This is like a signal booster to improve the links between the gas and electricity smart meters and between the electricity meter (that hosts the Comms hub) and the IHD.
alt-HAN has been developed by a cross industry body of which EON/EONNEXT are members.
I have found that the maximum usable reliable distance between the comms hub and any IHD is at most 10M. This measurement was done the open air by me basically walking away from the Smart Meter. Between 9m and 10m the signal dropped to zero.