Abstract: A communication frame for an OTFS transmission system includes at least one first-type and at least one second-type block. At least the first-type block includes data signals two-dimensionally arranged along the delay domain and the Doppler domain of which at least one has a superimposed pilot signal. The second-type block includes data signals two-dimensionally arranged along the delay domain and the Doppler domain which may or may not have superimposed pilot signals. At least one second-type block is preceded and followed, in the delay-domain, by first-type blocks, the first-type blocks preceding and following a second-type block having at least one identical data symbol and associated superimposed identical pilot symbol at an identical location in the two-dimensional arrangement. An OTFS transmitter generates and transmits the communication frame, and a receiver uses its properties for compensating oscillator frequency offset and channel estimation.

Abstract: A communication frame for an OTFS transmission system includes first-type and second-type blocks. The first-type block includes pilot signals, guard signals, and data signals, the second-type block exclusively includes data signals. The pilot symbols, guard signals, and data symbols of the first-type block, and the data symbols of the second-type block, are arranged along the points of a grid in the delay-Doppler domain. In the communication frame, a first-type block is followed by a second-type block, and a second-type block is followed by a first-type block. In the first-type block at least one pilot symbol is surrounded on at least three sides by one or more guard symbols. Points of the grid of the first-type blocks in the delay-Doppler domain that are not occupied by pilot symbols or guard symbols are used for data symbols. The communication frame permits determining oscillator frequency offset and channel coefficients in a receiver.

Abstract: A near-optimal Karhunen-Loeve basis expansion modeling (KL-BEM) orthogonal time frequency space (OTFS) receiver with superimposed pilots has been proposed for high-mobility communications with Doppler spread channel. First, an initial KL-BEM channel estimation is conducted by superimposed pilots, followed by the removal of superimposed pilots from the received OTFS signal and equalisation by message passing (MP) algorithm. After that, the detected data symbols are utilized as pseudo pilots along with the superimposed pilots to refine both KL-BEM channel estimation and equalisation in an iterative manner. Simulation results confirm the superior performance of the proposed KL-BEM OTFS receiver over the prior art in terms of the mean-square-error (MSE) of channel estimation and bit error rate (BER). It also has a close BER performance to the BER lower bound obtained by assuming perfect channel estimation. It contributes to high spectral efficiency and fast convergence performance.

Abstract: An OFDM receiver has a first, pilot-aided channel estimation block, an output of which is provided, along with the received signal, to a first equaliser block. An output of the first equaliser block is provided, along with the received signal, to a second, data-aided channel estimation block. An output of the second channel estimation block is provided, along with the output of the first equaliser block and the received signal, to an adjustable interference cancellation block. The output of the interference cancellation block and the output of the second channel estimation block are provided to a second equaliser block. An output of the second equaliser block is provided to a de-mapping block, and is provided to the second channel estimation block and the interference cancellation block, for allowing an iterative repetition of second channel estimation, interference cancellation and second equalisation for a received signal.

Abstract: Pilot symbols and data symbols of a communication frame for an OTFS transmission system are two-dimensionally arranged along the points of a grid in the delay-Doppler domain. The pilot symbols are surrounded by guard symbols. The number of guard symbols in each direction of the Doppler domain is twice the number of the basis expansion modelling (BEM) basis functions used for modelling the communication channel in a receiver, and twice the maximum time delay in terms of delay bins in each direction of the delay domain. The receiver performs an initial pilot-aided channel estimation using BEM of a first BEM order and using the pilot signals, followed by an initial estimation of data symbols using the initial channel estimation, and iteratively performs data aided channel estimation using BEM of a second BEM order and at least the received data signals, until a termination criterion is met.

Abstract: There is provided a method of receiving a transmitted signal over a time-varying channel. The method includes: obtaining a received symbol signal in frequency domain based on the transmitted signal; performing a first channel estimation based on the received symbol signal to obtain a plurality of first estimated BEM coefficients; performing a first equalization based on the received symbol signal and the plurality of first estimated BEM coefficients to obtain a plurality of first detected source symbols; and performing one or more rounds of a second channel estimation and a second equalization.

Abstract: There is provided a method of receiving a transmitted signal over a time-varying channel. The method includes: obtaining a received symbol signal in frequency domain based on the transmitted signal; performing a first channel estimation based on the received symbol signal to obtain a plurality of first estimated BEM coefficients; performing a first equalization based on the received symbol signal and the plurality of first estimated BEM coefficients to obtain a plurality of first detected source symbols; and performing one or more rounds of a second channel estimation and a second equalization.

Abstract: In a vehicle-to-vehicle communication system, an intersection-located road side unit (RSU) having two omni-antennas applies spatial filtering to the antennas' RX signals to recover first and second overlapping basic safety messages (BSMs) concurrently transmitted by two intersection-approaching vehicles that have no direct line of sight (NLOS) between them. The RSU retransmits each BSM for receipt by the other vehicle using either an omnidirectional retransmission technique in which the two messages are sequentially transmitted using an omnidirectional beam-pattern, a directional retransmission technique in which the two messages are sequentially transmitted using directional beam-patterns, or an XOR retransmission technique in which the RSU applies an XOR operation to the two BSMs and transmits the resulting XOR message using an omnidirectional beam-pattern. A receiving vehicle can apply an XOR operation to the XOR message and a local copy of the first BSM message to recover the second BSM message.

Abstract: In a vehicle-to-vehicle communication system, an intersection-located road side unit (RSU) having two omni-antennas applies spatial filtering to the antennas' RX signals to recover first and second overlapping basic safety messages (BSMs) concurrently transmitted by two intersection-approaching vehicles that have no direct line of sight (NLOS) between them. The RSU retransmits each BSM for receipt by the other vehicle using either an omnidirectional retransmission technique in which the two messages are sequentially transmitted using an omnidirectional beam-pattern, a directional retransmission technique in which the two messages are sequentially transmitted using directional beam-patterns, or an XOR retransmission technique in which the RSU applies an XOR operation to the two BSMs and transmits the resulting XOR message using an omnidirectional beam-pattern. A receiving vehicle can apply an XOR operation to the XOR message and a local copy of the first BSM message to recover the second BSM message.

Abstract: A method of preparing a digital medical image for secure transmission, the method comprising embedding data into the digital medical image using a reversible watermarking process, generating a code for tamper detection and localization from the digital medical image using a computational function, and embedding the code for tamper detection and localization into the digital medical image using the reversible watermarking process; and a method of reviewing a digital medical image prepared by the method of preparing, the method of reviewing comprising retrieving the code for tamper detection and localization from the digital medical image; reversing the watermarking processes to obtain a restored image; generating a code from the restored image using the computational function; and comparing the retrieved code for tamper detection and localization with the code generated from the restored image to detect and locate tampering.

Abstract: A method of preparing a digital medical image for secure transmission, the method comprising embedding data into the digital medical image using a reversible watermarking process, generating a code for tamper detection and localization from the digital medical image using a computational function, and embedding the code for tamper detection and localization into the digital medical image using the reversible watermarking process; and a method of reviewing a digital medical image prepared by the method of preparing, the method of reviewing comprising retrieving the code for tamper detection and localization from the digital medical image; reversing the watermarking processes to obtain a restored image; generating a code from the restored image using the computational function; and comparing the retrieved code for tamper detection and localization with the code generated from the restored image to detect and locate tampering.