I had supposed that Apple took the opportunity to build HSUPA on the upstream side, at either 1.4 or 1.9 Mbps speeds that are supported in many European networks that have already rolled out 7.2 Mbps HSDPA. But it turns out, Apple didn't. . .
After my HSPA article ran, reader Nick Dunklee pointed out in e-mail that a teardown at RapidRepair of an iPhone 3GS shows that it has a UMTS/HSDPA chip. UMTS is the earliest 3G standard deployed on GSM networks, and it tops out at 384 Kbps. It's easy to test, if you have an iPhone 3GS. Go to any speed tester, like Testmyiphone when you're outdoors with a good signal. Downstream, you might hit well over 1 Mbps; upstream, under 384 Kbps.
HSPA (High Speed Packet Access) is actually two separate standards: HSDPA (for downstream) at a raw rate of 7.2 Mbps and HSUPA (for upstream), likely at raw rates of 1.4 Mbps or 1.9 Mpbs, the two most popular upload speeds deployed by existing 7.2 HSPA carriers. The 7.2 Mbps downstream and 1.4/1.9 Mbps upstream rates represent the full bandwidth available in a given HSPA channel, but don't translate to what an individual user will see.
For AT&T's current HSPA system, the company claims range from 700 Kbps to 1.7 Mbps downstream, and 500 Kbps to 1.2 Mbps upstream.
Dunklee examined the specs on a number of GSM network smartphones, and found none included HSUPA. It's possible that there could be a firmware update from UMTS to HSUPA, but thats unlikely. There's usually a reason for using an older standard, which is related to power consumption, chip size, or cost.Smartphones using competing CDMA technology, such as those on Sprint and Verizon, however, do take advantage of the full upstream capacity, suggesting that the limitation is related to the use of GSM technology as the basis for these cellular networks.