This paper presents wireless OAM (orbital angular momentum) and OAM-MIMO (multi-input and multi-output) multiplexing in a 28 GHz frequency band. We have implemented transmission (Tx) and reception (Rx) antennas consisting of multiple uniform circular arrays (UCAs) to confirm the feasibility. Each UCA can concurrently transmit or receive five OAM mode signals (0, ±1, ±2). Using implemented antennas, we rectified mode-selective Rx SNR degradation caused by the inherent nature of OAM beams. With a combination of antenna selection and receiver diversity we have achieved a 45 Gbps transmission rate using five OAM modes. We also experimentally demonstrated the effectiveness of the OAM-MIMO multiplexing by using a total of eleven OAM modes (three OAM 0 modes and two sets of OAM ±1 and ±2 modes). Experimental results reached a new milestone in point-to-point transmission rates by achieving 100 Gbps at 10 m transmission distance.

An Experimental Demonstration of 28 GHz Band Wireless OAM-MIMO (Orbital Angular Momentum Multi-Input and Multi-Output) Multiplexing

This letter shows that it is possible to simultaneously generate, in the microwave frequency band, several pseudo-Bessel beams having an azimuthal field variation, characteristic of vortex modes, by making use of a single flat antenna. Specifically, a radial line slot array has been designed to prove the concept. The design benefits of a Butler matrix network to provide the correct phase progression along the azimuthal coordinate, and it makes use of a holographic approach to assure the required aperture field distribution.

Simultaneous Generation of Pseudo-Bessel Vortex Modes With a RLSA

This paper presents the development of prototype radio equipment for orbital angular momentum (OAM) mode and polarization multiplexing transmission in E-band, as well as the results of a field trial using the prototype. The equipment consists of a radio frequency unit (RF UNIT) and a base-band unit (BB UNIT). The RF UNIT has a uniform circular array with eight elements and E-band frequency converters for each element. The BB UNIT for the transmitter has OAM mode multiplexers and digital modulators, and one of the receivers has an adaptive OAM mode de-multiplexer and digital demodulators which can operate in real-time. Sixteen multiplexing transmissions (eight OAM modes and two polarizations) over a link distance of 40 m with 256 QAM and spectral efficiency of 85.7 bps/Hz have been achieved.

40 M Transmission of OAM Mode and Polarization Multiplexing in E-Band

This paper proposes a method that employs successive interference cancellation (SIC) to further enhance the capacity of uniform circular array (UCA)-based orbital angular momentum (OAM)- MIMO systems. The central feature of the proposed approach is to exploit the additional space diversity benefit in the remaining streams by means of SIC owing to the large difference in the received power among different UCAs in each OAM mode. Therefore, it is expected that the proposed method can further stabilize the performance of UCA-based OAM-MIMO along with the communication distance. Our numerical results show that the proposed method outperforms the traditional method without SIC in terms of the system capacity owing to the large received power difference among different UCAs.

Performance Enhancement of OAM-MIMO Using Successive Interference Cancellation

This paper proposes a method that employs successive interference cancellation (SIC) to further enhance the capacity of uniform circular array (UCA)-based orbital angular momentum (OAM)-MIMO systems. The main feature of the proposed method is to stabilize the performance of UCA-based OAM-MIMO systems by conducting SIC based on the results of parallel interference cancellation (PIC), which exploits the additional full space diversity benefit. The development of the proposed approach is motivated by the feature that large differences in the received power of different UCAs are advantageous to SIC. Moreover, the impact of the misalignment of the beam axis on the effectiveness of the proposed method is also investigated by considering a more realistic scenario. Our numerical results show that the effectiveness of the proposed method increases with increasing number of UCAs, and its advantage is retained within a certain amount of the misalignment of the beam axis.

Performance Analysis of OAM-MIMO using SIC in the Presence of Misalignment of Beam Axis

This paper discusses the generation of orbital angular momentum (OAM) produced by a parabolic reflector with a circular array (CA) feed. Simulated electromagnetic (EM) field verifies the behavior of OAM. Design parameters are numerically optimized for both the parabolic reflector and the circular array feed, in term of beam divergence associated with different OAM modes. Primitive estimations suggest that a few low-order-OAM modes can be transmitted simultaneously up to 100 meters in the mm-wave bands.

A study of orbital angular momentum generated by parabolic reflector with circular array feed

The feasibility of a high capacity radio link employing Orbital Angular Momentum (OAM) mode-multiplexing is discussed in this paper. Experiments are conducted with the supports of Software Defined Radio (SDR) based system for signal processing, A/D and D/A conversions, modulation and demodulation (MODEM), and dielectric lens fed by Uniform Circular Array (UCA) for OAM signals transmission and reception. We confirm the successful transmission of 14 different 16-QAM data streams corresponding to 7 OAM modes (0, ±1, ±2, ±3) in combination with 2 polarizations (±45deg) over a 0.5m link at 5.1GHz, which results in a high spectral efficiency of 56bps/Hz.

An experimental study on OAM mode-multiplexing with dielectric lens fed by uniform circular array

This paper reports the feasibility of a high-capacity radio link employing Orbital Angular Momentum (OAM) mode multiplexing. Experiments are conducted with the support of Software Defined Radio (SDR) system, E-band RF converter, and Uniform Circular Array (UCA) antenna for OAM signals transmission and reception. We confirm a successful transmission of 8 data streams with 16QAM modulation order, carried by 8 OAM modes (0, ±1, ±2, ±3, +4) over a 7m link at 74.5GHz, which results in a high spectral efficiency of 32bps/Hz.

Tung Nguyen

Papers

A study of orbital angular momentum generated by parabolic reflector with circular array feed

An experimental study on OAM mode-multiplexing with dielectric lens fed by uniform circular array

An Experimental Study of High-Capacity Link using Orbital Angular Momentum Mode Multiplexing in E-Band