Algebraic Number Precoded OFDM Transmission for Asynchronous Cooperative Multirelay Networks

This paper proposes a space-time block coding (STBC) transmission scheme for asynchronous cooperative systems. By combination of rotated complex constellations and Hadamard transform, these constructed codes are capable of achieving full cooperative diversity with the analysis of the pairwise error probability (PEP). Due to the asynchronous characteristic of cooperative systems, orthogonal frequency division multiplexing (OFDM) technique with cyclic prefix (CP) is adopted for combating timing delays from relay nodes. The total transmit power across the entire network is fixed and appropriate power allocation can be implemented to optimize the network performance. The relay nodes do not require decoding and demodulation operation, resulting in a low complexity. Besides, there is no delay for forwarding the OFDM symbols to the destination node. At the destination node the received signals have the corresponding STBC structure on each subcarrier. In order to reduce the decoding complexity, the sphere decoder is implemented for fast data decoding. Bit error rate (BER) performance demonstrates the effectiveness of the proposed scheme

Communication over Asynchronous Networks: Signaling and Rate-Reliability Analysis

Asynchronism inherently exists in many communication systems specially in multi-terminal networks mainly due to the effect of multi-path and propagation delay. While in theoretical analysis of communication systems perfect synchronization of the terminals is often presumed, in some cases in which the nodes are randomly distributed over a geometrical area, it might be impossible to synchronize the nodes even if an ideal infrastructure service provider is used. In this work, two major categories of multi-user communication systems, i.e., relay networks and interference channels, are considered and the effect of the asynchronism among the terminals on characteristic properties of these channels are investigated. In Chapter 2, the construction of distributed space-time codes for a general two-hop asynchronous cooperative relay network is considered. A novel algebraic structure is proposed and shown to achieve full diversity for arbitrary number of relays, arbitrary input alphabets, and arbitrary delay profiles among the relays. Unlike previously proposed delay tolerant schemes, the new design has minimum length which translates into smaller decoding complexity at the same transmission rate. Full-rate and full-diversity are achieved by the new designs with or without the use of guard intervals between successive transmissions. Simulation results confirm the mathematical analysis of the proposed codes. In Chapter 3, the underlying asynchronous network is examined for various relaying protocols such as non-orthogonal selection decode-and-forward, orthogonal selection decode-and-forward, non-orthogonal amplify-and-forward (NAF), and orthogonal amplify-and-forward (OAF). The transmitter nodes send pulse amplitude modulation (PAM) signals, in which information symbols are linearly modulated by a shaping waveform to be sent to the destination, asynchronously. We consider two different cases with respect to the type of the shaping waveforms used in the structure of the PAM signals. In the theoretical case where band-limited shaping waveforms are used, it is shown that the asynchronism does not affect the DMT performance of the system and the same DMT as that of the corresponding synchronous network is obtained for all the aforementioned protocols. In the practical case where time-limited shaping waveforms are used, it is shown that better diversity gains can be achieved at the expense of a bandwidth expansion. More precisely, in the decode-and-forward type protocols, the asynchronous network provides a better diversity gain than that of the corresponding synchronous network throughout the range of the multiplexing gain. In the amplify-and-forward type protocols, the asynchronous network provides the same DMT as that of the corresponding synchronous counterpart under the OAF protocol; however, a better diversity gain is achieved under the NAF protocol throughout the range of the multiplexing gain. In particular, in the single relay asynchronous network, the NAF protocol provides the same DMT as that of the 2 × 1 multiple-input single-output channel. In Chapter 4, a constant K-user interference channel in which the users are not symbol synchronous is considered. It is shown that the asynchronism among the users does not affect the total number of degrees of freedom (DOF) of this channel; however, it facilitates aligning interfering signals at each receiver node. To achieve the total K/2 DOF of this channel when single antenna nodes are used, a novel practical interference alignment scheme is proposed wherein the alignment task is performed with the help of asynchronous delays which inherently exist among the received signals at each receiver node. The asynchronism causes inter-symbol-interference (ISI) among transmitted symbols by different transmitters resulting in the underlying quasi-static links to be converted to ISI and accordingly into time varying channels. It is proved that this conversion solves the lack of channel variation required for the interference alignment in quasi-static scenarios. When each node is equipped with M > 1 antennas, it is argued that the same alignment scheme proposed for the single antenna nodes’ interference channel is sufficient to achieve the total MK/2 DOF of the medium provided that each pair of the transmitters and the receivers experience the same asynchronous delay for all the corresponding antennas. In contrast to previously proposed alignment schemes, the channel state information of the links does not need to be known at the transmitter nodes. Instead, the relative delays among the received signals at each receiver node are globally known to the entire network. While the asynchronism is usually treated as a troublesome factor in communication systems, in this dissertation, we are interested to introduce it as a useful property of the wireless medium similar to the fading which can improve the system performance in some communication scenarios or facilitate signaling over the medium in some other scenarios

Coding Theory

This book explores the latest developments, methods, approaches, and applications of coding theory in a wide variety of fields and endeavors. It consists of seven chapters that address such topics as applications of coding theory in networking and cryptography, wireless sensor nodes in wireless body area networks, the construction of linear codes, and more

Cryptographic Foundations For Control And Optimization: Making Cloud-Based And Networked Decisions On Encrypted Data

Advances in communication technologies and computational power have determined a technological shift in the data paradigm. The resulting architecture requires sensors to send local data to the cloud for global processing such as estimation, control, decision and learning, leading to both performance improvement and privacy concerns. This thesis explores the emerging field of private control for Internet of Things, where it bridges dynamical systems and computations on encrypted data, using applied cryptography and information-theoretic tools.Our research contributions are privacy-preserving interactive protocols for cloud-outsourced decisions and data processing, as well as for aggregation over networks in multi-agent systems, both of which are essential in control theory and machine learning. In these settings, we guarantee privacy of the data providers\u27 local inputs over multiple time steps, as well as privacy of the cloud service provider\u27s proprietary information. Specifically, we focus on (i) private solutions to cloud-based constrained quadratic optimization problems from distributed private data; (ii) oblivious distributed weighted sum aggregation; (iii) linear and nonlinear cloud-based control on encrypted data; (iv) private evaluation of cloud-outsourced data-driven control policies with sparsity and low-complexity requirements. In these scenarios, we require computational privacy and stipulate that each participant is allowed to learn nothing more than its own result of the computation. Our protocols employ homomorphic encryption schemes and secure multi-party computation tools with the purpose of performing computations directly on encrypted data, such that leakage of private information at the computing entity is minimized. To this end, we co-design solutions with respect to both control performance and privacy specifications, and we streamline their implementation by exploiting the rich structure of the underlying private data

Publications of the Jet Propulsion Laboratory, July 1969 - June 1970

JPL bibliography of technical reports released from July 1969 through June 197

Social work with airports passengers

Social work at the airport is in to offer to passengers social services. The main methodological position is that people are under stress, which characterized by a particular set of characteristics in appearance and behavior. In such circumstances passenger attracts in his actions some attention. Only person whom he trusts can help him with the documents or psychologically

The art and architecture of mathematics education: a study in metaphors

This chapter presents the summary of a talk given at the Eighth European Summer University, held in Oslo in 2018. It attempts to show how art, literature, and history, can paint images of mathematics that are not only useful but relevant to learners as they can support their personal development as well as their appreciation of mathematics as a discipline. To achieve this goal, several metaphors about and of mathematics are explored