Channel routing and crosstalk minimization are important issues while we talk about high-performance circuits for VLSI physical design automation. Interconnection among the net terminals satisfying constraints in an intelligent way is a necessity to realize a circuit in a minimum possible area, as this is a primary requirement to reduce cost as well as to increase yield. In this paper, along with area minimization, the performance of the computed circuits has also been enhanced by computing routing solutions with a specified amount of bottleneck crosstalk in two-layer channel routing. Usually, crosstalk is measured by the amount of overlapping of a pair of nets assigned to adjacent tracks. The crosstalk minimization problem in the reserved two-layer Manhattan channel routing model is NP-hard. Thus, in this paper, heuristic algorithms have been devised to optimize bottleneck crosstalk in order to augment circuit performance in two-layer channel routing. Experimental results obtained are highly encouraging.

Algorithms for Minimizing Bottleneck Crosstalk in Two-Layer Channel Routing

In graph theory, generation of random graphs finds a wide range of applications in different scheduling problems, approximation algorithms, problems involving modeling and simulation, different database applications, and obviously to test the performance of any algorithm. The algorithm, which has been devised in this paper, is mainly for the purpose of providing test bed for checking performance of other algorithms. It generates different non-isomorphic graph instances of a given order and having unique number of edges. The number of such instances possible for a graph of given order has also been subsequently formulated. Different such graph instances of different orders, generated in a uniform computing environment, and the computing time required for such generations have also been included in this paper. The simplicity and efficiency of the algorithm, subsequently proved in the paper, give us a new insight in the area of random graph generation and have called for further research scope in the domain.

Generation of Simple, Connected, Non-isomorphic Random Graphs

Crosstalk appears in various electrical circuits and chip design. This is due to stretches of overlapping wires that produce parasitic coupling between adjacent signal lines. In VLSI design, crosstalk creates a lot of problems. Crosstalk minimization problem is NP complete. The research is to find the solution with minimum crosstalk by using signal transition avoidance technique. We use simulated annealing algorithm to search for the optimal layout pattern. Different generation sequence of a graph give diverse alternatives for horizontal constraint graph of a VLSI channel. The energy function can be designed to take care of crosstalk in the channel. The optimization result, gives the routing solution with minimum crosstalk and minimal total energy. We reduce total energy through capacitance by rearranging wire signal transition. The crosstalk noise model is a proposed concept of effective signal transition consideration. The proposed technique is developed based on a decreasing coupling technique exhibiting a total energy of 6.9 as compared to average energy of all possible patterns. In addition, the result of optimal pattern is 24.4% less than cost of the original layout pattern.

Crosstalk minimization in VLSI design using signal transition avoidance

Hardness of crosstalk minimization in two-layer channel routing

In this paper we present the end to end routing feature of computer networks, having user requests as central requirements for achieving optimal communication. End to end routing is the technology making people able to communicate via user-centered p2p applications, minimizing a network's overall workloads, while keeping track of user application demands. Considered a research topic with a lot of focus on efficiency, portability, robustness and mostly reliability, user-centered design and it's depiction in computer networks has been made possible, through the persistent routing aspect of networking technology.

User-centered end to end optimal persistent routing

Crosstalk minimization is one of the most important high performance aspects in interconnecting VLSI circuits. With advancement of fabrication technology, devices and interconnecting wires are placed in closer proximity and circuits operate at higher frequencies. This results in crosstalk between wire segments. Crosstalk minimization problem for the reserved two-layer Manhattan channel routing is NP-hard, even if the channel instances are free from any vertical constraint (simplest channel instances). In this paper we have developed heuristic algorithms for computing reduced crosstalk two-layer channel routing solutions for simplest as well as general channel instances. In general, the results obtained are highly encouraging.

http://inet.vidyasagar.ac.in:8080/jspui/bitstream/123456789/711/2/JPS10art16.pdf

Algorithms for Reducing Crosstalk in Two-Layer Channel Routing

Algorithms for high performance two-layer channel routing

In this paper we have developed algorithms for generating random channel instances for their use in computing channel routing solutions in VLSI physical design. Channel instances are usually of two types: simple and general, and there are usually two kinds of inherent constraints involving channel routing problem: horizontal constraint and vertical constraint. Simple channel instances do not contain any vertical constraint, whereas, general channel instances contain both horizontal as well as vertical constraints. Most of the optimization problems in two-, three-, and multi-layer channel routing are NP-hard and, in fact, very few are polynomial time computable. Hence for each of the NP-hard problems in channel routing, it is unlikely to design a polynomial time deterministic algorithm. Developing heuristic algorithm may be a probable way out that hopefully provides good solutions for most of the instances available in literature. Novelty of a heuristic algorithm is judged better if it works for a variety of large number of randomly generated instances of the problem.

Algorithms for Generating Random Channel Instances for Channel Routing Problem

In this paper we develop algorithms for generating random channel specifications of channel routing problem in VLSI design. A channel is a rectangular routing region containing two sets of fixed terminals on two of its opposite sides and the other two opposite sides (of the rectangle) are open ends, may or may not contain any terminal of a net but the terminal position is not fixed before a routing solution is computed. Most of the problems in two-, three-, and multi-layer channel routing are beyond polynomial time computable. Hence for each of these problems it is unlikely to design a polynomial time deterministic algorithm. Developing heuristic algorithm might be a probable way out that hopefully provides good solutions for most of the instances occur in practice. Novelty of a heuristic algorithm is judged better if it works for a variety of large number of randomly generated instances of the problem. In fact, convergence of results of a heuristic algorithm is well established when the algorithm of a problem is executed for a huge number of randomly generated similar instances and the final result is computed making an average on all of them.

Debojit Kundu

Papers

Algorithms for Reducing Crosstalk in Two-Layer Channel Routing

Algorithms for high performance two-layer channel routing

Algorithms for Generating Random Channel Instances for Channel Routing Problem

Generation of random channel specifications for channel routing problem