Patent Publication Number: US-2009221237-A1

Title: Data sending and receiving apparatus and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-048460, filed on Feb. 28, 2008, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are directed to a data sending and receiving apparatus interposed between a terminal device and a communication device, for sending data, and to a data sending and receiving method. 
     BACKGROUND 
     Conventionally, in a communication system that provides communication service between portable phones or television programs, there is known a data sending and receiving apparatus, interposed between a terminal device (for example, portable phone) and a communication device (for example, base station device), for sending transmission data that is received from the communication device and addressed to the terminal device, while demodulating reception data from the terminal device and sending to the communication device (see Japanese Laid-open Patent Publication No. 2005-295396 and Japanese Laid-open Patent Publication No. 2007-189871). 
     In the following, the sending and receiving apparatus will be concretely explained by way of an example. As depicted in the reference ( 1 - 1 ) in  FIG. 15 , the sending and receiving apparatus modulates transmission data received from a communication device at a transmitting unit, generates a carrier wave containing the transmission data, and sends to a terminal device. 
     Meanwhile, as depicted in  FIG. 15 , the sending and receiving apparatus includes, as constituting elements that are involved in sending and receiving of reception data, a correction table, a reception data extracting unit, a Receive Signal Strength Indication (or Indicator) (RSSI) value measuring unit, an RSSI value correcting unit and a demodulator (DEM). 
     Among these, the correction table stores RSSI corrected value (corrected value) for correcting signal strength of reception data in correlation with an RSSI reported value (reported value) which is a measurement result of the signal strength of the reception data. 
     Under such a presumption, as depicted in the reference ( 2 - 1 ) of  FIG. 15 , the reception data extracting unit receives a carrier wave outgoing from the terminal device, extracts the reception data contained in the carrier wave, and inputs the reception data to the RSSI value measuring unit and the demodulator. 
     Subsequently, as depicted in the reference ( 2 - 2 ) of  FIG. 15 , the RSSI value measuring unit measures an RSSI value (for example, −101 dBm (decibels per milliwatt: unit indicating strength of signal by electricity)) of the reception data extracted by the reception data extracting unit, and inputs a measurement result to the RSSI value correcting unit as an RSSI reported value. 
     The RSSI value correcting unit having received the RSSI reported value from the RSSI value measuring unit corrects the RSSI reported value to an RSSI corrected value by referring to the correction table as depicted in the reference ( 2 - 3 ) of  FIG. 15 , and inputs the RSSI corrected value to the demodulator. For example, the RSSI value correcting unit corrects the RSSI reported value of −101 dBm received from the RSSI value measuring unit to an RSSI corrected value of −100 dBm and inputs the RSSI corrected value to the demodulator. 
     The demodulator having received the RSSI corrected value from the RSSI value correcting unit and received the reception data from the reception data extracting unit demodulates the reception data using the RSSI corrected value, as depicted in the reference ( 2 - 4 ) of  FIG. 15 , and sends to the communication device.  FIG. 15  is a view for explaining an outline of the conventional art. 
     The foregoing conventional sending and receiving apparatus faces a problem that quality deterioration may occur in demodulating the reception data. To be more specific, in the conventional sending and receiving apparatus, an error occurs in measurement result of RSSI value possessed by the reception data between the case where sending process of transmission data for the terminal device is not executed as depicted in ( 1 ) of  FIG. 16 , and the case where sending process of transmission data for the terminal device is executed as depicted in ( 2 ) of  FIG. 16 , and the measurement result of RSSI value is not corrected to a correct RSSI value depending on some situations. 
     Therefore, the conventional sending and receiving apparatus faces a problem that quality deterioration may occur in demodulation process of reception data.  FIG. 16  is a view for explaining the problem of the conventional art. 
     SUMMARY 
     According to an aspect of the invention, a data sending and receiving apparatus is interposed between a terminal device and a communication device, sends transmission data received from the communication device and addressed to the terminal device, and sends reception data from the terminal device to the communication device after demodulating. The data sending and receiving apparatus includes a sending state acquiring unit that monitors and acquires at least one of a sending process state indicating whether the sending process of the transmission data is being executed, and a signal strength of the transmission data; a signal strength measuring unit that measures a signal strength of the reception data; a measured value correcting unit that corrects a measured value of the signal strength of the reception data measured by the signal strength measuring unit, in accordance with at least one of the sending process state and an acquisition result of the signal strength of the transmission data acquired by the sending state acquiring unit; and a demodulating unit that demodulates the reception data using a corrected measured value corrected by the measured value correcting unit. 
     The objects and advantages of the invention will be realized and attained by unit of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING(S) 
         FIG. 1  is a view for explaining an outline and features of a sending and receiving apparatus according to a first embodiment; 
         FIG. 2  is a block diagram of a configuration of the sending and receiving apparatus according to the first embodiment; 
         FIG. 3  is a view depicting one example of information stored in a correction table according to the first embodiment; 
         FIG. 4  is a flowchart of a flow of process by the sending and receiving apparatus according to the first embodiment; 
         FIG. 5  is a block diagram of a configuration of the sending and receiving apparatus according to a second embodiment; 
         FIG. 6  is a view depicting one example of information stored in a correction table according to the second embodiment; 
         FIG. 7  is a flowchart of a flow of process by the sending and receiving apparatus according to the second embodiment; 
         FIG. 8  is a block diagram of a configuration of the sending and receiving apparatus according to a third embodiment; 
         FIG. 9  is a view depicting one example of information stored in a correction table according to the third embodiment; 
         FIG. 10  is a flowchart of a flow of process by the sending and receiving apparatus according to the third embodiment; 
         FIG. 11  is a block diagram of a configuration of the sending and receiving apparatus according to a fourth embodiment; 
         FIG. 12  is a view depicting one example of information stored in a reference table according to the fourth embodiment; 
         FIG. 13  is a view for explaining one example of process by a corrected value calculating unit according to the fourth embodiment; 
         FIG. 14  is a flow chart of a flow of process by the sending and receiving apparatus according to the fourth embodiment; 
         FIG. 15  is a view for explaining an outline of conventional art; and 
         FIG. 16  is a view for explaining a problem of conventional art. 
     
    
    
     DESCRIPTION OF EMBODIMENT(S) 
     Preferred embodiments of the data sending and receiving apparatus and method according to the present invention will be explained in detail with reference to accompanying drawings. In the following, a sending and receiving apparatus to which the present invention is applied will be explained as an example. 
     [a] First Embodiment 
     In the following first embodiment, an outline and features of a sending and receiving apparatus according to the first embodiment, a configuration of the sending and receiving apparatus, and a flow of process of the sending and receiving apparatus will be explained sequentially, and effect of the first embodiment will be lastly explained. 
     [Outline and Features of Sending and Receiving Apparatus According to the First Embodiment] 
     First, an outline and features of the sending and receiving apparatus according to the first embodiment will be explained with reference to  FIG. 1 .  FIG. 1  is a view for explaining an outline and features of the sending and receiving apparatus according to the first embodiment. 
     The sending and receiving apparatus according to the first embodiment is outlined such that the sending and receiving apparatus is interposed between a terminal device and a communication device and sends transmission data received from the communication device and addressed to the terminal device while sending reception data from the terminal device to the communication device after demodulating. The sending and receiving apparatus according to the first embodiment is mainly featured by demodulating the reception data with excellent quality. 
     Specifically, the sending and receiving apparatus according to the first embodiment monitors and acquires at least one of a sending process state indicating whether a sending process of transmission data is being executed and signal strength of transmission data. 
     The sending and receiving apparatus according to the first embodiment then corrects a measured value of signal strength of reception data according to at least one of an acquisition result of the sending process state and the signal strength, and demodulates the reception data using the corrected measured value. 
     One concrete example will be explained below. As depicted in  FIG. 1 , the sending and receiving apparatus according to the first embodiment corrects a measured value of the signal strength of the reception data −104 dBm to a corrected value of −100 dBm when acquiring a sending process state indicating that a sending process of the transmission data is being executed. On the other hand, the sending and receiving apparatus according to the first embodiment corrects the measured value of the signal strength of the reception data −101 dBm to the corrected value −100 dBm when acquiring a sending process state indicating that a sending process of transmission data is not being executed. 
     Consequently, the sending and receiving apparatus according to the first embodiment is able to demodulate the reception data with excellent quality as is the above-mentioned main features. 
     [Configuration of Sending and Receiving Apparatus] 
     Next, using  FIG. 2  and  FIG. 3 , a configuration of the sending and receiving apparatus depicted in  FIG. 1  will be explained.  FIG. 2  is a block diagram of a configuration of the sending and receiving apparatus according to the first embodiment.  FIG. 3  is a view depicting one example of information stored in the correction table according to the first embodiment. 
     [Configuration of Transmission Data Sending and Receiving Circuit] 
     As depicted in  FIG. 2 , a sending and receiving apparatus  10  includes, as constituting elements involved in sending and receiving of transmission data, a Modulator (MOD)  21 , a Digital to Analog Converter (DAC)  22 , an oscillator  23 , a mixer  24 , an Amplifier (AMP)  25 , an isolator  26 , a Transmitter Amplifier (TxAMP)  27 , a power unit  28  and a switch  29 . 
     Among these, the MOD  21  modulates transmission data received from the communication device, and inputs the modulated transmission data to the DAC  22 . The DAC  22  converts the transmission data in digital format received from the MOD  21  to transmission data in analog format, and inputs the transmission data to the mixer  24 . 
     The oscillator  23  generates a signal of a certain frequency, and inputs the signal to the mixer  24 . The mixer  24  changes frequency of the transmission data received from the DAC  22  using the signal of a certain frequency received from the oscillator  23 , and inputs the transmission data to the AMP  25 . 
     The transmission data signal input from the DAC  22  to the mixer  24  corresponds to a signal of Intermediate Frequency (IF) band, and the transmission data signal input from the mixer  24  to the AMP  25  corresponds to a signal of Radio Frequency (RF) band. 
     The AMP  25  amplifies the signal of the transmission data received from the mixer  24 , and inputs to the TxAMP  27  via the isolator  26 . The isolator  26  prevents sneak current from flowing from the TxAMP  27  to the AMP  25 . 
     The TxAMP  27  further amplifies the signal of the transmission data received from the AMP  25 , and sends a carrier wave containing the transmission data to the terminal device. 
     The power unit  28  supplies the TxAMP  27  with electricity. The switch  29  switches between whether the power unit  28  supplies the TxAMP  27  with electricity. 
     Here, when the power unit  28  supplies the TxAMP  27  with electricity under the control by the switch  29 , the TxAMP  27  sends a carrier wave containing the transmission data to the terminal device, whereas when the power unit  28  does not supply the TxAMP  27  with electricity under the control by the switch  29 , the TxAMP  27  stops sending the carrier wave containing the transmission data to the terminal device. 
     [Configuration of Reception Data Sending and Receiving Circuit] 
     The sending and receiving apparatus  10  includes, as constituting elements involved in sending and receiving of reception data, a Receiver Amplifier (RxAMP)  41 , a band-pass filter  42 , an oscillator  43 , a mixer  44 , a band-pass filter  45 , an AMP  46 , an Analog to digital Converter (ADC)  47 , a correction table  48 , an RSSI value measuring unit  49 , a correction information selecting unit  50 , an RSSI value correcting unit  51  and a Demodulator (DEM)  52 . 
     The correction table  48  may be referred to as a correction information holding unit, the RSSI value measuring unit  49  to as a signal strength measuring unit, the correction information selecting unit  50  to as one or both of a sending state acquiring unit and correction information acquiring unit, the RSSI value correcting unit  51  to as a measured value correcting unit, and the DEM  52  to as a demodulating unit. 
     Among these, the RxAMP  41  receives the carrier wave outgoing from the terminal device, and amplifies the signal of the carrier wave. The RxAMP  41  inputs the carrier wave to the band-pass filter  42 . The band-pass filter  42  clips the reception data contained in the carrier wave received from the RxAMP  41 , and inputs the reception data to the mixer  44 . 
     The oscillator  43  generates a signal of a certain frequency, and inputs the signal to the mixer  44 . The mixer  44  changes frequency of the reception data received from the band-pass filter  42  using the signal of a certain frequency received from the oscillator  43 , and inputs the reception data to the band-pass filter  45 . 
     The reception data input from the band-pass filter  42  to the mixer  44  corresponds to a signal of RF band, and the reception data input from the mixer  44  to the band-pass filter  45  corresponds to a signal of IF band. 
     The band-pass filter  45  removes noise contained in the reception data in association with change in frequency of reception data by the mixer  44 , and inputs the reception data to the AMP  46 . The AMP  46  amplifies the signal of the reception data received from the mixer  44 , and inputs the reception data to the ADC  47 . 
     The ADC  47  converts the reception data in analog format received from the AMP  46  to reception data in digital format, and inputs the reception data to the RSSI value measuring unit  49  and the DEM  52 . 
     Hereinafter, a series of processes from reception of the carrier wave by the RxAMP  41 , to input of the reception data from the ADC  47  to the RSSI value measuring unit  49  and the DEM  52  is referred to as “reception data extracting process”. 
     The correction table  48  holds pieces of correction information used for correction of a measured value of RSSI value of the reception data, for each sending process state indicating whether a sending process of the transmission data is being executed. Concretely, as depicted in  FIG. 3 , the correction table  48  stores, as under-sending correction information corresponding to a sending process state indicating that a sending process of the transmission data is being executed, RSSI corrected values for the respective correcting RSSI reported values, in correlation with the respective RSSI reported values. The correction table  48  also stores, as under-suspension correction information corresponding to a sending process state indicating that a sending process of the transmission data is not being executed, RSSI corrected values, in correlation with the respective RSSI reported values. 
     The RSSI value measuring unit  49  measures an RSSI value of the reception data. Concretely, the RSSI value measuring unit  49  measures an RSSI value of the reception data received from the ADC  47 , and inputs a measurement result to the RSSI value correcting unit  51  as an RSSI reported value. 
     The correction information selecting unit  50  acquires a sending process state indicating whether a sending process of the transmission data is being executed. Then the correction information selecting unit  50  selects a piece of the correction information corresponding to an acquisition result of sending process state from among the pieces of the correction information held by the correction table  48 . 
     Concretely, the correction information selecting unit  50  always monitors control of the power unit  28  by the switch  29 , and determines whether the power unit  28  supplies the TxAMP  27  with electricity, or the power unit  28  does not supply the TxAMP  27  with electricity, thereby acquiring a sending process state indicating whether a sending process of transmission data is being executed by the TxAMP  27 . 
     The correction information selecting unit  50  selects the under-sending correction information held by the correction table  48  when acquiring a sending process state indicating that a sending process of the transmission data is being executed by the TxAMP  27 , and sends the selection result to the RSSI value correcting unit  51 . 
     On the other hand, the correction information selecting unit  50  selects the under-suspension correction information held by the correction table  48  when acquiring a sending process state indicating that a sending process of the transmission data is not being executed by the TxAMP  27 , and sends the selection result to the RSSI value correcting unit  51 . 
     The RSSI value correcting unit  51  corrects the measured value of the RSSI value of the reception data measured by the RSSI value measuring unit  49 , in accordance with the acquisition result of sending process state. Concretely, the RSSI value correcting unit  51  corrects the measured value of the RSSI value of the reception data using the correction information selected by the correction information selecting unit  50 . 
     In one exemplary case, it is assumed that the RSSI value correcting unit  51  receives an RSSI reported value of −104 dBm from the RSSI value measuring unit  49  while receiving a selection result informing that the under-sending correction information is selected from the correction information selecting unit  50 . 
     At this time, the RSSI value correcting unit  51  corrects the RSSI reported value −104 dBm to an RSSI corrected value of −100 dBm by referring to the under-sending correction information held by the correction table  48 , and inputs the RSSI corrected value to the DEM  52 . 
     In other case, it is assumed that the RSSI value correcting unit  51  receives an RSSI reported value of −101 dBm from the RSSI value measuring unit  49  while receiving a selection result informing that the under-suspension correction information is selected from the correction information selecting unit  50 . 
     At this time, the RSSI value correcting unit  51  corrects the RSSI reported value −101 dBm to an RSSI corrected value of −100 dBm by referring to the under-suspension correction information held by the correction table  48 , and inputs the RSSI corrected value to the DEM  52 . 
     The DEM  52  demodulates the reception data using the measured value corrected by the RSSI value measuring unit  49 . Concretely, the DEM  52  demodulates the reception data received from the ADC  47  by using the RSSI corrected value received from the RSSI value correcting unit  51 . The DEM  52  then sends the demodulated reception data to the communication device. 
     [Process by Sending and Receiving Apparatus] 
     Next, referring to  FIG. 4 , a process by the sending and receiving apparatus  10  will be explained.  FIG. 4  is a flow chart of a flow of process by the sending and receiving apparatus according to the first embodiment. 
     In the following, a flow of a reception data sending and receiving process which is characteristic of the sending and receiving apparatus  10  according to the first embodiment will be explained on assumption that the sending and receiving apparatus according to the first embodiment always acquires a sending process state indicating whether a sending process of transmission data is being executed. 
     As depicted in  FIG. 4 , upon reception of a carrier wave outgoing from the terminal device (Yes at Step S 1001 ), the sending and receiving apparatus  10  executes a reception data extracting process (Step S 1002 ), and measures an RSSI value of the reception data (Step S 1003 ). 
     Here, when a sending process state indicating that a sending process of the transmission data is being executed is acquired (Yes in Step S 1004 ), the sending and receiving apparatus  10  selects the under-sending correction information (Step S 1005 ), and corrects a measured value of the RSSI value of the reception data by referring to the under-sending correction information (Step S 1006 ). 
     The sending and receiving apparatus  10  demodulates the reception data using the corrected measured value (Step S 1007 ), sends the demodulated reception data to the communication device (Step S 1008 ), and ends the reception data sending and receiving process. 
     Returning to explanation of Step S 1004 , when a sending process state indicating that a sending process of transmission data is not being executed is acquired (No at Step S 1004 ), the sending and receiving apparatus  10  selects the under-suspension correction information (Step S 1009 ), and corrects a measured value of the RSSI value of the reception data by referring to the under-suspension correction information (Step S 1010 ). 
     The sending and receiving apparatus  10  demodulates the reception data using the corrected measured value (Step S 1007 ), sends the demodulated reception data to the communication device (Step S 1008 ), and ends the reception data sending and receiving process. 
     [Effect of the First Embodiment] 
     As described above, according to the first embodiment, it is possible to demodulate the reception data with excellent quality. For example, according to the first embodiment, even when a noise occurring when the power unit  28  supplies the TxAMP  27  with electricity causes an error in measurement result of the RSSI value possessed by the reception data, the measurement result of the RSSI value can be corrected to a correct RSSI value, so that it is possible to demodulate the reception data with excellent quality. 
     [b] Second Embodiment 
     In the first embodiment, there may be a case that the error occurring in measurement result of RSSI value possessed by the reception data varies depending on the signal level possessed by transmission data. 
     In light of the above, in the second embodiment, the case where a measured value of the RSSI value of the reception data is corrected in accordance with the signal level possessed by the transmission data will be explained. In the second embodiment, after explaining configuration of a sending and receiving apparatus according to the second embodiment and a flow of process by the sending and receiving apparatus, an effect achieved by the second embodiment will be explained. 
     [Configuration of Sending and Receiving Apparatus According to the Second Embodiment] 
     First, referring to  FIG. 5  and  FIG. 6 , a configuration of the sending and receiving apparatus  10  according to the second embodiment will be explained.  FIG. 5  is a block diagram of a configuration of the sending and receiving apparatus according to the second embodiment.  FIG. 6  is a view depicting one example of information stored in the correction table according to the second embodiment. 
     The configuration of the sending and receiving apparatus  10  according to the second embodiment differs from the sending and receiving apparatus  10  according to the first embodiment in the points as will be described below, besides further including a sending level value acquiring unit  53 . The sending level value acquiring unit  53  may be referred to as a sending state acquiring unit. 
     Specifically, the sending level value acquiring unit  53  acquires a signal level of the transmission data. Concretely, the sending level value acquiring unit  53  measures a signal level of the transmission data input from the MOD  21  to the DAC  22 . Then the sending level value acquiring unit  53  inputs the measurement result of the signal level of the transmission data (for example, +46 dB (decibel: unit representing signal strength by electricity)) to the correction information selecting unit  50 . 
     The correction table  48  holds pieces of correction information used for correction of a measured value of the signal strength of the reception data for each signal strength of the transmission data, for the case where the sending process state indicates that a sending process of the transmission data is being executed, and holds a piece of correction information for the case where the sending process state indicates that a sending process of the transmission data is suspended. 
     Concretely, in the correction table  48 , as depicted in  FIG. 6 , under-sending correction information (+46 dB), under-sending correction information (+40 dB), and under-sending correction information (+35 dB) are held for the case where the sending process state indicates that a sending process of transmission data is being executed. The correction table  48  also holds under-suspension correction information for the case where the sending process state indicates that a sending process of transmission data is suspended. 
     The correction table  48  stores the RSSI corrected values in correlation with the respective RSSI reported values for each correction information. 
     The “under-sending correction information (+46 dB)” is correction information corresponding to a sending process state indicating that a sending process of the transmission data is being executed, and corresponding to the measurement result (+46 dB) of the signal level of the transmission data. 
     The “under-sending correction information (+40 dB)” is correction information corresponding to a sending process state indicating that a sending process of the transmission data is being executed, and corresponding to the measurement result (+40 dB) of the signal level of the transmission data. 
     The “under-sending correction information (+35 dB)” is correction information corresponding to a sending process state indicating that a sending process of the transmission data is being executed, and corresponding to the measurement result (+35 dB) of the signal level of the transmission data. 
     The “under-suspension correction information” is correction information corresponding to a sending process state indicating that a sending process of the transmission data is not being executed. 
     The correction information selecting unit  50  acquires a sending process state indicating whether a sending process of the transmission data is being executed. And the correction information selecting unit  50  acquires a piece of the correction information in accordance with at least one of an acquisition result of sending process state and an acquisition result of the signal strength from among the pieces of the correction information held by the correction table  48 . 
     Concretely, the correction information selecting unit  50  determines whether a sending process of the transmission data is being executed by the TxAMP  27 , and selects the under-sending correction information held by the correction table  48  when it determines that a sending process of transmission data is being executed by the TxAMP  27 . 
     Then the correction information selecting unit  50  further selects a piece of the under-sending correction information corresponding to the signal level value of the transmission data received from the sending level value acquiring unit  53  (for example, the under-sending correction information (+46 dB)) from among the pieces of the under-sending correction information held by the correction table  48 , and sends the selection result to the RSSI value correcting unit  51 . 
     On the other hand, the correction information selecting unit  50  selects the under-suspension correction information held by the correction table  48  when it determines that a sending process of transmission data is not being executed by the TxAMP  27 , and sends the selected result to the RSSI value correcting unit  51 . 
     The RSSI value correcting unit  51  corrects the measured value of the RSSI value of the reception data using the correction information selected by the correction information selecting unit  50 . An exemplification is made to the case where the RSSI value correcting unit  51  receives an RSSI reported value of −104 dBm from the RSSI value measuring unit  49 , while receiving a selection result informing that the under-sending correction information (+46 dB) is selected from the correction information selecting unit  50 . 
     At this time, the RSSI value correcting unit  51  corrects the RSSI reported value −104 dBm to an RSSI corrected value of −100 dBm by referring to the under-sending correction information (+46 dB) held by the correction table  48 , and inputs the RSSI corrected value to the DEM  52 . 
     [Process by Sending and Receiving Apparatus According to the Second Embodiment] 
     Next, a process by the sending and receiving apparatus according to the second embodiment will be explained by using  FIG. 7 .  FIG. 7  is a flowchart of a flow of process by the sending and receiving apparatus according to the second embodiment. 
     In the following, a flow of a reception data sending and receiving process which is characteristic of the sending and receiving apparatus  10  according to the second embodiment will be explained on assumption that the sending and receiving apparatus according to the second embodiment always acquires a sending process state indicating whether a sending process of the transmission data is being executed and always acquires a signal level value of the transmission data. 
     As depicted in  FIG. 7 , upon reception of a carrier wave outgoing from the terminal device (Yes at Step S 2001 ), the sending and receiving apparatus  10  executes a reception data extracting process (Step S 2002 ), and measures an RSSI value of the reception data (Step S 2003 ). 
     Here, when a sending process state indicating that a sending process of transmission data is being executed is acquired (Yes at Step S 2004 ), the sending and receiving apparatus  10  selects the under-sending correction information (Step S 2005 ), and further selects a piece of the under-sending correction information corresponding to the RSSI value possessed by the transmission data from among the pieces of the under-sending correction information (Step S 2006 ). 
     Subsequently, the sending and receiving apparatus  10  corrects the measured value of the RSSI value of the reception data using the selected correction information (Step S 2007 ), demodulates the reception data using the corrected measured value (Step S 2008 ), sends the demodulated reception data to the communication device (Step S 2009 ), and ends the reception data sending and receiving process. 
     Returning to the explanation of Step S 2004 , when a sending process state indicating that a sending process of the transmission data is not being executed is acquired (No in Step S 2004 ), the sending and receiving apparatus  10  selects the under-suspension correction information (Step S 2010 ), and corrects a measured value of the RSSI value of the reception data by referring to the under-suspension correction information (Step S 2011 ). 
     Then the sending and receiving apparatus  10  demodulates the reception data using the corrected measured value (Step S 2008 ), sends the demodulated reception data to the communication device (Step S 2009 ), and ends the reception data sending and receiving process. 
     [Effect of the Second Embodiment] 
     As described above, according to the second embodiment, even when an error occurs in a measurement result of RSSI value processed by the reception data, a measured value of the RSSI value of reception data is corrected according to a signal level value of the transmission data, so that it is possible to demodulate the reception data with excellent quality. 
     [c] Third Embodiment 
     The second embodiment explains the case where a measured value of the RSSI value of the reception data is corrected according to an acquisition result of sending process state, and an acquisition result of the signal level value of the transmission data, however, a measured value of the RSSI value of the reception data may be corrected without using an acquisition result of the sending process state. 
     In light of the above, in the third embodiment, the case where a measured value of the RSSI value of the reception data is corrected in accordance with an acquisition result of the signal level value of the transmission data will be explained. In the third embodiment, after explaining configuration of a sending and receiving apparatus according to the third embodiment and a flow of process by the sending and receiving apparatus, an effect achieved by the third embodiment will be explained. 
     [Configuration of Sending and Receiving Apparatus According to Third Embodiment] 
     First, a configuration of a sending and receiving apparatus  10  according to a third embodiment will be explained by using  FIG. 8  and  FIG. 9 .  FIG. 8  is a block diagram of configuration of the sending and receiving apparatus according to the third embodiment.  FIG. 9  is a view depicting one example of information stored in the correction table according to the third embodiment. Configuration of the sending and receiving apparatus  10  according to the third embodiment differs from that of the sending and receiving apparatus  10  according to the second embodiment in the following points. 
     To be more specific, the correction table  48  holds pieces of correction information used for correction of a measured value of the RSSI value of the reception data for each signal level value of the transmission data. 
     Concretely, the correction table  48  holds correction information (+46 dB), correction information (+40 dB), correction information (+35 dB), and correction information (0 dB) as depicted in  FIG. 9 . The correction table  48  stores RSSI corrected values in correlation with the respective RSSI reported values for each piece of correction information. 
     The “correction information (+46 dB)” is correction information corresponding to the measurement result (+46 dB) of the signal level of the transmission data, “correction information (+40 dB)” is correction information corresponding to the measurement result (+40 dB) of the signal level of the transmission data, “correction information (+35 dB)” is correction information corresponding to the measurement result (+35 dB) of the signal level of the transmission data, and “correction information (0 dB)” is correction information corresponding to the measurement result (0 dB) of the signal level of the transmission data. 
     The correction information selecting unit  50  acquires a piece of the correction information from among the pieces of the correction information held by the correction table  48  in accordance with an acquisition result of the signal strength. Concretely, the correction information selecting unit  50  selects a piece of the correction information corresponding to a signal level value of the transmission data received from the sending level value acquiring unit  53 , from among the pieces of the correction information held by the correction table  48 , and sends the selection result to the RSSI value correcting unit  51 . 
     In other words, the state that input of the transmission data from the MOD  21  to the DAC  22  is not made (namely, the state that the measurement result of the signal level of the transmission data is (0 dB)) can be determined as a state that a sending process of the transmission data is not being executed. This in turn means that the correction information selecting unit  50  determines whether a sending process of the transmission data is being executed by the TxAMP  27  based on a measurement result of the signal level of the transmission data. 
     [Process Executed by Sending and Receiving Apparatus According to Third Embodiment] 
     Next, by using  FIG. 10 , a process by the sending and receiving apparatus according to the third embodiment will be explained.  FIG. 10  is a flowchart of a flow of process by the sending and receiving apparatus according to the third embodiment. 
     In the following, a flow of process which is characteristic of the sending and receiving apparatus  10  according to the third embodiment will be explained on assumption that the sending and receiving apparatus according to the third embodiment always acquires a signal level value of transmission data. 
     As depicted in  FIG. 10 , upon reception of a carrier wave outgoing from the terminal device (Yes at Step S 3001 ), the sending and receiving apparatus  10  executes a reception data extracting process (Step S 3002 ), and measures an RSSI value of the reception data (Step S 3003 ). 
     Subsequently, the sending and receiving apparatus  10  selects a piece of the under-sending correction information corresponding to a signal level value possessed by the transmission data from among the pieces of the correction information (Step S 3004 ), and corrects the measured value of the RSSI value of the reception data using the selected correction information (Step S 3005 ). 
     Then the sending and receiving apparatus  10  demodulates the reception data using the corrected measured value (Step S 3006 ), sends the demodulated reception data to the communication device (Step S 3007 ), and ends the reception data sending and receiving process. 
     [Effect of Third Embodiment] 
     As described above, according to the third embodiment, it is possible to demodulate the reception data with excellent quality without determining whether a sending process of transmission data is being executed. 
     [d] Fourth Embodiment 
     In the second embodiment and the third embodiment, explanation was made for the case where the RSSI corrected values corresponding to the respective RSSI reported values are held for each signal level value of the transmission data, however, the RSSI corrected value may be calculated by using an acquisition result of the signal level value of the transmission data. In light of this, in the fourth embodiment, the case of calculating an RSSI corrected value will be explained. In the fourth embodiment, after explaining a configuration of a sending and receiving apparatus according to the fourth embodiment and a flow of process by the sending and receiving apparatus, an effect achieved by the fourth embodiment will be explained. 
     [Configuration of Sending and Receiving Apparatus According to Fourth Embodiment] 
     First, using  FIG. 11 ,  FIG. 12  and  FIG. 13 , a configuration of the sending and receiving apparatus  10  according to a fourth embodiment will be explained.  FIG. 11  is a block diagram of configuration of the sending and receiving apparatus according to the fourth embodiment.  FIG. 12  is a view depicting one example of information stored in a reference table according to the fourth embodiment.  FIG. 13  is a view for explaining one example of process by a corrected value calculating unit according to the fourth embodiment. 
     The sending and receiving apparatus  10  according to the fourth embodiment includes a reference table  54  in place of the correction table  48 , and includes a corrected value calculating unit  55  in place of the correction information selecting unit  50 . The reference table  54  corresponds to “correction information holding unit” and the corrected value calculating unit  55  corresponds to “corrected value calculating unit” described in claims. Configuration of the sending and receiving apparatus  10  according to the fourth embodiment further differs from that of the sending and receiving apparatus  10  according to the second embodiment in the following points. 
     To be more specific, the reference table  54  holds pieces of correction information used for correction of a measured value of the RSSI value of the reception data, for each predetermined reference value of the signal levels of the transmission data. Concretely, the reference table  54  holds correction information (+46 dB) and correction information (0 dB) as depicted in  FIG. 12 . The reference table  54  stores the RSSI corrected values in correlation with the respective RSSI reported values for each piece of correction information. 
     “+46 dB” and “0 dB” correspond to the predetermined reference values of the signal levels of the transmission data. 
     The corrected value calculating unit  55  calculates a corrected value for correcting the signal strength of the reception data using an acquisition result of the RSSI value by the sending level value acquiring unit  53  and each correction information held by the reference table  54 . For example, the corrected value calculating unit  55  calculates a corrected value for correcting the signal strength of the reception data by proportional calculation. 
     In one concrete example for explanation, it is assumed that the corrected value calculating unit  55  receives an RSSI reported value of −104 dBm from the RSSI value measuring unit  49 , while receiving the signal level “+23 dB” of the transmission data from the sending level value acquiring unit  53 . 
     At this time, the corrected value calculating unit  55  assigns “+23” to “x” of the formula depicted in  FIG. 13 . Also, the corrected value calculating unit  55  acquires an RSSI corrected value of −100 dBm corresponding to the RSSI reported value −104 dBm by referring to the correction information (+46 dB), and assigns “−100” to “z 2 ” of the formula depicted in  FIG. 13 . Also, the corrected value calculating unit  55  acquires an RSSI corrected value of −103 dBm corresponding to the RSSI reported value −104 dBm by referring to the correction information (0 dB), and assigns “−103” to “z 1 ” of the formula depicted in  FIG. 13 . “46” and “0” in the formula depicted in  FIG. 13  correspond to the predetermined reference values of the signal levels of the transmission data. 
     Then the corrected value calculating unit  55  calculates “y” (calculates y=−101.5 in the example) in the formula depicted in  FIG. 13  which corresponds to the corrected value for correcting the signal strength of the reception data. And the corrected value calculating unit  55  inputs the calculated corrected value to the RSSI value correcting unit  51 . 
     The RSSI value correcting unit  51  corrects the measured value of the signal strength of the reception data to the corrected value calculated by the corrected value calculating unit  55 . 
     [Process by Sending and Receiving Apparatus According to the Fourth Embodiment] 
     Next, using  FIG. 14 , a process by the sending and receiving apparatus according to the fourth embodiment will be explained.  FIG. 14  is a flowchart of a flow of process by the sending and receiving apparatus according to the fourth embodiment. 
     In the following, a flow of process which is characteristic of the sending and receiving apparatus  10  according to the fourth embodiment will be explained on assumption that the sending and receiving apparatus according to the fourth embodiment always acquires a signal level value of the transmission data. 
     As depicted in  FIG. 14 , upon reception of a carrier wave outgoing from the terminal device (Yes at Step S 4001 ), the sending and receiving apparatus  10  executes a reception data extracting process (Step S 4002 ), and measures an RSSI value of reception data (Step S 4003 ). 
     Subsequently, the sending and receiving apparatus  10  calculates a corrected value for correcting the signal strength of the reception data, using an acquisition result of the signal level value of the transmission data and each correction information (Step S 4004 ), and corrects a measured value of the signal strength of the reception data to the calculated corrected value (Step S 4005 ). 
     Then the sending and receiving apparatus  10  demodulates the reception data by using the corrected measured value (Step S 4006 ), sends the demodulated reception data to the communication device (Step S 4007 ), and ends the reception data sending and receiving process. 
     [Effect of Fourth Embodiment] 
     As described above, according to the fourth embodiment, it is possible to demodulate the reception data with excellent quality while flexibly responding to the signal level of the transmission data. Furthermore, according to the fourth embodiment, an effect arises that information amount of the correction information to be held can be controlled. 
     [d] Fifth Embodiment 
     While the first to fourth embodiments have been explained, the present invention may be practiced in various different forms other than the above embodiments. In the following, other embodiment will be explained as the fifth embodiment. 
     For example, in the first to fourth embodiments, the case where the RSSI corrected values are stored as the correction information in correlation with the respective RSSI reported values in the correction table  48  (reference table  54 ) is explained. However, the present example is not limited thereto. Application to the present example is allowed by holding information capable of correcting a measured value of the RSSI value of the measured reception data (for example, differential value of the RSSI values before and after correction, calculation formula for calculating the RSSI value after correction from the RSSI value before correction). 
     Further, in the first embodiment, the case where control of the power unit  28  by the switch  29  is monitored is explained, however, the present example is not limited thereto, and a driving state of a constituting element that causes an error in measurement result of the RSSI value processed by the reception data may be monitored. 
     Processing sequences, control sequences, concrete names, information including various data and parameters (for example, storage information depicted in  FIG. 3 ,  FIG. 6 ,  FIG. 9  and  FIG. 12  and calculation formula depicted in  FIG. 13 ) depicted in the specification and drawings may be arbitrarily changed unless otherwise specified. 
     Each constituting element of each depicted apparatus is given in a functionally conceptual manner, and is not necessarily requested to be configured physically as illustrated in drawings. That is, concrete forms of distribution and integration of each apparatus are not limited to those illustrated in drawings, and the whole or part thereof may be functionally or physically distributed or integrated by appropriate units depending on various loads or use situations. For example, the correction information selecting unit  50  and the RSSI value correcting unit  51  depicted in  FIG. 2  may be integrated. 
     Furthermore, each processing function executed by each apparatus may be fully or partly implemented by a CPU or a program analyzed and executed by the CPU, or implemented by hardware according to wired logic. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.