Tjeng Thiang Tjhung

Quasi-orthogonal STBC with minimum decoding complexity

In this paper, we consider a quasi-orthogonal (QO) space-time block code (STBC) with minimum decoding complexity (MDC-QO-STBC). We formulate its algebraic structure and propose a systematic method for its construction. We show that a maximum-likelihood (ML) decoder for this MDC-QO-STBC, for any number of transmit antennas, only requires the joint detection of two real symbols. Assuming the use of a square or rectangular quadratic-amplitude modulation (QAM) or multiple phase-shift keying (MPSK) modulation for this MDC-QO-STBC, we also obtain the optimum constellation rotation angle, in order to achieve full diversity and optimum coding gain. We show that the maximum achievable code rate of these MDC-QO-STBC is 1 for three and four antennas and 3/4 for five to eight antennas. We also show that the proposed MDC-QO-STBC has several desirable properties, such as a more even power distribution among antennas and better scalability in adjusting the number of transmit antennas, compared with the coordinate interleaved orthogonal design (CIOD) and asymmetric CIOD (ACIOD) codes. For the case of an odd number of transmit antennas, MDC-QO-STBC also has better decoding performance than CIOD.

Carrier Transmission of Binary Data in a Restricted Band

The spectra of digital frequency modulation (FM) signals have been observed to be narrow compared with the spectra of digital baseband signals or the corresponding amplitude modulation (AM) and phase modulation (PM) signals. This suggests a high efficiency of transmission in terms of occupied bandwidth for binary FM. Here the desirability of digital FM systems is investigated further with an examination of the probability of bit error. The FM receiver considered consists of a predetection filter, a limiter-discriminator, and a postdetection filter. New results are presented on the effect of predetection bandwidth restriction on the error performance of binary FM systems for various frequency deviations. Theoretical results have been obtained by a Fourier analysis of the distorted FM signals and by Rices click analysis of FM noise. The data presented permits an optimum selection of system parameters such as frequency deviation ratio and predetection filter bandwidth. It is found that in narrow-band operation a peak-to-peak frequency deviation of about 0.7 times the bit rate and a bandpass filter bandwidth of about 1.0 times the bit rate yield a minimum probability of error. Experimental measurements have been made and there is, in general, good agreement with the theory. A comparison of the error performance of noncoherent binary FM, coherent AM, and coherent PM in a restricted band is made. Narrow-band noncoherent FM proves superior to AM in any bandwidth. In narrow-band operation, the noncoherent FM gives a somewhat better error performance than the coherent PM. For example, for an error rate of 10-4and a bandpass filter bandwidth of one times the bit rate, the performance of a noncoherent FM system is 0.7 dB better than that of a coherent PM system.

Four-Group Decodable Space–Time Block Codes

A class of rate-one space-time block codes (STBC) allowing the decoding of transmitted symbols into four groups is recently proposed by Yuen, Guan and Tjhung. This code is called four-group decodable STBC (4Gp-STBC). In this paper, the equivalent channel of 4Gp-STBC is derived and a new method to decode 4Gp-STBC based on sphere decoders is presented. Furthermore, the performance of 4Gp-STBC is analyzed. A new signal rotation method is proposed, which performs better than the existing one.

Error probability performance of L-branch diversity reception of MQAM in Rayleigh fading

New exact expressions involving hypergeometric functions are derived for the symbol-error rate (SER) of M-ary quadrature amplitude modulation (MQAM) for L branch diversity reception in Rayleigh fading and additive white Gaussian noise (AWGN). The diversity combining techniques considered are maximum ratio combining (MRC) and selection combining (SC). MRC with identical channels and dissimilar channels are analyzed.

Quasi-orthogonal space-time block code

Overview of Quasi-Orthogonal STBC (QO-STBC) Fundamentals of QO-STBC QO-STBC with Minimum Decoding Complexity (MDC-QOSTBC) Differential QO-STBC Rates, Complexity, and Diversity Tradeoff in QO-STBC More on QO-STBC.

Fade statistics in Nakagami-lognormal channels

New expressions for the average level crossing rate (LCR) and average time fade duration (AFD) of the signal envelope in microcellular mobile radio channels, characterized by Nakagami (1960) fading and lognormal shadowing, so called Nakagami-lognormal (NLN) channels, are derived. New LCR and AFD are computed, and the effects of the Nakagami m factor and shadowing spread /spl sigma//sub s/ on these fade statistics are discussed. The generality of the NLN model is demonstrated by matching some LCR curves with previously reported measurement for the land mobile satellite channel, commonly described as the Rice-lognormal channels.

BER performance of OFDM-MDPSK system in frequency-selective Rician fading with diversity reception

A closed form formula is derived for the bit error rate (BER) of orthogonal-frequency-division-multiplexing (OFDM) with M-ary differential-phase-shift-keying (MDPSK) systems in frequency-selective Rayleigh and Rician fading channels with diversity reception. New BER curves are obtained as a function of the rms delay spread of the diffused component for three different types of delay profiles: (1) one-sided exponential, (2) uniform and (3) double spike profiles. Both slow and fast fading conditions are considered. It is shown that the existence of a strong line-of-sight (LOS) component and the use of reception diversity can effectively improve transmission performance.

Training sequence assisted channel estimation for MIMO OFDM

In this paper we present several results of our study on training sequence assisted channel estimation for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. After developing a linear matrix algebraic model for the cyclic prefix based MIMO OFDM systems, we define a generalised preamble structure which is a simple extension of the preambles used in single-input single-output (SISO) OFDM so that its good properties, such as low peak to average power ratio, can be maintained. We then derive the least squares (LS) and linear minimum mean squared error (LMMSE) channel estimation algorithms based on the proposed preamble design. In order to reduce the preamble length, we further propose a switched subcarrier preambles scheme in which the transmit antennas are divided into groups, and preambles are transmitted in alternative subset of subcarriers in each group. A LMMSE filter-based interpolation scheme and a DFT-based LS interpolation scheme are then used to obtain the channel estimates for all the subcarriers of interest. In all the proposed schemes in this paper, the filter parameters can be fixed and robust performance is obtained even when mismatched SNR and channel statistics are used in the filter parameter calculations.

Full-rate full-diversity STBC with constellation rotation

In this paper, a class of generalized quasi-orthogonal space-time block code is proposed to achieve full-rate transmission with low-complexity maximum likelihood decoding. Full transmit-diversity is achieved through the constellation rotation technique. Code construction criteria for this class of code are listed. Average 1/determinant criterion is proposed for optimizing the degree of constellation rotation in order to minimize the resultant frame error rate performance. Detailed code search and simulation studies for diversity levels of four and eight are conducted using QPSK modulation constellation. The results show that our proposed code structure can indeed produce many optimum full-rate full-diversity STBC codes with simplified maximum likelihood decoding.

Outage probability for lognormal-shadowed Rician channels

A new general outage probability expression for a Rician signal received among L Rician interferers is derived. This result is shown to cover previous published expressions involving Rayleigh signal/interferers as special cases. A new method is then applied to further extend the result to include the effect of lognormal shadowing on the outage probability (for microcellular mobile radio systems in Rician/Rician fading environments). New Rician/Rician outage probability curves against the normalized reuse distance and cluster size with and without lognormal shadowing effect are presented and discussed.