Current implementations of attendance checking in the University of the Philippines - Diliman (UPD) has been time consuming and easily cheated. The roll-call and pen-and-paper method cannot monitor student presence for the whole duration of the class session. Attendance checking systems using mobile technology and the Internet of Things attempt to mitigate these problems, but it also introduces new ones such as inclusivity, cost, and complex implementations. This study investigates the use of Bluetooth Low Energy (BLE) beacons, a mobile application, and a web server to create an attendance checking mechanism capable of eliminating queues and attendance cheating, monitoring student presence, and automating records. We created two procedures for sending information to our server, to determine the general advantages and disadvantages of each in terms of features, scalability, and cost-effectiveness. Procedure 1 mainly uses our Android application which was able to automate and record attendance checking in the background. Procedure 2 uses the ESP32 which was capable of scanning for information from these Android smartphones. Both of these Procedures send information to the web server to create reports based on available records. Overall, Procedure 1 served as the more scalable implementation due to its added features such as alarm systems, and ease of monitoring. However, Procedure 2 was simpler to set-up and more energy-efficient for smartphones since it relied on processing capabilities of the server.
In recent years, unmanned aerial vehicle (UAV) communication has not only attracted extensive discussion in academic circles, but also has been applied to practical scenarios. With the rapid development of UAV communication, its secrecy issues have gradually become prominent. In this paper, the physical layer security of mobile UAV relaying network is studied. We give a scheme of confidential communication to ensure the integrity and confidentiality of information. By optimizing the dynamic position of the UAV and transmit power, our goal is to maximize the minimum secrecy rate. Because the problem we put forward can not be solved directly by the solver, we divide the problem into two sub-problems to analyse. The simulation results show that our program improves the fairness of secrecy communication, and the physical layer security of the mobile UAV relaying network has been enhanced.
In this work, the performance of an eigenvalue-based cooperative spectrum sensing for multiuser multiple-input multiple-output (MIMO) cognitive radio networks is investigated under a correlated fading scenario. The secondary user (SU) is modeled as a MIMO system to detect the presence of primary user signal under incomplete channel state information (CSI) and Rayleigh faded channel model. At each SU, an energy detector is used to obtain the local decision statistic. Next, SU’s local decision is sent to the fusion center (FC) via numerous transmit antennas in order to get the transmitting diversity gain to combat the hidden node problem. Further, FC received the local decision statistic with multiple antennas under Racine faded correlated channel with perfect CSI. Finally, a global decision is made at FC based on an eigenvalue-based detection algorithm. The closed-form expression for the detection probabilities is derived at both SUs and FC. A simulation study shows that the target detection probability P_d≥ 0.95 is achieved even at a very low signal to noise ratio value of -5 dB.
Integration of full-duplex (FD) technology with cooperative device-to-device (CD2D) communications system has recently emerged as a potential candidate for the fifth-generation (5G) and beyond technologies to improve the spectral efficiency of a cellular system. This paper investigates the outage performance of a multicarrier FD CD2D communications system wherein, the D2D link source node (S) serves as an FD relay for uplink cellular transmission. The self-interference (SI) occurring at S is suppressed using analog cancellation schemes, and the residual SI (RSI) is further suppressed using digital domain (DD) RSI cancellation techniques. A probabilistic mathematical model is established for the performance evaluation of the proposed system. The closed-form expressions for D2D and cellular outage probability are derived. Simulation results show that the proposed FD CD2D communications system, along with minimum mean square error-based DD RSI cancellation, gives the optimum performance compared to the least square-based RSI cancellation scheme.
Channel Assignment (CA) in wireless mesh networks (WMNs) has not been well studied in scenarios where the network uses Dynamic Spectrum Access (DSA). This work aims to fill some of this gap. We compare metaheuristic algorithms for optimising the CA in a WMN that has both Wi-Fi and DSA radios (where DSA could be Television White Spaces or 6 GHz). We also present a novel algorithm used alongside these metaheuristic algorithms to ensure that the CA solutions are feasible. Feasible solutions meet the interface constraint, i.e. only as many channels are allocated to a node as it has radios. The algorithm also allows the topology to be preserved by maintaining links. Many previous studies tried to ensure feasibility and/or topology preservation by using two separate steps. The first step optimised without checking feasibility and the second step fixed infeasible solutions. This second step often negated the benefits of the previous step and degraded performance. Other CA algorithms tend to use simple on/off interference models, instead of models that more realistically reflect the physical layer environment, such as the Signal to Interference plus Noise Ratio (SINR). We present our more realistic SINR-based model and optimisation objective. Simulated Annealing (SA) and Genetic Algorithm (GA) are applied to the problem. Performance is evaluated and verified through simulation. We find that GA outperforms SA, finding higher quality solutions faster, although both metaheuristics are better than random allocations. GA can be used daily to find good CAs in changing conditions.
