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BladeRF x115 / YateBTS / Noise

Posted: Fri Apr 10, 2015 4:46 am
by dodolah
Hello,

Could you please help me (or point me to the appropriate tools) to reduce the "noise" on the board... What is the best tool(s) to (re)calibrate the board.

Serial #: 13d7b32e83118203e3e6db0b04de23bf
VCTCXO DAC calibration: 0x91b1
FPGA size: 115 KLE
FPGA loaded: yes
USB bus: 4
USB address: 2
USB speed: SuperSpeed
Backend: libusb
Instance: 0

bladeRF> version

bladeRF-cli version: 1.1.2-git-0295340
libbladeRF version: 1.2.1-git-0295340

Firmware version: 1.8.0
FPGA version: 0.1.2




I run some tests using yatebts and the connection was very unstable...

===================================

mbts noise
noise RSSI is -13 dB wrt full scale
MS RSSI target is -50 dB wrt full scale

mbts rxgain
current RX gain is 0 dB


===================================

-13db is the minimum reachable on the board.

I tried to calibrate the board with "kalibrate-bladeRF", and it looks even worse.

./src/kal -s GSM850 -m4

Actual filter bandwidth = 1500 kHz
rxvga1 = 20 dB
rxvga2 = 30 dB
kal: Scanning for GSM-850 base stations.
GSM-850:
chan: 128 (869.2MHz - 1.362kHz) power: 35627.82
chan: 129 (869.4MHz - 1.349kHz) power: 37119.38
chan: 130 (869.6MHz - 1.382kHz) power: 37840.33

./src/kal -v -c 128
Found lowest offset of 264.594208Hz at 869.200000MHz (0.304411 ppm) using DAC trim 0x8fff

=====

Thank you,

Re: BladeRF x115 / YateBTS / Noise

Posted: Sat Apr 18, 2015 12:52 am
by andrew77
Hello,
when you execute mbts noise and the result is:
noise RSSI is -13 dB wrt full scale
MS RSSI target is -50 dB wrt full scale

in my own experience it is because of the one of following things:
RX antenna not matched (not taylored for the band in use)
TX antenna too colse from the RXantenna
mbts rxgain set >0

I got the same your results in these cases,
but if you tray with a dummy load (50 ohm) on both RX and TX ports you get around -46 dB of noise RSSI (tray to set mbts rxgain =0)
for a well matched antenna I got around -30 dB of noise

Re: BladeRF x115 / YateBTS / Noise

Posted: Thu Nov 19, 2020 6:13 am
by avalori
Thanks for your post.
First of all it helped me to determine that a noise of -35 dB is not unusual on a bladeRF (although I have the x40 not the x115).
However, I am extremely puzzled by the stuff below bold for the main points.
I tried to run the noise command with rxgain as 75 and then after changing rxgain to 0.
What is puzzling is that the noise seems basically the same (-35 vs -34 dB).
Any ideas/suggestions?
Additionally, seems way higher than the recommended value by Yate ("Normal UL noise level is -64 or lower").
Indeed, I mange to have reasonable voice and SMS but horrible if any GPRS...

Many thanks in advance.


-----------------------------------------------------------------------------
mbts rawconfig rxgain 75
defined new config rxgain as "75"
mbts noise
noise RSSI is -35 dB wrt full scale
NOTE: Excessive UL noise will degrade performance. Normal UL noise level is -64 or lower.
MS GSM RSSI target is -50 dB wrt full scale
NOTE: GSM UL RSSI margin -15 too low for this noise level. Should raise GSM.Radio.RSSITarget to -27 dB or higher.
MS GPRS RSSI target is -25 dB wrt full scale
NOTE: GPRS UL RSSI margin 10 too low for this noise level. Should raise GPRS.MS.Power.RSSITarget to -21 dB or higher.
mbts rawconfig rxgain 0
rxgain changed from "75" to "0"
mbts noise
noise RSSI is -34 dB wrt full scale
NOTE: Excessive UL noise will degrade performance. Normal UL noise level is -64 or lower.
MS GSM RSSI target is -50 dB wrt full scale
NOTE: GSM UL RSSI margin -16 too low for this noise level. Should raise GSM.Radio.RSSITarget to -26 dB or higher.
MS GPRS RSSI target is -25 dB wrt full scale
NOTE: GPRS UL RSSI margin 9 too low for this noise level. Should raise GPRS.MS.Power.RSSITarget to -20 dB or higher.