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# Characteristics of Wireless Network

Wireless networks have different characteristics from wired networks in general.  In the Wireless Network   are many factors that affect the performanceand reliability of wireless networks. Some think are technically is Wavelength, the frequency used in data transmission, and amplitude (signalstrength), and the EIRP (Effective Isotropic Radiated Power). is commonly discussed above are also on the radio wave signals. Obviously because the Wireless Network uses radio wave for data transmission.

Because the media transmission using radio signals (RF) then surely many natural factors that influence. some explanation of the above are as follows :

1. Wavelength.

Wavelength is the distance between one end of the crest of a wave with the other tophorizontally. still remember this  signal was originally started as an AC signal which is generated by the transmitter / transmitter in an access Point (AP) and sent to the antenna, where theradiasikan as a sine wave. During this process, the flow of changing the electromagnetic field around the antenna, so that the antenna sends electrical and magnetic signals.

2. Frequency (Hz).

Frequency determines how often the signal looks / appears. Usual frequency scalemeasured in seconds.

3. Amplitudo.

Vertical distance between one crest of a wave with another wave is amplitude.Amplitude is the amount of energy that is provided in a signal. The people at the FCCand ETSI (European Telecommunications Standards Institute) set  the amplitide of which may be used.

Then what is EIRP? EIRP is the total energy issued by an access point and antenna.When an Access Point to send energy  to the antenna to be broadcast, a cable mayexist between them. Some reduction of the energy is going to happen in the cable. To offset this, adding an antenna power / gain, thereby increasing power. Number ofadditional power depending on the type of antenna is used. FCC and ETSI set ofpower that can be emitted by the antenna. EIRP is used to estimate the service areaof a wireless device.

The formula of the EIRP is:

EIRP  = Power Output Transmitter (AP) - Cable loss + Antenna Gain

Then there are several factors that influence the transmission of wireless signals in the air, like the free path loss, signal Absorption, Reflection Signal, Signal Troubleshooting, Diversion Signal and Line of Sight (LOS). What is Free Path Loss and his friends mentioned above?

The following brief explanation:

1. Free Path Loss

Model where a signal source is further away from the old one will disappear.Illustration like when you drop a stone vertically into a pool of water, will form a wavethat away from the point of a rock is dropped and the more distant increasinglydisappearing, but not stop, just disappeared. Just as radio wave signal.

2. Absorption.

As is known the greater the amplitude of the wave (Power) The farther the signal can be radiated. This is good because it can save you acess point and reach out more broadly. By reducing the large amplitude (power) of a signal, then the distance thesignal coverage will be reduced. Factors affecting the wireless transmission by reducing the amplituded (power) is called Absorption (absorption signal). The effect ofabsorption is hot. Problems that can be encountered when the signal is entirelyabsorbed, the signal stops. However, this effect does not affect / change the wavelength and frequency of the signal.

You must be wondering, what objects can absorb the signal. Wall, the human body, and the carpet can absorb/ dampen the signal. Objects that can absorb / muffle the sound can be muffled signal.this signal attenuation should be taken into account also when will deploy wirelessnetworks in buildings, especially when there is glass and capets. because in this case the signal attenuation will occur.

3. reflectance signal.

Radio signals can bounce off the mirror to see if / glass. Usually more common inoffice space in the bulkhead. Reflectance also depends on the frequency signal.There are several frequencies that are not affected as much as other frequencies. And one effect of the reflectance signal is the occurrence of multipath. Multipath means signal coming from two different directions. Characteristic is the recipient of the likelihood of receiving the same signal several times from different directions. It depends on the wavelength and the receiver’s position. Anothercharacteristic is the Multipath can cause signal to zero, meaning that cancel each other, or known as the Out Of Phase signal.

4. Scattering.

the issue of splitting the signal occurs when the signal dikrim in many directions. This can be caused enumerated by some object that can reflect signals and a sharp edge,such as dust particles in the water and air. The illustrations are the shining lights into the broken glass. The light will be reflected into many directions and spread. On a larger scale is imagine when the weather is rainy. The rain is great to have the ability to reflect the signal. therefore when rain, the wireless signal can be disrupted.

5. Refraction.

Refraction is a change in direction, or deflection of the signal when the signal passes through something different mass. For example, a signal that passes through theglass of water. Signals are the reflected and deflected there.

6. LOS (Line of Sight)

Line of Sight means a condition where the transmitter can see clearly without thehindrance of a receiver. Although LOS conditions occur, not necessarily no interference on the line. In this case is to be reckoned with - The absorption signal,the reflection signal, the signal resolution. Even in the longer distances of the earthinto an obstacle, such as the contour of the earth, mountains, trees, and other environmental obstacles.

To determine the influence of the wireless signal strength, there are a few things andmethods that can be used are:

1. Fresnel Zone

As background, Augustin-Jean Fresnel was a French physicist and civilian scholarwho live from 1778-1827. He correctly assumes that light travels as waves. Andbecause of his inventiona method to determine where the reflection will occurbetween sender and receiver, and was named as the name suggests. This is calledthe Fresnel Zone. Fresnel Zone formula can determine the position of the antennaheight with a distance that can penetrat the wireless signal. With precise calculationwill get satisfactory results and of course taken into account. But the application of the indoor signal is too short so as not to affect the indoor wifi network.

RSSI uses the value that is specific to each vendor. Therefore, assessment of vendorA vendor is not necessarily the same as B. RSSI used to be measured in dBm scale.One such tool is the remedy to determine RSSI Network Stumbler software.

3. Signal to Noise Ratio (SNR).

SNR is the term used to describe how strong the signal is compared with thedisturbances that interfere with the signal around. When the signal is stronger than theinterference / noise, the signal can be better captured by the receiver, and vice versaso. When the Noise around too big, then that will be captured by the receiver is a vague signal and data transmission are not understood. If the application you can useto report the measurement of SNR, the better when you get higher rates, but alsobuilds on its RSSI value, so it is also determined solely by the vendor.

Link Budget is the value that calculates all of the gain and loss between the senderand receiver, including the attenuation again / gain antennas, and other losses thatmay occur. Link Budget can be useful to determine how much power it takes totransmit a signal that can be understood by the receiver signal.

Here’s a simple formula to determine the Link Budget:

Received Power (dBm) = Transmitted Power (dBm) + Gains (dB) - Losses (dB)

By understanding a few things that can affect wireless signal and its characteristics,then we will be able to build a wireless network is more reliable and calculated as a whole. But it is not necessarily because it does not change with there arefactors that will change, for example, suddenly built a building that blocks thetransmitter and receiver antennas, the signal will be disrupted. But of course all themore understandable and some mystery questions can be answered with better