveguide routing problem can be formulated as planar channel routing. Signal losses become a major factor due to the insertion losses of planar waveguide crossings. Channel routing must therefore take into account these losses. This paper investigates methods for adapting traditional VLSI channel routing techniques for integrated optics - specifically, a technique based on left-edge-style track assignment. We show how incorporating waveguide crossing constraints into the underlying constraint model affects the routing solution, and describe the necessary modifications and extensions to the routing technique to properly exploit optical technology. We implement the channel router, describe the experimental results, and compare the cost of solutions with respect to waveguide crossings, corresponding to signal loss, and channel height

Channel routing: Efficient solutions using neural networks

Neural network architectures are effectively applied to solve the channel routing problem. Algorithms for both two-layer and multilayer channel-width minimization, and constrained via minimization are proposed and implemented. Experimental results show that the proposed channel-width minimization algorithms are much superior in all respects compared to existing algorithms. The optimal two-layer solutions to most of the benchmark problems, not previously obtained, are obtained for the first time, including an optimal solution to the famous Deutch\u27s difficult problem. The optimal solution in four-layers for one of the be lchmark problems, not previously obtained, is obtained for the first time. Both convergence rate and the speed with which the simulations are executed are outstanding. A neural network solution to the constrained via minimization problem is also presented. In addition, a fast and simple linear-time algorithm is presented, possibly for the first time, for coloring of vertices of an interval graph, provided the line intervals are given

Generating efficient layouts from optimized MOS circuit schematics

Also issued as Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1988.Includes bibliographical references.Supported by the U.S. Air Force--Office of Scientific Research. AFOSR-86-0164 Supported in part by a National Science Foundation Graduate Fellowship. Supported in part by Thinking Machines Corporation. 2305/B4Donald George Baltus

Minimizing Channel Density with Movable Terminals

We give algorithms to minimize density for VLSI channel routing problems with terminals that are movable subject to certain constraints. The main cases considered are channels with linear order constraints, channels with linear order constraints and separation constraints, channels with movable modules containing fixed terminals, and channels with movable modules and terminals. In each case, we improve previous results for running time and space by a factor of L/\lgn and L, respectively, where L is the channel length, and n is the number of terminals

A Heuristic for Manhattan Routing

Coordinated Science Laboratory was formerly known as Control Systems LaboratorySemiconductor Research Corporation / RSCH 83-01-03

Doctor of Philosophy

dissertationRecent breakthroughs in silicon photonics technology are enabling the integration of optical devices into silicon-based semiconductor processes. Photonics technology enables high-speed, high-bandwidth, and high-fidelity communications on the chip-scale-an important development in an increasingly communications-oriented semiconductor world. Significant developments in silicon photonic manufacturing and integration are also enabling investigations into applications beyond that of traditional telecom: sensing, filtering, signal processing, quantum technology-and even optical computing. In effect, we are now seeing a convergence of communications and computation, where the traditional roles of optics and microelectronics are becoming blurred. As the applications for opto-electronic integrated circuits (OEICs) are developed, and manufacturing capabilities expand, design support is necessary to fully exploit the potential of this optics technology. Such design support for moving beyond custom-design to automated synthesis and optimization is not well developed. Scalability requires abstractions, which in turn enables and requires the use of optimization algorithms and design methodology flows. Design automation represents an opportunity to take OEIC design to a larger scale, facilitating design-space exploration, and laying the foundation for current and future optical applications-thus fully realizing the potential of this technology. This dissertation proposes design automation for integrated optic system design. Using a buildingblock model for optical devices, we provide an EDA-inspired design flow and methodologies for optical design automation. Underlying these flows and methodologies are new supporting techniques in behavioral and physical synthesis, as well as device-resynthesis techniques for thermal-aware system integration. We also provide modeling for optical devices and determine optimization and constraint parameters that guide the automation techniques. Our techniques and methodologies are then applied to the design and optimization of optical circuits and devices. Experimental results are analyzed to evaluate their efficacy. We conclude with discussions on the contributions and limitations of the approaches in the context of optical design automation, and describe the tremendous opportunities for future research in design automation for integrated optics

Integrating LEO Satellite Constellations into Internet Backbone

Low Earth Orbit (LEO) satellite constellations have been used for ubiquitous and flexible Internet access services. However, a number of problems related to the integration of terrestrial with satellite hosts should be resolved for the effective exploitation of LEO constellations. LEO constellations are different from terrestrial Internet because of its special properties, which result in a lot of problems. A key issue is how to route Internet packets to the LEO constellation. In the thesis (1) the background of LEO constellations was introduced; (2) the obstacles of routing between the satellites and Internet were outlined; (3) The particular problem, which must be solved, is the routing burst stream traffic in LEO satellite constellations. Two novel routing algorithmsCControl Route Transmission (CRT) and CRT with bandwidth allocation (BCRT)Cwere utilized to address the bursts routing problem. CRT is an adaptive protocol which is able to minimize the congestion in the constellations. BCRT is a CRT extension which is allowed to class the traffic (e.g. video) with different QoS requirements and guarantees. Both of CRT and BCRT work in time epochs. Routes are computed on the basis of a directed weighted graph representing the global traffic traveling in the constellations. Both CRT and BCRT were evaluated via simulation and compared with other proposals in the literatures. The results showed that CRT is a simple algorithm, but the strategy produced by CRT could avoid the congestion and enhance the global resource usage in different traffic conditions. Moreover, the explicit reservation and reroute of BCRT greatly improve the performance of CRT. In particular, the dropping rate of BCRT is very low and the average delivery time is comparable with other proposals in the literatures.Low Earth Orbit (LEO) satellite constellations have been used for ubiquitous and flexible Internet access services. However, a number of problems related to the integration of terrestrial with satellite hosts should be resolved for the effective exploitation of LEO constellations. LEO constellations are different from terrestrial Internet because of its special properties, which result in a lot of problems. A key issue is how to route Internet packets to the LEO constellation. In the thesis (1) the background of LEO constellations was introduced; (2) the obstacles of routing between the satellites and Internet were outlined; (3) The particular problem, which must be solved, is the routing burst stream traffic in LEO satellite constellations. Two novel routing algorithmsCControl Route Transmission (CRT) and CRT with bandwidth allocation (BCRT)Cwere utilized to address the bursts routing problem. CRT is an adaptive protocol which is able to minimize the congestion in the constellations. BCRT is a CRT extension which is allowed to class the traffic (e.g. video) with different QoS requirements and guarantees. Both of CRT and BCRT work in time epochs. Routes are computed on the basis of a directed weighted graph representing the global traffic traveling in the constellations. Both CRT and BCRT were evaluated via simulation and compared with other proposals in the literatures. The results showed that CRT is a simple algorithm, but the strategy produced by CRT could avoid the congestion and enhance the global resource usage in different traffic conditions. Moreover, the explicit reservation and reroute of BCRT greatly improve the performance of CRT. In particular, the dropping rate of BCRT is very low and the average delivery time is comparable with other proposals in the literatures