esa-sceva/satcom-qa huggingface dataset:
Topic: TT&C

Question: What is TT&C in satellite communication?
Answer: TT&C stands for Telemetry, Tracking, and Command. It is a critical subsystem linking satellites with ground stations, enabling monitoring, control, and management of satellite health, orbit, and functionalities. TT&C ensures the satellite remains operational and on course throughout its mission.
Topic: Uplink

Question: What role does uplink power control play?
Answer: Uplink power control dynamically adjusts transmitter power to optimize signal strength while minimizing interference and preserving satellite transponder health, enhancing link efficiency and reliability.
Topic: 5G NTN

Question: How does 5G NTN help in disaster recovery and emergency communications?
Answer: In disaster scenarios, terrestrial networks may be damaged or unavailable. 5G NTN can quickly provide connectivity through satellites or high-altitude platforms, ensuring communication for first responders, relief teams, and affected communities. It enables real-time voice, video, and data transmission for coordinating rescue operations. NTN can reach remote or cut-off areas where terrestrial infrastructure is compromised, offering a resilient backup communication solution. This improves response times, situational awareness, and operational coordination during natural disasters, accidents, or humanitarian crises.

Question: How does 5G NTN support global connectivity?
Answer: 5G NTN combines terrestrial networks with satellites and aerial platforms to provide coverage across oceans, mountains, deserts, and other remote areas. It ensures continuous mobile broadband access even in regions without fiber or cell towers. This is particularly valuable for global IoT applications, maritime and aviation communication, and disaster response scenarios. By linking isolated areas to the 5G core network, NTN enables worldwide seamless communication, bridging the digital divide and allowing users everywhere to benefit from 5G services.
Topic: NTN

Question: How are NTNs integrated with terrestrial networks?
Answer: Integration involves hybrid network architectures leveraging gateways to connect satellite and terrestrial segments, enabling seamless roaming, consistent QoS, and unified service delivery across platforms.

Question: What applications drive the adoption of NTNs?
Answer: Use cases include global broadband internet, IoT connectivity in remote areas, mobile backhaul, emergency communication systems, maritime and aeronautical connectivity, and industrial applications requiring ubiquitous coverage.
Topic: Link Budget

Question: Calculate antenna gain in dBi from directivity.
Answer: Antenna gain G=D * efficiency,  often simplified to gain in dBi given in datasheets; no formula needed if gain is provided directly.

Question: Calculate antenna gain sum if transmitter antenna gain is 12 dBi and receiver is 14 dBi.
Answer: Total gain =12+14=26 dB

Question: Calculate free space path loss at 3 GHz and 1 km distance.
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44. FSPL (dB) =20 log(5)+20 log(2000)+32.44 FSPL=20log(1)+20log(3000)+32.44=0+69.54+32.44=101.98dB

Question: Calculate free space path loss using wavelength for 1 km.
Answer: Lfs = 20 log(4πd/λ) in dB = 20 log(4π*1000/0.125) = 100.47 dB

Question: Calculate free space path loss using wavelength λ and distance d.
Answer: Lfs = 20 log(4πd/λ) in dB

Question: Calculate FSPL at 2 GHz over 2 km distance.
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44. FSPL (dB) =20 log(5)+20 log(2000)+32.44 FSPL=20log(2)+20log(2000)+32.44=6.02+66.02+32.44=104.48dB

Question: Calculate FSPL for 1 GHz frequency over 5 km distance.
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44. FSPL (dB) =20 log(5)+20 log(2000)+32.44 
FSPL (dB) =20 log(5)+20 log(1000)+32.44 = 14+60+32.44=106.44 dB

Question: Calculate FSPL for 6 GHz at 0.5 km.
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44. FSPL (dB) =20 log(5)+20 log(2000)+32.44 FSPL=20log(0.5)+20log(6000)+32.44= -6.02 + 75.56 + 32.44 = 101.98 dB

Question: Calculate FSPL given wavelength 0.125 m and distance 3 km.
Answer: Lfs = 20 log(4πd/λ) in dB
Lfs = 20 log(4π*3000/0.125) = 20 log(301592)=110.58

Question: Calculate link budget with given:Ptx=10dBm, Gtx=9dB, L=90dB, Grx=12dB, Lothers=1dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx, where Prx = received power, Ptx = transmit power, Gtx and Grx are antenna gains, and Ltx, Lfs, Lp, Lrx are losses.
Prx=10+9-90+12-1=-60

Question: Calculate link margin if receiver sensitivity is -90 dBm andPrx=-75dBm.
Answer: Margin =Prx - sensitivity (both in dBm)
Margin = -75-(-90)=15 dB

Question: Calculate link margin ifPrx= -85dBm and receiver sensitivity is -95 dBm.
Answer: Margin =Prx - sensitivity (both in dBm) = -80-(-95)=15dB

Question: Calculate link margin ifPrx=-50 dBm and receiver sensitivity is -60 dBm.
Answer: Margin =Prx - sensitivity (both in dBm)
Margin = -50-(-60)=10 dB

Question: Calculate received power forPtx=35dBm, total gain 25 dB, total loss 140 dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx
Prx = 35 + 25 - 140= - 80 dBm

Question: Calculate received power if transmit power is 15 dBm, antenna gains total 20 dB and total losses are 120 dB.
Answer: The basic link budget is: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx, where Prx = received power, Ptx = transmit power, Gtx and Grx are antenna gains, and Ltx, Lfs, Lp, Lrx are losses.  
Prx=15+20-120=-85 dBm

Question: Calculate received power ifPtx=15dBm,Gtx=99dB,L=115dB,Grx=14dB,Lother=2dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
Prx = 15+9-115+14-2=-79 dBm

Question: Calculate receiver sensitivity margin if sensitivity is -95 dBm andPrx= -80 dBm.
Answer: Margin =Prx - sensitivity (both in dBm) = -80-(-95)=15dB
Topic: Link Budget

Question: Calculate required transmitter power for receiver sensitivity -85 dBm, total gains 40 dB, total losses 130 dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
Ptx=-85-40+130=5 dBm

Question: Calculate the transmitter power needed forPrx= -60 dBm, total losses 120 dB, total gains 25 dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
Ptx = -60-25-120=35 dBm

Question: Calculate the wavelength for 5 GHz frequency.
Answer: λ=  c/f, where c=speed of light 3*10^8 m/s
λ=c/5*10^9=0.06 m

Question: Calculate transmitter power required for receiver at -70 dBm, total gains 30 dB, total losses 110 dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
Ptx=-70-30+110=10 dBm

Question: Calculate wavelength for 900 MHz frequency.
Answer: λ=  c/f, where c=speed of light 3*10^8 m/s
λ=  c/(900*10^6) = 0.33m

Question: Calculate wavelength λ for frequency 2.4 GHz.
Answer: λ=  c/f, where c=speed of light 3*10^8 m/s
=c/2.4*10^9 = 0.125 m

Question: CalculatePrx if Ptx=15 dBm,Gtx=10dB, L=100dB,Grx=15 dB, no other losses.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx =
Prx = 15+10-100+15=-60 dBm

Question: Compute Prx if transmitter power 30 dBm, gains total 20 dB, total losses 140 dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
 Prx = 30+20-140=-90 dBm

Question: Convert 40 dBm power to watts.
Answer: Pwatts = 10^(PdBm/10)/1000 
Pwatts = 10^(40/10)/1000 = 10 watts

Question: Convert power 100 mW to dBm.
Answer: 10logâ

Question: Convert power 23 dBm to watts.
Answer: Pwatts = 10^(PdBm/10)/1000 = 10^2.3/1000=0.2 watts

Question: Convert power of 5 dBm to watts.
Answer: Pwatts=10^(PdBm/10)/1000
Pwatts=10^(5/10)/1000 = 000316 watts or 3.16 mW

Question: Convert received power of -30 dBm to watts.
Answer: Pwatts=10^(PdBm/10)/1000 = 10^-3/1000=10^-6W

Question: Convert transmitter power of 50 mW to dBm.
Answer: Pdm=10log(50)=16.99 = 17 dBm

Question: Find free space path loss at 10 km and 3 GHz frequency.
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44.
 FSPL (dB) =20 log(10)+20 log(3000)+32.44 = 20+69.54+32.4=122 dB

Question: Find link budget ifPtx=18dBm, Gtx=12dB, L=110dB,Grx=15dB,L others=3dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx, where Prx = received power, Ptx = transmit power, Gtx and Grx are antenna gains, and Ltx, Lfs, Lp, Lrx are losses.
Prx=18+12+110+15-3=-68

Question: Find received power if Ptx=10dBm,Gtx=8dB, path loss 90 dB,Grx=12dB, cable losses 4 dB.
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
Prx = 10+8-90+12-4=-64 dBm

Question: How to add antenna gains when both transmitter and receiver antennas have 15 dBi gain?
Answer: Total antenna gain = 15 + 15 = 30 dB.

Question: How to calculate free space path loss (FSPL)?
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44, where d is distance in km and f is frequency in MHz or GHz depending on formula version.

Question: How to calculate FSPL at 5 km for 2 GHz frequency?
Answer: FSPL (dB) =20 log(d)+20 log(f)+32.44. FSPL (dB) =20 log(5)+20 log(2000)+32.44 = 112.44.
Topic: Link Budget

Question: How to calculate link budget if Ptx=20 dBm, Gtx=10 dB, path loss L=100 dB, Grx=14 dB, other losses = 4 dB?
Answer: The basic link budget is: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx, where Prx = received power, Ptx = transmit power, Gtx and Grx are antenna gains, and Ltx, Lfs, Lp, Lrx are losses.
Prx = 20 + 10 - 100 + 14-4 = -60 dBM

Question: How to calculate margin if minimum receiver sensitivity is -75 dBm andPrx is -60 dBm?
Answer: Margin =Prx - sensitivity 
Margin = -60 - (-75) = 15 dB.

Question: How to calculate power in watts from dBm?
Answer: Pwatts=10^(PdBm/10)/1000. For example, 10 dBm = 0.01 watts.

Question: How to calculate received power with transmitter power 25 dBm, gains 18 dB, and losses 90 dB?
Answer: The basic link budget is: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx, where Prx = received power, Ptx = transmit power, Gtx and Grx are antenna gains, and Ltx, Lfs, Lp, Lrx are losses.
Prx=25+18-90=-47 dBm

Question: How to calculate required transmitter power if receiver sensitivity is -90 dBm and total losses are 150 dB and antenna gains sum to 40 dB?
Answer: Ptx = Prx - Gtx - Grx + Ltotal => Ptx = -90 -40 +150 =20dBm.

Question: How to calculate transmit power if receiver sensitivity is -80 dBm, total gains 35 dB, total losses 120 dB?
Answer: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx 
Ptx=-80-35+120=5 dBm

Question: How to compute received power at the receiver?
Answer: Prx = Ptx + Gtx + Grx - Ltotal, where Ltotal includes all losses like path loss, cable loss, etc.

Question: How to convert power from dBm to watts?
Answer: Pwatts = 10^(PdBm/10)/1000. For example, for 30 PdBm,P=1watt.

Question: How to convert wavelength λ in meters from frequency f in Hz?
Answer: λ=  c/f, where c=speed of light 3*10^8 m/s

Question: How to estimate the receiver sensitivity margin with knownPrx and Sensitivity?
Answer: Margin =Prx - sensitivity (both in dBm). Positive margin means good signal quality.

Question: How to find antenna gain from directivity 15 and efficiency 0.7?
Answer: Gain=Directivity*Efficiency = 15*0.7=10.5

Question: How to find maximum distance given FSPL and frequency?
Answer: d=(λ/4π)*10^(Lfs/20)

Question: How to find power loss due to cable attenuation of 0.5 dB per meter over 3 meters?
Answer: Cable loss  L = 0.5 * 3 = 1.5 dB.

Question: How to find the link margin from received power?
Answer: Link marginLM = Prx-Pmin, where Pmin is minimum receiver sensitivity needed for good reception.

Question: Transmitter power conversion for 0.5 W to dBm.
Answer: PdBm=10log(500)=26.99

Question: What formula represents total losses in link budget?
Answer: Total loss : Ltotal = Ltx + Lfs + Lprop + Lrx, sum of all loss components in dB.

Question: What is link margin if received power is -70 dBm and minimum sensitivity is -85 dBm?
Answer: Margin =Prx - sensitivity 
LM=-70-(-85)=15 dB

Question: What is the basic link budget equation?
Answer: The basic link budget is: Prx = Ptx + Gtx - Ltx- Lfs - Lp + Grx - Lrx, where Prx = received power, Ptx = transmit power, Gtx and Grx are antenna gains, and Ltx, Lfs, Lp, Lrx are losses.
Topic: Link Budget

Question: What is transmitter power in dBm if output power is 1 W?
Answer: Ptx (dBm) = 10 log(Pwatts x 1000) = 10 log (1000) = 30 dBm
Topic: Satellite User terminal

Question: How do user terminals differ for fixed versus mobile satellite communications?
Answer: Fixed terminals are installed at a permanent location with stable antennas, optimized for high data rates and steady links. Mobile terminals, used on vehicles, ships, or planes, include tracking and stabilization systems to maintain signal alignment while moving, with rugged design for various environments.
Topic: Satellite Bandwidth

Question: How does bandwidth impact satellite communication quality?
Answer: Bandwidth influences the volume of data sent and received over a satellite link. Larger bandwidth allows higher data rates, improving service quality for video streaming, internet browsing, and real-time communication. Insufficient bandwidth can lead to congestion, delays, and packet loss, impacting user experience.

Question: How does satellite bandwidth relate to network latency?
Answer: Bandwidth determines data rate capacity but not latency directly. However, limited bandwidth can cause congestion leading to queuing delays. Satellite communication has inherent latency due to long signal travel distance, which bandwidth alone cannot reduce but efficient bandwidth use helps manage traffic better.
Topic: TCP over satellite

Question: How do satellite network characteristics differ from terrestrial networks for TCP?
Answer: Satellite networks have long delays, higher error rates, bandwidth asymmetry, and frequent signal fades, while terrestrial networks have lower latency and error rates. These differences cause TCP congestion control and reliability mechanisms to behave sub-optimally on satellites.

Question: How does satellite latency impact TCP throughput?
Answer: Satellite latency, especially in geostationary orbits (~250 ms one-way), causes long round-trip times. TCP waits for acknowledgments before sending more data, severely limiting transmitter window size and thus throughput, often leaving high-capacity links underutilized.

Question: What are common issues TCP encounters due to asymmetric satellite links?
Answer: Asymmetric links cause delayed or lost ACKs on the uplink, triggering unnecessary retransmissions or window reductions, degrading throughput. TCP enhancements or buffering can mitigate adverse effects brought by asymmetry in satellite networks.

Question: What are TCP window size and its significance in satellite links?
Answer: TCP window size controls the amount of unacknowledged data in transit. For high bandwidth-delay product satellite links, a larger window is needed to fully utilize capacity. Standard small windows cause frequent idle periods waiting for ACKs, harming throughput.

Question: What challenges does TCP face in satellite communication environments?
Answer: TCP's performance is challenged by long satellite propagation delays causing high latency, large bandwidth-delay products, and asymmetric uplink and downlink speeds. These factors increase TCP congestion control delays, timeout occurrences, and reduce throughput, affecting applications reliant on reliable TCP transport.

Question: What TCP enhancements help improve performance over satellite?
Answer: Enhancements include larger initial congestion windows, selective acknowledgments (SACK), TCP window scaling, and Slow Start modifications. These help accommodate long delays, reduce retransmissions, and better manage congestion on satellite links.
Topic: Gateway station

Question: How do gateway stations support satellite broadband services?
Answer: Gateways connect end-user terminals to the internet backbone, managing IP data conversion, forwarding, and traffic routing. They ensure broadband users receive high-speed, low-latency internet over satellite networks.

Question: How do gateways contribute to satellite network scalability?
Answer: Gateways serve as central hubs allowing addition of more user terminals or satellites without major structural changes. They enable load balancing and efficient spectrum use, supporting network growth and service expansion.

Question: What are the primary functions of a satellite gateway?
Answer: The main functions include signal conversion, managing connectivity between satellite and terrestrial networks, transmitting data to/from user terminals, and handling content delivery. It supports various data types including voice, video, and internet traffic.

Question: What environmental considerations affect gateway station deployment?
Answer: Gateways require ample land for antennas, must avoid obstructions and interference, and are often built in remote or secure locations to minimize interruption. Structural resilience against weather and regulatory compliance are critical.

Question: What equipment is typically found in a satellite gateway?
Answer: Equipment includes large antennas, RF front ends, multiplexers, modulators, amplifiers, signal converters, and baseband connectivity modules. These components transmit signals to and receive signals from satellites, converting them into appropriate formats for terrestrial networks.

Question: What is the difference between a gateway station and a user terminal?
Answer: A gateway station interfaces the satellite system with the broader terrestrial network, handling large-scale data routing and signal conversion. User terminals are smaller devices at customer or enterprise premises that communicate via the satellite but do not manage network interconnections.
Topic: TCP over satellite

Question: How can we improve TCP over Satellite performance?
Answer: Increasing the TCP window size, using error correction, and applying performance-enhancing proxies (PEPs) help reduce delay effects in TCP over Satellite systems.

Question: How is TCP over Satellite different from normal TCP?
Answer: TCP over Satellite experiences much higher delay and possible signal loss, so it needs larger windows, optimized congestion control, and sometimes protocol modifications to maintain good performance.