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Hello,
Does anyone have any opinions if a distributed antenna system would actually work for wifi. It has been used for many years in a cellular and paging application. Probably due to the massive output power from the BDA in access of +80 dB.

My understanding is that they could only connect to one port of the AP to goto several antennas seperated by RF splitters.

Could this actually work? They are using this at Atlanta and Salt LAke airports.

google: DAS + atlanta airport

Any replys would be greatly appreciated.

Regards,
Darth802

Hi darth802

I have worked with DAS' and they can work - if the design is right. The customer must be educated on the RF propagation characteristics associated with WLAN DAS, compared to those that are just Cellular only. A site survey or assessment is a must, because there are many variables with a DAS...it requires a proper PPDIOO proccess.

It all depends on :

1- Budget--- What is the customer willing to pay for the WLAN DAS?....expense of the backbone infrastructure coax, UTP and fiber installation is what sometimes can be a shocker. Also the amount of antennas you need for reliable WLAN coverage compared to Cellular only, is almost doubled especially if you are looking at VoWLAN then look at tripling that.

2- Applications--- RF frequencies for transport of technologies in Wifi from 2.4 GHz to 6GHz require no coordination, but if cell is riding over the DAS system, you have to get carrier buy in , or be willing to pay to have the cell services ride the DAS. (Prepare your budget for the latter).
And carriers coming on board to support the DAS takes time.

3- Scalability---A DAS is not scalable to 802.11n at this present time.

The biggest factor is the transport mechanism which can be coaxial and or fiber based.

The best approach in my opinion so far is a a hybrid of the two.

I have designed and installed systems using MobileAcccess Networks. They do a hybrid DAS that works very well. They place the access points in the telco closets (for security) and push the signals over the coax through a "smart RF switch" that allows you to do some shaping of the signals to cover certain areas in a unique way. The access points you use have to have an external antenna connection to attach to the RF smart switch.

There are other vendors out there beside MobileAccess www.mobileaccess.com , that make DAS equipment


Some of the big ones are:

LGC Wireless
InnerWireless
PowerWave
Andrew
ADC
EMS

etc. etc, etc.

With converged networks on the horizon, a DAS can be a good thing...if your budget can handle it. ;)

what do you mena with DAS? Distributed Antenna Systems?

go to www.xirrus.com that AP uses an Antena Arrays like celular.....