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classdef MarginLock < handle
% Version: 0.1
% Description:
% If the smallest registered COM is above 3dB for some period,
% then assume it is safe to turn off the most "insignificant"
% tap (which now is, kind of, the smallest one)
%
% However, if smallest COM drops below 3dB for some period,
% then activate the fallback mechanism and turn on the recently
% disabled tap and terminate the algorithm
properties
lastDisabledTap
internalFFETapsMask
lastUpdateTime
reachedHighErr
cooldownPeriod
errCollectionPeriod
initialErrCounter
maxErr
runningMeanErr
errCounter
cooldownCounter
reachedHighCOM
reducedErrSeqCounter
increasedErrSeqCounter
end
methods
function obj = MarginLock(LMSUpdateObj)
obj.lastDisabledTap = -1;
obj.internalFFETapsMask = LMSUpdateObj.FFE_TapsMask;
obj.lastUpdateTime = LMSUpdateObj.StartFFEAdaptTime * LMSUpdateObj.WindowSize;
obj.reachedHighErr = 0;
obj.cooldownPeriod = 2;
obj.errCollectionPeriod = 10;
obj.initialErrCounter = 0;
obj.maxErr = 0;
obj.runningMeanErr = 0;
obj.errCounter = 0;
obj.cooldownCounter = 0;
obj.reachedHighCOM = 0;
obj.reducedErrSeqCounter = 0;
obj.increasedErrSeqCounter = 0;
end
function FFETapsMask = GetFFETapsMask(obj, LMSUpdateObj)
initialTogglingStart = LMSUpdateObj.LearningRatesAdjustTimes(1) + 8;
canStartAlgo = LMSUpdateObj.IterCount > initialTogglingStart * LMSUpdateObj.WindowSize;
errVecSize = max(size(LMSUpdateObj.ErrorVec));
inCooldown = obj.cooldownCounter > 0;
dlevDiff1 = LMSUpdateObj.Dlev_0p5 - LMSUpdateObj.Dlev_0p16;
dlevDiff2 = LMSUpdateObj.Dlev_0p16 - LMSUpdateObj.Dlev_m0p16;
dlevDiff3 = LMSUpdateObj.Dlev_m0p16 - LMSUpdateObj.Dlev_m0p5;
minDlevDiff = min([dlevDiff1 dlevDiff2 dlevDiff3]);
margin = minDlevDiff / 2;
% if eye is not open yet, monitor when high enough COM is
% reached
if canStartAlgo && ~obj.reachedHighCOM && ~obj.reachedHighErr
obj.maxErr = max(obj.maxErr, max(abs(LMSUpdateObj.ErrorVec)));
obj.initialErrCounter = obj.initialErrCounter + 1;
end
% since maximum error can not be used very accurately for
% monitoring high COM, the threshold for initial COM becomes 4dB
if canStartAlgo && ~obj.reachedHighCOM && ~obj.reachedHighErr
if obj.initialErrCounter >= 3 * LMSUpdateObj.WindowSize
approxMinCOM = 20*log10(margin / obj.maxErr);
if approxMinCOM >= 4
obj.reachedHighCOM = 1;
end
obj.initialErrCounter = 0;
obj.maxErr = 0;
end
end
if canStartAlgo && ~inCooldown && obj.reachedHighCOM && ~obj.reachedHighErr
obj.runningMeanErr = (sum(abs(LMSUpdateObj.ErrorVec)) + obj.runningMeanErr * obj.errCounter * errVecSize) / ((obj.errCounter + 1) * errVecSize);
obj.errCounter = obj.errCounter + 1;
end
if canStartAlgo && inCooldown && ~obj.reachedHighErr
obj.cooldownCounter = obj.cooldownCounter - 1;
end
weights = abs(LMSUpdateObj.TapWeights);
% Take into account the neighboring taps as well
weights_padded = [0 weights 0];
weights_avg = (weights_padded(1:end-2) + 2*weights_padded(2:end-1) + weights_padded(3:end)) / 3;
weights_avg(~obj.internalFFETapsMask) = inf;
[~, minTapIndex] = min(weights_avg);
if obj.errCounter >= obj.errCollectionPeriod * LMSUpdateObj.WindowSize && ~obj.reachedHighErr
std = obj.runningMeanErr * sqrt(pi / 2);
%std = std * 1.05; % due to ISI, samples are not all iid, so std is within +-5% with 95% CI
possibleMaxErr = 4.75 * std; % trying to find COM over 1e6 symbols with 90% confidence => using 5std
statMinCOM = 20*log10(margin / possibleMaxErr);
if statMinCOM >= 3
% Stop the LMS adaptation of FFE and DFE taps
LMSUpdateObj.setLearningRates(0, 0, LMSUpdateObj.MuDlev);
obj.internalFFETapsMask(minTapIndex) = 0;
obj.lastDisabledTap = minTapIndex;
obj.lastUpdateTime = LMSUpdateObj.IterCount;
% cooldown for some LMS iterations so that other taps can
% adapt to the recently turned off tap and then start
% measuring the error distribution
obj.cooldownCounter = obj.cooldownPeriod * LMSUpdateObj.WindowSize;
else
obj.reachedHighErr = 1;
if obj.lastDisabledTap ~= -1
obj.internalFFETapsMask(obj.lastDisabledTap) = 1;
end
% to make sure it throws an error in case tried being accessed
obj.lastDisabledTap = -1;
end
obj.errCounter = 0;
obj.runningMeanErr = 0;
end
FFETapsMask = obj.internalFFETapsMask;
end
end
end
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