Deployment Of Antenna Arrays Research Articles

Dilution of Precision in Three Dimensional Angle-of-Arrival Positioning Systems

Dilution of precision (DOP) for time-of-arrival (TOA) or time-difference-of-arrival (TDOA) positioning systems has been thoroughly investigated. This is not the case for angle-of-arrival (AOA) positioning systems, especially three dimensional AOA systems. However, the recent increase in deployment of antenna arrays and multipath mitigation techniques make AOA systems more attractive. In this paper, the DOPs for position systems using range measurements are reviewed and an expression for 3D AOA DOP is derived. The average values of DOPs for different deployments of base station geometries are examined. It is found that for a 3D AOA system, unlike TOA or TDOA systems, vertical DOP (VDOP) is generally smaller than horizontal DOP (HDOP), and the best VDOP can be achieved when the base stations are at the same height as the user. Moving the base stations away from the plane of the user may decrease the HDOP and Geometric DOP (GDOP) slightly, but it also increases the VDOP. For applications that the height of the user changes frequently, the base stations should be deployed with height close to half the height of the area of interest.

Optimization of Antenna Array Deployment for Partial Discharge Localization in Substations by Hybrid Particle Swarm Optimization and Genetic Algorithm Method

A radio frequency antenna array was adopted to localize partial discharge (PD) sources in an entire substation. The deployment of an antenna array is a significant factor affecting the localization accuracy, and the array needs to be carefully selected. In this work, a hybrid method of particle swarm optimization (PSO) and a genetic algorithm (GA) is proposed to optimize the array deployment. A direction-of-arrival (DOA) estimation algorithm applicable to arbitrary array configurations is firstly presented. The Cramér-Rao lower bound (CRLB) was employed to evaluate the localization accuracy of different arrays, and two objective functions characterizing the estimation errors of coordinates and the DOA are proposed. With the goal of minimizing the objective functions, the array deployments for the coordinate and DOA localizations were optimized by using the hybrid PSO/GA algorithm. Using the developed method, optimal antenna configurations for different constraint areas, aspect ratios, and numbers of sensors were investigated. The results indicate that the optimal deployments for coordinate and DOA estimations are different; specifically speaking, superior DOA performance is achieved when all antennas are placed on the outer boundary of the constraint area while part of the antennas in the optimal coordinate array are placed in the middle position.

Optimal Design of Uniform Circular Antenna Array in mmWave LOS MIMO Channel

The capacity of millimeter-wave (mmWave) line-of-sight (LOS) multiple-input multiple-output (MIMO) channel can be reduced due to the absence of rich scattering. However, the optimization of antenna array deployment can enable the maximum spatial multiplexing gain in the mmWave LOS MIMO channel, which can be applied to the long distance airborne data transmission. In this paper, we first establish the channel model of mmWave LOS MIMO based on a uniform circular antenna array (UCA) and derive the upper/lower bound of channel capacity. Aiming at achieving the maximum capacity of mmWave LOS MIMO channel, we propose the Newton-iterative method to obtain the optimal parameters of UCA. To simplify the optimization algorithm, the 2-D search can be transformed into 1-D search. Then, the analysis of bit error rate (BER) of the mmWave LOS MIMO system based on the UCA has been provided to quantify the mmWave LOS MIMO channel. Finally, numerical results demonstrate that the optimal parameters of UCA can be obtained by the Newton-iterative method and the BER of mmWave LOS MIMO communication system based on the corresponding optimized UCA can be minimized.

Evaluating Spatial Resolution and Channel Capacity of Sparse Cylindrical Arrays for Massive MIMO

How to design antenna arrays plays an important role in wireless communications, especially when there are hundreds of antennas. In massive multiple-input and multiple-output (MIMO), if the number of antennas and RF chains are increasing, the channel capacity and transmission efficiency could be obviously improved as well. Since in massive MIMO, antennas at the base station (BS) usually scale up greater than 100, the complexity and hardware requirement of the system are also increased. Many studies about massive MIMO are focused on the analysis of channel capacity, precoding, and so on, and very few are about the sparse antenna array deployment. Based on the sparse linear array structures as indicated by previous studies, three new arrays, namely co-prime cylindrical array (CCA), nested cylindrical array (NCA), and sparse nested cylindrical array (SNCA), are proposed, which are based on co-prime linear array, nested linear array, and sparse circular array, respectively. Compared with the traditional uniform cylindrical array (UCA), the proposed arrays vastly reduce the number of antennas used at the BS. In addition, the performance of spatial resolution and channel capacity of CCA, NCA, and SNCA are discussed in detail. The results show that our proposed sparse cylindrical arrays can obtain a higher resolution with much fewer antennas. Besides, the uplink channel capacity of all the three sparse cylindrical arrays is larger than the UCA with the same number of antennas at the BS.

Multi-User Massive MIMO Communication Systems Based on Irregular Antenna Arrays

In practical mobile communication engineering applications, surfaces of antenna array deployment regions are usually uneven. Therefore, massive multi-input–multi-output (MIMO) communication systems usually transmit wireless signals by irregular antenna arrays. To evaluate the performance of irregular antenna arrays, the matrix correlation coefficient and the ergodic received gain are defined for massive MIMO communication systems with mutual coupling effects. Furthermore, the lower bound of the ergodic achievable rate, symbol error rate, and average outage probability is first derived for multi-user massive MIMO communication systems using irregular antenna arrays. Asymptotic results are also derived when the number of antennae approaches infinity. Numerical results indicate that there exists a maximum achievable rate when the number of antennae keeps increasing in massive MIMO communication systems using irregular antenna arrays. Moreover, the irregular antenna array outperforms the regular antenna array in the achievable rate of massive MIMO communication systems when the number of antennae is larger than or equal to a given threshold.

Deployment Optimization of Uniform Linear Antenna Arrays for a Two-Path Millimeter Wave Communication System

This letter is concerned with the array design of a fixed point-to-point millimeter wave (MMW) communication system consisting of two paths between the transmitter and receiver. We assume uniform linear antenna arrays (ULAs) at both the transmitter and receiver and focus on the optimization of antenna deployment to maximize the system capacity with uniform power allocation. We analytically show that, at high signal-to-noise ratios (SNRs), the channel capacity depends on the spatial correlations between the two paths at both link ends. The optimal antenna array deployment that maximizes the channel capacity is derived. Numerical results show that the optimized antenna array deployment considerably improves the channel capacity, compared to the non-optimized deployment.

Statistical Analysis of Array Gain for Cooperative MISO Transmitters without CSI

Virtual Multiple-Input Single-Output (MISO) is recently proposed to extend the benefits of transmitter space diversity to networks in which the deployment of antenna arrays on individual nodes is infeasible from a practical point of view. Ad-hoc and sensor networks are examples of these type of networks. In these scenarios, nodes equipped with single antenna can cooperatively transmit to emulate an antenna array. However, cooperative transmissions require knowledge of the channel state either at the transmitter side or the receiver side in order to achieve full performance gains. Several solutions are proposed in the literature under these assumptions, but at the expense of increased overhead and energy consumption. In this paper, the array gain at the receiver from the non-coherent combining of the signals from multiple transmitters is analyzed in statistical sense, under the assumption that the channel knowledge is unavailable. The transmitters are assumed to be randomly spread over a circular region. More specifically, exact or very accurate closed-form expressions for the expectation and variance of the array gain are obtained, and then a complete statistical distribution is postulated and validated by means of heuristic procedures, goodness-of-fit tests and specialized software. The results obtained in this paper can be especially useful for the implementation of two-tiered wide area sensor networks.

Capacity Gain of Beamforming Techniques in a WCDMA System Under Channelization Code Constraints

This study addresses the performance of a wideband code-division multiple-access mobile communications system with beamforming antenna arrays (AAs) at the base station, synthesizing a grid of beams. In order to fully exploit the capacity gain from beamforming without jeopardizing the stability of the system, a directional power-based admission control (AC) scheme is applied. Due to the higher capacity offered by beamforming techniques, shortage of orthogonal channelization codes in the downlink becomes an increasingly important factor, which may result in blocking of users before the interference power limit is reached. The problem of channelization code shortage is addressed, and a solution based on splitting the cell into several code regions is proposed. For a network with circuit switched data services operated at 64 kb/s, the capacity gain for an eight-element AA is found to equal a factor of 2.5 for a universal mobile telecommunications equivalent system, with one channelization code set per cell. The capacity gain is limited by severe channelization code shortage under these circumstances. This problem is solved by deploying a cell splitting strategy with multiple code regions, which subsequently results in a capacity gain increase to a factor of 3.4. Furthermore, the soft capacity mechanism associated with partial deployment of AAs in a subset of the cells in the network is also addressed. It is demonstrated that a hot spot cell with AAs also helps increase the capacity of the surrounding cells with conventional sector antennas when using a power-based AC strategy.