UAV Relay Chain Formation
Build an airborne multi-hop relay chain and watch spacing, path loss, latency, and weakest-hop risk update together.
Place relay UAVs so the remote IoT target stays connected.
Split a long air-to-ground path into shorter hops. Move the mission distance, relay count, radio settings, terrain loss, and failure state to see which hop becomes the bottleneck.
UAV relay controls, formation map, and planning evidence
Relay formation map
Range rings are a planning guide. The dB link budget decides whether each hop has enough fade margin.
Run the formation
Step through the design checks or play a packet across the current chain.
Mission preset
Formation mode
Failure test
Planning controls
The chain is ready. Every active hop has positive fade margin and stays within the nominal planning range.
Hop B to R1 is the current bottleneck at 2.0 km and 15.3 dB margin.
Core idea
Each relay reduces hop distance. Shorter hops usually improve received power and margin, but every hop adds forwarding delay.
What moves
The packet token travels from the ground station through relay UAVs to the target. Link colors show the weakest path.
Tradeoff
More relays can fix range and obstacle loss, but they increase operational complexity, airtime load, and failure points.
Failure rule
A failed relay is skipped. The neighboring nodes must bridge the larger gap or downstream traffic is disconnected.
Technical accuracy notes
- This is a planning model for learning. Real UAV links also depend on antennas, polarization, multipath, regulation, modulation, coding, interference, and airframe orientation.
- The nominal range slider is an operational planning cap. The dB link-budget calculation is shown separately so learners do not confuse a range circle with guaranteed connectivity.
- Altitude appears in the map and notes because line-of-sight improves with height, but this simplified model does not compute earth curvature, Fresnel clearance, or detailed terrain profiles.
- End-to-end latency uses forwarding delay per hop plus propagation delay. Over these distances propagation delay is tiny; forwarding, queuing, and protocol overhead dominate.
Formulas and units
FSPL_dB = 32.44 + 20 log10(frequency_MHz) + 20 log10(distance_km)received_dBm = tx_dBm + tx_gain_dBi + rx_gain_dBi - FSPL_dB - obstacle_loss_dBlink_margin_dB = received_dBm - receiver_sensitivity_dBm - fade_margin_dBend_to_end_latency_ms = base_processing_ms + hops x forwarding_delay_ms + propagation_delay_msairtime_load_fraction = payload_Mbps x hops / nominal_link_rate_MbpsDesign lessons
- Do not judge a relay chain from total distance alone. One weak hop can break the entire path.
- Spacing at roughly 60 to 70 percent of the practical range gives reserve for fading, wind drift, and antenna motion.
- A bypass formation can avoid terrain shadowing, but the extra path length may still consume margin.
- Adding relays reduces hop distance but increases latency and the number of nodes that must stay healthy.
Practice prompts
- Set mission distance to 12 km with 3 relays. Which hop fails first, and which control fixes it with the smallest change?
- Switch between 915 MHz and 2.4 GHz. Why does the higher frequency need either shorter hops, more power, or better sensitivity?
- Turn on the middle relay failure. Can a staggered or ridge-bypass formation reconnect the chain without adding relays?
- Increase payload demand. At what point does airtime become the limiting factor even when dB margins still look healthy?