JP2011259200A - Radio apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio apparatus capable of completely detecting radio waves of a radio system sharing frequency bands.SOLUTION: The radio apparatus, belonging to a second radio system which is different from a first radio system and whose frequency band to be used is overlapped with that of the first radio system, includes: a transmission part that transmits a radio wave of the frequency band; a detection part that detects a radio wave of the first radio system in a predetermined detection period at predetermined detection timing; a transmission control part that stops transmission of the transmission part according to detection timing and detection period of the detection part and stops emission of a radio wave of the transmission part when the detection part detects a radio wave of the first radio system; and a synchronization part that synchronizes at least one of a detection period and a detection timing of the detection part with another radio device belonging to the second radio system.

Description

  The present invention relates to a radio apparatus that prevents interference in a radio system sharing a frequency band in advance.

  In the radio wave related industry, the development of a system that uses TVWS (TV White Space) is underway. In order to realize the TVWS communication, it is necessary to modify existing wireless communication systems so that the operation of these systems conforms to radio wave-related laws and regulations.

  The IEEE 802.11 working group has been working on TVWS technology. A task group called 802.11af has been active since 2009 and is working on standardization to enable 802.11 networks to operate in the TVWS frequency band. The planning policy of this task group is to reuse the existing mechanisms defined in the 802.11 standard family and add the operational procedures necessary to conform to the rules.

  The IEEE 802.11 2007 [2] standard, which is the basis of the IEEE 802.11 standard family, sets a quiet period (quiet period) to stop radio wave emission in order to detect high-priority primary users (for example, TV broadcast stations) using TVWS. Defines the procedure to generate. In this standard, a WLAN (Wireless LAN) access point (AP) can initiate a procedure by sending a beacon or probe frame containing a quiet period element. The quiet period elements represent the quiet period offset, frequency, and duration of the quiet period for the beacon. Since the device that has received the beacon or the probe frame stops transmission during the specified quiet period, the signal from the primary user can be easily detected.

  However, there are major problems with this mechanism. Since the coverage of a WLAN system is usually on the order of a few hundred meters, a plurality of WLAN systems can exist in close proximity. Also, because these WLANs operate under the control of individual access points, the quiet periods generated by different WLANs may not match each other. As a result, other WLANs in the vicinity can still transmit even during the WLAN quiet period, interfering with the primary user detection.

  Furthermore, such non-synchronized operations do not satisfy FCC rules regarding detection timing. According to the FCC rules, when a network starts operation, it is necessary to detect the channel at least once for 30 seconds. Also, it is necessary to detect the channel at least once for 60 seconds during communication. If the detection operation is performed at regular intervals, quiet periods that are not synchronized will cause interference to individual 802.11 networks.

FCC, “Second report and order and memorandum opinion and order,” no. FCC 08-260, Nov. 2008. IEEE Std 802.11TM-2007

  As described above, the conventional radio apparatus has a problem that it can interfere with radio wave detection of a radio system sharing a frequency band (particularly, a radio system having a higher priority than the self). The present invention has been made to solve such a problem, and an object thereof is to provide a wireless device capable of reliably detecting radio waves of a wireless system sharing a frequency band.

  In order to solve the above-described problem, a wireless device according to an embodiment of the present invention is a wireless device belonging to a second wireless system different from the first wireless system in which a frequency band to be used overlaps with the first wireless system. In accordance with a transmission unit that transmits radio waves in the frequency band, a predetermined detection period at a predetermined detection timing, a detection unit that detects radio waves of the first wireless system, and a detection timing and a detection period of the detection unit A transmission control unit for stopping transmission of the transmission unit and stopping emission of radio waves of the transmission unit when the detection unit detects radio waves of the first wireless system, and another wireless device belonging to the second wireless system And a synchronization unit that synchronizes at least one of the detection period and the detection timing of the detection unit.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless apparatus which can detect reliably the electromagnetic wave of the radio | wireless system which shares a frequency band can be provided.

It is a block diagram which shows the radio | wireless apparatus which concerns on embodiment, and its operating environment. It is a block diagram which shows the function structure of the synchronizer of the radio | wireless apparatus which concerns on embodiment. 6 is a flowchart illustrating an operation example of the wireless device according to the embodiment. 6 is a flowchart illustrating an operation example of the wireless device according to the embodiment. It is a figure which shows an example of a quiet period synchronization request frame. It is a figure which shows an example of a quiet period synchronization request | requirement element. It is a figure which shows an example of a quiet period synchronization request | requirement element. It is a figure which shows an example of a quiet period response frame. It is a figure which shows an example of a quiet period synchronous response element.

  Hereinafter, a wireless device according to an embodiment will be described in detail with reference to the drawings. As shown in FIG. 1, the wireless device 1 of this embodiment is an access point that wirelessly communicates with the client C1, and uses a frequency band that overlaps with the primary system PS. Around the wireless device 1, there is a wireless device 2 that shares a wireless system with the wireless device 1 and communicates wirelessly with the client C2. Similarly to the wireless device 1, the wireless device 2 uses a frequency band that overlaps with the primary system PS. The primary system PS has a higher priority for using the frequency band than the wireless device 1 and the wireless device 2, and the wireless device 1 and the wireless device 2 are in a state that should not interfere with the primary system PS. . In the example described below, it is assumed that the primary system PS is a wireless system that transmits television broadcast radio waves, and the wireless device 1 and the wireless device 2 are wireless LAN systems with limited coverage.

  As illustrated in FIG. 1, the wireless device 1 includes a reception unit 12, a transmission unit 13, and an interface unit 14. The receiving unit 12 receives the radio wave transmitted from the client C1 via the antenna 11, and demodulates it by a predetermined method. The transmitter 13 modulates information for the client C1 to generate a radio signal, and transmits the radio signal to the client C1 via the antenna 11. The interface unit 14 connects the receiving unit 12 and the transmitting unit 13 to a network 15 such as the Internet.

  The receiving unit 12 receives the radio wave from the client C1 via the antenna 11, demodulates it by a predetermined method, and sends it to the network 15 via the interface unit. On the other hand, information from the network 15 is sent to the transmission unit 13 via the interface unit 14, and the transmission unit 13 converts the information into a radio signal and transmits it to the client C1 via the antenna 11. That is, the reception unit 12, the transmission unit 13, and the interface unit 14 function as a WLAN access point that accommodates the client C1. The receiving unit 12 and the transmitting unit 13 can be realized using, for example, a system compliant with the IEEE802.11 standard. Note that the frequency band used by the receiving unit 12 and the transmitting unit 13 at least partially overlaps the frequency band used by the primary system PS. The transmission control unit 16 also has a function of stopping all radio wave emission of the wireless device 1 so as not to interfere with the primary system PS.

  The wireless device 1 includes a transmission control unit 16, a detection unit 17, and a synchronization unit 18. The transmission control unit 16 controls the emission of radio waves by the transmission unit 13. The transmission control unit 16 holds quiet period information including a timing at which the transmission unit 13 should stop transmission, a stop period, and the like, and controls the transmission unit 13 based on the quiet period information.

  The detection unit 17 detects radio waves of the primary system PS. The detection unit 17 may simply detect radio wave energy of a frequency used by the primary system PS, or accurately identify and detect radio waves of the primary system PS using a demodulation unit corresponding to the primary system PS. Also good. The detection unit 17 executes the radio wave detection operation of the primary system PS for a predetermined period at a predetermined timing based on the quiet period information.

  In the present embodiment, a frequency band in which the primary system PS and the transmission unit 13 of the wireless device 1 overlap (which may be completely the same or partially overlap) is used. Since the wireless device 1 has a lower priority to use the frequency band than the primary system PS, the transmitter 13 must stop emitting radio waves when the primary system PS is emitting radio waves. Therefore, the detection unit 17 detects the presence or absence of radio wave emission of the primary system PS. However, since the frequency bands used by each overlap, it is difficult for the detection unit 17 to detect radio waves while the transmission unit 13 is transmitting to the client C1. Therefore, the transmission control unit 16 periodically stops transmission of the transmission unit 13 based on the quiet period information, and the detection unit 17 is in a period during which the transmission unit 13 stops transmission (quiet period), Detect the radio wave of the primary system PS.

  The synchronization unit 18 has a function of synchronizing the quiet period information with the wireless devices belonging to the common wireless system. That is, it has a function to synchronize the quiet period with respect to a radio apparatus having a lower priority of radio wave emission than the primary system PS.

  When the wireless device 1 is present alone, radio wave detection by the detection unit 17 can be easily realized by controlling the transmission operation of the transmission unit 13 by itself. However, since small users such as WLAN can be arranged relatively freely by individual users, there is a possibility that other wireless devices exist in the vicinity of the wireless device 1. At this time, if the transmitting unit 13 emits a radio wave when another radio apparatus attempts to detect the radio wave of the primary system PS, the other radio apparatus is disturbed. On the other hand, if the other wireless device emits a radio wave when the detection unit 17 detects the radio wave of the primary system PS, the radio wave detection by the detection unit 17 becomes difficult. The synchronization unit 18 synchronizes the quiet period with a wireless device in a range that affects the detection of radio waves by the detection unit 17 so as to reliably detect each other's radio waves.

  In the example illustrated in FIG. 1, a wireless device 2 as another wireless device is disposed in a range where radio waves of the wireless device 1 can reach. The wireless device 2 includes an antenna 21, a receiving unit 22, a transmitting unit 23, an interface unit 24, a transmission control unit 26, a detecting unit 27, and a synchronizing unit 28, and has the same configuration and functions as the wireless device 1. ing. That is, the antenna 21, the receiving unit 22, the transmitting unit 23, the interface unit 24, the transmission control unit 26, the detecting unit 27, and the synchronizing unit 28 of the wireless device 2 are the antenna 11, the receiving unit 12, the transmitting unit 13, and the interface unit, respectively. 14 corresponds to the transmission control unit 16, the detection unit 17, and the synchronization unit 18, and each has a common function. Therefore, description of each configuration of the wireless device 2 is omitted.

  Here, the synchronization unit 18 will be described in detail with reference to FIG. As shown in FIG. 2, the synchronization unit 18 of this embodiment includes a request issuing unit 181, a response issuing unit 182, a transmission / reception unit 183, a determination unit 184, a clock generation unit 185, and a quiet period generation unit 186. Note that the detection unit 28 of the wireless device 2 also has the same configuration and function as the synchronization unit 18 of the wireless device 1, and thus redundant description is omitted.

  The request issuing unit 181 is a signal generator that generates a request signal that synchronizes quiet period information with other wireless devices around the wireless device 1. The response issuing unit 182 is a signal generator that generates a response signal that returns a response indicating whether synchronization is possible or not in response to the request signal transmitted from another wireless device around the wireless device 1. The transmission / reception unit 183 is a wireless unit that transmits / receives the request signal and the response signal generated by the request issuing unit 181 and the response issuing unit 182 to / from other wireless devices around the wireless device 1.

  The transmission / reception unit 183 may use a frequency band that is common to the frequency band used by the reception unit 12 and the transmission unit 13, or may use a different frequency band. Similarly, the transmission / reception unit 183 may be realized by the reception unit 12 and the transmission unit 13.

  The determination unit 184 analyzes a response signal sent from another wireless device or a request signal sent from another wireless device in accordance with the request signal generated by the request issuing unit 181 and holds the transmission control unit 16 It is determined whether or not the self-period information should be corrected. The clock generation unit 185 is an oscillator that provides a reference signal to the transmission control unit 16 and the synchronization unit 18. The quiet period generation unit 186 generates or corrects the quiet period information that the transmission control unit 16 should hold based on a request signal and a response signal sent from another wireless device.

  The request issuing unit 181, the response issuing unit 182, the determination unit 184, the clock generation unit 185, and the quiet period generation unit 186 may be realized by a combination of a computer program and a CPU, or may be realized as hardware by a digital circuit. Also good.

  Next, with reference to FIG. 3, an operation example in which the wireless device 1 issues a request signal among the operations of the wireless device 1 of this embodiment will be described.

  The quiet period generation unit 186 generates quiet period information at a predetermined timing (step 30. Hereinafter, it is expressed as “S30”). The transmission stop timing of the transmission unit 13 (= radio wave detection timing of the detection unit 17) and the length of the quiet period included in the quiet period information (= the length at which the radio wave of the transmission unit 13 stops and the detection unit 17 detects the radio wave) Can be determined according to laws and regulations. The timing at which the quiet period generation unit 186 generates the quiet period information is determined based on the clock signal of the clock generation unit 185. The quiet period generating unit 186 sends the generated quiet period information to the request issuing unit 181.

  Upon receiving the quiet period information, the request issuing unit 181 generates a quiet period synchronization request frame, and the transmission / reception unit 183 transmits the generated quiet period synchronization request frame as a beacon (S31).

  FIG. 5 shows an example of a quiet period synchronization request frame. The quiet period synchronization request frame can be realized by using, for example, a “Public Action Frame” which is a kind of management frame defined in IEEE802.11 2007. In the example shown in FIG. 5, as a quiet period synchronization request frame, a category and action field for identification purposes, a dialog token field identifying the request or report, a protocol information element identifying the protocol layer used to transmit the frame, and A quiet period synchronization request element in which details of quiet period information are defined is included.

  FIG. 6 shows an example of a quiet period synchronization request element. The quiet period synchronization request element serves to convey quiet period information to other wireless devices. In the example shown in FIG. 6, as the silence period synchronization request element, an element ID field that identifies an information element, a field length that indicates the length of the information element, and a silence period offset that indicates an offset from the reception of the frame preamble to the start of the silence period It includes a field, a silence period field indicating the interval between two consecutive silence periods, a silence duration field indicating the duration of the silence period, and an optional sub-element field.

  Further, FIG. 7 shows an example of the sub-element field. In the example shown in FIG. 7, the sub-element field includes an SSID field indicating the SSID of the wireless device to which the request is sent, and a vendor specific field including other information necessary for operation.

  When the beacon is transmitted, the transmission / reception unit 183 waits for reception of a response signal from another wireless device (S32). When the transmission / reception unit 183 receives a response signal indicating that synchronization is agreed within a predetermined time from the beacon transmission (Yes in S32), the determination unit 184 analyzes the response signal to determine whether the synchronization is correct or not, and the quiet period is The ID of the synchronized wireless device is sent to the quiet period generation unit 186. The quiet period generation unit 186 records the ID of the wireless device in the quiet period information (S33).

  The response signal may include a correction proposal for quiet period information as a condition for the synchronization request. As a result of the determination by the determination unit 184, if the response signal includes a correction proposal for quiet period information, the quiet period generation unit 186 can align its own quiet period information with the correction proposal. Thereby, quiet period information can be matched more strictly.

  When the transmission / reception unit 183 does not receive an agreement response signal within a predetermined time from beacon transmission (No in S32), the determination unit 184 determines that synchronization has failed, and the quiet period generation unit 186 generates the quiet period information originally generated. Is used as is. When the quiet period information is corrected and the content is confirmed, the quiet period generation unit 186 transmits the quiet period information to the client C1 via the transmission unit 13. This is for controlling the stop of radio wave emission by the client C1 (S34).

  On the other hand, the quiet period generation unit 186 sends the quiet period information to the detection unit 17 and the transmission control unit 16. Based on the clock signal from the clock generation unit 185, the detection unit 17 and the transmission control unit 16 wait until the start of the quiet period (No in S35).

  When the quiet period is reached (Yes in S35), that is, when the transmission stop timing of the transmission unit 13 specified by the quiet period information is reached, the transmission control unit 16 stops the transmission of the transmission unit 13 (S36).

  When the transmission unit 13 stops transmission, the detection unit 17 starts detecting radio waves of the primary system PS (S37). When the detection unit 17 has successfully detected the radio wave of the primary system PS (Yes in S37), the transmission control unit 16 continues to stop transmission of the transmission unit 13 (S38). At the same time, beacon emission by the transmission / reception unit 183 is also stopped. That is, since the primary system PS uses the frequency band and the radio wave emission of the transmission unit 13 can interfere with the primary system PS, the radio wave emission of the entire radio apparatus 1 is stopped.

  When the detection unit 17 cannot detect the radio wave of the primary system PS (No in S37), the transmission control unit 16 gives transmission permission to the transmission unit 13 (S39). Thereby, the transmission unit 13 can transmit radio waves to the client C1 until the next quiet period comes. That is, since the primary system PS does not use the frequency band (at least there is little possibility of causing interference), the wireless device 1 can continue operation.

  Next, with reference to FIG. 4, an operation example of receiving a request signal from another wireless device 2 adjacent to the wireless device 1 among the operations of the wireless device 1 of this embodiment will be described.

  The transmission / reception unit 183 waits for reception of a quiet period synchronization request frame addressed to itself from another wireless device (S40). Specifically, the transmission / reception unit 183 checks the BSSID included in the received signal and confirms whether the request is for itself (No in S40). Note that the transmission / reception unit 183 may simply wait for reception of radio waves. In this case, the collation of BSSID is omitted.

  When the transmission / reception unit 183 receives the quiet period synchronization request frame from the wireless device 2, the determination unit 184 determines whether or not the request from the wireless device 2 can be accepted (S41). The determination of acceptance can be based on, for example, that the quiet period has already been synchronized with another wireless device other than the wireless device 2.

  If it is acceptable as a result of the determination (Yes in S41), based on the quiet period information included in the quiet period synchronization request frame received by the transmission / reception unit 183, the quiet period generation unit 186 corrects its own quiet period information ( S42). Specifically, the quiet period generation unit 186 matches the transmission stop timing and the transmission stop period of the transmission unit 3 with the received quiet period information. When the quiet period information is matched, the response issuing unit 182 generates a response signal indicating that the synchronization is accepted, and the transmitting / receiving unit 183 transmits the response signal to the wireless device 2 (S43). As described above, the correction signal may include a correction proposal as a condition for agreeing to the synchronization.

  On the other hand, if the result of the determination is that acceptance is not possible (No in S41), the determination unit 184 identifies the reason for the impossibility of acceptance and sends it to the response issuing unit 182 (S44). Upon receipt of the reason that cannot be accepted from the determination unit 184, the response issuance unit 182 generates a response signal including that the synchronization is not accepted and the reason, and the transmission / reception unit 183 transmits the response signal to the wireless device 2. (S43). In this case as well, a correction proposal may be included as a condition for accepting the response signal.

  FIG. 8 shows an example of a quiet period response frame that forms a response signal, and FIG. 9 shows an example of elements of a quiet period synchronization response element included in the quiet period response frame. As shown in FIG. 8 and FIG. 9, the response signal including the quiet period response frame includes a BSSID for identifying the wireless device 1 to respond to, a result field indicating whether the request is accepted, and a case where the request is rejected. Contains a reason code field.

  When the response signal is transmitted, the quiet period generation unit 186 sends the quiet period information to the detection unit 17 and the transmission control unit 16. Here, when the determination unit 184 accepts a request from the wireless device 2, the quiet period information is corrected according to the request from the wireless device 2. At the same time, the quiet period generation unit 186 transmits the quiet period information to the client C1 via the transmission unit 13 (S45).

  The detection unit 17 and the transmission control unit 16 wait for a quiet period based on the clock signal from the clock generation unit 185 (No in S46).

  When the quiet period is reached (Yes in S46), that is, when the transmission stop timing of the transmission unit 13 defined in the quiet period information is reached, the transmission control unit 16 stops the transmission of the transmission unit 13 (S47).

  When the transmission unit 13 stops transmission, the detection unit 17 starts detecting the radio waves of the primary system PS (S48). When the detection unit 17 detects the radio wave of the primary system PS (Yes in S48), the transmission control unit 16 continues the transmission stop of the transmission unit 13 (S49).

  When the detection unit 17 cannot detect the radio wave of the primary system PS (No in S48), the transmission control unit 16 gives transmission permission to the transmission unit 13 (S50). Thereby, the transmission unit 13 can transmit radio waves to the client C1 until the next quiet period comes.

  According to this embodiment, since the wireless device functioning as an access point that accommodates the client synchronizes the quiet period with the wireless device that is an adjacent access point, it is possible to synchronize the quiet period over a wide range with certainty.

  In addition, this invention is not limited only to the said embodiment and its operation example. For example, in the above embodiment, the primary system PS has been described as having a higher priority for using the frequency band than the wireless device 1 and the wireless device 2, but the present invention is not limited to this. The present invention can be applied regardless of the priority of the frequency band. That is, even if the primary system PS does not have a higher priority than the wireless device 1 for using the frequency band, the wireless device 1 can prevent interference with the primary system PS belonging to another wireless system in advance. This allows different radio systems to be used in a common frequency band. Similarly, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Radio | wireless apparatus, 11 ... Antenna, 12 ... Reception part, 13 ... Transmission part, 14 ... Interface part, 15 ... Network, 16 ... Transmission control part, 17 ... Detection part, 18 ... Synchronization part.

Claims (6)

A radio device belonging to a second radio system different from the first radio system, wherein a frequency band to be used overlaps with the first radio system,
A transmitter for transmitting radio waves in the frequency band;
A detection unit that detects radio waves of the first wireless system for a predetermined detection period at a predetermined detection timing; and
The transmission of the transmission unit is stopped according to the detection timing and the detection period of the detection unit, and when the detection unit detects a radio wave of the first wireless system, emission of the radio wave of the transmission unit is stopped. A transmission control unit,
A synchronization unit that synchronizes at least one of the detection period and the detection timing of the detection unit with another wireless device belonging to the second wireless system;
A wireless device comprising:   The synchronization unit includes a request transmission unit that transmits a request signal for obtaining synchronization for at least one of the detection period and the detection timing to another wireless device belonging to the second wireless system. 2. The wireless device according to claim 1, wherein The synchronization unit is
A request receiving unit that receives a request signal for synchronizing at least one of the detection period and the detection timing transmitted from another wireless device belonging to the second wireless system with the other wireless device;
A quiet period correction unit that corrects the detection timing and the detection period based on the quiet synchronization information received by the request reception unit;
2. The radio apparatus according to claim 1, wherein the transmission control unit stops transmission of the transmission unit based on a detection timing and a detection period corrected by the quiet period correction unit. The second wireless system is a wireless LAN system that accommodates client devices,
2. The wireless device according to claim 1, wherein the transmission unit transmits radio waves to the client device.   2. The wireless device according to claim 1, wherein the first wireless system is a television broadcasting system, and the second wireless system is a wireless LAN system.   6. The radio apparatus according to claim 1, wherein the second radio system has a lower priority for using the frequency band than the first radio system.

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