Page "High-Speed Downlink Packet Access" Paragraph 9

The modulation scheme and coding are changed on a per-user basis, depending on signal quality and cell usage.

The initial scheme is Quadrature phase-shift keying ( QPSK ), but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates.

With 5 Code allocation, QPSK typically offers up to 1. 8 Mbit / s peak data rates, while 16QAM offers up to 3. 6 Mbit / s.

Additional codes ( e. g. 10, 15 ) can also be used to improve these data rates or extend the network capacity throughput significantly.