NTT DoCoMo and Huawei said they have completed a successful trial of Integrated Access Backhaul (IAB) technology using the 39-GHz mmWave band for 5G wireless backhaul.
The field trial, which took place in Yokohama, Japan’s Minato Mirai 21 waterfront area, tested wireless backhaul functionality between a 5G base station (IAB-donor) and a 5G relay node (IAB-node), and wireless access between the IAB-node and mobile user equipment, all using the 39-GHz band.
According to DoCoMo, the trial demonstrated that IAB can significantly improve mmWave coverage and capacity. The trial system achieved throughputs exceeding 650 Mbps with a low latency of 1.6ms with user equipment that was outside the range of the base station. Both the relay node and user equipment were under mobility condition during the tests.
Conventionally, mmWave signals 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 NR standard. The technology involves the use of a compact focal lens antenna made with metamaterials to achieve advanced beamforming (maximum gain of 31 dBi) that 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. In addition, IAB-nodes enable low-latency data transmissions through fast beam-switching for the uplink and downlink, and they efficiently coordinate radio resource scheduling between the backhaul and access links.
DoCoMo says the trial system demonstrated that IAB technology dramatically improves mmWave coverage and capacity, and facilitates the use of high-speed, low-latency 5G communication among tall buildings, on isolated islands and in mountain regions where laying fiber presents problems.