Georgia D. Ntouni

Optoelectronic technology is expected to be the cornerstone of sub-THz communication systems, enabling access to and use of the vast frequency resources found in this portion of the spectrum. In this work we demonstrate a photonics-enabled sub-THz wireless link operating in real-time settings, using a PIN-PD-based THz emitter, and a THz receiver based on an ultra-fast photoconductor. The real-time generation and detection of the information signal is performed by an intermediate frequency (IF) unit based on a commercially available mmWave platform, operating at 1.6 GBaud. The evaluation of our setup takes place on two phases. Firstly, a homodyne scenario is demonstrated, where the same pair of lasers is used at the transmitter and receiver side. Secondly, we demonstrate a heterodyne scheme, employing optical phase locking techniques at the receiver. Error-free operation was achieved in both scenarios at a bit rate of 3.2 Gb/s, over 1 m of free-space with ambient air. The broadband characteristics of our setup were validated, achieving error-free transmission over a 0.22 THz range, spanning from 90 up to 310 GHz. Finally, the stability of our real-time link was successfully demonstrated, showing stable SNR performance at the receiver with adaptive capabilities, over a time period of 5 min and 22 sec.

In this paper, a novel optimization algorithm, called the acceleration-aided particle swarm optimization (AAPSO), is proposed for reliable dynamic spectrum sensing in cognitive radio networks. In A-APSO, the acceleration variable of the particles in the swarm is also considered in the search space of the optimization problem. We show that the proposed A-APSO based spectrum sensing technique is more efficient in terms of performance than the corresponding one based on the standard particle swarm optimization algorithm.

The authors optimise the detection process of diffusion‐based molecular communication systems utilising the weighted sum detector with appropriate weight values. Interestingly, no optimisation technique has ever been proposed for the calculation of the weights. To this end, they build on the standard particle swarm optimisation (PSO) technique and propose a robust iterative optimisation algorithm, called acceleration‐aided PSO (A‐APSO). While modified swarm‐based optimisation algorithms focus on slight variations of the standard mathematical formulas, in A‐APSO, the acceleration variable of the particles in the swarm is also involved in the search space of the optimisation problem. Particularly, they implement the A‐APSO algorithm to evaluate the detector's weights that minimise the closed‐form expression of the error probability. Their findings reveal that, when employing the A‐APSO weights, the error performance is superior to that achieved by utilising the weight values already existing in the literature or those evaluated with the standard PSO algorithm.

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) has been recently proposed as an efficient technique to improve the error performance and enhance the spectral efficiency achieved by the classical OFDM. In this letter, we minimize the presence of intercarrier and intersymbol interference, experienced by OFDM-IM systems under mobility conditions and multipath scenarios, by selecting the appropriate tone spacing between adjacent subcarriers. Finally, we prove that the optimal value of tone spacing increases the system capacity, occupying only the necessary amount of bandwidth, and provide closed-form expressions for the interference power per active subcarrier.

We analyze the performance of the single-threshold detector (STD) for binary pulse position modulation in the presence of symmetric Gaussian mixture noise (GMN). We first derive a general closed-form expression for the average error probability that is later used to investigate the optimality of the STD with zero threshold, which is the simplest form of STD. We also establish conditions sufficient to guarantee minimum error rates with the low-complexity STD for a wide range of signal-to-noise ratio. The theoretical results are verified through simulations of GMN with various noise parameters.