338 lines
8.2 KiB
C++
338 lines
8.2 KiB
C++
/*
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* This file is part of the Owl Positioning System (OwlPS) project.
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* It is subject to the copyright notice and license terms in the
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* COPYRIGHT.t2t file found in the top-level directory of this
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* distribution and at
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* https://code.lm7.fr/mcy/owlps/src/master/COPYRIGHT.t2t
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* No part of the OwlPS Project, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms
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* contained in the COPYRIGHT.t2t file; the COPYRIGHT.t2t file must be
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* distributed along with this file, either separately or by replacing
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* this notice by the COPYRIGHT.t2t file's contents.
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*/
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#include "measurement.hh"
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#include "posexcept.hh"
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#include "configuration.hh"
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#include <iostream>
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#include <sstream>
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using namespace std ;
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/* *** Constructors *** */
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/**
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* Note that values pointed by #cp are not deleted.
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*/
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Measurement::~Measurement()
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{
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ss_list.clear() ;
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}
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/* *** Read accessors *** */
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/**
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* @returns The SS of the packet number `pkt_id.`
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* @returns 0 if the packet ID does not exist in the SS list.
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*/
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ss_t Measurement::get_ss(const pkt_id_t pkt_id) const
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{
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auto ss = ss_list.find(pkt_id) ;
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if (ss == ss_list.end())
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return 0 ;
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return ss->second ;
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}
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/* *** Write accessors *** */
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/**
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* @param packet_id The sequence number of the packet in the request,
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* as sent by the mobile.
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* @param ss_dbm The signal strength to add to #ss_list (in dBm).
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*/
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void Measurement::
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add_ss(const pkt_id_t packet_id, const ss_t ss_dbm)
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{
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// Add the new value (in dBm) along with the packet identifier:
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pair<pkt_id_t, ss_t> packet(make_pair(packet_id, ss_dbm)) ;
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if (! ss_list.insert(packet).second)
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{
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cerr
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<< "Cannot insert the packet (#" << packet_id << ", "
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<< static_cast<int_fast16_t>(ss_dbm) << " dBm)\n" ;
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return ;
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}
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// Update the average & variance with the new value:
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update_average(ss_dbm) ;
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}
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/**
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* Add an SS list to the current Measurement's SS list.
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* If the new SS list contains a packet with the same ID, the old one
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* is overwritten.
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*/
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void Measurement::
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add_ss_list(const map<pkt_id_t, ss_t> &_ss_list)
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{
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// We cannot use insert() here because we want to overwrite the
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// previous values with the same ID, if any.
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for (auto i = _ss_list.begin() ; i != _ss_list.end() ; ++i)
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ss_list[i->first] = i->second ;
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recalculate_average() ;
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}
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/**
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* Merge consists of adding the SS values of `source` to #ss_list. It
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* is possible only if the #cp of the two Measurement are identical.
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* Since add_ss_list() is used, if `source` contains packets with IDs
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* that already exist, the old ones will be overwritten.
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*
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* @throw cannot_merge if the CP of the two Measurement are different.
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*/
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void Measurement::merge(const Measurement &source)
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{
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if (cp != source.cp)
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throw cannot_merge(
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"error when trying to merge measurements, CPs are different") ;
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add_ss_list(source.ss_list) ;
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}
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/**
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* - #cp is not deleted, only initialised to nullptr.
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* - #ss_list is cleared.
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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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ss_list.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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cp = nullptr ;
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}
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/* *** Operations *** */
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/**
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* @returns The similarity score. A small number means an important
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* similarity, a big number means an important dissimilarity. The
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* scale of this score depends on the similarity method used (option
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* positioning.ss-similarity); the similarity scores are therefore
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* not comparable across the various methods.
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*/
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float Measurement::similarity(const Measurement &source) const
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{
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assert(! ss_list.empty()) ;
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assert(! source.ss_list.empty()) ;
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string algorithm(
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Configuration::string_value("positioning.ss-similarity")) ;
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if (algorithm == "mean")
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return ss_square_distance(source) ;
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if (algorithm == "interval")
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{
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unsigned int nb = nb_in_interval(source, get_std_deviation_mw()) ;
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if (nb != 0)
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return 1 / nb ;
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return 2 ;
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}
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/* Note: this score ranges from 0 (excluded) to 1 if at least one
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* packet was found within the interval. It is equals to 2 if no
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* packet was found in the interval. */
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if (algorithm == "interval2")
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{
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float std_dev = get_std_deviation_mw() ;
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unsigned int interval1 = nb_in_interval(source, 0.674 * std_dev) ;
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unsigned int interval2 = nb_in_interval(source, std_dev) ;
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/* Explanation: with a normal distribution, we normally have:
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* - 68% of the values within the interval
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* [mean-std.dev.;mean+std.dev.], and
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* - 50% of the value within the interval
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* [mean-.674*std.dev.;mean+.674*std.dev.] */
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float percent1 = interval1 * 100 / source.get_nb_ss() ;
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float percent2 = interval2 * 100 / source.get_nb_ss() ;
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return (percent1 - 50) * (percent1 - 50) +
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(percent2 - 68) * (percent2 - 68) ;
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/* Note: this distance (score) ranges from 0 (with
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* percent1==50 and percent2==68) to 7124 (with percent1
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* and percent2==0). */
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}
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throw bad_configuration(
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"Bad SS similarity algorithm name \""+ algorithm +"\"!") ;
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}
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unsigned int Measurement::
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nb_in_interval(const Measurement &source, const float bound) const
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{
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unsigned int nb_values = 0 ;
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for (auto ss = source.ss_list.begin() ; ss != source.ss_list.end() ;
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++ss)
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if (PosUtil::is_in_interval(average_dbm, bound, ss->second))
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++nb_values ;
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return nb_values ;
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}
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void Measurement::recalculate_average()
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{
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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 (auto i = ss_list.begin() ; i != ss_list.end() ; ++i)
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update_average(i->second) ;
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}
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void Measurement::update_average(const ss_t ss_dbm)
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{
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++variance_size ;
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assert(variance_size <= ss_list.size()) ;
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// Convert the new SS in mW:
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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_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_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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{
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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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/* *** Operators *** */
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Measurement& Measurement::operator=(const Measurement &m)
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{
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if (this == &m)
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return *this ;
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cp = m.cp ;
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ss_list = m.ss_list ;
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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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}
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bool Measurement::operator==(const Measurement &m) const
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{
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if (this == &m)
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return true ;
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return
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cp == m.cp &&
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ss_list == m.ss_list ;
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}
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const string Measurement::to_csv() const
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{
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ostringstream csv_line ;
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if (ss_list.empty())
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return "" ;
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string mac_cp("") ;
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if (cp)
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mac_cp = cp->get_mac_addr() ;
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for (auto i = ss_list.begin() ; i != ss_list.end() ; ++i)
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{
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if (i != ss_list.begin())
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csv_line << ';' ;
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csv_line
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<< mac_cp << ';'
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<< i->first << ';'
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<< static_cast<int_fast16_t>(i->second) ;
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}
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return csv_line.str() ;
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}
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ostream &operator<<(ostream &os, const Measurement &m)
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{
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// MAC address
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os
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<< "CP: " << (m.cp ? m.cp->get_mac_addr() : "Unknown_CP")
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<< ": " ;
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// List of SS
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if (m.ss_list.empty())
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os << "No values" ;
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else
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for (auto i = m.ss_list.begin() ; i != m.ss_list.end() ; ++i)
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{
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if (i != m.ss_list.begin())
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os << ';' ;
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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
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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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