# Patent

## Title
Method for transmitting response information in mobile communications system

## Abstract

A method for transmitting radio resources in a mobile communication system is disclosed. The method includes receiving a random access channel (RACH) preamble from a plurality of UEs and transmitting response information associated with the received preambles over a common channel wherein the plurality UEs can access the common channel and receive corresponding information. If a HARQ scheme is used when a UE transmits data to the eNode-B using uplink radio resources allocated over the RACH, the eNode-B does not pre-allocate uplink radio resources required for re-transmission and performs allocation of radio resources for a first transmission of HARQ. If the re-transmission is required, the eNode-B allocates the radio resources required for the re-transmission with the NACK signal. If re-transmission is not required, the present invention can reduce an amount of wasted radio resources.

## Background
This application is a continuation of U.S. application Ser. No. 12/278,566, filed on Aug. 6, 2008, which is a national stage application of PCT/KR2007/000654, filed on Feb. 7, 2007, which claims the benefit and right of priority to U.S. Provisional Application No. 60/771,305, filed on Feb. 7, 2006, U.S. Provisional Application No. 60/815,722, filed on Jun. 21, 2006 and Korean Application No. 10-2006-0107105, filed on Nov. 1, 2006, the contents of which are hereby incorporated by reference herein in their entirety.


TECHNICAL FIELD
The present invention is directed to a mobile communication system, and, specifically to a method for transmitting response information in a mobile communication system.
BACKGROUND ART
FIG. 1 is a structural diagram illustrating a Long Term Evolution (LTE) system which is a mobile communication system. The LTE system is an evolved version of a conventional UMTS system and has been standardized by the 3GPP (3rd Generation Partnership Project).
The LTE network may be generally classified into an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and a Core Network (CN). The E-UTRAN includes at least one eNode-B serving as a base station and an Access Gateway (AG) located at the end of the network so that it is connected to an external network.
The AG may be classified into a portion for processing user traffic and a portion for processing control traffic. The AG portion for processing user traffic and the AG portion for processing control traffic may be connected to each other via a new interface for communication. One or more cells may exist in an eNode-B. The eNode-Bs may be connected by an interface for the transmission of user traffic or control traffic.
The CN includes the AG and a node for registering a user of the user equipment (UE). An interface may also be provided in the E-UMTS in order to classify the E-UTRAN and the CN.
Radio interface protocol layers may be classified into the first layer (L1), the second layer (L2), and the third layer (L3) on the basis of three lower layers of an Open System Interconnection (OSI) reference model that is well known in the art. A physical layer of the first layer (L1) provides an information transfer service over a physical channel. A radio resource control (RRC) layer located at the third layer (L3) controls radio resources between the UE and the network.
The RRC layer exchanges RRC messages between the UE and the network for this purpose. The RRC layer may be distributed to a plurality of network nodes, such as eNode-B and AG, and may also be located at the eNode-B or the AG.
FIG. 2 is a conceptual diagram illustrating a control plane of a radio interface protocol structure between the UE and the UTRAN (UMTS Terrestrial Radio Access Network) based on the 3GPP radio access network standard. The radio interface protocol is horizontally represented by a physical layer, a data link layer and a network layer. The radio interface protocol is vertically represented by a user plane for transmitting data and the control plane for transmitting control signals.
The protocol layers of FIG. 2 may be classified into a physical layer, a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer and a Radio Resource Control (RRC) layer.
The physical layer, which is a first layer, provides an information transfer service to an upper layer over a physical channel. The physical layer is connected to a Medium Access Control (MAC) layer located there above via a transport channel.
The MAC layer communicates with the physical layer over the transport channel such that data is communicated between the MAC layer and the physical layer. Data is communicated among different physical layers, such as between a first physical layer of a transmission side and a second physical layer of a reception side.
The MAC layer of the second layer (L2) transmits a variety of services to the RLC (Radio Link Control) layer, which is its upper layer, over a logical channel. The RLC layer of the second layer (L2) supports reliable data transmission.
It should be noted that the RLC layer is depicted in dotted lines, because if the RLC functions are implemented in and performed by the MAC layer, the RLC layer itself may not need to exist.
The RRC (Radio Resource Control) layer located at the lowest portion of the third layer (L3) is defined by only the control plane. The RRC layer controls logical channels, transport channels and physical channels for the configuration, reconfiguration and release of Radio Bearers (RBs). An RB denotes a service provided by the second layer (L2) for data transfer between the UE and the F-UTRAN.
FIG. 3 is a conceptual diagram illustrating a user plane of a radio interface protocol structure between the UE and the UTRAN according to the 3GPP radio access network standard. The radio protocol user plane classifies into a physical layer, a MAC layer, a RLC layer and a PDCP (Packet Data Convergence Protocol) layer.
The physical layer of the first layer (L1) and the MAC and RLC layers of the second layer (L2) is used to effectively transmit data using an IP packet, such as IPv4 or IPv6, on a radio interface with a relatively narrow bandwidth. The PDCP layer performs header compression to reduce the size of a relatively-large IP packet header containing unnecessary control information.
Uplink and downlink channels for transmitting data between the network and the UE will hereinafter be described in detail. Downlink channels transmit data from the network to the UE. Uplink channels transmit data from the UE to the network.
Examples of downlink channels are a Broadcast Channel (BCH) for transmitting system information and a downlink Shared Channel (SCH) and a Shared Control Channel (SCCH) for transmitting user traffic or control messages. The use traffic or control messages of a downlink multicast service or broadcast service may be transmitted over the downlink shared channel (SCH) or may be transmitted over an additional multicast channel (MCH).
Examples of uplink channels are a Random Access Channel (RACH) and an uplink shared channel (SCH) and a shared control channel (SCCH) for transmitting user traffic or control messages.
FIG. 4 is a conceptual diagram illustrating a hybrid automatic repeat and request (HARQ) scheme. A method for implementing HARQ in the downlink physical layer of a radio packet communication system will be described with reference to FIG. 4.
Referring to FIG. 4, the eNode-B determines a UE that is to receive packets and the type of packet that is to be transmitted to the UE, such as a code rate, a modulation scheme and an amount of data. The eNode-B informs the UE of the determined information over a High-Speed Downlink Shared Control Channel (HS-SCCH) and transmits a corresponding data packet via High-Speed Downlink Shared Channel (HS-DSCH) at a time associated with the transmission of the information over the HS-SCCH.
The UE receives the downlink control channel, identifies a packet type to be transmitted and a transmission time point, and receives the corresponding packet. The UE then attempts to decode the received packet data.
The UE transmits a negative acknowledgement (NACK) signal to the eNode-B if the UE fails to decode a specific packet, such as data1. The eNode-B recognizes that packet transmission has failed and re-transmits the same data, such as data1, using the same packet format or a new packet format at a suitable time point. The UE combines the re-transmitted packet, such as data1, and a previously received packet for which packet decoding failed and re-attempts packet decoding.
The UE transmits an acknowledgement (ACK) signal to the eNode-B if the packet is received and decoded successfully. The eNode-B recognizes successful packet transmission and performs transmission of the next packet, such as data2.
A random access channel (RACH) indicates a channel for transmitting an initial control message from the UE to the network. The RACH is adapted to implement synchronization between the UE and the network. Furthermore, if there is no more data for transmission left in a UE that desires to transmit data in an uplink direction, the UE can acquire necessary radio resources over the RACH.
For example, when the UE is powered on it attempts to access a new cell. The UE performs downlink synchronization and receives system information from a target cell desired by the UE.
Upon receiving the system information, the UE must transmit an access request message to access the RRC layer. However, the UE is not synchronized with a current network and there is no guarantee of uplink radio resources since it uses the RACH.
In other words, the UE requests radio resources capable of transmitting the access request message to the network. If the eNode-B receives the radio-resource request signal from the UE, it allocates suitable radio resources to the UE to transmit a RRC connection request message. The UE can then transmit the RRC connection request message to the network using the allocated radio resources.
In another example, it is assumed that an RRC connection is established between the UE and the network. The UE receives radio resources from the network according to the radio resource scheduling process of the network such that data from the UE is transmitted to the network using the radio resources.
However, if there is no more data for transmission left in a buffer of the UE, the network no longer allocates uplink radio resources to the UE. If the network allocates the uplink radio resources to the UE, this allocation is considered to be ineffective. The buffer state of the UE is periodically or accidentally reported to the network.
Therefore, if new data is stored in the buffer of the UE having no radio resources, the UE utilizes the RACH since there are no uplink radio resources allocated to the UE. In other words, the UE requests radio resources required for data transmission to the network.
RACH as used in a Wideband Code Division Multiple Access (WCDMA) system will hereinafter be described in detail. The RACH is used for transmission of data with short length. Some RRC messages, such as an RRC connection request message, a cell update message, and a URA update message, are transmitted over the RACH.
A plurality of logic channels can be mapped to the RACH. For example, a common control channel (CCCH), a dedicated control channel (DCCH), and a dedicated traffic channel (DTCH) may be mapped to the RACH. The RACH is mapped to a physical random access channel (PRACH).
FIG. 5 is a conceptual diagram illustrating an example of a PRACH (Physical Random Access Channel) transmission method. As illustrated in FIG. 5, the PRACH which is an uplink physical channel is divided into a preamble part and a message part.
The preamble part performs a power-ramping function for adjusting power required for transmitting a message and an anti-collision function for preventing transmissions from several UEs from colliding with each other. The message part performs transmission of a MAC Protocol Data Unit (MAC PDU) to the physical channel from the MAC layer.
If the MAC layer of the UE indicates the physical layer of the UE to transmit the PRACH transmission, the physical layer of the UE selects a single access slot and a single signature and transmits the PRACH preamble in the uplink. The preamble can be transmitted during an access slot period of 1.33 ms and selects a single signature from among 16 signatures during an initial predetermined period of the access slot such that it can transmit the selected signature.
When the UE transmits the preamble, the eNode-B can transmit a response signal over an acquisition indicator channel (AICH) which is a downlink physical channel. The eNode-B transmits a positive response (ACK) or negative response (NACK) to the UE using a response signal transmitted over the AICH.
If the UE receives an ACK response signal, it transmits the message part. If the UE receives a NACK response signal, the MAC layer of the UE indicates the physical layer of the UE to perform PRACH retransmission after a predetermined time. If the UE does not receive a response signal corresponding to the transmitted preamble, it transmits a new preamble at a power level that is higher than that of a previous preamble by one level after a designated access slot.
Although the above-mentioned description has disclosed a response signal to the RACH preamble, it should be noted that the eNode-B can transmit data or control signals to the UE. There are a variety of control signals transmitted from the eNode-B to the UE, such as downlink scheduling information, uplink scheduling grant information, and response information associated with the UE s RACH preamble transmission.
DISCLOSURE OF INVENTION
Technical Problem
According to the conventional art, when the UE transmits data over the RACH, it transmits the RACH preamble to the eNode-B and the eNode-B transmits response information associated with the RACH preamble to the UE. However, if at least two UEs transmit their RACH preambles in order to use the RACH at the same or similar time, the eNode-B must inform each of the two UEs regarding response information associated with the respective preambles, thereby requiring the allocation of radio resources for transmitting the response information to each UE and wasting radio resources.
Provided that the UE uses the HARQ scheme when transmitting data to the eNode-B using the radio resources allocated over the RACH, the eNode-B pre-allocates not only first radio resources associated with initial transmission data but also second radio resources associated with re-transmission data. Therefore, the second radio resources for the re-transmission data are unnecessarily wasted if the UE successfully transmits data at a first transmission time.
Technical Solution
An object of the present invention is to provide a method for transmitting response information in a mobile communication system that reduces an amount of wasted radio resources and effectively uses radio resources. Another object of the present invention is to provide a mobile communication system which does not transmit response information associated with UEs separately when two or more UEs have transmitted RACH preambles at the same or similar time, but rather transmits RACH preamble response information to a specific UE, configures the associated response information in the form of a single data unit over a common channel, and transmits the configured data unit to the specific UE.
In one aspect of the present invention, a method for transmitting a specific preamble and receiving information in response to the specific preamble in a mobile communication system is provided. The method includes transmitting the specific preamble over a random access channel (RACH), receiving response information over a common channel, the response information including at least one response and identification information corresponding to the at least one response, the at least one response corresponding to at least one preamble transmitted during a specific time interval and processing the at least one response if the identification information indicates that the at least one response corresponds to the specific preamble.
It is contemplated that the method further includes transmitting data using radio resources allocated in the at least one response if the identification information indicates that the at least one response corresponds to the specific preamble. It is further contemplated that the method further includes receiving a first message including an indication that the transmitted data was not properly received and retransmitting the data using newly allocated radio resources.
It is contemplated that the first message includes the newly allocated radio resources. It is further contemplated that the method further includes receiving a second message including the newly allocated radio resources. Preferably, the common channel is a downlink shared channel (DL-SCH).
In another aspect of the present invention, a method for transmitting a preamble and receiving information in response to the preamble in a mobile communication system is provided. The method includes receiving at least one preamble over a random access channel (RACH) during a specific time interval and transmitting response information over a common channel, the response information including a response corresponding to the at least one preamble received during the specific time interval and identification information identifying a mobile communication terminal from which the at least one preamble was received,
It is contemplated that the method further includes allocating radio resources in the response, the radio resources associated with transmitting data from the mobile communication terminal from which the at least one preamble was received. It is further contemplated that the method further includes receiving data from the mobile communication terminal from which the at least one preamble was received, the data transmitted using the allocated radio resources, determining that the data was not properly received, transmitting a first message including additional allocated radio resources associated with retransmitting the data and receiving the data retransmitted using the radio resources allocated in the message.
It is contemplated that the method further includes including an indication in the first message that the data was not properly received. It is further contemplated that the method further includes transmitting a second message including an indication that the data was not properly received. Preferably, the common channel is a downlink shared channel (DL-SCH).
In another aspect of the present invention, a method for transmitting a specific preamble and receiving information in response to the specific preamble in a mobile communication system is provided. The method includes a specific mobile communication terminal transmitting the specific preamble over a random access channel (RACH), a network transmitting response information over a common channel, the response information including a response corresponding to at least one preamble received during a specific time interval and identification information identifying a mobile communication terminal from which the at least one preamble was received, the specific mobile communication terminal receiving the response information and the specific mobile communication terminal processing the at least one response if the identification information indicates that the at least one response corresponds to the specific preamble.
It is contemplated that the method further includes the network allocating radio resources in the response, the radio resources associated with transmitting data from the mobile communication terminal from which the at least one preamble was received. It is further contemplated that the method further includes the specific mobile communication terminal transmitting data using the radio resources allocated in the at least one response if the identification information indicates that the at least one response corresponds to the specific preamble.
It is contemplated that the method further includes the network receiving data from the mobile communication terminal from which the at least one preamble was received, the data transmitted using the allocated radio resources, the network determining that the data was not properly received, the network transmitting a first message including additional allocated radio resources associated with retransmitting the data, the specific mobile communication terminal retransmitting the data using the radio resources allocated in the first message and the network receiving the data retransmitted using the radio resources allocated in the message. It is further contemplated that the method further includes the network including an indication in the first message that the data was not properly received.
It is contemplated that the method further includes the network transmitting a second message including an indication that the data was not properly received. It is further contemplated that the common channel is a downlink shared channel (DL-SCH).
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
These and other embodiments will also become readily apparent to those skilled in the art from the following detailed description of the embodiments having reference to the attached figures, the invention not being limited to any particular embodiments disclosed.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. Features, elements, and aspects of the invention that are referenced by the same numerals in different figures represent the same, equivalent, or similar features, elements, or aspects in accordance with one or more embodiments.
FIG. 1 is a structural diagram illustrating a Long Term Evolution (LTE) system which is a mobile communication system.
FIG. 2 is a conceptual diagram illustrating each layer of a control plane of radio interface protocols
FIG. 3 is a conceptual diagram illustrating each layer of a user plane of radio interface protocols.
FIG. 4 is a conceptual diagram illustrating a hybrid ARQ (HARQ) scheme.
FIG. 5 is a conceptual diagram illustrating an example of a PRACH (Physical Random Access Channel) transmission method.
FIG. 6 is a flow chart illustrating a method for transmitting response information in a mobile communication system according to one embodiment of the present invention.
FIG. 7 is a conceptual diagram illustrating a method for transmitting response information to a UE over a common channel according to one embodiment of the present invention.
FIG. 8 is a flow chart illustrating a method for transmitting response information in a mobile communication system according to another embodiment of the present invention.
FIG. 9 is a flow chart illustrating a method for transmitting response information in a mobile communication system according to another embodiment of the present invention.



BEST MODE FOR CARRYING OUT THE INVENTION
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
A method for transmitting response information in a mobile communication system according to the present invention will hereinafter be described with reference to the accompanying drawings. For the convenience of description and better understanding of the present invention, the term “UE” will be used to indicate a transmission entity of an uplink signal and the term “eNode-B” will be used to indicate a reception entity of the uplink signal. However, it should be noted that the scope of the terminal and the base station is not limited to the above-mentioned terms and the term “UE” and the term “eNode-B” may also be used to indicate, respectively, a terminal and a base station.
FIG. 6 is a flow chart illustrating a method for transmitting response information in a mobile communication system according to one embodiment of the present invention. A method for transmitting response information associated with preamble transmission of at least one UE at a time will hereinafter be described.
The UE uses the RACH to perform a RRC connection request, a cell update, a handover, an uplink radio resource request and maintenance of synchronization associated with the eNode-B. The UE transmits a preamble prior to the transmitting of data. The preamble uses for adjusting transmission power required for data transmission and for preventing several UEs from colliding with each other.
When using RACH, the UE transmits the RACH preamble to the eNode-B and the eNode-B transmits RACH preamble response information to the UE. The eNode-B does not independently transmit response information associated with other UEs, each of which transmits RACH preambles at the same or similar time, but rather transmits the response information associated with the other UEs over a common channel at the same time.
For example, if a first UE, a second UE, and a third UE transmit their RACH preambles to the eNode-B within a predetermined period of time, the eNode-B configures response information associated with the first through third UEs in the form of a single data unit and transmits the single data unit to the first through third UEs over a common channel in order to reply to the RACH preambles of the first through third UEs.
As illustrated in FIG. 6, the first UE (UE1) transmits its RACH preamble to the eNode-B at step S60 and the second UE (UE2) transmits its RACH preamble to the eNode-B at the same time or a similar time as the RACH preamble of the first UE is transmitted. In other words, the first UE (UE1) and the second UE (UE2) transmit their RACH preambles to the eNode-B at the same or similar time.
Therefore, the eNode-B receives at least one RACH preamble from at least two UEs during a predetermined time (Δt).
Although FIG. 6 illustrates only the first (UE1) and second (UE2) UEs, it is obvious to those skilled in the art that the number of UEs may be N and the present invention may also be applied to N UEs.
The eNode-B receives RACH preambles of the first (UE1) and second (UE2) UEs and transmits response information of the received RACH preambles at step S62. The eNode-B transmits the response information over a common channel without allocating unique radio frequency RF channels to the first (UE1) and second (UE2) UEs in order to reply to the RACH preambles. The common channel allows all UEs within a cell to receive or read data from the eNode-B.
FIG. 7 is a conceptual diagram illustrating a method for transmitting response information to a UE over a downlink shared channel (DL-SCH) which is a common channel according to the one embodiment of the present invention. Generally, the DL-SCH is used to transmit data from the eNode-B to predetermined UEs or is used to transmit data to all UEs in a cell. Therefore, different UEs may receive data over the DL-SCH.
Although the eNode-B simultaneously transmits response information associated with a plurality of UEs over the DL-SCH, each UE can receive its response information from the eNode-B. The eNode-B transmits response information associated with the RACH preambles to the UEs over the DL-SCH. The single data unit of response information includes a plurality of response information associated with a plurality of UEs.
As illustrated in FIG. 7, the UE must first read the downlink shared control channel (DL-SCCH) in order to read data of the DL-SCH. The location information of the DL-SCH is transmitted over the DL-SCCH.
In other words, after transmitting the RACH preamble, the UE reads the DL-SCCH to receive response information from the eNode-B and then recognizes location information of the DL-SCH associated with the DL-SCCH. Control signals associated with the physical layer and/or the second layer are transmitted from the eNode-B to the UE over the DL-SCCH.
The DL-SCCH carries a variety of information, such as a UE ID (Identifier) for indicating which one of UEs will receive the data, location information related to frequency or time that indicates which DL-SCH data will be read by the UEs, specific information required by UEs that desire to read the DL-SCH data, and decoding information. In this way, it can be recognized which one of UEs will receive specific DL-SCH data by means of the UE ID included in DL-SCCH.
As illustrated in FIG. 6, the DL-SCH carries first response information for the first UE (UE1) and second response information for the second UE (UE2). In other words, the first UE (UE1) and the second UE (UE2) read the same DL-SCCH and determine the same DL-SCH location.
The first UE (UE1) and the second UE (UE2) read their unique response information over the same DL-SCH. The response information of the RACH preambles transmitted from the UEs at the same or similar time transmits to the UEs by multiplexing each response information for each UE at the second layer of the eNode-B.
The eNode-B configures the response information of the RACH preambles having been transmitted by the UEs at the same or similar time. The response information is configured in the form of a single MAC Protocol Data Unit (PDU).
A method for multiplexing the response information of the UEs to configure a single MAC PDU and transmitting the single MAC PDU will hereinafter be described with reference to Tables 1 and 2.
A representative example of a PDU configured by multiplexing of response information is shown in Table 1:













TABLE 1







First
First UE′
Second
Second UE′
. . .
N-thUE′
N-th UE′


UE′
response
UE′
response

header
response


header
information
header
information


information









As illustrated in Table 1, the eNode-B configures a first UE′ header prior to the first UE′ response information. The header includes a UE ID indicating for which UE the response information is intended to read and also includes specific information indicating the length of the response information.
The eNode-B configures the first UE′ response information after the first UE header. The response information for the first UE includes uplink radio resources allocated to the first UE, an identifier within a cell, a temporary identifier of the first UE, and a compensation value associated with synchronization with the eNode-B.
After configuring the first UE header and the first UE′ response information, the eNode-B configures the second UE′ header and the second UE′ response information. In this way, the PDU generated by including response information of several UEs in single response information may be configured.
Another example of a single PDU configured by the multiplexing of response information is shown in Table 2.
As illustrated in Table 2, a header including the first UE′ identifier and the length of response information is attached to the MAC PDU. The header serves the same function as that of the header illustrated in the Table 1.















TABLE 2







First
Second
. . .
N-thUE′
Indicator
First UE′
Second UE′
. . .
N-th UE′


UE′
UE′

header
header
response
response

response


header
header


end
information
information

information









The second UE′ header is the attached to the PDU after the first UE′ header. In this way, the PDU includes as many headers as the number (N) of UEs for which response information is to be included in single response information.
An indication indicating the end of the header is attached to the end of the header. The eNode-B can recognize the beginning of the response information using this header. Thereafter, the MAC PDU is formed by sequentially attaching response information of individual UEs.
The response information of each UE includes information of uplink radio resources allocated to the each UE, an identifier within a cell, a temporary identifier of the UE, and a compensation value associated with synchronization a with the eNode-B. Each UE recognizes its own response information from among a plurality of response information that have been multiplexed into the single response information and transmitted over the common channel. Each UE transmits data to the eNode-B using uplink radio resources allocated to the each UE in the response information associated with its RACH preamble.
FIG. 8 is a flow chart illustrating a method for transmitting response information in a mobile communication system according to another embodiment of the present invention. Specifically, FIG. 8 illustrates a scheduling method for a specific case in which a HARQ (Hybrid ARQ) scheme is used when data is transmitted to the eNode-B.
As illustrated in FIG. 8, a first UE (UE) transmits its RACH preamble to the eNode-B at step S70 and a second UE (UE2) transmits its RACH preamble to the eNode-B at step S71 in a manner similar to that illustrated in FIG. 6. The first UE (UE1) and second UE (UE2) receive response information configured in the form of a single data unit over a common channel, such as a DL-SCH, at step S72.
Each UE then transmits data to the eNode-B using uplink radio resources allocated to the each UE in the response information associated with each RACH preamble. It should be noted that FIG. 8 illustrates only a data transmission/reception process between the second UE (UE2) and the eNode-B after reception of the response information. It is obvious to those skilled in the art that the above-mentioned process can also be applied to the case of the first UE (UE1) in the same manner as for the second UE (UE2).
Provided that the HARQ scheme is used when each UE transmits data to the eNode-B using the uplink radio resources allocated over the RACH, uplink radio resources for data re-transmission are not pre-allocated but rather allocated and transmitted to each UE with a NACK signal when data re-transmission is required due to a decoding failure of the eNode-B. The uplink radio resources for data retransmission may be included in the NACK signal. A specific control signal may be used to allocate the uplink radio resources for re-transmission to the UE.
As illustrated in FIG. 8, the second UE (UE2) transmits data to the eNode-B at step S73 after receiving the response information from the eNode-B. The second UE (UE2) employs a HARQ scheme when transmitting the above-mentioned data to the eNode-B. The eNode-B informs the UEs of the setup of the HARQ scheme through system information.
The eNode-B receives the data from the second UE (UE2) and decodes the received data. If the eNode-B does not decode the data correctly, it transmits a NACK signal to the second UE (UE2) to indicate a decoding error at step S74.
The eNode-B allocates radio resources required for data re-transmission to the second UE (UE2), and transmits information associated with the allocated radio resources along with the NACK signal at the same time. In other words, the uplink radio resource allocation information in the response information is related only to the first transmission of the HARQ when the eNode-B transmits response information of the RACH preamble to the UE.
For example, if the radio resources required for data transmission after the RACH preamble have a specific value of 100 and the data requires re-transmission due to the HARQ operation, the UE re-requires the radio resources of 100. If the data retransmission is applied to a case in which the eNode-B allocates uplink radio resources according to the UE s RACH preamble, radio resources of 200 will be allocated to the UE.
However, when allocating radio resources as response information of the UE s RACH preamble, the eNode-B allocates only the 100 radio resources associated with the first transmission to the UE according to the present invention. Thereafter, if data re-transmission is required due to failure of a UE s data transmission, the eNode-B additionally allocates not only the NACK signal but also the 100 additional radio resources to the UE.
The specific control signal including the radio-resource allocation information required for data re-transmission may be transmitted according to the same format as that for the RACH preamble s response information. Also, a channel used when the eNode-B allocates radio resources to the UE may also be used as an example of the present invention.
The second UE (UE2) re-transmits the data at step S75 according to uplink radio resource allocation information that was transmitted with the NACK signal.
FIG. 9 is a flow chart illustrating a method for transmitting response information in a mobile communication system according to another embodiment of the present invention. Specifically, FIG. 9 illustrates a scheduling method for a specific case in which a HARQ (Hybrid ARQ) scheme is used when data is transmitted to the eNode-B. One of differences with the case of FIG. 8 is that uplink radio resources for data retransmission may not be included in the NACK signal but be transmitted separately with the NACK signal at the same or another time.
As illustrated in FIG. 9, a first UE (UE1) transmits its RACH preamble to the eNode-B at step S80 and a second UE (UE2) transmits its RACH preamble to the eNode-B at step S81 in a manner similar to that illustrated in FIG. 6 and FIG. 8. The first UE (UE1) and second UE (UE2) receive response information configured in the form of a single data unit over a common channel, such as a DL-SCH, at step S82.
Each UE then transmits data to the eNode-B by using uplink radio resources allocated to the each UE in the response information associated with each RACH preamble at the step S83. It should be also noted that FIG. 9 illustrates only a data transmission/reception process between the second UE (UE2) and the eNode-B after reception of the response information. It is obvious to those skilled in the art that the above-mentioned process can also be applied to the case of the first UE (UE1) in the same manner as for the second UE (UE2).
The second UE (UE2) employs a HARQ scheme when transmitting the above-mentioned data to the eNode-B. The eNode-B preferably informs the UEs of the setup of the HARQ scheme through system information.
Provided that the HARQ scheme is used when each UE transmits data to the eNode-B by using the uplink radio resources allocated over the RACH, uplink radio resources for data re-transmission are not pre-allocated but rather allocated and transmitted to each UE with a NACK signal when data re-transmission is required due to a decoding failure of the eNode-B. The NACK signal transmitted when data retransmission is required due to a decoding failure of the eNode-B at the step S84. And the uplink radio resources for data re-transmission are allocated. Namely, the uplink radio resources for data re-transmission are not pre-allocated but rather allocated and transmitted to each UE when re-transmission is necessary. A specific control signal may be used to allocate the uplink radio resources for re-transmission to the UE. The specific control signal may be a signal for SR (Scheduling Resources) from the eNode-B at the step S85. The specific control signal may be also a signal for scheduling information or any other signals.
The specific control signal including the radio resource allocation information required for data re-transmission may be transmitted according to the same format as that for the RACH preamble s response information. Also, a channel used when the eNode-B allocates radio resources to the UE may also be used as an example of the present invention.
The second UE (UE2) re-transmits the data at step S86 according to uplink radio resource allocation information that was transmitted with the specific control signal for example, SR.
As described herein, the method for transmitting response information in a mobile communication system according to the present invention can more effectively use radio resources, thereby reducing the amount of wasted radio resources.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims. Therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are intended to be embraced by the appended claims.
INDUSTRIAL APPLICABILITY
The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses.
The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structure described herein as performing the recited function and not only structural equivalents but also equivalent structures.

## Claims

1. A method for a user equipment (UE) to perform a random access in a mobile communication system, the method comprising:
transmitting a specific random access preamble;
receiving a medium access control packet data unit (MAC PDU) comprising one or more random access responses and a MAC header comprising one or more header parts, each of the header parts corresponding to each of the random access responses; and
processing information on a specific random access response, when the specific random access response comprises an identifier corresponding to the transmitted specific random access preamble,
wherein all of the header parts is in a first part of the MAC PDU and all of the random access responses is in a second part of the MAC PDU subsequent to the first part.

2. The method of claim 1, wherein the MAC PDU is received via a downlink common channel.

3. The method of claim 1, wherein the specific random access response comprises uplink resource information allocated to the UE, a temporary identifier of the UE and a timing synchronization related variable.

4. The method of claim 3, further comprising:
transmitting an uplink signal using the uplink resource information.

5. The method of claim 4, further comprising:
receiving a message indicating uplink resource information newly allocated to the UE; and
retransmitting the uplink signal using the newly allocated uplink resource information.

6. The method of claim 5, wherein the message comprising the newly allocated uplink resource information corresponds to a negative acknowledgement (NACK).

7. A method for a network to control a random access of a user equipment (UE) in a mobile communication system, the method comprising:
receiving a specific random access preamble from the UE; and
transmitting a medium access control packet data unit (MAC PDU) comprising one or more random access responses and a MAC header comprising one or more header parts, each of the header parts corresponding to each of the random access responses,
wherein all of the header parts is in a first part of the MAC PDU and all of the random access responses is in a second part of the MAC PDU subsequent to the first part, and
wherein when the MAC PDU comprises a specific random access response corresponding to the specific random access preamble, the specific random access response comprises an identifier corresponding to the specific random access preamble.

8. The method of claim 7, wherein the MAC PDU is transmitted via a downlink common channel.

9. The method of claim 7, wherein the specific random access response comprises uplink resource information allocated to the UE, a temporary identifier of the UE and a timing synchronization related variable.

10. The method of claim 9, further comprising:
receiving an uplink signal associated with the uplink resource information.

11. The method of claim 10, further comprising:
transmitting a message indicating an uplink resource information newly allocated to the UE; and
receiving a retransmitted uplink signal associated with the newly allocated uplink resource information.

12. The method of claim 11, wherein the message comprising the newly allocated uplink resource information corresponds to a negative acknowledgement (NACK).