Meaning
Quality metric describing the degree of separation between multiple parallel data paths in a multi-antenna communication link. Spatial stream isolation measures how well a receiver can distinguish between different data streams that are sent simultaneously over the same frequency. It determines whether the spatial multiplexing can actually deliver the promised increase in throughput.
If the streams are not well isolated, they leak into each other and cause errors that the decoder cannot fix.
MIMO Efficiency
Throughput scaling depends on the independence of the paths through the radio environment. High spatial stream isolation allows the system to send twice as much data using two antennas as it could with one. When the physical environment lacks enough scattering, the paths become too similar, and the isolation drops, forcing the system to fall back to a single stream.
This often happens in long-distance line-of-sight links where there are no nearby objects to reflect the radio waves and create diverse signal paths.
Receiver Processing
Signal separation involves complex matrix inversions to extract the individual streams from the combined received signal. The hardware uses the known channel state to maximize spatial stream isolation during the decoding process. Advanced algorithms like minimum mean square error are employed to balance the trade-off between noise enhancement and stream separation.
Multipath Propagation
Multipath propagation provides the variety of signal paths needed for high isolation. In a typical office or city, signals bounce off many surfaces, creating the unique spatial signatures that the receiver uses. Without these reflections, the spatial stream isolation remains poor, making high-speed MIMO modes impossible to maintain over long distances.
