CN103944702A - Pilot frequency overlapping method for multi-carrier Large-Scale MIMO system - Google Patents

Abstract

The invention relates to a pilot frequency overlapping method for a multi-carrier Large-Scale MIMO system. The pilot frequency overlapping method comprises the steps that firstly, data to be transmitted are coded according to MIMO codes; secondly, pilot frequencies of different transmitting antennas are inserted into the coded data to be transmitted according to preset rules; thirdly, time domain OFDM symbols are generated through fast Fourier transformation; fourthly, the data of the different antennas are processed and transmitted. The pilot frequency overlapping method is suitable for the MIMO system, particularly the Large-Scale MIMO system; the sparse characteristic and space-time correlation of MIMO channels are utilized in the method; by means of the pilot frequency overlapping method, frequency piloting cost can be effectively lowered, and high spectrum efficiency can be achieved; multiple MIMO channel estimations can be obtained simultaneously according to received overlapped pilot frequencies, so that high spectrum efficiency and usability are achieved. The invention further discloses a pilot frequency overlapping device for the multi-carrier Large-Scale MIMO system.

Description

A kind of overlapping pilot frequency system of multicarrier Large-Scale mimo system

Technical field

The present invention relates to digital information transmission technical field, relate in particular to a kind of overlapping pilot frequency system of multicarrier Large-Scale mimo system.

Background technology

OFDM(Orthogonal Frequency Division Multiplexing, OFDM) and MIMO(Multiple Input Multiple Output, Multiinputoutput) technology is due to its outstanding ability of anti-multipath and spectral efficient, is widely regarded as two key physical layer technology of future broadband wireless communication systems.

At present, the extensive a large amount of antenna of this concept utilization of MIMO technology, wherein antenna amount possibility hundreds of, even thousands of, in same running time-frequency resource, provide service to multiple users simultaneously, can obtain the spectrum efficiency even higher up to tens bit/s/Hz.For example, 12 × 12 mimo system has been demonstrated by Japanese NTT DoCoMo company, has realized the transmission rate of 4.92Gbps in the bandwidth of 100MHz, and its spectrum efficiency approaches 50bit/s/Hz; Also begin one's study 16 × 16 MIMO antenna configuration of the evolution standard IEEE802.11ac of WLAN, to realize the high-speed radio transmission of 1Gbit/s.

In MIMO-OFDM system, channel condition information is the important prerequisite that ensures its systematic function accurately.In short, the channel estimation methods in MIMO-OFDM system can be divided into two classes: frequency domain algorithm for estimating and time domain algorithm for estimating.Frequency domain algorithm for estimating utilizes orthogonal guide frequency the channel estimation problems in mimo system directly can be transferred to for the channel estimation problems in single-input single-output system (Single-Input Single-Output, SISO); On the other hand, the time-domain channel estimating method based on targeting sequencing (Preamble) has utilized all subcarriers, therefore can provide more reliable channel estimation results in slow change channel.

Frequency domain in channel estimation methods in MIMO-OFDM system is estimated computational methods, and required pilot number is linear increasing along with the increase of antenna number, and for the huge extensive MIMO technology of number of antennas, this can cause very high system pilot expense.In order to ensure that the pilot-frequency expense in mimo system can be not too high, common way is to reduce the equivalent pilot density of each antenna, but this can cause the obvious decline of precision of channel estimation.Time domain algorithm for estimating in channel estimation methods in MIMO-OFDM system on the other hand, while change when channel in extensive mimo system, targeting sequencing must frequently insert, and to follow the tracks of in time fast-changing channel, finally causes the expense of targeting sequencing still larger.

Summary of the invention

Technical problem to be solved by this invention is how effectively to reduce pilot-frequency expense and obtain high spectrum frequency.The present invention can obtain by the overlapping pilot tone receiving the estimation of multiple mimo channels simultaneously.

For this purpose, the present invention proposes a kind of overlapping pilot frequency system of multicarrier Large-Scale mimo system, described method specifically comprises:

S1: data to be transmitted is encoded according to MIMO coding;

S2: the data to be transmitted after the pilots insertion of different transmit antennas being encoded with preset rules;

S3: by fast Fourier transform, generate time domain OFDM symbol;

S4: the data of different antennae are launched through processing.

Particularly, the pilot tone common sparing of described different transmit antennas or whole identical subcarrier in frequency domain.

Particularly, the pilot tone of described different transmit antennas has corresponding pilot frequency sequence.

Further, described step S3 further comprises:

S31: the signal that extracts and obtain the corresponding subcarrier of pilot tone place;

S32: according to the Signal estimation channel relevant to different transmit antennas at the corresponding subcarrier of the pilot tone obtaining place.

For this purpose, the present invention proposes a kind of overlapping pilot tone device of multicarrier Large-Scale mimo system, comprising:

Coding module, for encoding transmission data according to MIMO coding;

Insert module, for the data to be transmitted after the pilots insertion of different transmit antennas being encoded with preset rules;

Time domain OFDM symbol generation module, for by fast Fourier transform, generates time domain OFDM symbol;

Transmitter module, for launching the data of different antennae through processing.

Particularly, described time domain OFDM symbol generation module also comprises:

Pilot frequency sequence generation unit, for generating pilot frequency sequence corresponding to different transmit antennas;

Pilot frequency design generation unit, the position of inserting frequency-domain OFDM symbol sub-carriers for generating pilot tone;

Time domain OFDM symbol generation unit, for generating time domain OFDM symbol according to frequency-domain OFDM symbol, and adds that protection interval forms the complete OFDM symbol at a band protection interval.

Further, also comprise:

Pilot extraction module, for extracting receiving terminal through the frequency domain data at the frequency-domain OFDM symbol pilot sub-carrier place of DFT acquisition;

Channel estimation module, for estimating according to the data acquisition mimo channel at the pilot tone place extracting.

By adopting the overlapping pilot frequency system of a kind of multicarrier Large-Scale mimo system disclosed in this invention, be applicable to mimo system, especially extensive mimo system.The method has been utilized sparse characteristic and the space-time correlation of mimo channel, utilize in the present invention overlapping pilot tone can effectively reduce pilot-frequency expense and obtain spectral efficient, channel estimating can obtain multiple mimo channels according to the overlapping pilot tone receiving simultaneously and estimate to have spectral efficient and ease for use.The invention also discloses a kind of overlapping pilot tone device of multicarrier Large-Scale mimo system.

Brief description of the drawings

Can more clearly understand the features and advantages of the present invention by reference to accompanying drawing, accompanying drawing is schematically to should not be construed as the present invention is carried out to any restriction, in the accompanying drawings:

Fig. 1 shows the flow chart of steps of the overlapping pilot frequency system of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention;

Fig. 2 shows the present invention and in OFDM frequency domain symbol, inserts the structural representation after pilot tone;

Fig. 3 shows the flow chart of steps of the channel estimation methods of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention;

Fig. 4 shows conventional orthogonal pilot frequency system and overlapping pilot frequency system contrast effect figure;

Fig. 5 (a) (b) (c) shows the structural representation of the overlapping pilot tone device of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, embodiments of the present invention is described in detail.

As shown in Figure 1, be the overlapping pilot frequency system of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention, the method specifically comprises the following steps:

Step S1: data to be transmitted is encoded according to MIMO coding.

Particularly, MIMO is encoded to the Space Time Coding theory based on existing maturation, as vertical-Belle experiment Layered Space-Time Coding Technology.

Step S2: the data to be transmitted after the pilots insertion of different transmit antennas being encoded with preset rules.Wherein, in OFDM frequency domain symbol, insert pilot tone, as shown in Figure 2.

Further, the pilot tone common sparing of different transmit antennas or whole identical subcarrier in frequency domain; The pilot tone of different transmit antennas has corresponding pilot frequency sequence.

Step S3: by fast Fourier transform, generate time domain OFDM symbol.

Step S4: the data of different antennae are launched through processing.

Particularly; the pilot frequency sequence of each transmitting antenna is orthogonal; can have Zadoff-Chu sequence with and cyclic shift version form; and the OFDM frequency domain symbol of the pilot tone of each transmitting antenna and frequency domain data frequency division multiplexing is transformed into time domain OFDM symbol by IDFT, and add that protection interval forms the complete OFDM symbol with protection interval.

As shown in Figure 3, the channel estimation methods of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention, its method specifically comprises the following steps:

Step S31: the signal that extracts and obtain the corresponding subcarrier of pilot tone place.

Step S32: according to the Signal estimation channel relevant to different transmit antennas at the corresponding subcarrier of the pilot tone obtaining place.

Particularly, at N _t× N _rin mimo system, i transmitting antenna receives pilot tone to j reception antenna and is:

$y^{(i,j)}=\mathrm{diag}\left\{s_i\right\}F{|}_{\mathrm{\Ω}}\left[\begin{array}{c}{h}^{(i,j)}\\ 0_{(N-L)\×1}\end{array}\right]+w^{(i,j)}=S_i{F}_L{|}_{\mathrm{\Ω}}{h}^{(i,j)}+w^{(i,j)}={\mathrm{\Φ}}_i{h}^{(i,j)}+w^{(i,j)}$

Here h ^{(i, j)}be i transmitting antenna to the channel impulse response between j reception antenna, maximum length is L; F| _Ωthat N × N dimension Fourier matrix F is got to part Fourier's matrix that row forms by Ω; Ω is pilot frequency design; s _ibe the pilot frequency sequence of i transmitting antenna, the pilot frequency sequence of different antennae can consist of Zadoff-Chu sequence and cyclic shift version thereof, because Zadoff-Chu sequence has good cyclic orthogonal experiment; Diag{s _ia diagonal matrix, diagonal element is by s _iform; S _i=diag{s _i; F _lbe a N × L dimension part Fourier matrix, formed by the front L row of F; Φ _i=S _if _l| _Ω.

Because the different antennae of making a start shares identical pilot frequency design, receiving pilot frequency sequence can be expressed as: $y^j=\underset{i=1}{\overset{N_t}{\mathrm{\Σ}}}{y}^{(i,j)}=[{\mathrm{\Φ}}_1,{\mathrm{\Φ}}_2,...{\mathrm{\Φ}}_{N_t}]\left[\begin{array}{c}{h}^{(1,j)}\\ h^{(2,j)}\\ .\\ .\\ .\\ h^{(N_t,j)}\end{array}\right]+\underset{i=1}{\overset{N_t}{\mathrm{\Σ}}}{w}^{(i,j)}=\mathrm{\Θ}{\tilde{h}}_j+w_j$

Here $\mathrm{\Θ}=[{\mathrm{\Φ}}_1,{\mathrm{\Φ}}_2,...{\mathrm{\Φ}}_{N_t}],{\tilde{h}}_j=\left[\begin{array}{c}{h}^{(1,j)}\\ h^{(2,j)}\\ .\\ .\\ .\\ h^{(N_t,j)}\end{array}\right],$ Due to the sparse characteristic of wireless channel, h ^{(i, j)}sparse, so also be sparse.For shape as underdetermined equation, be sparse, this can utilize the related algorithm of compressed sensing to come to recover higher-dimension channel impulse response from low-dimensional pilot tone

As shown in Figure 4, the overlapping pilot frequency system contrast effect figure of conventional orthogonal pilot frequency system and proposition.

Particularly, traditional orthogonal guide frequency method requires different transmit antennas pilot frequency design to keep orthogonal in frequency domain, time domain, code territory etc.; Overlapping pilot frequency system allows the pilot tone of different transmit antennas to share identical pilot frequency design.

If Fig. 5 (a) is (b) as shown in (c), the structure of the overlapping pilot tone device of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention.

Fig. 5 (a) is the overall structure of the overlapping pilot tone device of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention.

Particularly, coding module 501 is for encoding transmission data according to MIMO coding; Insert module 502 is for the data to be transmitted after the pilots insertion of different transmit antennas being encoded with preset rules; Time domain OFDM symbol generation module 503, for by fast Fourier transform, generates time domain OFDM symbol; Transmitter module 504 is for launching the data of different antennae through processing.

Fig. 5 (b) is the structure of the configuration device that transmits of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention.

Particularly, the said equipment comprises coding module 501 and time domain OFDM symbol generation module 503.

Further, time domain OFDM symbol generation module 503 also comprises: pilot frequency sequence generation unit 5031 is for generating pilot frequency sequence corresponding to different transmit antennas; Pilot frequency design generation unit 5032 inserts the position of frequency-domain OFDM symbol sub-carriers for generating pilot tone; Time domain OFDM symbol generation unit 5033 is for generating time domain OFDM symbol and adding that protection interval forms the complete OFDM symbol at a band protection interval according to frequency-domain OFDM symbol.

Fig. 5 (c) is the structure of the configuration device that transmits of a kind of multicarrier Large-Scale mimo system in the embodiment of the present invention.

Particularly, the said equipment comprises that pilot extraction module 505 is for receiving terminal is extracted through the frequency domain data at the frequency-domain OFDM symbol pilot sub-carrier place of DFT acquisition, and channel estimation module 506 is for estimating according to the data acquisition mimo channel at the pilot tone place extracting.

By adopting the overlapping pilot frequency system of a kind of multicarrier Large-Scale mimo system disclosed in this invention, be applicable to mimo system, especially extensive mimo system.The method has been utilized sparse characteristic and the space-time correlation of mimo channel, utilize in the present invention overlapping pilot tone can effectively reduce pilot-frequency expense and obtain spectral efficient, channel estimating can obtain multiple mimo channels according to the overlapping pilot tone receiving simultaneously and estimate to have spectral efficient and ease for use.

Although described by reference to the accompanying drawings embodiments of the present invention, but those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, such amendment and modification all fall into by within claims limited range.

Claims (7)

1. an overlapping pilot frequency system for multicarrier Large-Scale mimo system, is characterized in that, described method specifically comprises:

S1: data to be transmitted is encoded according to MIMO coding;

S2: the data to be transmitted after the pilots insertion of different transmit antennas being encoded with preset rules;

S3: by fast Fourier transform, generate time domain OFDM symbol;

S4: the data of different antennae are launched through processing.

2. the method for claim 1, is characterized in that, the pilot tone common sparing of described different transmit antennas or whole identical subcarrier in frequency domain.

3. the method for claim 1, is characterized in that, the pilot tone of described different transmit antennas has corresponding pilot frequency sequence.

4. the method for claim 1, is characterized in that, described step S3 further comprises:

S31: the signal that extracts and obtain the corresponding subcarrier of pilot tone place;

S32: according to the Signal estimation channel relevant to different transmit antennas at the corresponding subcarrier of the pilot tone obtaining place.

5. an overlapping pilot tone device for multicarrier Large-Scale mimo system, is characterized in that, comprising:

Coding module, for encoding transmission data according to MIMO coding;

Insert module, for the data to be transmitted after the pilots insertion of different transmit antennas being encoded with preset rules;

Time domain OFDM symbol generation module, for by fast Fourier transform, generates time domain OFDM symbol;

Transmitter module, for launching the data of different antennae through processing.

6. device as claimed in claim 5, is characterized in that, described time domain OFDM symbol generation module also comprises:

Pilot frequency sequence generation unit, for generating pilot frequency sequence corresponding to different transmit antennas;

Pilot frequency design generation unit, the position of inserting frequency-domain OFDM symbol sub-carriers for generating pilot tone;

Time domain OFDM symbol generation unit, for generating time domain OFDM symbol and adding that protection interval forms the complete OFDM symbol at a band protection interval according to frequency-domain OFDM symbol.

7. device as claimed in claim 5, is characterized in that, also comprises:

Pilot extraction module, for extracting receiving terminal through the frequency domain data at the frequency-domain OFDM symbol pilot sub-carrier place of DFT acquisition;

Channel estimation module, for estimating according to the data acquisition mimo channel at the pilot tone place extracting.