Next-gen packets

Boosting 3G downlink data rates

Svetlana Josifovska, Correspondent, EDN Europe/UK -- EDN, 11/1/2004

While 3G rollouts are just getting started, new technical updates continue to brew. At the 3GSM Congress in Cannes this year, the tongue-breaking HSDPA (High-Speed Downlink Packet Access) received frequent mention. HSDPA is a packet-based data service that enhances the downlink portion of mobile data transmission. (On the horizon there's also EUDCH, Enhanced Uplink Data Channel, for the uplink).

HSDPA is used within the WCDMA downlink (5-MHz bandwidth), offering a maximum data-transmission rate of up to 10 Mbps, with actual average rates somewhere between 4 and 8 Mbps. Further upgrades promise to take those rates to 20 Mbps. HSDPA aims is to offer higher data speeds and consistent QoS (quality of service). It also offers simultaneous delivery of voice and data to the same receiver.

Technically, HSDPA can be implemented mostly through software. However not in all cases, as various adaptations have to be made to the 3G base stations and handsets. These include the use of adaptive modulation and coding (AMC), hybrid automotive request (H-ARQ), fast cell search, and a MIMO (multiple-input multiple-output) antennas. HSDPA also mandates a switch to 16-QAM modulation, as opposed to the QPSK typically used in WCDMA.

HSDPA comes from the Third Generation Partnership Project (3GPP), the organization that controls the WCDMA specification. The group expects to include HSDPA in the spec's fifth release, with Release 6 containing the antenna adaptation. Release 4 provides the enhanced Internet Protocol (IP) support.

Some companies, including Agilent and UbiNetics, are offering HSDPA test systems now, and picoChip is offering an HSDPA base station reference design. On the silicon side, Bell Labs, Qualcomm, and Nokia are just a few of the firms working on this technology.