Zadoff-Chu sequence design for random access initial uplink synchronization

TL;DR

This paper presents a systematic method for designing Zadoff-Chu sequences to optimize initial uplink synchronization performance in LTE, addressing limitations of existing algorithms and improving their effectiveness.

Contribution

It introduces a novel ZC sequence design procedure based on sparse recovery theory to enhance uplink synchronization algorithms.

Findings

Significant performance improvements in synchronization algorithms with the proposed ZC sequences.

Uplink synchronization modeled as a sparse signal recovery problem.

Identification of a key factor influencing algorithm performance.

Abstract

The autocorrelation of a Zadoff-Chu (ZC) sequence with a non-zero cyclically shifted version of itself is zero. Due to the interesting property, ZC sequences are widely used in the LTE air interface in the primary synchronization signal (PSS), random access preamble (PRACH), uplink control channel (PUCCH) etc. However, this interesting property of ZC sequence is not useful in the random access initial uplink synchronization problem due to some specific structures of the underlying problem. In particular, the state of the art uplink synchronization algorithms do not perform equally for all ZC sequences. In this work, we show a systematic procedure to choose the ZC sequences that yield the optimum performance of the uplink synchronization algorithms. At first, we show that the uplink synchronization is a sparse signal recovery problem on an overcomplete basis. Next, we use the theory of sparse recovery algorithms and identify a factor that controls performance of the algorithms. We then suggest a ZC sequence design procedure to optimally choose this factor. The simulation results show that the performance of most of the state of the art uplink synchronization algorithms improve significantly when the ZC sequences are chosen by using the proposed technique.