JP7547859B2 - Topology calculation device, terminal, communication system, topology calculation method, and topology calculation program - Google Patents

Description

The present invention relates to a technology for compensating for Doppler shifts that occur when a terminal moves at high speed in wireless communication.

In order to demodulate data symbols with high accuracy in mobile wireless communications, it is important to achieve high-precision channel estimation. In particular, in high-speed moving environments such as bullet trains and linear motor cars, channel estimation accuracy can be significantly degraded due to Doppler shift.

Therefore, in channel interpolation, the amount of Doppler shift may be estimated by automatic frequency control (AFC) using pilot symbols.

An example of an automatic frequency control technique that compensates for Doppler shift is disclosed in Patent Document 1. The mobile wireless communication system described in Patent Document 1 includes a base station and a mobile station. The base station has a local station position information storage unit that stores the position information of the base station. The base station transmits transmission data including the position information of the base station to the mobile station. The mobile station includes a Doppler effect calculation unit and an internal oscillator. The Doppler effect calculation unit calculates the frequency error of the transmission data due to the Doppler effect based on the position information, speed information, and moving direction information of the mobile station that it has acquired and the position information of the base station included in the transmission data. The internal oscillator oscillates a frequency signal that has been corrected for the frequency error of the transmission data due to the Doppler effect. As a result of the above-mentioned configuration, in the mobile wireless communication system described in Patent Document 1, the mobile station performs frequency tracking that corrects the frequency error of the transmission data due to the Doppler effect.

An example of a technique for compensating for Doppler shift is disclosed in Patent Document 2. The multicarrier receiving device described in Patent Document 2 calculates channel characteristics at a data symbol position as a primary channel estimate based on channel characteristics estimated by a pilot symbol reception signal for multiple subcarriers. The multicarrier receiving device then performs channel compensation and decoding of each data symbol reception signal based on the primary channel estimate. The multicarrier receiving device then weights and adds the channel re-estimates at each symbol position estimated by the decoded signal to calculate channel characteristics at a predetermined symbol position as a secondary channel estimate. As a result of the above-mentioned configuration, the multicarrier receiving device described in Patent Document 2 obtains a channel estimate even in an environment where frequency selective fading and dynamic fading subject to Doppler frequency fluctuations exist.

JP 2014-160891 A JP 2004-364094 A

In general, the faster the terminal moves, the greater the amount of phase rotation due to the Doppler effect. Therefore, in a high-speed moving environment, if the amount of phase rotation due to the Doppler effect exceeds a certain value (e.g., 2π), it becomes difficult to correctly estimate the phase. For example, the techniques described in Patent Documents 1 and 2 do not disclose a method for correctly estimating the phase when the amount of phase rotation due to the Doppler effect is large. In such cases, there is a problem in that the accuracy of channel estimation in automatic frequency control deteriorates significantly.

As a method for solving the problem of deterioration in channel estimation accuracy, it is generally considered to shorten the interval at which pilot symbols are inserted (see, for example, the description in paragraph [0059] of Patent Document 2). However, when the interval at which pilot symbols are inserted is shortened, the proportion of pilot symbols in the transmission data increases, resulting in a problem of reduced transmission efficiency.

The present invention was made in consideration of the above problems, and its main objective is to correctly calculate the phase difference corresponding to the Doppler shift without increasing the ratio of pilot signals to the transmission signal, even when the Doppler shift is large in wireless communication.

In one aspect of the present invention, the phase calculation device includes a movement direction calculation means for calculating a direction of movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that performs wireless communication with the terminal is located, and a Doppler shift calculation means for calculating a phase difference in a received carrier corresponding to a Doppler shift caused by movement when the carrier is received based on the calculated direction, information representing the speed of the terminal when moving, information representing the frequency of the carrier used in wireless communication, and information representing the repetition period of a pilot signal modulated on the carrier. The range of possible values of the number of rotations representing the phase difference is greater than one rotation.

In one aspect of the present invention, a terminal includes a phase calculation device and a data signal demodulation means. The phase calculation device includes a movement direction calculation means for calculating a direction of movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that performs wireless communication with the terminal is located, and a Doppler shift calculation means for calculating a phase difference in a received carrier corresponding to a Doppler shift caused by movement when the carrier is received based on the calculated direction, information representing the speed of the terminal when moving, information representing the frequency of a carrier used in wireless communication, and information representing a repetition period of a pilot signal modulated on the carrier. The range of possible values of the number of rotations representing the phase difference is greater than one rotation. The terminal includes a channel estimation means, a channel interpolation means, and a data signal demodulation means. The channel estimation means estimates the channel of a pilot signal received from a base station. The channel interpolation means estimates the channel of a data signal received from a base station based on the calculation result of the phase difference calculated by the phase calculation device and the estimation result of the channel of the pilot signal estimated by the channel estimation means. The data signal demodulation means demodulates the data signal based on the estimation result of the channel of the data signal estimated by the channel interpolation means.

In one aspect of the present invention, a communication system includes a terminal and a base station. The terminal includes a phase calculation device and a data signal demodulation means. The phase calculation device includes a movement direction calculation means for calculating a direction of movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that performs wireless communication with the terminal is located, and a Doppler shift calculation means for calculating a phase difference in a received carrier corresponding to a Doppler shift caused by movement when the carrier is received based on the calculated direction, information representing the speed of the terminal when moving, information representing the frequency of a carrier used in wireless communication, and information representing a repetition period of a pilot signal modulated on the carrier. The size of the range of possible values of the number of rotations representing the phase difference is greater than one rotation. The terminal includes a channel estimation means, a channel interpolation means, and a data signal demodulation means. The channel estimation means estimates the channel of a pilot signal received from a base station. The channel interpolation means estimates the channel of a data signal received from a base station based on the calculation result of the phase difference calculated by the phase calculation device and the estimation result of the channel of the pilot signal estimated by the channel estimation means. The data signal demodulation means demodulates the data signal based on the channel estimation result of the data signal estimated by the channel interpolation means. The base station transmits the pilot signal and the data signal.

In one aspect of the present invention, the phase calculation method calculates the direction of movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that wirelessly communicates with the terminal is located, and calculates a phase difference in the received carrier that corresponds to a Doppler shift caused by the movement when the carrier is received based on the calculated direction, information representing the speed of the terminal when moving, information representing the frequency of the carrier used in wireless communication, and information representing the repetition period of a pilot signal modulated on the carrier. The range of possible values of the number of rotations representing the phase difference is greater than one rotation.

In one aspect of the present invention, the phase calculation program causes a computer included in the phase calculation device to execute a movement direction calculation process that calculates the direction of movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that wirelessly communicates with the terminal is located, and a Doppler shift calculation process that calculates a phase difference in a received carrier that corresponds to a Doppler shift caused by movement when the carrier is received, based on the calculated direction, information representing the speed of the terminal when moving, information representing the frequency of the carrier used in wireless communication, and information representing the repetition period of a pilot signal modulated on the carrier. The range of possible values of the number of rotations that represents the phase difference is greater than one rotation.

The present invention has the advantage that, in wireless communication, even when the Doppler shift is large, the phase difference corresponding to the Doppler shift can be correctly calculated without increasing the ratio of the pilot signal to the transmission signal.

1 is a block diagram showing an example of a configuration of a communication system according to a first embodiment of the present invention. FIG. 2 is a block diagram showing an example of a configuration of a base station in the first embodiment of the present invention. 2 is a block diagram showing an example of a configuration of a wireless communication transmitter unit in the first embodiment of the present invention; FIG. FIG. 2 is a block diagram showing an example of a configuration of a terminal according to the first embodiment of the present invention. 2 is a block diagram showing an example of a configuration of a wireless communication receiving unit in the first embodiment of the present invention; FIG. FIG. 2 is a block diagram showing an example of a configuration of a phase calculation unit in the first embodiment of the present invention. 5 is a flowchart showing an operation of a phase calculation unit in the first embodiment of the present invention. 5 is a flowchart showing an operation of a phase calculation unit in the first embodiment of the present invention. 5 is a flowchart showing the operation of a terminal in the first embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a resource block in the first embodiment of the present invention. 1 is a block diagram showing an example of a configuration of a communication system according to a first embodiment of the present invention. FIG. 11 is a block diagram showing an example of a configuration of a terminal according to a second embodiment of the present invention. FIG. 11 is a block diagram showing an example of the configuration of a base station in a second embodiment of the present invention. FIG. 13 is a block diagram showing an example of a configuration of a phase calculation device according to a third embodiment of the present invention. FIG. 13 is a block diagram showing an example of a configuration of a communication system which is an operating environment of a topology calculation device according to a fourth embodiment of the present invention. FIG. 13 is a block diagram showing an example of a configuration of a phase calculation device according to a fourth embodiment of the present invention. 13 is a flowchart showing an operation of a phase calculation device according to the fourth embodiment of the present invention. FIG. 2 is a block diagram showing an example of a hardware configuration capable of realizing a phase calculation device according to each embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.
First Embodiment
A first embodiment of the present invention will be described.

The configuration of this embodiment is explained below.

Fig. 1 is a block diagram showing an example of the configuration of a communication system in a first embodiment of the present invention. As shown in Fig. 1, the communication system 100 of this embodiment includes a base station 200 and a terminal 300. Below, a description will be given of downstream signals (downlink) from the base station 200 to the terminal 300, and an explanation of upstream signals (uplink) from the terminal 300 to the base station 200 will be omitted. The base station 200 and the terminal 300 are connected by wireless communication.

FIG. 2 is a block diagram showing an example of the configuration of a base station 200 in the first embodiment of the present invention. As shown in FIG. 2, the base station 200 includes a channel control unit 210 and a transmitting wireless communication unit 220.

In order to estimate the channel, the channel control unit 210 discretely places pilot symbols (an example of a pilot signal), which is a known pattern, in the resource block according to a predetermined setting. The channel control unit 210 also inputs the data to be transmitted and places data symbols (an example of a data signal) in the resource block. The channel control unit 210 outputs a resource block (transmission data) including data symbols, pilot symbols, etc., to the transmitting side wireless communication unit 220. The data symbols are symbols obtained by modulating the data to be transmitted (bit strings, audio data, video data, etc.). The data to be transmitted is supplied, for example, by a process that relays data from a server or another terminal.

Figure 3 is a block diagram showing an example of the configuration of the transmitting wireless communication unit 220 in the first embodiment of the present invention. As shown in Figure 3, the transmitting wireless communication unit 220 includes a D/A converter 510 (Digital to Analog converter), a carrier oscillator 520, a multiplier 530, an amplifier 540, an antenna 550, and the like. The transmitting wireless communication unit 220 transmits transmission data including data symbols (an example of a data signal) and pilot symbols input from the channel control unit 210 to the receiving wireless communication unit 310 (described later) via radio waves. The transmitting wireless communication unit 220 is a general transmission circuit that wirelessly transmits data symbols, pilot symbols, and the like. Therefore, further detailed explanation of the configuration of the transmitting wireless communication unit 220 is omitted.

Fig. 4 is a block diagram showing an example of the configuration of a terminal 300 in the first embodiment of the present invention. As shown in Fig. 4, the terminal 300 includes a receiving side wireless communication unit 310, a channel estimation unit 320, a phase calculation unit 400, a channel interpolation unit 330, and a data symbol demodulation unit 340.

Figure 5 is a block diagram showing an example of the configuration of the receiving wireless communication unit 310 in the first embodiment of the present invention. As shown in Figure 5, the receiving wireless communication unit 310 includes an A/D converter 610 (Analog to Digital converter), a carrier oscillator 620, a multiplier 630, an amplifier 640, an antenna 650, and the like. The receiving wireless communication unit 310 receives data symbols, pilot symbols, and the like from the transmitting wireless communication unit 220 via radio waves. The receiving wireless communication unit 310 is a general receiving circuit that has an automatic frequency control function and outputs data symbols, pilot symbols, and the like received by radio. Therefore, further detailed explanation of the configuration of the receiving wireless communication unit 310 is omitted. The receiving wireless communication unit 310 outputs received data including data symbols, pilot symbols, and the like to the data symbol demodulation unit 340 and the channel estimation unit 320.

The channel estimation unit 320 inputs pilot symbols from the receiving wireless communication unit 310 and outputs the channel estimation value of the input pilot symbols to the channel interpolation unit 330.

The phase calculation unit 400 holds information about the positions (e.g., latitude, longitude, and altitude) of the terminal 300 and the base station 200. Then, based on the held information about the positions of the terminal 300 and the base station 200, the phase calculation unit 400 calculates the phase of the received pilot symbol, which changes due to Doppler shift as the terminal 300 moves. Then, the phase calculation unit 400 outputs the calculated phase to the channel interpolation unit 330. Here, the phase calculation unit 400 may obtain the information about the positions of the terminal 300 and the base station 200 from a sensor or via a network, as necessary.

The channel interpolation unit 330 interpolates the channel estimation value of the data symbol based on the channel estimation value of the pilot symbol input from the channel estimation unit 320 and the phase of the pilot symbol input from the phase calculation unit 400. The channel interpolation unit 330 outputs the interpolated channel to the data symbol demodulation unit 340.

The data symbol demodulation unit 340 demodulates the source symbol based on the data symbol input from the receiving side wireless communication unit 310 and the interpolated channel input from the channel interpolation unit 330. Specifically, the data symbol demodulation unit 340 removes the influence of the transmission path by dividing the received data symbol by the channel estimation value, and demodulates the source symbol. The data symbol demodulation unit 340 then outputs the source data. The source data is processed, for example, by a process of an application program.

Figure 6 is a block diagram showing an example of the configuration of the phase calculation unit 400 in the first embodiment of the present invention. As shown in Figure 6, the phase calculation unit 400 includes a parameter acquisition unit 410, a position information acquisition unit 420, a position information storage unit 430, a movement direction calculation unit 440, a speed information acquisition unit 450, and a Doppler shift calculation unit 460.

The parameter acquisition unit 410 acquires the carrier frequency and the location information of the base station 200. The parameter acquisition unit 410 outputs the acquired carrier frequency to the Doppler shift calculation unit 460, and outputs the acquired location information of the base station 200 to the movement direction calculation unit 440. The parameter acquisition unit 410 acquires, for example, the carrier frequency and the location information of the base station 200 from notification information obtained when the terminal 300 starts connection in a communication area. The location information of the base station 200 may be acquired using a positioning system such as GPS (Global Positioning System), or may be acquired based on information on the location where the base station 200 is installed (latitude and longitude, address, etc.).

The location information acquisition unit 420 acquires location information of the terminal 300. The location information acquisition unit 420 outputs the acquired location information to the movement direction calculation unit 440 and the location information storage unit 430. The location information may be acquired, for example, from a system that manages the location of the terminal 300 (for example, a positioning system using GPS or base station positioning, etc.), or may be acquired based on an identification number of the communication area to which the terminal 300 belongs. Alternatively, the location information may be calculated using an acceleration sensor or a speed sensor, etc., that the terminal 300 has.

The location information storage unit 430 stores past location information of the terminal 300. The location information storage unit 430 outputs the stored location information to the movement direction calculation unit 440.

The moving direction calculation unit 440 calculates the moving direction of the terminal 300. The moving direction calculation unit 440 outputs the calculated moving direction to the Doppler shift calculation unit 460.

The speed information acquisition unit 450 acquires the moving speed (moving speed) of the terminal 300. The speed information acquisition unit 450 outputs the acquired moving speed to the Doppler shift calculation unit 460. The moving speed may be acquired, for example, from an acceleration sensor or a speed sensor that the terminal 300 has. Alternatively, the moving speed may be acquired from a system that manages the position of the terminal 300 (for example, a positioning system that uses GPS, base station positioning, etc.).

The Doppler shift calculation unit 460 calculates the Doppler shift. The Doppler shift calculation unit 460 outputs the calculated Doppler shift to the channel interpolation unit 330.

The operation of this embodiment will be explained.

Figures 7 and 8 are flowcharts showing the operation of the phase calculation unit 400 in the first embodiment of the present invention.

First, the parameter acquisition unit 410 acquires the position information (position O) of the base station 200 and outputs the acquired position information to the movement direction calculation unit 440 (step S110).

Next, the location information acquisition unit 420 acquires the current location information (position P) of the terminal 300 and outputs the acquired location information to the movement direction calculation unit 440 (step S120).

Next, the position information storage unit 430 acquires past position information (position P') of the terminal 300, and outputs the acquired position information to the movement direction calculation unit 440 (step S130). Here, the processing order of the above steps S110 to S130 may be arbitrary.

Next, the moving direction calculation unit 440 calculates the moving direction θ _m of the terminal 300 using, for example, equation (1) (step S140). Here, the moving direction θ _m refers to the angle P′OP.

Here, OP is the distance between position O and position P, OP' is the distance between position O and position P', and PP' is the distance between position P and position P'. The moving direction _θm may be expressed, for example, in radian measure (unit: radian), in degree measure (unit: degree), or in number of rotations (unit: rotation). In the following, an example will be described in which the moving direction _θm is expressed in radian measure and takes a value equal to or greater than 0 (radian) and less than π (radian).

Next, the movement direction calculation unit 440 outputs the calculated movement direction of the terminal 300 to the Doppler shift calculation unit 460 (step S150).

Next, the location information acquisition unit 420 stores the current location information of the terminal 300 in the location information storage unit 430 (step S160). The initial value of the current location information of the terminal 300 stored in the location information storage unit 430 may be the location information of the terminal 300 obtained when the terminal 300 starts communication, or the coordinates of the terminal 300 manually set by a person. Note that the processing order of the above steps S150 to S160 may be arbitrary.

Next, the parameter acquisition unit 410 acquires carrier frequency information (carrier frequency f _c ), and outputs the acquired carrier frequency information to the Doppler shift calculation unit 460 (step S210).

Next, the speed information acquisition unit 450 acquires the current speed information (speed v) of the terminal 300 and outputs the acquired speed information to the Doppler shift calculation unit 460 (step S220). Here, the processing order of the above steps S210 to S220 may be arbitrary.

Next, the Doppler shift calculation unit 460 calculates a phase difference θ _d (hereinafter also simply referred to as a “Doppler shift”) corresponding to the Doppler shift using, for example, equation (2) (step S230).

Here, c is the speed of light, v is the speed of movement of the terminal, and _Ts is the calculation period of the direction of movement or the speed of movement of the terminal (hereinafter, assumed to be a predetermined constant). Also, the Doppler shift _θd may be expressed, for example, in radian measure, in degree measure, or in number of rotations. In the following, an example will be described in which the Doppler shift _θd is expressed in radian measure. Also, the Doppler shift _θd may take a value of 0 (radian) or more, for example, and may take a value of 2π (radian) or more.

Next, the Doppler shift calculation unit 460 outputs information representing the calculated Doppler shift to the channel interpolation unit 330 (step S240).

Figure 9 is a flowchart showing the operation of the terminal 300 in the first embodiment of the present invention.

First, the channel estimation unit 320 calculates a channel estimation value _θp of the pilot symbol based on the received pilot symbol, and outputs the calculated value to the channel interpolation unit 330 (step S310). Here, the channel estimation value _θp is set to be equal to or greater than 0 (radian) and less than 2π (radian). In this embodiment, only the phase is considered as the channel estimation value.

Next, the channel estimation unit 320 calculates the true channel estimation value θ′ _p of the pilot symbol using, for example, equation (3) (step S320).

Here, [ ] indicates truncation to the nearest whole number. A true channel estimate is obtained by adding the integer part of the phase rotation number in the second term to the channel estimate in the first term. Here, the true channel estimate θ′ _p takes a value of 0 (radian) or more, and can take a value of 2π (radian) or more, for example.

Next, the channel interpolation unit 330 interpolates channel estimates of the data symbols (step S330). The channel interpolation unit 330 calculates channel estimates θ′ _p,n of N data symbols between the pilot symbol estimates θ _p and θ _p+1 , for example, using equation (4).

In this case, the channel estimates of the data symbols may be interpolated using other techniques.

The data symbol demodulation unit 340 demodulates the source symbol based on the data symbol obtained via the receiving wireless communication unit 310 and the channel estimation value interpolated by the channel interpolation unit 330 (step S340).

Fig. 10 is a schematic diagram showing an example of a resource block in the first embodiment of the present invention. For simplification, in Fig. 10, symbols are arranged only in the time direction in the resource block. As shown in Fig. 10, the channel estimation value θ' _p,n shown in equation (4) is interpolated corresponding to each received data symbol.

As described above, in the communication system 100 of this embodiment, the moving direction calculation unit 440 calculates the moving direction of the terminal 300 using the position information of the base station 200 and the position information of the terminal 300. Then, the Doppler shift calculation unit 460 calculates the Doppler shift θ _d using the moving direction and moving speed of the terminal 300. Here, the possible range of the estimated value θ _p of the pilot symbol in the channel estimation obtained by the general method is 0≦θ _p <2π. Therefore, when the Doppler shift θ _d is large, if the calculated Doppler shift is used as it is for the interpolation of the channel estimation, the interpolation accuracy may be deteriorated. However, as shown in formula (3), the channel estimation unit 320 calculates the true channel estimation value θ′ _p even when the Doppler shift θ _d is 2π or more. Then, the channel interpolation unit 330 calculates the channel estimation value θ′ _{p ,n} of the data symbol using the true channel estimation value θ′ p. Then, the data symbol demodulation section 340 demodulates the source symbol using the channel estimation value θ′ _p,n of the data symbol.

In addition, in the communication system 100 of the present embodiment, even if the Doppler shift _θd can be 2π or more, there is no need to shorten the repetition period of pilot symbols in order to suppress deterioration of channel estimation accuracy. In other words, the ratio of pilot symbols to the transmission data does not increase, so the transmission efficiency does not decrease.

Therefore, the communication system 100 of this embodiment has the advantage that, even when the Doppler shift is large in wireless communication, the phase difference corresponding to the Doppler shift can be correctly calculated without increasing the ratio of the pilot signal to the transmission signal.

In the communication system 100 of this embodiment, the Doppler shift _θd is used only for calculating the integer part of the number of phase rotations as shown in formula (3). Therefore, the communication system 100 of this embodiment has an advantage that it is possible to suppress deterioration of the channel estimation accuracy even when the accuracy or frequency of acquisition of the location information or moving speed of the terminal 300 is low.

Generally, a communication device includes only one carrier oscillator. For example, in the technology described in Patent Document 1, the Doppler shift is input to one internal oscillator (carrier oscillator), and the internal oscillator oscillates a frequency signal with the Doppler shift corrected. Therefore, when communication devices are communicating one to n (n is an integer of 2 or more), the correction of the Doppler shift for one communication device may adversely affect communication with another communication device. On the other hand, in the communication system 100 of this embodiment, the Doppler shift calculated by the phase calculation unit 400 is input to the channel interpolation unit 330. Therefore, in the communication system 100 of this embodiment, it is possible to feed back the Doppler shift to each communication device.
Second Embodiment
A second embodiment of the present invention will be described based on the first embodiment of the present invention. The first embodiment relates to downlink communication from a base station to a terminal, whereas the second embodiment relates to uplink communication from a terminal to a base station. This embodiment may be used alone or in combination with the first embodiment.

The configuration of this embodiment is explained below.

Fig. 11 is a block diagram showing an example of the configuration of a communication system in the first embodiment of the present invention. As shown in Fig. 11, the communication system 101 of this embodiment includes a base station 201 and a terminal 301. The base station 201 and the terminal 301 are connected by wireless communication. In the following, an upstream signal (uplink) from the terminal 301 to the base station 201 will be described, and a description of a downstream signal (downlink) from the base station 201 to the terminal 301 will be omitted.

Fig. 12 is a block diagram showing an example of the configuration of a terminal 301 in the second embodiment of the present invention. As shown in Fig. 12, the terminal 301 includes a channel control unit 210, a transmitting side wireless communication unit 221, and a phase calculation unit 400.

The transmitting wireless communication unit 221 transmits transmission data including data symbols and pilot symbols input from the channel control unit 210 and the phase calculation unit 400 to the receiving wireless communication unit 311 (described later) via radio waves. Here, the data symbols include information on the Doppler shift calculated by the phase calculation unit 400 (the phase of the received pilot symbol that changes due to the Doppler shift as the terminal 301 moves). The other configurations of the transmitting wireless communication unit 221 are the same as those of the transmitting wireless communication unit 220 in the first embodiment.

The other configuration of the terminal 301 is similar to the configuration of the base station 200 in the first embodiment.

Fig. 13 is a block diagram showing an example of the configuration of a base station 201 in the second embodiment of the present invention. As shown in Fig. 13, the base station 201 includes a receiving side wireless communication unit 311, a channel estimation unit 320, a channel interpolation unit 330, and a data symbol demodulation unit 340.

The receiving wireless communication unit 311 receives data symbols, pilot symbols, and the like from the transmitting wireless communication unit 221 via radio waves. The receiving wireless communication unit 311 outputs Doppler shift information contained in the data symbols received from the transmitting wireless communication unit 221 to the channel interpolation unit 330. The receiving wireless communication unit 311 outputs received data including data symbols, pilot symbols, and the like to the data symbol demodulation unit 340, the channel estimation unit 320, and the channel interpolation unit 330.

The channel interpolation unit 330 interpolates a channel estimation value of a data symbol based on the channel estimation value of the pilot symbol input from the channel estimation unit 320 and information on the Doppler shift included in the received data input from the receiving side radio communication unit 311. The channel interpolation unit 330 outputs the interpolated channel to the data symbol demodulation unit 340.
Other configurations of the wireless communication receiver 311 are similar to those of the wireless communication receiver 310 in the first embodiment.

The rest of the configuration of the base station 201 is the same as the configuration of the terminal 300 in the first embodiment.

The operation of this embodiment will be explained.

The communication system 101 of this embodiment operates in the same manner as the first embodiment, except that the Doppler shift is calculated on the transmitting side (terminal 301).

As described above, the communication system 101 of this embodiment operates in the same manner as the first embodiment, except that the Doppler shift is calculated on the transmitting side (terminal 301). Therefore, the communication system 101 of this embodiment has the same effects as the first embodiment.
Third Embodiment
A third embodiment of the present invention will be described below, which is based on the first or second embodiment of the present invention. In the first and second embodiments, the Doppler shift is calculated based on the measured position and speed of the terminal, whereas in this embodiment, the Doppler shift is calculated based on the position and speed of the underwater vehicle on which the terminal is present.

The configuration of this embodiment is explained below.

Figure 14 is a block diagram showing an example of the configuration of a phase calculation device 402 in the third embodiment of the present invention. As shown in Figure 14, the phase calculation device 402 in this embodiment includes a parameter acquisition unit 410, an operation information acquisition unit 472, a position information storage unit 430, a moving direction calculation unit 440, and a Doppler shift calculation unit 460. The phase calculation device 402 is a device that replaces the phase calculation unit 400 in the first and second embodiments. That is, in this embodiment, the operation information acquisition unit 472 is used instead of the position information acquisition unit 420 and the speed information acquisition unit 450 of the phase calculation unit 400 in the first and second embodiments.

The operation information acquisition unit 472 holds operation information of the watercraft (train, airplane, satellite, etc.) on which the terminal is present. The operation information acquisition unit 472 stores real-time position information and speed information of the watercraft moving with the terminal, for example, by linking with an operation management system of a railway company, a space airline, etc. The operation information acquisition unit 472 outputs the position information of the watercraft to the position information storage unit 430 as the position information of the terminal. The operation information acquisition unit 472 also outputs the speed information of the watercraft to the Doppler shift calculation unit 460 as the speed information of the terminal. Here, for example, the movement (position and speed) of the terminal and the watercraft may be matched by limiting the radio wave reception range (cell) of the terminal.

The rest of the configuration and operation of the phase calculation device 402 is the same as the configuration and operation of the phase calculation unit 400 in the first and second embodiments.

As described above, the phase calculation device 402 in this embodiment operates in the same manner as the phase calculation unit 400 in the first and second embodiments. Therefore, the phase calculation device 402 in this embodiment has the effect of being able to correctly calculate the phase difference corresponding to the Doppler shift without increasing the ratio of the pilot signal to the transmission signal, even when the Doppler shift is large in wireless communication.

Furthermore, the phase calculation device 402 in this embodiment does not include the position information acquisition unit 420 and the speed information acquisition unit 450 in the first and second embodiments. Therefore, the phase calculation device 402 in this embodiment has an advantage that it can correctly calculate a phase difference corresponding to a Doppler shift even when the GPS, acceleration sensor, etc. of the terminal cannot be used.
Fourth Embodiment
A fourth embodiment of the present invention, which is the basis of each embodiment of the present invention, will be described.

The configuration of this embodiment is explained below.

FIG. 15 is a block diagram showing an example of the configuration of a communication system 105 which is an operating environment of a phase calculation device in a fourth embodiment of the present invention. As shown in FIG. 15, the communication system 105 of this embodiment includes a base station 205 and a terminal 305. The base station 205 and the terminal 305 are connected by wireless communication. The carrier used for wireless communication has a frequency f _c (a predetermined value). The repetition period of the pilot signal modulated on the carrier is a period T _s (a predetermined value). The position where the base station 205 exists is represented by a first position O. The position where the terminal 305 existed is represented by a first position P', and the position where the terminal 305 existed after the terminal 305 moved is represented by a second position P. The speed of the terminal 305 during the movement is represented by a speed v. The terminal 305 includes a phase calculation device 405.

Figure 16 is a block diagram showing an example of the configuration of a phase calculation device 405 in the fourth embodiment of the present invention. As shown in Figure 16, the phase calculation device 405 of this embodiment includes a moving direction calculation unit 445 and a Doppler shift calculation unit 465.

The operation of this embodiment will be explained.

Figure 17 is a flowchart showing the operation of the phase calculation device 405 in the fourth embodiment of the present invention.

The movement direction calculation unit 445 calculates the direction of movement based on the information representing the first position P', the second position P, and the third position O (step S510).

The Doppler shift calculation unit 465 calculates the phase difference in the received carrier corresponding to the Doppler shift caused by the movement when the carrier was received, based on the information representing the direction, speed v, frequency f _c , and period T _s calculated by the movement direction calculation unit 445 (step S520). Here, the range of possible values of the number of rotations representing the phase difference is larger than one rotation (the phase difference can also take a value larger than one rotation).

As described above, in the phase calculation device 405 of this embodiment, the moving direction calculation unit 445 calculates the direction of movement of the terminal 305. Then, the Doppler shift calculation unit 465 calculates the phase difference in the received carrier corresponding to the Doppler shift based on the information representing the calculated moving direction and speed v. Here, the Doppler shift calculation unit 465 can calculate the phase difference even when the number of rotations representing the phase difference corresponding to the Doppler shift is one rotation or more. Therefore, the Doppler shift calculation unit 465 does not need to shorten the repetition period _Ts of the pilot signal in order to correctly calculate the phase difference. Therefore, the phase calculation device 405 of this embodiment has the effect of correctly calculating the phase difference corresponding to the Doppler shift without increasing the ratio of the pilot signal to the transmission signal even when the Doppler shift is large in wireless communication.

The Doppler shift calculation unit 465 may calculate the integer part of the number of rotations representing the phase difference as the calculation result of the phase difference. In this case, the decimal part of the number of rotations representing the phase difference is processed by the automatic frequency control function of the receiving wireless communication means (e.g., the receiving wireless communication units 310 and 311).

The moving direction calculation unit 445 may also obtain information representing the first position P' and the second position P from a positioning system that performs positioning of the terminal 305. The moving direction calculation unit 445 may also obtain information representing the speed v of the terminal 305 from an acceleration sensor or a speed sensor that the terminal 305 has, or from the positioning system.

In addition, the movement direction calculation unit 445 may obtain information regarding the position and speed of the watercraft from a traffic management system that manages the position of the watercraft on which the terminal 305 is located, as information representing the first position P', the second position P, and the speed v of the terminal 305.

Figure 18 is a block diagram showing an example of a hardware configuration capable of realizing the phase calculation unit 400 and phase calculation devices 402 and 405 (hereinafter referred to as "phase calculation devices, etc.") in each embodiment of the present invention.

The phase calculation device etc. 901 includes a storage device 902, a CPU (Central Processing Unit) 903, a keyboard 904, a monitor 905, and an I/O (Input/Output) device 908, which are connected by an internal bus 906. The storage device 902 stores the operation program of the CPU 903 of the phase calculation device etc. 901. The CPU 903 controls the entire phase calculation device etc. 901, executes the operation program stored in the storage device 902, and executes the program of the phase calculation device etc. 901 and transmits and receives data via the I/O device 908. Note that the above internal configuration of the phase calculation device etc. 901 is an example. The phase calculation device etc. 901 may be configured to connect the keyboard 904 and monitor 905 as necessary.

The topology calculation device etc. 901 in each of the above-mentioned embodiments of the present invention may be realized by a dedicated device, but other than the operation of the hardware in which the I/O device 908 executes communication with the outside, it can also be realized by a computer (information processing device). In this case, the computer reads the software program stored in the storage device 902 into the CPU 903 and executes the read software program in the CPU 903. In the case of each of the above-mentioned embodiments, the software program only needs to have a description capable of implementing the functions of each part of the topology calculation device etc. shown in Figures 6, 14, and 16 described above. However, it is also assumed that each of these parts includes appropriate hardware. In such a case, the software program (computer program) can be considered to constitute the present invention. Furthermore, a computer-readable storage medium in which the software program is stored can also be considered to constitute the present invention.

The present invention has been described above by way of example with reference to the above-mentioned embodiments and their modifications. However, the technical scope of the present invention is not limited to the scope described in the above-mentioned embodiments and their modifications. It is clear to those skilled in the art that various modifications or improvements can be made to the embodiments. In such cases, new embodiments incorporating such modifications or improvements may also be included in the technical scope of the present invention. This is clear from the matters described in the claims.

The present invention can be used to correct the effects of Doppler shift in fast-moving terminals in wireless communications.

100, 101, 105 Communication system 200, 201, 205 Base station 210 Channel control unit 220, 221 Transmitting side wireless communication unit 300, 301, 305 Terminal 310, 311 Receiving side wireless communication unit 320 Channel estimation unit 330 Channel interpolation unit 340 Data symbol demodulation unit 400 Phase calculation unit 402, 405 Phase calculation device 410 Parameter acquisition unit 420 Position information acquisition unit 430 Position information storage unit 440, 445 Moving direction calculation unit 450 Speed information acquisition unit 460, 465 Doppler shift calculation unit 472 Operation information acquisition unit 510 D/A converter 520 Carrier wave oscillator 530 Multiplier 540 Amplifier 550 Antenna 610 A/D converter 620 Carrier oscillator 630 Multiplier 640 Amplifier 650 Antenna 901 Phase calculation device etc. 902 Storage device 903 CPU
904 Keyboard 905 Monitor 906 Internal bus 908 I/O device

Claims (9)

a movement direction calculation means for calculating a direction of the movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that wirelessly communicates with the terminal is located;
a Doppler shift calculation means for calculating a phase difference in the received carrier, which corresponds to a Doppler shift caused by the movement when the carrier is received, based on the calculated direction, information representing the speed of the terminal during the movement, information representing the frequency of a carrier used in the wireless communication, and information representing a repetition period of a pilot signal modulated on the carrier,
A phase calculation device in which the range of possible values of the number of rotations representing the phase difference is greater than one rotation. 2. The phase calculation device according to claim 1, wherein said Doppler shift calculation means calculates an integer part of said rotation number as a calculation result of said phase difference. 3. The phase calculation device according to claim 1, wherein the moving direction calculation means acquires information representing the first position and the second position from a positioning system that performs positioning of the terminal, and acquires information representing the speed of the terminal from an acceleration sensor or a speed sensor possessed by the terminal, or from the positioning system. The phase calculation device according to any one of claims 1 to 3, wherein the movement direction calculation means acquires information regarding the position and speed of the underwater vehicle from a traffic management system that manages the position of the underwater vehicle on which the terminal is located, as information representing the first position, the second position, and the speed of the terminal 305. A phase calculation device according to any one of claims 1 to 4,
a channel estimation means for estimating a channel of the pilot signal received from the base station;
a channel interpolation means for estimating a channel of a data signal received from the base station based on a result of the phase difference calculated by the phase calculation device and a result of the estimation of the channel of the pilot signal estimated by the channel estimation means;
a data signal demodulation means for demodulating the data signal based on the result of the estimation of the channel of the data signal estimated by the channel interpolation means. A terminal according to claim 5;
and a base station transmitting the pilot signal and the data signal. The terminal also transmits another of the pilot signals and another of the data signals in an uplink from the terminal to the base station;
the other data signal in the uplink includes a calculation result of the phase difference calculated by the phase calculation device,
The communication system according to claim 6, wherein the base station estimates channels of the other pilot signal and the other data signal for the uplink based on the calculation result of the phase difference received from the terminal, and demodulates the other data signal based on the estimation result. calculating a direction of the movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that wirelessly communicates with the terminal is located;
A phase calculation method for calculating a phase difference in a received carrier, which corresponds to a Doppler shift caused by the movement when the carrier is received, based on the calculated direction, information representing a speed of the terminal during the movement, information representing a frequency of a carrier used in the wireless communication, and information representing a repetition period of a pilot signal modulated on the carrier, the method comprising:
A phase calculation method in which the range of possible values of the number of rotations representing the phase difference is greater than one rotation. The computer of the topology calculation device has
a movement direction calculation process for calculating a direction of the movement based on information representing a first position where the terminal was located, information representing a second position where the terminal was located after the terminal moved, and information representing a third position where a base station that wirelessly communicates with the terminal is located;
a Doppler shift calculation process for calculating a phase difference in the received carrier corresponding to a Doppler shift caused by the movement when the carrier is received, based on the calculated direction, information representing the speed of the terminal during the movement, information representing the frequency of a carrier used in the wireless communication, and information representing a repetition period of a pilot signal modulated on the carrier,
A phase calculation program in which the range of possible values of the number of rotations representing the phase difference is greater than one rotation.

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