JP6537466B2 - Communication apparatus, control method and program - Google Patents

Description

  The present invention relates to a frequency channel selection method used for communication.

  Currently, in LTE (Long Term Evolution), LAA-LTE (Licensed-Assisted Access using LTE) using non-licensed frequency band used in a wireless LAN or the like is being considered. In LTE, a base station apparatus schedules resources for which transmission of a signal by a terminal apparatus in uplink is permitted and resources in which a signal addressed to the terminal apparatus from the base station apparatus in downlink is transmitted. It communicates with the device (see Non-Patent Document 1). At this time, in the license frequency band, communication by a wireless communication system other than LTE is not performed, so the base station apparatus can execute scheduling without regard to communication by another wireless communication system.

  On the other hand, in the non-licensed frequency band, not only LTE but also other wireless communication systems will use that frequency band, so the base station apparatus and the terminal apparatus are from the communication by the other wireless communication system, and It is necessary to communicate in consideration of the influence on communication. For example, the base station apparatus and the terminal apparatus check whether the radio channel of the non-licensed frequency band is used before transmitting the signal, as in the case of the communication apparatus of the wireless LAN, and the radio channel is used. If not, send a signal. Thus, the base station apparatus and the terminal apparatus can communicate fairly with other wireless communication systems.

3GPP TS 36.300 v9.0.0, June 2009

  In the non-licensed frequency band, when communication is performed when the wireless channel is not used, communication can not be performed because the wireless channel is congested (that is, many communication devices are communicating on the wireless channel) Can occur. On the other hand, in general, a plurality of frequency channels exist in the non-licensed frequency band. For this reason, the base station apparatus and the communication apparatus can prevent a situation where communication can not be performed by selecting a frequency channel that is not relatively crowded among the plurality of frequency channels. However, even if the base station apparatus and communication apparatus move to a frequency channel determined to be not crowded, if the frequency channel is actually in a trend of increasing traffic, the degree of congestion increases after movement, and the result is May not be able to communicate. On the other hand, even when the base station apparatus and the communication apparatus determine that a certain frequency channel is congested and moves to another frequency channel, the congestion degree of the frequency channel before movement actually decreases. There may be.

  The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to select a frequency channel according to the tendency of increase and decrease in congestion degree.

In order to achieve the above object, the communication device according to the present invention obtains, for each of the plurality of periods, a value indicating the amount of traffic in a plurality of periods for a plurality of frequency channels, and the time of the value Selecting means for selecting a frequency channel to be used for communication from the plurality of frequency channels according to the change.

  According to the present invention, the communication device can select a frequency channel in accordance with the tendency of increase or decrease in congestion degree.

The figure which shows the structural example of a radio | wireless communications system. FIG. 2 is a diagram showing an example of the hardware configuration of a communication apparatus. FIG. 2 is a block diagram showing an example of the functional configuration of a communication apparatus. The figure for demonstrating the relationship between an electric field strength and signal detection. 5 is a flowchart showing an example of the flow of processing executed by the communication device.

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

(Wireless communication system)
FIG. 1 shows an example of the configuration of a wireless communication system according to this embodiment. The wireless communication system includes, for example, a base station apparatus (eNodeB) of Long Term Evolution (LTE) and a terminal apparatus. The base station apparatus may be a communication apparatus that can communicate according to another wireless standard. For example, the base station apparatus may be a base station apparatus of another wireless communication standard, such as a past or future cellular communication system.

  The base station apparatus according to the present embodiment is a license frequency band prepared for LTE and a non-license (for example, an industrial scientific medical (ISM) band, etc.) used for a wireless LAN etc. with a terminal apparatus. Communication can be performed using both the frequency band. Here, in this radio | wireless communications system, communication by LAA-LTE (Licensed-Assisted Access using LTE) shall be performed. That is, it is assumed that the base station apparatus and the terminal apparatus perform wireless communication in the non-licensed frequency band with the communication method defined by the LTE standard, not the communication method of the wireless LAN. Although an example in which the base station apparatus and the terminal apparatus perform wireless communication in the license frequency band and the non-license frequency band will be described below, the present invention is not limited thereto. That is, the following discussion applies to any system in which the communication device obtains a value indicating the amount of traffic in multiple frequency channels, and selects a frequency channel to be used based on the value. it can. Also, although the following description focuses mainly on the non-licensed frequency band in LAA-LTE, the present invention is not limited to this. That is, in any frequency band, the following discussion can be applied, and furthermore, there is no need to be able to communicate in two frequency bands between communication devices, and when communicating in some frequency band between communication devices, the following The arguments can apply.

  Although one base station apparatus and one terminal apparatus are shown in the example of FIG. 1, the present invention is not limited to this. That is, as in a general cellular communication system, a large number of base station devices may be arranged to provide the terminals with a seamless communicable area, and a large number of terminal devices may be connected to any of the base station devices. .

  In the non-licensed frequency band, for example, as described above, the base station apparatus or the terminal apparatus does not communicate on the frequency channel to be used before transmitting the signal, similarly to the communication apparatus of the wireless LAN. After confirming that it can send a signal. However, as described above, even if the base station apparatus or the terminal determines the frequency channel to be used according to the degree of congestion, the frequency channel is used according to the tendency of increase or decrease of traffic in the frequency channel. May not be appropriate. This is a problem that may occur in a wireless communication system that can select and communicate any of a plurality of frequency channels (for example, in a non-licensed frequency band), and is specific to a wireless communication system according to LAA-LTE. Please note that it is not an issue of

  On the other hand, the communication apparatus according to the present embodiment identifies the tendency regarding the amount of traffic for each of the plurality of frequency channels, and selects the frequency channel to be used according to the result. More specifically, the communication apparatus obtains, for each of the plurality of frequency channels, a value indicating the amount of traffic in the plurality of time periods. Then, the communication apparatus selects and uses a frequency channel to be used from among the plurality of frequency channels described above, in accordance with the time change of the acquired value. Here, when the communication device is, for example, communicating with or connected to another device in any frequency channel, if the frequency channel other than the frequency channel in use is selected as the frequency channel to be used, the frequency channel Switch between Also, the communication device is selected as a frequency channel to be used, for example, before starting communication with another device or when establishing a connection, when starting communication with the other device or establishing a connection. Use different frequency channels. Note that the communication apparatus here is a base station apparatus or terminal apparatus of LTE, and it may be a base station apparatus that determines the frequency channel to be used in particular, but is not limited thereto. That is, if it is a communication device that can communicate using any of a plurality of general frequency channels and can determine the frequency channel to be used, the following discussion is applied. can do.

  The communication apparatus may calculate, for each of the plurality of frequency channels, a weighted addition value obtained by multiplying the amount of traffic for each of the plurality of periods by the value of the weight corresponding to each of the plurality of periods and adding them. In this case, the communication apparatus selects a frequency channel to use based on the magnitude of the weighted addition value. For example, the communication apparatus may select any one of frequency channels for which the weighted addition value is equal to or less than a predetermined value as a frequency channel to be used. Note that, when there are a plurality of frequency channels in which the weighted addition value is less than or equal to the predetermined value, the communication apparatus is based on identification information of the frequency channel currently in use based on the value unique to the communication apparatus, for example. , Etc., can be used to select the frequency channel to use. Also, the communication apparatus may select a frequency channel with the lowest weighted sum value as a frequency channel to be used.

  In addition, the value of the weight used for calculation of this weighted addition value can be settable, for example according to the up-and-down tendency of the traffic calculated | required by statistics in geographically or temporally. For example, if traffic tends to increase at a predetermined interval, increase the value of the weight in the previous period by the time corresponding to the predetermined interval from the calculation target time point of the weighted addition value, and decrease the value of the weight in the other periods. sell. As a result, when the traffic amount is large in a period including a time that is a predetermined interval before the calculation target time of the weighted addition value, there is a high possibility that the traffic amount will increase at the calculation target time. Therefore, the communication apparatus can avoid the use of the frequency channel in which such a weighted addition value becomes large based on the weighted addition value using the weight value as described above. Note that various other weight values may be set, whereby the communication apparatus uses an appropriate frequency channel with a small amount of traffic, for example, when there is a statistical tendency to the amount of traffic. It can be selected as the power frequency channel.

  In addition, the communication apparatus selects a frequency channel to be used based on the (for example, first or second floor) differential value of the amount of traffic for a plurality of frequency channels and the amount of traffic within a predetermined period from the current time It is also good. The communication device may use, for example, an average value of the amount of traffic (for example, the latest one among the acquired ones) within a predetermined period from the current time and a slope of a value indicating the amount of traffic according to the first derivative. The amount of traffic expected at the selected time can be estimated. Then, the communication apparatus may select a frequency channel whose expected traffic amount is less than or equal to a predetermined amount as the frequency channel to be used. Also, the communication device can specify the speed at which the amount of traffic increases or decreases from the first derivative and the second derivative of the amount of traffic. Thus, the communication device may for example not select a frequency channel that tends to have a rapid increase in traffic volume. Also, the communication apparatus may select a frequency channel at a high frequency if the amount of traffic is at most high at this frequency channel.

  The communication apparatus detects the signal transmitted in each of the plurality of periods described above for each of the plurality of frequency channels described above, thereby indicating the number of the detected signals and the amount of traffic described above. It can be obtained as a value. Here, the communication device can specify whether a signal has been transmitted by measuring the electric field strength. The communication device may determine that the signal is transmitted, for example, when the electric field strength exceeds a predetermined value. At this time, the communication apparatus can detect that the transmission of the signal has ended, for example, in response to detecting that the electric field strength has become less than the predetermined value after exceeding the predetermined value. In the communication apparatus, even when the electric field intensity exceeds the predetermined value, the period in which the electric field intensity exceeds the predetermined value does not reach a predetermined period, for example, if it is a signal. It can be determined that the signal is not transmitted. In addition, when the communication apparatus detects that a predetermined amount of fluctuation has occurred in a predetermined short time period while the electric field strength exceeds the predetermined value, another signal is generated before and after the fluctuation. Can be determined to have been sent. That is, even if the electric field strength continues to exceed the predetermined value, the communication apparatus does not generate the electric field strength by one signal when the electric field strength fluctuates significantly. It can be determined that the signal is generated by two (or more) signals. This may be received at the location of the communication device if the signals are transmitted from a plurality of other devices at different distances from the communication device and / or the signals are transmitted with different powers from a plurality of other devices. This is because it is considered that a large fluctuation of the electric field strength occurs. Further, when the communication apparatus detects that the length of time when the electric field strength exceeds the predetermined value exceeds the predetermined time length, it determines that one signal is transmitted until the predetermined time length, and the predetermined After the time length, it may be determined that another signal has been transmitted. This means that, for example, when the time length of the period in which the electric field strength exceeds the predetermined value exceeds the maximum time length of the legal signal, the electric field strength is not due to one signal. Therefore, the communication apparatus can determine that two or more signals are detected when the time length of the period in which the electric field strength exceeds the predetermined value exceeds the predetermined time length.

  Note that the communication apparatus may obtain the use time rate of each of the plurality of frequency channels in each of the plurality of periods described above as a value indicating the amount of traffic described above. In this case, it is not necessary to specify the number of signals as described above, and the communication apparatus may specify, for example, the time rate at which the electric field strength exceeds a predetermined value in a certain frequency channel as the use time rate of that frequency channel. Can.

  Hereinafter, the configuration of a communication apparatus that performs such processing and an embodiment of the flow of processing that the communication apparatus executes will be described in detail.

(Hardware configuration)
FIG. 2 shows an example of the hardware configuration of the communication apparatus. In one example, the communication apparatus has a hardware configuration as illustrated in FIG. 2 and includes, for example, a CPU 201, a ROM 202, a RAM 203, an external storage device 204, and a communication circuit 205. In the communication device, for example, a program for realizing each function of the communication device as described above, which is recorded in any of the ROM 202, the RAM 203, and the external storage device 204, is executed by the CPU 201.

  Then, the communication apparatus controls the communication circuit 205 by, for example, the CPU 201 to communicate with another apparatus. Note that, for example, when the communication device is a base station device, the communication circuit 205 of the communication device communicates with the terminal device via a cellular wireless communication interface such as an LTE wireless interface, and also communicates with other base station devices. It can communicate via a wired or wireless communication interface. Also, for example, when the communication device is a terminal device, the communication circuit 205 of the communication device can communicate with a base station device or another communication device via a cellular wireless communication interface such as an LTE wireless interface. Here, the cellular radio communication interface performs communication not only using cellular communication in the license frequency band but also using the principle of cellular communication in the non-license frequency band. Also, the communication apparatus may have not only a cellular wireless communication interface but also, for example, a wireless LAN communication interface. Although the communication device in the configuration of FIG. 2 is a schematic diagram having one communication circuit 205, the present invention is not limited to this. For example, the communication device may comprise a first communication circuit for communication in the licensed frequency band and a second communication circuit for communication in the non-licensed frequency band.

  Note that the communication apparatus may include dedicated hardware for executing each function, or may execute a part of the hardware and a computer that operates a program to execute the other part. Also, all functions may be performed by a computer and a program.

(Functional configuration of communication device)
FIG. 3 shows an example of the functional configuration of the communication apparatus. The communication apparatus includes, as an example, a wireless communication unit 301, a traffic amount acquisition unit 302, and a use channel selection unit 303. The wireless communication unit 301 performs LTE communication with the other device using the licensed frequency band and the non-licensed frequency band. Although only the wireless communication unit 301 is shown in the present example, the communication apparatus may have, for example, a wired communication unit. The wireless communication unit 301 can switch and communicate, for example, a plurality of frequency channels in the non-licensed frequency band.

  The traffic amount acquisition unit 302 monitors, for example, the received electric field strength via the wireless communication unit 301, and detects whether or not each of a plurality of frequency channels is used in a plurality of periods. Then, the traffic amount acquisition unit 302 acquires a value indicating the amount of traffic in a plurality of periods for each frequency channel according to the detection result. The traffic amount acquisition unit 302 can control the wireless communication unit 301 so that, for example, detection of the electric field strength is performed by switching a plurality of frequency channels at a predetermined cycle. The traffic amount acquisition unit 302 has, for example, a list of available frequency channels, selects one of the frequency channels in the list, for example, in the order of listing or randomly, and uses that frequency channel. To detect whether the

  For example, the traffic amount acquisition unit 302 can acquire the number of signals transmitted from surrounding devices as a value indicating the amount of traffic based on the detected electric field strength within a period of performing detection. Here, with reference to FIGS. 4A to 4D, several examples of signal detection methods based on the electric field strength will be described.

  FIG. 4A shows an example in the case where the electric field intensity exceeds the predetermined threshold and becomes lower than the threshold. In this case, the traffic amount acquisition unit 302 determines that one signal has been transmitted. If the length of the period in which the electric field strength exceeds the predetermined threshold is very short, the traffic amount acquiring unit 302 determines that the electric field strength is not due to a signal but due to noise or the like, and the signal is detected. It can be determined that it is not.

  FIG. 4B shows an example in the case where the electric field strength becomes lower than the predetermined threshold and then lower than the threshold and then becomes lower than the threshold after exceeding the predetermined threshold again. In this case, the traffic amount acquisition unit 302 transmits one signal during a period in which the electric field strength first exceeds the predetermined threshold and then falls below the threshold, and then the electric field strength exceeds the predetermined threshold and then It can be determined that the second signal has been transmitted during the period when the threshold value is reached. That is, in the example of FIG. 4 (B), the traffic volume acquisition unit 302 can detect that two signals have been transmitted. As described above, the traffic amount acquisition unit 302 transmits a signal in each frequency channel by detecting a period in which the electric field strength exceeds a predetermined threshold and then becomes equal to or less than the threshold as a period in which one signal is transmitted. The number of signals can be counted.

  In FIG. 4C, while the electric field strength does not fall below the threshold while the electric field strength exceeds the predetermined threshold, the electric field strength is lowered (varied) by a predetermined amount or more in a predetermined short time period. An example is shown. In this case, the traffic amount acquisition unit 302 can determine that different signals are transmitted before and after the electric field strength fluctuates. If this is one signal, even if the electric field strength fluctuates, the fluctuation is often gradual, and a fluctuation of a predetermined amount or more occurs before and after a predetermined short time period. It is considered that another signal is transmitted in Although FIG. 4C shows an example in the case where the electric field strength decreases, the traffic amount acquiring unit 302 similarly to the case before the change even when the electric field strength increases by a predetermined amount or more in a short period of time. Later, it may be determined that another signal has been transmitted.

  FIG. 4D shows an example in which the length of the period in which the electric field strength exceeds the predetermined threshold exceeds the predetermined time length. This predetermined time length may, for example, correspond to the maximum time length of the legal signal. For example, in Japan, in the wireless LAN frequency band (5 GHz band), it is not permitted to continue to transmit a signal for more than 4 milliseconds. For this reason, the traffic amount acquisition unit 302 can determine that two or more signals have been transmitted, for example, when the electric field strength exceeds a predetermined threshold value for more than 4 milliseconds. More specifically, for example, the traffic amount acquisition unit 302 determines that one signal has been transmitted in a period from when the electric field strength exceeds a predetermined threshold to a predetermined time length, and thereafter, for the next predetermined time It can be determined that the second signal has been transmitted for the period up to the long. Similarly, the traffic amount acquisition unit 302 may determine that three or more signals have been transmitted when the state in which the electric field strength exceeds the predetermined threshold continues.

  The traffic amount acquisition unit 302 counts, for example, the number of signals transmitted in a certain period for the first frequency channel by the method illustrated in FIG. 4. Then, the traffic amount acquisition unit 302 switches the frequency channel and counts the number of transmitted signals in a period having the same length for the second frequency channel. After performing this process on all frequency channels, the traffic volume acquisition unit 302 switches the frequency channel to the first frequency channel again and counts the number of transmitted signals. By repeatedly executing these processes, the traffic volume acquisition unit 302 can acquire, for each of a plurality of frequency channels, a value indicating the amount of traffic over a plurality of time periods. Note that, for example, when the wireless communication unit 301 can monitor a plurality of frequency channels simultaneously, the traffic amount acquisition unit 302 indicates the amount of traffic in the plurality of frequency channels without switching the frequency channel. The values may be obtained simultaneously.

  The traffic amount acquisition unit 302 may detect the signal using a method other than that shown in FIG. For example, the traffic amount acquisition unit 302 can try to demodulate a signal (for example, a header) via the wireless communication unit 301, and when it can demodulate, it can determine that a significant signal has been transmitted. In this case, the wireless communication unit 301 can be configured to be able to receive a signal according to a communication scheme such as a wireless LAN other than LTE, for example.

  Also, the traffic amount acquisition unit 302 acquires, as a value indicating the amount of traffic, a usage time rate of a frequency channel that is a ratio of a time length in which the electric field strength exceeds a predetermined value to a time length of a period for performing detection. It can. The traffic amount acquisition unit 302 stores a value indicating the acquired amount of traffic together with information indicating the acquired time and the like.

  The use channel selection unit 303 determines which of the plurality of available frequency channels to use based on the time change of the value indicating the amount of traffic acquired by the traffic amount acquisition unit 302. For example, the used channel selection unit 303 calculates a weighted addition value obtained by multiplying each of a plurality of values indicating the amount of traffic acquired over a plurality of periods for each frequency channel by a weight value and adding them, and the weighted addition value Select the frequency channel to use based on. Here, the weighted addition value is a value obtained by, for example, multiplying the value indicating the amount of traffic acquired at the nth closest timing to the current time by the nth weight and adding the multiplication result It is. In addition, the value of the weight used here can be comprised so that it can be set by various factors, such as time and a place, or based on some empirical knowledge. The use channel selection unit 303 can select, for example, a frequency channel whose weighted addition value is equal to or less than a predetermined value as a frequency channel to be used. The use channel selection unit 303 may select a channel to be used based on a differential value or the like of a value indicating the amount of traffic.

(Flow of processing)
Subsequently, the flow of processing executed by the communication device will be described with reference to FIG. The communication apparatus monitors traffic for a plurality of time periods for a plurality of frequency channels, for example, in a non-licensed frequency band, and acquires a value indicating the amount of traffic (S501). The value indicating the amount of traffic may be, for example, the number of transmitted signals (packets) in each of a plurality of time periods, or the time usage rate at which the target frequency channel has been used.

  Thereafter, for example, each time the communication device obtains a value indicating the amount of traffic in S501, or when the communication device changes the frequency channel when connecting with another device, or when changing the frequency channel, The selection process is executed (S502). At this time, this selection process is executed based on the time change of the value indicating the amount of traffic acquired in S501. The communication apparatus prepares, for example, a plurality of weight values corresponding to each of a plurality of periods, calculates a weighted addition value by multiplying by adding a value indicating the amount of traffic for each of the plurality of periods, and adding The frequency channel to be used is selected based on the weighted addition value. Also, the communication apparatus may select a frequency channel to be used by predicting the time change of the traffic amount based on the time derivative value of the value indicating the traffic amount.

  As described above, the communication apparatus according to the present embodiment determines whether the traffic is likely to increase or decrease according to the time variation of the traffic amount, and determines the frequency channel to be used. Do. For this reason, the communication apparatus can select a frequency channel with high probability of not being congested in the future regardless of the amount of instantaneous traffic. Also, as a result, it is not necessary to switch frequency channels unnecessarily.

  The embodiments of the present invention have been described above. This embodiment is merely an example and clearly not intended to limit the invention to the form of the embodiment, and the present invention is described above within the scope defined by the appended claims. Various modifications to the embodiment are allowed.

Claims (9)

For each of a plurality of frequency channels to detect a signal transmitted have you to each of the plurality of periods, and acquires the number of the signal, as the value indicating the amount of traffic that pair to each of the plurality of periods Acquisition means,
Selecting means for selecting a frequency channel to be used for communication from the plurality of frequency channels according to a time change of the value;
A communication apparatus comprising: The selection means is a frequency channel used for communication based on a value of a weighted addition value obtained by multiplying the value for each of the plurality of periods by adding the value of the weight corresponding to each of the plurality of periods. To choose
The communication apparatus according to claim 1, The value of the weight is configurable,
The communication device according to claim 2, characterized in that: The acquisition means detects electric field strength in each of the plurality of frequency channels, and determines that a signal is transmitted when the electric field strength exceeds a predetermined value.
The communication apparatus according to any one of claims 1 to 3 , characterized in that: When the acquisition means detects that the electric field strength fluctuates by a predetermined amount or more during a predetermined time length while the electric field strength exceeds the predetermined value, another before and after the fluctuation is detected. Determine that a signal has been sent,
The communication apparatus according to claim 4 , When the acquisition means detects that the length of time during which the electric field strength exceeds the predetermined value exceeds a predetermined time length, it determines that one signal has been transmitted until the predetermined time length, After the predetermined time length, it is determined that another signal has been transmitted,
The communication device according to claim 4 or 5 , characterized in that: The acquisition means determines that the transmission of the signal is completed when detecting that the electric field strength has become equal to or less than the predetermined value after exceeding the predetermined value.
The communication device according to any one of claims 4 to 6 , characterized in that: A control method of the communication device,
Acquisition means, for each of a plurality of frequency channels to detect a signal transmitted have you to each of the plurality of periods, the number of the signal, and a value indicating the amount of traffic that pair to each of the plurality of periods Acquisition process to acquire
A selection step of selecting, from the plurality of frequency channels, a frequency channel to be used for communication according to a time change of the value;
A control method characterized by comprising: In a computer provided in the communication device,
For each of a plurality of frequency channels to detect a signal transmitted have you to each of the plurality of periods, the number of the signal, respectively were acquired as the value indicating the amount of traffic that pairs of the plurality of periods ,
The frequency channel to be used for communication is selected from the plurality of frequency channels according to the time change of the value,
Program for

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