(High Speed Downlink Packet Access): is the optimisation of the UMTS/WCDMA spectral technology through a new shared downlink channel, which significantly improves the maximum transfer capacity of information. It can reach speeds of up to 20 Mbps. It is an evolutionary upgrade of the third generation (3G) of mobile technology, known as 3.5G. It is regarded as the step before the fourth generation (4G).