Introduction

A Wi-Fi channel is the medium through which our wireless networks can transmit and receive data and Selecting the proper Wi-Fi channel is an important part of setting up your network correctly which can significantly improve your Wi-Fi coverage and performance. The first thing to know is that all Wi-Fi devices communicate through a channel. Each channel is characterized by a number, which corresponds to a precise radio frequency. 

In a wired network, any two devices that need to communicate with each other must be connected by a wire. The “wire” usually contain strands of metal or fiberoptic material and it must run continuously from one end to the other without any breaks in between. Furthermore, data that passes over the wire is also bounded by the physical properties of the wire. IEEE 802.3 set of standards defines strict guidelines for the Ethernet wire itself, in addition to how devices may connect, send, and receive data over the wire. Wired connections have tight constraints and few variables that might prevent successful communication like

  • the type and size of the wire strands,
  • the number of twists the strands must make around each other over a distance,
  • the maximum length of the wire

all these must adhere to the standard.

Therefore, it is safe to say that,  a wired network is essentially a bounded medium; data must travel over whatever path the wire takes between the two devices. If  the cable goes around a corner , the electrical signals used to carry the data must also go around a corner and because only two devices may connect to a wire, only those two devices may send or transmit data. The two devices can also transmit data to each other simultaneously because they each have a private, direct path to each other.

Wireless Network

Wireless communication usually involves wireless data  data exchange which travels through free space and between two devices  without the constraints of a wire. In a wireless LAN, many devices participate in sharing the medium for data exchanges. Wireless LANs must transmit a signal over radio frequencies (RF) to move data from one device to another. There are the 2.4 GHz band with 14 channels and 5 GHz band with 45 channels.  

In the free space environment, many variables can affect the data and its delivery. To minimize the variables, wireless engineering efforts must focus on two things:
■ Wireless devices must adhere to a common standard (IEEE 802.11).
■ Wireless coverage must exist in the area where devices are expected to use it.

1.11.a Nonoverlapping Wi-Fi Channels 

2.4 GHz Band

The 802.11 standard defines (14 ) 20MHz wide channels in the 2.4 GHz industrial, scientific, and medical (ISM) band. Wireless devices specified as 802.11b/g/n are capable of operating within this band. The channels available within different countries/regions is dictated by local governing authorities. In the United States, channels 1 through 11 are permitted and only three channels have non-overlapping frequency space: channels 1, 6, and 11. Because most of the channels overlap, 2.4 GHz is not the best choice for high density 802.11 deployments. Below is a diagram showing the 2.4 GHz channel plan. 

When designing a wireless LAN (WLAN), overlapping RF cell coverage is necessary to provide for seamless roaming. However, the overlapping coverage cells should not have overlapping frequency space like we see in 1,2,3,4,5, meaning, using channels that do not have overlapping frequencies. In the United States, there are only three channels (1, 6 and 11) that do not share frequency space and those are the Nonoverlapping Channels. RF is a half-duplex medium that allows for the transmission of only a single radio on any frequency channel, therefore when three or more 2.4 GHz APs are needed to cover an enterprise facility, only the non-overlapping channels of 1, 6 and 11 should be used.

Nonoverlapping Wi-Fi channels with Overlapping Coverage Cells

APs should be deployed with overlapping coverage cells and NOT Overlapping Frequencies. The importance of having overlapping cell coverage is that, it prevents packet loss which can occurs if a wireless client hits a dead zone when roaming between AP coverage cells. However, APs with overlapping coverage cells should not be on the same channel, if possible, because this can lead to increased channel utilization. The diagram below shows APs on different channels wherever their coverage is overlapping:

 

Figure 3 above shows a floor plan using seven APs to provide coverage. Note that only the non-overlapping channels of 1, 6 and 11 are used. This cell design is often referred to as a channel reuse pattern. 

A 1-6-11 channel reuse pattern in always the proper design in North America.

Overlapping Wi-Fi channels with Overlapping Coverage Cells

Figure 4 & 5 below shows an improper channel design using the same six APs. Note that channels 1-7 are used and all the channels share overlapping frequency space. The improper channel reuse design depicted in Figure 5 causes what is often known as adjacent cell interference. Data corruption is caused by your own APs transmitting at the same time over shared frequency space. The end result is decreased throughput and increased latency. Adjacent cell interference is simply RF interference caused by your own APs due to improper channel design.

 

1.11.b SSID

SSID is short for Service Set Identifier. All wireless networks have an SSID, often known only as network names or Wi-Fi names in everyday speech . In order to connect to a Wi-Fi network, you need to know or find this name, usually in combination with a password.

You can usually change the SSID setup in the settings of your router (or other wireless access point). A network name cannot be more than 32 characters long, but other than that, there are few restrictions on what you can choose as the SSID.

1.11.c RF

Very basically, Wi-Fi is made up of stations that transmit and receive data. Wireless transmissions are made up of radio frequency signals, or RF signals, which travel using a variety of movement behaviors (also called propagation behaviors). RF communication starts when radio waves are generated from an RF transmitter and picked up, or “heard” by a receiver at another location. In order to understand how these signals actually work, we must start with the basics of waves as they relate to the principles of data transmissions.  Air is the vehicle through which the data is carried, just as Ethernet uses copper cables. WLAN frequency ranges are in the 2.4GHz and 5GHZ bands. The most common legacy wireless standards, 802.11b and 802.11g, use the 2.4GHz range. IEEE 802.11a uses 5GHz exclusively. The newer 802.11n operates mostly in 5GHz but can also use the 2.4GHz band. The forthcoming 802.11ac standard operates in 5GHz.

An RF signal or wave radiates away from an antenna (often in a wireless access point) in a continuous pattern that is governed by properties such as wavelength, frequency, amplitude, and phase. However, the signal’s movement and behavior are also affected by other components such as absorption, reflection, scattering, refraction, diffraction, free space path loss, attenuation, and gain.

Why are all these terms important? These behaviors determine whether you receive enough of an RF signal to actually use the wireless network! Basic explanations of the RF signal behaviors are below-

Radio frequency propagates through space with different behaviors: reflection, absorption, refraction, diffraction and scattering.

  • Under reflection, RF signals bounce to another direction when they hit reflecting materials that are larger than the wave, i.e. metals; reflection highly occurs in indoor WLAN deployments.
  • Absorption occurs when RF signals are converted to heat and absorbed by certain materials, such as concrete or water.
  • In the case of refraction, RF signals change direction when they pass through a material with a different density; refraction mainly occurs in outdoor WLAN deployments, which are affected by changes in atmospheric conditions and air temperatures.  most materials will absorb some amount of RF signal as it is traveling between the antenna and the user device. Drywall absorbs a relatively small amount of signal while brick or concrete will absorb a significant amount of signal.
  • With diffraction, RF waves change direction when they move around an object of a certain size, shape or material.
  • Scattering can be intended as “many reflections of the RF wave”, and occurs when the wavelength of the RF signal is larger that the one of the medium/material/object the signal is passing through.

Being aware of how RF moves around a particular space is relevant to understand why, when positioning an access point in a location, radio frequency waves can or not reach certain places within a room and neighbor areas.

1.11.d Encryption

Wireless encryption secures your wireless network with an authentication protocol. It requires a password or network key when a user or device tries to connect. If your wireless network isn’t secure, unauthorized users could access your network and obtain personal information or use your internet connection for malicious or illegal activity. Your network speed or performance may decrease if people use your network without your knowledge.

Think of Wi-Fi encryption protocols like a foreign language that only you and those on your network can understand. Anything that you do online gets translated to this language, making it virtually unreadable by outsiders. There are three types of Wi-Fi encryption protocols: Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), and Wi-Fi Protected Access Version 2 (WPA2). These encryptions have one thing in common — protecting the data on your network — but the main difference lies in how well they do so. Think of these as ‘good, better, and best’.

The following information provides details about different types of wireless encryptions that are commonly supported on most Wi-Fi® enabled devices, adapters, and routers.

Wired Encryption Privacy or Wired Encryption Protocol (WEP)

Wired Equivalent Privacy (WEP): This encryption protocol is the first of its kind. As so, WEP has many security deficiencies and is easily hackable. While it is still used, it has been replaced by more secure alternatives.

Encryption Type

  • 64-bit: This configuration requires a ten character password when you use a hexadecimal (zero to nine and A-F) digits or eight characters when you use ASCII characters.
  • 128-bit: This configuration requires a 26 character password when you use hexadecimal digits or 14 characters when you use ASCII characters.

Advantages

  • Easy to configure.
  • Widely supported security system.
  • Secures your wireless network better than no encryption at all.

Disadvantages

  • Not fully secure.
  • Other encryption protocols are more secure.

Wi-Fi Protected Access (WPA and WPA2)

Wi-Fi Protected Access (WPA): WPA was born as a result of WEP flaws. There are two types of WPA protocols: pre-shared key (WPA-PSK) and Temporal Key Integrity Protocol (WPA-TKIP). While both provide some level of protection, WPA-PSK is much more secure. Think of WPA-TKIP like an electronic hotel room key-card. While it requires a validated card to enter the room, anyone could retrieve one of these cards from the hotel lobby. On the other hand, WPA-TKIP is like the dead bolt on the back of your hotel door — only you can unlock it. Most new routers already have one type of WPA (or WPA2) set up.

Wi-Fi Protected Access Version 2 (WPA2): WPA2 is an advancement of WPA and contains an even higher level of security encryption for wifi networks. WPA2 uses the Advanced Encryption Standard (AES) which is also used by the U.S. government to protect classified documents. This is the strongest level of security you can provide for your home wifi network.

Encryption Type

  • TKIP: Temporal Key Integrity Protocol
  • PSK: Pre-shared Key or Personal mode. 256-bit encryption that requires a 64 hexadecimal digit password or a 8 – 63 ASCII character passphrase.
  • EAP: Extensible Authentication Protocol

Advantages

  • Easy to configure.
  • Strong encryption.
  • Easy to manage.

Disadvantages

  • Not supported by all devices