KR20080039176A - Method for re-direction of uplink access - Google Patents

Abstract

The present invention relates to a method for quickly performing uplink redirection in a mobile communication network. When the terminal transmits a preamble including various random access information to the base station for initial random access to the network, the base station sends the preamble grant / reject information and the redirection information to the response message. Therefore, in the present invention, when the access request of the terminal is congested, the present invention can limit this through the first response message, compared to the second response message from the base station. Can increase.

Description

Method for re-direction of uplink access}

1 is a signal flow diagram illustrating an initial access procedure of a terminal discussed in a conventional LTE system.

2 illustrates a network structure of an E-UMTS as a mobile communication system to which the present invention is applied.

3 and 4 illustrate a structure of a radio interface protocol between a UE and a UTRAN based on the 3GPP radio access network standard.

5 is a signal flowchart briefly illustrating an initial random access procedure of an idle UE according to the present invention.

6 is a signal flowchart briefly illustrating an initial random access procedure of an RCC connected terminal according to the present invention.

7 illustrates a specific implementation of HARQ applied to a downlink physical layer of a wireless packet communication system.

The present invention relates to a method for quickly performing uplink redirection in a mobile communication network.

A terminal in idle mode in a mobile communication network uses a random access channel (RACH) to transmit an initial control message to the network. That is, in general, the RACH is used to synchronize the time with the network or to obtain radio resources when there is no uplink radio resource for transmitting the data when the UE intends to perform data transmission in uplink. do.

For example, when the terminal powers on and attempts to access a new cell for the first time, the terminal generally synchronizes the downlink, receives system information of the cell to be connected, and then, for RRC (Radio Resource Control) connection (RRC connection) The access request message should be transmitted in uplink. However, since the terminal is not in time synchronization with the current network and does not secure uplink radio resources, the UE requests radio resources for transmission of a connection request message through the RACH. The base station receiving the radio resource from the terminal allocates an appropriate radio resource to transmit the RRC connection request message to the terminal.

As another example, it is assumed that the RRC connection is formed between the UE and the network so that the UE is in an RRC connected mode. In this case, the terminal is allocated a radio resource according to the radio resource scheduling of the network, and transmits the user data to the network through the radio resource. However, if there is no more data to be transmitted in the buffer of the terminal, the network does not allocate any more radio resources to the terminal. At this time, the buffer status of the terminal is reported to the network periodically or event (event) occurrence. Here, even if new data is generated in the buffer of the terminal to which no radio resource is allocated, since there is no radio resource allocated to the terminal, the terminal requests the network to allocate a radio resource necessary for data transmission using the RACH.

Hereinafter, a process of initial access to a network through a RACH described above in a Long Term Evolution (LTE) system, which is drawing attention as a next-generation communication standard, will be described.

1 is a signal flow diagram illustrating an initial access procedure of a terminal discussed in a conventional LTE system.

The terminal selects a RACH signature and an RACH opportunity based on the system information received from the base station, and loads the RACH signature on a random access preamble to the base station (S101).

After receiving the random access preamble from the terminal, the base station transmits random access response information (Random Access Response) for the preamble to the terminal (S103). The random access response information includes timing offset information (TA), information on uplink radio resource allocation for transmitting an RRC connection request message, and the like.

After receiving the random access response information, the terminal transmits an RRC connection request message according to the information on the radio resource allocation included in the response information (S105).

After receiving the RRC connection request message from the terminal, the base station transmits an RRC connection establishment message or an RRC contention resolution message to the terminal according to circumstances (S107).

In the conventional RRC connection process using random access, when the RRC connection request message is frequently transmitted and needs to restrict the uplink access of the UE, the RRC connection rejection message includes redirection information. By transmitting a specific terminal is induced to be re-directed to another frequency band or another system (re-direction). However, since the conventional redirection is transmitted through the fourth message S107 of random access, there is a problem that the wireless network does not quickly suppress the uplink access of a specific terminal.

The present invention has been proposed to solve the above problems, including the information related to the random access in the preamble transmitted to the base station, and in response to the information required for the redirected access of the terminal to the terminal in a manner of transmitting The purpose is to enable fast suppression of uplinks.

One aspect of the present invention for achieving the above object relates to a method for the initial random access to the terminal in the network, the terminal transmitting a random access preamble to the base station, and a response message for the random access preamble from the base station And receiving, when the response message satisfies a predetermined condition, transmitting an access request message for redirection to the base station.

Another aspect of the present invention is a mobile communication network for transmitting a random access preamble to a base station, receiving a response message for the random access preamble from the base station, and transmitting a connection request message for redirection to the base station according to the response message. The present invention relates to a terminal performing redirection of an uplink.

According to another aspect of the present invention, when a random access preamble is transmitted from a terminal, a response message is transmitted to the terminal, and when a connection request message for redirection according to the response message is transmitted from the terminal, a connection establishment message is transmitted thereto. The present invention relates to a base station for performing redirection of uplink access in a mobile communication network transmitted to a terminal.

In the three aspects, the random access preamble includes a signature for terminal identification.

Further, the transmission of the access request message is performed under the condition that the response message includes the same signature as the signature, or that the response message specifies acceptance of the signature transmission.

If the response message does not include the same signature as the signature, the response message includes the rejection information of the signature transmission, and when the connection establishment message is not received from the base station for a predetermined time. If applicable, the random access preamble may be retransmitted to the base station.

The response message may further include a delay time for retransmission of the random access preamble. In this case, the retransmission of the random access preamble is preferably performed after a preset delay time has elapsed in the terminal.

The delay time may be set differently depending on any one of the number of signatures included in the response message, the size of the response message, and the reason for rejection of the signature transmission.

Meanwhile, when a plurality of terminals transmit the random access preamble using the same signature and the same radio resource at the same time and conflict with each other, the terminal receives a collision resolution message from a base station and resolves it. If the collision resolution message includes a terminal identifier previously transmitted by the terminal, it is determined as collision resolution and the uplink is established with the base station. If the collision resolution message does not include the terminal identifier, the random access preamble is transmitted to the base station. Resend.

Optionally, the collision resolution message may be received only when the channel for transmitting the collision resolution message includes a temporary terminal identifier of the terminal.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, the application background of the present invention will be described and the main embodiments of the present invention will be described.

2 illustrates a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS) as a mobile communication system to which the present invention is applied.

The E-UMTS system is an evolution from the existing UMTS system, and is currently undergoing basic standardization work in the 3rd Generation Partnership Project (3GPP) and may be called a Long Term Evolution (LTE) system.

The E-UMTS system can be largely divided into the E-UTRAN 100 and the CN 200.

The E-UTRAN 100 is located at the end of the network and connected to an external network (Access Gateway (hereinafter referred to as "AG") 110), the base station (hereinafter referred to as "eNode B") 120 And a user equipment (hereinafter referred to as “UE”) 130. The AG 110 may be divided into a portion that handles user traffic processing and a portion that handles control traffic. In this case, a new interface may be defined between an AG for handling new user traffic and an AG for controlling traffic, thereby communicating with each other. One or more cells may exist in one eNode B 120, and an interface for transmitting user traffic or control traffic may be used between the eNode Bs.

The CN 200 may be configured as a node for user registration of the AG 110 and other UEs 130, and the like. An interface for distinguishing the E-UTRAN 100 and the CN 200 may be used.

Layers of the Radio Interface Protocol between the terminal 130 and the network are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems. Layer), L2 (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 is referred to as a radio resource control (RRC) located in the third layer. ) 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. The RRC layer may be distributed to each node of the network such as the eNode B 120 and the AG 110, or may be located only in the eNode B 120 or the AG 110.

3 and 4 illustrate a structure of a radio interface protocol between a terminal based on a 3GPP radio access network standard and a UTRAN (UMTS Terrestrial Radio Access Network).

The air interface protocol between the UE and the UTRAN consists of a physical layer, a data link layer, and a network layer horizontally, and vertically controls for signal transmission. It is divided into a control plane (FIG. 3) and a user plane (FIG. 4) for data information transmission. The protocol layers of FIGS. 3 and 4 are based on the lower three layers of the Open System Interconnection (OSI) reference model, which are well known in communication systems, and include L1 (first layer), L2 (second layer), It may be classified as L3 (third layer).

The layers of the radio protocol control plane of FIG. 3 and the radio protocol user plane of FIG. 4 will now be described in detail.

The physical layer 10, which is the first layer, provides an information transfer service to an upper layer by using a physical channel. The physical layer 10 is connected to a medium access control layer 20 on the upper side through a transport channel, and the medium access control layer 20 and the physical layer through the transport channel. The data moves between (10). Then, data moves between different physical layers, that is, between physical layers of the transmitting side and the receiving side.

The second layer, Medium Access Control (hereinafter, referred to as MAC) 20, provides a service to a radio link control layer, which is a higher layer, through a logical channel. The radio link control (hereinafter referred to as RLC) layer 30 of the second layer supports reliable data transmission. Meanwhile, the function of the RLC layer 30 may be implemented as a functional block inside the MAC. In this case, the RLC layer may not exist. The PDCP layer 50 of the second layer is a header for reducing the IP packet header size, which is relatively large and contains unnecessary control information for efficient transmission in a wireless bandwidth where bandwidth is small when transmitting an IP packet such as IPv4 or IPv6. Performs the header compression function.

The radio resource control (RRC) layer 40 located at the bottom of the third layer is defined only in the control plane and configures a radio bearer (abbreviated as RB). It is responsible for the control of logical channels, transport channels, and physical channels with regard to re-configuration and release. In this case, RB means a service provided by the second layer for data transmission between the terminal and the UTRAN.

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

Next, a process of transmitting an initial control message to a network by a terminal in idle mode will be described in detail.

In Wideband Code Division Multiple Access (WCDMA), the RACH (Random Access Channel) is used for transmitting a control message upward or for transmitting a short length of data, and includes an RRC Connection Request message and a Cell Update message. Some RRC messages such as Update Message, URA Update Message, etc. are also transmitted via RACH. In addition, the common control channel (CCCH), dedicated control channel (DCCH), and dedicated traffic channel (DTCH) among the logical channels may be mapped to the RACH of the transport channel, and the RACH of the transport channel is again a physical channel physical random access channel (PRACH). ).

When the MAC layer of the UE instructs the PRACH transmission to the physical layer of the terminal, the terminal physical layer first selects one access slot and one signature and transmits the PRACH preamble upward. The preamble is transmitted during an access slot interval of 1.33 ms length, and selects and transmits one signature among 16 signatures during the first predetermined length of the access slot.

When the terminal transmits the preamble, the base station transmits a response signal through the downlink physical channel acquisition indicator channel (AICH). The AICH transmitted in response to the preamble transmits the signature selected by the preamble during the first predetermined length of an access slot corresponding to the access slot in which the preamble is transmitted. At this time, the base station transmits an acknowledgment (ACK) or a negative response (Not-Acknowledgment (NACK)) to the UE through the signature transmitted by the AICH. If the terminal receives the ACK, the terminal transmits a message portion of 10 ms or 20 ms length using an Orthogonal Variable Spreading Factor (OVSF) code corresponding to the transmitted signature. If the terminal receives the NACK, the terminal MAC instructs the terminal physical layer to transmit the PRACH again after a suitable time. On the other hand, if the terminal does not receive the AICH corresponding to the transmitted preamble, the terminal transmits a new preamble with a power higher than the previous preamble after a predetermined access slot.

Hereinafter, an initial random access process according to the present invention will be described in detail.

<Example 1>

5 is a signal flowchart briefly illustrating an initial random access procedure of an idle UE.

First, the terminal transmits a random access preamble to the base station (S201). In this case, the terminal may include uplink message information or channel measurement information in the preamble so that the base station can perform resource allocation for uplink transmission together with the signature.

The base station responds to the preamble with random access response information (S203). In this case, the response information message includes at least one of a signature transmitted by the terminal and acceptance or rejection information on the signature transmission, and here, a temporary network identifier (Temporary C-RNTI: Cell Radio) is allocated to the terminal. Network Temporary Identifier), radio resource allocation information and message size for the RRC connection request message, radio parameters (modulation and coding information, Hybrid ARQ information) for transmitting the RRC connection request message may be further included.

The transmission information of the response information message is informed by the L1 / L2 control channel related to the transmission of the response information message. The L1 / L2 control channel includes a RA-RNTI indicating transmission of response information and transmission parameters related to transmission of the response information message.

In addition, the response information message may further include re-direction information, wait time, and reject cause.

After receiving the response information message, if the signature transmitted by the terminal is included in the response information message, and if the acceptance of the signature transmission, the terminal transmits an RRC connection request message to the base station (S205). In this case, the terminal transmits the RRC connection request message using radio resource allocation information, message size, and radio parameters included in the response information message. The RRC connection request message may include a global terminal identifier such as an International Mobile Subscriber Identity (IMSI) or a Temporary Mobile Subscriber Identity (TMSI).

If the signature transmitted by the terminal is included in the response information message but there is a rejection of the signature transmission, or if the signature transmitted by the terminal is not included in the response information message, the terminal requests an RRC connection request. The preamble is retransmitted after a delay time or a predetermined time specified in the response information message without transmitting the message.

Optionally, when the response information includes the rejection information for the preamble, regardless of whether the response information includes the delay time, the terminal according to the delay time preset in the terminal itself for the RRC connection request The preamble may be retransmitted. Alternatively, when the response information includes rejection information for the preamble, regardless of whether the response information includes a delay time, the terminal is determined according to the number of signatures or the number of users included in the response information or the The preamble may be retransmitted by applying different delay times according to the message size of the response information or the reason for the rejection.

At this time, if there is redirection information in the response information message, the UE moves to another system or another frequency band (Frequency Band) according to the redirection information, selects a cell again, and retry random access.

When the RRC connection request message is received at the base station, the RRC layer of the base station transmits an RRC connection establishment message or an RRC conflict resolution message to the terminal (S207).

When a plurality of UEs transmit the preambles uplink simultaneously using the same signature and the same radio resource at the same time, collisions occur between transmissions. Accordingly, the base station transmits an RRC collision resolution message to each terminal to resolve the collision situation. The RRC collision resolution message includes a wireless network terminal identifier such as a C-RNTI, the wide area terminal identifier, and redirection information, and includes a wait time and a reject cause. It may further include.

Accordingly, the terminal recognizes that it has escaped from the collision when the RRC collision resolution message includes a global terminal identifier sent through the RRC connection request message. However, when the terminal has not received the RRC connection setup message including the wide area terminal identifier sent by the RRC connection request message for a predetermined time, the terminal retransmits the preamble after the delay time or after a predetermined time.

If the RRC collision resolution message does not include the global terminal identifier sent through the RRC connection request message, the UE recognizes that the UE has not escaped from the collision and the preamble after the delay time or after a predetermined time. Resend.

Preferably, when the RRC conflict resolution message does not include the wide-area terminal identifier that is sent through the RRC connection request message, regardless of whether a delay time is included in the RRC conflict resolution message, the UE requests an RRC connection request. The preamble is retransmitted according to the delay time set for the receiver. Or, if the RRC conflict resolution message does not include the global terminal identifier sent by the RRC connection request message, the terminal, regardless of whether the RRC conflict resolution message includes a delay time, the terminal of the RRC conflict resolution message The preamble may be retransmitted by applying different delay times according to contents (for example, the reason for rejection).

At this time, if there is redirection information in the response information message, the UE moves to another system or another frequency band (Frequency Band) according to the redirection information, selects a cell again, and retry random access.

In this case, the L1 / L2 control channel indicating the RRC collision resolution message includes the radio network temporary terminal identifier. Therefore, the terminal receives the RRC collision resolution message only when the L1 / L2 control channel includes the temporary network identifier.

<Example 2>

Next, the initial random access process of the RRC connection terminal in detail. 6 is a signal flowchart briefly illustrating an initial random access procedure in this case.

First, the terminal transmits a random access preamble to the base station (S301). In this case, the terminal may include uplink message information or channel measurement information in the preamble so that the base station can perform resource allocation for uplink transmission together with the signature.

The base station responds to the preamble with a response information message (S303). In this case, the response information message includes a signature transmitted by the terminal, acceptance or rejection information on the signature transmission, and a temporary network identifier (Temporary C-RNTI) and MAC scheduling request message allocated to the terminal. It may further include radio resource allocation information and message size, radio parameters (modulation and coding information, Hybrid ARQ information) for transmitting the MAC scheduling request message. Transmission information of the response information message is informed by the L1 / L2 (Layer 1 / Layer 2) control channel related to the transmission of the response information message. The L1 / L2 control channel includes a RA-RNTI indicating transmission of response information and transmission parameters related to transmission of the response information message.

The response information message preferably includes redirection information, and may further include a wait time and a cause of rejection.

After receiving the response information message, if the signature transmitted by the terminal is included in the response information message and if there is acceptance of the signature transmission, the terminal sends a MAC scheduling request message (or MAC resource request message) to the base station. It transmits (S305). In this case, the terminal transmits the MAC scheduling request message using radio resource allocation information, message size, and radio parameters included in the response information message. The MAC scheduling request message preferably includes a radio network terminal identifier such as C-RNTI.

However, when the signature transmitted by the terminal is included in the response information message but there is a rejection for the signature transmission, or when the signature transmitted by the terminal is not included in the response information message, the terminal may perform MAC scheduling. The preamble is retransmitted after a delay time or a predetermined time specified in the response information message without transmitting the request message.

Preferably, when the response information includes the rejection information for the preamble, regardless of whether the response information includes a delay time, the terminal retransmits the preamble according to the delay time set for the MAC scheduling request. Can be. Or if the response information includes rejection information for the preamble, regardless of whether the response information includes a delay time, the terminal is determined according to the number of signatures or users included in the response information or the response information. The preamble may be retransmitted by applying a different delay time according to the message size or according to the rejection reason.

At this time, if there is redirection information in the response information message, the UE moves to another system or another frequency band (Frequency Band) according to the redirection information, selects a cell again, and retry random access.

When the MAC scheduling request message is received at the base station, the MAC layer of the base station transmits a resource grant message or a MAC contention resolution message to the terminal according to circumstances (S307).

When a plurality of UEs transmit the preambles uplink simultaneously using the same signature and the same radio resource at the same time, collisions occur between transmissions. Accordingly, the base station transmits an RRC collision resolution message to each terminal to resolve the collision situation. The MAC collision resolution message includes a wireless network terminal identifier such as a C-RNTI, the wireless network temporary terminal identifier, the wide area terminal identifier, and re-direction information, and includes a wait time and a reason for rejection. (Reject Cause) may further include.

When the MAC collision resolution message includes a wireless network terminal identifier corresponding to the terminal, the terminal recognizes that the terminal is out of the collision. However, if the terminal has not received the resource allocation message including the radio network terminal identifier corresponding to the terminal for a predetermined time, the preamble is retransmitted after the delay time or after a predetermined time.

If the MAC collision resolution message does not include the radio network terminal identifier corresponding to the terminal, the terminal recognizes that the terminal has not escaped from the collision, and retransmits the preamble after the delay time or after a predetermined time.

Preferably, if the MAC collision resolution message does not include a wireless network terminal identifier corresponding to the self, regardless of whether the MAC collision resolution message includes a delay time, the terminal is a delay set for the RRC connection request The preamble may be retransmitted over time. Or, if the MAC collision resolution message does not include a wireless network terminal identifier corresponding to the self, regardless of whether the delay time is included in the MAC collision resolution message, the terminal content of the MAC collision resolution message (eg, The preamble may be retransmitted by applying different delay times according to the rejection reason.

At this time, if there is redirection information in the response information message, the terminal moves to another system or another frequency band (Frequency Band) according to the redirection information, selects a cell again, and retry random access.

In this case, when the MAC collision resolution message is transmitted to a MAC control PDU, the L1 / L2 control channel indicating the MAC collision resolution message includes the radio network temporary terminal identifier. Accordingly, the terminal receives the MAC collision resolution message only when the L1 / L2 control channel includes the temporary network identifier.

Meanwhile, in the present invention, the value of 'delay time' included in all the messages may be an actual time or a parameter value for calculating the delay time. If the value of the 'delay time' is the actual time, the terminal applies a delay according to the value. If the value of the "delay time" is a parameter value for calculating the delay time, the terminal calculates the delay time actually applied using the value of the "delay time" included in the message according to the specified formula. In this case, retransmitting the preamble by applying the different delay times is the same as retransmitting the preamble by applying different parameter values.

In step S207 of FIG. 5 or step S307 of FIG. 6, the following hybrid automatic repeat request (HARQ) mechanism of WCDMA may be used. 7 illustrates a specific implementation of HARQ applied to a downlink physical layer of a wireless packet communication system.

In FIG. 7, a base station determines a terminal to receive a packet and a format (coding rate, modulation scheme, data amount, etc.) of a packet to be transmitted to the terminal, and transmits this information to a downlink control channel (HS-SCCH; High Speed Downlink Shared). It notifies the terminal through transmission of a control channel and transmits a corresponding data packet (HS-DSCH: High Speed Downlink Shared Channel) at a time associated with the terminal. The terminal receives the downlink control channel to know the type and transmission time of the packet to be transmitted to the terminal, and may receive the packet. After receiving the packet, the terminal decodes the packet data, and if the decoding succeeds, the terminal transmits an ACK signal to the base station, and the base station receiving the ACK signal detects that the packet transmission to the terminal is successful and performs the next packet transmission operation. can do. If the terminal fails to decode the packet, the terminal transmits a NACK signal to the base station, and the base station receiving the NACK signal detects that the packet transmission to the terminal has failed, and transmits the same data in the same packet format or a new packet at an appropriate time. Can be retransmitted. At this time, the terminal attempts to decode again by combining the retransmitted packet with a packet that has previously failed to be decrypted.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by.

According to the present invention, the preamble includes the information related to the random access to the base station and transmits the information necessary for the redirected access of the terminal to the terminal in a response message to quickly suppress the uplink of the specific terminal, and ultimately Ensure the communication system is running smoothly.

Claims (9)

Transmitting, by the terminal, the random access preamble to the base station; And Receiving a response message for the random access preamble from a base station,  The method of claim 1, wherein the response message includes redirection information. The method of claim 1, The response message further includes a delay time or a reason for rejection. The method of claim 1, wherein the random access preamble is A method for redirection of uplink access in a mobile communication system, comprising a signature for identifying a terminal. The method of claim 3, The response message does not include the same signature as the signature, the response message includes the rejection information of the signature transmission, and the case in which the connection establishment message is not received from the base station for a predetermined time. And retransmitting the random access preamble. The method of claim 2, wherein the delay time The uplink redirection method of the mobile communication system, characterized in that the delay time for retransmission of the random access preamble. The method of claim 4, wherein Retransmission of the random access preamble is a redirection method of uplink access in a mobile communication system is performed after a predetermined delay time has elapsed in the terminal. The method of claim 6, wherein the delay time The method according to claim 1, wherein the number of signatures included in the response message, the size of the response message, and the reason for rejection of the signature transmission are differently set. The method of claim 1, When a plurality of UEs transmit the random access preamble at the same time using the same signature and the same radio resource, a collision occurs with each other, Receiving a conflict resolution message from the base station further comprises the method of the uplink redirection in a mobile communication system. The method of claim 8, If the collision resolution message includes a terminal identifier previously transmitted by the terminal, it is determined as collision resolution and an uplink is established with the base station; And retransmitting the random access preamble if the terminal identifier is not included in the contention resolution message.

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