Question

Why rate matching is required in LTE?

Answer 1

Rate matching is performed over code blocks and is performed after the code blocks have undergone turbo encoding. The turbo encoder performs a 1/3 rate encoding, i.e for every single input bit, it gives 3 output bits in which the first bit is the original input bit called as a systematic bit and the remaining two bits are interleaved version of the input bit called parity1 and parity2 bits. These three streams of systematic, partity1 and parity2 bits are fed as input to the rate matching module.