[Positioner] Measurement: variance in dBm
Along with the variance in mW, compute the variance of the dBm values.
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@ -108,7 +108,7 @@ void Measurement::merge(const Measurement &source)
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/**
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* - #ap is not deleted, only initialised to NULL.
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* - #ss_list is cleared.
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* - #average_dbm, #average_mw and #variance_mw are reset to 0.
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* - average and variance variables are reset to 0.
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*/
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void Measurement::clear()
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{
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@ -116,7 +116,9 @@ void Measurement::clear()
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average_dbm = 0 ;
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average_mw = 0 ;
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variance_mw = 0 ;
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variance_dbm = 0 ;
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variance_mw_m2 = 0 ;
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variance_dbm_m2 = 0 ;
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variance_size = 0 ;
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ap = NULL ;
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}
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@ -186,7 +188,9 @@ void Measurement::recalculate_average()
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average_dbm = 0 ;
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average_mw = 0 ;
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variance_mw = 0 ;
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variance_dbm = 0 ;
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variance_mw_m2 = 0 ;
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variance_dbm_m2 = 0 ;
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variance_size = 0 ;
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for (map<pkt_id_t, ss_t>::const_iterator
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@ -204,14 +208,19 @@ void Measurement::update_average(ss_t ss_dbm)
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float ss_mw = pow(10, static_cast<float>(ss_dbm) / 10.0) ;
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// Update the average:
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float delta = ss_mw - average_mw ;
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average_mw += delta / variance_size ;
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float delta_mw = ss_mw - average_mw ;
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average_mw += delta_mw / variance_size ;
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average_dbm = 10.0 * log10(average_mw) ;
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float delta_dbm = ss_dbm - average_dbm ;
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// Update the variance:
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variance_mw_m2 += delta * (ss_mw - average_mw) ;
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variance_mw_m2 += delta_mw * (ss_mw - average_mw) ;
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variance_dbm_m2 += delta_dbm * (ss_dbm - average_dbm) ;
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if (variance_size > 1)
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variance_mw = variance_mw_m2 / (variance_size - 1) ;
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{
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variance_mw = variance_mw_m2 / (variance_size - 1) ;
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variance_dbm = variance_dbm_m2 / (variance_size - 1) ;
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}
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}
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@ -229,7 +238,9 @@ Measurement& Measurement::operator=(const Measurement &m)
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average_dbm = m.average_dbm ;
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average_mw = m.average_mw ;
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variance_mw = m.variance_mw ;
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variance_dbm = m.variance_mw ;
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variance_mw_m2 = m.variance_mw_m2 ;
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variance_dbm_m2 = m.variance_mw_m2 ;
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variance_size = m.variance_size ;
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return *this ;
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@ -294,7 +305,13 @@ ostream &operator<<(ostream &os, const Measurement &m)
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os << static_cast<int_fast16_t>(i->second)
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<< '(' << i->first << ')' ;
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}
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os << " [AVG_dBm=" << m.average_dbm << ";AVG_mW=" << m.average_mw << ";VAR_mW=" << m.variance_mw << ";STD_mW=" << m.get_std_deviation_mw() << "]" ;
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os << " [AVG_dBm=" << m.average_dbm
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<< ";VAR_dBm=" << m.variance_dbm
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<< ";STD_dBm=" << m.get_std_deviation_dbm()
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<< ";AVG_mW=" << m.average_mw
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<< ";VAR_mW=" << m.variance_mw
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<< ";STD_mW=" << m.get_std_deviation_mw()
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<< "]" ;
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return os ;
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}
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@ -31,10 +31,14 @@ protected:
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float average_mw ;
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/// Variance of all the captured signal strengths (mW)
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float variance_mw ;
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/// Variance of all the captured signal strengths (dBm)
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float variance_dbm ;
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private:
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/// Intermediate variable used to compute the variance (mW)
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float variance_mw_m2 ;
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/// Intermediate variable used to compute the variance (dBm)
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float variance_dbm_m2 ;
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/// Number of elements taken into account in the variance computation
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unsigned int variance_size ;
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@ -56,14 +60,14 @@ protected:
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public:
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Measurement(const AccessPoint *_ap = NULL):
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ap(const_cast<AccessPoint*>(_ap)), average_dbm(0),
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average_mw(0), variance_mw(0), variance_mw_m2(0),
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variance_size(0) {}
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average_mw(0), variance_mw(0), variance_dbm(0),
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variance_mw_m2(0), variance_dbm_m2(0), variance_size(0) {}
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Measurement(const Measurement &source):
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ap(source.ap), ss_list(source.ss_list),
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average_dbm(source.average_dbm), average_mw(source.average_mw),
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variance_mw(source.variance_mw), variance_mw_m2(0),
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variance_size(0) {}
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variance_mw(source.variance_mw), variance_dbm(source.variance_dbm),
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variance_mw_m2(0), variance_dbm_m2(0), variance_size(0) {}
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~Measurement(void) ;
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@ -79,6 +83,8 @@ public:
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float get_variance_mw() const ;
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/// Returns the standard deviation of the SS list (mW)
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float get_std_deviation_mw() const ;
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/// Returns the standard deviation of the SS list (dBm)
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float get_std_deviation_dbm() const ;
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/// Returns the number of SS in the SS list
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int get_nb_ss() const ;
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//@}
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@ -158,6 +164,12 @@ inline float Measurement::get_std_deviation_mw() const
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}
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inline float Measurement::get_std_deviation_dbm() const
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{
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return sqrt(variance_dbm) ;
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}
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inline int Measurement::get_nb_ss() const
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{
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return ss_list.size() ;
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