Maja Ilic-Delibasic

A Novel Method for Performance Analysis of OFDM Polarization Diversity System in Ricean Fading Environment

OFDM (Orthogonal Frequency Division Multiplexing) is proven to be a very effective modulation and multiple access technique that enables high data rate transmission. Due to its good performance it is already implemented in several standardized technologies, and it is very promising technique for the next generation wireless communication systems. Still, further system performance improvements under severe frequency selective fading conditions are necessary, and they can be obtained implementing diversity, at either transmit or/and receive end of a wireless link. Since polarization diversity can be realized using only one compact, dual polarized antenna, it can be considered as an attractive, space and cost effective solution. Analysis presented in this paper shows that implementation of dual polarized antenna at the receiver can lead to significant performance improvement, under certain propagation conditions. In order to calculate BER (Bit Error Rate) for the considered OFDM polarization diversity system with a certain level of the received signals correlation, we propose a novel analytical method. The obtained results are compared with the ones attained by simulation.

Performance improvement of two-hop cooperative relay system under correlated Ricean fadings

This paper studies performance of two-hop cooperative relaying system employing regenerative decode-and-forward (DF) technique. Infrastructure based relay equipped with dual-polarized antenna is assumed, performing maximal ratio combining of the received signals. Link between the source and the relay is characterized as two correlated and non-identical Ricean fading channels. There is also direct communication between the source and the destination. In order to determine the level of improvement introduced through the implementation of polarization diversity, performances of the considered system are compared with the DF relay system with single antenna relay. The obtained results show that, using polarization diversity, the same BER (Bit Error Rate) values can be obtained with significantly lower SNR (Signal to Noise Ratio), despite a certain level of correlation and power unbalance between the diversity branches. In that manner, compared to the system with no diversity, the total needed transmit power for achieving the same level of system performances is reduced, and thus more energy efficient communication is enabled.

MRC Dual-Diversity System over Correlated and Non-Identical Ricean Fading Channels

Motivated by the importance of the Ricean statistical model in describing communication channels, in this paper we study the performance of a dual-branch receive diversity system operating in Ricean fading. Maximal ratio combining (MRC) of two correlated and non-identical Ricean fading channels is considered. A novel mathematical approach for the performance evaluation of the analyzed system is presented. The probability density and cumulative distribution functions of the total received signal-to-noise ratio at the MRC output are derived in a form of rapidly converging infinite sum. Based on the derived expressions, we further proceed with the calculation of the outage probability and the average bit error rate performance of the diversity system under study. The obtained analytical results are verified through an appropriate simulation model.

Performance improvement of two hop decode-and-forward relay systems using dual polarized antenna

This paper studies performance of two-hop decode-and-forward (DF) relay system with the implemented polarization diversity at the receiver. Two correlated and non-identical Ricean fading channels are assumed for the relay to destination link, and maximal ratio combining (MRC) of the received signals is performed at the receiver. Communication between source and relay is also assumed to be over the Ricean fading channel. In order to determine the level of improvement introduced through the implementation of polarization diversity, performances of the considered system are compared with the standard DF relay system with single antenna terminals. The obtained results show that, using polarization diversity, the same BER (Bit Error Rate) values can be obtained with significantly lower SNR (Signal to Noise Ratio), despite a certain level of correlation and power unbalance between the diversity branches. In that manner, compared to the system with no diversity, the total needed transmit power for achieving the same level of system performances is reduced, and thus more energy efficient communication is enabled.

A novel Ricean fading channel model with random K factor

In this paper we develop a new model of Ricean fading channel. Instead of commonly used fading model, where only instantaneous signal to noise ratio (SNR) is assumed to be random variable, we introduce additional random variable - Ricean K factor. Probability density function (PDF) and moment generating function (MGF) of such a new distribution are derived. We also analyze the impact of randomly changing Ricean K factor on statistical behavior and system performance of a wireless communication system. Then the average bit error rate (BER) and outage probability (OP) are obtained for single channel wireless systems.

Impact of random K factor on Ricean fading wireless system performance

In this paper we analyze performance of a wireless communication system in the case of Ricean fading environment. However, instead of commonly used fading model where only instantaneous signal to noise ratio is assumed to be random variable, whereas Ricean K factor is deterministic parameter, we examine the impact that randomly changing K factor have on system performance. A novel moment generating function (MGF) of a new distribution having not only instantaneous signal-to-noise ratio, but also K as random variable, is derived. Then the average bit error rate (BER) and outage probability (OP) are obtained for single channel wireless systems. The analysis is further extended to multichannel reception.

Performance analyzes of dual-hop relay system over Ricean fading channels

In this paper we present analytical model for performance evaluation of dual hop amplify-and-forward relay transmission over non-identical Ricean fading channels on both hops. Probability density function (PDF) and moment generating function (MGF) of total received SNR (signal-to-noise ratio) are presented as fast converging sum. Furthermore, adequate semi-closed form expressions for average bit error rate (BER) and outage probability (OP) are derived. Numerical and simulation results confirm the validity of the proposed analytical model. Additionally, we analyzed the impact of unbalanced SNRs of the two hops on the error performance of the considered relay system.

Performance improvement of decode-and-forward relay systems using dual polarized antenna

This paper studies performance of two-hop decode-and-forward (DF) relay system with the implemented polarization receive diversity system at the destination terminal. Communication between the source and the relay is assumed to be over the Ricean fading channel, while two correlated and non-identical Ricean fading channels are assumed for the relay to destination link. Maximal ratio combining (MRC) of the received signals is performed at the destination, and no direct communication between the source and the destination is considered. In order to determine the level of improvement introduced through the implementation of polarization diversity, performances of the considered system are compared with the standard DF relay system with single antenna terminals. The obtained results show that, using polarization diversity, the same BER (Bit Error Rate) values can be obtained with significantly lower SNR (Signal to Noise Ratio), despite a certain level of correlation and power unbalance between the diversity branches. In that manner, compared to the system with no diversity, the total needed transmit power for achieving the same level of system performances is reduced, and thus more energy efficient communication is enabled.

Performance analysis of dual diversity over correlated Ricean fading channels

In wireless communication systems, the received signal is usually affected by multipath fading due to multiple signal reflections that can seriously degrade their performance. Simple, yet effective, technique to decrease such effects of multipath fading is multiple antennas architecture (diversity). In this paper performance of dual diversity receivers operating over correlated and non-identical Ricean fading channels is analyzed. Various combining schemes, such as MRC (Maximal Ratio Combining), EGC (Equal Gain Combining) and SSC (Switch and Stay Diversity Combining), are considered. For the purpose of those analyses, a new model, based on linear transformation of correlated Ricean random variables into uncorrelated ones, is proposed. In that manner, it is enabled to apply standard procedure for performance analysis used when uncorrelated signals are transmitted over communication channels. MGF (Moment Generating Function) of the received SNR (Signal-to-Noise Ratio) is determined, enabling us to find numerically bit error rate (BER) for different modulation schemes. In this paper, the system with BPSK (Binary Phase Shift Keying) mapping of the input data stream is assumed. BER evaluations have been realized for different Ricean channel conditions, that is: for different values of Ricean K factor, correlation coefficient and power imbalance between diversity branches. The obtained results show that the average BER depends on the correlation between diversity branches and their power imbalance. These two parameters significantly affect system performance, no matter which combination technique is implemented. It is also shown that the influence of branch power imbalance on BER is greater than the influence of correlation coefficient.

Performance analysis of wireless communication system for Ricean fading channel with random K parameter

In this paper we analyze bit error probability of a digital wireless communication system over fading channel, where the random signal envelope fluctuations are described with Ricean fading distribution. Instead of considering only the envelope, i.e. instantaneous signal-to-noise ratio (SNR) as a random variable, whereas Ricean K factor is taken to be a deterministic parameter, we examine implications and insights that can be drawn from assuming a fading channel environment characterized with a random Ricean K factor. A novel moment generating function (MGF) of a such new distribution is derived and average bit error rate (BER) for a single and multi-channel receptions are obtained.