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 Did I Write the IoT / M2M Cookbook?    5
2 Fundamental considerations before starting the IoT / M2M project    6
3 Certifications and approvals    6
3.1 Examples for Radio approvals in EU and US    6
3.2 Examples for Radio approvals in US and Canada (PTCRB)    8
3.3 Examples for automotive related approvals in Europe    8
3.4 SAR – Specific Absorption Rate    9
4 Cellular data communication (GPRS, USSD, SMS, CSD, DTMF)    9
4.1 Voice communication    10
4.2 Modem / acoustic coupler / encryption    10
4.3 DTMF (Dual Tone Multi Frequency)    10
4.4 GPRS (General Packed Radio Service)    11
4.5 SMS    11
4.6 USSD (Unstructured Supplementary Service Data)    12
4.7 Comparison of power consumption (SMS, USSD and GPRS)    12
4.8 CSD (Circuit Switched Data)    13
5 Supply voltage    14
5.1 Power on timing and waiting (14.04.14)    14
5.2 Cellular module in power save mode (14.04.2014)    14
5.3 Internal resistance of batteries and linear voltage transformers    15
5.4 Switched mode voltage regulator    17
5.5 Simulation of a switched power supplies with LT Spice    17
5.6 Capacitors at power supply and cellular module (14.04.2014)    19
5.7 Supply voltage for GNSS antenna (14.04.2014)    19
6 Antennas for IoT / M2M devices    19
6.1 Monopole and dipole antennas    19
6.2 Nothing will interfere with your embedded antenna?    20
6.3 Why the embedded chip or patch antennas are resonant on the frequency?    21
6.4 How will the ground plane affect your embedded antenna?    21
6.5 How to connect your embedded antenna with your wireless module 04.11.2014    23
6.6 How to design an antenna matching circuit    25
6.7 Free of charge software to generate a matching circuit automatically    26
6.8 How to switch between an internal and external cellular or GNSS antenna cheap?    26
6.9 Which GPS antenna shall be used for a tracking device?    27
6.10 Which embedded antenna to select for a Bluetooth / GNSS application?    28
6.11 Dos and don’ts during embedded antenna design    30
6.12 Example: Embedded PCB antenna inside a vending machine    31
6.13 Example: Embedded antennas at Telematic device IN1 of GPSoverIP    32
7 Simulation of an embedded GSM PCB track antenna    32
7.1 Definition of the antenna simulation project    32
7.2 Description of the inverted F antenna    33
7.3 3D model of the simulation    34
7.4 Optimization – determination of antenna shape    35
7.5 Typical requirements of a quad band GSM antenna    35
7.6 Optimization of the quad band antenna GSM antenna shape    38
7.7 Directional characteristics of the antenna for two GSM frequencies    39
7.8 Influence on the antenna characteristics of the housing    41
7.9 Influence of the ground plane on the antenna characteristics    42
7.10 Optimisation of the simulated antenna with matching circuit (03.05.2014)    43
7.11 Design in of the simulated antenna to special GSM / GPS tracker (26.10.2014)    44
8 Components around the cellular module    45
8.1 SIM card    45
8.2 SIM card subscription    46
8.3 Low ESR capacitor    46
8.4 ESD protection (11.09.14)    47
8.5 Loudspeaker and microphone    47
8.6 Firmware update at final PCB    47
9 Examples for mistakes and errors during M2M development    47
9.1 Power down reset    48
9.2 SMS errors    48
9.3 CSD errors    49
9.4 IP connection errors    49
9.5 Analysing of a maximum of design mistakes in one M2M design    49
9.6 Analysing of mistakes at PCB track antenna for GSM    50
9.7 Analysing of GSM chip antenna on small ground plane    51
9.8 Analysing of a Swiss GSM watch    52
9.9 Analysing of embedded LTE antenna in detail (27.04.2014)    52
10 Radiation noise, maximum spurious, antenna radiation (13.10.2014)    53
10.1 Antenna radiation versus radiation noise    53
10.2 Conductive noise    55
10.3 Conductive noise transformed to radiated noise    55
10.4 Radiated noise transformed to conductive noise    55
10.5 Prevention against radiated noise    56
11 How to use a vector network analyser for IoT M2M development (02.01.2015)    57
11.1 Quick Start Guide Vector Analyser MiniVNA Tiny (06.10.2014)    59
11.2 Explanation S11, VSWR, return loss, reflection coefficient and antenna bandwidth    62
11.3 Unearth the truth – four cellular antennas tested with MiniVNA    64
11.4 A comparison of three Vector Network Analysers (07.02.2015)    70
12 Testing your M2M device    76
12.1 TX power peaks by cellular module test mode    76
12.2 Pseudo load of 2 Ampere peak load with self-made function generator (09.09.2014)    76
12.3 TX power peaks by GSM tester    77
12.4 Testing of the sensitivity    78
12.5 Testing of the radiated TX power    78
12.6 Where to get a cheap cellular tester?    78
12.7 Example of a measurement report by GSM test equipment (26.07.2014)    78
12.8 Ripple and peak voltage – visible by GSM test equipment (26.08.2014)    82
12.9 How to test an UMTS module on foreign band (26.08.2014)    84
12.10 Test with UMTS testers    84
12.11 How to test an LTE module on foreign bands (26.08.2014)    85
12.12 Expected trouble with LTE modules worldwide (26.08.2014)    85
12.13 Testing the GNSS module (28.08.2014)    86
12.14 Measurement of the cellular antenna in 3D    87
12.15 Summary of testing    87
13 AT Commands    87
13.1 AT commands during power on your cellular module evaluation kit    87
13.2 Hello World in GSM – AT commands to send a SMS    89
13.3 AT commands and logic loops for set up a communication channel    89
14 Project descriptions of IoT M2M devices (26.10.2014)    91
14.1 Project description of a long-term tracking device    91
14.2 Project description of a bendable tracking device of bank notes    92
15 Thank you    94

1 Why Did I Write the IoT / M2M Cookbook?

I have worked in the Wireless M2M for more than a quarter of a century. Twenty-five years ago, we didn’t even have a word for “M2M” or IoT. We developed Machine to Machine devices without knowing that decades later these creations would be called “M2M devices”. Twenty-five years ago, the GSM network for wireless data communication did not exist. I made my first steps in wireless data communication with Frequency Shift Keying (FSK) on Private Mobile Radios (PMR). On PMRs we achieved communication speeds of 3600 bits per second. A little later we started using public analogue trunked radios. These trunked radio systems provided local terrestrial wireless networks on FSK. Years ago, the final public analogue trunked radio network in Germany was taken out of service. GSM jumped in with its Short Message Service (SMS) and Circuit Switched Data (CSD). CSD provided us 9600 bits per second. We could use SMS and CSD for countrywide data communication easily. Later on GSM roaming offered us worldwide data communication. Today, GSM/GPRS is being gradually phased out and is being replaced by 3G and 4G technology.

In the US, the cellular operator AT&T does no longer accept new M2M applications on GSM/GPRS. AT&T will accept applications on 3G and 4G (UMTS, HSPA, LTE) only. Some people try to differentiate between M2M and IoT. Call it IoT or M2M – it does not matter. Applications for IoT or M2M often use the same wireless technology. IoT is the umbrella for a number of subsets of wireless data communications. M2M is one out of these subsets and maybe one of the oldest subsets as well.

This IoT / M2M Cookbook describes how to develop a tracking device based on cellular and GNSS modules. You can create a telemetric device by ignoring the GNSS aspect. Typical devices without GNSS include cellular routers with Ethernet ports or a cellular to Wi-Fi bridge. Nevertheless, the navigation system for trucks described in this book already uses six different wireless technologies (2G, 3G, GNSS, Classic Bluetooth, Bluetooth Low Energy and NFC) with five different antennas within one enclosure.

Cellular networks for GSM, HSPA and LTE are the popular Wireless Wide Area Networks (WWAN). However, in some regions we have WWAN over CDMA and WiMax.

Sometimes it is not easy to come up with the appropriate English word for the terms in this book. The common word for SMS in UK is “text message”. In this book, we will consistently use the term “SMS”. A prepaid SIM card in UK is called a “Pay as you go SIM card”. I will typically use the common words specified by ETSI – I will call it a prepaid SIM card. If I use the term “GSM module”, this will cover 3G and 4G modules as well, because the fall-back of UMTS, HSPA and LTE is still 2G (GSM/GPRS). GPS is fundamentally an incorrect term. The Global Positioning System (GPS) is just one out of several Global Navigation Satellite Systems (GNSS) that provide the functionality we refer to as “GPS”. We can currently access the Russian GNSS called Glonass. The Chinese GNSS is called Beidou. At some point we will be able to access the European GNSS called Galileo.

The IoT / M2M Cookbook is intended to help developers of wireless application save some time and perhaps provide some inspiring ideas. It is a book for makers and summarizes the collective experience across my different jobs. By leading a team of developers required to design a mobile GSM/GPS tracking device, I learned to think like a developer of an IoT / M2M device. In over fifteen years of working with manufacturing and distribution, I provided the same hints and recommendations to developers of wireless applications again and again. The origin of this book was a 14 page application note written in July 2010. In May 2012, I made the decision to convey the story that I deliver weekly to customers within a book. The goal of this book is to guide developers from the concept of an IoT / M2M device to the final mass-produced product. This book will not provide introductory detail support such as how an inverted F antenna works. To explain those concepts, I will provide links to relevant supporting information. In any case, this book will provide you with information that is often omitted in the official radio module and antenna manufacturers’ documentation. This book shows an inverted F PCB antenna for GSM in detail. It explains how to redesign it with your own PCB and how to encapsulate the whole design in epoxy resin. It also explains how to integrate a chip or PCB antenna with coaxial cable.

Some power supply concepts including LT Spice modules for DC/DC regulators and load generator for the 2 Ampere peak currents are included in the book, too. It should be noted that the power down reset is still the main fault in designs with cellular modules.
I hope you will enjoy reading the book and I hope it will save you some 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) gsm-modem.de

65 Comments

Add a Comment
  1. Hello Harald

    I am interested in your book, how do i proceed to get access it.

    Thanks
    Gordon

  2. Hi Harald,
    I am interested in your book. How do I download it? Thanks
    BJ Raval

  3. Pingback: Quora
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  5. Hi ,

    I am interested in ordering a pdf copy of your book.
    Please advice me the next step.

    Thank you .

  6. Welson, you get a link and password after placing an order and money on my account. You can pay by Paypal, debiting of your credit card by Paypal or wiring to my bank account.

  7. Hi Harald,

    I am interested ordering copy of your book, please advise how to proceed.

  8. Hi

    Suggest the cost for Cookbook PDF file and ways for payment.
    I am interested in PCB Antenna for GSM.

    Thanks
    Pavan

  9. Hi Pavan, you got an offer by email. The price is still Euro 90 and I do not plan to rise it.
    BTW, today I published “Can a magician reveal the magic tricks?”
    As many already know, I am interested in antennas. My great interest is integrated antennas. Such antennas can be found in gateways for electricity meters, but also in portable point of sale systems. Even permanently installed telematics devices use integrated antennas. For many developers integrated antennas are still magic.
    Is it allowed to reveal some magic tricks of the antennas?
    The advantages of integrated antennas are varied – Read more:
    http://www.gsm-modem.de/M2M/m2m-faq/can-a-magician-reveal-the-magic-tricks/

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