New progress of 5G below 6 GHz
At present, the most promising move to solve the bandwidth problem must be the first millimeter wave 5G solution. However, the reality is that there are at least two to three years or even longer before the completion of the large-scale deployment of millimeter wave 5G. During this period of time, various wireless service providers focused on developing hardware and making new samples of 5G NR frequency bands below 6 GHz. These new frequency bands cover 3300 MHz to 4200 MHz (n77), 3300 MHz to 3800 MHz (n78) and 4400 MHz to 5000 MHz (n79), and allow bandwidths up to 100 MHz. Due to different regulations, each country allows slightly different spectrum segments for 5G NR below 6 GHz. The most common frequency range is between 3400 MHz and 3800 MHz, and currently only a few countries allow spectrum to exceed 3800 MHz. For example, the United States has two frequency bands, one is an unlicensed/shared frequency band from 3550 MHz to 3700 MHz, and the other is a frequency band from 3700 MHz to 4200 MHz, which is suitable for 5G NR below 6 GHz. Although not necessarily relevant, many countries have worked hard to open up additional spectrum at 600 MHz and 700 MHz frequencies for wireless telecommunications (television white space). In the United States, this has become two 35 MHz licensed spectrum segments and 14 MHz unlicensed spectrum. It can also be used in mobile phones and fixed wireless devices and 5G NR bands below 6 GHz.
Several major modem chip suppliers have developed 5G NR modems below 6 GHz, and some can even facilitate non-independent millimeter wave 5G communications. Since sub-6 GHz technologies do not require beamforming and beam steering techniques to overcome the high RF path loss and atmospheric attenuation experienced by millimeter wave frequencies, the main focus of providing enhanced performance for 5G NR below 6 GHz relies on a large number of MIMO and carrier aggregation technology. These two capabilities require a large number of antenna elements with different RF paths, as well as the ability of RF front-ends and modems to work simultaneously with several traditional and new 5G NR bands. In order to achieve multi-user MIMO (Mu-MIMO) and carrier aggregation, many modem chips and a large number of radio frequency routes are required. In addition, to use this high-speed modem, a high-speed digital interface operating at a speed of several Gbps must be used. Although most of these new sub-6 GHz modems/radios/antennas are ideally integrated, a large number of RF/high-speed ports and paths have been brought in during sample making, testing, production, and even troubleshooting/maintenance Huge RF interconnection challenges.