Wi-Fi Back To The Basics: Radio Frequency And Antenna Concepts
In my last installment of my “Back to the Basics” blog series, I discussed 802.11 topologies. This time we will take a look at Antenna Concepts, and how they relate to wireless communication.
To review, in order for a wireless communication to occur successfully, the radio frequency (RF) signal must be radiated with enough power so that it is received and understood by the receiver. There are two types of gain, or amplification, that relate to this RF signal communication:
- The first type, active gain, is usually caused by the transceiver or the use of an amplifier on the wire between the transceiver and the antenna. Active gain requires the use of an external power source.
- The second type, passive gain, is accomplished by focusing the RF signal with the use of an antenna. Antenna (or passive) gain increases the signal strength of the wireless communication. Let’s take a closer look at antenna concepts:
The antenna design and installation in wireless networks is one of the most important aspects contributing to the success or failure of a wireless communication. One key factor that determines both how strong an antenna is and how far the signal can travel is called beamwidth. Beamwidth is the measurement of how broad or narrow the focus of the antenna is (these are measured both horizontally and vertically).
There are three main types of antenna, each with a unique beamwidth pattern:
1. Omnidirectional antennas: These types of antennas are designed to provide general coverage in all directions; think of a lightbulb in the middle of the room. These are the default antennas on most access points.
2. Semidirectional antennas: These types of antennas are designed to provide somewhat directed coverage across an area; think of a lightbulb in a wall sconce.
3. Highly directional antennas: These types of antennas are designed to focus coverage in a highly specific area; think of a flashlight or spotlight highlighting a sign. These are typically the default antennas on outdoor point to point access points.
As discussed in an earlier installment, wireless networks are prone to multipath signals. MIMO (multiple-input multiple-output) is an advanced form of antenna diversity that is being used in all modern wireless access points. MIMO systems can receive or transmit using multiple antennas at the same time, and can therefore take advantage of multipath signals.
Taking it a step further, MU-MIMI (multi-user MIMO) systems will enable one access point to talk to multiple devices at the same time. This is a more efficient use of the data stream and it will improve the overall performance of a wireless network.
To summarize, the antenna is a key component of successful RF communications. Choosing the correct antenna type for your deployment and installing access points and antennas correctly will make a big difference in the attainment of your ideal network.
In my next installment of “Back to the Basics” I will discuss WLAN architecture.
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