Postdetection Diversity Reception Research Articles

Multivariate η−μ fading distribution with arbitrary correlation model

ABSTRACTAn extensive analysis for the multivariate distribution with arbitrary correlation is presented, where novel analytical expressions for the multivariate probability density function, cumulative distribution function and moment generating function (MGF) of arbitrarily correlated and not necessarily identically distributed power random variables are derived. Also, this paper provides exact-form expression for the MGF of the instantaneous signal-to-noise ratio at the combiner output in a diversity reception system with maximal-ratio combining and post-detection equal-gain combining operating in slow frequency nonselective arbitrarily correlated not necessarily identically distributed -fading channels. The average bit error probability of differentially detected quadrature phase shift keying signals with post-detection diversity reception system over arbitrarily correlated and not necessarily identical fading parameters -fading channels is determined by using the MGF-based approach. The effect of fading correlation between diversity branches, fading severity parameters and diversity level is studied.

A Simple Expression of BER Performance in DPSK/OFDM Systems with Post-Detection Diversity Reception

In this letter, we propose a simple but accurate calculation method, that is, an approximate closed-form equation of average bit error rate in DPSK/OFDM systems with post-detection diversity reception over both time- and frequency-selective Rayleigh fading channels. The validity of the proposed method is verified by the fact that BER performances given by the derived equation coincide with those by Monte Carlo simulation.

Differential detection of GMSK signals with postdetection MRC over correlated and unbalanced Nakagami-m fading channels

Differential detection with postdetection diversity reception of Gaussian minimum shift keying (GMSK) signals has become increasingly important owing to its widespread use in wireless communications. Its error analysis, however, is not available in the literature. The authors derive a bit-error probability expression for the differential detection of GMSK signals with post-detection maximal ratio combing (MRC) in additive white Gaussian noise and slow frequency-nonselective arbitrarily correlated and unbalanced Nakagami-m fading channels, in which the diversity branches can have unequal signal-to-noise ratios (SNRs) as well as different severity parameters m. The effects of arbitrary values of the fading severity parameter m and the arbitrary correlation between the unbalanced L diversity channels are considered. The derived expression can be easily computed via numerical integration routines, and hence, can be usefully exploited in the performance evaluation of digital mobile radio systems.

Error-Bound Formulation for Multichannel Reception of<tex>$M$</tex>-DPSK and Pilot-Aided<tex>$M$</tex>-PSK Over Rayleigh-Fading Channels With Postdetection Combining

Upper bounds for symbol-error probability are developed for multichannel reception of M-ary phase-shift keying (M-PSK) over frequency-flat Rayleigh-fading channels. Differential coherent demodulation of differentially encoded M-PSK (M-DPSK), pilot-tone aided coherent demodulation of M-PSK (PTA M-CPSK) and pilot-symbol aided coherent demodulation of M-PSK (PSA M-CPSK) are considered in the formulation. The bounds enable the investigation of the effects of fading correlation and unequal average power level between channels using postdetection diversity reception with maximal-ratio combining. Error-performance degradation due to imperfect demodulation effects, such as Doppler spread in M-DPSK schemes, noisy reference signals in PTA M-CPSK, and PSA M-CPSK schemes can be taken into account in the formulation. Exact bit-error probabilities for both binary and quaternary phase-shift keying are also derived.

Noncoherent diversity reception over Nakagami-fading channels

A method for computing the average bit-error probability of binary differential phase-shift keying (DPSK) and frequency shift-keying (FSK) signals transmitted over Nakagami asymptotically slow fading channels with postdetection diversity reception is presented to extend previously published results. The previously published results apply only for maximum ratio combining, i.e., with predetection combining, where phase coherency is necessary. The results for postdetection combining are derived with the explicit expressions for the most practical cases of independent channels and particular cases of correlated channels.

Performances of 16QAM with fading compensation and postdetection diversity reception in satellite mobile channels

This paper studies the effects of N-branch postdetection selection diversity reception, where N = 1, 2, 3 or 4, incorporated with fading compensation on a digital satellite mobile system. The digital satellite mobile system transmits a pilot-symbol-aided 16-ary quadrature-amplitude modulated (PSA-16QAM) signal over the Rician channels. A selection method that makes use of the pilot symbols to select one of the N branches in the diversity reception system for signal detection, and a novel PSA technique that makes use of both the pilot symbols and data symbols for fading compensation, are proposed. Computer simulation tests are used to assess the effects of the proposed techniques on bit-error rate performances (BER) of the PSA-16QAM system in the presence of additive white Gaussian noise (AWGN) or co-channel interference (CCI) in the Rician faded channels. When frequency diversity is used, PSA-16QAM with 2-branch and 4-branch diversity reception occupies about the same bandwidths as quaternary phase-shift-keying (QPSK) without using diversity and with 2-branch diversity, respectively, yet achieving the same capacity. Thus, simulation tests on the BER performances of a QPSK system without diversity and with 2-branch diversity are also carried out and the results are used to determine the preferred system arrangements. © 1997 John Wiley & Sons, Ltd.

Performances of 16QAM with fading compensation and postdetection diversity reception in satellite mobile channels

This paper studies the effects of N-branch postdetection selection diversity reception, where N = 1, 2, 3 or 4, incorporated with fading compensation on a digital satellite mobile system. The digital satellite mobile system transmits a pilot-symbol-aided 16-ary quadrature-amplitude modulated (PSA-16QAM) signal over the Rician channels. A selection method that makes use of the pilot symbols to select one of the N branches in the diversity reception system for signal detection, and a novel PSA technique that makes use of both the pilot symbols and data symbols for fading compensation, are proposed. Computer simulation tests are used to assess the effects of the proposed techniques on bit-error rate performances (BER) of the PSA-16QAM system in the presence of additive white Gaussian noise (AWGN) or co-channel interference (CCI) in the Rician faded channels. When frequency diversity is used, PSA-16QAM with 2-branch and 4-branch diversity reception occupies about the same bandwidths as quaternary phase-shift-keying (QPSK) without using diversity and with 2-branch diversity, respectively, yet achieving the same capacity. Thus, simulation tests on the BER performances of a QPSK system without diversity and with 2-branch diversity are also carried out and the results are used to determine the preferred system arrangements. © 1997 John Wiley & Sons, Ltd.

Error performance of circular 16-DAPSK with postdetection diversity reception in Rayleigh fading channels

A closed-form expression for the average error probability of circular 16-ary differential amplitude and phase shift keying with postdetection diversity combining is obtained for frequency-nonselective Rayleigh fading channels. The effect of random FM noise is also considered in the evaluation. Since both amplitude and phase are encoded and decoded independently, their detailed performances are analysed separately. System parameters such as the ring ratio and decision thresholds have been optimised for a number of fading conditions. The optimal and suboptimal decision thresholds are evaluated. The optimal ring ratio of the modulation is generally a function of Doppler frequency. The results have shown that postdetection diversity is a powerful technique for reducing the effects of random FM noise.

Selection diversity combining with multiple antennas for MM-wave indoor wireless channels

Presents predetection and postdetection combining schemes for selection diversity reception with multiple antennas for MM-wave indoor radio channels. For those combining schemes, a reduction in complexity is achieved by limiting the number of combined signals to small values and by increasing the number of received signals. Bit error rate (BER) performance of binary phase shift keying (BPSK) with predetection combining of selected signals (CSS) and BER performance of differential BPSK with postdetection CSS are analyzed for slow fading and Rayleigh-distributed envelope statistics. Predetection maximal ratio combining of signals that comes from a single group or several groups of diversity channels as well as postdetection combining of received signals for groups of channels are considered. In comparing predetection combining with groups (PCG) and predetection combining of the best signals (PCB), we observe that the required SNR for achieving a certain BER is approximatively the same (with PCG having a slight advantage of 0.5 dB) for a given number, N, of diversity channels and L combined signals. Furthermore. PCG is equivalent to PCB for L=N since both techniques then correspond to conventional predetection maximal ratio combining (MRC), PCG and PCB are also equivalent when L=1 as both schemes then correspond to conventional selection combining. A small degradation of approximately 2 dB in the required SNR is observed when postdetection diversity reception with groups (PDG) is used instead of PCG. For L=N, PDG reduces to post detection MRC. The PDG technique is considered more suitable than PCB or PCG for MM-indoor wireless systems.

Experimental evaluation of combined postdetection diversity and concatenated channel coding

The combined effects of postdetection diversity reception and concatenated channel coding are experimentally evaluated for /spl pi//4-shift QDPSK signal transmission over a Rayleigh fading channel. Two-branch postdetection diversity reception using maximal ratio combining (MRC) and selection combining (SC) are considered. The concatenated channel coding uses the Reed-Solomon (15,k) code of GP(2/sup 4/) as the outer code and the BCH (7,4) code as the inner code (k=9,11,13). Measured bit error rate (BER) performance results are presented under cochannel interference (CCI) and multipath channel delay spread, as well as additive white Gaussian noise (AWGN).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Postdetection optimal diversity combiner for DPSK differential detection

Postdetection diversity reception weights and combines all the detector outputs before symbol decision to combat the effects of multipath fading. A theoretical analysis of a postdetection optimal diversity combiner that can minimize the symbol error probability for differential phase shift keying (DPSK) differential detection in the presence of multiplicative Rayleigh fading, and co-channel interference (CCI) is presented. The effect of unequal average powers among diversity branches is taken into account. It is shown that the postdetection maximal-ratio combiner (MRC) described previously by the author is not optimal unless all branches have the same average power. It is also found that the combiner optimized for the effect of CCI (fading induced random FM noise) should weight each branch detector output in inverse proportion to the average CCI power (desired signal power). Assuming two-branch diversity, calculated BER (bit-error-rate) performance of pi /4-shift QDPSK due to AWGN, CCI, and random FM is presented. In addition, the BER due to multipath channel delay spread (which is not treated in the theoretical analysis) is also computed to find the optimal combiner.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Combined effect of diversity reception/channel coding on error floor due to delay spread in DPSK mobile radio

The combined effect of postdetection diversity reception and concatenated channel coding on the BER floor of π/4-shift QDPSK due to multipath channel delay spread in Rayleigh fading environments is experimentally investigated. Twobranch postdetection MRC diversity and Reed-Solomon/BCH concatenated coding are applied. Experimental results show that for a BER floor of 10−5, the tolerable RMS delay spread can be increased by ̃70% over the uncoded, diversity reception case.

BER performance of QDPSK with postdetection diversity reception in mobile radio channels

The bit-error-rate performance of Nyquist raised-cosine-filtered quaternary differential phase shift keying (RC-QDPSK) and pi /4-shift RC-QDPSK with postdetection diversity reception is theoretically analyzed for Rayleigh fading channels. A selection combiner, equal-gain combiner, and maximal-ratio combiner are considered for postdetection diversity reception. Diversity improvements on the average BER due to additive white Gaussian noise, cochannel interference, random FM noise, and delay spread of the multipath channel are calculated. Also analyzed is the combined effect of diversity reception and error control. The required E/sub b//N/sub 0/ and allowable RMS delay spread for achieving a certain BER and spectrum efficiency in cellular mobile systems are calculated when short BCH forward error correcting codes are used. The performance of automatic repeat request combined with time diversity reception is investigated. >

Experimental evaluation of postdetection diversity reception of narrow-band digital FM signals in Rayleigh fading

Postdetection diversity is attractive for narrowband digital FM signal reception because the cophasing function, which may be difficult to realize in a fast Rayleigh fading environment, is not required. The combining scheme evaluated here is to weight each frequency demodulator (FD) output in proportion to the nu th power of the received signal envelope of that branch. Maximum diversity improvement can be obtained with nu =2 (this combiner is referred to as a postdetection maximal ratio chamber (MRC)). Experimental results are presented on postdetection diversity reception in the Gaussian minimum shift keying (GMSK) signal transmission system. Diversity combining and FD-decision algorithms (decision feedback equalizer (DFE) and maximum-likelihood sequence estimator (MLSE)) are performed by software on a computer using the data of the sampled FD output and received signal envelope obtained from a laboratory transmission system. It is shown that the MRC can attain about a 1-dB larger diversity gain than the selection combiner (SC) when two-branch diversity is used. The degradations of two-branch diversity improvement caused by the differences between demodulator sensitivities and between received signal envelope detector gains are evaluated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance analysis of GMSK frequency detection with decision feedback equalisation in digital land mobile radio

The bit-error-rate (BER) performance of premodulation Gaussian filtered MSK (GMSK) using frequency detection (FD) in conjunction with 1 bit decision feedback equalisation (DFE) is theoretically investigated. The introduction of the premodulation filter causes severe intersymbol interference (ISI) in the waveform of the input to the FM modulator. DFE is used for reducing the ISI effect and therefore improving the BER performance. Applying the analysis to additive white Gaussian noise (AWGN) channels (no fading) shows that a 1-bit DFE attains about 8.5 dB Eb/N0 improvement at BER = 10−3for the premodulation filter bandwidth-time product BbT = 0.25 (typical for mobile radio applications) when the receiver predetection bandpass filter bandwidth-time product BT is optimised. It is shown that the effect of error propagation due to DFE is negligible and the exact BER can be well approximated by the BER that is obtained assuming the decision 1-bit prior is correct. The analysis is then extended to the case of Rayleigh fading channels. Both predetection and postdetection diversity reception are considered. When two-branch predetection maximal-ratio combining (MRC) is used, the 1-bit DFE attains about 6.3 dB Eb/N0 improvement at BER = 10−3for BbT = 0.25.