Communication device and communication method

Abstract

To provide a communication device and a communication method that enable appropriate transmission of a multiplexed transmission frame in which signals corresponding to two or more OFDM frames having different frame lengths are appropriately multiplexed between a first device and a second device.SOLUTION: In a transmission system that transmits a multiplexed transmission frame in which a first broadcast signal and a second broadcast signal are multiplexed from a first device to a second device, a communication device includes a control unit that configures at least one of the first device and the second device, and sets the frame length of the multiplex transmission frame such that the frame length becomes an integral multiple of the frame length of a first OFDM frame related to the first broadcast signal.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a communication device and a communication method.

Background Art

[0002] A transmission method for a transmission frame in which a main signal and an SC (Service Channel) signal are multiplexed is defined from a first device (for example, a performance studio or a transmission station of a broadcasting station) to a second device (for example, a transmission station). The main signal includes a first broadcast signal related to terrestrial digital television broadcasting and V-Low terrestrial multimedia broadcasting (for example, a TS (Transport Stream) signal, a TMCC (Transmission and Multiplexing Configuration Control) signal, etc.). In such a transmission method, the link between the first device and the second device is called an STL (Studio To Transmitter Link) or a TTL (Transmitter To Transmitter Link) (for example, Non-Patent Document 1).

[0003] Since the transmission frames used in STL and TTL are integer multiples (5 times) of the OFDM (Orthogonal Frequency Division Multiplexing) frame related to the first broadcast signal, a situation where synchronization is achieved between the transmission frames used in STL and TTL and the first OFDM frame related to the first broadcast signal has been realized.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, with the expansion of STL / TTL, a technology (advanced STL / TTL) that multiplexes a second broadcast signal related to the terrestrial broadcast enhancement system into a transmission frame has been under consideration. It is assumed that the first broadcast signal and the second broadcast signal are multiplexed in the transmission frame used in advanced STL / TTL.

[0006] Under such circumstances, as a result of intensive studies, the inventors have found that synchronization between the transmission frame used in advanced STL / TTL and the first OFDM frame cannot be achieved, and appropriate transmission between the first device and the second device cannot be realized.

[0007] Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to provide a communication device and a communication method that enable appropriate transmission of a multiplexed transmission frame in which two or more OFDM frames having different frame lengths and corresponding signals are appropriately multiplexed between a first device and a second device.

Means for Solving the Problems

[0008] The communication device according to the disclosure constitutes at least one of the first device and the second device in a transmission system that transmits a multiplexed transmission frame in which a first broadcast signal and a second broadcast signal are multiplexed from the first device to the second device, and includes a control unit that sets the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of a first OFDM frame related to the first broadcast signal.

[0009] The communication method according to the disclosure includes a step of transmitting a multiplexed transmission frame in which a first broadcast signal and a second broadcast signal are multiplexed from a first device to a second device, and a step in which a communication device constituting at least one of the first device and the second device sets the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of a first OFDM frame related to the first broadcast signal.

Effects of the Invention

[0010] According to the present invention, a communication device and a communication method are provided that enable appropriate transmission of a multiplexed transmission frame in which two or more OFDM frames having different frame lengths and corresponding signals are appropriately multiplexed between a first device and a second device.

Brief Description of Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Next, embodiments of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the ratios of the respective dimensions are different from the actual ones.

[0013] Therefore, specific dimensions and the like should be determined in consideration of the following description. Of course, there are also parts where the relationships and ratios of the dimensions are different between the drawings.

[0014] [Summary of Disclosure] The communication device according to the summary of the disclosure constitutes at least one of the first device and the second device in a transmission system that transmits a multiplexed transmission frame in which a first broadcast signal and a second broadcast signal are multiplexed from the first device to the second device, and sets the frame length of the multiplexed transmission frame so as to be an integer multiple of the frame length of a first OFDM frame related to the first broadcast signal, and includes a control unit.

[0015] The communication method according to the disclosure includes: transmitting a multiplexed transmission frame in which a first broadcast signal and a second broadcast signal are multiplexed from a first device to a second device; and a communication device constituting at least one of the first device and the second device setting the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of a first OFDM frame related to the first broadcast signal.

[0016] In the summary of the disclosure, the communication device sets the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of a first OFDM frame related to the first broadcast signal. According to such a configuration, even when it is assumed that a multiplexed transmission frame in which a first broadcast signal and a second broadcast signal are multiplexed is transmitted from a first device to a second device, a multiplexed transmission frame in which signals corresponding to two or more OFDM frames having different frame lengths are appropriately multiplexed can be appropriately transmitted between the first device and the second device.

[0017] [Embodiment] (Digital Wireless Transmission System) Hereinafter, a digital wireless transmission system according to an embodiment will be described. FIG. 1 is a diagram showing a digital wireless transmission system 10 according to the embodiment. As shown in FIG. 1, the digital wireless transmission system includes a first device 100 and a second device 200.

[0018] In an embodiment, in a case where OFDM (Orthogonal Frequency Division Multiplexing) frames having different frame lengths are transmitted from a second device 200, the digital wireless transmission system relates to a system that transmits a multiplexed transmission frame in which two or more broadcast signals are multiplexed from a first device 100 to the second device 200. The first device 100 may be a performance venue of a broadcasting station or a transmission station. The second device 200 may be a transmission station. The link between the first device 100 and the second device 200 may be referred to as an STL (Studio To Transmitter Link) or may be referred to as a TTL (Transmitter To Transmitter Link). In the following, the link between the first device 100 and the second device 200 may be referred to as STL / TTL.

[0019] In the embodiment, a case where two or more broadcast signals include a first broadcast signal and a second broadcast signal will be described. The transmission capacity of the second method for the second broadcast signal may be larger than the transmission capacity of the first method for the first broadcast signal.

[0020] The first broadcast signal relates to a broadcast signal for terrestrial digital television broadcasting and V-Low terrestrial multimedia broadcasting (for example, it may include a TS (Transport Stream) signal, a TMCC (Transmission and Multiplexing. Configuration Control) signal, etc.). The first broadcast signal may include an SC (Service Channel) signal. The first method may be referred to as an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) method.

[0021] The second broadcast signal may include a second broadcast signal related to the terrestrial broadcast enhancement method. The second broadcast signal may be referred to as an XMI (Extensible Modulator Interface) signal. The terrestrial broadcast enhancement method may be an example of the second method. The second broadcast signal may include an SC (Service Channel) signal.

[0022] The frame length of the first OFDM frame related to the first broadcast signal may be different from the frame length of the second OFDM frame related to the second broadcast signal. Details of the frame length will be described later.

[0023] (The first device) Hereinafter, the first device according to the embodiment will be described. FIG. 2 is a block diagram showing the first device 100 according to the embodiment.

[0024] As shown in FIG. 2, the first device 100 includes a multiplexing unit 101, a modulation unit 103, a transmission unit 105, and a clock generation unit 107.

[0025] The multiplexing unit 101 multiplexes the first broadcast signal and the second broadcast signal. Here, the multiplexing unit 101 multiplexes the first broadcast signal and the second broadcast signal assuming a clock (hereinafter, STL / TTL clock) generated by the clock generation unit 107. In other words, the multiplexing unit 101 multiplexes the first broadcast signal and the second broadcast signal on the assumption that the frame length of the multiplexed transmission frame is an integer multiple of the frame length of the first OFDM frame. The multiplexing method may be time-division multiplexing. The multiplexing method may be a multiplexing method other than time-division multiplexing.

[0026] The modulation unit 103 generates a multiplex transmission frame by modulating a signal in which a first broadcast signal and a second broadcast signal are multiplexed (hereinafter, a multiplex signal) based on the STL / TTL clock. The multiplex signal may be represented in a format including header information. The multiplex transmission frame is an OFDM frame. As the modulation method, 64QAM (Quadrature Amplitude Modulation) may be used. As the modulation method, a modulation method higher than 64QAM (for example, up to 4096QAM) may be used.

[0027] The transmission unit 105 transmits the multiplex transmission frame output from the modulation unit 103 to the second device 200. The transmission unit 105 may have a function of converting an IF (Intermediate Frequency) signal into an RF (Radio Frequency) signal.

[0028] The clock generation unit 107 generates the STL / TTL clock. Specifically, the clock generation unit 107 generates the STL / TTL clock based on the FFT (Fast Fourier Transform) clock frequency of the first OFDM frame related to the first broadcast signal and the FFT clock frequency of the second OFDM frame related to the second broadcast signal. Hereinafter, the frequency of the STL / TTL clock is referred to as the STL / TTL clock frequency. Details of the STL / TTL clock frequency will be described later.

[0029] For example, the clock generation unit 107 may include a first clock generation unit that generates a clock (hereinafter, a first clock) for generating the FFT clock frequency of the first OFDM frame, and a second clock generation unit that generates a clock (hereinafter, a second clock) for generating the FFT clock frequency of the second OFDM frame. The clock generation unit 107 may generate the STL / TTL clock based on the first clock and the second clock. For example, the FFT clock frequency of the first OFDM frame may be 8.127 MHz (= 512 / 63), and the FFT clock frequency of the second OFDM frame may be 6.321 MHz (= 512 / 81).

[0030] Here, the clock generation unit 107 may be an example of a control unit that sets the frame length of the multiplexed transmission frame so as to be an integer multiple of the frame length of the first OFDM frame. In other words, the clock generation unit 107 generates an STL / TTL clock for setting the frame length of the multiplexed transmission frame.

[0031] (Second device) Hereinafter, the second device according to the embodiment will be described. FIGS. 3 and 4 are block diagrams showing the second device 200 according to the embodiment.

[0032] As shown in FIG. 3, the second device 200 includes a receiving unit 201, a demodulating unit 203, a separating unit 204, a clock generation unit 207, and a transmitting device 209.

[0033] The receiving unit 201 receives the multiplexed transmission frame from the first device 100. The receiving unit 210 may have a function of changing an RF signal into an IF signal. The receiving unit 201 may receive an OFDM frame as the multiplexed transmission frame.

[0034] The demodulating unit 203 demodulates the signal received by the receiving unit 201 based on the STL / TTL clock generated by the clock generation unit 207. As the demodulation method, 64QAM may be used. As the demodulation method, a demodulation method higher than 64QAM may be used.

[0035] The separating unit 205 separately separates the first broadcast signal and the second broadcast signal from the signal (multiplexed signal) demodulated by the demodulating unit 203. The multiplexed signal may be represented in a format including header information. Here, the separating unit 205 may specify the multiplexing method (such as ratio and order) of the first broadcast signal and the second broadcast signal, and separate the first broadcast signal and the second broadcast signal from the multiplexed signal. The multiplexing method may be known to the second device and may be stored in the header information included in the multiplexed signal. The separating unit 205 may separate the SC signal from the signal demodulated by the demodulating unit 203.

[0036] The clock generation unit 207 generates an STL / TTL clock. For example, the clock generation unit 207 may include a first clock generation unit that generates a first clock and a second clock generation unit that generates a second clock. The clock generation unit 207 may generate an STL / TTL clock based on the first clock and the second clock. Details of the STL / TTL clock frequency will be described later.

[0037] Here, the clock generation unit 207 may be an example of a control unit that sets the frame length of the multiplexed transmission frame so as to be an integer multiple of the frame length of the first OFDM frame. In other words, the clock generation unit 207 generates an STL / TTL clock for setting the frame length of the multiplexed transmission frame.

[0038] The transmission device 209 transmits a first OFDM frame related to the first broadcast signal. The transmission device 209 transmits a second OFDM frame related to the second broadcast signal. The transmission device 209 may have functions such as performing time interleaving processing, frequency interleaving processing, error correction coding processing, and the like.

[0039] (STL / TTL clock frequency) Hereinafter, details of the STL / TTL clock frequency according to the embodiment will be described. Hereinafter, a case will be exemplified in which the first broadcast signal is a broadcast signal corresponding to the ISDB-T system and the second broadcast signal is a broadcast signal corresponding to the advanced terrestrial broadcast system.

[0040] Furthermore, a case will be exemplified in which the transmission capacity of the second system related to the second broadcast signal is larger than the transmission capacity of the first system related to the first broadcast signal, and the multiplexed transmission frame is a multiplexed transmission frame defined for the second system (that is, the advanced terrestrial broadcast system).

[0041] In the embodiment, since the multiplex transmission frame related to STL / TTL is defined for the second system (i.e., the advanced terrestrial broadcasting system), it is not necessary to pay particular attention to the synchronization between the multiplex transmission frame and the second OFDM frame. In the following, the relationship between the frame length of the first OFDM frame related to the first broadcast signal and the frame length of the multiplex transmission frame will be mainly described.

[0042] Here, the frame length of the first OFDM frame related to the first broadcast signal can be expressed by the following formula.

[0043]

Equation

[0044] For example, F FFT_C may be a fixed value of 512 / 63 = 8.127 MHz. P FFT_C may be a value selected from 2048, 4096, and 8192. R GI_C may be a value selected from 1 / 4, 1 / 8, 1 / 16, and 1 / 32. N SF_C may be a fixed value of 204.

[0045] Therefore, the frame length of the first OFDM frame related to the first broadcast signal may be expressed by the following formula.

[0046]

Equation

[0047] Also, the frame length of the multiplex transmission frame can be expressed by the following formula.

[0048]

Equation

[0049] For example, F FFT_STLIt may be a value selected from among …, 8192 / 384, 8192 / 400, 8192 / 408, 8192 / 416, 8192 / 432, ….

[0050] Under such a background, in an embodiment, L FRAME_C ×A = L FRAME_STL ×B is considered for A and B that satisfy the equation. A and B are positive integers. For example, F FFT_STL Taking the case where there are 10 types, namely 8192 / 272, 8192 / 336, 8192 / 352, 8192 / 384, 8192 / 400, 8192 / 408, 8192 / 416, 8192 / 432, 8192 / 448, 8192 / 544, as an example, the following relational expressions hold.

[0051]

Number

[0052] Furthermore, taking F FFT_STL using clock No.1 (8192 / 272) as an example, assuming that P FFT_STL is tentatively 8192 and R GI_STL is tentatively 1 / 32, the case will be described. In such a case, L FRAME_C ×A = L FRAME_STL ×B can be expanded as shown below.

[0053]

Number

[0054] In such a case, when the relationship A = 11 and B = D×C is satisfied, the relationship 3×3×7 = 63 = N SF_STL is derived.

[0055] Furthermore, when the same operations are performed for clock No.2 to No.10, the results shown in FIG. 4 are obtained.

[0056] In FIG. 4, the STL / TTL clock frequency is the clock frequency for generating the multiplexed transmission frame. The magnification factor for the first OFDM frame is the number of first OFDM frames included in the multiplexed transmission frame (the value of A described above). N SF_STL is the number of symbols per multiplexed transmission frame. The division ratio for 512 / 81 is the division ratio of the STL / TTL clock frequency with respect to the FFT clock frequency (512 / 81) for the second OFDM frame. The division ratio for 512 / 63 is the division ratio of the STL / TTL clock frequency with respect to the FFT clock frequency (512 / 63) for the first OFDM frame. The division ratio for 10 MHz is the division ratio of the STL / TTL clock frequency with respect to the 10 MHz clock frequency. The total number of carriers is the total number of carriers utilized in the band used for transmitting the multiplexed transmission frame (here, 8.4 MHz or 8.5 MHz).

[0057] (Operation and Effect) In the embodiment, the communication device constituting at least one of the first device 100 and the second device 200 sets the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of the first OFDM frame. According to such a configuration, even when assuming a case where a multiplexed transmission frame in which the first broadcast signal and the second broadcast signal are multiplexed is transmitted from the first device to the second device, a transmission frame in which signals corresponding to two or more OFDM frames having different frame lengths are appropriately multiplexed can be appropriately transmitted between the first device and the second device.

[0058] [Modification Example 1] Hereinafter, Modification Example 1 of the embodiment will be described. Hereinafter, the differences from the embodiment will be mainly described.

[0059] In Modification Example 1, a case of setting the frame length of the multiplex transmission frame will be described in consideration of a case where an error correction code (for example, a Low Density Parity Check (LDPC) code) is applied to the multiplex transmission frame. Specifically, in Modification Example 1, attention is paid to the number of data carriers and the number of symbols (N SF_TSL ) included in the total number of carriers used for the transmission of the multiplex transmission frame.

[0060] Specifically, the first device and the second device set the frame length of the multiplex transmission frame such that the multiplication result of the number of data carriers and the number of symbols (N SF_TSL ) is an integer multiple of the error correction block. The number of data carriers may be around 90% of the total number of carriers. The number of symbols (N SF_TSL ) may be even assuming Multiple-Input Multiple-Output (MIMO).

[0061] [Other Embodiments] Although the present invention has been described by the above disclosure, the discussions and drawings forming a part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure.

[0062] In the above disclosure, a case where the control units that set the frame length of the multiplex transmission frame to be an integer multiple of the frame length of the first OFDM frame are the clock generation unit 107 and the clock generation unit 207 has been exemplified. However, the above disclosure is not limited thereto. The control unit may be considered as the multiplexing unit 101 that multiplexes the first broadcast signal and the second broadcast signal according to the STL / TTL clock, or may be considered as the separation unit 205 that separately separates the first broadcast signal and the second broadcast signal according to the STL / TTL clock. The control unit may be considered as the transmission unit 105, or may be considered as the reception unit 201.

[0063] Although not particularly mentioned in the above disclosure, regarding the setting of the frame length of the multiplex transmission frame, the term "setting" may be read as terms such as "transmission", "reception", "generation", "assumption", etc. For example, the first device 100 may generate or transmit a multiplex transmission frame having a frame length that is an integer multiple of the frame length of the first OFDM frame. The second device 200 may receive or assume a multiplex transmission frame having a frame length that is an integer multiple of the frame length of the first OFDM frame.

[0064] Although not particularly mentioned in the above disclosure, the transmission method between the first device 100 and the second device 200 may be an IF method or a TS transmission method.

[0065] Although not particularly mentioned in the above disclosure, the frame length of the multiplex transmission frame may be an integer multiple of the frame length of the second OFDM frame related to the second broadcast signal. However, when the second broadcast signal multiplexed in the multiplex transmission frame is in a packet format (for example, an XMI packet) and the frame period of the XMI packet is not constant, the above-mentioned relationship may not be satisfied.

[0066] Although not particularly mentioned in the above disclosure, a program for causing a computer to execute each process performed by the first device 100 and the second device 200 may be provided. Further, the program may be recorded on a computer-readable medium. By using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and for example, it may be a recording medium such as a CD-ROM or a DVD-ROM.

[0067] Alternatively, a chip constituted by a memory that stores a program for executing each process performed by the first device 100 and the second device 200 and a processor that executes the program stored in the memory may be provided.

Description of Reference Numerals

[0068] 10… Digital wireless transmission system, 100… First device, 101… Multiplexing unit, 103… Modulation unit, 105… Transmission unit, 107… Clock generation unit, 200… Second device, 201… Reception unit, 203… Demodulation unit, 205… Separation unit, 207… Clock generation unit, 209… Transmission device

Claims

1. A communication device, in a transmission system for transmitting a multiplexed transmission frame in which a first OFDM (Orthogonal Frequency Division Multiplexing) frame related to a first broadcast signal of a first system and a second OFDM frame related to a second broadcast signal of a second system which is a next-generation system of the first system are multiplexed from a first device to a second device, constituting at least one of the first device and the second device, comprising a control unit that sets the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of the first OFDM frame, The multiplexed transmission frame is a multiplexed transmission frame defined for the second system. A communication device.

2. The communication device according to claim 1, wherein the transmission capacity of the second system is larger than the transmission capacity of the first system.

3. A communication method, comprising the steps of transmitting, from a first device to a second device, a multiplexed transmission frame in which a first OFDM (Orthogonal Frequency Division Multiplexing) frame related to a first broadcast signal of a first system and a second OFDM frame related to a second broadcast signal of a second system which is a next-generation system of the first system are multiplexed, and a communication device constituting at least one of the first device and the second device setting the frame length of the multiplexed transmission frame to be an integer multiple of the frame length of the first OFDM frame, The multiplexed transmission frame is a multiplexed transmission frame defined for the second system. A communication method.

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