KR20180018313A - Transitioning method of state based on random access procedure in communication system - Google Patents

Abstract

A state transition method based on a random access procedure in a communication system is disclosed. A method for operating a terminal in a communication system includes: a step of transmitting a random access preamble to a base station when an uplink data unit exists in the terminal; a step of receiving a random access response that is the response of the random access preamble from the base station; and a step of transmitting a message including the uplink data unit to the base station through a resource indicated by the random access response. Therefore, the performance of a communication network can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a state transition method based on a random access procedure in a communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication technology, and more particularly, to a state transition method of a terminal based on a random access procedure in a communication system.

The communication system includes a core network (for example, a serving gateway (S-GW), a packet data network (PDN) -gateway), a mobility management entity (MME) . The base station can be connected to the S-GW and the MME of the core network and can provide communication services to terminals belonging to the cell coverage of the base station. That is, a terminal belonging to the coverage of the base station can perform communication with the base station. In such a communication system, a technique for improving the transmission performance between the base station and the terminal, a technique for reducing power consumption of the terminal, and a technique for reducing the transmission delay of the terminal are required.

Meanwhile, the UE may operate in a radio resource control (RRC) idle state or an RRC connected state. In a case where data communication with the base station is required, the operating state of the terminal can transition from the RRC idle state to the RRC connected state, and the terminal in the RRC connected state can perform data communication with the base station. In order to satisfy the aforementioned technical requirements (e.g., improved transmission performance, reduced power consumption, reduced transmission delay, etc.), a new operating state may be introduced to the communication system other than the RRC idle state and the RRC connected state have. In this case, state transition methods between RCC idle state, RRC connected state and new operating state, operations based on new operating state will be required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide state transition methods of a terminal in a communication system.

According to another aspect of the present invention, there is provided a method of operating a terminal in a communication system, the method comprising: operating the RRC in an RRC idle state, an active RRC active state, and an RRC connected state, The method comprising: transmitting a random access preamble to a base station when an uplink data unit exists in the terminal; receiving a random access response which is a response of the random access preamble from the base station; And transmitting the message including the uplink data unit to the base station.

Herein, the RRC idle state may be a state in which the terminal is not connected to the base station, and the active state and the RRC connected state of the RRC may be a state in which the terminal is connected to the base station, The RRC may not support the scheduling operation for the UE operating in the active state and the BS may support the scheduling operation for the UE operating in the RRC connection state.

Here, the random access preamble may be transmitted from the terminal to the base station when the size of the uplink data unit is less than or equal to a preset threshold value.

Here, the operation method of the UE may include: transitioning from an active state of the RRC to the RRC connected state when the size of the uplink data unit exceeds the preset threshold value; The UE operating in the RRC connected state may transmit the uplink data unit to the base station based on a scheduling operation of the base station.

Herein, the random access preamble may include an indicator for requesting transmission of the uplink data unit and size information of the uplink data unit.

Here, the random access preamble may be transmitted through PRACH indicated by DCI or system information received from the base station.

Here, the random access response may include information indicating the resource allocated for transmission of the uplink data unit.

Here, the message may further include information indicating a buffer status of the UE.

In order to achieve the above object, a method of operating a terminal in a communication system according to a second embodiment of the present invention is characterized in that the terminal operates in one of an RRC idle state, an RRC active state, and an RRC connected state, Transitioning from the RRC idle state to the RRC connected state based on a random access procedure between the terminal and the base station when the terminal operates in the RRC idle state; A transition from an RRC connection state to an RRC idle state or an RRC active state based on a request of the base station, and when the terminal is operating in an RRC active state, Based on the random access procedure between the UE and the Node B, the operation state of the UE is changed into the RRC active state And a step of transitions to the RRC connected state.

Herein, the RRC idle state may be a state in which the terminal is not connected to the base station, and the active state and the RRC connected state of the RRC may be a state in which the terminal is connected to the base station, The RRC may not support the scheduling operation for the UE operating in the active state and the BS may support the scheduling operation for the UE operating in the RRC connection state.

Herein, when the UE supports the low-delay service, the UE may transition from the RRC connection state to the RRC active state according to a request from the BS.

Here, when the paging channel is received from the base station, the operational state of the mobile station may transition from the RRC active state to the RRC connected state.

Here, the random access procedure for the transition from the RRC active state to the RRC connected state may be a procedure for resuming the RRC connection link between the UE and the BS.

In order to achieve the above object, in a communication system according to a third embodiment of the present invention, a terminal includes a processor, and a memory in which at least one command executed through the processor is stored. The terminal includes an RRC idle state, Wherein the at least one command is a random access preamble to the Node B if the uplink data unit is present in the UE and the Random Access Preamble And transmitting a message including the uplink data unit to the base station via a resource indicated by the random access response.

Herein, the RRC idle state may be a state in which the terminal is not connected to the base station, and the active state and the RRC connected state of the RRC may be a state in which the terminal is connected to the base station, The RRC may not support the scheduling operation for the UE operating in the active state and the BS may support the scheduling operation for the UE operating in the RRC connection state.

Here, the random access preamble may be transmitted from the terminal to the base station when the size of the uplink data unit is less than or equal to a preset threshold value.

If the size of the uplink data unit exceeds the preset threshold value, the at least one command transitions from the RRC active state to the RRC connected state, And the terminal operating in the active state transmits the uplink data unit to the base station based on the scheduling operation of the base station.

Herein, the random access preamble may include an indicator for requesting transmission of the uplink data unit and size information of the uplink data unit.

Here, the random access preamble may be transmitted through PRACH indicated by DCI or system information received from the base station.

Here, the message may further include information indicating a buffer status of the UE.

According to the present invention, in a communication system, a terminal can operate in an RRC idle state, an RRC connected state, or an RRC active state. For example, a terminal in an RRC idle state may transition to an RRC connected state or an RRC active state, and a terminal in an RRC connected state may transition to an RRC idle state or an RRC active state, May transition to the RRC Idle state or the RRC connected state. That is, in order to save power, the UE can operate in the RRC idle state, and the UE can operate in the RRC active state in order to improve the transmission performance and reduce the transmission delay.

In a communication system, system information can be classified into basic system information, additional system information, and the like. The terminal receiving the basic system information can request the base station to transmit the additional system information. The base station can transmit the additional system information to the terminal according to the request of the terminal, and the terminal can receive the additional system information from the base station. Alternatively, the additional system information may be transmitted without the request of the terminal. The system information is classified into the basic system information and the additional system information, and the additional system information is transmitted when necessary, so that the signaling overhead of the system information can be reduced and the system information can be efficiently transmitted. Therefore, the performance of the communication system can be improved.

1 is a conceptual diagram showing a first embodiment of a communication system.
2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
3 is a conceptual diagram showing a first embodiment of a type 1 frame structure.
4 is a conceptual diagram showing a first embodiment of a type 2 frame structure.
5 is a conceptual diagram showing a first embodiment of a resource grid of slots included in a subframe.
6 is a flow chart illustrating a first embodiment of a random access procedure in a communication system.
7 is a flow chart illustrating a second embodiment of a random access procedure in a communication system.
8 is a timing chart showing a first embodiment of a transmission / reception method of a random access preamble.
9 is a timing chart showing a first embodiment of a method of transmitting / receiving additional system information.
10 is a flowchart showing a second embodiment of a method of transmitting / receiving additional system information.
11 is a conceptual diagram showing an operation state of a terminal in a communication system.
12 is a conceptual diagram showing a second embodiment of the communication system.
13 is a flowchart showing a first embodiment of a method of transmitting and receiving a data unit based on a random access procedure.
14 is a conceptual diagram showing a third embodiment of the communication system.
15 is a timing diagram illustrating a first embodiment of a beamforming transmission performed by a base station in the communication system shown in Fig.
FIG. 16 is a timing chart showing a first embodiment of beamforming transmission performed by a terminal in the communication system shown in FIG. 14; FIG.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. 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 a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

A communication system to which embodiments of the present invention are applied will be described. The communication system to which the embodiments according to the present invention are applied is not limited to the following description, and the embodiments according to the present invention can be applied to various communication systems. Here, the communication system can be used in the same sense as a communication network.

1 is a conceptual diagram showing a first embodiment of a communication system.

1, a communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. The communication system 100 also includes a core network (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway, a mobility management entity .

The plurality of communication nodes may support 4G communication (e.g., long term evolution (LTE), advanced (LTE-A)), 5G communication, etc. defined in the 3rd generation partnership project (3GPP) standard. 4G communication can be performed in a frequency band of 6 GHz or less, and 5G communication can be performed in a frequency band of 6 GHz or more. For example, for 4G communication and 5G communication, a plurality of communication nodes may be classified into a code division multiple access (CDMA) based communication protocol, a wideband CDMA (WCDMA) based communication protocol, a time division multiple access (TDMA) A communication protocol based on FDMA (frequency division multiple access), a communication protocol based on orthogonal frequency division multiplexing (OFDM), a communication protocol based on Filtered OFDM, a communication protocol based on CP (cyclic prefix) A communication protocol based on Fourier transform-spread-OFDM), a communication protocol based on OFDMA (orthogonal frequency division multiple access), a communication protocol based on single carrier (SC) -FDMA, a non-orthogonal multiple access (NOMA) division multiplexing based communication protocol, FBMC (filter bank multi-carrier) based communication protocol, UFMC (universal filtered multi-carrier) based communication protocol, SDMA Division multiple access) -based communication protocol. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to the network to perform communication. The communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 and communicate with each other.

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods in accordance with embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be constituted of at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may comprise at least one of read-only memory (ROM) and random access memory (RAM).

Referring again to FIG. 1, the communication system 100 includes a plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2, a plurality of terminals 130- 1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3 and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4 and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5 and the sixth terminal 130-6 can belong to the cell coverage of the third base station 110-3 have. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1 and 120-2 includes a Node B, an evolved Node B, a base transceiver station (BTS) A radio base station, a radio transceiver, an access point, an access node, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5 and 130-6 includes a user equipment (UE), a terminal, an access terminal, May be referred to as a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, and the like.

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands, or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1 and 120-2 may be connected to each other via an ideal backhaul or a non-ideal backhaul, Or non-idle backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an idle backhaul or a non-idle backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130 130-2, 130-3, 130-4, 130-5, and 130-6, and transmits the signals received from the terminals 130-1, 130-2, 130-3, 130-4, Lt; / RTI >

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 performs MIMO transmission (for example, SU (single user) -MIMO, MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, direct device to device communication (D2D) proximity services). Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 includes base stations 110-1, 110-2, 110-3, and 120-1 , 120-2, and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2. For example, the second base station 110-2 can transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 can transmit a signal based on the SU-MIMO scheme And may receive a signal from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, the fourth terminal 130-4, And the fifth terminal 130-5 may receive signals from the second base station 110-2 by the MU-MIMO scheme.

Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 can transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, The terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by the CoMP method. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes terminals 130-1, 130-2, 130-3, 130-4 , 130-5, and 130-6) and the CA scheme. Each of the first base station 110-1, the second base station 110-2 and the third base station 110-3 controls the D2D between the fourth terminal 130-4 and the fifth terminal 130-5 And each of the fourth terminal 130-4 and the fifth terminal 130-5 can perform the D2D under the control of each of the second base station 110-2 and the third base station 110-3 .

Meanwhile, the communication system can support three types of frame structures. The Type 1 frame structure can be applied to a frequency division duplex (FDD) based communication system, the Type 2 frame structure can be applied to a time division duplex (TDD) based communication system, the Type 3 frame structure can be applied to a license- System (e. G., A licensed assisted access (LAA) based communication system).

3 is a conceptual diagram showing a first embodiment of a type 1 frame structure.

Referring to FIG. 3, a radio frame 300 may include 10 subframes, and a subframe may include 2 slots. Thus, the radio frame 300 may include 20 slots (e.g., slot # 0, slot # 1, slot # 2, slot # 3, ..., slot # 18, slot # 19). The length (T _f ) of the radio frame 300 may be 10 ms, the subframe length may be 1 ms, and the slot length (T _slot ) may be 0.5 ms. Here, T _s may indicate a sampling time and may be 1 / 30,720,000 s (second).

The slot may be composed of a plurality of OFDM symbols in the time domain and may be composed of a plurality of resource blocks (RBs) in the frequency domain. The resource block may be composed of a plurality of subcarriers in the frequency domain. The number of OFDM symbols constituting the slot may be changed according to the configuration of the CP (cyclic prefix). CP can be classified into a normal CP and an extended CP. If a normal CP is used, the slot may be composed of 7 OFDM symbols, in which case the subframe may be composed of 14 OFDM symbols. If an extended CP is used, the slot may be composed of six OFDM symbols, in which case the subframe may be composed of twelve OFDM symbols.

4 is a conceptual diagram showing a first embodiment of a type 2 frame structure.

Referring to FIG. 4, a radio frame 400 may include two half frames, and a half frame may include five subframes. Thus, the radio frame 400 may include 10 subframes. The length (T _f ) of the radio frame 400 may be 10 ms. The length of the half frame may be 5 ms. The subframe length may be 1 ms. Where T _s can be 1 / 30,720,000s.

The radio frame 400 may include a downlink subframe, an uplink subframe, and a special subframe. Each of the DL subframe and the UL subframe may include two slots. The slot length (T _slot ) may be 0.5 ms. Of the subframes included in the radio frame 400, each of the subframe # 1 and the subframe # 6 may be a special subframe. For example, if the downlink-uplink switching period is 5 ms, the radio frame 400 may include two special subframes. Alternatively, if the downlink-uplink switching period is 10ms, the radio frame 400 may include one special subframe. The special subframe may include a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS).

The downlink pilot time slot can be regarded as a downlink interval and can be used for cell search, time and frequency synchronization acquisition, channel estimation, etc. of the UE. The guard interval can be used to solve the interference problem of the uplink data transmission caused by the downlink data reception delay. In addition, the guard interval may include a time required for switching from the downlink data reception operation to the uplink data transmission operation. The uplink pilot time slot may be used for uplink channel estimation, time and frequency synchronization acquisition, and the like. Transmission of a physical random access channel (PRACH) or a sounding reference signal (SRS) may be performed in an uplink pilot time slot.

The lengths of each of the downlink pilot time slot, the guard interval, and the uplink pilot time slot included in the special subframe can be variably adjusted as needed. In addition, the number and position of each of the downlink subframe, the uplink subframe, and the special subframe included in the radio frame 400 may be changed as needed.

5 is a conceptual diagram showing a first embodiment of a resource grid of slots included in a subframe.

Referring to FIG. 5, a resource block of a slot included in a downlink subframe or an uplink subframe may be composed of 7 OFDM symbols in a time domain when a normal CP is used, and 12 subframes Carriers. Each of the seven OFDM symbols may be referred to as symbol # 0, symbol # 1, symbol # 2, symbol # 3, symbol # 4, symbol # 5, symbol # 6 and symbol # 7. Each of the 12 subcarriers includes subcarrier # 0, subcarrier # 1, subcarrier # 2, subcarrier # 3, subcarrier # 4, subcarrier # 5, subcarrier # 6, subcarrier # 7, subcarrier # 8, subcarrier # 9, subcarrier # 10 and subcarrier # 11. In this case, a resource constituted by one OFDM symbol in the time domain and one subcarrier in the frequency domain may be referred to as a "resource element (RE) ".

In the downlink transmission of the communication system, resource allocation for one UE can be performed in units of resource block pairs, and the length of the resource block pair in the time domain can be 1 ms. Resource mapping for an uplink control channel (e.g., a physical uplink control channel (PUCCH)) may be performed in units of resource block pairs. For example, the PUCCH may be mapped to one resource block included in the slot # 0 of the subframe # 0 and one resource block included in the slot # 1 of the subframe # 0. The mapping of reference signals, synchronization signals, etc. may be performed on a resource element basis.

Meanwhile, according to the numerology of the communication system, the radio frame can be set differently from the radio frame shown in FIG. 3 to FIG. For example, if the subcarrier spacing is 15 kHz in the radio frame shown in Figures 3 to 5 and the subcarrier interval is 30 kHz in a new communication system (e.g., a new radio communication system) In a new communication system, the length of a subframe may be 1 ms, the subframe may comprise two slots, the slot length may be 0.5 ms, and each slot may comprise 14 symbols.

Alternatively, if the subcarrier spacing is 15 kHz in the radio frame shown in FIGS. 3 to 5 and the subcarrier spacing is 120 kHz in the new communication system, the length of the subframe in the new communication system may be 0.25 ms, May comprise two slots, the slot length may be 0.125 ms, and each of the slots may comprise 14 symbols.

Alternatively, if the subcarrier interval is 15 kHz in the radio frame shown in Figs. 3 to 5 and the subcarrier interval is 240 kHz in the new communication system, the length of the subframe in the new communication system may be 0.125 ms, May comprise two slots, the slot length may be 0.0625 ms, and each of the slots may comprise 14 symbols.

Next, the operation methods of the communication node in the communication system will be described. The communication node may support a radio frame structure set according to the radio frame structure (for example, a subframe structure) or the numerology of the subframe interval shown in Figs. 3 to 5. Even if a method (e.g., transmission or reception of a signal) to be performed at the first communication node among the communication nodes is described, the corresponding second communication node is controlled by a method corresponding to the method performed at the first communication node For example, receiving or transmitting a signal). That is, when the operation of the terminal is described, the corresponding base station can perform an operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, the corresponding terminal can perform an operation corresponding to the operation of the base station.

■ Random access procedures based on fixed resources

A random access procedure based on fixed resources in a communication system can be performed as follows. The random access procedure may be performed when the UE attempts initial access to the Node B or when the Node B is not ready for a scheduling operation for the UE.

6 is a flow chart illustrating a first embodiment of a random access procedure in a communication system.

Referring to FIG. 6, the communication system may include a base station, a terminal, and the like. The base station may be the same as or similar to the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 shown in FIG. 1, 130-2, 130-3, 130-4, 130-5, 130-6). In addition, each of the base station and the terminal may be configured to be the same as or similar to the communication node 200 shown in Fig.

The base station may transmit a synchronization signal (e.g., primary synchronization signal (PSS), secondary synchronization signal (SSS)). A terminal belonging to the cell coverage of the base station can receive the synchronization signal from the base station and can be downlink synchronized to the base station based on the received synchronization signal. In addition, the base station may transmit system information (e.g., master information block (MIB), system information block (SIB)). The system information can be set by the base station. The system information includes time and frequency resource information (hereinafter referred to as "PRACH resource information") of the PRACH to which the random access preamble is transmitted, transmission period information of the random access preamble, Transmission power information, transmission frequency information, and preamble sequence information (e.g., a subset of preamble sequences). Here, the PRACH resource information may indicate a fixed resource.

The UE, which is downlink-synchronized with the base station, can receive the system information from the base station, and based on the received system information, the PRACH resource information, the transmission period information of the random access preamble, the transmission power information, the transmission number information, the preamble sequence information, Can be confirmed. The UE can generate the random access preamble based on the preamble sequence information included in the system information. Alternatively, the terminal may generate a random access preamble based on information obtained from the base station in a previous access procedure between the base station and the terminal. The UE can transmit the random access preamble through the PRACH indicated by the system information (S601). Alternatively, the UE can generate a random access preamble using an arbitrary preamble sequence, and can transmit a random access preamble through any resource.

The base station can receive the random access preamble through the PRACH and confirm the preamble sequence of the received random access preamble. The base station may generate a random access response based on the identified preamble sequence. The random access response includes timing advance information, a preamble sequence (e.g., a preamble sequence included in the random access preamble), uplink grant information (e.g., uplink resource information), a radio network temporary identifier, beamforming identifier, beam sweeping information (e.g., time of beam sweep, period and pattern), and the like. The base station can transmit a random access response (S602). When random access preambles are received from a plurality of terminals, the base station can transmit a random access response for each of a plurality of random access preambles.

The terminal can receive the random access response from the base station and can identify the information elements included in the received random access response. For example, the UE may be uplink-synchronized with the base station based on the TA information included in the random access response. On the other hand, if the random access response is not received within a predetermined time, the terminal can retransmit the random access preamble to the base station.

When the uplink synchronization between the BS and the MS is completed, the MS can generate an uplink signaling message (e.g., a radio resource control (RRC) signaling message). The uplink signaling message may include a terminal identifier, a preamble sequence, a beamforming identifier, beam sweeping information, and the like. The UE can transmit the uplink signaling message through the resource indicated by the uplink grant information included in the random access response (S603).

The BS can receive the uplink signaling message from the UE and confirm the information elements included in the uplink signaling message. For example, the base station can confirm the terminal identifier based on the uplink signaling message. If the uplink signaling message is successfully received, the base station may generate a downlink signaling message (e.g., an RRC signaling message). The downlink signaling message may include a terminal identifier (e.g., a terminal identifier included in an uplink signaling message), a beamforming identifier, beam sweeping information, and the like. The base station can transmit the downlink signaling message (S604).

The UE can receive the downlink signaling message from the base station and confirm the information elements included in the received downlink signaling message. For example, if the UE ID included in the UL signaling message and the UE ID included in the DL signaling message are identical, the UE can determine that the random access procedure has been successfully completed.

■ Random access procedures based on dynamic resources

A random access procedure based on dynamic resources in a communication system can be performed as follows. When a random access procedure is performed using dynamic resources instead of fixed resources, the availability of resources can be improved and the transmission delay can be reduced. Here, the PRACH allocation operation may be performed by a scheduler of a medium access control (MAC) layer instead of the RRC layer.

7 is a flow chart illustrating a second embodiment of a random access procedure in a communication system.

Referring to FIG. 7, the communication system may include a base station, a terminal, and the like. The base station may be the same as or similar to the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 shown in FIG. 1, 130-2, 130-3, 130-4, 130-5, 130-6). In addition, each of the base station and the terminal may be configured to be the same as or similar to the communication node 200 shown in Fig. The base station may transmit a synchronization signal (e.g., PSS, SSS). A terminal belonging to the cell coverage of the base station can receive the synchronization signal from the base station and can be downlink synchronized to the base station based on the received synchronization signal.

Meanwhile, the base station can transmit a physical downlink control channel (PDCCH) including a system information (SI) -RNTI (S701), and transmits PDSCH (SIB2) including system information (e.g., SIB2) indicated by the SI- physical downlink shared channel (S702). The system information includes a downlink control information (DCI) format (e.g., a DCI format for a random access procedure), uplink frequency information, uplink bandwidth information, preamble sequence information of a random access preamble Subset of sequences), and the like. If PRACH resource information is not included in the control information transmitted in step S703, the system information may further include PRACH resource information. The UE, which is downlink-synchronized with the base station, can receive the SI-RNTI through the PDCCH, receive the system information indicated by the SI-RNTI via the PDSCH, and confirm the information elements included in the received system information have.

On the other hand, the base station can generate control information including information elements necessary for the random access procedure. The control information may include information elements not included in the system information transmitted in step S702. For example, the control information may include PRACH resource information, transmission period information of the random access preamble, and transmission frequency information. The control information may further include a terminal identifier, information required for demodulating the PDSCH, transmission time information of the random access preamble, transmission power information, and the like. The control information may be configured in a DCI format for a random access procedure.

The control information may include PRACH resource information for one terminal or PRACH resource information for each of a plurality of groups. For example, the group may be assigned at least one PRACH resource. Here, the group may include at least one terminal. The control information for one UE may be indicated by C (cell) -RNTI, and the control information for the plurality of groups may be indicated by a C-RNTI (hereinafter referred to as a "Group C-RNTI" ≪ / RTI > The group C-RNTI may be included in system information transmitted in a broadcast manner, and may be transmitted to the UE in a previous access procedure between the BS and the MS. In addition, the PRACH available for all terminals can be indicated by the C-RNTI.

The size of the PRACH indicated by the control information may be the same as the size of the PRACH used in the random access procedure shown in Fig. For example, the size of the PRACH indicated by the control information may be six resource blocks. Alternatively, the size of the PRACH indicated by the control information may be variable. For example, the size of the PRACH indicated by the control information may be two resource blocks. The PRACH indicated by the control information may be located at the center of the system frequency band in the same manner as the FDD method. Alternatively, the PRACH indicated by the control information may be located in any region of the system frequency band. When a large number of PRACHs are required in a communication system, a large number of PRACHs can be allocated to facilitate connection of terminals.

The PRACH resource information may include a PRACH identification number. In this case, since the UE can transmit the random access preamble through the resource indicated by the PRACH identification number, the base station can receive the random access preamble of the UE without collision between the random access preambles. On the other hand, when the control information does not include the PRACH identification number, the UE can transmit the random access preamble through an arbitrary resource. The random access preamble transmitted through an arbitrary resource may include a PRACH identification number, and the PRACH identification number included in the random access preamble may be used for an uplink resource request, a D2D resource request, and the like. For example, a PRACH identification number set to "0 " may indicate an uplink resource request, and a PRACH identification number set to" 1 " may indicate a D2D resource request.

The base station can transmit the control information through the PDCCH (S703). The UE, which is downlink-synchronized with the base station, can receive the control information through the PDCCH, and based on the received control information, the PRACH resource information, the terminal identifier, the transmission period information of the random access preamble, Power information and so on.

For example, the terminal may generate a random access preamble based on at least one of system information and control information, and transmit a random access preamble through a resource (i.e., PRACH) indicated by at least one of system information and control information (S704). The random access preamble can be transmitted as follows.

8 is a timing diagram showing a first embodiment of a transmission / reception method of a random access preamble.

Referring to FIG. 8, if the transmission time information is not included in the control information received through the PDCCH of the subframe # 0, the UE transmits the control information after a predetermined time (for example, three subframes) A random access preamble can be transmitted. For example, the UE can transmit the random access preamble through the PRACH of the subframe # 3.

When the control information received through the PDCCH of the subframe # 2 contains the transmission time information, the UE determines from the reception time of the control information "the time indicated by the transmission time information + a predetermined time (for example, Frames ") "of the random access preamble. If the time indicated by the transmission time information is one subframe, the UE can transmit the random access preamble through the PRACH of the subframe # 6.

Referring back to FIG. 7, the base station can receive the random access preamble from the terminal. After the random access preamble is received at the base station, a random access response transmission / reception operation between the base station and the terminal (step S705), an uplink signaling message transmission / reception operation (step S706), and a downlink signaling message transmission / reception operation . The transmission / reception operation of the random access response (step S705) may be performed in the same or similar manner as the step S602 shown in FIG. 6, and the transmission / reception operation of the uplink signaling message (step S706) is the same as the step S603 shown in FIG. 6 And the transmission / reception operation of the downlink signaling message (step S707) may be performed in the same manner as or similar to that of step S604 shown in FIG.

A random access procedure based on a fixed preamble sequence

In a communication system, a random access procedure may be performed using a fixed preamble sequence. Here, the preamble sequence may refer to a "preamble index ". For example, the base station includes resource information (e.g., PRACH resource information) allocated for transmission of a random access preamble, resource information allocated for transmission of a random access response, fixed preamble sequence information set for each UE, and the like System information can be transmitted. The interval between the resources allocated for transmission of the random access preamble and the resources allocated for transmission of the random access response may be set to a predefined interval (for example, three subframes). The resources allocated for transmission of the random access preamble and the resources allocated for transmission of the random access response may be located at the center of the system frequency band. The resource allocated for the transmission of the random access response may be set to at least one of the PDCCH and the PDSCH.

The terminal can receive the system information from the base station, generate a random access preamble using the fixed preamble sequence indicated by the received system information, and transmit the resource indicated by the received system information (i.e., PRACH) To transmit the random access preamble. The base station can receive the random access preamble from the terminal and can transmit the random access response to the terminal in response to the random access preamble. The terminal may receive the random access response through the resources indicated by the system information.

(For example, step S603 of FIG. 6 or step S706 of FIG. 7) of the uplink signaling message between the base station and the terminal when the transmission and reception operation of the random access response is completed, the transmission and reception operations of the downlink signaling message , Step S604 in Fig. 6, step S707 in Fig. 7), and the like may be performed.

Procedure for transmitting and receiving system information based on the random access preamble

The system information is classified into basic system information (for example, common system information, minimum system information, system information block or system information message), additional system information (for example, additional system information message) . Additional system information may be referred to as "other system information "," additional system information "and the like. The basic system information may include information elements necessary for communication. For example, the basic system information includes a cell ID, a public land mobile network (PLMN) ID, a tracking area (TA) ID, downlink channel information, uplink channel information, A value tag indicating whether paging channel information, a beam identifier, presence (or change) of additional system information, broadcast information of additional system information (for example, SI (system information) scheduling information) .

In addition, when the basic system information includes many information elements, the basic system information is classified into a plurality of sub-basic system information (for example, sub-basic system information # 1, sub-basic system information # 2) . For example, the sub-basic system information # 1 may include essential information elements (e.g., downlink channel information, etc.) for the UE. Sub-basic system information # 2 may include information elements not included in sub-basic system information # 1. Basic system information # 1 may be transmitted through a fixed resource in a broadcast channel (e.g., a physical broadcast channel (PBCH)), sub-basic system information # 2 may be transmitted via a data channel ≪ / RTI > through a dynamic resource.

The additional system information may include information elements not included in the basic system information. For example, the changed information element among the information elements included in the basic system information may be set as additional system information. That is, the base station can change the information element when necessary, and the changed information element can be set to the additional system information. The additional system information may be an information element necessary for a UE operating in an RRC idle state, and may include information for a cell selection operation, information for a cell reselection operation, And the like.

Additional system information may be transmitted aperiodically. For example, additional system information may be transmitted by a request of the terminal or by a decision of the base station. The value tag included in the basic system information can indicate whether or not additional system information exists. For example, a value tag set to "0 " may indicate that no additional system information exists, and a value tag set to" 1 " may indicate that additional system information is present. Alternatively, the value tag included in the basic system information may indicate whether to change the additional system information. For example, a value tag set to "0 " may indicate that additional system information (e.g., information elements included in additional system information) is unchanged, and a value tag set to & (E.g., an information element included in the additional system information) has been changed. Methods of transmitting and receiving additional system information based on a value tag can be performed as follows.

9 is a timing chart showing a first embodiment of a method of transmitting / receiving additional system information.

Referring to FIG. 9, a base station can generate basic system information and transmit basic system information through a downlink sub-frame. If additional system information is present, the basic system information may include a value tag (e.g., a value tag set to "1 ") indicating that additional system information is present, For example, SI scheduling information).

To indicate that additional system information has changed, the basic system information may include a value tag (e.g., a value tag set to "1 ") indicating that additional system information has changed. The additional system information can be composed of a plurality of values, and the value tag can be displayed in plural.

The terminal can receive the basic system information from the base station and confirm the information elements included in the received basic system information. For example, the terminal can determine that the additional system information exists (or the additional system information is changed) based on the value tag included in the basic system information. Alternatively, the base station can indicate to the terminal the paging channel that the additional system information is changed or changed at a later time. In this case, the terminal can determine that the additional system information exists (or the additional system information is changed) based on the information obtained from the paging channel.

Accordingly, the UE can generate a random access preamble requesting transmission of additional system information, and can transmit the random access preamble through PRACH (e.g., PRACH indicated by basic system information). A plurality of terminals can transmit a random access preamble using the same resources.

Specifically, the base station can broadcast preamble resource information (for example, random access preamble resource information) for requesting transmission of the additional system information to the terminals through the basic system information. In the basic system information, mapping information between the transmission request preamble resource and the additional system information can also be displayed. The UE may transmit a preamble (e.g., a random access preamble) using a random access preamble resource (e.g., a preamble index, a time resource, a frequency location, etc.) mapped to necessary additional system information. Other terminals that need the same additional system information can transmit the preamble using the same preamble resource information.

The preamble resource for transmission of the system information can be set separately from the general preamble resource. The transmission period of the preamble for transmission of the system information can be set longer than the transmission period of the general preamble. For example, the transmission period of the preamble for transmission of the system information can be set to 10 ms, and the transmission period of the general preamble can be set to 5 ms. In this case, the Node B and the UE can use a resource not allocated as a preamble resource for transmission of system information as a general preamble resource.

The resource information of the additional system information used by the base station may include a transmission period, a transmission start time, a transmission period, etc., and the base station may use the resource information of the additional system information to broadcast additional system information can do.

If at least one random access preamble is received from the terminal, the base station may determine that transmission of additional system information is requested. In this case, the base station may generate a random access response and may transmit the generated random access response. The terminal may receive a random access response from the base station and may obtain additional system information that is transmitted in the received random access response. Alternatively, the additional system information may be transmitted from the base station to the terminal separately from the random access response. In this case, the additional system information may be transmitted to the terminal by broadcasting at the broadcast position indicated in the basic system information.

Specifically, when a random access response corresponding to the random access preamble is received after transmission of the random access preamble, the terminal can determine that the base station broadcasts the additional system information, and further system information Lt; / RTI > The receiving operation of the system information may be repeatedly performed for a preset time according to the period in which the corresponding system information is broadcasted. If the system information is not received within a predetermined time, the terminal can perform the request for the system information again. The terminal may receive a random access response corresponding to the random access preamble of the other terminal and may determine that other additional system information is broadcast from the base station based on the received random access response, . That is, the base station can transmit a random access response corresponding to the additional system information to be broadcasted, and the terminal, which has received the random access response from the base station, can transmit the random access response based on the received random access response, It can be determined that the system information is broadcast from the base station. In this case, since the terminal can acquire other additional system information, it may not transmit the random access preamble for acquiring additional system information. The terminal that has acquired the additional system information can maintain the RRC idle state.

On the other hand, when a lot of information elements are included in the additional system information, the additional system information can be classified into a plurality of sub-system information. For example, the additional system information may include sub-system information # 1, sub-system information # 2, sub-system information # 3, sub-system information # And so on. In this case, the value tag of the basic system information may include a field # 1 indicating the number of the plurality of sub-system information, a field # 2 indicating whether each of the plurality of sub- . Further, the value tag of the basic system information may further include a field # 3 indicating a transmission period of all sub-system information changed when all the sub-add system information is changed. The initial value of the field # 2 may be "0 ", and the field # 2 set to a value different from the initial value (for example," 1 ") may indicate that the corresponding sub-

The base station can set a preamble sequence used for transmission requests of each of a plurality of sub-addition system information. For example, the base station may generate a preamble sequence for each of sub-add system information # 1, sub-add system information # 2, sub-add system information # 3, # 1, preamble sequence # 2, preamble sequence # 3, preamble sequence # 4, and preamble sequence # 5. In addition, the base station can set the preamble sequence # 0 used for transmission request of all sub-system information. The preamble sequence information set by the base station may be transmitted to the terminal through the system information (e.g., basic system information) or the DCI.

In FIG. 9, when there are a plurality of sub-addition system information, the base station can transmit basic system information including a value tag and the like. The terminal can receive the basic system information from the base station and confirm the information elements included in the received basic system information. For example, the terminal can check the number of the plurality of sub-system information items based on the field # 1 of the value tag, and determine the number of sub-system information items based on the value indicated by the field # 2 of the value tag. Can be confirmed. The terminal determines that the value (for example, "4") indicated by the field # 2 of the value tag of the current basic system information is the value indicated by the field # 2 of the value tag of the previous basic system information (for example, "3"), it can be determined that the corresponding sub-addition system information has been changed.

If it is determined that the sub-addition system information # 2 has been changed, the UE can generate a random access preamble based on the preamble sequence # 2, and can transmit the generated random access preamble through the PRACH. The base station can receive the random access preamble from the UE and determine that the transmission of the supplementary-subsystem information # 2 corresponding to the preamble sequence # 2 included in the received random access preamble is requested. Thus, the base station can generate a random access response that includes the add-on subsystem information # 2 and can transmit the generated random access response. The terminal may receive a random access response from the base station and may obtain additional subsystem information # 2 from the received random access response. Alternatively, the additional-subsystem information # 2 may be transmitted from the base station to the terminal separately from the random access response.

Alternatively, when it is determined that the sub-addition system information # 3-4 has been changed, the terminal can generate a random access preamble based on the preamble sequence # 3-4, and can transmit the generated random access preamble through the PRACH . The base station can receive the random access preamble from the terminal and judge that transmission of the additional subsystem information # 3-4 corresponding to the preamble sequence # 3-4 is requested based on the received random access preamble. Thus, the base station can generate a random access response that includes the add-on subsystem information # 3-4, and can transmit the generated random access response. The terminal can receive the random access response from the base station and obtain the additional-subsystem information # 3-4 from the received random access response. Alternatively, the additional-subsystem information # 3-4 may be transmitted from the base station to the terminal separately from the random access response.

Alternatively, if it is determined that all sub-add system information has been changed, the UE can generate a random access preamble based on the preamble sequence # 0, and can transmit the generated random access preamble on the PRACH. The base station can receive the random access preamble from the terminal and judge that transmission of all the sub-add system information corresponding to the preamble sequence # 0 included in the received random access preamble is requested. Thus, the base station can generate a random access response including all sub-add system information, and can transmit the generated random access response. The terminal may receive a random access response from the base station and may obtain all sub-addition system information from the received random access response. Alternatively, all the additional subsystem information may be transmitted from the base station to the terminal separately from the random access response.

■ Random Access Preamble  Transmission and reception procedures of system information without transmission

Additional system information can be transmitted without a transmission / reception procedure of the random access preamble in the communication system. For example, when the additional system information is changed, the base station can transmit basic system information including a value tag indicating change of additional system information, transmission time information for the changed additional system information, and transmission period information, Additional system information may be transmitted based on the transmission time and transmission period indicated by the system information. Upon receiving the basic system information from the base station, the terminal can confirm that the additional system information has been changed based on the value tag, and can confirm the transmission time and transmission period of the changed additional system information. Therefore, the terminal can receive the changed additional system information from the base station based on the transmission time and transmission period indicated by the basic system information.

Alternatively, when the additional system information is changed, the base station can set a transmission interval for the changed additional system information. In addition, the base station can set the start time and the end time of the transmission interval. The base station can generate basic system information including a value tag indicating a change of additional system information, a transmission period for changed additional system information, a start time and an end time, and can transmit the generated basic system information. Alternatively, the value tag indicating the change of the additional system information can be transmitted from the base station to the terminal via the paging channel instead of the basic system information.

The terminal can receive the basic system information from the base station and can check the transmission period, the starting point and the ending point for the changed additional system information based on the received basic system information. Also, the UE can confirm that the additional system information is transmitted based on the value tag included in the paging channel (or the basic system information) received by the base station. If the start time of the transmission interval is not indicated by the basic system information, the terminal can calculate the start time based on Equation (1) below.

The system frame number (SFN) can indicate the number of the radio frame from which the basic system information is received, and the% can indicate the modulo operator. If the length of the transmission interval indicated by the basic system information is 80 ms and the result of Equation 1 is 1, the terminal determines that additional system information is transmitted from the base station for 80 ms from the time corresponding to the result of Equation 1 . If the length of the transmission interval indicated by the basic system information is 80 ms and the result of Equation 1 is 0, the terminal can determine that the paging channel is transmitted from the base station for 80 ms from the time corresponding to the result of Equation (1) have.

The base station may repeatedly transmit additional system information during the transmission interval. The terminal can receive additional system information from the base station by monitoring the basic system information and the transmission interval indicated by Equation (1).

Procedure for sending and receiving system information based on the transmission indicator

The basic system information may further include a value tag as well as a transmission indicator (Tx indicator). The transmission indicator may indicate whether additional system information is transmitted or not. A transmission indicator set to "0 " may indicate that additional system information is not transmitted while the basic system information is being transmitted, and a transmission indicator set to" 1 " may indicate that additional system information is transmitted while the basic system information is being transmitted Can be displayed. Alternatively, a transmission indicator set to "0 " may indicate that there is no additional system information corresponding to the basic system information, and a transmission indicator set to" 1 " Can be displayed. If it is confirmed that the transmission indicator of the basic system information is set to "1 ", the terminal can perform the receiving operation of the additional system information and can not transmit the random access preamble because the transmission request of the additional system information is unnecessary . If the reception of the additional system information fails, the terminal can request the transmission of the additional system information by transmitting the random access preamble to the base station. On the other hand, if it is confirmed that the transmission indicator of the basic system information is set to "0 ", the terminal may not perform the reception operation of the additional system information and may request broadcasting of the additional system information by transmitting the random access preamble.

Procedures for sending and receiving system information based on the update indicator

The base station can inform the terminals of a change in system information or a broadcast using the paging channel, for broadcasting of the system information (for example, basic system information or additional system information) changed or not broadcasted. The paging channel may be broadcast using a field indicating one or more system information (for example, the entire system information), and the terminal receiving the paging channel may perform the reception procedure of the corresponding system information.

If the paging channel indicates whether to broadcast or change additional system information, the terminal can not confirm whether the additional system information is broadcast or changed when the paging channel is not received. To solve this problem, the basic system information may further include an update indicator indicating whether or not to change the additional system information. An update indicator set to "0 " may indicate that additional system information has not been broadcast or changed since, and an update indicator set to" 1 " may indicate that additional system information has been broadcast or changed. If it is confirmed that the update indicator of the basic system information is set to "1 ", the terminal can receive the additional system information through the resource indicated by the basic system information. If it is confirmed that the indicator is set to "1 ", the UE may not transmit the random access preamble because the UE determines that the BS will broadcast additional system information. That is, the indicator can instruct the base station to broadcast the system information at a later time, and the terminal can confirm that the system information is broadcasted from the base station after a predetermined time based on the indicator, so that unnecessary random access preamble transmission Can be reduced. On the other hand, if it is confirmed that the update indicator of the basic system information is set to "0 ", the terminal can perform the transmission operation of the random access preamble when additional system information is needed.

SI (system information) Scheduling  Procedure for sending and receiving system information based on information

In the communication system, SI scheduling information including types of additional system information (for example, SIB, MIB), transmission resource information, and the like may be used.

10 is a flowchart showing a second embodiment of a method of transmitting / receiving additional system information.

Referring to FIG. 10, the communication system may include a base station, a terminal, and the like. The base station may be the same as or similar to the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 shown in FIG. 1, 130-2, 130-3, 130-4, 130-5, 130-6). In addition, each of the base station and the terminal may be configured to be the same as or similar to the communication node 200 shown in Fig.

The UE can generate a random access preamble for requesting transmission of the additional system information, and can transmit the generated random access preamble to the base station (S1001). The base station can receive the random access preamble from the terminal and confirm that the transmission of the additional system information is requested based on the received random access preamble. Thus, the base station may generate SI scheduling information for additional system information (e.g., at least one sub-add system information). The base station may transmit a random access response including SI scheduling information (S1002), and may transmit additional system information through the resource indicated by the SI scheduling information (S1003).

The UE can receive the random access response from the base station and confirm the SI scheduling information included in the random access response. Therefore, the UE can receive additional system information through the resources indicated by the SI scheduling information.

Alternatively, the base station may generate additional system information including SI scheduling information and so forth, and may transmit additional system information in a random access response. In this case, the SI scheduling information may be located in the front part of the additional system information. The UE can receive the SI scheduling information in response to the random access preamble, and can confirm the type of the additional system information, transmission resource information, and the like based on the received SI scheduling information. The UE can receive additional system information through the resources indicated by the SI scheduling information.

Specifically, the SI scheduling information may be configured as a bitmap, and in this case, the bitmap may indicate whether to broadcast additional system information. If the SI scheduling information is not included in the random access response, the UE can receive the system information after confirming the broadcast information using the additional system information included in the basic system information.

■ State transition method of terminal

Next, the state transition methods of the terminal in the communication system will be described.

11 is a conceptual diagram showing an operation state of a terminal in a communication system.

Referring to FIG. 11, the operation state of the UE can be classified into an RRC idle state, an RRC connected state, and an RRC active state. The RRC active state may be referred to as a " radio access network (RAN) controlled state ". The RRC idle state may indicate that the terminal is not connected to the base station. In the RRC idle state, the BS may not manage unique information of the UE (e.g., UE context information). A terminal operating in an RRC idle state can receive system information, a paging channel, and the like from a base station, and can perform a cell search procedure, a cell selection procedure, and the like. However, a terminal operating in the RRC idle state can not transmit or receive data units. When the operation state of the UE transitions from the RRC idle state to the RRC connected state according to the execution of the random access procedure, the data unit transmission / reception operation can be performed.

The RRC connection state can indicate the state where the terminal has connected to the base station. In the RRC connection state, the base station can manage unique information (e.g., UE context information) of a UE, a unique identifier (e.g., a UE ID), and transmits / Can be performed. A terminal operating in the RRC connected state can receive the control channel from the base station and can transmit and receive the data unit based on the scheduling of the base station. In addition, the UE operating in the RRC connected state can check the channel state, the beamforming state, and the like by performing the measurement procedure, and can transmit the channel state information, the beamforming state information, and the like to the base station. A handover procedure between the UE and the BS may be performed when the UE moves to a neighboring BS (e.g., a neighboring cell) in the RRC connection state.

The active state of the RRC may indicate the state where the terminal is connected to the base station. For example, the operation state of the UE may transition from the RRC connection state to the RRC active state. In this case, the RRC connection link established between the base station and the UE in the RRC connection state may be inactive. When an active state of the terminal transits from an active state to an RRC connected state, the inactive RRC connected link can be resumed. In the active state of the RRC, the base station can manage the unique information (e.g., UE context information) of the UE. However, the base station may not perform a scheduling operation for transmitting and receiving data units in the RRC active state.

A terminal operating in an active state, which is an RRC, can receive system information, a paging channel, and the like from a base station. A cell search procedure, a cell selection procedure, and the like may be performed when the mobile station moves to a neighboring base station (for example, a cell) in the active state of the RRC. That is, a cell search procedure, a cell selection procedure, and the like may be performed instead of the handover procedure to support the mobility of the terminal operating in the active state, which is the RRC. In the case where the active state of the UE transits from the active state to the RRC connected state, the transmission / reception operation of the data unit based on the scheduling of the base station can be performed. Alternatively, a terminal operating in an active state, which is an RRC, may transmit a data unit using a random access procedure without performing a state transition operation.

■ "RRC Connection State → RRC Idle State or RRC Inactive  State transition "

The operation state of the UE can transition from the RRC connection state to the RRC idle state or the RRC active state. When a terminal is initially connected to a base station based on a random access procedure, the base station can set a transition path of the operating state of the terminal. For example, the terminal can inform the base station of the service type information performed by the terminal in the connection procedure between the base station and the terminal, and the base station can set a transition path of the operation state of the terminal based on the service type information obtained from the terminal have.

For example, if a service requiring a fast connection (e.g., a low delay service) is performed by the terminal, the base station may set the transition path to "RRC connected state to RRC active state ". When the terminal does not support the low-delay service or operates in the power saving mode, the base station can set the transition path to "RRC connection state → RRC idle state ". The base station can inform the terminal of the transition path, and the terminal can perform the state transition operation based on the transition path received from the base station.

In addition, the base station can set a timer indicating a time point at which a state transition operation of the terminal is performed based on the service type information obtained from the terminal. In this case, the base station can notify the terminal of the transition path as well as the timer, and the terminal can receive the transition path and the timer from the base station. When the timer received from the base station expires, the terminal can perform a state transition operation based on the transition path received from the base station.

State transition operation in the "Active state from RRC to RRC connection state &

The operation state of the terminal can be transited from the active state of RRC to the RRC connected state. The state transition operation in the "RRC in active state to RRC connected state" can be performed according to the request of the terminal or the request of the base station.

1) state transition operation according to the request of the terminal

The UE can acquire information for the random access procedure in the initial access procedure between the Node B and the UE. The information for the random access procedure may include time and frequency resources for a random access preamble, preamble sequence information of a random access preamble, time and frequency resources for a random access response, beamforming information, and the like. The information for the random access procedure may be valid for a predetermined time, and the information for the random access procedure may be initialized when a predetermined time has elapsed. The UE operating in the RRC active state can generate the random access preamble based on the preamble sequence information set in advance and transmit the generated random access preamble to the base station via the preset resource to generate the RRC active state to the RRC connection state "Can be requested to perform the state transition operation. Here, the random access preamble may request the resumption of the RRC connection link established in the initial access procedure between the BS and the MS.

When a random access preamble is received from a terminal operating in an active state of RRC, the base station can determine that it is requested to perform a state transition operation of "RRC active state → RRC connected state ". The base station can generate a random access response based on the random access preamble received from the terminal and can transmit the generated random access response to the terminal. The UE can receive the random access response from the base station and compare the preamble sequence of the random access preamble with the preamble sequence of the random access response to confirm the success of the transmission and reception procedure of the response of the random access preamble. Here, the random access response may indicate the resumption of the RRC connection link established in the initial connection procedure between the BS and the MS, and the MS receiving the random access response may perform the resumption procedure of the RRC connection link.

(For example, when the preamble sequence of the random access preamble is the same as the preamble sequence of the random access response), the transmission / reception procedure of the uplink signaling message between the base station and the terminal , Step S603 of FIG. 6 or step S706 of FIG. 7) and a transmission / reception procedure of the downlink signaling message (for example, step S604 of FIG. 6 or step S707 of FIG. 7) may be performed. If the transmission / reception procedure of the uplink signaling message and the transmission / reception procedure of the downlink signaling message are successfully performed, the active state of the UE may transition from the active state of RRC to the RRC connected state.

Or, the transmission / reception procedure of the uplink signaling message and the transmission / reception procedure of the downlink signaling message may be omitted. In this case, the terminal that has completed the resumption procedure of the RRC connection link can transmit a message to the base station indicating completion of the resumption procedure of the RRC connection link. The base station can receive a message indicating the completion of the resumption procedure of the RRC connection link from the terminal and can determine that the resumption procedure of the RRC connection link is completed based on the received message. If the transmission / reception procedure of the message indicating the completion of the resumption procedure of the RRC connection link is successfully performed, the operation state of the terminal may transition from the active state of RRC to the RRC connection state.

On the other hand, when the transmission / reception procedure of the random access response is not successfully performed (for example, the preamble sequence of the random access preamble is different from the preamble sequence of the random access response), the terminal uses the existing collision- It is possible to connect to the base station. When the connection procedure between the terminal and the base station is completed, the operation state of the terminal may transition from the active state of RRC to the RRC connected state.

2) state transition operation according to the request of the base station

The base station can request to perform the state transition operation of "RRC in active state → RRC connected state" by transmitting the paging channel to the terminal. Information for transmission of the paging channel can be set in the initial access procedure between the base station and the terminal, and information for transmission of the paging channel can be shared between the base station and the terminal. Alternatively, the information for transmission of the paging channel may be transmitted from the base station to the terminal through the system information. The information for transmission of the paging channel includes time and frequency resources for a paging channel, a transmission period of a paging channel, a terminal identifier, beamforming information (e.g., beamforming information for a random access procedure), a preamble sequence of a random access preamble Information, and the like.

The paging channel may be classified into a plurality of sub-paging channels (e.g., sub-paging channel # 1, sub-paging channel # 2). For example, sub-paging channel # 1 may include a terminal identifier or the like, and sub-paging channel # 2 may include information elements not included in sub-paging channel # 1. In this case, the base station can transmit sub-paging channel # 1 and then sub-paging channel # 2. The information for transmission of the paging channel may be valid for a predetermined time, and information for transmission of the paging channel may be initialized when a preset time has elapsed.

The UE can estimate the location of the paging channel using a terminal identifier (e.g., C-RNTI, Temporary Mobile Subscriber Identity (TMSI)) according to a predetermined rule (e.g., a hash rule) And can receive the paging channel at the estimated location. Alternatively, the terminal can check the location of the paging channel based on the information or system information set in the initial access procedure between the base station and the terminal, and receive the paging channel at the identified location.

The UE receiving the paging channel from the base station can determine that it is requested to perform the state transition operation of "RRC Active State → RRC Connection State ", and confirm the information elements included in the paging channel. When the sub-paging channel # 1 and the sub-paging channel # 2 are used, the UE can receive the sub-paging channel # 1 from the base station. If the UE identifier included in the sub- Paging channel # 2, and information elements included in sub-paging channel # 2.

When the transmission / reception procedure of the paging channel (or the sub-paging channel # 1 and the sub-paging channel # 2) is completed, a random access procedure between the base station and the terminal can be performed. The random access procedure may be performed based on information obtained in the transmission / reception procedure of the paging channel, information for the random access procedure set in the initial access procedure between the base station and the terminal, and the like. The information for the random access procedure may include time and frequency resources for a random access preamble, preamble sequence information of a random access preamble, time and frequency resources for a random access response, beamforming information, and the like. The information for the random access procedure may be valid for a predetermined time, and the information for the random access procedure may be initialized when a predetermined time has elapsed.

In the random access procedure, the UE operating in the RRC active state can generate the random access preamble based on the preset preamble sequence information, and can transmit the generated random access preamble to the base station through the preset resource. Here, the random access preamble may request the resumption of the RRC connection link established in the initial access procedure between the BS and the MS.

The base station can receive the random access preamble from the terminal operating in the RRC active state, can generate the random access response based on the received random access preamble, and can transmit the generated random access response to the terminal. The UE can receive the random access response from the base station and compare the preamble sequence of the random access preamble with the preamble sequence of the random access response to confirm the success of the transmission and reception procedure of the response of the random access preamble. Here, the random access response may indicate the resumption of the RRC connection link established in the initial connection procedure between the BS and the MS, and the MS receiving the random access response may perform the resumption procedure of the RRC connection link.

(For example, when the preamble sequence of the random access preamble is the same as the preamble sequence of the random access response), the transmission / reception procedure of the uplink signaling message between the base station and the terminal , Step S603 of FIG. 6 or step S706 of FIG. 7) and a transmission / reception procedure of the downlink signaling message (for example, step S604 of FIG. 6 or step S707 of FIG. 7) may be performed. If the transmission / reception procedure of the uplink signaling message and the transmission / reception procedure of the downlink signaling message are successfully performed, the operation state of the UE may transition from the RRC active state to the RRC connection state.

Or, the transmission / reception procedure of the uplink signaling message and the transmission / reception procedure of the downlink signaling message may be omitted. In this case, the terminal that has completed the resumption procedure of the RRC connection link can transmit a message to the base station indicating completion of the resumption procedure of the RRC connection link. The base station can receive a message indicating the completion of the resumption procedure of the RRC connection link from the terminal and can determine that the resumption procedure of the RRC connection link is completed based on the received message. If the transmission / reception procedure of the message indicating the completion of the resumption procedure of the RRC connection link is successfully performed, the operation state of the terminal may transition from the active state of RRC to the RRC connection state.

On the other hand, when the transmission / reception procedure of the random access response is not successfully performed (for example, the preamble sequence of the random access preamble is different from the preamble sequence of the random access response), the terminal uses the existing collision- It is possible to connect to the base station. When the connection procedure between the terminal and the base station is completed, the operation state of the terminal may transition from the active state of RRC to the RRC connected state.

State transitions in "RRC active state → RRC idle state"

The state transition operation in the "RRC inactive state to RRC idle state" can be performed at the request of the base station. For example, the base station can generate a paging channel including an indicator requesting to perform a state transition operation of "RRC in active state → RRC idle state ", and can transmit the generated paging channel. The UE receiving the paging channel can determine that the status transition operation in the "RRC active state? RRC idle state" is requested, and the UE's active state can be transited from the active state to the RRC idle state . In this case, the base station can delete the unique information (e.g., UE context information) of the terminal, and the RRC connection link established between the base station and the terminal can be released.

Alternatively, the indicator requesting to perform the state transition operation of the "RRC active state → RRC idle state" may be transmitted to the terminal in the random access procedure instead of the transmission procedure of the paging channel. For example, a base station may transmit a paging channel, and a terminal receiving a paging channel may transmit a random access preamble to a base station. The base station can receive the random access preamble from the terminal and can transmit to the terminal a random access response including an indicator requesting to perform the state transition operation in the "RRC Active State → RRC Idle State ". The UE can receive the random access response from the base station and can determine that it is requested to perform the state transition operation of "RRC inactive state → RRC idle state" based on the random access response.

Alternatively, an indicator requesting to perform a state transition operation of "RRC in active state → RRC idle state" may be transmitted to the terminal through a downlink signaling message transmitted after a random access response instead of a random access response. Therefore, during the random access procedure, the UE can determine that the status transition operation of "RRC active state → RRC idle state" is requested while the UE is in the active access state, and transitions the active state of the UE from RRC active state to RRC idle state . In this case, the BS may delete the unique information (e.g., UE context information) of the UE, and the RRC connection link established between the BS and the UE may be released.

State transitions in "RRC Idle State → RRC Connection State"

The terminal operating in the idle state can perform the random access procedure shown in FIG. 6 or the random access procedure shown in FIG. 7, and when the random access procedure is successfully completed, the operating state of the terminal is changed from the RRC idle state to the RRC connection State.

■ How to support mobility of terminals operating in RRC active state

Next, mobility support methods of a terminal operating in an RRC active state in a communication system will be described.

12 is a conceptual diagram showing a second embodiment of the communication system.

Referring to FIG. 12, the communication system may include a first base station 1210, a second base station 1220, a terminal 1230, and the like. The terminal 1230 may belong to the cell coverage of the first base station 1210 and may operate in the RRC inactive state after the connection procedure between the terminal 1230 and the first base station 1210 is completed. In this case, the terminal 1230 can receive system information, paging channel, and the like from the first base station 1210, and the first base station 1210 can receive unique information (e.g., UE context information) And so on. In addition, the RRC connection link established between the first base station 1210 and the terminal 1230 may be in an inactive state.

Meanwhile, the terminal 1230 can move from the cell coverage of the first base station 1210 to the cell coverage of the second base station 1220. In this case, the signal strength received from the second base station 1220 may be greater than the signal strength received from the first base station 1210. If the difference between the signal strength received from the second base station 1220 and the signal strength received from the first base station 1210 is greater than or equal to a preset threshold value, the terminal 1230 transmits a random access procedure For example, the random access procedure shown in FIG. 6 or the random access procedure shown in FIG. 7).

In the random access procedure between the UE 1230 and the second Node B 1220, the UE 1230 can generate a random access preamble using the preamble sequence set by the second Node B 1220, To the second base station (1220). The second base station 1220 may receive the random access preamble from the terminal 1230 and may transmit a random access response to the terminal 1230 in response to the random access preamble. If a random access response is successfully received from the second base station 1220, the terminal 1230 may generate an uplink signaling message including a terminal identifier, a previous cell identifier, a beam identifier, Message to the second base station 1220. < RTI ID = 0.0 >

The second base station 1220 can receive the uplink signaling message from the terminal 1230 and can receive the unique information of the terminal 1230 (e.g., the uplink signaling message) based on the information (e.g., (E.g., UE context information) exists in the second base station 1220. If the unique information of the terminal 1230 does not exist in the second base station 1220, the second base station 1220 can request the transmission of the unique information of the terminal 1230 to the first base station 1210 or the core network . Accordingly, the second base station 1220 can acquire the unique information of the terminal 1230 from the first base station 1210 or the core network, and can manage the unique information of the acquired terminal 1230. [ The second base station 1220 may also send a message to the first base station 1210 requesting the release of the established RRC connection link between the first base station 1210 and the terminal 1230. The first base station 1210 can receive the message requesting the release of the RRC connection link and can release the RRC connection link between the first base station 1210 and the terminal 1230 based on the received message.

When the reception of the uplink signaling message is completed, the second base station 1220 can generate the downlink signaling message and transmit the generated downlink signaling message to the terminal 1230. The UE 1230 can receive the downlink signaling message from the second base station 1220 and identify the information elements included in the received downlink signaling message. When the random access procedure between the terminal 1230 and the second base station 1220 is completed, the terminal 1230 can operate in the RRC connection state or the RRC active state based on the control of the second base station 1220.

Meanwhile, the terminal 1230 may not receive a signal having an intensity of a predetermined threshold value or more from the Node Bs 1210 and 1220. In this case, the terminal 1230 may be in an active state (or an RRC Connection state) to the RRC idle state. The base stations 1210 and 1220 can delete the unique information of the terminal 1230 when the terminal 1230 fails to receive a signal from the terminal 1230 for a preset time.

A method of transmitting and receiving a data unit based on a random access procedure

A method of transmitting and receiving data units performed in a terminal operating in an RRC active state in a communication system will be needed.

13 is a flowchart showing a first embodiment of a method of transmitting and receiving a data unit based on a random access procedure.

Referring to FIG. 13, the UE can operate in an active state, which is an RRC. The UE can compare the size of the data unit stored in the transmission buffer with a predetermined threshold (S1301). If the size of the data unit stored in the transmission buffer of the UE is larger than a predetermined threshold value, the UE can perform a state transition operation of "active state to RRC connected state ", which is RRC (S1302). When the state transition operation is completed, the operating state of the terminal may transition from the active state of RRC to the RRC connected state. A UE operating in the RRC connection state can transmit a scheduling request (SR) indicator for uplink transmission of a data unit to a base station.

The base station receiving the scheduling request indicator can set the uplink resource for the UE and transmit the uplink grant including the uplink resource information to the UE. The terminal can receive the uplink grant from the base station and transmit the data unit to the base station through the resource indicated by the uplink grant (S1305). The base station may receive the data unit from the terminal and may transmit an acknowledgment (ACK) message to the terminal in response to the data unit if the data unit is successfully received. The terminal can receive an ACK message for the data unit from the base station (S1306), and can determine that the data unit has been successfully received from the base station based on the ACK message.

On the other hand, when the size of the data unit stored in the transmission buffer of the UE is equal to or less than a predetermined threshold value, the terminal operating in the active state of RRC performs the random access procedure without performing the state transition operation of "active state → RRC connected state" It is possible to transmit the data unit on the basis of this.

For example, the terminal may generate a random access preamble based on preamble sequence information (e.g., a preamble sequence subset) set by the base station. The random access preamble may indicate a scheduling request for uplink transmission of a data unit. For example, the random access preamble may include a scheduling request indicator for uplink transmission of a data unit. A preamble sequence for instructing a scheduling request for uplink transmission of a data unit between a UE and a base station may be set in advance and a random access preamble may be set based on a preamble sequence indicating a scheduling request for uplink transmission of a data unit .

In addition, the random access preamble may further include an indicator indicating the size of the data unit to be transmitted by the terminal (for example, the size of the data unit stored in the transmission buffer of the terminal). A data unit to be transmitted by the terminal (for example, a data unit stored in the transmission buffer of the terminal) may be referred to as an "uplink data unit ". Alternatively, a preamble sequence indicating the size of the UL data unit between the UE and the BS may be set in advance. For example, the preamble sequence # 1 may indicate that the size of the UL data unit is 1 RB, the preamble sequence # 2 may indicate that the size of the UL data unit is 2 RB, and the preamble sequence # It can indicate that the size of the link data unit is 3RB. Therefore, the random access preamble can be set based on a preamble sequence indicating the size of the UL data unit.

Alternatively, the indicator indicating the size of the UL data unit may be transmitted via a message separate from the random access preamble. A message including an indicator indicating the size of the uplink data unit may be transmitted from the terminal to the base station via a control channel (e.g., PUCCH) or a data channel (e.g., PUSCH). In this case, the random access preamble may include time and frequency resource information on which a message including an indicator indicating the size of the uplink data unit is transmitted.

The UE can transmit the random access preamble through a predetermined resource (e.g., PRACH) by the base station (S1303). The random access preamble may request scheduling for uplink transmission of data units. In addition, the random access preamble may further include an indicator for indicating the size of the uplink data unit. If the indicator indicating the size of the UL data unit is not included in the random access preamble, the UE may transmit a message including an indicator indicating the size of the UL data unit after transmission of the random access preamble.

When a beamforming scheme (for example, a beam sweep scheme) is applied to the random access procedure, the UE can repeatedly transmit the random access preamble based on the beamforming period. In this case, the same random access preamble can be repeatedly transmitted using the same resource.

The base station can receive the random access preamble from the terminal and confirm that the scheduling for uplink transmission of the data unit is requested based on the received random access preamble. Also, the base station may obtain an indicator indicating the size of the uplink data unit included in the random access preamble (or a preamble sequence) or an indicator indicating the size of the uplink data unit included in the separate message, The size of the uplink data unit can be confirmed based on the obtained indicator (or preamble sequence). When a beamforming scheme (for example, a beam sweep scheme) is applied to a random access procedure, a base station can receive a plurality of random access preambles, and a random access preamble having the largest signal strength among the plurality of received random access preambles It is possible to confirm the size of the uplink data unit and the scheduling request based on the access preamble.

If the random access preamble is successfully received from the terminal, the base station can generate a random access response. The random access response may include uplink grant information (e.g., uplink resource information), TA, a terminal identifier (e.g., a temporary identifier used to distinguish terminals that have transmitted a random access preamble) . The uplink grant information may include time and frequency resource information allocated for transmission of the UL data unit, transmission power information of the UL data unit, transmission time information, beamforming information, and the like. The time and frequency resources allocated for transmission of the UL data unit may be set based on an indicator (or a preamble sequence) indicating the size of the UL data unit received from the terminal. Alternatively, in a case where a resource for transmission of an uplink data unit is preset in the initial access procedure between the UE and the BS, the time and frequency resource information allocated for transmission of the UL data unit may be omitted from the UL grant information.

The base station can transmit a random access response to the terminal through a predetermined resource (e.g., a resource mapped to the random access preamble). The random access response may be transmitted based on the beamforming scheme. The terminal can receive a random access response from the base station (S1304). The UE can compare the preamble sequence of the random access preamble with the preamble sequence of the random access response and judge that the transmission and reception procedure of the random access response is successfully completed when the preamble sequence of the random access preamble is identical to the preamble sequence of the random access response . In this case, the UE can confirm the information elements included in the random access response (e.g., uplink grant information, TA, terminal identifier, etc.). On the other hand, if the random access response is not received from the base station for a preset time, the terminal can retransmit the random access preamble.

The terminal may generate a data unit based on a size of a preset data unit or a size of a time and frequency resource indicated by a random access response. The terminal may transmit a message including the data unit to the base station through the resource allocated by the base station (S1305). In addition, the message may further include information indicating the state of the transmission buffer of the terminal as well as the data unit. Further, the message may further include not only the data unit but also information indicating that the transmission of the data unit is completed (for example, information indicating that the uplink data unit is not present in the terminal).

The base station can receive a message including a data unit from the terminal. If the data unit is successfully received, the base station may send an ACK message to the terminal for the data unit. The terminal can receive an ACK message for the data unit from the base station (S1306), and can determine that the data unit has been successfully received from the base station based on the ACK message.

If the message received from the terminal includes information indicating the state of the transmission buffer of the terminal and the information indicating the state of the transmission buffer of the terminal indicates that the UL data unit exists in the terminal, The uplink resource for transmission of the link data unit can be allocated. The base station may transmit uplink grant information including uplink resource information to the terminal. In this case, the terminal can transmit the uplink data unit to the base station based on the uplink grant information. If there is no uplink data unit in the transmission buffer of the UE, the UE can terminate the transmission / reception procedure of the data unit based on the random access procedure.

In addition, when the message received from the terminal includes information indicating that the transmission of the data unit is completed, the base station can terminate the transmission / reception procedure of the data unit based on the random access procedure.

■ Random access procedure based on beamforming scheme

The random access procedure between the base station and the terminal may be performed based on a beamforming scheme (for example, a beam sweep scheme).

FIG. 14 is a conceptual diagram showing a third embodiment of the communication system, FIG. 15 is a timing chart showing a first embodiment of the beamforming transmission performed by the base station in the communication system shown in FIG. 14, 14 is a timing diagram illustrating a first embodiment of beamforming transmission performed by a terminal in a communication system shown in Figs.

14 through 16, the communication system may include a base station 1410, a terminal 1420, and the like. Each of the base station 1410 and the terminal 1420 may support a beamforming scheme (for example, a beam sweep scheme). For example, base station 1410 may use three beams (e.g., beam # 10, beam # 11, beam # 12) to provide communication services to terminals belonging to cell coverage. For example, base station 1410 can transmit signals in subframe # 0 using beam # 10, transmit signals in subframe # 1 using beam # 11, and transmit signals using subframe # It is possible to transmit a signal in frame # 2. The same signal can be transmitted through each of the three beams in one transmission period (e.g., subframe # 0 to # 2). Here, the signal may be system information, control information, a reference signal, a synchronization signal, a paging signal, a downlink data unit, or the like. The downlink transmission operation and the uplink reception operation of the base station based on the beamforming scheme can be performed in one subframe. That is, the transmission and reception of signals can be performed in the same subframe.

The terminal 1420 may use three beams (e.g., beam # 20, beam # 21, beam # 22). For example, terminal 1420 can transmit signals in subframe # 0 using beam # 20, transmit signals in subframe # 1 using beam # 21, and transmit signals using subframe # It is possible to transmit a signal in frame # 2. The same signal can be transmitted through each of the three beams in one transmission period (e.g., subframe # 0 to # 2). Here, the signal may be control information, a reference signal, an uplink data unit, or the like.

1) Procedures for sending and receiving system information

Base station 1410 may generate system information. The system information may include an indicator indicating whether beamforming is supported, a number of beams (e.g., three) used by the base station 1410, a beam index, and the like. For example, the beam index of beam # 10 may be set to "10", the beam index of beam # 11 may be set to "11", and the beam index of beam # 12 may be set to "12" have.

When the transmission period of the system information is one radio frame and the system information is transmitted based on the beamforming scheme in the subframes # 0 to # 2, the base station 1410 transmits the subframes # 0 to # 10 and may transmit system information using beam # 11 in subframe # 1 of each of the radio frames, and may transmit system information using beam # 12 in subframe # 2 of each of the radio frames System information can be transmitted. The beam index included in the system information of the beam # 10 may be set to "10", the beam index included in the system information of the beam # 11 may be set to "11" The beam index can be set to "12 ". The reference time of the base station 1410 may be the time at which the base station 1410 transmits the first beam (e.g., beam # 10).

Terminal 1420 can receive system information from base station 1410 and identify information elements included in the received system information. The terminal 1420 uses the beam # 12 of the base station 1410 for communication between the base station 1410 and the terminal 1420 because the strength of the signal received through the beam # 12 among the beams of the base station 1410 is greatest. , And can inform the base station 1410 of the beam index (i.e., "12") of beam # 12. Also, since the communication based on the beam # 12 of the base station 1410 is performed in the subframe # 2, the terminal 1420 can determine that downlink communication and uplink communication are possible in the subframe # 2. Therefore, the UE 1420 can transmit the random access preamble through the subframe # 2.

Also, the reception beam of the terminal 1420 may be determined in the system information reception procedure. For example, terminal 1420 may receive system information using all beams (e.g., beam # 20, beam # 21, beam # 22), and the intensity of the signal received via beam # The terminal 1420 can determine the beam # 21 as the beam used for communication between the base station 1410 and the terminal 1420. [ The beam pair for communication between the base station 1410 and the terminal 1420 may be determined as "beam # 12-beam # 21 ". The terminal 1420 can inform the base station 1410 of the beam index of the beam # 21 (i.e., "21") and can communicate with the base station 1410 using the beam # 21.

2) Transmission and reception procedure of paging channel

If the terminal 1420 is a non-mobile terminal, the base station 1410 transmits a paging channel based on the determined beam pair (e.g., "Beam # 12 - Beam # 21") based on the transmission / . For example, base station 1410 may transmit a paging channel using beam # 12. However, if a response to the paging channel is not received from the terminal 1420 for a predetermined amount of time, the base station 1410 may use the paging channel (e.g., Lt; / RTI >

3) Random access procedure

The UE 1420 can transmit the random access preamble through the subframe # 2 determined in the transmission / reception procedure of the system information. In this case, the terminal 1420 can repeatedly transmit the random access preamble using all of the beams (e.g., beam # 20, beam # 21, beam # 22). The random access preamble may include a beam index. For example, the beam index included in the random access preamble of beam # 20 may be set to "20 ", the beam index included in the random access preamble of beam # 21 may be set to & The beam index included in the random access preamble of 22 may be set to "22 ".

Alternatively, the terminal 1420 can transmit the random access preamble using the beam # 21 belonging to the beam pair determined in the transmission / reception procedure of the system information. However, if the valid period of the beam pair has elapsed, the terminal 1420 can repeatedly transmit the random access preamble using all the beams (e.g., beam # 20, beam # 21, beam # 22).

The base station 1410 may receive the random access preamble from the terminal 1420. When the system information of the base station 1410 is transmitted in subframe # 2 using beam # 12 and the random access preamble of terminal 1420 is received in subframe # 2, base station 1410 transmits beam # A beam used for communication between the terminal 1410 and the terminal 1420 can be determined. When a plurality of random access preambles are received from the terminal 1420, the base station 1410 transmits a beam (for example, beam # 21) to which the random access preamble having the largest strength among the plurality of random access preambles A beam used for communication between the terminal 1410 and the terminal 1420 can be determined. Alternatively, when one random access preamble is received from the terminal 1420, the base station 1410 transmits the transmitted beam (e.g., beam # 21) of the random access preamble to the communication between the base station 1410 and the terminal 1420 As shown in FIG.

If the random access preamble is successfully received, the base station 1410 may generate a random access response. The random access response may include uplink resource information, a TA, a preamble sequence, a beam index, and the like. The preamble sequence may be a preamble sequence of the random access preamble received at the base station 1410. The beam index may be a beam index (e.g., "21 ") of the random access preamble received at the base station 1410. Base station 1410 may transmit a random access response using beam # 12.

Terminal 1420 may receive a random access response from base station 1410 and may identify information elements included in the received random access response. The terminal 1420 may transmit the data unit or control information via the resource indicated by the random access response.

On the other hand, if a random access response is not received from the base station 1410 within a predetermined time, the terminal 1420 can retransmit the random access preamble using the beam # 21. For example, the UE 1420 can retransmit the random access preamble by the preset number of retransmissions. Alternatively, the terminal 1420 may repeatedly transmit a random access preamble for a time corresponding to a preset timer. In the retransmission procedure of the random access preamble, the transmission power may be higher than the transmission power in the transmission procedure of the previous random access preamble (for example, the initial transmission procedure of the random access preamble). If no random access response is also received by the retransmission procedure of the random access preamble, the terminal 1420 can repeatedly transmit the random access preamble using all the beams (e.g., beam # 20, beam # 21, beam # 22) have. In the retransmission procedure of the random access preamble, the terminal 1420 can reacquire the reference time of the base station 1410 by receiving the signal of the base station 1410. [

The methods according to the present invention can be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention or may be available to those skilled in the computer software.

Examples of computer readable media include hardware devices that are specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (20)

A method of operating a terminal in a communication system,
The UE operates in an RRC active state among a radio resource control (RRC) idle state, an RRC active state, and an RRC connected state,
Transmitting a random access preamble to a base station when an uplink data unit exists in the UE;
Receiving a random access response which is a response of the random access preamble from the base station; And
And transmitting a message including the uplink data unit to the base station through a resource indicated by the random access response. The method according to claim 1,
Wherein the RRC idle state is a state in which the UE is not connected to the base station, the RRC active state and the RRC connected state are states in which the UE is connected to the base station, Wherein the base station supports a scheduling operation for the UE operating in the RRC connection state without supporting a scheduling operation for the UE. The method according to claim 1,
Wherein the random access preamble is transmitted from the terminal to the base station when the size of the uplink data unit is less than or equal to a preset threshold value. The method according to claim 1,
A method of operating a terminal,
Transitioning from an active state of the RRC to an RRC connected state when the size of the uplink data unit exceeds the preset threshold value; And
Further comprising the step of the terminal operating in the RRC connection state transmitting the uplink data unit to the base station based on a scheduling operation of the base station. The method according to claim 1,
Wherein the random access preamble includes an indicator for requesting transmission of the uplink data unit and size information of the uplink data unit. The method according to claim 1,
Wherein the random access preamble is transmitted through a physical random access channel (PRACH) indicated by system information or DCI (downlink control information) received from the base station. The method according to claim 1,
Wherein the random access response includes information indicating the resource allocated for transmission of the uplink data unit. The method according to claim 1,
Wherein the message further comprises information indicating a buffer state of the terminal. A method of operating a terminal in a communication system,
The UE operates in one of a radio resource control (RRC) idle state, an RRC active state, and an RRC connected state,
Transitioning from the RRC idle state to the RRC connected state based on a random access procedure between the terminal and the base station when the terminal operates in the RRC idle state;
Transitioning from an RRC connection state to an RRC idle state or an RRC active state based on a request from the base station when the terminal operates in the RRC connected state; And
And transitioning from an active state of the RRC to an RRC connected state based on the random access procedure between the terminal and the base station when the terminal operates in the active state of the RRC. A method of operating a terminal. The method of claim 9,
Wherein the RRC idle state is a state in which the UE is not connected to the base station, the RRC active state and the RRC connected state are states in which the UE is connected to the base station, Wherein the base station supports a scheduling operation for the UE operating in the RRC connection state without supporting a scheduling operation for the UE. The method of claim 9,
Wherein the terminal transitions from the RRC connection state to the RRC active state upon the request of the base station when the terminal supports the low delay service. The method of claim 9,
Wherein when the paging channel is received from the base station, the operational state of the mobile station changes from the RRC active state to the RRC connected state. The method of claim 9,
Wherein the random access procedure for a transition from the RRC active state to the RRC connected state is a procedure for resuming an RRC connection link between the terminal and the base station. As a terminal in a communication system,
A processor; And
Wherein at least one instruction executed through the processor includes a memory,
The UE operates in an RRC active state among a radio resource control (RRC) idle state, an RRC active state, and an RRC connected state,
Wherein the at least one instruction comprises:
Transmitting a random access preamble to a base station when an uplink data unit exists in the terminal;
Receive a random access response that is a response of the random access preamble from the base station; And
And transmit the message including the uplink data unit to the base station via a resource indicated by the random access response. 15. The method of claim 14,
Wherein the RRC idle state is a state in which the UE is not connected to the base station, the RRC active state and the RRC connected state are states in which the UE is connected to the base station, Wherein the base station supports a scheduling operation for the UE operating in the RRC connection state. 15. The method of claim 14,
Wherein the random access preamble is transmitted from the terminal to the base station when the size of the uplink data unit is equal to or less than a preset threshold value. 15. The method of claim 14,
Wherein the at least one instruction comprises:
If the size of the uplink data unit exceeds the preset threshold value, the operation state of the UE transitions from the RRC active state to the RRC connected state; And
Wherein the terminal operating in an active state of the RRC is further adapted to transmit the uplink data unit to the base station based on a scheduling operation of the base station. 15. The method of claim 14,
Wherein the random access preamble includes an indicator for requesting transmission of the uplink data unit and size information of the uplink data unit. 15. The method of claim 14,
Wherein the random access preamble is transmitted via a physical random access channel (PRACH) indicated by system information received from the base station or downlink control information (DCI). 15. The method of claim 14,
Wherein the message further comprises information indicating a buffer state of the terminal.

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