GBR Bearer refers to "Guaranteed Bit Rate" Bearer. It is a type of data bearer in 4G mobile network that provides a guaranteed minimum data rate for the transmission of data.

The minimum bit rate of the GBR bearer is negotiated during the bearer establishment process. The network reserves the necessary network resources (e.g., bandwidth, radio resources) to ensure that the guaranteed bit rate of the bearer can be maintained.

GBR Bearers are suitable for real-time, delay-sensitive applications, such as Voice over IP (VoIP) calls.