NTT Docomo and and Huawei claimed to have proved integrated access backhaul (IAB) technology can significantly improve mmWave coverage and capacity during 5G trials.

A field test in Yokohama using the 39GHz band, the operator achieved a throughput of more than 650Mb/s with a low latency of 1.6m/s. The trial system also showed IAB enables the use of high-speed, low-latency 5G communication among tall buildings, on isolated islands or in mountainous regions where laying fibre presents problems.

Docomo said in a statement mmWave signals generally offer only limited coverage due to high propagation loss and interference from buildings. The need for a narrow directional beam to focus transmission power can further complicate efforts to achieve wide area coverage under non-line-of-sight conditions.

The 3GPP is now considering IAB technology as a 5G New Radio standard. The technology involves the use of a compact focal lens antenna to achieve advanced beamforming which concentrates radio waves in a specified direction for long-distance transmission. Beamforming mitigates interference between the wireless backhaul and wireless access links, and also enables simultaneous data transmissions over the same frequency.

Docomo added IAB-nodes enable low-latency data transmissions through fast beam switching for the uplink and downlink.