Short-Range Low Power Wireless Devices and Internet of Things (IoT)

By Mats Andersson

Contributed By Digi-Key Corporation


This paper discusses the topic of the “last 100 meters connectivity” in systems where small devices (such as various sensors) are connected to services on a wide-area Internet network. Subject matters covered are the requirements on the “last 100 meters connectivity” vision as well as what wireless technologies would be suitable for future Internet of Things (IoT) use cases. Also discussed is the background to why connectBlue envisions the “last 100 meters connectivity” as an important factor in the area of IoT and connectBlue’s view on the impact of IoT in general.

The last 100 meters connectivity in M2M


Background

IoT is a hot topic in which many important players in connectivity predict a large growth within the next ten years.

Device distribution in IoT

Figure 1: Device distribution in IoT.

Figure 1 shows predictions of future connected devices done by companies like Ericsson and Cisco. The graph shows a growth of the personal devices such as phones, tablets, laptops, game consoles; however, this growth is limited by the number people in the world. The largest growth is predicted from all other types of connected small devices in areas such as home automation, smart energy, elderly home care, transportation, asset tracking, and many others.

This growth is already underway, but most of the applications with Internet connected devices are today vertical, closed applications typically referred to as “silos”.

Applications as vertical “silos”

Figure 2: Applications as vertical “silos”.

The real impact of IoT will occur when data from the silos is combined to create complete new types of applications. This evolution will only be possible if the data from all the small devices is made available on the Internet. The data from the small devices combined with the new knowledge emerging in the area of “big data” will create the framework for many new types of applications. This progress will drive the growth of IoT.

The question is how to infuse this progress when there are many different wireless technologies in the IoT atmosphere.

Wireless technologies in the IoT space

Figure 3: Wireless technologies in the IoT space.

Figure 3 lists the main short-range international standards but there are many others (e.g. domain-specific standards within metering such as Wireless M-Bus and many others).

Focus on the “Last 100 Meters”

The “Last 100 Meters”

Figure 4: The “Last 100 Meters”.

Today, the devices used in the “last 100 meters” are typically not connected. The wide-area network is to a larger extent connected through smartphones, home routers (e.g. ADSL routers) and GSM/3G/4G Routers.

Market size and technologies

Figure 5: Market size and technologies.

The “last 100 meters” presents >90% of the potential, but how to achieve the connected vision is extremely diversified. Many different technologies compete in this space including international standards, domain-specific standards (used in one specific vertical) and many proprietary technologies. Requirements on “Last 100 Meters” Technology

"Last 100 Meters" architecture

Figure 6: "Last 100 Meters" architecture.

An architecture with a gateway that serves as an interface between the wide-area network (Internet) and the short-range network is required.

Fixed and mobile use cases

Figure 7: Fixed and mobile use cases.

For IoT, a required feature of the chosen short-range technology is support for mobile use cases where a smartphone or other mobile device can be used as a temporary gateway. There are also some applications where the same IoT device (sensor) is used for both mobile- and fixed-use cases (see Figure 7).

Some of the important drivers when selecting the appropriate short-range wireless technology for IoT use cases are the following:
  • Cost of the radio technology. As many of the devices (sensors) are small low-cost devices, the radio must not add too much additional cost to the bill-of-material. This also implies that the radio and device application in many cases need to share the same computing engine (microcontroller).
  • Power consumption. Many use cases require a battery or some kind of energy harvesting technology as a power source.
  • Ease-of-use. It must be easy to associate a device to the network and to the Internet service.
  • Security. Security (authentication and encryption) must be adequately supported by the wireless technology and sometimes end-to-security (all the way from sensors to the Web services) is required.
  • Available ecosystem. The possibility to connect to smartphones, tablets, PCs, home gateways, etc. is important. This requirement also drives volumes and has an important impact on the cost (a good example is Classic Bluetooth, where the large volumes of phones and phone accessories have lowered costs).
  • Range. The capability to cover enough range or have some capabilities to extend the coverage (repeaters, routers, etc.) without having too big of an impact on the system cost is needed.
  • An International Standard that is NOT domain-specific. Domain-specific standards will still be widely used, but the desire is to find and select basic wireless technologies that fit many verticals.
Which wireless technologies should one choose?

Short-range technologies

Figure 8: Short-range technologies with power consumptions, distances and data rates.

Figure 8 shows a graphic representation of the short range technologies that support the main part of the drivers and requirements listed above.

This graph mainly shows technologies that are available in mobile devices such as smartphones, laptops, and more. The reason for only showing wireless technologies available in mobile devices is the above mentioned requirement on an available ecosystem. One exception to the rule is 802.15.4 that both fulfills the requirement on an internationally used standard and is widely used in early IoT use cases, for example building automation and smart energy.

The illustrated range is point-to-point and heavily depends on the individual devices’ radio design and shall thus be considered as an indication only. The same concept applies for power consumption since the actual power consumption is use case dependent. This illustration indicates how well the different technologies support low power applications.

As the focus of this discussion is on the “last 100 meters”, we will look more into the wireless technologies situated to the left of the red line.

Technologies and verticals

Figure 9: Technologies and Verticals.

Figure 9 shows a table on how different wireless technologies fit specific verticals, according to connectBlue. Infrared and NFC can be ruled out except for very specific use cases or verticals. connectBlue believes that 802.15.4 based technologies will become a niche technology especially in those areas it is already established such as home and building automation and smart energy (see more on this in the conclusions section later).

A comparison of the three selected technologies seen from the drivers (requirements) identified earlier is shown below:

Comparison of wireless technologies

Figure 10: Comparison of wireless technologies and their usefulness in IoT.

Conclusions that can be drawn from the Figure 10 table include the following:
  • All three technologies have built-in link layer authentication and encryption which sometimes needs to be completed with end-to-end security from the sensor to the Web application.
  • Some IoT use cases may be fully behind an enterprise firewall (e.g., a use case inside a factory where the IoT Internet Service runs on a local server). There are also IoT systems operating on a wide-area network, but acting as local networks by the use of VPN tunnels or similar security mechanisms.
  • Correctly used, Bluetooth low energy has the potential for less power consumption than 802.15.4 (less overhead).
  • The lack of native support for 802.15.4 in the ecosystem’s important mobile devices (smartphones, tablets, laptops, etc.) is a problem, especially for mobile or temporarily mobile use cases.
  • The ecosystem with phones, tablets, laptops and phone accessories will drive down the cost for Bluetooth low energy.
  • 802.15.4 has a main advantage in its range since many 802.15.4 based technologies (e.g. ZigBee) support mesh whereby coverage can be extended by using routers.
  • Bluetooth low energy is very reliable with its support for Adaptive Frequency Hopping (AFH) and other features inherited from Classic Bluetooth.
  • WLAN, also commonly referred to as Wi-Fi, can be used in devices with less demands on low power consumption and as a wireless backbone in combination with other technologies (more on this later).
The connectBlue conclusion is that Bluetooth low energy has a high potential in becoming an important technology for the “last 100 meters” in low power, low cost, small devices. However, there will still be use cases where 802.15.4 based technologies are used, especially in areas where it is already established. In spite of its installed base in smart energy, home and building automation applications, connectBlue envisions that 802.15.4 will face competition from Bluetooth low energy in these applications as well. WLAN will be used in devices where cost, low power is less important and as a wireless backbone combined with the other wireless technologies. Which wireless technologies should one choose?

IoT architecture for short-range senors / devices

Figure 11: IoT architecture for short-range sensors / devices.

Gateways are a requirement when connecting small, low-power, short range devices. Sometimes the gateways are fixed devices connected to a backbone network and sometimes they are embedded within other devices, such as in an Internet router (ADSL or GSM/3G/4G routers or similar).

A mobile device can also act as a gateway and there are several use cases where this use can be applicable. For example, one use case is when the sensor or device is carried together with the phone, a body-worn sensor for example. Another possibility is that the smartphone becomes a temporary gateway when it approaches the sensor / device (e.g., an access control system where the phone is used to authenticate the access using an Internet service).

Traditional Bluetooth low energy use case

Figure 12: Traditional bluetooth low energy use case.

Figure 12 shows a use case where the traditional Bluetooth low energy concept of characteristics and services are exposed to the sensors / devices. This use case will typically require knowledge on behalf of the gateway on what services the sensors expose. Typically, the gateway will expose this knowledge as an Internet accessible API or by pushing data read from the sensors to an Internet based service.

IPv6 "All-the-way" and IoT

Figure 13: IPv6 "All-the-way" and IoT.

Figure 13 shows Bluetooth low energy and 802.15.4 used as transport for IPv6 based communication “end-to-end”. In this use case, an IP-based application in the sensor / device is transparently connected to an Internet service. This case typically uses compression techniques such as 6LoWPAN and CoAP to enable an efficient use of the limited resources of a Bluetooth low energy or an 802.15.4 network. This use case may also enable “end-to-end” security, although this will require more computing power in the sensor / device.

Use WLAN "Mini Gateways"

Figure 14: Use WLAN "Mini Gateways" to extend coverage and system size.

Figure 14 shows the use of WLAN serving as an intermediate backbone connecting islands of sensors / devices. This makes use of the multi-radio capability of the short-range radio chips already available, such as chipsets supporting simultaneous use of Bluetooth low energy and WLAN, to create miniature gateways. The gateways communicate via Bluetooth low energy down-stream and WLAN up-stream. The WLAN up-stream link is connected to a WLAN router connected further upwards to Internet services. This scenario may be used to extend the range or the system size.

Interconnecting multiple technologies

Figure 15: Interconnecting multiple technologies.

Figure 15 shows the use of gateways to create a system with interconnecting multiple technologies. The gateways are used to perform the necessary translation to a common backbone (e.g. an IPv6 backbone). This use is especially interesting and easy to use when interconnecting technologies via IPv6 “all-the-way” as described in Figure 13.

Summary

The following are the conclusions that can be inferred from the topics discussed:
  • There is huge potential for “last 100 meters” of “things”. The main part of future growth in wireless Internet connectivity indeed stems from this area.
  • Security and privacy, both for private enterprise level IoT use cases and public use cases, are essential and need to be individually investigated for each specific use case.
  • Low power, short-range radio technologies, like Bluetooth low energy and 802.15.4, are often a requirement to enable these use cases and various gateways are needed to connect all these low-power devices to the Internet.
  • Some of the gateways will be fixed devices connected to the Internet, but for some use cases there is a need for smartphones or other portable devices to serve as mobile gateways.
  • There will be several short-range, low power radios used in parallel, but Bluetooth low energy is a rising star that connectBlue believes will likely take a significant portion of this market.
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