TBS determination with multiple base graphs

A method implemented by a wireless device operable in a cellular communications network, the method comprising:

• determining a Transport Block Size (TBS) for a transport block communicated between a network node and the wireless device via a physical downlink shared channel (PDSCH) 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, wherein the formula is based on a number of code blocks C, an approximation of the TBS, and a number of CRC bits attached to each transport block of the PDSCH transmission, and the formula for determining the TBS is X·Y−Z, wherein:
• X is a value that is a function of C;
• Y is a value resulting from rounding a ratio Ynum/Ydenom to a nearest integer, where Ynum 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 Ydenom=X;
• and
• Z is the number of CRC bits attached to each transport block of the PDSCH transmission;
• and
• receiving the transport block according to the determined TBS.

A wireless device operable in a cellular communications network, wireless device comprising:

• a transmitting and a receiver in communication with a processing device, wherein the processing device is configured to:
• determine a Transport Block Size (TBS) for a transport block communicated between a network node and the wireless device via a physical downlink shared channel (PDSCH) transmission using a formula such that code block segmentation of the transport block results in equal sized code blocks of a first size for a first Low-Density Parity Code (LDPC) base graph and in equal size codes blocks of a second size for a second LDPC base graph, wherein the first size and the second size are different, and wherein the formula for TBS is X·Y−Z, wherein:
• X is a value that is a function of the number of code blocks C;
• Y is a value resulting from rounding a ratio Ynum/Ydenom, where Ynum is the sum of an approximation of the TBS and a number of CRC bits attached to each transport block of the PDSCH transmission and Ydenom=X;
• and
• Z is the number of CRC bits attached to each transport block of the PDSCH transmission;
• and
• receive or receive the transport block according to the determined TBS.