Near-Field Communications for Millimeter-Wave Ultra-Massive MIMO Wireless Networks

Description

The deployment of the latest fifth-generation (5G) wireless networks has tremendously  reshaped every aspect of our daily life and vitalized advanced development in the industry.  Qualcomm estimated that 5G will power the digital economy in global economic value by US$  13.2 trillion by 2035. Inspired by such impactful success, both academia and industry have  started to blueprint the next-generation 6G wireless networks. To support a plethora of thrilling  applications, e.g., the Internet of Everything (IoE), big data analytics, and augmented reality  (AR), 6G is expected to achieve extremely high data rates, ultra-wide frequency bands, and  massive connections. These stringent requirements call for revolutionary and transformative  wireless technologies for 6G network evolution.  Millimeter-wave (mm-wave) communication at 30 GHz to 300 GHz is such a disruptive  technology as it can crack the spectrum crunch crisis in current cellular systems and free up  spectrum in the order of GHz. Meanwhile, with the significantly reduced wavelength of  mm-wave signals, hundreds of thousands of antenna elements can be compactly deployed at  transceivers, agreeing with the newly-emerging concept of ultra-massive multiple-input  multiple-output (UM-MIMO). Nevertheless, leveraging UM-MIMO at mm-wave bands is not  merely a quantitative increase in both antenna size and carrier frequency, but more  importantly, a qualitative paradigm shift from conventional far-field communications to its  near-field counterpart. In particular, the enlarged antenna aperture and shortened wavelength  jointly expand the region defined as the near field, which was normally overlooked in  traditional wireless communications. Hence, this project will focus on near-field mm-wave  UM-MIMO communications, which is anticipated to be the typical transmission scenario in  next-generation 6G systems.  However, the abrupt transformation of communication mode introduces formidable challenges,  which shall be addressed in this project by developing novel physical (PHY) and medium  access control (MAC) layer techniques for near-field mm-wave UM-MIMO systems,  respectively. First, as the channel dimension becomes exceedingly large, the complexity of  signal processing for channel estimation and beamforming is daunting. Of particular interest is  the development of effective algorithms taking into account the unique characteristics of  near-field mm-wave channels and hardware limitations. Second, to achieve blockage-free  near-field mm-wave communications, it is of paramount importance to create scalable user  scheduling considering visible regions of UM-MIMO arrays and deployment strategies of  intelligent reflecting surfaces with theoretical supports. Finally, as future wireless networks  tend to be highly complex and heterogeneous, practical hybrid near- and far-field  communications will be investigated. Special attention shall be paid to utilizing smart antenna  selection methods for versatile hybrid-field mm-wave UM-MIMO systems.