请教：关于高通的灵敏度测试

非信令模式下的灵敏度测试有SE BER 和 SRB BER.
其中SE BER 又包括 Single-ended BER 和 Loopback BER，这三种 BER 分别是什么含义，有什么区别?

At SRB loopback (Switched Radio Block loopback), the bit error
rate can be measured using the MT8820B-demodulated uplink
RF signal looped back from the EGPRS terminal. The error rate
can be measured in parallel with transmitter measurements.