Circular $\theta$ -QAM: A Circle-Shaped QAM for Higher-Order Modulation

This paper proposes M-ary circular θ-quadrature amplitude modulation (CTQAM) for M = 2^l, l ≥ 4, which is constructed by rearrangement of the signal points based on θ-QAM. We provide a construction method for the signal constellation of CTQAM and analyze the symbol and bit error performances of M-ary CTQAM in additive white Gaussian noise (AWGN) and Nakagami-m fading channels. Through computer simulations, we validate theoretical results.