On April 1, the Ministry of Industry and Information Technology of China issued a notice to adjust the use plan of the 700MHz frequency band and formally use it for 5G networks. After this adjustment, the frequency band 702-798MHz will be adjusted for mobile communication systems, and the frequency bands 703-743MHz and 758-798MHz will be planned for mobile communication systems in frequency division duplex (FDD) mode. This frequency band is allocated to China Broadcast and Television Networks (CBN), and incorporated the international 5G network standard numbered TR38.888.
What are the advantages of the 700MHz band?
As the frequency increases, the attenuation of the radio signal will increase, and the signal's refraction and reflection capabilities will also decrease. At the same power, the signal coverage area of the 700MHz band is 9 times that of the 4.9GHz band. In other words, in the case of covering the same area, CBN using the 700MHz band only needs to build one base station, China Mobile Communications Corporation (CMCC) using the 2.6GHz band needs to build 5.2 base stations, and China Telecom using the 3.5GHz band (CTCC) and China United Network Communications Corporation (CUCC) need to build 6.3 base stations. If CMCC and CBN use the 4.9 GHz band, then 9 base stations need to be built.
And because of the weak penetration of high-frequency radio signals, it is difficult to receive high-frequency signals in many buildings. The low-frequency signals in the 700MHz band are unobstructed.
The limitations of CBN
The 700Mhz frequency band is now licensed for use in FDD-mode mobile communication network technology. The other three major telecommunications companies are also very jealous of the 700Mhz frequency band. However, because the 700Mhz wireless frequency is too low to support the key technology Massive Multi Input Multi Output (MIMO) among 5G base stations, the capacity of the 700Mhz band base station will also be insufficient.
Judging from the current technology, the 700Mhz 5G base station is basically equipped with 2 transmitting antennas and 4 receiving antennas, and the computer side configuration is basically only 1 transmitting antenna and 2 receiving antennas. As an overlay, it cannot be used as a capacity overlay in cities.
The CBN's additionally allocated high-frequency 4.9Ghz, and the construction of the 5G network in this band requires more costs than the 5G coverage of the other three major telecommunications companies, and here, it is also difficult to get compared to the relatively weak CBN Come out.
700MHz band influences mobile phone manufacturers
CBN's 700MHz band low-frequency networking will start in a short time. Due to the coverage advantages of the 700MHz band, it is conducive to the rapid formation of a network covering the whole country. Therefore, its construction and coverage speed may be faster than the CMCC's main frequency band of 4.9GHz. After the base station is established, it needs new mobile phone support.
The channel number of the 700MHz band approved by the Ministry of Industry and Information Technology of China in the international 5G network band is N28. Currently, only Mate 30 mobile phones from Huawei support this band. Other mobile phone companies do not support this band. It is said that Qualcomm's Snapdragon 765 chip and X55 baseband can support this band. However, due to the low frequency and long wavelength of the 700MHz band, this requires a redesign of the antenna of the mobile phone, and the length and layout of the antenna have a great influence on the signal. This is a new challenge for mobile phone manufacturers.