Wireless communication device

Abstract

To identify a radiation direction in which a mobile object is in a center of a transmitted beam while avoiding an impact on adjacent areas.SOLUTION: A wireless communication device 10 radiates, to a mobile object 20, transmission beams different in beam width in the same radiation direction while switching them. The wireless communication device 10 acquires respective radio wave intensities from the wireless communication device mobile object 20, finds an amount of change Er in radio wave intensity on the reception side due to the switching of a beam width, and determines a suitability of the radiation direction based on a difference ΔE between an amount Es of change in gain on a transmission side of an antenna gain and the amount Er of change in radio wave intensity on the reception side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wireless communication technology for emitting a transmission beam in the direction of a mobile object based on the radio wave intensity of a wireless signal transmitted from a wireless communication device, detected by the mobile object. [Background technology]

[0002] In recent years, wireless systems have been used that perform high-gain wireless communication with mobile objects by controlling the direction and shape of a transmission beam through beamforming using multiple antenna elements. A conventional technique proposed for such wireless systems involves sequentially emitting transmission beams from a wireless communication device in multiple different angular directions that are discretely set in advance, acquiring radio wave intensities from the mobile object for each of these transmission beams, and selecting the direction in which the highest radio wave intensity is obtained as the radiation direction of the transmission beam to be radiated to the mobile object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6859586 Summary of the Invention [Problem to be solved by the invention]

[0004] In such conventional technology, the relationship between the angular interval at which the transmission beam is emitted and the beam width of the transmission beam is important. For example, if the angular interval and beam width are made extremely narrow, it is possible to select a radiation direction that increases the number of radiations but provides relatively good communication quality. However, such an extremely narrow beam width causes the beam to reach adjacent areas, potentially resulting in interference with wireless communications. Furthermore, if the angular interval and beam width are widened to avoid such interference with adjacent areas, the number of radiations decreases, but the probability that a mobile object will be located in a position offset from the center of the transmission beam increases. In this case, the radio wave strength decreases as the mobile object moves away from the center of the transmission beam. Therefore, even if a direction provides higher radio wave strength than other directions, this does not necessarily mean that that direction will provide the best communication quality for wireless communications with the mobile object.

[0005] The present invention is intended to solve these problems and aims to provide a wireless communication technology that can identify the radiation direction in which a moving object is located at the center of a transmission beam while avoiding any impact on adjacent areas. [Means for solving the problem]

[0006] In order to achieve the above object, a wireless communication device according to the present invention includes a wireless I / F configured to perform wireless communication with a mobile body by transmitting and receiving wireless signals, and a control circuit configured to determine the suitability of a radiation direction of a transmission beam based on the radio wave intensity of the wireless signal transmitted from the wireless I / F, which is detected by the mobile body. The control circuit includes a radiation direction determination unit configured to switch between a first transmission beam having a first beam width and a second transmission beam having a second beam width narrower than the first beam width, and radiate them in the same radiation direction, acquire from the mobile body the first and second radio wave intensities at the time of radiation of the first and second transmission beams, respectively, calculate a receiving-side radio wave intensity change amount indicating the amount of change in the first and second radio wave intensities, and calculate a transmitting-side gain change amount indicating the amount of change in antenna gain of the first and second transmission beams, compare the difference between the transmitting-side gain change amount and the receiving-side radio wave intensity change amount with a predetermined reference threshold, and determine the suitability of the radiation direction based on the obtained result.

[0007] In addition, one configuration example of the wireless communication device according to the present invention further includes a radiation direction control unit configured such that, when wireless communication with the mobile body is established, the control circuit determines the radiation direction of the transmission beam using the radiation direction determination unit, and if the obtained determination result indicates an inappropriate state, the radiation direction determination unit repeatedly determines a new radiation direction obtained by fine-tuning the radiation direction until the determination result indicates an appropriate state. [Effects of the Invention]

[0008] According to the present invention, it is possible to identify the radiation direction in which a moving object is present at the center of a transmission beam while avoiding any influence on adjacent areas. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of a wireless communication device according to this embodiment. [Figure 2] FIG. 2 is a flowchart showing the radiation direction determination process. [Figure 3]FIG. 3 is an explanatory diagram showing an example of the radiation direction determination operation. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present invention will be described with reference to the drawings. [Wireless communication device] First, a wireless communication device 10 according to the present embodiment will be described with reference to the block diagram of FIG. This wireless communication device 10 is a general wireless communication device such as a base station or master station used in a wireless system, which performs wireless communication with a mobile object 20 by transmitting and receiving wireless signals, and is configured to control the radiation direction and shape of the transmitted beam by beamforming using multiple antenna elements.

[0011] [Principle of the present invention] The transmission beam has a certain beam width, and as the transmission beam moves away from the beam center (central axis) to the periphery, the radio wave intensity detected by the mobile object 20 gradually decreases. In addition, since the transmission beam is formed symmetrically along the horizontal plane from the beam center as viewed from the wireless communication device 10, the decrease in radio wave intensity also occurs symmetrically.

[0012] Therefore, when the mobile unit 20 is located at the beam center, if the beam width is switched to change the antenna gain of the wireless communication device 10 while the transmission power is constant, the radio wave intensity, i.e., the received power, on the mobile unit 20 side also changes by the same amount as the gain on the wireless communication device 10 side.

[0013] On the other hand, when the mobile object 20 is located at a position shifted from the beam center, changing the antenna gain of the wireless communication device 10 by switching the beam width while keeping the transmission power constant will result in a gain change in the received power on the mobile object 20 side that differs from that on the wireless communication device 10 side. This is because, even if the distance from the beam center to the mobile object 20 is the same, a transmission beam with a narrow beam width will attenuate the radio wave intensity at the mobile object 20 more than a transmission beam with a wide beam width.

[0014] The present invention focuses on the relationship between the position of the moving body 20 within such a transmission beam and the amount of change in radio wave intensity detected at the moving body 20 when the beam width is switched, and is configured to switch between transmission beams with different beam widths and radiate them in the same radiation direction from the wireless communication device 10 toward the moving body 20, obtain the radio wave intensity of each beam by wireless communication from the moving body 20 to determine the amount of change in radio wave intensity on the receiving side due to the switching of the beam width, and also determine the amount of change in antenna gain on the transmitting side, and determine whether the radiation direction is appropriate based on the difference between the amount of change in gain on the transmitting side and the amount of change in radio wave intensity on the receiving side.

[0015] This makes it possible to accurately determine whether the mobile object 20 is located at the center of the transmission beam emitted from the wireless communication device 10 when wireless communication with the mobile object 20 is established. Therefore, by fine-tuning the radiation direction of the transmission beam until it is determined that the radiation direction is appropriate, it is possible to identify the radiation direction that provides the best communication quality. Furthermore, since determining whether the radiation direction is appropriate only requires obtaining the amount of gain change on the transmitting and receiving sides due to switching of the beam width, there is no need to make the beam width of the transmission beam extremely narrow, and it is possible to avoid impacts on adjacent areas.

[0016] In the following, a configuration will be described in which the wireless communication device 10 identifies an appropriate direction in which the moving body 20 is located at the beam center and controls the radiation direction in that direction, but the present invention is not limited to this. Depending on the application to which the present invention is applied, only the configuration that identifies an appropriate direction in which the moving body 20 is located at the beam center may be applied.

[0017] [Wireless communication device details] Next, with reference to the block diagram of FIG. 1, the configuration of the wireless communication device according to this embodiment will be described in detail. The wireless communication device 10 includes a wireless I / F 11, a memory circuit 12, and a control circuit 13 as its main components.

[0018] [Wireless I / F] The wireless I / F 11 performs wireless communication with the mobile body 20 by transmitting and receiving wireless signals, and is configured to adjust the radiation direction and shape of the transmitted beam by beamforming using multiple antenna elements based on the control of the control circuit 13 when transmitting the wireless signal.

[0019] [Memory circuit] The memory circuit 12 is made up of a storage device such as a semiconductor memory, and is configured to store various processing data and programs used in the radiation direction control process of the mobile object 20 executed by the control circuit. This program is read out in advance from an external device or a recording medium (neither of which is shown) and stored in the memory circuit 12. The main processing data stored in the memory circuit 12 include a reference threshold value Eth used to determine the radiation direction and a fine adjustment angle width Θ for finely adjusting the transmission beam.

[0020] Of these, the reference threshold value Eth depends on various conditions such as the transmission power, transmitting antenna gain, and beam width of the transmission beam emitted from the wireless communication device 10 when determining the radiation direction, the receiving antenna gain of the mobile object 20, and the accuracy of determining the radiation direction, and therefore may be determined in advance by calculation processing or empirically by test operation.

[0021] Furthermore, the fine adjustment angle width Θ depends on the same conditions as the reference threshold value Eth and also on the time required to identify the appropriate radiation direction, so it may be determined in advance by calculation processing or empirically by test operation.

[0022] [Control circuit] The control circuit 13 has a CPU and its peripheral circuits, and is configured to read a program stored in the memory circuit 12 and operate in cooperation with the CPU to execute the radial direction control processing of the moving body 20 based on the processing data of the memory circuit 12. The main processing units realized by the control circuit 13 are a radiation direction determination unit 13A and a radiation direction control unit 13B.

[0023] [Radiation direction determination section] The radiation direction determination unit 13A switches between a transmission beam (first transmission beam) B1 having a beam width (first beam) W1 and a transmission beam (second transmission beam) B2 having a beam width (second beam width) W2 (W1>W2) narrower than the beam width B1, and radiates them in the same radiation direction in which the moving object 20 is present. The unit 13A acquires the radio wave intensities (first radio wave intensity, second radio wave intensity) Er1 and Er2 from the moving object 20 when radiating the transmission beams B1 and B2, respectively, and indicates the amount of change in the radio wave intensities Er1 and Er2. The circuit 12 is configured to calculate the receiving-side radio wave intensity change amount Er (=Er2-Er1) which indicates the change in the antenna gains (first antenna gain, second antenna gain) Es1, Es2 of the transmitting beams B1, B2, and to calculate the transmitting-side gain change amount Es (=Es2-Es1) which indicates the change in the antenna gains (first antenna gain, second antenna gain) Es1, Es2 of the transmitting beams B1, B2, compare the difference in change amount ΔE (=Es-Er) between the transmitting-side gain change amount Es and the receiving-side radio wave intensity change amount Er with a predetermined reference threshold value Eth stored in the memory circuit 12, and determine the suitability of the radiation direction based on the obtained results.

[0024] The radio wave intensity detected by the mobile object 20 may be transmitted to the wireless communication device 10 autonomously by the mobile object 20, or may be transmitted to the wireless communication device 10 by the mobile object 20 in response to a request from the wireless communication device 10. The wireless communication device 10 may refer to information on the radio wave intensity recorded in the mobile object 20.

[0025] [Radiation direction control section] The radiation direction control unit 13B is configured such that, when wireless communication with the moving body 20 is established, the radiation direction of the transmission beam is determined by the radiation direction determination unit 13A, and if the obtained determination result indicates an inappropriate state, the radiation direction determination unit 13A repeatedly determines a new radiation direction obtained by fine-tuning the radiation direction based on the fine-adjustment angle width Θ stored in the memory circuit 12 until the determination result indicates an appropriate state.

[0026] [Operation of this embodiment] Next, with reference to the flowchart of FIG. 2, the radiation direction control operation of the wireless communication device 10 according to the present embodiment will be described. First, the radiation direction control unit 13B selects, as the radiation direction of the transmission beam, a direction in which the mobile object 20 is present within the effective range of the transmission beam, for example, within the range of the beam half-value angle (3 dB beam width), and wireless communication with the mobile object 20 is established. This radiation direction does not require the mobile object 20 to be present at the center of the beam, so the radiation direction may be selected using, for example, the conventional technology described above.

[0027] Next, radiation direction control section 13B determines the radiation direction of the selected transmission beam using radiation direction determination section 13A. In response to this, the radiation direction determination unit 13A executes a radiation direction determination process as shown in the flowchart of FIG.

[0028] First, the radiation direction determination unit 13A emits a transmission beam B1 having a beam width W1 in the radiation direction selected by the radiation direction control unit 13B (step 100), and in response thereto, acquires the radio wave intensity Er1 detected by the mobile body 20 via wireless communication from the mobile body 20 (step 101).

[0029] Furthermore, the radiation direction determination unit 13A radiates a transmission beam B2 having a beam width W2 (W1>W2) in the same radiation direction as the transmission beam B1 (step 102), and acquires the radio wave intensity Er2 detected by the moving object 20 from the moving object 20 by wireless communication (step 103). At this time, the radiation order of the transmission beams B1 and B2 may be reversed.

[0030] Next, the radiation direction determination unit 13A calculates the receiving-side radio wave intensity change amount Er (=Er1-Er2) indicating the amount of change in the acquired radio wave intensities Er1 and Er2 (step 104), and also calculates the transmitting-side gain change amount Es indicating the amount of change in the antenna gain of the transmitting beams B1 and B2 (step 105). At this time, the antenna gains Es1 and Es2 of the transmitting beams B1 and B2 do not depend on the location of the moving object 20, so they may be calculated in advance based on parameters such as the beam widths W1 and W2, and the transmitting-side gain change amount Es (=Es2-Es1) may be calculated and stored in the memory circuit 12.

[0031] Thereafter, the radiation direction determination unit 13A calculates the change amount difference ΔE (=Es-Er) indicating the difference between the obtained receiving-side radio wave intensity change amount Er and the transmitting-side gain change amount Es (step 106), and compares it with the reference threshold value Eth stored in the memory circuit 12 (step 107). Here, if the change amount difference ΔE is less than or equal to the reference threshold value Eth (ΔE≦Eth) (step 107: YES), the radiation direction determination unit 13A determines that the radiation direction selected by the radiation direction determination unit 13A is appropriate (step 108), and terminates the series of radiation direction determination processes. On the other hand, if the change amount difference ΔE is greater than the reference threshold value Eth (ΔE>Eth) (step 107: NO), the radiation direction determination unit 13A determines that the radiation direction selected by the radiation direction determination unit 13A is inappropriate (step 109), and terminates the series of radiation direction determination processes.

[0032] The radiation direction control unit 13B acquires the judgment result of the selected radiation direction from the radiation direction judgment unit 13A, and if the judgment result indicates that the radiation direction is inappropriate, fine-adjusts the radiation direction of the transmission beam based on the fine-adjustment angle width Θ stored in the memory circuit 12, and the new radiation direction after the fine adjustment is repeatedly judged by the radiation direction judgment unit 13A. Regarding the direction in which the radiation direction is fine-adjusted, fine adjustment is repeated in either the left or right direction along the horizontal plane from the center of the beam, and if the difference in the amount of change ΔE becomes larger than the previous time, fine adjustment is performed in the opposite direction to the previous time. Furthermore, if the determination result acquired from the radiation direction determination unit 13A indicates appropriateness, the radiation direction control unit 13B ends the series of radiation direction control processes.

[0033] [Example of operation] Next, an example of the radiation direction determination operation of the wireless communication device 10 according to this embodiment will be described with reference to the explanatory diagram of Fig. 3. Here, it is assumed that the transmission power of the wireless communication device 10 is constant at 10 dBm, the beam width W2 of the transmission beam B2 is narrower than the beam width W1 of the transmission beam B1 (W1>W2), and the antenna gains Es1 and Es2 of the transmission beams B1 and B2 are 0 dBi and 10 dBi, respectively. In this case, the transmission side gain change amount Es (Es2-Es1) is 10 dBc and is independent of the position of the moving object 20.

[0034] First, as shown in Figure 3(a), in the case where the mobile body 20 is located at the center N of the transmission beams B1 and B2, when the transmission beams B1 and B2 are switched, the received power at the mobile body 20 changes by the amount of the antenna gain on the transmitting side, so the radio wave intensities Er1 and Er2 at the mobile body 20 become 10 dBm and 20 dBm, respectively, and the change in radio wave intensity on the receiving side Er (Er2 - Er1) becomes 10 dBc. Therefore, the difference in change ΔE (=Es-Er) between the amount of change in gain on the transmitting side Es (=10 dBc) and the amount of change in radio wave intensity on the receiving side Er (=10 dBc) is 0 dBc. Here, when the reference threshold value Eth is 0.5 dBc, ΔE≦Eth, so the radiation direction in this case is determined to be appropriate.

[0035] 3(b), in the case where the mobile object 20 is located at a position shifted from the center N of the transmission beams B1 and B2, when the transmission beams B1 and B2 are switched, the received power at the mobile object 20 is attenuated not only by the antenna gain on the transmitting side but also by the distance from the beam center to the mobile object 20. As a result, the radio wave intensities Er1 and Er2 at the mobile object 20 are 9 dBm and 16 dBm, respectively, and the change in radio wave intensity on the receiving side, Er (Er2 - Er1), is 7 dBc. Therefore, the difference in change ΔE (=Es-Er) between the transmission side gain change Es (=10 dBc) and the reception side radio wave strength change Er (=7 dBc) is 3 dBc. Here, when the reference threshold Eth is 0.5 dBc, ΔE>Eth, so the radiation direction in this case is determined to be inappropriate.

[0036] [Advantages of this embodiment] As described above, in this embodiment, the wireless communication device 10 switches between transmission beams with different beam widths and radiates them in the same radiation direction toward the moving object 20, acquires the radio wave strength of each beam from the moving object 20, calculates the amount of change Er in the receiving radio wave strength due to the switching of the beam width, calculates the amount of change Es in the transmitting gain of the antenna gain, and determines whether the radiation direction is appropriate based on the difference ΔE between the amount of change Es in the transmitting gain and the amount of change Er in the receiving radio wave strength.

[0037] This makes it possible to accurately determine whether the mobile object 20 is located at the center of the transmission beam emitted from the wireless communication device 10 when wireless communication with the mobile object 20 is established. Therefore, by fine-tuning the radiation direction of the transmission beam until it is determined that the radiation direction is appropriate, it is possible to identify the radiation direction that provides the best communication quality. Furthermore, since determining whether the radiation direction is appropriate only requires obtaining the amount of gain change on the transmitting and receiving sides due to switching of the beam width, there is no need to make the beam width of the transmission beam extremely narrow, and it is possible to avoid impacts on adjacent areas.

[0038] [Extended embodiment] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. [Explanation of symbols]

[0039] 10...wireless communication device, 11...wireless I / F, 12...memory circuit, 13...control circuit, 13A...radiation direction determination unit, 13B...radiation direction control unit, 20...mobile body, B1...transmission beam (first transmission beam), W1...beam width (first beam width), Er1...radio wave strength (first radio wave strength), Es1...antenna gain (first antenna gain), B2...transmission beam (second transmission beam), W2...beam width (second beam width), Er2...radio wave strength (second radio wave strength), Es2...antenna gain (second antenna gain), Es...transmission side gain change amount, Er...reception side radio wave strength change amount, ΔE...change amount difference, Eth...reference threshold, Θ...fine adjustment angle width.

Claims

1. A wireless communication device comprising: a wireless I / F configured to perform wireless communication with a mobile body by transmitting and receiving a wireless signal; and a control circuit configured to determine whether or not a radiation direction of a transmission beam is appropriate based on a radio wave intensity of the wireless signal transmitted from the wireless I / F, the radio wave intensity being detected by the mobile body; The control circuit a radiation direction determination unit configured to switch between a first transmission beam having a first beam width and a second transmission beam having a second beam width narrower than the first beam width, radiate the first and second transmission beams in the same radiation direction, acquire first and second radio wave intensities from the mobile object when radiating the first and second transmission beams, respectively, determine a receiving-side radio wave intensity change amount indicating a change in the first and second radio wave intensities, compare a difference between a transmitting-side gain change amount indicating a change in antenna gain of the first and second transmission beams and the receiving-side radio wave intensity change amount with a predetermined reference threshold, and determine whether the radiation direction is appropriate based on the obtained result; A wireless communication device comprising:

2. 2. The wireless communication device according to claim 1, The control circuit a radiation direction control unit configured to determine the radiation direction of the transmission beam by the radiation direction determination unit when wireless communication with the mobile object is established, and, if the obtained determination result indicates an inappropriate state, to repeatedly determine a new radiation direction obtained by finely adjusting the radiation direction by the radiation direction determination unit until the determination result indicates an appropriate state. A wireless communication device comprising:

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