JP6955236B2 - Wireless communication system and wireless communication method - Google Patents

Description

The present invention relates to wireless communication systems and wireless communication methods.

The traffic of wireless communication is rapidly increasing due to the expansion of the use of wireless LAN and the increase of devices with communication functions such as wireless surveillance cameras. To improve the frequency utilization efficiency and accommodate more traffic with limited wireless resources. Is required.

In a frequency band shared by multiple systems such as the ISM (Industry-Science-Medical) band, each system autonomously and decentrally determines the frequency used, so that the frequency channel used is biased.

On the other hand, LTE (Long Term Evolution) Release 8 (Rel-8), which is a conventional wireless communication system, for example, a wireless communication system standardized by 3GPP (3rd Generation Partnership Project), uses a band of up to 20 MHz. It is possible to communicate with each other.

Furthermore, in LTE-A (Long Term Evolution-Advanced), which is an advanced version of LTE, the bandwidth supported by LTE is the basic unit in order to realize further high-speed transmission while ensuring backward compatibility with LTE. Carrier aggregation (CA: Career Aggregation) technology, in which a plurality of component carriers (CCs) are bundled and used at the same time, is adopted, and wideband transmission of 100 MHz width can be realized by using a maximum of 5 CC (100 MHz width). However, such carrier aggregation is transmission using different channels in adjacent frequency bands.

Although the speed has been increased as described above, the demand for mobile communication traffic has been rapidly increasing in recent years with the spread of high-performance mobile terminals such as smartphones.

As a result, in addition to the conventional expansion of the use of wireless LAN (Local Area Network), offloading to wireless LAN has progressed due to the increase in mobile data traffic due to the spread of smartphones, and unlicensed bands (2.4 GHz band, 5 GHz band). ) Is increasing rapidly.

In addition, due to the development of the IoT (Internet Of Things) / M2M (Machine to Machine) society, there is concern that the above frequency bands and the 920 MHz band will become even tighter, and improving the frequency utilization efficiency of these frequency bands has become an urgent issue. There is.

Here, since the usage status of the wireless resource fluctuates depending on the time, place, frequency band, wireless channel, etc. as described above, a situation may occur in which only a part of the frequency band (or the wireless channel) is congested.

However, existing self-employed wireless systems (for example, IEEE802.11 wireless LAN) use a single frequency band or determine one band to be used in advance before communication. For example, IEEE802.11n presets whether to use the 2.4 GHz band or the 5 GHz band. Therefore, even if the existing self-employed wireless system as a whole has free wireless resources, congestion may occur.

Here, cognitive radio technology is attracting attention in order to make effective use of wireless communication resources. Cognitive radio technology means that a wireless terminal recognizes the usage status of surrounding radio waves and changes the wireless communication resource to be used according to the usage status. Cognitive radio technology includes a heterogeneous type in which different wireless communication standards are selected and used according to the situation, and a frequency sharing type in which a wireless terminal searches for a free frequency and secures a necessary communication band.

In the heterogeneous type, the cognitive radio recognizes multiple wireless systems operating in the vicinity, obtains information on the utilization of each system and feasible transmission quality, and connects to an appropriate wireless system. That is, the heterogeneous type cognitive radio indirectly enhances the utilization efficiency of frequency resources by increasing the utilization efficiency of wireless systems existing in the vicinity.

On the other hand, in the frequency sharing type, the cognitive radio has a frequency resource (this is called a white space) that is temporarily or not locally used in the frequency band in which another radio system is operated. Is detected, and signal transmission is performed using this. That is, the frequency sharing type cognitive radio directly enhances the utilization efficiency of frequency resources in a certain frequency band.

Then, as a method for solving the problem of increased traffic in the unlicensed band as described above, a plurality of wireless LAN standards having different frequency bands (for example, 2.4 GHz band wireless LAN standard and 5 GHz band wireless LAN standard) are used. A heterogeneous cognitive radio approach that is selected or used in parallel can be considered (for example, Patent Document 1 and Patent Document 2).

However, in this heterogeneous cognitive radio approach, it is necessary to divide the transmission data as appropriate and to divide in advance which frequency band each is to be transmitted. As a result, new problems such as a large difference in transmission delay depending on the frequency band used and a change in the order in which data arrives at the destination occur depending on the degree of congestion in each frequency band.

Therefore, it is desirable to realize cognitive wireless communication by sharing a frequency with an existing system in a plurality of frequency bands that are largely separated from each other, for example, a 2.4 GHz band wireless LAN and a 5 GHz band wireless LAN.

In this way, in the case of a configuration in which communication is selectively performed in any of a plurality of frequency bands separated from each other, in order to determine which frequency band is used at the next transmission timing, a plurality of frequencies are used. In order to efficiently grasp the usage status of radio channels in a band, it is necessary to sense channels in a plurality of radio frequency bands.

As such a channel sensing method, there is known a technique of "cooperative sensing" in which a plurality of wireless communication devices cooperate to sense a target channel.

For example, in the techniques disclosed in Non-Patent Document 1, Non-Patent Document 2 and Non-Patent Document 3, the existing cooperative sensing assumes a single sensing target, and in order to improve the detection accuracy, a plurality of wireless devices Collect the results sensed in.

In order to reduce the sensing cost, there is also a method of reducing the number of wireless devices that perform sensing and information exchange within a range in which the detection accuracy does not deteriorate.

Non-Patent Document 4 In the existing multi-channel sensing disclosed in Non-Patent Document 5, the sensing radio device senses a plurality of channels in a time-division manner.

Japanese Patent Application Laid-Open No. 2011-211433 Japanese Patent Application Laid-Open No. 2013-187651

Ian F. Akyildiz, Brandon F. Lo, and Ravikumar Balakrishnan, Cooperative spectrum sensing in cognitive radio networks: A survey Physical Communication, 2011. T. Yucek and H. Arslan, A survey of spectrum sensing algorithms for cognitive radio applications, IEEE Communications Surveys and Tutorials, vol. 11, no. 1, pp. 116-130, 2009. Nguyen-Thanh and Koo: A cluster-based selective cooperative spectrum sensing scheme in cognitive radio. EURASIP Journal on Wireless Communications and Networking 2013 2013: 176. Hoan, T.-N.-K .; Hiep, V.-V .; Koo, I.-S. Multichannel-Sensing Scheduling and Transmission-Energy Optimizing in Cognitive Radio Networks with Energy Harvesting. Sensors 2016, 16, 461. Umashankar G and Arun Pachai Kannu, Throughput Optimal Multi-Slot Sensing Procedure for a Cognitive Radio, IEEE COMMUNICATIONS LETTERS, VOL. 17, NO. 12, DECEMBER 2013.

However, in the techniques disclosed in Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3, each wireless device has one or more sensing objects, and the sensing objects are partially located between the wireless devices. No technology has been provided to appropriately determine a wireless device for sensing and exchanging information in the presence of duplication.

Further, the existing multi-channel sensing disclosed in Non-Patent Document 4 and Non-Patent Document 5 cannot sense all channels at the same time, and a time lag occurs in the sensing result, so that the sensing accuracy deteriorates.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to selectively communicate a frequency band used in a plurality of frequency bands separated from each other. It is an object of the present invention to provide a wireless communication system and a wireless communication method capable of realizing cooperative sensing that realizes channel sensing coverage for a plurality of wireless channels at the minimum cooperative cost.

According to one aspect of the present invention, there is a plurality of wireless communication systems for transmitting signals by using a plurality of wireless channels that perform random access control in each of a plurality of frequency bands separated from each other. The first wireless communication device and the second wireless communication device are provided, and the second wireless communication device is based on the information of the targetable wireless channel that can be channel-sensitized from each of the plurality of first wireless communication devices. The notification means is provided with a sharing determination means for specifying the wireless channel to which the first wireless communication device shares the channel sense, and a notification means for notifying the first wireless communication device of the determined wireless channel to be shared. Notifies the result of integrating the channel sensing information from the plurality of first wireless communication devices to each of the plurality of first wireless communication devices, and the sharing determination means shares and senses all of the plurality of wireless channels. In doing so, the division is determined so that the number of first wireless communication devices in charge of channel sensing is minimized .

Preferably, each first wireless communication device includes a digital signal processing unit for dividing transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands and generating a transmission packet for each frequency band. , A plurality of high-frequency signal processing units provided for each frequency band for converting a digital signal into a high-frequency signal for each corresponding frequency band, and a target radio notified of a plurality of radio channels in a plurality of frequency bands. A channel usage status observation unit that executes channel sensing for observing the channel usage status, a channel usage information transmission unit for transmitting the result of channel sensing, and channel sensing that is the result of channel sensing in other wireless communication devices. Based on the channel usage information receiving unit that receives the information and the channel sensing information from the channel usage information receiving unit, each partial data from the high frequency processing unit is synchronized and started to be transmitted as packets for each of multiple frequency bands at the same timing. Includes an access control unit.

Preferably, the sharing determination means updates the sharing of channel sensing when it determines that a predetermined condition is satisfied and the status of the devices participating in the wireless communication system has changed.

According to another aspect of the present invention, in a wireless communication system composed of an access point and a plurality of wireless communication devices, a plurality of wireless channels that perform random access control in each of a plurality of frequency bands separated from each other are used. It is a wireless communication method for transmitting a signal, and the access point shares the channel sense based on the information of the targetable wireless channel that can be channel-sensed from each of the plurality of wireless communication devices. The division determination step includes a division determination step for specifying the wireless channel to be performed , and the division determination step is performed by the number of first wireless communication devices in charge of channel sensing when the access point shares and senses all of a plurality of wireless channels. A notification step in which the access point notifies the wireless communication device of the determined wireless channel to be shared, and a plurality of each wireless communication device in a plurality of frequency bands, including a step of determining the sharing so as to be the minimum. A channel usage status observation step for observing the usage status of a specified target wireless channel among the wireless channels of the above, and a channel usage information transmission step for each wireless communication device to transmit the result of channel sensing. , The access point includes a notification step of notifying each of the plurality of wireless communication devices of the result of integrating the channel sensing information from the plurality of wireless communication devices.

Preferably, each wireless communication device receives a channel sensing information that is the result of channel sensing in another wireless communication device, and each wireless communication device transmits transmission data in a plurality of frequency bands, respectively. It divides into a plurality of partial data corresponding to, generates a transmission packet for each frequency band, converts a digital signal into a high frequency signal for each corresponding frequency band, and divides each partial data into a plurality of parts based on channel sensing information. As a packet for each frequency band of, an access control step that starts transmission at the same timing in synchronization is provided.

According to the present invention, it is possible to realize cooperative sensing that realizes channel sensing coverage for a plurality of target radio channels at the minimum cooperative cost.

According to the present invention, it is possible to improve frequency utilization efficiency by utilizing radio resources without waste by flexibly selecting or simultaneously using channels of a plurality of frequency bands by utilizing the result of cooperative sensing. Become.

It is a figure which shows the concept of channel sensing in communication between own station and partner station. It is a conceptual diagram for demonstrating the radio channel in a plurality of frequency bands separated from each other. It is a conceptual diagram for demonstrating the structure of the wireless communication system of this embodiment. It is a figure for demonstrating a specific example for mapping transmission data into a plurality of bands and transmitting, and collectively receiving and integrating on a receiving side. It is a functional block diagram for demonstrating the configuration of the transmission device 1000 of this embodiment. It is a conceptual diagram for demonstrating cooperative sensing. It is a conceptual diagram in the case of performing cooperative sensing in BSS. It is a conceptual diagram for demonstrating the problem when the cooperative sensing is simply carried out. It is a conceptual diagram which shows the example of the set of the wireless device which cooperates. It is a figure for demonstrating the flow in which an access point AP determines a wireless communication device which performs cooperative sensing. It is a conceptual diagram for demonstrating the concept of the process which determines the wireless communication apparatus which performs cooperative sensing. It is a sequence diagram for demonstrating the processing in cooperative sensing. It is a flowchart for demonstrating the process of updating the structure of a cooperative sensing database. It is a functional block diagram for demonstrating the example of the more detailed structure of the transmission device 1000. It is a functional block diagram for demonstrating the configuration of the receiving apparatus 2000 of this embodiment. It is a functional block diagram for demonstrating the example of the more detailed configuration of the receiving apparatus 2000.

Hereinafter, the configurations of the wireless communication system and the wireless communication device according to the embodiment of the present invention will be described. In the following embodiments, the components and processing steps having the same reference numerals are the same or equivalent, and the description thereof will not be repeated if they are not necessary.

In the following, as an example of explaining the receiving device of the present invention, a plurality of existing unlicensed bands (for example, 920 MHz band used for IoT and the like, used for wireless LAN), which are largely separated from each other as described above, are used. An embodiment of a transmission device in a wireless communication system capable of cognitive wireless communication by sharing a frequency with an existing system in (4 GHz band and 5 GHz band) will be described.

Further, in the following, "carrier sense" refers to sensing for detecting the presence or absence of a signal of a target wireless channel and determining the transmission timing by virtual carrier sense accompanied by power detection or decoding of a received signal. Meaning, "channel sensing" means, in addition to sensing as carrier sense, sensing that executes communication monitoring or the like in order to grasp the usage status of the target channel.
[Embodiment]
In the following, for the purpose of explaining the present embodiment, in order to determine when to set the next transmission timing in the case of a configuration in which communication is performed by random access control in each of a plurality of frequency bands separated from each other. A configuration for simultaneous channel sensing of multiple channels in the target band will be described.

However, communication using a plurality of frequency bands at the same time is not always essential for the present invention, and for example, communication is selectively performed in at least one of the plurality of frequency bands. In this case, it can be applied to a configuration in which multi-channel simultaneous channel sensing of the target band is performed in order to determine which frequency band is used at the next transmission timing.

FIG. 1 is a diagram showing the concept of channel sensing in communication between the own station and the partner station.

When the own station 10 intends to transmit to the partner station 20 from now on, the own station 10 first performs channel sensing for confirming the usage status of a plurality of channels in the used band.

Here, if there are other communication devices 310 to 30.4 that use either of the channels in the available band in the vicinity of the own station 10 or the partner station 20, these become interference sources and interfere waves. In order to avoid the influence of the above, the own station 10 detects and uses a channel in a vacant frequency band to communicate with the partner station 20.

FIG. 2 is a conceptual diagram for explaining radio channels in a plurality of frequency bands separated from each other.

In FIG. 2, as an example, the horizontal axis is a frequency, and the above-mentioned 920 MHz band, 2.4 GHz band, and 5 GHz band are shown as license-free bands. Each frequency band includes a plurality of radio channels selectively used in communication.

Here, the wireless communication device of the present embodiment, which will be described later, is generally a receiving device that uses a plurality of frequency bands separated from each other and performs communication in parallel at the same timing by the same wireless method. It is possible to apply.

FIG. 3 is a conceptual diagram for explaining the configuration of the wireless communication system of the present embodiment.

With reference to FIG. 3, on the transmission side, assuming that three frequency bands of 920 MHz band, 2.4 GHz band, and 5 GHz band are used, it is assumed that one radio channel is used in each band, and the transmission frame is used. To configure.

Although a plurality of channels may be used in each frequency band, it will be described below assuming that one channel is used for each frequency band.

In this embodiment, wireless access control having the following features is performed.

That is, first, the transmitting side senses and observes the usage status of a plurality of frequency bands (vacancy status of each radio channel, etc.) by a method as described later.

Subsequently, the transmitting side simultaneously transmits radio packets (frames) on one or more unused frequency bands / radio channels at a certain timing. At this time, the transmission data is mapped to a plurality of bands and transmitted.

On the other hand, on the receiving side, a plurality of bands are collectively received and data is integrated.

With such a configuration in transmission and reception, transmission opportunities can be secured even if the congestion situation is biased between bands, so improvement in frequency utilization efficiency and reduction in transmission delay can be expected, and the order of data arrival is changed. No problem occurs.

FIG. 4 is a diagram for explaining a specific example for mapping transmission data to a plurality of bands and transmitting the data, and collectively receiving and integrating the transmission data on the receiving side.

As shown in FIG. 4, the transmission data sequence is divided by the number of symbols proportional to the transmission rate Ri of each band to be used, and assigned to each band by serial / parallel conversion.

For example, if (5 GHz band transmission rate: 2.4 GHz band transmission rate: 920 MHz band transmission rate) = (R1: R2: R3) = (3: 2: 1), the transmission data series is divided into 6 symbols. The 5 GHz band (ch1), 2.4 GHz band (ch2), and 920 MHz band (ch3) are assigned 3 symbols, 2 symbols, and 1 symbol. It should be noted that when the transmission series is divided and assigned, it is not limited to such a case, and more generally, when m frequency bands are used, the ratio of the transmission rates of the frequency bands is set to (R1: R2). : ...: Rm) (Ratio is expressed as contracted), the transmission series is divided by (R1 + R2 + ... + Rm) x n (m, n: natural number) symbols, and (m, n: natural number) is assigned to each channel. R1 × n) symbols, (R2 × n) symbols, ..., (Rm × n) symbols may be assigned.

After such allocation, a physical header is attached to the transmission symbol for each band to form a packet, and these packets are transmitted simultaneously and in parallel at the same timing.

The number of symbols assigned to each band on the transmitting side is stored as information in this physical header or is preset as control information before transmission.

On the receiving side, synchronization and demodulation processing are performed using the physical headers on each band. The demodulated series are combined by parallel / serial conversion in the reverse process of the transmission side, and the frame is decoded.
[Transmission device configuration]
FIG. 5 is a functional block diagram for explaining the configuration of the transmission device 1000 of the present embodiment.

With reference to FIG. 5, the transmission device 1000 performs an error correction coding unit 1110 for performing an error correction coding process on a series of transmission data, and an interleave process on the data after the error correction coding. With respect to the interleaving unit 1112 to be performed, the serial / parallel conversion (hereinafter, S / P conversion) unit 1010 for performing the processing assigned to each frequency band as described in FIG. 4, and the data after the S / P conversion. Wireless frame generator 102 0.1 to 1020.3 for executing digital processing that forms wireless frames (packets) for communication by a predetermined wireless communication method, such as mapping processing and addition of physical headers for each frequency band. And, for the digital signal from the wireless frame generator 102 0.1 to 1020.3, digital analog conversion processing and modulation processing to a predetermined modulation method (for example, orthogonal modulation for a predetermined multi-value modulation method). Processing), up-conversion processing, power amplification processing, etc. are executed in the high-frequency processing unit (RF unit) 104 0.1 to 1040.3, and the antenna 1050 for transmitting the high-frequency signals of the RF unit 104 0.1 to 1040.3, respectively. .1 to 1050.3 are included. The operation of the RF unit 104 0.1 to 1040.3 is controlled based on the clock from the local oscillator 1030 provided in common with them.

Further, the transmission device 1000 includes a channel usage status observation unit 1060 for observing the usage status (vacancy status of each radio channel, etc.) of each frequency band (one or more radio channels in each frequency band), and a channel usage status. Based on the observation of the observation unit 1060, the channel usage status prediction unit 1070 that predicts the channel usage status at a predetermined timing, the processing timing of the radio frame generation unit 102 0.1 to 1020.3, and the transmission timing of the RF unit are determined. It includes an access control unit 1080 that controls and controls to simultaneously transmit radio packets in unused frequency bands and radio channels for a predetermined period at the same controlled transmission timing.

Here, the channel usage status observation unit 1060 is configured to execute the carrier sense and channel sensing described above.

Here, the access control unit 1080 selects and uses a channel that is found to be usable according to the result of carrier sensing the target band that is a candidate at the time of transmission, and is unused at the same controlled transmission timing. Wireless packets will be transmitted simultaneously in the frequency band and wireless channel.

A detailed operation example of the channel usage status prediction unit 1070 will be described later. However, the access control unit 1080 may control the transmission timing so as to use the frequency band determined to be available at the present time by directly using the observation result of the usage status observation unit 1060.

As described with reference to FIG. 4, the transmission device 1000 having such a configuration maps the data to a plurality of bands and transmits the data, and the receiving side collectively receives the plurality of bands and integrates the data.

FIG. 6 is a conceptual diagram for explaining cooperative sensing.

In order to perform efficient wireless communication, it is necessary for each wireless device to sequentially grasp the propagation status of the surroundings and the usage status of wireless resources, and to control access based on the results. However, when there are many wireless channels to be sensed, a very large-scale device is required to sense all channels with a single wireless device, which is unrealistic from the viewpoint of circuit scale and device cost. be.

According to cooperative sensing, by exchanging and sharing sensing information among multiple wireless devices, the wireless channel sensing information obtained by one wireless device performing real-time sensing while keeping the circuit scale of the wireless device small. More wireless channel sensing information can be obtained.

However, ideal sensing with cooperative sensing (“a state in which information on all observation targets is shared by all nodes” (all observation targets correspond to, for example, “all channels at all node positions”). In order to realize this, it is necessary to exchange information between all the nodes, which requires an excessive cooperation cost.

Therefore, it is necessary to reduce the information exchange to the extent that the deterioration of the frequency utilization efficiency can be sufficiently suppressed as compared with the case where the ideal sensing can be performed, and to suppress the sensing cost.

Here, in the explanation of the present embodiment, the terms are defined as follows.

“Sensing spectrum coverage” refers to a set of objects sensed by (plural) wireless communication devices.

"Ideal sensing spectrum coverage" refers to a set of all observation targets required to sufficiently minimize the deterioration of frequency utilization efficiency.

Although not particularly limited, the following situations will be described below.

The information to be exchanged does not necessarily have to be real-time information, but is a sensing result within a certain period of time. However, in each wireless communication device, the sensing itself is basically always performed.

Ideal sensing spectrum coverage is maintained by sharing information among multiple wireless communication devices in a coordinated manner.

FIG. 7 is a conceptual diagram in the case of performing cooperative sensing in BSS.

Here, "BSS (Basic Service Set)" refers to a network composed of one AP and a subordinate wireless LAN client terminal within the reach of the radio waves of the AP in the infrastructure mode of the wireless LAN. And.

The access point AP includes a wireless communication function in a wireless communication method equivalent to that of the wireless communication device STA, which will be described later, and a processor and a memory for executing determination and management of sharing of cooperative sensing. Since the processor and memory configurations are well known, the description thereof will be omitted.

With reference to FIG. 7, the protocol for exchanging information within the BSS can have the following configuration.

Sensing information is exchanged between the access point AP and the wireless communication devices STA-A to STA-F from the viewpoint of efficient information collection and development of information in the BSS.

In this case, the wireless communication devices STA-A to STA-F periodically report the sensing information to the access point AP, and the access point AP aggregates the sensing information to control the wireless communication device STA-A. ~ Expand the sensing information to STA-F.

FIG. 8 is a conceptual diagram for explaining a problem when cooperative sensing is simply performed.

In order to realize the protocol for exchanging information as described with reference to FIG. 7, the wireless communication devices STA1 to STA6 are used for all target channels of cooperative sensing (CH [a1] to CH [a3] at 5 GHz. 2.4 GHz. Then, CH [b1] to CH [b2]. At 920 MHz, CH [c1] to CH [c3]) are sensed according to their own criteria.

In that case, if the wireless communication devices STA1 to STA6 report the sensing result to the access point AP and the access point AP executes the aggregation and sharing processing of the sensing contents, for example, from the wireless communication devices STA1 to STA6. When reporting to the access point AP, the same information is reported twice, which wastes radio resources.

(Method of cooperative sensing according to this embodiment)
In the present embodiment, the following procedure is used as an algorithm for determining the cooperative device that reports the sensing information.

In order to realize the maximum sensing coverage at the minimum cooperative cost so as to minimize the number of wireless devices that acquire and report sensing information, the selection problem of the devices to be sensed is formulated based on the set theory and the set cover problem. , Solve this.

In other words, when co-sensing all of the wireless channels to be sensed, the division is determined so that the number of wireless communication devices in charge of the sensing is minimized. As a result, wasteful consumption of wireless resources can be suppressed, so that the overhead for periodical acquisition and reporting of sensing information can be suppressed as much as possible.

FIG. 9 is a conceptual diagram showing an example of a set of cooperating wireless devices.

In FIG. 9, the wireless communication devices STA-A to STA-F exist in the overlapping region of the two BSSs.

In this case, it is desirable that the wireless communication devices STA-A to STA-F capable of receiving the signal from the adjacent BSS are in charge of observing the interference source by the cooperative sensing. Further, for the wireless communication devices STA-A to STA-F, it is assumed that the sensing results are almost the same as long as they are for the same channel.

Therefore, in order to reduce the consumption of wireless resources, the access point AP determines a wireless communication device that acquires sensing information and reports to the access point AP, and as will be described later, performs a plurality of sensing of the sensing target channel. Cover by sharing with wireless communication equipment. From the shared wireless communication device, information on the sensing result for the wireless channel in charge is reported to the access point.

FIG. 10 is a diagram for explaining a flow in which the access point AP determines a wireless communication device that executes cooperative sensing.

Further, FIG. 11 is a conceptual diagram for explaining a concept of processing for determining a wireless communication device that executes cooperative sensing.

With reference to FIGS. 10 and 11, the access point AP first lists the wireless communication devices under its control that may be cooperatively sensed (S100).

Subsequently, the access point AP checks the channels that can be sensed by each device, and determines the device that can cover the most undetermined channels as the sensing device (S110).

Then, the access point AP repeats the process of step S110 until the sensing devices of all channels are determined (S120).

Explaining the process of step S110 in more detail, first, as shown in FIG. 11, each of the access point APs can be a sensing target from the wireless communication devices STA-A to STA-F that may be in charge of cooperative sensing. Information about the radio channel (target candidate radio channel) is collected (FIG. 11 (a)).

Subsequently, the access point AP first selects the terminal STA-D having the largest number of reported target candidate radio channels among the wireless communication devices STA-A to STA-F (FIGS. 11 (b) and (1)). ).

Next, the access point AP selects the wireless communication device STA-A, which is not the target candidate wireless channel of the terminal STA-D and can cover most of the channels 1 and 4 for which the sensing device is undecided (). 11 (b) and 11 (2)). When there are a plurality of wireless communication devices that cover the same number of undetermined channels, for example, one randomly selected from them can be selected.

Next, the access point AP selects the wireless communication device STA-F, which is a device that can cover the most for the channel 4 in which the sensing device is undecided, which is not the target candidate wireless channel of the terminals STA-D and STD-A. (FIGS. 11 (b) and 11 (3)).

With the above processing, all of the channels 1 to 6 to be sensed can be co-sensed by three wireless communication devices, and the ideal sensing spectrum coverage can be the target of sensing.

FIG. 12 is a sequence diagram for explaining the processing in the cooperative sensing.

Hereinafter, for the sake of simplicity, the access point is simply referred to as an AP, and the unrelated communication device under the AP is referred to as STA.

With reference to FIG. 12, first, as an initial phase, the AP queries each STA for the target candidate radio channel, and the response from the STA is returned to the AP.

In AP, the STA to perform sensing and its division are determined according to the procedure shown in FIG.

First, in Round 1 of the sensing report, polling for instructing sensing is executed by designating the STA and the channel in charge of sharing sensing from the AP. Accordingly, the STA group in charge reports the channel sensing result to the AP.

Next, the phase shifts to the aggregation and sharing phase of the sensing information, and the AP shares the channel sensing information by notifying the subordinate STA of the aggregated channel sensing information.

After that, round 2, round 3, ... Of the sensing report are repeated in the same manner until it is necessary to update the sharing of sensing.

FIG. 13 is a flowchart for explaining a process of updating the configuration of the cooperative sensing database.

When the predetermined update condition is satisfied, the access point AP executes the process of forming the cooperative sensing database by the following procedure.

Here, the "cooperative sensing database" is a database that stores a wireless communication device STA that executes cooperative sensing and a shared channel of each STA.

Further, as an update condition, for example, when it is detected that the STA newly joins the BSS or the STA leaves the BSS is an example.

With reference to FIG. 13, the access point AP first determines the target channel for sensing at that time (S200).

If a list of wireless communication devices in charge of sensing already exists for the determined target channel for sensing (Yes in S202), the access point AP sends the wireless communication device STA a list of target channels that can be sensed. Inquire (S204). On the other hand, when the target channel for sensing is not specified (No in S202), the access point AP inquires the wireless communication device STA for information on all the target channels that can be sensed in each wireless communication device (S206).

Subsequently, the access point AP determines the division of cooperative sensing based on the channel information that can be sensed by the wireless communication device STA collected in this way, and collects channel sense information for the channel to be sensed. (S208).

Next, the access point AP constitutes a subset of the channel information to be monitored by the individual wireless communication devices that responded to the inquiry (S210), and unified all the target channels based on the collection of the subset information. Configure channel sense information (S212).

By the above processing, it is possible to execute the cooperative channel sensing in response to the change of the situation in the BSS.

Further, by the configuration of the cooperative sensing described above, it is possible to realize the cooperative sensing that realizes the coverage of the channel sensing for a plurality of target wireless channels at the minimum cooperative cost.

Further, by utilizing the result of cooperative sensing and flexibly selecting or simultaneously using channels of a plurality of frequency bands, it is possible to utilize wireless resources without waste and improve frequency utilization efficiency.
[Detailed configuration of wireless communication device]
FIG. 14 is a functional block diagram for explaining an example of a more detailed configuration of the transmission device 1000.

The functional block diagram shown in FIG. 14 shows, as an example, a configuration of a transmission device that follows a wireless communication system similar to the wireless communication standard 802.11a.

That is, although the wireless communication standard 802.11a is a wireless LAN communication system in the 5 GHz band, in FIG. 14, the wireless communication system has the same configuration except that the frequency bands are different even in the 2.4 GHz and 920 MHz bands. The receiver shall be used according to.

Therefore, in each frequency band, the configuration of the preamble portion of the packet is common to a plurality of frequency bands.

However, it is not always necessary that the wireless communication methods of each frequency band have the same configuration, and even if the wireless communication methods (signal format, symbol length, subcarrier interval, etc.) are different for each frequency band. good. In this case, at least a single transmission sequence may be divided into each band and transmitted at the same time, and the configuration of the RF portion may be basically the same except that the frequency bands are different, and the configuration of the preamble portion of the packet is sufficient. (Preamble length, etc.) may be different for each of the plurality of frequency bands.

In FIG. 14, a configuration related to transmission in the 5 GHz band is illustrated as a representative. Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, the signal to be transmitted shall be OFDM (Orthogonal Frequency Division Multiplexing) modulated.

With reference to FIG. 14, the radio frame generation unit 1020.3 receives the transmission data distributed from the S / P conversion unit 1010 and executes the mapping unit 1122 for executing the mapping process and the inverse Fourier transform process. It includes an IFFT unit 1130 for adding a guard interval portion, a GI addition unit 1140 for adding a guard interval portion, and a digital-to-analog converter (DAC) 1150 for converting a digital signal into an analog signal of an I component and a Q component.

The high-frequency processing unit 1040.3 includes an orthogonal modulator 1210 for modulating the signal from the DAC 1150 into a predetermined multi-value modulation signal, an upconverter 1220 that upconverts the output of the orthogonal modulator 1210, and an output of the upconverter 1220. Includes a power amplifier 1230 for power amplification and transmission from the antenna 1050.3.

As a result, the RF section 1040.3 converts the baseband OFDM signal into a carrier band OFDM signal.

Further, the high frequency processing unit 1040.3 is based on the clock frequency conversion unit 1310 for converting the reference frequency signal from the local oscillator 1030 into the reference clock signal of the corresponding frequency band, and the reference clock from the clock frequency conversion unit 1310. Then, based on the clock generation unit 1320 that generates the clock used for the modulation processing in the orthogonal demodulator 1210 and the reference clock from the clock frequency conversion unit 1310, the clock used for the up-conversion processing in the upconverter 1220 is generated. The clock generation unit 1340 and the clock generation unit 1340 are included.

That is, the reference frequency signal from the local oscillator 1030 is used as a clock signal in the conversion of such a baseband OFDM signal to a carrier band OFDM signal. More generally, even when the wireless communication method is different, the reference frequency signal from the local oscillator 1030 is basically used as a clock signal in the conversion from the baseband signal to the carrier band signal.

As for the configuration and operation of the channel usage status observation unit 1060, the same one as described in the above-described cooperative sensing method can be used.

The channel usage status observation unit 1060 observes the usage status of each frequency band (for example, the availability status and busy probability of each radio channel) based on the sensing result of its own station and / or the sensing result of the sharing station, and predicts the channel usage status. The unit 1070 predicts the latest usage status of each frequency band, and the access control unit 1080 controls the transmission timing accordingly.
[Receiver configuration]
Hereinafter, the configuration of the receiving device used in the wireless communication system as described with reference to FIG. 4 will be described.

FIG. 15 is a functional block diagram for explaining the configuration of the receiving device 2000 of the present embodiment.

With reference to FIG. 15, the receiving device 2000 has an antenna 2011 to 2010.3 and an antenna 2010.1 for receiving signals in a plurality of frequency bands (920 MHz band, 2.4 GHz band, 5 GHz band), respectively. Commonly provided for the receiving unit 210 0.1 to 2100.3 and the receiving unit 210 0.1 to 2100.3 for executing reception processing such as down-conversion processing and demodulation / decoding processing of signals of ~ 2010.3. A local oscillator 2020 that generates a reference frequency signal, which is a clock that serves as a reference for the operation of the receiving unit 210 0.1 to 2100.3, and each sequence of signals from the receiving unit 210 0.1 to 2100.3 are used as the transmitting side. In the reverse process, it includes a parallel / serial conversion unit 2700 for combining by parallel / serial conversion.

The output of the integrated frame from the parallel / serial (P / S) conversion unit 2700 is passed to the upper layer.

The receiving device 2000 detects the frequency offset of the local oscillator 2020 from the preamble signal of the received signal, generates a signal (oscillation frequency control signal) for controlling the oscillation frequency of the local oscillator 2020, and performs carrier frequency synchronization processing. Also includes a synchronization processing unit 2600 that generates a signal (synchronization timing signal) for timing synchronization in digital signal processing from the received signal.

Upon receiving the signal from the antenna 2010.1, the receiving unit 2100.1 receives low noise amplification processing, down-conversion processing, demodulation processing for a predetermined modulation method (for example, orthogonal demodulation processing for a predetermined multi-value modulation method), and analog. High frequency processing unit (RF unit) 2400.1 for executing digital conversion processing, etc., and baseband for executing baseband processing such as demodulation / decoding processing for digital signals from RF unit 2400.1 Includes processing unit 2500.1.

The receiving unit 2100.2 also includes a high frequency processing unit (RF unit) 2400.2 and a baseband processing unit 2500.2 for performing the same processing for the corresponding frequency band. Further, the receiving unit 2100.3 also includes a high frequency processing unit (RF unit) 2400.3 and a baseband processing unit 2500.3 for performing the same processing for the corresponding frequency band.

The baseband processing unit 250 0.1 to 2500.3 and the parallel / serial (P / S) conversion unit 2700 are collectively referred to as a digital signal processing unit 2800.

FIG. 16 is a functional block diagram for explaining an example of a more detailed configuration of the receiving device 2000 shown in FIG.

The functional block diagram shown in FIG. 16 also shows, as an example, a configuration of a receiving device that follows the same wireless communication method as the wireless communication standard 802.11a.

Therefore, the configuration of the receiving device corresponds to the configuration of the transmitting device shown in FIG.

FIG. 16 also illustrates the configuration of the receiver 2100.3 in the 5 GHz band as a representative.

With reference to FIG. 16, the RF unit 2400.3 of the receiving unit 2100.3 is used to frequency-convert the outputs of the low-noise amplifier 3010 for amplifying the received signal from the antenna 2010.3 and the output of the low-noise amplifier 3010. Down converter 3020, automatic gain controller 3030 for controlling the output of the down converter 3020 so as to have a predetermined amplitude, orthogonal demodulator 3040 for demodulating a predetermined multi-valued modulated signal, and orthogonal demodulator. It includes an analog-to-digital converter (ADC) 3050 for converting the I component output and the Q component output of the 3040 into digital signals, respectively.

The RF unit 2400.3 is further based on the clock frequency conversion unit 3060 for converting the reference frequency signal from the local oscillator 2020 into the reference clock signal of the corresponding frequency band, and the reference clock from the clock frequency conversion unit 3060. Based on the clock generation unit 3070 that generates the clock used for the down-conversion process in the down converter 3020 and the reference clock from the clock frequency converter 3060, the clock used for the demodulation process in the orthogonal demodulator 3040 is generated. It includes a clock generation unit 3080.

Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, the transmitted signal is OFDM (Orthogonal Frequency Division Multiplexing) modulated. As a result, the RF section 2400.3 converts the carrier band OFDM signal into a baseband OFDM signal.

Then, the reference frequency signal from the local oscillator 2020 is used for carrier frequency synchronization in such conversion from the carrier band OFDM signal to the baseband OFDM signal. More generally, even when the wireless communication method is different, the reference frequency signal from the local oscillator 2020 is basically used for the carrier frequency synchronization in the conversion from the carrier band signal to the baseband signal.

The baseband processing unit 2500.3 receives the signal from the ADC 3050 and performs a fast Fourier transform on the GI removing unit 4010 for removing the guard interval portion and the signal from which the guard interval has been removed. It includes an FFT unit 4020 and a demapping unit 4032 for executing a demapping process on the output of the FFT unit 4020.

After performing guard interval removal, FFT processing, and demapping processing in the baseband processing unit 250 0.1 to 2500.3, after combining the signals of each frequency band with the P / S conversion unit 2700 for the received data, The deinterleave processing by the deinterleave unit 4042 and the error correction processing by the error correction unit 4040 are executed.

Here, the synchronization timing signal output from the synchronization processing unit 2600 is used for symbol timing synchronization or the like for detecting the start of the OFDM symbol.

More generally, even when the wireless communication method is different, basically, the synchronization timing signal output from the synchronization processing unit 2600 is used as the synchronization signal in the baseband processing.

With the above configuration, it is possible to efficiently execute multi-channel simultaneous sensing when communicating in parallel in a plurality of frequency bands separated from each other. Further, it is possible to map each transmission data to a plurality of frequency bands and adjust the transmission timing to perform data transmission.
(Predictive sensing: Reduction of the number of channels targeted for sensing by predicting the idle period)
In the following, a configuration will be described in which the channel usage status prediction unit 1070 predicts the probability that the channel will be in a busy state or an idle state based on the channel usage status information obtained by cooperative sensing. First, as a premise for explaining the operations of the channel usage status observation unit 1060 and the channel usage status prediction unit 1070, for the purpose of explaining the terms, a simple method for avoiding transmission collisions from each terminal in a wireless LAN is briefly described. Explain to.

In a wireless LAN, packets collide with each other unless they wait for transmission, and efficient communication cannot be established. Therefore, multiple terminals share the same line by transmitting after confirming that there are no other transmission signals. A method called "CSMA (Carrier Sense Multiple Access)" is adopted. At the time of transmission, a waiting time with randomness called "waiting time (DIFS: Distributed access Inter Frame Space)" and "contention window (CW)" is provided, and there is no other transmission signal after that. Confirm before sending. Such a method is called "CA (Collision Avoidance)".

In addition, after transmission, be sure to wait for "ACK (ACKnowledgement, arrival confirmation response)", and if ACK does not return, it is determined that a collision has occurred and re-transmission is performed. This is because in the case of wireless, it is difficult to reliably detect a collision during transmission.

In addition to this, as an access control mechanism peculiar to wireless LAN, for example, there is "RTS / CTS (Request to Send / Clear to Send)" devised as a countermeasure against hidden terminals. Here, the hidden terminal is a terminal that is out of the radio wave range from oneself but is within the radio wave range of the communication partner. Its existence cannot be known directly, but it causes interference.

Assuming that the reach of the radio wave is Lm, consider a situation in which the communication partner B (access point) of the wireless terminal A is Lm ahead and another wireless terminal C is further Lm ahead.

At this time, since the radio wave of the terminal C does not reach the terminal A, the existence of the terminal C cannot be known even if the terminal A checks whether another terminal is transmitting a signal (even if the carrier senses). It becomes a hidden terminal of terminal A. If no measures are taken, even if the terminal C is transmitting data to the access point B, the terminal A may also transmit data to the access point B. This causes a collision at the access point B, which causes a decrease in throughput.

The RTS / CTS is a mechanism in which a wireless device transmits a "RTS (transmission request)" packet before transmission, and when the receiving side receives the RTS, it responds with "CTS (receivable)". In the above example, the terminal C first transmits the RTS to the access point B. However, it is assumed that this RTS does not reach the terminal A.

After that, the access point B notifies the terminal C that it can be received by transmitting the CTS. Since this CTS also reaches the terminal A, the terminal A detects that communication is being performed in the vicinity and postpones the transmission. In the RTS / CTS packet, the scheduled occupancy period of the channel is written, and the terminal that receives this period suspends the communication. This period is called "NAV (Network Allocation Vector, transmission prohibition period)".

From the observation / measurement results for a predetermined period given from the channel usage status observation unit 1060 to the channel usage status prediction unit 1070, the usage status statistics of each radio channel calculated and predicted by the channel usage status prediction unit 1070 are as follows. There is something like.

a) Probability of becoming busy (temporal utilization rate)
b) Probability distribution of the duration of the busy and idle states c) The duration of the idle / busy state relative to the immediately preceding busy / idle state duration Occurrence probability distribution (for example, probability density function (PDF) or cumulative probability (CDF))
d) Occurrence pattern of busy state and idle state (period and duty ratio: when background traffic is periodic)
In the following, a specific example of the prediction information calculated by the channel usage status prediction unit 1070 will be described.

1) Calculation method of "probability distribution of occurrence probability of duration of idle state" The probability density function (PDF) p (τ) of the frame arrival interval τ of the wireless LAN is Pareto expressed by the following equation (1). It is known that it generally follows the (Pareto) distribution (see Reference 1 below).

Reference 1: Dashdorj Yamkhin and Youjip Won, "Modeling and analysis of wireless LAN traffic," Journal of Information Science and Engineering, vol. 25, no. 6, pp. 1783-1801, Nov. 2009.

ここで、ａは分布形状を決定する係数、τ_mは最小フレーム到来間隔である。

Here, a is a coefficient that determines the distribution shape, and τ _m is the minimum frame arrival interval.

Further, when a and τ _m are given, the mean μ and the variance σ ² of τ are given by the following equations (2) and (3) when a> 2.

例えばIEEE 802.11 DCF規格の場合、データフレームの最小到来間隔は、上述したＤＩＦＳ＋ＣＷ以上であるため、ＣＷの最小値をＣＷｍｉｎとしたときτ_m＝ＤＩＦＳ＋ＣＷｍｉｎと設定する。アイドル（idle） 状態の継続時間をフレーム到来間隔とし、チャネルセンシング結果からμやσ²を計測すれば、上の式を用いて、チャネル利用状況予測部１０７０は、ａの値を推定できる。

For example, in the case of the IEEE 802.11 DCF standard, since the minimum arrival interval of data frames is greater than or equal to DIFS + CW described above, τ _m = DIFS + CWmin is set when the minimum value of CW is CWmin. If the duration of the idle state is used as the frame arrival interval and μ and σ ² are measured from the channel sensing results, the channel usage prediction unit 1070 can estimate the value of a using the above equation.

Then, if the value of a is obtained, the channel usage status prediction unit 1070 obtains the occurrence probability distribution represented by the following equation as the probability C (τ) that the idle state continues for τ time or more.

使用予定の無線チャネルが アイドル（idle）状態となった場合、その時点からt後まで アイドル（idle）状態が継続する確率は、Ｃ（τ）から求めることができる。

When the wireless channel to be used becomes an idle state, the probability that the idle state continues from that point to after t can be obtained from C (τ).

2) As a result of sensing, if the idle duration and the busy duration are almost the same each time, and the channel usage prediction unit 1070 determines that the traffic is periodic, the idle (idle) duration and the busy (busy) duration are approximately the same each time. As the occurrence probability distribution of the duration of the idle state, for example, the idle (idle) from the start of the idle state to the average value (may be the median value or the minimum value) of the duration of the idle state. ) It may be a step function in which the continuation probability is 100% and thereafter it is 0%.

3) On the other hand, when the radio channel to be used is in a busy state (for example, the current state of the 5 GHz band in FIG. 7 described later), the frame described in the physical header of the incoming packet (frame). By decoding the length and the NAV value described in the MAC frame, the channel usage status prediction unit 1070 can acquire the duration of the busy state and predict the duration of the busy state.

With the wireless communication device STA and access point AP described above and the configuration of the cooperative sensing executed by them, it is possible to realize the cooperative sensing that realizes the coverage of the channel sensing for a plurality of target wireless channels at the minimum cooperative cost. be.

Further, by utilizing the result of cooperative sensing and flexibly selecting or simultaneously using channels of a plurality of frequency bands, it is possible to utilize wireless resources without waste and improve frequency utilization efficiency.

The embodiments disclosed this time are examples of configurations for concretely implementing the present invention, and do not limit the technical scope of the present invention. The technical scope of the present invention is indicated by the scope of claims, not the description of the embodiment, and includes modifications within the scope of the wording of the claims and the scope of equal meaning. Is intended.

1000 transmitter, 1010 S / P converter, 1016, 102 0.1 to 1020.3 radio frame generator, 1030 local oscillator, 104 0.1 to 1040.3 RF unit, 105 0.1 to 1050.3 antenna, 1060 channels Usage observation unit, 1070 channel usage prediction unit, 1080 access control unit, 1110 error correction coding unit, 1112 interleaving unit, 2000 receiver, 2011.10.2010.3 antenna, 2020 local oscillator, 2100.1-2100 .3 Reception unit, 240 0.1 to 2400.3 RF unit, 250 0.1 to 2500.3 base band processing unit, 2600 synchronization processing unit, 2700 P / S conversion unit, 2800 digital signal processing unit.

Claims (5)

It is a wireless communication system for transmitting signals by using a plurality of wireless channels that perform random access control in each of a plurality of frequency bands separated from each other.
With multiple first wireless communication devices,
Equipped with a second wireless communication device
The second wireless communication device is
A sharing determination means for specifying a radio channel to which the first wireless communication device shares a channel sense, based on information on applicable radio channels that can be channel-sensable from each of the plurality of first wireless communication devices.
It is provided with a notification means for notifying the first wireless communication device of the determined wireless channel to be shared.
The notification means notifies each of the plurality of first wireless communication devices of the result of integrating the channel sensing information from the plurality of first wireless communication devices .
The sharing determination means determines the sharing so that the number of the first wireless communication devices in charge of channel sensing is minimized when all of the plurality of wireless channels are shared and sensed. .. Each of the first wireless communication devices is
A digital signal processing unit for dividing transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands and generating a transmission packet for each of the plurality of frequency bands.
A plurality of high-frequency signal processing units provided for each of the frequency bands and for converting the digital signal into a corresponding high-frequency signal for each of the frequency bands.
A channel usage status observing unit that executes channel sensing for observing the usage status of the notified target radio channel among the plurality of radio channels in the plurality of frequency bands.
A channel usage information transmission unit for transmitting the result of the channel sensing, and
A channel usage information receiver that receives channel sensing information that is the result of channel sensing in other wireless communication devices,
Based on the channel sensing information from the channel usage information receiving unit, the access control unit that starts transmitting each of the partial data as packets for each of the plurality of frequency bands at the same timing from the high frequency processing unit. The wireless communication system according to claim 1, which includes. The wireless communication according to claim 1 or 2 , wherein the sharing determination means updates the sharing of channel sensing when it is determined that a predetermined condition is satisfied and the status of devices participating in the wireless communication system has changed. system. In a wireless communication system composed of an access point and a plurality of wireless communication devices, a radio for transmitting a signal using a plurality of wireless channels that perform random access control in each of a plurality of frequency bands separated from each other. It ’s a communication method,
The access point includes a sharing determination step of identifying a wireless channel to which the wireless communication device shares a channel sense based on information on a targetable wireless channel that can be channel-sensable from each of the plurality of wireless communication devices. ,
In the sharing determination step, when the access point shares and senses all of the plurality of wireless channels, the sharing is determined so that the number of the first wireless communication devices in charge of channel sensing is minimized. Including steps to
A notification step in which the access point notifies the wireless communication device of a determined wireless channel to be shared.
A channel usage status observation step in which each wireless communication device executes channel sensing for observing the usage status of a designated target wireless channel among the plurality of wireless channels in the plurality of frequency bands.
Each of the wireless communication devices has a channel usage information transmission step for transmitting the result of the channel sensing, and
A wireless communication method comprising a notification step in which the access point notifies each of the plurality of wireless communication devices of the result of integrating channel sensing information from the plurality of wireless communication devices. A channel usage information receiving step in which each wireless communication device receives channel sensing information that is the result of channel sensing in another wireless communication device, and
Each wireless communication device divides transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands, generates a transmission packet for each of the frequency bands, and converts the digital signal into the corresponding frequency. The claim includes an access control step of converting into a high frequency signal for each band and starting transmission of each of the partial data as packets for each of the plurality of frequency bands at the same timing based on the channel sensing information. 4. The wireless communication method according to 4.

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