Full Speed

HSDPA vs. UMTS

With all of the new cellular standards and acronyms, I have been in the dark about a couple of things. Specifically, HSDPA and UMTS. If you don’t know what these are and don’t care to learn about them, you will probably want to stop reading now. :) I know that these are both high(er) speed wireless communications protocols. That was the easy part. I also know that they are both faster than EDGE, a protocol that I have frequently used with cellphones in times of broadband outage.

Now this question isn’t something that I have been really racking my brain on. It’s just been a curiousity lingering in the back of my mind that surfaces whenever I read about the fancy new phones that are becoming available. It seemed to me that the two acronyms were often loosely interchanged. And without digging around to find the differences, I was beginning to think that they were the same thing.

Finally, I posed a question to a couple of fellow Engadget Mobile readers tonight. And as I typically do, I hammered it out and clicked submit before even thinking about doing a tiny bit of research.

So, within five minutes, I found myself on Wikipedia reading about all of the gory details of HSDPA, or High-Speed Downlink Packet Access. I found that I already knew some of this information, such as the fact that the protocol supports downlink speeds of up to 14.4 Mbit/s. (Wow!)

The real benefit for me from the Wikipedia article on HSDPA was mostly in the first paragraph:

HSDPA provides a smooth evolutionary path for Universal Mobile Telecommunications System (UMTS) networks allowing for higher data capacity. It is an evolution of the W-CDMA standard, designed to increase the available data rate by a factor of 5 or more. HSDPA defines a new W-CDMA channel, the high-speed downlink shared channel (HS-DSCH) that operates in a different way from existing W-CDMA channels, but is only used for downlink communication to the mobile.

Whew! In addition to the above, the UMTS page on Wikipedia says that UMTS “uses W-CDMA as the underlying standard.” Ok, so I’m seeing this as a progression: WCDMA→UMTS→HSDPA. The newer standards are evolutions of the older standards, using and expanding upon previous protocols. Elsewhere, I confirmed the following:

HSDPA is compatible with EDGE and is fully backwards compatible with WCDMA, and enterprise and rich multimedia applications developed for WCDMA will work with HSDPA. Most UMTS vendors support HSDPA.

So here are my conclusions:

1. HSDPA and USDPA devices should work on WCDMA networks and will possibly work on UMTS networks.
2. HSDPA devices should work on a UMTS network, but the reverse is not true.
3. HSDPA is blazing fast
4. As with most other wireless systems here in the US, we use different frequencies than other parts of the world. Don’t count on your shiny new phone to work with one of these 3G protocols both at home and in other parts of the world.
5. If given a choice, pick an HSDPA device.

These conclusions may be a bit off, but I feel that my questions have been answered. I didn’t get into EV-DO, as that is a protocol that isn’t offered by the GSM providers here and thus isn’t an option for me. Cingular is said to be planning to offer the Samsung SGH-ZX20 in the near future. That is looking like a winning option for early adopters and bandwidth freaks.