CN114826476A - Method and system for realizing GMP mapping in OTN - Google Patents
Method and system for realizing GMP mapping in OTN Download PDFInfo
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Abstract
A method for realizing GMP mapping in OTN relates to GMP (general mapping procedure) mapping field, the method includes: caching data at a client side through a FIFO (first in first out) caching module, and sampling a clock at the client side through a clock at a bearing side to obtain the number N of service clock samples between two otn _ fp signals; calculating C in GMP overhead from the number of service clock samples N and otn _ fp signals m And sigma C nD A value; according to C m And generating a bearing side read enabling signal for the FIFO buffer module, reading data from the FIFO buffer module, filling the data in a payload area of the OTN frame, and adding overhead specified by the OTN frame to complete the OTN framing. The invention reduces the transmission delay of the service, does not need to occupy the reserved overhead of the OTN, can be communicated with other manufacturer equipment, and can meet the rigorous requirement of CPRI service index.
Description
Technical Field
The invention relates to the field of GMP (general mapping procedure) mapping, in particular to a method and a system for realizing GMP mapping in an OTN (optical transport network).
Background
OTN (optical transport network) has become the mainstream technology of transport network due to its features of strong integrated service carrying capacity, reliable signal management and monitoring, flexible high-capacity service scheduling and grooming, etc. The ITU g.709 protocol defines the OTN frame structure, bit rate and format for mapping client signals. In the mapping method, GMP mapping can map various services of different types and rates to OTN frames well, so that transparent transmission of service clocks is realized, and the application is most extensive.
Realizing GMP mapping in OTN optical transport networkThe method comprises two aspects of processing content. The first is the insertion of the sending-end service data and the extraction of the receiving-end service data. C of originating current frame m The number of m-bit Client data entries (number of m-bit block Client data) value determines whether the next frame of the originating terminal is inserted and how many padding blocks are inserted, and the specific position of inserting the padding blocks is determined by the Sigma-Delta algorithm specified by the standard; the receiving end utilizes C of a frame on the receiving end m Stripping all filling blocks in the current frame, and solving the service data carried by the current frame; second, the receiving end utilizes the received C m And sigma C nD The value recovers the client side traffic clock. Different services have different requirements on indexes such as clock recovery quality and time delay, and GMP mapping implementation methods are also different.
The core of GMP mapping is how to accurately compute C in real time m And sigma C nD And C obtained m And sigma C nD The value change is minimal for service clock recovery. In the prior art, a sending end samples a waterline of a data path FIFO (First Input First Output) cache module, and low-pass filters the variable quantity of the waterline to generate smooth C m And sigma C nD The value is obtained. End use C m And sigma C nD The values recover the traffic data and the clock. The method is difficult to filter high-frequency jitter generated in GMP mapping and demapping processes, is effective for services with low clock quality requirements (such as Ethernet, low-order ODU and SDH), but cannot meet the clock transparent transmission requirements of wireless services. Some manufacturers transmit clock information of a wireless service through reserved overhead of an OTN frame, and a receiving end performs clock recovery using the reserved overhead clock information. The disadvantage of this approach is that when multiple small-grain services are mapped to OTN frames simultaneously, the reserved overhead is not necessarily sufficient and cannot be communicated with other factory devices.
In the face of the bearer requirement of a Common Public Radio Interface (CPRI), the traditional GMP mapping method cannot meet the harsh requirements of CPRI service indexes, such as a recovery clock frequency jitter of ± 2ppb and a delay jitter of ± 8.138 ns.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method and a system for realizing GMP mapping in an OTN (optical transport network), which can reduce the transmission delay of the service, do not need to occupy the reserved overhead of the OTN, can be communicated with other manufacturer equipment, and can meet the harsh requirement of CPRI (common public radio interface) service indexes.
In order to achieve the above object, in one aspect, a method for implementing GMP mapping in an OTN is adopted, including:
caching data at a client side through a FIFO (first in first out) caching module, and sampling a clock at the client side through a clock at a bearing side to obtain the number N of service clock samples between two otn _ fp signals;
calculating C in GMP overhead from the number of service clock samples N and otn _ fp signals m And sigma C nD A value;
according to C m And generating a bearing side read enabling signal for the FIFO buffer module, reading data from the FIFO buffer module, filling the data in a payload area of the OTN frame, and adding overhead specified by the OTN frame to complete the OTN framing.
Preferably, the calculating C in GMP overhead according to the number of service clock samples N and the otn _ fp signal m Values, including:
wherein K1 and K2 are both positive integers, and
P m,server the number of the client-side maximum data blocks with granularity which can be carried by the bearer side is represented, W2 represents the data bit width of the client side, ts represents the number of time slots occupied by the client side, and P represents the number of payload bits of the OTN frame or the multiframe of the bearer side.
Preferably, each time GMP mapping is performed, C is mapped m The decimal part is accumulated and summed with the remaining decimal part after each GMP mapping, and when the accumulated result is less than 1, C m The integer part of (2) directly as C of GMP overhead m Value, accumulated summed fractional part of straightD/C conversion nD A value;
when the accumulation result is greater than or equal to 1, C m Is added with 1 as C in GMP overhead m Value, accumulating the summed fractional part minus 1 and converting to sigma-C nD 。
Preferably, when (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ))<At the time of K2, the material is,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )；
Of the i-th GMP overhead
When (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) ) is not less than K2,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )+1；
Of the i-th GMP overhead
Where i is 1,2,3 … …, int () denotes the integer part of the data in parentheses, M denotes the mapping granularity, and n denotes Σ C nD The value is determined according to the OTN protocol.
Preferably, the obtaining the number N of service clock samples between two otn _ fp samples by the carrier side clock sampling the client side clock comprises:
generating OTN _ fp signals with high level and high effect at the bearing side of the OTN at intervals of X multiplied by F/W1 clock cycles; synchronizing otn _ fp signals to a service clock domain cli _ clk across two clock domains to obtain synchronized indication signals cli _ fp; finally, calculating the number N of service clock samples spaced between the two synchronized indication signals cli _ fp in a service clock domain; wherein F is the number of bits contained in an OTN frame or a multi-frame carrying a GMP overhead, X is the number of timeslots in a payload area, and W1 represents the data processing bit width.
In another aspect, a system for implementing GMP mapping in an OTN is provided, including:
the client side interface module is used for interfacing with client services and generating client side data which comprises a client side clock, a client side write enable and client side write data;
the FIFO buffer module is used for buffering the data of the client side; the data processing device is also used for returning the bearing side read data after receiving the bearing side read enable;
the client clock acquisition module is used for sampling a client side clock through a bearing side clock to obtain the number N of service clock samples between two otn _ fp signals;
C m and sigma C nD A generating module for calculating C in GMP overhead according to the service clock sampling number N and otn _ fp signal m And sigma C nD A value;
a bearer side framing module for framing according to C m And generating a bearing side read enabling signal to the FIFO cache module, receiving bearing side read data returned by the FIFO cache module, filling the bearing side read data in a payload area of the OTN frame, adding overhead specified by the OTN frame, and finishing the OTN framing.
Preferably, said C m And sigma C nD The generation module calculates C in GMP overhead according to the following formula m The value of the one or more of the one,
wherein K1 and K2 are both positive integers, and
P m,server denotes the number of client-side granularity maximum data blocks that the bearer side can bear, and W2 denotesThe data bit width of the client side, ts represents the number of time slots occupied by the client side, and P represents the payload bit number of the OTN frame or the multiframe of the bearing side.
Preferably, said C m And sigma C nD The generation module is further to:
c is to be m The decimal part is accumulated and summed with the remaining decimal part after GMP mapping, and when the accumulated result is greater than or equal to 1, C m Is added by 1 as C in GMP overhead m Value, the summed fractional part minus 1 and converted to sigma-C nD ；
When the accumulation result is less than 1, C m The integer part of (2) directly as C of GMP overhead m Value, accumulated summed fractional part direct conversion sigma-C nD The value is obtained.
Preferably, said C m And sigma C nD In the conversion process of the generation module,
when (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ))<At the time of K2, the material is,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )；
Of the i-th GMP overhead
When (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) ) is not less than K2,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )+1；
Of the i-th GMP overhead
Where i is 1,2,3 … …, int () denotes the integer part of the data in parentheses, M denotes the mapping granularity, and n denotes Σ C nD The value is determined according to the OTN protocol.
Preferably, the client clock acquisition module is configured to:
generating OTN _ fp signals with high level and high effect at the bearing side of the OTN at intervals of X multiplied by F/W1 clock cycles; synchronizing otn _ fp signals to a service clock domain cli _ clk across two clock domains to obtain synchronized indication signals cli _ fp; finally, calculating the number N of service clock samples spaced between the two indication signals cli _ fp in a service clock domain; wherein F is the number of bits contained in an OTN frame or a multi-frame carrying a GMP overhead, X is the number of timeslots in a payload area, and W1 represents the data processing bit width.
One of the above technical solutions has the following beneficial effects:
the invention obtains the sampling number N of the service clock mainly by sampling the clock of the client side through the clock of the OTN bearing side, because C m GMP mapped C linearly related to the number of service clock samples N (i.e., the number of service clock samples) nD The value can be represented by C m Is obtained, so that the client-side clock number can be converted to C in GMP overhead m And sigma C nD The method can be applied to scenes with higher requirements on clock recovery quality, reduces service transmission delay and does not need to occupy the retention overhead of the OTN. And OTN framing completely meets the standard, does not contain a proprietary protocol, and can be communicated with other factory equipment.
C produced by the invention m And sigma C nD The value jitter is very small, the bit level can be achieved, the precision is very high, and therefore the clock recovery performance is good; c m The value can be converged to a stable state quickly, the water level change of the buffer FIFO in the GMP mapping and demapping process is reduced, the service time delay is reduced, and meanwhile, the service clock recovery precision is improved.
Drawings
Fig. 1 is a flowchart of a method for implementing GMP mapping in an OTN according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a system for implementing GMP mapping in an OTN according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an OTN frame structure according to an embodiment of the present invention;
fig. 4 is a GMP mapping parameter diagram according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides an embodiment of a method for realizing GMP mapping in an OTN, which comprises the following steps:
s1, caching data at a client side through an FIFO (first in first out) cache module, and sampling a client side clock through a bearing side clock to obtain the number N of service clock samples between two otn _ fp signals.
S2, calculating C in GMP overhead according to the sampling number N of the service clock and otn _ fp signals m And sigma C nD The value is obtained.
S3, according to C m And generating a bearing side read enabling signal for the FIFO buffer module, reading data from the FIFO buffer module, filling the data in a payload area of the OTN frame, and adding overhead specified by the OTN frame to complete the OTN framing. Wherein OTN framing includes payload padding and overhead padding, C m For payload stuffing, C m And sigma C nD For overhead padding, the overhead specified by the OTN frame in the protocol includes the overhead according to C m And sigma C nD Overhead of padding.
In the g.709 standard, a complete OTN frame payload area is divided into a plurality of timeslots, and each timeslot corresponds to a GMP overhead.
In the step S1, it is assumed that the OTN frame or the multi-frame carrying a GMP overhead includes F bits, where the payload area includes P bits, the payload area is divided into X slots (X represents the number of slots), and the data processing bit width is W1 bits (W1 represents the data bit width of a clock cycle during OTN framing), then the number of clocks occupied by the OTN frame or the multi-frame carrying a GMP overhead is F/W1, it should be understood that the result of F/W1 in system design should be a positive integer, that is, the data amount of an OTN frame or the multi-frame occupies a positive integer of clock cycles, otherwise, the OTN framing and de-framing operation is difficult to implement due to data splicing.
Specifically, a OTN _ fp signal with a high effective beat level is generated at the bearing side of the OTN every X × F/W1 clock cycles, and since one GMP overhead corresponds to every 1 timeslot, the GMP overhead of X timeslots is transmitted within X × F/W1 OTN clock cycles. And (3) synchronizing the otn _ fp signals to a service clock domain cli _ clk across two clock domains, wherein the synchronized indication signals are represented by the cli _ fp, and the service clock number N between the two indication signals cli _ fp is calculated in the service clock domain, namely N is the obtained client side clock number. It is understood that OTN _ fp is an indication signal of the OTN clock domain carrier side, cli _ fp is a knowledge signal of the service clock domain client side, and OTN _ fp is obtained after clock domain synchronization.
In the above step S2, for better explanation, C in GMP overhead is calculated based on the number of samples N of the service clock and the otn _ fp signal m Values, a derivation of N and C is provided first m And sigma C nD Example of conversion rule of value, then how to generate C for GMP overhead in GMP mapping m And sigma C nD The value is obtained.
GMP mapping provides that for any given client-side signal of fixed bit rate, within one bearer frame period or bearer multiframe period, the number of client-side n-bit blocks that need to be carried is:
wherein,
f client represents: the data bit rate at the client side is,
f server represents: the payload data bit rate on the bearer side,note: data bit rate on the bearer side>Payload data bit rate on the bearer side>The data bit rate at the client side.
T server Represents: carrying side frame payload period or payload multiframe period
B server Represents: payload bit number of one frame period or multiple frame periods on bearing side
C n Represents: the number of client-side n-bit data blocks that need to be carried in one bearer frame period or multiframe period.
In the field of OTN optical transport networks, taking mapping of M byte block granularity as an example, the above equation (1) will be in the following form:
(2) c of formula m A non-integer, represented by the formula (2) C m The integer part of (2) is denoted as int (C) m ) The fractional part is denoted frac (C) m ) Changing the formula (2) into the following formula:
the number of the remaining unmapped n-bit blocks on the client side in a carrier frame or multiframe period is C nD ，C nD Having the following expression:
the formula (1), (3) and (4) can be used for obtaining:
(5) formula C illustrating GMP mapping nD The value can be represented by formula (2) C m The fractional part of (a).
Assume client-side dataThe processing bit width is W2 bit, then the clock frequency of the client side is
Assuming that the data of the client side occupies ts time slots in the X time slots of the bearer side, the data bit rate of the bearer side is
The data processing bit width of the bearing side OTN is W1bit, and the clock frequency of the bearing side OTN frame is W1bit
The ratio of the clock frequency of the client side to the clock frequency of the carrier side should be equal to the count ratio of two clocks in the same time interval, so that:
the formula (2) and (6) can be used for obtaining:
when the client side has a granularity of 8 × Mbit (ts slots are occupied), it can be known from the GMP mapping standard
P m,server Indicating the number of 8 x Mbit maximum data blocks that the bearer side can carry. Therefore, the formula (7) can be changed as follows:
when the system is designed, W2 is the data bit width of the client side, ts is the number of time slots occupied by the client side, the number of payload bits P of the OTN frame or the multiframe of the bearer side, and the number of the largest client side data blocks P capable of being borne m,server And (4) uniquely determining. (8) Description of formula C m And when in businessThe number of clock samples N is linearly related to one another, N can be equal to C m And (4) converting each other. (8) In the formula, the coefficient of the sampling number N of the service clock can be written as a simplest fractional form, that is:
wherein K1 and K2 are both positive integers, and
further, how C in GMP overhead is generated by the number N of service clock samples is described below m And sigma C nD The value is obtained. Due to C in the actual GMP overhead m 、ΣC nD Are all positive integers, and C of the actual GMP overhead is used to avoid confusion m 、ΣC nD Is marked as C m ′、ΣC nD '. C of first GMP mapping m ′、ΣC nD ' is represented by C m1 ′、ΣC nD1 ', C of the second GMP mapping m ′、ΣC nD ' is represented by C m2 ′、ΣC nD2 ', C of the ith GMP mapping m ′、ΣC nD ' is represented by C mi ′、ΣC nDi ', i denotes the i-th GMP mapping overhead, and takes a value of 1,2,3 … …
Assuming that the number of first service clock samples N is represented by N1, C in the corresponding equation (9) m With C m1 Represents; the number N of second service clock samples is represented by N2, and C is expressed by corresponding formula (9) m With C m2 Represents; the number N of ith service clock samples is represented by Ni, and C in corresponding formula (9) m With C mi And (4) showing. The definition symbol int () represents taking only the integer part of the data within the parentheses. int (C) m1 ) Is represented by C m1 Integer part of (2), int (C) m2 ) Is represented by C m2 Integer part of (2), int (C) mi ) Is represented by C mi The integer part of (c), and so on. C m ′、ΣC nD The generation process is as follows:
performing GMP mapping for the first time:
c of first GMP overhead m ′＝C m1 ′＝int(C m1 )；
The number of the remaining unmapped n-bit blocks on the client side is
Sigma-C for first GMP overhead nD ′＝ΣC nD1 ′＝int(C nD ) I.e. sigma C at first GMP mapping nD Is equal to C nD The integer part of (2).
When GMP mapping is performed for the second time, C is judged first m ′＝int(C m2 ) Whether the remaining cumulative number of bits exceeds the granularity of the GMP mapping when performing the mapping. The judgment process is as follows: due to C in the formula (9) m The decimal part of (2) represents the remaining number of bits which are not mapped in one mapping, the decimal part of C _ m in the formula (9) can be accumulated and summed, and when the accumulation result is less than 1, the remaining accumulated number of bits does not exceed the granularity of GMP mapping; when the accumulation result is 1 or more, the remaining accumulated number of bits exceeds the granularity of the GMP mapping.
Therefore, will
Compared with 1, the method can be converted into an integer comparison mode, namely K1 × N1-K2 × C, because the decimal calculation is not simple and convenient enough in the logic implementation process m1 ′+K1×N2-K2×int(C m2 ) Compare with K2.
C of second GMP overhead when the former is smaller than the latter m ′＝C m2 ′＝int(C m2 )；
Of second GMP overhead
When the former is not smaller than the latter:
c of second GMP overhead m ′＝C m2 ′＝int(C m2 )+1；
Of second GMP overhead
As can be seen from the above procedure, for each GMP mapping, C in the formula (9) m The decimal part and the remainder after GMP mapping are accumulated and summed, when the accumulated result is less than 1, the remaining accumulated bit number can not occupy one mapping granularity, (9) C in the formula m The integer part of (2) directly as C of GMP overhead m Value, accumulated summed fractional part direct conversion sigma-C nD The value is obtained. When the accumulation result is greater than or equal to 1, it indicates that the residual accumulated bit block number can occupy one mapping granularity, (9) formula C m The integer part of (2) needs to be added by 1 as C in GMP overhead m Value, accumulating the summed fractional part minus 1 and converting to sigma-C nD 。
For the ith GMP mapping, C of GMP overhead m ′、ΣC nD ' may be expressed as follows:
when (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ))<At the time of K2, the material is,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )；
Of the i-th GMP overhead
When (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) ) is not less than K2,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )+1；
Of the i-th GMP overhead
Wherein n represents Σ C nD The specific value of the precision of (a) is determined according to an OTN protocol, which is usually 1/8, 1, or 8.
As shown in fig. 2, the present invention provides an embodiment of a system for implementing GMP mapping in an OTN, which can be used to implement the above-mentioned embodiment. In this embodiment, the system includes a client side interface module, an FIFO buffer module, a client clock acquisition module, and a clock acquisition module m And sigma C nD The device comprises a generating module and a bearing side framing module.
The client side interface module is used for interfacing with client services and generating client side data, the client side data comprises a client side clock, a client side write enable and client side write data, the client side data is sent to the FIFO buffer module, and the client side clock is also sent to the client clock acquisition module.
The FIFO buffer module is used for buffering the data of the client side; and the data processing module is further configured to send the bearer side read data to the bearer side framing module after receiving the read enable sent by the bearer side framing module.
A client clock acquisition module for sampling the client side clock according to the otn _ fp signal sent by the carrier side framing module to obtain the number N of service clock samples between two otn _ fp signals, and sending the number N of service clock samples to the client side clock acquisition module m And sigma C nD And generating a module.
C m And sigma C nD A generation module for generating a time-based serviceThe number of clock samples N and otn _ fp signals, calculating C in GMP overhead m And sigma C nD And sending the value to a bearing side framing module.
A bearer side framing module for framing according to C m And generating a bearing side read enabling signal by the value, sending the bearing side read enabling signal to the FIFO cache module, receiving bearing side read data returned by the FIFO cache module, filling the bearing side read data in a payload area of the OTN frame, and adding overhead specified by the OTN frame to complete the OTN framing operation.
It will be appreciated that the FIFO buffer module and the bearer side framing module may be implemented by methods common in the art.
To further clearly illustrate the specific implementation of the GMP mapping, taking the GMP mapping from CPRI to some OTN frame as an example, the process of implementing the GMP mapping by the above system is described.
As shown in fig. 3, the frame structure of an OTN frame (hereinafter referred to as a FlexO _ FR frame) is shown. The FlexO _ FR frame structure is a 128-row x 5280-column structure, the 1 st row from 1 st to 256 th columns are AM (frame alignment area), the 1 st row from 257 st to 512 th columns are OH (overhead) area, the 5141 st to 5280 th columns of each row are FEC (forward error correction) area, the other are payload areas, and the payload areas are divided into 24 time slots. The GMP overhead is delivered over one multiframe (containing 8 FlexO-FR frames).
The protocol specifies that the CPRI service is mapped into the FlexO _ FR frame, and CPRI interface data needs to be decoded by 8B10B, then encoded by 64B66B, mapped into the ODUflex through BMP, and then mapped into the FlexO _ FR frame through GMP. As shown in fig. 4, a GMP mapping parameter graph is shown, where Y represents the word length of CPRI, and in terms of byte, different Y values correspond to different CPRI rates, and the CPRI traffic line rate is 491.52 mxyx 10/8. ts denotes the number of timeslots occupied by the CPRI on the bearer side.
In the above system, the client side clock acquisition module specifically includes:
firstly, generating a OTN _ fp signal with high level being effective at an interval of X × F/W1 clock cycles on the bearing side (clock domain) of the OTN; synchronizing otn _ fp signals to a service clock domain cli _ clk across two clock domains to obtain synchronized indication signals cli _ fp; finally, calculating the interval number between the two indication signals cli _ fp in the service clock domain, namely the number N of the service clock samples; wherein, F is the bit number contained in the OTN frame or the multiframe carrying a GMP overhead, X is the time slot number of the payload area, W1 represents the data processing bit width, and the error of each calculation N is plus or minus 1.
The following describes the specific implementation process of the client-side clock capture module by two embodiments.
Taking CPRI-7 mapped to a FlexO _ FR frame by GMP as an example, the OTN frame data bit width W1 is 80 bits when the system is designed. The OTN clock generates OTN _ fp signals every interval X × F/W1 ═ 24 × 5280 × 128 × 8/80 ═ 1622016 clock cycles; otn _ fp signal is synchronized to the service clock domain cli _ clk across the clock domain (by adopting a two-stage synchronization method), and the synchronized signal is cli _ fp; the period interval between two cli _ fp is counted in the service clock domain, and the count value is N. At the nominal frequency, the 1 st count value N1 is 1230621, the 2 nd count value N2 is 1230621, the 3 rd count value N3 is 1230622, and the error of each count N is ± 1.
Taking CPRI-4 mapped to a FlexO _ FR frame by GMP as an example, the OTN frame data bit width W1 is 80 bits when the system is designed. The OTN clock generates OTN _ fp signals every interval X × F/W1 ═ 24 × 5280 × 128 × 8/80 ═ 1622016 clock cycles; otn _ fp signal is synchronized to the clock domain of CPRI-4 across the clock domain (by adopting a two-stage synchronization method), and the synchronized signal is cli _ fp; the period interval between two cli _ fp is counted in the CPRI-4 clock domain, and the count value is N. At the nominal frequency, the 1 st count value N1 is 384569, the 2 nd count value N2 is 384569, the 3 rd count value N3 is 384570, the 4 th count value N4 is 384539.
In the above system, C m And sigma C nD Specific calculation of the Generation Module C m And sigma C nD The values are implemented as follows:
first, for a service clock sampling number N, C is calculated according to the formula (9) in the above embodiment m Value of C in the formula (9) m The fraction part of (a) is cumulatively summed with the fraction part remaining after each previous GMP mapping, and it should be noted that the fraction part remaining after the previous GMP mapping is cumulatively 0 at the time of the first GMP mapping. And further judging that the summation result isAnd if not, the number is more than or equal to 1.
C in GMP overhead when the accumulated result is greater than or equal to 1 m The integer part in the equation (9) is added with 1, and the summed fractional part is subtracted with 1 and then converted into sigma-C nD '. After the summed fractional part is reduced by 1, the residual fractional part which is not mapped is accumulated during GMP mapping before and this time.
C in GMP overhead when the accumulated result is less than 1 m ' equal to the integer part in equation (9), the summed fractional part being converted directly to Σ C nD ' the summed fractional part is used as the remaining fractional part that is accumulated during the current and previous GMP mapping without mapping.
This is explained in detail below with reference to fig. 3 and 4. A FlexO _ FR multiframe that fully carries GMP overhead contains 5280 × 128 × 8 bits with a payload of P ═ P (5140 × 128-4 × 128) × 8 bits. P m,server ＝41088。
Taking an example that CPRI-7 is mapped to a FlexO _ FR frame through GMP, when a system is designed, a client-side data bit width is that a CPRI-7 service line rate is decoded by 8B10B, a data processing bit width is 32bit, CPRI-7 data is encoded by 64B/66B, and is mapped into an ODUflex through BMP, the final equivalent client-side data bit width, that is, an ODUflex data bit width, is W1 × 66/64 × 239/238, the ODUflex occupies 8 timeslots of the FlexO _ FR frame, that is, ts is 8, and a mapping granularity M is 16 × 8 byte. The formula (8) in the above embodiment can be combined into the simplest fractional form:
the above equation can be simplified as:
in the above formula, the greatest common divisor of 32 × 32 × 41088 is 2629632.
Then the equation (9) is reduced to the simplest fraction, which can result in K1 being 7887 and K2 being 243712.
1 st GMP enantiomerAnd N1 is 1230621,
first, K1X (N1) -K2X (int (C) m1 ) Comparison with K2, the former K1X (N1) -K2X (int (C) m1 ) 77427, the former being smaller than the latter K2.
1 st GMP overhead
For the 2 nd GMP mapping, N1 is 1230621,
first, K1 × (N1+ N2) -K2 × (C) was judged m1 ′+int(C m2 ) As a result of comparison with K2, the former K1X (N1+ N2) -K2X (C) m1 ′+int(C m2 ) 154854, the former is smaller than the latter K2.
2 nd GMP overhead
3 rd GMP overhead
The 4 th GMP mapping, N1 ═ 1230622,
first, K1 × (N1+ N2+ N3+ N4) -K2 × (C) m1 ′+C m2 ′+C m3 ′+int(C m4 ) Comparison with K2, the former K1 × (N1+ N2+ N3+ N4) -K2 × (C) m1 ′+C m2 ′+C m3 ′+int(C m4 ) 39826, the former being larger than the latter K2.
4 th GMP overhead
The above is C of CPRI-7 service m And sigma C nD The generation module embodies the process, and so on for GMP mappings of 5 th, 6 th, 7.
Taking the case that CPRI-4 is mapped to the FlexO _ FR frame by GMP as an example, when the system is designed, the client-side data bit width is CPRI-4 service line rate, decoded by 8B10B, the data processing bit width is 32bit, the CPRI-4 data is encoded by 64B66B, and mapped to the ODUflex by BMP, the final equivalent client-side data bit width, that is, the ODUflex data bit width, is W1 — 32 × 66/64 × 239/238, the ODUflex occupies 3 slots of the FlexO _ FR frame, that is, ts is 3, and the mapping granularity M is 16 × 3 byte. And can be obtained by the formula (8) and reduced into a simplest fractional form:
the above formula can be simplified as follows:
in the above formula, the greatest common divisor of 32 × 32 × 41088 is 2629632, and then the simplest score of the formula (9) can result in K1 being 7887 and K2 being 91392.
For the 1 st GMP mapping, N1 is 384569,
first, K1X (N1) -K2X (int (C) m1 ) Comparison with K2, the former K1X (N1) -K2X (int (C) m1 ) 69939, the latter K2 is 91392, the former is smaller than the latter.
1 st GMP overhead
For the 2 nd GMP mapping, N1 is 384569,
first, K1 × (N1+ N2) -K2 × (C) was judged m1 ′+int(C m2 ) Comparison with K2, the former K1X (N1+ N2) -K2X (C) m1 ′+int(C m2 ) 139878, the latter K2 is 91392, the former being larger than the latter.
2 nd GMP overhead
For the 3 rd GMP mapping, N1 is 384570,
first, K1X (N1+ N2+ N3) -K2X (C) is judged m1 ′+C m2 ′+int(C m3 ) Comparison with K2, the former K1X (N1+ N2+ N3) -K2X (C) m1 ′+C m2 ′+int(C m3 ) 124692, the latter K2 is 91392, the former being larger than the latter.
3 rd GMP overhead
4 th GMP overhead
The above is the C of the CPRI-4 service m And sigma C nD The specific implementation procedure of the generation module may be similar to that of the 5 th, 6 th, 7 th GMP mapping of the CPRI-4 service.
The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.
Claims (10)
1. A method for implementing GMP mapping in an OTN, comprising:
caching data at a client side through a FIFO (first in first out) caching module, and sampling a clock at the client side through a clock at a bearing side to obtain the number N of service clock samples between two otn _ fp signals;
calculating C in GMP overhead from the number of service clock samples N and otn _ fp signals m Sum Σ C nD A value;
according to C m And generating a bearing side read enabling signal for the FIFO buffer module, reading data from the FIFO buffer module, filling the data in a payload area of the OTN frame, and adding overhead specified by the OTN frame to complete the OTN framing.
2. The method of implementing GMP mapping in an OTN according to claim 1, wherein the calculating C in GMP overhead from the number of service clock samples N and the OTN _ fp signal m Values, including:
wherein K1 and K2 are both positive integers, and
P m，server denotes the number of client-side maximum granularity data blocks that the bearer side can bear, W2 denotes the data bit width of the client side, ts denotes the client sideThe number of time slots occupied by the user side, P, represents the payload bit number of the OTN frame or the multiframe of the bearing side.
3. The method of implementing GMP mapping in an OTN according to claim 2, wherein C is mapped each time GMP mapping is performed m The decimal part is accumulated and summed with the remaining decimal part after each GMP mapping, and when the accumulated result is less than 1, C m The integer part of (2) directly as C of GMP overhead m Value, accumulated summed fractional part direct conversion ∑ C nD A value;
when the accumulation result is greater than or equal to 1, C m Is added with 1 as C in GMP overhead m The value, the summed fractional part minus 1, is converted to sigma C nD 。
4. A method for implementing GMP mapping in an OTN according to claim 3, characterized in that:
when (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) < K2) is contained in the container,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )；
Of the ith GMP overhead
When (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) ) is not less than K2,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )+1；
Of the i-th GMP overhead
Where i ═ 1,2, 3.. the int () represents the integer part of the data in parentheses, M represents the mapping granularity, and n represents Σ C nD The value is determined according to the OTN protocol.
5. The method of implementing GMP mapping in an OTN according to claim 1, wherein obtaining the number N of service clock samples between two OTN _ fp samples by the carrier-side clock sampling the client-side clock comprises:
generating OTN _ fp signals with high level and high effect at the bearing side of the OTN at intervals of X multiplied by F/W1 clock cycles; synchronizing the otn _ fp signal to a service clock domain cli _ clk across two clock domains to obtain a synchronized indication signal cli _ fp; finally, calculating the number N of service clock samples spaced between the two synchronized indication signals cli _ fp in a service clock domain; wherein F is the number of bits contained in an OTN frame or a multi-frame carrying a GMP overhead, X is the number of timeslots in a payload area, and W1 represents the data processing bit width.
6. A system for implementing GMP mapping in an OTN, comprising:
the client side interface module is used for interfacing with client services and generating client side data which comprises a client side clock, a client side write enable and client side write data;
the FIFO buffer module is used for buffering the data of the client side; the data processing device is also used for returning the bearing side read data after receiving the bearing side read enable;
the client clock acquisition module is used for sampling a client side clock through a bearing side clock to obtain the number N of service clock samples between two otn _ fp signals;
C m sum Σ C nD A generating module for calculating C in GMP overhead according to the service clock sampling number N and otn _ fp signal m Sum Σ C nD A value;
bearer side framingModule for according to C m And generating a bearing side read enabling signal to the FIFO cache module, receiving bearing side read data returned by the FIFO cache module, filling the bearing side read data in a payload area of the OTN frame, adding overhead specified by the OTN frame, and finishing the OTN framing.
7. The system for implementing GMP mapping in an OTN according to claim 6, wherein C m Sum Σ C nD The generation module calculates C in GMP overhead according to m The value of the one or more of the one,
wherein K1 and K2 are both positive integers, and
P m，server the number of the client-side maximum data blocks with granularity which can be carried by the bearer side is represented, W2 represents the data bit width of the client side, ts represents the number of time slots occupied by the client side, and P represents the number of payload bits of the OTN frame or the multiframe of the bearer side.
8. The system for implementing GMP mapping in an OTN according to claim 7, wherein C is m Sum Σ C nD The generation module is further to:
c is to be m The decimal part is accumulated and summed with the remaining decimal part after GMP mapping, and when the accumulated result is greater than or equal to 1, C m Is added with 1 as C in GMP overhead m Value, the fractional part of the sum being reduced by 1 and converted to sigma C nD ；
When the accumulation result is less than 1, C m The integer part of (2) directly as C of GMP overhead m Value, accumulated summed fractional part direct conversion ∑ C nD The value is obtained.
9. The system for implementing GMP mapping in an OTN according to claim 7, wherein C is m Sum Σ C nD In the conversion process of the generation module,
when (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) < K2) is contained in the container,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )；
Of the i-th GMP overhead
When (K1X (N1+ N2+ … + Ni) -K2X (C) m1 ′+C m2 ′+…+int(C mi ) ) is not less than K2,
c for i-th GMP overhead m ′＝C mi ′＝int(C mi )+1；
Of the i-th GMP overhead
Where i ═ 1,2, 3.. the int () represents the integer part of the data in parentheses, M represents the mapping granularity, and n represents Σ C nD The value is determined according to the OTN protocol.
10. The system for implementing GMP mapping in an OTN according to claim 6, wherein the customer clock acquisition module is configured to:
generating OTN _ fp signals with high level and high effect at the bearing side of the OTN at intervals of X multiplied by F/W1 clock cycles; synchronizing otn _ fp signals to a service clock domain cli _ clk across two clock domains to obtain synchronized indication signals cli _ fp; finally, calculating the number N of service clock samples spaced between the two indication signals cli _ fp in a service clock domain; wherein F is the number of bits contained in an OTN frame or a multi-frame carrying a GMP overhead, X is the number of timeslots in a payload area, and W1 represents the data processing bit width.
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