COMMUNICATION SYSTEM, COMMUNICATION METHOD, AND RECEIVER

Abstract

A communication method according to one embodiment of the present invention includes: a reception device receiving a training signal from a transmission device via a wired transmission line; the reception device receiving a training signal from the transmission device via a plurality of wireless transmission lines having different transmission line characteristics; the reception device comparing the training signal received via the wired transmission line and each of the training signals received via the plurality of wireless transmission lines having different transmission line characteristics and calculating, for each transmission line characteristic of the wireless transmission lines, a correction function to correct distortion of signals received thereafter via the wireless transmission lines having different transmission line characteristics; the reception device storing each of the calculated correction functions for each transmission line characteristic of the wireless transmission lines; and, when the wired transmission line is cut off, the reception device compensating the distortion of signals received via the wireless transmission lines as a backup for the wired transmission line, on the basis of the correction functions stored for each transmission line characteristic of the wireless transmission lines.

Description

[Technical field]

[0001] The present invention relates to a communication system, a communication method, and a receiving device. [Background technology]

[0002] 2. Description of the Related Art In wireless communication, a technique is known in which a receiving device receives a signal transmitted from a transmitting device by compensating for waveform distortion that occurs in a wireless transmission path.

[0003] For example, Non-Patent Document 1 discloses a technique for compensating for waveform distortion using an adaptive equalization algorithm that estimates a correction function that sequentially compensates for waveform distortion by modeling based on digital signal processing in a fading transmission path. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Hiroshi Suzuki, "Basic Technology for Mobile Communications, Part 1, 2: Adaptive Signal Processing in Mobile Communications", NTT DOCOMO Technical Journal Vol. 1, No. 2, New Technical Report, p. 14-20, October 1993 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventionally, there has been a problem that delays can occur when using an adaptive equalization algorithm, making it difficult to increase speed and accuracy.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a communication system, a communication method, and a receiving device that can compensate for waveform distortion occurring in a wireless transmission path with low delay while increasing the transmission capacity of wireless communication. [Means for solving the problem]

[0007] According to one aspect of the present invention, a communication system transmits a signal from a transmitting device to a receiving device via a wired transmission path and via a wireless transmission path having a plurality of different transmission path characteristics that change over time, the transmitting device has a wired signal transmitting unit that transmits a signal including a training signal to the receiving device via the wired transmission path, and a wireless signal transmitting unit that transmits the training signal to the receiving device via the wireless transmission path having a plurality of different transmission path characteristics and then transmits another signal to the receiving device as a backup for the wired transmission path, the receiving device has a wired signal receiving unit that receives the signal transmitted by the transmitting device via the wired transmission path, and a correction function calculation unit that compares a training signal previously received by the wired signal receiving unit with each of the training signals previously received by the wireless signal receiving unit via the wireless transmission paths having a plurality of different transmission path characteristics, and calculates in advance a correction function for correcting distortion of the signal received by the wireless signal receiving unit for each transmission path characteristic of the wireless transmission path; a storage unit that stores each of the correction functions calculated by the correction function calculation unit for each transmission path characteristic of the wireless transmission path; and an equalization unit that compensates for distortion of the signal received by the wireless signal receiving unit based on the correction function stored in the storage unit for each transmission path characteristic of the wireless transmission path when the wired transmission path is interrupted.

[0008] Moreover, a communication method according to one aspect of the present invention is a communication method for transmitting a signal from a transmitting device to a receiving device via a wired transmission path and via a wireless transmission path having a plurality of different transmission path characteristics that change over time, the communication method including the steps of: receiving a training signal from the transmitting device via the wired transmission path by the receiving device; receiving a training signal from the transmitting device via the wireless transmission path having a plurality of different transmission path characteristics by the receiving device; comparing the training signal received via the wired transmission path with each of the training signals received via the wireless transmission paths having a plurality of different transmission path characteristics by the receiving device, and then calculating a correction function for each transmission path characteristic of the wireless transmission path that corrects distortion of a signal received via the wireless transmission path having a plurality of different transmission path characteristics; storing each of the calculated correction functions by the receiving device for each transmission path characteristic of the wireless transmission path; and, when the wired transmission path is interrupted, compensating for distortion of the signal received via the wireless transmission path as a backup for the wired transmission path based on the correction function stored for each transmission path characteristic of the wireless transmission path by the receiving device.

[0009] Moreover, a receiving device according to one aspect of the present invention is characterized in that it comprises a wired signal receiving unit that receives a signal transmitted by a transmitting device via a wired transmission path; a wireless signal receiving unit that receives each of the signals transmitted by the transmitting device via wireless transmission paths having a plurality of different transmission path characteristics that change over time; a correction function calculation unit that compares a training signal previously received by the wired signal receiving unit with each of the training signals previously received by the wireless signal receiving unit via the wireless transmission paths having a plurality of different transmission path characteristics, and calculates in advance a correction function for correcting distortion of the signal received by the wireless signal receiving unit for each transmission path characteristic of the wireless transmission path; a memory unit that stores each of the correction functions calculated by the correction function calculation unit for each transmission path characteristic of the wireless transmission path; and an equalization unit that compensates for distortion of the signal received by the wireless signal receiving unit based on the correction function stored in the memory unit for each transmission path characteristic of the wireless transmission path when the wired transmission path is interrupted. Effect of the Invention

[0010] According to the present invention, it is possible to increase the transmission capacity of wireless communication and compensate for waveform distortion occurring in a wireless transmission path with low delay. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Diagram 2] FIG. 2 is a functional block diagram illustrating functions of a transmission device. [Diagram 3] FIG. 2 is a functional block diagram illustrating functions of a receiving device according to an embodiment. [Figure 4] 4 is a graph showing a schematic diagram of a signal analyzed by an analysis unit. [Diagram 5] FIG. 2 is a diagram illustrating an example of a main operation of a receiving device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of a communication system will be described below with reference to the drawings. Fig. 1 is a diagram showing a configuration example of a communication system 1 according to an embodiment. As shown in Fig. 1, the communication system 1 is configured such that, for example, an exchange 2 and an exchange 3 communicate with each other via a wired transmission path 4 and a wireless transmission path 5.

[0013] Hereinafter, the exchange 2 will be referred to as the transmitting device 2, and the exchange 3 will be referred to as the receiving device 3, and an example will be described in which the transmitting device 2 transmits a user signal to the receiving device 3. Note that the transmitting device 2 may have all the functions that the receiving device 3 has. Also, the receiving device 3 may have all the functions that the transmitting device 2 has.

[0014] The wired transmission path 4 is configured by connecting the transmitting device 2 and the receiving device 3 with, for example, an undersea optical cable, and is a wired section that enables two-way communication.

[0015] The wireless transmission path 5 is a wireless section that enables two-way communication including wireless transmission path states 51 to 53 (first wireless transmission path state to third wireless transmission path state) of multiple different transmission path characteristics that change over time, for example, becoming a multipath. Here, the wireless transmission path with different transmission path characteristics due to changes in weather and sea surface conditions over time (changes in the wireless transmission path environment) are distinguished as different transmission path states. For example, the wireless transmission path 5 becomes a wireless transmission path with three different transmission path characteristics, which are shown as wireless transmission path states 51 to 53, respectively. For example, the wireless transmission path 5 has multiple different transmission path characteristics that change over time, and is used as a backup line for the wired transmission path 4.

[0016] Fig. 2 is a functional block diagram illustrating functions of the transmission device 2. As shown in Fig. 2, the transmission device 2 includes, for example, an encoding unit 21, a modulation unit 22, an oscillation circuit (transmission unit) 23, a frequency conversion circuit 24, a wireless signal transmission unit 25, and a wired signal transmission unit 26.

[0017] The encoding unit 21 encodes a user signal and outputs the encoded user signal to the modulation unit 22. The encoding unit 21 also encodes a reference signal (training signal) for compensating for signal distortion occurring in the wireless transmission path 5, for example, and outputs the encoded user signal to the modulation unit 22.

[0018] The modulation unit 22 modulates the user signal input from the encoding unit 21, and outputs the modulated user signal to the frequency conversion circuit 24 and the wired signal transmission unit 26. In addition, the modulation unit 22 outputs the reference signal (training signal) input from the encoding unit 21 to the frequency conversion circuit 24 and the wired signal transmission unit 26.

[0019] The oscillator circuit 23 generates a signal of a reference frequency used for signal transmission by oscillation, and outputs the generated signal of the reference frequency to the frequency conversion circuit 24 and the wired signal transmission unit 26 .

[0020] The frequency conversion circuit 24 converts the frequency of the signal input from the modulation unit 22 to a predetermined frequency using the signal (reference frequency signal) input from the oscillation circuit 23, and outputs the frequency-converted signal to the radio signal transmission unit 25. For example, the frequency conversion circuit 24 converts an intermediate frequency signal (e.g., a 140 MHz band signal) to a radio carrier frequency signal (e.g., a 6 GHz band signal) using the reference frequency signal (e.g., a 10 MHz signal).

[0021] The wireless signal transmitting unit 25 has, for example, an RF (radio frequency) unit 250 and an antenna 252, and transmits a signal to the receiving device 3 via the wireless transmission path 5 (FIG. 1). For example, the RF unit 250 includes a transmission amplifier, a filter, and the like, and transmits the signal frequency-converted by the frequency conversion circuit 24 via the antenna 252.

[0022] Moreover, the wireless signal transmitting unit 25 transmits a training signal via a plurality of wireless transmission paths 5 having different transmission path characteristics, and then transmits another signal to the receiving device 3 as a backup for the wired transmission path 4.

[0023] The wired signal transmitting unit 26 uses the signal input from the oscillation circuit 23 to transmit a signal including the training signal input from the modulation unit 22 to the receiving device 3 via the wired transmission path 4. The wired signal transmitting unit 26 also transmits the signal input from the oscillation circuit 23 to the receiving device 3 via the wired transmission path 4 as a signal of a reference frequency.

[0024] Fig. 3 is a functional block diagram illustrating functions of a receiving device 3 according to an embodiment. As shown in Fig. 3, the receiving device 3 includes, for example, a wired signal receiving unit 30, an oscillator circuit (transmitter) 31, a synchronizing unit 32, a wireless signal receiving unit 33, a frequency converting circuit 34, an AD converter (A / D) 35, an estimating unit 36, a correction function calculating unit 37, an analyzing unit 38, a patterning unit 39, a storage unit 40, a switching unit 41, an equalizing unit 42, a decoding unit 43, and a control unit 44.

[0025] The wired signal receiving unit 30 receives a signal transmitted by the transmitting device 2 via the wired transmission path 4, and outputs the received signal to the synchronization unit 32 and the estimation unit 36. For example, the wired signal receiving unit 30 receives a signal including a training signal by utilizing the available capacity of the wired transmission path 4. The wired signal receiving unit 30 also receives a signal of a reference frequency transmitted by the transmitting device 2.

[0026] The oscillator circuit 31 generates a reference signal used for receiving a signal by oscillation, and outputs the generated reference signal to the synchronization unit 32 .

[0027] The synchronization unit 32 synchronizes the signal (reference signal) input from the oscillation circuit 31 with the signal of the reference frequency received by the wired signal receiving unit 30, and outputs the synchronized signal to the frequency conversion circuit .

[0028] The wireless signal receiving unit 33 has an antenna 330 and an RF unit 332, and receives signals via a plurality of wireless transmission paths 5 having different transmission path characteristics. Specifically, the antenna 330 receives signals via the wireless transmission path 5. The RF unit 332 includes a receiving amplifier, an AGC (automatic gain control), and the like, and outputs the signals received via the antenna 330 to the frequency conversion circuit 34.

[0029] The frequency conversion circuit 34 converts the frequency of the signal input from the wireless signal receiving unit 33 to a predetermined frequency using the reference signal input from the synchronization unit 32, and outputs the frequency-converted signal to the AD converter 35. For example, the frequency conversion circuit 34 converts a wireless carrier frequency signal (e.g., a 6 GHz band signal) to an intermediate frequency signal (e.g., a 140 MHz band signal) using a reference frequency signal (e.g., a 10 MHz signal).

[0030] The AD converter 35 converts the signal input from the frequency conversion circuit 34 into an AD signal, and outputs the converted signal to the estimation unit 36 ​​and the analysis unit 38 .

[0031] The estimation unit 36 ​​uses the training signal input from the wired signal receiving unit 30 to estimate the transmission path characteristics of each of the wireless transmission path states 51 to 53 based on the number of notches, frequency, and amplitude of each training signal received by the wireless signal receiving unit 33, and outputs the estimation results to the correction function calculation unit 37.

[0032] The correction function calculation unit 37 compares the training signal received in advance by the wired signal receiving unit 30 with each of the training signals received in advance by the wireless signal receiving unit 33 via each of the wireless transmission path states 51 to 53. Next, the correction function calculation unit 37 calculates in advance a correction function for correcting distortion of the signal received by the wireless signal receiving unit 33 for each of the wireless transmission path states 51 to 53 (different transmission path characteristics of the wireless transmission path 5).

[0033] That is, the correction function calculation unit 37 calculates a correction function for each of the wireless transmission path states 51 to 53 based on the transmission path characteristics estimated by the estimation unit 36 ​​for each of the wireless transmission path states 51 to 53. Then, the correction function calculation unit 37 outputs the calculated correction function to the patterning unit 39 and the switching unit 41.

[0034] The analysis section 38 analyzes the signal input from the AD converter 35 and outputs the analysis result to the equalization section 42 and the patterning section 39 .

[0035] 4 is a graph that shows a schematic diagram of a signal analyzed by the analysis unit 38. The analysis unit 38 performs spectrum analysis in the frequency domain on the signal input from the AD converter 35, and observes the frequency (notch frequency A) of the point (notch) where the amplitude is attenuated, its depth (notch depth B), and peak level (amplitude C), and patterns the waveform distortion of the received signal.

[0036] For example, the analysis unit 38 identifies, as a distortion pattern, when the amplitude level of the reflected wave is larger than that of the direct wave, when the amplitude level of the reflected wave is smaller, or when the delay time of the reflected wave causes the notch frequency, notch depth, and peak level to change over time depending on the state of the fading propagation path. Depending on the state of the propagation path, attenuation may be applied to the entire propagated signal waveform, lowering the amplitude level of the waveform peak. Also, the number of notches changes depending on the number of delayed waves.

[0037] The patterning unit 39 (FIG. 3) classifies the correction functions of the wireless transmission path states 51 to 53 input from the correction function calculation unit 37 into patterns by referring to the analysis results input from the analysis unit 38, and stores the correction functions into the memory unit 40 for each pattern.

[0038] The storage unit 40 is a database (DB) that stores the correction function for each pattern. That is, the storage unit 40 stores each of the correction functions calculated by the correction function calculation unit 37 for each wireless transmission path state (for each different transmission path characteristic of the wireless transmission path 5).

[0039] The switching unit 41 outputs, under the control of the control unit 44, to the equalization unit 42, one of the correction functions stored in the storage unit 40 or the correction function input from the correction function calculation unit 37.

[0040] For example, when the wired transmission path 4 transmits a signal (when the wired transmission path 4 is valid), the switching unit 41 outputs the correction function input from the correction function calculation unit 37 to the equalization unit 42. When the wired transmission path 4 does not transmit a signal (when the wired transmission path 4 is invalid due to a cutoff or the like), the switching unit 41 outputs any one of the correction functions stored in the storage unit 40 to the equalization unit 42.

[0041] The equalization unit 42 compensates for distortion of the signal input from the analysis unit 38 using the correction function input from the switching unit 41, and outputs the distortion-compensated signal to the decoding unit 43. For example, when the wired transmission path 4 is cut off, the equalization unit 42 compensates for distortion of the signal received by the wireless signal receiving unit 33 based on the correction function stored in the storage unit 40 for each different transmission path characteristic of the wireless transmission path.

[0042] The decoding unit 43 decodes the signal input from the equalization unit 42 and outputs it as a user signal.

[0043] The control unit 44 controls each unit constituting the receiving device 3. For example, the control unit 44 determines whether the wired transmission path 4 is valid or not based on the signal output from the wired signal receiving unit 30, and controls the switching unit 41.

[0044] In addition, each function possessed by each of the above-mentioned transmitting device 2 and receiving device 3 may be configured in part or in whole by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

[0045] For example, the transmitting device 2 and the receiving device 3 can each be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0046] Next, a description will be given of an operation example of the receiving device 3. Fig. 5 is a diagram illustrating a main operation example of the receiving device 3 according to an embodiment. As shown in Fig. 5, the receiving device 3 receives a training signal from the transmitting device 2 via the wired transmission path 4 (S100).

[0047] Next, the receiving device 3 receives the training signal from the transmitting device 2 via each of the wireless transmission path states 51 to 53 in which the state of sea surface waves differs due to the influence of weather, for example, in an ocean propagation path (S102).

[0048] Next, the receiving device 3 compares the training signal received via the wired transmission path 4 with each of the training signals received via each of the wireless transmission path states 51 to 53, and then calculates a correction function for each wireless transmission path state to correct distortion of the signal received via each of the wireless transmission path states 51 to 53 (S104).

[0049] Next, the receiving device 3 stores the calculated correction functions for each wireless transmission path state in the storage unit 40 (S106).

[0050] Then, when the wired transmission path 4 is interrupted, the receiving device 3 compensates for distortion of the signal received via the wireless transmission path 5 as a backup for the wired transmission path 4, based on the correction function stored for each wireless transmission path state (S108).

[0051] In this way, when the wired transmission path 4 is interrupted, the receiving device 3 in one embodiment compensates for distortion of the signal received by the wireless signal receiving unit 33 based on the correction function stored in the memory unit 40 for each wireless transmission path state, thereby making it possible to increase the transmission capacity of wireless communication while compensating for waveform distortion of the signal occurring in the wireless transmission path 5 with low delay.

[0052] Furthermore, the communication system 1 according to an embodiment transmits a training signal for correcting waveform distortion caused by fading in a wireless section via the wired transmission path 4, so that the transmission capacity of a main signal in a wireless section can be increased. [Explanation of symbols]

[0053] 1 communication system, 2 transmitting device, 3 receiving device, 4 wired transmission path, 5 wireless transmission path, 21 encoding unit, 22 modulation unit, 23 oscillation circuit, 24 frequency conversion circuit, 25 wireless signal transmitting unit, 26 wired signal transmitting unit, 30 wired signal receiving unit, 31 oscillation circuit, 32 synchronization unit, 33 wireless signal receiving unit, 34 frequency conversion circuit, Reference Signs List 5...AD converter, 36...estimation section, 37...correction function calculation section, 38...analysis section, 39...patterning section, 40...storage section, 41...switching section, 42...equalization section, 43...decoding section, 44...control section, 51-53...wireless transmission path state (first wireless transmission path state to third wireless transmission path state), 250...RF section, 252...antenna, 330...antenna, 332...RF section

Claims

1. In a communication system in which a signal is transmitted from a transmitting device to a receiving device via a wired transmission path and a wireless transmission path having a plurality of different transmission path characteristics that change over time, The transmitting device a wired signal transmitting unit that transmits a signal including a training signal to the receiving device via the wired transmission path; a wireless signal transmitting unit that transmits a training signal via the wireless transmission paths having a plurality of different transmission path characteristics, and then transmits another signal to the receiving device as a backup for the wired transmission path; having The receiving device includes: a wired signal receiving unit for receiving a signal transmitted by the transmitting device via the wired transmission path; a wireless signal receiving unit that receives signals transmitted by the transmitting device via the wireless transmission paths having different transmission path characteristics; a correction function calculation unit that compares a training signal received in advance by the wired signal receiving unit with each of the training signals received in advance by the wireless signal receiving unit via the wireless transmission paths having a plurality of different transmission path characteristics, and calculates in advance a correction function for correcting distortion of the signal received by the wireless signal receiving unit for each transmission path characteristic of the wireless transmission path; a storage unit that stores each of the correction functions calculated by the correction function calculation unit for each transmission path characteristic of the wireless transmission path; an equalization unit that compensates for distortion of a signal received by the wireless signal receiving unit based on a correction function stored in the storage unit for each transmission path characteristic of the wireless transmission path when the wired transmission path is interrupted; A communication system comprising:

2. The receiving device includes: an estimation unit that estimates a transmission path characteristic for each of the transmission path characteristics of the wireless transmission path based on the number of notches, the frequency, and the amplitude of each training signal received by the wireless signal receiving unit; and The correction function calculation unit calculating a correction function for each of the transmission path characteristics of the wireless transmission path based on the transmission path characteristics estimated by the estimation unit for each of the transmission path characteristics of the wireless transmission path; 2. The communication system according to claim 1,

3. The transmitting device The wired signal transmitting unit transmits a signal of a reference frequency used for transmitting a signal to the receiving device, The receiving device includes: the wired signal receiving unit receives the signal of the reference frequency transmitted by the wired signal transmitting unit, a synchronization unit that synchronizes a reference signal used for receiving a signal with a signal of a reference frequency received by the wired signal receiving unit; 3. The communication system according to claim 1, further comprising:

4. A communication method for transmitting a signal from a transmitting device to a receiving device via a wired transmission path and a wireless transmission path having a plurality of different transmission path characteristics that change over time, comprising: receiving a training signal from the transmitting device via the wired transmission path by the receiving device; receiving a training signal from the transmitting device via the wireless transmission paths having a plurality of different transmission path characteristics; the receiving device comparing a training signal received via the wired transmission path with each of the training signals received via the wireless transmission paths having a plurality of different transmission path characteristics, and then calculating a correction function for each transmission path characteristic of the wireless transmission path that corrects distortion of the signal received via the wireless transmission paths having a plurality of different transmission path characteristics; The receiving device stores each of the calculated correction functions for each transmission path characteristic of the wireless transmission path; when the wired transmission path is interrupted, the receiving device compensates for distortion of a signal received via the wireless transmission path as a backup for the wired transmission path, based on a correction function stored for each transmission path characteristic of the wireless transmission path; A communication method comprising:

5. The method further includes a step of estimating a transmission path characteristic for each of the wireless transmission paths based on a number, a frequency, and an amplitude of each of the training signals received via the wireless transmission paths, by the receiving device; When the receiving device calculates a correction function, the receiving device calculates the correction function for each transmission path characteristic of the wireless transmission path based on the transmission path characteristic estimated for each transmission path characteristic of the wireless transmission path.

5. The communication method according to claim 4, further comprising:

6. a step of receiving, by the receiving device, a signal having a reference frequency used by the transmitting device for transmitting a signal via the wired transmission path; a step of the receiving device synchronizing a reference signal used for receiving a signal with the received reference frequency signal; The communication method according to claim 4 or 5, further comprising:

7. a wired signal receiving unit that receives a signal transmitted by the transmitting device via a wired transmission path; a wireless signal receiving unit that receives signals transmitted by the transmitting device via a wireless transmission path having a plurality of different transmission path characteristics that change over time; a correction function calculation unit that compares a training signal received in advance by the wired signal receiving unit with each of the training signals received in advance by the wireless signal receiving unit via the wireless transmission paths having a plurality of different transmission path characteristics, and calculates in advance a correction function for correcting distortion of the signal received by the wireless signal receiving unit for each transmission path characteristic of the wireless transmission path; a storage unit that stores each of the correction functions calculated by the correction function calculation unit for each transmission path characteristic of the wireless transmission path; an equalization unit that compensates for distortion of a signal received by the wireless signal receiving unit based on a correction function stored in the storage unit for each transmission path characteristic of the wireless transmission path when the wired transmission path is interrupted; A receiving device comprising:

8. an estimation unit that estimates a transmission path characteristic for each of the transmission path characteristics of the wireless transmission path based on the number of notches, the frequency, and the amplitude of each training signal received by the wireless signal receiving unit; and The correction function calculation unit calculating a correction function for each of the transmission path characteristics of the wireless transmission path based on the transmission path characteristics estimated by the estimation unit for each of the transmission path characteristics of the wireless transmission path; 8. The receiving device according to claim 7,

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