WO2013051910A2

WO2013051910A2 - Method and apparatus for controlling random access channel congestion in wireless communication system

Info

Publication number: WO2013051910A2
Application number: PCT/KR2012/008125
Authority: WO
Inventors: 정상수; 조성연; 김성륜; 배범식; 이상훈; 이현관; 이범희; 김민철
Original assignee: 삼성전자 주식회사; 연세대학교 산학협력단
Priority date: 2011-10-06
Filing date: 2012-10-08
Publication date: 2013-04-11
Also published as: KR20130037382A; WO2013051910A3

Abstract

In a wireless communication system comprising at least one user equipment (UE) and a plurality of devices using the same wireless network used by the at least one UE, a base station determines whether congestion has occurred on a random access channel (RACH) due to random access by the plurality of devices, modifies system information so as to reduce the number of UEs using one preamble from preambles that belong to a first preamble group, when congestion has occurred on the RACH, and broadcasts the system information that is modified, wherein the first preamble group from a plurality of preamble groups comprises preambles that are used by the plurality of devices.

Description

Random access channel congestion control method and apparatus in wireless communication system

The present invention relates to a method and apparatus for controlling random access channel congestion in a wireless communication system.

Recently, with the development of information and communication technology, various types of communication technologies have been researched and developed in addition to the communication between people. This is a result of the efforts of operators to open up new markets in the current telecom market, which is more intense than in the past. Machine-to-Machine Communication (M2M) technology is a new type of communication technology. It is a communication technology in which a number of devices adaptively configure a wireless communication network and exchange information at high speed without human intervention or intervention. Indicates.

M2M communication technology may use both wired and wireless communication. In particular, as M2M communication technology using a wireless communication scheme. Currently, the 3rd Generation Partnership Project (3GPP) is actively researching M2M communication technology using Long Term Evolution (LTE) network under the name of Machine Type Communication (MTC). In 3GPP, the standardization of M2M communication technology is focused on using the existing 3GPP communication system. Therefore, a new method of M2M communication using an existing wireless communication network and various applications of MTC are proposed.

When MTC is used, multiple devices connect to the same wireless network. When the plurality of devices simultaneously access the wireless communication network, there is a high probability of congestion occurring on a random access channel (RACH).

As an example in which MTC is used, a smart metering and a bridge monitoring method using a sensor will be described. When the intelligent metering and a bridge monitoring method using a sensor are used, a large number of MTC devices are used. Distributed in a very high density in the area, the large number of MTC devices are very likely to transmit data at the same time. Specifically, since the meter reading data is transmitted at a specific time when the intelligent meter reading is used, the corresponding MTC devices have a high probability of simultaneously transmitting data at the same time interval. In addition, when the bridge monitoring method using the sensor is used, it is highly likely that the data monitored by the sensors is transmitted at the same time as the train passes the bridge.

As hundreds to thousands of MTC devices simultaneously transmit data, congestion occurs in wireless networks. In this case, since the UE and the MTC devices compete in the same RACH, the UE determines that there is much more congestion than when performing the conventional random access.

Accordingly, when congestion caused by a plurality of MTC devices is caused by a base station (Enhanced Node B: eNodeB, hereinafter called 'eNB') in order to control congestion on the RACH, a corresponding RRC connection (Radio Resource Control Connection) step is performed. Rejecting the connection of the MTC device by determining whether the device is an MTC device. However, in the related art, signaling overhead occurs because the eNB has no choice but to reject the access of the MTC device after performing random signaling (RA) after various signaling processes. In addition, conventionally, there is no method for distinguishing between the MTC device and the general UE using only the preamble received by the eNB before the RRC connection step. Accordingly, there is a need for a method of reducing signaling overhead and more efficiently reducing congestion of the RACH.

The present invention proposes a method and apparatus for controlling random access channel congestion in a wireless communication system.

In addition, the present invention proposes a method and apparatus for increasing access probability of a wireless communication network of a UE through random access channel congestion control in a wireless communication system.

The method proposed in the present invention; Random Access Channel (RACH) of a base station in a wireless communication system including at least one user equipment (UE) and a plurality of devices (Device) using the same wireless communication network as the at least one UE A congestion control method, comprising: determining whether congestion occurs on the RACH due to random access of the plurality of devices, and when congestion occurs on the RACH, a preamble included in the first preamble group Changing system information to reduce the number of UEs using one of the UEs, and broadcasting the changed system information, wherein the first preamble group is used by the plurality of devices among a plurality of preamble groups. Characterized in that the preamble group including the preamble.

The device proposed in the present invention; Congestion of a random access channel (RACH) in a wireless communication system including at least one user equipment (UE) and a plurality of devices using the same wireless communication network as the at least one UE In the base station for controlling the operation, determining whether congestion occurs on the RACH due to random access of the plurality of devices, and if congestion occurs on the RACH, one of the preambles included in the first preamble group And a controller configured to change system information to reduce the number of UEs using the UE, and a transmitter configured to broadcast the changed system information under control of the controller, wherein the first preamble group includes the plurality of devices among a plurality of preamble groups. Is a preamble group including the preambles used.

The present invention has the effect of controlling the congestion of the random access channel in a simpler and more efficient way in a wireless communication system. In addition, the present invention can solve the problem of signaling overhead when controlling the congestion of the random access channel, there is an effect that can increase the connection probability of the wireless communication network of the UE. In addition, the present invention has the advantage that can be used in various ways, such as being used to control the congestion of the random access channel, to solve the MME overload problem.

1 is a view showing the configuration of a preamble used in a conventional wireless communication system,

2 is a diagram illustrating a result of an RRC connection between an LP device and a UE performing RA in a wireless communication system according to an embodiment of the present invention;

3 is a signal flow diagram of a UE and an eNB for controlling congestion in a wireless communication system according to an embodiment of the present invention;

4 is a flowchart illustrating an operation of an eNB for controlling congestion of a RACH in a wireless communication system according to an embodiment of the present invention;

5 is a flowchart illustrating an operation of a UE performing RA in a wireless communication system;

6 is a block diagram of an eNB for controlling congestion of RACH in a wireless communication system according to an embodiment of the present invention;

7 is a block diagram of a UE performing RA in a wireless communication system according to an embodiment of the present invention;

8 illustrates the number of RA successful devices before the RACH congestion control method according to an embodiment of the present invention and the number of RA successful devices after the RACH congestion control method according to the embodiment of the present invention are used.

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

In the present specification, a method and apparatus for controlling congestion of a random access channel (RACH) in a wireless communication system are proposed. Specifically, in the present specification, at least one user equipment (UE) and a same wireless communication network (eg, Long Term Evolution (LTE) network) simultaneously with the at least one UE in the wireless communication system. A method and apparatus for controlling congestion that occurs when a plurality of devices performing wireless communication using a random access (RA) is performed.

The plurality of devices may include a Machine Type Communication (MTC) device, and the like, hereinafter, the plurality of devices will be referred to as a 'low device (LP) device'. In the present specification, a case in which the wireless communication system is an LTE communication system will be described as an example, but it will be apparent to those skilled in the art that the wireless communication system may be another communication system in addition to the LTE communication system.

According to an embodiment of the present invention, when congestion by a plurality of LP devices occurs, the preamble used by the plurality of LP devices to increase the RA collision probability of the plurality of LP devices, that is, restrict the connection of the plurality of LP devices. (Preamble) Changes the size of the group and the selection criteria of the preamble group. Accordingly, in the embodiment of the present invention, congestion on the RACH can be solved while ensuring the connection of the UE.

Prior to the detailed description of the embodiment of the present invention, the configuration of the preamble used in the conventional wireless communication system will be described.

1 is a diagram illustrating a configuration of a preamble used in a conventional wireless communication system.

Referring to FIG. 1, a total of 64 RA preambles 100 are used in a conventional wireless communication system. The 64 RA preambles 100 are dedicated RA preambles 110 for contention-free RAs and Non-dedicated RA preambles for contention-based RAs. 120. The non-dedicated RA preamble 120 includes a preamble group A 130 and a preamble group B 140.

When performing the contention-based RA, the UE first selects one of the preamble group A 130 and the preamble group B 140 in consideration of the pathloss value of the RACH and the size of an uplink message to be transmitted. Choose. The UE selects one of the preambles included in the selected preamble group to perform the RA.

Specifically, the UE preamble group B when the size of the uplink message to be transmitted is greater than a predetermined message size threshold value (MESSAGE_Threshold value) and the downlink path loss value is smaller than a preset path loss threshold value (PATHLOSS_Threshold value). Select 140. In addition, the UE may perform the preamble group when the size of the uplink message to be transmitted is equal to or less than the message size threshold value and the downlink path loss value is greater than or equal to the PATHLOSS_Threshold value. Select A 130. As such, when the channel condition is not good or the size of the uplink message to be transmitted is small, the preamble group A 130 is selected. In the LP device, since the size of an uplink message to be transmitted is generally small, there is a high probability that the preamble group A 130 is selected.

According to an embodiment of the present invention, when congestion occurs on the RACH by the plurality of LP devices in a wireless communication system in which at least one UE and a plurality of LP devices coexist and use an LTE network, a preamble used by the plurality of LP devices Adjust the size of the preamble group corresponding to. To this end, according to an embodiment of the present invention, an eNB (enhanced Node B: eNodeB, hereinafter referred to as 'eNB') may have a preamble in which some of the UEs that select a preamble of the same preamble group as the preamble group used by the plurality of LP devices are different. The following process is performed to select the preamble of the group.

The eNB is a preamble group used by the plurality of LP devices, included in a System Information Block (SIB), such that the number of UEs using the preamble included in the preamble group used by the plurality of LP devices is reduced. The number of preambles included and the group selection criterion information for the preamble group are changed and broadcasted. According to this process, in an embodiment of the present invention, it is possible to increase the RA collision probability of a plurality of LP devices to increase the access probability of the UE and to solve congestion at the same time.

On the other hand, in the embodiment of the present invention to control the congestion in the RA step. Conventionally, when congestion by a plurality of LP devices occurs, it is determined whether the corresponding device requesting the RRC connection is an LP device in an RRC connection (Radio Resource Control Connection) step, and when the corresponding device is determined as an LP device, the LP device is determined. A method of rejecting a connection by an eNB was used. Therefore, in order to solve congestion, various signaling processes have to be performed after the RA step. Thus, problems such as signaling overhead have occurred. However, when controlling congestion in the RA step as in the embodiment of the present invention, there is an advantage in that congestion can be controlled more quickly because procedural waste does not occur.

In an embodiment of the present invention, congestion is controlled by adjusting the size of a preamble group for a preamble used by a plurality of LP devices. Only the preamble of the LP device in the RA may be rejected to control congestion due to the plurality of LP devices. However, in the related art, there is no method of distinguishing the LP device from the UE by using only the preamble received by the eNB before the RRC step. Accordingly, in an embodiment of the present invention, congestion can be indirectly eliminated by restricting the connection of the LP device by adjusting the size of the preamble group for the preamble used by the plurality of LP devices.

In order to carry out the embodiments of the present invention, the following matters are assumed first.

The LP device may use only the preambles included in the preamble group A, and the UE may use both preambles included in the preamble groups A and B.

The eNB determines the number of LP devices and the number of UEs based on the number of RRC connected devices.

-when the congestion occurs, the eNB determines whether the congestion is caused by the LP device using a preset threshold.

When the congestion occurs by the LP device, the eNB increases the collision probability of the preambles included in the preamble group A by reducing the size of the preamble group A including the preamble used by the LP device, thereby reducing the connection of the LP device. .

Change the preamble group selection criterion information for the UE using the preamble included in the preamble group A to enable the UE to use the preamble included in the preamble group B;

Hereinafter, a congestion control method of a RACH in a wireless communication system according to an embodiment of the present invention will be described in detail.

2 is a diagram illustrating a result of an RRC connection between an LP device and a UE performing RA in a wireless communication system according to an embodiment of the present invention.

In FIG. 2, as an example, 1000 LP devices and 50 UEs using the preamble included in the preamble group A 200 attempt RA, and 100 UEs using the preamble included in the preamble group B 210. Tries RA. Then, 100 LP devices of the 1000 LP devices succeed in RA, 5 UEs of 50 UEs succeed in RA, and 10 UEs of 100 UEs succeed in RA. 50 LP devices among the 100 LP devices that have succeeded in the RA are connected by RRC, 3 UEs of the successful UE by the RA are connected by RRC, and 5 UEs of the 10 UEs who have succeeded by the RA are connected by RRC. To summarize these matters is as Table 1 below.

Table 1

The eNB periodically checks whether the wireless communication network is congested, and if congestion occurs, determines whether the congestion is caused by RA of a plurality of LP devices. Specifically, the eNB determines whether the congestion has occurred due to RA of a plurality of LP devices using Equation 1 below.

Equation 1

As shown in Equation 1, the eNB calculates a congestion value by dividing the number of RRC connected LP devices by the sum of the number of RRC connected LP devices and the number of RRC connected UEs, and divides the calculated congestion value into a preset threshold. Compare with the value ρ _th (= 0.8). And, when the congestion value is more than the ρ _th , the eNB determines that the congestion is caused by the RA of a plurality of LP devices.

In the embodiment of FIG. 2, the congestion value corresponds to the number of RRC connected LP devices 50, the number of RRC connected LP devices 50, the number of UEs in the RRC connected preamble group A 200, and the RRC connected preamble group B 210. It is calculated by dividing by the sum of the number of UEs 5). That is, the congestion value is

It is calculated as

The calculated congestion value is 0.86, which is greater than 0.8, the ρ _th . Accordingly, in FIG. 2, the eNB determines that congestion has occurred due to RAs of a plurality of LP devices, and performs an operation for the congestion value to have a value smaller than ρ _th .

In order for the congestion value to have a value smaller than ρ _th , the number of ①, that is, the number of RRC connected LP devices must be reduced. To this end, the eNB reduces the size of the preamble group A 200 to limit the access of the LP device. That is, the eNB reduces the number of preambles included in the preamble group A 200 until the congestion value is smaller than ρ _th . For example, the eNB may reduce the number of preambles included in the preamble group A 200 to be half (1/2) of the previously set number.

On the other hand, the eNB is configured to preset the number of preambles included in the preamble group A (200) when the congestion is resolved or when the congestion situation is not due to the LP device, that is, the congestion value is smaller than the ρ _th. Continue increasing by a constant C. For example, when the preset constant C is 5, the number of preambles included in the preamble group A 200 is increased by five. This method is similar to the Adaptive Increase / Multicative Decrease (AIMD) method used for TCP Congestion Window Size control.

When the size of the preamble group A 200 is adjusted as described above, the eNB enables the UEs using the preambles included in the preamble group A 200 to use the preambles included in the preamble group B 210. The group selection criterion information for the A 200 is changed.

The UE receives a system information block (hereinafter referred to as 'system information') from the eNB and selects a preamble group based on group selection criteria information for the preamble group A included in the received system information. The group selection criterion information for the preamble group A includes uplink message size information corresponding to the preamble group A (hereinafter, referred to as 'MessgeSizeGroupA'). The MessgeSizeGroupA is set to a value of '56 bits, 144 bits, 208 bits, or 256 bits', and UEs selecting the preamble group A 200 are determined according to the MessgeSizeGroupA value. For example, when MessgeSizeGroupA is set to 56 bits, the UE having an uplink message size of 56 bits or less selects the preamble group A 200.

In an embodiment of the present invention, when congestion by the LP device occurs, the eNB changes the value of the MessgeSizeGroupA to a value smaller than the currently set value. For example, when the currently set value of the MessgeSizeGroupA is 208 bits, the eNB changes the value of the MessgeSizeGroupA to 144 bits.

And, when congestion by the LP device does not occur, the eNB changes the value of the MessgeSizeGroupA to a value larger than the currently set value. For example, the eNB changes the MessgeSizeGroupA to 256 bits when the currently set value of the MessgeSizeGroupA is 208 bits.

As described above, when the information on the number of preambles included in the preamble group A and the group selection criterion information for the preamble group A are changed, the eNB broadcasts the system information including the changed information.

Hereinafter, a signal flow between a UE and an eNB for controlling congestion in an LTE communication system according to an embodiment of the present invention will be described with reference to FIG. 3.

3 is a signal flowchart of a UE and an eNB for controlling congestion in a wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, in step 320, the eNB 300 includes uplink message size information (MessgeSizeGroupA) for preamble group A and preamble number information included in preamble group A (hereinafter, referred to as 'SizeOfRA_PreablesGroupA'). Send information to the UE 310.

The UE 310 selects a preamble group using MessgeSizeGroupA, SizeOfRA_PreablesGroupA, etc. included in the system information, and selects one of the preambles included in the selected preamble group in step 330. In operation 340, the UE 310 transmits the selected preamble to the eNB 300 to perform RA.

If it is determined in step 350 that congestion by the LP device has occurred, the eNB 300 updates system information by changing the MessgeSizeGroupA and SizeOfRA_PreablesGroupA. In addition, the eNB 300 broadcasts the updated system information in step 360.

Hereinafter, the operation of the eNB 300 in step 350 will be described in detail with reference to FIG. 4.

4 is a flowchart illustrating an operation of an eNB for controlling congestion of a RACH in a wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, in step 400, the eNB determines whether congestion has occurred in the RA process. As an example, the eNB may determine that congestion has occurred when the total number of devices that have succeeded in RA during 100 ms is 16 or more (that is, 16 machines / 100 ms (= 10,000 machines / 60 sec)).

When the congestion does not occur, the eNB terminates the process of FIG. 4 and performs a general RA process. When the congestion occurs, the eNB determines whether the congestion has occurred by a plurality of LP devices in step 410. Since the eNB cannot distinguish between the LP device and the UE in the RA process, whether the congestion by a plurality of LP devices is generated using the number of RRC connected LP devices and the number of UEs in the RRC connected preamble groups A and B has occurred. To judge.

In other words, if the eNB is not less than, RRC threshold number and the value divided by the sum of the number of connected UE preset RRC of the LP device to be connected to RRC of the associated LP device ρ _th, as described above in equation (1), wherein the congestion It is determined that it is caused by a number of LP devices.

If it is determined that the congestion has occurred due to the plurality of LP devices, the eNB proceeds to step 420 to decrease the value of SizeOfRA_PreablesGroupA. That is, the eNB reduces the number of preambles included in the preamble group A and sets the eNB to the value of SizeOfRA_PreablesGroupA. For example, the eNB may change the value of SizeOfRA_PreambleGroupA to half the value previously set (that is, SizeOfRA_PreambleGroupA = SizeOfRA_PreambleGroupA / 2). Here, when the changed value of SizeOfRA_PreambleGroupA is less than 1, the eNB sets the value of SizeOfRA_PreambleGroupA to 1.

If the value of SizeOfRA_PreambleGroupA is decreased as described above, the eNB proceeds to step 430 to decrease the value of MessgeSizeGroupA. That is, the eNB changes the value of the MessgeSizeGroupA to a value smaller than the currently set value. For example, the eNB changes the value of the MessgeSizeGroupA to 144 bits when the currently set value of the MessgeSizeGroupA is 208 bits.

On the other hand, if it is determined in step 410 that the congestion is not caused by a plurality of LP devices, the eNB proceeds to step 440 to increase the value of SizeOfRA_PreablesGroupA. That is, the eNB increases the number of preambles included in preamble group A and sets the value to the value of SizeOfRA_PreablesGroupA.

For example, the eNB increases the value of SizeOfRA_PreambleGroupA by a predetermined constant (for example, when the predetermined constant is 5, SizeOfRA_PreambleGroupA = SizeOfRA_PreambleGroupA + 5). When the value of the SizeOfRA_PreambleGroupA exceeds the total number of preambles allocated for preamble groups A and B (for example, corresponding to 54 bits), the eNB sets the value of SizeOfRA_PreambleGroupA to the number of the total preambles (ie, Number corresponding to 54 bits).

In step 450, the eNB increases the value of MessgeSizeGroupA. That is, the eNB changes the value of the MessgeSizeGroupA to a value larger than the currently set value. As an example, the eNB changes the value of the MessgeSizeGroupA to 256 bits when the currently set value of the MessgeSizeGroupA is 208 bits. The eNB maintains the value of MessgeSizeGroupA as 256 bits when the currently set value of MessgeSizeGroupA is 256 bits, which is the largest value among the values that can be set as the value of MessgeSizeGroupA.

Next, the operation of the UE according to an embodiment of the present invention will be described with reference to FIG. 5.

5 is a flowchart illustrating an operation of a UE performing RA in a wireless communication system.

Referring to FIG. 5, in step 500, a UE receives system information including SizeOfRA_PreambleGroupA, MessageSizeGroupA, etc. from an eNB. In the embodiment of FIG. 5, as an example, the value of SizeOfRA_PreambleGroupA is 20 and the value of MessageSizeGroupA is set to 144 bits. The case in which the uplink message size of the UE is 144 bits will be described as an example.

In step 502, the UE selects a preamble group based on the system information, and selects one of the preambles included in the selected preamble group. The UE determines that the preamble group A should be selected when the uplink message size is 144 bits or less based on the value of the MessageSizeGroupA set to 144 bits.

The UE selects preamble group A according to its uplink message size (144 bits). Subsequently, the UE determines that preamble group A includes 20 preambles based on the value of SizeOfRA_PreambleGroupA set to 20, and selects one of the 20 preambles. In operation 504, the UE transmits the selected preamble to the eNB to perform RA.

When the UE fails due to congestion due to RAs of a plurality of LP devices, the UE receives updated system information from the eNB in step 506. Values of SizeOfRA_PreambleGroupA and MessageSizeGroupA included in the updated system information are smaller than values of SizeOfRA_PreambleGroupA and MessageSizeGroupA respectively included in the system information received in step 500. For example, values of SizeOfRA_PreambleGroupA and MessageSizeGroupA included in the updated system information may be set to 10 and 56 bits, respectively.

In step 508, the UE selects a preamble group based on the updated system information and selects one of the preambles included in the selected preamble group. The UE determines that the preamble group A should be selected when the uplink message size is 56 bits or less based on the value of the MessageSizeGroupA set to 56 bits. The UE selects another preamble group (eg, preamble group B) other than preamble group A according to its uplink message size (56 bits). The UE selects one of the preambles included in the selected preamble group. In step 510, the UE performs an RA procedure using the selected preamble.

Hereinafter, a configuration of an eNB according to an embodiment of the present invention will be described with reference to FIG. 6.

6 is a block diagram of an eNB for controlling congestion of RACH in a wireless communication system according to an embodiment of the present invention.

The eNB includes a controller 600, a transmitter 610, a receiver 620, and a memory 630.

The controller 600 controls the overall operation of the eNB by controlling the transmitter 610, the receiver 620, and the memory 630.

The controller 600 determines whether congestion has occurred in the RA process based on the number of UEs that have succeeded in RA. The controller 600 performs a general RA process when congestion does not occur. In addition, when the congestion occurs, the controller 600 determines whether the congestion has occurred by the LP device. If the value obtained by dividing the number of RRC connected LP devices by the sum of the number of RRC connected LP devices and the number of RRC connected UEs is greater than or equal to a predetermined threshold value ρ _th , the congestion may be caused by a plurality of LP devices. To judge.

If it is determined that the congestion is caused by a plurality of LP devices, the controller 600 decreases the values of SizeOfRA_PreablesGroupA and MessgeSizeGroupA. That is, the eNB reduces the number of preambles included in the preamble group A and sets the eNB to the value of SizeOfRA_PreablesGroupA. The controller 600 changes the value of the MessgeSizeGroupA to a value smaller than the currently set value. The controller 600 updates the system information to include the updated SizeOfRA_PreablesGroupA and MessgeSizeGroupA, and broadcasts the updated system information through the transmitter 610.

On the other hand, if it is determined that the congestion is not caused by a plurality of LP devices, the controller 600 increases the values of SizeOfRA_PreablesGroupA and MessgeSizeGroupA. That is, the controller 600 increases the number of preambles included in the preamble group A and sets the value to the value of SizeOfRA_PreablesGroupA. The controller 600 changes the value of the MessgeSizeGroupA to a value larger than the currently set value. The controller 600 updates the system information to include the updated SizeOfRA_PreablesGroupA and MessgeSizeGroupA, and broadcasts the updated system information through the transmitter 610.

The transmitter 610 and the receiver 620 are components for communicating with the LP device and the UE. The transmitter 610 broadcasts initial system information and the updated system information under the control of the controller 600. The receiver 620 receives messages transmitted for preamble and RRC connection from the LP device and the UE.

The memory 630 stores values of SizeOfRA_PreablesGroupA and MessgeSizeGroupA included in system information under the control of the controller 600.

Next, a configuration of a UE according to an embodiment of the present invention will be described with reference to FIG. 7.

7 is a block diagram of a UE performing RA in a wireless communication system according to an embodiment of the present invention.

The UE includes a controller 700, a transmitter 710, a receiver 720, and a memory 730.

The controller 700 controls the overall operation of the UE by controlling the transmitter 710, the receiver 720, and the memory 730.

The controller 700 receives system information including SizeOfRA_PreambleGroupA, MessageSizeGroupA, etc. from the eNB through the receiver 720. The controller 700 selects a preamble group based on the system information, and selects one of the preambles included in the selected preamble group. Subsequently, the controller 700 controls the transmitter 710 to transmit the selected preamble to the eNB for the RA.

If the controller 700 fails due to congestion due to RA of the LP device, the controller 700 receives updated system information from the eNB. Values of SizeOfRA_PreambleGroupA and MessageSizeGroupA included in the updated system information have smaller values than previously set values.

The controller 700 selects a preamble group based on the updated system information, and selects one of the preambles included in the selected preamble group. Subsequently, the controller 700 performs the RA process using the selected preamble.

The transmitter 710 and the receiver 720 are components for performing communication with the eNB. The transmitter 710 transmits messages for the selected preamble and RRC connection to the eNB under the control of the controller 700. In addition, the receiver 720 receives initial system information and updated system information from the eNB.

The memory 730 stores values of SizeOfRA_PreablesGroupA and MessgeSizeGroupA, selected preamble group information, preamble information, and the like included in the received system information under the control of the controller 700.

As described above, in the embodiment of the present invention, when RACH congestion occurs by the LP device, connection of the LP device is limited by reducing the number of preambles included in the preamble group used by the LP device. Accordingly, in the embodiment of the present invention, congestion in the RACH affecting the UE can be minimized, and the probability of success of the LP device can be lowered by reducing the number of preambles used by the LP device. In addition, in order to prevent the UE from using the preamble of the preamble group A used by the LP device from lowering the probability of success, the UE using the preamble included in the preamble group A performs the preamble of the preamble group B when the next RA is performed. Change the group selection criteria for preamble group A to use.

As described above, the process of reducing the preamble number of the preamble group used by the LP device and changing the group selection criterion of the preamble group is continuously performed until congestion in the RACH is resolved. In the embodiment of the present invention, when congestion in the RACH is resolved, the number of preambles of the preamble group used by the LP device is increased again, and the connection success probability of the LP device is increased while changing the group selection criteria of the preamble group again. .

Hereinafter, the congestion control result of the RACH in the wireless communication system according to an embodiment of the present invention will be described with reference to FIG. 8.

8 (a) is a view showing the number of RA successful devices before the RACH congestion control method according to an embodiment of the present invention, Figure 8 (b) is a RACH congestion control method according to an embodiment of the present invention It is a figure which shows the number of RA successful devices after being used.

As shown in FIGS. 8A and 8B, as the RACH congestion control method according to an embodiment of the present invention is used, the number of RA successful LP devices is reduced from 100 to 50, and the preamble group The number of UEs using the preamble of A 800 has been reduced from five to three. In contrast, the number of UEs using the preamble of the preamble group B 810 was increased from 10 to 12, and the total number of UEs that succeeded in RA was before (5 + 10 = 15) and after use of the RACH congestion control method. 3 + 12 = 15) remained unchanged.

Specific simulation results are as follows.

In order to compare the performance analysis before and after using the RACH congestion control method according to an embodiment of the present invention, the number of UEs and the number of collisions for which the RA succeeded for 60 seconds were analyzed. The sum of the uplink message sizes indicates the transmission message sizes of UEs that have succeeded in RA. The transmission message size represents a cumulative value of 'msg3'. The msg3 is a message indicating that the UE has received an RA response after the preamble is transmitted to the eNB without collision. The eNB performs uplink resource allocation using the sum of the uplink message sizes.

In the simulation, the ratio of the number of LP devices to the number of UEs is set to 9: 1 to assume that there are a large number of LP devices. In other words, it is assumed that 90% of all devices are LP devices. In this environment, the experiment was repeated 100 times for 60 seconds for the total number of devices 5000 and 10000 to obtain the average value.

Table 2 below shows the results of repeating the experiment 100 times for 60 seconds for all 5000 devices when the RACH congestion control method according to the embodiment of the present invention is not used.

TABLE 2

In addition, Table 3 below shows the results of repeating the experiment 100 times for 60 seconds for all 5000 devices when the RACH congestion control method according to an embodiment of the present invention is used.

TABLE 3

In addition, Table 4 below shows the results of repeating the experiment 100 times for 60 seconds for all 10000 devices when the RACH congestion control method according to an embodiment of the present invention is not used.

Table 4

In addition, Table 5 below shows the results of repeating the experiment 100 times for 60 seconds for all 10,000 devices when the RACH congestion control method according to an embodiment of the present invention is used.

Table 5

As shown in Table 2 to Table 5, when the RACH congestion control method according to an embodiment of the present invention is used, the number of LP devices with RA success is reduced. Instead, the number of UEs using the preamble of the preamble group A 800 is drastically reduced, and the number of UEs using the preamble of the preamble group B 810 is increased. When the RACH congestion control method according to the embodiment of the present invention is used, more preamble collisions are generated in the preamble group A 800, so that a larger number of UEs can use the preamble included in the preamble group B 810. This is the result.

On the other hand, when the RACH congestion control method according to an embodiment of the present invention is used, the sum of the uplink message sizes of each UE is increased. Increasing the sum of the uplink message sizes indicates that the eNB has allocated more bits as uplink resources to each UE, and that each UE has sent more bits of messages, resulting in a lower degree of congestion on the RACH. It can be seen.

As described above, according to an embodiment of the present invention, when congestion occurs by a plurality of LP devices, there is an advantage of reducing congestion of the RACH by reducing the connection of the LP device. On the other hand, the RACH congestion control method and apparatus according to an embodiment of the present invention can reduce the number of LP devices connected to the MME when the overload occurs in the MME is used to solve the MME overload problem, etc. It is also possible.

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

Claims

Random Access Channel (RACH) of a base station in a wireless communication system including at least one user equipment (UE) and a plurality of devices (Device) using the same wireless communication network as the at least one UE In a congestion control method,

Determining whether congestion occurs on the RACH due to random access of the plurality of devices;

Changing system information such that when congestion occurs on the RACH, the number of UEs using one of the preambles included in the first preamble group is reduced;

And broadcasting the changed system information.

Wherein the first preamble group is a preamble group including preambles used by the plurality of devices among a plurality of preamble groups.
The method of claim 1,

Determining whether congestion occurs on the RACH due to random access of the plurality of devices,

And determining whether congestion has occurred on the RACH by using the number of devices wirelessly connected to the base station and the number of UEs wirelessly connected to the base station.
The method of claim 2,

Determining whether congestion occurs on the RACH due to random access of the plurality of devices,

Calculating a congestion value by dividing the number of devices wirelessly connected to the base station by the sum of the number of devices wirelessly connected to the base station and the number of UEs wirelessly connected to the base station;

Comparing the calculated congestion value with a preset threshold value;

And determining whether congestion has occurred on the RACH based on the comparison result.
The method of claim 1,

The process of changing the system information,

In order to reduce the number of UEs using one of the preambles included in the first preamble group, information on the number of preambles included in the first preamble group included in the system information and group selection criteria for the first preamble group A congestion control method comprising the step of changing information.
The method of claim 1,

The process of changing the system information,

Changing the information on the number of preambles included in the first preamble group to a value smaller than a previously set value;

And changing uplink transmission message size information used as group selection criterion information for the first preamble group to a value smaller than a previously set value.
The method of claim 1,

If congestion does not occur on the RACH due to random access of the plurality of devices, changing and broadcasting system information to increase the number of UEs using one of the preambles included in the first preamble group Congestion control method further comprising.
The method of claim 6,

The process of changing the system information to increase the number of UEs using the preamble included in the first preamble group,

Changing information about the number of preambles included in the first preamble group included in the system information and group selection criterion information for the first preamble group so that the number of UEs using the preamble included in the first preamble group is increased. Congestion control method comprising the process.
The method of claim 6,

The process of changing the system information to increase the number of UEs using the preamble included in the first preamble group,

Changing the information on the number of preambles included in the first preamble group to a value greater than a previously set value;

And changing uplink transmission message size information used as group selection criterion information for the first preamble group to a value larger than a previously set value.
The method of claim 1,

If congestion does not occur on the RACH due to random access of the plurality of devices, the number of preambles included in the first preamble group is increased, and system information including information about the increased number of preambles is broadcast. Congestion control method further comprising the process of casting.
Congestion of a random access channel (RACH) in a wireless communication system including at least one user equipment (UE) and a plurality of devices using the same wireless communication network as the at least one UE In the base station for controlling the,

It is determined whether congestion occurs on the RACH due to random access of the plurality of devices, and when congestion occurs on the RACH, the number of UEs using one of the preambles included in the first preamble group is reduced. A control unit for changing system information,

And a transmitter for broadcasting the changed system information under the control of the controller.

And the first preamble group is a preamble group including preambles used by the plurality of devices among a plurality of preamble groups.
The method of claim 10,

The controller determines whether congestion has occurred on the RACH by using the number of devices wirelessly connected to the base station and the number of UEs wirelessly connected to the base station.
The method of claim 11,

The controller calculates a congestion value by dividing the number of devices wirelessly connected with the base station by the sum of the number of devices wirelessly connected with the base station and the number of UEs wirelessly connected with the base station, and calculating the congestion value in advance. And compare with a threshold and determine whether congestion has occurred on the RACH based on the comparison result.
The method of claim 10,

The controller may provide information about the number of preambles included in the first preamble group included in the system information and the first preamble group so that the number of UEs using one of the preambles included in the first preamble group is reduced. A base station characterized by changing the group selection criteria information.
The method of claim 10,

The control unit changes the number information of the preambles included in the first preamble group to a value smaller than a previously set value so that the number of UEs using one of the preambles included in the first preamble group is reduced. And a base station for changing uplink transmission message size information used as group selection criterion information for one preamble group to a value smaller than a previously set value.
The method of claim 10,

When the congestion does not occur on the RACH due to the random access of the plurality of devices, the control unit changes the system information so that the number of UEs using one of the preambles included in the first preamble group is increased so that the transmitting unit changes. A base station characterized by broadcasting through.
The method of claim 15,

The controller may include information about the number of preambles included in the first preamble group included in the system information and a group of the first preamble group so that the number of UEs using one of the preambles included in the first preamble group is increased. A base station characterized by changing the selection criteria information.
The method of claim 15,

The control unit changes the number information of the preambles included in the first preamble group to a value larger than a previously set value such that the number of UEs using one of the preambles included in the first preamble group is increased. And a base station for changing uplink transmission message size information used as group selection criterion information for one preamble group to a value larger than a previously set value.
The method of claim 10,

The controller increases the number of preambles included in the first preamble group when no congestion occurs on the RACH due to random access of the plurality of devices, and includes the information on the increased number of preambles. And broadcasts information through the transmitter.