Shih-Yi Yuan

An O(n log n) path-based obstacle-avoiding algorithm for rectilinear Steiner tree construction

For the obstacle-avoiding rectilinear Steiner minimal tree problem, this paper presents an O(n log n)-time algorithm with theoretical optimality guarantees on a number of specific cases, which required O(n3) time in previous works. We propose a new framework to directly generate O(n) critical paths as essential solution components, and prove that those paths guarantee the existence of desirable solutions. The path-based framework neither generates invalid initial solutions nor constructs connected routing graphs, and thus provides a new way to deal with the OARSMT problem. Experimental results show that our algorithm achieves the best speed performance, while the average wirelength of the resulting solutions is only 1.1% longer than that of the best existing solutions.

Obstacle-Avoiding Rectilinear Steiner Tree Construction: A Steiner-Point-Based Algorithm

For the obstacle-avoiding rectilinear Steiner minimal tree (OARSMT) problem, we present a Steiner-point-based algorithm that achieves the best practical performance among existing heuristics. We first propose a new concept of Steiner point locations, creating a linear-space routing graph with satisfactory Steiner point candidates to resolve the bottleneck of most existing heuristics. Then, we propose a Steiner-point-based framework to yield a solution, which is close to the key to the handling of the OARSMT problem. Experimental results show that this algorithm achieves excellent solution quality and speed performance at the same time. We also extend the Steiner-point-based framework to the obstacle-avoiding preferred direction Steiner tree problem with a good performance.

Obstacle-avoiding rectilinear Steiner tree construction based on Steiner point selection

For the obstacle-avoiding rectilinear Steiner minimal tree (OARSMT) problem, this paper presents a Steiner-point based algorithm to achieve the best practical performance in wirelength and run time. Unlike many previous works, the Steiner-based framework is more focused on the usage of Steiner points instead of the handling of obstacles. This paper also proposes a new concept of Steiner point locations to provide an effective as well as efficient way to generate desirable Steiner point candidates. Experimental results show that this algorithm achieves the best solution quality in Θ(n log n) empirical time, which was originally generated by applying the maze routing on an Ω(n2)-space graph. The Steiner-point based framework and the new concept of Steiner point locations can be applied to future research on the OARSMT problem and its generations, such as the multi-layer OARSMT problem. Categories and Subject Descriptors: B.7.2 [Integrated Circuits]: Design Aids General Terms: Algorithms, Performance, Design

High-performance obstacle-avoiding rectilinear steiner tree construction

Rectilinear Steiner trees are used to route signal nets by global and detail routers in VLSI design for a long time. However, in current IC industry, there are significantly increasing obstacles to be considered, such as large-scale power networks, pre-routed nets, IP blocks, and antenna jumpers. Accordingly, the obstacle-avoiding rectilinear Steiner minimal tree (OARSMT) problem has become more important. In this article, we propose a new routing graph, obstacle-avoiding routing graph (OARG), for the OARSMT problem. Due to the important properties of OARG, we construct a 3-step algorithm and a local refinement scheme, which both can take advantage of these properties, to find a suboptimal solution efficiently. Furthermore, each step of our 3-step algorithm as well as the local refinement scheme has theoretical or practical benefits. Therefore, each of them can be applicable to other existing works for general or specific considerations such as efficiency or effectiveness. Extensive experimental results show that our method outperforms all existing works in terms of wirelength and achieves the best speed performance.

An Efficient Graph-Based Algorithm for ESD Current Path Analysis

The electrostatic discharge (ESD) problem has become a challenging reliability issue in nanometer-circuit design. High voltages that resulted from ESD might cause high current densities in a small device and burn it out, so on-chip protection circuits for IC pads are required. To reduce the design cost, the protection circuit should be added only for the IC pads with an ESD current path, which causes the ESD current path analysis problem. In this paper, we first introduce the analysis problem for ESD protection in circuit design. We then model the circuit as a constraint graph, decompose the ESD connected components (ECCs) linked with the pads, and apply breadth-first search (BFS) to identify the ECCs in each constraint graph and, thus, the current paths. Experimental results show that our algorithm can very efficiently and economically detect all ESD paths. For example, our algorithm can detect all ESD paths in a circuit with more than 1.3 million vertices in 1.39 s and consume only 44-MB memory on a 3.0-GHz Intel Pentium 4 PC. To the best of our knowledge, our algorithm is the first point tool available to the public for the ESD analysis.

ICI Self-Cancellation With Cosine Windowing in OFDM Transmitters Over Fast Time-Varying Channels

We propose the application of cosine windowing for the orthogonal frequency-division multiplexing (OFDM) systems to self-cancel intercarrier interference (ICI) in fast time-varying channels prior to receptions. With a time-domain cosine window immediately after the inverse discrete Fourier transform (IDFT) unit in OFDM transmitters, the ICI fractions from adjacent subcarriers significantly cancel one another at the expense of the orthogonality violation among subcarriers in the main lobe. As a result, the frequency-domain channel matrix reshaped by the cosine windowing can be closely approximated to a strictly banded matrix. In the complex exponential basis expansion model (CE-BEM), we present the estimation of the channel matrix with the assistance of the pilot clusters. Simulation results show that the receivers implementing the CE-BEM channel estimation and the low-complexity block turbo minimum mean square error (MMSE) equalization perform with considerably lower bit error rates (BER) even in very fast time-varying channels.

Quantum authentication protocol using entanglement swapping

In this paper, we use the technique of entanglement swapping to exchange quantum message among sharing parties. For Bell measurements, quantum teleportation can provide long-distance quantum transmission when sharing parties are disconnected. The proposed mutual authentication protocol has the capability to securely identify each other under an unsafe routing path. Eavesdropping and malicious nodes may exist in the routing path. For quantum authentication protocol, it is called location-release problem. The proposed approach can solve this problem. Furthermore, source can transfer quantum message to destination in a secure way.

Reversible quantum circuits and quantum transmission integrity

This paper proposes a novel work to design reversible quantum circuits. The function of this circuit is to investigate quantum transmission integrity in the quantum communication networks. This work is to verify quantum transmission sequence of a quantum frame by using reversible quantum model. This model designs control module to derive the correlation between two quantum strings: quantum input sequence and quantum output sequence. If a quantum frame reserves the correlation, then we can obtain quantum transmission sequence. So, quantum transmission integrity of a quantum frame can be verified.

Randomised and distributed methods for reliable peer-to-peer data communication in wireless ad hoc networks

Peer-to-peer (P2P) communications have attracted a great deal of attention from the network research community in recent years. However, due to the fundamental limitations of wireless environments, providing reliable data availability for P2P applications over wireless ad hoc networks is still a major challenge. To address the problem, a distributed and randomised scheme based on self-avoiding walks is proposed. The scheme concatenates disparate network layers, with the goal of recovering from routing failures that disrupt P2P data accessibility. In addition, a probabilistic approach is presented that explores the tradeoffs between several system parameters. Some new analysis tools, such as path coupling, are utilised which provide a better understanding of the systems operations. That the proposed concepts and techniques make a significant contribution to the design of effective and efficient P2P applications in wireless ad hoc networks is believed.

On the Banded Approximation of the Channel Matrix for Mobile OFDM Systems

In mobile orthogonal frequency-division multiplexing (OFDM) systems, a frequency-domain channel matrix represents the same-carrier channel frequency response in the diagonal and intercarrier interference (ICI) between the subcarriers in the off-diagonals, respectively. A variety of the banded equalizers manipulated the banded approximation of the channel matrix to be exploited by the low-complexity equalizations. In this paper, we derive a simple and tight lower bound on the variance of the individual coefficients in the channel matrix for insights into the banded approximations. We obtain the errors introduced with the banded approximation and the ICI-mitigation gains of the banded equalizers in simple closed forms. The derivations of the banded approximation errors (BAEs) are beneficially applicable to the equalizers that perform the minimum mean square error (MMSE) estimation with the banded channel matrix. Simulations show that both the block MMSE banded equalizers and the block turbo MMSE banded equalizers significantly reduce the error floors by considering the BAEs.