Interpolated linear precoding and space-frequency coding for MIMO-OFDM systems (original) (raw)
Related papers
Improved space-time coding for MIMO-OFDM wireless communications
IEEE Transactions on Communications, 2001
Improved space-time coding for multiple-input and multiple-output orthogonal frequency division multiplexing is studied for wireless systems using QPSK modulation for four transmit and four receive antennas. A 256-state code is shown to perform within 3 dB of outage capacity (and within 2 dB with perfect channel estimation), which is better than any other published result without using iterative decoding.
Space-time-frequency (STF) coding for MIMO-OFDM systems
IEEE Communications Letters, 2000
We consider the capacity of multiple-input-multiple-output (MIMO) systems that use OFDM as the modulation format. We point out a basic equivalence between antennas and OFDM-tones. This similarity immediately allows us to essentially reuse all space-time codes designed for flat-fading channels in MIMO-OFDM systems operating in frequency-selective channels. An optimum code would thus code across all antennas and tones (as well as time) simultaneously. Since this can become very complex, we propose a method for grouping antennas and codes in such a way that the inherent diversity is retained, while the complexity is greatly reduced. Capacity computations between the full-complexity and the reduced-complexity systems illustrate this tradeoff.
Limited-Feedback Precoding for Closed-Loop Multiuser MIMO OFDM Systems with Frequency Offsets
IEEE Transactions on Wireless Communications, 2008
Frequency offsets negatively impact the performance of closed-loop multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. Particularly, when multiple users are active, the impact can be high. Linear precoding and non-linear Tomlinson-Harashima precoding (THP) are thus developed for spatially-multiplexed multiuser OFDM and orthogonal space-time block-coded (OS-TBC) OFDM. The proposed precoders employ a limited feedback structure, which is implemented with a shared codebook of precoding matrices, and only the index of the selected optimal matrix is fed back to the transmitter. The conventional limitedfeedback design criterion for flat-fading MIMO channels is only applicable to single-user OFDM without frequency offsets. We show that the ICI matrix due to frequency offset does not impact users' precoding individually, and precoding on a per-subcarrier basis is possible. Exploiting this property, the conventional design is generalized to multiuser OFDM with frequency offsets. Nonlinear precoding uses a modulo arithmetic precoding matrix (which reduces the power efficiency loss inherent in linear precoding and leads to a lower error rate) and outperforms linear precoding. Our precoders not only offer significant bit error rate (BER) improvement for spatially-multiplexed multiuser MIMO OFDM with frequency offsets, but are equally effective for both OSTBC MIMO OFDM and spatially correlated channels. Index Terms-Limited feedback precoding, multiuser multipleinput multiple-output (MIMO), orthogonal frequency-division multiplexing (OFDM), frequency offset. I. INTRODUCTION C LOSED-LOOP multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) techniques exploit spatial diversity, provide higher link capacity and throughput, and improve system performance [1]. Typically, either spatial multiplexing (SM) or space-time coding is used to exploit the benefits offered by MIMO links. The special case of space-time diversity coding known Manuscript
2007 IEEE Wireless Communications and Networking Conference, 2007
This paper presents precoding design for errorrate improvement in closed-loop multiuser orthogonal space-time block-coded (OSTBC) multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) downlink, where both mean feedback and covariance feedback are available. We derive adaptive linear precoding and non-linear Tomlinson-Harashima precoding (THP) over a transmit-antenna-correlated, frequency-selective fading MIMO channel with estimation errors and feedback delay. In our precoder, mean-feedback precoding or covariance-feedback precoding, is adaptively chosen at the user terminal. The maximum achievable signal-to-noise power ratio (SNR) is used as the precoding-mode selection criterion. Each user calculates the selection metric and decides whether mean feedback is necessary. We confirm the intuition that mean-feedback precoding offers BER gains over covariance-feedback precoding when mean feedback becomes sufficiently accurate. Our adaptive precoding outperforms either mean-feedback precoding or covariance-feedback precoding in multiuser OSTBC OFDM, and considerably reduces the bit error rate (BER). Non-linear adaptive precoding is shown to outperform linear adaptive precoding.
Combining Orthogonal Space-Frequency Block Coding and Spatial Multiplexing In MIMO-OFDM System
proc. International OFDM …
In the present work, we have combined Orthogonal Space-Frequency Block Coding (OSFBC) and Spatial Multiplexing (SM) in one transmission scheme for Orthogonal Frequency Division Multiplexing (OFDM) systems. In the combined transmission scheme, both spatial diversity and multiplexing benefits are possible to achieve. Simple Alamouti coding as the S-F coding across spatial multiplexing branches and a simplified linear receiver instead of a complex successive interference cancellation receiver are used in our scheme. In the initial analysis, it is found that SM-OSFBC-OFDM system is near to the optimum system capacity for any 4 × 2 MIMO-OFDM system.
IEEE Vehicular Technology Conference, 2006
Orthogonal space-time block-coded (OSTBC) orthogonal frequency-division multiplexing (OFDM) links for frequency-selective multiple-input multiple-output (MIMO) channels with correlated paths and transmit antennas are considered. In such systems, optimal precoding with only covariance feedback is derived using the minimum pair-wise error probability (PEP) criterion; linear and non-linear precoders are designed. The proposed precoding only needs the statistical knowledge of the channel at the transmitter, which significantly reduces the feedback requirements. Both linear and non-linear precoders substantially improve the system bit error rate (BER) for OSTBC OFDM in transmit-antenna and path-correlated channels. The proposed non-linear precoder outperforms the linear precoder.
A precoding method for closed-loop MIMO-OFDM systems
2008 International Conference on Advanced Technologies for Communications, 2008
This paper presents a precoding method for closed loop MIMO-OFDM systems. For precoding, the codeword is selected by comparing the unitary channel matrix, obtained from the SVD method, with a predefined codebook. The performance of closed and open-loop MIMO-OFDM systems is investigated for the case of perfect and imperfect CSI, as well as for different level of quantization. The simulation results show that the first one outperforms the later one in all case. The system performance gain depends on the number of bits using for feedback channel.
Combined beamforming with space-time-frequency coding for MIMO–OFDM systems
AEU - International Journal of Electronics and Communications, 2015
Multiple antennas can be used in wireless systems to achieve good quality of service and high data rate communication. Recently, efficient space-time-frequency (STF) codes have been developed to improve the diversity gain. This paper aims at performance analysis of multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system using STF Coding and random beamforming. The proposed approach which combines beamforming with STF code offers improved performance over STF in term of bit error rates (BER). It is also observed that the proposed scheme gives better performance as compared to the combined space-time block code (STBC) with beamforming. Computational complexity of the proposed scheme is also calculated.
IEEE Globecom 2006, 2006
This paper presents non-linear precoding design in closed-loop multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) over spatiallycorrelated, frequency-selective fading channels. Our analysis takes into consideration receiver channel mismatch due to imperfect channel estimates, and transmitter channel mismatch due to estimation errors, channel variations over feedback delay and feedback noise. We present a general spatially-correlated, frequency-selective fading MIMO channel model and derive the conditional means of the channel response. Exploiting the channel statistics, which are only available at the receiver, we design new non-linear zero-forcing (ZF) Tomlinson-Harashima precoding (THP) for uncoded MIMO OFDM. The channel statistics do not need to be sent back to the transmitter, which avoids the possible maximum-Doppler-shift transmitter mismatch. Our proposed precoders are robust against time variations, channel estimation errors and antenna correlations, and offer a significant system performance gain over conventional THP.
Space-Time-Frequency Spreading and Coding for Multi-User MIMO-OFDM Systems
2008 IEEE International Conference on Communications, 2008
In this paper, we propose a multiple-input-multipleoutput, orthogonal frequency division multiplexing, code-division multiple-access (MIMO OFDM-CDMA) scheme. The main objective is to provide extra flexibility in user multiplexing, and offer better diversity/multi-user-multiplexing tradeoff. This is done by spreading on all the signal domains; i.e, space-timefrequency spreading is employed to transmit users' signals. Our study and simulation results show that MIMO OFDM-CDMA is capable of flexible data rates and easy user multiplexing, while simultaneously suppressing the multiuser interfering signals. In addition, our scheme achieve a diversity gain significantly larger than that of the conventional 2-D CDMA OFDM scheme. This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the ICC 2008 proceedings.