JP2017092814A - Antenna array, base station, wireless communication system, and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an advantageous technique for providing an efficient wireless communication service to an aircraft during cruising flight.SOLUTION: An antenna array for a ground-based base station that provides wireless communication to a communication device mounted on an aircraft includes a plurality of antenna elements capable of independently setting beam directions. Each beam direction is set so that beams formed by the plurality of antenna elements are distributed at a navigational altitude of the aircraft.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an antenna array, a base station, a wireless communication system, and a communication apparatus.

  2. Description of the Related Art Conventionally, a wireless communication service for a user terminal in a sailing aircraft is provided by a satellite communication system that transmits and receives signals using geostationary orbit satellites. However, the satellite communication system is expensive, it is difficult to provide a real-time service due to a long propagation delay, and the L-band communication bandwidth used in the satellite communication system is not wide. It has drawbacks such as being difficult to provide. Therefore, Patent Documents 1 to 4 propose providing a wireless communication service to a user terminal in a traveling aircraft using a base station installed on the ground. In this wireless communication service, a multiple access scheme such as TDMA (time division multiple access) or CDMA (code division multiple access) is used, and a multicell scheme composed of a plurality of cells is used.

JP 2014-75834 A Special table 2013-511177 gazette US Patent Application Publication No. 2014/0200045 US Patent No. 7640016

  In order to efficiently provide a broadband communication service to user terminals in an aircraft, it is desired to increase the frequency utilization efficiency while simultaneously providing services to a plurality of aircraft that navigate in the service area. However, the techniques proposed in the cited documents 1 to 4 have room for improvement in frequency utilization efficiency. An object of the present invention is to provide an advantageous technique for providing an efficient wireless communication service to a traveling aircraft.

  In view of the above problems, an antenna array for a ground-mounted base station that provides wireless communication to a communication device mounted on an aircraft, and includes a plurality of antenna elements that can independently set the beam direction An antenna array is provided in which the direction of each beam is set so that the beams formed by the plurality of antenna elements are distributed at the navigation altitude of the aircraft.

  By the above means, an advantageous technique is provided for providing an efficient wireless communication service to a sailing aircraft.

The figure explaining the structural example of the radio | wireless communications system of some embodiment. The figure explaining an example of the base station of FIG. The figure explaining an example of the communication apparatus mounted in the aircraft of FIG. The figure explaining the cell divided | segmented into the sector.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Throughout the various embodiments, similar elements are given the same reference numerals, and redundant descriptions are omitted. In addition, each embodiment can be appropriately changed and combined. Some embodiments of the invention relate to wireless communication systems for aircraft. An example of a wireless communication system for aircraft will be described with reference to FIG. A wireless communication system for aircraft described below is based on a wireless communication system for mobile phones and has the same components as the wireless communication system for mobile phones.

  The wireless communication system of FIG. 1 includes, among other things, a plurality of base stations 100, a relay station 102, a control station 103, and a communication device 301 (FIG. 3) mounted on the aircraft 101. The plurality of base stations 100, the relay station 102, and the control station 103 are installed on the ground. Therefore, a system composed of these components installed on the ground may be called a ground system. The wireless communication system provides a wireless communication service to the user terminal 310 (FIG. 3) in the aircraft 101 during navigation. The terrestrial system may be a network using a dedicated infrastructure or may be an overlay network constructed on a wireless communication system for an existing mobile phone.

  Base station 100 wirelessly transmits and receives signals to and from communication device 301 mounted on aircraft 101. Each base station 100 constitutes one cell. A cell is a range in which a radio communication service is provided by one base station 100. The cell size (radius centered on the base station 100) is, for example, 100 kilometers or more. By arranging about eight base stations 100 in Japan, the wireless communication system can communicate wirelessly over the entire airspace in Japan. Service can be provided. The distance between two adjacent base stations 100 is, for example, about 100 to 200 kilometers.

  Base station 100 is connected to control station 103 via relay station 102. The control station 103 connects the base station and the external network 104 and functions as a gateway for the user terminal in the aircraft 101 to communicate with the external network 104. The external network 104 is, for example, the Internet or a core network of a communication system for mobile phones. The control station 103 bypasses and relays data and signaling from the base station 100.

  Next, a configuration example of the base station 100 will be described with reference to FIG. The base station 100 includes an antenna array 201 and a control device 202. The antenna array 201 includes a plurality of antenna elements 201a to 201d. In the example of FIG. 2, the antenna array 201 is configured by four antenna elements, but is not limited thereto, and the antenna array 201 may be configured by two, three, or five or more antenna elements. The control device 202 controls the operation of the antenna array 201. Specifically, the control device 202 uses the antenna array 201 to communicate signals with the communication device 301 mounted on the aircraft. The control device 202 controls the beam intensity and beam direction of each antenna element.

  For the sake of explanation, an xyz coordinate system 200 is set. The x direction is a direction parallel to the ground surface 105, the y direction is a direction parallel to the ground surface 105 and orthogonal to the x direction, and the z direction is a direction orthogonal to the ground surface 105. That is, the xy plane is a plane horizontal to the ground surface 105, and the z direction is a direction opposite to the gravitational direction (vertical direction). FIG. 2A shows a view of the base station 100 viewed from the y direction, and FIG. 2B shows a cross-sectional view taken along line AA of FIG.

  The antenna elements 201a to 201d form beams 203a to 203d, respectively. All of the beams 203a to 203d are two-dimensional beams. Beams 203a-203d extend in directions 204a-204d, respectively. The directions 204a to 204d are all parallel to the xz plane. Further, the elevation angles of the directions 204a to 204d are small in this order. That is, the beam 203a is upward from the beam 203b, the beam 203b is upward from the beam 203c, and the beam 203c is upward from the beam 203d. By setting the directions of the beams 203a to 203d in this way, the plurality of beams 203a to 203d are aligned in the direction of gravity and distributed to the aviation altitude of the aircraft 101. The aviation altitude of the aircraft 101 is, for example, in the range of about 8 to 12 kilometers from the ground surface 105. The directions of the beams 203a to 203d of the antenna elements 201a to 201d are set by controlling the tilt angle of the antenna elements. For example, the tilt angle of the antenna element 201d that forms the beam 203d closest to the ground surface 105 is about 0 °, and the tilt angle of the antenna element 201a that forms the beam 203a farthest from the ground surface 105 is about 40 °.

  The communication device 301 mounted on the aircraft 101 is capable of not only direct waves of the beams 203a to 203d but also the beams 203a to 203d on the ground surface 105 (especially mountains and hills) while the aircraft 101 is navigating (especially at low altitudes). ) Is also received. Therefore, the direction 204d (particularly the elevation angle) of the beam 203d closest to the ground surface 105 may be set so that the influence of the reflected wave is small. Further, since the intensity of the reflected wave differs depending on the shape of the ground surface 105, the direction 204d of the beam 203d may be set so as to be different for each base station 100. For example, when the influence of the reflected wave by the beam 203d of the first base station 100, which is greatly influenced by the reflected wave, is larger than that of the second base station 100, the elevation angle of the beam 203d of the first base station 100 is changed to the first angle. It may be larger than that of the two base stations. By setting the beam direction for each base station 100 in this manner, the coverage hole in the area can be reduced while reducing the influence of the reflected wave.

  Since the beam 203a farthest from the ground surface 105 has a large elevation angle, it may interfere with the satellite communication system. Therefore, the direction 204a of the beam 203a may be set so that interference with the satellite communication system is reduced. Further, since the relative position of the communication satellite differs for each base station 100, the direction 204d (particularly the elevation angle) of the beam 203a may be set so as to differ for each base station 100.

  Further, when the wireless communication system of the present embodiment is an overlay network constructed on an existing wireless communication system for mobile phones, the ground surface 105 is used in order to avoid interference with the wireless communication system for mobile phones. The direction 204d of the beam 203d closest to is set so that the beam 203d does not overlap the service area of the wireless communication system for mobile phones. Also in this case, the direction 204d of the beam 203d closest to the ground surface 105 may be set so as to be different for each base station 100. Thus, by setting the distribution of the beams 203a to 203d individually for each base station 100, it is possible to efficiently provide a wireless communication service.

  Each of the plurality of antenna elements 201a to 201d has a structure capable of transmitting cross-polarized waves. Therefore, the control apparatus 202 can perform cross polarization multiplexing communication (for example, orthogonal polarization multiplexing communication) using the plurality of antenna elements 201a to 201d. As a result, spatial multiplexing is realized, so that the transmission speed can be further increased.

  In some embodiments, the plurality of antenna elements 201a to 201d transmit the same signal, so that one cell is configured by the plurality of antenna elements 201a to 201d. As shown in FIG. 4, when one cell 401 is divided into a plurality of sectors 402, one sector 402 is constituted by a plurality of antenna elements 201a to 201d, and is separated by another plurality of antenna elements (not shown). One sector 402 may be configured. As shown in FIG. 4, the plurality of sectors 402 are adjacent in the horizontal direction. Since a plurality of aircrafts 101 rarely overlap in the direction of gravity, only a single sector 402 may be configured in the direction of gravity. Alternatively, the communication capacity may be further expanded by configuring the antenna array 201 so that a plurality of sectors 402 are also configured in the direction of gravity.

  Next, the communication device 301 mounted on the aircraft 101 will be described with reference to FIG. The communication device 301 communicates with the base station 100 and also communicates with a user terminal 310 (for example, a smartphone, a notebook computer, etc.) in the aircraft 101. That is, the user terminal 310 communicates with the base station 100 and the external network 104 beyond it via the communication device 301.

  The communication device 301 includes an antenna 302, a network interface 303, and a control unit 304. The antenna 302 is an antenna for communicating with the antenna array 201 of the base station 100. Antenna 302 is installed outside aircraft 101. The antenna 302 is, for example, a directional antenna or a two-dimensional beam forming antenna array. The network interface 303 is a network interface for communicating with the user terminal 310, and may be a network card for performing wired communication or an antenna for performing wireless communication, for example. The network interface 303 is installed inside the aircraft 101.

  The control unit 304 controls communication by the antenna 302 and the network interface 303. When the antenna array 201 can perform cross-polarization multiplexing communication, the control unit 304 regenerates orthogonality between the polarized waves that are broken when passing through the propagation path in order to receive cross-polarization multiplexing. A propagation path equalization device or an interference cancellation device may be included.

  In some embodiments, the communication device 301 functions as a base station for generating a cell (pico cell) of a wireless communication system (eg, LTE) for mobile phones. In this case, for the communication between the base station 100 and the communication device 301, a relay communication function or the like in LTE can be used. In this case, the base station 100 has not only a wireless communication function with the communication apparatus 301 but also a backhaul communication function that is wireless communication between base stations with the control station 103. The backhaul communication in this case is multiplexed and communicated.

  In some embodiments, the communication device 301 functions as a wireless LAN (eg, WiFi) access point. In this case, if the user terminal 310 complies with WiFi, the user terminal 310 can communicate with the communication device 301.

  The control unit 304 of the communication device 301 performs Doppler compensation and frequency conversion of the radio signal received by the antenna 302 based on flight data supplied from a navigation system such as a device mounted on the aircraft 101, for example, a cruise speed measurement device. You may implement at least one of these. When the ground system and the communication device 301 perform wireless communication using two different center frequencies, the control unit 304 performs this frequency conversion. When the same center frequency is used, the control unit 304 may not perform frequency conversion. Similarly, the control device 202 of the base station 100 receives flight data from the communication device 301, and based on this flight data, performs at least one of Doppler compensation and frequency conversion of the radio signal received by the antenna array 201. You may implement.

  Furthermore, the control station 103 of the wireless communication system according to the present embodiment may use navigation data supplied from a GPS receiver mounted on the aircraft 101 or a conventional aircraft navigation system. In this case, the control unit 304 of the communication device 301 may acquire navigation data such as a navigation route and a speed from the navigation control system in the aircraft and transmit the navigation data to the control station 103. The control station 103 may use the acquired navigation data to execute the handover of the communication device 301. Further, the control unit 304 of the communication device 301 identifies the base station 100 that is not communicating with the communication device 301 based on the reference signal and control signal from each base station 100 and the position information of the aircraft 101, You may cancel the incoming wave from this base station 100 by digital signal processing.

  The operations of the control device 202 and the control unit 304 described above may be implemented by executing a computer program by a processor such as a CPU. For example, an FPGA (Field Programmable Gate Array) or an ASIC (specific application) It may be implemented by hardware such as an integrated circuit) or DSP (digital signal processor).

100 base station, 101 aircraft, 102 relay station, 103 control station, 201 antenna array, 202 control device, 301 communication device

Claims (12)

An antenna array for a ground-based base station that provides wireless communication to a communication device mounted on an aircraft,
It has multiple antenna elements that can set the beam direction independently,
An antenna array, wherein the direction of each beam is set so that beams formed by the plurality of antenna elements are distributed at a navigation altitude of the aircraft.   The antenna array according to claim 1, wherein the direction of each beam is set so that beams from the plurality of antenna elements are arranged in a gravitational direction.   The antenna array according to claim 1, wherein each of the plurality of antenna elements is capable of transmitting cross polarization.   4. The antenna array according to claim 1, wherein beam directions of the plurality of antenna elements are set by controlling tilt angles of the plurality of antenna elements. 5. The cell configured by the base station is divided into a plurality of sectors,
The antenna array according to claim 1, wherein one sector is constituted by the plurality of antenna elements. A ground-based base station,
An antenna array according to any one of claims 1 to 5,
A control device that communicates signals with a communication device mounted on an aircraft using the antenna array;
A base station comprising:   The base station according to claim 6, wherein the control device performs at least one of Doppler compensation and frequency conversion of a signal received by the antenna array based on flight data of the aircraft. A base station according to claim 6 or 7,
A control station connecting the base station and an external network;
A wireless communication system comprising: A communication device mounted on an aircraft,
An antenna for communicating with the antenna array of any of claims 1-5;
A network interface for communicating with user terminals in the aircraft;
A control unit for controlling communication by the antenna and the network interface;
A communication apparatus comprising:   The communication device according to claim 9, wherein the control unit includes a propagation path equalization device or an interference cancellation device.   The communication device according to claim 9 or 10, wherein the control unit performs at least one of Doppler compensation and frequency conversion of a signal received by the antenna based on flight data of the aircraft.   The communication apparatus according to any one of claims 9 to 11, wherein the communication apparatus functions as an LTE base station or a WLAN access point.