Physical Layer Security for Mimo Wireless Systems

A steadily growing portion of modern communication systems in use today is based on wireless technologies that make use of smaller and more portable electronic devices. As a result, the need to provide a light-weight security strategy for these systems is becoming a more important problem. This thesis focuses on two techniques that belong to an active research area known as Physical Layer Security (PLS). While the underlying techniques of PLS have been known for some time, the potential secrecy benefits of them need further investigation. These potential benefits have generated a rising interest with the development of Multiple Input Multiple Output (MIMO) multi-antenna systems. The first PLS technique considered in this thesis is that of beamforming which is made possible using MIMO. Here a sender can focus the information signal in the direction of the intended receiver while reducing the quality of the signal observed by a potential eavesdropper. In addition to beamforming, the technique of artificial noise (AN) is also investigated. AN requires the sender to generate a random noise signal in addition to the information signal to further degrade an eavesdropper’s ability to detect and decode the information signal being directed to the intended receiver. MATLAB simulations based on these PLS techniques are performed and the results presented

Impact of Correlation and Pointing Error on Secure Outage Performance over Arbitrary Correlated Nakagami Turbulent Fading Mixed RF-FSO Channel

Funding Information: Manuscript received September 8, 2020; revised February 11, 2021; accepted February 14, 2021. Date of publication February 16, 2021; date of current version March 10, 2021. This research was supported in part by the National Research Foundation of Korea grant funded by the Korean government (Ministry of Science and ICT; 2019R1A2C1083988), in part by the Ministry of Science and ICT, Korea, under the Information Technology Research Center support program (IITP-2020-2016-0-00313) supervised by the Institute for Information & Communications Technology Planning & Evaluation, and in part by Sejong University through its faculty research program (20212023). (Sheikh Habibul Islam, A. S. M. Badrud-duza, and S. M. R. Islam contributed equally to this work and co-first authors.) Corresponding authors: A. S. M. Badrudduza; Heejung Yu (e-mail: [email protected]; [email protected]).)Peer reviewedPublisher PD

Performance Analysis of Channel-Aware Media Access Control Schemes

This thesis proposes a new Channel-Aware MAC (CA-MAC) protocol that allows more than two simultaneous transmissions to take place within a single wireless collision domain. In this proposed work, Multiple-Input Multiple-Output (MIMO) system is used to achieve higher spectral efficiency. The MIMO-based PHY layer has been adopted to help in controlling the transmission and to avoid any collisions by using weights gains technique on the antenna transmission, and by recovering any possible collisions using ZigZag decoding. In order to develop CA-MAC algorithm, to exploit the full potential of MIMO system, the library of 802.11x standard has been modified. NS-2 based simulations were conducted to study the performance of the proposed system. Detailed analysis and comparisons with current protocols schemes are presented

Rapid mapping of digital integrated circuit logic gates via multi-spectral backside imaging

Modern semiconductor integrated circuits are increasingly fabricated at untrusted third party foundries. There now exist myriad security threats of malicious tampering at the hardware level and hence a clear and pressing need for new tools that enable rapid, robust and low-cost validation of circuit layouts. Optical backside imaging offers an attractive platform, but its limited resolution and throughput cannot cope with the nanoscale sizes of modern circuitry and the need to image over a large area. We propose and demonstrate a multi-spectral imaging approach to overcome these obstacles by identifying key circuit elements on the basis of their spectral response. This obviates the need to directly image the nanoscale components that define them, thereby relaxing resolution and spatial sampling requirements by 1 and 2 - 4 orders of magnitude respectively. Our results directly address critical security needs in the integrated circuit supply chain and highlight the potential of spectroscopic techniques to address fundamental resolution obstacles caused by the need to image ever shrinking feature sizes in semiconductor integrated circuits

Two-Layered Superposition of Broadcast/Multicast and Unicast Signals in Multiuser OFDMA Systems

We study optimal delivery strategies of one common and $K$ independent messages from a source to multiple users in wireless environments. In particular, two-layered superposition of broadcast/multicast and unicast signals is considered in a downlink multiuser OFDMA system. In the literature and industry, the two-layer superposition is often considered as a pragmatic approach to make a compromise between the simple but suboptimal orthogonal multiplexing (OM) and the optimal but complex fully-layered non-orthogonal multiplexing. In this work, we show that only two-layers are necessary to achieve the maximum sum-rate when the common message has higher priority than the $K$ individual unicast messages, and OM cannot be sum-rate optimal in general. We develop an algorithm that finds the optimal power allocation over the two-layers and across the OFDMA radio resources in static channels and a class of fading channels. Two main use-cases are considered: i) Multicast and unicast multiplexing when $K$ users with uplink capabilities request both common and independent messages, and ii) broadcast and unicast multiplexing when the common message targets receive-only devices and $K$ users with uplink capabilities additionally request independent messages. Finally, we develop a transceiver design for broadcast/multicast and unicast superposition transmission based on LTE-A-Pro physical layer and show with numerical evaluations in mobile environments with multipath propagation that the capacity improvements can be translated into significant practical performance gains compared to the orthogonal schemes in the 3GPP specifications. We also analyze the impact of real channel estimation and show that significant gains in terms of spectral efficiency or coverage area are still available even with estimation errors and imperfect interference cancellation for the two-layered superposition system

An Analytical Model of Packet Collisions in IEEE 802.15.4 Wireless Networks

Numerous studies showed that concurrent transmissions can boost wireless network performance despite collisions. While these works provide empirical evidence that concurrent transmissions may be received reliably, existing signal capture models only partially explain the root causes of this phenomenon. We present a comprehensive mathematical model that reveals the reasons and provides insights on the key parameters affecting the performance of MSK-modulated transmissions. A major contribution is a closed-form derivation of the receiver bit decision variable for arbitrary numbers of colliding signals and constellations of power ratios, timing offsets, and carrier phase offsets. We systematically explore the root causes for successful packet delivery under concurrent transmissions across the whole parameter space of the model. We confirm the capture threshold behavior observed in previous studies but also reveal new insights relevant for the design of optimal protocols: We identify capture zones depending not only on the signal power ratio but also on time and phase offsets.Comment: Accepted for publication in the IEEE Transactions on Wireless Communications under the title "On the Reception of Concurrent Transmissions in Wireless Sensor Networks.

Cloud computing resource scheduling and a survey of its evolutionary approaches

A disruptive technology fundamentally transforming the way that computing services are delivered, cloud computing offers information and communication technology users a new dimension of convenience of resources, as services via the Internet. Because cloud provides a finite pool of virtualized on-demand resources, optimally scheduling them has become an essential and rewarding topic, where a trend of using Evolutionary Computation (EC) algorithms is emerging rapidly. Through analyzing the cloud computing architecture, this survey first presents taxonomy at two levels of scheduling cloud resources. It then paints a landscape of the scheduling problem and solutions. According to the taxonomy, a comprehensive survey of state-of-the-art approaches is presented systematically. Looking forward, challenges and potential future research directions are investigated and invited, including real-time scheduling, adaptive dynamic scheduling, large-scale scheduling, multiobjective scheduling, and distributed and parallel scheduling. At the dawn of Industry 4.0, cloud computing scheduling for cyber-physical integration with the presence of big data is also discussed. Research in this area is only in its infancy, but with the rapid fusion of information and data technology, more exciting and agenda-setting topics are likely to emerge on the horizon

Interference Suppression in WCDMA with Adaptive Thresholding based Decision Feedback Equaliser

WCDMA is considered as one of the 3G wireless standards by 3GPP. Capacity calculation shows that WCDMA systems have more capacity compared to any other multiple access technique such as time division multiple access (TDMA) or frequency division multiple access (FDMA). So it is widely used. Rake receivers are used for the detection of transmitted data in case of WCDMA communication systems due to its resistance to multipath fading. But rake receiver treat multiuser interference (MUI) as AWGN and have limitation in overcoming the effect of multiple access interference (MAI) when the SNR is high. A de-correlating matched filter has been used in this thesis, which eliminates and improves system performance. But the given receiver works well only in the noise free environment. A DFE, compared to linear equaliser, gives better performance at severe ISI condition. The only problem in this equalisation technique is to select the number of symbols that are to be fed back. This thesis gives an idea on multiple symbol selection, based on sparity where an adaptive thresholding algorithm is used that computes the number of symbols to feedback. Simulated results show a significant performance improvement for Regularised Rake receiver along with thresholding in terms of BER compared to a rake receiver, de-correlating rake receiver and regularised rake receiver. The performance of the receiver in different channels is also analysed

High reliability downlink MU-MIMO with new encoded OSTBC approach and superposition modulated side information

Abstract. The promise of Fifth Generation Mobile Network (5G) heralded 5G-era with apparently unlimited potential outcomes. It resulted in the emergence of new paradigms of thought, better approaches to lead business, new innovative solutions, services and products, and is expected to transform the world as we know it. With the advent of some of those new technologies and use cases which deviate from the traditional human-centric, delay tolerant applications, the need for Ultra-Reliable Low-Latency Communications (URLLC) in the 5G wireless network has become indispensable. In this thesis we investigate how to improve the reliability of a downlink multiuser (MU) MIMO transmission scheme with the use of a new approach of orthogonal space time block codes (OSTBC) and network coding with superposition modulated system and side information. The main advantage here is that we show multiple users can be accommodated with the same resource. This is quite useful in a wireless system where resources are always restricted. This therefore is a combination of two techniques to further enhance reliability. Orthogonality is useful in terms of resolving different signals from multiple antennas in a reduced complexity configuration. Superposition modulation with side information is important as it facilitates the recovery of symbols while still keeping the energy normalized. Thus we carried out a detailed analysis with the new OSTBC approach. It is shown that the performance of a multiuser (MU) MIMO system can be improved significantly in terms of bit, block and frame error rates (BER, BLER and FER) as reliability measures. By accommodating a reasonable number of multiple users, high reliability is achieved at the expense of bringing down the rate. To compensate for the low rate, conventional OSTBC is considered as well, where, as a penalty to pay, multiple orthogonal resources are required