For fast fading channels, a spectrally efficient technique than can achieve more than 2 b/s/Hz with a built-in fade canceler is proposed. Recent studies show that fading in digital mobile communications can be canceled by adding redundant bits to the customer data or with pilot-aided techniques. This concept is extended to a more spectrally efficient class-IV quadrature partial response signaling (QPRS) system. However, in such schemes if the pilot is corrupted by the phase noise caused by the pilot-data interference, the fade cancellation will not effectively remove the error floor. The class-IV system has an inherent advantage in that it has a spectral null at DC and a low energy content at the ends of the band. Such systems also have a higher speed tolerance. It is shown that a small bandwidth around DC can be vacated to insert the pilot. Preliminary results show that residual error floor can be reduced from 10/sup -2/ to 10/sup -5/ in fast fading channels.
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机译：对于快速衰落的信道，提出了一种频谱有效的技术，该技术可通过内置的衰落消除器实现超过2 b / s / Hz的频率。最近的研究表明，可以通过在客户数据中添加冗余位或使用飞行员辅助技术来消除数字移动通信中的衰落。该概念被扩展到频谱效率更高的IV类正交部分响应信令（QPRS）系统。但是，在这种方案中，如果导频因导频数据干扰引起的相位噪声而损坏，则衰落消除将无法有效地消除误差底限。 IV类系统具有一个固有的优势，因为它在DC处具有零频谱，在频带末端具有低能量含量。这样的系统还具有较高的速度公差。结果表明，可以腾出DC周围的小带宽来插入导频。初步结果表明，在快速衰落信道中，残留误差本底可以从10 / sup -2 /降低到10 / sup -5 /。
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