Backward compatible orthogonal time frequency space signal communication

Abstract

A digital communication method includes assigning, to a transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and causing transmission of a transmission waveform for the first transmission signal.

Description

International Patent Application 119314.8124.WO00 BACKWARD COMPATIBLE ORTHOGONAL TIME FREQUENCY SPACE SIGNAL COMMUNICATION CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application No.63 / 657,048, filed on June 6, 2024 and U.S. Provisional Application No., 63 / 666,971, filed July 2, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety. TECHNICAL FIELD

[0002] The present document relates to digital communication. BACKGROUND

[0003] Due to an explosive growth in the number of wireless user devices and the amount of wireless data that these devices can generate or consume, current wireless communication networks are fast running out of bandwidth to accommodate such a high growth in data traffic and provide high quality of service to users.

[0004] Various efforts are underway in the telecommunication industry to come up with next generation of wireless technologies that can keep up with the demand on performance of wireless devices and networks. Many of those activities involve situations in which a large number of user devices may be served by a network. SUMMARY

[0005] This document discloses techniques that may be used in wireless networks to use orthogonal time frequency space (OTFS) modulation physical layer, and re-use higher layer building blocks and numerology from legacy network protocols.

[0006] In one example aspect, a digital communication method is disclosed. The method includes assigning, to a first transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; assigning, to a second transmission signal, second transmission resources in the delay- Doppler domain transmission grid according to a multiplexing scheme; and causing transmission of a transmission waveform for the first transmission signal and the second transmission signal. 1 180851577.4International Patent Application 119314.8124.WO00

[0007] In another example aspect, another digital communication method is disclosed. The method includes assigning, to a transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and causing transmission of a transmission waveform for the first transmission signal.

[0008] In another example aspect, another digital communication method is disclosed. The method includes receiving, by a receiver apparatus from a transmission apparatus, a transmission waveform comprising a first transmission signal and a second transmission signal, wherein the first transmission signal and the second transmission signal are multiplexed along a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit, and wherein the first transmission signal occupies first transmission resources in the delay-Doppler domain transmission grid and the second transmission signal occupies second transmission resources in the delay- Doppler domain transmission grid; and demodulating, from the transmission waveform, the first transmission signal to recover information bits transmitted from the transmission apparatus.

[0009] In another example aspect, another digital communication method is disclosed. The method includes receiving, by a receiver apparatus from a transmission apparatus, a transmission waveform comprising a first transmission signal, wherein the first transmission signal occupies transmission resources along a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), and wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and demodulating, from the transmission waveform, the first transmission signal to recover information bits transmitted from the transmission apparatus.

[0010] In another example aspect, another method configuring an electronic apparatus to operate using an orthogonal time frequency space (OTFS) physical layer and a legacy-compatible higher layer protocol stack, wherein the OTFS physical layer is configured according to a numerology of a legacy orthogonal frequency division multiplexing (OFDM)-based wireless protocol; and wherein the legacy-compatible higher layer protocol stack is configured according to the legacy OFDM-based wireless protocol.

[0011] In another example aspect, a wireless communication apparatus that implements the above- described methods is disclosed. The wireless communication apparatus may include a transmitter circuit and / or a receiver circuit to perform signal transmissions or receptions and at least one processor to implement various signal processing techniques described in the present document.

[0012] In yet another example aspect, a wireless system in which one or more of the above-described methods are implemented is disclosed. 2 180851577.4International Patent Application 119314.8124.WO00

[0013] In yet another example aspect, the method may be embodied as processor-executable code and may be stored on a computer-readable program medium.

[0014] These, and other, features are described in this document. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG.1 shows an example communication network.

[0016] FIG.2 shows a simplified example of a wireless communication system in which uplink and downlink transmissions are performed.

[0017] FIG.3 is a block diagram of an example of a transmitter.

[0018] FIG.4 is a block diagram of an embodiment of signal generation.

[0019] FIG.5 is a block diagram of another embodiment of signal generation.

[0020] FIG.6 is a block diagram of another embodiment of signal generation.

[0021] FIG.7 shows an example of obtaining delta trains ∆^^,^^^ .

[0022] FIG.8 shows an example of a hardware

[0023] FIGS.9 and 10A-10C are flowcharts for various methods of digital communication.

[0024] FIG.11 shows an example of a communication apparatus.

[0025] FIG.12 shows an example of physical resource block (PRB) tiling.

[0026] FIG.13 shows another example of PRB tiling.

[0027] FIGS.14A-14B show example depictions of OTFS frames.

[0028] FIG.15 shows an example of a time-frequency tiling of a PRB.

[0029] FIG.16 shows an expanded view of the delay-Doppler domain organization of transmission resources.

[0030] FIG.17 shows another example of time frequency domain tiling of PRBs.

[0031] FIG.18 shows an example of tiling along delay-Doppler axis.

[0032] FIG.19 shows an example arrangement along delay-Doppler plane for eight PRBs.

[0033] FIG.20 shows an example of a quadrature amplitude modulation (QAM) constellation.

[0034] FIG.21 shows an example of organization of transmission resource along the delay-Doppler two- dimensional axes

[0035] FIG.22 shows examples of transmission resource assignments performed in various embodiments.

[0036] FIG.23 shows an example of multiplexing of two different OTFS frames.

[0037] FIG.24 shows an example of a pulse-tone (e.g., PulsoneTM) pulse.

[0038] FIG.25 shows an arrangement of a transmission frame in 14 transmission slots.

[0039] FIG.26 shows an example of a waveform resulting from multiplexed OTFS transmissions. 3 180851577.4International Patent Application 119314.8124.WO00

[0040] FIG.27 shows an example mathematical model used to model communication in a wireless communication system.

[0041] FIG.28 shows an example block diagram of an exemplary OTFS communication system.

[0042] FIG.29 illustrates components of an example OTFS transceiver.

[0043] FIG.30 depicts another example of an end-to-end wireless system implementation, at least partly using OTFS technology.

[0044] FIG.31 depicts example waveforms in a pulse-tone generation.

[0045] FIG.32 depicts the relationship between the time, frequency, and Zak domains.

[0046] FIG.33 pictorially depicts an example wherein the Zak domain and time / frequency Zak transforms realizing the signal space realization lie in between time and frequency realizations.

[0047] FIG.34 shows an example of generation of a Pulse-tone waveform.

[0048] FIGS.35A and 35B show examples of pilot symbols in a delay-Doppler plane.

[0049] FIG.36 shows an example of a delay-Doppler plan in which symbols that contain information bits rate show.

[0050] FIG.37 shows another example of pilot symbols in a delay-Doppler plane.

[0051] FIG.38 shows an example of an orthogonal time frequency space (OTFS) waveform having a power-boosted pilot signal.

[0052] FIG.39 pictorially depicts an example of spreading of a pulse signal.

[0053] FIG.40 shows an example of spectrum puncturing.

[0054] FIG.41 shows an example of guard bands in an OTFS transmission.

[0055] FIG.42 pictorially depicts the concept of twisted convolution.

[0056] FIG.43 shows an example of an OTFS waveform.

[0057] FIG.44 shows an example of localization properties of a transmission waveform in delay- Doppler domain.

[0058] FIG.45A shows an example of a transmission method in which a delay-Doppler grid is transformed to a time-frequency grid using a Symplectic Fast Fourier Transform (SFFT).

[0059] FIG.45B shows an example of a transmission method in which a delay-Doppler grid is transformed to a time-frequency sub-grid.

[0060] FIG.45C shows an example of transmission method in which a delay-Doppler grid is transformed to an OTFS waveform using a Zak transform over the Doppler dimension.

[0061] FIG.45D shows an example of a reception method in which Inverse SFFT (ISFFT) is used to recover information bits from a received waveform.

[0062] FIG.45E shows an example of a reception method in which Inverse SFFT (ISFFT) is used to recover information bits from an OTFS sub-grid of a received waveform. 4 180851577.4International Patent Application 119314.8124.WO00

[0063] FIG.45F shows an example of a reception method in which an inverse Zak transform over the time dimension is used to recover information bits from a received waveform.

[0064] FIG.46 shows a block diagram of an example iterative receiver apparatus.

[0065] FIG.47 is a block diagram showing an example of a multi-level transmission system.

[0066] FIG.48 shows a block diagram of an example iterative receiver apparatus that uses multi-level decoding.

[0067] FIG.49 is a block diagram showing an example 2-D iterative equalizer. DETAILED DESCRIPTION

[0068] To make the purposes, technical solutions and advantages of this disclosure more apparent, various embodiments are described in detail below with reference to the drawings. Unless otherwise noted, embodiments and features in embodiments of the present document may be combined with each other.

[0069] Section headings are used in the present document to improve readability of the description and do not in any way limit the discussion or the embodiments to the respective sections only. Furthermore, certain standard-specific terms are used for illustrative purpose only, and the disclosed techniques are applicable to any wireless communication systems.

[0070] 1. Introduction

[0071] The wireless or time-variant nature of the communication channel poses several challenges in designing a transmission protocol suitable for wireless communication scenarios. These days, users expect their wireless devices to work everywhere and in a variety of mobile or stationary situations.

[0072] The relative movement of transmitters and receivers with respect to each other cause signal distortions such as varying channel delay, Doppler and / or angular spread, signal degradation due to ground clutter, sea clutter, and so on. Another example of signal degradation is flat fading in which an entire channel occupied by a transmission signal will experience fading or attenuation that may be relatively constant across the channel. In practice, a transmission scheme may need to be designed to fit within a certain link budget, maximum power constraint, or linearity of electronics used for transmitting or receiving signals.

[0073] Most of the widely deployed wireless systems in the present days are based on interoperability standards published by standards organizations such as Institute of Electrical and Electronics Engineers (IEEE) and Third Generation Partnership Project (3GPP). These conventional, or legacy, wireless systems operate in well-defined frequency bands, some of which are licensed while others are unlicensed. Furthermore, due to its superior performance in general, orthogonal frequency division multiplexing (OTFS) modulation forms the underlying transmission physical layer for most such systems. 5 180851577.4International Patent Application 119314.8124.WO00

[0074] Wide-scale deployment of such wireless systems raises the logistical and technical challenges for deploying a newer wireless communication technology such as the orthogonal time frequency space (OTFS) technology which is described in the present application. Among other challenges faced by introduction of such a new technology are technical challenges related to “horizontal co-existence” and “vertical co-existence” of the new system with legacy systems.

[0075] Here, horizontal co-existence refers to the technical challenges raised by side-by-side deployment of two different wireless technologies such as the OTFS technology and an existing 3GPP or IEEE technology. Some of the issues include, e.g., mutual interference, ability for wireless device to migrate from one technology to the other technology, and so on.

[0076] Vertical co-existence refers to the implementation issues raised by the introduction of new physical layer modulation scheme. For example, wireless devices are often implemented using a protocol stack model in which different layers (e.g., physical layer L1 and other layers above the physical layer such as the link layer, the medium access control layer, all the way up to the application layer) interface with each other based on a well-defined application programming interface (API). Therefore, introduction of a new physical layer that requires corresponding changes to the higher layers may pose technical challenges related to interoperability, increased complexity and therefore operators and implementors may be reluctant to adopt such a new technology.

[0077] The technology disclosed in the present document addresses the above-discussed technical problems, among others. A new waveform, called pulse-tone waveform, is disclosed with its fundamental underpinning in the OTFS technology. Furthermore, superior technical features of using such a waveform and impact on design and implementation of numerology of wireless communication and receiver / transmitter side implementation are disclosed.

[0078] In Section 2, some basic concepts of a wireless system are described. Section 3 provides an overview of the OTFS waveform. Section 4 provides additional details of the OTFS technology. Specifically, OTFS modulation concepts are described in Section 4.1. The mathematical concepts of OTFS are introduced in Section 4.2. Section 4.3 discloses some possible options of pulse shaping that may be used in the new wireless system being proposed based on the OTFS technology. Section 4.4 address some issues related to pulse shaping specifically for the above-discussed co-existence technical problem. In sections 4.5 to 4.9, some specific implementations of transmitter, receiver, iterative equalization and 2D equalization are disclosed. Sections 5, 6 and 7 provide some additional details of an OTFS transmitter, an OTFS modulator and an OTFS receiver. Section 8 provides examples of use cases for wireless technology based on the concepts disclosed in the present document. Section 9 provides further comments on the backwards compatibility of the proposed OTFS technology implementation. Some physical layer implementation examples are given in Section 10., with Section 11 disclosing power 6 180851577.4International Patent Application 119314.8124.WO00 domain multiplexing and Section 12 directed specifically to low latency aspects of the proposed implementations. Section 13 summarizes example technical benefits that are referenced throughout the document. Finally, Section 14 provides additional implementation details and preferred technical solutions.

[0079] 2. Example wireless systems

[0080] FIG.1 shows an example of a wireless communication system 100 in which a transmitter device 102 transmits signals to a receiver 104. The signals may undergo various wireless channels and multipaths, as depicted. Some reflectors such as buildings and trees may be static, while others such as cars, may be moving scatterers. The transmitter device 102 may be, for example, a user device, a mobile phone, a tablet, a computer, or another Internet of Things (IoT) device such as a smartwatch, a camera, and so on. The receiver device 104 may be a network device such as the base station. The signals transmitted from the base station to the transmitter 102 may experience similar channel degradations produced by static or moving scatterers. The techniques described in the present document may be implemented by the devices in the wireless communication system 100. The terms “transmitter” and “receiver” are simply used for convenience of explanation. As further described herein, depending on the direction of transmission (uplink or downlink), the network station may be transmitting or receiving and user device may be receiving or transmitting.

[0081] FIG.2 shows a simplified wireless network to highlight certain aspects of the disclosed technology. A transmitter transmits wireless signals to a receiver in the wireless network. Some transmissions in the network, variously called as downlink or downstream transmissions, a network-side node such as a base station acts as a transmitter of wireless signals and one or more user devices act as the receiver of these wireless signals. For some other transmissions, as depicted in FIG.2, the direction of transmission may be reversed. Such transmissions are often called uplink or upstream transmissions. For such transmissions, one or more user devices act as transmitters of the wireless signals and a network-side node such as a base station acts as the receiver of these signals (as depicted in FIG.2). Other type of transmissions in the network may include device-to-device transmissions, sometimes called direct or sideband transmissions. While the present document primarily uses the terms “downlink” and “uplink” for the sake of convenience, similar techniques may also be used for other situations in which transmissions in two directions are performed - e.g., inbound or incoming transmissions that are received by a wireless device and outbound or outgoing transmissions that are transmitted by a wireless device. For example, downlink transmissions may be inbound transmissions for a user device, while outbound transmissions for a network device. Similarly, uplink transmission may be inbound transmissions for a network device while outbound transmissions from a wireless device. Therefore, for some embodiments, the disclosed techniques may also be described using terms such as “inbound” and “outbound” 7 180851577.4International Patent Application 119314.8124.WO00 transmission without importing any 3GPP-specific or other wireless protocol-specific meaning to the terms “uplink” and “downlink.”

[0082] In frequency division multiplexing (FDM) networks, the transmissions to a base station and the transmissions from the base station may occupy different frequency bands (each of which may occupy continuous or discontinuous spectrum). In time division multiplexing (TDM) networks, the transmissions to a base station and the transmissions from the base station occupy a same frequency band but are separated in time domain using a TDM mechanism such as time slot-based transmissions.

[0083] 3. OTFS Waveform Overview

[0084] The OTFS waveform is constructed from symbols assigned to a grid in a two-dimensional domain called the delay-Doppler. The grid is characterized by a Doppler period ^^^, typically satisfying^^^ ^ 2 ∙ ^^ௗ, where ^^ௗ is the maximum expected Doppler shift, and a delay period, ^^^ ൌ 1 / ^^^. The gridhas ^^ ^ ^^^^ ∙ ^^^ elements along Doppler and ^^ ^ ^^^^ ∙ ^^^^^ elements along delay, where ^^^^ is thebandwidth of the OTFS signal and ^^ is its duration. On top of the information bearing symbols (typically quadrature amplitude modulation QAM), the grid may include pilot symbols used for channel detection and estimation.

[0085] The OTFS waveform in the time domain, may be considered to be a super-position of pulse-tone multiplied by the grid elements ேି^ ெି^ ^^^^^^ ^ ^ ^^^^^, ^^^ ∙ ^^^^,^^^^^^(1)

[0086] where ^^^^^,^^^are^ ^^^^,^^^^^^ ≜ ∗ ^^^^^^^ ∙ ^ ^^^ଶగ^∆ఔ^ఛ ^^Δ^^(2)

[0087] where ^^ఛ^^^^a ∗ a^^௧^^^^ ൌ ℱି^^^^ఔ^ is the inverse Fourier transform of a pulse in the Doppler domain, Δ^^ ൌ ^^^ / ^^ and∆^^ ൌ ^^^ / ^^ are the delay and Doppler grid resolutions, respectively, and ^^^∙^ is the Dirac delta function.In general, the Pulse-tones may be considered to be basis signals used for the delay-Doppler grid.

[0088] In this document, we will use the notation ∆^^,^^^ ^^^^ for the second term of (2), which represents an infinite delta train, with rotating phases,a time window: ^ ^^,^^^^^^ ^^^^^^ ^(3) 180851577.4International Patent Application 119314.8124.WO00

[0089] In practical implementations, the infinite summation of equation (3) can be truncated to the effective duration of the time window ^^௧.

[0090] Additional details of OTFS technology are described below.

[0091] 4. OTFS Technology

[0092] 4.1 Brief introduction to orthogonal time frequency space (OTFS) modulation

[0093] The OTFS method is based at least in part upon the realization that in many cases various advantages may accrue from spreading the data of a single symbol over multiple time-spreading intervals shared with other symbols. In contrast with prior art modulation techniques, the OTFS method may involve convolving a single data symbol over both a plurality of time slots, a plurality of frequencies or spectral regions (spread spectrum), and a plurality of spectral shapes. This approach to data convolution results in superior performance over impaired communications links.

[0094] In one aspect, and as is indicated below by Equation (1), the OTFS method recognizes that a wireless channel may be represented as a weighted superposition of combination of time and Doppler shifts: (4)

[0095] In contrast to (τ,u) of Equation (4) are are The time-frequency weights (τ, u) are intended to represent essentially all of the diversity branches existing in the wireless channel. This is believed to substantially minimize the fading effects experienced by the OTFS system and other communication systems generally based upon two-dimensional channel models relative to the fading common in systems predicated upon one-dimensional models. Finally, in contrast to the non-stationary, one-dimensional channel models employed in conventional communication systems, the time-frequency weights (τ, u) of Equation (4) are substantially stationary; that is, the weights change very slowly relative to the time scale of exemplary embodiments of the OTFS system.

[0096] Use of the two-dimensional channel model of Equation (4) in embodiments of the OTFS communication system affords a number of advantages. For example, use of the channel model of Equation (4) enables both channel multipath delay and Doppler shift to be accurately profiled simultaneously. Use of this model and the OTFS modulation techniques described herein also facilitate the coherent assembly of channel echoes and the minimization of fading phenomena, since every symbol experience substantially all of the diversity branches present within the channel. Given that the two- dimensional channel model is essentially stationary, every symbol is deterministically distorted (smeared) according to substantially the same two-dimensional pattern. This stable, accurate characterization of the communication channel in two dimensions on an ongoing basis further enables the OTFS system to 9 180851577.4International Patent Application 119314.8124.WO00 minimize data distortion by "customizing" how each bit is delivered across the channel. Finally, use of a two-dimensional channel model enables effective signal separation by decoupling and eliminating mutual interference between multiple sources.

[0097] FIG.27 illustrates an example of a mathematical model 200 that can be used to model time / frequency selective fading. A transmit side of the model 200 includes a pre-equalizer 210, a transmitter / modulation component 220, a channel model 230, and additive noise 240 which is combined with the transmitted signal via a summer 250. A receive side of the model 200 includes a receiver / demodulator 260 and a post equalizer 270.

[0098] The pre-equalizer 210 is used to model a pre-distortion transfer function htthat can be used to make up for changing channel conditions in the channel model hcbased on feedback received over the channel from the receive side of the model, as determined by measurements made by the receiver / demodulator 260 and / or the post equalizer 270. The transmitter / modulator 220 uses modulation schemes described herein to transmit the data over the channel 230.

[0099] The receiver / demodulator 260 demodulates the signal received over the channel 230. The received signal has been distorted by time / frequency selective fading, as determined by the channel transfer function hc, and includes the additive noise 240. The receiver / demodulator 260 and the post equalizer 270 utilize methods discussed herein to reduce the distortion caused by the time / frequency selective fading and additive noise due to the channel conditions. The mathematical model 200 can be used to determine the nature of the equalized data Deqby performing a mathematical combination of three transfer functions operating on the original data D. The three transfer functions include the transmitter transfer function ht, the channel transfer function hcand the equalizer transfer function hr.

[0100] Embodiments of the OTFS methods and systems described herein are based, in part, upon the realization that spreading the data for any given symbol over time, spectrum, and / or spectral shapes in the manner described herein yields modulated signals which are substantially resistant to interference, particularly interference caused by Doppler effects and multi-path effects, as well as general background noise effects. Moreover, the OTFS method is believed to require less precise frequency synchronization between receiver and transmitter than is required by existing communication systems (e.g., OFDM systems).

[0101] In essence, the OTFS method convolves the data for a group of N2symbols (herein called a "frame") over both time, frequency, and in some embodiments spectral shape in a way that results in the data for the group of symbols being sent over a generally longer period of time than in prior art methods. Use of the OTFS method also results in the data for any given group of symbols being accumulated over a generally longer period of time than in prior art methods. However, in certain embodiments the OTFS method may nonetheless enable favorable data rates to be achieved despite the use of such longer 10 180851577.4International Patent Application 119314.8124.WO00 transmission periods by exploiting other transmission efficiencies enabled by the method. For example, in one embodiment a group of symbols may be transmitted using the same spread-spectrum code. Although this could otherwise result in confusion and ambiguity (since each symbol would not be uniquely associated with a code), use of the OTFS method may, for example, enable the symbols to be sent using different (but previously defined) spread-spectrum convolution methods across a range of time and frequency periods. As a consequence, when all of the data corresponding to the symbols is finally accumulated within the receiver, the entire frame or group of symbols may be reconstructed in a manner not contemplated by prior art techniques. In general, one trade-off associated with the disclosed approach is that either an entire multi-symbol frame of data will be correctly received, or none of the frame will be correctly received; that is, if there is too much interference within the communication channel, then the ability to successfully deconvolve and retrieve multiple symbols may fail. However, as will be discussed, various aspects of the OTFS may mitigate any degradation in performance which would otherwise result from this apparent trade-off.

[0102] Using an OTFS model of a channel, a channel can be modeled using a small set of dominant reflectors. Such a representation of the channel provides a concise and robust channel representation that is mathematically less complex (compared to traditional channel acquisition techniques). Furthermore, use of second order statistics allowed for prediction of channel at a different (future) time, or in a different frequency band, based on delay-Doppler domain modeling of a channel. Such a compact model thus allows for robust acquisition, estimation and prediction of channel.

[0103] One advantageous aspect of OTFS is the use of second order statistics for channel representation allows for a stationary channel model that does not need to be changed frequently. In some embodiments, a channel may be modeled into a stationary portion and a non-stationary portion that is updated on an occasional basis. Such a model reduced the bandwidth overhead of reference signal and / or feedback signal transmissions. Put differently, the channel state information (CSI) remains relatively static and required less frequent updates than conventional 4G or 5G New Radio (NR) technology.

[0104] As further described in the present document, OTFS waveform allows for spreading of information bits across different delay and / or Doppler values, and therefore provides mathematical ability to be invariant to mobility. Furthermore, signal precoding in delay-Doppler domain may be used to further achieve efficiency of transmission.

[0105] Other advantages of OTFS technology include:

[0106] Low Complexity - this may be achieved due to efficient channel modeling (sparse channel representation) that requires infrequent updates. 11 180851577.4International Patent Application 119314.8124.WO00

[0107] Scheduling - channel characteristics in a different frequency band or at a future time can be predicted with high accuracy, thereby allowing accurate scheduling, including, for example, centralized scheduling in a cooperative network.

[0108] Scalable Pairing - user devices may be paired for transmission using scalable transmissions (e.g., beamforming).

[0109] Large Number of users & Number of Layers - the use of OTFS based spectral shaping in spatial domain allows for a compact communication scheme that accommodates a large number of user devices.

[0110] Backward compatibility - Several of the channel estimation techniques can work without the need of an explicit feedback for spatial multiplexing and therefore can be implemented in networks that include legacy or previous generation device.

[0111] Co-existence 4G & 5G - OTFS spectrum can be transmitted using an orthogonal frequency division multiplexing (OFDM) scheme and be made compatible with conventional 4G and 5G technologies.

[0112] Cloud-RAN Architecture - due to the ability of OTFS to perform channel estimation using a sparse channel representation and the ability to predict future channels, the channel estimation can be made robust to computational delays. This lends itself to be able to operate a cloud based channel estimation / precoding / scheduling of a radio access network (RAN), in which the backhaul delays for communication of channel estimates do not impact system performance.

[0113] Scheduler disaggregation - for a similar reason as above, the scheduling function of a network of cellular communication cells can be controlled using a scheduler that is dis-aggregated from a base station function (radio access) and can be implemented in the cloud.

[0114] Joint scheduling and Coordinated multisite - as described above, the joint scheduling of cells using a disaggregated or a cloud based scheduler allows for efficient use of spectrum within a cell and more particularly in overlapping areas of different cells.

[0115] Analytics - the cloud-based architecture that collects channel state feedback from different user devices in different cells allows for generation of analytics in which user device locations, network topology and other information about a network can be extracted for further robust operation of a wireless network.

[0116] CoMP - Cooperative Multi-Point operation of base stations is possible using the above- described scheduler aggregation and cloud-RAN techniques.

[0117] FIG.28 is a block diagram of components of an exemplary OTFS communication system 300. As shown, the system 300 includes a transmitting device 310 and a receiving device 330. The transmitting device 310 and the receiving device 330 include first and second OTFS transceivers 315-1 and 315-2, 12 180851577.4International Patent Application 119314.8124.WO00 respectively. The OTFS transceivers 315-1 and 315-2 communicate, either unidirectionally or bidirectionally, via communication channel 320 in the manner described herein. Although in the exemplary embodiments described herein the system 300 may comprise a wireless communication system, in other embodiments the communication channel may comprise a wired communication channel such as, for example, a communication channel within a fiber optic or coaxial cable. As was described above, the communication channel 320 may include multiple pathways and be characterized by time / frequency selective fading.

[0118] FIG.29 illustrates components of an exemplary OTFS transceiver 400. The OTFS transceiver 400 can be used as one or both of the exemplary OTFS transceivers 315 illustrated in the communication system 300 of FIG.3. The OTFS transceiver 400 includes a transmitter module 405 that includes a pre- equalizer 410, an OTFS encoder 420 and an OTFS modulator 430. The OTFS transceiver 400 also includes a receiver module 455 that includes a post-equalizer 480, an OTFS decoder 470 and an OTFS demodulator 460. The components of the OTFS transceiver may be implemented in hardware, software, or a combination thereof. The disclosed OTFS methods will be described in view of the various components of the transceiver 400. In some embodiments, the receiver module 455 may be configured to implement iterative equalization and decoding as described in Sections 4.8 and 4.9 below.

[0119] In one aspect a method of OTFS communication involves transmitting at least one frame of data ([D]) from the transmitting device 310 to the receiving device 330 through the communication channel 320, such frame of data comprising a matrix of up to N2data elements, N being greater than 1. The method comprises convolving, within the OTFS transceiver 315-1, the data elements of the data frame so that the value of each data element, when transmitted, is spread over a plurality of wireless waveforms, each waveform having a characteristic frequency, and each waveform carrying the convolved results from a plurality of said data elements from the data frame [D]. Further, during the transmission process, cyclically shifting the frequency of this plurality of wireless waveforms over a plurality of times so that the value of each data element is transmitted as a plurality of cyclically frequency shifted waveforms sent over a plurality of times. At the receiving device 330, the OTFS transceiver 315-2 receives and deconvolves these wireless waveforms thereby reconstructing a replica of said at least one frame of data [D]. In the exemplary embodiment the convolution process is such that an arbitrary data element of an arbitrary frame of data ([D]) cannot be guaranteed to be reconstructed with full accuracy until substantially all of these wireless waveforms have been transmitted and received.

[0120] FIG.30 depicts another example of an end-to-end wireless system implementation, at least partly using OTFS technology. As described herein, various beneficial aspects include enablement of cooperative processing, channel estimation / equalization in delay-Doppler domain, ability to provide 13 180851577.4International Patent Application 119314.8124.WO00 additional control in time / frequency domain and spatial processing to form layered communication to increase density of devices in a cell.

[0121] An OTFS waveform is an efficient way of transmitting data on a wireless channel. Generating an OTFS waveform is based on a two-dimensional delay-Doppler pulse, which may be described as a (twisted) convolution of two orthogonal pulses, ^^ఛon delay and ^^ఔDoppler: ^^ ൌ ^^ఛ ∗ ^^ఔ (5)

[0122] In this document, we discuss pulse shaping methods for ^^ఛand ^^ఔ, in OTFS systems.

[0123] 4.2 Mathematical description of an OTFS Waveform

[0124] An OTFS data frame is allocated on a delay-Doppler grid. Let us denote the number of Doppler elements by ^^ and the number of delay elements by ^^. The grid spacing is Δ^^ and Δ^^ in delay andDoppler, respectively, with periods ^^^ ൌ ^^Δ^^, ^^ℎ^^^^^^ Δ^^ ൌ 1 / ^^^^ and ^^^ ൌ ^^Δ^^,Δ^^ ൌ 1 / ^^, where^^^^ is the signal’s bandwidth, ^^ is the signal’s duration and ^^^ ∙ ^^^ ൌ 1.

[0125] Each data symbol (typically a quadrature amplitude modulation QAM symbol), ^^^^^,^^^, where^^ ൌ 0, … , ^^ െ 1 and ^^ ൌ 0, … , ^^ െ 1, is carried over a waveform called a pulse-tone (e.g., PulsoneTM ,a combination of a pulse train and a tone). The construction of a pulse-tone is described as follows. Let ^^^^,^^^^^^^^be a quasi-periodic Dirac delta train for data symbol ^^^^^, ^^^, defined as:^^^^,^^^^ ^^^^ ൌ ^^^^^, ^^^ ∙ ∑^^ଶగ^^ఔ^ఛ^ୀି^ ^^ ^^^൫^^ െ ^^Δ^^ െ ^^^^^൯(6) (7)

[0126] A pulse-which is the inverse Fourier transform of the Doppler pulse, ^^ ି^௧ ൌ ℱ ^^^ఔ^, and then convolving it with adelay pulse, ^^ఛ: ^^^^,^^^^^^ ൌ ^^^^,^^ఛ∗ ^^^௧ ∙ ^^^^^^^^^ (8)

[0127] This concept is illustratedwith time has the horizontal axis is passed through a time window of a certain shape and then convolved with a Doppler pulse (indicated by the * operation) to generate a desired delay-Doppler pulse 3100.

[0128] For all the data symbols on the delay-Doppler grid, we can compute the OTFS waveform as: ^^^^^^^^^^^^ ൌ ∑ேି^ெି^ ^^,^^^ୀ^ ∑^ୀ^ ^^ ^^^^(9)

[0129] Equivalently, we can firstwindow and delay pulse convolution: ^^^^^^^^ ൌ ∑ேି^ ^ୀ^ ∑ெ^ିୀ^^^^^^,^^^^^^^^ (10) 180851577.4International Patent Application 119314.8124.WO00

[0130] The signals described in this document may be represented by describing the waveforms in the time domain, in the frequency domain, or in the delay-Doppler domain (e.g., Zak domain). Because these three represent three different ways of describing the signals, signal in one domain can be converted into signal in the other domain via a transform. For example, a time-Zak transform may be used to convert from Zak domain to time domain. For example, a frequency-Zak transform may be used to convert from the Zak domain to the frequency domain. For example, the Fourier transform (or its inverse) may be used to convert between the time and frequency domains.

[0131] In signal processing, it is traditional to represent signals (or waveforms) either in time or in the frequency domain. Each representation reveals different attributes of the signal. The dictionary between these two realizations is the Fourier transform:

[0132] The periods are assumed to satisfy the Nyquist condition τr^vr=1. Zak domain signals are related to time and frequency domain signals through canonical transforms that are called the time and frequency Zak transforms. The time and frequency Zak transforms are principally geometric projections: the time Zak transform is integration along the Doppler variable and reciprocally the frequency Zak transform is integration along the delay variable. The different signal domains and the transformations connecting between them are depicted in FIG.32.

[0133] The Zak transform plays for OTFS the same role the Fourier transform plays for OFDM. For example, the time Zak transform is integration along the Doppler dimension (taking the DC component) for every point of time. Reciprocally, the frequency Zak transform is Fourier transform along the delay dimension. In other words, the pair of Zak trans-forms constitute a square root decomposition of the Fourier transform, reinforcing the interpretation of the Zak realization as residing between the time and the frequency realizations (see FIG.33).

[0134] An example of an OTFS waveform in shown in FIG.34. As depicted in the top waveform, the OTFS waveform includes a train of pulses separated in time by ^^^such that the phases of each subsequent pulse are rotated with respect to each other, as indicated by the curved arrows above each pulse. The lower graph shows a corresponding waveform.

[0135] After the interaction with the channel, the received OTFS signal, ^^, is processed in a reversed order to the transmitter. First it is convolved with a pulse, ^^ఛோ௫, then it is multiped by a time window, ^^௧ோ௫, and finally an inverse Zak transform is applied to the received data, to obtain the received delay-Doppler grid elements: 15 180851577.4International Patent Application 119314.8124.WO00 ^^ᇱ ൌ ^^ோ௫௧ ∙ ^^^ோ௫ఛ ∗ ^^^^ 1 ^^^^^^, ^^^ ൌ ି^ଶ^^^ ^^ గ^^ఔ^ఛ^^^ᇱ൫^^ െ ^^Δ^^ െ ^^^^^൯

[0136] 4.3 Pulse

[0137] An OTFSknown data symbol, called as a pilot symbol. Typically, the pilot symbol will be cyclically surrounded by empty grid elements (value of zero) that will be used at the receiver, as a channel estimation area and possibly a guard area from interfering data symbols. An example of such an arrangement is illustrated in FIG.35A. In FIGS.35A and 35B, a frame of transmission resources is depicted along the Delay (vertical) and Doppler (horizontal) dimensions. The corner regions “O” are reserved for pilot, however, in general, pilots may be inserted anywhere within the frame in a predetermined position known to both the transmitter-side and the receiver-side.

[0138] After the interaction of the waveform with a wireless channel, replicas of the pilot symbol (with a complex gain) will appear at the receiver in the channel estimation area (corresponding to the physical reflectors of the channel). Detection of these replicas forms a channel estimation and enables equalization of the received signal. However, at low Signal to Noise Ratios (SNR), it will be very difficult to distinguish between replicas of the pilot symbol and noise at the channel estimation area. For example, at 0 dB SNR, the strongest replica will have the same energy as the noise. Therefore, to enable adequate channel estimation, the power of the pilot symbol must be boosted, such that the pilot replicas can be detected in the presence of noise. Note, that in the creation of the waveform, the unassigned transmission power to the grid elements of the channel estimation area, may be used to boost the power of the pilot. For example, for a delay-Doppler grid with an average data symbol power of 1 and ^^^ாgrid elements reserved for channel estimation (including the pilot location), the pilot symbol may be assigned as: ^^^^^^^^^^ ൌ ^^^^ா (13)

[0139] An example of such an

[0140] FIG.36 shows an example of a delay-Doppler plane in which symbols that contain information bits are shown. In FIG.36, the horizontal axis is the delay axis and the vertical axis is Doppler axis. Each dot in the graphs shows a modulation symbol that comprises information bits. One example of a symbol 3602 in the delay domain is shown by a tall rectangle that comprises all modulated bits having a same delay, but different Doppler values. Another example of a symbol 3604 in the Doppler domain is shown by a wide rectangle that comprises all modulated bits have a same Doppler value, but different delay values. The example depicted in FIG.36 shows a delay-Doppler grid where N = 16 (elements along 16 180851577.4International Patent Application 119314.8124.WO00 Doppler direction) and M = 512 (elements along delay direction). Here, delay resolution is reciprocal of channel bandwidth. The Doppler resolution is inversely proportional to the frame time used for the communication.

[0141] If we examine the OTFS waveform, generated from a power-boosted pilot, we can see that the pulse train has a boosted pulse at a delay location corresponding to the location of the pilot, as seen in FIG.37. This waveform suffers from a high Peak-to-Average-Power-Ratio (PAPR), which is undesirable. For example, in FIG.37, the high peaks 3701 are shown to have an amplitude or signal power that is greater than the “typical” pulse peaks, e.g., 3703. Depending on run-time conditions and values of N and M, the high PAPR may amount to 6 to 12 dB greater than the nominal pulse power.

[0142] To reduce the PAPR, while keeping the power of the pilot boosted, the OTFS waveform must be spread over time. Unlike some other spread spectrum (or spread time) techniques, this spreading does not extend the bandwidth or the duration of the OTFS waveform. One possible method to achieve this is to convolve the OTFS waveform with a spreading signal, such as a chirp. This is equivalent to convolving the delay pulse with a spreading signal, ^^^^^^, resulting in a new combined delay pulse: ^^^^^^^ௗఛ ൌ ^^ఛ ∗ ^^^^^^ (14)

[0143] For example, a chirp spreadingin FIG.38 (compared to FIG.31). The remains the same, but the data and pilotsymbols are spread over the entire duration OTFS resulting in a lower PAPR signal.

[0144] At the receiver, the inverse of the spreading signal is applied to regain the non-spread waveform. For example, a conjugated chirp signal is applied at the receiver. Afterwards, the receiver operations are the same. Alternatively, the receiver may use a combined pulse, ^^^^^^^ௗ,ோ௫ఛ instead of ^^ఛோ௫.

[0145] 4.4 Pulse shaping an OTFS waveform for

[0146] Spatial multiplexing enables coexistence of an OTFS waveform with other waveforms, where each waveform is carried by an orthogonal beam. However, the non-OTFS waveforms, may require from time to time to transmit broadcast information on a wide beam, which cannot be orthogonal to the OTFS beam. Such broadcast information may be synchronization signals or a control channel (such as 3GPP 5G NR, synchronization signal blocks SSB and physical downlink control channel PDCCH). To maintain coexistence in the presence of broadcast transmissions of other waveforms, the OTFS signal may be punctured in frequency, time or both for the bandwidth and duration of the broadcast signal.

[0147] With the appropriate pulse shaping design of the delay pulse or the Doppler pulse of the OTFS waveform, puncturing in frequency and / or time can be achieved. More specifically, to puncture a certain bandwidth where the OTFS signal is attenuated and does not interfere with other transmissions, the spectrum of the delay pulse, ^^^௨^^௧௨^^ఛ must have these spectral properties. Similarly, to puncture a 17 180851577.4International Patent Application 119314.8124.WO00 certain period where the OTFS signal is attenuated and does not interfere with other transmissions, the time characteristics of the Doppler pulse, ^^^௨^^௧௨^^ఔ must have these properties.

[0148] As an example, we demonstrate spectrum puncturing by designing a delay pulse that punctures 1 / 4 of the bandwidth at a normalized frequency offset of 0.2 (other values of these parameters may be used also). A broadcast signal transmitted in the frequency window, will coexist with the OTFS waveform. The delay pulse is a linear combination of two raised cosine pulses, parameterized by ^^ the pulse roll-off, ^^ the relative bandwidth to be punctured and ^^ the relative frequency shift. Let us define: ^^^ఛ ൌ ^^^^^^^^^^^^^^^^^^^^^^^^^^^, ^^^ఛ^ (15)^^ଶ ൌ ^ ^ ଶ^ ^ଶగఓఛఛ ^^^^^^^^^^^^^^^^^^^^^^^ ^^ ∙ ^^, ^^ఛ ∙ ^^ (16)^^^௨^^௧௨^^ ൌ ^^^ െ ^ ଶఛ ఛ ^ ∙ ^^ఛ (17)

[0149] When we assign:inFIG.39. In FIG.39, frequency portions 3904 show examples of frequency portions used byOTFS waveform, while the frequency 3902 shows a frequency portion where the OTFS waveform power level is “sufficiently” attenuated to permit co-existence of another transmissions waveform. Here, the term “sufficiently” may mean that the OTFS waveform is attenuated below a certain threshold that allows transmission and reception of the other waveform with a certain performance (such as a target bit error rate). In the graph shown in FIG.39, the attenuation threshold is approximately 20 dB. In various embodiments, the number K1 of OTFS frequency bands and the number K2 of attenuated portions may be different. FIG.39 shows the example where K1 = 2 and K2 = 1. In various embodiments, the threshold may be a relative number that is relative to a maximum power in the passbands or may be a pre-specified fixed number and may depend on the desired signals transmissions in the “stopband” where OTFS waveform is attenuated.

[0150] An equivalent pulse design may be applied for the time window, for puncturing of the OTFS waveform in time. Note that puncturing does not mean that spreading cannot be applied. Both methods, described in this document, can be applied together for a combined pulse: ^^^^^^^ௗ,^௨^^௧௨^^ ^௨ఛ ൌ ^^ ^^௧௨^^ఛ ∗ ^^^^^^ (18)

[0151] 4.5

[0152] The Doppler pulse shape at the transmitter and receiver, or their time window equivalents, affects the packing of consecutive OTFS frames, similarly to how the spectrum of the delay pulse affects packing an OTFS channel with adjacent channels. For some Doppler pulses, a guard interval (typically at the order of the delay spread of the channel) may be required, as shown in FIG.40. The top graph in FIG.40 shows the example where frames are transmitted without any gaps, with the inter-frame separation (center to center gap separation of consecutive frames, 1 / ∆ν; where ∆ν; which is the separation of Doppler elements 18 180851577.4International Patent Application 119314.8124.WO00 along the delay-Doppler grid). Compared to this, the lower graph shows a transmission where the inter- frame guard bands result in inter-frame separation that is greater than the graph (a) in FIG.40.

[0153] It will be appreciated that the shape of the Doppler pulse affects the spacing of the OTFS frames.In implementations that use a bandlimited Doppler pulse, OTFS frames may be spaced every ^^ ൌ 1 / Δ^^seconds. However, for implementations where Doppler pulse is not bandlimited, spacing between theframes (e.g., center of one frame to the center of next frame) with a ^^ ^ 1 / Δ^^, due to the roll-off shape ofthe transformed Doppler pulse to time (see, e. g., FIG.41).

[0154] FIG.42 pictorially depicts the concept of twisted convolution. Starting from left to right, the two- dimensional arrangement of symbols in the delay-Doppler domain is depicted on the transmitter side. During transmission from the transmitter TX to a receiver Rx, the signal may get blurred or distorted based on a 2D impulse response of the channel. This alteration is depicted as channel blur. The received signal in the delay-Doppler domain may be recovered using deblurring to obtain estimates of the transmitted symbols. The end-to-end process is considered to include twisted convolution due to the changes in delay-Doppler position of the transmission waveform.

[0155] FIG.43 shows another depiction of an OTFS waveform. As depicted, an OTFS waveform can be conceptually considered to comprise time-localized pulses (4304) that are frequency localized due to modulation from a phase function (4302) which modifies the pulses along time axis.

[0156] FIG.44 shows an example of a delay-Doppler pulse in delay-Doppler domain. Here, the vertical axis represents frequency and horizontal axis represents time. A conventional pulse that is frequency limited, is not limited in time, while another convention pulse that is time limited, will not be limited in frequency. By contrast, the delay-Doppler pulse, shown in the center, will maintain its 2-D localized shape that remains quasi periodic (same shape, different phase) throughout the delay-Doppler plane.

[0157] 4.6 Examples of OTFS transmission and reception

[0158] The dimensions of the channel estimation area (e.g., the pilot signal regions depicted in FIGS. 35A and 35B) depend on the expected channel response and its delay and Doppler spreads. Within the channel estimation area, pilot symbols may be placed. A pilot symbol has a known value, and its power may be larger than the other data symbols.

[0159] The delay-Doppler grid may be transformed to a transmission waveform in one of the following methods: 1. Transformation to a time-frequency equivalent grid via a discrete Symplectic Fast Fourier Transform (SFFT). This method creates a time-frequency grid, like the one used for OFDM modulation. This OTFS transformed grid may be multiplexed with other time-frequency elements in the OFDM grid, as shown in FIG. 45A, thus allowing multi-user data multiplexing. Then, an OFDM waveform may be generated using an inverse Fourier transform (IFFT) over each OFDM symbol. 19 180851577.4International Patent Application 119314.8124.WO00 2. Transformation to a time-frequency equivalent sub-grid via discrete SFFT, as shown in FIG.45B. The sub-grid is part of a larger time-frequency grid and has ^^ elements along frequency and ^^ elements along time. Then, an OFDM waveform may be generated using an inverse Fourier transform (IFFT) over each OFDM symbol. 3. Direct transformation to the time domain using a Zak transform over the Doppler dimension of the grid (after extending the grid in a quasi-periodic manner and applying a two-dimensional transmission pulse), as shown in FIG.45C.

[0160] FIG.45A shows an example of transmission method 1, where a delay-Doppler grid is transformed to a time-frequency grid using a Symplectic Fast Fourier Transform (SFFT). This transformed grid, denoted as “#3 OTFS”, is multiplexed with the data of other OFDM users (denoted as #1, #2 and #4) in the overall OFDM time-frequency grid. An inverse Fast Fourier Transform (IFFT) may be applied to the OFDM symbols to generate the transmission waveform.

[0161] FIG.45B shows an example of transmission method 2, where a delay-Doppler grid is transformed to a time-frequency sub-grid with ^^ elements along the time dimension and ^^ elements along the frequency dimension, using a Symplectic Fast Fourier Transform (SFFT). Note, that the sub-grid may not take all the time-frequency resources and other sub-grids may be also allocated for other delay-Doppler transformations (possibly of different users).

[0162] FIG.45C shows an example of transmission method 3, where a delay-Doppler grid is transformed to an OTFS waveform using the Zak transform over the Doppler dimension.

[0163] 4.7 Examples of receiver-side signal processing

[0164] At a receiver, the received waveform is transformed back to delay-Doppler for further processing. This transformation depends on how the waveform was transmitted: 1. A waveform of transmission method 1, is first transformed to a time-frequency grid using a Fast Fourier Transform (FFT) and then the OTFS section of the grid is extracted and converted to delay-Doppler via the Inverse Symplectic Fast Fourier Transform (ISFFT). An example for this is given in FIG.45D. 2. A waveform of transmission method 2, is first transformed to a time-frequency grid using a Fast Fourier Transform (FFT) and then the OTFS sub-grid is extracted and converted to delay-Doppler via the Inverse Symplectic Fast Fourier Transform (ISFFT). An example for this is given in FIG.45E. 3. A waveform of transmission method 3, is transformed directly to delay-Doppler via an inverse Zak transform over the time dimension, as shown in FIG.45F. Afterwards, a receive two-dimensional pulse may be applied to it.

[0165] FIG.45D depicts a receiver processing example for a waveform generated by transmission method 1. The received waveform is transformed to a time-frequency grid using a Fast Fourier Transform 20 180851577.4International Patent Application 119314.8124.WO00 (FFT) and the OTFS part (denoted as “#3 OTFS”) is extracted and transformed to delay-Doppler via an Inverse Symplectic Fast Fourier Transform (ISFFT).

[0166] FIG.45E depicts a receiver processing example for a waveform generated by transmission method 2. The received waveform is transformed to a time-frequency grid using a Fast Fourier Transform (FFT) and the OTFS sub-grid is extracted and transformed to delay-Doppler via an Inverse Symplectic Fast Fourier Transform (ISFFT).

[0167] FIG.45F depicts a receiver processing example for a waveform generated by transmissionmethod 3. The received OTFS waveform is arranged in a grid ^^ ൈ ^^ elements and transformed to delay-Doppler via the inverse Zak transform over the time dimension. It is noted that in the description of OTFS signal generation and reception as described in the present document, while reference signals are not specifically described, in practical systems, some resources may be allocated to various reference signals for monitoring or calibration of the channel between a transmitter and a receiver.

[0168] In some embodiments, the described embodiments include receiver signal processing that can be configured to implement iterative equalization and decoding of multi-level encoded symbols (in Section 4.8) and iterative two-dimensional (2-D) equalization (in Section 4.9).

[0169] 4.8 Examples of iterative equalization and decoding for multi-level encoding

[0170] In general, iterative receivers exchange extrinsic information between the equalizer and the FEC (forward error correction) decoder to achieve close to optimal performance, as shown in FIG.46 for an OTFS receiver 4600. The extrinsic information may include a priori knowledge of which transmission resources (e.g., time slots of subcarriers) use which particular FEC. For example, the equalizer 4602 uses prior information on the data symbols coming from the FEC feedback path to improve the equalization of the symbols. This feedback path comprises a symbol mapper 4610 and OTFS transformation module 4612. Then, these symbols are converted to bit likelihoods that are FEC decoded. Several iterations are performed until all the source data is decoded correctly, or until some other stopping criteria is met. An inverse OTFS transform module 4604 may apply inverse OTFS transform and a symbol demapper 4606 may recover bits from modulation symbols.

[0171] Compared to other techniques described next, the error-rate performance of the scheme 4600 may be degraded. One reason for the degradation may be because of the mixture of bits with different level of reliability in every FEC codeword that is being decoded. The constellation bits with low reliability make it harder for the FEC decoder to converge to the correct codeword and therefore, the feedback to the equalizer has less information to improve the equalization.

[0172] When multi-level encoding is applied at the transmitter (e.g., as shown in FIG.47), the iterative receiver 4800, in each decoding iteration, decodes only a part of the constellation bits. It typically starts with the most reliable bits and then proceeds in the next iterations to less reliable ones. This scheme, 21 180851577.4International Patent Application 119314.8124.WO00 shown in FIG.48, allows the equalizer to receive in earlier iterations priors, which are dominant from the constellation symbols point of view and better improve the equalization. When the FEC has successfully decoded one level, it switches to decode the next one. The receiver continues to iterate until all levels have been decoded successfully or until some other stopping criteria is met. The most reliable bits are often bits that are used to decide the "macro" region within the constellation map where a symbol lies-- e.g., the quadrant in which a constellation symbol of a 4 or 8 QAM signal lies, followed by sub-quadrant within the quadrant, and so on. Thus, as shown in FIG.48 the received signal may be equalized by the equalizer 4802. In the forward path, the equalized signal may undergo an inverse OTFS transform (4804), and the symbols from the resulting transformed signal may be demapped for decoding by multiple different FECs FEC1 to FECq (modules 4858a to 4858q). In the feedback path, the decoded symbol (bit) outputs of the FEC modules may be mapped to symbols (4810) and transformed into OTFS domain signals (symbols) for feedback to the equalizer 4802. As described above, in some implementations, different forward error correction codes are used for symbols from the multiple symbols corresponding to header and payload portions of the bits from the signal.

[0173] 4.9 Examples of iterative 2-D equalization

[0174] FIG.49 is a block diagram of an example embodiment of an iterative 2-D equalizer 4901. The 2- D Iterative equalizer, illustrated in FIG.49, iterates between the 2-D equalizer 4903 and the FEC MAP decoder 4905, by passing information from one to the other. After several iterations, the MAP decoder outputs estimation on the information bits. In various embodiments, the iteration termination criteria may be based on a total number of iterations, meeting, but not exceeding, a time budget for the iterative process, the improvement in successive iterations falling below a threshold, and so on.

[0175] 4.9.1 2-D equalizer (4903)

[0176] In some embodiments, the 2-D equalizer may be implemented as an affine MMSE (minimum mean square error) equalizer, computing the Wiener estimator of X ^^^ ൌ ^^^^ ^ ^^^ െ ^^^^^^ത^ (19)

[0177] Herein, ^^ ൌ ^^^^^^^ି^and I is the identity matrix. Note that C is a function of RXand RW. For the first iteration there is no prior information on the symbols of X, therefore we set X=0 and RX=I. The 2-D equalizer also computes the variance of the estimation error, denoted as RE.

[0178] 4.9.2 2-D SFFT (4907)

[0179] The estimated symbols and error variances, ^^^ and RErespectively, are transformed from the 2-D Time-Frequency grid to the 2-D Delay-Doppler grid via a 2-D Symplectic Fourier transform to ^^^ and Rerespectively.

[0180] 4.9.3 Likelihoods (4909) 22 180851577.4International Patent Application 119314.8124.WO00

[0181] Likelihoods for the coded bits ^^ா^^^^^, are computed from the symbols ^^^. Gaussian distribution may be assumed for ^^^ and the likelihoods can be derived from it. The probabilities for this case are ି భ^௫^ିఓ^ఠ^మ^^^^^^|^^ ൌ ^^^ ∝ ^^ೃೋ ,^^(20)

[0182] Herein, ^^ ∈ Ω is a ^^ ^^ ൌ ^^^^ ^ ^1 െ^^^^̅^ ((21)). Note that ^̅^ is defined in. coded bits log likelihoods ratio (LLR) can be derived as

[0183] Herein, constellationsymbol ω and P .

[0184] 4.9.4 Deinterleaver (4911)

[0185] The deinterleaver permutes the likelihoods ^^ா^^^^^ to L(C). These likelihoods will be used as a priori information for the MAP decoder. In some implementations this deinterleaver might be optional.

[0186] 4.9.5 MAP decoder (4905)

[0187] The maximum a posteriori (MAP) decoder computes the a posteriori probabilities (APP's) of the information bits and also the extrinsic probabilities for the coded bits, which when using LLRs, are the APP's minus the a priori inputs.

[0188] 4.9.6 Interleaver (4913)

[0189] The interleaver permutes the likelihoods ^^^^^^^ to ^^^^^^^. These likelihoods will be used as a priori information for the MAP decoder. Note that in some implementations this interleaver might be optional.

[0190] 4.9.7 Symbol mapper (4915)

[0191] The symbol mapper estimates the probabilities of each constellation symbol ^^ ∈ Ω from thelikelihood values ^^^^^^^:

[0192] Thesethe variance: 23 180851577.4International Patent Application 119314.8124.WO00

[0193] 4.9.8 2-D

[0194] The 2-D to ^ത^ and RXin the 2-D Time-Frequency domain using a 2-D Inverse Symplectic Fourier transform to transform from the delay-Doppler domain to the Time-Frequency domain. These are used as priors to the 2-D Equalizer in the next iteration. In some embodiments, the 2-D transforms used by operation 4907 and 4917 may be swapped. In other words, an inverse SFFT may be used in the operation 4907, while an SFFT may be used in the operation 4917.

[0195] In some embodiments, the iterative 2-D Equalizer may be operated so that the receiver gets side information about some resource elements in the time-frequency grid that have been "erased" (e.g., not transmitted, or not useable) and the receiver can ignore them. The receiver may skip equalization for these resources and directly use the prior estimates as outputs for the equalizer. In this case, Equation (19)simply becomes for these resources: ^^^ ൌ ^ത^.

[0196] 5. OTFS Transmitter Examples

[0197] In some embodiments, the OTFS transmitter encodes information bits in one or more Forward- Error-Correction (FEC) codes, corresponding to one or more symbol constellation levels (denoted by ^^), interleave the coded bits and map them to symbols (typically QAM) which are then assigned to delay- Doppler grid elements. Some of the delay-Doppler grid elements may not be assigned with any symbols (value of zero) and others may be assigned with known symbols (pilots). Finally, the OTFS modulator is applied to the delay-Doppler grid. FIG.3 shows an example of such a transmitter.

[0198] FIG.3 shows an example of generating an OTFS waveform. From left to right, source bits (e.g., data bits) are input to a number of FEC stages, each operating at a corresponding code rate. The FEC coded outputs are interleaved through corresponding interleavers. The resulting signals are mapped to symbols and mapped to a delay-Doppler grid along with pilot signals. The resulting mapped signal is processed through an OTFS modulator to generate n OTFS waveform.

[0199] 6. OTFS Modulator Examples

[0200] In some embodiments, the OTFS modulator implements equation (1), generating a time-domain signal ^^^^^^. This equation may be implemented in multiple ways, such as using the Zak transform (e.g., US Patent US11190379 B2, incorporated herein by reference in its entirety), a 2-dimensional transform 24 180851577.4International Patent Application 119314.8124.WO00 such as a Fast Fourier Transform (FFT) that is a symplectic transform, or using pulse-tones. FIGS.4 to 6 show three examples for different implementations of equations (1) and (2),

[0201] FIG.4 shows an example method of OTFS waveform generation in which the delta trains ∆^^,^^^^^^^are multiplied by the delay-Doppler grid elements ^^^^^, ^^^. The resulting signal is combinedand convolved with ^^ఛ^^^^to obtain the output signal. Here, the signal is composed in the delay domain.

[0202] FIG.5 shows an embodiment in which the convolution operation is performed before adding the resulting signals together. In other words, signal is composed in the Doppler domain.

[0203] FIG.6 shows an example where pulse-tones are multiplied by grid elements and the result is combined to obtain the transmission waveform.

[0204] Note, that there may be other equivalent implementation of equations (1)-(3). For example, the time-domain signal can be rewritten as ெି^ ேି^ ^ ^^^^^^ ൌ ^^ఛ^^^^ ∗ ^ ^^௧^^^^ ^ ^^^^^, ^^^ ∙ ^ ^^^ଶగ^∆ఔ^ఛ^^^൫^^ െ ^^Δ^^ െ ^^^^^൯

[0205]

[0206] FIG.7 shows an example embodiment where Wtis multiplied by (n, m) to obtain delta trains ^^,^^Receiver Examples receiver structures for OTFS are feasible Equalization in the delay-Doppler domain maybe performed, when using OTFS with a set of predefined basis signals. For example, as described in the present document, the basis signals may combine certain mathematical properties of a pulse and a tone, and may be called pulse-tone (e.g., Pulsones™).

[0209] Channel estimation may be performed by assigning to one or more delay-Doppler grid elements a known symbol (pilot) at the transmitter. At the receiver, the received signal may be processed for finding out the grid elements and their values where the pilot symbol was transformed to by the channel interaction.

[0210] Let’s consider a pilot symbol that was assigned at the transmitter to the grid location ൫^^^,^^^൯,and received after the channel interaction at grid locations ^^^^ , ^^^^ with received values1,2, … ,Ω.

[0211] To equalize symbols other than the pilot, a receiver may transform the estimated channel response obtained from the pilot to other locations on the grid, by rotating it: ℎ^^^^^, ^^^ ൌ ℎ^ ∙ ^^^ଶగ∙^൫^,^,^^,^^,ே,ெ൯(26) 25 180851577.4International Patent Application 119314.8124.WO00

[0212] where ^^^∙^is a function of the grid location^^^, ^^^, the pilot location ൫^^^, ^^^൯ and the griddimensions ^^ ൈ ^^.

[0213] 8. Example OTFS Use Cases

[0214] An OTFS waveform generated as described herein may be used in a variety of different digital communication scenarios such as Under water acoustic wave communications, Deep-space communication, communication with non-terrestrial equipment such as satellites, airborne devices such as airplanes, balloons, drones, etc. The communication channel in such cases may comprise aerial-to- ground, ground-to-aerial or ariel-to-ariel communication, underwater acoustic wave communication deep space communication and so on. Furthermore, the disclosed techniques may be applied in generally any frequency range - from sub-MHz (e.g., underwater acoustics that uses 10 Hz to 1 MHz), MHz, GHz or THz and beyond.

[0215] 9. Further comments on OTFS deployments for backward compatibility

[0216] Currently, most popular cellular wireless technology deployments are based on interoperability standards published by the third generation partnership project (3GPP) consortium. These technologies are known by various acronyms, and generally grouped into third generation (3G), 4G, 5G (also called new radio NR) and the upcoming 6G technologies. In particular, the transmission signals defined by these standards use certain architectural building blocks referred to as numerology (frequency planning), logical groupings of transmission resources. For example, a resource element (RE) represents a basic minimum unit of transmission resource. Along the time axis, the resources are represented in various units such a frame, divided into two subframes, which are divided into a number of slots, which carry a number of transmission symbols and so on. Along the frequency axis, the resources are represented by a subcarrier bandwidth or a resource block (comprising an integer number of subcarriers) and so on. Furthermore, these standards define some reference signals such as the primary and secondary synchronization signals (PSS, SSS), demodulation reference signal (DMRS), channel state information reference signal (CSI-RS), sounding reference signal (SRS), and so on. Each standard defines various rules of how the reference signals are constructed and transmitted, and also rules of how the reference signals are received and processed.

[0217] Currently, it is not known how OTFS transmissions may be organized in a future wireless deployment. In particular, as disclosed herein (such as in Section 4), transmission resources in an OTFS transmission scheme may be disclosed along a delay-Doppler grid. The present document discloses various embodiments in which architectural building blocks similar to the current 3GPP standards are used in order to maintain a backward compatibility between OTFS physical layer and 3GPP-like medium access control (MAC) and higher layers for organization of MAC-PHY interface in a transmitter or a receiver. 26 180851577.4International Patent Application 119314.8124.WO00

[0218] 10. Example PHY embodiments

[0219] With reference to the following, including FIGS.14A to 26, some additional implementation examples of OTFS technology are described.

[0220] For instance, an OTFS transmitter may include one or more of the following features: Tiling the Time Frequency and Mapping OTFS frames onto respective tiles;

[0221] Maintain Numerology in particular grids corresponding to OFDM PRB grid (12 x 14) though aspect ratio permuted (Example- 12 doppler & 14 delay vs 14 symbols & 12 tone);

[0222] The partition addresses the multiuser problem;

[0223] How to transport information across the Time frequency and the delay doppler correspondingly;

[0224] Multiplexing in the time frequency or in the delay doppler or in both;

[0225] Each tiling has advantages and disadvantages (Performance, Complexity, orthogonality under various channel conditions);

[0226] Non orthogonal Pilot Overlay in the power domain.

[0227] Those skilled in the art will appreciate that the above-disclosed implementations are useful to reduce complexity, resilient to Doppler fading, and will be able to accommodate numerology of 3GPP to OTFS transmission schemes.

[0228] Furthermore, the disclosed implementations can also map 3GPP OFDM frame constituents & protocol abstracts to equivalent OTFS frame counterpart(s) (example- PRB, reference signals, etc…)

[0229] As shown in FIG.14A, one example implementation may use 1 millisecond time units over available transmission bandwidth. This transmission resource unit may be divided into a 14x1272 dimension OTFS frame (as further disclosed below.)

[0230] FIGS.14A and 14B further shows an example of time slots used within the 1 ms time resource for each of the 14 OTFS frame. One example (FIG.14B, top row) shows 1 ms time split into 180 KHz frequency resource units, which makes up 106 OTFS frames in a 14 x 12 grid.

[0231] Another implementation (FIG.14B, bottom row) shows transmission resources split into 0.5 msec units, each having 360 KHz bandwidth, which also results in 106 OTFS frames in a 14x12 grid.

[0232] Tiling with multiple OTFS frames for Orthogonal Multiuser

[0233] FIG.15 shows an example of a time-frequency tiling of a physical resource block. Here, each PRB may correspond to 12 units in the delay dimension and 14 units in the Doppler dimension. As shown in FIG.15, PRBs are tiled along time / frequency dimensions such that each PRB corresponds to an OTFS frame that includes a first number of Doppler units (14, in the drawing) and a second number of delay units (12, in the drawing). The PRBs are organized along the frequency axis as having a first bandwidth (168 times (1 plus alpha) KHz) and along time axis as having a certain time duration (1 ms). The 12 delay units of PRB 5 are shown as an example illustration. 27 180851577.4International Patent Application 119314.8124.WO00

[0234] FIG.16 shows an expanded view of the delay-Doppler domain organization of transmission resources, showing 14 frequency domain units, each representing 180 KHz, corresponding to 12 subcarriers spaced at 15 KHz.

[0235] FIG.17 shows a similar example of time frequency domain tiling of PRBs. Here, the units of time and frequency correspond to the embodiment depicted in the bottom row of FIG.14B, with 0.5 msec time units and 336*(1+alpha) frequency units along the frequency axis.

[0236] Tiling with OTFS frames Non Orthogonal Multiuser

[0237] FIG.18 shows an example of tiling along delay-Doppler axis. Here, the unit used in the time- frequency plane comprises 1 msec time, and an entire frequency bandwidth. The PRBs are depicted along the delay-Doppler two-dimensional plane as OTFS frames comprising 14 Doppler units and 12 delay units in each PRB.

[0238] FIG.19 shows an example arrangement along delay-Doppler two-dimensional plane in which eight PRBs are depicted. In some embodiments, a guardband (guard band) may be used in the delay domain.

[0239] Non orthogonal spread Pilot overlay in the Power domain

[0240] FIGS.20 to 22 depict examples of implementations in which a spread pilot is overlaid in the power domain in a non—orthogonal manner.

[0241] FIG.20 shows an example of a quadrature amplitude modulation (QAM) constellation illustrating how different bits correspond to different power level. The large circle in the middle represents power of the MSB (most significant bit), with the successively smaller circles in the top-right representation smaller and smaller bits representing signal values.

[0242] FIG.21 shows an example of organization of transmission resource along the delay-Doppler two- dimensional axes. As shown in top left, in the time domain, time frames may be organized as a number of “ticks” of the pulse-tone representing an OTFS waveform. For example, values of 7 ticks or 14 ticks may be used to make up one time unit.

[0243] As depicted in the lower part of FIG.21, the train of OTFS pulses, that represents a time domain frame (or subframe), may be multiplexed with other types of transmissions. For example, the multiplexing may be performed by having different OTFS pulses on top of each other along the power domain (in terms of bit positions being coded), or multiplexed along delay domain (e.g., a reference signal or a PSS).

[0244] In some embodiments, the reference signal may be a single OTFS symbol that represents a pilot. The pilot may be protected from other signals via a guardband (guard band) in the delay-Doppler domain. In some embodiments, overlaid pilot signals may be used such that a pilot signal is spread over the delay- Doppler domain to occupy a certain pre-defined region. In some embodiments, the pre-defined region 28 180851577.4International Patent Application 119314.8124.WO00 may be a one-dimensional (1-D) signal along either delay or Doppler dimension. In some embodiments, the pre-defined region may be a two-dimensional (2-D) signal along both delay and Doppler dimensions. One of the design considerations in the selection of the pre-defined region may be an amount of power that is to be used for the reference signal. For example, greater power would mean a bigger area of reference signal. Another design criterion for the pre-defined region may be a nature of the channel on which the OTFS signal is being transmitted. For example, for a static, slowly or non-varying channel, a thin two-dimensional or a 1-D pre-defined region may be sufficient. Conversely, a channel that is experiencing large variations in delay or in Doppler characteristics may entail use of a broader reference signal region along that axis. For example, a reference signal that occupies the inner thin rectangle in FIG. 21 will facilitate detection of delay spread, but may not be as effective against Doppler spread in the channel.

[0245] In some implementations, the exact region occupied by the reference signal is pre-defined using a set of rules known a priori to both the transmit side and the receive side. As such, a transmitter may, on the fly, be able to change the transmission resources occupied by the reference signal in the delay Doppler domain.

[0246] A similar region-tailoring approach may be used for other channels and reference signal transmissions such as PSS and physical random access channels (PRACH). In current 3GPP technologies, PSS occupies frequency resources (approximately 2 MHz) smaller than channel bandwidth (127 of 240 subcarriers). Although this frees up transmission resources for other transmissions, it also limits the precision of synchronization. By contrast, OTFS may use PSS signals that occupy the entire Doppler domain PRB.

[0247] It will be appreciated by one of skill in the art that the various schema described with respect to FIG.21 operate in a manner where pulses, or bursts, are repeated a certain number of times in time domain on a per-frame basis, while being overlaid on data (due to separation in the delay-Doppler domain or power domain). Therefore, from a receiver perspective, such a signal can be received by performing joint decoding and detection. The reception may be performed iteratively.

[0248] In some embodiments, the power multiplexing may be achieved based on modulating using different significant bits. For example, using binary representation, a more significant bit has an amplitude double that of an immediately lesser significant bit, meaning 6 dB gain in power when appropriate bit-to-symbol mapping is used. This property can be exploited such that the higher power bits may carry pilot signals, which allow an earlier / faster acquisition of the channel at a receiver. The boost in power can be increased even more by using more than one MSBs for reference signals. The lower bits will be used for carrying information signals (e.g., user data). It will be appreciated that the various 29 180851577.4International Patent Application 119314.8124.WO00 transmission resource assignment schemes depicted in FIG.21 can be adapted according to channel conditions.

[0249] In some embodiments, the above-described design principles for the PSS may also be used for assignment of transmission resources to PRACH signal. In current 3GPP standards, PRACH is a signal that occupies 1 to 2 millisecond transmission time where no other signals are transmitted. Different from this, using the OTFS based multiplexing as described herein, PRACH may be multiplexed with other transmissions.

[0250] In another advantageous aspect, the transmission scheme described with respect to FIG.21 can also be adapted for uplink transmissions in which every data packet may be accompanied with a reference signal transmission such that base stations are able to recover signal transmissions from UEs. A base station may also be able to train a precoder, e.g., a Tomlinson Harashima precoder that reduces implementation complexity at UE-side, which enables simpler UE designs.

[0251] FIG.22 shows examples of transmission resource assignments performed in various embodiments. The resource allocation scheme in the lowest row shows delay Doppler transmission resources being allocated to two paired groups A and B, and a multiplexed DMRS associated with each of the paired groups. A paired group represents all UEs that can receive transmissions from same delay Doppler resources at same time. Such devices may be, for example, served via different transmission beams. In the transmission scheme, DMRS may also be precoded using same precoder as the data carried by the “paired group” transmission resources. In some embodiments, DMRS may be occupying separate (non-overlapping) regions that are multiplexed on top of the paired group. One such example of a contiguous DMRS region is shown in the middle row of FIG.22. As depicted herein, in some cases, a guardband of PRB may be used to provide isolation between two different transmissions to ensure that uncertainty in delay spread does not cause signal degradation. Although shown as UE1 and UE2, the transmission resource regions may represent paired groups also. The top row of FIG.22 shows the example of allocating entire transmission resources within a frame to a single UE, with a DMRS multiplexed on top of the data signal.

[0252] Referring back to FIG.19, in some cases, the guardband based scheme may be used to separate out transmissions between multiple paired groups (PG). Furthermore, the exact position of placement of the guardband can be made responsive to an expected behavior of a channel. For example, because the placement is done in delay and Doppler domains, an expected range uncertainty or velocity uncertainty of the receiver position may be directly used for determining position placement of the transmission resources allocated to the guardband.

[0253] Pilot spread construction

[0254] FIG.23 depicts examples of construction of a pilot spread. 30 180851577.4International Patent Application 119314.8124.WO00

[0255] FIG.23 shows an example of multiplexing of two different OTFS frames. As depicted, frame B may be overlaid with frame A in interleaved insertion manner (top) or spread / spaced concatenation manner or contiguous concatenation manner.

[0256] Waveform samples

[0257] FIGS.24 to 26 depict examples of waveforms. Here, FIG.24 shows an example of a pulse-tone pulse that carries an OTFS signal. FIG.25 shows an arrangement of a transmission frame in 14 transmission slots, each carrying signals that are allocated a grid within N x M delay-Doppler transmission resources. Here, a signal may occupy an entire Doppler bandwidth or an entire delay bandwidth or both. FIG.26 shows an example of a waveform resulting from multiplexed OTFS transmissions that may take the form of time-defined pulses that carry OTFS modulated signals. In the depicted example, the pulses are separated by 5.56 microseconds, and organized as 1 / 15 msec slots, representing 180 KHz transmission bandwidth.

[0258] 11. Examples of power domain multiplexing

[0259] Multiplexing in power domain mean that some bits used to represent digital value of signals are coded using different scheme. For example, least significant N bits (N = 1 or more) and / or most significant M bits ( M = 1 or more) may be used for multiplexing.

[0260] 12. Examples of low latency implementations

[0261] One beneficial aspect of using OTFS modulation scheme is to allow multiplexing of different signals in a latency-sensitive manner. For example, in the conventional OFDM systems such as LTE and NR, transmission resources are organized in terms of frames or subframes that are made up of a certain number of OFDM symbol transmissions. As an example, in LTE Type 1, each frame may correspond to 10 msec of transmission time (made up of subframes), organized into 20 individual slots. Each slot consists of 6 or 7 OFDM symbols, depending on cyclic prefix length. Thus, each subframe comprises14 OFDM symbols. The structure of a subframe is usually represented as a 2D resource grid of time and frequencies. The grid includes from 72 to 1200 subcarriers. Each cell on the grid is known as a resource element. A resource block is a 12-by-7 set of resource elements. Typically, control information is sent on earlier symbols in a frame.

[0262] Different from OFDM based resource grids, in an OTFS system, resource assignment for transmissions may be performed in the delay-Doppler domain. Using the advantages of OTFS signal generation, a grid in the OTFS domain may be mapped into a tile in the time-frequency domain.

[0263] FIG.12 shows examples of time frequency tiles that can be allocated to various signals. The area of each of the tiles correlates to the amount of data that can be carried using the transmission resources represented by the tile. Different examples show assignments that are “square” in both time and frequency dimensions, or skinny-tall, meaning narrowband but using more time resources or wide-short, meaning 31 180851577.4International Patent Application 119314.8124.WO00 higher bandwidth but less transmission time. It will be appreciated that because of the underlying OTFS modulation mechanism, the tiles can be individually demodulated at the receiving side. Thus, the OTFS based tiling of PRB offers a design-trade off with respect to latency (smaller latency for tiles that occupy smaller time) and spectrum occupancy.

[0264] For example, often, in digital communication, a latency budget or a bandwidth budget is allocated to a particular data flow (or service). This prescribed bandwidth or latency may impact how transmission resources should be allocated for that particular transmission.

[0265] FIG.13 shows another example of tiling where tiles may be selected to have time and frequency domain measurements that are integer multiple of a smallest unit. In the depicted drawing, 0.125 msec is the smallest unit of time and 1 / 12thfrequency band is the smallest unit of frequency. In some embodiments, data portion may be mapped to the 1 ms wide tile (rightmost four tiles in FIG.13), while control channels may be assigned to the different rectangular tile options on the left. Use of such a signal in digital communication may alleviate a need on the receiver device side to buffer large amounts of data by making control channel transmissions available in a relatively short time period. On the receiver side, knowing the tile dimensions, such samples can be recovered using a rectangular grid of received time- frequency samples (basically a train of pulses of a certain width and a certain bandwidth), converting into OTFS domain and recover underlying information therefrom.

[0266] In some systems, the tiles may be separated from each other using guard bands to take into account finite roll-offs of filters in typical software or hardware implementations.

[0267] 13. Example technical benefits

[0268] The OTFS transmission schemes described herein may be advantageously used to maintain a same numerology as legacy standards, which may benefit network planning, co-existence and design of certain system components such as analog amplifiers and so on. Furthermore, using a numerology that is identical to a legacy system allows simplified upper layer designs to operate with the physical layer of OTFS. Because OTFS signals do not require a channel prefix, additional transmission capacity can be gained by eliminating the need of using cyclic prefixes to separate the time domain pulses representing OTFS waveforms. In a typical OFDM system, the complexity may be represented on the order of M*N * log2(N), where M represents number of symbols transmitted in a frame, with N representing number of subcarriers in a symbol. The typical TX-RX chain of modulation, precoding, channel estimation and demodulation using FFT results in the above-described order of complexity. Different from this, using OTFS systems, the complexity will be of the order of N*M*log2(M). Therefore, the complexity ratio is approximately log(M) / log(N). Depending on the numerology, this may result in of 70, 62.77, 58.7, 53.7 percent at 100, 2010 and 5 MHz channel bandwidths. In particular, Tomlinson Harashima precoder / precoding will also alleviate channel equalization complexity at the receiver. It will be 32 180851577.4International Patent Application 119314.8124.WO00 appreciated that a big savings comes from reducing the dimension of the fast Fourier transform (FFT) that is used for OTFS transmission / reception, compared to OFDM transmission / reception.

[0269] U. S. Patent 10,063,295 B2, incorporated herein by reference in its entirety, provides examples of Tomlinson Hiroshima precoding embodiments.

[0270] 14. Examples of implementation details

[0271] FIG.8 is a block diagram representation of a wireless hardware platform 800 which may be used to implement the various methods described in the present document. The hardware platform 800 may be incorporated within a base station or a user device. The hardware platform 800 includes processor electronics such as at least processor 802, a memory 804 (this may be optional and in some cases the memory may be internal to the processor electronics) and a transceiver circuitry 806. The processor may execute instructions, e. g., by reading from the memory 804, and control the operation of the transceiver circuitry 806 and the hardware platform 800 to perform the methods described herein. In some embodiments, the memory 804 and / or the transceiver circuitry 806 may be partially or completely contained within the processor 802 (e.g., same semiconductor package).

[0272] The following solutions may be preferably implemented by some embodiments.

[0273] 1. A method of digital communication (e.g., method 900 in FIG.9), comprising: assigning (902), to a first transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; assigning (904), to a second transmission signal, second transmission resources in the delay-Doppler domain transmission grid according to a multiplexing scheme; and causing (906) transmission of a transmission waveform for the first transmission signal and the second transmission signal.

[0274] 2. A method of digital communication (e.g., method 1000 in FIG.10A), comprising: assigning (1002), to a transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and causing (1004) transmission of a transmission waveform for the first transmission signal. In the present document, “delay-Doppler domain transmission grid” may also be considered to be a two-dimensional delay- Doppler plan with resources mapped along delay and Doppler axis.

[0275] 3. A method of digital communication (e.g., method 1010 in FIG.10B), comprising: receiving (1012), by a receiver apparatus from a transmission apparatus, a transmission waveform comprising a first transmission signal and a second transmission signal, wherein the first transmission signal and the second transmission signal are multiplexed along a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse 33 180851577.4International Patent Application 119314.8124.WO00 occupying a resource element defined by a delay unit and a Doppler unit, and wherein the first transmission signal occupies first transmission resources in the delay-Doppler domain transmission grid and the second transmission signal occupies second transmission resources in the delay-Doppler domain transmission grid; and demodulating (1014), from the transmission waveform, the first transmission signal to recover information bits transmitted from the transmission apparatus.

[0276] 4. A method of digital communication (e.g., method 1020 in FIG.10C), comprising: receiving (1022), by a receiver apparatus from a transmission apparatus, a transmission waveform comprising a first transmission signal, wherein the first transmission signal occupies transmission resources along a delay- Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), and wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and demodulating (1024), from the transmission waveform, the first transmission signal to recover information bits transmitted from the transmission apparatus.

[0277] 5. The method of any of solutions 1 to 4, wherein the multiplexing scheme multiplexes the first transmission resources and the second transmission resources along a delay dimension of the delay- Doppler domain.

[0278] 6. The method of any of solutions 1 to 5, wherein the multiplexing scheme multiplexes the first transmission resources and the second transmission resources along a Doppler dimension of the delay- Doppler domain.

[0279] 7. The method of any of solutions 1 to 6, wherein the multiplexing scheme multiplexes the first transmission resources and the second transmission resources along a power dimension.

[0280] 8. The method of solution 7, wherein the first transmission signal is a data signal and the second transmission signal is a reference signal, wherein the reference signal occupies a pre-defined region of the delay-Doppler plane.

[0281] 9. The method of solution 8, wherein the pre-defined region of the delay-Doppler plane is a function of an expected delay spread or an expected Doppler spread of a channel over which the transmission waveform is transmitted.

[0282] 10. The method of solution 8, wherein the pre-defined region of the delay-Doppler plane is a function of both an expected delay spread and an expected Doppler spread of a channel over which the transmission waveform is transmitted.

[0283] 11. The method of any of solutions 8 to 10, wherein the pre-defined region of the delay-Doppler plane is pre-defined using a set of rules known a priori to both a transmitting side and a receiving side.

[0284] 12. The method of any of solutions 8 to 11, wherein the reference signal is separated from other signals by a guard band in the delay-Doppler plane. 34 180851577.4International Patent Application 119314.8124.WO00

[0285] 13. The method of any of solutions 8 to 12, wherein the reference signal is received by performing joint decoding and detection.

[0286] 14. The method of solution 13, wherein the joint decoding and detection is performed iteratively.

[0287] 15. The method solution 7, wherein the multiplexing scheme that multiplexes the first transmission resources and the second transmission resources along a power dimension is based on modulating using different significant bits.

[0288] 16. The method of solution 15, wherein the first transmission signal is a data signal and the second transmission signal is a reference signal, wherein one or more most significant bits of the different significant bits is used for the reference signal, and wherein one or more least significant bits of the different significant bits is used for the data signal.

[0289] 17. The method of any of solutions 1 to 7, wherein the first transmission signal comprises a physical random access channel (PRACH) signal that is multiplexed with the second transmission signal in the delay-Doppler domain, or wherein the second transmission signal comprises the PRACH signal that is multiplexed with the first transmission signal in the delay-Doppler domain.

[0290] 18. The method of any of solutions 1 to 17, wherein the transmission waveform is generated in absence of cyclic prefixes between consecutive pulses.

[0291] 19. The method of any of solutions 1 to 18 wherein the first transmission signal and the second transmission signal are transmitted by processing through a same precoding operation.

[0292] 20. The method of any of solutions 1 to 19, wherein the first transmission resources and the second transmission resources comprise time-frequency domain rectangular tiles, and wherein the assignings (e.g., the assignment or the resources) are based on a type, a latency requirement or a bandwidth requirement of the first transmission signal or the second transmission signal.

[0293] 21. The method of solution 20, wherein the time-frequency domain rectangular tiles are separated by guard bands.

[0294] 22. The method of solution 20 or 21, wherein each of the time-frequency domain rectangular tiles corresponds to a respective PRB of the PRBs in the delay-Doppler domain

[0295] 23. An apparatus for digital communication comprising at least one processor and a transceiver, wherein the at least one processor is configured to cause the apparatus to perform signal processing operations recited in any of solutions 1 to 22 and the transceiver is configured to transmit or receive a signal under control of the at least one processor.

[0296] 24. A computer-readable medium having code stored thereon; the code, upon execution by at least one processor, causing the at least one processor to control an apparatus to implement a method recited in any of solutions 1 to 22. 35 180851577.4International Patent Application 119314.8124.WO00

[0297] 25. A method of processing information signals, comprising: configuring an electronic apparatus to operate using an orthogonal time frequency space (OTFS) physical layer and a legacy-compatible higher layer protocol stack, wherein the OTFS physical layer is configured according to a numerology of a legacy orthogonal frequency division multiplexing (OFDM)-based wireless protocol; and wherein the legacy-compatible higher layer protocol stack is configured according to the legacy OFDM-based wireless protocol. Various examples of legacy OFDM based technologies and numerologies are provided in the present document.

[0298] 26. The method of solution 25, wherein the legacy OFDM-based wireless protocol comprises a fifth generation new radio (5G NR) protocol.

[0299] 27. The method of solution 25, wherein the legacy OFDM-based wireless protocol comprises a long term evolution (LTE) protocol.

[0300] 28. The method of solution 25, wherein the numerology is associated with at least one of: a time duration or a slot, a frequency bandwidth, a pulse spacing, a time duration of a frame, or bandwidth of signals.

[0301] 29. An apparatus for processing information signals (e. g., apparatus 1100 in FIG.11), comprising: a processor-implemented higher layer protocol stack (1102) that is configured to operate using an orthogonal time frequency space (OTFS) physical layer; and a transceiver (1104) configured to operate according to the OTFS physical layer; wherein the OTFS physical layer is configured according to a numerology of a legacy orthogonal frequency division multiplexing (OFDM)-based wireless protocol; and wherein the higher layer protocol stack is configured according to the legacy OFDM-based wireless protocol. The apparatus may be a transmitter of OTFS signals or a receiver of OTFS signals.

[0302] 30. The apparatus of solution 29, wherein the legacy OFDM-based wireless protocol comprises fifth generation new radio (5G NR) protocol.

[0303] 31. The apparatus of solution 29, wherein the legacy OFDM-based wireless protocol comprises long term evolution (LTE) protocol.

[0304] 32. The apparatus of solution 29, wherein the numerology is associated with at least one of: a time duration or a slot, a frequency bandwidth, a pulse spacing, a time duration of a frame, or bandwidth of signals.

[0305] Other sections in this document such as Section 10 including FIG 14A to FIG.26 provide further examples of embodiments and techniques that may be adopted by any of the above-listed solutions.

[0306] In the above-listed solutions a receiver may receive the first transmission signal by performing one or more of demultiplexing, channel estimation, synchronization, data demodulation, error correction decoding, according to how the data is generated and transmitted in a given network. In some embodiments, iterative joint estimation and decoding may be used. The receiver may further receive 36 180851577.4International Patent Application 119314.8124.WO00 higher layer messages (explicitly) or implicitly know the transmission resources allocated to the reference signals and / or PRACH.

[0307] In the above-described method and apparatus, numerology may refer to the time duration or a slot, frequency bandwidth, pulse spacing, time duration of a frame, bandwidth of signals, and so on. It will be appreciated that although legacy protocols are entirely silent about dividing transmission resources along delay and Doppler axes, the presently disclosed techniques use of transmission signals and control messages that indicate transmit resources to use similar messaging structures in describing the transmission grid of time-frequency in legacy protocols using different units – namely delay and Doppler.

[0308] It will be appreciated that the present document provides techniques that may be used to plan OTFS based wireless system deployments, including numerology and reference signal / data signal multiplexing schemes for the transmissions. In one advantageous aspect, reference signals may be customized to the delay or Doppler characteristics of a channel and laid over data transmissions in a non- orthogonal manner (e.g., occupying same delay or doppler coordinates in the delay-Doppler plane). In another advantageous aspect, the power allocated to reference signals can be higher than corresponding power allocated to data carrying constellation points. Furthermore, the disclosed transmission schemes allow for designs of PRACH resources to enable fast access to a network by a UE, even when the distance between a base station and a UE is not known or is uncertain.

[0309] The disclosed and other embodiments, modules and the functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in combinations of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, which is generated to encode information for transmission to suitable receiver apparatus. 37 180851577.4International Patent Application 119314.8124.WO00

[0310] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0311] The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0312] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read -only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0313] While this patent document contains many specifics, these should not be construed as limitations on the scope of an invention that is claimed or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, 38 180851577.4International Patent Application 119314.8124.WO00 although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub- combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

[0314] Only a few examples and implementations are disclosed. Variations, modifications, and enhancements to the described examples and implementations and other implementations can be made based on what is disclosed. 39 180851577.4

Claims

International Patent Application 119314.8124.WO00 CLAIMS 1. A method of digital communication, comprising: assigning, to a first transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; assigning, to a second transmission signal, second transmission resources in the delay-Doppler domain transmission grid according to a multiplexing scheme; and causing transmission of a transmission waveform for the first transmission signal and the second transmission signal.

2. A method of digital communication, comprising: assigning, to a transmission signal, first transmission resources in a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and causing transmission of a transmission waveform for the first transmission signal.

3. A method of digital communication, comprising: receiving, by a receiver apparatus from a transmission apparatus, a transmission waveform comprising a first transmission signal and a second transmission signal, wherein the first transmission signal and the second transmission signal are multiplexed along a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit, and wherein the first transmission signal occupies first transmission resources in the delay-Doppler domain transmission grid and the second transmission signal occupies second transmission resources in the delay- Doppler domain transmission grid; and demodulating, from the transmission waveform, the first transmission signal to recover information bits transmitted from the transmission apparatus.

4. A method of digital communication, comprising: receiving, by a receiver apparatus from a transmission apparatus, a transmission waveform comprising a first transmission signal, wherein the first transmission signal occupies transmission 40 180851577.4International Patent Application 119314.8124.WO00 resources along a delay-Doppler domain transmission grid comprising a plurality of physical resource blocks (PRBs), and wherein each PRB comprises one or more pulses, each pulse occupying a resource element defined by a delay unit and a Doppler unit; and demodulating, from the transmission waveform, the first transmission signal to recover information bits transmitted from the transmission apparatus.

5. The method of any of claims 1 to 4, wherein the multiplexing scheme multiplexes the first transmission resources and the second transmission resources along a delay dimension of the delay-Doppler domain.

6. The method of any of claims 1 to 5, wherein the multiplexing scheme multiplexes the first transmission resources and the second transmission resources along a Doppler dimension of the delay-Doppler domain.

7. The method of any of claims 1 to 6, wherein the multiplexing scheme multiplexes the first transmission resources and the second transmission resources along a power dimension.

8. The method of claim 7, wherein the first transmission signal is a data signal and the second transmission signal is a reference signal, wherein the reference signal occupies a pre-defined region of the delay-Doppler domain.

9. The method of claim 8, wherein the pre-defined region of the delay-Doppler domain is a function of an expected delay spread or an expected Doppler spread of a channel over which the transmission waveform is transmitted.

10. The method of claim 8, wherein the pre-defined region of the delay-Doppler domain is a function of both an expected delay spread and an expected Doppler spread of a channel over which the transmission waveform is transmitted.

11. The method of any of claims 8 to 10, wherein the pre-defined region of the delay-Doppler domain is pre-defined using a set of rules known a priori to both a transmitting side and a receiving side.

12. The method of any of claims 8 to 11, wherein the reference signal is separated from other signals by a guard band in the delay-Doppler domain. 41 180851577.4International Patent Application 119314.8124.WO00 13. The method of any of claims 8 to 12, wherein the reference signal is received by performing joint decoding and detection.

14. The method of claim 13, wherein the joint decoding and detection is performed iteratively.

15. The method claim 7, wherein the multiplexing scheme that multiplexes the first transmission resources and the second transmission resources along a power dimension is based on modulating using different significant bits.

16. The method of claim 15, wherein the first transmission signal is a data signal and the second transmission signal is a reference signal, wherein one or more most significant bits of the different significant bits is used for the reference signal, and wherein one or more least significant bits of the different significant bits is used for the data signal.

17. The method of any of claims 1 to 7, wherein the first transmission signal comprises a physical random access channel (PRACH) signal that is multiplexed with the second transmission signal in the delay- Doppler domain, or wherein the second transmission signal comprises the PRACH signal that is multiplexed with the first transmission signal in the delay-Doppler domain.

18. The method of any of claims 1 to 17, wherein the transmission waveform is generated in absence of cyclic prefixes between consecutive pulses.

19. The method of any of claims 1 to 18, wherein the first transmission signal and the second transmission signal are transmitted by processing through a same precoding operation.

20. The method of any of claims 1 to 19, wherein the first transmission resources and the second transmission resources comprise time-frequency domain rectangular tiles, and wherein the assignings are based on a type, a latency requirement or a bandwidth requirement of the first transmission signal or the second transmission signal.

21. The method of claim 20, wherein the time-frequency domain rectangular tiles are separated by guard bands. 42 180851577.4International Patent Application 119314.8124.WO00 22. The method of claim 20 or 21, wherein each of the time-frequency domain rectangular tiles corresponds to a respective PRB of the PRBs in the delay-Doppler domain.

23. An apparatus for digital communication comprising at least one processor and a transceiver, wherein the at least one processor is configured to cause the apparatus to perform signal processing operations recited in any of claims 1 to 22 and the transceiver is configured to transmit or receive a signal under control of the at least one processor.

24. A computer-readable medium having code stored thereon; the code, upon execution by at least one processor, causing the at least one processor to control an apparatus to implement a method recited in any of claims 1 to 22.

25. A method of processing information signals, comprising: configuring an electronic apparatus to operate using an orthogonal time frequency space (OTFS) physical layer and a legacy-compatible higher layer protocol stack, wherein the OTFS physical layer is configured according to a numerology of a legacy orthogonal frequency division multiplexing (OFDM)-based wireless protocol; and wherein the legacy-compatible higher layer protocol stack is configured according to the legacy OFDM-based wireless protocol.

26. The method of claim 25, wherein the legacy OFDM-based wireless protocol comprises a fifth generation new radio (5G NR) protocol.

27. The method of claim 25, wherein the legacy OFDM-based wireless protocol comprises a long term evolution (LTE) protocol.

28. The method of claim 25, wherein the numerology is associated with at least one of: a time duration or a slot, a frequency bandwidth, a pulse spacing, a time duration of a frame, or bandwidth of signals.

29. An apparatus for processing information signals, comprising: a processor-implemented higher layer protocol stack that is configured to operate using an orthogonal time frequency space (OTFS) physical layer; and a transceiver configured to operate according to the OTFS physical layer; 43 180851577.4International Patent Application 119314.8124.WO00 wherein the OTFS physical layer is configured according to a numerology of a legacy orthogonal frequency division multiplexing (OFDM)-based wireless protocol; and wherein the higher layer protocol stack is configured according to the legacy OFDM-based wireless protocol.

30. The apparatus of claim 29, wherein the legacy OFDM-based wireless protocol comprises a fifth generation new radio (5G NR) protocol.

31. The apparatus of claim 29, wherein the legacy OFDM-based wireless protocol comprises a long term evolution (LTE) protocol.

32. The apparatus of claim 29, wherein the numerology is associated with at least one of: a time duration or a slot, a frequency bandwidth, a pulse spacing, a time duration of a frame, or bandwidth of signals. 44 180851577.4

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