Orthogonal Time Frequency Space (OTFS) modulation is a novel two-dimensional modulation technique that operates in the delay-Doppler domain. Unlike traditional methods such as OFDM, OTFS is designed to exploit full channel diversity over both time and frequency, converting time-varying wireless channels into time-independent channels with constant complex gains. This design eliminates the need for transmitter adaptation and simplifies system operation. OTFS is shown to provide significant performance improvements in systems with high Doppler, short packets, and large antenna arrays, with simulation results indicating several dB of block error rate improvement over OFDM in these settings. OTFS is particularly beneficial for 5G applications, where traditional OFDM assumptions (such as knowledge of channel state information at the transmitter) are not met. By operating in the delay-Doppler domain, OTFS can be interpreted as modulating information symbols onto two-dimensional orthogonal basis functions in the time-frequency plane. This allows for full channel diversity and almost-constant channel gain, reducing the overhead and complexity of physical layer adaptation. Additionally, OTFS provides a robust, slowly varying channel suitable for TCP/IP and delay-sensitive 5G applications. OTFS can be implemented as an overlay to existing systems, such as OFDM, by using the existing hardware for the Heisenberg/Wigner transform. This approach simplifies implementation and reduces complexity compared to SC-FDMA. OTFS also enables efficient multiplexing in the delay-Doppler domain, allowing different users to be separated at the receiver. The full diversity of OTFS ensures that it can achieve a diversity order equal to the number of multipath components, providing better performance in fast-varying channels. OTFS also offers advantages in terms of Peak to Average Power Ratio (PAPR), reducing uplink PAPR by spreading the signal over a longer time-frequency window. This makes OTFS more suitable for high-mobility scenarios and systems with latency constraints. The almost-constant channel gain also enables simplified equalizers and decoders, as well as precoders, leading to improved performance and reduced complexity. Overall, OTFS provides a robust and efficient modulation scheme for next-generation wireless communication systems.Orthogonal Time Frequency Space (OTFS) modulation is a novel two-dimensional modulation technique that operates in the delay-Doppler domain. Unlike traditional methods such as OFDM, OTFS is designed to exploit full channel diversity over both time and frequency, converting time-varying wireless channels into time-independent channels with constant complex gains. This design eliminates the need for transmitter adaptation and simplifies system operation. OTFS is shown to provide significant performance improvements in systems with high Doppler, short packets, and large antenna arrays, with simulation results indicating several dB of block error rate improvement over OFDM in these settings. OTFS is particularly beneficial for 5G applications, where traditional OFDM assumptions (such as knowledge of channel state information at the transmitter) are not met. By operating in the delay-Doppler domain, OTFS can be interpreted as modulating information symbols onto two-dimensional orthogonal basis functions in the time-frequency plane. This allows for full channel diversity and almost-constant channel gain, reducing the overhead and complexity of physical layer adaptation. Additionally, OTFS provides a robust, slowly varying channel suitable for TCP/IP and delay-sensitive 5G applications. OTFS can be implemented as an overlay to existing systems, such as OFDM, by using the existing hardware for the Heisenberg/Wigner transform. This approach simplifies implementation and reduces complexity compared to SC-FDMA. OTFS also enables efficient multiplexing in the delay-Doppler domain, allowing different users to be separated at the receiver. The full diversity of OTFS ensures that it can achieve a diversity order equal to the number of multipath components, providing better performance in fast-varying channels. OTFS also offers advantages in terms of Peak to Average Power Ratio (PAPR), reducing uplink PAPR by spreading the signal over a longer time-frequency window. This makes OTFS more suitable for high-mobility scenarios and systems with latency constraints. The almost-constant channel gain also enables simplified equalizers and decoders, as well as precoders, leading to improved performance and reduced complexity. Overall, OTFS provides a robust and efficient modulation scheme for next-generation wireless communication systems.