High Speed Uplink Packet Access

High Speed Uplink Packet Access (HSUPA) is an upgrade to UMTS-HSDPA that uses the Enhanced Dedicated Channel (E-DCH) to constitute a set of improvements to optimize uplink performance. These improvements include higher throughput, reduced latency and increased spectral efficiency. HSUPA was standardized in 3GPP Release 6 and combined with High Speed Downlink Packet Access (HSDPA), is commonly referred to as High Speed Packet Access (HSPA). In other words, Release 5 HSDPA upgraded to Release 6 HSUPA is considered mobile broadband HSPA.

HSUPA results in an approximated 85 percent increase in overall cell throughput on the uplink and an approximated 50 percent gain in user throughput. HSUPA also reduces packet delays. HSUPA improves HSDPA uplink speeds from 384 kbps to a peak theoretical network rate of 5.8 Mbps while providing 14 Mbps peak theoretical network rates on the downlink. Many operators initially launched HSPA at the peak rates of 3.6 Mbps, and have upgraded their networks to 7.2 Mbps. At the end of 2008, many notebooks were supporting HSPA at 7.2 Mbps downlink with 2 Mbps uplink, in addition to EDGE. In fact, more than 83 percent of UMTS-HSPA devices with speeds of 3.6 Mbps or higher also support EDGE technology (GSA, May 2009 survey).

Today, typical HSPA downlink user achievable rates are 1 to 4 Mbps and typical user achievable HSPA uplink speeds are 500 kbps to 2 Mbps. Theoretical peak speeds are significantly higher at 14.4 Mbps on the downlink and 5.8 Mbps on the uplink in a 5 MHz channel. Further evolutions of the technology to HSPA+ will deliver peak throughput rates of 21 Mbps and later 42 Mbps through techniques such as dual-carriers and MIMO antenna systems.

HSUPA was first commercially deployed by Mobilkom Austria in February 2007. As of May 2009, there were 77 commercial HSUPA networks with an additional 92 planned. It is expected that all UMTS networks will evolve to HSUPA-HSPA.

HSUPA achieves its performance gains through the following approaches:

• An enhanced dedicated physical channel
• A short Transmission Time Interval (TTI), as low as 2 milliseconds (ms), which allows faster responses to changing radio conditions and error conditions
• Fast Node-B-based scheduling, which allows the base station to efficiently allocate radio resources
• Fast Hybrid Automatic Repeat reQuest (HARQ), which improves the efficiency of error processing. The combination of TTI, fast scheduling, and fast HARQ also serves to reduce latency, which can benefit many applications as much as improved throughput. HSUPA can operate with or without HSDPA on the downlink, though it is likely that most networks will use the two approaches together. The improved uplink mechanisms also translate to better coverage, and for rural deployments, larger cell sizes.

HSUPA-HSPA is an upgrade to UMTS networks that usually requires only new software and base station channel cards, instead of necessitating the replacement of major pieces of infrastructure. As a result, operators can deploy HSPA quickly and cost-effectively. Vendors, 3G Americas and many analysts expect that virtually all of the operators who deploy UMTS will also choose to deploy HSPA and in fact, most new deployments are HSPA-ready today.

HSPA also benefits operators by making more efficient use of spectrum: up to three times more capacity than UMTS. This efficiency means that operators can easily and cost-effectively accommodate more users and services without having to buy additional spectrum just to keep up with growth. That efficiency also reduces operators' overhead costs, and thus makes them better able to price their HSPA services at a point that is competitive yet profitable.

HSPA is backward-compatible with UMTS, EDGE and GPRS. This design benefits customers when they travel to areas that haven't yet been upgraded to HSPA, as their HSPA-enabled handsets and modems will still provide fast packet-data connections. This design also benefits operators and application developers because applications designed for UMTS also run on HSPA networks.

HSPA benefits from the scope and scale of the GSM ecosystem of vendors. Vendors currently offer more than 1,300 models of HSPA devices at a variety of price points. Besides handsets and PC card modems, HSPA is also embedded in many laptops from major vendors such as Acer, Dell, Fujitsu Siemens, HP, Lenovo and Panasonic. HSPA devices also are available at most GSM frequencies, enabling global roaming.