We introduce and characterize the operational diversity order (ODO) in fading channels, as a proxy to the classical notion of diversity order at any arbitrary operational signal-to-noise ratio (SNR). Thanks to this definition, relevant insights are brought up in a number of cases: (i) We quantify that in dominant line-of-sight scenarios an increased diversity order is attainable compared to that achieved asymptotically, even in the single-antenna case; (ii) this effect is attenuated, but still visible, in the presence of an additional dominant specular component; (iii) the decay slope in Rayleigh product channels increases very slowly, never fully achieving unitary slope for a finite SNR.

翻译：本文引入并表征了衰落信道中的操作分集阶数（ODO），作为经典分集阶数概念在任意操作信噪比（SNR）下的替代度量。基于此定义，我们在多种情况下获得了重要见解：（i）量化结果表明，在主导视距场景中，即使是在单天线情况下，也能获得比渐近情况下更高的分集阶数；（ii）在存在额外主导镜面分量的情况下，该效应虽有所减弱但仍可观测；（iii）瑞利乘积信道的衰减斜率增长极为缓慢，在有限信噪比下始终无法完全达到单位斜率。