EP4695904A1

EP4695904A1 - Method and apparatus for digital pre-distorter compensation

Info

Publication number: EP4695904A1
Application number: EP23932407.2A
Authority: EP
Inventors: Yahui Liu; Junfeng JIE; Haiying CAO; Hao YE
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-04-11
Filing date: 2023-04-11
Publication date: 2026-02-18
Also published as: WO2024212108A8; WO2024212108A1; CN120937252A

Abstract

Embodiments of the present disclosure provide a method, apparatus, and computer readable storage medium for DPD compensation. In the method, a set of compensation representations is determined from a look-up table based on an input power of a DPD in front of a power amplifier. Each compensation representation at least comprises a first value representing a candidate for the input power and a second value representing a DPD compensation result for the candidate. First values in the set of compensation representations are adjusted to be third values, one of which is equal to a predetermined value. Based on the third values as well as second values in the set of compensation representations, a DPD compensation result is determined for the input power. In this way, accuracy of DPD compensation can be improved.

Description

METHOD AND APPARATUS FOR DIGITAL PRE-DISTORTER COMPENSATION

TECHNICAL FIELD

The non-limiting and example embodiments of the present disclosure generally relate to the technical field of telecommunications, and specifically to a method, an apparatus, and a medium for digital pre-distorter (DPD) compensation.

BACKGROUND

This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Power amplifiers (PAs) are essential components in overall performance and throughput of communication systems, but they are inherently nonlinear. The nonlinearity generates spectral re-growth, which leads to adjacent channel interference and violations of the out-of-band emissions standards mandated by regulatory bodies. It also causes in-band distortion, resulting in degradation of its error vector magnitude (EVM) performance. digital pre-distortion is a technique to increase linearity or compensate for non-linearity in power amplifiers, which is a cost-effective linearization technique and aims to provide improved linearity, better efficiency, and take full advantage of power amplifiers. Its principle is to insert a digital pre-distorter in front of PA, which has the inverse nonlinear characteristics of that of the PA, so that the cascaded PD-PA system has a linear behavior. Among various DPD techniques, three solutions are popularly used. They are look-up table (LUT) , polynomial model and neural network based DPDs.
The basic principle of LUT is to evenly divide the power range of the input signal into several consecutive segments. Each segment has its own bin address. When the input signal arrives, the power of the signal is calculated and indexed to the corresponding bin address. Then the corresponding compensation value in the LUT is found according to the bin address and make DPD compensation for the signal.
Generally, the more power segments are divided, the more bin addresses are generated. This has the advantage of accurate signal compensation, but it may cause the LUT size to be very large. However, a large LUT not only occupies too much memory but also takes more logic to calculate coefficients in LUTs. Due to the limitation of ASIC resources in practice, it is impossible to use enough memory to ensure that the LUT meets the accuracy required for DPD compensation. Because of this limitation, for LUT with fixed size, accuracy of DPD compensation needs to be improved.
SUMMARY
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
To overcome or mitigate at least one of the above-mentioned problems or other problems or provide a useful solution, embodiments of the present disclosure propose a method, an apparatus and a medium for DPD compensation.
In a first aspect of the present disclosure, there is provided a method of DPD compensation. In the method, a set of compensation representations is determined from a look-up table based on an input power of a DPD in front of a power amplifier. Each compensation representation at least comprises a first value representing a candidate for the input power and a second value representing a DPD compensation result for the candidate. First values in the set of compensation representations are adjusted to be third values, one of which is equal to a predetermined value. Based on the third values as well as second values in the set of compensation representations, a DPD compensation result is determined for the input power.
In an embodiment, a first compensation representation is determined from the look-up table. The first value in the first compensation representation is equal to or slightly different from the input power. The difference between the first value in the first compensation representation and the input power is less than a first threshold. A predetermined number of consecutive compensation representations which comprise the first compensation representation are determined from the look-up table as the set of compensation representations.
In an embodiment, the first value in the first compensation representation is a median of first values in the predetermined number of consecutive compensation representations.
In an embodiment, when adjusting the first values to be the third values, a reference value is first determined from the first values; and the third values are obtained by subtracting the reference value from the first values.
In an embodiment, the reference value may be determined, from the first values, based on a median of the first values. The difference between the reference value and the median of the first values is less than a second threshold.
In an embodiment, the number of the first values is an odd number, and the reference value is equal to the median of the first values.
In an embodiment, the DPD compensation result corresponding to the input power may be obtained based on a fitting curve. The fitting curve may be constructed for the DPD compensation based on the high order polynomial with a plurality of parameters for a high order polynomial. The plurality of parameters may be determined based on the second values and the third values.
In an embodiment, during the determination of the plurality of parameters, a first parameter of the plurality of parameters may be determined based on the second values and the third values, and the remaining parameters of the plurality of parameters may be determined based on the second values and fourth values. The fourth values may comprise the third values excluding the one equal to the predetermined value.
In an embodiment, the remaining parameters may be determined based on a plurality of third matrices which are obtained by reducing a second matrix. The second matrix may be obtained by performing a row transformation to a first matrix composed of the fourth values.
In an embodiment, the predetermined value is 0.
In a second aspect of the present disclosure, there is provided an apparatus for DPD compensation. The apparatus comprises a processor and a memory coupled to the processor, the memory containing instructions executable by the processor, whereby the apparatus is operative to perform the method according to the first aspect.
In a third aspect of the present disclosure, there is provided an apparatus for DPD compensation. The apparatus comprises means for performing the method according to the first aspect.
In a fourth aspect of the disclosure, there is provided a computer-readable storage medium having instructions stored thereon, the instructions, which when executed by at least one processor, causing the at least one processor to perform the method according to the first aspect.
With the present disclosure, accuracy of DPD compensation can be improved effectively. Meanwhile, radio power consumption as well as computing and memory resources can be saved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:
FIG. 1A is a diagram showing a device comprising a digital pre-distorter and a power amplifier;
FIG. 1B is a diagram showing inaccuracy of conventional DPD compensation approaches;
FIG. 2 is a diagram showing an example digital pre-distorter of DPD compensation in accordance with some embodiments of the present disclosure;
FIG. 3 is a diagram showing an example of translating a curve;
FIG. 4 is a flow chart showing an example process of DPD compensation according to some embodiments of the present disclosure;
FIG. 5 is a flow chart showing an example process of determination of a set of compensation representations according to some embodiments of the present disclosure;
FIG. 6 is a flow chart showing an example process of adjustment of the set of compensation representations according to some embodiments of the present disclosure;
FIG. 7 is a flow chart showing an example process of obtaining a DPD compensation result according to some embodiments of the present disclosure;
FIG. 8 is a diagram showing an example of a set of compensation representations according to some embodiments of the present disclosure;
FIG. 9 is a diagram showing an example of adjustment of the set of compensation representations according to some embodiments of the present disclosure;
FIG. 10 is a schematic diagram showing an apparatus for DPD compensation in accordance with some embodiments of the present disclosure;
FIG. 11 is a schematic diagram showing a computer readable storage medium in accordance with some embodiments of the present disclosure;
FIG. 12 is a block diagram showing an example of a communication system in accordance with some embodiments;
FIG. 13 is a block diagram showing a terminal device in accordance with some embodiments; and
FIG. 14 is a block diagram showing a network node in accordance with some embodiments.

DETAILED DESCRIPTION

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.
Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.
Reference throughout this specification to features, advantages, or similar language does not imply that all the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.
As used herein, the term "network" , or "communication network/system" refers to a network/system following any suitable communication standards, such as new radio (NR) , long term evolution (LTE) , LTE-Advanced, wideband code division multiple access (WCDMA) , high-speed packet access (HSPA) , and so on. Furthermore, the communications between a terminal device and a network node in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , 4G, 4.5G, 5G communication protocols, and/or any other protocols either currently known or to be developed in the future.
The term "network node" refers to a network device with accessing function in a communication network via which a terminal device accesses to the network and receives services therefrom. The network node may include a base station (BS) , an access point (AP) , a multi-cell/multicast coordination entity (MCE) , a controller or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNodeB or gNB) , a remote radio unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth.
Yet further examples of the network node comprise multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs) , base transceiver stations (BTSs) , transmission points, transmission nodes, positioning nodes and/or the like. More generally, however, the network node may represent any suitable device (or group of devices) capable, configured, arranged, and/or operable to enable and/or provide a terminal device access to a wireless communication network or to provide some service to a terminal device that has accessed to the wireless communication network.
The term "terminal device" refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device may refer to a user equipment (UE) , or other suitable devices. The UE may be, for example, a subscriber station, a portable subscriber station, a mobile station (MS) or an access terminal (AT) . The terminal device may include, but not limited to, portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable device, a personal digital assistant (PDA) , a vehicle, and the like.
Yet another specific example, in an Internet of things (IoT) scenario, a terminal device may also be called an IoT device and represent a machine or other device that performs monitoring, sensing and/or measurements etc., and transmits the results of such monitoring, sensing and/or measurements etc. to another terminal device and/or a network equipment. The terminal device may in this case be a machine-to-machine (M2M) device, which may in a 3rd generation partnership project (3GPP) context be referred to as a machine-type communication (MTC) device.
As one example, the terminal device may be a UE implementing the 3GPP narrow band Internet of things (NB-IoT) standard. Examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, e.g., refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment, for example, a medical instrument that is capable of monitoring, sensing and/or reporting etc. on its operational status or other functions associated with its operation.
As used herein, the terms "first" , "second" and so forth refer to different elements. The singular forms "a" and "an" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises" , "comprising" , "has" , "having" , "includes" and/or "including" as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term "based on" is to be read as "based at least in part on" . The term "one embodiment" and "an embodiment" are to be read as "at least one embodiment" . The term "another embodiment" is to be read as "at least one other embodiment" . Other definitions, explicit and implicit, may be included below.
As mentioned above, among various DPD techniques, three solutions are popularly used, which are LUT, polynomial model and neural network based DPDs. The neural network has an excellent capability to accurately approximate nonlinear functions. Hence, it can be used to linearize the PA. But the training process of neural network is complex and time-consuming. Its hardware implementation is difficult in practical applications. Polynomial model-based DPD include the well-known Volterra series (VS) , which is more accurate but also more complex. Compared with neural network and polynomial model, the LUT based DPD has the advantage of simplicity, but its linearization performance depends on the LUT size. To improve the linearization performance with limited LUT dimension, some interpolated techniques are introduced in LUT-based DPDs.
The basic principle of LUT is to evenly divide the power range of the input signal into several consecutive segments. When the input signal arrives, the power of the signal is calculated and indexed to the corresponding bin address of a segment. Thus, the DPD compensation result can be obtained in the LUT according to the bin address. As introduced above, the more power segments are divided, the more bin addresses are generated. Due to memory resource limitation, there is a need to improve accuracy of DPD compensation for LUT with a fixed size.
FIG. 1A is a diagram showing a device 100 comprising a digital pre-distorter (DPD) 110 and a power amplifier (PA) 120. The device 100 may be a terminal device, a network device/network node or any device that needs power control in a communication device.
The DPD 110 is a signal processing apparatus used to linearize the output of the PA 120. The goal of the DPD 110 is to reduce distortion in the output signal caused by the non-linear behavior of the PA 120.
In practice, the DPD 110 is provided to improve the performance of a PA 120. The DPD 110 takes the input signal and applies a pre-distortion function to it before it is amplified by the PA 120. The pre-distortion function is designed to counteract the non-linear behavior of the PA 120, resulting in a more linear output signal. In other words, the PA 120 relies on the DPD 110 to provide a pre-distorted signal that will result in a more linear output.
FIG. 1B is a diagram showing inaccuracy of conventional DPD compensation approaches. Specifically, FIG. 1B shows an influence of fitting curve accuracy on DPD compensation. It is assumed that the curve in FIG. 1B represents an ideal compensation result. Only the discrete points corresponding to each bin address are known here, the ideal curve between these discrete points is unknown.
If the power of an input signal is A₀, it is between two adjacent Bin addresses (X₀, X₁) . Assume that the corresponding value of A₀ on the ideal compensation curve is A₀C, as shown by the green dot on the left in the figure. The easiest way without any additional calculation of fitting curve to determine the A₀’s compensation value is to select the bin address nearest to it (X₀) . However, if X₀C is selected as the compensation result of A₀ in this way, it is obvious that there is a large difference between x₀C and A₀'s ideal result A₀C, which will lead to a large error in the DPD compensation of the signal.
According to the previous introduction, it is necessary to introduce fitting curve calculation to make the intermediate value more approximate to the ideal result. When fitting with a linear function, the compensation result of A₀ will be A₀C’ . The difference between A₀C’ and ideal value A₀C is much smaller than that of X₀C. This seems good, but it is not good when the signal power is A₁. It can be seen from the figure that the gap between A₁C’ and A₁C is greater than the gap between X₂C and A₁C, and both are very far from the ideal value A₁C.
Therefore, fitting curves with more complex higher order polynomial can be closer to the real results, but the calculation should be as simple as possible. In addition, there are other ways to solve such problems. For example, Cubic Spline Interpolation (CSI) can fit a relatively smooth curve through cubic polynomial fitting, but compared with the solution claimed in this patent, it still requires more calculation and system resource.
To solve the above and other potential issues, embodiments of the present disclosure propose a solution of DPD compensation. In this solution, a set of compensation representations is determined from a look-up table based on the power of an input signal (also referred to as “input power” hereafter) of a DPD in front of a power amplifier. Each compensation representation at least comprises a first value representing a candidate for the input power and a second value representing a DPD compensation result for the candidate. First values in the set of compensation representations are adjusted to be third values, one of which is equal to a predetermined value. Based on the third values as well as second values in the set of compensation representations, a DPD compensation result is determined for the input power. In this way, accuracy of DPD compensation for fixed-size LUT can be improved. Meanwhile, radio power consumption as well as computing and memory resources can be saved.
FIG. 2 is a diagram showing an example digital pre-distorter 200 of DPD compensation in accordance with some embodiments of the present disclosure.
As shown in FIG. 2, the digital pre-distorter 200 at least comprises two modules, one is DPD LUT 210 and the other is DPD Translation Curve Calibrator (TCC) 220. An input power 201 of a signal is input into the DPD LUT 210. Upon receiving the input power, the digital pre-distorter 200 will find a compensation result 202 corresponding to the input power 201 through a LUT. The LUT may be stored in the DPD LUT 210 or accessible to the DPD LUT 210.
In some cases, the compensation result 202 corresponding to the input power 201 can be accurately found in the LUT, and the DPD LUT 210 can directly output the compensation result 202.
In some other cases, it is difficult to find an accurate compensation result for the input power 201 in the LUT. To obtain better compensation accuracy for LUT with fixed size, the whole data is fitted by segments. In embodiments of the present disclosure, it is determined from the LUT a segment where the input power 201 is located. Then, the input value 201 and information of the determined segment are provided to the DPD TCC 220 to obtain the result of the DPD compensation.
For example, a segment is shown in FIG. 3, which is diagram showing an example of translating a curve 310 to another curve 320. For each segment of the curve 310, a better result can be obtained by using n-order polynomial fitting. In general, a n-order polynomial needs to inverse a matrix of order N+1, which will involve the complexity of O ( (n+1) ³) .
As shown in FIG. 3, the curve 310 comprises 10 points, B0, B1, B2, …, B9. These points are translated to the left to the place where the abscissa is symmetrical about the origin. As shown in FIG. 3, the curve 310 is translated to be the curve 320 comprising 10 points, A0, A1, A2, …, A9. The abscissa of the point of the curve 320 is symmetrical about the origin.
Decomposition of large matrices is a common way to solve an inverse problem of large matrices. Due to the symmetry of the abscissa, the calculation process of polynomial coefficients can be simplified. The constant coefficient can be directly obtained at the origin, and other coefficients can also be simply calculated by decomposing the original matrix into small matrices according to the symmetry of the abscissa.
In this way, the DPD compensation curve can be quickly fitted through a small amount of calculation, thus improving the fixed size LUT compensation accuracy.
Suppose 5 points are taken as 1 fitting segment, then point M may appear in 4 fitting segments (A₂-A₆, A₃-A₇, A₄-A₈, A₅-A₉) . The method of selection is to select the segment with M in the middle, which can ensure more accurate fitting results under the same amount of calculation. It is to be understood that the above example is just discussed for illustration, rather than suggest any limitation. In another example, A₃-A₇ and A₄-A₈ are also a good choice in this case.
Returning to embodiments discussed with respect to FIG. 2, when determining a segment from the LUT, the DPD LUT 210 may determine a segment in which the input power 201 is roughly in the middle, so as to improve computing efficiency and compensation accuracy.
The DPD TCC 220 then performs curve fitting on LUT points contained in the input segment. According to embodiments of the present disclosure, in the fitting process, the input segment is shifted to the X axis origin symmetrically, to reduce the calculation required for matrix inversion. In this way, the fitting curve with high accuracy can be obtained with less calculation effort. Then, according to the fitting value of the input power on the fitting curve, the corresponding compensation result 202 of the input power 201 is obtained. In this way, an accurate compensation value of DPD can be obtained.
Based on the above process, an input power 201 will get a more accurate compensation result 202 than conventional solutions. Solutions of the present disclosure only need a relatively simple calculation to obtain a higher order fitting result, which can save system computing resources and LUT storage resources.
More details will be further discussed with reference to FIGS. 4 to 11. FIG. 4 is a flow chart showing an example process 400 of DPD compensation according to some embodiments of the present disclosure. To discussion, the process 400 will be described from the perspective of the digital pre-distorter 200 shown in FIG. 2.
At block 410, the digital pre-distorter 200 determines, from a look-up table, a set of compensation representations based on an input power 201 of a DPD in front of a power amplifier.
The look-up table may comprise one or more compensation representations. According to embodiments of the present disclosure, a compensation representation refers to a representation for DPD compensation. The compensation representation may comprise a variety of elements representing, for example, but not limited to, an input power, a compensation result, a type of a digital pre-distorter, and the like. The compensation representation may be implemented as a vector, a matrix or in other appropriate form.
According to embodiments of the present disclosure, each compensation representation in the set of compensation representations determined at block 410 at least comprises two elements, one is a first value representing a candidate for the input power, and the other one is a second value representing a DPD compensation result for the candidate.
The set of compensation representations may be determined in a variety of ways. FIG. 5 is a flow chart showing an example process 500 of the determination of the set of compensation representations according to some embodiments of the present disclosure. The process 500 may be implemented, for example, in the DPD LUT 210 of the digital pre-distorter 200 in FIG. 2.
The digital pre-distorter 200 may determine, at block 510, a first compensation representation from the look-up table. For example, the digital pre-distorter 200 may compare a first value in a compensation representation in the look-up table and the input power and select out of the look-up table the first compensation representation whose first value is very close or equal to the input power.
At block 520, the digital pre-distorter 200 may determine one or more consecutive compensation representations, including the first compensation representation, from the look-up table. In this way, the set of compensation representations are determined from the look-up table. The set of compensation representations comprise a predetermined number of consecutive compensation representations comprising the first compensation representation.
In some embodiments, the first compensation representation may be determined from the look-up table by determining whether a difference between the first value of a compensation representation in the look-up table and the input power is less than a first threshold. The difference may be an absolute value of the result of subtracting the input power from the first value of the compensation representation in the look-up table. The first threshold may be a predefined value or a predetermined value. For example, the first threshold may be 0. In this case the first compensation representation determined from the look-up table may have the first value equal to the input power. In another example, the first threshold may be a value larger than 0, and the first value of the first compensation representation may be the closest first value in the look-up table. For both situations, it can be determined that the first compensation representation matches the input power.
Alternatively, in some embodiments where the input power is embodied in the form of multiple bits, the difference may be obtained by counting the number of “1” in a bitmap indicating differences of bits of the input power and bits of a first value of a compensation representation in the LUT. In such situation, the first threshold may be a predefined or predetermined number for comparing with the number of “1” in the bitmap, that is, the difference. If the difference is less than the first threshold, it can be determined that the compensation representation that is being compared matches the input power. This compensation representation thus can be considered as the first compensation representation.
With the first compensation representation, the digital pre-distorter 200 may select consecutive compensation representations around the first compensation representation. In this way, a set of compensation representations are obtained from the look-up table.
In some embodiments, the first value in the first compensation representation may be a median of first values in the predetermined number of consecutive compensation representations. In this situation, the first compensation representation may be the middle one in the set of compensation representations. For instance, the digital pre-distorter 200 may select 5 consecutive compensation representations, in which first values of two consecutive compensation representations are less than the first value of the first compensation representation and first values of the other two consecutive compensation representations are less than the first value of the first compensation representation.
It is to be understood that the above embodiments are just discussed for example, rather than limitation. In some other embodiments of the present disclosure, the first compensation representation does not need to be the middle one in the set of compensation representations. Actually, it may be in any position in the set of compensation representations.
Still referring to FIG. 4, at block 420, the digital pre-distorter 200 adjusts first values in the set of compensation representations to be third values.
The goal of the adjustment is to make sure that one of the third values is equal to a predetermined value. To achieve this, the third values may be obtained by applying a function to the first values in the set of compensation representations, by simply increasing or reducing these first values, or in other suitable ways.
The predetermined value may be predefined or determined according to some rules or requirements. For instance, the predetermined value may be 0. In some embodiments, the third value corresponding to one of first values (also referred to as the “reference value” ) in the set of compensation representations determined at block 410 is adjusted to be equal to the predetermined value. Meanwhile, other third values corresponding to the remaining first values may be obtained by adjusting the remaining first values with the same size as the adjustment of the reference value.
FIG. 6 shows an example process 600 of adjustment of the set of compensation representations according to some embodiments of the present disclosure. The process 600 may be implemented, for example, in the DPD TCC 220 of the digital pre-distorter 200 in FIG. 2.
In the embodiments described with respect to FIG. 6, the digital pre-distorter 200 determines, at block 610, the reference value from the first values. The reference value may be one of the first values or may be a value very close to one of the first values. In some embodiments, the reference value may be determined based on a median of the first values. The reference value is very close or equal to the median of the first values. For instance, a difference between the reference value and the median of the first values is less than a second threshold. The second threshold may be predefined or predetermined, for instance, according to certain requirements or rules.
Then, the digital pre-distorter 200 obtains, at block 620, the third values by subtracting the reference value from the first values. In this way, the third values can be obtained by adjusting the first values of the set of the compensation representations with the reference value.
Depending on the number of the compensation representations in the set of the compensation representations, the number of the first values may be an odd number or an even number. In some embodiments, the first values are uniformly distributed. If the number of the first values is an odd number, the reference value may be equal to the median of the first values. For example, the set of compensation representations comprise 5 compensation representations, namely, (0.2, 0.4) , (0.4, 0.5) , (0.6, 0.4) , (0.8, 0.55) , and (1.0, 0.6) . The first values of the 5 compensation representations are 0.2, 0.4, 0.6, 0.8 and 1.0, and the second values of the 5 compensation representations are 0.4, 0.5, 0.4, 0.55 and 0.6. When one of the first values, for example, 0.6 is adjusted to be 0, the reference value can be determined as 0.6. Accordingly, by subtracting the reference value, other first values may be adjusted to be -0.4, -0.2, 0.2 and 0.4. As such, the first values, 0.2, 0.4, 0.6, 0.8 and 1.0, are adjusted to be the third values -0.4, -0.2, 0, 0.2 and 0.4, respectively. After the above adjustment, the third values are symmetric about the value 0.
Still referring to FIG. 4, at block 430, the digital pre-distorter 200 determines a DPD compensation result 202 for the input power 201 based on second values in the set of compensation representations and the third values.
FIG. 7 is a flow chart showing an example process 700 of obtaining a DPD compensation result according to some embodiments of the present disclosure. Like the process 600, the process 700 may be implemented, for example, in the DPD TCC 220 of the digital pre-distorter 200 in FIG. 2 as well.
At block 710, the digital pre-distorter 200 determines a plurality of parameters for a high order polynomial based on the second values and the third values. In some embodiments, the digital pre-distorter 200 may first determine a first parameter of the plurality of parameters based on the second values and the third values. Then, remaining parameters of the plurality of parameters may be determined based on the second values and fourth values. The fourth values comprise the third values excluding the one equal to the predetermined value. Specifically, in an example, by performing a row transformation to a first matrix composed of the fourth values, a second matrix may be obtained and then reduced into a plurality of third matrices. Based on the plurality of third matrices, the remaining parameters may be determined quickly and efficiently.
At block 720, the digital pre-distorter 200 constructs a fitting curve for the DPD compensation based on the high order polynomial with the plurality of parameters. At block 730, the digital pre-distorter 200 obtains the DPD compensation result corresponding to the input power based on the fitting curve.
In view of the above embodiments, the coordinate axis of the curve to be fitted is made symmetrical, only fitting the segment rather than the whole curve, which ensures that on the premise of a fixed LUT, a smaller amount of calculation can be used to obtain a result with high fitting accuracy.
In practice, the ideal curve of DPD compensation can be better fitted by using higher order polynomial. However, higher order polynomial will lead to more calculations for matrix inversion. With the proposed solution, the calculation process of matrix inversion can be simplified by translating the abscissa of the curve. More details will be discussed below.
FIG. 8 shows an example of a set of compensation representations according to some embodiments of the present disclosure. The set of compensation representations comprise, for example, 5 compensation representations which correspond to 5 points in FIG. 8. As shown, these 5 points form a curve shown in FIG. 8. The curve, for example, may be fit using the following 4-order polynomial:
ax⁴+bx³+cx²+dx+e=y (1)
where a, b c, d and e represent coefficients of the 4-order polynomial, respectively.
As shown in FIG. 8, the coordinates of the 5 points are (x_n, y₀) , (x_n+1, y₁) , (x_n+2, y₂) , (x_n+3, y₃) , and (x_n+4, y₄) , respectively. The coefficients may be expressed by a coefficient matrix A. By substituting the coordinates of the five points into the polynomial, the coefficient matrix A may be calculated according to a matrix X and a matrix Y as follows:
X ·A = Y (2)
where the matrixis obtained based on first values of the compensation representations corresponding the 5 points, that is, x_n, x_n+1, x_n+2, x_n+3, and x_n+4; and the matrix Y is a 5*1 matrix which comprises second values of the 5 compensation representations, that is, y₀, y₁, y₂, y₃, and y₄.
To calculate the coefficient matrix A, it is necessary to find the inverse matrix X^-1 of matrix X as follows:
A = X^-1·Y (4)
In general, for the inversion of large matrices, conventional algorithms such as Singular Value Decomposition (SVD) or QR decomposition need to involve a lot of calculations. In this case, the proposed solution can be used to simplify the matrix in advance by translating the abscissa axis.
First, the 5 points may be moved to the left to the symmetrical position about the origin. Then, the first values (values of x) change to be third values while the corresponding second values (values of y) remain unchanged. Assuming the distance between each pair of adjacent first values is equal, the 5 first values x_n, x_n+1, x_n+2, x_n+3, x_n+4 may be adjusted to be third values as follows:
-x₂, -x₁, 0, x₁, x₂
Therefore, the coordinates of the original five points change from (x_n, y₀) , (x_n+1, y₁) , (x_n+2, y₂) , (x_n+3, y₃) , (x_n+4, y₄) to (-x₂, y₀) , (-x₁, y₁) , (0, y₂) , (x₁, y₃) , (x₂, y₄) . In other words, the set of compensation representations (x_n, y₀) , (x_n+1, y₁) , (x_n+2, y₂) , (x_n+3, y₃) , (x_n+4, y₄) are adjusted to be a new set of compensation representations (-x₂, y₀) , (-x₁, y₁) , (0, y₂) , (x₁, y₃) , (x₂, y₄) .
FIG. 9 is a diagram showing an example of adjustment of the set of compensation representations according to some embodiments of the present disclosure. As shown in FIG. 9, x-coordinates of 5 points corresponding to the new set of compensation representations are the third values, -x₂, -x₁, 0, x₁, x₂.
Then, the new coordinates of these five points are substituted into equation (3) as follows:
The result of multiplying the third row of matrix X and matrix A in the above equation is as follows:
a*0⁴+b*0³+c*0²+d*0+e= y₂ (6)
Thus,
e= y₂ (7)
It can be determined that the value of e in matrix A is y₂. Therefore, the original polynomial may be simplified as
ax⁴+bx³+cx²+dx=y -y₂ (8)
From this, new matrices X’ and A’ may be obtained as follows:
X’·A’ = Y’ (9)
Obviously, the matrixis simplified by one order compared with the original matrix X, and the unknown coefficient in matrix A is also reduced by one to matrix A’ . Currently, the calculation of X'^-1 is much simpler than before.
In addition, the abscissa axis x has symmetry after moving. Therefore, the fourth and third rows are subtracted from the first and second rows in matrix X’ , respectively, and the first and second rows of matrix X’ are added to the fourth and third rows, respectively.
The following can be thus obtained:
The above can be divided into 2 binary linear equations as follows.
Thus, it is easy to calculate the inverse of the 2x2 matrices X_odd and X_even on the left to obtain the values of b, d and a, c.
In some embodiments of the present disclosure, by translating the abscissa axis, the original 5×5 matrix X inversion may be changed to only two 2×2 matrices (X_odd and X_even) inversions, which greatly reducing the calculation required for matrix inversion. As such, the complexity of matrix inversion can be significantly reduced, for example, from the original O (5³) to O (2³) when using Gauss–Jordan elimination.
Fitting a curve with a N-order polynomial will produce a (N+1) -order matrix X. In embodiments of the present disclosure, if N is an even number, then the simplified X_odd and X_even areorder; if N is an odd number, then the simplified X_odd and X_even areorder.
From the above, it can be seen that, by translating the abscissa axis of the points to be fitted and making them symmetrical about the x-axis origin, the calculation of fitting curves with higher order polynomials can be simplified. Meanwhile, the accuracy of DPD compensation under a fixed LUT can be improved as well.
The proposed solution can help the system to fit a better DPD compensation curve with less memory resources, so that DPD compensation is more accurate without increasing the LUT size to calculate coefficients. Thus, storage resources will not be consumed due to excessive LUT.
Piecewise fitting requires less calculation than overall fitting because it only needs to focus on the segment of a single point, so it can more accurately fit the curve of the relevant line segment with less calculation and resources. In this way, an accurate value of corresponding compensation result of the point can be obtained.
When using high-order polynomial to fit DPD compensation curve piecewise, the proposed solution can effectively reduce the amount of calculation required to obtain fitting coefficients through the symmetry of the curve.
Moreover, the proposed solution can effectively help DPD improve the compensation accuracy, and save the radio power consumption, computing and memory resources.
FIG. 10 shows an apparatus 1000 for DPD compensation in accordance with some embodiments. The apparatus 1000 may be implemented at a network node such as a BS or a terminal device such as a UE or any other devices provided with one or more PAs.
As shown in FIG. 10, the apparatus 1000 may comprise a processor 1005 and a memory 1010. The memory 1010 may contain instructions 1015 executable by the processor 1005, whereby the apparatus 1000 may be operative to: determine, based on an input power of a DPD in front of a power amplifier, a set of compensation representations from a look-up table, each compensation representation at least comprising a first value representing a candidate for the input power and a second value representing a DPD compensation result for the candidate; adjust first values in the set of compensation representations to be third values, one of the third values being equal to a predetermined value; and determine a DPD compensation result for the input power based on second values in the set of compensation representations and the third values.
In an embodiment, the apparatus 1000 may be further operative to implement processes, actions or operations according to any of the above-mentioned embodiments.
The processor 1005 may be any kind of processing component, such as one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs) , special-purpose digital logic, and the like. The memory 1010 may be any kind of storage component, such as read-only memory (ROM) , random-access memory, cache memory, flash memory devices, optical storage devices, etc.
FIG. 11 shows a computer readable storage medium in accordance with some embodiments.
As shown in FIG. 11, the computer readable storage medium 1100 comprising instructions 1015 which when executed by a processor of a device, cause the device to perform any above-mentioned embodiments.
The computer readable storage medium 1100 may be configured to include memory such as RAM, ROM, programmable read-only memory (PROM) , erasable programmable read-only memory (EPROM) , electrically erasable programmable read-only memory (EEPROM) , magnetic disks, optical disks, floppy disks, hard disks, removable cartridges, or flash drives.
In some embodiments, an apparatus capable of performing any of the above discussed processes (for example, processes 400-700) may comprise means for performing the respective operations of the processes 400-700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The apparatus may be implemented as or included in the digital pre-distorter 200 as shown with respect to FIG. 2.
According to embodiments of the present disclosure, the apparatus comprises means for determining, based on an input power of a DPD in front of a power amplifier, a set of compensation representations from a look-up table, each compensation representation at least comprising a first value representing a candidate for the input power and a second value representing a DPD compensation result for the candidate; means for adjusting first values in the set of compensation representations to be third values, one of the third values being equal to a predetermined value; and means for determining a DPD compensation result for the input power based on second values in the set of compensation representations and the third values.
In some embodiments, means for determining the set of compensation representations comprises: means for determining a first compensation representation from the look-up table, a difference between the first value in the first compensation representation and the input power is less than a first threshold; and means for determining, from the look-up table, a predetermined number of consecutive compensation representations comprising the first compensation representation.
In some embodiments, the first value in the first compensation representation is a median of first values in the predetermined number of consecutive compensation representations.
In some embodiments, means for adjusting the first values to be the third values comprises: means for determining a reference value from the first values; and means for obtaining the third values by subtracting the reference value from the first values.
In some embodiments, means for determining the reference value comprises: means for determining, from the first values, the reference value based on a median of the first values, a difference between the reference value and the median of the first values is less than a second threshold.
In some embodiments, the number of the first values is an odd number, and the reference value is equal to the median of the first values.
In some embodiments, means for determining the DPD compensation result for the input power comprises: means for determining a plurality of parameters for a high order polynomial based on the second values and the third values; means for constructing a fitting curve for the DPD compensation based on the high order polynomial with the plurality of parameters; and means for obtaining the DPD compensation result corresponding to the input power based on the fitting curve.
In some embodiments, means for determining the plurality of parameters comprises: means for determining a first parameter of the plurality of parameters based on the second values and the third values; and means for determining remaining parameters of the plurality of parameters based on the second values and fourth values, the fourth values comprising the third values excluding the one equal to the predetermined value.
In some embodiments, means for determining the remaining parameters comprises: means for obtaining a second matrix by performing a row transformation to a first matrix composed of the fourth values; means for reducing the second matrix into a plurality of third matrices; and means for determining the remaining parameters based on the plurality of third matrices.
In some embodiments, the predetermined value is 0.
FIG. 12 shows an example of a communication system 1200 in accordance with some embodiments of the present disclosure. In the example, the communication system 1200 includes a telecommunication network 1202 that includes an access network 1204, such as a radio access network (RAN) , and a core network 1206, which includes one or more core network nodes 1208. The access network 1204 includes one or more access network nodes, such as network nodes 1210a and 1210b (one or more of which may be generally referred to as network nodes 1210) , or any other similar 3^rd Generation Partnership Project (3GPP) access node or non-3GPP access point. The network nodes 1210 facilitate direct or indirect connection of user equipment (UE) , such as by connecting terminal devices 1212a, 1212b, 1212c, and 1212d (one or more of which may be generally referred to as terminal devices 1212) to the core network 1206 over one or more wireless connections.
Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1200 may include any number of wired or wireless networks, network nodes, terminal devices, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 1200 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.
The terminal devices 1212 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 1210 and other communication devices. Similarly, the network nodes 1210 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the terminal devices 1212 and/or with other network nodes or equipment in the telecommunication network 1202 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 1202.
In the depicted example, the core network 1206 connects the network nodes 1210 to one or more hosts, such as host 1216. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1206 includes one or more core network nodes (e.g., core network node 1208) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the terminal devices, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1208. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC) , Mobility Management Entity (MME) , Home Subscriber Server (HSS) , Access and Mobility Management Function (AMF) , Session Management Function (SMF) , Authentication Server Function (AUSF) , Subscription Identifier De-concealing function (SIDF) , Unified Data Management (UDM) , Security Edge Protection Proxy (SEPP) , Network Exposure Function (NEF) , and/or a User Plane Function (UPF) .
The host 1216 may be under the ownership or control of a service provider other than an operator or provider of the access network 1204 and/or the telecommunication network 1202, and may be operated by the service provider or on behalf of the service provider. The host 1216 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of terminal devices, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.
As a whole, the communication system 1200 of FIG. 12 enables connectivity between the terminal devices, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM) ; Universal Mobile Telecommunications System (UMTS) ; Long Term Evolution (LTE) , and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G) ; wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi) ; and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax) , Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.
In some examples, the telecommunication network 1202 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 1202 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1202. For example, the telecommunications network 1202 may provide Ultra Reliable Low Latency Communication (URLLC) services to some terminal devices, while providing Enhanced Mobile Broadband (eMBB) services to other terminal devices, and/or Massive Machine Type Communication (mMTC) /Massive IoT services to yet further terminal devices.
In some examples, the terminal devices 1212 are configured to transmit and/or receive information without direct human interaction. For instance, a terminal device may be designed to transmit information to the access network 1204 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1204. Additionally, a terminal device may be configured for operating in single-or multi-RAT or multi-standard mode. For example, a terminal device may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR-DC) , such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio –Dual Connectivity (EN-DC) .
In the example, the hub 1214 communicates with the access network 1204 to facilitate indirect communication between one or more terminal devices (e.g., terminal device 1212c and/or 1212d) and network nodes (e.g., network node 1210b) . In some examples, the hub 1214 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding terminal devices. For example, the hub 1214 may be a broadband router enabling access to the core network 1206 for the terminal devices. As another example, the hub 1214 may be a controller that sends commands or instructions to one or more actuators in the terminal devices. Commands or instructions may be received from the terminal devices, network nodes 1210, or by executable code, script, process, or other instructions in the hub 1214. As another example, the hub 1214 may be a data collector that acts as temporary storage for terminal device data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1214 may be a content source. For example, for a terminal device that is a VR headset, display, loudspeaker or other media delivery device, the hub 1214 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1214 then provides to the terminal device either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub 1214 acts as a proxy server or orchestrator for the terminal devices, in particular if one or more of the terminal devices are low energy IoT devices.
The hub 1214 may have a constant/persistent or intermittent connection to the network node 1210b. The hub 1214 may also allow for a different communication scheme and/or schedule between the hub 1214 and terminal devices (e.g., terminal device 1212c and/or 1212d) , and between the hub 1214 and the core network 1206. In other examples, the hub 1214 is connected to the core network 1206 and/or one or more terminal devices via a wired connection. Moreover, the hub 1214 may be configured to connect to an M2M service provider over the access network 1204 and/or to another terminal device over a direct connection. In some scenarios, terminal devices may establish a wireless connection with the network nodes 1210 while still connected via the hub 1214 via a wired or wireless connection. In some embodiments, the hub 1214 may be a dedicated hub –that is, a hub whose primary function is to route communications to/from the terminal devices from/to the network node 1210b. In other embodiments, the hub 1214 may be a non-dedicated hub –that is, a device which is capable of operating to route communications between the terminal devices and network node 1210b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.
FIG. 13 shows a terminal device 1300 in accordance with some embodiments. As used herein, the terminal device 1300 is also called as a UE 1300, which refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other devices. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA) , wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , smart device, wireless customer-premise equipment (CPE) , vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP) , including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.
A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC) , vehicle-to-vehicle (V2V) , vehicle-to-infrastructure (V2I) , or vehicle-to-everything (V2X) . In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller) . Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter) .
The UE 1300 includes processing circuitry 1302 that is operatively coupled via a bus 1304 to an input/output interface 1306, a power source 1308, a memory 1310, a communication interface 1312, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 13. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.
The processing circuitry 1302 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1310. The processing circuitry 1302 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs) , application specific integrated circuits (ASICs) , etc. ) ; programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP) , together with appropriate software; or any combination of the above. For example, the processing circuitry 1302 may include multiple central processing units (CPUs) .
In the example, the input/output interface 1306 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1300. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc. ) , a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.
In some embodiments, the power source 1308 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet) , photovoltaic device, or power cell, may be used. The power source 1308 may further include power circuitry for delivering power from the power source 1308 itself, and/or an external power source, to the various parts of the UE 1300 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1308. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1308 to make the power suitable for the respective components of the UE 1300 to which power is supplied.
The memory 1310 may be or be configured to include memory such as random access memory (RAM) , read-only memory (ROM) , programmable read-only memory (PROM) , erasable programmable read-only memory (EPROM) , electrically erasable programmable read-only memory (EEPROM) , magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1310 includes one or more application programs 1314, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1316. The memory 1310 may store, for use by the UE 1300, any of a variety of various operating systems or combinations of operating systems.
The memory 1310 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID) , flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM) , synchronous dynamic random access memory (SDRAM) , external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs) , such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC) , integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card. ’ The memory 1310 may allow the UE 1300 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 1310, which may be or comprise a device-readable storage medium.
The processing circuitry 1302 may be configured to communicate with an access network or other network using the communication interface 1312. The communication interface 1312 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1322. The communication interface 1312 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network) . Each transceiver may include a transmitter 1318 and/or a receiver 1320 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth) . Moreover, the transmitter 1318 and receiver 1320 may be coupled to one or more antennas (e.g., antenna 1322) and may share circuit components, software or firmware, or alternatively be implemented separately.
In the illustrated embodiment, communication functions of the communication interface 1312 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA) , Wideband Code Division Multiple Access (WCDMA) , GSM, LTE, New Radio (NR) , UMTS, WiMax, Ethernet, transmission control protocol/internet protocol (TCP/IP) , synchronous optical networking (SONET) , Asynchronous Transfer Mode (ATM) , QUIC, Hypertext Transfer Protocol (HTTP) , and so forth.
Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1312, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature) , random (e.g., to even out the load from reporting from several sensors) , in response to a triggering event (e.g., when moisture is detected an alert is sent) , in response to a request (e.g., a user initiated request) , or a continuous stream (e.g., a live video feed of a patient) .
As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.
A UE, when in the form of an Internet of Things (IoT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR) , a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal-or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV) , and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an IoT device comprises circuitry and/or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE 1300 shown in Figure 13.
As yet another specific example, in an IoT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.
In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.
FIG. 14 shows a network node 1400 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points) , base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs) ) .
Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs) , sometimes referred to as Remote Radio Heads (RRHs) . Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS) .
Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs) , base transceiver stations (BTSs) , transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs) , Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs) ) , and/or Minimization of Drive Tests (MDTs) .
The network node 1400 includes a processing circuitry 1402, a memory 1404, a communication interface 1406, and a power source 1408. The network node 1400 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc. ) , which may each have their own respective components. In certain scenarios in which the network node 1400 comprises multiple separate components (e.g., BTS and BSC components) , one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 1400 may be configured to support multiple radio access technologies (RATs) . In such embodiments, some components may be duplicated (e.g., separate memory 1404 for different RATs) and some components may be reused (e.g., a same antenna 1410 may be shared by different RATs) . The network node 1400 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1400, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1400.
The processing circuitry 1402 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 1400 components, such as the memory 1404, to provide network node 1400 functionality.
In some embodiments, the processing circuitry 1402 includes a system on a chip (SOC) . In some embodiments, the processing circuitry 1402 includes one or more of radio frequency (RF) transceiver circuitry 1412 and baseband processing circuitry 1414. In some embodiments, the radio frequency (RF) transceiver circuitry 1412 and the baseband processing circuitry 1414 may be on separate chips (or sets of chips) , boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1412 and baseband processing circuitry 1414 may be on the same chip or set of chips, boards, or units.
The memory 1404 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM) , read-only memory (ROM) , mass storage media (for example, a hard disk) , removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD) ) , and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 1402. The memory 1404 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry 1402 and utilized by the network node 1400. The memory 1404 may be used to store any calculations made by the processing circuitry 1402 and/or any data received via the communication interface 1406. In some embodiments, the processing circuitry 1402 and memory 1404 is integrated.
The communication interface 1406 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface 1406 comprises port (s) /terminal (s) 1416 to send and receive data, for example to and from a network over a wired connection. The communication interface 1406 also includes radio front-end circuitry 1418 that may be coupled to, or in certain embodiments a part of, the antenna 1410. Radio front-end circuitry 1418 comprises filters 1420 and amplifiers 1422. The radio front-end circuitry 1418 may be connected to an antenna 1410 and processing circuitry 1402. The radio front-end circuitry may be configured to condition signals communicated between antenna 1410 and processing circuitry 1402. The radio front-end circuitry 1418 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1418 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1420 and/or amplifiers 1422. The radio signal may then be transmitted via the antenna 1410. Similarly, when receiving data, the antenna 1410 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1418. The digital data may be passed to the processing circuitry 1402. In other embodiments, the communication interface may comprise different components and/or different combinations of components.
In certain alternative embodiments, the network node 1400 does not include separate radio front-end circuitry 1418, instead, the processing circuitry 1402 includes radio front-end circuitry and is connected to the antenna 1410. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1412 is part of the communication interface 1406. In still other embodiments, the communication interface 1406 includes one or more ports or terminals 1416, the radio front-end circuitry 1418, and the RF transceiver circuitry 1412, as part of a radio unit (not shown) , and the communication interface 1406 communicates with the baseband processing circuitry 1414, which is part of a digital unit (not shown) .
The antenna 1410 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna 1410 may be coupled to the radio front-end circuitry 1418 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna 1410 is separate from the network node 1400 and connectable to the network node 1400 through an interface or port.
The antenna 1410, communication interface 1406, and/or the processing circuitry 1402 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna 1410, the communication interface 1406, and/or the processing circuitry 1402 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.
The power source 1408 provides power to the various components of network node 1400 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component) . The power source 1408 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1400 with power for performing the functionality described herein. For example, the network node 1400 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 1408. As a further example, the power source 1408 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.
Embodiments of the network node 1400 may include additional components beyond those shown in Figure 14 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node 1400 may include user interface equipment to allow input of information into the network node 1400 and to allow output of information from the network node 1400. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1400.
The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding apparatus described with an embodiment comprises not only prior art means, but also means for implementing the one or more functions of the corresponding apparatus described with the embodiment and it may comprise separate means for each separate function or means that may be configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more apparatuses) , firmware (one or more apparatuses) , software (one or more modules) , or combinations thereof. For a firmware or software, implementation may be made through modules (e.g., procedures, functions, and so on) that perform the functions described herein.
Exemplary embodiments herein have been described above with reference to block diagrams and flowchart illustrations of methods and apparatuses. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various means including computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flowchart block or blocks.
Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to some embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.
While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any implementation or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular implementations. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The above-described embodiments are given for describing rather than limiting the disclosure, and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the disclosure as those skilled in the art readily understand. Such modifications and variations are within the scope of the disclosure and the appended claims. The protection scope of the disclosure is defined by the accompanying claims.
Abbreviation Explanation
3GPP 3rd Generation Partnership Project
NR New Radio
LTE Long Term Evolution
WCDMA Wideband Code Division Multiple Access
HSPA High-Speed Packet Access
DPD Digital Pre-distorter
LUT Look-Up Table
NR New Radio
PA Power Amplifier
EVM Error Vector Magnitude
VS Volterra Series
TCC Translation Curve Calibrator
CSI Cubic Spline Interpolation
IoT Internet of Things

Claims

A method (400) of digital pre-distorter, DPD, compensation, comprising:

determining (410) , based on an input power of a DPD in front of a power amplifier, a set of compensation representations from a look-up table, each compensation representation at least comprising a first value representing a candidate for the input power and a second value representing a DPD compensation result for the candidate;

adjusting (420) first values in the set of compensation representations to be third values, one of the third values being equal to a predetermined value; and

determining (430) a DPD compensation result for the input power based on second values in the set of compensation representations and the third values.
The method (400) of claim 1, wherein determining (410) the set of compensation representations comprises:

determining (510) a first compensation representation from the look-up table, a difference between the first value in the first compensation representation and the input power is less than a first threshold; and

determining (520) , from the look-up table, a predetermined number of consecutive compensation representations comprising the first compensation representation.
The method (400) of claim 2, wherein the first value in the first compensation representation is a median of first values in the predetermined number of consecutive compensation representations.
The method (400) of claim 1, wherein adjusting (420) the first values to be the third values comprises:

determining (610) a reference value from the first values; and

obtaining (620) the third values by subtracting the reference value from the first values.
The method (400) of claim 4, wherein determining (610) the reference value comprises:

determining, from the first values, the reference value based on a median of the first values, a difference between the reference value and the median of the first values is less than a second threshold.
The method (400) of claim 5, wherein the number of the first values is an odd number, and the reference value is equal to the median of the first values.
The method (400) of claim 1, wherein determining (430) the DPD compensation result for the input power comprises:

determining (710) a plurality of parameters for a high order polynomial based on the second values and the third values;

constructing (720) a fitting curve for the DPD compensation based on the high order polynomial with the plurality of parameters; and

obtaining (730) the DPD compensation result corresponding to the input power based on the fitting curve.
The method (400) of claim 7, wherein determining (710) the plurality of parameters comprises:

determining a first parameter of the plurality of parameters based on the second values and the third values; and

determining remaining parameters of the plurality of parameters based on the second values and fourth values, the fourth values comprising the third values excluding the one equal to the predetermined value.
The method (400) of claim 8, wherein determining the remaining parameters comprises:

obtaining a second matrix by performing a row transformation to a first matrix composed of the fourth values;

reducing the second matrix into a plurality of third matrices; and

determining the remaining parameters based on the plurality of third matrices.
The method (400) of any of claims 1 to 9, wherein the predetermined value is 0.
An apparatus (1000) for digital pre-distorter, DPD, compensation, comprising:

a processor (1005) and a memory (1010) , the memory containing instructions (1015) executable by the processor whereby the apparatus is operative to perform the method (400) of any one of claims 1-10.
A computer readable medium (1100) having instructions (1015) stored thereon, the instructions, when executed by at least one processor, causing the at least one processor to perform a method (400) according to any of claims 1 to 10.