JP2012175196A - Multimode wireless equipment, and method of finding connection destination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a multimode wireless equipment to find a communication system suitable for connection quickly in a region where a plurality of communication systems sharing the same frequency band coexist.SOLUTION: A multimode wireless equipment has: a connection destination system determination part determining a connection destination communication system based on a signal inputted to an antenna; an operation mode controller setting a value of a communication parameter at least including a transmission format and a center frequency of a communication signal to a value used in the connection destination communication system; and a communication part connected to the connection destination communication system by using the communication parameter that is set by the operation mode controller to perform wireless communication. The connection destination system determination part calculates a periodic autocorrelation value of the signal inputted to the antenna with respect to the parameter in a predetermined range, distinguishes the parameter that causes a relatively strong periodic autocorrelation value, and determines a communication system corresponding to the parameter as the connection destination communication system.

Description

  The present invention relates to a method for discovering a multi-mode radio and a connected system.

  With the diversification of communication services, users can use various communication systems. The type and number of such communication systems are expected to increase further in the future. Usually, since the communication method differs for each communication system, it is extremely inconvenient if a dedicated radio is required for each communication system. From such a viewpoint, it is preferable to use a multi-mode radio that can operate in a plurality of communication systems.

  In general, multimode radios are either hardware based or software based. The hardware-based multi-mode wireless device separately includes signal processing hardware for each of the plurality of communication systems, thereby enabling communication in the plurality of communication systems. In this case, since the hardware exists redundantly, there is an advantage that even if one of the communication system hardwares fails, the communication in another communication system is not affected. However, since the number of communication systems is not small, there is a concern that the bulk of the multi-mode wireless device will increase.

  In contrast, software-based multimode radios share signal processing hardware in a plurality of communication systems as much as possible and rewrite signal processing programs to enable communication in a specific communication system. The software-based multi-mode radio is referred to as “software radio” or SDR (Software Defined Radio). A multi-mode radio based on software has less hardware redundancy, but can meet the demand for miniaturization and can flexibly support various communication systems. In recent years, in order to increase the utilization efficiency of communication resources, it has been realized that a plurality of communication systems can use the same frequency band, and it is easy to implement common hardware in a plurality of communication systems. A conventional software defined radio is described in Non-Patent Document 1.

J. Mitola, “The Software Radio Architecture”, IEEE Communications Magazine, vol. 33, issue. 5, pp. 26-38, May 1995.

  When a conventional multi-mode radio based on software is connected to any communication system, the connection destination must be determined while sequentially switching software for controlling the operation of each of the plurality of communication systems. For example, the multimode radio rewrites (switches) software for the first communication system and attempts to receive a control signal. If it can be properly received, the first communication system becomes the connection destination, but if it cannot be properly received, the software for the second communication system is rewritten (switched), and the same processing continues. Therefore, a lot of time and power may be consumed before an appropriate connection destination can be found. Although the first and second communication systems can be connected together, the second communication system may be able to communicate with higher quality. Even in this case, when a connection is first attempted for the first communication system, the first communication system is determined as the connection destination. In this case, there is a problem that a non-best communication system is determined as a connection destination.

  An object of the present invention is to enable a multimode radio to quickly find a communication system suitable for connection in an area where a plurality of communication systems sharing the same frequency band coexist.

A multi-mode radio according to one embodiment is
A connection destination system determination unit that determines a communication system of a connection destination based on a signal input to the antenna;
An operation mode control unit for setting a value of a communication parameter including at least a transmission format and a center frequency of a communication signal to a value used in the communication system of the connection destination;
A communication unit configured to connect to the communication system of the connection destination and perform wireless communication using the communication parameter set by the operation mode control unit, and the connection destination system determination unit is input to the antenna In addition, the periodic autocorrelation value of the signal is calculated for a parameter within a predetermined range, a parameter that provides a relatively strong periodic autocorrelation value is determined, and a communication system corresponding to the parameter is defined as the communication system of the connection destination. It is a multimode radio to be determined.

  According to one embodiment, a multi-mode radio can quickly find a communication system suitable for connection in an area where a plurality of communication systems sharing the same frequency band coexist.

The figure which shows the radio | wireless communications system used in an Example. The figure for demonstrating an example of a waveform feature-value. The figure which shows the multi-mode radio | wireless machine used in an Example. The figure which shows a mode that a peak arises in the cyclic frequency different for every communication system. The figure which shows the example of calculation of the cyclic autocorrelation value CAF with respect to an OFDM signal. The figure which shows the example of calculation of the cyclic autocorrelation value CAF with respect to a CDMA signal. The figure which shows the operation example of the multimode radio | wireless machine in an Example. The figure for demonstrating an operation | movement outline | summary. The figure which shows a mode that three signals are contained in the same frequency range.

  A multimode radio according to an embodiment calculates a cyclic autocorrelation value CAF of a signal input to an antenna for a parameter within a predetermined range, determines a parameter that provides a relatively strong cyclic autocorrelation value CAF, and A communication system corresponding to the parameter is determined as a connection destination communication system. Since the communication system is determined based on the cyclic autocorrelation value CAF, the multimode radio does not need to rewrite signal processing software for each possible communication system. The multimode radio simply needs to store information on what parameter the signal of each communication system causes the peak of the cyclic autocorrelation value CAF. Even if the reception level (for example, SNR) of a signal from a certain communication system is low, the presence of the communication system can be detected if the cyclic autocorrelation value CAF of the communication system can be appropriately calculated. In order to calculate the cyclic autocorrelation value CAF appropriately, the observation length is simply increased. Furthermore, even when signals from multiple communication systems are included in the same frequency range, the cyclic autocorrelation value CAF of each communication system signal peaks at different parameters, so the communication systems are properly distinguished. can do. For this reason, according to the present embodiment, it is possible to easily and efficiently find a communication system to which the multi-mode wireless device should be connected.

  Examples will be described from the following viewpoints.

1． Wireless communication system
2． Multimode radio
3． Example of operation

<1. Wireless communication system>
FIG. 1 shows a wireless communication system used in the embodiment. FIG. 1 shows a first communication system using a wireless regional area network (WRAN), a second communication system using a wireless local area network (WLAN), and a wireless personal area network (Wireless Personal Area Network). A third communication system by Network: WPAN) and a multimode radio are shown. In the figure, “WS use” indicates that communication is performed using a white space (WS) in a frequency band. The “white space” in the present application means an unused frequency, and for example, a frequency that is licensed to a certain person but not actually used by the certain person. In addition, frequencies that are not licensed to a specific person and are not used for actual communication also correspond to white space. For simplicity of illustration, only three communication systems and one multimode radio are shown, but these numbers are arbitrary. Because white space changes with time and place. A frequency band used for communication by a communication system using a white space also changes depending on time and place. The present invention can be applied to a multi-mode radio connected to a communication system using a white space. However, the present invention is not limited to a white space. For multi-mode radios connected to a communication system that dynamically changes a frequency band to be used. Is applicable.

  The multi-mode wireless device is an arbitrary wireless device configured to perform wireless communication in a plurality of communication systems by hardware or software. Such a wireless device is typically a movable wireless device (mobile device), but may be a fixed wireless device. The multi-mode radio may be a radio used by a user such as a user device, a mobile phone, an information terminal, a high-function mobile phone, a smartphone, a personal digital assistant, a portable personal computer, a base station or an access It may be a wireless device that enables user communication such as points.

  Since the first to third communication systems perform communication using different communication methods, the communication parameters such as the transmission format, center frequency, bandwidth, transmission power, symbol length, etc. depending on the data modulation method and channel coding rate are Different for each system. For this reason, the signal which each communication system uses has the characteristic peculiar to a communication system. Such a feature is an amount that is found by statistically analyzing the signal, and is referred to as a “waveform feature” in the present application.

  Hereinafter, the waveform feature amount will be described.

  An example of the waveform feature amount is a cyclic autocorrelation function (CAF) of a signal. In this case, the value of the periodic autocorrelation value of the signal increases only when a specific parameter is used for the calculation of the periodic autocorrelation value due to the modulation scheme used for the signal. The parameters include cyclic frequency and lag parameters. It has also been proposed to assign different periodic steadiness feature quantities to signals using the same modulation method. The cyclic autocorrelation value CAF is an example of a waveform feature amount, and the waveform feature amount can be expressed from various other viewpoints. Since the waveform feature amount is an amount unique to the communication system, the correspondence relationship between the communication system and the waveform feature amount is known to the multi-mode wireless device and is stored in the storage unit of the multi-mode wireless device. For this reason, the multi-mode wireless device can know what kind of communication system exists around the multi-mode wireless device by examining the waveform feature amount of the signal input to the antenna.

  FIG. 2 is a diagram for explaining a feature quantity of periodic steadiness caused by the influence of a filter as an example of a feature quantity of a signal. (1) in FIG. 2 represents a frequency spectrum of a signal having a bandwidth B [Hz] subjected to band limitation using an ideal filter. When an ideal filter is used, the frequency spectrum can be rectangular, but in practice it is difficult to realize such a steep spectrum. For this reason, a filter having a frequency spectrum with a somewhat gentle slope is usually used for band limitation. (2) in FIG. 2 represents a frequency spectrum when band limitation is performed using a normal realistic filter. As shown in (2) of FIG. 2, compared with the case where an ideal filter is used, a frequency band is slightly widened in a band limiting filter that is normally used. In this widened frequency band, the region indicated by P spread on the right side has the same signal component as the region indicated by P ′ on the left side, and the region indicated by Q ′ spread on the left side is the right Q Have the same signal component. Therefore, the part of P ′ in the signal (3) obtained by frequency shifting the signal of (2) in FIG. 2 by B [Hz] has the same signal component as P of (2), and the part of Q ′ in (3) is ( Since it has the same signal component as Q in 2), it provides a high correlation value.

  In this way, the signal whose band is limited by the filter has a high correlation (periodic autocorrelation) between the original signal and the signal obtained by frequency shifting the original signal. This correlation value can be used as a feature amount of the waveform. In the illustrated example, the correlation between a certain signal and a signal obtained by shifting the signal in the frequency direction has been considered, but it is also conceivable that the signal is similarly shifted in the time direction.

  In addition to the periodic continuity derived by calculating the correlation value between a signal and the signal shifted in some direction, the statistical value that can be used as the waveform feature value is the variance value of the signal amplitude, that is, the second order. There is a second order cumulant. In general, the second order cumulant corresponds to the variance of the possible values of the amplitude. For example, a signal with a very high peak power to average power ratio (PAPR), such as a signal using an orthogonal frequency division multiple access (OFDM) method (OFDM signal), and a signal using a code division multiple access (CDMA) method (CDMA signal) The value of the secondary cumulant is greatly different from the single carrier constant envelope signal and noise. Since the former takes various amplitude values, the dispersion is large, and the dispersion of the latter is relatively small. By utilizing such a property, it is possible to detect whether or not an OFDM signal is included in the received signal. In the case of an OFDM signal, one symbol includes a guard interval and an effective symbol, and the guard interval is a copy of a part of the effective symbol. Therefore, the correlation value between the OFDM signal and a signal obtained by shifting the OFDM signal by the effective symbol length in the time axis direction shows a high peak. Such a property may be used as the waveform feature amount. Further, in the frequency axis direction of the OFDM signal, when N subcarriers and another N subcarriers separated by a certain bandwidth have the same content, the OFDM signal and the OFDM signal are A correlation value with a signal separated by a certain bandwidth in the direction also shows a high peak. Such a property may be used as the waveform feature amount. Furthermore, even when the pilot channel is mapped away by a certain bandwidth, the correlation value between the OFDM signal and the signal separated from the OFDM signal by a certain bandwidth in the frequency axis direction shows a high peak. This property may be used as a waveform feature amount.

  As a statistic that can be used as a waveform feature amount in addition to the periodic stationarity and the second-order cumulant, the frequency correlation characteristics of the signal can be used as well. In the case of frequency correlation characteristics, transmission is performed with a bias of signal power applied to the subcarrier frequency component of a multicarrier signal such as OFDM, and the frequency correlation value of the signal is calculated on the receiving side. The number, the frequency interval between a plurality of peaks, and the like can be detected as the waveform feature amount. In this embodiment, both the periodic autocorrelation value and the frequency correlation value are referred to as the periodic autocorrelation value.

  As described above, the waveform feature amount representing the feature of the signal waveform may be based on the correlation value of the signal or may be based on a statistical value such as variance. However, for convenience of explanation, in the following example, a waveform feature amount expressed by a secondary periodic autocorrelation value CAF is used.

  The value CAF of the second-order periodic autocorrelation function for the signal x (t) is calculated by the following equation.

ここで、＊は複素共役を表す。Iは観測時間長を表す。αはサイクリック周波数（cyclic frequency）を表す。τはラグパラメータ（lag parameter）を表す。

Here, * represents a complex conjugate. I represents the observation time length. α represents a cyclic frequency. τ represents a lag parameter.

Regarding CAF, in general, if R _x ^α (τ) ≠ 0 when α ≠ 0, x (t) has periodic stationarity.

  Also, the discrete time expression of equation (1) is as follows.

ここで、I₀は観測サンプル数を表す。νはラグパラメータの離散時間表現を表す。なお、x[i]≡x（iTs）であり、Tsはサンプリング周期を表す。

Here, I ₀ represents the number of observation samples. ν represents a discrete time representation of the lag parameter. Note that x [i] ≡x (iTs), and Ts represents a sampling period.

<2. Multimode radio>
FIG. 3 shows a multimode radio used in the embodiment. The configuration shown in FIG. 3 may be used for the multimode radio in FIG. FIG. 3 shows functions particularly related to the present embodiment among various functions provided in the multimode radio. Specifically, an antenna 31, a transmission / reception separation unit 32, a connection destination system determination unit 33, an operation mode control unit 34, a reception signal acquisition unit 35, a transmission signal generation unit 36, and a storage unit 37 are shown.

  The transmission / reception separating unit 32 appropriately separates the signal received via the antenna 31 and the signal transmitted via the antenna 31. Specifically, the transmission / reception separation unit 32 provides the signal received from the antenna 32 to the connection destination system determination unit 33 or the reception signal acquisition unit 35, and provides the signal from the transmission signal generation unit 36 to the antenna 31.

  The connection destination system determination unit 33 extracts the waveform feature amount from the signal received via the antenna 31 and the transmission / reception separation unit 32, and determines a communication system suitable for connection with the multimode radio. The waveform feature amount is an amount indicating a statistical characteristic of the signal waveform. In the following description, the second-order periodic autocorrelation value CAF is used as the waveform feature quantity. However, as described above, other quantities may be used as the waveform feature quantity.

  The connection destination system determination unit 33 calculates the periodic autocorrelation value CAF of the signal input to the antenna 31 for a parameter within a predetermined range, determines a parameter that causes a relatively strong periodic autocorrelation value, A corresponding communication system is determined as a connection destination communication system. The parameters are generally both cyclic frequency and lag parameters, but in some cases only the cyclic frequency may be used.

FIG. 4 shows how the cyclic autocorrelation value CAF of a signal input to the antenna is calculated for a cyclic frequency α within a certain range. In the case of the illustrated example, a relatively high peak occurs when the cyclic frequency α is α ₁ , α ₂ , α ₃ . The cyclic frequency at which the cyclic autocorrelation value CAF is generated differs depending on the communication system. Accordingly, in the illustrated example, the first communication system corresponding to the cyclic frequency α ₁ , the second communication system corresponding to the cyclic frequency α ₂ , and the third communication system corresponding to the cyclic frequency α ₃ However, it exists that it exists in the periphery of a multimode radio | wireless machine.

The connection destination system determination unit 33 determines the cyclic frequency corresponding to the highest peak. In the example shown in FIG. 4, since such a cyclic frequency is the alpha _1, a first communication system corresponding thereto is determined as a communication system to connect to. For the sake of simplicity, the case where the first to third systems are distinguished only by the cyclic frequency has been described, but this is not essential in the present embodiment. As described above, the parameters necessary for calculating the cyclic autocorrelation value CAF are the cyclic frequency α and the lag parameter ν. Therefore, more generally, the combination (α, ν) of the cyclic frequency and the lag parameter is different for each communication system. FIG. 5 shows an example in which the cyclic autocorrelation value CAF for the OFDM signal is calculated for various combinations of the cyclic frequency α and the lag parameter ν. FIG. 6 shows an example in which the cyclic autocorrelation value CAF for the CDMA signal is calculated for various combinations of the cyclic frequency α and the lag parameter ν. As shown in the figure, the parameters (α, ν) that result in relatively high peaks differ depending on the signals used, and this difference makes it possible to distinguish communication systems suitable for connection.

  The operation mode control unit 34 in FIG. 3 sets the values of the communication parameters including the transmission format center frequency and bandwidth of the communication signal to values used by the communication system determined as the connection destination. As a result, the software or program for controlling the hardware of the multimode radio is rewritten (switched) so that the signal of the communication system to be connected can be transmitted and received. The communication parameters include information necessary for starting the connection procedure, and are stored in the storage unit 37. The transmission format may be expressed as a combination of a data modulation scheme and a channel coding rate, or may be expressed as a combination of a data modulation scheme and a data size. In the latter case, the channel coding rate can be derived from the relationship between the data modulation scheme and the data size.

  The reception signal acquisition unit 35 acquires necessary information from the communication system of the connection destination in accordance with the communication parameters set by the operation mode control unit 34.

  The transmission signal generation unit 36 generates a signal to be transmitted to the connection destination communication system in accordance with the communication parameters set by the operation mode control unit 34. After connecting to the communication system of the connection destination, the multi-mode radio transmits and receives radio signals in the communication system.

  The storage unit 37 stores information necessary for the multimode radio to connect to some kind of communication system. Specifically, the storage unit 37 stores peak information of the cyclic autocorrelation value CAF for various communication systems, information necessary for starting a connection procedure for each communication system, and the like. The peak information indicates what combination of the cyclic frequency α and the lag parameter ν the periodic autocorrelation value CAF of the communication system has. The minimum information necessary for starting the connection procedure is, for example, information (transmission format, center frequency, etc.) for acquiring information broadcast in the communication system.

<3. Example of operation>
FIG. 7 shows an operation example of the multi-mode wireless device.

  In step S71, the multimode radio receives surrounding radio signals. Reception in this case simply means that a signal is input to the antenna, and does not include processing such as demodulation.

  In step S73, the connection destination system determination unit 33 of the multimode radio calculates the waveform feature quantity of the signal input to the antenna, and determines a parameter that causes a relatively strong peak. In the case of the above example, the connection destination system determination unit 33 calculates the cyclic autocorrelation value CAF of the signal input to the antenna, and determines the cyclic frequency that causes a relatively strong peak. A communication system corresponding to the determined cyclic frequency is determined as a connection-destination communication system.

  In step S75, the operation mode control unit 34 of the multimode radio sets the communication parameter value to a value in the communication system that causes a relatively strong peak. As a result, the operation mode of the multi-mode radio is switched for the communication system to which it is connected.

  In step S77, the reception signal acquisition unit 35 and the transmission signal generation unit 36 of the multimode radio establish a communication link according to the set communication parameters, and thereafter, transmission / reception of signals is performed (step S79).

  FIG. 8 shows how the multi-mode radio moves in the order of (A), (B), and (C) in the vicinity of the first to third communication systems. The cyclic autocorrelation values CAF of the signals of the first to third communication systems generally have respective peaks at cyclic frequencies as shown in FIG. The peak value of the cyclic autocorrelation value CAF takes different values as the multi-mode radio moves in the order of (A), (B), (C).

  In the case of (A), since the multimode radio is in the vicinity of the first communication system, the signal from the first communication system is received most strongly. As a result, the first communication system is determined as the connection destination system.

  In the case of (B), since the multimode radio is in the vicinity of the second communication system, the signal from the second communication system is received most strongly. As a result, the second communication system is determined as the connection destination system.

  In the case of (C), since the multimode radio is in the vicinity of the third communication system, the signal from the third communication system is received most strongly. As a result, the first communication system is determined as the connection destination system.

When the frequency allocation of each of the first to third communication systems as shown in FIG. 8 is fixed, a carrier sense multiple access method (Carrier Sense Multiple Access) that performs collision avoidance for each frequency band of the communication system. By performing signal detection based on power such as with Collision Avoidance (CSMA / CA), it is possible to determine a communication system to be connected. When the frequency usage as shown in Fig. 8 is not fixed and dynamically fluctuates, or when searching for an unused band without frequency information, communication that should be connected only by detecting the signal power The system may not be properly determined. For example, the frequency utilization status by the first to third communication systems is as shown in FIG. In this case, only detecting the power of the signal can only tell that there is some signal in the frequency range from f _L to f _H. Whether or not a plurality of signals are included and what kind of signals are included cannot be determined only by power detection, and it is necessary to analyze the waveform feature amount. When analyzing the waveform feature quantity such as the cyclic autocorrelation value CAF over the entire frequency range to be searched from f _min to f _max , the result shown in FIG. 4 is obtained. However, it can be seen that the first communication system is suitable as a connection destination.

When searching for the communication system of the connection destination, it is also conceivable to use both signal power detection and waveform feature value analysis. For example, when signal power is first detected over the entire frequency range to be searched from f _min to f _max, it can be seen that some signal (significant signal) exists within the frequency range from f _L to f _H. . Next, by analyzing the cyclic autocorrelation value CAF only in the frequency range from f _L to f _H , not in the entire frequency range, the signals of the first to third communication systems fall within that frequency range. It can be seen that it is included. A communication system suitable for connection is found from the peak size of the cyclic autocorrelation value CAF. In the case of this method, it is preferable in that the range that requires analysis of the cyclic autocorrelation value CAF that has a relatively large calculation burden can be limited to a narrow range.

  Although the present invention has been described with reference to particular embodiments, they are merely exemplary and those skilled in the art will appreciate various variations, modifications, alternatives, substitutions, and the like. For example, the present invention can be used in any situation where a plurality of communication systems sharing the same frequency band coexist. Multiple communication systems include W-CDMA systems, HSDPA / HSUPA W-CDMA systems, LTE systems, LTE-Advanced systems, IMT-Advanced systems, WiMAX and Wi-Fi systems. There is a system, but it is not limited to these. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. Although specific mathematical formulas have been described to facilitate understanding of the invention, these mathematical formulas are merely examples, unless otherwise specified, and any appropriate mathematical formula may be used. The classification of the examples or items is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in another example. Or it may be applied to the matters described in the item (unless there is no contradiction). For convenience of explanation, an apparatus according to an embodiment of the present invention has been described using a functional block diagram, but such an apparatus may be realized by hardware, software, or a combination thereof. The software is available on random access memory (RAM), flash memory, read only memory (ROM), EPROM, EEPROM, registers, hard disk (HDD), removable disk, CD-ROM, database, server and any other suitable storage medium May be. The present invention is not limited to the above embodiments, and various modifications, modifications, alternatives, substitutions, and the like are included in the present invention without departing from the spirit of the present invention.

31 Antenna
32 Transmit / Receive Separator
33 Destination system determination section
34 Operation mode controller
35 Received signal acquisition unit
36 Transmission signal generator
37 Memory

Claims (4)

A connection destination system determination unit that determines a communication system of a connection destination based on a signal input to the antenna;
An operation mode control unit for setting a value of a communication parameter including at least a transmission format and a center frequency of a communication signal to a value used in the communication system of the connection destination;
A communication unit configured to connect to the communication system of the connection destination and perform wireless communication using the communication parameter set by the operation mode control unit, and the connection destination system determination unit is input to the antenna In addition, the periodic autocorrelation value of the signal is calculated for a parameter within a predetermined range, a parameter that provides a relatively strong periodic autocorrelation value is determined, and a communication system corresponding to the parameter is defined as the communication system of the connection destination. Multimode radio to decide.   The connection destination system determining unit detects signal power over a predetermined frequency range, limits the frequency range in which a significant signal exists, and sets a periodic autocorrelation value of the signal input to the antenna within a predetermined range. The multi-mode wireless device according to claim 1, wherein a parameter that produces a relatively strong cyclic autocorrelation value is determined, and a communication system corresponding to the parameter is determined as the communication system of the connection destination. .   3. The multimode radio according to claim 1, wherein the parameter includes at least a cyclic frequency. Determining a communication system to connect to based on a signal input to the antenna;
Setting a value of a communication parameter including at least a transmission format and a center frequency of a communication signal to a value used in the connection destination communication system;
Using the communication parameter set in the setting step and connecting to the communication system of the connection destination and performing wireless communication, and in the step of determining the communication system of the connection destination, input to the antenna A periodic autocorrelation value of the received signal is calculated for a parameter within a predetermined range, a parameter that causes a relatively strong cyclic autocorrelation value is determined, and a communication system corresponding to the parameter is set as the communication system of the connection destination Determine how to find the destination system.

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