Transmitter and receiver for, and method of, transmitting and receiving symbols over time varying channels with doppler spread

A method of receiving a binary data sequence over an orthogonal time-frequency space (OTFS) communication channel susceptive to doubly-selective fading, the method comprising:

• receiving a continuous time-domain signal representing a communication frame including one or more first-type blocks and one or more second-type blocks, the one or more first-type blocks comprising pilot signals, guard signals, and data signals, the one or more second-type blocks exclusively comprising data signals, the pilot symbols, guard signals, and data symbols of the one or more first-type blocks, and the data symbols of the one or more second-type blocks, being arranged along the points of a grid in a delay-Doppler domain, the one or more first-type blocks being followed by one, or several consecutive, second-type blocks, and the one of one or more second-type blocks, or a last one of one or the several consecutive second-type blocks, being followed by another one of the one or more first-type blocks, the one or more first-type blocks each having at least one pilot symbol this is surrounded on at least three sides by one or more guard symbols, the points of the grid of the one or more first-type blocks in the delay-Doppler domain that are not occupied by pilot symbols or guard symbols being used for data symbols, the continuous time domain signal being received over the OTFS communication channel,
• transforming, in a first receiver-side transformation unit, the continuous time-domain signal representing the communication frame into a two-dimensional arrangement of information symbols in a time-frequency domain that is available at an output of the first receiver-side transformation unit,
• transforming, in a second receiver-side transformation unit, the two-dimensional arrangement of information symbols comprising pilot and data signals in the time-frequency domain into a two-dimensional communication frame comprising pilot signals and data signals in the delay-Doppler domain that is available at an output of the second receiver-side transformation unit,
• estimating an oscillator frequency offset (OFO) from the one or more first-type blocks of the communication frame,
• providing the estimated OFO to a basis expansion modelling (BEM) bases generation unit and the generated BEM bases to a channel estimation, for incorporating the OFO estimate into a channel estimation function applied,
• providing at least the pilot signals output from the second receiver-side transformation unit to a first channel estimation unit, for obtaining a first estimation of a time-domain channel matrix at an output of the first channel estimation unit,
• providing the first estimation of the time-domain channel matrix, as well as at least the data signals output from the second receiver-side transformation unit or the pilot and data signals output from the second receiver-side transformation unit, to an equalizer unit, for obtaining an estimated set of at least data signals at an output of the equalizer unit,
• estimating, in a second channel estimation unit, an estimation of the time-domain channel matrix, from the estimated set of the at least data signals that are output from the equalizer unit, as well as from at least the pilot signals obtained after a second transformation in the second receiver-side transformation unit or the pilot and data signals output from the second receiver-side transformation unit,
• providing the estimation of the time-domain channel matrix available at an output of the second channel estimation unit, as well as at least the data signals obtained after the second transformation in the second receiver-side transformation unit or the pilot and data signals output from the second receiver-side transformation unit, to the equalizer unit, for obtaining a further estimated set of at least data signals, and
• iteratively repeating estimating the time-domain channel matrix in the second channel estimation unit and estimating sets of the at least data signals in the equalizer unit until a termination criterion is met.