8-antenna and 16-antenna arrays using the quad-antenna linear array as a building block for the 3.5-GHz LTE MIMO operation in the smartphone
Massive MIMO system is very promising for 5G communications. The achievable channel capacity can be greatly increased for the massive MIMO system, especially when the numbers of the MIMO antennas in both the smartphone and base station are comparable. It is hence very attractive to deploy a large number of MIMO antennas in the smartphone so as to effectively increase the channel capacity. However, owing to the very limited space in the smartphone, it is very challenging to embed a large number of MIMO antennas (for example, at least eight antennas) therein with good isolation and low envelope correlation coefficients (ECCs).
In this article, promising 8 and 16 MIMO antennas in the smartphone formed by using the quad-antenna linear (QAL) array as a building block for the 3.5-GHz LTE MIMO operation are presented. The MIMO antennas are operated in the 3.5-GHz band (3400~3600 MHz), which has been recently identified in WRC-15 (World Radio communication conference 2015) for global mobile broadband services in the future. The achievable channel capacity of the 8-antenna array formed by two QAL arrays disposed along two opposite edges can reach about 37 bps/Hz for the 8×8 MIMO operation. On the other hand, the 16-antenna array formed by four QAL arrays can reach a channel capacity of about 68 bps/Hz for the 16×16 MIMO operation. Related results are presented in the article.
Recently, the calculated MIMO channel capacities for the proposed compact 8 MIMO antennas are verified using the MIMO OTA (over-the-air) test platform built in the National Sun Yat-sen University (see the attached figure). With a 20-MHz bandwidth, the obtained throughput of the 8 MIMO antennas in the smartphone for the 8 x 4 MIMO operation at 20-dB Signal-to-noise ratio and 256 QAM has been measured to be about 425 MB per second. For operated in the 8×8 MIMO system, the throughput is expected to be about 800 MB per second and will be tested in the very near future. With a wider bandwidth, the throughput can be easily larger than 1 GB per second. The results indicate that the Massive MIMO operation with at least eight antennas in the smartphone is promising for 5G mobile communications.
Figure Legend: 8×8 MIMO OTA test platform built in the National Sun Yat-sen University
Featured authors information:
Corresponding author: Kin-Lu Wong, affiliation and publication information available at Google Scholar https://scholar.google.com.tw/scholar?hl=zh-TW&q=kin+lu+wong&btnG=&lr=
Kin-Lu Wong1,*, Jun-Yu Lu1, Li-Yu Chen1,Wei-Yu Li2 andYong-Ling Ban3Show Affiliations
- Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan
- Information and Communications Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan
- Institute of Electromagnetics and School of Electrical Engineering, University of Electronic Science and Technology of China, Chengdu, China
Using the quad-antenna linear (QAL) array as a building block, the 8-antenna and 16-antenna arrays for the 3.5-GHz long term evolution multiple-input multiple-output (MIMO) operation in the smartphone are demonstrated. The QAL array has a planar structure of narrow width 3 mm (0.035λ) and short length 50 mm (0.58λ), with λ being the wavelength at 3.5 GHz. For the 8-antenna array, two QAL arrays are disposed along two opposite side edges (denoted as Array A) or the same side edge (denoted as Array B) of the system circuit board of the smartphone. The obtained envelope correlation coefficient values of the antennas in Array A and B are shown. The calculated channel capacities for Array A and B applied in an 8 × 8 MIMO system are also analyzed. The 16-antenna array formed by four QAL arrays disposed along two opposite side edges (denoted as Array C) is then studied. For operating in a 16 × 16 MIMO system, the calculated channel capacity of Array C can reach about 66–70 bps/Hz with a 20-dB signal-to-noise ratio. The obtained channel capacity is about 5.7–6.1 times that (11.5 bps/Hz) of the upper limit of an ideal 2 × 2 MIMO system with 100% antenna efficiency for the antennas therein. Details of the proposed Array A, B, and C are described, and the obtained results are presented. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:174–181, 2016
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