Performance of block diagonalization scheme for various array antennas in multiuser MIMO system

This paper reports the performance of Block Diagonalization (BD) scheme for different array antenna structures used in a multiuser Multiple Input Multiple Output (MIMO) system. The assessment is performed in terms of sum rate capacity. Theoretical analysis as well as computer simulations shows that the spatial correlation downgrades downlink performance of BD. The simulations also reveal that the system equipped with Uniform Circular Array (UCA) has a better performance than the one employing Uniform Linear Array (ULA). © 2010 IEEE

A Coordinated Approach to Channel Estimation in Large-scale Multiple-antenna Systems

This paper addresses the problem of channel estimation in multi-cell interference-limited cellular networks. We consider systems employing multiple antennas and are interested in both the finite and large-scale antenna number regimes (so-called "massive MIMO"). Such systems deal with the multi-cell interference by way of per-cell beamforming applied at each base station. Channel estimation in such networks, which is known to be hampered by the pilot contamination effect, constitute a major bottleneck for overall performance. We present a novel approach which tackles this problem by enabling a low-rate coordination between cells during the channel estimation phase itself. The coordination makes use of the additional second-order statistical information about the user channels, which are shown to offer a powerful way of discriminating across interfering users with even strongly correlated pilot sequences. Importantly, we demonstrate analytically that in the large-number-of-antennas regime, the pilot contamination effect is made to vanish completely under certain conditions on the channel covariance. Gains over the conventional channel estimation framework are confirmed by our simulations for even small antenna array sizes.Comment: 10 pages, 6 figures, to appear in IEEE Journal on Selected Areas in Communication

Dealing with Interference in Distributed Large-scale MIMO Systems: A Statistical Approach

This paper considers the problem of interference control through the use of second-order statistics in massive MIMO multi-cell networks. We consider both the cases of co-located massive arrays and large-scale distributed antenna settings. We are interested in characterizing the low-rankness of users' channel covariance matrices, as such a property can be exploited towards improved channel estimation (so-called pilot decontamination) as well as interference rejection via spatial filtering. In previous work, it was shown that massive MIMO channel covariance matrices exhibit a useful finite rank property that can be modeled via the angular spread of multipath at a MIMO uniform linear array. This paper extends this result to more general settings including certain non-uniform arrays, and more surprisingly, to two dimensional distributed large scale arrays. In particular our model exhibits the dependence of the signal subspace's richness on the scattering radius around the user terminal, through a closed form expression. The applications of the low-rankness covariance property to channel estimation's denoising and low-complexity interference filtering are highlighted.Comment: 12 pages, 11 figures, to appear in IEEE Journal of Selected Topics in Signal Processin

Impact of Antenna Placement on Frequency Domain Adaptive Antenna Array in Hybrid FRF Cellular System

Frequency domain adaptive antenna array (FDAAA) is an effective method to suppress interference caused by frequency selective fading and multiple-access interference (MAI) in single-carrier (SC) transmission. However, the performance of FDAAA receiver will be affected by the antenna placement parameters such as antenna separation and spread of angle of arrival (AOA). On the other hand, hybrid frequency reuse can be adopted in cellular system to improve the cellular capacity. However, optimal frequency reuse factor (FRF) depends on the channel propagation and transceiver scheme as well. In this paper, we analyze the impact of antenna separation and AOA spread on FDAAA receiver and optimize the cellular capacity by using hybrid FRF

MIMO application for the quadrifilar helix antenna

Capacity increase of the current land mobile satellite (LMS) communication systems is highly desirable to cater for more data-centric applications such as broadcasting. Since the Multiple-input Multiple-output (MIMO) offers high spectral efficiency without additional bandwidth and transmit power, its implementation in the LMS system has been widely investigated in terms of channel characterisation, channel modelling and coding algorithms. However, the aspect of receive antenna design and its performance evaluation has not yet been considered even though it has enormous impacts on the system performance. This thesis presents a study on designing a novel dual circularly polarised receive antenna system for the LMS MIMO system that utilises the printed quadrifilar helix antenna (PQHA) and also the required performance evaluation methods. The PQHA was miniaturised using two new methods, which are the element folding and combination of element folding and meandering where more than 50% size reduction can be achieved. These miniaturised PQHAs were combined to create a variety of dual circularly polarised arrays such as the dual circularly polarised single folded PQHA (SFPQHA) horizontal array and folded meandered PQHA (FMPQHA) vertical array. For evaluating the branch power ratio of these arrays, a newly derived formulation of the mean effective gain (MEG) in a Ricean fading channel that incorporates the polarisation of the line-of-sight (LoS) component and the corresponding antenna gain has been proposed. Further evaluation of these arrays as the receive antenna in this system was carried out using measurement campaigns. Results show that both arrays provide substantial capacity increase when compared to a single link system in both LoS and NLoS channels. A more comprehensive study on the effect of antenna properties was conducted using a newly, developed channel model that integrates the array characteristics with the propagation channel. This modelling approach allows for a performance comparison between the designed SFPQHA array and other antennas to be easily implemented, which is very useful in the process of designing MIMO antennas.EThOS - Electronic Theses Online ServiceGBUnited Kingdo