Mitigating interferences on LEO satellite downlinks of Earth exploration services by cognitive radio, adaptive modulation and coding techniques

ARAUJO, RODOLFO ANTONIO DA SILVA; SILVA, LUCIANO B.C. DA; SANTOS, WALTER ABRAHÃO DOS; SOUZA, MARCELO L. DE OLIVEIRA E

doi:10.1590/0001-3765202420230487

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ENGINEERING SCIENCES • An. Acad. Bras. Ciênc. 96 (suppl 1) • 2024 • https://doi.org/10.1590/0001-3765202420230487 linkcopy

Mitigating interferences on LEO satellite downlinks of Earth exploration services by cognitive radio, adaptive modulation and coding techniques

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Upcoming Earth Exploration Satellite Services (EESS) missions, especially to monitor Brazilian diversified biomes, will require progressively higher data rates for downlink transmissions, besides the ability to share its frequency spectrum with cellular base stations. Both impact issues on spectral efficiency (in bps/Hz) and coexistence in frequency, time, location, etc. This paper proposes a technique suitable for LEO Earth Observation Satellites (EOS) by combining two strategies. We initially present the Cognitive Radio (CR) spectrum awareness and exploitation approaches to propose techniques for improving their uses. Next, we detail the Adaptive MODulation and CODing (MODCOD) techniques (ACM) based on DVB-S2X systems to increase RF power and spectral efficiencies. Finally, we evaluate our solution by monitoring the Signal to Interference plus Noise Ratio (SINR) and combining CR/MODCOD techniques. Two case studies are presented that demonstrate the proposed approach on Brazilian satellites developed by the National Institute for Space Research (INPE). A real in-situ characterization of the interfering scenarios was performed during the passes of the two EESS satellites that proves the effectiveness of spectral efficiency and coexistence.

Key words Cognitive radio; Earth Exploration Satellite Services; high throughput satellites; modulation and coding; spectrum efficiency; spectral coexistence

Frequency band MHz	Service	Limit in dB(W/m2) for angle of arrival (𝛿) above the horizontal plane			Reference Bandwidth
8025-8500	Earth Exploration	0 - 5°	5° - 25°	25° - 90°	4 kHz
8025-8500	Satellite	-150	-150+.5(𝛿-5)	-140	4 kHz

CBERS-4 – WFI FM as-built link budget 𝜃 = 62,5°, Plane 𝜙 = 0°, Freq = 8.29 GHz
MWT ANTENNA		Satellite	Receive Site
E/S LOCATION			Cuiabá
LONGITUDE (+)W (-)E	deg		56,0
LATITUDE (+)N (-)S	deg		-17,7
SATELLITE LOCATION
HEIGHT	Km	778
TRANSPONDER
TX EIRP	dBW	14,5
ANTENNA GAIN	dBi	4,50
TX OUTPUT POWER	dBW	10,0
CABLE LOSSES	dB	0,0
MODULATION
MODULATION		QPSK
INFORMATION RATE	Mbps	51,28
CODE EFFICIENCY	bps/Hz	1,0
SIGNAL BANDWIDTH	MHz	,28
PROPAGATION
DOWNLINK FREQUENCY	MHz	8290,00
CLEAR SKY DOWNLINK LOSS	dB	,34
LOSSES
ATMOSPHERIC / RAIN LOSSES	dB	1,80
EARTH STATION:(E/S)
RECEIVER G/T	dB/K	34,5
POLARIZATION LOSS	dB	0,5
ANTENNA POINTING LOSS	dB	0,5
DOWNLINK BUDGET
EIRP	dBW	,5
LOSSES	dB	-182,14
G/T EARTH STATION	dB/K	,5
BOLTZMANNS CONSTANT	dBJ/K	,6
Received C/No (DOWN)	dBHz	,46
OVERALL LINK BUDGET
Received C/No (DOWN)	dBHz	,5
Received Eb/No - loss	dB	,4
Received Eb/No	dB	,4
IMPLEMENTATION LOSSES	dB	,0
DEMODULATION LOSSES	dB	,0
OTHER LOSSES	dB	,0
DESIRED Eb/No (BER= 1e-6)	dB	,5
INITIAL MARGIN	dB	,9
C/I	dB	,4
Eb/I0	dB	,4
Received Eb/(N0+I0)	dB	,95
MARGIN	dB	-5,55
INR = I₀/N₀ (dB)	dB	,00
POWER FLUX DENSITY	dBW/m² /4kHz	$- 166, 10$

MODCOD	ID	Spectral Efficiency	E_s/N₀ (dB) Ideal Frame of 64800 bits	E_b/N₀(dB)	Symbol BW (MHz)
QPSK 1/3	9	0.656448	$-1.24$ ~~	0.587996705	78.12
QPSK 3/5	8	1.188304	2.23	1.48072441	43.15
QPSK 5/6	7	1.654663	5.18	2.992904443	30.99
QPSK 9/10	6	1.788612	6.42	3.894838598	28.67
8PSK 3/4	5	2.228124	7.91	4.430606434	23.01
8PSK 5/6	4	2.478562	9.35	5.40800213	20.69
8PSK 9/10	3	2.679207	10.98	6.699937308	19.14
16APSK 5/6	2	3.300184	11.61	6.424618456	15.54
32APSK 8/9	1	4.397854	15.69	9.257591924	11.66

OVERALL LINK BUDGET		QPSK $\frac{𝟏}{𝟑}$	QPSK $\frac{𝟑}{𝟓}$	QPSK $\frac{𝟓}{𝟔}$	QPSK $\frac{𝟗}{𝟏𝟎}$	8PSK $\frac{𝟑}{𝟒}$	8PSK $\frac{𝟓}{𝟔}$	16APSK $\frac{𝟓}{𝟔}$	8PSK $\frac{𝟗}{𝟏𝟎}$	32APSK $\frac{𝟖}{𝟗}$
		ID=9	ID=8	ID=7	ID=6	ID=5	ID=4	ID=3	ID=2	ID=1
Received C/N₀ (Down)	dBHz	95.5	95.5	95.5	95.5	95.5	95.5	95.5	95.5	95.5
Received E_b/N₀ - loss	dB	15.4	15.4	15.4	15.4	15.4	15.4	15.4	15.4	15.4
Received E_b/N₀	dB	18.4	18.4	18.4	18.4	18.4	18.4	18.4	18.4	18.4
Implementation Losses	dB	3.0	3.0	3.0	3.0	3.0	3.0	3.0	3.0	3.0
Demodulation Losses	dB	3.0	3.0	3.0	3.0	3.0	3.0	3.0	3.0	3.0
Other Losses	dB	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Desired E_b/N₀ (BER = 1×10^-6)	dB	0.6	1.5	3.0	3.7	4.4	5.4	6.4	6.7	9.3
C/I	dB	1.9	5.4	8.4	9.6	11.3	12.8	15.2	14.6	19.9
E_b/I₀	dB	3.9	4.9	6.5	7.6	8.2	9.4	10.7	11.1	15.2
Received E_b /(N₀+I₀ )	dB	3.58	4.48	5.98	6.91	7.45	8.42	9.43	9.69	12.26
Specified Margin (M)	dB	2.99	3.00	2.99	3.01	3.02	3.02	3.001	2.994	2.998
INR = I₀/N₀ (Max Supported)	dB	14.62	13.69	12.10	11.14	10.56	9.49	8.34	8.02	4.88

ELEVATION (°)	INR (dB)	% of time⁽²⁾ (CCSDS 2013)	R_b ⁽¹⁾ Mbps	T_hr ⁽²⁾ Gbits
90	8.01	16.6	51.28	30.988
75	8.37	13.6	51.28
60	9.44	25.2	51.28
30	11.45	35.4	39.65
5.7	13.70	9.2	6.45

C/I dB	INR dB	ELEVATION (°)	MODCOD ID	% of time ⁽²⁾	R_b ⁽¹⁾ Mbps
14.6	8.01	90	8PSK 9/10	16.6	137.39
15.2	8.37	75	16APSK 5/6	13.6	169.23
12.8	9.44	60	8PSK 5/6	25.2	127.1
9.6	11.45	30	QPSK 9/10	35.4	91.92
5.4	13.70	5.7	QPSK 3/5	9.2	51.28

Elevation (°)	I (dBm)
0	-33
10	-21
20	-32,5
30	-40,5
40	-47,5
50	-40,5
60	-45
70	-44
77,8	-26,5
80	-39
90	-44
Opposite side (Az=211,9°)¹
100	-42
110	-42,5
120	-42,5
130	-41,5
140	-40
150	-37
160	-33,5
170	-34,5
172,63	-32
180	-34

Elevation (°)	I (dBm)	C (dBm)	C/I (dB)	INR (dB)⁽¹⁾	MODCOD (ID)	R_b(Mbps)	Time⁽²⁾%
10	-21	-20,2	0,8	18,97	9 →	0	5,88
					→ M=-1.05dB
20	-32,5	-19,7	12,8	6,97	4	121	5,88
30	-40,5	-18,7	21,8	-2,03	1	225,52	5,88
40	-47,5	-18,4	29,1	-9,33	1	225,52	5,88
50	-40,5	-17,9	22,6	-2,83	1	225,52	5,88
60	-45	-16,4	28,6	-8,83	1	225,52	5,88
70	-44	-16,2	27,8	-8,03	1	225,52	5,88
77,8	-26,5	-14,7	11,8	-7,97	5	114,26	5,88
90	-44	-14,1	29,9	-10,13	1	225,52	5,88
100	-42	-14,2	27,8	-8,03	1	225,52	5,88
110	-42,5	-15,2	27,3	-7,53	1	225,52	5,88
120	-42,5	-15,2	27,3	-7,53	1	225,52	5,88
130	-41,5	-16,7	24,8	-5,03	1	225,52	5,88
140	-40	-17,7	22,3	-2,53	1	225,52	5,88
150	-37	-18,2	18,8	0,97	3	169,23	5,88
160	-33,5	-18,7	14,8	4,97	2	137,39	5,88
170	-33	-18,7	14,3	5,47	4	127,10	5,88

Elevation (°)	P_I (dBm/52 MHz)	P_signal (dBm)(max pass)	P_signal dBm/52MHz)	C/_I (dB)	INR (dB) ₍₁₎	MODCOD (ID)	R_b (Mbps)
5,39	-49	-54	-43,2	5,8	13,97	8	60,94
10	-60	-54	-43,2	16,8	2,97	2	137,39
20	-61	-54	-43,2	17,8	1,97	2	137,39
30	-57,5	-54	-43,2	14,3	5,47	4	127,10
40	-55	-53,5	-42,7	12,3	7,47	5	114,26
50	-58,5	-53,5	-42,7	15,8	3,97	2	137,39
60	-60,5	-53	-42,2	18,3	1,47	3	169,23
70	-63,5	-53	-42,2	21,3	-1,53	1	225,52
80	-70	-52,5	-41,7	28,3	-8,53	1	225,52
90	-70	-52,5	-41,7	28,3	-8,53	1	225,52
100	---	-52,5	-41,7			1	225,52
110	---	-53	-42,2			1	225,52
120	---	-53	-42,2			1	225,52
130	---	-54	-43,2			1	225,52
140	---	-55	-44,2			1	225,52
150	---	-56	-45,2			1	225,52
160	---	-56	-45,2			1	225,52
170	---	-56	-45,2			3	169,23
180	---	-56	-45,2			3	169,23

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[1] NOTE: Given the system spectral efficiency 𝜂tot the ratio between the energy per information bit and single sided noise power spectral density: E_b/N₀ = E_s/N₀ − 10log₁₀(𝜂_tot).