KR20090105666A - Power control apparatus and method for minimizing uplink interference of indoor base station in wireless communication system - Google Patents

Abstract

PURPOSE: A power control device for minimizing uplink interference of an indoor base station in a mobile communication system and a method thereof are provided to minimize the interference about outdoor user and transmit uplink data of high quality. CONSTITUTION: A power control device for minimizing uplink interference of an indoor base station in a mobile communication system and a method thereof are as follows. An interference and noise level information are acquired from the outdoor base station(302). The maximum permissible interference amount of the inside of a user terminal is adaptively controlled according to an interference and noise level. The maximum transmission electric power of the inside of the user terminal is calculated by the maximum permissible interference amount of the inside(316).

Description

Power control device and method for minimizing uplink interference of indoor base station in mobile communication system {POWER CONTROL APPARATUS AND METHOD FOR MINIMIZING UPLINK INTERFERENCE OF INDOOR BASE STATION IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to power control of a mobile communication system, and more particularly, to an uplink power control apparatus and method for minimizing interference to an uplink of an outdoor base station by an indoor micro base station located in a service area of an outdoor base station.

Increasing competition and profitability in the telecommunications market, diversifying consumer demands and increasing the cost of telecommunications, and the development of wired and wireless convergence services are facilitating the emergence and development of wired and wireless convergence services. Is rising. The femtocell is a service area of an ultra-small base station for mobile communication (hereinafter referred to as an indoor small base station) used indoors such as homes or offices. It has the advantage of improving the call quality and efficiently providing various wired / wireless convergence services.

A technical prerequisite to be solved for the successful development and operation of an indoor small base station such as a femtocell is to suppress co-channel interference occurring between an outdoor base station and an indoor small base station. Unlike high-powered outdoor base stations installed by operators, indoor small base stations installed by users are installed in multiple floors in a building. In this case, the signal of the indoor small base station causes additional interference to the outdoor base station. The effect of the additional interference not only degrades the quality of service to the outdoor base station user terminals near the indoor small base station but also causes a call drop phenomenon. Therefore, it is necessary to provide excellent quality services to users in the building (called indoor users) while minimizing the influence of interference on the outside of the building. Here, the indoor user is a terminal located in the femtocell area of the indoor small base station to receive the service.

In particular, when the outdoor base station and the indoor small base station using the same frequency channel are located close to each other, the uplink transmission signal transmitted by the indoor user to the indoor small base station corresponds to the uplink signal transmitted by the outdoor user to the outdoor base station. It will act as a significant interference. In such an environment, in order to minimize the influence of interference on the outside of the building, it is necessary to strictly limit the maximum transmission power of the indoor user than the outdoor user.

Looking at the conventional uplink power control, each user terminal, the amount of interference of interference user terminals belonging to the neighboring base station, the path loss and shadowing (loss) and thermal noise with the base station connected to each user terminal, and transmit in the uplink The transmission power P _t is determined according to the modulation and coding scheme (MCS) level of the data. The user terminal ensures that the determined transmit power P _t does not exceed the maximum transmit power P _max every time data is transmitted. Here, the maximum transmit power P _max is the maximum transmit power of the user terminal for satisfying spectral masks and an error vector magnitude (hereinafter, referred to as "EVM") request.

In the uplink power control scheme, the maximum transmit power P _max is given to the uplink of the outdoor base station by an indoor user because the maximum transmission power P _max is not considered an additional interference generated when the service area of the outdoor base station and the indoor small base station overlaps. Interference degrades performance. This is because the user terminal of the indoor small base station located in the service area of the outdoor base station should restrict the maximum transmission power more strictly than the outdoor user terminal in order to minimize interference with the outdoor base station. Therefore, in consideration of the uplink interference situation of the outdoor base station, it is necessary to adaptively determine the maximum transmit power value of the indoor user. In addition, since the amount of interference the indoor user has on the outdoor base station is very different according to the channel environment between the indoor user and the outdoor base station, the maximum transmission power should be optimized for each indoor user terminal in consideration of the channel environment for each indoor user.

An apparatus and method for minimizing uplink interference of an indoor small base station located in a service area of an outdoor base station in a mobile communication system are proposed.

According to a first aspect of the present invention for achieving the above object, in the power control method of the indoor user terminal to minimize the uplink interference of the outdoor base stations in the mobile communication system, each interference and from a plurality of outdoor base stations Considering a process of acquiring noise & interference (NI) level information, adaptively adjusting a maximum allowable interference amount of an indoor user terminal according to the interference and noise level, and considering a maximum allowable interference amount of the indoor user terminal To calculate the maximum transmission power of the indoor user terminal, characterized in that it comprises a.

According to a second aspect of the present invention for achieving the above object, in the power control method of the indoor user terminal to minimize the uplink interference of the outdoor base stations in the mobile communication system, each radio link with the outdoor base stations Calculating a path loss with respect to the path loss, selecting a path having a minimum path loss among the path losses, and using the minimum path loss value, the maximum transmission power so as not to exceed the maximum allowable interference amount of the indoor user terminal. It characterized in that it comprises a process of calculating.

According to a third aspect of the present invention for achieving the above object, in the power control device of the indoor user terminal to minimize the uplink interference of the outdoor base stations in the mobile communication system, each interference and from a plurality of outdoor base stations An interference and noise level setting unit for acquiring noise & interference (NI) level information, and adaptively adjusting a maximum allowable interference amount of an indoor user terminal according to the interference and noise level, and allowing a maximum allowance of the indoor user terminal. In consideration of the amount of interference, it characterized in that it comprises a power controller for calculating the maximum transmission power of the indoor user terminal.

According to a fourth aspect of the present invention for achieving the above object, in the power control device of the indoor user terminal to minimize the uplink interference of the outdoor base stations in the mobile communication system, each radio link with the outdoor base stations A path loss calculator for calculating a path loss with respect to the path loss calculator, a controller for selecting a path having a minimum path loss among the path losses, and the maximum path loss value so as not to exceed the maximum allowable interference amount of the indoor user terminal using the minimum path loss value. It characterized in that it comprises a power controller for calculating the transmission power.

As described above, within the range in which uplink interference for the outdoor user of the indoor user is allowed in the mobile communication system, the indoor user transmits data at the maximum transmission power, thereby minimizing the interference for the outdoor user. There is an advantage in that uplink data transmission of good quality can be performed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, the present invention will be described an apparatus and method for indoor power uplink power control of the indoor user to minimize the interference of the indoor base station in the service area of the outdoor base station in the mobile communication system to the uplink of the outdoor base station; do.

Particularly, in the indoor user terminal power control scheme proposed by the present invention, the transmission power determined by the conventional uplink power control scheme is proposed by the present invention while using the uplink power control scheme that has been conventionally used for each communication system. It is a technique to avoid exceeding the maximum transmit power value determined for each user. In the following description, a broadband wireless communication system (IEEE 802.16) is described as an example, but it is also applicable to other mobile communication systems.

1 illustrates an example for determining a maximum transmit power of an indoor user terminal in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 1, the outdoor base station 100 communicates with terminals (called outdoor user terminals) in a macro cell 102 area to provide a service. The indoor small base station 120 is located inside the building and communicates with the terminal 110 (hereinafter, referred to as indoor user terminal) within the building in the femtocell area 112 to provide a service. The indoor small base station 120 is located in the service cell 102 area of the outdoor base station 100, and connects a mobile phone and the Internet indoors, such as at home or office, to provide a wired / wireless convergence service at a low cost. To provide.

When the outdoor base station 100 and the indoor small base station 120 using the same frequency channel are located in close proximity, the uplink transmission signal transmitted by the indoor user terminal 110 to the indoor small base station 120 is outdoors. The user (not shown) acts as a significant interference to the uplink signal transmitted to the outdoor base station 100. In order to minimize the interference effect on the outside of the building in such an environment, it is necessary to strictly limit the maximum transmission power of the indoor user terminal 110 than the outdoor user terminal (not shown).

To this end, the indoor user terminal 110 adaptively adjusts the maximum transmission power value for each indoor user in consideration of the uplink interference situation of the outdoor base station 100 and the channel environment between the outdoor base station 100 and the indoor user 110. Should be decided. The maximum transmit power value may be determined by an open loop determination method and a closed loop determination method.

In the case of the open loop determination method, the indoor user terminal 110 measures the received power from the outdoor base station 100 (105), and from the outdoor base station 100 through the indoor small base station 120 through the outdoor In step 125, EIRP _out information, which is an effective isotropically radiated power (EIRP) of the base station 100, is received. Here, the outdoor base station 100 transmits its EIRP _out information to the indoor small base station 120 through the backbone network 130 (125). The indoor user terminal 110 calculates an average path loss between the indoor user terminal 110 and the outdoor base station 100 using the received power 105 and the EIRP _out information 125. The maximum transmission power of the indoor user terminal 110 is determined so as not to exceed the maximum allowable interference amount of the indoor user terminal 110 for the outdoor base station 100. The maximum allowable interference amount means a value that can allow the interference to the outdoor base station 100 to the maximum when the indoor user terminal 110 transmits uplink data to the indoor small base station 120. The open loop determination procedure will be described in detail with reference to FIG. 2.

In the closed loop determination method, in addition to the open loop determination method, NI _out , which is interference and noise level information of the outdoor base station 100, is received and is indoors according to the current interference and noise level of the outdoor base station 100. The maximum transmission power of the user 110 is determined. The closed loop determination procedure will be described in detail with reference to FIG. 3.

As described above, in order to perform the proposed open loop determination method, the indoor user terminal 110 should be able to receive the EIRP _out of the outdoor base station 100 through the indoor small base station 120. In addition, in order to perform the proposed closed loop determination method, the indoor user terminal 110 is EIRP _out. In addition to the information, additionally, NI _out of the outdoor base station 100 should be able to be transmitted through the indoor small base station 120.

2 is a flowchart illustrating an open loop power control for determining a maximum transmit power of an indoor user terminal 110 in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the indoor user terminal 110 measures the received power R _{out , k} of signals received from at least one outdoor base station 100 in step 200. Where k is the index of the outdoor base station.

In other words, the indoor user terminal 110 continuously observes the received power of the signal received from the N _out neighboring outdoor base stations, and removes the instantaneous change in the received power due to the small fading effect. The average is taken to find the average received power {R _{out , k} } k = 1, ..., N _out (dBm) from the k-th outdoor base station. Here, the number N _out of the outdoor base stations from which the indoor user can observe the received power depends on the location of the indoor base station and the channel environment.

In step 202, the indoor user terminal 110 receives transmission power information (eg, EIRP) T _{out , k} of a plurality of outdoor base stations from the indoor small base station 120. That is, transmission power information {T _{out , k} } k = 1, ..., N _out (dBm) of surrounding outdoor base stations is transmitted to the indoor small base station to which the indoor user terminal belongs through the backbone network, and the indoor The small base station is {T _{out , k} } k = 1, ..., N _out Information is transmitted to indoor user terminals through a downlink signaling channel.

Thereafter, the indoor user terminal 110 performs {R _{out , k} } k = 1, ..., N _{out in} step 204. And {T _{out, k} } k = 1, ..., N _out information, the average path loss between the indoor user terminal 110 and the outdoor base station 100 is calculated. For each indoor user terminal, the average path loss L _k (dB) from the surrounding kth outdoor base station to the corresponding indoor user terminal is calculated as shown in Equation 1 below.

Where L _k is the path loss between the indoor user terminal and the outdoor base station, R _{out , k} is the received power from the k-th outdoor base station measured by the indoor user terminal, and T _{out , k} is the transmit power of the k-th outdoor base station. , F _in is the reception antenna gain [dB] of the indoor user terminal, F _out is the transmission antenna gain of the outdoor base station antenna, the unit is dB.

In step 206, the indoor user terminal 110 selects the smallest average path loss value among the average path loss values for the N _out outdoor base stations. The average loss, the lower the path, the indoor user terminals because a large interference to the outdoor base station, the minimum path loss in the path loss for the N _out of outdoor base stations _{L min = min (L 1,} L 2, ... , N _out ) to select the maximum transmit power of the indoor user.

In step 208, the indoor user terminal 110 transmits the transmit power P _in of the indoor user such that the maximum interference power I _max for the outdoor base station and the maximum allowable interference amount I _th (dBm) predetermined by the system are not exceeded. dBm) is limited as shown in Equation 2 below.

Here, P _in is the transmission power of the indoor user terminal, L _min is the minimum path loss, G _in and G _out are the transmission antenna gain of the indoor user and the receiving antenna gain of the outdoor base station antenna, respectively, in dB.

In conclusion, the maximum transmit power (P _{in , max that the} indoor user terminal can use) (dBm) is determined as in Equation 3 below.

Here, the maximum allowable interference I _th predetermined in the system may be different for each system, and as a representative example, may be determined as α times the noise power of the outdoor base station, such as I _th = α × NF _out × N ₀ × W. Here, NF _out , N ₀ , and W, which determine the noise power of the outdoor base station, are noise figure, noise spectral density, and bandwidth used of the external base station, respectively. The above-described maximum transmission power determination process is performed for each indoor user terminal to determine the maximum transmission power for each indoor user terminal.

Thereafter, the indoor user terminal 110 transmits data according to the maximum transmission power calculated in step 210.

Thereafter, the indoor user terminal ends the power control procedure.

As described above, the open loop determination method for determining the maximum transmission power of the indoor user terminal 110 calculates the amount of interference that the indoor user terminal may have on the outdoor base station alone, and does not exceed a predetermined maximum allowable interference amount. This is a technique for limiting the transmission power of indoor users. Since the maximum allowable interference amount determined in advance by the system does not consider the instantaneous interference and noise level of the outdoor base station, the transmission power of the indoor base station may be more than necessary depending on the situation. Specifically, for example, if the outdoor base station is currently experiencing low interference and noise levels, by increasing the maximum allowable interference amount for indoor users, the indoor users can use higher transmission power to provide better quality service. It is desirable to. Therefore, by additionally using the information on the interference and noise level currently experienced by the external base station, by adaptively adjusting the maximum allowable interference amount for the indoor user, a closed loop method for allowing the indoor user to actively use the transmission power It demonstrates in FIG.

3 is a flowchart of a closed loop power control for determining a maximum transmit power of an indoor user terminal 110 in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the indoor user terminal initializes n to “0” in order to temporarily adjust the maximum transmit power of the indoor user terminal in the closed loop method in step 300. N is an index for updating the maximum transmission power of the indoor user terminal and counts the maximum transmission power update.

In step 302, the indoor user terminal transmits EIRP _out and NI _out through the backbone network from the corresponding outdoor base stations. Obtain information. In other words, N _out indoor base stations to which the indoor user terminal may interfere, estimate the current interference and noise level NI _{out, k} (0) and transmit the same to the indoor user terminal through the backbone network.

Then, the indoor user terminal is the EIRP _out of the outdoor base station in step 304 Using the information, calculate the average path loss (L _k ) (dB). In the same manner as the open loop described above with reference to FIG. 2, the average received power {R _{out , k} } k = 1, ..., N _out from the measured kth outdoor base station and transmit power information of the transmitted outdoor base stations { T _{out , k} } k = 1, ..., N _out , the average path loss L _k (dB) from the surrounding kth outdoor base station to the corresponding indoor user for each indoor user terminal as shown in Equation 1 above. Calculate

Then, when the indoor user terminal is n = 0 in step 306, the indoor user terminal proceeds to step 308 to set the interference and noise level NI _{out , k} (0) estimated by each outdoor base station to NI _{target , k} . The NI _{out , k} (0) is the interference and noise level experienced by the k-th outdoor base station before the indoor user transmits data, and the NI _{target , k} is the interference and noise level targeted by the k-th outdoor base station. n = 0 means that the maximum transmission power update of the outdoor base station is in an initial state.

In other words, when the NI _{target , k} value is set to the NI _{out , k} (0), the interference and noise level of the k-th outdoor base station is set to the interference and noise of the current outdoor base station without interference by the indoor user terminal. Keep level NI _{out , k} (0).

If n ≠ 0 in step 306, that is, when the maximum transmit power of the outdoor base station is updated at least once, the process proceeds to step 310 and the current values of NI _{out , k} (n) and NI _{out , k} (0) Compare. If NI _{out , k} (n) ≥NI _{out , k} (0), go to step 308 to reset the NI _{target, k} value to NI _{out , k} (0). This means that the interference and noise level of the corresponding outdoor base station will be greater than the interference and noise level NI _{out , k} (0) of the outdoor base station without interference by the indoor user terminal due to the interference of the newly added indoor user terminal. do.

If NI _{out , k} (n) <NI _{out , k} (0) _, in step 310, the NI _{target , k} value is set to NI _{out , k} (n). This means that even if the interference of the new indoor user terminal is added, the interference and noise level of the corresponding outdoor base station is kept lower than the interference and noise level NI _{out , k} (0) of the outdoor base station without interference by the indoor user.

In step 314, the indoor user terminal sets the maximum allowable interference amount I _{th , k} (n) for the _{k- th} outdoor base station to be β times the NI _{target , k} of the corresponding outdoor base station.

That is, when n = 0, the maximum allowable interference amount I _{th , k} (n) for the _{k- th} outdoor base station is β of the interference and noise level NI _{out, k} (0) of the current outdoor base station without interference by the indoor user. It is doubled. Here, β may be determined for each system.

On the other hand, the maximum allowable interference amount NI _{target , k} set by NI _{out , k} (n) ≥NI _{out , k} (0) is substantially reduced to β × NI _{out , k} (0), resulting in k-th outdoor base station. The maximum allowable transmit power of indoor users is also reduced.

NI _{out , k} (n) ≥NI _{out , k} (0) occurs when the existing amount of interference (interference other than interference by a new indoor user) of the outdoor base station decreases, so in this case, NI _{Set the target , k} (n) value to NI _{out , k} (n) so that the maximum permissible interference NI _{target, k} (n) value includes the new interference for indoor users, thus substantially eliminating the k-th outdoor base station. Increase the maximum allowable transmit power of indoor users.

In step 316, the indoor user terminal determines the maximum allowable transmit power P _{in , max , and k} of the indoor user allowed to the k-th outdoor base station as shown in Equation 4 below.

Where P _{in , max , k} are the maximum transmit power of the indoor user terminal, Ith, k is the maximum allowable interference amount for the k-th outdoor base station, G _in and G _out are the transmission antenna gain of the indoor user and the Receive antenna gain, in dB. L _k is a path loss between the indoor user terminal and the k-th outdoor base station.

In step 318, the indoor user terminal determines that the maximum interference power for the k-th outdoor base station does not exceed the maximum allowable interference amount I _{th , k} (n) _, as shown in Equation 4, in step 318. The maximum allowable transmit power P _{in , max , k} for indoor users is selected. As shown in Equation 5 below, the indoor user has the maximum allowable transmit power for the calculated N _out outdoor base stations {P _{in , max , k} } k = 1, ..., N _out. Is selected as the maximum transmit power value of the indoor user.

This means that the indoor user terminal determines the maximum transmit power value of the indoor user with respect to the outdoor base station that has the most interference.

Thereafter, the indoor user terminal increases to n + 1 in step 320 and repeats steps 302 to 318.

Thereafter, the indoor user terminal ends the power control procedure.

As described above, the closed loop method keeps the total amount of interference and noise received by the outdoor base station at a constant level, and when the existing amount of interference (interference other than new interference by the indoor user) of the outdoor base station decreases, indoors. Increasing the maximum transmit power of the user allows the indoor user to be provided with higher quality service using higher transmit power.

4 illustrates a power control apparatus for determining a maximum transmit power of an indoor user terminal 110 in a broadband wireless communication system according to an embodiment of the present invention.

Referring to FIG. 4, the indoor user terminal device includes a base station RF processor 401, an ADC 403, an OFDM demodulator 405, a decoder 407, a controller 409, a path loss calculator 411, and a power controller. 411, an interference and noise level setting unit 415, an encoder 319, an OFDM modulator 419, a DAC 421, and an RF processor 423.

First, the time controller 427 controls the switching operation of the switch 425 based on time synchronization. For example, if the signal receiving section, the time controller 427 controls the switch 425 so that the antenna and the RF processor 401 of the receiving end is connected, and if the signal transmitting section, the time controller 427 The switch 427 is controlled to connect the RF processor 325.

During the reception period, the RF processor 401 converts a radio frequency (RF) signal received through an antenna into a baseband analog signal. The ADC 403 converts the analog signal from the RF processor 401 into sample data and outputs the sample data. The OFDM demodulator 405 converts the sample data output from the ADC 403 into data of a frequency domain by fast Fourier transform (FFT), and selects and outputs data of subcarriers to be actually received from the data of the frequency domain. . The decoder 407 demodulates and decodes the data from the OFDM demodulator 405 according to a predetermined modulation level (MCS level).

The control unit 407 controls the overall operation of the terminal, and the control unit 407 performs the corresponding processing for the control information so as not to interfere with the uplink of the outdoor base station in the femtocell environment, and also generates information to be transmitted. do. In addition, a message is generated with various pieces of information provided from the controller 409 and output to the encoder 417 of the physical layer.

The interference and noise level setting unit 415 obtains respective interference and noise (NI) level information from a plurality of outdoor base stations and provides them to the power controller 413. The path loss calculator 411 calculates a path loss for each radio link with outdoor base stations and provides the path loss to the power controller 413.

The power controller 413 adaptively adjusts the maximum allowable interference amount of the indoor user terminal according to the interference and noise level, and considers the maximum allowable interference amount of the indoor user terminal to determine the maximum transmit power of the indoor user terminal. Calculate In addition, the maximum transmission power is calculated using the minimum path loss value so as not to exceed the maximum allowable interference amount of the indoor user terminal.

The power controller 413 initially transmits data of an interference and noise level (NI _{target , k} ) targeted by the k-th outdoor base station at an initial stage (n = 0) of updating the maximum transmission power of the indoor user terminal. It sets the interference and noise level (NI _{out , k} (0)) experienced by the k-th outdoor base station before. In addition, the power controller 413 is n time of updating the second indoor maximum transmit power of the user terminals, _{out NI, k} (n) ≥NI _out, if _k (0), one _{target NI,} value NI _out a _{k, k} Reset to (0) and set NI _{target , k} to NI _{out, k} (n) if NI _{out , k} (n) <NI _{out , k} (0). Here, the NI _{out , k} (0) is the interference and noise level experienced by the k-th outdoor base station before the indoor user transmits data, and the NI _{target , k} is the interference and noise level targeted by the k-th outdoor base station. .

The encoder 417 codes and modulates the data from the controller 409 in accordance with a predetermined modulation level (MCS level). The OFDM modulator 419 outputs sample data (OFDM symbols) by performing IFFT (Inverse Fast Fourier Transform) on the data from the encoder 417. The DAC 421 converts the sample data into an analog scene and outputs the analog scene. The RF processor 423 converts an analog signal from the DAC 421 into a radio frequency (RF) signal and transmits the same through an antenna.

In the above-described configuration, the controller 411 is a protocol controller and controls the path loss calculator 409, the power controller 413, and the interference and noise level setting unit 415. That is, the controller 409 may perform the functions of the path loss calculator 409, the power controller 413, and the interference and noise level setting unit 415. In the present invention, it is separately configured to describe each function separately. Therefore, in actual implementation, all of them may be configured to be processed by the controller 411, and only some of them may be configured to be processed by the controller 409. In addition, the controller 311 receives necessary information during the protocol processing to the corresponding component of the physical layer, or generates a control signal to the corresponding component of the physical layer.

In the present invention, in consideration of the uplink interference situation of the outdoor base station and the channel environment between the outdoor base station and the indoor user terminal, an open loop and closed loop method for adaptively determining the maximum transmission power value for each indoor user is proposed. In order to analyze the performance of the open and closed loop method for determining the maximum transmit power of the proposed indoor user terminal, we compare and analyze the performance of the indoor user terminal with the fixed method of 23dBm through system level simulation. Consider a two-tier wireless communication network consisting of 19 outdoor base stations formed of three sectors for system level simulation. A total of 57 sectors of outdoor base stations use frequency reuse factor 3. In each sector, the indoor base station is located 100 m away from the side of the outdoor base station and uses the same frequency band as the outdoor base station. It is assumed that the frequency band used is 10 MHz and the building transmission loss is 10 dB. Ten outdoor users and four indoor users are uniformly distributed in each sector.

5 shows a performance graph according to an embodiment of the present invention.

The outdoor uplink capacity loss rate (TL), which represents the uplink capacity of the outdoor base station reduced by the uplink interference of the indoor user, is defined as Equation 6 as a performance analysis measure.

Where T _{w / o indoor BS} indicates uplink capacity of the outdoor base station when there is no indoor base station, and T _{w indoor BS} represents uplink capacity of an outdoor base station considering uplink interference of an indoor user terminal.

Referring to FIG. 5, an open-loop method for determining a maximum transmit power of an indoor user, a closed-loop method, and an outdoor uplink capacity loss rate in which the maximum transmit power is fixed at 23 dBm. TL was compared. In the open loop method, it is determined as I = _th α NF _out N W and α is assumed to be 1/4. In the closed loop method, β is also assumed to be 1/4 to determine the maximum allowable interference amount NI _{target , k} (n). As a result, it can be seen that the proposed method of determining the maximum transmission power by the open loop method and the closed loop method suppresses the uplink capacity loss of the outdoor base station to less than 4% even in the 10MHz system. It can be seen that the uplink capacity loss rate is considerably lower than the indoor user always uses the maximum transmit power of 23dBm. It can be seen that the TL by the closed loop method is slightly higher than the open loop method. This is because the closed loop method has a higher maximum transmit power value for indoor users than the open loop method. The effect of this can be seen through the uplink capacity attainment rate TA of the indoor base station shown in FIG. 6, which shows that the TA by the open loop method is slightly higher than the closed loop method. The uplink capacity achievement rate TA of the indoor base station is defined as in Equation 7 below.

Here, C _{closed / open - loop} represents the uplink capacity of the indoor base station by the proposed closed loop or open loop method, and C _fixed indicates the uplink capacity of the indoor base station when the indoor user always uses the maximum transmit power of 23 dBm. to be.

Referring to FIG. 6, the TA of the open loop method is slightly higher than that of the closed loop method, which means that the closed loop method provides uplink capacity of a high indoor base station. In both cases, a 10MHz or more TA can be seen. Therefore, it can be seen that the proposed open loop and closed loop methods for determining the maximum transmission power of the indoor user increase the capacity of the indoor base station uplink while minimizing the outdoor base station uplink interference by the indoor user.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described. However, various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is an exemplary diagram for determining a maximum transmission power of an indoor user terminal in a broadband wireless communication system according to an embodiment of the present invention;

2 is an open loop power control flowchart for determining a maximum transmit power of an indoor user terminal 110 in a broadband wireless communication system according to an embodiment of the present invention;

3 is a closed loop power control flowchart for determining a maximum transmit power of an indoor user terminal 110 in a broadband wireless communication system according to an embodiment of the present invention;

4 is an apparatus diagram for determining a maximum transmit power of an indoor user terminal 110 in a broadband wireless communication system according to an embodiment of the present invention;

5 is a first performance graph according to an embodiment of the present invention;

6 is a second performance graph according to an embodiment of the present invention;

Claims (22)

In the power control method of the indoor user terminal to minimize the uplink interference of the outdoor base stations in the mobile communication system, Obtaining respective interference & noise (NI) level information from a plurality of outdoor base stations; Adaptively adjusting the maximum allowable interference amount of the indoor user terminal according to the interference and noise level; And calculating the maximum transmit power of the indoor user terminal in consideration of the maximum allowable interference amount of the indoor user terminal. The method of claim 1, According to the interference and noise level, the process of adaptively adjusting the maximum allowable interference amount of the indoor user terminal, Initially when the maximum transmission power of the indoor user terminal is updated (n = 0), the k-th outdoor base station before the indoor user transmits data to the interference and noise level (NI _{target , k} ) targeted by the k-th outdoor base station Power control method characterized by setting the interference and noise level (NI _{out , k} (0)). The method of claim 1, According to the interference and noise level, the process of adaptively adjusting the maximum allowable interference amount of the indoor user terminal, When updating the maximum transmit power of the nth indoor user terminal, set NI _{target , k back} to NI _{out , k} (0) when NI _{out , k} (n) ≥NI _{out , k} (0) A power control method comprising setting an NI _{target , k} value to NI _{out , k} (n) when _{out , k} (n) <NI _{out , k} (0). Here, the NI _{out , k} (0) is the interference and noise level experienced by the k-th outdoor base station before the indoor user transmits data, and the NI _{target , k} is the interference and noise level targeted by the k-th outdoor base station. . The method of claim 1, The maximum transmission power is a power control method, characterized in that calculated by Equation (8).

Where P _{in , max , k} are the maximum transmit powers of the indoor user terminal, I _{th , k} are the maximum allowable interference amount for the k-th outdoor base station, G _in and G _out are the indoor user's transmit antenna gain and the outdoor base station antenna, respectively Receive antenna gain in units of dB. L _k is a path loss between the indoor user terminal and the k-th outdoor base station. The method of claim 1, And selecting the maximum transmission power having the minimum value among the maximum transmission power values of the indoor user terminal as the maximum transmission power of the indoor user. The method of claim 1, To calculate a path loss for each radio link between the plurality of outdoor base stations and the indoor user terminal, Obtaining transmission power information from the plurality of outdoor base stations; And controlling the reception power from the plurality of outdoor base stations. In the power control method of the indoor user terminal to minimize the uplink interference of the outdoor base stations in the mobile communication system, Calculating a path loss for each radio link with the outdoor base stations; Selecting a path having a minimum path loss among the path losses; And calculating a maximum transmit power so as not to exceed an allowable maximum interference amount of the indoor user terminal by using the minimum path loss value. The method of claim 7, wherein The maximum transmission power is a power control method characterized in that determined by the following equation (9).

Where P _{in and max} are the maximum transmit power of the indoor user terminal, L _min is the minimum path loss, G _in and G _out are the transmit antenna gain of the indoor user terminal and the receive antenna gain of the outdoor base station, respectively, and I _th is the system. The maximum allowable interference amount of the indoor user terminal predefined in. The method of claim 8, The maximum allowable interference amount of the indoor user terminal is determined by α times the noise power of the outdoor base station and is calculated by Equation 10 below.

Where α is the weight, NF _out is the noise figure of the outdoor base station, N ₀ is the noise power spectral density, and W is the bandwidth used. The method of claim 7, wherein The maximum transmission power is determined for each indoor user terminal to determine the maximum transmission power for each indoor user. The method of claim 7, wherein The path loss for each radio link with the outdoor base stations is And calculating power of signals received from the outdoor base stations, obtaining transmission power information from the outdoor base stations, and calculating the power. An apparatus for controlling power of an indoor user terminal to minimize uplink interference of outdoor base stations in a mobile communication system, An interference and noise level setting unit for obtaining respective interference & noise (NI) level information from a plurality of outdoor base stations; And a power controller that adaptively adjusts the maximum allowable interference amount of the indoor user terminal according to the interference and noise level, and calculates the maximum transmit power of the indoor user terminal in consideration of the maximum allowable interference amount of the indoor user terminal. Device characterized in that. The method of claim 12, The power controller Initially when the maximum transmission power of the indoor user terminal is updated (n = 0), the k-th outdoor base station before the indoor user transmits data to the interference and noise level (NI _{target , k} ) targeted by the k-th outdoor base station Power control device characterized in that it is set to the level of interference and noise experienced (NI _{out , k} (0)). The method of claim 12, The power controller When updating the maximum transmit power of the nth indoor user terminal, set NI _{target , k back} to NI _{out , k} (0) when NI _{out , k} (n) ≥NI _{out , k} (0) A power control device comprising setting the NI _{target , k} value to NI _{out , k} (n) when _{out , k} (n) <NI _{out , k} (0). Here, the NI _{out , k} (0) is the interference and noise level experienced by the k-th outdoor base station before the indoor user transmits data, and the NI _{target , k} is the interference and noise level targeted by the k-th outdoor base station. . The method of claim 12, The maximum transmission power is a power control device, characterized in that calculated by the following equation (11).

Where P _{in , max , k} are the maximum transmit powers of the indoor user terminal, I _{th , k} are the maximum allowable interference amount for the k-th outdoor base station, G _in and G _out are the indoor user's transmit antenna gain and the outdoor base station antenna, respectively Receive antenna gain in units of dB. L _k is a path loss between the indoor user terminal and the k-th outdoor base station. The method of claim 12, And a maximum transmission power having a minimum value among the maximum transmission power values of the indoor user terminal is selected as the maximum transmission power of the indoor user. The method of claim 12, To calculate a path loss for each radio link between the plurality of outdoor base stations and the indoor user terminal, And a path loss calculator for acquiring transmission power information from the plurality of outdoor base stations and measuring reception power from the plurality of outdoor base stations. An apparatus for controlling power of an indoor user terminal to minimize uplink interference of outdoor base stations in a mobile communication system, A path loss calculator for calculating path loss for each radio link with the outdoor base stations; A controller for selecting a path having a minimum path loss among the path losses; And a power controller that calculates a maximum transmission power so as not to exceed an allowable maximum interference amount of the indoor user terminal using the minimum path loss value. The method of claim 18, The maximum transmission power is a power control device, characterized in that determined by the following equation (12).

Where P _{in and max} are the maximum transmit power of the indoor user terminal, L _min is the minimum path loss, G _in and G _out are the transmit antenna gain of the indoor user terminal and the receive antenna gain of the outdoor base station, respectively, and I _th is the system. The maximum allowable interference amount of the indoor user terminal predefined in. The method of claim 19, The maximum allowable interference amount of the indoor user terminal is determined by α times the noise power of the outdoor base station and is calculated by Equation (13).

Where α is the weight, NF _out is the noise figure of the outdoor base station, N ₀ is the noise power spectral density, and W is the bandwidth used. The method of claim 18, The maximum transmission power is determined for each indoor user terminal so that the maximum transmission power is determined for each indoor user. The method of claim 18, The path loss calculator And measuring power of signals received from the outdoor base stations, and obtaining transmission power information from the outdoor base stations.

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