ATM Radio
Understanding ATM Radio Backhaul
When 2G and 3G cell towers needed to send voice and data traffic back to the network core, the transport of choice was often a point-to-point microwave radio link carrying ATM cells. ATM Radio combined the QoS-guaranteed ATM protocol with the rapid deployment and lower cost of microwave links compared to buried fiber.
The Microwave Backhaul Advantage
In many markets — especially developing countries and rural areas — deploying fiber optic cable to every cell tower was prohibitively expensive. A microwave radio link could be installed in days: mount antennas on each end, align them visually, and commission the link. ATM cells flowed over the microwave channel with the same deterministic QoS characteristics as a fiber-connected ATM switch.
The Migration to Ethernet
The transition to 4G LTE eliminated ATM from the backhaul requirement. LTE's S1 and X2 interfaces use IP/Ethernet transport natively. Microwave radio vendors addressed this transition by releasing hybrid platforms that could carry both ATM and Ethernet traffic simultaneously on the same radio link, enabling carriers to gradually migrate base stations from 3G/ATM to 4G/Ethernet without replacing the microwave radio hardware.
Key Equations
ATM Radio refers to point-to-point microwave radio links that transport Asynchronous Transfer Mode (ATM) cell traffic as their native payload. In 2G and 3G cellular...
Key specifications:
38 GHz | 1 a | 32.44 dB | 60 km | 99.999 % | 45 dB
Path loss: FSPL = 20log(d)+20log(f)+32.44
Comparison
| Aspect | ATM Radio Spec | Typical Range | Impact | Design Note |
|---|---|---|---|---|
| Primary function | ATM Radio refers to point-to-point micro... | Application-dep. | Critical | Verify in sim |
| Operating range | These microwave radios provided an alter... | Application-dep. | Critical | Verify in sim |
| Performance | ATM Radio systems mapped ATM cells direc... | Application-dep. | Critical | Verify in sim |
| Integration | ATM Radio combined the QoS-guaranteed AT... | Application-dep. | Critical | Verify in sim |
| Trade-off | The Microwave Backhaul Advantage In many... | Application-dep. | Critical | Verify in sim |
Frequently Asked Questions
What frequency bands are used for microwave backhaul?
Licensed microwave backhaul operates across a wide range of bands: 6–11 GHz for long-haul links (15–50 km), 15–23 GHz for medium-haul links (5–15 km), and 26–42 GHz for short-haul high-capacity links (1–5 km). Higher frequencies provide more bandwidth (higher data rates) but suffer greater rain attenuation, limiting link distance. Band selection is a trade-off between required capacity and maximum link distance for the local climate.
How much capacity did ATM Radio links provide?
Early ATM microwave radios provided 4×E1 (8 Mbps) capacity, sufficient for a single 2G BTS. Advanced systems scaled to STM-1 (155 Mbps) using higher-order modulation (64-QAM, 128-QAM) and wider channels. This capacity was adequate for 3G UMTS but insufficient for 4G LTE, which drove the transition to Gigabit Ethernet microwave radios using 256-QAM and 1024-QAM modulation with channel aggregation.
Are ATM Radio links still in operation?
Yes, though declining. Many carriers in developing markets still operate legacy 2G/3G networks with ATM-based microwave backhaul. These links will be decommissioned as carriers shut down 2G/3G services and upgrade to all-IP 4G/5G networks. However, the physical microwave radio hardware (antennas, towers, frequency licenses) is typically retained and upgraded to Ethernet-native operation for 4G/5G backhaul.