Satellite direct to device in a mountain valley. A mountain valley: the village is covered by a cell on the spur; the road to the pass is not.

Layers

Scenario

A mountain valley: the village is covered by a cell on the spur; the road to the pass is not.

01/05

n28 700 MHz: 703–803 MHz · λ 40 cm · Coverage layer, NB-IoT and LTE-M anchor · 3GPP TS 38.101-1

Network scenes

Satellite direct to device in a mountain valley

Where the valley cell cannot reach, phones on the pass road connect straight to a low-orbit satellite, which relays through its feeder link to a gateway. Slant range, delay, Doppler and SNR are computed for the pass geometry.

The place: Alpine valley

In this scene

LEO satellite with a regenerative payload

A low-orbit satellite whose spot beam (about 50 km across at 600 km) serves standard phones in the S band; drawn far lower than its true height. (3GPP TS 38.300 §16.14 (NR NTN), 3GPP TR 38.821, 3GPP TS 38.101-5)
Scene input: TR 38.821 set 1, LEO-600 S-band: 34 dBW/MHz EIRP density

Satellite gateway (feeder link)

The ground station that links the satellite to the core network over a Ka-band feeder link; it may be hundreds of kilometres away. (3GPP TR 38.821, ITU RR Art. 5)

Valley cell site

A 700 MHz sector on the spur above the village: it covers the valley floor; the ridges shadow the pass road. (3GPP TS 38.104, 3GPP TR 38.901 UMa)

Computed for this scenario

Outdoor area at SINR ≥ 10 dB

55 %

Median SINR

13.1 dB

Shannon bound at median, 20 MHz

88 Mbit/s

Cell edge (5th percentile)

-8.9 dB · 3 Mbit/s

Slant range

718 km at 55° elevation

Free-space loss (P.525)

155.6 dB at 2.00 GHz

One-way delay

2.39 ms

Doppler, worst case at this elevation

±13.2 ppm · 26 kHz

Downlink SNR, handheld, 5 MHz

15.4 dB

Scenarios

Pass at 55°

The satellite is 55° above the horizon: about 720 km of slant range.

Low pass at 25°

Low on the horizon the slant range doubles, the loss grows by about 5 dB and the Doppler rises.

Overhead

Directly overhead the path is shortest and the Doppler goes to zero.

Tour transcript

1. A mountain valley: the village is covered by a cell on the spur; the road to the pass is not.
2. The valley cell at 700 MHz: the ridges cast its shadow over the switchbacks.
3. A low-orbit satellite serves phones on the pass directly and relays through its Ka-band feeder link to a gateway.
4. Low on the horizon the slant range doubles and the Doppler rises: the readouts are recomputed.
5. Overhead, the shortest path and no Doppler.

How the numbers are computed

Slant range on a spherical Earth for the elevation angle, free-space loss (ITU-R P.525) at 2 GHz, one-way delay as range over c, and the worst-case Doppler v cos ε · Re/(Re + h) / c at that elevation (3GPP TR 38.821 geometry). Downlink SNR uses the TR 38.821 set-1 LEO-600 S-band EIRP density over 5 MHz to a 0 dBi handheld with a 7 dB noise figure. The valley cell uses TR 38.901 UMa with line of sight tested against the terrain.