KR101910475B1 - Mobile terminal and method for controlling power to process random access thereof - Google Patents

Abstract

The present invention relates to a method of controlling power for random access in a terminal and a terminal in a mobile communication system using a distributed antenna system (DAS), and more particularly, The method includes receiving system information including power information, calculating transmission power using the received transmission power information, and transmitting the random access preamble using the calculated transmission power. Accordingly, when the UE performs random access, the transmission power of the random access preamble is minimized, thereby reducing power consumption of the UE and minimizing intra-cell interference.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a power control method for performing random access in a terminal and a terminal,

The present invention relates to a power control method for performing random access in a terminal and a terminal, and more particularly, to a power control method and apparatus in a case where a terminal performs random access in a mobile communication system (Distributed Antenna System) .

The mobile communication system has evolved into a high-speed and high-quality wireless packet data communication system for providing data service and multimedia service apart from providing initial voice-oriented service. Recently, 3GPP's High Speed Downlink Packet Access (HSDPA), HSUPA (Long Term Evolution), Long Term Evolution Advanced (LTE), High Rate Packet Data (3GPP2) And 802.16, have been developed to support high-speed, high-quality wireless packet data transmission services. In particular, LTE system is developed to efficiently support high - speed wireless packet data transmission and maximizes wireless system capacity by utilizing various wireless connection technologies. The LTE-A system is an advanced wireless system in LTE systems and has improved data transmission capabilities compared to LTE.

Existing third generation wireless packet data communication systems such as HSDPA, HSUPA, and HRPD use technologies such as Adaptive Modulation and Coding (AMC) and Channel Adaptive Scheduling to improve transmission efficiency. With the AMC method, the transmitter can adjust the amount of data to be transmitted according to the channel state. That is, if the channel condition is not good, the transmitter can reduce the amount of data to be transmitted, thereby adjusting the reception error probability to a desired level. Also, if the channel condition is good, the transmitter can increase the amount of data to be transmitted, so that the probability of receiving error can be effectively transmitted while adjusting to a desired level.

Using the channel-responsive scheduling resource management method, the transmitter selectively services a user having a good channel state among a plurality of users, so that the system capacity increases as compared with a case where a channel is allocated and serviced to a single user. This increase in capacity is called a so-called multi-user diversity gain. In other words, the AMC method and the channel responsive scheduling method can be a method of applying a proper modulation and coding scheme to a time point determined to be most efficient by receiving feedback of partial channel state information from a receiver.

The AMC method may also include a function of determining the number or rank of spatial layers of a transmitted signal when used with a Multiple Input Multiple Output (MIMO) transmission scheme. In this case, the AMC method considers only how many layers are to be transmitted using MIMO without considering coding rate and modulation scheme simply in determining the optimum data rate.

In general, LTE and LTE-A systems use Orthogonal Frequency Division Multiple Access (OFDMA) as a multiple access method. The OFDMA scheme divides data or control information of each user by allocating and operating the data or control information so that the time-frequency resources to be transmitted are not overlapped with each other, that is, orthogonality is established. It is known that the OFDMA scheme can be expected to increase the capacity as compared with the CDMA (Code Division Multiple Access) scheme used in the existing second and third generation mobile communication systems. One of the various causes of capacity increase in the OFDMA scheme is that frequency domain scheduling can be performed on the frequency axis. As the channel gains the capacity gain by the channel adaptive scheduling method according to the time varying characteristics, the channel gain the capacity gain by using different characteristics according to the frequency. In the prior art, a mobile communication system composed of a plurality of cells provides a mobile communication service using various methods described above.

1 is a diagram illustrating a structure of a conventional mobile communication system in which a centralized antenna is disposed. In other words, in a mobile communication system composed of three cells, transmission / reception antennas are arranged at the center of each cell.

Referring to FIG. 1, a first cell 100 of a first cell 100, a second cell 110, and a third cell 120 includes a central antenna 130 and a first user equipment (UE) Equipment or an MS (Mobile Station) 140 and a second terminal 150 exist. The central antenna 130 provides mobile communication services to the two terminals 140 and 150 located in the first cell 100. The first terminal 140 receiving the mobile communication service using the center antenna 130 is relatively far from the center antenna 130 as compared with the second terminal 150. [ Therefore, the data transmission rate that can be supported by the first terminal 150 is relatively lower than that of the second terminal 150.

The mobile communication system shown in FIG. 1 has a CAS (Central Antenna System) in which a cell-by-cell antenna is disposed at the center of a corresponding cell. In case of CAS, even though a plurality of antennas are arranged for each cell, these antennas are arranged in the center of the cell and are operated to perform communication for the service area of the cell.

In the mobile communication system as shown in FIG. 1, when antennas for respective cells are arranged and operated in the form of CAS, a reference signal (RS) or a pilot signal is transmitted to measure a downlink channel state for each cell. For this purpose, in the case of 3GPP LTE-A (Long Term Evolution Advanced) system, a UE measures a channel state between a Node B and a UE using CSI-RS (Channel Status Information Reference Signal) transmitted from the Node B.

2 is a diagram illustrating a location of a CSI-RS transmitted from a base station to a mobile station in the LTE-A system according to the related art.

In Fig. 2, the abscissa represents the time domain and the ordinate axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDMA symbol, and N _symb ^DL OFDM symbols form one slot 222 and 223. Then, two slots form one sub-frame 224. The minimum transmission unit in the frequency domain is a subcarrier, and the total system transmission band consists of a total of N _BW subcarriers. N _BW has a value proportional to the system transmission band. In a time-frequency domain, a basic unit of resources can be defined as an OFDM symbol index and a subcarrier index as resource elements (REs). A resource block (RB, 220, 221) is defined as N _symb ^DL consecutive OFDM symbols in the time domain and N _sc ^RB consecutive subcarriers in the frequency domain. Therefore, one RB is composed of N _symb ^DL x N _sc ^RB of RE. In general, the minimum transmission unit of data or control information is RB unit.

The downlink control channel is transmitted within the first 3 OFDM symbols of the subframe. The physical downlink shared channel (PDSCH), which is a downlink physical data channel, is transmitted during the remaining subframe periods in which the downlink control channel is not transmitted. DM-RS (Demodulation Reference Signal) is a reference signal that the UE refers to for demodulating the PDSCH.

It is designed to transmit signals for two CSI-RS antenna ports at positions 200 to 219 in FIG. That is, the BS transmits a signal for two CSI-RS antenna ports for downlink measurement to the MS at one location, such as reference numeral 200. The antenna port is a logical concept, and the CSI-RS is defined for each antenna port and is operated to measure the channel status for each antenna port. If the same CSI-RS is transmitted from multiple physical antennas, the terminal can not distinguish between the physical antennas and recognizes it as a single antenna port.

As shown in FIG. 2, in a mobile communication system having a plurality of cells, a CSI-RS can be transmitted by allocating a separate location for each cell. For example, in the case of the cell 100 shown in FIG. 1, a CSI-RS may be transmitted at a location 200, and in the case of a cell 110, a CSI-RS may be transmitted at a location 205. And in the case of cell 120 the CSI-RS may be transmitted at location 210. The allocation of the time and frequency resources for the CSI-RS transmission at different locations in each cell is to prevent CSI-RSs of different cells from mutually interfering with each other. However, as shown in FIG. 1, in the case of the CAS, since the transmission and reception antennas of each base station are concentrated in the center of the cell, there is a limitation in supporting a high data rate to a terminal that is off the center of the cell.

3 is a diagram showing an example of a system configuration in which a CAS and a DAS (Distributed Antenna System) are constructed together in a mobile communication system according to the related art. More specifically, FIG. 3 illustrates that a transmission / reception antenna is disposed at a center of each cell in a mobile communication system composed of three cells, and distributed antennas are disposed at different positions in a cell.

Referring to FIG. 3, a central antenna 330 and a first user equipment (UE) 320 are located in a first cell 300 of the first cell 300, the second cell 310, and the third cell 320, (MS) 330, a second terminal 350, a first dispersion antenna 360, a second dispersion antenna 370, a third dispersion antenna 380, and a fourth dispersion antenna 390, Lt; / RTI > The center antenna 330 and the plurality of dispersion antennas 360, 370, 380, and 390 are all connected together and under the control of the central controller.

The central antenna 330 provides mobile communication services to all terminals located in the first cell 300. However, the first terminal 340 receiving the mobile communication service using the center antenna 330 has a relatively long distance to the center antenna 330 as compared with the second terminal 350. Accordingly, the data transmission rate that can be supported by the first terminal 340 through the central antenna 330 is relatively low.

Generally, the longer the transmission path of the signal to be transmitted is, the lower the reception quality of the signal is. Therefore, it is possible to improve data transmission speed by arranging a plurality of base station dispersion antennas in a cell and selecting an optimal base station dispersion antenna according to the position of the mobile station to provide a mobile communication service. For example, the first terminal 340 performs communication with the fourth distributed antenna 390 having the best channel environment, and the second terminal 350 performs communication with the first distributed antenna 360 having the best channel environment Thereby providing a relatively high-speed data service.

In this case, the central antenna 330 plays a role of supporting general mobile communication services other than high-speed data service and inter-cell mobility of the terminal. Also, the central antenna 330 and each of the dispersion antennas 360, 370, 380 and 390 may be composed of a plurality of antennas.

4 is a diagram showing a system configuration in which a central antenna according to the related art is distributedly arranged in various areas within a cell.

4, a first central antenna 430, a second central antenna 431, and a second center antenna 430 are provided in a first cell 400 of the first cell 400, the second cell 410, and the third cell 420, A third central antenna 432, a fourth central antenna 433, a fifth central antenna 434, a first terminal 440, a second terminal 450, a first dispersion antenna 460, A fourth dispersion antenna 470, a third dispersion antenna 480, and a fourth dispersion antenna 490 exist. The central antennas 430, 431, 432, 433, and 434 shown in FIG. 4 support general mobile communication services other than the high-speed data service and inter-cell mobility of the UE, and the distributed antennas provide high- .

A central antenna port (D-port) and a distributed antenna port (D-port) are defined as follows. The central antenna and the distributed antenna shown in FIG. 3 or 4 can be logically divided .

The C-port defines the CSI-RS (Channel Status Information Reference Signal) to support CAS for each antenna port, and the terminal can measure the channel status for each antenna port of the C-port. The CSI-RS transmitted through the C-port covers the entire area of the cell in the same cell. The D-port defines the CSI-RS to support DAS for each antenna port, and the terminal can measure the channel status for each antenna port of the D-port. The CSI-RS transmitted over the D-port covers some area within the cell. If the same CSI-RS is transmitted from multiple physical antennas, each physical antenna can not be identified by the terminal regardless of its geographically located location and is recognized as a single antenna port.

For example, when the third distributed antenna 380 and the fourth distributed antenna 390, which are geographically separated in the system structure as shown in FIG. 3, transmit CSI-RS # 1 and CSI-RS # 2 of different patterns , The UE can measure channel conditions between the CSI-RS # 1 and the CSI-RS # 2 between the respective distributed antennas and the UEs. In this case, the third distributed antenna 380 is referred to as D-port # 1, and the fourth distributed antenna 390 is referred to as D-port # 2.

If the third distributed antenna 380 and the fourth dispersed antenna 390 transmit CSI-RS # 3 having the same pattern, the UE transmits a third distributed antenna 380 and a fourth distributed antenna 390) can not be distinguished. The UE measures a channel state between the UE and the distributed antennas from the CSI-RS # 3. In this case, the third dispersion antenna 380 and the fourth dispersion antenna 390 are combined to be called D-port # 3. At this time, the time-frequency resources for CSI-RS transmission to the C-port and the D-port do not overlap with each other and mutual interference is not caused.

When the UE first accesses the system in the LTE-A system, the UE first performs downlink time and frequency domain synchronization through a cell search and acquires a cell ID. The base station receives system information from the base station and acquires basic parameter values related to transmission and reception such as system bandwidth. The terminal then performs a random access procedure to switch the link with the base station to a connected state. Will be described in detail with reference to FIG.

5 is a diagram illustrating a random access procedure according to the prior art.

Referring to FIG. 5, as a first step 501 of a random access procedure, a UE transmits a random access preamble to a BS. Then, the BS measures the transmission delay value between the UE and the BS and adjusts uplink synchronization. In this case, the UE randomly selects which random access preamble to use in the pre-set random access preamble. The initial transmission power of the random access preamble is determined by the pathloss between the base station and the mobile station measured by the mobile station.

In the second step 502, the base station transmits a timing adjustment command to the UE from the transmission delay value measured in the first step. The base station also transmits uplink resources and power control commands to be used by the UE as scheduling information. If the UE does not receive the random access response from the base station in the second step 502, the UE proceeds to the first step 501 again.

In a third step 503, the terminal transmits uplink data (message 3) including its own terminal ID to the base station through the uplink resource allocated in the second step 502. At this time, the transmission timing and the transmission power of the terminal follow the command received from the base station in the second step 502. If it is determined in step 504 that the UE has performed random access without colliding with another UE, in step 503, the Node B transmits data including the ID of the UE that transmitted the uplink data message 4 To the corresponding terminal. When the MS receives a signal transmitted from the BS in the fourth step 504, the MS determines that the random access is successful.

If the data transmitted from the terminal in the third step 503 collides with data from other terminals and the base station fails to receive a data signal from the terminal, the base station does not transmit any more data to the terminal. If the UE fails to receive data transmitted in the fourth step 504 from the base station during a predetermined time interval, the UE determines that the random access procedure has failed and resumes from the first step 504. If the random access is successful, the UE sets the initial transmission power of the uplink data channel or the control channel to be transmitted to the base station based on the transmission power value of the UE controlled by random access.

Therefore, when the UE performs a random access procedure in a system in which a DAS or a DAS and a CAS are mixed, a method for efficiently determining a random access preamble transmission power is needed. Accordingly, an object of the present invention is to provide a method and an apparatus for effectively controlling power when a terminal performs random access when a DAS (Distributed Antenna System) is constructed based on an LTE-A system.

According to an aspect of the present invention, there is provided a power control method including: receiving system information including an antenna reference transmission power information for transmitting a random access preamble from a base station; Calculating a power, and transmitting the random access preamble with the calculated transmit power.

Also, in order to solve the above problems, the present invention provides a power control terminal comprising: a receiver for receiving system information including antenna reference transmission power information for transmitting a random access preamble from a base station; A power control controller for controlling a random access preamble transmission power; and a transmission unit for transmitting the random access preamble with the calculated transmission power.

According to the present invention, when a terminal performs random access in a distributed antenna system (DAS), it provides an effective power control method, thereby preventing unnecessary power consumption of the terminal and minimizing the amount of interference to the system.

1 illustrates a structure of a cellular mobile communication system in which a centralized antenna according to the related art is disposed.
2 is a diagram illustrating a location of a CSI-RS transmitted from a base station to a mobile station in an LTE-A system according to the prior art;
3 is a diagram showing an example of a system configuration in which a CAS (Central Antenna System) and a DAS (Distributed Antenna System) are built together in a conventional cellular mobile communication system.
4 shows a system configuration in which a central antenna according to the related art is distributed and arranged in various areas within a cell.
FIG. 5 shows a random access procedure according to the prior art; FIG.
6 is a conceptual diagram illustrating a transmission power control method according to an embodiment of the present invention;
FIG. 7 illustrates a mobile communication system for transmission power control according to a first embodiment of the present invention; FIG.
8 is a diagram illustrating a random access procedure of a terminal according to a first embodiment of the present invention.
9 is a diagram illustrating a procedure for a base station to perform random access from a terminal according to a first embodiment of the present invention;
10 is a diagram illustrating a mobile communication system for transmission power control according to a second embodiment of the present invention.
11 is a diagram illustrating a random access procedure of a terminal according to a second embodiment of the present invention.
12 is a diagram illustrating a random access procedure of a base station according to a second embodiment of the present invention.
13 is a diagram illustrating a terminal apparatus according to an embodiment of the present invention.
14 illustrates a base station apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and these may be changed according to the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

Although the LTE-A (or Advanced E-UTRA) system will be the main object in explaining the embodiments of the present invention, the main point of the present invention is to provide a communication system It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system and a method for transmitting data between a terminal and a respective antenna port in a system in which DAS or DAS (Distributed Antenna System) and CAS (Central Antenna System) The terminal can perform random access through a link having an excellent environment. To do so, the UE calculates transmission power information for transmitting a random access preamble using the antenna reference transmission power information received from the base station. Here, the antenna reference transmission power information includes a channel state reference signal for calculating a pathloss for each antenna, and a power adjustment parameter for an antenna located closest to the terminal. According to the present invention, there is provided an effective method of minimizing transmission power of a random access preamble of a UE, thereby reducing power consumption and interference of the UE

6 is a conceptual diagram illustrating a transmission power control method according to an embodiment of the present invention.

6, a first antenna 610 and a second antenna 620 are geographically dispersed in a cell, and a path loss (PL) of a wireless path and a terminal 630 for each antenna are PL1 and PL2 . Since PL1 is smaller than PL2 (PL1 <PL2), it can be said that the channel environment between the first antenna 610 and the terminal 630 is relatively better than the channel environment between the second antenna 620 and the terminal 630 have.

The first antenna 610 and the second antenna 620 define independent CSI-RSs so that the terminal can measure the channel state for each antenna. In this case, the first antenna 610 may be referred to as a logical conceptual antenna port 1, and the second antenna 620 may be referred to as a logical conceptual antenna port 2. If the same CSI-RS is transmitted from a plurality of physical antennas, the terminal 630 can not identify each physical antenna and recognizes the same as an antenna port.

Pathloss is one indicator of good and bad channel environment. The larger the value, the worse the channel environment. The pathloss is characterized by a small variation over time. The pathloss (PL) is calculated from Equation (1) from the RS (Reference Signal) received by the terminal from the base station.

In Equation (1), 'referenceSignalPower' indicates the base station transmission power of the RS informed by the BS through signaling, and 'RSRP' indicates the received signal strength of the RS measured by the terminal receiving the RS .

As the pathloss increases, the UE must transmit the signal with a relatively large transmission power in order to overcome a bad channel environment. However, if the transmission power of the terminal is large, the power consumption of the terminal becomes large as a result. Also, the amount of interference increases, which has an adverse effect on system performance. Therefore, if the transmission power of the UE can be adjusted by adaptively selecting the link having the best channel environment among the multiple links between the terminal and the plurality of antennas of the base station in the DAS mobile communication system, the power consumption of the UE can be reduced, Will also be reduced.

Hereinafter, embodiments of the present invention will be described with reference to specific examples.

&Lt; Embodiment 1 >

The first embodiment describes a method for adaptively setting a random access preamble transmission power using a pathloss measured by a terminal for each antenna. The main points of the first embodiment will now be described with reference to Fig.

7 is a diagram illustrating a mobile communication system for transmission power control according to a first embodiment of the present invention.

7, a central antenna 710, a first distributed antenna 720, and a second distributed antenna 730 form one cell to perform communication with the terminal 740 . Here, it is assumed that each of the center antenna 710, the first dispersion antenna 720, and the second dispersion antenna 730 transmits CSI-RS of different patterns. The CSI-RS of different patterns is transmitted for each antenna, so that the terminal 740 can measure the channel state for each antenna.

In FIG. 7, it is assumed that the center antenna 710 is mapped to the C-port, the first dispersion antenna 720 to the D-port # 1, and the second dispersion antenna 730 to the D-port # 2. It is assumed that the central antenna 710, the first dispersion antenna 720, and the second dispersion antenna 730 are connected to the central controller of the base station. The terminal 740 is closest geographically to the first distributed antenna 720 and is located most distantly from the second distributed antenna 730. Therefore, it is assumed that there is no difference in features between the terminal 740 and the respective antennas 710, 720 and 730, the terminal 740, the central antenna 710, the first dispersion antenna 720, 730 are PL2 < PL1 < PL3. PL1 represents a pathloss between the terminal 740 and the center antenna 710, PL2 represents a pathloss between the terminal 540 and the first distributed antenna 720, PL3 represents the pathloss between the terminal 740 and the second distributed antenna 730, Lt; / RTI &gt; The UE can measure a pathloss for each antenna through a channel state information reference signal (CSI-RS) defined for each antenna port.

In the CAS scheme of the LTE-A system, the random access preamble transmission power (PPRACH) of the UE is determined as shown in Equation (2) expressed in dBm.

- P _CMAX : Maximum transmission power allowed for the terminal, which is determined by the setting of the terminal class and upper signaling.

- PREAMBLE_RECEIVED_TARGET_POWER: The random access preamble receive power required by the base station to receive the random access preamble, which is determined by the parameters that are signaled higher.

- PL: pathloss between base station and terminal

However, unlike the CAS, since the transmission and reception antennas of the base station are geographically dispersed in the DAS, the pathlosses between the terminal 740 and the respective antennas 710, 720 and 730 have different values.

Reference numerals 750, 760, and 770 in FIG. 7 denote antennas 740 and 710, a terminal 740 and a first dispersion antenna 720, a terminal 740, and a second dispersion antenna 730) is applied to Equation (2) for calculating the transmission power in the CAS scheme. The calculated random access preamble transmission power of the terminal 740 may be 791, 792, and 793, respectively. The transmission power between the terminal 740 and the central antenna 710 is reference numeral 792 and the transmission power between the terminal 740 and the first dispersion antenna 720 is reference numeral 791. The transmission power between the terminal 740 and the central antenna 710 is' The transmission power between the base stations 730 and 730 may be 793.

If the UE determines and transmits the random access preamble transmission power by reference numeral 791, at least the first distributed antenna 720 can successfully receive the random access preamble. When the UE 740 determines and transmits the random access preamble transmission power by reference numeral 792, at least the central antenna 710 can successfully receive the random access preamble. Also, when the UE determines and transmits the random access preamble transmission power by reference numeral 793, at least the second dispersion antenna 730 can successfully receive the random access preamble.

The central antenna 710, the first dispersion antenna 720, and the second dispersion antenna 730 are connected to the central controller. Therefore, if the random access preamble is successfully received through at least one of the antennas from the viewpoint of the base station, the random access preamble is finally received successfully. If the transmission power of the terminal 740 is minimized as much as possible, the power consumption of the terminal 740 can be minimized. In addition, from the viewpoint of the system, unnecessary interference does not occur and system performance deterioration is prevented. Therefore, in the first embodiment, the terminal 740 proposes a method of determining the transmission power using the smallest pathloss value among the pathlosses per antenna. That is, the UE can determine the random access preamble transmission power by replacing [Equation 2] with [Equation 3] at the time of calculating the transmission power.

-PL (k) is the pathloss between the terminal and the kth antenna port

Reference numeral 780 in FIG. 7 shows an example in which the random access preamble transmission power of the UE is determined to be 790 by applying Equation (3).

8 is a diagram illustrating a procedure for performing random access in a terminal according to the first embodiment of the present invention.

Referring to FIG. 8, in step 801, the UE adjusts downlink time and frequency synchronization through a cell search and acquires a cell ID. In step 802, the UE receives the system information including the antenna reference transmission power information for transmitting the random access preamble from the base station. Here, the UE receives CSI-RS pattern information for measuring pathloss (PL) for each antenna port, which is antenna reference transmission power information for transmitting a random access preamble, a parameter related to a random access, Obtain the basic parameter values related to sending and receiving.

The terminal measures and compares the pathloss between the terminal and each antenna port from the CSI-RS pattern information acquired in step 803. [ In step 804, the UE determines a transmission power required for random access preamble transmission using Equation (3). That is, the UE measures the pathloss of each UE and each antenna, and confirms the smallest pathloss among the measured pathloss values. Then, the terminal determines the transmission power by applying the smallest pathloss value that has been confirmed to Equation (3).

The MS transmits a random access preamble to the determined transmission power in step 805. [ In step 806, the terminal determines whether a random access response is received from the base station. If the UE does not receive the random access response for a predetermined time, the UE returns to step 805 and performs the random access preamble transmission again. However, if the random access response is received in step 806, the UE transmits message 3 to the BS according to the scheduling information included in the random access response in step 807.

In step 808, the terminal determines whether message 4 has been received from the base station. If message 4 is not received even after a predetermined time has elapsed, the UE moves to step 805 and performs random access preamble transmission again. However, if message 4 is received in step 808, all random access procedures at the terminal are successfully terminated.

9 is a diagram illustrating a procedure for a base station to perform random access from a terminal according to a first embodiment of the present invention.

Referring to FIG. 9, in step 901, the BS transmits basic parameter values related to transmission and reception, such as system information, random access related parameters, and CSI-RS pattern information for each antenna port, to the MS. In step 902, the BS determines whether a random access preamble has been received from the MS. If the random access preamble is not received, the base station returns to step 902 and waits until it receives a random access preamble from the mobile station.

On the other hand, if the random access preamble is successfully received, the base station generates a random access response including a timing adjustment command and scheduling information from the random access preamble received from the mobile station in step 903, and transmits the random access response to the mobile station. In step 904, the BS determines whether message 3 has been received from the MS. If the MS 3 successfully receives the message 3, the BS transmits the message 4 to the MS in step 905. On the other hand, if message 3 is not received, the base station returns to step 902 and waits until it receives the next random access preamble from the mobile station.

As a modified example of the first embodiment, the BS may signal and specify a random access preamble to be used by the UE, without arbitrarily selecting which random access preamble to use. The random access preamble that the base station has specified and informed to the terminal is referred to as a &quot; dedicated random access preamble &quot;. In the random access procedure using the 'dedicated random access preamble', there is no possibility of random access collision between different terminals. Therefore, steps 807 and 808 of FIG. 8 and step 904 and 905 of FIG. 9 of the random access procedure of the base station are not required in the UE random access procedure.

In addition, a random access procedure may be required when performing a handover, which is a procedure of switching between cells of a mobile station. In more detail, if the base station instructs the terminal to perform handover from the cell A to the cell B, the terminal performs random access to the cell B and proceeds to perform communication in the cell B. In this case, according to a modification of the first embodiment, in step 802, the base station informs the UE of a cell A, a cell B, and a set of CSI-RS pattern information for PL measurement by antenna for a plurality of cells.

For example, the base station transmits CSI-RS pattern information set = {CSI-RS pattern information # 1, CSI-RS pattern information # 2, CSI- RS pattern information # 3, CSI- Information # 5, CSI-RS pattern information # 6}. The base station further informs by signaling which of the CSI-RS pattern information is to be used for the actual PL measurement by the UE.

If the UE is located in the cell A, the BS determines CSI-RS pattern information # 1, CSI-RS pattern information # 2, and CSI-RS pattern information # 3 to be used for PL measurement by the UE in the CSI- Of course. The CSI-RS pattern information # 4, the CSI-RS pattern information # 5, and the CSI-RS pattern information to be used for the PL measurement by the UE in the CSI-RS pattern information set, -RS pattern information # 6. Through these processes, the BS can inform the UE of the CSI-RS pattern information for PL measurement by an antenna in the entire system without discrimination between cells. Also, the BS may inform the UE to use some CSI-RS pattern information for PL measurement according to the situation. Then, the UE measures the PL using the CSI-RS pattern information notified from the base station and determines the transmission power. In this case, as shown in Equation (3), the UE can determine the transmission power using the smallest PL value among the PLs for each antenna corresponding to the CSI-RS pattern notified to the terminal. Alternatively, the UE can determine the transmission power by determining PL as an average value of PLs for each antenna corresponding to the CSI-RS pattern received from the UE.

&Lt; Embodiment 2 >

The second embodiment describes a method of determining a random access preamble transmission power by signaling a parameter for compensating for a channel environment with a predetermined antenna from a base station. The main points of the second embodiment will be described below with reference to FIG.

10 is a diagram illustrating a mobile communication system for transmission power control according to a second embodiment of the present invention.

10, a central antenna 1010, a first distributed antenna 1020, and a second distributed antenna 1030 constitute a cell to communicate with the terminal 1040 . &Lt; / RTI &gt; Each of the central antenna 1010 and the first and second dispersion antennas 1020 and 1030 transmits CSI-RS of different patterns. That is, the center antenna 1010 is mapped to the C-port, the first dispersion antenna 1020 to the D-port # 1, and the second dispersion antenna 1030 to the D-port # 2. It is assumed that all the central antennas 1010 and the first and second dispersion antennas 1020 and 1030 are connected to the central controller of the base station.

In the second embodiment, the terminal measures the pathloss between the C-port and the terminal covering the entire cell, assuming that the pathloss measurement is performed for one antenna. Based on the location information of the UE, the BS signals an additional power adjustment parameter? To adjust the random access preamble transmission power of the UE. Then, the UE determines the random access preamble transmission power according to the following equation (4).

- P _CMAX : Maximum transmission power allowed by the terminal, determined by the class of the terminal and the setting of the upper signaling.

- PREAMBLE_RECEIVED_TARGET_POWER: This is determined by the parameters that are signaled upstream by the base station's random access preamble receive power required to receive the random access preamble.

- PL: pathloss between base station and terminal

- [Delta] is an additional power adjustment parameter for adjusting the UE's random access preamble transmission power, and may be changed according to the location information of the UE.

Reference numeral 1050 in FIG. 10 shows an example in which the UE determines the random access preamble transmission power to be 1080 using an additional power adjustment of? (1060) according to Equation (4). Here,? Is a power adjustment parameter generated based on an antenna close to the UE according to the position information of the UE. Accordingly,? Can have a value of '0' or a negative value.

If the UE calculates the transmission power of the random access preamble by Equation (2), it becomes reference numeral 1070. However, when the UE calculates the random access preamble transmission power using?, It consumes less transmission power by? (1060) than the transmission power calculated by Equation (2).

11 is a diagram illustrating a procedure for performing random access of a terminal according to a second embodiment of the present invention.

Referring to FIG. 11, in step 1101, the UE adjusts downlink time and frequency synchronization through a cell search and acquires a cell ID. In step 1102, the UE receives the system information including the antenna reference transmission power information for transmitting a random access preamble from the base station. Then, the UE acquires basic parameter values related to transmission and reception, such as system bandwidth, random access related parameters, and Δ information for adjusting the random access preamble transmission power, which is the antenna reference transmission power information, using the system information. Δ is a parameter set by the base station for confirming the location information of the terminal and controlling transmission power based on the antenna close to the location of the identified terminal.

The UE determines whether it is necessary to transmit the random access preamble by Equation (4) using the random access-related parameters acquired in step 1103 and the pathloss measurement values for the? Information and the C-port, which are power adjustment parameters for adjusting the random access preamble transmission power. And determines the transmission power. The UE transmits a random access preamble to the determined transmission power in step 1104.

In step 1105, the MS determines whether a random access response is received from the BS. If the UE does not receive the random access response for a predetermined time, the UE returns to step 1104 to perform random access preamble transmission again. However, if the random access response is received in step 1105, the mobile station moves to step 1106 and transmits message 3 to the base station according to the scheduling information included in the random access response.

In step 1107, the terminal determines whether message 4 is received from the base station. If message 4 is not received even after a predetermined time elapses, the UE moves to step 1104 and performs random access preamble transmission again. However, if message 4 is received in step 1107, all random access procedures are successfully terminated.

12 is a diagram illustrating a random access procedure of a base station according to the second embodiment.

Referring to FIG. 12, in step 1201, the BS transmits basic parameter values related to transmission and reception, such as system information, random access parameters, and? Information for adjusting the random access preamble transmission power, to the UE. In step 1202, the Node B determines whether a random access preamble has been received from the UE. If the random access preamble is not received, the base station waits until a random access preamble is received from the mobile station in step 1202.

On the other hand, if the random access preamble is successfully received, the BS generates a random access response including a timing adjustment command and scheduling information from the random access preamble received from the MS in step 1203, and transmits the random access response to the MS. In step 1204, the BS determines whether message 3 is received from the MS. If message 3 is not received, the BS moves to step 1202 and waits until the next random access preamble is received from the MS. On the other hand, if message 3 is successfully received, the BS transmits message 4 to the UE in step 1205. Then, the UE can terminate the random access procedure by successfully receiving the message 4.

The second embodiment can be modified in various ways. For example, the BS may signal a random access preamble to be used by the UE without arbitrarily selecting which random access preamble to use. The random access preamble that the base station has specified and informed to the terminal is referred to as a &quot; dedicated random access preamble &quot;. In this case, the base station can reduce the additional signaling overhead by deliberately knowing from? Designated random access preamble? Without signaling?. For example, the relationship between the 'designated random access preamble' and Δ may be defined in advance as follows so that the base station and the terminal can be operated in a common manner.

Designated random access preamble 1 ~ Designated random access preamble k1 => Δ1

Designated random access preamble k1 + 1 ~ Designated random access preamble k2 => Δ2

Designated random access preamble k2 + 1 ~ Designated random access preamble k3 => Δ3

...

As described above, in the random access procedure using the 'designated random access preamble', there is no possibility of random access collision between different terminals. Therefore, steps 1106 and 1107 of FIG. 11 for the random access procedure of the UE, which corresponds to the procedure, and steps 1204 and 1205 of FIG. 12 of the random access procedure of the base station may be deleted.

13 is a diagram illustrating a terminal device according to an embodiment of the present invention.

13, in order to transmit a random access preamble, a UE includes a random access preamble generator 1310 for generating a random access preamble to be transmitted, an RE (RE) for mapping a signal to be transmitted to a RE A RE mapper 1320 and a random access preamble generated by the UE are mapped to a predetermined frequency region through the RE mapper 1320 and then transmitted through an IFFT processing 1330 to an intermediate frequency And a radio frequency (RF) processing unit 1340 and is transmitted to the base station through a TX unit 1350. [

The terminal receives the system information from the base station through the receiving unit (RX) 1360. In this case, the system information includes basic parameter values related to transmission and reception such as system bandwidth, random access-related parameters, CSI-RS pattern information for each antenna, and Δ information for adjusting the random access preamble transmission power.

The terminal checks the pathloss between the base station and the terminal or the pathloss between each antenna and the terminal from the pathloss estimator (1370). The terminal acquires a random access-related parameter provided from the base station through a parameter acquisition unit 1380. Next, the UE adjusts the random access preamble transmission power of the UE in the power control controller 1390 using the determined pathloss and the random access related parameters. Specifically, the UE determines a random access preamble transmission power value according to the method described in the first embodiment or the second embodiment of the present invention. The power control controller 1390 controls the random access preamble generator 1310 or the IF / RF processor 1340 to adjust the power of the random access preamble.

14 is a diagram illustrating a base station apparatus according to an embodiment of the present invention.

14, the base station includes an RF / IF unit 1402 for processing an RF / IF signal received from a terminal through a receiving unit (RX) 1401, an FFT unit 1403 for performing Fast Fourier Transform (FFT) An RE demapper 1404, a random access preamble detector 1405, and a power control controller 1406. The Random Access Preamble

The power control controller 1406 generates a power control parameter for transmission of an appropriate random access preamble according to the location of the UE and applies the generated power control parameter to a control information generator 1407. The control information generator 1407 receives information on the power control parameter received from the power control controller 1406 and whether the base station has successfully received the random access preamble from the random access preamble detector 1405, Information. The generated control information is provided with an error correction capability through an encoder 1408. The generated control information is composed of modulation symbols in a modulator 1409 and then modulated by a RE mapper 1410 to a predetermined time- Lt; / RTI &gt; Then, the signal is transmitted to the terminal through the intermediate frequency (IF) processing unit 1411 and the RF (radio frequency) processing unit 1412 through the IFFT processing unit 1411 and the TX unit 1413.

The embodiments of the present invention disclosed in the present specification and drawings are merely illustrative examples of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

Claims (12)

1. A power control method for performing random access of a terminal in a wireless communication system,
Receiving reference signal information on a plurality of reference signals for a plurality of antenna ports of the base station from a base station through an upper layer;
Measuring a plurality of path loss values for the plurality of antenna ports of the base station using reference signal power information included in the reference signal information and the plurality of reference signals;
Calculating a transmission power of the random access preamble using the smallest value of the plurality of measured path loss values;
And transmitting the random access preamble to the base station with the calculated transmit power. The method according to claim 1,
Wherein the reference signal information is related to a channel state information reference signal (CSI-RS) for each antenna port. 3. The method of claim 2,
Wherein the reference signal information includes CSI-RS pattern information for measuring path loss for each antenna port of the base station. The method according to claim 1,
Wherein the wireless communication system is configured as a distributed antenna system. The method according to claim 1,
Wherein the plurality of reference signals are transmitted through the antenna ports of the base station. The method according to claim 1,
The transmission power of the random access preamble (P _PRACH )
_{P PRACH = min {P CMAX,} PREAMBLE-_RECEIVED_
TARGET_POWER + min (PL (k))} [dBm]
Lt; / RTI &gt;
The P _CMAX represents a maximum UE transmission power based on a UE class and an upper layer signaling setting,
PREAMBLE_RECEIVED_TARGET_POWER indicates the random access preamble reception power required for the base station to receive the random access preamble and determined by the upper layer signaling setting,
And PL (k) represents a path loss between the terminal and the kth antenna port. A terminal in a wireless communication system,
A receiver for receiving reference signal information on a plurality of reference signals for a plurality of antenna ports of the base station from a base station through an upper layer;
Measuring a plurality of path loss values for the plurality of antenna ports of the base station using the reference signal power information included in the reference signal information and the plurality of reference signals, A power control controller for calculating a transmission power of a random access preamble using a small value, and a transmitter for transmitting the random access preamble at the calculated transmission power. 8. The method of claim 7,
Wherein the reference signal information is related to a channel state information reference signal (CSI-RS) for each antenna port. 9. The method of claim 8,
Wherein the reference signal information includes CSI-RS pattern information for measuring path loss for each antenna port of the base station. 8. The method of claim 7,
Wherein the wireless communication system is configured as a distributed antenna system. 8. The method of claim 7,
Wherein the plurality of reference signals are transmitted through the antenna ports of the base station. 8. The method of claim 7,
The transmission power of the random access preamble (P _PRACH )
_{P PRACH = min {P CMAX,} PREAMBLE-_RECEIVED_
TARGET_POWER + min (PL (k))} [dBm]
Lt; / RTI &gt;
The P _CMAX represents a maximum UE transmission power based on a UE class and an upper layer signaling setting,
PREAMBLE_RECEIVED_TARGET_POWER indicates the random access preamble reception power required for the base station to receive the random access preamble and determined by the upper layer signaling setting,
And PL (k) represents a path loss between the terminal and the kth antenna port.

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