JP5376628B2 - Simple base station, channel identification method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a suitable channel in a simple base station. <P>SOLUTION: If the electric field strength of a carrier frequency does not exceed a threshold indicating natural noise, a simple base station 100 constituting a femtocell temporarily detects a channel allowed to use for radio communication with a mobile communication terminal MS as an unused channel. When a frequency band used for the unused channel does not exceed the threshold indicating the natural noise, the simple base station 100 sets the detected unused channel as a channel usable for the simple base station 100 based on the electric field strength measured in all ranges of a frequency band used for the detected unused channel. If the electric field strength of the frequency band does not exceed a threshold indicating a weak electric field even when the electric field strength of the frequency band exceeds the threshold indicating the natural noise, a diffusion code used for the frequency band is detected and a diffusion code which does not interfere with the detected diffusion code is used to make the frequency as a frequency allowed to use for the simple base station 100. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a simple base station, a channel specifying method, and a program, and more particularly, to a simple base station, a channel specifying method, and a program suitable for a small cell such as a femto cell.

  In mobile communication systems such as mobile phones, a large number of wireless base stations that perform wireless communication with mobile communication terminals are installed by communication carriers (carriers). However, for example, radio waves from a radio base station (hereinafter referred to as a “commercial base station”) installed by a communication carrier may not reach a high floor or a basement of a building. That is, even in a region with a high coverage rate, a place that is outside the service area may exist locally. In order to eliminate such inconvenience, a simple base station (ultra-small base station apparatus) that can be easily installed by a carrier or an individual who is not a communication carrier may be used.

  Such a simple base station constitutes a small wireless communication area (so-called femtocell) having a radius of several meters, and is installed indoors in a building (for example, a building, a commercial facility, or a house). This complements the communication area of commercial base stations.

  Since the simple base station is intended to complement the communication area of the commercial base station, wireless communication that interferes with the wireless communication of the commercial base station must not be performed. In addition, if the radio communication of the simple base station is interrupted by the radio wave of the commercial base station, it becomes impossible to provide a good communication environment. That is, the simple base station needs to be operated so as not to interfere with the surrounding commercial base stations and femtocell groups.

  As a method of operating so as not to interfere with neighboring commercial base stations and femtocell groups, a method of performing radio wave resource allocation calculation is conceivable. However, since a myriad of femtocells can be installed in the wireless communication area of commercial base stations with a radius of several hundreds of meters to several kilometers, it is difficult to perform radio wave resource allocation calculations within a finite time. is there. In addition, since it is necessary to set for each femtocell by an engineer who has expertise in radio interference after installing an automatic allocation adjustment system by a telecommunications carrier, a femtocell cannot be easily constructed.

  In order to eliminate such inconveniences, a technique has been proposed in which a simple base station autonomously investigates radio wave usage and selects a free frequency (for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-313477

  In the technique of Patent Document 1, an available channel is selected by measuring a received electric field strength for each channel and creating a free channel list. However, in such a method, when a spread spectrum method such as a code division multiple access method is used for wireless communication, even if the carrier frequencies are different, the frequency bands to be used are overlapped and cannot be handled.

  In addition, since the installation status of commercial base stations changes from time to time due to new establishment or abolition, channels that can be used by simple base stations also change. Therefore, in order to maintain a stable communication environment in the femtocell, it is necessary to be able to respond quickly to such changes.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a simple base station and a program capable of realizing stable wireless communication in a femtocell using a spread spectrum system. .

In order to achieve the above object, a simple base station according to the first aspect of the present invention provides:
A simple base station that performs wireless communication with a communication terminal device,
Channel selection means for selecting a channel from a plurality of selectable channels;
First field strength measuring means for measuring the field strength at the carrier frequency of the channel selected by the channel selecting means;
First electric field strength determining means for determining whether or not the electric field strength measured by the first electric field strength measuring means exceeds a predetermined threshold;
Unused channel provisional means for provisionally setting the channel of the carrier frequency determined by the first electric field strength determination means to be an electric field intensity not exceeding the predetermined threshold as an unused channel;
Second electric field strength measuring means for measuring electric field strength in a plurality of frequency bands from a lower limit to an upper limit of a frequency band used by the provisional channel by the unused channel provisional means;
Channel setting means for setting a channel tentatively used as the unused channel as a channel usable in the simple base station when the electric field strength measured by the second electric field strength measuring means does not exceed the threshold value ; Prepare
It is characterized by that.

In the simple base station,
The wireless communication can be modulated and demodulated by a spread spectrum method, in this case,
The channel setting means includes
Based on the field intensity the second field strength measuring means were measured boss, the second field strength discriminating means for frequency bands used in the channel is determined whether or not the field strength does not exceed a predetermined threshold When,
Spreading code detecting means for detecting a spreading code used in the frequency band by performing despreading in a frequency band where the electric field intensity does not exceed the threshold;
It is desirable to further comprise spreading code setting means for setting a spreading code that does not interfere with the spreading code detected by the spreading code detecting means as a spreading code that can be used in the unused channel.

In the simple base station,
When the first electric field strength measuring means uses different frequencies for transmission and reception in communication with the communication terminal device, it is desirable to measure the electric field strength at each frequency.

In the simple base station,
The first electric field strength measuring unit preferably measures the electric field strength when there is no connection with the communication terminal device.

The simple base station
It is desirable to have two or more receiving means, in this case,
The first electric field strength measuring means preferably measures the electric field strength by a receiving operation of a receiving means that is not used for communication with the communication terminal device among the two or more receiving means.

In order to achieve the above object, a channel specifying method according to the second aspect of the present invention includes:
A method for identifying a channel that can be used without radio wave interference in wireless communication using a spread spectrum method,
A channel selection step for selecting a channel from the selectable channels;
A first field strength measurement step for measuring the field strength at the carrier frequency of the selected channel;
A first electric field strength determination step for determining whether or not the electric field strength measured in the first electric field strength measurement step exceeds a predetermined threshold;
An unused channel provisional step in which the channel of the carrier frequency determined as the electric field intensity not exceeding the predetermined threshold in the first electric field intensity determination step is provisionally used as an unused channel;
A second electric field strength measuring step for measuring electric field strength in a plurality of frequency bands from a lower limit to an upper limit of a frequency band used in a channel provisional in the unused channel provisional step ;
If the field intensity measured at the second field strength measuring step does not exceed the threshold value, the provisional been Ji Yaneru as the unused channels, a channel specifying step of specifying a usable channel,
It is characterized by including.

The above channel identification method is:
When the electric field intensity measured in the second electric field intensity measurement step does not exceed a threshold value indicating a weak electric field, the spreading code used in the frequency band is detected by performing despreading in the frequency band. A spreading code detection step;
It is desirable to further include a spreading code specifying step that specifies a spreading code that does not interfere with the spreading code detected in the spreading code detecting step as a spreading code that can be used in the frequency band.

In order to achieve the above object, a program according to the third aspect of the present invention is:
In a computer that controls a wireless communication device that performs wireless communication using a spread spectrum system,
A channel selection function for selecting a channel from a plurality of selectable channels;
A first field strength measurement function for measuring a field strength at a carrier frequency of a channel selected by the channel selection function;
A first electric field strength determination function for determining whether or not the electric field strength measured by the first electric field strength measurement function exceeds a predetermined threshold;
An unused channel provisional function for provisionally setting the channel of the carrier frequency determined as the electric field strength not exceeding the predetermined threshold by the first electric field strength determination function as an unused channel;
A second electric field strength measurement function for measuring electric field strength in a plurality of frequency bands from a lower limit to an upper limit of a frequency band used by the provisional channel of the unused channel provisional function;
A channel setting function for setting a channel tentatively used as the unused channel as a channel that can be used in the simple base station when the field strength measured by the second field strength measurement function does not exceed the threshold;
It is characterized by realizing.

The above program
In the computer,
When the electric field intensity measured by the second electric field intensity measurement function does not exceed a threshold value indicating a weak electric field, the spreading code used in the frequency band is detected by performing despreading in the frequency band. Spreading code detection function;
A spread code specifying function for specifying a spread code that does not interfere with the spread code detected by the spread code detection function as a spread code usable in the frequency band;
It is desirable to realize

  ADVANTAGE OF THE INVENTION According to this invention, the stable radio | wireless communication in the femtocell comprised by a simple base station is easily realizable.

  Embodiments according to the present invention will be described below with reference to the drawings. In this embodiment, a case where a femto cell for mobile communication is configured by using a simple base station according to the present invention will be described as an example.

  The femtocell system 1 according to the present embodiment in this case will be described with reference to FIG. FIG. 1 is a diagram schematically showing a configuration of a femtocell system 1 according to the present embodiment.

  As shown in the figure, the femtocell system 1 includes a simple base station 100, a mobile communication terminal MS that performs radio communication with the simple base station 100, and the like. Here, the simple base station 100 is a micro wireless base station that constitutes a small wireless communication area (so-called femtocell) having a radius of about several meters, and is installed by a communication carrier (communication carrier). It functions as a base station that complements the base station.

  That is, the simple base station 100 according to the present embodiment is installed in a place where radio waves from commercial base stations do not reach (for example, a high floor or a basement of a building) and wireless access (not shown) for a predetermined communication carrier It is connected to a trunk line NW connected to a network (communication network connecting a radio network controller (RNC) and a base station). Then, by performing wireless communication with the mobile communication terminal MS in the femtocell configured by the simple base station 100, voice communication and data communication by the mobile communication terminal MS are realized.

(Embodiment 1)
An example of the simplified base station 100 used for wireless communication in such a femtocell will be described below as a first embodiment. First, the configuration of the simple base station 100 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram schematically showing a hardware configuration of the simple base station 100 according to the embodiment of the present invention.

  As illustrated, the simple base station 100 includes a control unit 110, a storage unit 120, a backbone communication unit 130, a wireless communication unit 200, and the like.

  The control unit 110 includes, for example, an arithmetic device such as a CPU (Central Processing Unit) and a storage device such as a RAM (Random Access Memory), and executes a program stored in the storage unit 120. By doing so, various processes are performed and each part of the simple base station 100 is controlled.

  The storage unit 120 is configured by, for example, a non-volatile semiconductor storage device such as a flash memory, and stores a program executed by the control unit 110 and stores data necessary for processing, processing result data, and the like. .

  The backbone communication unit 130 is composed of, for example, a signal demultiplexing circuit and the like, converts a signal received by the wireless communication unit 200 through wireless communication into a signal format of the backbone line NW, multiplexes, and transmits the signal to the wireless network control device. At the same time, a signal (a signal in which a plurality of communications are multiplexed) transmitted from the wireless network control device is separated into channels for each communication and input to the wireless communication unit 200.

  The wireless communication unit 200 is configured to perform a wireless communication operation in the simple base station 100. The configuration of the wireless communication unit 200 according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration of the wireless communication unit 200.

  As described above, the simple base station 100 according to the present embodiment performs transmission / reception by radio communication with the mobile communication terminal MS. Therefore, as illustrated in FIG. 3, the wireless communication unit 200 includes a transmission unit 300 and a reception unit 400.

  As shown in FIG. 3, the transmission unit 300 includes a modulation processing unit 310, an RF unit 320, a transmission antenna 330, and the like.

  The modulation processing unit 310 includes a modulation circuit that modulates transmission target data, a DAC (Digital-Analog Converter) that converts a modulation signal into an analog signal, and the like, and is input from the backbone communication unit 130. The transmission target data is modulated by a modulation operation according to the wireless communication method adopted by the femtocell system 1 and converted into an analog signal.

  The RF unit 320 converts the converted analog signal into a high-frequency radio signal (RF signal (RF: Radio Frequency)). The RF unit 320 converts, for example, an intermediate frequency radio signal by an intermediate frequency oscillator, a quadrature modulation circuit, or the like, and then converts it to a radio frequency (RF) signal by a radio frequency oscillator, an HPA (High Power Amplifier), or the like. The data is converted and transmitted from the transmitting antenna 330 to the mobile communication terminal MS.

  Next, the configuration of the receiving unit 400 will be described. As shown in FIG. 3, the receiving unit 400 includes a receiving antenna 410, an RF unit 420, a demodulation processing unit 430, and the like.

  The receiving antenna 410 receives a high-frequency radio signal (RF signal (RF: Radio Frequency)) transmitted from the mobile communication terminal MS.

  The RF unit 420 includes, for example, a high-frequency amplifier circuit such as an LNA (Low Noise Amplifier), a radio frequency oscillator, an AGC (Automatic Gain Control), and the like. The reception level of the RF signal is corrected. In addition, an input analog modulation signal is converted into digital data by an ADC (Analog-Digital Converter).

  The demodulation processing unit 430 includes a demodulation circuit that demodulates the digital data input from the RF unit 420, and demodulates the signal received from the mobile communication terminal MS and inputs the demodulated signal to the backbone communication unit 130.

  Note that the configuration and basic functions of the wireless communication unit 200 in the simple base station 100 according to the present embodiment are the same as those of a normal commercial base station or a known simple base station. Further, in the configuration illustrated in FIG. 3, each of the transmission unit 300 and the reception unit 400 has an antenna. However, for example, a configuration in which an antenna is shared by using an antenna sharing switch or the like may be used.

  The above is the main configuration of the simple base station 100 according to the present embodiment, but these are the configurations necessary for realizing the present invention, and are necessary for realizing the main functions and additional functions as the simple base station. It is assumed that other configurations are appropriately provided.

  In the femtocell system 1 according to the present embodiment, CDMA (Code Division Multiple Access) is adopted as a modulation / demodulation method for wireless communication between the simple base station 100 and the mobile communication terminal MS. Shall. That is, a signal in which a plurality of frequencies (channels) are multiplexed by the spread spectrum method is transmitted / received in the femtocell. That is, a plurality of communications are multiplexed and transmitted / received at the same frequency by using different spreading codes.

  Here, in the present embodiment, the operation of the receiving unit 400 is controlled by the control unit 110, so that the frequency (channel) that the simple base station 100 can use without causing radio wave interference with the adjacent commercial base station or other femtocells. ) Is automatically detected and set.

  The functions realized by the control unit 110 for performing such operations are shown in FIG. FIG. 4 is a functional block diagram illustrating functions realized when the control unit 110 executes the program stored in the storage unit 120. As illustrated, the control unit 110 functions as a communication processing unit 111, a measurement timing determination unit 112, a measurement processing unit 113, and the like.

  The communication processing unit 111 controls the transmission unit 300, the reception unit 400, and the backbone communication unit 130, and controls operations related to communication between the simple base station 100 and the mobile communication terminal MS.

  The measurement timing determination unit 112 determines the execution timing of the measurement operation performed by the simple base station 100 based on the operations of the transmission unit 300, the reception unit 400, the backbone communication unit 130, and the like. Here, the measurement operation performed by the simple base station 100 is to measure the electric field strength by the reception operation by the reception unit 400 in order to investigate the channels that the simple base station 100 can use. For this reason, the receiving operation for measurement can be performed when the receiving unit 400 is not used for communication with the mobile communication terminal MS. Therefore, the measurement timing discriminating unit 112 discriminates that it is the execution timing of the measurement operation when the receiving unit 400 is not used for communication with the mobile communication terminal MS, based on the communication status with the mobile communication terminal MS. To do.

  The measurement processing unit 113 controls the reception unit 400 of the wireless communication unit 200 to execute the above-described measurement operation, and based on the measurement result, the simple base station 100 is used for wireless communication with the mobile communication terminal MS. Set the channel to be used.

  In the present embodiment, the above functions are logically realized by the control unit 110 executing a program. For example, hardware such as an ASIC (Application Specific Integrated Circuit) is used. Each of the above functions may be realized.

  An operation performed by the simple base station 100 will be described. Here, the “channel setting process (1)” according to the first embodiment will be described with reference to the flowchart shown in FIG. This “channel setting process (1)” is started when the measurement timing determination unit 112 determines that it is the measurement operation timing. That is, this process is started when the receiving unit 400 is not used for communication with the mobile communication terminal MS.

  The measurement processing unit 113 initializes a channel designation pointer P for designating a channel to be measured (step S1101). Since the simple base station 100 is for performing mobile communication for a predetermined communication carrier, the base station 100 performs wireless communication with the mobile communication terminal MS in the range of the frequency band defined for each communication carrier. . That is, since the channel assigned to the communication carrier is determined in advance, information indicating which channel (priority channel) can be used by the simplified base station 100 is stored in the storage unit 120 in advance, for example. ing.

  For example, the priority channels that can be used by the simple base station 100 can be recorded in a list format, and the channel designation pointer P is recorded in such a list (priority channel list). A pointer for sequentially designating priority channels. Here, if priority channels 1 to n are recorded and priority channels are designated in the order of 1 to n, initialization in step S1101 is to set channel designation pointer P to “1”. It becomes.

  The measurement processing unit 113 designates an intermediate frequency for the Pth priority channel recorded in the priority channel list stored in the storage unit 120 (step S1102), and the reception unit performs the reception operation of this intermediate frequency. 400 is controlled. As a result, the receiving unit 400 of the wireless communication unit 200 operates and performs reception at the intermediate frequency of the designated priority channel (step S1103).

  The intermediate frequency received in this case is a frequency that is intermediate in the frequency bandwidth of the carrier frequency (carrier frequency) of the designated priority channel. That is, the carrier frequency has a frequency band width as shown in FIG. 7, and an intermediate frequency between the lower limit frequency and the upper limit frequency is designated as the carrier frequency of the channel and received.

  The measurement processing unit 113 measures the electric field strength of the signal received by the reception operation at the carrier frequency of the priority channel (step S1104). Here, the field strength of a received signal (so-called RSSI (Received Signal Strength Indicator)) is measured using a known field strength measurement technique.

  The measurement processing unit 113 compares the measured electric field strength with a preset threshold value, and determines whether the electric field strength does not exceed the threshold value (step S1105). As the threshold here, for example, a value indicating natural noise (environmental noise) is used. In this case, an RSSI value (for example, −106 dBm) indicating the electric field intensity corresponding to natural noise is set as the threshold value.

  Here, in the case where the simple base station 100 exists in the area covered by the commercial base station around the simple base station 100, or when the femtocell of the simple base station 100 overlaps with the surrounding femtocell, When these commercial base stations and other femtocells are using the intended channel, the electric field strength of the channel exceeds the natural noise over the entire frequency band as shown in FIG.

  Therefore, if the measured electric field strength of the priority channel exceeds the natural noise, the channel is already used in a nearby commercial base station or other femtocell. Therefore, when the channel is used by the simplified base station 100, there is a possibility of interference with a nearby commercial base station or other femtocells.

  In this case (step S1105: No), the measurement processing unit 113 designates the next priority channel by updating the channel designation pointer P by +1 (step S1106). Here, when there is no priority channel that can be designated by the updated channel designation pointer P in the priority channel list (step S1107: No), this processing is terminated.

  On the other hand, when the next priority channel can be designated by the updated channel designation pointer P (step S1107: Yes), the measurement processing unit 113 performs the operations of steps S1102 to S1105 for the priority channel designated by the channel designation pointer P. To do.

  Here, when there is a priority channel whose electric field intensity of the carrier frequency does not exceed the threshold (natural noise) (step S1105: Yes), the measurement processing unit 113 tentatively detects the priority channel as an unused channel (step S1105). S1108). That is, it is determined that there is a high possibility that the channel is not used in commercial base stations and other femtocells around the simple base station 100.

  Here, because the carrier frequency may be shifted depending on the communication method and communication carrier, or may use a plurality of carrier frequencies, even if it is an unused channel detected based on the electric field strength of the carrier frequency, It must be confirmed that the peripheral band is not used from the lower limit to the upper limit. Therefore, the measurement processing unit 113 executes “frequency band scanning process” for confirming whether or not the frequency band used by the detected unused channel is used (step S1200). This “frequency band scanning process” will be described with reference to the flowchart shown in FIG.

  When the processing is started, the measurement processing unit 113 becomes the lower limit of the frequency band used in downlink communication (direction from the simple base station 100 to the mobile communication terminal MS) in communication with the mobile communication terminal MS. The frequency is set to a measurement frequency (measurement frequency) (step S1201). That is, for the carrier frequency used for downlink communication with the detected unused channel, the frequency that is the lower limit of the frequency bandwidth is set as the measurement frequency.

  The measurement processing unit 113 controls the reception unit 400 of the wireless communication unit 200 to perform the reception operation at the measurement frequency set in step S1201. Thereby, the receiving unit 400 performs a receiving operation at the set measurement frequency (step S1202).

  The measurement processing unit 113 measures the electric field strength from the reception signal obtained by the reception operation of the reception unit 400, and records it by storing it in the RAM (step S1203).

  When the electric field intensity at the set measurement frequency is measured, the measurement processing unit 113 increases the measurement frequency by increasing the measurement frequency by the frequency resolution, for example (step S1204). If the increased frequency does not exceed the upper limit of the carrier frequency (step S1205: No), the measurement processing unit 113 causes the reception unit 400 to perform a reception operation at the increased measurement frequency (step S1202), and the electric field The intensity is measured and recorded (step S1203).

  Thereafter, the measurement frequency is sequentially increased until the upper limit of the carrier frequency is exceeded, and each electric field strength is measured. In this case, the RSSI values of the measured electric field strength are all recorded in the RAM.

  When the measurement frequency exceeds the upper limit of the carrier frequency (step S1205: Yes), the measurement processing unit 113 indicates that the communication method employed by the simple base station 100 is an uplink in communication with the mobile communication terminal MS. It is determined whether or not the frequency is different between the downlink and the downlink (step S1206).

  Here, when the frequency is different between uplink and downlink (step S1206: Yes), the measurement processing unit 113 performs the above-described step S1201 for the frequency used for uplink (direction from the mobile communication terminal MS to the simple base station 100). The same operation as in step S1205 is performed (step S1207 to step S1211). That is, the lower limit of the frequency band used in the uplink is set as the measurement frequency, and the electric field strength is measured and recorded while increasing the frequency until the upper limit is reached.

  From the RSSI value measured in this way, the measurement processing unit 113 determines a representative value of the electric field strength (step S1212), and returns to the flow of “channel setting process (1)”. Here, if the same frequency is used for uplink and downlink, the representative value is determined from the RSSI value recorded in step S1203. On the other hand, if different frequencies are used for uplink and downlink, the representative value is determined from the RSSI values recorded in steps S1203 and S1209. Here, for example, the highest recorded RSSI value is determined as the representative value.

  When the representative value of the electric field strength measured from the lower limit to the upper limit of the frequency band is determined, the measurement processing unit 113 determines that the determined representative value of the electric field strength is predetermined in the flow of “channel setting process (1)” (FIG. 5). It is determined whether or not the threshold value is not exceeded (step S1109). Here, as in step S1105, a value indicating natural noise (for example, an RSSI value of −106 dBm) is used as the threshold value.

  In other words, regarding the priority channel detected as an unused channel, if the electric field strength does not exceed natural noise even in a plurality of frequency bands from the lower limit to the upper limit of the used frequency band, none of the frequency bands are used. Become. Therefore, if the representative value of the electric field strength determined in the “frequency band scanning process” (FIG. 6) does not exceed the threshold value (natural noise) (step S1109: Yes), the measurement processing unit 113 detects the priority detected in step S1108. The channel is set as a channel that does not interfere with the adjacent commercial base station or other femtocells even if the simplified base station 100 is used. That is, it sets as a channel which can be used with the simple base station 100 (step S1110), and complete | finishes a process.

  On the other hand, if the representative value of the electric field strength determined in the “frequency band scanning process” (FIG. 6) exceeds the threshold value (natural noise) (step S1109: No), the priority channel detected as an unused channel has an intermediate frequency. When the frequency shifts or when a plurality of carrier frequencies are used, there is a possibility that the frequency band is used by commercial base stations or other femtocells around the simplified base station 100. Therefore, the measurement processing unit 113 does not set a channel temporarily detected as an unused channel as a usable channel, and performs measurement for the next priority channel recorded in the priority channel list (step S1106, Step S1107: Yes, Step S1102 to Step S1105).

  Even in this case, if a priority channel that can be provisionally set as an unused channel is detected, the “frequency band scanning process” (FIG. 6) is executed (step S1200), and the representative value of the electric field strength determined there is a threshold value. If it does not exceed (natural noise) (step S1109: Yes), it is set as a usable channel (step S1101).

  Here, when the “channel setting process (1)” described above is executed, a channel that can be set as an available channel may not be detected. In this case, for example, a commercial base station is newly installed around the simple base station 100, so that radio waves from the commercial base station can be received even if the simple base station 100 is installed. Can be considered. In such a case, the simplified base station 100 whose purpose is to supplement an area where radio waves from the commercial base station do not reach does not need to assume the role. Therefore, when a usable channel cannot be set, the simple base station 100 stops radio wave communication, for example, so that radio interference does not occur with neighboring commercial base stations and other femtocells.

  In addition, since the radio wave condition around the simple base station 100 changes at any time, the location of the simple base station 100 whose operation is stopped may be an area where the radio wave of the commercial base station does not reach. In such a case, the simple base station 100 can be complemented quickly by operating again. In order to perform such an operation, it is desirable that the simple base station 100 periodically executes the “channel setting process (1)” even when the operation related to the wireless communication is stopped.

  By detecting the unused channel based on the electric field strength measured by the receiving operation by the operation described above, and measuring the electric field strength by scanning from the lower limit to the upper limit of the frequency band used by the channel, It can be confirmed that the frequency band to be used and the peripheral frequency band are not used. Then, since the channel that has been confirmed not to be used up to the frequency band is set as a channel used by the simplified base station 100, a plurality of frequency bands are multiplexed on one carrier frequency (carrier frequency) such as CDMA. Even in the case of using a communication system that is converted into a single channel, it is possible to set a usable channel without interfering with neighboring commercial base stations and other femtocells.

  Even if the carrier frequency is shifted or the communication method uses a plurality of carrier frequencies, an appropriate channel setting can be performed.

  Furthermore, when different frequencies are used for uplink and downlink in communication with the mobile communication terminal MS, the field strength is measured for each of the uplink and downlink, so that such communication is performed. Even when the method is used, appropriate channel setting can be performed.

  Since such an operation is performed at a timing when communication with the mobile communication terminal MS is not performed, the channel setting may be automatically changed using the receiving means used for communication with the mobile communication terminal MS. it can. Thereby, a quick setting change according to the change of the surrounding radio wave environment is automatically performed.

(Embodiment 2)
When modulation / demodulation is performed by a spread spectrum method such as CDMA, which is multiplexed by spreading using a spread code, different communications can be multiplexed on the same frequency by changing the spread code. In this case, if the multiplicity is increased, the electric field strength increases, but the signal strength / electric field strength ratio decreases, so the communication quality decreases. From this tendency, it can be considered that a frequency with a small electric field strength has a surplus in multiplicity.

  Therefore, even if the carrier frequency channel is already used in a commercial base station or other femtocells around the simplified base station 100, if a spreading code with sufficient multiplicity and less interference is used. The channel can be used by the simplified base station 100.

  In the present embodiment, a simple base station 100 that can detect and set a channel having such characteristics will be described. The hardware configuration of the simple base station 100 according to the present embodiment and the functional configuration realized by the control unit 110 are the same as those shown in the first embodiment, but the operation by the measurement processing unit 113 is different from the first embodiment.

  The “channel setting process (2)” according to the present embodiment will be described with reference to the flowchart shown in FIG. This “channel setting process (2)” is started when the measurement timing determination unit 112 determines that it is the measurement operation timing, as in the “channel setting process (1)” exemplified in the first embodiment. The

  When the processing is started, the measurement processing unit 113 of the control unit 110 sets the channel designation pointer P for designating the priority channel of the priority channel list stored in the storage unit 120 to, for example, the initial value “1”. After initialization (step S2101), the Pth priority channel recorded in the priority channel list is designated (step S2102).

  For the designated priority channel, the measurement processing unit 113 sets the lower limit of the frequency band used for downlink communication in communication with the mobile communication terminal MS as the frequency to be measured for electric field strength (hereinafter referred to as “measurement frequency”). (Step S2103).

  The measurement processing unit 113 controls the reception unit 400 to perform a reception operation of the set measurement frequency. As a result, the reception unit 400 of the wireless communication unit 200 operates and performs reception at the set measurement frequency (step S2104). The measurement processing unit 113 measures the electric field strength at the measurement frequency from the reception operation by the reception unit 400 and records it in the RAM (step S2105).

  When the electric field strength is measured at the set measurement frequency, the measurement processing unit 113 increases the measurement frequency set at the lower limit of the frequency band (step S2106). In this case, for example, the frequency is increased by an increase width corresponding to the frequency resolution. If the upper limit frequency of the channel is not exceeded (step S2107: No), the reception operation is performed at the measurement frequency, and the electric field strength is measured and recorded (steps S2104 and S2105). That is, scanning is performed from the lower limit to the upper limit of the frequency band used in the selected channel, and the electric field strength is measured in each frequency band.

  In this way, when the electric field strength is measured over the entire frequency band of the selected channel (step S2107: Yes), the measurement processing unit 113 determines whether there is a frequency band in which the electric field strength does not exceed a predetermined threshold value. (Step S2108). The threshold value used here may be an RSSI value indicating natural noise (for example, −106 dBm), but the simple base station 100 for configuring the femtocell has a place with poor communication quality, that is, a weak electric field. Therefore, an RSSI value indicating a weak electric field (for example, a value of −90 dBm or less) may be used as the threshold value.

  As described above, in the CDMA system, the communication quality is maintained as long as the ratio of signal strength / electric field strength is a certain level or higher. In the communication system having such characteristics, it can be said that when the simple base station 100 is installed in a place where the electric field is weak, the multiplexing power is locally large. Further, since the output of the simple base station 100 is minimal, it does not interfere with surrounding commercial base stations. Therefore, even if the peripheral band of the carrier frequency is used, if it is weak, the simple base station 100 can use the frequency band.

  Therefore, if the electric field strength of the set measurement frequency does not exceed a value indicating a weak electric field (for example, −90 dBm), it exceeds a value indicating natural noise (for example, −106 dBm), Even if it is determined that it is used by a station, etc., it is used without interfering with neighboring commercial base stations by multiplexing using a spreading code that does not interfere with the spreading code being used. be able to.

  Therefore, if there is a frequency band in which the electric field strength does not exceed the threshold (weak electric field) (step S2108: Yes), it can be determined that there is room for multiplexing in the frequency. A “spreading code detection process” for detecting the spreading code being used is executed (step S2200). This “spreading code detection process” will be described with reference to the flowchart shown in FIG.

  In this process, frequency bands that have electric field strengths that do not exceed a threshold value indicating a weak electric field are sequentially specified, and a spreading code used in the frequency band is detected. In this case, the measurement processing unit 113 performs despreading using a pilot signal (unmodulated signal) in the designated frequency band (step S2201). Here, the radio wave received at the frequency in the designated frequency band is despread with a spreading code usable by the simple base station 100, and it is determined whether or not the pilot signal has been demodulated (step S2202).

  If the pilot signal can be demodulated with the spreading code used by the simple base station 100, the same spreading code is also used in the surrounding commercial base stations using the frequency. Therefore, in this case (step S2202: Yes), provisional registration is performed as a candidate that needs to select another spreading code.

  Here, if the temporary registration is the first time (step S2203: No), the spreading code used for despreading is associated with the RSSI value indicating the measured electric field intensity, and another spreading code needs to be selected. Is temporarily registered (step S2205). In this case, information indicating the spread code and the RSSI value is held on, for example, the RAM.

  On the other hand, if the pilot signal cannot be demodulated by despreading (step S2202: No), a spreading code other than the spreading code used for despreading is used, so that the simple base station 100 can use the spreading code. Even if it uses, it does not interfere. Therefore, provisional registration is not performed because it is not necessary to select another spreading code.

  In this way, when despreading is performed at the frequency of the designated frequency band, the measurement processing unit 113 designates the next frequency band (frequency band where the electric field strength is equal to or less than the weak electric field) (step S2206), and becomes a target. If there is a frequency band (step S2207: No), the processing from step S2201 to step S2205 is performed for the designated frequency band. That is, despreading using the pilot signal is performed for all frequency bands where the electric field strength does not exceed the weak electric field.

  Here, when the pilot signal can be demodulated by despreading after provisional registration has already been performed (step S2202: Yes, step S2203: Yes), the measurement processing unit 113 determines that the electric field strength measured in the frequency band is It is determined whether or not the electric field strength is higher than the temporarily registered frequency band (step S2204).

  Here, since the spreading code that is most likely to interfere is a spreading code that is used at a frequency with the strongest electric field strength, if the electric field strength is stronger than the electric field strength of a frequency that has already been provisionally registered (step S2204: Yes), the contents of provisional registration are updated (step S2205). That is, when a plurality of frequency bands in which the electric field strength does not exceed the weak electric field are detected, when there are a plurality of frequencies that can demodulate the pilot signal by despreading using the spreading code used by the simple base station 100, Of the frequencies, the frequency showing the strongest electric field strength is provisionally registered as a candidate that needs to select another spreading code.

  If the pilot signal cannot be decoded by despreading in any of the target frequency bands (step S2202: No), provisional registration is not performed.

  When the above processing is performed for all frequency bands in which the electric field strength does not exceed the weak electric field (step S2207: Yes), the measurement processing unit 113 has different frequencies for uplink and downlink in communication with the mobile communication terminal MS. Whether or not is used is determined (step S2208).

  Here, when different frequencies are used for uplink and downlink (step S2208: No), the measurement processing unit 113 sets the lower limit of the frequency band used for uplink as the measurement frequency (step S2209), and receives at that frequency. The receiver 400 is controlled to perform the operation (step S2210). Then, the measurement processing unit 113 measures the electric field strength from the radio wave received by this reception operation (step S2211), and determines whether or not the threshold value indicating the weak electric field is not exceeded (step S2212).

  Here, if the electric field strength of the set measurement frequency does not exceed a threshold value (eg, −90 dBm) indicating a weak electric field (step S2212: Yes), the measurement frequency is increased by an increase amount corresponding to the frequency resolution (step S2213). If the frequency does not exceed the upper limit frequency of the upstream frequency band (step S2214: No), the electric field strength is measured (step S2211), and it is determined whether or not the threshold value indicating the weak electric field is not exceeded (step S2212). That is, the electric field strength is measured sequentially from the lower limit to the upper limit of the frequency band used for uplink communication.

  Here, when there is a frequency at which the electric field strength exceeds a threshold value indicating a weak electric field (step S2212: No), the measurement processing unit 113 determines that the frequency band cannot be used in the simple base station 100 (step S2215). . In other words, even if a frequency band used for downlink communication is usable, if the frequency band of the electric field strength exceeding the weak electric field is included in the uplink frequency band used as a pair in the communication, the frequency band Judge that you can not use.

  In the upstream frequency band, the electric field strength does not exceed the threshold value indicating the weak electric field in all frequency bands (step S2214: Yes), or the frequency bands used in the upstream and downstream are the same (step S2208). : Yes), the measurement processing unit 113 determines whether or not the frequency at which the pilot signal can be demodulated by despreading has been provisionally registered by the processing of steps S2201 to S2205 (step S2216).

  Here, when there is provisional registration (step S2216: Yes), the measurement processing unit 113 determines that the frequency can be used in the simple base station 100 if a spreading code other than the provisionally registered spreading code is used. (Step S2217).

  On the other hand, when there is no provisional registration (step S2216: No), it is determined that the simple base station 100 can use any spreading code (step S2218).

  When these determinations are made, the flow returns to the flow of “channel setting process (2)” (FIG. 8). In the flowchart of “channel setting process (2)”, it is determined whether there is a frequency band that can be used in the priority channel specified in step S2102 based on the determination result in “spreading code detection process” (step S2109). ).

  Here, it is determined in step S2217 of “spreading code detection process” (FIG. 9) that “use is possible if the spreading code is changed”, and in step S2218 it is determined that “any spreading code can be used”. If it is determined that there is a usable frequency band (step S2109: Yes).

  In this case, the measurement processing unit 113 selects a spreading code that does not interfere based on the result of the “spreading code detection process” (step S2110). That is, when the pilot signal can be demodulated by the despreading performed in the “spreading code detection process”, it is set to use a spreading code other than the spreading code used for the despreading.

  For example, in the case of CDMA2000, since the spreading code is expressed with a PN offset of 512 periods, no interference occurs if the PN offset is deviated. When the commercial base station cell around the simple base station 100 is a sector cell, if the shift amount of the PN offset is small, there may be sectors using the same PN offset. Therefore, in the simple base station 100 using such a spreading code, it is desirable to use a PN offset shifted by 256, which is a 1/2 cycle.

  When the simple base station 100 is used in a plurality of femtocells arranged in a cell of a commercial base station having a relatively large output, if the shift amount is only 1/2 period, the shift is performed in each of the plurality of femtocells. Since all the PN offsets may have the same value, the PN offset may be further shifted using a random number or hash calculation.

  On the other hand, if the pilot signal could not be demodulated by despreading, it is arbitrarily selected from the spreading codes that can be used by the simple base station 100 and set.

  Then, the priority channel specified in step S2102 is set as a channel that can be used in the simple base station 100 (step S2111), and the process is terminated. In this case, the measurement processing unit 113 sets to perform communication using the frequency band determined to be usable in step S2109 and the spreading code selected in step S2110 among the frequency bands usable in the channel.

  On the other hand, in the frequency band used in the priority channel specified in step S2102, there is no frequency band in which the electric field strength does not exceed the threshold value indicating the weak electric field (step S2108: No), or the electric field strength indicates the weak electric field. There is a frequency band that does not exceed the threshold value, but when it is determined that there is no usable frequency band because the electric field strength exceeds the threshold value indicating a weak electric field in either the up or down direction (step S2109: No). The processing unit 113 increments the channel designation pointer P by 1 (step S2112).

  If the P-th priority channel recorded in the priority channel list can be designated (step S2113: Yes), the above-described processing is performed for the priority channel. On the other hand, if the P-th priority channel cannot be specified because it does not exist in the list (step S2113: No), the process ends.

  With the above processing, even if the frequency band used in the selectable channel is used in a nearby commercial base station or the like, if the electric field strength does not exceed the threshold value indicating a weak electric field, diffusion without interference Frequency bands that can be used can be detected and set by multiplexing using codes.

  In the second embodiment, the selected priority channel is processed. However, in the “channel setting process (1)” (FIG. 5) illustrated in the first embodiment, the electric field strength of the carrier frequency (carrier frequency) is The above-described processing may be performed for a channel that is determined to exceed a threshold value indicating natural noise. Since there is a high possibility that the priority channel, which is a frequency to be used for the mobile communication terminal MS to search for a base station, is already used, the simple base station 100 can be used only by the method illustrated in the first embodiment. Although it may be impossible to find a frequency, combining the method of the first embodiment with the method of the first embodiment increases the possibility of finding a usable frequency.

(Embodiment 3)
In the first embodiment and the second embodiment, since the simple base station 100 having the configuration shown in FIG. 3 is used to measure the electric field strength, the reception operation related to the measurement is used for communication with the mobile communication terminal MS. Performed by the receiving unit 400. Therefore, even if the reception operation related to the measurement of the electric field strength is performed at a timing when communication with the mobile communication terminal MS is not performed, the simple base station 100 having a high communication frequency with the mobile communication terminal MS There is a possibility that the operation frequency for performing channel setting becomes low and channel setting according to changes in the surrounding radio wave environment cannot be performed.

  Therefore, by configuring the measurement receiver 500, which is a receiver for use in the measurement of electric field strength, in the simple base station 100 as shown in FIG. 10, the above-described processes can be executed at an arbitrary timing. it can. In this case, the control unit 110 controls the measurement receiving unit 500 to perform the receiving operation in each process exemplified in the first embodiment or the second embodiment. In addition, the configuration of the measurement receiving unit 500 is the same as that of the receiving unit 400, and the reception operation of the frequency specified by the control unit 110 is performed using the measurement receiving antenna 510. However, the measurement receiving unit 500 is connected to the mobile communication terminal MS. In order not to be used for communication, it is desirable that the main communication unit 130 is not linked.

  As described above, by applying the present invention as in the above embodiment, an appropriate channel setting can be easily performed in a simple base station configuring a femto cell.

  The said embodiment is an example and the application range of this invention is not restricted to this. That is, various applications are possible, and all embodiments are included in the scope of the present invention.

  In the above embodiment, when measuring the electric field strength, scanning is performed from the lower limit of the frequency band toward the upper limit, but the scanning direction may be from the upper limit to the lower limit.

  In the first embodiment, a value indicating natural noise is used as a threshold value for detecting a channel or frequency that is not used. However, it is possible to detect that it is not used in a nearby commercial base station or the like. If present, the value used for the threshold is not limited to a value indicating natural noise. In addition, when comparing with the measured electric field strength, a margin may be taken for the value used for the threshold value.

  In the “channel setting process (1)” of the first embodiment, when a carrier frequency having an electric field strength not exceeding the threshold is found, the channel is set as an unused channel. After measurement, comparison with a threshold value may be performed to detect unused channels.

  When measuring the electric field strength, the instantaneous value can be used as the measurement result, and the maximum value obtained by continuous reception for a fixed time or a plurality of reception operations can be used as the measurement result. According to such a method, it is possible to perform more reliable measurement of electric field strength even in a communication method employing a time division multiplexing method or a variable power method.

  In the “frequency band scanning process” of the first embodiment, the representative value of the electric field intensity is set to the maximum value. However, the present invention is not limited to this. For example, an average value may be used as the representative value. In the “frequency band scanning process”, all frequencies are scanned, but each time the electric field strength is measured, a comparison is made with a threshold value, and scanning is terminated when an electric field strength that does not exceed the threshold value is detected. It may work.

  In the “spreading code detection process” of the second embodiment, the spreading code used at the frequency of the strongest electric field strength is obtained. However, the present invention is not limited to this, and a method for listing all the spreading codes used is listed. It may be. In this case, a spreading code other than the listed spreading codes may be selected.

  In the electric field strength measurement in each of the above embodiments, it is desirable to consider the influence of the transmission operation by the transmission unit 300. In the case where the electric field strength is measured at a timing when communication with the mobile communication terminal MS is not performed as in the first embodiment and the second embodiment, the transmitter 300 is configured to perform the above-described processes. By stopping the operation, the influence of the transmission radio wave of the transmission unit 300 can be excluded. Further, it is possible to prevent communication with the mobile communication terminal MS from being started while performing processing for channel setting.

  On the other hand, when the measurement receiving unit 500 is provided as in the third embodiment, when the electric field strength measurement for channel setting is performed in parallel with the communication with the mobile communication terminal MS, the simple base station 100 performs the mobile communication terminal. Since the frequency band and transmission output used for communication with the MS are self-explanatory, by reducing the electric field strength according to the transmission output of the transmission unit 300 from the result of the electric field strength measurement performed in each process described above, A measurement result equivalent to when the transmission unit 300 is stopped can be obtained.

  In addition, it is possible to provide an existing simple base station as a simple base station according to the present invention by applying a program as well as providing a simple base station having a configuration for realizing the functions according to the present invention in advance. . That is, by applying a program for realizing each functional configuration by the control unit 110 exemplified in the above embodiment so that a computer (such as a CPU) that controls an existing simple base station can be executed, the simple according to the present invention is applied. It can function as a base station.

  Such a program distribution method is arbitrary. For example, the program can be distributed by being stored in a recording medium such as a memory card or a CD-ROM, or can be distributed via a communication medium such as the Internet.

  Moreover, if the method according to the present invention is used, the present invention can be applied to various devices without being limited to the simple base station. By applying the method according to the present invention, for example, it is possible to realize a measuring apparatus that measures a radio wave condition at a planned installation location such as a simple base station.

It is a figure which shows typically the structure of the femtocell system concerning embodiment of this invention. It is a block diagram which shows the structure of the simple base station shown in FIG. It is a block diagram which shows the structure of the radio | wireless communication part shown in FIG. It is a functional block diagram which shows the function structure implement | achieved by the control part shown in FIG. It is a flowchart for demonstrating "channel setting process (1)" concerning Embodiment 1 of this invention. 6 is a flowchart for explaining a “frequency band scanning process” executed in the “channel setting process (1)” shown in FIG. 5. It is a figure for demonstrating the relationship between a carrier frequency and a frequency band. It is a flowchart for demonstrating "channel setting process (2)" concerning Embodiment 2 of this invention. 9 is a flowchart for explaining a “spreading code detection process” executed in the “channel setting process (2)” shown in FIG. It is a block diagram which shows the structure of the simple base station concerning Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Femtocell system, MS ... Mobile communication terminal, NW ... Main line, 100 ... Simple base station, 110 ... Control part, 111 ... Communication processing part, 112 ... Measurement timing discrimination | determination part, 113 ... Measurement processing part, 120 ... Storage unit, 130 ... backbone communication unit, 200 ... wireless communication unit, 300 ... transmission unit, 310 ... modulation processing unit, 320 ... RF unit, 330 ... transmission antenna, 400 ... reception unit, 410 ... reception antenna, 420 ... RF unit, 430 ... demodulation processing unit, 500 ... reception unit for measurement, 510 ... reception antenna for measurement

Claims (9)

A simple base station that performs wireless communication with a communication terminal device,
Channel selection means for selecting a channel from a plurality of selectable channels;
First field strength measuring means for measuring the field strength at the carrier frequency of the channel selected by the channel selecting means;
First electric field strength determining means for determining whether or not the electric field strength measured by the first electric field strength measuring means exceeds a predetermined threshold;
Unused channel provisional means for provisionally setting the channel of the carrier frequency determined by the first electric field strength determination means to be an electric field intensity not exceeding the predetermined threshold as an unused channel;
Second electric field strength measuring means for measuring electric field strength in a plurality of frequency bands from a lower limit to an upper limit of a frequency band used by the provisional channel by the unused channel provisional means;
Channel setting means for setting a channel tentatively used as the unused channel as a channel usable in the simple base station when the electric field strength measured by the second electric field strength measuring means does not exceed the threshold value ; Prepare
A simple base station characterized by that. The wireless communication is to be modulated and demodulated by a spread spectrum method,
The channel setting means includes
Based on the field intensity the second field strength measuring means were measured boss, the second field strength discriminating means for frequency bands used in the channel is determined whether or not the field strength does not exceed a predetermined threshold When,
Spreading code detecting means for detecting a spreading code used in the frequency band by performing despreading in a frequency band where the electric field intensity does not exceed the threshold;
Spreading code setting means for setting a spreading code that does not interfere with the spreading code detected by the spreading code detecting means as a spreading code that can be used in the unused channel;
The simple base station according to claim 1. When the first electric field strength measuring means uses different frequencies for transmission and reception in communication with the communication terminal device, the electric field strength is measured at each frequency.
The simple base station according to claim 1 . The first electric field strength measuring means measures the electric field strength when there is no connection with the communication terminal device.
The simple base station according to any one of claims 1 to 3, wherein Comprising two or more receiving means,
The first electric field strength measuring unit measures the electric field strength by a receiving operation of a receiving unit that is not used for communication with the communication terminal device among the two or more receiving units.
The simple base station according to claim 1, wherein: A method for identifying a channel that can be used without radio wave interference in wireless communication using a spread spectrum method,
A channel selection step for selecting a channel from the selectable channels;
A first field strength measurement step for measuring the field strength at the carrier frequency of the selected channel;
A first electric field strength determination step for determining whether or not the electric field strength measured in the first electric field strength measurement step exceeds a predetermined threshold;
An unused channel provisional step in which the channel of the carrier frequency determined as the electric field intensity not exceeding the predetermined threshold in the first electric field intensity determination step is provisionally used as an unused channel;
A second electric field strength measuring step for measuring electric field strength in a plurality of frequency bands from a lower limit to an upper limit of a frequency band used in a channel provisional in the unused channel provisional step ;
If the field intensity measured at the second field strength measuring step does not exceed the threshold value, the provisional been Ji Yaneru as the unused channels, a channel specifying step of specifying a usable channel,
A channel identification method comprising: When the electric field intensity measured in the second electric field intensity measurement step does not exceed a threshold value indicating a weak electric field, the spreading code used in the frequency band is detected by performing despreading in the frequency band. A spreading code detection step;
A spread code specifying step of specifying a spread code that does not interfere with the spread code detected in the spread code detection step as a spread code usable in the frequency band;
The channel specifying method according to claim 6 . In a computer that controls a wireless communication device that performs wireless communication using a spread spectrum system,
A channel selection function for selecting a channel from a plurality of selectable channels;
A first field strength measurement function for measuring a field strength at a carrier frequency of a channel selected by the channel selection function;
A first electric field strength determination function for determining whether or not the electric field strength measured by the first electric field strength measurement function exceeds a predetermined threshold;
An unused channel provisional function for provisionally setting the channel of the carrier frequency determined as the electric field strength not exceeding the predetermined threshold by the first electric field strength determination function as an unused channel;
A second electric field strength measurement function for measuring electric field strength in a plurality of frequency bands from a lower limit to an upper limit of a frequency band used by the provisional channel of the unused channel provisional function;
A channel setting function for setting a channel tentatively used as the unused channel as a channel that can be used in the simple base station when the field strength measured by the second field strength measurement function does not exceed the threshold;
A program characterized by realizing. In the computer,
When the electric field intensity measured by the second electric field intensity measurement function does not exceed a threshold value indicating a weak electric field, the spreading code used in the frequency band is detected by performing despreading in the frequency band. Spreading code detection function;
A spread code specifying function for specifying a spread code that does not interfere with the spread code detected by the spread code detection function as a spread code usable in the frequency band;
The program according to claim 8 , wherein the program is realized.

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