Cross-layer optimization is an escape from the pure waterfall-like concept of the OSI communications model with virtually strict boundaries between layers.
For example, having knowledge of the current physical state will help a channel allocation scheme or automatic repeat request (ARQ) strategy at the MAC layer in optimizing tradeoffs and achieving throughput maximization.
[clarification needed] Any highly dynamic change of resource allocation might affect the intelligibility of voice or the steadiness of videos.
The control adjusted to availability of limited resources is the first mandatory step to achieve at least a minimum level of quality.
[10][11] In some communications channels (for example, in power lines), noise and interference may be non-stationary and might vary synchronously with the 50 or 60 Hz AC current cycle.