In the previous blog “IoT Connectivity Technologies” we described in brief the various wireless connectivity options available for developing an IoT device. In this blog we discuss in detail about bluetooth technology — covering the physical and higher network layers and the classifications that make bluetooth technology one of the most widely adopted short-range wireless standards in the world. From consumer wearables to industrial sensors, bluetooth technology underpins a growing family of connected products. Embien's Digital Transformation Services and Industrial Communication and Connectivity Services leverage bluetooth technology to accelerate IoT product development across all major market segments.
Bluetooth Technology Introduction
Bluetooth is a wireless technology standard that uses short-wavelength Ultra High Frequency radio waves in the licence-free Industrial, Scientific, and Medical (ISM) frequency band. Bluetooth technology is managed by Bluetooth SIG (Special Interest Group), originally formed by five companies: Ericsson, Nokia, IBM, Toshiba, and Intel. The Bluetooth SIG publishes and updates the Bluetooth specifications. IEEE standardised bluetooth technology as IEEE 802.15.1, though it no longer maintains the standard. The Bluetooth radio interface enables reliable communications over short distances, supporting multiple channels with different power levels and reliable modulation schemes.
Bluetooth ISM Band Frequency Hopping Fundamentals: Physical Layer
Understanding Bluetooth ISM band frequency hopping fundamentals is essential to designing robust wireless systems. Bluetooth frequencies are located within the 2.4 GHz ISM band, spanning 2400 MHz to 2483.5 MHz. There is a 1 MHz space between each Bluetooth channel starting from 2402 MHz and ending at 2480 MHz, calculated as 2401 + n where n ranges from 1 to 79. This channel arrangement gives a guard band of 2 MHz at the lower end and 3.5 MHz at the upper end, preventing interference with adjacent spectrum users.
Bluetooth employs a technique called Frequency Hopping Spread Spectrum (FHSS) by which radio signals are transmitted by rapidly switching the carrier signal among various frequency channels. The transmitted data is divided into packets and sent on one of 79 designated channels switched randomly at a rate of 1600 times per second. The main drawback of this approach is the risk of collision with another wireless device such as Wi-Fi operating in the same environment. This is where the second pillar of Bluetooth ISM band frequency hopping fundamentals becomes important: Adaptive Frequency Hopping (AFH).
The Adaptive Frequency Hopping technique allows bluetooth technology to adapt to its environment by excluding fixed sources of interference (bad channels) from the available channel list. This re-mapping reduces the number of channels used, improving coexistence. The following figure illustrates the collision resulting from random frequency hopping in a congested environment:
Random Frequency Hopping
The following figure illustrates how Adaptive Frequency Hopping avoids those collisions:
Adaptive Frequency Hopping
Digital data is conveyed using Gaussian Frequency Shift Keying (GFSK), where binary 1 is represented by a positive frequency deviation and binary 0 by a negative deviation. This achieves the basic data rate (BR) of 1 Mbps. Higher data rates are achieved using Phase Shift Keying: π/4-DQPSK reaches 2 Mbps and 8DPSK reaches 3 Mbps under enhanced data rate (EDR) mode. Further improvement to 24 Mbps is achieved by cooperating with an IEEE 802.11g physical layer.
Bluetooth Low Energy also operates in the same 2.4 GHz ISM band as Classic Bluetooth, but instead of 79 one-MHz channels it uses 40 two-MHz channels. BLE transmits using GFSK at 1 Mbps, the same bit rate as Classic BR mode, but achieves dramatically lower power consumption — a central advantage of bluetooth technology for battery-powered IoT devices. With a solid grasp of Bluetooth ISM band frequency hopping fundamentals, developers can make better design decisions for RF layout, antenna selection, and coexistence filtering.
Bluetooth-Enabled Pulse Oximeter Design: Healthcare IoT Applications
One of the most compelling uses of bluetooth technology in healthcare is the Bluetooth-enabled pulse oximeter design, where a photoplethysmography (PPG) sensor measures blood-oxygen saturation and transmits readings wirelessly to a smartphone or gateway. A Bluetooth-enabled pulse oximeter design relies on BLE's low-power connection intervals to extend battery life while still delivering real-time SpO2 and heart-rate data. Embien has delivered multiple Bluetooth-enabled pulse oximeter design projects as part of its healthcare wearable portfolio, combining precision analog front-ends with optimised BLE firmware stacks.
Audio Processing Embedded: Bluetooth for Audio and Medical Devices
Bluetooth technology is also a cornerstone of audio processing embedded applications — from wireless headsets and hearing aids to conference room speakerphones and medical-grade audio monitoring devices. Embedded audio processing pipelines that use BLE or Classic Bluetooth must handle codec negotiation, synchronisation, and latency management within strict real-time constraints, making the choice of SoC and firmware architecture as important as the RF design itself.
Bluetooth Communication
Bluetooth communication takes place in a short-range ad hoc network known as a Piconet. A Piconet starts with two connected devices and can grow to eight connected devices. One device acts as the master (controlling unit) and the others as slaves; each slave is assigned a specific time slot to transmit data without collision. Bluetooth core specification supports the connection of two or more Piconets to form a Scatternet, in which a device of one Piconet can simultaneously play a slave role in another, enabling communication across more than eight devices. The following figure depicts the concept of a Scatternet:
Concept of Scatternet
Bluetooth Classification
Multiple versions of bluetooth technology have been developed to meet the specific requirements of each era, with each version fixing issues from the previous one. All updated versions maintain backward compatibility. The following table describes the different versions of bluetooth technology available:
Bluetooth Classifications
Why There Is So Much Hype on BLE?
Bluetooth Classic faced critical challenges including rapid battery drain and frequent connection loss requiring re-pairing. BLE overcomes these by intelligently managing connections while preserving battery power. Rather than maintaining constant bit streams, BLE sends small chunks of data when required and sleeps during idle periods. This sleep-wake pattern, combined with Bluetooth ISM band frequency hopping fundamentals inherited from Classic Bluetooth, makes BLE ideal for coin-cell-powered devices.
BLE falls under the Personal Area Network (PAN) connectivity category. An IoT device with bluetooth technology connectivity can use a smartphone as a gateway to the internet. Most modern smartphones are Bluetooth Smart Ready — capable of communicating with both Classic Bluetooth and BLE devices — making smartphones a natural hub for healthcare wearables, home automation controls, and Bluetooth-enabled pulse oximeter design products. Bluetooth Smart devices such as smart watches, car key fobs, and heart rate monitors are standalone, battery-operated devices focused on minimising power consumption.
Security is also evolving with bluetooth technology. Embien has developed a quantum secure ble module that applies post-quantum cryptographic algorithms to BLE connections, future-proofing embedded wireless products against emerging threats — a capability increasingly relevant as bluetooth technology is adopted in critical infrastructure and medical devices.
With this understanding of bluetooth technology and its classifications, our next blog discusses in detail the design considerations for developing IoT devices with BLE connectivity.
About Embien
Embien Technologies is a leading provider of embedded design services for the Semiconductor, Industrial, Consumer, and Healthcare segments. Our expertise spans bluetooth technology system design, Bluetooth ISM band frequency hopping fundamentals, Bluetooth-enabled pulse oximeter design, audio processing embedded systems, and quantum secure ble module development. Embien has successfully executed many IoT projects including healthcare wearables, gateways, and data analytics platforms. Embien also offers wearable design collections complete with electronics, firmware, and cloud integration to significantly reduce product development costs and time-to-market.