JP4177830B2 - Wireless communication system and wireless communication terminal - Google Patents

Description

  The present invention relates to a radio communication system and a radio communication terminal using cognitive radio that changes a communication scheme by recognizing external information by sharing one frequency band in a plurality of systems.

  Conventionally, in some of the standards proposed for Ultra Wide Band (UWB), interference with other systems is reduced by holding a signal below a noise level and a communication frequency band is shared (for example, , See Patent Document 1).

In addition, in wireless LAN, there is a standard (IEEE 802.11h) that performs carrier sense in a certain frequency band and changes the frequency band to be used if there is interference from a radar or other wireless LAN system in that frequency band (for example, IEEE 802.11h) , See Patent Document 2).
JP 2005-12776 A JP 2004-297150 A

  However, in a method such as UWB, since a signal is superimposed and transmitted in the communication band of another system, only signal power of noise level can be used, and although it can be applied to PAN that is short-range communication, There is a problem that it cannot be applied to wireless communication using medium and long distances such as LAN and cellular radio.

  Even if a method such as wireless LAN using IEEE802.11h is used, there are multiple terminals that communicate using a communication method that occupies a fixed bandwidth for a long time in a system that presupposes frequency sharing. Even though there are unused bands, it is not possible to secure a continuous unused band for performing broadband communication. For this reason, there is a problem that resources such as frequency bands cannot be fully utilized.

  The present invention has been made to solve the above-described problems, and can be applied not only to short-distance communication but also to medium / long-distance communication, and further to a radio communication system with improved frequency utilization efficiency and An object is to provide a wireless communication terminal.

In order to solve the above-described problem, a wireless communication system according to the present invention is configured to perform communication with a first wireless communication apparatus using a part of a first frequency band in a certain frequency band. A wireless communication terminal and a second wireless communication apparatus different from the first wireless communication apparatus using a part of the second frequency band within the certain frequency band, which is different from the first frequency band; In a wireless communication system comprising a second wireless communication terminal that performs communication between
The first wireless communication terminal includes an adjacent band measuring unit that measures an interference amount for a high frequency band and a low frequency band adjacent to the first frequency band, and an interference amount corresponding to each of the interference amounts. A movement deciding means for deciding to move the first frequency band to an adjacent high frequency band or low frequency band equal to or less than one threshold; and to which frequency band decided by the movement deciding means, the first frequency band A movement information notification means for notifying the first wireless communication apparatus of movement information indicating whether the first wireless communication apparatus is to be moved; and a notification that the first wireless communication apparatus has recognized the movement information. A movement notification acquisition means acquired from the movement information, and a movement means for moving the first frequency band to the frequency band indicated in the movement information,
The second wireless communication terminal includes an adjacent band measuring unit that measures an interference amount for a high frequency band and a low frequency band adjacent to the second frequency band, and an interference amount corresponding to each of the interference amounts. in at least one of the high-frequency band and low frequency band adjacent below second threshold, the expansion determination means for determining to increase the bandwidth of the second frequency band, which frequency determined by the extension decision means Extended information notification means for notifying the second wireless communication device of extended information indicating whether to extend the second frequency band to a band, and notification that the second wireless communication device has recognized the extended information the provided and extended notification acquisition means for acquiring from said second wireless communication device, and a expansion means for expanding said second frequency band in which the frequency band indicated in the extension information, said extension decision hand It applies been extended frequency band extended by the extension means instead of the second frequency band, decides to extend the repetition bandwidth, said expanding means is characterized by expanding the frequency band .

  According to the wireless communication system and the wireless communication terminal of the present invention, it can be applied not only to short-distance communication but also to medium / long-distance communication, and frequency utilization efficiency can be improved.

Hereinafter, a wireless communication system and a wireless communication terminal according to an embodiment of the present invention will be described in detail with reference to the drawings.
1 to 4 show examples of the wireless communication system in the embodiment of the present invention. In the wireless communication system of the present invention, it is assumed that a plurality of systems independently determine frequency bands for communication.
FIG. 1 shows an example in which a hot spot system (base station 101 and wireless communication terminal 102) and an ad hoc system (wireless communication terminal 103 and wireless communication terminal 104) are mixed. In such a situation, when the hotspot base station 101 and the wireless communication terminal 102 are performing communication using a part of the frequency band F1 of a certain frequency band F, the wireless communication terminal 103 and the wireless communication terminal 104 are not connected to each other. Communication is performed using a part of the frequency band F2 while avoiding the frequency band F1 without going through the station 101.
FIG. 2 is an example in which a plurality of hot spot systems are mixed. In such a situation, when the hotspot base station 201 and the wireless communication terminal 202 communicate with each other using a part of the frequency band F1 of the frequency band F, the wireless communication terminal 204 has the frequency band F1. By recognizing that it is used, communication is performed with the base station 203 using the frequency band F2 while avoiding the frequency band F1.
Similarly, in the example of FIG. 3, a base station 301 that covers a relatively large area, wireless communication terminals 302, 303, 304, and 305 that communicate with the base station 301, and a base station 306 that covers a relatively small area. And wireless communication terminals 307 that communicate with the base station 306 are mixed. In such a case, the wireless communication terminal 307 performs communication by determining the frequency band of the communication 317 while avoiding the bands of the communication 312, the communication 313, the communication 314, and the communication 315 used by the base station 301.
In FIG. 4, wireless communication terminals communicate individually with each other as in ad hoc communication. Similarly, in such a case, when the wireless communication terminal 401 and the wireless communication terminal 402 communicate using the frequency band F1, the wireless communication terminal 403 and the wireless communication terminal 404 use the frequency band F1. Communication is performed using the frequency band F2 while avoiding the frequency band F1.
Although the present invention can be applied to any of the system configurations shown in FIGS. 1 to 4, the case where the system configuration is as shown in FIG. 3 will be described in detail below.

A wireless communication terminal according to an embodiment of the present invention will be described with reference to FIG. This wireless communication terminal can move in a communication frequency band. In other words, this wireless communication terminal is for communication that needs to be maintained at a relatively low speed for a long time, such as a voice call using circuit switching.
As shown in FIG. 5, the wireless communication terminal according to the present embodiment includes radio frequency processing circuits (RF) 501, 509, 515, 518, analog-digital conversion processing units (ADC) 502 and 510, and a bandpass filter (BPF). 503, 505, 507, 511, reception processing units 504, 512, signal power measurement units 506, 508, communication band change determination processing unit 513, multiple processing unit (MUX) 514, digital analog conversion processing unit (DAC) 516, 519 , Transmission processing units 517 and 520 are provided.

  The RF 501 converts a signal received via an antenna into a baseband signal. The RF 501 uses Fc_Rx as the carrier signal frequency of the received signal. The ADC 502 converts the output signal of the RF 501 into a digital signal.

  The BPF 503 receives the output signal of the ADC 502 and passes only the signal in the frequency band in which communication is performed according to F_COM specified as the communication frequency band. The reception processing unit 504 performs reception processing such as transmission path estimation, demodulation, and decoding on the signal of the frequency band F_COM output from the BPF 503. Then, the reception processing unit 504 outputs the reception processing result to the upper layer as an audio signal or a data signal.

  The BPFs 505 and 507 each receive an output signal of the ADC 502, and signals in frequency bands of F_COM + α (corresponding to the high frequency side) and F_COM-α (corresponding to the low frequency side), which are adjacent to the communication frequency band F_COM, respectively. Only pass through. The signal power measuring units 506 and 508 measure the power of the signals that have passed through the BPFs 505 and 507, respectively, and measure the power of the received signals in the respective frequency bands.

  The RF 509 converts a signal received via the antenna into a baseband signal. The RF 509 is for receiving a control signal. RF509 uses Fc_control as the carrier signal frequency of the received signal. The ADC 502 converts the output signal of the RF 501 into a digital signal. The ADC 510 converts the output signal of the RF 509 into a digital signal. The BPF 511 receives the output signal of the ADC 510 and passes only the signal in the frequency band designated as the communication frequency band. The reception processing unit 512 performs each reception process such as transmission path estimation, demodulation, and decoding on the frequency band signal output from the BPF 511.

  Here, the description has been made on the assumption that the frequency band input to Fc_control and BPF 511 is always constant, but when the control signal dedicated frequency band is changed due to some request, the variable band RF 509 or BPF511 is used.

  The communication band change determination processing unit 513 determines a frequency band for communication or changes a communication frequency band according to the received control signal and input signal power. Through these processes, the communication band change determination processing unit 513 sets the reception signal carrier frequency band Fc_Rx, the transmission signal carrier frequency band Fc_Tx, the reception signal frequency band F_COM, the high frequency band F_COM + α adjacent to the reception signal frequency band, and the reception signal frequency band. An adjacent low frequency band F_COM-α is set for each processing unit. Further, the communication band change determination processing unit 513 uses the power of the received signal measured by the signal power measurement units 506 and 508 as the amount of interference. The operation of the communication band change determination processing unit 513 for determining the frequency band for communication in accordance with the received control signal and the input signal power will be described later with reference to the flowcharts of FIGS. explain. The operation in which the communication band change determination processing unit 513 changes the communication frequency band will be described later with reference to the flowcharts of FIGS. 17, 19, and 20.

The transmission processing unit 520 receives the communication carrier frequency bands Fc_Rx, Fc_Tx and the communication frequency band F_COM determined by the communication band change determination processing unit 513, modulates and codes these pieces of information, and performs transmission processing. In order to negotiate with the communication partner, it is necessary to transmit the communication carrier frequency bands Fc_Rx, Fc_Tx and the communication frequency band F_COM to the communication partner. The DAC 519 converts the output signal of the transmission processing unit 520 into an analog signal. The RF 518 performs RF processing using the control signal carrier frequency band Fc_control.
The transmission processing unit 517 performs transmission processing on transmission signals such as audio signals and data signals generated from the upper layer. The DAC 516 converts the output signal of the transmission processing unit 517 into an analog signal. The RF 515 performs RF processing using the transmission signal carrier frequency band Fc_Tx. The MUX 514 multiplexes these transmission signals output from the RFs 515 and 518 and transmits them from the antenna.

A wireless communication terminal according to an embodiment of the present invention will be described with reference to FIG. This wireless communication terminal can move the communication frequency band or extend the communication frequency band. In other words, this wireless communication terminal has a relatively low speed such as a voice call using circuit switching that needs to be maintained at a relatively low speed for a long time, and a data transfer using packet switching. However, the present invention is for a system that performs communication that has both communication in which communication is completed in a short time or communication that occurs in bursts. In FIG. 6, the same parts as those of the wireless communication terminal of FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted.
The wireless communication terminal shown in FIG. 6 includes a reception processing unit 601 instead of the reception processing unit 504, a communication band change determination processing unit 602 instead of the communication band change determination processing unit 513, and a transmission processing unit instead of the transmission processing unit 517. 5 is different from the wireless communication terminal of FIG. 5 only in that a DAC 606 is provided instead of the ADC 605 and the DAC 516 instead of the ADC 604 and the ADC 502, and a communication method determination processing unit 603 is newly provided.

  Based on the reception processing method determined by the communication method determination processing unit 603, the reception processing unit 601 performs reception processing such as transmission path estimation, demodulation, and decoding on the reception signal of the frequency band F_COM by the BPF 503. The reception processing unit 601 outputs the obtained reception processing result to the upper layer as an audio signal or a data signal.

  The communication band change determination processing unit 602 determines a frequency band for communication according to the received control signal and input signal power, or changes the communication frequency band. Through these processes, the communication band change determination processing unit 602 sets the reception signal carrier frequency band Fc_Rx, the transmission signal carrier frequency band Fc_Tx, the reception signal frequency band F_COM, the high frequency band F_COM + α adjacent to the reception signal frequency band, and the reception signal frequency band. An adjacent low frequency band F_COM-α is set for each processing unit. The operation of the communication band change determination processing unit 602 for determining the frequency band for communication according to the received control signal and the input signal power will be described later with reference to the flowcharts of FIGS. explain. The operation in which the communication band change determination processing unit 602 moves the communication frequency band will be described later with reference to the flowcharts of FIGS. 17, 19, and 20. The operation of the communication band change determination processing unit 602 for extending the communication frequency band will be described later with reference to the flowcharts of FIGS. 18, 19, and 20.

  The communication method determination processing unit 603 instructs the reception processing unit 601 and the ADC 502 about the reception processing method and the sampling frequency. Similarly, the communication method determination processing unit 603 instructs the transmission processing unit 604 and the DAC 606 regarding the transmission processing method and the sampling frequency.

  Based on the transmission processing method determined by the communication method determination processing unit 603, the transmission processing unit 604 performs transmission processing on transmission signals such as audio signals and data signals generated from higher layers.

  The ADC 605 converts the output signal of the RF 501 into a digital signal based on the sampling frequency determined by the communication method determination processing unit 603. The DAC 606 converts the output signal of the transmission processing unit 604 into an analog signal based on the sampling frequency determined by the communication method determination processing unit 603.

Next, regarding the exchange of signals between the base station 301 and the wireless communication terminals 302, 303, 304, and 305 and the exchange of signals between the base station 306 and the wireless communication terminal 307 in the case of the system configuration shown in FIG. Will be described with reference to FIG.
The base station 301 starts communication with the wireless communication terminals 302, 303, 304, and 305. For example, as shown in steps S701, S702, S703, and S704 in FIG. 7, the base station 301 and each wireless communication terminal start communication. Thereafter, when the base station 301 is communicating with each of the wireless communication terminals 302, 303, 304, and 305, it is assumed that communication is started between the base station 306 and the wireless communication terminal 307 (step S721). The signal power measuring units 506 and 508 of the wireless communication terminal 307 measure the amount of interference in the high frequency band and the low frequency band adjacent to the band in which communication is performed. When interference is not measured (step S722), the wireless communication terminal 307 issues a communication band expansion request to the base station 306 (step S723). In this case, the frequency band on the high frequency side and / or the low frequency side adjacent to the currently communicating communication band is measured for interference, and the communication band is expanded to the frequency side without interference.

  The base station 306 receives the communication band expansion request from the wireless communication terminal 307 and returns ACK (step S724). Thereafter, the base station 306 and the wireless communication terminal 307 simultaneously expand the communication band (steps S725 and S726). This timing information may be included in the ACK or may be determined to be a certain time after the ACK is received. By the way, when interference is detected in all the frequency bands adjacent to the communication band in step S722, the communication band currently being communicated cannot be expanded.

  For example, the wireless communication terminals 302, 303, 304, and 305 determine whether there is interference in adjacent frequency bands at predetermined time intervals. Now, it is assumed that interference is detected in the adjacent frequency band between the radio communication terminal 303 and the radio communication terminal 304 as a result of the base station 306 and the radio communication terminal 307 extending the communication band (steps S705 and S706). In this case, in order to avoid the frequency band in which interference is detected, the wireless communication terminal 303 and the wireless communication terminal 304 issue a communication band movement request to the base station 301 (steps S707 and S708). The base station 301 receives the communication band shift request from the wireless communication terminal 303 and the wireless communication terminal 304, and returns ACK (steps S709 and S710). Thereafter, the base station 301, the wireless communication terminal 303, and the wireless communication terminal 304 move in the communication band at the same time (steps S711, S712, and S713). This timing information may be included in the ACK or may be determined to be a certain time after the ACK is received. The communication band shift sequence consisting of steps S705 to S713 and the communication band extension sequence consisting of steps S721 to S726 are repeated as shown in steps S714 and S727, respectively, and is performed between the base station 306 and the wireless communication terminal 307. The communication bandwidth required for communication can be secured.

When the communication band can be moved or expanded as in the communication band change determination processing unit 602, the currently used communication band is moved according to the requested communication band requested. Or to expand. The communication band change determination processing unit 602 moves the used communication band when the requested communication band is smaller than the used communication band, and extends the used communication band when the requested communication band is larger than the used communication band.
Since the required communication bandwidth differs for each wireless communication terminal, if a certain wireless communication terminal has a bandwidth extension function, the used communication bandwidth may be expanded, and other wireless communication terminals have a bandwidth transfer function. In some cases, the used communication band may be moved.

Next, changes in the status of the communication frequency band F (801 shown in FIG. 8 and subsequent figures) by the wireless communication terminal of this embodiment will be described in order with reference to FIGS. 8 to 13.
The base station 301 and the wireless communication terminals 302, 303, 304, and 305 communicate with each other using communication frequency bands 312, 313, 314, and 315 within the communication frequency band 801. Here, it is assumed that these wireless communication terminals are communications that require a relatively long time, a low required transmission rate, and a narrow communication bandwidth, such as circuit-switched communications.

  Each of the base station 301 and the wireless communication terminals 302, 303, 304, and 305 measures the amount of interference in adjacent frequency bands near the band in which the base station 301 is communicating. In each wireless communication terminal, signal power measuring sections 506 and 508 measure the amount of interference. In the stage of FIG. 8, the interference measured between the base station 301 and the wireless communication terminals 302, 303, 304, and 305 is relatively low, and the interference component is mainly caused by thermal noise.

  Here, it is assumed that the base station 306 and the wireless communication terminal 307 make a request to perform communication at a high transmission rate using a relatively wide band. At this time, at least one of the base station 306 and the wireless communication terminal 307 performs interference measurement in the communication frequency band 801. As a result of the interference measurement, it is assumed in this example that the frequency band in which the base station 306 and the wireless communication terminal 307 perform communication 317 is determined as shown in FIG. The communication band determination method will be described later with reference to FIGS. Here, the communication bandwidth for performing the communication 317 may be smaller than the communication bandwidth required for the communication 317.

  FIG. 10 shows the state of the communication frequency band 801 when the base station 306 and the wireless communication terminal 307 start the communication 317. In this situation, at least one of the base station 306 and the wireless communication terminal 307 measures the amount of interference in a frequency band adjacent to the communication frequency band 317. FIG. 10 shows a case where the communication 313 and the communication 314 are arranged sufficiently apart from each other in frequency band, and the interference amount between the base station 306 and the wireless communication terminal 307 is relatively low. In such a situation, when the transmission rate required for the communication 317 between the base station 306 and the wireless communication terminal 307 is high and the current communication bandwidth is insufficient, as shown in FIG. The communication terminal 307 performs interference measurement and expands the communication area by the bandwidth for which interference was not measured.

  Here, it can be seen that the radio communication terminal 303 and the base station 301 performing the communication 313 have large interference in the adjacent frequency band on the high frequency side as a result of the interference amount measurement. It can also be seen that the interference is relatively small in the low frequency region adjacent to the communication 313. In such a case, as shown in FIG. 12, the radio communication terminal 303 and the base station 301 move the communication frequency band 313 by the adjacent low frequency band for which the amount of interference was measured. Similarly, the communication 314 performed between the base station 301 and the wireless communication terminal 304 also moves by the amount of the adjacent high frequency band whose interference amount has been measured. As shown in FIG. 12, the communication 313 and the communication 314 move in the communication frequency band, so that a larger frequency band is available between the communication 313 and the communication 314. Therefore, the base station 306 and the wireless communication terminal 307 Communication 317 can be further expanded. By repeating this, if there is a free communication frequency band, the frequency bandwidth of the communication 317 can be expanded to the required communication bandwidth as shown in FIG.

Next, a communication frequency band determination method at the start of communication will be described with reference to FIGS.
Basically, a wireless communication terminal and a base station that have requested to start communication search for an available frequency band, and if the amount of interference is equal to or less than a threshold as a result of the search, communication is started using that frequency band. FIG. 14 shows one example of a flowchart for searching for a free frequency band for starting communication.
In this example, first, the communication band change determination processing unit 513 or 602 selects an arbitrary frequency band F1 using a random number from the communication frequency band 801 (step S1401). Next, the signal power measurement units 506 and 508 measure the amount of interference for the selected frequency band F1 (step S1402). Thereafter, the communication band change determination processing unit 513 or 602 determines whether or not the amount of interference measured in the frequency band F1 is equal to or less than a threshold (step S1403). This threshold mainly depends on the thermal noise power of the wireless communication terminal and the filter performance of the wireless communication terminal. In addition, this threshold value also depends on the transmission power of the base station and the transmission power of the wireless communication terminal. Based on these, the threshold value is determined for each wireless communication terminal.

  If the measured interference amount in the frequency band is larger than the threshold value, an arbitrary frequency band F2 is again selected from the communication frequency band 801 using a random number (step S1401), and interference in the frequency band F2 is performed. The amount is measured (step S1402).

  On the other hand, if the interference amount is equal to or smaller than the threshold value in step S1403, the frequency band is determined as a frequency band for starting communication, and the communication band change determination processing unit 513 or 602 starts communication in this frequency band. In response to this, it is determined whether or not the communication partner's consent has been obtained (step S1404). If consent is obtained, the process proceeds to step S1405. If consent is not obtained, the process returns to step S1401. In step S1405, communication is started in the frequency band in which the amount of interference determined in step S1401 is measured.

  In this way, by searching for a band in which communication is performed using random numbers each time, a plurality of wireless communication terminals are distributed and started without being concentrated in a certain frequency band. Therefore, communication with a relatively wide required frequency band is less likely to push out communications with a relatively narrow required frequency band, so that the overhead for moving the communication band is reduced and the system throughput can be improved.

FIG. 15 also shows one example of a flowchart for searching for a free frequency band for starting communication. Hereinafter, the same steps as those shown in other drawings are denoted by the same reference numerals, and the description thereof will not be repeated.
The communication band change determination processing unit 513 or 602 determines whether or not the measured interference amount of the selected frequency band F1 is equal to or smaller than the threshold value in step S1403 (step S1501). If the amount of interference is less than or equal to the threshold, the process proceeds to step S1404. If the amount of interference is greater than the threshold, the process proceeds to step S1502.

In step S1502, the communication band change determination processing unit 513 or 602 sets the frequency band for measuring the interference amount to a higher frequency band F2 adjacent to the band F1 determined in step S1401 in the nearest past. Then, the communication band change determination processing unit 513 or 602 determines whether or not the set frequency band F2 is within the predetermined communication frequency band 801 (step S1503). If the frequency band F2 is in the communication frequency band 801, the process returns to step S1402, and the signal power measurement units 506 and 508 measure the interference amount. On the other hand, if the frequency band F2 is not in the communication frequency band 801, the process proceeds to step S1504.
In step S1504, the frequency band for measuring the interference amount is set to the lowest frequency band F3 from the communication frequency band 801. Thereafter, similarly, the amount of interference in the frequency band F3 is measured (step S1402).

In this way, by searching for a band in which communication is performed using random numbers each time and searching for adjacent frequency bands, communication is started in a distributed manner without concentrating on a certain frequency band. Accordingly, communication with a relatively wide required frequency band is less likely to spread communication with a relatively narrow required frequency band, so that overhead for moving the communication band is reduced and system throughput can be improved. In addition, since the frequency bands are searched in order, if the time required for measuring the interference amount is relatively short, unnecessary frequency band searches can be reduced.
In the example of FIG. 15, the adjacent higher frequency band is set as the next interference measurement target in step S1502, but a lower frequency band may be set as the next interference measurement target. In this case, in step S1504, the frequency band for measuring the interference amount may be set to the highest frequency band of the frequency band 801.

FIG. 16 also shows one example of a flowchart for searching for a free frequency band for starting communication.
First, before starting communication, it is determined whether or not the requested communication bandwidth exceeds a threshold value (step S1601). This threshold is predetermined, for example, a communication bandwidth necessary for voice communication requiring relatively low speed communication and a communication bandwidth necessary for packet communication requiring relatively high speed communication. Is set as a threshold. If the requested communication bandwidth is equal to or less than the threshold value, that is, if low speed communication is requested, the process proceeds to step S1602. On the other hand, if the requested communication bandwidth is larger than the threshold value, that is, if high-speed communication is requested, the process proceeds to step S1603.

  In step S1602, the frequency band for measuring the amount of interference is set to the lowest band in the communication frequency band 801. Next, the amount of interference is measured (step S1402). If the measured amount of interference in the frequency band is equal to or less than the threshold, the process proceeds to step S1404. If it is determined in step S1404 that consent from the communication partner to communicate using the frequency band set in step S1602 cannot be obtained, the process returns to step S1602. In step S1503 in FIG. 16, if the frequency band F2 is not in the communication frequency band 801, the process returns to step S1602.

  In step S1603, the frequency band for measuring the interference amount is set to the highest band among the communication frequency bands 801. Thereafter, the amount of interference is measured for the set frequency band (step S1402), and it is determined whether the amount of interference in the measured frequency band is equal to or less than a threshold value (step S1604). If the amount of interference is less than or equal to the threshold, the process proceeds to step S1404. If the amount of interference is greater than the threshold, the process proceeds to step S1605.

  In step S1605, the communication band change determination processing unit 513 or 602 sets the frequency band for measuring the interference amount to the lower frequency band F4 adjacent to the band determined in step S1603 in the nearest past. Then, the communication band change determination processing unit 513 or 602 determines whether or not the set frequency band F4 is within the predetermined communication frequency band 801 (step S1606). When the frequency band F4 is in the communication frequency band 801, the process returns to step S1402, and the signal power measurement units 506 and 508 measure the interference amount. On the other hand, if the frequency band F4 is not in the communication frequency band 801, the process proceeds to step S1603.

  In this way, a system that performs low-speed communication and high-speed communication by determining a place to start a search of a frequency region where communication is started according to the required frequency band width allows And each will be solidified. For this reason, a wireless communication terminal that performs low-speed communication is less likely to change the communication band, so that the system throughput can be improved. In addition, since a wireless communication terminal that performs high-speed communication is more likely to find a large vacant frequency band when starting communication, the system throughput can be improved.

  In the example of FIG. 16, in step S1601, if the requested communication bandwidth is equal to or smaller than the threshold, the process proceeds to step S1602, and if greater than the threshold, the process proceeds to step S1603. If the requested communication bandwidth is larger than the threshold, the process proceeds to step S1602. If the requested communication bandwidth is smaller than the threshold, the same effect can be expected even if the process proceeds to step S1603.

Hereinafter, a procedure for moving and extending a band during communication after communication is established will be described with reference to FIGS. FIG. 17 shows a flowchart example of frequency band change (also referred to as frequency band movement) for communication that needs to be maintained at a relatively low speed for a long time, such as a voice call using circuit switching.
First, the signal power measurement units 506 and 508 measure the amount of interference in two bands, a high frequency band and a low frequency band adjacent to the frequency band in which communication is currently performed (step S1701). Next, the communication band change determination processing unit 513 or 602 compares the measured interference amounts of the two bands, and determines whether or not the absolute value of the difference is equal to or greater than a threshold value (step S1702). This threshold is used to determine whether or not there is an interference signal in one of the two bands, and there is no interference signal in either of the two bands and the amount of interference is only noise. This threshold is set based on the thermal noise power of the wireless communication terminal and the measurement error of the measured power of the wireless communication terminal.

  If the absolute value of the difference between the interference amounts of the two bands is smaller than the threshold value in step S1702, it is determined that there is no interference signal in both the high frequency band and the low frequency band, or there is an interference signal in both. In this case, the processing is terminated without moving the communication band in which communication is currently being performed.

  On the other hand, if it is determined in step S1702 that the absolute value of the difference between the amount of interference in the high frequency band and the amount of interference in the low frequency band is greater than or equal to the threshold, an interference signal exists in either the high frequency band or the low frequency band. In order to confirm whether or not to do so, the observed interference amounts in the high frequency band and the low frequency band are compared (step S1703). Here, it is assumed that the interference amount in the high frequency band is larger than the interference amount in the low frequency band. In this case, furthermore, the amount of interference measured in the high frequency band is compared with the threshold (step S1704), and only when the amount of interference is large, another wireless communication is performed in the high frequency band adjacent to the communication band in which communication is currently performed. It is determined that there is an interference signal of the terminal or another system, and there is no interference signal in the adjacent low frequency band, and the observed low frequency band is in the communication frequency band 801, and the communication partner agrees If obtained, the communication band is changed to the adjacent low frequency band (step S1705). Note that the threshold values in step S1704 and later-described step S1706 are the same as the threshold values in step S1403 described above.

  Similarly, when it is determined in step S1703 that the amount of interference in the low frequency band is greater than or equal to the amount of interference in the high frequency band, the amount of interference measured in the low frequency band is compared with a threshold (step S1706). Only when the amount of interference is larger than the threshold value, there is an interference signal of another wireless communication terminal or another system in the low frequency band adjacent to the communication band in which communication is currently performed, and in the adjacent high frequency band. If it is determined that there is no interference signal and the observed high frequency band is within the communication frequency band 801 and the consent of the communication partner is obtained, the communication band is changed to this adjacent high frequency band (step S1707).

Next, FIG. 18 shows a change in frequency band for communication such as data transfer using packet switching, which is relatively fast but completes communication in a short time, or communication in which burst communication occurs. An example of a flowchart is shown.
First, the communication band change determination processing unit 513 or 602 compares the communication bandwidth currently being communicated with the requested communication bandwidth (step S1801). If the current communication bandwidth is equal to or larger than the requested communication bandwidth, the communication bandwidth is not expanded, assuming that a sufficient communication bandwidth is secured. When the communication bandwidth currently being communicated is smaller than the requested communication bandwidth, it is determined that the communication bandwidth needs to be widened because the communication bandwidth does not satisfy the request, and the process proceeds to step S1701. A procedure for expanding the communication bandwidth is performed.

  Next, the signal power measuring units 506 and 508 measure the amount of interference in two bands, a high frequency band and a low frequency band adjacent to the frequency band in which communication is currently performed (step S1701). It is determined whether the amount of interference between the high frequency band and the low frequency band is equal to or less than a threshold value (step S1802). This threshold value is the same as the threshold value in step S1403 described above. In addition, threshold values in steps S1803 and S1804, which will be described later, are similar to the threshold values in step S1403. If any of these interference amounts is equal to or less than the threshold value, the process proceeds to step S1805, and if it is greater than the threshold value, the process proceeds to step S1803.

  In step S1803, it is determined whether the amount of interference in the high frequency band is equal to or less than a threshold value. If the amount of interference in the high frequency band is less than or equal to the threshold value, the process proceeds to step S1806, and if greater than the threshold value, the process proceeds to step S1804.

  In step S1805, it is determined that communication by another wireless communication terminal or another system is not performed in the high frequency band and the low frequency band adjacent to the currently communicating band, and the communication partner is within the communication frequency band 801. Is obtained, the communication frequency band is expanded to the adjacent high frequency band and low frequency band, and the process is terminated.

  In step S1806, it is determined that the communication of the other wireless communication terminal and the other system is performed in the low frequency band and the communication is not performed in the high frequency band, and this high frequency band is the communication frequency band. If the consent of the communication partner is obtained, the communication frequency band in which communication is currently being performed is expanded to this high frequency band, and the process ends.

  In step S1804, it is determined whether the amount of interference in the low frequency band is equal to or less than a threshold value. If the amount of interference in the low frequency band is less than or equal to the threshold value, the process proceeds to step S1807. On the other hand, if the amount of interference is larger than the threshold value, the process is terminated because the frequency band cannot be expanded.

  In step S1807, it is determined that communication between another wireless communication terminal and another system is performed in the high frequency band, and these communication is not performed in the low frequency band. If it is within the band 801 and the consent of the communication partner is obtained, the communication frequency band in which communication is currently performed is expanded to this low frequency band, and the process is terminated.

Next, communication that needs to be maintained at a relatively low speed for a long time, such as a voice call using circuit switching, and communication that is relatively fast, such as data transfer using packet switching, in a short time. The change of the frequency band for a system that performs communication that has both communication that is terminated or that generates communication in a burst manner will be described with reference to the flowchart examples of FIGS. 19 and 20.
First, the communication bandwidth change determination processing unit 513 or 602 compares the communication bandwidth in which communication is currently performed with the requested communication bandwidth (step S1801). If the bandwidth currently being communicated is equal to or greater than the requested communication bandwidth, the communication bandwidth is not expanded assuming that a sufficient communication bandwidth is secured. In this case, the communication band change determination processing unit 513 or 602 determines whether or not the requested communication bandwidth is smaller than the current communication bandwidth, and if smaller, the process proceeds to step S1902 to decrease the communication bandwidth. If not, the process proceeds to step S1701 (step S1901). In step S1902, since the extra communication bandwidth is occupied, the communication bandwidth used for communication is reduced to the requested communication bandwidth. Steps S1701 and after are the same as those in the flowchart shown in FIG. In step S1801, if the bandwidth currently being communicated is smaller than the requested communication bandwidth, the process proceeds to step S1701. Steps S1701 and after are the same as those in the flowchart shown in FIG.

  Here, the required communication bandwidth will be described in detail. It is conceivable that the communication bandwidth requirement varies depending on various factors. For example, when data is accumulated in a buffer for data to be transmitted, it is necessary to increase the communication bandwidth so that the buffer does not overflow. On the other hand, when the buffer amount of data to be transmitted is small, it is not necessary to request a large communication bandwidth. Also, in communications that require real-time performance, such as voice and videophone calls, it is necessary to secure a certain amount of data during the communication period, so a relatively narrow frequency bandwidth is required and a constant communication speed is required. Secure. On the other hand, when the demand for real-time property is low as in data transfer, it is possible to improve the frequency utilization efficiency by requesting a wide frequency bandwidth and transferring data in a short time.

  The remaining battery level can also be one of the factors that determine the required frequency bandwidth. When the remaining battery capacity is large, requesting a wide frequency band increases power consumption, but enables high-speed data communication. On the other hand, when the remaining amount of thought remains, by requesting a narrow frequency band, it is possible to perform longer communication, although the quality is lowered. It is also conceivable to switch between antennas and radio frequency circuits. In such a case, if these components are compatible with a wide frequency band, a wide frequency band can be requested, but if these components are not compatible with a wide frequency band, a narrow frequency band is required. You must request.

  Further, in a system in which circuit-switched communication and packet-switched communication are mixed, it is possible to request a narrow communication frequency bandwidth in communication that performs circuit switching and request a wide communication frequency band in communication that performs packet switching. . By doing so, communication is performed for a long time using circuit switching, and even if there is not enough free frequency band in the communication band for performing packet switching, if communication for performing packet switching is started, the circuit is switched. Since the exchange communication moves away from the vicinity of the frequency band of the communication for performing packet exchange, a sufficiently free frequency band can be secured.

  Further, the requested frequency band may be changed according to user-specific information, for example, the basic charge level. If a wireless communication terminal for a user with a low basic charge uses an algorithm that requires only a narrow frequency band, and a wireless communication terminal for a user with a high basic charge can request a wider frequency band, A difference in the communication speed can be easily established depending on the price.

Next, a system throughput simulation result to which the present invention is applied will be described with reference to FIG.
In this simulation, it is assumed that each wireless communication terminal performs communication by sharing a communication bandwidth of 80 MHz. Each wireless communication terminal communicates with a probability of the degree of congestion per unit time (horizontal axis in FIG. 21). There are 26 wireless communication terminals in the target area, and when communication is started, voice communication is performed with a probability of 60% and packet data transfer is performed with a probability of 40%. Voice communication always occupies a bandwidth of 2 MHz and performs communication for 50 unit hours. In packet data transfer, 200 packets of data are transferred with a requested bandwidth of 10 MHz. Note that the amount of data that can be transmitted in one unit time with a bandwidth of 1 MHz is one packet. The throughput represented by the vertical axis in FIG. 21 is obtained by converting the amount of data that can be transmitted in 10,000 unit times into the number of packets.

  From the graph of FIG. 21, when the degree of congestion of the communication band is low, the system throughput is almost unchanged. This is considered because there is almost no signal in the communication band. When the degree of congestion is high, it can be seen that the wireless communication system using the present invention exhibits superior system throughput compared to the wireless communication system using the conventional method. This is because the communication band is changed so that the wireless communication terminal performing voice communication in the congested communication band can take a larger frequency band than the wireless communication terminal performing packet communication. Is due to.

  As described above, in the system using the present invention, when both the communication using the narrow bandwidth and the communication using the wide bandwidth are shared in the same frequency band, the communication using the narrow bandwidth is combed. By using a band in a similar manner, it is possible to prevent a communication using a wide bandwidth from being disabled even though an unused frequency band exists, and to provide a radio communication system with improved frequency utilization efficiency it can.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows an example of the radio | wireless communications system in which a hot spot system and an ad hoc system are mixed. The figure which shows an example of the radio | wireless communications system in which a some hot spot system is mixed. The figure which shows an example of the radio | wireless communications system in which a wide area communication system and a hot spot system are mixed. The figure which shows an example of the radio | wireless communications system by an ad hoc system. The block diagram of the radio | wireless communication terminal which concerns on embodiment of this embodiment. The block diagram of the radio | wireless communication terminal different from FIG. 5 based on embodiment of this embodiment. FIG. 4 is a sequence diagram showing signal exchange between a base station and a plurality of wireless communication terminals and another base station and another wireless communication terminal in the wireless communication system of FIG. 3. The figure which shows the mode of communication in the communication frequency band which the radio | wireless communication terminal of this embodiment uses. The figure which showed the frequency band which measures the amount of interference in FIG. The figure which shows a mode that new communication is performed in the frequency band which measured the interference amount in FIG. The figure which shows a mode that the frequency band which performed new communication in FIG. 10 is expanded. The figure which showed a mode that the communication frequency band of the both sides of the frequency band which performed new communication in FIG. 10 is moved. The figure which shows a mode that the frequency band which performed new communication in FIG. 10 is extended to the communication bandwidth requested | required. The flowchart which shows an example of the operation | movement which searches the vacant frequency band for starting communication. The flowchart which shows another example of the operation | movement which searches the vacant frequency band for starting communication. The flowchart which shows another example of the operation | movement which searches the vacant frequency band for starting communication. The flowchart which shows the operation | movement for moving a communication frequency band. The flowchart which shows the operation | movement for extending a communication frequency band. 19 is a flowchart showing operations of both the movement shown in FIG. 17 and the expansion shown in FIG. 20 is a flowchart showing the continuation of the operation of FIG. The figure which shows the simulation result to which this embodiment is applied.

Explanation of symbols

101, 201, 203, 301, 306 ... base station, 102, 103, 104, 202, 204, 302, 303, 304, 305, 307, 401, 402, 403, 404 ... wireless communication terminals, 312, 313, 314 315, 317 ... communication frequency band, 501, 509, 515, 518 ... radio frequency processing circuit, 502, 510, 605 ... analog / digital conversion processing unit, 503, 505, 507, 511 ... band pass filter, 504, 512 ... Reception processing unit, 506, 508 ... Signal power measurement unit, 513 ... Communication band change determination processing unit, 514 ... Multi-processing unit, 516, 519, 606 ... Digital / analog conversion processing unit, 517,520 ... Transmission processing unit, 601 ... Reception processing unit, 602... Communication band change determination processing unit, 603... Communication method determination processing unit, 604. Processing unit, 801 ... communication frequency band

Claims (12)

The first wireless communication terminal that communicates with the first wireless communication device using a part of the first frequency band within a certain frequency band is different from the first frequency band, or And a second wireless communication terminal that communicates with a second wireless communication device that is different from the first wireless communication device using a part of the second frequency band within the frequency band. In a wireless communication system,
The first wireless communication terminal is
Adjacent band measuring means for measuring an interference amount for a high frequency band and a low frequency band adjacent to the first frequency band;
In accordance with each of the interference amounts, movement determining means for determining to move the first frequency band to an adjacent high frequency band or low frequency band whose interference amount is equal to or less than a first threshold value ;
Movement information notification means for notifying the first wireless communication device of movement information indicating to which frequency band the first frequency band is moved to which frequency band is determined by the movement determination means;
A movement notification acquisition means for acquiring from the first wireless communication apparatus a notification that the first wireless communication apparatus has recognized the movement information;
Moving means for moving the first frequency band to the frequency band indicated in the movement information,
The second wireless communication terminal is
Adjacent band measuring means for measuring an interference amount for a high frequency band and a low frequency band adjacent to the second frequency band;
Expansion determining means for determining to extend the bandwidth of the second frequency band to at least one of the adjacent high frequency band and low frequency band whose interference amount is equal to or less than the second threshold value according to each interference amount. When,
Extended information notification means for notifying the second wireless communication apparatus of extension information indicating which frequency band determined by the extension determination means is to extend the second frequency band ;
Extended notification acquisition means for acquiring from the second wireless communication device a notification that the second wireless communication device has recognized the extended information;
Extending means for extending the second frequency band to the frequency band indicated in the extension information ,
The extension determining means applies the extended frequency band extended by the extending means instead of the second frequency band and determines to repeatedly extend the bandwidth, and the extending means extends the frequency band. A wireless communication system. The first wireless communication terminal and the second wireless communication terminal are:
A determination means for determining which of the requested frequency bandwidth requested and the communication frequency bandwidth communicating is larger;
The movement determining means determines to move the first frequency band when the determining means determines that the required frequency band is not larger than the communication frequency band,
The extension determining means determines to extend the bandwidth of the second frequency band when the determining means determines that the required frequency band is larger than the communication frequency band. The wireless communication system according to claim 1. The first radio communication device or the second radio using a part of a third frequency band within the certain frequency band, which is different from the first frequency band and the second frequency band. A third wireless communication terminal that communicates with a third wireless communication device that is one of the communication devices;
The third wireless communication terminal is
Adjacent band measuring means for measuring the amount of interference for each of a high frequency band and a low frequency band adjacent to the third frequency band;
A movement determining means for determining to move the third frequency band to an adjacent high frequency band or low frequency band according to the amount of interference;
Movement information notifying means for notifying the third wireless communication device of movement information related to movement determined by the movement determining means;
Movement notification acquisition means for acquiring notification from the third wireless communication apparatus that the third wireless communication apparatus has recognized the movement information;
Moving means for moving the third frequency band based on the movement information;
Expansion determining means for determining to expand the bandwidth of the third frequency band to at least one of the adjacent high frequency band and low frequency band according to the amount of interference;
Extended information notification means for notifying the third wireless communication apparatus of extension information related to the extension determined by the extension determination means;
Extended notification acquisition means for acquiring from the third wireless communication device a notification that the third wireless communication device has recognized the extended information;
Expansion means for extending the third frequency band based on the extension information;
Band determining means for determining whether to move or expand a frequency band used for communication according to the required frequency band, and
The movement determining unit determines that the band determining unit determines to move the frequency band, and the determination unit determines that the requested frequency band is not greater than the communication frequency band. Decide to move the frequency band,
The extension determining unit determines that the band determining unit extends the frequency band, and when the determining unit determines that the required frequency band is larger than the communication frequency band, the third frequency The wireless communication system according to claim 1, wherein it is determined to expand a bandwidth of the band. The second wireless communication terminal is
When the determination means determines that the required frequency bandwidth is smaller than the communication frequency bandwidth, the determination means further comprises a reduction means for reducing the communication frequency bandwidth in accordance with the required frequency band. The wireless communication system according to claim 2 or claim 3. The first wireless communication terminal and the second wireless communication terminal are:
An interference amount measuring means for measuring an interference amount in a certain frequency band within the certain frequency band when communication is started;
If the measured interference amount is less than the interference amount threshold value, further comprising setting means for setting the certain frequency band in which the interference amount is measured as a communication frequency band,
The interference amount measuring means measures an interference amount of another frequency band within the certain frequency band when the measured interference amount is equal to or greater than an interference amount threshold value. The wireless communication system according to any one of the above.   6. The radio communication system according to claim 5, wherein the interference amount measuring means sets a bandwidth of a frequency band for measuring the interference amount to be equal to or smaller than a required frequency bandwidth. The first wireless communication terminal and the second wireless communication terminal are:
When the requested frequency bandwidth requested is equal to or less than the bandwidth threshold, the frequency band in which the interference amount measuring unit measures the interference amount is adjacent in order from the lowest band or the highest band in the frequency band. First band setting means for setting a frequency band;
When the requested frequency bandwidth requested is larger than the bandwidth threshold, the frequency band in which the interference amount measuring unit measures the interference amount is sequentially set from the frequency band opposite to the first band setting unit. 7. The wireless communication system according to claim 5, further comprising: a second band setting unit configured to set an adjacent frequency band.   8. The interference amount measuring means further comprises selection means for selecting a frequency band for measuring the interference amount from the certain frequency band based on a random number. The wireless communication system according to any one of the above.   The wireless communication system according to any one of claims 5 to 8, wherein the adjacent band measuring unit and the interference amount measuring unit measure an interference amount based on received signal power.   The movement determining means determines to move the first frequency band by the adjacent low frequency band whose interference amount has been measured, and the moving means is configured to move the first frequency by the low frequency band. The wireless communication system according to any one of claims 1 to 9, wherein the bandwidth of the band is moved.   The movement determining means determines to move the first frequency band by an adjacent high frequency band whose interference amount has been measured, and the moving means is configured to move the first frequency band by the high frequency band. The wireless communication system according to any one of claims 1 to 9, wherein the bandwidth is moved.   The extension determining means determines to extend the bandwidth of the second frequency band by a bandwidth whose amount of interference measured by the adjacent band measuring means is equal to or less than a third threshold, and the extension means The wireless communication system according to any one of claims 1 to 11, wherein a bandwidth of the second frequency band is expanded by a width.

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