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indoor small-cell Networks with 3D MIMO Array Antennas

Periodic Reporting for period 1 - is3DMIMO (indoor small-cell Networks with 3D MIMO Array Antennas)

Reporting period: 2017-01-01 to 2018-12-31

It is predicted that wireless network traffic will increase 1000 times in the next decade. The exponential traffic growth is not uniform across geographical areas and mainly takes place in indoor hot spots. Hence, high capacity indoor venues represent the biggest network capacity increase challenge. The recently emerged 3-dimensional multiple-input multiple-output (3D MIMO) technology provides a promising dimension to provide extra capacity gain in hot spots. In particular, the 3D deployment of small cells (SCs) equipped with 3D MIMO antenna arrays will take advantage of 3D distribution of user equipment (UE) in typical high capacity venues, and represents an excellent technical combination to address the indoor high capacity challenge.

The 3D deployment of SCs with 3D MIMO antenna arrays faces technical challenges ranging from 3D MIMO antenna array design, performance evaluation, the lack of understanding of 3D MIMO SC network performance limits to the optimal 3D SC network deployment. The is3DMIMO project aims to address these technical challenges by assembling a team of academic and industrial partners with complementary expertise from the UK, Sweden, the Netherlands, and China. The is3DMIMO project has the following research and innovation (R&I) objectives:
• characterize and model indoor 3D MIMO channels for typical indoor environments;
• develop a reliable over-the-air (OTA) antenna characterization method for 3D MIMO SCs;
• characterize OTA performance in laboratory conditions as compared to real-life 3D MIMO small cell scenarios;
• obtain a fundamental understanding of the network performance gains achievable by 3D SCs with 3D MIMO antenna arrays;
• develop techniques for jointly optimizing the deployment locations of SC access points (APs) and their 3D MIMO configurations; and
• provide 3D MIMO SC network planning and deployment guidelines for typical 3D indoor scenarios.

The achievement of the above objectives will provide crucial inputs for multiple-antenna and 5G & beyond 5G system design and will increase network capacity in indoor hot spots by 20-30%.
The R&I efforts are structured around Work Packages (WPs) 1-3 and are carried out through researcher secondments and sharing of knowledge and skills. The work performed from the beginning of the project to the end of the first reporting period has achieved the following results.

WP1 studies indoor 3D MIMO channel measurement, characterization, and modeling, which form the foundation of the theoretical analysis, design, simulation, and evaluation for indoor 3D MIMO small-cell (SC) networking. We have completed Task 1.1 on indoor 3D ray launching channel simulation incorporating elevation sub-path generation, where the mechanisms of sub-path generation have been studied for indoor environments. We have carried out Task 1.2 on 3D MIMO channel characterization. The 3D MIMO channel path parameters and sub-path parameters have been obtained from extensive 3D MIMO channel simulations using the 3D ray launching based channel model established in Task 1.1 and theoretical analysis based on the sub-path model.

WP2 develops new over-the-air (OTA) characterization methods and performance metrics of 3D MIMO antennas. We have carried out Task 2.1 on optimization of array antennas for 3D spatial multiplexing (SMX) and 3D beamforming, where the initial design of a 3D MIMO antenna system based on a millimeter-wave ultra-wideband antenna has been completed. We have also carried out Task 2.2 on OTA characterization of array antennas and have devised an OTA characterization methodology that can properly evaluate the performance of 3D MIMO array antennas.

WP3 focuses on the planning and optimization of 3D indoor deployment of small-cell access points (APs) equipped with 3D MIMO array antennas. We have carried out Task 3.1 on deriving fundamental performance limits of 3D MIMO small-cell (SC) networks in 3D indoor environments and have completed the interference modeling for a single-floor densely deployed indoor SC network with randomly located interior walls under a stochastic-geometry based framework. The coverage probability of a typical user equipment (UE) has been derived and validated by Monte Carlo simulations. We have also carried out Task 3.2 on analyzing the spectral efficiency (SE) achievable from the dense deployment of 3D MIMO small cells in indoor environments. The analytical expressions for three performance metrics, including the coverage probability, SE, and area spectral efficiency (ASE), have been derived and verified by Monte Carlo simulations.
The R&I progress of the project beyond the state of the art and the expected results until the end of the project are summarized as follows. WP1 advances the state-of-the-art of indoor 3D MIMO channel characterisation and modelling by characterising mechanisms of elevation sub-path generation and incorporating them into ray-launching channel simulation; constructing an indoor 3D MIMO channel model by identifying the path and sub-path parameters through extensive 3D ray launching based simulation in indoor environments; and developing a 3D MIMO channel sounder and performing indoor 3D MIMO channel measurements to verify the indoor 3D MIMO channel model and 3D ray launching based channel simulation platform.

WP2 advances the state-of-the-art of the over-the-air (OTA) aided design of 3D MIMO array antennas for indoor small cells by producing a new paradigm for the OTA characterization of wireless devices, i.e. testing of 3D MIMO array antennas in both the rich isotropic multipath (RIMP) and the random line of sight (RLOS) environments; characterizing antenna performance from a system perspective, through their 3D throughput patterns that are especially suitable for 3D MIMO antenna systems instead of the traditional 3D radiation patterns; and correlating the performance of 3D MIMO array antennas in RIMP and RLOS environments with that in indoor small cells.

WP3 advances the state-of-the-art of indoor 3D MIMO small-cell network optimization by: (i) theoretically analyzing and numerically verifying the performance gains achievable from indoor 3D deployment of small-cell APs equipped with optimized 3D MIMO configurations; (ii) addressing the special challenges in deploying 3D MIMO small cells in indoor environments, including complex building structures, high penetration losses, interference scenarios, high user density coupled with high traffic demand per user; (iii) deriving the optimal 3D MIMO small cell deployment strategy in conjunction with optimized 3D MIMO configurations for typical indoor environments; and (iv) providing 3D MIMO small-cell network planning and deployment guidelines for typical indoor scenarios.

The major expected impacts of the project are as follows: (i) enhancing EU R&I competitiveness in 5G/B5G systems and technologies; (ii) developing lasting academic and industrial collaborations leading to interdisciplinary and intersectoral R&I programmes; (iii) contributing to the strengthening of EU innovation capacity by sharing knowledge and fostering highly-skilled human resources; (iv) raising public awareness of the importance and benefits of R&I on people’s daily lives and the development of e-society; and (v) generating public interest, in particular of the young generation, in pursuing a career in science and technology.