The choice of antennas for base stations rarely receives any attention. Antennas are regarded as a cheap commodity that will “do its job” regardless of which antenna you choose.
Nothing could be further from the truth. Antennas have a tremendous impact on coverage, performance, capacity and efficiency, and choosing the right ones can make or break a mobile operator’s ability to cope with the rapidly increasing demand for data.
Looking at the installed base, one could get the impression that the obvious, or even optimal, choice for almost all sites would be the traditional 18 dBi antenna. This antenna has 65° of horizontal beamwidth and around 6.5° of vertical beam width, as do about 80% of all installations on 1,700 to 2,100 MHz.
The 15 dBi antenna is still quite common, especially on the lower frequencies, with a vertical beam width of around 14°.
There are also high-gain 21 dBi antennas and new, so-called ultra high-efficiency antennas using air as dielectric and virtually eliminating power losses. These antennas improve base stations’ transmission capacity, resulting in higher signal strength, an increase in geographical area coverage, improved indoor penetration, increased traffic, improved data throughput and reduced production costs per call.
The choice for 18 dBi antennas comes down to historical reasons – it was the highest gain available from antenna vendors able to deliver antennas in mass quantities, and was such an obvious choice that it became almost a de facto standard and installed almost without a second thought.
However, the 18 dBi antenna does not deliver the highest gain anymore – high-gain, ultra high-efficiency antennas do. With data surpassing voice in new 3G and 4G mobile networks, interference is different and so must the antennas be to stay effective. Most sectors would benefit significantly from an antenna with higher gain and a sharper upper roll-off curve than the standard 18 dBi can offer.