CN114173404A

CN114173404A - Device and method for dynamically adjusting base station power amplifier working point according to service load condition

Info

Publication number: CN114173404A
Application number: CN202111514523.4A
Authority: CN
Inventors: 赵建平; 游飞; 唐锟
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2021-12-13
Filing date: 2021-12-13
Publication date: 2022-03-11
Anticipated expiration: 2041-12-13
Also published as: CN114173404B

Abstract

The invention discloses a method and a device for dynamically adjusting a power amplifier point of a base station according to service load conditions, wherein the method comprises the steps of identifying a service load factor L1 of a target cell and a service load factor L2 of a nearest cell; if the load factor L2 of the nearest neighbor cell is smaller than the threshold Alpha and the load factor L1 of the cell is close to or even exceeds 100%, if yes, the next adjustment step is carried out, and if not, the method is ended; and adjusting the working point of the power amplifier according to whether the service load of the target cell is increased, wherein the adjustment comprises the control operation of driving gain, power backspacing, digital predistortion and a power supply. The invention can improve the power efficiency without influencing the coverage of the base station, and the influence on the capacity is controllable.

Description

Device and method for dynamically adjusting base station power amplifier working point according to service load condition

Technical Field

The invention relates to the technical field of mobile communication networks, in particular to a device and a method for dynamically adjusting a power amplifier working point of a base station according to a service load condition.

Background

As more frequency bands (such as using C band and Sub 3GHz band), update systems (such as 5G and its evolution), and the use of more channels (such as Massive MIMO) are used in mobile communication, the power consumption of the mobile communication network is greatly increased. Specifically, the power consumption of the base station is larger than that of other mobile communication network elements, the radio frequency unit (RRU/ARU) of the base station is larger than that of the baseband unit (BBU), and the power amplifier part in the radio frequency unit is larger than that of other radio frequency circuits, so that the power amplifier is the most critical part of the green mobile communication.

The existing adopted green mobile communication measures are mostly developed around a power amplifier, the total transmission power can be adjusted according to the capacity requirement, for example, when the capacity is small, partial channels, partial time slots and partial carriers can be turned off or partial channel power is reduced, and the problem brought by the energy-saving effect is that the coverage and the customer experience are partially reduced. More extreme cases may be where the base station unit to which the cell belongs is dormant. For example, chinese patent application No. cn201910393026.x, entitled "an energy saving method based on cell base station dynamic dormancy", proposes an energy saving method of dynamic dormancy, in which when a load of a certain cell base station is low, the base station with a low load is turned off to enter a dormant state, a service load of the cell is transferred to a neighboring cell base station, when a load of a surrounding cell base station is high, a neighboring dormant cell base station is activated, and a part of user service loads of the surrounding cell is transferred to the activated dormant cell base station. Also, for example, chinese patent application No. CN201210376338.8, entitled "a dynamic cell dormancy method oriented to green energy saving", provides dormancy control based on time periods. Generally these methods belong to the methods for total power parameter adjustment based on cell load, the adjustment procedure finds that the output power and the non-linear index of that channel are unchanged.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention provides a device and a method for dynamically adjusting the power amplifier working point of a base station according to the service load condition.

The invention adopts the following technical scheme:

a method for dynamically adjusting a base station power amplifier working point according to a service load condition comprises the following steps:

identifying a target cell traffic load factor L1 and a nearest neighbor cell traffic load factor L2;

if the service load factor L2 of the nearest cell is smaller than the threshold value Alpha and the service load factor L1 of the cell is close to or even exceeds 100%, entering the next adjustment step, otherwise ending;

and adjusting the working point of the power amplifier according to whether the service load factor L1 of the target cell is increased, wherein the adjustment comprises the control operation of driving gain, power backspacing, digital predistortion and power supply.

Further, the adjusting of the power amplifier operating point is performed according to whether the target cell service load factor L1 is increased, where the adjusting includes driving gain, power backoff, digital predistortion, and control operation of the power supply, and specifically includes:

when the service load factor of the target cell is increased, maintaining the power supply voltage, improving the driving gain to increase the output power, reducing the power back-off and weakening or turning off the digital pre-distortion;

when the service load factor of the target cell is reduced, reducing the driving gain to reduce the output power, reducing the voltage by adopting a power supply modulation mode to reduce the power back-off, and weakening or turning off the digital pre-distortion;

when the target cell traffic load factor is unchanged, the driving gain is maintained to maintain the output power, maintain the supply voltage, and attenuate or turn off the digital predistortion.

Further, the threshold value Alpha causes 1% of the neighbor cell load to be lost when ACLR is reduced.

Further, the target cell traffic load factor L1 is a percentage value comparing the current target cell traffic load with the zone traffic safety load.

Further, the nearest neighbor cell traffic load factor L2 is a percentage value that compares the sum of all nearest neighbor cell current traffic loads to the sum of all nearest neighbor cell traffic safety loads.

Further, the method also comprises an evaluation step of the influence of the adjustment of the power amplifier working point on the system, and specifically comprises the following steps:

wherein ACS is a fixed value for the base station, ACIR is the total effect of ACS and ACLR on the nonlinear interference of the base station.

Further, the target cell traffic load factor increase/decrease is compared to the historical contemporaneous value for that cell.

Further, the digital predistortion comprises three types of high-complexity predistortion, low-complexity digital predistortion and bypass.

A device for dynamically adjusting the power amplifier working point of a base station according to the service load condition comprises: the system comprises a service load identification module, a digital predistortion module, a power driving module, a power amplifier module and a power supply module;

the service load identification module: the system is used for identifying the service load information of a target cell and the nearest cell in the base station, and controlling the digital predistortion module, the power driving module, the power amplifier module and the power supply module according to the service load information of the target cell.

Further, the digital predistortion module comprises a high complexity predistortion unit, a low complexity digital predistortion unit and a bypass unit.

The invention has the beneficial effects that:

under the condition that the load of the cell with the minimum adjacent cell load is small, the power amplifier working point of the target cell is adjusted according to the load of the target cell and the load of the minimum adjacent cell, and under the condition of properly sacrificing nonlinear indexes, the green energy-saving effect is obtained.

Drawings

FIG. 1 is a diagram illustrating the non-linearity of DPD in the prior art;

FIG. 2 is a diagram of a base station user in the prior art;

FIG. 3 is a diagram illustrating the relationship between base station capacity and ACIR;

FIG. 4 is a schematic diagram of the apparatus of the present invention;

FIG. 5 is a flowchart of the operation of an embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating adjustment of the operating point of the power amplifier when the output power increases according to an embodiment of the present invention;

FIG. 7 is a schematic diagram illustrating adjustment of the operating point of the power amplifier when the output power is reduced according to an embodiment of the present invention;

fig. 8 is a schematic diagram illustrating adjustment of the operating point of the power amplifier when the output power is not changed according to the embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited to these examples.

Examples

As shown in fig. 4, a device for dynamically adjusting a power amplifier operating point of a base station according to a service load condition firstly has a service load identification module for reading service load data of a local cell and an adjacent cell, and can provide a decision basis for a power amplifier operating point adjustment strategy; the whole transmitting link has the capability of adjusting the working point according to the service load from the digital predistortion module, the power driving module, the power amplifier module and the configurable power supply module. Specifically, the baseband digital predistortion module comprises a high-complexity predistortion unit with high-complexity DPD algorithm resources, a low-complexity digital predistortion unit with low-complexity DPD algorithm resources and the capability of bypassing, namely closing the DPD module, wherein the low-complexity digital predistortion unit has a remarkable power consumption reduction effect compared with the traditional algorithm due to the simple algorithm; the power driving module has the gain adjustment capability, for example, the gain adjustment range can reach or be better than +/-3 dB; the power amplifier module can correspondingly change the output power when the driving power is changed or the supply voltage is changed, and can meet the ACLR index better than-35 dBc under the condition of reducing the back-off power by 3 dB; the configurable power module should be able to regulate the output voltage under control, the regulation speed should be better than 100 mus.

Due to the fact that the mobile network has obvious space dynamics and time dynamics, the space dynamics is particularly characterized in that part of cells bear extremely high load, peripheral cells bear less load, namely the space dynamics, and the time dynamics is characterized in that the cells have tide effect in different time periods. The power adjustment of the radio frequency unit can be performed not only for the cell with less load but also for the cell with large load, the power amplifier output power adjustment for the cell with less load is a traditional method, and the power amplifier working point adjustment for the cell with large load is the method of the invention.

Based on the characteristics of the mobile network, the invention discloses a method for adjusting the working point of a power amplifier of a base station based on the device, wherein the adjustment of the working point of the power amplifier comprises adjustment measures such as power amplifier driving quantity, power amplifier backspacing quantity, high complexity/low complexity/bypass digital predistortion selection, power supply voltage and the like, the adjustment of the working point is generally expressed in the change of nonlinear characteristics, and ACLR (adjacent channel leakage ratio) is the most important measurement index.

As shown in fig. 5, the method comprises the following steps:

s1 identifies a target cell traffic load factor L1 and a nearest neighbor cell traffic load factor L2.

The specific definition is as follows:

a target cell traffic load factor L1 and the target cell nearest neighbor cell traffic load factor L2 are defined. The L1 factor is a percentage value comparing the current traffic load with the traffic safety load, wherein 100% indicates that the current load reaches the safety load, and 50% indicates that the current traffic load is half of the safety load. Similarly, the L2 factor is a percentage value of the sum of the current traffic loads of all the nearest neighbor cells compared with the sum of the traffic safety loads of all the nearest neighbor cells, wherein 100% represents the full load operation of the peripheral cells, and 50% represents the average half of the safety load of the peripheral cells. The nearest neighbor cells are the neighbor cells of the base station to which the target cell belongs and the cells of the nearest neighbor base stations around the target cell.

S2, if the load factor L2 of the nearest neighbor cell is smaller than the threshold Alpha and the load factor L1 of the cell does not exceed the safety load too much (for example, L1 is less than or equal to 120%), the next step S3 is carried out, otherwise, the adjustment step is finished;

alpha is determined by the fact that ACLR decreases by a certain value, say more than 10dB, which can lead to significant energy savings, while the capacity impact is less than 1%, this parameter being the application network dependence, which can be determined with reference to fig. 3.

The Alpha determination principle is referred to the following formula:

that is, the Alpha determination rule is the neighbor load amount that makes the capacity loss 1% satisfied when ACLR decreases.

S3, judging whether the target cell service load factor is increased, namely judging whether the L1 is increased compared with the historical synchronization value, if so, entering S4, otherwise, entering S5;

and S4, increasing, and then the specific operation of adjusting the power amplifier working point is as follows: maintaining the supply voltage, increasing the driving gain to increase the output power, reducing the power back-off, and weakening, namely adopting a low-complexity predistortion unit or even a bypass DPD, and ending the process.

The evaluation index of the method is ACLR, the energy is saved more by switching off or adopting the bypass DPD, but the ACLR deterioration is more serious, and the capacity deterioration is larger; although the DPD weakening effect is slightly poor, the ACLR deterioration is slightly small, the capacity influence is also small, and the system is safer

S5, judging whether the target cell service load factor is reduced, namely judging whether the history value L1 is reduced, if so, entering S6, otherwise, entering S7;

s6: reducing the driving gain to reduce the output power, reducing the back-off and the voltage by adopting a power supply modulation mode, weakening the DPD, namely adopting low-complexity pre-distortion and even bypassing the DPD, and ending the process;

s7: and maintaining the driving gain to maintain the output power, maintaining the power supply voltage, weakening the DPD, namely, adopting a low-complexity predistorter, and ending the process.

Table 1 summarizes the description of the adjustment of the service load oriented power amplifier operating point in the method. The working point setting principle is that after the power amplifier working point is adjusted, although the nonlinear indexes such as ACLR and the like are properly reduced, the capacity is reduced within an acceptable range, and the efficiency of the power method is remarkably improved to achieve the aim of green energy conservation. Fig. 6-8 respectively illustrate an example of adjusting the operating point and the ACLR index of the output spectrum when the power amplifier output power increases, decreases and does not change under different cell traffic loads, where fig. 6 corresponds to Case 2 of table 1, fig. 7 corresponds to Case3 of table 1, and fig. 8 corresponds to Case 1 of table 1.

TABLE 1

The characteristic pairs of the working point adjusting method and the prior technical measures provided by the invention are shown in the following table 2, the standard power amplifier referred in the following table example has the transmitting power of 43dBm, the backspacing of 9dB, the ACLR of 45dBc, the average efficiency of 30% (including DPD) and the system power consumption of 74W.

Table 2 shows the specific tuning parameters corresponding to fig. 6-8 when ACLR decreases from-45 dBc to-35 dBc, the power consumption decreases by about 9%, 50%, and 7%, respectively. It can be seen from fig. 3 that the capacity is small for the network.

TABLE 2

Description of the feasibility of the process:

as shown in fig. 1, 100MHz wideband signal linearization tests with or without DPD (digital predistortion).

ACLR is 25dBc and 45dBc, respectively, and considering that the DPD algorithm significantly increases power consumption, it is obvious that the mobile communication system at present sacrifices certain power efficiency to obtain a strict non-linear index (typically 45 dBc). In contrast, neither WiFi (typically less than 30dBc) nor 5G mm-wave mobile communication (typically 28dBc) requires a high ACLR, which is a low complexity system requirement, and more importantly, because the adjacent band interference control is essentially the inter-cell interference control, and the interference between the two types of system cells is small, so the requirement can be relaxed appropriately.

In order to quantify the influence of the power amplifier operating point on the system, the role of ACLR in the system was evaluated. System simulations are performed with reference to 3GPP standard 36.942, and typical parameters are: FDD duplex mode, 2000MHz carrier, 4 transmit and 4 receive, typical sector antenna and station to station distance 500 meters, figure 2 is a base station and user distributionThe snapshot shows that the relationship between the ACLR and the system capacity is obtained on the basis as shown in fig. 3, the ACIR is defined as the overall effect of the ACS and the ACLR on the nonlinear interference of the base station, specifically, the overall effect is

Since ACS is constant for the base station-here the simulation assumes infinitesimal to be negligible, in fact this evaluation also reflects the impact of ACLR on capacity completely. From fig. 3, ACIR (i.e., ACLR) from 45dBc to 15 dBc: when all cells are operating with the same normalized load of 100%, the system capacity is lost by 14%, where the baseline assumes ACIR is infinite; the service load of the nearest cell including the adjacent cell in the base station is zero, and when the normalized load of other farther cells is 1, the capacity of the nearest single cell can be defined, and the system capacity is only lost by 1.6 percent and is almost ignored; when the nearest neighbor cell has only 20% load and the other more distant cells have normalized load of 100%, the system capacity is lost by 3.4%.

Analyzing the reason, the nearest neighbor cell brings far more than 50% of total out-of-cell interference, so that the interference caused by non-linearity to the surrounding cells becomes smaller because of lower load of the surrounding cells, that is, the influence of non-linearity on capacity becomes smaller because of the reduced load of the surrounding cells. If the operating point of the base station is adjusted at this time, for example, reducing the backoff, turning off the DPD or starting the low complexity DPD will bring considerable energy saving effect, and will not affect the expected capacity effect of the operator.

From the above analysis, the method is a feasible green energy-saving method.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A method for dynamically adjusting a base station power amplifier working point according to a service load condition is characterized by comprising the following steps:

2. The method according to claim 1, wherein the adjusting of the power amplifier operating point according to whether the target cell traffic load factor L1 is increased or not is performed, and the adjusting includes driving gain, power backoff, digital predistortion, and power supply control operations, specifically:

when the target cell traffic load factor L1 increases, the supply voltage is maintained, the drive gain is increased to increase the output power, the power back-off is reduced, and the digital predistortion is attenuated or turned off;

when the target cell service load factor L1 is reduced, reducing the driving gain to reduce the output power, reducing the voltage by adopting a power supply modulation mode to reduce the power back-off, and weakening or turning off the digital pre-distortion;

when the target cell traffic load factor L1 is constant, the drive gain is maintained to maintain output power, maintain supply voltage, and attenuate or turn off digital predistortion.

3. The method of claim 1, wherein the threshold Alpha is such that 1% of the neighbor cell load is lost when ACLR is reduced.

4. The method of claim 2, wherein the target cell traffic load factor L1 is a percentage value of the current target cell traffic load compared to the zone traffic safety load.

5. The method of claim 2, wherein the nearest neighbor cell traffic load factor L2 is a percentage value comparing the sum of the current traffic loads of all nearest neighbor cells with the sum of the traffic safety loads of all nearest neighbor cells.

6. The method according to any one of claims 1 to 5, further comprising the step of evaluating the influence of the adjustment of the power amplifier operating point on the system, specifically:

7. The method of claim 1 wherein the target cell traffic load factor L1 increases/decreases are compared to historical contemporaneous values for the cell.

8. The method of claim 1, wherein the digital predistortion comprises three types, a high complexity predistortion, a low complexity digital predistortion and a bypass.

9. An apparatus for implementing the method of claims 1-8, comprising: the system comprises a service load identification module, a digital predistortion module, a power driving module, a power amplifier module and a power supply module;

10. The apparatus of claim 9, wherein the digital predistortion module comprises a high complexity predistortion unit, a low complexity digital predistortion unit, and a bypass unit.