Generalized Filter Bank OFDM: Low-Complexity Expectation Propagation Detection in Space–Terrestrial Integrated Network

The space-terrestrial integrated network (STIN), a fundamental component of the broader space-air-ground integrated network, plays a critical role in the future communication infrastructure by facilitating global connectivity, efficient resource allocation, and robust service delivery. The generalized filter bank orthogonal frequency division multiplexing (GFB-OFDM) has emerged as an innovative waveform in this network that enables flexible subband processing, achieves low out-of-band emissions, and seamlessly supports both terrestrial and satellite systems. To further investigate the GFB-OFDM detection, this paper first derives the input-output relation of the communication system using the GFB-OFDM in a matrix form, which is then used to formulate both the linear and the nonlinear detection. Considering the tradeoff between limited reliability and high computational complexity of the existing detection schemes, a low-complexity expectation propagation detector is proposed for the GFB-OFDM system to strike a better balance. By applying the second-order Richardson iteration, the posterior mean vector of the transmitted symbols is approximated to avoid the direct matrix inversion, thereby reducing the computational complexity. We then adopt an approach to approximate the eigenvalues in each iteration such that the computational complexity involved by the matrix decomposition is significantly reduced while maintaining a competitive error performance. Furthermore, the computational complexities of various detection schemes are precisely analyzed and evaluated focusing on the numbers of the complex multiplications. At last, the error performance, the power spectral density and the peak-to-average power ratio of the GFB-OFDM and other waveforms are evaluated in the space-terrestrial scenario. The extensive simulation results validate our conclusion making it a promising solution for practical deployment in STIN scenarios such as low earth orbit satellite broadband communication.