No abstract

This paper investigates an uplink coordinated multipoint (CoMP) coverage scenario, in which multiple mobile users are grouped for sparse code multiple access (SCMA), and served by the remote radio head (RRH) in front of them and the RRH behind them simultaneously. We apply orthogonal time frequency space (OTFS) modulation for each user to exploit the degrees of freedom arising from both the delay and Doppler domains. As the signals received by the RRHs in front of and behind the users experience respectively positive and negative Doppler frequency shifts, our proposed OTFS-based SCMA (OBSCMA) with CoMP system can effectively harvest extra Doppler and spatial diversity for better performance. Based on maximum likelihood (ML) detector, we analyze the single-user average bit error rate (ABER) bound as the benchmark of the ABER performance for our proposed OBSCMA with CoMP system. We also develop a customized Gaussian approximation with expectation propagation (GAEP) algorithm for multi-user detection and propose efficient algorithm structures for centralized and decentralized detectors. Our proposed OBSCMA with CoMP system leads to stronger performance than the existing solutions. The proposed centralized and decentralized detectors exhibit effective reception and robustness under channel state information uncertainty.

OAM-based reconfigurable doppler shifts enable PAPR reduction for multi-carrier doppler diversity

No abstract

Orbital Angular Momentum (OAM) transmission is expected to be implemented for large capacity communication. However, the conical beam and the coaxial all-phase reception brings painful difficulties. As a promising solution to overcome this difficulty, an OAM multiplexing transmission method is proposed for use in a satellite formation relay scheme in this paper. Specifically, the channel model of the OAM wave from the base station to the relay satellites and then forwarded by relays to the central receiver is established and analyzed. In order to explore the feasibility of the scheme and its influencing factors, we analyze the influence of orbit distribution and random jitter on channel capacity based on the orbit parameters of actual satellite formations. The simulation results show that the uniform and evenly spaced satellite formation has the highest multiplexed channel capacity and anti-interference performance.