Multi-user multiplexing of orthogonal time frequency space signals

Abstract

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

Description

[0001] Cross-references to related applications

[0002] This patent document claims the benefit and priority of U.S. Provisional Patent Application No. 62 / 374,705, filed August 12, 2016, entitled "Multi-user Multiplexing of Orthogonal Time-Frequency Spatial Signals". The entire contents of the aforementioned patent application are incorporated herein by reference as a part of the disclosure of this application. Technical Field

[0003] This document relates to wireless communication, and more specifically, to the transmission and reception of multi-user signals in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems. Background Technology

[0004] Due to the explosive growth in the number of wireless user devices and the amount of wireless data these devices can generate or consume, current wireless communication networks are rapidly exhausting their bandwidth to accommodate this high growth in data traffic and to provide users with high-quality service.

[0005] The telecommunications industry is making various efforts to develop next-generation wireless technologies that can meet the demands of wireless devices and network performance. Summary of the Invention

[0006] This document discloses techniques for multiplexing signals from / to multiple user facilities in the uplink and / or downlink directions.

[0007] In one example, a method is disclosed for performing downlink transmission from a transmitter to multiple user devices using transmission resources from a multidimensional resource grid. The method includes logically dividing the transmission resources into multiple segments, assigning one or more of the transmission resources from the multiple segments to a given user device among the multiple user devices, and performing downlink transmission by using at least some of the transmission resources assigned to the given user device to perform an orthogonal time-frequency space (OTFS) transformation on data or signals to be transmitted to the given user device.

[0008] In another aspect, a wireless communication method is disclosed for performing uplink transmissions from multiple user equipments using transmission resources from a multidimensional resource grid to a receiving device. The method includes logically dividing the transmission resources into multiple segments, assigning one or more of the transmission resources from the multiple segments to a given user equipment, and performing uplink transmissions from the given user equipment using at least some of the transmission resources assigned to the given user equipment, wherein the uplink transmissions include data that has undergone orthogonal time-frequency space (OTFS) transformation.

[0009] In another aspect, a method for performing transmission between a wireless device and a plurality of user devices is disclosed. The method includes logically grouping the plurality of user devices into a first group of user devices and a second group of user devices; allocating the first group of transmission resources to the first group of user devices by multiplexing along a first dimension of a first multidimensional representation of transmission resources; allocating the second group of transmission resources to the second group of user devices; allocating transmission resources from the first group of transmission resources to the user devices in the first group by multiplexing along a second dimension of a second multidimensional representation of transmission resources; and performing transmission between the wireless device and at least one user device using the corresponding allocated transmission resources.

[0010] In another aspect, a wireless communication method implemented at a network-side equipment for receiving multiplexed orthogonal time-frequency space (OTFS) signals including uplink transmissions from multiple user equipments is disclosed. The method includes performing joint equalization on the multiplexing to generate jointly equalized symbols, extracting symbols corresponding to a given transmitting device from the jointly equalized symbols based on extrinsic information about the transmission resource locations of the symbols, demapping the extracted symbols and performing forward error correction to generate output bits, and generating a feedback signal based on the output bits to improve the joint equalization in the next iteration.

[0011] In another aspect, a method for receiving an orthogonal time-frequency space (OTFS) signal is disclosed, the OTFS signal comprising transmit multiplexing for multiple receiving devices. The method includes performing joint equalization on the multiplexing to generate jointly equalized symbols, extracting symbols corresponding to one or more receiving devices from the jointly equalized symbols, demapping the extracted symbols and performing forward error correction to generate output bits, and generating a feedback signal based on the output bits to improve the joint equalization in the next iteration.

[0012] In another aspect, a wireless device is disclosed, which includes a processor configured to implement one of the methods described above.

[0013] In another aspect, a computer-readable storage medium is disclosed that stores instructions which, when executed by a processor, cause the processor to perform one of the described methods.

[0014] These and other features and embodiments are described in this document. Attached Figure Description

[0015] The accompanying drawings described herein are provided to offer further understanding and form part of this application. The exemplary embodiments and their descriptions are used to explain the technology and not to limit its scope.

[0016] Figure 1 An example communication network is shown.

[0017] Figure 2 An example of multiplexing-based launch resource allocation in a delay-Doppler grid along the delay dimension is shown.

[0018] Figure 3 An example of a multi-user uplink communication system is shown.

[0019] Figure 4 An example of a multi-user downlink communication system is shown.

[0020] Figure 5 A block diagram of an example implementation of a multi-user iterative receiver.

[0021] Figure 6 This illustrates an example of allocating launch resources along the frequency dimension in a time-frequency grid.

[0022] Figure 7 An example is shown of allocating transmission resources for transmission between one or more user equipment and wireless devices by multiplexing in both the delay-Doppler domain and the time-frequency domain.

[0023] Figure 8 A flowchart illustrating an example of a wireless communication downlink transmission method is shown.

[0024] Figure 9 A flowchart illustrating an example of an uplink transmission method for wireless communication is shown.

[0025] Figure 10 An example of a wireless transceiver device is shown.

[0026] Figure 11 A flowchart illustrating an example of a wireless communication method.

[0027] Figure 12 A flowchart illustrating an example of a wireless communication method.

[0028] Figure 13 A flowchart illustrating an example of a wireless communication method. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this disclosure clearer, various embodiments are described in detail below with reference to the accompanying drawings. Unless otherwise stated, the embodiments and features in this document can be combined with each other.

[0030] Chapter headings are used in this document, including appendices, to improve the readability of the descriptions and not in any way to limit the discussion to individual chapters.

[0031] Figure 1An example communication network 100 is shown, in which the disclosed techniques can be implemented. Network 100 may include a base station transmitter that transmits a wireless signal s(t) (downlink signal) to one or more receivers 102, and a received signal denoted as r(t), which may be located in various locations, including inside or outside buildings and in moving vehicles. Receivers may transmit uplink signals to a base station, which is typically located near the wireless transmitter. The techniques described herein can be implemented at receiver 102.

[0032] A brief introduction

[0033] Orthogonal time-frequency space (OTFS) transformation can be used to transform constellation symbols placed on a delay-Doppler grid into symbols on a time-frequency grid. These time-frequency symbols can then be modulated using orthogonal frequency division multiplexing (OFDM) and transmitted through the fading channel of a wireless system.

[0034] Wireless systems are typically configured with a base station on the network side and multiple user equipment (users) deployed in an area. Transmissions from a user equipment to the base station are called uplink transmissions, while transmissions from the base station to a user equipment are called downlink transmissions. To accommodate transmissions to and from user equipment, two multi-user schemes exist, which are typically used in different communication systems:

[0035] Multi-user uplink – where different users transmit simultaneously (subject to time division multiplexing), share bandwidth, but experience different channels and all signals are received by a single receiver (e.g., a base station), which decodes all users' signals.

[0036] Multi-user downlink – where a single transmitter sends data to multiple different users via a shared bandwidth. Each user equipment receives a signal that traverses typically different channels and decodes only the data specific to itself.

[0037] While this document describes various transmission and reception techniques with reference to uplink and downlink transmission, these techniques are also applicable to other situations where transmission occurs in both directions between transmitting wireless devices and between multiple wireless devices. Examples of this include, for instance, ad hoc networks that can be established between wireless devices.

[0038] When using OTFS signals, conventional OFDM transmission techniques do not provide a way to efficiently multiplex OTFS transmissions. The techniques disclosed in this document can be used by multiple users to share and decode OTFS signals.

[0039] Although various embodiments are described using examples of transmission resources in the delay-Doppler domain or time-frequency domain, in general, transmission bandwidth can be represented in multiple dimensions, each of which is orthogonal to the other dimensions.

[0040] Multiplexing in the delay-Doppler domain

[0041] One possible way to share OTFS signals (or OTFS transmit resources) among multiple user facilities is to multiplex user facilities in the delay-Doppler domain, which means allocating different portions of the resource grid to different users. This allocation can be arbitrary, but for receiver simplicity, it may be better to multiplex users along one of the grid dimensions, or along either the delay or Doppler dimensions. Figure 2 This illustrates an instance of user reuse in a delay-Doppler grid along the delay dimension.

[0042] Multi-user uplink transmission scheme

[0043] Figure 3 An example of three user units (User 1, User 2, and User 3) multiplexed (along the delay) in a delay-Doppler grid is shown. Each user occupies a different portion of the delay-Doppler grid, where the rest of the grid is unassigned (zero). Each user can add a specific reference signal to its transmission to enable channel estimation at the receiver. The users transmit simultaneously through different channels (H1, ..., H3) and receive together at a single receiver. After applying the inverse OTFS transform, the receiver's delay-Doppler grid contains all the receiving users. Figure 3 As described, an uplink signal from a user facility can be converted into an OFDM signal using an OTFS transform. A waveform generator can allocate transmit resources to the OFDM signal along a time-frequency grid. Additionally, the waveform generator may include a reference signal. The resulting signal can be transmitted to a multi-user receiver. At the receiver, the received signal can be inversely transformed using an inverse OTFS transform, and the resulting signal can be demultiplexed into signals originating from multiple user facilities.

[0044] Example of a multi-user downlink transmission scheme

[0045] Figure 4 This illustration shows an example of three users sharing a transmission after passing through three different channels and receiving it from three different receivers. Each user decodes only its specific data. As depicted, a single transmitter can multiplex signals from multiple user facilities, transforming them into an OFDM time-frequency grid, optionally adding a reference signal, and transmitting them to the user facilities. At the user facilities, each user facility can receive the transmission and extract the data intended to be transmitted to the user facility.

[0046] Examples of Multi-User Iterative Receiver Implementations

[0047] One possible implementation of a multi-user receiver includes an iterative scheme in which an equalizer obtains extrinsic prior information about user symbols. This extrinsic information may include information that allows the receiver device to successfully demultiplex signals transmitted from multiple transmitters. For example, the extrinsic information may include the schedules allocated to the multiple transmitters. The equalizer may perform linear minimum mean square error (MMSE) filtering for each user device to extract the corresponding estimated symbols on a time-frequency grid. These symbols are then transformed into a delay-Doppler grid using an inverse OTFS transform, converted to bit likelihood, and possibly decoded using forward error correction (FEC). Based on the FEC for each user, the likelihood of the coded bits is converted into prior information for the symbols and transformed back to the time-frequency grid using an OTFS transform. The equalization for each particular user may also take into account the prior information of all other users. Figure 5 An example of such a receiver for three uplink users is shown. An equivalent receiver for downlink users may contain only a single processing chain for the specific target user.

[0048] Multiplexing in the time-frequency domain

[0049] Generally, other types of multiplexing are also possible in various embodiments, such as multiplexing users in a time-frequency grid. Figure 6 Or a combination of delay-Doppler multiplexing and time-frequency multiplexing. Figure 7 In particular, such as Figure 7 As described, in some embodiments, multiplexing can be implemented in two stages. In the first stage, transmissions from multiple user facilities in a first group can be multiplexed in the delay dimension, and a second group can be multiplexed separately in the delay dimension (or along another suitable dimension of the multidimensional resource grid). The resulting signal output can then be multiplexed in the frequency domain into a first user group (user group 1) and a second user group (user group 2). Figure 7 In this context, user device 1, user device 2, etc., in the first user group and the second user group can represent different user devices. Generally, user groups can have different numbers of user devices (N1 and N2, where N1 and N2 are equal to 1 or more).

[0050] Figure 8 This is a flowchart of an example method 800 for performing downlink transmission from a transmitter to multiple user devices using transmission resources from a multidimensional resource grid. The method includes logically partitioning (802) the transmission resources into multiple segments, assigning (804) one or more of the transmission resources from the multiple segments to a given user device among the multiple user devices, and performing (806) downlink transmission by using at least some of the transmission resources assigned to the given user device to perform an orthogonal time-frequency space (OTFS) transformation on the data or signal to be transmitted to the given user device.

[0051] In some embodiments, the logical partitioning of transmission resources includes multiplexing transmission resources along one dimension of a multidimensional resource grid. In some embodiments, the multidimensional resource grid includes a delay dimension and a Doppler dimension, and multiplexing transmission resources includes multiplexing transmission resources along the delay dimension. Alternatively, in some embodiments, the multidimensional resource grid includes a delay dimension and a Doppler dimension, and multiplexing transmission resources includes multiplexing transmission resources along the Doppler dimension. In some embodiments, the multidimensional grid or resource includes a time dimension and a frequency dimension, and multiplexing transmission resources includes multiplexing transmission resources along the frequency dimension. In some embodiments, the multidimensional grid or resource includes a time dimension and a frequency dimension, and multiplexing transmission resources includes multiplexing transmission resources along the time dimension.

[0052] In some embodiments, downlink transmissions include a reference signal to enable channel estimation by a given user equipment. For example, the reference signal is based on the identifier of the given user equipment. In some embodiments, the multidimensional grid may represent a two-dimensional resource grid, such as a time-frequency grid or a delay-Doppler resource grid. In some embodiments, the partitioning of resources may be non-uniformly spaced within the multidimensional resource grid. For example, some user equipments may be allocated more transmission resources than others based on their application layer bandwidth requests.

[0053] Figure 9 This is a flowchart of an example method 900 for performing uplink transmissions from multiple user equipments using transmission resources from a multidimensional resource grid to a receiving device. Method 900 includes logically partitioning (902) transmission resources into multiple segments, assigning (904) one or more of the multiple segments of transmission resources to a given user equipment among the multiple user equipments, and performing (906) uplink transmissions from the given user equipment using at least some of the transmission resources assigned to the given user equipment, wherein the uplink transmissions contain data that has undergone orthogonal time-frequency space (OTFS) transformation.

[0054] In some embodiments, the logical partitioning of transmission resources includes multiplexing transmission resources along one dimension of a multidimensional resource grid. In some embodiments, the multidimensional grid or resource includes a delay dimension and a Doppler dimension, and multiplexing transmission resources includes multiplexing transmission resources along the delay dimension. In some embodiments, the multidimensional grid or resource includes a delay dimension and a Doppler dimension, and multiplexing transmission resources includes multiplexing transmission resources along the Doppler dimension. In some embodiments, the two-dimensional grid or resource includes a delay dimension and a Doppler dimension, and multiplexing transmission resources includes multiplexing transmission resources along the frequency dimension. In some embodiments, the two-dimensional grid or resource includes a delay dimension and a Doppler dimension, and multiplexing transmission resources includes multiplexing transmission resources along the time dimension.

[0055] In some embodiments, the uplink transmission includes a reference signal to enable channel estimation by the receiving device. The reference signal may be based on an identifier of the received signal. For example, the reference signal may be specifically designed to allow the receiving design to perform channel equalization and other optimization functions.

[0056] Figure 10 An example of a wireless transceiver device 500 is shown. Device 500 can be used to implement method 200. Device 500 includes a processor 502 and a memory 504 that stores processor-executable instructions and data during computations performed by the processor. Device 500 includes receiving and / or transmitting circuitry 506, for example, including radio frequency operations for receiving or transmitting signals.

[0057] Figure 11 This is a flowchart of a method 1100 for performing a transmission between a wireless device and a plurality of user devices. Method 1100 includes: logically grouping (1102) a plurality of user devices into a first group of user devices and a second group of user devices; allocating (1104) a first group of transmission resources to the first group of user devices and allocating (1104) a second group of transmission resources to the second group of user devices by multiplexing along a first dimension of a first multidimensional representation of the transmission resources; allocating (1106) transmission resources from the first group of transmission resources to user devices in the first group by multiplexing along a second dimension of a second multidimensional representation of the transmission resources; and performing (1108) a transmission between the wireless device and at least one user device using the corresponding allocated transmission resources.

[0058] In some embodiments, the first multidimensional representation includes a time-frequency representation, and the second multidimensional representation includes a delay-Doppler representation. In various embodiments, the first dimension may be a frequency or time dimension, and the second dimension may be a delay or Doppler dimension. In some embodiments, the user group may include one or more devices.

[0059] Figure 12 This is a flowchart of a method 1200 for receiving an orthogonal time-frequency space (OTFS) signal, the OTFS signal comprising multiplexing of transmissions from multiple transmitting devices. Method 1200 includes performing (1202) joint equalization on the multiplexing to generate jointly equalized symbols, extracting (1204) symbols corresponding to a given transmitting device from the jointly equalized symbols based on extrinsic information about the transmission resource locations of the symbols, demapping (1206) the extracted symbols and performing forward error correction to generate output bits, and generating (1208) a feedback signal based on the output bits to improve the joint equalization in the next iteration.

[0060] In some embodiments, generating a feedback signal includes performing symbol mapping, followed by OTFS transformation on the result of the symbol mapping to generate the feedback signal. In some embodiments, generating output bits for a user device includes performing inverse OTFS modulation.

[0061] Figure 13 A flowchart representation of method 1300 for receiving an orthogonal time-frequency space (OTFS) signal, the OTFS signal comprising transmit multiplexing for multiple receiving devices. Method 1300 includes performing (1302) joint equalization on the multiplexing to generate jointly equalized symbols, extracting (1304) symbols corresponding to one or more receiving device phases from the jointly equalized symbols, demapping the extracted symbols and performing forward error correction to generate output bits, and generating (1306) a feedback signal based on the output bits to improve the joint equalization in the next iteration.

[0062] In some embodiments, generating a feedback signal includes performing symbol mapping, followed by OTFS transformation on the result of the symbol mapping to generate the feedback signal. In some embodiments, generating output bits for a receiving device includes performing inverse OTFS modulation.

[0063] It should be understood that the disclosed techniques can be used to improve the reception performance of wireless devices and / or reduce the complexity of implementation methods.

[0064] The disclosed and other embodiments, modules, and functional operations described herein can be implemented in digital electronic circuits, or in computer software, firmware, or hardware (including the structures disclosed herein and their 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 control of the operation of a data processing device. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a combination of substances influencing machine-readable propagation signals, or a combination of one or more of these. The term "data processing device" encompasses all devices, apparatuses, and machines for processing data, including, for example, programmable processors, computers, or multiple processors or computers. In addition to hardware, the device may contain code that creates an execution environment for the computer program under discussion, for example, code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of these. The propagation signal is an artificially generated signal, such as a machine-generated electrical signal, optical signal, or electromagnetic signal, which is generated to encode information for transmission to a suitable receiver device.

[0065] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any programming language, including compiled or interpreted languages, and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in markup language documentation), in a single file dedicated to the program in question, or in multiple coordinating files (e.g., files storing one or more modules, subroutines, or portions of code). A computer program can be deployed to be executed on a single computer or on multiple computers located at a single site or distributed across multiple sites and interconnected via a communication network.

[0066] The processes or logic flows described in this document can be executed by one or more programmable processors that execute one or more computer programs to perform functions by manipulating input data and generating outputs. These processes or logic flows can also be executed by devices, and the devices can be implemented as special-purpose logic circuits, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits).

[0067] As examples, processors suitable for executing computer programs include general-purpose and special-purpose microprocessors, as well as any one or more processors in any type of digital computer. Typically, a processor receives instructions and data from read-only memory or random access memory, or both. Essential components of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more storage devices (e.g., magnetic disks, magneto-optical disks, or optical disks) for storing data, or operatively coupled to receive data from or transmit data to, or both receive and transmit data to, or transmit data to. However, a computer does not need to 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, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROMs and DVD-ROMs. The processor and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0068] Although this patent document contains numerous details, these details should not be construed as limiting the scope of the claimed invention or any claimable invention, but rather as descriptions of features specific to particular embodiments. Some features described in this document in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Moreover, although features above may be described as operating in certain combinations and even initially claimed in this way, one or more features from the claimed combination may, in certain circumstances, be separate from the combination, and the claimed combination may be for sub-combinations or variations thereof. Similarly, although operations are depicted in a specific order in the drawings, this should not be construed as requiring such operations to be performed in the specific order shown or in an ordered sequence, or that all described operations may be performed to achieve the desired result.

[0069] Only a few examples and implementations are disclosed. Variations, modifications, and enhancements to the described examples and implementations, as well as other implementations, can be made based on the disclosed content.

Claims

1. A wireless communication method for performing transmissions between a wireless device and a plurality of user devices, comprising: The plurality of user devices are logically grouped into a first group of user devices and a second group of user devices; By multiplexing along the first dimension of the first multidimensional representation of the transmission resources, a first set of transmission resources is allocated to the first group of user equipment, and a second set of transmission resources is allocated to the second group of user equipment. The transmission resources are allocated from the first group of transmission resources to user devices in the first group of user devices by multiplexing along the second dimension of the second multidimensional representation of the transmission resources; as well as Transmission is performed between the wireless device and at least one user device using the corresponding allocated transmission resources.

2. The method of claim 1, wherein the first multidimensional representation comprises a time-frequency representation, and the second multidimensional representation comprises a delay-Doppler representation.

3. The method according to claim 2, wherein the first dimension represented by the first multidimensionality includes a frequency dimension.

4. The method according to claim 2, wherein the first dimension represented by the first multidimensionality includes a time dimension.

5. The method of claim 2, wherein the second dimension represented by the second multidimensionality includes a delay dimension.

6. The method of claim 2, wherein the second dimension represented by the second multidimensionality includes a Doppler dimension.

7. The method of claim 2, wherein the transmission is performed from the wireless device to the at least one user device.

8. The method of claim 2, wherein the transmission is performed from the at least one user device to the wireless device.

9. The method according to any one of claims 1 to 8, wherein the first group of user equipment comprises one or more receiving devices, and the second group of user equipment comprises one or more receiving devices.

10. The method of claim 1, wherein the transmission includes a reference signal to enable channel estimation by a given receiving device.

11. The method of claim 10, wherein the reference signal is based on an identifier of a transmitting device corresponding to the given receiving device.

12. A wireless communication device comprising a processor configured to implement the method of any one of claims 1 to 11.

13. A wireless communication device comprising a memory for storing instructions and a processor, wherein, When executed by the processor, the instructions cause the processor to perform the method described in any one of claims 1 to 11.

Images