Wireless connectivity is the enabler for Internet of Things (IoT) applications.IoT). It allows you to place actuators and sensor nodes where they are needed and have them communicate with servers and other nearby devices as soon as they are ready. But wireless connectivity comes in many forms. The choice of network protocol may seem bewildering at first, but each has characteristics that suit different markets and applications. Now that the device market IoT is beginning to mature, some of the protocols are also beginning to take a leading position, especially for short-range wireless communication. The first option is distance. Devices used in buildings often use short-haul networks and take advantage of the greater simplicity and lower power consumption of protocols calibrated for this environment. Normally, the installer has nearby gateways that transmit data to the internet.
Sensors for smart agriculture or to control public services require a much greater range since any gateway device or base station can be several kilometers away. In the short-range sector, there are two technologies that are taking dominant positions in wireless communications. Both benefit from already being large-scale successes in the consumer electronics market. And they continue to enjoy a continued program of improvements. While its parent protocol was developed for phone-centric personal area networks, the creation of Bluetooth Low Energy has opened the door to a much broader range of applications. Previously, the devices IoT they could choose between niche protocols like Zigbee for home automation, or 6LowPAN for industrial automation. Bluetooth Low Energy now offers 6LowPAN compatibility and supports several key features originally designed for Zigbee. One of those features is the mesh network. Bluetooth includes the Scatternet option since 2013, which allows nodes to switch between master and slave modes to make them more flexible.
For example, a smart node could collect data from several simple slave devices and then transmit that data to a smartphone temporarily acting as a slave. The mesh networking capability now available in Bluetooth allows the reach of a single gateway to be extended continuously by using intermediate nodes as mount points for packets. Bluetooth 5, released in the summer of 2016, brought improvements including the ability to trade range for maximum data rate. Using an adaptive protocol, the range can be extended up to four times that of Bluetooth 4.2 with a data rate of approximately 125 kb/s. In direct line of sight conditions outdoors, this range is close to 200 m. Alternatively, for devices closer together, the maximum data rate can be as high as 2 Mb/s, although packet overhead typically reduces the maximum achievable payload data rate to about 1,6 Mb/s . for the traffic IoT high-speed data, Wi-Fi now offers a viable option.
Transceiver costs have dropped dramatically, and support for the protocol allows conventional home routers to access the Internet instead of relying on specialized gateways. From the beginning, WiFi has focused on providing high-bandwidth communication to mobile devices. The availability of the 5 GHz band in addition to the 2,4 GHz industrial, scientific, and medical (ISM) band used by the original WiFi protocol, Bluetooth, 6LowPAN, and Zigbee, provides access to a less congested part of the RF spectrum. This is useful for applications that require continuous high-speed data transfer. There are now multiple versions of WiFi available. Although many applications IoTWhile even those that need high-bandwidth communication for real-time audio or video can use older WiFi variants, today it's often worth standardizing on the 802.11ac variant. This version broadcasts to multiple antennas that boost the aggregate data rate to at least 1 Gb/s in the 5 GHz band. Devices IoT that support 802.11ac will help maintain the highest possible data rate by allowing your home or office router to take full advantage of antenna diversity. Falling back to a slower, older protocol can slow down the entire network when the device IoT be active. many devices IoT will support both WiFi and Bluetooth, as the cost is often only slightly higher than a WiFi-only transceiver. This can be leveraged to make tasks like installation easier. For example, a simple Bluetooth connection to an application hosted on a mobile device can be used to configure the device.
Once configured, it can be changed to use the WiFi protocol for data transfer. Another option of recent appearance is the DECT of ultra low consumption (ULE). Has the advantage over many short range protocols IoT, to have a dedicated RF spectrum instead of shared access to the 2,4 GHz ISM band. The range of DECT ULE can be extended up to 300m outdoors and 50m indoors. The DECT protocol allows multiple gateways to cooperate to extend the reach of a single network well beyond the basic 300m. Although DECT was originally developed for wireless telephony, the UE version provides low-power communication for sensor nodes. IoT. In the short range environment, the gateway is normally controlled by the user. In the Low Power Long Range Network (LPWAN) environment, the gateway can be private, but access can also be through public networks. One protocol that offers that choice is LoRA. Based on a transceiver design from semiconductor vendor Semtech, LoRA uses unlicensed spectrum and gives users the option to deploy their own gateways or have their devices communicate with third-party networks. Some cities have deployed LoRa-based networks that are free to access, and service providers have emerged that rent access to their gateways.
To avoid interference problems from other users in the same RF band, LoRA uses a spread spectrum modulation scheme that supports data rates from 300 b/s to 50 kb/s. The range can be up to 10 km and the use of comparatively low frequencies makes it possible to reach devices buried underground, such as water meters. Sigfox uses ultra-narrowband transmission to extend its range up to 50 km in rural areas. While LoRA is designed to support two-way communication, Sigfox is optimized for one-way, low-rate data transfers – typically from sensor node to server. Datarates range from 10 b/s to 1 kb/s. Sigfox is not completely unidirectional: the protocol supports packet acknowledgment for the sensor node to determine if a communication has been received, and it also supports applications such as security alarms. One advantage of Sigfox focusing on one-way data transfers is that it can help preserve power at the sensor node, thus extending battery life. If the node should only wait for acknowledgments, which are received very shortly after transmission, the node need not wake up on a regular cycle to listen for gateway downlinks.
While LoRA offers the option for users to control their own gateways, all communication in Sigfox goes through the company's own gateways. While this offers less operational flexibility, it has the benefit of providing users with a single provider offering network support in a wide number of countries. Cellular connectivity is already widely used for machine-to-machine applications. In recent years, the industry has augmented the basic GPRS offerings with a variety of protocols that support both higher data rates and low power operations. A key benefit of cellular connectivity is that carriers can manage congestion and interference much faster than with unlicensed spectrum, improving long-term reliability. The open nature of the protocols themselves provides a wide assortment of compatible RF modules and components.
The first change came with Enhanced GSM Coverage (ECGSM), which increases the ability of cellular signals to reach distant nodes or connect to sensor nodes. EC-GSM handles signals 20 dB weaker than standard GPRS and supports data rates of up to 10 kb/s. The advent of Long Term Evolution (LTE) has brought with it several options for connectivity IoT thanks to the more efficient use of the RF spectrum by the 4G protocol. The first to arrive was Cat-M, which supports data rates of 1 Mb/s for both uplinks and downlinks using half-duplex communication. Cat-M also offers energy saving enhancements. Compared to the basic LTE protocol used by mobile phones, Cat-M works with fewer updates from the base station. The frequency of updates can be reduced to the point that the sensor node only needs to wake up every ten minutes or so, which greatly preserves battery life for devices monitoring low-changing conditions, such as soil moisture .
El IoT Narrowband Wi-Fi (NBIoT) offers additional improvements for energy efficiency. NBIoT uses a much narrower transmission band than full LTE: 1,4 MHz and not 20 MHz. This is accompanied by a reduction in transmission power to further extend battery life. In a process of ongoing enhancements, 14GPP's Release 3 LTE standard has further improved efficiency, supporting techniques that allow nodes to quickly disconnect after a transmission to reduce power losses. Data rates of 50 kb/s on the downlink and 20 kb/s on the uplink are possible, extending to 50 kb/s if multi-tone signaling is used for the uplink. Thanks to the wide selection of adaptable protocols for IoTWhether working in short or long range situations, developers and integrators can be sure to find one that suits their application. Independent module providers such as Murata can advise on the best option for each situation and offer solutions based on the best silica available on the market.
