Cisco Wireless Networking

EM waves can pass through some objects, and can also be reflected off of objects. In many cases, part of the signal’s energy attempts to penetrate the object, while the rest of the energy of the signal is reflected. (Imagine ... [full story]

Anyone who has tried to listen to a radio while driving in rural areas knows that signals get weaker the farther you get from the source.This weakening of a signal is known as attenuation.There are several factors that cause attenuation, ... [full story]

One of the principle requirements for wireless communication is that the transmitted EM wave must reach the receiver with ample power to allow the receiver to distinguish the wave from the background noise. An analogy can be made to human ... [full story]

In order for wireless communications to function, the signal must have a path from the transmitter and the receiver and arrive with enough power left in the signal for the receiver to comprehend what is being sent.There are many factors ... [full story]

Radios transmit and receive signals over vast distances in the form of EM waves, at a particular frequency level that differentiates them from other EM waves in the frequency spectrum, such as infrared (IR) or X-rays (discussed later in this ... [full story]

A common problem with WLAN or wired LAN implementations is that users can easily add their own APs to the network. Obviously, this creates a large security risk as anyone can connect to these APs and they are usually not ... [full story]

The German scientist Heinrich Hertz demonstrated in 1887 that electrical energy could be transmitted through space by way of EM waves. Even though Professor Hertz was the first to demonstrate this phenomenon, he did not grasp the impact of his ... [full story]

This section covers the scientific principles that make wireless communication possible. Radio components and their associated frequency range is the primary mode of transmission in the wireless industry. Radio is the wireless transmission and reception of electric impulses or signals ... [full story]

Security has always been a major issue with traditional wired LANs, and is even more critical with WLANs, as the physical medium is easily accessible by intruders.The Cisco wireless-aware LAN framework takes the issue of overall LAN security in mind ... [full story]

Besides the features of the WLSE centralized management tool already discussed, there are some additional features that can help with management of the WLAN and the devices on the WLAN.With large WLAN environments, upgrading the firmware on all APs in ... [full story]

Site surveys are a critical part of any WLAN design.These surveys help the design team identify placement locations for APs, determine how many APs are needed, identify possible areas of RF interference, and determine the expected range of the WLAN ... [full story]

Another common problem in WLAN implementation is the detection and elimination of RF interference.This is typically done via an initial site survey where any pre-existing interference is detected and removed, if possible, followed by periodic follow-up surveys. Besides being time ... [full story]

A common problem with WLAN or wired LAN implementations is that users can easily add their own APs to the network. Obviously, this creates a large security risk as anyone can connect to these APs and they are usually not ... [full story]

Wireless domain services (WDS) is another new offering from Cisco that is part of their wireless-aware framework. WDS is basically a batch of Cisco IOS software features that help enhance client mobility in the WLAN and simplify the WLAN deployment ... [full story]

Cisco defines their wireless-aware LAN framework as “a highly scalable, secure, and manageable solution that simplifies WLAN deployment and management and maximizes wireless network uptime.”To this end, the wireless-aware LAN framework provides the following features:  Integrated wired and WLAN ... [full story]

A wireless-aware LAN is Cisco’s new approach to designing and implementing WLANs into an existing Cisco LAN infrastructure.This approach is an attempt to address and eliminate the issues that network engineers and management face in the implementation of a WLAN. ... [full story]

WLANs can function in two primary modes of operation—“ad-hoc mode” (also referred to as “peer-to-peer mode”) and “AP mode.” Each one functions in a slightly different way and each has advantages within specific situations. Some networks actually make use of ... [full story]

When implementing a WLAN, the concepts generally associated with network management come into a whole new light.With a traditional wired LAN, most network management can be done through configuration of switches, routers, and the layout of the physical cable plant. ... [full story]

Some of the major drawbacks to the implementation of a wireless network are the inherent security issues. In a typical wired LAN, access to the physical network is controlled by the physical locations of switches, wall ports, and so on. ... [full story]

Physical considerations are classified into two major groups of issues that can affect wireless connectivity and performance—path fading and propagation losses. Below these two groups are specific causes that produce either propagation loss or path fading.The following sections explain propagation ... [full story]

Applications play a significant role in the determination of a wireless implementation. Due to the high bandwidth utilization of some applications, you may need to modify or completely remove a wireless design as an infrastructure solution. If the high bandwidth ... [full story]

Harmonics occur when signals are produced at two or three times the station’s operating frequency in addition to the desired signals (see Figure 4.8). If the harmonics fall on another locally used frequency, such as an AP channel, they are ... [full story]

Interference usually occurs when radio transmitters and electronic equipment are operated within close range of each other.The following causes interference:  Incorrectly installed radio transmitting equipment  An intense radio signal from a nearby transmitter  Unwanted signals generated by ... [full story]

Radio frequency interference is extraneous energy that impedes the reception of signals. It can be caused by a radio emission from another transmitter at approximately the same frequency. When we talk about the frequency that an AP radio operates on, ... [full story]

A main consideration of any point-to-point design is the Fresnel zone. An electromagnetic signal traveling between two antennas does not travel in a straight line. The wave spreads out as it propagates.The individual waves that make up the signal do ... [full story]

In order to create a design for a wireless system, you must consider common WLAN transmission and reception impairments such as attenuation, RF interference, and application and structural considerations. Many environmental factors can also affect your WLAN design.This section explains ... [full story]

There are many obvious benefits to using a WLAN design, most of which hinge around the problems with typical wired LANs. Convenience is certainly a benefit to using wireless communications.With wireless, as long as you are in range of an ... [full story]

The standards used for Wireless LAN (WLAN) communications are based on the Institute of Electrical and Electronic Engineers (IEEE’s) 802.11 series.The 802.11 standards are responsible for defining the Physical and Media Access Control (MAC) layers of operation in a WLAN.The ... [full story]

A WLAN is a LAN that uses radio waves as the physical medium. In a traditional wired LAN, individual network stations are linked via some type of physical cabling.This cabling can vary from shielded copper wires to fiber-optic cables. Most ... [full story]

Who Uses Wireless Technology? Some of the largest users of wireless technology can be seen in the transportation and shipping industry; Federal Express and United Parcel are good examples. Another area is that of automated vehicle location systems that are supported through a combination of ... [full story]

Bridged Networks To diagnose problems with bridges can cause issues. The following helps to address those issues. Line-of-Sight Networks If you employ a bridging technology to connect two sites, you are likely to use line-of-sight to forge that connection. Line-of-sight is a technology ... [full story]

Slow WLAN Network Throughput Ideally, you should construct your WLAN to please all your users. However, as time passes, it is likely that the network will start to slow down. This section examines some common sources of throughput deterioration in WLANs. Cisco ... [full story]