JP2008153833A - Radio communication equipment and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately correct a reception signal by estimating a propagation path with high precision. <P>SOLUTION: The phase offset of an oscillator in an RF circuit between a transmitter and a receiver is estimated based on a propagation path measurement result. Then, a time difference from the propagation path measurement result is decided until data reception is started is measured, and the propagation path measurement result is corrected according to a phase offset quantity acquired from the phase offset estimation circuit. Thus, it is possible to compensate an error of the propagation path measurement value caused by the phase offset since the propagation path measurement value is decided until the data reception is started. Therefore, it is possible to achieve data demodulation based on the correct propagation path measurement value, and to eliminate the risk of demodulation processing resulting in breakdown. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method for performing mutual communication between a plurality of wireless stations such as a wireless LAN (Local Area Network) or a PAN (Personal Area Network), and in particular, transmission by an ultra-wide band method. The present invention relates to a wireless communication apparatus and a wireless communication method for performing reception processing of a received signal.

  More particularly, the present invention relates to a radio communication apparatus and radio communication method for correcting a received signal distorted due to the influence of a propagation path such as a multipath, and in particular, high accuracy regardless of the phase offset of an oscillator between a transmitter and a receiver. The present invention relates to a wireless communication apparatus and a wireless communication method for estimating a propagation path and correcting a received signal accurately.

  In recent years, a wireless communication system called “ultra wide band (UWB) communication” that uses a very wide frequency band and enables high-speed transmission of 100 Mbps or more has attracted attention. For example, in the United States, a spectrum mask for UWB is defined by FCC (Federal Communications Commission), and UWB transmission can be performed in a band of 3.1 GHz to 10.6 GHz in an indoor environment. UWB communication is a short-distance wireless communication system because of transmission power, but high-speed wireless transmission is possible, so a PAN (Personal Area Network) with a communication distance of about 10 m is assumed, and short-range ultra-high speed Practical use is expected as a wireless communication system that realizes transmission.

  As UWB transmission systems, the DSSS (Direct Sequence Spread Spectrum) -UWB system, in which the spreading speed of DS (Direct Spread) information signals is increased to the limit, and OFDM (Orthogonal Frequency Division Multiplexing: Multiplexed Multiplexing Modulation) An OFDM_UWB system that employs the above has been studied.

  Here, in the OFDM transmission system, a plurality of data output by serial-parallel conversion of information sent serially for each symbol period slower than the information transmission rate is assigned to each subcarrier, and the amplitude and the amplitude for each subcarrier. By performing phase modulation and performing inverse FFT on the plurality of subcarriers, each subcarrier on the frequency axis is converted into a signal on the time axis, and OFDM modulation is performed. On the OFDM receiver side, the reverse operation, that is, FFT is performed to convert the time-axis signal into the frequency-axis signal, and each subcarrier is demodulated in accordance with the modulation method, and parallel-serial converted. Reproduce the information sent in the original serial signal. The frequency of each subcarrier is set so as to be orthogonal to each other within the symbol interval. That subcarriers are orthogonal to each other means that the peak point of the spectrum of an arbitrary subcarrier always coincides with the zero point of the spectrum of another subcarrier. Therefore, since transmission data is distributed and transmitted to a plurality of carriers having different frequencies, the bandwidth of each carrier is narrow, the frequency utilization efficiency is very high, and it is strong against frequency selective fading interference.

  On the other hand, according to the SS system, the required C / I for enabling normal communication can be set to a level lower than 0 dB even in an environment where communication systems using the same frequency band coexist. If you detect someone else ’s signal at the same level as your signal, you ’ll still be able to communicate). In particular, in the case of UWB, since the occupied bandwidth is wide, it is easy to use the SS method. In the DSSS system, the transmission side spreads the occupied band by multiplying the information signal by a random code sequence called a PN (Pseudo Noise) code, and the reception side multiplies the received spread information signal by the PN code. Despreading is performed to reproduce the information signal.

  Further, a frequency hopping (FH) method for flexibly changing the frequency band to be used is known. According to the FH system, packets are transmitted / received while changing the frequency randomly each time, and communication may be disabled due to the influence of other systems. However, communication is hardly interrupted by constantly changing the frequency. Absent. That is, it can coexist with other systems, has excellent fading resistance, and is easy to scale.

  In the standardization conference in IEEE802.15.3, the band from 3.1 GHz to 10.6 GHz defined by FCC is divided into a plurality of subbands each having a width of 528 MHz in both the DSSS-UWB system and the OFDM_UWB system. Therefore, a multiband scheme (hereinafter referred to as “MB-OFDM scheme”) that performs frequency hopping (FH) between subbands has been studied.

  In the future, WPAN (Wireless Personal Access Network) of near field communication represented by UWB is expected to be installed in all home appliances and CE (Consumer Electronics) devices, and P-to-P between CE devices exceeding 100 Mbps. Realization of transmission and home network is expected. When the use of the millimeter wave band becomes widespread, short-range radio over 1 Gbps is possible, and ultra-high-speed short-range DAN (Device Area Network) including storage devices and the like can be realized.

  By the way, in wireless communication, there is a problem that a signal sent from a transmitter is received by a receiver under the influence of a propagation path such as multipath. Specifically, since the phase of the transmission signal rotates on the propagation path and the signal amplitude fluctuates, the receiver side cannot correctly decode the original data from the received signal. For this reason, the receiver needs to perform correction such as measuring propagation path characteristics and correcting the amount of phase rotation and amplitude of the received signal.

  Propagation path measurement is generally obtained by transmitting and receiving a known sequence between a transmitter and a receiver. That is, the transmitter includes the training sequence for propagation path measurement included in the packet preamble, and the receiver multiplies the received preamble by the known training sequence, whereby the phase rotation amount and amplitude fluctuation on the propagation path are multiplied. The amount can be corrected by performing an operation of obtaining the amount, reversely rotating the information signal (payload) by the amount of phase rotation, and restoring the amplitude.

  In addition, there is a phase offset in the oscillator mounted on each transceiver. The phase offset is generated between the IQ modulation unit and the demodulation unit of the analog unit of the transceiver. Looking at the data in the frequency domain of the FFT value on the receiver side, the low frequency component of the phase offset can be observed as a phenomenon that the phase of all subcarriers is rotated by almost the same angle for each OFDM symbol. Although the angle of phase rotation for each OFDM symbol varies, the angle for each subcarrier is observed to be the same. For this reason, it is necessary on the receiver side to perform carrier tracking and perform correction so as to obtain an optimum phase rotation amount.

  For example, a phase rotation unit is disclosed in which the carrier tracking method differs depending on whether the transmission rate is faster or slower than the upper limit speed of the AD converter (see, for example, Patent Document 1). That is, when the transmission rate is lower than the upper limit operation speed of the AD converter, the square value of the sampled values is averaged to obtain a phase offset, and a process of returning only the offset is performed. In this case, since it corresponds to rotational correction based on the measurement result of the propagation path, there is a speed limit, but the accuracy is high. On the other hand, in the case of a transmission rate faster than the upper limit speed of the AD converter, a template in which a phase offset value calculated in advance by 45 degrees from the I-axis component and Q-axis component of the received signal is passed through a simple comparison. Perform matching. Then, the output from the comparator corresponding to the offset closest to the phase offset calculated from the value to be sampled is selected and set as the value after carrier tracking.

  As described above, on the receiver side, the propagation path is measured using the training sequence included in the preamble of the packet. In other words, at least at the start of packet reception, the received signal is corrected using the propagation path measurement result obtained from the training sequence as it is. In such a case, since the propagation path measurement result includes an error due to the phase offset, it cannot be said to be an accurate measurement value. For example, there is a problem that data demodulation fails if the amount of phase rotation in a period from when the propagation path measurement value is determined to when reception of the information signal starts exceeds a certain value.

JP 2004-159196 A

  An object of the present invention is to provide an excellent wireless communication apparatus and wireless communication method capable of suitably performing reception processing of a signal transmitted by the UWB system.

  A further object of the present invention is to provide an excellent radio communication apparatus and radio communication method capable of accurately correcting a received signal distorted by the influence of a propagation path such as a multipath.

  A further object of the present invention is to provide an excellent wireless communication apparatus and wireless communication method capable of accurately correcting a received signal by estimating a propagation path with high accuracy regardless of the phase offset of the oscillator between the transceivers. There is to do.

The present invention has been made in consideration of the above problems, and is a wireless communication apparatus that performs reception processing of a signal to which a preamble including a known sequence for propagation path measurement is added,
An RF circuit unit for processing the received RF signal;
A propagation path measuring unit that measures a propagation path using a preamble portion of the RF-processed received signal;
A phase offset estimation unit that estimates a phase offset with the transmitter side based on a propagation path measurement result by the propagation path measurement unit;
A phase correction time measuring unit for measuring a phase correction time from a determination time of a propagation path measurement result by the propagation path measurement unit to a reception start time of an information signal following a preamble;
Based on the phase correction time measured by the phase correction time measurement unit and the phase offset value estimated by the phase offset unit estimation unit, a phase correction amount of the propagation channel measurement value is obtained, and the propagation channel is obtained at the start of the information signal. A propagation path measurement result correction unit for correcting the measurement result of the propagation path by the measurement unit;
A wireless communication apparatus comprising:

  In wireless communication, the signal sent from the transmitter is received by the receiver under the influence of the propagation path such as multipath. Therefore, the receiver measures the propagation path characteristics and the amount of phase rotation with respect to the received signal. In addition, it is necessary to perform correction such as correcting the amplitude.

  On the receiver side, the propagation path can be measured using the training sequence included in the preamble of the packet. However, at the start of packet reception, the propagation path measurement result obtained from the training sequence includes an error due to the phase offset. For this reason, there is a problem that data demodulation fails if the amount of phase rotation in a period from the time when the propagation path measurement value is determined to the start of reception of the information signal exceeds a certain value.

  Therefore, the wireless communication apparatus according to the present invention includes a phase offset estimation unit that estimates a phase offset with respect to the transmitter side based on a propagation path measurement result by the propagation path measurement unit on the receiver side. The phase correction time measurement unit measures the phase correction time from the time when the propagation path measurement result is determined by the propagation path measurement unit to the time when the reception of the information signal following the preamble starts. Then, the propagation path measurement result correction unit obtains the phase correction amount of the propagation path measurement value based on the phase correction time measured by the phase correction time measurement unit and the phase offset value estimated by the phase offset unit estimation unit. The measurement result of the propagation path by the propagation path measurement unit is corrected at the start of the signal.

  This compensates for errors in the propagation path measurement value due to the phase offset from the time of determination of the propagation path measurement value to the start of data reception, so data demodulation can be performed based on the correct propagation path measurement value. The risk that the demodulation process will fail is eliminated.

  The wireless communication apparatus according to the present invention includes a RAKE combining unit that RAKE-receives a received signal RF-processed by an RF circuit unit based on a propagation path measurement result corrected by a propagation path measurement result correcting unit, and a combining unit by the RAKE combining unit A carrier tracking unit that detects a carrier phase offset based on the result is further provided, and the RAKE combining result by the RAKE combining unit can be corrected based on the carrier phase offset obtained by the carrier tracking unit.

Here, the carrier tracking unit maps the RAKE reception result obtained by integrating each component of the I-axis and the Q-axis on the IQ plane until the RAKE combining data output in the RAKE combining unit is determined. Determination values (P _{err — I} , P _{err — q} ) can be obtained. Then, in response to the phase offset determination value exceeding a predetermined threshold, the carrier tracking unit sets the phase offset determination value (P _{err_I} , P _{err_q} ) to a predetermined value in the direction opposite to the phase offset on the IQ plane. The RAKE synthesis result is corrected by rotating only by the rotation. The carrier tracking unit corrects the phase and counts the total of the observed phase offsets, and performs AD conversion in the RF circuit unit so that the chip position of the carrier signal is opposite to the observed phase offset. Sampling timing is controlled.

  Therefore, the radio communication apparatus according to the present invention can perform highly accurate carrier tracking. Since most of such carrier tracking processing is performed by a digital circuit, it is not necessary to control the carrier frequency in the RF circuit. In addition, since carrier tracking is performed by switching AD conversion timing, it is necessary to use an expensive oscillator such as VCX (Voltage Controlled Crystal Oscillator) -TCXO (Temperature Compensated Crystal Oscillator). Therefore, the RF circuit can be mounted more easily.

  The radio communication apparatus according to the present invention further includes a preamble end detection unit that detects a signal indicating the end of the preamble. The propagation path measuring unit selects a predetermined number of paths having a large signal level, and outputs each position and energy value. The preamble end detection unit detects a signal indicating the end of the preamble for the path having the maximum energy value.

  The preamble added to the packet includes a plurality of short code patterns having good autocorrelation characteristics. Therefore, the propagation path measurement unit and the preamble end detection unit can perform propagation path measurement and detection of the end position value of the preamble using the respective short code patterns.

  The propagation path measurement unit generates a sequence for despreading based on the chip timing, and performs despreading by multiplying the received signal digitally processed by the RF circuit unit in a complex manner, thereby obtaining a propagation path. Measure. Here, the despreading operation performed by one despreading circuit for one clock is equal to the number of parallel inputs.

  The preamble end detection unit determines the path having the maximum energy as the symbol / pulse position, performs despreading operation with a short code for detecting the preamble end at the pulse position, and detects the end position of the preamble. Then, the RAKE combining unit starts the RAKE combining process in accordance with the detection timing by the preamble end detecting unit. Accordingly, the end point (end) position of the preamble (that is, the start (start) position of the information signal) can be detected accurately and at high speed, which leads to improvement in reception performance.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding radio | wireless communication apparatus and radio | wireless communication method which can correct | amend correctly the received signal distorted by the influence of propagation paths, such as a multipath, can be provided.

  In addition, according to the present invention, there is provided an excellent wireless communication apparatus and wireless communication method capable of accurately correcting a received signal by estimating a propagation path with high accuracy regardless of a phase offset of an oscillator between a transmitter and a receiver. Can be provided.

  The wireless communication apparatus according to the present invention enables high-speed and high-accuracy propagation path measurement. Since the error of the propagation path measurement value due to the phase offset from the time when the propagation path measurement value is determined until the start of data reception is compensated, data demodulation can be performed based on the correct propagation path measurement value. The risk of bankruptcy is resolved.

  In addition, the wireless communication apparatus according to the present invention enables highly accurate carrier tracking. In addition, since most of the carrier tracking processing is performed by a digital circuit, it is not necessary to control the carrier frequency in the RF circuit, and the RF circuit can be configured more simply. Further, since carrier tracking is performed by switching the timing of AD conversion, it is not necessary to use a highly accurate oscillator, and the RF circuit can be more easily mounted.

  In addition, since the wireless communication apparatus according to the present invention can detect the end point (end) position of the preamble (that is, the start (start) position of the information signal) accurately and at high speed, the reception performance is improved.

  In addition, the wireless communication device according to the present invention can realize improvement in circuit use efficiency and reduction in circuit scale.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows the configuration of an RF unit in a wireless communication apparatus according to an embodiment of the present invention. The illustrated RF section is a typical π / 2 shift BPSK (BiPhase Shift Keying) type transceiver. In the following description, it is assumed that the carrier frequency of the RF unit is 4 GHz, the sample rate (that is, the chip rate) of AD conversion is 1 GHz, and the clock frequency of the baseband unit is 125 MHz. The illustrated transmitter / receiver has a configuration capable of switching the phase of a sampling frequency of 1 GHz in four stages by a control signal from the baseband side after A / D conversion.

  In the transmission system, a transmission signal transmitted from a baseband processing unit (not shown in FIG. 1) is subjected to parallel-serial conversion, and is then alternately distributed to odd timing and even timing at a timing of 500 MHz and is subjected to pulse shaping. The These are each subjected to BPSK modulation by a 4 GHz carrier having an orthogonal relationship, added, amplified by a power amplifier, and then wirelessly transmitted from an antenna via an RF filter. FIG. 2 shows an image of I-axis and Q-axis signals having a phase difference of 90 degrees and a signal waveform after the multiplication (Envelop).

  In the receiving system, a radio signal received by an antenna passes through an RF filter and a low noise amplifier, and is subjected to quadrature detection by performing frequency detection with a center frequency signal 4 GHz and a frequency signal having a phase difference of 90 degrees, thereby performing I-axis and The signals are separated into Q-axis signals, and each is subjected to AGC (Automatic Gain Control) based on RSSI (received signal electric field strength). Then, it is sampled as a digital signal at an interval of 1 GHz by the A / D converter. Further, the sampled I / Q signal is subjected to serial-parallel conversion, and is thereafter subjected to digital processing by the baseband processing unit.

  A local frequency of 4 GHz generated by the local oscillator is a carrier frequency in the RF section.

  The carrier frequency is divided by a quarter and supplied as a sample rate of the A / D converter, that is, a chip rate of 1 GHz.

  Further, the chip rate of 1 GHz is further divided by 1/8, and is given as a clock frequency of 125 MHz of a baseband processing unit (described later).

  Here, the clock frequency of the baseband processing unit may be selected from an operating speed that can be realized by a process that is an integral number of a chip rate. In the case of an ordinary spread spectrum (SS) receiver, the baseband processing unit can operate at the same clock frequency as the chip rate. However, in the UWB system, the power consumption becomes excessive at the same clock frequency as the chip rate, so that the chip rate is set to 1 / integer.

  The oscillator also has a mechanism for switching the chip timing, that is, the in-chip phase from 0/4 to 2/4 in response to a phase shift command (Phase Shift) from the baseband processing unit. Can be shifted in phase.

  FIG. 3 schematically shows the configuration of the baseband processing unit in the wireless communication apparatus according to the embodiment of the present invention. The illustrated baseband processing unit 10 includes a spread modulation unit (Direct Spreader) 11 that performs spreading processing of an information signal as a transmission system, and a propagation path measurement unit (Channel Measurement) that performs delay profile measurement of a propagation path as a reception system. 12, a preamble end detection unit (PreambleEndDetect) 13 for detecting the end of the preamble signal, and a RAKE combining unit 14 for demodulating the signal by RAKE combining the energy of the multipath signal. Each of the functional circuit units 11 to 14 of the transmission / reception system is centrally controlled by a physical layer sequence control unit (PhySequenceControl) 15.

  In the transmission system of the illustrated baseband processing unit 10, the transmission signal transmitted from the MAC layer hardware circuit corresponding to the upper layer of the communication protocol is directly spread (DS) by the spread modulation unit 11, and transmitted by the RF unit. Send to the system. The signal processing procedure in the reception system of the baseband processing unit 10 will be described later.

  In the present embodiment, a carrier tracking block is provided in the physical layer sequence control unit 15, but the configuration and operation will be described in detail later.

  FIG. 4 schematically shows a format configuration example of a signal used for wireless transmission in the embodiment of the present invention.

  As shown in the figure, the transmission signal is composed of a preamble part for performing processing such as signal detection and synchronization acquisition, a PHY header part describing control information for the PHY layer, and a payload part. The The payload part can be further separated into a MAC header part and a MAC payload part. However, the configuration of the MAC frame itself is not directly related to the gist of the present invention, and thus the description thereof is omitted here.

  The preamble part is composed of a short code pattern (Spread Sequence) consisting of 128 chips. In this embodiment, two short code patterns A and B having good autocorrelation characteristics are prepared.

  At the beginning of the preamble portion, the short code pattern B is repeated a plurality of times and used as an area for stabilizing the gain of AGC. In the example shown in FIG. 4, the short code pattern B is repeated 8 times for AGC. However, it is necessary to secure the area for the period during which AGC is stabilized.

  Further, after the AGC region, a propagation path measurement training pattern configured by using five symbols of the short code pattern A is repeatedly arranged five times.

  Further, after the training pattern, a preamble end detection pattern configured by using four short code patterns B is arranged.

  However, the gist of the present invention is not limited to the format configuration shown in FIG. 4, and parameter values constituting each pattern can be appropriately changed.

  FIG. 5 shows the configuration of the reception system shown in FIG. 3 in more detail. The reception system of the baseband processing unit includes a channel measurement unit (Channel Measurement) 12 that measures a delay profile of the channel, a preamble end detection unit (PreambleEndDetect) 13 that detects the end of the preamble signal, and the energy of the multipath signal. A RAKE combining unit 14 that demodulates a signal by RAKE combining is provided, and is generally controlled by a physical layer sequence control unit (PhySequenceControl) 15.

  In the following description, the carrier frequency of the RF unit is 4 GHz, the sample rate of A / D conversion, that is, the chip rate is 1 GHz, and the clock frequency of the baseband processing unit is 125 MHz.

  Here, the clock frequency of the baseband processing unit 10 may be selected from an operation speed that can be realized by a process that is 1 / integer of the chip rate. In this embodiment, the clock frequency of 125 MHz corresponds to 1/8 of the chip rate of 1 GHz. In the case of an ordinary spread spectrum (SS) receiver, the baseband processing unit can operate at the same clock frequency as the chip rate. However, in the UWB system, the power consumption becomes excessive at the same clock frequency as the chip rate, so that the chip rate is set to 1 / integer.

  The preamble signal received by the RF unit is quadrature detected by a carrier frequency of 4 GHz and a frequency having a phase difference of 90 degrees and separated into an I-axis signal and a Q-axis signal. These I-axis and Q-axis signals are converted into A / D converters. Is sampled at a chip rate of 1 GHz. The sampled data is converted into 8 parallels for each of I and Q, and is input to the propagation path measurement unit (ChannelMeasure) 12, where the delay profile of the propagation path is measured.

  In the case of an ordinary spread spectrum (SS) receiver, the baseband processing unit 10 can be operated at the same clock frequency as the chip rate. In this case, the propagation path can be measured by taking the sliding correlation. However, in the UWB system, the power consumption becomes excessive at the same clock frequency as the chip rate, and the number of baseband clocks is set to 1 / integer of the chip rate. Therefore, propagation path measurement using sliding correlation is performed. I can't.

  For this reason, in this embodiment, the propagation path measurement unit 12 performs propagation path measurement by performing despreading for each short code. The interval to be measured is the number of short code chips 128 × chip rate 1 nanosecond = 128 nanoseconds.

  The propagation path measurement unit 12 measures the propagation path in response to a propagation path measurement command (MeasureControl) from the physical layer sequence control unit 15. Specifically, a despreading sequence is generated based on the chip timing, and despreading is performed by multiplying the received digitally processed signal in a complex number. Here, the despreading operation performed by one despreading circuit for one clock is equal to the number of parallel inputs. Then, these multiplication results are integrated in a complex manner in the symbol interval to obtain received symbols (RxSymbol I, RxSymbol Q) in a complex number. Further, a correlation output can be obtained from the sum of squares of each received symbol after despreading (I × I + Q × Q). Then, the propagation path measuring unit 12 selects a predetermined number of paths having a large signal level out of 128 points, and outputs each position (BigPathIndex) and energy value (BigPathEnergy) to the physical layer sequence control unit 15.

  When detecting the signal, the physical layer sequence control unit 15 ends the propagation path measurement, and passes the position (Index) of the path where the maximum energy is detected to the preamble end detection unit 13. The preamble end detection unit 13 determines the path having the maximum energy as a symbol / pulse position, performs a despreading operation with a short code for preamble end detection at the pulse position, and detects the end position of the preamble. Then, the preamble end detection unit 13 returns the obtained value (PreambleEndDetectDecisionValue) to the physical layer sequence control unit 15. Then, the physical layer sequence control unit 15 determines the end of the preamble by using the PreambleEndDetectDetectionValue.

  One of the problems in transmitting and receiving wireless signals is multipath fading. This is a phenomenon in which a communication signal is reflected on a building or other object to reach the receiving side through a different route, and a reception signal is disturbed by radio waves arriving from different directions interfering with each other.

  RAKE reception means that a plurality of radio waves are received, and a desired signal is separated by despreading processing from a reception signal on which a plurality of delayed waves are superimposed by a multipath propagation path, and the dispersed signal power is collected into one. That is, by using the time-resolving effect of despreading that direct spectrum spreading has, the signals of each separated path are combined with the same time and phase (for example, weighted according to the S / N ratio of the path to obtain the maximum ratio). Synthesized). According to RAKE reception, desired signal power dispersed in time can be effectively combined.

  In the present embodiment, when the end of the preamble is found by the above-described operation, the data body (that is, the PHY header and payload) arrives soon. In accordance with this timing, the physical layer sequence control unit 15 sets the propagation path complex amplitude values and spreading factors of the N paths in the RAKE combining unit 14 and starts the RAKE combining process. The I-axis component of the output of the RAKE combining unit 14 that is a received symbol is demodulated data.

  As already described, in this embodiment, carrier tracking is performed in the physical layer sequence control unit 15. FIG. 6 shows the configuration of the carrier tracking unit.

  The output of the RAKE combining unit 14 is sent to the next process (not shown) as I-axis and Q-axis received data, and is returned to the physical layer sequence control unit 15 to detect the carrier phase offset of each axis component. It is.

  In the data accumulation unit (Data Accumulation) 21 in the carrier tracking unit, the addition is performed until the output of the RAKE combining unit 14 is determined (that is, the data enable signal of the RAKE combining unit).

  FIG. 7 illustrates a circuit configuration that performs addition processing of each component of the I axis and the Q axis in the data storage unit 21. As shown in the figure, the absolute value of the I-axis component of the RAKE composite output is added. On the other hand, when the polarity of the corresponding I-axis component is negative, the Q-axis component is added after inverting the polarity. FIG. 8 shows an operation on the IQ plane for performing addition processing of each component of the I axis and the Q axis. As shown in the figure, an operation corresponding to collecting all reception points on a plane of I> 0 is performed.

The phase offset detection and channel response rotating unit 22 supplies phase offset determination values (Phase Error Estimation Value) of each component of the I axis and the Q axis, that is, (P _{err_I} , P _{err_q} ). On the other hand, the integrated value of each component of the I axis and Q axis in the data storage unit 21 is output at the next clock of the data enable signal of the RAKE combining unit 15, a phase offset determination value after passing through the filter _(P err_I, P _{err_q} ) is added.

  FIG. 9 shows the carrier phase offset on the IQ plane. As can be seen from the figure, the carrier phase offset is observed as a rotation in one direction. In the example shown in the figure, when the reception carrier frequency is higher than the transmission carrier frequency, it rotates counterclockwise, and when the reception carrier frequency is lower than the transmission carrier frequency, it rotates on the IQ plane.

As described above, the phase offset detection and channel response rotation unit 22 obtains the phase offset determination values (P _{err_I} , P _{err_q} ) by mapping the RAKE reception result performed based on the propagation path measurement value on the IQ plane. ing.

The phase offset detection and channel response rotation unit 22 has a function of detecting that the carrier phase offset exceeds 5.625 degrees on the IQ plane. 10A and 10B show the operation of the phase offset detection and channel response rotation unit 22 when the carrier phase offset exceeds 5.625 degrees. In the illustrated example, the propagation path estimated value and the carrier phase offset determination value (P _{err — I} , P _{err — q} ) are each rotated by 11.25 degrees in the direction opposite to the phase offset. As a result, the carrier phase offset can be kept within ± 5.625 degrees. As described above, since most of the carrier tracking processing can be performed by the baseband processing unit constituted by a digital circuit, it is not necessary to control the carrier frequency in the RF circuit.

In addition, the phase offset detection and channel response rotation unit 22 performs phase correction of the propagation path estimation value and the carrier phase offset determination value (P _{err — I} , P _{err — q} ), and at the same time, the phase correction direction is set in an internal counter (not shown). Add -1 if positive, +1 if negative. When the positive and negative phase offsets and the counter values are ± 15 and ± 16, it can be considered that a phase offset of ± 180 degrees in total has been observed. This corresponds to a reception position offset of 1/8 chip. Therefore, the phase offset detection and channel response rotation unit 22 transmits to the RF unit a phase shift command for correcting the chip position of the carrier signal by ¼ chip in the direction opposite to the observed phase offset. .

  The oscillator in the RF unit is provided with a mechanism for switching the chip timing, that is, the phase in the chip from 0/4 to 2/4 in response to the phase shift command from the baseband processing unit. And the phase of the RF section can be corrected by ¼.

  The carrier tracking unit repeatedly performs the above-described operation until RAKE reception ends.

  As described above, on the receiver side, the propagation path is measured using the propagation path measurement sequence included in the preamble of the packet. In such a case, at the start of packet reception, the propagation path measurement result obtained from the propagation path measurement sequence includes an error due to the phase offset. For this reason, there is a problem that data demodulation fails if the amount of phase rotation in a period from the time when the propagation path measurement value is determined to the start of reception of the information signal exceeds a certain value.

  Therefore, the wireless communication apparatus according to the present embodiment estimates, on the receiver side, the phase offset with the oscillator in the RF circuit of the transmitter that is the communication partner based on the propagation path measurement result by the propagation path measurement unit 12. Equipped with a phase offset estimation circuit. Then, the time difference from the determination time of the propagation path measurement result to the data reception start time is measured, and the propagation path measurement result is corrected according to the phase offset amount obtained from the phase offset estimation circuit. This compensates for errors in the propagation path measurement value due to the phase offset from the time of determination of the propagation path measurement value to the start of data reception, so data demodulation can be performed based on the correct propagation path measurement value. The risk that the demodulation process will fail is eliminated.

  FIG. 11 shows a configuration example of a phase offset estimation circuit that estimates based on a propagation path measurement result. In the same circuit, despreading is performed by performing complex multiplication of the I and Q components (digitally processed received signals) as propagation path measurement values from the propagation path measurement unit 12 (or preamble termination detection unit 13) with a despreading sequence. When the received symbol is received, the phase offset value is obtained from the arctan. Then, in order to suppress the error of the phase offset value, the phase offset value over several sample periods (5 periods in the illustrated example) is latched, and the phase offset calculation unit takes these average values and sequentially obtains them as the phase offset value. Output.

  Then, the propagation path measurement is performed according to the phase offset amount generated in the period from the time when the propagation path measurement value is determined by the propagation path measurement unit 12 until the reception of the information signal is started ("phase correction time" shown in FIG. 12). Since the result is corrected, it is necessary to measure the time difference from the determination time of the propagation path measurement result to the data reception start time.

  FIG. 13 shows a configuration example of a phase correction time measuring circuit for measuring the time difference from the time when the propagation path measurement result is determined to the time when data reception is started. The illustrated circuit measures the phase correction time based on, for example, the determination timing of the propagation path measurement value supplied from the propagation path measurement unit 12, the detection timing of the preamble end from the preamble end detection unit 13, and the counter input. It is like that.

  Based on the phase offset value and the phase correction time, the phase correction amount of the propagation path measurement value is obtained. Thereafter, the propagation path measurement result in the propagation path measurement unit 12 is corrected at the start of reception of data (information signal) following the preamble. FIG. 14 schematically shows the circuit configuration. FIG. 15 shows how the propagation path measurement values are corrected in the IQ space.

  Carrier tracking is started from the corrected propagation path measurements.

  As described above, the wireless communication apparatus according to the present invention can perform high-speed and high-accuracy propagation path measurement. Since the error of the propagation path measurement value due to the phase offset from the time when the propagation path measurement value is determined until the start of data reception is compensated, data demodulation can be performed based on the correct propagation path measurement value. The risk of bankruptcy is resolved.

  In addition, the wireless communication apparatus according to the present invention enables highly accurate carrier tracking. In addition, since most of the carrier tracking processing is performed by a digital circuit, it is not necessary to control the carrier frequency in the RF circuit, and the RF circuit can be configured more simply.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In the present specification, the present invention has been described mainly with respect to an embodiment in which ultra-wideband communication is applied by spread spectrum. However, the gist of the present invention is not limited to this, and communication in which normal spread spectrum is performed. It goes without saying that the present invention can be realized in the same way even if the system is used.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram schematically showing a configuration of an RF unit in a wireless communication apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing an image of I-axis and Q-axis signals having a 90-degree phase difference and a signal waveform after the multiplication. FIG. 3 is a diagram schematically illustrating the configuration of the baseband processing unit in the wireless communication apparatus according to the embodiment of the present invention. FIG. 4 is a diagram schematically illustrating a format configuration example of a signal used for wireless transmission in the embodiment of the present invention. FIG. 5 is a diagram showing the configuration of the reception system shown in FIG. 3 in more detail. FIG. 6 is a diagram illustrating a configuration of the carrier tracking unit. FIG. 7 is a diagram showing a circuit configuration for performing addition processing of each component of the I axis and the Q axis in the data storage unit 21. FIG. 8 is a diagram showing an operation on the IQ plane for performing addition processing of each component of the I axis and the Q axis. FIG. 9 is a diagram showing the carrier phase offset on the IQ plane. FIG. 10A is a diagram showing an operation of rotating the carrier phase by 11.25 degrees in the reverse direction to keep the phase offset within ± 5.625 degrees when the clockwise carrier phase offset exceeds 5.625 degrees. is there. FIG. 10B is a diagram showing an operation of rotating the carrier phase by 11.25 degrees in the reverse direction to keep the phase offset within ± 5.625 degrees when the counterclockwise carrier phase offset exceeds 5.625 degrees. It is. FIG. 11 is a diagram illustrating a configuration example of a phase offset estimation circuit that estimates based on a propagation path measurement result. FIG. 12 is a diagram for explaining the phase correction time from when the propagation path measurement value is determined by the propagation path measurement unit 12 until reception of the information signal is started. FIG. 13 is a diagram illustrating a configuration example of a phase correction time measurement circuit for measuring a time difference from a determination time of a propagation path measurement result to a data reception start time. FIG. 14 is a diagram illustrating a circuit configuration example for correcting the propagation path measurement result in the propagation path measurement unit 12. FIG. 15 is a diagram showing how the propagation path measurement values are corrected in the IQ space.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Baseband process part 11 ... Spreading modulation part 12 ... Propagation path measurement part 13 ... Preamble end detection part 14 ... RAKE combining part 15 ... Physical layer sequence control part 21 ... Data storage part 22 ... Phase offset detection and channel response rotation part

Claims (13)

A wireless communication apparatus that performs reception processing of a signal to which a preamble including a known sequence for propagation path measurement is added,
An RF circuit unit for processing the received RF signal;
A propagation path measuring unit for measuring a propagation path using a preamble portion of a reception signal RF-processed by the RF circuit unit;
A phase offset estimation unit that estimates a phase offset with the transmitter side based on a propagation path measurement result by the propagation path measurement unit;
A phase correction time measuring unit for measuring a phase correction time from a determination time of a propagation path measurement result by the propagation path measurement unit to a reception start time of an information signal following a preamble;
Based on the phase correction time measured by the phase correction time measurement unit and the phase offset value estimated by the phase offset unit estimation unit, a phase correction amount of the propagation channel measurement value is obtained, and the propagation channel is obtained at the start of the information signal. A propagation path measurement result correction unit for correcting the measurement result of the propagation path by the measurement unit;
A wireless communication apparatus comprising: A RAKE combining unit that RAKE-receives a reception signal RF-processed by the RF circuit unit based on the propagation path measurement result corrected by the propagation path measurement result correction unit;
A carrier tracking unit that detects a carrier phase offset based on a combination result by the RAKE combining unit;
Correcting the RAKE combining result by the RAKE combining unit based on the carrier phase offset obtained by the carrier tracking unit;
The wireless communication apparatus according to claim 1. The carrier tracking unit determines the phase offset by mapping the RAKE reception result obtained by integrating the components of the I axis and the Q axis on the IQ plane until the RAKE combining data output in the RAKE combining unit is determined. Get the values (P _{err_I} , P _{err_q} ),
The wireless communication apparatus according to claim 2. It said carrier tracking unit, in response to the phase offset determination value exceeds a predetermined threshold value, the phase offset determination value _(P err_I, P err_q) a on the IQ plane by a predetermined value in a direction opposite to the phase offset Correct the RAKE synthesis result by rotating,
The wireless communication apparatus according to claim 3. The carrier tracking unit performs phase correction and counts the total of the observed phase offset, and performs AD conversion in the RF circuit unit so that the chip position of the carrier signal is opposite to the observed phase offset. Control the sampling timing,
The wireless communication apparatus according to claim 4. The propagation path measurement unit selects a predetermined number of paths having a large signal level, and outputs each position and energy value.
The wireless communication apparatus according to claim 1. A preamble end detection unit for detecting a signal indicating the end of the preamble for a path having the maximum energy value;
The wireless communication apparatus according to claim 6. The preamble includes a plurality of short code patterns having good autocorrelation characteristics,
The propagation path measurement unit and the preamble end detection unit perform propagation path measurement and detection of the end position value of the preamble using the respective short code patterns.
The wireless communication apparatus according to claim 7. The propagation path measurement unit generates a sequence for despreading based on chip timing, and performs despreading by multiplying the received signal digitally processed by the RF circuit unit in a complex number manner.
The wireless communication apparatus according to claim 1. The despreading operation performed by one despreading circuit on one clock is equal to the parallel number of the inputs.
The wireless communication apparatus according to claim 9. The preamble end detection unit determines a path having the maximum energy as a symbol / pulse position, performs a despreading operation with a short code for preamble end detection at the pulse position, and detects a preamble end position.
The wireless communication apparatus according to claim 8. Further comprising a preamble end detection unit that detects a preamble end position based on a propagation path measurement result in the propagation path measurement unit;
The RAKE combining unit starts a RAKE combining process in accordance with a detection timing by the preamble end detection unit.
The wireless communication apparatus according to claim 2. A radio communication method for performing reception processing of a signal to which a preamble including a known sequence for propagation path measurement is added,
An RF processing step for processing the received RF signal;
A propagation path measuring step for measuring a propagation path using a preamble portion of the received signal subjected to RF processing in the RF processing step;
A phase offset estimation step for estimating a phase offset with the transmitter side based on a propagation path measurement result in the propagation path measurement step;
A phase correction time measuring step for measuring a phase correction time from the determination time of the propagation path measurement result in the propagation path measurement step to the reception start time of the information signal following the preamble;
A phase correction amount of a propagation path measurement value is obtained based on the phase correction time measured in the phase correction time measurement step and the phase offset value estimated in the phase offset unit estimation step, and the propagation path is measured at the start of the information signal. A propagation path measurement result correction step for correcting the measurement result of the propagation path in the measurement step;
A wireless communication method comprising:

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