CN108540415A - Adaptive layered modulation under high-speed mobile environment and service integration transmission method - Google Patents
Adaptive layered modulation under high-speed mobile environment and service integration transmission method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
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Abstract
An embodiment of the present invention provides in a kind of high-speed mobile environment adaptive layered modulation and service integration transmission method.This method includes：The channel state information of estimation is sent to transmitting terminal by receiving terminal, and the conditional probability distribution function of the signal-to-noise ratio of current time slots is calculated by the channel state information for transmitting terminal；Robustness hierarchical modulation scheme, the signal-to-noise ratio based on current time slots is used to obtain the average error rate expression formula of each bit high-speed railway scene；Distribution is scheduled to multi-service based on robustness hierarchical modulation scheme, bit bit allocation is carried out according to the signal-to-noise ratio of reception and modulation parameter, obtains the tactful switching table of optimal modulation transmission；Adaptive Modulation transmission plan is executed, optimal modulation transmission strategy corresponding with current channel condition information is chosen in optimal modulation transmits Policy Table；Transmitting terminal transmits tactful transmission data according to optimal modulation.Adaptive, efficient transmission can be achieved in the present invention, can improve performance of mobile communication system.
Description
Technical field
The present invention relates to the adaptive layered tune under wireless communication technology field more particularly to a kind of high-speed mobile environment
System and service integration transmission method.
Background technology
Hierarchical modulation is the different service quality requirement according to multiple business, and channel status is quantified as different channels matter
The grade of amount, each channel quantitative grade correspond to some specific business service quality demand.The good channel of run-of-the-mill
The corresponding business service quality of quantification gradation is higher, and the corresponding business service quality of ropy channel quantitative grade is relatively low.From
The channel state information (CSI) that hierarchical modulation can be obtained according to channel estimation is adapted to, rational power distribution, sub- load are passed through
Wavelength-division with etc., can make the multinomial business of system bearing weight rate and be greatly improved.
A kind of Adaptive Modulation transmission method in the prior art is：Transmitter is according to receiver momentary channel quality shape
Condition and the most suitable downlink modulation of current resource selection and coding mode, make receiver reach data throughput high as possible
Rate.
The shortcomings that above-mentioned Adaptive Modulation transmission method in the prior art is：When wireless transmitter is in high-speed mobile
Under state (such as mobile Communication System for High Speed Railway), transmitter is difficult to obtain accurate CSI's.Reason is from two aspects：It is first
First, receiver is influenced by factors such as channel estimation errors, quantization error, feedback errors, it is difficult to be carried out accurate channel and be estimated
Meter；Secondly, the time varying characteristic of High-speed mobile Channel becomes apparent, and channel-estimation information is fed back to the anti-of transmitter by receiver
Postponing a meeting or conference when feedback causes CSI information expired, and can not obtain accurate CSI will cause transmitter that can not select suitable transmission power
With the parameters such as modulation system, then the spectrum efficiency of mobile communication system and the weight of business and rate will be by significant shadows
It rings.
Therefore, it is necessary to design a kind of adaptive layered modulation transmissions scheme suitable under high-speed mobile environment, protecting
Demonstrate,prove different business different bit error rates require under the premise of, improve multi-service transport spectrum efficiency or weight rate and.
Invention content
It is modulated the embodiment provides the adaptive layered in a kind of high-speed mobile environment and service integration transmits
Method, to solve the problems in above-mentioned background technology.
To achieve the goals above, this invention takes following technical solutions：
Adaptive layered modulation under a kind of high-speed mobile environment that the embodiment of the present invention provides and service integration transmission
Method, which is characterized in that including：
The channel state information of estimation is sent to transmitting terminal by receiving terminal, and the transmitting terminal is believed by the channel status
The conditional probability distribution function of the signal-to-noise ratio of current time slots is calculated in breath；
Robustness hierarchical modulation scheme is used to high-speed railway scene, based on the signal-to-noise ratio of the current time slots, is obtained every
The average error rate expression formula of a bit；
Distribution is scheduled to multi-service based on the robustness hierarchical modulation scheme, according to the signal-to-noise ratio and tune of reception
Parameter processed carries out bit bit allocation, obtains the tactful switching table of optimal modulation transmission；
Adaptive Modulation transmission plan is executed, selection and current channel condition in the optimal modulation transmits Policy Table
The corresponding optimal modulation transmission strategy of information；
The transmitting terminal transmits strategy according to the optimal modulation, and current data is sent.
Preferably, the channel state information of estimation is sent to transmitting terminal by the receiving terminal, and the transmitting terminal passes through institute
The conditional probability distribution function that the signal-to-noise ratio of current time slots is calculated in channel state information is stated, including：
Channel estimator is set in the receiving terminal, constantly channel is estimated using the channel estimator, and
The channel state information of estimation is sent to transmitting terminal by feedback link；
The channel state information and time slot related coefficient of the transmitting terminal based on reception are calculated, and are obtained and are worked as
The conditional probability distribution function of the signal-to-noise ratio of preceding time slot.
Preferably, it is described receiving terminal be arranged channel estimator, using the channel estimator constantly to channel into
Row estimation, and the channel state information of estimation is sent to by transmitting terminal by feedback link, including：
The channel estimator of the receiving terminal feeds back the channel gain estimated to transmitting terminal：Wherein,
Feedback delay is τ；
If the multipath channel between the transmitting terminal and the receiving terminal is flat, varying Channels, then each diameter channel
The real and imaginary parts of parameter obey that mean value is 0, variance isMutually independent multiple Gauss random process, i.e.,：Wherein, i=0,1 ..., N-1 indicate notation index；
Between be divided into the channel state information h [i] of τ withRelationship indicate it is as follows：
Wherein,For the perfect channel estimation of receiving terminal, ρ [τ] isIt is instantaneous related between h [i]
Coefficient, w [i] are channel gain variable caused by the Link Feedback period interior time-varying characteristics by fast fading channel, and w [i] is independent
InAndUsing Clarke model, ρ [τ] can be expressed as：J0(2
πfDτ), J0() is first kind zeroth order Bei Saer functions, fDFor maximum doppler frequency.
Preferably, the channel state information and time slot related coefficient of the transmitting terminal based on reception are counted
It calculates, obtains the conditional probability distribution function of the signal-to-noise ratio of current time slots, including：
The channel state information h [i] obeys independent identically distributed rayleigh distributed, and the i in formula (1) is removed, obtains two
A time slot related coefficient：ρ [τ] andAnd meet：
With ρ [τ] andFor condition, defined variable V, and satisfaction： V is obeyed certainly
By spending the non-central chi square distribution for 2, wherein decentralization parameter is：
Then the conditional probability distribution function of V is：
DefinitionFor average transmission power, the noise of receiving terminal be mean value be 0, variance isMultiple additive white gaussian make an uproar
Channel is normalized sound, obtains：E[|h|2]=1, the then average signal-to-noise ratio that the receiving terminal receives are：The signal-to-noise ratio of i-th of the symbol received is expressed as：
The channel estimator of the known receiving terminal sends the channel estimated to the transmitting terminal by feedback link and increases
BenefitIt selects, then has for the adaptive modulation scheme to signal： ByThe conditional probability that γ can be obtained is：
Wherein, I0For modified first kind zero Bessel function；
For Rayleigh channel,Probability density function be：
Preferably, described that robustness hierarchical modulation scheme is used to high-speed railway scene, based on the current time slots
Signal-to-noise ratio obtains the average error rate expression formula of each bit, including：
To the robustness hierarchical modulation scheme that high-speed railway scene is applicable in, using 4/16 layering of the gray mappings of broad sense
Modulation constellation, including：The roads I and the roads Q, the roads multilayer I and the roads multilayer Q be respectively formed 4 constellation points 4-QAM high priorities and
The second priority of 16-QAM of 16 constellation points, European variableWithFirst priority on the roads I and the roads Q, Europe are indicated respectively
Formula distanceWithThe layering level on second priority on the expression roads I and the roads Q respectively, the roads I and the roads Q is expressed as：I1,I2...,
IYAnd Q1,Q2..., QZ, I1And IYThe respectively the highest-order bit on the roads I and lowest bit position, Q1And QZThe respectively highest ratio on the roads Q
Special position and lowest bit position, Y and Z indicate the maximum value on the roads I and the roads the Q number of plies respectively；
The Euclidean distance vector d on the roads IIWith the Euclidean distance vector d on the roads QQIt is defined as：
IfThenIndicate that minimum euclidean distance, corresponding modulation parameter are defined as：
The energy of transmission symbol is expressed as：
Wherein,For a temporary variable；
For awgn channel, N0For the noise power spectral density of awgn channel, then received signal to noise ratio is expressed as：
The error rate BER of the y bits in the roads I is expressed as：
The error rate BER of the y bits in the roads Q is expressed as：
The error rate BER expression formula of the roads the I bit of 4-QAM is：
The error rate BER expression formula of the roads the Q bit of 4-QAM is：
Wherein,
The error rate BER expression formula of the roads the I bit of 8-QAM is：
The error rate BER expression formula of the roads the Q lowest bit position of 8-QAM is：
The error rate BER expression formula of the roads the Q the highest-order bit of 8-QAM is：
Wherein,
The error rate BER expression formula of the roads the I lowest bit position of 64QAM is：
The error rate BER expression formula of the second bit of the roads I of 64QAM is
The error rate BER expression formula of the roads the I the highest-order bit of 64QAM is：
The error rate BER expression formula of the roads the Q lowest bit position of 64QAM is：
The error rate BER expression formula of the second bit of the roads Q of 64QAM is：
The error rate BER expression formula of the roads the Q the highest-order bit of 64QAM is：
Under high-speed railway scene, it is based onLayering 4-QAM the roads I bit error rateIt is expressed as：
Erfc () using two exponential functions and carry out approximate obtain：
Wherein, a1=1/6, b1=-1, a2=1/2, b2=-3/4, m isScalar parameter.
Formula (25) is updated in formula (24),It is reconfigured to：
Wherein,
It is based onLayering 4-QAM the roads Q bit error rateIt is expressed as：
For hierarchical modulation 8-QAM, it is based onBit error rate expression formula it is as follows：
For hierarchical modulation 64-QAM, it is based onBit error rate expression formula it is as follows：
Similarly, the roads the Q error rate BER expression formula of 64-QAM only need to be by the α in the roads I BER expression formulas in 64-QAM1It replaces
For β1, α2Replace with β2, α3Replace with 1.
Preferably, described that distribution is scheduled to multi-service based on the robustness hierarchical modulation scheme, according to reception
Signal-to-noise ratio and modulation parameter carry out bit bit allocation, obtain the tactful switching table of optimal modulation transmission, including：
The three classes business required equipped with different bit error rates：Business-Ι, business-Π, business-Π Ι, the relationship of target BER
For：Give the lowest bit bit allocation on the roads Q in M-QAM planispheres to business-Ι,
Remaining log2M-1 bit distributes to other business according to the modulation parameter of selection；
Known snr threshold SNR is：Γk, SNR region divisions are K+1 decline region by k=1,2 ..., K,
In, K is modulating mode coefficient, and the modulation system of the same number of constellation point, constellation point quantity are distributed in the same decline region
Select rule for：WhenWhen, constellation point quantity is Mk=2k+1, for a given fading zone
Domain, in layered modulation constellation figure the distribution of bit depend on received signal to noise ratio SNR and modulation parameter；
K-th of decline region is divided into k+1 sub-regions, when the Signal to Noise Ratio (SNR) of feedback is located at s-th of subregion, s=
1,2 ..., k+1, according to the bit distribution condition of each decline subregion, using the expression formula of error rate BER to sub- region thresholdModulation parameterWithIt is solved；
The subregion threshold valueModulation parameterWithForm optimal modulation strategy switching table.
Preferably, the execution Adaptive Modulation transmission plan, the optimal modulation transmit Policy Table in choose with
The corresponding optimal modulation transmission strategy of current channel condition information, including：
After acquiring optimal decline subregion threshold value, optimal modulation transmissions Policy Table is determined；
The transmitting terminal obtains the channel state information of the receiving terminal feedback by feedback link, in the optimal tune
It is chosen in system transmission Policy Table and transmits strategy with the optimal modulation of current channel condition information matches, and carry out power control, really
Distribution power needed for fixed.
Preferably, the transmitting terminal transmits strategy according to the optimal modulation, and current data is sent, including：
The transmitting terminal is dynamically adjusted according to the feeding back channel state information received by the channel state information
The whole optimal modulation strategy switching table, makes data carry out adaptive transmission.
The embodiment of the present invention passes through in receiving terminal it can be seen from the technical solution that embodiments of the invention described above provide
The channel state information of estimation is sent to transmitting terminal, current time slots are calculated by the channel state information in transmitting terminal
Signal-to-noise ratio conditional probability distribution function；Robustness hierarchical modulation scheme is used to high-speed railway scene, is based on current time slots
Signal-to-noise ratio, obtain the average error rate expression formula of each bit；Multi-service is carried out based on robustness hierarchical modulation scheme
Dispatching distribution carries out bit bit allocation according to the signal-to-noise ratio of reception and modulation parameter, obtains optimal modulation transmission strategy switching
Table；Adaptive Modulation transmission plan is executed, is chosen in optimal modulation transmits Policy Table corresponding with current channel condition information
Optimal modulation transmission strategy；Transmitting terminal transmits tactful transmission data according to optimal modulation.The present invention can be achieved adaptive, efficient
Transmission, performance of mobile communication system can be improved.
The additional aspect of the present invention and advantage will be set forth in part in the description, these will from the following description
Become apparent, or practice through the invention is recognized.
Description of the drawings
In order to illustrate the technical solution of the embodiments of the present invention more clearly, making required in being described below to embodiment
Attached drawing is briefly described, it should be apparent that, drawings in the following description are only some embodiments of the invention, right
For those of ordinary skill in the art, without having to pay creative labor, it can also be obtained according to these attached drawings
Other attached drawings.
Fig. 1 is adaptive layered modulation and service integration in a kind of high-speed mobile environment provided in an embodiment of the present invention
The planisphere of the generalized hierarchical modulation of transmission method；
It is the business for carrying three kinds of difference BER and requiring under high-speed railway scene that Fig. 2, which is provided in an embodiment of the present invention,
When, the bit distribution diagram of the 64-QAM hierarchical modulations based on feeding back channel state information；
Fig. 3 is adaptive layered modulation and service integration in a kind of high-speed mobile environment provided in an embodiment of the present invention
The spectrum efficiency performance of transmission method with average signal-to-noise ratio change curve；
Fig. 4 is adaptive layered modulation and service integration in a kind of high-speed mobile environment provided in an embodiment of the present invention
The spectrum efficiency of transmission method with movement speed change curve；
Fig. 5 is adaptive layered modulation and service integration in a kind of high-speed mobile environment provided in an embodiment of the present invention
The process chart of transmission method；
Wherein,
Curve 1a indicates total number of bits when current signal condition,
The number of bits of business S1 is distributed to when curve 1b expression current signal conditions,
The number of bits of business S2 is distributed to when curve 1c expression current signal conditions,
Curve 1d indicates to distribute to the number of bits of business S3 when current signal condition；
It is 300km/h that curve 2a, which is movement speed, spectrum efficiency curve when modulation system is hierarchical modulation,
It is 300km/h that curve 2b, which is movement speed, spectrum efficiency curve when modulation system is homogeneous modulation,
It is 400km/h that curve 2c, which is movement speed, spectrum efficiency curve when modulation system is hierarchical modulation,
It is 400km/h that curve 2d, which is movement speed, spectrum efficiency curve when modulation system is hierarchical modulation,
It is 500km/h that curve 2e, which is movement speed, spectrum efficiency curve when modulation system is hierarchical modulation,
Curve 2f is that movement speed is 500km/h, spectrum efficiency curve when modulation system is hierarchical modulation；
Curve 3a be S1 business, modulation system be hierarchical modulation when spectrum efficiency curve,
Curve 3b be S2 business, modulation system be hierarchical modulation when spectrum efficiency curve,
Curve 3c be S3 business, modulation system be hierarchical modulation when spectrum efficiency curve,
Curve 3d be S1 business, modulation system be homogeneous modulation when spectrum efficiency curve,
Curve 3e be S2 business, modulation system be homogeneous modulation when spectrum efficiency curve,
Curve 3f is S3 business, spectrum efficiency curve when modulation system is homogeneous modulation.
Specific implementation mode
Embodiments of the present invention are described below in detail, the example of the embodiment is shown in the accompanying drawings, wherein from beginning
Same or similar element or element with the same or similar functions are indicated to same or similar label eventually.Below by
The embodiment being described with reference to the drawings is exemplary, and is only used for explaining the present invention, and cannot be construed to the limit to the present invention
System.
Those skilled in the art of the present technique are appreciated that unless expressly stated, singulative " one " used herein, " one
It is a ", " described " and "the" may also comprise plural form.It is to be further understood that is used in the specification of the present invention arranges
It refers to there are the feature, integer, step, operation, element and/or component, but it is not excluded that presence or addition to take leave " comprising "
Other one or more features, integer, step, operation, element, component and/or their group.It should be understood that when we claim member
Part is " connected " or when " coupled " to another element, it can be directly connected or coupled to other elements, or can also deposit
In intermediary element.In addition, " connection " used herein or " coupling " may include being wirelessly connected or coupling.It is used herein to arrange
Diction "and/or" includes any cell of one or more associated list items and all combines.
Those skilled in the art of the present technique are appreciated that unless otherwise defined, all terms used herein (including technology
Term and scientific terminology) there is meaning identical with the general understanding of the those of ordinary skill in fields of the present invention.Also answer
It should be appreciated that those terms such as defined in the general dictionary should be understood that with in the context of the prior art
The consistent meaning of meaning, and unless defined as here, will not be explained with the meaning of idealization or too formal.
For ease of the understanding to the embodiment of the present invention, done into one by taking several specific embodiments as an example below in conjunction with attached drawing
The explanation of step, and each embodiment does not constitute the restriction to the embodiment of the present invention.
Embodiment one
An embodiment of the present invention provides in a kind of high-speed mobile environment adaptive layered modulation and service integration transmission side
Method, for realizing adaptive, efficient transmission, to improve performance of mobile communication system.
An embodiment of the present invention provides in a kind of high-speed mobile environment adaptive layered modulation and service integration transmission side
The process chart of method is as shown in figure 5, specifically include following processing step：
S510：The channel state information of estimation is sent to transmitting terminal by receiving terminal, and the transmitting terminal passes through the channel shape
The conditional probability distribution function of the signal-to-noise ratio of current time slots is calculated in state information.
The channel estimator of receiving terminal carries out estimation and by feedback link by several time slots before estimation to channel
Channel state information is sent to transmitting terminal, and transmitting terminal is calculated by the related coefficient of the received signal to noise ratio of feedback and two time slots
Obtain the conditional probability distribution function of the signal-to-noise ratio of current time slots.
Receiver persistently to channel estimate and obtains received signal to noise ratio with channel state information, according to receiving
Signal-to-noise ratio variation, transmitter selects different modulation transmissions schemes.
The channel estimator for receiving end side feeds back the channel gain estimated to transmitting terminalFor adaptively adjusting
System transmission, wherein feedback delay are τ.
If the multipath channel between the transmitting terminal and the receiving terminal is flat, varying Channels, then each diameter channel
The real and imaginary parts of parameter obey that mean value is 0, variance isMutually independent multiple Gauss random process, i.e.,：Wherein, i=0,1 ..., N-1 indicate notation index.
Between be divided into the channel state information h [i] of τ withRelationship indicate it is as follows：
Wherein,For the perfect channel estimation of receiving terminal, ρ [τ] isIt is instantaneous related between h [i]
Coefficient, w [i] are channel gain variable caused by the Link Feedback period interior time-varying characteristics by fast fading channel, and w [i] is independent
InAndUsing Clarke model, ρ [τ] can be expressed as：J0(2
πfDτ), J0() is first kind zeroth order Bei Saer functions, fDFor maximum doppler frequency.
The channel state information h [i] obeys independent identically distributed rayleigh distributed, and the i in formula (1) is removed, obtains two
A time slot related coefficient：ρ [τ] andAnd meet：
With ρ [τ] andFor condition, defined variable V, and satisfaction： V is obeyed
The non-central chi square distribution that degree of freedom is 2, wherein decentralization parameter is：
Then the conditional probability distribution function of V is：
DefinitionFor average transmission power, the noise of receiving terminal be mean value be 0, variance isMultiple additive white gaussian make an uproar
Channel is normalized sound, obtains：E[|h|2]=1, the then average signal-to-noise ratio that the receiving terminal receives are：The signal-to-noise ratio of i-th of the symbol received is expressed as：
From system model it is found that the channel estimator of receiving terminal sends the letter estimated by feedback link to transmitting terminal
Road gainSelection for the adaptive modulation scheme to signal.
The channel estimator of the known receiving terminal sends the channel estimated to the transmitting terminal by feedback link and increases
BenefitIt selects, then has for the adaptive modulation scheme to signal： ByThe conditional probability that γ can be obtained is：
Wherein, I0For modified first kind zero Bessel function.
For Rayleigh channel,Probability density function be：
S520：Robustness hierarchical modulation scheme, the signal-to-noise ratio based on current time slots is used to obtain high-speed railway scene
The average error rate expression formula of each bit.
To the robustness hierarchical modulation scheme that high-speed railway scene is applicable in, using 4/16 layering of the gray mappings of broad sense
Modulation constellation.
4/16 layered modulation constellation figure of the gray mappings of broad sense is as shown in Figure 1, wherein big by four virtual 4- QAM
Grey constellation point point indicates high priority, European variableWithFirst priority on the roads I and the roads Q is indicated respectively；By white
The constellation point for the virtual 16-QAM that hollow dots indicate indicates the second priority, wherein Euclidean distanceWithI is indicated respectively
Second priority on road and the roads Q.For the M- QAM, M=2 of a broad senseY+Z, the layering level on the roads I and the roads Q can be expressed as：
I1,I2..., IY(I1And IYThe respectively the highest-order bit on the roads I and lowest bit position) and Q1,Q2..., QZ(Q1And QZRespectively Q
The highest-order bit on road and lowest bit position), wherein Y and Z indicate the maximum value on the roads I and the roads the Q number of plies respectively.
The Euclidean distance vector d on the roads IIWith the Euclidean distance vector d on the roads QQIt is defined as：
IfThenIndicate that minimum euclidean distance, corresponding modulation parameter are defined as：
The energy of transmission symbol is expressed as：
Wherein,For a temporary variable；
For awgn channel, N0For the noise power spectral density of awgn channel, then received signal to noise ratio is expressed as：
The error rate BER of the y bits in the roads I is expressed as：
The error rate BER of the y bits in the roads Q is expressed as：
The error rate BER expression formula of the roads the I bit of 4-QAM is：
The error rate BER expression formula of the roads the Q bit of 4-QAM is：
Wherein,
The error rate BER expression formula of the roads the I bit of 8-QAM is：
The error rate BER expression formula of the roads the Q lowest bit position of 8-QAM is：
The error rate BER expression formula of the roads the Q the highest-order bit of 8-QAM is：
The error rate BER expression formula of the roads the I lowest bit position of 64QAM is：
The error rate BER expression formula of the second bit of the roads I of 64QAM is
The error rate BER expression formula of the roads the I the highest-order bit of 64QAM is：
The error rate BER expression formula of the roads the Q lowest bit position of 64QAM is：
The error rate BER expression formula of the second bit of the roads Q of 64QAM is：
The error rate BER expression formula of the roads the Q the highest-order bit of 64QAM is：
Under high-speed railway scene, it is based onLayering 4-QAM the roads I bit error rateIt is expressed as：
Erfc () using two exponential functions and carry out approximate obtain：
Wherein, a1=1/6, b1=-1, a2=1/2, b2=-3/4, m isScalar parameter.
Formula (25) is updated in formula (24),It is reconfigured to：
Wherein,
It is based onLayering 4-QAM the roads Q bit error rateIt is expressed as：
For hierarchical modulation 8-QAM, it is based onBit error rate expression formula it is as follows：
For hierarchical modulation 64-QAM, it is based onBit error rate expression formula it is as follows：
Similarly, the roads the Q error rate BER expression formula of 64-QAM only need to be by the α in the roads I BER expression formulas in 64-QAM1It replaces
For β1, α2Replace with β2, α3Replace with 1.
S530：Distribution is scheduled to multi-service based on the robustness hierarchical modulation scheme, according to the signal-to-noise ratio of reception
Bit bit allocation is carried out with modulation parameter, obtains the tactful switching table of optimal modulation transmission.
Without loss of generality, it is assumed that have the three classes business that different bit error rates require：Business-Ι (voice), business-Π (number
According to), business-Π Ι (video), the relationship of target BER is： Since speech business is to need
It wants minimum to protect and be continuous fixed-rate transmission, therefore the lowest bit bit allocation on the roads Q in M- QAM constellations is given
Business-Ι, remaining log2M-1 bit distributes to other business according to the modulation parameter of selection.If channel condition
Good business-the Π to the business-Ι that can transmit 1 bit and 1 bit, then being exactly to be transmitted by 4-QAM at this time.Otherwise,
It can be transmitted with regard to no data service.
According to SNR threshold values Γk, k=1,2 ..., K, the regions SNR can be divided into K+1 decline region, wherein K be adjust
Mode coefficient processed.Distribute to the modulation system of the same number of constellation point in the same decline region.Constellation point quantity selection rule
To work asWhen, constellation point quantity is Mk=2k+1.For a given decline region, hierarchical modulation
The distribution of bit depends on receiving SNR and modulation parameter in planisphere.K-th of decline region is divided into k+1 sub-regions,
When the SNR of feedback is located at s-th of subregion (s=1,2 ..., k+1), modulation parameterWithIt can be according to BER expression formulas
Solution obtains.Therefore bit allocation table, i.e., optimal modulation strategy switching table be can be obtained by.The layering 64- of three kinds of business
The bit allocation scheme of the different subregions of QAM is as shown in table 1.
Table 1
In a given decline region, if SNR moves on to next sub-regions from a sub-regions, it is meant that letter
Road condition improves, and the business-Π of 1 bit will be replaced by the business-Π Ι of 1 bit, because business-Π Ι are needed than business-Π
It more to protect.The purpose of this transmission strategy is to improve the spectrum efficiency for the multi-service transport for having different BER to need.
Subregion threshold valueAnd modulation parameterWithNumber can be acquired by being layered the BER equatioies of 64-QAM modulation
Value solution.By taking 8-QAM as an example, i.e., the bit distribution in second decline region, second decline subregion is as shown in table 1, i.e. I
The lowest bit that the bit on road distributes to the roads business-Π, Q distributes to the highest bit on the roads business-Π Ι, Q and distributes to business-Ι
1, the modulation parameter and decline subregion threshold value of second sub-regions in second decline region can pass through solution formula
(28), (29), (30) obtain, and are determined according to bit distribution condition and solve equation group, and solution formula is specific as follows：
When feedback SNR fromTo infinite, in order to guarantee fairness, the 50% of transmission time be respectively divided into business-Π and
Business-Π Ι.
The subregion threshold valueModulation parameterWithForm optimal modulation strategy switching table.
S540：Adaptive Modulation transmission plan is executed, selection and present channel in the optimal modulation transmits Policy Table
The corresponding optimal modulation transmission strategy of status information.
After acquiring optimal decline subregion threshold value, the optimal modulation transmissions Policy Table of this programme can be confirmed.Transmitting terminal is logical
It crosses feedback link and obtains the channel state information of receiving terminal feedback, selection and present channel in optimal modulation transmits Policy Table
The matched optimal modulation transmission strategy of status information simultaneously carries out power control in transmitting terminal, to reach maximum spectral efficiency
Purpose.
The optimal modulation transmission strategy refers to specific bit allocation scheme as shown in Table 1.
S550：The transmitting terminal transmits strategy according to the optimal modulation, and current data is sent.
After confirming current desired distribution power, modulation transmission, transmitting terminal transmission data.
Transmitting terminal dynamically adjusts institute according to the feeding back channel state information received, by the channel state information
Optimal modulation strategy switching table is stated, data is made to carry out adaptive transmission.
Embodiment two
This embodiment offers in a kind of high-speed mobile environment adaptive layered modulation and service integration transmission method,
It can dynamically adjust tactful switching table for verifying this method with the variation of channel state feedback information and keep data adaptive
It should transmit, carry out following emulation, illustrate the case effect of the inventive embodiments and the raising of spectrum efficiency.
The modulation of the adaptive layered in high-speed mobile environment and service integration transmission are carried out with the method for the embodiment of the present invention
Detailed process it is similar with preceding method embodiment, details are not described herein again.
The default value of simulation parameter is：Carrier frequency fc=0.9GHz, average signal-to-noise ratioTrain moves
Speed v=300km/h, feedback delay τ=0.3ms, constellation point quantity M=[4,8,16,32,64].The target of three business
BER is
According to transmission strategy, the bit distribution in the different regions SNR is as shown in Figure 2.For 64-QAM, SNR threshold values are used
To select optimal transmission mode.For covering for the continuous and reliable cell of communication quality, in high-speed railway communication system
SNR in system is about 30dB.Consider quick time-varying fading channels, being transmitted when the SNR of estimation is less than 25.2dB can stop.
WhenBusiness-Ι can always distribute 1 bit, and business-Π or business-Π Ι can also be carried out at the same time biography
It is defeated.WhenIncrease, the transmitted bit number of all business also increases accordingly.WhenIncrease to another sub-district from a sub-regions
When domain, the business-Π of 1 bit can be replaced by the business-Π Ι of 1 bit, when SNR threshold values are intended to infinite, business-Π and industry
Business-Π Ι alternate transports.
The spectrum efficiency for the non-homogeneous 64-QAM mechanism of robustness that the embodiment of the present invention proposes is as shown in Figure 3.Uniform 64-
QAM mechanism all provides identical BER in all bits, therefore only passes a kind of business in a sub-regions.Spectrum efficiency
Expression formula is：
Circle points indicate the simulation result of spectrum efficiency.In figure 3, for specific movement speed, two kinds of modulation schemes
Spectrum efficiency all increase with the increase of SNR；For given SNR, the spectrum efficiency of two kinds of modulation schemes is with movement
The increase of speed and reduce；The difference comparsion of two kinds of modulation schemes is small when low SNR, but when movement speed increases to 500km/
H, the mechanism that the embodiment of the present invention proposes can improve 15% spectrum efficiency.The reason is that when channel condition is relatively good,
The SNR threshold values in the decline region of hierarchical modulation will be less than corresponding homogeneous modulation.This result illustrates that the embodiment of the present invention proposes
Robustness hierarchical modulation mechanism be suitable for high-speed mobile communication system.
It is that non-even laminating 64-QAM is modulated and the spectrum efficiency of uniform 64-QAM modulation is with mobile speed as shown in Figure 4
The trend chart of degree, it can be seen that for business-Ι and business-Π Ι, the frequency spectrum of non-homogeneous layering 64-QAM modulation
Efficiency is better than uniform 64-QAM modulation.But for business-Π, the spectrum efficiency of uniform 64-QAM modulation is but better than
The spectrum efficiency of non-homogeneous layering 64-QAM modulation.This is because the bit bit allocation of homogeneous modulation and the selection ratio of SNR threshold values
It is more conservative.For example, for the decline subregion in layering 64- QAMOnce the SNR of estimation is more than the threshold of decline subregion
Business-the Π of value, 1 bit will be replaced by the business-Π Ι of 1 bit.However uniformly 64-QAM decline region at one can only
Unique transmission services, without chance transmission services-Π Ι.Therefore a symbol in the scheme that the embodiment of the present invention proposes
Multiple business can be carried.Under high-speed railway scene, compared to homogeneous modulation, robustness hierarchical modulation mechanism can provide more
More business fairness.
In conclusion the embodiment of the present invention is modulated by using the adaptive layered in a kind of high-speed mobile environment and industry
Business multiplex transmission method, solves under the conditions of wireless transmitter can not obtain precise channel information, and adaptive layered modulation passes
The problem of defeated performance can be remarkably decreased.The present invention proposes that wireless transmitter is only capable of obtaining the inaccurate channel state information in part
Under the conditions of, under the premise of ensureing the different service quality demand of different business, carry out the calculating of adaptive layered modulation thresholding, work(
Rate controls and the method for hierarchical modulation scheme selection.The present invention can improve system spectral efficiency, ensure that system reaches maximum
Multi-service weight rate and, can also adaptive system average signal-to-noise ratio variation, make communication system better adapt to high speed move
Rotating ring border.
One of ordinary skill in the art will appreciate that：Attached drawing is the schematic diagram of one embodiment, module in attached drawing or
Flow is not necessarily implemented necessary to the present invention.
Each embodiment in this specification is described in a progressive manner, identical similar between each embodiment
Just to refer each other for part, and each embodiment focuses on the differences from other embodiments.Especially for dress
Set or system embodiment for, since it is substantially similar to the method embodiment, so describe fairly simple, related place ginseng
See the part explanation of embodiment of the method.Apparatus and system embodiment described above is only schematical, wherein institute
It states the unit illustrated as separating component may or may not be physically separated, the component shown as unit
It may or may not be physical unit, you can be located at a place, or may be distributed over multiple network element
On.Some or all of module therein can be selected according to the actual needs to achieve the purpose of the solution of this embodiment.Ability
Domain those of ordinary skill is without creative efforts, you can to understand and implement.
The foregoing is only a preferred embodiment of the present invention, but protection scope of the present invention be not limited to
This, any one skilled in the art in the technical scope disclosed by the present invention, the variation that can readily occur in or replaces
It changes, should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection of claim
Subject to range.
Claims (8)
1. the adaptive layered modulation under a kind of high-speed mobile environment and service integration transmission method, which is characterized in that including：
The channel state information of estimation is sent to transmitting terminal by receiving terminal, and the transmitting terminal is calculated by the channel state information
Obtain the conditional probability distribution function of the signal-to-noise ratio of current time slots；
Each ratio is obtained based on the signal-to-noise ratio of the current time slots using robustness hierarchical modulation scheme to high-speed railway scene
The average error rate expression formula of special position；
Distribution is scheduled to multi-service based on the robustness hierarchical modulation scheme, according to the signal-to-noise ratio and modulation parameter of reception
Bit bit allocation is carried out, the tactful switching table of optimal modulation transmission is obtained；
Adaptive Modulation transmission plan is executed, is chosen and current channel condition information pair in the optimal modulation transmits Policy Table
The optimal modulation transmission strategy answered；
The transmitting terminal transmits strategy according to the optimal modulation, and current data is sent.
2. the adaptive layered modulation under high-speed mobile environment according to claim 1 and service integration transmission method,
It is characterized in that, the channel state information of estimation is sent to transmitting terminal by the receiving terminal, and the transmitting terminal passes through the channel
The conditional probability distribution function of the signal-to-noise ratio of current time slots is calculated in status information, including：
Channel estimator is set in the receiving terminal, constantly channel is estimated using the channel estimator, and passes through
The channel state information of estimation is sent to transmitting terminal by feedback link；
The channel state information and time slot related coefficient of the transmitting terminal based on reception are calculated, and obtain current time slots
Signal-to-noise ratio conditional probability distribution function.
3. the adaptive layered modulation under high-speed mobile environment according to claim 2 and service integration transmission method,
It is characterized in that, it is described that in receiving terminal, channel estimator is set, constantly channel is estimated using the channel estimator,
And the channel state information of estimation is sent to by transmitting terminal by feedback link, including：
The channel estimator of the receiving terminal feeds back the channel gain estimated to transmitting terminal：Wherein, it feeds back
Time delay is τ；
If the multipath channel between the transmitting terminal and the receiving terminal is flat, varying Channels, then each diameter channel parameter
Real and imaginary parts obey that mean value is 0, variance isMutually independent multiple Gauss random process, i.e.,：Wherein, i=0,1 ..., N-1 indicate notation index；
Between be divided into the channel state information h [i] of τ withRelationship indicate it is as follows：
Wherein,For the perfect channel estimation of receiving terminal, ρ [τ] isWith the instantaneous related coefficient between h [i],
W [i] is channel gain variable caused by time-varying characteristics by fast fading channel in the Link Feedback period, w [i] independently ofAndUsing Clarke model, ρ [τ] can be expressed as：J0(2πfD
τ), J0() is first kind zeroth order Bei Saer functions, fDFor maximum doppler frequency.
4. the adaptive layered modulation under high-speed mobile environment according to claim 2 and service integration transmission method,
It is characterized in that, the channel state information and time slot related coefficient of the transmitting terminal based on reception are calculated, and are obtained
The conditional probability distribution function of the signal-to-noise ratio of current time slots, including：
The channel state information h [i] obeys independent identically distributed rayleigh distributed, the i in formula (1) is removed, when obtaining two
Gap related coefficient：ρ [τ] andAnd meet：
With ρ [τ] andFor condition, defined variable V, and satisfaction： V is obeyed freely
Degree for 2 non-central chi square distribution, wherein decentralization parameter is：Then
The conditional probability distribution function of V is：
DefinitionFor average transmission power, the noise of receiving terminal be mean value be 0, variance isMultiple additive white Gaussian noise, will
Channel is normalized, and obtains：E[|h|2]=1, the then average signal-to-noise ratio that the receiving terminal receives are：
The signal-to-noise ratio of i-th of the symbol received is expressed as：
The channel estimator of the known receiving terminal sends the channel gain estimated by feedback link to the transmitting terminalIt selects, then has for the adaptive modulation scheme to signal： ByThe conditional probability that γ can be obtained is：
Wherein, I0For modified first kind zero Bessel function；
For Rayleigh channel,Probability density function be：
。
5. the adaptive layered modulation under high-speed mobile environment according to claim 1 and service integration transmission method,
It is characterized in that, it is described that robustness hierarchical modulation scheme is used to high-speed railway scene, based on the signal-to-noise ratio of the current time slots,
The average error rate expression formula of each bit is obtained, including：
To the robustness hierarchical modulation scheme that high-speed railway scene is applicable in, using 4/16 hierarchical modulation star of the gray mappings of broad sense
Seat figure, including：The roads I and the roads Q, the roads multilayer I and the roads multilayer Q are respectively formed the 4-QAM high priorities and 16 constellations of 4 constellation points
The second priority of 16-QAM of point, European variableWithFirst priority on the roads I and the roads Q, Euclidean distance are indicated respectively
WithThe layering level on second priority on the expression roads I and the roads Q respectively, the roads I and the roads Q is expressed as：I1,I2..., IYAnd Q1,
Q2..., QZ, I1And IYThe respectively the highest-order bit on the roads I and lowest bit position, Q1And QZRespectively the highest-order bit on the roads Q and
Lowest bit position, Y and Z indicate the maximum value on the roads I and the roads the Q number of plies respectively；
The Euclidean distance vector d on the roads IIWith the Euclidean distance vector d on the roads QQIt is defined as：
IfThenIndicate that minimum euclidean distance, corresponding modulation parameter are defined as：
The energy of transmission symbol is expressed as：
Wherein,For a temporary variable；
For awgn channel, N0For the noise power spectral density of awgn channel, then received signal to noise ratio is expressed as：
The error rate BER of the y bits in the roads I is expressed as：
The error rate BER of the y bits in the roads Q is expressed as：
The error rate BER expression formula of the roads the I bit of 4-QAM is：
The error rate BER expression formula of the roads the Q bit of 4-QAM is：
Wherein,
The error rate BER expression formula of the roads the I bit of 8-QAM is：
The error rate BER expression formula of the roads the Q lowest bit position of 8-QAM is：
The error rate BER expression formula of the roads the Q the highest-order bit of 8-QAM is：
Wherein,
The error rate BER expression formula of the roads the I lowest bit position of 64QAM is：
The error rate BER expression formula of the second bit of the roads I of 64QAM is
The error rate BER expression formula of the roads the I the highest-order bit of 64QAM is：
The error rate BER expression formula of the roads the Q lowest bit position of 64QAM is：
The error rate BER expression formula of the second bit of the roads Q of 64QAM is：
The error rate BER expression formula of the roads the Q the highest-order bit of 64QAM is：
Under high-speed railway scene, it is based onLayering 4-QAM the roads I bit error rateIt is expressed as：
Erfc () using two exponential functions and carry out approximate obtain：
Wherein, a1=1/6, b1=-1, a2=1/2, b2=-3/4, m isScalar parameter.
Formula (25) is updated in formula (24),It is reconfigured to：
Wherein,
It is based onLayering 4-QAM the roads Q bit error rateIt is expressed as：
For hierarchical modulation 8-QAM, it is based onBit error rate expression formula it is as follows：
For hierarchical modulation 64-QAM, it is based onBit error rate expression formula it is as follows：
Similarly, the roads the Q error rate BER expression formula of 64-QAM only need to be by the α in the roads I BER expression formulas in 64-QAM1Replace with β1, α2
Replace with β2, α3Replace with 1.
6. the adaptive layered modulation under high-speed mobile environment according to claim 1 and service integration transmission method,
It is characterized in that, it is described that distribution is scheduled to multi-service based on the robustness hierarchical modulation scheme, according to the noise of reception
Than carrying out bit bit allocation with modulation parameter, the tactful switching table of optimal modulation transmission is obtained, including：
The three classes business required equipped with different bit error rates：Business-Ι, business-Π, business-Π Ι, the relationship of target BER are：Give the lowest bit bit allocation on the roads Q in M-QAM planispheres to business-Ι, remaining
log2M-1 bit distributes to other business according to the modulation parameter of selection；
Known snr threshold SNR is：Γk, SNR region divisions are the K+1 region that declines, wherein K is by k=1,2 ..., K
The modulation system of the same number of constellation point, constellation point quantity selection rule are distributed in modulating mode coefficient, the same decline region
It is then：WhenWhen, constellation point quantity is Mk=2k+1, for a given decline region, layering is adjusted
The distribution of bit depends on received signal to noise ratio SNR and modulation parameter in planisphere processed；
K-th of decline region is divided into k+1 sub-regions, when the Signal to Noise Ratio (SNR) of feedback is located at s-th of subregion, s=1,
2 ..., k+1, according to the bit distribution condition of each decline subregion, using the expression formula of error rate BER to sub- region threshold
Modulation parameterWithIt is solved；
The subregion threshold valueModulation parameterWithForm optimal modulation strategy switching table.
7. the adaptive layered modulation under high-speed mobile environment according to claim 1 and service integration transmission method,
It is characterized in that, the execution Adaptive Modulation transmission plan, is chosen in the optimal modulation transmits Policy Table and current letter
The corresponding optimal modulation transmission strategy of channel state information, including：
After acquiring optimal decline subregion threshold value, optimal modulation transmissions Policy Table is determined；
The transmitting terminal obtains the channel state information of the receiving terminal feedback by feedback link, is transmitted in the optimal modulation
Chosen in Policy Table with the optimal modulations of current channel condition information matches transmission strategy, and carry out power control, determine needed for
Distribution power.
8. the adaptive layered modulation under high-speed mobile environment according to claim 1 and service integration transmission method,
It being characterized in that, the transmitting terminal transmits strategy according to the optimal modulation, and current data is sent, including：
The transmitting terminal is dynamically adjusted described according to the feeding back channel state information received by the channel state information
Optimal modulation strategy switching table, makes data carry out adaptive transmission.
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