Antenna Arrays for Line-of-Sight Massive MIMO: Half Wavelength Is Not Enough

Abstract

Abstract:The aim of this paper is to analyze the array synthesis for 5 G massive MIMO systems in the line-of-sight working condition. The main result of the numerical investigation performed is that non-uniform arrays are the natural choice in this kind of application. In particular, by using non-equispaced arrays, we show that it is possible to achieve a better average condition number of the channel matrix and a significantly higher spectral efficiency. Furthermore, we verify that increasing the array size is beneficial also for circular arrays, and we provide some useful rules-of-thumb for antenna array design for massive MIMO applications. These results are in contrast to the widely-accepted idea in the 5 G massive MIMO literature, in which the half-wavelength linear uniform array is universally adopted.

3D Multi-Beam and Null Synthesis by Phase-Only Control for 5G Antenna Arrays

“…The first example refers to a 9×9 uniform square array with an interelement spacing equal to 3/4 λ [9]. This implies that the array side is lower than 7 cm, making it suitable for usage on typical commercial smartphones.…”

“…Basically, the design of an antenna array has to deal with two main problems: the development of the physical system (i.e., the geometry of the array and the selection of the radiating elements) [9,10], and the evaluation of the excitations that better satisfy the pattern synthesis requirements [11,12]. For this second task, several algorithms have been developed considering the geometry of the array, the shape of the desired pattern, and the degrees of freedom that characterize the array excitations [13][14][15].…”

Empirical Modeling of Radiowave Angular Power Distributions in Different Propagation Environments at 60 GHz for 5G

“…g NCC max = N r (10) Equations (9) and (10) indicate that there is a maximum value for the combining improvement that depends exclusively on the number of combined beams. Results given in Table 4 and in reference [36] comply with these limits.…”

“…Massive multiple-input-multiple-output (MIMO) techniques [7,8] will have to be implemented in 5G systems to deal with the data traffic growth. Base stations are expected to be equipped with a very high number (even hundreds) of antennas [9] that will serve simultaneously several terminals, which will be also equipped with a number of antennas.…”

Efficient Large Sparse Arrays Synthesis by Means of Smooth Re-Weighted L1 Minimization

“…Antenna arrays are one of the most important technologies that allows responding to the challenges of the close future communication systems, particularly in the 5G and IoT frameworks [1][2][3][4]. In this perspective, the use of sparse, non-regular, arrays is particularly appealing, since it has been shown that a sparse array is often capable of achieving the same performance of regular lattice ones, with a much lower number of radiating elements, and a strong reduction of the issue of grating lobes.…”