Performance Analysis of Space-Time Block Codes in Flat Fading MIMO Channels with Offsets (original) (raw)
Related papers
IEEE Transactions on Signal Processing, 2008
In this paper, the problem of joint channel and carrier frequency offset (CFO) estimation is studied in the context of multiple-input multiple-output (MIMO) communications based on orthogonal space-time-block codes (OSTBCs). A new blind approach is proposed to jointly estimate the channel matrix and the CFO parameters using a relaxed maximum likelihood (ML) estimator that, for the sake of simplicity, ignores the finite alphabet constraint. Although the proposed technique can be applied to the majority of OSTBCs, there are, however, a few codes that suffer from an intrinsic ambiguity in the joint channel, CFO, and symbol estimates. For such specific OSTBCs, a semiblind modification of the proposed approach is developed that resolves the aforementioned estimation ambiguity. Our simulation results demonstrate that although the finite alphabet constraint is relaxed, the performance of the proposed techniques approaches that of the informed (fully frequency-synchronized and coherent) receiver, provided that a sufficient number of data blocks is available for each channel realization. Index Terms-Blind channel and carrier frequency offset estimation, multiple-input multiple-output (MIMO) communications, orthogonal space-time block codes. I. INTRODUCTION S PACE-TIME coding has recently gained much interest because of its ability to combat fading by means of exploiting spatial diversity provided by multiple-input multiple-output (MIMO) communication channels [1]-[3]. Among different space-time coding techniques proposed so far, orthogonal space-time codes (OSTBCs) are of great interest as they collect full diversity at low decoding complexity. The optimal ML decoder for OSTBCs amounts to a simple linear matched filter (MF) receiver followed by a symbol-by-symbol decoder. It has recently been shown in the literature that for the majority of OSTBCs, the MIMO channel is blindly identifiable Manuscript
The impact of channel estimation error on space-time block codes
Proceedings IEEE 56th Vehicular Technology Conference
In this paper, we demonstrate the performance of space-time block codes when the decoding is performed using imperfect estimates of the channel. A brief explanation of the system model is given and the results of performance simulations discussed. Simulation results are introduced to characterize the performance of a space-time block code using two transmit antennas, one receive antenna, and QPSK modulation. The performance of this system is shown when there is perfect channel state information, and also when there are amplitude and/or phase errors in the channel estimates.
Orthogonal space-time block codes: performance analysis and comparisons
… and Signal Processing, 2003 and the …, 2003
We derive a simple method to directly compute the exact bit error probabilities (BEPs) of orthogonal space-time block codes (OSTBCs) over Rayleigh fading channels for arbitrary L-PSK and square L-QAM signal constellations with coherent detection. Based on the derived BEPs, we study the performance of various OSTBCs for numerous numbers of receive antennas and bit rates. Our analysis shows that even at low bit rates and with only a single receive antenna, OSTBC for four transmit antennas would be the best choice for most practical cases. Furthermore, if the receiver has multiple antennas, OSTBCs for more than four transmit antennas only degrade performance while adding more complexity. We conclude that in most cases, OSTBCs for four transmit antennas or less should be the choice.
Accurate BER analysis of orthogonal space-time block codes with MMSE channel estimation
Spread Spectrum Techniques and …, 2008
In this paper, we investigate the effect of imperfect channel estimation on the bit error rate (BER) performance of orthogonal space-time block codes (OSTBCs). The multiple-input multiple-output (MIMO) propagation channel is assumed to be affected by uncorrelated flat Rayleigh block fading. We consider a mismatched maximum-likelihood (ML) receiver, which estimates the channel matrix from known pilot symbols according to a minimum mean-square error (MMSE) criterion, and uses the channel estimate in the symbol-by-symbol detection algorithm as if it were the true channel matrix. For both PAM and QAM constellations and OSTBCs satisfying a proposed criterion, we present simple exact closed-form expressions for the BER of the mismatched receiver and the corresponding BER degradation as compared to a receiver that knows the true channel matrix. For OSTBCs that do not satisfy this criterion, a simple approximation of the BER and the associated BER degradation is derived, assuming PAM and QAM constellations. By means of computer simulations, this approximation is shown to be very accurate.
Effects of imperfect channel estimation on space–time coding performance
IEE Proceedings - Communications, 2005
The effect of imperfect channel estimation on the bit error rate (BER) of multiple-input multiple-output communication systems utilising space-time coding is investigated. A multipath channel is considered and a given level for the channel estimation error is assumed. The receiver employs an equaliser to reduce the ISI in the received signal. A closed-form expression for the SNR at the output of the equaliser that employs the results of the channel estimation is derived. The theoretical SNR derived is used as a basis to assess the performance of the system. Results are applicable to any channel estimation technique. Analysis shows that the deterioration of performance in the multiple transmit antenna scheme outweighs the benefits achieved over the single antenna case when the SNR and channel estimation error are large. The degradation in the transmit diversity scheme exceeds 8 dB to achieve a BER of 10 À4 when the channel estimation error is 5% relative to the perfect channel estimation case.
Performance analysis of space-time coding with imperfect channel estimation
IEEE Transactions on Wireless Communications, 2005
We analyze the error performance of a space-time coding system using transmit and receive antennas with imperfect channel estimation in flat Rayleigh fading. A least-squares estimate of the channel matrix is obtained by using a sequence of pilot code vectors. The estimate is found to be perturbed by an perturbation matrix with zero-mean circular Gaussian entries. Using the characteristic function of the decision variable, we derive a closed-form expression for the pairwise error probability (PEP). From the same expression, the PEP in case of perfect channel estimation is also obtained. Numerical results show the degradation in performance due to imperfect channel estimation that can be compensated by increasing the number of receive antennas.
IEEE Transactions on Communications, 2000
Many existing works on space-time block codes (STBC) assume the channels are block-wise constant, but this assumption does not always hold. In the more general case of time-selective channels, the channel matrix is no longer orthogonal, so inter-symbol interference (ISI) is generated and the performance is greatly reduced. Several decoders have been proposed to eliminate the ISI, but it remains unclear how and to what extent the performance is affected by the ISI. In this paper, we introduce an approach to analyze the performance of STBC over time-selective channels, with arbitrary numbers of antennas for which orthogonal STBC's are defined. Exact error performances are obtained in closed form. Furthermore, the analysis reveals the relationship between the ISI and the structure of STBC matrices. Considering Gi systems, we then propose one proposition and two design criteria, following which it is easy to design or search for better STBC's that have less ISI compared with the original code matrix. Index Terms-Bit-error probability (BEP), design criteria, optimum code, orthogonal STBC, time-selective channel. I. INTRODUCTION O RTHOGONAL space-time block codes (STBC) [1] are commonly used in MIMO systems, due to the simple maximum likelihood (ML) decoding structure. However, this decoding structure is based on the assumption that the channels are block-wise constant, which is not always true in practice. If the channels vary from symbol to symbol, the orthogonality will be corrupted and inter-symbol interference (ISI) is introduced, so the linear ML decoder [1] is no longer optimum. Considering time-selective channels, [2]-[12] proposed different decoders for orthogonal STBC. Reference [2] first proposed a suboptimum detection scheme with the conventional linear decoder. It retains the linear decoding structure, but has an irreducible error floor in the high signal-to-noise ratio (SNR) region. Later, zero-forcing (ZF) decoders for two transmit antennas were presented in [3], [4], where the ISI was completely removed. The ZF decoder was extended to threeand four-transmit-antenna cases in [5]-[7]. Besides the linear decoders above, there are also non-linear decoders, including
2010 IEEE 11th International Symposium on Spread Spectrum Techniques and Applications, 2010
In this contribution, we present a novel closed-form approximation of the bit error rate (BER) for square orthogonal space-time block codes (OSTBCs) under arbitrarily correlated Rayleigh fading with imperfect channel estimation. Although derived for a mismatched maximum-likelihood receiver that obtains the channel state information through pilot-based linear minimum mean-square error (LMMSE) channel estimation, the presented expression is shown to yield very accurate BER results for both LMMSE and least-squares channel estimation, over a wide range of signal-to-noise ratios. The information symbols are assumed to belong to a pulse amplitude modulation or square quadrature amplitude modulation constellation.
International Conference on Information, Communications and Signal Processing, 2003
This paper discusses the maximum likelihood (ML) frequency offset estimation and subsequent correction for a space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) system. Carrier frequency offset in OFDM system destroys the orthogonality between subcarriers resulting in performance deterioration. Also, it considerably reduces the diversity gain for STBC. Accurate frequency offset estimation and subsequent correction will significantly improve the performance
BER performance of OSTBCs on correlated fading channels with imperfect channel estimation
Future Network and …, 2010
In this contribution, we examine the bit error rate (BER) performance of orthogonal space-time block codes (OSTBCs) under flat-fading channels with imperfect channel state information. We present new exact BER expressions for PAM and QAM signal constellations, regardless of the fading distribution. Furthermore, we show how these expressions can be efficiently and accurately evaluated for the case of arbitrarily correlated Nakagami-m fading channels. As the high diversity order resulting from the application of OSTBCs gives rise to small BER values, the numerical evaluation of the presented BER expressions is much faster than straightforward computer simulations.