IAB feature is a rel 16 feature of 3GPP (quite recent) but Huawei had the IAB solution ready since more than 2 years ago (https://www.huawei.com/en/news/2018/5/IAB-Value-5G-Test-39-GHz-Band), for both 4G and 5G.
IAB is said to reduce the number of sites that needs fiber by 60-70%.
It works better than microwave (that is affected by fog and mist) and even when it’s not a line of sight between transmitter and receiver with the drawback that IAB consumes radio resources meaning is not suitable for heavy traffic sites.
Otherwise is a great solution to skip fiber installation when fiber installation is too expensive, takes too much time or the business case is not there to justify fiber installation.
IAB solution is a good and quick solution to rollout sites.
As traffic will increase IAB will be replaced by fiber for those sites.
IAB feature works best with massive MIMO especially with MU-MIMO ( because when MU-MIMO is active IAB feature will not affect the capacity of the site).
In 2019 Huawei trial a project called ‘rural star’ in Vietnam.
Using 4G LTE wireless 5Mhz as transmission link for remote 3G site.
The distance from 4G donor site to remote 3G site is ~ 10km.
In remote 3G site, there are instaled new Yagi antenna to receive LTE signal.
Rural Star already implemented in several spots here in Indonesia.
Not only 3G site, but also 4G as well. As we have 15Mhz bandwidth in 900Mhz spectrum.
It works quite well especially for tourism resorts & vacation spots (which located in the middle of nowehere).
The drawback is availability sometimes degrading over time.