# US 11,451,333 B2 · TBS determination with multiple base graphs

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- Number: US 11,451,333 B2
- Document ID: US11451333B2
- Status: Granted
- Kind: B2
- Application number: 16/082,875
- Filed: 2018-05-10
- Published: 2021-06-17
- Granted: 2022-09-20
- Earliest claimed: 2017-10-03
- Assignees: Telefonaktiebolaget L M Ericsson (publ)
- Applicants: Telefonaktiebolaget L M Ericsson (Publ)
- Inventors: Mattias Andersson; Yufei Blankenship; Sara Sandberg
- Web page: https://patentgrep.com/patent/US11451333B2

## CPC

- H04L 1/0058: {Block-coded modulation}
- H04L 1/0083: {Formatting with frames or packets; Protocol or part of protocol for error control}
- H04L 1/0004: {applied to control information}
- H04L 1/0057: {Block codes (H04L1/0061, H04L1/0064 take precedence)}
- H04L 1/0061: {Error detection codes}
- H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## 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 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 LDPC base graphs is used for the code block segmentation. The method further comprises transmitting or receiving the transport block according to the determined TBS.

## Claims

### Claim 1

A method implemented by a wireless device operable in a cellular communications network, the method comprising:
determining, by processing circuitry of the wireless device, 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 a number of code blocks C;
Y is a value resulting from rounding a ratio Ynum/Ydenom, where Ynum is a sum of an approximation of the TBS and a number of Cyclic Redundancy Check (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
receiving, by the processing circuitry of the wireless device, the transport block according to the determined TBS.

### Claim 2 (depends on 1)

The method of claim 1, wherein the formula is based on a target code rate R for the PDSCH transmission determining the TBS comprises:
determining that a target code rate R for the PDSCH transmission is less than or equal to ¼; and
upon determining that R is less than or equal to ¼:
determining the number of code blocks C for the PDSCH transmission based on the approximation of the TBS, the number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the PDSCH transmission, and a number of CRC bits, if any, attached to each code block of the PDSCH transmission when using the first LDPC base graph for the code block segmentation; and
determining the TBS for the PDSCH 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 PDSCH transmission.

### Claim 3 (depends on 2)

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 PDSCH transmission and B is a difference of a maximum code block size for the first LDPC base graph and the number of CRC bits, if any, attached to each code block of the physical channel transmission.

### Claim 4 (depends on 2)

The method of claim 2, wherein both the number of CRC bits attached to each transport block of the PDSCH transmission and the number of CRC bits, if any, attached to each code block of the physical channel transmission are equal to 24.

### Claim 5 (depends on 1)

The method of claim 1, wherein X is equal to a least common multiple of C and 8.

### Claim 6 (depends on 1)

The method of claim 1 wherein determining the TBS comprises:
determining that a target code rate R for the PDSCH 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 PDSCH transmission based on an approximation of the TBS, a number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the PDSCH transmission, and a number of CRC bits, if any, attached to each code block of the PDSCH transmission when using a first base graph for code block segmentation; and
determining the TBS for the PDSCH 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 PDSCH transmission.

### Claim 7 (depends on 6)

The method of claim 6, 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 PDSCH 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 PDSCH transmission.

### Claim 8 (depends on 6)

The method of claim 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.

### Claim 9 (depends on 1)

The method of claim 1, 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.

### Claim 10 (depends on 9)

The method of claim 9, wherein all consecutive entries kl and kl+1 in the table have values such that
k
l
k
l
+
1
is less than or equal to a predetermined value.

### Claim 11 (depends on 9)

The method of claim 9, 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 M0 is the number of CRC bits attached to the transport block if the first LDPC base graph is used, Z1 is a predetermined maximum TBS for a first one of the two different LDPC base graphs, M1 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 LDPC base graph is used, M2 is a number of CRC bits attached to the transport block if the second LDPC base graph is used, Z2 is is a maximum TBS for a second one of the two different LDPC base graphs, and M3 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 LDPC base graph is used.

### Claim 12

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.

### Claim 13 (depends on 12)

The method of claim 12 wherein X is equal to the least common multiple of C and 8.

### Claim 14

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.

### Claim 15 (depends on 14)

The wireless device of claim 14, wherein the formula is based on a target code rate R for the PDSCH transmission determining the TBS comprises:
determining that a target code rate R for the PDSCH transmission is less than or equal to ¼; and
upon determining that R is less than or equal to ¼:
determining the number of code blocks C for the PDSCH transmission based on the approximation of the TBS, the number of Cyclic Redundancy Check, CRC, bits attached to each transport block of the PDSCH transmission, and a number of CRC bits, if any, attached to each code block of the PDSCH transmission when using a first base graph for the code block segmentation; and
determining the TBS for the PDSCH 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 PDSCH transmission.

### Claim 16 (depends on 14)

The wireless device of claim 14, wherein X is equal to a least common multiple of C and 8.

### Claim 17 (depends on 14)

The wireless device of claim 14, further comprising 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 PDSCH 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 PDSCH transmission.