CN204517851U - A kind of non-orthogonal multi-carrier digital modulation and demodulating equipment - Google Patents

Abstract

The utility model discloses a kind of non-orthogonal multi-carrier digital modulation and demodulating equipment, the receiver module comprise sending module, being connected by wireless channel with sending module, described sending module comprises digital modulation processing unit, D/A converter, power amplifier, the wireless launcher that order is connected, and described receiver module comprises wireless receiver, preamplifier, A/D converter, the digital demodulation processing unit that order is connected.Device of the present utility model, overcomes the impact of carrier wave frequency deviation on orthogonal multiple carrier wave systems such as OFDM, can realize the higher availability of frequency spectrum, has again good anti-Doppler.

Description

A kind of non-orthogonal multi-carrier digital modulation and demodulating equipment

Technical field

The utility model relates to the communications field, particularly a kind of non-orthogonal multi-carrier digital modulation and demodulating equipment.

Background technology

In wireless communications, limited channel width, the multi-path jamming of signal and Doppler frequency shift etc. affect the development of radio communication.For making full use of channel resource, improving the utilance of frequency band, introducing OFDM (OFDM) in the communications.

The multicarrier that OFDM technology is chosen is mutually orthogonal, spectrum overlapping.Orthogonality between multicarrier (supposing that number is N) is as described below:

$\frac{1}{T}{\∫}_0^T{e}^{j{\mathrm{\ω}}_{i}t}\·e^{-j{\mathrm{\ω}}_{j}t}\mathrm{dt}=\left\{\begin{array}{cc}1& (i=j)\\ 0& (i\≠j)\end{array}\right.---\left(1\right)$

Wherein T is the symbol period of OFDM, ω _iand ω _jbe i-th and j carry wave frequency, i, j ∈ [0,1 ... N-1].In time domain, orthogonality makes each subcarrier contain an integral multiple cycle within an OFDM symbol cycle, and differs several fixed cycles between adjacent multicarrier; On frequency domain, at a sub-spectrum of carrier peak value place, the value of other subcarrier be all zero and the frequency spectrum of each subcarrier have 1/2 overlap, so OFDM technology has the very high availability of frequency spectrum.

If each sub carries allocation of ofdm system to data symbol be d _i(i=0,1 ... N-1), i-th overloading wave frequency is: f _i=f ₀+ i/T, wherein f ₀it is the frequency of the 0th subcarrier.If rectangular function rect (t)=1, | t|≤T/2, from t=t _sin the moment, the ofdm signal after modulation is:

$s\left(t\right)={\mathrm{\Σ}}_{i=0}^{N-1}{d}_i\mathrm{rect}({t-t}_s-\frac{T}{2})e^{j2\mathrm{\π}{f}_i\left({t-t}_s\right)},(t_s\≤t\≤t_s+T)---\left(2\right)$

To simplify the analysis, by t _sbe set to 0, and ignore rectangular function rect (t), then the sampling that sampling rate is N/T is carried out to signal s (t) of (formula 2), obtain OFDM digital signal:

$s_k=s\left(\frac{\mathrm{kT}}{N}\right)={\mathrm{\Σ}}_{i=0}^{N-1}{d}_i{e}^{j\frac{2\mathrm{\πik}}{N}},(0\≤k\≤N-1)---\left(3\right)$

At receiving terminal, can baseband signal be demodulated by the orthogonality between subcarrier:

${\hat{d}}_i={\mathrm{\Σ}}_{k=0}^{N-1}{s}_k{e}^{-j\frac{2\mathrm{\πik}}{N}},(0\≤k\≤N-1)---\left(4\right)$

It is large that the symbol period of the every sub-channels in OFDM technology carries out the serial signal cycle before OFDM modulation relatively, adds and introduce protection interval, make ofdm system have very strong anti-multipath jamming ability.

In wireless communications, because receiving terminal and transmitting terminal exist relative motion and cause the Doppler frequency shift of carrier wave to be difficult to avoid.When carrier frequency shift occurs OFDM, recover the orthogonality of each subcarrier at demodulating end by Frequency Estimation and compensation, then carry out demodulation.In actual applications, OFDM only has when frequency displacement is less relative to intercarrier spacing, just compensates by Frequency Estimation and recovers orthogonality, when frequency displacement is larger, cannot orthogonality correctly between the reinsertion of carrier, and the error rate of demodulating end is raised rapidly.Such as under the channel of additive white Gaussian noise, ofdm system requires that frequency deviation is less than 4% of the carrier spacing, under fading channel, requires that frequency deviation is less than 1% ~ 2% of the carrier spacing.

From analyzing above, OFDM has the features such as the availability of frequency spectrum is high, ability of anti-multipath is strong, but OFDM requires subcarrier strict orthogonal, responsive to frequency deviation.And Doppler frequency shift is the phenomenon being difficult in radio communication avoid, therefore Doppler frequency shift becomes affects the communication quality of OFDM and the key factor of application.Further, carrier wave frequency deviation become impact all based on the key factor of orthogonal multiple carrier technology in the application of the communications field.

Utility model content

The purpose of this utility model is that the shortcoming overcoming prior art is with not enough, a kind of non-orthogonal multi-carrier digital modulation and demodulating equipment are provided, overcome the impact of carrier wave frequency deviation on orthogonal multiple carrier wave systems such as OFDM, all do not require multi-carrier orthogonal at transmitting terminal and receiving terminal.

The purpose of this utility model is realized by following technical scheme:

A kind of non-orthogonal multi-carrier digital modulation and demodulating equipment, the receiver module comprise sending module, being connected by wireless channel with sending module, described sending module comprises digital modulation processing unit, D/A converter, power amplifier, the wireless launcher that order is connected, and described receiver module comprises wireless receiver, preamplifier, A/D converter, the digital demodulation processing unit that order is connected.

Described wireless launcher comprises up-converter module and transmitter module, and up-converter module is selected according to embody rule, and the analog signal after power amplification, through up-converter module, is moved the frequency of applicable wireless channel propagation, then launched by transmitter module.

Described transmitter module is radio-frequency antenna, or is electro-acoustic transducer.Transmitter module can also be the reflector of other wireless signals.

Described wireless receiver comprises wireless receiving module and down conversion module, and wireless receiving module is converted to the signal of telecommunication the signal received from wireless channel, and the signal of telecommunication is moved and obtained baseband signal by down conversion module, and down conversion module can be selected according to embody rule.

Described wireless receiving module for receiving electromagnetic antenna, or is sound-electric transducer.Wireless receiving module can also be the receiver of other form wireless signals.

Described wireless channel is underwater acoustic channel.

A kind of non-orthogonal multi-carrier digital modulation and demodulation method, comprise the step of following order:

S1. according to channel characteristics, exploitable channel is divided into several sub-carrier channels;

S2. the input data from outside are carried out message sink coding, chnnel coding, mapping, multi-carrier modulation and are added the process of protection interval by digital modulation processing unit, obtain multiple carrier digital signal;

Concrete, first, after being input to digital modulation processing unit from the data of outside, carry out message sink coding, chnnel coding and mapping process respectively to improve reliability and the validity of transfer of data.Then, digital modulation processing unit carries out serial/parallel conversion to data, and the parallel data after conversion to be modulated on multicarrier and to add protection interval, obtains digital multi-carrier signal.

S3.D/A transducer converts multiple carrier digital signal to analog signal, then is amplified by power amplifier, is finally transmitted in wireless channel by wireless launcher;

S4. the signal of reception is converted to the signal of telecommunication by wireless receiver, after being amplified, then by A/D converter, analog signal is converted to digital received signals by preamplifier;

Baseband signal is input to preamplifier and is amplified to the size being applicable to carrying out subsequent treatment.Because signal is through the decay of wireless channel, the signal received at receiving terminal will diminish, and for carrying out follow-up process, needs the amplification carrying out amplitude.The signal that enlarge leadingly exports, through A/D converter, is converted to digital received signals, is then input to digital demodulation processing unit.Digital demodulation processing unit in described receiving terminal processes the digital received signals that A/D converter obtains; comprise functional modules such as removing protection interval, parameter Estimation, demapping, channel decoding and source decoding, wherein parameter Estimation is the key realizing nonopiate digital demodulation.Described parameter Estimation refers to and utilizes high-performance parameter algorithm for estimating to carry out the isoparametric estimation of frequency, amplitude and phase place and parameter marshalling, obtains orderly amplitude phase estimation value combination.After parameter Estimation completes, digital demodulation processing unit carries out planisphere demapping, channel decoding and source decoding acquisition transmission data more further.The power supply of receiving terminal is all unit module energy supplies of receiving terminal.

S5. by parameter estimation algorithm, digital received signals is estimated, obtain overloading wave frequency, amplitude and phase place, and then complete demodulation and data are exported.

Described non-orthogonal multi-carrier digital modulation and demodulation method, concrete steps are as follows:

(1) according to channel characteristics, exploitable channel is divided into N number of sub-carrier channels; If the subcarrier of signal is:

Transmission signal is encoded and after planisphere maps, carries out serial/parallel conversion, single channel high-speed data is converted into the N road low speed data that walks abreast and is modulated on multicarrier; Multi-carrier signal after modulation is:

$s\left(n\right)={\mathrm{\Σ}}_{i=0}^{N-1}{A}_i\cos (2\mathrm{\π}{f}_{i}n+{\mathrm{\φ}}_i)---\left(6\right)$

I ∈ [0,1 ... N-1], wherein A is carrier amplitude, and f is carrier frequency, and φ is carrier phase; Corresponding to f ₀<f ₁< ... <f _n-1, have amplitude phase value to combine { (A ₀, φ ₀), (A ₁, φ ₁) ... (A _n-1, φ _n-1) carry transmission information, namely send the modulates information of signal to (A _i, φ _i) on;

(2) D/A conversion is carried out to multi-carrier signal s (n) modulated and obtain modulated-analog signal s (t), s (t) carries out power amplification by power amplifier, signal moved by up-converter module the frequency range that applicable wireless channel transmits, then launched by wireless transmitter module;

(3) at receiving terminal, wireless receiver receives wireless signal and is converted to the signal of telecommunication, then utilizes down conversion module that signal is moved base band, and baseband signal, after preamplifier amplifies, carries out A/D conversion, obtains digital received signals;

(4) digital received signals carries out digital demodulation: adopt high performance parameter estimation algorithm to carry out parameter Estimation to digital received signals, obtain the estimated value of the frequency of each subcarrier, amplitude and phase place

(5) to the N group estimated parameter obtained by parameter estimation algorithm, according to estimated frequency between relative size, to corresponding amplitude and phase place sort, obtain the N group amplitude phase value of carry information; Concrete, parameter estimation algorithm obtains if then determine that the built-up sequence of amplitude and phase place is can be obtained by N group estimated parameter the combination of this estimates of parameters carries transmission information;

(6) combined by amplitude phase value carry out the operations such as planisphere demapping and decoding and send data to obtain.

In step (1), described is divided into N number of sub-carrier channels by exploitable channel, and the parameter estimation algorithm according to channel performance and receiving terminal is selected.Desirable larger of the frequency band virgin carrier frequency separation of channel performance difference, desirable very little of the local subcarrier spacing that channel performance is good; Selected method for parameter estimation frequency resolution is low, then sub-carrier frequencies interval can obtain greatly; Selected method for parameter estimation frequency resolution is high, then sub-carrier frequencies interval can obtain little.System does not require subcarrier strict orthogonal, only requires and meets carrier frequency separation condition, that is: the frequency interval of subcarrier is greater than maximum frequency shift and is more than or equal to the frequency resolution of parameter estimation algorithm.When meeting this condition, when there is frequency displacement in subcarrier, the relative size between them can not change, and carries out the estimation of frequency, amplitude and phase place by parameter estimation algorithm.

Described parameter estimation algorithm is the reasonable combination parameter algorithm for estimating of spectral line, obtains receiving digital signals after, the process obtaining frequency, amplitude and phase place can be summarized as:

A, signal to N point zero padding to 2N point, and to the signal after zero padding carry out the FFT of 2N point;

B, by 2N point signal fFT spectrum obtain power spectrum p (k) and phase spectrum D (k);

C, obtain N number of spectrum peak by power spectrum p (k), be designated as k _i, i ∈ [0,1 ... N-1], and the estimation angular frequency of each subcarrier is obtained according to formula (7):

${\widehat{\mathrm{\&omega;}}}_i=\frac{p(k_i+1)-p(k_i-1)}{\mathrm{\&mu;}\&times;[p(k_i+1)-p(k_i-1)]+v\&times;p\left(k_i\right)}---\left(7\right)$

Wherein by estimation angular frequency estimated frequency can be obtained and easily obtain estimated amplitude

D, solving on the basis obtaining frequency and amplitude, can obtain estimating phase place according to phase spectrum D (k) and formula (8):

${\widehat{\mathrm{\&phi;}}}_i=\frac{{\mathrm{\&Sigma;}}_{k_i=k_i-1}^{k_i=k_i+1}(D\left(k_i\right)-\frac{({\widehat{\mathrm{\&omega;}}}_i-k_i{\mathrm{\&omega;}}_s)(N-1)}{2})}{2k_i+1}---\left(8\right)$

Wherein ${\mathrm{\&omega;}}_s=\frac{\mathrm{\&pi;}}{N}.$

Compared with prior art, tool has the following advantages and beneficial effect the utility model:

(1) the frequency division multi-carrier communications systems based on spectrum overlapping that can overcome carrier wave frequency deviation is achieved.

Because carrier spectrum of the present utility model can be overlapping, and do not require subcarrier strict orthogonal at transmitting terminal and receiving terminal, only require and meet carrier frequency separation condition, so the utility model can realize the higher availability of frequency spectrum, to there is again good anti-Doppler.

(2) requirement of the utility model sub-carrier is low, easily meets, and can make full use of band resource.

The carrier frequency separation of frequency division multi-carrier communications systems under specific application environment has certain requirement, and be strict with the communication system of sub-carrier orthogonality relative to OFDM etc., carrier frequency separation condition of the present utility model easily meets.Meeting under carrier frequency separation condition, carrier frequency separation can be little as far as possible, substantially increases the band efficiency of system.

(3) the utility model is feasible.

Key of the present utility model realizes high performance parameter Estimation, and on software, existing multiple high performance parameter estimation algorithm is suggested, and comprises the parameter estimation algorithm of time domain and frequency domain; On hardware, along with the raising of modern computer computing capability, computer can be used as digital demodulation processing unit, carry out high performance parameter Estimation at receiving terminal, realize digital demodulation.

(4) digital modulation of the present utility model and demodulation are flexibly.

Along with the raising of modern computer computing capability, computer can be used as digital modulation processing unit and digital demodulation processing unit, the Programmable Dynamic modulation of multicarrier is flexibly carried out at transmitting terminal, carry out programmable high-performance parameter flexibly at receiving terminal to estimate, improve the flexibility of system and reduce the complexity of system hardware.

(5) a kind of useful solution is provided for wireless multi-carrier communication system overcomes carrier wave frequency deviation.

The utility model only requires that the feature that bandwidth partition meets carrier frequency separation condition makes the orthogonal multiple carrier communication systems such as the non-orthogonal multi-carrier communication system similar with the utility model and OFDM after a small amount of change carrying out modulation and demodulation rule, the utility model all can be adopted directly to carry out digital demodulation to received signal, be conducive to the impact overcoming carrier wave frequency deviation.

Accompanying drawing explanation

Fig. 1 is that spectral bandwidth divides schematic diagram;

Fig. 2 is the structural representation of non-orthogonal multi-carrier digital modulation described in the utility model and demodulating equipment;

The functional block diagram of the digital modulation unit that Fig. 3 is device described in Fig. 2;

Fig. 4 is the functional block diagram of the digital demodulation unit of device described in Fig. 2;

Fig. 5 is the flow chart of non-orthogonal multi-carrier digital modulation described in the utility model and demodulation method.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the utility model is described in further detail, but execution mode of the present utility model is not limited thereto.

As Fig. 2,3,4, a kind of non-orthogonal multi-carrier digital modulation and demodulating equipment, the receiver module comprise sending module, being connected by wireless channel with sending module, described sending module comprises digital modulation processing unit, D/A converter, power amplifier, the wireless launcher that order is connected, and described receiver module comprises wireless receiver, preamplifier, A/D converter, the digital demodulation processing unit that order is connected.

Described wireless launcher comprises up-converter module and transmitter module, and up-converter module is selected according to embody rule, and the analog signal after power amplification, through up-converter module, is moved the frequency of applicable wireless channel propagation, then launched by transmitter module.

Described transmitter module is radio-frequency antenna, or is electro-acoustic transducer.Transmitter module can also be the reflector of other wireless signals.

Described wireless receiver comprises wireless receiving module and down conversion module, and wireless receiving module is converted to the signal of telecommunication the signal received from wireless channel, and the signal of telecommunication is moved and obtained baseband signal by down conversion module, and down conversion module can be selected according to embody rule.

Described wireless receiving module for receiving electromagnetic antenna, or is sound-electric transducer.Wireless receiving module can also be the receiver of other form wireless signals.

Described wireless channel is underwater acoustic channel.

As shown in Figure 5, a kind of non-orthogonal multi-carrier digital modulation and demodulation method, comprise the step of following order:

(1) as Fig. 1, according to channel characteristics, exploitable channel is divided into several sub-carrier channels.Desirable larger of the frequency band virgin carrier frequency separation of channel performance difference, desirable smaller of the local subcarrier spacing that channel performance is good.Be located at frequency band f ₁~ f ₂place's channel condition is poor, frequency band f ₃~ f ₄place's channel condition is better, so at frequency band f ₁~ f ₂inside K is set ₁individual subcarrier, at frequency band f ₃~ f ₄inside K is set ₂individual subcarrier.Wherein, K ₁<K ₂.If K ₁+ K ₂=N, therefore a total N subcarriers.

(2) the input data from outside are carried out message sink coding, chnnel coding, mapping, multi-carrier modulation and are added the process such as protection interval by digital modulation processing unit, obtain multiple carrier digital signal.This module can adopt DSP and micro processor combination to realize, and high-performance computer also can be used to realize.

First, data carry out message sink coding, chnnel coding and mapping process after being input to digital modulation processing unit respectively.Due to the time varying channel that underwater acoustic channel is complicated, for making data transmit quickly and accurately, different codings and mapping can be taked for different channels.Such as, when signal to noise ratio is low, for reducing the error rate of system, the compound mode that forward error correction coding, intertexture and 2ASK modulate can be adopted.

Then, digital modulation processing unit carries out serial to parallel conversion to data, highspeed serial data stream is converted to N road and to walk abreast low rate data streams be modulated to and multicarrier add protection interval, obtain multi-carrier signal.If sub-carrier signal is:

Multi-carrier signal after modulation is:

$s\left(n\right)={\mathrm{\&Sigma;}}_{i=0}^{N-1}{A}_i\cos (2\mathrm{\&pi;}{f}_{i}n+{\mathrm{\&phi;}}_i)---\left(6\right)$

Because scheme of the present utility model does not require strict orthogonal between multicarrier, so baseband signal can be modulated to respectively on each multicarrier, also combined modulation can be carried out.

(3) multi-carrier signal s (n) that digital modulation processing unit obtains is input to D/A converter and converts analog signal s (t) to, amplified by power amplifier again, finally by electro-acoustic transducer, the s (t) after amplification is transmitted in underwater acoustic channel.

(4) first, the sound-electric receive MUT of receiving terminal from the acoustical signal of underwater acoustic channel, and converts the signal of telecommunication to.Then preamplifier is adopted the signal of telecommunication changed through wireless receiver to be enlarged into the value of an applicable subsequent conditioning circuit process.Finally, A/D converter carries out analog/digital conversion to the signal after amplification, and analog signal is converted to digital received signals

(5) digital received signals obtained by step (4) adopt high-performance parameter algorithm for estimating, estimate overloading wave frequency, amplitude and phase place, and then demodulate transmission data.

Realize the digital demodulation processing unit functional structure of estimation demodulation as shown in Figure 4; comprise functional modules such as removing protection interval, parameter Estimation, demapping, channel decoding and source decoding; can be realized by DSP and micro processor combination, high-performance computer also can be used to realize.

Utilizing parameter estimation algorithm to carry out parameter Estimation is important step of the present utility model, the algorithm that still can reach certain estimated accuracy when middle low signal-to-noise ratio has a few class: the maximum likelihood method of Frequency Estimation, be transformed to the frequency domain algorithm for estimating of rough estimate with DFT, based on the time domain algorithm for estimating of auto-correlation function and the parameter estimation algorithm etc. based on subspace.

The present embodiment, for the reasonable combination parameter algorithm for estimating of spectral line, this algorithm is a kind of frequency domain algorithm for estimating being transformed to rough estimate with DFT: obtain receiving digital signals after, the process obtaining frequency, amplitude and phase place can be summarized as:

A, signal to N point zero padding to 2N point, and to the signal after zero padding carry out the FFT of 2N point;

B, by 2N point signal fFT spectrum obtain power spectrum p (k) and phase spectrum D (k);

C, obtain N number of spectrum peak by power spectrum p (k), be designated as k _i, i ∈ [0,1 ... N-1], and the estimation angular frequency of each subcarrier is obtained according to formula (7):

${\widehat{\mathrm{\&omega;}}}_i=\frac{p(k_i+1)-p(k_i-1)}{\mathrm{\&mu;}\&times;[p(k_i+1)-p(k_i-1)]+v\&times;p\left(k_i\right)}---\left(7\right)$

Wherein by estimation angular frequency estimated frequency can be obtained and easily obtain estimated amplitude

D, solving on the basis obtaining frequency and amplitude, can obtain estimating phase place according to phase spectrum D (k) and formula (8):

${\widehat{\mathrm{\&phi;}}}_i=\frac{{\mathrm{\&Sigma;}}_{k_i=k_i-1}^{k_i=k_i+1}(D\left(k_i\right)-\frac{({\widehat{\mathrm{\&omega;}}}_i-k_i{\mathrm{\&omega;}}_s)(N-1)}{2})}{2k_i+1}---\left(8\right)$

Wherein ${\mathrm{\&omega;}}_s=\frac{\mathrm{\&pi;}}{N}.$

Parameter estimation algorithm can obtain the sequence of parameter is carried out again according to the relative size of estimated frequency.On concrete, if then determine that the built-up sequence of amplitude and phase place is can be obtained by N group estimated parameter the combination of this amplitude phase value carries the information sending data.

Finally according to the mapping relations of system, carry out demapping to obtaining orderly amplitude phase value combination, then carry out channel decoding and source decoding acquisition transmission data.

(6) transmission data are exported to user.

Above-described embodiment is the utility model preferably execution mode; but execution mode of the present utility model is not restricted to the described embodiments; change, the modification done under other any does not deviate from Spirit Essence of the present utility model and principle, substitute, combine, simplify; all should be the substitute mode of equivalence, be included within protection range of the present utility model.

Claims (6)

1. a non-orthogonal multi-carrier digital modulation and demodulating equipment, it is characterized in that: the receiver module comprise sending module, being connected by wireless channel with sending module, described sending module comprises digital modulation processing unit, D/A converter, power amplifier, the wireless launcher that order is connected, and described receiver module comprises wireless receiver, preamplifier, A/D converter, the digital demodulation processing unit that order is connected.

2. non-orthogonal multi-carrier digital modulation according to claim 1 and demodulating equipment, it is characterized in that: described wireless launcher comprises up-converter module and transmitter module, up-converter module is selected according to embody rule, analog signal after power amplification is through up-converter module, move the frequency of applicable wireless channel propagation, then launched by transmitter module.

3. non-orthogonal multi-carrier digital modulation according to claim 2 and demodulating equipment, is characterized in that: described transmitter module is radio-frequency antenna, or is electro-acoustic transducer.

4. non-orthogonal multi-carrier digital modulation according to claim 1 and demodulating equipment, it is characterized in that: described wireless receiver comprises wireless receiving module and down conversion module, wireless receiving module is converted to the signal of telecommunication the signal received from wireless channel, the signal of telecommunication is moved and is obtained baseband signal by down conversion module, and down conversion module can be selected according to embody rule.

5. non-orthogonal multi-carrier digital modulation according to claim 4 and demodulating equipment, is characterized in that: described wireless receiving module for receiving electromagnetic antenna, or is sound-electric transducer.

6. non-orthogonal multi-carrier digital modulation according to claim 1 and demodulating equipment, is characterized in that: described wireless channel is underwater acoustic channel.