765 research outputs found
Multiple Beamforming with Perfect Coding
Perfect Space-Time Block Codes (PSTBCs) achieve full diversity, full rate,
nonvanishing constant minimum determinant, uniform average transmitted energy
per antenna, and good shaping. However, the high decoding complexity is a
critical issue for practice. When the Channel State Information (CSI) is
available at both the transmitter and the receiver, Singular Value
Decomposition (SVD) is commonly applied for a Multiple-Input Multiple-Output
(MIMO) system to enhance the throughput or the performance. In this paper, two
novel techniques, Perfect Coded Multiple Beamforming (PCMB) and Bit-Interleaved
Coded Multiple Beamforming with Perfect Coding (BICMB-PC), are proposed,
employing both PSTBCs and SVD with and without channel coding, respectively.
With CSI at the transmitter (CSIT), the decoding complexity of PCMB is
substantially reduced compared to a MIMO system employing PSTBC, providing a
new prospect of CSIT. Especially, because of the special property of the
generation matrices, PCMB provides much lower decoding complexity than the
state-of-the-art SVD-based uncoded technique in dimensions 2 and 4. Similarly,
the decoding complexity of BICMB-PC is much lower than the state-of-the-art
SVD-based coded technique in these two dimensions, and the complexity gain is
greater than the uncoded case. Moreover, these aforementioned complexity
reductions are achieved with only negligible or modest loss in performance.Comment: accepted to journa
MIMO-OFDM Optimal Decoding and Achievable Information Rates Under Imperfect Channel Estimation
Optimal decoding of bit interleaved coded modulation (BICM) MIMO-OFDM where
an imperfect channel estimate is available at the receiver is investigated.
First, by using a Bayesian approach involving the channel a posteriori density,
we derive a practical decoding metric for general memoryless channels that is
robust to the presence of channel estimation errors. Then, we evaluate the
outage rates achieved by a decoder that uses our proposed metric. The
performance of the proposed decoder is compared to the classical mismatched
decoder and a theoretical decoder defined as the best decoder in the presence
of imperfect channel estimation. Numerical results over Rayleigh block fading
MIMO-OFDM channels show that the proposed decoder outperforms mismatched
decoding in terms of bit error rate and outage capacity without introducing any
additional complexity
A joint-channel diagonalization for multiuser MIMO antenna systems
In this paper, we address the problem of improving the performance of multiuser space-division multiplexing (SDM) systems where multiple independent signal streams can be transmitted in the same frequency and time slot. The problem is important in multiuser multiple-input multiple-output systems where communication from one base station to many mobile stations can occur simultaneously. Our objective is to devise a multiuser linear space-time precoder for simultaneous channel diagonalization of the multiuser channels enabling SDM. Our new approach is based on diagonalizing the multiuser channel matrices and we use a variation of successive Jacobi rotations. In addition to the diagonalization, our approach attempts to optimize the resultant channel gains for performance enhancement. Our method is valid for both frequency-flat and frequency-selective fading channels but we assume that the base station knows all the channels and that they are quasi-stationary
Matrix Completion-Based Channel Estimation for MmWave Communication Systems With Array-Inherent Impairments
Hybrid massive MIMO structures with reduced hardware complexity and power
consumption have been widely studied as a potential candidate for millimeter
wave (mmWave) communications. Channel estimators that require knowledge of the
array response, such as those using compressive sensing (CS) methods, may
suffer from performance degradation when array-inherent impairments bring
unknown phase errors and gain errors to the antenna elements. In this paper, we
design matrix completion (MC)-based channel estimation schemes which are robust
against the array-inherent impairments. We first design an open-loop training
scheme that can sample entries from the effective channel matrix randomly and
is compatible with the phase shifter-based hybrid system. Leveraging the
low-rank property of the effective channel matrix, we then design a channel
estimator based on the generalized conditional gradient (GCG) framework and the
alternating minimization (AltMin) approach. The resulting estimator is immune
to array-inherent impairments and can be implemented to systems with any array
shapes for its independence of the array response. In addition, we extend our
design to sample a transformed channel matrix following the concept of
inductive matrix completion (IMC), which can be solved efficiently using our
proposed estimator and achieve similar performance with a lower requirement of
the dynamic range of the transmission power per antenna. Numerical results
demonstrate the advantages of our proposed MC-based channel estimators in terms
of estimation performance, computational complexity and robustness against
array-inherent impairments over the orthogonal matching pursuit (OMP)-based CS
channel estimator.Comment: This work has been submitted to the IEEE for possible publication.
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BER performance of MIMO system employing fast antenna selection scheme under imperfect channel state information
In this paper, a closed-form expression for Bit Error rate (BER) of a Multiple-Input Multiple-Output (MIMO) system employing the Minimum Mean Square Error MMSE channel estimation method is derived. The numerical results show that when the Channel State Information (CSI) is free of estimation errors BER decreases when the number of receive antennas increases. However under imperfect CSI, BER is getting worse when the number of Rx antennas is increased. In order to improve BER, a fast antenna selection scheme is proposed. The obtained numerical results prove that the proposed antenna selection scheme indeed improves the MIMO system BER performance. ©2010 IEEE
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