IoT – Internet of Things generally described as a system of interrelated devices with unique identifiers armed with the ability to transfer data over a network without requiring human or computer interactions. IoT has good market potential in Home automation, healthcare, automotive and industrial sectors. There are many use cases in these market segments and in design engineer point of view it is easy to define a use case, but very hard to build and realize the system. To realize a thing in IoT we need five components such as sensors, connectivity, processor, power supply and cloud. At present there are many semiconductor manufacturers provide best in class solutions for these components. Among them, connectivity is the most critical component to select.
There are plenty of connectivity options available and selecting the best connectivity for an IoT device requires a concern on the following factors,
1. The range of the communication
2. Data throughput
3. Power consumption
4. Location and Physical size of the embedded devices
Further in this blog we will discuss about the various wireless connectivity options available for developing an IoT device.
Wireless Connectivity options
At present there are many choices of wireless connectivity options available for electronics engineers to design an IoT system. Most commonly used wireless connectivity’s are as follows,
ZigBee is a wireless technology traditionally found in home automation. ZigBee profile is based on IEEE 802.15.4 standard operating at 2.4GHz mainly focusing on applications that require infrequent data transfers at low data rates around 250Kbps within a physical range of 10m to 20m. ZigBee also operates at unlicensed bands such as 915 MHz in USA and Australia, 784 MHz in China and 868 MHz in Europe.
The main advantage of ZigBee protocol is the ability to support mesh networking of up to 65,000 nodes. In mesh network, nodes are interconnected with other nodes such that multiple pathways connect each node. Connections between the nodes are updated dynamically and optimized through a sophisticated built-in mesh routing table.
ZigBee PRO is the advanced version of ZigBee offering significant advantages in many areas of operations such as scalability of large networks, ease of commissioning, network resilience and security. ZigBee/ZigBee PRO can be a good choice for many IoT devices connectivity in medical and naturally home automation segments.
ZigBee modules are cheaply available in markets for few cents and can be easily integrated to any device via UART, SPI interfaces. The module can run in simple battery power supply for a year sending periodic sensor data’s. Many semiconductors manufacturers such as NXP, Texas Instruments, STMicroelectronics, Microchip, Atmel, etc provide ZigBee IC’s most commonly in QFN packages with reference design very much useful for prototyping before mass production. Based on the available real estate either modules or IC’s can be chosen for design.
Bluetooth is a short range technology that is already available in most of the consumer electronics devices. Bluetooth has classic and low energy versions different from each other in many factors such as range, data rate and power consumption. The nominal frequency of Bluetooth is 2.4 GHz for both classic and low energy versions.
Bluetooth Low Energy (BLE) is considered to be the most common connectivity option particularly for wearable products connecting to smart phones. It offers almost similar range to Bluetooth at reduced power consumption. Reduced power consumption is achieved by sacrificing the data rates. Traditional Bluetooth classic supports high data rate of 1-3 Mbps whereas BLE supports maximum of 1Mbps. There are plenty of semiconductor manufacturers such as NXP, Renesas, TI, STM, Nordic, etc provide BLE transceiver IC’s supporting multiple RF standards such as ZigBee, ZigBee RF4CE, 6LoWPAN, etc selectable with the software stack running on top of it. Also the wireless IC includes MCU inbuilt by which it can act as a standalone IC with rich peripheral support such as UART, SPI, I2C, ADC, etc controlling the external sensors and monitoring modules.
Z-Wave, supported by Z-Wave Alliance, is another low power RF communication technology similar to ZigBee operating in sub GHz band primarily designed for home automation. It is optimized for low latency communication of small data packets with data rates up to 100Kbits per second with communication range up to 30m. It is immune to interferences from WiFi and other wireless technologies in 2.4 GHz range such as Bluetooth and ZigBee.
Z-Wave communication technology enables control of up to 232 devices. Its simple protocol enables faster and simpler development. The only drawback is that there is only one manufacturer named Sigma Designs providing Z-Wave chips when compared to multiple sources for other wireless technologies such as ZigBee, BLE, etc.
Wi-Fi is renowned long range communication technology which strikes when the bandwidth requirements of a particular application is big. Wi-Fi, with its array of 802.11 variants, offers fast data rates and ability to handle high quantities of data. At present the most common Wi-Fi standard used in home and other domain is 802.11n operating on both 2.4GHz and 5 GHZ band. It offers higher throughput ranging from 11-600Mbps sufficient for file transfers but may be too power-consuming for many IoT applications. The distance may range up to 100m.
New emerging 802.11ac uses the 2.5 – 5 GHz band with a combined bandwidth of 5.3 Gbps. A key challenge for the IoT developers is the power requirements. Wi-Fi communication requires far more power than other technologies. Hence Wi-Fi option is limited to the devices where it may be possible to deliver wired power. For more power limited budgets it may be possible by adding techniques such as sending data at pre-determined intervals and then go to sleep in order to preserve the battery lives.
Cellular communication technologies such as GPRS, EDGE, 3G, 4G are most popular on movable IoT devices such as cars, ambulance, trains etc. They have advantage of coverage and availability in large areas. They operate in frequencies ranging from 900 MHz in GSM standard to 2100 MHz in 4G mode. Most cellular based IoT devices aim to use 3G and Long Term Evolution (LTE) 4G networks. 3G and LTE both provide excellent bandwidth throughputs. LTE provides almost 300Mbits/second but the major problem is the recurring costs of the cellular connectivity since cellular operation requires plans from the service providers.
Apart from the 3G/4G communication there are low cost options such as GPRS/EDGE (2G) with low data rates up to 170 Kbps for GPRS and 384 Kbps for EGDE. The power consumption of cellular communication will be too high for many applications and this can be reduced by switching the modem off when not in use and ON while short burst of data is needed. The range for cellular communication may vary between 35 Km for GSM and 200 Km for 3G.
Sigfox is a long range communication technology which in terms of range lies between Wi-Fi and cellular. It operates in 900MHz frequency band, which does not require licenses to transmit the data to and from the connected devices. Sigfox will be a better connectivity option when an IoT application when running on small batteries where Wi-Fi range will be too short and cellular becomes too expensive. Sigfox is designed to handle only low data transfer rate of 10 to 1000 bits per second. Its power consumption is only 50 microwatts which is very low compared to 5000 microwatts for cellular communication.
Sigfox offers robust and power efficient communication that can be well suited for battery operated devices for various IoT/M2M applications such as smart meters, patient monitors, street lighting, security devices, etc. The range of the communication is about 30-50 km in rural environments and 3-10 km for urban environments. There are many silicon vendors such as Silicon labs, TI, Atmel, ON semiconductors provide hardware solutions in transceiver IC, SoC and in module form.
Another alternate option similar to Sigfox is Nuel which operates in sub 1GHz band capable of leveraging very small slices of TV white space spectrum to deliver high coverage, scalability, low power and low cost wireless networks for IoT. Nuel is based on a communication technology called Weightless, a new wide area networking technology designed specifically for the IoT, achieving coverage, battery life, low module cost and efficiency better than today’s GPRS, 3G and LTE WAN solutions.
Nuel transfers data at rate of few bits per second up to 100 kbps with low power consumption as little as 20 to 30 mA with range extends up to 10 Km.
At present Iceni chip by Neul is the only chip available for small footprint M2M applications and cost effective broadband Customer-Premises Equipment (CPE) to communicate on NuelNET networks. It can operate over the entire TV white space frequency range from 470 MHz to 790 MHz.
LoRA is a Low Power Wide Area Network (LPWAN) intended for wireless battery operated IoT applications. LoRA is targeted for the IoT applications which require secure bi-directional communication, mobility and localization services. It provides seamless interoperability between IoT devices without the need of local installations thus giving full freedom to the developer enabling the IoT.
Communication between end-devices and gateways is spread out on different frequency channels and data rates. Data rates ranges from 0.3 kbps to 50 kbps. It minimizes the power consumption by managing the data rate and RF output of each end-device individually by using a special scheme called Adaptive Data Rate (ADR). The physical range of LoRA network is 2-5 km for urban environment and 15 km for suburban environment. Lairdtech, Microchip, LinkLabs are some of the providers of LoRA modules.
Apart from the above IoT connectivity technologies there are other low power wireless options that compete for the same space such as 6LowPAN, MiWi, ANT operating in 2.4 MHz frequency band. Amongst them ANT is the popular wireless system architecture. ANT is well suited for wireless sensor networks and requires minimal memory for the stack and can run in a coin cell battery for years typically for low data rate applications. In addition to ANT providing the basic functionality, ANT+ protocol supports interoperability between ANT system nodes. ANT/ANT+ is widely used for Personal Area Network applications in fitness, wellness, sports and home health. The maximum data rate of ANT is 20kbps to 60kbps with average current consumption for low data rates less than 60 micro amps and can range up to 30 meter distance. ANT wireless, Dynastream innovations Inc, Nordic semiconductor offers modules with embedded ANT protocol designed to speed development of ANT/ANT+ applications.
Choice of Communication technology
With so many connectivity technologies, it may seem the designer is spoilt for choices. But in reality most of these are suitable for specific use cases. Baring a few technologies, each of them has unique feature that will suit particular application – long vs. short distance, low vs. high data rate, power hungry vs. low power operation, uni-directional vs. bi-directional, small form factor vs larger foot print etc. It is important to take in to account all these considerations when selecting the communication technology.
In the fore coming series of blogs, we will discuss in detail about these IoT Connectivity technologies in detail beginning with Bluetooth, their classifications and design considerations.
Embien Technologies is a leading provider of embedded design services for the Semi-conductor, Industrial, Consumer and Health Care segments. Embien has successfully executed many projects based on IoT such as healthcare Wearables, Gateways, and Data Analytics etc. Embien also offers a set of wearable design collections complete with electronics, firmware and Cloud that can be used to shorten product development costs and time significantly.