JP5156676B2 - Transmitting station - Google Patents

Description

  The present invention relates to a transmitting station that transmits digital broadcast waves.

  In the digital broadcasting service, in order to deliver the same information to a large area, the service area is divided into a number of cells, and a transmitting station is arranged in each cell to transmit the same information. The transmitting station normally transmits radio waves using a horizontal omnidirectional antenna. At the cell boundary, radio waves from a plurality of transmitting stations arrive at substantially the same level, so it is essential to take measures to prevent interference with each other.

  One method for preventing mutual interference is a method of assigning different frequencies to adjacent transmitting stations. However, since a plurality of frequency channels are required, the method cannot be applied when the frequency bandwidth is limited.

  As another method, there is a method of operating at a single frequency by using Frequency Division Multiplex (OFDM). In the case of the OFDM method, when a plurality of radio waves carrying the same information transmitted from a plurality of transmitting stations arrive, if the arrival time difference is shorter than the guard interval length set by the OFDM signal, they do not interfere with each other. Can receive.

JP-A-10-28105 JP 2001-333040 A

  However, if the arrival time difference exceeds the guard interval length, they interfere with each other and cannot be received correctly. Therefore, it is necessary to set the guard interval length sufficiently long or set the cell radius sufficiently small so that the arrival time differences of radio waves arriving from a plurality of base stations do not exceed the guard interval. However, in the former case, the frequency utilization efficiency is deteriorated, and in the latter case, there is a problem that more transmitting stations need to be arranged.

  The present invention has been made in view of the above points, and can improve the frequency utilization efficiency, and can prevent interference of radio waves transmitted by each transmitting station while securing a wide service area with fewer transmitting stations. The purpose is to provide.

  The present invention is a transmitting station that transmits broadcast waves, the receiving antenna unit that receives broadcast waves transmitted by other transmitting stations, and the broadcast waves based on the broadcast waves received by the receiving antenna unit. A radio wave arrival direction estimator for estimating the direction of arrival and a broadcast wave carrying broadcast data distributed in common to each transmitting station by delaying the broadcast data by a predetermined delay time from the reception time of the broadcast data. A transmission station comprising: a transmission antenna unit that transmits in a direction 180 degrees opposite to the direction in which the broadcast wave estimated by the direction estimation unit arrives.

  The present invention further includes a delay time calculation unit that calculates the predetermined delay time, and the transmission antenna unit transmits the broadcast wave after being delayed by the delay time calculated by the delay time calculation unit. This is a characteristic transmitting station.

  In the transmission station of the present invention, the delay time calculation unit calculates the delay time based on the reception time of the broadcast data and the time when the broadcast wave transmitted from the other transmission station arrives. It is characterized by.

  In addition, the present invention is a transmission station having a plurality of directional antennas arranged in different directions.

  Moreover, the present invention is a transmission station having an array antenna.

  ADVANTAGE OF THE INVENTION According to this invention, frequency utilization efficiency can be improved and interference of the electromagnetic wave which each transmission station transmits can be prevented, ensuring a wide service area with fewer transmission stations.

It is the block diagram which showed the structure of the broadcast transmission system in one Embodiment of this invention. It is the figure which showed the time when the electromagnetic wave which the central transmitting station and the transmitting station in this embodiment transmitted arrives at the point A. It is the block diagram which showed the structure of the transmission station in this embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a broadcast transmission system of the present embodiment. In the illustrated example, the broadcast transmission system includes a broadcast center facility 1, a central transmission station 2, and transmission stations 3-1, 3-2. Further, FIG. 1 shows an area 21 in which a radio wave transmitted by the central transmitting station 2 reaches, an area 22 in which a radio wave transmitted by the transmitting station 3-1 reaches, and a point A. .

  The central transmission station 2 is assumed to be an upper transmission station (upper transmission station) of the transmission station 3-1. The transmitting station 3-2 is a subordinate transmitting station of the transmitting station 3-1. That is, a transmission station closer to the central transmission station 2 than the own transmission station is set as an upper transmission station, and a transmission station far from the central transmission station 2 from the own transmission station is set as a lower transmission station. For example, the transmission station 3-1 is a higher-order transmission station of the transmission station 3-2.

  The broadcast center facility 1 transmits broadcast data having contents to be broadcast to the central transmission station 2 and the transmission stations 3-1 and 3-2. The central transmission station 2 and the transmission stations 3-1 and 3-2 transmit the broadcast data transmitted from the broadcast center facility 1 on radio waves (broadcast waves). A range within which a radio wave transmitted by the central transmission station 2 reaches is an area 21. In addition, a range in which a radio wave transmitted by the transmitting station 3-1 is an area 22. Therefore, the radio wave transmitted by the central transmission station 2 and the radio wave transmitted by the transmission station 3-1 reach the point A. Note that the distance between the central transmission station 2 and the point A is different from the distance between the transmission station 3-1 and the point A.

  Since the distance between the central transmitting station 2 and the point A and the distance between the transmitting station 3-1 and the point A are different, the central transmitting station 2 and the transmitting station 3-1 simultaneously transmitted radio waves carrying broadcast data. In this case, at the point A, the radio wave transmitted by the central transmission station 2 interferes with the radio wave transmitted by the transmission station 3-1. In order to avoid this, the transmitting station 3-1 has a predetermined delay time from the timing at which the central transmitting station 2 transmits radio waves so that it reaches the point A at the same timing as the radio waves transmitted by the central transmitting station 2. Send radio waves with a delay.

  Further, the transmitting station 3-1 is 180 degrees away from the direction in which the radio wave transmitted by the central transmitting station 2 arrives so that the radio waves transmitted by the central transmitting station 2 and the transmitting station 3-1 simultaneously arrive at a plurality of points. Radio waves are transmitted with the maximum radiation direction of directivity directed in the opposite direction.

  Next, a specific example for preventing interference between the radio wave transmitted by the central transmission station 2 and the radio wave transmitted by the transmission station 3-1. FIG. 2 is a diagram illustrating the time at which the radio wave transmitted from the central transmission station 2 reaches the point A and the time at which the radio wave transmitted from the transmission station 3-1 reaches the point A. A radio wave 201 is a radio wave transmitted by the central transmission station 2. The radio wave 301 is a radio wave transmitted by the transmission station 3-1.

  FIG. 2A shows the time when the radio wave arrives at the point A when the central transmitting station 2 and the transmitting station 3-1 transmit radio waves at the same time. FIG. 2B shows the time when the radio wave arrives at the point A when the transmission station 3-1 transmits the radio wave after a delay of a predetermined time after the central transmission station 2 transmits the radio wave.

  In the example shown in FIG. 2A, the difference between the time when the radio wave 201 transmitted by the central transmission station 2 and the radio wave 301 transmitted by the transmission station 3-1 reach the point A is larger than the guard interval length. At the point A, the radio wave 201 and the radio wave 301 interfere with each other.

  In the example shown in FIG. 2 (b), since the transmission station 3-1 transmits the radio wave with a predetermined delay after the central transmission station 2 transmits the radio wave, the radio wave transmitted by the central transmission station 2 is transmitted. 201 and the radio wave 301 transmitted by the transmitting station 3-1 reach the point A at the same time. Thereby, at the point A, interference between the radio wave 201 and the radio wave 301 can be prevented.

  The predetermined time delayed by the transmission station 3-1 is, for example, the time until the radio wave reaches the transmission station 3-1 after the central transmission station 2 transmits the radio wave. Thereby, the transmitting station 3-1 may transmit the same radio wave as the radio wave transmitted by the central transmitting station 2 at the same time as the radio wave transmitted by the central transmitting station 2 reaches the transmitting station 3-1. it can.

  As described above, the transmission station 3-1 transmits the radio wave with a predetermined time delay after the central transmission station 2 transmits the radio wave, and the direction in which the radio wave transmitted by the central transmission station 2 has arrived. Radio waves are transmitted with the maximum radiation direction of directivity directed in the direction opposite to 180 degrees. Thereby, interference between the radio wave transmitted by the central transmission station 2 and the radio wave transmitted by the transmission station 3-1 can be prevented.

  Next, a specific operation of the transmission station 3-1 for preventing interference between the radio wave transmitted by the central transmission station 2 and the radio wave transmitted by the transmission station 3-1.

  FIG. 3 is a configuration diagram showing the configuration of the transmitting station 3-1 of the present embodiment. In the illustrated example, the transmission station 3-1 includes a broadcast data reception unit 31, an encoding unit 32, a modulation unit 33, a reception antenna unit 34, a delay time calculation unit 35, and a radio wave arrival direction estimation unit 36. A delay time setting unit 37, a delay unit 38, a radio wave transmission direction setting unit 39, and a transmission antenna unit 40.

  The broadcast data receiving unit 31 receives broadcast data transmitted from the broadcast center facility 1. The broadcast data receiving unit 31 inputs the received broadcast data to the encoding unit 32 and the delay time calculating unit 35. The encoding unit 32 encodes the input broadcast data into encoded data. In addition, the encoding processing unit 32 inputs the encoded data to the modulation unit 33.

  The modulation unit 33 converts the encoded data into an OFDM (Orthogonal Frequency Division Multiplexing) signal as a broadcast wave signal. Further, the modulation unit 33 inputs the OFDM signal to the delay unit 38.

  The receiving antenna unit 34 includes m directional antennas 341-1 to 341-m and m upper broadcast wave receiving units 342-1 to 342-m. The directional antennas 341-1 to 341-m are arranged so as to receive radio waves arriving from different directions. In addition, the directional antennas 341-1 to 341-m receive radio waves arriving from different directions and input them to the higher-order broadcast wave receiving units 342-1 to 342-m.

  The upper broadcast wave receiving units 342-1 to 342-m demodulate the input radio wave. The upper broadcast wave receiving units 342-1 to 342-m input the demodulated broadcast data to the delay time calculating unit 35 and the radio wave arrival direction estimating unit 36.

  Thereby, the receiving antenna part 34 can receive the broadcast data transmitted from the higher-order transmitting station. The receiving antenna unit 34 can input broadcast data based on the radio waves received by the directional antennas 341-1 to 341-n to the delay time calculating unit 35 and the radio wave arrival direction estimating unit 36.

  The delay time calculation unit 35 has the higher transmission station (central transmission station 2) put the broadcast data on the basis of the broadcast data input from the broadcast data reception unit 31 and the broadcast data input from the reception antenna unit 34. After transmitting the radio wave, the time (delay time) until the broadcast data reaches the transmitting station 3-1 is calculated. In addition, the delay time calculation unit 35 inputs the calculated delay time to the delay time setting unit 37.

  For example, in the present embodiment, the time when the broadcast center facility 1 transmits broadcast data to the central transmission station 2 and the transmission stations 3-1 and 3-2, that is, the broadcast data received by the broadcast data reception unit 31 is transmitted. The time at which the central transmission station 2 transmits broadcast data is substantially the same time.

  As a result, by calculating the difference between the time when the receiving antenna unit 34 receives the broadcast data transmitted from the upper transmission station and the time when the broadcast data received by the broadcast data receiving unit 31 is transmitted, the upper transmission station The delay time from when the radio wave carrying the broadcast data is transmitted until the broadcast data reaches the transmitting station 3-1 can be calculated.

  Based on the broadcast data input from the receiving antenna unit 34, the radio wave arrival direction estimation unit 36 estimates from which direction the radio wave transmitted by the higher-level transmission station has arrived. The radio wave arrival direction estimation unit 36 inputs information indicating the arrival direction of the radio wave to the radio wave transmission direction setting unit 39.

  For example, in the present embodiment, the reception antenna unit 34 includes m directional antennas 341-1 to 341-m. In addition, the directional antennas 341-1 to 341-m are arranged so as to receive radio waves arriving from different directions. With this arrangement, the directional antennas 341-1 to 341-n facing in the direction in which the radio waves arrive can receive radio waves at a higher reception level than the other directional antennas 341-1 to 341-n. . That is, it can be estimated that the radio wave has arrived from a direction in which the directional antennas 341-1 to 341-n having a high radio wave reception level can be received.

  Thus, the radio wave arrival direction estimation unit 36 can estimate the radio wave arrival direction based on the level of the broadcast data input from the reception antenna unit 34.

  The delay time setting unit 37 inputs the delay time input from the delay time calculation unit 35 to the delay unit 38. The delay unit 38 delays the OFDM signal input from the modulation unit 33 by the delay time input from the delay time calculation unit 35 and inputs the delayed signal to the transmission antenna unit 40.

  The radio wave transmission direction setting unit 39 directs the maximum radiation direction of directivity in a direction 180 degrees opposite to the radio wave arrival direction based on the information indicating the radio wave arrival direction input from the radio wave arrival direction estimation unit 36. The transmission antenna unit 40 is controlled so as to transmit radio waves.

  The transmission antenna unit 40 includes a power distributor 401 and n directional antennas 402-1 to 402-n. Directional antennas 402-1 to 402-n are arranged to transmit radio waves in different directions. The power distributor 401 is directed to the directional antennas 402-1 to 402-n that transmit the radio waves in the direction of the maximum radiation direction of the directivity in a direction 180 degrees opposite to the arrival direction of the radio waves transmitted by the upper transmission station. The OFDM signal input from the delay unit 38 is input.

  As a result, the transmitting antenna unit 40 directs the radio wave carrying the broadcast data received from the broadcasting center facility 1 with the maximum radiation direction of directivity in the direction 180 degrees opposite to the arrival direction of the radio wave transmitted by the upper transmission station. Thus, transmission can be performed with a delay of the delay time calculated by the delay time calculator 35. That is, the transmitting station 3-1 can transmit radio waves so as not to interfere with the radio waves transmitted by the higher-level transmitting station.

  As described above, according to the present embodiment, the transmitting station can transmit a radio wave so as not to interfere with the radio wave transmitted by the higher-level transmitting station. Therefore, the transmitting station of this embodiment can improve frequency utilization efficiency and can prevent interference of radio waves transmitted by each transmitting station while securing a wide service area with fewer transmitting stations.

  Further, according to the present embodiment, the transmitting station can automatically adjust the direction in which the radio wave is transmitted based on the arrival direction of the radio wave transmitted by the higher-level transmitting station. For example, even when the arrival direction of the radio wave transmitted by the higher-level transmission station changes due to the change in the propagation state of the radio wave, the transmission station can automatically adjust the direction in which the radio wave is transmitted.

  Note that the receiving antenna unit 35 includes an array antenna and a higher-order broadcast wave instead of the m directional antennas 341-1 to 341-m and the m higher-order broadcast wave reception units 342-1 to 342-m. And a receiving unit. Then, the radio wave arrival direction estimation unit 36 may estimate the arrival direction of a radio wave transmitted from a higher-level transmission station using an arrival direction estimation algorithm such as a beam forming method or a MUSIC method.

  The transmission antenna unit 40 may include a phased array antenna instead of the n directional antennas 402-1 to 402-n. Then, the power distributor 401 may adjust the transmission direction by adjusting the power feeding phase to the antenna element included in the phased array antenna.

  In addition, the delay time calculated by the delay time calculation unit 36 and the arrival direction of the radio wave transmitted by the higher-level transmission station estimated by the radio wave arrival direction estimation unit 36 are substantially the same values unless the environment changes such as transfer of the transmission station. It becomes. Therefore, the delay time setting unit 37 stores the delay time, and performs processing using the stored delay time if the environment does not change. In addition, the radio wave transmission direction setting unit 39 stores information indicating the arrival direction of the radio wave transmitted by the upper transmission station, and performs processing using the stored information indicating the arrival direction of the radio wave if the environment does not change. .

  Further, the estimation of the delay time performed by the delay time calculation unit 36 and the estimation of the arrival direction of the radio wave performed by the radio wave transmission direction setting unit 39 are preferably performed in a state in which the transmission antenna unit 40 stops the transmission of the radio wave. . This is because when the transmission antenna unit 40 is transmitting radio waves, the radio wave transmitted by the transmission antenna unit 40 wraps around the reception antenna unit 35. Therefore, the reception antenna unit 35 receives the radio wave transmitted by the transmission antenna unit 40 in addition to the radio wave transmitted by the higher-level transmission station, and estimates the arrival direction of the radio wave transmitted by the higher-level transmission station and the delay time. This is because the calculation may not be performed correctly.

  The transmission station 3-1 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an external memory (not shown), and an external memory. A configuration having a computer system including a storage device and the like may be employed.

  The encoding unit 32, the modulation unit 33, the delay time calculation unit 35, the radio wave arrival direction estimation unit 36, the delay time setting unit 37, the delay unit 38, and the radio wave transmission direction setting unit 39 described above are used. The process to be performed may be stored in a computer-readable recording medium in the form of a program, and the process may be performed in each unit by the computer reading and executing the program.

  That is, the processes in the encoding unit 32, the modulation unit 33, the delay time calculation unit 35, the radio wave arrival direction estimation unit 36, the delay time setting unit 37, the delay unit 38, and the radio wave transmission direction setting unit 39 are as follows. A configuration may be realized in which a central processing unit such as a CPU reads the program into a main storage device such as a ROM or a RAM and executes information processing and arithmetic processing.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the above-described one, and various design changes and the like can be made without departing from the scope of the present invention. Is possible.

  DESCRIPTION OF SYMBOLS 1 ... Broadcast center equipment, 2 ... Central transmitting station, 3-1, 3-2 ... Transmitting station, 31 ... Broadcast data receiving part, 32 ... Encoding part, 33 ... Modulation unit, 38 ... reception antenna unit, 35 ... delay time calculation unit, 36 ... radio wave arrival direction estimation unit, 37 ... delay time setting unit, 38 ... delay unit, 39 ... Radio wave transmission direction setting unit, 40... Transmission antenna unit, 341-1 to 341-m, 402-1 to 402-n .. directional antenna, 342-1 to 342-m. , 401... Power distributor

Claims (5)

A transmitting station that transmits broadcast waves,
A receiving antenna for receiving broadcast waves transmitted by other transmitting stations;
Based on the broadcast wave received by the receiving antenna unit, a radio wave arrival direction estimation unit that estimates a direction in which the broadcast wave has arrived;
The direction of arrival of the broadcast wave estimated by the radio wave arrival direction estimation unit by delaying a broadcast wave carrying broadcast data distributed in common to each transmitting station by a predetermined delay time from the reception time of the broadcast data A transmitting antenna unit that transmits in a direction opposite to 180 degrees;
A transmitting station comprising: A delay time calculating unit for calculating the predetermined delay time;
The transmission station according to claim 1, wherein the transmission antenna unit transmits the broadcast wave with a delay by the delay time calculated by the delay time calculation unit. The delay time calculation unit calculates the delay time based on a reception time of the broadcast data and a time at which a broadcast wave transmitted from the other transmission station arrives. Transmitter station. The transmitting station according to any one of claims 1 to 3, comprising a plurality of directional antennas arranged in different directions. It has an array antenna. The transmission station of any one of Claims 1-3 characterized by the above-mentioned.

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