6282895
Timing analysis including clock skew
Clock skew is an increasing concern for high-speed circuit designers. Circuit designers use transparent latches and skew-tolerant domino circuits to hide clock skew from the critical path and take advantage of shared portions of the clock network to budget less skew between nearby elements than across the entire die, but current timing analysis algorithms do not handle correlated clock skews. This paper extends the Sakallah-Mudge-Olukotun (SMO) latch-based timing analysis to include different amounts of clock skew between different elements. The key change is that departure times from each latch must be defined with respect to launching clocks so that the skew between the launching and receiving clocks can be determined at each receiver. The exact analysis leads to an explosion in the number of timing constraints, but most constraints are not tight in practical situations and a modified version of the Szymanski-Shenoy relaxation algorithm gives exact results with only a small increase in runtime. The timing analysis formulation also captures the effects of skew on edge-triggered flip-flops, domino circuits, and min-delay constraints. Our exact algorithm, applied to a supercomputer node controller with over 12000 clocked elements, finds the system can run 50-90 ps faster than a single skew analysis would predict and requires searching fewer than 4% more latch departures than conventional algorithms. With the less conservative skew budgets enabled by better timing analysis, we expect clocked systems will remain viable to multi-GHz frequencies.
53748903
A Framework for Designing Reusable Analog Circuits
12123652
Analysis of blocking dynamic circuits
In order for dynamic circuits to operate correctly, their inputs must be monotonically rising during evaluation. Blocking dynamic circuits satisfy this constraint by delaying evaluation until all inputs have been properly setup relative to the evaluation clock. By viewing dynamic gates as latches, we demonstrate that the optimal delay of a blocking dynamic gate may occur when the setup time is negative. With blocking dynamic circuits, cascading low-skew dynamic gates allows each dynamic gate to tolerate a degraded input level. The larger noise margin provides greater flexibility with the delay vs. noise margin trade-off (i.e. the circuit robustness vs. speed tradeoff). This paper generalizes blocking dynamic circuits and provides a systematic approach for assigning clock phases, given delay and noise margin constraints. Using this framework, one can analyze any logic network consisting of blocking dynamic circuits.
38675279
On-Line Learning Control for Discrete Nonlinear Systems Via an Improved ADDHP Method
This paper mainly discusses a generic scheme for on-line adaptive critic design for nonlinear system based on neural dynamic programming (NDP), more exactly, an improved action-depended dual heuristic dynamic programming (ADDHP) method. The principal merit of the proposed method is to avoid the model neural network which predicts the state of next time step, and only use current and previous states in the method, as makes the algorithm more suitable for real-time or on-line application for process control. In this paper, convergence proof of the method will also be given to guarantee the control to reach the optimal. At last, simulation result verifies the performance.
53235721
Establishing pairwise keys in distributed sensor networks
Pairwise key establishment is a fundamental security service in sensor networks; it enables sensor nodes to communicate securely with each other using cryptographic techniques. However, due to the resource constraints on sensor nodes, it is not feasible to use traditional key management techniques such as public key cryptography and key distribution center (KDC). A number of key predistribution techniques have been proposed for pairwise key establishment in sensor networks recently. To facilitate the study of novel pairwise key predistribution techniques, this paper develops a general framework for establishing pairwise keys between sensor nodes using bivariate polynomials. This paper then proposes two efficient instantiations of the general framework: a random subset assignment key predistribution scheme, and a hypercube-based key predistribution scheme. The analysis shows that both schemes have a number of nice properties, including high probability, or guarantee to establish pairwise keys, tolerance of node captures, and low storage, communication, and computation overhead. To further reduce the computation at sensor nodes, this paper presents an optimization technique for polynomial evaluation, which is used to compute pairwise keys. This paper also reports the implementation and the performance of the proposed schemes on MICA2 motes running TinyOS, an operating system for networked sensors. The results indicate that the proposed techniques can be applied efficiently in resource-constrained sensor networks.
14012169
Efficient k nearest neighbor queries on remote spatial databases using range estimation
We propose a k-NN query processing algorithm that uses one or more window queries to retrieve the nearest neighbors of a given query point. We also propose two different methods to estimate the ranges to be used by the window queries. Each range estimation method requires different statistical knowledge about the spatial databases. Our experiments on the TIGER data allow us to study the behavior of the proposed algorithm using different range estimation methods. Apart from not requiring direct access to the spatial indices, the window queries used in the proposed algorithm can be easily supported by non-spatial database systems containing spatial objects.
5968490
Attack-resistant location estimation in sensor networks
Many sensor network applications require sensors' locations to function correctly. Despite the recent advances, location discovery for sensor networks in hostile environments has been mostly overlooked. Most of the existing localization protocols for sensor networks are vulnerable in hostile environments. The security of location discovery can certainly be enhanced by authentication. However, the possible node compromises and the fact that location determination uses certain physical features (e.g., received signal strength) of radio signals make authentication not as effective as in traditional security applications. This paper presents two methods to tolerate malicious attacks against beacon-based location discovery in sensor networks. The first method filters out malicious beacon signals on the basis of the "consistency" among multiple beacon signals, while the second method tolerates malicious beacon signals by adopting an it era lively refined voting scheme. Both methods can survive malicious attacks even if the attacks bypass authentication, provided that the benign beacon signals constitute the majority of the "consistent" beacon signals. This paper also presents the implementation of these techniques on MICA2 motes running TinyOS, and the evaluation through both simulation and field experiments. The experimental results demonstrate that the proposed methods are promising for the current generation of sensor networks.
30709401
T-graphs and the channel assignment problem
Abstract T -colorings arose from the channel assignment problem in communications. Given a finite set T of non-negative integers, a T -coloring of a simple graph G is an assignment of a non-negative integer (channel) on every vertex of G , such that the difference of channels of two adjacent vertices does not fall in T . The T -span of G , denoted by sp T ( G ), is the minimum span among all possible T -colorings of G , where the span of a T -coloring is the difference between the largest and smallest channels used. This article applies T -graphs to explore the sets T that belong to these two collections: G = { T : greedy (or first-fit) algorithm provides T -spans for all complete graphs}, and E = { T : spt ( G ) = sp T ( K χ ( G ) ) for all graphs G , where χ is the chromatic number}. Given T , its T -graph has the vertex set of all non-negative integers so that two vertices are adjacent if their difference does not fall in T . We show that for any a ∈ Z + , the T -graph of aT is isomorphic to a disjoint product of a copies of the T -graph of T , where aT is the set obtained by multiplying every element of T by a . Based on this characterization, the following two results are attained. For any a ∈ Z + , T ∈ E if and only if aT ∈ E , and T ∈ G if and only if aT ∈ G . The second fact has been proven by Cozzens and Roberts (1991) from a different approach. We will completely solve the family of sets T = {0, s , s + 1,…, l } by providing a different proof of the fact T ∈ G (Tesman, 1989), and showing that T ∈ E if and only if l is a multiple of s . In addition, complete solutions for a more general family are obtained: for any a , s , l ∈ Z + with s ⩽ l , T = {0, as , a ( s + 1), a ( s + 2),…, al } ∪ A ∈ E , and T ϵ E if and only if l = ms for some m , where A ⊆{ as + 1, as + 2, …, al - 1}.