Wireless network basics pdf

Networking Fundamentals Networking Media Cable Testing Ethernet Fundamentals Ethernet Technologies Ethernet Switching Routing Fundamentals and Subnets Target Audience Anyone desires a practical, technical introduction to the field of networking. High-school, community college, and lifelong-learning students interested in careers as network technicians, network engineers, network administrators, and network help-desk staff. In addition, instruction and training are provided in the proper care, maintenance, and use of networking software, tools, and equipment and all local, state, and federal safety, building, and environmental codes and regulations.

Course Objectives The CCNA certification indicates knowledge of networking for the small-office, home-office SOHO market and the ability to work in small businesses or organizations whose networks have fewer than nodes. Approximately 35 hours will be designated to lab activities and 35 hours on curriculum content. They have a good connection because the signal strength between them is strong.

Below, we can see the same routers, but with more distance between them. In this case, the routers have a weaker connection because the signal is near the limit of what the routers can hear. The speed between the routers will be less.

The optimal signal range for outdoor wireless equipment is between dBm and dBm. This will ensure the connection can maintain the highest bandwidth possible. Wireless routers have different types of antennas. Some routers will have antennas built in, and sometimes the routers will have a choice of antenna you can attach to the router.

There are many specific types of antennas, but three basic types are used most of the time, and will be useful in building a wireless network. The first type of antenna is also the most common--omnidirectional. Using omnidirectional antennas has the benefit of creating connections in any direction. If there is enough signal between nodes, they should connect. The all-direction strength of these antennas comes with the drawback of transmitting a weaker signal. Since the signal is going in all directions, it spreads out and gets weaker with distance very fast.

If nodes or clients are far away, they may not connect well. Also, if there are only nodes or clients in one direction of the router, then the signals going in the opposite direction are wasted:. 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.

These are often long, rectangular antennas that are separate or integrated in to a router. A focused antenna sends out a narrow beam of signal - it is normally around 5 to 10 degrees wide, but it can be a little wider as well.

These are often dishes or have a mesh bowl reflecting signal behind them. Using directional antennas has the benefit of increasing the distance a signal will travel in one direction, while reducing it in all other directions. Since the signal is all going one way, the power that would be sent out in all directions with omnidirectional nodes is now focused, increasing the power in that direction. It can also decrease the interference received at the node.

There are fewer signals coming in to the antenna, since the node is only listening to signals from the direction it is pointing. This reduces the signals it needs to sort out, and allows it to focus on other signals more, increasing the quality of those connections. However, directional antennas also have the drawback of requiring more planning to create links in your neighborhood. Since you are defining and limiting the areas where wireless signals go, you need to think about how those signals cover your neighborhood.

If there are areas that are then left out, how will those areas be included in the network? Also, the node has a very powerful signal in a single direction. If omnidirectional units, or lower power units such as laptops, are connecting to the node, they may not connect properly. The laptop will hear the node very well, but the directional node may not hear the laptop.

This will create the situation where it looks like there is a strong signal, but you cannot connect. Networking concepts are important when dealing with wireless. If you are interested in learning more about Wi-Fi and wireless technology, there is a lot of information out there.

There are also excellent documents on Wikipedia about Wi-Fi and wireless signals. Similarly, an Internet search will most likely answer any questions you can think of, as wireless is a very popular technology. For more information on what frequencies are available in your country or regulatory area, please see this article on Wikipedia on wireless channels. Introduction This document covers the basics of how wireless technology works, and how it is used to create networks.

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 Here is the tie-in: In standard LANs, data is propagated over wires such as an Ethernet cable, in the form of electrical signals.

The discovery that Hertz made opens the airways to transfer the same data, as electrical signals, without wires. Therefore, the simple answer to the relationship between WLANs and the other discoveries previously mentioned is that a WLAN is a LAN that does not need cables to transfer data between devices, and this technology exists because of the research and discoveries that Herschel, Maxwell, Ampere, and Hertz made. This is accomplished by way of Radio Frequencies RF. With RF, the goal is to send as much data as far as possible and as fast as possible.

The problem is the numerous influences on radio frequencies that need to be either overcome or dealt with. One of these problems is interference, which is discussed at length in Chapter 5, "Antennae Communications. To begin to understand how to overcome the issues, and for that matter what the issues are, you need to understand how RF is used.

To send data over the airwaves, the IEEE has developed the No licensing is required to use the The FCC governs not only the frequencies that can be used without licenses but the power levels at which WLAN devices can operate, the transmission technologies that can be used, and the locations where certain WLAN devices can be deployed. Other countries have different regulatory bodies. To achieve bandwidth from RF signals, you need to send data as electrical signals using some type of emission method.

One such emission method is known as Spread Spectrum. In , the FCC agreed to allow the use of spread spectrum in the commercial market using what is known as the industry, scientific, and medical ISM frequency bands.

To place data on the RF signals, you use a modulation technique. Modulation is the addition of data to a carrier signal. You are probably familiar with this already. To send music, news, or speech over the airwaves, you use frequency modulation FM or amplitude modulation AM.

The last time you were sitting in traffic listening to the radio, you were using this technology. As you place more information on a signal, you use more frequency spectrum, or bandwidth. You may be familiar with using terms like bits, kilobits, megabits, and gigabits when you refer to bandwidth. In wireless networking, the word bandwidth can mean two different things.

In one sense of the word, it can refer to data rates. In another sense of the word, it can refer to the width of an RF channel. Note - This book uses the term bandwidth to refer to the width of the RF channel and not to data rates.

When referring to bandwidth in a wireless network, the standard unit of measure is the Hertz Hz. A Hertz measures the number of cycles per second. One Hertz is one cycle per second. In radio technology, a Citizens' Band CB radio is pretty low quality. It uses about 3 kHz of bandwidth. FM radio is generally a higher quality, using about kHz of bandwidth.

Compare that to a television signal, which sends both voice and video over the air.