Tolga Girici

In vehicle-to-everything (V2X) applications, roadside units (RSUs) can be tasked with both sensing and communication functions to enable sensing-assisted communications. Recent studies have demonstrated that distance, angle, and velocity information obtained through sensing can be leveraged to reduce the overhead associated with communication beam tracking. In this work, we extend this concept to scenarios involving multiple distributed RSUs and distributed MIMO (multiple-input multiple-output) systems. We derive the state evolution model, formulate the extended Kalman-filter equations, and implement predictive beamforming for distributed MIMO. Simulation results indicate that, when compared with a co-located massive MIMO antenna array, distributed antennas lead to more uniform and robust sensing performance, coverage, and data rates, while the vehicular user is in motion.

With the increasing popularity of Integrated Sensing and Communication (ISAC) systems in recent years, numerous studies have been conducted on the use of a joint waveform for both radar and communication functions in these systems. When defining the joint waveform, the most important criterion to consider is that it meets the system requirements for range and Doppler resolution in radar functionality. On the other hand, parameters such as symbol error rate (SER) and bit rate are also crucial for the communication function. The ambiguity function is used by radar designers to analyze the effects of radar waveforms on radar performance (range and Doppler resolution). Therefore, in this study, the ambiguity function is mathematically derived and analyzed for biphasecoded waveforms for ISAC systems. Theoretical expressions have been compared with simulation results. Additionally, to improve the radar and communication performance of the system, optimal binary phase codes were generated using a genetic algorithm, and the performance of the Barker-coded waveform was compared with that of the generated binary codes for both the radar and communication functions.

In today's world, particularly in civilian sectors where situational awareness is paramount, research is being conducted on concepts that enable the joint realization of both sensing and communication functions with the upcoming 6G technology planned for near-future deployment, especially in sectors like automotive. On the other hand, efforts in the military domain to enhance situational awareness and counter evolving air threats have gained momentum with the development of systems incorporating multiple sensors for joint operation, known as radar network architectures. However, when multiple radar systems operate together, bandwidth allocation must be performed in order to avoid interference. As a contribution to the literature, this study proposes a joint radar and communication network concept applied to air defense systems, aiming to enhance their situational awareness by adopting the joint radar and communication concept commonly addressed in civilian applications. Additionally, a resource optimization problem has been addressed to maximize the performance of both radar and communication functions within the joint radar and communication network.

Nowadays, especially with the developments in the automotive industry, it has become a highly popular topic for radar and communication systems to operate on the same platform and perform joint tasks to increase situational awareness. Sharing the hardware of the radar and communication systems and using a joint waveform for both functions eliminate interference problems between the systems, increasing the effectiveness of the joint task. In studies where radar signals are utilised for communication functions, continuous wave frequency modulation or intra‐pulse frequency modulation is generally employed to transmit communication signals. There are a few studies in the literature on joint radar and communication waveforms using phase modulation. In these studies, phase modulation is not employed directly for both functions. As a contribution to the literature, this study evaluates the usage of joint radar and communications waveforms, such as Barker sequences and Zadoff–Chu sequences as opposed to linear frequency modulation. We compare these waveforms terms of range‐speed detection and symbol error rate.

This paper provides a reliability, availability and Mean Time Between Failure (MTBF) analysis for a sample DC/DC converter and Discrete I/O electronic circuit stages. These analyses were performed using the Failure Tree Analyses (FTA) approach. The reason for choosing these structures is that they are frequently used in today's electronic design. In this study, the effect of the importance of reliability on the whole system, starting from a component in electronic circuit design, has been demonstrated.

This article proposes a pre-equalization method to remove inter-numerology interference (INI) that occurs in multi-numerology OFDM frame structures of fifth-generation New Radio (5G-NR) and beyond, on the transmitter side. In the literature, guard bands, filters, and interference cancellation methods are used to reduce the INI. In this work, we mathematically model how the INI is generated and show how it can be removed completely for multi-numerology systems by deploying a pre-equalization matrix on the transmitter side. With this pre-equalization method, the need for guard bands and filters is eliminated and spectral efficiency is improved.

As communication systems evolve to better cater to the needs of machine-type applications such as remote monitoring and networked control, advanced perspectives are required for the design of link layer protocols. The age of information (AoI) metric has firmly taken its place in the literature as a metric and tool to measure and control the data freshness demands of various applications. AoI measures the timeliness of transferred information from the point of view of the destination. In this study, we experimentally investigate AoI of multiple packet flows on a wireless multi-user link consisting of a transmitter (base station) and several receivers, implemented using software-defined radios (SDRs). We examine the performance of various scheduling policies under push-based and pull-based communication scenarios. For the push-based communication scenario, we implement age-aware scheduling policies from the literature and compare their performance with those of conventional scheduling methods. Then, we investigate the query age of information (QAoI) metric, an adaptation of the AoI concept for pull-based scenarios. We modify the former age-aware policies to propose variants that have a QAoI minimization objective. We share experimental results obtained in a simulation environment as well as on the SDR testbed.

This article proposes a pre-equalization method to remove inter-numerology interference (INI) that occurs in multi-numerology OFDM frame structures of fifth-generation New Radio (5G-NR) and beyond on the transmitter side. In the literature, guard bands, filters and interference cancellation methods are used to reduce the INI. In this work, we mathematically model how the INI is generated and how it can be removed completely for multi-numerology systems on the transmitter side.

This work studies the problem of jointly optimal routing and minimum length scheduling in a Successive Interference Cancellation (SIC) - enabled distributed wireless ad hoc network. The optimal solution finds the minimum number of time slots needed for the scheduling frame at a given flow rate in the presence of the SIC technique. Performance of the optimal solution that uses SIC is compared to the case wherein the interference is assumed as noise during reception. Numerical results show that the optimal solution with SIC shows significantly improved performance compared to the optimal solution without SIC.

In this letter, a channel switching problem is investigated in the presence of jamming based on a game theoretic approach. First, a convex formulation of the optimal channel switching problem is proposed for a given jamming strategy. Then, considering a fixed channel switching strategy, an explicit solution of the optimal jammer power allocation problem is obtained. Consequently, a game theoretic formulation is proposed and the existence of a pure-strategy Nash equilibrium is shown for the proposed channel switching game between the transmitter and the jammer.