Conference Paper

# Linear Pre-Coding Performance in Measured Very-Large MIMO Channels.

DOI: 10.1109/VETECF.2011.6093291 Conference: Proceedings of the 74th IEEE Vehicular Technology Conference, VTC Fall 2011, 5-8 September 2011, San Francisco, CA, USA

Source: DBLP

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**ABSTRACT:**The performance of massive multiple-input multiple-output (MIMO) system is limited by pilot contamination. To reduce the pilot contamination, uplink and downlink precoding algorithms are put forward based on interference alignment criterion. In the uplink receiving processing, the target function aligns the pilot contamination and the interference signals to the same null space and acquires the maximal space degree of the desired signals. The uplink receiving precoding matrix is solved on maximal signal to interference plus noise ratio (SINR) criterion considering the impact of the pilot contamination on channel estimations. The uplink receiving precoding matrix is used as the downlink transmitting precoding matrix. Exploiting the channel reciprocity, it is proved that, if the uplink receiving precoding matrix achieves maximal SINR, the identical precoding matrix can be used in the downlink transmission and acquires maximal signal to leakage plus noise ratio (SLNR). Simulations show that the spectrum efficiency of the proposed algorithm can reach about 1.5 times higher than that of popular matched filtering (MF) precoding algorithm, and about 1.1 times higher than multi-cell minimum mean square error (MMSE) precoding algorithm. The performance of the proposed algorithm can be improved approximately linearly with the increasing of the number of antennas.The Journal of China Universities of Posts and Telecommunications 08/2014; 21(4):19–24. -
##### Article: Limited Feedback MU Massive MISO Systems with Differential TCQ in Temporally Correlated Channels

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**ABSTRACT:**We propose a differential trellis coded quantization (TCQ) scheme for limited feedback multiuser (MU) massive multiple-input single-output (MISO) frequency division duplexed systems in temporally correlated channels. We begin by deriving the mean signal-to-interference-plus-noise ratio (SINR) expressions for a system with both perfect channel direction information (CDI) and random vector quantization (RVQ) CDI, using the matched-filter precoding scheme. We show that the number of bits required by the RVQ codebook to match even a small fraction of the perfect CDI SINR performance is very large. With such large numbers of bits, the exhaustive search required by conventional codebook approaches makes them impractical for massive MISO systems. This motivates the proposed differential TCQ scheme. Utilizing temporal correlation present in the channel, the proposed differential TCQ scheme transforms a source constellation at each stage in a trellis using 2D translation and scaling techniques, such that the source constellation centers around the previously selected source constellation point. We derive a scaling parameter for the source constellation which is a function of the temporal correlation and the number of BS antennas. Simulation results show that the proposed differential TCQ scheme outperforms the existing differential noncoherent TCQ (NTCQ) method, by improving the sum rate and reducing the feedback overhead of the system in temporally correlated channels.05/2014; - [Show abstract] [Hide abstract]

**ABSTRACT:**Massive multiple-input multiple-output (MIMO) wireless communications refers to the idea equipping cellular base stations (BSs) with a very large number of antennas, and has been shown to potentially allow for orders of magnitude improvement in spectral and energy efficiency using relatively simple (linear) processing. In this paper, we present a comprehensive overview of state-of-the-art research on the topic, which has recently attracted considerable attention. We begin with an information theoretic analysis to illustrate the conjectured advantages of massive MIMO, and then we address implementation issues related to channel estimation, detection and precoding schemes. We particularly focus on the potential impact of pilot contamination caused by the use of non-orthogonal pilot sequences by users in adjacent cells. We also analyze the energy efficiency achieved by massive MIMO systems, and demonstrate how the degrees of freedom provided by massive MIMO systems enable efficient single-carrier transmission. Finally, the challenges and opportunities associated with implementing massive MIMO in future wireless communications systems are discussed.IEEE Journal of Selected Topics in Signal Processing 10/2014; 8(5):742-758. · 3.63 Impact Factor

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