CN106230767B - A kind of adaptive modulation coding method based on double Block Error Rates and signal-to-noise ratio difference - Google Patents
A kind of adaptive modulation coding method based on double Block Error Rates and signal-to-noise ratio difference Download PDFInfo
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Abstract
The invention belongs to fields of communication technology, are related to a kind of adaptive modulation coding method based on double Block Error Rates and signal-to-noise ratio difference.The present invention total PER current using system, foundation of the section PER and SNR difference as judgement, under conditions of system meets reliable transmission, the upper of section PER is adaptively adjusted according to channel condition, Lower Threshold, the more reasonably situation of change of adaptive channel during communication data transfer, change the MCS of system in real time, the total Block Error Rate of system is set to meet index request, thus have and realizes simply, it is strong to channel adaptability, system transmission performance is good, can while ensuring information transmission reliability further lifting system spectrum efficiency, the features such as being conducive to the practical application of engineering.
Description
Technical field
The invention belongs to fields of communication technology, are related to a kind of based on the Adaptive Modulation of double Block Error Rates and signal-to-noise ratio difference volume
Code method.
Background technique
As the key technology of future communications, OFDM (Orthogonal Frequency Division
Multiplexing, orthogonal frequency division multiplexing) technology becomes the hot spot in Communication Studies field, by OFDM technology and Adaptive Modulation
Coding techniques combine be this research field an important topic.In wireless communications, the characteristic of channel is to become at any time
Change, how to effectively utilize limited band resource at this time is an important research direction.Adaptive Modulation and Coding is one
Kind improves the technology of the availability of frequency spectrum, it can adaptively change the modulating-coding ginseng of system according to the variation of the characteristic of channel
Number, to achieve the purpose that improve system spectral efficiency and maximize average throughput.
Traditional Adaptive Modulation and Coding algorithm (M.Moustafa.Threshold decision based on fixed threshold
adaptive modulation and coding schemes for OFDM communications[C].Proceedings
of the Sixth international conference on Wireless and Optical Communications
Networks, 2009,133-136), with channel quality --- signal-to-noise ratio (Signal to Noise Ratio, SNR), which is used as, to be sentenced
Disconnected foundation, required for the general switching by setting MCS (Modulation and Coding Scheme, modulation coding scheme)
SNR threshold value, compared with the obtained SNR of estimation, and then provide MCS index value.Fig. 1 be it is traditional based on fixed threshold from
The ofdm system structural block diagram for adapting to modulating-coding, in the system, transmitter: the information bit channel of user is encoded
Code bit, bit of the coded-bit after channel interleaving is interweaved, the bit after intertexture, which obtains modulation by QAM modulation, to be believed
Number vector, the signal after modulation treatment are emitted after the processing such as OFDM symbol generation, D/A transformation, up-conversion；After transmitting
Signal reaches receiver by wireless channel；Receiver: the signal that receiver will receive is converted by down-converted, A/D
Base band (reception) signal is obtained, base band (reception) signal handles to obtain data-signal by solving OFDM symbol, and data-signal is through QAM
Demodulation, channel deinterleave, are reduced to the bit signal after transmitting after channel decoding, and the bit signal is using BLER statistic
Handle the Block Error Rate situation of available system；It can by signal-to-noise ratio (SNR) estimation by the data-signal that solution OFDM symbol is handled
SNR thresholding needed for switching MCS with signal SNR, the SNR thresholding output estimated, SNR thresholding and the SNR estimated are passed through
The MCS that next subsystem work is obtained after MCS selection processing, send respectively to channel coding, QAM modulation and QAM demodulation, channel and translates
Code completes the Adaptive Modulation and Coding processing of system.
The above-mentioned OFDM Adaptive Modulation and Coding mode based on fixed threshold adaptively changes according to the variation of channel quality
The MCS of change system, if channel conditions are preferable, just selects high-order MCS under the constraint condition for meeting error rate of system index, if
Channel conditions are poor, then selecting low order MCS, MCS is that the SNR thresholding of the SNR by estimating and setting determines, i.e. influence MCS
Main two factors of selection are as follows: first is that the setting of SNR thresholding, second is that SNR evaluated error.It the advantage is that when SNR estimates very
When accurate, system Block Error Rate and system spectral efficiency better performances, but the method have the shortcomings that it is obvious: first is that needing to carry out
SNR estimates, to increase system complexity；Second is that the error of SNR estimation influences the accuracy of MCS selection；Third is that SNR thresholding
Setting is difficult, because the characteristic of channel changes with the time in the wireless channel environment of variation, in different channel conditions
Under, SNR thresholding required by the identical Block Error Rate of system is not identical, it is difficult to ideal SNR thresholding be arranged；Thus such method is deposited
The selection difficulty of SNR threshold value is big, SNR evaluated error influences that big, adaptive modulation coding method is complicated, frequency on system performance
The defects such as spectrum efficiency is low.
Two-parameter self-adaptive modulation method (a kind of two-parameter self-adaptive modulation method of orthogonal FDM communication system,
Application number: 201410263702.9) using the two-parameter foundation as adjustment, based on the received total Block Error Rate (Packet Error
Rate, PER) and section Block Error Rate obtain MCS index value.Fig. 2 is the ofdm system structural block diagram of two-parameter Adaptive Modulation, this is
In system, transmitter: the information bit channel of user encodes to obtain coded-bit, and coded-bit is interweaved by channel interleaving
Bit afterwards, the bit after intertexture obtain modulated signal vector by QAM modulation, and the signal after modulation treatment is raw through OFDM symbol
At being emitted after the processing such as, D/A transformation, up-conversion；Signal after transmitting reaches receiver by wireless channel；Receiver:
The signal that receiver will receive converts to obtain base band (reception) signal, base band (reception) signal by down-converted, A/D
It handles to obtain data-signal by solving OFDM symbol, data-signal is demodulated through QAM, channel deinterleaves, is restored after channel decoding
For the bit signal after transmitting, which handles the total PER and section PER feelings of available system using BLER statistic
Condition；Total PER index provides total PER performance indicator of system, handles calculated total PER, section PER through BLER statistic and through total
The PER performance requirement that PER index provides is obtained next time after being selected processing based on two-parameter Adaptive Modulation and Coding mode
The MCS of system work send respectively to channel coding, QAM modulation and QAM demodulation, channel decoding, completes the Adaptive Modulation of system
Coded treatment.
It is above-mentioned based on two-parameter OFDM adaptive modulation coding method and the OFDM Adaptive Modulation based on fixed threshold
Coding method is compared, exist do not need estimation SNR and be arranged SNR thresholding, more adapt to different channel circumstances, realize it is more simple
The advantages that, but this method still remains following deficiency: it is more suitable for system performance variation slowly without channel coding communication system,
Have in the wireless communication system of channel coding, at certain MCS, error rate of system declines with the increase of SNR quickly, if only
MCS is adjusted dependent on total PER and section PER, ping-pong may be generated in certain 1 boundary's points of SNR, MCS index value is caused
Concussion is returned, the error bit ability of system is influenced.
Summary of the invention
It is to be solved by this invention, just it is to provide a kind of Adaptive Modulation and Coding based on double Block Error Rates and signal-to-noise ratio difference
Method, three total PER of this method based on system, section PER and SNR difference (Δ SNR) parameters complete the Adaptive Modulation of system
Coding, and using the Δ SNR thresholding of adaptive PER thresholding and robust, to overcome traditional fixed threshold method in different nothings
The problem of SNR thresholding setting difficulty under line channel circumstance, and can overcome based on two-parameter adaptive modulation coding method
MCS ping-pong effectively improve the performance of system to reach optimization Adaptive Modulation and Coding, ensuring communication system number
While according to transmission reliability the purpose of further lifting system spectrum efficiency.
Solution of the invention be under conditions of the basic procedure of OFDM transmitter and operation of receiver remains unchanged,
It is wanted in the Adaptive Modulation and Coding processing module based on double Block Error Rates and SNR difference of system with total Block Error Rate index of system
The foundation to constrain, using total PER of system, section PER and these three parameters of Δ SNR as adjustment MCS is sought, in communication process
Change the MCS of system to the middle variation real-time adaptive according to channel, to realize its goal of the invention.
Now the principle to of the present invention using the adaptive modulation coding method based on double Block Error Rates and SNR difference and according to
According to being described below:
Fig. 3 be the present invention is based on the ofdm system functional-block diagram of double Block Error Rates and the Adaptive Modulation and Coding of SNR difference,
Block Error Rate (PER) statistical module can be obtained the current total PER of system and section PER, SNR estimation module and real-time SNR can be obtained and estimate
Evaluation simultaneously calculates the difference DELTA SNR between last time estimated value, is transported to Adaptive Modulation and Coding resume module, the tune of output
Channel coding, QAM modulation, QAM demodulation channel decoding are handled to change current MCS in real time again for system, coding mode.
The modulation system that the present invention uses includes: BPSK, QPSK, 16QAM, 64QAM, corresponding order of modulation is followed successively by 2,
4,16,64；Channel coding is encoded using Turbo, including three kinds of code rates: 1/3,1/2 and 2/3,12 kinds of MCS combinations are shared in this way,
It sorts from low to high according to spectrum efficiency, generates 12 MCS index values；In simulations, according to actually measured error performance,
Only retain one kind in the very close index value of two performances, finally selects 8 MCS indexes；Each dispatching cycle updates
MCS index value corresponds to certain modulation system and coding mode, so as to adjust MCS；Under certain signal-to-noise ratio, MCS index value
Every reduction level-one, the rate of information throughput will reduce, system spectral efficiency can also reduce, but PER can reduce；When MCS index value
When increase, the rate of information throughput will be improved, system spectral efficiency also will increase, but PER will increase；Therefore essence of the invention
It is: as total PER and section PER larger, reduces PER by reducing MCS index, guarantee system transmission performance, but can reduce and be
System spectrum efficiency；As total PER and section PER smaller, and Δ SNR be greater than thresholding when increase MCS index then to improve system spectrum
Efficiency, and guarantee system transmission performance, while avoiding the ping-pong of MCS；Remaining situation does not adjust MCS index value then；Adjustment
Purpose is to make system in the case where meeting total PER indicator conditions, select the MCS index for being most suitable for current radio channel to reach system frequency
The maximization of spectrum efficiency.
In order to easily describe the contents of the present invention, some parameters are illustrated first:
1 parameter declaration of table
The technical scheme is that a kind of adaptive modulation coding method based on double Block Error Rates and signal-to-noise ratio difference,
Characterized by comprising the following steps:
S1, parameter setting: according to the reliability requirement of system, setting the upper and lower threshold value of total PER of system, on section PER,
Lower Threshold initial value, section PER thresholding adjusting step value, Δ SNR thresholding are Δ SNRth, initialize MCS index value；
S2, it receives system current PE R: receiving the system sent of system BLER statistic module currently total PER and section PER；
S2, signal-to-noise ratio difference: the current SNR value SNR sent according to signal-to-noise ratio (SNR) estimation module is calculatediWith the last time of preservation
SNR estimated value SNRi-1, calculate current signal difference DELTA SNR: Δ SNR=SNRi-SNRi-1, and update SNRi-1: SNRi-1=
SNRi；Subscript i is the natural number more than or equal to 1；
S4, adaptive adjustment MCS and section PER thresholding: according to system currently total PER, section PER and Δ SNR and preset
The upper and lower thresholding of total PER, the upper and lower thresholding of section PER, section PER thresholding adjusting step value and Δ SNR thresholding, self-adapted adjustment system
MCS obtains new MCS, while being adaptively adjusted the upper and lower thresholding of section PER, if current MCS index value adjusted is Mi；Tool
Body method are as follows:
S41, the relationship for judging total PER Yu the upper and lower thresholding of total PER go to S42 if total PER is less than total PER Lower Threshold,
If total PER goes to S43 between the upper and lower thresholding of total PER, if total PER is greater than total PER Upper threshold, S44 is gone to；
S42, total PER are less than the processing of total PER Lower Threshold: when section PER is less than section PER Lower Threshold, if Mi-1It is not highest
Rank, and last time MCS is not downward or last time MCS is to lower Δ SNR > Δ SNR simultaneouslyth, then MCS raises level-one；Work as section
When PER is between the upper and lower thresholding of section PER, the upper and lower threshold value of section PER is raised, if Mi-1It is not most high-order and under MCS is not
It adjusts, Δ SNR > Δ SNRthWhen, MCS raises level-one；When section PER is greater than section PER Upper threshold, the upper and lower threshold value of section PER is raised,
MCS is constant；Then go to S45；
The processing of S43, total PER between the upper and lower thresholding of total PER: when section PER is less than section PER Lower Threshold, section is lowered
The upper and lower threshold value of PER, if Mi-1It is not most high-order, and MCS is not downward, Δ SNR > Δ SNRthWhen, MCS raises level-one；Work as section
When PER is between the upper and lower thresholding of section PER, do not adjust；When section PER is greater than section PER Upper threshold, the upper and lower door of section PER is raised
Limit value, if Mi-1It is not lowest-order, MCS lowers level-one；Then go to S45；
S44, total PER are greater than the processing of total PER Upper threshold: when section PER is less than section PER Lower Threshold, on downward section PER,
Lower threshold, MCS are constant；When section PER is between the upper and lower thresholding of section PER, the upper and lower threshold value of section PER is lowered, if Mi-1No
It is lowest-order, MCS lowers level-one；When section PER is greater than section PER Upper threshold, if Mi-1It is not lowest-order, MCS lowers level-one；So
After go to S45；
S45, the change flag Flag for calculating MCS index valuemcsIf: Mi>Mi-1, then Flagmcs=1；If Mi=Mi-1,
Then Flagmcs=0；If Mi<Mi-1, then Flagmcs=-1；Update Mi-1: Mi-1=Mi；Wherein, Flagmcs=1: indicating on MCS
It adjusts, Flagmcs=0: indicating that MCS is remained unchanged, Flagmcs=-1: indicating that MCS is lowered；
S46: output adaptive adjusts result: current MCS index value Mi, MCS change flag Flagmcs, adjusted section
PER Lower Threshold PERsl, adjusted section of PER Upper threshold PERsu；
S5, more new system MCS: it send new MCS to the QAM modulation started to system and Turbo coding module, and send to receipts
The QAM demodulation Turbo decoding module at end is received and dispatched while updating modulation coding scheme；
S6, judge whether communication terminates: if communication process terminates, going to S7, otherwise go to S2；
S7, MCS adjustment terminate.
Further, the upper and lower thresholding of section PER step S42, is raised described in S43, S44 method particularly includes:
Raise section PER Lower Threshold PERsl: PERsl=min (PERsl(1+FPER),0.2PERtu)；
Raise section PER Upper threshold PERsu: PERsu=min (10PERsl,PERtu)；
Step S42, the upper and lower thresholding of section PER is lowered described in S43, S44 method particularly includes:
Lower section PER Lower Threshold PERsl: PERsl=max (PERsl(1-FPER),10-6)；
Lower section PER Upper threshold PERsu: PERsu=min (10PERsl,PERtu)。
Beneficial effects of the present invention are that the present invention is using the current total PER of system, section PER and SNR difference as judgement
Foundation the upper and lower thresholding of section PER is adaptively adjusted according to channel condition under conditions of system meets reliable transmission,
More reasonably the situation of change of adaptive channel, the real-time MCS for changing system make the total Block Error Rate of system during communication data transfer
Meet index request, thus has and realize that simple, strong to channel adaptability, system transmission performance is good, can be transmitted ensuring information
Further lifting system spectrum efficiency while reliability is conducive to the features such as practical application of engineering.
Detailed description of the invention
Fig. 1 is traditional Adaptive Modulation and Coding ofdm system schematic diagram based on fixed threshold；
Fig. 2 is based on two-parameter Adaptive Modulation and Coding ofdm system schematic diagram；
Fig. 3 is that the present invention is based on the Adaptive Modulation and Coding ofdm system schematic diagrams of double Block Error Rates and SNR difference；
Fig. 4 is that the present invention is based on the flow diagrams of double Block Error Rates and the adaptive modulation coding method of SNR difference；
Fig. 5 is the detailed annotation that MCS and section PER thresholding are adaptively adjusted in Fig. 4；
Fig. 6, Fig. 7 are the specific embodiment of the invention and traditional Adaptive Modulation and Coding based on fixed threshold respectively
Ofdm system simulation run at additive white Gaussian noise channel (Additive White Gaussian Noise, AWGN)
The performance comparison schematic diagram of system bit error rate and information source average information rate.
Fig. 8, Fig. 9 are the specific embodiment of the invention and traditional Adaptive Modulation and Coding based on fixed threshold respectively
Ofdm system maximum Doppler be extended to 70Hz extension vehicle channel model (Extended Vehicular Amodel,
EVA the system bit error rate of simulation run under) and the performance comparison schematic diagram of information source average information rate.
Specific embodiment
With reference to the accompanying drawings and examples, the technical schemes of the invention are described in detail:
Present embodiment launching technique (process), method of reseptance (process) are identical as background technique, using ofdm system, letter
Road coding uses Turbo coding mode, modulation system BPSK, QPSK, 16QAM, 64QAM, between coding and modulation module
15 times of spread spectrum is increased, modulation coding scheme uses the Adaptive Modulation and Coding based on double Block Error Rates and SNR difference, MCS rope
Draw that table is as shown in the table, wherein channel information rate is the transmission rate of modulation bit, information source information rate be consider spread spectrum,
The transmission rate of information source information bit after pilot tone and synchronization overhead.
2 MCS index of table
Below with reference to embodiment and attached drawing, the technical solution that the present invention will be described in detail.
S1, parameter setting: according to the reliability requirement of system, total PER Upper threshold PER of system is settuFor 0.1, total PER
Lower Threshold PERtlIt is 0.0001, section PER Lower Threshold PERslInitial value is 0.01, section PER Upper threshold PERsuInitial value is 0.1, section PER
Thresholding adjusting step FPERIt is 0.5, Δ SNRthIt is (resulting not according to emulation testing in order to reduce implementation complexity to be set as 2.5dB
With MCS, the mean value of corresponding Δ SNR thresholding is as Δ SNRth), initial MCS index M is setiIt is 1；
S2, it receives system current PE R: receiving the system sent of system BLER statistic module currently total PER (PERt) and
Section PER (PERs)；
S3, signal-to-noise ratio difference: the current SNR (SNR sent according to signal-to-noise ratio (SNR) estimation module is calculatedi) and save last time
SNR estimated value (SNRi-1), calculate current signal difference DELTA SNR: Δ SNR=SNRi-SNRi-1, and update SNRi-1: SNRi-1
=SNRi, seasonal Δ SNR=0 is estimated in first time；
S4, adaptive adjustment MCS and section PER thresholding: include:
S41, the relationship for judging total PER Yu the upper and lower thresholding of total PER, if total PER is less than total PER Lower Threshold (PERt<
PERtl), S42 is gone to, if total PER (PER between the upper and lower thresholding of total PERtl≤PERt≤PERtu), S43 is gone to, if
Total PER is greater than total PER Upper threshold (PERt>PERtu), go to S44；
S42, total PER are less than the processing of total PER Lower Threshold: (the PER when section PER is less than section PER Lower Thresholds<PERsl), if
Mi-1It is not most high-order, and if last time MCS is not to lower (i.e. Flagmcs> -1) or if last time MCS is to lower (i.e.
Flagmcs=-1) simultaneously Δ SNR > Δ SNRth, MCS up-regulation level-one (Mi=Mi-1+1)；When section PER is between the upper and lower thresholding of section PER
Between when (PERsl≤PERs≤PERsu), the upper and lower threshold value of section PER is raised, PER is enabledsl=min (PERsl(1+FPER),
0.2PERtu), PERsu=min (10PERsl,PERtu), if Mi-1It is not most high-order and Flagmcs> -1, Δ SNR > Δ SNRthWhen,
MCS raises level-one (Mi=Mi-1+1)；(the PER when section PER is greater than section PER Upper thresholds>PERsu), raise the upper and lower thresholding of section PER
Value, enables PERsl=min (PERsl(1+FPER),0.2PERtu), PERsu=min (10PERsl,PERtu), the constant (M of MCSi=
Mi-1)；Then go to S45；
The processing of S43, total PER between the upper and lower thresholding of total PER: (PER when section PER is less than section PER Lower Thresholds<
PERsl), the upper and lower threshold value of section PER is lowered, PER is enabledsl=max (PERsl(1-FPER),10-6), PERsu=min (10PERsl,
PERtu), if Mi-1It is not most high-order, and Flagmcs> -1, Δ SNR > Δ SNRthWhen, MCS raises level-one (Mi=Mi-1+1)；Work as section
(PER when PER is between the upper and lower thresholding of section PERsl≤PERs≤PERsu), do not adjust (Mi=Mi-1,PERslAnd PERsuNo
Become)；(the PER when section PER is greater than section PER Upper thresholds>PERsu), the upper and lower threshold value of section PER is raised, PER is enabledsl=min
(PERsl(1+FPER),0.2PERtu), PERsu=min (10PERsl,PERtu), if Mi-1It is not lowest-order, MCS lowers level-one (Mi
=Mi-1-1)；Then go to S45；
S44, total PER are greater than the processing of total PER Upper threshold: (the PER when section PER is less than section PER Lower Thresholds<PERsl), under
The upper and lower threshold value of section PER is adjusted, PER is enabledsl=max (PERsl(1-FPER),10-6), PERsu=min (10PERsl,PERtu), MCS
Constant (Mi=Mi-1)；(the PER when section PER is between the upper and lower thresholding of section PERsl≤PERs≤PERsu), lower section PER on,
Lower threshold enables PERsl=max (PERsl(1-FPER),10-6), PERsu=min (10PERsl,PERtu), if Mi-1It is not minimum
Rank, MCS lower level-one (Mi=Mi-1-1)；(the PER when section PER is greater than section PER Upper thresholds>PERsu), if Mi-1It is not minimum
Rank, MCS lower level-one (Mi=Mi-1-1)；Then go to S45；
S45, the change flag Flag for calculating MCS index valuemcsIf: Mi>Mi-1, then Flagmcs=1；If Mi=Mi-1,
Then Flagmcs=0；If Mi<Mi-1, then Flagmcs=-1；Then M is updatedi-1: Mi-1=Mi；
S46: output adaptive adjusts result: exporting and saves current MCS index value Mi, MCS change flag Flagmcs, section
PER Lower Threshold PERsl, section PER Upper threshold PERsu；
S5, more new system MCS: by new MCS value MiThe QAM modulation started to system and Turbo coding module are sent, and is sent
To the QAM demodulation Turbo decoding module of receiving end, receives and dispatches while updating MCS；
S6, judge whether communication terminates: if communication process terminates, going to S7, otherwise go to S2；
S7, MCS adjustment terminate.
Since tradition can reach optimality in perfect channel estimation based on the Adaptive Modulation and Coding mode of fixed threshold
Can, therefore emphasis of the present invention and the traditional approach carry out performance comparison.
Fig. 6 and Fig. 7 is the specific embodiment of the invention and traditional Adaptive Modulation and Coding based on fixed threshold respectively
Ofdm system the system bit error rate of simulation run and performance of information source average information rate in awgn channel compare；Wherein adopt
8 kinds of modulation coding schemes are shown in Table 2；Sample frequency is 30.72MHz, and FFT points are 2048, and subcarrier spacing is
15kHz, each OFDM symbol occupy 1200 subcarriers, circulating prefix-length 146, spreading gain 15, adaptive scheduling
Period is 210 OFDM symbol times (about 15ms), i.e., each statistical piece dispatching cycle PER, updates total PER, estimation SNR；If
Setting traditional target bit based on fixed threshold adaptive modulation coding method is≤10-3, in the method for the present invention is
Unite total PER Upper threshold PERtuFor 0.1, total PER Lower Threshold PERtlIt is 0.0001, section PER Lower Threshold PERslInitial value is 0.01, section
PER Upper threshold PERsuInitial value is 0.1, section PER thresholding adjusting step FPERIt is 0.5, Δ SNR threshold delta SNRthFor 2.5dB, initially
MCS index is that 1, SNR estimation includes the non-ideal estimation that error-free perfect estimation and evaluated error are less than 2dB, emulation points
It is 107；Emulation shows: under the conditions of awgn channel, -16dB≤SNR≤0dB, when signal-to-noise ratio does not have evaluated error, and the present invention
Meet system performance requirements with the BER of traditional approach, the average information rate of two kinds of algorithms is close；When signal-to-noise ratio (SNR) estimation error not
When greater than 2dB, the BER fluctuation under traditional approach is very big, and error rate of system is unsatisfactory for system requirements, the system under mode of the present invention
BER is more stable, has minor fluctuations in system index claimed range, insensitive to SNR evaluated error, and error bit ability is bright
Aobvious to be better than traditional approach, information average information rate is slightly below conventional method.
Fig. 8 and Fig. 9 is the specific embodiment of the invention and traditional Adaptive Modulation and Coding based on fixed threshold respectively
The system bit error rate and information source average information of ofdm system simulation run in the EVA channel that maximum Doppler frequency domain is 70Hz
The performance of rate compares；System parameter setting is the same as the setting in Fig. 6 and Fig. 7；Emulation shows: under EVA70Hz channel condition,
As -12dB≤SNR≤4dB, BER of the invention is more stable, insensitive to channel estimation errors, and BER fluctuates smaller, information source
Average information rate is higher, and the BER under traditional approach has larger fluctuation, and information source average information rate is slightly below mode of the present invention.
Therefore, of the invention based on double Block Error Rates compared with tradition is based on the Adaptive Modulation and Coding mode of fixed threshold
There is better robustness with the Adaptive Modulation and Coding of signal-to-noise ratio difference, not to different channels characteristic and signal-to-noise ratio (SNR) estimation error
Sensitivity has better adaptability to the variation of channel, under conditions of guaranteeing system reliable transmission, has preferable frequency spectrum benefit
With rate, there is very strong application value.
Claims (2)
1. a kind of adaptive modulation coding method based on double Block Error Rates and signal-to-noise ratio difference, which is characterized in that including following step
It is rapid:
S1, parameter setting: according to the reliability requirement of system, the upper and lower threshold value of total PER of system, the upper and lower door of section PER are set
Initial value, section PER thresholding adjusting step value are limited, Δ SNR thresholding is Δ SNRth, initialize MCS index value；
S2, it receives system current PE R: receiving the system sent of system BLER statistic module currently total PER and section PER；
S3, signal-to-noise ratio difference: the current SNR value SNR sent according to signal-to-noise ratio (SNR) estimation module is calculatediEstimated with last time SNR of preservation
Value SNRi-1, calculate current signal difference DELTA SNR: Δ SNR=SNRi-SNRi-1, and update SNRi-1: SNRi-1=SNRi；Subscript
I is the natural number more than or equal to 1；
S4, adaptive adjustment MCS and section PER thresholding: according to system currently total PER, section PER and Δ SNR and preset total
The upper and lower thresholding of PER, the upper and lower thresholding of section PER, section PER thresholding adjusting step value and Δ SNR thresholding, self-adapted adjustment system
MCS obtains new MCS, while being adaptively adjusted the upper and lower thresholding of section PER, if current MCS index value adjusted is Mi；Tool
Body method are as follows:
S41, the relationship for judging total PER Yu the upper and lower thresholding of total PER go to S42 if total PER is less than total PER Lower Threshold, if
Total PER goes to S43 between the upper and lower thresholding of total PER, if total PER is greater than total PER Upper threshold, goes to S44；
S42, total PER are less than the processing of total PER Lower Threshold: when section PER is less than section PER Lower Threshold, if Mi-1It is not most high-order,
And last time MCS is not downward or last time MCS is to lower Δ SNR > Δ SNR simultaneouslyth, then MCS raises level-one；As section PER
When between the upper and lower thresholding of section PER, the upper and lower threshold value of section PER is raised, if Mi-1It is not most high-order and MCS is not downward, Δ
SNR>ΔSNRthWhen, MCS raises level-one；When section PER is greater than section PER Upper threshold, the upper and lower threshold value of section PER is raised, MCS is not
Become；Then go to S45；
The processing of S43, total PER between the upper and lower thresholding of total PER: when section PER is less than section PER Lower Threshold, section PER is lowered
Upper and lower threshold value, if Mi-1It is not most high-order, and MCS is not downward, Δ SNR > Δ SNRthWhen, MCS raises level-one；As section PER
When between the upper and lower thresholding of section PER, do not adjust；When section PER is greater than section PER Upper threshold, the upper and lower thresholding of section PER is raised
Value, if Mi-1It is not lowest-order, MCS lowers level-one；Then go to S45；
S44, total PER are greater than the processing of total PER Upper threshold: when section PER is less than section PER Lower Threshold, lowering the upper and lower door of section PER
Limit value, MCS are constant；When section PER is between the upper and lower thresholding of section PER, the upper and lower threshold value of section PER is lowered, if Mi-1It is not most
Low order, MCS lower level-one；When section PER is greater than section PER Upper threshold, if Mi-1It is not lowest-order, MCS lowers level-one；Then turn
To S45；
S45, the change flag Flag for calculating MCS index valuemcsIf: Mi>Mi-1, then Flagmcs=1；If Mi=Mi-1, then
Flagmcs=0；If Mi<Mi-1, then Flagmcs=-1；Update Mi-1: Mi-1=Mi；Wherein, Flagmcs=1: indicate MCS up-regulation,
Flagmcs=0: indicating that MCS is remained unchanged, Flagmcs=-1: indicating that MCS is lowered；
S46: output adaptive adjusts result: current MCS index value Mi, MCS change flag Flagmcs, the adjusted section of Xiamen PER
Limit PERsl, adjusted section of PER Upper threshold PERsu；
S5, more new system MCS: it send new MCS to the QAM modulation started to system and Turbo coding module, and send to receiving end
QAM demodulation Turbo decoding module is received and dispatched while updating modulation coding scheme；
S6, judge whether communication terminates: if communication process terminates, going to S7, otherwise go to S2；
S7, MCS adjustment terminate.
2. a kind of adaptive modulation coding method based on double Block Error Rates and signal-to-noise ratio difference according to claim 1,
It is characterized in that, the upper and lower thresholding of section PER step S42, is raised described in S43, S44 method particularly includes:
Raise section PER Lower Threshold PERsl: PERsl=min (PERsl(1+FPER),0.2PERtu)；
Raise section PER Upper threshold PERsu: PERsu=min (10PERsl,PERtu)；
Wherein, FPERFor section PER thresholding adjusting step, PERtuFor total PER Upper threshold；
Step S42, the upper and lower thresholding of section PER is lowered described in S43, S44 method particularly includes:
Lower section PER Lower Threshold PERsl: PERsl=max (PERsl(1-FPER),10-6)；
Lower section PER Upper threshold PERsu: PERsu=min (10PERsl,PERtu)。
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