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Prospective Multiple Antenna Technologies for Beyond 5G (1910.00092v3)

Published 30 Sep 2019 in cs.IT, eess.SP, and math.IT

Abstract: Multiple antenna technologies have attracted large research interest for several decades and have gradually made their way into mainstream communication systems. Two main benefits are adaptive beamforming gains and spatial multiplexing, leading to high data rates per user and per cell, especially when large antenna arrays are used. Now that multiple antenna technology has become a key component of the fifth-generation (5G) networks, it is time for the research community to look for new multiple antenna applications to meet the immensely higher data rate, reliability, and traffic demands in the beyond 5G era. We need radically new approaches to achieve orders-of-magnitude improvements in these metrics and this will be connected to large technical challenges, many of which are yet to be identified. In this survey paper, we present a survey of three new multiple antenna related research directions that might play a key role in beyond 5G networks: Cell-free massive multiple-input multiple-output (MIMO), beamspace massive MIMO, and intelligent reflecting surfaces. More specifically, the fundamental motivation and key characteristics of these new technologies are introduced. Recent technical progress is also presented. Finally, we provide a list of other prospective future research directions.

Citations (622)

Summary

  • The paper presents advanced multiple antenna solutions—cell-free massive MIMO, beamspace MIMO, and IRS—that tackle key challenges in spectral efficiency and network reliability.
  • It employs a methodology combining distributed access point coordination, scalable hybrid beamforming, and programmable metasurfaces for improved interference mitigation.
  • The study paves the way for future research into robust power control, dynamic channel estimation, and low-complexity IRS control to enhance beyond-5G network performance.

An Overview of Prospective Multiple Antenna Technologies for Beyond 5G

The paper by Jiayi Zhang et al. provides a focused exploration of advanced multiple antenna technologies poised to address the unmet demands of wireless communication in a post-5G era. Specifically, it explores cell-free massive MIMO, beamspace massive MIMO, and intelligent reflecting surfaces (IRS) as promising candidates to enhance data rates, reliability, and traffic handling capabilities.

Cell-Free Massive MIMO

The paper asserts cell-free massive MIMO as a promising evolution of cellular architectures to tackle well-known limitations such as inter-cell interference and cell-edge performance issues. This inverse cellular paradigm uses distributed antennas, coordinated through cloud-edge processing, to achieve nearly uniform user performance across coverage areas. It boasts substantial improvements in 95%-likely per-user spectral efficiency compared to small cells and traditional cellular massive MIMO.

System Model and Advances

The authors explore the system model, illustrating an innovative architecture where distributed access points (APs) collaboratively serve users by harnessing time-division duplex (TDD) mode and channel reciprocity. Enhancements in spectral efficiency were achieved using scalable processing algorithms, where local maximal-ratio or minimum mean-square error techniques balance computational feasibility and performance gains. The work suggests further research into robust power control schemes and scalable implementation techniques.

Beamspace Massive MIMO

Beamspace massive MIMO capitalizes on spatial channel structures to minimize complexity while retaining performance efficacy. The paper discusses leveraging lens arrays for spatial division multiplexing and beamforming. Emphasis is placed on hybrid beamforming, which features prominently in current and future transceiver designs owing to its advantage in cost and processing reduction.

Technical Challenges

Challenges include adapting lens arrays for dynamic channel estimation and mitigating the impacts of hardware impairments. Innovations in this field can drive more efficient multi-user communications by optimizing spatial resources inherent to beamspace technology.

Intelligent Reflecting Surfaces (IRS)

IRS technology represents a novel approach to enhancing wireless link performance through programmable metasurfaces that control signal propagation. Such surfaces enable anomalous reflections, thereby optimizing signal paths and improving link quality without active RF chain consumption.

Practical Considerations

Despite its clear potential in achieving high energy efficiency and flexible deployment, IRS requires robust solutions for channel estimation and control protocols. The work underscores the necessity for developing low-complexity algorithms that dovetail with IRS’s passive nature, ensuring operational practicality and cost-effectiveness.

Future Directions and Impacts

In discussing the implications of integrating these advanced technologies, the paper acknowledges several avenues for further research. These include refining fronthaul/backhaul provisioning for scalability, improving hardware components, and developing new network architecture paradigms that incorporate distributed processing. The potential symbiosis between UAV-assisted networks and cell-free MIMO, as well as the viability of sub-terahertz communications, are presented as future research frontiers.

Conclusion

The paper provides a substantive investigation into the roles of emerging antenna technologies in advancing the capabilities and efficiencies of next-generation wireless systems. While offering substantial insights into the current state and future prospects of cell-free massive MIMO, beamspace massive MIMO, and IRS, the discussion also sets a platform for ongoing exploration to address the highlighted open challenges and opportunities in the field.