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Digi Edge Compute with AWS Greengrass

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Edge compute, messaging, data caching, sync, and ML inference capabilities for connected devices

AWS Partner Network logoDigi ConnectCore® embedded solutions along with AWS Greengrass are designed to support edge devices with cloud connectivity.

Based on the NXP i.MX line of application processors, Digi ConnectCore embedded SOMs and SBCs deliver the compute power necessary to run Greengrass Core and interact directly with the cloud.

Developers can use AWS Greengrass to integrate Lambda functions locally and then conveniently deploy them to connected devices at the edge of the network.

AWS connectivity
Source: Amazon Web Services

With Digi SOMs and SBCs, you can move quickly from idea, to prototype, to deployment with the powerful combination of AWS Greengrass and Digi ConnectCore:

  • • Implemented on Yocto Project Linux for embedded devices
  • • Integration of embedded AWS Lambda device-level functions
  • • Digi TrustFence® device-level security with features such as secure connections, authenticated boot, and secure physical ports
  • • Remote device monitoring with Digi Remote Manager®
  • • Secure firmware update to group devices using AWS-based firmware images via the Greengrass Core

Related white paper: IoT Device Security — Built-in, Not Bolt-on: The 10 Security Factors Every Device Designer Should Consider

“Building connected devices for the industrial IoT requires secure local device level intelligence without dependency on constant connectivity,” said Scott Nelson, Chief Product Officer at Digi International.

“The unique combination of Digi TrustFence device security, local Lambda extensions, Digi Remote Manager® integration, and Amazon Web Services’ Greengrass delivers the vision for the next generation of IoT edge intelligence in embedded devices.”

>> Learn about Digi’s strategic embedded solutions for scalable, future-proof connectivity.

How to Pick the Right 4G LTE Technology for Your Business Needs and Applications

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With the shutdown of 2G and 3G networks looming on the horizon, many organizations are faced with the difficult question of “So, what’s next?” The key question to really ask is, “Well, what is the application?” Meaning, what is the current or projected use case and how will it be impacted by the new LTE technology. In addition, ask yourself where are you today and where do you want to be in five years; and most importantly, what business problems are you trying to solve with the new network capabilities?

You’ll soon find there are many items associated with those key business and technology questions that need to be further analyzed:

  • Bandwidth: determine whether you need data transferred in bursts or as a steady feed over time; and decide if you need to transfer only a few bytes or several GB each day.
  • Data Plan: evaluate if data will be needed in real time, or if a several second, minute or hour delay is tolerable, and choose the most economical plan.
  • Connectivity: decide if your organization’s communication requirement is to be localized across a building, plant, or a city – or even across a country or worldwide. Consider whether you must always remain online, and if downtime could put you at the risk of lost revenue, regulatory penalties or safety violations.
  • Environmental: assess whether your equipment will be in a climate-controlled environment or outdoors in harsh, even hazardous settings. Determine if AC power will be available, or if battery or solar power is the only option.
  • What about 5G? Finally, weigh the pros and cons of waiting for 5G. Do you want to take on a bleeding-edge technology in its initial stages, or would you rather rely on a proven leading-edge technology like 4G? Will a bleeding edge technology make your application or its output better? Keep in mind that 4G is also evolving into 5G over time.

Today, we are at a fork in the road. One path can leverage Gigabit LTE for high-speed applications in retail, enterprise or transportation industries that need to connect sites or people with mains-powered, high bandwidth – and higher cost – solutions. The other path can leverage 4G LTE optimized for IoT applications in industrial locations to connect machines and other critical assets that require low bandwidth, low cost, and low- or battery-power as indicated by the chart below.

4G LTE Evolution for IoT

Each 4G LTE technology has its pros and cons, while carriers considering a roll out of LTE-M or NB-IoT as a secondary network only adding to the complexity. Here’s a deeper dive into the technology options for IoT devices:

  • CAT 1: represents a good fit for many single-device IoT applications with mains-power, such as digital signage and kiosks, industrial controllers and security cameras. It is globally available where LTE is accessible.
  • CAT 3/4: with the potential of speeds up to 100-150 Mbps, this technology is designed for IoT routers connecting multiple devices. However, it may be excessive for most single-device IoT applications.
  • CAT-M/LTE-M: fits traditional 2G-type applications, devices that require mobility, such as asset trackers, as well as battery-powered IoT sensors. Defined in 2016, it is not yet fully globally available, but is predominant in North and Latin American and Asian markets with early LTE adoption.
  • NB-IoT: best fit for battery-powered devices that do not require mobility, such as fixed-asset sensors. Also defined in 2016, it is not globally available as this time, but suits markets with late LTE adoption, like Europe.

4G LTE Evolution for Gigabit LTE

Now let’s go down the other path with a look at Gigabit LTE and the 4G evolution to 5G.
The 3rd Generation Partnership Project (3GPP) is a collaborative group of telecommunications associations that defines the standards to build the foundation of cellular networks, such as LTE.

Since its initial release in 2008, LTE (Long Term Evolution) has evolved, and continues to evolve towards 5G over time. Typically, 3GPP releases a major update of the standard every three years, followed by a minor release. To differentiate between major LTE releases, 3GPP introduced marketing names such as LTE-Advanced and LTE Advanced Pro. Release 13/14 were a key milestone for Gigabit LTE because the speed doubled to 1.2Gbps. Release 15, to be released later in 2018, will be the first standard defining 5G.

Source: Telit


Four Requirements to Achieve Gigabit LTE Speeds

1. More RF channels and carrier aggregation: think multiple highways to transport more vehicles. Gives you better us of the available spectrum, as many carriers don’t have 20 MHz of licensed spectrum per band available.

  • Higher peak data rates
  • More capacity for bursts of usage
Source: Qualcomm

2. Higher-order modulation (HOM) (see Figure #2): think of a bus versus a car to transport more people (i.e., data) per vehicle, where the cellular network and device are constantly adjusting the modulation based on signal conditions. The downside of HOM is that a noisy or weak signal is harder to demodulate, which can result in retransmissions and lower speeds.

  • 16-QAM: 4 bits/symbol
  • 64-QAM: 6 bits/symbol, 25% improvement over QAM-16
  • 256-QAM: 8 bits/symbol, 33% improvement over QAM-64
  • 1024-QAM: 10 bits/symbol, 25% improvement over QAM-256.

3. More MIMO (Multiple Input, Multiple Output) antennas: think multi-lane highway with traffic moving on two directions (using multiple antennas to both transmit and receive data in parallel). Most devices today have two antennas per cellular modem, while Gigabit LTE devices will require four antennas to achieve higher speeds. For many devices, this means moving from direct-attach to cabled antennas.

4. More spectrum: the use of licensed, shared or unlicensed spectrum (3.5GHz/5GHz) for additional bandwidth now includes License Assisted Access (LAA) and Citizens Broadband Radio system (CBRS).

  • Citizens Broadband Radio System (CBRS)
    1. As of April 2015, the FCC authorized shared commercial access of the 3.5GHz band with incumbent military radars and fixed satellite stations
    2. The CBRS spectrum is assigned individually by Spectrum Allocation Server (SAS), 3 priority access levels
  • MulteFire
    1. MulteFire Alliance is a new industry alliance promoting private networks based on LTE technology
    2. MulteFire scales from LTE for IoT to Gigabit LTE
    3. It is not part of any 3GPP standard yet, but is considered for Rel. 16
    4. MulteFire could someday replace Wi-Fi networks

Private LTE networks provide new opportunities for either enterprises to deploy secure communication for increased flexibility and added security, or for the Industrial IoT (IIoT) to build a private network, for example in remote farming or mining sites to run industrial IoT devices and applications.

4G LTE Advanced Pro is here today and paving the way to 5G as outlined above. Though, you will not see Gigabit LTE speeds right away. You can expect speeds above 100 Mbps under good conditions on licensed LTE networks. Even higher speeds will become possible where unlicensed spectrum and infrastructure become available.

How to Ensure a Successful Migration from 2G and 3G to 4G LTE

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As wireless communication networks continue to rapidly evolve and more carriers announce their plans to discontinue legacy networks, it is imperative that corporate network managers, industrial network operators, and device manufacturers understand the challenges of conducting a 3G to 4G LTE migration . In order to better understand these 4G LTE migration challenges and to prepare for a seamless transition from 3G to 4G LTE networks, you should first answers these four questions:

  1. How many 3G devices are currently active on the field?
    This is an important number to identify and know in order to actually answer the following questions.
  2. What is it going to cost to transition these devices to 4G LTE?
    Migration costs to consider include the cost of hardware, cost of truck roll, manpower hours, and updated carrier plans.
  3. How long will a 2G or 3G to 4G migration take?
    Once the number of devices and migration cost have been identified, you can start to successfully map out the transition timeline based on the carrier’s 4G network introduction plan.
  4. What are my application connectivity needs?
    Lastly, understanding specific needs of existing legacy devices and the needs of highly capable devices today, can maximize your investment, lower design costs and increase higher volume deployments.. A few specification options to consider include battery life, power consumption, data usage, bandwidth, mobility, geographic coverage, etc.

In conclusion, the migration away from legacy networks have already started because device manufactures can no longer rely on 2G or 3G for Internet of Things (IoT) applications. With 2G shutdowns already occurring and 3G network shutdowns on the horizon, long-term transition plans and migration strategies are vital for network engineers and administrators to capitalize on the advantages of 4G, 5G, and LTE.

>>Read the Any-G to LTE whitepaper for more details on migrating to 4G, 5G, and beyond

Understanding the Zigbee 3.0 Protocol

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Zigbee is a wireless technology developed as an open global standard to address the unique needs of low-cost, low-power wireless IoT networks. The Zigbee standard operates on the IEEE 802.15.4 physical radio specification and operates in unlicensed bands including 2.4 GHz, 900 MHz and 868 MHz.

The 802.15.4 specification upon which the ZigBee stack operates gained ratification by the Institute of Electrical and Electronics Engineers (IEEE) in 2003. The specification is a packet-based radio protocol intended for low-cost, battery-operated devices. The protocol allows devices to communicate in a variety of network topologies and can have battery life lasting several years.


The Zigbee 3.0 protocol has been created and ratified by member companies of the Zigbee Alliance. Over 300 leading semiconductor manufacturers, technology firms, OEMs and service companies comprise the Zigbee Alliance membership. The Zigbee protocol was designed to provide an easy-to-use wireless data solution characterized by secure, reliable wireless network architectures.


The Zigbee 3.0 protocol is designed to communicate data through noisy RF environments that are common in commercial and industrial applications. Version 3.0 builds on the existing Zigbee standard but unifies the market-specific application profiles to allow all devices to be wirelessly connected in the same network, irrespective of their market designation and function. Furthermore, a Zigbee 3.0 certification scheme ensures the interoperability of products from different manufacturers. Connecting Zigbee 3.0 networks to the IP domain opens up monitoring and control from devices such as smartphones and tablets on a LAN or WAN, including the Internet, and brings the true Internet of Things to fruition.

Zigbee protocol features include:

  • Support for multiple network topologies such as point-to-point,
    point-to-multipoint and mesh networks
  • Low duty cycle – provides long battery life
  • Low latency
  • Direct Sequence Spread Spectrum (DSSS)Up to 65,000 nodes per network
  • 128-bit AES encryption for secure data connections
  • Collision avoidance, retries and acknowledgements

>>Check out the newest Digi XBee3 Zigbee video to learn more.

Sum of Smarts: Security, Reliability, Certifications & ROI

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Digi XBee3’s smart security, reliability and certifications all add up to the very smartest return on your investment. While you’re speeding your product to market with your mind at ease, you’re also delivering more funds to the bottom line. Products built with Digi XBee3 can be released sooner and will run more smoothly, creating revenue earlier while greatly reducing costs over the long-term. Here’s how it all adds up in your favor:

Smart Security

Digi XBee3 offers comprehensive security with flexible options to match your application’s needs. Digi TrustFence™ is a suite of security features that provides system protection, authentication and data privacy inside every Digi XBee3.

  • Secure Boot ensures that only properly signed and authorized firmware will run on your modules. Any attempt to load non-approved firmware will fail immediately since firmware is checked both during initial installation and at every runtime.
  • Authentication services are available for both data and device identity to ensure that only your actual devices can send their real data into your system, with rouge devices or modified data locked out by default. Secure Connections encrypt your data in transit and ensure data integrity over the air.
  • Electronic security must always be combined with physical security so that physical access to a single device can’t supply access to your entire network. Digi XBee3’s Protected Ports harden and control access to I/O ports preventing local intrusion and keeping your security keys and private information locked down even when your device can’t be.
  • That physical protection doesn’t stop on the outside. By implementing Secured Storage, Digi XBee3 performs file system level encryption so that sensitive information stays private no matter what. The security landscape is constantly changing, so Digi’s security team constantly evaluates new risks and can quickly supply authorized firmware updates to address any emerging concerns. Digi XBee3’s built-in smart security speeds development, protects deployments and ensures your organization can stay focused on what it does best.

Smart Reliability

Great IoT solutions are always available, always up-to-date and always accurate. Digi XBee3 delivers the whole package, with predictable high-quality manufacturing you can depend on, and long product lifecycles all from a stable partner. Smart Reliability is designed into Digi XBee3 on many levels. Modules communicate reliably right out of the box to help speed the evaluation process as well as providing a known reliable state to fall back on throughout development.

  • Standards-Based – Standard physical and electrical pinouts and a common command set mean that your code and designs work reliably even when supporting multiple protocols. It also means that Digi XBee3 will operate reliably on a variety of development boards available from third-party vendors in addition to the standard reference models provided by Digi International.
  • Mesh Networking – Connection reliability features are provided for all Digi XBee3 variants. Mesh protocols such as DigiMesh and ZigBee offer reliable ad-hoc network creation in a self-healing mesh, so that no unit ever becomes a single point of failure.
  • Digi SureLink™ – Cellular connections stay dependable with automatic retries, connection monitoring and cloud-level alerts so your staff is informed of any outages in the network before your customers are even aware. All Digi XBee3 modules come with a full one-year warranty from a company that’s provided reliable, award-winning communications equipment for over 30 years.

Smart Certifications

Digi XBee3 modules carry international end-device certifications to permit implementation around the globe, often without any further efforts. This can save months of time, tens of thousands in expenditures and help lock down delivery dates. In many cases, Digi XBee3 can be properly included in a product simply by following labeling guidelines, with no additional testing or confirmation required. This will have a direct impact on the bottom line and help maintain focus on building great product rather than struggling to satisfy regulators.

Smart ROI

Let’s do the math. Smart Security + Smart Reliability + Smart Certifications equals the Smartest ROI. Having each of these features built in to Digi XBee3 lowers your non-recurring engineering (NRE) costs while speeding time to market. Faster to market means faster to revenue. You’ll be spending less to get to market sooner. Smart Reliability protects your investment in the field, improving service while reducing or eliminating maintenance expenses. Smart Security deploys quickly and prevents unwanted disruptions, keeping customers happy and revenue flowing unimpeded. Smart Programmability can eliminate unneeded external components and dramatically reduce data costs. Smart Power management allows smaller and less costly batteries to do the work of larger more expensive ones. It also extends battery replacement cycles, lowering ongoing maintenance expenses. You can see why we call Digi XBee3 smart!

Use Case

Here’s an example showing how all of this comes together:

Modern vehicles use electronic networks to communicate between components inside your car. For example, a speed sensor near the transmission sends digitized data over the car’s onboard network to an electronic speedometer display—mechanical connections are a thing of the past. Nearly everything in the car communicates with data, from the gas pedal to the windows. All this data is available through standardized ports, though the format and features vary by manufacturer and model.

A technology startup wants to connect car owners with all the electronic data being generated by their vehicle. They specify a cellular-connected product that sends data from the vehicle’s standard OBD-II port to the cloud. The data must be kept secure in transit, with cloud server access keys stored on the device. Their investors need to see revenue as quickly as possible, therefore development must be fast, and certification delays should be eliminated to meet the schedule and budget. The device should be unobtrusive so components need to be small. Depending upon region and carrier, different cellular modules will be required, so common physical and electronic footprints are mandatory. The automotive environment is challenging; therefore high reliability is essential to product success. Watch this video for more Digi XBee3 Cellular use cases explained:

Digi XBee3 Cellular is the perfect fit. It is already end-device certified so governmental and carrier approval is in place, saving perhaps 3 months on the development schedule. The Digi XBee3 standard command set and API frames, along with its supporting libraries speed up the code-writing and debugging process tremendously. Digi TrustFence security is built right in, including both the SSL/TLS encryption and the secure storage required for protecting cloud authentication keys on the device itself. The common device footprint makes swapping protocols a breeze. Changing an LTE Cat 1 solution to 3G or NB-IoT is as simple as plugging in a new module. The Smart Size and flexible antenna options all help keep the device itself unobtrusive, a plus for customer satisfaction. The whole solution is backed up by Digi’s ongoing reliability and security monitoring efforts, as well as the company’s long product life cycles that protect against component obsolescence. Now drivers can read vehicle diagnostics and also gain access to customizing button-press audio feedback, improving engine tuning or even creating their own remote ignition system. This startup is on its way to getting the best return on their innovation investment–because Digi XBee3 summed up to being the Smartest solution.

>>Check out this latest whitepaper for more advantages of Digi XBee3 Cellular.

Sum of Smarts Featuring: Modularity and Programmability

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Digi XBee3™ IoT modules go straight to the head of the class. One reason is outstanding flexibility. A single socket allows you to connect with IoT networks around the globe. Digi XBee3 pin-compatible footprints support multiple protocols and unified command frameworks while retaining superior implementation flexibility. As new protocols emerge, Digi XBee3 series will offer them using these same pin-outs, future-proofing your designs. Digi XBee3 also features programmable on-board intelligence. By creating applications on your Digi XBee3 using its MicroPython framework, you can implement business rules for money-saving solutions like intelligent bandwidth control, dynamic power conservation or full outage management. New behaviors can be dynamically implemented over the air so as your business changes, your solution can rise to meet the challenge.


Digi XBee3 currently lets you choose between eight different protocols, and easily change between them without learning new command frameworks, writing new code or even changing your board layout. They include:

  • 802.15.4 for point-to-multipoint local connections
  • ZigBee 3.0 for creating interoperable mesh networks
  • DigiMesh for fast, single-source mesh solutions
  • Cellular for gateway-free applications worldwide including:
    • 3G for legacy compatibility
    • LTE Cat 1 for modern connections
    • LTE-M for lower data needs and improved power management
    • NB-IoT when only minimal cellular bandwidth is required.

Plus, Bluetooth Low Energy is coming soon as a dual-mode add-on protocol for the entire Digi XBee3 line, enabling connections to external wireless sensors and smartphones.

Choice of Command Sets
Configure any way you like. Digi XBee3 offers four interchangeable methods for handling configurations, commands and communications. For easy access to the full configuration, all Digi XBee3 models support AT commands that can be issued from any serial terminal program. For structured interactions with microcontrollers and external devices, every Digi XBee3 supports a standard frame-based API that’s perfect for machine-to-machine transactions. Local configuration is made easy with the graphical user interface provided by Digi’s XCTU software, and remote configuration is enabled from the cloud using Digi Remote Manager. No matter which you choose, the command frameworks are all the same.

Unified Frameworks
All Digi XBee3 AT commands and API frames are standardized across all form factors and protocols. All commands work the same way across all modules, with protocol differences kept to a minimum so that changing between modules is as quick and transparent as possible.

Choice of Gateways
Certain protocols require gateways to connect to the Internet. Digi offers a variety of Wi-Fi, Ethernet and Cellular Digi XBee3 Gateways for use with XBee3 in both commercial and industrial-rated packages. Third party gateways can easily be developed around Digi’s ConnectCore® 6UL embedded platform, or using a custom platform of your own design.




Modules in the Digi XBee3 series all run applications written in MicroPython, an embedded variant of the popular Python programming language. There are so many great reasons for intelligence at the edge:

  • Saving bandwidth costs by only sending useful data
  • Saving battery and replacement costs by using only the power that your application requires
  • Controlling local behaviors dynamically without the cost of unnecessary cloud connections
  • Managing directly connected sensors and actuators, to keep simple projects simple
  • Allowing devices to behave intelligently during communication outages
  • Caching data locally during network outages, then sending it immediately as soon as connectivity returns
  • Adapting to changing business needs by securely accepting new behaviors over the air
  • Testing and debugging deployed applications by dynamically modifying code over-the-air
  • Addressing host device problems from the cloud rather than paying for needless truck rolls

Programmability doesn’t live on its own of course, it takes an ecosystem. Digi XBee3 has the tools and resources you need including full documentation online, software development environments, sample code, example programs, training and open-source expandability. Let your imagination run wireless!

Use Case

How can programmability at the edge can make a difference in real-world IoT systems? Outdoor municipal street lighting is a perfect example. Street lights typically use considerable energy and government maintenance resources. Lights shine brightly all night, whether or not anyone is even in the area. When a streetlight malfunctions, repairs depend upon citizen reports, which may not occur for days or even months after an initial failure. This is a big problem, and just the type that can benefit from intelligence at the edge.

With Digi XBee3 wireless modules, the behaviors needed to improve energy use, reliability and safety can be installed right inside every streetlight. Apps running on each Digi XBee3 module can process motion sensor inputs and intelligently set that streetlight’s brightness accordingly. For example, while a street is unoccupied, lighting can be dimmed to 50%, then smoothly increased to 90% whenever a pedestrian or bicycle’s motion is detected. Since the application runs locally on Digi XBee3, no cloud communication or external microcontrollers are required. This improves reliability while keeping bandwidth and system costs low, at the same time saving so much energy that the system pays for itself. If a streetlight malfunctions, its neighbors can detect the outage locally and increase their own brightness to compensate. This level of safety can be maintained even through network outages, very important during major storms. Naturally the Digi XBee3 application will report outages to the cloud as soon as possible, so that maintenance can begin immediately. Municipalities can test out new ideas by loading upgraded application code to a subset of streetlights as a pilot, before deploying the new code to the entire city.

In this street lighting application, Digi XBee3’s programmability enables energy savings, improves customer service, maintains reliability and reduces maintenance costs while providing a clear path forward for innovation. It can revolutionize your systems in the same way.

>>Want to learn more? Check out this latest whitepaper Wireless Future: Partnering for What Comes Next

How to Choose the Right Antenna for Your IoT Application

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Antennas come in many shapes and sizes, for many different uses. Some are attached externally to the product for the correct functionality, while others must be designed into the end device so it is both invisible and functional. For example, if you have a device enclosed in a metal box, like a router, your antenna is going to be connected externally. For a mobile device or wearable, however, you probably want a smaller antenna that is built into the internal design. The types of antennas for these different applications vary not only due to size and placement, but also properties and functionality.

In this post, we’ve provided an overview of the most prevalent antenna types and their common IoT applications. Note that most categories of antennas have several sub-types. Additionally, the topic of antennas can quickly get into deep technical detail and mathematical formulas, which is beyond the scope of this post. . If you need further assistance with your antenna selection, our Wireless Design Services team can help.

Topics in this blog

  1. Dipole Antennas
  2. Monopole Antennas
  3. Loop Antennas
  4. Helical Antennas
  5. Patch Antennas
  6. Slot Antennas

1) Dipole Antennas

Dipole antennas are omni-directional, which means they radiate signals in all directions on at least one plane. They are typically large since they are half wavelength structures. This amounts to about 6 inches in length for cellular antennas. These antennas are nearly always used externally, such as for metal box devices like routers and gateways. They may ship with the device or may need to be ordered separately.

Properties of Dipole Antennas

Dipole antennas are very efficient antennas with a consistent performance, omni-directional radiation pattern, and reliable polarization. A dipole antenna has a radiation pattern that is not dependent on the size of the box or the ground plane.  This is accomplished because the dipole has balanced currents on both antenna arms resulting in little current flow on the ground plane or chassis. The radiation pattern looks like a donut with most of the energy being emitted from the broadside of the antenna. The antenna isolates itself from the metal box (chassis), which acts as the ground plane.

Common Applications for Dipole Antennas

Use a dipole antenna when you need to talk in all directions (omni-directional) and don’t know the location of the receiving link. Common applications for dipole antennas include cellular and Wi-Fi applications; there are different dipole models for each of these communication types. (Dipole has limited bandwidth, so different lengths are required for difference frequency bands.) The dipole antenna will work well for an external antenna mounted on a metal enclosure, regardless of the enclosure size. Metal enclosures are very common with industrial applications in harsh environments and external antennas are a near certainty under these constraints. Also, due to their high efficiency and consistent radiation pattern, labs often use dipoles for reference antennas to calibrate antenna measurement systems.

2) Monopole Antennas

Monopole antennas are small, omni-directional, quarter wavelength antennas. They are typically installed internally within a device, but can also be external.

Properties of Monopole Antennas

Monopole antennas are like dipole antennas, but with a single antenna arm that is a quarter wavelength. The monopole antenna utilizes a ground plane as the other half of the dipole, and can therefore be made smaller than the dipole and is easier to implement. It is important to note that with a monopole, the radiation pattern is dependent on the cable length and metal enclosure (external antenna) size or ground plane size. There are deviations of the monopole; most notably the Inverted F Antenna (IFA) which is typically a trace that is etched onto a PCB. The IFA was created to reduce the size of the antenna and still maintain a 50 Ω impedance over a small bandwidth. A variant of the IFA (also derived from the patch antenna) is a PIFA, which is a Planar IFA. The PIFA is typically a 3D structure (not etched onto a PCB) and has wider conductive sections than the IFA. Since the PIFA uses wider conductors and takes up more volume than the IFA, it typically has higher efficiency and bandwidth.

Common Applications for Monopole Antennas

Use monopole whip antennas when you need an inexpensive, narrowband, external antenna and can’t use a dipole antenna due to the antenna size. A more elegant solution is the PIFA, which can be made much shorter than the monopole and more mechanically robust, yet at the expense of a distorted omni-directional radiation pattern. Cellular phones are the most common application for PIFAs today. The PIFA is easy to manufacture and touts good efficiency and bandwidth in a small form factor. Wearables often use an IFA or PIFA as well. Embedded wireless devices often use IFAs etched onto the PCB due to their very low cost.

3) Loop Antennas

Small loop antennas are omni-directional, but as the loop gets bigger (diameter approaches one wavelength), it becomes bidirectional. Loop antennas will always be larger than monopole or dipoles antennas in order to achieve the same radiation efficiency, so they are not as common for wireless embedded devices.

Properties of Loop Antennas

Loop antennas have dominant magnetic near fields, which means they are less influenced by electric conductors, such as a metal plate or even salt water, which have more influence over electric fields than magnetic. This makes them particularly useful for wearables, since humans have very limited magnetic properties.

Note that these properties relate to near field performance; in a far field all antennas do the same thing, but in a near field the device is more dependent on the type of antenna.

Common Applications for Loop Antennas

Wearables such as exercise trackers and implantable devices are common applications for loop antennas. For example, an antenna implanted near the heart would have a lot more performance degradation with an electric near field antenna, such as a monopole or dipole antenna, than a magnetic near field loop antenna.

4) Helical Antennas

Helical antennas are essentially very small monopole antennas that are wound in a helix form. Imagine taking a piece of conducting wire that goes straight up, and winding it around a bobbin to reduce its overall height. The overall length is very similar to a standard monopole antenna.

Properties of Helical Antennas

Helical antennas have an omnidirectional radiation pattern like a monopole antenna. Winding it in a helical fashion makes it possible to place these long antennas in small spaces. Because they are much smaller than a monopole,
you’re giving up a little efficiency and bandwidth in order to shrink the antenna considerably.

Common Applications for Helical Antennas

Helical antennas are highly compact, which makes them useful for portable communications equipment. They are commonly used for equipment that operates on lower frequency bands, including HF, VHF, and UHF bands. For example, a 433 MHz monopole antenna would be about  7” in length; because many devices are much smaller than this, a helical antenna is used to achieve good antenna efficiency and near 50 Ω impedance in a small form factor.

5) Patch Antennas

Patch antennas are directional, which means your application must have line-of-sight communications between devices for best performance: Device A will only talk to Device B and they are always oriented so the patch antenna on the devices faces one another. Since we know where the devices will always be, there is no need for omni-directional radiation.

Properties of Patch Antennas

Patch antennas are very low-profile, lightweight antennas that are easy to manufacture. The natural resonance of a patch is a half wavelength (like a dipole), yet the patch size is often shrunk considerably with the use of dielectrics. Due to the dielectric loaded small patch size and limited volume it entails, the patch is very narrowband. Patch antennas are also sometimes called “microstrip antennas” and can be etched directly on a PCB.

Common Applications for Patch Antennas

Patch antennas are very useful when you have a direct line-of-sight (los) path between the transmitter and receiver, and the required bandwidth is minimal (low data rates). GPS communications are one example, as they make use of satellites, and you know they are always located in the sky and use a very low data rate. The patch is ideal for vehicle tracking since it is low profile and inexpensive, and when you position it on the hood or top of a vehicle, all the energy is focused where you actually need it.

6) Slot Antennas

Slot antennas are typically comprised of a metal plate or PCB with slots cut out. The slots radiate in a similar fashion to dipole antennas and are half wavelength, yet have the opposite polarization of the dipole. They are very efficient antennas and have a bi-directional radiation pattern. It is easy to achieve a unidirectional radiation pattern by enclosing one end of the slot with a metal enclosure.

Properties of Slot Antennas

The slot has a simple design and extremely low profile that make it very versatile. Slot antennas were originally created for television broadcasting purposes. The antenna’s radiation pattern is determined by the size of the slots, their shape, and the driving frequency.

Common Applications for Slot Antennas

Slot antennas are very useful for metal enclosures where you can’t use an external antenna. Common applications include navigation systems on naval vessels and planes where external antennas are at environmental risk.


The antenna is very dependent on device size and tolerable antenna size; and this comes down to physics and practical limitations. To ensure good wireless performance, choose your antenna type and overall device size appropriately for the given application.


Who Is Responsible for IoT Device Security?

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If this was a test question on a college exam, you would have a set of multiple choice answers, such as:


    1. The device manufacturer that initially builds the device.


    1. The device integrator, who builds the device into an end-user product.


    1. The value added reseller that distributes the device to consumers.


    1. The customer, who installs or sets up the device or third-party product in the end-user environment.


    All of the above.

The answer may be surprising to some, but it is of course “E. All of the above.” Everyone along the chain from manufacturing to integrating and using the product plays a role in ensuring that the device is properly set up to thwart improper access, device hacking and malware attacks.

Many people believe that security can be fully implemented by the device manufacturer, or that it’s possible to install a security-focused software program to detect and thwart hacking. But in fact, true device security is a combination of technologies, processes and best practices.

Why Device Security Requires a Multi-Pronged Approach

There are several key reasons why device security requires multiple technologies and practices across the chain from manufacturing to end-use:

  1. Each enterprise has a different security requirement. Retail and financial institutions that process transactions need a high level of security to protect customer data. Healthcare organizations that handle sensitive personal information also require a very high level of security. At the other end of the spectrum, there are many use cases in which extreme security is not required, and it does not make sense to take the extra measures, as it results in additional cost to the consumer.
  2. The threats change. The technologies and practices in use today may not be enough to thwart the attackers of tomorrow. See our previous post, Lessons Learned from the KRACK Vulnerability, for additional insights.
  3. Consumers do not want to pay for the amount and type of built-in security that businesses require.

Device Security from the Manufacturing Perspective

In this post, we will talk specifically about the key security measures that should be designed into the product by your device manufacturer if you are a product integrator or value added reseller, so that others further down the chain can implement proper security. For example, if you are seeking to incorporate one or more vendors’ embedded modules and radio frequency products into your product design, it is important to review the security measures taken in the manufacturing phase.

In these instances, the devices must enable secure functionality. The device manufacturer’s responsibility is to build in secure features, which can then be implemented by the integrator or end-user. As a best practice, the manufacturer should include a comprehensive set of controls that can be enabled as needed. These controls are essentially the laws that govern the product and ensure it behaves in a secure manner. In this article, we refer to this set of controls as a “manufacturer security framework.”

To demonstrate, let’s look at some specific examples.

Example 1: A Security Feature Implemented Within a Device

In this example, we will discuss a feature called “secure boot.” The intent of secure boot is to make sure no unauthorized code ever runs on the device. At Digi, for example, we have defined a number of controls within our manufacturer security framework for this purpose.

The controls we have assigned to secure boot include the following:

  • When the device boots, all code objects that are loaded are cryptographically verified as coming from the device manufacture.
  • When software is updated, all updates are cryptographically verified as coming from the device manufacturer.

While we require the secure boot control, our developer has many technical options for how to implement it. For example, when sourcing a manufacturer’s CPU, our developer must first evaluate the capabilities of that component to determine how to implement the control. In the case of secure boot, if the CPU offers the High Assurance Boot (HAB) feature, the Digi developer can implement the HAB on the product under development to meet the secure boot control requirement.

This security framework ensures that a full range of critical security controls is built in during the development of the product, but still provides the developer with some choice as to the method. When all security controls are in place and development is complete, each of these controls must then be tested and validated.

Example 2: A Security Feature Implemented by the End User

Another example of a secure code feature is the ability to do code validation on end-user code that runs on a device. With the future trend of edge computing, code validation and the infrastructure to support this on an edge device is becoming critical. Validating scriptable end-user objects does not happen at the manufacturer’s level, but at the end-user level. The manufacturer needs to support the functions to make this happen. End-users must then enable these functions on their devices and code upon deployment.

It is important to note that it is the validation of a control that ensures secure operation. This happens not only at the manufacturing level, but across all phases of product implementation. For a set of framework controls for end users to implement for device security, see the Center for Internet Security (CIS) site at www.cisecurity.org.

Digi’s framework of manufacturer security controls, called Digi TrustFence™, includes:

  • Secure boot
  • Authentication and secure connections
  • Encrypted storage
  • Secure updates
  • Certificate and policy management
  • Protected hardware ports
  • Device identity
  • Ongoing monitoring and support

The Digi TrustFence™ solution is not a single security feature, such as a software program that can be hacked. It is a multi-pronged approach designed to ensure that devices are secure from common attacks, and that device integrators and end users have the ability and functions needed to establish a secure configuration in deployment.

The intent of Digi TrustFence™ is to start the secure IoT story from the manufacturing perspective. If you are an integrator, or application developer, there are similar security frameworks such as the OWASP top 10 (www.owasp.org) for security controls on IoT devices. These frameworks provide controls that can be implemented at multiple phases from the manufacturer to the end user.

To continue this story, your own organization must assess what you have in place for a security framework. Does your organization have a set of published best practices? Does your supplier offer a security framework for its customers? Are you fully implementing all available controls to avoid any single point of failure?

>>Take a look at  Digi TrustFence for more details on how to solve security challenges across the IoT landscape.

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