Frequency Domain Preamble-Based Channel Estimation and Equalization in LoRa

This paper deals with multipath channel estimation and equalization in LoRa. It is suggested to take advantage of the cyclic property of the symbols in the LoRa frame preamble to obtain an interference-free version of the symbols in the frequency domain. Then, estimation methods used in multicarrier systems can be applied, such as the least square (LS), and the minimum mean square error (MMSE) estimators. It is shown that the cyclic property in LoRa is inherently independent of the length of the channel, making these estimation techniques robust to any frequency-selective channel. In addition the frequency domain zero-forcing (ZF) equalizer is used, and an original phase equalizer is introduced, taking advantage of the constant modulus property of LoRa symbols in the frequency domain. The performance of the investigated estimators and equalizers is shown through simulations, and applications to the presented results are further discussed.

Frequency Domain Preamble-Based Channel Estimation and Equalization in LoRa

This paper deals with multipath channel estimation and equalization in LoRa. It is suggested to take advantage of the cyclic property of the symbols in the LoRa frame preamble to obtain an interference-free version of the symbols in the frequency domain. Then, estimation methods used in multicarrier systems can be applied, such as the least square (LS), and the minimum mean square error (MMSE) estimators. It is shown that the cyclic property in LoRa is inherently independent of the length of the channel, making these estimation techniques robust to any frequency-selective channel. In addition the frequency domain zero-forcing (ZF) equalizer is used, and an original phase equalizer is introduced, taking advantage of the constant modulus property of LoRa symbols in the frequency domain. The performance of the investigated estimators and equalizers is shown through simulations, and applications to the presented results are further discussed.

The Rainfall Intensity Effects on 1–13 GHz UWB-Based 5G System for Outdoor Applications

This paper reports a research contribution on tropical outdoor channel characterization in 1–13 GHz band for 5G systems. This 1–13 GHz ultra-wideband (UWB) channel characterization is formulated with rain intensity as the most important variable, from 20 mm/h to 200 mm/h. Tropical rain will cause pulse broadening and distorts the transmitted symbols, so the probability of symbol errors will increase. In this research, the bit error rate (BER) performance evaluation is done using both matched filtering or correlator-based receivers. At no rain conditions, BER 10−6 will be attained at signal to noise ratio (SNR) 5 dB, but at rainfall intensity 200 mm/h, the BER will fall to 10−2 for matched filter and 5×10-2 for correlator-based receivers. For improving the BER performance, an adaptive nonlinear phase equalizer is proposed which adopts multiple allpass biquad infinite impulse response (IIR) filters combined with low-order finite impulse response (FIR) filter to mitigate the nonlinearity phase and differential attenuation of magnitude responses due to antenna and tropical outdoor UWB channel effects. Our simulation results show that the proposed equalizer has worked successfully with BER 10−6 on the rain rate that is exceeded for 0.01% of the time (R0.01) rain intensity or 99.99% availability. In addition, at rainfall rate 120 mm/h, the proposed nonlinear phase equalizer can give 9 dB signal improvement.