KR20100041642A - Method of random access - Google Patents

Abstract

PURPOSE: A random access method is provided to reduce a waiting time, a handover time, and a network connection time by preventing the delay in random access. CONSTITUTION: A terminal and a network are performed in random access. A terminal transmits the random access preamble to a network(S1810). The terminal receives a random access response from the network according to the preamble of random access(S1820). A transmitted random access response includes radio resource assignment information. The terminal transmits a scheduled messages according to the size and number of allocation resources through a plurality of assigner circles(S1830). A dedicated random access preamble is allocated to the terminal from the base station. The terminal transmits random access preamble to the base station through PRACH resource. The terminal receives a random access response corresponding to the dedicated random access preamble.

Description

Random access method {METHOD OF RANDOM ACCESS}

The present invention relates to wireless communication, and more particularly, to a random access method in a wireless communication system.

3rd generation partnership project (3GPP) mobile communication systems based on wideband code division multiple access (WCDMA) wireless access technology are widely deployed around the world. High Speed Downlink Packet Access (HSDPA), which can be defined as the first evolution of WCDMA, provides 3GPP with a highly competitive wireless access technology in the mid-term future. However, as the demands and expectations of users and operators continue to increase and the development of wireless access technologies is in progress, new technological evolution in 3GPP is required to be competitive in the future. Reduced cost per bit, increased service availability, the use of flexible frequency bands, simple structure and open interface, and adequate power consumption of the terminal are demanding requirements.

In general, one or more cells are arranged in one base station. A plurality of terminals may be located in one cell. In general, a terminal undergoes a random access procedure to access a network. The purpose of the UE to perform a random access process to the network may be an initial access (initial access), handover (handover), radio resource request (Scheduling Request), timing synchronization (timing alignment).

The random access process may be divided into a contention based random access procedure and a non-contention based random access procedure. The biggest difference between the contention-based random access process and the non- contention-based random access process is whether a random access preamble is assigned to one UE.

Here, contention refers to two or more terminals attempting a random access procedure using the same random access preamble through the same resource. In the contention-based random access process, there is a possibility of contention because the terminal uses a randomly selected random access preamble.

In the random access procedure, when the terminal transmits the random access preamble, the network transmits a random access response to the terminal, and the terminal transmits a scheduled message back to the network. The random access process will be described in more detail later with the embodiments of the present invention.

The random access response includes a random access preamble ID and radio resource allocation information for transmitting a scheduled message. If the terminal does not have enough allocated radio resources to transmit the scheduled message, the random access process may be performed again. The waiting time continues until the radio resource is reassigned through the scheduling request. Therefore, a delay time occurs until the random access process is completed, thereby causing problems such as handover delay and network connection delay of the terminal.

The present invention seeks to prevent delay of the random access procedure and to reduce call setup time. Therefore, it is intended to prevent the network connection delay or the user waiting time of the terminal due to the delay of the random access process.

In addition, we want to increase the efficiency of resource allocation in radio resource allocation.

According to an aspect of the present invention, there is provided a random access method, comprising: transmitting a random access preamble to a network, a plurality of radio resource allocation information and a random access preamble ID corresponding to each of the radio resource allocation information, and identifying the random access preamble Receiving a random access response including a from the network, Transmitting one or more scheduled messages to the network through a plurality of allocated resources according to the plurality of radio resource allocation information.

In addition, the random access method according to another aspect of the present invention comprises the steps of receiving a random access preamble from the terminal, a random access preamble for specifying the terminal to which the radio resources are allocated according to a plurality of radio resource allocation information and the radio resource allocation information Generating a random access response including an ID, transmitting the random access response to the terminal, one or more scheduled messages transmitted through allocation resources which are radio resources allocated to the terminal according to the radio resource allocation information Receiving from the terminal.

According to an embodiment of the present invention, it is possible to prevent a delay of a random access process and to shorten a call setup time.

In addition, according to an embodiment of the present invention, by preventing the delay of the random access process, it is possible to shorten the time required for network connection or handover and to prevent the user waiting time from lengthening.

In addition, according to an embodiment of the present invention can increase the efficiency when allocating and using radio resources, it is possible to reduce the use of the downlink channel for radio resource allocation.

1 is a block diagram illustrating a wireless communication system. This may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may be referred to as a Long Term Evolution (LTE) system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) includes a base station (BS) 20 that provides a control plane and a user plane.

The UE 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, and the like. The base station 20 generally refers to a fixed station communicating with the terminal 10, and may be referred to as other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), and an access point. have. One or more cells may exist in one base station 20. An interface for transmitting user traffic or control traffic may be used between the base stations 20. Hereinafter, downlink means communication from the base station 20 to the terminal 10, and uplink means communication from the terminal 10 to the base station 20.

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

2 is a block diagram illustrating a functional split between an E-UTRAN and an EPC. The hatched box represents the radio protocol layer and the white box represents the functional entity of the control plane.

Referring to FIG. 2, the base station performs the following function. (1) Radio resource management such as radio bearer control, radio admission control, connection mobility control, and dynamic resource allocation to a terminal RRM), (2) Internet Protocol (IP) header compression and encryption of user data streams, (3) routing of user plane data to S-GW, and (4) paging messages. Scheduling and transmission of (5) scheduling and transmission of broadcast information, and (6) measurement and measurement report setup for mobility and scheduling.

The MME performs the following functions. (1) Non-Access Stratum (NAS) signaling, (2) NAS signaling security, (3) Idle mode UE Reachability, (4) Tracking Area list management , (5) Roaming, (6) Authentication.

S-GW performs the following functions. (1) mobility anchoring, (2) lawful interception. P-GW (P-Gateway) performs the following functions. (1) terminal IP (allocation) allocation (allocation), (2) packet filtering.

3 is a block diagram illustrating elements of a terminal. The terminal 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit 55. . The processor 51 is implemented with layers of the air interface protocol to provide a control plane and a user plane. The functions of each layer may be implemented through the processor 51. The memory 52 is connected to the processor 51 to store a terminal driving system, an application, and a general file.

The display unit 54 displays various information of the terminal, and may use well-known elements such as liquid crystal display (LCD) and organic light emitting diodes (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to a processor and transmits and / or receives a radio signal.

Layers of the radio interface protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) model, which is well known in communication systems. (Second layer) and L3 (third layer).

Among these, the physical layer belonging to the first layer provides an information transfer service using a physical channel, and a radio resource control (RRC) layer located in the third layer. Plays a role of controlling radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the UE and the network.

4 is a block diagram illustrating a radio protocol architecture for a user plane. 5 is a block diagram illustrating a radio protocol structure for a control plane. This shows the structure of the air interface protocol between the terminal and the E-UTRAN. The data plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

4 and 5, a physical layer (PHY), which is a first layer, provides an information transfer service to a higher layer using a physical channel. The physical layer is connected to the upper Media Access Control (MAC) layer through a transport channel, and data between the MAC layer and the physical layer moves through this transport channel. Data moves between physical layers between physical layers, that is, between physical layers of a transmitting side and a receiving side.

The MAC layer of the second layer provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The RLC layer of the second layer supports reliable data transmission. In the RLC layer, there are three operation modes according to a data transmission method: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). The AM RLC provides a bidirectional data transmission service, and supports retransmission when an RLC Protocol Data Unit (PDU) fails to transmit.

The Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function to reduce the IP packet header size.

The radio resource control (RRC) layer of the third layer is defined only in the control plane. The RRC layer is responsible for controlling logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers (RBs). RB means a service provided by the second layer for data transmission between the UE and the E-UTRAN. If there is an RRC connection (RRC Connection) between the RRC of the terminal and the RRC of the network, the terminal is in the RRC Connected Mode, otherwise it is in the RRC Idle Mode.

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

6 shows a mapping between a downlink logical channel and a downlink transport channel. 7 shows mapping between an uplink logical channel and an uplink transport channel. These include 3GPP TS 36.300 V8.3.0 (2007-12) Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; See section 6.1.3 of Stage 2 (Release 8).

6 and 7, in the downlink, a paging control channel (PCCH) is mapped to a paging channel (PCH), and a broadcast control channel (BCCH) is mapped to a broadcast channel (BCH) or a downlink shared channel (DL-SCH). do. Common Control Channel (CCCH), Dedicated Control Channel (DCCH), Dedicated Traffic Channel (DTCH), Multicast Control Channel (MCCH) and Multicast Traffic Channel (MTCH) are mapped to DL-SCH. MCCH and MTCH are also mapped to MCH (Multicast Channel). In uplink, CCCH, DCCH, and DTCH are mapped to uplink shared channel (UL-SCH).

Each logical channel type is defined by what kind of information is transmitted. There are two types of logical channels: control channels and traffic channels.

The control channel is used for transmission of control plane information. BCCH is a downlink channel for broadcasting system control information. PCCH is a downlink channel that transmits paging information and is used when the network does not know the location of the terminal. CCCH is a channel for transmitting control information between the terminal and the network, and is used when the terminal does not have an RRC connection with the network. The MCCH is a point-to-multipoint downlink channel used for transmitting multimedia broadcast multicast service (MBMS) control information and is used for terminals receiving MBMS. DCCH is a point-to-point one-way channel for transmitting dedicated control information between the terminal and the network, and is used by a terminal having an RRC connection.

The traffic channel is used for transmission of user plane information. DTCH is a point-to-point channel for transmitting user information and exists in both uplink and downlink. MTCH is a point-to-many downlink channel for transmission of traffic data, and is used for a terminal receiving an MBMS.

Transport channels are classified according to how and with what characteristics data is transmitted over the air interface. The BCH has a predefined transmission format that is broadcast and fixed in the entire cell area. DL-SCH supports hybrid automatic repeat request (HARQ). Support for dynamic link adaptation by changing modulation, coding and transmission power, possibility of broadcast, possibility of beamforming, support for dynamic / semi-static resource allocation, and support for discontinuous reception (DRX) to save terminal power And MBMS transmission support. PCH is characterized by DRX support for terminal power saving and broadcast to the entire cell area. MCH is characterized by broadcast to the entire cell and MBMSN (MBMS Single Frequency Network) support.

The uplink transport channel includes a UL-SCH and a random access channel (RACH). The UL-SCH is characterized by support of dynamic link adaptation that changes transmission power and modulation and coding, HARQ support, and support of dynamic and semi-static resource allocation. RACH is characterized by limited control information and collision risk.

8 shows a mapping between a downlink transport channel and a downlink physical channel. 9 shows mapping between an uplink transport channel and an uplink physical channel.

8 and 9, in downlink, BCH is mapped to a physical broadcast channel (PBCH), MCH is mapped to a physical multicast channel (PMCH), and PCH and DL-SCH are mapped to a physical downlink shared channel (PDSCH). do. PBCH carries the BCH transport block, PMCH carries the MCH, and PDSCH carries the DL-SCH and PCH. In uplink, the UL-SCH is mapped to a physical uplink shared channel (PUSCH), and the RACH is mapped to a physical random access channel (PRACH). The PRACH carries a random access preamble.

There are several physical control channels used in the physical layer. The physical downlink control channel (PDCCH) informs the UE of resource allocation of the PCH and DL-SCH and HARQ information related to the DL_SCH. The PDCCH may carry an uplink scheduling grant informing the UE of resource allocation of uplink transmission. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for PDCCHs and is transmitted every subframe. PHICH (physical Hybrid ARQ Indicator Channel) carries a HARQ ACK / NAK signal in response to uplink transmission. Physical uplink control channel (PUCCH) carries uplink control information such as HARQ ACK / NAK, scheduling request, and CQI for downlink transmission.

10 shows the structure of a radio frame.

One radio frame consists of 10 subframes, and one subframe consists of two slots. The time it takes for one subframe to be transmitted is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.

The structure of the radio frame described with reference to FIG. 10 is merely an example, and the number of subframes included in the radio frame or the number of slots included in the subframe and the number of OFDM symbols included in the slot may be variously changed. have.

11 is an exemplary diagram illustrating a resource grid for one downlink slot.

Referring to FIG. 11, a downlink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain. Here, one downlink slot includes 7 OFDM symbols and one resource block includes 12 subcarriers in a frequency domain, but is not limited thereto.

Each element on the resource grid is called a resource element, and one resource block includes 12 × 7 resource elements. The number NDL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth set in the cell.

12 shows a structure of a subframe.

Referring to FIG. 12, a subframe includes two consecutive slots. Up to three OFDM symbols of the first slot in the subframe are the control region to which the PDCCH is allocated, and the remaining OFDM symbols are the user region to which the PDSCH is allocated. The PCFICH carries information about the number of OFDM symbols used for transmission of PDCCHs in a subframe.

The random access procedure will be described below.

First, the UE may perform a random access procedure to the base station in the following cases.

(1) When the terminal does not have an RRC connection with the base station and performs initial access (initial access)

(2) When the UE first accesses the target cell in the handover process

(3) When requested by the command of the base station

(4) When uplink data occurs when uplink time synchronization is not correct or when uplink radio resources are not allocated.

(4) In case of recovery process in case of radio link failure or handover failure

The random access process may be divided into a contention based random access procedure and a non-contention based random access procedure. The biggest difference between the contention-based random access process and the non- contention-based random access process is whether a random access preamble is dedicated to one UE. In the contention-free random access process, since the terminal uses a dedicated random access preamble designated only to the terminal, contention (or collision) with another terminal does not occur. Here, contention refers to two or more terminals attempting a random access procedure using the same random access preamble through the same resource. In the contention-based random access process, there is a possibility of contention because the terminal uses a randomly selected random access preamble. The non-contention based random access procedure may be used only when requested by the handover procedure or the command of the base station among the above-described random access reasons.

13A is a flowchart illustrating a contention based random access procedure.

Referring to FIG. 13A, in step S110, the UE randomly selects one random access preamble from a random access preamble set, and transmits the selected random access preamble to the base station through a PRACH resource. Information on the configuration of the random access preamble set may be obtained from a base station through a part of system information or a handover command message.

In step S120, the terminal attempts to receive its random access response within the random access response reception window. The random access response receiving window may be indicated through a part of the system information or a handover command message, and refers to a window for monitoring a random access response. In more detail, the random access response is transmitted in the form of a MAC PDU, and the MAC PDU is transmitted on a PDSCH which is a physical channel. The reception information of the PDSCH is obtained through a PDCCH which is a control channel. The PDCCH carries information of a terminal to receive the PDSCH, radio resource allocation information of the PDSCH, a transmission format of the PDSCH, and the like. The UE first monitors the PDCCH in a subframe belonging to the random access response reception window, and upon successful reception of the PDCCH, receives the random access response on the PDSCH indicated by the PDCCH.

The random access response includes a time alignment (TA) value for uplink synchronization of the terminal, uplink radio resource allocation information, and a random access preamble identifier (RAPID) for identifying terminals performing random access. And a temporary identifier of the terminal, such as a temporary C-RNTI (Cell-Radio Network Temporary Identity). The random access preamble identifier is for identifying the received random access preamble.

In step S130, the terminal applies the time synchronization value, and transmits a scheduled message including a random access identifier to the base station by using the uplink radio resource allocation information.

The random access identifier is used by the base station to identify a terminal performing a random access process. The random access identifier can be obtained in two ways. The first method uses the cell identifier as the random access identifier if the terminal already has a valid cell identifier (eg, C-RNTI) allocated in the corresponding cell before the random access procedure. In the second method, if the terminal has not been assigned a valid cell identifier before the random access procedure, the terminal uses its own unique identifier (SAE Temporary Mobile Station Identifier (S-TMSI) or higher layer identifier) as the random access identifier. The terminal starts a contention resolution timer according to the transmission of the scheduled message.

In step S140, after receiving the scheduled message, the base station transmits a contention resolution message including the random access identifier to the terminal.

Contention in a contention-based random access process occurs because the number of possible random access preambles is finite. Since the UE cannot assign a unique random access preamble to all UEs in the cell, the UE randomly selects and transmits one random access preamble from the random access preamble set. Accordingly, two or more terminals may select and transmit the same random access preamble through the same PRACH resource. This is the case where contention has occurred. The base station receiving the random access preamble transmits a random access response to the random access preamble without knowing whether there is contention.

However, since contention has occurred, two or more terminals receive the same random access response, and the terminals each transmit a scheduled message based on the information included in the random access response. This means that two or more terminals transmit different scheduled messages through uplink radio resource allocation information included in the random access response. At this time, transmission of the scheduled message all fails, or only the scheduled message of the specific terminal is successfully received by the base station according to the location or transmission power of the terminals.

When the scheduled message is successfully received at the base station, the base station transmits a contention resolution message using the random access identifier included in the scheduled message. Upon receiving its random access identifier, the UE may know that contention resolution is successful. In the contention-based random access process, contention resolution may be performed so that the UE knows whether contention fails or succeeds.

Use a contention resolution timer to resolve contention. The contention resolution timer is started after receiving the random access response. The contention resolution timer may be started when the terminal transmits the scheduled message. When the contention resolution timer expires, it is determined that contention resolution is not successful, and a new random access procedure is started. Upon receiving a contention resolution message that includes its random access identifier, the contention resolution timer stops and determines that contention resolution is successful.

If the terminal already has a unique cell identifier such as C-RNTI before the random access procedure, the terminal transmits a scheduled message including its cell identifier to the base station and then starts a contention resolution timer. If the PDCCH addressed by its cell identifier is received before the contention resolution timer expires, the UE determines that the contention has succeeded in contention and ends the random access process normally.

Alternatively, when the terminal does not have a C-RNTI, the upper layer identifier may be used as a random access identifier. After transmitting the scheduled message including the higher layer identifier, the terminal starts a contention resolution timer. If the contention resolution message including its higher identifier is received on the DL-SCH before the contention resolution timer expires, the terminal determines that the random access procedure is successful.

The contention resolution message is received using the PDCCH indicated by the temporary C-RNTI. However, if the contention resolution message including its random access identifier is not received on the DL-SCH until the contention resolution timer expires, the terminal determines that the contention failed.

13B is a flowchart illustrating a non-contention based random access procedure.

Referring to FIG. 13B, in step S210, the UE is assigned a dedicated random access preamble from the base station. For the contention-free random access procedure, it is necessary to allocate a dedicated random access preamble from the base station without collision. The dedicated random access preamble may be included in the handover command message or transmitted on the PDCCH. When the random access procedure is performed during the handover procedure, the UE may obtain a dedicated random access preamble from the handover command message. When the random access procedure is performed at the request of the base station, the terminal may obtain a dedicated random access preamble through the PDCCH.

In step S220, the terminal transmits a dedicated random access preamble to the base station through the PRACH resources.

In step S230, the terminal receives a random access response corresponding to the dedicated random access preamble. Compared to the contention-based random access process, by receiving a random access response in the contention-free random access process, it is determined that the random access process is normally performed, and ends the random access process.

Thereafter, the terminal may transmit the scheduled message to the network by using the radio resource allocated in the random access process.

14 shows a MAC PDU structure for a random access response. The MAC PDU includes a MAC header and a MAC payload. The MAC payload includes at least one MAC random access response (RAR). The MAC header includes at least one MAC subheader, which is divided into a RAPID MAC subheader and a backoff indicator (BI) MAC subheader. Each RAPID MAC subheader corresponds to one MAC RAR. In an embodiment of the present invention, the MAC header for the random access response is a random access response header, the MAC payload is a random access response payload, and the MAC random access response (RAR) is random access response information. It is called.

15 through 16 illustrate subheaders included in a MAC header for a random access response. 15 shows a RAPID MAC subheader, and FIG. 16 shows a BI MAC subheader.

15 shows a RAPID MAC subheader. The E (extentsion) field is a flag indicating whether other fields exist in the MAC header. The T (type) field is a flag indicating whether the MAC subheader includes RAPID or BI. The RAPID field is used to distinguish the transmitted random access preamble.

16 illustrates a BI MAC subheader. The E (extentsion) field is a flag indicating whether other fields exist in the MAC header. The T (type) field is a flag indicating whether the MAC subheader includes RAPID or BI. The R (reserved) field represents a reserved bit. The BI field is used to identify when the next random access will be attempted according to the overloaded state in the cell.

17 shows random access response information (MAC RAR). The random access response information includes various information about the random access response for each random access preamble through a plurality of fields. The TA (time alignment) field indicates an adjustment necessary for uplink transmission timing used for timing synchronization. The UL Grant field represents uplink radio resource allocation information. The temporary C-RNTI indicates a temporary identifier used by the terminal during random access.

18A is a flowchart illustrating a random access method according to an embodiment of the present invention.

The terminal and the network perform a random access process. The terminal first transmits a random access preamble to the network (S1810). In operation S1820, a random access response is received from a network corresponding to the random access preamble.

The random access response transmitted by the network to the terminal includes radio resource allocation information for transmitting a message scheduled by the terminal to the terminal, that is, information on an allocated resource which is a radio resource to be allocated to the terminal. According to an embodiment of the present invention, the terminal is allocated a radio resource through information of a plurality of allocation resources included in the MAC PDU received in response to the random access of the network.

In order to transmit the above-described scheduled message during the random access process, the UE needs to be allocated radio resources suitable for the size of the scheduled message. The scheduled message may be transmitted to the network at a specific time according to the wireless environment. There may be no radio resource of the size.

In this case, delaying radio resource allocation until sufficient radio resources are prepared increases the call set-up time or the waiting time of the user. Therefore, even if the size is insufficient to carry the scheduled message to be transmitted at once, if there is a radio resource that can be assigned immediately, the network can allocate the radio resources that can be allocated. In this case, a plurality of radio resource allocation information for a plurality of allocated resources corresponding to one same random access preamble ID may be included in the random access response. Here, a plurality of radio resources may be allocated in a plurality of subframes. In addition, when a plurality of allocation resources are allocated from a plurality of subframes, one allocation resource is allocated from one subframe, respectively, and thus a plurality of allocation resources are allocated to the terminal.

The terminal then sends the scheduled message to the network several times through a plurality of allocated resources. That is, the scheduled message is transmitted through a plurality of allocated resources, and as a result, transmission of the entire scheduled message is completed. When the scheduled message is transmitted several times to the allocated radio resource through one random access response, it waits until one radio resource having a sufficient size is prepared in the network or the radio resource is several times. Call set-up time or user wait time may be shorter than that of the case of receiving a call allocation. However, transmission of a scheduled message through a plurality of allocated resources does not necessarily need to be performed within one TTI. This is because allocation resources can be allocated from a plurality of subframes.

In addition, since a plurality of radio resource allocation information is included in one random access response, when allocating a plurality of allocation resources at once, the PDCCH may be used only once compared to the case of allocating radio resources several times. If the radio resource allocation information is transmitted several times, the PDCCH would have to be consumed in order to transmit an uplink scheduling grant for every radio resource allocation. However, according to an embodiment of the present invention, since radio resource allocation information for a plurality of allocated resources is transmitted to the terminal only once for radio resource allocation, the PDCCH does not need to be used multiple times.

Upon receiving the random access response, the terminal first determines how many random access preamble IDs corresponding to the terminal are included in the random access response. When a plurality of random access preamble IDs corresponding to the terminal are repeatedly included in the random access response, the terminal may recognize that a plurality of allocated resources are allocated for the transmission of the scheduled message.

The random access response includes a random access response payload and a random access response header. The random access response payload includes time and frequency information for a plurality of allocated resources allocated according to the size of the scheduled message. The random access response header includes a random access preamble ID for specifying a terminal to which the allocated resources are allocated. It is included in correspondence with the number of allocated resources. When there are several random access preamble IDs having the same value, there is also a plurality of random access response information included in the random access response payload. The radio resource allocation information is included in the random access response information, and the random access response payload is composed of one or more random access response information.

Herein, the random access response payload means the MAC payload among the MAC PDUs for the random access response described with reference to FIG. 14, and the random access response header refers to the MAC header among the MAC PDUs for the random access response described with reference to FIG. 14. do.

The terminal decodes the payload of the random access response corresponding to the plurality of random access preamble IDs to obtain radio resource allocation information about the allocated resources. The radio resource allocation information is information about time or frequency of allocated resources allocated by the terminal.

The terminal transmits all the scheduled messages according to the size and the number of allocated resources through the plurality of allocated resources (S1830). There may be one or several scheduled messages transmitted to the network through a plurality of allocated resources.

18B is a flowchart illustrating a random access method according to another embodiment of the present invention. The terminal and the network perform a random access process, but a contention-based random access process is performed here.

The terminal is allocated a dedicated random access preamble from the base station (s1840). The dedicated random access preamble may be included in the handover command message or transmitted on the PDCCH, as described above with reference to FIG. 13B.

The terminal transmits the dedicated random access preamble to the base station through the PRACH resource (S1850). The terminal receives a random access response corresponding to the dedicated random access preamble (S1860).

The random access response transmitted by the network to the terminal includes radio resource allocation information for transmitting a message scheduled by the terminal to the terminal, that is, information on an allocated resource which is a radio resource to be allocated to the terminal.

In order to transmit the above-described scheduled message during the random access process, the UE needs to be allocated radio resources suitable for the size of the scheduled message. The scheduled message may be transmitted to the network at a specific time according to the wireless environment. There may be no radio resource of the size.

Accordingly, a network that knows the overall situation in which radio resources are allocated may allocate various frequency resources from the one or more subframes to the terminal as allocation resources. When a plurality of allocated resources capable of transmitting all scheduled messages are allocated at one time through one random access response, wait until all the scheduled messages can be transmitted using only one radio resource, or may be allocated radio resources several times. Latency can be shorter than sending a scheduled message over several transmissions.

The terminal transmits all of the scheduled messages according to the size and number of allocated resources through the plurality of allocated resources (S1870).

19A and 19B illustrate a structure of an uplink subframe in which allocation resources are indicated according to an embodiment of the present invention. According to the embodiment of the present invention, the allocation resources are distributed in the subframes as shown in FIGS. 19A and 19B.

19A and 19B, one uplink subframe includes two slots. The uplink subframe includes a control region to which a physical uplink control channel (PUCCH) carrying uplink control information is allocated in a frequency domain and a physical uplink shared channel (PUSCH) to carry user data. region). In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH.

PUCCH for one UE is allocated as a pair of resource blocks (RBs) in a subframe, and two resource blocks belonging to one resource block pair are different subcarriers in each of two slots. Occupies. In this regard, it is said that a resource block pair allocated to a PUCCH is frequency hopping at a slot boundary.

PUCCH may support multiple formats. That is, uplink control information having different numbers of bits per subframe may be transmitted according to a modulation scheme.

The hatched portion represents available radio resources remaining when the random access response of the network is transmitted, and may be allocated resources 1901, 1902, 1903, and 1904, 1905, and 1906 allocated to the terminal according to an embodiment of the present invention. .

Here, FIG. 19A shows allocation resources when frequency hopping is not applied in a subframe, and FIG. 19B shows allocation resources when frequency hopping is applied in a subframe. The former and the latter differ in whether the location of allocated resources in the first slot and the second slot is on the same frequency. Each of the allocated resources 1901 to 1906 is insufficient to transmit all scheduled messages, but when the terminal uses all of the allocated resources 1901 to 1906, all of the scheduled messages may be transmitted.

Each allocation resource 1901 to 1906 is allocated in one or a plurality of subframes and TTIs, but distributed. Accordingly, radio resource allocation information such as time and frequency for each allocation resource 1901 to 1906 and information for specifying a terminal corresponding to the allocation resource 1901 to 1906 such as a random access preamble ID are included in the random access response. Should be included. It is for this reason that the same random access preamble ID is repeatedly loaded in the random access response header and different radio resource allocation information is generated corresponding to the same plurality of random access preamble IDs. The radio resource allocation information is included in the random access response payload, and one or more random access response information constitutes the random access response payload.

In addition, when the terminal transmits the scheduled message using the allocation resources 1901 to 1906, all scheduled messages arrive in the network in one subframe.

In the embodiment described with reference to FIGS. 19A and 19B, allocated resources are allocated within several subframes, and thus a scheduled message is transmitted to various TTIs through various allocated resources.

20 illustrates a header of a MAC PDU for a random access response transmitted in a random access process according to an embodiment of the present invention.

Octet 1 is the BI MAC subheader shown in FIG. 16, and each octet below octet 2 is the RAPID MAC subheader shown in FIG. 15.

The network allocates radio resources according to the size of data to be transmitted by the terminal. When there is no radio resource large enough to transmit a scheduled message at one time, in the embodiment of the present invention, Allocate a plurality of radio resources that are smaller than the capacity of the messages scheduled for transmission. In this way, the total number of small allocated resources allocated together adds capacity to send all scheduled messages. At this time, the allocated resources are allocated in different TTIs.

As described above, the terminal that is allocated the allocation resource is identified by loading the random access preamble ID corresponding to each allocation resource in the subheader of the random access response header.

The random access preamble ID for specifying a terminal to which radio resources are to be allocated is carried in the MAC header. When there are several allocation resources allocated corresponding to the size of the scheduled message of one terminal, a plurality of random access preamble IDs are displayed in the MAC header according to the number of allocated resources (oct 3, oct 4 and oct 5). RAPID (Y)). In this case, the random access preamble IDs are displayed in subheaders constituting the random access response header. RAPID (X) and RAPID (Z) indicate a random access response to be transmitted to another terminal.

Therefore, according to an embodiment of the present invention, since multiple allocation resources are allocated to one terminal, subheaders carrying the same random access preamble ID may exist in duplicate. However, the terminal receiving the random access response may omit decoding on the duplicate random access preamble ID.

As such, since the same random access preamble ID may be included in one random access response, a plurality of allocated resources for transmission of the scheduled message may be allocated to one terminal at a time without delay. Accordingly, the terminal does not have to wait until transmission of the scheduled message using only one radio resource is possible, and user waiting time can be shortened.

Random access response information including radio resource allocation information is generated for each random access preamble ID. In the case of different random access preamble IDs as well as multiple identical random access preamble IDs, random access response information is generated corresponding to each random access preamble ID. The random access response payload includes one or more random access response information, and the random access response information includes information for radio resource allocation, that is, time and frequency information corresponding to the allocated resources.

21 is a diagram illustrating a data transmission method according to another embodiment of the present invention.

The network receives a random access preamble from the terminal (S2110). In order for a network to receive a scheduled message from a terminal to perform a random access procedure, it is necessary to allocate as many radio resources as necessary to the terminal. At this time, the information on the radio resources to be allocated to the terminal is transmitted along with the random access response that is a response to the random access preamble.

However, the wireless environment changes dynamically, and thus there may exist a time when the radio resource to be allocated to the terminal is not sufficiently prepared. And although the amount of radio resources remaining is sufficient, there may be a case where only radio resources of a size insufficient to transmit a scheduled message at a time remain. In this case, according to an embodiment of the present invention, the network is insufficient to carry the scheduled message of the terminal at one time, but may allocate a plurality of radio resources scattered in one or a plurality of subframes to the terminal. When all of these radio resources are used, all scheduled messages can be transmitted.

Therefore, the network generates and transmits a random access response including the allocation information for these radio resources to the terminal (S2120 to S2130). These radio resources allocated to the terminal are called allocation resources. First of all, a header of a MAC PDU for a random access response (hereinafter, referred to as a random access response header) includes a random access preamble ID capable of specifying a terminal to which each allocated resource is allocated. The number of random access preamble IDs for one terminal transmitted in a random access response is the same as the number of allocated resources allocated to the corresponding terminal.

Here, the random access response header is composed of a plurality of subheaders. The random access preamble ID is included in one subheader. Therefore, according to an embodiment of the present invention, since multiple allocation resources are allocated to one terminal, subheaders carrying the same random access preamble ID may exist in duplicate. However, the terminal receiving the random access response may omit decoding on the duplicate random access preamble ID.

The network then generates a RAR of the random access response payload according to the number of allocated resources. The random access response payload is composed of a plurality of RARs. The random access response payload includes information on a plurality of allocated resources allocated to the terminal. That is, time and frequency information of the allocated resources are included in the random access response payload.

The network may receive all of the scheduled message (scheduled message # 1, scheduled message # 2, scheduled message # 3,…) transmitted from the terminal through the plurality of allocated resources according to the radio resource allocation information included in the random access response. It may be (S2140). These scheduled messages in principle include a header. The header includes information for identifying the terminal that sent the scheduled message, information for indicating the number of scheduled messages.

However, the network allocates an uplink radio resource necessary for transmitting a scheduled message at a time. Thus, the network already knows how many scheduled messages will be sent from the terminal. In this case, the UE does not need to inform the network of the number of messages corresponding to the transmission of the scheduled message while transmitting the messages scheduled by the plurality of transmission cases, through the header. Accordingly, when the terminal divides and transmits the scheduled messages through a plurality of allocated resources to a plurality of resources, according to an embodiment of the present invention, the second transmission from the second transmission is generally the header (MAC header, RLC) of the message required for communication Header or PDCP header) may be omitted.

If the UE omits the header portion of the scheduled message from the second and subsequent transmissions in the transmission of the scheduling message, it is possible to save the radio resources consumed for the transmission of the header and to use the saved radio resources for the actual transmission of the message. The efficiency of resource utilization is increased.

According to an embodiment of the present invention, when a plurality of allocated resources are distributed in different subframes, and one allocated resource per one subframe is allocated to the corresponding terminal for all subframes, a scheduled message Transmission of # 1, scheduled message # 2, scheduled message # 3,…) is performed to different TTIs.

The invention can be implemented in hardware, software or a combination thereof. In hardware implementation, an application specific integrated circuit (ASIC), a digital signal processing (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, and a microprocessor are designed to perform the above functions. It may be implemented in a processor, another electronic unit, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram illustrating functional division between an E-UTRAN and an EPC.

3 is a block diagram illustrating elements of a terminal.

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

5 is a block diagram illustrating a radio protocol architecture for a control plane.

6 illustrates a mapping between a downlink logical channel and a downlink transport channel.

7 illustrates mapping between an uplink logical channel and an uplink transport channel.

8 illustrates mapping between a downlink transport channel and a downlink physical channel.

9 illustrates mapping between an uplink transport channel and an uplink physical channel.

10 illustrates a structure of a radio frame.

11 shows an example of a resource grid for one downlink slot.

12 illustrates a structure of a subframe.

13A is a flow diagram illustrating a contention based random access procedure.

13B is a flow diagram illustrating a non-contention based random access procedure.

14 illustrates a MAC PDU structure for random access response.

15 to 16 illustrate subheaders included in a MAC header for a random access response.

17 illustrates random access response information (MAC RAR).

18A is a flowchart illustrating a random access method according to an embodiment of the present invention.

18B is a flowchart illustrating a random access method according to another embodiment of the present invention.

19A and 19B illustrate a structure of an uplink subframe in which allocated resources are indicated according to an embodiment of the present invention.

20 illustrates a header of a MAC PDU for a random access response transmitted in a random access procedure according to an embodiment of the present invention.

21 is a diagram showing a data transmission method according to another embodiment of the present invention.

Claims (12)

Sending a random access preamble to the network; Receiving a random access response from the network corresponding to the radio resource allocation information and the radio resource allocation information and including a random access preamble ID for identifying the random access preamble; And transmitting one or more scheduled messages to the network through a plurality of allocated resources according to the plurality of radio resource allocation information. The method of claim 1, The random access response is a medium access control (MAC) protocol data unit (PDU) for a random access process, and includes a random access response header and a random access response payload. The method of claim 2, The random access response header includes a plurality of subheaders, wherein each of the subheaders includes the random access preamble IDs one by one. The method of claim 3, The random access response payload includes a plurality of random access response information (RAR), wherein the random access response information includes the radio resource allocation information and respectively corresponds to the sub header. Random access method. The method of claim 1, Random access method, characterized in that for selecting the random access preamble from among a plurality of random access preamble to transmit to the network. The method of claim 1, The allocated resources are random access method, characterized in that allocated in different transmission time interval (TTI). The method of claim 1, The allocated resources are random access method, characterized in that included in different subframes. The method of claim 1, And assigning a dedicated random access preamble corresponding to a terminal from the network before transmitting the random access preamble, wherein the random access preamble is the dedicated random access preamble. Receiving a random access preamble from a terminal; Generating a random access response including a plurality of radio resource allocation information and a random access preamble ID for identifying the terminal to which radio resources are allocated according to the radio resource allocation information; Transmitting the random access response to the terminal; And receiving from the terminal at least one scheduled message transmitted through allocation resources which are radio resources allocated to the terminal according to the radio resource allocation information. 10. The method of claim 9, The random access response is a medium access control (MAC) protocol data unit (PDU) for a random access process, includes a random access response header and a random access response payload, and includes a plurality of subheaders included in the random access header. Random access method, characterized in that for loading the random access preamble ID corresponding to the terminal one by one. The method of claim 10, The random access response payload includes a plurality of random access response information (RAR), The random access response information includes the radio resource allocation information and is generated to be equal to the number of the allocated resources for allocating the subheaders to one terminal so as to correspond to the subheaders, respectively, and generate the random access response information. And generating the random access response to correspond to the subheader one by one. 10. The method of claim 9, Random access method, characterized in that for allocating the allocated resources in different transmission time interval (TTI).

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