WO2005050858A1 - 受信方法および装置 - Google Patents
受信方法および装置 Download PDFInfo
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- WO2005050858A1 WO2005050858A1 PCT/JP2004/016757 JP2004016757W WO2005050858A1 WO 2005050858 A1 WO2005050858 A1 WO 2005050858A1 JP 2004016757 W JP2004016757 W JP 2004016757W WO 2005050858 A1 WO2005050858 A1 WO 2005050858A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
Definitions
- the present invention relates to a receiving technique, and more particularly, to a receiving method and apparatus for receiving a spread spectrum signal.
- a wireless LAN Local Area Network
- the wireless LAN achieves a maximum transmission speed of 11 Mbps by CCK (Complementary Code Keying) modulation.
- the bandwidth of the wireless LAN is set at 26 MHz by the Radio Law, so the upper limit of the chip rate in the direct spreading method is also 26 Mcps.
- the chip rate of 26 Mcps is band-limited by an ideal Nyquist filter, the sampling frequency of DZA conversion is 40 MHz, and a sharp band limit after DZA conversion is also required, which is not very realistic.
- the chip rate is not more than the Nyquist filter, but the baseband band is limited by the analog filter after DZA conversion!
- a receiving apparatus that supports such CCK modulation prepares a plurality of transmitted signal waveform patterns in advance, and uses a transmission signal having a waveform closest to the received signal waveform as a demodulation result (for example, see Patent Document 1.).
- Patent Document 1 Japanese Patent Application Laid-Open No. 2003-168999
- a receiving apparatus receives a signal in which a plurality of combinations of signal powers are CCK-modulated, and performs an FWT (Fast Walsh Transformation) operation on the received signal to derive a plurality of correlation values. Further, a plurality of correlation values are selected with the largest correlation value, and a combination of signals corresponding to the selected correlation value is reproduced.
- the correlation value obtained by the FWT calculation includes an error due to the influence of noise or a multipath transmission path, multiple signals may be generated. In some cases, a combination of symbols is selected by mistake. Under such circumstances, the inventor has come to recognize the following problems.
- one of the plurality of phase signals included in the combination of the signals may be incorrect.
- a plurality of phase signals included in the signal combination are each phase-modulated.
- the phase modulation method is QPSK (Quadrature Phase Shift Keying)
- QPSK Quadrature Phase Shift Keying
- the phase force of the phase signal may be incorrect by ⁇ ⁇ 2 from the phase of the correct phase signal.
- a combination composed of a plurality of signals having the second correlation value may be a correct combination. In other words, a combination of a plurality of signal powers that should have the largest correlation value may become the second largest.
- the present invention has been made in view of such a situation, and an object of the present invention is to provide a receiving technique for estimating a signal transmitted with high accuracy from a result of Walsh transform. Means for solving the problem
- One embodiment of the present invention relates to a receiving device.
- a plurality of Walsh codes are generated based on a combination of a plurality of phase signal powers including a differentially coded phase signal, and the generated plurality of Walsh codes are combined into one.
- a receiving unit that receives a signal that is a symbol of the symbol, a Walsh transform unit that performs a Walsh transform on the received signal in units of one symbol, and generates a plurality of correlation values, respectively.
- a first derivation unit that selects one correlation value and derives a combination of a plurality of phase signals corresponding to the selected correlation value as a first phase signal, and a plurality of phases corresponding to the first phase signal
- a second deriving unit that derives a combination of a plurality of phase signals other than the combination of the signal powers as a second phase signal, and the differential included in the derived first phase signal and the derived second phase signal, respectively.
- the derived first phase signal and the derived second phase signal are generated by repeating a plurality of correlation processes, so that the power of the signal is amplified, and the power is amplified. And delay detection, and the first phase is determined by the resulting relative value. Since the signal or the second phase signal is selected, the accuracy of selecting the phase signal is improved.
- Another embodiment of the present invention also relates to a receiving device.
- a plurality of Walsh codes are generated based on a combination of a plurality of phase signal powers including a differentially coded phase signal, and the generated plurality of Walsh codes are combined into one.
- a receiving unit that receives a signal that is a symbol of the symbol, a Walsh transform unit that performs a Walsh transform on the received signal in units of one symbol, and generates a plurality of correlation values, respectively.
- a first derivation unit that selects one correlation value and derives a plurality of combinations of phase signal powers corresponding to the selected correlation value as a first phase signal, and a first derivation unit that derives a first phase signal based on the derived first phase signal.
- a second deriving unit for deriving a combination of a plurality of phase signals other than a combination of a plurality of phase signals corresponding to the first phase signal as a second phase signal; and deriving the derived first phase signal. did Based on each contain a differentially encoded phase signals to two phase signals, and a first phase signal and an output unit for outputting a plurality of phase signals corresponding to one of the second phase signal.
- the derived first phase signal and the derived second phase signal are generated by repeating a plurality of correlation processes, so that the power of the signal is amplified, and the power is amplified. Since the first phase signal or the second phase signal is selected based on the relative value obtained as a result of the delay detection in the state where the phase detection is performed, the accuracy of the phase signal selection is improved.
- the second deriving unit is configured to recover the phase of the shift force of the plurality of phase signals other than the differentially encoded phase signal among the plurality of phase signal forces corresponding to the derived first phase signal. And a plurality of second phase signal candidates generated by changing the phase signal whose phase is to be further rotated among the plurality of phase signals to generate a plurality of second phase signal candidates.
- a selection unit that selects the second phase signal based on the magnitude of the corresponding correlation value.
- the candidate generation unit should rotate the phase up to the phase adjacent to the phase where the phase signal whose phase is to be rotated is originally arranged, among a plurality of phases in which the phase signal may be arranged.
- the phase of the phase signal may be rotated to generate a second phase signal candidate.
- the “original arranged phase” corresponds to, for example, in the case of QPSK, 0, ⁇ 2, ⁇ , 3 ⁇ 2, that is, corresponds to the phase in which the signal is arranged on the transmission side.
- the first deriving unit further derives an identification number corresponding to the first phase signal
- the second deriving unit further manages a plurality of combinations of the phase signal powers based on the identification numbers.
- the unit may derive the identification number of the second phase signal from the management unit based on the derived identification number of the first phase signal.
- the output unit outputs the first phase signal when the difference between the magnitude of the correlation value corresponding to the derived first phase signal and the magnitude of the correlation value corresponding to the derived second phase signal is equal to or greater than a predetermined threshold. May be output.
- the output unit is configured to output a plurality of phase signals among the plurality of phase signals that also output the output unit power in the past with respect to the differentially encoded phase signals included in the derived first phase signal and the derived second phase signal.
- a delay detection unit for delay-detecting the differentially coded phase signals of the differential phase encoding, respectively, and the differentially encoded phase signals included in the derived first phase signal and the derived second phase signal, respectively.
- a comparison unit that compares the result of the delay detection and selects one of the first phase signal and the second phase signal may be included.
- the comparison unit performs differential detection on the differentially encoded phase signals included in the derived first phase signal and the derived second phase signal, respectively, and includes the result of the differential detection. You can compare each possible phase and select the difference between the first and second phase signals! / ⁇ .
- Still another embodiment of the present invention also relates to a receiving device.
- a plurality of Walsh codes are generated based on a combination of a plurality of phase signal powers including a differentially encoded phase signal, and the generated Walsh codes are combined into one.
- a receiving unit that receives a signal as a symbol, a Walsh transform unit that performs a Walsh transform on the received signal in units of one symbol to generate a plurality of correlation values, and a Walsh transform unit that generates a plurality of correlation values based on the magnitude of the plurality of generated correlation values.
- a first derivation unit that selects one correlation value and derives a combination of a plurality of phase signals corresponding to the selected correlation value as a first phase signal, and a first derivation unit based on the magnitude of the plurality of generated correlation values.
- a second deriving unit for deriving a combination of a plurality of phase signal colors other than a combination of a plurality of phase signals corresponding to the first phase signal as a second phase signal; and a deriving first phase signal. Based on the differential encoding phase signal included respectively in the second phase signal derived as pairs to either the first phase signal and a second phase signal And an output unit for outputting a plurality of corresponding phase signals.
- the derived first phase signal and the derived second phase signal are generated by repeating a plurality of correlation processes, so that the signal power is amplified, and the power is amplified. Since the first phase signal or the second phase signal is selected based on the relative value obtained as a result of the delay detection in the state where the phase detection is performed, the accuracy of the phase signal selection is improved.
- the first derivation unit selects a correlation value having the largest magnitude from among the plurality of generated correlation values, and determines a combination of a plurality of phase signal colors corresponding to the selected correlation value as a first combination.
- the second derivation unit selects a correlation value next to the correlation value selected by the first derivation unit from among the plurality of generated correlation values, and generates a plurality of correlation values corresponding to the selected correlation value.
- a combination of the phase signals may be derived as the second phase signal.
- the second derivation unit selects a correlation value having a magnitude equal to or larger than a predetermined threshold value from the plurality of generated correlation values, and selects a plurality of phase signal curves corresponding to the selected correlation value.
- the output unit outputs the first phase signal when the difference between the magnitude of the correlation value corresponding to the derived first phase signal and the magnitude of the correlation value corresponding to the derived second phase signal is equal to or greater than a predetermined threshold. May be output.
- the output unit is configured to output a plurality of phase signals output in the past with respect to the differentially coded phase signals included in the derived first phase signal and the derived second phase signal, respectively.
- a delay detection unit for delay-detecting the differentially coded phase signals of the differential phase encoding, respectively, and the differentially encoded phase signals included in the derived first phase signal and the derived second phase signal, respectively.
- a comparison unit that compares the result of the delay detection and selects one of the first phase signal and the second phase signal may be provided.
- the comparison unit performs differential detection on the differentially coded phase signals included in the derived first phase signal and the derived second phase signal, respectively, and compares the differentially coded signal with the differentially coded signal. May be compared with each other to select the difference between the first phase signal and the second phase signal! / ⁇ .
- Still another embodiment of the present invention relates to a receiving method.
- a plurality of Walsh codes are generated based on a combination of a plurality of phase signal forces including differentially encoded phase signals, and the generated plurality of Walsh codes are combined into one.
- Deriving a combination of signal powers as a second phase signal and, based on the differentially encoded phase signals included in the derived first phase signal and the derived second phase signal, respectively! Outputting a plurality of phase signals corresponding to any one of the first phase signal and the second phase signal.
- Still another embodiment of the present invention relates to a receiving method.
- a plurality of Walsh codes are generated based on a combination of a plurality of phase signal forces including differentially encoded phase signals, and the generated plurality of Walsh codes are combined into one.
- Receiving a signal as a symbol performing a Walsh transform on the received signal in units of one symbol to generate a plurality of correlation values, and generating one correlation value based on the magnitude of the plurality of generated correlation values.
- Selecting a correlation value deriving a plurality of combinations of phase signals corresponding to the selected correlation value as a first phase signal, and generating a first phase signal based on the derived first phase signal.
- Still another embodiment of the present invention also relates to a receiving method.
- a plurality of Walsh codes are generated based on a combination of a plurality of phase signal forces including differentially encoded phase signals, and the generated plurality of Walsh codes are combined into one.
- Receiving a signal as a symbol performing a Walsh transform on the received signal in units of one symbol to generate a plurality of correlation values, and generating one correlation value based on the magnitude of the plurality of generated correlation values.
- Selecting a correlation value deriving a plurality of combinations of phase signals corresponding to the selected correlation value as a first phase signal, and generating a first phase signal based on the magnitudes of the plurality of generated correlation values.
- Combination that also has multiple phase signal power corresponding to the signal Deriving a combination of a plurality of phase signals other than the set as a second phase signal, and based on the differentially encoded phase signals included in the derived first phase signal and the derived second phase signal, respectively. And outputting a plurality of phase signals corresponding to the difference between the first phase signal and the second phase signal.
- a signal transmitted with high accuracy can be estimated from the result of the Walsh transform.
- FIG. 1 is a diagram showing a burst format of a communication system according to Embodiment 1 of the present invention.
- FIG. 2 is a diagram showing a configuration of a communication system according to Embodiment 1 of the present invention.
- FIG. 3 is a diagram showing a configuration of a baseband processing unit in FIG. 2.
- FIG. 4 is a diagram showing a configuration of an FWT calculation unit in FIG. 3.
- FIG. 5 is a diagram showing a configuration of a first ⁇ 2 estimator in FIG. 4.
- FIG. 6 is a diagram showing a configuration of a maximum value search unit in FIG. 3.
- FIG. 7 is a diagram showing a data structure of an index preset in a maximum value index storage unit in FIG. 6;
- FIG. 8 is a diagram showing a configuration of a second phase signal deriving unit in FIG. 3.
- FIG. 9 is a diagram showing a first candidate force sixth candidate generated by the candidate generation unit in FIG. 8.
- FIG. 10 is a diagram illustrating a configuration of a phase signal determining unit in FIG. 3.
- FIG. 11 is a diagram showing an outline of the operation of a comparison unit in FIG. 10.
- FIG. 12 is a diagram showing a configuration of a baseband processing unit according to Embodiment 2 of the present invention.
- FIG. 13 is a diagram showing an outline of the operation of a determining unit in FIG. 12.
- FIG. 14 is a diagram showing a configuration of a baseband processing unit according to Embodiment 3 of the present invention.
- Embodiment 1 of the present invention relates to a receiving device of a wireless LAN system conforming to the IEEE802.11 standard.
- the receiving apparatus derives a plurality of correlation values by FWT calculation after receiving a signal in which a combination of a plurality of phase signals is CCK-modulated. Further, the receiving apparatus selects the correlation value having the largest magnitude from the plurality of correlation values, and selects a combination of phase signals corresponding to the selected correlation value (hereinafter, the combination of the selected phase signals is referred to as a ⁇ first phase signal ").
- the phase signal combination includes four phase signals, and one of them is differentially coded.
- phase signals (hereinafter, collectively these phase signals, or one of these phase signals is referred to as a “spreading code signal”) are each subjected to QP SK modulation. Then, one of the spread code signals included in the first phase signal is rotated by + ⁇ ⁇ 2 or ⁇ ⁇ 2, and further, the signal to be rotated is changed in the spread code signal, and a combination of six types of phase signals ( Hereafter, a combination of the six types of phase signals is generated from a “first candidate” to a “sixth candidate”, respectively, and the one having the largest correlation value is selected (hereinafter, the six types of phase combinations). Signal combination selected One combination is called "second phase signal.”
- the differentially encoded signal included in the first phase signal is delayed. Detected, and outputs the delayed detected signal and the spread code signal included in the first phase signal.
- the differential code included in the first phase signal and the second phase signal respectively. The resulting signals are differentially detected, and two types of delayed detection results are obtained.
- the phase where the delay detection result may be placed, for example, 0, ⁇ / 2, ⁇ , or 3 ⁇ 2 when differential QPSK modulation is used as differential coding (hereinafter these phases are referred to as Calculate the error between the above two types of differential detection results for the “phase before differential encoding”. Further, the first phase signal or the second phase signal corresponding to the smaller one of the two calculated errors is selected. Finally, a spread code signal corresponding to the selected one and a signal subjected to delay detection are output.
- CCK modulation unit 8 bits are defined as one unit (hereinafter, this unit is referred to as “CCK modulation unit”), and these 8 bits are named dl, d2,.
- the lower 6 bits of the CCK unit are mapped to the QPSK constellation in [d3, d4], [d5, d6], and [d7, d8] units, respectively.
- the mapped phases are respectively ( ⁇ 2, ⁇ 3, ⁇ 4).
- ⁇ 8 is generated from the eight types of spreading codes PI from the phases ⁇ 2, ⁇ 3, and ⁇ 4 as follows.
- the upper two bits [dl, d2] of the CCK modulation unit are mapped to a signal point constellation of DQPSK (Differential encoding Quadrature Phase Shift Keying).
- the mapped phase is ⁇ 1.
- eight kinds of chip signals X0 to X7 are generated as follows.
- the transmitting device transmits the chip signals in the order of # 0 to # 7 (hereinafter, the time-series unit composed of chip signals # 0 to # 7 is also referred to as“ CCK modulation unit ”and ⁇ ⁇ ) .
- a signal obtained by modulating the phase of DBPSK or DQPSK is spread by a known spreading code and transmitted.
- FIG. 1 shows a burst format of the communication system according to the first embodiment.
- This burst format corresponds to ShortPLCP of the IEEE802.11b standard.
- the burst signal includes a preamble, a header, and a data area as shown. Furthermore, the preamble is transmitted at a transmission rate of 1 Mbps using the DBP SK modulation method, the header is transmitted at a transmission rate of 2 Mbps using the DQPSK modulation method, and the data is transmitted at a transmission rate of 11 Mbps using the CCK modulation method.
- the preamble includes 56-bit SYNC and 16-bit SFD, and the header includes 8-bit SIGNAL, 8-bit SERVICE, 16-bit LENGTH, and 16-bit CRC.
- the length of the PSDU corresponding to the data is variable.
- FIG. 2 shows a configuration of the communication system 100 according to the first embodiment.
- the communication system 100 includes a receiving device 10 and a transmitting device 12. Further, the receiving device 10 includes a receiving antenna 14, a radio Unit 18, quadrature detection unit 20, AGC (Automatic Gain Control) 22, AZD conversion unit 24, baseband processing unit 26, and control unit 28.
- Transmission device 12 includes transmission antenna 16, radio unit 30, modulation unit Including 32.
- the signal includes a digital reception signal 200 and an output signal 202.
- Modulation section 32 performs CCK modulation processing on information to be transmitted, or spread processing on a phase-modulated signal.
- the radio unit 30 performs frequency conversion and amplification between a baseband signal output from the modulation unit 32 and a radio frequency signal.
- the transmitting antenna 16 transmits a radio frequency signal, and the receiving antenna 14 receives a radio frequency signal.
- the radio unit 18 converts the frequency of the received radio frequency signal into an intermediate frequency signal.
- the quadrature detection section 20 performs quadrature detection on the intermediate frequency signal and outputs a baseband signal.
- a baseband signal is represented by two components, an in-phase component and a quadrature component.
- the AGC 22 automatically controls the gain so that the amplitude of the baseband signal falls within the dynamic range of the AZD converter 24 described later.
- the AZD converter 24 converts a baseband analog signal into a digital signal, and outputs a digital received signal 200 composed of a plurality of bits.
- Baseband processing section 26 despreads and demodulates digital received signal 200 and outputs output signal 202.
- the control unit 28 controls the timing and the like of the receiving device 10.
- FIG. 3 shows a configuration of the baseband processing unit 26.
- the baseband processing unit 26 includes an equalizer 42, a correlator 44, a demodulation unit 46, an FWT calculation unit 50, a maximum value search unit 52, a holding unit 150, a second phase signal derivation unit 152, and a phase signal determination unit 154. , Including the switch section 60.
- the signals include a despread signal 204, a first phase correlation value signal 208, a first phase index signal 210, a second phase correlation value signal 212, a second phase index signal 214, and a Walsh transform value FWT.
- the equalizer 42 removes the effect of the multipath transmission path included in the digital reception signal 200.
- the equalizer 42 is constituted by a transversal type filter. It should be noted that a configuration in which a DFE is added to a transversal filter may be employed.
- the correlator 44 despreads the signal output from the equalizer 42 in order to despread the preamble of the burst format in FIG. 1 and the phase modulation signal spread by a predetermined spreading code such as a header area.
- a predetermined spreading code such as a header area.
- Correlation processing is a sliding type correlation processing. Or a matched filter type correlation process.
- the correlator 44 also operates in the burst format of FIG. 1 when the power data that operates only with the preamble and the header is a phase modulated signal spread with a predetermined spreading code.
- Demodulation section 46 demodulates despread signal 204 despread by correlator 44. Since the modulation scheme of the despread signal 204 is DBPSK or DQPSK, demodulation is performed by differential detection.
- the FWT calculation unit 50 performs a FWT calculation on a CCK-modulated signal such as the data area of the burst format in FIG. 1, and outputs a Walsh transform value FWT. More specifically, a chip signal in units of CCK modulation is input, and 64 Poorsh transform values FWT, that is, correlation values are output by correlation processing between chip signals.
- the maximum value search unit 52 inputs 64 Walsh transform values FWT and selects one Walsh transform value FWT based on their magnitudes. Further, a first phase correlation signal 208, which is a selected Walsh transform value FWT, and a first phase index signal indicating a combination of phases ⁇ 2 to ⁇ 4 corresponding to the Walsh transform value FWT by an index number. The signal 210 is output. The first phase index signal 210 corresponds to a spread code signal in the first phase signal, and the first phase correlation value signal 208 corresponds to a differentially coded signal in the first phase signal.
- the holding unit 150 holds the Walsh transform values FWT output from the FWT calculation unit 50 in units of 64.
- Second phase signal deriving section 152 receives first phase index signal 210, and generates a second phase signal.
- the second phase signal is generated based on the index number indicated in the first phase index signal 210.
- the index number of the corresponding spread code signal is generated as the second phase index signal 214.
- Walsh transform value FWT corresponding to the second phase signal is selected from Walsh transform values FWT held in holding section 150, and is output as second phase correlation value signal 212.
- the phase signal determination unit 154 selects one of the first phase signal and the second phase signal. That is, the difference between the magnitudes of the first phase correlation value signal 208 and the second phase correlation value signal 212 is predicted. If the threshold value is equal to or greater than the predetermined threshold value, the first phase signal is selected. On the other hand, if the difference between the magnitudes of the first phase correlation value signal 208 and the second phase correlation value signal 212 is smaller than a predetermined threshold value, the first phase correlation value signal 208 And the second phase correlation signal 212 are differentially detected. The result of differential detection is compared with the phase before differential encoding, and the error is small! , The first phase signal or the second phase signal corresponding to the one selected.
- the first phase signal when the first phase signal is selected, a combination of a plurality of signals corresponding to the first phase index signal 210 and a signal obtained by delay-detecting the first phase correlation value signal 208 are used. Output.
- the second phase signal if the second phase signal is selected, a combination of a plurality of signals corresponding to the second phase index signal 214 and a signal obtained by delay detection of the second phase correlation value signal 212 are output. .
- the switch unit 60 selects one of the signal output from the demodulation unit 46 and the signal output from the phase signal determination unit 154, and outputs it as an output signal 202.
- the signal output from the demodulation section 46 is selected in the section of the burst format preamble and the header area in FIG. 1, and the signal output from the phase signal determination section 154 is selected in the section of the burst format data area. And outputs an inverted signal of the selected signal.
- This configuration can be realized in hardware by a CPU, a memory, or another LSI of an arbitrary computer, and is realized in software by a program having a reservation management function loaded into the memory.
- the functional blocks realized by their cooperation are drawn. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.
- FIG. 4 shows a configuration of the FWT calculation unit 50.
- the FWT calculation unit 50 includes a first ⁇ 2 estimation unit 80a, a second ⁇ 2 estimation unit 80b, a third ⁇ 2 estimation unit 80c, and a fourth ⁇ 2 estimation unit 80d, ⁇ 3 It includes a first ⁇ 3 estimator 82a, a second ⁇ 3 estimator 82b, and a ⁇ 4 estimator 84 collectively referred to as an estimator 82.
- the first correlation value ⁇ is generally referred to as ⁇ 0-0, ⁇ 0-1, ⁇ 0-2, ⁇ 0-3, Y1-0, Y1-1, Y1-2, Y1-3, ⁇ 2-0, ⁇ 2 — 1, ⁇ 2—2, ⁇ 2—3, ⁇ 3—0, ⁇ 3—1, ⁇ 3—2, ⁇ 3—3, the second correlation value ⁇ ⁇ 0, ⁇ 1, ⁇ 15, ⁇ 16, ⁇ 17, ⁇ 31, ⁇ onoresh Includes FWT0, FWT1, and FWT63, which are collectively called converted values FWT.
- the ⁇ 2 estimating unit 80 receives two chip signals X, for example, ⁇ and XI, respectively, rotates the phase of ⁇ by 0, ⁇ ⁇ 2, ⁇ , 3 ⁇ ⁇ 2, and rotates ⁇ by XI. Are added, and ⁇ ⁇ -0 force ⁇ -3 is output.
- ⁇ ⁇ -0 force ⁇ -3 is output.
- the phase obtained by rotating ⁇ is equal to the phase of ⁇ 2
- the magnitude of the corresponding first correlation value ⁇ becomes large.
- ⁇ 2 can be estimated.
- the ⁇ 3 estimation unit 82 operates in the same manner as the ⁇ 2 estimation unit 80. For example, ⁇ -0 to ⁇ -3 and Y1-0 to Y1-3 are input, and Z15 is output from ⁇ . Then, ⁇ 3 can be estimated from the magnitude of the second correlation value ⁇ .
- the ⁇ 4 estimating section 84 operates in the same manner as the ⁇ 2 estimating section 80, inputs Z31 from ⁇ , outputs FWT63 from FWTO, and can estimate ⁇ 4 from the magnitude of the Walsh transform value FWT.
- FIG. 5 shows a configuration of the first ⁇ 2 estimation unit 80a.
- the first ⁇ 2 estimator 80a includes a first adder 94a collectively referred to as a 0 phase rotator 86, a ⁇ 2 phase rotator 88, a ⁇ phase rotator 90, a 3/2 ⁇ phase rotator 92, and an adder 94.
- a second addition unit 94b, a third addition unit 94c, and a fourth addition unit 94d is referred to as a 0 phase rotator 86, a ⁇ 2 phase rotator 88, a ⁇ phase rotator 90, a 3/2 ⁇ phase rotator 92, and an adder 94.
- a second addition unit 94b, a third addition unit 94c, and a fourth addition unit 94d is referred to as a 0 phase rotator 86, a ⁇ 2 phase rotator 88, a ⁇ phase rotator 90, a 3/2
- the 0 phase rotation unit 86, the ⁇ ⁇ 2 phase rotation unit 88, the ⁇ phase rotation unit 90, and the 3/2 ⁇ phase rotation unit 92 rotate the phase of ⁇ by 0, ⁇ / 2 ⁇ , and 3 ⁇ 2, respectively. These outputs are each added to XI in the calorie calculator 94.
- FIG. 6 shows a configuration of the maximum value search unit 52.
- the maximum value searching unit 52 includes a first comparing unit 114a, a second comparing unit 114b, a third comparing unit 114c, a fourth comparing unit 114d, and a fifth comparing unit collectively referred to as a selecting unit 110, a calculating unit 112, and a comparing unit 114.
- the selection unit 110 inputs 64 data of FWT63 from the FWTO and outputs 8 data at a time. For example, FWTO output FWT7 at the first timing, and output FWT8 to FWT15 at the next timing.
- the calculator 112 calculates the Walsh transform value FWT, that is, the magnitude of the FWT 63 from the FWTO.
- the magnitude R is obtained as follows.
- the comparing unit 114 compares the eight Rs and selects each of the Walsh transform values FWT having the largest magnitude.
- the maximum value comparing unit 116 compares the maximum value of the Walsh transform values FWT in eight units output from the seventh comparing unit 114g with the maximum value of the Walsh transform values FWT up to then, and calculates Select one of the Walsh transform values FWT. Such an operation is performed in the CCK modulation unit, and finally, the Walsh transform value FWT having the largest size in the FWT63 is selected from the FWTO. The selected Walsh transform value FWT is stored in the maximum value storage unit 118.
- Maximum value Index storage section 120 selects an Index number corresponding to Walsh transform value FWT finally stored in maximum value storage section 118, and outputs it as first phase index signal 210.
- FIG. 7 shows a data structure of the Index preset in the maximum value Index storage unit 120. “0” to “63” are defined as Indexes, which correspond to combinations of phases ⁇ 2 to ⁇ 4, respectively.
- FIG. 8 shows a configuration of second phase signal deriving section 152.
- Second phase signal deriving section 152 includes candidate generating section 156, FWT acquiring section 158, and second phase signal determining section 160.
- the candidate generation unit 156 receives the first phase index signal 210, and generates a second phase signal candidate, that is, a sixth candidate from the first candidate, from a combination of phases corresponding to the first phase index signal 210.
- FIG. 9 shows the first candidate sixth candidate generated by the candidate generator 156.
- “6” is input as the first phase index signal 210, and the corresponding values of ⁇ 2, ⁇ 3, and ⁇ 4 are “0”, “ ⁇ / 2”, and “ ⁇ ”, respectively. I have.
- the candidate generation unit 156 rotates one of the phases of ⁇ 2, ⁇ 3, and () 4 by + vortex 72 and vortex 72, and applies the rotation to all of ⁇ 2, ⁇ 3, and ⁇ 4.
- To generate a combination of six types of phases that is, a first candidate to a sixth candidate. For example, for ⁇ 2, a first candidate and a second candidate are generated from “3 ⁇ 2” and “ ⁇ / 2j”.
- the FWT acquisition unit 158 acquires the Walsh transform value FWT corresponding to the first candidate force generated by the candidate generation unit 156 and corresponding to the sixth candidate.
- Second phase signal determination section 160 compares the magnitude of Walsh transform value FWT corresponding to the first candidate force sixth candidate and selects the largest Walsh transform value FWT. Furthermore, the second corresponding to the selected Walsh transform value FWT One of the sixth candidates is determined as the second phase signal.
- the magnitude of the Walsh transform value FWT corresponding to the second phase signal is output as a second phase correlation value signal 212, and the Index number corresponding to the second phase signal is output as a second phase index signal 214.
- FIG. 10 shows a configuration of the phase signal determination unit 154.
- Phase signal determining section 154 includes a first delay detecting section 162, a second delay detecting section 164, a comparing section 166, a threshold holding section 168, and a selecting section 170.
- the signal includes a first differential detection signal 216 and a second differential detection signal 218.
- the first delay detection section 162 delay-detects the past phase ⁇ 1 and the first phase correlation value signal 208 already selected by the comparison section 166. Therefore, the past phase ⁇ 1 is input from the comparison unit 166 to the first delay detection unit 162 via a signal line (not shown).
- the result of the differential detection is output as a first differential detection signal 216.
- the phase ⁇ 1 is DQPSK-modulated as described above, the phase of the first differential detection signal 216 is 0, ⁇ / 2, ⁇ , 3 ⁇ / 2 if there is no influence of noise or the like. ⁇ !
- the second delay detector 164 performs delay detection on the past phase ⁇ 1 and the second phase correlation value signal 212 already selected by the comparator 166. Therefore, the past phase ⁇ 1 is input from the comparison unit 166 to the second delay detection unit 164 via a signal line (not shown). The result of the differential detection is output as a second differential detection signal 218.
- the phase of the second differential detection signal 218 is one of 0, ⁇ / 2, ⁇ , and 3 ⁇ 2 if there is no influence of noise or the like as in the case of the first differential detection signal 216.
- the comparing section 166 subtracts the magnitude of the second phase correlation value signal 212 from the magnitude of the first phase correlation value signal 208, and when the subtraction result is equal to or larger than the threshold value held in the threshold value holding section 168, If so, the first phase signal is selected, and as a result, the first differential detection signal 216 is output. On the other hand, if the subtraction result is smaller than the threshold value, the following processing is executed. This processing will be described based on an outline of the operation of the comparing unit 166 shown in FIG. In the figure, the phases 0, ⁇ / 2, ⁇ , and 3 ⁇ 2 where the delay detection ⁇ 1 is to be placed are indicated by ⁇ , and the signals of the first delay detection signal 216 and the second delay detection signal 218 are shown.
- phase error between any one of the phases 0, ⁇ 2, ⁇ , and 3 ⁇ 2 closest to the first delay detection signal 216 and the phase difference between the first delay detection signal 216 is denoted by 0 1
- phase error between the second delay detection signal 218 and The phase error between any of the close phases 0, ⁇ 2, ⁇ , 3 ⁇ 2 and the second differential detection signal 218 is denoted by ⁇ 2.
- the phase error ⁇ 1 is compared with ⁇ 2, and if the phase error ⁇ 1 is small, the first differential detection signal 216 is selected, and if the phase error ⁇ 2 is small, the second differential detection signal 218 is selected. Further, the selected first delay detection signal 216 or second delay detection signal 218 is output to selection section 170.
- the power value is amplified from the power value of the chip signal.
- the above processing is executed because the phase obtained by delay detection of the Walsh transform value FWT thus amplified is accurate.
- Selection section 170 outputs a corresponding signal according to first delayed detection signal 216 or second delayed detection signal 218 input from comparison section 166. That is, when the first differential detection signal 216 is input, based on [dl, d2], which has determined the first differential detection signal 216, and the first phase index signal 210! /, [D3, d4 ], [D5, d6], and [d7, d8], and outputs [dl-d8].
- the correlator 44 despreads the signal equalized by the equalizer 42, and the demodulator 46 demodulates and outputs the output signal 202.
- the FWT calculation unit 50 calculates the Walsh transform value FWT by performing the FWT calculation on the signal equalized by the equalizer 42, and the maximum value search unit 52 calculates the Walsh transform value FWT from the magnitude of the Walsh transform value FWT.
- the first phase correlation value signal 208 and the first phase index signal 210 are output as the first phase signal corresponding to the largest Walsh transform value FWT.
- the second phase signal deriving unit 152 Based on the first phase index signal 210, the second phase signal deriving unit 152 generates the first candidate force obtained by rotating V, ⁇ 2 to ⁇ 4 !, or the deviation by + ⁇ 2 or 1 ⁇ 2. One of the candidates is generated as a second phase signal.
- the first delay detection section 162 delay-detects the first phase correlation value signal 208 and outputs a first delay detection signal 216
- the second delay detection section 164 delay-detects the second phase correlation value signal 212.
- the second delay detection signal 218 is output.
- the comparing section 166 stores the difference between the magnitudes of the first phase correlation value signal 208 and the second phase correlation value signal 212 in the threshold value retaining section 168.
- the phase of the first differential detection signal 216 and the phase of the second differential detection signal 218 are compared with any one of 0, ⁇ 2, ⁇ , and 3 ⁇ 2, respectively, to obtain an error.
- the error of the second differential detection signal 218 is small, a combination of signals corresponding to the second phase signal is output.
- the phase signal combination is selected in order to select the phase signal combination.
- the selection is accurate and the reception characteristics are improved.
- the second phase signal for comparing with the first phase signal having the largest FWT calculation result can be generated by rotating any of the plurality of phase signals included in the first phase signal, It can be realized by simple processing.
- the second embodiment of the present invention relates to a receiving device of a wireless LAN system conforming to the 802.11b standard.
- the receiving apparatus derives a plurality of correlation values by FWT calculation after receiving a signal in which a combination of a plurality of phase signals is CCK-modulated. Further, the receiving apparatus selects a correlation value having the largest intermediate magnitude of a plurality of correlation values, and selects a combination of phase signals corresponding to the selected correlation value (hereinafter, the combination of the selected phase signals is referred to as a “first phase Signal ⁇ ).
- the combination of the phase signals includes four phase signals, one of which is differentially encoded, and the remaining phase signals (hereinafter, these phase signals are collectively or One of these phase signals is called “spreading code signal”), and each is QPSK modulated.
- the receiving apparatus selects a correlation value of the second magnitude from the plurality of correlation values, and selects a combination of phase signals corresponding to the selected correlation value (hereinafter, a combination of the selected phase signals). Is derived as "second phase signal” and ⁇ ⁇ )
- the difference between the magnitude of the correlation value corresponding to the first phase signal and the magnitude of the correlation value corresponding to the second phase signal is a threshold! /
- the coded signal is subjected to delay detection, and the delay-detected signal and the spread code signal included in the first phase signal are output.
- the difference between the magnitude of the correlation value corresponding to the first phase signal and the magnitude of the correlation value corresponding to the second phase signal is smaller than the threshold, the difference is included in the first phase signal and the second phase signal, respectively.
- Differential coded signals are differentially detected, and two types of differential detection results are obtained.
- phase before differential encoding any of 0, ⁇ / 2, ⁇ , and 3 ⁇ 2 Calculate the error of the above two types of differential detection results with respect to the phase (referred to as “phase before differential encoding”). Further, a first phase signal or a second phase signal corresponding to the smaller one of the two calculated errors is selected. Finally, a spread code signal corresponding to the selected one and a signal subjected to delay detection are output.
- FIG. 12 shows the configuration of the baseband processing unit 26.
- the baseband processing unit 26 includes an equalizer 42, a correlator 44, a demodulation unit 46, an FWT calculation unit 50, a maximum value search unit 52, a first ⁇ 1 demodulation unit 54a collectively called a ⁇ 1 demodulation unit 54, and a second It includes a ⁇ 1 demodulation unit 54b, a second maximum value search unit 180, a level comparison unit 182, a determination unit 184, and a switch unit 60.
- the signals include a despread signal 204, a first phase correlation value signal 208, a first phase index signal 210, a second phase correlation value signal 212, a second phase index signal 214, a first delay detection signal 216, and a second delay detection.
- the equalizer 42 removes the influence of the multipath transmission path included in the digital reception signal 200.
- the equalizer 42 is constituted by a transversal type filter. It should be noted that a configuration in which a DFE is added to a transversal filter may be employed.
- the correlator 44 despreads the signal output from the equalizer 42 in order to despread the preamble of the burst format in FIG. 1 and the phase modulation signal spread by a predetermined spreading code such as a header area.
- a predetermined spreading code such as a header area.
- the correlation process may be a sliding type correlation process or a matched filter type correlation process.
- the correlator 44 also operates in the burst format of FIG. 1 when the power data that operates only with the preamble and the header is a phase modulated signal spread with a predetermined spreading code.
- Demodulation section 46 demodulates despread signal 204 despread by correlator 44. Since the modulation scheme of the despread signal 204 is DBPSK or DQPSK, demodulation is performed by differential detection.
- the FWT calculation unit 50 performs a FWT calculation on a CCK-modulated signal such as the data area of the burst format in FIG. 1, and outputs a Walsh transform value FWT.
- CCK modulation A chip signal is input as a unit, and 64 Pokesh transform values FWT, that is, correlation values are output by correlation processing between chip signals.
- the maximum value search unit 52 receives the 64 Walsh transform values FWT and selects one Walsh transform value FWT that maximizes the Walsh transform value FWT. Further, a first phase correlation signal 208, which is one selected Walsh transform value FWT, and a first phase index signal 210, which indicates the combination of the phases ⁇ 2 to ⁇ 4 corresponding to the corresponding Walsh transform value FWT by an index number, Is output.
- the first phase index signal 210 corresponds to a spread code signal in the first phase signal, and the first phase correlation value signal 208 corresponds to a differentially coded signal in the first phase signal.
- the second maximum value search unit 180 receives the 64 Walsh transform values FWT and selects one Walsh transform value FWT having the second Walsh transform value FWT. Further, a second phase correlation signal 212, which is a selected Walsh transform value FWT, and a second phase index signal 214 indicating a combination of the phases ⁇ 2 to ⁇ 4 corresponding to the Walsh transform value FWT by an index number. Is output.
- the second phase index signal 214 corresponds to a spread code signal in the second phase signal, and the second phase correlation value signal 212 corresponds to a differentially coded signal in the second phase signal.
- information relating to the first phase signal is transmitted from the maximum value searching unit 52 to the second maximum value searching unit 180 via a signal line (not shown), and the 63 signals excluding the Walsh transform value FWT corresponding to the first phase signal are transmitted.
- One Walsh transform value FWT that maximizes the Walsh transform value FWT may be selected from the Walsh transform value FWT.
- the level comparing section 182 calculates the difference between the magnitude of the first phase correlation value signal 208 output from the maximum value searching section 52 and the magnitude of the second phase correlation value signal 212 output from the second maximum value searching section 180. Is compared with a predetermined threshold. If the difference is equal to or larger than the threshold, the operation of the second ⁇ 1 demodulation unit 54b is stopped so that the 8-bit signal in the CCK modulation unit included in the first phase signal is output. On the other hand, if the difference is smaller than the threshold value, the second ⁇ 1 demodulation unit 54b is operated so that the decision unit 184 selects either the first phase signal or the second phase signal.
- the first ⁇ 1 demodulation unit 54a includes the past phase ⁇ 1 already selected by the decision unit 184 and the first phase phase Delay detection of the function signal 208 is performed. Therefore, the past phase ⁇ 1 is input to the first ⁇ 1 demodulation unit 54a by the signal line (not shown). The result of the differential detection is output as a first differential detection signal 216.
- the phase ⁇ 1 is DQPSK-modulated as described above, if there is no influence of noise or the like, the phase of the first differential detection signal 216 is 0, ⁇ ⁇ 2, ⁇ , or 3 ⁇ ⁇ 2. become.
- the first phase index signal 210 is also output as it is.
- the second ⁇ 1 demodulation unit 54b performs delay detection of the past phase ⁇ 1 already selected by the determination unit 184 and the second phase correlation value signal 212. Therefore, the past phase ⁇ 1 is also input to the second ⁇ 1 demodulation unit 54b by the signal line (not shown).
- the result of the differential detection is output as a second differential detection signal 218.
- the phase of the second differential detection signal 218 is 0, ⁇ 2, ⁇ , or 3 ⁇ 2 if there is no influence of noise or the like as in the first differential detection signal 216.
- the second phase index signal 214 is also input, it is output as it is.
- the determination unit 184 selects one of the first and second phase signals based on the first and second delayed detection signals 216 and 218.
- the selection process will be described based on the outline of the operation of the comparing unit 166 shown in FIG.
- the phases 0, ⁇ / 2, ⁇ , 3 ⁇ 2 where ⁇ 1 detected by delay detection should be arranged are indicated by ⁇ , and the signal points of the first delay detection signal 216 and the second delay detection signal 218 Are also shown.
- the phase error between any one of the phases 0, ⁇ / 2, ⁇ , and 3 ⁇ 2 closest to the first delay detection signal 216 and the phase difference between the first delay detection signal 216 is denoted by ⁇ 1, and the second delay detection signal is denoted by ⁇ 1.
- phase error between any one of the phases 0, ⁇ 2, ⁇ , and 3 ⁇ 2 closest to 218 and the second differential detection signal 218 is denoted by ⁇ 2. Further, the phase error ⁇ 1 and ⁇ 2 are compared, and if the phase error ⁇ 1 is small, the first delay detection signal 216 is selected, and if the phase error ⁇ 2 is small, the second delay detection signal 218 is selected. Although the details will be described later, since the ⁇ -Orche transform value FWT is obtained as a result of three correlation values, its power value is amplified from the power value of the chip signal. The above-described processing is executed because the phase obtained by delay detection of the Walsh transform value FWT thus amplified is accurate.
- determining section 184 outputs a corresponding signal in accordance with selected first differential detection signal 216 or second differential detection signal 218. That is, when the first differential detection signal 216 is selected, [dl, d2] that determined the first differential detection signal 216 and the first phase index signal Based on 210! / [D3, d4], [d5, d6], [d7, d8] are combined to output [dl-d8]. On the other hand, when the second delay detection signal 218 is selected, [dl, d2] that determines the second delay detection signal 218 and [d3, d4], [d5, d6] based on the second phase index signal 214 , [D7, d8] and output [dl—d8].
- the switch unit 60 selects one of the signal output from the demodulation unit 46 and the signal output from the determination unit 184, and outputs it as an output signal 202. For example, in the section of the preamble and the header area of the burst format in FIG. 1, the signal output from the demodulation section 46 is selected, and in the section of the data area of the burst format, the signal output from the decision section 184 is selected. And outputs an inverted signal of the selected signal.
- the FWT calculation unit 50, the first ⁇ 2 estimation unit 80a, and the maximum value search unit 52 according to the second embodiment are the same type of the FWT calculation unit 50 and the first ⁇ 2 This is indicated by the estimating section 80a and the maximum value searching section 52.
- the second maximum value search unit 180 in FIG. 12 is configured similarly to the maximum value search unit 52, and operates similarly except for the first phase signal notified from the maximum value search unit 52.
- the correlator 44 despreads the signal equalized by the equalizer 42, and the demodulator 46 demodulates and outputs the output signal 202.
- the FWT calculation unit 50 calculates the Walsh transform value FWT by performing FWT calculation on the signal equalized by the equalizer 42, and the maximum value search unit 52 calculates the Walsh transform value FWT
- the first phase correlation value signal 208 and the first phase index signal 210 are output as the first phase signal corresponding to the largest Walsh transform value FWT.
- Second maximum value searching section 180 outputs second phase correlation value signal 210 and second phase index signal 214 as second phase signals corresponding to the second largest Walsh transform value FWT.
- Level comparing section 182 compares the magnitudes of first phase correlation value signal 208 and second phase correlation value signal 212, and, if smaller than a threshold value, outputs first ⁇ 1 demodulating section 54a and second ⁇ 2 demodulating section 54a. 1 Operate the demodulation unit 54b together.
- the first ⁇ 1 demodulation section 54a delay-detects the first phase correlation value signal 208 and outputs a first delay detection signal 216
- the second ⁇ 1 demodulation section 54b delays the second phase correlation value signal 212. Detects and outputs the second delayed detection signal 218.
- the decision unit 184 determines the first differential detection signal 21 6 and the phase of the second delayed detection signal 218 are compared with any one of 0, ⁇ / 2, ⁇ , and 3 ⁇ 2 to determine the error.
- the error of the second differential detection signal 218 is small, a signal combination corresponding to the second phase signal is output.
- the phase signal combination is selected in order to select the phase signal combination.
- the selection is accurate and the reception characteristics are improved.
- the second phase signal having the second magnitude is added to the processing target according to the result of the FWT calculation, and the second phase signal is highly likely to be inverted with the second phase signal due to noise or the like.
- the selection of the combination of the phase signals becomes accurate.
- a first phase signal and a second phase signal are selected from a plurality of correlation values obtained by the FWT calculation based on their magnitudes.
- the signal having the largest correlation value is selected as the first phase signal
- the signal having the second correlation value is selected as the second phase signal.
- the second phase signal is selected. That is, the number of the second phase signals is not limited to one, and may be plural.
- FIG. 14 shows a configuration of the baseband processing unit 26 according to the third embodiment.
- the baseband processing unit 26 in FIG. 14 has a comparison unit 186 and a threshold holding unit 188 added to the baseband processing unit 26 in FIG. 12, and the maximum value search unit 52, the second maximum value search unit 180, and the level Comparison section 182 removed
- the comparison unit 186 selects the Walsh transform value FW T having the largest neutral strength of the 64 Walsh transform values FWT output from the FWT calculation unit 50 in the same configuration as the maximum value search unit 52. , And derive a corresponding first phase signal. Further, the magnitude of the remaining 63 Walsh transform values FWT is compared with the threshold value held in advance in the threshold value holding unit 188, and the Walsh transform value FWT having a magnitude greater than or equal to the threshold value! And selects the corresponding second phase signal. When the magnitudes of the plurality of Walsh transform values FWT are equal to or larger than the threshold, there are a plurality of second phase signals.
- the ⁇ 1 demodulation unit 54 and the determination unit 184 form a duplicate from the first phase signal and the second phase signal as described above. Choose one combination that is number signal strength. However, unlike in the second embodiment, there may be a plurality of second phase signals, so that the ⁇ 1 demodulation unit 54 and the determination unit 184 have configurations corresponding thereto.
- the combination of the phase signals is selected in order to select the combination of the phase signals.
- the selection is accurate and the reception characteristics are improved.
- the selection of the combination of the phase signals becomes accurate.
- the calculation unit 112 calculates the magnitude R of the Walsh transform value FWT.
- the present invention is not limited to this.
- it may be obtained by the sum of absolute values, or the approximate value R of the magnitude of the Walsh transform value FWT may be obtained as follows!
- A1 and A2 are arbitrary values.
- the error between the phase of the Walsh transform value FWT and the phase where the Walsh code is arranged is calculated with respect to the deviation force, and the coefficient is calculated so that the smaller the error is, the larger it becomes.
- the approximate value R may be obtained by multiplying the sum of squares of I and Q of the Walsh transform value FWT by a coefficient.
- a phase correction circuit for correcting the absolute phase of the digital reception signal 200 or the output signal of the equalizer 42 may be added to the baseband processing unit 26. According to this modification, the reception characteristics can be further improved. In other words, the closer the phase of the Walsh transform value FWT is to any of the phases in which the Walsh codes are arranged, the larger the magnitude of the approximate value R should be.
- a signal transmitted with high accuracy can be estimated from the result of the Walsh transform.
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US7630457B2 (en) * | 2003-12-18 | 2009-12-08 | Freescale Semiconductor, Inc. | Method and apparatus for demodulating a received signal within a coded system |
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JP2004229189A (ja) * | 2003-01-27 | 2004-08-12 | Matsushita Electric Ind Co Ltd | 受信装置および受信方法 |
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KIM T. ET AL: "A new architecture of CCK modem based on iterative different ial-modulation and phase-detection", THE 8TH IEEE INTERNATIONAL CONFERENCE ON, ELECTRONICS, CIRCUITS AND SYSTEMS, 2001, ICECS2001, 5 September 2001 (2001-09-05), XP010563002 * |
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