Concentric UCAs Based Low-Order OAM for High Capacity in Radio Vortex Wireless Communications

摘要

Due to the potential capacity-boosting forwireless communications, radio vortex wireless communication(RowComm) over orthogonal states/modes oforbital angular momentum (OAM) has been paid muchattention to in recent years. A uniform circular array(UCA), as an efficient and convenient antenna structure,can transmit/receive multiple OAM beams with differentOAM-modes simultaneously when the transmitter andreceiver are aligned. However, for high-order OAMmodes,the OAM beams are divergent accompaniedby severe attenuation. Thus, it is difficult to directlyuse high-order OAM-modes to achieve high capacityfor RowComms. To obtain high capacity potentiallyoffered by OAM-modes, in this paper we transformthe singular UCA into the concentric UCAs, where highcapacity can be achieved using multiple parallel low-orderOAM-modes instead of all high-order OAM-modes, toincrease the capacity of transmitter-receiver aligned Row-Comms. In particular, we study two cases: 1). concentricUCAs based RowComms without co-mode interference;2). concentric UCAs based RowComms with co-modeinterference. We propose a co-mode-interference-free anda co-mode-interference-contained mode-decompositionschemes to recover transmitted signals for these two cases,respectively. Additionally, we develop optimal powerallocation schemes to maximize the capacity for these twocases. Numerical simulations are presented to validateand evaluate that our developed concentric UCAs basedlow-order RowComms can significantly increase thecapacity as compared with that of singular UCA basedRowComms.