In the rapidly growing Internet of Things (IoT), applications from personal electronics to industrial machines and sensors are getting wirelessly connected to the Internet. Covering a wide variety of use cases, in various environments and serving diverse requirements, no single wireless standard can adequately prevail. With numerous standards deployed in the market, spreading over multiple frequency bands and using different communication protocols, choosing the right wireless connectivity technology for an IoT application can be quite challenging.
Network range
A network’s range is typically categorized into four classes: Personal Area Network (PAN), Local Area Network (LAN), Neighborhood Area Network (NAN) and Wide Area Network (WAN).
PANs are usually wireless and cover a range of about 10 meters. The data payload varies from simple sensor data to audio streams being sent device to device. A common wireless PAN is a smartphone connected over Bluetooth® to handful of accessories such as wireless headset, watch or fitness device. The implementation of PANs can be either chipset or module, the associated technology around these solutions is low requiring few components around the chipset or module. PANs are not considered Internet Protocols (IP) and thus require the use of a gateway to connect a PAN to a back-end cloud system for data collection. In many solutions, a smart device can act as the gateway, using either the 802.11 or cellular connection to backhaul the data back to the cloud and application
LANs are either wired or wireless (or a combination of the two) and expand the distance devices can communicate. Wireless LANs (WLANs) usually cover a range up to 100 meters and can transmit data payloads up to 54Mbits and beyond. More costly and complex than a PAN implementation, LANs are often described as ubiquitous, meaning access to LAN access is quite available. LAN solutions come in chipset and module form, but require a higher level of technical expertise to implement a solution. Power consumption can be managed and today’s LAN chips and modules have evolved where long term battery operation for sensors and other IoT devices can be achieved. A predominant example is a home Wi-Fi network providing Internet access to personal computers, smartphones, TVs and home IoT devices such as thermostats and home appliances.
NANs are usually wireless and can reach more than 25Km. NANs are typically non-IP based and used a high power amplifier to boost the signal for transmission. NAN solutions are offered as chipset and modules, in fact many module manufactures use the common “Xbee” form factor. Designing with NAN solutions are relatively easy, but in these high power systems care around the antenna sub-system is paramount to achieving the long term transmission required. NANs transmit at high power levels, but usually relay relatively low data traffic. An example of NAN is a smart grid network used to transmit electric meters readings from homes to the utility company using a proprietary protocol over a 900 MHz radio.
Finally, WANs are spread across a very large area. An example of a WAN is cellular networks. Of all the architectures mentioned cellular provides the most ubiquitous coverage. Cellular solutions come in many forms including chip set, module, embedded module and box level solutions. When considering adding cellular capability into a new or existing product it is best to seek the help of experienced 3rd party design services if cellular design is not a core competency. The Internet is considered a WAN and it is built of a complex mix of wired and wireless connections.
Network topology and size
Wireless networks can be also be categorized by their topology - the way nodes in the network are arranged and connected to each other. The first two fundamental network topologies are star and mesh as depicted in Figure 2. In a star topology, all the nodes are connected to one central node, which is typically also used as the gateway to the Internet. A popular example of a star topology is a Wi-Fi network, where the center node is called an access point and the other nodes are called stations.
In a mesh network, every node can connect to multiple other nodes. One or more nodes in the network serve as an Internet gateway. In the example of Figure 2 every node in the network is connected to every other node. In real life mesh topology is simpler. A popular example of a mesh network is a ZigBee Light LinkTM network where multiple lights form a mesh network to extend the network reach in large buildings. One of the ZigBee nodes is called a coordinator, and it usually serves also as an Internet gateway.
However, mesh networks are more complex to design and can exhibit a longer delay routing a message from a remote node through the mesh, compared to star networks. The benefit of a mesh topology is that it can extend the range of the network through multiple hops, while maintaining low radio transmission power. They can also achieve better reliability by enabling more than one path to relay a message through the network.
Network size, or the maximum number of simultaneously connected devices, is also an important consideration in system design. Some technologies like Bluetooth support up to 20 connections; others technologies, like ZigBee, can support thousands of connections.
Now let’s look at the most common wireless connectivity technologies being used for IoT applications.
Wi-Fi
Wi-Fi technology, based on the IEEE 802.11 standard, was developed as a wireless replacement for the popular wired IEEE 802.3 Ethernet standard. As such, it was created from day one for Internet connectivity. Although Wi-Fi technology primarily defines the link layer of a local network, it is so natively integrated with the TCP/IP stack, that when people say they are using Wi-Fi they implicitly mean that they are also using a TCP/IP for Internet connectivity.
Riding on the huge success of smartphones and tablets, Wi-Fi has become so ubiquitous that people often refer to it as just “wireless”. Wi-Fi Access Points (Aps) are deployed today in most homes, as well as in almost all offices, schools, airports, coffee shops and retail stores. The huge success of Wi-Fi is largely due to the remarkable interoperability programs run by the Wi-Fi Alliance and to the increasing demand in the market for easy and cost effective Internet access.
Wi-Fi is integrated already into all new laptops, tablets, smartphones and TVs. Taking advantage of the existing vast deployed infrastructure in homes and enterprise, Wi-Fi’s natural next step is to connect the new age of things to the Internet.
Wi-Fi networks have a star topology, with the AP being the Internet gateway. The output power of Wi-Fi is high enough to allow full in-home coverage in most cases. In enterprise and in large buildings, more than one AP is often deployed in different locations inside the building to increase the network coverage. In large concrete buildings dead spots may be found due to multipath conditions. To overcome dead signal receptions spots in some cases, various Wi-Fi products include two antennas for diversity.
Most Wi-Fi networks operate in the ISM 2.4 GHz band. Wi-Fi can also operate in the 5 GHz band where more channels exist and higher data rates are available. However, since the range of 5 GHz radios inside buildings is shorter compared to 2.4 GHz, 5 GHz is mainly used in enterprise applications along with multiple APs to ensure good Wi-Fi coverage.
Wi-Fi and TCP/IP software are fairly large and complex. For laptops and smartphones with powerful microprocessors (MPUs) and large amounts of memory, this imposes no issue. Until recently, adding Wi-Fi connectivity to devices with little processing power such as thermostats and home appliances was not possible or cost effective. Today, silicon devices and modules coming out on the market embed the Wi-Fi software and the TCP/IP software inside the device. These new devices eliminate most of the overhead from the MPU and enable wireless Internet connectivity with the smallest microcontroller (MCU). The increasing level of integration in these Wi-Fi devices also eliminates all required radio design experience and reduces the barriers of Wi-Fi integration.
To enable high data rates (over 100Mbps in some cases) and good indoor coverage, Wi-Fi radios have fairly large power consumption. For some IoT devices, which run on batteries and cannot be charged frequently, Wi-Fi can be too power hungry. Although the peak current of Wi-Fi radios cannot be reduced by much, new devices apply advanced sleep protocols and fast on/off time to reduce the average power consumption dramatically. Since most IoT products do not need the maximum data rates Wi-Fi offers, clever power management design can efficiently draw bursts of current from the battery for very short intervals and keep products connected to the Internet for over a year using two AA alkaline batteries.
TI’s SimpleLink Internet-on-a-chipTM solutions offer the low power operation and deliver ease of design discussed above. With the CC3100, developers can add Wi-Fi to any microcontroller (MCU) or program an application on the CC3200, the first single-chip Wi- Fi solution with user-dedicated ARM® Cortex®-M4 MCU. Additionally, TI’s WiLink 8 solutions provide a combination of Wi-Fi, Bluetooth and Bluetooth low energy in one easy to integrate module.
Bluetooth
Bluetooth technology, named after an ancient Scandinavian king, was invented by Ericsson in 1994 as a standard for wireless communication between phones and computers. The Bluetooth link layer, operating in the 2.4 GHz ISM band, was previously standardized as IEEE 802.15.1, but today the IEEE standard is no longer maintained and the Bluetooth standard is controlled by the Bluetooth SIG.
Bluetooth became very successful in mobile phones, so much that all mobile phones today, even entry level phones, have Bluetooth connectivity. The main use case that made Bluetooth popular initially was hands-free phone calls with headsets and car kits. Thereafter, as mobile phones became more capable, more use cases like high fidelity music streaming and data-driven cases such as health and fitness accessories evolved.
As mentioned earlier, Bluetooth is a PAN technology primarily used today as a cable replacement for short-range communication. It supports data throughput up to 2Mbps, and although more complex topologies are included in its specifications, Bluetooth is primarily used in a point-to-point or in a star network topology. The technology is fairly low power; devices typically use small rechargeable batteries, or two alkaline batteries.
Bluetooth low energy (also known as Bluetooth Smart) is a more recent addition to the Bluetooth specification. Designed for lower data throughput, Bluetooth low energy significantly reduces the power consumption of Bluetooth devices and enables years of operation using coin cell batteries. Supported by new generation of smartphones and tablets, Bluetooth low energy has accelerated Bluetooth market growth and enabled a wide range of new applications spanning health and fitness, toys, automotive and industrial spaces. Bluetooth low energy also introduced proximity capabilities that opened the door to location-based services like beaconing and to geo-fencing applications.
The Bluetooth “classic” standard can support up to eight devices connected in a star network simultaneously. The Bluetooth low energy standard removes this limitation and can theoretically support an unlimited number of devices, but the practical number of simultaneously connected devices is between 10 and 20.
One of the advantages of the Bluetooth standard is that it includes application profiles. These profiles define in great detail how applications exchange information to achieve specific tasks. To name one example, the Audio/Video Remote Control Profile (AVRCP) defines how a Bluetooth remote control interfaces with audio and video equipment to relay commands like play, pause, stop, etc. The comprehensive certification programs defined by the Bluetooth SIG cover the entire protocol stack as well as the application profile, helping Bluetooth achieve excellent interoperability in the market.
So how is Bluetooth related to IoT? It connects wireless accessories the last 10 meters to a smartphone or tablet, which acts as an Internet gateway. A wearable heart rate monitor logging its data on a fitness cloud server, and a phone-controlled door lock reporting its status to a security company are just two examples of the many IoT applications enabled by Bluetooth technology.
TI has a broad portfolio of Bluetooth and Bluetooth low energy devices. The SimpleLink Bluetooth and Bluetooth low energy dual- mode CC2564MODN in an optimized, small form factor (7mm x 7 mm) module, which enables cost savings, quicker time to market and design flexibility. For the Bluetooth Smart market, TI’s SimpleLink CC2541 is a low power, highly integrated wireless MCU with an RF transceiver, MCU and Flash on-chip. TI is expanding its Bluetooth Smart offering with the SimpleLink CC2540T, a high temperature Bluetooth low energy wireless MCU targeted at industrial and lighting applications.
ZigBee
ZigBee technology is interestingly named after the Waggle Dance that bees do when coming back from a field flight, to communicate to others in their hive the distance, direction and type of food they found. This analogy hints to the mesh nature of ZigBee, where data hops from node to node in multiple directions and paths throughout large scale networks.
Based on the IEEE802.15.4 link layer standard, ZigBee is a low throughput, low power and low cost technology. It mainly operates in the 2.4 GHz ISM band although the spec also supports the 868 MHz and 915 MHz ISM bands. ZigBee can deliver up to 250KBps of data throughput, but is typically used at much lower data rates. It also has the capability to maintain very long sleep intervals and low operation duty cycles to be powered by coin cell batteries for years. New ZigBee devices coming to the market can even enable energy harvesting techniques for battery-less operation.
The ZigBee standard is maintained by the ZigBee Alliance. The organization runs certification programs ensuring interoperability between devices, which allows products to wear the ZigBee Certified logo. The standard defines the higher networking layers on top of the 802.15.4 link layer and various application profiles enable full-system interoperable implementations. ZigBee can be used in multiple applications, but it has gained the largest momentum and success in smart energy, home automation and in lighting control applications, each of which has a specific ZigBee profile and certification. Another reason the ZigBee standard has done so well in these application areas is because of the mesh network topology that can include up to thousands of nodes.
Although the ZigBee standard has an IP specification, it is separated from the popular smart energy, home automation and light link profiles, and has not gotten much traction in the industry. To connect to the IoT, ZigBee networks require an application-level gateway. The gateway participates as one of the nodes in the ZigBee network and in parallel runs a TCP/IP stack and application over Ethernet or Wi-Fi to connect the ZigBee network to the Internet.
TI has a portfolio of ZigBee solutions for various markets. For home automation, gateway and metering applications, the SimpleLink ZigBee CC2538 wireless MCU provides an integrated, low power 2.4 GHz RF transceiver, ARM® Cortex®-M3 solution with on-chip Flash and RAM and security accelerators. The SimpleLink CC2530 wireless MCU is optimized for lighting, home automation and wireless sensor network applications.
6LoWPAN
6LoWPAN is an acronym for IPv6 over Low power Wireless Personal Area Networks. The promise of 6LoWPAN is to apply IP to the smallest, lowest-power and most limited processing power device. 6LoWPAN is really the first wireless connectivity standard that was created for the IoT. The term “Personal Area Networks” within the 6LoWPAN acronym can be confusing because 6LoWPAN is typically used to form LANs.
The standard was created by the 6LoWPAN working group of the IETF and formalized under RFC 6282 “Compression format for IPv6 datagrams over IEEE802.15.4-based networks”, in September 2011. As indicated by the RFC title, the 6LoWPAN standard only defines an efficient adaptation layer between the 802.15.4 link layer and a TCP/IP stack.
The term 6LoWPAN is loosely used in the industry to refer to the entire protocol stack that includes the 802.15.4 link layer, the IETF IP header compression layer, and a TCP/IP stack. But sadly, there is no industry standard for the entire protocol stack, nor is there a standard organization to run certification programs for 6LoWPAN solution. Since the 802.15.4 link layer has multiple optional modes, different vendors can implement solutions that are not interoperable at the local network level, and still call all of them “6LoWPAN networks.” The good news is that 6LoWPAN devices running on different networks can communicate with each other over the Internet, provided that they use the same Internet application protocol. Furthermore, a 6LoWPAN device can communicate with any other IP-based server or device on the Internet, including Wi-Fi and Ethernet devices.
IPv6 was chosen as the only supported IP in 6LoWPAN (excluding IPv4) because it supports a larger addressing space, hence much larger networks, and also because it has built-in support for network auto configuration.
6LoWPAN networks require an Ethernet or Wi-Fi gateway to access the Internet. Similar to Wi-Fi, the gateway is an IP-layer gateway and not an application layer gateway, which allows 6LoWPAN nodes and applications direct access to the Internet. Since most of the deployed Internet today is still using IPv4, a 6LoWPAN gateway typically includes an IPv6 to IPv4 conversion protocol.
6LoWPAN is fairly new to the market. Initial deployments use both the 2.4 GHz and the 868 MHz/ 915 MHz ISM bands. Building on the 802.15.4 advantages - mesh network topology, large network size, reliable communication and low power consumption – and on the benefits of IP communication, 6LoWPAN is well positioned to fuel the exploding market of Internet-connected sensors and other low data throughput and battery operated applications.
TI offers several solutions for 6LoWPAN including the SimpleLink CC2538 wireless MCU. The CC2538 provides the performance, low power and security needed for 6LoWPAN networks in the 2.4 GHz band. For Sub-1 GHz 6LoWPAN operation, TI offers the CC1200 RF transceiver which can be paired with a microcontroller such as the MSP430.
Radio Transceivers and Proprietary Protocols
Many industrial applications today use proprietary protocols running over radio transceivers. The radio transceiver provides the link layer of the network, (or often times just the physical layer). The rest of the network protocol is implemented by the OEM. Systems architected in this way leave more flexibility to the system designer at the expense of interoperability and development effort.
These proprietary radio systems primarily use the lower ISM frequency bands 433 MHz, 868 MHz and 915 MHz and therefore are commonly referred to as Sub-1 GHz solutions. Sub-1 GHz solutions often transmit high power and can reach over 25 km with a simple point-to-point or star topology. Many utility companies have created proprietary NANs to relay meter readings to a neighborhood collection point. Other popular applications for Sub-1 GHz radios are security systems and industrial control and monitoring.
To connect to the IoT, Sub-1 GHz systems need an application-layer Internet gateway. In many cases this is simply a personal computer connected running a TCP/IP stack.
Featuring range significantly beyond 25-kilometers and 65-dB adjacent channel rejection, the SimpleLink Sub-1 GHz RF performance line family provides an unmatched solution for industrial, scientific and medical (ISM) frequency bands at 169, 433, 868, 915 and 950 MHz. The CC1200 is suited for low-power, high-performance systems, with a data rate up to 1 Mbps and years of life for battery-powered applications through low-power operation with sniff modes and fast settling time. TI offers several other RF transceivers including the CC1120, which delivers up to 200 kbps data rate.
Near Field Communication (NFC)
NFC is a radio technology that enables bi-directional point-to-point short-range communication between devices. It is widely adopted in smartphones and smart cards as a secure method for identification, data exchange and payments. While it wasn’t always thought of as an IoT technology, NFC is an important wireless communication technology in many IoT applications including health and fitness, wearables and personal electronic devices.
NFC operates in the 13.56 MHz ISM band and is designed for very short-range communication – less than 10cm – to provide inherent proximity based security and supports data rates between 108Kbps and 424Kbps. NFC standards are governed by the NFC forum and are largely based on the International Organization for Standardization (ISO) standards such as ISO 14443A/B and ISO 15693. These standards vary in the communication range and data rates they can support; therefore, choosing the right standard is an important consideration when selecting NFC tags and the corresponding readers.
NFC provides many benefits for IoT applications; it can enable easy “tap and go” pairing between Bluetooth devices and smartphone as well as easy provisioning of Wi-Fi devices to routers or other wireless devices to gateways. Taking advantage of its wide deployment in smartphones, NFC feature can be used to retrieve diagnostic data from devices to a phone and to download firmware updates from a phone to a device.
NFC readers are extremely low power, and NFC tags can even work without a battery making the technology ideal for low power sensor nodes that require extended battery life or battery-free operation.
TI offers several NFC solutions including the RF430CL33xH dynamic NFC tag and the TRF7970A NFC transceiver that supports all three NFC operating modes: reader/writer, peer to peer and card emulation.
Not Only Wireless
The wireless connectivity market is rapidly growing because of the IoT. Nevertheless, many IoT applications are connected to the Internet with wires. Ethernet connectivity, power line communication (PLC) and industrial communication standards such as Fieldbus are just a few examples.
Conclusion
There are many wireless technologies in the world – each one has benefits, no one is perfect. The question that you need to answer is “which technology is the best one for my application?” Hopefully this discussion has helped you better understand the popular wireless technologies for IoT and their strengths and weaknesses. There are considerations when selecting wireless connectivity including regional frequency coverage, native support of IP and range and throughput, which are covered in more depth in this IoT whitepaper.
Texas Instruments and the IoT
With the industry’s broadest IoT-ready portfolio of wired and wireless connectivity technologies, microcontrollers, processors, sensors and analog signal chain and power solutions, TI offers cloud-ready system solutions designed for IoT accessibility. From high performance home, industrial and automotive applications to battery-powered wearable and portable electronics or energy- harvested wireless sensor nodes, TI makes developing applications easier with hardware, software, tools and support to get anything connected within the IoT.