Performance Assessment of OTFS Modulation in High Doppler Airborne Communication Networks

Abstract

Emerging 5G and future 6G mobile networks are expected to cater for high mobility scenarios ranging from vehicle-to-vehicle communications to unmanned aerial vehicles and airborne platforms. Communications in this type of deployments suffer from severe Doppler shifts which require new modulation waveforms. Orthogonal time frequency space (OTFS) modulation has recently been proposed as a promising technology for coping with high Doppler channels. OTFS converts a time-varying fading channel into a time-independent channel in the two-dimensional delay-Doppler (DD) domain. The transmit symbols are multiplexed into a nearly constant channel with a complex channel gain in the DD domain. In this paper, we consider a high Doppler airborne communication network where relative mobile node speeds can be above 1200 m/s. The considered system represents a mobile ad-hoc network where the airborne mobile nodes can join or leave the network. Furthermore, each node is equipped with an antenna array that supports directed communication among mobile nodes. The Doppler shifts in this airborne communication network are in the order of 52-72 kHz and may potentially be even higher depending on the selected carrier frequency and the relative speed among the airborne platforms. As such, OTFS modulation is used in this work to efficiently compensate for the high Doppler shifts in the DD domain. In particular, a comprehensive performance assessment in terms of bit error rate (BER) is conducted to reveal the potential of OTFS modulation in dealing with such extreme transmission scenarios. The impact of physical layer parameters, number of delay-Doppler bins in the DD domain used for OTFS modulation, directed versus two-ray channels, and the combination of multiple-input multiple-output (MIMO) systems with OTFS modulation on the BER is assessed. It is shown that both OTFS modulation over a two-ray channel as well as MIMO-OTFS modulation provide a reliable airborne communication network with low BER.

Modulations for Terahertz Band Communications: Joint Analysis of Phase Noise Impact and PAPR Effects

“…The DFT size is set to less than that of the number of subcarriers, due to the requirements of DFT-s-OFDM. The Doppler bins are chosen to keep the complexity and PAPR low as higher grid sizes will influence those parameters [41], [61]. As noted earlier, a reduced cyclic prefix is best to provide performance with minimal overhead [27].…”

Reduction of PAPR for STFBC MIMO F-OFDM using Enhancement Asymmetric Arithmetic Coding Scheme

“…At the receiver, the filtered signal is subdivided into a number of consecutive OFDM symbols and encounters channel equalization. Mitigation of the signal interference (remove CP) shows its capacity and capability to get PAPR and BER degradation [13]. Finally, the data symbols are processed in AAC decoder to refine STFBC MIMO F-OFDM decoded by the extraction from the corresponding subcarriers.…”