Mehmet Akif Yazıcı

Istanbul Technical University · Institute of Informatics

Flying Ad-Hoc Networks are wireless ad-hoc networks that unmanned aerial vehicles are used as communication nodes in environments where it is difficult to establish a proper communication infrastructure. FANET systems have high dynamism levels because the nodes move at very high speeds and UAVs can have various mobility models to use. The fact that...

Physical layer authentication is an important technique for cybersecurity, especially in military scenarios. Device classification using radio frequency fingerprinting, which is based on recognizing device-unique characteristics of the transient waveform observed at the beginning of a transmission from a radio device, is a promising method in this...

Recent developments in telecommunication world have allowed customers to share the storage and processing capabilities of their devices by providing services through fast and reliable connections. This evolution, however, requires building an incentive system to encourage information exchange in future telecommunication networks. In this study, we...

We present an analytical framework to obtain the distribution of frozen, low quality, and high quality video in a setting with two video quality levels where the channel is dynamic and the data rate the user can achieve varies with time. The presented model, which is based on multi-regime Markov fluid queues, is also capable of producing the distri...

We propose an analytical method for an M/M/1 vacation queue with workload dependent service rates. We obtain the distribution of the workload in the system, and consider a power-saving and performance trade-off problem. Numerical experiments reveal that square root service rate function has lower cost than that of linear and quadratic service funct...

This paper presents a comprehensive survey of existing cyber security solutions for fog-based smart grid SCADA systems. We start by providing an overview of the architecture and the concept of fog-based smart grid SCADA systems and its main components. According to security requirements and vulnerabilities, we provide a classification of these solu...

We propose a Markov fluid queue-based analytical framework for the computation of freeze probability of video playout in a cellular communication setting. We draw several conclusions from the numerical results as to the effects of initial buffering, initial state, and adaptive playout.

We present an exact analytical model for single-wavelength quality of service (QoS) differentiation in a two-class optical packet switch. In this system, QoS differentiation is achieved by limiting the set of fiber delay lines (FDLs) to the low-priority class, whereas the high-priority class is allowed to access the entire FDL bank. The analytical...

We present a new numerical method to obtain the finite- and infinite-horizon ruin probabilities for a general continuous-time risk problem. We assume the claim arrivals are modeled by the versatile Markovian arrival process, the claim sizes are PH-distributed, and the premium rate is allowed to depend on the instantaneous risk reserve in a piecewis...

We propose a numerical algorithm for finding the steady-state queue occupancy distribution for a workload-dependent MAP/PH/1 queue in which the arrival process and the service rate depend continuously on the instantaneous workload in the system. Both infinite and finite queue capacity scenarios are considered, including partial rejection and comple...

Conventional multi-rate IEEE 802.11 Wireless LANs (WLANs) are associated with the so-called performance anomaly to describe the phenomenon of high bit rate nodes being dragged down by slower nodes. This anomaly is known to be an impediment to obtaining high cumulative throughputs despite the employment of effective link adaptation mechanisms. To co...

Optical Burst Switching (OBS) has been proposed as a candidate technology for the next-generation Internet. In OBS, packets are assembled into a burst, and a burst control packet is sent in advance to inform and reserve resources at the optical nodes in the path of the burst. In this study, we analyze the horizon-based reservation scheme in OBS usi...

WLANs employing IEEE802.11 standards suffer from a performance anomaly that drags down the fast nodes in the WLAN due to the slow nodes. Air time fairness has been proposed to battle this anomaly. We propose a novel distributed method to achieve air time fairness in this study.

Çok-akişli eşler-arasi video, gelecek nesil isteğe bağli video sistemleri iÇin kullanilmaya aday teknolojilerdendir. Çok-akişli video sistemlerinin sorunlarindan birisi, eş dalgalanmasi adi verilen, eşlerin ağla olan bağlantilarinin kopup düzelmesi durumudur. Eş dalgalanmasinin bütşn eşler-arasi sistemlerde olumsuz etkileri olduğu bilinmektedir. Bu...