Grassmannian Beamforming for MIMO-OFDM Systems with Frequency and Spatially Correlated Channels Using Huffman Coding (original) (raw)

Precoding for MIMO systems with Grassmannian codebooks

In this paper, we investigate limited feedback precoding for two single-user MIMO systems. The first one employs spatial diversity at the transmitter and Maximum Ratio Combining at the receiver. The second one uses spatial multiplexing at the transmitter and V-BLAST signal processing at the receiver. For both systems, the precoder is selected at the receiver among a codebook and its index is conveyed to the transmitter through an error free feedback channel. For the first system, we consider two Grassmannian precoding codebooks and show through simulation results that a small number of feedback bits can reach the theoretical performance. For the case of a single-user system based on spatial multiplexing, we propose a novel criterion for selecting among codebook matrices the optimum precoding matrix at the receiver which maximizes the minimum signal to interference and noise ratio over the transmitted substreams. Simulation results show that our proposed selection criterion outperforms three other criteria introduced in the literature for the spatial muliplexing MIMO system. They also show a significant enhancement over the unprecoded spatial multiplexing system.

Impact of Limited Feedback on Mimo- Ofdm Systems Using Joint Beamforming

International Journal of Wireless & Mobile Networks (IJWMN), 2011

In multi input multi output antenna systems, beamforming is a technique for guarding against the negative effects of fading. However, this technique requires the transmitter to have perfect knowledge of the channel which is often not available a priori. A solution to overcome this problem is to design the beamforming vector using a limited number of feedback bits sent from the receiver to the transmitter. In the case of limited feedback, the beamforming vector is limited to lie in a codebook that is known to both the transmitter and receiver.When the feedback is strictly limited, important issues are how to quantize the information needed at the transmitter and how much improvement in associated performance can be obtained as a function of the amount of feedback available.In this paper channel quantization schema using simple approach to codebook design (random vector quantization)is illustrated. Performance results show that even with a few bits of feedback, performance can be clos...

Grassmannian precoding for multi-user MIMO system based on the maximal SJNR criterion

2010 7th International Symposium on Wireless Communication Systems, 2010

In this paper, our purpose is to use the maximal signal-to-jamming-and noise ratio (SJNR) criterion to design a Grassmannian codebook for a precoding scheme in a multiuser MIMO broadcast channel. The proposed approach includes two schemes. In the first, we assume that the channel information at the base station is available. The second scheme is under limited feedback. Both schemes aim to reduce computational complexity and enhance system performances. A comparison of computer simulations with a recent approach based on the maximal system capacity criterion shows that our approach provides greater system performances enhancement with reduced complexity, a key point, by a factor of 10 using low users and codebook size and more than 100 for more than 4 users with a codebook size of 16.

Interpolated linear precoding and space-frequency coding for MIMO-OFDM systems

2008 42nd Asilomar Conference on Signals, Systems and Computers, 2008

We investigate the design of space-frequency codes and efficient feedback-aided precoding schemes for multipleinput multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Inspired by the statistical structure of the MIMO-OFDM channel matrix, the proposed transceiver structure consists of two components: i) a fixed space-frequency code, and ii) a set of spatial precoding matrices that are adapted based on limited feedback from the receiver. For the fixed component, we propose a structured space-frequency coding scheme that spreads the source symbols across space and frequency. The space-frequency coded symbols are then processed with a spatial precoding matrix for each OFDM tone before transmission. The spatial precoding matrices use the limited feedback from the receiver to adapt the spatial directions and corresponding power allocation for different spatial symbols, in order to improve both the mutual information and error rate. Since the spatial channel statistics are invariant across frequency, one codebook of spatial precoding matrices suffices for all OFDM tones. This codebook is designed using a systematic algorithm that we had previously developed for narrowband spatially correlated MIMO channels. Finally, to reduce the computational complexity at the receiver and the amount of feedback to the transmitter, we propose a new interpolation algorithm in which the codebook indices are fed back to the transmitter for a subset of tones-precoding matrices for the other tones are computed at the transmitter using the precoding matrices for tones in the subset.

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.

Time-Frequency Grassmannian Signalling For MIMO Multi-Channel-Frequency-Flat Systems

IEEE Communications Letters, 2015

In this paper, we consider the application of noncoherent Grassmannian signalling in practical multi-channelfrequency-flat multiple-input multiple-output (MIMO) wireless communication systems. In these systems, Grassmannian signalling, originally developed for single-channel block-fading systems, is not readily applicable. In particular, in such systems, the channel coefficients are constant across time and frequency, which implies that spectrally-efficient signalling ought to be jointly structured over these domains. To approach this goal, we develop a concatenation technique that yields a spectrally-efficient time-frequency Grassmannian signalling scheme, which enables the channel coherence bandwidth to be regarded as an additional coherence time. This scheme is shown to achieve the high signalto-noise ratio non-coherent capacity of MIMO channels when the fading coefficients are constant over a time-frequency block. This scheme is also applicable in fast fading systems with coherence bandwidth exceeding that of one subchannel. The proposed scheme is independent of the symbol duration, i.e., the channel use duration, and is thus compatible with the transmit filter designs in current systems.

Recursive and trellis-based feedback reduction for MIMO-OFDM with transmit beamforming

2005

We consider a MIMO-OFDM system with transmit beamforming applied on each OFDM subcarrier, where each beamforming vector is drawn from a codebook with finite size. Depending on the channel realization, the receiver decides the optimal beamforming vector on each subcarrier, and informs the transmitter through a rate-limited feedback link. Exploiting the fact that the channel responses across OFDM subcarriers are correlated, we propose two methods to reduce the amount of needed feedback. One is recursive feedback encoding that selects the optimal beamforming vectors sequentially across the subcarriers, and adopts a smaller-size time-varying codebook per subcarrier depending on prior decisions. The other is trellisbased feedback encoding that selects the optimal beamforming vectors for all subcarriers at once along a trellis structure via the Viterbi algorithm. The trellis-based feedback encoding outperforms the recursive feedback encoding at the expense of encoding complexity at the receiver. Simulation results demonstrate that our trellis-based approach outperforms an existing interpolationbased alternative, as the latter incurs diversity loss at high SNR.

Combined Beamforming with Orthogonal Space Time Block Code for MIMO-OFDM with Simple Feedback

Indonesian Journal of Electrical Engineering and Computer Science, 2016

In this paper, we introduce a proposed scheme to enhance the performance of orthogonal space time block code (OSTBC) with four time slots and two antennas by combing OSTBC with random beamforming to can use it in the downlink transmission for a mobile system. Multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system has been recognized as one of the most promising techniques to achieve a good service and increase data rate in the next generation (4&5G) broadband wireless communications. So, we apply Space time block code (STBC) for MIMO-OFDM system with linear decoding. Also, we perform STBC with beamforming for MIMO-OFDM system to improve the performance of a system. Simulation results show that the beamforming improves bit error rate (BER) performance of OSTBC and STBC-OFDM for different types of modulation and diversity.

Multi-Stage Beamforming for Coded OFDM with Multiple Transmit and Multiple Receive Antennas

IEEE Transactions on Wireless Communications, 2007

Conventionally, subcarrier based beamforming was used in an OFDM (Orthogonal Frequency Division Multiplexing) system under MIMO (Multiple-Input and Multiple-Output) channels to achieve optimal performance, where many DFT/IDFT (Discrete Fourier Transform/Inverse DFT) blocks, each corresponding to one antenna, are required. To reduce the complexity induced by the DFT/IDFT processing, symbol based beamforming was recently proposed with only one IDFT block at the transmitter and one DFT block at the receiver. However, this approach results in a significant performance loss especially when the number of distinct paths in the channel is large. In this paper, we propose a multi-stage beamforming (MSB) scheme for MIMO-OFDM systems employing both the principles of subcarrier level beamforming and symbol level beamforming to effectively tradeoff system performance and complexity. Using the proposed MSB scheme and with a little complexity increase compared with the symbol based beamforming, system performance can be significantly improved. Under some channel conditions, the proposed MSB scheme can achieve a performance close to the optimal subcarrier based beamforming scheme but with much lower complexity. For the MSB scheme, we propose an iterative algorithm to jointly optimize the symbol level and subcarrier level weighting coefficients. To reduce the complexity of the joint weighting coefficients calculation algorithm, we propose a reduced complexity algorithm to first obtain the symbol level weighting coefficients and then the subcarrier level weighting coefficients. Simulation results show that good performance can be achieved using the proposed weighting coefficients calculation algorithms with reasonable complexity.