Optimized Architecture for Computing Zadoff-Chu Sequences with Application to LTE

An optimized algorithm and a corresponding reconfigurable architecture for computing Zadoff-Chu (ZC) complex sequence elements based on the CORDIC algorithm are proposed. The algorithm computes ZC-sequence elements both in time domain and frequency domain using a simple duality relationship. Algorithm transforms are employed to compute the elements recursively and eliminate multipliers with nonconstant terms. The algorithm is applied in a searcher block for detecting the physical random access channel (PRACH) in LTE PHY layer. The PRACH transmits a preamble constructed from ZC sequences to establish initial access along with uplink synchronization with the base station. A reconfigurable hardware architecture was implemented to generate these preambles on the fly with high accuracy based on the proposed algorithm, eliminating the need for storing a large number of long complex ZC sequence elements. Simulation results demonstrate that the proposed architecture is capable of achieving detection error rates for LTE PRACH that are close to ideal rates achieved using floating-point precision.