24.10.2023

The graphical user interface design work under Tübitak-120E307 has been carried out to cover the functional features and performance outputs of the project.

The graphical user interface design with Tübitak-120E307 was completed by creating a MATLAB-based software library to present theoretical and symmetrical results of the analytical outputs obtained under the project.

The basic outputs produced for the MATLAB-based creation of the software library are shown. Here is an interface that allows the user to analyze the performance of the system to cover all the work packages envisaged under the project under the heads of physical layer security in the UAV-RIS assisted heterogeneous networks, including, respectively, the classical and DL-based channel shortcuts in UAV-RIS assisted heterogenic networks and the orbital design of the energy-efficient UAV assisted HetNet model and the stochastic battery consumption model, the spectral and energy efficiency analysis of the UAV-RIS supported hetero-network structure and the meta-surface manipulation attacks.

http://icrg.itu.edu.tr/wp-content/uploads/2023/10/guı.zip

12.07.2023

S. Kosu, M. Babaei, S. Ö. Ata, L. Durak-Ata and H. Yanikomeroglu, “Linear/Non-Linear Energy Harvesting Models via Multi-Antenna Relay Cooperation in V2V Communications," IEEE Trans. Green Commun., June 2023, doi: 10.1109/TGCN.2023.3279326.

Vehicle-to-vehicle (V2V) communications is a part of next-generation wireless networks to create smart cities with the connectivity of intelligent transportation systems. Besides, green communications is considered in V2V communication systems for energy sustainability and carbon neutrality. In this scope, radio-frequency (RF) energy harvesting (EH) provides a battery-free energy source as a solution for the future of V2V communications. Herein, the employment of RF-EH in V2V communications is considered where the bit error probability (BEP) of a dual-hop decode-and-forward relaying system is obtained depending on the utilization of antennas at the relay. The multiple antenna power-constraint relay harvests its power by applying dedicated antenna (DA)/power splitting (PS) EH modes and linear (L)/nonlinear (NL) EH models. Moreover, the links between nodes are exposed to double-Rayleigh fading. Finally, the performance of different system parameters is compared using theoretical derivations of BEP. The results provide a comprehensive analysis of the proposed system considering PS/DA-EH modes and L/NL-EH models, as well as deterministic/uniformly distributed placement of nodes. It is observed that PS-EH outperforms DA-EH assuming a placement of an equal number of antennas and distances. Moreover, optimal performance of PS/DA-EH is achieved by allocating more power and increasing the number of antennas for EH, respectively.

05.07.2023

M. Namdar, A. Basgumus, H. Alakoca, S.O. Ata, and L. Durak-Ata, “IRS-aided Communication Systems in the Presence of Multiple Eavesdroppers," IEEE Signal Proc. Commun. Appl. Conf. (SIU’22), 5-8 Jul. 2023, Istanbul, Turkey. (presented)

In this study, a performance analysis is conducted on the communication system model with the aid of an intelligent reflecting surface (IRS) in urban mobile networks, considering the presence of multiple covert listeners, both cooperating and non-cooperating. The analysis focuses on the secret capacity and secret outage probability. In both approaches, the system model pertaining to physical layer security for legitimate users is designed with the assistance of IRS, and realistic security problems and solutions are evaluated.

22.05.2023

S. Koşu, M. Babaei and L. Durak-Ata, “Integrated Satellite-Terrestrial Relay Network over Generalized-K Fading Channel", IEEE Int. Black Sea Conf. Commun. and Networking (BLACKSEA’23), 4-7 July 2023, Istanbul, Turkey. (accepted)

Current satellite communication solutions propose a network solution that is compatible with the existing network and 6G architecture in order to provide global coverage for rural areas and emergency applications worldwide. Therefore, integrated satellite-terrestrial technologies will enable ubiquitous connectivity for any type of end user. In this paper, we propose cooperative communication in which the satellite station transmits its information to the ground base station. The signal is then transmitted to the receiver using a decode-and-forward relaying protocol. The satellite link is presumed to be shadowed Rician, whereas the terrestrial link is referred to as GeneralizedK fading since it is the generalized representation of conventional small-scale channel models in cellular communications. Alternatively, assuming a special case in which the end user is a vehicular node, the appropriate channel is selected as double Rayleigh fading on the terrestrial link. Due to the mobility of the ground user, it is assumed that the distance over the terrestrial link is uniformly distributed. In addition, several system parameters are considered when evaluating system performance, including outage probability and bit-error probability. In order to confirm the derived mathematical formulas, computer-based Monte Carlo simulations are conducted. The results indicate that the shadowing parameter of the satellite link and the distance of the terrestrial link has a significant impact on the proposed system performance.

22.05.2023

S. Aldirmaz-Colak, M. Basaran, N.A. Bastug, N. Calik, E. Basar, L. Durak-Ata, “Estimation of Correlated Channels in Reconfigurable Intelligent Surfaces-Enabled 6G Networks,” IEEE Int. Black Sea Conf. Commun. and Networking (BLACKSEA’23), 4-7 July 2023, Istanbul, Turkey. (accepted)

Reconfigurable intelligent surfaces (RIS) are one of the possible candidate technologies for 6th generation (6G) wireless communications owing to their robustness against weak channel conditions. They allow using of an additional reflecting surface to assist the information transmission between the base station (BS) and user equipments (UEs) to improve the communication system performance resulting in a more favorable communication environment. In this paper, an overall perspective for RIS-enabled channel estimation is presented where the channels are modeled as correlated (i.e., as the realistic case) due to the spatial deployment of transceiver antennas. Accordingly, two main channel estimation approaches are considered to determine the performance of the overall RIS-enabled wireless communication. These approaches include i) least squares-based conventional estimation for the effective channel consisting of a direct channel and RIS-assisted cascaded channel and ii) deep learning (DL)-aided estimation. Computer simulation results show that the channel estimation performance improves as the channel correlation coefficient increases and bit error rate performance enhances when the number of RIS elements increases. The presented framework is important in the overall evaluation of the channel estimation performance of RIS-enabled 6G communication systems.

 

10.05.2023

M. Ardanuc, M. Basaran, Y. Hmamouche, L. Durak-Ata and H. Yanikomeroglu, “Energy Efficiency Analysis in Heterogeneous Networks: A Stochastic Geometry Perspective," IEEE Open Journal of Vehicular Technology, doi: 10.1109/OJVT.2023.3269890. [IEEE OJVT] [ResearchGate]

In this paper, we present the energy efficiency (EE) analysis of a multi-tier cellular network, where intra- and inter-tier dependence in the base station (BS) locations are captured via point processes, i.e., three variants of hard-core point processes (HCPPs) and the Poisson hole process (PHP). The analytical expression for EE is derived by approximating both the average power consumption of BSs and the coverage probability using an approximate signal-to-interference ratio analysis based on the Poisson point process (PPP). It is demonstrated that the proposed Matérn HCPP Type-I-PHP model provides better EE results compared to the other HCPP-PHP and PPP models.

 

09.03.2023

Our Ph.D. Student’s Paper is on the IEEE Best Readings List
It was deemed worthy of being listed among the best publications (IEEE Best Readings) of the last 5 years (2018-2023) in the field of physical layer security for 6G networks by the IEEE Communications Society. 

 

24.02.2023

H. Maleki, M. Basaran, L. Durak-Ata, “Handover-enabled dynamic computation offloading for vehicular edge computing networks,” IEEE Transactions on Vehicular Technology (Early Access, available as of 22 Feb. 2023, DOI: 10.1109/TVT.2023.3247889). [IEEE TVT] [ResearchGate]

The computation offloading technique is a promising solution that empowers computationally limited resource devices to run delay-constrained applications efficiently. Vehicular edge computing incorporates the processing capabilities into the vehicles, and thus, provides computing services for other vehicles through computation offloading. Mobility affects the communication environment and leads to critical challenges for computation offloading. In this paper, we consider an intelligent task offloading scenario for vehicular environments including smart vehicles and roadside units, which can cooperate to perform resource sharing. Intending to minimize the average offloading cost which takes into account energy consumption together with the delay in transmission and processing phases, we formulate the task offloading problem as an optimization problem and implement an algorithm based on deep reinforcement learning with Double Q-learning which allows user equipment to learn the offloading cost performance by observing the environment and make steady sequences of offloading decisions despite the uncertainties of the environment. Besides, concerning the high mobility of the environment, we propose a handover-enabled computation offloading strategy that leads to a better quality of service and experience for users in beyond 5G and 6G heterogeneous networks. Simulation results demonstrate that the proposed scheme achieves low-cost performance compared to the existing offloading decision strategies in the literature.

 

18.11.2022

H. Alakoca, M. Namdar, S. Aldirmaz-Colak, M. Basaran, A. Basgumus, L. Durak-Ata, H. Yanikomeroglu, “Metasurface Manipulation Attacks: Potential Security Threats of RIS-Aided 6G Communications," IEEE Communications Magazine, vol. 61, no. 1, pp. 24-30, January 2023, doi: 10.1109/MCOM.005.2200162. [IEEE COMMAG] [ResearchGate]

The physical layer security (PLS) of reconfigurable intelligent surfaces (RIS) is critical for providing secure and reliable communications in the 6th-generation (6G) wireless systems. This paper contributes to a debate on many aspects of unique vulnerabilities that can arise in the PLS of RIS with malicious attacks on signal processing (SP) in 6G networks. We address and categorize future security threats in RIS-aided networks considering PLS aspects. Metasurface manipulation attacks (MSMA) are based on manipulating metasurface behavior for malicious purposes. In this study, we present the potential hostile activities of MSMA considering the impact of electromagnetic and time-frequency deterioration. In addition, we evaluate various interference-based MSMA and eavesdropping booster-based MSMA (EaB-MSMA), which are novel potential PLS attacks that involve manipulating phase-shifting activity with SP on malicious RIS. We also compare performance degradation in the presence of hostile interference-based MSMA through the manipulation of maliciously configured RIS. Additionally, in the EaB-MSMA case, the loss of secrecy capacity is shown to be considerably greater in passive eavesdropping scenarios.

 18.11.2022

H. Alakoca and L. Durak-Ata, “Secrecy Performance of RIS-enabled Linear Interference Alignment Multi-User MIMO Network”, 30th Telecommunications forum TELFOR 2022, Nov. 2022, Belgrade, Serbia. [IEEE TELFOR] [ResearchGate]

In this study, a reconfigurable intelligent surface (RIS)-enabled linear interference alignment (IA) is examined for multiuser multiple-input multiple-output (MU-MIMO) in a presence of an eavesdropper. Modified precoder and postcoder matrix designs are introduced to minimize interference for legitimate users which is used as ensuring secure communications. According to our findings, the secrecy sum rate of the IA-based RIS-enabled MU-MIMO outperforms that without IA case due to the intensive interference of the communication environment.

 

 

8.11.2022

Recently Accepted “IEEE Communications Magazine" Paper

The paper entitled “Metasurface Manipulation Attacks: Potential Security Threats of RIS-Aided 6G Communications" has been accepted for publication in IEEE Communications Magazine.

Link: https://ieeexplore.ieee.org/document/9941040

Summary: This paper contributes to a debate on many aspects of unique vulnerabilities that can arise in the physical layer security (PLS) of reconfigurable intelligent surfaces (RIS) with malicious attacks on signal processing in 6G networks. We address and categorize future security threats in RIS-aided networks considering PLS aspects.

Authors: Hakan Alakoca, Mustafa NAMDAR, Sultan Aldirmaz, Mehmet Basaran, Arif Basgumus, Lutfiye Durak Ata, Halim Yanikomeroglu.

26.09.2022

The Current Status of Research Project [Outputs]

In the context of the studies in the one and half year of the project,

A. Papers Published/Accepted

1 journal paper on the “Energy Harvesting” has been accepted and published at “Sensors (MDPI)”
[J1] M. Babaei, L. Durak-Ata, U. Aygolu, “Performance Analysis of Dual-Hop AF Relaying with Non-Linear/Linear Energy Harvesting”. Sensors. 2022; 22(16):5987

2 IEEE conference proceedings (IEEE Signal Proc. Commun. Appl. Conf. (SIU’22)), one in English and one in Turkish, have been published.

• [C2] M.E. Kechagia, S. Aldirmaz-Colak, M. Basaran, L. Durak-Ata, “Sum-rate analysis in reconfigurable intelligent surface-aided UAV networks,” IEEE Signal Proc. Commun. Appl. Conf. (SIU’22), 16-18 May 2022, Karabuk, Turkey (in Turkish, hybrid conf., presented virtually).
• [C1] A. Hashi, S. Aldirmaz-Colak, M. Basaran, L. Durak-Ata, “Channel estimation effect on sum-rate analysis of RIS-aided UAV-based MISO systems,” IEEE Signal Proc. Commun. Appl. Conf. (SIU’22), 16-18 May 2022, Karabuk, Turkey (in English, hybrid conf., presented virtually).

B.Papers Under Review

• 1 journal paper study on “Energy efficiency analysis in heterogeneous networks: A stochastic geometry perspective” has been submitted to “IEEE Systems Journal” on Sep. 25, 2022.
• 1 journal paper submission on “Potential Security Threats in RIS-Aided Communications” has received the “Major Revision” decision by IEEE Communications Magazine (2 months is allowed for the revision and the revised version submitted on Sep. 05, 2022).
• 1 journal paper submission on “Handover-enabled dynamic computation offloading for vehicular edge computing networks” has received the “Minor Revision” decision by “IEEE Transactions on Vehicular Technology” and the revised version submitted on Aug. 22, 2022.

C.Papers In Preparation

• 2 journal papers focusing on “PLS and channel estimation in RIS-aided communications” are in preparation (minor modifications are needed only) and planned to be submitted within the next few months.
•  

26.09.2022

Second Progress Report Approval [Successful]

Second progress report of Tubitak 1001 research project with ID:120E307 has been reviewed and approved by Tubitak on Aug. 29, 2022 and found to be successful for the evaluation of the outputs obtained during the period of six months after the completion of first one year.

The second progress report addresses i) WP1 – the conventional least squares- and deep learning-based channel estimation in intelligent reflecting surfaces (IRS)-assisted wireless communications, ii) WP2 – trajectory design for IRS-UAV deployed HetNet considering the energy efficiency and stochastic battery consumption modeling, iii) WP3- stochastic geometry modeling of base station deployments for energy efficient design of communication systems and iv) WP4 – PHY-layer security of IRS-UAV-aided HetNets.

 

22.09.2022

H. Alakoca, M. Babaei, L. Durak-Ata and E. Basar, “RIS-Empowered Non-Linear Energy Harvesting Communications over Nakagami-m Channels,"  IEEE Communications Letters, vol. 26, no. 9, pp. 2215-2219, Sept. 2022, doi: 10.1109/LCOMM.2022.3182482. [IEEE Comm Letter] [ResearchGate]

We propose novel reconfigurable-intelligent-surface (RIS)-based energy harvesting (EH) systems with linear EH (L-EH) and non-linear EH (NL-EH) models where channels are exposed to Nakagami- m fading. We also compare two RIS-based EH systems in terms of RIS locations, namely RIS-EH and RIS-information processing (RIS-IP). In the RIS-EH, RIS increases the amount of harvested energy, while in the RIS-IP, RIS is utilized to improve the information processing link. Closed-formed expressions of throughput, outage probability, and average harvested power are derived and confirmed via simulation. The L-EH model overestimates system performance, while the NL-EH model provides a realistic interpretation of EH system design.

19.09.2022

M. Babaei, L. Durak-Ata, U. Aygolu, “Performance Analysis of Dual-Hop AF Relaying with Non-Linear/Linear Energy Harvesting”. Sensors. 2022; 22(16):5987. [MDPI SENSORS] [ResearchGate]

Massive device-to-device communication nodes and Internet of Things (IoT) devices are expected to be crucial components in next-generation wireless networks. However, the energy constraint of these nodes presents a challenge since the energy of the batteries is limited. Motivated by this, radio frequency energy harvesting (EH) has been developed as an efficient strategy to overcome the energy constraint of IoT devices and sensor networks. In this paper, a wireless-powered dual-hop amplify-and-forward relaying system, in the absence of a direct link between the source (S) and the destination (D), is considered. It is assumed that a dedicated power beacon (PB) transmits an energy-bearing signal from which the power-constrained S and relay (R) harvest energy. Theoretical derivations of bit error probability, outage probability, and throughput expressions are performed for both linear and non-linear energy harvesting models. Moreover, the theoretical results provided for different system parameters are validated via Monte Carlo simulations. The obtained results reveal the difference between the realistic non-linear EH model and the conventional linear EH model, which overestimates the system performance at high levels of harvested energy. Thus, it leads to misunderstanding the real performance of the EH systems. However, at low levels of harvested energy, both models behave similarly and provide realistic results.

17.09.2022

New Scholarship Researchers

3 Ph.D. students; Homa Maleki, Mohammad Reza Babaei, and Abdulgani Ibrahim have joined the project to contribute the project with their expertise areas including but not limited to vehicular communication, free-space optical communication, and energy harvesting in cognitive-communication, respectively, as of September 2022. We believe their experiences will improve the success of the project significantly.

30.06.2022

The First Progress Report Summary of the Project

Sixth-generation (6G) wireless networks are predicted to enable massive-connectivity, low latency, high data rates, widespread coverage, and high reliability. In this regard, 6G networks are considered to cover not only terrestrial networks but also flyable network elements, and thus, infrastructure functionality will vary greatly for both terrestrial and non-terrestrial networks. Non-terrestrial networks will consist of a combination of various vertical elements such as satellites and unmanned aerial vehicle (UAV) enabled flying base stations (BSs). Wireless networks using UAV can provide communication continuity in unexpected extraordinary situations by acting autonomously in hard-to-reach areas, as opposed to fixed positioned terrestrial BSs. Additionally, intelligent reflective surfaces (IRS), designed as the next generation transceivers, come to the fore with the low power consumption and secure communication features in heterogeneous networks (HetNets). These communication nodes which can be used as either the BSs or users in the network connection are predicted to become more common in the near future. HetNet planning is the area that is open to development in the current literature and communication industry, especially in energy-efficient and secure UAV-based communications. HetNet studies also include improving communication efficiency and the physical layer security for the users. Moreover, the widespread use of energy and communication-efficient HetNets significantly improves conventional network planning management.

In this project proposal, a reliable, energy-efficient, and effective vertical HetNet (VHetNet) architecture is proposed. For this purpose, a realistic Poisson point process-based configuration will be designed in the terrestrial HetNet structure. It is aimed to reveal the energy and communication efficiencies and physical layer security of the VHetNet using UAV and IRS in terms of trajectory, location, and altitude. Additionally, the communication channel estimation for UAV-assisted VHetNets and UAV trajectory design based on the battery consumption model will be analyzed within the scope of the project. Firstly, with the VHetNet communication simulation, it is planned to realize the performance analysis by both conventional and deep learning (DL) based approaches considering the environmental channel effects. Markov fluid queue (MFQ) theorem is going to be used in the battery consumption model. Next, UAV-based VHetNet analysis will be evaluated by the network clustering approach, location, and trajectory optimization. In the proposal, UAV-based network scenarios, coverage, trajectory, position, and height will be discussed to maximize spectral efficiency. Energy-efficient signal processing approaches will be determined for IRS-aided VHetNets. Finally, the graphical user interface design will be studied and a MATLAB-based simulation library will be created to present the theoretical and simulation results of the obtained analytical derivations.

The project team consists of one project manager from Istanbul Technical University (ITU) and five researchers from three different universities (ITU, Kocaeli University, and Kütahya Dumlupinar University) and the industry. The project comprises 5 main work packages with a duration of 30 months. Different expertise of the researchers in communication and statistical signal processing areas will contribute to the successful completion of the project.

The outputs and widespread impact of the project can be evaluated by contributing to our country to reach an important point in the field of global communication. In our country, it is of great importance to deepeninghigh-impactthe research activities, especially for 6G. Moreover, the realization of the project with the participation of the universities and the industry will help a long-term scientific cooperation among partners. At the end of the project, an important part of the theses of 3 PhD and 1 MSc scholarship students is aimed to be constituted. It is aimed to publish high impact IEEE journal articles and international conference papers with the achieved project results.

19.06.2022

M.E. Kechagia, S. Aldirmaz-Colak, M. Basaran, L. Durak-Ata, “Sum-rate analysis in reconfigurable intelligent surface-aided UAV networks,” IEEE Signal Proc. Commun. Appl. Conf. (SIU’22), 16-18 May 2022, Karabuk, Turkey (in Turkish, hybrid conf., presented virtually). [IEEE SIU] [ResearchGate]

Reconfigurable intelligent surfaces (RIS) have emerged as one of the promising systems for energy efficiency in wireless communications in recent years. In this study, the downlink scenario with an RIS-assisted unmanned aerial vehicle (UAV) networks is discussed. The effect of direct link on the capacity of RIS-assisted systems is examined, taking into account the situations whether there exists link between the users and the UAV. In addition, the optimum phase shift matrix of RIS is obtained by fixed point iteration method. In the simulation results, it has been observed that the direct link between the UAV and the user positively affects the achievable sum-rate when the optimum phase shift matrix is used. In addition, in the absence of a direct link, it is concluded that the user closest to RIS has the highest sum-rate.

19.06.2022

A. Hashi, S. Aldirmaz-Colak, M. Basaran, L. Durak-Ata, “Channel estimation effect on sum-rate analysis of RIS-aided UAV-based MISO systems,” IEEE Signal Proc. Commun. Appl. Conf. (SIU’22), 16-18 May 2022, Karabuk, Turkey (in English, hybrid conf., presented virtually). [IEEE SIU] [ResearchGate]

In this paper, we investigate channel estimation performance on sum-rate for reconfigurable intelligent surface (RIS) assisted unmanned aerial vehicles (UAV)-based multiple-input single-output (MISO) systems with multi-users. We assume that a drone with a predetermined trajectory acts as a base station. The channel estimation is performed by PARAllel FACtor (PARAFAC) decomposition method. Sum-rate simulations are performed for the cases where the channel is perfectly known and unknown. From the simulation results, it has been observed that the number of pilot signals used for channel estimation is quite effective on the total transmission speed as it improves the channel estimation.

19.06.2022

Project Goal

Designing 6G-compatible wireless heterogeneous network systems through the integration of UAVs and intelligent reflective surfaces.