Q&A: HSUPA
What is HSUPA?
What are the main benefits of HSUPA?
When will HSUPA be available?
Where does HSUPA lie in the GSM evolutionary path?
What is HSUPA?
As the use of IP-based services increases, so does demand to improve coverage and throughput as well as reduce uplink delay. 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 is standardized by the 3GPP in Release 6.
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What are the main benefits of HSUPA?
HSUPA increases UMTS upload speeds from 384 kbps to peak user-achievable throughput rates well over 1 Mbps, three times faster than Release 99. These speeds will increase over time with enhanced terminals and network capabilities. HSUPA will result in an approximately 85 percent increase in overall cell throughput on the uplink and an approximately 50 percent gain in user throughput. HSUPA also reduces packet delays.
The increased throughput and latency speeds provided by HSUPA will enable a wider range of data applications, including IP Multimedia Subsystem (IMS) and voice over IP (VoIP). Applications that can benefit from an enhanced uplink include services like multimedia and video, e-mail, gaming, video-streaming, VoIP, and more.
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, 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 (ARQ), which improves the efficiency of error processing
The combination of TTI, fast scheduling, and Fast Hybrid ARQ also serves to reduce latency, which can benefit many applications as much as improved throughput. HSUPA can operate with or without HSDPA in 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.
The same upgraded or enhanced UMTS radio channel can support a mixture of terminals, including those based on 3GPP Release 99, Release 5, and Release 6. In other words, a network supporting Release 5 features (e.g., HSDPA) can support Release 99, Release 5, and Release 6 terminals (e.g., HSUPA) operating in a Release 5 mode. Alternatively, a network supporting Release 6 features can support Release 99, Release 5, and Release 6 terminals. This flexibility assures the maximum degree of forward and backward compatibility.
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When will HSUPA become available?
HSUPA user devices and services are expected to be commercially available in 2007.
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Where does HSUPA lie in the GSM evolutionary path?
HSUPA is part of a long, clearly defined, standards-based evolution. It is the next major step after UMTS enhanced with HSDPA. HSDPA and HSUPA increasingly are referred to by the catch-all term “HSPA” because they complement each other. Operators typically will upgrade their networks to HSUPA even as they continue to upgrade their existing HSDPA infrastructure to support peak download speed of 3.6 Mbps, 7.2 Mbps and beyond. This approach means that HSDPA/HSUPA devices and networks will provide increasingly fast upload and download speeds. That near-symmetry is important for users who send large files as often as they receive them and for bandwidth-intensive applications such as videoconferencing.
After HSPA, the next major step is Long Term Evolution (LTE), which is expected to be commercially available by 2009. LTE is being designed to support peak download rates of 100 Mbps and peak upload rates of 50 Mbps. LTE also will feature all-IP network infrastructure.
For more details about HSUPA and LTE, see the September 2006 white paper “Mobile Broadband: EDGE, HSPA and LTE” and the July 2006 white paper “Mobile Broadband: The Global Evolution of UMTS/HSPA – 3GPP Release 7 and Beyond.”
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