Arun K. Gurung

Performance analysis of amplify-forward relay in mixed Nakagami-m and Rician fading channels

The performance of a dual-hop amplify-and forward relay system is analyzed in terms of outage probability and average symbol error rate. The source-relay and relay-destination channels experience mixed fading distributions namely, Rician and Nakagami-m. Analytical expressions for Cumulative Distribution Function (CDF) and Probability Density Function (PDF) of end-end signal-to-noise-ratio (SNR) are derived and confirmed with Monte-Carlo simulation. Approximate lower bound for outage probability is also derived, which becomes tight at high SNR values. The expressions are given in terms of infinite sum series of modified Bessel function, which converges after finite iterations. The derived expressions are valid for different fading scenarios (depending on m factor), and specialize to previously published results for m = 1.

Power Savings Analysis of Clipping and Filtering Method in OFDM Systems

The clipping and filtering method is analyzed in terms of power savings. The analysis takes account of the gain in the amplifier efficiency due to peak-to-average-power-ratio (PAPR) reduction. Assuming a linear amplifier and a typical digital signal processor, the power savings is shown to be in the order of Watts.

Spectral efficiency of maximum ratio combining (MRC) over slow fading with estimation errors

In this paper, we derive closed-form expressions for capacity statistics of the maximal ratio combining (MRC) system, taking into account the effect of imperfect channel estimation at the receiver. The channel considered is a slowly varying flat Rayleigh fading that is also spatially independent. The combiner weights are assumed to be affected by Gaussian errors at the receiver. In particular, we derive the moment generating function (MGF), complementary cumulative distribution function (CDF) and the probability density function (PDF) of the capacity. Furthermore, we derive closed-form expressions for the system capacity when employing different adaptive transmission schemes such as (1) optimal power and rate adaptation (opra); (2) constant power with optimal rate adaptation (ora); and (3) channel inversion with fixed rate (cifr). Analytical results show accurately the impact of the channel estimation error on the achievable spectral efficiency.

One-Iteration-Clipping-Filtering (OICF) scheme for PAPR reduction of OFDM signals

A new scheme for iterative clipping and filtering (ICF) method is proposed for PAPR (peak-to-average power ratio) reduction of OFDM (orthogonal frequency division multiplexed) signals. The proposed one-iteration-clipping-filtering (OICF) scheme achieves target PAPR in one iteration, instead of K (>1) iterations as in conventional ICF method. An empirical expression is derived to scale original clipping threshold so that the target PAPR can be achieved in first iteration.

Selection Decode-And-Forward Relay Networks with Rectangular QAM in Nakagami-m Fading Channels

In this paper, we investigate the average symbol error probability (SEP) of fixed decode-and-forward relay networks over independent but not identically distributed Nakagami-m fading channels. We have derived closed form expression of SEP for general rectangular quadrature amplitude modulation (QAM) under relay selection scheme where only the best relay forwards message from the source to the destination. The expressions are in terms of hypergeometric series which can be efficiently numerically evaluated. The numerical results are validated with Monte-Carlo simulations.

Spectral efficiency evaluation for selection combining diversity (SCD) scheme over slow fading

In this paper we derive closed-form expressions for the single-user capacity of selection combining diversity (SCD) system, taking into account the effect of imperfect channel estimation at the receiver. The channel considered is a slowly varying spatially independent flat Rayleigh fading channel. The complex channel estimate and the actual channel are modelled as jointly Gaussian random variables with a correlation that depends on the estimation quality. Three adaptive transmission schemes are analysed: 1) optimal power and rate adaptation opra; 2) constant power with optimal rate adaptation ora; and 3) channel inversion with fixed rate cifr. Furthermore, we derive in this paper analytical results for capacity statistics including moment generating function (MGF), complementary cumulative distribution function (CDF) and probability density function (PDF). These statistics are valid for arbitrary number of receive antennas. Our numerical results show the effect of Gaussian channel estimation error on the achievable spectral efficiency.

Closed-form expressions for symbol error rates of MIMO-MRC with channel estimation error

In this paper, we derive closed form expressions for average symbol error rate of M-ary signalling for MIMO-MRC (MRT) systems over Rayleigh fading channels taking account of channel estimation errors. Following the moment generating function (mgf), we formulate the final expressions in the form of hypergeometric functions. The expressions are valid for an arbitrary number of antennas and any modulation levels. MRT system suffers significant performance degradation due to Gaussian estimation errors. Evenly distributed antenna system offers better trade-offs.

Performance Evaluation of Generalized Selection Combiners Over Slow Fading with Estimation Errors

In this paper we derive closed-form expressions for the single-user adaptive capacity of generalized selection combining (GSC) system, taking into account the effect of imperfect channel estimation at the receiver. The channel considered is a slowly varying spatially independent flat Rayleigh fading channel. The complex channel estimate and the actual channel are modelled as jointly Gaussian random variables with a correlation that depends on the estimation quality. Three adaptive transmission schemes are analyzed: (1) optimal power and rate adaptation; and (2) constant power with optimal rate adaptation, and (3) channel inversion with fixed rate. In addition to deriving an exact expression for the capacity of the aforementioned adaptive schemes, we analyze the impact of channel estimation error on the capacity statistics and the symbol error rate for GSC systems. The capacity statistics derived in this paper are the moment generating function, complementary cumulative distribution function and probability density function for arbitrary number of receive antennas. Moreover, exact closed-form expressions for M-PAM/PSK/QAM employing GSC are derived. As expected, the channel estimation error has a significant impact on the system performance.

Performance evaluation of generalized selection combiners (GSC) over slow fading channels with estimation errors

In this paper, we analyze the impact of channel estimation error on the capacity statistics and the symbol error rate (SER) for generalized selection combiners (GSC) systems. The channels are assumed slow flat Rayleigh fading and spatially independent. The capacity statistics moment generating function(MGF), complementary cumulative distribution function (CDF) and probability density function (PDF) are valid for arbitrary number of receive antennas. Moreover, exact closed-form expressions for M-PAM/PSK/QAM are derived. As expected, the channel estimation error has significant impact on the system performance.

Performance analysis of maximal ratio combiner in correlated rayleigh fading

In this contribution, we investigate the impact of channel correlation on the ergodic capacity, capacity statistics and symbol error rate (SER) for maximal ratio combiner (MRC) multichannel diversity systems over correlated Rayleigh fading channels. We derive exact closed-form expressions for average channel capacity, an upper bound and its asymptotically tight approximation. The capacity statistics moment generating function (MGF), complementary cumulative distribution function (CDF) and probability density function (PDF) derived are valid for arbitrary number of receive antennas. Furthermore, we derive an exact closed expression for general M-PSK modulation. Correlation among channels degrades the system performance as expected.