tes 50/km2 5G at Spectrum Per operatorin >50 GHz [MHz] downlink 5G at 24- >1 Tbps 3000 MHz 39 GHz 5G/LTE 800 MHz 100 Gbps sub-6 GHz 200 MHz 10 Gbps today 1-2 Gbps 50 MHz Site density [/km2] 30/km2 50/km2 150/km2 300/km2 Figure 10.66 Maximum traffic density per km². 10 5G Performance Setups per second per site 100 000 10 000 IoT activity frequency [second] Figure 10.67 Signaling transactions per base station per second. 10.12 Ultra-Reliability for Mission-Critical Communication The quality of the radio connection has a major impact on the overall system reliabil- ity and latency. SINR is used to measure the quality of the radio link. The higher the SINR, the lower the packet error probability, which results in higher reliability and lower latency communication. We will consider the technical solutions that can improve SINR values. 10.12.1 Antenna Diversity The increased number of antennas results in better coverage. 2TX2RX is commonly used in today's LTE networks, with some operators also using the 4TX4RX base station both in FDD and in TDD, and 8TX8RX in TDD. Some LTE networks utilize also massive MIMO with 64TRX. For the 5G system, significant diversity enhancements using a very large number of antennas can be utilized. 10.12.2 Macro-Diversity and Multi-Connectivity Mobility and handover are critical for ultra-reliability and low latency. The break-before-make method of LTE produces interruption times of a few 10 ms, which become an obstacle for reliable communication. Virtually zero interruption time must be the target for 5G, with make-before-break at every handover for always-available data connectivity. The main concept consists of multiple base stations transmitting synchronously the same information, which is then combined at the receiver. This helps combat shadowing effects, by means of diversity and redundancy, and increases the total received power of the desired signal. Multi-connectivity can also be obtained with Packet Data Convergence Protocol (PDCP) duplication. 10.12 Ultra-Reliability for Mission-