Transmit-power reduction for class-1 Bluetooth-enabled indoor cordless phones

Class-1 Bluetooth devices support a transmission range of about 100m and are useful for indoor cordless telephony with advantages of wider coverage, greater user mobility, and more convenience. To minimize the transmit power of class-1 devices, feedback power control specified in the Bluetooth specification can be used. This paper shows that further transmit-power reduction is possible by reducing the Golden Receive Power Range (GRPR) from the specified value of 20dB. For typical indoor lognormal-shadowing channels, more than 4dB reduction in the mean transmit power can usually be obtained by reducing the GRPR to 10dB. However, using a smaller GRPR increases the frequency of making power-adjustment requests through the Link Manager Protocol (LMP), thereby pre-empting more voice packets and affecting the voice quality. We compute the overhead cost due to power control, defined as the percentage of the total number of packets used for power-adjustment requests, when the GRPR is set at 10dB ± 6dB, wherein 6dB is the tolerance allowed in implementation.