Non-coherent OFDM-Subcarrier Power Modulation for Low Complexity and High Throughput IoT Applications

Abstract

Aiming to reduce the transceiver complexity and power consumption of communication systems dedicated to serving future Internet of Things (IoT) applications, researchers have taken many approaches with varying degrees of success. A promising candidate solution that can reduce complexity significantly a n d t h u s a l s o e n h ance p o wer-saving i s t h e u s e o f n o n -coherent m o d ulation-based schemes. Utilizing a non-coherent structure rids the system of any dependency on the knowledge of the phase of the transmitted signal during demodulation. However, although most of the available non-coherent techniques in the literature reduce the complexity of the system, they, unfortunately, suffer from a drawback of some sort, especially in reducing the overall spectral efficiency o f t he s ystem. T o a ddress t his p roblem, w e p ropose a new non-coherent modulation scheme called orthogonal frequency division multiplexing with subcarrier power modulation and differential phase-shift keying (OFDM-SPM-DPSK), as an effective modulation technique for future 6G and beyond systems. The proposed technique has the potential to reduce complexity, enhance power-saving while improving spectral efficiency s i g nificantly, re su lt ing in a sp ec tr al efficiency performance twice that of a conventional OFDM system. Furthermore, receive diversity is implemented through maximal ratio combining to overcome the bit error degradation brought by the adoption of a noncoherent structure. Additionally, the computational complexity is discussed and shown to be as efficient as OFDM, where the proposed scheme does not add further complexity over conventional OFDM.

NC-OFDM-SPM: A Two-Dimensional Non-Coherent Modulation Scheme for Achieving the Coherent Performance of OFDM along with Sending an Additional Data-stream

“…The theoretical BER for the Power − st r eam is not plotted here because this curve is not the at the core of this study where the optimization focuses on the DP SK − st r eam instead. We direct the reader to [14] for a detailed derivation of the theoretical bit error rate expression of this curve. Third, the curve B E R C oher ent OF D M −B P SK and the curve B E R Di f f er ent i al OF D M −B P SK are plotted for comparison purposes and they, respectively, denote the theoretical error rate of coherent OFDM with binary phase shift keying (OFDM-BPSK) expressed by Eq.…”

“…Moreover, the generalization of the OFDM-SPM design to quadrature signal constellations was studied in [13] to demonstrate the fact that OFDM-SPM performance does not degrade compared to its counterparts when higher order modulations are used. Furthermore, A non-coherent version of OFDM-SPM has recently been introduced in [14], where the basic idea of its design was established. The development of non-coherent OFDM-SPM is motivated by the points discussed in the section above, where its non-coherence ensures low design complexity and the exploration of the power as a second dimension enhances the spectral efficiency of the system, where it is capable of doubling the data rate per device compared to a conventional OFDM system.…”

STBC-assisted OFDM with Subcarrier Power Modulation

“…OFDM-SPM manipulates the power of the subcarriers of an OFDM block and uses it as an additional degree of freedom to convey extra data bits. Also, the author in [5] proposes a non-coherent modulation scheme called orthogonal frequency division multiplexing with sub-carrier power modulation and differential phase-shift keying (OFDM-SPM-DPSK), as an effective modulation technique for future 6G and beyond systems. The proposed technique has the potential to reduce complexity, enhance power-saving while improving spectral efficiency significantly.…”