CN103684696A - Channel equalization system and method for independent error correction code modulation of subcarriers in optical OFDM (orthogonal frequency division multiplexing) - Google Patents
Channel equalization system and method for independent error correction code modulation of subcarriers in optical OFDM (orthogonal frequency division multiplexing) Download PDFInfo
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Abstract
The invention discloses a channel equalization system and method for independent error correction code modulation of subcarriers in optical OFDM (orthogonal frequency division multiplexing), and relates to the field of optical fiber communication. The method includes the steps: distributing serial data onto a plurality of parallel subcarriers after the serial data pass a serial-parallel converter of a transmitting end, independently performing error correction code and modulation format mapping by each subcarrier, arranging the subcarriers with the same error correction code type and the same modulation format mapping type into a group, equalizing the transmitting power of the subcarriers in the same group, keeping the SNR (signal to noise ratio) of a receiving end by the subcarriers with the same error correction code and modulation format mapping, converting signals from frequency domain to time domain by the aid of inverse Fourier transform, and performing parallel-serial conversion and electro-optical conversion; enabling the process of the receiving end to be opposite to that of the transmitting end. Error correction code and modulation format mapping combinations of the subcarriers can be flexibly selected, spectral efficiency utilization of each subcarrier is optimized, and point-to-multipoint application requirements are met.
Description
Technical field
The present invention relates to fiber optic communication field, specifically relate to a kind of channel equalization system and method for smooth OFDM sub-carriers independence error correction coding modulation.
Background technology
Along with the fast development of multimedia technology, people constantly increase the demand of information.For meeting growing capacity requirement, super 100bit/s is just like a raging fire the carrying out in the whole world of research of the follow-on optical transfer network key technology of 1Tb/s even.In order to promote the capacity of existing wavelength-division multiplex system, high spectrum efficiency modulation format and single channel two-forty are considered to effective solution, yet due to electronic device limit bandwidth, the for example bandwidth of digital to analog converter and sample rate restriction, simple by promoting monochromatic light carrier wave baud rate in conjunction with high order modulation form, its channel speed promotes limited.In order to break through the restriction of electronic device bandwidth, realize the single channel transmission rate of higher rate, utilize the multiplexing mode of many light carriers, the light carrier of low rate modulation is parallel multiple on frequency domain, be used for promoting the method for channel optical transmission speed, be considered to T bit-level transmission preferred option.
Traditional light OFDM(Orthogonal Frequency Division Multiplexing, OFDM) owing to being subject to the impact of the factors such as signal source frequency response, modulator frequency response and receiver frequency and even optical channel frequency response, cause frequency response unevenness at receiving terminal.Due to the unevenness of channel frequency response, at light OFDM receiving terminal, the subcarrier performance difference of different signal to noise ratios is very large.
Traditional light OFDM transmission technology is when addressing this problem, generally that power is balanced on the signal of telecommunication of transmitting terminal, make all available subcarriers basically identical at the power of receiving terminal, i.e. SNR(Signal to Noise Ratio, signal to noise ratio) basically identical.Because the signal of telecommunication gross power of transmitting terminal is limited, the subcarrier that SNR is lower carries out power ascension, will inevitably make the good subcarrier Quality Down of original SNR quality.Power equalization is just based on the transmission spectrum of the channel reality of receiving terminal acquisition, at transmitting terminal, carries out the reverse precompensation on electric territory, makes at the SNR of all subcarriers of receiving terminal basically identical.All subcarriers are all used identical modulation format and error correction coding.This method is actually sacrifices the higher subcarrier performance of SNR, is used for compensating the subcarrier performance that SNR is lower.
It is effective that channel power equalization methods is adjusted to the fixing point-to-point transmission system of the degree of depth for transmission range with transmission, it can guarantee constant transmissions distance, fixed modulation format mapping and one fixedly under error correction coding condition, modulation format mapping comprises n-QAM(Quadrature Amplitude Modulation, quadrature amplitude modulator), n-PSK(Phase-Shift Keying, phase shift keying) etc., in light ofdm signal, the transmission quality of all subcarriers is basically identical.
Shown in Figure 1, in traditional ofdm signal modulation flow process, mapping is all consistent to all subcarrier error correction codings with modulation format, the serial data sending is after unified error correction coding, enter deserializer, data allocations is carried out to unified modulation format mapping to each way carrier wave of frequency domain.Afterwards, parallel data flow is passed through to inverse Fourier transform, parallel frequency-region signal is become to parallel time-domain signal, finally by mistake parallel-serial conversion, become the time-domain signal of serial, through amplifying, be modulated on light carrier.At receiving terminal, take reverse flow process.
Owing to being used at some electric flux of transmitting terminal to resist, the frequency domain that bandwidth of a device and channel frequency response cause is uneven, rather than all energy are all for transmitting data.Therefore,, for the spectrum efficiency of transmission, this balanced way might not be best.And for some point-to-multipoint light OFDM transmission application scenario, the subcarrier that different receiving terminals is accepted is different, performance performance is different, and transmission bandwidth and distance are also different.Traditional transmitting terminal unified channel power equalization is for these situations, and the flexibility that just seems is not enough, urgently improves.
Summary of the invention
The object of the invention is in order to overcome the deficiency of above-mentioned background technology, a kind of channel equalization system and method for smooth OFDM sub-carriers independence error correction coding modulation is provided, in light ofdm signal, each way carrier wave can independently carry out error correction coding and modulation format mapping, according to the SNR condition of each way carrier wave in channel, flexibly, freely select each subcarrier error correction coding and the combination of modulation format mapping, the optimization that realization utilizes the spectrum efficiency of every way carrier wave, each way carrier wave can independently receive, can not only meet the application demand of point-to-point, can also meet point-to-multipoint application demand.
The invention provides a kind of channel equalization system of smooth OFDM sub-carriers independence error correction coding modulation, comprise transmitting terminal and receiving terminal, described transmitting terminal comprises the first deserializer, N forward error correction FEC coding unit, N modulation format map unit, transmitted power balanced unit, inverse Fourier transform unit, the first parallel-to-serial converter and electrical to optical converter, N is more than or equal to 2 integer, each sub-carrier channels of transmitting terminal comprises a FEC coding unit and a modulation format map unit, receiving terminal comprises optical-electrical converter, the second deserializer, Fourier transformation unit, N modulation format demodulating unit, N FEC demodulating unit and the second parallel-to-serial converter, each sub-carrier channels of receiving terminal comprises a modulation format demodulating unit and a FEC demodulating unit,
Serial data stream is through the first deserializer of transmitting terminal, through going here and there and changing, become parallel data stream, parallel data stream is assigned on N parallel subcarrier in electric ofdm signal, determine error correction coding type and the modulation format map type of each way carrier wave, data in electricity ofdm signal on every way carrier wave enter the FEC coding unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding, then enter the modulation format map unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format mapping, by error correction coding type and modulation format map type all identical subcarrier to compile be one group, enter transmitted power balanced unit, transmitted power balanced unit carries out transmitted power equilibrium treatment to the subcarrier in same group, make to adopt the subcarrier of identical error correction coding and the mapping of identical modulation format to be kept in balance at the SNR of receiving terminal, each subcarrier through transmitted power equilibrium treatment enters inverse Fourier transform unit, through inverse Fourier transform, electricity ofdm signal is converted to time domain from frequency domain, enter again the first parallel-to-serial converter, through parallel-serial conversion, become electric OFDM symbol stream, electricity OFDM symbol flows to into electrical to optical converter, through electric light conversion, change light ofdm signal into, light ofdm signal transmits by optical fiber link,
Light ofdm signal is transferred to the optical-electrical converter of receiving terminal by optical fiber link, through opto-electronic conversion, change electric OFDM symbol stream into, electricity OFDM symbol flows to into the second deserializer, through going here and there and changing, become the parallel subcarrier in N road, the parallel subcarrier in N road enters Fourier transformation unit, through Fourier transform, the parallel subcarrier in N road becomes frequency-region signal from time-domain signal, each way carrier wave enters respectively the modulation format demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format demodulation, then enter the FEC demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding demodulation, recover N channel parallel data, N channel parallel data enters the second parallel-to-serial converter, through parallel-serial conversion, become serial data stream.
On the basis of technique scheme, the error correction coding type of described each way carrier wave and modulation format map type by corresponding sub-carrier channels in the SNR size of receiving terminal, non-linear, the Dispersion Limitation of the transmission rate of subcarrier, distance, actual light channel decide, to guarantee that all subcarriers all obtain maximum spectrum efficiency.
On the basis of technique scheme, described in be distributed in subcarrier on each frequency and use same error correction coding and modulation format mapping, or use different error correction codings and modulation format mapping.
On the basis of technique scheme, the error correction coding mode that described FEC coding unit adopts comprises that decoding threshold is respectively 0.0038,0.02 error correction coding, low density parity check code LDPC.
On the basis of technique scheme, the modulation format mapping mode that described modulation format map unit adopts comprises 4-QAM, 16-QAM, 8-QAM, 8-PSK, 32-QAM.
The present invention also provides the channel equalization method of the light OFDM sub-carriers independence error correction coding modulation based on said system, comprises the following steps:
A, serial data stream is through the first deserializer of transmitting terminal, through going here and there and changing, become parallel data stream, parallel data stream is assigned on N parallel subcarrier in electric ofdm signal, determine error correction coding type and the modulation format map type of each way carrier wave, data in electricity ofdm signal on every way carrier wave enter the FEC coding unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding, then enter the modulation format map unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format mapping, by error correction coding type and modulation format map type all identical subcarrier to compile be one group, enter transmitted power balanced unit, transmitted power balanced unit carries out transmitted power equilibrium treatment to the subcarrier in same group, make to adopt the subcarrier of identical error correction coding and the mapping of identical modulation format to be kept in balance at the SNR of receiving terminal, each subcarrier through transmitted power equilibrium treatment enters inverse Fourier transform unit, through inverse Fourier transform, electricity ofdm signal is converted to time domain from frequency domain, enter again the first parallel-to-serial converter, through parallel-serial conversion, become electric OFDM symbol stream, electricity OFDM symbol flows to into electrical to optical converter, through electric light conversion, change light ofdm signal into, light ofdm signal transmits by optical fiber link,
B, light ofdm signal is transferred to the optical-electrical converter of receiving terminal by optical fiber link, through opto-electronic conversion, change electric OFDM symbol stream into, electricity OFDM symbol flows to into the second deserializer, through going here and there and changing, become the parallel subcarrier in N road, the parallel subcarrier in N road enters Fourier transformation unit, through Fourier transform, the parallel subcarrier in N road becomes frequency-region signal from time-domain signal, each way carrier wave enters respectively the modulation format demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format demodulation, then enter the FEC demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding demodulation, recover N channel parallel data, N channel parallel data enters the second parallel-to-serial converter, through parallel-serial conversion, become serial data stream.
On the basis of technique scheme, the error correction coding type of each way carrier wave described in steps A and modulation format map type by corresponding sub-carrier channels in the SNR size of receiving terminal, non-linear, the Dispersion Limitation of the transmission rate of subcarrier, distance, actual light channel decide, to guarantee that all subcarriers all obtain maximum spectrum efficiency.
On the basis of technique scheme, the subcarrier being distributed in described in steps A on each frequency is used same error correction coding and modulation format mapping, or uses different error correction codings and modulation format mapping.
On the basis of technique scheme, the error correction coding mode that described FEC coding unit adopts comprises that decoding threshold is respectively 0.0038,0.02 error correction coding, low density parity check code LDPC.
On the basis of technique scheme, the modulation format mapping mode that described modulation format map unit adopts comprises 4-QAM, 16-QAM, 8-QAM, 8-PSK, 32-QAM.
Compared with prior art, advantage of the present invention is as follows:
The single error correction coding balanced with traditional employing channel power compared with the optical OFDM system of modulation format mapping, in smooth ofdm signal of the present invention, each way carrier wave independently carries out error correction coding and modulation format mapping, each subcarrier in system can be used same error correction coding and modulation format mapping, also can use different error correction codings and modulation format mapping.System is according to the SNR condition of each way carrier wave in channel, in conjunction with the state of application scenario, transmission link, client's the factors such as performance requirement, can flexibly, freely select each subcarrier error correction coding and the combination of modulation format mapping, the optimization that realization utilizes the spectrum efficiency of every way carrier wave, each way carrier wave can independently receive, the application demand of point-to-point not only can be met, point-to-multipoint application demand can also be met.
Accompanying drawing explanation
Fig. 1 is the structured flowchart of traditional optical OFDM system.
Fig. 2 is the structured flowchart of the channel equalization system of light OFDM sub-carriers independence error correction coding modulation in the embodiment of the present invention.
Fig. 3 is the spectrogram of transmitting terminal training sequence in the embodiment of the present invention.
Fig. 4 is the SNR schematic diagram of receiving terminal training sequence subcarrier in the embodiment of the present invention.
Fig. 5 is the power spectrum schematic diagram of the final transmission signal after transmitting terminal power equalization in the embodiment of the present invention.
Fig. 6 is the SNR figure of the final reception channel distortion experienced of receiving terminal in the embodiment of the present invention.
Embodiment
Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.
Shown in Figure 2, the embodiment of the present invention provides a kind of channel equalization system of smooth OFDM sub-carriers independence error correction coding modulation, comprise transmitting terminal and receiving terminal, transmitting terminal comprises the first deserializer, N FEC(Forward Error Correction, forward error correction) coding unit, N modulation format map unit, transmitted power balanced unit, inverse Fourier transform unit, the first parallel-to-serial converter and electrical to optical converter, N is more than or equal to 2 integer, each sub-carrier channels of transmitting terminal comprises a FEC coding unit and a modulation format map unit, receiving terminal comprises optical-electrical converter, the second deserializer, Fourier transformation unit, N modulation format demodulating unit, N FEC demodulating unit and the second parallel-to-serial converter, each sub-carrier channels of receiving terminal comprises a modulation format demodulating unit and a FEC demodulating unit.
The embodiment of the present invention also provides a kind of channel equalization method of the light OFDM sub-carriers independence error correction coding modulation based on said system, comprises the following steps:
A, serial data stream is through the first deserializer of transmitting terminal, through going here and there and changing, become parallel data stream, parallel data stream is assigned on N parallel subcarrier in electric ofdm signal, determine error correction coding type and the modulation format map type of each way carrier wave, data in electricity ofdm signal on every way carrier wave enter the FEC coding unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding, then enter the modulation format map unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format mapping, the subcarrier being distributed on each frequency can be used same error correction coding and modulation format mapping, also can use different error correction codings and modulation format mapping, the error correction coding type of each way carrier wave and modulation format map type are big or small at the SNR of receiving terminal by corresponding sub-carrier channels, the transmission rate of subcarrier, distance, actual light channel non-linear, the factors such as Dispersion Limitation decide, to guarantee that all subcarriers all obtain maximum spectrum efficiency, by error correction coding type and modulation format map type all identical subcarrier to compile be one group, enter transmitted power balanced unit, transmitted power balanced unit carries out traditional transmitted power equilibrium treatment to the subcarrier in same group, make to adopt the subcarrier of identical error correction coding and the mapping of identical modulation format to be kept in balance at the SNR of receiving terminal, each subcarrier through transmitted power equilibrium treatment enters inverse Fourier transform unit, through inverse Fourier transform, electricity ofdm signal is converted to time domain from frequency domain, enter again the first parallel-to-serial converter, through parallel-serial conversion, become electric OFDM symbol stream, electricity OFDM symbol flows to into electrical to optical converter, through electric light conversion, change light ofdm signal into, light ofdm signal transmits by optical fiber link,
B, light ofdm signal is transferred to the optical-electrical converter of receiving terminal by optical fiber link, through opto-electronic conversion, change electric OFDM symbol stream into, electricity OFDM symbol flows to into the second deserializer, through going here and there and changing, become the parallel subcarrier in N road, the parallel subcarrier in N road enters Fourier transformation unit, through Fourier transform, the parallel subcarrier in N road becomes frequency-region signal from time-domain signal, each way carrier wave enters respectively the modulation format demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format demodulation, then enter the FEC demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding demodulation, recover N channel parallel data, N channel parallel data enters the second parallel-to-serial converter, through parallel-serial conversion, become serial data stream.
The error correction coding mode that FEC coding unit adopts comprises that decoding threshold is respectively 0.0038,0.02 error correction coding, LDPC(Low Density Parity Check Code, low density parity check code) etc., the modulation format mapping mode that modulation format map unit adopts comprises 4-QAM, 16-QAM, 8-QAM, 8-PSK, 32-QAM etc.
The decoding threshold of take is below respectively two kinds of error correction codings of 0.0038,0.02 and these two kinds of planisphere modulation formats of 4-QAM, 16-QAM and is elaborated as example.
The electric ofdm signal of system transmitting terminal has 30 available subcarriers, and every way carrier frequency is spaced apart 100 megahertzes, and the order from low frequency to high frequency compiles subcarrier for No. 1-30.
First, at transmitting terminal, send three groups of given datas of using separately these two kinds of planisphere modulation formats of 4-QAM, 16-QAM, thereby obtain in the receiving terminal error rate minimum lower than the needed SNR of two kinds of error correction coding thresholdings (0.0038 and 0.02), ginseng is shown in Table 1, and the data in table 1 are only reference for example.
Table 1,4-QAM and 16-QAM modulation format error code thresholding and the lowest signal-to-noise value table of comparisons
| Error Correct Threshold/modulation format | 4-QAM | 16-QAM |
| 0.0038 | 8.8dB | 15.5dB |
| 0.02 | 5.0dB | 11.7dB |
Decoding threshold is that 0.0038 error correction coding efficiency of transmission is 93.45%, and the error correction coding efficiency of transmission that decoding threshold is 0.02 is that the speed of 83.33%, 16-QAM modulation is 2 times of 4-QAM modulation.Obtain after above data, according to actual transmissions efficiency, sort, obtain following result: use the 16-QAM modulation transmissions of the error correction coding that decoding threshold is 0.0038 most effective, secondly for using the 16-QAM modulation of the error correction coding that decoding threshold is 0.02, for using the 4-QAM modulation of the error correction coding that decoding threshold is 0.0038, what efficiency of transmission was minimum is the 4-QAM modulation of using the error correction coding that decoding threshold is 0.02 again.
Then, system sends one section of training sequence on each way carrier wave with same modulation format at transmitting terminal, the training sequence signal spectrum of transmitting terminal is shown in Figure 3, as can be seen from Figure 3: the electrical power of making a start of 1-30 work song carrier wave is 30dbm, power on the every way carrier wave of transmitting terminal is all consistent, and makes the gross electric capacity of transmitted signal maximum simultaneously in the situation that of conditions permit.
After actual light transmission, receiving terminal training sequence signal to noise ratio is shown in Figure 4, as can be seen from Figure 4: the signal to noise ratio of each way carrier wave of receiving terminal is along with the increase of frequency presents the trend of a linear attenuation, the reason that causes this decay be sending and receiving end electric limit bandwidth and the decay of optical channel, so Fig. 4 actual be exactly the frequency response characteristic of whole smooth OFDM channel.The receiving terminal signal to noise ratio >15.5dB of 1-14 work song carrier wave, therefore can be used the combination of the error correction coding that 16-QAM modulation and decoding threshold are 0.0038; The receiving terminal signal to noise ratio >11.7dB of 15-20 work song carrier wave, therefore can be used the combination of the error correction coding that 16-QAM modulation and decoding threshold are 0.02; The receiving terminal signal to noise ratio >8.8dB of 21-25 work song carrier wave, therefore can be used the combination of the error correction coding that 4-QAM modulation and decoding threshold are 0.0038; The receiving terminal signal to noise ratio >5.0dB of 26-30 work song carrier wave, therefore can be used the combination of the error correction coding that 4-QAM modulation and decoding threshold are 0.02.
After this, utilize the receiving terminal frequency response characteristic having obtained, to using the subcarrier of same modulating-coding form to carry out transmitted power equilibrium in the formal light OFDM data that send of transmitting terminal.The object of this step is: allow and use the subcarrier of same modulating-coding form all to have identical performance at receiving terminal, simultaneously each subcarrier the signal to noise ratio of receiving terminal than table 1 in listed lowest signal-to-noise exceed certain surplus, thereby make system more reliable and more stable.Transmitting terminal power spectrum signal in the embodiment of the present invention after transmitted power equilibrium is shown in Figure 5, as can be seen from Figure 5: 1-14 work song carrier wave adopts the combination of the error correction coding that 16-QAM modulation and decoding threshold are 0.0038, the power of each subcarrier is arranged according to the backward of the channel frequency response being obtained by Fig. 4 before, each following way carrier wave all by that analogy: 15-20 work song carrier wave adopts the combination of the error correction coding that 16-QAM modulation and decoding threshold are 0.02; 21-25 work song carrier wave adopts the combination of the error correction coding that 4-QAM modulation and decoding threshold are 0.0038; 26-30 work song carrier wave adopts the combination of the error correction coding that 4-QAM modulation and decoding threshold are 0.02.The power of each group subcarrier distributes and all according to the backward of the channel frequency response being obtained by Fig. 4 before, arranges.
The signal to noise ratio that final receiving terminal recovers each subcarrier of ofdm signal is shown in Figure 6,4 groups of subcarriers with modulation format and error correction coding different grouping, 4 smooth ladders have been formed: receiving terminal 1-14 work song carrier wave adopts the combination of the error correction coding that 16-QAM modulation and decoding threshold are 0.0038, the signal to noise ratio of all subcarriers is all in 21dB left and right, higher than the lowest signal-to-noise 15.5dB without error code demodulation listing in table 1; 15-20 work song carrier wave adopts the combination of the error correction coding that 16-QAM modulation and decoding threshold are 0.02, and the signal to noise ratio of all subcarriers is all in 13.5dB left and right, higher than the listed lowest signal-to-noise 11.7dB without error code demodulation of table 1; 21-25 work song carrier wave adopts the combination of the error correction coding that 4-QAM modulation and decoding threshold are 0.0038, and the signal to noise ratio of all subcarriers is all in 9.8dB left and right, higher than the listed lowest signal-to-noise 8.8dB without error code demodulation of table 1; 26-30 work song carrier wave adopts the combination of the error correction coding that 4-QAM modulation and decoding threshold are 0.02, and the signal to noise ratio of all subcarriers is all in 6.4dB left and right, higher than the listed lowest signal-to-noise 5.0dB without error code demodulation of table 1; All subcarriers all can be without error code demodulation.
Kind and the quantity of the error correction coding that each independent sub-carriers of transmitting terminal adopts and modulation format mapping, be not limited in the listed example of enumerating in the embodiment of the present invention, also comprise other all kinds of error correction codings, LDPC(Low Density Parity Check Code for example, low density parity check code), also comprise other modulation format mapping, such as 8-QAM, 8-PSK, 32-QAM etc., its kind and quantity are all determined the requirement of transmission performance and software and hardware complexity by application scenario, the receiving terminal of system.
Judge that each subcarrier is used the standard of any error correction coding and modulation format mapping combination to be not limited in the signal to noise ratio factor of cited each subcarrier of receiving terminal of the embodiment of the present invention, also can be any factor that meets system needs, such as non-linear, Dispersion Limitation of the transmission rate of different sub carrier, distance, actual light channel etc.For example: lower to rate requirement, and the occasion that transmission range is had relatively high expectations can be used low-order-modulated format mapping in conjunction with the error correction coding combination of higher Error Correct Threshold, to improve transmission range; And higher for rate requirement, transmission range is required to lower occasion, can use high order modulation format mapping in conjunction with the error correction coding combination of lower Error Correct Threshold.In a word, as long as used each subcarrier independently to carry out that modulation format shines upon and the method for error correction coding, all belong to the protection range of this patent in optical OFDM system.
Those skilled in the art can carry out various modifications and variations to the embodiment of the present invention, if these revise and modification within the scope of the claims in the present invention and equivalent technologies thereof, these modifications and modification are also within protection scope of the present invention.
The prior art that the content of not describing in detail in specification is known to the skilled person.
Claims (10)
1. the channel equalization system of light OFDM sub-carriers independence error correction coding modulation, comprise transmitting terminal and receiving terminal, it is characterized in that: described transmitting terminal comprises the first deserializer, N forward error correction FEC coding unit, N modulation format map unit, transmitted power balanced unit, inverse Fourier transform unit, the first parallel-to-serial converter and electrical to optical converter, N is more than or equal to 2 integer, each sub-carrier channels of transmitting terminal comprises a FEC coding unit and a modulation format map unit, receiving terminal comprises optical-electrical converter, the second deserializer, Fourier transformation unit, N modulation format demodulating unit, N FEC demodulating unit and the second parallel-to-serial converter, each sub-carrier channels of receiving terminal comprises a modulation format demodulating unit and a FEC demodulating unit,
Serial data stream is through the first deserializer of transmitting terminal, through going here and there and changing, become parallel data stream, parallel data stream is assigned on N parallel subcarrier in electric ofdm signal, determine error correction coding type and the modulation format map type of each way carrier wave, data in electricity ofdm signal on every way carrier wave enter the FEC coding unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding, then enter the modulation format map unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format mapping, by error correction coding type and modulation format map type all identical subcarrier to compile be one group, enter transmitted power balanced unit, transmitted power balanced unit carries out transmitted power equilibrium treatment to the subcarrier in same group, make to adopt the subcarrier of identical error correction coding and the mapping of identical modulation format to be kept in balance at the SNR of receiving terminal, each subcarrier through transmitted power equilibrium treatment enters inverse Fourier transform unit, through inverse Fourier transform, electricity ofdm signal is converted to time domain from frequency domain, enter again the first parallel-to-serial converter, through parallel-serial conversion, become electric OFDM symbol stream, electricity OFDM symbol flows to into electrical to optical converter, through electric light conversion, change light ofdm signal into, light ofdm signal transmits by optical fiber link,
Light ofdm signal is transferred to the optical-electrical converter of receiving terminal by optical fiber link, through opto-electronic conversion, change electric OFDM symbol stream into, electricity OFDM symbol flows to into the second deserializer, through going here and there and changing, become the parallel subcarrier in N road, the parallel subcarrier in N road enters Fourier transformation unit, through Fourier transform, the parallel subcarrier in N road becomes frequency-region signal from time-domain signal, each way carrier wave enters respectively the modulation format demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format demodulation, then enter the FEC demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding demodulation, recover N channel parallel data, N channel parallel data enters the second parallel-to-serial converter, through parallel-serial conversion, become serial data stream.
2. the channel equalization system that smooth OFDM sub-carriers independence error correction coding as claimed in claim 1 is modulated, it is characterized in that: the error correction coding type of described each way carrier wave and modulation format map type by corresponding sub-carrier channels in the SNR size of receiving terminal, non-linear, the Dispersion Limitation of the transmission rate of subcarrier, distance, actual light channel decide, to guarantee that all subcarriers all obtain maximum spectrum efficiency.
3. the channel equalization system that smooth OFDM sub-carriers independence error correction coding as claimed in claim 1 is modulated, it is characterized in that: described in be distributed in subcarrier on each frequency and use same error correction coding and modulation format mapping, or use different error correction codings and modulation format mapping.
4. the channel equalization system that light OFDM sub-carriers independence error correction coding is modulated as claimed any one in claims 1 to 3, is characterized in that: the error correction coding mode that described FEC coding unit adopts comprises that decoding threshold is respectively 0.0038,0.02 error correction coding, low density parity check code LDPC.
5. the channel equalization system that light OFDM sub-carriers independence error correction coding is modulated as claimed any one in claims 1 to 3, is characterized in that: the modulation format mapping mode that described modulation format map unit adopts comprises 4-QAM, 16-QAM, 8-QAM, 8-PSK, 32-QAM.
6. the channel equalization method of the modulation of the light OFDM sub-carriers independence error correction coding based on system described in any one in claim 1 to 5, is characterized in that, comprises the following steps:
A, serial data stream is through the first deserializer of transmitting terminal, through going here and there and changing, become parallel data stream, parallel data stream is assigned on N parallel subcarrier in electric ofdm signal, determine error correction coding type and the modulation format map type of each way carrier wave, data in electricity ofdm signal on every way carrier wave enter the FEC coding unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding, then enter the modulation format map unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format mapping, by error correction coding type and modulation format map type all identical subcarrier to compile be one group, enter transmitted power balanced unit, transmitted power balanced unit carries out transmitted power equilibrium treatment to the subcarrier in same group, make to adopt the subcarrier of identical error correction coding and the mapping of identical modulation format to be kept in balance at the SNR of receiving terminal, each subcarrier through transmitted power equilibrium treatment enters inverse Fourier transform unit, through inverse Fourier transform, electricity ofdm signal is converted to time domain from frequency domain, enter again the first parallel-to-serial converter, through parallel-serial conversion, become electric OFDM symbol stream, electricity OFDM symbol flows to into electrical to optical converter, through electric light conversion, change light ofdm signal into, light ofdm signal transmits by optical fiber link,
B, light ofdm signal is transferred to the optical-electrical converter of receiving terminal by optical fiber link, through opto-electronic conversion, change electric OFDM symbol stream into, electricity OFDM symbol flows to into the second deserializer, through going here and there and changing, become the parallel subcarrier in N road, the parallel subcarrier in N road enters Fourier transformation unit, through Fourier transform, the parallel subcarrier in N road becomes frequency-region signal from time-domain signal, each way carrier wave enters respectively the modulation format demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out modulation format demodulation, then enter the FEC demodulating unit of corresponding sub-carrier channels, the subcarrier being distributed on each frequency independently carries out error correction coding demodulation, recover N channel parallel data, N channel parallel data enters the second parallel-to-serial converter, through parallel-serial conversion, become serial data stream.
7. the channel equalization method that smooth OFDM sub-carriers independence error correction coding as claimed in claim 6 is modulated, it is characterized in that: the error correction coding type of each way carrier wave described in steps A and modulation format map type by corresponding sub-carrier channels in the SNR size of receiving terminal, non-linear, the Dispersion Limitation of the transmission rate of subcarrier, distance, actual light channel decide, to guarantee that all subcarriers all obtain maximum spectrum efficiency.
8. the channel equalization method that smooth OFDM sub-carriers independence error correction coding as claimed in claim 6 is modulated, it is characterized in that: the subcarrier being distributed in described in steps A on each frequency is used same error correction coding and modulation format mapping, or use different error correction codings and modulation format mapping.
9. the channel equalization method of the modulation of the light OFDM sub-carriers independence error correction coding as described in any one in claim 6 to 8, is characterized in that: the error correction coding mode that described FEC coding unit adopts comprises that decoding threshold is respectively 0.0038,0.02 error correction coding, low density parity check code LDPC.
10. the channel equalization method of the modulation of the light OFDM sub-carriers independence error correction coding as described in any one in claim 6 to 8, is characterized in that: the modulation format mapping mode that described modulation format map unit adopts comprises 4-QAM, 16-QAM, 8-QAM, 8-PSK, 32-QAM.
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