Modulation-mode assignment for SVD-assisted and iteratively detected downlink multiuser MIMO transmission schemes

In this contribution we jointly optimize the number of multiple-input multiple-output (MIMO) layers and the number of bits per symbol within an iteratively-detected multiuser MIMO downlink (DL) transmission scheme under the constraint of a given fixed data throughput and integrity. Instead of treating all the users jointly as in zero-forcing (ZF) multiuser transmission techniques, the investigated singular value decomposition (SVD) assisted DL multiuser MIMO system takes the individual user's channel characteristics into account. In analogy to bit-interleaved coded irregular modulation, we introduce a MIMO-BICM scheme, where different user-specific signal constellations and mapping arrangement were used within a single codeword. Extrinsic information transfer (EXIT) charts are used for analyzing and optimizing the convergence behaviour of the iterative demapping and decoding. Our results show that in order to achieve the best bit-error rate, not necessarily all user-specific MIMO layers have to be activate

On Mode Adaptation for MIMO-OFDM-BICM Based on Measured Indoor Channels

Abstract—This paper examines mode adaptation for MIMOOFDM-BICM systems. Our results are based on measured MIMO-OFDM channels in an indoor environment at 5 GHz. We demonstrate that a simple zero-forcing spatial multiplexing system using four transmitters and four receivers can achieve four times the SISO data rate over the real measured channels with less than 6 dB increase in SNR. We also observe that it in fact has less mode switching compared to SISO, which can have certain implementation advantages

URLLC in IRS-Aided MIMO Systems: Finite Blocklength Analysis and Design

This paper investigates the ultra reliable and low latency communication (URLLC) performance of the IRS-aided MIMO system. The upper and lower bounds of the optimal average error probability (OAEP) for the coding rate 1/sqrt(Mn) of the capacity are derived, where n and M represent the blocklength and the number of transmit antennas, respectively. To achieve this goal, a new central limit theorem (CLT) for the mutual information density over the IRS-aided MIMO system is derived in the asymptotic regime where the block-length, the IRS size, and number of the antennas go to infinity with the same pace. The CLT is then utilized to derive the closed form upper and lower bounds for the OAEP. Based on the analysis result, a gradient-based algorithm is proposed to minimize the lower bound of the OAEP by optimizing the phase shift of the IRS. Simulation results validate the fitness of the CLT and the effectiveness of the proposed algorithm in optimizing the theoretical bound, as well as the performance of practical LDPC code.Comment: 8 pages, 3 figures, accepted by Asilomar Conference on Signals, Systems, and Computers 2023. arXiv admin note: text overlap with arXiv:2210.0883

Second-Order Coding Rate of Quasi-Static Rayleigh-Product MIMO Channels

With the development of innovative applications that require high reliability and low latency, ultra-reliable and low latency communications become critical for wireless networks. In this paper, the second-order coding rate of the coherent quasi-static Rayleigh-product MIMO channel is investigated. We consider the coding rate within O(1/\sqrt(Mn)) of the capacity, where M and n denote the number of transmit antennas and the blocklength, respectively, and derive the closed-form upper and lower bounds for the optimal average error probability. This analysis is achieved by setting up a central limit theorem (CLT) for the mutual information density (MID) with the assumption that the block-length, the number of the scatterers, and the number of the antennas go to infinity with the same pace. To obtain more physical insights, the high and low SNR approximations for the upper and lower bounds are also given. One interesting observation is that rank-deficiency degrades the performance of MIMO systems with FBL and the fundamental limits of the Rayleigh-product channel approaches those of the single Rayleigh case when the number of scatterers approaches infinity. Finally, the fitness of the CLT and the gap between the derived bounds and the performance of practical LDPC coding are illustrated by simulations

Diversity Analysis of Bit-Interleaved Coded Multiple Beamforming with Orthogonal Frequency Division Multiplexing

For broadband wireless communication systems, Orthogonal Frequency Division Multiplexing (OFDM) has been combined with Multi-Input Multi-Output (MIMO) techniques. Bit-Interleaved Coded Multiple Beamforming (BICMB) can achieve both spatial diversity and spatial multiplexing for flat fading MIMO channels. For frequency selective fading MIMO channels, BICMB with OFDM (BICMB-OFDM) can be applied to achieve both spatial diversity and multipath diversity, making it an important technique. However, analyzing the diversity of BICMB-OFDM is a challenging problem. In this paper, the diversity analysis of BICMB-OFDM is carried out. First, the maximum achievable diversity is derived and a full diversity condition RcSL <= 1 is proved, where Rc, S, and L are the code rate, the number of parallel steams transmitted at each subcarrier, and the number of channel taps, respectively. Then, the performance degradation due to the correlation among subcarriers is investigated. Finally, the subcarrier grouping technique is employed to combat the performance degradation and provide multi-user compatibility.Comment: accepted to journa

Capacity and performance of MIMO-BICM with zero-forcing receivers

This paper considers multiple-input multiple-output bit-interleaved coded modulation (MIMO-BICM) with linear zero-forcing (ZF) receivers. We derive the link-level capacity (LLC) under ideal fast-fading conditions, and show that it approaches the maximum-likelihood (ML) LLC as the number of receive antennas approach infinity. We also derive tight analytical bounds on the coded bit-error rate, and prove that with Nt transmit and Nr receive antennas, the diversity order is Nr - Nt + 1 multiplied by the free Hamming distance of the convolutional code. For the case of a ML receiver, we show that a tight bound is not possible, in general. Our analysis provides insights to explain the relative performance of the ZF and ML receivers. Finally, we validate the analytical results and assess the performance in a practical environment with orthogonal frequency-division multiplexing and channel estimation. © 2005 IEEE