Broadband beam steering for misaligned multi-mode OAM communication systems

Orbital angular momentum(OAM)at radio frequency(RF)has attracted more and more attention as a novel approach of multiplexing a set of orthogonal OAM modes on the same frequency channel to achieve high spectral efficiency(SE).However,the precondition for maintaining the orthogonality among different OAM modes is perfect alignment of the transmit and receive uniform circular arrays(UCAs),which is difficult to be satisfied in practical wireless communication scenarios.Therefore,to achieve available multi-mode OAM broadband wireless communication,we first investigate the effect of oblique angles on the transmission performance of the multi-mode OAM broadband system in the non-parallel misalignment case.Then,we compare the UCA-based RF analog and baseband digital transceiver structures and corresponding beam steering schemes.Mathematical analysis and numerical simulations validate that the SE of the misaligned multi-mode OAM broadband system is quite low,while analog and digital beam steering(DBS)both can significantly improve the SE of the system.However,DBS can obtain higher SE than analog beam steering especially when the bandwidth and the number of array elements are large,which validates that the baseband digital transceiver with DBS is more suitable for multi-mode OAM broadband wireless communication systems in practice.

A Promising Technology for 6G Wireless Networks:Intelligent Refl ecting Surface

The intelligent information society,which is highly digitized,intelligence inspired,and globally data driven,will be deployed in the next decade.The next 6G wireless communication networks are the key to achieve this grand blueprint,which is expected to connect everything,provide full dimensional wireless coverage and integrate all functions to support full-vertical applications.Recent research reveals that intelligent reflecting surface(IRS)with wireless environment control capability is a promising technology for 6G networks.Specifically,IRS can intelligently control the wavefront,e.g.,the phase,amplitude,frequency,and even polarization by massive tunable elements,thus achieving fine-grained 3-D passive beamforming.In this paper,we first give a blueprint of the next 6G networks including the vision,typical scenarios,and key performance indicators(KPIs).Then,we provide an overview of IRS including the new signal model,hardware architecture,and competitive advantages in 6G networks.Besides,we discuss the potential application of IRS in the connectivity of 6G networks in detail,including intelligent and controllable wireless environment,ubiquitous connectivity,deep connectivity,and holographic connectivity.At last,we summarize the challenges of IRS application and deployment in 6G networks.As a timely review of IRS,our summary will be of interest to both researchers and practitioners engaging in IRS for 6G networks.