140 Mbit/s 32QAM cross-polarized co-frequency trial results

The frequency reuse technique can be adopted for doubling the capacity (bits/hertz) of digital radio systems. The newly developed 140-Mb/s 32QAM (quadrature amplitude modulation) Telettra modems equipped with a cross polar interference canceller (XPIC) have been tested successfully on a 60-km 4-GHz link in the north of Italy. The authors present the main results observed during the period of August-December 1991. The performance of a 2×140 Mb/s 32QAM system is comparable to that of a 1×140 Mb/s 16QAM system in the same conditions. The good XPIC performance in terms of outage probability reduction and sync-recovering speed shows the soundness of design and construction technologies