JP6729386B2 - Communication terminal and channel selection method for communication terminal - Google Patents

Description

The present invention relates to a communication terminal and a channel selection method for the communication terminal.

In order to increase the frequency utilization efficiency, research on cognitive radio that is used temporarily by recognizing and recognizing frequencies that are not used geographically or temporally by radio license holders, so-called white spaces, is under way. .. Cognitive radio requires a technology for dynamically allocating frequencies. For example, it has been proposed to use information on the frequency usage status of existing wireless communication systems (primary users) in the vicinity. Further, a method using a database having a function of calculating an available frequency for each position/time has also been proposed. A frequency selection method has also been proposed in which a frequency is dynamically assigned to a wireless communication terminal (secondary user) by using a spectrum sensing function possessed by the wireless communication terminal.

As a means for grasping the surrounding frequency utilization situation, for example, a method is known in which a database manages frequencies vacant temporally and spatially in a TV frequency band. One of such methods is a method using so-called Geo-Location Database (GDB). Further, spectrum sensing using a fixed period (Quiet Period) in which the terminal does nothing can be cited as a realization means. These methods acquire a frequency that the secondary user can use for each position at the “current time” and a frequency with good communication quality. The communication quality here means that maximum communication performance can be achieved, for example. Various techniques as described above have been proposed.

For example, Patent Document 1 discloses a method of detecting a received radio wave intensity for each frequency for which a channel is set and selecting a channel to be used. In this technique, the received radio wave intensity is regarded as an interfering wave level, and a higher priority is given to a detected channel with a low received radio wave intensity. By selecting the channel to be used based on this priority, it is possible to select the channel with less interference.

Patent Document 2 discloses a method of selecting a channel that can be used the longest as a secondary user by using information in a database when an in-vehicle terminal moves. The database holds, for each available frequency, information (map) on the interference region where the channel cannot be used. Then, when the vehicle-mounted terminal transmits the current position and the moving direction, the available distance is shown for each channel from the database, and the channel having the longest distance can be selected.

Further, in Patent Document 3, a method of selecting a channel with a better communication environment by referring to the communication environment information for each area and its own current position, predicting a change in the communication environment when the user moves Is disclosed.

JP, 2009-77224, A International Publication No. 2013/069688 JP2012-209744A

However, each of the above prior arts has problems.

Patent Document 1 has a problem that communication performance deteriorates when the radio wave environment changes. The interference wave level (received radio wave intensity) in this technology is only at the “current time”, and the frequency at which the maximum communication performance is exhibited at the “current time” is selected. Therefore, when the interference wave level of the channel being used rises, it becomes necessary to reselect the frequency and switch the channel. Therefore, when the radio wave environment changes drastically, the channel is frequently switched, and the communication is interrupted each time. Factors that cause changes in the radio wave environment include movement of the user and changes in operating conditions of external communication devices.

Further, in the technique of Patent Document 2, the system is constructed on the assumption that the interference area information held in the database does not change. For this reason, when the interference region itself changes, there is a high possibility that a channel will be selected based on data that does not match the current situation, resulting in incorrect selection.

Since the technique of Patent Document 3 is premised on the use of communication environment information for each fixed area, it has the same problem as the technique of Patent Document 2.

The present invention has been made in view of the above problems, and an object thereof is to provide a communication terminal capable of selecting a channel having high communication performance even when the radio wave environment changes.

In order to solve the above-mentioned problems, a communication terminal of the present invention is a communication terminal used in a wireless communication system that uses radio waves of a plurality of channels having different frequencies, and is a radio wave representing a characteristic of a radio wave environment in a predetermined first period. A radio wave environment characteristic amount acquisition unit that acquires an environment characteristic amount, a required communication performance storage unit that stores a required communication performance required for communication, and a radio wave environment variation in a second period after the present based on the radio wave environment characteristic amount. And a channel selection means for selecting the channel to be used based on the estimated radio environment variation and the required communication performance.

An advantage of the present invention is that it is possible to provide a communication terminal that can select a channel with high communication performance even when the radio wave environment changes.

It is a block diagram which shows the communication terminal of 1st Embodiment. FIG. 3 is a conceptual diagram showing a first period T1 in the first embodiment. FIG. 5 is a conceptual diagram showing a second period T2 in the first embodiment. 3 is a flowchart showing the operation of the first embodiment. It is a block diagram which shows the communication terminal of 2nd Embodiment. 6 is a graph showing an example of fluctuations in received radio wave intensity according to the second embodiment. 7 is a graph showing an example of estimation of fluctuations in received radio wave intensity according to the second embodiment. It is a graph which shows the example of a transmission capacity fluctuation estimation of 2nd Embodiment. It is a flow chart which shows operation of a 2nd embodiment. It is a conceptual diagram which shows the comparative example of 2nd Embodiment and prior art. It is a block diagram which shows the communication terminal of 3rd Embodiment. It is a top view which shows the specific example of the situation to which 3rd Embodiment is applied. 9 is a graph showing an example of fluctuations in received radio wave intensity according to the third embodiment. 11 is a graph showing an example of estimation of fluctuations in received radio wave intensity according to the third embodiment. 10 is a graph showing another example of fluctuations in received radio wave intensity according to the third embodiment. 11 is a graph showing another example of estimation of fluctuations in received radio wave intensity according to the third embodiment. It is a block diagram which shows the communication terminal of 4th Embodiment. It is a graph explaining the characteristic amount acquisition period adjustment method of 4th Embodiment. It is a flowchart which shows operation|movement of 4th Embodiment. 9 is a graph for explaining a specific example 1. It is a top view showing the situation where example 1 is applied. 9 is a graph showing fluctuations in received radio wave intensity for explaining the second specific example. 7 is a graph showing an example of estimation of fluctuations in received radio wave intensity for explaining the second specific example. It is a block diagram which shows the communication terminal of 5th Embodiment. It is a top view which shows the specific example of the situation which applies 5th Embodiment. It is a graph which shows a received electric wave strength variation for explaining a 5th embodiment. 16 is a graph showing an example of received electric wave strength variation estimation for explaining the fifth embodiment. It is a graph which shows the transmission capacity fluctuation estimation example of 5th Embodiment. It is a flowchart which shows operation|movement of 5th Embodiment.

Hereinafter, the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a first embodiment of the present invention. The communication terminal 100 of this embodiment is used for a wireless communication system that uses radio waves of a plurality of channels having different frequencies.

The communication terminal 100 has a radio wave environment characteristic amount acquisition means 110, a radio wave environment variation estimation means 120, a required communication performance storage means 130, and a channel selection means 140. The radio wave environment characteristic amount acquisition unit 110 acquires a radio wave environment characteristic amount representing the characteristic of the radio wave environment in the predetermined first period. Specifically, the physical quantity representing the characteristics of the radio wave environment is measured or acquired as information from the outside. The radio wave environment variation estimating means 120 estimates the radio wave environment variation in the second period after the present based on the acquired radio wave environment characteristic amount. The required communication performance storage unit 130 stores the required communication performance determined by the communication application. The channel selecting means 140 selects a channel to be used based on the radio wave environment fluctuation estimated by the radio wave environment fluctuation estimating means 120 and the required communication performance stored in the required communication performance storing means 130. Specifically, the priority order based on the high communication performance is determined for a plurality of usable channels. Then, based on this priority, a channel selection circuit or the like (not shown) is controlled to select a channel to be used for communication.

According to the present embodiment described above, it is possible to select a channel having high communication performance even in an environment where the radio wave environment fluctuates.

Here, the first period for acquiring the characteristic amount of the radio wave environment and the second period for estimating the fluctuation of the radio wave environment will be described. FIG. 2 is a conceptual diagram showing the first period T1. The first period T1 is a period from a certain time t1 to t2 before the present time. The first period T1 is a time required to grasp the characteristics of the surrounding radio wave environment, and its length may be determined according to the changing speed of the surrounding radio wave environment. Alternatively, it may be fixedly set such as 10 seconds, 1 minute, 10 minutes, 1 hour.

FIG. 3 is a conceptual diagram showing the second period T2. The second period T2 is a period from a certain time t3 to t4 after the present. The second period T2 can be determined, for example, according to the communication application. Specifically, for example, it can be set as a minimum time required by the application and communication should not be interrupted. Alternatively, it can be fixedly set to 10 seconds, 1 minute, 10 minutes, 1 hour, or the like.

Next, the operation of the communication terminal will be described. FIG. 4 is a flowchart showing the operation of the communication terminal. The communication terminal first stores the required communication performance determined by the communication application (S1). Next, the characteristic amount of the radio wave environment in the first period T1 is acquired (S2). Next, based on the acquired characteristic amount of the radio wave environment, the change in the radio wave environment in the second period T2 is estimated (S3). Next, a channel is selected based on the estimated radio wave environment variation and the required communication performance (S4). As described above, a channel with high communication performance can be selected. The order of S1 and steps from S2 to S3 may be reversed.

As described above, according to the present embodiment, it is possible to select a channel having high communication performance in the period T2 after the present in the environment where the radio wave environment changes.

(Second embodiment)
In the present embodiment, the configuration and operation of the communication terminal that uses the received radio wave intensity as one of the radio wave environment characteristic amounts will be described.

FIG. 5 is a block diagram showing the communication terminal 200 of this embodiment. The communication terminal 200 includes a radio wave environment characteristic amount acquisition unit 210, a radio wave environment fluctuation estimation unit 220, a required communication performance storage unit 230, and a channel selection unit 240.

The radio wave environment characteristic amount acquisition unit 210 acquires the radio wave environment characteristic amount representing the characteristic of the radio wave environment in the predetermined first period. In the present embodiment, an example in which the received radio wave intensity is acquired as one of the radio wave environment characteristic amounts is shown. Therefore, the radio wave environment characteristic amount acquisition unit 210 has a received electric wave intensity variation characteristic amount acquisition unit 211. The received radio wave intensity fluctuation characteristic amount acquisition unit 211 acquires the characteristic amount of the received radio wave intensity fluctuation in the predetermined first period T1. The received radio wave intensity can be obtained using, for example, spectrum sensing, but may be obtained from the outside by sharing information with other communication terminals, inquiring a database, or the like.

The radio wave environment variation estimation unit 220 estimates the radio wave environment variation in the second period after the present based on the acquired radio wave environment characteristic amount. Here, since the received radio wave intensity is used as the characteristic amount, the radio wave environment variation estimation unit 220 has a received radio wave intensity variation estimation unit 221 and a transmission capacity variation estimation unit 222. The received radio wave intensity variation estimation unit 221 estimates the received radio wave intensity variation in the second period T2 based on the received radio wave intensity variation feature amount acquired by the received radio wave intensity variation feature amount acquisition unit 211. The transmission capacity fluctuation estimation section 222 estimates the transmission capacity fluctuation at T2 based on the received radio field strength fluctuation at T2 estimated by the received radio field strength fluctuation estimation section 221.

The required communication performance storage unit 230 stores the required communication performance determined by the communication application. The required communication performance referred to here is the transmission rate required by the application, the transmission capacity required by the user, and the communication maintenance time. For example, when a large size data such as a moving image is to be transmitted, the required communication performance is high, and conversely, when a small size data such as a character is to be transmitted, the required communication performance can be low.

The channel selection unit 240 selects a channel to be used based on the estimated variation in the radio wave environment and the required communication performance. Therefore, it has a channel priority setting unit 241. The channel priority setting unit 241 sets the channel priority based on the transmission capacity fluctuation at T2 estimated by the transmission capacity fluctuation estimation unit 222 and the required communication performance stored in the required communication performance storage unit 230. The communication performance here is an index that means a matching rate or satisfaction with respect to the required performance. Generally, the longer the communication duration, the higher the performance. It is also considered that the performance is higher as the transmission capacity is larger. The channel priority order setting unit 241 sets the priority order of channels based on the above-mentioned high communication performance. The channel selection unit 240 controls a channel selection circuit or the like (not shown) based on the set priority order to select a channel used for communication.

Next, the procedure for setting the priority order will be described in detail using a specific example.

First, in the communication terminal, the received electric wave intensity fluctuation characteristic amount acquisition unit 211 acquires the received electric wave intensity fluctuation characteristic amount in the first period T1. FIG. 6 is a graph showing an example of the received fluctuations in the received radio wave intensity. Here, the radio wave whose intensity is acquired is a radio wave existing in the environment, and becomes a disturbing wave for itself. That is, when the received radio wave intensity is higher than a certain level, it means that the frequency is already used or the noise is large. Therefore, that frequency cannot be used as a channel. Therefore, it is assumed that the threshold value Sth for the received radio wave intensity is defined and the frequency at which the received radio wave intensity is less than Sth is selected. From the example of FIG. 6, the following characteristics are acquired regarding the received radio wave intensity in the period T1 of each channel.

ch1 changes periodically. It vibrates for two cycles during T1, and there is a period where it exceeds Sth in the mountain portion. ch2 fluctuates periodically. It vibrates for 3 cycles during T1, and there is a period where it exceeds Sth in the mountain portion. Its amplitude is smaller than ch1 and shorter than ch1 but there is a period exceeding Sth. ch3 hardly changes during T1 and is always smaller than Sth during T1.

Next, the received signal strength variation estimation unit 221 estimates the received signal strength variation in the second period T2.

FIG. 7 is a graph showing an example of the estimation result. Since the received radio wave intensity variation at T1 is a periodic variation within the range, it is estimated that a similar periodic variation is repeated at T2. Therefore, ch1 and ch2 have the same amplitude and cycle of T1 and periodic fluctuations, and each has a period exceeding Sth. ch3 hardly changes and is constantly smaller than Sth during T2.

Next, the transmission capacity variation estimation unit 222 estimates the transmission capacity variation at T2. FIG. 8 is a graph showing the estimation result of the transmission capacity fluctuation. The vertical axis represents the transmission capacity ratio (arbitrary unit). As described above, the acquired received radio wave intensity is the interference wave level, and it can be considered that the channel is vacant as the received radio wave intensity is smaller. Therefore, it can be considered that the transmission capacity ratio has an inverse relationship with the received radio field intensity. That is, the smaller the received radio wave strength, the larger the transmission capacity, and the larger the received radio wave strength, the smaller the transmission capacity. When the received radio wave intensity exceeds the threshold value Sth, it is considered that the transmission capacity is 0, that is, communication becomes impossible.

From the above viewpoint, referring to FIG. 8, it can be seen that there is a period in which ch1 has a large transmission capacity, but a period in which the transmission capacity becomes 0 periodically occurs. It can be seen that ch2 also has a period in which the transmission capacity is large, and periods in which the transmission capacity becomes 0 periodically occur. However, the period in which the transmission capacity becomes 0 is shorter than that in ch1. ch3 maintains a substantially constant transmission capacity within the period of T2.

Next, the channel priority setting unit 241 sets the priority for selecting a channel. The priority is set according to the high communication performance in the second period. As described above, the communication performance in the present embodiment is an index that means a match rate or satisfaction with respect to the required communication performance. Therefore, the result of priority setting varies depending on the required communication performance.

Therefore, a specific comparison method and an example of comparison results will be described separately for some cases in which required communication performances are different.

1) When the required performance prioritizes communication maintenance time For example, a case where communication interruption within a predetermined period is not allowed is included. In the example of FIG. 8, ch1 and ch2 have a period in which the transmission capacity is zero. On the other hand, in ch3, communication is maintained for the entire T2 period. Therefore, only ch3 is the highest priority channel, and ch1 and ch2 cannot be selected.
2) When the required performance allows communication interruption for a predetermined period Since the interruption period is ch2<ch3 and ch3 has no interruption period, the priority order is ch3, ch2, ch1.
3) When it is desirable that the transmission capacity is large regardless of the interruption period When the integrated value or the average value of the communication capacities in the period T2 is compared, the order is ch3, ch2, and ch1, and the priority order in this case is also the same. ..

As illustrated above, it is possible to select a channel with high communication performance based on the required communication performance and the estimated transmission capacity fluctuation.

Here, the outline of the above procedure will be described collectively. FIG. 9 is a flowchart showing the above procedure. First, the received radio wave intensity variation characteristic amount acquisition section 211 obtains the received radio wave intensity variation characteristic amount in the first period T1 (S101). Next, the received signal strength variation estimation unit 221 estimates the received signal strength variation in the second period T2 (S102). Next, the transmission capacity variation estimation unit 222 estimates the transmission capacity variation at T2 (S103). Next, the channel priority order setting unit 241 sets the channel priority order based on the estimated transmission capacity fluctuation and the required communication performance stored in the required communication performance storage unit 230 (S104). Then, the channel selection unit 240 selects a channel based on the channel priority order (S105).

As described above, according to the present embodiment, the communication terminal can acquire the received radio wave intensity variation as the characteristic amount of the radio wave environment and estimate the communication performance for each channel that is exhibited after the present. Then, the communication terminal can set priorities to the channels in descending order of communication performance and select a channel with high communication performance.

Although the present embodiment has been described using three channels, the number of channels is not limited to this. The same applies to other numbers of channels.

(Comparative example)
As described above, the main purpose of this embodiment is to select a channel that exhibits high communication performance in the second period T2. In order to clarify the effect, the difference between the present embodiment and the technique of selecting the channel with the smallest received radio wave intensity at the present time as in Patent Document 1 will be described. A technique similar to Patent Document 1 will be referred to as Prior Art 1.

FIG. 10 is a conceptual diagram showing the channel selection according to the present embodiment and the channel selection according to the prior art 1 in the environment where the transmission capacity changes as shown in FIG. The estimated variation of the transmission capacity ratio is also shown in the upper part of the figure.

In the present embodiment, it is estimated that the communication performance within the period is stable, channel 3 is selected, and channel switching is not performed within the period as shown in the middle part of FIG. On the other hand, in Prior Art 1, since the channel having the maximum transmission capacity is selected at each time point, channel switching frequently occurs. When switching channels, a communication suspension period inevitably occurs, so if switching occurs frequently, total communication performance will drop. As a result, this embodiment can obtain a larger total transmission capacity within the period.

As described above, according to this embodiment, it is possible to select a channel having high communication performance even when the radio wave environment changes.

(Third Embodiment)
In the second embodiment, the example in which the received radio wave intensity fluctuation is used as the characteristic quantity of the radio wave environment has been shown, but other characteristic quantities can be acquired and used for estimating the radio wave environment fluctuation at T2. In the present embodiment, an example will be described in which the characteristic amount of another radio wave source is acquired and used in the first period T1.

FIG. 11 is a block diagram showing the communication terminal 300 of this embodiment. Similar to the second embodiment, the communication terminal 300 includes a radio wave environment characteristic amount acquisition unit 310, a radio wave environment variation estimation unit 320, a required communication performance storage unit 330, and a channel selection unit 340. .. The radio wave environment characteristic amount acquisition unit 310 has a characteristic amount acquisition unit 312 of another radio wave source. The other radio wave source is, for example, another terminal, a broadcasting station, a machine that generates radio wave noise, or the like. The characteristic amount acquisition unit 312 of the other radio wave sources acquires the characteristic amounts of these radio wave sources. The characteristic amount of another radio wave source can be acquired by, for example, sharing information with another communication terminal in the vicinity or inquiring a database. However, the method is not limited to these examples, and other methods may be used for acquisition.

FIG. 12 is a conceptual diagram showing an example of acquiring the position information and the used channel of another radio wave source as the characteristic amount of another radio wave source. There are three radio wave sources near the communication terminal 300. The radio wave source A uses ch1, the radio wave source B uses ch2, and the radio wave source C uses ch3. Here, the communication terminal 300 itself is represented by the symbol X.

The above-mentioned position information can be acquired by, for example, positioning by GPS (Global Positioning System) or inquiry to a database. However, these methods may not be available depending on the radio wave environment. In that case, for example, the approximate position or relative position or the moving speed may be estimated by using the fluctuations in the received radio wave intensity of the same radio wave source or the received radio wave intensity of a plurality of radio wave sources (triangulation or the like). As described above, the present embodiment is not limited to the method of acquiring position information.

Here, it is assumed that the radio wave source B has moved so as to approach X as indicated by an arrow in FIG. 12 during the period T1, that is, between times t1 and t2. The X grasps the current position and moving speed of the radio wave source B from the acquired position information. Then, it becomes possible to estimate the position after the present.

Further, in the above situation, it is assumed that the received radio wave intensity variation shown in FIG. 13 is obtained. Here, the received radio wave intensity is ch2<ch3<ch1, and neither of them has significantly changed within the period T1. Therefore, if the received radio wave intensity variation is estimated only from the received radio wave intensity, ch2 is estimated to be minimum even in the period T2, and ch2 is selected.

On the other hand, when the position information and the used channel are obtained as the radio wave environment characteristic amount, it is understood that the radio wave source B is close to X. Therefore, it is possible to estimate the received electric wave strength variation in the period T2 in consideration of the information. An example of the result estimated by this method is shown in FIG. In this example, the received radio wave intensity is in the order of ch2<ch3<ch1 in the initial period of T2. However, when the radio wave source B approaches at the moving speed acquired in T1, it can be estimated that the radio wave intensity of ch2 rapidly increases, and the channel with good communication performance is lost early in T2. Then, ch3 is set as the highest priority channel.

As described above, according to the application of the present embodiment, it is possible to more accurately estimate the variation of the radio wave environment and select the channel.

The communication terminal can also acquire the communication schedule of the radio wave source as the characteristic amount of the other radio wave source acquired in the first period T1. A method of using the communication schedule of another radio wave source for radio wave environment estimation will be described using a specific example.

FIG. 15 is a graph showing an example of fluctuations in received radio wave intensity acquired in the first period T1. In this example, the received signal strengths of ch1 and ch2 change in a range smaller than the threshold Sth, and ch3 changes in a range larger than the threshold Sth.

On the other hand, separately from this, it is assumed that the characteristic amount acquisition unit 312 of the other radio wave source acquires information that the radio wave source using ch3 suspends communication in the second period T2. In a common example, this situation is the case where a broadcasting station stops broadcasting. FIG. 16 shows an example of the result of estimating the received electric wave intensity fluctuation in the second period T2 by taking this information into consideration. By stopping the radio source that uses ch3. It is estimated that the received radio wave intensity of ch3 is greatly reduced. Based on this estimation result, the priority of ch3 is set higher than that of ch1 and ch2. This makes it possible to select a channel that is realistic.

It should be noted that, although the communication stop of another radio wave source has been described above, a communication start schedule can be acquired conversely to lower the priority of the channel. Although the description has been made using three channels, the present embodiment can be applied without being limited to this number of channels.

As described above, according to the present embodiment, it is possible to improve the accuracy of the radio environment fluctuation estimation by reflecting the communication schedules of other radio sources.

(Fourth Embodiment)
FIG. 17 is a block diagram showing the fifth embodiment. The communication terminal 400 of the present embodiment includes a radio wave environment characteristic amount acquisition unit 410, a radio wave environment fluctuation estimation unit 420, a required communication performance storage unit 430, and a channel selection unit 440, as in the second embodiment. Have The radio wave environment characteristic amount acquisition unit 410 includes a characteristic amount acquisition period adjustment unit 413. The characteristic amount acquisition period adjustment unit 413 adjusts the length of the period T1 for acquiring the radio wave environment characteristic amount. Hereinafter, this adjustment will be described.

Here, an example in which the received radio wave intensity is used as the radio wave environment characteristic amount will be described. FIG. 18 is a graph for explaining a method of adjusting T1 when the characteristic acquisition of the received radio wave intensity is the rate-determining factor for the radio environment characteristic amount acquisition. The period radio field intensity acquisition unit starts reception radio field intensity acquisition at time t5. At this time, it is assumed that the original first period T1 is set longer than t6-t5.

When the received radio wave intensity changes as shown in FIG. 18, data for two cycles of periodic fluctuation can be acquired for ch1 by time t6. As a result, it can be understood that ch1 periodically changes and is changing within a certain range. In addition, it is possible to grasp the characteristics such as that there is a portion where the threshold value Sth is exceeded in the peak of the fluctuation. Similarly, the characteristic that ch2 has a periodic fluctuation of three cycles from t1 to t2 and may exceed the threshold value Sth for a short time is grasped. It can be seen that ch3 has a characteristic that it is always less than the threshold value Sth and hardly changes.

As described above, if it is possible to grasp the fluctuation tendency of the received radio wave intensity in the period from t5 to t6 in FIG. 18, the acquisition of the feature amount can be terminated in a period shorter than the originally set T1. Based on this result, the feature amount acquisition period adjustment unit 413 adjusts T1 so that T1=t6−t5, for example. That is, in this example, T1 is adjusted so as to be a period in which data for two cycles can be acquired when there is a periodic fluctuation. The criterion for determining whether or not the above-described characteristic amount has been acquired is merely an example, and can be arbitrarily set by the user. Further, here, the received electric field intensity is described as an example, but other characteristic amount grasps may be used as a reference. Further, T1 may be set by aborting the acquisition of the feature quantity at an appropriate predetermined time.

The above operation will be described with reference to the flowchart of FIG. First, the radio wave environment characteristic amount acquisition unit 410 starts the radio wave environment characteristic amount acquisition (S201). Next, the radio wave environment characteristic amount acquisition unit 410 determines whether or not the characteristics of the radio wave environment have been grasped (S202). When it is determined that the feature can be grasped (S202_Yes), the feature amount acquisition period adjustment unit 413 sets T1 based on the time until grasping. On the other hand, when the feature cannot be grasped in the predetermined period (S202_No), the feature amount acquisition period adjustment unit 413 sets T1 based on the predetermined period (S204).

As described above, according to the present embodiment, the radio wave environment characteristic amount acquisition period can be shortened when the radio wave environment characteristic amount can be acquired early. This enables high-speed channel selection.

(Specific example 1)
By using the technique of the third embodiment, it is possible to estimate the relationship between the radio wave environment characteristic amount and the factors that bring about the characteristic and obtain a suggestion as to what characteristic amount should be acquired. Hereinafter, a specific example will be described.

Now, it is assumed that the received electric wave intensity fluctuation graph of FIG. 20 is obtained in the first period T1. From this graph, ch1 periodically fluctuates in the cycle (t10-t8), and there is a period exceeding Sth in the mountain portion. ch2 periodically fluctuates in a cycle (t9-t7). In the mountain part, there is a period exceeding Sth. ch3 hardly changes during T1 and is always smaller than Sth during T1. Such features can be extracted.

Here, it is assumed that the transmission power of each radio wave source is the same, and that the fluctuation of the received radio wave intensity is caused mainly by the position change. Then, it is possible to estimate the position variation of each radio wave source as shown in FIG. 21, for example. FIG. 21 is a plan view showing the positional relationship between the communication terminal X and another radio wave source. There are a radio wave source A that uses ch1, a radio wave source B that uses ch2, and a radio wave source C that uses ch3.

The radio wave source A approaches or departs from X at a cycle (t10-t8). The radio wave source B approaches or departs from X at a cycle (t9-t7). The radio wave source C is stationary or is moving so that the distance from X is almost unchanged. The situation is estimated.

Therefore, it is found to be useful to acquire the position information of each radio wave source. If the position information is acquired and there is a correlation with the received radio wave intensity fluctuation, it can be judged that the estimation was valid. Further, if there is no correlation with the fluctuation of the received radio wave intensity, it can be judged that it is useful to obtain information on the transmission power.

As described above, according to the present embodiment, it is possible to estimate the radio wave environment variation and its factors, and narrow down the characteristic amount useful for estimating the radio wave intensity variation in the second period T2.

(Specific example 2)
As a specific example of the transition of the received radio wave intensity, which is one of the radio wave environment characteristic amounts, consider a case where there is a channel in which the received radio wave intensity rises temporarily and returns immediately within the first period T1. The priority setting method at this time will be described below.

First, suppose that the transition of the received radio field intensity as shown in FIG. 22 is acquired during the period T1. ch1 and ch2 each have periodic fluctuations during the period T1. Although ch3 is stable under the threshold value Sth, it rises only once and returns to the original level. Such a phenomenon may occur when the radio wave source of ch3 passes the communication terminal X. If they pass each other, it is a one-time phenomenon, but it is assumed that they occur at the same frequency as the worst case. By doing so, it is possible to estimate the fluctuation of the received radio wave intensity on the safety side.

FIG. 23 shows the estimation result. The channel priority is determined by matching with the required communication performance. For example, as the required communication performance, it is possible to give priority to a period in which the total communication interruption time at T2 is short. In the case of the example in FIG. 23, the communication interruption time is a period in which the received radio wave intensity exceeds the threshold value Sth. Therefore, since the total communication interruption time is the shortest for ch3, the order of priority is ch3, ch2, ch1.

As described above, according to the present embodiment, even when there is a temporary change in the radio wave environment, it is possible to determine the channel priorities in reality in consideration of the worst case.

(Fifth Embodiment)
In the first to fourth embodiments, channel priorities are determined solely for the convenience of the communication terminal itself. On the other hand, in the present embodiment, the channel priority order is determined in consideration of the channel selected by another communication terminal. By doing so, it is possible to improve the throughput of the entire communication system including a plurality of communication terminals.

FIG. 24 is a block diagram showing the communication terminal 500 of this embodiment. The communication terminal 500 includes a radio wave environment characteristic amount acquisition unit 510, a radio wave environment fluctuation estimation unit 520, a required communication performance storage unit 530, and a channel selection unit 540, as in the third embodiment. ..

The radio wave environment characteristic amount acquisition unit 510 includes a received electric wave intensity fluctuation characteristic amount acquisition unit 511, a characteristic amount acquisition unit 512 of another radio wave source, and a selected channel information sharing unit 513. The selected channel information sharing unit 513 holds information on the channel in use and a selectable channel between the communication terminal 500 itself and another terminal. The information can be acquired, for example, by exchanging messages with other communication terminals or accessing a database. Note that, similarly to the third embodiment, the received radio wave intensity variation characteristic amount acquisition unit 511 acquires the received radio wave intensity in a predetermined first period T1, and the feature amount acquisition units 512 of other radio wave sources are different from each other. Acquire the feature quantity of the radio wave source of.

The radio wave environment fluctuation estimation unit 520 includes a received radio wave intensity fluctuation estimation unit 521, a transmission capacity fluctuation estimation unit 522, and a selected channel estimation unit 523 of another communication terminal. The selected channel estimation unit 523 of the other communication terminal estimates the channel selected by the other communication terminal. Note that, similarly to the third embodiment, the received radio wave strength fluctuation estimation unit 521 estimates the received radio wave strength fluctuation in the second period T2, and the transmission capacity fluctuation estimation unit 522 estimates the transmission capacity fluctuation in the second period. To do.

In the present embodiment, the radio wave environment fluctuation estimating unit 520 estimates the radio wave environment fluctuation by reflecting the obtained selection channel estimation result of the other communication terminal. Therefore, if it is estimated that another communication terminal in the vicinity will use a certain channel, the priority of the channel will be lowered. As a result, interference caused by the communication terminal 500 using the same channel as other communication terminals in the vicinity is avoided. Hereinafter, the details will be described using a specific example.

FIG. 25 is a plan view showing the positional relationship of each communication terminal and the channel in use in the wireless system using a plurality of communication terminals of this embodiment. There is a communication terminal 500(X), a communication terminal A using ch1, a communication terminal B using ch2, and a communication terminal C using ch3. Here, a situation is shown in which a communication terminal D using ch2 approaches a communication terminal B and a communication terminal X from a distance.

At this time, the communication terminals X and A, B, and C share information about the channel in use and the selectable channel. Here, it is assumed that the communication terminal B can select only ch3 in addition to ch2. Further, it is assumed that X has acquired the position information of each communication terminal. In this situation, the fluctuation of the received radio wave intensity that the communication terminal X acquires in the first period T1 is as shown in FIG. 26, for example.

On the other hand, the communication terminal X understands from the position information of each terminal that B, which is using ch2, is approaching B, which is also using ch2. Therefore, X estimates that B will switch channels to avoid interference with D. Here, B has no switchable channel other than ch3. Collecting these pieces of information, the selected channel estimation unit 523 of another communication terminal included in X estimates that B selects ch3. Then, the result is output to the radio wave environment variation estimation unit 520. The radio wave environment variation estimating unit 520 estimates the radio wave environment variation assuming that the communication terminal B selects ch3. FIG. 27 shows an example of estimation of fluctuations in received radio wave intensity and FIG. 28 shows an example of estimation of fluctuations in transmission capacity in this case. In FIG. 28, assuming that the communication terminal B has switched the channel to ch3, the estimated transmission capacity ratio of ch3 is lowered. In response to the result, the channel selection unit 540 prevents the communication terminal X from selecting ch3. On the other hand, it is estimated that the transmission capacity ratio of ch2 in which B stops using the channel increases. Therefore, the priority of ch2 becomes high.

The operation described using the above specific example will be described using the flowchart of FIG. First, the selected channel information sharing unit 513 shares information about a channel in use and a selectable channel between itself and another terminal (S301). Next, the received radio wave intensity variation estimation unit 521 estimates the received radio wave intensity variation based on the feature amount of another radio wave source and the selected channel information stored in the selected channel information sharing unit 513 (S302). Next, the selected channel estimation unit 523 of the other communication terminal estimates the selected channel of the other communication terminal based on the estimation result of the received radio wave intensity fluctuation (S303). Next, the radio wave environment characteristic amount acquisition unit 510 acquires the radio wave environment characteristic amount in the first period T1 of itself (S304). Next, the radio wave environment variation estimation unit 520 estimates the radio wave environment variation in the second period T2 based on the acquired radio wave environment characteristic amount and the estimated selection channel of another communication terminal (S305). Then, the channel selection unit 540 determines the priority order of the channel to be selected based on the estimated radio wave environment fluctuation, and selects the channel based on the priority order (S306). The order of S301 to S303 and S304 may be reversed.

As described above, according to the present embodiment, it is possible to determine the channel priority order so as to avoid interference with the channel selected by another communication terminal.

A program that causes a computer to execute the processes of the above first to fifth embodiments and a recording medium that stores the program are also included in the scope of the present invention. As the recording medium, for example, a magnetic disk, a magnetic tape, an optical disk, a magneto-optical disk, a semiconductor memory, or the like can be used.

The present invention has been described above using the above-described embodiment as an exemplary example. However, the present invention is not limited to the above embodiment. That is, the present invention can apply various aspects that can be understood by those skilled in the art within the scope of the present invention.

This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2014-232284 for which it applied on November 17, 2014, and takes in those the indications of all here.

100, 200, 300, 400, 500 Communication terminal 110 Radio wave environment characteristic amount acquisition means 120 Radio wave environment variation estimation means 130 Required communication performance storage means 140 Channel selection means 210, 310, 410, 510 Radio wave environment characteristic amount acquisition part 211, 311 411, 511 reception radio wave intensity fluctuation characteristic amount acquisition unit 220, 320, 420, 520 radio wave environment fluctuation estimation unit 221, 521 reception radio wave intensity fluctuation estimation unit 222, 522 transmission capacity fluctuation estimation unit 230, 330, 430.530 request communication Performance storage unit 240, 340, 440, 540 Channel selection unit 241 Channel priority setting unit 312, 412, 512 Feature amount acquisition unit of other radio sources 413 Feature amount acquisition period adjustment unit 513 Selected channel information sharing unit 523 Other communication Selected channel estimation unit of terminal

Claims (25)

A communication terminal used for a wireless communication system using radio waves of a plurality of channels having different frequencies,
A radio wave environment characteristic amount acquiring means for acquiring a radio wave environment characteristic amount representing a characteristic of the radio wave environment variation in the first period before the present;
Required communication performance storage means for storing required communication performance required by communication,
A radio wave environment variation estimating means for estimating a radio wave environment variation in a second period after the present based on the radio wave environment characteristic amount;
Have a channel selection means for selecting the channel to be used based estimated with the radio wave environment varies with the request communication performance,
The channel selecting means has a priority order setting means for setting a priority order to the channel based on the radio environment change and the required communication performance,
The communication terminal, wherein the radio wave environment characteristic amount acquisition means adjusts the length of the first period on the basis of having acquired at least one of the periodicity and the fluctuation width of the radio wave environment variation . The communication terminal according to claim 1 , wherein the radio wave environment characteristic amount acquiring means includes a reception radio wave strength variation acquiring means for acquiring a reception radio wave strength variation for each channel in the first period. Claim 1 wherein the radio environment feature value acquiring means, characterized by having a characteristic amount obtaining means other radio sources for acquiring a feature amount in the first period of the other radio sources existing around the own Alternatively, the communication terminal according to claim 2 . According to claim 3, characteristic amount obtaining means of said other radio sources, characterized in that to obtain the feature quantity including at least one of said other radio sources of location information, or in the use frequency or transmit power variation Communication terminal. The radio wave environment fluctuation estimation means, the communication terminal according to any one of claims 1 to 4, characterized in that estimating the transmission capacity in the second period. The communication terminal according to claim 5 , wherein the radio wave environment variation estimating means estimates the transmission capacity in the second period based on the received radio wave intensity variation for each channel acquired in the first period. .. The communication terminal according to any one of claims 1 to 6, characterized in that said required communication performance is determined the duration of communication in the second period as a measure. The communication terminal according to any one of claims 1 to 7, characterized in that said required communication performance is determined the transmission capacity in the second period as a measure. The communication terminal according to any one of claims 1 to 6, characterized in that said required communication performance is determined and the transmission capacity and the allowable communication interruption time in the second period as a measure. The feature amount acquisition means of the other radio wave source obtains information of channels selectable with other communication terminals existing around itself and information of channels used in the first period. Share selected channel information sharing means,
The radio wave environment fluctuation estimating means includes a selected channel estimating means of another communication terminal for estimating a channel selected by another communication terminal in the second period based on the information acquired by the selected channel information sharing means. The communication terminal according to claim 3 or 4 , characterized in that. The communication terminal according to claim 10 , wherein the priority setting means lowers the priority of the channel estimated to be selected by the other communication terminal by the selected channel estimation means of the other communication terminal. A communication system comprising a plurality of communication terminals according to any one of claims 1 to 11 . A channel selection method for a communication terminal used in a wireless communication system using radio waves of different channels having different frequencies,
Acquires the radio wave environment characteristic amount that represents the characteristics of the radio wave environment fluctuation in the first period before the present,
Stores the required communication performance required by communication,
Estimating the variation of the radio wave environment in the second period from the present on the basis of the radio wave environment characteristic amount,
Select the channel to be used based on the estimated variation in the radio environment and the required communication performance ,
A channel selection method for a communication terminal, wherein the length of the first period is adjusted on the basis of the acquisition of at least one of the periodicity or fluctuation range of the radio wave environment fluctuation . 14. The channel selection method for a communication terminal according to claim 13 , wherein priorities are set for the channels based on the variation of the radio wave environment and the required communication performance. The channel selection method for a communication terminal according to claim 13 or 14 , characterized in that the received radio wave intensity variation for each channel in the first period is acquired. The channel selection method for a communication terminal according to claim 15 , wherein the transmission capacity in the second period is estimated based on the received radio wave intensity variation for each channel acquired in the first period. The channel selection method for a communication terminal according to any one of claims 13 to 16, characterized in that the feature amount of another radio wave source existing around itself is acquired during the first period. 18. The channel selection method for a communication terminal according to claim 17, further comprising: acquiring positional information of the other radio wave source, a frequency being used, or a characteristic amount including at least one of fluctuations in transmission power. The channel selection method of the communication terminal according to claim 17 or 18 , wherein the transmission capacity in the second period is estimated based on the characteristic amount of the other radio wave source in the first period. The channel selection method for a communication terminal according to any one of claims 13 to 19, wherein the required communication performance is determined by using a communication duration in the second period as a scale. The channel selection method for a communication terminal according to any one of claims 13 to 20, wherein the required communication performance is defined by using a transmission capacity in the second period as a scale. 20. The channel selection method for a communication terminal according to any one of claims 13 to 19, wherein the required communication performance is determined by using an allowable communication interruption time and a transmission capacity in the second period as a criterion. .. Information of a channel that can be selected by each of the other communication terminals existing around itself and information of a channel used in the first period are shared, and the channel information and the first information are shared. The channel selection method for a communication terminal according to claim 13 , wherein a channel selected by another communication terminal in the second period is estimated based on information on a channel used in the period. 24. The channel selection method for a communication terminal according to claim 23 , wherein the priority of the channel estimated to be selected by the other communication terminal is lowered. For communication terminals used in wireless communication systems that use radio waves of multiple channels with different frequencies,
A step of acquiring a radio wave environment characteristic amount representing the characteristics of the radio wave environment variation in the first period before the present,
Storing the required communication performance required by the communication,
Estimating a change in the radio wave environment in a second period after the present time based on the radio wave environment characteristic amount;
Selecting the channel to be used based on the estimated radio environment fluctuation and the required communication performance,
A channel selection program for executing
A channel selection program in which the length of the first period is adjusted on the basis that at least one of the periodicity and the fluctuation range of the radio wave environment fluctuation is acquired .

Images