Adaptive equalisation for a distributed digital-radio telephone network has contrasting receiver design objectives. When using PI/4 DQPSK modulation in AWGN channel, a receiver using a limiter discriminator integrator detector (LDID) is a cost effective solution, where standard FM hardware and a moving averager realised as a 4th order analog filter as an integrator can be used with 0.5 dB error performance degradation. In time dispersive channels, LDID requires equalisation at IF and is very sensitive to frequency offsets. Consequently, baseband equalisation and a non-coherent differential detection is attractive but has to be equipped with fast online time delay and complex channel impulse response (CCIR) estimation along with an effective technique for synthesizing the equalisation filter. The strategy adopted here is to consider minimum and maximum phase CCIRs separately and link the equalisation problem with the connectivity protocol of the distributed digital-radio telephone network.
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