###### Abstract  
Non-line-of-sight (NLOS) communication with severe loss always leads to performance degradation in unmanned aerial vehicle (UAV) payload communication. In this paper, a UAV NLOS communication scheme based on single-carrier frequency domain equalization with cyclic prefix and cyclic suffix (CP/CS-SC-FDE) is designed. First, the reasons behind the generation of later intersymbol interference (LISI) in UAV NLOS communication are investigated. Then, the frame structure of conventional single-carrier frequency domain equalization with cyclic prefix (CP-SC-FDE) is improved, and the UAV NLOS communication frame structure based on cyclic prefix (CP) and cyclic suffix (CS) is designed. Furthermore, a channel estimation algorithm applicable to this scheme is proposed. The numerical results show that this UAV communication scheme can eliminate intersymbol interference (ISI) in NLOS communication. Compared with the conventional CP-SC-FDE system, this scheme can achieve excellent performance in the Rayleigh channel and other standard NLOS channels. In the CP/CS-SC-FDE system, the BER result is similar to that under ideal synchronization. U  
A _Article_  
A Design of NLOS Communication Scheme Based on SC-FDE with Cyclic Suffix for UAV Payload Communication  
[PERSON], [PERSON], [PERSON], R.  
by reflection and scattering. When the UAV flies at low altitude, the LOS path between the UAV and the ground station is easily blocked by buildings and trees, leading to non-line-of-sight (NLOS) communication [12; 13; 14]. There are significant differences between NLOS communication and LOS communication. In contrast to LOS communication, the power of the signal arriving through the LOS path in NLOS communication is very low and may even be zero. This means that the power of signals reached by other paths in NLOS communication accounts for a large proportion of the total signal power [15]. Then, the multipath effect of UAV NLOS communication is more significant, and the UAV communication performance degrades more seriously. As is well known, the most common UAV channel model for LOS communication is the Ricean channel. For the NLOS case, the Rayleigh channel model typically provides a better fit [16; 17; 18]. A distinctive feature of the Rayleigh channel is that its path with maximum power (PwMP) may not be the first arrival path (FAP), which will cause time offset during synchronization and later intersymbol interference (LISI). The interpretation of LISI is that the decision of the current symbol is interfered with by later symbols. Experiments show that LISI will lead to a significant increase in the UAV communication bit error rate (BER). In a LOS channel, there is only preceding intersymbol interference (PISI), i.e., the decision of the current symbol is interfered with only by preceding symbols. PISI is known as ISI. Inspired by the elimination of ISI, i.e., PISI, through CP, this paper eliminates LISI through cyclic suffix (CS). In [19; 20; 21], CS is applied to the super-Nyquist technology to eliminate interblock interference (IIB). These references did not analyze the principle of the CS and clarify the relationship between the CS and NLOS communication. Since PISI and LISI exist in NLOS communication, the SC-FDE NLOS communication scheme based on CP and CS for UAV PC is proposed in this paper. The main contributions of our work are given as follows. 1. We investigate the reason behind the generation of LISI in UAV NLOS communication. Moreover, the frame structure of conventional SC-FDE with CP (CP-SC-FDE) is improved, and we design an NLOS communication scheme based on SC-FDE with CP and CS (CP/CS-SC-FDE) for UAV PC. In addition, the scheme can be compatible with both LOS and NLOS communication. 2. A channel estimation algorithm applicable to this scheme is proposed, which can eliminate the ISI in UAV NLOS communication. Compared with the conventional CP-SC-FDE system, this scheme can achieve excellent performance in Rayleigh channel simulation.