A random access preamble (RAP) consists of CP (cyclic prefix), SEQ and GT (guard time).

Due to GT, the time delay between eNB and UE is compensated at a eNB.

However, why not make the RAP consists of only CP and SEQ by substituting the GT to CP)

I think CP can not only compensate the time delay, but also make maintain orthogonality of Zadoff-Chu sequences.

Is the reason of complexity of trade-off?

Thanks in advance.