RFBLE (Bluetooth Low Energy) Basics
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There are various wireless technologies developed for short-range applications such as voice, data, audio, and video. Bluetooth and Bluetooth Low Energy are among them. Traditional Bluetooth is connection-oriented. When a device is connected, a link is maintained, even if there is no data flowing.
Here, sniff modes allow devices to sleep, which reduces power consumption and hence provides months of battery life. Peak transmit current is typically around 25 mA. Even though Bluetooth has been independently shown to be lower power compared to other radio standards, it is still not low enough power for coin cells and energy harvesting applications. Hence, BLE (Bluetooth Low Energy) technology is developed for these low-power applications.
It is one of the technologies used in IoT (Internet of Things). In IoT, things have data which is needed by Web Services. Bluetooth Low Energy provides the technology to connect these two. It uses an asynchronous connectionless MAC which helps to achieve low latency and fast transactions (e.g. 3ms from start to finish). BLE uses a new PHY, new radio, and a new protocol stack compared to generic Bluetooth.
Following are the features of BLE, referred to as Bluetooth Low Energy:
| Specification/Feature | BLE (Bluetooth Low Energy) |
|---|---|
| Support | |
| Range | Typically 5-10 m, 150 meters can be achieved in open field (implementation specific) |
| Output power | 10 mW (10dBm) |
| Max. current | 15mA (implementation specific) |
| Latency | 3 ms |
| Data rate (Throughput) | 1 Mbps (But it is not optimized for file transfer application) |
| Topology | Star connections > 2 billion |
| Modulation | GFSK at 2.4 GHz |
| Robustness | Adaptive frequency hopping, 24 bit CRC |
| Security | 128 bit AES CCM |
| Sleep current | Approx. 1 µA (Implementation specific) |
| Modes | broadcast, connection, event data models, reads, writes |
| RF Band | 2400 MHz |
| Spreading | FHSS (2 MHz channel BW) |
Above Figure 1 depicts BLE network topologies.
