There is, of course, a scientific explanation that can be understood by a non-WLAN professional. That explanation is the subject of this blog post. The first thing to understand is that all wireless transmission is accomplished through waves. Consider the example of when a rock is thrown into a body of water producing circular waves emanating from the point of impact. The waves produced in the medium of water is a repeating pattern comprised of higher densities of molecules followed by lower densities, followed by higher densities and so on.
When we hear a sound, we experience the impact of a wave being transmitted through the air. So just like on water except now in three dimensions the source of the sound emanates a force which produces higher densities of air molecules, followed by lower densities, followed by higher densities and so on. These spherical sound waves then come into contact with the eardrum to produce a vibration which the brain then translates into the experience or perception of sound.
In the case of Wi-Fi, the waves are produced on the electromagnetic spectrum. The electromagnetic spectrum consists of many different types of waves that make up the spectrum. The smallest type of waves is the gamma-ray, followed by X-rays.
Further down the spectrum is the visible spectrum of light. Further, still are micro-waves. When there is more than one route between transmitter and receiver, we call such channel a multipath channel. We know, that receiver must deal with the distorted and mixed signal to decode the data. This is not a trivial task since captured signal contains a big amount of unwanted components. To make this task easier we take some additional steps in the transmitter.
Before sending user data, transmitter is performs encoding. This operation appends additional bits to the message, which makes data recovery in receiver easier. After encoding bits are mapped onto symbols, modulated and passed to the antenna. In this blogpost we covered overview of wireless. Starting from where we most commonly use it, where it begins and how it travels in the environment. In the end we discussed one way to deal with channel conditions like pathloss and multipath, namely channel encoding.
To see other posts on network and wireless fundamentals — for example about pathloss , shadowing or MIMO — see our explained section. To subscribe to our mailing list for our online platform where you can learn all this and more visit GrandmetricWatch. We will inform you when it will be live. For now, you can watch our Youtube video about wireless:. His research interest covers a wide spectrum of image and video processing. In particular, image quality assessment, which is his PhD topic.
In Grandmetric, Mateusz researches and develops IoT and wireless solutions. In addition to some background information, this document covers six basic concepts: Wireless signals - what they are and how signals can differ.
Wireless devices - the differences and uses for receivers and transmitters. Wi-Fi Modes - how networks are made up of clients, access points, or ad-hoc devices. Wi-Fi Signals - the unique characteristics of Wi-Fi, and how signals are organized. Power and Receiver sensitivity - how far each wireless device can go, and how well a router can listen and filter out interference and noise. Antennas - how the type of antenna changes the way the router broadcasts.
What is a wireless signal? Types of Wireless Signals There are many, many types of wireless technologies. Frequency First of all, wireless signals occupy a spectrum, or wide range, of frequencies: the rate at which a signal vibrates. Example Frequency Ranges Below we can see the span of frequencies that are commonly used in communications. An un-modulated AM wave might look like: And a modulated AM radio wave has higher and lower energy amplitude waves indicating higher and lower audio frequencies in the signal: From left to right, we have the normal, un-modulated wave, then the lower amplitude wave representing low points in audio waves , then the higher amplitude wave representing crests or high points in audio waves.
A more detailed version of an AM signal is below: The audio signal is the wave on the top, with the corresponding Amplitude Modulated wave below it. An un-modulated FM wave might look like: And a modulated FM radio wave has higher and lower frequencies indicating higher and lower audio frequencies in the signal: From left to right, we have the normal, un-modulated wave, then the lower frequency wave representing lower audio amplitudes , then the higher frequency wave representing higher audio amplitudes.
Receivers and Transmitters When a device sends out a wireless signal, it is called a transmitter. Fill in some examples below each type: Transmitter Receiver Transceiver Examples: Examples: Examples: Do you use more transmitters, receivers, or transceivers throughout the day?
Wi-Fi Signals When building a network, you will be using Wi-Fi technology, which has some unique characteristics you will need to know. There are two types of Wi-Fi signal, based on the frequencies they use: 2. Many devices use it, so the signals can become more crowded and interfere with each other.
It can pass through walls and windows fairly well. It cannot pass through walls and windows as well as the 2. This will minimize interference caused by partially overlapping Wi-Fi signals: You could use other sets of Wi-Fi channels, as long as they are 5 channels apart - for instance 3, 8 and This may not always be true -- more and more wireless equipment is starting to use the 5GHz In the United States, only channels available for building mesh networks are 36, 40, 44, 48, , , , , and Power and Receiver Sensitivity Many people want to know how far wireless signals will go.
A few examples of the transmit power levels in common Wi-Fi hardware is below: 10mW 10dBm : Laptop or smartphone, or very low cost Wi-Fi router. About 25 to 50 meters mW 20dBm : Indoor home or office router. About 50 to meters mW 20dBm : Outdoor sector router. About 10 to 20 kilometers or more Wireless transmitter power is only one half of the connection.
Antennas Wireless routers have different types of antennas. Omnidirectional Antennas An omnidirectional antenna sends a signal out equally in all directions around it. Also, if there are only nodes or clients in one direction of the router, then the signals going in the opposite direction are wasted: Directional Antennas The next type of antenna is known as directional--it sends out a signal in a more focused way.
There are two main types of directional antennas: Sector Antenna Focused Antenna Sector antennas send out a pie-shaped wedge of signal - it can be anywhere between 30 degrees and degrees wide. Quick Activity: What are the best uses for the different kinds of antennas?
Definitions Omnidirectional When a node has an omnidirectional antenna attached, it can send and receive wireless signals in all directions around it equally. Directional antenna When a node has a directional antenna attached, the wireless signal is very strong in one direction, and has a very weak or no signal in every other direction. This generally forms a cone or wedge shaped area from the front of the antenna.
Receive sensitivity The minimum level of a received signal required for a device to understand the signal. Access point A device that allows wireless devices to connect to a wired network using Wi-Fi. The most common power levels for Wi-Fi devices are in the range of milliwatts - or thousandths of a watt. External Resources If you are interested in learning more about Wi-Fi and wireless technology, there is a lot of information out there.
Please share any derivative works. Many types of signals - voice, audio, video, data Many modulation types - analog and digital Many, many frequencies - MHz, MHz, Bluetooth - digital modulation at MHz. AM Radio - AM modulation from 0. Sector Antenna. Focused Antenna.
Sector antennas send out a pie-shaped wedge of signal - it can be anywhere between 30 degrees and degrees wide. It also provides the means by which a wireless network operator transmits more bits in the same time period, which effectively increases the bandwidth.
Click To Tweet. QAM is a modulation scheme that transmits data by changing the amplitude, or power level, of two signals: first in-phase with the incoming data and the second 90 degrees out of phase.
QAM relates to the number of bits of information encoded in each time period. For example, eight bits defines the number of combinations that are possible for those two signals in phase and 90 degrees out of phase. If there are combinations possible for those eight bits, then it is referred to as QAM. While higher order modulation rates are able to offer much faster data rates and higher levels of spectral efficiency for the radio communications system, this comes at a price.
The higher order modulation schemes are considerably less resilient to noise and interference. The key point here is that the higher the modulation signal, the more symbols are being transmitted and the closer together those symbols are. As a result of this, many radio communications systems now use dynamic adaptive modulation techniques.
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