--- title: "Radio access in a city centre | Nexus Observatory" description: "A three-sector macro site on the tallest roof and small cells on street poles: their coverage, interference and beams computed over the streets and buildings…" url: https://observatory.global/environments/networks/ran-city/ publisher: Nexus Observatory Inc. updated: 2026-10-29 --- Radio access in a city centre. A city centre with a macro site on the tallest roof and small cells at four junctions. The red map is the SINR the radios give the street. Layers Scenario A city centre with a macro site on the tallest roof and small cells at four junctions. The red map is the SINR the radios give the street. 01/08 500 MHz 1 GHz 2 GHz 5 GHz 10 GHz 20 GHz 40 GHz n78 3.5 GHz: 3.30–3.80 GHz · λ 84.4 mm · Main 5G capacity layer, massive MIMO · 3GPP TS 38.101-1 Network scenes # Radio access in a city centre A three-sector macro site on the tallest roof and small cells on street poles: their coverage, interference and beams computed over the streets and buildings of the drawing. [Radio access in a city centre](https://observatory.global/environments/networks/ran-city/) [Open RAN in a suburb](https://observatory.global/environments/networks/oran-suburb/) [AI-RAN at a stadium](https://observatory.global/environments/networks/ai-ran-stadium/) [Private 5G in an open-pit mine](https://observatory.global/environments/networks/private5g-mine/) [Private 5G at a container port](https://observatory.global/environments/networks/private5g-port/) [LoRaWAN across a farm and village](https://observatory.global/environments/networks/iot-farm/) [IoT in the city: a street-light mesh and LoRaWAN](https://observatory.global/environments/networks/iot-city/) [Industrial IoT in a process plant](https://observatory.global/environments/networks/iot-plant/) [Satellite direct to device in a mountain valley](https://observatory.global/environments/networks/ntn-d2d/) [Microwave backhaul across a river valley](https://observatory.global/environments/networks/backhaul-fresnel/) The place: [City centre](https://observatory.global/environments/city-centre/) ## In this scene **Macro gNB, three sectors**: Three 64-element active antenna units on the tallest roof, one per 120° sector, carrying the 3.5 GHz capacity layer and the 700 MHz coverage layer. (3GPP TS 38.104 (wide area BS), 3GPP TS 38.211) Scene input: 73 dBm EIRP per n78 sector, 8° downtilt · Array: 8 × 8 elements, λ/2 spacing **Small cell on a street pole**: Street-level capacity at about 11 m on existing poles: n78 today, a 26 GHz mmWave radio where the street is busy. (3GPP TS 38.104 (local area BS), 3GPP TR 38.901 UMi) Scene input: 46 dBm EIRP at n78, 60 dBm at n258 **Small cell**: **Small cell**: **Small cell**: **Exchange: baseband hub and edge**: The street-level radios terminate here on dark fibre; baseband for the small cells runs on pooled servers next to the edge cache. (3GPP TS 38.401, O-RAN.WG4.CUS.0) ## Links and interfaces **Fronthaul fibre**: Dark fibre in the street ducts from each small cell to the exchange; the one-way delay is read from its routed length. (O-RAN.WG4.CUS.0 (split 7.2x), eCPRI 2.0) **Backhaul**: The macro site reaches the exchange over fibre; from there the core network is in the operator cloud. (3GPP TS 38.410 (NG)) ## Computed for this scenario **Outdoor area at SINR ≥ 10 dB**: 55 % **Median SINR**: 11.4 dB **Shannon bound at median, 100 MHz**: 390 Mbit/s **Cell edge (5th percentile)**: 0.1 dB · 101 Mbit/s **SSB beams per burst (TS 38.213)**: 8 **User beams steered**: 5 **Array gain, 64 elements**: 18.1 dB **Beamwidth, azimuth**: 12.8° **Fronthaul fibre**: 139 m · 0.7 µs one way **Fronthaul fibre**: 629 m · 3.1 µs one way **Backhaul**: 755 m · 3.7 µs one way ## Scenarios **Normal**: All macro sectors and small cells on air at 3.5 GHz. **Sector A off**: Macro sector A is off for maintenance; neighbouring sectors and the small cells carry its streets. **Interference**: A co-channel transmitter switches on in the north-east block; SINR collapses around it. **26 GHz layer**: The small cells switch to their 26 GHz radios: much more bandwidth, but only where the street gives line of sight. **Crowd**: An event fills the streets; the macro steers a beam to each busy group. ## Tour transcript 1. A city centre with a macro site on the tallest roof and small cells at four junctions. The red map is the SINR the radios give the street. 2. Three sectors of 64-element antennas. The lobes are the TR 38.901 pattern; the arcs are the wavefronts leaving each sector. 3. An SSB burst sweeps eight beams across the sector; then the panel steers one beam to each user it serves. 4. A small cell on a street pole fills the street canyon the macro cannot see into. 5. Switch sector A off: its streets fall back to the other sectors and the small cells. 6. A co-channel interferer: SINR, not signal strength, decides what a user can do. 7. At 26 GHz the small cells reach only the streets in their line of sight. 8. Fronthaul fibre runs in the street ducts to the exchange; its length sets the delay. ## How the numbers are computed Coverage is the strongest carrier at 1.5 m above the street on a 72 × 72 grid. Path loss follows 3GPP TR 38.901 (UMa for the macro, UMi street canyon for the small cells), with line of sight tested against the drawn buildings; the macro pattern is the TR 38.901 sector element with an 8° downtilt; SINR sums every co-channel transmitter and thermal noise (−174 dBm/Hz plus a 7 dB noise figure). The beams are the array factor of an 8 × 8 panel steered to each user; the SSB burst has 8 beams at 3.5 GHz (TS 38.213). © 2026 Nexus Observatory Inc. **Legal** [Privacy notice](https://observatory.global/legal/privacy/) · [Terms of use](https://observatory.global/legal/terms/) · [Cookie policy](https://observatory.global/legal/cookies/) · [Accessibility](https://observatory.global/legal/accessibility/) · [Official languages](https://observatory.global/official-languages/) · [Trademarks](https://observatory.global/trademarks/) · [Notices](https://observatory.global/notices/) **Company** [About](https://observatory.global/about/) · [Stewardship](https://observatory.global/consortium/) · [Contact](https://observatory.global/contact/)