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http://oasis.postech.ac.kr/handle/2014.oak/418
2018-07-20T00:37:44ZInverse Multipath Fingerprinting for Millimeter Wave V2I Beam Alignment
http://oasis.postech.ac.kr/handle/2014.oak/51044
Title: Inverse Multipath Fingerprinting for Millimeter Wave V2I Beam Alignment
Authors: VA, VUTHA; CHOI, JUNIL; SHIMIZU, TAKAYUKI; BANSAL, GAURAV; HEATH, ROBERT
Abstract: Efficient beam alignment is a crucial component in millimeter wave systems with analog beamforming, especially in fast-changing vehicular settings. This paper proposes to use the vehicle's position (e.g., available via GPS) to query a multipath fingerprint database, which provides prior knowledge of potential pointing directions for reliable beam alignment. The approach is the inverse of fingerprinting localization, where the measured multipath signature is compared to the fingerprint database to retrieve the most likely position. The power loss probability is introduced as a metric to quantify misalignment accuracy and is used for optimizing candidate beam selection. Two candidate beam selection methods are developed, where one is a heuristic while the other minimizes the misalignment probability. The proposed beam alignment is evaluated using realistic channels generated from a commercial ray-tracing simulator. Using the generated channels, an extensive investigation is provided, which includes the required measurement sample size to build an effective fingerprint, the impact of measurement noise, the sensitivity to changes in traffic density, and beam alignment overhead comparison with IEEE 802.11ad as the baseline. Using the concept of beam coherence time, which is the duration between two consecutive beam alignments, and parameters of IEEE 802.11ad, the overhead is compared in the mobility context. The results show that while the proposed approach provides increasing rates with larger antenna arrays, IEEE 802.11ad has decreasing rates due to the higher beam training overhead that eats up a large portion of the beam coherence time, which becomes shorter with increasing mobility.2018-05-01T00:00:00ZScaling Laws of Ergodic Spectral Efficiency of MIMO Ad-hoc Networks
http://oasis.postech.ac.kr/handle/2014.oak/40924
Title: Scaling Laws of Ergodic Spectral Efficiency of MIMO Ad-hoc Networks
Authors: LEE, JUNSE; LEE, NAMYOON; Baccelli, François
Abstract: In this paper, we examine the benefits of multiple antenna communication in random wireless networks, the topology of which is modeled by stochastic geometry. The setting is the Poisson bipolar model introduced in [1], which is a natural model for ad-hoc and device-to-device networks. The primary finding is that, with the knowledge of channel state information between a receiver and its associated transmitter, by zero-forcing successive interference cancellation, and for appropriate antenna configurations, the ergodic spectral efficiency can be made to scale linearly with both: 1) the minimum of the number of transmit and receive antennas and 2) the density of nodes. This scaling law is achieved by using the multiple transmit antennas to send multiple data streams (e.g., through an open-loop transmission method) and by exploiting the receive antennas to cancel interference. Furthermore, when a receiver is able to learn channel state information from a certain number of near interferers, higher scaling gains can be achieved when a successive interference cancellation method is used. Both results require rich scattering environments. A major implication of the derived scaling laws is that, under this scattering assumption, spatial multiplexing transmission methods are essential for obtaining better and eventually optimal scaling laws in random wireless networks with multiple antennas.2018-04-01T00:00:00ZThreshold voltage variation depending on single grain boundary and stored charges in an adjacent cell for vertical silicon-oxide-nitride-oxide-silicon (SONOS) NAND flash memory
http://oasis.postech.ac.kr/handle/2014.oak/40929
Title: Threshold voltage variation depending on single grain boundary and stored charges in an adjacent cell for vertical silicon-oxide-nitride-oxide-silicon (SONOS) NAND flash memory
Authors: OH, HYEON GWAN; JIWON, KIM; BAEK, ROCK HYUN; LEE, JEONG SOO
Abstract: The effects of single grain boundary (SGB) position and stored electron charges in an adjacent cell in silicon–oxide–nitride–oxide–silicon (SONOS) structures on the variations of threshold voltage (V th) were investigated using technology computer-aided design (TCAD) simulation. As the bit line voltage increases, the SGB position causing the maximum V th variation was shifted from the center to the source side in the channel, owing to the drain-induced grain barrier lowering effect. When the SGB is located in the spacer region, the potential interaction from both the SGB and the stored electron charges in the adjacent cell becomes significant and thus resulting in larger V th variation. In contrast, when the SGB is located at the center of the channel, the peak position of potential barrier is shifted to the center, so that the influence of the adjacent cell is diminished. As the gate length is scaled down to 20 nm, the influence of stored charges in adjacent cells becomes significant, resulting in larger V th variations.2018-04-01T00:00:00ZIEEE 802.11ad-Based Radar: An Approach to Joint Vehicular Communication-Radar System
http://oasis.postech.ac.kr/handle/2014.oak/50101
Title: IEEE 802.11ad-Based Radar: An Approach to Joint Vehicular Communication-Radar System
Authors: KUMARI, PREETI; CHOI, JUNIL; González-Prelcic, NURIA; HEATH, ROBERT
Abstract: Millimeter-wave (mmWave) radar is widely used in vehicles for applications such as adaptive cruise control and collision avoidance. In this paper, we propose an IEEE 802.11ad-based radar for long-range radar (LRR) applications at the 60 GHz unlicensed band. We exploit the preamble of a single-carrier physical layer frame, which consists of Golay complementary sequences with good correlation properties that make it suitable for radar. This system enables a joint waveform for automotive radar and a potential mmWave vehicular communication system based on the mmWave consumer wireless local area network standard, allowing hardware reuse. To formulate an integrated framework of vehicle-to-vehicle communication and LRR, we make typical assumptions for LRR applications, incorporating the full duplex radar operation. This new feature is motivated by the recent development of systems with sufficient isolation and self-interference cancellation. We develop single- and multi-frame radar receiver algorithms for target detection as well as range and velocity estimation for both single- and multi-target scenarios. Our proposed radar processing algorithms leverage channel estimation and time-frequency synchronization techniques used in a conventional IEEE 802.11ad receiver with minimal modifications. Analysis and simulations show that in a single-target scenario, a gigabits-per-second data rate is achieved simultaneously with cm-level range accuracy and cm/s-level velocity accuracy. The target vehicle is detected with a high probability (above 99.99%) at a low false alarm rate of 10(-6) for an equivalent isotropically radiated power of 40 dBm up to a vehicle separation distance of about 200 m. The proposed IEEE 802.11ad-based radar meets the minimum accuracy/resolution requirement of range and velocity estimates for LRR applications.2018-04-01T00:00:00Z