In radio communication networks, such as the Long Term Evolution (LTE) or the LTE-Advanced (LTE-A) of the 3rd Generation Partnership Project (3GPP), physical random access channel (PRACH) may be used by a user equipment (UE) to request random access to the network. PRACH carries a random access preamble, which is typically generated by using a constant amplitude zero autocorrelation (CAZAC) waveforms. Zadoff-Chu (ZC) sequences are well known CAZAC sequences. The main benefit of using a CAZAC, or a ZC, sequences is that their out-of-phase periodic (cyclic) autocorrelation is equal to zero. This makes it easier to detect the signals at the receiver, such as at a base station or at an enhanced node B (eNB), for example.
However, several problems are related to the detection of the preamble when UEs with high speeds are present. This may be the case when the transmitting UE is located in a high speed train. Compensation methods based on frequency offset estimation cannot be applied due to lack of prior frequency offset estimate. Thus, it is important to provide a solution for reliably configuring the PRACH so that the detection of the preamble at the receiver is also reliable.
USPTO Backgrounds
USPTO Backgrounds