Orthogonal time frequency space modulation technology

La presente investigación bibliográfica recopila los conceptos básicos de la tecnología de modulación en el Espacio de Tiempo-Frecuencia Ortogonal (OTFS), que será utilizada para la comunicación móvil de quinta generación (5G), la cual presenta ventajas inherentes frente a la modulación de Multiplexación por División de Frecuencia Ortogonal (OFDM) utilizada en la comunicación móvil de cuarta generación (4G). Entre ellas podemos destacar su capacidad de transformar un canal que se desvanece aleatoriamente dentro del espacio de tiempofrecuencia en un canal estacionario, no aleatorio y sin desvanecimiento, entre el transmisor y el receptor. Además, el hecho de que la modulación OTFS opere en dominios en los que el canal puede caracterizarse en una forma muy compacta tiene implicaciones significativas para la solución de los cuellos de botella de estimación de canales, que afectan los sistemas actuales de antenas múltiples, y puede ser una tecnología clave para abordar problemas similares en futuros sistemas masivos de múltiples entradas y múltiples salidas (MIMO). Finalmente, el beneficio clave de la modulación OTFS es su capacidad para operar fácilmente en canales Doppler extremos; esto no solo es útil en las comunicaciones de alta movilidad, sino que también puede ser una tecnología que habilite los sistemas en la banda de frecuencia de onda milimétrica significativamente, para su operatividad en condiciones donde los efectos Doppler se amplifican.This bibliography research gathers together the basics of the Orthogonal Time Frequency Space (OTFS) modulation technology, that will be used in the fifth generation (5G) mobile communications; it has inherent advantages in the face of the Orthogonal Frequency Division Multiplexing (OFDM) modulation technique, used in the fourth generation mobile communication (4G). One of these profits is its skill to transform a channel that randomly fades within the timefrequency space into a stationary, deterministic and non-fading channel between the transmitter and the receiver. In addition, there is the fact that OTFS modulation operates in a domain in which the channel can be characterized in a very compact way; this has significant implications for tackling the channel estimation bottlenecks that affect current multi-antenna systems and can be an implementing key technology for addressing similar problems in future massive MIMO systems. Finally, the main benefit of OTFS modulation is its ability to easily operate in extreme Doppler channels; this is not only useful in high mobility communications, but can also be an enabling technology for mmWave systems, where Doppler effects will be significantly amplified.Universidad de Costa Rica/[805-B9-609]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de FísicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI

AFDM vs OTFS: A Comparative Study of Promising Waveforms for ISAC in Doubly-Dispersive Channels

This white paper aims to briefly describe a proposed article that will provide a thorough comparative study of waveforms designed to exploit the features of doubly-dispersive channels arising in heterogeneous high-mobility scenarios as expected in the beyond fifth generation (B5G) and sixth generation (6G), in relation to their suitability to integrated sensing and communications (ISAC) systems. In particular, the full article will compare the well-established delay-Doppler domain-based orthognal time frequency space (OTFS) and the recently proposed chirp domain-based affine frequency division multiplexing (AFDM) waveforms. Both these waveforms are designed based on a full delay- Doppler representation of the time variant (TV) multipath channel, yielding not only robustness and orthogonality of information symbols in high-mobility scenarios, but also a beneficial implication for environment target detection through the inherent capability of estimating the path delay and Doppler shifts, which are standard radar parameters. These modulation schemes are distinct candidates for ISAC in B5G/6G systems, such that a thorough study of their advantages, shortcomings, implications to signal processing, and performance of communication and sensing functions are well in order. In light of the above, a sample of the intended contribution (Special Issue paper) is provided below