sdr
/
gr-gsm
8
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

apps/grgsm_trx: add baseband frequency shift feature 

An ability to shift the baseband frequency would allow one to
run both base stations and (OsmocomBB-based) mobile stations on
any frequency (e.g. in 2.4 GHz WiFi band)!

This is achieved by adding a given frequency offset to the
result of "ARFCN -> RX/TX frequency" calculation.

Usage example:

  grgsm_trx --freq-offset -500M

Both RX (Downlink) and TX (Uplink) frequencies will be shifted
by 500 MHz back, e.g. tuning request to ARFCN 105 would result
in tuning the radio to 456.0 MHz (instead of 956.0 MHz).

Related: OS#3520 (https://osmocom.org/versions/136)
Change-Id: I42e397e47402a87f4141ef31b25eff4c8c1267e2
This commit is contained in:
Vadim Yanitskiy 2018-08-10 05:29:23 +07:00
parent 840885fe3c
commit 97dc84e9f3
2 changed files with 26 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
apps/grgsm_trx
View File

@ -25,6 +25,8 @@ import signal
import getopt
import sys
from gnuradio import eng_notation
from grgsm.trx import ctrl_if_bb
from grgsm.trx import radio_if
from grgsm.trx import fake_pm
@ -45,6 +47,7 @@ class Application:
# PHY specific
phy_sample_rate = 4 * 1625000 / 6
phy_freq_offset_hz = None
phy_tx_antenna = "TX/RX"
phy_rx_antenna = "RX2"
phy_rx_gain = 30
@ -67,6 +70,10 @@ class Application:
self.bind_addr, self.remote_addr,
self.base_port)
# Optional frequency offset
if self.phy_freq_offset_hz is not None:
self.radio.freq_offset_hz = self.phy_freq_offset_hz
# Power measurement emulation
# Noise: -120 .. -105
# BTS: -75 .. -50
@ -110,6 +117,7 @@ class Application:
" -G --tx-gain Set TX gain (default %d)\n" \
" --rx-antenna Set RX antenna (default %s)\n" \
" --tx-antenna Set TX antenna (default %s)\n" \
" --freq-offset Shift baseband freq. (e.g. -500M)\n" \
" --ppm Set frequency correction (default %d)\n"
print(s % (
@ -128,7 +136,7 @@ class Application:
"i:b:p:a:s:g:G:h",
["help", "remote-addr=", "bind-addr=", "base-port=",
"device-args=", "sample-rate=", "rx-gain=", "tx-gain=",
"ppm=", "rx-antenna=", "tx-antenna="])
"ppm=", "rx-antenna=", "tx-antenna=", "freq-offset="])
except getopt.GetoptError as err:
# Print(help and exit)
self.print_help()
@ -167,6 +175,10 @@ class Application:
self.phy_tx_antenna = v
elif o in ("--ppm"):
self.phy_ppm = int(v)
elif o in ("--freq-offset"):
# Convert /\d+(\.\d+)?(M|k)?/ to Hz
offset_hz = eng_notation.str_to_num(v)
self.phy_freq_offset_hz = offset_hz
def sig_handler(self, signum, frame):
print("Signal %d received" % signum)

14
python/trx/radio_if.py
View File

@ -4,7 +4,7 @@
# GR-GSM based transceiver
# Follow graph implementation
#
# (C) 2016-2017 by Vadim Yanitskiy <axilirator@gmail.com>
# (C) 2016-2018 by Vadim Yanitskiy <axilirator@gmail.com>
# (C) 2017 by Piotr Krysik <ptrkrysik@gmail.com>
#
# All Rights Reserved
@ -29,6 +29,7 @@ import grgsm
from math import pi
from gnuradio import eng_notation
from gnuradio import digital
from gnuradio import blocks
from gnuradio import uhd
@ -59,6 +60,7 @@ class dict_toggle_sign(gr.basic_block):
class radio_if(gr.top_block):
# PHY specific variables
freq_offset_hz = None
rx_freq = 935e6
tx_freq = 890e6
osr = 4
@ -274,11 +276,21 @@ class radio_if(gr.top_block):
return self.ppm / 1.0e6 * 2 * pi * fc / self.sample_rate
def set_rx_freq(self, fc):
if self.freq_offset_hz is not None:
fc += self.freq_offset_hz
print("[#] Shifting RX freq. to %s (offset is %s)"
% (eng_notation.num_to_str(fc),
eng_notation.num_to_str(self.freq_offset_hz)))
self.phy_src.set_center_freq(fc, 0)
self.rotator_src.set_phase_inc(self.calc_phase_inc(fc))
self.rx_freq = fc
def set_tx_freq(self, fc):
if self.freq_offset_hz is not None:
fc += self.freq_offset_hz
print("[#] Shifting TX freq. to %s (offset is %s)"
% (eng_notation.num_to_str(fc),
eng_notation.num_to_str(self.freq_offset_hz)))
self.phy_sink.set_center_freq(fc, 0)
self.rotator_sink.set_phase_inc(-self.calc_phase_inc(fc))
self.tx_freq = fc