Abstract: A method for signal transmission using precoded symbol information involves estimating a two-dimensional model of a communication channel in a delay-Doppler domain. A perturbation vector is determined in a delay-time domain wherein the delay-time domain is related to the delay-Doppler domain by an FFT operation. User symbols are modified based upon the perturbation vector so as to produce perturbed user symbols. A set of Tomlinson-Harashima precoders corresponding to a set of fixed times in the delay-time domain may then be determined using a delay-time model of the communication channel. Precoded user symbols are generated by applying the Tomlinson-Harashima precoders to the perturbed user symbols. A modulated signal is then generated based upon the precoded user symbols and provided for transmission over the communication channel.

Abstract: Fiber, cable, and wireless data channels are typically impaired by reflectors and other imperfections, producing a channel state with echoes and frequency shifts in data waveforms. Here, methods of using pilot symbol waveform bursts to automatically produce a detailed 2D model of the channel state are presented. This 2D channel state can then be used to optimize data transmission. For wireless data channels, an even more detailed 2D model of channel state can be produced by using polarization and multiple antennas in the process. Once 2D channel states are known, the system turns imperfect data channels from a liability to an advantage by using channel imperfections to boost data transmission rates. The methods can be used to improve legacy data transmission modes in multiple types of media, and are particularly useful for producing new types of robust and high capacity wireless communications using non-legacy data transmission methods as well.

Abstract: Methods, systems and devices for forward error correction in orthogonal time frequency space (OTFS) communication systems using non-binary low-density parity-check (NB-LDPC) codes are described. One exemplary method for forward error correction includes receiving data, encoding the data via a non-binary low density parity check (NB-LDPC) code, wherein the NB-LDPC code is characterized by a matrix with binary and non-binary entries, modulating the encoded data to generate a signal, and transmitting the signal. Another exemplary method for forward error correction includes receiving a signal, demodulating the received signal to produce data, decoding the data via a NB-LDPC code, wherein the NB-LDPC code is characterized by a matrix with binary and non-binary entries, and providing the decoded data to a data sink.

Abstract: Device, methods and systems for aspects of channel estimation for orthogonal time frequency space (OTFS) modulation in wireless systems are described. In an aspect, a method for wireless communication may include receiving, using multiple receive antennas, from a number of user devices, non-orthogonal pilots wherein at least some transmissions of the non-orthogonal pilots from different user devices overlap in at least some time and frequency resources, estimating individual pilots from the number of user devices by computing a pilot separation filter for each antenna, and estimating the wireless channel at time and frequency resources used by the non-orthogonal pilots by filtering the receiving signal at the multiple receiver antennas.

Abstract: Methods, systems and devices for providing transmission resources that achieve transmission diversity while reducing pilot signal overhead are described. An exemplary wireless communication method may be implemented in a wireless communication system in which transmission resources are allocated on a per physical resource block (PRB) basis, where a PRB corresponds to a two dimensional resource pattern comprising a first number of subcarriers along a frequency dimension and a second number time slots along a time dimension. The method includes logically dividing subcarriers in each PRB into an integer number of sub-groups of sub-carriers, wherein the integer number is greater than one, allocating, to a transmission, transmission resources corresponding to one or more of the sub-groups of subcarriers, performing the transmission in the wireless communication system.

Abstract: An Orthogonal Time Frequency Space Modulation (OTFS) modulation scheme that maps data symbols, along with optional pilot symbols, using a symplectic-like transformation such as a 2D Fourier transform and optional scrambling operation, into a complex wave aggregate and be backward compatible with legacy OFDM systems, is described. This wave aggregate may be processed for transmission by selecting portions of the aggregate according to various time and frequency intervals. The output from this process can be used to modulate transmitted waveforms according to various time intervals over a plurality of narrow-band subcarriers, often by using mutually orthogonal subcarrier “tones” or carrier frequencies. The entire wave aggregate may be transmitted over various time intervals. At the receiver, an inverse of this process can be used to both characterize the data channel and to correct the received signals for channel distortions, thus receiving a clear form of the original data symbols.

Abstract: Orthogonal Time Frequency Space (OTFS) is a novel modulation scheme with significant benefits for 5G systems. The fundamental theory behind OTFS is presented in this paper as well as its benefits. We start with a mathematical description of the doubly fading delay-Doppler channel and develop a modulation that is tailored to this channel. We model the time varying delay-Doppler channel in the time-frequency domain and derive a new domain (the OTFS domain) where we show that the channel is transformed to a time invariant one and all symbols see the same SNR. We explore aspects of the modulation like delay and Doppler resolution, and address design and implementation issues like multiplexing multiple users and evaluating complexity. Finally we present some performance results where we demonstrate the superiority of OTFS.

Abstract: A fixed wireless access system is implemented using orthogonal time frequency space multiplexing (OTFS). Data transmissions to/from different devices share transmission resources using—delay Doppler multiplexing, time-frequency multiplexing, multiplexing at stream and/or layer level, and angular multiplexing. Time-frequency multiplexing is achieved by dividing the time-frequency plan into subgrids, with the subsampled time frequency grid being used to carry the OTFS data. Antenna implementations include a hemispherical antenna with multiple antenna elements arranged in an array to achieve multiplexing.

Abstract: The computer-implemented method includes simulating, by a processor, using an electromagnetic solver including ray launching or ray tracing, multiple rays that reach a vicinity of a receiver of a wireless channel, determining locations of interactions of the rays with an environment of the wireless channel, post-processing, using one or more of the multiple rays, information about received signal at the receiver to obtain temporal variations therein, and determining a characteristic of the wireless channel using results of the post-processing.

Abstract: Methods, systems and devices for providing transmission resources that achieve transmission diversity while reducing pilot signal overhead are described. An exemplary wireless communication method may be implemented in a wireless communication system in which transmission resources are allocated on a per physical resource block (PRB) basis, where a PRB corresponds to a two dimensional resource pattern comprising a first number of subcarriers along a frequency dimension and a second number time slots along a time dimension. The method includes logically dividing subcarriers in each PRB into an integer number of sub-groups of sub-carriers, wherein the integer number is greater than one, allocating, to a transmission, transmission resources corresponding to one or more of the sub-groups of subcarriers, performing the transmission in the wireless communication system.

Abstract: An antenna system includes a lens portion that has a spherical surface, and an antenna feed structure coupled to a surface of the lens portion. The antenna feed structure includes one or more feed tiles supported by an electrical connectivity layer conforming to the spherical surface. The antenna system also includes one or more offset structures positioned between the one or more feed tiles and an outer surface of the antenna system.

Abstract: Methods, systems and devices for lattice reduction in decision feedback equalizers for orthogonal time frequency space (OTFS) modulation are described. An exemplary wireless communication method, implementable by a wireless communication receiver apparatus, includes receiving a signal comprising information bits modulated using OTFS modulation scheme. Each delay-Doppler bin in the signal is modulated using a quadrature amplitude modulation (QAM) mapping. The method also includes estimating the information bits based on an inverse of a single error covariance matrix of the signal, with the single error covariance matrix being representative of an estimation error for all delay-Doppler bins in the signal.

Abstract: An airborne RF-head platform system and method. Here, much of the computational burden of transmitting and receiving wireless RF waveforms is shifted from the airborne platform to a ground baseband unit (BBU). The airborne platform, which will often be a high altitude balloon or drone type platform, generally comprises one or more remote radio heads, configured with antennas, A/D and D/A converters, frequency converters, RF amplifiers, and the like. The airborne platform communicates with the ground baseband units either directly via a laser communications link, or indirectly through another airborne relay platform. The airborne RF-head communicates via various wireless protocols to various user equipment such as smartphones by using the BBU and the laser communications link to precisely control the function of the airborne A/D and D/A converters and antennas. This system reduces the power needs, weight, and cost of the airborne platform, and also improves operational flexibility.

Abstract: Described are devices, systems and methods for scheduling multi-user (MU) multiple input multiple output (MIMO) transmissions in a fixed wireless access (FWA) system. One method for scheduling a large number of user devices in a wireless communication system includes a preselection process to pare down the number of user devices to be simultaneously scheduled, and then scheduling that subset of users. In an example, and assuming each user device communicates over a corresponding wireless channel, the preselection process includes determining a number of sets based on a first characteristic of the wireless channels, where each set includes at least one user device, and then determining a subset of user devices by selecting at most one user device from each of the sets. The scheduling of the selected subset of users is based on a scheduling algorithm and a second characteristic of the wireless channels.

Abstract: Computerized wireless transmitter/receiver system that automatically uses combinations of various methods, including transmitting data symbols by weighing or modulating a family of time shifted and frequency shifted waveforms bursts, pilot symbol methods, error detection methods, MIMO methods, and other methods, to automatically determine the structure of a data channel, and automatically compensate for signal distortions caused by various structural aspects of the data channel, as well as changes in channel structure. Often the data channel is a two or three dimensional space in which various wireless transmitters, receivers and signal reflectors are moving. The invention's modulation methods detect locations and speeds of various reflectors and other channel impairments. Error detection schemes, variation of modulation methods, and MIMO techniques further detect and compensate for impairments.

Abstract: A system and method for orthogonal time frequency space communication and waveform generation. The method includes receiving a plurality of information symbols and encoding an N×M array containing the plurality of information symbols into a two-dimensional array of modulation symbols by spreading each of the plurality of information symbols with respect to both time and frequency. The two-dimensional array of modulation symbols is then transmitted using M mutually orthogonal waveforms included within M frequency sub-bands.

Abstract: A method for performing downlink transmissions from a transmitting device to multiple user devices using transmission resources from a multi-dimensional grid of resources is described. The method includes logically partitioning the transmission resources into multiple segments, assigning, to a given user device of the multiple user devices, transmission resources of one or more of the multiple segments, and performing, using at least some of the assigned transmission resources for the given user device, a downlink transmission using an orthogonal time frequency space (OTFS) transformation on data or signals to be transmitted to the given user device.

Abstract: A wireless telecommunications system that mitigates infrasymbol interference due to Doppler-shift and multipath and enables multiple access in one radio channel. Embodiments of the present invention are particularly advantageous for wireless telecommunications systems that operate in high-mobility environments, including high-speed trains and airplanes.

Abstract: Co-existence between an Orthogonal Time Frequency Space (OTFS) modulation system and a Long Term Evolution (LTE) system is achieved by generating a number of transmission beams for a first group of user equipment operating using LTE, and a second group of user equipment operating using the OTFS protocol, and transmitting a first group of data packets formatted according to the LTE protocol to the first group of user equipment and a second group of data packets formatted according to the OTFS protocol to the second group of user equipment. The transmissions are performed by precoding and modulating the first group of data packets according to an LTE modulation scheme, and precoding and modulating the second group of data packets according to an OTFS modulation scheme.

Abstract: Techniques for performing channel estimation in an orthogonal time, frequency and space (OTFS) communication system include receiving a wireless signal comprising a data signal portion and a pilot signal portion in which the pilot signal portion includes multiple pilot signals multiplexed together in the OTFS domain, performing two-dimensional channel estimation in a time-frequency domain based on a minimum mean square error (MMSE) optimization criterion, and recovering information bits using a channel estimate obtained from the two-dimensional channel estimation.