A New Loopback GSM/DCS Bit Error Rate Test Method On Baseband I/Q Outputs

The Bit Error Rate (BER) evaluation in one of the key parameters to reach QoS (Quality of Service) requirement of modern digital communication of the next generation (3 and 4G). This paper presents a new loopback BER Test (BERT) method based on measurements on baseband IQ outputs. The interest of this method is that it allows quantifying separately from digital stage, the RF stage influence on BER performances. This test principle has been validated introducing 4 instruments in the loop plus a GSM/DCS monochip as device under test. Unfortunately at the moment, one of the instruments capabilities limits the bit rate to one third of demodulation bandwidth, i.e. 200kHz. Replacing this instrument by a pure digital demodulator in the loop will eliminate this restriction in the future. So any kind of baseband IQ BERT could be performed using that method.