Efficient Preamble Detection and Time-of-Arrival Estimation for Single-Tone Frequency Hopping Random Access in NB-IoT

The narrowband internet of things (NB-IoT) standard
is a new cellular wireless technology, which has been
introduced by the 3rd Generation Partnership Project (3GPP)
with the goal to connect massive low-cost, low-complexity and
long-life IoT devices with extended coverage. In order to improve
power efficiency, 3GPP proposed a new Random Access
(RA) waveform for NB-IoT based on a single-tone frequencyhopping
scheme. RA handles the first connection between user
equipments (UEs) and the base station (BS). Through this,
UEs can be identified and synchronized with the BS. In this
context, receiver methods for the detection of the new waveform
should satisfy the requirements on the successful user detection
as well as the timing synchronization accuracy. This is not a
trivial task, especially in the presence of radio impairments
like carrier frequency offset (CFO) which constitutes one of the
main radio impairments besides the noise. In order to tackle
this problem, we propose a new receiver method for NB-IoT
Physical Random Access Channel (NPRACH). The method is
designed to eliminate perfectly the CFO without any additional
computational complexity and supports all NPRACH preamble
formats. The associated performance has been evaluated under
3GPP conditions. We observe a very high performance compared
both to 3GPP requirements and to the existing state-of-the-art
methods in terms of detection accuracy and complexity.