Bluetooth Low Energy (BLE) and WiFi: How to Manage Coexistence for IoT

The smart home and home automation industry is transforming rapidly, with new use cases and applications emerging daily. 

The Internet of Things (IoT), which spans industrial, consumer, commercial, and infrastructure sectors, has evolved significantly from simple LED control to encompass a wide range of applications, including home automation, wearables, security, autonomous driving, and many more. Wireless technology, a fundamental component of these applications, has also undergone significant advancements. 

In the past, simple use cases relied heavily on Bluetooth technology. However, Bluetooth's limitations, including its power inefficiency for battery-operated devices and coexistence challenges with collocated WiFi, have led to the development of more efficient alternatives.

In recent years, Bluetooth Low Energy (BLE) has gained traction in the industry due to its power efficiency and scheduled communication slots. Today, BLE has become a foundational component of IoT devices, with research and development centered around this technology.

A typical smart home application requires BLE for communication with sensors, switches, and peripheral nodes, while WiFi is used for cloud connectivity. 

As the demand for BLE-enabled devices and peripherals grows, so do the challenges of coexistence. Both BLE and WiFi operate in the 2.4 GHz frequency band, which can lead to mutual interference, network congestion, retransmissions, and increased battery drain, ultimately resulting in a poor user experience.

IoT Market Statistics

The number of connected IoT devices is estimated to grow at a 14 percent rate to 40 billion by 2030. Wi-Fi, Bluetooth (BLE), and cellular make up nearly 80 percent of all IoT connections. The top three applications for IoT connections are home security & monitoring (10.9 billion connections), smart meters (1 billion connections), and home appliances (1 billion connections). Annual IoT connection revenue will nearly double from US$21.4 billion in 2025 to more than US$40 billion by 2030, at a CAGR of 14 percent.

Global IoT Market Forecast

Due to the strong growth of connected consumer electronics like security systems, smart locks, etc, combined with the growing adoption of LE Audio - peripherals will continue to drive the growth of single-mode Bluetooth LE device shipments. 

As per ABI research shown below, overall Bluetooth Low Energy (BLE) radio shipment is expected to grow at 8 percent CAGR with 7.5 billion Bluetooth/BLE shipments by 2028.

Bluetooth Enabled Device Shipments

Power and Coexistence Challenges

BLE Central device must send a POLL packet at every anchor point for communication.  BLE Central and Peripheral perform Poll and Null transactions for every anchor point, even when there is no data at the BLE connection anchor point instant as shown below.

In applications (say sensors), where BLE Bandwidth requirements are low to moderate, BLE Central with multiple peripherals associated ends up paying below penalties.

Penalty 1: Power Consumption

Even if BLE Central doesn’t have any data at a particular BLE Connection anchor point, it must transmit an empty packet to inquire about the availability of BLE Peripheral data.

This way, BLE Central ends up Consuming a lot of power by polling all its associated Peripherals at their agreed anchor points to realize whether Peripheral has data or not.

Penalty 2: Channel Efficiency

Reduced channel efficiency due to multiple POLL-NULL messaging, leaving less airtime for collocated WiFi devices. In scenarios where passive isolation is less, Time Division Multiplexing of the Medium between BLE and WiFi is the best option, but when BLE Central is associated with Multiple Peripherals, it would forcefully take away and consume medium from Co-Existing radio like WLAN, 802.15.4.

Penalty 3: Increased System Active Time

The entire system must wake up from intermediate sleep at different anchor points to transmit an empty Payload packet. Similarly, Battery-operated Peripheral devices have to wake up to listen for Packets.

Such communication overheads lead to overall coexistence performance impact and reduced battery life for battery-operated BLE peripherals.

Leverage BLE Periodic Advertising with Response (PAwR)

Without coordination between wireless radio chips, BLE and WiFi can create significant mutual interference, leading to poor connectivity performance, frequent disconnects, higher latency, and increased power consumption.

Bluetooth 5.4 has introduced Periodic Advertising with Response (PAwR), which now allows for bidirectional transfer of application data between a central device and a large number of peripheral devices in a star network topology. 

PAwR builds upon Periodic Advertising introduced in Bluetooth 5.0, where the procedure of acquiring advertising synchronization information is obtained by an observer during scanning. PAwR enables bidirectional connectionless transfer of small amounts of data by adding response slots as periodic advertising subevents during a periodic advertising interval.

The diagram below shows periodic PAwR subevents and response slots within subevents where peripheral devices can send data or messages.

PAwR

These challenges can be mitigated by employing careful coexistence architecture using Periodic Advertising with Response (PAwR) defined in Bluetooth 5.4 specification and appropriate techniques. 

These techniques include how to set and use the PAwR link and choosing appropriate subevent interval/length to avoid unnecessary wakes at peripheral, conserve battery life, and improve overall WiFi/BLE coexistence performance. 

For assuming a piconet of 12 peripherals, the total number of BLE transmissions without PAwR increases even when there is no data to transfer, compared to a single transmission with PAwR as shown below in Figure 6. This scheme helps to boost the battery life by reducing BLE Tx transmissions and by helping the system sleep for longer durations.

BLE Transmissions

Growth in BLE Connectivity

The IoT industry is witnessing unprecedented growth in BLE/WiFi connectivity, driven by the demand for innovative user experiences and cutting-edge features in advanced smart homes, home automation, and other IoT applications. 

The BT 5.4 PAwR feature has emerged as a promising solution for applications with light to moderate traffic aggressiveness, offering significant reductions in system power consumption and coexistence challenges. 

As the IoT landscape continues to evolve, OEMs must prioritize seamless connectivity and optimal performance in their system designs, futureproofing their solutions to meet the growing demand for BLE-WiFi solutions. 

With the IoT use cases expected to proliferate exponentially, the demand for efficient and reliable BLE-WiFi connectivity is poised to skyrocket, presenting immense opportunities for innovation and growth.