Abstract
Index Modulation (IM) is a technique that activate k out of n subcarriers of an OFDM symbol to transmit p(1) = right perpendicularlog(2) (n k)left perpendicular bits in symbol's indexes. Since both the symbol's spectrum width and transmission air-time duration remain the same, OFDM-IM outperforms OFDM's Spectral Efficiency (SE) for larger values of (n k). However, OFDM-IM requires an extra step called Index Selector (IxS) which takes T-alpha time units to map a given p(1)-bit input to its corresponding pattern of active subcarriers. This extra overhead virtually enlarges the symbol duration, which is not captured by the classic SE definition. To fulfill this gap, in this work we present the Spectro-Computational Efficiency (SCE) metric. SCE parameterizes either the absolute runtime of T-alpha on a reference hardware or its computational complexity T-alpha(n; k) as function of n and k. Based on SCE, we present theoretical case studies to identify the asymptotic bounds for T-alpha(n, k) across different choices of k. if T-alpha(n, n=2) is at most linear on n the resulting overhead is asymptotically negligible and IxS can handle an arbitrarily large OFDM symbol. Otherwise, OFDM-IM's SCE tends to zero regardless of the hardware processor speed. Also, we situate the inflection-point values for OFDM-IM's SCE between (6 3) and (14 7) in some practical case studies.

Abstract
We propose an adaptive secrecy scheme using polar codes with random frozen bits for a general wiretap channel, in which to protect the data from a potential eavesdropper, part or all of the frozen bits are randomly generated per message. To assess the secrecy level of the proposed scheme, three types of decoding strategies are evaluated: a matching decoder which knows the positions of all inserted bits inside the blocklength and tries to estimate them using the same decoding techniques, a blind decoder which treats all the frozen bits as the same value, and a random decoder which considers those dynamic bits as random at the receiver. Results are presented in terms of the system security gap, assuming an adaptive decoding strategy. It is shown that the system achieves combined secrecy and reliability. The proposed scheme does not assume knowledge of the eavesdropper's channel when defining the indices of information and frozen bits. © 2019 IEEE.

Abstract
This paper presents a practical physical-layer security scheme based on coding methodologies combined with self-jamming to combat advantaged eavesdroppers, i.e., eavesdroppers that may possess an equal or even better channel than the legitimate receiver. We introduce a strengthened security gap notion, where reliability is assured by typical bit-error rate (BER) measurements, but secrecy is guaranteed by considering the entire distribution of messages upon reception, instead of average measures. Relying on this new security gap notion, we then propose a scheme that combines concatenated coding with self-jamming by the legitimate receiver for effective security and reliability even when eavesdroppers possess a channel with equal or better conditions than the legitimate receiver.

Abstract
We consider privacy of obfuscated location reports that can be correlated through time/space to estimate the real position of a user. We propose a user-centric Location Privacy Preserving Mechanism (LPPM) that protects users not only against single reports, but also over time, against continuous reports. Our proposed mechanism, designated clustering geo-indistinguishability, creates obfuscation clusters to aggregate nearby locations into a single obfuscated location. To evaluate the utility of the mechanism, we resorted to a real use-case based on geofencing. Our evaluation results have shown a suitable privacy-utility trade-off for the proposed clustering geo-indistinguishability mechanism.

Abstract
We propose a coding methodology for physical layer security with adaptive characteristics, whereby adaptive we mean that the system must be tunable to different operational points/signal-to-noise ratio levels of both the legitimate receiver and the eavesdropper. Based on interleaving and scrambling as techniques that shuffle the original message before transmission, we consider puncturing over an interleaving/scrambling key and/or over the message as a mechanism to provide the required adaptability to channel conditions. The proposed techniques have shown suitable adaptability to different channel quality levels of the legitimate receiver and eavesdropper, while still guaranteeing the desired reliability for the legitimate receiver and secrecy against the eavesdropper.

Abstract
We propose adding an irregular quadrature amplitude modulation (QAM) constellation to a wireless transmission scheme in order to obtain greater control over the signal-to-noise ratio (SNR) required to successfully decode the signal. By altering the separation between adjacent symbols, the minimum required SNR is raised without degradation in the performance of the scheme. This allows the system to adapt to preferable channel conditions for the authorized user, making it harder for eavesdroppers to intercept and decode the transmission, thus making the communication safer. In addition, we show that by overlaying a coset code onto the QAM constellation, a new, stronger security gap metric can be further improved. Results show the effectiveness of this strategy with an interleaved coding for secrecy with a hidden key (ICSHK) scheme.