Patent Description:
Non-orthogonal multiple access (NOMA) has been proposed as a technique for fifth generation (<NUM>) networks and beyond. In Long Term Evolution (LTE) Release <NUM>, a study item on downlink power-domain multiplexing NOMA, has been referred to as multi-user superposition transmission (MUST). The fundamental idea behind this technique is to multiplex multiple users in the power domain at the transmitter side based on superposition coding, and then to perform multi-user signal separation, i.e., interference cancellation at the receiver side based on successive interference cancellation (SIC) processing. That is to say that the NOMA technique exploits an extra new domain to accommodate multiple users within the same orthogonal time-frequency resource block (RB), which is not sufficiently exploited in the current LTE systems.

Since NOMA utilizes this additional power domain, it should always outperform the traditional orthogonal multiple access (OMA) schemes, e.g., frequency division multiple access (FDMA)/time division multiple access (TDMA)/code division multiple access (CDMA)/orthogonal frequency division multiple access (OFDMA), in terms of sum-throughput. Another feature of NOMA, is that throughput-fairness among users may be improved as compared with other arrangements, because NOMA allocates more power to users with poor channel conditions and less power for users with better channel conditions. Specifically, this feature may have importance for some applications in <NUM> networks, such as Internet-of-Things (IoT). In the IoT, the massive number of devices that require only a small amount of data can be served in the same band. For this application, achieving high connectivity may be more desirable than achieving high data rate to satisfy high quality-of-service (QoS) requirements.

Reaping the benefits of NOMA may depend on making optimal use of the limited power resource in the network. Particularly, in NOMA with SIC, the power allocation to a certain user impacts the achievable throughput of not only that user, but also other users due to inter-user interference. Hence, improper power allocation can significantly deteriorate the overall performance of NOMA. There have been numerous investigations into the impact of power allocation on the performance of NOMA systems. For instance, researchers have investigated features of optimal/non-optimal power allocation, high complexity/low complexity implementations, different type of fairness, different scenario single-channel power amplifiers (PA), multichannel/cluster PA.

For making non-orthogonal transmission feasible, advanced transmission/ reception techniques, such as dirty paper coding (DPC) or SIC, may be used at the wireless device (WD) receivers. In past research, application of SIC to the WD receivers was considered in the cellular downlink for interference cancellation. Additionally, in some cases it is assumed that the SIC receivers are capable of perfectly cancelling the interference in NOMA. However, in practice this assumption cannot be readily realized due to inaccurate power amplification (PA) and imperfect channel decoding, resulting in inter-user error propagation that makes difficult the implementation of SIC. Hence, to mitigate the error propagation at SIC receivers, the power allocation among WDs should be handled carefully. Taking the discrete property of power allocation into consideration is used by many existing technologies. Restricting the power allocations to be discrete simplifies the hardware design and reduces the cost of practical transmitters. Although some consider continuous transmit power to find the solutions, applying those schemes in practical systems can be problematic. For example, rounding does not guarantee optimality and rounding may cause inaccurate power allocation. Thus, this convenient continuous power assumption has mainly been due to either the limitations of the optimization tools applied and/or the high computational complexity involved in addressing the more realistic discrete power allocation/control.

Document "<NPL>, discloses a technique pertaining to NOMA that allows multiple users to access the same channel by adapting successive interference cancellation (SIC) and multiplexing in power domain. This causes the clustering problem to become critical as higher channel gain users need to cancel out the signals of lower channel gain users while the latter has to receive less interference. The document formulates the user clustering as a correlation clustering problem, transforms the problem by relaxing the clustering variables, and solves using semidefinite programming (SDP). Moreover, a simple iterative power allocation algorithm is nominated.

Document "<NPL>, discloses a technique pertaining to NOMA to increase the throughput of wireless multicast. To achieve optimal user assignment and discrete power control, the document formulates a combinatorial optimization problem. In particular, the document concentrates on the general case in which a user duster consists of an arbitrary number of users. To enhance scalability, the document proposes algorithms for finding out an optimal pair of user assignment and transmission power vector for NOMA multicast.

Document "<NPL>, discloses a technique pertaining to user scheduling and power allocation scheme for a millimeter wave non-orthogonal multiple access system. To reduce the feedback overhead, random beamforming is adopted at a base station. The optimization problem is formulated to maximize the energy efficiency. To solve this problem, the document first addresses the user scheduling and power allocation problem separately, then an iterative algorithm is proposed to jointly optimize the user scheduling and power allocation.

Some embodiments advantageously provide a method and system for discrete power allocation for a non-orthogonal multiple access (NOMA) wireless communication system.

According to the present disclosure, methods, a network node, a wireless device and computer storage devices according to the independent claims are provided. Developments are set forth in the dependent claims.

Some embodiments provide a fairness-aware power allocation algorithm for energy efficiency (EE) maximization (which can be measured in bits/Joule) in downlink NOMA systems. Unlike previous related efforts, a throughput-fairness constraint applying a weighted Jain's fairness index is imposed, and the transmit power levels are constrained to assume discrete, rather than continuous values, which renders the algorithm developed herein amenable to practical systems. However, the restriction on the power levels to be discrete, and a non-concave objective usually result in difficult-to-solve non-convex combinatorial formulations. The optimal, but computationally prohibitive, approach for solving such combinatorial problems is to perform an exhaustive search. To reduce the computational complexity of the exhaustive search, some embodiments exploit the structure of NOMA with SIC and devise a low-complexity algorithm. The devised algorithm not only may yield an optimal solution, but also enables power allocation optimization for NOMA with a relatively high number of power levels. The devised algorithm may also be applicable to any desired objective function with any set of constraints.

Some advantages of some embodiments are summarized as follows and include:.

According to one aspect, a method for a network node for discrete power allocation for a non-orthogonal multiple access, NOMA, system is provided. The method includes determining a set of discrete power allocation values, each power allocation value being assigned to a particular wireless device, WD, in a set of WDs, the determining including subjecting the power allocation values to at least one constraint to reduce a number of power allocation value combinations. The method further includes transmitting to the WDs in the set, a plurality of superimposed data signals, each data signal intended for a different one of the WDs in the set and having a different power allocation value, each WD in the set receiving all the plurality of superimposed data signals. The method also includes transmitting to each WD in the set of WDs a different control signal, the control signal including an indication of the power level allocation values of the set of discrete power allocation values.

According to this aspect, in some embodiments, the control signal for a first WD includes the power allocation values of all the WDs in the set, the control signal for a second WD in the set includes the power allocation values of all the WDs in the set other than the first WD, the control signal for a third WD in the set includes the power allocation values of all the WDs in the set other than the first and second WDs, wherein the control signal for a last WD in the set includes the power allocation value of only the last WD. In some embodiments, the control signal for the first WD includes a modulation and coding scheme, MCS, for all but the first WD, the control signal for the second WD includes an MCS for all but the first and second WD, wherein the control signal for the last WD does not include an MCS for the last WD or for any other WD in the set. In some embodiments, the control signal for the first WD includes an identifier for all but the first WD, the control signal for the second WD includes an identifier for all but the first and second WD, wherein the control signal for the last WD does not include an identifier for the last WD or for any other WD in the set. In some embodiments, the at least one constraint comprises a total power constraint. In some embodiments, the total power constraint specifies that a sum of the power allocation values for the WDs in the set is less than a predetermined total power value. In some embodiments, the at least one constraint comprises a constraint specifying that the WDs in the set are ordered for assignment of power allocation values based on a channel quality of each WD in the set. In some embodiments, determining a set of discrete power allocation values includes constraining the power allocation values to satisfy an inequality having terms consisting of a product of a power allocation value and a channel gain, an algebraic sum of the terms being less than a power difference determined to distinguish between a signal to be decoded and remaining non-decoded message signals.

According to another aspect, a network node configured for discrete power allocation for a non-orthogonal multiple access, NOMA, system. The network node includes processing circuitry configured to: determine a set of discrete power allocation values, each power allocation value being assigned to a particular wireless device, WD, in a set of WDs, the determining including subjecting the power allocation values to at least one constraint to reduce a number of power allocation value combinations. The processing circuitry is configured to transmit to the WDs in the set, a plurality of superimposed data signals, each data signal intended for a different one of the WDs in the set and having a different power allocation value, each WD in the set receiving all the plurality of superimposed data signals. The processing circuitry is further configured to transmit to each WD in the set of WDs a different control signal, the control signal including an indication of the power level allocation values of the set of discrete power allocation values.

According to this aspect, in some embodiments, the control signal for a first WD includes the power allocation values of all the WDs in the set, the control signal for a second WD in the set includes the power allocation values of all the WDs in the set other than the first WD, the control signal for a third WD in the set includes the power allocation values of all the WDs in the set other than the first and second WDs, wherein the control signal for a last WD in the set includes the power allocation value of only the last WD. In some embodiments, the control signal for the first WD includes a modulation and coding scheme, MCS, for all but the first WD, the control signal for the second WD includes an MCS for all but the first and second WD, wherein the control signal for the last WD does not include an MCS for the last WD or for any other WD in the set. In some embodiments, the control signal for the first WD includes an identifier for all but the first WD, the control signal for the second WD includes an identifier for all but the first and second WD, wherein the control signal for the last WD does not include an identifier for the last WD or for any other WD in the set. In some embodiments, the at least one constraint comprises a total power constraint. In some embodiments, the total power constraint specifies that a sum of the power allocation values for the WDs in the set is less than a predetermined total power value. In some embodiments, the at least one constraint comprises a constraint specifying that the WDs in the set are ordered for assignment of power allocation values based on a channel quality of each WD in the set. In some embodiments, the determining a set of discrete power allocation values includes constraining the power allocation values to satisfy an inequality having terms consisting of a product of a power allocation value and a channel gain, an algebraic sum of the terms being less than a power difference determined to distinguish between a signal to be decoded and remaining non-decoded message signals.

According to another aspect, computer storage device is provided for storing a computer program that, when executed by at least one processor in a network node, performs at least one method described below.

Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to discrete power allocation for a non-orthogonal multiple access (NOMA) system. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

The term "network node" used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term "radio node" used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node.

The WD (or UE) herein can be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD).

It can be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).

According to some embodiments, a method and apparatus for finding the optimum transmission power used for each WD in a NOMA system where the transmission powers are a subset of discrete power levels is provided. In some embodiments, the optimal power levels are signaled to the WDs using semi-static signaling, e.g., RRC signaling, or more dynamically using MAC control elements (MAC CE) or downlink control information (DCI).

Returning to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in <FIG> a schematic diagram of a communication system <NUM>, according to an embodiment, such as a 3GPP-type cellular network that may support standards such as LTE and/or NR (<NUM>), which comprises an access network <NUM>, such as a radio access network, and a core network <NUM>. The access network <NUM> comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes <NUM>), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas <NUM>). Each network node 16a, 16b, 16c is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16c. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16a. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices <NUM>) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node <NUM>. Note that although only two WDs <NUM> and three network nodes <NUM> are shown for convenience, the communication system may include many more WDs <NUM> and network nodes <NUM>.

A network node <NUM> is configured to include a power allocation unit <NUM> which is configured to determine a power allocation for a cluster of WDs <NUM>. A wireless device <NUM> is configured to include a successive interference cancellation (SIC) unit <NUM> which is configured to cancel signals embedded in a signal received by the WD <NUM>.

The host application <NUM> may be operable to provide a service to a remote user, such as a WD <NUM> connecting via an OTT connection <NUM> terminating at the WD <NUM> and the host computer <NUM>. The "user data" may be data and information described herein as implementing the described functionality. In one embodiment, the host computer <NUM> may be configured for providing control and functionality to a service provider and may be operated by the service provider or on behalf of the service provider. The processing circuitry <NUM> of the host computer <NUM> may enable the host computer <NUM> to observe, monitor, control, transmit to and/or receive from the network node <NUM> and or the wireless device <NUM>.

The communication system <NUM> further includes a network node <NUM> provided in a communication system <NUM> and comprising hardware <NUM> enabling it to communicate with the host computer <NUM> and with the WD <NUM>.

Thus, the network node <NUM> further has software <NUM> stored internally in, for example, memory <NUM>, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node <NUM> via an external connection. The processing circuitry <NUM> may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by network node <NUM>. Processor <NUM> corresponds to one or more processors <NUM> for performing network node <NUM> functions described herein. The memory <NUM> is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software <NUM> may include instructions that, when executed by the processor <NUM> and/or processing circuitry <NUM>, causes the processor <NUM> and/or processing circuitry <NUM> to perform the processes described herein with respect to network node <NUM>. For example, processing circuitry <NUM> of the network node <NUM> may include a Power Allocation unit <NUM> which is configured to determine a power allocation for a cluster of WDs.

The processing circuitry <NUM> may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD <NUM>. The processor <NUM> corresponds to one or more processors <NUM> for performing WD <NUM> functions described herein. The WD <NUM> includes memory <NUM> that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software <NUM> and/or the client application <NUM> may include instructions that, when executed by the processor <NUM> and/or processing circuitry <NUM>, causes the processor <NUM> and/or processing circuitry <NUM> to perform the processes described herein with respect to WD <NUM>. For example, the processing circuitry <NUM> of the wireless device <NUM> may include a successive interference cancellation (SIC) unit <NUM> which is configured to cancel signals embedded in a signal received by a the WD <NUM>.

In some embodiments, the network node <NUM> is configured to, and/or the network node's <NUM> processing circuitry <NUM> is configured to perform the functions and/or methods described herein for preparing/initiating/maintaining/ supporting/ending a transmission to the WD <NUM>, and/or preparing/terminating/ maintaining/supporting/ending in receipt of a transmission from the WD <NUM>.

In some embodiments, the WD <NUM> is configured to, and/or comprises a radio interface <NUM> and/or processing circuitry <NUM> configured to perform the functions and/or methods described herein for preparing/initiating/maintaining/ supporting/ending a transmission to the network node <NUM>, and/or preparing/ terminating/maintaining/supporting/ending in receipt of a transmission from the network node <NUM>.

Although <FIG> and <FIG> show various "units" such as power allocation unit <NUM>, and SIC unit <NUM> as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

A power control scheme for a simple transmission scenario is shown in <FIG>, where a network node <NUM> with a single antenna transmits a superposition of three signals, x1, x2 and x3, to three wireless devices WD-<NUM><NUM>-<NUM>, WD-<NUM><NUM>-<NUM> and WD-<NUM><NUM>-<NUM>, the superposition of the three signals being transmitted with a single antenna, over the same resource block (RB). Although three signals are shown here, carrying over the analysis to the case with an m-user downlink NOMA cluster, or to the case of multiple antennas at both the BS and the users, is contemplated. Thus, in other embodiments, one or more antennas may be used to transmit a superposition of m≥<NUM> signals x1,. xm, to a cluster of m WDs <NUM>. Here it assumed that the WD <NUM>-<NUM>, WD <NUM>-<NUM> and WD <NUM>-<NUM> have been pre-selected for the NOMA transmission based on a user-clustering algorithm. User-clustering algorithms are beyond the scope of this disclosure.

According to the multiuser superposition transmission scheme, the transmitted signal may be formed as x̂ = x<NUM> + x<NUM> + x<NUM>, and <MAT>, where si is the symbol for user i with E[|si|<NUM>] = <NUM>, and Pi is the transmit power associated with si. The channel gains of the users, U<NUM>, U<NUM>, and U<NUM>, are respectively H<NUM> = |h<NUM>|<NUM>, H<NUM> = |h<NUM>|<NUM>, H<NUM> = |h<NUM>|<NUM>, where hi is the complex channel coefficient between Ui and the BS, and H<NUM> > H<NUM> > H<NUM>. It is assumed that the transmit power of the users is allocated in inverse proportion to their channel gains, and SIC is employed at the receivers of users to reduce the interference from the other users on the same resource block (RB).

Thus, for this example, the signal x3 intended for WD-<NUM>22c is allocated greater power than the power allocated to signal x2 intended for WD-<NUM>22b, which is greater than the power allocated to signal x1 intended for WD-<NUM>. This is shown in the plot of power versus frequency <NUM> in <FIG>. At WD-<NUM>22a, successive interference cancellation <NUM> of the strongest signal x3 is performed. Then, WD-<NUM>22a performs successive interference cancellation <NUM> of the next strongest signal x2. Then, x1 is decoded <NUM>. At WD-<NUM>22b, successive interference cancellation <NUM> of the only signal stronger than x2, i.e., signal x3, is applied, followed by decoding <NUM> of x2. At WD-<NUM>22c, since the power of signal x3 is larger than the power of signals x1 and x2, decoding <NUM> of signal x3 can be performed without a step of successive interference cancellation.

The SIC operations at the receivers of the WDs <NUM> may be thus summarized as follows: The achievable throughput for signal in a <NUM>-user NOMA system, Ri, can be expressed as <MAT>, where W is the bandwidth of each RB, and N<NUM> is the power spectral density of the additive white Gaussian noise (AWGN). The signal processing structures in WD-<NUM>22a, WD-<NUM>22b and WD-<NUM>22c that may be used to achieve the signal decoding described above are shown in <FIG>. In some embodiments, these signal processing functions may be performed by SIC unit <NUM>. Thus, in the WD-<NUM>22a, the top branch decodes x3 when combined with x1 and x2, the middle branch decodes x2 when combined with x1, and the lower branch decodes x1. In the WD-<NUM>22b, the top branch decodes x3 when combined with x1 and x2, and the lower branch decodes x2 when combined with x1. In the WD-<NUM>22c, x3 is decoded when combined with x1 and x2.

In some embodiments, orthogonal frequency division multiplexing (OFDM) signaling with a cyclic prefix to eliminate inter-symbol interference and non-orthogonal user multiplexing may be assumed. Also, a downlink MUST Category-<NUM> transmission scheme may be assumed, in which component constellations are directly linear superposed, without ensuring Gray mapping. Due to the inferior property of a non-Gray mapped constellation as compared with a Gray mapped constellation, an advanced receiver at the user implementing codeword-level successive interference cancellation (CWIC) may be considered. Superposition coding at the transmitter with SIC at the receiver may achieve the capacity of a single-input single output (SISO) broadcast channel.

A structure of an example transmitter of the radio interface <NUM> at a network node <NUM> is shown in <FIG>. For each user data signal, an encoder <NUM>, such as a turbo encoder, performs channel encoding, and a modulator <NUM> performs data modulation, and then the three data signals are superimposed <NUM> according to a predefined power ratio determined by the power allocation unit <NUM> that may be separate from the transmitter of the radio interface <NUM>, as shown in <FIG>. Then, the superimposed signal is OFDM modulated <NUM> and converted to analog <NUM> before up conversion <NUM> to the carrier frequency.

A structure of an example receiver of the radio interface <NUM> at the WD <NUM>-<NUM>22a is shown in <FIG>. The received signal is first down-converted <NUM> and converted to a digital signal <NUM>. Channel estimation <NUM> is performed and the resultant signal is provided for further processing. CWIC is applied to cancel the strong interference of signal x3. First, x3 is demodulated <NUM>, decoded <NUM>, encoded <NUM> and modulated <NUM> to generate an x3 replica, which is subtracted from the received signal to achieve first interference cancellation <NUM>. The functions of interference cancellation unit <NUM> may be performed by the SIC unit <NUM>, which may be separate from the receiver of the radio interface <NUM>, as shown in <FIG>. Similarly, the WD <NUM>-<NUM> demodulates the data of signal x2 <NUM>, decodes the signal x2 <NUM>, encodes the signal <NUM>, modulates the signal <NUM> and subtracts the signal, via interference canceller <NUM>, from the signal remaining from subtracting x1. Then, the signal from interference canceller <NUM> is data demodulated <NUM> and decoded to obtain signal x1, <NUM>. The function of interference canceller <NUM> may be performed by the SIC unit <NUM>, as shown in <FIG>. <FIG> is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of <FIG> and <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG>. In a first step of the method, the host computer <NUM> provides user data (block S100). In an optional substep of the first step, the host computer <NUM> provides the user data by executing a host application, such as, for example, the host application <NUM> (block S102). In a second step, the host computer <NUM> initiates a transmission carrying the user data to the WD <NUM> (block S104). In an optional third step, the network node <NUM> transmits to the WD <NUM> the user data which was carried in the transmission that the host computer <NUM> initiated, in accordance with the teachings of the embodiments described throughout this disclosure (block S106). In an optional fourth step, the WD <NUM> executes a client application, such as, for example, the client application <NUM>, associated with the host application <NUM> executed by the host computer <NUM> (block S108).

<FIG> is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG> and <FIG>. In a first step of the method, the host computer <NUM> provides user data (block S110). In an optional substep (not shown) the host computer <NUM> provides the user data by executing a host application, such as, for example, the host application <NUM>. In a second step, the host computer <NUM> initiates a transmission carrying the user data to the WD <NUM> (block S112). In an optional third step, the WD <NUM> receives the user data carried in the transmission (block S114).

<FIG> is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG> and <FIG>. In an optional first step of the method, the WD <NUM> receives input data provided by the host computer <NUM> (block S116). In an optional substep of the first step, the WD <NUM> executes the client application <NUM>, which provides the user data in reaction to the received input data provided by the host computer <NUM> (block S118). Additionally or alternatively, in an optional second step, the WD <NUM> provides user data (block S120). In an optional substep of the second step, the WD provides the user data by executing a client application, such as, for example, client application <NUM> (block S122). In providing the user data, the executed client application <NUM> may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the WD <NUM> may initiate, in an optional third substep, transmission of the user data to the host computer <NUM> (block S124). In a fourth step of the method, the host computer <NUM> receives the user data transmitted from the WD <NUM>, in accordance with the teachings of the embodiments described throughout this disclosure (block S126).

<FIG> is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG> and <FIG>. In an optional first step of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the network node <NUM> receives user data from the WD <NUM> (block S128). In an optional second step, the network node <NUM> initiates transmission of the received user data to the host computer <NUM> (block S130). In a third step, the host computer <NUM> receives the user data carried in the transmission initiated by the network node <NUM> (block S132).

<FIG> is a flowchart of an example process in a network node <NUM> for discrete power allocation for a NOMA system. The process includes determining, via the power allocation unit <NUM>, a set of discrete power allocation values, each power allocation value being assigned to a particular WD <NUM> in a set of WDs, the determining including subjecting the power allocation values to at least one constraint to reduce a number of power allocation value combinations (block S134). The process also includes transmitting, via the radio interface <NUM>, to the WDs in the set, a plurality of superimposed data signals, each data signal intended for a different one of the WDs in the set and having a different power allocation value, each WD in the set receiving all the plurality of superimposed data signals (block S136). The process also includes transmitting, via the radio interface <NUM>, to each WD in the set of WDs a different control signal, the control signal including an indication of the power level allocation values of the set of discrete power allocation values (block S138).

<FIG> is a flowchart of an example process in a wireless device <NUM> according to some embodiments of the present. The process includes receiving, via the radio interface <NUM>, the plurality of superimposed data signals, each data signal intended for a different one of a plurality of WDs in a set and having a power allocation value (block S <NUM>). The process also includes receiving, via the radio interface <NUM>, a control signal that indicates power allocation values for a number of WDs in a set, the control signal having information that enables the WD to decode the data signal intended for the WD (block S <NUM>). The process further includes decoding, via the SIC unit <NUM>, the data signal by treating all but one of the superimposed data signals as interference and applying successive interference cancellation of the all but one of the superimposed data signals (block S144).

Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide additional details and examples of arrangements for discrete power allocation for a non-orthogonal multiple access (NOMA) system.

The power allocation problem for energy-efficiency maximization in downlink NOMA can be formulated as<MAT> <MAT> <MAT> <MAT> <MAT> <MAT> where Rmin is the minimum rate requirement, R1, R2 and R3 are the respective rates for each WD <NUM>, Jo is a desired Jain's fairness level, Ptotal is total power constraint, wi is the i-th user weight, q is the power amplifier efficiency constant, Pconstant is circuitry power consumption at the base station (BS), and <MAT> denotes the set of power levels, where L is the cardinality of the set. Any or all of R1, R2 and R3 can be set to the same or different values. The Jain's fairness level may be a number between <NUM>/n (worst case) and <NUM> (best case), where n is the number of WDs <NUM>. For example, Jo may be chosen as <NUM>.

An algorithm to find a combination of transmit powers is presented as shown in the flowchart of <FIG>. In some embodiments, this algorithm may be performed by the power allocation unit <NUM> of the network node <NUM>. The set of all possible combinations of the power levels is denoted by SP. The cardinality of SP is represented as |SP|, e.g., for L = <NUM>, |SP| = <NUM><NUM>. The number of such combinations can grow prohibitively high. To lower the number of combinations, the formulation structure is investigated, and some observations are made. For instance, when the users are ordered based on their channel quality, as in block S200, for L = <NUM>, the number of combinations can be reduced to <MAT>, where <MAT> is the set of reduced combinations. For this case, the cardinality of the set of reduced combinations of the power levels can be found by using the closed-form expression, <MAT>. Note that the reduction is more pronounced for a higher number of power levels. In addition to this observation, there are few more assumptions regarding the power allocations by the power allocation unit <NUM>, which will help to further reduce the complexity of the algorithm. For instance, for efficient SIC at the WD <NUM>-<NUM> receiver, the following conditions for power allocation may be satisfied:.

Similarly, for efficient SIC at the WD <NUM>-<NUM>22b receiver, the following conditions for power allocation may be satisfied,.

After these additional observations for the SIC receiver are applied (block S202), the cardinality of the set of reduced combinations of the power levels can be significantly reduced. For instance, if Ptol is assumed to be zero, then for L = <NUM>, the number of combinations can be reduced to <MAT>, where <MAT> is the set of further reduced combinations. Thus, a reduced set of combinations of power levels can be determined (block S204). Then, power allocation optimization for each combination of power levels in the reduced set can be calculated as described above (block S206). Then, the overall energy efficiency of each combination is determined (block S208) and the combination with the best overall energy efficiency may be chosen (block S210).

Control signaling may include (<NUM>) providing WDs <NUM> with assistance information for interference cancellation, and (<NUM>) configuring a WD for MUST operation. The assistance information which may be used by WD <NUM>-<NUM> and WD <NUM>-<NUM> may include the following: the modulation order, transmission block size, hybrid automatic repeat request (HARQ) information, limited buffer rate matching assumption, parameters for descrambling and cyclic redundancy check of the paired user, and the transmission power levels of other respective users. For instance, for WD <NUM>-<NUM>, information for signals x2 and x3 may be required, and for WD <NUM>-<NUM> only information for signal x3 may be required.

Applicable control signaling to the WDs <NUM> to implement the embodiments described above may be summarized as follows:.

Thus, in some embodiments, the following steps and conditions may be implemented for communicating data and control signals in the NOMA system described in some embodiments herein.

According to one aspect, a method for a network node <NUM> for discrete power allocation for a non-orthogonal multiple access, NOMA, system is provided. The method includes determining (block S134) a set of discrete power allocation values, each power allocation value being assigned to a particular wireless device, WD <NUM>, in a set of WDs <NUM>, the determining including subjecting the power allocation values to at least one constraint to reduce a number of power allocation value combinations. The method further includes transmitting (block S <NUM>) to the WDs <NUM> in the set, a plurality of superimposed data signals, each data signal intended for a different one of the WDs <NUM> in the set and having a different power allocation value, each WD <NUM> in the set receiving all the plurality of superimposed data signals. The method also includes transmitting (block S138) to each WD <NUM> in the set of WDs <NUM> a different control signal, the control signal including an indication of the power level allocation values of the set of discrete power allocation values.

According to this aspect, in some embodiments, the control signal for a first WD <NUM> includes the power allocation values of all the WDs <NUM> in the set, the control signal for a second WD <NUM> in the set includes the power allocation values of all the WDs <NUM> in the set other than the first WD <NUM>, the control signal for a third WD <NUM> in the set includes the power allocation values of all the WDs <NUM> in the set other than the first and second WDs <NUM>, wherein the control signal for a last WD <NUM> in the set includes the power allocation value of only the last WD <NUM>. In some embodiments, the control signal for the first WD <NUM> includes a modulation and coding scheme, MCS, for all but the first WD <NUM>, the control signal for the second WD <NUM> includes an MCS for all but the first and second WD <NUM>, wherein the control signal for the last WD <NUM> does not include an MCS for the last WD <NUM> or for any other WD <NUM> in the set. In some embodiments, the control signal for the first WD <NUM> includes an identifier for all but the first WD <NUM>, the control signal for the second WD <NUM> includes an identifier for all but the first and second WD <NUM>, wherein the control signal for the last WD <NUM> does not include an identifier for the last WD <NUM> or for any other WD <NUM> in the set. In some embodiments, the at least one constraint comprises a total power constraint. In some embodiments, the total power constraint specifies that a sum of the power allocation values for the WDs <NUM> in the set is less than a predetermined total power value. In some embodiments, the at least one constraint comprises a constraint specifying that the WDs <NUM> in the set are ordered for assignment of power allocation values based on a channel quality of each WD <NUM> in the set. In some embodiments, determining a set of discrete power allocation values includes constraining the power allocation values to satisfy an inequality having terms consisting of a product of a power allocation value and a channel gain, an algebraic sum of the terms being less than a power difference determined to distinguish between a signal to be decoded and remaining non-decoded message signals.

According to another aspect, a network node <NUM> configured for discrete power allocation for a non-orthogonal multiple access, NOMA, system. The network node <NUM> includes processing circuitry <NUM> configured to: determine a set of discrete power allocation values, each power allocation value being assigned to a particular wireless device, WD <NUM>, in a set of WDs <NUM>, the determining including subjecting the power allocation values to at least one constraint to reduce a number of power allocation value combinations. The processing circuitry <NUM> is configured to transmit to the WDs <NUM> in the set, a plurality of superimposed data signals, each data signal intended for a different one of the WDs <NUM> in the set and having a different power allocation value, each WD <NUM> in the set receiving all the plurality of superimposed data signals. The processing circuitry <NUM> is further configured to transmit to each WD <NUM> in the set of WDs <NUM> a different control signal, the control signal including an indication of the power level allocation values of the set of discrete power allocation values.

According to this aspect, in some embodiments, the control signal for a first WD <NUM> includes the power allocation values of all the WDs <NUM> in the set, the control signal for a second WD <NUM> in the set includes the power allocation values of all the WDs <NUM> in the set other than the first WD <NUM>, the control signal for a third WD <NUM> in the set includes the power allocation values of all the WDs <NUM> in the set other than the first and second WDs <NUM>, wherein the control signal for a last WD <NUM> in the set includes the power allocation value of only the last WD <NUM>. In some embodiments, the control signal for the first WD <NUM> includes a modulation and coding scheme, MCS, for all but the first WD <NUM>, the control signal for the second WD <NUM> includes an MCS for all but the first and second WD <NUM>, wherein the control signal for the last WD <NUM> does not include an MCS for the last WD <NUM> or for any other WD <NUM> in the set. In some embodiments, the control signal for the first WD <NUM> includes an identifier for all but the first WD <NUM>, the control signal for the second WD <NUM> includes an identifier for all but the first and second WD <NUM>, wherein the control signal for the last WD <NUM> does not include an identifier for the last WD <NUM> or for any other WD <NUM> in the set. In some embodiments, the at least one constraint comprises a total power constraint. In some embodiments, the total power constraint specifies that a sum of the power allocation values for the WDs <NUM> in the set is less than a predetermined total power value. In some embodiments, the at least one constraint comprises a constraint specifying that the WDs <NUM> in the set are ordered for assignment of power allocation values based on a channel quality of each WD <NUM> in the set. In some embodiments, the determining a set of discrete power allocation values includes constraining the power allocation values to satisfy an inequality having terms consisting of a product of a power allocation value and a channel gain, an algebraic sum of the terms being less than a power difference determined to distinguish between a signal to be decoded and remaining non-decoded message signals.

According to another aspect, computer storage device is provided for storing a computer program that, when executed by at least one processor in a network node <NUM>, performs at least one method described below.

According to yet another aspect, a method for a wireless device, WD <NUM>, for decoding a data signal in a plurality of superimposed data signals in a non-orthogonal multiple access, NOMA, system is provided. The method includes receiving (block S140) the plurality of superimposed data signals, each data signal intended for a different one of a plurality of WDs <NUM> in a set and having a power allocation value. The method also includes receiving (block S142) a control signal that indicates power allocation values for a number of WDs <NUM> in a set, the control signal having information that enables the WD <NUM> to decode the data signal intended for the WD <NUM>. The method further includes decoding (block S144) the data signal by treating all but one of the superimposed data signals as interference and applying successive interference cancellation of the all but one of the superimposed data signals. According to this aspect, in some embodiments, the control signal includes the power allocation values of all but one of the WDs <NUM> in the set.

According to another aspect, a wireless device, WD <NUM>, configured to decode a data signal in a plurality of superimposed data signals in a non-orthogonal multiple access, NOMA, system is provided. The WD <NUM> includes processing circuitry <NUM> configured to: receive the plurality of superimposed data signals, each data signal intended for a different one of the WDs <NUM> in the set and having a power allocation value; receive a control signal that indicates power allocation values for a number of WDs <NUM> in a set, the control signal having information that enables the WD <NUM> to decode the data signal intended for the WD <NUM>; and decode the data signal by treating all but one of the superimposed data signals as interference and applying successive interference cancellation of the all but one of the superimposed data signals. According to this aspect, the control signal includes the power allocation values of all but one of the WDs <NUM> in the set. According to yet another aspect, a computer storage device is provided for storing a computer program that, when executed by at least one processor in a wireless device, performs at least some methods described below.

Claim 1:
A method for a network node (<NUM>) for discrete power allocation for a non-orthogonal multiple access, NOMA, system (<NUM>), the method comprising:
determining (S134) a set of discrete power allocation values, each particular wireless device, WD, in a set of WDs (<NUM>) being assigned to one of the set of discrete power allocation values, the determining including subjecting the power allocation values to at least one constraint to reduce a number of power allocation value combinations;
transmitting (S136) to the WDs (<NUM>) in the set, a plurality of superimposed data signals, each data signal intended for a different one of the WDs (<NUM>) in the set and having a different power allocation value, each WD (<NUM>) in the set receiving all the plurality of superimposed data signals; and
transmitting (S138) to each WD (<NUM>) in the set of WDs (<NUM>) a different control signal, the control signal including an indication of the power level allocation values of the set of discrete power allocation values.