[UPDATE: AT&T claims, on their Facebook page, to have "implemented an alternative" somehow that "provides normal 3G uplink speeds and consistent performance for affected customers." Is it true? Post your results in comments.]
According to a statement just released by AT&T, the cause of the widely-reported slowdowns in iPhone upload speeds has been traced to a software defect in particular cell-site gear. The problem with Alcatel-Lucent UMTS base stations that they say "impacts less than two percent" of all AT&T customers "under certain conditions." There is a fix coming, the company says, but won't say when, other than that there is a "definite timeline" for it. Somehow, however, they claim to be providing "normal upload speeds" anyway.
The upload speed crunch was noticed starting late last week in some larger cities, with reports pouring in from less-populated areas as the holiday weekend wore on. iPhone 4 users that had been enjoying uploads in the mid-1.5 Mb/s range were suddenly seeing performance throttled to 100 kb/s. Other users in the same geographic areas were seeing no effect, leading to the conjecture that the problem was relegated to particular cells. Today's statement, apparently sent to everyone who inquired with AT&T corporate communications about the issue, confirmed that, saying that firmware on Alcatel-Lucent equipment was to blame for problems.
AT&T and Alcatel-Lucent jointly identified a software defect -- triggered under certain conditions – that impacted uplink performance for Laptop Connect and smartphone customers using 3G HSUPA-capable wireless devices in markets with Alcatel-Lucent equipment. This impacts less than two percent of our wireless customer base. While Alcatel-Lucent develops the appropriate software fix, we are providing normal 3G uplink speeds and consistent performance for affected customers with HSUPA-capable devices.
thanks to yoTelefono "Quatro" for the tip.