Characterization of error events and design of a robust receiver for PRACH detection

In wireless cellular networks a user equipment can be scheduled for uplink transmission only if the timing is correctly synchronized. Hence, a dedicated channel must be established, i.e. the Physical Random-Access Channel (PRACH), which has a key role as interface between the non-synchronized users’ equipment and the uplink orthogonal transmission scheme. Due to the stringent requirements in terms of delay and influence of noise and multipath fading on the signal detection, the design of a robust PRACH receiver is a critical issue. Moreover, with the introduction of new type of services in fifth generation (5G) New Radio (NR) systems, such as ultra-reliable low-latency communications or machine-type communications, and with the need for mechanisms that are able to dynamically adapt to the changing environment, the design of a robust PRACH receiver is a priority but, at the same time, it opens the way to the development of new solutions. The performance of preamble detection in PRACH worsens when channels become more time dispersive. In order to guarantee an acceptable performance for most of users in a cell, in this paper we provide an improved PRACH receiver design that reduces the combined effect of different error events that determine the total missed detection probability. Considering the difficulty of achieving an accurate detection in some scenarios, a new robust three-step approach is proposed to overcome the issues of conventional PRACH signal detection. It is shown that the proposed approach outperforms the traditional peak detection one when the time-dispersion of the channel increases. The benefits of the proposed solution are demonstrated by means of Monte Carlo simulations.