Oguz Kucur

ICI reduction in OFDM systems by using improved sinc power pulse

In this paper, we propose a new pulse shape to reduce the average ICI power of OFDM systems. Numerical and simulation results show that the proposed pulse is superior to the conventional pulse shapes in terms of ICI power reduction, SIR and BER performance.

A novel framework on exact average symbol error probabilities of multihop transmission over amplify-and-forward relay fading channels

In this paper, we propose an analytical framework on the exact computation of the average symbol error probabilities (ASEP) of multihop transmission over generalized fading channels when an arbitrary number of amplify-and-forward relays is used. Our approach relies on moment generating function (MGF) framework to obtain exact single integral expressions which can be easily computed by Gauss-Chebyshev Quadrature (GCQ) rule. As such, the derived results are a convenient tool to analyze the ASEP performance of multihop transmission over amplify-and-forward relay fading channels. Numerical and simulation results, performed to verify the correctness of the proposed formulation, are in perfect agreement.

Better wavelet packet tree structures for PAPR reduction in WOFDM systems

This paper presents a proper way to reduce the peak-to-average power ratio (PAPR) in Daubechies (Db) wavelet-based OFDM (WOFDM) by searching better wavelet packet tree (BWPT) structures. These BWPT structures are obtained by using a brute force search algorithm. Numerical and simulation results also show that BWPT structures have lower PAPR values than conventional Mallat structures without any degradation in bit error rate (BER) performance for the same bandwidth occupancy. In addition, this PAPR reduction method does not introduce any additional complexity to WOFDM system since BWPT structures are obtained by selecting the proper ones from wavelet packet tree space.

On the sum of gamma random variates with application to the performance of maximal ratio combining over Nakagami-m fading channels

The probability distribution function (PDF) and cumulative density function of the sum of L independent but not necessarily identically distributed gamma variates, applicable to maximal ratio combining receiver outputs or in other words applicable to the performance analysis of diversity combining receivers operating over Nakagami-m fading channels, is presented in closed form in terms of Meijer G-function and Fox H̅-function for integer valued fading parameters and non-integer valued fading parameters, respectively. Further analysis, particularly on bit error rate via PDF-based approach, too is represented in closed form in terms of Meijer G-function and Fox H̅-function for integer-order fading parameters, and extended Fox H̅--function (Ĥ) for non-integer-order fading parameters. The proposed results complement previous results that are either evolved in closed-form, or expressed in terms of infinite sums or higher order derivatives of the fading parameter m.

Performance Analysis of Joint Single Transmit and Receive Antenna Selection in Nakagami-m Fading Channels

In this paper, multi-antenna systems employing both single transmit and single receive antenna selection (single TAS/single RAS) are examined for independent and identically distributed (i.i.d.) flat Nakagami-m fading channels. In this joint selection scheme, signal transmission and reception is performed over a single communication link with the highest signal-to-noise ratio (SNR). Exact bit/symbol error rate expressions for binary modulation, M-ary phase shift keying and square M-ary quadrature amplitude modulation signals are derived by using the moment generating function based analysis method. Also, upper bounds are obtained in order to show that the investigated systems achieve full diversity orders at high SNRs. Besides, outage probability analysis is carried out for examining system capacity. Analytical results are validated by simulations.

New results on the sum of Gamma random variates with application to the performance of wireless communication systems over Nakagami-m fading channels†

The probability density function (PDF) and cumulative distribution function of the sum of L independent but not necessarily identically distributed Gamma variates, applicable to the output statistics of maximal ratio combining (MRC) receiver operating over Nakagami-m fading channels or in other words to the statistical analysis of the scenario where the sum of squared Nakagami-m distributions are user-of-interest, is presented in closed-form in terms of well-known Meijers G function and easily computable Foxs H-bar function for integer valued and non-integer valued m fading parameters. Further analysis, particularly on bit error rate via a PDF-based approach is also offered in closed form in terms of Meijers G function and Foxs H-bar function for integer valued fading parameters, and extended Foxs H-bar function (H-hat) for non-integer valued fading parameters. Our proposed results complement previous known results that are either expressed in terms of infinite sums, nested sums, or higher order derivatives of the fading parameter m.

Exact performance of wireless multihop transmission for M-ary coherent modulations over generalized gamma fading channels

Closed-form moment generation function (MGF) expressions for the harmonic mean of N independent and not identically distributed generalized gamma random variables (RVs) are presented and some well known special cases are accentuated. The statistical results are also applied in order to obtain exact symbol error rate (SER) performance of wireless multihop transmission with non-regenerative relays and M-ary coherent modulations over generalized gamma flat fading channels.

Performance of Transmit Antenna Selection and Maximal-Ratio Combining in Dual Hop Amplify-and-Forward Relay Network over Nakagami-m Fading Channels

In this paper, we study end-to-end performance of transmit antenna selection (TAS) and maximal ratio combining (MRC) in dual hop amplify-and-forward relay network in flat and asymmetric Nakagami-m fading channels. In the network, source and destination communicate by the help of single relay and source-destination link is not available. Source and destination are equipped with multiple antennas, and relay is equipped with single antenna. TAS and MRC are used for transmission at the source and reception at the destination, respectively. The relay simply amplifies and forwards the signal sent by the source to the destination by using channel state information (CSI) based gain or fixed gain. By considering relay location, for CSI based and fixed relay gains, we derive closed-form cumulative distribution function, moments and moment generating function of end-to-end signal-to-noise ratio, and closed-form symbol error probability expression. Moreover, asymptotical outage probability and symbol error probability expressions are also derived for both CSI based and fixed gains to obtain diversity order of the network. Analytical results are validated by the Monte Carlo simulations. Results show that diversity order is minimum of products of fading parameter and number of antennas at the end in each hop. In addition, for optimum performance the relay must be closer to the source when the diversity order of the first hop is smaller than or equal to that of the second hop.

Performance Analysis of Maximal-Ratio Transmission/Receive Antenna Selection in Nakagami-

This paper focuses on multi-antenna systems that employ both maximal-ratio transmission and receive antenna selection (MRT&RAS) in independent and identically distributed Nakagami-m flat-fading channels with channel estimation errors (CEE) [or feedback quantization errors (FQE)] and feedback delay (FD). Useful statistics of the postprocessing signal-to-noise ratio (SNR) such as the probability density function, cumulative distribution function, moment-generating function, and th-order moments are presented. To examine the capacity and the error performances of the MRT&RAS scheme, ergodic capacity, outage probability, and bit error rates/symbol error rates (BERs/SERs) for binary and M-ary modulations are analyzed. Exact analytical expressions for all the performance metrics are separately derived for practical situations that consist of CEE (or FQE) and FD, as well as ideal estimation and feedback conditions. By considering approximations for the statistics of the postprocessing SNR, it is shown that, at high SNRs, the investigated system achieves full-diversity orders in the ideal case, whereas it keeps maintaining receive diversity at practical impairments. The performance superiority of the MRT&RAS scheme to other diversity schemes is also shown by numerical comparisons. In addition, analytical performance results related to the outage probability and BERs/SERs are validated by Monte Carlo simulations.

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In this work, the performance of wavelet based OFDM (WOFDM) is studied and compared to that of conventional OFDM over multipath Rayleigh fading channels with exponential power delay profile. Results show that WOFDM has better bit error rate (BER) performance than conventional OFDM without cyclic prefix (CP) for all signal-to-noise ratios (SNRs) and also outperforms OFDM with CP for low SNR values in indoor and outdoor environments. Therefore, WOFDM might be an alternative to conventional OFDM since it also has better bandwidth efficiency.