Selasa, 09 Juni 2009

Wireless Modems Technology - by Hank Volpe

Sometimes I feel so left out. All my friends seem always to be connected. Instant messaging to phones, blackerry e-mail, you know the drill. Of course, since most of my time is spent in front of a traditional computer, I miss the reasons for staying so tightly in touch. Those who travel for work realize how much more productive they are when connected. So much time is wasted just waiting to get on a plane, and unfortunately most hotels still lack high-speed internet connectivity (or charge quite a bit for it). Finally, just lugging the laptop past security, on a plane, off the plane is a pain.

The big problem with going wireless is speed. For e-mails, the blazing 19.2 kb you get with a traditional cell phone data connection is fine. But most road-warriors handle documents, and documents need bandwidth. There are complete solutions for broadband access from companies, but that access is generally limited to major metropolitan areas or airports. The speed on these devices is also worse than lower-end residential DSL. Plus, the number of users on sharing an access point cause bottlenecks...and most of these solutions still require you carrying your laptop with you. There is a new technology coming soon that will greatly improve wireless data access.

High-Speed Downlink Packet Access (HSDPA) is rolling out nationwide (right now only in "select cities). HDSPA is a 3.5G ( "3½G") standard. Since it is packet-based, it can be easily routed and bandwidth can also be balanced. Tests show downlink speeds in the 6-8 Mbit/sec range. The technology can be adapted to MIMO systems using OFDM. OFDM coding and MIMO receivers effectively get rid of data-transmission "ghosting", which reduces errors and the re-transmission of data to correct errors. In MIMO systems, speeds near 20 Mbit/sec have been achieved over 3G mobile telephone networks. However, before you think your getting a cable modem in your hand, remember these are theoretical and don't account for potentially hundreds of users on-line simultaneously shipping packets here and there. In the "real" world, you could see 400kb/sec - 760kb/sec speeds...again like low-end DSL. However the difference with HSDPA is you are not tied to a propriety broadband network in an airport or city. HSDPA will be nationwide and part of the cell phone network. Eventually phones will handle HSDPA, bringing fast access into your hands. You can finally leave your laptop home!

Check with your cell phone carrier to see when HSDPA will be available. Cingular Wireless has announced plans to use Novatel Wireless's Merlin U730 PC Cards.

If you're interested in HSDPA, you can find some good background on at Lucent . Alcatel has a background file on the evolution of 3G networks to HSDPA. Finally, there is a good overview of HDSPA and 3.5G on the Mobilecomms/Technologycomms website.

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