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Underwater acoustic communication (UAC) system designers tend to transmit as much information as possible, per unit of time, at as low as possible error rate. However, the bit rate achieved in UAC systems is much lower than for wire or radio-communication systems. This is due to disadvantageous properties of the UAC channels, namely the sea and inland waters. Estimation of UAC channel transmission...
Mobile video traffic is exploding and it is particularly challenging to stream video when high density of users are "on the move", e.g., in public transport systems. It becomes increasingly problematic as video traffic is predicted to account for more than 80% of Internet traffic by 2019. This will be exacerbated by factors such as cellular network coverage issues and unstable network throughput...
Cooperative multi-AUV localization has the potential to outperform single-AUV localization, by taking advantage of data sharing among the team members. Unlike terrestrial communication links, underwater communication links have many issues pertaining to the channel stability and bandwidth, and therefore a decentralized localization is preferred. However this opens up new challenges to team members...
We study the design of moderate-length discrete-time pulse-shaping filters used in data communications, focusing on the tradeoff between ISI, out-of-band power, and filter length. Oversampling ratio M=2 and 4 is studied for both symmetric and asymmetric impulse responses. Numerical minimization of out-of-band power, subject to constraints on ISI, is our primary tool.
Impedance analyzers are often used for characterization of many electrochemical devices, such as photovoltaic cells, fuel cells and batteries, that are commonly utilized in renewable energy applications. Depending upon specifications of these devices, they are quite expenseive and their use in many low-cost applications is limited. This study demonstrates a practical impedance analyzer application...
Correlation measure is an important indicator of the performance any code sequence family used for communication system. Frequency Hopping (FH) codes are similar in construction of Time Hopping (TH) codes used in Ultra Wide Band (UWB) communication systems. Since the development of TH codes is not yet fully established, in this paper an effort has been made to utilize FH code families as TH codes...
Two philosophically different approaches to the analysis of signals with imperfect cyclostationarity or polycy-clostationarity of the autocorrelation function due to warping are presented. The first approach consists of directly estimating the time-warping function (or its inverse) in a manner that transforms data having an empirical autocorrelation with irregular cyclicity into data having regular...
A possible approach to address spectrum congestion is to develop signaling schemes that allow for spectrum sharing with minimum system interference. In this paper, we consider the problem of co-existence between radar and communications systems by designing a common signaling scheme to jointly optimize the performance of both systems. In particular, we derive constraints on the parameters of linear...
This paper considers the problems of efficiency estimation of using different types of modulation of hydroacoustic signals of AUV communication, navigation and control systems. The types of signal were investigated: simple signal, linear frequency modulation signal and direct sequence spread spectrum. The signals were compared by the noise immunity, time resolution and detection probability with usage...
This paper examines the low-probability-of-exploitation (LPE) characteristics of a noncontiguous orthogonal frequency division multiplexing (NC-OFDM) system. NC-OFDM transmission is similar to OFDM transmission but only uses a subset of the frequencies either to avoid incumbent transmissions or due to tactical considerations. This paper considers an NC-OFDM transmission with a given set of active...
The paper introduces a novel method for distance estimation based on an OFDM signal combined with the Zadoff-Chu sequences. By exploiting the properties of these sequences, it is possible to evaluate the distance between two active nodes with a very good precision and accuracy. The technique effectiveness is demonstrated by measuring the distance between a single transmitter and a synchronized receiver...
The design of low power and side-channel-attack resistant encryption engine is a key challenge to enhance security of resource-constrained platforms. This paper present case studies to show that the low-power requirement is a challenge as well as an opportunity for improving side-channel resistance. On one hand, low-power encryption architecture can be more vulnerable to power-attack; and the countermeasures...
Inspired by recent progress in parallel and distributed optimization, we propose parallel least-squares policy iteration (parallel LSPI) in this paper. LSPI is a policy iteration method to find an optimal policy for MDPs. As solving MDPs with large state space is challenging and time demanding, we propose a parallel variant of LSPI which is capable of leveraging multiple computational resources. Preliminary...
Although there are various researches for the sonar processing gain of replica correlation under noise dominant environments, it seems no reports have been published for the reverberation limited region researches. In this paper a theoretical approach under reverberation dominant environments is presented using a reverberation modeling with large frequency modulation LFM transmissions. The result...
The Acoustic Vector Sensor can measure both pressure and particle velocity information of acoustic field at a point in space. By using the acoustic pressure and particle velocity information, a single AVS can get the unbiased estimation of target's bearing. But when the phase of each channel is inconsistent, the estimation precision will be badly affected. In order to solve this problem, this paper...
A Fractional Fourier Transform (FrFT) based waveform design for joint radar-communication systems (Co-Radar) that embeds data into chirp sub-carriers with different time-frequency rates has been recently presented. Simulations demonstrated the possibility to reach data rates as high as 3.660 Mb/s while maintaining good radar performance compared to a Linear Frequency Modulated (LFM) pulse that occupies...
In this work, we analyze the use of a WiFi network deployed in a large-scale technical university. To this extent, we leverage three weeks of WiFi traffic data logs and characterize the spatio-temporal correlation of the traffic at different granularities (each individual access point, groups of access points, entire network). The spatial correlation of traffic across nearby access points is also...
In this work we report the final results of the field demonstration of the European FP7 mPlane project concerning the evaluation of the network performance with particular details regarding the access Quality of Service and traffic monitoring. We show how the proposed and experimented architecture of this measurement plane is fundamental for many future internet evolutions concerning user perception,...
Cyber-attacks appear to have grown in the past few years. Many policy changes have been made to control them, however, a clear path to a safe and secure cyber world is not visible. A mere technical view to confront the cyber-attacks could be futile if motivations behind attacks are not understood. To understand the motives behind cyber-attacks, we look at cyber-attacks as societal events associated...
Using a compressive sensing framework, we investigate the performance of a practicable sub-Nyquist radar system, which is based on a set of parallel bandpass filters for extracting range information of sparse target objects. In particular, the system employs an equivalent measurement matrix optimized based on a sparse ruler approach known from combinatorical number theory. First, we address the connection...
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