Why does the basic geographic unit of mobile cell in cellular system have a hexagonal shape? What is the height of this hexagonal cell? :)
Mobile phone cell area.
BTS cell. ( Base station transceiver )
What is the height of this hexagonal cell? :)
Good Answers (9)
Sandeep C.
Sr. Solution Architect / Head of Mobile at Ironroad AB
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Hi Jayaprakash,
I didn't get the place to attach the image that shows about hexagonal shape.
so i have written the answer in detail in my blog ... from there you can refer the answer.
http://mobi-solutions.blogspot.com/2010/04/magic-behind-operatorcell-towerbts.html
I think linkedin should give a option in Q&A to upload a image.
Let me know if you have any questions on this after going through the given link.
- Sandeep Choudhary
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Geoff F.
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Basic geometry - Hexagons tile, all sides matching those of adjoining hexagons. In truth though, it's not a hexagon but interlinking circles. It simply works best to show the towers principle area of responsibility as a hexagon. A pattern of circles intersecting yields a hexagon, in fact if you remember grade school geometry, this was one of the exercises you had.
I'm not sure what you mean by "height" but the area that a tower can handle has to do with terrain.
Tibby B.
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I was/ am and early cellular telecom nerd. The questions is not "exact" enough to answer...
In tech diagrams and renderings, the hexgon is used as a symbol, by "standards", just as a "cloud" is used to symbolize the internet, when the level of detail in the drawing doesn't need to include that info.
In the real world the shape of a single cell site is generally a hezagon shape too, BUT is impacted by the ajoining cells and building density, antenea placement, service area, etc. Lots of factors, so in an open field, low power, with no other cell sites at the margin, and no impediments you would "see" a hexagon shape because the central tower would have 6 antenna wrapped around the "pole". Each broadcasting to a 60 degree field of view. 6x60 degrees is 360 degree "circle" of coverage.
That's as non-techinal as i can get it. hope that helps.
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In the practical scenario , there is no uniformity as if it the cell is hexagonal/circle in shape . It will all depend on the geographical scenarios relating to terrain , water bodies , rural/urban area etc . RF coverage & capacity planning for a network is done keeping all the geographical and traffic density factors in mind , so it is not necessary that one would see a regular hexagon/circular shaped cell.
Another important factor here can be the antenna tuning , signal attenuation , overshoot/interference and neighbor lists for specific cells / sectors.
I am not clear about the question on height of the hexagon cell , but if you are referring to height of the Radio's on the tower , it will still depend on all the aforementioned factors with rural / urban geographical factor playing the most important role.
Hartej S. also suggests these experts on this topic:
I am going to try and answer this by memory. If I recall correctly, the original Bell Labs concept for an Analog/AMPS cell site structure was 3 sectors using 105 degree pressurized antennas. Each sector actually had 3 antennas, 1 for transmit and 2 for diversity receive. When actual implementation took place Carriers used anywhere from 105-120 degree antennas. I believe that Motorola implemented a different strategy of having a 6 sector site use 6 x 60 degree antennas. This would actually approach a hexagonal shape, but not really in practice. I do not know of anyone using a 6 sector site any longer.
I will try to answer the height question. When cell sites are/were implemented to brand new areas, carriers used the highest ERP and relatively high sites in order to gain coverage, capacity was not an issue. As the system grew and more subscribers were in a given cell site coverage area, cell splitting occurred (several cell sites replace one larger cell site). The the geographical coverage area you wanted to cover decreased and capacity per area increased as antennas were lowered, down-tilted and power levels decreased. There is no given correct height. It is a mixture of tower availability, capacity needs, frequency reuse/interference and future needs.
Eduard G.
Lecturer (Assistant Professor) at Barcelona-Tech, UPC
Best Answers in: Telecommunications (2), Wireless (2)
The actual shape of a cell would be a circle in ideal (theoretical) conditions. Under such conditions (as G. Feldman said) we can consider that a pattern of circles intersecting yields a pattern of adjacent hexagons.
However, I agree with H. Sadhu, in the real world, the presence of obstacles (e.g. buildings, hills, etc.), interference from other systems or even the weather and other phenomena, affect the shape of the coverage area.
The hexagon is just a symbolic representation of the cell coverage (only valid “on paper”). Thanks to its geometric properties, the use of hexagonal areas eases the mathematical analysis involved in network planning tasks (for example frequency planning). It is specially useful with bi or tri-sectorized cell-sites (the BTS has two or three sectors, each of which covers 180 or 120º of the ideal circular area).
Note that the coverage are in 3D would we a doughnut (or a toroid, in technical words) with a small hole centered at the BTS. Therefore the height will depend on the distance from the center, the height of the antenna, the transmitted power (the presence of obstacles, interference,…and a long etc.).
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u cant know exact size of the cell because it splits into number of cells if required..this is what i have learned ...dont know exactly
Bernard G.
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Because it's easier for mapping, and the difference between the hexagon and the equivalent circle is small, compared to the variation in boundary caused by all the many factors that affect size of cell.
The cell really has no height - it's indended to indicate coverage at ground level, and most antennae are dierected horizontally. In practice the height near the centre of the cell is close to the cell's radius (but somewhat less due to alignment of antennae) droppin off as an approximate sphere to no height at the edge of the cell, but the usable area varies a lot.
The idea was that the BTS would be in the center of a cell and the farthest ends of the cell should be at the same distance from the BTS.Now the best geometrical shape to eachieve this would be a circle but then circles would be a challenge for cell adjacency as that would leave gaps to ensure non-overlapping(refer Sandeep's diagram)
So to overcome the issue of non-overlapping cells the closest shape is that of a hexagon -that is why a cell is denoted by a hexagon though practically it can deviate a bit.Its actually a simplistic model of the radio-coverage of each station.The other choices could have been a square or equilateral traingle but a cell must be designed to serve even the weakest mobiles at its edge which should be as far as possible.It s only the hexagon which has the largest area for a distance between its center and farthest perimeter point .You require a large cell--so that fewer cells can cover a region and the hexagon approximates a radiation pattern similar to to that of an omnidirectional BTS
It also aids in easy analysis and planning of a cellular system
Height of the Hexagon/Cell
I am not aware of any thing defined as such.Normally directional antennas point in three directions say north,southwest and southeast.Signals travel along the height of the antenna(which is arrived at after careful calculations) and some of the signals leak upwards.Now this height above the antenna height can be betwen 400 m and 35km (u have got to be very lucky)
