Duality of antennas and subcarriers in massive MIMO-OFDM downlink system

Massive multiple-input-multiple-output (MIMO) can significantly outperform conventional MIMO in terms of spectrum efficiency and link reliability. For massive MIMO, there are still theoretical and practical issues that have to be addressed. The capacity of the massive MIMO-orthogonal frequency division multiplexing (OFDM) downlink system is derived and analysed and the duality of antennas and subcarriers in such system is demonstrated analytically and by simulation. A detailed comparison between massive MIMO, massive MIMO-OFDM and MIMO-OFDM with large subcarriers is presented.Peer reviewe

Proportional Fair MU-MIMO in 802.11 WLANs

We consider the proportional fair rate allocation in an 802.11 WLAN that supports multi-user MIMO (MU-MIMO) transmission by one or more stations. We characterise, for the first time, the proportional fair allocation of MU-MIMO spatial streams and station transmission opportunities. While a number of features carry over from the case without MU-MIMO, in general neither flows nor stations need to be allocated equal airtime when MU-MIMO is available

Capacity and coverage enhancements of MIMO WLANs in realistic environments

Recently, there has been an explosion of growth in research on MIMO systems, but little has been published characterising performance in realistic environments. This paper quantifies the performance of MIMO WLANs in outdoor environments, and compares performance between spatial multiplexing and space time block coding processing approaches. Packet Error Rate (PER) and throughput performance results are presented under different channel conditions. A WLAN physical layer simulator employing MIMO techniques and a propagation modelling tool are combined in order to evaluate the coverage and throughput enhancements of WLANs for the 2x2 and 4x4 MIMO case

MIMO Networks: the Effects of Interference

Multiple-input/multiple-output (MIMO) systems promise enormous capacity increase and are being considered as one of the key technologies for future wireless networks. However, the decrease in capacity due to the presence of interferers in MIMO networks is not well understood. In this paper, we develop an analytical framework to characterize the capacity of MIMO communication systems in the presence of multiple MIMO co-channel interferers and noise. We consider the situation in which transmitters have no information about the channel and all links undergo Rayleigh fading. We first generalize the known determinant representation of hypergeometric functions with matrix arguments to the case when the argument matrices have eigenvalues of arbitrary multiplicity. This enables the derivation of the distribution of the eigenvalues of Gaussian quadratic forms and Wishart matrices with arbitrary correlation, with application to both single user and multiuser MIMO systems. In particular, we derive the ergodic mutual information for MIMO systems in the presence of multiple MIMO interferers. Our analysis is valid for any number of interferers, each with arbitrary number of antennas having possibly unequal power levels. This framework, therefore, accommodates the study of distributed MIMO systems and accounts for different positions of the MIMO interferers.Comment: Submitted to IEEE Trans. on Info. Theor

Low-Complexity Design of Generalized Block Diagonalization Precoding Algorithms for Multiuser MIMO Systems

Block diagonalization (BD) based precoding techniques are well-known linear transmit strategies for multiuser MIMO (MU-MIMO) systems. By employing BD-type precoding algorithms at the transmit side, the MU-MIMO broadcast channel is decomposed into multiple independent parallel single user MIMO (SU-MIMO) channels and achieves the maximum diversity order at high data rates. The main computational complexity of BD-type precoding algorithms comes from two singular value decomposition (SVD) operations, which depend on the number of users and the dimensions of each user's channel matrix. In this work, low-complexity precoding algorithms are proposed to reduce the computational complexity and improve the performance of BD-type precoding algorithms. We devise a strategy based on a common channel inversion technique, QR decompositions, and lattice reductions to decouple the MU-MIMO channel into equivalent SU-MIMO channels. Analytical and simulation results show that the proposed precoding algorithms can achieve a comparable sum-rate performance as BD-type precoding algorithms, substantial bit error rate (BER) performance gains, and a simplified receiver structure, while requiring a much lower complexity.Comment: 7 figures, 10 pages. IEEE Transactions on Communications, 2013. arXiv admin note: text overlap with arXiv:1304.647