Method for compressive sensing based LPWAN communication

Patent metadata

Field	Value
Publication number	US-11051153-B1
Application number	US-202017062186-A
Country	US
Kind code	B1
Filing date	Oct 2, 2020
Priority date	Jul 31, 2020
Publication date	Jun 29, 2021
Grant date	Jun 29, 2021

Abstract

A LoRa device for communicating sensor signals in a low power wide area network (LPWAN) includes a physical layer using Hamming encoding and Gray indexing with chirp spread signal (CSS) modulation to encode and modulate the sensor signals and a medium access layer (MAC) including a compressive sensing sub-layer which reduces encoded, modulated signals to sparse vectors. A transmission packet is formed by combining the sparse vectors with a selected set of sparse vectors representing past measurements and the incoming velocity of the sensor signals. A receiver decompresses the transmission packet by reconstructing, at a sparse recovery sub-layer of a receiver MAC layer, the encoded, modulated sensor signals. A decoder path removes the CSS modulation and Gray indexing, and Hamming decodes the sensors signals.

First claim

The invention claimed is:

1. A method for compressive sensing based communications of low range (LoRa) devices in a low power wide area network (LPWAN) comprising at least one sensor selected from the group consisting of an accelerometer, an altimeter, and a temperature sensor; a GPS module and an antenna, said method comprising:
receiving, by a physical layer of a LoRa device, a bit stream of sensor measurements from the at least one sensor at an incoming velocity;
encoding the bit stream to generate an encoded bit stream;
modulating the encoded bit stream by chirp spread spectrum modulation to generate a chirp modulated encoded bit stream;
forming a first transmission packet including at least a preamble, the chirp modulated encoded bit stream and a cyclic redundancy check (CRC);
receiving the first transmission packet by a multiple access layer (MAC) of the LoRa device;
compressing the chirp modulated encoded bit stream of the first transmission packet into sparse vectors;
combining the sparse vectors with a linear combination of a randomly selected set of sparse vectors representing past measurements and the in-coming velocity of the bit stream to generate a payload;
forming a second transmission packet including the preamble, the payload and the cyclic redundancy check;
transmitting, the second transmission packet through the antenna at a randomly selected time.

2. The method of claim 1 , further comprising:
encoding the bit stream by:
encoding the bits with a Hamming encoder, by using Hamming forward error correction to form a first coded bit sequence;
interleaving the first coded bit sequence to form a second coded bit sequence; and
applying Gray indexing to the second coded bit sequence to prevent off-by-one errors when resolving symbols to generate a third coded bit sequence.

3. The method of claim 2 , further comprising:
modulating the encoded bit stream by combining the third coded bit sequence with a base chirp signal generated by a local oscillator at a chirp rate.

4. The method of claim 3 , further comprising:
selecting a channel bandwidth from the group consisting of 125 kHz, 250 kHz and 500 kHz;
matching a coding rate to a channel coding rate, wherein the coding rate is selected from

R
c

=

4

4
+
n

⁢

⁢
where

n
=

{

1
,
2
,
3
,
4

}

;

and
encoding the signal bits by using Hamming forward error correction at the coding rate.

5. The method of claim 4 , further comprising:
compressing the chirp modulated encoded bit stream of the first transmission packet into sparse vectors by retaining only non-zero values of the sparse vectors.

6. The method of claim 5 , further comprising:
mapping the second transmission packet to in-phase and quadrature transmission paths; and
transmitting the second transmission packet according to the mapping.

7. The method of claim 6 , further comprising:
transmitting the second transmission packet according to a Class A protocol, in which the LoRa device sleeps until it wakes for transmission at the randomly selected time.

Assignees

• Univ King Abdulaziz

Inventors

• Aljohani Abdulah
• Alasmary Waleed

Classifications

• H04W4/38

  for collecting sensor information · CPC title

• H04B2001/6912

  using chirp · CPC title

• H04B1/69

  Spread spectrum techniques · CPC title

• Y02D30/70

  in wireless communication networks · CPC title

• H04L1/0071

  Use of interleaving (interleaving per se H03M13/27) · CPC title