CN101267414B - A flexible OFDM download communication system and its communication method - Google Patents

Abstract

An OFDMA (orthogonal frequency division multiple access) downlink communication system and a communication method, which makes communication information to be sent to each user at a transmitting terminal undergo IFFT transform with larger points and analog conversion (d/a conversion) to obtain a wide band analog OFDM signal, and makes RF signals to be received at a plurality of receiving terminal undergo each treatment so that each receiving terminal obtains a corresponding user narrow band discrete signal respectively, and makes the user narrow band discrete signal undergo each treatment including d/a conversion, spectrum removal and filtering to obtain a discrete narrow band base-band signal respectively, and obtains corresponding communication message by FFT transform with less points, so that radio resource of the wide band communication system is flexibly adaptable to various service requirement and terminal processing ability of multi-user, so as to reduce accomplishment complexity of mobile terminal and power consumption.

Description

A kind of OFDM downlink communication system and communication means

Technical field

The present invention relates to a kind of OFDM downlink communication system and communication means.

Background technology

In wireless communication system, especially in wide-band mobile communication system, the aerial signal transmission technology is just becoming the focus of research.For making wide-band mobile communication system obtain higher spectrum efficiency, for example up to the spectrum efficiency of 10bps/Hz, make the communication requirement of its support several scenes and support various adaptive control technologies, its signal transmission technology must have more any similar technology more performance than in the past, can keep the implementation complexity that can control simultaneously.

And the signal transmission technology of present wide-band mobile communication is the single carrier multiple access technology of representative with code division multiple access (CDMA) mainly and is the multicarrier multiple access technology of representative with OFDM (OFDM).Under the broadband wireless communications environment, be the influence of compensate for channel decline, complicated day by day based on the receiving terminal equalizer of the single carrier transmitting system of CDMA, thus limited this The Application of Technology.And be the multicarrier multi-address system of representative with OFDM, support flexibly frequency domain resource scheduling, simple receiving terminal equalization algorithm and be easy to and plurality of advantages such as multi-antenna technology combines because of it has, make it become one of main multiple access technology solution of future wireless system day by day.

At existing transmission system such as WiMAX, among the WiBro etc., down link portable terminal transmitter and base station receiver have adopted symmetrical structure, i.e. the Fourier transform (FFT) that count and the receiver of the inverse fourier transform (IFFT) of transmitter employing adopt is counted identical.And in following wide-band mobile communication system, along with the development of the more and more wideer and many speed of system's operation bandwidth, multimedia service, down link list CU bandwidth will be more and more asymmetric with system bandwidth.At this moment, if adopt the existing systems transmission plan, for the terminal of only supporting low rate traffic, it is the OFDM symbol of demodulation carrying low rate traffic, the also FFT conversion that must support and count more greatly, and like this, its implementation complexity and cost are difficult to control.

Therefore, how to solve the problem that exists in the existing OFDM technology and become the technical task that those skilled in the art need to be resolved hurrily in fact.

Summary of the invention

The object of the present invention is to provide a kind of OFDM downlink communication system and communication means, so that the Radio Resource of wide-band communication system adaptive multi-user's different business demand and terminal processing capacity deftly, and then reduce the implementation complexity and the power consumption of portable terminal.

Reach other purposes in order to achieve the above object, the invention provides a kind of OFDM downlink communication system and communication means, wherein, the OFDM downlink communication system of described dexterity comprises: transmitting terminal, it is used for sending to each user's communications information and carries out every processing to obtain broadband simulation orthogonal frequency-division multiplex base band signal, and according to default carrier frequency the orthogonal frequency-division multiplex base band signal is simulated in described broadband and carry out frequency translation to obtain radiofrequency signal, and with described radiofrequency signal and the described information that will send to each user the subcarrier allocation information in described broadband simulation orthogonal frequency-division multiplex base band signal is launched, wherein, every processing that the information that be transmitted to each user is carried out comprises subcarrier mapping processing, default first inverse fourier transform of counting and carry out digital-to-analogue conversion according to default first sampling interval; And a plurality of receiving terminals, it is used for receiving the subcarrier allocation information of radiofrequency signal that described transmitting terminal is emitted to and each user's information at described broadband simulation orthogonal frequency-division multiplex base band signal, and the radiofrequency signal that receives carried out every processing so that each receiving terminal obtains the discrete baseband signal in each self-corresponding user arrowband, and the discrete baseband signal in described user arrowband carried out behind default separately second Fourier transform of counting again according to corresponding each the telex network information of described subcarrier allocation information extraction, wherein, every processing that the radiofrequency signal of described reception is carried out comprises information the subcarrier allocation information in broadband simulation orthogonal frequency-division multiplex singal of each receiving terminal according to each user who receives, default processing bandwidth and default carrier frequency carry out frequency translation, filtering and analog-to-digital conversion.

Described transmitting terminal comprises: be used for to send to through ovennodulation described each user's communications information mapping to each the subcarrier mapping block on the corresponding subcarrier, be used for described each subcarrier is carried out the inverse fourier transform module of described first inverse fourier transform of counting, be used for adding the cyclic prefix adding module of prefix in the signal of process inverse fourier transform according to default rule, be used for the signal of described cyclic prefix adding module output is carried out digital-to-analogue conversion to obtain the D/A converter module of broadband simulation orthogonal frequency-division multiplex base band signal with described first sampling interval, be used for described broadband simulation orthogonal frequency-division multiplex base band signal is carried out frequency translation to obtain the up-conversion module of radiofrequency signal with default carrier frequency, any one receiving terminal in described a plurality of receiving terminal comprises: be used for carrying out first down conversion module of correspondent frequency conversion with the first wideband analog signal that obtains should having mutually frequency deviation according to the described radiofrequency signal that the information of default carrier frequency and the relative users that receives is received in the subcarrier allocation information butt joint of described broadband simulation orthogonal frequency-division multiplex base band signal, be used for having the first wideband analog signal of frequency deviation to carry out analogue low pass filtering with described to obtain first low-pass filtering module of corresponding user arrowband analog baseband signal according to the processing bandwidth of default relative users, be used for described user arrowband analog baseband signal being carried out analog-to-digital conversion to obtain first analog-to-digital conversion module of the discrete baseband signal in described user arrowband with second sampling interval according to the processing bandwidth of default relative users, be used for removing first prefix removal module of the prefix of the discrete baseband signal in described user arrowband according to default rule, be used for the discrete baseband signal in the user arrowband of removing prefix is carried out first Fourier transform module of second Fourier transform of counting, be used for separating mapping block from first subcarrier that the signal of described first Fourier transform module output obtains the signal on each CU subcarrier according to the subcarrier allocation information that receives, the signal that is used for described first subcarrier is separated mapping block output carries out the first channel equalization module that frequency domain equalization is handled, in addition, any one receiving terminal in described a plurality of receiving terminal also can comprise: be used for according to default carrier frequency the described radiofrequency signal that receives being carried out the correspondent frequency conversion to obtain second down conversion module of the second wideband analog signal, be used for first sampling interval described second wideband analog signal being carried out analog-to-digital conversion to obtain second analog-to-digital conversion module of the discrete baseband signal in first broadband according to the processing bandwidth of default relative users, be used in the subcarrier allocation information of described broadband simulation orthogonal frequency-division multiplex singal the discrete baseband signal in described first broadband being carried out corresponding frequency spectrum is moved the discrete baseband signal in second broadband of frequency deviation with acquisition frequency spectrum shift module according to the information of the relative users that receives, be used for having the discrete baseband signal in second broadband of frequency deviation to carry out second low-pass filtering module of corresponding filtering to described with the discrete baseband signal in arrowband of acquisition relative users over-sampling according to the processing bandwidth of default relative users, be used for the discrete baseband signal in the arrowband of described user's over-sampling being carried out the down sample module of corresponding down-sampling with the discrete baseband signal in user arrowband that obtains threshold sampling according to the processing bandwidth of the bandwidth of default broadband simulation orthogonal frequency-division multiplex base band signal and default relative users, be used for removing second prefix removal module of the prefix of the discrete baseband signal in described user arrowband according to default rule, be used for carrying out second Fourier transform module of second Fourier transform of counting according to the user arrowband that the processing bandwidth of default relative users will the be removed prefix baseband signal that disperses, be used for according to the subcarrier mapping ruler information that receives, second subcarrier that obtains the signal on each CU subcarrier from the signal of described second Fourier transform module output is separated mapping block, the signal that is used for described second subcarrier is separated mapping block output carries out the second channel balance module that frequency domain equalization is handled, wherein, second of the Fourier transform that described a plurality of receiving terminal adopts is separately counted and is less than or equal to first of inverse fourier transform that described transmitting terminal adopts respectively and counts, and second of the Fourier transform that adopts separately when described a plurality of receiving terminals is counted and is respectively N ₁, N ₂N _n, second sampling interval of Cai Yonging is respectively T separately ₁, T ₂T _n, first of the inverse fourier transform that described transmitting terminal adopts is counted and is N, and its first sampling interval of adopting is T, then satisfies condition: N _kT _k=NT, k=1,2 ... n, n are descending receiving terminal number, and described subcarrier allocation information comprises each user's frequency deviation positional information and subcarrier mapping ruler.

Described OFDM downlink communication means comprises step: 1) will send to each user's communications information and carry out respective sub mapping processing after preliminary treatment; 2) will preset first inverse fourier transform of counting through the communication information that the subcarrier mapping is handled; 3) add prefix in sending to each user's communications information according to preset rules through the described of described inverse fourier transform; 4) information of adding prefix is carried out digital-to-analogue conversion to form broadband simulation orthogonal frequency-division multiplex base band signal with the first default sampling interval; 5) according to default carrier frequency described broadband simulation orthogonal frequency-division multiplex base band signal is carried out frequency-conversion processing to obtain radiofrequency signal; 6) send described radiofrequency signal and the described subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user; 7) receive radiofrequency signal and the described subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user be sent to, and handle bandwidth and described default carrier frequency is converted to the discrete baseband signal in each user arrowband with described radiofrequency signal according to described subcarrier allocation information, each default user; 8) remove the prefix of the discrete baseband signal in described each user arrowband according to preset rules; 9) each the user arrowband discrete signal that will remove prefix carries out corresponding each default second Fourier transform of counting according to each default user processing bandwidth; 10) in the process signal of Fourier transform, extract each user's communications signal according to described subcarrier allocation information, and described signal of communication is carried out equilibrium treatment to obtain corresponding each telex network information.

Wherein, described preliminary treatment comprises chnnel coding and digital modulation, described second counts is less than or equal to described first and counts, and described step 7) also comprises step: (1) is converted to described radiofrequency signal the first wideband analog signal that frequency deviation is respectively arranged according to described subcarrier allocation information and default carrier frequency; (2) the processing bandwidth according to each default user has the wideband analog signal process analogue low pass filtering of frequency deviation to obtain user arrowband analog baseband signal with described; (3) respectively described user arrowband analog baseband signal is carried out analog-to-digital conversion to obtain the discrete baseband signal in each corresponding user arrowband according to each default user processing bandwidth with the second default separately sampling interval, and described separately second counts equals described first product of counting with described first sampling interval with the product in corresponding second sampling interval, in addition, described step 7) also can comprise step: (1) is converted to the second wideband analog signal according to default carrier frequency with described radiofrequency signal, and the centre frequency of the described second wideband analog signal is zero; (2) with first sampling interval described second wideband analog signal is carried out analog-to-digital conversion to obtain the discrete baseband signal in first broadband according to default broadband simulation orthogonal frequency-division multiplex base band signal bandwidth; (3) according to each user's who receives the subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal the discrete baseband signal in described first broadband being carried out corresponding frequency spectrum moves to obtain respectively to have the discrete baseband signal in second broadband of frequency deviation; (4) the processing bandwidth according to each default user has the discrete baseband signal in second broadband of frequency deviation to carry out the corresponding digital low-pass filtering with the discrete baseband signal in the arrowband that obtains over-sampling to described; 5) according to the bandwidth of default broadband simulation orthogonal frequency-division multiplex base band signal and each user's processing bandwidth the discrete baseband signal in the arrowband of described each over-sampling is carried out corresponding down-sampling with the discrete baseband signal in the user arrowband that obtains each threshold sampling, described first count the product with described first sampling interval equals described second product of counting with described second sampling interval, and described subcarrier allocation information comprises each user's frequency deviation positional information and subcarrier mapping ruler.

In sum, OFDM downlink communication system of the present invention and the communication means IFFT conversion that (sub-carrier number) can be less than or equal to transmitting terminal because the FFT conversion of receiving terminal is counted count (sub-carrier number), therefore the present invention's Radio Resource the different business demand and terminal processing capacity of adaptive multi-user deftly that can make wide-band communication system, thus the implementation complexity and the power consumption of portable terminal reduced.

Description of drawings

Fig. 1 is the basic framework schematic diagram of the OFDM downlink communication system of dexterity of the present invention.

Embodiment

See also Fig. 1, the OFDM downlink communication system of dexterity of the present invention comprises at least: transmitting terminal and a plurality of receiving terminal, be simplicity of illustration, and only illustrate two receiving terminals among Fig. 1, promptly first receiving terminal and second receiving terminal so are not to exceed with this diagram.

Described transmitting terminal is used for sending to each user's communications information and carries out every processing to obtain broadband simulation orthogonal frequency-division multiplex base band signal, and according to default carrier frequency the orthogonal frequency-division multiplex base band signal is simulated in described broadband and carry out frequency translation to obtain radiofrequency signal, and with described radiofrequency signal and the described information that will send to each user the subcarrier allocation information in described broadband simulation orthogonal frequency-division multiplex base band signal is launched, wherein, every processing that the information that will be transmitted to each user is carried out comprises subcarrier mapping processing, default first inverse fourier transform of counting and carry out digital-to-analogue conversion according to default first sampling interval, described subcarrier allocation information comprises each user's frequency deviation positional information and subcarrier mapping ruler.

Described transmitting terminal mainly comprises: a channel coding module, a modulation module, a subcarrier mapping block, an inverse fourier transform module, a cyclic prefix adding module, a D/A converter module, a up-conversion module and a transmitter module.

Described channel coding module is used for the original bit information that will send to each user is encoded, and its coded system is known to those skilled in the art to be known, and is no longer given unnecessary details at this.

Described modulation module is used for the bit information through coding that will send to each user is carried out digital modulation, and its modulation system is known to those skilled in the art to be known, and is no longer given unnecessary details at this.

Described subcarrier mapping block is used for the described information symbol that will send to each user through ovennodulation mapped on each corresponding subcarrier by the mapped specific rule and transmits, because the subcarrier that does not take transmission zero, each information symbol of establishing through ovennodulation is $\{{\tilde{a}}_k\left(m\right),m=\mathrm{0,1},...,N_k-1\}$ , it is output as parallel symbol data block { a after shining upon through subcarrier _k(m), m=0,1 ..., N-1} supposes through after the subcarrier mapping N of modulation _kThe OFDM symbol subcarrier sequence number collection that individual information symbol takies is Ω, and should group N _kThe frequency offset in all subcarriers of OFDM symbol of individual subcarrier is ε _kIndividual subcarrier is noted that, described mapped specific rule is known by those skilled in the art, does not repeat them here.

Described inverse fourier transform module is used for described each subcarrier is carried out described first inverse fourier transform of counting, for example, and to parallel symbol data block { a _k(m), m=0,1 ..., N-1} carries out forming corresponding data block sequence { b after the N point IFFT conversion _k(m), m=0,1 ..., N-1}, relation is each other obeyed $b_k\left(n\right)=\frac{1}{\sqrt{N}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right)\exp (j2\mathrm{\πmn}/N),$ Here, { b _kAlso represent a number of elements, it is the same column vector of IFFT transform size N.

Described cyclic prefix adding module is used for adding prefix in the signal through inverse fourier transform according to default rule; usually the protection of adding a length-specific at the head of the parallel data block of IFFT conversion output at interval; be used to reduce interchannel interference (preferably, this protection length at interval should greater than channel maximum delay extension length).For example, the part of the data block afterbody of described IFFT conversion output is copied to its front end, forms the data block symbols of final band Cyclic Prefix, soon data sequence { b _k(n), n=0,1 ..., N-1} is transformed into complete OFDM symbol data sequence { c _k(n), n=-C ... ,-1,0,1 ..., N-1}, wherein, C is a circulating prefix-length, obviously, $c_k\left(n\right)=\frac{1}{\sqrt{N}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right)\exp (j2\mathrm{\πmn}/N),$ n＝-C，...，-1，0，1，...，N-1。

Described digital-to-analogue (D/A) modular converter is used for the signal of described cyclic prefix adding module output is carried out digital-to-analogue conversion to obtain analog signal with described first sampling interval, is about to discrete data sequence { c _k(n), n=-C ... ,-1,0,1 ..., N _k-1} carries out digital-to-analogue conversion with the first sampling interval T and obtains continuous OFDM symbol waveform s _k(t), and $s_k\left(t\right)=\frac{1}{\sqrt{\mathrm{NT}}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right)\exp \left(j2\mathrm{\πm\ΔFt}\right),$ T=[-CT, NT), Δ F is the OFDM symbol subcarrier spacing of base station.

Described up-conversion module is used for described analog signal is carried out frequency translation to obtain radiofrequency signal with default carrier frequency, is about to analog signal s _k(t) be transformed into radiofrequency signal ${\tilde{s}}_k\left(t\right)=R_e\left[s_k\left(t\right)\exp \left(j2\mathrm{\π}{f}_{c}t\right)\right],$ R wherein _eReal part, f are got in [] expression _cThe carrier frequency that transmits for described transmitting terminal.

Described transmitter module is used for sending described radiofrequency signal and the described information that will send to each user (supposes that herein the frequency deviation position is ε in the subcarrier allocation information of described broadband simulation orthogonal frequency-division multiplex base band signal _kIndividual subcarrier).Suppose herein k user the processing bandwidth for N _kThe occupied bandwidth of individual subcarrier, according to the difference of subcarrier mapping ruler, handling bandwidth can be greater than occupied bandwidth.

Described a plurality of receiving terminal, be respectively applied for the reception radiofrequency signal that described transmitting terminal was sent to and each user's the subcarrier allocation information (it comprise each user's frequency deviation positional information and subcarrier mapping ruler) of information in described broadband simulation orthogonal frequency-division multiplex base band signal, and the radiofrequency signal that receives carried out every processing so that each receiving terminal obtains the discrete baseband signal in each self-corresponding user arrowband, after the more discrete baseband signal in described user arrowband being carried out default separately second Fourier transform of counting, then according to corresponding each user communications signals of described subcarrier allocation information extraction, at last by after the channel equalization, obtain corresponding each telex network information, every processing that the radiofrequency signal of described reception is carried out comprises information the subcarrier allocation information in broadband simulation orthogonal frequency-division multiplex singal of each receiving terminal according to each user who receives, default processing bandwidth and default carrier frequency carry out frequency translation, filtering and analog-to-digital conversion etc.Be noted that, second of the Fourier transform that described a plurality of receiving terminal adopts is separately counted and is less than or equal to first of inverse fourier transform that described transmitting terminal adopts respectively and counts, if second the counting and be respectively N of the Fourier transform that described a plurality of receiving terminals adopt separately ₁, N ₂... N _n, second sampling interval of Cai Yonging is respectively T separately ₁, T ₂... T _n, first of the inverse fourier transform that described transmitting terminal adopts is counted and is N, and its first sampling interval of adopting is T, then satisfies condition: N _kT _k=NTK=1,2...n

If described a plurality of receiving terminals all adopt the structure of described first receiving terminal, then each receiving terminal comprises at least: one first receiver module, first down conversion module, first low-pass filtering module, first analog-to-digital conversion module, first prefix removal module, first Fourier transform module, first subcarrier are separated mapping block and one first channel equalization module.

Described first receiver module is used to receive the radiofrequency signal that is sent to and carries out message pick-up by antenna usually, frequency deviation positional information and the subcarrier mapping ruler information of described each user's information in described broadband simulation orthogonal frequency-division multiplex base band signal can be in system be transmitted and is received by minimal configuration user's the specific signaling channel of receiving ability design, this technology is known to those skilled in the art to be known, and does not repeat them here.

Described first down conversion module is used in the frequency deviation positional information of broadband simulation orthogonal frequency-division multiplex base band signal the described radiofrequency signal that receives being carried out the correspondent frequency conversion to obtain should having mutually the first wideband analog signal of frequency deviation according to the information of the relative users of presetting carrier frequency and receiving, wherein, the negative value of the frequency deviation of the information that the described centre frequency that the first wideband analog signal of frequency deviation arranged is a respective user in described broadband simulation orthogonal frequency-division multiplex base band signal, establishing described carrier frequency is f _c, its carrier frequency with described transmitting terminal is identical, and the frequency deviation positional information of described user's information in described broadband simulation orthogonal frequency-division multiplex base band signal represents with the carrier shift amount that usually for example k receiving terminal particular carrier wave side-play amount is made as Δ f _k, it is receiving terminal OFDM modulated sub-carriers integral multiple at interval, i.e. Δ f _k=ε _kΔ F, described down conversion module is with the radiofrequency signal that receives

Shift frequency-(f _c+ Δ f _k), make it be transformed to the first wideband analog signal r of frequency deviation _k(t), if supposition signal that k receiving terminal received is for passing through the signal that the quasistatic multipath channel is sent to, so signal is in the time range of this Channel Transmission, and the equivalent base band impulse response of this channel can be expressed as $h_k\left(t\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\mathrm{\δ}(t-{\mathrm{\τ}}_l){\mathrm{\α}}_l,$ N=0 ..., τ _Max-1, wherein L is the channel path sum, α _lBe the multiple decay factor of l paths, τ _lBe the time delay expansion of l paths, τ _MaxFor the expansion of the maximum delay in all paths, easy for analyzing, if further hypothesis receiving terminal ideal synchronisation, and omit noise item, then k user has the first wideband analog signal r of frequency deviation _k(t) can be expressed as

$r_k\left(t\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}{s}_k(t-{\mathrm{\τ}}_l){\mathrm{\α}}_l\exp (-j2\mathrm{\π\Δ}{f}_{k}t)$

$=\frac{1}{\sqrt{\mathrm{NT}}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right){\mathrm{\α}}_l\exp \left(j2\mathrm{\πm\ΔF}(t-{\mathrm{\τ}}_l)\right)\exp (-j2\mathrm{\π\Δ}{f}_{k}t).$

Described first low-pass filtering module is used for having the first wideband analog signal of frequency deviation to carry out analogue low pass filtering to obtain corresponding user arrowband analog baseband signal according to the processing bandwidth of default relative users with described, k user is had the first wideband analog signal r of frequency deviation _k(t) but carry out the outer interference signal of band of low-pass filtering filtering received signal, suppose low-pass filtering filtering out of band signal fully, then k user arrowband analog baseband signal can be expressed as:

$\stackrel{\‾}{r_k}\left(t\right)=\frac{1}{\sqrt{\mathrm{NT}}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m\∈\mathrm{\Ω}}{\mathrm{\Σ}}{a}_k\left(m\right){\mathrm{\α}}_l\exp \left(j2\mathrm{\πm\ΔF}(t-{\mathrm{\τ}}_l)\right)\exp (-j2\mathrm{\π\Δ}{f}_{k}t),$ Ω is the sub-carrier set that comprises useful signal.

Described first modulus (A/D) modular converter is used for according to the processing bandwidth of default relative users described user arrowband analog baseband signal being carried out analog-to-digital conversion to obtain the discrete baseband signal in described user arrowband, to k user arrowband analog baseband signal with second sampling interval Sample with the second sampling interval Tk, if set through A/D converting users arrowband analog baseband signal

Be transformed to discrete baseband signal { d _k(n) }, then at nT _kSampled value constantly can be expressed as:

$d_k\left(n{T}_k\right)=\frac{1}{\sqrt{N_k{T}_k}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m\∈\mathrm{\Ω}}{\mathrm{\Σ}}{a}_k\left(m\right){\mathrm{\α}}_l\exp \left(j2\mathrm{\πm\ΔF}(n{T}_k-{\mathrm{\τ}}_l)\right)\exp (-j2\mathrm{\π\Δ}{f}_{k}n{T}_k),$ Accordingly, the discrete baseband signal in k user arrowband of A/D conversion output can be expressed as:

$d_k\left(n\right)=\frac{1}{\sqrt{N_k}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m\∈\mathrm{\Ω}}{\mathrm{\Σ}}{a}_k\left(m\right){\mathrm{\α}}_l\exp (j2\mathrm{\πm}(n-{\widetilde{\mathrm{\τ}}}_l)/N_k)\exp (-j2\mathrm{\π}{\mathrm{\ϵ}}_{k}n{/N}_k),$ Wherein

Be sampling interval T _kThe time delay expansion of normalized l paths, ε _kBe receiving terminal OFDM demodulation subcarrier spacing normalized k portable terminal particular carrier wave side-play amount, i.e. ε _k=Δ f _k/ Δ F, and ε _kBe integer.

Described first prefix removal module is used for removing according to default rule the prefix of the discrete baseband signal in described user arrowband, for example, and with k user arrowband discrete signal sequence { d of A/D conversion output _k(n) } preceding C sampled value in cast out, and N the sampled value formation length of getting thereafter is N _kParallel data sequence { e _k(n), n=0,1,2 ..., N _k-1}, and e _k(n)=d _k(n+C+1), n=0,1,2 ..., N _k-1.

Described first Fourier transform module is used for the discrete baseband signal in the user arrowband of removing prefix is carried out second Fourier transform of counting, promptly to parallel data sequence { e _k(n), n=0,1,2 ..., N _k-1} carries out Nk point FFT conversion, and through the FFT conversion, parallel data sequence is transformed into corresponding parallel data sequence { g _k(m), m=0,1,2 ..., N _k-1}, relation is each other obeyed $g_k\left(m\right)=\frac{1}{\sqrt{N}}\underset{n=0}{\overset{N_k-1}{\mathrm{\Σ}}}{e}_k\left(n\right)\exp (-j2\mathrm{\πmn}/N_k).$

In fact,

$g_k\left(m\right)=\frac{1}{N}\underset{m\′\∈\mathrm{\Ω}}{\mathrm{\Σ}}{H}_k(m\′)a_k(m\′)\underset{n=0}{\overset{N_k-1}{\mathrm{\Σ}}}\exp (j2\mathrm{\π}(m\′-m-{\mathrm{\ϵ}}_k)n/N_k)$

$=H_k(m+{\mathrm{\ϵ}}_k)a_k(m+{\mathrm{\ϵ}}_k),$

0≤m≤N _k-1，m+ε _k∈Ω

Wherein, $H_k(m\′)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}{\mathrm{\α}}_l\exp (-j2\mathrm{\πm}\′{\widetilde{\mathrm{\τ}}}_l/N_k),$ Be k the channel frequency response on the individual subcarrier of receiving terminal m '.It should be noted that, for the subcarrier bandwidth that guarantees each receiving terminal demodulating ofdm symbol identical with the subcarrier bandwidth of OFDM symbols transmitted, the duration of the OFDM symbol live part (not comprising Cyclic Prefix) that each receiving terminal receives must be identical with the duration of the live part of the OFDM symbol of base station, that is N _kT _k=NT, wherein, T _kBe second sampling interval of the A/D modular converter employing of k receiving terminal, N _kBe second the counting of FFT conversion in the FFT conversion module of k receiving terminal, N is first the counting of IFFT conversion in the transmitting terminal IFFT conversion module, and T is first sampling interval of D/A conversion in the transmitting terminal D/A modular converter.

Described first subcarrier is separated mapping block and is used for extracting the signal of communication of each user on respective sub according to receiving subcarrier allocation information from the signal through Fourier transform, by the output signal g of Fourier transform _k(m)=H _k(m+ ε _k) a _k(m+ ε _k), 0≤m≤N _k-1, m+ ε _k∈ Ω as seen, m the signal of communication that subcarrier is separated mapping output for the signal of transmission at m+ ε _kIndividual subcarrier is uploaded defeated data symbol.

The described first channel equalization module is used for that described subcarrier is separated on the respective sub of mapping output transmission communication signal carries out frequency domain equalization and handles, and for ZF (ZF) equilibrium, and adopts ideal communication channel to estimate, the signal phasor of setting output is { y _k(m) }, then

y _k(m)=g _k(m)/H _k(m+ ε _k), m=0 ..., N _k-1, m+ ε _k∈ Ω, wherein H _k(m+ ε _k) be that k user is at m+ ε _kChannel frequency response on the individual subcarrier.

If described a plurality of receiving terminals all adopt the structure of described second receiving terminal, then each receiving terminal comprises at least: second receiver module, second down conversion module, second analog-to-digital conversion module, frequency spectrum shift module, second low-pass filtering module, down sample module, second prefix removal module, second Fourier transform module, second subcarrier are separated mapping block and second channel balance module.

Described second receiver module is used to receive the communication information that is sent to, described second down conversion module is used for according to default carrier frequency the described radiofrequency signal that receives being carried out the correspondent frequency conversion to obtain the second wideband analog signal, wherein, the centre frequency of the described second wideband analog signal is 0, described second analog-to-digital conversion module is used for first sampling interval described second wideband analog signal being carried out analog-to-digital conversion to obtain the discrete baseband signal in first broadband according to each default user processing bandwidth, described frequency spectrum shift module is used in the frequency deviation positional information of described broadband simulation orthogonal frequency-division multiplex base band signal the discrete baseband signal in described first broadband being carried out corresponding frequency spectrum according to the information of the relative users that receives and moves to obtain should have mutually the discrete baseband signal in second broadband of frequency deviation, wherein, the centre frequency of the discrete baseband signal in described second broadband that frequency deviation arranged is the negative value of the frequency deviation of information in described broadband simulation orthogonal frequency-division multiplex base band signal of respective user, described second low-pass filtering module is used for having the discrete baseband signal in second broadband of frequency deviation to carry out corresponding low-pass filtering with the discrete baseband signal in the arrowband that obtains over-sampling according to the processing bandwidth of default relative users to described, the described module that adopts down is used for according to the bandwidth of default broadband simulation orthogonal frequency-division multiplex base band signal and the processing bandwidth of relative users the discrete baseband signal in the arrowband of described over-sampling being carried out corresponding down-sampling with the discrete baseband signal in the user arrowband that obtains threshold sampling, described second prefix removal module is used for removing according to default rule the prefix of the discrete baseband signal in described user arrowband, described second Fourier transform module is used for carrying out second Fourier transform of counting according to the user arrowband that the processing bandwidth of default relative users will the be removed prefix baseband signal that disperses, described second carrier wave is separated mapping block and is used for extracting the signal of communication of each user on respective sub from the signal through Fourier transform, described second channel balance module is used for that described subcarrier is separated the signal of communication that shines upon output and carries out the frequency domain equalization processing, wherein, described first count the product with described first sampling interval equals described second product of counting with described second sampling interval, from the above, the structure of the structure of second receiving terminal and first receiving terminal is different only to be that it finishes the frequency spectrum shift and the low-pass filtering of radiofrequency signal in discrete domain, so no longer the internal structure of its each module is described in detail at this.

In addition, described a plurality of receiving terminals also can adopt different structures, and for example, a part of receiving terminal adopts the structure of first receiving terminal, and another part receiving terminal adopts the structure of second receiving terminal, does not repeat them here.

The OFDM downlink communication means of dexterity of the present invention mainly may further comprise the steps:

1) will send to each user's communications information and after preliminary treatment, carry out the respective sub mapping.

2) will preset first inverse fourier transform of counting through the communication information of subcarrier mapping, wherein, described preliminary treatment comprises the chnnel coding of signal of communication and digital modulation etc., those skilled in the art also can carry out different preliminary treatment to signal of communication according to actual needs, and each information of establishing through ovennodulation is parallel symbol data block { a _k(m), m=0,1 ..., N-1}, it carries out forming corresponding data block sequence { b after the N point IFFT conversion _k(m), m=0,1 ..., N-1}, relation is each other obeyed:

$b_k\left(n\right)=\frac{1}{\sqrt{N}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right)\exp (j2\mathrm{\πmn}/N)\{{\tilde{a}}_k\left(m\right),m=\mathrm{0,1},...,N_k-1\}.$

3) add prefix in sending to each user's communications information according to preset rules through the described of described inverse fourier transform, normally will be copied to its front end through the symbol of the afterbody certain-length of resulting signal behind the inverse fourier transform and form Cyclic Prefix, for example the part with the data block afterbody of described IFFT conversion output is copied to its front end, form the data block symbols of final band Cyclic Prefix, be about to data sequence { b _k(n), n=0,1 ..., N-1} is transformed into complete OFDM symbol data sequence { c _k(n), n=-C ... ,-1,0,1 ..., N-1}, wherein, C is a circulating prefix-length, obviously, $c_k\left(n\right)=\frac{1}{\sqrt{N}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right)\exp (j2\mathrm{\πmn}/N),$ n＝-C，...，-1，0，1，...，N-1。

4) information of adding prefix is carried out digital-to-analogue conversion to form broadband simulation orthogonal frequency-division multiplex base band signal, for example with discrete data sequence { c with the first default sampling interval _k(n), n=-C ... ,-1,0,1 ..., N _k-1} carries out digital-to-analogue conversion with the first sampling interval T and obtains continuous OFDM symbol waveform s _k(t), then:

$s_k\left(t\right)=\frac{1}{\sqrt{\mathrm{NT}}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right)\exp \left(j2\mathrm{\πm\ΔFt}\right),$ T=[-CT, NT), Δ F is the OFDM symbol subcarrier spacing of base station.

5) according to default carrier frequency described broadband simulation orthogonal frequency-division multiplex base band signal is carried out frequency-conversion processing to obtain radiofrequency signal, in the present embodiment, default carrier frequency is f _c, be about to analog signal s _k(t) be transformed into radiofrequency signal ${\tilde{s}}_k\left(t\right)=R_e\left[s_k\left(t\right)\exp \left(j2\mathrm{\π}{f}_{c}t\right)\right],$ R wherein _eReal part, f are got in [] expression _cThe carrier frequency that transmits for described transmitting terminal.

6) send described radiofrequency signal and the described subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user, wherein, described subcarrier allocation information comprises each user's frequency deviation positional information and subcarrier mapping ruler information.

7) receive radiofrequency signal and the described subcarrier allocation information (be each user's frequency deviation positional information and subcarrier mapping ruler information) of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user that is sent to, and according to described each user's frequency deviation positional information with handle bandwidth and described default carrier frequency is converted to the discrete baseband signal in each user arrowband with described radiofrequency signal, if at analog domain described radiofrequency signal is carried out frequency conversion process, then described step 7) further comprises step:

(1) described radiofrequency signal is converted to the first wideband analog signal that frequency deviation is respectively arranged according to described each user's frequency deviation positional information and default carrier frequency, wherein, the negative value of the frequency deviation of the information that the described centre frequency that the first wideband analog signal of frequency deviation respectively arranged is a respective user in described broadband simulation orthogonal frequency-division multiplex base band signal, for example, for K receiving terminal, its radiofrequency signal to receiving

Shift frequency-(f _c+ Δ f _k), make it be transformed to the wideband analog signal r of frequency deviation _k(t), under the situation of desirable synchronous regime and omission noise item, k the wideband analog signal r that frequency deviation is arranged _k(t) can be expressed as

$r_k\left(t\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}{s}_k(t-{\mathrm{\τ}}_l){\mathrm{\α}}_l\exp (-j2\mathrm{\π\Δ}{f}_{k}t)$

$=\frac{1}{\sqrt{\mathrm{NT}}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{a}_k\left(m\right){\mathrm{\α}}_l\exp \left(j2\mathrm{\πm\ΔF}(t-{\mathrm{\τ}}_l)\right)\exp (-j2\mathrm{\π\Δ}{f}_{k}t).$

(2) the processing bandwidth according to each default user respectively has the first wideband analog signal process analogue low pass filtering of frequency deviation to obtain each corresponding user arrowband analog baseband signal with described respectively, for example, to k the first wideband analog signal r that frequency deviation is arranged _k(t) but carry out the outer interference signal of band of low-pass filtering filtering received signal, suppose low-pass filtering filtering out of band signal fully, then K user arrowband analog baseband signal can be expressed as:

$\stackrel{\‾}{r_k}\left(t\right)=\frac{1}{\sqrt{\mathrm{NT}}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m\∈\mathrm{\Ω}}{\mathrm{\Σ}}{a}_k\left(m\right){\mathrm{\α}}_l\exp \left(j2\mathrm{\πm\ΔF}(t-{\mathrm{\τ}}_l)\right)\exp (-j2\mathrm{\π\Δ}{f}_{k}t),$ Ω is the sub-carrier set that comprises useful signal.

(3) with the second default sampling interval described each user arrowband analog baseband signal is carried out analog-to-digital conversion to obtain user arrowband discrete baseband signal, for example analog baseband signal r according to each default user processing bandwidth _k(t) carrying out back k the user arrowband discrete signal of exporting of A/D conversion can be expressed as:

$d_k\left(n\right)=\frac{1}{\sqrt{N_k}}\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{m\∈\mathrm{\Ω}}{\mathrm{\Σ}}{a}_k\left(m\right){\mathrm{\α}}_l\exp (j2\mathrm{\πm}(n-{\widetilde{\mathrm{\τ}}}_l)/N_k)\exp (-j2\mathrm{\π}{\mathrm{\ϵ}}_{k}n{/N}_k),$ Wherein

Be sampling interval T _kThe time delay expansion of normalized l paths, ε _kBe receiving terminal OFDM demodulation subcarrier spacing normalized k portable terminal particular carrier wave side-play amount, i.e. ε _k=Δ f _k/ Δ F, and ε _kBe integer.

And if in discrete domain described radiofrequency signal is carried out frequency spectrum shift, then described step 7) comprises step:

(1) according to default carrier frequency described radiofrequency signal is converted to the second wideband analog signal, the centre frequency of the described second wideband analog signal is zero;

(2) with first sampling interval described second wideband analog signal is carried out analog-to-digital conversion to obtain the discrete baseband signal in first broadband according to default broadband simulation orthogonal frequency-division multiplex base band signal bandwidth;

(3) according to each user's of receiving the frequency deviation positional information of information in described broadband simulation orthogonal frequency-division multiplex base band signal the discrete baseband signal in described first broadband is carried out corresponding frequency spectrum and move obtaining to have the discrete baseband signal in second broadband of frequency deviation, the centre frequency of the described discrete baseband signal in second broadband that frequency deviation arranged is the negative value of each user's the frequency deviation of information in described broadband simulation orthogonal frequency-division multiplex base band signal;

(4) the processing bandwidth according to each default user has the discrete baseband signal in second broadband of frequency deviation to carry out the corresponding digital low-pass filtering with the discrete baseband signal in the arrowband that obtains over-sampling to described;

(5) according to the bandwidth of default broadband simulation orthogonal frequency-division multiplex base band signal and each user's processing bandwidth the discrete baseband signal in the arrowband of described user's over-sampling is carried out corresponding down-sampling with the discrete baseband signal in the user arrowband that obtains threshold sampling.

8) according to the prefix of the discrete baseband signal in described each the user arrowband of preset rules removal, usually the Cyclic Prefix of the discrete baseband signal in described each user arrowband is removed, for example with k user arrowband discrete signal sequence { d _k(n) } preceding C sampled value in cast out, and N the sampled value formation length of getting thereafter is N _kParallel data sequence { e _k(n), n=0,1,2 ..., N _k-1}, then e _k(n)=d _k(n+C+1), n=0,1,2 ..., N _k-1

9) the discrete baseband signal in each user arrowband that will remove prefix is carried out corresponding each default second Fourier transform of counting to obtain corresponding communication information according to each default user processing bandwidth, certainly for obtaining corresponding communication information, also need the signal through Fourier transform is carried out frequency domain equalization processing etc., this technology of knowing known to those skilled in the art, no longer described in detail at this, for example, to parallel data sequence { e _k(n), n=0,1,2 ..., N _k-1} carries out Nk point FFT conversion and obtains corresponding parallel data sequence { g _k(m), m=0,1,2 ..., N _k-1}, then:

$g_k\left(m\right)=\frac{1}{N}\underset{m\′\∈\mathrm{\Ω}}{\mathrm{\Σ}}{H}_k(m\′)a_k(m\′)\underset{n=0}{\overset{N_k-1}{\mathrm{\Σ}}}\exp (j2\mathrm{\π}(m\′-m-{\mathrm{\ϵ}}_k)n/N_k)$

$=H_k(m+{\mathrm{\ϵ}}_k)a_k(m+{\mathrm{\ϵ}}_k),$

0≤m≤N _k-1，m+ε _k∈Ω

Wherein, $H_k(m\′)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}{\mathrm{\α}}_l\exp (-j2\mathrm{\πm}\′{\widetilde{\mathrm{\τ}}}_l/N_k),$ Be k the channel frequency response on the individual subcarrier of receiving terminal m '.

10) in the process signal of Fourier transform, extract the signal of communication of each user on respective sub according to receiving subcarrier allocation information.

11) described subcarrier being separated on the respective sub of mapping output transmission communication signal carries out frequency domain equalization and handles.Only be noted that, for the subcarrier bandwidth that guarantees each receiving terminal demodulating ofdm symbol identical with the subcarrier bandwidth of OFDM symbols transmitted, the duration of the OFDM symbol live part (not comprising Cyclic Prefix) that each receiving terminal receives must be identical with the duration of the live part of the OFDM symbol of base station, that is N _kT _k=NT, wherein, T _kBe second sampling interval of the A/D modular converter employing of k receiving terminal, N _kBe second the counting of FFT conversion in the FFT conversion module of k receiving terminal, N is first the counting of IFFT conversion in the transmitting terminal IFFT conversion module, T is first sampling interval of D/A conversion in the transmitting terminal D/A modular converter, this shows that second of Fourier transform in the OFDM downlink communication means of described dexterity is counted to be less than or equal to first of inverse fourier transform and to count.

In sum, the OFDM downlink communication system of dexterity of the present invention and communication means are by adopting higher sample frequency and the IFFT conversion of counting more greatly at transmitting terminal, form the wideband OFDM a-signal, at each receiving terminal then by frequency translation and filtering to obtain each user's narrowband baseband signal, and employing demodulates each user's information symbol than the FFT conversion of small point, the Radio Resource that can make wide-band communication system is adaptive multi-user's different business demand and terminal processing capacity deftly, and then reduces the implementation complexity and the power consumption of portable terminal.

Claims (14)

1. OFDM downlink communication system is characterized in that comprising:

Transmitting terminal, be used for to send to each user's communications information and carry out every processing to obtain broadband simulation orthogonal frequency-division multiplex base band signal, and according to default carrier frequency the orthogonal frequency-division multiplex base band signal is simulated in described broadband and carry out frequency translation to obtain radiofrequency signal, again described radiofrequency signal and the described subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user are launched, wherein, every processing that the information that be transmitted to each user is carried out comprises subcarrier mapping processing, default first inverse fourier transform of counting and carry out digital-to-analogue conversion according to default first sampling interval;

A plurality of receiving terminals, be respectively applied for the subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that receives described radiofrequency signal and each user, and the radiofrequency signal that receives carried out every processing so that each receiving terminal obtains the discrete baseband signal in each self-corresponding user arrowband, and to the discrete baseband signal in described user arrowband carry out with behind default second Fourier transform of counting separately again according to corresponding each the telex network information of described subcarrier allocation information extraction, wherein, every processing that the radiofrequency signal of described reception is carried out comprises information the subcarrier allocation information in broadband simulation orthogonal frequency-division multiplex singal of each receiving terminal according to each user who receives, default processing bandwidth and default carrier frequency carry out frequency translation, filtering and analog-to-digital conversion.

2. OFDM downlink communication system as claimed in claim 1 is characterized in that: second of the Fourier transform that described a plurality of receiving terminals adopt is separately counted and is less than or equal to first of inverse fourier transform that described transmitting terminal adopts and counts.

3. OFDM downlink communication system as claimed in claim 1 is characterized in that: second of the Fourier transform that described a plurality of receiving terminals adopt is separately counted and is respectively N ₁, N ₂... N _n, the second default sampling interval of carrying out separately that analog-to-digital conversion adopted is respectively T ₁, T ₂... T _n, first of the inverse fourier transform that described transmitting terminal adopts is counted and is N, and its first sampling interval of adopting is T, then satisfies condition: N _kT _k=NT, k=1,2...n, n are descending receiving terminal number.

4. OFDM downlink communication system as claimed in claim 1 is characterized in that described transmitting terminal comprises:

The subcarrier mapping block, be used for through described each user's communications information mapping that will send to of ovennodulation to each corresponding subcarrier;

The inverse fourier transform module is used for described each subcarrier is carried out described first inverse fourier transform of counting;

Cyclic prefix adding module is used for adding prefix in the signal through inverse fourier transform according to default rule;

D/A converter module is used for the signal of described cyclic prefix adding module output is carried out digital-to-analogue conversion to obtain broadband simulation orthogonal frequency-division multiplex base band signal with described first sampling interval;

The up-conversion module is used for described broadband simulation orthogonal frequency-division multiplex base band signal is carried out frequency translation to obtain radiofrequency signal with default carrier frequency.

5. OFDM downlink communication system as claimed in claim 1 is characterized in that any one receiving terminal of described a plurality of receiving terminals comprises:

First down conversion module is used for carrying out the correspondent frequency conversion to obtain the first wideband analog signal of frequency deviation according to the described radiofrequency signal that the information of the relative users of presetting carrier frequency and receiving is received in the subcarrier allocation information butt joint of described broadband simulation orthogonal frequency-division multiplex base band signal;

First low-pass filtering module is used for having the first wideband analog signal of frequency deviation to carry out analogue low pass filtering to obtain corresponding user arrowband analog baseband signal according to the processing bandwidth of default relative users with described;

First analog-to-digital conversion module is used for according to the processing bandwidth of default relative users described user arrowband analog baseband signal being carried out analog-to-digital conversion to obtain the discrete baseband signal in corresponding user arrowband with second sampling interval;

First prefix removal module is used for the prefix that the default rule of basis is removed the discrete baseband signal in described user arrowband;

First Fourier transform module is used for the discrete baseband signal in the described user arrowband of removing prefix is carried out second Fourier transform of counting;

First subcarrier is separated mapping block, is used for according to the described subcarrier allocation information that receives, and obtains the signal on each CU subcarrier from the signal of described first Fourier transform module output;

The first channel equalization module is used for that the signal that described first subcarrier is separated mapping block output is carried out frequency domain equalization and handles.

6. OFDM downlink communication system as claimed in claim 1 is characterized in that any one receiving terminal of described a plurality of receiving terminals comprises:

Second down conversion module is used for according to default carrier frequency the described radiofrequency signal that receives being carried out the correspondent frequency conversion to obtain the second wideband analog signal, and wherein, the centre frequency of the described second wideband analog signal is zero;

Second analog-to-digital conversion module is used for first sampling interval described second wideband analog signal being carried out analog-to-digital conversion to obtain the discrete baseband signal in first broadband according to the processing bandwidth of default relative users;

The frequency spectrum shift module is used in the subcarrier allocation information of described broadband simulation orthogonal frequency-division multiplex base band signal the discrete baseband signal in described first broadband being carried out corresponding frequency spectrum according to the information of the relative users that receives and moves to obtain to have the discrete baseband signal in second broadband of frequency deviation;

Second low-pass filtering module is used for having the discrete baseband signal in second broadband of frequency deviation to carry out the corresponding digital low-pass filtering with the discrete baseband signal in the arrowband that obtains corresponding over-sampling according to the processing bandwidth of default relative users to described;

Down sample module is used for according to the bandwidth of default broadband simulation orthogonal frequency-division multiplex base band signal and the default processing bandwidth of relative users the discrete baseband signal in the arrowband of described over-sampling being carried out corresponding down-sampling with the discrete baseband signal in the user arrowband that obtains threshold sampling;

Second prefix removal module is used for the prefix that the default rule of basis is removed the discrete baseband signal in described user arrowband;

Second Fourier transform module is used for carrying out second Fourier transform of counting according to the described user arrowband that the processing bandwidth of default relative users will the be removed prefix baseband signal that disperses;

Second subcarrier is separated mapping block, is used for according to the subcarrier allocation information that receives, and obtains the signal on each CU subcarrier from the signal of described second Fourier transform module output;

The second channel balance module is used for that the signal that described second subcarrier is separated mapping block output is carried out frequency domain equalization and handles.

7. OFDM downlink communication system as claimed in claim 1 is characterized in that: described subcarrier allocation information comprises each user's frequency deviation positional information and subcarrier mapping ruler.

8. OFDM downlink communication means is characterized in that comprising step:

1) will send to each user's communications information and after preliminary treatment, carry out subcarrier mapping processing;

2) will preset first inverse fourier transform of counting through the communication information that the subcarrier mapping is handled;

3) add prefix in sending to each user's communications information according to preset rules through the described of described inverse fourier transform;

4) information of adding prefix is carried out digital-to-analogue conversion to form broadband simulation orthogonal frequency-division multiplex base band signal with the first default sampling interval;

5) according to default carrier frequency described broadband simulation orthogonal frequency-division multiplex base band signal is carried out frequency-conversion processing to obtain radiofrequency signal;

6) send described radiofrequency signal and the described subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user;

7) receive radiofrequency signal and the described subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal that will send to each user that is sent to, and described radiofrequency signal is converted to the discrete baseband signal in each user arrowband according to described subcarrier allocation information, default processing bandwidth and described default carrier frequency;

8) remove the prefix of the discrete baseband signal in described each user arrowband according to preset rules;

9) each the user arrowband discrete signal that will remove prefix carries out corresponding each default second Fourier transform of counting according to each default user processing bandwidth;

10) in the process signal of Fourier transform, extract each user's communications signal according to described subcarrier allocation information, and described signal of communication is carried out equilibrium treatment to obtain corresponding each telex network information.

9. OFDM downlink communication means as claimed in claim 8 is characterized in that: described preliminary treatment comprises chnnel coding and digital modulation.

10. OFDM downlink communication means as claimed in claim 8 is characterized in that: described second counts is less than or equal to described first and counts.

11. OFDM downlink communication means as claimed in claim 8 is characterized in that described step 7) also comprises step:

(1) described radiofrequency signal is converted to the first wideband analog signal that frequency deviation is respectively arranged according to described subcarrier allocation information and default carrier frequency;

(2) the processing bandwidth according to each default user respectively has the first wideband analog signal process analogue low pass filtering of frequency deviation to obtain each corresponding user arrowband analog baseband signal with described respectively;

(3) respectively described each user arrowband analog baseband signal is carried out analog-to-digital conversion to obtain the discrete baseband signal in each corresponding user arrowband according to each default user processing bandwidth with the second default separately sampling interval.

12. OFDM downlink communication means as claimed in claim 8 is characterized in that described step 7) also comprises step:

(1) according to default carrier frequency described radiofrequency signal is converted to the second wideband analog signal, the centre frequency of the described second wideband analog signal is zero;

(2) with first sampling interval described second wideband analog signal is carried out analog-to-digital conversion to obtain the discrete baseband signal in first broadband according to default broadband simulation orthogonal frequency-division multiplex base band signal bandwidth;

(3) respectively the discrete baseband signal in described first broadband being carried out corresponding frequency spectrum according to each user's who receives the subcarrier allocation information of information in described broadband simulation orthogonal frequency-division multiplex base band signal moves to obtain respectively to have the discrete baseband signal in second broadband of frequency deviation;

(4) describedly there is the discrete baseband signal in second broadband of frequency deviation to carry out the corresponding digital low-pass filtering to each respectively according to each default user processing bandwidth with the discrete baseband signal in the arrowband that obtains each over-sampling;

(5) respectively the discrete baseband signal in the arrowband of described each over-sampling is carried out corresponding down-sampling with the discrete baseband signal in the user arrowband that obtains each threshold sampling according to the bandwidth of default broadband simulation orthogonal frequency-division multiplex base band signal and each user's processing bandwidth.

13. OFDM downlink communication means as claimed in claim 11 is characterized in that: described first count the product with described first sampling interval equals described second product of counting with described second sampling interval.

14. OFDM downlink communication means as claimed in claim 8 is characterized in that: described subcarrier allocation information comprises each user's frequency deviation positional information and subcarrier mapping ruler.

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