Code word in NR

Codeword definition ：

A codeword is in a TTI The message sent on contains CRC Bit and encoded （Encoding） Match the rate （Ratematching） Subsequent independent transmission block （transportblock）.

Advantages and disadvantages of codewords ：

The number of codewords does not change the limit of traffic , Multi codeword is just to improve the control of particles ： The same piece of data , When using a single code word , All layers must be dispatched uniformly , When there are multiple codewords, they can be scheduled separately according to the mapping relationship between codewords and layers , Each codeword has its own scheduling information and feedback information , Environmental differences that cannot be layered can be distinguished by code words that cannot be . However, multiple codewords occupy more resources than single codewords , Including scheduling
And feedback is also consumption . It's not always good to have more code words 、

The relationship between codewords and layers ：

The relationship protocol between codeword and layer has been stipulated , The previous layer corresponds to a codeword , The following layer corresponds to another codeword .
The number of layers is less than or equal to 4 When , It can only be a single code word , The number of layers is greater than 4 It must be multi codeword .