Patent Publication Number: US-2023164749-A1

Title: Method and apparatus for performing fractional subframe transmission

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/582,630 filed on Jan. 24, 2022, which is a continuation of U.S. patent application Ser. No. 16/692,407 filed on Nov. 22, 2019, which is issued as U.S. Pat. No. 11,272,505, which is a continuation of U.S. patent application Ser. No. 15/302,066 filed on Oct. 5, 2016, which is issued as U.S. Pat. No. 10,512,077, which is a National Stage of International Application No. PCT/CN2015/072144 filed on Feb. 3, 2015, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of the present invention generally relate to communication techniques. More particularly, embodiments of the present invention relate to a method and apparatus for performing fractional subframe transmission. 
     BACKGROUND OF THE INVENTION 
     In 3rd Generation Partnership Project (3GPP), the network structure and various technologies needed for a terminal&#39;s movement between a 3GPP wireless communication network and a Wireless Local Area Network (WLAN) network are called interworking WLAN. The multi-mode wireless communication technology has evolved to use multiple wireless communication technologies at the same time. The use of multiple wireless communication technologies simultaneously thereby increases transfer rates per unit time or improves the reliability of the terminal. 
     In wireless communication, spectrum is very rare resource. A licensed band represents a frequency band that is exclusively licensed to a specific operator to provide specific wireless services. On the other hand, an unlicensed band represents a frequency band that is not allocated to a specific operator, but is opened so that all entities meeting the predefined requirements may use the frequency band. 
     In some regions in the world, unlicensed band technologies need to abide to certain regulations, for example, Listen-Before-Talk (LBT), and channel bandwidth occupancy requirements. LBT results in an uncertainty of channel availability. For instance, an unlicensed band may be available at any time during a subframe. 
     WLAN that uses Wireless Fidelity (WiFi) is the typical wireless communication technology used in the unlicensed band. Time granularity of current Long Term Evolution (LTE) is much larger than that of WiFi, which leads to the low competitive strength of License Assisted Access (LAA) with LBT. As such, fair coexistence between LTE and other technologies such as WiFi as well as between LTE operators is expected. In order to be more competitive in the unlicensed band, fractional subframe transmission may be performed. 
     The fractional subframe transmission may use at least one fractional subframe. Since merely a portion of symbols of a factional subframe are available for data transmission, the end of the fractional subframe transmission may be uncertain. However, for both a transmitter and a receiver, the end of the fractional subframe transmission is an important factor for perform the fractional subframe transmission efficiently. Therefore, there is a need to estimate the end of the fractional subframe transmission. 
     SUMMARY OF THE INVENTION 
     The present invention proposes a solution regarding fractional subframe transmission. Specifically, the present invention provides a method and apparatus for estimate the end of the fractional subframe transmission. 
     According to a first aspect of embodiments of the present invention, embodiments of the invention provide a method for performing fractional subframe transmission. The method may comprise: determining first temporal information that indicates when a channel becomes available; and determining, based on the first temporal information and transmission opportunity information, second temporal information that indicates an end of the fractional subframe transmission. The method may be performed at a transmitter or a receiver. 
     According to a second aspect of embodiments of the present invention, embodiments of the invention provide an apparatus for performing fractional subframe transmission. The apparatus may comprise: a first determining unit configured to determine first temporal information that indicates when a channel becomes available; and a second determining unit configured to determine, based on the first temporal information and transmission opportunity information, second temporal information that indicates an end of the fractional subframe transmission. The apparatus may be implemented at a transmitter or a receiver. 
     Other features and advantages of the embodiments of the present invention will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where 
         FIG.  1    illustrates a flow chart of a method  100  for performing fractional subframe transmission according to an embodiment of the invention; 
         FIG.  2    illustrates a flow chart of a method  200  for performing fractional subframe transmission at a transmitter according to an embodiment of the invention; 
         FIG.  3    illustrates a flow chart of a method  300  for performing fractional subframe transmission at a receiver according to an embodiment of the invention; 
         FIG.  4    illustrates a schematic diagram  400  of fractional subframe transmission according to embodiments of the invention; 
         FIG.  5    illustrates a schematic diagram  500  of fractional subframe transmission according to embodiments of the invention; 
         FIG.  6    illustrates a schematic diagram  600  of fractional subframe transmission according to embodiments of the invention; and 
         FIG.  7    illustrates a block diagram of an apparatus  710  of a transmitter and an apparatus  720  of a receiver for performing fractional subframe transmission according to embodiments of the invention. 
       Throughout the figures, same or similar reference numbers indicate same or similar elements. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The subject matter described herein will now be discussed with reference to several example embodiments. It should be understood these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein, rather than suggesting any limitations on the scope of the subject matter. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof 
     It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two functions or acts shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. 
     Embodiments of the present invention are directed to a solution for performing fractional subframe transmission. The solution may be carried out between a receiver and a transmitter. In particular, the transmitter may determine first temporal information that indicates when a channel becomes available and determine second temporal information that indicates an end of the fractional subframe transmission based on the first temporal information and transmission opportunity information. The receiver may determine the second temporal information in a similar way. As such, both the transmitter and the receiver may determine the end of the fractional subframe transmission without introducing signalling overhead. 
     In embodiments of the present invention, a fractional subframe may refer to a subframe for downlink transmission or a subframe for uplink transmission, wherein one part of the fractional subframe is used for transmission of control information or data and the other part is not used for the transmission. For example, for a subframe comprising 14 symbols, if only the last 6 symbols are used for transmission while the first 8 symbols are not used for the transmission, this subframe may be considered as a factional subframe. For another example, if the first 7 symbols of a subframe are used for transmission while the remaining symbols of the subframe are not used for the transmission, this subframe may be considered as a factional subframe as well. 
     In the disclosure, the fractional subframe transmission may refer to the transmission performed on one or more subframes, and at least one of the one or more subframes is a fractional subframe. By way of example, the fractional subframe transmission may comprise various cases, such as the first subframe being a fractional subframe, the last subframe being a fractional subframe, both the first and the last subframes being fractional subframes, and the like. 
     In some embodiments, the fractional subframe transmission may be downlink or uplink cellular transmission. In downlink transmission, the receiver may comprise user equipment (UE), such as a terminal, a Mobile Terminal (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), Mobile Station (MS), or an Access Terminal (AT). Meanwhile, the transmitter may comprise a base station (BS), such as a node B (NodeB or NB), or an evolved NodeB (eNodeB or eNB). In uplink transmission, the transmitter may comprise a UE and the receiver may comprise a BS. 
     According to some other embodiments of the present invention, the fractional subframe transmission may be D2D transmission. In this regard, the receiver may be a Device-to-Device (D2D) receiver and the transmitter may be a D2D transmitter. 
     Embodiments of the present invention may be applied in various communication systems, including but not limited to a Long Term Evolution (LTE) system or a Long Term Evolution Advanced (LTE-A) system. Given the rapid development in communications, there will of course also be future type wireless communication technologies and systems with which the present invention may be embodied. It should not be seen as limiting the scope of the invention to only the aforementioned system. 
     Now some exemplary embodiments of the present invention will be described below with reference to the figures. Reference is first made to  FIG.  1   , which illustrates a flow chart of a method  100  for performing fractional subframe transmission at a transmitter according to an embodiment of the invention. The method  100  may be performed at a transmitter and other suitable device. Alternatively, the method  100  may be performed at a receiver and other suitable device. 
     The method  100  starts at step S 110 , in which first temporal information is determined, wherein the first temporal information indicates when a channel becomes available. 
     In context of the disclosure, a subframe may comprise a plurality of symbols. By way of example, a subframe may be 1 ms and comprise 14 symbols, for example, symbols 0 to 13. A position, such as a potential position, a target position, a current position, a next position, may refer to a time point or a time period in the subframe. In some embodiments, a position may correspond to an instant in a subframe. As an alternative, a position may correspond to a symbol of a subframe. In this regard, the position may occupy a time period, for example, the time period of a symbol. A target position may refer to a position from which the fractional transmission may start, and a potential position may refer to a predefined position that is a candidate of the target position. 
     There may be one or more potential positions predefined in a subframe. Each of the potential positions may correspond to a symbol of the subframe periodically or aperiodically. In some embodiments, the potential positions may comprise every three symbols, for example, symbols 0, 3, 6, 9 and 12. For instance, the potential positions may be set at 
       mod ( N, Nd )= x ( x ∈[0, Nd− 1]),  (1)
 
     where N represents the index of a symbol in a subframe, and Nd represents the interval between two potential positions and may be an integer ranged from 1 to the total number of symbols in the subframe, for example 14. According to equation (1), it may be determined that the smaller the Nd is, the denser the potential positions are. In some embodiments, each symbol in a subframe may be predefined as a potential position. 
     It is to be noted that the above examples are illustrated for example, rather than limitation. It can be appreciated that, in alternative embodiments, there may be aperiodic configurations of the potential positions. For instance, the potential positions may correspond to the symbols 0, 3, 8 and 12. 
     Clear Chanel Assessment (CCA) or Extended Clear Chanel Assessment (eCCA) may be performed, for example by the transmitter, to detect whether a channel is available. In response to detecting that the channel becomes available, whether a current position is a potential position may be detected. If the current position is a potential position, the current position may be determined as the target position; otherwise, a channel occupation signal may be transmitted from the current position until a potential position, and this potential position may be determined as the target position. In some embodiments, this potential position may be a potential position immediately following the current position. For example, if the current position corresponds to symbol 5, and there are three predefined potential positions corresponding to symbols 0, 7 and 11, it may be determined that the potential position corresponding to symbol 7 is a potential position immediately following the current position and may be determined as the target position. 
     According to embodiments of the present invention, the fractional subframe transmission may be symbol-level transmission. In other words, the fractional subframe transmission may be ended at any symbol of a subframe. In this case, it is possible that the last subframe of the fractional subframe transmission is a fractional subframe. The first temporal information may be determined in several ways. In some embodiments, whether the channel becomes available at a symbol of a first subframe may be determined. 
     In response to determining that the channel becomes available, the first temporal information may be determined as comprising an index of the symbol. Alternatively, in some embodiments, in response to determining that the channel becomes available, the first temporal information may be determined as comprising a potential position predefined in the first subframe, wherein the potential position is immediately prior to the symbol. Details will be described with reference to  FIGS.  2  and  3   . 
     Alternatively, the fractional subframe transmission may be subframe-level transmission. In this case, the fractional subframe transmission may be ended at a complete subframe. In other words, the last subframe of the fractional subframe transmission is a complete subframe, instead of a fractional subframe. According to embodiments of the present invention, at step S 110 , a first subframe at which the channel becomes available may be determined. Then, the first temporal information may be determined as comprising an index of the first subframe. 
     In some embodiments, step S 110  may be performed by the transmitter. In this case, the first subframe may be determined based on CCA/eCCA performed by the transmitter. In particular, when the transmitter detect a channel becomes available at a subframe, this subframe may be determined as the first subframe. 
     In some other embodiments, step S 110  may be performed by the receiver. In an exemplary embodiment, the transmitter may notify the first temporal information, for example, by sending an indicator regarding the first temporal information to the receiver. In this way, the index of the first subframe at which a channel becomes available may be indicated explicitly. Thus, at step S 110 , the receiver may determine the first temporal information by detecting the indicator. In an alternative embodiment, the transmitter may not send the indicator, and the receiver may make blind decoding for control information of the fractional subframe transmission at a potential position. In response to that the blind decoding is success, the receiver may determine the index of the first subframe of the fractional subframe transmission. 
     At step S 120 , second temporal information that indicates an end of the fractional subframe transmission may be determined based on the first temporal information and transmission opportunity information. 
     According to embodiments of the present invention, the transmission opportunity information may include channel occupancy time, for example, maximum channel occupancy time, average channel occupancy time, and so on. The transmission opportunity information may be determined based on regulations or other possible aspects. Additionally or alternatively, the transmission opportunity information may be configured by higher layer signalling or may be preset as being fixed. 
     In some embodiments where the symbol-level transmission is performed, at step S 120 , a number of symbols used by the fractional subframe transmission may be determined based on the transmission opportunity information. Then, a number of end symbols may be determined based on the first temporal information and the number of symbols used by the fractional subframe transmission, wherein the end symbols are used by the fractional subframe transmission and belong to a last subframe of the fractional subframe transmission. Details will be described with reference to  FIGS.  2  and  3   . 
     Alternatively, in some embodiments where the subframe-level transmission is performed, at step S 120 , an index of a last subframe used by the fractional subframe transmission may be determined based on the first temporal information and transmission opportunity information. 
     In an exemplary embodiment, the index of the last subframe may be determined as follows: 
         Ne=N 1+floor( TXOP )−1  (2)
 
     where N1 represents the index of the first subframe, Ne represents the index of the last subframe, TXOP represents the channel occupancy time in millisecond (i.e., ms), and floor( ) indicates an operation of rounding down. 
       FIG.  6    illustrates a schematic diagram  600  of subframe-level fractional subframe transmission according to embodiments of the invention. As shown in  FIG.  6   , there are 4 subframes, i.e., subframes  0  to  3 . With respect to subframe  0 , there are two potential positions  621  and  622 , wherein the first potential position  621  corresponds to the start of subframe  0 . CCA/eCCA may start from the first potential position  621 , and the potential position  622  may be determined as the target position. The factional subframe transmission then may start from the target position and ends at the end of subframe  2 . Thus, the real channel occupation time, which indicates the actual time period occupied by the fractional subframe transmission, may correspond to a time period from the positions  622  to  623 . Assuming that TXOP is 3 ms and corresponds to a time period from the position  622  to the position  624 , it may be determined that the actual channel occupation time is from the position  622  to the position  623  and a time period from the position  623  to the position  624  is not occupied. In the embodiments of  FIG.  6   , since the first subframe is subframe  0 , the index of the first subframe is 0. Thus, according to equation (2), it may be determined that the index of the last subframe Ne is 0+3−1=2. In other words, the last subframe may be determined as subframe  2 . 
     According to embodiments of the present invention, optionally, if the symbol-level transmission is performed, the method  100  may further comprise a step of comparing the number of end symbols with a predetermined threshold. Responsive to that the number of end symbols is less than or equal to a predetermined threshold, the last subframe may be released. In an alternative embodiment, responsive to that the number of end symbols is less than or equal to a predetermined threshold, the end symbols may be combined with a subframe immediately prior to the last subframe. In the disclosure, the combination of the end symbols and the subframe immediately prior to the last subframe may be referred as to a “super subframe”. According to embodiments of the present invention, the predetermined threshold may be set as a fixed value, for example, 3 or a value that is changed dynamically. It is to be understood that the above example embodiments are only for the purpose of illustration, without suggesting any limitations on the subject matter described herein. The predetermined threshold may be implemented in any other suitable ways. 
     According to embodiments of the present invention, optionally, if the transmitter performs the method  100 , the transmitter may determine a transport block size based on the number of end symbols and transmit data of the transport block size in the last subframe. Details may be described with reference to  FIG.  2   . 
     According to embodiments of the present invention, optionally, if the receiver performs the method  100 , the receiver may determine a transport block size based on the number of end symbols and receive data of the transport block size in the last subframe. Details may be described with reference to  FIG.  3   . 
     Reference is now made to  FIG.  2   , which illustrates a flow chart of a method  200  for performing fractional subframe transmission at a transmitter according to an embodiment of the invention. The method  200  may be considered as a specific implementation of the method  100  described above with reference to  FIG.  1    and performed by the transmitter. However, it is noted that this is only for the purpose of illustrating the principles of the present invention, rather than limiting the scope thereof 
     Method  200  begins at step S 210 , a symbol of a first subframe at which the channel becomes available is determined. 
     According to embodiments of the present invention, whether a channel is available may be determined in several ways, such as energy detection, carrier sensing, and so on. In some embodiments, strength of energy from a further transmitter may be measured on the channel. The further transmitter may be a transmitter that may use the same channel and is different from the transmitter performing the method according to embodiments of the present invention. If the energy strength is not strong, it may be determined that the channel is idle. In this regard, the energy strength may be compared with a strength threshold. In response to that the measured strength is less than the strength threshold, the channel may be determined as being available. The strength threshold may be a predetermined threshold, which may be set according to system requirements, specifications, channel quality, and so on. According to embodiments of the present invention, the strength threshold may be set as a fixed value or a value that is changed dynamically. It is to be understood that the above example embodiments are only for the purpose of illustration, without suggesting any limitations on the subject matter described herein. The strength threshold may be implemented in any other suitable ways. 
     Alternatively, the channel availability may be detected based on carrier sensing. By way of example, a signalling from a further transmitter may be detected on the channel. The further transmitter may be a transmitter that may use the channel and is different from the transmitter performing the method according to embodiments of the present invention. 
     Based on the signalling, whether the channel is available may be determined. When the transmitter detect a channel becomes available at a symbol, the subframe comprising the symbol may be determined as the first subframe. 
     It is to be noted although the above embodiments illustrate a further transmitter, there may be a plurality of further transmitters in a communication system according to embodiments of the present invention. In such embodiments, energy detection and carrier sensing may be performed with respect to the plurality of further transmitters. 
     At step S 220 , the first temporal information is determined as comprising a potential position immediately prior to the symbol, wherein the potential position is predefined in the first subframe. 
     In an exemplary embodiment, if the symbol determined at step S 210  is symbol 5, and there are three predefined potential positions corresponding to symbols 0, 7 and 11, respectively, the transmitter may determine that the potential position corresponding to symbol 0 is a potential position immediately prior to the current position. As such, at step S 220 , the first temporal information may comprise the potential position corresponding to symbol 0. 
     It is to be noted that, in some alternative embodiments, the first temporal information may be determined as comprising an index of the symbol determined at step S 210 . By way of example, if the symbol determined at step S 210  is symbol 5, the first temporal information may be determined as comprising an index of symbol 5. As can be appreciated by those skilled in the art, the first temporal information may comprise an index of the symbol determined at step S 210 , a potential position immediately prior to the symbol, or any symbol between the symbol determined at step S 210  and the potential position immediately prior to the symbol. The above example embodiments are only for the purpose of illustration, without suggesting any limitations on the subject matter described herein. 
     At step S 230 , the number of symbols used by the fractional subframe transmission is determined based on the transmission opportunity information. 
     In some embodiments, the transmission opportunity information may comprise channel occupancy time. In an exemplary embodiment, the channel occupancy time may be 3.5 ms, for example. For a subframe of 1 ms which includes M symbols, for example M=14, it may be determined that 1 symbol may occupy about 0.071 ms. In view of the length of the channel occupancy time and the symbol, for example, by means of dividing the channel occupancy time by 0.071, the transmitter may determine that the number of symbols used by the fractional subframe transmission as 49. 
     At step S 240 , the number of end symbols is determined based on the first temporal information and the number of symbols used by the fractional subframe transmission, wherein the end symbols are used by the fractional subframe transmission and belong to a last subframe of the fractional subframe transmission. 
     As discussed above, the first temporal information may comprise the potential position immediately prior to the symbol determined at step S 210 . In some embodiments, the last symbol of the fractional subframe transmission may be determined as follows: 
         Se=S 1+ TXOP   (3)
 
     where S1 represents the potential position immediately prior to the symbol determined at step S 210 , Se represents the index of the last symbol, and TXOP represents the channel occupancy time (for example, how many symbols). 
     In an exemplary embodiment, S1 is the first symbol (i.e., symbol 0) of the first subframe and TXOP is 49 symbols. Thus, the last symbol may be determined as the 49th symbol of the fractional subframe transmission. If a subframe comprises M symbols, for example M=14, it may be determined that the fractional subframe transmission occupy 4 subframes, wherein the first three subframes are fully occupied and the first seven symbols (symbol 0 to 6) of the last subframe are occupied. According to embodiments of the present invention, the first seven symbols (symbol 0 to 6) of the last subframe may be determined as ending symbols. Accordingly, at step S 240 , it may be determined that the number of the ending symbols is 7. 
     At step S 250 , a transport block size is determined based on the number of end symbols. 
     The transport block size indicates the size of a data block to be transmitted in the fractional subframe transmission. According to embodiments of the present invention, the transport block size may be determined in various ways. In some embodiments, the end symbols of the last subframe may be considered as available symbols of a fractional subframe. The transmitter may determine a scaling factor associated with the number of the available symbols, and then determine the transport block size based on the scaling factor. The scaling factor may be defined in several ways. Table 1 illustrates an example of scaling factors associated with different numbers of available symbols. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Number of available symbols 
                 Scaling factor 
               
               
                   
                   
               
             
            
               
                   
                 1, 2, 3 
                 N/A 
               
               
                   
                 4 
                 0.25 
               
               
                   
                 5 
                 0.25, 0.375 
               
               
                   
                 6 
                 0.375 
               
               
                   
                 7 
                 0.375, 0.5 
               
               
                   
                 8 
                 0.5, 0.75 
               
               
                   
                 9, 10, 11, 12 
                 0.75 
               
               
                   
                 13, 14 
                 1 
               
               
                   
                   
               
            
           
         
       
     
     In some embodiments, if the number of the available symbols is 1, 2 or 3, the transmitter may use the available symbols to transmit control information of the fractional subframe transmission, and may determine that the available symbols are not enough for transmitting data after the transmission of the control information. In this regard, the scaling factor may be designed as a value of “N/A”, which indicates that the scaling factor is “not available”. In an exemplary embodiment, if the number of the available symbols is 4, the transmitter may determine that the associated scaling factor is 0.25. In an exemplary embodiment, if the number of the available symbols is 5, the transmitter may determine that the associated scaling factor is 0.25 or 0.375. In an exemplary embodiment, if the number of the available symbols is 6, the transmitter may determine that the associated scaling factor is 0.375. In an exemplary embodiment, if the number of the available symbols is 7, the transmitter may determine that the associated scaling factor is 0.375 or 0.5. In an exemplary embodiment, if the number of the available symbols is 8, the transmitter may determine that the associated scaling factor is 0.5 or 0.75. In an exemplary embodiment, if the number of the available symbols is 9, 10, 11 or 12, the transmitter may determine that the associated scaling factor is 0.75. In an exemplary embodiment, if the number of the available symbols is 13 or 14, the transmitter may determine that the associated scaling factor is 1. 
     In some embodiments, the transport block size may be determined based on the scaling factor in several ways. By way of example, a first resource block number which indicates a number of resource blocks allocated for transmission may be obtained. For the transmitter, the first resource block number may be determined by the transmitter in real time. Then, a second resource block number may be determined based on the first resource block number and the scaling factor. In an exemplary embodiment, the second resource block number may be determined as follows: 
         N   PRB =max{└ N′   PRB ×Factor┘,1}  (4)
 
     wherein N′ PRB  represents the first resource block number, N PRB  represents the second resource block number, Factor represents the scaling factor. 
     Based on the second resource block number, the transport block size may be determined. In some embodiments, a transport block size table may be used for determining the transport block size. Table 2 illustrates an exemplary transport block size table. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 MCS 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 0 
                 16 
                 32 
                 56 
                 88 
                 120 
                 152 
                 176 
                 208 
                 224 
                 256 
               
               
                 1 
                 24 
                 56 
                 88 
                 144 
                 176 
                 208 
                 224 
                 256 
                 328 
                 344 
               
               
                 2 
                 32 
                 72 
                 144 
                 176 
                 208 
                 256 
                 296 
                 328 
                 376 
                 424 
               
               
                 3 
                 40 
                 104 
                 176 
                 208 
                 256 
                 328 
                 392 
                 440 
                 504 
                 568 
               
               
                 4 
                 56 
                 120 
                 208 
                 256 
                 328 
                 408 
                 488 
                 552 
                 632 
                 696 
               
               
                 5 
                 72 
                 144 
                 224 
                 328 
                 424 
                 504 
                 600 
                 680 
                 776 
                 872 
               
               
                 6 
                 328 
                 176 
                 256 
                 392 
                 504 
                 600 
                 712 
                 808 
                 936 
                 1032 
               
               
                 7 
                 104 
                 224 
                 328 
                 472 
                 584 
                 712 
                 840 
                 968 
                 1096 
                 1224 
               
               
                 8 
                 120 
                 256 
                 392 
                 536 
                 680 
                 808 
                 968 
                 1096 
                 1256 
                 1384 
               
               
                 9 
                 136 
                 296 
                 456 
                 616 
                 776 
                 936 
                 1096 
                 1256 
                 1416 
                 1544 
               
               
                 10 
                 144 
                 328 
                 504 
                 680 
                 872 
                 1032 
                 1224 
                 1384 
                 1544 
                 1736 
               
               
                 11 
                 176 
                 376 
                 584 
                 776 
                 1000 
                 1192 
                 1384 
                 1608 
                 1800 
                 2024 
               
               
                 12 
                 208 
                 440 
                 680 
                 904 
                 1128 
                 1352 
                 1608 
                 1800 
                 2024 
                 2280 
               
               
                 13 
                 224 
                 488 
                 744 
                 1000 
                 1256 
                 1544 
                 1800 
                 2024 
                 2280 
                 2536 
               
               
                 14 
                 256 
                 552 
                 840 
                 1128 
                 1416 
                 1736 
                 1992 
                 2280 
                 2600 
                 2856 
               
               
                 15 
                 280 
                 600 
                 904 
                 1224 
                 1544 
                 1800 
                 2152 
                 2472 
                 2728 
                 3112 
               
               
                 16 
                 328 
                 632 
                 968 
                 1288 
                 4608 
                 1928 
                 2280 
                 2600 
                 2984 
                 3240 
               
               
                 17 
                 336 
                 696 
                 1064 
                 1416 
                 1800 
                 2152 
                 2536 
                 2856 
                 3240 
                 3624 
               
               
                 18 
                 376 
                 776 
                 1160 
                 1544 
                 1992 
                 2344 
                 2792 
                 3112 
                 3624 
                 4008 
               
               
                 19 
                 408 
                 840 
                 1288 
                 1736 
                 2152 
                 2600 
                 2984 
                 3496 
                 3880 
                 4264 
               
               
                 20 
                 440 
                 904 
                 1384 
                 1864 
                 2344 
                 2792 
                 3240 
                 3752 
                 4136 
                 4584 
               
               
                 21 
                 488 
                 1000 
                 1480 
                 1992 
                 2472 
                 2984 
                 2496 
                 4008 
                 4584 
                 4968 
               
               
                 22 
                 520 
                 1064 
                 1608 
                 2152 
                 2664 
                 3240 
                 3752 
                 4264 
                 4776 
                 5352 
               
               
                 23 
                 552 
                 1128 
                 1736 
                 2280 
                 2856 
                 3496 
                 4008 
                 4584 
                 5160 
                 5736 
               
               
                 24 
                 584 
                 1192 
                 1800 
                 2408 
                 2984 
                 3624 
                 4264 
                 4968 
                 5544 
                 5992 
               
               
                 25 
                 616 
                 1256 
                 1864 
                 2536 
                 3112 
                 3752 
                 4392 
                 5160 
                 5736 
                 6200 
               
               
                 26 
                 712 
                 1480 
                 2216 
                 2984 
                 3752 
                 4392 
                 5160 
                 5992 
                 6712 
                 7480 
               
               
                   
               
            
           
         
       
     
     The horizontal direction of Table 2 may correspond to a resource block number, for example, the second resource block number in the embodiments, and the vertical direction may correspond to a Modulation and Coding Scheme (MCS). In the embodiments, when the transmitter determines the second resource block number as well as the MCS that is employed currently, it may determine the transport block size by looking up the Table 2 based on the second resource block number and the MCS. By way of example, if the second resource block number is 8, and the MCS is 8 the transport block size may be determined as 1096. 
     It is to be noted that although the dimension of Table 2 is 10×27, it is simplification of 3GPP TS36.213 whose dimension is 34×110. It is further to be noted that the above example table is only for the purpose of illustration, without suggesting any limitations on the subject matter described herein. Any other suitable table may be used in the determination of the transport block size. 
     At step S 260 , data of the transport block size is transmitted in the last subframe. 
     In some embodiments, the transmitter may transmit other possible information, such as Reference Signal (RS), Primary Synchronous Signal (PSS), Secondary Synchronous Signal (SSS), and so on in data region of the factional subframe transmission, for example, Physical Downlink Shared Channel (PDSCH), if necessary. 
     Reference is now made to  FIG.  3   , which illustrates a flow chart of a method  300  for performing fractional subframe transmission at a receiver according to an embodiment of the invention. The method  300  may be considered as a specific implementation of the method  100  described above with reference to  FIG.  1    and performed by the receiver. However, it is noted that this is only for the purpose of illustrating the principles of the present invention, rather than limiting the scope thereof 
     Method  300  begins at step S 310 , a symbol of a first subframe at which the channel becomes available is determined. 
     In some embodiments, the transmitter may notify the receiver the first temporal information, for example, the index of the symbol of the first subframe at which a channel becomes available. In an exemplary embodiment, the transmitter may send an indicator regarding the first temporal information to the receiver. In this way, the index of the symbol of the first subframe may be indicated explicitly. Thus, at step S 310 , the receiver may determine the symbol of the first subframe by detecting the indicator. In an alternative embodiment, the transmitter may not send the indicator, and the receiver may make blind decoding for control information of the fractional subframe transmission at a potential position. In response to that the blind decoding is success, the receiver may determine the symbol of a first subframe at which the channel becomes available. 
     At step S 320 , the first temporal information is determined as comprising a potential position immediately prior to the symbol, wherein the potential position is predefined in the first subframe. 
     In an exemplary embodiment, if the symbol determined at step S 320  is symbol 5, and there are three predefined potential positions corresponding to symbols 0, 7 and 11, respectively, the receiver may determine the potential position corresponding to symbol 0 is a potential position immediately prior to the current position. As such, at step S 320 , the first temporal information may comprise the potential position corresponding to symbol 0. 
     It is to be noted that, in some alternative embodiments, the first temporal information may be determined as comprising an index of the symbol determined at step S 320 . By way of example, if the symbol determined at step S 320  is symbol 5, the first temporal information may be determined as comprising an index of symbol 5. As can be appreciated by those skilled in the art, the first temporal information may comprise an index of the symbol determined at step S 320 , a potential position immediately prior to the symbol, or any symbol between the symbol determined at step S 320  and the potential position immediately prior to the symbol. The above example embodiments are only for the purpose of illustration, without suggesting any limitations on the subject matter described herein. 
     At step S 330 , the number of symbols used by the fractional subframe transmission is determined based on the transmission opportunity information. 
     In some embodiments, the transmission opportunity information may comprise channel occupancy time. In an exemplary embodiment, the channel occupancy time may be 3.5 ms, for example. For a subframe of 1 ms which includes M symbols, for example M=14, it may be determined that 1 symbol may occupy about 0.071 ms. In view of the length of the channel occupancy time and the symbol, for example, by means of dividing the channel occupancy time by 0.071, the receiver may determine that the number of symbols used by the fractional subframe transmission as 49. 
     At step S 340 , the number of end symbols is determined based on the first temporal information and the number of symbols used by the fractional subframe transmission, wherein the end symbols are used by the fractional subframe transmission and belong to a last subframe of the fractional subframe transmission. 
     As discussed above, the first temporal information may comprise the potential position immediately prior to the symbol determined at step S 310 . In some embodiments, the receiver may determine the last symbol of the fractional subframe transmission according to equation (3), for example. 
     At step S 350 , a transport block size is determined based on the number of end symbols. 
     The transport block size indicates the size of a data block to be transmitted in the fractional subframe transmission. According to embodiments of the present invention, the transport block size may be determined in various ways. In some embodiments, the end symbols of the last subframe may be considered as available symbols of a fractional subframe. The receiver may determine a scaling factor associated with the number of the available symbols, and then determine the transport block size based on the scaling factor. The scaling factor may be defined in several ways. As discussed above, Table 1 illustrates an example of scaling factors associated with different numbers of available symbols. 
     In an exemplary embodiment, if the number of the available symbols is 4, the receiver may determine that the associated scaling factor is 0.25. In an exemplary embodiment, if the number of the available symbols is 5, the receiver may determine that the associated scaling factor is 0.25 or 0.375. In an exemplary embodiment, if the number of the available symbols is 6, the receiver may determine that the associated scaling factor is 0.375. In an exemplary embodiment, if the number of the available symbols is 7, the receiver may determine that the associated scaling factor is 0.375 or 0.5. In an exemplary embodiment, if the number of the available symbols is 8, the receiver may determine that the associated scaling factor is 0.5 or 0.75. In an exemplary embodiment, if the number of the available symbols is 9, 10, 11 or 12, the receiver may determine that the associated scaling factor is 0.75. In an exemplary embodiment, if the number of the available symbols is 13 or 14, the receiver may determine that the associated scaling factor is 1. 
     In some embodiments, the transport block size may be determined based on the scaling factor in several ways. By way of example, a first resource block number which indicates a number of resource blocks allocated for transmission may be obtained. For the receiver, the first resource block number may be notified by the transmitter. Then, a second resource block number may be determined based on the first resource block number and the scaling factor. In an exemplary embodiment, the second resource block number may be determined according to equation (4). Based on the second resource block number, the transport block size may be determined. In some embodiments, a transport block size table, for example Table 2, may be used for determining the transport block size. In particular, if the receiver determines the second resource block number as well as the MCS which is employed currently, it may determine the transport block size by looking up the Table 2. 
     At step S 360 , data of the transport block size is received in the last subframe. 
     In some embodiments, the receiver may receive other possible information, such as Reference Signal (RS), Primary Synchronous Signal (PSS), Secondary Synchronous Signal (SSS), and so on in data region of the factional subframe transmission, for example, Physical Downlink Shared Channel (PDSCH), if necessary. 
       FIG.  4    illustrates a schematic diagram  400  of fractional subframe transmission according to embodiments of the invention.  FIG.  4    exemplarily shows four subframes, subframes  0  to  3 . With respect to subframe  0 , there are three potential positions  421 ,  422  and  423 , wherein the first potential position  421  corresponds to the start of subframe  0 , for example, symbol 0 of subframe  0 . CCA/eCCA  401  may start from the first potential position  421 . During the CCA/eCCA  401 , the transmitter may determine that the channel is available at a position  424 . Since the position  424  is not a potential position, the transmitter may transmit channel occupation signals from the position  424  until a potential position, for example, the potential position  422 , and determine the potential position  422  as the target position. The factional subframe transmission then may start from the target position, wherein control information may be transmitted on Physical Downlink Control Channel (PDCCH) at time periods  403 ,  405 ,  407  and  409 , and data may be transmitted on PDSCH at time periods  404 ,  406 ,  408  and  410 . As shown, the factional subframe transmission ends at a position  425 . 
     As shown in  FIG.  4   , the symbol of a first subframe at which the channel becomes available may be determined as a symbol corresponding to the position  424 . Since the potential position immediately prior to the determined symbol is the potential position  421 , it may be determined that the channel occupation time starts at the potential position  421 . Assuming the transmission opportunity information comprises TXOP of 3.5 ms, it may be determined that the number of symbols used by the fractional subframe transmission is 49. As illustrated by  FIG.  5   , the TXOP corresponds to a time period from the position  421  to the position  425 , and the actual channel occupation time is from the position  424  to the position  425 . Thus, a time period from the position  421  to the position  424  is not occupied. Then, based on the potential position  421  and the number of symbols used by the fractional subframe transmission, the end symbols may be determined as the first seven symbols of subframe  3 , and the number of the end symbols is 7. In this way, the end of the fractional subframe transmission can be estimated. 
     According to embodiments of the present invention, optionally, the method  200  or  300  may further comprise a step of comparing the number of end symbols with a predetermined threshold. Responsive to that the number of end symbols is less than or equal to a predetermined threshold, the last subframe may be released. In an alternative embodiment, responsive to that the number of end symbols is less than or equal to a predetermined threshold, the end symbols may be combined with a subframe immediately prior to the last subframe as a super subframe. The super subframe is exemplarily shown in  FIG.  5   , which illustrates a schematic diagram  500  of fractional subframe transmission according to embodiments of the invention. As shown in  FIG.  5   , there are four subframes, subframe  0  to  3 . Since the number of end symbols of the last subframe (subframe  3 ) is less than the predetermined threshold, for example, 3, the end symbols may be combined with subframe  2  as a super subframe. As shown, the super subframe may correspond to a time period from the start of subframe  2   501  to the last one of the end symbols  502 . 
       FIG.  7    illustrates a block diagram of an apparatus  710  of a transmitter and an apparatus  720  of a receiver for performing fractional subframe transmission according to embodiments of the invention. As shown in  FIG.  7   , the apparatus  710  may transmit data in a fractional subframe to the apparatus  720 . According to embodiments of the present invention, the apparatus  710  may be implemented in the transmitter or may be coupled with the transmitter in any suitable way. Similarly, the apparatus  720  may be implemented in the receiver or may be coupled with the receiver in any suitable way. 
     As shown, the apparatus  710  comprises: a first determining unit  711  configured to determine first temporal information that indicates when a channel becomes available; 
     and a second determining unit  712  configured to determine, based on the first temporal information and transmission opportunity information, second temporal information that indicates an end of the fractional subframe transmission. 
     According to embodiments of the present invention, the first determining unit  711  may comprise: a first symbol determining unit configured to determine a symbol of a first subframe at which the channel becomes available; and a first information determining unit configured to determine determining the first temporal information as comprising an index of the symbol. 
     According to embodiments of the present invention, the first determining unit  711  may comprise: a second symbol determining unit configured to determine a symbol of a first subframe at which the channel becomes available; and a second information determining unit configured to determine the first temporal information as comprising a potential position immediately prior to the symbol, wherein the potential position is predefined in the first subframe. 
     According to embodiments of the present invention, the second determining unit  712  may comprise: a first number determining unit configured to determine a number of symbols used by the fractional subframe transmission based on the transmission opportunity information; and a second number determining unit configured to determine a number of end symbols based on the first temporal information and the number of symbols used by the fractional subframe transmission, wherein the end symbols are used by the fractional subframe transmission and belong to a last subframe of the fractional subframe transmission. 
     According to embodiments of the present invention, the apparatus  710  may further comprise a comparing unit configured to compare the number of end symbols with a predetermined threshold; and a processing unit configured to, responsive to that the number of end symbols is less than or equal to a predetermined threshold, release the last subframe, or combine the end symbols with a subframe immediately prior to the last subframe. 
     According to embodiments of the present invention, the apparatus  710  may further comprise a first size determining unit configured to determine a transport block size based on the number of end symbols; and a transmitting unit configured to transmit data of the transport block size in the last subframe. 
     According to embodiments of the present invention, the first determining unit  711  may comprise: a first subframe determining unit configured to determine a first subframe at which the channel becomes available; and a third information determining unit configured to determine the first temporal information as comprising an index of the first subframe. 
     According to embodiments of the present invention, the second determining unit  712  may comprise: a last subframe determining unit configured to determine, based on the first temporal information and transmission opportunity information, an index of a last subframe used by the fractional subframe transmission. 
     As shown, the apparatus  720  comprises: a first determining unit  721  configured to determine first temporal information that indicates when a channel becomes available; and a second determining unit  722  configured to determine, based on the first temporal information and transmission opportunity information, second temporal information that indicates an end of the fractional subframe transmission. 
     According to embodiments of the present invention, the first determining unit  721  may comprise: a first symbol determining unit configured to determine a symbol of a first subframe at which the channel becomes available; and a first information determining unit configured to determine determining the first temporal information as comprising an index of the symbol. 
     According to embodiments of the present invention, the first determining unit  721  may comprise: a second symbol determining unit configured to determine a symbol of a first subframe at which the channel becomes available; and a second information determining unit configured to determine the first temporal information as comprising a potential position immediately prior to the symbol, wherein the potential position is predefined in the first subframe. 
     According to embodiments of the present invention, the second determining unit  722  may comprise: a first number determining unit configured to determine a number of symbols used by the fractional subframe transmission based on the transmission opportunity information; and a second number determining unit configured to determine a number of end symbols based on the first temporal information and the number of symbols used by the fractional subframe transmission, wherein the end symbols are used by the fractional subframe transmission and belong to a last subframe of the fractional subframe transmission. 
     According to embodiments of the present invention, the apparatus  720  may further comprise a comparing unit configured to compare the number of end symbols with a predetermined threshold; and a processing unit configured to, responsive to that the number of end symbols is less than or equal to a predetermined threshold, release the last subframe, or combine the end symbols with a subframe immediately prior to the last subframe. 
     According to embodiments of the present invention, the apparatus  720  may further comprise a first size determining unit configured to determine a transport block size based on the number of end symbols; and a receiving unit configured to receive data of the transport block size in the last subframe. 
     According to embodiments of the present invention, the first determining unit  721  may comprise: a first subframe determining unit configured to determine a first subframe at which the channel becomes available; and a third information determining unit configured to determine the first temporal information as comprising an index of the first subframe. 
     According to embodiments of the present invention, the second determining unit  722  may comprise: a last subframe determining unit configured to determine, based on the first temporal information and transmission opportunity information, an index of a last subframe used by the fractional subframe transmission. 
     It is also to be noted that the apparatuses  710  and  720  may be respectively implemented by any suitable technique either known at present or developed in the future. Further, a single device shown in  FIG.  7    may be alternatively implemented in multiple devices separately, and multiple separated devices may be implemented in a single device. The scope of the present invention is not limited in these regards. 
     It is noted that the apparatus  710  may be configured to implement functionalities as described with reference to  FIGS.  1  and  2   , and the apparatus  720  may be configured to implement functionalities as described with reference to  FIG.  1  or  3   . Therefore, the features discussed with respect to the method  100  or  200  may apply to the corresponding components of the apparatus  710 , and the features discussed with respect to the method  100  or  300  may apply to the corresponding components of the apparatus  720 . It is further noted that the components of the apparatus  710  or the apparatus  720  may be embodied in hardware, software, firmware, and/or any combination thereof. For example, the components of the apparatus  710  or the apparatus  720  may be respectively implemented by a circuit, a processor or any other appropriate device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation. 
     In some embodiment of the present disclosure, the apparatus  710  or the apparatus  720  may comprise at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus  710  or the apparatus  720  may further comprise at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compliable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus  710  to at least perform according to the method  100  or  200  as discussed above, or to cause the apparatus  720  to at least perform according to the method  100  or  300  as discussed above. 
     Based on the above description, the skilled in the art would appreciate that the present disclosure may be embodied in an apparatus, a method, or a computer program product. In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. 
     The various blocks shown in  FIGS.  1 - 3    may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). At least some aspects of the exemplary embodiments of the disclosures may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, FPGA or ASIC that is configurable to operate in accordance with the exemplary embodiments of the present disclosure. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     Various modifications, adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. 
     Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. 
     Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purpose of limitation.