Shortcoming and defect at power control in the above-mentioned prior art, this patent has proposed the method for power control in a kind of CDMA mobile communication systems, utilize path loss in the regular hour, to have the variation that certain correlation is come the predicted path loss, thereby obtain the variation of the signal interference ratio that receiver receives, produce corresponding power control command, make the variance minimum of the signal interference ratio that receiver receives.
To achieve these goals, this patent provides the method for power control in a kind of CDMA mobile communication systems, variation by the calculating path loss is predicted and is reduced in the described close-loop power controlling method because the power departure that the time delay of power control command is brought the value of future time signal interference ratio, at least may further comprise the steps: (1) receiver is measured the variation (3) of signal interference ratio (2) the calculating path loss of received signal and is predicted that the value (4) of future time signal interference ratio produces power control command, adjusts the transmitting power of transmitter
Wherein, in the step (2) with of the variation of path loss one jump as path loss, calculation procedure is: the signal interference ratio that the previous moment of taking-up receiver storage measures, measuring signal interference ratio with current time subtracts each other, add the influence of the power control command that the previous moment receiver sends, the influence of above-mentioned power control command is that the step-length and the previous moment power control command of transmitter power adjustment multiplies each other.
Described in the step (3) future time signal interference ratio value signal interference ratio that can measure by path loss one jump, current time and the power control command that sends of previous moment the signal interference ratio of future time done linear single order prediction obtain.The power control command that signal interference ratio that a jump that also can be by path loss and two jumps and current time measure and previous moment are sent is done the linear second-order prediction to the signal interference ratio of future time and is obtained, and described path loss two jumps can utilize a jump of the path loss of the previous moment of storing in jump of the path loss that current time calculates and the receiver to subtract each other and obtain.
The size of above-mentioned previous moment can be adjusted according to the time delay of closed power control, the value of signal interference ratio is the mean value in a measuring period, and the signal interference ratio of power control command, received signal can be stored in register, internal storage location or any similar equipment.
Transmitter is compared according to signal interference ratio of being predicted and pre-set thresholding in the above-mentioned step (4), if predicted value is greater than thresholding, send the order that reduces power control so, if predicted value is less than thresholding, send the order of rising power control so, transmitting power is adjusted with this.
Simultaneously, can do further correction to a jump of above-mentioned path loss.
Utilize the method for this patent to be used for controlling the power output of cdma communication system transmitter, can reduce in the closed power control because the power departure that the time delay of power control command is brought, power output to transmitter is accurately controlled, thereby can effectively reduce the extra interference that the user is caused, improve communication quality, helped increasing power system capacity.
Below in conjunction with drawings and Examples the present invention is further detailed, wherein:
At first referring to Fig. 1 and Fig. 2, the variation of Fig. 1 delegated path loss, in Fig. 2, the signal interference ratio SIR0 of the signal that t0 receiver measurement constantly receives, SIR0 is greater than pre-set threshold value, and according to former Poewr control method, this moment, receiver should send the power control command of " reduction ", because the transmission and the processing of power control command have certain time delay, therefore the power control command that produces constantly at t0 obtains t2 to carry out constantly.
As seen from Figure 1, it is ever-increasing being carved into t2 path loss constantly during from t0, and this signal interference ratio SIR2 with regard to the signal that caused receiver and receive constantly will be lower than thresholding along with the increase of path loss at t2.And the t2 power control command that produces " reductions " at t0 constantly carried out of transmitter constantly, make like this receiver t2 moment actual reception to signal interference ratio SIR3 depart from thresholding more, as shown in Figure 2.
From the above mentioned, the problem of traditional close-loop power controlling method is may make the power output that has reduced transmitter in the power that should raise on the contrary because power control command has certain time delay from producing execution, has caused the error of power control.We address this problem in order to following scheme: receiver is at first measured the signal interference ratio of received signal, this value and the value of measuring in the past are used for the variation of calculating path loss, and the variation of path loss of prediction future time and the value of signal interference ratio, thereby produce power control command.This power control command is sent to the power output that transmitter is used to adjust transmitter.
We suppose that the time-delay of power control command is two time slots, and promptly the power control command that produces constantly of t0 obtains carrying out at t2 constantly.If the time-delay of power control command can be changed according to the spirit of the inventive method for other values in the real system certainly, still do not break away from the category of the inventive method.
At first, receiver is by measuring the t0 signal interference ratio SIR0 of received signal constantly, and then comes a jump of calculating path loss according to the power control command that measured value and preceding two moment recipients in this moment and the previous moment send.Because path loss has certain correlation in the regular hour, therefore can suppose that a jump of path loss remains unchanged in a period of change of path loss.So the power control command that can produce according to a jump of the path loss that calculates and previous moment recipient and the measured value SIR0 of current time predict along with the variation of path loss t2 constantly receiver with the signal interference ratio SIR of the signal that receives
*Compare with this predicted value and pre-set thresholding, if predicted value, is sent the power control command of " reduction " so greater than thresholding; If predicted value, is sent the power control command of " rising " so less than thresholding.As shown in Figure 2, after t0 predicts t2 signal interference ratio constantly constantly, send the power control command of " rising ", make t2 signal interference ratio constantly in fact be controlled to SIR
*, reduced the error that power is controlled.
Describe below in conjunction with embodiment, Fig. 3 is the process chart of above-mentioned Forecasting Methodology, and processing procedure receives the signal 21 that transmitter sends from receiver, and the receiver measurement receives the signal interference ratio 22 of signal, then a jump 23 of calculating path loss.Computing formula is:
ΔL(j)=SIR(j-1)+stepsize·TPC(j-2)-SIR(j) (1)
Wherein: SIR (j) is j the signal interference ratio (unit is dB) of the received signal that measures of receiver constantly; SIR (j-1) is (j-1) value (unit is dB) of the signal interference ratio of the measured received signal that obtains constantly of receiver storage; TPC (j-2) is the power control command that (j-1) of receiver storage sends constantly, more than two values can be to be stored in register, internal storage location or any similar equipment; Stepsize is the step-length (unit is dB) that transmitter power is adjusted; Δ L (j) is a jump (unit is dB) of j path loss that constantly calculates.
Then, receiver predicts 24 to (j+2) signal interference ratio SIR^ (j+2) constantly.Because the time-delay of power control command is two time slots, the power control command that produces in (j+1) moment of launching opportunity execution (j-1) constantly.Therefore when signal interference ratio is predicted constantly to (j+2), to consider the influence of (j-1) power control command constantly.(j+2) signal interference ratio constantly that is predicted according to a jump of path loss is:
SIR(j+2)=SIR(j)+stepsize·TPC(j-1)-2*ΔL(j) (2)
Receiver uses predicted value and pre-set thresholding to compare 25, and sends power control command 26.The value of the signal interference ratio that this is measured constantly and this power control command that produces constantly store 27 at last, use so that calculate next time.These two values can be stored in register, internal storage location or any other similar equipment.
In the present embodiment, only consider the influence of the signal interference ratio of the signal that path loss and transmit power variation receive receiver, and ignored the variation of the signal interference ratio that the variation of interference power causes.But because when number of users is many, the multiple access in the cdma system disturbs can regard Gaussian process as, and promptly interference power can be thought and remains unchanged, and the change of therefore ignoring interference power is rational.As non-special instruction, all handle among the following embodiment by this hypothesis.
More than first kind of embodiment of the inventive method is described, introduce second embodiment of the inventive method below.
Fig. 4 is the process chart of the inventive method second embodiment, and processing procedure receives the signal 31 that transmitter sends from receiver, and the receiver measurement receives the signal interference ratio 32 of signal, then a jump 33 of basis (1) formula calculating path loss.One jump Δ L (j-1) of the path loss in a last moment of storing in a jump Δ L (j) who utilizes the path loss that current time calculates and the receiver can calculate two jumps 34 to path loss, and computing formula is:
Δ
2L(j)=ΔL(j)-ΔL(j-1) (3)
Wherein: Δ
2L (j) is two jumps (unit is dB) of j path loss that constantly calculates.
Then, receiver predicts 35 to (j+2) signal interference ratio SIR^ (j+2) constantly.Because the time-delay of power control command is two time slots, the power control command that produces in (j+1) moment of launching opportunity execution (j-1) constantly.Therefore when signal interference ratio is predicted constantly to (j+2), to consider the influence of (j-1) power control command constantly.(j+2) signal interference ratio constantly that is predicted according to a jump and two jumps of path loss is: SIR^ (j+2)=SIRU (j)+stepsizeTPC (j-1)-2 Δ L (j)-3 Δ
2L (j) (4)
Receiver uses prediction feelings and pre-set thresholding to compare 36, and sends power control command 37.The value of the signal interference ratio that this is measured constantly and this power control command that produces constantly and this path loss that calculates constantly one jump store 37 at last, use so that calculate next time.In the system of reality, because receiver has certain error to the measurement of signal interference ratio, because interference power also has certain fluctuation, may make predicted value that bigger random fluctuation is arranged in addition, thereby cause erroneous judgement disconnected, introduced the method that reduces this random fluctuation among the following embodiment.
As shown in Figure 5, processing procedure receives the signal 41 that transmitter sends from receiver, and the receiver measurement receives the signal interference ratio 42 of signal, then a jump 43 of basis (1) formula calculating path loss.Then path loss one jump that calculates is revised 44.In the correction value substitution formula (2) with path loss single order difference, prediction (j+2) signal interference ratio 45 constantly.Receiver uses predicted value and pre-set thresholding to compare 46 then, and sends power control command 47 and make transmitter change transmitting power.The value of the signal interference ratio that this is measured constantly and this power control command that produces constantly and this path loss that calculates constantly one jump store 48 at last, use so that calculate next time.
Fig. 6 has provided the process chart that path loss one jump that calculates is revised, and this is a kind of method that a jump of path loss is revised.At first, calculate current path loss one jump 50 according to formula (1).Take out the path loss single order difference 51 that is stored in preceding n the calculating in the receiver then.Add the single order difference of currency like this with regard to a total n+1 path loss.Check a current jump that calculates and last one constantly a jump symbol whether identical 52, if it is identical then this n+1 value is asked average 53, and with the correction value (54) of this mean value, with prediction (j+2) signal interference ratio 55 constantly in this correction value substitution formula (2) as current path loss one jump.Store this path loss that calculates constantly one jump 57 simultaneously and use so that calculate next time.If current time and last a symbol constantly is inequality, then the single order difference with the current path loss refreshes n single order difference storing value 55 of storage in the past, currency is not done and is revised 56, directly in the substitution formula (2) prediction (j+2) letter constantly in than 58.Store this path loss that calculates constantly one jump 57 simultaneously and use so that calculate next time.
Fig. 7 has drawn the another kind of method that a jump of path loss is revised.At first, calculate current path loss one jump 60 according to formula (1).Take out the correction value 61 of path loss one jump that is stored in preceding n the calculating in the receiver then.Add that so the current single order difference that calculates is with regard to a total n+1 value.Check a current jump that calculates and last one constantly a jump symbol whether identical 62, if it is identical then this n+1 value is asked average 63, and with the correction value 64 of this mean value, with prediction (j+2) signal interference ratio 68 constantly in this correction value substitution formula (2) as current path loss one jump.Storing the correction value 67 of this path loss that calculates constantly one jump simultaneously uses so that calculate next time.If current time and last a symbol constantly is inequality, then the single order difference with the current path loss refreshes the storing value 65 of n single order difference of storage in the past, currency is not done and revised 66, directly prediction (j+2) signal interference ratio 68 constantly in the substitution formula (2).Store this path loss that calculates constantly one jump 67 simultaneously and use so that calculate next time.
Embodiment by the invention described above method is based on away the description of the closed power control of step-length, is not difficult to judge that the inventive method also can be used for the long power control of adjusting of multistep.
Simultaneously, linear single order that the foregoing description of the inventive method all is to use or second order predicted method can certainly adopt other forms of Forecasting Methodology, still do not break away from the category of the inventive method.
In addition, in invention, use and ask average method that path loss one jump is revised, can predict, also have additive method similarly to revise and do not break away from the category of the inventive method.
The inventive method is applicable to the especially closed power control procedure of cdma communication system of communication system.
So far set forth the present invention with reference to specific embodiment; but the invention is not restricted to these embodiment; be appreciated that those skilled in the art can revise or improve the present invention under the situation that does not break away from the scope of the invention and spirit, but can not exceed the scope that the present invention protects.