JP2005333473A - Radio terminal for switching transmission media, and method for switching transmission media - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio terminal capable of selecting the optimum transmission medium in accordance with the quality of a transmission signal, being applied to a plurality of broadcasting and communication systems and improving convenience, and to provide a transmission media switching method. <P>SOLUTION: A received signal quality determining part 31 calculates a new received signal level on the basis of an inputted received signal level and a stored conversion value and outputs quality information being the new received signal level. A transmission medium selecting/control part 32 selects a transmission medium on the basis of inputted quality information, stored selection algorithm and reference information such as priority. In addition, the transmission medium selecting/control part 32 specifies modulation and demodulation software and downloads the modulation and demodulation software from a modulation and demodulation software storing part 33 to software radio modulating and demodulating parts 10 and 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for downloading modulation / demodulation software in a broadcasting / communication system using software defined radio technology, and more particularly to a wireless terminal that selects an optimal broadcasting / communication medium from a plurality of media and downloads the modulation / demodulation software.

  A conventional method of downloading modulation / demodulation software in a broadcasting / communication system using software defined radio technology relates to a procedure in a single communication system, for example (see Non-Patent Document 1). In this download method, when a wireless terminal performs a series of wireless modulation / demodulation processing for detecting, demodulating, and performing packet processing on a received signal, a single transmission medium determined in advance for the modulation / demodulation processing unit is used. Modulation / demodulation software corresponding to In this download method, the quality of the received signal is not judged and the optimum transmission medium is not selected. That is, since the conventional wireless terminal is applied to a single communication system, it does not have a specific cooperation means when a plurality of communication systems are linked. For example, a broadcasting system and a communication system are linked. In some cases it was not applicable.

“A Study on Wireless Downloading Method for Software Defined Radio”, IEICE Software Radio Study Group, April 2000, SR00-07, p. 47-52

  Currently, in software radio, radio terminals capable of receiving various signals and performing modulation / demodulation processing under a broadcasting / communication system are being studied. Specifically, there is a demand for a wireless terminal having an advantage that it is not necessary to change the hardware configuration of the wireless terminal by specifying and downloading modulation / demodulation software applicable to each broadcasting / communication system. Such a wireless terminal can receive signals corresponding to a plurality of broadcasting / communication systems by selecting an optimal transmission medium (transmission method / transmission path for wireless communication) and downloading modulation / demodulation software corresponding thereto. It will be. This is expected to improve the convenience of users of broadcasting / communication systems. For this purpose, it is necessary to select an optimum transmission medium under a plurality of broadcasting / communication systems, and specific cooperation means for linking the respective systems is necessary.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to select a plurality of transmission media in accordance with the quality of a received signal in a broadcasting / communication system using software defined radio technology. An object of the present invention is to provide a wireless terminal and a transmission media switching method that can cope with broadcasting / communication systems and can improve convenience.

  In order to achieve the above object, the wireless terminal of the present invention receives broadcast and communication system signals and uses a transmission media modulation / demodulation software applied to the system to perform a series of signal processing such as detection and demodulation. A wireless terminal that provides a predetermined service based on data output from the modulation / demodulation unit, a storage unit that stores a plurality of modulation / demodulation software for each transmission medium, and determination information regarding the quality of the signal And a selection control unit that selects transmission media based on the determination information and outputs modulation / demodulation software of the transmission media from the storage unit to the modulation / demodulation unit.

  The wireless terminal of the present invention includes two or more modulation / demodulation units and a switch that inputs data output from each of the modulation / demodulation units and outputs one of these data, Unit outputs determination information for each modulation / demodulation unit, and the selection control unit selects a transmission medium based on each determination information, and outputs modulation / demodulation software of the transmission medium from the storage unit to the modulation / demodulation unit. The switch is controlled so that signal processing is performed using software.

  The radio terminal according to the present invention is characterized in that the selection control unit newly selects a transmission medium based on the determination information when the predetermined quality is not satisfied. The selection control unit may select a transmission medium according to a preset algorithm or priority based on the determination information. Further, the determination unit includes a received signal level, a C / N margin that is a ratio between the received signal level and a predetermined level, a bit error rate, a packet error rate, a bit rate, and a packet rate related to data output by the modem unit Is output as determination information.

  Further, the transmission media switching method of the present invention includes a modulation / demodulation unit that receives a broadcast and communication system signal and performs a series of signal processing such as detection and demodulation using transmission media modulation / demodulation software applied to the system. The transmission medium switching method when a wireless terminal including a storage unit storing a plurality of modulation / demodulation software for each transmission medium provides a predetermined service based on data output from the modulation / demodulation unit. A step of outputting determination information regarding the quality of the signal, a step of selecting a transmission medium based on the determination information, a step of outputting modulation / demodulation software of the selected transmission medium from the storage unit to the modulation / demodulation unit, And performing the signal processing using the modulation / demodulation software.

  According to the present invention, in a broadcasting / communication system using software defined radio technology, an optimal transmission medium can be selected according to the quality of a received signal, and a plurality of broadcasting / communication systems can be supported. Therefore, a user having a wireless terminal can receive a broadcast / communication service with good reception quality, and can improve convenience for the user.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First embodiment]
FIG. 1 is a block diagram showing a configuration of a wireless terminal 1 according to the first embodiment of the present invention. The radio terminal 1 includes a system A software radio modulation / demodulation unit 10 having a detection unit 11, a demodulation unit 12, and a packet processing unit 13, and a system B software radio modulation / demodulation unit having a detection unit 21, a demodulation unit 22, and a packet processing unit 23. Unit 20, system switch 34, application processing unit 35, received signal quality determination unit 31, transmission media selection / control unit 32, and modulation / demodulation software storage unit 33.

  The software radio modulation / demodulation units 10 and 20 are devices that can change the contents of signal processing of the detection units 11 and 21, the demodulation units 12 and 22, and the packet processing units 13 and 23, respectively, such as a DSP (Digital Signal Processor). And FPGA (Field Programmable Gate Array). The software is stored in the modulation / demodulation software storage unit 33 as modulation / demodulation software corresponding to the contents of signal processing in the software radio modulation / demodulation units 10 and 20. The transmission medium selection / control unit 32 selects a transmission medium by a method described later, specifies modulation / demodulation software according to the selection result, and downloads it from the modulation / demodulation software storage unit 33 to the software radio modulation / demodulation units 10 and 20. As a result, the software defined radio modulation / demodulation units 10 and 20 execute modulation / demodulation software corresponding to the selected transmission medium and perform predetermined signal processing. As described above, the wireless terminal 1 is a so-called software wireless terminal, and by changing the modulation / demodulation software, the software wireless modulation / demodulation units 10 and 20 and the application processing unit 35 are different transmission media using the same hardware. Various signals of a plurality of broadcast / communication systems can be received.

  The radio terminal 1 shown in FIG. 1 includes two systems (system A and system B) of software radio modems 10 having detectors 11 and 21, demods 12 and 22 and packet processors 13 and 23 having the same functions. , 20. Here, it is assumed that the software radio modulation / demodulation unit 10 of the system A among the two systems receives a broadcast / communication signal, and the software radio modulation / demodulation unit 20 of the system B is a standby system. The software radio modulation / demodulation units 10 and 20 are in a state in which different modulation / demodulation software is input from the modulation / demodulation software storage unit 33 by the transmission media selection / control unit 32 and processing by the modulation / demodulation software can be performed.

  Next, functions of each unit of the wireless terminal 1 will be described in detail. The detection unit 11 of the software radio modulation / demodulation unit 10 and the detection unit 21 of the software radio modulation / demodulation unit 20 receive an RF (Radio Frequency) signal and an IF (intermediate Frequency) signal after frequency conversion from a receiving antenna (not shown). Then, an RF signal or the like is converted into a baseband signal and output. The demodulating units 12 and 22 receive baseband signals from the detecting units 11 and 21, perform digital demodulation, and output a bit stream. The packet processing units 13 and 23 receive baseband signals from the demodulation units 12 and 22, perform transmission packet processing by TCP / IP, MPEG-2 TS (Transport Stream), etc., and output the packets as received data.

  The system switching unit 34 receives received data from the packet processing units 13 and 23, inputs a switching signal (to be described later) from the transmission media selection / control unit 32, performs system switching based on the switching signal, and the packet processing unit 13 , 23, one of the received data is output. The application processing unit 35 receives the received data from the system switch 34, performs processing according to the content of the broadcast / communication service, and outputs the received data to the display, VTR, speaker, etc. (not shown) as application unit received data.

  The functions of the received signal quality determination unit 31, the transmission media selection / control unit 32, and the modulation / demodulation software storage unit 33 will be described in detail using the received signal level as an example. The detectors 11 and 21 output the received signal level such as the input RF signal to the received signal quality determination unit 31. The received signal quality determination unit 31 holds reference information of converted values in order to convert the input received signal level. The reference information of the converted value is, for example, a gain of signal amplitude in a filter circuit and an amplifier of a high frequency circuit (not shown) provided between the receiving antenna and the software radio modulation / demodulation units 10 and 20. In addition, in order to perform conversion processing when the input signal to the received signal quality determination unit 31 is an IF signal or baseband signal after frequency conversion, the gain by a frequency conversion circuit (not shown) is also held as a converted value. ing. Then, the received signal quality determination unit 31 calculates a new received signal level based on the received signal level input from the detectors 11 and 21 and the stored conversion value, and determines the new received signal level as the received signal. The quality information is output to the transmission media selection / control unit 32. That is, the reception signal quality determination unit 31 outputs the quality information of the system A and the quality information of the system B to the transmission medium selection / control unit 32 as reception signal determination information.

  The transmission medium selection / control unit 32 holds priority, selection algorithm, etc. as reference information for selecting a transmission medium, and further receives a quality judgment reference value of the received signal level as reference information for judging the quality of the received signal. keeping. Then, the quality information in the systems A and B is input from the received signal quality determination unit 31, and the transmission medium is selected based on the quality information in the systems A and B and the held reference information. Further, the transmission media selection / control unit 32 specifies the modulation / demodulation software corresponding to the selected transmission medium, and downloads the modulation / demodulation software from the modulation / demodulation software storage unit 33 to the software radio modulation / demodulation unit 10 or the software radio modulation / demodulation unit 20. Further, a switching signal for switching the system to the software radio modulation / demodulation unit 10 or the software radio modulation / demodulation unit 20 to which the modulation / demodulation software is downloaded is output to the system switch 34.

  Next, the processing flow of the selection algorithm for selecting the transmission medium will be described with reference to FIG. 2 by taking the received signal level as an example. The software radio modulation / demodulation units 10 and 20 are downloaded with different modulation / demodulation software and perform signal processing by the respective modulation / demodulation software. The system switch 34 receives the data received from the software radio modulation / demodulation unit 10 of the system A. Is switched to output to the application processing unit 35.

  First, the transmission media selection / control unit 32 compares the received signal level, which is the quality information in the input system A, with the held quality judgment reference value of the received level (step S1). If the received signal level is equal to or higher than the quality judgment reference value, it is determined that the quality of the received signal in system A is good, and no new transmission medium is selected (step 2). As a result, the wireless terminal 1 uses the software wireless modulation / demodulation unit 10 of the system A to continuously perform the signal processing of the broadcasting / communication system with the currently selected transmission medium.

  If the received signal level of the system A is lower than the quality judgment reference value in Step 1, the received signal level, which is the quality information in the inputted system B, is compared with the quality judgment reference value of the received signal level (Step 1). S3). If the received signal level is equal to or higher than the quality judgment reference value, the quality of the received signal in system B is assumed to be good, and a switching signal for switching from system A to system B is output to system switch 34 (step S4). . As a result, the wireless terminal 1 performs signal processing of the broadcasting / communication system using a transmission medium different from that of the system A using the software radio modulation / demodulation unit 20 of the system B.

  In step 3, when the received signal level of the system B is lower than the quality judgment reference value, it is determined that the quality of the received signal in the system B is not good, and another transmission medium different from the current transmission medium is selected. Then, the modulation / demodulation software corresponding to the selected transmission medium is specified, and the modulation / demodulation software is downloaded from the modulation / demodulation software storage unit 33 to the B system software radio modulation / demodulation unit 20 (step S5). Then, the process returns to step 3, and the input received signal level of the system B is again compared with the quality judgment reference value (step 3).

  As described above, when the received signal level, which is the quality information of the system A, is equal to or higher than the quality determination reference value, the transmission media selection / control unit 32 causes the software radio modulation / demodulation unit 10 of the system A to transmit the signal of the broadcasting / communication system. Continue processing. In addition, as long as the received signal level that is quality information of the system A is below the quality determination reference value and the received signal level that is quality information of the system B is below the quality determination reference value, the current transmission medium is The process of selecting another different transmission medium, specifying the modulation / demodulation software corresponding to the selected transmission medium, and downloading the modulation / demodulation software from the modulation / demodulation software storage unit 33 to the software radio modulation / demodulation unit 20 of the B system is continued. On the other hand, when the received signal level that is quality information of the system B is equal to or higher than the quality determination reference value, a switching signal for switching from the system A to the system B is output to the system switch 34. As a result, the system A is switched to the system B, and the software radio modulation / demodulation unit 20 of the system B performs signal processing of the broadcasting / communication system.

  Here, the transmission media selection / control unit 32 can select not only the transmission media based on the selection algorithm shown in FIG. 2, but also the transmission media based on the stored priority order. In this case, the priority order is determined by using the received signal level, communication cost such as communication cost, transmission bit rate, service area of the broadcasting / communication system, etc. alone or in combination. Is done. In addition, for example, when there are a plurality of pieces of input quality information, the priorities are ranked respectively. This ranking is freely set by a user who has the wireless terminal 1 and receives broadcasting / communication service.

[Second Embodiment]
FIG. 3 is a block diagram showing the configuration of the wireless terminal 51 according to the second embodiment of the present invention. The wireless terminal 51 includes a software radio modulation / demodulation unit 60 having a detection unit 61, a demodulation unit 62, and a packet processing unit 63, an application processing unit 75, a received signal quality determination unit 71, and a transmission media selection / control unit. 72 and a modem software storage unit 73. These correspond to the software defined radio modulation / demodulation units 10 and 20, the application processing unit 35, the received signal quality determination unit 31, the transmission media selection / control unit 32, and the modulation / demodulation software storage unit 33 shown in FIG. , Have the same function. The reception signal quality determination unit 71, transmission media selection / control unit 72, and modulation / demodulation software storage unit 73 in FIG. 3 perform one system of processing, whereas the reception signal quality determination unit 31, transmission media selection shown in FIG. The control unit 32 and the modulation / demodulation software storage unit 33 are different in that they perform two systems of processing. The wireless terminal 51 is different in that it does not include the system switch 34 shown in FIG.

  The modulation / demodulation software storage unit 73 stores a plurality of modulation / demodulation software corresponding to the contents of signal processing in the software radio modulation / demodulation unit 60. The wireless terminal 51 is a so-called software wireless terminal, and by changing the modulation / demodulation software, one software defined radio modulation / demodulation unit 60 and application processing unit 75 can transmit a plurality of broadcast / communications with the same hardware using different transmission media. Various signals of the system can be received. Here, the software radio modulation / demodulation unit 60 receives predetermined modulation / demodulation software from the modulation / demodulation software storage unit 73 by the transmission media selection / control unit 72 and performs signal processing by the modulation / demodulation software.

  Hereinafter, functions of the received signal quality determination unit 71, the transmission media selection / control unit 72, and the modulation / demodulation software storage unit 73 will be described in detail using the received signal level as an example. The reception signal quality determination unit 71 performs the same processing as the reception signal quality determination unit 31 shown in FIG. 1 as follows. The reception signal quality determination unit 71 calculates a new reception signal level based on the reception signal level input from the detection unit 61 and the conversion value held in advance. Then, the received signal quality determination unit 71 outputs the quality information that is a new received signal level to the transmission media selection / control unit 72 as received signal determination information.

  The transmission medium selection / control unit 72 holds reference information such as a priority order for selecting a transmission medium, a selection algorithm, and quality determination reference value reference information for determining the quality of a received signal. Then, quality information is input from the received signal quality determination unit 71, and a transmission medium is selected based on the quality information and the stored reference information. Then, the transmission medium selection / control unit 72 specifies the modulation / demodulation software corresponding to the selected transmission medium, and downloads the modulation / demodulation software from the modulation / demodulation software storage unit 73 to the software radio modulation / demodulation unit 60.

  Next, a processing flow of a selection algorithm for selecting a transmission medium will be described. The transmission media selection / control unit 72 compares the received signal level, which is the input quality information, with the held quality judgment reference value. When the received signal level is equal to or higher than the quality judgment reference value, it is determined that the received signal quality is good and no new transmission medium is selected. As a result, the wireless terminal 51 uses the software wireless modulation / demodulation unit 60 to continue signal processing of the broadcasting / communication system using the currently selected transmission medium.

  When the received signal level is lower than the quality judgment reference value, it is determined that the quality of the received signal is not good, and another transmission medium different from the current transmission medium is selected. Then, the transmission medium selection / control unit 72 identifies the modulation / demodulation software corresponding to the selected transmission medium, and downloads the modulation / demodulation software from the modulation / demodulation software storage unit 73 to the software radio modulation / demodulation unit 60. Accordingly, the wireless terminal 51 performs signal processing of the broadcasting / communication system with the new transmission medium using the software wireless modulation / demodulation unit 60.

  As described above, when the received signal level, which is quality information, is equal to or higher than the quality determination reference value, the transmission medium selection / control unit 72 performs software radio modulation / demodulation using the current transmission medium without selecting a new transmission medium. The unit 60 continues the signal processing. Further, as long as the received signal level is below the quality judgment reference value, another transmission medium different from the current transmission medium is selected, the modulation / demodulation software corresponding to the selected transmission medium is specified, and the modulation / demodulation software storage unit 73 The process of downloading the modulation / demodulation software to the software radio modulation / demodulation unit 60 is continued.

  Note that the transmission medium selection / control unit 72 not only selects a transmission medium based on the above-described selection algorithm, but also selects a transmission medium based on the stored priority order as in the first embodiment. You can also.

  As described above, according to the first and second embodiments of the present invention, the received signal quality determination units 31, 71 output the new received signal level obtained by converting the received signal level as quality information, and transmit it. The media selection / control units 32 and 72 select the transmission medium based on the quality information and the reference information. This makes it possible to select an optimal transmission medium according to the quality of the received signal.

  According to the first and second embodiments of the present invention, the modulation / demodulation software storage units 33 and 73 are applicable to a plurality of broadcasting / communication systems, and store a plurality of modulation / demodulation software corresponding to the transmission media. Then, the transmission media selection / control units 32 and 72 specify the modulation / demodulation software and download it from the modulation / demodulation software storage units 33 and 73 to the software defined radio modulation / demodulation units 10, 20, and 60. As a result, the software radio modulation / demodulation units 10, 20, and 60 perform signal processing in accordance with the modulation / demodulation software, so that the radio terminals 1 and 51 can be applied to a plurality of broadcast / communication systems. Therefore, for example, if the user who owns the wireless terminals 1 and 51 goes out of the service area of the broadcasting / communication system, he / she can receive services by other broadcasting / communication systems. It becomes possible to receive various services without being conscious.

  Further, according to the first and second embodiments of the present invention, the transmission medium selection / control units 32 and 72 select the transmission medium based on the priority set by the user. As a result, the priority order according to the user's wishes can be set, so that it becomes possible to select a transmission medium according to the user's wishes.

  Further, according to the first embodiment of the present invention, the software radio modulation / demodulation unit 10 of the system A and the software radio modulation / demodulation unit 20 of the system B perform signal processing using the downloaded modulation / demodulation software, respectively. The transmission media selection / control unit 32 outputs a signal for switching the system to the system switch 34 below. Thereby, since the signal processing is not interrupted, the system can be switched instantaneously and seamlessly.

  In the first embodiment, the software radio modulation / demodulation unit provided in the radio terminal 1 has two systems A and B, and the signal processing is performed independently for each system. It is not limited to this. For example, only one of the two systems may perform signal processing, or three or more software radio modulation / demodulation units may be provided.

  In the first and second embodiments, the received signal quality determination units 31 and 71 receive the received signal level from the detection units 11, 21 and 61 of the software defined radio modulation / demodulation units 10, 20, and 60. The level is converted to calculate a new received signal level, and the new received signal level is output as quality information regarding the quality of the received signal. However, the present invention is not limited to this. For example, a bit stream may be input from the demodulation units 12, 22, and 62, and reception data may be input from the packet processing units 13, 23, and 63. These pieces of information may be converted and output as quality information. In this case, the received signal quality determination units 31 and 71 need to hold conversion values corresponding to the respective information, and the transmission media selection / control units 32 and 72 need to hold quality determination reference values. Further, the received signal quality information may be calculated based on power, level fluctuation, frequency spectrum shape, frequency spectrum fluctuation, etc., in addition to the above-mentioned received signal level, bit stream and received data. Also in this case, the received signal quality determination units 31 and 71 need to hold conversion values for the respective information, and the transmission media selection / control units 32 and 72 need to hold quality determination reference values. Information necessary for the determination may be input from each processing unit such as the system switch 34 and the application processing units 35 and 75 other than the software radio modulation / demodulation units 10, 20, and 60.

  Also, the received signal quality determination units 31 and 71 and the transmission media selection / control units 32 and 72 have a C / N margin that is a ratio between the received signal level and the required level of the transmission media, and the signals of the software radio modulation / demodulation units 10 and 20. One of the bit error rate and packet error rate calculated from the processing result, the bit rate calculated from the processed data of the software radio modems 10 and 20 and the application processing units 35 and 75, and the packet rate May be handled as quality information.

  The transmission media selection / control units 32 and 72 randomly select a transmission medium from among a plurality of transmission media, and randomly modulate / demodulate the modulation / demodulation software stored in the modulation / demodulation software storage units 33 and 73. Software may be specified. In addition, a transmission medium that is not used by the software radio modulation / demodulation units 10 and 20 may be selected to specify modulation / demodulation software.

  In the first embodiment, the transmission media selection / control unit 32 selects a transmission medium according to the selection algorithm shown in FIG. 2 and downloads the modulation / demodulation software to the software radio modulation / demodulation units 10 and 20. However, it is also possible to simply select a system with good reception signal quality from the systems A and B and output the switching signal to the system switching unit 34 so as to perform signal processing in that system. This makes it possible to use a transmission medium with good reception quality without downloading modulation / demodulation software.

  In the second embodiment, the transmission media selection / control unit 72 selects the transmission media and downloads the modulation / demodulation software based on the quality of the received signal, using the selection algorithm described above. The reception data is always output to the application processing unit 75, but the reception data may be output only when the quality of the reception signal is good. Thereby, the application processing unit 75 can input the received data and perform a predetermined process only when the quality of the received signal is good, so that the user can receive a high-quality service. .

  The present invention has been described with reference to the examples. However, the above description is intended to help the understanding of the present invention, and does not limit the scope of the claims of the present invention. Accordingly, various modifications can be made without departing from the gist of the present invention, and can be appropriately changed within the scope of achieving the object of the present invention and producing effects.

It is a block diagram which shows the structure of the radio | wireless terminal which concerns on 1st Example of this invention. FIG. 2 is a flowchart illustrating a transmission media selection algorithm in the wireless terminal of FIG. 1. It is a block diagram which shows the structure of the radio | wireless terminal which concerns on 2nd Example of this invention.

Explanation of symbols

1, 51 Radio terminals 10, 20, 60 Software radio modulation / demodulation units 11, 21, 61 Detection units 12, 22, 62 Demodulation units 13, 23, 63 Packet processing units 31, 71 Received signal quality judgment units 32, 72 Transmission media selection Control unit 33, 73 Modulation / demodulation software storage unit 34 System switch 35, 75 Application processing unit

Claims (6)

Based on the data output from the modulation / demodulation unit, including a modulation / demodulation unit that receives a signal of a broadcast and a communication system and performs a series of signal processing such as detection and demodulation using modulation / demodulation software of a transmission medium applied to the system In a wireless terminal that provides a predetermined service,
A storage unit that stores a plurality of modulation / demodulation software for each transmission medium, a determination unit that outputs determination information regarding the quality of the signal, a transmission medium is selected based on the determination information, and the modulation / demodulation software of the transmission medium is A wireless terminal comprising: a selection control unit that outputs data from a storage unit to a modem unit. The wireless terminal according to claim 1,
Two or more modulation / demodulation units, and a switch that inputs data output from each of the modulation / demodulation units and outputs one of these data,
The determination unit outputs determination information for each modulation / demodulation unit, the selection control unit selects a transmission medium based on each determination information, and outputs modulation / demodulation software of the transmission medium from the storage unit to the modulation / demodulation unit, A wireless terminal that controls the switch so that signal processing is performed using the modulation / demodulation software. In the wireless terminal according to claim 1 or 2,
The radio terminal according to claim 1, wherein the selection control unit selects a new transmission medium based on the determination information when the predetermined quality is not satisfied. In the wireless terminal according to claim 1 or 2,
The radio terminal according to claim 1, wherein the selection control unit selects a transmission medium according to a preset algorithm or priority based on the determination information. In the wireless terminal according to claim 1 or 2,
The determination unit includes at least one of a received signal level, a C / N margin that is a ratio between the received signal level and a predetermined level, a bit error rate, a packet error rate, a bit rate, and a packet rate related to data output by the modem unit. A wireless terminal that outputs one as determination information. A modulation / demodulation unit that receives a broadcast and communication system signal and performs a series of signal processing such as detection and demodulation using modulation / demodulation software of a transmission medium applied to the system, and a plurality of modulation / demodulation software for each transmission medium are stored. A wireless terminal provided with a storage unit provides a predetermined service based on data output from the modem unit, the transmission medium switching method,
A step of outputting determination information regarding the quality of the signal; a step of selecting a transmission medium based on the determination information; a step of outputting modulation / demodulation software of the selected transmission medium from the storage unit to the modulation / demodulation unit; And a step of performing the signal processing using software.

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