Description:TECHNICAL FIELD
[0001] The present disclosure, in general, relates to managing power in a wireless communication device in a network, and in particular, relates to systems and methods for adaptive average power tracking with power amplifier protection in a wireless communication system, for example, 5G system.
BACKGROUND
[0002] The fifth-generation (5G) macro base station (BS) with multiple antennas has a huge coverage area. It uses a high-power amplifier (HPA) for each antenna to boost the signal so that it can reach the edges of the coverage area. It 10 requires a large amount of transmit power and results in a huge amount of energy consumption. Operating the HPA in the saturation region increases the overall energy efficiency of the BS. However, in 5G BS, the envelope of the transmit signal varies significantly over time, which prevents operating the HPA in the saturated state. This means a loss of efficiency since HPAs are most efficient when operated 15 at their peak output power. The HPA is forced to operate way below its peak output power at low instantaneous powers. As a result, a significant amount of power is dissipated as heat. Similar scenario occurs in other 5G devices like user equipment (UE), smartphones, customer premises equipment (CPE), and the like.
[0003] To overcome the above problem, average power tracking (APT) is 20 applied in conventional systems. The idea of APT is to dynamically adjust the supply voltage of the PA according to the average power of Radio Frequency (RF) input signal over a given period of time. By modulating the supply voltage, the HPA’s efficiency is significantly increased. This yields a low power budget of 5G devices. 25
[0004] A conventional architecture of a system (100) is shown in FIG. 1. A System on Chip (SoC) contains a processing system and programming logic for baseband processing of the incoming data and other control functions. A higher layer (104) consists of Medium Access Control (MAC) and Radio Link Control (RLC) layers. A Physical (PHY) layer (106) processes the incoming bits from the 30 higher layers into the time domain in-phase quadrature (IQ) symbols. Digital front
3
end (DFE) (108) processes the time domain IQ symbols with crest factor reduction (CFR), digital predistortion (DPD), and digital upconverter (DUC). Digital to Analog converter (DAC) (110) converts the digital signal into an analog signal. HPA (112) is an amplifier that amplifies the signal with the desired output power before transmission. An Average Power Detector (APD) (114-1) calculates the 5 average power of the time-domain IQ symbols over a given period of time. Look-up table (LUT) (116) provides a modulated voltage supply (Vdd) value based on the calculated average power. A Delay unit (118) delays the modulated voltage supply value so that RF input signal at PA output and modulated voltage supply are aligned in time. A supply modulator (120) generates the modulated voltage supply for the 10 HPA (112) accordingly.
[0005] Generally, APD (114-1) calculates the average power of the signal over the fixed duration of time which may be one or more slot durations. 4G/Long Term Evolution (LTE) has single numerology which means that all the slots in one radio frame have same duration. Thus, it may be easy to maintain the periodicity of APT. 15 However, the same is not true for 5G due to the flexible structure of 5G radio frame.
[0006] Modern applications such as autonomous vehicles, Internet of Things (IoT), and high-speed video streaming have different demands which may not be fulfilled by the rigid frame structure. Thus, the 5G frame structure has been designed to adapt itself according to the requirements of each application, making 20 the entire network more efficient. The 5G frame structure is based on a slot and symbol-based design. With the mixed numerologies, the duration of slot and symbols are different, as given in Error! Reference source not found. below. Furthermore, the mini-slots allow the 5G frame structure to provide faster response times for certain applications. 25
µ
??? (kHz)
??slotframe,??
??slot (us)
??symbolNormal (us)
0
15
10
1000
71.35
1
30
20
500
35.68
2
60
40
250
17.84
4
3
120
80
125
8.92
4
240
160
62.5
4.46
5
480
320
31.25
2.23
6
960
640
15.625
1.12
where
- ?? is the subcarrier spacing configuration.
- ??? is the subcarrier spacing.
- ??slotframe,?? is the number of slots per frame for ??.
- ??slot is the slot duration.
- ??symbolNormal is the symbol duration with normal CP.
Table A
[0007] Periodic APT (i.e., fixed averaging window) may not be an optimal solution for the 5G network, because it may not dynamically adjust the duration of each slot/symbol.
[0008] Therefore, there is a need for a system and a method for adaptive 5 average power tracking in a wireless communication system.
OBJECTS OF THE PRESENT DISCLOSURE
[0009] It is an object of the present disclosure to provide a system and a method for adaptive average power tracking in a wireless communication system. 10
[0010] It is an object of the present disclosure to prevent power amplifier and other components in the wireless communication system from damage.
[0011] It is an object of the present disclosure to utilize information from a higher layer to optimize hardware resource utilization.
15
SUMMARY
[0012] In an aspect, the present disclosure relates to a method for adaptive average power tracking in a wireless communication system, including determining, by a processor, an average power of each of a plurality of Orthogonal Frequency-Division Multiplexing (OFDM) symbols in a radio frame based on a set 20
5
of power scaling factors and a number of Resource Elements (REs) associated with each OFDM symbol, comparing, by the processor, the average power of each of the plurality of OFDM symbols with a power threshold value, detecting, by the processor, one or more faulty OFDM symbols among the plurality of OFDM symbols based on the comparison, modifying, by the processor, the one or more 5 faulty OFDM symbols, determining, by the processor, an average power of a set of OFDM symbols, including the one or more modified OFDM symbols, corresponding to an averaging window, and generating, by the processor, a modulated voltage supply for a power amplifier in the wireless communication system based on the determined average power of the set of OFDM symbols. 10
[0013] In an embodiment, determining, by the processor, the average power of each of the plurality of OFDM symbols may include receiving, by the processor, the set of power scaling factors of physical channels and reference signals from a higher layer in the wireless communication system, determining, by the processor, power scaling factors of multiple-input multiple-output (MIMO) precoding weights 15 and/or beamforming weights for each transmit chain associated with the wireless communication system, and determining, by the processor, the number of REs associated with the physical channels and the reference signals mapped to each OFDM symbol.
[0014] In an embodiment, the average power of each of the plurality of OFDM 20 symbols may be determined based on at least one of: the set of power scaling factors of the physical channels and the reference signals, the power scaling factors of the MIMO precoding weights and/or the beamforming weights, and the number of REs associated with the physical channels and the reference signals.
[0015] In an embodiment, detecting, by the processor, the one or more faulty 25 OFDM symbols may include, for each of the plurality of OFDM symbols, determining, by the processor, whether the average power of a given OFDM symbol is less than the power threshold value, in response to a determination that the average power of the given OFDM symbol is less than the power threshold value, identifying, by the processor, that the given OFDM symbol is not faulty, and in 30 response to a determination that the average power of the given OFDM symbol is
6
greater than the power threshold value, identifying, by the processor, that the given OFDM symbol is a faulty OFDM symbol.
[0016] In an embodiment, modifying, by the processor, the one or more faulty OFDM symbols may include, for each of the one or more faulty OFDM symbols, initiating, by the processor, a timer for a predetermined time period, and a counter 5 to zero, transmitting, by the processor, an error flag corresponding to a given faulty OFDM symbol to a higher layer in the wireless communication system, and determining, by the processor, whether the higher layer responds with updated parameters corresponding to the given faulty OFDM symbol within the predetermined time period. 10
[0017] In an embodiment, the method may include in response to a determination that the higher layer does not respond within the predetermined time period, configuring, by the processor, zeroes in REs of the given faulty OFDM symbol, or in response to a determination that the higher layer responds within the predetermined time period, determining, by the processor, an updated average 15 power of the given faulty OFDM symbol, based on the updated parameters received from the higher layer, determining, by the processor, whether the updated average power is less than the power threshold value, and in response to a determination that the updated average power is greater than the power threshold value, increasing, by the processor, a count of the counter and determining, by the 20 processor, whether the count is less than a counter threshold value.
[0018] In an embodiment, the method may include in response to a determination that the count is less than the counter threshold value, re-transmitting, by the processor, the error flag to the higher layer, or in response to a determination that the count is greater than the counter threshold value, configuring, by the 25 processor, the zeroes in the REs of the given faulty OFDM symbol.
[0019] In an embodiment, the method may include determining, by the processor, whether the averaging window is periodic or adaptive.
[0020] In an embodiment, in case of the averaging window being periodic, the method may include determining, by the processor, a periodicity of the averaging 30 window, and storing, by the processor, the average power of the set of OFDM
7
symbols corresponding to the averaging window and an index of a start of the averaging window in a database.
[0021] In an embodiment, in case of the averaging window being adaptive, the method may include determining, by the processor, a structure of the radio frame, and storing, by the processor, the average power of the set of OFDM symbols 5 corresponding to the averaging window and an index of a first OFDM symbol corresponding to one of: the set of OFDM symbols within a mini-slot, the set of OFDM symbols having same numerology, or the set of OFDM symbols where the average power of a number of consecutive OFDM symbols lies in same range of a Look-Up Table (LUT). 10
[0022] In an embodiment, generating, by the processor, the modulated power supply may include receiving, by the processor, a symbol indicator of a first OFDM symbol of the set of OFDM symbols from a timing module in the wireless communication system, converting, by the processor, the average power of the set of OFDM symbols into a codeword using a LUT at the symbol indicator of the first 15 OFDM symbol, and generating, by the processor, the modulated power supply based on the codeword, wherein the modulated power supply may be delayed to align with an input signal at the power amplifier.
[0023] In an aspect, the present disclosure relates to a system for adaptive average power tracking, including a processor, and a memory operatively coupled 20 with the processor, wherein the memory includes processor-executable instructions which, when executed by the processor, cause the processor to determine an average power of each of a plurality of OFDM symbols in a radio frame based on a set of power scaling factors and a number of REs associated with each OFDM symbol, compare the average power of each of the plurality of OFDM symbols with 25 a power threshold value, detect one or more faulty OFDM symbols among the plurality of OFDM symbols based on the comparison, modify the one or more faulty OFDM symbols, determine an average power of a set of OFDM symbols, including the one or more modified OFDM symbols, corresponding to an averaging window, and generate a modulated voltage supply for a power amplifier in the 30 system based on the determined average power of the set of OFDM symbols.
8
BRIEF DESCRIPTION OF DRAWINGS
[0024] The accompanying drawings, which are incorporated herein, and constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed methods and systems which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not 5 necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that disclosure of such drawings includes the disclosure of electrical components, electronic components, 10 or circuitry commonly used to implement such components.
[0025] FIG. 1 illustrates an example architecture of a conventional system.
[0026] FIG. 2 illustrates an example representation of a proposed system, in accordance with an embodiment of the present disclosure.
[0027] FIG. 3 illustrates a high-level flow chart of an example method for 15 adaptive average power tracking, in accordance with an embodiment of the present disclosure.
[0028] FIG. 4 illustrates a flow chart of an example method for symbol average power calculation, in accordance with an embodiment of the present disclosure.
[0029] FIG. 5 illustrates a flow chart of an example method for early power 20 warning detection and mitigation, in accordance with an embodiment of the present disclosure.
[0030] FIG. 6 illustrates a flow chart of an example method for adaptive average power tracking, in accordance with embodiments of the present disclosure.
[0031] FIG. 7 illustrates an example representation of average power tracking 25 with periodicity of two Orthogonal Frequency Division Multiplexing (OFDM) symbols, in accordance with an embodiment of the present disclosure. [0032] FIG. 8 illustrates an example computer system in which or with which embodiments of the present disclosure may be implemented.
[0033] The foregoing shall be more apparent from the following more detailed 30 description of the disclosure.
9
DETAILED DESCRIPTION
[0034] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific 5 details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address all of the problems discussed above or might address only some of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. 10
[0035] The ensuing description provides exemplary embodiments only and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an exemplary embodiment. It should be understood that various changes may be made in the 15 function and arrangement of elements without departing from the spirit and scope of the disclosure as set forth.
[0036] The various embodiments throughout the disclosure will be explained in more detail with reference to FIGs. 2-8.
[0037] FIG. 2 illustrates an example architecture of a system (200) for adaptive 20 average power tracking, in accordance with an embodiment of the present disclosure.
[0038] In particular, the system (200) includes a System on Chip (SoC) (102), a higher layer (104), a Physical (PHY) layer (106), Digital Front End (DFE) blocks (108), Digital to Analog Converter (DAC) (110), and a Power Amplifier (PA) 25 (112), for example, a High-PA (HPA) (112). Further, the system (200) includes a timing module (122), a Symbol Average Power (SAP) calculator (124), an Early Warning Detector (EWD) (126), an adaptive Average Power Detector (APD) (114-2), a Look-Up Table (LUT) (116), a delay unit (118), and a supply modulator (120).
[0039] Referring to FIG. 2, the timing module (122) may generate indicators 30 for each symbol boundary (e.g., Orthogonal Frequency Division Multiplexing
10
(OFDM) symbol), for each slot boundary, and for each frame boundary. The SAP calculator (124) may read parameters from the higher layer (104). The parameters may include, but not limited to, a set of power scaling factors of physical channels and reference signals related to a next frame. In some embodiments, the SAP calculator (124) may determine the power scaling factors introduced by multiple-5 input multiple-output (MIMO) precoding and/or beamforming weights for each transmit chain. The SAP calculator (124) may determine a number of Resource Elements (REs) associated with all the physical channels and the reference signals, which are mapped to different OFDM symbols. In some embodiments, the SAP calculator (124) may determine an average power of each of a plurality OFDM 10 symbols in a radio frame based on the set of power scaling factors and the number of REs associated with each OFDM symbol.
[0040] The EWD (126) may check the average power of each OFDM symbol (????,??,??) with a power threshold value (????h) in order to detect data overflow in the DAC output (110). It may help in protecting the HPA (112) from damage. It may 15 be appreciated that the power threshold value is configurable and can be defined as per design implementation. In some embodiments, the EWD (126) may detect one or more faulty OFDM symbols. In some embodiments, the EWD (126) may notify the higher layer (104) in case the average power of any OFDM symbol violates the power threshold value. In such a scenario, the EWD (126) may modify the faulty 20 OFDM symbols with updated parameters (e.g., updated power scaling factors) if the higher layer (104) responds with the updated parameters. In some other embodiments, the EWD (126) may put zeros in the whole OFDM symbol to protect the HPA (112) as well as to maintain the data transmission continuity.
[0041] Referring to FIG. 2, the adaptive APD (114-2) may determine an 25 average power of a set of OFDM symbols including the modified OFDM symbols corresponding to an averaging window. The adaptive APD (114-2) may determine whether the averaging window is periodic or adaptive. If the averaging window is periodic, the adaptive APD (114-2_ may determine periodicity of the averaging window, and based on the periodicity, the adaptive APD (114-2) may determine the 30 number of OFDM symbols that arrive in that period. The adaptive APD (114-2)
11
may read the average power of each OFDM symbol from the EWD (126) and measure their average power. In some embodiments, the adaptive APD (114-2) may wait for an indicator signal coming from the timing module (122) to release the average power to the LUT (116).
[0042] In some embodiments, the LUT (116) may provide a modulated voltage 5 supply (Vdd) value based on the calculated average power of the set of OFDM symbols. The delay unit (118) may delay the modulated voltage supply value so that radio frequency (RF) input signal at the HPA output (112) and the modulated voltage supply are aligned in time. In some embodiments, the supply modulator (120) may generate the modulated voltage supply for the HPA (112) accordingly. 10
[0043] In some embodiments, the system (200) may be associated with a processor and a memory, such that the memory includes processor-executable instructions which, when executed by the processor, cause the processor to perform the methods described herein. It may be appreciated that the system (200) may correspond to a base station such as Next-Generation Node B (gNodeB), Evolved 15 Node B (eNodeB), etc., a Customer Premises Equipment (CPE), user equipment, smartphone, or the like.
[0044] FIG. 3 illustrates a high-level flow chart of an example method (300) for adaptive average power tracking in a wireless communication system, in accordance with an embodiment of the present disclosure. 20
[0045] Referring to FIG. 3, at block 302, the method (300) includes SAP calculation by the SAP calculator (124). The method (300) may include calculating an average power of each OFDM symbol based on parameters from a higher layer (104). At block 304, the method (300) includes early warning detection and mitigation by the EWD (126). In some embodiments, the method (300) may include 25 determining whether the calculated average power of each OFDM symbol violates a power threshold value or not. In some embodiments, the method (300) may include mitigating the early warning.
[0046] At block 306, the method (300) includes adaptive average power detection by the adaptive APD (114-2). The method (300) may include determining 30 an averaging window and calculating the average power of the OFDM symbols
12
mapped to the averaging window. At block 308, the method (300) includes LUT conversion by the LUT (116). Based on the average value received from the adaptive APD (114-2), a codeword may be selected from the LUT (116) for appropriate supply voltage. The LUT (116) depends on the HPA characteristics and may be generated as per the design implementation. The LUT (116) may be 5 generated offline and saved in a local memory of the SoC (102).
[0047] Referring to FIG. 2, at block 310, the method (300) includes applying delay by the delay unit (118). The method (300) may include apply a delay value, which helps synchronize the modulated supply voltage and input signal to the HPA (112). In some embodiments, the value of delay may be provided by the timing 10 module (122). In some other embodiments, I value of delay may be determined according to the design implementation. At block 312, the method (300) includes supply modulator processing by the supply modulator (120) such that on receiving the codeword, the supply modulator (120) may change the supply voltage of the HPA (112). The method (300) will be discussed in detail throughout the disclosure. 15
[0048] FIG. 4 illustrates a flow chart of an example method (400) for SAP calculation (302), in accordance with an embodiment of the present disclosure.
[0049] Referring to FIG. 4, at block 402, the method (400) includes determining a set of scaling factors (ß) of all downlink physical channels and reference signals from the higher layer (104). For example, the physical channels and the reference 20 signals used for downlink in the 5G new radio (NR) have different scaling factor as defined in the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 38.211 and TS 38.214. The same is as shown in Error! Reference source not found..
25
PHYSICAL CHANNEL OR REFERENCE SIGNAL
SCALING FACTOR
PHYSICAL BROADCAST CHANNE (PBCH)
??PBCH
PHYSICAL DOWNLINK CONTROL CHANNEL (PDCCH)
??PDCCH
13
PHYSICAL DOWNLINK SHARED CHANNEL (PDSCH)
??PDSCH
PBCH-DEMODULATION REFERENCE SIGNAL (DMRS)
??PBCHDMRS
PDCCH-DMRS
??PDCCHDMRS
PDSCH-DMRS
??PDSCHDMRS
PHASE-TRACKING REFERENCE SIGNALS (PT-RS)
??PT-RS
POSITIONING REFERENCE SIGNAL (PRS)
??PRS
CHANNEL-STATE INFORMATION REFERENCE SIGNAL (CSI-RS)
??CSIRS
PRIMARY SYNCHRONIZATION SIGNAL (PSS)
??PSS
SECONDARY SYNCHRONIZATION SIGNAL (SSS)
??SSS
Table 1
[0050] At block 404, the method (400) includes determining scaling factors of MIMO precoding and/or beamforming weights for all transmit chains. Generally, MIMO precoding and/or beamforming operations in the downlink maintain the total power of the system (200) in the spatial domain. However, there is a possibility 5 that MIMO precoding and/or beamforming operations may change the average power of OFDM symbols which are allocated to different physical antenna ports. In the case of MIMO precoding (for both codebook and non-codebook), the method (400) may include determining the scaling factor ??Precoding for each OFDM symbol from the assigned precoding weights by the higher layer (104). In the case 10 of beamforming (for both frequency and time domain), the method (400) may include determining the scaling factor ??BF for each OFDM symbol from the beamforming weights assigned by the higher layer (104).
[0051] At block 406, the method (400) includes determining the scaling factors introduced by system design for all the transmit chains. The design factors in the 15 system (200) may impact the average power of the OFDM symbol. These factors may be additional weights for antenna calibration, the scaling factor of inverse Fast Fourier Transformation (iFFT) operation, and the like. These factors may be
14
determined by the system parameters as per the design implementation. The scaling factor ??Sys can be used to represent the collective scaling factor introduced by the system (200).
[0052] Referring to FIG. 4, at block 408, the method (400) includes determining a number of REs associated with all the physical channels and the reference signals 5 mapped to each OFDM symbol, for example, by determining the layer mapping and antenna port mapping from the higher layer (104). At block 410, the method (400) includes calculating the average power of each OFDM symbol. The average power of ??th OFDM symbol (????,??,??) for physical antenna port ?? and subcarrier spacing configuration ?? may be defined as: 10
????,??,??=??Precoding??BF??Sys????(??PSS????,??,??PSS+??SSS????,??,??SSS+??PBCH????,??,??PBCH+??PBCHDMRS????,??,??PBCH-DMRS+??PRS????,??,??PRS+??RIM????,??,??RIM+??CSIRS????,??,??CSIRS+??PT-RS,??????,??,??PT-RS+??PDCCH????,??,??PDCCH+??PDCCHDMRS????,??,??PDCCH-DMRS+??PDSCH????,??,??PDSCH+??PDSCHDMRS????,??,??PDSCH-DMRS )
Where, 15
- ???? is the FFT size. For example, it may be 4096 for 5G NR.
- ????,??,????is the number of REs carrying the physical channels or Demodulation Reference Signal (DMRS) of physical channels or reference signals with time-domain index ?? for physical antenna port ?? and subcarrier spacing configuration ??. 20
[0053] FIG. 5 illustrates a flow chart of an example method (500) of early warning detection (304) and mitigation, in accordance with an embodiment of the present disclosure.
[0054] Referring to FIG. 5, at block 502, the method (500) includes reading an average power of each OFDM symbol (????,??,??) from the SAP calculator (122) and 25 comparing with a power threshold value ????h. The value of the power threshold value ????h may depend upon the DAC resolution, data bits for unity average power, and reserved bits for power scaling factors. For example, consider the DAC (110) with 14-bit resolution in which the first most significant bit (MSB) is used as a sign
15
bit, and the remaining 13 bits are used as data bits. 11 least significant bits (LSBs) are considered data transmission bits with unity power, and the remaining 2 bits are reserved. In an event when the power scaling factors increase the average power of the OFDM symbol, then 11 bits are inadequate to represent in-phase quadrature (IQ) samples. In such a case, the remaining 2 bits can be used along with 11 bits to 5 represent the IQ samples. Each reserved bit can be used to represent the IQ samples with 3dB additional power. This means 2 reserved bits with 11 bits can represent the IQ samples when the average power is increased by at most 6dB. If it is more than 6dB, then there will be data overflow in the DAC (110), which may lead to HPA burnout. In this case, 6dB is used to define the power threshold value. In some 10 embodiments, when ????,??,??