Multilayer transmission using interdependent transmission symbols on multiple layers

Abstract

Various examples of the disclosure generally pertain to a multilayer transmission and modulation schemes used for determining transmission symbols associated with different layers of the multilayer transmission.

Description

[0001] MULTILAYER TRANSMISSION USING INTERDEPENDENT TRANSMISSION SYMBOLS ON MULTIPLE LAYERS

[0002] TECHNICAL FIELD

[0003] Various examples of the disclosure pertain to a multilayer transmission of data. Various examples pertain to the selection of modulation schemes for each of multiple layers of the multilayer transmission.

[0004] BACKGROUND

[0005] A wireless transmission can employ multiple layers. Such multilayer transmission can enhance data throughput and / or reliability if compared to a single-layer transmission. In a multilayer transmission, multiple transmission symbols are transmitted simultaneously over the same frequency band but through different layers. These layers are typically associated with different spatial paths of the radio channel. Thus, spatial diversity of the environment is employed to achieve the enhanced data throughput and / or reliability.

[0006] To optimize the wireless multilayer transmission (e.g., in terms of data throughput), the appropriate digital modulation scheme is to be selected for each layer of a multilayer transmission.

[0007] SUMMARY

[0008] A need exists for advanced techniques of wireless communication. A need exists for advanced techniques of selecting the appropriate modulation scheme for a multilayer transmission.

[0009] This need is met by the features of the independent claims. The features of the dependent claims define embodiments.

[0010] A method for use in a transmit node of a multilayer transmission is disclosed. The method includes obtaining a sequence of L data bits of data to be transmitted. The method further includes (e.g., upon a first multilayer transmission mode being activated): determining a first transmission symbol. The first transmission symbol is for a first layer of the multilayer transmission. The first transmission symbol is determined based on a first set of M data bits. This first set of M data bits is selected from the sequence of L data bits. The first transmission symbol is determined using a first modulation scheme. The first modulation scheme das 2U(i.e. , 2AU) transmission symbols. The method further includes (e.g., upon the first multilayer transmission mode being activated): determining a second transmission symbol for a second layer of the multilayer transmission. The second transmission symbol is determined based on a second set of / V data bits. The second set of / V data bits is selected from the sequence of L data bits. The second transmission symbol is determined using a second modulation scheme. The second modulation scheme has 2V(i.e. , 2AV) transmission symbols. The first set and the second set are at least partially overlapping.

[0011] Program code is disclosed. The program code can be executed by a compute circuitry of a transmit node of a multilayer transmission. Execution of the program code causes the compute circuitry to perform such method as disclosed above.

[0012] A transmit node configured to participate in a multilayer transmission is disclosed. The transmit node comprises a processor and a memory. The processor is configured to load program code from the memory and to execute the memory. Execution of the program code causes the processor to perform a method. The method includes obtaining a sequence of L data bits of data to be transmitted. The method further includes, upon a first multilayer transmission mode being activated: determining a first transmission symbol. The first transmission symbol is for a first layer of the multilayer transmission. The first transmission symbol is determined based on a first set of M data bits. This first set of M data bits is selected from the sequence of L data bits. The first transmission symbol is determined using a first modulation scheme. The first modulation scheme das 2U(i.e., 2AU) transmission symbols. The method further includes, upon the first multilayer transmission mode being activated: determining a second transmission symbol for a second layer of the multilayer transmission. The second transmission symbol is determined based on a second set of N data bits. The second set of N data bits is selected from the sequence of L data bits. The second transmission symbol is determined using a second modulation scheme. The second modulation scheme has 2V(i.e., 2AV) transmission symbols. The first set and the second set are at least partially overlapping.

[0013] A method for use in a receive node is disclosed. The method includes receiving a first transmission symbol on a first layer of the multilayer transmission. The method also includes receiving a second transmission symbol on a second layer of the multilayer transmission. The method also includes (e.g., upon a first multilayer transmission mode being activated) determining a first set of M data bits selected from a sequence of L data bits and in accordance with a first modulation scheme. The first modulation scheme has 2Utransmission symbols. The method further includes (e.g., upon the first multilayer transmission mode being activated) determining a second set of N data bits selected from the sequence of L data bits and in accordance with a second modulation scheme having 2Vtransmission symbols. The first set and the second set are at least partially overlapping. Program code is disclosed. The program code can be executed by a compute circuitry of a receive node of a multilayer transmission. Execution of the program code causes the compute circuitry to perform such method as disclosed above.

[0014] A receive node configured to participate in a multilayer transmission is disclosed. The receive node includes a processor and a memory. The processor is configured to load program code from the memory and to execute the program code. Execution of the program code causes the processor to perform a method. The method includes receiving a first transmission symbol on a first layer of the multilayer transmission. The method also includes receiving a second transmission symbol on a second layer of the multilayer transmission. The method also includes (e.g., upon a first multilayer transmission mode being activated) determining a first set of M data bits selected from a sequence of L data bits and in accordance with a first modulation scheme. The first modulation scheme has 2Utransmission symbols. The method further includes (e.g., upon the first multilayer transmission mode being activated) determining a second set of N data bits selected from the sequence of L data bits and in accordance with a second modulation scheme having 2Vtransmission symbols. The first set and the second set are at least partially overlapping.

[0015] A method for use in a receive node of a multilayer transmission is disclosed. The method includes sounding each of multiple layers of the multilayer transmission. The method further includes, depending on said sounding: selectively activating a first multilayer transmission mode using interdependent transmission symbols on multiple layers of the multilayer transmission.

[0016] Program code is disclosed. The program code can be executed by a compute circuitry of a receive node of a multilayer transmission. Execution of the program code causes the compute circuitry to perform such method as disclosed above.

[0017] A receive node configured to participate in a multilayer transmission is disclosed. The receive node includes a processor and a memory. The processor is configured to load program code from the memory and to execute the program code. Execution of the program code causes the processor to perform a method. The method includes sounding each of multiple layers of the multilayer transmission. The method further includes, depending on said sounding: selectively activating a first multilayer transmission mode using interdependent transmission symbols on multiple layers of the multilayer transmission.

[0018] A method for use in a receive node of a multilayer transmission is disclosed. The method includes sounding a channel of the multilayer transmission. The method further includes, depending on said sounding: selectively activating a first multilayer transmission mode using interdependent transmission symbols on multiple layers of the multilayer transmission. Program code is disclosed. The program code can be executed by a compute circuitry of a receive node of a multilayer transmission. Execution of the program code causes the compute circuitry to perform such method as disclosed above.

[0019] A receive node configured to participate in a multilayer transmission is disclosed. The receive node includes a processor and a memory. The processor is configured to load program code from the memory and to execute the program code. Execution of the program code causes the processor to perform a method. The method includes sounding a channel of the multilayer transmission. The method further includes, depending on said sounding: selectively activating a first multilayer transmission mode using interdependent transmission symbols on multiple layers of the multilayer transmission.

[0020] It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the invention.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 schematically illustrates a communication system including multiple layers of a multilayer transmission according to various examples.

[0023] FIG. 2 schematically illustrates a node according to various examples.

[0024] FIG. 3 is a flowchart of a method for use in at least one transmit node according to various examples.

[0025] FIG. 4 is a constellation diagram.

[0026] FIG. 5 is a constellation diagram.

[0027] FIG. 6 is a constellation diagram.

[0028] FIG. 7 schematically illustrates mutual information as a function of signal-to-noise.

[0029] FIG. 8 schematically illustrates mutual information as a function of signal-to-noise.

[0030] FIG. 9 schematically illustrates a processing pipeline for determining and transmitting transmission symbols according to various examples.

[0031] FIG. 10 schematically illustrates a processing pipeline for determining and transmitting transmission symbols according to various examples.

[0032] FIG. 11 is a flowchart of a method for use in a receive node according to various examples. DETAILED DESCRIPTION

[0033] Some examples of the present disclosure generally provide for a plurality of circuits or other electrical devices. All references to the circuits and other electrical devices and the functionality provided by each are not intended to be limited to encompassing only what is illustrated and described herein. While particular labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation for the circuits and the other electrical devices. Such circuits and other electrical devices may be combined with each other and / or separated in any manner based on the particular type of electrical implementation that is desired. It is recognized that any circuit or other electrical device disclosed herein may include any number of microcontrollers, a graphics processor unit (GPU), integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, any one or more of the electrical devices may be configured to execute a program code that is embodied in a non-transitory computer readable medium programmed to perform any number of the functions as disclosed.

[0034] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. It is to be understood that the following description of embodiments is not to be taken in a limiting sense. The scope of the invention is not intended to be limited by the embodiments described hereinafter or by the drawings, which are taken to be illustrative only.

[0035] The drawings are to be regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0036] Hereinafter, techniques of wireless transmission are disclosed. For instance, uplink (UL) or downlink (DL) transmission can employ the techniques as disclosed herein. UL transmission is from a wireless device to a cellular network and DL transmission is from the cellular network to the wireless device. The techniques described herein can also be used for device-to-device transmission. Aspects of a multilayer transmission are disclosed. Using a multilayer transmission (if compared to a single-layer transmission) can enhance data throughput and / or reliability. Multiple transmission symbols are transmitted (typically contemporaneously) over the same frequency band but through different layers. These layers are typically associated with different spatial paths of the radio channel. Thus, spatial diversity of the environment is employed to achieve the enhanced data throughput and / or reliability.

[0037] Each of the multiple layers can be associated with respective precoding. I.e., if an antenna panel is available including multiple antenna elements, different layers can be selected by applying different amplitude and / or phase shifts at each of the multiple antenna elements. Different transmit (TX) beams can be used to select different layers.

[0038] Each of the multiple layers may, in some examples, be associated with a respective antenna port. An antenna port is a logical entity which is distinct from a physical antenna or antenna panel. Each antenna port is associated with a specific set of reference signals - e.g., Channel State Information (CSI) reference signals in accordance with the 3rd Generation Partnership Project (3GPP) 4G or 5G radio-access technology (RAT) - such that the spatial path over which a symbol is transmitted on that antenna port can be distinguished from the spatial path over which another symbol is conveyed on the same antenna port. Two antenna ports are said to be quasi-co-located if the large-scale properties of the spatial path over which a symbol is conveyed on one antenna port can be inferred from the spatial path over which a symbol is conveyed on another antenna port. In other examples, it would be possible that the number of layers is different than the number of antenna ports.

[0039] It would be possible that all of the multiple layers are associated with a single wireless device. In other words, it would be possible that a single wireless device - e.g., a cellular phone - includes multiple antenna ports. In another variant, each of the multiple layers is associated with a respective wireless device (WD) and multiple WDs participate in the multilayer transmission Different layers are associated with different WDs. I.e., multiple TX nodes can transmit transmission symbols on the different layers.

[0040] For instance, two WDs can be part of a device collaboration group. WDs of a collaboration group may share a similar mobility pattern and may communicate on a wireless sidelink, e.g., having another radio-access technology than used by the WDs to access a cellular network. The particular implementation of the wireless sidelink is not germane for the techniques disclosed herein; prior art techniques can be employed. For instance, a WD can have an assisting WD in close vicinity. Examples include a laptop with assisting phone nearby, a phone with assisting smartwatch (or vice versa), etc. For instance, a WD (e.g., a smart watch) of a collaboration group may have limited transmit power if compared to a further WD (e.g., a smart phone) of the collaboration group. A transmitter capability of a WD of a collaboration group may be different than the transmitter capability of another WD of that collaboration group. For example, it would be possible that one of the WDs has an antenna panel with multiple antenna elements; while another one of the multiple WDs only has a single antenna element. For instance, a data throughput capacity of the transmitter of one of the WDs can be higher than the data throughput capacity of the wireless transmitter of another one of the WDs in the collaboration group. If a first WD and a second WD collaborate with respect to the multilayer transmission of data originating at the first WD (and not at the second WD), then the second WD serves as a capacity booster. The second WD helps the first WD to transmit its data. Thus, the second WD can be labeled assisting WD (A-WD); while the WD at which the data to be transmitted originates may be labeled master WD (M-WD). For instance, it would be possible that multiple WDs set up a device collaboration group to collaborate on a multilayer transmission. Then, responsive to setting up such collaboration group, it is possible to indicate, to the radio access network to which the WDs are connected, that the particular WD of the device collaboration group acting as M-WD has multiple antenna ports. For instance, a total or maximum number of antenna ports may be indicated to the radio access network. The antenna ports can be implemented by one or more A-WDs. Thus, the concepts of device collaboration and antenna ports can be combined.

[0041] According to various examples, one or more TX nodes participating in the multilayer transmission determine transmission symbols for the multiple layers in a dependent manner. I.e., a transmission symbol for a first layer and another transmission symbol for a second layer depend on each other (are interdependent). This interdependency of the transmission symbols is in contrast to conventional multi-user multi-input multi-output (MIMO) transmission. This interdependency means that at least one bit of the data to be transmitted is taken into account when determining both transmission symbols. Also, for the receiver (RX) node perspective, the RX node needs to demodulate both transmission symbols to unambiguously determine the data that was transmitted. Such transmission mode may be labeled “interdependent multilayer transmission mode”. This is because the transmissions on the multiple layers are not completely decoupled from each other, but interdependent. Interdependent transmission symbols are transmitted on the multiple layers. Such interdependent or intertwined multilayer transmission mode is different from a conventional transmission mode in which the transmission symbols transmitted on the multiple layers are completely decoupled. Such conventional transmission mode may, accordingly, be referred to as “orthogonal multilayer transmission mode”. The RX node can independently process the received transmission symbols. It has been found that an interdependent multilayer transmission mode offers higher data throughput and / or higher reliability if compared to an orthogonal multilayer transmission mode, at least for certain channel conditions of the radio channel of the multiple layers. According to various examples, it is possible to selectively activate interdependent multilayer transmission mode. According to various examples, it is possible to switch back and forth between and interdependent multilayer transmission mode and an orthogonal multilayer transmission mode and / or a single-layer transmission mode. For instance, it would be possible to selectively activate the interdependent multilayer transmission mode depending on a channel sounding of the radio channel. For example, it would be possible to determine the rank of the channel. It would also be possible to sound multiple layers of the radio channel, e.g., using precoded reference signals / pilot signals. Based on a sounding procedure, the performance of the multilayer transmission can be optimized under varying channel conditions.

[0042] FIG. 1 schematically illustrates a wireless communication system 90. The wireless communication system 90 includes a radio channel 80 with two layers 81 , 82. The first layer 81 is associated with a first TX entity 91 and the second layer 82 is associated with a second TX entity 92. The TX entities 91 , 92 execute a multilayer transmission to an RX node 75. Both layers 81, 82 are used for the multilayer transmission.

[0043] The RX node 75 may be a base station (BS) of a radio-access network (RAN) of a cellular network).

[0044] The first TX entity 91 and the second TX entity 92 may be logical units or may be hardware units. For instance, the first TX entity 91 may be a first antenna port and the second TX entity 92 may be a second antenna port. The first TX entity 91 may be a first WD and the second TX entity 92 may be a second WD; the first and second WDs may communicate on a wireless sidelink (not shown), e.g., using the same or another radio-access technology than the RAN. For instance, the first TX entity 91 may be associated with first precoding (e.g., selecting a certain TX beam) and the second TX entity 92 may be associated with second precoding (e.g., selecting another TX beam).

[0045] The different TX entities 91, 92 can have different TX power limitations. For example, the TX entity 91 can support a higher TX power than the TX entity 92.

[0046] As will be appreciated, the wireless communication system includes one or more TX nodes.

[0047] The communication system 90 may optionally include a separate control node that controls and configures the multilayer transmission (not shown). However, in the illustrated scenario, the RX node implements the control node.

[0048] While FIG. 1 is illustrated for two layers, as a general rule, the multilayer transmission may employ more than two layers. FIG. 2 schematically illustrates a node 60, e.g., a TX node or an RX node or a control node. The node 60 may be a WD connected to a cellular network. The node 60 may be a base station (BS) of a cellular network.

[0049] The node 60 includes a processor 61 and a memory 62. The processor 61 can load program code from the memory 62 and execute the program code. Executing the program code causes the processor 61 to perform techniques as disclosed herein, e.g.: participating in a multilayer transmission, e.g., by transmitting and or receiving via a respective communication interface 63; determining one or more transmission symbols (also referred to as modulation symbols) using one or more modulation schemes; transmitting transmission symbols by accessing a certain layer of a radio channel; receiving transmission symbols; demodulating transmission symbols; configuring a multilayer transmission; switching between multiple multilayer transmission modes; etc.

[0050] FIG. 3 is a flowchart of a method according to various examples. The method of FIG. 3 is executed by at least one TX node. The at least one TX node participates in a multilayer transmission. The at least one TX node has data to be transmitted to an RX node. For instance, the method of FIG. 3 may be executed by at least one WD. A M-WD may collaborate with an A- WD to implement transmission of UL data to a BS of a cellular network. The method of FIG. 3 can be executed by a processor, upon loading program code from a memory and upon executing the program code. For instance, the method of FIG. 3 may be executed by the processor 61 upon loading and executing program code that is stored in the memory 62.

[0051] FIG. 3 exemplifies the operation for a multilayer transmission using two layers; but, as a general rule, the multilayer transmission may use more than two layers.

[0052] At box 905, the multilayer transmission is configured.

[0053] The at least one TX node and a control node, e.g., the RX node, may exchange information to configure the multilayer transmission. Box 905 may also include communication with one or more further TX nodes collaborating with the TX node in the multilayer transmission.

[0054] For instance, a capability information may be provided to the control node. The capability information may be indicative of a capability of the TX node to participate in the multilayer transmission. The capability information may be indicative of the capability of the TX node to participate in a device collaboration group. The capability information may be indicative of a capability of the TX node to support a certain multilayer transmission mode or to support multiple multilayer transmission modes. The capability information may be indicative of a capability of the TX node to switch between multiple multilayer transmission modes. Information may be provided to the RX node that a rank-X multilayer transmission is implemented, with X>1. For instance, X may be indicated, i.e., the rank of the multilayer transmission. The number of layers may be indicated.

[0055] It is possible to provide, to the RX node, an indication of a number of antennas. For instance, the number of transmit antennas and / or the number of receive antennas may be provided. The number of antennas may correlate with the availability of using different precodings to access different layers.

[0056] It is possible to provide, to the RX node, an indication of multiple antenna ports. The multiple antenna ports can be associated with the multiple layers of the multilayer transmission. For instance, a WD may indicate to a radio-access network (RAN) of a cellular network, e.g., to a BS of the RAN, that it has multiple antenna ports. The count of the antenna ports may be indicated. If the WD is a WD collaborating with another WD to implement the multilayer transmission, the WD may indicate that it has multiple antenna ports, wherein a first one of the multiple antenna ports is implemented by the WD and another one of the multiple antenna ports is implemented by the another WD.

[0057] It would be possible to indicate the maximum number of available antenna ports. Antenna port limitations can be indicated. A number of additional antenna ports can be indicated. For instance, a WD may have previously indicated its number of antenna ports. Upon forming a device collaboration group, additional antenna ports can become available due to the collaboration.

[0058] In such a case of collaboration on, e.g., UL transmission, collaboration may or may not extend to DL transmission. Thus, it would be possible to indicate, to the RAN, that the number of antenna ports is different for UL and DL.

[0059] It is possible to indicate a TX power limitation for one or more of the antenna ports. For instance, a power limitation for each of the multiple antenna ports may be indicated. For instance, a scenario would be possible in which the multiple antenna ports are implemented by different WDs. The different WDs may have hardware transmit power limitations and it is possible to indicate such transmit power limitations at box 905.

[0060] The at least one TX node may report a maximum constellation size that may be used to determine each transmission symbol per antenna port. The maximum number of bits may be independent of the channel quality. Such limitation may depend on the quality and / or throughput limitations of the sidelink between collaborating WDs (as will be later on explained in connection with box 926).

[0061] Box 905 may include participating in a channel and / or layer sounding procedure. Channel sounding reference signals may be transmitted / received by all antenna ports. More generally, at least one layer of the multiple layers of the multilayer transmission may be sounded. For instance, UL CSI (e.g., SRS) reference signals may be transmitted by one or more TX nodes. Layer-specific reference signals may be used. These layer-specific reference signals may be precoded.

[0062] Box 905 can include obtaining configuration information for one or more transmission modes. For instance, a configuration for an interdependent multilayer transmission mode may be obtained. For instance, a control node may indicate which particular modulation schemes are to be used. A control node can indicate the bitmaps used for determining transmission symbols. A control node can indicate which modulation scheme to use for each layer or antenna port. A control node can indicate one or more trigger criteria for switching between different multilayer transmission modes, e.g., for switching between an interdependent multilayer transmission mode and an orthogonal multilayer transmission mode.

[0063] Phase rotations <p to be applied per layer or specifically per port can be indicated. The phase rotation can be determined based on the channel obtained from the channel sounding procedure. CSI reference signals may be used to determine the phase rotations. Alternatively, precoder matrices can be indicated for the various layers or antenna ports.

[0064] At box 906, a sequence of L data bits to be transmitted is obtained. The sequence of L data bits may be obtained from transmission data, e.g., from a higher layer of a transmission protocol stack. For instance, Layer 3 data can be obtained. For instance, payload data or application data can be obtained.

[0065] Box 906 may include scrambling. Scrambling of a bit sequence prior to modulation is a process where the original binary data is intentionally randomized.

[0066] At optional box 910, either a first or second transmission mode is selected for the transmission of the sequence of L data bits (in some instances, it would also be possible that the interdependent multilayer transmission mode is fixedly activated and in such a scenario, box 910 is not required).

[0067] It is possible to switch between an interdependent multilayer transmission mode (branch 911) and an orthogonal multilayer transmission mode (branch 912) at box 910.

[0068] Box 910 may be based on an activation signal provided by a control node, e.g., the RX node which may be a BS of a cellular network. It would be possible that the activation signal is obtained after obtaining the sequence of data bits at box 906. For instance, such activation signal may be part of an uplink grant allocating resources to the transmission symbols encoding the data bits. It would, however, also be possible that the activation signal is provided prior to obtaining the data bits to be transmitted. For instance, the activation signal may be indicative of a certain time duration during which the respective multilayer transmission mode remains activated, i.e., a corresponding selection may be prospectively executed prior to data being scheduled for transmission. For instance, the activation signal may be obtained as part of box 905. For instance, the activation signal may be provided responsive to the TX node providing certain information such as including multiple antenna ports or a TX power asymmetry of the multiple antenna ports (i.e., different power limits),

[0069] The activation signal could be an explicit signal. A signal having no further functionality other than activating the particular transmission mode could be used. The activation signal could be an implicit signal. The activation signal could indicate the activation of a particular transmission mode in combination with a pre-configuration or other parameters that have been previously signaled or are fixed by the communication protocol employed by the participating nodes. The activation signal may be implemented by a message. The activation signal could be implemented by an information element carried in a message. The activation signal could be piggy-backed to another signal, e.g., another message. The activation signal could be a Layer 1 activation signal, i.e., communicated on the Physical Layer. The activation signal could also be a higher layer signal, e.g., a Layer 2 or Layer 3, e.g., Radio Resource Control (RRC) message. The activation signal may be transmitted per data instance. I.e., each set of bits that is transmitted may be associated with a respective activation signal. The activation signal may alternatively have an extended validity and may not be linked to a particular data instance. For instance, once an activation signal is received, a given transmission mode may remain activated until a further activation signal overwriting the previous activation signal is received. The activation signal may also indicate a temporal validity.

[0070] Next, aspects with respect to the interdependent multilayer transmission mode are disclosed (branch 911):

[0071] At box 915, the interdependent multilayer transmission mode is activated. Box 915 can include selecting modulation schemes for each of the multiple layers of the multilayer transmission. This may be based on a configuration of box 905. Also, configuration data may be obtained from a control node at box 915. Such configuration could also be based on a current channel estimate executed at box 915.

[0072] Activation of the interdependent transmission mode at box 915 can also include associating each of the multiple layers with a respective modulation scheme for instance, it would be possible that the multiple layers of the multilayer transmission are associated with multiple antenna ports. The multiple antenna ports may have different transmit power limitations. It is possible that the modulation schemes are associated based on the transmit power limitations. While such association is described in connection with box 915, it would also be possible to execute the association of modulation schemes and layers / antenna ports at box 905. Various rules for associating modulation schemes with layers can be used. Some are mentioned next: For instance, the modulation scheme employing the larger constellation (i.e. , larger count of transmission symbols supported by the constellation) can be associated with the layer or specifically antenna port having larger transmit power. Alternatively or additionally, the modulation scheme having transmission symbols encoding more bits than constellation size (e.g., M larger than U in the example below) can be associated with the layer or specifically antenna port having the smaller transmit power.

[0073] At box 920, a first transmission symbol is determined for the first layer of the multilayer transmission. The first transmission symbol is determined based on a first set of M data bits. The M data bits are selected from the sequence of L data bits. M < L.

[0074] The first transmission symbol is determined using a first modulation scheme. The first modulation scheme has 2Utransmission symbols. I.e., the size of the constellation is 2U. M may not be smaller than II, i.e., M may be larger or equal than U, M > U.

[0075] At box 925, a second transmission symbol is determined using a second modulation scheme; the second transmission symbol is determined based on N data bits selected from the sequence of L data bits. N < L. The second modulation scheme has 2Vtransmission symbols. N may not smaller than V, i.e, / V may be larger or equal than V, N > V.

[0076] The first set of M data bits and the second set of N data bits are at least partially overlapping. I.e., at least one of bits included in the first set is also included in the second set. This means that the first transmission symbol determined at box 920 and the second transmission symbol determined at box 925 are dependent on each other. This is a characteristic of the interdependent multilayer transmission mode.

[0077] The second modulation scheme used at box 925 is generally different than the first modulation scheme used at box 920. I.e., different bitmaps I constellation diagrams are used.

[0078] At box 926, the first and second transmission symbols determined at box 920 and box 925, respectively, are transmitted. The radio channel is accessed. This may include indicating one of the first and second transmission symbols to a collaborating WD on a sidelink. If the sidelink has a throughput restriction, then the maximum constellation size may have been previously indicated as part of the capability or configuration at box 905; this ensures that the one of the first and second transmission symbol can be signaled to the collaborating WD.

[0079] The first and second transmission symbols may be contemporaneously transmitted. If multiple WDs are associated with the multiple layers, a synchronization between the multiple WDs may be used to ensure contemporaneous transmission. Next, the orthogonal multilayer transmission mode (branch 912) is explained.

[0080] At box 930, the orthogonal multilayer transmission mode is activated. Box 930 can include selecting modulation schemes for each of the multiple layers of the multilayer transmission. This may be based on a configuration of box 905. Also, configuration data may be obtained from a control node at box 930. Such configuration could also be based on a current channel estimate executed at box 930.

[0081] At box 935 a third transmission symbol is determine. The third transmission symbol may be different than the first and second transmission symbols of box 920, 925. The third transmission symbol is for the first layer of the multilayer transmission. The third transmission symbol is determined based on a third set of M* data bits selected from the sequence of L data bits and using the third modulation scheme having 2U* transmission symbols. M* may not larger than U*, i.e. , M* is smaller or equal than U*.

[0082] At box 940, a fourth transmission symbol is determined. The fourth transmission symbol is for the second layer of the multilayer transmission. The fourth transmission symbol may be different than the first and second transmission symbols of box 920, 925. The fourth transmission symbol is determined based on a fourth set of N* data bits selected from the sequence of L data bits using a fourth modulation scheme having 2 * transmission symbols, wherein L* may not larger than V*, i.e., L* is smaller or equal than V*. Typically, L* equals V* and M* equals U*.

[0083] The third modulation scheme may be the same as the fourth modulation scheme.

[0084] The third set and the fourth set are non-overlapping. I.e., any bit of the sequence of L data bits is either included in the third set or in the fourth set, but not in both the third set and the fourth set. This is characteristic for the orthogonal multilayer transmission mode of branch 912.

[0085] At box 941, the third and fourth transmission symbols determined at box 935 and box 940, respectively, are transmitted. This may include indicating one of the third and fourth transmission symbols to a collaborating WD on a sidelink. The radio channel is accessed.

[0086] The third and fourth transmission symbols may be contemporaneously transmitted. If multiple WDs are associated with the multiple layers, a synchronization between the multiple WDs may be used to ensure contemporaneous transmission.

[0087] Next, the functionality of the method of FIG. 3 is explained in further detail. While the interdependent and orthogonal multilayer transmission modes are applicable for a wide variety of modulation schemes, settings and parameters, a specific example will be provided to explain effects attained thereby.

[0088] A multilayer uplink transmission is considered in which a single-antenna M-WD of a device collaboration group including the M-WD and an A-WD has a sequence of four bits (L=4) of uplink data to be transmitted to a BS of a cellular network (cf. box 906). This sequence may be denoted as {b1;b2,b2, b4}. TheA-WD also has a single antenna.

[0089] The A-WD and the M-WD collaborate to transmit the sequence of four bits. In the specific example, the A-WD assists the M-WD by transmitting two of the four bits.

[0090] In the illustrated example, the BS implementing the RX node is not aware that that the A-WD and the M-WD collaborate in the multilayer UL transmission. From the perspective of the BS, the M-WD informs the BS that it has two transmit antennas and / or two antenna ports, but the BS is not aware that the one antenna port is implemented by the M-WD and the other antenna port is implemented by the A-WD.

[0091] First, the orthogonal multilayer transmission mode (branch 912) is discussed. In the orthogonal multilayer transmission mode (branch 912), the third transmission symbol determined at box 935 is a quadrature phase shift keying (QPSK) symbol x3; the fourth transmission symbol determined at box 940 is also a QPSK symbol x4where bits b , b2determine x3and bits b2, b4determine x4. I.e., different / orthogonal bits are used to determine the two transmission symbols, respectively. The M-WD determines both the third and fourth transmission symbol and, at box 945, provides an indication of the fourth transmission symbol to the A-WD on the respective sidelink.

[0092] Second, the interdependent multilayer transmission mode (branch 911) is discussed. At box 920 and box 925, two 4-QPSK transmission symbols x4(first transmission symbol) and x2(second transmission symbol) are determined. The two bits b1,b2( / W=2) determine x4and all four bits b^b^ bz.b (N=L=4) determine x2. As will be appreciated, the first set of bits {b1,b2} based on which the first transmission symbol is determined and the second set of bits {b1,b2,b3, b4} overlap, because the bits b , b2are included in both the first set as well as the second set.

[0093] At box 926, the M-WD signals, via a sidelink, x2to the A-WD, and / P^1x1and 7^%2aretransmitted from the M-WD and the A-WD, respectively, at box 926. Here, Pmand Padenote the TX power limitations of the M-WD and the A-WD (and accordingly of the thus defined antenna ports), respectively.

[0094] The bitmap of first modulation scheme - a 4-QPSK modulation scheme - used to determine the first transmission symbol at box 920 is given by:

[0095] %i = (1 - 2b1) + ;(1 - 2b2)

[0096] (1) This bitmap of Eq. 1 is illustrated by the constellation diagram 315 in FIG. 4. The first modulation scheme has four transmission symbols, i.e., U=2. Hence, M = U = 2. I.e., based on the first transmission symbol alone, the RX node is able to unambiguously determine b1, b2.

[0097] The bitmap of the second modulation scheme - also a 4-QPSK modulation scheme - used to determine the second transmission symbol at box 925 is given by: = -(1 - 2&1)(1 - 2b3) — j(l - 2b2)(l - 2b4).

[0098] (2)

[0099] The respective constellation diagram 320 of the bitmap of Eq. 2 is illustrated in FIG. 5. The second modulation scheme also has 4 transmission symbols, i.e., V = 2. Accordingly, N > V. This means that based on the second transmission symbol alone (without the first transmission symbol) it is not possible for the RX node to unambiguously determine all four bits b1, b2, b3, b4. It is possible to unambiguously determine all four bits based on a combination of the first transmission symbol and the second transmission symbol. This is because of the choice of the bitmaps of the first and second modulation schemes: The bitmaps are connected to a 16- Quadrature Amplitude Modulation (QAM) constellation scheme that is collaboratively implemented by the first and second modulation scheme. The first expression “(1 - 2h4)(2 - (1 - 2b3)) + j(l - 2b2)(2 - (1 - 2b4))“ of the bitmap of Eq. 2 is a 16-QAM transmission symbol. See, e.g., 3GPP Technical Specification (TS) 38.211 , section 5.1.4, version 18.0.0. The second expression 2(1 - 2b4) -;2(1 - 2b2) of the bitmap of Eq. 2 - which equals 2xl ti.e., is proportional to the first transmission symbol - can be seen an indication of the quadrant of the constellation diagram in which the first expression belongs. With that the second transmission symbol x2is the selected point from a 4-QPSK constellation formed by the four points in the selected quadrant. This is illustrated in FIG. 6. The large open circles define the (center points of the) quadrant selected by the second expression of the bitmap of Eq. 2; starting from the selected quadrant, the small filled circles define the actual 16-QAM symbol based on the first expression of the bitmap of Eq. 2. For example, if {b1;b2, b2, b4= {1100}, the second expression of the bitmap of Eq. 2 gives -2 - 2j, i.e., the southwestern quadrant in FIG. 6. The first expression equals -1 - j. Calculating x2gives x2= 1 + j, which is, taking the open large circle in the southwestern quadrant as the origin, to the northeast, i.e., arrow 307. This process may be intuitively described as follows: two 4-QAM transmission symbols x±and x2are found from a mother constellation, namely 16-QAM constellation, and x±the quadrant while x2represents the location within the quadrant. In even further detail, the received signal at the RX node is: with n being complex Gaussian noise with covariance matrix N0I, H is a 2 x 2 channel matrix capable of supporting two layers (i.e. , a 2x2 full-rank channel matrix), and <p is a phase rotation that may be used to optimally align the transmitted signal to the current channel. The RX node can apply a max-log-map (MLM) demodulator, and thereby computes 4 log-likelihood ratios (one per bit) A1,A2,A3,A4. In detail, the RX node can first determine - based on x1 - the first two bits b1,b2(or, more precisely, respective likelihood ratios). Then, based on the knowledge of these two bits (selecting the quadrant of the 16-QAM constellation, cf. FIG. 6), all four bits can be determined.

[0100] Running the MLM demodulator a large number of times allows, through Monte Carlo computation, determine the mutual information I(bkAk). By symmetry it follows that I±= / (bijAi) = I(b2 2) and I2= / (b3;A3) = I(b4A4). The sum 2( / , + / 2) is usually refered to as the BICM capacity (or in some texts, the BCJR-once rate), and operationally corresponds to the highest rate that the system can support. It turns out that for both the interdependent multilayer transmission mode as well as the orthogonal multilayer transmission mode, the same value / , is obtained. But the values of I2differ. This is explained in further detail below.

[0101] To demonstrate a technical effect of the bitmaps according to Eq. 1 and Eq. 2 - as an example how an interdependent multilayer transmission mode using dependent transmission symbols on multiple layers hereinbelow cases for which I2of the orthogonal multilayer transmission mode is inferior to the interdependent multilayer transmission mode are disclosed. The channel matrix H plays a pivotal role for the performance of the various disclosed multilayer transmission modes: for some H the interdependent multilayer transmission mode is superior, and for other H the orthogonal multilayer transmission mode is superior. This is why it is helpful to be able to switch between both modes, cf. FIG. 3: box 910. To illustrate this, two example corner cases are considered, (i) an orthogonal channel matrix / / = [1 0; 0 1], and (ii) a rank-1 channel matrix / / = [1 1; 0 0], The ensuing rates / , and I2for (i) are depicted in FIG. 7; and for (ii) in FIG. 8. Dashed line 701 denotes I2 for interdependent multilayer transmission mode; dashed line 702 denotes I2 for the orthogonal multilayer transmission mode; and the continuous line 703 denotes 11 for both transmission modes. In the scenario of FIG. 8, i.e., case (ii), there is a significant gain of the interdependent multilayer transmission mode; while for case (i) in FIG. 7, the collaborative and orthogonal multilayer transmission modes perform similarly at medium-high signal-to-noise rations (SNR); in FIG. 8, a loss occurs at low SNR. As cases (i) and (ii) represent corner cases, there is a large fraction of channels for which the interdependent multilayer transmission mode outperforms the orthogonal multilayer transmission mode.

[0102] FIG. 9 illustrates a processing pipeline in a TX circuitry for determination of transmission symbols for the orthogonal multilayer transmission mode (cf. FIG. 3: branch 912). At box 821 scrambling to an input sequence of bits is performed. This yields the sequence of bits to be transmitted (cf. box 906 of FIG. 3). At box 822, two or more transmission symbols are determined; these two or more transmission symbols are independent of each other, because each bit is used for determining only one of these two or more transmission symbols. At box 823, it is then possible to map the two or more transmission symbols of box 822 to two or more layers. At box 824, precoding can be applied; e.g., different precoding for different layers of the two or more layers. For single-antenna antenna ports, the precoding corresponds to different phase shifts, optionally using a variable gain.

[0103] FIG. 10 illustrates determination of transmission symbols for the collaborative multilayer transmission mode (cf. FIG. 3: branch 911). At box 831 scrambling to an input sequence of bits is performed. This yields the sequence of bits to be transmitted (cf. box 906 of FIG. 3). At box 832, the bits are mapped to the two or more layers and at box 833 the two or more transmission symbols are determined (box 832 and box 833 may also be arranged in reverse order); these two or more transmission symbols are not independent of each other, because at least one bit us used for determining at least two of the two or more transmission symbols. This is indicated by the dashed line in FIG. 10. Example bitmaps that may be used at box 833 was described in Eq. 1 and Eq. 2. The RX node requires all two or more transmission symbols to be able to deduce all of the bits; the RX node cannot determine those bits based on which multiple transmission symbols are determined based on only one of those transmission symbols. At box 834, precoding is applied; e.g., different precoding for different layers of the two or more layers. For single-antenna antenna ports, the precoding corresponds to different phase shifts, optionally using a variable gain.

[0104] FIG. 11 is a flowchart of a method according to various examples. The method of FIG. 11 is executed by an RX node. The RX node participates in a multilayer transmission. The RX node receives data from at least one TX node. The at least one TX node can operate in accordance with the method of FIG. 3. For instance, the method of FIG. 11 may be executed by a base station of a cellular network. The method of FIG. 11 can be executed by a processor, upon loading program code from a memory and upon executing the program code. For instance, the method of FIG. 11 may be executed by the processor 61 upon loading and executing program code that is stored in the memory 62.

[0105] FIG. 11 exemplifies the operation for a multilayer transmission using two layers; but, as a general rule, the multilayer transmission may use more than two layers. The method of FIG. 11 can employ concepts as previously explained in connection with FIG. 3. The RX node executing the method of FIG. 11 operates in an inter-related manner with the at least one TX node executing the method of FIG. 3.

[0106] At box 955, the multilayer transmission is configured. The RX node may exchange information with a control node and / or the at least one TX node.

[0107] For instance, capability information may be provided to a control node. The capability information may be indicative of a capability of the RX node to participate in the multilayer transmission. The capability information may be indicative of a capability of the RX node to support a certain multilayer transmission mode or to support multiple multilayer transmission modes. The capability information may be indicative of a capability of the RX node to switch between multiple multilayer transmission modes.

[0108] Alternatively or additionally to providing such capability information to a control node, capability information from the at least one TX node may be obtained. This is, in particular, helpful if the RX node implements the control node. Various information that can be provided by the at least one TX node has been previously discussed in connection with FIG. 3: box 905.

[0109] Information may be obtained from the at least one TX node that a rank-X multilayer transmission is implemented, with X>1. For instance, X may be indicated. The number of layers may be indicated.

[0110] As previously explained in connection with box 905 in FIG. 3, various information can be obtained from the at least one TX node. This includes a rank of the multilayer transmission. The RX node may obtain information regarding multiple antenna ports. The multiple antenna ports can be associated with the multiple layers of the multilayer transmission. For instance, a WD may indicate that it includes multiple antenna ports. It may be transparent to the RX node whether the multiple antenna ports are implemented by multiple WDs or a single WD. It may be transparent to the RX node whether multiple WDs form a device collaboration group.

[0111] The at least one TX node may report a maximum number of bits that may be used to determine each transmission symbol for antenna port.

[0112] Box 955 can include providing configuration information for one or more transmission modes. For instance, a configuration for an interdependent multilayer transmission mode may be provided. For instance, the RX node (implementing a control node) may indicate which particular modulation schemes are to be used. The RX node can indicate the bitmaps used for determining transmission symbols. The RX node can indicate which modulation scheme to use for which layer or antenna port. The RX node can indicate one or more trigger criteria for switching between different multilayer transmission modes, e.g., for switching between an interdependent multilayer transmission mode and an orthogonal multilayer transmission mode. Phase rotations to be applied per port can be indicated. The phase rotation can be determined based on the channel obtained from the channel sounding procedure. Alternatively, precoder matrices can be indicated for the various layers or antenna ports.

[0113] At box 960, a selection is made. Specifically, at branch 961 , and interdependent multilayer transmission mode is selectively activated. This may be based on channel sounding executed at box 960 (aspects with such channel sounding have been previously explained in connection with FIG. 3). A selection can be made between the interdependent multilayer transmission mode (branch 961) on the one hand, and an orthogonal multilayer transmission mode (branch 962) or even a single layer transmission mode (not shown in FIG. 11).

[0114] Upon selecting the interdependent multilayer transmission mode, box 965 is executed. At box 965, the interdependent multilayer transmission mode is activated. A respective activation signal can be provided to the at least one WD. Details with respect to such activation signal have been disclosed in connection with box 910. It would be possible to associate certain modulation schemes with certain antenna ports used for accessing the multiple layers; this association can be based on respective transmit power limitations indicated previously in box 955 by the at least one WD. It would be possible that such association is already made at box 955.

[0115] At box 970, first and second transmission symbols are received on the first and second layers. Respective aspects have been previously explained in connection with FIG. 3: box 920 - first transmission symbol -, as well as FIG. 3: box 920 - second transmission symbol.

[0116] Then, at box 975, the first transmission symbol is processed (e.g., demodulated), to determine a first set of M data bits of a sequence of L data bits. The first transmission symbol is modulated in accordance with a first modulation scheme that has 2Utransmission symbols.

[0117] Then, at box 980, the second transmission symbol is processed, to determine a second set of N data bits selected from the sequence of L data bits. The second transmission symbol is modulated in accordance with a second modulation scheme that has 2Vtransmission symbols. The first and second set are at least partially overlapping. This means that the first and second transmission symbols are interdependent on each other. To be able to unambiguously determine the second set of N data bits, the RX node takes into account the first set of M data bits, as previously explained in connection with FIG. 6.

[0118] At box 995, it is then possible to provide the sequence of data bits obtained from the demodulation process, e.g., to a higher layer of a transmission protocol stack.

[0119] Upon selecting the orthogonal multilayer transmission mode (branch 962), box 985 is executed. At box 985, the orthogonal multilayer transmission mode is activated. A respective activation signal indicative of the orthogonal multilayer transmission mode can be provided to the at least one WD.

[0120] At box 990, third and fourth transmission symbols are received on the first and second layers. Respective aspects have been previously explained in connection with FIG. 3: box 935 - third transmission symbol as well as FIG. 3: box 940 - fourth transmission symbol.

[0121] Then, box 991 and box 992 can be executed independently of each other. At box 991 , the third transmission symbol is processed to determine a third set of M* data bits selected from the sequence of L data bits. This is done in accordance with a third modulation scheme having 2U* transmission symbols. At box 992, the fourth transmission symbol is processed to determine a fourth set of / V'data bits selected from the sequence of L data bits. This is done in accordance with a fourth modulation scheme having 2V* transmission symbols.

[0122] M* is not larger than II*, and L* is not larger than V*. Also, the third and fourth sets are nonoverlapping, i.e. , disjunct. Thus, box 991 and box 992 can be executed independently. Knowledge of the data bits encoded by the third transmission symbol is not required to demodulate the fourth transmission symbol.

[0123] Then, box 995 is executed.

[0124] Summarizing, techniques have been disclosed that enable an interdependent multilayer transmission mode. An additional gain of dependent layer bitmaps of multiple modulation schemes of the interdependent multilayer transmission was disclosed.

[0125] The multiple layers can be associated with multiple antenna ports. These antenna ports can have different transmit power limitations. It has been disclosed how different modulation schemes can be associated with the different antenna ports depending on these transmit power limitations.

[0126] Transmit power limitations associated with different antenna ports can stem from different antenna ports being implemented by different WDs. For instance, multiple WDs can form a device collaboration group. Uplink data of a M-WD can be transmitted jointly by the master WD and one or more A-WDs. The device collaboration may be transparent to the BS.

[0127] In such setting, a performance boost to the communication system is achieved if the constellation bitmap is not independent across layers. Further, in some cases the performance is further boosted if different layers carries different constellations.

[0128] Further summarizing, at least the following EXAMPLES have been disclosed. EXAMPLE 1. A method for use in a transmit node of a multilayer transmission, the method comprising:

[0129] - obtaining (906) a sequence of L data bits of data to be transmitted, wherein the method further comprises, upon a first multilayer transmission mode being activated:

[0130] - determining (920) a first transmission symbol for a first layer (81) of the multilayer transmission based on a first set of M data bits selected from the sequence of L data bits and using a first modulation scheme having 2Utransmission symbols, and

[0131] - determining (925) a second transmission symbol for a second layer (82) of the multilayer transmission based on a second set of N data bits selected from the sequence of L data bits and using a second modulation scheme having 2Vtransmission symbols, the first set and the second set are at least partially overlapping.

[0132] EXAMPLE 2. The method of claim 1 , wherein the first modulation scheme is different than the second modulation scheme.

[0133] EXAMPLE 3. The method of claim 1 or 2, further comprising:

[0134] - obtaining, from a control node associated with the multilayer transmission, an activation signal activating the first multilayer transmission mode.

[0135] EXAMPLE 4. The method of claim 3, wherein the activation signal is obtained in association with a grant for transmitting at least one of the first transmission symbol or the second transmission symbol.

[0136] EXAMPLE 5. The method of claim 3, wherein the activation signal is obtained in a configuration phase of the multilayer transmission prior to obtaining the sequence of L data bits.

[0137] EXAMPLE 6. The method of any one of the preceding claims, further comprising:

[0138] - obtaining a further sequence of L* data bits of data, wherein the method further comprises, upon a second multilayer transmission mode being activated:

[0139] - determining a third transmission symbol for the first layer of the multilayer transmission based on a third set of M* data bits selected from the further sequence of L* data bits and using a third modulation scheme having 2U* modulation symbols, wherein M* is not larger than U*, and - determining a fourth transmission symbol for the second layer of the multilayer transmission based on a fourth set of / V* data bits selected from the further sequence of L* data bits using a fourth modulation scheme having 2 * modulation symbols, wherein L* is not larger than V*, the third set and the fourth set being non-overlapping.

[0140] EXAMPLE 7. The method of claim 6, wherein the third modulation scheme is the same as the fourth modulation scheme.

[0141] EXAMPLE 8. The method of any one of the preceding claims, wherein the first layer (81) and the second layer (82) are associated with different ones of multiple antenna ports, wherein the method further comprising:

[0142] - providing, to a control node (75) associated with the multilayer transmission, an indication of the multiple antenna ports.

[0143] EXAMPLE 9. The method of claim 8, wherein the multiple antenna ports are associated with different transmit power limitations, wherein the method further comprises:

[0144] - providing, to the control node (75), an indication of the transmit power limitations of the multiple antenna ports.

[0145] EXAMPLE 10. The method of claim 9, further comprising:

[0146] - obtaining, from the control node associated with the multilayer transmission, an activation signal activating the first multilayer transmission mode responsive to providing the indication of the transmit power limitations of the multiple antenna ports.

[0147] EXAMPLE 11. The method of any one of the preceding claims, wherein the first layer (81) is associated with a first wireless device connected to a radioaccess network of a cellular network, wherein the second layer is associated with a second wireless device connected to the radio-access network of the cellular network wherein the first wireless device and the second wireless device are part of a device collaboration group.

[0148] EXAMPLE 12. A method for use in a receive node, the method comprising: - receiving a first transmission symbol on a first layer of the multilayer transmission,

[0149] - receiving a second transmission symbol on a second layer of the multilayer transmission,

[0150] - upon a first multilayer transmission mode being activated: determining a first set of M data bits selected from a sequence of L data bits and in accordance with a first modulation scheme having 2Utransmission symbols, and

[0151] - upon the first multilayer transmission mode being activated: determining a second set of N data bits selected from the sequence of L data bits and in accordance with a second modulation scheme having 2Vtransmission symbols, wherein the first set and the second set are at least partially overlapping.

[0152] EXAMPLE 13. The method of claim 12, wherein the second set of N data bits is determined based on the first set of M data bits, wherein the first set M of data bits is not determined based on the second set N of data bits.

[0153] Although the invention has been shown and described with respect to certain preferred embodiments, equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications and is limited only by the scope of the appended claims.

[0154] For illustration, above scenarios have been disclosed in which an interdependent multilayer transmission mode is selectively activated. Specifically, scenarios have been disclosed in which a selection in between, firstly, the interdependent multilayer transmission mode and, secondly, an orthogonal multilayer transmission mode is made. It would be likewise possible to make a selection between, firstly, the interdependent multilayer transmission mode and secondly, a single layer transmission mode. In other words, it would be possible that multilayer transmission is only selectively activated if a interdependent multilayer transmission mode is beneficial. Otherwise, a fallback to single layer transmission may be employed.

Claims

C L A I M S1. A method for use in a transmit node of a multilayer transmission, the method comprising:- obtaining (906) a sequence of L data bits of data to be transmitted, wherein the method further comprises, upon a first multilayer transmission mode being activated:- determining (920) a first transmission symbol for a first layer (81) of the multilayer transmission based on a first set of M data bits selected from the sequence of L data bits and using a first modulation scheme having 2Utransmission symbols, and- determining (925) a second transmission symbol for a second layer (82) of the multilayer transmission based on a second set of N data bits selected from the sequence of L data bits and using a second modulation scheme having 2Vtransmission symbols, the first set and the second set are at least partially overlapping.

2. The method of claim 1 , wherein the first modulation scheme is different than the second modulation scheme.

3. The method of claim 1 or 2, further comprising:- obtaining, from a control node associated with the multilayer transmission, an activation signal activating the first multilayer transmission mode.

4. The method of claim 3, wherein the activation signal is obtained in association with a grant for transmitting at least one of the first transmission symbol or the second transmission symbol.

5. The method of claim 3, wherein the activation signal is obtained in a configuration phase of the multilayer transmission prior to obtaining the sequence of L data bits.

6. The method of any one of the preceding claims, further comprising:- obtaining a further sequence of L* data bits of data, wherein the method further comprises, upon a second multilayer transmission mode being activated:- determining a third transmission symbol for the first layer of the multilayer transmission based on a third set of M* data bits selected from the further sequence of L* databits and using a third modulation scheme having 2U* modulation symbols, wherein M* is not larger than U*, and- determining a fourth transmission symbol for the second layer of the multilayer transmission based on a fourth set of N* data bits selected from the further sequence of L* data bits using a fourth modulation scheme having 2 * modulation symbols, wherein L* is not larger than V*, the third set and the fourth set being non-overlapping.

7. The method of claim 6, wherein the third modulation scheme is the same as the fourth modulation scheme.

8. The method of any one of the preceding claims, wherein the first layer (81) and the second layer (82) are associated with different ones of multiple antenna ports, wherein the method further comprising:- providing, to a control node (75) associated with the multilayer transmission, an indication of the multiple antenna ports.

9. The method of claim 8, further comprising:- obtaining, from the control node, an activation signal activating the first multilayer transmission mode responsive to providing the indication of the multiple antenna ports.

10. The method of claim 8 or 9, wherein the multiple antenna ports are associated with different transmit power limitations, wherein the method further comprises:- providing, to the control node (75), an indication of the transmit power limitations of the multiple antenna ports.11 . The method of claim 10, further comprising:- obtaining, from the control node associated with the multilayer transmission, an activation signal activating the first multilayer transmission mode responsive to providing the indication of the transmit power limitations of the multiple antenna ports.

12. The method of any one of the preceding claims, wherein the first layer (81) is associated with a first wireless device connected to a radioaccess network of a cellular network,wherein the second layer is associated with a second wireless device connected to the radio-access network of the cellular network.

13. The method of claim 12, wherein the data originates at a higher layer of only the first wireless device.

14. The method of claim 12 or 13, wherein the first wireless device and the second wireless device are part of a device collaboration group.

15. The method of any one of claims 8 to 11 , as well as of claim 14, wherein the indication of the multiple antenna ports is provided responsive to establishing the device collaboration group.

16. The method of any one of the preceding claims, wherein the first layer and the second layer are associated with different ones of multiple antenna ports, wherein the method further comprises:- associating the first modulation scheme with either the first layer or the second layer depending on transmit power limitations of the multiple antenna ports.

17. The method of any one of the preceding claims, wherein the first modulation scheme is a first 4-QPSK modulation scheme, wherein the second modulation scheme is a second 4-QPSK modulation scheme.

18. The method of any one of the preceding claims, wherein L=4, wherein M=2, wherein U=2, wherein A / =4, and wherein V=2.

19. The method of claims 17 and 18, wherein the first transmission symbol selects a quadrant of a constellation diagram of a 16-QAM modulation scheme that is collaboratively implemented by the first modulation scheme and the second modulation scheme,wherein the second transmission symbol selects a position within the selected quadrant of the constellation diagram.

20. The method of any one of the preceding claims, wherein the sequence of L bits is b1 , b2, b3, b4, wherein the first modulation scheme comprises the following bitmap: (1-2xb1)+j(1-2xb2); and wherein the second modulation scheme comprises the following bitmap: -(1 -2xb1 )x(1 -2xb3)-j(1 -2xb2)x(1 -2xb4).

21. The method of any one of the preceding claims, wherein M is larger than U and / or wherein N is larger than V.

22. The method of any one of the preceding claims, wherein M is different than N.

23. The method of any one of the preceding claims, wherein U is equal to V.

24. The method of any one of the preceding claims, wherein M is larger than II.

25. The method of any one of the preceding claims, wherein N is larger than V.

26. The method of any one of the preceding claims, wherein M divided by N is not smaller than II divided by V.

27. The method of any one of the preceding claims, further comprising:- transmitting the first transmission symbol, and- transmitting the second transmission symbol.

28. A method for use in a receive node, the method comprising:- receiving a first transmission symbol on a first layer of the multilayer transmission,- receiving a second transmission symbol on a second layer of the multilayer transmission,- upon a first multilayer transmission mode being activated: determining a first set of M data bits selected from a sequence of L data bits and in accordance with a first modulation scheme having 2Utransmission symbols, and- upon the first multilayer transmission mode being activated: determining a second set of N data bits selected from the sequence of L data bits and in accordance with a second modulation scheme having 2Vtransmission symbols, wherein the first set and the second set are at least partially overlapping.

29. The method of claim 28, wherein the second set of N data bits is determined based on the first set of M data bits, wherein the first set M of data bits is not determined based on the second set N of data bits.

30. A method for use in a receive node of a multilayer transmission, the method comprising:- sounding each of multiple layers of the multilayer transmission,- depending on said sounding: selectively activating a first multilayer transmission mode using interdependent transmission symbols on multiple layers of the multilayer transmission.

31. The method of claim 30, further comprising:- upon not activating the first multilayer transmission mode that uses the interdependent transmission symbols, activating a second multilayer transmission mode that uses orthogonal transmission symbols.

32. The method of claim 30, further comprising:- upon refraining from activating the first multilayer transmission mode that uses the interdependent transmission symbols, activating a single-layer transmission mode.

33. A transmit node configured to participate in a multilayer transmission, the transmit node comprising a processor and a memory, the processor being configured to load program code from the memory and to execute the program code, execution of the program code causing the processor to:- obtain (906) a sequence of L data bits of data to be transmitted,- upon a first multilayer transmission mode being activated, determine (920) a first transmission symbol for a first layer (81) of the multilayer transmission based on a first set of M data bits selected from the sequence of L data bits and using a first modulation scheme having 2Utransmission symbols, and- upon the first multilayer transmission mode being activated, determine (925) a second transmission symbol for a second layer (82) of the multilayer transmission based on a second set of / V data bits selected from the sequence of L data bits and using a second modulation scheme having 2Vtransmission symbols, the first set and the second set are at least partially overlapping.

34. The transmit node of claim 33, wherein execution of the program code causes the processor to perform the method of any one of claims 1 to 27.

35. A receive node configured to participate in a multilayer transmission, the receive node comprising a processor and a memory, the processor being configured to load program code from the memory and to execute the program code, execution of the program code causing the processor to:- receive a first transmission symbol on a first layer of the multilayer transmission,- receive a second transmission symbol on a second layer of the multilayer transmission,- upon a first multilayer transmission mode being activated: determine a first set of M data bits selected from a sequence of L data bits and in accordance with a first modulation scheme having 2Utransmission symbols, and- upon the first multilayer transmission mode being activated: determine a second set of N data bits selected from the sequence of L data bits and in accordance with a second modulation scheme having 2Vtransmission symbols, wherein the first set and the second set are at least partially overlapping.

36. The receive node of claim 35, wherein execution of the program code causes the processor to perform the method of any one of claims 30 to 32.

37. A system, comprising the transmit node of claim 33 or 34 and the receive node of claim 35 or 36.

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