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WO2009093810A1 - Émetteur et procédé pour mise à l'échelle de sous-porteuses dans une station mobile d'un système ofdma - Google Patents

Émetteur et procédé pour mise à l'échelle de sous-porteuses dans une station mobile d'un système ofdma Download PDF

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Publication number
WO2009093810A1
WO2009093810A1 PCT/KR2008/007613 KR2008007613W WO2009093810A1 WO 2009093810 A1 WO2009093810 A1 WO 2009093810A1 KR 2008007613 W KR2008007613 W KR 2008007613W WO 2009093810 A1 WO2009093810 A1 WO 2009093810A1
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WO
WIPO (PCT)
Prior art keywords
subcarriers
scaling
control value
value
transmission signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/KR2008/007613
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English (en)
Inventor
Dong-Kyu Kim
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Posdata Co Ltd
Original Assignee
Posdata Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Posdata Co Ltd filed Critical Posdata Co Ltd
Publication of WO2009093810A1 publication Critical patent/WO2009093810A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/52—Transmission power control [TPC] using AGC [Automatic Gain Control] circuits or amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0014—Three-dimensional division
    • H04L5/0016—Time-frequency-code
    • H04L5/0017—Time-frequency-code in which a distinct code is applied, as a temporal sequence, to each frequency
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0037—Inter-user or inter-terminal allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/0064—Rate requirement of the data, e.g. scalable bandwidth, data priority
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0091—Signalling for the administration of the divided path, e.g. signalling of configuration information
    • H04L5/0094—Indication of how sub-channels of the path are allocated
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/22—TPC being performed according to specific parameters taking into account previous information or commands
    • H04W52/226—TPC being performed according to specific parameters taking into account previous information or commands using past references to control power, e.g. look-up-table
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0473—Wireless resource allocation based on the type of the allocated resource the resource being transmission power

Definitions

  • the present invention relates to transmission and reception of data in a mobile station of Orthogonal Frequency Division Multiplexing Access (OFDMA), and more particularly, to a transmitter and method which can adjust subcarriers used in a transmission unit of a modem according to the number of subcarriers allocated from a base station for transmission of uplink data.
  • OFDMA Orthogonal Frequency Division Multiplexing Access
  • a base station In communication environments of OFDMA, a base station generally transmits the allocation information of subcarriers for the transmission of uplink data to each subscriber station (hereinafter, referred to as "SS") by using downlink data. Accordingly, the SS receiving the downlink data checks the allocation information of the received downlink data, and allocates subcarriers as many as subcarriers allocated thereto and transmits the uplink data.
  • FIG. 1 illustrates the configuration of a general transmitter/receiver in an OFDMA SS for the transmission/reception of data.
  • the transmitter/receiver in the SS includes a modem processing a digital signal, and a Radio Frequency (RF) unit 10 processing an analog signal.
  • RF Radio Frequency
  • the modem includes a transmission unit 20 of OFDM communication system for processing the digital signal, a reception unit 30 of OFDM communication system for processing the digital signal, a subcarrier processing unit 41 processing data to be carried in a subcarrier allocated from a base station, a subcarrier processing unit 42 processing received data, and a frequency domain processing unit 50. Since the transmission unit 20 and the reception unit 30 are well known, their detailed description will be omitted.
  • the RF unit 10 includes a power amplifier amplifying a transmission signal, and controls the power amplifier according to a control value (P ).
  • the control value (P ) is a transmission power value indicated by the base station.
  • the number of subcarriers allocated from the base station for the transmission of uplink data is very variable.
  • the OFDMA SS generates a standardized transmission signal irrespective of the number of the subcarriers and transmits it to the base station. For example, if the magnitude of Fast Fourier Transform (FFT) used for OFDM modulation is 1024, the number of subcarriers which the base station can allocate to each SS is 1 to 1024.
  • FFT Fast Fourier Transform
  • the output signals of the SS are seen as FIGS. 2 and 3.
  • the output signals seen in FIGS. 2 and 3 are an in-phase signal or a quadrature signal among FFT outputs.
  • a signal using the 840 subcarriers is distributed in the entire input/output section of a digital-to-analog controller (DAC).
  • DAC digital-to-analog controller
  • FIG. 3 it can be seen that a signal using the 24 subcarriers is distributed only in approximately a sixth of the input/output section of the DAC when it is transmitted as it is without being adjusted.
  • the size of used DAC bits is 10, only about 7.5 bits among the 10 bits of the DAC are used and the remaining about 2.5 bits are not used when a signal to which the 24 subcarriers are allocated is transmitted, and thus the DAC cannot be utilized to the utmost. Disclosure of Invention Technical Problem
  • An aspect of the present invention provides a transmitter and method which can adjust subcarriers according to the number of allocated subcarriers in order to use the entire bit of a digital-to-analog controller (DAC) even when the number of the subscribers, which are allocated to a SS from a base station for the transmission of uplink data, is small in Orthogonal Frequency Division Multiplexing Access (OFDMA) communication environments.
  • DAC digital-to-analog controller
  • a transmitter for subcarrier scaling in a SS of Orthogonal Frequency Division Multiplexing Access including: a modem calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, calculating a correction control value according to the scaling control value, adjusting the subcarriers allocated to the transmission signal according to the scaling control value, and outputting the transmission signal to which the adjusted subcarriers are allocated; and a Radio Frequency (RF) unit adjusting power of the transmission signal by the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.
  • OFDMA Orthogonal Frequency Division Multiplexing Access
  • a transmitter for subcarrier scaling in a SS of OFDMA including: a control unit calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, and calculating a correction control value according to the scaling control value; a scaling unit adjusting the subcarriers allocated to the transmission signal according to the scaling control value; a transmission unit performing a digital signal processing on a signal to which the adjusted subcarriers are allocated, and outputting an analog transmission signal; and a RF unit adjusting power of the transmission signal output from the transmission unit by the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.
  • a method for subcarrier scaling in a SS of OFDMA including: allocating subcarriers to a transmission signal according to a searched maximum number of subcarriers by using allocation information transmitted from a base station; calculating a scaling control value of the subcarriers according to the searched maximum number of the subcarriers, and calculating a correction control value according to the scaling control value; adjusting the subcarriers allocated to the transmission signal according to the scaling control value; performing a digital signal processing on a signal to which the adjusted subcarriers are allocated, and outputting an analog transmission signal; adjusting power of the transmission signal by the correction control value; and amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to the base station.
  • Embodiments of the present invention can increase power of a transmission signal, i.e., amplitude of the transmission signal, by subcarrier scaling in a modem being a digital module in a transmitter of an Orthogonal Frequency Division Multiplexing Access (OFDMA) SS, and thus can decrease the power amplification of a Radio Frequency (RF) unit being an analog module. Accordingly, when subcarriers less than the total number of available subcarriers are used, embodiments of the present invention can solve the limitation that the amplitude of an up-link signal is relatively reduced, and can save the consumption power of the analog module occupying a considerable amount of consumption power.
  • OFDMA Orthogonal Frequency Division Multiplexing Access
  • FIG. 1 illustrates the configuration of a general transmitter/receiver in an OFDMA
  • FIGS. 2 and 3 are characteristic diagrams of signals generated in a time domain processing unit according to the number of allocated subcarriers in a general SS;
  • FIG. 4 is a block diagram of a transmitter/receiver in an OFDMA SS according to an embodiment of the present invention
  • FIG. 5 is a flowchart illustrating a method for subcarrier scaling in the OFDMA SS according to an embodiment of the present invention
  • FIG. 6 is a flowchart illustrating the operation of the control unit of the transmitter according to an embodiment of the present invention.
  • FIGS. 7 and 8 are characteristic diagrams illustrating the output characteristics of the fast fourier transformer of the receiver when scaling is not performed on a signal using subcarriers.
  • FIG. 9 is a characteristic diagram illustrating the output characteristics of the fast fourier transformer of the receiver when scaling is performed on a signal using subcarriers according to an embodiment of the present invention.
  • the following description will be made by applying a SS in Orthogonal Frequency Division Multiplexing Access (OFDMA) communication environments.
  • the number of subcarriers is allocated to the SS from a base station, and the SS includes a transmitter of a novel configuration which has a subcarrier scaling function added to a general transmission unit for adjusting each subcarrier according to the number of allocated subcarriers.
  • the following description will be focused on the transmitter of the novel configuration.
  • the receiver of the SS is not included in the scope of the present invention, but summary description thereof will be made by applying a general receiver of OFDMA for convenience of the description of the transmitter.
  • FIG. 4 is a block diagram of a transmitter/receiver in an OFDMA SS according to an embodiment of the present invention.
  • the transmitter/receiver may greatly be divided into a modem and a Radio Frequency (RF) unit 110.
  • RF Radio Frequency
  • the modem includes a frequency domain processing unit 120, a control unit 130, subcarrier allocating units 140a and 140b, a scaling unit 150, a transmission unit 160, and a reception unit 170.
  • the control unit 130 is included in the modem and performs an overall control.
  • the control unit 130 can be configured in the outside of the modem and can control the modem overall.
  • the RF unit 110 includes a power amplifier, and adjusts the power of a transmission signal output from the modem to a low level and amplifies the adjusted power according to a correction control value received from the control unit 130. That is, the RF unit 110 decreases the power of the transmission signal by a power level of subcarriers increased by the scaling unit 150, and amplifies the transmission signal.
  • the control unit 130 searches the number of subcarriers to be transmitted per each
  • the control unit 130 calculates a scaling control value according to the number of subcarriers to be allocated to the transmission signal by using a predetermined look-up table, and calculates the correction control value in accordance with to the scaling control value to thereby transfer it to the RF unit 110.
  • the correction control value is a value for controlling the power amplification of the transmission signal, and a specific calculation method thereof will be described below.
  • the scaling control value may be a multiplication value multiplied by the complex number of the subcarriers, or may be a shift value for shifting the each subcarrier by a bit unit.
  • the subcarrier allocating unit 140a allocates subcarriers to the transmission signal according to the allocation information transmitted from the control unit 130, that is, the number of the searched maximum number of the subcarriers.
  • the subcarrier allocating unit 140b allocates subcarriers to a reception signal.
  • the scaling unit 150 is configured between the subcarrier allocating unit 140a and the transmission unit 160.
  • the scaling unit 150 receives the scaling control value from the control unit 130 and adjusts subcarriers allocated by the subcarrier allocating unit 140a according to the received scaling control value, thereby increasing the power of the transmission signal.
  • the scaling unit 150 receives a multiplication value as the scaling control value and uses a multiplication scheme
  • the scaling unit 150 can be configured with a multiplier.
  • the scaling unit 150 receives a shift value as the scaling control value and uses a shift scheme
  • the scaling unit 150 can be configured with a shifter.
  • the transmission unit 160 includes an inverse fast fourier transformer (IFFT) 161, a parallel-to-serial converter (P/S) 162, a Cyclic Prefix (CP) adder 163, a time domain processing unit 164, and a digital-to- analog converter (DAC) 165.
  • IFFT inverse fast fourier transformer
  • P/S parallel-to-serial converter
  • CP Cyclic Prefix
  • DAC digital-to- analog converter
  • the reception unit 170 includes a Fast Fourier Transformer (FFT) 171, a serial- to-parallel converter (S/P) 172, a Cyclic Prefix (CP) remover 173, a time domain processing unit 174, and an analog-to-digital converter (ADC) 175.
  • FFT Fast Fourier Transformer
  • S/P serial- to-parallel converter
  • CP Cyclic Prefix
  • ADC analog-to-digital converter
  • the transmitter/receiver of the OFDMA SS having such a configuration, it is required to calculate the scaling control value for the number of used subcarriers as listed in the following Table 1 in order to adjust the transmission signal and transmit the adjusted signal to the base station.
  • Table 1 represents a case, in which the subcarriers are used by multiples of 24, as an example.
  • the following Table 1 represents the calculated values of the total power of an OFDMA symbol on the each multiple of 24. Specifically, when the symbol power is compared with the total power of the OFDMA symbol using the number of subcarriers capable of being allocated to the utmost, the following Table 1 represents the difference between the symbol power and the total power of the OFDMA symbol.
  • the number (No subca) of the subcarriers of the first column and a multiplication value (optimal scaling value) which is the scaling control value of the fourth column or a shift value (approximated scaling value) which is the scaling control value of the firth column may be preset in the look-up table, wherein the shift value (approximated scaling value) is the scaling control value of when a shift is performed by a bit unit.
  • the control unit 130 can know a scaling power value and a relative difference value in accord with the scaling in the modem by using the preset values.
  • K K, I K, Q scaling control value is "a" which is a multiplication value
  • the control unit 130 performs scaling by multiplying a real part and an imaginary part by a as expressed in Equation (1) below.
  • X K , adj aX k ,i +jaX K ,Q (1)
  • K is a subcarrier index
  • X K ,1 is the value of the real part (or In-phase) of a complex value (X K )
  • X K ,Q is the value of the imaginary part (or Quadrature) of the complex value (X ).
  • Table 1 a scheme of shifting by a bit unit can be applied. Such a scheme can obtain a result such as the multiplication of the index number of 2.
  • Table 2 represents the increased power of when a left shift is performed by 1 to 3 bits, and it can be seen from the following Table 2 that the increased power is approximately a multiple of 6[dB]. Accordingly, scaling can simply be approximated by the left shift as expressed in Equation (2) below. [45] Table 2
  • X K,adj (X K,I «b)+j(X K,Q «b) (2) [48] where A «b means a bit-shift operation that shifts a complex value (A) to the left by a shift value (b bit). Accordingly, the control unit 130 respectively shifts the complex value (X , X ) of the output of the subcarrier allocating unit 140a by b and adjusts the power of a signal.
  • FIG. 5 is a flowchart illustrating a method for scaling in the OFDMA SS according to an embodiment of the present invention.
  • the SS searches the maximum number of subcarriers by using allocation information transmitted from the base station, and allocates the subcarriers to the transmission signal according to the searched maximum number of the subcarriers by the subcarrier allocating unit 140a.
  • the SS calculates the scaling control value of the subcarriers according to the searched maximum number of the subcarriers by the control unit 130 and calculates the correction control value in accordance with the scaling control value. The calculations on the scaling control value and the correction control value will be described below in detail.
  • the SS performs scaling for the subcarriers allocated to the transmission signal according to the calculated scaling control value by the scaling unit 150, and thereafter transmits the signal, to which the adjusted subcarriers are allocated, to the transmission unit 160.
  • the SS performs a digital signal processing on the signal transmitted from the scaling unit 150 to output an analog transmission signal. That is, the transmission unit 160 performs Inverse Fast Fourier Transform (IFFT) on the signal by the inverse fast fourier transformer 161, and converts the transformed signal into a serial signal by the parallel-to-serial converter 162. Subsequently, the transmission unit 160 adds a Cyclic Prefix (CP) to the converted serial signal by the CP adder 163, converts it into the time domain by the time domain processing unit 164, converts the converted signal into an analog signal, and transmits the converted analog signal as a transmission signal to the RF unit 110.
  • IFFT Inverse Fast Fourier Transform
  • CP Cyclic Prefix
  • the RF unit 110 of the SS receives the analog transmission signal from the transmission unit 160, and reduces the power of the transmission signal by the correction control value transmitted from the control unit 130.
  • the SS amplifies the transmission signal to the adjusted power level by the RF unit 110 and transmits the amplified signal to the base station.
  • the power of the transmission signal output from the antenna of the RF unit 110 must be in accordance with a numerical value indicated by the base station irrespective of scaling. That is, in a case of the transmission signal, since the power increased by the modem is again reduced according to the correction control value output from the RF unit 110, it can be seen that the power of the transmission signal is in accordance with the numerical value indicated by the base station.
  • FIG. 6 is a flowchart illustrating the operation of the control unit of the transmitter according to an embodiment of the present invention.
  • the control unit 130 of the transmitter of the SS receives subcarrier allocation information from the base station.
  • the control unit 130 searches the maximum number of the subcarriers on the basis of the subcarrier allocation information, and transmits allocation information associated with the searched maximum number of the subcarriers to the subcarrier allocating unit 140a.
  • the control unit 130 calculates the scaling control value by using the predetermined look-up table, calculates the correction control value for controlling the power amplifier (not shown) of the RF unit 110, and transfers the scaling control value and the correction control value to the RF unit 110.
  • the scaling control value may be calculated using the multiplication or shift scheme, and consequently the values of the above Table 1 can be obtained.
  • the correction control value may be calculated by using Equation (3) below.
  • P is a control value, i.e., the correction control
  • Tx _ Amp adj value for controlling the power amplifier when the subcarriers are adjusted
  • P is obtained by multiplying a value corresponding to the third column of the above Table 1 by - 1 when the multiplication scheme is applied
  • P is a value corresponding to the sixth column of the above Table 1 when the shift scheme is applied.
  • the modem amplifies the transmission signal by 15.44[dB], and thus the amplification degree of the Radio Frequency (RF) is reduced by 15.44[dB]. Accordingly, the correction control value (P Tx _ Amp , adj ) is "P Tx _ Amp -15.44[dB]".
  • the control unit 130 transmits the calculated scaling control value to the scaling unit 150. Therefore, the scaling unit 150 applies the scaling control value to the complex value of the subcarriers output from the subcarrier allocating unit 140a and increases the level of the subcarriers by the scaling control value.
  • control unit 130 transfers the calculated correction control value to the RF unit 110. Accordingly, the RF unit 110 amplifies the output analog signal, i.e, the transmission signal and transmits the amplified signal to the base station. At this point, the RF unit 110 amplifies the power of the transmission signal by the correction control value transmitted from the control unit 130.
  • FIG. 9 When the subcarriers of the signal to be transmitted to the base station are adjusted and transmitted by the above-described processes, the output of the fast fourier transformer of the receiver is seen as FIG. 9. This is the same as FIG. 8, and is identical to when scaling is not performed as seen in FIGS. 7 and 8. More accurately, when scaling is performed, the quality of a signal is improved when a small number of subcarrier is used, but the influence is very small in general wireless communication environments when a signal to noise ratio (SNR) is 35 [dB] or less. This is because a noise power is relatively higher than an improved value.
  • FIGS. 7 and 8 are characteristic diagrams illustrating the output characteristics of the fast fourier transformer of the receiver when a 10-bit DAC conversion is performed on the respective signals using 840 subcarriers and 24 subcarriers and the converted signals are transmitted.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Transmitters (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un émetteur pour la mise à l'échelle de sous-porteuses dans une station d'abonné (SS) d'un système d'accès multiple par répartition orthogonale de la fréquence (OFDMA), comprenant un modem calculant une valeur de contrôle de mise à l'échelle de sous-porteuses selon le nombre de sous-porteuses à affecter à un signal d'émission, calculant une valeur de contrôle de correction selon la valeur de contrôle de mise à l'échelle, réglant les sous-porteuses affectées au signal d'émission selon la valeur de contrôle de mise à l'échelle, et produisant en sortie le signal d'émission auquel les sous-porteuses réglées sont affectées, ainsi qu'une unité radiofréquence (RF) réglant la puissance du signal d'émission au moyen de la valeur de contrôle de correction, amplifiant le signal d'émission selon le niveau de la puissance réglée, et émettant le signal amplifié en direction d'une station de base.
PCT/KR2008/007613 2007-12-28 2008-12-23 Émetteur et procédé pour mise à l'échelle de sous-porteuses dans une station mobile d'un système ofdma Ceased WO2009093810A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR10-2007-0139693 2007-12-28
KR1020070139693A KR100902017B1 (ko) 2007-12-28 2007-12-28 직교주파수분할다중접속 방식의 단말기에서 부반송파의크기 조정을 위한 송신 장치 및 방법

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WO2009093810A1 true WO2009093810A1 (fr) 2009-07-30

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6128350A (en) * 1999-08-24 2000-10-03 Usa Digital Radio, Inc. Method and apparatus for reducing peak to average power ratio in digital broadcasting systems
US20070242600A1 (en) * 2004-05-01 2007-10-18 Neocific, Inc. Methods and Apparatus for Multi-Carrier Communications with Variable Channel Bandwidth

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6128350A (en) * 1999-08-24 2000-10-03 Usa Digital Radio, Inc. Method and apparatus for reducing peak to average power ratio in digital broadcasting systems
US20070242600A1 (en) * 2004-05-01 2007-10-18 Neocific, Inc. Methods and Apparatus for Multi-Carrier Communications with Variable Channel Bandwidth

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