CN105262525A - Subcarrier clustering pre-coding method of multi-input-multi-output orthogonal frequency division multiplexing system - Google Patents

Abstract

The invention discloses a subcarrier clustering pre-coding method of a multi-input-multi-output orthogonal frequency division multiplexing system. The method comprises the steps of: utilizing a training sequence Ts to estimate a channel autocorrelation function R (t, f); utilizing an absolute capacity loss formula or a relative channel capacity loss formula to calculate a channel correlation threshold [zeta] under constraint of a capacity loss threshold Th; carrying out clustering on subcarriers according to a clustering rule; utilizing the training sequence Ts to estimate a channel fading matrix on a clustering central subcarrier (nc, kc), and updating the channel autocorrelation function; calculating the channel capacity on a central carrier, and distributing code stream speeds according to the capacity after loss; and finally carrying out clustering pre-coding on transmitted code streams according to a carrier clustering result, and returning a signal sequence Ps after the clustering pre-coding process.

Description

Multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding

Technical field

The present invention is subordinate to intelligent Large Copacity wireless communication field, the problem of process multi-I/O OFDM (MIMO-OFDM) system sub-carriers intelligence sub-clustering precoding.

Background technology

MIMO-OFDM system combines the Large Copacity of multiple-input and multiple-output (MIMO) technology, anti-fading characteristic and the anti-multipath of OFDM (OFDM) technology, the advantage of mitigating frequency-selective fading, while raising communications system transmission speed, effectively improve system reliability.

In order to support the demodulation of receiving terminal MIMO signal, transmitting terminal needs to carry out precoding when known complete channel state (CSI) to transmission signal, pre-encode operation can reduce receiving terminal demodulated complex degree, promote channel utilization, but materially increases the encoder complexity of transmitting terminal.When antenna number and number of sub carrier wave more, for communication system, this complexity can cause serious system resource overhead.Effective solution is exactly that sub-carrier carries out sub-clustering at present, utilizes the CSI of bunch central subcarrier to be similar to and portrays the sub-carrier channel state of same bunch and carry out precoding, reduce the exponent number of pre-coding matrix significantly, thus reduce encoder complexity.But this subcarrier cluster-dividing method can introduce certain mismatch between coding and sub-carrier channels, causes channel capacity to lose.

Consider a MIMO-OFDM communication system as shown in Figure 1.Transmitting terminal number of antennas is N _t, receiving terminal number of antennas is N _r, OFDM number of sub carrier wave is K.Within the system, the signal on each road antenna transmitting terminal through serioparallel exchange and carry out K rank-IFFT operate after be namely assigned on K OFDM subcarrier.Signal on each subcarrier is extracted separately the MIMO signal be on each OFDM subcarrier.Contiguous several subcarriers are divided into cluster, are designated as sub-clustering size S with the number of sub carrier wave in cluster, use unified pre-coding matrix to carry out precoding to the subcarrier of the S in same cluster, be subcarrier sub-clustering precoding algorithms.Use this kind of algorithm can effectively reduce precoding complexity, but have also been introduced the mismatch between channel and encoder matrix simultaneously, cause capacitance loss.Therefore, between capacitance loss and system complexity, there is certain balance.

Summary of the invention

For the problems referred to above, the invention provides a kind of method large according to the sub-clustering of channel capacity loss threshold adaptive adjustment sub-clustering precoding sub-carriers.

To achieve the above object of the invention, multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding of the present invention, described method comprises:

Training sequence Ts is utilized to estimate channel auto-correlation R (t, f);

Predetermined channel capacitance loss threshold value T _h;

Calculate described channel capacity loss threshold value T _hchannel auto-correlation threshold value ζ under constraint;

Based on sub-clustering rule, the subcarrier (n, k) meeting sub-clustering rule is divided into cluster, described sub-clustering rule is: $(f^{(k,k_c)},t^{(n,n_c)})\∈X=\left\{\right(f,t\left)\right|R(f,t)\≥\mathrm{\ζ}\},$ Wherein

represent a kth subcarrier and kth _cdifference on the frequency between individual subcarrier;

represent the n-th time slot and n-th _ctime difference between individual time slot;

K is carrier index, represents that current sub-carrier is a kth subcarrier in K subcarrier;

K _ccentered by subcarrier subscript, represent the subscript of carrier wave grouping rear center subcarrier;

N is slot index, represents the n-th time slot from Signal transmissions;

N _ccenter time slot subscript, represents the subscript of carrier wave grouping rear center's subcarrier place time slot;

Further, also comprise:

Training sequence Ts is utilized to estimate sub-clustering central subcarrier (n _c, k _c) on channel fading matrix

Channel capacity on computer center's carrier wave, and according to the capacity assigned code flow rate after loss;

Based on carrier wave sub-clustering result, sub-clustering precoding is carried out to transmission code stream, obtain the burst P after sub-clustering precoding _s.

Particularly, channel capacity loss T _hwith the pass of channel auto-correlation threshold value ζ be:

$f_{ABloss}={\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}(\mathrm{\ρ}/N_t,\mathrm{\ζ})---\left(1\right)$

With

$f_{REloss}=\frac{{\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}(\mathrm{\ρ}/N_t,\mathrm{\ζ})}{{\log }_2\left(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{1k}\underset{i=1}{\overset{k-1}{\Π}}\left(u-i\right)\right)},---\left(2\right)$

Wherein,

F _aBlossfor absolute channel capacitance loss, f _rElossfor Relative channel capacitance loss;

Wherein, when with n-th _ctime slot, kth _ccSI on individual subcarrier is to the n-th time slot, _kwhen individual subcarrier carries out precoding, channel capacity is lost change with the change of channel mismatch, channel capacity is lost the upper bound be:

Wherein for the power on every root antenna;

${\mathrm{\γ}}_e=\frac{{\mathrm{\σ}}_{x_n^{\left(k\right)}}^2}{{\mathrm{v\σ}}_{h_{n,n_c}^{(k,k_c)}}^2{\mathrm{\σ}}_{x_n^{\left(k\right)}}^2+{\mathrm{\σ}}_{w_n^{\left(k\right)}}^2}I$ For the equivalent signal-to-noise ratio of mismatched channel;

be the channel status on the n-th time slot, a kth subcarrier, formula is expressed as:

Getting above-mentioned formula (3) expects ergodic capacity loss is:

${\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}={\log }_2\left(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{1k}\underset{i=1}{\overset{k-1}{\Π}}\left(u-i\right)\right)-{\log }_2\left(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{2k}{e}^{\underset{i=0}{\overset{k-1}{\Σ}}\mathrm{\ψ}(u-i)}\right);$

Wherein,

Maximum u=max{N in transmitting terminal and receiving terminal antenna number _t, N _r, v=min{N _t, N _r; ,

$\mathrm{\ψ}\left(x\right)=-\mathrm{\ζ}+\underset{r=1}{\overset{x-1}{\Σ}}\frac{1}{r};$

Constant ζ=0.577215649 ... α _k=γ ^kv (v-1) ... (v-k+1)/k! ;

α _1kwith α _2kfor substituting into adaptive and mismatch equivalent signal-to-noise ratio γ respectively _eα in situation _k;

Equivalent signal-to-noise ratio γ _ebe defined as follows

Channel auto-correlation and channel mismatch relation be expressed as follows;

${\mathrm{\σ}}_{h_{n,n_c}^{(k,k_c)}}^2=2(1-R_f(f^{(k,k_c)}\left)R_t\right(t^{(n,n_c)}\left)\right),$

Wherein, subcarrier k and k _cbetween frequency difference;

what represent is frequency domain autocorrelation value;

time slot n and n _cbetween the time difference

what represent is time domain autocorrelation value.

Particularly, every cluster sub-carriers number S is

Wherein B _t, B _fbe respectively time-domain and frequency-domain subcarrier spacing.

Multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding of the present invention, for MIMO-OFDM precoding technique sub-carriers self adaptation sub-clustering problem, provide a kind of method carrying out Intelligent adjustment subcarrier sub-clustering size according to system service quality requirement.Thus the effective control realized system service quality, and make system can obtain effective compromise between capacitance loss and complexity overhead.When channel quality is poor, system can reduce capacitance loss threshold value by the mode of reduction subcarrier sub-clustering size, namely obtains preferably system service quality by increasing system complexity expense; And under good channel circumstance, user is insensitive to the reduction of system service quality, and system then can reduce system complexity expense by the mode suitably increasing subcarrier sub-clustering size.

Accompanying drawing explanation

Fig. 1 is MIMO-OFDM communication system illustraton of model of the present invention;

Fig. 2 is multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding of the present invention, uses a series of rhombus carrier wave to be carried out to the schematic diagram carrier wave sub-clustering schematic diagram of sub-clustering under different time sections, different situation.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

As shown in Figure 1, a MIMO-OFDM communication system illustraton of model.Transmitting terminal number of antennas is N _t, receiving terminal number of antennas is N _r, OFDM number of sub carrier wave is K.Within the system, the signal on each road antenna transmitting terminal through serioparallel exchange and carry out K rank-IFFT operate after be namely assigned on K OFDM subcarrier.Signal on each subcarrier is extracted separately the MIMO signal be on each OFDM subcarrier.Contiguous several subcarriers are divided into cluster, are designated as sub-clustering size S with the number of sub carrier wave in cluster, use unified pre-coding matrix to carry out precoding to the subcarrier of the S in same cluster, be subcarrier sub-clustering precoding algorithms.Use this kind of algorithm can effectively reduce precoding complexity, but have also been introduced the mismatch between channel and encoder matrix simultaneously, cause capacitance loss.Therefore, between encoder complexity and channel capacity, there is balance displacement.

Embodiment 1

The present embodiment multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding, described method comprises:

Training sequence Ts is utilized to estimate channel auto-correlation R (t, f);

Predetermined channel capacitance loss threshold value T _h;

Calculate described channel capacity loss threshold value T _hchannel auto-correlation threshold value ζ under constraint;

Based on sub-clustering rule, the subcarrier (n, k) meeting sub-clustering rule is divided into cluster, described sub-clustering rule is: $(f^{(k,k_c)},t^{(n,n_c)})\∈X=\left\{\right(f,t\left)\right|R(f,t)\≥\mathrm{\ζ}\},$ Wherein

represent a kth subcarrier and kth _cdifference on the frequency between individual subcarrier;

represent the n-th time slot and n-th _ctime difference between individual time slot;

K is carrier index, represents that current sub-carrier is a kth subcarrier in K subcarrier;

K _ccentered by subcarrier subscript, represent the subscript of carrier wave grouping rear center subcarrier;

N is slot index, represents the n-th time slot from Signal transmissions;

N _ccenter time slot subscript, represents the subscript of carrier wave grouping rear center's subcarrier place time slot.

The present embodiment, regulates the method for sub-clustering precoding sub-carriers sub-clustering size S according to channel capacity loss threshold adaptive.The present embodiment, according to capacitance loss threshold value T _h(one-to-one relationship is by absolute channel capacitance loss f for anti-release auto-correlation threshold value ζ _aBlosswith Relative channel capacitance loss f _rElossmonotonicity ensure), can obtain sub-clustering scheme is be divided into cluster to carry out precoding all subcarriers (n, k) meeting sub-clustering rule.

Be below the present embodiment capacitance loss threshold value T _hthe concrete derivation of anti-release auto-correlation threshold value ζ.

When with n-th _ctime slot, kth _ccSI on individual subcarrier is to the n-th time slot, _kwhen individual subcarrier carries out precoding, channel capacity is lost change with the change of channel mismatch, channel capacity is lost the upper bound be:

Wherein for the power on every root antenna;

${\mathrm{\γ}}_e=\frac{{\mathrm{\σ}}_{x_n^{\left(k\right)}}^2}{{\mathrm{v\σ}}_{h_{n,n_c}^{(k,k_c)}}^2{\mathrm{\σ}}_{x_n^{\left(k\right)}}^2+{\mathrm{\σ}}_{w_n^{\left(k\right)}}^2}I$ For the equivalent signal-to-noise ratio of mismatched channel;

be the channel status on the n-th time slot, a kth subcarrier, formula is expressed as:

Getting above-mentioned formula (3) expects ergodic capacity loss is:

${\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}={\log }_2\left(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{1k}\underset{i=1}{\overset{k-1}{\Π}}\left(u-i\right)\right)-{\log }_2\left(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{2k}{e}^{\underset{i=0}{\overset{k-1}{\Σ}}\mathrm{\ψ}(u-i)}\right);$

Wherein,

Maximum u=max{N in transmitting terminal and receiving terminal antenna number _t, N _r, v=min{N _t, N _r; ,

$\mathrm{\ψ}\left(x\right)=-\mathrm{\ζ}+\underset{r=1}{\overset{x-1}{\Σ}}\frac{1}{r};$

Constant ζ=0.577215649 ... α _k=γ ^kv (v-1) ... (v-k+1)/k! ;

α _1kwith α _2kfor substituting into adaptive and mismatch equivalent signal-to-noise ratio γ respectively _eα in situation _k;

Equivalent signal-to-noise ratio γ _ebe defined as follows

Channel auto-correlation and channel mismatch relation be expressed as follows;

${\mathrm{\σ}}_{h_{n,n_c}^{(k,k_c)}}^2=2(1-R_f(f^{(k,k_c)}\left)R_t\right(t^{(n,n_c)}\left)\right),$

Wherein, subcarrier k and k _cbetween frequency difference;

what represent is frequency domain autocorrelation value;

time slot n and n _cbetween the time difference

what represent is time domain autocorrelation value.

In the present embodiment, channel capacity loss T _hwith the pass of channel auto-correlation threshold value ζ be:

$f_{ABloss}={\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}(\mathrm{\ρ}/N_t,\mathrm{\ζ})---\left(1\right)$

With

$f_{REloss}=\frac{{\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}(\mathrm{\ρ}/N_t,\mathrm{\ζ})}{{\log }_2\left(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{1k}\underset{i=1}{\overset{k-1}{\Π}}\left(u-i\right)\right)},---\left(2\right)$

Wherein,

F _aBlossfor absolute channel capacitance loss, f _rElossfor Relative channel capacitance loss.

Further, according to the detachable property of the auto-correlation function under independent scattering condition, this encoding scheme can be expressed as intuitively: use time domain direction diagonal line length frequency domain direction diagonal line length a series of rhombuses carrier wave plane is divided, the subcarrier in same rhombus is divided into cluster.As shown in Figure 2, the schematic diagram for using a series of rhombus carrier wave to be carried out to sub-clustering under different time sections, different situation.A, b, c, d tetra-part figure represent along with the autocorrelative continuous change of channel, the process that nested design parameter constantly regulates.Such as, packet parameters in a part no longer meets system capacity requirements at that time because channel auto-correlation changes in time, therefore formulate new packet parameters as shown in green portion for new channel autocorrelation parameter, time block length obtains lengthening, frequency block length reduced.

Carry out sub-clustering according to method sub-carrier described in the present embodiment, every cluster sub-carriers number S is

Wherein B _t, B _fbe respectively time-domain and frequency-domain subcarrier spacing.

Embodiment 2

The present embodiment the present embodiment multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding, the basis of embodiment 1 also comprises the steps also namely carry out precoding to transmission code stream, wherein said method for precoding is as follows:

Training sequence Ts is utilized to estimate sub-clustering central subcarrier (n _c, k _c) on channel fading matrix

Channel capacity on computer center's carrier wave, and according to the capacity assigned code flow rate after loss;

Based on carrier wave sub-clustering result, sub-clustering precoding is carried out to transmission code stream, obtain the burst P after sub-clustering precoding _s.

The running of method of the present invention is as follows:

Input:

MIMO-OFDM structure { N _t, N _r, K};

Training sequence Ts;

Receiving terminal work signal to noise ratio

Capacitance loss threshold value T _h;

Export:

Burst P after sub-clustering precoding _s.

The implication that symbol in the present invention is corresponding with it refers to following table.

Above; be only preferred embodiment of the present invention, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, the protection range that protection scope of the present invention should define with claim is as the criterion.

Claims (4)

1. a multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding, is characterized in that, described method comprises:

Training sequence Ts is utilized to estimate channel auto-correlation R (t, f);

Predetermined channel capacitance loss threshold value T _h;

Calculate described channel capacity loss threshold value T _hchannel auto-correlation threshold value ζ under constraint;

Based on sub-clustering rule, the subcarrier (n, k) meeting sub-clustering rule is divided into cluster, described sub-clustering rule is: $(f^{(k,k_c)},t^{(n,n_c)})\∈X=\left\{\right(f,t\left)\right|R(f,t)\≥\mathrm{\ζ}\},$ Wherein

represent a kth subcarrier and kth _cdifference on the frequency between individual subcarrier;

represent the n-th time slot and n-th _ctime difference between individual time slot;

K is carrier index, represents that current sub-carrier is a kth subcarrier in K subcarrier;

K _ccentered by subcarrier subscript, represent the subscript of carrier wave grouping rear center subcarrier;

N is slot index, represents the n-th time slot from Signal transmissions;

N _ccenter time slot subscript, represents the subscript of carrier wave grouping rear center's subcarrier place time slot.

2. multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding according to claim 1, is characterized in that, also comprise:

Training sequence Ts is utilized to estimate sub-clustering central subcarrier (n _c, k _c) on channel fading matrix

Channel capacity on computer center's carrier wave, and according to the capacity assigned code flow rate after loss;

Based on carrier wave sub-clustering result, sub-clustering precoding is carried out to transmission code stream, obtain the burst P after sub-clustering precoding _s.

3. multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding according to claim 1, is characterized in that,

Channel capacity loss T _hwith the pass of channel auto-correlation threshold value ζ be:

$f_{ABloss}={\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}(\mathrm{\ρ}/N_t,\mathrm{\ζ})---\left(1\right)$

With

$f_{REloss}=\frac{{\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}(\mathrm{\ρ}/N_t,\mathrm{\ζ})}{{\log }_2(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{1k}\underset{i=1}{\overset{k-1}{\Π}}(u-i))}---,\left(2\right)$

Wherein,

F _aBlossfor absolute channel capacitance loss, f _rElossfor Relative channel capacitance loss;

Wherein, when with n-th _ctime slot, kth _ccSI on individual subcarrier is to the n-th time slot, _kwhen individual subcarrier carries out precoding, channel capacity is lost change with the change of channel mismatch, channel capacity is lost the upper bound be:

Wherein for the power on every root antenna;

for the equivalent signal-to-noise ratio of mismatched channel;

be the channel status on the n-th time slot, a kth subcarrier, formula is expressed as:

Getting above-mentioned formula (3) expects ergodic capacity loss is:

${\mathrm{\ϵ}}_{n,n_c}^{(k,k_c)}={\log }_2(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{1k}\underset{i=1}{\overset{k-1}{\Π}}\left(u-i\right))-{\log }_2(1+\underset{k=1}{\overset{v}{\Σ}}{\mathrm{\α}}_{2k}{e}^{\underset{i=1}{\overset{k-1}{\Π}}\mathrm{\ψ}(u-i)});$

Wherein,

Maximum u=max{N in transmitting terminal and receiving terminal antenna number _t, N _r, v=min{N _t, N _r; ,

$\mathrm{\ψ}\left(x\right)=-\mathrm{\ζ}+\underset{r=1}{\overset{x-1}{\Σ}}\frac{1}{r};$

Constant ζ=0.577215649 α _k=γ ^kv (v-1) (v-k+1)/k! ;

α _1kwith α _2kfor substituting into adaptive and mismatch equivalent signal-to-noise ratio γ respectively _eα in situation _k;

Equivalent signal-to-noise ratio γ _ebe defined as follows

Channel auto-correlation and channel mismatch relation be expressed as follows:

${\mathrm{\σ}}_{h_{n,n_c}^{(k,k_c)}}^2=2(1-R_f(f^{(k,k_c)}\left)R_t\right(t^{(n,n_c)}\left)\right),$

Wherein, subcarrier k and k _cbetween frequency difference;

what represent is frequency domain autocorrelation value;

time slot n and n _cbetween the time difference

what represent is time domain autocorrelation value.

4., according to the arbitrary described multi-input multi-output orthogonal frequency division multiplexing system subcarrier sub-clustering method for precoding of claims 1 to 3, it is characterized in that, every cluster sub-carriers number S is

Wherein B _t, B _fbe respectively time-domain and frequency-domain subcarrier spacing.