n78 (3500 MHz)

n78 (3500 MHz), or commonly referred to as TD 3500, 3.5 GHz 5G band, or C-band 5G, is the most commonly tested and deployed 5G frequency. The n78 band's popularity is due to its relatively common availability, with lower cellular spectrum already in use by 3G and 4G networks.

Performance objectives of the 5G standard require large blocks of contiguous spectrum in order to operate large channel widths. With spectrum an extremely valuable resource, operators have had little choice but to implement 5G NR on higher cellular bands. The 3.5 GHz band has been historically used in small, adhoc WiMAX and WTTx multipoint networks. Many countries requested smaller ISP operators to vacate spectrum from 3300 to 3800 MHz ahead of national auctions to reallocate the band for 5G services.

n78 coverage is naturally limited by the propagation characteristics of the higher frequencies, however the effect has in some ways been mitigated by advanced processing techniques such as massive MIMO, beam-forming, and beam-tracking. Observed propagation has been reported to be similar to early B3 (1800 MHz) 4G networks. The shorter wavelength does have the advantage of making 5G's complex antenna technologies (such as 128T128R) more compact and hence more feasible to deploy.

Early n78 networks such as those deployed prior to spectrum auctions have used smaller channel widths. The most popular channel width for fully deployed n78 5G networks is the maximum 100 MHz.