Beng Soon Tan

Performance Analysis of LDPC Codes with Maximum-Ratio Combining Cascaded with Selection Combining over Nakagami-m Fading

Low-density parity-check (LDPC) codes combined with cascade combining are able to achieve excellent bit-error rate (BER) performance over multipath fading channels. Cascade combining, which involves two stages of diversity combining, is very useful for situations where site diversity exists and it can reduce the complexity of the combiner when the number of diversity branches increases. The average output signal-to-noise ratio and the uncoded BER expressions of cascade combining over independent and identically distributed (i.i.d.) Nakagami-m fading channels are derived. The BER expressions of cascade combining with LDPC codes over i.i.d. Nakagami-m fading channels are derived based on the Gaussian approximation (GA) approach. These expressions include selection combining and maximum-ratio combining as special cases. The signal-to-noise ratio (SNR) thresholds for error-free decoding are obtained using density evolution (DE). Comparisons among GA analysis, DE analysis, and simulations show that they are in good agreement. The expressions obtained from the GA analysis provide better theoretical understanding of the system performance and allow us to compute the BER and SNR threshold more efficiently as compared to DE and simulations. Lastly, the stability conditions for GA and DE analyses, which are found to be exactly the same, are also presented.

Symbol-error rate of selection combining over two-wave with diffuse power fading

Symbol-error rate expressions of selection combining over the two-wave with diffused power (TWDP) fading channel are derived using the moment-generating function approach. The TWDP fading model is characterized by two specular waves in the presence of other diffused waves and has both the Rayleigh and Rician fading channels as special cases. The TWDP fading model is applicable to both the narrow-band and wide-band operations and when directional antennas are used. The derived theoretical expressions are validated by simulation results.

Performance analysis of LDPC codes with selection diversity combining over identical and non-identical rayleigh fading channels

Selection diversity combining employed in conjunction with low-density parity-check codes is able to mitigate the effects of fading. The closed-form bit-error rate expressions of this scheme over independent and non-identically distributed and independent and identically distributed flat Rayleigh fading channels are derived using the extrinsic information transfer chart and Gaussian approximation. The derived expressions are compared with simulation results as well as the Eb/N0 threshold using density evolution (DE). They are in good agreement with simulation results and have the advantage of reduced computational complexity over DE.

Performance Study of Transmit Antenna Selection With Switch-and-Examine Combining Over Rayleigh Fading

In this paper, we propose a diversity combining system with transmit antenna selection at the transmitter and switch-and-examine combining (TAS/SEC) at the receiver. This system has lower processing complexity as compared with the existing TAS systems such as TAS/maximum-ratio combining (TAS/MRC) and TAS/selection combining (TAS/SC). The performance of the TAS/SEC system with different modulation schemes over an independent and nonidentically distributed (i.n.d.) Rayleigh fading channel is investigated. The expressions of the outage probability, average output signal-to-noise ratio (SNR), and symbol error rate (SER) are derived and validated by simulation results. The performance of TAS/SEC is compared with TAS/SC in terms of the SER and the average number of branches to be estimated. It is shown that, as compared with TAS/SC, the TAS/SEC system is able to achieve a lower SER with fewer branches to be estimated.

Analysis of MIMO Diversity With LDPC Codes Based on a Gaussian Approximation Approach Over Rayleigh Fading Channels

A low-density parity-check (LDPC)-coded multiple-input-multiple-output (MIMO) system is able to achieve excellent bit-error-rate (BER) performance over fading channels. The two types of MIMO systems examined in this paper are the transmit antenna selection/generalized selection combining (TAS/GSC) and orthogonal space-time block code (STBC). The approximate BER expressions of these two systems with LDPC codes using binary phase-shift keying signals over a Rayleigh fading channel are derived based on the Gaussian approximation (GA) approach. These expressions provide a computationally efficient method of analyzing the system performance, as compared with density evolution (DE) and simulation. The stability conditions for both systems using the DE and GA approaches are also presented.

Transmit Antenna Selection Systems: A Performance Comparison of Different Types of Receiver Schemes

In this survey article, we compare the performance of single transmit antenna selection (TAS) systems with different kinds of receiver schemes. These systems include the TAS/switch-and-examine combining (TAS/SEC), TAS/SEC with postselection (TAS/SECPS), TAS/generalized selection combining (TAS/GSC), and TAS/output-threshold generalized selection combining (TAS/OT-GSC) systems. The performance comparisons are made in terms of the average output signal-to-noise ratio (SNR), symbol-error rate (SER), the number of channel estimates Ne, and the number of branches required for processing Np . It is shown that the TAS/SECPS and TAS/OT-GSC systems can achieve similar performance compared with the TAS/selection combining (SC) and TAS/GSC systems, respectively, with a reduced number of both channel estimates and branches required for processing when the predetermined SNR threshold is optimized.

Analysis of Transmit Antenna Selection With Switch-and-Examine Combining With Postselection at the Receiver Over Rayleigh Fading Channels

A diversity-combining system using transmit antenna selection at the transmitter and switch-and-examine combining with postselection (TAS/SECPS) at the receiver is proposed. This system has lower processing complexity as compared with the existing TAS schemes with maximal-ratio combining and selection combining (TAS/SC) at the receiver. The performance of the TAS/SECPS system with different modulation schemes over independent and nonidentically distributed Rayleigh fading channels is examined. The expressions of average output signal-to-noise ratio (SNR) and symbol error rate (SER) are derived and validated by simulation. It is shown that the proposed TAS/SECPS is able to achieve similar average output SNR and SER performance as compared with TAS/SC when the predetermined SNR threshold is optimized. Moreover, the TAS/SECPS requires less number of channel estimates.

Analysis of switch diversity combining over two wave with diffuse power fading

The two wave with diffused power (TWDP) fading model is a very useful fading model characterised by two specular waves in the presence of other diffused waves and is applicable to both the Rayleigh and Rician fading channels as special cases. The performance of switch diversity with binary modulation schemes over the TWDP fading channel is examined. The four types of switch diversity investigated in this study comprise of the switch-and-stay combining, switch-and-examine combining, switch-and-examine combining with post-selection and scan-and-wait combining. The expressions of the average output signal-to-noise ratio (SNR) at the receiver and bit-error rate (BER) are derived and presented. The pre-determined SNR thresholds of the switch diversity over the TWDP fading channel are optimised to obtain the minimum BER. Analytical results are validated by simulation.

Performance Analysis of Orthogonal Space-Time Block Code With Minimum-Selection Generalized Selection Combining Receiver Over Rayleigh Fading

An orthogonal space-time block code (OSTBC) with a minimum-selection generalized selection combining (MS-GSC) receiver is proposed and analyzed. The motivation behind the proposition of this scheme is a reduction in complexity and processing power at the receiver, compared with a conventional OSTBC system utilizing the maximum-ratio-combining receiver. In addition, it was shown that the OSTBC/MS-GSC can achieve similar performance, compared with the OSTBC/GSC with reduced processing when the predetermined threshold is optimized. In the analysis of this OSTBC/MS-GSC system over a Rayleigh-fading channel, the moment-generating function is presented, where it can be conveniently used to numerically compute the symbol error rate (SER). The average number of branches that is being selected for processing at the receiver is computed and compared. The analytical results are validated by the simulation results.

Bit-error rate analysis of low-density parity-check codes with generalised selection combining over a Rayleigh-fading channel using Gaussian approximation

Bit-error rate (BER) expressions of generalised selection combining with low-density parity-check (LDPC) codes, using binary phase-shift keying signals, over an independent and identically distributed Rayleigh-fading channel are derived using the Gaussian approximation (GA) approach. BER results for both selection combining and maximum-ratio combining can be computed from this BER expression as special cases. The symmetry and stability conditions of both density evolution (DE) and GA analysis are also studied. The degree distribution for irregular LDPC codes is optimised using differential evolution. The theoretical results are compared with both simulation results and DE thresholds. These BER expressions allow us to achieve a significant reduction in computational complexity for analysing the system performance as compared to simulation and DE.