Orhan Gazi

Collision free row column S-random interleaver

Parallel decodable turbo codes (PDTCs) are suitable for concurrent decoding and hence have low latency. Memory collision issue is an important problem met during parallel processing. In this article, we propose a collision free interleaver for parallel processing operations. The performance of PDTCs is analyzed with the proposed random interleaver preventing the memory collision problem. Distance spectra of PDTCs with the proposed interleaver are computed and compared to those with S-random interleaver.

Fast Decodable Turbo Codes

Decoding delay is an important consideration for the use of turbo codes in practical applications. We propose a new structure for turbo codes which is very suitable for parallel decoding. It is shown by union bound analysis and simulation results that the proposed system performance is comparable to that of the classical turbo codes

On Parallelized Serially Concatenated Codes

Serial concatenated codes show very good performance at low signal to noise ratios. However, large decoding delays due to long input frame lengths constitute a major disadvantage for these type of codes. In this study we introduce a new class of concatenated convolutional codes which are very suitable for parallel decoding, thus have much less decoding delays and also show comparable performance to that of classical serial concatenated convolutional codes. The analytical upper bound expressions for performance of the proposed structures are derived using the uniform interleaver concept.

Applications of cognitive radio networks: recent advances and future directions

1Department of Information and Communication Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea 2Department of Computer Science, Texas Southern University, Houston, TX 77004, USA 3Department of Electric and Communication Engineering, Cankaya University, 06790 Ankara, Turkey 4Department of Electrical, Electronic and Power Engineering, Aston University, Birmingham B4 7ET, UK 5Department of Computer and Network Science, Telecom ParisTech, 75013 Paris, France

Prunable Collision Free Random Interleaver Design

In this article we introduce a new collision free prunable random interleaver. The suggested interleaver is a joint structure involving rectangular and S-random interleaver. It comprises a general model for all kind of collision free prunable random interleavers. In addition, it can be designed for any number of parallel processors and any length of information sequence vector and can be considered also as a template for collision free prunable interleavers. The proposed interleaver can be used with all kind of turbo-like codes. The performance of the proposed interleaver is measured with parallel decodable serially concatenated convolutional codes (PDSCCCs) and compared to the PDSCCCs’ performance with collision full S-random interleaver.

Bounds for Generalized Gamma Distributed Fading Channels

In this article, upper bounds for the outage probability and moment generating functions of the fading channels with α-μ distribution are derived. The proposed upper bound for the moment generating function is used in the performance evaluation of M-PSK communication systems. The derived expressions are simple to use and do not require complex software tools to evaluate. We verified the proposed expressions via numerical computations.

Multirate Signal Processing

Digital signals are obtained from continuous time signals via sampling operation. Continuous time signals can be considered as digital signals having infinite number of samples. Sampling is nothing but selecting some of these samples and forming a mathematical sequence called digital signal. And these digital signals can be in periodic or non-periodic forms.

New early termination methos for turbo decoders

Turbo codes have large latency due to iterative decoding steps and complex decoding algorithms. To decrease the decoding delay it is essential to terminate the decoding operation as soon as there is sufficient information for data bits. Early termination can be achieved by defining stopping criteria beyond which negligible achievement is observed. In this article, we investigate some efficient stopping criteria based on the variance of extrinsic information and population of the bits below a predetermined threshold. We show that variance based method is better than its previously suggested counterparts, and threshold based method is the least complex one considering the available methods.

A new companding technique for PAPR reduction in OFDM communication systems

One of the major disadvantages of OFDM communication systems is their high peak-to-average power ratio (PAPR) which degrades system performance when nonlinear power amplifiers are employed. Among the proposed PAPR techniques companding is favorable due to its simplicity and easy of implementation. In this article, using the arctangent function we propose a new compading technique for PAPR reduction. We compare the proposed technique to the previously suggested exponential companding, and μ-law companding methods. Via computer simulations it is verified that the proposed technique is better than exponential and μ-law companding methods for PAPR reduction.

Entity, Architecture and VHDL Operators

VHDL stands for “very high speed integrated circuits hardware description language”, and first developed by the US department of defense in 1980s. It is used to describe the behavior of an electronic circuit. VHDL programs consist of program modules. A module is nothing but a program segment written for some specific purposes. For instance, we have package modules, test modules, and main VHDL modules, i.e., main programs.