CN101489295A - Power controlling method for OFDM system base station receiver - Google Patents

Abstract

The present invention provides a power control method of base station receiver applied in OFDM system, wherein the method comprises the following steps: a. RSSI calculating, executing multi-frame averaging and measured value abnormity point elimination for overcoming the abnormal power adjustment caused by abnormal measured value; b. calculating the deviation value between RSSI value and power reference value, executing loop filtering to the calculated deviation value with a variable loop filtering coefficient; and c. checking whether the present transmission power of SS obtains the maximum transmittable power, if the maximum transmittable power is obtained and the power correction value is a non-negative value, stopping transmitting power control information to SS, and until the SS transmission power is less than the maximum transmittable power or the power correction value is a negative value, transmitting power adjusting information to SS for informing power adjustment. The method according to the invention reduces the unnecessary information transmission and increases the system stability.

Description

A kind of Poewr control method of ofdm system base station receiver

Technical field

The present invention relates to a kind of Poewr control method, relate in particular to the Poewr control method of the base station receiver in a kind of OFDM of being applied to (OrthogonalFrequency Division Multiple) system.

Background technology

The same with other wireless communication systems, the main purpose of power control is to overcome transmission path loss and power fluctuation in the ofdm system, thereby solves the power consumption of near-far interference, control interference, control terminal.Control does not have special requirement to ofdm system to descending power, mainly is uplink power control.Uplink power control is divided into closed loop and open loop dual mode.So-called closed power control mainly is that the size that power control is adjusted is controlled by BS (Base Station, base station); And so-called open Loop Power control, SS (Subscriber Station) thus need the calculating path loss to obtain transmitted power.

In ofdm system, closed power control is essential, and open Loop Power control is optional.The total transmitting power of SS is made up of standing part and dynamic adjustment member, and dynamically adjustment member is by the BS FEEDBACK CONTROL.After BS receives the upward signal of certain SS, measure its power, according to certain criterion rated output correction value, transmitted power is proofreaied and correct the transmitting power that message changes SS.If the SS power measurement values occurs unusual, will directly cause the power correction value unusual, thereby influence the accuracy and the performance of power control; If directly power and the deviation of measuring between the reference value sent to SS as the power correction value, the one step is put in order put in place, it is excessive probably to cause power to be adjusted, and reduces the stability or the reliability of system.Moreover, but, BS whether do not reached its maximum transmitting power detection if not carrying out SS before the SS transmitted power is adjusted message, as long as have deviation between power measurement values and the reference value, no matter but whether SS has reached its maximum transmitting power, BS adjusts message for the SS transmitted power, so just have many unnecessary messages and transmit, reduced the stability of system.

Therefore, need a kind of simple effective method, solve the above problem that uplink closed loop exists in the ofdm system, improve the stability and the validity of power control.

Summary of the invention

The object of the present invention is to provide a kind of simple and effective Poewr control method, especially propose a kind of close-loop power controlling method that is applicable to the base station receiver in the ofdm system.

The Poewr control method that the present invention proposes, minimum RSSI (the Receive SignalStrength Indicator) value that the BS reception is reached capacity is controlled reference value as power, RSSI and the difference between the reference value of power being controlled the SS that receives that calculates send to SS as the power correction value by power adjustment message, make it carry out the power adjustment.Described method comprises the steps:

A.RSSI calculates, and the RSSI that measures is carried out multi-frame mean, measured value abnormity point elimination to overcome the unusual power adjustment that causes owing to unusual measured value;

B. calculate the deviate between RSSI value and the value and power reference, calculated deviation value is carried out loop filtering, wherein variable loop filtering coefficient;

But c. utilize a controlling mechanism to detect the SS current transmit power and whether reached its maximum transmitting power, but if reach its maximum transmitting power and power correction value is nonnegative value, then stop to SS transmission power control message, but is negative value up to the SS transmitting power less than its maximum transmitting power or power correction value, adjust message to the SS transmitted power, notify it to carry out the power adjustment.

The RSSI computational methods of wherein describing among a are to calculate the mean value of the N frame RSSI value that the measurement receive reports, be designated as RSSI, symbolization criterion rejecting abnormalities value then, the concrete grammar of symbol criterion are mean value RSSI poor of each frame rssi measurement value and this N frame in the comparison N frame, are designated as Δ RSSI _i, add up the symbol accumulated value of N frame then $S_{\mathrm{sign}}=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{Sgn}\left({\mathrm{\ΔRSSI}}_i\right),$ Wherein

If S _SignAbsolute value greater than the non-negative thresholding SIGN_TH of a setting, then in the N frame, reject symbol and S _SignInconsistent, with remaining N ' (N '≤N) the mean value RSSI of frame compares with reference value as this statistics; If S _Sign=0, then with the mean value RSSI of N frame as this statistics, compare with reference value; Other situation explanation values are unusual, do not carry out operation subsequently, finish this power control.

Described method further comprises: the loop filtering of describing among the b comprises: adopt a loop filter, value and power reference is carried out loop filtering with the difference DELTA power that obtains after relatively through the RSSI value after the statistical computation: Δ Adjust_value=K * Δ power, wherein Δ Adjust_value is this power adjustment that sends to SS, K is a loop filtering coefficient, wherein the K value is got different value according to the size of the absolute value of Δ power, when the absolute value of Δ power is set thresholding greater than one, the K value is K1 (0.7≤K1≤0.8), when the absolute value of Δ power was set thresholding less than one, the K value was K2 (0.4≤K2≤0.5).

Described method further comprises: whether the employing one controlling mechanism detection SS transmitting power of describing among the c reaches its maximum transmission power comprises: SS will report its current transmit power to the base station at regular intervals, if this current transmit power that reports is identical with last time, and the base station is not 0 to the power adjustment sum that SS sends in the time interval reporting for this twice, then count parameter same_pwr_num is added 1, otherwise count parameter same_pwr_num is changed to 0; When parameter s ame_pwr_num sets thresholding SAME_PWR_TH greater than one, illustrate that but SS has reached its maximum transmitting power, as long as SS does not change its transmitting power and the power correction value is a nonnegative value, just not to SS transmission power control message, stop this power control, when detecting SS and change its transmitting power or power correction value and be negative value, just restart to send corresponding power control messages to SS.The Poewr control method of the base station receiver that the present invention proposes, statistical computation by RSSI, overcome because the unusual power adjustment that unusual measured value causes, variable loop filter coefficient ripple has guaranteed the unification of convergence rate and opposing noise ability, the stability and the reliability of system have been guaranteed simultaneously, but whether SS reaches the maximum transmitting power detect, reduced the unnecessary messages transmission, improved the stability of system.

Description of drawings

Fig. 1 is a Poewr control method flow chart of the present invention;

Fig. 2 is a RSSI statistical computation process block diagram of the present invention;

Detect block diagram but whether Fig. 3 is SS of the present invention reaches its maximum transmitting power.

Specific implementation method

Below in conjunction with description of drawings, describe the specific embodiment of the present invention in detail.

The invention provides a kind of ascending power control method of ofdm system base station receiver, the minimum RSSI value that the BS reception is reached capacity is controlled reference value as power, RSSI and the difference between the reference value of power being controlled the SS that receives that calculates send to SS as the power correction value by power adjustment message, make it carry out the power adjustment.Fig. 1 is the flow chart of Poewr control method of the present invention, and concrete steps are as follows:

Step 1, RSSI calculate

Computational process such as Fig. 2 comprise operations such as rssi measurement value multi-frame mean, rssi measurement value abnormality value removing, and the residue frame behind the rejecting abnormalities point is averaged the statistics as RSSI.

For the accuracy that guarantees to measure, the RSSI value that multiframe (N frame, N 〉=1) is measured is done on average, that is: $\stackrel{\‾}{\mathrm{RSSI}}=\frac{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{RSSI}}_i}{N}.$

In order to overcome the influence of exceptional value, need abnormality value removing, exceptional value symbolization criterion is judged.The concrete grammar of symbol criterion is mean value RSSI poor of at first calculating each frame rssi measurement value and this N frame in the N frame, that is: Δ RSSI _i=RSSI _i-RSSI adds up the symbol accumulated value of N frame then $S_{\mathrm{sign}}=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{Sgn}\left({\mathrm{\ΔRSSI}}_i\right),$ Wherein

If S _SignAbsolute value greater than the non-negative thresholding SIGN_TH of a setting, then in the N frame, reject symbol and S _SignInconsistent, with remaining N ' (1≤N '≤N) the mean value RSSI ' of frame carries out deviation calculation operation subsequently as this statistics; If S _Sign=0, then with the mean value RSSI of N frame as this statistics, carry out deviation calculation operation subsequently; Other situation explanation values are unusual, do not carry out operation subsequently, finish this power control.

Step 2, power deviation calculate

The difference Δ power of the RSSI value that rated output reference value and step 1 calculate.

Step 3, loop filtering

Adopt a loop filter, Δ power carried out loop filtering:

ΔAdjust_value＝K×Δpower

Wherein Δ Adjust_value is this power adjustment that sends to SS, and K is loop filtering coefficient (K＜1).The K value is big, and power is regulated the speed soon, but when Δ power convergence 0, promptly when the RSSI that calculates approached value and power reference, near 1, it is excessive that possible emergent power is adjusted as if the K value, RSSI will fluctuate about value and power reference like this, can't reach a stable status; And if K value less (as K≤0.5), can emergent power adjust excessive, but when power deviation Δ power absolute value is big, because the K value is less, each power adjustment Δ Adjust_value is little more a lot of than actual power deviation, power is regulated the speed too slow, directly influences the performance of power control.Therefore, in order to guarantee convergence rate and the unification of resisting the noise ability, the K value is got different value according to the size of the absolute value of Δ power.Set a threshold value (being taken as about 5～10 usually), when the absolute value of Δ power is set thresholding greater than this, the K value is K1, make the adjustment of SS power be in the coarse adjustment stage, wherein the K1 span is 0.7≤K1≤0.8, can adjust SS power faster like this, simultaneously because Δ power absolute value is big and K1 smaller or equal to 0.8, excessive phenomenon can not appear adjusting; Set thresholding when the absolute value of Δ power less than this, when promptly approaching the saturated restriction of BS, the K value is K2, make the adjustment of SS power be in the fine tuning stage, wherein the K2 span is 0.4≤K2≤0.5, because the K2 value is less, excessive phenomenon can not occur adjusting like this.

If Δ Adjust_value is a nonnegative value, forwards step 4 to, otherwise forward step 5 to.

But whether step 4, SS have reached its maximum transmitting power detect

Testing process such as Fig. 3, SS will report its current transmit power to BS at regular intervals, after receiving the current transmit power that SS reports, compare with the value of last time, if the two identical and reporting for this twice the base station is not 0 to the power adjustment sum that SS sends in the time interval, then count parameter same_pwr_num is added 1, wherein same_pwr_num is the consecutive identical number of times of current transmit power that SS reports, otherwise count parameter same_pwr_num is changed to 0.

If same_pwr_num〉SAME_PWR_TH, wherein SAME_PWR_TH is the identical number of times thresholding of power of setting, but illustrates that SS has reached its maximum transmitting power, the power that does not carry out is subsequently adjusted the message transmission, finishes this power control process; Otherwise, forward step 5 to.

Step 5, transmission power control message

To SS transmission power control message, notify it to carry out the corresponding power adjustment.

The power control scheme that adopts the present invention to propose, amount of calculation is little, and is effectively simple, overcome because the unusual power adjustment that unusual measured value causes has reduced the unnecessary messages transmission, improved the stability and the reliability of system.

Claims (5)

1, a kind of Poewr control method that is applied to the base station receiver in the ofdm system can be according to the transmitting power of received signal strength control SS, and described method comprises the steps:

A.RSSI calculates, and the RSSI that measures is carried out multi-frame mean, measured value abnormity point elimination to overcome the unusual power adjustment that causes owing to unusual measured value; B. calculate the deviate between RSSI value and the value and power reference, calculated deviation value is carried out loop filtering, wherein variable loop filtering coefficient;

But c. utilize a controlling mechanism to detect the SS current transmit power and whether reached its maximum transmitting power, but if reach its maximum transmitting power and power correction value is nonnegative value, then stop to SS transmission power control message, but is negative value up to the SS transmitting power less than its maximum transmitting power or power correction value, adjust message to the SS transmitted power, notify it to carry out the power adjustment.

2, according to method described in the claim 1, it is characterized in that: the RSSI computational methods of describing among a are to calculate the mean value of the N frame RSSI value that the measurement receive reports, be designated as RSSI, symbolization criterion rejecting abnormalities value then, the concrete grammar of symbol criterion is mean value RSSI poor of each frame rssi measurement value and this N frame in the comparison N frame, is designated as Δ RSSI _i, add up the symbol accumulated value of N frame then $S_{\mathrm{sign}}=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{Sgn}\left(\mathrm{\Δ}{\mathrm{RSSI}}_i\right),$ Wherein

3, according to the method for claim 2, it is characterized in that: if S _SignAbsolute value greater than the non-negative thresholding SIGN_TH of a setting, then in the N frame, reject symbol and S _SignInconsistent, with remaining N ' (N '≤N) the mean value RSSI of frame compares with reference value as this statistics; If S _Sign=0, then with the mean value RSSI of N frame as this statistics, compare with reference value; Other situation explanation values are unusual, do not carry out operation subsequently, finish this power control.

4, according to method described in the claim 1, it is characterized in that: the loop filtering of describing among the b comprises: adopt a loop filter, value and power reference is carried out loop filtering with the difference DELTA power that obtains after relatively through the RSSI value after the statistical computation: Δ Adjust_value=K * Δ power, wherein Δ Adjust_value is this power adjustment that sends to SS, K is a loop filtering coefficient, wherein the K value is got different value according to the size of the absolute value of Δ power, when the absolute value of Δ power is set thresholding greater than one, the K value is K1 (0.7≤K1≤0.8), when the absolute value of Δ power was set thresholding less than one, the K value was K2 (0.4≤K2≤0.5).

5, according to method described in the claim 1, it is characterized in that: whether the employing one controlling mechanism detection SS transmitting power of describing among the c reaches its maximum transmission power comprises: SS will report its current transmit power to the base station at regular intervals, if this current transmit power that reports is identical with last time, and the base station is not 0 to the power adjustment sum that SS sends in the time interval reporting for this twice, then count parameter same_pwr_num is added 1, otherwise count parameter same_pwr_num is changed to 0; When parameter s ame_pwr_num sets thresholding SAME_PWR_TH greater than one, illustrate that but SS has reached its maximum transmitting power, as long as SS does not change its transmitting power and the power correction value is a nonnegative value, just not to SS transmission power control message, stop this power control, when detecting SS and change its transmitting power or power correction value and be negative value, just restart to send corresponding power control messages to SS.

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