Hasan Dincer

FFT and filter bank based spectrum sensing for WLAN signals

As wireless communication devices have increased rapidly, much attention has been paid to the spectrum resources. Cognitive Radio (CR) technology has received increasing attention as a potential approach to utilize more effectively the radio frequency bands. CRs need to dynamically and reliably determine spectral holes which could be used for secondary transmissions. In this study, wideband multichannel spectrum sensing techniques are considered, using either FFT or filter bank based spectrum analysis. We focus on detecting spectral gaps between OFDM-based WLAN signals in the 2.4 GHz ISM band. It is found out that the limited spectral purity of WLAN signals, allowed by the 802.11g specifications, significantly restricts the ability to detect possible weaker signals in the spectral gaps between WLAN channels. Improved spectral purity of the primary signals greatly enhances the sensitivity of spectrum sensing, provided that spectrally well-contained filter bank based spectrum analysis methods are used.

Adaptive Neuro-Fuzzy-Based Control of Drying of Baker's Yeast in Batch Fluidized Bed

A control system was designed using adaptive neuro-fuzzy inference system (ANFIS) for industrial-scale batch drying of bakers yeast. The temperature and flow rate of inlet air were considered as the manipulated variables to control the temperature and dry matter of the product, respectively, resulting in two adaptive fuzzy controllers. The membership functions for all inputs were adjusted by a hybrid learning algorithm. The database used in this work comprises large quantities of industrial-scale data (about 570 batches) obtained under different working conditions over one year. This database was used for learning and testing phases of the ANFIS controller. The performance of the proposed controller demonstrates the effectiveness and potential of the proposed ANFIS-based controller.

Evaluation of FPGA-based Software Radio Beamformers for 3G Wireless

This paper presents implementation of some CDMA system compatible antenna array algorithms such as least mean square (LMS), constant modulus (CM) and space code correlator (SCC) on FPGA (such as Xilinx Virtex II Pro FPGA). Implementation issues such as architecture complexity and weight vector computation times are presented. For the signal modeling, cdma2000 reverse link signal model is considered using uniform linear array (ULA) topology. Results show that FPGA based implementation provides relatively short weight vector computation times compared to previously obtained DSP based implementations

Design of impedance matching network for B&K 8104 hydrophone via Direct Computational Technique for underwater communication

Underwater acoustic communication is a rapidly growing field of applied research and is a technique of sending and receiving message below water. There are several ways of doing such communication but the most common one is realized by using transducers. In underwater acoustic communication, one of the most important problems is driving the transducers with matched network. In this study, design of impedance matching network for B&K 8104 hydrophone that can be used for underwater communication was performed via Direct Computational Technique (DCT).

Desing of an underwater communication receiver pre-amplifier

Underwater acoustic communication is a rapidly growing field of applied research and engineering. The need for underwater wireless communication exists in applications such as remote control in off-shore oil industry, pollution monitoring in environmental systems, collection of scientific data recorded at ocean-bottom station and by unmanned underwater vehicles, speech transmission between divers and mapping of the ocean floor for objects detection and recovery. The lack of these applications are due to large size and high cost of receiver system. In this study, design of a modular receiver pre-amplifier that can be used for underwater communication and data acquisition applications in between 200 Hz and 16 kHz with B&K 8103 hydrophone was performed.

Implementation of underwater communication with TMS320VC5509A DSK

Underwater acoustic communication is a rapidly growing field of research and engineering as the applications. Especially it is necessary for submarine-ship, submarine-submarine and ship-submarine communications. The last several years have seen rapid advances in DSP (digital signal processor) architecture technologies. These advances have made it possible for DSPs to be used for applications previously considered unsuitable for them. In this paper, we implement an prototype for underwater acoustic communication via the transmitter and receiver sides on two TMS320VC5509A DSK boards with using upper sideband-suppressed carrier (SSB) and selectable carrier frequencies 8,0875 kHz - 39 kHz including the frequencies defined in the STANAG 1074.

Gait trainer for children with spastic cerebral palsy

A device is developed to improve the walking ability of children with spastic cerebral palsy, who have damage to the area of their brain which controls muscle tone and that causes trouble walking by using their toes instead of applying a steady force to their heels. This device can be adjusted to a correct pressure level to the heels and variations from this value can be displayed by audio and visual signals. In addition to all these valuable signals, the data collected during the walking therapy is stored in a microcontroller and transferred to a computer to provide a database for physical therapy (PT) and for children with cerebral palsy. By using this data, a better walking therapy program can be developed by special PT teachers.

Fuzzy Logic Control of High Voltage DC Transmission System

This paper introduces a fuzzy controller of the rectifier side in high voltage direct current (HVDC) system. Especially, rectifier side of the typical point-to-point system has been taken consideration. In the rectifier, thyristors are used as control devices that can handle high voltage and power. Turn on, turn off, triggering and protections of these devices have lots of problem and are very sensitive. Especially, in changing voltage and frequency, these problems are appeared itself. Therefore, dc current of the rectifier output becomes unstable. Also, device dissipation, transmission losses and effects of environments cause increasing of these problems. In this study, a fuzzy controller is designed to solve these problems. Finally, a comparative study has been performed with and without fuzzy control.