We all know that short cycles in Tanner Graph are detrimental in error performance. So, Why standardized 5G NR LDPC codes have 4-cycles? 3rd generation Partnership Project (3GPP) had announced Base Matrix 1 and 2. I lifted them properly. I realized there are 4 cycles. What are main reasons to keep 4 cycles, even though they are detrimental in error rate?
To clarify it more, in Coding Theory, LDPC codes, short cycles are avoided. Because Short Cycles are bad for error correcting capability. Given this, in practice, standardized channel codes have 4 cycles. For example, 5G New Radio LDPC codes, released by 3GPP, has many 4 cycles. Why is it so? What are the benefits of keeping 4 cycles, even though we know short cycles are bad for error correcting capability? Why standard LDPC codes, used in 5G communication, have short cycles in their parity matrices?
