To establish a bi-direction connection between devices (such as a smart watch to a phone). ![]() ![]() In Bluetooth ® low energy there are two reasons to advertise/broadcast: So great, we know we’re advertising, and have “x” number of octets for payload, but why are we advertising? This is where the PDU Type comes in. The Length may be between 6 – 37 octets and is defined by PDU Type. how much stuff we can advertise (Figure 2A). The Length field is 6 bits and defines the size of the payload, i.e. We’ll focus on the Length and PDU Type fields/segments (Figure 2B). The advertising header defines 6 segments. This packet consist of four components: preamble (1 octet), access address (4 octets), Protocol Data Unit – PDU (2-257 octets), and Cyclic Redundancy Check – CRC (3 octets) see Figure 1A. Whether it’s a beacon (transmitting location, weather, or other data) or a fitness watch making a long term connection with a host (tablet or phone), all peripheral devices, at least initially, begin in advertising mode.Īdvertising allows devices to broadcast information defining their intentions.įor ease of use, Bluetooth defines a single packet format for both advertising and data transmissions. As such, 3 of these 40 channels are dedicated to advertising and 37 to data. Bluetooth defines two transmissions types: data and advertising transmissions. ![]() So how does Bluetooth work? Bluetooth low energy has 40 physical channels in the 2.4GHz ISM band, each separated by 2MHz. Bluetooth technology is growing and is expected to have an install base of over 48 billion by 2021 (per ABI Internet of Everything Market Tracker). Bluetooth ® technology is all around us: electronic beacons guiding firefighters through buildings wearable medical devices sending patient’s biological data to a physician’s tablets manufacturing equipment monitoring in 400,000 square foot warehouses and more.
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