Abstract:
A method and apparatus for wireless transmit receive unit (WTRU) to transmit a time transmission interval (TTI) bundle. The TTI bundle conflicts with a measurement gap, and the WTRU is configured to construct TTI bundle comprising a plurality of sub-frames, determine at least one of the plurality of sub-frames is in conflict with a measurement gap, determine a first of the plurality of sub-frames not in conflict with the measurement gap, associate the first of the plurality of sub-frames not in conflict with the measurement gap with a first redundancy version (RV), and transmit the first of the plurality of sub-frames in association with the first RV.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/079,611 filed on Jul. 10, 2008, which is incorporated by reference as if fully set forth. 
     
    
     TECHNICAL FIELD 
       [0002]    This application is related to wireless communications. 
       BACKGROUND 
       [0003]    In Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) wireless communication systems, transmission time interval (TTI) bundling is used in uplink (UL) communication to improve coverage for wireless transmit/receive units (WTRUs) near an edge of a cell. For LTE frequency division duplex (FDD) systems, a hybrid automatic repeat request (HARQ) process and the redundancy versions (RV) associated with the HARQ process are bundled and transmitted in a fixed number of consecutive TTIs, such as four (4), for example. 
         [0004]      FIG. 1  shows a method of uplink TTI bundling  100  in accordance with the prior art. The HARQ RTT time  102  is the minimum number of sub-frames before a downlink (DL) HARQ retransmission is expected by the WTRU. As shown in  FIG. 1 , data  110  is transmitted in sub-frame  1  ( 102 ), sub-frame  2  ( 104 ), sub-frame  3  ( 106 ) and sub-frame  4  ( 108 ). A negative acknowledge signal (NACK)  112  for sub-frame  4  ( 108 ) is received by the WTRU in sub-frame  8  ( 114 ). The WTRU then retransmits sub-frame  4  ( 108 ), the sub-frame that was NACKed, in four (4) sub-frames ( 116  through  122 ) after the RTT time  102 . 
         [0005]    When a WTRU is in connected mode, it uses measurement gaps to stop active communication and take measurements of neighboring cells for possible handover. The measurement gaps are scheduled by an eNodeB (eNB). The eNB may schedule the measurement gap without consideration for the possibility that the WTRU may need to retransmit sub-frames as part of a HARQ process. Therefore, the eNB may schedule a measurement gap for the WTRU at the same time the WTRU is retransmitting due to a NACK. If that occurs, the TTI bundle may overlap with the measurement gap, and the WTRU may be required to perform two mutually exclusive processes.  FIG. 2  shows a measurement gap overlapping with a TTI bundle  200  in accordance with the prior art. The measurement gap  202  overlaps sub-frame  1  ( 204 ) of the TTI bundle  206 . As the WTRU cannot perform HARQ retransmission and measurements at the same time, only a fraction of the TTI bundle  206  may be transmitted. 
       SUMMARY 
       [0006]    A method and apparatus is disclosed for a wireless transmit receive unit (WTRU) to transmit a time transmission interval (TTI) bundle that conflicts with a measurement gap. The WTRU may construct the TTI bundle that includes multiple sub-frames, determine that at least one sub-frame is in conflict with the measurement gap, and determine that at least one sub-frame is not in conflict with the measurement gap. The WTRU may then associate the first non-conflicted sub-frame with a first redundancy version (RV), the second non-conflicted sub-frame, if available, with a second RV and, the third non-conflicted sub-frame, if available, with a third RV. The non-conflicted sub-frames are transmitted, and the conflicted sub-frames are not transmitted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]    A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: 
           [0008]      FIG. 1  shows a method of uplink TTI bundling in accordance with the prior art. 
           [0009]      FIG. 2  shows a measurement gap overlapping with a TTI bundle in accordance with the prior art; 
           [0010]      FIG. 3  shows a wireless communication system including a plurality of WTRUs and an e Node B (eNB); 
           [0011]      FIG. 4  is a functional block diagram of the WTRU and the eNB of the wireless communication system of  FIG. 3 ; 
           [0012]      FIG. 5  shows a TTI bundle in accordance with one embodiment; 
           [0013]      FIG. 6  shows a method of transmitting a TTI bundle with a first overlapped sub-frame in accordance with one embodiment; 
           [0014]      FIG. 7  shows the method of transmitting a TTI bundle with a last overlapped sub-frame in accordance with one embodiment; 
           [0015]      FIG. 8  shows the method for transmitting a TTI bundle with the first two sub-frames overlapped in accordance with one embodiment; 
           [0016]      FIG. 9  shows the method for transmitting the TTI bundle with the last two sub-frames overlapped in accordance with one embodiment; 
           [0017]      FIG. 10  shows the method for transmitting the TTI bundle with the first three sub-frames overlapped in accordance with one embodiment; and 
           [0018]      FIG. 11  shows the method for transmitting the TTI bundle with the last three sub-frames overlapped in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION  
       [0019]    When referred to herein, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to herein, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment. 
         [0020]      FIG. 3  shows a wireless communication system  300  including a plurality of WTRUs  310  and an e Node B (eNB)  320 . As shown in  FIG. 3 , the WTRUs  310  are in communication with the eNB  320 . Although three WTRUs  310  and one eNB  320  are shown in  FIG. 3 , it should be noted that any combination of wireless and wired devices may be included in the wireless communication system  300 . 
         [0021]      FIG. 4  is a functional block diagram  400  of a WTRU  310  and the eNB  320  of the wireless communication system  300  of  FIG. 3 . As shown in  FIG. 3 , the WTRU  310  is in communication with the eNB  320 . The WTRU  310  is configured to perform measurements as required. If the WTRU  310  is in connected mode, the WTRU  310  is configured to perform the measurement routines during a measurement gap. The WTRU  310  is also configured to transmit signals in sub-frames grouped into TTI bundles. 
         [0022]    In addition to the components that may be found in a typical WTRU, the WTRU  310  includes a processor  415 , a receiver  416 , a transmitter  417 , and an antenna  418 . The WTRU  310  may also include a user interface  421 , which may include, but is not limited to, an LCD or LED screen, a touch screen, a keyboard, a stylus, or any other typical input/output device. The WTRU  310  may also include memory  419 , both volatile and non-volatile as well as interfaces  420  to other WTRU&#39;s, such as USB ports, serial ports and the like. The receiver  416  and the transmitter  417  are in communication with the processor  415 . The antenna  418  is in communication with both the receiver  416  and the transmitter  417  to facilitate the transmission and reception of wireless data. 
         [0023]    In addition to the components that may be found in a typical eNB, the eNB  320  includes a processor  425 , a receiver  426 , a transmitter  427 , and an antenna  428 . The receiver  426  and the transmitter  427  are in communication with the processor  425 . The antenna  428  is in communication with both the receiver  426  and the transmitter  427  to facilitate the transmission and reception of wireless data. 
         [0024]      FIG. 5  shows a TTI bundle  500  in accordance with one embodiment. Within one TTI bundle  500  transmission, the same data is transmitted over 4 consecutive sub-frames using, or associated with, different redundancy versions (RV). 
         [0025]    An RV specifies a starting point in a circular buffer to start reading out bits. Different RV&#39;s are specified by defining different starting points to enable HARQ operation. RV 0  may be selected for the first transmission, as this allows the transmission of as many systematic bits as possible. Different RVs may be selected for retransmission of the same packet to support various types of HARQ combining. Several RV sequences may be used for TTI bundling. For example, a sequence of RV 0 , RV 2 , RV 3 , and RV 1  may be used. By way of another example, a sequence of RV 0 , RV 1 , RV 2 , and RV 3  may be used. In general, any sequence starting with RV 0  may be used, as RV 0  includes the most systematic bits. As used herein, RV i  with i=1, 2, 3 or 4, is an index and may reference any RV. For example, RV 1  may refer to RV 3 . 
         [0026]    Turning back to  FIG. 5 , the first sub-frame  502  includes data associated with RV 0 . RV 0  includes most systematic bits. The second sub-frame  504  includes data associated with RV 1 . The third sub-frame  506  includes data associated with RV 2  and the third sub-frame  508  includes data associated with RV 3 . When at least part of the TTI bundle  500  overlaps with a measurement gap, the portion of the TTI bundle  500  that overlaps with the measurement gap will not be transmitted. The non-overlapping portion of the TTI bundle  500  will be transmitted. 
         [0027]    When one sub-frame overlaps with the measurement gap, the RV sequence {rv 0 , rv 1 , rv 2 } may used for sub-frames that are not overlapped by the measurement gap. The RV sequence may be used when the first sub-frame is overlapped or the last sub-frame is overlapped.  FIG. 6  shows a method of transmitting a TTI bundle  600  with a first overlapped sub-frame in accordance with one embodiment. The measurement gap  602  overlaps the first sub-frame  604 . Therefore, the first overlapped sub-frame  604  is not transmitted. The second sub-frame  606  is the first transmitted sub-frame and includes data associated with RV 0 . The third sub-frame  608  and the fourth sub-frame  610  are also both transmitted, and include data associated with RV 1  and RV 2 , respectively. 
         [0028]      FIG. 7  shows the method of transmitting a TTI bundle  600  with a last overlapped sub-frame in accordance with one embodiment. In  FIG. 7 , the measurement gap  702  overlaps the fourth sub-frame  704  of the TTI bundle. Therefore, the fourth sub-frame  704  of the TTI bundle is not transmitted. The first sub-frame  706  of the TTI bundle includes data associated with RV 0 , the second sub-frame  708  of the TTI bundle includes data associated with RV 1 , and the third sub-frame of the TTI bundle  710  includes data associated with RV 2 . The first sub-frame  706 , the second sub-frame  708  and the third sub-frame  710  are transmitted. 
         [0029]    Two of the four sub-frames in a TTI bundle may overlap with the measurement gap.  FIG. 8  shows the method for transmitting a TTI bundle  600  with the first two sub-frames overlapped in accordance with one embodiment. The measurement gap  802  overlaps 2 sub-frames, the first sub-frame  804  and the second sub-frame  806 . The first sub-frame  804  and the second sub-frame  806  are not transmitted. The third sub-frame  808  includes data associated with RV 0  and is transmitted first. The fourth sub-frame  810  includes data associated with RV 1  and is transmitted second. The RV sequence {rv 0 , rv 1 } is used for TTIs that are not affected by the measurement gap. 
         [0030]      FIG. 9  shows the method for transmitting the TTI bundle  600  with the last two sub-frames overlapped in accordance with one embodiment. The measurement gap  902  overlaps 2 sub-frames, the last sub-frame  904  and the second to last sub-frame  906 . The last sub-frame  904  and the second to last sub-frame  906  are not transmitted. The first sub-frame  908  includes data associated with RV 0  and is transmitted first. The second TTI sub-frame  910  includes data associated with RV 1  and is transmitted second. The RV sequence {rv 0 , rv 1 } is again used for sub-frames that are not affected by the measurement gap. Alternatively, RV sequence {rv 2 , rv 3 } may be used when two sub-frames overlap with measurement gap. 
         [0031]    If three sub-frames overlap with the measurement gap, RV 0  may be selected for the sub-frame that is not affected by the measurement gap.  FIG. 10  shows the method for transmitting the TTI bundle  600  with the first three sub-frames overlapped in accordance with one embodiment. The measurement gap  1002  overlaps three (3) sub-frames, the first sub-frame  1004 , the second sub-frame  1006  and the third sub-frame  1008 . These sub-frames are not transmitted. The last sub-frame  101  includes data associated with RV 0  and is transmitted. The RV sequence {rv 0 } is used for the TTI that is not affected by the measurement gap. 
         [0032]      FIG. 11  shows the method for transmitting the TTI bundle  600  with the last three sub-frames overlapped in accordance with one embodiment. The measurement gap  1102  overlaps three (3) sub-frames, the second sub-frame  1106 , the third sub-frame  1108  and the fourth sub-frame  1110 . These sub-frames are not transmitted. The first sub-frame  1104  includes data associated with RV 0  and is transmitted. The RV sequence {rv 0 } is used for the TTI that is not affected by the measurement gap 
         [0033]    Alternatively, the TTI bundle transmission may be cancelled when part of the TTI bundle overlaps with a measurement gap. If any k, with k being an integer between 1 and 4, sub-frames of the TTI bundle overlap with a measurement gap, the transmission of the TTI bundle may be cancelled. 
         [0034]    Although the features and elements of the present invention are described in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. 
         [0035]    While the present invention has been described in terms of the preferred embodiment, other variations which are within the scope of the invention will be apparent to those skilled in the art. 
         [0036]    Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methods or flow charts provided herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). 
         [0037]    Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. 
         [0038]    A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB) module.