New-Tech Europe Magazine | April 2019

using an adaptive protocol, the range can be extended to be around four times higher than that of Bluetooth 4.2 at a datarate of approximately 125kb/s. Assuming line-of-sight conditions outdoors, this range can approach 200m. Alternatively, for devices that are more closely spaced, the maximum datarate can reach as high as 2Mb/s, although packet overhead typically reduces the peak achievable payload datarate to around 1.6Mb/s. For high-datarate IoT traffic, WiFi now offers a viable option. Transceiver costs have fallen dramatically and support for the protocol makes it possible to use conventional home routers for access to the internet instead of relying on specialised gateways. WiFi, from the start, has been focused on delivering high- bandwidth communication to mobile devices. The availability of the 5GHz band in addition to the 2.4GHz industrial, scientific and medical (ISM) 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 need continuous high-speed data transfer. There are now multiple versions of WiFi available. Although many IoT applications, even those that need high bandwidth communication for real-time audio or video, can make use of the older variants of WiFi, it often makes sense to standardise today on the 802.11ac variant. This version caters for multiple antennas to boost aggregate datarates to at least 1Gb/s on the 5GHz band. IoT devices that support 802.11ac will help maintain the maximum possible datarate by allowing the home or office router to make full use of antenna diversity. Falling back to a slower, older protocol can slow down the entire network when the IoT device is active. Many IoT devices will support both

Figure 1: The choice of network protocol can seem baffling at first but each of them has features that suit different markets and applications.

networking (LPWAN) environment, the gateway can be privately owned but access can also be through public networks. A protocol that offers the choice of either is LoRA. Based on a transceiver design by semiconductor supplier Semtech, LoRA employs unlicensed spectrum and provides users with the option to deploy their own gateways or have their devices communicate with third- party networks. Some cities have deployed networks based on LoRA that are free to access and service providers have appeared that rent access to their gateways. To avoid interference problems from other users on the same RF band, LoRA uses a spread-spectrum modulation scheme supporting datarates 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 below ground, such as water meters. Sigfox uses ultra-narrowband transmission to extend its range to as much as 50 km in rural areas.

WiFi and Bluetooth as the cost of supporting both is often only marginally higher than that for a WiFi- only transceiver. This can be leveraged to ease tasks such as installation. First, a simple Bluetooth connection to an app hosted by a mobile device can be used to set up the device. Once configured, it can switch to using the WiFi protocol for data transfers. A further option that has emerged recently is DECT Ultra Low Energy (ULE). It has the advantage over many of the IoT short-range protocols of having dedicated RF spectrum instead of shared access to the 2.4GHz ISM band. DECT ULE’s range can extend as far as 300m outdoors and 50m indoors. The DECT protocol lets multiple gateways cooperate to extend the range of a single network much further than the core 300m. Although DECT was originally developed for wireless telephony, the ULE version provides low-power communication for IoT sensor nodes. In the short-range environment, the gateway is normally managed by the user. In the low-power wide-area

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