Carrier & Symbol Timing Recovery for N QAM

This model implements a contemporary symbol timing and carrier recovery scheme for 2-256 QAM.

Timing recovery is a critical aspect of Digital Communications Receivers. This model uses a fractional sample delay implemented with a Farrow filter to create a symbol rate timing recovery subsystem. This is combined with a decision aided Carrier Recovery PLL. For testing, a transmitter with continuosly variable carrier frequency error and symbol rate error is included. Two versions of the transmitter are provided. One version uses Simulink's variable step solver to create a continuous time signal for re-sampling by the receiver. The other version uses the same fractional sample delay as in the receiver to implement the transmitter entirely in discrete time.
The updated version of these files supports QAM modulation of order 2 to 256 inclusive. It therefore supports PSK (2 QAM) and QPSK (4 QAM) as well.
References are cited in the models.