Block differential modulation for doubly-selective wireless fading channels

Differential encoding is known to simplify receiver complexity because it by-passes channel estimation. However, over rapidly fading wireless channels, extra transceiver modules are necessary to enable differential transmission. Relying on a basis expansion model for time and frequency selective (doubly-selective) channels, we derive such a generalized block differential (BD) codec that achieves the maximum Doppler and multi-path diversity gains, while affording low-complexity maximum likelihood (ML) decoding. We further show that existing BD systems over frequency-selective or time-selective channels follow as special cases of our novel system. Simulations corroborate our theoretical analysis.