JP2003092561A - Receiver and receiving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver and a receiving method capable of estimating a transmission path even though a state of the transmission path fluctuates and receiving a transmitted signal by stably controlling not only FFT timing but also an AGC (automatic gain control). SOLUTION: This receiver is provided with a burst detecting means 4 for detecting a data symbol of a burst cycle from a received signal and also measuring the intensity of the received signal, a gain controlling means 6 for amplifying the received signal from the level of the detected received signal with a gain control amplifying means 1 to be a prescribed level, also holding an amplification gain ever period from a reference symbol to the next reference symbol and updating the amplification gain at prescribed update timing, and a timing controlling means 5 for generating update timing for updating the amplification gain for the gain controlling means 6 so as to be a positive integer multiple of a reference symbol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a wireless communication system and is suitable for use in an environment having a relatively gradual time change such as an indoor multipath environment.
GC (Automatic Gain Contro)
l: automatic gain control) The present invention relates to a receiving apparatus and a receiving method for receiving information transmitted by realizing control characteristics.

[0002]

2. Description of the Related Art For example, wireless
s) 1394, IEEE 802.11a, HIPERL
High-speed digital communication systems in the 5 GHz band have been developed indoors and outdoors according to wireless communication standards such as AN / 2.

The main cause of transmission-specific degradation in these wireless communication systems is multipath fading due to reflection of multiple paths. Since the wavelength in the 5 GHz band is about 6 cm, the state of multipath fading changes not only due to slight changes in the position of the wireless device, but also due to movement of surrounding objects and human bodies, and the received power at the receiver changes greatly.

As a modulation method for realizing high-speed image transmission by wireless communication, OFDM (Orthogon) is used.
al Frequency Division Mul
A technique known as "tiplex: orthogonal frequency division multiplexing" is known. The OFDM modulation method is a multi-carrier modulation method and is a method of transmitting a signal in which digital modulated waves having quadrature carrier frequencies of several tens to several hundreds or, in some systems, several thousand are multiplexed.

This modulation method is resistant to frequency selective fading, and DFT (Di
scet Fourier Transform: discrete Fourier transform) or FFT capable of high-speed operation
(Fast Fourier Transform: Fast Fourier Transform) is used.

In an OFDM communication system, the performance of AGC is important because the error correction characteristics are greatly deteriorated by signal distortion. AGC is automatic gain control. In the receiver, it is a circuit that functions to keep the output constant by lowering the gain for strong radio waves and increasing the gain for weak radio waves. It automatically controls the amplification degree of the output and keeps the output constant regardless of the strength of the received radio wave.

In the conventional wireless communication system, the time constant of the AGC is set to be relatively large and the envelope of signal power is made to follow. For this reason, the AGC cannot follow in the section where the received signal greatly drops, and a decoding error occurs. This decoding error can be corrected using time interleaving.

However, in the indoor 5 GHz band wireless communication system, the signal strength changes relatively slowly. Therefore, it is necessary to lengthen the time interleave length,
The memory for this process becomes too large to be practical. Moreover, this is all the more true in a wireless communication system applied to an image transmission application that performs high-speed data communication.

Burst communication is used for intermittently transmitting a group of data, but since the transmission line characteristics change, in the communication of the wireless 1394 standard, a reference symbol is inserted in the middle of the burst and this reference symbol is used. Is used to estimate the transmission path. In this way, decoding errors are reduced by inserting reference symbols in the middle of the burst.

There has been a radio communication system for inserting a reference symbol in the middle of such a burst, and it is disclosed in, for example, Japanese Patent Laid-Open No. 2000-151548. However, unlike broadcast, burst communication ends in a short time in burst communication, so once the AGC gain is fixed with the preamble at the beginning of the burst,
I was trying to maintain that gain until the end of the burst.

Further, in the conventional indoor application, FM (Frequency Modulation) modulation is exclusively used, and in FM modulation, a limiter amplifier is used, so that AGC is not necessary.

FIG. 11 is a block diagram showing the structure of a conventional receiver. In FIG. 11, the automatic gain control amplification means 111 performs automatic gain control on the received signal to obtain an optimum signal level, and after the analog / digital converter 117 converts the analog signal into a digital signal, the OFD at the subsequent stage.
It outputs to the M demodulation means 112, the delay means 113, and the burst detection means 114.

The OFDM demodulation means 112 demodulates the modulated signal and outputs the demodulated signal. In the prior application by the present applicant (Japanese Patent Laid-Open No. 1-205278), the modulation signal is O
Since the FDM modulation method is described, the demodulation means is limited to the OFDM demodulation means.

The delay means 113 delays the received signal after the gain control by the automatic gain control amplification means 111 by the burst period.

The burst detecting means 114 detects the burst signal having the cycle determined by the communication system by correlating the received signal after the gain control by the automatic gain control amplifying means 111 and the delay signal by the delay means 113.

The packet detecting means 115 detects the unique word at the head of the packet from the demodulated signal burst-detected by the burst detecting means 114, and detects whether or not the packet is demodulated correctly.

Whether or not the automatic gain amplification control means 116 fixes the automatic control gain for the automatic gain control amplification means 111 based on the burst detection result by the burst detection means 114 and the packet detection result by the packet detection means 115. Take control. Automatic gain amplification control means 11
Reference numeral 6 fixes the automatic control gain for the automatic gain control amplifying means 111 when it judges that a packet is detected based on the burst detection result by the burst detection means 114 and the packet detection result by the packet detection means 115.

FIG. 12 is a flowchart showing the conventional AGC control. In FIG. 12, in step S11,
It will be in the state of waiting for the arrival of the received signal. Specifically, the burst detection unit 114 waits for the arrival of the burst signal. In step S12, it is determined whether or not a burst has been detected. Specifically, the burst detection unit 114 detects the preamble.

When a burst is detected in step S12, the AGC gain is fixed in step S13. Specifically, the automatic gain control amplification means 111 measures the energy of the detected preamble and adjusts and fixes the AGC gain to an appropriate gain.

In step S14, the AGC gain is fixed during demodulation and the process returns to step S11. Specifically, OF
When the DM demodulation means 2 starts demodulation, the demodulation operation is performed for a prescribed burst length. When the demodulation data to be demodulated by the OFDM demodulation means 2 is completed, the burst detection means 114 waits for the arrival of the burst signal again. If no burst is detected in step S12, the process returns to step S11. In this way, the AGC gain was controlled so as to be maintained at a constant value during the burst.

[0021]

In such a conventional communication system, MPEG (Moving) is one of the technologies attracting attention in high-speed wireless data transmission in a house.
Picture Experts Group) 2 and D
Transmission of V (Digital Video) images has been used. A transmitter applied to these applications needs to intermittently transmit a relatively long burst of about several msec. Then, in the receiver applied to these applications, when the AGC gain is fixed within one burst, the signal strength within the burst changes, so it becomes necessary to follow the AGC gain.

In recent years, the OFDM communication system has been used in the 5 GHz band, and the linearity has been required to be high in the decoding operation of the receiver. Therefore, AGC
Behavior is very important. However, there is a disadvantage that there is no receiver for tracking the AGC gain in order to perform such burst communication.

Furthermore, the change in the intensity of the received signal and the change in the channel response due to multipath fading are closely related. Therefore, it is necessary to estimate the channel response at the same time as AGC. But,
There is a disadvantage that there is no receiver capable of estimating the channel response at the same time as such AGC.

The present invention has been made in view of the above circumstances, and can perform transmission channel estimation even when the transmission channel state changes, and stably control not only FFT timing but also AGC. It is an object of the present invention to provide a receiving device and a receiving method capable of receiving a signal transmitted by the above.

[0025]

The receiving device and the receiving method of the present invention have the following operations by the following means. In a wireless communication system based on the wireless (Wireless) 1394 standard, a reference symbol can be inserted in the middle of a burst. Therefore, the AGC control gain is changed immediately before the timing of the reference symbol, and the gain is switched instantaneously. By the way, the channel estimation is performed again using the reference symbols.

As described above, if the AGC gain is changed immediately before the reference symbol, stable transmission signals can be received without affecting the transmission path estimation result.

Unlike the conventional radio communication system which performs AGC with a slow time constant, the present invention is characterized in that it follows a relatively high-speed change in signal strength of, for example, several Hz. Therefore, AGC control satisfying the following requirements is performed.

First, the time response of AGC is required. The time response of AGC is very fast, switching the gain between data symbols and reference symbols. In order to perform channel estimation and energy measurement after the gain is stabilized after switching, the time until the gain is stabilized needs to be an instant of several hundreds nsec, for example.

Second, the AGC gain is required to be kept constant. The AGC gain is kept constant in the section between the reference symbol and the next reference symbol.

Third, a time interval for switching the AGC gain is required. The time interval for switching the AGC gain is matched with the interval of reference symbols or an integral multiple thereof.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The receiving apparatus according to the present embodiment is a wireless LAN (L
A receiving device for performing burst-synchronous wireless communication such as an optical area network, in which a reference symbol is inserted into a data signal at regular intervals, and the level of the received signal is finely adjusted for each reference symbol. , More accurately realizes level correction in a multipath environment.

The present embodiment will be described below. FIG. 1 is a block diagram showing the configuration of a receiving apparatus of a burst communication system applied to this embodiment. In FIG. 1, the gain control amplification means 1 controls the received signal by the gain G to obtain an optimum signal level, and the analog / digital converter 8
After converting the analog signal into a digital signal by the, the signal is output to the OFDM demodulation means 2, the delay means 3 and the burst detection means 4 in the subsequent stage.

The OFDM demodulation means 2 demodulates the modulated signal and outputs the demodulated signal. The delay unit 3 delays the received signal after the gain control by the gain control amplification unit 1 by the burst period.

The burst detecting means 4 detects the burst signal having the cycle determined by the communication system by correlating the received signal after the gain control by the gain control amplifying means 1 and the delayed signal by the delay means 3.

The timing control means 5 decodes the packet information at the head of the packet from the demodulated signal burst detected by the burst detection means 4 and detects whether or not the packet is demodulated correctly. Also, the timing control means 5
Detects parameters related to packet and frame structure and outputs a sync timing window signal.

The gain control means 6 is a reception signal after the gain control by the gain control amplification means 1, a reception signal level by the reception signal power observing means 7 described later, a burst detection result (ΔPrx) by the burst detection means 4 and a timing control means. The gain control amplification means 1 according to the synchronization burst detection timing based on the synchronization timing window signal
The control gain G is changed to output a control gain signal for performing control so that the reception signal after gain control has an optimum signal level.

The received signal power observing means 7 observes the received signal power Prx and outputs the received signal power signal PrxRF.

An automatic gain control system for a 5 GHz band wireless LAN system will be described below as an example of a burst synchronous wireless communication system.

The 5 GHz band wireless LAN system employs the OFDM modulation method in order to realize excellent communication performance over a wide band.

The OFDM modulation system has high strength against ghosts and multipaths, but weak against circuit non-linearity. Therefore, if distortion occurs due to the conversion of the received signal in the analog / digital converter or the like, the quality of the received signal is significantly deteriorated.

For this reason, in the 5 GHz band wireless LAN system, a 1 called a preamble signal is added at the beginning of the modulated signal.
It is necessary to insert a burst signal of 0 to 20 μsc and perform timing synchronization within this section, while capturing the level of the voltage amplitude of the received signal input to the analog / digital converter 8 within a signal allowable range in which no distortion occurs. is there.

The second half of the preamble signal, μse
In c, a reference signal for observing a frequency characteristic of a transmission line called a reference symbol and correcting a data signal (actual communication data) following the preamble signal is contained. In the reference signal and the data signal, analog / It is not allowed to change the level of the digital signal after the digital converter 8, and therefore it is necessary to keep the gain by the gain control amplification means 1 constant.

Therefore, in the 5 GHz band wireless LAN system, a high-speed and high-performance automatic gain amplification system is required which captures a level within a signal allowable range in which distortion does not occur in 10 μsec.

In order to realize high-speed and high-performance level acquisition performed within the above-mentioned preamble section, the following four levels of level acquisition are performed.

As the first step, at the start of burst detection, the gain control means 6 outputs the gain control signal at the maximum value, the gain control amplification means 1 makes the gain control the maximum gain, and the burst detection means 4 makes the gain control amplification. Correlation between the received signal after the maximum gain control by the means 1 and the delay signal by the delay means 3 is performed to detect a burst signal having a cycle determined by the communication system.

At this time, the digital signal output of the analog / digital converter 8 is distorted, but since it is a preamble signal which is not a data signal, the quality of the received signal is not deteriorated.

Even if the preamble signal contains multipath distortion, burst detection can be performed without lowering the detection rate by using an autocorrelator in the burst detection means 4.

In this way, the arrival of the preamble signal at the head of the received signal is waited for. At the same time, the received signal power observing means 7 observes the received signal power Prx,
The received signal power signal PrxRF is output to the gain control means 6. Here, the steeple value is detected instead of the average value in order to cope with a sharp signal change. In addition, when the burst detection is started, a reset signal is given to reset the steeple value detection circuit,
Be sure to observe the maximum peak value after that.

As a second step, at the time of burst detection, the burst detection means 4 outputs a burst detection signal to the gain control means 6. In response to this, the gain control means 6 outputs a gain control signal to the gain control amplification means 1.

The gain control signal at this time is obtained by calculating the gain G based on the received signal power signal PrxPF observed by the received signal power observing means 7. This calculation formula assumes that the received signal power 1 is the received signal power observed by the received signal power observing means 7 and the reference signal power value 1 is an appropriate value that does not distort the digital signal output of the analog / digital converter 8. It is expressed by the following formula 1.

[0051]

## EQU1 ## Control gain 1 [dB] = received signal power 1 [dB]
v] -reference signal power value 1 [dBv]

However, the gain at this time includes analog signal processing in the process of calculating the steeple value of the received signal power,
A slight variation is included, and coarse gain control is performed.

Therefore, after passing through the analog / digital converter 8 without distortion with this gain, the gain control means 6 integrates the digital value of the received signal to measure an accurate signal power.

As a third step, after a certain amount of time has passed in the second step, the timing control means 5 outputs the synchronization timing signal to the gain control means 6. In response to this,
The gain control means 6 outputs to the gain control amplification means 1 a control gain signal calculated based on the digital integration value of the received signal which has passed through the analog / digital converter 8 without distortion, and the gain control amplification means 1 outputs the gain. Optimize. This calculation formula is obtained by integrating the received signal power 2 by the gain control means 6 and calculating analog /
When the received signal power after passing through the digital converter 8 and the reference signal power value 2 are the optimum values of the received signal power after gain control, they are expressed by the equation (2).

[0055]

## EQU00002 ## Control gain 2 [dB] = received signal power 2 [dB]
v] -reference signal power value 2 [dBv]

Thus, the optimized gain value is once fixed. In the conventional example, the gain remains fixed until the end of the burst thereafter.

The present embodiment is characterized by the operation of the fourth stage. That is, after the AGC gain is fixed in the third stage, the next reference symbol is sent after a lapse of time Tr. The timing control means 5 measures this time Tr and quickly updates the AGC gain at the boundary between the data signal and the reference symbol. For the control gain updated here, the same algorithm as the equation 2 is applied again. Thereafter, this fourth stage is applied repeatedly until the burst ends. As a result, it is possible to realize fast and accurate level capture to the optimum gain value.

In order to supplement the above description, 5GH
A description of some of the z-band wireless LAN systems will be given.

In the 5 GHz band wireless LAN system, the IE
EE802.11a, BRAN (HIPERLAN /
2) and wireless (Wireless) 1394.

Representative preamble signals for each system are shown in FIGS. 2-4 below. FIG. 2 shows the IEEE802.1
It is a figure which shows the structure of the preamble signal of 1a. In FIG. 2, B16 represents a burst pattern and a burst cycle, C32 represents a guard interval part, and C64 represents a reference signal.

FIG. 3 shows BRAN (HIPERLAN /
It is a figure which shows the structure of the preamble signal of 2). In FIG. 3, A16 represents the first burst pattern and the burst period, IA16 represents the first burst pattern in which the phase is inverted, B16 represents the second burst pattern and the period of the burst, and IB16 is the phase inverted. It represents the second burst pattern, C32 represents the guard interval part, and C64 represents the reference signal.

FIG. 4 shows a wireless network.
It is a figure which shows the structure of the 1394 preamble signal. In FIG. 4, A16 represents a burst pattern and a burst period, IA16 represents a phase-inverted burst pattern, C32 represents a guard interval part, and C64 represents a reference signal.

FIG. 5 shows a wireless network.
It is a figure which shows an example of the burst structure employ | adopted by 1394. Since the wireless communication system based on the wireless (Wireless) 1394 standard supports the synchronous transfer mode, it is possible to communicate temporally continuous signals such as video signals. However, when a data signal is communicated for a long period of time, in a multipath environment, the transmission characteristic of the burst B changes from the transmission characteristic of the reference signal R1 following the preamble signal P at the beginning of the received signal when it is received. As a result, the reception performance deteriorates.

Therefore, the reference signals R1, R2, R3, R4, R5 ... Are inserted in the data signal sections D1, D2, D3, D4, D5. Thereby, the reference signals R1 and R
The transmission characteristics are measured again every 2, R3, R4, R5, ... To prevent deterioration of the reception performance.

In this way, wireless (Wireless
s) In the 1394 standard wireless communication system, in order to support the synchronous transfer mode, the data signal sections D1, D
Reference signals R1, R2, R3, R4, R5 ... Are inserted at constant intervals Tr into 2, D3, D4, D5.

Therefore, in the present embodiment, the gain control from the gain control means 6 is performed at the timings T1, T2, T3, T4, T5 ... Of the reference signals R1, R2, R3, R4, R5. It is configured to change the signal. In this way, the reference signals R1, R2, R
3, R4, R5 ... Timing T1, T2, T3
At T4, T5, ..., By changing the gain control signal from the gain control means 6, fine adjustment of the level capture can be performed, thereby maintaining high quality reception performance in the synchronous transfer mode. Is possible.

Reference signals R1, R2, R
3, R4, R5 ... Timing T1, T2, T3
At T4, T5, ..., the gain control signals output from the gain control means 6 are the previous reference signals R1, R2, R.
It can be calculated using the equation 2 based on the integral value of the reference signals of 3, R4, R5 ...

According to the present embodiment described above, the wireless LA
In a burst-synchronous radio receiving apparatus such as N, when receiving a burst in which reference symbols are inserted in a data signal at regular intervals, level adjustment is finely adjusted for each reference symbol to enable It is possible to more accurately realize the level capture under the path environment.

FIG. 6 is a block diagram showing the structure of a transmitter of a general OFDM communication system. FIG. 6 shows a transmitter that transmits a burst in which reference symbols are inserted in a data signal at regular intervals.

In the OFDM modulation method, 16QAM (Qua
draw Amplitude Modulat
ion (Amplitude and Phase S
When combining multi-level modulation such as shift keying)), it is necessary to realize by synchronous detection.

In FIG. 6, the OFDM block 61 is
For example, a FEC Code (Forward E
After performing coding such as convolutional coding in the error correction unit, the MAP unit (not shown)
O for data D that has been mapped such as 6QAM
IFFT (Inverse FF) of the FDM block 61
The T) unit 62 performs an inverse FFT operation. After the inverse FFT operation, a GI (Gird Interval) inserting unit 63 inserts a guard interval to generate OFDM data.

Based on the timing signal from the timing control unit 66, the OFDM data generated by inserting the guard interval in the GI insertion unit 63 after the inverse FFT operation and the preamble generated by the preamble generation unit 64 are generated. Switching by the switching unit 65, the D / A (Dig
After being converted into an analog signal in the ital / Analog) section 67, the RF section 68 passes through an analog circuit section for high frequency processing, and is transmitted as a radio wave to a space which is a transmission path by an antenna 69. In this case, the reference repetition cycle is Tr.

FIG. 7 is a flowchart showing the AGC control. In FIG. 7, in step S1, the state of waiting for the arrival of the received signal is entered. Specifically, the burst detection means 4
Waits for the arrival of the burst signal. In step S2, it is determined whether or not a burst is detected. In particular,
The burst detection means 4 detects the preamble.

When a burst is detected in step S2, the AGC gain is fixed and the time Δ is increased in step S3.
Let t = 0. Specifically, the gain control means 6 measures the energy of the detected preamble and adjusts and fixes the AGC gain of the control gain signal to an appropriate gain. OFD
When the M demodulation means 2 starts demodulation, the demodulation operation is performed for a prescribed burst length. The gain control means 6 monitors the change in energy of the data signal during the burst.

In step S4, it is determined whether or not the burst has ended. Specifically, the burst detection means 4 detects the end of the burst after the start of demodulation. If the burst has not ended in step S4, the time Δ
When t = NTr (N is a positive integer, Tr is the interval between reference symbols), the AGC gain of the control gain signal is updated. After step S5, time Δt = 0 is set again in step S6, and the process returns to step S4. Specifically, since the reference signal arrives when the time Δt = NTr elapses after the start of the demodulation, the gain control means 6 adjusts the AGC gain to an appropriate gain immediately before this, thereby performing control at each reference symbol interval Tr. AGC of gain signal
Update the gain. The AGC gain of the control gain signal is maintained at a constant value during the interval Tr from the current reference symbol to the next reference symbol.

When no burst is detected in step S2, or when the burst ends in step S4, the process returns to step S1. Specifically, when the demodulated data to be demodulated by the OFDM demodulation means 2 is completed, the burst detection means 4 again waits for the arrival of the burst signal.

FIG. 8 is a block diagram showing the detailed structure of the receiver. FIG. 8 shows the structure of the OFDM demodulation means of the receiver shown in FIG. 1 in detail and explains the timing of updating the control gain signal. The parts corresponding to those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 8, the signal received by the antenna 9 is supplied to the gain control amplifying means 1 through the RF circuit (not shown) and the analog circuit part for high frequency processing.

The gain control amplifying means 1 applies the gain G to the received signal.
The analog signal is converted to a digital signal by the analog / digital converter 8 to be an optimum signal level controlled by the signal generator, and then output to the OFDM demodulation means 2, delay means 3 and burst detection means 4 in the subsequent stage.

The digital signal converted by the analog / digital converter 8 is synchronized by a synchronizing circuit such as packet synchronization, and the input data for the FFT operation is cut out by the GI removing unit (not shown) and then cut out. The input data for FFT calculation is supplied to the FFT unit 2a of the OFDM demodulation means 2. The OFDM demodulation means 2 demodulates the modulated signal and outputs the demodulated signal.

The data returned on the frequency axis, which has been subjected to the FFT operation on the basis of the FFT window Tw, which will be described later, in the FFT section 2a, and the update timing Tn, which will be described later, in the transmission path estimating means 2b.
The transmission path is estimated based on The data of which the transmission path has been estimated is corrected for the amplitude and phase of the signal by an equalizer (not shown) in the subsequent stage. Therefore, the equalizer is placed after the FFT transform process of the receiver. The equalizer estimates the state of the transmission line using a signal, reference symbol, and pilot carrier that are known in advance from the transmitter side.

Here, the symbol means when 64 points of data are cut out in the FFT conversion process.
Data of 52 points out of the 64 points is called a symbol. The reference symbol is an OFDM signal having a known pattern. The data symbol of user data is composed of a data carrier and a pilot carrier.

The output of the FFT conversion processing is 52 pieces of data for 52 carriers. With this data, the amplitude and phase distortion due to the influence of the transmission path such as multipath can be removed by finely adjusting the AGC gain of the control gain signal in the gain control amplification means 1 described later.

The delay means 3 delays the received signal after the gain control by the gain control amplification means 1 by the burst period.

The burst detecting means 4 detects the burst signal having the cycle determined by the communication system by correlating the received signal after the gain control by the gain control amplifying means 1 and the delayed signal by the delay means 3. Here, the delay unit 3 and the burst detection unit 4 form a correlator. Then, the burst detection means 4 uses a trigger Tr indicating the start timing of the burst.
ig is output to the timing control means 5a and the signal energy ΔPrx is output to the gain control means 6.

The timing control means 5 decodes the packet information at the head of the packet from the demodulated signal burst detected by the burst detection means 4 and detects whether or not the packet has been demodulated correctly. Also, the timing control means 5
Detects the parameters related to the packet and frame structure, and based on the trigger Trig, the FFT window signal Tw
Is output to the FFT unit 2a and the update timing signal Tn of the control gain signal is output to the gain control means 6 and the transmission path estimation means 26.

The update timing signal Tn of the control gain signal output from the timing control means 5 is the timing immediately before the reference signal.

The gain control means 6 is a reception signal after the gain control by the gain control amplification means 1, a reception signal level by the reception signal power observing means 7 described later, a burst detection result (ΔPrx) by the burst detection means 4 and a timing control means. Based on the synchronization timing window signal Tw by 5, the control gain G for the gain control amplification means 1 is changed in accordance with the synchronization burst detection timing, and control is performed so that the reception signal after gain control becomes the optimum signal level. Output a control gain signal for

The received signal power observing means 7 observes the received signal power Prx and outputs the received signal power signal PrxRF to the gain control means 6.

The received signal power Prx is the received signal power signal PrxRF output from the received signal power observing means 7.
And the signal energy ΔPrx output from the burst detecting means 4 is obtained by the following equation (3).

[0091]

(3) Prx = PrxRF + ΔPrx

When the input power of the FFT section 2a is PBB, the AGC gain G is determined so that PBB has a constant value, that is, the equation (4).

[0093]

(4) PBB = Prx / G = constant

Since Prx changes and PBB changes every time Tr, the AGC gain G is updated so that PBB becomes a constant value.

Another concrete method of monitoring the signal power will be described below. To update the AGC gain at time t = NTr (N is a positive integer), there is a method of utilizing the energy of the reference signal before Δt = NTr. The energy Prx {(N-1) Tr} of the reference at t = (N-1) Tr is PrxRF and ΔPr.
Calculate from x and save. A new gain G (NTr) is obtained from these values and updated at time t = NTr.

In a multi-level modulation method such as 16QAM in which information is placed on the amplitude, the receiver must correct the phase and amplitude for each carrier, and an equalizer for this purpose is required. The equalizer is a device for performing a process of returning the transmitted signal to its original state when the transmitted signal is distorted such as a change in amplitude or a rotation of phase due to the influence of a transmission line such as fading.

The principle of the equalizer is realized by estimating the transfer function of the transmission line and applying the inverse filter to the received signal to cancel the distortion of the transmission line. In a wireless communication system based on the OFDM modulation method, data on the frequency axis can be held after the FFT conversion processing, and thus an equalizer for the OFDM modulation method is often arranged after the FFT conversion processing.

FIG. 9 is a waveform diagram showing AGC control.
9A shows the received power Prx, FIG. 9B shows the transmitted signal, FIG. 9C shows the FFT input, FIG. 9D shows the AGC gain of the control gain signal, and FIG. 9E shows the FFT input after control.

FIG. 9A shows the time change of the received power Prx. In FIG. 9B, a burst signal pattern indicating the positions of the preamble P, the reference R, and the data symbol D of the burst is shown. In FIG. 9C, the time change of the envelope 91 of the FFT input is shown.
In FIG. 9D, the time variation of the AGC gain of the control gain signal 92 is shown. In FIG. 9E, the amplitude 93 of the signal after gain control by AGC is represented.

As shown in FIG. 9A, when the received power Prx, which is the signal strength, changes, if the AGC gain of the control gain signal is fixed as in the conventional case, the signal as shown by the envelope 91 of the FFT input in FIG. 9C is obtained. What caused the intensity to change and the demodulation error to increase is also shown in FIG. 9D for each timing Tr of the reference symbol R shown in FIG. 9B.
By changing the AGC gain of the control gain signal 92 as described above, the signal strength is maintained at a substantially constant value and the demodulation error is reduced as shown in the controlled signal amplitude 93 of the FFT input after control in FIG. 9E. You will be able to.

FIG. 10 shows AGC update timing and FFT.
It is a figure which shows generation | occurrence | production of a window timing. In FIG.
The timing control means 5a generates the AGC update timing Tn at which the control gain signal is updated and the FFT window timing Tw indicating the start of the FFT calculation section. The two timings are as follows. First, the AGC update timing Tn is output at the timing immediately before the reference R. When the fixed offset time OFS has elapsed from the AGC update timing Tn output at the timing immediately before the reference R, the FFT window timing Tw
Is output.

In this way, the AGC gain of the control gain signal is updated at the AGC update timing Tn, and the received signal after control is subjected to the FFT section at the FFT window timing Tw for the data symbol of 52 points out of the 64 points of the OFDM symbol. FF of OFDM demodulator 2
The FFT calculation is performed by the T unit 2a.

As a result, by changing the AGC gain of the control gain signal at each reference symbol timing, the controlled signal amplitude of the FFT input after control becomes substantially constant, and the signal strength is maintained at a substantially constant value. Therefore, the demodulation error due to the FFT calculation can be reduced.

Further, since the FFT window timing Tw is output when the fixed offset time OFS has passed from the AGC update timing Tn, the FFT window timing Tw is applied to the 52-point data symbol of the 64 OFDM symbol points. FFT by the FFT unit 2a of the OFDM demodulation unit 2 at extremely high speed in the FFT section
Can perform operations.

In the above-described present embodiment, wireless (Wireless) that defines a wireless network is defined.
s) Although the example in 1394 is shown, the invention is not limited to this, and may be applied to other IEEE 802.11a and HIPERLAN / 2.

[0106]

The receiving apparatus of the present invention receives a modulated signal wirelessly transmitted by modulating a signal in which a plurality of reference symbols are inserted in a data symbol insertion area for burst communication by a predetermined wireless communication method. In the receiving device that demodulates by demodulating, the burst detection means for detecting the data symbol of the burst period from the received signal and measuring the intensity of the received signal, and the received signal is amplified by the gain control amplification means from the level of the detected received signal. To a predetermined level and the gain of amplification is held every reference symbol period from the reference symbol and updated at a predetermined update timing, and an update timing to update the gain of amplification to the automatic gain control means. Control means for generating a value such that is a positive integer multiple of the reference symbol Since it is equipped with a burst-synchronous radio receiving device such as a wireless LAN, when a burst in which reference symbols are inserted in a data signal at regular intervals is received, level adjustment is finely adjusted for each reference symbol. By doing so, it is possible to more accurately realize level capture in a multipath environment, and it is possible to prevent deterioration of communication quality in a multipath environment.

Further, in the above-described radio communication system, the receiving apparatus of the present invention is a radio communication system in which a signal in which a plurality of reference symbols are inserted in a data symbol insertion area for burst communication is modulated by using a plurality of carriers. It is a frequency division multiplexing system, and further comprises fast Fourier transform means capable of high speed computation for demodulating a plurality of carriers, and the timing control means further generates the start timing of the computation period for the fast Fourier transform means.
By changing the control gain signal at each reference symbol timing, the controlled signal amplitude of the FFT input after control becomes almost constant and the signal strength is maintained at a substantially constant value, so that the demodulation error due to the FFT calculation is reduced. There is an effect that can be done.

Further, in the above-described receiving apparatus of the present invention, since the start timing of the calculation period for the fast Fourier transform means generated by the timing control means is generated based on the update timing, only the offset time is added from the update timing. Since the operation timing is output when the time has elapsed, the FFT operation by the fast Fourier transform means of the OFDM demodulation unit is performed very quickly in the FFT section with the operation timing for the data symbol of 52 points out of the 64 points of the OFDM symbol. There is an effect that it can be performed.

Further, according to the receiving method of the present invention, a signal in which a plurality of reference symbols are inserted in a data symbol insertion area for burst communication is modulated by a predetermined wireless communication system to receive a modulated signal wirelessly transmitted. In the receiving method of demodulating by demodulating, a burst detection step of detecting a data symbol of a burst period from the received signal and measuring the intensity of the received signal, and amplifying the received signal by the gain control amplification means from the level of the detected received signal. To a predetermined level and the gain of amplification is held every reference symbol period from the reference symbol and updated at a predetermined update timing, and an update timing to update the gain of amplification for the automatic gain control step. To generate a positive integer multiple of the reference symbol. And a burst synchronization type wireless reception method for a wireless LAN or the like, wherein a level for each reference symbol is received when receiving a burst in which reference symbols are inserted in a data signal at regular intervals. By finely adjusting the acquisition, it is possible to more accurately realize the level acquisition in the multipath environment, and it is possible to prevent the deterioration of the communication quality in the multipath environment.

Further, in the above-mentioned receiving method of the present invention, the wireless communication method is an orthogonal method for modulating a signal in which a plurality of reference symbols are inserted in a data symbol insertion area for burst communication using a plurality of carriers. It is a frequency division multiplexing system, and further comprises a fast Fourier transform step capable of high-speed calculation for demodulating a plurality of carrier waves,
Since the timing control step further generates the start timing of the calculation period for the fast Fourier transform step, by changing the control gain signal at each timing of the OFDM reference symbol, the controlled signal amplitude of the FFT input after control is almost the same. Since the signal strength becomes constant and the signal strength is maintained at a substantially constant value, it is possible to reduce the demodulation error due to the FFT calculation.

In the above receiving method of the present invention, since the start timing of the calculation period for the fast Fourier transform step generated by the timing control step is generated based on the update timing, the OFD
It is possible to perform the FFT operation by the fast Fourier transform means of the OFDM demodulation unit very quickly in the FFT interval at the operation timing for the data symbol of 52 points out of the 64 points of the M symbol at the operation timing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a receiver of a burst communication system applied to this embodiment.

FIG. 2 is a diagram showing a preamble structure of IEEE 802.11a.

FIG. 3 is a diagram showing a preamble structure of BRAN (HIPERLAN / 2).

FIG. 4 is a diagram showing a preamble structure of wireless 1394;

FIG. 5 is a diagram showing an example of a structure of a burst adopted in Wireless (1394).

FIG. 6 is a block diagram showing a configuration of a transmitter.

FIG. 7 is a flowchart showing AGC control.

FIG. 8 is a block diagram showing a detailed configuration of a receiver.

9A and 9B are waveform diagrams showing AGC control, FIG. 9A is received power, FIG. 9B is a transmitted signal, FIG. 9C is FFT input, and FIG. 9D.
Is the AGC gain, and FIG. 9E is the FFT input after control.

FIG. 10 is a diagram showing generation of AGC update timing and FFT window timing.

FIG. 11 is a block diagram showing a configuration of a conventional receiver.

FIG. 12 is a flowchart showing conventional AGC control.

[Explanation of symbols]

1 ... Gain control amplification section, 2 ... OFDM demodulation section,
3 ... Delay means, 4 ... Burst detection means, 5 ... Timing control means, 6 ... Gain control means, 7 ... Received signal power observation means, 8 ... Analog / digital converter, 9 ...
... antenna, B16 ... burst, A16 ... burst, IB16 ... phase inversion pattern, IA16 ... phase inversion pattern, C32 ... guard interval, C64.
...... Reference, P ... Preamble, R1 to R5 ...
... Reference, D1-D5 ... Data, B ... Burst, T1-T5 ... AGC gain update timing, Tr
...... Reference timing, 61 …… OFDM block, 62 …… IFFT, 63 …… GI insertion section, 64 ……
Preamble generator, 65 ... Switching unit, 66 ... Timing control unit, 67 ... D / A unit, 68 ... RF unit, 69
... antenna, 2a ... FFT, 2b ... transmission path estimation means, 5a ... timing control means, 91 ... envelope, 9
2 ... Gain control signal, 93 ... Controlled signal amplitude, 5
a ... timing control means, Tn ... AGC update timing, Tw ... FFT window timing, OFS ... fixed offset

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Komori             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Masataka Wakamatsu             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Kazuyuki Saijo             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Shinichi Tanabe             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Hideo Morohashi             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Kazuhiro Fujimura             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5K022 DD01 DD33

Claims (6)

[Claims] 1. A receiving apparatus for modulating a signal, in which a plurality of reference symbols are inserted into a data symbol insertion area for burst communication, by a predetermined wireless communication method to receive and demodulate a modulated signal wirelessly transmitted, Burst detection means for detecting the data symbol of the burst period from the received signal and measuring the strength of the received signal, and the received signal is amplified to a predetermined level by the gain control amplification means from the detected level of the received signal. At the same time, the gain of the amplification is held by the automatic gain control means for holding it for each period of the next reference symbol from the reference symbol and updating it at a predetermined update timing, and the update timing for updating the gain of the amplification for the automatic gain control means. Timing control procedure to generate a positive integer multiple of the reference symbol A receiver comprising a step. 2. The receiving apparatus according to claim 1, wherein the wireless communication system modulates a signal in which a plurality of reference symbols are inserted in a data symbol insertion area for burst communication using a plurality of carrier waves. It is a frequency division multiplex system, and further comprises a fast Fourier transform means capable of high speed computation for demodulating the plurality of carrier waves, and the timing control means further generates start timing of a computation period for the fast Fourier transform means. A receiving device characterized by the above. 3. The receiving apparatus according to claim 2, wherein the start timing of the calculation period for the fast Fourier transform means generated by the timing control means is generated based on the update timing. apparatus. 4. A reception method for modulating a signal in which a plurality of reference symbols are inserted into a data symbol insertion area for burst communication by a predetermined wireless communication system to receive and demodulate a modulated signal wirelessly transmitted, A burst detection step of detecting the data symbol of the burst period from the received signal and measuring the intensity of the received signal, and amplifying the received signal from the detected level of the received signal to a predetermined level by gain control amplification means. At the same time, the gain of the amplification is held for each period of the next reference symbol from the reference symbol and updated at a predetermined update timing, and the update timing for updating the gain of the amplification with respect to the automatic gain control step. A tie that is generated to be a positive integer multiple of the reference symbol. And a ming control step. 5. The receiving method according to claim 4, wherein in the wireless communication system, a signal in which a plurality of reference symbols are inserted in a data symbol insertion area for burst communication is modulated using a plurality of carrier waves. It is a frequency division multiplexing system, and further comprises a fast Fourier transform step capable of high-speed computation for demodulating the plurality of carrier waves, and the timing control step further generates a start timing of a computation period for the fast Fourier transform step. A receiving method characterized by the above. 6. The reception method according to claim 5, wherein the start timing of the calculation period for the fast Fourier transform step generated by the timing control step is generated based on the update timing. Method.