As Szymon Slupik, CTO at Silvair and Chair of the Bluetooth Mesh Working Group, often says, the math is simple: the shorter the packet the fewer collisions. The reliability of any wireless system is all about spectral efficiency. According to Slupik, the size of Bluetooth mesh packets is one of the biggest reasons why Bluetooth mesh networking is “the first wireless standard capable of meeting the enormous expectations of the IoT era.”
Slupik is not alone in his praise for the packet. Woolley references the Bluetooth mesh packet in relation to scalability and capacity of a high-density device network. As Woolley says:
The less radio airtime a packet requires, the lower the probability of a collision. The small packet size of Bluetooth® mesh and the high symbol rate of the Bluetooth LE radio reduce the required airtime for a packet and means that Bluetooth mesh networks fare well in this respect.
But Bluetooth packets don’t just have size and speed on their side. They’re also good at avoiding conflict.
Adaptive Frequency Hopping
Spread spectrum techniques can increase the resiliency of a wireless technology in busy radio environments where collisions and interference are more likely to occur. Adaptive Frequency Hopping is a unique spread spectrum technique Bluetooth technology utilizes to avoid interference.
To understand how Adaptive Frequency Hopping works, it helps to look at how Bluetooth technology divides the 2.4 GHz ISM band. First, like many wireless communication protocols, Bluetooth technology uses more than one radio channel. Bluetooth Low Energy (LE) divides the 2.4GHz ISM radio band into 40 channels, while Bluetooth BR/EDR divides it into 80 channels.
Bluetooth technology also hops between transmission channels to further decrease the probability of collisions with other in-range transmissions. Frequency hopping frees up more radio capacity for messages, making communication more reliable. Frequency hopping is not necessarily unique to Bluetooth technology. But what happens next is.
Adaptive Frequency Hopping adds intelligence to frequency hopping and enables Bluetooth packets to adapt to avoid active, congested channels. Channels that are noisy and busy are marked and not used. The list of reliable channels and busy channels can change quickly, as other wireless communication devices and noise in the environment come and go. Adaptive Frequency Hopping allows Bluetooth technology to dynamically track which channels are functioning best and find the most reliable path.
Bluetooth® packets avoid conflict.