Why timing matters in 5G — TDD, CA, CoMP

TDD Synchronization Requirements

Time Division Duplex is the dominant duplexing mode for 5G NR in mid-band and mmWave spectrum. TDD requires all cells in a geographic area to switch between downlink and uplink transmission at precisely the same instant. If adjacent cells are not synchronized, one cell transmitting downlink will interfere with a neighboring cell trying to receive uplink, causing severe cross-link interference. 3GPP specifies that TDD cell phase alignment must be within plus or minus 1.5 microseconds to limit inter-cell interference to acceptable levels. This translates to a maximum time error of three…