Abstract:
A cell setting apparatus is provided for scheduling a packet data service in a mobile communication system supporting the packet data service. A signaling receiver receives information on a cell to be added to an active set and information on a change in a best cell, from a terminal. A signaling transmitter transmits configuration information for the packet data service and the packet data to a source base station or a target base station. A memory stores information on the active set. A data path decision unit allows the terminal to update the active set and to set configuration information newly set for the packet data service, transmits the information on the cell to be added to the active set to the target base station in response to the information on the cell to be added to the active set, and allows the target base station to perform the packet data service scheduling for the terminal in response to the information on the change in the best cell.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application entitled “Fast Cell Selection Method and Apparatus for High Speed Downlink Packet Access System” filed in the Korean Intellectual Property Office on Oct. 5, 2005 and assigned Serial No. 2005-93616, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method and apparatus for allowing a target cell to most efficiently perform scheduling on packet data service when a serving cell for the packet data service changes from a source cell to a target cell in a mobile communication system supporting packet data service. In addition, the present invention also relates to a fast cell selection method and apparatus for High Speed Downlink Packet Access (HSDPA) used in a Wideband Code Division Multiple Access (WCDMA) system. More particularly, the present invention relates to a method and apparatus for allowing a target cell to rapidly perform HSDPA scheduling when an HSDPA serving cell changes from a source cell to a target cell.  
         [0004]     2. Description of the Related Art  
         [0005]     A mobile communication system has been developed from an early communication system that provides voice service into a high-speed, high-quality wireless data packet communication system that provides data service and multimedia service. The 3 rd  Generation (3G) mobile communication system, which is currently divided into 3 rd  Generation Partnership Project (3GPP) and 3 rd  Generation Partnership Project 2 (3GPP2), is now under standardization for high-speed, high-quality wireless data packet service. For example, standardization for HSDPA is being conducted in 3GPP, and under standardization for 1xEV-DV is being carried out in 3GPP2. Such standardization can be considered as an attempt to find a solution for high-speed, high-quality wireless data packet transmission service at 2 Mbps or higher in the 3G mobile communication system, and the 4 th  Generation (4G) mobile communication system aims at providing the high-speed, high-quality multimedia service.  
         [0006]     Generally, the HSDPA scheme refers to a scheme for transmitting control information and packet data through a High Speed Dedicated Shared Channel (HS-DSCH), which is a downlink channel for supporting high-speed packet data transmission, in an asynchronous Universal Mobile Terrestrial System (UMTS) mobile communication system.  
         [0007]     HSDPA needs an advanced technology which is capable of increasing adaptability to the channel variation in addition to the conventional technology provided in the existing mobile communication system.  
         [0008]     Therefore, Adaptive Modulation and Coding (AMC) and Hybrid Automatic Re-transmission Request (HARQ) for supporting high-speed packet transmission have been proposed in HSDPA.  
         [0009]      FIG. 1  is a diagram illustrating a process of performing conventional HSDPA serving cell change which uses a Radio Network System Application Part (RNSAP) protocol and a Node B Application Part (NBAP) protocol of WCDMA.  
         [0010]     In step  110 , a User Equipment (UE)  101  is receiving HSDPA data from a source Node B  102 . In step  115 , the UE  101  notifies a Serving Radio Network Controller (SRNC)  104  of the fact that a new cell should be added to an active set as a result of monitoring a pilot channel and the like (such an event is called “EVENT 1A” in WCDMA), using an RRC MEASUREMENT REPORT procedure. If the active set is changed, the SRNC  104  sends to the UE  101  a command to change the active set in step  120 . Upon receipt of the command, the UE  101  updates the active set and adds the resulting radio link (RL) in step  125 , and then proceeds to step  130  where it notifies the SRNC  104  that active set update is completed.  
         [0011]     In step  135 , the UE  101  notifies the SRNC  104  of the fact that the best cell among the cells included in the active set is changed as a result of monitoring a pilot channel and the like (such an event is called “EVENT 1D” in WCDMA), using an RRC MEASUREMENT REPORT procedure.  
         [0012]     Upon recognizing the change in the best cell, the SRNC  104  delivers the information required by a Node B to schedule a UE, such as buffer information, to a target Node B  103  and receives information on the HSDPA resource allocated from the target Node B  103  in step  140 , in order to allow HSDPA service to be performed in a new best cell. Step  145  corresponds to a step of instructing the old cell to perform no more HSDPA scheduling. Step  140  and step  145  both use a Synchronous Radio Link Reconfiguration procedure.  
         [0013]     In step  150 , the SRNC  104  sends to the UE  101  a RADIO BEARER (RB) RECONFIGURATION message with HSDPA configuration information in the new cell. Upon receipt of the RADIO BEARER RECONFIGURATION message from the SRNC  104 , the UE  101  delivers an RB RECONFIGURATION COMPLETE message in response thereto to notify the SRNC  104  of correct receipt of the new HSDPA configuration information. Upon receipt of the RB RECONFIGURATION message, the UE  101  monitors High Speed Shared Control Channels (HS-SCCHs) transmitted from the new cell beginning at the arrival of a Connection Frame Number (CFN) included in the message in step  155 , to determine whether there is any HSDPA data transmitted thereto.  
         [0014]     Because the SRNC  140  used the Synchronous Radio Link Reconfiguration procedure in step  140  and step  145 , it sends RL RECONFIGURATION COMMIT messages to the source Node B  102  and the target Node B  103  in step  160 , so as to stop HSDPA scheduling in the source cell  102 , or the old serving cell, and to start HSDPA scheduling in the target cell  103 , or the new serving cell. From now on, the SRNC  140  changes its HSDPA data path from the source Node B  102  to the target Node B  103 . Thereafter, the target Node B  103  starts scheduling on the UE  101  in step  165  and step  170 .  
         [0015]     It can be noted from the foregoing process that there is a considerable time difference between the time where the best cell was changed in step  135  and the time where HSDPA data is actually transmitted from the new best cell  103  in step  165 . This problem may be relived to some extent with the use of a method proposed in the present invention in which HSDPA configuration is previously prepared in the target Node B. In addition, it is possible to facilitate fast HSDPA serving cell change by improving the Synchronous Radio Link Reconfiguration procedure performed in the foregoing process.  
         [0016]     In the foregoing conventional Synchronous Radio Link Reconfiguration procedure, as the Synchronous Radio Link Reconfiguration procedure commonly defined in RNSAP and NBAP, an SRNC (or Controlling RNC (CRNC)) transmits new radio link configuration information to a Drift RNC (DRNC) (or Node B) along with an RL RECONFIGURATION PREPARE message. Upon receipt of the RL RECONFIGURATION PREPARE message, the DRNC (or Node B) transmits an RL RECONFIGURATION READY message in response thereto to the SRNC (or CRNC) and at the same time, stores the radio link configuration information. Thereafter, upon receipt of the RL RECONFIGURATION COMMIT message for requesting commitment of radio link configuration, the DRNC commits the radio link configuration according to a connection frame number (CFN) included in the received message if the current CFN is equal to the CFN included in the received message.  
         [0017]     Currently, because the RL RECONFIGURATION COMMIT message should necessarily include the CFN as shown in Table  1  below, the SRNC delivers this message to the Node B after the best cell is changed, and the new cell performs HSDPA scheduling after a lapse of a predetermined time taking the CFN into account.  
                                                                 TABLE 1                                   IE Type and   Semantics       Assigned       IE/Group Name   Presence   Range   Reference   Description   Criticality   Criticality                                Message Type   M           YES   ignore       Transaction ID   M           —       CFN   M           YES   ignore       Active Pattern   0       FDD   YES   ignore       Sequence           only       Information                  
 
       SUMMARY OF THE INVENTION  
       [0018]     Accordingly, the present invention has been made to address at least the above problems and/or disadvantages, and an object of the present invention is to provide a method and apparatus for allowing a best cell newly selected using a fast cell selection method to efficiently transmit packet data in a mobile communication system supporting packet data service.  
         [0019]     According to one aspect of the present invention, a cell setting method for scheduling a packet data service in a mobile communication system supporting the packet data service is provided. The method includes receiving information on a cell to be added to an active set from a terminal. In response to the information on the cell to be added to the active set, configuration information is transmitted for the packet data service to a target base station and the target base station is allowed to establish a radio link. The terminal is allowed to update the active set, and to set configuration information for the packet data service. Information on a change in a best cell from the terminal is received. In response to the information on the change in the best cell, the target base station is allowed to perform packet data service scheduling for the terminal, and a source base station is allowed to stop the packet data service scheduling for the terminal.  
         [0020]     According to another aspect of the present invention, a method for receiving a packet data service by a terminal in a mobile communication system supporting the packet data service is provided. The method includes transmitting information on a cell to be added to an active set to a serving RNC. The active set is updated according to control of the serving RNC, and configuration information for the packet data service is re-set. Information on a change in a best cell to the serving RNC is transmitted. Scheduling information for the packet data service from both a source base station and a target base station is monitored essentially simultaneously. The packet data service from the target base station is received, if the target base station performs scheduling on the packet data service according to control of the serving RNC.  
         [0021]     According to further another aspect of the present invention, a cell setting apparatus for scheduling a packet data service in a mobile communication system supporting the packet data service is provided. The apparatus includes a signaling receiver for receiving information on a cell to be added to an active set and information on a change in a best cell, from a terminal. A signaling transmitter transmits configuration information for the packet data service and the packet data to a source base station or a target base station. A memory stores information on the active set. A data path decision unit allows the terminal to update the active set and to set configuration information newly set for the packet data service, transmits the information on the cell to be added to the active set to the target base station in response to the information on the cell to be added to the active set, and allows the target base station to perform the packet data service scheduling for the terminal in response to the information on the change in the best cell.  
         [0022]     According to yet another aspect of the present invention, an apparatus for receiving a packet data service in a mobile communication system supporting the packet data service is provided. The apparatus includes a signaling receiver for generating information on a cell to be added to an active set and information on a change in a best cell based on strengths of signals transmitted from a plurality of cells, simultaneously monitoring scheduling information for the packet data service from both a source base station and a target base station, and receiving the packet data service from the target base station, if the target base station performs scheduling on the packet data service according to control of a serving RNC. A signaling transmitter transmits the information on the cell to be added to the active set and the information on the change in the best cell, to the serving RNC. A memory updates the active set according to control of the serving RNC, and stores newly set configuration information for the packet data service.  
         [0023]     Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:  
         [0025]      FIG. 1  is a diagram illustrating the conventional High Speed Downlink Packet Access (HSDPA) serving cell change procedure;  
         [0026]      FIG. 2  is a signaling diagram according to a first exemplary embodiment of the present invention;  
         [0027]      FIG. 3  is a diagram illustrating a brief structure of a User Equipment (UE) according to an exemplary embodiment of the present invention;  
         [0028]      FIG. 4  is a diagram illustrating a structure of a Node B according to an exemplary embodiment of the present invention;  
         [0029]      FIG. 5  is a diagram illustrating a structure of an Serving Radio Network Controller (SRNC) according to an exemplary embodiment of the present invention;  
         [0030]      FIG. 6  is a signaling diagram according to a second exemplary embodiment of the present invention;  
         [0031]      FIG. 7  is a signaling diagram illustrating according to a third exemplary embodiment of the present invention;  
         [0032]      FIG. 8  is a signaling diagram according to a fourth exemplary embodiment of the present invention;  
         [0033]      FIG. 9  is a signaling diagram according to a fifth exemplary embodiment of the present invention; and  
         [0034]      FIG. 10  is a signaling diagram according to a sixth exemplary embodiment of the present invention. 
     
    
       [0035]     Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0036]     The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention and are merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
         [0037]     The present invention is based on the system of transmitting packet data, such as evolution Dara&amp;Voice(EV-DV), Long Term Evolotion(LTE) Wideband Code Division Multiple Access (WCDMA) High Speed Downlink Packet Access (HSDPA).An exemplary embodiment of the present invention will be described herein with reference to a WCDMA HSDPA. In the annexed drawings and the following description, a Drift RNC (DRNC) is not separately specified in the situation where a Controlling RNC (CRNC) and a Serving Radio Network Controller (SRNC) of WCDMA are different. However, it may be noted that an RNSAP message transmitted from the SRNC to the DRNC is substantially equal to the Node B Application Part (NBAP) message transmitted from the SRNC to a Node B, specified in the drawings and the following description. It may also be noted that the proposed message format is shown herein in the form of the table used in 3 rd  Generation Partnership Project (3GPP).  
         [0038]     An exemplary implementation of a method for allowing a newly selected best cell to efficiently transmit packet data, if an SRNC previously configures HSDPA information in all cells belonging to an active set using a Fast Cell Select (FCS) scheme and then provides this information to a Node B managing the best cell in case of the change in the best cell, then the Node B performs HSDPA scheduling on the new best cell from now on.  
         [0039]     The FCS scheme is a method for rapidly selecting the cell with a good channel state among a plurality of cells, when a UE using HSDPA is located in a cell overlapping area, such as soft handover region. For example, if the UE using HSDPA enters the cell overlapping area between the old Node B and the new Node B, the UE establishes radio links to a plurality of cells (or Node Bs). Herein, a set of the cells whose radio links are established to the UE is called an active set.  
         [0040]     The UE receives packet data for HSDPA only from the cell maintaining the best channel state among the cells included in the active set, thereby reducing the overall interference. Herein, the cell maintaining the best channel state among the cells included in the active set is called a best cell. To this end, the UE periodically detects channel states of the cells belonging to the active set, to monitor whether there is any cell having a channel state better than that of current best cell.  
         [0041]     If any cell having the better channel state exists, the UE transmits a best cell indicator and the like to the cells belonging to the active set. The best cell indicator is an indicator used for requesting a change in cell from the current best cell to the newly detected cell having the better channel state, and includes an identifier of the cell selected as the best cell. Then the cells in the active set receive the best cell indicator, and determine the cell identifier included in the best cell indicator. In this way, each of the cells in the active set determines whether the received best cell indicator is a best cell indicator mapped to the cell itself. As a result of the determination, the corresponding cell selected as the best cell transmits packet data to the UE using an HS-DSCH.  
         [0042]     The operational principle of exemplary embodiments of the present invention will be described in detail hereinbelow.  
       First Exemplary Embodiment  
       [0043]     A first exemplary embodiment of the present invention provides a method in which after an SRNC sends HSDPA-related radio link configuration information of a target cell to a Node B using an Asynchronous Radio Link Reconfiguration procedure, the Node B starts HSDPA scheduling beginning at the receipt of a new message for requesting the start of HSDPA scheduling from the SRNC. The first exemplary embodiment of the present invention uses the existing Synchronous Radio Link Reconfiguration procedure as a method for stopping HSDPA scheduling of a source cell.  
         [0044]      FIG. 2  is a signaling diagram according to a first exemplary embodiment of the present invention.  
         [0045]     Referring to  FIG. 2 , a process in steps  210  to  245 , which is a first aspect according to the first exemplary embodiment of the present invention, is a process of previously configuring HSDPA configuration information in a target Node B before an HSDPA serving cell is actually changed, and then providing the information to a UE.  
         [0046]     Specifically, in step  210 , a UE  201  is receiving HSDPA data from a source Node B  202 . In step  215 , the UE  201  informs an SRNC  204  of the fact that a new cell should be added to an active set as a result of monitoring a pilot channel and the like (such an event is called “EVENT 1A” in WCDMA), using an RRC MEASUREMENT REPORT procedure. In step  220 , when a new cell is added to the active set, an Asynchronous Radio Link Reconfiguration procedure is used as a procedure for providing HSDPA configuration information of the new cell to a target Node B  203 .  
         [0047]     According to an exemplary implementation, the SRNC  204  transmits HSDPA configuration information to the target Node B  203  along with an RL RECONFIGURATION REQUEST message, and upon receipt of this message, the target Node B  203  sends an RL RECONFIGURATION RESPONSE message to the SRNC  204  in response thereto. Because the target Node B  203  is not yet receiving HSDPA data from the SRNC  204 , it is not performing HSDPA scheduling on the UE  201 . Step  225  corresponds to a process of instructing the source Node B  202 , or the old HSDPA serving Node B, to prepare for deletion of HSDPA configuration information in case that an HSDPA serving cell will be changed later. The Synchronous Radio Link Reconfiguration procedure is used in this process.  
         [0048]     In step  230 , the SRNC  204  sends to the UE  201  a command for requesting a change in the active set. Upon receipt of this command, the UE  201  updates the active set and adds the resulting radio link in step  240 . In step  235 , the SRNC  204  provides HSDPA configuration information in the new cell to the UE  201 . Upon receipt of a RADIO BEARER RECONFIGURATION message from the SRNC  204 , the UE  201  sends an RB RECONFIGURATION COMPLETE message in response thereto in step  245 , to notify the SRNC  204  of correct receipt of the new HSDPA configuration information. Here, the UE  201  can provide the SRNC  204  with a state of the current radio link control (RLC) as well.  
         [0049]     A process in steps  250  to  280 , which is a second aspect according to the first exemplary embodiment of the present invention, is a process in which upon recognizing the change in the best cell, the SRNC  204  notifies this fact to the target Node B  203  and the source Node B  202 , thereby to change the HSDPA serving cell. In this process, the target Node B  203  schedules the actual data to the UE  201  through an HSDPA channel using the HSDPA configuration information previously set in the first aspect.  
         [0050]     In step  250 , the UE  201  notifies the SRNC  204  of the fact that the best cell among the cells included in the active set is changed as a result of monitoring a pilot channel and the like (such an event is called “EVENT 1D” in WCDMA), using an RRC MEASUREMENT REPORT procedure. Thereafter, in step  255 , the UE  201  starts monitoring High Speed Shared Control Channels (HS-SCCHs) transmitted from the source cell  202  and the target cell  203 . In a process of steps  260  and  265 , upon recognizing the change in the best cell from the RRC message of step  250 , the SRNC  204  notifies this fact to the source Node B  202  and the target Node B  203  to change the HSDPA serving cell. For example, in step  260 , the SRNC  204  sends new NBAP and RNSAP messages to the target Node B  203  to the target Node B  203  that it should perform HSDPA scheduling because HSDPA data will soon arrive at the target Node B  203 .  
         [0051]     In  FIG. 2 , a new so-called HSDPA COMMIT message is used as the NBAP and RNSAP messages, by way of example. In step  265 , the SRNC  204  stops the HSDPA scheduling in the source cell  202  using the existing RL RECONFIGURATION COMMIT message, because the Synchronous Radio Link Reconfiguration procedure was used in step  255 . Table 2 shows an exemplary HSDPA COMMIT message used in step  260 .  
                                                                 TABLE 2                                   IE Type and   Semantics       Assigned       IE/Group Name   Presence   Range   Reference   Description   Criticality   Criticality                                Message   M           —           Discriminator       Message type   M           YES   ignore       Transaction ID   M           —       Node B   M       The   YES   ignore       Communication           reserved       Context ID           value                   “All                   NBCC”                   shall not                   be used.                  
 
         [0052]     While sending the HSDPA COMMIT message to the target Node B  203  in step  260 , the SRNC  204  sends the HSDPA data targeting the UE  201  to the target Node B  203  rather than the source Node B  202 . Upon receipt of the HSDPA COMMIT message in step  260 , the target Node B  203  immediately performs HSDPA scheduling from now on. That is, step  270  corresponds to a process in which the target Node B  203  delivers the scheduling information to the UE  201  through an HS-SCCH. In step  275 , the target Node B  203  actually transmits HSDPA data to the UE  201  according to the scheduling. In step  280 , the UE  201  monitors the HS-SCCH from only the target cell from the time when it recognized the fact that its own ID is included in the HS-SCCH received in step  270 . In this way, the overall HSDPA serving cell change (or overall HSDPA serving cell switching) is completed.  
         [0053]      FIG. 3  is a diagram illustrating a brief structure of a UE according to an exemplary embodiment of the present invention.  
         [0054]     Referring to  FIG. 3 , a signaling receiver  300  receives various signals and messages transmitted from an RNC or a Node B. The signaling receiver  300  includes a signal strength measurement and decision unit  301  for receiving a pilot channel and measuring strength thereof, an RRC message receiver  302  for receiving a message from an RNC, an HS-SCCH receiver  303  for receiving HSDPA scheduling information of a Node B, and an HS-DSCH receiver  304  for actually receiving HSDPA data. A signaling transmitter  310  monitors a pilot channel and the like and notifies EVENT ID to an SRNC using an RRC MEASUREMENT REPORT procedure in step  250  of  FIG. 2 . In the signaling receiver  300 , the HS-SCCH receiver  303  simultaneously monitors HS-SCCHs transmitted from a source cell  202  and a target cell  203  as shown in step  255  of  FIG. 2 . The signaling transmitter  310 , a part for transmitting signaling to an RNC, includes an RRC message transmitter  311  for transmitting a novel RRC message proposed in an exemplary embodiment of the present invention to an RNC. A memory  320  includes an active set information storage  321  for storing information on an active set, and the active set information storage  321  includes an HS configuration storage  322  for storing an HSDPA configuration set in each cell. The memory  320  can simultaneously store HSDPA configuration information from both the target Node B  203  and the source Node B  204  of  FIG. 2 . The signaling transmitter  310 , the signaling receiver  300 , and the memory  320 , being interconnected to one another, perform the operation of  FIG. 2 .  
         [0055]      FIG. 4  is a diagram illustrating a structure of a Node B according to an exemplary embodiment of the present invention.  
         [0056]     Referring to  FIG. 4 , a Node B includes an Iub interface  400  to an RNC, a Uu interface  410  to a UE, a signaling transmitter  420 , a signaling receiver  430 , a memory  450 , and an HSDPA scheduler  440 . The signaling transmitter  420  and the signaling receiver  430  are each connected to the Iub interface  400  and the Uu interface  410 , and take charge of data exchange. The signaling transmitter  420  includes an NBAP message transmitter  421 , an HS-SCCH transmitter  422 , and an HS-DSCH transmitter  423 , and the signaling receiver  430  includes an NBAP message receiver  431 , an RRC message receiver  432  and an HS-DSCH receiver  433 . The memory  450  includes an HS configuration storage  451  for storing HSDPA configuration information. The HSDPA scheduler  440  immediately performs HSDPA scheduling upon receipt of an HSDPA COMMIT message in step  260  of  FIG. 2 . In addition, the HSDPA scheduler  440  has a function of performing HSDPA scheduling, such as a function of delivering the scheduling information in step  270  to a UE through an HS-SCCH.  
         [0057]      FIG. 5  is a diagram illustrating a structure of an SRNC according to an exemplary embodiment of the present invention.  
         [0058]     Referring to  FIG. 5 , an SRNC includes an Iur/Iub interface  500  which is an interface to another RNC and a Node B, a signaling transmitter  510 , a signaling receiver  520 , a handover/data path decision unit  540 , and a memory  530 .  
         [0059]     The signaling transmitter  510  includes an NBAP message transmitter  511 , an RRC message transmitter  512 , and an HS-DSCH transmitter  513 , and the signaling receiver  520  includes an NBAP message receiver  521  and an RRC message receiver  522 . The memory  530  includes an active set information storage  531  for storing information on an active set, and the active set information storage  531  includes an HS configuration storage  532  for storing an HSDPA configuration set in each cell.  
         [0060]     As for handover decision and data path decision, the handover/data path decision unit  540  sends new NBAP and RNSAP messages to the target Node B  203  in step  260  of  FIG. 2  taking into account the RRC MEASUREMENT REPORT received from the signaling receiver  520 , to notify the target Node B  203  that it should perform HSDPA scheduling because HSDPA data will soon arrive at the target Node B  203 . Here, a new so-called HSDPA COMMIT message is used as the NBAP and RNSAP messages in  FIG. 2 , by way of example.  
       Second Exemplary Embodiment  
       [0061]     A second exemplary embodiment of the present invention, similarly to the first embodiment, provides a method in which after an SRNC sends HSDPA-related radio link configuration information of a target cell to a Node B using an Asynchronous Radio Link Reconfiguration procedure, the Node B starts HSDPA scheduling beginning at the receipt of a new message for requesting the start of HSDPA scheduling from the SRNC. While in an exemplary implementation of the first embodiment the stop of HSDPA scheduling is previously notified to a source cell as a method for stopping the HSDPA scheduling of the source cell, the second embodiment uses the Asynchronous Radio Link Reconfiguration procedure.  
         [0062]      FIG. 6  is a signaling diagram according to a second exemplary embodiment of the present invention.  
         [0063]     Referring to  FIG. 6 , a process in steps  610  to  640 , which is a first aspect according to the second exemplary embodiment of the present invention, is a process of previously configuring HSDPA configuration information in a target Node B  603  before an HSDPA serving cell is actually changed, and then providing the information to a UE  601 . In terms of this aspect, the second embodiment is different from the first embodiment in that step  255  of the first embodiment is skipped in the second embodiment. For example, while the first embodiment previously notifies the stop of HSDPA scheduling even to the source Node B  202  before the change in the best cell in preparation for the expected change in the serving cell in step  225 , the second embodiment omits this process.  
         [0064]     A process in steps  645  to  675 , which is a second aspect according to the second exemplary embodiment of the present invention, is a process in which upon recognizing the change in the best cell, an SRNC  604  notifies this fact to a target Node B  603  and a source Node B  602 , thereby to change the HSDPA serving cell. The target Node B  603  schedules actual data to the UE  601  through an HSDPA channel using the HSDPA configuration information previously set in the first aspect. In an exemplary implementation, the second embodiment is different from the first embodiment in that while the SRNC  204  sends an RL RECONFIGURATION COMMIT message indicating when it will commit the HSDPA scheduling stop previously notified through the Synchronous Radio Link Reconfiguration procedure in step  265 , to the source Node B  202  in the first aspect in the first embodiment, an SRNC  604  notifies the HSDPA scheduling stop to the source Node B  602  using the Asynchronous Radio Link Reconfiguration procedure in step  660  in the second embodiment.  
         [0065]     Upon receipt of the RL RECONFIGURATION REQUEST message in step  660 , the source Node B  602  stops the HSDPA scheduling and sends an RL RECONFIGURATION RESPONSE message to the SRNC  604  in response thereto. The operations of the target Node B  603  and the UE  601  in the second embodiment are similar to those in the first embodiment, so a description thereof will be omitted.  
       Third Exemplary Embodiment  
       [0066]     A third exemplary embodiment of the present invention, similar to the second embodiment, provides a method in which after an SRNC sends HSDPA-related radio link configuration information of a target cell to a Node B using an Asynchronous Radio Link Reconfiguration procedure, the Node B starts HSDPA scheduling beginning at the receipt of a new message for requesting the start of HSDPA scheduling from the SRNC. In addition, the third embodiment, similar to the second embodiment, sends a message for requesting stop of the HSDPA scheduling after the change in the best cell as a method for stopping HSDPA scheduling of the source cell. The third embodiment, unlike the second embodiment, stops the HSDPA scheduling of the source cell using a message configured in the same format as the message sent for requesting commitment of the HSDPA scheduling to the target cell, without using the Synchronous or Asynchronous Radio Link Reconfiguration procedure in the source cell.  
         [0067]      FIG. 7  is a signaling diagram illustrating according to a third exemplary embodiment of the present invention.  
         [0068]     Referring to  FIG. 7 , a process in steps  710  to  740 , which is a first aspect according to the third exemplary embodiment of the present invention, is a process of previously setting HSDPA configuration information in a target Node B before an HSDPA serving cell is actually changed, and then providing the information to a UE. This process is equal to the process in steps  610  to  640  in the second embodiment.  
         [0069]     A process in steps  745  to  775 , which is a second aspect according to the third exemplary embodiment of the present invention, is a process in which upon recognizing the change in the best cell, an SRNC  704  notifies this fact to a target Node B  703  and a source Node B  702 , thereby to change the HSDPA serving cell. The target Node B  703  schedules actual data to the UE  701  through an HSDPA channel using the HSDPA configuration information previously set in the first aspect. In this process, the third embodiment is different from the second embodiment in that while the second embodiment notifies the stop of the HSDPA scheduling using the Asynchronous Radio Link Reconfiguration procedure in step  660 , the third embodiment uses the message configured in the same format as the message sent for requesting commitment of the HSDPA scheduling from now on to the target Node B  703  in step  755 .  
         [0070]     Upon receipt of an HSDPA COMMIT message in step  760 , the source Node B  702  stops the HSDPA scheduling. The operations of the target Node B  703  and the UE  701  in the third embodiment are equal to those in the first and second embodiments, so a description thereof will be omitted.  
         [0071]     For example, because the HSDPA COMMIT message used in step  760  optionally has a separate CFN field as shown in Table 3, the source cell can stop the HSDPA scheduling after a lapse of a predetermined time.  
                                                                 TABLE 3                                   IE Type and   Semantics       Assigned       IE/Group Name   Presence   Range   Reference   Description   Criticality   Criticality                                Message   M           —           Discriminator       Message type   M           YES   ignore       Transaction ID   M           —       Node B   M       The   YES   ignore       Communication           reserved       Context ID           value                   “All                   NBCC”                   shall not                   be used.       CFN   0           YES   ignore                  
 
       Fourth Exemplary Embodiment  
       [0072]     A fourth exemplary embodiment of the present invention, unlike the first to third embodiments, provides a method in which after an SRNC sends HSDPA-related radio link configuration information of a target cell to a Node B using a Synchronous Radio Link Reconfiguration procedure, the Node B starts HSDPA scheduling beginning at the receipt of an RL RECONFIGURATION COMMIT message from the SRNC. However, unlike the existing Synchronous Radio Link Reconfiguration procedure, the new Synchronous Radio Link Reconfiguration procedure does not include CFN in the RL RECONFIGURATION COMMIT message in the fourth embodiment. Upon receipt of the RL RECONFIGURATION COMMIT message with no CNF, the Node B can immediately commit the new configuration received and stored from the RL RECONFIGURATION PREPARE message.  
         [0073]      FIG. 8  is a signaling diagram according to a fourth exemplary embodiment of the present invention.  
         [0074]     Referring to  FIG. 8 , a process in steps  810  to  845 , which is a first aspect according to the fourth exemplary embodiment of the present invention, is a process of previously setting HSDPA configuration information in a target Node B before an HSDPA serving cell is actually changed, and then providing the information to a UE. In this aspect, the fourth embodiment is different from the first embodiment in that while the first embodiment uses RL RECONFIGURATION REQUEST/RESPONSE, which is the Asynchronous Radio Link Reconfiguration procedure, in step  220 , the fourth embodiment uses RL RECONFIGURATION PREPARE/READY which is the Synchronous Radio Link Reconfiguration procedure.  
         [0075]     A process in steps  850  to  880 , which is a second aspect of the fourth exemplary embodiment of the present invention, is a process in which upon recognizing the change in the best cell, an SRNC  804  notifies this fact to a target Node B  803  and a source Node B  802 , thereby to change the HSDPA serving cell. The target Node B  803  schedules actual data to the UE  801  through an HSDPA channel using the HSDPA configuration information previously set in the first aspect.  
         [0076]     In this process, when the SRNC  804  notifies each Node B that HSDPA scheduling should be performed in the target Node B  803  due to the change in the best cell in steps  860  and  865 , a new radio link configuration can be directly applied because the CFN that should necessarily be specified in the RL RECONFIGURATION COMMIT message used in the existing Synchronous Radio Link Reconfiguration procedure is not specified. The other steps of the fourth embodiment are equal to the corresponding steps of the first embodiment, so a description thereof will be omitted.  
         [0077]     Table 4 and Table 5 show exemplary RL RECONFIGURATION COMMIT messages that can be used in steps  860  and  865  of the fourth exemplary embodiment of the present invention. In Table 4, CNF is changed to an optional value, and if the CFN is not included in this message, the modified configuration will be immediately committed. In Table 5, as another example of the RADIO LINK RECONFIGURATION COMMIT, a new “Immediate flag” field is added to the message, and if the “Immediate flag” field is included in the message, the modified configuration will be directly committed, ignoring the CFN.  
                                                                 TABLE 4                                   IE Type and   Semantics       Assigned       IE/Group Name   Presence   Range   Reference   Description   Criticality   Criticality                                Message   M           —           Discriminator       Message type   M           YES   ignore       Transaction ID   M           —       Node B   M       The   YES   ignore       Communication           reserved       Context ID           value                   “All                   NBCC”                   shall not                   be used.       CFN   0           YES   ignore       Active Pattern   0       FDD   YES   ignore       Sequence           only       Information                  
 
         [0078]    
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                   
               
               
                   
                   
                   
                 IE Type and 
                 Semantics 
                   
                 Assigned 
               
               
                 IE/Group Name 
                 Presence 
                 Range 
                 Reference 
                 Description 
                 Criticality 
                 Criticality 
               
               
                   
               
             
             
               
                 Message 
                 M 
                   
                   
                   
                 — 
                   
               
               
                 Discriminator 
               
               
                 Message type 
                 M 
                   
                   
                   
                 YES 
                 ignore 
               
               
                 Transaction ID 
                 M 
                   
                   
                   
                 — 
               
               
                 Node B 
                 M 
                   
                   
                 The 
                 YES 
                 ignore 
               
               
                 Communication 
                   
                   
                   
                 reserved 
               
               
                 Context ID 
                   
                   
                   
                 value 
               
               
                   
                   
                   
                   
                 “All 
               
               
                   
                   
                   
                   
                 NBCC” 
               
               
                   
                   
                   
                   
                 shall not 
               
               
                   
                   
                   
                   
                 be used. 
               
               
                 CFN 
                 M 
                   
                   
                   
                 YES 
                 ignore 
               
               
                 Active Pattern 
                 0 
                   
                   
                 FDD 
                 YES 
                 ignore 
               
               
                 Sequence 
                   
                   
                   
                 only 
               
               
                 Information 
               
               
                 Immediate flag 
                 0 
                   
                 1 bit 
                   
                 YES 
                 ignore 
               
               
                   
               
             
          
         
       
     
       Fifth Exemplary Embodiment  
       [0079]     A fifth exemplary embodiment of the present invention, similar to the fourth embodiment, provides a method in which after an SRNC sends HSDPA-related radio link configuration information of a target cell to a Node B using a Synchronous Radio Link Reconfiguration procedure, the Node B starts HSDPA scheduling beginning at the receipt of an RL RECONFIGURATION COMMIT message from the SRNC. Here, unlike the existing Synchronous Radio Link Reconfiguration procedure, the new Synchronous Radio Link Reconfiguration procedure does not include CFN in the RL RECONFIGURATION COMMIT message in the fifth embodiment. Upon receipt of the RL RECONFIGURATION COMMIT message with no CNF, the Node B can immediately commit the new configuration received and stored from the RL RECONFIGURATION PREPARE message. The fifth embodiment is different from the fourth embodiment in that it uses the existing Asynchronous Radio Link Reconfiguration procedure after the change in the best cell, instead of previously notifying the HSDPA scheduling stop to the source cell, as a method for stopping the HSDPA scheduling of the source cell.  
         [0080]      FIG. 9  is a signaling diagram according to a fifth exemplary embodiment of the present invention.  
         [0081]     Referring to  FIG. 9 , a process in steps  910  to  940 , which is a first aspect according to the fifth exemplary embodiment of the present invention, is a process of previously setting HSDPA configuration information in a target Node B before an HSDPA serving cell is actually changed, and then providing the information to a UE. In this aspect, the fifth embodiment is different from the fourth embodiment in that the process in step  825  of the fourth embodiment is not performed in the fifth embodiment. That is, while the fourth embodiment previously notifies the stop of HSDPA scheduling even to the source Node B  802  before the change in the best cell in preparation for the expected change in the serving cell in step  825 , the fifth embodiment omits this process.  
         [0082]     A process in steps  945  and  975 , which is a second aspect according to the fifth exemplary embodiment of the present invention, is a process in which upon recognizing the change in the best cell, an SRNC  904  notifies this fact to a target Node B  903  and a source Node B  902 , thereby to change the HSDPA serving cell. The target Node B  903  schedules actual data to the UE  901  through an HSDPA channel using the HSDPA configuration information previously set in the first aspect. In this process, when the SRNC  904  notifies the target Node B  903  that HSDPA scheduling should be performed in the target Node B  903  due to the change in the best cell in step  955 , a new radio link configuration can be directly applied because the CFN that should necessarily be specified in the RL RECONFIGURATION COMMIT message used in the existing Synchronous Radio Link Reconfiguration procedure is not specified.  
         [0083]     In this process, the fifth embodiment is different from the fourth embodiment in that the fourth embodiment sends an RL RECONFIGURATION COMMIT message indicating when it will commit the HSDPA scheduling stop previously notified through the Synchronous Radio Link Reconfiguration procedure in step  865 , to the source Node B  802  in the first aspect, the fifth embodiment notifies the HSDPA scheduling stop using the Asynchronous Radio Link Reconfiguration procedure in step  960 .  
         [0084]     Upon receipt of the RL RECONFIGURATION REQUEST message in step  960 , the source Node B  902  stops the HSDPA scheduling. The operations of the target Node B  903  and the UE  901  in the fifth embodiment are equal to those in the fourth embodiment, so a description thereof will be omitted.  
         [0085]     Table 4 and Table 5 described in the fourth embodiment can be equally used even in step  955  of the fifth exemplary embodiment of the present invention.  
       Sixth Exemplary Embodiment  
       [0086]     A sixth exemplary embodiment of the present invention, similar to the fourth and fifth embodiments, provides a method in which after an SRNC sends HSDPA-related radio link configuration information of a target cell to a Node B using a Synchronous Radio Link Reconfiguration procedure, the Node B starts HSDPA scheduling beginning at the receipt of an RL RECONFIGURATION COMMIT message from the SRNC. Here, unlike the existing Synchronous Radio Link Reconfiguration procedure, the new Synchronous Radio Link Reconfiguration procedure does not include CFN in the RL RECONFIGURATION COMMIT message in the sixth embodiment.  
         [0087]     Upon receipt of the RL RECONFIGURATION COMMIT message with no CNF, the Node B can immediately commit the new configuration received and stored from the RL RECONFIGURATION PREPARE message. The sixth embodiment, like the fifth embodiment, sends a message for requesting the stop of the HSDPA scheduling after the change in the best cell, instead of previously notifying the HSDPA scheduling stop to the source cell, as a method for stopping the HSDPA scheduling of the source cell. Unlike the fifth embodiment, the sixth embodiment uses the HSDPA COMMIT message used in step  760  of the third embodiment, without using the Synchronous or Asynchronous Radio Link Reconfiguration procedure in the source cell.  
         [0088]      FIG. 10  is a signaling diagram according to a sixth exemplary embodiment of the present invention.  
         [0089]     Referring to  FIG. 10 , a process in steps  1010  to  1040 , which is a first aspect according to the sixth exemplary embodiment of the present invention, is a process of previously setting HSDPA configuration information in a target Node B  1003  before an HSDPA serving cell is actually changed, and then providing the information to a UE  1001 . This aspect is equal to that in the fifth embodiment.  
         [0090]     A process in steps  1045  to  1075 , which is a second aspect according to the sixth exemplary embodiment of the present invention, is a process in which upon recognizing the change in the best cell, an SRNC  1004  notifies this fact to a target Node B  1003  and a source Node B  1002 , thereby to change the HSDPA serving cell. The target Node B  1003  schedules actual data to the UE  1001  through an HSDPA channel using the HSDPA configuration information previously set in the first aspect. In this process, when the SRNC  1004  notifies the target Node B  1003  that HSDPA scheduling should be performed in the target Node B  1003  due to the change in the best cell in step  1055 , a new radio link configuration can be directly applied because the CFN that should necessarily be specified in the RL RECONFIGURATION COMMIT message used in the existing Synchronous Radio Link Reconfiguration procedure is not specified.  
         [0091]     In this process, the sixth embodiment is different from the fifth embodiment in that while the fifth embodiment notifies the stop of the HSDPA scheduling using the Asynchronous Radio Link Reconfiguration procedure in step  960 , the message sent to the source Node B  1002  in step  1060  of the sixth embodiment is the HSDPA COMMIT message used in step  760  of the third embodiment.  
         [0092]     Upon receipt of the HSDPA COMMIT message in step  1060 , the source Node B  1002  stops the HSDPA scheduling. The operations of the target Node B  1003  and the UE  1001  in the sixth embodiment are equal to those in the fourth and fifth embodiments, so a description thereof will be omitted. For reference, because the HSDPA COMMIT message used in step  1060  optionally has a separate CFN field as shown in Table 3, the source cell can stop the HSDPA scheduling after a lapse of a predetermined time.  
         [0093]     Table 4 and Table 5 described in the fourth embodiment can be equally used even in step  1055  of the sixth exemplary embodiment of the present invention.  
         [0094]     As can be understood from the foregoing description, exemplary implementation of certain embodiments of the present invention can change the HSDPA serving cell soon after the change in the best cell, thereby facilitating better utilization of radio resources.  
         [0095]     Certain aspects of the present invention can also be embodied as computer readable code on a computer readable recording medium. A computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. Also, functional programs, code, and code segments for accomplishing the present invention can be easily construed by programmers skilled in the art to which the present invention pertains.  
         [0096]     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.