Slashdot Mirror
Vanu Replacing Cell Tower Equipment With PCs
Dwight Schwartz writes "As reported in an
article on the ScienceDaily site, researchers from
Vanu, Inc. of Cambridge, MA,
have successfully tested a system, the Vanu Software Radio(tm), that can replace a cellular tower's room full of communications hardware with a
Pentium-based computer running Linux. The system
offers the hope of making cellular technology more affordable for small, rural communities." The systems have been tested for the last several months in parts of Texas, with wider adoption planned for the near future.
Have a look at the original release from the US National Science Foundation. With some nice pictures. :-)
GSM is pretty low-bandwidth stuff (around 13kbps). Further, the line cards handle a lot of the framing and general cookery for the interconnects (whether it's a wired E1, or microwave, or whatever). So even a fairly low-end Pentium would handle a few calls. The article does say that it needs a fairly large Linux server, but an ordinary PC would work for a relatively small node. The Digitalk telephone switches we use are really just dual PII-500 machines, and they handle 120 simultaneous wired calls.
Because according to the article (as well as the writeup for this topic), they are targeted for rural communities, wehere by definition the towers will be so far apart that service will be entirely lost for that area because there will not be another tower close enough to pick up the slack....
--guru
I'm originally from Stephenville, Texas - just down the road from these two communities. There are no third-generation networks available out there. My Sprint PCS phone doesn't work there, either - not even in analog mode. But just 20 miles away I have full signal strength in Vision mode.
I still have some friends in the region using Mid-Tex, and they haven't mentioned anything odd about their service. I guess that means it's a success as far as consumers are concerned.
I'm a student of telecommunications at an university of technology in Finland, and we've had compact basestations gathering dust at a student lab facility for _years_. (one Nokia and one Siemens, if I remember right)
The unit was about two mid-tower cases of volume, had an integrated PC, integrated antennaes, the whole bunch. Everything you need for a GSM basestation. And it really is an old model. Modern models are at least more efficient (with directional tracking antennaes, etc) and more inconspicious (they can look like fake chimneys, parts of wall, etc, so that it doesn't disturb the landscape.)
Probably we're not even talking about the same things since calling a basestation unit a "tower" is ridiculous. Maybe they've replaced the switching centre with a PC? Though I doubt it, since a PC/Pentium would be severely bandlimited to handle thousands of connections. Perhaps with dedicated hardware which is merely controlled by a PC..
The poster should have included this link (pdf) - much more interesting.
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Incremental repeaters are already available. They must be low enough power to fall beneath the regulated power levels of the FCC, generally not more than 4-5 watts, I think.
aceteq.com has some good repeaters, even the 1900 mhz repeaters for US GSM for less than $800. Other systems can be $3000 or more, and can cover larger areas (I've seen some that were capable of 25,000 sq ft.)
So you would have to do a running line of small repeaters to get service to an area, similar to the 802.11 repeaters we've seen here. You might be able to convert it to line-of-sight and do it that way, too.
But the short of it is, it can be done, albeit somewhat expensively.
I'm CTO at Vanu, Inc. Here's some additional info that some posters to this thread have asked about.
- Linux version: we're using a Debian 2.4 release with the real time patches. All the signal processing code runs as an standard application level process.
- A/D and D/A: we're using an external RF front end that provides over 90 dB spurious free dynamic range. The poster who said these are big and hot was right; it's a little smaller than a PC case all by itself, with a hefty fan to dissipate the heat of the power amp. It covers 25 MHz worth of spectrum and costs a lot more than the HP server that does the signal processing.
- software features: the linux applications running on the HP server handle the complete transmit and receive chains. We go from raw digital samples on one side (exchanged with the A/D and D/A converters) to voice and data packets on the other. A separate HP server runs the Base Station Controller functions, which are the protocol logic, handover control, and similar functions.
- reliability: a huge advantage of building the GSM software on top of linux is that it's portable. Some operators want the level of reliability that comes with commercial grade servers; some want the level that comes with telco grade servers. The GSM basestation software runs on whatever they need.
It's great to see how much interest there is in the slashdot community about this.
-john chapin