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# pathloss-func.py
# (C) 2016 by Harald Welte <laforge@gnumonks.org>
# All Rights Reserved
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
from Gnumeric import GnumericError, GnumericErrorVALUE
import Gnumeric
import string
import math
def lambda_by_mhz(freq_mhz):
return 300/freq_mhz
def func_fsl(freq_mhz, dist_m):
'@FUNCTION=PATHLOSS_FREESPACE\n'\
'@SYNTAX=pathloss_freespace(freq_mhz, dist_m)\n'\
'@DESCRIPTION=Compute Free Space Path Loss (in dB)\n'\
'@SEEALSO=pathloss_egli,pathloss_hata\n'
wavelen = lambda_by_mhz(freq_mhz)
return -20 * math.log10(wavelen / (4*3.1416*dist_m))
def func_fsl_inverse(freq_mhz, path_loss):
'@FUNCTION=RF_RANGE_FREESPACE\n'\
'@SYNTAX=rf_range_freespace(freq_mhz, path_loss_db)\n'\
'@DESCRIPTION=Compute Signal Range (in m) as per Free Space Loss Model\n'\
'@SEEALSO=pathloss_freespace,rf_range_egli,rf_range_hata\n'
wavelen = lambda_by_mhz(freq_mhz)
dist_m = (wavelen/10**(path_loss/-20)) / (4*3.1416)
return dist_m
def hata_ch(envi, freq_mhz, rx_ant_m):
logfreq = math.log10(freq_mhz)
ch = 0
if envi == 'city_small' or envi == 'city_medium':
ch = 0.8 + (1.1 * logfreq - 0.7)*rx_ant_m - (1.56 * logfreq)
elif envi == 'city_large':
if freq_mhz < 200:
ch = 8.29 * math.pow(math.log10(1.54*rx_ant_m), 2) - 1.1
elif freq_mhz > 200:
ch = 3.2 * math.pow(math.log10(11.75*rx_ant_m), 2) - 4.97
return ch
def hata_cm(envi, freq_mhz):
logfreq = math.log10(freq_mhz)
att = 0
if freq_mhz <= 1500:
if envi == 'open_area' or envi == 'rural':
# https://en.wikipedia.org/wiki/Hata_model_for_open_areas
att = -4.78 * math.pow(logfreq, 2) + 18.33 * logfreq - 40.94
elif envi == 'suburban':
# https://en.wikipedia.org/wiki/Hata_model_for_suburban_areas
att = -2 * math.pow(logfreq/28, 2) - 5.4
else:
if envi == 'city_large':
att = 3
else:
att = 0
return att
def hata_c0(freq_mhz):
# http://morse.colorado.edu/~tlen5510/text/classwebch3.html
if freq_mhz <= 1500:
c0 = 69.55
else:
c0 = 46.3
return c0
def hata_cf(freq_mhz):
# http://morse.colorado.edu/~tlen5510/text/classwebch3.html
if freq_mhz <= 1500:
cf = 26.16
else:
cf = 33.9
return cf
def func_hata(envi, freq_mhz, dist_m, bts_ant_m, ms_ant_m):
'@FUNCTION=PATHLOSS_HATA\n'\
'@SYNTAX=pathloss_hata(environment, freq_mhz, dist_m, bts_ant_m, ms_ant_m)\n'\
'@DESCRIPTION=Compute Path Loss (in dB) as per Hata Model\n'\
'@SEEALSO=pathloss_freespace,pathloss_hata\n'
# FIXME: valid for 150MHz - 2GHz, MS 1-10m, BS 30-200m, dist # 1-10km
environs = ('open_area', 'rural', 'suburban', 'city_small',
'city_medium', 'city_large')
if not envi in environs:
raise GnumericError,GnumericErrorVALUE
# https://en.wikipedia.org/wiki/Hata_model_for_urban_areas
hata = hata_c0(freq_mhz) + hata_cf(freq_mhz) * math.log10(freq_mhz)
hata -= 13.82 * math.log10(bts_ant_m)
hata -= hata_ch(envi, freq_mhz, ms_ant_m)
hata += (44.9 - 6.55 * math.log10(bts_ant_m)) * math.log10(dist_m/1000)
# subtract correction for open_area / suburban
hata += hata_cm(envi, freq_mhz)
return hata
def func_hata_inverse(envi, freq_mhz, path_loss, bts_ant_m, ms_ant_m):
'@FUNCTION=RF_RANGE_HATA\n'\
'@SYNTAX=rf_range_hata(environment, freq_mhz, path_loss_db, bts_ant_m, ms_ant_m)\n'\
'@DESCRIPTION=Compute Signal Range (in m) as per Hata Model\n'\
'@SEEALSO=pathloss_hata,rf_range_freespace,rF_range_egli\n'
l = hata_c0(freq_mhz) + hata_cf(freq_mhz) * math.log10(freq_mhz)
l -= 13.82 * math.log10(bts_ant_m)
l -= hata_ch(envi, freq_mhz, ms_ant_m)
l += hata_cm(envi, freq_mhz)
# subtract all non-distance related losses from path loss,
# remainder is the only term depending on distance
r = path_loss - l
mult = (44.9 - 6.55 * math.log10(bts_ant_m))
att_dist = r / mult
# now we just need the inverse of log10
dist_km = 10 ** att_dist
return dist_km * 1000
def func_egli(freq_mhz, dist_m, tx_ant_m, rx_ant_m):
'@FUNCTION=PATHLOSS_EGLI\n'\
'@SYNTAX=pathloss_egli(freq_mhz, dist_m, tx_ant_m, rx_ant_m)\n'\
'@DESCRIPTION=Compute Path Loss (in dB) as per Egli Model\n'\
'@SEEALSO=pathloss_freespace,pathloss_hata\n'
# https://en.wikipedia.org/wiki/Egli_model
att = -20 * math.log10(rx_ant_m*tx_ant_m / (dist_m*dist_m))
att += 20 * math.log10(freq_mhz/40)
return att
def func_egli_inverse(freq_mhz, path_loss, bts_ant_m, ms_ant_m):
'@FUNCTION=RF_RANGE_EGLI\n'\
'@SYNTAX=rf_range_egli(freq_mhz, path_loss_db, bts_ant_m, ms_ant_m)\n'\
'@DESCRIPTION=Compute Signal Range (in m) as per Egli Model\n'\
'@SEEALSO=pathloss_egli,rf_range_freespace,rf_range_hata\n'
l = 20 * math.log10(freq_mhz/40)
r = path_loss - l
x = ms_ant_m*bts_ant_m
dist_m = math.sqrt(x/(10**(r/-20)))
return dist_m
pathlossfunc_functions = {
'pathloss_freespace': ('ff', 'freq_mhz, dist_m', func_fsl),
'rf_range_freespace': ('ff', 'freq_mhz, path_loss', func_fsl_inverse),
'pathloss_egli': ('ffff', 'freq_mhz, dist_m, tx_ant_m, rx_ant_m', func_egli),
'rf_range_egli': ('ffff', 'freq_mhz, path_loss_db, bts_ant_m, ms_ant_m', func_egli_inverse),
'pathloss_hata': ('sffff', 'environ, freq_mhz, dist_m, bts_ant_m, ms_ant_m', func_hata),
'rf_range_hata': ('sffff', 'environ, freq_mhz, path_loss_db, bts_ant_m, ms_ant_m', func_hata_inverse),
}
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