Since T-Mobile USA and its iPhone customers are in a bit of a quandary, I propose a potential option that would allow their iPhone customers to obtain HSDPA speeds without having the fully compatible HSDPA radio spectrum.Wikipedia
states that, "EDGE can carry data speeds up to 236.8 kbit/s for 4 timeslots (theoretical maximum is 473.6 kbit/s for 8 timeslots) in packet mode and will therefore meet the International Telecommunications Union's requirement for a 3G network..." That is a higher theoretical maximum than HSDPA's 384kbps theoretical maximum for uploading. And even at the lower 236.8kbps it is still fast enough to HSDPA's upload rate to maintain iPhone users on T-Mobile's network.
What I am proposing is that—once T-Mobile USA gets their 3G network up and running—T-Mobile customers can use the the compatible 3G 2100MHz band for downloading data and their compatible EDGE bands for uploading. On the surface, this appears to me as only a firmware update. GSM and UMTS radios already run independently and are used with in conjunction with each other. Similar to when one is using Safari via WiFi on the iPhone while also on a call; I believe this is how 3G capable devices are able to browse the internet while making a call.
The Pros I see here (if possible) are that using EDGE for the upload could reduce the UMTS chip's load thus making the device more power efficient. It may also be slightly faster processing the data as there are now an independent chips sharing the uplink and downlink data loads.
The Cons I see here (again, if possible) that the system may have issues shuffling both tasks adequately across each platform, though the iPhone does a great job of mixing WiFi and GSM and switching between EDGE and WIFI as needed. If you were using your GSM bands for uploading you would loose the ability to make calls while downloading at 3G speeds over HSDPA.Disclaimer: My knowledge of cell tech is quite recent and is mostly beget by the clever posters on AI schooling me since the iPhone was announced. If my premise is completely hare-brained feel free to berate me all you want, but I encourage you to make clear how and why it is incorrect.