NC-OFDM Satellite Communication Based on Compressed Spectrum Sensing

Abstract

With the fast development of giant LEO constellations, the effective spectrum utilization has been regarded as one of the key orientations for satellite communications. This paper focuses on improving the spectrum utilization efficiency of satellite communications by proposing a non-continuous orthogonal frequency division multiplexing (NC-OFDM) method. Based on the models of NC-OFDM system, we first propose a sub-carrier allocation method by using spectrum sensing to efficiently perceive and utilize the spectrum holes in the satellite communication system. Then, a hybrid genetic particle swarm optimization method is adopted to allocate the channel resources effectively. Finally, simulation results verify that the proposed algorithm can significantly improve the spectrum efficiency of satellite communications.

Conjugate Gradient Least Squares Algorithm for OFDM Nonlinear Equalization in Intelligent Future IoT Transportation Systems

“…Although the MMSE equalizers perform superior to other linear equalization techniques, their complexity makes them impractical for scenarios involving long symbols, such as broadcasting applications. This is primarily due to the computationally intensive matrix inversion process, as indicated by equation (12). Many alternative equalizers have been devised to tackle the intricacies connected with MMSE equalization.…”

“…The MMSE equations pose a challenge due to the computational complexity associated with matrix inversion, as demonstrated in equation (12). One innovative way to simplify the MMSE equations is to execute the matrix inversion iteratively.…”

“…The inclusion of Q off-diagonal components above and below the main diagonal in the band structure of 𝑩𝑩 𝑛𝑛 leads to the formation of a band structure for the matrix (𝑩𝑩 𝑛𝑛 𝑩𝑩 𝑛𝑛 𝐻𝐻 ). This approach simplifies the computation of the MMSE equaliser in equation (12). However, as the value of ( 19) is time-dependent, the estimation 𝒅𝒅 � 𝑛𝑛 = 𝑾𝑾 𝑛𝑛,𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝒓𝒓 � 𝑛𝑛 can be obtained without explicitly stating the specific value of 𝑾𝑾 𝑛𝑛,𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 .…”

“…Satellite Communications: OFDM is employed in satellite communication systems to efficiently utilize satellite transponders and robust data transmission in challenging atmospheric conditions [12].…”