A new approach to over-the-cell channel routing

In this paper, we study the over-the-cell channel routing problem for the cell model in which all the pins are positioned along a horizontal line inside the corresponding cell. We present an efficient approach to the problem under the assumption that two metal layers are available for routing in each of the two over-the-cell regions and three metal layers are available for routing in the channel. The idea of our approach is to treat the three routing regions as a two-layer expanded channel, and to generate a two-layer channel routing solution first. The solution is then transformed into the final over-the-cell channel routing solution with the objective of minimizing the resulting width of the original channel. The transformation problem is reduced to the constrained two-processor scheduling problem for which we develop a polynomial time optimal algorithm. Our approach has been implemented in C language, and experimental results are also provided to support it