CN101577567B - Power control method for downward closed loop in TD-SCDMA system - Google Patents

Abstract

The invention discloses a power control method for a downward closed loop in a TD-SCDMA system, which comprises the following steps: (a) measuring an instantaneous signal interference ratio SIR_M(n-1)'of a current n-1 moment, and filtering the SIR_M(n-1)'to obtain SIR_M(n-1); (b) calculating an estimated error SIR_E(n-1)'of the instantaneous signal interference ratio SIR_M(n-1)'and an ideal signal interference ratio SIR_R(n-1), and adopting a least mean square algorithm to adaptively filter the error so as to obtain SIR_E(n-1); (c) carrying out SIR_E(n-1) compensation on SIR_M(n-1), and predicting a signal interference ratio SIR_P of a No.n moment according to a compensation result and a power control TPC command generated at a previous moment; and (d) comparing the SIR_P with a target signal interference ratio SIR<target> and generating a new TPC command according to a comparing result so as to control downward power according to the command. Because LSM is adopted to carry out the adaptive filtering, the SIR obtained by measuring not only has small dynamic range, but also has low control frequency, thus great resources are saved, and the performance for measuring the SIR is improved, thereby quickly and effectively realizing the power control of the downward closed loop.

Description

Power control method for downward closed loop in the TD-SCDMA system

Technical field

The present invention relates to TD-SCDMA (TD SDMA) system field, relate in particular to the power control method for downward closed loop in this system.

Background technology

In the TD-SCDMA system, power control is divided into open loop, closed loop (comprising outer shroud and interior ring) control.The function of this three part in real system and effect are different, but interosculate again, have formed whole power control system.Open Loop Power control generally is used for system initial state.After open Loop Power control, system just enters closed power control.

Closed power control typically refers to receiving terminal according to the signal interference ratio SIR and the target signal interference ratio SIR that receive _Target(from external circule power control) result relatively produces TPC (power control) order and controls transmitting power.For the sir target value corresponding variation along with the variation of network and wireless environment that makes exterior ring power control, adjust to the lucky level that can guarantee received signal quality, needing inner loop power to be controlled to be exterior ring power control provides dynamically signal-to-interference ratio measurement value accurately.

Generally speaking, the closed power of descender control sequential be example with D (delay)=2 among this figure as shown in Figure 1, represents that namely the TPC order of current generation is sent out in next subframe, controls the down transmitting power of next subframe again.Thereby, order the TPC order to be worked from downlink data receiving generation TPC and understand time-delay 2 subframes, in order more effectively descending power to be controlled, the following Poewr control method of general employing: according to the instantaneous signal interference ratio SIR_M ' of current measurement and ordering through filtered signal interference ratio SIR_M and TPC of constantly obtaining before, predict the signal interference ratio SIR_P in following certain moment; Then, according to SIR_P and target signal interference ratio SIR _TargetSize produce the TPC order, with this order by sending out on next subframe constantly, constantly down transmitting power after order was controlled accordingly after received the base station.

Because wireless channel environment changes the existence of factors such as fast and multipath fading, in order to obtain relatively accurate predicted value SIR_P, not only need SIR_M ' value is carried out filtering, and need carry out filtering to the error SIR_E ' of SIR_M after the filtering and desirable signal interference ratio SIR_R and obtain SIR_E, again SIR_M is carried out the SIR_E compensation, thereby obtain SIR_P comparatively accurately.And usually SIR_E ' is adopted simple IIR (Infinite Impulse Response at present, infinite impulse response) filtering method or do not adopt any filtering method, the sir value dynamic range of utilizing this method to obtain is bigger, and control frequency height, cause the very big wasting of resources, thereby can not realize the control of downlink closed-loop power rapidly.

Summary of the invention

Technical problem to be solved by this invention provides the power control method for downward closed loop fast and effectively of a kind of TD-SCDMA of being applicable to system.

For solving the problems of the technologies described above, the present invention is achieved by the following technical solutions:

Power control method for downward closed loop in a kind of TD-SCDMA system may further comprise the steps:

A, measure current n-1 instantaneous signal interference ratio SIR_M (n-1) ' constantly, and it is carried out filtering obtain SIR_M (n-1); Namely according to the SIR_M (n-2) of previous moment, by SIR_M (n-1)=(1-p) * SIR_M (n-2)+p*SIR_M (n-1) ' to SIR_R (n-1) ' carry out filtering, wherein, p is filter factor;

B, calculate the evaluated error SIR_E (n-1) ' of instantaneous signal interference ratio SIR_M (n-1) ' and desirable signal interference ratio SIR_R (n-1), and the employing least mean square algorithm carries out adaptive-filtering to this error and obtains SIR_E (n-1); Described desirable signal interference ratio SIR_R (n-1) calculates according to signal-to-interference ratio measurement value and the power control TPC order in the moment before;

C, SIR_M (n-1) is carried out SIR_E (n-1) compensation, according to this compensation result and before the power control TPC order prediction n signal interference ratio SIR_P constantly that produces constantly;

D, comparison SIR_P and target signal interference ratio SIR _TargetSize, produce new TPC order accordingly, and then according to this order descending power controlled.

Wherein, in the described steps d, if SIR_P is less than SIR _Target, TPC orders to reducing power; Otherwise the TPC order is for increasing power.

The present invention has following beneficial effect:

Below table 1 be not use the downlink closed-loop circule power control method (Bang_bang) of any filtering and use under the closed-loop power control method of the present invention (APC) result of portable terminal sir measurement filtering.The simulated conditions of whole closed power control is: go up behavior 1 user, take 1 code channel, spreading factor is 8; Following behavior 1 user takies 2 code channels, and spreading factor is 16; Emulation piece number is 200.

Table 1

Illustrate: the max in 1. showing, min, ave, var are respectively maximum, minimum value, average, the variances of sir measurement filter value, var=sum ((measuring the SIR-SIR desired value) ^2)/length; 2. the variation of SIR (dB) measured value is respectively as Fig. 2～shown in Figure 5, abscissa is testing time, ordinate is the sir measurement filter value, wherein, Fig. 2 and Fig. 3 are respectively under the case11 variation schematic diagram that adopts the SIR that Bang_bang method and APC method measure, and Fig. 4 and Fig. 5 are respectively the variation schematic diagram that adopts the SIR that Bang_bang method and APC method measure under the case33.

From the variation schematic diagram of SIR as can be seen, compare with existing method, the present invention is owing to adopted LMS (Least Mean Squre, least mean square algorithm) carries out adaptive-filtering, the SIR that measures not only dynamic range is little, and control frequency is low, has saved very large resource like this, improved and measured the performance of SIR, thereby realized descending not busy ring power control fast and effeciently.

Description of drawings

Fig. 1 is downlink closed-loop power control sequential schematic diagram;

Fig. 2 is the variation schematic diagram of the SIR that employing Bang_bang method measures under case11;

Fig. 3 is the variation schematic diagram that adopts the measured SIR that obtains of APC method under case11;

Fig. 4 is the variation schematic diagram of the SIR that employing Bang_bang method measures under case33;

Fig. 5 is the variation schematic diagram of the SIR that employing APC method measures under case33;

Fig. 6 is the power control method for downward closed loop flow chart of the embodiment of the invention;

Fig. 7 is the method flow diagram that the signal interference ratio evaluated error is carried out LMS filtering.

Embodiment

The present invention is described in further detail below in conjunction with the accompanying drawings and the specific embodiments:

Core concept of the present invention is:

At first, measure current n-1 instantaneous signal interference ratio SIR_M (n-1) ' constantly, and it is carried out filtering obtain SIR_M (n-1).

Secondly, calculate the evaluated error SIR_E (n-1) ' of instantaneous signal interference ratio SIR_M (n-1) ' and desirable signal interference ratio SIR_R (n-1), and this error is obtained SIR_E (n-1) by LMS filtering; Because channel variation is fast, cause SIR_E ' also changing at any time, for track channel change rapidly, the present invention has adopted LMS adaptive-filtering method to this value.Wherein, SIR_R can be according to calculating through filtered signal interference ratio SIR_M and TPC order of constantly obtaining before.

Then, SIR_M (n-1) is carried out SIR_E (n-1) compensation, the TPC that produces constantly before reaching according to this compensation result predicts n signal interference ratio SIR_P constantly.

At last, compare SIR_P and target signal interference ratio SIR _TargetSize, produce new TPC order accordingly, and then according to this order descending power controlled.

Below be one embodiment of the present of invention, as shown in Figure 6, specifically may further comprise the steps:

601, measure current n-1 instantaneous signal interference ratio SIR_M (n-1) ' constantly.

602, the current n-1 moment instantaneous signal interference ratio SIR_M (n-1) ' is carried out filtering with eve SIR_M (n-2), i.e. SIR_M (n-1)=(1-p) * SIR_M (n-2)+p*SIR_R (n-1) '; Wherein, p is filter factor.

603, calculate the evaluated error SIR_E (n-1) ' of instantaneous signal interference ratio SIR_M (n-1) '.If the previous moment measured value is SIR_M, after TPC order control, be SIR_R (n-1) at n-1 desirable measured value constantly, then SIR_M (n-1) ' is evaluated error with SIR_R (n-1) difference, namely

SIR_E(n-1)＝SIR_M(n-1)′-SIR_R(n-1)；

SIR_R(n-1)＝SIR_M(n-3)+TPC(n-4)*step+TPC(n-3)*step；

Wherein, step is the power control step-length.

604, evaluated error SIR_E (n-1) ' is carried out LMS filtering.If the row vector of being made up of previous moment and current time measure error is E=[SIR_E (n-2), SIR_E (n-1) '], LMS initial weight factor column vector is W=[0,0] ' (' expression W transposition is column vector), then the flow chart of LMS filtering is seen Fig. 7.Wherein, step is the filtering step-length.

605, the signal interference ratio SIR_P of prediction n frame.Described SIR_P is obtained by the TPC of SIR_M (n-1), SIR_E (n-1) and moment generation before, that is:

SIR_P＝SIR_M(n-1)+TPC(n-2)*step+SIR_E(n-1)。

606, comparison prediction value SIR_P and target signal interference ratio SIR _TargetSize, produce to be used for accordingly currently going up the TPC order of sending out, and then according to this order descending power to be controlled.Wherein, when SIR_P more than or equal to SIR _TargetThe time, the TPC order is increase power, otherwise, for reducing power.

The above only is preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (2)

1. the power control method for downward closed loop in the TD-SCDMA system is characterized in that, may further comprise the steps:

A, measure current n-1 instantaneous signal interference ratio SIR_M (n-1) ' constantly, and it is carried out filtering obtain SIR_M (n-1); Namely according to the SIR_M (n-2) of previous moment, by SIR_M (n-1)=(1-p) * SIR_M (n-2)+p*SIR_M (n-1) ' to SIR_R (n-1) ' carry out filtering, wherein, p is filter factor;

B, calculate the evaluated error SIR_E (n-1) ' of instantaneous signal interference ratio SIR_M (n-1) ' and desirable signal interference ratio SIR_R (n-1), and the employing least mean square algorithm carries out adaptive-filtering to this error and obtains SIR_E (n-1); Described desirable signal interference ratio SIR_R (n-1) calculates according to signal-to-interference ratio measurement value and the power control TPC order in the moment before;

C, SIR_M (n-1) is carried out SIR_E (n-1) compensation, according to this compensation result and before the power control TPC order prediction n signal interference ratio SIR_P constantly that produces constantly;

D, comparison SIR_P and target signal interference ratio SIR _TargetSize, produce new TPC order accordingly, and then according to this order descending power controlled.

2. the power control method for downward closed loop in the TD-SCDMA as claimed in claim 1 system is characterized in that, in the described steps d, if SIR_P is less than SIR _Target, TPC orders to reducing power; Otherwise the TPC order is for increasing power.

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