Tbs determination with multiple base graphs

Abstract

Systems and methods are disclosed herein for determining and using a Transport Block Size (TBS) when two or more Low Density Parity Check (LDPC) base graphs can be used for LPDC coding. In some embodiments, a method comprises determining an approximate TBS for a transport block communicated between a network node and a wireless device via a physical channel transmission, determining a TBS for the transport block based on a smallest entry in a table that is larger than or equal to the approximate TBS, and transmitting or receiving the transport block according to the determined TBS.

1 . A method, comprising:
 determining a Transport Block Size, TBS, for a transport block communicated between a network node and a wireless device via a physical channel transmission using a formula such that code block segmentation of the transport block results in equal sized code blocks independent of which of two different Low-Density Parity Code, LDPC, base graphs is used for the code block segmentation; and   transmitting or receiving the transport block according to the determined TBS.   
     
     
         2 . The method of  claim 1 , wherein determining the TBS comprises:
 determining that a target code rate R for the physical channel transmission is less than or equal to ¼; and   upon determining that R is less than or equal to ¼:
 determining a number of code blocks C for the physical channel transmission based on an approximation of the TBS, a number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the physical channel transmission, and a number of CRC bits, if any, attached to each code block of the physical channel transmission when using a first base graph for the code block segmentation; and 
 determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         3 . The method of  claim 2  wherein determining the number of code blocks C comprises rounding up a ratio A/B to a nearest integer, wherein A is a sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and B is a difference of a maximum code block size for the first base graph and the number of CRC bits, if any, attached to each code block of the physical channel transmission. 
     
     
         4 . The method of  claim 3 , wherein determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission comprises:
 determining the TBS as X·Y−Z, wherein:
 X is a value that is a function of C; 
 Y is a value resulting from rounding a ratio Y_num/Y_denom to a nearest integer, where Y_num is the sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and Y_denom=X; and 
 Z is the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         5 . The method of  claim 4  wherein X=C·8. 
     
     
         6 . The method of  claim 4  wherein X is equal to a least common multiple of C and 8. 
     
     
         7 . The method of any of  claims 2 - 6 , wherein both the number of CRC bits attached to each transport block of the physical channel transmission and the number of CRC bits, if any, attached to each code block of the physical channel transmission are equal to 24. 
     
     
         8 . The method of  claim 1  wherein determining the TBS comprises:
 determining that a target code rate R for the physical channel transmission is greater than ¼;
 determining that an approximation of the TBS is greater than a threshold; and upon determining that R is greater than ¼ and determining that the approximation of the TBS is greater than the threshold: 
 determining a number of code blocks C for the physical channel transmission based on an approximation of the TBS, a number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the physical channel transmission, and a number of CRC bits, if any, attached to each code block of the physical channel transmission when using a first base graph for code block segmentation; and 
 determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission. 
 
 
     
     
         9 . The method of  claim 8 , wherein determining the number of code blocks C comprises:
 determining the number of code blocks C by rounding up a ratio A/B to a nearest integer;   wherein A is a sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and B is a difference of a maximum code block size for the first base graph and the number of CRC bits, if any, attached to each code block of the physical channel transmission.   
     
     
         10 . The method of  claim 9 , wherein determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission comprises:
 determining the TBS as X·Y−Z, wherein:
 X is a value that is a function of C; 
 Y is a value resulting from rounding a ratio Y_num/Y_denom to a nearest integer, where Y_num is the sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and Y_denom=X; and 
 Z is the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         11 . The method of  claim 10  wherein X=C·8. 
     
     
         12 . The method of  claim 10  wherein X is equal to the least common multiple of C and 8. 
     
     
         13 . The method of any of  claims 8 - 12  wherein both the number of CRC bits attached to each transport block of the physical channel transmission and the number of CRC bits, if any, attached to each code block of the physical channel transmission are equal to 24. 
     
     
         14 . The method of any of  claims 1 - 13 , wherein the TBS is determined using the formula, as a consequence determining that an approximation of the TBS is greater than a predetermined value, and wherein another TBS for another transport block communicated between the network node and the wireless device via another physical channel transmission is determined using a table, as a consequence of determining that an approximation for the another TBS is less than or equal to the predetermined value. 
     
     
         15 . The method of  claim 14 , wherein all consecutive entries k l  and k l+1  in the table have values such that 
       
         
           
             
               
                 k 
                 l 
               
               
                 k 
                 
                   l 
                   + 
                   1 
                 
               
             
           
         
       
       is less than or equal to a predetermined value. 
     
     
         16 . The method of  claim 14 , wherein all entries (k) in the table satisfy the following conditions: k is a multiple of 8, 
       
         
           
             
               
                 
                   
                     ( 
                     
                       k 
                       + 
                       
                         M 
                         0 
                       
                     
                     ) 
                   
                   ⁢ 
                   mod 
                   ⁢ 
                   
                     ⌈ 
                     
                       
                         k 
                         + 
                         
                           M 
                           0 
                         
                       
                       
                         
                           Z 
                           1 
                         
                         - 
                         
                           M 
                           1 
                         
                       
                     
                     ⌉ 
                   
                 
                 = 
                 0 
               
               , 
               
                 
                   and 
                   ⁢ 
                       
                   
                     ( 
                     
                       k 
                       + 
                       
                         M 
                         2 
                       
                     
                     ) 
                   
                   ⁢ 
                   mod 
                   ⁢ 
                   
                     ⌈ 
                     
                       
                         k 
                         + 
                         
                           M 
                           2 
                         
                       
                       
                         
                           Z 
                           2 
                         
                         - 
                         
                           M 
                           3 
                         
                       
                     
                     ⌉ 
                   
                 
                 = 
                 0 
               
               , 
             
           
         
       
       where M 0  is the number of CRC bits attached to the transport block if the first basegraph is used, Z 1  is a predetermined maximum TBS for a first one of the two different base graphs, M 1  is a number of CRC bits attached to each code block after segmentation if a number of code blocks is greater than 1 and the first basegraph is used, M 2  is a number of CRC bits attached to the transport block if the second basegraph is used, Z 2  is is a maximum TBS for a second one of the two different base graphs, and M 3  is a number of CRC bits attached to each code block after segmentation if the number of code blocks is greater than 1 and the second basegraph is used. 
     
     
         17 . A method, comprising:
 determining a Transport Block Size, TBS, for a transport block communicated between a network node and a wireless device via a physical channel transmission; and
 performing code block segmentation on the transport block according to the determined TB S, wherein performing the code block segmentation comprises selectively inserting filler bits into code blocks to achieve equal sized code blocks based on whether the code block segmentation is performed with a first Low-Density Parity Code, LDPC, base graph or a second LDPC base graph; and 
 transmitting or receiving the transport block according to the TBS. 
   
     
     
         18 . The method of  claim 17  wherein determining the TBS comprises determining the TBS in accordance with any one of  claims 1  to  14 . 
     
     
         19 . The method of  claim 17 , wherein selectively inserting the filler bits comprises inserting the filler bits during code block segmentation when a code rate for the physical channel transmission is greater than ¼. 
     
     
         20 . The method of  claim 17 , wherein the TBS is determined by the wireless device based on Downlink Control Information, DCI, received from the network node, and the transport block is received by the wireless device from the network node according to the determined TBS. 
     
     
         21 . The method of  claim 17 , wherein the TBS is determined by the wireless device based on Downlink Control Information, DCI, received from the network node, and the transport block is transmitted from the wireless device to the network node according to the determined TBS. 
     
     
         22 . The method of  claim 17 , wherein the TBS is determined by the network node, and the transport block is transmitted by the network node to the wireless device. 
     
     
         23 . A method comprising:
 determining an approximate Transport Block Size (TBS) for a transport block communicated between a network node and a wireless device via a physical channel transmission;   determining a TBS for the transport block based on a smallest entry in a table that is larger than or equal to the approximate TBS; and   transmitting or receiving the transport block according to the determined TBS.   
     
     
         24 . The method of  claim 23 , wherein all entries in the table are multiples of eight. 
     
     
         25 . A radio node in a cellular communications network, the radio node adapted to perform the method of any one of  claims 1 - 24 . 
     
     
         26 . The radio node of  claim 25  wherein the radio node is a base station. 
     
     
         27 . The radio node of  claim 26  wherein the radio node is a User Equipment, UE. 
     
     
         28 . A radio node in a cellular communications network, comprising:
 an interface operable to wirelessly transmit signals to and/or wirelessly receive signals from another node in the cellular communications network; and   processing circuitry associated with the interface, the processing circuitry operable to:
 determining a Transport Block Size (TBS) for a transport block communicated between a network node and a wireless device via a physical channel transmission using a formula such that code block segmentation of the transport block results in equal sized code blocks independent of which of two different Low-Density Parity Code (LDPC) base graphs is used for the code block segmentation; and 
 transmitting or receiving the transport block according to the determined TBS. 
   
     
     
         29 . The radio node of  claim 28  wherein the radio node is a base station. 
     
     
         30 . The radio node of  claim 28  wherein the radio node is a User Equipment, UE. 
     
     
         31 . The method of  claim 23 , wherein the method is performed by a wireless device. 
     
     
         32 . The method of  claim 23 , wherein the method is performed by a network node. 
     
     
         33 . The method of  claim 23 , wherein all entries in the table give rise to equal size code blocks when code block segmentation is performed with a first base graph having a first predetermined maximum code block size after attachment of transport block level and code block level Cyclic Redundancy Code (CRC) bits. 
     
     
         34 . The method of  claim 23 , wherein and all entries in the table give rise to equal size code blocks when code block segmentation is performed with a second base graph having a second predetermined maximum code block size after attachment of transport block level and code block level CRC bits. 
     
     
         35 . The method of  claim 23 , wherein determining the TBS comprises:
 determining that a target code rate R for the physical channel transmission is less than or equal to ¼; and   upon determining that R is less than or equal to ¼:
 determining a number of code blocks C for the physical channel transmission based on an approximation of the TBS, a number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the physical channel transmission, and a number of CRC bits, if any, attached to each code block of the physical channel transmission when using a first base graph for the code block segmentation; and 
 determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         36 . The method of  claim 35 , wherein determining the number of code blocks C comprises rounding up a ratio A/B to a nearest integer, wherein A is a sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and B is a difference of a maximum code block size for the first base graph and the number of CRC bits, if any, attached to each code block of the physical channel transmission. 
     
     
         37 . The method of  claim 36 , wherein determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission comprises:
 determining the TBS as X·Y−Z, wherein:
 X is a value that is a function of C; 
 Y is a value resulting from rounding a ratio Y_num/Y_denom to a nearest integer, where Y_num is the sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and Y_denom=X; and 
 Z is the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         38 . The method of  claim 37 , wherein X=C·8. 
     
     
         39 . The method of  claim 37 , wherein X is equal to a least common multiple of C and 8. 
     
     
         40 . The method of any of  claim 35 , wherein both the number of CRC bits attached to each transport block of the physical channel transmission and the number of CRC bits, if any, attached to each code block of the physical channel transmission are equal to 24. 
     
     
         41 . The method of  claim 23 , wherein determining the TBS comprises:
 determining that a target code rate R for the physical channel transmission is greater than ¼;
 determining that an approximation of the TBS is greater than a threshold; and upon determining that R is greater than ¼ and determining that the approximation of the TBS is greater than the threshold: 
 determining a number of code blocks C for the physical channel transmission based on an approximation of the TBS, a number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the physical channel transmission, and a number of CRC bits, if any, attached to each code block of the physical channel transmission when using a first base graph for code block segmentation; and 
 determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         42 . The method of  claim 41 , wherein determining the number of code blocks C comprises:
 determining the number of code blocks C by rounding up a ratio A/B to a nearest integer;   wherein A is a sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and B is a difference of a maximum code block size for the first base graph and the number of CRC bits, if any, attached to each code block of the physical channel transmission.   
     
     
         43 . The method of  claim 42 , wherein determining the TBS for the physical channel transmission based on the number of code blocks C, the approximation of the TBS, and the number of CRC bits attached to each transport block of the physical channel transmission comprises:
 determining the TBS as X·Y−Z, wherein:
 X is a value that is a function of C; 
 Y is a value resulting from rounding a ratio Y_num/Y_denom to a nearest integer, where Y_num is the sum of the approximation of the TBS and the number of CRC bits attached to each transport block of the physical channel transmission and Y_denom=X; and 
 Z is the number of CRC bits attached to each transport block of the physical channel transmission. 
   
     
     
         44 . The method of  claim 43 , wherein X=C·8. 
     
     
         45 . The method of  claim 43 , wherein X is equal to the least common multiple of C and 8. 
     
     
         46 . The method of any of  claim 41  wherein both the number of CRC bits attached to each transport block of the physical channel transmission and the number of CRC bits, if any, attached to each code block of the physical channel transmission are equal to 24.