0 Replies Latest reply: Jan 18, 2014 2:21 PM by Harald Naumann RSS

M2M IoT Cookbook

Harald Naumann Master

How to develop a device based on wireless modules?

1    Why to write the M2M IoT Cookbook?    5
2    Fundamental considerations before starting the M2M project    5
3    Certifications and approvals    6
3.1    Examples for Radio approvals in EU and US 6
3.2    Examples for Radio approvals in US    7
3.3    Examples for automotive related approvals in EU    7
3.4    SAR – Specific Absorption Rate    8
4    Cellular data communication (GPRS, USSD, SMS, CSD, DTMF)    9
4.1    Voice communication    9
4.2    Modem / acoustic coupler    9
4.3    DTMF (Dual Tone Multi Frequency)    10
4.4    GPRS (General Packed Radio Service)    10
4.5    SMS    11
4.6    USSD (Unstructured Supplementary Service Data)    11
4.7    Comparison of power consumption (SMS, USSD and GPRS)    12
4.8    CSD (Circuit Switched Data)    13
5    Supply voltage    13
5.1    Internal resistance of batteries and linear voltage transformers    13
5.2    Switched mode voltage regulator    15
6    Antennas for M2M devices    16
6.1    Monopole and dipole antennas    16
6.2    Nothing will interfere with your embedded antenna?    16
6.3    Why the embedded chip or patch antennas are resonant on the frequency?    17
6.4    How will the ground plane affect your embedded antenna?    18
6.5    How to connect your embedded antenna with your wireless module? 19
6.6    PCB trace impedance / transmission line calculators    20
6.7    How to design an antenna matching circuit? 20
6.8    How to switch between an internal and external cellular or GNSS antenna cheap?    21
6.9    Which GPS antenna shall be used for a tracking device?    22
6.10    Which embedded antenna to select for a Bluetooth / GNSS application?    23
6.11    Dos and don’ts during embedded antenna design    24
6.12    Examples for good and bad M2M designs with embedded antennas    25
7    Simulation of an embedded GSM PCB track antenna 26
7.1    Definition of the antenna simulation project 26
7.2    Description of the inverted F antenna 26
7.3    3D model of the simulation    27
7.4    Optimization – determination of antenna shape 28
7.5    Typical requirements of a quad band GSM antenna    28
7.6    Optimization of the quad band antenna GSM antenna shape    31
7.7    Directional characteristics of the antenna for two GSM frequencies    31
7.8    Influence on the antenna characteristics of the housing    34
7.9    Influence of the ground plane on the antenna characteristics    35
8    Components around the cellular module    36
8.1    SIM card    36
8.2    SIM card subscription    36
8.3    Low ESR capacitor    37
8.4    Firmware update at final PCB    37
9    Examples for mistakes and errors during M2M development    37
9.1    Power down reset    37
9.2    SMS errors    37
9.3    CSD errors    38
9.4    IP connection errors    38
10    Testing your M2M device    39
10.1    Emulation of TX power peaks    39
10.2    TX power peaks by cellular module test mode 39
10.3    TX power peaks by GSM tester    39
10.4    Testing of the sensitivity    39
10.5    Testing of the radiated TX power    40
10.6    Where to get a cellular tester cheap? 40
11    AT Commands    40
12    Thank you    41
13    Glossary    41

1 Why to write the M2M IoT Cookbook?

Since more than a quarter I am in Wireless M2M. 25+ years ago we had no word for M2M. We developed Machine to Machine devices without to know that these devices will be decades later will be called M2M. 25 years ago there was no GSM for data communication. The first steps in wireless data communication I made with FSK on Private Mobile Radios. On PMR we reached 3600 bit per second. A while later we got public analogue trunked radios. These trunked radios systems offered local terrestrial networks with FSK data communication. Years ago the last public analogue trunked radio network in Germany was taken out of service. GSM jumped in with its Short Message Service and Circuit Switched Data. CSD offered us already 9600 bit per second. SMS and CSD we could use for countywide communication easy up to worldwide by roaming. And today GSM/GPRS is facing out step by step and will be replaced to 3G and 4G. In US the cellular operator AT&T does not accept new M2M applications on GSM anymore.

The M2M IoT Cookbook describes how to develop a tracking device based on cellular and GNSS modules. A telemetric M2M device you get by ignoring the GNSS part.

Sometimes it is not easy to use the use the right words in English language. The common word for SMS in UK is “text message”. In this book it will be still named SMS. A prepaid SIM card in UK they call a “Pay as you go SIM card”. I will mainly use the common words used of ETSI. If I use the word GSM module, then this covers 3G and 4G modules as well, because the fallback of UMTS, HSPA and LTE is still 2G (GSM/GPRS). Today GPS is already the wrong word. GPS is just one out of several Global Navigation Satellite Systems. Today we can access to the Russian GNSS called Glonass as well. And sooner or later we will get access to the European GNSS called Galileo.

The M2M IoT Cookbook shall help developers of wireless M2M application to save some time and maybe inspire some ideas. The book is just the summary of experience collected in my different jobs. By leading a team of developers with the order to design a mobile GSM/GPS tracking device I learned to think like a system integrator. In my more than 15 years working with a manufacturer and in distribution I gave the same hints and recommendations that to developers of wireless applications again and again. In May 2012 I made the decision to write the story that I have to tell weekly to customers in a book. The target is to guideline developers from the idea for a M2M / IoT device to a final product for mass production. It will not tell you how an inverted F antenna is working. To tell that I will use links. Nevertheless the book will tell you details that are often missed in the official documentation of manufacturers of radio modules and antennas.

I hope you will enjoin it and I hope it will save some of your time as well.

If you an interest to get pre version with free of charge updates until the final version then do not hesitate to drop an email to harald.naumann (at) gsm-modem.de