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Using a unique dataset collected from a large classified ads website in China, we investigate the future purchase probability of coupon redeemers, particularly how it differs between users who redeem coupons right after the coupon drop and those who delay redemptions. We find that, coupon redeemers have a higher probability to make future purchases than non-redeemers no matter on which day the coupon...
Delay performance is crucial in distributed storage systems and it can greatly impact user experience. Both direct and k-access reads are common in storage systems. However, much of previous research only considers k-access reads and many schemes, such as Redundant Scheme, are only shown to reduce delay for k-access reads. We have no idea whether those existing schemes can also work for direct reads...
Our paper presents solutions using erasure coding, parallel connections to storage cloud and limited chunking (i.e., dividing the object into a few smaller segments) together to significantly improve the delay performance of uploading and downloading data in and out of cloud storage. TOFEC is a strategy that helps front-end proxy adapt to level of workload by treating scalable cloud storage (e.g....
Network performance has been the subject of much research over the past decades. However, the impact of performance on a network's users is much less understood from a scientific standpoint. This gap in our knowledge is particularly stark since the primary role of real-world network performance is to increase user satisfaction, and encourage user behaviors that lead to greater monetization. As an...
The constant frequency pulse trains of Radar can produce the high peak sidelobes. Stepped frequency signal is used to reduce these lobes with wider overall bandwidth while having small instantaneous bandwidth. For uniform frequency stepped pulse trains, there can be undesirable peaks of the autocorrelation function, known as grating lobes, around the main lobe. In this paper we address this issue,...
The Double Estimation Technique (DET) is a GNSS signal-tracking concept. DET has the capability to produce reliable unambiguous, full-precision delay estimates from the Binary Offset Carrier (BOC) signals which have been adopted by the modernized and new GNSS, including the European Galileo constellation. DET is robust, being able to function under conditions of low C/N0, strong multipath and filtering...
Pre-correlation differential detection (PDD) scheme is studied for global navigation satellite systems (GNSS) receiver design. By performing a differential detection at the chip or sample level before correlation process, the effect of both data and residual carrier is eliminated which in turn allows for frequency independent code phase acquisition. Hence the search space and computational complexity...
This work considers the problem of quickest detection of signals in a system of 2 sensors coupled by a negatively correlated noise, which receive continuous sequential observations from the environment. It is assumed that the signals are time invariant and with equal strength, but that their onset times may differ from sensor to sensor. The objective is the optimal detection of the first time at which...
The next generation of Global Navigation Satellite Systems (GNSS) are implementing Binary Offset Carrier (BOC) modulation. These signals were expected to provide not only better precision in the estimation of the signal's delay and phase but also more robustness to multipath effects. The advantage of BOC signals is that the main lobe of the correlation is very narrow although they present side lobes...
In this paper we present a study aimed at assessing the Quality of Experience in video streaming when the user is employing a tablet devices. The study has been conducted on a database containing subjective assessment scores relative to 216 streaming sessions of video sequences encoded with H.264/AVC and corrupted by typical wireless channel transmission errors. Four 20sec-long video sequences at...
Time-interleaved analog-to-digital converters (TIADCs) are essential in wide-band communication systems for providing high-speed data conversion. However, TIADCs are sensitive to the sample time mismatch, which results in significantly degraded performance. A new calibration technique is proposed to minimize sample time mismatches among interleaved channels. Correlation between adjacent channels based...
Ensuring data privacy of wireless communication systems has been a challenging problem for various reasons. The simplicity of eavesdropping on wireless transmissions makes the barrier to entry lower for wireless than for wired systems. Due to size and power constraints, wireless systems are sometimes unable to implement the complex cryptographic algorithms that can ensure the privacy of their data,...
In this paper, we introduce a novel multipath mitigation technique for binary offset carrier signals in global navigation satellite system (GNSS). The proposed technique is based on nonlinear operator called Teager - Kaiser Operator, which initially has been used to obtain energy of physical process. Moreover, the proposed multipath mitigation technique tries to reduce or remove the error caused by...
Scale Time Offset Robust Modulation (STORM) is a waveform design technique involving the simultaneous transmission of a base waveform as well as a time-scaled and time-delayed copy of that waveform. For some applications this technique is attractive as a possible candidate to enhance synchronization performance, due to the different tradeoffs of its performance properties. This paper first presents...
In wireless sensor networks, all data packets are routed from the individual sensor nodes towards an in-situ base-station (BS). Such traffic pattern makes the BS vulnerable to adversary's attack. Basically, an adversary would intercept the ongoing transmissions and localize their sources. Then by employing traffic analysis techniques, an adversary would correlate the intercepted transmissions to uncover...
Traditional OFDM systems present some embedded features that may be exploited in order to intercept the wireless transmitted signal. However, such a possibility is not accepted in military applications where security is a very important issue. Cyclic prefix is one of the most obvious OFDM parameters that induce cyclostationarity features. Aiming to suppress these features, some classical solutions...
Spread spectrum communication systems excel in their ability to provide enhanced security and channel sharing, yet they do so at the expense of data throughput provided to each individual user. This paper introduces an alternative modulation mechanism, pulse rotation modulation (PRM), for increasing the data throughput in wideband direct sequence or chaotic sequence code-based spread spectrum systems...
This paper aims to introduce the relationships between some Voice over IP Key Performance Indicators (KPIs) and to address them through the background of possible network or platform problems, resulting in KPIs degradation. We present extensions of a generic Quality of Service (QoS) monitoring strategy by describing a variety of correlations between the QoS metrics. For echo correlation for instance,...
This paper describes a hardware approach of one part of GPS receiver — the acquisition and tracking of GPS code and the frequency tracking. Method used for acquisition and tracking code is Fast Fourier Transform, which provides fast acquisition at first step. Costas loop is used for frequency tracking and demodulating GPS signal. The design is implemented in FPGA with support of mega-core functions.
This paper reports experimental analysis of human characteristic in the lever operation by utilizing the stabilization task of cart-pendulum system. Previous studies have shown that there was a difference in the velocity distribution of the cart in the difference of the skill level. Then, cart-pendulum simulator is newly constructed and training that does the stabilization operation is done for five...
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