Page 84 - Kaleidoscope Academic Conference Proceedings 2021

2021 ITU Kaleidoscope Academic Conference

the proposed method has a significant improvement on TO
estimation. The underlying reason is that the received signals
in the adjacent subcarriers provide extra information to the
estimation.
The TO/FO estimation error is also affected by the FFT size
in the calculation of J(D, ∆ f ). The FFT size determines
ˆ
the search granularity of the best (D, ∆ f ). In Figure 7, a
preamble with N N PRACH = 12 is used to evaluate the effect
rep
of the FFT size. The parameter S f is increased from 1024 (a) (b)
to 8192, i.e., the search granularity in the frequency domain
decreases from 3.66Hz to 0.46Hz. It can be seen that the
FO estimation error is reduced by about 1Hz. However, with
respect to the SCS 3.75kH, the estimation error of 1Hz is
negligible. So in this simulation the parameter S f is chosen
N PRACH
as 1024 when N rep = 12.

(c) (d)
Figure 8 – Evaluation of interference of multiple UEs

no. 9, pp. 32-40, September 2015.

[2] “New Study WID on NB-IoT/eTMC support for NTN,”
MediaTek RP-193235, Dec. 2019.
(a) (b)
[3] “Study on New Radio (NR) to support non terrestrial
Figure 7 – Comparison of FO estimation errors of different networks,” 3GPP TR 38.811, Jun. 2018.
FFT sizes
[4] “Frequency compensation in NTN,” Ericsson
In Subsection 3.3, the interference of multiple UEs in the R1-1813362, Nov. 2018.
preamble detection is already analyzed. In this simulation,
it is assumed that two UEs simultaneously transmit their [5] S. Sesia, M. Baker, and I. Toufik, “LTE-The UMTS
NPRACH preambles with independently chosen TO and FO. Long Term Evolution: From Theory to Practice,”
The subcarriers of their first symbol groups are set to be Hoboken, NJ, USA: Wiley, 2011.
adjacent. According to the hopping pattern defined in [7], one
half, or all, of their following symbol groups are adjacent. The [6] “Evolved Universal Terrestrial Radio Access
Figure 8 shows that in the proposed method the performance (E-UTRA); Physical channels and modulation,”
degradation caused by multiple UE interference is very small. 3GPP TS 38.211, Mar. 2019.
It is because the design of weights in combination in Equation [7] “Physical channels and modulation,” 3GPP TS 36.211,
(12) can effectively suppress the interference from adjacent Dec. 2019.
subcarriers.
[8] X. Lin, A. Adhikary and Y. -P. Eric Wang,
“Random Access Preamble Design and Detection for
5. CONCLUSION
3GPP Narrowband IoT Systems,” in IEEE Wireless
In NB-IoT over NTN, the IoT devices may suffer from large Communications Letters, vol. 5, no. 6, pp. 640-643,
residual FO in initialization of wireless access. With the Dec. 2016.
large FO, the power of a transmitted NPRACH preamble [9] J. Hwang, C. Li and C. Ma, "Efficient Detection and
will leak into adjacent subcarriers and interfere with other Synchronization of Superimposed NB-IoT NPRACH
preambles. In this paper, the leaked signal is investigated and Preambles," in IEEE Internet of Things Journal, vol.
coherently combined in the proposed NPRACH receiver. It 6, no. 1, pp. 1173-1182, Feb. 2019.
is theoretically proven that the proposed receiver can improve
the performance of preamble detection. [10] Q. Wu, P. Wu, W. Wen, T. Yang and M. Xia,
"An Efficient NPRACH Receiver Design For NB-IoT
Systems," in IEEE Internet of Things Journal, vol. 7,
REFERENCES
no. 10, pp. 10418-10426, Oct. 2020.
[1] S. Andreev et al., "Understanding the IoT connectivity
landscape: a contemporary M2M radio technology
roadmap," in IEEE Communications Magazine, vol. 53,

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