Tutorial on Wireless Networking

June 12, 2013 at 10:00 AM

 

Wireless network antenna and devices

Entire cities and even countries are looking into ways to expand communications access for their residents as the Internet has shifted from a luxury to an imperative. The most promising solution: wireless networking.

 

Why? Wireless networking allows a non-physical (well, at least non-cabled) connection to a wireless LAN (WLAN) and onto the World Wide Web for users. So what are you waiting for? Cut the cord!

 

Be mindful of this though- issues such as network and band congestion, security, signal range and propagation, power demands, and more make WLANs tricky to implement for all but the most informed network engineers and IT professionals. Yet there's no stopping this technology in its rapid advance, with solutions such as distributed antenna systems (DAS) and MESH networks beginning to show promise. For you to get started, here's a basic wireless tutorial on terminology and concepts.

 


Wireless Standards

 

Radio frequency signals can take a lot of different forms, so in order for devices made by different manufacturers to communicate, the IEEE has provided several standards including the mainstay for wireless Ethernet: 802.11.

 

The 802.11 standard specifies the band and IP protocol used to transmit data, and provides guidelines to maximize the speed of transmission. 802.11a, for instance, uses the 5Ghz band and can typically transmit at speeds up to 54 Mbps in shorter ranges. 802.11b, 802.11g, 802.11n, and the new 802.11ac all use various methods to increase the speed and range. The latest IEEE wireless standard, 802.11ac boasts transmission speeds of up to 1 Gbps!

 

Each standard typically requires wireless routers, access points, and other transmission equipment to match its designation, though there are many that can operate in multiple standards (such as routers that are 802.11b/g/n compliant).

 


Wireless Bands

 

In attempt to maintain order within the entire radio frequency spectrum that is available to us, the FCC and other global communications standardization organizations have designated or set aside specific ranges of frequencies for specific uses. We call these "ISM bands". ISM stands for industrial, scientific and medical to denote where these frequencies are used.  ISM bands (specifically the 2.4 GHz and 5 GHz frequencies) are also used in commercial wireless networks. 

 

Typically access points, antennas, and amplifiers all use either the 2.4 GHz band, 5.8 GHz band, or both for WiFi. Other ISM bands have been set aside for things like cell phone use, RFID chips, emergency/municipal use, and military use.

 


Wireless Security

 

As mentioned previously, one of the big emerging issues with wireless networking is security. Without a physical cable that can be plugged and unplugged, the only method to control who can do what on a network is to build it into the software and protocol. That means it is critical to set up a wireless network with appropriate security measures and to be aware of the security status of any network you connect to.

 

For most small networks, methods such as WPA, WPA2, or WPA-PSK allow the safe identification of nodes that should be allowed on a network with passwords and other controls. Wireless routers can also use access passwords to allow administrators to adjust or update security features as required.

 
If you have questions about a wireless project or application, contact L-com's technical support line for a live response and expert advice!
 

Picking the Right Antenna for Your Application

May 29, 2013 at 10:00 AM

 

How-To 

 

A log periodic antenna mounted on a pole or mast

If you are new to wireless technology, the multitude of antenna shapes, sizes, styles and gains can be bewildering at first. Will you need a dish antenna, a grid, a Yagi or just a rubber duck?

 

Fortunately, by following a few rules of thumb, you can get a hang of the different styles and the applications they fill. It starts with a complete survey of the area where you need coverage: its shape, size and obstructions found within it. With these details on hand, you'll need to consider the following factors:


 

Beam Width


One of the key differences between antenna styles is the "beam width" and direction. In general, the narrower the beam width the more powerful the signal is in a particular direction. That's not to say Omni directional antennas are weak, but merely that the signal strength is spread in a different way (which may or may not be appropriate for your application).

 

Read this article for more information on signal gain patterns and wireless network design.

 

Vertical and horizontal beam patterns
Beam Pattern of a Log Periodic Antenna

 

 

Antenna Polarity

 

Another aspect of antennas to keep in mind is the polarity. While wireless signals travel, they move as a wave. Just like ripples on the surface of water, waves that move in the same direction cancel each other out. Waves in different directions do not. In a similar way, too many antennas set up in a vertical polarization in an area can cancel each other out, resulting in extremely poor signals.

 

In the case where a lot of wireless signals in the same band may be required, setting up antennas with different polarities can improve the performance of each signal. In some instances, you may want to set up "dual polarized" antennas, which include both vertical and horizontal polarities. These and other types of polarities (such as "cross polarized" and "circular polarized") can improve the strength and distance of signals in multiple ways.

 

This article offers some great information on antenna polarization.

 

Antenna Polarization Diagrams
WiFi Antenna Polarization Schemes

 

 

Antenna Gain

 

The final consideration for choosing your antenna is antenna gain. Measured in decibels (dB), it is commonly written as a number followed by "dBi" (the "i" at the end is for "Isotropic", and indicates that the number is relative to an imaginary, "perfect" dipole radiation). In general, the higher the dBi the stronger the signal in whatever direction it is going.

 

While it may seem tempting to simply buy the antenna with the highest gain for your beam width and polarization, it may not be relevant for your application. You should seek a dBi relative to the size of the space that the signal needs to cover. In many cases, a high gain will provide poor coverage closer to the antenna and better coverage further away.

 

For instance, setting up an Omni directional antenna in the center of a small cafe would require a smaller gain. If you use an antenna with too large a gain, people using devices in the street outside of the cafe would have better signal than those in the cafe itself because the total signal would be stretched.

 

This article explains why too much gain is a bad thing.

 

Small gain antenna used in 300-foot courtyardLarge gain antenna used in 1000-foot courtyard
An 8 dBi Omni directional antenna is more appropriate for a 300' space in a cafe courtyard than a 14 dBi antenna.
 

Quick note: L-com's technical resources section has tons of helpful information for the WiFi newbie or established expert alike. Also, for help selecting an antenna, try the Antenna Product Wizard.

 

What is an Omni directional antenna for 2.4 GHz?

May 15, 2013 at 10:00 AM

 

Omnidirectional antenna

As wireless technology continues to grow and develop, several antenna shapes and designs have arisen to provide different types of coverage. An Omni directional antenna is so called because it provides a wireless signal in a 360° radius, or in "all directions". These types of antennas are very common, and typically look like a very straight, stick-like shape.

 

Since the energy of the signal is not directional or pointed in a specific way, Omni directional antennas tend to be of lower gain than directional antennas such as parabolic dish, Yagi, and panel style antennas. However, higher gain isn't usually required for small installations such as Wi-Fi "hotspots" in stores and cafes. For those kinds of applications, a single Omni directional antenna installed near the center of the location often does the trick.

 

The 2.4 GHz band is typically designated for Wi-Fi use, and is the most common band for things like laptop and tablet wireless access. Therefore, if you are setting up a network for customers or visitors to access the Internet wirelessly, you'll often be installing a 2.4 GHz antenna. However, check the specifications of the access point that is being hooked up to the antenna to make sure the frequencies match. 

 

Quick note: L-com has a huge selection of 2.4 GHz antennas, from parabolic dish antennas, to Omni directional and everything in between.
 

Identifying Array Antennas

April 17, 2013 at 10:00 AM

What are they?


An antenna array is a group of two or more directional (usually panel style) antennas that are grouped together to form an Omni directional signal. Many times an RF splitter is used to connect the multiple antennas to a single access point or WiFi amplifier.

 

The benefit of using an antenna array over a single Omni directional antenna is that the antenna array provides radiation patterns that a single Omni antenna would not. Many times antenna arrays provide greater coverage than a single Omni antenna could.

 

 

Antenna array mounted on a pole RF splitter connected to an antenna array
Antenna array mounted on a pole RF splitter connected to an antenna array

Down tilt mounting feature
Down tilt mounting feature 

 



Where Would You Use Them?


Antenna arrays are used in outdoor point-to-multipoint applications. L-com's antenna arrays are available in 90° (4 panels), 120° ( 3 panels), and 180° (2 panels) configurations and include appropriate splitter and cables. Additionally, these antenna arrays feature zero to 20° down tilt capability to compensate for the geography of the installation location. This helps ensure maximum wireless signal coverage in the service area.

 

 

Antenna Array Configurations Available

 

 

Antenna Arrays with four 90° sectorial antennas Antenna Arrays with four 90° sectorial antennas
Antenna Arrays with three 120° sectorial antennas Antenna Arrays with three 120° sectorial antennas
Antenna Arrays with two 180° sectorial antennas Antenna Arrays with two 180° sectorial antennas
 

All sectorized omni array configurations are designed to all-weather operation. They feature both heavy-duty polymer antenna radomes and stainless steel mounting systems. 

 
  
© L-com, Inc. All Rights Reserved. L-com, Inc., 50 High Street, West Mill, Third Floor, Suite 30, MA 01845