  While fifth-generation (5G) communications are being rolled out around the
world, sixth-generation (6G) communications have attracted much attention from
both the industry and academia. Compared with 5G, 6G will have a wider
frequency band, higher transmission rate, spectrum efficiency, greater
connection capacity, shorter delay, wider coverage and stronger
anti-interference capability, so as to meet the various network requirements
for industries. In this paper, we present a survey of potential essential
technologies in 6G. In particular, we will introduce artificial intelligence,
intelligent surfaces, terahertz communications technologies in detail, while
giving a brief introduction to other potential technologies, including visible
light communications, Blockchain-enabled wireless network, advanced duplex and
holographic radio.
