JP2006005498A - Wireless communication system, wireless communication apparatus, wireless communication method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily receive a reflected wave from a reflector with respect to a carrier wave transmitted from a reflected wave reader, regardless of influences such as attenuation on a transmission path.
A reflected wave reader increases the output of a carrier wave when it is determined that the reception state of the reflected wave from the reflector is poor based on the RSSI value. The reception situation where the output of the carrier wave is reflected in the output of the reflected wave is improved. By setting the reception sensitivity for the reflected wave in the reflected wave reader to a known value and setting the difference between the received sensitivity and the measured received signal intensity as the increment of the carrier output, the output of the carrier wave on the reflected wave reader side, It can be adaptively controlled according to the positional relationship with the reflector and the communication status.
[Selection] Figure 1

Description

  The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program that realize a communication operation with low power consumption between devices in a relatively short distance, and in particular, a carrier wave from the reflected wave reader side. Wireless communication system, wireless communication apparatus and method, and computer program for performing data communication using reflected wave modulation based on switching of antenna load impedance on the reflector side, etc. About.

  More specifically, the present invention relates to a radio communication system, a radio communication apparatus, and a radio communication that can properly receive a reflected wave from a reflector with respect to a carrier wave transmitted by a reflected wave reader regardless of the position and situation of the reflector. In particular, a radio communication system, a radio communication apparatus, and a computer program for receiving a reflected wave from a reflector with respect to a carrier wave transmitted by a reflected wave reader, irrespective of influences such as attenuation on a transmission path, and the like The present invention relates to a wireless communication method and a computer program.

  By connecting a plurality of devices to the network, it is possible to achieve efficient command and data transmission, sharing information resources, and sharing hardware resources. More recently, wireless networks have attracted attention as systems that release users from wired wiring.

  As a standard for wireless networks, IEEE (The Institute of Electrical and Electronics Engineers) 802.11 (for example, refer to Non-Patent Document 1), HiperLAN / 2 (for example, Non-Patent Document 2 or Non-Patent Document) 3), IEEE 802.15.3, Bluetooth communication, and the like. In recent years, wireless LAN systems have become popular, coupled with the fact that wireless LAN systems have become cheaper and have been built into PCs as standard.

  A relatively small wireless communication system is used for data transmission between a host device and a terminal device in a home or the like. Examples of the host device mentioned here include stationary home appliances such as a television, a monitor, a printer, a PC, a VTR, and a DVD player. Examples of terminal devices include mobile devices such as digital cameras, video cameras, mobile phones, personal digital assistants, and portable music players that want to minimize power consumption. An application of this type of system is uploading image data taken with a mobile phone with a camera or a digital camera to a PC via a wireless LAN.

  However, the wireless LAN is originally designed and developed on the assumption that it is used in a computer, and its power consumption becomes a problem when mounted on a mobile device. Many of the IEEE802.11b wireless LAN cards currently on the market have a power consumption of 800 mW or more when transmitting and 600 mW or more when receiving. This power consumption is a heavy burden for battery-powered portable devices.

  Even if the wireless LAN function is operated in a limited range and the transmission power is reduced, the power consumption can be reduced by only about 80%. In particular, since transmission from an image input device such as a digital camera to the image display device is in a communication form in which the transmission ratio occupies the entire communication, wireless transmission means with low power consumption is still required.

  As for Bluetooth communication, the maximum transmission speed is as low as 720 kbps, and it is time-consuming and inconvenient for the recent high-quality image transmission.

  On the other hand, according to wireless transmission using reflected waves based on the back scatter method used in RFID, that is, reflected wave transmission, for example, in a communication mode in which the transmission ratio occupies most of the communication between devices, low power consumption Can be realized.

  The reflected wave transmission system includes a reflector that transmits data using a reflected wave subjected to modulation processing, and a reflected wave reader that reads data from the reflected wave from the reflector. During data transmission, the reflected wave reader transmits an unmodulated carrier. On the other hand, the reflector transmits data by performing modulation processing according to transmission data on an unmodulated carrier by using antenna load impedance operation such as on / off of the terminal end of the antenna, for example. The reflected wave reader side can receive the reflected wave, demodulate and decode it, and acquire transmission data.

  In a reflected wave transmission system, an antenna switch for performing back scattering is generally composed of an IC of gallium arsenide, and its power consumption is several tens of μW or less. As an average power when data transmission is performed, In the case of the delivery confirmation method, data transmission is possible at 10 mW or less, and in the unidirectional transmission, data transmission is several tens of μW. This is an overwhelming performance difference compared to the average power consumption of a general wireless LAN (see, for example, Non-Patent Document 4).

  For example, a reflector is incorporated in a mobile terminal device such as a digital camera, a video camera, a mobile phone, a personal digital assistant, a portable music player, etc. to minimize power consumption, and a TV, monitor, printer, PC, A reflected wave reader is incorporated in a host device such as a VTR, DVD player, or other stationary home appliances. For example, image data taken with a camera-equipped mobile phone or digital camera can be uploaded to a PC via a reflected wave transmission path, and image data can be stored, displayed, and printed out.

  FIG. 5 shows a configuration example of the reflected wave transmission system.

  The host 1 includes an RF function unit 11, a host communication control function unit 12, and a host function unit 13. The RF function unit 11 operates as a reflected wave reader in the reflected wave transmission system.

  Data transmitted from the host function unit 13 is modulated by the modulation function unit 121 of the host communication control function unit 12 via the control interface 14. The modulated signal 15 is transmitted on the carrier wave 31 generated by the carrier generation source 111 of the RF function unit 11 and transmitted to the terminal 2.

  On the other hand, the terminal 2 includes an RF function unit 21, a terminal communication function control function unit 22, and a terminal function unit 23. The RF function unit 21 operates as a reflector in the reflected wave transmission system. The RF function unit 21 of the terminal 2 receives the carrier wave 31 from the host 1 and obtains the demodulated signal 25. The demodulated signal 25 is demodulated by the demodulation function unit 223 and is received by the terminal function unit 23 via the control interface 24.

  The data transmitted by the terminal function unit 23 of the terminal 2 is modulated by the modulation function unit 222 of the communication control function unit 22. The modulated signal 26 is placed on the reflected wave 32 obtained by detecting the carrier wave 31 in the RF function unit 26 and transmitted to the host 1. The RF function unit 11 of the host 1 receives the reflected wave 32 and obtains the demodulated signal 16. The demodulated signal 16 is demodulated by the demodulation function unit 123 and received by the host function unit 13 via the control interface 14.

  Further, in addition to the data transmission / reception function described above, the host 1 and the terminal 2 can be provided by providing the protocol function units (121, 221) that mutually function in the host 1 and the terminal 2 in the respective communication control function units (12, 22). Protocol control such as connection and disconnection is realized.

  As described above, in the reflected wave transmission system, since the RF generation unit 21 of the terminal 2 does not require a carrier generation source, the system can be driven with low consumption. Further, by performing multi-level modulation on the terminal side, high-speed communication from the terminal to the host direction can be realized. Note that ASK is used for the modulation in the host in consideration of the ease of detection on the terminal side. This results in a low data rate.

  The terminal 1 is, for example, a digital still camera or a digital video camera, and the host 2 is, for example, a television or a printer. A still image or a video is uploaded from the terminal 1 to the host 2 and displayed, printed out, etc. Is assumed to be performed.

  In such a reflected wave transmission system, the terminal does not have a carrier generation source, but reflects the carrier wave received from the host and uses it as a carrier wave. The carrier wave is attenuated while reaching the terminal from the host, and the reflected wave is attenuated while reaching the host from the terminal.

  For this reason, when the output of the carrier wave transmitted from the host is fixed, there is a problem that the position and situation of the host and the terminal where the host can satisfactorily receive the reflected wave from the terminal are limited. That is, since it is restricted by the positional relationship between the reflected wave device and the reflected wave reader that can perform good communication, it is not convenient for the user.

  A method is also conceivable in which the output of the carrier wave is sufficiently increased so that a good reflected wave can be received regardless of the positional relationship between the host and the terminal. However, if they are installed in a place where they can communicate with each other, useless power is consumed for the output of the carrier wave. Further, the output of an excessive carrier wave becomes a disturbing wave to other wireless communication systems. In particular, in the reflected wave transmission system using the 2.4 GHz band, there is a concern about the influence on the proximity system because it overlaps the normal frequency band used for wireless LAN.

International Standard ISO / IEC 8802-11: 1999 (E) ANSI / IEEE Std 802.11, 1999 Edition, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layers (PH) ETSI Standard ETSI TS 101 761-1 51.3.1. 1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part 1: Basic Trunk Data Control ETSI TS 101 761-2 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part2: Radio Link Control (LC) Japanese Patent Application No. 2003-291809 Specification

  It is an object of the present invention to suitably perform data communication using transmission of a carrier wave from the reflected wave reader side and modulation of the reflected wave based on an antenna load impedance switching operation on the reflector side, etc. To provide a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program excellent in a scatter method.

  A further object of the present invention is to provide an excellent wireless communication system, wireless communication, which can satisfactorily receive a reflected wave from a reflector with respect to a carrier wave transmitted by a reflected wave reader, regardless of a position and a situation where the reflector is installed. To provide a communication device, a wireless communication method, and a computer program.

  A further object of the present invention is to provide an excellent radio communication system, radio that can satisfactorily receive the reflected wave from the reflector with respect to the carrier wave transmitted by the reflected wave reader, regardless of the influence of attenuation or the like on the transmission path. To provide a communication device, a wireless communication method, and a computer program.

  The present invention has been made in consideration of the above problems, and is a wireless communication system for performing reflected wave transmission by transmitting a carrier wave from the reflected wave reader side and modulating the reflected wave in accordance with transmission data on the reflector side A radio communication system that controls a transmission output of a carrier wave from the reflected wave reader based on an intensity of a received signal in the reflected wave reader of a reflected wave with respect to the carrier wave from the reflector. It is.

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not.

  The wireless transmission system according to the present invention is intended to realize low power consumption in a communication mode in which a transmission ratio occupies most of communication between devices that are relatively limited to a short distance, Wireless transmission is performed using modulation of reflected waves based on the back scatter method used in RFID. The RFID system itself is widely known in the art as an example of a wireless communication means that can be applied only at an extremely short distance.

  Here, in the reflected wave transmission system, the carrier wave is attenuated while reaching the reflector from the reflected wave reader, and the reflected wave is further attenuated while reaching the reflected wave reader from the reflector. For this reason, in order for a reflected wave reader to obtain a favorable reflected wave, there exists a problem that the positional relationship and communication condition of a reflector and a reflected wave reader will be limited.

  On the other hand, according to the wireless communication system according to the present invention, the reflected wave reader includes a measuring means for measuring the received signal electric field strength (RSSI) with respect to the reflected wave from the reflector, and the carrier wave according to the RSSI value. And a control means for controlling the output.

  Therefore, the reflected wave reader increases the output of the carrier wave when it is determined that the reception state of the reflected wave from the reflector is poor based on the RSSI value. Since the output of the carrier wave is reflected in the output of the reflected wave, the reception situation is improved. As a result, the problem that the position and situation between the reflected wave reader and the reflector are limited when the output of the carrier wave is fixed is solved.

  For example, the reception sensitivity for the reflected wave in the reflected wave reader is set to a known value, and the difference between the received sensitivity and the measured received signal intensity is set as the increment of the carrier wave output. Can be adaptively controlled according to the positional relationship with the reflector and the communication status.

  By giving the difference between the received sensitivity value given as the existing value and the obtained RSSI value as the increment of the carrier wave output, if the reflected wave RSSI is insufficient for the received sensitivity in the reflected wave reader, the received sensitivity is The carrier power can be controlled to reach. On the other hand, when RSSI has sufficient reception sensitivity, it is possible to reduce the power consumption of the carrier generation source in the reflected wave reader by reducing the carrier output within a range in which good reception can be maintained.

  Advantageous Effects of Invention According to the present invention, an excellent radio communication system and radio communication that can receive a reflected wave from a reflector with respect to a carrier wave transmitted by a reflected wave reader, irrespective of the position and situation of the reflector. An apparatus, a wireless communication method, and a computer program can be provided.

  Further, according to the present invention, an excellent wireless communication system capable of receiving the reflected wave from the reflector with respect to the carrier wave transmitted by the reflected wave reader, regardless of the influence of attenuation on the transmission path, A wireless communication device, a wireless communication method, and a computer program can be provided.

  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.

  The present invention is a communication mode in which the transmission ratio occupies most of the communication between devices that are relatively limited to a short distance. The purpose is to realize transmission and mutual communication, and wireless transmission is performed using a reflected wave based on the back scatter method used in RFID.

  The RFID system itself is widely known in the art as an example of wireless communication means that can be applied only locally. Examples of the communication method between the tag and the reader / writer include an electromagnetic coupling method, an electromagnetic induction method, and a radio wave communication method. The present invention relates to a radio wave communication system using a microwave such as a 2.4 GHz band.

  The basic operation of the reflected wave transmission system that performs back-scatter data transmission is as described with reference to FIG.

  FIG. 1 shows a configuration example on the side of a reflected wave reader operating as a communication host in the reflected wave transmission system according to the present invention.

  As illustrated, the host 1 includes an RF function unit 11, a communication control function unit 12, a host function unit 13, and a control interface 14. The RF function unit 11 operates as a reflected wave reader in the reflected wave transmission system.

  Data transmitted from the host function unit 13 is modulated by the modulation function unit 121 of the host communication control function unit 12 via the control interface 14. The modulated signal 15 is transmitted on a carrier wave 31 generated by the carrier generation source 111 of the RF function unit 11 and transmitted to a terminal (not shown).

  In the present embodiment, the RF function unit 11 of the host 1 includes an RSSI measurement function unit 112 and an output control function unit 113 as functions in addition to the original function as a reflected wave reader in the reflected wave transmission system. . The carrier generation source 111 is configured so that the carrier wave output is variably controlled. In terms of mounting, a power amplifier capable of output control is installed.

  The RSSI measurement function unit 112 receives the reflected wave 32, measures the received signal strength RSSI, and notifies the output control function unit 113 of the RSSI value. Regarding the notification, a voltage corresponding to the RSSI value is generally output as a level. For the measurement of RSSI, for example, a well-known technique such as a detection diode that rectifies an AC oscillating electric field applied to its surroundings and outputs it as a DC signal can be used.

  The output control function unit 113 is a function unit that controls the carrier wave output of the carrier generation source 111 in response to the notification of the RSSI value. In terms of mounting, it becomes a circuit unit for controlling the power amplifier.

  A method of carrier wave output control by the output control function unit 113 will be described with reference to FIG.

  In the present embodiment, it is assumed that the reception sensitivity of the reflected wave at the host is fixed and determined. The reception sensitivity is defined as, for example, the minimum RSSI value at which the bit error rate or packet error rate (PER) of transmission / reception data does not exceed a certain rate (for example, 10%).

  In the reflected wave transmission system according to the present invention, the carrier wave is attenuated while reaching the reflector from the reflected wave reader, and the reflected wave is further attenuated while reaching the reflected wave reader from the reflector, and then the RSSI. Obtained as a value. If the RSSI value does not reach the reception sensitivity value, the increment of the carrier wave output is obtained by the difference between the reception sensitivity value and the RSSI value.

  Assuming that the initial carrier wave output is 10 dBm and the RSSI value of the reflected wave is −70 dBm, the attenuation at this time is 10 − (− 70) = 80 dB. When the optimum received signal strength of the host is −50 dBm, the carrier wave output to achieve this is −50 + 80 = 30 dBm assuming that the attenuation does not change. At this time, the increment of the output is 30-10 = 20 dB. This corresponds to the difference between the received strength optimum value given as known and the measured RSSI value.

  Here, it is assumed that the optimum reception strength value is defined as the minimum RSSI reception strength at which the packet error rate (PER) is determined to be good, and is measured in advance and given as knowledge information. For example, when the relationship is as shown in FIG. 3, the optimum reception strength is −70 dBm.

  When the output control function unit 113 obtains the difference between the reception sensitivity value given as the existing value and the RSSI value obtained by the RSSI measurement function unit 112, the control signal for the carrier generation source 111 is input to, for example, a power amplifier. It is given as a voltage signal.

  FIG. 4 shows a processing procedure for determining the carrier wave output in the form of a flowchart.

  When the reflected wave reader is turned on (step S1), the reflected wave reader sets its initial value P_init as the carrier wave output P (step S2).

  Then, the output of the carrier wave is started, and when the reflected wave returns from the reflector, the received signal electric field strength RSSI is measured (step S3).

  Next, a difference (Sub) between the optimum received strength value and the RSSI measurement value is calculated (Step S4), and it is determined whether Sub is zero (or within an allowable value) (Step S5).

  Here, if Sub is zero (or within an allowable value), the carrier wave output is not controlled. On the other hand, when Sub is not zero (or exceeds the allowable value), the carrier wave output is increased by the difference Sub.

  When the sub is positive, if the output is increased, the reflected wave reader increases the reception intensity of the reflected wave, so that it is expected that the PER will be improved.

  In addition, when Sub is negative, when the output is increased, the carrier wave output is reduced, so that power consumption can be reduced.

  By such a processing procedure, when the RSSI of the reflected wave is insufficient for the reception sensitivity, the carrier wave output can be controlled so as to reach the reception sensitivity. Conversely, even when RSSI satisfies the reception sensitivity, it is possible to reduce the power consumption of the carrier generation source in the host by reducing the carrier output within a range where good reception can be maintained.

  In the reflected wave transmission system, generally, a modulation method such as ASK or BPSK is adopted for reflected wave transmission. For example, by manipulating the load impedance of the directional antenna (on / off of the antenna termination) on the reflector side, signals 0 and 1 can be arranged in the signal space, and BPSK modulation can be easily realized. However, these modulation methods have a problem in terms of transmission speed. On the other hand, on the reflector side, in addition to the operation of load impedance such as antenna termination processing, a phase difference is given on the signal path on which the reflected wave reciprocates, so that a higher bit rate such as QPSK or 8-phase PSK modulation can be obtained. A modulation scheme can be realized. For example, Japanese Patent Application No. 2003-352223 already assigned to the present applicant discloses a back scatter type communication system incorporating QPSK modulation processing.

  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 embodiment of the present invention has been described with reference to an example of a reflected wave transmission system that transmits a carrier wave from the reflected wave reader side and modulates the reflected wave with transmission data on the reflector side. The gist of the present invention is not limited to this. Even in another wireless communication system that uses media other than reflected wave transmission, the present invention is preferably applied in order to obtain good reception quality on the receiving side regardless of the positional relationship between communication devices and communication conditions. be able to.

  In the embodiment described in the present invention, the reflected wave reader controls the output of the carrier wave based on the received signal intensity of the reflected wave. You may make it control the output of a carrier wave using the other measuring means which can acquire the influence of a communication condition.

  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 section described at the beginning should be considered.

FIG. 1 is a diagram showing a configuration example on the side of a reflected wave reader operating as a communication host in the reflected wave transmission system according to the present invention. FIG. 2 is a diagram for explaining a carrier wave output control method in the reflected wave reader. FIG. 3 is a diagram for explaining the optimum value for receiver use. FIG. 4 is a flowchart showing a processing procedure for determining the carrier wave output. FIG. 5 is a diagram illustrating a configuration example of a reflected wave transmission system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Host 11 ... RF function part 111 ... Carrier generation source 112 ... RSSI measurement function part 113 ... Output control function part 12 ... Communication control function part 121 ... Modulation function part 122 ... Modulation function part 123 ... Demodulator function part 13 ... Host Equipment 14 ... Control interface

Claims (7)

A wireless communication system that performs reflected wave transmission by transmitting a carrier wave from the reflected wave reader side and modulating the reflected wave according to transmission data on the reflector side,
Controlling the transmission output of the carrier wave from the reflected wave reader based on the intensity of the received signal at the reflected wave reader of the reflected wave with respect to the carrier wave from the reflector;
A wireless communication system. The reception sensitivity for the reflected wave in the reflected wave reader is a known value, and the difference between the reception sensitivity and the measured received signal intensity is the increment of the carrier output.
The wireless communication system according to claim 1. A wireless communication device that performs reflected wave communication using modulation of a reflected wave with respect to a carrier wave,
A transmission means for transmitting a carrier wave;
Receiving means for receiving data on a reflected wave with respect to the carrier wave transmitted by the transmitting means;
Measuring means for measuring the intensity of the received signal with respect to the reflected wave;
Control means for controlling the transmission output of the carrier in the transmission means based on the measured strength of the received signal;
A wireless communication apparatus comprising: The control means sets the reception sensitivity with respect to the reflected wave to a known value, and sets the difference between the reception sensitivity and the measured received signal intensity as the increment of the carrier output.
The wireless communication apparatus according to claim 3. A wireless communication method for performing reflected wave communication using modulation of a reflected wave with respect to a carrier wave,
A transmission step of transmitting a carrier wave;
A receiving step of receiving data on a reflected wave with respect to the carrier wave transmitted in the transmitting step;
A measurement step for measuring the intensity of the received signal with respect to the reflected wave;
A control step of controlling a transmission output of a carrier wave in the transmission step based on the measured strength of the received signal;
A wireless communication method comprising: In the control step, the reception sensitivity with respect to the reflected wave is set to a known value, and the difference between the reception sensitivity and the measured received signal intensity is set to the increment of the carrier wave output.
The wireless communication method according to claim 5. A computer program written in a computer-readable format to execute processing for performing reflected wave communication using modulation of reflected waves on a carrier wave on a computer system,
A transmission step of transmitting a carrier wave;
A receiving step of receiving data on a reflected wave with respect to the carrier wave transmitted in the transmitting step;
A measurement step for measuring the intensity of the received signal with respect to the reflected wave;
A control step of controlling a transmission output of a carrier wave in the transmission step based on the measured strength of the received signal;
A computer program comprising:

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