CN101179308A

CN101179308A - Downlink power control method and device thereof

Info

Publication number: CN101179308A
Application number: CNA2007101106304A
Authority: CN
Inventors: 李圣春; 孙毅; 王燕云
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2007-06-06
Filing date: 2007-06-06
Publication date: 2008-05-14

Abstract

The invention relates to a method controlling a downlink power and a device thereof, wherein the method includes the following steps: the downlink TPC error-receiving rate PTPC_BER_Est is measured in real-time and is estimated according to the uplink dedicated channel pilot error-receiving rate PBER_Cur; the current downlink TPC PTPC(k) is maintained if the current downlink TPC error-receiving rate PTPC_BER_Est is lower than or equal to the default threshold PTPC_BER_Target, otherwise, the current downlink TPC TPTC(k) is set to zero to perform real-time inner ring power control. The device comprises an estimation module for the downlink TPC error-receiving rate and a regulation module for the downlink power which are sequentially connected with each other. The method and the device determine the quality of the uplink signal through measuring the pilot error-receiving rate, then evaluates the reliability of the downlink TPC power control command received by the network side as a foundation to the downlink power control, thereby avoiding the overdeviation of the downlink power caused by the poor quality of the uplink signal.

Description

A kind of method for controlling downlink power and device thereof

Technical field

The present invention relates to mobile communication, be specifically related to a kind of method for controlling downlink power and device thereof, relate generally to method for controlling downlink power and device thereof in the WCDMA system.

Background technology

Fast development along with the third generation mobile technology, the application of mobile data and multi-media communication will be more and more widely, traditional second generation global system for mobile communications Global System for mobileCommunication, be called for short the GSM communication network and can't adapt to new development trend, for this reason, GSM will progressively carry out the transition to the third generation mobile system.Wherein, third generation partner program 3rdGeneration Partnership Project, be called for short 3GPP, the Wideband Code Division Multiple Access (WCDMA) WidebandCode Division Multiple Access of standard, be called for short WCDMA, constantly improve and mature technique standard, flexible net framework, level and smooth many advantages such as evolution pattern with it, and develop into the major technique of third generation mobile gradually, and accepted by increasing mobile communications operator and equipment supplier.

Power control is one of core technology of WCDMA, and power control fast and accurately can overcome near-far interference, opposing rapid fading effectively, saves system power dissipation, and self-interference in the minimizing system provides power system capacity, the WCDMA technology is moved to maturity and uses.

Power control mainly comprises open Loop Power control and closed power control in the WCDMA system.The main purpose of open Loop Power control is to determine initial transmitting power for public and special-purpose physical channel.The purpose of closed-loop power control is in order to adjust the transmitting power of each travelling carriage, to reduce the influence of this near-far interference, guarantees that as far as possible the power that the base station receives all travelling carriages all equates, thereby makes each user can both satisfy the Qos of transport service.Closed power control comprises inner loop power control and exterior ring power control, and inner loop power control is divided into the inner loop power control of up direction and the inner loop power control of down direction again.

Inner loop power control for down direction, user terminal UE controls according to the quality sum of all down links, that is: may there be multilink in same UE, and UE only sends unique descending TPC power control commands at every turn, all associated network sides receive identical descending TPC power control commands, and adjust descending power according to this TPC.After estimating k TPC power control commands, UTRAN is adjusted into new transmitting power P (k) by following formula with current descending power P (k-1):

P(k)＝P(k-1)+P _TPC(k)+P _bal(k) (1)

P wherein _TPC(k) k power adjustment in the expression inner loop power control procedure, descending TPC is 1 and gets+Δ _TPC, descending TPC is 0 and gets-Δ _TPC, Δ _TPCBe power control step-length, P _Bal(k) expression is drawn close to a common reference power for the power of balance Radio Link, a correction value that obtains according to the descending power control procedure.

Thought about inner-loop power control, Qualcomm is existing detailed description the in detail in american documentation literature " Method and apparatusfor adjusting a signal-to-interference threshold in a closed loop power controlcommunications system ", this patent author is Stein A.Lundby, publication number Publication number is US Patent 6529482, the detailed process of inner-loop power control also has detailed description in the 3GPP25.214 agreement in addition, the problem that this inner-loop power control method exists is, when uplink quality poor, the descending TPC power control information of carrying in the up link receives when unreliable at network side, the down transmitting power shift phenomenon will occur.

In fact, because the complexity of wireless environment, uplink quality can't be guaranteed, and it is higher that error code appears in network side decode uplink TPC sometimes, causes descending power to be adjusted in the opposite direction, and descending power sends not accurate enough.If descending power mistake on the low side causes call drop at most easily; If higher mistake has been wasted descending power at most; cause extra interference to other UE; influence power system capacity; may cause power amplifier to reach the overpower protection state when serious; in the sub-district; other need the UE of bring to power owing to can't obtain more down transmitting power and call drop, have a strong impact on the overall performance of system.

The reason that causes network side to receive descending TPC error code has a lot, specifically includes, but are not limited to following two kinds:

(1) UE enters a shadow region suddenly, perhaps UE is up is subjected to a strong jamming in short-term suddenly, the ascending power of UE also is not able to do in time to catch up with fast, the up degradation of UE, must cause network side to receive descending TPC power control commands accuracy descends, error code is too high, and descending TPC erroneous judgement is determined, and then has caused the descending power adjustment to depart from the adjustment direction of expection.

(2) be in Zone switchedly as UE, also can cause quality of uplink signal too poor when soft handover removes leg, network side receives descending TPC error code, and down transmitting power is forbidden phenomenon.As shown in Figure 1, UE is initially located among the cell 1, only has RL1 to be connected with UE, along with UE moves to cell 2 directions gradually, Event 1A incident takes place, UE adds leg, and this moment, UE kept being connected with RL1, RL2 simultaneously, and UE continues to move to cell 2 directions, Event 1B incident takes place, UE removes leg, and RL1 is removed among the cell 1, and UE only keeps being connected with RL2.In this process, two district pilots signal qualitys as shown in Figure 2.When UE keeps being connected with RL1 and RL2 simultaneously, when UE moves to the cell2 direction, RL1 is removed the eve, up-downgoing path loss between UE and cell1 increases, the uplink downlink quality just progressively worsens, and meanwhile, the up-downgoing path loss that UE and cell are 2 reduces, and the uplink downlink quality just progressively improves.

In (two) kind situation, we know according to WCDMA system inner-loop power control principle, and in the inner-loop power control, UE controls according to the quality sum of all down links, and UE only sends unique upward signal and unique descending TPC power control commands at every turn.Though RL1 may be because the uplink downlink degradation, require UE lifting ascending power, but since this moment 2 of UE and cell the up-downgoing path loss reduce, the uplink downlink quality just progressively improves, network side cell2 may keep the good reception to the UE up link, send up TPC power control commands simultaneously to UE, require UE progressively to reduce uplink transmission power, so UE must keep a lower ascending power, cell2 can correctly receive, and cell 1 is because the increase of path loss can't guarantee the quality of reception, the result has caused the decoding error of 1 pair of descending TPC power control commands of network side cell, and then cause that cell 1 descending power is higher, and cause extra interference to other UE, influence power system capacity and systematic function.And in fact, this moment, UE and cell 2 kept good, correct power control relation, and UE can correctly receive the downstream signal of cell 2, does not need the lifting of downstream signal power in cell 1 sub-district.

Summary of the invention

The technical issues that need to address of the present invention provide a kind of method for controlling downlink power and device thereof, can avoid receiving the down transmitting power shift phenomenon that occurs under the unreliable situation of descending TPC at network side.

Above-mentioned first technical problem of the present invention solves like this, and a kind of method for controlling downlink power is provided, and utilizes default thresholding P _{TPC_BER_T arg et}, may further comprise the steps:

1.1) measure special uplink channel pilot reception error rate P in current single time slot in real time _{BER_Cur}, and the capable in history dedicated channel pilot reception error rate P of associating _{BER_Hist}Estimate current special uplink channel pilot reception error rate P _{BER_Est}, estimate that according to this current descending TPC receives error rate P _{TPC_BER_Est}

1.2) receive error rate P according to current descending TPC _{TPC_BER_Est}Be less than or equal to default thresholding P _{TPC_BER_T arg et}According to current descending TPC P _TPC(k) carry out real-time inner-loop power control, that is: descending TPC power control commands is credible, carries out normal inner-loop power control; Otherwise with current descending TPC P _TPC(k) be made as zero and carry out real-time inner-loop power control, that is: descending TPC power control commands is incredible, and stop normal inner-loop power control this moment, and the Radio Link descending power is only made adjustment with download power balancing.

According to method provided by the invention, described P _{BER_Est}Method of estimation can be P _{BER_Est}=α P _{BER_Cur}+ (1-α) P _{BER_Hist}, wherein, filter coefficient alpha between 0～1, historical special uplink channel pilot reception error rate P _{BER_Hist}Special uplink channel pilot reception error rate P for a last time slot _{BER_Est}, initial p _{BER_Hist}Be zero, later on P _{BER_Est}Adjust.

According to method provided by the invention, the filter coefficient alpha value determines that according to simulation study or outfield actual measurement experience α desirable 0.5.

According to method provided by the invention, described P _{TPC_BER_Est}Method of estimation can be P _{TPC_BER_Est}=f (P _{BER_Est}), functional relation P wherein _{TPC_BER_Est}=f (P _{BER_Est}) can determine according to probability theory knowledge, also can determine according to emulation is approximate.

According to method provided by the invention, described default thresholding P _{TPC_BER_T arg et}Be emulation thresholding or measured value, this default thresholding is based on descending TPC and receives error rate P _{TPC_BER_Est}Determine with descending power deviation probability distribution relation.

According to method provided by the invention, described inner-loop power control is P (k)=P (k-1)+P _TPC(k)+P _Bal(k), wherein, P (k) is current descending power, and P (k-1) is the descending power of a last time slot, P _Bal(k) be the download power balancing adjustment amount; In the inventive method, when descending TPC power control commands when being insincere, with current descending TPC P _TPC(k) be made as zero, only use download power balancing adjustment amount P _Bal(k).

According to method provided by the invention, this method is applied in the WCDMA system, and described special uplink channel is up DPCCH physical channel.

According to method provided by the invention, this method is applied in cdma 2000 systems, and described special uplink channel is the R-PICH physical channel.

According to method provided by the invention, this method is applied in the TD-SCDMA system, and described special uplink channel is up DPCH physical channel.

Above-mentioned another technical problem of the present invention solves like this, and a kind of descending power control device is provided, and output connects the base station sender, comprises that output connects successively from being input to:

Descending TPC receives error rate estimation module, estimates that according to the special uplink channel pilot reception error rate of real-time measurement current descending TPC receives the error rate;

The descending power adjusting module receives the descending TPC of the error rate and the selective reception of predetermined threshold comparative result or descending TPC is made as the zero real-time inner-loop power control that carries out according to current descending TPC.

According to device provided by the invention, the input that described descending TPC receives error rate estimation module and descending power adjusting module is connected or also connects the receiver that is used to receive pilot signal and descending TPC.

Method for controlling downlink power provided by the invention, determine quality of uplink signal by the method for measuring the special uplink channel pilot reception error rate, and then the reliability of the descending TPC power control commands of assessment network side reception, be used as the foundation of descending power control with this, avoided since quality of uplink signal too the descending power that comes of difference band adjust the deviation problems of too, saved down transmitting power, reduced the extra interference that causes to other UE, improve system descending capacity and entire system operation stability performance, compared with prior art had following clear superiority: thus 1. avoid causing downlink transmission power to adjust the low call drop that causes because of descending TPC decoding error code; Thereby 2. avoid because of descending TPC decoding error code cause downlink transmission power adjust the too high power dissipation that causes and to the extra interference of other UE; 3. prevent effectively that the power amplifier that above reason causes from entering the call drop that the overpower protection state reaches a large amount of UE in the same sub-district of bringing thus, improves system descending capacity and entire system operation stability performance.

Description of drawings

Further the present invention is described in detail below in conjunction with the drawings and specific embodiments.

Fig. 1 is a WCDMA system soft switching process schematic diagram.

Fig. 2 is a pilot signal quality curve chart in the WCDMA system soft switching process.

Fig. 3 is descending power control realization flow figure among the present invention.

Fig. 4 is before downlink power control improves, the down transmitting power curve chart under case of soft handover.

Fig. 5 is after downlink power control improves, the down transmitting power curve chart under case of soft handover.

Embodiment

At first, inventive concept is described: the network side base station receives the up-link wireless signal of UE, error condition according to pilot portion in the upward signal physical layer channel that receives, judge that current up-link wireless link-quality is good and poor, adopt different downlink power control strategies for different quality situations, not only satisfied rapid power control but also avoided the purpose that descending power departs from thereby reach.

Second step illustrated apparatus of the present invention, mainly comprised descending TPC and received error rate estimation module and descending power adjusting module, was respectively described below:

(1) descending TPC receives error rate estimation module, the up-link wireless link-quality that is used for the assesses user terminal UE, when the dedicated channel pilot reception error rate is low, illustrate that the up-link wireless link-quality is good at this moment, the descending TPC power control commands that network side receives is believable, carries out normal inner-loop power control; When the dedicated channel pilot reception error rate too high, when surpassing predetermined thresholding, illustrate that the up-link wireless link-quality is too poor at this moment, the descending TPC power control commands that network side receives is incredible, stop normal inner-loop power control this moment, and the Radio Link descending power is only made adjustment with download power balancing.

(2) descending power adjusting module, be used to adjust the network side down transmitting power, the descending power adjusting module receives the estimation court verdict of error rate estimation module according to descending TPC, take corresponding downstream power to adjust measure, add the adjustment amount that the download power balancing algorithm obtains, obtain the down transmitting power of current time slots base station.

The 3rd goes on foot, and the specific implementation step of the inventive method is described, as shown in Figure 3, comprising:

Step 1: the network side base station receives the up-link wireless signal of UE, and upward signal is carried out descrambling and de-spreading, extracts the pilot portion information in the up DPCCH physical channel.

Step 2:, calculate the special uplink channel pilot reception error rate P in the current time slots according to the pilot portion information in the up DPCCH physical channel _{BER_Cur}

Step 3: set a filter coefficient alpha and initialization P _{BER_Hist}: set a filter coefficient alpha before the operation, α is between 0～1, and the α value can be determined voluntarily according to simulation study or outfield actual measurement experience; Historical special uplink channel pilot reception error rate P _{BER_Hist}Special uplink channel pilot reception error rate P for a last time slot _{BER_Est}, initialization P when bringing into operation _{BER_Hist}=0, P subsequently _{BER_Hist}With P _{BER_Est}Adjust.

Step 4: according to P _{BER_Est}=α P _{BER_Cur}+ (1-α) P _{BER_Hist}Estimate current special uplink channel pilot reception error rate P _{BER_Est}, P wherein _{BER_Cur}Be the special uplink channel pilot reception error rate in current single time slot, P _{BER_Hist}Be the historical special uplink channel pilot reception error rate, the special uplink channel pilot reception error rate estimated value in the promptly last time slot processing procedure adopts this formula to estimate P _{BER_Est}Has smoothing effect, i.e. P _{BER_Est}Not only with current single time slot in P _{BER_Cur}Relevant, also with historical P _{BER_Hist}Relevant.

Step 5: according to P _{TPC_BER_Est}=f (P _{BER_Est}) estimate that current descending TPC receives the error rate, compares P _{TPC_BER_Est}＞P _{TPC_BER_T arg et}If greater than execution in step 6, otherwise execution in step 7.Functional relation P wherein _{TPC_BER_Est}=f (P _{BER_Est}) can determine according to probability theory knowledge, also can determine according to emulation is approximate; P _{TPC_BER_T arg et}Be predefined thresholding, this thresholding can be determined according to emulation.

Step 5_1: determine that according to emulation the descending TPC of network side receives error rate P _{TPC_BER_Est}With special uplink channel pilot reception error rate P _{BER_Est}Between relation curve P _{TPC_BER_Est}=f (P _{BER_Est}).

Step 5_2: determine network side special uplink channel pilot reception error rate P according to emulation _{BER_Est}With descending power deviation probability distribution relation curve, thereby determine that descending TPC receives error rate P _{TPC_BER_Est}With descending power deviation probability distribution relation curve, a suitable judging threshold P in view of the above makes a strategic decision _{TPC_BER_T arg et}

Step 6: because current descending TPC receives error rate P _{TPC_BER_Est}Greater than predetermined threshold P _{TPC_BER_T arg et}, explanation thus, the up-link wireless link-quality is too poor, will there be higher error code in the descending TPC power control commands that the network side base station receives at this moment, and descending TPC power control commands is insincere, is unsuitable for continuing on for the control of down transmitting power, so stop inner loop power control, get P _TPC(k)=0.

Step 7: because current descending TPC receives error rate P _{TPC_BER_Est}Be less than or equal to predetermined threshold P _{TPC_BER_T arg et}, explanation thus, the up-link wireless link-quality is enough good, the descending TPC power control commands that the network side base station receives at this moment is correct or has higher confidence level, descending TPC power control commands is still effective, is applied to the control of down transmitting power, so carry out inner loop power control.

Step 8: obtain download power balancing adjustment amount P according to the download power balancing algorithm _Bal(k), according to formula P (k)=P (k-1)+P _TPC(k)+P _Bal(k) obtain the interior down transmitting power P (k) of this time slot.

Step 9: with P _{BER_Est}Assignment is given P _{BER_Hist}, as the historical estimated value of the special uplink channel pilot reception error rate of next time slot, P _{BER_Hist}=P _{BER_Est}, repeating step 1-9.

The 4th step, by with prior art relatively further specify the present invention:

(1) prior art

As shown in Figure 4, in the mobile communication soft switching process, the down transmitting power curve chart of Cell 1 and Cell 2 is among the figure

Line is the down transmitting power of Cell 1, Line is the down transmitting power of Cell 2,

Line is the radio chains way among the corresponding C ell 1,

Line is the radio chains way among the corresponding Cell 2.

Soft switching process contrasts Fig. 4 and specifically describes as follows as shown in Figure 1:

4 UE are in Cell 1 zone, have 4 UE among the Cell 1 simultaneously, have 0 UE among the Cell 2, and each UE only has 1 leg.

It is Zone switched that 4 UE successively enter, and add the leg success in Cell 2, all has 4 UE among Cell 1 and the Cell 2, and each UE all has 2 legs.

It is Zone switched that 4 UE leave, and is in Cell 2 zones, and successively removes leg in Cell 1, and simultaneously exist 4 UEs among the Cell 2 this moment, has 0 UE among the Cell 2,, each UE only has 1 leg.

By the down transmitting power curve chart of Cell among Fig. 41 and Cell 2 as can be seen, UE goes the leg process at soft handover, and the lifting phenomenon has appearred suddenly in the descending power of Cell 1.Its analysis of causes is as follows, UE is in the process of leaving the Zone switched Cell of entering 2 zones, the up-downgoing path loss that UE and Cell are 1 increases gradually, the ascending power of UE does not increase when this moment, because this moment, the up-downgoing path loss of 2 of UE and Cell reduced just gradually, under the inner-loop power control effect of Cell 2, the ascending power of UE does not need lifting, cause thus for Cell 1, upward signal progressively worsens, network side receives descending TPC power control commands and a large amount of error codes occur, has finally caused down transmitting power randomness to raise.

(2) the inventive method:

In view of this, adopt such scheme among the present invention, descending power control has been improved, be intended to avoid the descending power control deviation that causes thus.In the concrete enforcement of scheme, error rate of physical channel decision threshold P is determined by emulation in filter coefficient alpha=0.5 _{TPC_BER_T arg et}=20%, when receiving error rate estimation module, descending TPC monitors P _{TPC_BER_Est}Greater than P _{TPC_BER_T arg et}=20% o'clock, stop inner loop power control, only do download power balancing control.Same soft switching process, under new method for controlling downlink power effect, the down transmitting power curve of Cell 1 and Cell 2 has avoided descending power too great deviations to occur as shown in Figure 5 thus, has obtained good effect.

In addition, the foregoing description illustrates under case of soft handover, is without loss of generality, and in the UE of single-link, above-described method for controlling downlink power also is same being suitable for, in case it is poor excessively uplink quality to occur, also starts this method and is controlled.

At last; the above is the preferable embodiment of the present invention; institute is understood that; protection scope of the present invention is not limited thereto; anyly be familiar with the people of this technology in claim protection range of the present invention; any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims

1. a method for controlling downlink power is characterized in that, may further comprise the steps:

1.2) receive error rate P according to current descending TPC _{TPC_BER_Est}Be less than or equal to default thresholding P _{TPC_BER_Target}According to current descending TPC P _TPC(k), otherwise with current descending TPC P _TPC(k) be made as zero, carry out real-time inner-loop power control.

2. according to the described method of claim 1, it is characterized in that described P _{BER_Est}Method of estimation is P _{BER_Est}=α P _{BER_Cur}+ (1-α) P _{BER_Hist}, wherein, the filter coefficient alpha between 0～1 is determined historical special uplink channel pilot reception error rate P according to simulation study or outfield actual measurement _{BER_Hist}Special uplink channel pilot reception error rate P for a last time slot _{BER_Est}, initial p _{BER_Hist}Be zero.

3. according to the described method of claim 1, it is characterized in that described P _{TPC_BER_Est}Method of estimation is P _{TPC_BER_Est}=f (P _{BER_Est}), functional relation P wherein _{TPC_BER_Est}=f (P _{BER_Est}) determine according to probability theory knowledge, or determine according to emulation is approximate.

4. according to the described method of claim 1, it is characterized in that described default thresholding P _{TPC_BER_Target}Be emulation thresholding or measured value, this default thresholding is based on descending TPC and receives error rate P _{TPC_BER_Est}Determine with descending power deviation probability distribution relation.

5. according to the described method of claim 1, it is characterized in that described inner-loop power control is P (k)=P (k-1)+P _TPC(k)+P _Bal(k), wherein, P (k) is current descending power, and P (k-1) is the descending power of a last time slot, P _Bal(k) be the download power balancing adjustment amount.

6. according to the described method of claim 1, it is characterized in that this method is applied in the WCDMA system, described special uplink channel is up DPCCH physical channel.

7. according to the described method of claim 1, it is characterized in that this method is applied in cdma 2000 systems, described special uplink channel is the R-PICH physical channel.

8. according to the described method of claim 1, it is characterized in that this method is applied in the TD-SCDMA system, described special uplink channel is up DPCH physical channel.

9. descending power control device, output connects the base station sender, it is characterized in that, comprises that output connects successively from being input to:

10. according to the described device of claim 9, it is characterized in that the input that described descending TPC receives error rate estimation module and descending power adjusting module also is connected the receiver that is used to receive pilot signal and descending TPC.