CN102710404A - Transmission method for low transmitting power and single carrier-frequency division multiplexing access system - Google Patents

Abstract

The invention discloses a transmission method for a low transmitting power and single carrier-frequency division multiplexing access system. Under the basic background that a demodulated reference signal is from a finite set, a method for finding the demodulated reference signal with smaller PAPR (Peak to Average Power Ratio) by iterating is provided. According to the method, for each system composition, smaller PAPR is found by calculating and is formed into a combined demodulated reference signal form. Compared with the prior method, the method has the advantages that the disadvantages of the system caused by the demodulated reference signal with high PAPR are effectively overcome; and once the form is generated, the form can be reused and further the complexity is low. According to the transmission method disclosed by the invention, the problem that a demodulated detection signal with high PAPR is easily distorted when passing through an amplifier is effective solved; and the PAPR is reduced while no error rate of the system is lost.

Description

The transmission method of low transmitting power single carrier-frequency division multiple access system

Technical field

The invention belongs to the mobile communication technology field, particularly the carrier aggregation of LTE-A (CA, Carrier Aggregation) technology.

Background technology

The evolution process from LTE to the LTE-Advanced system, more the demand of wide spectrum will become the key factor that influences evolution, and for this reason, 3GPP proposes carrier aggregation technology as one of key technology of LTE-Advanced system.Its basic goal is that the carrier aggregation with a plurality of relative arrowbands becomes a wideer frequency spectrum, thereby satisfies the requirement of LTE-Advanced.In the LTE-A system; Each member carrier (CC; Component Carrier) demodulated reference signal (SRS, Sounding Reference Signal) is all independently arranged, but when a plurality of CC; Different demodulated reference signal stacks will increase the peak-to-average force ratio (PAPR, Peak to Average Power Ratio) that sends signal.Here PAPR is formulated as:

Wherein, x _nThe output signal of expression through obtaining after the IFFT computing, max [] representes maximum, E [] representes mean value.And when high peak valve signal gets into the power amplifier saturation region of system's transmitting terminal, can produce very big inband distortion and out-of-band radiation, cause the interference of distorted signals and adjacent band to cause system performance degradation.For undistorted transmission SC-FDMA signal, require transmitting terminal to have the very big range of linearity, the cost that this has just improved system design has limited range of application.

Proposed a lot of methods to the PAPR that how to reduce signal, but the method for the relevant PAPR that how to reduce demodulated reference signal seldom.LTE Rel-8 has provided two kinds and reduced cube approach of system coefficient: a kind of is to adopt the different sequences group for different CC, and another kind is with different cyclic shifts for different CC.But document does not provide the concrete reference signal based on low PAPR and chooses scheme.Particular content sees for details: 3GPP R1-100308, NEC Group, NTT DOCOMO, " CM reduction of UL RS for carrier aggregation in LTE-A, " 2010.

Summary of the invention

In order to overcome the above-mentioned shortcoming of prior art; The invention provides a kind of transmission method of low transmitting power single carrier-frequency division multiple access system; Through searching optimal demodulation reference signal, and process form, from form, select the combined demodulation reference signal; The PAPR of the demodulated reference signal that this method is selected is less, and can not reduce the performance of system.

The technical solution adopted for the present invention to solve the technical problems is: a kind of transmission method of low transmitting power single carrier-frequency division multiple access system comprises the steps:

(1) user's transmission information bit at first passes through signal encoding, and PSK or QAM modulation forms modulation symbol then;

(2) modulation symbol is carried out the DFT precoding;

(3) choosing of demodulated reference signal: for first subframe signal, at first seek the optimal demodulation reference signal, and process form, from form, select the combined demodulation reference signal; For later subframe signal, directly from form, select;

(4) each CC precoded signal and the combined demodulation reference signal of selecting are mapped on the subcarrier of user's use, and will shine upon all member carrier polymerizations of accomplishing;

(5) signal with the CC polymerization carries out the IFFT conversion;

(6) add Cyclic Prefix, generation transmits.

Compared with prior art; Good effect of the present invention is: through the basic background of demodulated reference signal from finite aggregate; Propose a kind of iteration and sought the method for the demodulated reference signal of less PAPR; This method constitutes to each system, through the less PAPR of seek, and is made into combined demodulation reference signal form.This method is compared with existing method, the demodulated reference signal that not only efficiently solves high PAPR to system bring unfavorable, and form is just reusable in case generate, so complexity is very low.The present invention efficiently solves demodulation detectable signal easy problem that distortion takes place through amplifier time of high PAPR, when assurance has the error rate of loss system, has not reduced PAPR.

Description of drawings

The present invention will explain through example and with reference to the mode of accompanying drawing, wherein:

Fig. 1 is the flow chart of the inventive method;

Fig. 2 is a kind of choosing method sketch map of demodulated reference signal;

Fig. 3 is the choosing method sketch map of another kind of demodulated reference signal;

Fig. 4 is the simulation result sketch map.

Embodiment

Before setting forth embodiment, at first introduce wherein used term and the theorem that wherein uses:

LTE upstream physical layer multiple access scheme is SC-FDMA, supports FDD and TDD mode.In the wireless frame structure based on FDD, the duration of a radio frames is 10ms, is made up of 10 sub-frame, wherein comprises two time slots in each subframe.(Resource Grid RG) constitutes the resource grid that the signal of each slot transmission is made up of continuous

individual SC-FDMA symbol on

number of sub-carrier continuous on the frequency domain and the time domain.The value of

is determined by system bandwidth.A Resource Block (Resource Block; RB) constitute by individual SC-FDMA symbol and

number of sub-carrier; Under the regular circulation prefix,

For the LTE system under the regular circulation prefix, on the time domain, the 4th SC-FDMA symbol is reference signal, and on the frequency domain, reference signal has adopted centralized pilot tone modes of emplacement, and the frequency bandwidth between its frequency bandwidth and the data symbol is identical.

The expression formula of alternative demodulated reference signal is:

$r_{u,v}^{\left(\mathrm{\&alpha;}\right)}\left(n\right)=e^{\mathrm{j\&alpha;n}}{\stackrel{\&OverBar;}{r}}_{u,v}\left(n\right),$ $0\&le;n<M_{\mathrm{sc}}^{\mathrm{RS}}$

Wherein is the length of demodulated reference signal, and α is a cyclic shift value

α=2πN _CS/12

$N_{\mathrm{CS}}=(n_{\mathrm{DMRS}}^{\left(1\right)}+n_{\mathrm{DMRS}}^{\left(2\right)}+n_{\mathrm{PRS}}\left(n_s\right))\mathrm{mod}12$

In a radio frames, n _s=0,1 ..., 19; By the higher level parameters configuration,

By uplink scheduling information configuration, n _PRS(n _s) generate by pseudo-random generator:

Each basic sequence is broken down into 30 sequence set (Sequence Group; SG); U ∈ { 0; 1; ...; 29} is a group number, and v is a basic sequence among the SG number, and every group comprises a length for or the basic sequences of two length for

.

When the Resource Block number of distributing is 1 or 2; Be that reference signal length is 12 or 24 o'clock; Basic sequence

adopts computer search sequence (Computer Generated Sequences, CG Sequences).

When the Resource Block number of distributing more than or equal to 3 the time, promptly reference signal length was more than or equal to 36 o'clock, basic sequence adopts the Zadoff-Chu sequence.Zadoff-Chu sequence

is produced by following formula:

${\stackrel{\&OverBar;}{r}}_{u,v}\left(n\right)=x_q\left(n\mathrm{mod}{N}_{\mathrm{ZC}}^{\mathrm{RS}}\right),0\&le;n<M_{\mathrm{sc}}^{\mathrm{RS}}$

$x_q\left(m\right)=e^{-j\frac{\mathrm{\&pi;qm}(m+1)}{N_{\mathrm{ZC}}^{\mathrm{RS}}}},$ $0\&le;m\&le;N_{\mathrm{ZC}}^{\mathrm{RS}}-1$

Wherein,

is the largest prime number less than reference signal length, and q is determined by following formula again:

$\stackrel{\&OverBar;}{q}=N_{\mathrm{ZC}}^{\mathrm{RS}}\&CenterDot;(u+1)/31$

As shown in Figure 1, a kind of transmission method of low transmitting power single carrier-frequency division multiple access system comprises the steps:

(1) coding, the PSK&QAM modulation.User's transmission information bit at first passes through signal encoding, and PSK or QAM modulation forms modulation symbol then.What the present invention provided is the example of K CC, and input bit converts the matrix of J * K, J=log to ₂(R)+log ₂(M _Ary), R is a code efficiency, M _AryIt is order of modulation.

(2) modulation symbol is carried out the DFT precoding that L is ordered.

$X_m=\underset{n=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{x}_n{e}^{-j\frac{2\mathrm{\&pi;}}{L}\mathrm{mn}},$ for?m=0,1,…,L-1

(3) choosing of demodulated reference signal: for first subframe signal, at first seek the optimal demodulation reference signal, and process form, from form, select the combined demodulation reference signal.For later subframe signal, directly from form, select.

The method of seeking the optimal demodulation reference signal comprises following two kinds:

Method one, calculate the PAPR of all combined demodulation detection reference signals, therefrom select the minimum M kind combination of PAPR.As shown in Figure 2, comprise the steps:

Suppose total K CC in the system, each CC has Q alternative demodulated reference signal.

The PAPR of all combined demodulation detection reference signals of step 11, a calculating K CC, a total G=Q ^KPlant combination, from small to large ordering successively.

Step 12, the above all combined demodulation reference signals of storage are processed form, when system configuration and parameter constant; Can directly from form, transfer data, if system configuration and parameter change, need be according to step 11; Form new form, so that subsequent use.

Method two, seek next demodulated reference signal according to previous demodulated reference signal.As shown in Figure 3, comprise the steps:

Suppose total K CC in the system, each CC has Q alternative demodulated reference signal.

Step 21, calculate the PAPR of Q the alternative demodulated reference signal of first CC, select wherein m ₁The less demodulated reference signal of individual PAPR is as candidate's demodulated reference signal of first CC;

The m of step 22, known first CC ₁On the basis of individual candidate's demodulated reference signal,, calculate the PAPR of Q the alternative demodulated reference signal of second CC, therefrom select m to each candidate's demodulated reference signal ₂The demodulated reference signal that individual PAPR is less.In conjunction with the selection of two CC, present one total m ₁* m ₂Plant the combined demodulation reference signal.

Step 23, for k CC, the m of (k-1) individual CC before known ₁* m ₂* m _K-1Plant on the basis of combined demodulation reference signal,, calculate the PAPR of Q the alternative demodulated reference signal of k CC, therefrom select m to each combination _kThe demodulated reference signal that individual PAPR is less.In conjunction with the selection of k CC, present one total m ₁* m ₂* m _K-1* m _kPlant the combined demodulation reference signal.

Step 24, repeating step 23 are up to all CC of traversal.

Step 25, the above all combined demodulation reference signals of storage are processed form, when system configuration and parameter constant; Can directly from form, transfer data; If system configuration and parameter change, need form new form according to step 21～step 25, so that subsequent use.

(4) each CC precoded signal and the combined demodulation reference signal of selecting are mapped on the subcarrier of user's use.And will accomplish all CC polymerizations of shining upon.

(5) signal with carrier aggregation carries out the IFFT conversion.

(6) add Cyclic Prefix (CP, Cyclic Prefix), generation transmits.

In order to verify the correctness of method proposed by the invention, simulated environment is in the clustered-DFT-S-OFDM system, and 2 CC and the two are at a distance of 11RB, and each CC has 2 cluster, and size is respectively 2RB and 3RB.Can see from Fig. 4; Under the identical situation of candidate combinations demodulation detection reference signal number; The PAPR of the demodulated reference signal of method one is less than method two, and the PAPR of two kinds of methods reduces along with the minimizing of candidate combinations demodulation detection reference signal number.

Claims (3)

1. the transmission method of a low transmitting power single carrier-frequency division multiple access system is characterized in that: comprise the steps:

(1) user's transmission information bit at first passes through signal encoding, and PSK or QAM modulation forms modulation symbol then;

(2) modulation symbol is carried out the DFT precoding;

(3) choosing of demodulated reference signal: for first subframe signal, at first seek the optimal demodulation reference signal, and process form, from form, select the combined demodulation reference signal; For later subframe signal, directly from form, select;

(4) each member carrier precoded signal and the combined demodulation reference signal of selecting are mapped on the subcarrier of user's use, and will accomplish all member carrier polymerizations of mapping;

(5) signal with the member carrier polymerization carries out the IFFT conversion;

(6) add Cyclic Prefix, generation transmits.

2. the transmission method of low transmitting power single carrier-frequency division multiple access system according to claim 1; It is characterized in that: the method for the described searching optimal demodulation of step (3) reference signal is: the PAPR that calculates all combined demodulation detection reference signals; Therefrom select the minimum M kind combination of PAPR, concrete steps are following:

Suppose total K member carrier in the system, each member carrier has Q alternative demodulated reference signal,

The PAPR of all combined demodulation detection reference signals of step 11, a calculating K member carrier, a total G=Q ^KPlant combination, from small to large ordering successively;

Step 12, the above all combined demodulation reference signals of storage are processed form, when system configuration and parameter constant, directly from form, transfer data; When system configuration and parameter change,, form new form, so that subsequent use according to step 11 step～step 12.

3. the transmission method of low transmitting power single carrier-frequency division multiple access system according to claim 1; It is characterized in that: the method for the described searching optimal demodulation of step (3) reference signal is: seek next demodulated reference signal according to previous demodulated reference signal, concrete steps are following:

Suppose total K member carrier in the system, each member carrier has Q alternative demodulated reference signal;

Step 21, calculate the PAPR of Q the alternative demodulated reference signal of first member carrier, select wherein m ₁The less demodulated reference signal of individual PAPR is as candidate's demodulated reference signal of first member carrier;

The m of step 22, known first member carrier ₁On the basis of individual candidate's demodulated reference signal,, calculate the PAPR of Q alternative demodulated reference signal of second member carrier, therefrom select m to each candidate's demodulated reference signal ₂The demodulated reference signal that individual PAPR is less; In conjunction with the selection of two member carriers, total m ₁* m ₂Plant the combined demodulation reference signal;

Step 23, for k member carrier, the m of k-1 member carrier before known ₁* m ₂* m _K-1Plant on the basis of combined demodulation reference signal,, calculate the PAPR of Q alternative demodulated reference signal of k member carrier, therefrom select m to each combination _kThe demodulated reference signal that individual PAPR is less, in conjunction with the selection of k member carrier, total m ₁* m ₂* m _K-1* m _kPlant the combined demodulation reference signal;

Step 24, repeating step 23 are up to all member carriers of traversal;

Step 25, the above all combined demodulation reference signals of storage are processed form, when system configuration and parameter constant, directly from form, transfer data; When system configuration and parameter change, form new form according to step 21～step 25, so that subsequent use.

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