Secure Federated Learning for Cognitive Radio Sensing

This paper considers reliable and secure Spectrum Sensing (SS) based on Federated Learning (FL) in the Cognitive Radio (CR) environment. Motivation, architectures, and algorithms of FL in SS are discussed. Security and privacy threats on these algorithms are overviewed, along with possible countermeasures to such attacks. Some illustrative examples are also provided, with design recommendations for FL-based SS in future CRs.Comment: 7 pages, 6 figure

Newly Developed Mg2+–Selective Fluorescent Probe Enables Visualization of Mg2+ Dynamics in Mitochondria

Mg2+ plays important roles in numerous cellular functions. Mitochondria take part in intracellular Mg2+ regulation and the Mg2+ concentration in mitochondria affects the synthesis of ATP. However, there are few methods to observe Mg2+ in mitochondria in intact cells. Here, we have developed a novel Mg2+–selective fluorescent probe, KMG-301, that is functional in mitochondria. This probe changes its fluorescence properties solely depending on the Mg2+ concentration in mitochondria under physiologically normal conditions. Simultaneous measurements using this probe together with a probe for cytosolic Mg2+, KMG-104, enabled us to compare the dynamics of Mg2+ in the cytosol and in mitochondria. With this method, carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP)–induced Mg2+ mobilization from mitochondria to the cytosol was visualized. Although a FCCP–induced decrease in the Mg2+ concentration in mitochondria and an increase in the cytosol were observed both in differentiated PC12 cells and in hippocampal neurons, the time-courses of concentration changes varied with cell type. Moreover, the relationship between mitochondrial Mg2+ and Parkinson's disease was analyzed in a cellular model of Parkinson's disease by using the 1-methyl-4-phenylpyridinium ion (MPP+). A gradual decrease in the Mg2+ concentration in mitochondria was observed in response to MPP+ in differentiated PC12 cells. These results indicate that KMG-301 is useful for investigating Mg2+ dynamics in mitochondria. All animal procedures to obtain neurons from Wistar rats were approved by the ethical committee of Keio University (permit number is 09106-(1))

A Utility-Based Approach for Adaptive QAM with Diversity and Ambiguous CSI

Adaptive M -ary quadrature amplitude modulation (M -QAM) with subset diversity (SSD) is a way to cope with quality of service variations in small and large-scale fading chan- nels. We consider a slow adaptive modulation (SAM) technique that adapts the constellation size to the slow variation of the channel due, for example, to shadowing. SAM technique is more practical than fast adaptive modulation (FAM) techniques, that require adaptation to fast fading variations, even if it has been has been shown to provide substantial increase in throughput with respect to fixed schemes while maintaining an acceptable low bit error outage (BEO). In addition SAM is less complex than FAM and requires a lower feedback rate to the transmitter. Performance of adaptive modulation and SSD techniques are affected by non-ideal channel estimation. Here, we propose an analytical framework to evaluate spectral efficiency and BEO for slow adaptive QAM with SSD and imperfect channel knowledge. We propose a utility-based approach to SAM, which accounts for the abovementioned CSI imperfections. Our utility-based approach is relevant to the game-theoretic approach, in which a particular strategy (the transmitted power and the modulation constellation option) is chosen by the decision-making control- unit of the transceiver as a response to the set of possible (however uncertain) channel conditions

Utility-Based QAM Adaptation with Diversity and Ambiguous CSI under Energy Constraints

Adaptive M -ary quadrature amplitude modulation (M-QAM) with subset diversity is a way to cope with the quality of service variations in small and large-scale fading channels. We consider a pilot-assisted slow adaptive modulation (SAM) technique that adapts the constellation size and the pilots energy to slow variations of the channel due to shadowing. The SAM technique is less complex and requires a lower feedback rate with respect to fast adaptive modulation techniques. We present an analytical framework to evaluate the bit-error probability for pilot-asisted slow adaptive QAM with subset diversity and imperfect channel state information (CSI) together with a utility-based approach to SAM. It accounts for the imperfect CSI, and is related to the game-theoretic approach, in which a particular strategy (the pilots energy and the constellation signaling) is chosen as a response to the set of possible channel conditions

Degrees of freedom for energy savings in practical adaptive wireless systems

We present a new design concept for adaptive wireless communications with new trade-offs between system performance and energy consumption. The system performance, in terms of bit error rate, outage probability, and achieved spectral efficiency, depends on constellation signaling, applied diversity, and channel estimation. Resources dedicated to channel estimation and feedback traffic contribute to the overall system and network energy consumption, and the resulting CO2 emission. We cons ider the trade-offs among different methodologies and parameters toward an energy-efficient green communication system design. Below, we discuss the degrees of freedom in the design of communications systems with imperfect channel estimation and diversity, and investigate their energy saving options. We present the case studies of single and multicarrier systems applying both margin adaptive and rate-adaptive pilot-assisted transmission