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Saturday, November 6, 2010

Cellphones in Tall Buildings

Metropolitan might have discovered that cellphone reception at 40 to 50 stories above ground level is generally poor. This is not surprising. Cellphone reception at street level is usually better as most cell-site antennas beam downwards. It makes perfect technical and business sense as majority of customers make phone calls and use mobile internet when they are stationed at level 5 or below. 

If you pay attention to the outdoor cellphone antennas around town, you can noticed that they are usually physically tilted downwards. Even if the tilting angle does not appear to be significant, they are electrically beamed downwards (controlled by computer programs). These antennas are usually installed on the tall buildings in the suburb.
Antenna tilting downwards

Since most of us make phone calls and use mobile internet when we are at street level, mobile network operators install antennas (cell sites) at locations that offers the best street coverage. If most buildings in that suburb are around 5 to 10 stories, the cell site antennas would usually be at that level. If most buildings are at 20 to 30 stories, additional antennas are installed at these levels. If you are stationed at the only 70 stories skyscraper in town, your cellphone reception might be poor, unless indoor micro-cells were installed. Micro-cells are low-power site intended to serve customers within that building only, as it not energy efficient to transmit radio waves from the top of a 70 stories building into free space (ie. open air space with virtually no customers).

The billboard stole the attention from the antenna.
The other reason is the potential health risks and the general public's concern of health risks. Installing a extra high power transmitter at a mountain top that constantly beams strong signals to every cellphones in town would require a lot of power; and poses a health risks to the residents near that mountain. No body likes to have or likes to know that there are cell phone transmitters around where we work or live. Although every cell sites are designed to transmit and receive at safe (health wise) power levels, the feeling of having a transmitter around us make most of us uncomfortable (at yet ironically we are happy to put a transmitter, the cellphone, right next to our brains all day). It is a challenge to address the public's concern and provide good cellphone reception at the same time. Providing good cellphone reception to 20 to 40 stories apartment blocks is always a big challenge as residence would often rejects installing cell site on the top of apartment buildings.

Your cellular network operator is trying their best to install cell sites at key locations that makes technical, energy and business sense. They care about your concerns and tried their best to hide the transmit and receive antennas from your sight. Let's hope they can keep the cost down at the same time.

Can you find the hidden antenna?