From GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband

3.11 High-Speed Uplink Packet Access (HSUPA)

Owing to the emergence of peer-to-peer applications like multimedia calls, video conferencing and social networking applications, the demand for uplink bandwidth is continually increasing. Other applications like sending e-mails with large file attachments or large MMS messages sent by a user also benefit from higher uplink datarates. UMTS uplink speeds have not been enhanced until 3GPP Release 6. Hence, for a long time the uplink was still limited to 64–128 kbit/s and to 384 kbit/s in some networks under ideal conditions despite the introduction of HSDPA in 3GPP Release 5. The solution to satisfy the increasing demand in the uplink direction is referred to as Enhanced Uplink (EUL) in 3GPP. In the public, the feature is referred to as High-Speed Uplink Packet Access (HSUPA). HSUPA increases theoretical uplink user datarates up to 5.76 Mbit/s in 3GPP Release 6 and 11.5 Mbit/s in 3GPP Release 7. When taking realistic radio conditions into account, the number of simultaneous users, mobile device capabilities, etc. user speeds of 1–2 Mbit/s and beyond are reached in practice today.

For the network, HSUPA has a number of benefits as well. For HSDPA, an uplink DCH is required for all mobile devices that receive data via the HSDSCHs for TCP acknowledgements and other user data. This is problematic for bursty applications as a DCH in the uplink direction wastes uplink resources of the cell despite the mobile device reducing its power output ...