Full Digital Adaptive Equalization in 64-QAM Radio Systems

In view of a digital implementation of most of the signal processing required in a QAM demodulation-equalization Structure, a performance analysis as a function of equalizer complexity, A/D conversion resolution, and precision of internal arithmetic is presented. The analysis is focused on a 140 Mbit/s 64-QAM modulation scheme (corresponding to CEPT-4 or
3 \times DS3
systems), but extension to other QAM constellations is straightforward. Considerations of currently available technology, overall computational complexity, and related optimal quantization formats are presented. For high-speed 64 QAM, it is shown that satisfactory performance may be expected from a full digital implementation of reasonable complexity, using current technology.