CN1355657A - Method based on joint transmission and predistortion technique for processing signals to be transmitted - Google Patents

Abstract

A handing method of transmitting signal based on united transmitting and pre-distortion technology provided by the present invention includes the steps as follows: determining the average powder for united transmission, obtaining the maximum emission threshold power of predistortion according to the preset clipping rate, emitting the united transmitting signal having the emission power within the maximum emission threshold power of predistortion in no distortion mode and to emitting the signal exceeding the threshold power as the power of the threshold, or processing the united emission signal in non-linear predistortion. The present invention not only can make the power amplifying requirement of united transmitting signal not exceed the linear range of power amplifier, but also can raise the performance of the system as a whole.

Description

Based on the transmission signal processing method of uniting transmission and pre-distortion technology

Technical field

The present invention relates to the transmission technology of wireless communication system, relate in particular in digital mobile communication system to adopt and unite the transmission signal processing method that transmission (joint transmission is abbreviated as JT) technology and predistortion (pre-distortion) technology combine.

Background technology

In communication system, the peak-to-average ratio of transmit signal power is than higher sometimes, and this dynamic range and linearity to the amplifier in the transmitter requires very strict.Adopt the delivery plan of associated transmission technology just this problem to occur.Fig. 1 is for adopting the mobile communication system schematic diagram of associated transmission technology.Fig. 2 is for adopting the travelling carriage receiving equipment structural representation of associated transmission technology.Unite that to send be a kind of downlink transmission mode in time division duplex (TDD) system that professor P.W.Baier by Germany proposes.In tdd systems, if the time interval between the uplink and downlink transmission time slot is enough short, the impulse response correlation of uplink and downlink channel is enough big, just can utilize estimated information to come preliminary treatment to send signal in the base station to up channel, and the estimation that makes the receiver of travelling carriage needn't carry out down channel more just can be deciphered, just needn't transmit descending training sequence so in theory, improve power system capacity, also reduce the complexity of travelling carriage simultaneously effectively.

What send in the associating transmission is through the pretreated signal of the characteristic of channel.Yet because the influence of the characteristic of channel, it sends the peak-to-average ratio higher (particularly the bigger spike of energy more after a little while can occur the user) of signal, thereby in real system, the transmission of signal will be subjected to the restriction of linearity of amplifier scope.If the range of linearity of amplifier is higher, cost will be very high.If the range of linearity is not enough, just can not undistorted ground transmission signals, thus cause systematic function to descend.In addition, the spike that occurs in the transmitting power may burn out electronic device, makes the system can't operate as normal.

Summary of the invention

Have the problem that higher peak-to-average ratio brings at uniting the transmission signal, the present invention proposes a kind of based on the transmission signal processing method of uniting transmission and pre-distortion technology.

Sending and the transmission signal processing method of pre-distortion technology based on uniting among the present invention may further comprise the steps:

(1) determines to unite the instantaneous power P that sends signal s _InThereby, obtain uniting the average power that sends signal, wherein P _In=‖ s ‖ ²/ 2;

(2), obtain the emission maximum threshold power P of predistortion according to predetermined slicing rate _Max, P wherein _MaxEqualing the slicing rate multiply by and unite the average power that sends signal;

(3) with transmitting power at predistortion emission maximum threshold power P _MaxWithin unite and send signal and launch undistortedly, will be above this emission maximum threshold power P _MaxSignal with power P _MaxEmission, thus the transmission signal of uniting after treatment is: $s^{\&prime;}={\{}_{\sqrt{2P_{\max }}\&CenterDot;\frac{s}{\left|\right|s\left|\right|},{\left|\right|s\left|\right|}^2/2\&GreaterEqual;P_{\max }}^{s,{\left|\right|s\left|\right|}^2/2<P_{\max }}.$

Perhaps, of the present invention based on the transmission signal processing method of uniting transmission and pre-distortion technology, may further comprise the steps:

(1) determines to unite the instantaneous power P that sends signal s _InThereby, obtain uniting the average power that sends signal, wherein P _In=‖ s ‖ ²/ 2;

(2), obtain the emission maximum threshold power P of predistortion according to predetermined slicing rate _Max, P wherein _MaxEqualing the slicing rate multiply by and unite the average power that sends signal;

(3) send signal and carry out non-linear predistortion and handle uniting, thereby unite the transmission signal after obtaining handling: , wherein α is a constant.

Adopt method of the present invention, not only can make and unite the range of linearity that the power amplification that sends signal requires to be no more than power amplifier, but also can improve the overall performance of whole system.

Description of drawings

Fig. 1 shows the schematic diagram of existing mobile communication system;

Fig. 2 shows the structural representation of the existing travelling carriage receiving equipment that adopts the associating transmission;

Fig. 3 shows the architecture of base station schematic diagram that transmission and predistortion are united in employing according to the present invention;

Fig. 4 shows the structure according to pre-distortion of the present invention unit;

Fig. 5 shows the pre-distortion characteristics curve;

Fig. 6 shows the curve that improves of system performance;

Fig. 7 shows the curve of the selection of slicing rate for the systematic function influence.

Specific implementation

Core concept based on the transmission signal processing method of uniting transmission and pre-distortion technology of the present invention is, between associating transmitter unit and transmitting antenna, increase a signal predistortion processing unit, as shown in Figure 3, thereby send before signal sends into transmitting antenna uniting, carry out pre-distortion sending signal.According to the present invention, send the pre-distortion process combine and generally comprise with uniting: unite and send determining of signal transient power, the determining and three steps of pre-distortion of predistortion emission maximum threshold power.The pre-distortion unit can be added in the digital baseband processing section uniting between transmission signal processing unit and the power amplifier, also can be added in the analog part.

Describe of the present invention based on uniting the transmission signal processing method that sends with pre-distortion technology below in conjunction with accompanying drawing.

1. determine to unite the instantaneous power that sends signal

The base band transmit of traditional associating delivery plan can be expressed as

s＝H ^HC(C ^HHH ^HC) ^-1d (1)

Wherein, H is the matrix of the representative characteristic of channel, and C is the spreading code matrix, and d is the user data vector.

According to formula P _In=‖ s ‖ ²/ 2 obtain uniting the instantaneous power that sends signal, and can obtain uniting the average power that sends signal.

2. determine the emission maximum threshold power P of predistortion _Max

In the present invention, the emission maximum threshold power of predistortion equals the slicing rate and multiply by and unite the average power that sends signal.

So-called slicing rate is meant the ratio of average power and the power of original transmission signal after the pre-distortion.The slicing rate can be subjected to the influence of factors such as base-station environment, travelling carriage quantity and channel.In the present invention, the slicing rate is at different application systems, promptly under different environment and condition, by using simulation software to carry out emulation or determine by field measurement, and is depicted as table.In the application afterwards, can select different best slicing rates according to different applied environments, with the performance of safeguards system.This is an innovative point of the present invention.

3. pre-distortion

After the maximum transmission power thresholding of determining to unite the instantaneous power that sends signal and predistortion, carry out pre-distortion.The pre-distortion method has a variety of, such as pre-slicing and non-linear predistortion.Below, we specifically introduce these two kinds for uniting the method that signal carries out pre-distortion that sends.

(1) pre-slicing

With transmitting power at predistortion emission maximum threshold power P _MaxWithin signal launch undistortedly, and will scabble above the signal of this emission maximum threshold power.

In the present invention, after pre-slicing processing, unite the transmission baseband signal and become: $s^{\&prime;}={\{}_{\sqrt{2P_{\max }}\&CenterDot;\frac{s}{\left|\right|s\left|\right|},{\left|\right|s\left|\right|}^2/2\&GreaterEqual;P_{\max }}^{s,{\left|\right|s\left|\right|}^2/2<P_{\max }}---\left(2\right)$

Wherein, ‖ s ‖ ²/ 2 for uniting the instantaneous power that sends signal s.

(2) non-linear predistortion

The model of non-linear predistortion has multiple, and what formula (3) was described is model commonly used. $g\left(A\right)=\frac{1}{{(1+A^{2a})}^{1/2a}}---\left(3\right)$

In the present invention, , be the signal transient power of associating transmitting element and the ratio of maximum transmission power.α is a constant, and representative value is 2-3.

Like this, sending signal through uniting behind the non-linear predistortion among the present invention is $s^{\&prime;}=\frac{s}{{[1+{({\left|\right|s\left|\right|}^2/2/P_{\max })}^{2a}]}^{1/4a}}----\left(4\right)$

Fig. 5 is two kinds of pre-distortion characteristics curves, and the instantaneous power wherein horizontal, that the longitudinal axis is represented associating transmitting element signal respectively and this are united the transmission signal through the power output (at the normalization of predistortion emission maximum threshold power) after the pre-distortion.The requirement of the complexity and the systematic function of system is depended in the selection of these two kinds of pre-distortion methods.In actual applications, can select neatly for the best joint of complexity and performance requirement according to communication system.

The system performance of associated transmission technology after in conjunction with pre-distortion technology improved curve as shown in Figure 6, wherein solid line is represented the ber curve of the associating delivery plan that professor P.W.Baier proposes, and does not promptly consider the resulting ber curve of the range of linearity range of linearity infinity of amplifier (promptly think) of amplifier; Chain-dotted line and long dotted line are represented respectively to handle the resulting ber curve of transmission signal through pre-slicing and non-linear predistortion.As can be seen from Figure 6, pre-distortion is united the transmission signal, not only solved well unite higher peak-to-average ratio in the transmission the transmission signal for the strict problem of transmitter, and systematic function is increased.

Fig. 7 shows the influence of the selection of slicing rate for systematic function.The resulting curve of Fig. 7 is that to utilize simulation software to carry out emulation resulting.In pre-distortion of the present invention, the selection of slicing rate is very important.As can be seen from Figure 7, under different environment and condition, suitably selecting different slicing rates, is useful to the assurance of systematic function.Shown in Figure 7 is a kind of situation of two travelling carriages, is 8 o'clock in the slicing rate as can be seen, and the error rate of system is less, and promptly the best slicing rate under this condition is 8.In general, the slicing rate of choosing should be greater than 2.But the slicing rate neither be the bigger the better, if the slicing rate is too big, the present invention is with ineffective.

The present invention has been described above in conjunction with specific embodiments.Yet, to those skilled in the art, under the prerequisite that does not deviate from the spirit and scope of the present invention, can make different improvement and modification to the present invention.Thereby all various modifications and variations that fall into claim scope of the present invention all should belong within protection scope of the present invention.

Claims (14)

1. one kind sends and the transmission signal processing method of pre-distortion technology based on uniting, and comprises step:

(1) determines to unite the instantaneous power P that sends signal s _InThereby, obtain uniting the average power that sends signal, wherein P _In=‖ s ‖ ²/ 2;

(2), obtain the emission maximum threshold power P of predistortion according to predetermined slicing rate _Max, P wherein _MaxEqualing the slicing rate multiply by and unite the average power that sends signal;

(3) with transmitting power at predistortion emission maximum threshold power P _MaxWithin unite and send signal and launch undistortedly, will be above this emission maximum threshold power P _MaxSignal with power P _MaxEmission, thus the transmission signal of uniting after treatment is: $s^{\&prime;}={\{}_{\sqrt{{2P}_{\max }}\&CenterDot;\frac{s}{\left|\right|s\left|\right|},{\left|\right|s\left|\right|}^2/2\&GreaterEqual;P_{\max }}^{s,{\left|\right|s\left|\right|}^2/2<P_{\max }}.$

2. according to the process of claim 1 wherein that this processing method realizes uniting to send between signal processing unit and the power amplifier.

3. according to the process of claim 1 wherein that this processing method realizes in the digital baseband processing section.

4. according to the process of claim 1 wherein that this processing method realizes in the analog part.

5. according to the process of claim 1 wherein that the slicing rate is at different application systems, determines by emulation mode or field measurement.

6. according to the process of claim 1 wherein that the slicing rate is greater than 2.

7. one kind sends and the transmission signal processing method of pre-distortion technology based on uniting, and comprises step:

(1) determines to unite the instantaneous power P that sends signal s _InThereby, obtain uniting the average power that sends signal, wherein P _In=‖ s ‖ ²/ 2;

(2), obtain the emission maximum threshold power P of predistortion according to predetermined slicing rate _Max, P wherein _MaxEqualing the slicing rate multiply by and unite the average power that sends signal;

(3) send signal and carry out non-linear predistortion and handle uniting, thereby unite the transmission signal after obtaining handling: , wherein a is a constant.

8. according to the method for claim 7, wherein the model of this non-linear predistortion processing is: $g\left(A\right)=\frac{1}{{(1+A^{2a})}^{1/2a}}$ Wherein $A=P_{\mathrm{in}}/P_{\max }={\left|\right|s\left|\right|}^2/2/P_{\max }.$

9. according to the method for claim 7, wherein α is 2-3.

10. according to the method for claim 7, wherein this processing method realizes uniting to send between signal processing unit and the power amplifier.

11. according to the method for claim 7, wherein this processing method realizes in the digital baseband processing section.

12. according to the method for claim 7, wherein this processing method realizes in the analog part.

13. according to the method for claim 7, wherein the slicing rate is at different application systems, determines by emulation mode or field measurement.

14. according to the method for claim 7, wherein the slicing rate is greater than 2.

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