Transmitting data to network node, receiving data from network node, and determining constellation points for signal transmission

Abstract

Methods and apparatus are provided. In an example, a method of communicating data to a network node is provided. The method includes selecting one of a plurality of first constellation points on the Grassmann manifold based on data to be transmitted to the network node, where the first constellation points include a plurality of groups of the first constellation points, and a distance between the first constellation points in each group is less than a distance between the groups of the first constellation points. The method further includes transmitting a sequence of reference signal symbols associated with the selected first constellation point to a network node.

Description

Technical Field

[0001] Example embodiments of the present disclosure relate to transmitting data to and / or receiving data from a network node, such as, for example, a reference signal symbol sequence. Example embodiments also relate to determining constellation points for signal transmission, such as, for example, constellation points on a Grassmannian manifold. Background Art

[0002] The demand for wireless communications, such as for example according to fifth generation (5G) standards and beyond, has continued to grow, leading to the fact that communication technologies that can achieve high spectral efficiency while reducing computational complexity and energy usage will become increasingly important given the limited radio spectrum.

[0003] In some examples of wireless communications, a receiver requires channel information (also known as channel state information, CSI) to detect a data sequence transmitted from a UE. The accuracy of CSI affects the overall performance of data transmission, such as spectral efficiency. In order to obtain CSI between a base station and a UE, a training method based on reference signals has been used. In such a scenario, the UE transmits pilot (i.e., reference) symbols known by both the transmitter and the receiver, and the receiver estimates the CSI based on the pilot symbols. Although this training method results in reliable and high-precision channel estimation, the associated pilot overhead leads to a decrease in overall spectral efficiency.

[0004] To reduce pilot overhead and improve spectrum efficiency, many methods have been proposed, such as the superimposed pilot method, which simultaneously transmits pilot and data by simply adding a pilot signal to the data signal and transmitting the combination within the same time and frequency resource block. However, this superimposed pilot method is limited in terms of channel estimation accuracy.

[0005] New Radio (NR) uses CP-OFDM (Cyclic Prefix Orthogonal Frequency Division Multiplexing) in both the downlink (DL) (i.e., from the network node, gNB, or base station to the user equipment, or UE) and uplink (UL) (i.e., from the UE to the gNB). Discrete Fourier Transform (DFT)-spread OFDM is also supported in the uplink. In the time domain, the NR downlink and uplink are organized into equal-sized subframes of 1 ms each. The subframes are further divided into multiple slots of equal duration. The slot length depends on the subcarrier spacing. For a subcarrier spacing of Δf = 15 kHz, there is only one slot per subframe, and each slot consists of 14 OFDM symbols. Data scheduling in NR is typically based on slots. Figure 1An example of an NR time domain structure with 15kHz subcarrier spacing is shown in Figure 1, which has a 14-symbol time slot, where the first two symbols contain the Physical Downlink Control Channel (PDCCH) and the remaining symbols contain the Physical Shared Data Channel, either PDSCH (Physical Downlink Shared Channel) or PUSCH (Physical Uplink Shared Channel).

[0006] Different subcarrier spacing values ​​are supported in NR. The supported subcarrier spacing values ​​(also called different parameter sets) are given by Δf = (15 × 2 μ )kHz, where μ = {0, 1, 2, 3, 4}. Δf = 15kHz is the basic subcarrier spacing. The time slot duration under different subcarrier spacing is given by given.

[0007] In the frequency domain, the system bandwidth is divided into resource blocks (RBs), each of which corresponds to 12 consecutive subcarriers. RBs are numbered starting with 0 from one end of the system bandwidth. Figure 2 An example of an NR physical time-frequency resource grid is shown in FIG, where only one resource block (RB) within a 14-symbol slot is shown. One OFDM subcarrier during one OFDM symbol interval forms one resource element (RE).

[0008] In NR Rel-15, the PDCCH can be used to dynamically schedule uplink data transmission. The UE first decodes the uplink grant in the PDCCH and then transmits data on the PUSCH based on the decoded control information in the uplink grant, such as the modulation order, coding rate, uplink resource allocation, etc.

[0009] The demodulation reference signal (DM-RS) for PUSCH consists of an UL reference signal consisting of a pseudo-random QPSK sequence for CP-OFDM or a low peak-to-average power ratio (PAPR) sequence for DFT-S-OFDM. The DM-RS is used for PUSCH demodulation, enabling the receiver (i.e., gNB) to handle time-varying and frequency-selective channels. The DM-RS is limited to the scheduled PUSCH bandwidth and duration.

[0010] The mapping of DM-RS to REs is configurable in both the frequency and time domains. In the frequency domain, there are two mapping types: Type 1 (comb-based) or Type 2 (non-comb-based). In the time domain, DM-RS can be single-symbol or dual-symbol, where the latter means that the DM-RS is mapped in pairs of two adjacent symbols. In addition, the UE can be configured with one, two, three, or four single-symbol DM-RSs and one or two dual-symbol DM-RSs. In low Doppler scenarios, one DM-RS symbol may be sufficient, while in high Doppler scenarios, additional DM-RS symbols may be required.

[0011] The frequency domain starting position of DM-RS is the same as the frequency domain starting position of PUSCH. The time domain starting position of DM-RS depends on the PUSCH mapping type:

[0012] For PUSCH mapping type A (slot-based scheduling), the first DM-RS symbol is in the third or fourth symbol of the slot (i.e., symbol 2 or 3), as configured by the higher-layer parameter DM-RS-TypeA-Position in the Master Information Block (MIB) broadcast by the gNB.

[0013] For PUSCH mapping type B (non-slot-based scheduling), the first DM-RS symbol of a slot is the same as the first PUSCH symbol of the slot.

[0014] The DM-RS for PUSCH is configured in the Radio Resource Control (RRC) through the DM-RS-UplinkConfig information element (IE) for PUSCH scheduled via Downlink Control Information (DCI) format 0_1 ​​or DCI format 0_2. According to 3GPP TS 38.331 version 16.1.0, the DM-RS for PUSCH is configured in RRC.

[0015] DM-RS for PUSCH can be configured for the following aspects:

[0016] DM-RS frequency domain mapping type (Type 1 or Type 2), configured by the RRC parameter DM-RS-Type. Type 1 is a comb based on 2 code division multiplexing (CDM) groups, while Type 2 is not a comb based on 3 CDM groups. For DFT-S-OFDM, only Type 1 is supported. Figure 3 The symbol positions of DM-RS symbols for two DM-RS types 1 and 2 in a resource block are shown. Specifically, Figure 3 (a) shows the DM-RS symbol position of a DM-RS type 1 single symbol; Figure 3 (b) shows the DM-RS symbol position of DM-RS type 1 double symbol; Figure 3 (c) shows the DM-RS symbol position of a DM-RS type 2 single symbol; and Figure 3 (d) shows the DM-RS symbol positions for DM-RS type 2 double symbols. Figure 3 In (a)-(d), the shaded resource element indicates the DM-RS symbol transmitted in that resource element. Note that each CDM group has multiple DM-RS ports, separated by frequency domain (and time domain, for dual-symbol DM-RS) orthogonal cover codes (OCC):

[0017] o For single-symbol DM-RS, there are 4 and 6 orthogonal DM-RS ports for type 1 and type 2, respectively (2 DM-RS ports per CDM group, separated by a frequency-domain orthogonal cover code FD-OCC of length 2).

[0018] For dual-symbol DM-RS, there are 8 and 12 orthogonal DM-RS ports for type 1 and type 2, respectively (4 DM-RS ports per CDM group, separated using a frequency-domain orthogonal cover code (FD-OCC) of length 2 in combination with a time-domain orthogonal cover code (TD-OCC) of length 2).

[0019] Any additional DM-RS symbols (0, 1, 2, or 3 for single-symbol DM-RS, and 0 or 1 for dual-symbol DM-RS) are configured by the RRC parameter DM-RS-AdditionalPosition. The position of the additional DM-RS depends on the PUSCH mapping type and PUSCH duration according to a predefined table. Note that it is not possible to configure TD-OCC on additional (i.e., non-contiguous) DM-RS. Figure 4 An example of the symbol position of DM-RS symbols of DM-RS type 1 with additional DM-RS symbols in a resource block is shown. Specifically, Figure 4 (a) shows the DM-RS symbol positions for DM-RS type 1 (single symbol) with two additional DM-RS symbols, and Figure 4 (b) shows the DM-RS symbol positions of DM-RS type 1 (double symbol) with one additional DM-RS symbol.

[0020] • The associated Phase Tracking Reference Signal (PT-RS), if any, may be configured by the RRC parameter phaseTrackingRS.

[0021] • The maximum number of adjacent DM-RS symbols (1 or 2) can be configured by the RRC parameter maxLength.

[0022] If transform precoding is disabled (i.e., if the waveform is CP-OFDM), the DM-RS for PUSCH can be additionally and optionally configured for scrambling IDs 0 and 1, which are configured by the RRC parameters scramblingID0 and scramblingID1, respectively, which are used to generate pseudo-random DM-RS sequences.

[0023] DM-RS ports are mapped to resource elements within a CDM group. DM-RS ports belonging to the same CDM group are separated by an FD-OCC of length 2 (and a TD-OCC of length 2 for dual-symbol DM-RS). In NR Rel-16, DM-RS sequences are mapped to the following subcarriers (for DFT-S-OFDM, only DM-RS type 1 is supported):

[0024]

[0025] Here, k is the subcarrier index (which starts / ends at the first / last subcarrier within the scheduled PUSCH bandwidth), n∈{0,1,2,...}, k′∈{0,1} and Δ is an offset that depends on the CDM group.

[0026] In Tables 1 and 2, we show the port-specific parameters for DM-RS Type 1 and Type 2. Here, w f (k′) (where k′∈{0,1}) is FD-OCC, and w t (l') (where l' = 0 for single-symbol DM-RS and l' ∈ {0, 1} for dual-symbol DM-RS) is the TD-OCC. Note that DM-RS ports in different CDM groups are separated by different offsets, and DM-RS ports within the same CDM group are separated by coding.

[0027] Table 1: Parameters for PUSCH DM-RS configuration type 1 (copied from Table 6.4.1.1.3-1 of 3GPP TS 38.211). Here, Refers to the DM-RS port.

[0028]

[0029] Table 2: Parameters for PUSCH DM-RS configuration type 2 (copied from Table 6.4.1.1.3-2 of 3GPP TS 38.211). Here, Refers to the DM-RS port.

[0030]

[0031] From the transmitter's perspective, the number of DM-RS ports used for PUSCH transmission corresponds to the transmission rank, i.e., one DM-RS port per transmission layer. The DM-RS port mapping is signaled from the gNB to the UE via DCI. Tables 3 and 4 below show this indication for DCI 0_1, CP-OFDM, single-symbol DM-RS type 1, and for transmission ranks 1 and 2, respectively. Similar tables can be found in 3GPP TS 38.212 Version 16.10.0 for ranks 3 and 4, dual-symbol DM-RS, and DM-RS type 2. Subcarriers associated with the CDM group that are not used for DM-RS can be used for PUSCH. After layer mapping, the DM-RS and associated PUSCH are mapped to the physical antennas using precoding.

[0032] Table 3: Antenna ports for single-symbol DM-RS type 1, transform precoding disabled, rank 1 transmission (copied from Table 7.3.1.1.2-8 of 3GPP 38.212 Version 16.10.0).

[0033]

[0034] Table 4: Antenna ports for single-symbol DM-RS type 1, transform precoding disabled, rank 2 transmission (copied from Table 7.3.1.1.2-9 of 3GPP 38.212 Version 16.10.0).

[0035]

[0036] The training methods mentioned above are already used in typical wireless communication standards. For high-mobility scenarios, spectral efficiency inevitably deteriorates due to the fact that more reference symbols are required to accurately track and estimate the changing channel, which increases communication overhead. This necessitates finding methods to eliminate or reduce the overhead caused by the use of reference symbols to achieve higher spectral efficiency for 5G-advanced and beyond.

[0037] One approach to addressing pilot overhead is to use differential space-time coding (DSTC). This eliminates the need for periodic pilot symbols and supports scenarios where CSI fluctuates rapidly over time. By encoding information into the signal differences between time slots, it enables non-coherent detection. However, due to the nature of differential coding, one must tolerate a maximum 3dB loss in signal-to-noise ratio (SNR) and low spectral efficiency.

[0038] Semi-blind methods have been proposed to reduce pilot overhead. These methods first roughly estimate CSI using a short reference signal sequence and aim to improve it by utilizing data and performing joint channel and data detection. While this approach improves spectral efficiency compared to its coherent counterpart, transmitting reference signals still limits the improvement.

[0039] Another approach estimates CSI by using the second-order statistics of the received signal and algebraic properties of the symbols. The main problem with this approach is the difficulty in determining the phase of the channel response in the complex domain, resulting in poor channel estimation performance. To address this issue, pilot elements are transmitted or asymmetric constellations are used. This uses orthogonal space-time block coding (OSTBC) symbols and estimates CSI based on the covariance matrix of the received signal. This requires a long coherence time to obtain CSI, resulting in significant latency.

[0040] Finally, some methods superimpose pilot symbols onto data symbols in the complex domain. This enables simultaneous estimation of the channel and data at the receiver. In massive MIMO scenarios, superimposed pilots can effectively mitigate pilot contamination in both uplink and downlink. However, this approach reduces spectral efficiency as the transmit power allocated to data symbols decreases.

[0041] In general, the above methods are shown to be limited in terms of channel estimation performance or spectrum efficiency [1], while being incompatible with the 3GPP standard signaling structure. Summary of the Invention

[0042] Examples of the present disclosure may have certain advantages. For example, embodiments of the present disclosure may provide signal constellations or related symbol sequences that allow for reduced decoding complexity while maintaining or substantially maintaining channel estimation performance and / or symbol error rate (SER) performance.

[0043] One aspect of the present disclosure provides a method (500) for transmitting data to a network node. The method includes selecting one of a plurality of first constellation points on a Grassmann manifold based on the data to be transmitted to the network node, wherein the first constellation point includes a plurality of groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between the groups of first constellation points. The method also includes transmitting a reference signal symbol sequence associated with the selected first constellation point to the network node.

[0044] Another aspect of the present disclosure provides a method (600) for receiving data from a network node. The method includes receiving (602) a reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold from the network node, wherein the first constellation point comprises a plurality of groups of first constellation points, and a distance between the first constellation points in each group is less than a distance between the groups of first constellation points. The method also includes determining data transmitted by the network node based on the reference signal symbol sequence.

[0045] Another aspect of the present disclosure provides a method for determining a plurality of first constellation points for signal transmission. The method includes selecting a plurality of second constellation points on a Grassmann manifold and mapping each second constellation point to a group of first constellation points on the Grassmann manifold such that a distance between the first constellation points in each group is less than a distance between groups of first constellation points.

[0046] Additional aspects of the present disclosure provide an apparatus for transmitting data to a network node. The apparatus includes a processor and a memory. The memory contains instructions executable by the processor, such that the apparatus is operable to: select one of a plurality of first constellation points on a Grassmann manifold based on the data to be transmitted to the network node, wherein the first constellation points include a plurality of groups of first constellation points, and a distance between the first constellation points in each group is less than a distance between the groups of first constellation points; and transmit a reference signal symbol sequence associated with the selected first constellation point to the network node.

[0047] Another aspect of the present disclosure provides an apparatus for receiving data from a network node. The apparatus includes a processor and a memory. The memory contains instructions executable by the processor, such that the apparatus is operable to: receive, from the network node, a reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold, wherein the first constellation point comprises a plurality of groups of first constellation points, and a distance between the first constellation points in each group is less than a distance between the groups of first constellation points; and determine data transmitted by the network node based on the reference signal symbol sequence.

[0048] Another aspect of the present disclosure provides an apparatus for determining a plurality of first constellation points for signal transmission. The apparatus includes a processor and a memory. The memory contains instructions executable by the processor, causing the apparatus to: select a plurality of second constellation points on a Grassmann manifold, and map each second constellation point to a group of first constellation points on the Grassmann manifold such that a distance between the first constellation points in each group is less than a distance between groups of first constellation points.

[0049] Yet another aspect of the present disclosure provides an apparatus for transmitting data to a network node. The apparatus is configured to: select one of a plurality of first constellation points on a Grassmann manifold based on the data to be transmitted to the network node, wherein the first constellation points include a plurality of groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between the groups of first constellation points; and transmit a reference signal symbol sequence associated with the selected first constellation point to the network node.

[0050] Another aspect of the present disclosure provides an apparatus for receiving data from a network node. The apparatus is configured to: receive, from the network node, a reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold, wherein the first constellation point comprises a plurality of groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between the groups of first constellation points; and determine data transmitted by the network node based on the reference signal symbol sequence.

[0051] Additional aspects of the present disclosure provide an apparatus for determining a plurality of first constellation points for signal transmission. The apparatus is configured to select a plurality of second constellation points on a Grassmann manifold and map each second constellation point to a group of first constellation points on the Grassmann manifold such that a distance between the first constellation points in each group is less than a distance between groups of first constellation points. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] For a better understanding of examples of the present disclosure, and to more clearly show how the same may be implemented, reference will now be made, by way of example only, to the following drawings, in which:

[0053] Figure 1 An example of an NR time domain structure with 15kHz subcarrier spacing is shown;

[0054] Figure 2 An example of an NR physical time-frequency resource grid is shown;

[0055] Figure 3 The symbol positions of DM-RS symbols for DM-RS types 1 and 2 in a resource block are shown;

[0056] Figure 4 An example of symbol positions of DM-RS symbols in a resource block for DM-RS type 1 with additional DM-RS symbols is shown;

[0057] Figure 5 shows examples of the normalized mean square error (NMSE) performance of different Grassmann constellations when used for data transmission;

[0058] Figure 6shows examples of symbol error rate (SER) performance of different Grassmann constellations when used for data transmission;

[0059] Figure 7 An example of the complexity order required to decode a matrix reference signal representing a multi-dimensional constellation point is shown;

[0060] Figure 8 is a flow chart of an example of a method of transmitting data to a network node;

[0061] Figure 9 An example of constellation points on a Grassmann manifold is shown;

[0062] Figure 10 is a flow chart of an example of a method of receiving data from a network node;

[0063] Figure 11 Examples of single-symbol and dual-symbol Type 1 Grassman DM-RS are shown;

[0064] Figure 12 An example of repetition of a Grassmann-based DM-RS sequence in the frequency domain is shown;

[0065] Figure 13 An example of a Grassmann-based DM-RS sequence that is divided into groups for DM-RS ports while utilizing consecutive OFDM symbols is shown;

[0066] Figure 14 An example of the use of both a conventional DM-RS and a DM-RS according to the present disclosure is shown;

[0067] Figure 15 is a flow chart of an example of a method of determining a plurality of first constellation points for signal transmission;

[0068] Figure 16 shows examples of decoding complexity for examples of the present disclosure and prior art methods;

[0069] Figure 17 Examples of symbol error rate (SER) performance relative to signal-to-noise ratio (SNR) are shown for examples of the present disclosure and prior art methods;

[0070] Figure 18 An example of the normalized mean square error (NMSE) performance relative to SNR of the disclosed embodiments and prior art methods is shown;

[0071] Figure 19 is a schematic diagram of an example of an apparatus for transmitting data to a network node;

[0072] Figure 20is a schematic diagram of an example of an apparatus for receiving data from a network node; and

[0073] Figure 21 is a schematic diagram of an example of an apparatus for determining a plurality of first constellation points for signal transmission. DETAILED DESCRIPTION

[0074] For the purpose of explanation and not limitation, specific details, such as specific embodiments or examples, are described below. Those skilled in the art will appreciate that, in addition to these specific details, other examples may also be used. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted to avoid obscuring the description with unnecessary details. Those skilled in the art will appreciate that hardware circuits (e.g., analog and / or discrete logic gates, application-specific integrated circuits (ASICs), programmable logic arrays (PLAs), etc., interconnected to perform dedicated functions) and / or software programs and data may be used in conjunction with one or more digital microprocessors or general-purpose computers to implement the described functions in one or more nodes. Nodes communicating using an air interface also have suitable radio communication circuits. In addition, where appropriate, the technology may additionally be considered to be fully embodied in any form of computer-readable memory, such as solid-state memory, magnetic disks, or optical disks, containing an appropriate set of computer instructions that will cause a processor to execute the technology described herein.

[0075] Hardware implementations may include or comprise, but are not limited to, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry, including but not limited to application specific integrated circuit(s) (ASICs) and / or field programmable gate array(s) (FPGA(s)), and, where appropriate, state machines capable of performing such functionality.

[0076] Example embodiments of the present disclosure may enable improvements in spectral efficiency by replacing reference signals (e.g., DM-RS in NR) with codewords (such as, for example, codewords from a Grassmann manifold), where each codeword may convey a data bit. Example embodiments may also reduce the impact of overhead from reference signals such as DM-RS. This may be particularly beneficial in networks such as, for example, 5G and 6G networks, which may have very small amounts of data to transmit and therefore the overhead caused by reference signal symbols may be significant. It is assumed that in the future, networks may need to be adapted to transmit smaller chunks of data, such as, in some examples, a data chunk that may be carried by only one symbol of a resource block (RB). Therefore, reducing the impact of reference signals is particularly useful, such as in the example methods of the present disclosure, which may utilize reference signal symbols to transmit data.

[0077] As disclosed herein, the challenge of constructing a Grassmann constellation for an example of Grassmann-based reference signal and data transmission is the tradeoff between the estimation performance of the reference signal X and the channel H. More specifically, for example, in Figure 5 and Figure 6 The normalized mean square error (NMSE) and symbol error rate (SER) performance of different Grassmann constellations for data transmission are shown in Figure 2, where the NMSE and SER performance are shown relative to the signal-to-noise ratio (SNR). The constellations for which performance is shown are Exponential Mapping, Cube-Split, and ManOpt, while the NMSE performance of the Zadoff-Chu sequence (ZCS) is included as a baseline. Figure 5 Note that ZCS is a conventional reference signaling method and may not transmit data, unlike the Grassmann sequences used in this paper; therefore, it can be considered as a channel estimation performance baseline, for example. The ManOpt constellation is a numerically optimized Grassmann constellation for which the performance is demonstrated using the publicly available optimization solver "Pymanopt."

[0078] Figure 7 An example of the level of complexity required to decode a matrix reference signal X representing the number of bits B represented by the constellation points (or corresponding codewords or symbol sequences) is shown. Figure 5 and Figure 6 The decoding process can be, for example, the process described in equation (2) below. Figure 7 As shown in , the level of complexity required to decode the reference signal X increases exponentially with respect to the number of bits encoded by the constellation points or codewords. That is, increasing the number of bits allows more data to be sent within a given resource block, while increasing the decoding complexity.

[0079] Compare Figure 5 and Figure 6 From the SER and NMSE performance shown in

[15] , it can be seen that there is a clear trade-off between SER and NMSE. In other words, exponential mapping is the best of the methods shown in terms of channel estimation performance, but the worst in terms of SER performance. Similarly, the Cube-Split and ManOpt methods are shown to perform better than exponential mapping in terms of SER, but at the expense of worse channel estimation performance. In view of the above, the Grassmann constellation method, which addresses this trade-off (i.e., improving channel estimation NMSE performance while maintaining SER performance), is the focus of example embodiments of the present disclosure.

[0080] In summary, embodiments of the present disclosure can provide transmitter and receiver methods, signal constellation constructions, and corresponding devices that allow signals such as data-carrying reference signaling to achieve similar NMSE performance with minimal SER loss compared to prior art methods, while significantly reducing decoding complexity. For example, the disclosed methods can provide a grouping structure within Grassmann codewords, resulting in an exponential reduction in the decoding search space. Simulation results demonstrate that, in some examples, decoding complexity can be approximately 10 times lower than prior art methods while maintaining comparable SER and NMSE performance.

[0081] Figure 8 8 is a flow chart of an example of a method 800 for transmitting data to a network node. In some examples, the network node is a radio access network (RAN) node, such as a base station, gNodeB, eNodeB, etc. In such examples, the method 800 may be performed by a user equipment (UE). Alternatively, in some examples, the network node is a UE, and the method 800 may be performed by a RAN node, such as a base station, gNodeB, eNodeB, etc.

[0082] The method includes, in step 802, selecting one of a plurality of first constellation points on a Grassmann manifold based on data to be transmitted to a network node, wherein the first constellation points include a plurality of groups of first constellation points, and a distance (e.g., a Euclidean distance) between the first constellation points in each group is less than a distance between the groups of first constellation points. Next, step 804 of method 800 includes transmitting a reference signal symbol sequence associated with the selected first constellation point to the network node.

[0083] Since the distance between the first constellation points in each group is smaller than the distance between the groups of first constellation points, the receiver (e.g., demodulator, decoder, etc.) can use this feature to reduce complexity. For example, for a received symbol sequence, the receiver can first estimate which group the symbol sequence belongs to, and then estimate which symbol sequence among the symbol sequences in the group has been received. Therefore, compared with the example of comparing the received symbol sequence with all possible symbol sequences, the search space for estimating which symbol sequence has been received can be reduced. Figure 10 Describes other examples of methods in a receiver.

[0084] Compared to a case where the constellation points are evenly spaced (e.g., particularly in the presence of interference and / or noise), a distance between the first constellation points in each group that is smaller than a distance between groups of first constellation points can allow a receiver to more reliably estimate the group to which a received sequence belongs. In some examples, the distance between the first constellation points in each group is smaller than a distance between any two groups of first constellation points.

[0085] about Figure 8 In the method 800 of claim 1, selecting one of the plurality of first constellation points in step 802 may include selecting one of a group of first constellation points based on a network node, and selecting one of the first constellation points in the selected group based on data to be transmitted to the network node. Selecting the group based on the network node may include, for example, selecting a first group if data is being transmitted to a first network node, and selecting a different second group if data is being transmitted to a second network node. In some examples, this may implement "constellation division multiple access," where, for example, a receiver may first estimate to which group a received symbol sequence belongs. If the group is associated with the receiver, it may then estimate which sequence in the group has been received, and thereby estimate the received data, but if the group is not associated with the receiver, the receiver may ignore the received symbol (e.g., it may be intended for a different receiver).

[0086] In other words, in some examples, each group of first constellation points can be associated with one or more corresponding network nodes, the network nodes configured to receive a reference signal symbol sequence associated with the first constellation point in the group. In some examples, method 800 can include sending one or more reference signal symbol sequences associated with a first constellation point in a first group of the groups of first constellation points to one or more first network nodes. Method 800 can also include sending one or more reference signal symbol sequences associated with a first constellation point in a second group of the groups of first constellation points to one or more second network nodes. Thus, constellation division multiple access can be used, for example, to transmit different data to different network nodes.

[0087] In some examples, each group of first constellation points includes a corresponding second constellation point from a plurality of second constellation points on a Grassmann manifold mapped to the first constellation points in the group using a space-time coding matrix. Thus, for example, a constellation including second constellation points can be provided, and each of these constellation points can be mapped or converted to a corresponding group of first constellation points using a corresponding space-time coding matrix. The space-time coding matrix can be the same or different for each group of first constellation points. In some examples, the distance between the first constellation points in each group is less than the distance between any two second constellation points.

[0088] Figure 9An example of constellation points on a Grassmann manifold 900 is shown. In this particular example, a second constellation point 902 is shown on the manifold 900. Each second constellation point 902 in this example is mapped or converted to four first constellation points, and thus each group of constellation points includes four first constellation points. As an example, one of the second constellation points 902 is mapped to a group of four first constellation points 904. However, in other examples, a first constellation point may be provided on the manifold 900 without the second constellation point 902, e.g., the first constellation point may be predetermined or specified without reference to the second constellation point (although in such an example, the first constellation point may or may not be mapped from the second constellation point).

[0089] exist Figure 9 In the example shown in , the Grassmann manifold 900 has three dimensions, and therefore, in some examples, each constellation point on the manifold can be represented by three quantities. For example, a constellation point can be represented by a symbol in two resource elements (REs), with each RE specifying a phase and an amplitude, thus providing four quantities that can be used to represent a constellation point on the manifold. In this example, one quantity may not be used, and therefore a more efficient example may use constellation points on a four-dimensional manifold. More generally, any dimensional Grassmann constellation can be used, where at least an appropriate number of REs are used to convey the symbol sequence representing each constellation point. However, in a specific example, a 2n-dimensional manifold can be used, where n is the number of REs (or symbols) representing the constellation point in the symbol sequence. Here, it is assumed that each symbol or RE can convey two pieces of information, such as phase and amplitude. It should be noted that in examples of the present disclosure, a symbol sequence can include multiple two-dimensional symbols, each of which is conveyed or transmitted in a single resource element (RE).

[0090] In some examples, each first constellation point is associated with a different value of data. Thus, for example, a symbol sequence of reference signal symbols associated with a constellation point or transmission of the constellation point conveys data via the selected particular constellation point. In some examples, each first constellation point within a group of first constellation points is associated with a different value of data, while constellation points within different groups can be associated with the same value of data. This can enable schemes such as constellation division multiple access, as mentioned above and explained further below.

[0091] In a specific example, there are n reference signal symbols (or resource elements RE) in the sequence, and the number of reference signal symbol sequences from which the transmitted reference signal symbol sequence is selected (based on the selected constellation point) is 2 B , where B is the number of bits encoded in the reference signal symbol sequence.

[0092] In some examples, the Grassmann manifold can be at least a 2n-dimensional manifold, where n is the number of reference signal symbols. Thus, for example, each reference signal symbol (or resource element RE) in the sequence transmitted in step 804 can convey a two-dimensional selected constellation point on the Grassmann manifold.

[0093] In some examples, the reference signal symbol sequence can be repeated, such as, for example, in the same resource block, time slot, mini-time slot, subframe and / or frame. Method 800 can therefore include transmitting the selected reference signal symbol sequence in a plurality of first resource elements and repeating the reference signal symbols in a plurality of second resource elements. In some examples, the first plurality of resource elements can be within a first frequency range, and the second plurality of resource elements can be, for example, within a second frequency range that does not overlap with the first frequency range. The first and second plurality of resource elements can overlap, partially overlap, or not overlap in time. The first resource element and the second resource element can be, for example, within a resource block, time slot, mini-time slot, subframe and / or frame.

[0094] In some examples, the transmitted reference signal symbol sequence may correspond to the first antenna port. In such examples, method 800 may include, for each of the one or more additional antenna ports, transmitting an additional reference signal symbol sequence to the network node (e.g., in the same resource block, slot, mini-slot, subframe, and / or frame as the reference signal symbol sequence transmitted in step 804). Method 800 may also include, for each of the one or more additional antenna ports, selecting an additional reference signal symbol sequence for transmission based on a constellation point associated with the corresponding additional data to be transmitted to the network node. The constellation point may be selected in a manner similar to that selected in step 802 above, e.g., from a plurality of constellation points on a Grassmann manifold. Alternatively, for example, the additional reference signal symbol sequence(s) may include a legacy reference signal.

[0095] In some examples, method 800 may further include transmitting at least one additional reference signal symbol sequence to the network node, wherein the additional reference signal symbol sequence(s) correspond to a legacy reference signal (e.g., in the same resource block, slot, mini-slot, subframe, and / or frame as the symbol sequence transmitted in step 802). Thus, for example, a resource block, slot, mini-slot, subframe, and / or frame may include both legacy reference signal symbols and reference signal symbols conveying data.

[0096] In some examples, the transmitted reference signal symbol sequence may be a demodulation reference signal (DM-RS) or other reference signal.

[0097] Figure 101 is a flow chart of an example of a method 1000 for receiving data from a network node. In some examples, the network node is a radio access network (RAN) node, such as a base station, gNodeB, eNodeB, etc. In such examples, method 1000 may be performed by a user equipment (UE). Alternatively, in some examples, the network node is a UE, and method 1000 may be performed by a RAN node, such as a base station, gNodeB, eNodeB, etc. In some examples, the network node from which the data is received performs method 800 mentioned above.

[0098] Method 1000 includes, at step 1002, receiving a reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold from a network node, wherein the first constellation point comprises a plurality of groups of first constellation points, and a distance between the first constellation points in each group is less than a distance between the groups of first constellation points. For example, a distance between the first constellation points in each group is less than a distance between any two groups of first constellation points. Step 1004 of method 1000 includes determining data to be transmitted by the network node based on the reference signal symbol sequence.

[0099] In some examples, determining the data transmitted by the network node in step 1004 includes determining a group that includes one of the first constellation points, and then determining which of the first constellation points in the group is associated with the received reference signal symbol sequence. In some examples, this can reduce complexity at the receiver. For example, as indicated above, the search space used to estimate which symbol sequence has been received can be reduced compared to the example of comparing the received symbol sequence with all possible symbol sequences.

[0100] In some examples, method 1000 is performed by a node associated with one of the groups of constellation points. That is, for example, a reference signal transmitted using a constellation point from a particular group may be intended for only a subset of UEs, such as one or more specific UEs. For example, this may be referred to as "constellation division multiple access" as indicated above. Thus, in some examples, method 100 may include determining a group that includes one of the first constellation points, and if the determined group is a group associated with the node, determining which of the first constellation points in the group is associated with the received reference signal symbol sequence. If the determined group is not a group associated with the node, the node may ignore the received reference signal symbol sequence, or alternatively, may use the received sequence as a reference signal (e.g., for channel estimation) while ignoring the data it conveys. In such examples employing constellation division multiple access, each first constellation point in a group of first constellation points is associated with a different data value, while constellation points in different groups may be associated with the same data value (e.g., conveying the same value to different UEs associated with different groups). Otherwise, in some examples, each first constellation point in any group may be associated with a different data value.

[0101] As suggested above, in some examples, each group of first constellation points may include a corresponding second constellation point from a plurality of second constellation points on a Grassmann manifold, the corresponding second constellation point being mapped to the first constellation point in the group using a space-time coding matrix. The method of claim 28, wherein the distance between the first constellation points in each group is less than the distance between any two second constellation points.

[0102] In some examples, there may be at least 2 B First constellation points, where B is the number of data bits encoded by each reference signal symbol sequence. Additionally or alternatively, in some examples, the Grassmann manifold is at least a 2n-dimensional manifold, where n is the number of reference signal symbols in each reference signal symbol sequence.

[0103] In some examples, the reference signal symbol sequence may repeat. Method 1000 may therefore include receiving the reference signal symbol sequence in a plurality of first resource elements and receiving repetitions of the reference signal symbol sequence in a plurality of second resource elements. The first plurality of resource elements may be within a first frequency range, and the second plurality of resource elements may be, for example, within a second frequency range that does not overlap with the first frequency range. The first and second plurality of resource elements may overlap, partially overlap, or not overlap in time. The first resource element and the second resource element may be, for example, within a resource block, a time slot, a mini-time slot, a subframe, and / or a frame.

[0104] In some examples, the reference signal symbol sequence corresponds to the first antenna port. In such examples, method 1000 may include, for each of the one or more additional antenna ports, receiving a corresponding additional reference signal symbol sequence from the network node (e.g., in the same resource block, slot, mini-slot, subframe, and / or frame as the plurality of reference signal symbols selected in step 502). Method 1000 may also include, for each of the one or more additional antenna ports, determining corresponding additional data transmitted by the network node based on the additional reference signal symbol sequence. This may be determined in a manner similar to step 1004 of method 1000 described above, e.g., from a plurality of symbol sequences, from a plurality of constellation points, or from a plurality of constellation points on a Grassmann manifold. Alternatively, the additional reference symbols may include, for example, conventional reference signal symbols.

[0105] In some examples, method 1000 may further include receiving one or more additional reference signal symbol sequences from the network node, wherein the additional reference signal symbol sequence(s) correspond to a legacy reference signal (e.g., in the same resource block, slot, mini-slot, subframe, and / or frame as the reference signal symbol sequence received in step 1002). Thus, for example, a resource block, slot, mini-slot, subframe, and / or frame may include both legacy reference signal symbols that do not convey data and the reference signal symbol sequence determined or estimated in step 1004 of method 1000 that conveys data.

[0106] As indicated above, in examples of the present disclosure, a Grassmann constellation can be used to select symbols for DM-RSs that carry data, e.g., instead of conventional DM-RSs. The Grassmann manifold can be used to construct DM-RS symbols that can carry data compared to conventional DM-RS symbols. In some examples, the Grassmann-based DM-RS can be configured in a user equipment by a network node (e.g., a base station, eNodeB, gNodeB) via radio resource control (RRC) signaling.

[0107] A specific example based on the use of Grassmann manifolds is now described, although the concepts described may also be applied to other examples using other Grassmann-based constellations and / or symbol sequences.

[0108] Some non-coherent transmission methods based on Grassmann have been reported, among which several multi-dimensional Grassmann constellations have been proposed. Despite such Grassmann constellation designs, there is no prior art proposal to use the Grassmann constellation to replace the reference signal in the 5G NR configuration.

[0109] Transmission based on Grassmann manifolds

[0110] Consider a UE with M antennas transmitting to a gNB with N antennas. The received signals are concatenated over time length T, where T > M. The received signal model can be given by:

[0111] Y=XH+V, (1)

[0112] in is the received signal matrix, is the transmitted matrix constructed from the T-dimensional Grassmann manifold [1], is the effective channel matrix consisting of the precoding matrix, receiver filter, and fading channel matrix, and is the noise matrix. Next, possible methods for estimating the transmitted matrix X and the channel matrix H are described.

[0113] Estimate of the transmitted matrix X

[0114] To estimate the channel matrix, we first estimate the transmitted matrix X, where X is one of the discrete points represented by the predefined MT-dimensional Grassmann manifold. Although any reasonable detection method can be considered to detect the transmitted matrix X, the generalized likelihood ratio test (GLRT) is proposed here to solve the following maximization problem:

[0115]

[0116] in is an estimate of the transmitted matrix X, and is a set of discrete points in the MT-dimensional space defined by a predetermined Grassmann manifold. Due to the discreteness of , digital data symbols can be encoded at each discrete point in the MT-dimensional space. The difference from digital modulation is that, unlike the complex space of digital modulation schemes such as QAM or PSK (i.e., )compared to, The discrete points are defined in multidimensional space.

[0117] The estimated matrix H is transmitted

[0118] Given an estimate The channel matrix H can also be estimated by any channel estimation method that assumes knowledge of the matrix X. For example, in the case of a zero-forcing method, the estimate of H is given by:

[0119]

[0120] Alternatively, assuming that the covariance matrix Cov(V) of the receiver noise is available, the estimate H of the minimum mean square error (MMSE) estimator is given by:

[0121]

[0122] In a similar embodiment, joint detection of the matrix H and the matrix X may be considered.

[0123] In some examples, a method is provided for applying a Grassmann manifold-based DM-RS to demodulation of transmitted symbols in an NR system. Although in the following examples, the method is described for uplink NR transmission from a user equipment (UE) to a gNodeB (gNB), the method (and other methods of the present disclosure) can be applied to any general wireless communication system, including uplink, downlink, direct link, peer-to-peer, and other, as well as wireless communication systems between any two network nodes. Furthermore, in this example, PUSCH data symbols are transmitted using DM-RS, although in other examples, any reference signal or other signal can be used to transmit any data.

[0124] Unlike conventional DM-RS, data such as PUSCH data symbols in the examples of this disclosure are superimposed on the Grassmann-based DM-RS, resulting in higher spectral efficiency. Therefore, consider a user equipment (UE) with υ DM-RS antenna ports serving a gNB. Considering that the DM-RS sequences for the ports are distributed over N s The received signal of the DM-RS port transmitted on the same OFDM symbol but different subcarriers (given by Given), it can be given by the following formula:

[0125] y u =X u H u +V u , (5)

[0126] in is the received signal matrix, is a block diagonal matrix such that in is N transmitted via the i-th DM-RS port s dimensional Grassmann manifold[1], is the effective channel matrix containing the precoding matrix, receiver filter, and propagation channel matrix, and is the noise matrix. At the gNB, the transmitted matrix and the channel matrix can be estimated in a similar way to that described above. Note that although a Grassmann manifold is used in this example to describe joint pilot and data transmission, the general principle applies to any multidimensional constellation on which data symbols (PUSCH / PDSCH) can be carried.

[0127] In the example, with length N s The Grassmann sequence of each port of can be mapped to resource elements (REs) in a manner similar to the conventional type 1 DM-RS mapping described above, giving two DM-RS ports. Furthermore, in the time domain, the DM-RS can be as follows Figure 3 (a)-(d) as shown in single or double symbols. Figure 11 As shown in Two and four Grassmann-based DM-RS ports may have one and two time-domain DM-RS symbols, respectively. Figure 11 (a) shows an example of a single symbol Type 1 Grassman DM-RS, and Figure 11 (b) shows an example of a dual-symbol Type 1 Glassman DM-RS. In a related example, the Glassman-based DM-RS can be used for conventional DM-RS. Figure 3 (c) and (d) show that the type 2 pattern is mapped to REs. Note that the Grassmann-based DM-RS can be configured with arrangements other than types 1 and 2 because they can carry PUSCH thereon.

[0128] Although in the above examples, the DM-RS port for each frequency and time resource (i.e., the same subcarrier and time resource (e.g., (one or more) the same resource elements)) is limited to one, in some examples, code division multiplexing (CDM) using orthogonal cover codes (OCC) can be mapped onto the Glassman-based DM-RS to transmit more than one DM-RS port using the same frequency and time resources in some examples. In another example, where the DM-RS is a dual symbol such as type 2 mentioned above, one OFDM symbol in the dual symbol can be a traditional DM-RS, and the other OFDM symbol can be a DM-RS carrying data according to the present disclosure, such as, for example, a Glassman-based DM-RS.

[0129] In some examples of the present disclosure, the accuracy of the channel estimation depends on the frequency selectivity of the channel. For frequency-flat channels, the channels across the allocated bandwidth are equivalent, giving accurate channel estimates. However, as the frequency selectivity increases, the accuracy of the channel estimation may decrease in some examples of Grassmann-based DM-RS. In addition, the decoding complexity may increase with the length N of the Grassmann-based DM-RS sequence. s Therefore, in some examples, N s Can be divided into smaller equal length Make Therefore, the shorter based The Grassmann DM-RS sequence is repeated 1 times to cover N ssubcarriers, as proposed above with reference to method 500 or 600. This may, for example, allow estimation over a smaller bandwidth with lower frequency selectivity, while having lower complexity for each smaller sequence. As an example, in Figure 12 The above embodiment is shown in FIG, which shows an example of repetition of a DM-RS sequence based on Grassmann in the frequency domain. Specifically, Figure 12 (a) shows an example of a Grassmann-based DM-RS sequence divided into groups for DM-RS ports, where each group occupies a type 1 arrangement. subcarriers, and Figure 12 (b) shows a type 2 arrangement subcarriers.

[0130] In a related example, if a more accurate channel estimate is required, then The Grassmann-based DM-RS sequence is transmitted on two or more consecutive OFDM symbols, resulting in Modifications and:

[0131]

[0132] where T is the number of consecutive OFDM symbols, and is N transmitted through the i-th DM-RS port at the t-th OFDM symbol s dimensional Grassmann manifold [1]. This can allow more accurate channel estimation for high-frequency selective channels by exploiting the time domain. Figure 13 An example of this is shown in , where the Grassmann-based DM-RS sequences are divided into groups for DM-RS ports while utilizing T = 2 consecutive OFDM symbols.

[0133] Specifically, Figure 13 (a) shows an example of a single symbol Type 1 Grassman DM-RS, and Figure 13 (b) shows an example of a single symbol type 2 Glassman DM-RS. This example involves a front-loaded PUSCH with a duration of 14 symbols (i.e., PUSCH mapping type A). The Glassman-based DM-RS sequence is divided into groups for DM-RS ports, where each group occupies a type 1 and type 2 arrangement, respectively. subcarriers and These figures show two such groups for resource blocks, ie i=1,2.

[0134] The frequency domain and time domain starting positions of the DM-RS according to the present disclosure (such as, for example, a Glassman-based DM-RS or any other example of a data-carrying DM-RS) can follow a configuration similar to that of the conventional DM-RS described above. In low Doppler scenarios, similar to conventional DM-RS, one Glassman-based DM-RS symbol may be sufficient, while in high Doppler scenarios, additional Glassman-based DM-RS symbols may be useful or required in some examples.

[0135] Although in some examples, traditional DM-RS can have the advantages of higher channel estimation accuracy and low decoding complexity, the DM-RS according to the present disclosure (e.g., Glassman-based DM-RS) can impart additional spectral efficiency by superimposing PUSCH on the Glassman-based DM-RS sequence. Therefore, in some examples, both traditional DM-RS and DM-RS according to the present disclosure can be used (e.g., in resource blocks, time slots, mini-time slots, subframes and / or frames) to achieve the advantages of both traditional DM-RS and DM-RS according to the present disclosure. For example, in a high Doppler scenario, the first DM-RS symbol in a resource block can be a traditional DM-RS, and subsequent DM-RS can be a DM-RS according to the present disclosure, such as, for example, a Glassman-based DM-RS. In Figure 14 An example is shown in . Specifically, for a single symbol DM-RS, Figure 14 (a) shows an example of configuring one additional DM-RS position for Type 1, and Figure 14 (b) shows an example of configuring one additional DM-RS position for type 2. This example involves a preamble PUSCH with a duration of 14 symbols (i.e., PUSCH mapping type A). The first DM-RS symbol uses a legacy sequence, while the two additional DM-RS symbols in the slot use a Grassman-based DM-RS.

[0136] In some examples, the use of one or both of the legacy DM-RS and / or the DM-RS according to the present disclosure may be signaled to a network node (such as a UE) by another network node (such as a gNB). This may be accomplished, for example, through higher-layer RRC signaling by including additional information elements in the DM-RS-config parameter structure (discussed in Section 2.1.2.1). Examples of additional parameters may include one or more of the following:

[0137] 'DM-RS-Sequence' may signal the use of legacy DM-RS, DM-RS according to the present disclosure, or both,

[0138] ● 'DM-RS-AdditionalSequence' signals a bit sequence equal to the number of DM-RS symbols in a slot to indicate the use of legacy DMRS or DM-RS according to the present disclosure in each DM-RS symbol position, where the positions of legacy DM-RS and / or DM-RS according to the present disclosure may be signaled by the gNB over the RRC connection using the DM-RS-AdditionalPosition information element in the DM-RS-config parameter structure.

[0139] In a related example, where a phase tracking reference signal (PT-RS) is configured in a time slot, the PT-RS may be signaled to occupy subcarriers and OFDM symbols such that they do not overlap with DM-RS (e.g., a DM-RS according to the present disclosure, such as a Glassman-based DM-RS), if used in the time slot. Alternatively, the DM-RS may be configured to not overlap with the PT-RS REs.

[0140] As in the above-described methods 800 and 1000, specific example embodiments for reducing decoding complexity via a packet-structured Grassmann constellation for reference signaling carrying data are described below. Such examples can reduce decoding complexity while maintaining comparable SER and NMSE performance to prior art methods.

[0141] Define ε={E1,E2,…,E K} is a set of K different Grassmann constellation points, and is a set of L different space-time coding matrices. Following the same notation as in the above system model, E i Each Grassmann constellation point represented by is a T times M matrix, that is And each space-time code matrix C j is (TM) multiplied by the M matrix, that is

[0142] Example steps for constructing the proposed grouped Grassmann codewords or constellation points are disclosed. Each Grassmann constellation point E i can be viewed as a unique basis matrix for mapping the space-time coding matrix, resulting in a nested structure that can be exploited to reduce the overall decoding search space. Thus, in some examples, each Grassmann constellation point E i It may correspond to the second constellation point mentioned above.

[0143] An example method for determining a plurality of first constellation points for signal (or data) transmission includes the following steps:

[0144] Extract the i-th Grassmann constellation matrix Ei (e.g. the matrix of the second constellation point), where i∈{1,2,…,K} and calculate its orthogonal matrix Make and

[0145] ●Define the matrix Make

[0146] ● Define the i-th group as Make where j∈{1,2,…,L} ij Denotes the jth constellation point belonging to the i-th group (for example, the first constellation point mentioned above). This can be achieved by using the basis matrix E i For the space-time coding matrix C j Encode to get X ij In an embodiment, X can be obtained by the following equation ij :

[0147]

[0148] where exp(·) represents the matrix exponential and α is a tunable parameter. Therefore, this method can be used, for example, to convert Figure 9 The second constellation point 902 in is mapped to the first constellation point 904.

[0149] ·Will is defined as the set of resulting grouped Grassmann constellation matrices such that

[0150] In some examples, the space-time code matrix This can be any of the prior art Grassmann constellations shown in [1, 2], or a set of matrices that are numerically optimized to optimize some criterion (e.g., chordal distance). In another example, the space-time code matrix Can be a collection of orthogonal matrices.

[0151] Figure 15 1 is a flow chart of an example method 1500 for determining a plurality of first constellation points for signal transmission. The method 1500 includes, in step 1502, selecting a plurality of second constellation points on a Grassmann manifold. Step 1504 of the method 1500 includes mapping each second constellation point to a group of first constellation points on the Grassmann manifold such that a distance between the first constellation points in each group is less than a distance between the groups of first constellation points.

[0152] In some examples, method 1500 includes sending information identifying a plurality of first constellation points to a transmitter, the transmitter configured to transmit one or more reference signal symbol sequences associated with one or more of the first constellation points. Additionally or alternatively, method 1500 may, for example, include sending information identifying a plurality of reference signal symbol sequences to a receiver, the receiver configured to receive the one or more reference signal symbol sequences associated with one or more of the first constellation points.

[0153] The method 1500 may also include transmitting one or more reference signal symbol sequences associated with one or more of the first constellation points and / or receiving one or more reference signal symbol sequences associated with one or more of the first constellation points.

[0154] In some examples, the distance between the first constellation points in each group is less than the distance between any two groups of first constellation points. Additionally or alternatively, for example, the distance between the first constellation points in each group is less than the distance between any two second constellation points.

[0155] The following provides an example of how to use the grouping structure of the Grassmann constellation points at the receiver to reduce decoding complexity. To this end, a two-stage decoding process of group estimation and codeword estimation can be used to decode the constellation. The example method includes the following steps:

[0156] Denoising: As a preprocessing step, the received signal Y is denoised. For example, the first M left singular vectors of Y are calculated and a rough estimate U = [u1,…u M ], where u m is the mth largest left singular vector of Y.

[0157] Group estimation: Estimate to which group the transmitted reference signal X belongs. For this purpose, GLRT can be used as an example:

[0158]

[0159] where the search space is ε (ie, K candidates).

[0160] Codeword estimation: Estimate which constellation point in the estimated group is transmitted. For example, the following GLRT can be used:

[0161]

[0162] The search space is now (ie, L candidates).

[0163] Comparing equation (2) above, which describes the prior art decoding process, with the 2-stage decoding process above, equation (2) requires testing KL different candidates to estimate the received codeword, unlike the 2-stage decoding process above, where the number of required tests is reduced to K+L. In the specific example, the prior art method requires testing 2 8 = 256 candidates to recover 8 coded bits, while the disclosed method only needs to test 32 candidates (i.e., K = 16 and L = 16) to recover 8 coded bits, which is 8 times less complex than the prior art. Note that K and L can be selected in some examples by selecting the set ε and The desired size of the parameter to set.

[0164] In some examples, KL codewords derived from K groups of L constellation points are calculated offline and signaled between the transmitter and receiver prior to channel estimation and data communication. In other examples, the KL codewords and corresponding grouping information may be provided in the specification text and / or they may be explicitly agreed upon via bilateral vendor agreement. For example, in 5G / 6G communications for downlink (DL), the KL codewords and corresponding grouping information may be part of the 3GPP specification and / or explicitly agreed upon via bilateral vendor agreement, where the KL codewords are calculated by the transmitter or receiver vendor or calculated jointly by the vendors. In some examples, the gNB may signal the use of such a constellation in a reference signal (e.g., DMRS) via radio resource control (RRC) signaling or downlink control information (DCI), or other suitable means of notifying the transmitter and / or receiver of the specific constellation to be used.

[0165] In some examples, in multi-receiver transmissions, such as in the "constellation division multiple access" mentioned above, K Grassmann constellation groups can be assigned to (or associated with) ≤ K different receivers. For example, the group assignment to the UE(s) can be signaled between the transmitter and the receivers before channel estimation and data communication. For example, when the transmitter is scheduled to transmit to R ≤ K receivers, each of the (R-1) receivers can be assigned Grassmann constellation groups, where the Rth receiver is assigned groups. While dividing the K groups among the R receivers can reduce the number of information bits that can be transmitted using the Grassmann constellation, it allows information bits to be transmitted to the R receivers simultaneously, thereby implementing constellation division multiple access within the reference signal symbol. Furthermore, in some examples, because the constellation points assigned to each receiver are orthogonal to each other (the constellation points belong to different groups), this can avoid inter-receiver interference for channel estimation, thereby facilitating, for example, subsequent conventional multiple access-only data transmission between the receivers. In a related example, the transmitter can assign and signal to the receivers the corresponding (one or more) Grassmann constellation groups for joint data and reference signal transmission. For example, in 5G / 6G communications, where the transmitter and receivers are informed of all KL codepoints (according to the above-described embodiments), the gNB can also signal one or more group IDs (each representing a Grassmann constellation group) to each receiver via RRC signaling or DCI.

[0166] The performance of an example of the disclosed grouped Grassmann constellation method for reference signaling carrying data is shown below via a Grassmann constellation. However, the presented results may be extended to other scenarios and parameters, and the disclosed method may not be limited to the case simulated herein.

[0167] As indicated above, examples of the present disclosure may allow for reduced decoding complexity while maintaining performance comparable to prior art methods. Figure 16 An example of decoding complexity for an example of the present disclosure using grouped Grassmann constellation points and prior art methods is shown. Figure 16 As can be seen from the above, compared with the prior art methods, the embodiments of the present disclosure can significantly reduce the complexity level. As the number of coding bits increases, the complexity reduction gain increases (approximately more than 10 times in the case of 8 bits or more).

[0168] Despite the greatly reduced decoding complexity, examples of the present disclosure may also provide symbol error rate (BER) and normalized mean square error (NMSE) performance comparable to prior art methods. Figure 17 An example of the present disclosure is shown (in Figure 17 An example of SER performance of a method (called “Grouped Grassmann” in

[15] ) relative to the prior art method, where M=1, T=4, B=8 are considered as system parameters and the space-time coding matrix is ​​set to Among them, s1,s2∈Gray-codedQPSK. In addition, Figure 18 An example of NMSE performance relative to SNR of the disclosed embodiment and the prior art method is shown. Figure 17 and 18As shown in , the disclosed method can provide similar SER and NMSE performance as the prior art methods, where the parameter α is shown to be able to further optimize the performance of the embodiments of the present disclosure.

[0169] Figure 19 1 is a schematic diagram of an example of a device 1900 for transmitting data to a network node. Device 1900 includes processing circuitry 1902 (e.g., one or more processors) and memory 1904 in communication with processing circuitry 1902. Memory 1904 contains instructions, such as computer program code 1910, executable by processing circuitry 1902. Device 1900 also includes an interface 1906 in communication with processing circuitry 1902. Although interface 1906, processing circuitry 1902, and memory 1904 are shown as being connected in series, these may alternatively be interconnected in any other manner, such as via a bus.

[0170] In one embodiment, the memory 1904 contains instructions executable by the processing circuit 1902, so that the device 1900 is operable / configured to: select one of a plurality of first constellation points on the Grassmann manifold based on data to be transmitted to the network node, wherein the first constellation point includes a plurality of groups of first constellation points, and the distance between the first constellation points in each group is less than the distance between the groups of first constellation points; and transmit a reference signal symbol sequence associated with the selected first constellation point to the network node. In some examples, the device 1900 is operable / configured to perform the above reference Figure 8 Method 800 is described.

[0171] Figure 20 2 is a schematic diagram of an example of a device 2000 for receiving data from a network node. The device 2000 includes a processing circuit 2002 (e.g., one or more processors) and a memory 2004 in communication with the processing circuit 2002. The memory 2004 contains instructions executable by the processing circuit 2002, such as computer program code 2010. The device 2000 also includes an interface 2006 in communication with the processing circuit 2002. Although the interface 2006, the processing circuit 2002, and the memory 2004 are shown as being connected in series, these may alternatively be interconnected in any other manner, such as via a bus.

[0172] In one embodiment, the memory 2004 contains instructions executable by the processing circuit 2002, so that the device 2000 is operable / configured to: receive a reference signal symbol sequence associated with one of a plurality of first constellation points on the Grassmann manifold from the network node, wherein the first constellation point includes a plurality of groups of first constellation points, and a distance between the first constellation points in each group is less than a distance between the groups of first constellation points; and determine data transmitted by the network node based on the reference signal symbol sequence. In some examples, the device 2000 is operable / configured to perform the above reference Figure 10 Method 1000 is described.

[0173] Figure 21 2 is a schematic diagram of an example of a device 2100 for determining a plurality of first constellation points for signal transmission. The device 2100 includes a processing circuit 2102 (e.g., one or more processors) and a memory 2104 in communication with the processing circuit 2102. The memory 2104 contains instructions executable by the processing circuit 2102, such as computer program code 2110. The device 2100 also includes an interface 2106 in communication with the processing circuit 2102. Although the interface 2106, the processing circuit 2102, and the memory 2104 are shown as being connected in series, these may alternatively be interconnected in any other manner, such as via a bus.

[0174] In one embodiment, the memory 2104 includes instructions executable by the processing circuit 2102 such that the device 2100 is operable / configured to: select a plurality of second constellation points on the Grassmann manifold, and map each second constellation point to a group of first constellation points on the Grassmann manifold such that a distance between the first constellation points in each group is less than a distance between the groups of first constellation points. In some examples, the device 2100 is operable / configured to perform the above-referenced Figure 15 Method 1500 is described.

[0175] It should be noted that the examples mentioned above illustrate rather than limit the present invention, and those skilled in the art will be able to design many alternative examples without departing from the scope of the appended claims. The word "comprising" does not exclude the existence of elements or steps other than those listed in the claims, and "a or an" does not exclude multiple, and a single processor or other unit can implement the functions of several units described in the following statements. When using the terms "first", "second", etc., they should only be understood as labels that are convenient for identifying specific features. In particular, unless otherwise expressly stated, they should not be interpreted as describing the first or second feature (that is, the first or second of such features that occur in time or space) of multiple such features. Unless otherwise expressly stated, the steps in the method disclosed herein can be performed in any order. Any reference symbols in the statement should not be interpreted as limiting its scope.

[0176] References

[0177] 1. I. Kammoun and J.C. Belfiore, “A new family of Grassmann space-time codes for non-coherent MIMO systems,” IEEE Communications Letters, Vol. 7, No. 11, pp. 528–530, November 2003

[0178] 2. K.H.N. Go, A.Decurninge, M.Guillaud, and S.Yang, “Transmitter and receiver communication apparatus for non-coherent communication,” U.S. Patent No. US11258649B2, February 2022.

Claims

1. A method (800) for transmitting data to a network node, the method comprising: selecting (802) one of a plurality of first constellation points on a Grassmann manifold based on the data to be transmitted to the network node, wherein the first constellation points include a plurality of groups of first constellation points and a distance between the first constellation points in each group is smaller than a distance between the groups of first constellation points; and A reference signal symbol sequence associated with the selected first constellation point is transmitted (804) to the network node.

2. The method according to claim 1, wherein Selecting (802) one of the plurality of first constellation points comprises: selecting one of the groups of first constellation points based on the network node; and One of the first constellation points in a selected group is selected based on the data to be transmitted to the network node.

3. The method according to claim 1 or 2, comprising: sending one or more reference signal symbol sequences associated with a first constellation point in a first group of said groups of first constellation points to one or more first network nodes; as well as One or more reference signal symbol sequences associated with a first constellation point in a second group of the groups of first constellation points are sent to one or more second network nodes.

4. The method according to any one of claims 1 to 3, wherein Each group of first constellation points is associated with one or more respective network nodes for receiving a reference signal symbol sequence associated with the first constellation point in the group.

5. The method according to any one of claims 1 to 4, wherein The distance between the first constellation points in each group is smaller than the distance between any two groups of first constellation points.

6. The method according to any one of claims 1 to 5, wherein Each group of first constellation points comprises corresponding second constellation points among a plurality of second constellation points on the Grassmann manifold that are mapped to the first constellation points in the group using a space-time coding matrix.

7. The method according to claim 6, wherein: The distance between the first constellation points in each group is smaller than the distance between any two second constellation points.

8. The method according to any one of claims 1 to 7, wherein Each first constellation point within the group of first constellation points is associated with a different value of the data.

9. The method according to claim 8, wherein Each first constellation point is associated with a different value of the data.

10. The method according to any one of claims 1 to 9, wherein Selecting (802) one of the first constellation points comprises selecting from 2 B The first constellation point is selected from the first constellation points, wherein B is the number of data bits encoded by each first constellation point and / or the reference signal symbol sequence.

11. The method according to any one of claims 1 to 10, wherein The Grassmann manifold is at least a 2n-dimensional manifold, where n is the number of reference signal symbols in the reference signal symbol sequence.

12. The method according to any one of claims 1 to 11, comprising transmitting (804) the sequence of reference signal symbols across a plurality of first resource elements.

13. The method of claim 12, comprising repeating transmission of the reference signal symbol sequence across a plurality of second resource elements.

14. The method according to claim 13, wherein: The first plurality of resource elements are in a first frequency range and the second plurality of resource elements are in a second frequency range that does not overlap with the first frequency range.

15. The method according to claim 13 or 14, wherein: The first resource element and the second resource element are within a resource block, a time slot, a mini-time slot, a subframe and / or a frame.

16. The method according to any one of claims 1 to 15, wherein The reference signal symbol sequence is transmitted to the network node in one or more time-domain symbol periods.

17. The method according to any one of claims 1 to 16, comprising transmitting at least one additional reference signal symbol sequence to the network node, wherein The at least one additional reference signal symbol sequence corresponds to a legacy reference signal.

18. The method according to any one of claims 1 to 17, wherein The reference signal symbol sequence is a pilot signal or a demodulation reference signal (DM-RS).

19. The method according to any one of claims 1 to 18, wherein The network node comprises a user equipment (UE).

20. The method according to claim 19, wherein The method is performed by a Radio Access Node (RAN).

21. The method according to any one of claims 1 to 18, wherein The network nodes include radio access nodes (RAN).

22. The method according to claim 21, wherein The method is performed by a user equipment (UE).

23. The method according to any one of claims 1 to 22, wherein The reference signal symbol sequence and / or the first constellation point are determined according to the method of any one of claims 46 to 55.

24. A method (1000) of receiving data from a network node, the method comprising: receiving (1002) from the network node a reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold, wherein the first constellation point comprises a plurality of groups of first constellation points and a distance between the first constellation points in each group is less than a distance between the groups of first constellation points; and Based on the reference signal symbol sequence, data transmitted by the network node is determined (1004).

25. The method according to claim 24, wherein Determining (1004) the data transmitted by the network node comprises: determining a group including said one of said first constellation points; and It is determined which of the first constellation points in the group is associated with a received reference signal symbol sequence.

26. The method according to claim 24 or 25, wherein The method is performed by a node associated with one of the group of constellation points, and comprises: determining a group including said one of said first constellation points; and If the determined group is a group associated with the node, determining which of the first constellation points in the group is associated with the received reference signal symbol sequence.

27. The method according to any one of claims 24 to 26, wherein The distance between the first constellation points in each group is smaller than the distance between any two groups of first constellation points.

28. The method according to any one of claims 24 to 27, wherein Each group of first constellation points includes corresponding second constellation points of a plurality of second constellation points on the Grassmann manifold that are mapped to the first constellation points in the group using a space-time coding matrix.

29. The method according to claim 28, wherein The distance between the first constellation points in each group is smaller than the distance between any two second constellation points.

30. The method according to any one of claims 24 to 29, wherein Each first constellation point within the group of first constellation points is associated with a different value of the data.

31. The method according to claim 30, wherein Each first constellation point is associated with a different value of the data.

32. The method according to any one of claims 24 to 31, wherein Existence 2 B first constellation points, wherein B is the number of data bits encoded by each first constellation point and / or the reference signal symbol sequence.

33. The method according to any one of claims 24 to 32, wherein The Grassmann manifold is at least a 2n-dimensional manifold, where n is the number of reference signal symbols in the reference signal symbol sequence.

34. The method according to any one of claims 24 to 33, wherein The reference signal symbol sequence is received across a plurality of first resource elements.

35. The method of claim 34, comprising receiving repetitions of the reference signal symbol sequence across a plurality of second resource elements.

36. The method of claim 35, wherein: The first plurality of resource elements are in a first frequency range and the second plurality of resource elements are in a second frequency range that does not overlap with the first frequency range.

37. The method according to claim 35 or 36, wherein The first resource element and the second resource element are within a resource block, a time slot, a mini-time slot, a subframe and / or a frame.

38. The method according to any one of claims 24 to 37, wherein The reference signal symbol sequence is received in one or more time-domain symbol periods.

39. The method according to any one of claims 24 to 38, comprising receiving at least one additional reference signal symbol sequence from the network node, wherein The at least one additional reference signal symbol sequence corresponds to a legacy reference signal.

40. The method according to any one of claims 24 to 39, wherein The reference signal symbol sequence is a pilot signal or a demodulation reference signal (DM-RS).

41. The method according to any one of claims 24 to 40, wherein The network node comprises a user equipment (UE).

42. The method according to claim 41, wherein The method is performed by a Radio Access Node (RAN).

43. The method according to any one of claims 24 to 40, wherein The network nodes include radio access nodes (RAN).

44. The method according to claim 43, wherein The method is performed by a user equipment (UE).

45. The method according to any one of claims 24 to 44, wherein The reference signal symbol sequence and / or the first constellation point are determined according to the method of any one of claims 46 to 55.

46. ​​A method (1500) for determining a plurality of first constellation points for signal transmission, the method comprising: selecting (1502) a plurality of second constellation points on the Grassmann manifold; as well as Each second constellation point is mapped (1504) to a group of first constellation points on the Grassmann manifold such that a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points.

47. The method of claim 46, comprising: sending information identifying the plurality of first constellation points to a transmitter, the transmitter configured to transmit one or more reference signal symbol sequences associated with one or more of the first constellation points; and / or Information identifying the plurality of reference signal symbol sequences is sent to a receiver configured to receive one or more reference signal symbol sequences associated with one or more of the first constellation points.

48. The method of claim 46 or 47, comprising: transmitting one or more reference signal symbol sequences associated with one or more of the first constellation points; and / or One or more reference signal symbol sequences associated with one or more of the first constellation points are received.

49. The method according to any one of claims 46 to 48, wherein The distance between the first constellation points in each group is smaller than the distance between any two groups of first constellation points.

50. The method according to any one of claims 46 to 49, wherein The distance between the first constellation points in each group is smaller than the distance between any two second constellation points.

51. The method according to any one of claims 46 to 80, wherein Each first constellation point within the group of first constellation points is associated with a different value of the data.

52. The method of claim 51, wherein Each first constellation point is associated with a different value of the data.

53. The method according to claim 46 or 52, wherein Existence 2 B first constellation points, where B is the number of data bits encoded by each first constellation point.

54. The method according to any one of claims 46 to 53, wherein The Grassmann manifold is at least a 2n-dimensional manifold, where n is the number of reference signal symbols in the corresponding reference signal symbol sequence associated with each first constellation point.

55. The method according to any one of claims 46 to 54, wherein The first constellation point includes a constellation point of a pilot signal or a demodulation reference signal (DM-RS).

56. An apparatus (1900) for transmitting data to a network node, the apparatus comprising a processor (1902) and a memory (1904), the memory containing instructions executable by the processor such that the apparatus is operable to: Based on the data to be transmitted to the network node, one of a plurality of first constellation points on a Grassmann manifold is selected (802), wherein The first constellation points include multiple groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points; as well as A reference signal symbol sequence associated with the selected first constellation point is transmitted (804) to the network node.

57. The apparatus of claim 56, wherein The memory (1904) contains instructions executable by the processor (1902) such that the apparatus is operable to perform the method (800) according to any one of claims 2 to 23.

58. An apparatus (2000) for receiving data from a network node, the apparatus comprising a processor (2002) and a memory (2004), the memory containing instructions executable by the processor such that the apparatus is operable to: A reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold is received (1002) from the network node, wherein The first constellation points include multiple groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points; as well as Based on the reference signal symbol sequence, the data transmitted by the network node is determined (1004).

59. The apparatus of claim 58, wherein The memory (2004) contains instructions executable by the processor (2002) such that the apparatus is operable to perform the method (1000) according to any one of claims 25 to 45.

60. An apparatus (2100) for determining a plurality of first constellation points for signal transmission, the apparatus comprising a processor (2102) and a memory (2104), the memory containing instructions executable by the processor such that the apparatus is operable to: selecting a plurality of second constellation points on the Grassmann manifold; and Each second constellation point is mapped to a group of first constellation points on the Grassmann manifold, such that a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points.

61. The apparatus of claim 60, wherein The memory (2104) contains instructions executable by the processor (2102) such that the apparatus is operable to perform the method (1500) according to any one of claims 47 to 55.

62. An apparatus for transmitting data to a network node, the apparatus being configured to: Based on the data to be transmitted to the network node, one of a plurality of first constellation points on a Grassmann manifold is selected (802), wherein The first constellation points include multiple groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points; as well as A reference signal symbol sequence associated with the selected first constellation point is transmitted (804) to the network node.

63. The apparatus of claim 62, wherein The device is configured to perform the method (800) according to any one of claims 2 to 23.

64. An apparatus for receiving data from a network node, the apparatus being configured to: A reference signal symbol sequence associated with one of a plurality of first constellation points on a Grassmann manifold is received (1002) from the network node, wherein The first constellation points include multiple groups of first constellation points, and a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points; as well as Based on the reference signal symbol sequence, the data transmitted by the network node is determined (1004).

65. The apparatus of claim 64, wherein The device is configured to perform a method (1000) according to any one of claims 25 to 45.

66. An apparatus for determining a plurality of first constellation points for signal transmission, the apparatus being configured to: selecting a plurality of second constellation points on the Grassmann manifold; and Each second constellation point is mapped to a group of first constellation points on the Grassmann manifold, such that a distance between the first constellation points in each group is smaller than a distance between groups of first constellation points.

67. The apparatus of claim 66, wherein The device is configured to perform a method (1000) according to any one of claims 47 to 55.

Images