KR100581222B1 - Method for determining reference power of power balancing in mobile communication system - Google Patents

Abstract

 The present invention relates to a method for determining a reference power used for power balancing of soft handover in a control station of a mobile communication system, the method comprising: a user terminal received from base stations belonging to an active set; Demodulating a signal to select a base station having the best channel condition, increasing a counter value of the selected base station, comparing counter values of the base stations at a predetermined time period, and selecting a base station having the largest value And reading the transmission power of the selected base station previously received and stored from the memory, and determining the transmission power as the reference power. As described above, the present invention saves wasted transmission power while matching transmission powers between base stations similarly, thereby increasing system capacity.

Soft Handover, Reference Power, RNC, Power Balance

Description

METHOD FOR DETERMINING REFERENCE POWER OF POWER BALANCING IN MOBILE COMMUNICATION SYSTEM}             

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a Probability Density Function (PDF) showing transmission power in case 1 presented in 3Gpp TS25.101 when power control is performed.

2 is a diagram schematically showing the configuration of an asynchronous mobile communication system according to the present invention;

3 is a diagram for explaining soft handover.

4 is a diagram illustrating a procedure for determining a reference power used for power balancing of soft handover in a radio network controller (RNC) according to an embodiment of the present invention.

The present invention relates to a method for controlling the transmission power of a base station involved in handover in a mobile communication system, and more particularly, to a method for determining a reference power used for power balance of soft handover. .

The reference power is specified in "3GPP TS25.433 UTRAN iub Interface NBAP Signaling". The reference power is a parameter used for power balancing, a technique used for soft handover, and is expressed as a power ratio for a pilot channel. The power balance is a technique for minimizing the power difference between the Node Bs that occurs due to an error of a power control bit, etc., as represented by Equation 1 below.

Here, P1 (i) represents the transmit power of the next slot in the first base station node B 1, P1 (i) represents the transmit power of the current slot in the first base station node B 1, and P2 (i + 1) indicates the transmission power of the next slot in the second base station (node B 2), P2 (i) indicates the transmission power of the current slot in the second base station (node B 2). R represents an adjustment ratio, P_ref represents a reference power, and TPC represents a transmit power control.

As can be seen from Equation 1, the reference power is used as a reference parameter for the transmission power between the base stations. The existing reference power is determined by using the median of the maximum power and the minimum power or initial transmission power allocated to a user at the base station. This is expressed by the following equations (2) and (3).

Here, MAX_PWR represents the maximum power that can be allocated to one user, and MIM_PWR represents the minimum power that can be allocated to one user.

Here, INIT_PWR represents the power at the first transmission to the user.

However, the conventional method as described above may cause the following problem when the reference power differs from the transmission power required for the actual service.

First, if the reference power is higher than necessary, the transmission power can be calculated more than necessary, in this case affects the total transmission power of the system and eventually affects the capacity. On the other hand, if the reference power is lower than necessary, it may cause an error in a transmitted slot or frame because the received power required for service is not satisfied. Above all, it is inevitable that an error occurs in a radio channel that changes in time when the reference power is fixed.

FIG. 1 is a PDF (Probability Density Function) showing transmission power in case 1 presented in 3Gpp TS25.101 when power control is performed, which is a data showing the difference between the reference power and the actual transmission power. FIG. 1 is simulated in a Rayleigh fading environment and may be different when the channel model is different. However, in case 1, the difference between the reference power and the actual transmission power is 20 dB or more, even when slow fading is not considered. You can see that it can fly.

In FIG. 1, G represents 'geometry' and is expressed as follows mathematically.

는 활성집합(active set)에 존재하는 기지국(node B)으로부터의 수신전력을 나타내며, I_oc는 활성집합에 존재하지 않는 기지국(node B)으로부터의 수신전력을 나타내고, N_t는 온도 잡음(Thermal Noise)을 나타내며, E_c는 한 채널에 할당되는 송신 에너지를 나타내고, I_or는 활성집합에 존재하는 기지국의 송신전력을 나타낸다.Meanwhile, Ec / Ior represents power allocated to one channel of Node B transmission power,

Is the reception power from the base station node B present in the active set, I _oc represents the reception power from the base station node B which is not in the active set, and N _t is the thermal noise. Noise), E _c represents the transmission energy allocated to one channel, and I _or represents the transmission power of the base station present in the active set.

As shown in Figure 1, according to the prior art it can be seen that there is a significant difference between the reference power and the actual transmission power. In this case, as mentioned above, transmission power may be wasted or various problems such as frame error may be caused. Therefore, there is a demand for a method for reducing the difference between the reference power and the actual transmission power of the base station.

 Accordingly, an object of the present invention is to provide a method for adjusting a reference power used to perform handover in a mobile communication system to a level similar to that of a base station.

Another object of the present invention is to provide a method for performing accurate power control by minimizing a difference between a reference power and an actual transmit power when performing a handover in a mobile communication system.

According to a first aspect of the present invention for achieving the above objects, there is provided a method for determining a reference power used for power balancing of soft handover in a control station of a mobile communication system. Demodulating the signal of the user terminal received from the base stations belonging to the step of selecting a base station having the best channel condition, increasing the counter value of the selected base station, comparing the counter values of the base stations at a predetermined time period, Selecting a base station having the largest value, reading a transmission power of the selected base station previously received and stored from a memory, determining the transmission power as the reference power, and determining the determined reference power And transmitting to base stations belonging to the active set.

According to a second aspect of the present invention for achieving the above objects, there is provided a method for determining a reference power used for power balancing of soft handover in a control station of a mobile communication system. Transmitting the signals of the received user terminal and the transmission power of the signal transmitted to the user terminal to the control station, the base station belonging to the user terminal received from the base stations belonging to the active set Selecting a base station having the best channel condition by demodulating a signal, increasing a counter value of the selected base station, comparing counter values of the base stations at a predetermined time period, and selecting a base station having the largest value. Reading out the transmission power received from the selected base station from a memory; Characterized by comprising the step of transmitting a group with transmission power and the step of determining by the reference power, the base station belonging to the determined reference power in the active set.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, the present invention will be described a method for adjusting a reference power used to perform handover in asynchronous mobile communication system to a level similar to that of a base station.

2 schematically illustrates the configuration of an asynchronous mobile communication system according to the present invention.

Referring to FIG. 2, first, a user equipment (UE) 100 represents a mobile communication terminal, and includes a USIM (Mobile Equipment) 102 serving as a wireless modem and subscriber authentication information. It includes a Universal Service Identification Module (CARD) card.

The radio access network 110 includes Node Bs 111 and 112 and RNCs 113 and 114. The Node Bs 111 and 112 transform the data flow between the Iub and Uu interfaces. That is, it performs radio signal transmission and reception, radio channel encoding and decoding, signal strength and quality measurement (uplink), baseband signal processing, diversity, radio resource management, and self maintenance. The Radio Network Controller (RNC) 113, 114 performs functions such as matching with Node Bs 111 and 112, handover processing between cells, call control, and the like and an external access signal link with a mobile service center (MSC) and SGSN. And bearer channel connection.

Core network 120 comprises MSC / VLR 121, SGSN 122, HLR 123, GMSC 124, GGSN 125. The MSC / VLR (Mobile Services Center / Visitor Location Register) 121 is a switch (MSC) and a database (VLR) provided to a user equipment (UE) at a current location for a circuit switched (CS) service. . The function of the MSC is used for the exchange of CS tasks, and the VLR function keeps a more accurate copy of the location of the UE within the support system as well as the service profile of the visiting user.

The Serving GPRS Support Node (SGSN) 112 is similar to that of the MSC / VLR 100 but is generally used for Packet Switching (PS) services. The portion of the network that is connected via SGSN 112 is often considered a PS domain.

The HLR 112 is a database located in a user home system that stores a master copy of a user service profile. For example, a service profile consists of supplementary service information such as allowed service information, forbidden roaming area, number of call transfers and call transfer status. It is created when a new user joins the system and remains stored while subscribed. For the purpose of sending a task (call or short message) to the UE, the HLR stores the UE location at the MSC / VLR and SGSN levels, which are supported system levels.

The Gateway MSC (GMSC) 124 is a switch at the point where the UMTS PLMN is connected to the external CS network 130. All incoming and outgoing CS connections go through the GMSC 124. The Gateway GPRS Support Node (GGSN) 125 is close to the functionality of the GMSC 124 but is associated with a Packet Switched (PS) service. The GGSN 125 is a GPRS gateway node that directly connects to a packet data network or the Internet. The GGSN 125 performs GTP tunneling and IP (Internet Protocol) routing functions by maintaining routing information to the SGSN 122.

The soft handover processing operation in the mobile communication system having the above configuration is as follows. 3 is a diagram for explaining soft handover.

Assuming that a user terminal UE, which has been serviced through a serving base station Node_B_1, moves to a service area of an adjacent target base station Node_B_2, the service area of the serving base station Node_B_1 and the target. Soft handover occurs under the control of the radio network controller (RNC) in the handover area (or OverLand) area where the service area of the base station Node_B_2 overlaps. At this time, the user terminal UE receives the signal from the target base station Node_B_2 at a preset value T_add as it moves to the handover area and notifies the radio network controller RNC. The radio network controller (RNC) checks whether the target base station Node_B_2 is in a usable state in response thereto, and if available, the serving base station Node_B_1 and the target base station Node_B-2 as shown in FIG. 3. ) Provides a service to the user terminal (UE).

At this time, power balancing according to the present invention is performed. The radio network controller (RNC) demodulates signals of the user terminal (UE) received from each of the serving base station Node_B_1 and the target base station Node_B_2, selects a base station having a good channel condition, and selects a counter value of the selected base station. To increase. After performing this operation for a predetermined time, the transmission power of the base station having a large counter value is determined as a reference power, and the serving base station Node_B_1 and the target base station Node_B_2 are notified.

During this process, when the user terminal UE continues to move to the target base station 111-2, when the output strength of the serving base station Node_B_1 falls below a preset value T_drop, the serving base station Node_B_1. ) And receive service from the target base station Node_B_2. The base station is not dropped as soon as the reception strength of the base station falls below the T_drop, but is dropped when the T_drop value is lower even during the guard time with a guard time T_Tdrop of a predetermined time.

FIG. 4 illustrates a procedure for determining a reference power used for power balancing of soft handover in a radio network controller (RNC) according to an embodiment of the present invention.

Referring to FIG. 4, first, in step 401, the RNC determines whether the user terminal is in a handover region based on signal strengths of base stations received from the user terminal (UE). If the user terminal does not exist in the handover area, the RNC proceeds to step 437 to perform the corresponding mode. If the user terminal exists in the handover area, the RNC proceeds to step 403 to provide a service to the user terminal through two base stations Node_B_1 and Node_B_2 involved in handover.

In step 405, the RNC drives a timer having a predetermined time period. In step 407, the RNC sets the counter value count1 of the serving base station Node_B_1 and the counter value count2 of the target base station Node_B_2 to '0'. Initialize The RNC demodulates the signal of the user terminal received from the serving base station in step 411 and simultaneously demodulates the signal of the user terminal received from the target base station in step 413. In step 413, the RNC determines the channel condition using the signals of the demodulated user terminal. In step 415, the RNC determines whether the channel condition of the serving base station is better than that of the target base station. In this case, the channel condition may be determined by a bit error rate (BER).

If the channel condition of the serving base station is better, the RNC proceeds to step 417 and increases the counter value count1 of the serving base station by '1' and then proceeds to step 419. If the channel condition of the target base station is better, the RNC proceeds to step 431 and increases the counter value count2 of the target base station by '1' and then proceeds to step 419.

Thereafter, the RNC checks whether the timer expires in step 419. If the timer has not expired, the RNC returns to step 409 to perform the following step again. If the timer has expired, the RNC determines whether the counter value of the serving base station is greater than or equal to the counter value of the target base station in step 421.

If the counter value of the serving base station is greater than or equal to the counter value of the target base station, the RNC proceeds to step 423 to read the transmission power (Node_B_1 Tx Power) of the serving base station previously received and stored from the serving base station from the memory. do. In step 425, the RNC determines the transmission power of the read serving base station as the reference power P_ref (P_ref = Node_B_1 Tx Power). Thereafter, the RNC informs the serving base station and the target base station of the reference power set as the transmission power of the serving base station in step 427 and proceeds to step 429.

If the counter value of the target base station is greater than the counter value of the serving base station, the RNC proceeds to step 433 and reads from the memory the transmission power (Node_B_2 Tx Power) of the target base station previously received and stored from the target base station. . In operation 435, the RNC determines the transmission power of the read target base station as the reference power P_ref (P_ref = Node_B_2 Tx Power). Thereafter, the RNC proceeds to step 427 and notifies the serving base station and the target base station of the reference power set as the transmission power of the target base station, and then proceeds to step 429.

Meanwhile, the RNC determines whether the user terminal has escaped the handover area based on the signal strength of the base stations received from the user terminal in step 429. If the RNC exits the handover area, the RNC terminates the present algorithm. If the handover area still exists, the RNC returns to step 405 to perform the following steps again.

The above-described embodiment describes a case in which two base stations participate in handover. As another example, a plurality of base stations may be included in an active set. In this case, the transmission power of the base station having the best channel condition among the base stations belonging to the active set may be set as the reference power (P-ref).

As described above, the present invention first transmits the power transmitted by the base stations Node_B to the user terminal and the received signal received from the user terminal to the RNC. The RNC then demodulates the signal of the user terminal received from the base stations to select a better link (or channel). At this time, the counter value of the selected base station is increased. On the other hand, by comparing the counter values in a predetermined period, the transmission power (Tx Power) of the base station having a large counter value is substituted as the reference power (P_ref). The RNC transmits the reference power to each base station.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible 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 defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the present invention makes the reference power similar to the level of the transmission signal that satisfies the quality of service, so that when power balancing, the reference power P_ref and the transmission power P of the base station P The value of (i)) can be minimized. In this case, it is possible to save wasted transmission power while matching transmission powers between base stations similarly, thereby increasing system capacity.

Claims (6)

A method for determining a reference power used for power balancing of soft handover at a control station of a mobile communication system, Selecting a base station having the best channel condition by demodulating a signal of a user terminal received from base stations belonging to an active set; Increasing a counter value of the selected base station; Comparing the counter values of the base stations at a predetermined time period and selecting a base station having the largest value; Reading transmission power of the selected base station previously received and stored from a memory; Determining the transmission power as the reference power; And transmitting the determined reference power to base stations belonging to the active set. The method of claim 1, And the control station is a radio network controller (RNC) configured in an asynchronous mobile communication system. delete A method for determining a reference power used for power balancing of soft handover at a control station of a mobile communication system, Transmitting, by the base stations belonging to the active set, the signal of the received user terminal and the transmission power of the signal transmitted to the user terminal to the control station; Selecting, by the control station, a base station having the best channel condition by demodulating a signal of the user terminal received from base stations belonging to the active set; Increasing a counter value of the selected base station; Comparing the counter values of the base stations at a predetermined time period and selecting a base station having the largest value; Reading the transmission power received from the selected base station from a memory; Determining the transmission power as the reference power; And transmitting the determined reference power to base stations belonging to the active set. The method of claim 4, wherein And the control station is a radio network controller (RNC) configured in an asynchronous mobile communication system. delete

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