Wideband delay paths and frequency diversity

Determine when delayed artificial-scatterer paths in wideband repeater-assisted MIMO provide exploitable frequency diversity and when the resulting interference and receiver complexity outweigh that benefit.

Background

Repeater-assisted MIMO systems can create additional propagation paths whose delays arise from both physical propagation and repeater RF, baseband, and processing components. In an OFDM system, a sufficiently strong delayed path that remains within the cyclic prefix can reduce frequency correlation and increase frequency diversity, whereas a path approaching or exceeding the cyclic-prefix duration can cause inter-symbol and inter-carrier interference.

The unresolved issue is to characterize the boundary between these beneficial and harmful regimes while accounting for path power, delay separation, power-delay profiles, waveform numerology, frequency-dependent repeater gains, colored amplified noise, signaling, and receiver processing. This is important because optimizing only narrowband received power may produce poor wideband performance.