KR20190071448A - Method for performing random access in wireless communication network, terminal and base station for performing random access - Google Patents

Abstract

The present invention relates to a method for performing random access, configured to prevent performance deterioration of a random access channel caused by congestion occurring when terminals establish connection setup, in a wireless mobile communication network, with a base station for data transmission. According to one embodiment of the present invention, the method for performing random access in a wireless mobile communication network comprises: a first message transmitting step in which a terminal transmits a first message including a preamble to a base station; a second message receiving step in which the terminal receives, from the base station, a second message including a random access response corresponding to the first message, wherein the second message includes a temporary identifier; a third message transmitting step in which the terminal transmits a third message including a connection request to the base station; and a fourth message receiving step in which the terminal receives, from the base station, a fourth message including a connection resolution corresponding to the third message. The third message transmitting step may include a transmission power determining step in which the terminal determines transmission power based on the number of retransmission of the third message.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for performing random access in a wireless mobile communication network, a terminal and a base station performing the random access,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for performing random access in a wireless mobile communication network, and more particularly, To a random access method, a terminal, and a base station capable of reducing performance degradation of a random access channel.

As the demand for the Internet of Things (IoT) service grows, it becomes important to support it in the wireless mobile communication network. IoT communication has different characteristics from existing human-to-human communication. In the cell, there are many IoT terminals, the terminals mainly perform small data transmission, the uplink-oriented communication is mainly used, and the connection is established only when there is data to be transmitted in order to reduce energy consumption. (RACH) congestion problem has become an urgent problem to be solved. A related prior art document is disclosed in Japanese Patent Laid-Open No. 10-2017-0049273.

Therefore, it is necessary to study a technique for reducing the performance degradation of a random access channel due to congestion when establishing a connection between a terminal and a base station.

An object of the present invention is to provide a random access performing method of a wireless mobile communication network capable of reducing performance degradation of a random access channel due to congestion in connection establishment of a base station in a wireless mobile communication network, .

According to an aspect of the present invention, there is provided a method of performing random access in a wireless mobile communication network, the method comprising: transmitting a first message including a preamble to a base station; Receiving, by the terminal, a second message including a random access response corresponding to the first message from the base station, the second message including a temporary identifier; The UE transmitting a third message including a connection request to the base station; And receiving, by the terminal, a fourth message including connection resolution corresponding to the third message from the base station, wherein the third message transmission step includes a step of transmitting the third message retransmission number And determining a transmission power based on the transmission power.

According to an aspect of the present invention, there is provided a method of performing random access in a wireless mobile communication network, the method comprising: receiving a first message including a preamble from a terminal; The BS transmitting to the MS a second message including a random access response corresponding to the first message, the second message including a temporary identifier; The base station receiving a third message including a connection request from the terminal; And transmitting, by the base station, a fourth message including a connection resolution corresponding to the third message to the terminal, wherein the fourth message transmission step comprises: And selecting a terminal to which the fourth message is to be transmitted based on a capture probability from the terminal, wherein the capture probability is calculated using the transmission power of the terminal at the time of transmitting the third message A method of performing an access is disclosed.

According to an aspect of the present invention, there is provided a terminal for performing random access in a wireless mobile communication network, the terminal including a preamble and a connection request message for performing the random access, A transmitting unit for transmitting the data; A receiving unit for receiving a random access response corresponding to the preamble message and a connection resolution message for the connection request from the base station, the random access response message including a temporary identifier; A transmission power determination unit that determines a transmission power based on the number of retransmission of the connection request message; And a control unit for controlling the transmission unit, the reception unit, and the transmission power determination unit.

According to an aspect of the present invention, there is provided a base station for performing random access in a wireless mobile communication network, the base station including: a receiver for receiving a preamble and a connection request message from a terminal; A transmitting unit for transmitting a random access response message corresponding to the preamble message and a connection resolution message corresponding to the connection request message to the terminal, wherein the random access response message includes a temporary identifier; A terminal capturing unit for selecting a terminal to transmit the connection resolution message based on the capture probability among a plurality of terminals staying in the network, the capturing probability being calculated using the reception power of the base station at the time of receiving the connection request message -; And a controller for controlling the receiving unit, the transmitting unit, and the terminal capturing unit.

A method of performing random access in a wireless mobile communication network according to an embodiment of the present invention, a terminal performing a random access and a base station, performing a random access channel performance due to congestion in connection establishment of a base station in a wireless mobile communication network Reduction can be reduced.

1 is a flowchart illustrating a method for performing random access in a wireless mobile communication network according to an embodiment of the present invention.
2 is a block diagram of the terminal shown in FIG.
3 is a block diagram of the base station shown in FIG.
4 is a diagram for explaining a process of selecting a terminal using a power capture effect by a base station performing random access in a wireless mobile communication network according to an embodiment of the present invention.
FIG. 5 is a graph comparing performance between a method of performing random access of a wireless mobile communication network and another method according to an embodiment of the present invention.

Hereinafter, a method of performing random access in a wireless mobile communication network according to an embodiment of the present invention, a terminal and a base station performing the random access will be described with reference to the drawings.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this specification, the terms "comprising ", or" comprising "and the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

In a wireless mobile communication network, a terminal must establish a connection with a network in order to transmit data. To establish a connection to the network, the terminal transmits a random access signal to the base station, and the base station transmits a random access response message to the terminal.

Hereinafter, a method in which IoT terminals perform random access for establishing a connection with a base station (eNB) for data transmission will be described.

FIG. 1 is a flowchart illustrating a method of performing random access in a wireless mobile communication network according to an embodiment of the present invention. FIG. 2 is a block diagram of a terminal shown in FIG. 1, Block diagram.

As shown, the wireless mobile communication system may include a terminal 100 and a base station 200.

The terminal 100 may include a transmission unit 110, a reception unit 220, a transmission power determination unit 130, and a control unit 140.

The base station 200 may include a receiving unit 210, a transmitting unit 220, a terminal capturing unit 230, and a control unit 240.

The MS 100 to establish a connection transmits a first message Msg1 including a preamble through a predetermined random access channel (RACH channel) to the BS 200 in step S110. That is, the transmitting unit 110 transmits the first message through the randomly selected random access channel. At this time, since the first message (Msg1) is randomly selected and transmitted in the preamble pool, if a large number of terminals attempt to access at the same time, a plurality of terminals can select and transmit the same preamble. This may be defined as a first message (Msg1) collision. The base station 200 does not detect a collision phenomenon on the reception of Msg1 due to the characteristics of the preamble. That is, even if congestion occurs in the first message when the receiving unit 210 receives the first message, the congestion of the first message can not be detected.

Meanwhile, the terminal 100 can determine the transmission power by the power control technique when the first message is transmitted. The transmission power determination unit 130 can determine the transmission power at the time of the first message transmission according to Equation (1).

는 단말(100)이 RACH를 통하여 제1메시지를 전송할 때의 전송 파워이며,

[dBm]는 단말의 최대 전송 파워; PL　[dB]는 path-loss 값, 그리고 PRTP　[dBm] 는 preamble received target power로 타겟파워이다. PRTP의 경우는 하기 수학식 2와 같이 표현될 수 있다.

Is the transmission power when the terminal 100 transmits the first message through the RACH,

[dBm] is the maximum transmission power of the terminal; PL [dB] is the path-loss value, and PRTP [dBm] is the preamble received target power. PRTP can be expressed by the following equation (2).

는 power initial received target 으로 일종의 타겟 파워,

는 오프셋 값, 그리고 PRS는 power ramping step이며, r은 단말의 ramping number이다.

Is a power initial received target, a kind of target power,

Is the offset value, PRS is the power ramping step, and r is the terminal ramping number.

에 도달할 때까지 power ramping을 하게 된다.The use of the power control scheme for the first message (Msg1) is to prevent the base station 200 from detecting it because of too low power. The power control technique increases the transmission power by PRS as the number of retransmissions increases. That is, the r value basically follows the number of retransmissions and the total value

Power ramping is performed.

When the receiving unit 210 of the base station 200 receives the first message Msg1, the transmitting unit 220 of the base station 200 transmits a second random access response And transmits the message Msg2 to the terminal 100 (S120). The second message is transmitted through a physical down control channel (PDCCH). The second message may include a temporary identifier of the wireless network and an uplink grant for the next message.

The MSs that have transmitted the first message set the RAR window and receive a second message for the corresponding preamble in the window, and transmit a third message (Msg3) including a connection request according to the determined uplink grant, (S130).

The third message (Msg3) is transmitted through a physical uplink shared channel (PUSCH). In the past, since IoT terminals that selected the same preamble transmit the same uplink grant, a collision occurs again on the PUSCH in the case of the third message (Msg3). Due to such a collision, the base station can not decode Msg3, and all the terminals selected for the corresponding preamble fail the random access procedure.

However, according to an embodiment of the present invention, the terminal 100 determines the transmission power according to a power control strategy (power ramping scheme) even when the third message is transmitted. The transmission power determination unit 130 can determine the transmission power at the time of the third message transmission according to the following equation (3).

Where P _msg3 is the transmission power when transmitting a third message, P _cmax is the maximum transmission power, and, P _target is the target power and, PL is a path-loss value at the time to transmit a third message of the terminal, r is ramping number, and PRS is the power ramping step.

In the case of a radio signal, the base station 200 can analyze one signal even if there is a collision, when there is a difference in received power. This is called a power capture effect.

4 is a diagram for explaining a process of selecting a terminal using a power capture effect by a base station performing random access in a wireless mobile communication network according to an embodiment of the present invention.

As shown in the figure, when there is a difference in reception power between the plurality of terminals 100, T2, and T3 when receiving the third message, the base station 200 selects one of the terminals 100, ) Can be interpreted.

The selected terminal 100 may be a terminal having a high capture probability. The capturing probability can be expressed by Equation (4).

는 단말 i가 capture될 확률이며, P_i는 단말 i의 기지국에서의 수신 파워, β는 capture threshold이다.At this time,

P _i is the reception power at the base station of terminal i, and β is the capture threshold.

The terminal capturing unit 230 of the base station can select the terminal having the largest capture probability calculated according to Equation (4). That is, the probability of selecting a terminal that has stayed in the network for a long time (a lot of retransmissions) becomes higher. The efficiency of the PUSCH can be increased since the reception rate of the third message can be increased despite the collision of the first message (Msg1) by selecting any one terminal using the power capture effect. Also, the probability of connection setup increases for the terminal.

The transmitting unit 220 of the BS 200 may transmit a fourth message Msg4 including a connection resolution corresponding to the connection request to the selected MS 100 in operation S140. When the steps S110 to S140 are completed, the random access procedure is terminated. In this case, the terminal 100 succeeds in establishing a connection with the base station 200.

FIG. 5 is a graph comparing performance between a method of performing random access of a wireless mobile communication network and another method according to an embodiment of the present invention.

FIG. 5 shows the superiority of the third message (Msg3) power ramping technique according to an embodiment of the present invention. (a-c), the power ramping technique and the power capture effect when the third message is transmitted according to an exemplary embodiment of the present invention are shown. Analysis of results with different sizes of PRS for each result is also included.

It can be seen that the performance is significantly improved in terms of channel throughput and connection failure probability of the UE when the technique proposed in the embodiment of the present invention is used. When PRS is set to 3db, the best performance is achieved. In this case, the throughput can be improved to about 105%. In case of the connection failure probability, the performance improvement of about 42% can be expected when the proposed technique according to the embodiment of the present invention is not used. Although the average energy consumption increases by about 13% in (c), it can be expected that the channel throughput and the connection failure probability can be greatly improved in comparison with the energy used. (d) shows the performance improvement when the access class barring and the proposed technique are used together.

As described above, according to an embodiment of the present invention, a method for performing random access in a wireless mobile communication network, a terminal and a base station performing the random access, It is possible to reduce the performance degradation of a random access channel due to congestion.

The method for performing the random access of the wireless mobile communication network may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable recording medium. At this time, the computer-readable recording medium may include program commands, data files, data structures, and the like, alone or in combination. On the other hand, the program instructions recorded on the recording medium may be those specially designed and configured for the present invention or may be available to those skilled in the art of computer software.

The computer-readable recording medium includes a magnetic recording medium such as a magnetic medium such as a hard disk, a floppy disk and a magnetic tape, an optical medium such as a CD-ROM and a DVD, a magnetic disk such as a floppy disk, A magneto-optical media, and a hardware device specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like.

The recording medium may be a transmission medium, such as a light or metal line, a wave guide, or the like, including a carrier wave for transmitting a signal designating a program command, a data structure, and the like.

The program instructions also include machine language code, such as those generated by the compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

The above-described method for performing random access in the wireless mobile communication network, the terminal and the base station performing the random access can be applied to a limited configuration and method of the above-described embodiments, All or some of the embodiments may be selectively combined.

100: terminal
110:
120: Receiver
130: Transmission power determination unit
140:
200: base station
210:
220:
230: terminal capture unit
240:

Claims (16)

A method for performing random access in a wireless mobile communication network,
Transmitting a first message including a preamble to a base station;
Receiving, by the terminal, a second message including a random access response corresponding to the first message from the base station, the second message including a temporary identifier;
The UE transmitting a third message including a connection request to the base station; And
And receiving, from the base station, a fourth message including a connection resolution corresponding to the third message,
And the third message transmission step includes the step of the terminal determining transmission power based on the number of times of the third message retransmission.
2. The method of claim 1, wherein the transmission power determined in the transmission power determination step is
Is determined according to the following equation (1).
[Equation 1]

(Where P _msg3 is the transmission power when transmitting a third message, P _cmax is the maximum transmission power, and, P _target is the target power and, PL is a path-loss value at the time to transmit a third message of the terminal, r is ramping number, and PRS is the power ramping step.)
The method according to claim 1,
The terminal receiving the fourth message has a high probability of capturing from the base station among the plurality of terminals staying in the network,
And the capture probability is calculated using the transmission power of the terminal at the time of the third message transmission.
The method of claim 3,
Wherein the capture probability is expressed by the following equation (2).
&Quot; (2) "

(At this time,

Is the probability that terminal i is captured, P _i is the received power at base station i, and β is the capture threshold.
A method for performing random access in a wireless mobile communication network,
The base station receiving a first message including a preamble from a terminal;
The BS transmitting to the MS a second message including a random access response corresponding to the first message, the second message including a temporary identifier;
The base station receiving a third message including a connection request from the terminal; And
The base station transmitting a fourth message including a connection resolution corresponding to the third message to the mobile station,
Wherein the fourth message transmission step includes selecting a terminal to transmit the fourth message based on a capture probability from the base station among a plurality of terminals staying in the network,
And the capture probability is calculated using the transmission power of the terminal at the time of the third message transmission.
6. The method of claim 5,
Wherein the capture probability is expressed by Equation (1).
[Equation 1]

(At this time,

Is the probability that terminal i will be captured, P _i is the transmit power of terminal i, and β is the capture threshold.
6. The method of claim 5,
And the UE determines a transmission power based on the number of times of the third message retransmission.
8. The method of claim 7,
Wherein the transmission power is determined according to Equation (2).
&Quot; (2) "

(Where P _msg3 is the transmission power when transmitting a third message, P _cmax is the maximum transmission power, and, P _target is the target power and, PL is a path-loss value at the time to transmit a third message of the terminal, r is ramping number, and PRS is the power ramping step.)
A terminal performing random access in a wireless mobile communication network,
A transmitter for transmitting a preamble and a connection request message for performing the random access to a base station;
A receiving unit for receiving a random access response corresponding to the preamble message and a connection resolution message for the connection request from the base station, the random access response message including a temporary identifier;
A transmission power determination unit that determines a transmission power based on the number of retransmission of the connection request message; And
And a control unit for controlling the transmission unit, the reception unit, and the transmission power determination unit.
10. The apparatus of claim 9, wherein the transmission power determining unit
Wherein the transmission power is determined according to Equation (1).
[Equation 1]

(Where P _msg3 is the transmission power when transmitting the connection request message, P _cmax is the maximum transmission power, and, P _target is the target power when transmitting the connection request message, PL is a path-loss value of the terminal, r Is the ramping number, and PRS is the power ramping step.
10. The method of claim 9,
The terminal receiving the connection solving message is a terminal having a high probability of capturing from the base station among a plurality of terminals staying in the network,
Wherein the capturing probability is calculated using a transmission power of a terminal at the time of transmitting the connection request message.
12. The method of claim 11,
Wherein the capturing probability is expressed by Equation (2).
&Quot; (2) "

(At this time,

Is the probability that terminal i will be captured, P _i is the transmit power of terminal i, and β is the capture threshold.
A base station for performing random access in a wireless mobile communication network,
A receiving unit for receiving a preamble and a connection request message from a terminal;
A transmitting unit for transmitting a random access response message corresponding to the preamble message and a connection resolution message corresponding to the connection request message to the terminal, wherein the random access response message includes a temporary identifier;
A terminal capturing unit for selecting a terminal to transmit the connection resolution message based on the capture probability among a plurality of terminals staying in the network, the capturing probability being calculated using the reception power of the base station at the time of receiving the connection request message -; And
And a controller for controlling the receiving unit, the transmitting unit, and the terminal capturing unit.
14. The method of claim 13,
Wherein the capture probability is expressed by Equation (1).
[Equation 1]

(At this time,

Is the probability that terminal i will be captured, P _i is the transmit power of terminal i, and β is the capture threshold.
14. The method of claim 13,
Wherein the terminal determines a transmission power based on the number of retransmission times of the connection request message.
16. The method of claim 15,
And determines the transmission power according to Equation (2).
&Quot; (2) "

(Where P _msg3 is the transmission power when transmitting the connection request message, P _cmax is the target power when the maximum transmission power of the terminal and, P _target is to send the connection request message, and PL is path-loss value, r is ramping number, and PRS is the power ramping step.)

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