Recently, the official website of the Ministry of Industry and Information Technology released an announcement approving China Unicom to use the 900MHz frequency resources currently used in 2G/3G/4G systems for 5G systems. This news has aroused heated discussion in the industry. In my opinion, China Unicom has obtained the license of 900MHz heavy farming for 5G, which is of great significance to the ecological construction of low-frequency 5G industry, and is also an important measure to achieve the balanced development of 5G in China, reflecting the strong support of spectrum policy for 5G industry development. Looking back on the development of China Unicom's 900MHz low frequency band in the past few years, due to historical reasons, the lack of low frequency spectrum resources has become a "hard wound" in the development of China Unicom, forming a sharp contrast with the other two operators. Previously, the three major operators had corresponding spectrum resources under Sub 1GHz, of which China Mobile had 889-909MHz and 934-954MHz spectrum resources, and both uplink and downlink had 20MHz bandwidth, which was initially used for 2G deployment and later re cultivated for 2G/4G/NB IoT deployment; China Telecom has 824-835MHz and 869-880MHz spectrum resources. Both uplink and downlink have 11MHz bandwidth. At first, it was used for 2G and 3G deployment. Later, after re cultivation, its 2G and 3G networks gradually withdrew, mainly for 4G and NB IoT. China Unicom, on the other hand, only obtained 909-915MHz and 954-960MHz spectrum resources at first. The uplink and downlink bandwidth was only 6MHz. At first, it was used for the deployment of 2G GSM. Later, with the development of business, it also needed to carry 3G, 4G and NB IoT. If only the 2G network is supported, the 6MHz bandwidth is sufficient. However, the rise of 3G and 4G, which focus on data services, has increasingly high requirements for spectrum bandwidth. China Unicom's shortage of bandwidth resources in the low frequency band is very obvious, and the only limited bandwidth has to meet the requirements of 3G, 4G and NB IoT, which is obviously an impossible task. The lack of low-frequency frequencies has increased the cost of network construction, affected the experience of the network, and formed a passive situation in the development. Take NB IoT as an example. In 2016, after the NB IoT standard was frozen, China Telecom quickly built the world's first largest NB IoT network with its 800MHz band advantage, while China Mobile quickly built a nationwide NB IoT network with its 900MHz band. In contrast, China Unicom cannot effectively carry its NB IoT network at 900MHz due to the lack of low-frequency resources. Many base stations can only be carried at 1800MHz, lagging behind the other two operators in the narrow band Internet of Things field. The turnaround took place in 2018. In April of that year, the Ministry of Industry and Information Technology issued the LTE FDD license to China Mobile. At the same time, the Ministry of Industry and Information Technology required China Mobile to accelerate the take-off of the 900 MHz frequency band, and allocated the 2 * 5 MHz frequency resources of the 904-909/949-954 MHz to China Unicom to increase support for China Unicom's 4G network and cellular IoT