Capacity Enhancement of Cooperative NOMA over Rician Fading Channels with Orbital Angular Momentum

Abstract

This letter proposes the usage of orbital angular momentum (OAM) for cooperative non-orthogonal multiple access (CNOMA) to enhance sum capacity (SC) for the future cellular communication system. The proposed CNOMA-OAM scheme is analyzed and compared with other schemes, i.e., conventional CNOMA, conventional orthogonal multiple access (OMA) with OAM. The impact of the power allocation factor for OAM beam over SC is also analyzed. The analytical result is justified by simulation results which demonstrate that the proposed CNOMA-OAM provides higher SC compared to other schemes.

Channel Capacity Enhancement of SWIPT based CNOMA Downlink Transmission with Orbital Angular Momentum over Rician Fading Channel

“…l 1 > l 2 to reduce the attenuation of the OAM signal for CEU, because higher mode of OAM beam has greater hollow part which increases the attenuation for the receiver with comparatively substandard channel condition. 27,34 d 1 and d 2 are the respective normalized distances of CCU and CEU from BS in Figure 1. Independent Rician fading channel coefficients of BS-to-CCU (Link 1), BS-to-CEU (Link 2), and CCU-to-CEU (Link 3) are denoted as h 1 , h 2 , and h 3 , respectively.…”

“…It is assumed that CCU can perfectly decode symbol x 2 in the first time slot in Figure 1. 25,27 Power splitting (PS) based SWIPT is considered at CCU for energy harvesting to perform the relay the decoded x 2 from CCU to CEU. PS SWIPT provides better capacity since it required less time slot than time switching (TS) based SWIPT.…”

“…PS SWIPT provides better capacity since it required less time slot than time switching (TS) based SWIPT. 18,22,24 The received SINR at CEU for symbol x 2 by relaying from the CCU can be expressed as 22,24,27 γ…”

“…The additional symbol transmission by different OAM modes will enhance the capacities. 27 . Due to the assumed LOS, Rician fading channel is considered here 25,27 .…”

“…OAM utilizes a new degree of freedom which is known as OAM mode for signal transmission. [25][26][27] OAM exploits the phase variation with respect to the azimuth angle of the propagated electromagnetic waves. This leads to the helical phase structure of the wave.…”