The Internet of Things (IoT) is employing multiple RF connectivity options along with a focus on hardware security, and here, Bluetooth stands out as a popular short-range wireless technology often being complemented with Wi-Fi or long-range cellular technologies like LTE-M and NB-IoT.

Moreover, the traditional divide between silicon vendors and module suppliers is blurring. So far, low-volume IoT designs preferred pre-programmed and certified modules while OEMs are producing hundreds of thousands of units of Bluetooth chips with their own firmware and development tools. But that started to change with the advent of IoT designs in the mid-2010s.

In 2015, for instance, chipmaker Silicon Labs bought Bluegiga Technologies Oy, a supplier of Bluetooth and Wi-Fi modules as well as software stacks, development tools and software development kits (SDKs). The acquisition of Espoo, Finland-based Bluegiga, was a clear sign of how chipmakers wanted to simplify the wireless connectivity while offering highly integrated solutions and thus accelerate the IoT design cycles.

On the outset, Silicon Labs was able to set up a design outpost in Europe. But a closer look reveals that chipmakers were also expanding into the module business to control a larger part of the design value chain.

The Bluetooth Wi-Fi combo

Fast forward to September 2018, Silicon Labs announced the availability of the Wireless Xpress platform that included certified Bluetooth 5 Low Energy (LE) and Wi-Fi modules along with integrated protocol stacks and easy-to-use tools. It controlled the on-board wireless stacks through a high-level Xpress Command API.

First and foremost, such pre-programmed and pre-qualified platforms eliminate the daunting development work related to numerous and complicated wireless interfaces. In other words, IoT developers don’t need to invest in wireless connectivity expertise.

Second, instead of requiring developers to write hundreds of hours of code, these modules take on as much firmware responsibility as possible. Third, they offload a host processing device — whether a microcontroller or microprocessor — from network processing tasks. As a result, IoT developers can use a barebone 8-bit MCU instead of more expensive 32-bit MCU equipped with RAM, flash, etc.

Another testament of the popularity of Bluetooth and Wi-Fi combination came in summer 2019 when u?blox, a supplier of Wi-Fi modules, acquired the Bluetooth modules business of Rigado. The intent of this deal seemed clear: complement two popular short-range wireless technologies to offer more comprehensive IoT design solutions.

Other RF module suppliers like Telit are carrying out this integration of Wi-Fi and Bluetooth connectivity in-house. Telit's WL865E4-P module has combined the Wi-Fi and BLE connectivity technologies for high-bandwidth applications such as smart home, industrial control, and video surveillance. It supports 802.11 a, b, g and n as well as BLE 5.0 in a 595 mm² footprint and is built around Qualcomm’s QCA4020 system-on-chip (SoC) that features dedicated CPUs for Wi-Fi and BLE to maximize performance.

The module also incorporates security hardware to facilitate secured boot, flash encryption, copy protection, HTTPS and WPA/WPA2 Personal and Enterprise security modes. These safeguards go a long way in smart health care and other IoT designs that mandate network security and data privacy.

Integration beyond Wi-Fi

Another notable combination is 802.15.4 standard for low-rate wireless personal area networks (LR-WPANs) alongside Bluetooth. IEEE 802.15.4, which provides the PHY and MAC layers, leaving the upper layers to be developed for specific standards such as Thread, Zigbee and 6LoWPAN, facilitates communications over distances up to about 10 m and with maximum transfer data rates of 250 Kbps.

The RS13100 module from Redpine Signals integrates dual-mode Bluetooth 5 with 802.15.4 connectivity to enable battery-operated designs such as smart locks, fitness bands, industrial control units, and location tags. The DSP co-processor in RS13100’s ARM Cortex-M4F application processor can accelerate the artificial intelligence (AI) algorithms.

RS13100, featuring the trusted execution environment (TEE) and a separate security processor, offers suite-B Crypto HW accelerators, secure boot, secure firmware upgrade, secure XIP, and secure peripherals. These security features are crucial in applications like mobile point-of-sale terminals, smart locks, patient monitoring devices, and secure voice-based ordering.

However, Wi-Fi and 802.15.4 are still short-range wireless connectivity vehicles, complementing Bluetooth in terms of range and network capacity. And they are viable in specific IoT environments such as connected home, CCTV surveillance, smart appliances, etc.

What about IoT use cases like asset tracking that require Bluetooth combo with long-range wireless technologies such as LTE-M and NB-IoT? Here, multi-wireless modems combine low-power cellular LTE and Bluetooth connectivity technologies. That allows Bluetooth-enabled sensors to connect with cloud platforms over LTE networks.

Bluetooth in Cellular IoT

The Pinnacle 100 modem from Laird Connectivity offers complete Bluetooth 5 functionality along with LTE CAT-M1 and NB-IoT capabilities. It aims to simplify the bridging of wireless sensor data to cloud services like AWS IoT over low-power LTE connections. And it offers antenna flexibility by allowing users to employ external antennas, including Laird’s pre-integrated Revie Flex LTE and NB-IoT antennas.

Another prominent blend with low-power LTE comes from Bluetooth specialist Nordic Semiconductor. Thingy:91, a cellular IoT prototyping platform, is based on the nRF9160 system-in-package (SiP) that integrates a multimode LTE-M/NB-IoT modem with nRF52840, a multiprotocol SoC supporting Bluetooth 5, Thread, Zigbee, and ANT.

Thingy:91 comes bundled with a Nano (4FF) eSIM card from iBasis; it’s preloaded with 10 MB of data and facilitates automatic, instant, and out-of-the-box cellular LTE-M and NB-IoT connectivity along with roaming features.

The above design examples demonstrate the critical importance of Bluetooth connectivity in highly diverse IoT designs. And Bluetooth often works in tandem with other wireless technologies to build versatile connectivity solutions for IoT applications.