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aligned to the datasheet rev5. the variable names were changed. some of 

the return values are added.
values are
master
Shoichi Sakane 2017-10-08 11:44:33 +09:00
parent 93213cb784
commit c8a2f3fa17
1 changed files with 56 additions and 38 deletions
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lorawan_toa.py
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@ -1,8 +1,8 @@
#!/usr/bin/env python #!/usr/bin/env python
# -*- coding: utf-8 -*- # -*- coding: utf-8 -*-
# 4.1.1.6. LoRaTM Packet Structure, SX1276/77/78/79 Datasheet # 4.1.1.6. LoRaTM Packet Structure, SX1276/77/78/79 Datasheet Rev.5 Aug 2016
# http://www.semtech.com/images/datasheet/sx1276_77_78_79.pdf # http://www.semtech.com/images/datasheet/sx1276.pdf
import math import math
@ -18,45 +18,57 @@ def mpsrange(a, b):
def get_toa(n_size, n_sf, n_bw=125, enable_dro=1, disable_h=0, n_cr=1, def get_toa(n_size, n_sf, n_bw=125, enable_dro=1, disable_h=0, n_cr=1,
n_preamble=8): n_preamble=8):
''' '''
return the time on air in milisecond. Parameters:
n_size: n_size:
PL in the fomula. PHY Payload size in byte (= MAC Payload + 5) PL in the fomula. PHY Payload size in byte (= MAC Payload + 5)
n_sf: SF (12 to 7) n_sf: SF (12 to 7)
n_bw: Bandwidth in kHz. default is 125 kHz for AS923. n_bw: Bandwidth in kHz. default is 125 kHz for AS923.
enable_dro: enable_dro:
DE in the fomula. DE in the fomula.
1 when the low data rate optimization is enabled. 1 when the low data rate optimization is enabled.
0 for disabled. 0 for disabled.
LoRaWAN always use the low data optimization. LoRaWAN always use the low data optimization.
disable_eh: disable_eh:
H in the fomula. IH in the fomula.
0 when the explicit header is enabled. 0 when the explicit header is enabled.
1 when no header is present. 1 when no header is present.
LoRaWAN always use the header. LoRaWAN always use the header.
n_cr: n_cr:
CR in the fomula, should be from 1 to 4. CR in the fomula, should be from 1 to 4.
Coding Rate = (n_cr/(n_cr+1)). Coding Rate = (n_cr/(n_cr+1)).
LoRaWAN takes alway 1. LoRaWAN takes alway 1.
n_preamble: n_preamble:
The preamble length in bit. The preamble length in bit.
default is 8 in AS923. default is 8 in AS923.
Return:
dict type contains below:
r_sym: symbol rate in *second*
t_sym: the time on air in millisecond*.
t_preamble:
v_ceil:
n_payload:
t_payload:
t_packet: the time on air in *milisecond*.
''' '''
t_sym = math.pow(2, n_sf) / (n_bw*1000.) * 1000. r_sym = (n_bw*1000.) / math.pow(2,n_sf)
t_sym = 1000. / r_sym
t_preamble = (n_preamble + 4.25) * t_sym t_preamble = (n_preamble + 4.25) * t_sym
a = 8.*n_size - 4.*n_sf + 28 + 16 - 20.*disable_h a = 8.*n_size - 4.*n_sf + 28 + 16 - 20.*disable_h
b = 4.*(n_sf-2.*enable_dro) b = 4.*(n_sf-2.*enable_dro)
v_ceil = a/b v_ceil = a/b
nb_sym_payload = 8 + max(math.ceil(a/b)*(n_cr+4), 0) n_payload = 8 + max(math.ceil(a/b)*(n_cr+4), 0)
t_payload = nb_sym_payload * t_sym t_payload = n_payload * t_sym
t_frame = t_preamble+ t_payload t_packet = t_preamble+ t_payload
ret = {} ret = {}
ret["r_sym"] = r_sym
ret["t_sym"] = t_sym ret["t_sym"] = t_sym
ret["n_preamble"] = n_preamble
ret["t_preamble"] = t_preamble ret["t_preamble"] = t_preamble
ret["v_ceil"] = v_ceil ret["v_ceil"] = v_ceil
ret["nb_sym_payload"] = nb_sym_payload ret["n_payload"] = n_payload
ret["t_payload"] = t_payload ret["t_payload"] = t_payload
ret["t_frame"] = round(t_frame, 3) ret["t_packet"] = round(t_packet, 3)
return ret return ret
@ -102,8 +114,6 @@ if __name__ == "__main__" :
opt = parse_args() opt = parse_args()
ret = get_toa(opt.n_size, opt.n_sf, n_bw=opt.n_bw, enable_dro=opt.v_de, ret = get_toa(opt.n_size, opt.n_sf, n_bw=opt.n_bw, enable_dro=opt.v_de,
disable_h=opt.v_h, n_cr=opt.n_cr, n_preamble=opt.n_preamble) disable_h=opt.v_h, n_cr=opt.n_cr, n_preamble=opt.n_preamble)
ret0 = get_toa(0, opt.n_sf, n_bw=opt.n_bw, enable_dro=opt.v_de,
disable_h=opt.v_h, n_cr=opt.n_cr, n_preamble=opt.n_preamble)
if opt.f_verbose: if opt.f_verbose:
print "PHY payload size : %d Bytes" % opt.n_size print "PHY payload size : %d Bytes" % opt.n_size
print "MAC payload size : %d Bytes" % (opt.n_size-5) print "MAC payload size : %d Bytes" % (opt.n_size-5)
@ -112,15 +122,23 @@ if __name__ == "__main__" :
print "Low data rate opt. : %s" % ("enable" if opt.v_de else "disable") print "Low data rate opt. : %s" % ("enable" if opt.v_de else "disable")
print "Explicit header : %s" % ("disable" if opt.v_h else "enable") print "Explicit header : %s" % ("disable" if opt.v_h else "enable")
print "CR (coding rate) : %d (4/%d)" % (opt.n_cr, 4+opt.n_cr) print "CR (coding rate) : %d (4/%d)" % (opt.n_cr, 4+opt.n_cr)
print "Symbol Rate : %.3f symbol/s" % ret["r_sym"]
print "Symbol Time : %.3f msec/symbol" % ret["t_sym"]
print "Preamble size : %d symbols" % opt.n_preamble print "Preamble size : %d symbols" % opt.n_preamble
print "Other symbol size : %d symbols" % ret["nb_sym_payload"] print "Packet symbol size : %d symbols" % ret["n_payload"]
print "Symbol Time : %.3f msec" % ret["t_sym"]
print "Preamble ToA : %.3f msec" % ret["t_preamble"] print "Preamble ToA : %.3f msec" % ret["t_preamble"]
print "Payload ToA : %.3f msec" % ret["t_payload"] print "Payload ToA : %.3f msec" % ret["t_payload"]
print "Time on Air : %.3f msec" % ret["t_frame"] print "Time on Air : %.3f msec" % ret["t_packet"]
if opt.debug_level: if opt.debug_level:
print "MAC frame data rate : %.3f bps" % ((8.*(opt.n_size-5)) / ret0 = get_toa(0, opt.n_sf, n_bw=opt.n_bw,
((ret["t_frame"]-ret0["t_frame"])/1000.)) enable_dro=opt.v_de, disable_h=opt.v_h,
n_cr=opt.n_cr, n_preamble=opt.n_preamble)
print "PHY PL=0 ToA : %.3f msec" % (ret0["t_packet"])
# preamble=8 cr=1? payload-len=7? crc=16 (payload) payload-crc=16
# =? 48 ==> 6 bytes ?
t0 = (ret["t_packet"]-ret0["t_packet"])/1000.
print "PHY fr.dr.(48b) 7:15: %.3f bps" % ((8.*opt.n_size+48)/t0)
print "MAC frame DR : %.3f bps" % ((8.*(opt.n_size)) /t0)
print "Ceil(x) : %.3f" % ret["v_ceil"] print "Ceil(x) : %.3f" % ret["v_ceil"]
else: else:
print "%.3f" % ret["t_frame"] print "%.3f" % ret["t_packet"]