WO2010137507A1

WO2010137507A1 - Communication apparatus

Info

Publication number: WO2010137507A1
Application number: PCT/JP2010/058469
Authority: WO
Inventors: 博昭平井
Original assignee: 三菱電機株式会社
Priority date: 2009-05-28
Filing date: 2010-05-19
Publication date: 2010-12-02
Also published as: JPWO2010137507A1

Abstract

A communication apparatus at the transmitting side of a data transmission system is provided with a transmission signal generation unit (10) and a transmitter unit (11). The transmission signal generation unit (10) converts transmission data to parallel data to generate a plurality of data sequences, and based on the plurality of data sequences, generates redundant data sequences to be used for error correction, further, imparts transmission error detection information, for detecting transmission errors, to each of the plurality of data sequences and redundant data sequences to generate a plurality of transmission signals. The transmitter unit (11) is comprised of a number of transmitter devices the same as the plurality of transmission signals, and each transmitter device wirelessly transmits one signal from among the plurality of transmission signals.

Description

Communication device

The present invention relates to a communication apparatus that performs data transmission requiring real-time characteristics on a wireless transmission channel.

In recent years, work on the development of standards for transmitting wide-band moving image signals has been actively performed in Japan, Europe, and the United States, with a focus on the Society of Motion Picture and Television Engineers (SMPTE). For example, in Non-Patent Document 1 below, the luminance signal Y and the color difference are used as 4: 2: 2 component digital parallel interface of the size used in television broadcasting such as NTSC (National Television System Committee) system and PAL (Phase Alternating Line) system. It is defined that signals CB and CR are bundled in a digital bus. When the bundled signals are sampled at 27 MHz, for example, if the gradation is defined by 10 bits, the signal is 270 Mbps (in the case of Japanese television broadcasting).

In the NTSC video signal (Video signal), SAV (Start of Active Video data) and EAV (End of Active Video data) are used as timing signals for frame synchronization so that the horizontal and vertical of the screen can be defined on the receiving side. It is embedded. The values of these SAV and EAV change according to the line number for vertical synchronization.

Further, a serial digital interface for efficiently transmitting a video signal as described above is standardized in Non-Patent Document 2 below, and is called SD-SDI (Standard Definition Serial Digital Interface). At present, HD-SDI (High Definition SDI) having a transmission band of about 1.5 Gbps and 3G-SDI having a transmission band of about 3 Gbps are about the following

non-patent documents

3 and 4 with the development of high definition television broadcasting. Each is planned.

In addition, Non-Patent Document 5 below describes a method for realizing SDI transmission with a small number of wires.

Since the above-mentioned conventional technology (the technology described in Non-Patent Document 5) is realized on the premise that there is almost no communication error by using a metal cable or an optical fiber cable, the communication error frequently occurs. There is a problem that it can not be applied to wireless communication that performs communication control on the premise of. In recent years, broadband video signals have low delay and low cost for the purpose of reducing wiring cost, wiring cost, and physical cost for wiring. The realization of a wireless communication system that can transmit at

The present invention has been made in view of the above, and it is an object of the present invention to obtain a communication apparatus capable of low-latency transmission of a large amount of data via a wireless transmission channel.

In order to solve the problems described above and achieve the object, the present invention is a communication apparatus on the transmission side of a data transmission system, which converts transmission data into parallel data to generate a plurality of data strings, and In order to generate a redundant data string for performing error correction on the receiving side based on a plurality of data strings, and to detect a transmission error on the receiving side for each of the plurality of data strings and the redundant data string. And transmission devices for generating transmission signals by adding transmission error detection information, and transmission devices of the same number as the plurality of transmission signals, each of the transmission devices being any of the plurality of transmission signals And transmission means for wirelessly transmitting one or more of them.

According to the present invention, it is possible to realize low delay transmission of a large amount of data between communication apparatuses via a wireless transmission channel.

FIG. 1 is a diagram showing an example of the configuration of a transmission side communication apparatus in a data transmission system. FIG. 2 is a diagram showing an example of the configuration of video data to be subjected to channel coding processing. FIG. 3 is a diagram showing an example of a signal obtained by performing the transmission path coding process. FIG. 4 is a diagram showing the correspondence on the time axis of video data, a parallel clock, and a timing signal (horizontal synchronization signal) among input signals to the transmission signal generation unit. FIG. 5 is a diagram showing data after performing 10 to 3 parallel-parallel conversion. FIG. 6 is a diagram showing a data configuration after setting a synchronization signal (specified fixed pattern) in an invalid period. FIG. 7 is a diagram illustrating an exemplary configuration of a transmission device. FIG. 8 is a view showing an example of the configuration of a communication apparatus on the receiving side in the data transmission system. FIG. 9 is a diagram showing an example of a general BTR process. FIG. 10 is a diagram illustrating an exemplary configuration of a receiving device.

Hereinafter, embodiments of a communication apparatus according to the present invention will be described in detail based on the drawings. The present invention is not limited by the embodiment.

Embodiment.
First, the transmission side communication apparatus in the data transmission system will be described. FIG. 1 is a diagram showing an example of the configuration of a transmission side communication apparatus in a data transmission system. Note that only the components related to the transmission operation are shown.

The communication device illustrated in FIG. 1 includes a transmission signal generation unit 10 and a transmission unit 11. The transmission signal generation unit 10 generates a transmission signal using the illustrated input signals (video data, parallel clock, timing signal, auxiliary data), and outputs the transmission signal as parallel data together with the parallel clock. The transmission unit 11 includes a plurality of transmission devices, and each transmission device receives any one of the transmission signals output in parallel from the transmission signal generation unit 10, executes predetermined transmission processing, Space transmission to the receiving communication device). Note that some transmission devices spatially transmit transmission signals generated based on redundant data for performing error correction on the reception side. That is, to the transmitting device, a transmitting device for transmitting actual data (hereinafter referred to as “first transmitting device if necessary” and “differently referred to as necessary”) and a transmitting device for transmitting redundant data (hereinafter referred to as necessary) (Referred to as a second transmission device). The ratio of the first transmission device to the second transmission device is determined in consideration of the occurrence rate of transmission errors in the used transmission line, the transmission quality required by the system, and the like.

Subsequently, operations of the transmission signal generation unit 10 and the transmission unit 11 will be described in detail. First, the transmission signal generation unit 10 sequentially performs each processing of parallel / parallel conversion, timing information addition, synchronization pattern addition, channel coding, CRC addition, and scrambling on input video data.

In parallel-to-parallel conversion processing, input video data that is parallel data is converted into parallel data according to the number of transmission devices included in the transmission unit 11. Specifically, it is converted into parallel data (a plurality of data strings) having the same number of parallels as the number of transmission devices (the number of first transmission devices) for transmitting actual data.

In the timing information addition process, information (alternative timing information) having the same purpose as the vertical and horizontal timing information (SAV, EAV) when forming the screen, which is included in the normal video data, is It is added to each of a plurality of data strings obtained by performing the parallel-to-parallel conversion processing. The information to be added and the addition method will be described later.

In the synchronization pattern addition process, the synchronization pattern (fixed bit string known on the reception side) used when the reception side of the signal transmitted from each transmission device performs timing synchronization as communication data is added with the above alternative timing information. For each data string of Although one synchronization pattern was used in the above-described conventional SDI transmission, in the data transmission system according to the present embodiment, each data string is used so that the communication apparatus on the receiving side can perform timing synchronization for each data string. Add synchronization pattern to.

In the channel coding process, each data string to which the above-mentioned synchronization pattern is added is coded. At this time, in consideration of a case where a part of the signals becomes an error during space transmission due to shielding or equipment failure, etc., redundant data is generated to restore the signal that has become a transmission error on the receiving side. Turn The specific method of the encoding process will be described later.

In the CRC attachment process, an error detection code (for checking on the receiving side whether or not the data is normally received for each of a plurality of code word sequences obtained by performing the above-mentioned channel coding process) Add CRC).

In the scrambling process, randomization is performed for each of the codeword sequences after the above-described CRC addition process is performed. This randomization process is a process of rearranging bits so that the ratio of bits having a value of 0 and bits having a value of 1 becomes equal in data during space transmission, and bit synchronization or a frame on the receiving side is performed. It is performed for the purpose of facilitating timing synchronization and channel state detection.

Here, the details of the channel coding process will be described. As an example, transmission path coding processing in an environment where five transmission paths can be used and four out of five can be transmitted without errors will be described. In such an environment, the communication apparatus on the transmission side uses five transmission devices, transmits actual data in four of them, and transmits redundant data in the remaining one. In this case, in channel coding processing, channel coding processing is performed on data of the configuration shown in FIG. In FIG. 2, video data (actual data) is a 4-bit value. X ^k indicates the k-th video data, and X _m indicates the m-th bit in one video data.

FIG. 3 is a diagram showing an example of a signal obtained by performing channel coding processing, and as shown in the figure, in this channel coding processing, redundant data (for each of 4-bit video data) is shown. Redundant bit) Y is added to generate a code word. Y ^k indicates redundant data (k-th redundant data) to be added to the k-th video data, and Y _n indicates the n-th bit in the redundant data (in this example, it is a fixed value of n = 1 ). Also, redundant data is calculated according to the following equation (1). In equation (1), “^” indicates exclusive OR (XOR).

Therefore, on the receiving side, even if one bit of video data simultaneously transmitted using four of the available five transmission paths can not be received, redundant data Y is used for the original. Video data (4 bits of information transmitted simultaneously) can be reproduced (restored). For example, when the first bit in the k-th video data becomes a transmission error, it can be restored by executing the processing shown in the following equation (2). The method of determining the bit that caused the transmission error by the communication apparatus on the receiving side will be described in the description of the operation on the receiving side.

Next, the details of the timing information addition process will be described. As an example, a video data to be input to the transmission signal generation unit 10 is a 10-bit value, and an operation example in the case of parallel transmission of the video data according to the number of transmission devices included in the transmission unit 11 will be shown. Note that there are three transmission devices constituting the transmission unit 11, and transmission is performed in an environment where a transmission error may occur in a maximum of one system. That is, real data is transmitted by two systems, and redundant data is transmitted by the remaining one system.

FIG. 4 shows correspondence among video data, a parallel clock (described as a clock in FIG. 4), and a timing signal (horizontal synchronization signal) among input signals to the transmission signal generation unit 10 on a time axis. FIG. In addition to the illustrated horizontal synchronization signal, the vertical synchronization signal is also included in the timing signal, but only the horizontal synchronization signal necessary for the description here is shown. In addition, the clock for drawing is 27 MHz. Therefore, the signal bandwidth as video data is 270 Mbps. On the receiving side of video data, in general, drawing is performed using a synchronization signal as a cue. Video data includes an invalid section which is not displayed in a fixed width. In FIG. 4, an interval of 4 clocks of X ^k (k = 1, 2, 3, 4) is an invalid period, and a signal unnecessary as video data.

In addition, there are three transmission devices constituting the transmission unit 11, and an operation in the case where transmission is performed in a state where a transmission error may occur in a maximum of one system will be described. In this case, each transmitting device performs 135 Mbps transmission in space transmission so that a signal bandwidth of 270 Mbps can be achieved for any two systems.

Therefore, the transmission signal generation unit 10 first performs simple 5-to-1 parallel-serial conversion processing (2 bits in which the input 10-bit parallel video data is made to correspond to the number of transmission paths used for transmission of actual data). Executes a process of converting into parallel video data, and adds timing information and a synchronization pattern to the video data of 2 systems, and then executes the transmission path coding process described above to generate 2 systems of data. By expanding into 3 systems of data (2 systems of real data and 1 system of redundant data), 10 to 3 parallel / parallel conversion is performed. The data after performing this conversion is shown in FIG. As illustrated, the horizontal synchronization signal, which is one clock wide in FIG. 4 (before conversion), is extended to five clocks. In addition, as video data, an interval of 20 clocks that is 5 times that before conversion is an invalid period. Here, the transmission signal generation unit 10 sets, as timing information, a signal for synchronization in an invalid section between the 20 clocks (see FIG. 6). FIG. 6 is a diagram showing a data configuration after setting a synchronization signal (specified fixed pattern) in the invalid period. The specific fixed pattern, which is timing information, is a bit string unique to each system and known at the receiving side. In addition, the transmission signal generation unit 10 removes the horizontal synchronization signal running in parallel. Even if the horizontal synchronization signal is removed, the reception side can generate (restore) the horizontal synchronization signal by finding a specific unique pattern for each channel.

Finally, the transmitting device constituting the transmitting unit 11 will be described. FIG. 7 is a view showing a configuration example of a transmission device, and the transmission device shown includes a level conversion unit 12, a light emission unit 13 and a lens 14. The level conversion unit 12 performs conversion so that the input electrical signal has a desired signal level, and the issuing unit 13 causes an LED or LD (Laser Diode) to emit light according to the signal after the level conversion. . The lens 14 condenses and transmits the light from the light emitting unit 13. Depending on the distance, a lens may not be necessary. Here, the illustration of light shows an example for multiplexing a plurality of signals in space, and the transmitting device may multiplex signals using different frequencies instead of using light. Even if the same frequency is used, CDMA is used to change code spreading, MIMO using antenna multiplexing is used, or millimeter wave communication with high linearity and optical communication with different wavelengths are used respectively. Also good.

Subsequently, the communication apparatus on the receiving side of the data transmission system will be described. FIG. 8 is a diagram showing a configuration example of a communication apparatus on the receiving side in the data transmission system according to the present invention. Note that only the components related to the receiving operation are shown.

The communication device shown in FIG. 8 includes a receiving unit 20 and a signal reproduction unit 21. The receiving unit 20 is composed of a plurality of receiving devices, and each receiving device receives any one of a plurality of signals spatially multiplexed and transmitted from the communication apparatus on the opposite side of transmission, and executes a predetermined reception process. , To the signal reproduction unit 21. The signal reproduction unit 21 reproduces (restores) the data transmitted from the communication apparatus on the transmission side based on the input signal from the reception unit 20. When it is detected that a part of the actual data can not be received correctly from the signals input in parallel from the reception unit 20, the redundant data input at the same time is used to restore the data that caused the transmission error. Do.

The operation of the signal reproduction unit 21 will be described in detail. The signal reproduction unit 21 performs BTR (Bit Timing Recovery), transmission path state detection, descrambling, CRC check, transmission path decoding, frequency timing synchronization, frame timing synchronization, parallel-parallel conversion, and the like for input parallel data. Implement each process in order.

In the BTR processing (bit timing recovery processing), the frequency deviation between the communication apparatus on the transmission side is extracted based on the received signal, and the execution timing of signal processing (the execution timing of bit determination) is adjusted to an appropriate timing. In addition, the signal reproduction unit 21 examines each transmission quality (transmission quality for each transmission path) between the transmission device and the reception device using the result of the BTR processing. FIG. 9 is a diagram showing an example of a general BTR process. In BTR processing, oversampling is performed on a transmission signal. FIG. 9 shows an example in which a 25 Mbps transmission signal is oversampled by four times. In BTR processing, a moving average is performed on each sampling value acquired by executing oversampling, at an integral multiple of the oversampling value (an integer multiple of 4 in the example of FIG. 9), and a correlation value is generated at a bit period. . Then, the transmission clock is regenerated by detecting the high (or low) position of the correlation value as the bit switching timing. Here, when the signal can not be received, the high (or low) part of the correlation value can not be obtained, and a transmission error occurs due to some cause between the devices. Therefore, in such a case, the communication apparatus on the receiving side performs signal regeneration without using the signal (data) from this transmission path. That is, the data that has become a transmission error is restored based on the normally received data and the redundant data, and signal generation is performed using the restored data and the normally received data.

In the transmission path state detection process, the state of the transmission path (the transmission path between the transmitting device and the corresponding receiving device) is detected, and the reliability of the signal transmitted through each transmission path, that is, a transmission error occurs. Determine if you are not. Also, in this process, in addition to detecting the state of the transmission path, for example, monitoring the power supply and component abnormal state of the receiving device, periodically transmitting fixed patterns (fixed patterns known on the receiving side) from the transmitting side. In this case, a signal line with low reliability is detected by performing fixed pattern detection, and when transmitting signals at the same timing from the transmitting side, observe simultaneously the signal patterns output from the receiving device. An error within an assumed range can be detected by (detecting a signal line whose detection signal does not go up) or the like.

In the descrambling process, a process opposite to the scrambling process performed by the communication apparatus on the transmission side (the transmission signal generation unit 10, see FIG. 1) is executed, and the bit string is returned in the original arrangement order.

In the CRC check process, the transmission quality between each device is confirmed. This is implemented in order to select data between devices with high communication quality from received data and use it to improve the reliability in reproducing video data. As an implementation, a check is performed on the one to which the CRC is added in the space transmission unit.

In the transmission path decoding processing, decoding processing is performed on the reliable signal data detected in the transmission path state detection processing, and transmission video data is reproduced.

In the frequency timing synchronization process, the transmission video data reproduced by the transmission path decoding process is synchronized with the internal clock of the communication apparatus (the communication apparatus on the receiving side).

In frame timing synchronization processing, output is performed in accordance with horizontal and vertical synchronization signals of video data. In this process, timing information added in timing information addition processing on the transmission side is used.

In the parallel-to-parallel conversion process, a process opposite to the parallel-to-parallel conversion process performed on the transmission side is performed, and the state before transmission (video data before being input to the transmission signal generation unit 10 on the transmission side) is restored.

Next, the receiving device constituting the receiving unit 20 will be described. FIG. 10 is a diagram showing a configuration example of the receiving device, and shows a configuration example corresponding to the transmitting device shown in FIG. The receiving device includes a lens 22, a photodiode 23, a transimpedance amplifier 24, a comparing unit 25, and a level converting unit 26.

The lens 22 condenses the incoming light signal. The photodiode 23 converts the light collected by the lens 22 into an electrical signal, and the transimpedance amplifier 24 converts a current signal, which is an electrical signal output from the photodiode 23, into a voltage signal. The comparison unit 25 determines the voltage signal output from the transimpedance amplifier 24 and converts it into a signal of 0 and 1. The level converter 26 adjusts the level of the signal output from the comparator 25. A lens is unnecessary depending on the distance to the communication apparatus on the transmission side. In addition, an amplifier that performs the same process may be provided without using the transimpedance amplifier 24 and the comparison unit 25. As long as it is a method that can be separated by each receiving device provided on the receiving side, if wireless communication is used, demodulation processing corresponding to the modulation processing performed on each of the transmitting devices provided on the transmitting side is performed , To reproduce the signal.

As described above, in the data transmission system according to the present embodiment, the communication apparatuses on both the transmitting side and the receiving side are provided with a plurality of transmitting / receiving means (sending device, receiving device), and are assumed in the wireless section among the plurality of devices. It was decided to transmit redundant data for error correction on the receiving side of a signal that has become a transmission error, using a number of devices according to the transmission quality. As a result, low delay transmission of a large amount of data can be realized in a wireless transmission channel where transmission errors are expected to occur frequently.

As described above, the present invention is useful for realizing low delay transmission of a large amount of data, and is particularly suitable for the transmission side communication apparatus of a data transmission system for realizing low delay transmission in a wireless transmission channel. .

DESCRIPTION OF REFERENCE NUMERALS 10 transmission signal generation unit 11 transmission unit 12 level conversion unit 13 light emission unit 14, 22 lens 20 reception unit 21 signal reproduction unit 23 photodiode 24 transimpedance amplifier 25 comparison unit 26 level conversion unit

Claims

A communication apparatus on the transmission side of a data transmission system,
The transmission data is converted into parallel data to generate a plurality of data strings, and based on the plurality of data strings, a redundant data string for error correction is generated on the receiving side, and the plurality of data strings are further generated. And transmission signal generation means for generating transmission signals by adding transmission error detection information for detecting a transmission error on the reception side to each of the redundant data strings.
Transmission means comprising the same number of transmission devices as the plurality of transmission signals, each of the transmission devices wirelessly transmitting any one of the plurality of transmission signals;
A communication apparatus comprising:
When generating the plurality of data strings, the transmission signal generation unit converts the transmission data into data strings according to the number of transmission devices and the number of transmission errors in the transmission path. The communication device according to claim 1.
The communication apparatus according to claim 1, wherein the transmission error detection information is a CRC.
3. The communication apparatus according to claim 1, wherein the transmission error detection information is a bit string of a fixed pattern known on the receiving side.
Let the transmission data be video data,
The transmission signal generation means arranges auxiliary information for recovering, on the reception side, a signal used in frame synchronization processing in video data reproduction with respect to a portion corresponding to an invalid area of video data among the plurality of transmission signals. The communication apparatus according to any one of claims 1 to 4, characterized in that:
The communication apparatus according to any one of claims 1 to 5, wherein each of the transmission devices transmits the plurality of transmission signals using light emitted by an LED or an LD.
The communication apparatus according to any one of claims 1 to 5, wherein each of the transmission devices transmits the plurality of transmission signals using MIMO technology.
The communication apparatus according to any one of claims 1 to 5, wherein each of the transmission devices transmits the plurality of transmission signals using different frequencies.
The communication apparatus according to any one of claims 1 to 5, wherein each transmission device transmits the plurality of transmission signals using CDMA technology.
A communication device for receiving a signal transmitted from the communication device according to any one of claims 1 to 8, comprising:
A communication apparatus characterized by determining whether a transmission error has occurred for each of a plurality of transmission signals transmitted from a communication apparatus on the transmission side, based on a sampling result in bit timing recovery processing.
When the signal generated based on the video data is received, the information used in the frame synchronization process is restored based on the auxiliary information arranged in the portion corresponding to the invalid area of the video data. The communication device according to 10.