Wireless Infrastructure 101

November 23, 2017 at 8:00 AM

 

You would be hard pressed to find a business, industry or home that doesn’t use wireless communication in some way. We depend on wireless networks used by our mobile devices, laptops, tablets and gaming systems to keep us connected, entertained and informed every day. Here, we’ll look at indoor and outdoor wireless infrastructure design considerations.

 

Frequencies

 

For wireless communication to work, radio frequency (RF) and microwaves are used to transmit voice, video and data. Radio frequencies are usually used in wireless networks, they range from 3 kHz to 300 GHz and are also used for AM broadcasting, navigational beacons and shortwave radio. Microwaves range from 300 MHz to 300 GHz and are typically used for television, FM broadcasting, aviation communications, and radar and satellite links. Most home, business and government networks operate on the Industrial, Scientific and Medical (ISM) frequency bands that range from 900 MHz to 5 GHz. The ISM band frequencies incorporate many of the IEEE 802.11wireless standards.

 


Design Considerations

 

When designing a wireless network, you must always take into consideration the environmental variables in the installation area that will or could affect network performance.

 


Indoor RF Wireless Networks

 

During installation or expansion, indoor networks present a special set of factors to consider. Most wireless access points and routers have a typical range capability specified by the manufacturer. But these ranges are based on having clear line of sight, which requires an unobstructed view of the antenna from the remote point in the link. Unfortunately, this is not the case in most indoor installations, there is usually some type of obstacle present. For example, signals typically will not penetrate concrete walls and the other building materials such as metal studs, aluminum siding, foil-backed insulation, pipes, electrical wiring and furniture. All of these common obstacles can reduce signal range and affect the coverage area. Plus, other wireless equipment such as cordless phones, microwave ovens, radio transmitters and electrical equipment can cause interference and decrease the signal range.

 


Outdoor RF Wireless Networks

 

Outdoor wireless networks face many of the same challenges as indoor networks, such as reflections and multipath. Having a clear line of sight is also critical for an outdoor network, trees and leaves can obstruct 802.11 frequencies and block the signal completely. A site survey is recommended before an outdoor wireless network is deployed, it might also be necessary to clear obstacles.

 

To help you plan and design your wireless network, we offer a series of wireless calculators to get you started.

What You Need to Know about Line of Sight

August 25, 2016 at 8:00 AM


When designing a wireless network, one of the most significant factors to consider is Line of Sight (LOS) - the path between two antennas. Obstructions in the LOS path can wreak havoc on a Wi-Fi signal so determining what, if anything, is between the antennas is crucial to your network working properly. Here, we’ll examine the main concepts you need to know in order to clear the path for Line of Sight and make sure your wireless network is a success.

 

The first step in navigating Line of Sight is to determine the LOS conditions. Once the conditions are defined, the correct type of wireless system can be chosen for the network area. There are three main Line of Sight conditions:

 

1.       Full Line of Sight (LOS) – no obstacles between the two antennas

2.       Near Line of Sight (nLOS) – partial obstructions between the two antennas, such as tree tops

3.       Non Line of Sight (NLOS) – full obstructions between the two antennas, such as an entire tree  

 

Outdoor networks may encounter the largest obstacles, but Line of Sight is also important for indoor wireless networks. Obstacles like walls, ceilings and furniture have to be considered because they will also affect the wireless signal reception.                                                                                                                         

In addition to obstructions, there are three other factors to consider that can affect Line of Sight:

 

1.       Multipath and Reflections

2.       Fresnel Zone

3.       Path Loss

 

In wireless transmissions, multipath and reflections are as important as signal strength because they too can degrade the performance of the network. Multipath is when wireless signals travel in multiple paths and arrive at the receiver at different times. Reflections occur when wireless signals "bounce" off of objects. When signals are transmitted through walls and ceilings and are reflected off of metallic objects, they will also have peaks and nulls in amplitude and changes in polarization (vertical or horizontal).

 

Fresnel Zone is an electromagnetic phenomenon where light waves or radio signals get diffracted or bent by solid objects near their path. The reflected waves/signals become out-of-sync with those that traveled directly to the receiving antenna, this delay reduces the power of the received signal.

 

Path Loss is another area of concern when determining Line of Sight. Some radio frequencies travel well through certain objects while other frequencies are not able to pass through, resulting in path loss. For example, 2.4 GHz radio waves easily pass through walls but experience path loss when going through trees and leaves. This is because walls are very dry, trees contain high levels of moisture and 2.4 GHz radio waves are easily absorbed into water. On the other hand, 900 MHz radio waves are not as easily absorbed by water. In cases like this, when trees cause nLOS or NLOS conditions, 900 MHz is a better frequency to use than 2.4 GHz to avoid path loss.

 

There are many factors to consider when designing a wireless network, but with proper site evaluation and planning you can correctly navigate Line of Sight obstacles to achieve peak performance.

 

 Comments on this post? Other topics you’d like us to cover? Email us at engineeringhub@l-com.com

 

Simplifying Your Life - Wireless Calculators

January 28, 2016 at 8:00 AM

 

Confused by conversions? Overwhelmed by Power Budget? Frazzled by the Fresnel Zone?

 

Site planning for a wireless network installation can be a daunting task.  There are multiple variables to consider and you must have a good understanding of the equipment required.

 

Lucky for you, we just simplified your life by adding a few more tools to your tool belt. L-com’s wireless calculators take the guess work out of planning a wireless network and make installation much easier. We offer five wireless calculators to help you, no matter what site planning challenges you’re facing. 

 

Power Budget Wireless Calculator

  • ·    Use this wireless calculator to determine your Power Budget
  • ·    The Power Budget is the total power being output from the wireless system in dBm

Free-Space Loss Wireless Calculator

  • ·    Free-space Loss is the loss of power over distance (assuming there is no Fresnel Effect and nothing in the way)
  • ·    This will give you a reasonable approximation of the actual loss over distance

Fresnel Zones Wireless Calculator

  • ·    Determine how high your antenna should be or how much more than Line-of-Sight (LOS)
  • ·     This calculator defines how much clearance you need and for longer links, greater than 3 Km or 2 miles, whether you may have a ground clearance problem

System Performance Wireless Calculator

  • ·    Can be used determine 3 different calculations:
    •   - Operating Margin
    •   - Maximum distance of margin operation
    •   - Required antenna power

Power Conversion Wireless Calculator

  • ·  Converts milliWatts to dBm and vice versa
 

How Line of Sight (LoS) Can Affect Your Wireless Installation

September 18, 2014 at 10:00 AM

 

Though the term Line of Sight seems self explanatory, there’s actually more than meets the eye when it comes to LoS and installing a wireless network.

 

As you might already know, Line of Sight is the path between two antennas. One of the first questions you’ll want to ask yourself when designing an outdoor wireless network is what is between point A (antenna 1) and point B (antenna 2)?

 

These details are important since Line of Sight does not only apply to a straight line. Wireless signals being sent from point A to point B can and will, most likely, run into to some obstacles that will alter the path they take.

 

When light waves or radio signals get diffracted or bent due to solid objects near their path, it’s an electromagnetic phenomenon referred to as The Fresnel Zone (referenced in the diagram below). The radio waves reflecting off the objects may arrive out of phase with the signals that traveled directly to the receiving antenna, thus reducing the power of the received signal.

 

It is important to also note that the line of site broadens with wavelength, which means that for low frequency, high wavelength signals, you need to have a larger Fresnel radius free of obstructions.  

 

 

 

 

As you can see, there are three main categories of Line of Sight to use as guidelines:

1.       Full Line of Sight (LOS), where no obstacles reside between the two antennas.

2.       Near Line of Sight (nLOS) which includes partial obstructions, such as tree tops between the two antennas.

3.        Non Line of Sight (NLOS), where full obstructions exist between the two antennas.

 

By determining the specific line of sight conditions in the WiFi network area, you can then determine the correct type of wireless system to install.

 

For example, most WiFi systems typically run on the 2.4 GHz and 5.8 GHz frequencies. Both of these frequencies are very dependent on a clear line of sight to obtain good performance, so clear LoS is very important.

 

View L-com’s comprehensive WiFi antenna offering

 

 

Use L-com's Online Wireless Calculators for Site Planning

February 27, 2014 at 10:00 AM

 

Are you doing an installation, looking to understand a particular network conversion, or trying to determine what equipment to use for your wireless network?

 

Give our wireless calculators a try! L-com can help you plan your wireless network installations. These handy tools provide detailed information such as Power Budget, Free Space Loss, Fresnel Zone and more. By using these free tools you can better understand the equipment required to accomplish your wireless link.

 

Here are some examples of Wireless Calculators:


 

Power Budget Wireless Calculator

 

Use this wireless calculator to determine your Power Budget. The 'Power Budget' is the total power being output from the wireless system, or the total system gain. The FCC regulates 36 dBm as the maximum output for 2.4 GHz ISM band applications, so use this calculator to make sure you aren’t exceeding the legal limit and to determine the right antenna and radio to use for your application.

 

The total power is the sum of:

  • PLUS Radio Transmit Power 
  • MINUS cables and connectors losses 
  • PLUS antenna gain 

 

Note that in order to enter your amount of cable loss you’ll need to know what type of cable you are using.

 

 

 

 

Free Space Loss Wireless Calculator


Free Space Loss is the loss of power over distance (assuming there’s noFresnel Effect and nothing is in the way). In practice, everything interferes with the signal but this will give you a reasonable approximation of the signal loss over distance.

 

 

 

 

Fresnel Zones Wireless Calculator


This calculator defines how much clearance you need (you will require more than simple Line-of-Sight). For longer links > 3 Km (2 miles), you can determine whether you may have a ground clearance problem.

 

 

 

View all of our Wireless Calculator Tools

 

One thing to note however is that due to the nature of radio frequency propagation and the numerous factors that can affect operating range, we do not guarantee that you will achieve any specific range for your application. These wireless calculators are for estimation purposes only.

 

 

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