CN102801457A - Modulation and coding mode processing method and device - Google Patents
Modulation and coding mode processing method and device Download PDFInfo
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Abstract
The invention discloses a modulation and coding mode processing method and a modulation and coding mode processing device. The method comprises the following steps of: determining a weighting factor according to a value obtained by spatial correlation estimation; and weighting a signal to noise ratio from a terminal by using the weighting factor, and determining a modulation and coding mode according to the weighted signal to noise ratio. By the method and the device, the problem that the system performance is affected by the inaccuracy of a downlink signal to noise ratio estimated by the terminal is solved, and the system performance is improved.
Description
Technical field
The present invention relates to the communications field, in particular to a kind of modulation coding mode processing method and device.
Background technology
Adaptive Modulation and Coding (Adaptive Modulation and Coding the abbreviates AMC as) scheme of using wireless communication system realizes the best data rate transmission for the user.At multiple-input and multiple-output (Multiple Input Multiple Output; Abbreviate MIMO as) in the system; Adopt the AMC scheme, can utilize the advantage of the multi-antenna technology maximum gain ground raising availability of frequency spectrum and message transmission rate, improved the reliability and the throughput of system of link.At present, the AMC implementation mainly is access and the exit criteria that the corresponding downstream modulating-coding is set, according to the variation of descending signal to noise ratio numerical value, and the adjustment downlink modulation coding mode.
In mimo system, descending signal to noise ratio information is given the base station by terminal feedback, and the descending signal to noise ratio that the terminal is estimated maybe be accurate inadequately, thereby has influenced the performance of system.
Summary of the invention
Main purpose of the present invention is to provide a kind of modulation coding mode processing method and device, to address the above problem at least.
According to an aspect of the present invention, a kind of modulation coding mode processing method is provided, has may further comprise the steps: the value that estimation obtains according to spatial coherence is confirmed weighted factor; Use said weighted factor that the signal to noise ratio from said terminal is carried out weighting, and confirm modulation coding mode according to the signal to noise ratio after the weighting.
Before estimating that according to spatial coherence the value that obtains is confirmed said weighted factor, also comprise: carry out the estimation of spatial coherence according to terminal pilot transmitted information.
The estimation of carrying out spatial coherence according to the said pilot frequency information of said terminal emission comprises: obtain the channel estimation value on the reception antenna from said pilot frequency information; Said channel estimation value is write as vector form and carried out auto-correlation computation, obtained correlation matrix; Said correlation matrix is done the value that characteristic value decomposition obtains said spatial coherence, wherein, through separating equation det (the A-λ that eigenvalue satisfies
I)=0 obtains eigenvalue, and said spatial coherence estimates that the value that obtains is the ratio of maximum said characteristic value with the said characteristic value of minimum, and wherein, A is said correlation matrix, and I is a unit matrix, and det is the corresponding determinant of matrix; Perhaps, the square formation that to establish said correlation matrix A be N * N, a
IjBe the element of the capable j row of i in the said correlation matrix, A
IjFor A removes the residue determinant that i is capable and the j row obtain afterwards, the determinant of A can be expressed as
Said spatial coherence estimates that the value that obtains is det (A).
Under the situation that adopts many antennas, estimate that according to said spatial coherence the value that obtains obtains said weighted factor and comprises: the pattern of definite many antennas that adopted; Confirm under this pattern, to estimate that according to said spatial coherence the value that obtains obtains the mode of said weighted factor.
Estimate that according to said spatial coherence the value that obtains obtains said weighted factor and comprises: estimate the value that obtains for spatial coherence and divide different scopes, the corresponding weighted factor of each scope; The residing scope of value according to said spatial coherence estimation obtains is confirmed the weighted factor that it is corresponding; Perhaps, value that spatial coherence estimates to obtain and the mathematical relationship between the said weighted factor are set in advance, obtain spatial coherence through said data relationship and estimate the corresponding weighted factor of value that obtains.
Estimate that according to said spatial coherence the value that obtains confirms also to comprise: according to the scope of confirming modulation coding mode from the signal to noise ratio of the said weighted factor weighting of not using of said terminal before the said weighted factor.
According to a further aspect in the invention, a kind of modulation coding mode processing unit is provided, has comprised: determination module is used for the value that estimation obtains according to spatial coherence and confirms weighted factor; Weighting block is used to use said weighted factor that the signal to noise ratio from said terminal is carried out weighting, and confirms modulation coding mode according to the signal to noise ratio after the weighting.
This device also comprises: estimation module is used for before estimating that according to spatial coherence the value that obtains is confirmed said weighted factor, carrying out the estimation of spatial coherence according to terminal pilot transmitted information.
Said estimation module comprises: acquisition module is used for obtaining the channel estimation value on the reception antenna from said pilot frequency information; Computing module is used for said channel estimation value is write as vector form and carried out auto-correlation computation, obtains correlation matrix; Decomposing module is used for said correlation matrix is done the value that characteristic value decomposition obtains said spatial coherence, wherein, and through separating equation det (the A-λ that eigenvalue satisfies
I)=0 obtains eigenvalue, and said spatial coherence estimates that the value that obtains is the ratio of maximum said characteristic value with the said characteristic value of minimum, and wherein, A is said correlation matrix, and I is a unit matrix, and det is the corresponding determinant of matrix; Perhaps, the square formation that to establish said correlation matrix A be N * N, a
IjBe the element of the capable j row of i in the said correlation matrix, A
IjFor A removes the residue determinant that i is capable and the j row obtain afterwards, the determinant of A can be expressed as
Said spatial coherence estimates that the value that obtains is det (A).
Adopting under the situation of many antennas, said determination module comprises: first determination module is used to confirm the pattern of many antennas of being adopted; Second determination module is used to confirm under this pattern, estimate that according to said spatial coherence the value that obtains obtains the mode of said weighted factor.
Said second determination module also is used to the different scope of value division that the spatial coherence estimation obtains, the corresponding weighted factor of each scope; The residing scope of value according to said spatial coherence estimation obtains is confirmed the weighted factor that it is corresponding; Perhaps, value that spatial coherence estimates to obtain and the mathematical relationship between the said weighted factor are set in advance, obtain spatial coherence through said data relationship and estimate the corresponding weighted factor of value that obtains.
Through the present invention, adopt the value that estimation obtains according to spatial coherence to confirm weighted factor; Use said weighted factor that the signal to noise ratio from said terminal is carried out weighting; And confirm modulation coding mode according to the signal to noise ratio after the weighting; The descending signal to noise ratio that has solved the terminal estimation possibly accurately cause having influenced system performance problems inadequately, and then has improved the performance of system.
Description of drawings
Accompanying drawing described herein is used to provide further understanding of the present invention, constitutes the application's a part, and illustrative examples of the present invention and explanation thereof are used to explain the present invention, do not constitute improper qualification of the present invention.In the accompanying drawings:
Fig. 1 is the flow chart according to the modulation coding mode processing method of the embodiment of the invention;
Fig. 1 a is the sketch map according to the available shared channel mapping mode of part in the subframe of the embodiment of the invention;
Fig. 2 is the structured flowchart of the modulation coding mode processing unit of enforcement according to the present invention;
Fig. 3 is the structured flowchart according to estimation module in the modulation coding mode processing unit of the embodiment of the invention;
Fig. 4 is the structured flowchart according to determination module in many antennas situation modulated coded system processing unit of the embodiment of the invention;
Fig. 5 be according in the multiaerial system of this preferred embodiment based on the flow chart of the AMC method of wireless channel spatial coherence;
Fig. 6 is the flow chart of the multi-antenna mode modulation coding mode adaptive process of VViMAX system according to the preferred embodiment of the invention.
Embodiment
Hereinafter will and combine embodiment to specify the present invention with reference to accompanying drawing.Need to prove that under the situation of not conflicting, embodiment and the characteristic among the embodiment among the application can make up each other.
Only consider and recently confirm the coarse problem of coded system according to noise; In following examples; Introduced the notion of weighted factor, this weighted factor is relevant with spatial coherence, through the weighting of weighted factor to signal to noise ratio; The descending signal to noise ratio that can solve estimation to a certain extent possibly accurately cause occurring the affected problem of systematic function (for example, prolonged the time that self adaptation is adjusted, influenced the throughput of system etc.) inadequately.
Based on this, a kind of modulation coding mode processing method is provided in the present embodiment, Fig. 1 is the flow chart according to the modulation coding mode processing method of the embodiment of the invention, and is as shown in Figure 1, this method may further comprise the steps:
Step S102, the value that estimation obtains according to spatial coherence is confirmed weighted factor;
Step S104 uses weighted factor that the signal to noise ratio of coming self terminal is carried out weighting, and confirms modulation coding mode according to the signal to noise ratio after the weighting.
Carry out spatial coherence and estimate that the method for the value of obtaining has a variety of modes in the prior art; Can be explained hereinafter; No matter which kind of mode obtains spatial coherence; As long as obtained this spatial coherence estimated value, all can address the above problem to a certain extent, only whether obtaining of this value accurately can bring some influences.Be explained below.
Fig. 1 a is the sketch map according to the available shared channel mapping mode of part in the subframe of the embodiment of the invention, shown in Fig. 1 a, * be pilot frequency information, 0 is data, and horizontally-arranged is represented symbol, and vertical setting of types is represented subcarrier.Can utilize pilot frequency information to obtain channel estimating information.
The principle of channel estimating is following: receive data behind fast Fourier transform (FFT), signal model can be expressed as Z
Mn=X
MnH
Mn+ N
Mn, m representes carrier index, n representes notation index; Z
MnRepresent the m carrier wave, the reception data on the n symbol; X
MnRepresent the m carrier wave, the transmission data on the n symbol; H
MnRepresent the m carrier wave, the channel response on the n symbol; N
MnRepresent the m carrier wave, the noise on the n symbol.
Work as m,
The time, X
MnFor known pilot data, establish X
Mn=A, A are constants.
H
MnLS be estimated as: Y
Mn=Z
Mn/ X
Mn=H
Mn+ N
Mn/ A.
Y
MnBe channel estimation value, H
MnThe channel response that expression is actual.Like this, Y can regard real channel response and noise addition as.Pilot frequency information is a known constant A, so, with receiving signal Z, divided by this constant A, has just obtained channel estimation value Y.
The reception signal Z that receive according to every antenna the base station; Calculate after the channel estimating Y, write channel estimating the form of column vector as, multiply each other with its conjugate transpose (row vector); Draw the matrix of a channel estimating relevant like this, just be called channel correlation matrix with the reception antenna number.
After obtaining channel estimation value, can adopt multiple mode to obtain spatial coherence, for example:
Mode one; The patent No. is that CN200510069203 " discriminating space relativity method and working mode of multi-antenna system method of adjustment " provides a kind of method of the power of spatial coherence being differentiated through calculating channel dafing depth parameter, comprising: the average of first calculating channel impulse response matrix; The standard deviation of calculating channel impulse response matrix again; With standard deviation divided by average, as the channel fading depth parameter.This parameter has been reacted spatial coherence.
Mode two is directly according to definition computer memory correlation.Document " Correlation analysis based on mimochannel measurements in an indoor environment " IEEE JOURNAL ON SELECTED AREASIN COMMUNICATIONS; VOL.21; NO.5; Provided the definition that directly utilizes correlation among the JUNE 2003 and calculated the spatial coherence of mimo channel decline, formula is following:
In the formula, the computing of mathematic expectaion is asked in E [] expression; μ and v represent complex random variable respectively, the channel estimation value of expression antenna receiving signal in mimo system, ρ
ComplexThe expression multiple correlation coefficient, * representes complex conjugate operation.
Mode three, the employing singular value decomposition is calculated the spatial coherence of wireless channel.The patent No. is US2005094598 " Multiple-input; Multiple-output (MIMO) systems with multiple transmission modes " propose a kind of multi-antenna technology and selected the method used; This invention is the method for channel impulse response being carried out singular value decomposition, asks for channel relevancy.
These above-mentioned modes need at first calculate channel estimation value or channel impulse response value.
Three kinds of different and above-mentioned modes; Also provide in the present embodiment and preferably carried out the spatial coherence estimation approach; Consider the terminal in the present embodiment owing to receive the restriction of pilot frequency information; The descending signal to noise ratio of estimating maybe be accurate inadequately, before step S102, carries out the estimation of spatial coherence according to terminal pilot transmitted information.Can obtain the channel estimation value on the reception antenna from pilot frequency information, then, channel estimation value write as vector form and carried out auto-correlation computation, obtain correlation matrix.Obtain a value (following mode four and mode five) according to correlation matrix then, use then and should value calculate weighted factor.
The preferred implementation one of present embodiment (being mode four) is established the square formation that correlation matrix A is N * N, a
IjBe the element of the capable j row of i in the matrix, A
IjRemove the residue determinant that i is capable and the j row obtain afterwards for matrix A, be called a
IjComplementary minor, then the determinant of matrix A can be expressed as
That is, calculate weighted factor according to the value of det (A).For example, when channel was uncorrelated channel, correlation matrix A was a unit matrix, and then the value of determinant is 1, and when channel is that complete correlated channels is, correlation matrix A is complete a burst of, and then the value of determinant is 0.
The preferred implementation two of present embodiment (being mode five) is done the value that characteristic value decomposition obtains spatial coherence with correlation matrix in this mode.This optimal way ratio is easier to realize.For example, can obtain eigenvalue through separating the satisfied equation det (A-λ I)=0 of eigenvalue, wherein; A is a correlation matrix; I is a unit matrix, and det is the corresponding determinant of matrix, and the value of this spatial coherence can be expressed as the ratio of the characteristic value of biggest characteristic value and minimum.Certainly, this only is one and preferably correlation matrix is done the execution mode that characteristic value decomposition obtains spatial coherence, obtains spatial coherence and also has identical effect thereby decompose through other mode.Spatial coherence through such is represented mode, and when channel was uncorrelated channel, correlation matrix was a unit matrix, and then each characteristic value of matrix equates, conditional number is 1; When channel when relevant fully, correlation matrix is one complete 1 a matrix, then matrix has only non-0 characteristic value, conditional number is ∞.
Pass through above-mentioned steps; Considered the restriction of pilot frequency information; And use the weighted factor that obtains from pilot frequency information that the signal to noise ratio from terminal feedback is carried out weighting, and in prior art, only confirm recently that through the noise of terminal feedback the mode of modulating-coding is more accurate, improved systematic function.
For multiple-input and multiple-output (Multiple Input Multiple Output abbreviates MIMO as) wireless communication system, it has multiple implementation, for example, and transmit diversity mode, spatial multiplexing mode and beam shaping mode etc.In the present embodiment, can adopt different implementations, for example when the spatial coherence of wireless channel hangs down, adopt transmit diversity can obtain better transmission performance to different wireless channel conditions; When spatial coherence is higher, adopt the beam shaping mode can obtain better transmission property.Adopting under the situation of many antennas, more excellent ground, the pattern of the many antennas that can at first confirm to be adopted confirms that then estimation obtains according to spatial coherence under this pattern value obtains the mode of weighted factor.That is, the mode that weighted factor obtains is relevant with the pattern of many antennas, that is, pattern is different, and the mode that the value that estimation obtains according to spatial coherence obtains weighted factor is also different.For example, can compare with the predetermined threshold under each pattern, different weights is set to weighted factor according to the value that the spatial coherence estimation obtains.
No matter for which kind of implementation; Provide a kind of in the present embodiment and preferably estimated that according to spatial coherence the value that obtains obtains the mode of weighted factor: can be to set up the value that spatial coherence estimates to obtain and the corresponding relation of weighted factor in advance, obtain weighted factor, perhaps also can formulate a formula in advance according to this corresponding relation; Calculate weighted factor through this formula; Formula can be formulated influence on SNR according to spatial coherence, for example, smallerly can adopt linear function formula (y=ax+b if influence; Y representes weighted factor; X representation space correlation is estimated the value obtain, and a and b can be the constants definite according to actual conditions), influence can adopt bigger the time secondary or repeatedly function formula (like y=ax
2+ b etc.).Provide preferred embodiment a kind of in an embodiment: estimate the value that obtains for spatial coherence and divide different scopes, the corresponding weighted factor of each scope; The residing scope of value according to space tracking obtains is confirmed the weighted factor that it is corresponding.Suppose that predetermined threshold is a1 and a2, the conditional number that obtains through the correlation matrix computing and the comparison of predetermined threshold are NdB if conditional number, then is provided with weighted factor greater than a1; If conditional number, then is provided with weighted factor less than a2; If it is 0dB that conditional number between a1 and a2, then is provided with weighted factor.This mode realizes simply, can certainly adopt the comparatively complicated mode that obtains weighted factor, illustrates no longer one by one at this.
Preferably, when implementing, consider the error rate of terminal feedback signal to noise ratio; Obtaining modulation coding mode possibly be an approximate range; Exist the different error rates corresponding to different signal to noise ratios, one preferred embodiment in, before estimating that according to spatial coherence the value obtain is confirmed weighted factor; Can also comprise: confirm the scope of modulation coding mode according to the signal to noise ratio of not using the weighted factor weighting of coming self terminal, this preferred implementation has increased the consideration to the error rate.
A kind of modulation coding mode processing unit also is provided in the present embodiment, and this processing unit is used to realize the foregoing description and preferred embodiment, has carried out explanation, repeats no more, and describes in the face of the module that relates in this processing unit down.As following employed, the combination of the software and/or the hardware of predetermined function can be realized in term " module ".Although the described system and method for following examples is preferably realized with software, hardware, perhaps the realization of the combination of software and hardware also maybe and be conceived.
Fig. 2 is the structured flowchart of the modulation coding mode processing unit of enforcement according to the present invention, and is as shown in Figure 2, and this device comprises determination module 22 and weighting block 24.Describe in the face of this device down.
Determination module 22 is used for the value that estimation obtains according to spatial coherence and confirms weighted factor; Weighting block 24 is connected to determination module 24, is used to use weighted factor that the signal to noise ratio of coming self terminal is carried out weighting, and confirms modulation coding mode according to the signal to noise ratio after the weighting.
Preferably, this device also comprises: estimation module 26, be connected to determination module 22, and be used for before estimating that according to spatial coherence the value that obtains is confirmed said weighted factor, carrying out the estimation of spatial coherence according to terminal pilot transmitted information.
Fig. 3 is the structured flowchart according to estimation module in the modulation coding mode processing unit of the embodiment of the invention, and is as shown in Figure 3, and this estimation module 26 comprises: acquisition module 262 is used for obtaining the channel estimation value on the reception antenna from pilot frequency information; Computing module 264 is used for channel estimation value is write as vector form and carried out auto-correlation computation, obtains correlation matrix; Decomposing module 266 is used for correlation matrix is done the value that characteristic value decomposition obtains spatial coherence.Wherein, decomposing module 266 is used for through separating equation det (the A-λ that eigenvalue satisfies
I)=0 obtains characteristic value, and the value of spatial coherence is the ratio of the characteristic value of biggest characteristic value and minimum, and wherein, A is a correlation matrix, and I is a unit matrix, and det is the corresponding determinant of matrix.Perhaps, establish the square formation that correlation matrix A is N * N, a
IjBe the element of the capable j row of i in the correlation matrix, A
IjFor A removes the residue determinant that i is capable and the j row obtain afterwards, the determinant of A can be expressed as
Spatial coherence estimates that the value that obtains is det (A).
Fig. 4 is the structured flowchart according to determination module in many antennas situation modulated coded system processing unit of the embodiment of the invention; As shown in Figure 4; Adopting under the situation of many antennas, this determination module 24 comprises: first determination module 242 is used to confirm the pattern of many antennas of being adopted; Second determination module 244 is used to confirm under this pattern, estimate that according to spatial coherence the value that obtains obtains the mode of weighted factor.Wherein, this second determination module also is used to the different scope of value division that the spatial coherence estimation obtains, the corresponding weighted factor of each scope; The residing scope of value that estimation obtains according to spatial coherence is confirmed the weighted factor that it is corresponding; Perhaps, value that spatial coherence estimates to obtain and the mathematical relationship between the weighted factor are set in advance, obtain spatial coherence through this data relationship and estimate the corresponding weighted factor of value that obtains.
Describe below in conjunction with a preferred embodiment, the preferred embodiment has combined the foregoing description and preferred implementation.
In this preferred embodiment; The base station utilizes the descending signal to noise ratio of terminal feedback to determine the value of current available downlink modulation coding mode; Utilize simultaneously terminal pilot transmitted information is estimated radio channel status information, judge whether current channel relevancy is applicable to current MIMO mode, the weighted factor of current channel relevancy as signal to noise ratio; In the scope of available modulation coding mode exponent number, the current MIMO pattern at this terminal is carried out the self adaptation adjustment of code modulation mode.In the AMC of this multiaerial system method; One side is according to the signal to noise ratio of terminal feedback; The adjusting range of confirming modulating-coding strategy (MCS) (needs explanation; The modulating-coding strategy that below uses is a modulation coding mode), the factor of on the other hand spatial coherence of wireless channel being adjusted as code modulation mode is carried out weighting to code modulated exponent number.Thereby make that multiaerial system can be according to the concrete condition of wireless channel, adaptively choose suitable modulation coding mode, avoided the frequent switching between the multi-antenna technology, improved systematic function.
Fig. 5 be according in the multiaerial system of this preferred embodiment based on the flow chart of the AMC method of wireless channel spatial coherence, as shown in Figure 5, this flow process comprises the steps:
Step S502, the base station is according to the terminal feedback signal to noise ratio, confirms corresponding MCS span, (signal to noise ratio that is terminal feedback is that the exponent number with MCS is corresponding); In this step; The error rate of terminal feedback signal to noise ratio is considered according to MCS mode corresponding under the predefined signal to noise ratio condition in the base station, and different signal to noise ratios exists the different error rates; In conjunction with the signal to noise ratio information of the up-to-date feedback of base station throughput and terminal, confirm the MCS span;
Step S504, the base station is carried out the spatial coherence of wireless channel and is estimated according to terminal pilot transmitted information;
Step S506, the weighted factor of MCS value is calculated in the base station to the spatial coherence of estimating;
Step S508 confirms the value of descending MCS through signal to noise ratio and weighted factor.
In step S504, at first need calculate the channel estimation value on each reception antenna, with its form of being write as vector, this vector is carried out auto-correlation computation, obtain correlation matrix; Then the correlation matrix of channel impulse response is done characteristic value decomposition, claim the conditional number of compute matrix again, with the correlation information of this conditional number as the space.
For example, definition matrix conditional number is the ratio between this matrix eigenvalue of maximum and the minimal eigenvalue, and then the solving condition problem of counting converts into and finds the solution eigenvalue problem.λ is for to satisfy separating of linear equation det (A-λ I)=0 for the defined feature value, does ordering to finding the solution the characteristic value that obtains, and draws conditional number cond (A) and is defined as:
Wherein, λ
MaxBe eigenvalue of maximum, λ
MinBe minimal eigenvalue.When channel was uncorrelated channel, correlation matrix was a unit matrix, and then each characteristic value of matrix equates, conditional number is 1, when channel when being correlated with fully, correlation matrix is complete 1 matrix, then matrix has only non-0 characteristic value, conditional number is ∞.
In step S506, the conformity relation according to MIMO technology implementation method and spatial coherence quantizes conditional number; For example when the spatial coherence of wireless channel hangs down; System adopts spatial emission diversity can obtain better transmission performance; If the condition value cond that calculates is also less, then the weighted value of corresponding modulation coding mode channel relevancy weighted factor dalta is made as NdB; If condition value cond is bigger, then corresponding weighted factor weighted value is made as-NdB; If conditional number is between predetermined threshold, then the weighted factor weighted value is made as 0dB.
In step S508; The demodulation threshold of signal to noise ratio and modulation coding mode exists mapping table (for example; Under the white Gaussian noise condition), can be according to the weighted factor dalta that calculates, with the terminal signal to noise ratio CINR addition of feedback in real time; New CINR value with obtaining inquires suitable modulation coding mode in the demodulation threshold relation table of signal to noise ratio and modulation coding mode, system uses new modulation coding mode to carry out the downlink data emission.
Describe with the example that is embodied as of this preferred embodiment in the WiMAX system below, this preferred embodiment equally also is applicable to other system.
In the WiMAX system, the multi-antenna technology of employing comprises:
1, beam shaping: a kind of many antennas lift-off technology; The base station obtains the weight vectors of one group of effective weights as each transmitting antenna downstream signal through using terminal uplink sub-carrier channel information; To reach the anti-fading and antijamming capability reinforcement of the downstream signal that this terminal is received; To enlarge base station range, improve the downstream signal transmission quality.
2, spatial reuse: the BLAST structure is adopted in the base station; The space encoding matrix utilizes transmitting antenna to launch unlike signal simultaneously for
, makes downlink traffic double.
3, spatial emission diversity: Alamouti-STC (Space Time Coding) scheme is adopted in the base station; The space encoding matrix utilizes the signal of antenna emission repetition for
, obtain diversity gain.
Under the certain condition of bandwidth, the conversion of throughput is determined by modulation coding mode; The exponent number of modulation coding mode is high more, and throughput is big more.When for example bandwidth was constant, code modulation mode 16QAM1/2 doubled than the throughput of QPSK1/2.The demodulation coding ability at terminal is limit by received signal power intensity, so the conversion of signal to noise ratio has influenced the conversion of throughput.
The gain of multi-antenna technology can realize the lifting of downlink throughput capacity through the signal to noise ratio that improves terminal reception signal, and the base station utilizes the descending signal to noise ratio of terminal feedback, selects suitable downlink modulation coding mode transmitting downstream data according to channel conditions.Under current conditions; The terminal is limit by the quantity of descending pilot frequency to the estimation of descending signal to noise ratio, there are certain deviation in estimated value and actual value, and the base station is adopted and existed the estimated value of deviation to carry out the adjustment of downlink modulation coding mode; Can increase the time of self adaptation adjustment, reduce the lifting of throughput.Therefore; Wireless channel environment to current is assessed; Judge whether channel condition is fit to the current multi-antenna technology of selecting for use; And with weighted factor with the signal to noise ratio of feedback condition as the adjustment modulation coding mode, can more objectively reflect the gain improvement situation of system, realize the self adaptation of many antennas condition modulated coded system.
In this preferred embodiment; Calculate the correlation of wireless channel under many antennas condition; Can be according to the adaptation situation of multi-antenna mode of selecting for use and wireless channel correlation; The correlation of wireless channel is quantified as the weighted factor relevant with signal to noise ratio, with weighted factor and the unified consideration of signal to noise ratio, selects the downlink modulation coding mode transmitting downstream data that are suitable at last.For can comprising the steps: of difference computer memory correlation method
Step S1 calculates the correlation matrix H that receives the signaling channel impulse response;
Step S2 carries out characteristic value decomposition to correlation matrix, and the compute matrix conditional number is according to concerning between matrix conditional number and the predetermined threshold, as the strong and weak indication of the spatial coherence of wireless channel;
Step S3, many antennas mode of the current employing of system can be space multiplexing mode, beam shaping pattern or spatial emission diversity pattern; According to the spatial coherence scene that different multi-antenna technologies is suitable for, calculate the corresponding weighted factor of matrix conditional number under the different antennae pattern;
Step S4 with the descending signal to noise ratio addition of weighted factor and terminal feedback, selects suitable downlink modulation coding mode then, sends downlink data information.
Fig. 6 is the flow chart of the multi-antenna mode modulation coding mode adaptive process of VViMAX system according to the preferred embodiment of the invention, and as shown in Figure 6, this flow process comprises the steps:
Step S602, the base station obtains the correlation matrix of channel impulse response through carrying out channel estimating to received signal;
Step S604 carries out conditional number to the correlation matrix of channel impulse response and calculates, and tries to achieve the spatial coherence of system's this moment;
Step S606 according to the multi-antenna mode that current system adopts, asks the weighted factor under the different antennae pattern;
Step S606a if the current multi-antenna pattern is the beam shaping mode, compares with predetermined threshold threshold1 the conditional number of calculating: equal NdB if conditional number, then defines weighted factor greater than threshold1 with threshold2; If conditional number, then defines weighted factor less than threshold2; If conditional number is between threshold1 and threshold2, the definition weighted factor is 0dB;
Step S606b if the current multi-antenna pattern is a spatial multiplexing mode, compares with predetermined threshold threshold3 the conditional number of calculating: equal-NdB if conditional number, then defines weighted factor greater than threshold3 with threshold4; If it is NdB that conditional number, then defines weighted factor less than threshold4; If conditional number is between threshold3 and threshold4, the definition weighted factor is 0dB;
Step S606c if the current multi-antenna pattern is the spatial emission diversity mode, compares with predetermined threshold threshold5 the conditional number of calculating: equal NdB if conditional number, then defines weighted factor greater than threshold5 with threshold6; If conditional number, then defines weighted factor less than threshold6; If conditional number is between threshold5 and threshold6, the definition weighted factor is 0dB;
Step S608 is provided with the uniting and adjustment table in the base station, the corresponding relation between signal to noise ratio and the MCS is provided in the uniting and adjustment table.Value after the signal to noise ratio addition of weighted factor and feedback is as the snr value that upgrades, and the snr value according to this renewal finds the suitable modulation coding mode of terminal demodulates decoding threshold again, uses the uniting and adjustment table, and the downlink coding modulation system is adjusted.
In the above-mentioned parameter, N value and thresholding are rule of thumb set, and also can obtain according to emulation.
Through the foregoing description, the descending signal to noise ratio that has solved the terminal estimation possibly accurately cause having influenced system performance problems inadequately, and then has improved the performance of system.
Obviously; It is apparent to those skilled in the art that above-mentioned each module of the present invention or each step can realize that they can concentrate on the single calculation element with the general calculation device; Perhaps be distributed on the network that a plurality of calculation element forms; Alternatively, they can be realized with the executable program code of calculation element, carried out by calculation element thereby can they be stored in the storage device; Perhaps they are made into each integrated circuit modules respectively, perhaps a plurality of modules in them or step are made into the single integrated circuit module and realize.Like this, the present invention is not restricted to any specific hardware and software combination.
The above is merely the preferred embodiments of the present invention, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.All within spirit of the present invention and principle, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (11)
1. modulation coding mode processing method is characterized in that may further comprise the steps:
The value that estimation obtains according to spatial coherence is confirmed weighted factor;
Use said weighted factor that the signal to noise ratio from said terminal is carried out weighting, and confirm modulation coding mode according to the signal to noise ratio after the weighting.
2. method according to claim 1 is characterized in that, before estimating that according to spatial coherence the value that obtains is confirmed said weighted factor, also comprises:
Carry out the estimation of spatial coherence according to terminal pilot transmitted information.
3. method according to claim 2 is characterized in that, the estimation of carrying out spatial coherence according to the said pilot frequency information of said terminal emission comprises:
Obtain the channel estimation value on the reception antenna from said pilot frequency information;
Said channel estimation value is write as vector form and carried out auto-correlation computation, obtained correlation matrix;
Said correlation matrix is done the value that characteristic value decomposition obtains said spatial coherence; Wherein, obtain eigenvalue through separating the satisfied equation det (A-λ I)=0 of eigenvalue, said spatial coherence estimates that the value that obtains is the ratio of maximum said characteristic value with the said characteristic value of minimum; Wherein, A is said correlation matrix, and I is a unit matrix, and det is the corresponding determinant of matrix; Perhaps, the square formation that to establish said correlation matrix A be N * N, a
IjBe the element of the capable j row of i in the said correlation matrix, A
IjFor A removes the residue determinant that i is capable and the j row obtain afterwards, the determinant of A can be expressed as
Said spatial coherence estimates that the value that obtains is det (A).
4. method according to claim 1 is characterized in that, under the situation that adopts many antennas, estimates that according to said spatial coherence the value that obtains obtains said weighted factor and comprises:
The pattern of definite many antennas that adopted;
Confirm under this pattern, to estimate that according to said spatial coherence the value that obtains obtains the mode of said weighted factor.
5. method according to claim 1 is characterized in that, estimates that according to said spatial coherence the value that obtains obtains said weighted factor and comprises:
Estimate the value that obtains for spatial coherence and divide different scopes, the corresponding weighted factor of each scope; The residing scope of value according to said spatial coherence estimation obtains is confirmed the weighted factor that it is corresponding; Perhaps,
Value that spatial coherence estimates to obtain and the mathematical relationship between the said weighted factor are set in advance, obtain spatial coherence through said data relationship and estimate the corresponding weighted factor of value that obtains.
6. method according to claim 1 is characterized in that, estimates that according to said spatial coherence the value that obtains confirms also to comprise before the said weighted factor:
According to the scope of confirming modulation coding mode from the signal to noise ratio of the said weighted factor weighting of not using of said terminal.
7. modulation coding mode processing unit is characterized in that comprising:
Determination module is used for the value that estimation obtains according to spatial coherence and confirms weighted factor;
Weighting block is used to use said weighted factor that the signal to noise ratio from said terminal is carried out weighting, and confirms modulation coding mode according to the signal to noise ratio after the weighting.
8. device according to claim 7 is characterized in that, also comprises:
Estimation module is used for before estimating that according to spatial coherence the value that obtains is confirmed said weighted factor, carrying out the estimation of spatial coherence according to terminal pilot transmitted information.
9. device according to claim 8 is characterized in that, said estimation module comprises:
Acquisition module is used for obtaining the channel estimation value on the reception antenna from said pilot frequency information;
Computing module is used for said channel estimation value is write as vector form and carried out auto-correlation computation, obtains correlation matrix;
Decomposing module is used for said correlation matrix is done the value that characteristic value decomposition obtains said spatial coherence, wherein; Obtain eigenvalue through separating the satisfied equation det (A-λ I)=0 of eigenvalue; Said spatial coherence estimates that the value that obtains is the ratio of maximum said characteristic value with the said characteristic value of minimum, and wherein, A is said correlation matrix; I is a unit matrix, and det is the corresponding determinant of matrix; Perhaps, the square formation that to establish said correlation matrix A be N * N, a
IjBe the element of the capable j row of i in the said correlation matrix, A
IjFor A removes the residue determinant that i is capable and the j row obtain afterwards, the determinant of A can be expressed as
Said spatial coherence estimates that the value that obtains is det (A).
10. device according to claim 7 is characterized in that, under the situation that adopts many antennas, said determination module comprises:
First determination module is used to confirm the pattern of many antennas of being adopted;
Second determination module is used to confirm under this pattern, estimate that according to said spatial coherence the value that obtains obtains the mode of said weighted factor.
11. device according to claim 10 is characterized in that, said second determination module also is used to the different scope of value division that the spatial coherence estimation obtains, the corresponding weighted factor of each scope; The residing scope of value according to said spatial coherence estimation obtains is confirmed the weighted factor that it is corresponding; Perhaps, value that spatial coherence estimates to obtain and the mathematical relationship between the said weighted factor are set in advance, obtain spatial coherence through said data relationship and estimate the corresponding weighted factor of value that obtains.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110136446.3A CN102801457B (en) | 2011-05-24 | Modulation coding mode processing method and processing device | |
| PCT/CN2011/080815 WO2012159408A1 (en) | 2011-05-24 | 2011-10-14 | Modulation and coding manner processing method and device |
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| CN201110136446.3A CN102801457B (en) | 2011-05-24 | Modulation coding mode processing method and processing device |
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