CN104837189A - Closed-loop power control correction method based on LET-A system - Google Patents

Abstract

The invention discloses a closed-loop power control correction method based on the LTE-A system, which calculates the distance between the user and the base station and estimates the path loss, shadow fading and antenna related gain; determines the relevant path loss compensation factor according to the path loss α; According to the common reference signal and path loss sent by the base station, statistically measure the received power RSRP of the reference signal of all UEs in the cell; divide the cell into three areas: UE is located in the superior area, and continues to increase the transmit power on the basis of the original transmit power Power; UE is located in the middle area, and the path loss is properly compensated as the path loss increases, that is, as the path loss increases, the transmit power gradually increases; UE is located in the edge area, and the transmit power is adjusted on the basis of the closed-loop power Decrease; re-send the TPC command according to the above correction factor, and select the transmission power according to the area where the UE is located. The invention takes into account the three factors of the average throughput of the cell, the throughput of the edge user and the interference to the adjacent cell.

Description

A correction method for closed-loop power control based on LTE-A system

technical field

The invention relates to the technical field of LTE communication, in particular to a power control algorithm in the LTE-A system.

Background technique

"Mobile changes life". With the development of mobile communications and the issuance of 4G licenses, 4G has gradually entered people's lives. The technology's high throughput, low bit error rate, minimized interference, and maximized battery life The superiority appears directly in the communication process. These technological advances are inseparable from power control technology. Whether for the base station or the UE itself, power is the most important resource after frequency in the communication process. We hope to communicate with reasonable power as much as possible to ensure a good While improving communication quality and user experience, power consumption is saved to the greatest extent.

Although the maximum transmit power corresponds to the maximum throughput, the cell edge user throughput and the capacity of the entire system will be limited due to inter-cell interference. The loss of intercommunication will cause a certain degree of frequency offset, which will lead to interference in the cell, so the power cannot be increased blindly, and the transmit power of the UE should be determined according to the QoS requirements of the UE.

The essence of power control is an optimization method, which is to guide the power to be transmitted at an appropriate size by sending certain instructions on the physical control channel. A good power control strategy has the following five functions: one is to compensate the impact of loss and shadow fading on the communication link; the other is to enable the eNodeB or UE to transmit signals at a reasonable power to ensure good communication quality, thereby reducing Interference to adjacent cells; the third is to increase the capacity of cell edge users and the entire system; the fourth is to ensure data transmission with as low power as possible, thereby prolonging the service life of the battery; the fifth is to adjust the dynamic reception of the receiver This is because if the dynamic receiving range is too large, the sub-carriers in SC-FDMA will lose their orthogonality, thereby causing intra-cell interference. In the process of power control, the impact of power control on interference and energy consumption should be realized with a higher control speed and a lower control delay as possible.

From the perspective of the actual network, due to the adoption of OFDMA technology, the power of the existing downlink is mainly determined by the average power allocation method to determine the transmit power of the base station, while the power control of the uplink is more complicated. The current common uplink power control There are two strategies: one is open-loop power control OLPC; the other is closed-loop power control CLPC. The basic principle of OLPC is to set the transmission power based on the UE's own measurement value; the basic principle of CLPC is that the UE needs to feedback information to the eNodeB, that is to say, the UE can transmit power according to more accurate control information sent by the eNodeB, so this The performance of this power control mechanism is better, but it also takes up more channels and generates greater time delay to send control signaling.

Through the simulation of the above two different power control strategies, it is found that the two have their own advantages and disadvantages in effect, which are specifically reflected in:

From the above comparison results, in the two existing power control schemes, the average throughput of the cell and the throughput of edge users are in a trade-off relationship, which is something we do not want to see in the communication process. Therefore, it is necessary to propose a better power control scheme that can better compromise and balance between the average throughput of the cell and the throughput of edge users. Compared with the existing power control scheme, the present invention modifies the power control algorithm in the protocol to a certain extent, adopts different transmission power control schemes for UEs in different environments and different regions on the basis of the original power control, and makes When it comes to "power applied by UE", and taking into account the average throughput of the cell, the throughput of edge users, and the interference to adjacent cells, a new power control scheme is proposed.

Contents of the invention

Combining the above-mentioned prior art, the present invention proposes a closed-loop power control correction method based on the LTE-A system. Certain corrections and improvements are made on the basis of closed-loop power control, aiming at ensuring edge user throughput when closed-loop power control is adopted. While the throughput is improved to a certain extent, the average throughput of the cell is guaranteed and the impact of inter-cell interference caused by the increase of edge UE power on the overall performance of the system is reduced.

The present invention proposes a closed-loop power control correction method based on the LTE-A system, the method comprising the following steps:

Step 201, calculating the distance between the user and the base station and estimating the path loss, shadow fading and antenna related gain;

Step 202, determining a relevant path loss compensation factor α according to the path loss;

Step 203, according to the common reference signal sent by the base station and the path loss, statistically measure the received power RSRP of the reference signal of all UEs in the cell, and determine the value range of RSRP (RSRP _min , RSRP _max );

Step 204, to determine the threshold RSRP _th1 and RSRP _th2 of which area the UE is located in, set the step size Then RSRP _th2 = RSRP _min + l, RSRP _th1 = RSRP _max -l; according to the two thresholds RSRP _th1 and RSRP _th2 and the received power RSRP _self of the current UE's own reference signal to determine the current cell location of the UE, and then UEs located in three different locations adopt different power control schemes. We divide the cell into three areas according to two thresholds, namely the marginal area, the middle area and the excellent area;

Step 205. If RSRP _self >RSRP _th1 is satisfied, the location of the UE is an excellent area, and the transmit power is increased on the basis of the original transmit power by g*△ _RSRP , where g is the reference power difference compensation factor, △ _RSRP Correction factor for improved closed-loop power control;

Step 206: If RSRP _th2 <RSRP _self <RSRP _th1 is satisfied, the UE is located in the central area, and the path loss is appropriately compensated according to the protocol formula as the path loss increases, that is, as the path loss increases, the transmit power gradually increase;

Step 207. If RSRP _self <RSRP _th2 , determine that the location of the UE is the edge area, and reduce the transmit power of this part of the UE on the basis of the closed-loop power, and the reduction step is g*| _ΔRSRP | Throughput of cell edge users; on the basis of closed-loop power control, slightly reduce the power of these UEs to reduce their interference to neighboring cells;

Step 208 , according to the correction factor added on the basis of the closed-loop power control, send the TPC command again, so as to select different transmit powers according to the area where the UE is located.

The process for determining the correction factor includes the following steps:

Step 301, calculating the distance between the user and the base station to estimate path loss, shadow fading and antenna correlation gain;

Step 302, determining the carrier power of the downlink common reference signal CRS of the current neighboring cell;

Step 303, the UE determines the reference signal received power RSRP _neighbor of all neighboring cells according to the carrier power and related coupling loss of all common reference signals in the current neighboring cell list;

Step 304, select the maximum value RSRP _neighbor-max from all RSRP _neighbors , and determine the base station that generates the strongest interference to itself;

Step 305. Determine the power control improvement factor △ _RSRP , △ _RSRP = RSRP _self - RSRP _neighbor-max ;

Step 306: When the UE is located in an excellent area, △ _RSRP > 0, increase the power of these UEs; when the UE is located in a marginal area, take the absolute value of △ _RSRP , and then subtract this value from the original closed-loop power control, Therefore, the power of edge UEs is fine-tuned by first increasing and then decreasing, which takes into account inter-cell interference coordination on the basis of ensuring cell edge user throughput.

Compared with the existing power control scheme, the present invention modifies the power control algorithm in the protocol to a certain extent, adopts different transmission power control schemes for UEs in different environments and different regions on the basis of the original power control, and makes When it comes to "power applied by UE", as a new type of power control scheme, the average throughput of the cell, the throughput of edge users, and the interference to adjacent cells are taken into account.

Description of drawings

Figure 1 is a schematic diagram of a standard closed-loop power control.

Figure 2 is a flow chart of the improved closed-loop power control.

FIG. 3 is a flow chart of determining a correction factor for the improved closed-loop power control.

Detailed ways

In the existing uplink power control strategy, when the value of the path loss compensation factor α _c is constant, as the UE path loss increases, more path loss compensation is given. That is to say, when the UE is located in the center of the cell, because its PL is relatively small, the power compensation for the users in the center of the cell is also small. Similarly, when the UE is located at the edge of the cell, due to its relatively large path loss, the Relatively, the power compensation it gets is more. This kind of strategy of "the high ones look up to them, and the low ones lift them up" is undoubtedly a fairer strategy for users. However, it is found through simulation that the existing closed-loop power control scheme has an average 47.82% improvement in cell edge user throughput compared with the open-loop power scheme, but this improvement is achieved by sacrificing 24.66% of the average cell throughput. Therefore, the present invention proposes a new uplink power control strategy for the closed-loop power control scheme, and divides the cells into three different types, namely "excellent area", "middle area" and "edge area", for UEs located in different areas Different transmit power strategies are adopted to achieve "power due to UE", so as to achieve a good compromise between the average throughput of the cell and the throughput of edge users.

The technical solution of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

According to the relevant provisions of the agreement, the present invention only performs power control on uplink PUSCH (Physical Uplink Shared Channel), PUCCH (Physical Uplink Control Channel), SRS (Sounding Reference Signal), PRACH (Random Access Channel) and other channels.

PRACH adopts open-loop power control when sending the preamble, and both PUSCH and PUCCH are closed-loop power control, because their working process is to set an initial power control first, and then send TPC commands according to the actual environment during the process (cumulative type) To adjust the power, the purpose of the SRS is to detect the quality of the uplink channel, so in order to save resources, it is generally not sent. In the communication system, PUSCH carries data signals, RRC control signals superimposed on it and aperiodic CQI signaling, and mainly completes the transmission of user data. If the system bandwidth is 10MHz (50 RBs), PUSCH needs to occupy 48 RB, it can be seen that the corresponding power control directly determines the size of the data throughput. It can be seen that power control mainly refers to the power control of PUSCH. Since data transmission is carried out on PUSCH, the research on PUSCH power control is particularly important, which directly determines the size of system throughput and user experience. The PUSCH power control formula specified in the protocol TS36.213 is:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PUSCH</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}\begin{array}{}\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; CMAX</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\\ \mathrm{<span\; class="notranslate">\; 10</span>}{\mathrm{<span\; class="notranslate">\; lpg</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; PUSCH</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; PUSCH</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PL</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; TF</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>\end{array}\right\}\end{array}$

The unit is dBm. From the path loss compensation part α _c (j)·PL _c in the formula, it can be seen that when the value of the path loss compensation factor α _c is constant, as the UE path loss increases, the given path loss compensation more and more. That is to say, when the UE is located in the center of the cell, since its path loss PL is relatively small, the power compensation for the user in the center of the cell is also small. Similarly, when the UE is located at the edge of the cell, due to its relatively large path loss , so the relatively more power compensation it obtains, so the edge UE throughput of closed-loop power control is improved to a certain extent compared with open-loop power control. At the same time, because it obtains more power compensation , so it causes relatively greater interference to neighboring cells.

RSRP (Reference Signal Receiving Power, reference signal receiving power) is an absolute value that can represent the strength of the received signal measured by the UE. To a certain extent, it can reflect the distance between the mobile station and the base station, so it can be used to measure the downlink of the system wireless network coverage. To sum up, if the distance from UE to eNodeB is farther, the RSRP is smaller and the path loss is larger. That is to say, the smaller the RSRP, the closer to the edge, and the theoretically higher transmit power at this time. Of course, the transmit power of the UE cannot With the reduction of RSRP, there is no limit to increase.

The cell is divided into three parts as a whole, and all users in the cell are divided into three categories according to their own RSRP values, that is, according to the measured channel conditions, namely "excellent area (central area)", "middle area" and "edge area". ”, using different power control schemes for UEs located in three different locations. The basic idea of the revised PUSCH transmit power control is as follows:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PUSCH</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}\begin{array}{}\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; CMAX</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\\ \mathrm{<span\; class="notranslate">\; 10</span>}{\mathrm{<span\; class="notranslate">\; log</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; PUSCH</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; PUSCH</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; PL</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \&PlusMinus;</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; RSRP</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; TF</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>\end{array}\right\}\end{array}$

The specific implementation steps are as follows:

As shown in Figure 1, the standard closed-loop power control process includes the following steps:

Step 101: the base station sends a common reference signal to UEs in the cell according to the average power allocation rule;

Step 102: UE evaluates the received reference signal received power;

Step 103: The UE evaluates the path loss between the base station and the UE according to the received reference signal received power, and estimates the correlation loss between its location and the base station;

Step 104: The UE uses the measured downlink path loss as the basis for the path loss when it transmits uplink power, so as to calculate and determine its current transmit power according to the protocol formula;

Step 105: If it is open-loop power control, directly transmit power; but if it is closed-loop power, the UE will send an SRS sounding signal request to the base station;

Step 106: The base station evaluates the received signal SINR according to the sounding signal, so as to evaluate the quality of the uplink channel that the UE will communicate with;

Step 107: The base station sends a TPC (transmission power control) command to the UE through the PDCCH according to the evaluation result;

Step 108: The UE transmits power according to the TPC command and the power calculation formula of the closed-loop power control to realize communication.

As shown in Fig. 2, it is the improved closed-loop power control flowchart of the present invention, and this flow process comprises the following steps:

Step 201: Calculate the distance between the user and the base station and estimate the path loss, shadow fading and antenna related gain;

Step 202: Determine the relevant path loss compensation factor α according to the size of the path loss;

Step 203: Estimate and statistically measure the reference signal received power RSRP of all UEs in the cell according to the common reference signal sent by the base station and the coupling loss, list and determine the value range of this RSRP (RSRP _min , RSRP _max );

Step 204: Determining thresholds for the criteria for defining the location of the cell where the UE is located, that is, determining the thresholds RSRP _th1 and RSRP _th2 for judging which area the UE is located in. This value is determined by (RSRP _min , RSRP _max ) actually measured in this cell, and this threshold can also be set in advance according to empirical values. set step size but RSRP _th1 = RSRP _max -l; determine the cell location of the current UE according to the two reference thresholds of RSRP and the reference signal received power RSRP _self of the current UE, and then adopt different power control for UEs in three different locations plan. We divide the community into three areas according to two thresholds, and the specific division rules are shown in the table below:

Step 205: If RSRP _self >RSRP _th1 is satisfied, determine that the location of the UE is the "excellent area (central area)", and continue to increase the transmission power on the basis of the original transmission power, and the increase is g*△ _RSRP , where g is the reference The power difference compensation factor, △ _RSRP will be determined in Fig. 3. The purpose of this is to ensure the average throughput of the cell. Because the UE located in this area has a better channel condition, it can transmit at a higher power to ensure the transmission of more data. At the same time, because it is far away from other cells The interference caused by the increase of its power to other cells can be ignored.

Step 206: If RSRP _th2 <RSRP _self <RSRP _th1 is satisfied, determine that the location of the UE is in the "central area". This part of the UE is relatively centered from the base station and other cells, so it can be calculated according to the protocol formula as the path loss increases. Appropriate compensation for the path loss is enough, that is, as the path loss increases, the transmit power gradually increases.

Step 209: If RSRP _self <RSRP _th2 , determine that the location of the UE is a "marginal area", and appropriately reduce the transmit power of this part of the UE on the basis of the closed-loop power, and the reduction step is g*|Δ _RSRP |. Since the transmit power of these UEs is appropriately increased during closed-loop power control, the throughput of cell-edge users is improved compared with open-loop power control, but at the same time, the power of UEs located at the cell There will be a certain degree of interference to neighboring cells, so slightly reducing this part of power on the basis of closed-loop power control can reduce the interference to neighboring cells on the basis of improving the UE throughput at the cell edge.

Step 210: Resend the TPC command according to the correction factor added on the basis of the closed-loop power control, so as to select different transmit power schemes according to the area where the UE is located.

As shown in Figure 3, in order to determine the flow chart of the improved closed-loop power control correction factor, the following steps are included:

Step 301: Calculate the distance between the user and the base station to estimate the path loss, shadow fading and antenna related gain;

Step 302: Determine the carrier power of the downlink common reference signal CRS of the current neighboring cell;

Step 303: The UE determines the reference signal received power RSRP _neighbor of all neighboring cells according to the carrier power and related coupling loss of all common reference signals in the current neighboring cell list;

Step 304: Select the maximum value RSRP _neighbor-max from all RSRP _neighbors , and determine the base station that generates the strongest interference to itself;

Step 305: Determine the power control improvement factor Δ _RSRP , Δ _RSRP = RSRP _self - RSRP _neighbor-max .

Step 306: When the UE is located in the "excellent area (central area)", △>0, since it is relatively far away from adjacent cells, increasing the power of these UEs will not cause interference to adjacent cells; when the UE is located in In the "marginal area", the sign of △ _RSRP cannot be determined, so in order to ensure the correctness of the algorithm, we take the absolute value of it, and then subtract this value from the original closed-loop power control, so that the power of the edge UE is first adopted The fine-tuning after increasing and decreasing takes into account multiple factors such as inter-cell interference coordination on the basis of ensuring the throughput of users at the edge of the cell.

Claims (2)

1., based on a close-loop power control modification method for lte-a system, it is characterized in that, the method comprises the following steps:

Step 201, calculate the distance between user and base station and estimate the related gain of path loss, shadow fading and antenna;

Step 202, determine the path loss compensating factor α that is correlated with according to path loss;

Step 203, according to base station send public reference signal and path loss, the received power RSRP of the reference signal of all UE in this community of statistical measurement, and the span (RSRP determining RSRP _min, RSRP _max);

Step 204, for judging that UE is positioned at the thresholding RSRP in which region _th1and RSRP _th2if, step-length then RSRP _th2=RSRP _min+ l, RSRP _th1=RSRP _max-l; According to two thresholding RSRP _th1and RSRP _th2and the received power RSRP of the reference signal of current UE self _selfdetermine the subdistrict position residing for current UE, then different power control schemes is adopted to the UE being positioned at three kinds of diverse locations.Microzonation is divided into three regions according to two thresholdings by us, i.e. marginal zone, middle district and excellent district;

If step 205 meets RSRP _self>RSRP _th1, then UE position is excellent district, and the basis of former transmitting power is continued increase transmitting power, recruitment is g* △ _rSRP, wherein g is reference power difference compensating factor, △ _rSRPfor improving close-loop power control modifying factor;

If step 206 meets RSRP _th2<RSRP _self<RSRP _th1, then UE position is middle district, and according to agreement formula along with the increase of path loss carries out suitable compensation to path loss, namely along with the increase of path loss, transmitting power increases gradually;

If step 207 RSRP _self<RSRP _th2time, then determine that UE position is marginal zone, the basis of closed power reduces the transmitting power of this part UE, reducing step-length is g*| Δ _rSRP|, promote the throughput of Cell Edge User; The basis of close-loop power control reduces the power of this part UE slightly, to reduce the interference that it produces adjacent cell;

Step 208, according to above-mentioned modifying factor of adding on close-loop power control basis, re-start the transmission of TPC command, thus select different transmitting powers according to UE region.

2. a kind of close-loop power control modification method based on lte-a system as claimed in claim 1, it is characterized in that, described modifying factor constant current journey really, comprises the following steps:

The related gain of step 301, the range estimation path loss calculating user and base station, shadow fading and antenna;

Step 302, determine the carrier power of the descending public reference signal CRS of current neighbor cell;

Step 303, UE determine the Reference Signal Received Power RSRP of all neighbor cells according to the carrier power of public reference signals all in current neighbor cell list and correlative coupling loss _neighbour;

Step 304, from all RSRP _neighbourselect maximum RSRP _neighbor-max, determine to produce the most strongly disturbing base station to oneself;

Step 305, really constant dc power control improve factor △ _rSRP, △ _rSRP=RSRP _self-RSRP _neighbor-max;

Step 306, when UE is positioned at excellent district, △ _rSRP>0, increases the power of this part UE; When UE is positioned at marginal zone, get △ _rSRPabsolute value, then on original close-loop power control basis, deduct this value, thus the power of edge UE adopts the fine setting of first increases and then decreases, on the basis ensureing cell edge user throughput, has taken into account Inter-Cell Interference Coordination.