CDMA Ev-DO At Large

As promised (and as I was hoping...), I already have some days of playing with the ADU 635 modem behind me. A short explanation. ADU 635 is a dual mode CDMA / GSM usb modem. I got mine from Orange.PL. Orange has a CDMA Ev-DO mobile data network running in the 450MHz band - the band they have had since the early 1990's, when analog NMT mobile network was operating there. Orange has a GSM - UMTS network too, so dual mode CDMA / GSM - UMTS device makes sense for them.

My personal goal wast to test the 450MHz Ev-DO network performance on the go. I often travel on a train from Krakow to Warsaw, and it usually takes three hours one way, so together this is six hours per day. Trains, operated by a state - owned company are not the state of the art and they do not have an on board broadband connection. So people (like myself) use cellular modems. These modems are GSM / EDGE / UMTS, but the UMTS network is not available along the way. EDGE is sometimes very bad (I assume this is when many people try to connect and all available timeslots are occupied) and sometimes bearable... But by no means Internet over the EDGE connection is comfortable. It is just painfully slow. At the same time MNOs do not rush to upgrade the network to UMTS / HSDPA along the railroad.

So I have had really high hopes for the new CDMA network. 450MHz cells are much larger, compared to 2100MHz UMTS cells. Because they are large and cover quite large area, they can be quickly filled up in highly populated urban areas. But they have perfect characteristics for scarcely populated areas outside cities. At the same time CDMA Ev-DO promises very good mobile data experience.

After I unpacked the ADU-635 modem, I found out it is more complicated than common USB "sticks". The modem itself is raughly the size of a cigarette pack. That is including the battery cradle it slips into. Yes, it has a battery of its own. No idea why... But it simply does not work on USB power. On the other hand when not connected, the battery charges form the USB port (or supplied charger). The software installation went pretty straightforward. Looking at the process of Windows "discovering" new devices, it looks like there are simply two USB modems inside (one for CDMA and one for GSM - UMTS) and a USB hub. The connection manager has a radio option for choosing either of the two connections. There is an "automatic" option too - it simply checks what networks are available. If classic GSM/GPRS and CDMA - it offers CDMA connection. If CDMA and HSDPA - it offers HSDPA (which by my tests not always has to be faster). The modem also has two antenna sockets - one for 450MHz CDMA and one for GSM/UMTS, and a small CDMA antenna with magnetic base is supplied.

So on Friday morning I took a windows seat and connected all the cables, battery and the antenna to my modem. When the train was still at the station, the connection was similar to what I experienced testing the Axesstel router at home a week ago. Roughly 1Mbps downlink and about 30% of that uplink. The train left the station and the connection stayed that way. Actually it was 80% of the time above 1Mbps. My jaw was dropping repeatedly... The train covered 300km and there was my personal 1Mbps connection over the entire trip. Web pages were very responsive. And I could watch YouTube clips in the background without interruption. The modem lost the connection three times. The first time when the train entered a tunnel and then when I played with it disconnecting the antenna. Unfortunately it had problems restoring the connection automatically, so I had to hang up and redial again... The good thing is the time to connect is quite short - about five seconds. This may be a problem on the network side, or in the modem's firmware, so I hope Orange or AnyData will have that fixed. Apart from that it worked flawlessly with really impressive data speed, in fact a mobile speed I have never experienced before for such a long time and distance.

The only downside I noticed is the ADU 635 does not support EDGE. While this may not be a big problem (as CDMA 450 should be available in most places), it is still hard to understand why...

I hope things stay that way... I will be testing the CDMA modem for the next couple of weeks, so if there is anything interesting to share, I certainly will (and there are things in the pipeline...). Stay tuned...