Two-Way Relaying for Single-Active Orbital Angular Momentum Index Modulation

In this paper, infrastructure-based two-way relaying with single-active orbital angular momentum index modulation (SA-OAM-IM), a special case of OAM-IM, is proposed for radio frequency line-of-sight communication. In the first time slot or transmission phase, two source/destination nodes simultaneously transmit information blocks to a relay node. After decoding, in the second time slot or transmission phase, the relay forms a single information block via network coding, which is then forwarded to the source/destination nodes. The information block is then decoded at the respective destination node via network coding. Hence, exchange of information blocks is achieved between the source/destination nodes. The scheme demonstrates a significantly improved bit error performance compared to its one-way relaying counterpart. The theoretical average bit error probability at the destination node is formulated for the proposed scheme and validated by Monte Carlo simulation results. A low-complexity near-maximum likelihood detector for SA-OAM-IM is further investigated.