Differential detection of pi /4-shifted-DQPSK for digital cellular radio

A high-capacity digital cellular system is being developed in the US. This system will use filtered pi /4-shifted-DQPSK (differential quaternary phase-shift keying) modulation, achieving a spectral efficiency of 1.62 b/Hz. The BER (bit error rate) performance of this modulation was studied using differential detection. A tangent-type differential detector with an integrated sample and carrier frequency error correction algorithm is presented. Theoretical and simulation BER results are presented for static and flat fading channels. Additional results are provided on the BER sensitivity to Doppler, time delay spread, carrier frequency errors, and DC offsets.<
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