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I believe the situation being discussed on the call where the phase search appeared ill-behaved was one where the optimum sampling phase was not within the initial sweep or a valid FOM had not yet been found (e.g., because the sweep was too coarse). The local
search shoudl behave similar to acquisition and tracking of sampling phase. Once you find a valid sampling phase, you generally don't lose it except in very pathological channels (e.g., with unterminated stubs, which we generally don't see). Such channels
would be problematic anyways, as tracking loops would also get stuck in these local minima.
Note that slide 3 of the presentation (https://www.ieee802.org/3/ad_hoc/COM/public/telecon/260901/gregory_COM_01_260901.pdf) states the requirements below and
specifically warns against this. The resolution of the initial sweep needs to be sufficient to sample the open eye (which I believe is needed for a valid FOM, if I understand the statement below correctly)
The text from slide 3 is below. It may be useful to consider better guidance on just what "far away" is.
-george
(from slide 3)
It requires:
• Valid FOM has been found
• Local Search is enabled
• One full sweep of sampling phase has finished
If the current sample phase is far away from the best sample phase, don’t run it. Far away is defined by the Local Search parameter, which is usually set to 2
George Zimmerman, Ph.D. President & Principal CME Consulting, Inc. Experts in Advanced PHYsical Communications 310-920-3860
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