Abstract:
A radio access network comprises a serving radio network controller (S-RNC). The S-RNC receives successfully received medium access control (MAC) packet data units (PDUs), discards duplicates of MAC PDUs, reorders the non-discarded MAC PDUs based on serial numbers of the MAC PDUs and delivers the MAC PDUs to a radio link control protocol layer. A controlling radio network controller (C-RNC) provides information to Node-Bs under its control for use in scheduling uplink transmissions. A plurality of Node-Bs schedule uplink transmissions in response to the information provided by its C-RNC, transmit scheduling information to user equipments of its cells, receive MAC PDUs from user equipments of its cells using hybrid automatic repeat request and forward the successfully received MAC PDUs to an associated S-RNC.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/784,336, filed Apr. 6, 2007, which is a continuation of U.S. patent application Ser. No. 10/939,256, filed Sep. 10, 2004, which issued as U.S. Pat. No. 7,206,581 on Apr. 17, 2007, which claims priority from U.S. Provisional Patent Application Ser. No. 60/517,779, filed Nov. 5, 2003, the contents of which are hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of wireless communications. More specifically, the present invention relates to processing data blocks in a multi-cell wireless communication system, such as a frequency division duplex (FDD) or time division duplex (TDD) system. 
     BACKGROUND 
     Methods for improving uplink coverage, throughput and transmission latency are currently being investigated in third generation partnership project (3GPP) in the context of the Release 6 (R6) universal mobile telecommunications system (UMTS) study item “FDD uplink enhancements”. 
     It is widely anticipated that in order to achieve these goals, Node-B (base station) will take over the responsibility of scheduling and assigning uplink resources (physical channels) to users. The principle is that Node-B can make more efficient decisions and manage uplink radio resources on a short-term basis better than the radio network controller (RNC), even if the RNC retains coarse overall control. A similar approach has already been adopted in the downlink for Release 5 (R5) high speed downlink packet access (HSDPA) in both UMTS FDD and TDD modes. 
     It is also envisioned there could be several independent uplink transmissions processed between a wireless transmit/receive unit (WTRU) and a universal terrestrial radio access network (UTRAN) within a common time interval. One example of this would be medium access control (MAC) layer hybrid automatic repeat request (HARQ) or simply MAC layer automatic repeat request (ARQ) operation where each individual transmission may require a different number of retransmissions to be successfully received by UTRAN. To limit the impact on system architecture, it is expected that protocol layers above the MAC should not be affected by introduction of the enhanced uplink dedicated channel (EU-DCH). One requirement that is introduced by this is the in-sequence data delivery to the radio link control (RLC) protocol layer. Therefore, similar to HSDPA operation in the downlink, a UTRAN re-ordering function is needed to organize the received data blocks according to the sequence generated by the WTRU RLC entity. 
     A soft handover macro-diversity operation requires centralized control of uplink transmissions in each cell within an active set. The active set may include a plurality of Node-Bs. Retransmissions are generated until successful transmission is realized by at least one of the Node-Bs. Successful transmission is not guaranteed at all of the Node-Bs. Therefore, since a complete set of successful transmissions may not be available within any one Node-B, re-ordering of successful transmissions cannot be accomplished. 
     SUMMARY 
     A radio access network comprises a serving radio network controller (S-RNC). The S-RNC receives successfully received medium access control (MAC) packet data units (PDUs), discards duplicates of MAC PDUs, reorders the non-discarded MAC PDUs based on serial numbers of the MAC PDUs and delivers the MAC PDUs to a radio link control protocol layer. A controlling radio network controller (C-RNC) provides information to Node-Bs under its control for use in scheduling uplink transmissions. A plurality of Node-Bs schedule uplink transmissions in response to the information provided by its C-RNC, transmit scheduling information to user equipments of its cells, receive MAC PDUs from user equipments of its cells using hybrid automatic repeat request and forward the successfully received MAC PDUs to an associated S-RNC. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example, and to be understood in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a block diagram of a wireless communication system for processing data blocks in a serving-RNC in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a flowchart of a process including method steps for processing data blocks in the system of  FIG. 1 ; 
         FIG. 3  is a block diagram of a wireless communication system for processing data blocks in a controlling-RNC in accordance with an alternate embodiment of the present invention; and 
         FIG. 4  is a flowchart of a process including method steps for processing data blocks in the system of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described with reference to the drawing figures wherein like numerals represent like elements throughout. 
     Hereafter, the terminology “WTRU” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point or any other type of interfacing device in a wireless environment. 
     The present invention may be further applicable to TDD, FDD, and time division synchronous code division multiple access (TD-SCDMA), as applied to UMTS, CDMA 2000 and CDMA in general, but is envisaged to be applicable to other wireless systems as well. With respect to CDMA2000, the present invention may be implemented in EV-DO (i.e., data only) and EV-DV (i.e., data and voice). 
     The features of the present invention may be incorporated into an IC or be configured in a circuit comprising a multitude of interconnecting components. 
     During soft handover, higher layers maintain an active subset of EU cells for which EU-DCHs are maintained in a soft handover macro diversity state. Those cells in the active subset may be controlled by different EU-SHO Node-Bs. 
       FIG. 1  shows a wireless communication system  100  including an S-RNC  105  and at least two (2) EU-SHO Node-Bs  110  ( 110 A . . .  110 N) operating in accordance with a preferred embodiment of the present invention. One or more re-ordering function entities  115  are implemented at the S-RNC  105  for each WTRU with and without soft handover. The HARQ or ARQ processes for handling EU-DCH functionalities are located in a MAC entity  120  located within each respective EU-SHO Node-B  110 . Each re-ordering function entity  115  communicates with higher protocol layers  125  within the S-RNC  105  and includes an associated data buffer (not shown). 
       FIG. 2  is a flowchart of a process  200  including method steps for processing data blocks, i.e., packet data units (PDUs), in the system  100  during a soft handover. In step  205 , a data block, (i.e., an EU data block), is received at each EU-SHO Node-B  110  from a WTRU. In step  210 , each EU-SHO Node-B  110  decodes the received data block, and the decoded data block is forwarded to the S-RNC  105 . It should be noted that each EU-SHO Node-B  110  will attempt to decode received EU transmissions. When there is a CRC error, the EU-SHO Node-B  110  cannot forward the received data block to the S-RNC  105 , unless the identity of the WTRU and logical channel/MAC-d flow is known by other means. All successfully decoded blocks with good CRC check results are forwarded to the S-RNC  105 . 
     Still referring to  FIG. 2 , a determination is made as to whether or not at least one copy of a successfully decoded data block is received by the S-RNC  105  from an EU-SHO Node-B  110  (step  215 ). If it is determined in step  215  that the S-RNC  105  has not received any copy of a successfully decoded data block, the forwarded data block is regarded as not having been correctly received (step  220 ). If, in step  215 , it is determined that at least one copy of a successfully decoded data block has been received by the S-RNC  105  from an EU-SHO Node-B  110 , a determination is then made as to whether or not multiple copies of the successfully decoded data block are received from different EU-SHO Node-Bs  110  (step  225 ). 
     If step  225  determines that multiple copies of the successfully decoded data block are received from different EU-SHO Node-Bs  110 , only one copy will be stored in a re-ordering buffer (not shown) maintained by a re-ordering function entity  115  in the S-RNC  105  as a correctly received data block, and any extra received copies of the successfully decoded data block are discarded as redundant data (step  230 ). 
     Finally, in step  235 , the successfully decoded data block is processed by the re-ordering function entity  115  in the S-RNC  105 . The re-ordering function entity  115  in the S-RNC  105  performs a re-ordering procedure on those successfully decoded data blocks that are correctly received in the re-ordering function entity  115  so as to support in-sequence delivery to the higher protocol layers  125 . 
     Process  200  is beneficial because data blocks received from different EU-SHO Node-Bs  110  can be combined and organized in-sequence for delivery to the higher protocol layers  125  of the S-RNC  105 . The re-ordering function entity  115  located within the S-RNC  105  allows enhanced uplink MAC PDU&#39;s to be processed for successful reception and proper delivery to higher layers independent of which Node-B(s) that provided reception of each PDU, resulting in the reduction of loss of MAC data and RLC recoveries. 
       FIG. 3  shows a wireless communication system  300  including a C-RNC  305  and at least two (2) EU-SHO Node-Bs  110  ( 110 A . . .  110 N) operating in accordance with an alternate embodiment of the present invention. One or more re-ordering function entities  315  are implemented at the C-RNC  305  for support of soft handover. The HARQ or ARQ processes for handling EU-DCH functionalities are located in a MAC entity  320  located within each respective EU-SHO Node-B  310 . Each re-ordering function entity  315  communicates with higher protocol layers  325  external to the C-RNC  305  and includes an associated buffer (not shown). 
       FIG. 4  is a flowchart of a process  400  including method steps for processing data blocks, i.e., PDUs, in the system  300  during a soft handover. In step  405 , a data block (i.e., an EU data block) is received at each EU-SHO Node-B  310  from a WTRU. In step  410 , each EU-SHO Node-B  310  decodes the received data block, and the decoded data block is forwarded to the C-RNC  305 . It should be noted that each EU-SHO Node-B  310  will attempt to decode received EU transmissions. When there is a CRC error, the EU-SHO Node-B  310  cannot forward the received data block to the C-RNC  305 , unless the identity of the WTRU and logical channel/MAC-d flow is known by other means. All successfully decoded blocks with good CRC check results are forwarded to the C-RNC  305 . 
     Still referring to  FIG. 4 , a determination is made as to whether or not at least one copy of a successfully decoded data block is received by the C-RNC  305  from an EU-SHO Node-B  310  (step  415 ). If it is determined in step  415  that the C-RNC  305  has not received any copy of a successfully decoded data block, the decoded data block forwarded by the EU-SHO Node-Bs  310  is regarded as not having been correctly received (step  420 ). 
     If, in step  415 , it is determined that at least one copy of a successfully decoded data block has been received by the C-RNC  305  from an EU-SHO Node-B  310 , a determination is then made as to whether or not multiple copies of the successfully decoded data block are received from different EU-SHO Node-Bs  110  (step  425 ). 
     If step  425  determines that multiple copies of the successfully decoded data block are received from different EU-SHO Node-Bs  310 , only one copy will be stored in a re-ordering buffer (not shown) maintained by a re-ordering function entity  315  in the C-RNC  305  as a correctly received data block, and any extra received copies of the successfully decoded data block are discarded as redundant data (step  430 ). 
     Finally, in step  435 , the successfully decoded data block is processed by the re-ordering function entity  315  in the C-RNC  305 , which performs a re-ordering procedure on those successfully decoded data blocks that are correctly received in the re-ordering function entity  315  so as to support in-sequence delivery to the higher protocol layers  325 . 
     Process  400  is beneficial because data blocks received from different EU-SHO Node-Bs  310  can be combined and organized in sequence for delivery to the higher protocol layers  325 , provided that these Node-Bs  310  have the same C-RNC  305 . This is frequently the case, although its applicability is somewhat more restrictive than placing a re-ordering function in an S-RNC  105 . However, this restriction is offset by other considerations. For example, a benefit of C-RNC operation is reduced latency for H-ARQ operation. The performance benefits of minimizing this latency are well understood in the art. During soft handover, it is also desirable to have a common uplink scheduler in the C-RNC  305  for all of the cells that are in the active EU subset, including cells that are controlled by different Node-Bs  310 . 
     While this invention has been particularly shown and described with reference to preferred embodiments, 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 scope of the invention described hereinabove.