JP2016174318A - Digital radio transmission device and digital radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital radio transmission device capable of giving a transmission signal directivity by reducing the amount of relative movement to the earth.SOLUTION: A digital radio transmission device 2000 comprises: a linear array antenna 10 arranged along the travel direction of a movable body; a signal switching unit 20 for sequentially switching an antenna element made transmittable in the direction opposite to the travel direction of the movable body; a weighting processing unit 408 for performing weighting processing to give a transmission signal prescribed directivity; and a filter processing unit 402 for performing filter processing to suppress spurious involved in antenna switching.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a configuration of a receiving apparatus for a mobile that performs digital communication between a base station and a mobile station.

  Mobile communication terminals such as smartphones are now a daily necessities, and the amount of communication is increasing even in buses, trains, and airplanes.

  In an environment where a large number of terminals exist and involve movement, it is more efficient for each terminal to communicate via a relay device installed in the moving body than to individually communicate with a base station outside the moving body. It is preferable also from a surface. Public wireless LAN (Local Area Network) services using this method have already been provided for buses and trains. However, due to the recent increase in the number of terminals and traffic volume, a shortage of entrance lines is becoming apparent.

  In the Shinkansen, LCX (Leaky Coaxial cable) is used for the entrance line, and research to improve performance (for example, see Non-Patent Document 1) has been conducted. However, there is a concern that the capacity will be insufficient. Considering the introduction of a new entrance line, multi-level modulation such as 256QAM and 1024QAM, massive MIMO, and use of high frequencies such as millimeter waves are assumed. However, conventional equalization based on a reference signal is fast. Since the performance is significantly degraded due to channel fluctuation, new countermeasures are required.

  By the way, in the past, in order to reduce the Doppler shift that occurs with high-speed movement and reduce the fluctuation speed of fading, Patent Document 1 uses a plurality of antennas arranged along the traveling direction of the moving body. Based on a plurality of received signals received from a base station, a method for estimating a received signal at a point fixed relative to the ground and estimating or demodulating a modulation parameter using this estimated value is shown. ing.

  And in patent document 2, each of each of the moving distance estimation part which estimates the moving distance of the moving body from the position in a symbol timing from the speed of a moving body and the symbol synchronizing signal of a received signal, and the antenna row | line | column arrange | positioned linearly An interpolation calculation unit that receives the received signal from the antenna and the output of the moving distance estimation unit as input, and interpolates the received signal from the antenna array to estimate a compensated received signal at a point corresponding to the moving distance of the moving object; There is disclosed a fading compensation apparatus including a symbol synchronization estimation unit that generates a symbol synchronization signal from a compensated reception signal and a digital demodulation unit that demodulates the compensation reception signal.

JP 2002-152105 A JP 2002-51095 A

Ohashi, Akinori et al., Mitsubishi Electric Technical Review, pp.595, Nov. 2012.

  However, when trying to apply the methods of Patent Document 1 and Patent Document 2 to a wireless system that adopts an existing wireless standard, the existing wireless standard forms a frame composed of a plurality of symbols, and a propagation path in units of this frame. Therefore, there is a problem that it is difficult to equalize the propagation path. In addition, when a certain amount of time has elapsed from a specific point in time, a signal that is simultaneously received by a plurality of antennas is used to compensate for a signal that is considered fixed to the ground even when the certain antenna has elapsed. It is. For this reason, providing directivity with respect to reception by a plurality of antennas is not assumed in the first place. Furthermore, no consideration has been given to providing directivity to the transmitted radio wave during transmission.

  The present invention has been made to solve the above-described problems, and is a digital radio transmission apparatus capable of reducing the amount of movement relative to the ground and providing directivity to a transmission signal. And providing a digital wireless communication system.

  According to one aspect of the present invention, there is provided a digital radio transmission apparatus for a mobile station that performs digital radio communication, and a plurality of antennas arranged along a traveling direction of the mobile station, and transmission is possible among the plurality of antennas. An antenna switching unit for sequentially switching the antenna to be moved in a direction opposite to the moving direction of the mobile station, an encoding / modulation means for encoding and modulating data for transmission, and a predetermined transmission signal Weighting processing means for performing weighting processing for giving directivity, high-frequency processing means for converting the output of the weighting processing means into a high-frequency transmission signal after analog conversion, and spurious associated with antenna switching Filter processing means for executing a filter process for suppressing the noise, and the antenna switching unit cuts off the signal from the filter processing means. Place was supplied to the antenna.

  Preferably, the mobile station is a vehicle that moves on an orbit, and the plurality of antennas are arranged on the outer upper portion of the mobile station along the traveling direction of the mobile station.

  According to another aspect of the present invention, a digital wireless communication system for performing digital wireless communication, comprising a ground station that transmits a digital wireless signal and a mobile station that receives the digital wireless signal, A plurality of antennas arranged along the traveling direction of the mobile station, an antenna switching unit for sequentially switching a plurality of antennas that can be transmitted in a direction opposite to the moving direction of the mobile station, and for transmitting Encoding / modulating means for encoding and modulating data, weighting processing means for performing weighting processing for giving a predetermined directivity to a transmission signal, and output of the weighting processing means are converted into analog signals Later, high-frequency processing means for converting to a high-frequency transmission signal and filter processing for suppressing spurious due to antenna switching are executed. And a fit of the filtering means, the antenna switching unit supplies the signal from the filter processing unit, the switching antennas.

  According to the digital radio transmission apparatus and the digital radio communication system of the present invention, the linear array antenna composed of a plurality of antennas arranged along the traveling direction of the mobile station is used in the direction opposite to the movement of the mobile station. By sequentially switching antennas to be transmitted, it is possible to reduce the amount of movement relative to the ground and to impart directivity to the transmission signal.

It is a functional block diagram for demonstrating the structure of the digital radio | wireless communications system 1000 of embodiment. It is a conceptual diagram for demonstrating the process which switches the antenna made into a receiving state in the linear array antenna. It is a functional block diagram for demonstrating the structure of the digital radio | wireless transmitter / receiver 2000 of embodiment. FIG. 6 is a diagram showing a configuration in the case of one changeover switch 201.

  Hereinafter, a radio communication system according to an embodiment of the present invention will be described with reference to the drawings. 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 description, it is assumed that in wireless communication, one is a base station fixed on the ground and the other is a device (mobile station) that operates on a mobile body.

(Outline of wireless communication system)
FIG. 1 is a functional block diagram for explaining a configuration of a digital wireless communication system 1000 according to the embodiment.

  In the following, a train moving on a track is taken as an example of the moving body.

  In this embodiment, paying attention to the one-dimensional movement of the train 2010, a multi-element antenna is installed and the elements to be received are sequentially switched to reduce the channel fluctuation. This technique uses a linear array antenna 10 in which a large number of antenna elements 10.1 to 10.2n are arranged in a straight line along the traveling direction of a train as shown in FIG.

  A radio signal is transmitted from the ground station 200 to the train, and the antenna elements 10. i (1 ≦ i ≦ 2n) is switched by the signal switching unit 20.

  The linear array antenna 10, the signal switching unit 20, and the digital signal processing unit 50 function as an in-vehicle relay station.

  The received signal from the digital signal processing unit 50 is converted again into a wireless signal (for example, a wireless LAN signal) of a predetermined communication standard via the in-vehicle access point 60, and the terminals 510.1 to 510. sent to m.

  FIG. 2 is a conceptual diagram for explaining processing for switching the antenna to be received in the linear array antenna 10.

  As shown in FIG. 2, the receiving elements of the linear array antenna 10 are sequentially switched in reverse to the traveling direction according to the movement of the train 2010 between the times t1 to tm, and the entire length of the linear array antenna 10 is changed. In the movement within a certain range determined by the length L, the reception point is substantially fixed at the certain position P, so that the occurrence of channel fluctuation and Doppler shift is ideally eliminated. Even if the reception point is moved at such a high speed that it is difficult to ideally fix the reception point at the fixed position P, it is possible to reduce channel fluctuation and Doppler shift.

  Therefore, a greater effect can be expected as the carrier frequency increases and the movement speed increases.

  In the switching control of the signal switching unit 20, the switching period and timing consider the sampling of the A / D converter, and the symbol period and FFT window position in the case of OFDM.

  In addition, the signal switching unit 20 performs switching so as to synchronize with the frame period detected by a well-known method on the receiving side at the timing of switching from the rear end element that performs reception to the first element at the end of the frame period. Do.

  That is, the length L of the switching range in the linear array antenna is determined by the maximum speed assumed by the mobile body and the maximum frame length adopted in the communication system. Here, the switching range may be a part of the entire length of the linear array antenna 10.

  For example, if the frame length time is Tf (s) and the maximum speed of the moving body is V (m / s), at least the length L of the range in which the linear array antenna 10 is switched is L = Tf × V The above is necessary. This is, for example, about 30 cm when V = 100 km / h and Tf = 10 ms.

  Then, as described above, the received signal switching control unit 308 prevents an operation for switching from the last antenna in the moving direction to the first antenna in the frame within the length L of the range to be switched.

  Then, in order to reduce deterioration in the A / D conversion process, antenna switching timing in a period that is an integer ratio of symbol periods is employed.

  FIG. 3 is a functional block diagram for explaining the configuration of the digital wireless transmission / reception apparatus 2000 according to the embodiment.

  As described above, digital wireless transmission / reception apparatus 2000 is installed in a mobile body and receives a signal transmitted from a ground station (for example, a base station).

  Referring to FIG. 3, digital wireless transmission / reception device 2000 includes linear array antenna 10 aligned in one direction. The linear array antenna includes 2n antennas, and when it is necessary to distinguish each antenna, it is described as antennas 10.1 to 10.2n as described above.

  The digital wireless transmission / reception apparatus 2000 further detects a moving speed of the train 2010 and a signal switching unit 20 for sequentially selecting and switching the antennas in the reception state from the antennas 10.1 to 10.2n. A vehicle moving speed detection unit 22 and a digital signal processing unit 50 for performing signal processing on a signal from the signal switching unit 20 are included.

  The signal switching unit 20 includes a changeover switch 200.1 for switching the odd-numbered antennas 10.1 to 10.2n-1 of the antennas 10.1 to 10.2n, and the antennas 10.1 to 10.2n. The moving speed detected by the vehicle moving speed detector 22 is the changeover switch 200.2 for switching the even-numbered antennas 10.2 to 10.2n and the changeover operation of the changeover switches 200.1 and 200.2. and a switching control unit 200.3 that controls at a frequency according to v.

  In the following description, the antenna 10 is described as being divided into two groups, odd and even, but the number of groups to be divided (group division number) may be larger than this. In that case, a reception and transmission system may be provided in accordance with the number of group divisions. In the following description, it is assumed that there are two systems.

  The switching frequency fsw (Hz) at which the change control unit 200.3 switches the changeover switches 200.1 and 200.2 is calculated by the following equation.

Here, v (m / s) is the speed of the array antenna movement, and d (m) is the distance between the antenna elements.

  The digital signal processing unit 50 switches between reception processing and transmission processing in time division (corresponding to TDD: Time Division Duplex), a mode switching unit 24 for switching between a reception path and a transmission path, and an operation in the reception mode. The reception unit 30 includes a reception unit 30 that performs reception processing on a signal that has been received by the antennas 10.1 to 10.2n via the changeover switches 200.1 and 200.2 of the signal switching unit 20.

  The receiving unit 30 is an RF unit for performing high-frequency signal processing on the signals received by the antennas 10.1 to 10.2n via the changeover switches 200.1 and 200.2 of the signal switching unit 20, respectively. 302.1 and 302.2, and A / D conversion units 304.1 and 304.2 for performing analog-digital conversion on the signals from the RF units 302.1 and 302.2, respectively, and A / The weighting processing unit 306 performs weighting processing on signals sequentially supplied from the D conversion units 304.1 and 304.2 by well-known control, so that reception is performed from a predetermined directivity direction. The decoding / error correction unit 312 performs decoding processing and error correction processing on the signal demodulated by the unit 308, and outputs a received signal.

  On the other hand, the digital signal processing unit 50 transmits a transmission signal from the antennas 10.1 to 10.2n via the mode switching unit 24 and the switching switches 200.1 and 200.2 in the operation in the transmission mode. 40 is included.

  The transmission unit 40 encodes a transmission signal, a modulation unit 410 that modulates the encoded signal, and a predetermined weighting process (phase shift process) on the modulated signal, thereby performing a predetermined process. A weighting processing unit 408 for generating transmission directivity, D / A conversion units 406.1 and 406.2 for performing digital-analog conversion on the weighted signal, and D / A, respectively. RF signals 404.1 and 404.2 for performing high-frequency signal processing on signals sequentially supplied from conversion units 406.1 and 406.2, and outputs of RF units 404.1 and 404.2. And a filter processing unit 402 that executes filter processing. The output of the filter processing unit 402 is given to the signal switching unit 20 via the mode switching unit 24.

  Here, the changeover switches 200.1 and 200.2 can be configured to alternately switch one by one in the direction opposite to the moving direction, for example.

  In order to contrast with such operations of the changeover switches 200.1 and 200.2, a configuration in which one changeover switch and the antenna elements 10.1 to 10.2n are sequentially changed will be considered.

  FIG. 4 is a diagram showing a configuration in the case of such one changeover switch 201.

  As shown in FIG. 4, if one antenna element is simply switched sequentially with one changeover switch 201, the movement becomes a sawtooth waveform. That is, the movement between the two antenna elements cannot be performed smoothly.

  On the other hand, as shown in FIG. 3, if two antenna elements are used at the same time and this power ratio is changed for transmission, the two antenna elements are combined and apparently move between the elements. By doing so, it is possible to realize a state close to being more stationary.

  In addition, even if it is the structure which uses two antenna elements simultaneously as demonstrated above, there exists a possibility that a spurious may arise if it switches to higher speed. To cope with this, the above configuration is expanded from a state where two antenna elements are used at the same time to use more antenna elements, and at the same time, a large number of antenna elements transmit with different powers. As for the antenna, the transition from transmission off to full power transmission can be made gradual, and spurious can be reduced. At this time, the directivity can be made variable by changing the phase of each element together. When the directivity is formed, some elements close to the virtual transmission point transmit at full power.

  The filter processing unit 402 performs the following processing.

  When high-speed switching is performed by a mechanical switch or the like at the time of transmission, spurious is generated. Therefore, in OFDM or the like in which spurious to the adjacent frequency deteriorates, this technique is usually used only for reception.

  As a result, even if performance can be improved in reception, there is no effect in transmission, and in TDD, there is an error between the channel estimation result from the uplink signal in the base station and the actual downlink channel. There is.

  Therefore, transmission is performed using a plurality of antenna elements, and each element is not switched stepwise so that a large spurious is not generated, but is switched with a gradual transition by the filter processing unit 402. The apparent movement of the array antenna in the opposite direction is the same as when the reception point is switched by weight synthesis during reception. Each element is weighted so as to suppress spurious motion while moving.

  For example, in TDD, when a base station estimates a propagation path from a received signal and uses the reciprocity of the propagation path for precoding for propagation path equalization at the time of transmission and antenna directivity formation, If the transmission point and the reception point are different, it causes deterioration. Therefore, it is desirable to fix the transmission point corresponding to the reception point with the configuration described above.

  At this time, since beam forming can be performed since simultaneous reception or simultaneous transmission of a plurality of elements whose phases are controlled by the weighting processing unit 306 and the weighting processing unit 408, a gain can be obtained in a specific direction.

  In the above description, one side of the wireless communication is described as being a wireless communication device that operates on a moving body such as a train or a bus. This is because, as described above, it is necessary to reduce channel fluctuation and Doppler shift accompanying movement as one side is a moving body. However, in the technique of the present embodiment, the mobile station is not limited to such a case. For example, short-wave radio waves such as millimeter waves are also effective when a notebook PC or the like is moved one-dimensionally (for example, sliding on a desk). Therefore, wireless communication devices that can move in this way are collectively referred to as mobile stations, and the technique of the present embodiment can be applied to such mobile stations.

  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.

  10 linear array antenna, 10.1 to 10.2n antenna element, 20 signal switching unit, 22 vehicle moving speed detection unit, 24 mode switching unit, 30 receiving unit, 40 transmitting unit, 50 digital signal processing unit, 60 in-vehicle access point , 302.1 to 302.2 RF unit, 304.1 to 304.2 A / D conversion unit, 306 weighting processing unit, 308 demodulation unit, 312 decoding / error correction unit, 402 filter processing unit, 404.1 to 404 .2 RF unit, 406.1 to 406.2 D / A conversion unit, 408 weighting processing unit, 410 modulation unit, 414 encoding processing unit, 500 ground station, 510.1-510. m terminal, 1000 digital radio communication system, 2000 digital radio transceiver, 2010 train.

Claims (3)

A transmission device for a mobile station that performs digital wireless communication,
A plurality of antennas arranged along the traveling direction of the mobile station;
An antenna switching unit for sequentially switching an antenna that can transmit among the plurality of antennas in a direction opposite to a moving direction of the mobile station;
Encoding / modulating means for encoding and modulating data to be transmitted;
Weighting processing means for performing weighting processing for giving a predetermined directivity to the transmission signal;
High frequency processing means for converting the output of the weighting processing means into a high frequency transmission signal after analog conversion;
Filter processing means for executing filter processing for suppressing spurious due to switching of the antenna,
The antenna switching unit is a digital radio transmission apparatus that supplies a signal from the filter processing means to a switched antenna. The mobile station is a vehicle that moves on a track,
The digital radio transmission apparatus according to claim 1, wherein the plurality of antennas are arranged on an outer upper portion of the mobile station along a traveling direction of the mobile station. A digital wireless communication system for performing digital wireless communication,
A ground station that transmits digital radio signals;
A mobile station for receiving the digital radio signal, the mobile station,
A plurality of antennas arranged along the traveling direction of the mobile station;
An antenna switching unit for sequentially switching an antenna that can transmit among the plurality of antennas in a direction opposite to a moving direction of the mobile station;
Encoding / modulating means for encoding and modulating data to be transmitted;
Weighting processing means for performing weighting processing for giving a predetermined directivity to the transmission signal;
High frequency processing means for converting the output of the weighting processing means into a high frequency transmission signal after analog conversion;
Filter processing means for executing filter processing for suppressing spurious associated with switching of the antenna,
The antenna switching unit is a digital radio communication system that supplies a signal from the filter processing means to a switched antenna.