KR20030068768A - Method for Down Link Power Control in SSDT mode - Google Patents

Abstract

PURPOSE: A forward power control method in an SSDT(Site Selection Diversity Transmission) is provided to perform an effective forward power control by adding weight values to powers of signals received from several cells and generating a command for controlling a forward power, in a UE(User Equipment), in case that the UE is operated as an SSDT mode in a soft hand-over area. CONSTITUTION: Each of SIR(Signal to Interference Ratio) measuring units(10a-10n) measures an SIR of a DPCCH(Dedicated Physical Control CHannel) of a receiving signal according to a node B. Each of comparing units(11a-11n) calculates the difference of the measured node B-classified SIR value and a designated SIR target value. Each of multiplying units(12a-12n) multiplies the difference by a weight value. An accumulating unit(13) adds the multiplied values. A comparing unit(14) compares the result of the accumulating unit(13) with zero, transmits a message, for decreasing a forward power, to the node B when a sign is positive, and transmits a message, for increasing the forward power, to the node B when the sign is negative.

Description

Forward power control method in SSTD {Method for Down Link Power Control in SSDT mode}

According to the present invention, when the UE operates in the SSDT mode in the soft handover region, the UE generates a command for forward power control by weighting signal power received from several cells, thereby effectively performing forward power. The present invention relates to a forward power control method in an SSDT mode in which control can be made.

UMTS (Universal Mobile Terrestrial System) is a third-generation mobile communication system that evolved from the Global System for Mobile Communications (GSM) system, the second-generation European mobile communication standard.The GSM Core Network and Wideband Code Division Multiple Access (WCDMA) It aims to provide better mobile communication service based on access technology.

The first generation mobile communication refers to the analog method, the second generation mobile communication means the evolution to the digital method, and the third generation method is commonly called IMT-2000, and it means a breakthrough in communication capability.

For the international standardization of UMTS, in December 1998, national or national standards-setting bodies such as ETSI in Europe, ARIB / TTC in Japan, T1 in the United States, and TTA in Korea were established by the Third Generation Mobile Standardization Group (Third Generation). The Partnership Project (hereinafter abbreviated as 3GPP) is formed, and through this 3GPP, detailed specification of UMTS, a European IMT-2000 system, is defined.

In 3GPP, UMTS standardization work is divided into 5 Technical Specification Groups (hereinafter abbreviated as TSG) in consideration of the independence of network components and their operation for rapid and efficient technology development of UMTS. I'm going. Each TSG is responsible for the development, approval, and management of standards within the relevant areas, among which the Radio Access Network (hereinafter referred to as RAN) group (TSG-RAN) is a WCDMA access technology (asynchronous) in UMTS. Develop specifications for the functions, requirements, and interfaces of the UMTS Terrestrial Radio Access Network (hereinafter referred to as UTRAN), a new radio access network to support CDMA).

The TSG-RAN Group is again composed of a Plenary Group and four Working Groups. Working Group 1 (WG1) develops standards for the Physical Layer (WG1), while the second Working Group (WG2) works with the Data Link Layer (2nd Layer) and Network Layer (WG2). Role of the third tier). In addition, the third operation group defines standards for interfaces between base stations, radio network controllers (hereinafter referred to as RNCs) and core networks in the UTRAN, and the fourth operation group relates to radio link performance. Discuss requirements and requirements for radio resource management.

1 is a diagram showing the structure of the UTRAN of the 3GPP system to which the conventional and the present invention is applied.

Referring to FIG. 1, the UTRAN 110 is composed of one or more Radio Network Sub-systems (hereinafter, referred to as RNS) 120 and 130, and each RNS 120 and 130 includes one RNC 121 and 131. It consists of one or more base stations (Node B) 122, 123, 132, 133 managed by the RNC 121, 131. The RNCs 121 and 131 are connected to a mobile switching center (MSC) 141 for circuit-switched communication with a GSM network, and SGSN (for packet-switched communication with a general packet radio service (GPRS) network). Serving GPRS Support Node) 142.

The base station (Node B) 122, 123, 132, 133 is managed by the RNC (121, 131), and receives the information sent from the physical layer of the terminal 150 in the uplink, and the terminal 150 in the downlink It serves as an access point of the UTRAN to the terminal transmitting to. The RNCs 121 and 131 are in charge of allocating and managing radio resources. The RNC, which is responsible for the direct management of the base station Node B, is called a control RNC (CRNC), and is in charge of managing a common radio resource. A place that manages dedicated radio resources allocated to each terminal is called a serving RNC (SRNC). The control RNC and the responsible RNC may be the same, but when the terminal moves out of the area of the responsible RNC to the area of another RNC, the control RNC and the responsible RNC may be different. The various components in the UMTS network can be in different locations, so an interface is needed to connect them. The base station Node B and the RNC are connected by an Iub interface, and the RNC is connected through an Iur interface. The interface between the RNC and the core network is called Iu.

On the other hand, in a mobile communication system having geographically fixed base stations and mobile terminals, as the terminal moves, it is necessary to transfer (hand over) communication with the terminal from a source base station to a target base station. There is. In a cellular communication situation, as the mobile station leaves the original cell and moves to the target cell, communication with the mobile station must be carried forward from the base cell's base station to the target cell's base station. These conventional handovers come in three forms, depending on the multiple access system employed in a communication system called hard handover, soft handover, and softer handover.

Hard handover is characterized by instantaneous disconnection of the forward and reverse channels and is typical in a frequency division multiple access (FDMA) or time division multiple access (TDMA) environment. This procedure is sometimes called interruption before connection. Since hard handover is completed by a temporary disconnection of the call channel, the information in the received signal may be lost.

Soft handovers (such as those used in CDMA environments) alleviate this temporary disconnect problem. In soft handover, two or more received signals through different cells are simultaneously demodulated, combined and decoded by the same receiver device. In a CDMA environment, soft handover does not require any disconnection of the talk channel because the receiver can simultaneously demodulate, combine and decode signals from two or more base stations. As long as you move into the service area of another base station, you do not need to change its reception or origination frequency. Soft handover may be characterized by initiating communication using a new code string at the same CDMA frequency before terminating the communication by the old code string.

The prior art will be described below.

SSDT is one of the multiplexing techniques in soft handover mode and is optional in 3GPP network UTRAN. SSDT is used to solve the following problems in soft handover.

1) In the forward direction, since several base stations (Node B) transmit power for the same data at the same time, the capacity of the forward link is reduced by acting as interference for different links.

2) By allocating a limited finger at a terminal to a link received from several base stations to receive power of several other links, it is impossible to receive all of the multipath for a given link. Multiple paths that are not received at the finger all act as interference and degrade the reception quality.

3) An error may occur when the base station receives the forward link power control message transmitted by the terminal to the base stations. Thus, due to the error of the forward power control message, the base stations do not transmit the same power to one terminal, but are transmitted at different powers and are transmitted at unnecessary power or at a power level below the required level. Adversely affects.

In order to reduce the decrease in the forward link capacity and the increase in the interference caused by the above problems, the SSDT transmits the DPDCH only at the base station having the best forward link quality and transmits the DPDCH power at 0 in the remaining base stations.

Brief description of the operation description of the prior art is as follows.

First, the basic operation of SSDT is as follows.

A) The UE measures the received signal code power (RSCP) of the Common Pilot Channel (CPICH) received from the base station in the active set.

B) UE determines a base station having the largest RSCP measured in A) as a primary cell.

C) The terminal transmits a primary cell identifier indicating the primary cell to the base station through the S field of the FBI field of the reverse DPCCH. 2 is a table illustrating an example of setting identifier codes for a 1-bit FBI field, and FIG. 3 is a table illustrating an example of setting identifier codes for a 2-bit FBI field.

D) The base stations receiving the primary cell identifier transmitted by the terminal determines whether the primary cell or the non-primary cell is compared with the cell identifier assigned from the network. The UE determines the non-primary cell only when the quality of the received primary cell identifier is greater than a given threshold Qth to ensure reliability, and the received primary cell identifier does not match its cell identifier. The reason for this is that an error occurs in the primary cell identifier so that all base stations do not transmit on the DPDCH.

E) The primary cell is updated with a period between 3 and 15 slots. This period is determined by the network. For reference, Figure 4 is a table showing the primary cell update cycle.

In the SSDT mode, a base station that needs to operate as a non-primary cell operates as a primary cell so that two or more base stations operate as primary cells. At this time, the non-primary cell should operate as a primary cell, but the base station operating as a primary cell is defined as a false primary cell.

If there is more than one false primary cell in such SSDT, it is necessary to define a method for generating a forward power control command for the forward power control in the terminal. Possible forward power control methods are as follows.

(A) Method for generating a power control command by combining all the DPDCH received at the terminal.

(b) Method for generating a power control command using only the DPDCH or DPCCH received from the base station designated by the terminal as the primary cell.

(c) A method of generating a power control command by combining all the DPCCHs received from the terminal as in the conventional forward power control method.

In the case of the method (a), since the power control is performed by combining data from the primary cell and the false primary cell designated by the terminal, the primary cell in addition to the reception power of the primary cell determined to have the highest reception quality is performed. Power is reflected. Therefore, when a command for power control is generated, the instantaneous channel condition change of the false primary cell affects the overall power control, so that the influence of the primary cell is reduced, resulting in the same operation as that of normal soft handover rather than SSDT. do.

In the case of the method (b), power control is performed only by a signal received from a primary cell designated by the terminal to meet the original purpose of the SSDT, but the network does not consider the power transmitted by the false primary cell, so that the network does not consider each base station. Even if the star power is adjusted, the operation of the terminal is not reflected at all.

Also, in the case of the method (c), since the power of the DPCCH is transmitted even in the non-primary cell which does not transmit the power of the DPDCH at all, if the power control is performed based on this, the power is controlled even for the link that is not actually received. Can't.

As shown in FIG. 5, when data transmitted by the primary cell and the false primary cell are received by the UE, the quality of the link is displayed as HIGH and LOW depending on whether the reference SIR is satisfied or not. do. In case of normal SSDT operation, the false primary cell does not exist, and thus, the UE sends a power control command to the forward link according to the quality of the primary cell. However, in the case of Figure 5, two or more links are combined to send the final power control command. At this time, when the primary cell falls short of the SIR target value and the false primary cell satisfies the SIR target value as shown in? Of FIG. Thus, the terminal transmits a power control command to reduce the base station power. If the primary cell update message is transmitted immediately in the transmission slot that transmitted the power control command, and the false primary cell is recognized as the non-primary cell, the transmission of the DPDCH is stopped to reduce the power of the poor primary cell. Transmitted to a status increase system error. Even in the case of ② of FIG. 5 at the primary cell update boundary as shown in ④ of FIG. 5, a result of wasting more power than necessary may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problem, and by weighting the SIR of data received from primary cells and false primary cells, from the primary cell determined to have the best link performance in the terminal. An object of the present invention is to provide a forward power control method in an SSDT capable of performing some power control on the received power and the received power from a false primary cell.

1 is a structure of a 3GPP UTRAN.

2 is a table showing identifier code settings for 1 bit FBI.

3 is a table showing identifier code settings for a 2-bit FBI.

4 shows a primary cell update period.

5 is a diagram illustrating a link quality state according to whether a reference SIR is satisfied when a terminal receives data transmitted from a conventional primary cell and a horse primary cell;

6 is a configuration diagram illustrating a forward power control method in the SSDT according to the first embodiment of the present invention.

7 is a configuration diagram illustrating a forward power control method in the SSDT according to the second embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10a to 10n, 20a to 20n ... SIR measurement section 11a to 11n ... SIR comparison section

12a to 12n, 21a to 21n ... Multiplication part 13, 22 ... Accumulation part

14,23 ... Comparative

In order to achieve the above object, the forward power control method in the SSDT mode according to the present invention,

In the forward power control method when the terminal operates in SSDT (Site Selection Diversity Transmission) mode in the soft handover area,

Receiving signals from the primary and false primary cells;

Measuring each base station of the SIR of the received signal;

And multiplying the measured SIR by a predetermined weight and controlling the power of the forward link according to a result of the sum.

Preferably, after the step of measuring the SIR, the step of obtaining a difference between the determined SIR target value for each base station divided by the SIR target value for the forward power control by the number of base stations; Multiplying the difference between the SIR and a predetermined base station SIR target value by the weight, and accumulating each sum; And if the accumulation result sign is positive, transmitting a message for decreasing forward power to the base station, and if the sign is negative, transmitting a message for increasing forward power to the base station.

Preferably, after the SIR measuring step, multiplying each of the measured SIR by a weight; Summing all of the SIRs multiplied by the weights, and obtaining a difference from a value obtained by dividing the SIR sum value by a predetermined base station SIR target value divided by the number of base stations; And if the sign of the difference value is positive, transmitting a message for decreasing forward power to the base station, and if the sign is negative, transmitting a message for forward increasing to the base station.

Specifically, the weight is calculated by the ratio of the SIR of the CPICH received from the primary cell and the false primary cells.

In detail, the weight is calculated by the SIR ratio of the primary CPICH received from the primary cell and the false primary cells.

Specifically, the weight is calculated by the SIR ratio of the secondary CPICH received from the primary cell and the false primary cells.

In detail, the weight is calculated by the DPCCH received from the primary cell and each false primary cell.

In detail, the weight is calculated by the DPDCH received from the primary cell and each false primary cell.

In detail, the SIR target value for each base station may be obtained by dividing the SIR target value for forward power control by the number of base stations including a primary cell and a false primary cell.

The forward power control method in the SSDT mode according to the embodiment of the present invention configured as described above is as follows.

First embodiment;

FIG. 5 is a configuration diagram illustrating a forward power control method in the SSDT mode according to the first embodiment of the present invention.

Referring to FIG. 5, when the terminal operates in the SSDT mode in the soft handover region, the base station, which should operate as the non-primary cell designated by the terminal, does not normally receive the primary cell identifier and operates as the primary cell. In the mode, the terminal receives signals from n base stations (one primary cell and n-1 false-primary cells).

In this case, as shown in FIG. 5, the UE measures the Signal to Interference Ratio (SIR) of the DPCCH of the received signal by each base station in each SIR measuring unit (10a to 10n) and compares the measured SIR values for each base station. The difference between the SIR target values (SIR _target / n) determined by the Compare with target SIR 11a to 11n is obtained. At this time, the determined SIR target value for each base station is a value obtained by dividing the SIR _target value (SIR _target ) for forward power control by n. The weights (w _k : w ₁ , w ₂ , ..., w _n ) are multiplied by the difference between the SIR _k and the (SIR _target / n) of the received signal (SIR _k -SIR _target / n). And multiply each by and accumulate in the accumulating unit 13.

At this time, the weight can be calculated in three ways. The first method is implemented by the ratio of the SIR of the common pilot channel (CPICH) received from each base station. This is the same as Equation 1.

Equation 1 is obtained by dividing SIR values (SIR _{i, CPICH} ) of CPICH of a corresponding base station by the sum of all SIRs of CPICH received for each base station for forward link power control. Here, the CPICH includes a primary CPICH (P-CPICH) or a secondary CPICH (S-CPICH).

The second method implements the weight w _k with a Dedicated Physical Control Channel (DPCCH) received from the primary cell and each false primary cell. This is the same as Equation 2.

That is, Equation 2 is obtained by dividing the SIR values SIR _{i and DPCCH} of the DPCCH of the base station by the sum of the SIR values received for each base station for forward power control.

The third method implements a weight w _k with a dedicated physical data channel (DPDCH) received from a primary cell and each fake primary cell. This is the same as Equation 3.

That is, Equation 3 is obtained by dividing the SIR values SIR _{i and DPDCH of the DPDCH} of the base station by the sum of all the SIR values of the DPDCH received for each base station for forward power control.

At this time, the result of the accumulator 13 is compared in a compare with zero 14, and if the sign is positive, a message (DL Power DOWN) for reducing forward power control is transmitted to the base station. Negative (-) transmits a message (DL Power UP) to increase the forward power to the base station.

Second embodiment;

6 is a block diagram illustrating a forward power control method in the SSDT mode according to a second embodiment of the present invention.

6, the user terminal respective weighting the DPCCH SIR of the received signal to the base station by SIR value measured by the base station is measured in each SIR measurement unit (20a ~ 20n) in a multiplier (21a ~ 21n) (w _k After multiplying: w ₁ , w ₂ , ..., w _n , the accumulators (22) are added together, where the sum of the accumulators (22) Obtain as

The comparison unit 23 measures the sum of the sum of the accumulation units 22 for each base station, compares the SIR target value with a predetermined SIR target value, and if the result is a positive sign, transmits a message for decreasing forward power to the base station. If negative, a message is sent to the base station increasing the forward power. That is, the comparison unit 23 Obtained by

In other words, the second embodiment multiplies and sums SIRs of signals received from n base stations, and compares them with a predetermined SIR target value. In this case, the weight w _k may be generated in CPICH, DPCCH, or DPDCH as shown in Equations 1, 2 and 3 shown in the description of FIG. 5.

As such, when the terminal operates in the SSDT mode in the soft handover region, the SIR of the received signal is measured for each base station, and the forward power control message is transmitted to the base station by giving a weight obtained by a predetermined method to the measured SIR.

As described above, according to the forward power control method in the SSDT mode according to the present invention, the terminal gives a weight to the SIR of the data received from the base station in the soft handover region so that the performance of the link in the terminal is determined to be the best. The reception power from the head cell and the reception power from the false primary cell are also reflected in the power control to some extent, thereby effectively performing power control.

Claims (12)

In the forward power control method when the terminal operates in SSDT (Site Selection Diversity Transmission) mode in the soft handover area, Receiving signals from the primary and false primary cells; Measuring each base station of the SIR of the received signal; And multiplying the measured SIR by a predetermined weight, and controlling power of a forward link according to a result of the sum of the measured SIRs. The method of claim 1, After the SIR measuring step, obtaining a difference between a predetermined base station SIR target value, which is a value obtained by dividing the measured SIR by a base station number for an SIR target value for forward power control; Multiplying the difference between the SIR and a predetermined base station SIR target value by the weight, and accumulating each sum; And if the accumulation result sign is positive, transmitting a message for decreasing forward power to a base station, and if the sign is negative, transmitting a message for increasing forward power to a base station. . The method of claim 1, After the SIR measuring step, multiplying each of the measured SIRs by weights; Summing all of the SIRs multiplied by the weights, and obtaining a difference from a value obtained by dividing the SIR sum value by a predetermined base station SIR target value divided by the number of base stations; Forward power control in the SSDT mode, if the sign of the value of the difference is positive, transmitting a message for decreasing forward power to the base station; Way. The method of claim 1, And the weight is calculated as the ratio of the SIR of the CPICH received from the primary cell and the false primary cells. The method of claim 4, wherein And the weight is obtained by dividing the SIR values of CPICHs of primary cells and false primary cells by the sum of the SIRs of CPICHs of respective cells. The method of claim 1, The weight is calculated by the SIR ratio of the primary CPICH (P-CPICH) received from the primary cell and the false primary cells. The method of claim 6, The weight is calculated by the SIR ratio of the secondary CPICH (S-CPICH) received from the primary cell and the false primary cells. The method of claim 1, The weighting method is the forward power control method in SSDT mode, characterized in that calculated by the primary cell and the DPCCH received from each of the false primary cell. The method of claim 8, The weight is calculated by dividing the SIR of the DPCCH of the primary cell and the false primary cells by the SIR of the DPCCH of each cell. The method of claim 1, The weighting method is the forward power control method in the SSDT mode, characterized in that calculated by the DPDCH received from the primary cell and each false primary cell. The method of claim 10, The weight is calculated by dividing the received SIR of the DPDCH of the corresponding primary cell and the false primary cell by the sum of the SIRs of the DPDCH of each cell. The method of claim 1, The SIR target value for each base station is calculated by dividing the SIR target value for forward power control by the number of base stations including a primary cell and a false primary cell.