Random access channel (RACH) parameters optimization in WCDMA systems

The random access procedure, defined by the 3rd Generation Partnership Project (3GPP), is based on a slotted Aloha approach with fast acquisition indication, that is carried out in uplink by the random access channel (RACH) and acquisition indicator channel (AICH) in the downlink. In this paper, the RACH performance in a single omni cell under shadowing and fast-fading conditions is analyzed. An optimization procedure is performed to obtain, according to random access delay and random access success ratio, optimal values for RACH radio parameters such as the power offset between consecutive preambles (Δ_pp) and the preamble target signal to interference ratio (SIR_t). Furthermore, curves of preamble signal to interference ratio (SIR), measured at base station point, are presented.