Friday, September 23, 2011

How far can you go?

Being able to walk in the office and talk is a great thing! But how far can you go? Because DECT is relatively new in the USA there are many misunderstandings in this area. Marketing always loves to print hard numbers in the datasheet. But it dep0ends a lot on where you put the devices and what material is in the middle. Generally speaking, metal and concrete are a problem. If there is just the air between the base and the handset, you can go pretty far (maybe even 300 yards), but this is just the most optimistic case. Even one yard might be a challenge if you have a 13 inch metal from the Bismarck world war II battle ship armor plating between the base and the handset. So I did a couple of field trials. Here is my report.

In our office, if I put the base station in the middle, I can pretty much go anywhere, even outside where the restrooms are (if I have to; but watch out when flushing the toilet, people might notice). Of course we have a lot of electronic gear in our office, and I am sure our neighbors upstairs and downstairs too. But that does not seem to be a problem as DECT uses a different frequency as WLAN. As soon as I go into the elevator, the game is over. The metal of the elevator seems to keep the signals out and the conversation ends. I guess we all know this problem from the cell phone world. Surprisingly, when leaving the building I am picking up a signal again, and I can even go to the mall, which is like 100 yards away, and even after going inside I still have a signal (though the voice starts to break up). Walking a few more yards, that’s it and the connection is lost. So for the office the bottom line is: as long as I stay in the office everything is good; it ends at the elevator. Maybe in summer I could also sit outside and get a few phone calls done. I would say our office is 50 yards long and has up to seven drywalls between the base and the handset.

At home, things are easier. Thanks to the US building style (wood and drywall) we have perfect reception everywhere in the house, even in the basement. I can even hang out in the neighbor’s garden and have a beer while still connected to the base at home. No problem there.

If you are living in an apartment, things might get more difficult. Usually there is a lot of concrete and steel in high rise buildings; at least for the floors. For the floor that’s a feature because your neighbors will not be able to register with your base (see my blog about the PIN code). Unless you have the luxury that your apartment covers several apartments there is no problem. Usually inside the apartment there is not too much concrete being used, so there is also no problem. Actually I believe the designers of DECT had the case in mind that a whole high-rise apartment building is using DECT in every apartment and they still want to be able to provide service to all of them. A too strong signal would be counterproductive.

I had a case with a house that had concrete floors and where the DECT base was in the basement. The signal was very weak in the first floor already, and the second floor was completely dark. Anyway, WLAN did not make it even to the first floor. Putting the base in the first floor solved the problem.

1 comment:

  1. IMHO the outdoor range is actually the more accurate benchmark for the radio signal strength of a DECT base station. The indoor range can always have restricted coverage, not due to the antennae, but more so due to the network topology or the building material used.