Preamble Design and Collision Resolution in a Massive Access IoT System

Abstract

How to support massive access efficiently is one of the challenges in the future Internet of Things (IoT) systems. To address such challenge, this paper proposes an effective preamble collision resolution scheme to sustain massive random access (RA) for an IoT system. Specifically, a new sub-preamble structure is first proposed to reduce the preamble collision probability. To identify different devices that send the same preamble to the gNB on the same physical random access channel (PRACH), a multiple timing advance (TA) capturing scheme is then proposed. Thereafter, an RA scheme is designed to sustain massive access and the performance of the scheme is studied analytically. Finally, the effectiveness of the proposed RA scheme is validated by extensive simulation experiments in terms of preamble detection probability, preamble collision probability, RA success probability, resource efficiency and TA capturing.

Enhancing Uplink Performance of NR RedCap in Industrial 5G/B5G Systems

“…The latter is defined as the ratio between the total number of detected preambles with the correct timing estimate and the total number of transmitted preambles within an observation interval. This key performance indicator (KPI) is important because it indicates whether the base station correctly received the preamble and determined the timing estimation, which are the key steps in the random access procedure [23]. The obtained results for PRACH Pd are summarized in Fig.…”

“…Long preambles are used in the SUL (PRACH format 0), while short preambles are used in the UL (PRACH format B4), as given in Table III. According to [23], long preambles have extended Zadoff-Chu (ZC) root sequences, which can better capture the timing advance (TA) at the base station side and thus offer an improved PRACH detection. Another important observation in Fig.…”