Wireless communication device and wireless communication system

Abstract

To improve communication efficiency by reducing the number of arranged pilot carriers.SOLUTION: A wireless communication device communicates using a plurality of radio resources for which pilot carriers and data carriers are arranged according to a predetermined pattern. The wireless communication device includes: a pilot carrier extraction unit that extracts pilot carriers from a received signal; a pilot carrier restoration unit that restores pilot carriers previously reduced on the transmission side; and a propagation path characteristic estimation unit that restores the reduced pilot carriers using a model generated based on characteristics of a propagation path and estimates the characteristics of the propagation path.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to digital wireless communication, and more particularly to a communication method that improves communication efficiency. [Background technology]

[0002] There is a wireless communication system that communicates using pilot signals. The following prior art is included as background art in this technical field. Patent Document 1 (JP Patent Publication 2012-85084 A) describes an OFDM signal transmission device that has a plurality of mapping patterns in which the number of pilot symbols per resource block is the same and the frequency interval for arranging the pilot symbols varies according to the delay spread of the transmission path, and a pilot insertion pattern control circuit 6 stores the values ​​of the delay spread and the mapping patterns in association with each other, selects a mapping pattern corresponding to the delay spread of the input transmission path, and instructs the mapping circuit and the pilot insertion circuit of the mapping pattern, and the mapping circuit allocates data to resource blocks according to the mapping pattern, and the pilot insertion circuit inserts pilot symbols.

[0003] Furthermore, Patent Document 2 (JP 2013-165351 A) describes a wireless communication system and method that includes a base station (BS) and a terminal station (CPE), in which a channel estimation unit of the CPE obtains an estimate of the propagation path based on the preamble of the DS received signal, interpolates it in the frequency axis direction to calculate a propagation path estimation result for each subcarrier, calculates a propagation path characteristic value (h) by taking a moving average of the propagation path estimation result over several frames in the time axis direction, equalizes the received subcarriers based on the propagation path characteristic value, and outputs the propagation path characteristic value to a pre-channel estimation unit of the CPE transmission processing unit, and the pre-channel estimation unit multiplies the subcarrier for the US transmission signal by the reciprocal (1 / h) of the propagation path characteristic value to pre-compensate for the propagation path characteristics.

[0004] The background art will be described with reference to Figures 4 and 5. Figure 4 is a block diagram showing the configuration of an OFDM transceiver in the background art, and Figure 5 is a diagram showing an example of the arrangement of pilot carriers in the background art.

[0005] The OFDM transceiver shown in Fig. 4 includes an encoding unit 401, a known signal generating unit 402, a subcarrier mapping unit 403, an IFFT unit 404, a D / A conversion unit 405, a radio transmission unit 406, a transmitting antenna 407, a receiving antenna 408, a radio reception unit 409, an A / D conversion unit 410, an FFT unit 411, a pilot carrier extraction unit 412, a channel characteristic estimation unit 413, an equalization / demodulation unit 414, and a decoding unit 415. In the conventional carrier arrangement example shown in Fig. 5, pilot carriers 501 are arranged continuously in the time direction and discretely in the frequency direction, and data carriers 502 are arranged between the pilot carriers 501.

[0006] At the transmitting side, main line data such as voice data and image data is input to an encoding unit 401, and after encoding for error correction at the receiving side, the data is input to a subcarrier mapping unit 403. Also, a known signal generating unit 402 generates a known signal common to both transmitting and receiving, the format of which is predetermined, and inputs the signal to a subcarrier mapping unit 403. The subcarrier mapping unit 403 assigns the encoded main line data as a data carrier and the known signal as a pilot carrier to subcarriers. Here, the method of subcarrier assignment differs depending on the standard, but for example, the arrangement shown in FIG. 5 is used.

[0007] The signals assigned to the subcarriers are converted from frequency domain signals to time domain signals in IFFT section 404, converted to analog signals in D / A conversion section 405, and input to radio transmission section 406. Radio transmission section 406 frequency-converts the baseband signals input from D / A conversion section 405 to radio frequencies, and the frequency-converted radio signals are transmitted from transmission antenna 407.

[0008] On the receiving side, a signal is received by a receiving antenna 408, and a receiving radio section 409 performs frequency conversion of the radio signal to a baseband signal. Then, an A / D conversion section 410 converts the baseband signal into a digital signal, and an FFT section 411 converts the signal from a time domain signal to a frequency domain signal and inputs it to a pilot carrier extraction section 412 and an equalization / demodulation section 414.

[0009] The pilot carrier extraction unit 412 extracts pilot carriers inserted at the transmitting side from the received signal and inputs them to the channel characteristic estimation unit 413. The channel characteristic estimation unit 413 estimates channel characteristics in the frequency direction based on the pilot carriers. For example, various estimation methods can be adopted, such as zero-order interpolation (hold), first-order interpolation (linear interpolation), and interpolation using a filter. The estimation results of the channel characteristics obtained by these estimation methods are input to the equalization and demodulation unit 414. The equalization and demodulation unit 414 performs equalization and demodulation processing on the output from the FFT unit 411 and the output from the channel characteristic estimation unit 413 described above. Thereafter, the decoding unit 415 performs error correction processing. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2012-85084 A [Patent Document 2] JP 2013-165351 A Summary of the Invention [Problem to be solved by the invention]

[0011] In order to perform equalization and demodulation on the receiving side, it is necessary to estimate the propagation path characteristics using known pilot carriers transmitted from the transmitting side. Since pilot carriers are not user data that is intended to be transmitted, it is desirable to reduce the number of pilot carriers to suppress the decrease in transmission efficiency. On the other hand, considering the sampling theorem, in order to ensure communication quality, it is desirable to arrange pilot carriers more densely than twice the fluctuation period of the propagation path characteristics in the time direction or frequency direction. In particular, in an environment with a short fluctuation period, the arrangement interval of pilot carriers becomes dense, and the transmission efficiency decreases.

[0012] For this reason, there is a demand for a wireless communication system in which pilot carriers are sparsely arranged to improve transmission efficiency. [Means for solving the problem]

[0013] A representative example of the invention disclosed in the present application is as follows: That is, a wireless communication device that communicates using a plurality of wireless resources in which pilot carriers and data carriers are arranged according to a predetermined pattern, comprising a pilot carrier extraction unit that extracts pilot carriers from a received signal, a pilot carrier restoration unit that restores pilot carriers that have been reduced in advance on the transmitting side, and a propagation path characteristic estimation unit that restores the reduced pilot carriers using a model generated based on the characteristics of the propagation path to estimate the propagation path characteristics. and a reducible position detection unit that detects the position of a pilot carrier that can be reduced from the estimation result of the propagation path characteristics, and the reducible position detection unit determines the position of the pilot carrier that can be reduced according to the restoration degree of the pilot carrier using the model. It is characterized by the above.

[0014] Moreover, a wireless communication device according to an example of the present invention is characterized in that it includes a channel characteristic learning unit that learns a reception result of non-reduced pilot carriers and an arrangement pattern of the pilot carriers to generate the model.

[0015] Moreover, a wireless communication device according to an example of the present invention is characterized in that it includes a channel characteristic learning unit that learns the reception result of unreduced pilot carriers and the channel characteristic estimation result obtained based on the reception result, and generates the model.

[0017] Also, a transmitter that communicates with a wireless communication device according to an embodiment of the present invention is characterized in that it transmits data by arranging new redundant data in positions of the reduced pilot carriers. Effect of the Invention

[0018] According to one aspect of the present invention, the efficiency of communication can be improved by reducing the number of pilot carriers arranged. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0019] [Figure 1] 1 is a block diagram showing a configuration of an OFDM transmitter / receiver according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an example of the arrangement of pilot carriers in the present embodiment. [Diagram 3] FIG. 13 illustrates a process for restoring reduced pilot carriers. [Figure 4] FIG. 1 is a block diagram showing a configuration of an OFDM transmitter / receiver in the background art. [Diagram 5] FIG. 1 is a diagram showing an example of the arrangement of pilot carriers in the background art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] In the wireless communication system according to the embodiment of the present invention, first, when the transmitter and receiver are installed, wireless communication is performed by a conventional method in which pilot carriers are arranged at all of the predetermined pilot carrier positions, and the receiving side learns the received pilot carriers and the correct pilot carriers (or the propagation path characteristics) to create a model. When the learning is completed and inference using the model becomes possible, the transmitting side reduces the arrangement of the pilot carriers and performs wireless communication. By inference using the model thus learned, the reduced pilot carriers can be restored, and the propagation path characteristics can be accurately estimated.

[0021] An embodiment of the present invention will be described with reference to Figures 1, 2 and 3. Figure 1 is a block diagram showing the configuration of an OFDM transceiver according to this embodiment. Figure 2 is a diagram showing an example of pilot carrier allocation according to this embodiment. Figure 3 is a diagram showing a process of restoring reduced pilot carriers. As shown in Figure 2, in this embodiment, pilot carriers are reduced in advance on the transmitting side and allocated sparsely, as compared to the conventional technology described above.

[0022] As shown in FIG. 1 , the OFDM transceiver of this embodiment includes an encoding unit 101, a known signal generating unit 102, a pilot carrier insertion control unit 103, a subcarrier mapping unit 104, an IFFT unit 105, a D / A conversion unit 106, a radio transmission unit 107, a transmitting antenna 108, a receiving antenna 109, a radio reception unit 110, an A / D conversion unit 111, an FFT unit 112, a pilot carrier extraction unit 113, a pilot carrier restoration unit 114, a propagation path characteristics learning unit 115, a path switching unit 116, a propagation path characteristics estimation unit 117, a pilot carrier reduction possible position detection unit 118, an equalization / demodulation unit 119, and a decoding unit 120.

[0023] At the transmitting side, main line data such as voice data and image data is input to an encoding unit 101, and after encoding for error correction at the receiving side, the data is input to a subcarrier mapping unit 104. Also, a known signal generating unit 102 generates a known signal common to both transmitting and receiving, the format of which is predetermined, and inputs the signal to a subcarrier mapping unit 104. The subcarrier mapping unit 104 assigns the encoded main line data as a data carrier and the known signal as a pilot carrier to subcarriers. Here, the method of subcarrier assignment differs depending on the standard, but for example, the arrangement shown in FIG. 2 is used.

[0024] In the carrier arrangement example of this embodiment shown in Fig. 2, pilot carriers 201 are arranged continuously in the time direction and discretely in the frequency direction within radio resources divided in the time direction and the frequency direction, and data carriers 202 are arranged between the pilot carriers 201. In the carrier arrangement example of this embodiment, the degree of discreteness in the frequency direction is higher than in the conventional arrangement example shown in Fig. 5.

[0025] The pilot carrier insertion control unit 103 receives notification of the positions of pilot carriers that can be eliminated, detected by the pilot carrier elimination possible position detection unit 118 on the receiving side, and notifies the known signal generation unit 102 and the subcarrier mapping unit 104 of the positions of the pilot carriers to be inserted.

[0026] The signals assigned to the subcarriers are converted from frequency domain signals to time domain signals in IFFT section 105, converted to analog signals in D / A conversion section 106, and input to radio transmission section 107. Radio transmission section 107 frequency-converts the baseband signals input from D / A conversion section 106 to radio frequencies, and the frequency-converted radio signals are transmitted from transmission antenna 108.

[0027] On the receiving side, a signal is received by a receiving antenna 109, and a receiving radio unit 110 frequency-converts the radio signal to a baseband signal. Then, an A / D conversion unit 111 converts the baseband signal into a digital signal, and an FFT unit 112 converts the signal from a time domain signal to a frequency domain signal. The signal is input to a pilot carrier extraction unit 113 and an equalization / demodulation unit 119.

[0028] The pilot carrier extraction unit 113 extracts pilot carriers inserted at the transmitting side from the received signal, and inputs the extracted pilot carriers to the channel characteristic estimation unit 117 via the switch 116. The channel characteristic estimation unit 117 estimates the channel characteristic in the frequency direction by interpolating between the extracted pilot carriers. For example, various estimation methods such as zero-order interpolation (hold), first-order interpolation (linear interpolation), and interpolation using a filter can be adopted. The estimation results of the channel characteristic obtained by these estimation methods are input to the equalization and demodulation unit 119. The equalization and demodulation unit 119 performs equalization and demodulation processing on the output from the FFT unit 112 and the output from the channel characteristic estimation unit 117 described above. Thereafter, the decoding unit 120 performs error correction processing.

[0029] The pilot carrier restoration unit 114 restores the pilot carriers that have been reduced based on the pilot carriers extracted by the pilot carrier extraction unit 113, using the learning model learned by the propagation path characteristics learning unit 115. The propagation path characteristics learning unit 115 learns the data sequence indicated by the input pilot carriers, and generates a model. The propagation path characteristics learning unit 115 may also generate a model by learning the reception results of the pilot carriers that have not been reduced, and the propagation path characteristics estimation results obtained based on the reception results. The model that is generated may be a neural network to which AI technology is applied, or may be constructed using a mathematical model. According to the learning model generated in this way, the pilot carriers that have been lost due to reduction can be restored, similar to the restoration technology using AI that complements or restores the missing parts of the learned image or data sequence. The pilot carrier reduction possible position detection unit 118 detects the position of the pilot carrier that can be reduced from the estimation result of the propagation path characteristics.

[0030] Next, the process of learning channel characteristics using AI technology and the process of inferring pilot carriers in this embodiment will be described with reference to FIG.

[0031] The operation of the transmitting side during learning is the same as that of the conventional technology, and the processing up to the extraction of pilot carriers from the received signal by pilot carrier extraction unit 113 is also the same on the receiving side. Pilot carrier extraction unit 113 outputs the extracted pilot carriers to propagation path characteristic learning unit 115 and route switching unit 116. Propagation path characteristic learning unit 115 learns the data sequence indicated by the pilot carriers sequentially input, and outputs the learned model to pilot carrier restoration unit 114. The operation of pilot carrier restoration unit 114 after the learning result is input will be described later.

[0032] When the path switching unit 116 selects the b side, the pilot carriers output from the pilot carrier extraction unit 113 are input to the channel characteristic estimation unit 117. The channel characteristic estimation unit 117 estimates the channel characteristic by interpolating between the extracted pilot carriers. Thereafter, as in the conventional technology, the equalization and demodulation unit 119 executes equalization and demodulation processing, and the decoding unit 120 executes decoding processing. The channel characteristic estimation unit 117 also inputs the channel characteristic estimation result to the pilot carrier reduction possible position detection unit 118. The pilot carrier reduction possible position detection unit 118 detects the position of the pilot carrier that can be reduced from the estimation result of the channel characteristic, and notifies the pilot carrier insertion control unit 103 and the pilot carrier extraction unit 113 of the detected reduction possible position. The pilot carrier reduction possible position detection unit 118 may determine the reduction possible rate or the reduction possible number using the suppression of performance deterioration due to the reduction of the pilot carrier as an index, and may determine the position where the pilot carrier is reduced based on the determined reduction possible rate or the reduction possible number. For example, it is advisable to consider not reducing pilot carriers at positions where the change in propagation path characteristics is large due to the influence of narrowband interference or a dip in the propagation path characteristics. In addition, the pilot carrier reduction possible position detection unit 118 may detect the reduction possible position based on the evaluation result of the restoration degree using the learning model, the frequency propagation characteristics, and the demodulation result (e.g., error rate). The pilot carrier reduction possible position detection unit 118 may notify the pilot carrier insertion control unit 103 of the reduction possible position offline, or if two-way communication is possible, a data field may be provided for storing information to be fed back from the receiving side to the transmitting side, and the receiving side may notify the transmission side of the reduction possible position via radio at a predetermined timing (e.g., periodically). Various methods can be adopted. The above process is repeated until the propagation path characteristics learning unit 115 generates a learning model.

[0033] Next, an inference process using the learned model will be described. On the transmitting side, the pilot carrier insertion control unit 103 controls the known signal generation unit 102 and the subcarrier mapping unit 104 according to the reducible position detected by the above-mentioned pilot carrier reducible position detection unit 118, and inserts a pilot carrier with a part of the pilot carrier reduced as shown in FIG. 2. After that, a signal is output from the antenna 108 by the same process as the conventional technology. On the receiving side, the pilot carrier extraction unit 113 extracts pilot carriers based on pilot carrier position information notified by the pilot carrier reducible position detection unit 118, and outputs the extraction result to the pilot carrier restoration unit 114.

[0034] The pilot carrier restoration unit 114 restores the reduced pilot carriers based on the pilot carriers extracted by the pilot carrier extraction unit 113, using the learning model generated by the channel characteristic learning unit 115.

[0035] In this embodiment, as shown in FIG. 3, conventional wireless communication is performed without reducing pilot carriers until a learning model is generated. During that time, the pilot carriers extracted on the receiving side are treated as learning data 301 in FIG. 3, a model is generated in the propagation path characteristic learning unit 115, and the generated model is output to the pilot carrier restoration unit 114.

[0036] After the learning model is generated and the pilot carrier reduction possible positions are notified, the transmitting side reduces some of the pilot carriers and transmits and outputs, so that the reduced received pilot carriers 302 are output from the pilot carrier extraction unit 113. The pilot carrier restoration unit 114 performs inference using the learning model and generates restored pilot carriers 303. The pilot carrier restoration unit 114 inputs the restored pilot carriers to the propagation path characteristic estimation unit 117 via the path switching unit 116 selected for side a. Thereafter, as in the conventional technology, the equalization and demodulation unit 119 performs equalization and demodulation processing, and the decoding unit 120 performs decoding processing.

[0037] For example, in a trial operation after the wireless transmitter and wireless receiver are installed, the path switching unit 116 may be switched to side b to generate a learning model, and in the subsequent actual operation, the path switching unit 116 may be switched to side a to generate pilot carriers 303 restored from the reduced pilot carriers 302.

[0038] In addition, after starting communication with all pilot carriers inserted and generating a learning model, a signal with fewer pilot carriers may be transmitted as an auxiliary signal to additionally learn the generated learning model.

[0039] Furthermore, the positions of the eliminated pilot carriers 302 are utilized as data carriers 202, while the new data carriers may be used as user data to improve the data communication speed, or may be used as redundant data to improve error resilience.

[0040] By the above learning and inference processes, the reduced pilot carriers can be restored on the receiving side, and the restored pilot carriers can be input to the propagation path characteristic estimation unit 117, making it possible to decode with the same quality as the conventional technology even in a state in which the pilot carriers are reduced. Although the ability to follow the fluctuations in the communication environment decreases due to the reduction in the pilot carriers, it is effective in improving communication efficiency in a fixed environment where the fluctuations in the communication environment are small. In addition, wireless communication is possible even when the pilot carriers are arranged in such a way that the sampling theorem is not satisfied with respect to the change period of the propagation path on the transmitting side.

[0041] The present invention is not limited to the above-described embodiments, and includes various modified examples and equivalent configurations within the spirit of the appended claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. Furthermore, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Furthermore, the configuration of another embodiment may be added to the configuration of one embodiment. Furthermore, a part of the configuration of each embodiment may be added, deleted, or replaced with another configuration.

[0042] In addition, each of the above-mentioned configurations, functions, processing units, processing means, etc. may be realized in hardware, for example by designing some or all of them as an integrated circuit, or may be realized in software by a processor interpreting and executing a program that realizes each function.

[0043] Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or in a recording medium such as an IC card, an SD card, or a DVD.

[0044] In addition, the control lines and information lines shown are those considered necessary for the explanation, and do not necessarily show all the control lines and information lines necessary for implementation. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0045] 101, 401: Encoding section 102, 402: known signal generating unit 103: Pilot carrier insertion control unit 104, 403: Subcarrier mapping unit 105, 404: IFFT section 106, 405: D / A conversion section 107, 406: Transmitting radio section 108, 407: Transmitting antenna 109, 408: Receiving antenna 110, 409: Receiving radio section 111, 410: A / D conversion section 112, 411:FFT section 113, 412: Pilot carrier extraction unit 114: Pilot Carrier Restoration Department 115: Propagation path characteristic learning unit 116: Route switching unit 117, 413: Propagation path characteristic estimation unit 118: Pilot carrier reduction possible position detection unit 119, 414: Equalization and demodulation section 120, 415: Decoding section 201, 501: Pilot Carrier 202, 502: Data carrier 301: Learning data 302: Reduced received pilot carrier 303:Restored Pilot Carrier

Claims

1. A wireless communication device that communicates using a plurality of wireless resources in which pilot carriers and data carriers are arranged according to a predetermined pattern, a pilot carrier extraction unit that extracts a pilot carrier from a received signal; A pilot carrier restoration unit that restores pilot carriers that have been previously reduced on the transmitting side; a propagation path characteristic estimating unit that estimates propagation path characteristics by restoring the reduced pilot carriers using a model generated based on the characteristics of the propagation path; a reducible position detection unit that detects a position of a reducible pilot carrier from a result of estimating a propagation path characteristic; The wireless communication device, wherein the reducible position detection unit determines positions of pilot carriers that can be reducible depending on a degree of restoration of the pilot carriers using the model.

2. 2. The wireless communication device according to claim 1, A wireless communication device comprising: a propagation path characteristics learning unit that learns a reception result of non-reduced pilot carriers and an arrangement pattern of pilot carriers to generate the model.

3. 2. The wireless communication device according to claim 1, A wireless communication device comprising: a propagation path characteristics learning unit that learns a reception result of unreduced pilot carriers and a propagation path characteristics estimation result obtained based on the reception result, and generates the model.

4. A wireless communication system, A transmitter and a receiver are provided for communicating using a plurality of radio resources in which pilot carriers and data carriers are arranged according to a specific pattern, The receiver includes: a pilot carrier extraction unit that extracts a pilot carrier from a received signal; A pilot carrier restoration unit that restores pilot carriers that have been previously reduced by the transmitter; a propagation path characteristic estimating unit that estimates propagation path characteristics by restoring the reduced pilot carriers using a model generated based on the characteristics of the propagation path; a reducible position detection unit that detects a position of a reducible pilot carrier from the estimation result of the propagation path characteristics, The reducible position detection unit determines a position of a pilot carrier that can be reducible according to a restoration degree of the pilot carrier using the model, A wireless communication system, wherein the transmitter transmits data by reducing pilot carriers at the determined positions.

5. A wireless communication system as claimed in claim 4, A wireless communication system, wherein the transmitter transmits data by placing new redundant data in positions of the reduced pilot carriers.

6. A wireless communication system according to claim 4 or 5, The wireless communication system according to the present invention, wherein the receiver has a propagation path characteristic learning unit that learns a reception result of non-reduced pilot carriers and an arrangement pattern of pilot carriers to generate the model.

7. A wireless communication system according to claim 4 or 5, The receiver includes a propagation path characteristic learning unit that learns the reception result of unreduced pilot carriers and the propagation path characteristic estimation result obtained based on the reception result, and generates the model.

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