隨著各種多媒體應用在手機平台的普及，手機用戶對於頻寬需求也越來越大。世界許多國家 包括政府與通訊大廠都已針對下世代第五代行動通訊的相關技術與標準積極投入，預計在2018年 完成標準的制定，2020年商用推廣。目前METIS (Mobile and wireless communications Enablers for the Twenty-twenty Information Society)已針對第五代行動通訊在2020年之後的使用情境與技術需 求完成討論，有鑒於現行4G標準中相關技術已經將頻譜效率推近至理論極限，增加頻寬勢必無可 避免。由於目前微波頻段已經相當擁擠，要獲取更大頻寬，毫米波頻段成為一熱門選項。在綜合 空氣吸收率、波段使用現況以及可用連續頻寬之考量， 38GHz被選為工研院5G計畫的操作波段。 雖然38GHz頻段能提供相當大的頻寬，但也包含許多新的技術與挑戰。

As the population of variant multi-media applications on mobile phones, user terminal demands wider and wider bandwidth for it. Many main communication companies in the world -wide have devoted actively into the related technologies and standardization of 5G. It is pla nned to finalize the standardization of 5G by 2018 and to be commercialized from 2020. METIS has finished the discussion and definition of 5G scenario and technology needs. Since i n the current 4G standard, the spectral efficiency has been pushed to approach the theoretical limit, it is inevitably to increase the bandwidth to achieve the defined peak data rate. And since the spectrum in the microwave band has been very crowded, mm-wave band is an important option to get the wide enough bandwidth. In the consideration of absorption rate of O2 and H2O, the available continuous spectrum and the path loss, 38GHz band is chosen as the potential operation band of ITRI’s 5G project. Although it can get the enough bandwidth in the 38GHz band, it also induces a lot of new technology challenges.