Ma J.,University of Washington |
Karadayi K.,University of Washington |
Ali M.,Texas Instruments |
Kim Y.,University of Washington |
Kim Y.,Creative IT
Ultrasonics | Year: 2014
Phase rotation beamforming (PRBF) is a commonly-used digital receive beamforming technique. However, due to its high computational requirement, it has traditionally been supported by hardwired architectures, e.g., application-specific integrated circuits (ASICs) or more recently field-programmable gate arrays (FPGAs). In this study, we investigated the feasibility of supporting software-based PRBF on a multi-core DSP. To alleviate the high computing requirement, the analog front-end (AFE) chips integrating quadrature demodulation in addition to analog-to-digital conversion were defined and used. With these new AFE chips, only delay alignment and phase rotation need to be performed by DSP, substantially reducing the computational load. We implemented the delay alignment and phase rotation modules on a Texas Instruments C6678 DSP with 8 cores. We found it takes 200 μs to beamform 2048 samples from 64 channels using 2 cores. With 4 cores, 20 million samples can be beamformed in one second. Therefore, ADC frequencies up to 40 MHz with 2:1 decimation in AFE chips or up to 20 MHz with no decimation can be supported as long as the ADC-to-DSP I/O requirement can be met. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography. One DSP being able to handle both beamforming and back-end processing could lead to low-power and low-cost ultrasound machines, benefiting ultrasound imaging in general, particularly portable ultrasound machines. © 2013 Elsevier B.V. All rights reserved.
Shin I.,KAIST |
Kim J.-J.,Creative IT |
Lin Y.-S.,IBM |
Proceedings of the International Symposium on Low Power Electronics and Design | Year: 2013
We present a new timing error correction scheme which allows each pipeline stage to halt for one cycle only. The small timing penalty for the error correction operation in the proposed scheme makes it possible to eliminate the extra timing guardband that was needed to accommodate timing uncertainty due to process variations. As a result, lower supply voltage can be used with the proposed scheme for low power operations. Compared to the previous 1-cycle error correction scheme which uses two-phase transparent latch based pipeline , the proposed scheme can be applied to the pipeline based on more popular clocking elements such as flip-flop or pulsed latch. © 2013 IEEE.
Shin I.,KAIST |
Kim J.-J.,Creative IT |
Proceedings of the Asia and South Pacific Design Automation Conference, ASP-DAC | Year: 2014
We present a new 1-cycle timing error correction method, which enables aggressive voltage scaling in a pipelined architecture. The proposed method differs from the state-of-the-art in that the pipeline stage where the timing error occurs can continue to receive input data without halting to avoid data collision. The feature allows the pipeline to avoid recurring clock gating when timing errors happen at multiple stages or timing errors continue to occur at a certain stage. Compared to a state-of-the-art method, the proposed method shows 2-6% energy reduction for a 5-stage pipeline and 7-11% reduction for a 10-stage pipeline. In addition, the proposed logic to propagate clock gating signal is much simpler than that of the previous method  by eliminating reverse propagation path of clock gating signal. © 2014 IEEE.
Yu S.-C.,Creative IT |
Yuh J.,Korea Aerospace University |
Ocean Engineering | Year: 2013
Conventional underwater manipulation is performed by a remotely operated vehicle (ROV) equipped with a rigidly connected multi-link arm. However, accurate manipulation requires the ROV to have excellent maneuverability, which limits the design flexibility and capabilities of the vehicle. This paper instead proposes the use of a small, deployable, and highly maneuverable agent ROV as an end effector, which is connected to the main vehicle by a flexible smart cable. This cable tracks the relative position of the agent, thus eliminating the need for additional positioning sensors and allowing significant size reduction for the agent. In addition, to compensate for the limited lifting capability of the small agent, it is equipped with active buoyancy control. The proposed system can be applied to common autonomous underwater vehicles (AUVs) with minimal modification for coarse station-keeping. The whole system is operated as a conventional AUV under normal operating conditions, but the agent is deployed when manipulation or precise monitoring is necessary. Numerical simulations were performed for dynamic analysis and prototype design of the agent vehicle, and this design was implemented as a model-scale system for experiments in a test tank. This implementation confirmed the feasibility and potential capabilities of the proposed manipulation system concept. © 2013 Elsevier Ltd.
Yum D.H.,Pohang University of Science and Technology |
Lee P.J.,Pohang University of Science and Technology |
Lee P.J.,Creative IT
IEEE Transactions on Wireless Communications | Year: 2012
As wireless sensor networks are often deployed in adverse or hostile environments, key management schemes are required for sensor nodes. The random key predistribution (RKP) scheme is a probabilistic key management scheme where each node is preloaded with a subset of keys that are randomly selected from a pool of keys. If a pair of neighbor nodes have a common key, it can be used to establish a secure link between the nodes. The q-composite RKP scheme requires that a pair of neighbor nodes have at least q common keys for a secure link. In this article, we show that the previous security analysis (i.e., resilience against node capture) of the q-composite RKP scheme is inaccurate and present new formulae for resilience in the RKP scheme and the q-composite RKP scheme. © 2002-2012 IEEE.