Frequency-selective Slow Rayleigh Fading Research Articles

Performance of Rake receiver assisted adaptive-modulationbased CDMA overfrequency selective slow Rayleigh fading channels

A closed form expression of the average bit error rate (BER) is derived for a Rake receiver adaptive-modulation scheme over frequency selective slow Rayleigh fading channels. Multidimensional minimisation of a cost function based on the derived closed form BER expression is performed to optimise the switching levels for a constant BER adaptive modulation system.

BER analysis of 2PSK, 4PSK, and 16QAM with decision feedback channel estimation in frequency-selective slow Rayleigh fading

The average bit error rate (BER) performances of coherently detected 2PSK, 4PSK, and 16QAM in frequency-selective slow Rayleigh fading are analyzed. Decision feedback channel estimation (DFCE) is considered, in which the past L-received signal samples are remodulated to remove the modulation phase by feeding back the detected symbol sequence and then averaged. Analytical expressions for the conditional BER for the given transmitted symbol sequence are derived, and the average BER performances are evaluated by Monte Carlo simulation. It is shown that as L increases, the BER performance improves and approaches that of ideal coherent detection (with perfect channel estimation), and the loss in E/sub b//N/sub 0/ required for BER=0.1% relative to ideal coherent detection becomes as small as 0.4 dB when L=10. It is found that while the best performance is achieved by 2PSK and 4PSK when additive white Gaussian noise (AWGN) is the predominant cause of error (i.e., low E/sub b//N/sub 0/ regions), 16QAM modulation can achieve almost the same performance as 4PSK when the delay spread is the predominant cause of error (i.e., large E/sub b//N/sub 0/ regions), and the worst performance in this case is by 2PSK. The effects of power delay profile shape (double-spike, exponential, and Gaussian profiles assumed), rolloff factors of the Nyquist transmit/receive filters, and the transmitted symbol sequence pattern on the average BER performance are discussed.

Micro- and macrodiversity MDPSK on shadowed frequency-selective channels

The performance of M-ary differential phase shift keying (MDPSK) on frequency-selective slow Rayleigh fading, lognormal shadowed channels with diversity combining is analyzed for mobile and portable applications. The use of L-branch equal gain postdetection microdiversity combining to mitigate the effects of fading and P-port macrodiversity to alleviate the effects of shadowing are investigated. Four performance criteria are considered for a frequency-selective multipath fading, intersymbol interference channel. These are, the short term bit error rate (BER), the irreducible BER, the complementary distribution over the lognormal shadowing of the average BER, and the probability that the instantaneous BER exceeds a threshold value, averaged over a spatial environment. Closed-form expressions for the four performance criteria are obtained. The BER and outage performance results show that diversity combining is an effective method for improving the system performance (and hence system reliability), when the normalized delay spread is not large. It is also seen that, in most cases, 4DPSK gives the best performance followed by 8DPSK and 2DPSK, respectively, for a given information throughput.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of diversity with simple block coding on correlated frequency-selective fading channels

We investigate the effects of correlation on the performance of diversity systems in wideband wireless radio environments. Specifically, the average bit error rate (BER) performance of M-ary differential phase shift keying (MDPSK) on correlated frequency-selective slow Rayleigh fading channels is analyzed. A two-branch diversity receiver with postdetection equal gain combining is considered. Nyquist pulse shaping is used and differential detection is employed at the receiver. The effects of cochannel interference on the system performance are assessed using a Gaussian interference model. To further enhance the system performance, the effects of combined diversity and forward error correction (FEC) coding on the average BER are investigated. Results using short cyclic block codes with perfect bit interleaving are obtained. The effects of the root mean square (RMS) delay spread, the amount of correlation, and the level of modulation, M, on the average BER are investigated in detail for both coded and uncoded systems. The results show that dual branch diversity combining with a correlation coefficient of 0.5 outperforms (in terms of BER) short block codes with perfect bit interleaving, and that combined diversity and coding strategies are effective in combatting the effects of frequency-selective fading.

Bit error rate of decision feedback equaliser for indoor wireless communications

The bit error rate is evaluated using computer simulation for a 4-QAM indoor data communication system with decision feedback equaliser. The indoor wireless environment is modelled by a frequency-selective slow Rayleigh fading channel. The results are compared with the unequalised system and the system using a linear adaptive equaliser.