Wednesday, May 28, 2008

HSUPA Joins HSDPA for Cellular Broadband

AT&T is nearly finished building out its upgraded cellular broadband network called HSPA or High Speed Packet Access. Just in time, too. The new BlackBerry Bold and the rumored iPhone upgrade will make good use of the higher data bandwidths that are now online at the cell towers. While most of the attention has focused on the download link, AT&T has quietly been upgrading the upload link also. What does this tell us about the next generation of mobile applications?

HSPA is part of the alphabet soup that is mobile technology. It's a network upgrade to the first installation of high speed cellular data for GSM networks. EDGE or Enhanced Data rates for GSM Evolution was good for jump starting applications such as video and music downloads, email, and Web browsing. But with speeds at the low end of what is available from DSL, around 230 Kbps, EDGE starts to feel noticeably poky for general Web browsing and streaming video. The HS in HSPA implies something much faster.

There are actually two pieces to the HSPA puzzle. HSDPA is the first and most important for most users. HSDPA stands for High Speed Download Packet Access. The download link has a maximum capacity of 14.4 Mbps or somewhere between 1 and 7 Mbps in practice. It's a huge improvement from EDGE and similar to Cable broadband speeds. Like most data links designed around Internet access, the uplink speed is much less. For HSDPA, it's 384 kbps maximum. That's perfectly acceptable if most of what you do is request Web pages, corporate data packages, software upgrades, email, music and video. The uplink requests are relatively small and infrequent. The big data blast is on the download link.

AT&T has pretty much completed its upgrade to HSDPA and now in the process of adding the second piece of the HSPA service, HSUPA or High Speed Uplink Packet Access. What HSUPA does in increase the uplink capacity from 384 kbps to a range of 500 to 800 kbps out of a maximum theoretical value of 5.76 Mbps. That complements AT&T download speeds of 1.4 Mbps.

Why bother upgrading the uplink? You don't need it for casual Web browsing, but it does have value for uploading larger files or running real-time applications such as mobile video conferencing. It also speeds things like posting to blogs, updating Web sites, or sending photos with high resolutions or video clips. Our impression that the nature of mobile services is changing is confirmed by wireless network upgrades such as HSUPA.

HSPA gives AT&T a fully functional 3G network, just in time to start working on further upgrades to 4G. HSPA has an evolutionary path called HSPA+ that increases downlink speeds to 42 Mbps and uplink speeds to 22 Mbps. Whether that path will be fully exploited remains to be seen, as AT&T is also committed to another technology called LTE or Long Term Evolution that ramps up the data bandwidth to 300 Mbps on the downlink and 75 Mbps on the uplink. This technology won't be fully deployed for at least a few years, giving us time to come up with HD video and other applications that can make good use of these incredible 4G speeds.

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