KR101497151B1 - A method of managing radio resource - Google Patents

Abstract

A method for managing a radio resource according to an exemplary embodiment of the present invention includes stopping use of a control resource of a mobile station when a time synchronization timer of the mobile station has expired, synchronizing with the mobile station, Resuming use of the control resource, and releasing the control resource if synchronization with the terminal is not achieved. The amount of message transmission can be reduced and radio resources can be efficiently used.

Uplink data, time synchronization, resource release.

Description

[0001] A METHOD OF MANAGING RADIO RESOURCE [

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to wireless communication, and more particularly, to a method of managing or using radio resources when synchronization is not achieved in a wireless communication system.

A 3rd Generation Partnership Project (3GPP) mobile communication system based on WCDMA (Wideband Code Division Multiple Access) radio access technology is widely deployed all over the world. HSDPA (High Speed Downlink Packet Access), which can be defined as the first evolutionary phase of WCDMA, provides 3GPP with highly competitive wireless access technology in the mid-term future. However, since the development of wireless access technology that continues to increase and compete with the requirements and expectations of users and operators continues, development of new technologies in 3GPP is required for future competitiveness. Reduced cost per bit, increased service availability, the use of flexible frequency bands, simple structure and open interfaces, and proper power consumption of terminals are becoming a requirement.

One of the systems considered in the third generation and later systems is an Orthogonal Frequency Division Multiplexing (OFDM) system capable of attenuating the inter symbol interference effect with low complexity. OFDM converts data symbols input in series into N parallel data symbols, and transmits the data symbols on N subcarriers separated from each other. The subcarriers maintain orthogonality at the frequency dimension. Each orthogonal channel experiences mutually independent frequency selective fading, and the interval of transmitted symbols becomes longer, so that the inter-symbol interference can be minimized.

In the OFDM-based wireless communication system, it is important to synchronize the time synchronization between the terminal and the base station in order to minimize interference between users. A random access procedure is performed for uplink synchronization between the UE and the BS. During the random access procedure, the UE adjusts time synchronization through the time synchronization correction value transmitted from the base station. When uplink synchronization is performed, the UE operates a Time Alignment Timer. If the time synchronization timer is in operation, the terminal and the base station are assumed to be uplink synchronized with each other. If the time synchronization timer expires or does not operate, the terminal and the base station are not synchronized with each other, and transmission to the uplink is not performed except for the random access preamble transmission.

Generally, if uplink synchronization is not performed because the time synchronization timer expires or does not operate, the UE releases the control resource and acquires time synchronization, and then transmits the uplink data by resetting the control resource.

However, if the uplink synchronization fails, it is inefficient to release the control resource and reset the control resource even though the uplink data can be received only by obtaining the uplink synchronization, resulting in a time delay.

In particular, when the dedicated uplink control resource is reallocated, a problem arises in that the size of the message for reallocation becomes unnecessarily large. Also, since the message for releasing resources and the message for reallocation are each transmitted at least once, there is a problem in reliability of message transmission. Even if reliability is supplemented with the help of HARQ and ARQ, time delay due to retransmission occurs do.

Therefore, there is a need for a method for efficiently transmitting uplink data even when the time synchronization timer expires or does not operate.

The present invention provides a radio resource management method capable of reducing a required message transmission amount when a UE transmits data in an uplink and is not synchronized, and efficiently using already allocated radio resources without releasing them immediately.

According to an aspect of the present invention, there is provided a method for controlling a terminal, the method comprising: stopping use of a control resource of the terminal when a time synchronization timer of the terminal expires; synchronizing with the terminal; And releasing the control resource if synchronization with the terminal is not achieved.

According to another aspect of the present invention, there is provided a method for controlling a mobile station, comprising: receiving a control resource deactivation message for stopping use of a control resource from a base station when a time synchronization timer expires; stopping transmission of data through the control resource; And receiving a control resource resumption message for resuming use of the control resource from the base station.

According to the embodiment of the present invention, when the mobile station transmits data in the uplink and becomes out of synchronization, it can efficiently use the already allocated radio resource without immediately releasing it. It also reduces the amount of message transfer required to re-synchronize and resume data transfer.

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 an LTE (Long Term Evolution) 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.

A user equipment (UE) 10 may be fixed or mobile and may be referred to as another term such as a mobile station (MS), a user terminal (UT), a subscriber station (SS) The base station 20 generally refers to a fixed station that communicates with the terminal 10 and may be referred to as another term such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point have. One base station 20 may have more than one cell. An interface for transmitting user traffic or control traffic may be used between the base stations 20. Hereinafter, downlink refers to communication from the base station 20 to the terminal 10, and uplink refers to communication from the terminal 10 to the base station 20.

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

2 is a block diagram illustrating a functional split between the E-UTRAN and the EPC.

Referring to FIG. 2, the hatched block represents a radio protocol layer and the empty block represents a functional entity of a control plane.

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

The MME performs the following functions. (2) security control, (3) idle state mobility control, (4) SAE bearer control, (5) NAS (Non-Access) Stratum signaling ciphering and integrity protection.

The S-GW performs the following functions. (1) termination of user plane packets for paging, and (2) user plane switching to support terminal mobility.

3 is a block diagram showing 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 implements layers of the air interface protocol to provide a control plane and a user plane. The functions of the respective layers can be implemented through the processor 51. [ The memory 52 is connected to the processor 51 and stores a terminal driving system, an application, and general files. The display unit 54 displays various information of the terminal and can use well known elements such as a liquid crystal display (LCD) and an organic light emitting diode (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 the processor to transmit and / or receive a radio signal.

The layers of the radio interface protocol between the terminal and the network are classified into L1 (first layer), L2 (first layer), and L2 (third layer) based on the lower three layers of the Open System Interconnection (Second layer), and L3 (third layer). 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 at the third layer Controls the radio resources between the UE 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 wireless protocol structure for a control plane. This represents the structure of the radio interface protocol between the UE and the E-UTRAN. The data plane is a protocol stack for transmitting user data, and the control plane is a protocol stack for transmitting control signals.

Referring to FIGS. 4 and 5, a physical layer (PHY) layer of the first layer provides an information transfer service to an upper layer using a physical channel. The physical layer is connected to an upper layer MAC (Medium Access Control) layer through a transport channel, and data is transferred between the MAC layer and the physical layer through the transport channel. Data moves between physical layers between different physical layers, that is, between a transmitting side and a receiving physical layer. The physical channel is modulated by an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and time and frequency can be utilized as radio resources.

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

The Packet Data Convergence Protocol (PDCP) layer of the second layer contains relatively large and unnecessary control information in order to efficiently transmit packets in a radio section having a small bandwidth during transmission of an IP (Internet Protocol) packet such as IPv4 or IPv6 And performs header compression to reduce the size of the IP packet header.

The third layer of Radio Resource Control (RRC) layer is defined only in the control plane. The RRC layer is responsible for the control of logical channels, transport channels and physical channels in connection with the configuration, re-configuration and release of radio bearers (RBs). RB denotes a service provided by the second layer for data transmission between the UE and the E-UTRAN. If there is an RRC connection between the RRC of the UE and the RRC of the network, the UE is in the RRC Connected Mode, and if not, the UE is in the RRC Idle Mode.

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

The downlink transport channel for transmitting data from the network to the terminal includes a broadcast channel (BCH) for transmitting system information, a downlink-shared channel (DL-SCH) for transmitting user traffic or control messages . And may be transmitted through a DL-SCH in case of a traffic or control message of the DL broadcast service. The uplink transmission channel for transmitting data from the UE to the network includes a random access channel (RACH) for transmitting initial control messages and a UL-SCH (Uplink-Shared Channel) for transmitting user traffic or control messages.

The downlink physical channel mapped to the downlink transport channel includes a physical broadcast channel (PBCH) for transmitting BCH information, a physical downlink shared channel (PDSCH) for transmitting PCH and DL-SCH information, and a downlink or uplink And a Physical Downlink Control Channel (PDCCH) for transmitting control information provided by the first layer and the second layer, such as radio resource allocation information (DL / UL Scheduling Grant). The PDCCH is also referred to as a downlink L1 / L2 control channel. The uplink physical channel mapped to the uplink transport channel includes a Physical Uplink Shared Channel (PUSCH) for transmitting UL-SCH information, a Physical Random Access Channel (PRACH) for transmitting RACH information, a HARQ ACK / NACK signal, A Physical Uplink Control Channel (PUCCH) for transmitting control information provided by the first layer and the second layer, such as a Scheduling Request signal and a CQI (Channel Quality Indicator).

Hereinafter, time alignment (Time Alignment) will be described. In an OFDM (Orthogonal Frequency Division Multiplex) based system, it is important to synchronize the time synchronization between the UE and the base station in order to minimize interference between users.

A random access procedure is performed in order to synchronize uplink time synchronization between the UE and the BS. That is, the BS measures the time synchronization value through the random access preamble transmitted by the MS and provides the time synchronization correction value to the MS through the random access response. Upon receiving the random access response message, the UE applies the time synchronization correction value and starts a time alignment timer. In addition, the base station may measure the time synchronization value of the terminal by a method other than the random access preamble. At this time, the base station can provide the terminal with the time synchronization correction value as needed.

When the time synchronization timer is set, if the terminal periodically receives a time synchronization command, the terminal applies the time synchronization command and starts a time synchronization timer, or if the time synchronization timer is already in operation, Restart the timer. If the time synchronization timer expires or does not operate, a random access procedure is attempted to acquire uplink time synchronization before transmitting the uplink data. Also, when the time synchronization timer expires, the terminal releases the PUCCH and SRS (Sounding Reference Signal) resources.

During the operation of the time synchronization timer, time synchronization between the terminal and the base station is maintained. If the time synchronization timer expires or does not operate, time synchronization between the terminal and the base station is not maintained. If time synchronization between the UE and the BS is not maintained, PUCCH resources for SR (Scheduling Request) and CQI (Channel Quality Indicator) are lost, and the UE can not transmit other uplink data except for the random access preamble. At this time, the UE starts a random access procedure to adjust uplink time synchronization.

FIG. 6 shows an operation of the terminal when the time synchronization timer according to the related art has expired.

Referring to FIG. 6, when the time synchronization timer expires (S600), the terminal informs the RRC layer of the terminal from the MAC layer of the terminal that the time synchronization timer has expired (S601). Next, the MS transmits a control resource release command from the RRC layer of the MS to the PHY layer of the MS (S602). Here, the control resources include PUCCH and SRS. In addition, the UE requests to start a random access procedure from the RRC layer of the UE to the MAC layer of the UE.

Next, the UE transmits a random access preamble to the base station (S603). The random access preamble is transmitted from the MAC layer of the UE to the MAC layer of the BS. The base station receiving the random access preamble transmits a random access response message to the mobile station (S604). The random access response message includes a time alignment value of the UE and uplink radio resource allocation information. The random access response message is transmitted from the MAC layer of the base station to the RRC layer of the UE.

The MS receiving the random access response message transmits RRC signaling for uplink data transmission from the RRC layer of the UE to the RRC layer of the BS in step S605. Here, the RRC signaling is transmitted using the uplink radio resource allocation information included in the random access response message. The base station receiving the RRC signaling transmits RRC signaling for uplink data transmission from the RRC layer of the base station to the RRC layer of the terminal in step S605. The base station transmits control resource information to the RRC signaling. The MS receiving the control resource information sets the control resource from the RRC layer of the MS to the PHY layer of the MS in step S606.

The MS transmits a scheduling request message to the BS (S607). The BS receiving the scheduling request message transmits the uplink radio resource allocation information to the UE through the PDCCH (S608). The MS transmits a message including the MS identifier to the BS through the allocated uplink radio resource (S609). The steps S607 to S609 are performed between the MAC layer of the UE and the MAC layer of the BS.

As described above, if the UE has data to be transmitted in the uplink, if the time synchronization timer expires or does not operate, time synchronization is performed through a random access procedure. However, according to FIG. 6, when the time synchronization timer expires, the UE releases the control resource such as the PUCCH resource and the SRS resource, and then receives the control resource from the base station.

Here, there is a problem that the uplink data transmission is delayed because additional time is required in releasing and resetting the control resource. Accordingly, there is a need for a method for quickly and efficiently transmitting uplink data when the time synchronization timer expires or does not operate.

FIG. 7 shows an operation of the UE according to an embodiment of the present invention when time synchronization becomes inconsistent.

If the time synchronization between the terminal and the base station does not match, the time synchronization timer expires (S700). Generally, the time synchronization timer restarts upon receiving a downlink time synchronization MAC Control Element (Control Element) transmitted from the base station to the terminal, but if the time synchronization MAC Control Element is not received until the time synchronization timer expires The time synchronization timer expires.

If time synchronization between the terminal and the base station is not satisfied, the base station stops using the control resource of the terminal (S701). Here, the control resource is a PUCCH resource, an SRS resource, or the like, which means a dedicated uplink control resource. If the uplink time synchronization does not match, uplink data transmission is not performed except for the random access preamble. Here, the BS may stop using the control resource by transmitting a control resource use suspension message to the UE.

In step S702, the base station stops allocating the control resource to another terminal except the terminal. The BS does not allocate the control resources allocated to the UE to the other UE until the UE is synchronized with the BS.

The base station performs synchronization with the terminal (S703).

The base station may receive a random access preamble from the terminal, for example, to synchronize with the terminal. The UE transmits a random access preamble to obtain uplink time synchronization, and is part of a contention based random access procedure. In general, a terminal transmits a random access preamble through a selected PRACH resource (PRACH Resource) using system information transmitted from a base station. The system information includes information on a set of possible random access preambles, and the terminal transmits randomly selected random access preambles from the set of random access preambles.

The base station receiving the random access preamble transmits a random access response message to the mobile station. The random access response message includes a time alignment value for uplink synchronization, uplink radio resource allocation information, an index of a random access preamble received to identify terminals performing random access, and a temporary C-RNTI (Temporary Cell-Radio Network Temporary Identity). The terminal receiving the time synchronization correction value can restart the time synchronization timer by applying the time synchronization correction value.

The UE receiving the random access response message transmits a scheduling message including the UE unique identifier to the Node B using the uplink radio resource allocation information. Here, the terminal unique identifier may be a C-RNTI or an upper layer identifier. A unique identifier is also used for contention resolution and is also called a contention resolution identifier.

The base station receiving the message including the UE unique identifier transmits a contention resolution message including the uplink radio resource allocation information to the UE. At this time, if the uplink radio resource allocation information is the same as the uplink radio resource allocation information designated by the terminal unique identifier transmitted by the terminal, it is determined that the contention is resolved.

When the synchronization process between the UE and the BS is performed between the MAC layer of the UE and the MAC layer of the BS, uplink synchronization can be achieved simply and quickly compared with the case of performing RRC signaling.

Through this process, the base station determines whether synchronization with the terminal has been performed (S704). Here, instead of directly detecting or recognizing whether the base station is synchronized, a message indicating that the base station is synchronized from the terminal may be received if the synchronization is successfully performed.

As a result of the synchronization, when the terminal and the base station are synchronized with each other, the base station resumes using the control resource (S705). At this time, the BS may transmit a control resource resume message or a control resource resume message to the MS to inform the MS that the control resource is resumed. When the use of the control resource is resumed, the terminal transmits data through the resumed control resource (S706).

The control resource use resume message or the control resource resume message transmitted by the base station to notify the resumption of the use of the control resource suspended message or the control resource that has been suspended from the terminal to suspend the use of the control resource, MAC control element, MAC message, or PDCCH. This is possible because it is not a new allocation of control resources. Also, in case of transmission through the PDCCH, the reliability of message transmission can be increased without requiring HARQ ACK / NACK as compared with transmission through the DL-SCH

It is possible to independently generate a new message format or to add a new field to an existing message format.

A message transmitted by the base station to stop using the control resource to the terminal or a message transmitted to inform that the use of the control resource that has been suspended is resumed can be similarly applied to the following embodiments .

FIG. 8 shows the operation of the terminal according to another embodiment of the present invention when the time synchronization becomes inconsistent.

If the synchronization between the terminal and the base station is not met, the time synchronization timer expires (S800). The base station then stops using the control resource of the terminal (S801). Herein, the BS may inform the UE that the control resource is disabled by transmitting a control resource stop message in a predetermined format. It is also prohibited that the control resource is allocated to another terminal (S802).

The terminal and the base station perform synchronization (S803). At this time, the terminal and the base station perform synchronization but may not be synchronized (S804).

Thereafter, the base station may determine or recognize that synchronization with the terminal is not performed (S805). Here, instead of detecting whether or not the base station has succeeded in synchronization, if the terminal fails to synchronize, it may transmit a message informing the base station of the synchronization failure.

If it is determined that the attempted synchronization is unsuccessful while the control resource is disabled, the base station can release the control resource (S806).

9 shows a data transmission method according to an embodiment of the present invention.

Referring to FIG. 9, if the synchronization between the terminal and the base station is not satisfied, the base station stops using the control resources of the terminal (S901). Also, the BS may stop using the control resource by transmitting a control resource use suspension message to the UE. Also, the control resource is prohibited from being allocated to another terminal (S902).

Then, the control resource resumption timer is started (S903). The control resource resumption timer may be included in the base station or the terminal. The control resource resumption timer is a timer that is started after the use of the control resources of the terminal is stopped due to inconsistency of synchronization, and is released when synchronization is resumed.

In operation S904, when the control resource resumption timer is started and the synchronization operation between the terminal and the base station is started in operation S904, the operation of the base station and the base station is different depending on whether synchronization is performed until the control resource resumption timer is started and expires in operation S905.

If the uplink synchronization does not match and the time synchronization timer expires, the UE may attempt a random access procedure to obtain uplink synchronization. If the synchronization between the UE and the BS is synchronized before the control resource resumption timer expires by performing a random access procedure or the like, the UE can transmit a message indicating that the UE is synchronized with the BS in step S906. Then, the base station resumes using the control resource of the corresponding terminal (S907). Likewise, the base station may also transmit a control resource resumption message to the terminal to inform the terminal that the control resource has been resumed. In step S908, the MS transmits uplink data through the resumed control resource.

If the random access procedure is not successful within a predetermined time, the base station releases the corresponding control resource. That is, if synchronization is not performed within a predetermined time, the control resource timer expires (S909). Then, the base station releases the control resource that has stopped the use (S910).

All of the methods described above may be performed by a processor such as a microprocessor, controller, microcontroller, application specific integrated circuit (ASIC) or the like, or a processor of the terminal shown in FIG. 3, have. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system;

2 is a block diagram illustrating a functional split between an E-UTRAN and an EPC;

3 is a block diagram showing 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 wireless protocol structure for a control plane.

6 is a diagram illustrating an operation of a terminal when the time synchronization timer according to the related art expires;

FIG. 7 is a diagram illustrating an operation of a terminal according to an embodiment of the present invention when time synchronization is disabled; FIG.

8 is a diagram illustrating an operation of a terminal according to another embodiment of the present invention in a case where time synchronization becomes inconsistent.

9 illustrates a data transmission method according to an embodiment of the present invention.

Claims (13)

Stopping the use of the control resource for the terminal when the time synchronization timer of the terminal expires; The base station transmits a control resource use suspension message to another terminal except for the terminal and stops allocating control resources to the other terminal; Synchronizing the base station with the terminal; Resuming use of the control resource if synchronization with the terminal is established, and releasing the control resource if synchronization with the terminal is not achieved. The method according to claim 1, Further comprising: after the base station stops using the control resource, initiating a control resource resume timer, And resuming use of the control resource when the synchronization with the terminal is synchronized before the control resource resumption timer expires, and receiving data through the resumed control resource. The method according to claim 1, Further comprising: after the base station stops using the control resource, initiating a control resource resume timer, And releases the control resource when the control resource resumption timer expires before the synchronization is met. The method according to claim 1, When the use of the control resource is stopped, transmitting a control resource use suspension message to the terminal, Wherein the control resource resumption message is transmitted to the MS when resuming use of the control resource. A base station in a wireless communication system, Memory; And a processor coupled to the memory, wherein the processor stops using the control resource for the terminal when the time synchronization timer of the terminal expires, The base station transmits a control resource use suspension message to another terminal except for the terminal, stops the control resource allocation to the other terminal, Synchronizing with the terminal; Resumes use of the control resource if the synchronization with the terminal is synchronized, and releases the control resource if synchronization with the terminal is not achieved. delete delete delete delete delete delete delete delete

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