Maximizing LoS MIMO capacity using reconfigurable antenna arrays (original) (raw)
Related papers
Design of MIMO Antenna Array Architecture for Higher Channel Capacity
2015
In many extensive researches, the channel capacity of narrowband multiple-input multiple-output (MIMO) communication systems in indoor Line-of-Sight (LOS) environment is investigated and proved that the LOS signal can get the high channel capacity by designing the antenna arrays. On the other hand, MIMO systems offer significant capacity enhancements in non Line-of-Sight (LOS) environments where rich scattering is present. However, the wireless propagation mechanisms and antenna array orientation should be considered when designing the wireless network to get more precise results and improve the performance. This paper investigates the performance of MIMO system based on two ray ground reflection model. In this system, the LOS signal and the LOS signal with one ground reflected ray can provide the optimum MIMO capacity performance if specific designed antenna arrays are employed at both sides of the communications link. For achieving the optimal MIMO capacity in a LOS environment, t...
Design and Evaluation of a Reconfigurable Antenna Array for MIMO Systems
IEEE Transactions on Antennas and Propagation, 2000
New reconfigurable antenna array is demonstrated for multiple input multiple output (MIMO) communication systems that improves link capacity in closely spaced antenna arrays. The antenna system consists of an array of two printed dipoles separated by a distance of a quarter wavelength. Each of the dipoles can be reconfigured in length using PIN diode switches. The switch configuration can be modified in a manner adaptive to changes in the environment. The configuration of switches effects the mutual coupling between the array elements, and subsequently, the radiation pattern of each antenna, leading to different degrees of pattern diversity which can be used to improve link capacity. The PIN diode-based reconfigurable antenna solution is first motivated through a capacity analysis of the antenna in a clustered MIMO channel model. A new definition of spatial correlation coefficient is introduced to include the effects of antenna mismatch and radiation efficiency when quantifying the benefit of pattern diversity. Next, the widespread applicability of the proposed technique is demonstrated, relative to conventional half wavelength printed dipoles, using computational electromagnetic simulation in an outdoor and indoor environment and field measurements in an indoor laboratory environment. It is shown for the 2 2 system considered in this paper, that an average improvement of 10% and 8% is achieved in link capacity for a signal to noise ratio (SNR) respectively of 10 dB and 20 dB in an indoor environment compared to a system employing non reconfigurable antenna arrays.
Maximizing MIMO Capacity in Sparse Multipath With Reconfigurable Antenna Arrays
IEEE Journal of Selected Topics in Signal Processing, 2007
Emerging advances in reconfigurable radio-frequency (RF) front-ends and antenna arrays are enabling new physical modes for accessing the radio spectrum that extend and complement the notion of waveform diversity in wireless communication systems. However, theory and methods for exploiting the potential of reconfigurable RF front-ends are not fully developed. In this paper, we study the impact of reconfigurable antenna arrays on maximizing the capacity of multiple input multiple output (MIMO) wireless communication links in sparse multipath environments. There is growing experimental evidence that physical wireless channels exhibit a sparse multipath structure, even at relatively low antenna dimensions. We propose a model for sparse multipath channels and show that sparse channels afford a new dimension over which capacity can be optimized: the distribution or configuration of the sparse statistically independent degrees of freedom (DoF) in the available spatial signal space dimensions. Our results show that the configuration of the sparse DoF has a profound impact on capacity and also characterize the optimal capacity-maximizing channel configuration at any operating SNR. We then develop a framework for realizing the optimal channel configuration at any SNR by systematically adapting the antenna spacings at the transmitter and the receiver to the level of sparsity in the physical multipath environment. Surprisingly, three canonical array configurations are sufficient for near-optimum performance over the entire SNR range. In a sparse scattering environment with randomly distributed paths, the capacity gain due to the optimal configuration is directly proportional to the number of antennas. Numerical results based on a realistic physical model are presented to illustrate the implications of our framework.
Design and Analysis of High-Capacity MIMO System in Line-of-Sight Communication
Sensors
The phase of the channel matrix elements has a significant impact on channel capacity in a mobile multiple-input multiple-output (MIMO) communication system, notably in line-of-sight (LoS) communication. In this paper, the general expression for the phase of the channel matrix at maximum channel capacity is determined. Moreover, the optimal antenna configuration of the 2 × 2 and 3 × 3 transceiver antenna array is realized for LoS communication, providing methods for n×n optimal antenna placement, which can be used in short-range LoS communication and non-scattering environment communication, such as coupling train communication and inter-satellite communication. Simulation results show that the 2 × 2 rectangular antenna array is more suitable for the communication of coupling trains, while the 3 × 3 circular arc antenna array is more suitable for virtual coupling trains according to antenna configurations. Moreover, the 2 × 2 antenna rectangular configuration proposed in this paper ...
Design of Optimal High-Rank Line-of-Sight MIMO Channels
IEEE Transactions on Wireless Communications, 2007
This doctoral thesis contains a collection of five papers preceded by an introduction. The papers investigate channel models for, design of, and performance analysis of wireless multiple-input multiple-output (MIMO) systems which are subject to a strong line-of-sight (LOS) channel component. MIMO technology is embraced as one of the key technologies for fulfilling the demand for increased throughput and improved quality of service (QoS) in future wireless applications. This technology can both be employed to increase reliability, through diversity schemes such as e.g. maximum ratio combining and Alamouti coding, or to increase the spectral efficiency by spatial multiplexing schemes such as e.g. eigenmode transmission and V-BLAST. The performance of a wireless MIMO system is heavily dependent on the condition of the channel matrix, in the sense that the channel matrix should be of high rank for the MIMO system to achieve good performance. When the channel is such that the major part of the received power at the receiver (Rx) is due to multipath, fulfilling the high rank criteria is dependent on low correlation between the different subchannels. On the other hand, if the dominant component at the Rx is the deterministic LOS component, fulfilling the high rank criteria becomes dependent on the design of the two antenna arrays employed. In this thesis we derive optimal antenna array designs for pure LOS channels with respect to mutual information (MI), when any combination of uniform linear arrays (ULAs) and uniform planar arrays (UPAs) are employed at the transmitter (Tx) and Rx. The important parameters with respect to design will be shown to be the antenna separation, antenna orientation, wavelength, transmission distance, and MIMO dimension. Moreover, we characterize the effects of these parameters deviating from their optimal values. The pure LOS channel matrix utilized is subsei iii PREFACE which have made my last three and a half years very instructive and exiting. I also want to thank Nera Networks, and especially Karl Martin Gjertsen, who has been the project leader and thus in control of the finances. He has always had a positive answer when I have been asking for more money for conferences, equipment, etc. Moreover, I want to thank Nera Satcom for lending me an office at Billingstad after Nera Research was split between the two companies Nera Networks and Nera Satcom. Furthermore, I would like to thank all the fantastic colleagues I have had the pleasure to get to know during my PhD studies. Both from the Department of Electronics and Telecommunications at NTNU, the wireless communication people at UniK, and the Research Department at Nera. You have made the PhD period an interesting and enjoyable experience. I would especially like to thank fellow PhD students Duc Van Duong, Sébastien de la Kethulle de Ryhove, Vegard Hassel, and Hans Jørgen Bang for both our scientific and social gatherings. My thanks also go to Vegard Hassel for reviewing the introduction of this thesis. Finally, I would like to express gratitude to my family and friends. You have supported me and kept me in shape both socially and physically during the PhD work. You have always been there when I needed some time away from "channel models" and "Shannon capacity", and for that I am very thankful.
American Academic Scientific Research Journal for Engineering, Technology, and Sciences, 2021
Multi-input Multi-output (MIMO) systems are of the most promising ones in the field of wireless communications as they provide high data rates and reduce the bit error rate (BER) using spatial multiplexing (SM) and diversity gain techniques, respectively. The deep review of MIMO systems shows that most of them are based on the utilization of uniform linear antennas (ULA) arrays. For further performance enhancement, a new digital array beamforming technique for linear antenna arrays optimization is introduced for both singleuser and multiuser MIMO systems to achieve maximum gain. In our proposed technique, the antenna arrays are implemented for a higher gain by adjusting the feeding and the distance between the antenna elements. The modified mathematical model for our proposed digital array beamforming MIMO system has been derived and merged to the current linear detection techniques such as Maximum Likelihood (ML), Zero Forcing (ZF), and Minimum Mean Square Error (MMSE). The simulation results demonstrated the superiority of our proposed technique over the traditional MIMO systems in terms of BER and spectral efficiency (SE).
Effect of line of sight propagation on capacity of an indoor MIMO system
2005
In this paper the performance of a Multiple Input Multiple Output (MIMO) wireless communication system operating in an indoor environment, featuring both Line of Sight (LOS) and Non-Line of Sight (NLOS) signal propagation, is assessed. In the model the scattering objects are assumed to be uniformly distributed in an area surrounding the transmitting and receiving array antennas. Mutual coupling effects in the arrays are treated in an exact manner. However interactions with scattering objects are taken into account via a single bounce approach. Computer simulations are carried out for the system capacity for varying inter-element spacing in the receiving array for assumed values of LOS/NLOS power fraction and Signal to Noise Ratio (SNR).
The Ideal MIMO Channel: Maximizing Capacity in Sparse Multipath with Reconfigurable Arrays
2006 IEEE International Symposium on Information Theory, 2006
While the intense research on multi-antenna (MIMO) wireless communication channels was pioneered by results based on an i.i.d. channel model representing a rich multipath environment, there is growing experimental evidence that physical wireless channels exhibit a sparse multipath structure, even at relatively low antenna dimensions. In this paper, we propose a model for sparse multipath channels and study coherent MIMO capacity as a function of SNR for a fixed number of antennas. In a recent work, we had shown that the spatial distribution of the sparse multipath has a significant impact on capacity and had also characterized the optimal distribution (the Ideal MIMO Channel) that maximizes capacity at any operating SNR. In this paper, we refine these results and develop a framework for maximizing MIMO capacity at any SNR by systematically adapting the array configurations (antenna spacings) at the transmitter and receiver to the level of sparsity. Surprisingly, three canonical array configurations are sufficient for near-optimum performance over the entire SNR range. In a scattering environment with randomly distributed paths, the capacity gain due to optimal configuration is directly proportional to the number of antennas at low SNR's. Numerical results based on a realistic physical model are presented to illustrate capacity gains with reconfigurable antenna arrays.
Characterization of Reconfigurable Mimo Antennas for Channel Capacity in an Indoor Environment
Progress In Electromagnetics Research C, 2016
In this paper, three different frequency reconfigurable multiple-input-multiple output (MIMO) antennas are characterized in terms of their channel capacity performance in an indoor environment. Two 2 × 2 and one 4 × 4 MIMO antenna configurations are investigated. A complete MIMO system is implemented using software defined radio (SDR) platform. The antenna under test can be used at either transmitter or receiver ends. The channel capacity of the system is evaluated by computing the channel coefficient matrix. The measurements are performed at 2.45 GHz for line of sight (LOS) and non-line of sight (NLOS) scenarios. A comparison of the antennas is performed with an ideal system scenario with totally uncorrelated channels as well as an array of standard monopoles which are half-wavelength apart. The effects of antenna element efficiencies, radiation patterns and spacings on the channel capacity are discussed.
On the Covariance Matrix and Capacity Evaluation of Reconfigurable Antenna Array Systems
IEEE Transactions on Wireless Communications, 2014
In this paper, we derive analytical expressions to compute the covariance matrix of the signals impinging on a reconfigurable antenna array. We consider a receiver equipped with a linear antenna array where each antenna element can be independently configured to create a directive radiation pattern toward a selected direction. In our derivation, we assume a multimodal truncated Laplacian distribution to model the power angular spectrum (PAS) of the signals arriving at the array. Using the derived expressions, we are able to evaluate the correlation between the received signals as a function of the signal spatial distribution, the antenna array topology, and the radiation pattern characteristics of each element in the array. We also study the capacity of a reconfigurable multiple-input multipleoutput (RE-MIMO) system and illustrate its relation to radiation pattern configurations and characteristics. We demonstrate how the derived expressions can be used to efficiently choose the configuration for each reconfigurable antenna element in the array that leads to an optimal compromise between low receive correlation and high receive power in order to maximize the link capacity. Simulation results are provided to validate our analytical expressions.