Patent Publication Number: US-2022225366-A1

Title: Blind scheduling apparatus and method in a mobile communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/907,106 filed on Jun. 19, 2020, now U.S. Pat. No. 11,291,027, issued Mar. 29, 2022, which is a continuation of U.S. patent application Ser. No. 16/259,951 filed on Jan. 28, 2019, now U.S. Pat. No. 10,694,537, issued Jun. 23, 2020, which is a continuation of Ser. No. 15/194,378 filed on Jun. 27, 2016, now U.S. Pat. No. 10,194,458 issued on Jan. 29, 2019, which is a continuation of U.S. patent application Ser. No. 13/165,202 filed on Jun. 21, 2011, now U.S. Pat. No. 9,414,403 issued on Aug. 9, 2016, which claims priority to Korean Patent Application No. 10-2010-0058717 filed on Jun. 21, 2010, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to a blind scheduling apparatus and method in a mobile communication system. 
     2. Description of Related Art 
     Next-generation communication systems have evolved to provide a variety of high-speed, high-capacity services to User Equipment&#39;s (UEs). Long Term Evolution (LTE) communication system, an example of the next-generation communication systems, uses various resource allocation schemes, one of which is blind scheduling. 
     The blind scheduling is a scheme in which an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) periodically allocates a dedicated uplink (UL) resource without prior information about the amount of data that a UE will transmit over an UL. The LTE communication system considers using blind scheduling for latency reduction. The amount of data that a UE will transmit over a UL may be detected using the buffer status. For convenience, a dedicated UL resource that is periodically allocated to a UE using blind scheduling will be referred to herein as a ‘UL grant’. 
     When employing blind scheduling, an eNB continuously allocates a dedicated UL resource or a UL grant to a UE for a relatively long period. So, the UE is continuously allocated the UL grant by the eNB such that, even when the UE has no data, it will actually transmit on a UL. 
     Semi-Persistent Scheduling (SPS) is one of the blind scheduling schemes. When using SPS, an eNB periodically allocates a UL grant to a UE to which an SPS Cell Radio Network Temporary Identifier (C-RNTI) has been allocated. The eNB may inform the UE of a UL grant allocation period using an SPS configuration Information Element (IE). The UE may transmit data to the eNB using the periodically allocated UL grant. Therefore, the UE may skip the UL resource allocation process that it should perform with the eNB to be allocated a UL resource, contributing to a reduction in the latency. 
     When the LTE communication system uses SPS, the latency may be reduced due to the possible skip of the UL resource allocation process. However, a UE should transmit padding Medium Access Control (MAC) Protocol Data Units (PDUs) using a UL grant even when it has no data to transmit on a UL, which may cause a waste of the UE battery and lead to signaling overhead caused by the transmission of the padding MAC PDUs. In addition, the eNB unnecessarily decodes the padding MAC PDUs, causing a padding MAC PDU decoding processing load. 
     SUMMARY 
     To address the above-discussed deficiencies of the prior art, it is a primary object to provide a blind scheduling apparatus and method in a mobile communication system. 
     Another aspect of the present invention is to provide a blind scheduling apparatus and method for minimizing a waste of a UE battery caused by the transmission of padding MAC PDUs in a mobile communication system. 
     Another aspect of the present invention is to provide a blind scheduling apparatus and method for minimizing a signaling overhead caused by the transmission of padding MAC PDUs in a mobile communication system. 
     Yet another aspect of the present invention is to provide a blind scheduling apparatus and method for minimizing a processing load caused by the decoding of padding MAC PDUs in a mobile communication system. 
     In accordance with one aspect of the present invention, there is provided a blind scheduling method of a User Equipment (UE) in a mobile communication system. The blind scheduling method includes detecting a type of an uplink (UL) grant, while the UE is periodically allocated a UL grant. When there is no data to transmit using the UL grant, whether to transmit a padding Medium Access Control (MAC) Protocol Data Unit (PDU) to an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) using the UL grant according to the type of the UL grant is determined. 
     In accordance with another aspect of the present invention, there is provided a blind scheduling method of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) in a mobile communication system. The blind scheduling method includes determining whether data is detected from an Explicit uplink (UL) grant that the eNB allocates to a User Equipment (UE). A new Explicit UL grant is allocated to the UE when no data is detected from the Explicit UL grant. And when data is detected from the Explicit UL grant, Hybrid Automatic Retransmission Request (HARQ) feedback information is transmitted to the UE according to a success/failure in decoding the data. The Explicit UL grant is a UL grant that serves as resource allocation information received from the eNB over a Physical Downlink Control Channel (PDCCH) without separate configuration, among UL grants which are allocated after being mapped to a Cell Radio Network Temporary Identifier (C-RNTI). 
     In accordance with another aspect of the present invention, there is provided a blind scheduling method of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) in a mobile communication system. The blind scheduling method includes determining whether data is detected from a Fast Access Scheduling (FAS) grant that the eNB allocates to a User Equipment (UE). A new FAS grant is allocated to the UE when no data is detected from the FAS grant. And when data is detected from the FAS grant, Hybrid Automatic Retransmission Request (HARQ) feedback information is transmitted to the UE according to a success/failure in decoding the data. The FAS grant is an uplink (UL) grant that is allocated after being mapped to a FAS Cell Radio Network Temporary Identifier (C-RNTI). The FAS C-RNTI is a C-RNTI that is allocated to a UE to allow the UE to not transmit a padding MAC PDU using the FAS grant. 
     In accordance with another aspect of the present invention, there is provided a blind scheduling method of a user equipment (UE) in a mobile communication system. The blind scheduling method includes determining whether there is data to transmit using an uplink (UL) grant, while the UE is periodically allocated the UL grant. And when there is no data to transmit using the UL grant, no padding Medium Access Control (MAC) Protocol Data Unit (PDU) is transmitted to an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) using the UL grant. 
     In accordance with another aspect of the present invention, there is provided a blind scheduling method of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) in a mobile communication system. The blind scheduling method includes allocating an uplink (UL) grant to a user equipment (UE) using Semi-Persistent Scheduling (SPS). And when no data is detected from the UL grant, it is determined that the UE transmits no data using the UL grant. 
     In accordance with another aspect of the present invention, there is provided a user equipment (UE) for a mobile communication system. The UE includes a control unit detects a type of an uplink (UL) grant while the UE is periodically allocated a UL grant. And when there is no data to transmit using the UL grant, the UE determines whether to allow a transmission unit to transmit a padding Medium Access Control (MAC) Protocol Data Unit (PDU) to an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) using the UL grant according to the type of the UL grant. 
     In accordance with another aspect of the present invention, there is provided an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) for a mobile communication system. The eNB includes a resource allocation unit that allocates an Explicit Uplink (UL) grant under specific control. A transmission unit transmits Hybrid Automatic Retransmission Request (HARQ) feedback information to a user equipment (UE) under specific control. And a control unit determines whether data is detected from the Explicit UL grant, controls the resource allocation unit to allocate a new Explicit UL grant to the UE when no data is detected from the Explicit UL grant, and controls the transmission unit to transmit HARQ feedback information to the UE according to a success/failure in decoding data when data is detected from the Explicit UL grant. The Explicit UL grant is a UL grant that serves as resource allocation information received from the eNB over a Physical Downlink Control Channel (PDCCH) without separate configuration, among UL grants which are allocated after being mapped to a Cell Radio Network Temporary Identifier (C-RNTI). 
     In accordance with another aspect of the present invention, there is provided an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) for a mobile communication system. The eNB includes a resource allocation unit, a transmission unit, and a control unit. The resource allocation unit allocates a Fast Access Scheduling (FAS) grant under specific control. The transmission unit transmits Hybrid Automatic Retransmission Request (HARQ) feedback information to a user equipment (UE) under specific control. And the control unit determines whether data is detected from the FAS grant, controls the resource allocation unit to allocate a new FAS grant to the UE when no data is detected from the FAS grant, and controls the transmission unit to transmit HARQ feedback information to the UE according to a success/failure in decoding data when data is detected from the FAS grant. The FAS grant is an uplink (UL) grant that is allocated after being mapped to a FAS Cell Radio Network Temporary Identifier (C-RNTI), and the FAS C-RNTI is a C-RNTI that is allocated to a UE to allow the UE to not transmit a padding MAC PDU using the FAS grant. 
     In accordance with another aspect of the present invention, there is provided a user equipment (UE) for a mobile communication system. The UE includes a control unit that determines whether there is data to transmit using an uplink (UL) grant while the UE is periodically allocated the UL grant, and when there is no data to transmit using the UL grant, determines to allow a transmission unit to not transmit a padding Medium Access Control (MAC) Protocol Data Unit (PDU) to an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) using the UL grant. 
     In accordance with another aspect of the present invention, there is provided an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) for a mobile communication system. The eNB includes a resource allocation unit and a control unit. The resource allocation unit allocates an uplink (UL) grant to a user equipment (UE) using Semi-Persistent Scheduling (SPS) under specific control. And a control unit controls the resource allocation unit to allocate the UL grant to the UE using SPS, and when no data is detected from the UL grant, determines that the UE transmits no data using the UL grant. 
     Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG. 1  illustrates a process of a UE in an LTE communication system using a first blind scheduling scheme according to an embodiment of the present invention; 
         FIG. 2  is a signaling diagram of a signal exchange process between an eNB and a UE in an LTE communication system using the first blind scheduling scheme according to an embodiment of the present invention; 
         FIG. 3  illustrates a process of the eNB  213  in  FIG. 2 ; 
         FIG. 4  illustrates a process of the UE  211  in  FIG. 2 ; 
         FIG. 5  is a signaling diagram of an example process of transmitting a FAS configuration IE to a UE by an eNB in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention; 
         FIG. 6  is a signaling diagram of an another example process of transmitting a FAS configuration IE to a UE by an eNB in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention; 
         FIG. 7  illustrates a process of a UE in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention; 
         FIG. 8  is a signaling diagram of a signal exchange process between an eNB and a UE in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention; 
         FIG. 9  illustrates a process of the eNB  813  in  FIG. 8 ; 
         FIG. 10  illustrates a process of the UE  811  in  FIG. 8 ; 
         FIG. 11  is a diagram of an internal structure of an eNB in an LTE communication system according to an embodiment of the present invention; and 
         FIG. 12  is a diagram of an internal structure of a UE in an LTE communication system according to an embodiment of the present invention. 
     
    
    
     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures. 
     DETAILED DESCRIPTION 
       FIGS. 1 through 12 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communication system. In the following description, specific details such as detailed configuration and components are merely provided to assist the overall understanding of embodiments of the present invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
     An embodiment of the present invention provides a blind scheduling apparatus and method in a mobile communication system. In the following description of embodiments of the present invention, the mobile communication system is assumed to be a Long Term Evolution (LTE) communication system. However, it will be apparent to those skilled in the art that the blind scheduling apparatus and method proposed in the embodiments of the present invention may be used other mobile communication systems as well as the LTE communication system. 
     The blind scheduling method proposed in embodiments of the present invention may be roughly classified into a first blind scheduling scheme, a second blind scheduling scheme, and a third blind scheduling scheme, each of which will be described below. 
     In the first blind scheduling scheme, if a User Equipment (UE) being periodically allocated a dedicated uplink (UL) resource has no data to transmit on a UL, the UE determines whether to transmit padding Medium Access Control (MAC) Protocol Data Units (PDUs) according to the type of the allocated dedicated UL resource. For convenience, a dedicated UL resource that is periodically allocated to a UE will be referred to herein as a ‘UL grant’. 
     In the second blind scheduling scheme, when having no data to transmit on a UL, a UE transmits no padding MAC PDU regardless of the type of a UL grant. 
     In the third blind scheduling scheme, if a UE being allocated a UL grant has no data to transmit on a UL, the UE determines whether to transmit padding MAC PDUs according to the type of a Cell Radio Network Temporary Identifier (C-RNTI). 
     A process of a UE in an LTE communication system using a first blind scheduling scheme according to an embodiment of the present invention will be described with reference to  FIG. 1 . 
       FIG. 1  illustrates a process of a UE in an LTE communication system using a first blind scheduling scheme according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the UE detects a type of a UL grant in block  111 , and determines in block  113  whether the detected type of the UL grant is an Explicit UL grant. The Explicit UL grant represents a UL grant that merely serves as resource allocation information received from an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) over a Physical Downlink Control Channel (PDCCH) without separate configuration, among UL grants which are allocated after being mapped to a C-RNTI. The Explicit UL grant may also be used to dynamically allocate transmission resources. 
     If the detected type of the UL grant is an Explicit UL grant, the UE determines in block  115  whether it has data to transmit using the Explicit UL grant. If the UE has no data to transmit using the Explicit UL grant, the UE ends its process. Specifically, in the conventional LTE communication system, even when having no data to transmit using a UL grant, a UE transmits padding MAC PDUs using the UL grant, thereby causing a waste of UE battery due to the transmission of padding MAC PDUs, a signaling overhead due to the exchange of padding MAC PDUs, and a processing load due to the decoding of padding MAC PDUs by an eNB. However, when using the first blind scheduling scheme, the UE transmits no padding MAC PDUs if it has no data to transmit using the Explicit UL grant, thereby preventing the above and other problems and disadvantages caused by the transmission of padding MAC PDUs. 
     However, if it is determined in block  115  that the UE has data to transmit using the Explicit UL grant, the UE transmits the data using the Explicit UL grant in block  117 . 
     If it is determined in block  113  that the detected type of the UL grant is not an Explicit UL grant but a Configured UL grant, the UE proceeds to block  119 . The Configured UL grant represents a UL grant that is allocated to a UE that has received a separate SPS configuration Information Element (IE) such as an SPS C-RNTI. Resource allocation information regarding the Configured UL grant is transmitted using a PDCCH, and once allocated, a transmission resource is valid until it is released or changed. 
     In block  119 , the UE determines if it has data to transmit using the Configured UL grant. If the UE has no data to transmit using the Configured UL grant, the UE transmits padding MAC PDUs using the Configured UL grant in block  121 , and then ends the process. 
     However, if it is determined in block  119  that the UE has data to transmit using the Configured UL grant, the UE transmits the data using the Configured UL grant in block  123 , and then ends the process. 
     In  FIG. 1 , having data to transmit using an Explicit UL grant and a Configured UL grant means that transmittable data is present in the data stored in the UE. The data stored in the UE may be classified into data that can be transmitted and data that should not be transmitted, at an arbitrary time corresponding to a predetermined condition, e.g., a retransmission window status and a transmission window status. 
     As described with reference to  FIG. 1 , when having no data to transmit on a UL, the UE determines whether to transmit padding MAC PDUs according to the type of a UL grant. If the type of the UL grant is an Explicit UL grant, the UE transmits no padding MAC PDUs when it has no data to transmit on a UL. A signal exchange process between an eNB and a UE performed in this situation will be described with reference to  FIG. 2 . 
       FIG. 2  illustrates a signal exchange process between an eNB and a UE in an LTE communication system using the first blind scheduling scheme according to an embodiment of the present invention. 
     Referring to  FIG. 2 , an eNB  213  sets a value of a New Data Indicator (NDI) for a Hybrid Automatic Retransmission Request (HARQ) process x to ‘0’, and allocates an Explicit UL grant for the HARQ process x to a UE  211  in an n-th frame in step  215 . Here, ‘x’ indicates a unique number of a HARQ process. In step  217 , the UE  211  performs no operation because it has no data to transmit on a UL in (n+4)-th frame. That is, because the type of a UL grant is an Explicit UL grant, the UE  211  does not need to transmit padding MAC PDUs when it has no data to transmit on a UL. 
     Because the eNB  213  has received no data from the UE  211  even though it allocated the Explicit UL grant in the n-th frame, the eNB  213  sets a value of the NDI to ‘1’ and allocates an Explicit UL grant for the HARQ process x to the UE  211  in an (n+8)-th frame in step  219 . When having data to transmit on a UL, the UE  211  transmits the data using the Explicit UL grant in an (n+12)-th frame in step  221 . 
     The eNB  213  decodes the data received from the UE  211  and transmits HARQ feedback information according to the success/failure in decoding. As for the HARQ feedback information, a HARQ ACK is transmitted when the decoding is successful, and a HARQ NACK is transmitted when the decoding is failed. Assuming in  FIG. 2  that the eNB  213  has failed to decode the data received from the UE  211 , the eNB  213  transmits a HARQ NACK to the UE  211  in an (n+16)-th frame in step  223 . As the UE  211  receives the HARQ NACK from the eNB  213 , the UE  211  retransmits the previously transmitted data to the eNB  213  in an (n+20)-th frame in step  225 . 
     An operation of the eNB  213  in  FIG. 2  will now be described in detail with reference to  FIG. 3 . 
       FIG. 3  illustrates a process of the eNB  213  in  FIG. 2 . 
     Referring to  FIG. 3 , the eNB  213  determines in block  311  whether data is detected from an allocated Explicit UL grant. If no data is detected from the Explicit UL grant, the eNB  213  proceeds to block  313 . Detecting no data from an Explicit UL grant indicates that the UE  211  has not transmitted data using the Explicit UL grant or the eNB  213  has failed to receive data even though the UE  211  has transmitted the data using the Explicit UL grant. Therefore, considering the situation in which the eNB  213  has failed to receive data even though the UE  211  has transmitted the data using the Explicit UL grant, the eNB  213  sets a value of an NDI to ‘1’ and allocates an Explicit UL grant to the UE  211  in block  313 . That is, the eNB  213  may normally operate, even though the UE  211  transmits no padding MAC PDUs as it has no data to transmit on a UL. 
     However, if it is determined in block  311  that data is detected from the Explicit UL grant, the eNB  213  decodes the detected data in block  315 , and determines in block  317  whether it has succeeded in decoding the detected data. If the eNB  213  has succeeded in decoding the detected data, the eNB  213  transmits an HARQ ACK to the UE  211  in block  319 . 
     However, if it is determined in block  317  that the eNB  213  has failed in decoding the detected data, the eNB  213  transmits an HARQ NACK to the UE  211  in block  321 . 
     The operation of the eNB  213 , described above with reference to  FIG. 3 , may be performed more effectively when its energy detection reliability is relatively high. 
     Next, an operation of the UE  211  in  FIG. 2  will be described in detail with reference to  FIG. 4 . 
       FIG. 4  illustrates a process of the UE  211  in  FIG. 2 . 
     Referring to  FIG. 4 , the UE  211  determines in block  411  whether HARQ feedback information is received from the eNB  213 . If no HARQ feedback information is received from the eNB  213 , the UE  211  determines in block  413  whether it is allocated an Explicit UL grant from the eNB  213 . If the UE  211  is allocated an Explicit UL grant, the UE  211  determines in block  415  whether there is previously transmitted data. If there is previously transmitted data, the UE  211  terminates a HARQ process being performed on the previously transmitted data in block  417 . In block  419 , the UE  211  determines if it has data to transmit using the Explicit UL grant. If the UE  211  has data to transmit using the Explicit UL grant, the UE  211  transmits the data using the Explicit UL grant in block  421 . If it is determined in block  415  that there is no previously transmitted data, the UE  211  proceeds to block  419 . 
     If it is determined in block  411  that HARQ feedback information has been received from the eNB  213 , the UE  211  determines in block  423  whether there is previously transmitted data. If there is previously transmitted data, the UE  211  determines in block  425  whether the received HARQ feedback information is a HARQ ACK. If the received HARQ feedback information is not a HARQ ACK but a HARQ NACK, the UE  211  initializes a retransmission process of the HARQ process being performed on the previously transmitted data in block  427 . However, if it is determined in block  425  that the received HARQ feedback information is a HARQ ACK, the UE  211  proceeds to block  417 . 
     As described with reference to  FIGS. 1 to 4 , when allocated an Explicit UL grant, a UE is allowed not to transmit padding MAC PDUs if it has no data to transmit on a UL. Even though the UE transmits no padding MAC PDUs, the HARQ process between the UE and the eNB may be normally performed. 
     Next, operations of a UE and an eNB in an LTE communication system using the second blind scheduling scheme according to an embodiment of the present invention will be described. 
     When the conventional LTE communication system uses SPS, a scheme of terminating the use of SPS may be roughly classified into two schemes: an implicit scheme and an explicit scheme. 
     In the implicit scheme, if a UE transmits a padding MAC PDU using a Configured UL grant a predetermined number of times or more, the UE itself terminates the use of SPS. The information about the predetermined number of times is included in an SPS configuration IE, and a format of the conventional SPS configuration IE is as shown Table 1 below. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 SPS-ConfigUL ::= 
                 CHOICE { 
               
               
                  release 
                  NULL, 
               
               
                  setup 
                  SEQUENCE { 
               
            
           
           
               
               
            
               
                   semiPersistSchedIntervalUL 
                 ENUMERATED { 
               
               
                   
                 sf10, sf20, sf32, sf40, sf64, sf80, 
               
               
                   
                 sf128, sf160, sf320, sf640, spare6, 
               
               
                   
                 spare5, spare4, spare3, spare2, 
               
               
                   
                 spare1}, 
               
               
                   implicitReleaseAfter 
                 ENUMERATED {e2, e3, e4, e8}, 
               
            
           
           
               
            
               
                   ... 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In Table 1, a semiPersistSchedIntervalUL field represents an interval for which a Configured UL grant is allocated, and for example, if a value of the semiPersistSchedintervalUL field is ‘sfL’, it indicates that a Configured UL grant is allocated every L subframes. Among values of the semiPersistSchedIntervalUL field, ‘spareM’ represents a spare value of the semiPersistSchedIntervalUL field, which is to be used in the future. Herein, a value of the semiPersistSchedIntervalUL field that the eNB actually transmits in an SPS configuration IE is any one of the ‘sfL’ values. 
     In Table 1, an implicitReleaseAfter field represents the number of transmissions of a padding MAC PDU which is used to terminate the use of SPS using the implicit scheme. For example, ‘eN’ indicates that the UE may terminate the use of SPS after transmitting a padding MAC PDU N times. Herein, a value of the implicitReleaseAfter field that an eNB actually transmits in an SPS configuration IE is any one of the ‘eN’ values. 
     When using the implicit scheme, an eNB terminates the allocation of a Configured UL grant to a UE if the UE transmits a padding MC PDU as many times as the value of the implicitReleaseAfter field. That is, if the UE transmits a padding MAC PDU as many times as the value of the implicitReleaseAfter field, both the UE and the eNB no longer use SPS, so they can no longer use the Configured UL grant. 
     In the second blind scheduling scheme proposed by the present invention, a UE transmits no padding MAC PDUs using a Configured UL grant if it has no data to transmit using the Configured UL grant. Conventionally, as described with reference to Table 1, when using SPS, if a UE has no data to transmit using a Configured UL grant a predetermined number of times or more, i.e., the UE transmits a padding MAC PDU a predetermined number of times or more, the use of SPS is terminated. However, in the second blind scheduling scheme according to an embodiment of the present invention, a modified SPS configuration IE format is proposed such that the use of SPS may not be terminated even if a UE has no data to transmit using a Configured UL grant, i.e., if the UE does not transmit data using the Configured UL grant. The modified SPS configuration IE format is as shown in Table 2 below. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 SPS-ConfigUL ::= 
                 CHOICE { 
               
               
                  release 
                  NULL, 
               
               
                  setup 
                  SEQUENCE { 
               
            
           
           
               
               
            
               
                   semiPersistSchedIntervalUL 
                 ENUMERATED { 
               
               
                   
                 sf10, sf20, sf32, sf40, sf64, sf80, 
               
               
                   
                 sf128, sf160, sf320, sf640, spare6, 
               
               
                   
                 spare5, spare4, spare3, spare2, 
               
               
                   
                 spare1}, 
               
               
                   implicitReleaseAfter 
                 ENUMERATED {e2, e3, e4, e8, 
               
               
                   
                 none}, 
               
            
           
           
               
            
               
                   ... 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     As illustrated in Table 2, while a semiPersistSchedIntervalUL field is the same as the semiPersistSchedlntervalUL field in the conventional SPS configuration IE, an implicitReleaseAfter field is modified to represent ‘none’, which indicates that the use of SPS is not terminated even when a UE does not transmit data using a Configured UL grant. Herein, a value of the implicitReleaseAfter field that an eNB transmits in the modified SPS configuration IE is ‘none’. 
     When using the modified SPS configuration IE, if a UE has no data to transmit on a UL, the use of SPS is not terminated even though the UE does not transmit padding MAC PDUs using a Configured UL grant. 
     In contrast, if a UE transmits as many padding MAC PDUs as a value of the implicitReleaseAfter field using a Configured UL grant, an implicit release operation of an SPS may be granted to automatically release a Configured UL grant if the UE does not transmit data during a Configured UL grant occasion corresponding to a value indicated by the implicitReleaseAfter field, instead of automatically releasing the Configured UL grant. In this situation, the conventional SPS configuration IE format may be used. The Configured UL grant occasion will be described in detail below. 
     An SPS grant repeatedly occurs at regular intervals beginning from the time a Configured UL grant is allocated to a UE over a PDCCH. For example, once a Configured UL grant is allocated to a UE at a time ‘x’, the Configured UL grant repeatedly occurs in x+interval, x+2*interval, x+3*interval, and so on, and the UE performs UL transmission using the Configured UL grants. The time at which the Configured UL grant occurs is called a Configured UL grant occasion, and the UE automatically releases the Configured UL grant if the UE does not transmit data using the Configured UL grant as it has no data to transmit, during a Configured UL grant occasion corresponding to the value of the implicitReleaseAfter field. That is, the UE automatically releases a Configured UL grant if the UE does not continuously use the Configured UL grant as many times as the value of the implicitReleaseAfter field. The reason for defining the scheme of automatically releasing a Configured UL grant is to minimize the malfunction problems which may occur when a UE mistakes an SPS resource allocated to another UE for an SPS resource allocated to the UE itself because of its failure to detect residual errors. 
     Next, operations of a UE and an eNB in an LTE communication system using the third blind scheduling scheme according to an embodiment of the present invention will be described. 
     In the third blind scheduling scheme proposed by the present invention, anew C-RNTI is proposed to not allow transmitting padding MAC PDUs using a UL grant mapped to a pertinent C-RNTI, and the newly proposed C-RNTI will be referred to as Fast Access Scheduling (FAS) C-RNTI. That is, a UE may not transmit padding MAC PDUs using a UL grant mapped to the FAS C-RNTI. An eNB may allocate a FAS C-RNTI to a UE in advance in a process before it allocates a UL grant, and a process in which the FAS C-RNTI is allocated may be, for example, a Radio Resource Control (RRC) Connection Setup process. It will be apparent to those skilled in the art that the eNB may allocate a FAS C-RNTI to a UE in any process other than the RRC Connection Setup process as long as it is a process before the eNB allocates a UL grant. For convenience, a scheduling scheme using the FAS C-RNTI will be referred to herein as a ‘FAS scheme’. 
     The eNB may allocate a FAS C-RNTI to UEs when its load is relatively low. In addition, when there are UEs requiring periodic fast access, the eNB may allocate a FAS C-RNTI to the UEs. 
     The eNB determines a UL grant mapped to a FAS C-RNTI taking into account the Modulation and Coding Scheme (MCS) level, the Transport Block (TB) size, the number of Radio Bearers (RBs), and such. For convenience, a UL grant mapped to a FAS C-RNTI will be referred to herein as a ‘FAS grant’. 
     The eNB may inform a UE of an allocation cycle of a FAS grant using a FAS configuration IE and may transmit resource allocation information for a FAS grant to a UE using a PDCCH. On the other hand, the eNB may transmit resource allocation information for a FAS grant to a UE using a PDCCH at any time without using the FAS configuration IE. 
     The FAS configuration IE is as shown in Table 3. 
     
       
         
           
               
               
             
               
                 TABLE 3 
               
               
                   
               
             
            
               
                 FAS-ConfigUL ::= 
                 CHOICE { 
               
               
                  release 
                  NULL, 
               
               
                  setup 
                  SEQUENCE { 
               
            
           
           
               
               
            
               
                   FastAccessSchedIntervalUL 
                 ENUMERATED { 
               
               
                   
                 sf1, sf2, sf5, sf10, sf20, sf32, 
               
               
                   
                 sf40, sf64, sf80, sf128, sf160, 
               
               
                   
                 sf320, sf640, spare3, spare2, 
               
               
                   
                 spare1}, 
               
            
           
           
               
            
               
                   ... 
               
               
                  } 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     In Table 3, a FastAccessSchedIntervalUL field represents an interval during which a FAS grant is allocated. For example, if a value of the FastAccessSchedIntervalUL field is ‘sfL’, it indicates that a FAS grant is allocated every L subframes. Among values of the FastAccessSchedlntervalUL field, ‘spareM’ represents a spare value of the FastAccessSchedIntervalUL field, which is to be used in the future. Herein, a value of the FastAccessSchedIntervalUL field that the eNB transmits in a FAS configuration IE is any one of the ‘sfL’ values. 
     A process of transmitting a FAS configuration IE to a UE by an eNB will now be described with reference to  FIGS. 5 and 6 . 
       FIG. 5  illustrates an example process of transmitting a FAS configuration IE to a UE by an eNB in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention. 
     Referring to  FIG. 5 , a UE  511  transmits an RRC Connection Request message to an eNB  513  in step  515 . Upon receiving the RRC Connection Request message, the eNB  513  transmits an RRC Connection Setup message to the UE  511  in step  517 . The RRC Connection Setup message includes a FAS C-RNTI allocated to the UE  511 , and a FAS configuration IE (represented by ‘FAS-Config’ in  FIG. 5 ). 
     Upon receiving the RRC Connection Setup message, the UE  511  transmits a RRC Connection Setup Complete message to the eNB  513  in step  519 . When the RRC Connection Setup process between the UE  511  and the eNB  513  is completed, the eNB  513  allocates a FAS grant to the UE  511  and transmits resource allocation information for the FAS grant to the UE  511  through a PDCCH (FAS grant on DPCCH) in step  521 . 
       FIG. 6  illustrates another example process of transmitting a FAS configuration IE to a UE by an eNB in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention. 
     Referring to  FIG. 6 , an eNB  613  transmits an RRC Connection Reconfiguration message to a UE  611  in step  615 . The RRC Connection Reconfiguration message includes a FAS configuration IE (represented by ‘FAS-Config’ in  FIG. 6 ). 
     Upon receiving the RRC Connection Reconfiguration message, the UE  611  transmits an RRC Connection Reconfiguration Complete message to the eNB  613  in step  617 . When the RRC Connection Reconfiguration process between the UE  611  and the eNB  613  is completed, the eNB  613  allocates a FAS grant to the UE  611 , and transmits resource allocation information for the FAS grant to the UE  611  through a PDCCH (FAS grant on DPCCH) in step  619 . 
     A process of a UE in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention will now be described with reference to  FIG. 7 . 
       FIG. 7  illustrates a process of a UE in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention. 
     Referring to  FIG. 7 , the UE detects a type of a UL grant in block  711 , and determines in block  713  whether the detected type of the UL grant is a FAS grant. If the detected type of the UL grant is not a FAS grant, the UE performs an operation corresponding to the detected type of the UL grant in block  715 . 
     However, if it is determined in block  713  that the detected type of the UL grant is a FAS grant, the UE determines in block  717  whether it has data to transmit using the FAS grant. If the UE has no data to transmit using the FAS grant, the UE no ends the process. That is, as described above, the UE may not transmit padding MAC PDUs using the FAS grant. 
     However, if it is determined in block  717  that the UE has data to transmit using the FAS grant, the UE transmits the data using the FAS grant in block  719 . 
     As described with reference to  FIG. 7 , if the type of the UL grant is a FAS grant, the UE transmits no padding MAC PDUs when it has no data to transmit on a UL. A signal exchange process between an eNB and a UE performed in this situation will be described with reference to  FIG. 8 . 
       FIG. 8  illustrates a signal exchange process between an eNB and a UE in an LTE communication system using a third blind scheduling scheme according to an embodiment of the present invention. 
     The signal exchange process between an eNB and a UE illustrated in  FIG. 8  is substantially the same as that described with reference to  FIG. 2  except that the UL grant replaces a FAS grant, so a detailed description thereof will be omitted. 
     A process of the eNB  813  in  FIG. 8  will be described in detail with reference to  FIG. 9 . 
       FIG. 9  illustrates a process of the eNB  813  in  FIG. 8 . 
     The process of the eNB  813  illustrated in  FIG. 9  is substantially the same as that described with reference to  FIG. 3  except that the UL grant replaces a FAS grant, so a detailed description thereof will be omitted herein. Likewise, the process of the eNB  813 , illustrated in  FIG. 9 , may be performed more effectively when its energy detection reliability is relatively high. 
     Next, a process of the UE  811  in  FIG. 8  will be described in detail with reference to  FIG. 10 . 
       FIG. 10  illustrates a process of the UE  811  in  FIG. 8 . 
     The process of the UE  811  illustrated in  FIG. 10  is substantially the same as that described with reference to  FIG. 4  except that the UL grant replaces a FAS grant, so a detailed description thereof will be omitted herein. 
     As described with reference to  FIGS. 7 to 10 , when allocated a FAS grant, the UE is not allowed to transmit padding MAC PDUs even though it has no data to transmit on a UL. Even though the UE transmits no padding MAC PDUs, the HARQ process between the UE and the eNB may be performed normally. 
     Next, an internal structure of an eNB in an LTE communication system according to an embodiment of the present invention will be described with reference to  FIG. 11 . 
       FIG. 11  illustrates an internal structure of an eNB in an LTE communication system according to an embodiment of the present invention. 
     Referring to  FIG. 11 , the eNB includes a control unit  1111 , a resource allocation unit  1113 , a transmission unit  1115 , and a reception unit  1117 . 
     The control unit  1111  controls the overall operation of the eNB to perform operations corresponding to the first to third blind scheduling schemes proposed by the present invention. These operations corresponding to the first to third blind scheduling schemes and performed by the eNB have been described above, so detailed descriptions thereof will be omitted herein. 
     The resource allocation unit  1113  allocates resources or UL grants under control of the control unit  1111 , and a type of a UL grant allocated by the resource allocation unit  1113  is determined according to the first to third blind scheduling schemes, as described above. 
     The transmission unit  1115  transmits resource allocation information for a UL grant allocated by the resource allocation unit  1113  under control of the control unit  1111 . The transmission unit  1115 , under control of the control unit  1111 , transmits HARQ feedback information for the data received through the reception unit  1117 , and transmits a control message such as an RRC Connection Setup message. The resource allocation information and control messages transmitted by the transmission unit  1115  have been described together with the first to third blind scheduling schemes, so detailed descriptions thereof will be omitted herein. 
     The reception unit  1117 , under control of the control unit  1111 , receives data from a UL grant and decodes the received data. The reception unit  1117  receives control messages such as an RRC Connection Request message, and the control messages received through the reception unit  1117  have been described together with the first to third blind scheduling schemes, so detailed descriptions thereof will be omitted herein. 
     Next, an internal structure of a UE in an LTE communication system according to an embodiment of the present invention will be described with reference to  FIG. 12 . 
       FIG. 12  illustrates an internal structure of a UE in an LTE communication system according to an embodiment of the present invention. 
     Referring to  FIG. 12 , the UE includes a control unit  1211 , a transmission unit  1213 , and a reception unit  1215 . 
     The control unit  1211  controls the overall operation of the UE to perform operations corresponding to the first to third blind scheduling schemes proposed by the present invention. These operations corresponding to the first to third blind scheduling schemes and performed by the UE have been described above, so detailed descriptions thereof will be omitted herein. 
     The transmission unit  1213  transmits data using a UL grant allocated from an eNB under control of the control unit  1211 . The transmission unit  1213  transmits control messages such as an RRC Connection Request message under control of the control unit  1211 . The control messages transmitted by the transmission unit  1213  have been described together with the first to third blind scheduling schemes, so detailed descriptions thereof will be omitted herein. 
     The reception unit  1215  receives HARQ feedback information and control messages such as RRC Connection Setup messages from an eNB, under control of the control unit  1211 . The control messages received through the reception unit  1215  have been described together with the first to third blind scheduling schemes, so detailed descriptions thereof will be omitted herein. 
     As is apparent from the forgoing description, the present invention enables blind scheduling that prevents unnecessary transmission of padding MAC PDUs, thereby minimizing a waste of the UE battery due to the transmission of padding MAC PDUs, minimizing a signaling overhead caused by the exchange of padding MAC PDUs, and minimizing a processing load due to the decoding of padding MAC PDUs by an eNB. 
     Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.