Method and device for controlling power of downlink closed-loop
A closed-loop power control and power control command technology, applied in power management, wireless communication, electrical components, etc., can solve problems such as inability to achieve accurate control of transmission power, poor signal-to-noise ratio prediction performance, and inability to achieve real-time processing. Accurate control, improved accuracy, and reduced power consumption
Active Publication Date: 2011-05-11
ST ERICSSON SEMICON BEIJING
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Problems solved by technology
On the one hand, the existing techniques have poor predictive performance for the SNR in the control loop in the case of slow fading
On the other hand, since the signal demodulation and signal-to-noise ratio prediction cannot be processed in real time due to the limitation of the firmware, the power control command word may be transmitted uplink to the base station after a certain delay
like image 3 As shown, the base station measures and predicts subframe n, and at the time of subframe n+2, the power control command word is transmitted uplink to the base station; the base station also has a certain delay in processing the control command word. image 3 In , the base station controls the transmit power corresponding to the mobile terminal at the time of subframe n+3. Therefore, it is expected to control the transmit power of the mobile terminal at the time of subframe n+1, but it is delayed until the time of subframe n+3. This obviously cannot achieve accurate control of the transmit power
Method used
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[0036] Embodiments of the present invention first select a set of historical record values: (x 1 ,y 1 ), (x 2 ,y 2 ),..., (x n ,y n ), where x i is the sample point (that is, the subframe number), y i is the sample point x i The corresponding signal-to-noise ratio measurements are then fitted with a curve f(x) that minimizes the error:
[0037]
[0038] The embodiment of the present invention adopts least square criterion to carry out fitting, promptly assumes this fitting curve is the polynomial of order m, and expression is as follows:
[0039] y=a 0 +a 1 x+…+a m x m
[0040] Use the above formula to set the historical record value (x 1 ,y 1 ), (x 2 ,y 2 ),..., (x n ,y n ) is approximated so that it has the smallest squared error:
[0041]
[0042] Here, a 0 ,...,a m is a set of unknown coefficients, in order to obtain the minimum square error, for a i The first-order reciprocal of has zero value, that is:
[0043] ...
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The present invention provides a method and a device for controlling power of downlink closed-loop, wherein the method comprises the following steps: A. pre-establishing a predictive matrix used for calculating the coefficient of fitting curve; B. recording the measured value of signal-to-noise ratio of current subframe and n-1 subframes before the current subframe; C. calculating the coefficientof fitting curve according to the measured value of predictive matrix and the recorded n signal-to-noise ratios for further obtaining the assured fitting curve; D. calculating the predicted value of signal-to-noise ratio of next subframe time according to the assured fitting value; and E. comparing the predicted value of signal-to-noise ratio with the target value of signal-to-noise ratio, and generating power control command word according to the comparing result. The method and the device of the invention realizes an accurate control to the downlink transmitting power thereby reducing the power consumption of whole network.
Description
technical field [0001] The invention belongs to the field of wireless communication, and in particular relates to a downlink closed-loop power control method and device. Background technique [0002] In a communication system, transmission power is a precious resource, and the base station sends data to the terminal according to the set transmission power. In the downlink of the communication system, the distance between each user terminal equipment and the base station is different. In this way, when the transmission power of the base station to each terminal equipment is the same, the signal received by the terminal equipment closer to the base station will be stronger, and the signal received by the farther terminal equipment will be stronger. The signal received by the terminal equipment is weak, so that the terminal equipment located at the far end of the base station cannot work normally; moreover, the problem of "shadow effect" is often encountered in the propagation ...
Claims
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IPC IPC(8): H04W52/08H04W52/12
Inventor 杨文学牟秀红许百成
Owner ST ERICSSON SEMICON BEIJING