IoT M2M blog

The home of free hints and tips about wireless IoT / M2M

IoT M2M Cookbook

How to develop a device based on Wireless Wide Area Network modules

Table of contents

1 Why to write the IoT / M2M Cookbook? 5
2 Fundamental considerations before starting the IoT / 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 Europe 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 / encryption 9
4.3 DTMF (Dual Tone Multi Frequency) 10
4.4 GPRS (General Packed Radio Service) 10
4.5 SMS 10
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 Cellular module in power save mode (14.01.2014) 14
5.2 Internal resistance of batteries and linear voltage transformers 14
5.3 Switched mode voltage regulator 16
5.4 Capacitors at power supply and cellular module (14.04.2014) 16
5.5 Supply voltage for GNSS antenna (14.04.2014) 16
6 Antennas for IoT / M2M devices 17
6.1 Monopole and dipole antennas 17
6.2 Nothing will interfere with your embedded antenna? 17
6.3 Why the embedded chip or patch antennas are resonant on the frequency? 18
6.4 How will the ground plane affect your embedded antenna? 18
6.5 How to connect your embedded antenna with your wireless module? 20
6.6 How to design an antenna matching circuit? 21
6.7 Free of charge software to generate a matching circuit automatically 22
6.8 How to switch between an internal and external cellular or GNSS antenna cheap? 22
6.9 Which GPS antenna shall be used for a tracking device? 23
6.10 Which embedded antenna to select for a Bluetooth / GNSS application? 24
6.11 Dos and don’ts during embedded antenna design 25
6.12 Example: Embedded PCB antenna inside a vending machine of NeoNumus 26
6.13 Example: Embedded antennas at Telematic device IN1 of GPSoverIP 28
7 Simulation of an embedded GSM PCB track antenna 28
7.1 Definition of the antenna simulation project 28
7.2 Description of the inverted F antenna 29
7.3 3D model of the simulation 30
7.4 Optimization – determination of antenna shape 31
7.5 Typical requirements of a quad band GSM antenna 31
7.6 Optimization of the quad band antenna GSM antenna shape 34
7.7 Directional characteristics of the antenna for two GSM frequencies 35
7.8 Influence on the antenna characteristics of the housing 37
7.9 Influence of the ground plane on the antenna characteristics 38
7.10 Optimisation of the simulated antenna with matching circuit (03.05.2014) 39
8 Components around the cellular module 39
8.1 SIM card 39
8.2 SIM card subscription 40
8.3 Low ESR capacitor 40
8.4 ESD protection, shielding , PCB routing(11.09.14) 41
8.5 Loudspeaker and microphone (14.04.14) 42
8.6 Firmware update at final PCB 42
9 Examples for mistakes and errors during M2M development 42
9.1 Power down reset 43
9.2 SMS errors 43
9.3 CSD errors 44
9.4 IP connection errors 44
9.5 Analysing of a maximum of design mistakes in one M2M design 45
9.6 Analysing of mistakes at PCB track antenna for GSM 45
9.7 Analysing of GSM chip antenna on small ground plane 46
9.8 Analysing of a Swiss GSM watch 47
9.9 Analysing of embedded LTE antenna in detail (27.04.2014) 47
10 Quick Start Guide Vector Analyser MiniVNA Tiny (06.10.2014) 48
10.1 Explanation S11, VSWR, return loss, reflection coefficient and antenna bandwidth 50
10.2 Unearth the truth – four cellular antennas tested with MiniVNA 52
11 Testing your M2M device 58
11.1 TX power peaks by cellular module test mode 58
11.2 Pseudo load of 2 Ampere peak load with self-made function generator (09.09.2014) 59
11.2.1 Schematic diagram of the self-made function generator 59
11.2.2 Pseudo load with 2 Ampere peak by standard function generator 59
11.3 TX power peaks by GSM tester 60
11.4 Testing of the sensitivity 60
11.5 Testing of the radiated TX power 60
11.6 Where to get a cheap cellular tester? 60
11.7 Example of a measurement report by GSM test equipment (26.07.2014) 61
11.8 Example of a measurement report by GSM test equipment (26.08.2014) 65
11.9 How to test an UMTS module on foreign band (26.08.2014) 66
11.10 Test with UMTS testers 66
11.10.1 Tests without UMTS tester 67
11.11 How to test an LTE module on foreign bands (26.08.2014) 67
11.12 Expected trouble with LTE modules worldwide (26.08.2014) 67
11.13 Testing the GNSS module (28.08.2014) 68
11.14 Measurement of the cellular antenna in 3D 69
11.15 Summary of testing 69
12 AT Commands 69
12.1 AT commands during power on your cellular module evaluation kit 70
12.2 Hello World in GSM – AT commands to send a SMS 71
12.3 AT commands and logic loops for set up a communication channel 71
13 Nice tools to make the IoT / M2M development easier (27.04.2014) 72
14 Thank you 72


1    Why to write the IoT / M2M Cookbook?

Since more than a century 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 called M2M devices. 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 a communication speed of 3600 bit per second. A while later we got public analogue trunked radios. These trunked radio 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. Nevertheless, SMS and CSD we could use for countywide communication easy and with roaming worldwide data communication came true. And today GSM/GPRS is phasing out step by step and will be replaced to 3G and 4G technology. In US the cellular operator AT&T does not accept new M2M applications on GSM/GPRS anymore. Some people try to split in M2M and IoT. IoT or M2M – it does not matter, both often use the same wireless link.
The IoT / M2M 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 specified by 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). 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 IoT / M2M Cookbook shall help developers of wireless 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 developer of an IoT / M2M device. In my more than 15 years working with a manufacturer and in distribution I gave the same hints and recommendations 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 an IoT / M2M device to a final product with mass production. The book will not tell you how an inverted F antenna is working. To explain this I will use links to files that tell the details. Anyhow the book will tell you facts 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 read the IoT / M2M Cookbook then do not hesitate to drop an email to harald.naumann (at)


Add a Comment
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  6. Hi Harald
    I chanced upon your website through google search and think it is very useful. I am interested in developing an application using GNSS + 3G connectivity and think your book may be useful.
    How much does it cost and how do I buy it ?


  7. Thank you for the interest in my IoT M2M Cookbook. I will come back to you by email.

    A major part of the book is about embedded antennas and ground plane. It includes a simulation of a GSM IFA antenna in different versions. The simulation includes the results by changing the size of the ground plane, enclosure and further parameters. This engineering job has already a value of Euro 3.500.

    The book got a zone for download in the meantime ( ). Here you’ll get for example the Touchtone export file out of the simulation for an upload to the free of charge software to design a matching circuit. This means you can play with the simulated antenna and will learn what will happen by changing components in the matching circuit.

    Every reader gets an in detail explained antenna shape and will be able to use the learned lessons for integration of any kind of self-made or out of the shelf antenna.
    Other chapters explain common mistakes of developers that I have seen during the last 20 years. Since January 2014 several PDF files were delivered. In parallel I consult a few wireless projects with embedded cellular antennas. The feedback of the readers and the feedback out of the projects trigged some new chapters or additional text in existing chapters.

    I still accept sponsoring of the book. The money out of the sponsoring I will use to finance the proof reading by an English native speaker and changing of some graphics. The latest sponsor is . They helped with four proposals for the book cover.

    I would be glad when you will be a reader of the book as well. I hope that you will enjoy reading and I hope it will save some of your time, too.

    Best regards from Germany

  8. Hi Harald,

    I came across this book thru a post of yours on linkedin. How do I get access to it?


  9. Dear Ramki, I offer the book as a PDF for download. Just have a look in your email inbox. You will find an email that will descripe the next steps. Have a nice weekend.

  10. Hi,
    I would be very interested in taking a look at your book
    Please advise how I can access a copy

  11. Mr. Naumann,

    I am also interested in your e-book. I can tell there is a lot of useful information from the chapter titles alone!

    Best regards,

    Adam Fuller

  12. Hi Harald,

    Please can I have access to the pdf download too? If you need any help with proof-reading, I may be able to help.

    – Niels

  13. Hi Niels, I will come back to you with an offer. The pro reading will be done by somebody from UK. This will move forward as soon I finished a new chapter. I bought a GSM tester Willtek 4202s like listed here:
    and explained in detail how to use such a tester. On top I offer the consulting at customers office. The customer and me sit together in front of the Willtek 4202s test together. We start with a standard mobile phone and move in second step with testing their own IoT / M2M devices.

  14. Hi Harald
    I’m developing a traking device and I think your book may be very useful.
    How I can have it?


  15. Dear Mikey, yes I have a price. I charge Euro 90 including all updates. Right now, my book readers got an update with the right to ask for further content. I would like to freeze the book end of the year and order the proof reading. I bought a GSM tester like listed here:
    and made some measurement reports taken by the tester public. I explained what to do with such a tester and why. In parallel I started to offer consultancy local, by email and phone. My target is to make the life of IoT M2M developers easy. As soon the first book is finished I will start to write the next book. The concept for the next book is already in my mind.

  16. Hi Harold ,

    I am interested in buying your book. How can I get access to it.



  17. Hi Adithya, I will come back to you by email. Please help with your postal address. This is neccesray to write the proforma invoice and later on the final invoice.

  18. Dear Laurent, I will come back to you by email. Just to let you know, that the book will contain all updates up to the final version. Right now, I try to follow the wishes of the book readers and write updates of chapters or complete new chapters. I plan to finish it including proof reading by native speaker for end of this year.
    One of the latest chapters is the testing of IoT M2M devices on GSM by GSM tester. I bought such a GSM tester and made the test reports public. I also explained which tests shall be done and why. On top I offer consulting local at customer office, telephone and email.
    My latest tool is the MiniVNA Tiny listed here:
    I got training by a very high skilled engineer yesterday. The RF engineer runs a small company and produces its own VNA with small bandwidth (2400 MHz range). The result out of the training I will try to make public. Testing of embedded antennas on PCB is real difficult. I will try to explain it so detailed, that the book readers will be able to follow or at least will understand, that you will worst case have a need of a third party for the tuning.

  19. Hi Herald,

    We are developers of IoT solutions for our industrial customers. As part of our solution, we also integrate with some of the things you mentioned like GPS, GSM/GPRS. Would be keen to know your learnings and see if we can help add some more. Could you please share the ebook.

    Thanks & regards,

  20. Hi Mahesh,
    I will come back with an email. My first IoT M2M Cookbook is related to cellular modules (GSM/GPRS, UMTS, HSPA, LTE) plus GNSS (GPS, Glonass, Galileo), because I am close to 20 years in GSM+GPS. Right now the updates of the book are driven by the readers. I try to follow their wishes.
    Bye for now

  21. Hi Harald,
    I came across your IoT cookbook through our common friends on linkedin. Can I get access to it?



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  23. Hi Jan, I will come back with an proforma invoice to you. After that I help with a copy by download.
    BTW, will you stay at electronica in Munich? I will stay the whole week at the stand of Compotek / Tekmodul Hall A4 / 342. Can we meet in Munich?

  24. Hi Harald,

    I am interested in your book, can you send me a copy?

    Thank you, regards.

  25. Dear Kumar, yes every IoT M2M developer can get a copy. Please be so kind and email me to harald.naumann (at) I need your postal address to write the proforma invoice. Will you stay at electromica in Munich next week? I will stay the whole week at the stand of Compotek / Tekmodul Hall A4 / 342. I will show the latest version of the book plus some antenna shapes on customer PCBs.

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  28. Dear Artur, I will come back to you by email. BTW, I met your company years ago at Hanover Industry Fair in Hanover. I would be glad to meet again. See you.

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