Detection of precoded signals using a receiver with non-coherent front end

In a high-speed wireless communications network with mobile terminals, an appealing way to off-load hardware complexity to the base station is to use transmitter precoding in the downlink direction. A modification to the conventional DQPSK receiver is presented for processing the extended precoded constellations without requiring good phase synchronization. To avoid the related severe noise multiplication effect, an alternative receiver is developed, incorporating a discrete-time phase tracker so that the constellation size can be reduced before the differential detection operation. With a 2nd-order estimator filter, this receiver approaches the performance of coherent detection for transmitter precoding.