WO2015174745A1

WO2015174745A1 - Method for performing random access procedure in mtc device

Info

Publication number: WO2015174745A1
Application number: PCT/KR2015/004821
Authority: WO
Inventors: 어베이카네스 아브라함; 정성훈
Original assignee: 엘지전자 주식회사
Priority date: 2014-05-14
Filing date: 2015-05-14
Publication date: 2015-11-19

Abstract

According to an embodiment of the present specification, a method for performing a random access procedure in a machine type communication (MTC) device is provided. The method may comprise the steps of: when a random access procedure is triggered, determining, by the MTC device, a maximum delay tolerance value T on the basis of the type of the MTC device and the type of a service by which the random access procedure has been triggered; determining a tolerance factor Tf on the basis of the maximum delay tolerance value T; selecting, on the basis of the tolerance factor Tf, a radio frame in which to transmit a random access preamble; and transmitting the random access preamble in the selected radio frame.

Description

How to perform a random access procedure on your MTC device

The present invention relates to wireless communication, and more particularly, to Machine Type Communication (MTC).

The 3rd Generation Partnership Project (3GPP) long term evolution (LTE), an improvement of the Universal Mobile Telecommunications System (UMTS), is introduced as a 3GPP release 8. 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) in uplink. A multiple input multiple output (MIMO) with up to four antennas is employed. Recently, a discussion on 3GPP LTE-Advanced (LTE-A), an evolution of 3GPP LTE, is underway.

On the other hand, in recent years, there has been an active research on the communication which occurs between devices or between devices and servers without human interaction, that is, without human intervention, that is, machine type communication (MTC). As such, MTC is expected to use lower traffic than human to human communication.

However, since MTC devices may exist individually for each service and use, a huge number of MTC devices may be located in the coverage of the base station.

This can cause network congestion.

Disclosure of the Invention It is an object of the present disclosure to solve the above problems.

In order to achieve the above object, according to an embodiment of the present disclosure, a method of performing a random access procedure in a machine type communication (MTC) device is provided. The method includes determining, when the random access procedure is triggered, the MTC device based on its type and the type of service that triggered the random access procedure; Determining a tolerance factor Tf based on the maximum delay tolerance T value; Selecting a radio frame to transmit a random access preamble based on the tolerance factor Tf; The method may include transmitting a random access preamble on the selected radio frame.

The method may further comprise obtaining a network load interworking N value. Here, the tolerance factor Tf may be determined based on the maximum delay tolerance T value and the network load interworking N value.

The radio frame may be determined in consideration of a UEID indicating an identifier of the MTC device, the allowance factor Tf, and a radio frame number (SFN).

The determined radio frame may be a radio frame satisfying UEID mod Tf = SFN mod Tf.

The method includes calculating a random wait time Wdt when the transmission of the random access preamble is not successful; After waiting for the calculated random waiting time Wdt, the method may further include transmitting a random access preamble.

The transmitting of the random access preamble includes: if the transmission of the random access preamble is not successful, waiting for a backoff time; The method may include waiting for the random waiting time Wdt.

In order to achieve the above object, according to one embodiment of the present specification, a machine type communication (MTC) device performing a random access procedure is provided. When the MTC device triggers a random access procedure, the MTC device determines a maximum delay tolerance T value based on its type and the type of service that triggered the random access procedure, and based on the maximum delay tolerance T value. A processor that determines a tolerance factor Tf and then selects a radio frame to transmit a random access preamble based on the tolerance factor Tf; It may include a transceiver for transmitting a random access preamble on the selected radio frame.

According to one disclosure of the present specification, a problem of the prior art is solved.

1 shows a wireless communication system to which the present invention is applied.

FIG. 2 is a block diagram illustrating a radio protocol architecture for a user plane.

3 is a block diagram illustrating a radio protocol structure for a control plane.

4 illustrates an operation of a UE and a base station in a contention based random access procedure.

5 illustrates an operation of a UE and a base station in a non-contention based random access procedure.

6 illustrates an example of machine type communication (MTC).

7 is a flowchart illustrating a method according to one disclosure of the present specification.

8 is a flowchart illustrating a method according to another disclosure of the present specification.

9 shows an example in which approaches according to the disclosures of the present disclosure have been applied.

10 is a block diagram illustrating a wireless communication system in which an embodiment of the present invention is implemented.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments, and are not intended to limit the present invention. In addition, the technical terms used in the present specification should be interpreted as meanings generally understood by those skilled in the art unless they are specifically defined in this specification, and are overly inclusive. It should not be interpreted in the sense of or in the sense of being excessively reduced. In addition, when the technical terms used herein are incorrect technical terms that do not accurately represent the spirit of the present invention, it should be replaced with technical terms that can be understood correctly by those skilled in the art. In addition, the general terms used in the present invention should be interpreted as defined in the dictionary or according to the context before and after, and should not be interpreted in an excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In the present application, terms such as “consisting of” or “comprising” should not be construed as necessarily including all of the various components, or various steps described in the specification, wherein some of the components or some of the steps It should be construed that it may not be included or may further include additional components or steps.

In addition, terms including ordinal numbers, such as first and second, as used herein may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When a component is said to be "connected" or "connected" to another component, it may be directly connected or connected to that other component, but there may be other components in between. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof is omitted. In addition, it should be noted that the accompanying drawings are only for easily understanding the spirit of the present invention and should not be construed as limiting the spirit of the present invention by the accompanying drawings. The spirit of the present invention should be construed to extend to all changes, equivalents, and substitutes in addition to the accompanying drawings.

Hereinafter, although a terminal is shown in the figure, the terminal may include a user equipment (UE), a mobile equipment (ME), a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device (Wireless Device), It may be called a handheld device or an access terminal (AT). The terminal may be a portable device having a communication function such as a mobile phone, a PDA, a smart phone, a wireless modem, a laptop, or the like, or a non-portable device such as a PC or a vehicle-mounted device. .

This may also be called an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN), or Long Term Evolution (LTE) / LTE-A system.

The E-UTRAN includes a base station (BS) 20 that provides a control plane and a user plane to a user equipment (UE) 10. The UE 10 may be fixed or mobile and may have other terms such as terminal, user terminal (UT), mobile station (MS), subscriber station (SS), mobile terminal (MT), and wireless device (Wireless Device). Can be referred to as The base station 20 refers to a fixed station communicating with the UE 10, and may be referred to in other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like.

The base stations 20 may be connected to each other through an X2 interface. The base station 20 is connected to a Serving Gateway (S-GW) through an MME (Mobility Management Entity) and an S1-U through an Evolved Packet Core (EPC) 30, more specifically, an S1-MME through an S1 interface.

EPC 30 is composed of MME, S-GW and P-GW (Packet Data Network-Gateway). The MME has information about the UE's access information or the UE's capability, and this information is mainly used for mobility management of the UE. S-GW is a gateway having an E-UTRAN as an endpoint, and P-GW is a gateway having a PDN as an endpoint.

Layers of the Radio Interface Protocol between the UE and the network are based on the lower three layers of the Open System Interconnection (OSI) reference model, which are well known in communication systems. L2 (second layer), L3 (third layer) can be divided into the physical layer belonging to the first layer of the information transfer service (Information Transfer Service) using a physical channel (Physical Channel) is provided, The RRC (Radio Resource Control) layer located in the third layer plays a role of controlling radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the base station.

FIG. 2 is a block diagram illustrating a radio protocol architecture for a user plane. 3 is a block diagram illustrating a radio protocol structure for a control plane.

The data plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

2 and 3, a physical layer (PHY) layer provides an information transfer service to a higher layer using a physical channel. The physical layer is connected to a medium access control (MAC) layer, which is an upper layer, through a transport channel. Data is moved between the MAC layer and the physical layer through the transport channel. Transport channels are classified according to how and with what characteristics data is transmitted over the air interface.

Data moves between physical layers between physical layers, that is, between physical layers of a transmitter and a receiver. The physical channel may be modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes time and frequency as radio resources.

The functions of the MAC layer include mapping between logical channels and transport channels and multiplexing / demultiplexing into transport blocks provided as physical channels on transport channels of MAC service data units (SDUs) belonging to the logical channels. The MAC layer provides a service to a Radio Link Control (RLC) layer through a logical channel.

Functions of the RLC layer include concatenation, segmentation, and reassembly of RLC SDUs. In order to guarantee the various Quality of Service (QoS) required by the radio bearer (RB), the RLC layer has a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (Acknowledged Mode). Three modes of operation (AM). AM RLC provides error correction through an automatic repeat request (ARQ).

Functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include delivery of user data, header compression, and ciphering. The functionality of the Packet Data Convergence Protocol (PDCP) layer in the user plane includes the transfer of control plane data and encryption / integrity protection.

The RRC (Radio Resource Control) layer is defined only in the control plane. The RRC layer is responsible for the control of logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers. RB refers to a logical path provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, PDCP layer) for data transmission between the user equipment (UE) and the network.

The establishment of the RB means a process of defining characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and operation method. RB can be further divided into SRB (Signaling RB) and DRB (Data RB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

If an RRC connection is established between the RRC layer of the UE (UE) and the RRC layer of the E-UTRAN, the UE is in an RRC connected state (or referred to as RRC connected mode). In this case, it is in an RRC idle state (or RRC idle mode).

Downlink transmission channels for transmitting data from the network to the UE include a broadcast channel (BCH) for transmitting system information and a downlink shared channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, uplink transport channels for transmitting data from a UE to a network include a random access channel (RACH) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or control messages.

It is located above the transport channel, and the logical channel mapped to the transport channel is a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic (MTCH). Channel).

The physical channel is composed of several OFDM symbols in the time domain and several sub-carriers in the frequency domain. One sub-frame consists of a plurality of OFDM symbols in the time domain. The RB is a resource allocation unit and includes a plurality of OFDM symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific OFDM symbols (eg, the first OFDM symbol) of the corresponding subframe for the physical downlink control channel (PDCCH), that is, the L1 / L2 control channel. Transmission Time Interval (TTI) is a unit time of subframe transmission.

Hereinafter, the RRC state and the RRC connection method of the UE will be described in detail.

RRC state refers to whether or not the RRC layer of the UE is in logical connection with the RRC layer of the E-UTRAN.If connected, the RRC connected state, if not connected, is RRC idle. This is called the RRC idle state. Since the UE in the RRC connected state has an RRC connection, the E-UTRAN can grasp the existence of the corresponding UE in a cell unit, and thus can effectively control the UE. On the other hand, the UE in the RRC idle state cannot be identified by the E-UTRAN, and is managed by the core netwrok (CN) in units of a tracking area, which is a larger area than a cell. That is, the UE in the RRC idle state is identified only in a large area unit, and must move to the RRC connected state in order to receive a normal mobile communication service such as voice or data.

When a user first powers up a UE, the UE first searches for an appropriate cell and then stays in an RRC idle state in that cell. When the UE in the RRC idle state needs to establish an RRC connection, the UE establishes an RRC connection with the E-UTRAN through an RRC connection procedure and transitions to the RRC connected state. There are several cases where a UE in RRC idle state needs to establish an RRC connection. For example, an upstream data transmission is necessary due to a user's call attempt, or a paging message is sent from E-UTRAN. If received, a response message may be sent.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

In order to manage the mobility of the UE in the NAS layer, two states are defined, EMM-REGISTERED (EPS Mobility Management-REGISTERED) and EMM-DEREGISTERED, which are applied to the UE and the MME. The initial UE is in an EMM-DEREGISTERED state, and the UE performs a process of registering with the corresponding network through an initial attach procedure in order to access the network. If the attach procedure is successfully performed, the UE and the MME enter the EMM REGISTERED state.

In order to manage a signaling connection between the UE and the EPC, two states are defined, an EPS Connection Management (ECM) -IDLE state and an ECM-CONNECTED state, and these two states apply to the UE and the MME. When the UE in the ECM-IDLE state makes an RRC connection with the E-UTRAN, the UE is in the ECM-CONNECTED state. The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes an S1 connection with the E-UTRAN. When the UE is in the ECM-IDLE state, the E-UTRAN does not have context information of the UE. Accordingly, the UE in the ECM-IDLE state performs UE-based mobility related procedures such as cell selection procedure or cell reselection procedure without the need of a network command. In this case, the cell selection procedure means that the UE selects a cell to access a network service. The cell reselection procedure means finding the best cell that can be configured as a serving cell.

On the other hand, when the UE is in the ECM-CONNECTED state, the mobility of the UE is managed by the command of the network. In the ECM-IDLE state, if the location of the UE is different from the location known by the network, the UE informs the network of the location of the UE through a tracking area update procedure.

The following is a description of system information.

The system information includes essential information that the UE needs to know in order to connect to the base station. Therefore, the UE must receive all system information before accessing the base station, and must always have the latest system information. And since the system information is information that every UE in a cell should know, the base station periodically transmits the system information.

According to Section 5.2.2 of 3GPP TS 36.331 V8.7.0 (2009-09) "Radio Resource Control (RRC); Protocol specification (Release 8)", the system information includes a master information block (MIB) and a scheduling block (SB). It is divided into SIB (System Information Block). The MIB allows the UE to know the physical configuration of the cell, such as bandwidth. SB informs transmission information of SIBs, for example, a transmission period. SIB is a collection of related system information. For example, some SIBs contain only information of neighboring cells, and some SIBs contain only information of an uplink radio channel used by the UE.

The base station transmits a call message to inform the UE whether to change the system information. In this case, the call message includes a system information change indicator. The UE receives the call message according to the paging DRX, and if the call message includes the system information change indicator, receives the system information transmitted through the logical channel BCCH.

In an LTE system, a base station allocates a designated random access preamble to a specific UE, and the UE provides a non-competitive random access procedure for performing a random access procedure with the random access preamble. In other words, in the process of selecting a random access preamble, a contention based random access procedure in which a UE selects one randomly within a specific set and a random access preamble allocated by a base station only to a specific UE are used. There is a non-contention based random access procedure. The difference between the two random access processes is whether a collision problem occurs due to contention, which will be described later. The non- contention based random access procedure may be used only when requested by the handover process or the command of the base station described above.

Hereinafter, the illustrated step S410 will be described. In contention-based random access, a UE selects one random access preamble randomly from a set of random access preambles indicated by system information or a handover command, and transmits the random access preamble. Select to send.

Hereinafter, the illustrated step S420 will be described. After transmitting the random access preamble as described above, the UE attempts to receive its random access response within the random access response reception window indicated by the base station through system information or a handover command. In more detail, the random access response information is transmitted in the form of MAC PDU, and the MAC PDU is transmitted in PDSCH. In addition, the PDCCH is also delivered to the UE to properly receive the information delivered to the PDSCH. That is, the PDCCH includes information of a UE that should receive the PDSCH, frequency and time information of radio resources of the PDSCH, a transmission format of the PDSCH, and the like. Once the UE succeeds in receiving the PDCCH coming to it, it properly receives the random access response sent to the PDSCH according to the information of the PDCCH. The random access response includes a random access preamble identifier (ID), a UL Grant (uplink radio resource), a Temporary C-RNTI (temporary cell identifier), and a Time Alignment Command. The reason why the random access preamble discriminator is needed is that since one random access response may include random access response information for one or more UEs, indicating to which UE the UL Grant, Temporary C-RNTI and the TAC are valid. It is for. The random access preamble identifier corresponds to the random access preamble selected by the user in step 1.

Hereinafter, the illustrated step S430 will be described. When the UE receives a valid random access response to the UE, it processes each of the information included in the random access response. That is, the UE applies the TAC and stores the Temporary C-RNTI. In addition, by using the UL Grant, data stored in the buffer of the UE or newly generated data is transmitted to the base station. Once among the data included in the UL Grant, an identifier of the UE must be included essentially. This is because, in the contention-based random access procedure, it is not possible to determine which UEs perform the random access procedure in the base station, since the UE needs to be identified for future collision resolution. In addition, there are two methods for including the identifier of the UE. In the first method, if the UE already has a valid cell identifier assigned to the cell before the random access procedure, the UE transmits its cell identifier through the UL Grant. On the other hand, if a valid cell identifier has not been allocated before the random access procedure, the UE transmits its own unique identifier (eg, S-TMSI or Random Id). In general, the unique identifier is longer than the cell identifier. If the UE has transmitted data through the UL Grant, the UE starts a contention resolution timer.

Hereinafter, the illustrated step S440 will be described. After the UE transmits data including its identifier through the UL Grant included in the random access response, it waits for an indication of the base station to resolve the collision. That is, it attempts to receive a PDCCH to receive a specific message. There are two methods for receiving the PDCCH. As mentioned above, when its identifier transmitted through the UL Grant is a cell identifier, an attempt is made to receive a PDCCH using its cell identifier, and when the identifier is a unique identifier, it is included in the random access response. Attempt to receive the PDCCH using the Temporary C-RNTI. Then, in the former case, if the PDCCH is received through its cell identifier before the conflict resolution timer expires, the UE determines that the random access procedure has been normally performed and ends the random access procedure. In the latter case, if the PDCCH is received through the temporary cell identifier before the conflict resolution timer expires, the data transmitted by the PDSCH indicated by the PDCCH is checked. If the unique identifier is included in the content of the data, the UE determines that the random access procedure has been normally performed, and terminates the random access procedure.

In addition, compared to the contention-based random access process, in the non- contention-based random access process, by receiving the random access response information, it is determined that the random access process is normally performed, and ends the random access process.

Hereinafter, the illustrated step S510 will be described. As mentioned above, the non-contention based random access procedure may exist firstly in the case of a handover procedure and secondly, in a case requested by a command of a base station. Of course, the contention-based random access procedure may be performed in both cases. First of all, it is important to receive a designated random access preamble from the base station that has no possibility of collision for the non- contention-based random access procedure. In order to receive the random access preamble, there are a handover command and a PDCCH command.

Hereinafter, the illustrated step S520 will be described. The UE transmits the preamble to the base station after receiving the random access preamble assigned to itself as the base station.

Hereinafter, the illustrated step S530 will be described. The method of receiving random access response information is the same as in the contention-based random access procedure.

Hereinafter, a detailed method for resolving collision in a random access process will be described.

The reason why collision occurs in the random access process is because the number of random access preambles is basically finite. That is, since the base station cannot grant UE-specific random access preamble to all UEs, the UE randomly selects and transmits one of the common random access preambles. Accordingly, when two or more UEs select and transmit the same random access preamble through the same PRACH resource, the base station determines that one random access preamble is transmitted from one UE. For this reason, the base station transmits a random access response to the UE, and predicts that the random access response will be received by one UE. However, as described above, since collision may occur, two or more UEs receive one random access response, and thus, each UE performs an operation according to reception of a random access response. That is, a problem occurs in that two or more UEs transmit different data to the same radio resource by using one UL Grant included in the random access response. Accordingly, the transmission of the data may all fail, and only the data of a specific UE may be received at the base station according to the location or transmission power of the UEs. In the latter case, since two or more UEs assume that the transmission of their data was successful, the base station should inform UEs that have failed in the race about the fact of the failure. That is, to inform the information about the failure or success of the competition is called contention resolution. There are two methods of conflict resolution. One method is to use a contention resolution timer (hereinafter referred to as a CR timer), and the other is to transmit an identifier of a successful UE to the UEs. The former case is used when the UE already has a unique cell identifier (C-RNTI) before the random access procedure. That is, the UE which already has the cell identifier transmits data including its cell identifier to the base station according to the random access response, and operates the collision resolution timer. Then, if the PDCCH information including its cell identifier is received before the conflict resolution timer expires, the UE determines that it has succeeded in the competition, and ends the random access process normally. On the contrary, if the PDCCH containing the cell identifier is not transmitted before the conflict resolution timer expires, it is determined that it has failed in the race, re-performs the random access procedure, or notifies the upper layer of the failure. Done. The latter case of the collision resolution method, that is, a method of transmitting an identifier of a successful UE is used when the UE does not have a unique cell identifier before the random access procedure. That is, when the UE itself does not have a cell identifier, the UE transmits data including an identifier higher than the cell identifier (S-TMSI or Random Id) according to UL Grant information included in the random access response, and the UE operates a collision resolution timer. Let's do it. Before the conflict resolution timer expires, if data including its higher identifier is transmitted to the DL-SCH, the UE determines that the random access procedure is successful. On the other hand, when the conflict resolution timer expires, if the data including its higher identifier is not transmitted to the DL-SCH, the UE determines that the random access procedure has failed.

Hereinafter, the MTC will be described.

6 illustrates an example of machine type communication (MTC).

Machine Type Communication (MTC) is an exchange of information through the base station 200 between MTC devices 100 without human interaction or information through a base station between the MTC device 100 and the MTC server 700. Say exchange. In this sense, human interaction is also called M2M (Machine to Machine) communication. In contrast to this, communication between humans may also be referred to as human to human (H2H) communication.

The MTC server 700 is an entity that communicates with the MTC device 100. The MTC server 700 executes an MTC application and provides an MTC specific service to the MTC device.

The MTC device 100 is a wireless device that provides MTC communication and may be fixed or mobile.

The services offered through MTC are different from those in existing human-involved communications, and there are various categories of services such as tracking, metering, payment, medical services, and remote control. exist. More specifically, services provided through the MTC may include meter reading, level measurement, utilization of surveillance cameras, inventory reporting of vending machines, and the like.

The uniqueness of the MTC device is that the amount of data transmitted is small and the up / down link data transmission and reception occur occasionally. Therefore, it is effective to lower the cost of the MTC device and reduce battery consumption in accordance with such a low data rate.

Hereinafter, the characteristics according to the type of MTC device is summarized in the table below.

Table 1

Type of MTC Device	Data Processing Speed	Error Rate Requirements	Delay sensitivity
Smart meter	lowness	lowness	lowness
Vehicle management	lowness	lowness	Middle price
Point of sale terminal (POS)	lowness	middle	height
Live video	lowness	lowness	lowness

As described above, unlike the general UE, the MTC device does not require a wide range of services, but has a feature of requiring only a small number of special services.

As such, since MTC devices may exist individually for each service and use, a huge number of MTC devices may be located in the coverage of the base station. However, since such a large number of MTC devices are placed in the coverage of the base station, there is a possibility that the quality of H2H communication may be degraded.

To address this scenario, the 3GPP Release 10 standard document considers adding “Delay tolerant access” as the RRC establishment cause value. This allows the network to reject RRC connection requests with an extended wait timer. However, even with this solution, it is not effective when the MTC device continuously attempts random access and transmits an RRC connection request. As a better solution, consider preventing random access attempts if delays are acceptable for the MTC device's access. This solution can be very effective in terms of battery savings.

On the other hand, smartphones are currently installed with various kinds of applications running in the background. While data by some of the many applications may be delayed, data by some other applications may be very sensitive to delay. However, these are not distinguished and are inefficient.

Several patents have been filed previously as a solution to these problems.

For example, referring to US Patent Publication No. US2011 / 0201307, a method of dividing an access class in consideration of a device type is proposed. Specifically, this patent restricts access to MTC devices in order not to affect existing H2H communications.

For another example, referring to PCT International Publication WO2012 / 045909, a scheme is disclosed in which a network delivers information for an access class barring (ACB) differently for each UE to block access of a specific UE.

For another example, referring to PCT International Publication WO2013 / 160727, a method of blocking access of a specific service by providing a different access class for each service of a UE is proposed.

All patents given so far are directed to blocking access by a particular UE or a particular service. However, this can be problematic because access is blocked at the source.

<본 명세서의 개시에 따른 방안> <Method according to the disclosure of the present specification>

Accordingly, the disclosures of the present disclosure aim to provide a method of performing access control on a device or a service having a high delay tolerance in order to solve the above problem.

Specifically, one disclosure of the present specification is intended to propose a method for preventing a network from being congested by data having a high delay tolerance among data generated by an MTC device (or an M2M device).

In order to achieve the above object, one disclosure of the present specification proposes a method for adding a condition that an MTC device (or M2M device) generating high delay tolerance data can initiate random access.

Hereinafter, with reference to the drawings will be described in detail.

As can be seen with reference to FIG. 7, when a random access procedure is triggered in the MTC device (S101), the MTC device selects a maximum delay allowance T value (S103). The maximum delay tolerance T value may be any one of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, and 1024. Specifically, the MTC device may select any one of the maximum delay tolerance T values according to its type and service type. More specifically, if the type of the MTC device can perform various services, one of the maximum delay tolerance T values may be selected according to the type of the service that triggered the current random access procedure.

Next, the MTC device obtains a load interworking N value broadcast in the network (S105), and checks whether the load interworking N value is 0 (S107). The load interlocking N value is T / 1024, T / 512, T / 256, T / 128, T / 64, T / 32, T / 16, T / 8, T / 4, T / 2, T, 2T, It may be any one of 4T, 8T, 16T, 32T, 64T, 128T, 256T, 512T, and 1024T.

If the load interlocking N value is 0, it waits until the load interlocking N value is not 0 (S108). That is, it waits until a non-zero load interworking N value is broadcast.

However, if the load-linked N value is not 0, the MTC device calculates a Tf value, which is a tolerance factor, based on the maximum delay tolerance value T and the load-linked N value (S109). The calculated Tf value may be any one of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 and 1024.

Subsequently, the MTC device checks whether UEID mod Tf = SFN mod Tf using its ID (S111). Here, SFN means a system frame number.

If UEID mod Tf = SFN mod Tf, the UE 100 transmits a random access preamble on the subframe of the SFN (S113).

As described above, according to one disclosure of the present specification, an MTC device capable of delay may transmit a random access preamble only on a subframe within a frame in which UEID mod Tf = SFN mod Tf is satisfied.

Here, the UEID may mean an international mobile subscriber identity (IMSI) mod 1024 SFN.

On the other hand, the allowable factor Tf may be calculated differently for each MTC device based on the T value, which is the maximum delay allowable value, and the load interworking N value.

[Equation 1]

Tf = 1, if Tf <1

= 1024, if Tf> 1024

= T * N

As a variant of the scheme shown in Fig. 7, the tolerance factor Tf can be calculated as follows.

According to a first modification, the tolerance factor Tf may be stored in the MTC device differently according to the delay tolerance of the MTC device. If the MTC device can perform various services, different Tf values may be stored in the MTC device according to the delay tolerance of each service. This first modification has the advantage that the problem can be solved only by the improvement of the MTC device without improvement in the network.

According to a second variant, the network may broadcast the value of the tolerance factor Tf in the system information. For example, the tolerance factor Tf may be included in SIB2 and broadcast. This second variant is advantageous in that the network can change the tolerance factor from time to time according to its current load. If the current network load is not high, the tolerance factor Tf is set to a low value, allowing more MTC devices to transmit a random access preamble. For example, when Tf = 1, many MTC devices can transmit a random access preamble in every radio frame. However, when the load increases in the network, Tf may be increased to about 1024, which reduces the probability that the MTC device transmits a random access preamble.

On the other hand, according to the third modification, when the network broadcasts a special value for the tolerance factor Tf, the MTC device may not perform a random access procedure. For example, when the network broadcasts by setting the allowable factor Tf value to 0 or broadcasts by setting the N value to 0, the MTC device cannot perform a random access procedure. This third variant can be used to completely block access of the MTC device in an emergency.

Alternatively, the MTC device may be set a special value for the value of IMSI, in which case UEID mod Tf = SFN mod Tf is not satisfied in step S111 described above, so that the MTC device transmits a random access preamble. May be limited.

Alternatively, the MTC device may randomly select a value within a range of setting a specific value as a minimum value and a maximum delay allowable value T as a maximum value at a uniform probability according to its type and service type. When traffic occurs, the UE waits for the selected value and then attempts a random access procedure in a subframe in which a random access preamble resource exists. The specific value is a specific constant value equal to or greater than zero and the maximum delay tolerance T.

Alternatively, in order to limit the random access preamble transmission of the MTC device, the maximum number of random access preambles that can be transmitted in a specific length of time may be determined. The maximum number of times is set to a value with which the maximum delay tolerance T is associated. The time intervals appear in succession repeatedly in time. When the MTC terminal transmits the random access preamble by the maximum number of times in a specific time interval for traffic transmission, the UE stops transmitting the random access preamble in the time interval and waits until the next time interval. When the next time interval arrives, the UE may perform random access preamble transmission.

The scheme illustrated in FIG. 8 further includes processes S115, S117, and S119 compared to the scheme illustrated in FIG. 7. Therefore, the following description will focus on the processes S115, S117, and S119.

After transmitting the random access preamble (S113), the MTC device determines whether it is successful (S115).

If not successful, the MTC device calculates a random waiting time Wdt (S119). The random wait time Wdt means a wait time until the next random access attempt. The MTC device waits until the timer according to the calculated random wait time Wdt expires (S121).

On the other hand, if not successful, after the MTC device waits for the backoff time (S117), it may further wait until the timer according to the random waiting time Wdt expires (S119).

The random wait time Wdt may be generated by a random number generation function. The random wait time Wdt generated by the random number generation function may vary depending on the delay tolerance of the MTC device.

The relationship between the allowable delay and the wait time may be as shown in the table below.

TABLE 2

Device type / service type	Allowable delay	waiting time
Smart meter	One day	2 hours
Smart vending machine	3 hours	30 minutes
Voice call	No Delay Allowed, Immediate Needed	0 (No waiting)
Update of applications running in the background	1 hours	20 minutes
Update information on SNS running in the background	10 minutes	3 minutes

On the other hand, as a variation of the scheme shown in Figure 8, the random waiting time Wdt can be calculated as follows.

According to a first variant, the random wait time Wdt may be generated by the network and included in the system information and broadcasted. For example, the random wait time Wdt may be included in SIB2 and broadcasted.

According to a second variant, the random waiting time Wdt may be calculated based on a d1 value (ie, a value according to the delay tolerance factor of the MTC device) and a d2 value (a load interworking value broadcast from the network). For example, the Wdt may be calculated as follows.

Wdt = dl + d2

In this case, an upper limit and a lower limit may be imposed on the arbitrary waiting time Wdt. Also, if the network is lightly loaded, the d2 value may be negative in order for the MTC device to restart the random access procedure as soon as possible.

Referring to FIG. 9, UE # a 10a, UE # b 10b, and MTC device 100 exist within coverage of the base station 200. The base station broadcasts the load interworking N value = 2 and d2 = 10 minutes through the SIB.

Assume that the maximum delay allowance T value is set to 64 and the d1 value is set to 30 minutes in the MTC device 100. Then, the MTC device 100 calculates Tf = T * N, and calculates Tf = 128. The MTC device 100 transmits a random access preamble on a subframe within a radio frame that meets UEID mod Tf = SFN mod Tf.

If the transmission of the random access preamble fails, the MTC device may transmit the random access preamble again only after 40 minutes as a result of calculating Wdt = dl + d2.

The embodiments described so far may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof. Specifically, this will be described with reference to FIG. 12.

The base station 200 includes a processor 201, a memory 202, and an RF unit 203. The memory 202 is connected to the processor 201 and stores various information for driving the processor 201. The RF unit 203 is connected to the processor 201 to transmit and / or receive a radio signal. The processor 201 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 201.

The MTC device 100 includes a processor 101, a memory 102, and an RF unit 103. The memory 102 is connected to the processor 101 and stores various information for driving the processor 101. The RF unit 103 is connected to the processor 101 and transmits and / or receives a radio signal. The processor 101 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the MTC device may be implemented by the processor 101.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

Claims

As a method of performing a random access procedure in a machine type communication (MTC) device,

If a random access procedure is triggered, determining, by the MTC device, a maximum delay tolerance T value based on its type and the type of service that triggered the random access procedure;

Determining a tolerance factor Tf based on the maximum delay tolerance T value;

Selecting a radio frame to transmit a random access preamble based on the tolerance factor Tf;

Transmitting a random access preamble on the selected radio frame.
The method of claim 1,

Obtaining a network load interworking N value,

Wherein the tolerance factor Tf is determined based on the maximum delay tolerance T value and the network load interworking N value.
The method of claim 1, wherein the radio frame is

And a UEID indicating an identifier of the MTC device, the tolerance factor Tf, and a radio frame number (SFN).
The method of claim 3, wherein the determined radio frame is

UEID mod Tf = Method characterized in that the radio frame meets the SFN mod Tf.
The method of claim 1,

Calculating a random wait time Wdt when the transmission of the random access preamble is not successful;

And waiting for the calculated random waiting time Wdt, and then transmitting a random access preamble.
The method of claim 5, wherein transmitting the random access preamble

If the transmission of the random access preamble is not successful, waiting for a backoff time;

Waiting for the random waiting time Wdt.
Machine type communication (MTC) device performing a random access procedure,

When a random access procedure is triggered, the MTC device determines a maximum delay tolerance T value based on its type and the type of service that triggered the random access procedure, and based on the maximum delay tolerance T value, a tolerance factor Tf. Determine a signal, and then select a radio frame to transmit a random access preamble based on the tolerance factor Tf;

And a transceiver for transmitting a random access preamble on the selected radio frame.
The method of claim 7, wherein

The transceiver unit acquires a network load interworking N value,

Here, the allowable factor Tf is determined based on the maximum delay tolerance T value and the network load interworking N value.
The method of claim 7, wherein the radio frame is

MTC device, characterized in that determined in consideration of the UEID indicating the identifier of the MTC device, the allowable factor Tf, radio frame number (SFN).
The method of claim 9, wherein the determined radio frame is

UEID mod Tf = MTC device, characterized in that the radio frame meets the SFN mod Tf.
8. The processor of claim 7, wherein the processor is

And if the transmission of the random access preamble is unsuccessful, calculates a random wait time Wdt, waits for the calculated random wait time Wdt, and then transmits a random access preamble.