JP2018170692A - Radio communication system and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide collaborative sensing for realizing a coverage of channel sensing at a minimum collaborative cost when communicating using a plurality of frequency bands separated from each other. A second wireless communication apparatus STA1 to STA1 to STA1 to STA1 to STA1 to STA1 to STA1 to STA1 based on information of target radio channels capable of channel sensing from a plurality of first wireless communication apparatuses STA1 to STA6. 6 specifies a wireless channel to share the channel sense, and notifies the determined wireless channels to be shared to the first wireless communication devices STA1 to STA6. Further, the second wireless communication device AP notifies the respective first wireless communication devices STA1 to STA6 of the result of integrating the channel sensing information from the plurality of first wireless communication devices STA1 to STA6. [Selection diagram] Fig. 12

Description

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

  Wireless communication traffic is rapidly increasing due to the expansion of wireless LAN usage and the increase of devices with communication functions such as wireless surveillance cameras, etc., improving frequency utilization efficiency and accommodating more traffic on limited wireless resources. Is required.

  In a frequency band common to a plurality of systems such as an ISM (Industry-Science-Medical) band, each system determines a use frequency in an autonomous and distributed manner, so that a use frequency channel is biased.

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

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

  Although speeding up as described above has been achieved, in recent years, the demand for mobile communication traffic has increased rapidly with the spread of highly functional portable terminals such as smartphones.

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

  In addition, due to the progress of IoT (Internet Of Things) / M2M (Machine to Machine) society, there are concerns about further tightening of the above frequency band and 920 MHz band, and improving the frequency utilization efficiency of these frequency bands is an urgent issue Yes.

  Here, since the usage state of the radio resource varies depending on the time, place, frequency band, radio channel, and the like as described above, a situation in which only a part of the frequency band (or radio channel) is congested may occur.

  However, existing private wireless systems (for example, IEEE 802.11 wireless LAN) use a single frequency band or perform communication after determining one band to be used in advance. For example, IEEE 802.11n presets which of the 2.4 GHz band and the 5 GHz band is used. For this reason, there is a possibility that congestion may occur even when there is a vacant radio resource in the existing private wireless system as a whole.

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

  In the heterogeneous type, the cognitive radio recognizes a plurality of radio systems operating in the vicinity, obtains information on the usage and feasible transmission quality of each system, and connects to an appropriate radio system. In other words, the heterogeneous cognitive radio indirectly increases 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 white space) that is not used temporarily or locally in a 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 increases the utilization efficiency of frequency resources in a certain frequency band.

  As a method for solving the problem of the increase in traffic in the license-free band as described above, a plurality of wireless LAN standards (for example, 2.4 GHz band wireless LAN standard and 5 GHz band wireless LAN standard) having different usage frequency bands are used. A heterogeneous cognitive radio approach that can be 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 transmission data as appropriate and assign in advance which frequency band to transmit. As a result, depending on the degree of congestion of each frequency band, problems such as transmission delays greatly differing depending on the used frequency band and the order in which data arrives at the destination are newly generated.

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

  As described above, 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 to use at the next transmission timing, a plurality of frequencies are used. It is necessary to sense channels in a plurality of radio frequency bands in order to efficiently grasp the usage status of the band radio channels.

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

  For example, in the technologies disclosed in Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3, existing cooperative sensing assumes a single sensing object, and in order to increase its detection accuracy, a plurality of wireless devices Collect the results of sensing with.

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

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

JP 2011-111433 A JP 2013-187561 A

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 technologies disclosed in Non-Patent Document 1, Non-Patent Document 2 and Non-Patent Document 3, each wireless device has one or more sensing targets, and the sensing targets are partially between the wireless devices. There is no technology for appropriately determining a wireless device for sensing and information exchange when there is an overlap.

  In addition, the existing multi-channel sensing disclosed in Non-Patent Document 4 and Non-Patent Document 5 cannot simultaneously sense all channels, and the sensing result deteriorates in time, so that the sensing accuracy deteriorates.

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to selectively communicate frequency bands to be used in a plurality of frequency bands separated from each other. 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 a minimum cooperative cost.

  According to one aspect of the present invention, there is provided a radio communication system for transmitting a signal using a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other. A first wireless communication device; and a second wireless communication device, the second wireless communication device being based on information on a targetable wireless channel capable of channel sensing from each of the plurality of first wireless communication devices. The first wireless communication apparatus includes a sharing determination unit that identifies a wireless channel that shares the channel sense, and a notification unit that notifies the first wireless communication apparatus of the determined wireless channel to be shared. Notifies the plurality of first wireless communication devices of the result of integrating the channel sensing information from the plurality of first wireless communication devices.

  Preferably, each first wireless communication apparatus divides transmission data into a plurality of partial data corresponding to each of a plurality of frequency bands, and generates 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 from a plurality of radio channels in the plurality of frequency bands A channel usage monitoring unit that performs channel sensing for observing channel usage, a channel usage information transmitter for transmitting channel sensing results, and channel sensing that is the result of channel sensing in other wireless communication devices Based on channel sensing information from the channel usage information receiver and the channel usage information receiver for receiving information. , Each part data from the high frequency processing unit as a packet for a plurality of frequency bands, and an access control unit that starts transmission at the same timing in synchronization.

  Preferably, the sharing determination unit determines the sharing so that the number of first wireless communication apparatuses in charge of channel sensing is minimized when sharing and sensing all of the plurality of wireless channels.

  Preferably, the sharing determination unit updates the sharing of the 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.

  According to another aspect of the present invention, in a wireless communication system including an access point and a plurality of wireless communication devices, a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other are used. A wireless communication method for transmitting a signal, wherein the wireless communication device shares channel sense based on information on a targetable wireless channel from which each access point can perform channel sensing. A sharing determination step for identifying a wireless channel to be performed, a notification step in which the access point notifies the wireless communication device of the determined wireless channel to be shared, and each wireless communication device has a plurality of wireless channels in a plurality of frequency bands. Channel sensing to observe the usage status of the specified target radio channel A channel usage status observation step to be executed, a channel usage information transmission step for each wireless communication device to transmit a result of channel sensing, and an access point integrating a result of channel sensing information from a plurality of wireless communication devices. And a notification step of notifying each of the plurality of wireless communication devices.

  Preferably, each wireless communication device receives channel sensing information that is a result of channel sensing in another wireless communication device, and each wireless communication device transmits transmission data to each of a plurality of frequency bands. Is divided into a plurality of partial data, a transmission packet is generated for each frequency band, a digital signal is converted into a high-frequency signal for each corresponding frequency band, and each partial data is divided into a plurality of pieces based on channel sensing information. And an access control step for starting transmission at the same timing as packets for each frequency band.

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

  According to the present invention, it is possible to use radio resources without waste by using the results of cooperative sensing and flexibly selecting or simultaneously using channels in a plurality of frequency bands, thereby improving frequency utilization efficiency. Become.

It is a figure which shows the concept of the channel sensing in communication with an own station and a partner station. It is a conceptual diagram for demonstrating the several radio channel in the frequency band isolate | separated mutually. It is a conceptual diagram for demonstrating the structure of the radio | wireless communications system of this Embodiment. It is a figure for demonstrating the specific example for mapping and transmitting transmission data to a several zone | band, and receiving and unifying collectively by the receiving side. It is a functional block diagram for demonstrating the structure of the transmitter 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 at the time of implementing cooperative sensing simply. It is a conceptual diagram which shows the example of the group of the radio | wireless apparatus which cooperates. It is a figure for demonstrating the flow in which the access point AP determines the radio | wireless communication apparatus which performs cooperative sensing. It is a conceptual diagram for demonstrating the concept of the process which determines the radio | wireless communication apparatus which performs cooperative sensing. It is a sequence diagram for demonstrating the process in cooperative sensing. It is a flowchart for demonstrating the process which updates the structure of a cooperative sensing database. It is a functional block diagram for demonstrating the example of a more detailed structure of the transmitter 1000. FIG. It is a functional block diagram for demonstrating the structure of the receiver 2000 of this Embodiment. 3 is a functional block diagram for explaining an example of a more detailed configuration of receiving apparatus 2000. FIG.

  Hereinafter, configurations of a wireless communication system and a wireless communication apparatus according to an embodiment of the present invention will be described. In the following embodiments, components and processing steps given the same reference numerals are the same or equivalent, and the description thereof will not be repeated unless necessary.

  In the following, as an example for explaining the receiving apparatus of the present invention, a plurality of existing unlicensed bands (for example, 920 MHz band used for IoT etc., 2 used for wireless LAN, which are largely separated from each other as described above). (.4 GHz band and 5 GHz band) will be described with reference to an example of a transmission apparatus in a wireless communication system capable of performing cognitive wireless communication by sharing a frequency with an existing system.

In the following, “carrier sense” refers to sensing for detecting the presence or absence of a signal of a target radio channel and determining transmission timing by virtual carrier sense accompanied by power detection or decoding of a received signal. This means that “channel sensing” means sensing that performs communication monitoring or the like in order to grasp the usage status of the target channel in addition to sensing as carrier sense.
[Embodiment]
In the following, in order to explain the present embodiment, in order to determine when to perform the next transmission timing in the case of a configuration in which communication is performed by random access control in a plurality of frequency bands separated from each other, A configuration for performing multi-channel simultaneous channel sensing in the target band will be described.

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

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

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

  Here, when there are other communication devices 30.1 to 30.4 that use any of the channels in the usable band in the vicinity of the own station 10 or the partner station 20, these become interference sources, and the interference wave Therefore, the local station 10 communicates with the partner station 20 by detecting and using a vacant frequency band channel.

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

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

  Here, the radio communication apparatus according to the present embodiment, which will be described later, generally uses a plurality of frequency bands that are separated from each other, and is used as a reception apparatus that performs simultaneous and parallel communication at the timing synchronized with the same radio system. It is possible to apply.

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

  Referring to FIG. 3, on the assumption that the transmission side uses three frequency bands of 920 MHz band, 2.4 GHz band, and 5 GHz band, a transmission frame is assumed to use one radio channel in each band. Configure.

  In addition, although it is good also as using several channels in each frequency band, below, it demonstrates as what uses one channel for every frequency band.

  In this embodiment, radio access control having the following characteristics is performed.

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

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

  On the other hand, the receiving side collectively receives data from a plurality of bands and integrates the data.

  In such a transmission / reception, such a configuration can ensure a transmission opportunity even if there is a bias in the congestion situation between bands, so that it can be expected to improve frequency utilization efficiency and reduce transmission delay, and the data arrival order may be switched. There is no problem.

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

  As shown in FIG. 4, the number of symbols proportional to the transmission rate Ri of each band using the transmission data series is divided 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 every 6 symbols, Three symbols, two symbols, and one symbol are allocated to the 5 GHz band (ch1), 2.4 GHz band (ch2), and 920 MHz band (ch3). Note that dividing and allocating a transmission sequence is not limited to such a case, and more generally, when m frequency bands are used, the ratio of frequency band transmission rates is set to (R1: R2). : ...: Rm) (assuming that the ratio is expressed as irreducible), the transmission sequence is divided into (R1 + R2 + ... + Rm) × n (m, n: natural number) symbols. R1 × n) symbols, (R2 × n) symbols,..., (Rm × n) symbols may be assigned.

  After such assignment, for each band, a physical header is attached to the transmission symbol 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 transmission side is stored as information in this physical header, or preset as control information before transmission.

On the receiving side, synchronization and demodulation processing are performed using a physical header on each band. The demodulated sequences are combined by parallel / serial conversion in the reverse process of the transmission side, and the frame is decoded.
[Configuration of transmitter]
FIG. 5 is a functional block diagram for explaining the configuration of transmitting apparatus 1000 according to the present embodiment.

  Referring to FIG. 5, transmitting apparatus 1000 performs error correction encoding section 1110 for performing error correction encoding processing on a transmission data sequence, and interleaving processing for data after error correction encoding. For the interleaving unit 1112 to be performed, the serial / parallel conversion (hereinafter referred to as S / P conversion) unit 1010 for performing processing assigned to each frequency band as described in FIG. 4, and the data after S / P conversion, Radio frame generation units 1020.1 to 1020.3 for executing digital processing for forming a radio frame (packet) for communication by a predetermined radio communication method, such as mapping processing and addition of a physical header, for each frequency band And digital-analog conversion processing and predetermined conversion for the digital signals from the radio frame generation units 1020.1 to 1020.3, respectively. RF processing units (RF units) 1040.1 to 1040.3 for performing modulation processing (for example, orthogonal modulation processing for a predetermined multi-level modulation method), up-conversion processing, power amplification processing, and the like, and RF And antennas 1050.1 to 1050.3 for transmitting the high-frequency signals of the sections 1040.1 to 1040.3, respectively. The operations of the RF units 1040.1 to 1040.3 are controlled based on a clock from a local oscillator 1030 provided in common to these units.

  Furthermore, the transmission apparatus 1000 includes a channel usage status monitoring unit 1060 that monitors usage statuses (such as availability of each radio channel) 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 units 1020.1 to 1020.3, and the transmission timing of the RF unit And an access control unit 1080 that controls to simultaneously transmit wireless packets in unused frequency bands and wireless channels for a predetermined period at the same controlled transmission timing.

  Here, it is assumed that the channel usage state monitoring unit 1060 performs the above-described carrier sense and channel sensing.

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

  An example of detailed operation of the channel usage status prediction unit 1070 will be described later. However, the access control unit 1080 may be configured to 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 apparatus 1000 configured as described above maps and transmits data to a plurality of bands, 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 surrounding propagation state and wireless resource utilization state, and to perform access control based on the result. However, when there are many radio channels to be sensed, if a single radio device is used to sense all channels, a very large device is required, which is impractical from the viewpoint of circuit scale and device cost. is there.

  According to cooperative sensing, wireless channel sensing information obtained by real-time sensing by one wireless device while keeping the circuit size of the wireless device small by exchanging and sharing sensing information among multiple wireless devices. Sensing information of more radio channels can be obtained.

  However, the ideal sensing by cooperative sensing ("the state where all the observation target information is shared by all nodes") (all observation targets are equivalent to, for example, "all channels at all node positions") To achieve this, information exchange between all nodes is required, and excessive cooperation costs are required.

  Therefore, it is necessary to reduce the exchange of information within a range in which the deterioration of frequency utilization efficiency can be suppressed to a sufficiently small range compared to the case where ideal sensing can be performed, thereby reducing the sensing cost.

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

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

  “Ideal sensing spectrum coverage” refers to a set of all observation objects necessary to sufficiently suppress deterioration in frequency utilization efficiency.

  In addition, although not particularly limited, a case where the situation is as follows will be described below.

  The information to be exchanged does not necessarily need to be real-time information, and is a sensing result within a certain time. However, each wireless communication device basically performs sensing itself at all times.

  By sharing information among a plurality of wireless communication apparatuses in cooperation, ideal sensing spectrum coverage is maintained.

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

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

  The access point AP includes a wireless communication function in a wireless communication system equivalent to the wireless communication device STA described later, and a processor and a memory for determining and managing the sharing of cooperative sensing. Since the configuration of the processor and the memory is well known, description thereof is omitted.

  Referring to FIG. 7, the protocol for exchanging information in the BSS can be configured as follows.

  Sensing information is exchanged between the access point AP and the wireless communication apparatuses STA-A to STA-F from the viewpoint of efficient information collection and deployment 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, and the subordinate wireless communication device STA-A Develop sensing information in STA-F.

  FIG. 8 is a conceptual diagram for explaining a problem when the 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 perform all the target channels for cooperative sensing (CH [a1] to CH [a3] at 2.4 GHz, 2.4 GHz. , CH [b1] to CH [b2], and CH [c1] to CH [c3]) at 920 MHz) are sensed according to their own standards.

  In this case, when 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 repeatedly reported, so that radio resources are wasted.

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

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

  In other words, when cooperative sensing is performed on all wireless channels to be sensed, the sharing is determined so that the number of wireless communication devices in charge of the sensing is minimized. Thereby, in order to suppress useless radio resource consumption, it is possible to suppress overhead for obtaining and reporting periodic sensing information as much as possible.

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

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

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

  Therefore, in order to reduce the consumption of radio resources, the access point AP determines a radio communication apparatus that acquires sensing information and reports to the access point AP, and performs sensing of a sensing target channel as described later. Cover the wireless communication device. From the assigned wireless communication device, information on the sensing result for the assigned wireless channel is reported to the access point.

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

  FIG. 11 is a conceptual diagram for explaining the concept of processing for determining a wireless communication device that performs cooperative sensing.

  With reference to FIG. 10 and FIG. 11, the access point AP first enumerates wireless devices that are likely to perform cooperative sensing among the wireless communication devices under its control (S100).

  Subsequently, the access point AP checks the channels that can be sensed by each device, and determines a device that can cover the most channels that have not been determined by the sensing device as a sensing device (S110).

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

  The processing in step S110 will be described in more detail. First, as shown in FIG. 11, the access point AP can make each of the sensing targets from wireless communication apparatuses 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. 11A).

  Subsequently, the access point AP first selects the terminal STA-D having the largest number of reported target candidate radio channels from the radio communication apparatuses STA-A to STA-F (FIGS. 11B and 11). ).

  Next, the access point AP selects the wireless communication device STA-A that is the device that can cover the largest number of channels 1 and 4 that have not yet been determined by the sensing device, which is not the target candidate wireless channel of the terminal STA-D ( FIG. 11 (b) (2)). When there are a plurality of wireless communication apparatuses that cover the same number of undetermined channels, for example, a configuration may be adopted in which one selected at random is selected.

  Next, the access point AP selects the wireless communication device STA-F that is the device that can cover the largest number of channels 4 that have not yet been determined by the sensing device, which is not the target candidate radio channel of the terminals STA-D and STD-A. (FIGS. 11B and 3).

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

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

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

  Referring to FIG. 12, first, as an initial phase, an inquiry about the target candidate radio channel is executed from each AP to each STA, and an answer from the STA is returned to the AP.

  In the AP, STAs that perform sensing and their sharing 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 responsible channel sharing the sensing from the AP. In response, the channel sensing result is reported to the AP from the STA group in charge.

  Next, the process proceeds to a sensing information aggregation and sharing phase, and the AP shares the channel sensing information by notifying the subordinate STAs of the aggregated channel sensing information.

  Thereafter, round 2, round 3, and so on of sensing are repeated in the same manner until sensing sharing needs to be updated.

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

  When a predetermined update condition is satisfied, the access point AP executes processing for configuring the cooperative sensing database according to the following procedure.

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

  In addition, as an update condition, for example, when a new STA joins the BSS or when it is detected that the STA has left the BSS is an example.

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

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

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

  Next, the access point AP configures 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).

  Through the processing as described above, it is possible to execute cooperative channel sensing in response to a change in the situation in the BSS.

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

Further, by using the result of cooperative sensing and flexibly selecting or simultaneously using channels in a plurality of frequency bands, it is possible to use radio 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 apparatus 1000.

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

  That is, although the wireless communication standard 802.11a is a wireless LAN communication system of 5 GHz band, in FIG. 14, only the frequency band is different even in the 2.4 GHz and 920 MHz bands. It shall be assumed that a receiver conforming to is used.

  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 system of each frequency band has the same configuration, even if the wireless communication system (signal format, symbol length, subcarrier interval, etc.) differs for each frequency band. Good. In this case, at least a single transmission sequence is divided into each band and transmitted at the same time, and the configuration of the RF section is basically the same except that the frequency bands are different, and the configuration of the preamble portion of the packet (Preamble length, etc.) may be different for each of a plurality of frequency bands.

  FIG. 14 exemplarily shows a configuration related to transmission in the 5 GHz band. Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, a signal to be transmitted is subjected to OFDM (Orthogonal Frequency Division Multiplexing) modulation.

  Referring to FIG. 14, radio frame generation section 1020.3 receives transmission data distributed from S / P conversion section 1010, and executes mapping section 1122 for executing mapping processing and inverse Fourier transform processing. An IFFT unit 1130 for adding a guard interval, a GI adding unit 1140 for adding a guard interval portion, and a digital-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 a quadrature modulator 1210 for modulating a signal from the DAC 1150 into a predetermined multilevel modulation signal, an upconverter 1220 for upconverting the output of the quadrature modulator 1210, and an output of the upconverter 1220. And a power amplifier 1230 for amplifying and transmitting the signal from the antenna 1050.3.

  As a result, the baseband OFDM signal is converted into a carrier band OFDM signal by the RF unit 1040.3.

  Further, the high frequency processing unit 1040.3 is based on a clock frequency conversion unit 1310 for converting a reference frequency signal from the local oscillator 1030 into a reference clock signal in a corresponding frequency band, and a reference clock from the clock frequency conversion unit 1310. Based on the reference clock from the clock frequency conversion unit 1310 and the clock generation unit 1320 that generates the clock used for the modulation processing in the quadrature demodulator 1210, the clock used for the up-conversion processing in the up-converter 1220 is generated. Clock generation unit 1340.

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

  Note that the configuration and operation of the channel usage status observation unit 1060 can be the same as those described in the cooperative sensing method described above.

The channel usage status monitoring unit 1060 observes the usage status of each frequency band (for example, the availability of each radio channel and the busy probability) based on the sensing result of the local station and / or the sensing result of the sharing station, and predicts the channel usage status Unit 1070 predicts the most recent usage situation of each frequency band, and access control unit 1080 controls transmission timing accordingly.
[Receiver configuration]
Below, the structure of the receiver used in the radio | wireless communications system which was demonstrated in FIG. 4 is demonstrated.

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

  Referring to FIG. 15, receiving apparatus 2000 includes antennas 201. 1 to 200.3 and antennas 201. 1 for receiving signals in a plurality of frequency bands (920 MHz band, 2.4 GHz band, and 5 GHz band), respectively. Common to the receiving units 2100.1 to 2100.3 and the receiving units 2100.1 to 2100.3 for executing reception processing such as down-conversion processing, demodulation / decoding processing, etc. A local oscillator 2020 that generates a reference frequency signal that is a clock serving as a reference for the operation of the receiving units 2100.1 to 2100.3, and each sequence of signals from the receiving units 2100.1 to 2100.3 as a transmitting side. In the reverse process, a parallel / serial conversion unit 2700 for coupling by parallel / serial conversion is included.

  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 received preamble signal, generates a signal (oscillation frequency control signal) for controlling the oscillation frequency of the local oscillator 2020, and performs carrier frequency synchronization processing. And a synchronization processing unit 2600 that generates a signal (synchronization timing signal) for timing synchronization in digital signal processing from the received signal.

  Receiving section 2100.1 receives the signal from antenna 2010.1, and performs low-noise amplification processing, down-conversion processing, demodulation processing for a predetermined modulation scheme (for example, orthogonal demodulation processing for a predetermined multilevel modulation scheme), analog A high-frequency processing unit (RF unit) 2400.1 for executing digital conversion processing and the like, and a baseband for executing baseband processing such as demodulation / decoding processing on the digital signal from the RF unit 2400.1 A processing unit 2500.1 is included.

  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 similar processing for the corresponding frequency band. 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 similar processing for the corresponding frequency band.

  The baseband processing units 2500.1 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 receiving apparatus 2000 shown in FIG.

  The functional block diagram shown in FIG. 16 also shows the configuration of a receiving device according to the same wireless communication scheme as the wireless communication standard 802.11a as an example.

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

  FIG. 16 also exemplarily shows the configuration of the receiving unit 2100.3 in the 5 GHz band.

  Referring to FIG. 16, RF section 2400.3 of receiving section 2100.3 performs low-frequency amplifier 3010 for amplifying the received signal from antenna 2010.3 and frequency conversion of the output of low-noise amplifier 3010. Down converter 3020, automatic gain controller 3030 for controlling the output of down converter 3020 to have a predetermined amplitude, quadrature demodulator 3040 for demodulating a predetermined multilevel modulation signal, and quadrature demodulator And an analog-digital converter (ADC) 3050 for converting the I component output and the Q component output of 3040 into digital signals.

  The RF unit 2400.3 is further based on a clock frequency conversion unit 3060 for converting the reference frequency signal from the local oscillator 2020 into a reference clock signal in a corresponding frequency band, and a reference clock from the clock frequency conversion unit 3060. Based on the reference clock from the clock frequency conversion unit 3060 and the clock generation unit 3070 for generating the clock used for the down-conversion processing in the down converter 3020, the clock used for the demodulation processing in the quadrature demodulator 3040 is generated. A clock generation unit 3080.

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

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

  The baseband processing unit 2500.3 receives the signal from the ADC 3050, and performs a fast Fourier transform on the GI removal unit 4010 for removing the guard interval portion and the signal from which the guard interval is removed. An FFT unit 4020 and a demapping unit 4032 for executing a demapping process on the output of the FFT unit 4020 are included.

  After performing guard interval removal, FFT processing and demapping processing in the baseband processing units 2500.1 to 2500.3, after combining the signals of each frequency band by the P / S conversion unit 2700 with respect to the received data, Deinterleaving processing by the deinterleaving unit 4042 and 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 for detecting the start of an OFDM symbol.

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

With the configuration as described above, multi-channel simultaneous sensing can be efficiently performed when communication is performed in parallel in a plurality of frequency bands separated from each other. Further, it is possible to perform data transmission by mapping each transmission data to a plurality of frequency bands and adjusting the transmission timing.
(Predictive sensing: Reducing the number of sensing channels by predicting idle periods)
The following describes a configuration in which the channel usage status prediction unit 1070 predicts the probability of a channel being busy or idle 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, a general method for avoiding a transmission collision from each terminal in a wireless LAN will be briefly described for explanation of terms. Explained.

  In wireless LAN, if terminals do not wait for transmission, packets collide and efficient communication cannot be established. Therefore, multiple terminals share the same line by transmitting after confirming that there is no other transmission signal. A method called “CSMA (Carrier Sense Multiple Access)” is adopted. At the time of transmission, there should be a waiting time with randomness called “Distributed access Inter Frame Space (DIFS)” and “Contention Window (CW)”, and no other transmission signal after that. Confirm before sending. Such a method is called “CA (Collision Avoidance)”.

  Further, after transmission, it always waits for “ACK (ACKnowledgement, arrival confirmation response)”. If ACK does not return, it is determined that a collision has occurred, and retransmission is performed. This is because, in the case of radio, it is difficult to reliably detect a collision during transmission.

  In addition to this, there is “RTS / CTS (Request to Send / Clear to Send)” devised for countermeasures against hidden terminals, for example, as a wireless LAN-specific access control mechanism. Here, the hidden terminal is a terminal that is out of the radio range from itself but is in the radio range of the communication partner. Although it cannot be known directly, it causes interference.

  Assuming that the reach of radio waves 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 terminal C does not know the existence of the terminal C even if the terminal A checks whether another terminal is transmitting a signal (even if carrier sense is performed). It becomes a hidden terminal of terminal A. If no measures are taken, even if terminal C is transmitting to access point B, terminal A will also transmit data to access point B. This causes a collision at the access point B and causes a reduction in throughput.

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

  Thereafter, the access point B notifies the terminal C that it can be received by transmitting a CTS. Since this CTS also reaches the terminal A, the terminal A senses that communication is performed in the vicinity, and postpones transmission. In the RTS / CTS packet, the scheduled occupation period of the channel is written. During this period, the terminal that has received this holds the communication. This period is called “NAV (Network Allocation Vector)”.

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

a) Probability of becoming busy (time utilization rate)
b) Probability distribution of duration between busy and idle states c) Duration of idle / busy state duration relative to previous busy / idle state duration Occurrence probability distribution (for example, probability density function (PDF) or cumulative distribution function (CDF))
d) Occurrence pattern of busy and idle states (period and duty ratio: when background traffic is periodic)
Below, the specific example of the prediction information which the channel utilization condition prediction part 1070 calculates among the above is demonstrated.

1) Method of calculating “idle state duration occurrence probability distribution” The probability density function (PDF) p (τ) of the frame arrival interval τ of the wireless LAN is a Pareto represented by the following equation (1): It is known that it generally follows the (Pareto) distribution (see Document 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.

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

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.

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

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

When a radio channel scheduled to be used is in an idle state, the probability that the idle state continues from that point until t can be obtained from C (τ).

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

  3) On the other hand, when the wireless channel to be used is busy (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 value of the NAV described in the MAC frame, the channel usage state prediction unit 1070 can acquire the busy state duration and predict the busy state duration.

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

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

  Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  1000 Transmitter, 1010 S / P converter, 1016, 1020.1 to 1020.3 Radio frame generator, 1030 Local oscillator, 1040.1 to 1040.3 RF unit, 1050.1 to 1050.3 Antenna, 1060 channels Usage status monitoring unit, 1070 channel usage status prediction unit, 1080 access control unit, 1110 error correction coding unit, 1112 interleaving unit, 2000 receiving apparatus, 2011-2010.3 antenna, 2020 local oscillator, 2100.1-2100 .3 receiving unit, 2400.1 to 2400.3 RF unit, 2500.1 to 2500.3 baseband processing unit, 2600 synchronization processing unit, 2700 P / S conversion unit, 2800 digital signal processing unit.

Claims (6)

A wireless communication system for transmitting signals using a plurality of wireless channels performing random access control in each of a plurality of frequency bands separated from each other,
A plurality of first wireless communication devices;
A second wireless communication device,
The second wireless communication device is:
Sharing determination means for specifying a wireless channel shared by the first wireless communication device based on channel-capable target wireless channel information from each of the plurality of first wireless communication devices;
Notification means for notifying the first wireless communication device of the determined wireless channel to be shared,
The notification unit is a wireless communication system that notifies each of the plurality of first wireless communication devices of a result of integrating channel sensing information from the plurality of first wireless communication devices. 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 frequency bands;
A plurality of high-frequency signal processing units provided for each of the frequency bands, for converting the digital signal into a corresponding high-frequency signal for each frequency band;
In the plurality of frequency bands, a channel usage status observation unit that performs channel sensing for observing the usage status of the notified target radio channel among the plurality of radio channels;
A channel usage information transmitter for transmitting the result of the channel sensing;
A channel usage information receiving unit that receives channel sensing information that is a result of channel sensing in another wireless communication device;
Based on the channel sensing information from the channel usage information receiving unit, an access control unit that starts transmitting each partial data from the high frequency processing unit synchronously as a packet for each of the plurality of frequency bands at the same timing; The wireless communication system according to claim 1, further comprising:   The sharing determination means determines sharing so that the number of the first wireless communication devices in charge of channel sensing is minimized when sharing and sensing all of the plurality of wireless channels. Or the radio | wireless communications system of 2.   4. The wireless communication according to claim 1, wherein the sharing determination unit updates the sharing of the channel sensing when it is determined that a predetermined condition is satisfied and a status of devices participating in the wireless communication system has changed. system. Radio for transmitting signals using a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other in a radio communication system including an access point and a plurality of radio communication devices A communication method,
A sharing determination step for the wireless communication device to identify a wireless channel shared by the wireless communication device based on information on a targetable wireless channel capable of channel sensing from each of the plurality of wireless communication devices;
A notification step in which the access point notifies the wireless communication device of the determined wireless channel to be shared;
A channel usage state observing step in which each of the wireless communication devices performs channel sensing for observing a usage state of a designated target wireless channel among the plurality of wireless channels in the plurality of frequency bands;
Each wireless communication device transmits a channel usage information for transmitting the result of the channel sensing;
A notification step in which the access point notifies each of the plurality of wireless communication devices of a result of integrating channel sensing information from the plurality of wireless communication devices. Each wireless communication device receives channel sensing information that is a result of channel sensing in another wireless communication device;
Each of the wireless communication devices 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 transmits the digital signal to the corresponding frequency An access control step of converting to a high-frequency signal for each band and starting transmission of each of the partial data as a packet for each of the plurality of frequency bands synchronously at the same timing based on the channel sensing information. 5. The wireless communication method according to 5.