Improved physical random access channel estimation in UTRA TDD

Abstract

In the Universal Mobile Telecommunications System (UMTS), a random access channel (RACH) is used to carry control information and small data packets from a mobile to the network. In particular, the RACH may be used to initiate a connection. During initial access, mobiles' timing positions are unknown to the network and, as such, their uplink transmissions carrying RACH may arrive at varying times at the base station. In UMTS terrestrial radio access (UTRA) TDD, due to the structure of a burst training sequence, this may lead to restricted cell size operation. We investigate an approach to channel estimation which removes this restriction, thus allowing UTRA TDD to operate over larger cell radii.