244 ITU‐T's Technical Reports and Specifications Mainly, optical cables are used for backbone broadband network. However, wireless broadband technology complement to the optical cables is also required to meet the telecommunication demand for more flexibility. In some cases, it is difficult to lay cables. Such cases include providing services around waterway crossings and between buildings. In other cases, it is not efficient to lay cables. Such cases include providing services for use at temporary events and for rapid network recovery in emergency occasions like big natural disasters. The following figures show use cases of the technology: Setting transmission equipment at each of two sites (Figure below), the distance between them is several kilometers; data is to be transmitted between them wirelessly. Operating in the millimeter wave allows the system to access to a wider radio frequency spectrum and prevents the radio wave from interfering with other radio waves as a result of the rectilinear propagation characteristic. Transmission rate of few Gbps comparable to optic cables is achieved.