Two existing blind equalisation tap update recursions suitable for 64-point and greater QAM signal constellations are studied, along with existing and novel carrier and timing recovery techniques. It is determined that the superior tap update recursion is the one known as the "constant modulus algorithm." Carrier recovery requires a modified second-order decision-directed digital phase-locked loop. A novel all-digital implementation of bandedge timing recovery is used. With 14.4 kbps outbound transmission using CCITT V.33 trelliscoded 128-QAM signals having 12.5% excess bandwidth, a prototype blind retrain procedure is developed to demonstrate feasibility of the new techniques for high-speed multipoint modems. A WE' DSP32-based real-time digital signal processor was employed to successfully test the retrain over a set of severely impaired channels.
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