Does the channel impulse response change over time?

Let's suppose we have an emitter and a receiver in fixed positions the emitter sends a signal $$s_1(t)$$ and after a period $$T$$ it sends $$s_2(t)$$, the receiver receives $$r_1(t)$$ and $$r_2(t)$$. My question is if $$s_1(t)=s_2(t)$$, is it true that $$r_1(t) = r_2(t)$$?

• If the channel doesn't change, yes, if it does, no, that simple. Could you reformulate your question to make it easier to give non-trivial answers? I mean it's probably obvious that every channel changes over time, but if that change is slow compared to $T$ you can probably ignore it, otherwise you can't. – Matt L. Jul 12 at 18:45