Well, I'm not sure how well that would work... The "dither" on the RTT can't go negative (for obvious reasons :-) ).
Sure it can. We're not talking RTT in the Internet sense. In a spread spectrum system, deterministic pseudo-random sequences are used for the spreading codes; the receiver always knows the future of the sequence. We generate ours with conventional linear feedback shift registers. The mobile phone tracks the code phase of the cell site and slaves its own coded transmissions to that. All you'd have to do is to add a random time-varying phase to the tracking loop. That would cause the measured delay to be either greater than or less than the real value. There would be limits to how far you could vary the delay, but the tolerance at the cell has to be on the order of the cell radius for the system to work anyway. Phil