	US 11,799,513 B2
	Non-coherent long-range (LoRa) communication system based on multiple-input multiple-output (MIMO) technology
Yi Fang, Guangzhou (CN); Huan Ma, Guangzhou (CN); and Yiwei Tao, Guangzhou (CN)
Assigned to Guangdong University of Technology, Guangzhou (CN)
Filed by Guangdong University of Technology, Guangzhou (CN)
Filed on Jan. 13, 2023, as Appl. No. 18/154,789.
Claims priority of application No. 202210169872.5 (CN), filed on Feb. 23, 2022.
Prior Publication US 2023/0155626 A1, May 18, 2023
Int. Cl. H04B 1/69 (2011.01); H04B 7/0413 (2017.01)

CPC H04B 1/69 (2013.01) [H04B 7/0413 (2013.01); H04B 2001/6912 (2013.01)]

4 Claims

1. A non-coherent long-range (LoRa) communication system based on multiple-input multiple-output (MIMO) technology, comprising:

a transmitter; and

a receiver;

wherein the transmitter is configured to transmit a signal to the receiver, and the receiver is configured to receive and demodulate the signal;

the transmitter comprises a bit-symbol converter, a space-time mapper, and a plurality of transmitting antennas; the bit-symbol converter is configured to convert a bit stream into a modulating signal x_m; the space-time mapper is configured to select a transmitting antenna from the plurality of transmitting antennas for the signal within each transmission time slot and transmit a base Chirp signal x₀and the modulating signal x_mto the receiver in different time slots;

the receiver comprises a plurality of receiving antennas; each of the plurality of receiving antennas is configured to preprocess the signal transmitted from the transmitter to obtain a first cache matrix and a second cache matrix, and perform Hadamard product operation on the first cache matrix and the second cache matrix; and operation results of the plurality of receiving antennas are accumulated and demodulated to obtain a demodulated signal, and a demodulated information bit is output;

the bit stream is input to the bit-symbol converter to be converted into decimal symbols; a spreading factor of the non-coherent LoRa communication system is defined as SF; the spreading factor determines a size of the decimal symbols into which the bit stream is split; one LoRa signal contains SF bits; and a number of modulable symbols is also determined by the spreading factor SF, and is 2^SF;

the base Chirp signal x₀is expressed as:

the modulating signal x_mis expressed as:

the space-time mapper is operated through steps of:

respectively selecting the plurality of transmitting antennas to transmit the base Chirp signal x₀in 1^stto N^thtime slots; and in N+1^thto 2N^thtime slots, respectively selecting the plurality of transmitting antennas to transmit the modulating signal x_m, wherein N is a number of the plurality of transmitting antennas;

the first cache matrix and the second cache matrix are obtained through steps of:

storing (M−1)·2^SF+1^thto M·2^{SF th}sampling points into the first cache matrix B_M,1; and storing (2M−1)·2^SF+1^thto 2M·2^{SF th}sample points into the second cache matrix B_M,2wherein M represents a number of the plurality of receiving antennas;

the receiver further comprises a Fourier transformer; the Fourier transformer is a 2^SF-point Fourier transformer; the operation results of the plurality of receiving antennas are accumulated to obtain the demodulated signal, and then the demodulated signal is input to the Fourier transformer for Fourier transformation;

the demodulated signal is subjected to 2^SF-point discrete Fourier transformation with to obtain discrete Fourier transform result

containing 2^SFvalues; wherein k is an integer; Z(k) is a complex additive white Gaussian noise (AWGN); P is a transmitting power; and h is a complex envelope amplitude;

real parts of the discrete Fourier transform result are removed, and then an index m of a maximum value is selected, expressed as:

the receiver further comprises a symbol-bit converter; and an input of the symbol-bit converter is a selected index, and an output of the symbol-bit converter is the demodulated information bit.