Wireless Local Area Network (also called WLAN, W-LAN, Wireless LAN or Wi-Fi) is the name for a local wireless network where the standards usually are from the IEEE-802.11 - family.
The wireless communication is increasing. Especially the use in private areas has increased a lot in the past few years. Almost every internet provider offers its customers a free Wi-Fi router with the conclusion of contract. Hotels and campsites offer internet access through the in-house wireless to their visitors. Cafes and restaurants offer internet access through so-called „HotSpot“ systems.
Therewhile there are many different Wi-Fi standards according to IEEE-802.11 norm with different on the producer depending specific extensions (like Turbo Mode or Range eXtend). To keep this instruction clear and especially understnading we are distinguishing in this text for now only between these two groups: WIFI networks according to IEEE standard in 2,4 GHz (2400 MHz bis 2485 MHz) frequency band and WIFI networks according to IEEE standard in 5 GHz (5150 MHz bis 5725 MHz) frequency band.
What does that mean? Whre is the difference? To what should the attention be paid to?
The both groups differ essentially in the use of their frenquency band they are working with. With only a few exeptions 2.4 GHz networks are normally being operated in private sectors of application as well as in public accessable wireless networks (Hot-Spots). 5 GHz networks are being used for long point to point links in commercial areas and are rarely used for public or private networks. Actually 5GHz networks are used for local private wireless networks more often now because of the raising number of private WiFi networks.
Devices, which are designed for the 2.4 GHz frequency band can not communicate with devices which are working in the 5GHz frequency band. It is the same with the accessories. An WiFi Antenna which is designed for the 2.4 GHz frequency band only works for 2.4 GHz and not for 5 GHz.
Please ensure that you are informed about whether you operate a 2.4 GHz or a 5 GHz network or with which you want to be connected, before buying antennas, accessories etc.
The 2.4 GHz frequency band contains the standards IEE802.11b (up to 11 Mbps data transmission rate), IEE802.11g (up to 54 Mbps data transmission rate) and the IEE802.11n standard with a transmission rate up to 300 Mbps. These three standards use the same frequencies. A 2.4Ghz WiFi antenna can be used for all the three standards. Especially private WiFi networks use mostly the 2.4 GHz frequency band. All common commercially available WiFi routers, access points, PCI cards, USB sticks etc. work usually with this freuquency band. The biggest problem with the 2.4 GHz frequency band is the small and limited amount of avaialble channels which can be used. There are 13 channels accessable in Europe, though only 3 can be used without overlapping. Mainly in large conurbations you can find a big amount of wireless networks in small areas. On top of that other types of devices are being used (like bluetooth, micro waves, baby phones) in this frequency band. This causes disturbances and interference.
The 5 GHz frequency band contains the standards IEEE 802.11a / IEEE 802.11n as well as the new and IEEE 802.11ac standard. These are often used in professional point-to-point WiFi bridges in commercial areas, like company networks or locations links. The components are due to the less popular use comparable more expensive and need to be bought at specialist retailers. Clear advantage: The frequency band is much bigger and offers therefore much more channels without overlaps. You may work with a higher transmission power. Disadvantage: The regulations of the EU are clearly tighter in this frequency band.
The higher the frequency the smaller the wavelength is. This means in particular that the WiFi is less vulnerable in the 5-GHz area for a site full of obstacles through its higher frequency. But the higher frequency also has disadvantages: With the decreasing wave length the loss which results from the air is increasing. Thats why WiFIi in the 5GHz area has a clearly lower range than a 2.4GHz Wi-Fi if it’s in the same transmission power. Actually this would mean the end for the 5GHz frequency used for WiFi but there is a loophole: the allowed transmission power.
The allowed transmission power:
The legislators have set a maximal transmission power of 100mW / 20dBm for the 2.4GHz frequency.
For the 5 GHz area the law allows a maximal transmission (TX)) power of 1000mW / 1 Watt / 30dBm under specific conditions.
Because the air causes less loss for the 2.4GHz frequency band the range with 100mW / 20dBm and the right WiFi antenna is quite far. If you’re working with legal means and have ideal site conditions you can achieve a maximum range of 12 to 15 km. But to be honest the bandwidth is very slow (ca. 1 Mbps/s) on such high range links.
You can only achieve a slightly higher range in comparison with 2,4GHz through the higher air loss, but through other transmission methods according to the IEEE 802.11a / 802.11ac standards you achieve significant higher bandwidths.
In a direct comparison and under ideal site conditions the two wiFi-frequencybands are not differing significantly. Differences manifest elsewhere.
Ideal conditions are given if the site is clear and open, with few or no trees at all and both antennas are on a hill, building or mast.
If the site is flat, hilly and tree-covered the conditions are challenging. The location search for the antennas can be very time-consuming because you always need to make sure that there is a visual contact with a free Fresnel zone inbetween the two antennas.
The site provides an indication which WIFI technique is better suitable.