Investigations of Bluetooth Link Quality

Bluetooth is a wireless system for short-range communication between many types of devices, with ranges of e.g. 10 cm to 10 m for a 0 dBm device. The system uses frequency hopping in a bandwidth of about 80 MHz in the ISM band 2.402-2.482 GHz. The properties of the radio channel used by the Bluetooth application are relatively unknown, with the slowly moving terminals and a short-range distance between the transmitter and receiver. The main challenge is to ensure sufficient received power in the fading channel. In [Pedersen and Eggers, 2000(d)] the radio link is investigated using two 20 dBm Bluetooth PC cards by measurements made both indoor and outdoor. For an almost static indoor channel it was found that the link quality is good within a range of about 10 m and if the line of sight is not too obstructed the range is up to about 25 m. The throughput depends strongly on the position and orientation; see Figure 4.5.7 (Coverage of Bluetooth link) in CPK Annual Report 2000. Without line of sight between the transceivers the link breaks down at 20-30 m. Depending on building materials the coverage may be confined to a single room. In the outdoor case the maximum distance is somewhat larger, up to 220 m was found. (Gert F. Pedersen and Patrick C.F. Eggers, Kim Olesen)