Mehmet Safak

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This paper proposes opportunistic beamforming with multiple orthogonal beams and superposition coding on each beam for the downlink transmission in a single-cell environment. By exploiting limited feedback SINRs, the base station schedules simultaneous data transmission on multiple beams to the pairs of users with the largest SINRs. This paper presents the(More)
This paper presents a comparison between the outage capacity of MIMO channels predicted by the Kronecker and Müller models as a function of the number of scatterers, transmit and receive antennas. The Müller model is based on the single-scattered rays between arrays of transmitand receive antennas, while the Kronecker model considers only double scattering.(More)
The performance of DMT systems is studied in impulsive noise channels by using Middleton's Class A noise distribution. A statistical model is developed to generate Class A distributed impulsive noise samples and this model is used for the performance analysis. An exact expression is derived for the subchannel SER. By employing the central limit theorem, the(More)
This paper presents the bit error probability performance, in a Rayleigh fading channel, of a 3×3 multiple input multiple output (MIMO) system in which only one of the transmitter antennas is fed, whereas the others are used as parasitic elements. The transmit power, which feeds only one of the transmit antennas, is used more efficiently than the(More)
In this paper, the construction of GMSK modulated SDR (Software defined radio) design which could be processed in nano-satellites is discussed. A Gaussian FIR filter which is controllable and has the coefficients arranged with different BT values (0.3, 0.5, 0.7, and 1.0) has been formed. After the filter which works on the Cyclone II FPGA has been(More)
This paper examines the performances of spatial multiplexing (SM) and maximal ratio combining (MRC) systems in the presence of the polarization diversity. It is assumed that dual-polarized antennas are used at both the transmitter and the receiver. The symbol error rate (SER) for SM and MRC systems is obtained as a function of cross polarization(More)
This paper presents a comparison between the outage capacity of multiple-input multiple-output (MIMO) channels predicted by Kronecker and Muller models as a function of the number of scatterers, transmit-and receive antennas. The results show that the channel capacity predictions by the Muller model are higher than those by the Kronecker model. This is(More)
This paper presents a shadowing model due to diffraction from multiple knife-edge obstacles. By using the ray-tracing method, the statistical character of the shadowing phenomenon is determined and the results are compared with the statistical model based on log-normal shadowing. The effects of the number of obstacles, the distances between them, variations(More)