JP2011172001A - Device and method for reproducing client clock - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately reproduce the clocks of various kinds of client signals. <P>SOLUTION: A transmission side client clock reproducing device includes: a frequency information generating part 14 for measuring the clock of a client signal reproduced by a clock data reproducing part 11, to generate frequency information; a mapping processing part 12 for storing the client signal in an OTN frame; and an overhead inserting part 13 for inserting the frequency information to the overhead of the OTN frame, to transmit the information. A reception side client clock reproducing device takes out the frequency information from the received OTN frame and reproduces the clock of the client signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a demapping technique for extracting a client signal from an OTN signal transmitted in a frame format. In particular, the present invention relates to a client clock reproducing apparatus for transmitting frequency information of a client signal and outputting a client signal based on the frequency information.

In 2001, OTN (Optical Transport Network) was standardized by the international standard organization ITU-T as a basic platform of an optical transport system (see Non-Patent Document 1). OTN has adopted an operation and management system that incorporates the concept of an optical path in a WDM (Wavelength Division Multiplexing) system. By introducing an error correction technique, an economical optical transport system can be constructed.
At the beginning of the OTN regulations, three types of bit rates, OTU1 (Optical Channel Transport Unit, 2.5G), OTU2 (10G), and OTU3 (40G), are defined according to the bit rate, and these are widely used in backbone networks. The bit rate is set in consideration of accommodation of SDH (Synchronous Digital Hierarchy) (see Non-Patent Document 2). Currently, with the explosive spread of Ethernet (registered trademark), the bit rate of OTU4 (100G) considering the accommodation of Ethernet (registered trademark) has been newly defined.
In addition to SDH and Ethernet (registered trademark), multiplexing called ODU (Optical Channel Data Unit) Flex that accommodates new client signals such as Fiber Channel, SDI (Serial Digital Interface), and CPRI (Common Public Radio Interface) A new layer has been defined, and it has become possible to provide clients with a 1.25G payload capacity, enabling more efficient accommodation.

ITU-T Recommendation G.709 “Interfaces for the Optical Transport Network (OTN)” ITU-T Recommendation G.707 “Network node interface for the synchronous digital hierarchy (SDH)” SMPTE 424M “3 Gb / s Signal / Data Serial Interface” ITU-T Recommendation G.8251 “The control of jitter and wander within the optical transport network (OTN)”

  However, while various client signals can be accommodated, some client signals have relatively strict jitter requirements. For example, the third generation (3G) SDI that handles uncompressed video signals has an interface defined by SMPTE (Society of Motion Picture and Television Engineers) 424M (see Non-Patent Document 3). It is necessary to suppress jitter generation up to [MHz] within 2 UI with Peak to peak.

On the other hand, in the conventional SDH jitter specification (see Non-Patent Document 4), which is a client signal, Jitter generation is performed in an observation band of 5 [KHz] to 20 [MHz] by taking an STM-16 signal as an example. There is a demand to keep it below 5 UI. Normally, an LPF (Low Pass Filter) inside a PLL (Phase Locked Loop) is designed to have a narrow band so as to satisfy the jitter requirement, but there is a problem that it takes time until the pull-in.
In addition, since it is necessary to prepare a PLL that matches the requirements of the client signal, there is a problem that the number of parts increases. With the same PLL design, jitter specifications may be required depending on the type of client signal. There is a fear that it cannot be satisfied.

  The present invention has been made in view of the above points. When a client signal is extracted from an OTN signal, the occurrence of jitter is suppressed using the same PLL without changing the time until pull-in. An object of the present invention is to provide a clock recovery apparatus and a clock recovery method for accurately reproducing a clock of a signal. It is another object of the present invention to provide a clock recovery method that selects a clock recovery method according to jitter requirement conditions of a client signal and satisfies the jitter specification of the client signal.

  In order to achieve the above-described object, the present invention relates to client clock recovery in a transmission system in which a client signal is accommodated or multiplexed in an OTN frame, and the accommodated or multiplexed client signal is output from the received OTN frame. A transmission side that accommodates or multiplexes and transmits the client signal in the OTN frame, and measures the reproduced clock and a first reproduction unit that reproduces the clock and data of the client signal; A frequency information generation unit that generates frequency information of the clock; a mapping processing unit that accommodates the client signal in an OTN frame; and an overhead insertion unit that inserts the frequency information into an overhead of the OTN frame. From the OTN frame to the accommodation. Includes a second reproducing unit that reproduces the clock and data of the received OTN frame, and a frequency information obtaining unit that obtains the frequency information from the overhead of the OTN frame, on the receiving side that outputs the multiplexed client signal. A client clock recovery unit that recovers the clock of the client signal using the frequency information, and a demapping processing unit that recovers the client signal from the OTN frame using the clock of the recovered client signal. Is a client clock reproducing device characterized by the above.

  Further, according to the present invention, the transmission side further includes a client signal identification unit that identifies a type of the client signal, and a frequency information generation function switching unit that switches a frequency information generation function according to the type of the client signal. The frequency information generation unit on the transmission side has a plurality of different frequency information generation functions depending on the type of client signal, and corresponds to the type of client signal according to the switching instruction from the frequency information generation function switching unit. Generating frequency information by a frequency information generating function, wherein the receiving side further comprises a client signal type acquisition unit for acquiring a signal for identifying a type of a client signal from the overhead of the OTN frame, and the client clock The playback unit has multiple frequency information generation functions that differ depending on the type of client signal. And which is reproduced using a reproduction function corresponding to the type of the client signals the client signal type acquiring unit has acquired, wherein the.

  Further, according to the present invention, the transmission side frequency information generation unit in the client clock recovery device bifurcates the client clock, gives a delay to one, and obtains frequency information by performing phase comparison with the other. , Provided.

  The present invention is also a client clock recovery device in a transmission system that accommodates or multiplexes and transmits a client signal in an OTN frame, and outputs the accommodated or multiplexed client signal from the received OTN frame. A transmission side that accommodates or multiplexes and transmits a client signal in the OTN frame includes a first reproduction unit that reproduces the clock and data of the client signal, and a mapping processing unit that accommodates the client signal in the OTN frame. Then, on the receiving side that outputs the received or multiplexed client signal from the received OTN frame, the second reproducing unit that reproduces the clock and data of the received OTN frame, and the reproduced clock are measured. , Frequency information of the clock A frequency information generator for generating a client signal, a client clock recovery unit for recovering a clock of the client signal using the frequency information, and a data for recovering the client signal from the OTN frame using the clock of the recovered client signal. A client clock reproduction device comprising a mapping processing unit.

Further, the present invention provides the above-described invention, wherein the frequency information generation unit measures and holds a clock of OTN frames for a predetermined number of frames, and a client signal is obtained by averaging the clocks with the number of frames. Output as frequency information.
Further, according to the present invention, in the above-described invention, the frequency information generation unit measures clocks of OTN frames for a predetermined number of frames, multiplies the measured clock numbers by a weighting coefficient, and outputs the weights. The frequency information is generated by dividing the sum of the number of clocks added by the number of frames.
In the invention described above, the frequency information generation unit may generate frequency information by comparing phases of a clock reproduced from the reproduction unit and a synchronization clock of the OTN frame. And

  The present invention is also a client clock recovery method in a transmission system for accommodating and multiplexing a client signal in an OTN frame and outputting the accommodated or multiplexed client signal from the received OTN frame. A step of reproducing a clock and data of the client signal on a transmitting side which accommodates or multiplexes a client signal in the OTN frame, and a step of measuring the reproduced clock and generating frequency information of the clock; Receiving the client signal in an OTN frame; inserting the frequency information into the overhead of the OTN frame; and receiving the multiplexed or received client signal from the received OTN frame. Regenerating the received clock and data of the OTN frame; obtaining the frequency information from the overhead of the OTN frame; regenerating the clock of the client signal using the frequency information; and Restoring the client signal from the OTN frame using the clock of the client signal.

  In the present invention, the clock of the client signal is measured by the client clock recovery device on the transmission side, frequency information is generated, inserted into the overhead (unused area) of the OTN frame, transmitted to the reception side, and the client clock on the reception side The reproduction apparatus reproduces the clock of the client signal by controlling the PLL using the frequency information. Therefore, the PLL can reproduce the clocks of various clients with high accuracy without changing the structure of the OTN frame.

It is a schematic functional block block diagram of the transmission side client clock reproducing | regenerating apparatus concerning embodiment of this invention. It is a figure which shows the structure of the overhead of the OTN frame which concerns on the same embodiment. FIG. 2 is a schematic functional block diagram of a reception-side client clock recovery device according to the embodiment. 3 is a schematic functional block diagram of a demapping processing unit and a client clock recovery unit according to the embodiment. FIG. It is a general | schematic functional block diagram of the transmission side client clock reproduction | regeneration apparatus concerning the 2nd Embodiment of this invention. FIG. 2 is a schematic functional block diagram of a reception-side client clock recovery device according to the embodiment. It is a functional block block diagram of the frequency information generation part which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating operation | movement of the frequency information generation part which concerns on the same embodiment. FIG. 2 is a schematic functional block diagram of a reception-side client clock recovery device according to the embodiment. It is a figure showing an example of OPU OH concerning the embodiment. It is a functional block block diagram of the frequency information generation part which concerns on the 4th Embodiment of this invention. It is a figure for demonstrating operation | movement of the frequency information generation part which concerns on the same embodiment. It is a functional block block diagram of the frequency information generation part which concerns on the 5th Embodiment of this invention. It is a figure for demonstrating operation | movement of the phase comparison part which concerns on the same embodiment. It is a general | schematic functional block diagram of the transmission side client clock reproduction | regeneration apparatus based on the 6th Embodiment of this invention. It is a figure for demonstrating operation | movement of the delay detection part which concerns on the same embodiment. It is a figure for demonstrating operation | movement of the delay detection part which concerns on the same embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic functional block configuration diagram of a transmission-side client clock recovery device according to an embodiment of the present invention. The transmission-side client clock recovery device 1 includes a clock / data recovery unit 11, a mapping processing unit 12, an overhead insertion unit 13, and a frequency information generation unit 14. The clock / data reproducing unit 11 reproduces the clock and data of the client signal. The mapping processing unit 12 accommodates the client signal in the OTN frame.

  The frequency information generation unit 14 measures the frequency of the client signal and generates frequency information. The overhead insertion unit 13 inserts the overhead (OH) of the OTN frame, and stores the frequency information generated by the frequency information generation unit 14 in the overhead. For example, the frequency information generation unit 14 counts the number of bits of the client signal included in one frame period of OTN to obtain frequency information. The overhead insertion unit 13 stores the frequency information in the overhead of the OTN frame.

  FIG. 2 is a diagram illustrating a configuration of the OTN frame. The OTN frame is composed of OTN OH, ODU OH, OPU OH, and OPU payload. A client signal is accommodated in the OPU payload. In Mapping & Concat. Specific in OPU OH, a RES (Reserved) area of 2 to 7 bytes is prepared according to the client signal. This RES area is an unused byte (undefined byte), and the frequency information of the client signal generated by the frequency information generation unit 14 is stored in the RES area by the overhead insertion unit 13. It is also possible to store in the RES area in the ODU OH.

  Here, as a method of expressing frequency information, the number of bits of a client signal included in one frame (for example, 1, 2, 3,..., 121864 [bits] in the case of an OPU3 frame) is expressed as a binary number (01, 10, 11 ,..., 11101110000001000) and stored. When frequency information is transmitted in units of bits, a maximum 17-bit OH area is required. Therefore, it is possible to store frequency information in bytes and reduce the necessary OH area. For example, in the case of the OPU3 frame, if (1, 2, 3,..., 15233 [bytes]) are converted into binary numbers and (01, 10, 11,..., 11101110000001), the necessary OH area is The maximum is 14 bits.

  In addition, the OTN can normally accommodate a client signal having a frequency deviation of ± 20 [ppm], and can store a change from the nominal bit rate of the client signal as frequency information. For example, when accommodating STM256 in OPU3, the maximum number of bits of an STM256 signal included in one frame is 120837 [bit] (when the clock frequency deviation on the network side is −20 ppm and the clock deviation of the client signal is +20 ppm), The minimum is 120827 [bits] (when the clock frequency deviation on the network side is +20 ppm and the clock deviation of the client signal is −20 ppm). Therefore, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 [bits] are converted into binary numbers based on the nominal value 120832 [bits] and transmitted as frequency information. It is also possible.

In addition, the frequency information has been generated by displaying the number of bits or bytes until now, but it is also possible to generate the frequency information by displaying the frequency. For example, when accommodating a client signal in the OPU 3, if the number of bits of the client signal included in one frame is 120837 [bits], the frequency of the client signal is 39.8112 [Gbit / s] × (1208337/120732) = 39.81477 [Gbit / s], and it is possible to convert 39.8477 × 10 ⁹ into a binary number and transmit it as 100101000101001001010010110101010000.

Also, if the frequency deviation of the client signal is ± 20 [ppm], maximum bit rate 39.81392 × 10 ^9, the minimum bit rate from 39.81312 × 10 ⁹ for a 39.81232 × 10 ⁹ Change amount -0.000796 × 10 ^{9 to} 0.000796 × 10 ⁹ can be converted into binary numbers 011000010011001100110 to 111000010011001100110 (“0” indicates minus and “1” indicates plus) in the first bit) and can be transmitted. is there. It is also possible to generate frequency information by frequency deviation display. When the frequency deviation of the client signal is ± 20 ppm and the frequency deviation of the clock on the network side is ± 20 ppm, the maximum frequency deviation is +40 ppm and the minimum frequency deviation is −40 ppm. "0" indicates a minus and "1" indicates a plus).
In addition, the number of bits for transmitting frequency information is not limited to the number of bits, but the number of bits of frequency information to be transmitted can be increased to improve the accuracy of the frequency information.
Further, as will be described later, the accuracy of the frequency information can be increased depending on the format of the frequency information to be transmitted.

  FIG. 3 is a diagram showing a functional block configuration of the receiving-side client clock recovery device. The reception-side client clock reproduction device 2 receives the OTN signal transmitted from the transmission-side client clock reproduction device 1 and reproduces the client signal. The receiving-side client clock recovery device 2 includes a clock / data recovery unit 21, a frequency information acquisition unit 22, a client clock recovery unit 23, and a demapping processing unit 24.

  The clock / data recovery unit 21 recovers the clock and data of the OTN frame received from the transmission-side client clock device 1. The frequency information acquisition unit 22 reads and acquires the frequency information stored in the overhead of the OTN frame. The client clock reproduction unit 23 reproduces the clock of the client signal based on the frequency information read by the frequency information acquisition unit 22. The demapping processing unit 24 reproduces the client signal from the OTN frame based on the clock of the client signal reproduced by the client clock reproduction unit 23.

  FIG. 4 is a diagram illustrating the functional block configuration of the client clock recovery unit 23 and the demapping processing unit 24. The demapping processing unit 24 includes a JC determination unit 31, a write address generation unit 33, a read address generation unit 34, and a usage amount monitor unit 35. The JC determination unit 31 determines that the bit in the OPU frame is stuff or data. The write address generation unit 33 generates a write address to a FIFO (First in First out) 40. The read address generation unit 34 generates an address of a read position when reading data from the FIFO 40. The usage amount monitor unit 35 monitors the usage amount in the FIFO 40 and outputs a control signal when a predetermined threshold value is exceeded.

  The frequency information acquisition unit 22 acquires frequency information from the overhead (OH) in the OTN frame, and controls the PLL according to the acquired frequency information. The client clock recovery unit 23 includes a phase comparator (PC) 36, a voltage controlled oscillator (VCO) 37, and an overflow underflow control unit 38. The PC 36 performs phase comparison of input signals. The VCO 37 oscillates at a frequency corresponding to the bit rate of the client signal. The overflow / underflow control unit 38 controls the phase of the clock signal input to the PC 36 in order to suppress the overflow and underflow of the FIFO 40 based on the signal output from the usage monitoring unit 35.

Next, a second embodiment of the present invention will be described.
FIG. 5 is a diagram showing a functional block configuration of the transmission-side client clock recovery device 1A according to the second embodiment of the present invention. 5A includes a clock / data recovery unit 11A, a mapping processing unit 12A, an overhead insertion unit 13A, a client signal identification unit 15A, a frequency information generation function switching unit 16A, and a frequency information generation unit 17A. Have. The clock / data reproducing unit 11A reproduces the clock and data of the client signal. The mapping processing unit 12A accommodates the client signal in the OTN frame. The overhead insertion unit 13A inserts the overhead of the OTN frame and writes the frequency information in the overhead. The client signal identification unit 15A determines the type of the client signal. The frequency information generation function switching unit 16A switches frequency information generation means according to the type of the client signal. The frequency information generation unit 17A has a plurality of frequency information generation means corresponding to the type of client, and generates frequency information using the frequency information generation means corresponding to the type of client. The difference from the first embodiment is that a client signal identification unit 15A and a frequency information generation function switching unit 16A are provided, and clock reproduction according to the type of the client signal becomes possible.

  The client signal identification unit 15A can determine the type of the client signal from the method of determining the type of the client signal from the data string of the client signal or the type of the client signal interface installed in the transmission apparatus. The frequency information generation function switching unit 16A switches the frequency information generation unit 17A according to the type of the client signal, and stores the type of the client signal in the overhead of the OTN frame.

  FIG. 6 is a diagram illustrating a functional block configuration of the reception-side client clock recovery device 2A according to the second embodiment. 6A includes a clock / data recovery unit 21A, a demapping processing unit 22A, a client signal type acquisition unit 23A, a client clock recovery function switching unit 24A, a frequency information acquisition unit 25A, and a client clock recovery. Part 26A. The clock / data recovery unit 21A recovers the data and clock of the OTN signal output from the transmission-side client clock recovery device. The client signal type acquisition unit 23A acquires client signal type information stored in the overhead of the OTN frame. The client clock recovery function switching unit 24A switches the processing of the client clock recovery unit 26A from the client signal type information acquired by the client signal type acquisition unit 23A. The frequency information acquisition unit 25A reads and acquires the frequency information stored in the overhead of the OTN frame. The client clock reproduction unit 26A has a reproduction function for reproducing the clock of the client signal based on the frequency information for each client signal type information, and corresponds to the frequency information read by the frequency information acquisition unit 25A. Play using the playback function. The demapping processing unit 22A reproduces the client signal from the OTN frame based on the reproduced client signal clock.

Next, a third embodiment of the present invention will be described.
FIG. 7 is a diagram illustrating an outline of a functional block configuration of a frequency information generation unit in the third embodiment of the present invention. The frequency information generation unit 44 illustrated in FIG. 7 corresponds to the frequency information generation unit 14 in the transmission-side client clock reproduction device 1 illustrated in FIG. The frequency information generation unit 44 includes a clock counter 51 and a frequency information average processing unit 52. The clock counter 51 counts the clock of the client signal. The frequency information average processing unit 52 holds the number of clocks counted over the past N frames and outputs the average value thereof. That is, the difference between the frequency information generation unit 14 and the frequency information generation unit 44 shown in FIG. 1 is that the clock measured by the clock counter 51 is averaged over the past N frames and output.

  The frequency deviation of the client signal input to the transmission-side client clock recovery device 1 is not constant in time and may be converted at a slow cycle. Therefore, by generating the frequency information by averaging, when the frequency deviation of the client signal changes, it is possible to suppress the steep change and generate the frequency information with high accuracy.

FIG. 8 is a diagram for explaining the operation of the frequency information generation unit 44. The frame period pulse generator 53 generates a pulse corresponding to one period of the OTN frame. The clock counter 51 measures the clock of the client signal with the pulse output from the frame period pulse generator 53 as a trigger. The clock counter 51 measures the clock (M _N bits, N = 1,..., N) for one frame, and then outputs the measured value to the frequency information average processing unit 52. The frequency information average processing unit 52 sequentially holds new inputs for N frames in the FIFO, and outputs an averaged value ((M ₁ + M ₂ +... + M _n ) ÷ N) as frequency information.

  Similarly to the first embodiment, the frequency information can be transmitted after being converted into bit units, byte units, or a deviation from the nominal frequency value of the client signal. Information after the decimal point can be transmitted by determining the effective digits in advance. For example, when 121855 [bits], 121856 [bits], and 121855 [bits] are counted in N = 3 frames, 3 frames The average value of the minutes is “121855.33333...”, And when the significant digit of the decimal point when converted to the binary number is 4, the average value “121855.33333...” Is converted to the binary number “11101101111111111.0001” and transmitted. It is possible.

In addition, although the transmission side client clock recovery device 1 includes the frequency information generation unit 44, the reception side client clock recovery device may include the frequency information generation unit 44.
FIG. 9 is a diagram illustrating a functional block configuration of a reception-side client clock recovery device including a frequency information generation unit. The reception-side client clock recovery device 81 includes a clock / data recovery unit 82, a demapping processing unit 83, a frequency information generation unit 85, and a client clock recovery unit 86.

  The clock / data recovery unit 82 recovers the clock and data of the OTN frame. The demapping process 83 includes a JC determination unit 84 that performs JC processing for determining whether the data is stuff data or data, and restores the client signal from the OTN frame. The frequency information generation unit 85 generates frequency information from the result of the JC processing of the JC determination unit 84. The client clock reproduction unit 86 reproduces the clock of the client signal based on the frequency information obtained from the frequency information acquisition unit 85.

  When the receiving side includes the frequency information generating unit 85, the frequency of the client signal is measured from the JC processing. NJO (Negative Justification Opportunity) and PJO (Positive Justification Opportunity) used for JC processing indicate how many client signals are included in the OPU payload, and generate frequency information only on the receiving side using JC processing. Is possible. FIG. 10 is a diagram illustrating the relationship between the OPU OH and the JC byte, the NJO, and the PJO byte when accommodating the signals of CBR2G5, CBR10G, and CBR40G.

The JC determination unit 84 performs JC processing for each frame according to the frequency deviation of the client signal. The JC byte indicates whether the NJO and PJO bytes are handled as data or stuff. For example, in the case of “JC = 01”, it can be seen that the NJO and PJO bytes are data, so the client signal included in one frame Can be determined to be 15297 bytes. Frequency information can be generated by the averaging process based on the number of bytes obtained in this way.
When generating frequency information on the transmission side, it is possible to transfer frequency information with higher accuracy.

Next, a fourth embodiment of the present invention will be described.
FIG. 11 is a functional block configuration diagram of a frequency information generation unit in the fourth embodiment. The frequency information generation unit 91 includes a clock counter 92, a frequency information average processing unit 93, and a weighting processing unit 94. The clock counter 92 counts clock pulses. The weighting processing unit 94 weights the value counted by the clock counter 92. The frequency information average processing unit 93 averages the values weighted by the weighting processing unit 94 to generate frequency information of the client signal. The difference between the frequency information generation unit 14 shown in FIG. 1 and the frequency information generation unit 44 shown in FIG. 7 is that the value of the clock counter 92 held by N frames is weighted and averaged to obtain a frequency. To generate information.

FIG. 12 is a diagram for explaining the operation of the frequency information generation unit 91. The frame period pulse generator 95 generates a pulse corresponding to one period of the OTN frame. The clock counter 92 measures the clock of the client signal with the pulse output from the frame period pulse generator 95 as a trigger. The clock counter 51 stores the measured number of clocks for one frame (M _N bits, N = 1,..., N) in the frequency information average processing unit 93 and weights the number of clocks observed for the past N frames. Multiplication coefficients (g ₁ , g ₂ ,..., G _n ) and average processing (M ₁ × g ₁ + M ₂ × g ₂ +... + M _n × g _n ) / (g ₁ + g ₂ +... + G _n ) I do. As a method of determining the weighting coefficient, there are a method of changing the weighting coefficient linearly, a method of changing the weighting coefficient with an exponential function, and the like.

For example, in the method of linearly changing the weighting coefficient, if the step width of the weighting coefficient is Δt, the weighting coefficient is determined as follows.
g _N = g _N-1 + Δt (1)
For example, if the number of clocks for 4 frames (N = 4) is held, the weighting coefficient is g ₄ = 10, and the weighting coefficient step width Δt = 2, g ₄ = 10, g ₃ = 8, g _{Since 2} = 6 and g ₁ = 4, the frequency information can be derived as ((4 × M ₁ + 6 × M ₂ + 8 × M ₃ + 10 × M ₄ ) / 28).

In the method of varying the weighting factor by an exponential function, if the frequency information of the k th frame starting from the frame began observation was f _k,
f _k = α × M _N + (1−α) × f _k−1 (2)
The frequency information can be generated as Here, α is a smoothing coefficient, and α = 2 / (N + 1).

For example, the frequency information averaging processing unit 93 holds the number of clocks (M ₁ , M ₂ ,..., M _n ) for N frames in the initial state, and divides the sum by the number of observation frames N (( M ₁ + M ₂ +... + M _n ) / N) as frequency information f _k and waits until the next clock number is input. Then, when the number of clocks is newly input, the frequency information f _k is generated using Equation (2). Thereafter, the frequency information average processing unit 93 generates the frequency information f _k using the equation (2) every time the clock number _MN is updated. In the initial state, clocks for N frames are averaged to obtain frequency information f _k , but initial frequency information f _k may be generated using the linearly changing weighting coefficient.

Next, a fifth embodiment of the present invention will be described.
FIG. 13 is a functional block configuration diagram of the transmission-side client clock recovery device according to the fifth embodiment. The transmission-side client clock recovery device 101 includes a clock / data recovery unit 111, a mapping processing unit 112, an overhead insertion unit 113, a phase comparison unit 114, and a frequency information generation unit 115.

  The clock / data recovery unit 111 recovers the clock and data of the client signal. The mapping processing unit 112 accommodates the client signal in the OTN frame. The overhead insertion unit 113 inserts the overhead (OH) of the OTN frame. The phase comparator 114 detects the phase difference between the clock of the client signal and the synchronization clock. The frequency information generation unit 115 generates the frequency information of the client signal based on the signal from the phase comparison unit 114.

The difference between the transmission-side client clock recovery device 101 and the transmission-side client clock recovery device (FIGS. 1, 7, and 11) is that the client is based on the phase difference between the clock of the client signal and the synchronization clock. It is a point that generates frequency information of a signal.
The phase comparator 114 can be either an analog type or a digital type. FIG. 14 is a diagram for explaining the operation of the phase comparison unit. As illustrated in FIG. 14, the phase comparison unit 114 determines a plurality of threshold values in advance according to the phase difference, detects the phase difference at the frame period, and generates frequency information according to the magnitude of the phase difference.

By using the phase comparator 114, it is possible to generate frequency information of one bit step or less, and therefore it is possible to generate accurate frequency information.
For example, when the detection of the phase difference is set to 1/2 UI (= 1 half of 1 bit), the frequency information is (..., -1, -1/2, 0, 1/2, 1, ...). (..., -2, -1, 0, 1, 2,...) It is also possible to convert these into binary numbers and transmit them.

Next, a sixth embodiment of the present invention will be described.
FIG. 15 is a functional block configuration diagram of the transmission-side client clock recovery device 201 in the sixth embodiment. The transmission-side client clock recovery device 201 includes a clock / data recovery unit 211, a mapping processing unit 212, an overhead processing unit 213, a delay detection unit 214, and a frequency information generation unit 215. The clock / data recovery unit 211 recovers the data of the received client signal and the clock. The delay detection unit 214 performs delay detection of the clock of the reproduced client signal. The mapping processing unit 212 accommodates the client signal in the OTN frame. The frequency information generation unit 215 generates frequency information based on the data output from the delay detection unit. The overhead insertion unit 213 inserts an OTN frame and stores the frequency information output from the frequency information generation unit 215 in the overhead. The difference from the transmission-side client clock recovery device in the above-described embodiment is that the frequency of the client signal is detected by delay detection.

  FIG. 16 is a functional block diagram showing a processing flow of the delay detection unit 214. The delay detection unit 214 illustrated in FIG. 16 includes a delay processing unit 2141 that gives a specific delay, and a phase comparison unit 2142 that performs phase comparison of inputs. The clock of the client signal is branched into two in the delay detection unit 214, one is input to the phase comparator 2142, and the other is input to the phase comparator 2142 via the delay processing unit 2141. The delay processing unit 2141 gives a specific delay to the clock of the client signal and outputs it. When the nominal value of the clock frequency of the client signal is known, the delay processing unit 2141 gives a delay so that the output after the phase comparator 2142 becomes 0, so that the output after the phase comparator 2142 according to the change in frequency. Changes. Since the output from the phase comparator 2142 increases as the frequency deviation increases, the frequency information can be detected by monitoring the output voltage.

  FIG. 17 is a diagram for explaining another form of the phase detector 214A, which is different from the sixth embodiment in FIG. 16 in that frequency information is generated based on the delay amount of the variable delay processor 2145. . The delay detection unit 214A illustrated in FIG. 17 includes a variable delay processing unit 2145 that gives a specific delay, and a phase comparator 2146 that performs a two-input phase comparison. The client clock is branched into two in the delay detection unit 214A, one is input to the phase comparator, and the other is input to the phase comparator 2146 via the variable delay processing unit 2145. The output from the phase comparator 2146 is fed back to the variable delay processing unit 2145. The variable delay processing unit 2145 adjusts the delay amount so that the output of the signal fed back becomes zero. When the output of the signal to be fed back becomes 0, the delay amount is output as frequency information. Since the delay amount at which the signal output from the phase comparator 2146 becomes 0 according to the frequency is uniquely determined, it is possible to detect frequency information with this configuration, and when this configuration is used, the client signal The present invention can be applied even when the clock frequency is not known. Note that it is possible to detect not only the clock of the client signal but also the frequency information of the synchronous clock using the same configuration. Further, it is possible to transmit the clock frequency information of the client signal and the frequency information of the synchronous clock together.

  In addition, you may make it combine each embodiment mentioned above.

DESCRIPTION OF SYMBOLS 1, 1A, 101, 201 ......... Sending side client clock reproduction | regeneration apparatus 2, 2A, 81 ......... Reception side client clock reproduction | regeneration apparatus 11, 11A, 211 ......... Clock / data reproduction | regeneration part 12, 12A, 212 ... ... Mapping processing unit 13, 13A, 213 ... Overhead insertion unit 14, 17A, 44, 91, 215 ... Frequency information generation unit 15A ... Client signal identification unit 16A ... Frequency information generation function switching unit 21 , 21A ......... Clock and data recovery unit 22, 22A ......... Frequency information acquisition unit 23A ......... Client signal type acquisition unit 24A ......... Client clock recovery function switching unit 23, 26A ......... Client clock recovery unit 24 ……… Demapping processing unit 25A ……… Frequency information acquisition unit 214 ……… Delay detection unit 2141... Delay processing units 2142 and 2146... Phase comparator 2145.

Claims (8)

A client clock recovery device in a transmission system for accommodating or multiplexing a client signal in an OTN frame and outputting the received or multiplexed client signal from the received OTN frame,
On the transmission side that accommodates or multiplexes the client signal in the OTN frame,
A first reproduction unit for reproducing the clock and data of the client signal;
A frequency information generator that measures the regenerated clock and generates frequency information of the clock;
A mapping processing unit for accommodating the client signal in an OTN frame;
An overhead insertion unit that inserts the frequency information into the overhead of the OTN frame;
On the receiving side that outputs the client signal accommodated or multiplexed from the received OTN frame,
A second reproducing unit for reproducing the clock and data of the received OTN frame;
A frequency information acquisition unit that acquires the frequency information from the overhead of the OTN frame;
A client clock recovery unit for recovering a clock of the client signal using the frequency information;
A demapping processing unit that restores the client signal from the OTN frame using a clock of the reproduced client signal;
A client clock reproducing apparatus comprising: The sender side
A client signal identifying unit for identifying the type of the client signal;
A frequency information generation function switching unit that switches a frequency information generation function according to the type of the client signal;
The frequency information generating unit on the transmission side has a plurality of different frequency information generating functions depending on the type of client signal, and corresponds to the type of client signal according to the switching instruction from the frequency information generating function switching unit. Generate frequency information by frequency information generation function,
The receiving side further includes:
A client signal type acquisition unit for acquiring a signal for identifying the type of the client signal from the overhead of the OTN frame,
The client clock reproduction unit has a plurality of different frequency information generation functions depending on the type of client signal, and reproduces using a reproduction function corresponding to the type of client signal acquired by the client signal type acquisition unit.
2. The client clock reproducing apparatus according to claim 1, wherein: The frequency information generating unit on the transmission side in the client clock reproducing device is:
A delay detector that bifurcates the client clock, gives a delay to one, and obtains frequency information by performing phase comparison with the other;
The client clock recovery device according to claim 1 or 2, further comprising: A client clock recovery device in a transmission system for accommodating or multiplexing a client signal in an OTN frame and outputting the received or multiplexed client signal from the received OTN frame,
On the transmission side that accommodates or multiplexes the client signal in the OTN frame,
A first reproduction unit for reproducing the clock and data of the client signal;
A mapping processing unit for accommodating the client signal in an OTN frame;
With
On the receiving side that outputs the client signal accommodated or multiplexed from the received OTN frame,
A second reproducing unit for reproducing the clock and data of the received OTN frame;
A frequency information generator that measures the regenerated clock and generates frequency information of the clock;
A client clock recovery unit for recovering a clock of the client signal using the frequency information;
A demapping processing unit that restores the client signal from the OTN frame using a clock of the reproduced client signal;
A client clock reproducing apparatus comprising:   The frequency information generating unit measures and holds clocks of OTN frames for a predetermined number of frames, and outputs a clock averaged by the number of frames as frequency information of a client signal. The client clock reproducing device according to claim 1 or 4.   The frequency information generation unit measures clocks of OTN frames for a predetermined number of frames, multiplies the measured number of clocks by a weighting coefficient, and divides the total sum of the weighted clocks by the number of frames. 5. The client clock reproducing apparatus according to claim 1, wherein the frequency information is generated.   5. The client according to claim 1, wherein the frequency information generation unit generates the frequency information by comparing phases of a clock reproduced from the reproduction unit and a synchronization clock of the OTN frame. Clock recovery device. A client clock recovery method in a transmission system that accommodates or multiplexes a client signal in an OTN frame and outputs the received or multiplexed client signal from the received OTN frame.
On the transmission side that accommodates or multiplexes the client signal in the OTN frame,
Regenerating the clock and data of the client signal;
Measuring the regenerated clock and generating frequency information of the clock;
Accommodating the client signal in an OTN frame;
Inserting the frequency information into the overhead of the OTN frame;
On the receiving side that outputs the client signal accommodated or multiplexed from the received OTN frame,
Regenerating the clock and data of the received OTN frame;
Obtaining the frequency information from the overhead of the OTN frame;
Regenerating the clock of the client signal using the frequency information;
Restoring the client signal from the OTN frame using a clock of the regenerated client signal;
A client clock reproduction method comprising:

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