added lorawan applications examples and explanation of demodulation

presentation/plots/chirp.py

@@ -152,6 +152,48 @@ def symbol():
         plt.savefig('lora_symbols_{}.png'.format(i))
         plt.show()
 
+def demodulation():
+    # demodulation
+    fs = 8000
+    T = 10
+    t = np.linspace(0, T, T*fs, endpoint=False)
+
+    for i in range(0,3):
+        frac = 0.3
+        t_jump = T * (1 - frac)
+
+        # 250, 500, 750, 1000, 1250, 1500, 1750
+        t1 = (frac)*T
+
+        if i == 0:
+            symbol_p1 = chirp(t[0:int(frac*len(t))], f0=250, f1=1750, t1=T, method='linear')
+            symbol_p2 = chirp(t[int(frac*len(t)):], f0=250, f1=1750, t1=T, method='linear')
+        elif i == 1:
+            symbol_p1 = chirp(t[0:int(frac * len(t))], f0=1750, f1=250, t1=T, method='linear')
+            symbol_p2 = chirp(t[int(frac * len(t)):], f0=1750, f1=250, t1=T, method='linear')
+        elif i == 2:
+            symbol_p1 = chirp(t[0:int(frac * len(t))], f0=700, f1=700, t1=T, method='linear')
+            symbol_p2 = chirp(t[int(frac * len(t)):], f0=700, f1=700, t1=T, method='linear')
+
+        symbol = np.hstack((symbol_p2, symbol_p1))
+        ff, tt, Sxx = spectrogram(symbol, fs=fs, noverlap=256, nperseg=512,
+                                          nfft=2048)
+
+        #chirp = np.hstack((upchirp, upchirp))
+        #ff, tt, Sxx = spectrogram(chirp, fs=fs, noverlap=256, nperseg=512,
+        #                                  nfft=2048)
+
+        plt.figure(5)
+        plt.yticks([250, 1000, 1750], ['868.1 MHz - 62.5 kHz', '868.1 MHz', '868.1 MHz + 62.5 kHz'] )
+        plt.pcolormesh(tt, ff[:513], Sxx[:513])
+
+        plt.title("LoRa Symbol")
+        plt.xlabel('time')
+        plt.ylabel('frequency')
+        plt.tight_layout()
+        plt.savefig('lora_demodulation_{}.png'.format(i))
+        plt.show()
+
 
 def spreading_factor():
     fs = 8000
@@ -188,6 +230,7 @@ def spreading_factor():
 
 
 #symbol()
-spreading_factor()
+#spreading_factor()
+demodulation()
 
 plt.show()

presentation/presentation.tex

@@ -253,7 +253,9 @@ Important: \includegraphics[trim=0cm 4cm 0 0cm, scale=0.11]{images/lora.jpg} $\l
 \item \textbf{A}mplitude \textbf{S}hift \textbf{K}eying (ASK)
 \end{itemize}
 \includegraphics[scale=0.35]{images/unmodulated.png}
-\includegraphics[scale=0.35]{images/amplitude_modulation.png}
+\includegraphics<1>[scale=0.35]{images/amplitude_modulation.png}
+\includegraphics<2>[scale=0.35]{images/amplitude_modulation_2.png}
+
 \end{frame}
 
 \begin{frame}{Digital modulation}
@@ -264,7 +266,8 @@ https://en.wikipedia.org/wiki/Chirp\_spread\_spectrum
 \item \textbf{F}requency \textbf{S}hift \textbf{K}eying (FSK)
 \end{itemize}
 \includegraphics[scale=0.35]{images/unmodulated.png}
-\includegraphics[scale=0.35]{images/frequency_modulation.png}
+\includegraphics<1>[scale=0.35]{images/frequency_modulation.png}
+\includegraphics<2>[scale=0.35]{images/frequency_modulation_2.png}
 \end{frame}
 
 \begin{frame}{Digital modulation}
@@ -303,12 +306,15 @@ Thanks Valentin and Stefan (DM4SG) for providing this data
 \begin{frame}{Chirps and Symbols}
 \begin{overlayarea}{\textwidth}{\textheight}
 \begin{center}
-\includegraphics<1>[scale=0.4]{images/lora_symbols_0.png}
+\includegraphics<1>[scale=0.38]{images/lora_symbols_0.png}
-\includegraphics<2>[scale=0.4]{images/lora_symbols_1.png}
+\includegraphics<2>[scale=0.38]{images/lora_symbols_1.png}
-\includegraphics<3>[scale=0.4]{images/lora_symbols_2.png}
+\includegraphics<3>[scale=0.38]{images/lora_symbols_2.png}
-\includegraphics<4>[scale=0.4]{images/lora_symbols_3.png}
+\includegraphics<4>[scale=0.38]{images/lora_symbols_3.png}
-\includegraphics<5>[scale=0.4]{images/lora_symbols_4.png}
+\includegraphics<5>[scale=0.38]{images/lora_symbols_4.png}
-\includegraphics<6>[scale=0.4]{images/lora_symbols_5.png}
+\includegraphics<6>[scale=0.38]{images/lora_symbols_5.png}
+\includegraphics<7>[scale=0.35]{images/lora_demodulation_0.png}
+\includegraphics<7>[scale=0.35]{images/lora_demodulation_1.png}
+\includegraphics<8>[scale=0.38]{images/lora_demodulation_2.png}
 \end{center}
 \only<2->{
 Time of frequency jump determines which data is encoded\\
@@ -319,6 +325,15 @@ Time of frequency jump determines which data is encoded\\
 \only<5>{Example: \texttt{data = }\texttt{00011}}
 \only<6>{Example: \texttt{data = }\texttt{10110}}
 \end{center}
+\only<7->{
+\vspace{-0.75cm}
+\textbf{Demodulation:}
+\begin{itemize}
+\item De-chirp signal by multiplying (mixing) with conjugate chirp
+\item Fourier Transform
+\item Alignment using detect sequence at start of transmission 
+\end{itemize}
+}
 \end{overlayarea}
 \end{frame}
 
@@ -337,7 +352,7 @@ Time of frequency jump determines which data is encoded\\
 
 \begin{frame}{Demodulation}
 \begin{itemize}
-\item Signal is multiplied by (mixed with) Down-Chirp
+\item De-chirp signal by multiplying (mixing) with conjugate chirp
 \item Fourier Transform
 \end{itemize}
 \end{frame}
@@ -354,6 +369,7 @@ Reason: allows to detect and fix errors that occur during transmission (due to i
 \end{itemize}
 \end{frame}
 
+\subsection{Packet format}
 \begin{frame}{LoRa package format}
 \begin{reference}{0mm}{70mm}
 Source: SX1276/77/78/79 datasheet
@@ -370,6 +386,7 @@ Source: SX1276/77/78/79 datasheet
 \end{itemize}
 \end{frame}
 
+\subsection{Data rate and air time}
 \begin{frame}{Data rate and air time}
 \begin{itemize}
 \item Data rate depends on bandwidth (BW), spreading factor (SF) and coding rate (CR)\\[0.3cm]
@@ -424,6 +441,7 @@ $\rightarrow$ max. 600 messages per hour on SF7 \\
 
 \section{Playground Part I}
 \begin{frame}[fragile]{Playground Part I}
+\begin{small}
 \begin{itemize}
 \item Module used: \textbf{Wemos® TTGO LORA32 868Mhz ESP32}
 \begin{minipage}{0.6\textwidth}
@@ -458,8 +476,11 @@ lora.send_string("Hello World!")
 lora.send([0x01, 0x02, 0x03])
 \end{python}
 \end{spacing}
-\item Have a look at SX1276 datasheet
+\vspace{-0.1cm}
+\item Alternative: HopeRF \textbf{RFM95W} chip
+\item For "documentation" see: \url{https://imaginaerraum.de/git/Telos4/LoRa-Workshop}
 \end{itemize}
+\end{small}
 \end{frame}
 
 \begin{frame}[fragile]{Playground Part I}
@@ -500,6 +521,7 @@ lora.setSyncWord(0x34)
 \end{frame}
 
 \section{LoRaWAN}
+\subsection{Network topology}
 \begin{frame}{LoRaWAN}
 \begin{reference}{2mm}{80mm}
 https://www.thethingsnetwork.org/docs/lorawan/
@@ -516,6 +538,7 @@ https://www.thethingsnetwork.org/docs/lorawan/
 \end{itemize}
 \end{frame}
 
+\subsection{TheThingsNetwork}
 \begin{frame}{Device registration}
 \begin{itemize}
 \item \textbf{TheThingsNetwork} aims to build a global LoRaWAN network
@@ -580,11 +603,42 @@ http://www.techplayon.com/lora-long-range-network-architecture-protocol-architec
 Useful link:
 \begin{itemize}
 \item LoRaWAN packet decoder {\small \url{https://lorawan-packet-decoder-0ta6puiniaut.runkit.sh/}}
-
 \end{itemize}
 \end{frame}
 
-\section{Practical Part II}
+\subsection{Applications}
+\begin{frame}{Use cases}
+\begin{reference}{0mm}{80mm}
+\url{https://www.semtech.com/lora/resources/lora-white-papers}
+\end{reference}
+\begin{minipage}{0.5\textwidth}
+\begin{flushleft}
+\textbf{Smart farming}
+\end{flushleft}
+\includegraphics[scale=0.09]{images/smart_farming.png}
+\end{minipage}%
+\begin{minipage}{0.5\textwidth}
+\begin{flushright}
+\textbf{Smart parking}
+\end{flushright}
+\includegraphics[scale=0.09]{images/smart_parking.png}
+\end{minipage}
+\begin{minipage}{0.5\textwidth}
+\begin{flushleft}
+\textbf{Smart home}
+\end{flushleft}
+\includegraphics[scale=0.09]{images/smart_home.png}
+\end{minipage}%
+\begin{minipage}{0.5\textwidth}
+\begin{flushright}
+\textbf{Smart waste management}
+\end{flushright}
+\includegraphics[scale=0.09]{images/smart_waste.png}
+\end{minipage}%
+
+\end{frame}
+
+\section{Playground Part II}
 \begin{frame}[fragile]{Playground Part II}
 Example code for sending data to \textbf{TheThingsNetwork}:
 \begin{spacing}{0.85}
@@ -640,24 +694,24 @@ For testing you can use the following device addresses and keys:
   4:  26 01 17 83		13:  26 01 19 40
   5:  26 01 1B 5C		14:  26 01 19 96
   6:  26 01 1E B5		15:  26 01 18 FF
-  7:  26 01 13 DA
+  7:  26 01 13 DA		16:  26 01 12 5B
-  8:  26 01 1E 8F
+  8:  26 01 1E 8F		17:  26 01 13 63
-  9:  26 01 18 F1
+  9:  26 01 18 F1		18:  26 01 12 09
 \end{python}
-\item Watch incoming data at
+\item Watch incoming data (forwarded as HTTP POST request) at 
 \begin{center}
-\url{https://enny86r86c66.x.pipedream.net}
+\url{https://t1p.de/ocp6}
 \end{center}
-and check the gateway logs at (@BayernWLAN wifi)
+and check the gateway log at (connected to @BayernWLAN wifi)
 \begin{center}
-\url{http://192.168.1.1/}
+\url{http://192.168.1.1:1337}
 \end{center}
 \end{itemize}
 \end{frame}
 
-\begin{frame}{References and further reading}
+\begin{frame}{References and more information}
 \begin{footnotesize}
-References:
+\textbf{References:}
 \begin{itemize}
 \item Decoding LoRa \url{https://revspace.nl/DecodingLora}
 \item \textit{LoRa und The Things Network} - talk by Hubert Högl (FH Augsburg)
@@ -666,14 +720,14 @@ References:
 \item \href{https://www.youtube.com/playlist?list=PLmL13yqb6OxdeOi97EvI8QeO8o-PqeQ0g}{Mobilefish.com LoRa youtube tutorials}
 \end{itemize}
 
-Further reading:
+\textbf{Further reading:}
 \begin{itemize}
 \item TTN Applications: APIs, Python SDK, Integrations {\scriptsize \url{https://www.thethingsnetwork.org/docs/applications/}}
 \item Best practices to reduce payload size: {\scriptsize \url{https://www.thethingsnetwork.org/forum/t/best-practices-to-limit-application-payloads/1302}}
 \item Forum about all things LoRa: \url{https://www.thethingsnetwork.org/forum/}
 \begin{itemize}
 \item Gateway guides
-\item Antenna recommendations
+\item Radio module/antenna recommendations
 \item ...
 \end{itemize}
 \item Cayenne Low Power Payload (LPP)