JP6219772B2 - Wireless communication apparatus and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method.

  In a wireless communication system using CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance), if a wireless communication apparatus having data to be transmitted performs carrier sense and other wireless communication apparatuses are not transmitting, a transmission opportunity is provided. get. The wireless communication apparatus transmits data after acquiring a transmission opportunity, and ends the communication when the data transmission is completed. When performing communication again, the wireless communication apparatus acquires a transmission opportunity and transmits data after waiting for a back-off time (Non-Patent Document 1).

IEEE Standard for Information technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, 12 June 2007

  Another wireless communication system (hereinafter referred to as a secondary system) is newly provided in an area where an existing wireless communication system using CSMA / CA (hereinafter referred to as a primary system) is operated. When coexisting with the system, the following problems arise. When the secondary system operates using CSMA / CA, there is a high possibility that a transmission opportunity will not be obtained in the primary system, and the influence of the secondary on the primary system will increase. In addition, by reducing the bandwidth occupancy time by segmenting the data to be transmitted in the secondary system to suppress the decrease in the frequency of acquisition of transmission opportunities in the primary system, the throughput decreases due to overhead such as backoff time in the secondary system. End up.

  In view of the above circumstances, an object of the present invention is to provide a wireless communication apparatus and a wireless communication method that can suppress a decrease in throughput while reducing the influence on other wireless communication systems.

  One aspect of the present invention is a usage status acquisition unit that performs carrier sense on a plurality of frequency channels, and assigns a lower priority than the other frequency channels to the frequency channel used when transmitting data, A channel selection unit that selects a predetermined number of frequency channels based on the result of carrier sense in order from the frequency channel with the highest priority assigned to the plurality of frequency channels, and the frequency selected by the channel selection unit A wireless communication apparatus comprising: a transmission unit configured to transmit data using a channel, wherein the channel selection unit updates priorities for the plurality of frequency channels when the transmission unit finishes transmitting data. is there.

  Further, according to one aspect of the present invention, in the above wireless communication device, the channel selection unit assigns the frequency channel used in the previous transmission to a low priority group, and performs the previous transmission among the plurality of frequency channels. When priority is updated by assigning a frequency channel that has not been used to a high priority group, and data is transmitted with priority given to the frequency channel assigned to the high priority group over the frequency channel assigned to the low priority group The frequency channel to be used is selected.

  Further, according to one aspect of the present invention, in the above wireless communication apparatus, the channel selection unit cannot secure a band required for data transmission even when all the frequency channels assigned to the high priority group are used. In this case, the frequency channel assigned to the low priority group is also selected as a frequency channel to be used when transmitting data.

  One embodiment of the present invention is a wireless communication method performed by a wireless communication device, the use state obtaining step of performing carrier sense for a plurality of frequency channels, and the frequency channel used when transmitting data. A lower priority than the other frequency channels is assigned to the frequency channels, and a predetermined number of frequency channels are selected based on the result of carrier sense in order from the frequency channels with the highest priority assigned to the plurality of frequency channels. A channel selection step, a transmission step of transmitting data using the frequency channel selected in the channel selection step, and a priority update step of updating priorities for the plurality of frequency channels after the transmission step. A wireless communication method characterized by the above.

  According to the present invention, it is possible to suppress the selection bias that frequently selects a specific frequency channel by sequentially selecting the frequency channel to be used for transmission from the frequency channel with the highest priority. It is possible to reduce the influence on other wireless communication systems located in the network. In addition, since the wireless communication apparatus does not perform segmentation of transmission data, the influence on other wireless communication systems can be reduced without reducing the throughput.

It is a figure which shows the radio | wireless communications system using the radio | wireless communication apparatus 10 in this embodiment. It is a block diagram which shows the structural example of the radio | wireless communication apparatus 10 in the embodiment. It is a flowchart which shows the frequency channel selection process in which the channel selection part 17 in the embodiment selects a frequency channel. It is a figure which shows the operation example of the radio | wireless communication apparatus 10 of the secondary system in the embodiment.

  Hereinafter, a wireless communication apparatus and a wireless communication method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a wireless communication system using a wireless communication device 10 according to the present embodiment. The wireless communication system includes at least two wireless communication devices 10 (10A, 10B). A wireless communication system (hereinafter referred to as a secondary system) is operated in the vicinity of another wireless communication system (hereinafter referred to as a primary system) that has already been operated. The primary system includes at least two wireless communication devices 50 (50A, 50B).

  Each wireless communication device in the primary system and the secondary system transmits data by wireless communication using CSMA / CA. The frequency band used by the primary system for wireless communication and the frequency band used by the secondary system for wireless communication are at least partially overlapped. Moreover, as shown in FIG. 1, the communication area 1 of the secondary system and the communication area 5 of the primary system partially overlap. The wireless communication device 10 provided in the secondary system performs communication between the wireless communication devices 10 by selecting a frequency channel so as to reduce the influence on the wireless communication in the primary system.

  Although FIG. 1 shows a case where there is one primary system, two or more primary systems may be operated in the vicinity of the secondary system.

  FIG. 2 is a block diagram illustrating a configuration example of the wireless communication device 10 according to the present embodiment. As shown in the figure, the wireless communication device 10 includes a reception unit 11, a demodulation unit 12, an external communication interface unit 13, a modulation unit 14, a priority storage unit 15, a usage status acquisition unit 16, a channel selection unit 17, and a transmission unit 18. have.

  The receiving unit 11 receives a radio signal via an antenna provided in the radio communication device 10. The receiving unit 11 performs signal processing such as amplification, filtering, and frequency conversion on the received radio signal. The reception unit 11 outputs a reception baseband signal obtained by signal processing to the demodulation unit 12 and the usage status acquisition unit 16.

  The demodulator 12 demodulates and decodes the received baseband signal output from the receiver 11 to obtain received data. The demodulation unit 12 outputs the acquired reception data to the external communication interface unit 13.

  The external communication interface unit 13 transmits the reception data output from the demodulation unit 12 to an external device. Further, the external communication interface unit 13 receives transmission data to be transmitted to another wireless communication device 10 from an external device. The external communication interface unit 13 outputs the received transmission data to the modulation unit 14.

  The modulation unit 14 encodes and modulates transmission data output from the external communication interface unit 13 to generate a transmission baseband signal. The modulation unit 14 outputs the generated transmission baseband signal to the transmission unit 18.

  The priority storage unit 15 stores priority information indicating the priority of each frequency channel. The frequency channels whose priority is indicated by the priority information are all frequency channels that can be used by the wireless communication device 10. The priority information in the present embodiment is information indicating whether a frequency channel belongs to a high priority group or a low priority group. The priority associated with each frequency channel in the priority information is either “high” indicating that the frequency channel belongs to the high priority group or “low” indicating that the frequency channel belongs to the low priority group. Takes a value. The priority in the priority information may be information indicating other attributes or a numerical value. In addition, as the priority of each frequency channel in the priority information, information belonging to the high priority group is set as an initial value.

  The usage status acquisition unit 16 determines whether each frequency channel is used by another device based on the reception baseband signal output from the reception unit 11. The usage status acquisition unit 16 acquires the usage status of each frequency channel based on the determination result. The frequency channels to be determined by the usage status acquisition unit 16 are all frequency channels that can be used by the wireless communication device 10. The usage status acquisition unit 16 outputs usage status information indicating frequency channels not used by other devices to the channel selection unit 17.

  The channel selection unit 17 reads priority information from the priority storage unit 15. The channel selection unit 17 selects a frequency channel to be used when transmitting transmission data to the destination device based on the usage status information and priority information output by the usage status acquisition unit 16. The channel selection unit 17 outputs selected channel information indicating the selected frequency channel to the transmission unit 18. When the transmission using the frequency channel selected by the transmission unit 18 is finished, the channel selection unit 17 updates the priority of the selected frequency channel to “low”.

  The transmission unit 18 frequency-converts the transmission baseband signal output from the modulation unit 14 to each frequency channel indicated by the selected channel information to generate a radio signal. The transmission unit 18 performs filtering and power amplification on the radio signal and transmits the result from the antenna.

  FIG. 3 is a flowchart showing frequency channel selection processing in which the channel selection unit 17 in the present embodiment selects a frequency channel. When the channel selection unit 17 starts the frequency channel selection process, “0” is substituted for the variable i indicating the number of selected frequency channels, and the variable i is initialized (step S11).

  The channel selection unit 17 selects one frequency channel that has not yet been selected from the frequency channels assigned to the high priority group in the priority information (step S12). The channel selection unit 17 increases the value of the variable i by “1” (step S13).

  In step S12, when one unselected frequency channel is selected from the frequency channels assigned to the high priority group, for example, the highest frequency channel or the lowest frequency channel is selected. To do. Note that the method for selecting one frequency channel may be a method other than those described above, or one frequency channel may be selected at random.

  The channel selection unit 17 determines whether or not the number of selected frequency channels (value of the variable i) is N or more (step S14). If the value of i is greater than or equal to N (step S14: YES), the channel selector 17 advances the process to step S19. On the other hand, when the value of i is not N or more (step S14: NO), the channel selection unit 17 advances the processing to step S15. Here, N is the number of frequency channels used when the wireless communication apparatus 10 transmits transmission data. The frequency channel number N may be a predetermined value or may be a value calculated by the modulation unit 14. Further, the frequency channel number N is a value of 1 or more.

  The channel selection unit 17 determines whether there is a frequency channel that is not yet selected among the frequency channels assigned to the high priority group (step S15). When there is an unselected frequency channel (step S15: YES), the channel selection unit 17 returns the process to step S12, and repeats the processes after step S12. On the other hand, when all the frequency channels are selected (step S15: NO), the channel selection unit 17 advances the process to step S16.

  The channel selection unit 17 selects one frequency channel that has not yet been selected from the frequency channels assigned to the low priority group in the priority information (step S16). The channel selection unit 17 increases the value of the variable i by “1” (step S17). Note that the method for selecting one unselected frequency channel from the frequency channels assigned to the low priority group in step S16 is the same as the method for selecting one frequency channel in step S12.

  The channel selection unit 17 determines whether or not the number of selected frequency channels (variable i) is N or more (step S18). When the value of i is N or more (step S18: YES), the channel selection unit 17 advances the process to step S19. On the other hand, when the value of i is not N or more (step S18: NO), the channel selection unit 17 returns the process to step S16 and repeats the processes after step S16.

  The channel selection unit 17 generates selection channel information indicating the selected N frequency channels and outputs the selection channel information to the transmission unit 18 (step S19), and ends the frequency channel selection process.

  When transmission of transmission data using the frequency channel selected in the frequency channel selection process is completed, the channel selection unit 17 updates the priority information. Specifically, the channel selection unit 17 changes the priority of the N frequency channels indicated by the selection channel information output to the transmission unit 18 to “low”, and other than the N frequency channels indicated by the selection channel information. Change the priority for the frequency channel to high.

  Note that the plurality of wireless communication devices 10 provided in the secondary system assign the frequency channel used for transmission data transmission to the wireless communication device 10 that is the destination of transmission data via at least one predetermined control dedicated channel. Notice. Transmission data is transmitted and received using the frequency channel selected by the channel selection unit 17 by negotiation notified through the control-dedicated channel. When the control dedicated channel is not provided, the radio communication device 10 always receives all the usable frequency channels, determines whether or not the received signal includes a signal destined for the own device, Detect a signal addressed to the device itself. In this case, the wireless communication device 10 arranges predetermined destination information at the head of the wireless signal when transmitting transmission data so that the other wireless communication device 10 can detect the destination.

  FIG. 4 is a diagram illustrating an operation example of the wireless communication apparatus 10 of the secondary system in the present embodiment. In the figure, the horizontal axis indicates time, and the vertical axis indicates frequency (frequency channel). Further, in the figure, three primary systems (primary systems A to C) are located in the vicinity of the secondary system, and the radio communication device 10 of the secondary system can use ten frequency channels (frequency channels a to j). An example of operation in the case is shown.

  In this operation example, “5” is defined as the number of frequency channels (N) used by the wireless communication apparatus 10 for transmission of transmission data. Also, “high” is set as an initial value for the priority of each frequency channel in the priority information.

The primary system A transmits and receives data using a frequency band having _a frequency fa as _a center frequency. The frequency band used by the primary system A overlaps the frequency bands of the frequency channels a to d among the frequency channels that can be used by the wireless communication device 10. The primary system B transmits and receives data using a frequency band having the frequency _fb as the center frequency. The frequency band used by the primary system B overlaps the frequency bands of the frequency channels c to g among the frequency channels that can be used by the wireless communication device 10. The primary system C transmits and receives data using a frequency band having the frequency _fc as a center frequency. The frequency band used by the primary system C overlaps the frequency bands of the frequency channels f to j among the frequency channels that can be used by the wireless communication device 10.

  At time T1, transmission data to be transmitted to another wireless communication device 10B is input to the wireless communication device 10A provided in the secondary system. In the wireless communication device 10A, the usage status acquisition unit 16 performs carrier sense of each frequency channel, and outputs usage status information indicating frequency channels that are not used by other devices over the back-off time to the channel selection unit 17. . At this time, since data is transmitted in the primary system B, the usage status information indicates the frequency channels a, b, h, i, and j.

  The channel selection unit 17 selects to use the frequency channels a, b, h, i, and j when transmitting the transmission data based on the priority information and the usage status information. The transmission unit 18 transmits transmission data using the frequency channels a, b, h, i, and j. When the transmission of the transmission data is finished, the channel selection unit 17 changes the priority of the frequency channels a, b, h, i, and j in the priority information to “low”.

  At time T2, transmission data to be transmitted to another wireless communication device 10B is input to the wireless communication device 10A provided in the secondary system. In the wireless communication device 10A, the usage status acquisition unit 16 performs carrier sense of each frequency channel, and outputs usage status information indicating frequency channels that are not used by other devices over the back-off time to the channel selection unit 17. . At time T2, all frequency channels are not used. However, since data transmission is started in the primary system A at the subsequent backoff time, the usage status information indicates the frequency channels e, f, g, h, i, and j.

  The channel selection unit 17 selects a frequency channel when transmitting transmission data based on the priority information and the usage status information. Specifically, the channel selection unit 17 selects the frequency channels e, f, and g assigned to the high priority group, and the frequency channel h from the frequency channels h, i, and j assigned to the low priority group. And i. The transmission unit 18 transmits transmission data using the frequency channels e, f, g, h, and i. When the transmission of the transmission data ends, the channel selection unit 17 changes the priority of the frequency channels e, f, g, h, and i in the priority information to “low”. Further, the channel selection unit 17 changes the priority of the frequency channels a, b, c, d, and j in the priority information to “high”.

  As described above, the wireless communication apparatus 10 according to the present embodiment determines the priority of the frequency channel used in the immediately previous transmission lower than the priority of the frequency channel not used in the immediately previous transmission. The radio communication apparatus 10 can suppress the selection bias that frequently selects a specific frequency channel by sequentially selecting the frequency channels used for transmission from the frequency channel with the highest priority. By suppressing the selection bias of the frequency channel, the possibility of occupying a specific frequency channel (frequency band) in the secondary system including the wireless communication device 10 is reduced, and the influence on the primary system located in the vicinity is reduced. Can be made. Further, since the secondary system does not perform segmentation of transmission data, the influence on the primary system can be reduced without reducing the throughput of the secondary system.

  In the above-described embodiment, the configuration in which the priority information is updated by assigning the frequency channel used for transmission by the wireless communication apparatus 10 to the low priority group and assigning the frequency channel not used for transmission to the high priority group. explained. However, the present invention is not limited to this configuration. In the secondary system, priority is assigned by assigning the frequency channel used by one of the wireless communication apparatuses 10 to the low priority group and assigning the frequency channel not used for transmission to the high priority group. The degree information may be updated in all the wireless communication devices 10 in the secondary system. Thereby, it can suppress that the frequency channel used in a secondary system is biased to a specific frequency channel.

  In the above-described embodiment, the configuration using information indicating whether the frequency channel belongs to the high priority group or the low priority group has been described as the priority in the priority information. However, without being limited to this configuration, the channel selection unit 17 may set a value inversely proportional to the frequency channel usage frequency as the priority. As a result, the channel selection unit 17 preferentially selects a frequency channel with a low usage frequency, and reduces the possibility that the wireless communication device 10 will occupy a specific frequency channel (frequency band). The impact on the primary system can be reduced.

Further, as shown in FIG. 4, the radio communication device 10 detects whether or not other devices are transmitting on each frequency channel even during a period in which transmission data is being transmitted (c) ₁ to c ₆₎ may be performed.

  You may make it implement | achieve the wireless communication apparatus 10 in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” is a program that dynamically holds a program for a short time, like a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  In an environment where other wireless communication systems are operating, it can be applied to applications where it is indispensable to reduce the influence on existing wireless communication systems when a new wireless communication system is provided.

DESCRIPTION OF SYMBOLS 1 ... Secondary system communication area 5 ... Primary system communication area 10, 10A, 10B, 50, 50A, 50B ... Wireless communication device 11 ... Reception unit 12 ... Demodulation unit 13 ... External communication interface unit 14 ... Modulation unit 15 ... Priority Degree storage unit 16 ... usage status acquisition unit 17 ... channel selection unit 18 ... transmission unit

Claims (4)

A usage status acquisition unit that performs carrier sense on a plurality of frequency channels;
The assignment of lower priority than the other of the frequency channel to frequency channel, the priority and the plurality of frequency channels are allocated to the plurality of frequency channels used when the device itself transmits data A channel selection unit that selects a predetermined number of frequency channels in descending order of the priority from the frequency channels not used by other wireless communication devices based on the result of carrier sense for
A transmission unit for transmitting data using the frequency channel selected by the channel selection unit,
The channel selector
The wireless communication apparatus, wherein when the transmission unit finishes transmitting data, the priority for the plurality of frequency channels is updated. The wireless communication device according to claim 1,
The channel selector
Assign the frequency channel used in the previous transmission to the low priority group, update the priority by assigning the frequency channel not used in the previous transmission among the plurality of frequency channels to the high priority group,
The radio communication apparatus, wherein the frequency channel assigned to the high priority group is selected as a frequency channel to be used when data is transmitted with priority over the frequency channel assigned to the low priority group. The wireless communication device according to claim 2,
The channel selector
The frequency used when the frequency channel allocated to the low priority group also transmits data when the band required for data transmission cannot be secured even if all the frequency channels allocated to the high priority group are used. A wireless communication apparatus characterized by selecting a channel. A wireless communication method performed by a wireless communication device,
A usage acquisition step of performing carrier sense for a plurality of frequency channels;
The assignment of lower priority than the other of the frequency channel to frequency channel, the priority and the plurality of frequency channels are allocated to the plurality of frequency channels used when the device itself transmits data A channel selection step of selecting a predetermined number of frequency channels in descending order of priority from the frequency channels not used by other wireless communication devices based on the result of carrier sense for
A transmission step of transmitting data using the frequency channel selected in the channel selection step;
A wireless communication method comprising: a priority update step of updating priorities for the plurality of frequency channels after the transmission step.

Images