1. Esteban L. Vallés The Aerospace Corporation El Segundo, CA
Future HRIT/EMWIN Concerns HRIT/EMWIN Receiver User Equipment RF Compatibility
Esteban L. Vallés The Aerospace Corporation El Segundo, CA
April 30th , 2015

2. User Equipment Performance with Latest Frequency Allocations
The Aerospace Corporation has developed throughout the years prototype user equipment for receiving HRIT/LRIT/EMWIN signals
EMWIN: Emergency Managers Weather Information Network
LRIT:  Low-Rate Information Transmission System
HRIT:  High-Rate Information Transmission System
In this presentation we present some results on the impact of frequency adjacent signals on our receivers
A frequency band immediately adjacent to HRIT/EMWIN has been auctioned to be used for Mobile data
This band has only been auctioned for Mobile usage (for now) in the United States
It is very hard to predict how many mobile users will be present in this band and their physical proximity to an HRIT/EMWIN receiver
What we can predict is that the reliability of our receiver will be compromised

3. GOES-R Frequency Plan DOWNLINKS
(RAW DATA DOWNLINK NOT SHOWN)
(OQPSK, Linear Pol (N-S or E-W), 8220 MHz, BW=120 MHz)
Housekeeping
Telemetry
BPSK/RHC
MHz
BW=80 kHz
DCPR
8PSK/FDM
Linear Pol to
MHz
BW=0.7 MHz
GRB
Dual CP
MHz
8PSK
BW=9.8 MHz
or QPSK
BW=10.9 MHz
ORTT&C
Telem & Rng
BPSK/PM
RHC Pol
MHz
BW=4.93 MHz
DCPC
QPSK/DSSS
RHC
MHz
MHz
BW=95 kHz
HRIT/EMWIN
BPSK/Lin Pol
MHz
BW=1.205 MHz
SAR
Bi-Φ/FDM/RHC
MHz
BW=90 kHz
Radiosondes
MHz
1675 to
1695 to 1710 MHz
is proposed for
internet mobile radio
470
1545
1670
1675
1680
1685
1690
1695
1700
2210
UPLINKS
DCPC
QPSK/DSSS
RHC Pol
MHz
MHz
BW=95 kHz
Command
BPSK/RHC
MHz
BW=128 kHz
GRB
Dual Lin Pol
7216.6MHz
8PSK
BW=9.8 MHz
or QPSK
BW=10.9 MHz
DCPR
8PSK/FDM(†)
RHC Pol
401.7 MHz to
402.4 MHz
BW=0.7 MHz
SAR
Bi-Φ/FDM(†)
Linear/RHC
MHz
BW=90 kHz
HRIT/EMWIN
BPSK/RHC
MHz
BW=1.205 MHz
ORTT&C Cmd
and Ranging
BPSK/PM/RHC
MHz
BW=1.45 MHz
400
405
2025
2030
2035
7210
7215
7220
7225
NOTES
†: DCPR (8PSK) and SAR (Bi-Φ) are individual uplinks FDM'ed in the spacecraft transponder.
: Indicates possible extra GRB bandwidth for QPSK modulation
GRfreqPlan1July2011.pptx
Peter Woolner 7/01/11

4. HRIT / LRIT / EMWIN Spectrum
The center frequency of the HRIT/EMWIN signal is MHz
It occupies a band with frequencies up to ~
Spectrum has been auctioned in bands of 5 MHz, starting at 1695 to 1710 MHz.
This implies that the guard band between both signals is less than 500 kHz
Mobile telephony already occupies bands from MHz
What is the impact of a 15 MHz-wide LTE uplink band on HRIT/EMWIN users ?
We will show some results using LRIT/EMWIN rates and bandwidths
HRIT results were not cleared for outside release in time

5. Receiver Hardware Overview
Low Noise L-band downconverter was designed at DCID is an alternative to Quorum’s LNB
The parts cost for this LNB is less than ¼ of the current commercial solution by Quorum
Downconverted, Amplified Signal
Digitizer Options:
USRP1, USRP2
OSMO SDR
Aerospace AID
Blade RF
Operating Systems:

6. HRIT/EMWIN Software Defined Radio (SDR)
System is platform agnostic: runs on any PC with a USB port (Windows, Linux, iOS) that loads the Linux OS on a thumb drive
Developer Mode
User can customize and modify software radio blocks
User Mode
User uses predefined setup to receive HRIT/EMWIN signals  Default
Completely Free Software
SDR runs on Linux  free Operating system
Software Radio is based on the open source GNURadio
SDR Plugin: We’ve created a USB drive that any user can plug into a PC regardless of the operating system in their hard drive

7. RF Compatibility Work

8. L-Band Test Schematic
A 5 MHz wide, LTE-shaped signal, located between 1695 and 1700 MHz
Eb/N0 level is set by the signal generator at the input to the LRIT/EMWIN system

9. IF-Band Test Schematic
A 5 MHz wide, LTE-shaped signal, located between and MHz
Eb/N0 level is set by the signal generator at the input to the LRIT/EMWIN system

10. Software Radio Setup
The interference test were performed comparing the performance of uncoded BPSK with and without an LTE interferer on an adjacent band
BER at this point was chosen because it’s the first point in the receiver where a performance metric is available to the user

11. BER Test Result – No Interference Present
Digitizer + SDR Implementation BER 1E-5: ~0.15 dB
LNB +Digitizer + SDR Implementation BER 1E-5: ~0.7 dB

12. Spectrum: Signal + Interference
Image shows the mixed-down spectrum to IF
LRIT signal is mixed from MHz to MHz
LTE signal is mixed from MHz to 144 MHz
3.4 MHz
600 kHz

13. LRIT Results: Interference to Signal Ratio (I/S)
The plot shows that the maximum I/S that the LRIT receiver can tolerate under these testing conditions is I/S < 24 dB
It is likely that at HRIT rates, the tolerable I/S would be smaller, since the guard band will be narrower

14. How far away do we need to be to avoid interference?
+30 dBm Maximum Mobile User Terminal Power = I
Interference Signal needs to drop 130 dB so that I/S=24 dB at the HRIT Antenna surface
130 dB
Math Review: Factor of 2 times 10*log10(2)= 3 dB
1.E *log10(1E10)=100 dB
1.E *log10(1E13)=130 dB
154 dB
+24 dB Tolerable I/S
-124 dBm HRIT Earth Signal Power = S

15. How far away do we need to be to avoid interference?
It’s a very hard question since it depends on the propagation model and our Tx/Rx assumptions
Sample Case #1
INTERFERENCE
Center Frequency
MHz
LRIT / HRIT Earth Signal Power
-124
dBm
I/S [dB] Threshold 24 dB
Tx Power of LTE Signal at Source 30
dBW
I/S [dB] at LTE Tx Antenna
154
LTE Loss to Avoid Interference on NOAA
130
Fixed Parameters
Light Speed
3.00E+08
m/s
Wavelength m
Fading Power
2.0
Terrain Variables
Unit
Mobile Antenna Height
1.5
[m]
Interference Antenna Height
Okumura-Hata Fading Model
a(H_mobile, Freq.) Low
Equivalent Fading Coeff.
3.009
Loss using Okumura-Hata
129.80
distance (Tx,Rx)
0.29 km
290
Free Space Fading Model for O-H Loss
43.45
43451
Under these assumptions
Urban Fading model > 300 meters
Line of Sight
46 km
This is not a typo 

16. Conclusions
For the power levels that are within the dynamic range of the digitizer, the presence of adjacent interference significantly affected our receiver for I/S levels above 24 dB
For HRIT rates (HRIT signal is wider) the I/S threshold will be even lower (HRIT can tolerate less interference due to its proximity)
The results of the current test combine the effects on the RF front end and on the IF digitizer due to adjacent interference
These results are a simple example that simply want to illustrate that there will be issues with HRIT/EMWIN. How serious the impact is depends on many factors that can be hard to predict
User equipment, Number of interferers and their distribution
Things as 3rd order intermods can also be a factor
Users can add front end filters to filter out noise, but the frequency guard band is so small that it’s really hard to have effective, sharp, small filters that can help
Reliability will be compromised.
How effective is a an unreliable emergency weather system ?

17. Questions ?

18. Aerospace El Segundo GOES-R Team
Esteban Valles (Lead, Software)
Alan Choy (Hardware, RF)
Jared Dulmage (Software,RF)
Summer Interns: Software, Testing

19. Same user Interface handles all hardware options

20. Current Implementations of the HRIT/EMWIN End User Receivers
Legacy Receivers
AeroReceiver

21. Theoretical BPSK BER Performance
We tested uncoded BPSK at an energy per bit over noise density ratio Eb/N0 of about 7 dB at the input to the software radio.
The Eb/N0 levels at the input of the receiver will set the bit and frame error rates (BER /FER) at the output of the receiver
* NOTE: HRIT IRD 417-R-IRD-0168 Eb/No requirement is 4.6 dB when Convolutional + RS coding is used. However, at the Eb/No the number of uncoded bits was too high

22. Test #1: Determine Minimum Signal Power Needed
SKIP
Determine the minimum signal strength that the system can handle before degrading its performance
Adjacent Interference: OFF
Eb/N0= Fixed at 7 dB
Conclusion:
If the signal strength is below – 60 dBm then there may be some performance degradation due to insufficient input power

23. Test #2: BER Test Description
Goal:
Measure the implementation loss for receiving uncoded BPSK without any interference present and compare it to theory
Procedure
Step 1: Disconnect the LNB and do the experiment in IF. Quantify the digitizer’s and software radio implementation loss
Step 2: Repeat the experiment injecting the signal at L-band with the LNB to quantify the total implementation loss of the receiver
Signal:
Load noiseless RAW CCSDS formatted data into a vector signal generator
Modulate this data using the LRIT waveform
Center Signal Frequency: MHz (IF) (L-Band)
Bit Rate: 293,883 ksps  LRIT data rate
Signal Power: Between -38 and -28 dBm
Noise Bandwidth= 40 MHz (this will be filtered by the front end filter in the digitizer)
Interference: Disabled

24. How far away do we need to be to avoid interference?
It’s a very hard questions since it depends on the propagation model and our Tx/Rx assumptions
Sample Case #2
INTERFERENCE
Center Frequency
MHz
LRIT / HRIT Earth Signal Power
-124
dBm
I/S [dB] Threshold 24 dB
Tx Power of LTE Signal at Source 30
dBW
I/S [dB] at LTE Tx Antenna
154
LTE Loss to Avoid Interference on NOAA
130
Fixed Parameters
Light Speed
3.00E+08
m/s
Wavelength m
Fading Power
2.0
Terrain Variables
Unit
Mobile Antenna Height
1.5
[m]
Interference Antenna Height 33
Okumura-Hata Fading Model
a(H_mobile, Freq.) Low
Equivalent Fading Coeff.
2.749
Loss using Okumura-Hata
128.25
distance (Tx,Rx)
0.651 km
651
Free Space Fading Model for O-H Loss
36.35
36350