JP4977092B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system that performs wireless communication using a frequency hopping method.

In recent years, in short-range wireless communication, wireless USB has attracted attention because it can realize high-quality communication of video and sound and exchange of a large amount of data between personal computers and AV devices. This wireless USB employs a UWB (Ultra Wideband) system promoted by WiMedia Alliance as a wireless communication system. UWB has low power consumption, and can communicate at a speed much higher than the currently popular IEEE802.11a / b / g. It is expected to be installed in various devices.
6 to 8 are diagrams showing frequency band usage methods in the UWB method.
In UWB, as shown in FIG. 6, the 3.1 to 10.6 GHz band is divided into 14 bands by 1 band of 528 MHz band, and numbers are assigned as band # 1 and band # 2 from the lower band. Three bands are grouped and called channels # 1 to # 5. Further, when communication is performed on channel # 1, depending on the hopping pattern, communication may be performed using only one band as shown in FIG. 7, or communication may be performed using three bands as shown in FIG. it can. When the hopping pattern uses three bands, communication is performed using a very wide band of 1584 MHz because three bands of one 528 MHz band are used.
Thus, UWB communicates using a very wide frequency band. However, it is very difficult to design the frequency characteristics of components such as antennas, filters, baluns, RF chips (such as LNA (Low Noise Amplifier) and Mixer) flat over a wide band. For this reason, it is rare that the frequency characteristics of the band used for communication are flat.

FIG. 9 is a diagram illustrating an example of frequency characteristics of channel # 1. Compared to band # 2, band # 1 has less attenuation of 2 dB power, whereas band # 3 attenuates power by 2.2 dB more. When performing frequency hopping in such a band having non-flat frequency characteristics, AGC (Auto Gain Control) processing is always a problem. In UWB, 21 symbols are provided as a packet synchronization signal. During this period, not only AGC but also packet detection and symbol position synchronization must be established.
Furthermore, since one symbol is as short as 312.5 nsec, the time available for AGC is very short. Therefore, it is difficult to perform AGC processing in each of the three bands. In general, therefore, the gain is determined by averaging the symbols of the three bands. However, if AGC processing is performed with an average of three bands, a problem occurs when the frequency characteristics are not flat as shown in FIG.
In other words, in FIG. 9, if the AGC process is performed with the average of three bands and the gain is set, the band # 2 can be set with an almost appropriate gain and can be received without error, but the band # 3 is further attenuated, so the reception The amplitude of the signal waveform is reduced. In UWB, the sampling frequency of ADC becomes high due to its wide bandwidth, and it is generally difficult to use a high resolution ADC, and a low resolution ADC is often used. The error is likely to occur due to the influence of the conversion error.
In band # 1, the signal waveform is further severe and the signal waveform is not sufficiently attenuated, so that the waveform is clipped and distorted by the ADC, so that an error is more likely to occur and the throughput is reduced.

In order to solve this problem, in the technique disclosed in Patent Document 1, transmission power is controlled using a noise level measured in advance. By using this technique, the SNR (S / N ratio) in each band becomes constant, but the transmission power differs depending on the noise, so naturally the amplitude of the received signal waveform differs in each band.
Therefore, it is indispensable to perform AGC processing for each band. However, since the processing is difficult as described above, an appropriate gain cannot be set, and an error is likely to occur due to quantization error or distortion, resulting in a decrease in throughput. There was a problem.
In the technique disclosed in Patent Document 2, the transmission power is controlled according to the spatial propagation loss characteristic corresponding to the hopping frequency. However, this technique corrects the frequency characteristics in each band of the transmitter and corrects a certain amount of spatial propagation loss. However, since the frequency characteristics of the receiver cannot be predicted at all, an appropriate gain cannot be set, and quantum There is a problem that errors are likely to occur due to conversion errors and distortions, and throughput is reduced.
Japanese Patent Laid-Open No. 2005-198094 JP 2005-269202 A

  In view of the above problems, the present invention controls transmission power based on power attenuation in each band of a wireless communication apparatus measured in advance in a broadband wireless communication system using a frequency hopping method, and flattens frequency characteristics between the bands. Accordingly, an object of the present invention is to provide a wireless communication system that can prevent the AGC process from being complicated and the throughput from being lowered.

  In order to solve such a problem, the invention according to claim 1 uses a plurality of frequency bands to transfer data between the first wireless communication device on the reception side and the second wireless communication device on the transmission side. A radio communication system using a frequency hopping method for transmitting and receiving, wherein the first radio communication device receives a high frequency radio signal composed of a plurality of frequency bands from the second radio communication device. A receiving-side RF unit that performs frequency conversion processing of the received high-frequency radio signal, and a power attenuation amount from an input to the receiving-side antenna unit to an output from the receiving-side RF unit for each of a plurality of frequency bands First storage means for measuring and storing in advance, and when performing a connection operation with the second wireless communication apparatus, the power attenuation amount stored in the first storage means Wireless communication equipment And the second wireless communication device converts the signal for transmission to the first wireless communication device into a high-frequency wireless signal composed of a plurality of frequency bands, and a conversion side RF unit A transmission-side antenna unit that transmits the high-frequency radio signal that has been transmitted to the first wireless communication device, and transmission power from the transmission-side antenna unit based on the power attenuation amount transmitted from the first wireless communication device Transmission power control means for controlling the transmission.

In the invention according to claim 2, the second wireless communication apparatus is configured such that, for each of a plurality of frequency bands, power attenuation from input to the transmission-side RF unit to output from the transmission-side antenna unit. Second storage means for measuring and storing the power in advance, wherein the transmission power control means transmits the power attenuation amount transmitted from the first wireless communication apparatus and the power attenuation amount stored in the second storage means. The wireless communication system according to claim 1, wherein transmission power from the transmission side antenna unit is controlled based on the transmission side antenna unit.
The invention according to claim 3 is characterized by the wireless communication system according to claim 1 or 2 using a communication path different from data transmission / reception in the connection operation.

  According to the present invention, in a broadband wireless communication system using a frequency hopping method, transmission power is controlled by a power attenuation amount in each band of a wireless communication apparatus measured in advance, and frequency characteristics between the bands are flattened. Thus, it is possible to provide a wireless communication system capable of preventing the throughput from decreasing without complicating the AGC process.

Hereinafter, preferred embodiments of the present invention will be described.
FIG. 1 is a configuration diagram of a typical communication system to which a wireless communication apparatus of the present invention is applied.
For example, it is composed of a printer A incorporating a first wireless communication device as a reception side and a personal computer B incorporating a second wireless communication device as a transmission side. Assume wireless communication.
FIG. 2 is a diagram illustrating a detailed configuration example of the wireless communication system of the present invention, where (a) is a diagram illustrating a configuration of the first wireless communication device, and (b) is a configuration of the second wireless communication device. FIG.
Here, only functional units related to the present invention are shown, and other functional units related to reception and transmission are omitted.
In FIG. 2A, the first wireless communication apparatus performs reception and transmission antennas 1 and 2 for performing frequency conversion processing for transmitting and receiving high-frequency wireless signals composed of a plurality of frequency bands with the second wireless communication apparatus. The RF unit (reception side RF unit) 3 that performs the frequency conversion processing by transmitting the RF signal performed to the transmitting antenna 2 and receiving the RF signal from the receiving antenna 1 and digitally converting the signal from the RF unit 3 ADC (Analog Digital Converter) unit 4, baseband unit 5 including demodulation unit 6 that demodulates the converted received data and modulation unit 7 that modulates transmission data, connection operation control, and transmission power by transmission power control unit 9 The protocol control unit 8 performs control, the DAC (Digital Analog Converter) unit 10 converts transmission data into an analog signal, and the ROM (first storage device) 11.
The transmission power control unit 9 may be provided not only in the protocol control unit 8 but also in the baseband unit 5. The antennas 1 and 2 may be shared for transmission and reception.

In FIG. 2B, the second wireless communication device performs a frequency conversion process with the reception antenna 21 and the transmission antenna 22 that transmit and receive high-frequency wireless signals composed of a plurality of frequencies with the first wireless communication device. The RF unit (reception side RF unit) 23 that transmits the received RF signal to the transmitting antenna 22 and receives the RF signal from the receiving antenna 21 and performs frequency conversion processing, and digitally converts the signal from the RF unit 23 An ADC (Analog Digital Converter) unit 24, a baseband unit 25 including a demodulation unit 26 that demodulates converted reception data and a modulation unit 27 that modulates transmission data, connection operation control, and transmission power control by a transmission power control unit 29 A protocol control unit 28 for performing transmission and a DAC (Digital Analog Converter) unit 30 for converting transmission data into an analog signal.
The transmission power control unit 29 may be provided not only in the protocol control unit 28 but also in the baseband unit 25. The antennas 21 and 22 may be shared for transmission and reception.
Before performing communication such as during a manufacturing test, use a measuring device such as a signal generator to measure the power attenuation for each frequency band (for each band) in the RX chain part (from antenna input to RF part output) in FIG. deep. At this time, measurement may be performed using a single tone signal or using a UWB signal. The measured power attenuation amount is stored in the ROM 11.
FIG. 3 is a table showing the amount of power attenuation when the lowest band in each channel is used as a reference.
Since communication using three bands can transmit 10 LOG10 (3) dB transmission power larger than communication using only one band, the limiter does not increase the transmission power by more than 10 LOG10 (3) dB than the reference value. It is okay to spend. Further, the power attenuation amount stored in the ROM may be a relative value or an absolute value as shown in FIG.

FIG. 4 is a diagram showing a part of a connection procedure in the wireless communication system of the present invention.
As shown in FIG. 4, when USB wireless communication is performed between the first wireless communication device (printer A) and the second wireless communication device (PC B), after connection operation of identification, authentication, and permission is performed. Encrypted data communication is performed, but after identification and authentication, the power attenuation in the RX chain unit measured by the first wireless communication device and stored in the ROM 11 is transmitted to the second wireless communication device. is doing.
Thereafter, the second wireless communication apparatus transmits data while controlling the transmission power in each band based on the power attenuation amount in the first wireless communication apparatus received during the connection operation. For example, when transmission is performed on channel # 1 using the power attenuation amount of FIG. 3, band # 2 is attenuated by 2 dB more than band # 1, so when transmitting band # 2, it is 2 dB more than band # 1. Increase transmission power.
In this way, by controlling the transmission power using the power attenuation measured in advance, it is possible to correct the difference between the bands of the frequency characteristics generated in the receiver and flatten the frequency characteristics. In addition, in order to ensure connectivity, power attenuation is generally sent to the transmitter during connection operations that are transmitted at the lowest data rate, so the effects of differences in frequency characteristics between bands are minimized. And a reduction in throughput during data transmission can be prevented.
In the example of FIG. 4, the power attenuation amount is transmitted after identification and authentication, but may be transmitted by any procedure of connection operation. The transmission of the power attenuation amount may be added to the end of the authentication or permission frame, even if it is not a special procedure. This connection procedure is generally performed at the lowest data rate to ensure connectivity. Therefore, it is strong against the influence of the frequency difference between the bands, and an error hardly occurs.

Next, another embodiment of the wireless communication system of the present invention will be described.
FIG. 5 is a diagram illustrating a configuration example of the second wireless communication apparatus in the present embodiment.
As shown in FIG. 5, the second wireless communication apparatus includes a ROM (second storage device) 31 in addition to the configuration of FIG.
Before performing communication such as during a manufacturing test, a first radio communication device is measured by measuring the power attenuation amount of the TX chain unit (from the RF unit input to the antenna output) in FIG. 5 using a measuring device such as a signal generator. Is stored in the ROM 41 in the same manner as the power attenuation amount of the RX chain portion. Based on the power attenuation amount in the TX chain of the second wireless communication device stored in the ROM 41 in addition to the power attenuation amount in the first wireless communication device received during the connection operation as shown in FIG. Data is transmitted while the transmission power control unit 29 controls the transmission power in each band.
In this way, in addition to the difference between the frequency characteristic bands generated in the first wireless communication device (reception side), the difference between the frequency characteristic bands generated in the second wireless communication device (transmission side) is also corrected. Since the frequency characteristic can be flattened, it is possible to prevent the throughput from further decreasing.

By the way, in wireless USB, in order to establish a connection, information called a connection context (CC) must be shared between the host and the device. Therefore, in order to connect, it is necessary to transfer the CC from the host to the device in advance. Among these transfer methods, the method with the highest security performs CC transfer using a USB cable or the like without using UWB wireless communication. That is, at the time of CC transfer performed before the procedure of FIG. 4, the power attenuation amount in the RX chain unit measured by the first wireless communication device and stored in the ROM 11 is transmitted to the second wireless communication device via the USB cable. . The subsequent connection operation and data transmission are performed while controlling the transmission power in each band by the power attenuation amount as described above.
In this way, by using a communication path that is different from normal data transmission, such as a cable, for connection operation, it is possible to prevent errors due to differences in frequency characteristics between bands during connection operation. The transmitted power attenuation can prevent the throughput from decreasing even during data transmission.

The block diagram of the typical communication system to which the wireless communication apparatus of this invention is applied. The figure which shows the detailed structural example of the radio | wireless communications system of this invention. The figure which showed the amount of power attenuation | damping when using the lowest band in each channel as a table | surface. The figure which showed a part of connection procedure in the radio | wireless communications system of this invention. The figure which shows the structural example of the 2nd radio | wireless communication apparatus in this embodiment. The figure which shows the usage method (the 1) of the frequency band in UWB. The figure which shows the usage method (the 2) of the frequency band in UWB. The figure which shows the usage method (the 3) of the frequency band in UWB The figure which shows an example of the frequency characteristic of channel # 1.

Explanation of symbols

  1,21 Reception antenna unit, 22 Transmitting antenna, 3, 23 RF unit, 4, 23 ADC unit, 5, 25 Baseband unit, 6, 26 Demodulation unit, 7, 27 modulation unit, 8, 28 Protocol control unit 9, 29 Transmission power control unit, 10, 30 DAC unit, 31 ROM

Claims (3)

A wireless communication system that uses a frequency hopping method that transmits and receives data between a first wireless communication device on a reception side and a second wireless communication device on a transmission side using a plurality of frequency bands,
The first wireless communication device is:
A receiving-side antenna unit that receives a high-frequency wireless signal composed of a plurality of frequency bands from the second wireless communication device;
A receiving-side RF unit that performs frequency conversion processing of the received high-frequency radio signal;
For each of a plurality of frequency bands, the first storage means for measuring and storing in advance power attenuation from the input to the reception side antenna unit to the output from the reception side RF unit,
When performing a connection operation with the second wireless communication device, the power attenuation amount stored in the first storage unit is transmitted to the second wireless communication device,
The second wireless communication device is:
A transmission-side RF unit that converts a signal to be transmitted to the first wireless communication device into a high-frequency wireless signal composed of a plurality of frequency bands;
A transmitting-side antenna unit that transmits the converted high-frequency radio signal to the first radio communication device;
Transmission power control means for controlling transmission power from the transmission-side antenna unit based on the power attenuation amount transmitted from the first wireless communication device;
A wireless communication system comprising: The second wireless communication device is:
For each of a plurality of frequency bands, a second storage means for measuring and storing in advance power attenuation from the input to the transmission-side RF unit to the output from the transmission-side antenna unit is provided,
The transmission power control unit controls transmission power from the transmission side antenna unit based on the power attenuation amount transmitted from the first wireless communication apparatus and the power attenuation amount stored in the second storage unit. The wireless communication system according to claim 1, wherein:   3. The wireless communication system according to claim 1, wherein a communication path different from data transmission / reception is used in the connection operation.

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