Is the Envelope Beneficial to Non-Orthogonal Multiple Access?

TL;DR

This paper introduces NOMA with informative envelope (NOMA-IE), a novel scheme that enhances spectral and energy efficiency by encoding data in the signal envelope, showing significant performance gains over traditional OFDM and NOMA methods.

Contribution

The paper proposes a new NOMA scheme utilizing the signal envelope for data transmission, including theoretical analysis and performance evaluation demonstrating its advantages.

Findings

NOMA-IE outperforms OFDM and OFDM-NOMA in high SNR regimes.

Analytical expressions for spectral and energy efficiency are derived.

Error performance is mainly affected by imperfect SIC and index errors.

Abstract

Non-orthogonal multiple access (NOMA) is capable of serving different numbers of users in the same time-frequency resource element, and this feature can be leveraged to carry additional information. In the orthogonal frequency division multiplexing (OFDM) system, we propose a novel enhanced NOMA scheme, called NOMA with informative envelope (NOMA-IE), to explore the flexibility of the envelope of NOMA signals. In this scheme, data bits are conveyed by the quantified signal envelope in addition to classic signal constellations. The subcarrier activation patterns of different users are jointly decided by the envelope former. At the receiver, successive interference cancellation (SIC) is employed, and we also introduce the envelope detection coefficient to eliminate the error floor. Theoretical expressions of spectral efficiency and energy efficiency are provided for the NOMA-IE. Then, considering the binary phase shift keying modulation, we derive the asymptotic bit error rate for the two-subcarrier OFDM subblock. Afterwards, the expressions are extended to the four-subcarrier case. The analytical results reveal that the imperfect SIC and the index error are the main factors degrading the error performance. The numerical results demonstrate the superiority of the NOMA-IE over the OFDM and OFDM-NOMA, especially in the high signal-to-noise ratio (SNR) regime.