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    Dual RADIO Connectivity: Best of both worlds in IoT

    Vishal GOYAL
    Vishal GOYAL – Group Manager Technical Marketing
    South Asia and India


    According to statistica, IoT market is expected to reach $1.6trillion by 2025 from $248billion in 2020. Meteorical rise in IoT devices is also expected to increase their complexity and versatility in wide range of use cases.  Choosing right connectivity option is a critical decision for any IoT device but often it is not possible to use a single connectivity option for all features in a device. This article highlights the need of optimizing the combination of short- and long-range technologies to significantly increase the performance and versatility of the devices. The article also put special focus on Bluetooth® Low Energy [BLE] and Sigfox as they have emerged as a technology of choice for optimized architectural decisions.

    Topology for IoT devices Connectivity

    IoT connected devices can be broadly categorized in three categories:

    • Devices directly connected to long distance Infrastructure

    Technologies such as GPRS, CDMA allows our Smartphones or IoT devices to be connected directly to Telecom towers. With the advent of LPWAN technologies such as Sigfox, LoRa and NBIOT it is possible to get similar connectivity range but with reduced current consumption and data rate. These devices allow roaming of IoT connected devices and need not be confined to one particular place.

    • Devices connected to a local gateway which in turn is connected to long distance Infrastructure

    Wireless technologies such as WiFi or wired technologies such as LAN, IO-Link, PLC etc allow interfacing gateway with locally connected IoT devices. With this approach one can connect multiple devices to the Cloud with a single connected gateway. In general, these technologies are very high data rate and are used for High bandwidth uses such as Internet browsing, online video or Audio etc. The advantage of this approach is that you can control or monitor several devices at your home, office or Industry remotely. So, it is also used in many control applications of IoT devices. But as they are dependent on gateway they cannot move outside the premises as first approach.

    • Device which are locally connected to Smart phone or each other with or without internet connectivity

    Technologies such as Bluetooth, Zigbee, Thread and Bluetooth Low Energy [BLE] enable peer to peer communication in shorter distance. In many scenarios they use mobile phone as the gateway to the Cloud. The advantage of short-range communication is that they can work independently without any requirement of Cloud network.

    With the advent of Human-Machine Interface (HMI), connected devices such as Mobile phones and laptops etc. are normally powered by more than one connectivity technologies such as BLE, Bluetooth, Wi-Fi, GPRS etc. However, majority of IoT devices are designed to execute one particular task so are connected by only one of the three approaches discussed above. However, it also limits the usability, longevity and versatility of those devices.

    Optimized Dual Connectivity

    An optimized architecture with a combination of long-range technology and short-range technology can be a milestone in penetration of IoT device in wide range of applications. Long-range connectivity will enable communication directly with communication infrastructure and even allows for roaming. Short-range technology in the same device will enable independent short-range communication for wide range of requirements.

    Bluetooth Low Energy [BLE] is an incredible short-range technology which can complement long-range connectivity technology in wide range of usage scenarios. BLE can offer short-range direct connectivity whereas long-range connectivity can give Cloud connectivity to IoT devices.

    Some of the features enabled by BLE for an IoT device are

    • User Interface

    A BLE connected device can connect to a smartphone App which in-turn enables user to interact with device in intuitive way. This can also reduce number of buttons or display needed on device making it cheaper, lighter and water or dust proof.

    • Configurability

    BLE can also be used to configure the device to act in a certain way. Allowing configurability at user’ end, device maker need not customize the product at the factory. Device can even be configured to range of customized features such as pedometer working as per wearing position, setting alarms or toggle LEDs etc. Even industrial products such as LED drivers can be configured using BLE to suit the type of LED configuration needed by the consumers

    • Local Monitoring

    Presence of BLE based interfaces enable direct monitoring of sensor data in absence of Cloud connectivity. This is particularly important where a fast local response is needed. It can also be used to optimize the cost of data as user can decide which data need to send to Cloud and which is to be monitored locally

    • Diagnostic

    Often when a device breaks down the service engineer need to open the device or connect a cable to device to get into the device. This is complicated and limits the creativity and features in the device. For example, the device may not be waterproof if it has open ports and can be opened easily by screws. A BLE interface can facilitate getting into the device wirelessly in case main system fails and BLE interface is enabled. In many scenarios, BLE may not be made available to user but activated only for diagnostic purposes.

    • Firmware Upgrade

    Firmware upgrade features allows to update the firmware of device after shipping. This is important to provide new features and bugs update even after the device is shipped. Using firmware upgrade a device functionality can also be configured as per the use cases. Firmware upgrade is also an important diagnostic feature.

    BLE can be complemented with other long-range technology such as GPRS or LPWAN to offer long-range connectivity. An important and versatile low-power long-range technology is Sigfox. When a BLE SOC drives a Sigfox radio, it can enable wide new features and use cases with a minimal increment in power, form factor and price. Sigfox is a LPWAN technology which offers global Cloud, long-range connectivity, and consumes very low current. Sigfox devices can freely connect around the world without the need of any separate agreement or roaming charges with network operators.

    Some features which can be implemented by implementing long-range technology in the same device. Let us understand the same using Sigfox implementation.

    • Remote Monitoring

    Sensors data can be sent to Cloud using Sigfox network without the need of local gateways. The device can uplink the data directly to Sigfox gateways operated by Sigfox operators. These gateways can be connected directly up to few kilometers.

    • Data aggregation

    Data from gas meters, water meters or other sensors need to be aggregated in Cloud for consolidation, billing or analytics purpose. The data sent over time over Sigfox network can be used for this purpose.

    • Tracking and Positioning

    Tracking and positioning is one the most widely used use case of IoT devices. In case an accurate positioning is required, the GPS coordinate can be sent to Cloud over Sigfox network. Many use cases such as fleet monitoring accept accuracy of few kilometers. In such use cases, Sigfox network enables positioning using triangulation method using Sigfox network itself without the need of GPS signals. Sigfox has introduced a new feature, called Monarch, to recognize radio service and manage radio frequency changes as per local regulations. Using this feature, the device can roam across national boundaries and still remain connected.

    • Notification of events

    When someone opens a lock using BLE, the information also need to be recorded on Cloud using an independent network. Similarly, events such opening of door, crossing a threshold of a sensor, burglar alarm, fire alarm etc need to work independently of local interface. A device powered with right sensors, logic and Sigfox radio can do it with ease.

    • Diagnostic and assistance

    An IoT device can raise an alarm over Sigfox network in case it needs assistance or if some part of the device is malfunctioning. Sigfox also allows downlink message to configure device in diagnostic mode and provide relevant data.

    STMicroelectronics has introduced a unique solution to combine BLE and Sigfox radio into a common solution. The dual radio will offer long-range connectivity via Sigfox and Smartphone connectivity using BLE. Smartphone connectivity to Sigfox devices will enable User Interface [UI], over the Air firmware update [FUOTA], direct configuration and control.

    STDES-MONARCH is Sigfox Verified and is provided free of charge with all the necessary design documents and software. This reference design embeds both BlueNRG-2 low-power BLE system-on-chip (SoC) and S2-LP narrow band ultra-low power sub-1GHz transceiver.

    The BlueNRG-2 from STMicroelectronics is an ultralow-power BLE 5.0 certified wireless processor, which provides seamless connection with sensors, Privacy 1.2, Secure Connection 4.2, Data Length Extension, 8dBm of output power, and a reliable BLE link to IOT devices. Besides, it supports standard fully compliant SIG BLE Mesh.

    Mesh connectivity over BLE enables connecting multiple BLE devices in Mesh networks of IOT solutions. Introduction of the Mesh solution has made it possible to be connected even when devices are not in direct range of a network.

    The S2-LP is a high performance ultra-low power RF transceiver, intended for RF wireless applications in the sub-1GHz band. It can be programmed to operate at sub-1GHz frequencies in the 413-479 MHz, 452-527 MHz, 826-958 MH, 904-1055 MHz bands. The S2-LP supports different modulation schemes: 2(G)FSK, 4(G)FSK, OOK and ASK. The S2-LP shows an RF link budget higher than 140 dB for long communication ranges and meets the regulatory requirements applicable in territories worldwide, including Europe, Japan, South Asia, India, China and the USA.


    As IoT use cases will develop, there would be need of more connectivity options in the same device. This will enhance usability, versatility and reliability of devices. A combination of BLE SoC driving a sub-1Ghz radio is expected to gain momentum as it brings additional connectivity without compromising on cost, power consumption and form factor. STMicroelectronics has adopted this architecture with two world class radios and witness huge response from its customers.

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