latest ccna braindumps

latest ccna braindumps.In order to send data over radio waves, the IEEE developed the 802.11 specification, which defines a half-duplex mode of operation for transmit and receive operations in a WLAN using the same frequency. The use of the 802,11 standard does not require any license, but must comply with the regulations set forth by the FCC. The standards developed by the IEEE help to operate within the FCC rules. The FCC manages not only the frequency resources that can be used without a license, but also 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.Note: The FCC is a regulatory agency of the United States. The European Telecommunications Standards Institute (ETSI, EuropeanTelecommunications StandardsInstitute) is the European equivalent of the FCC. Other countries also have their own regulatory bodies.In order to obtain bandwidth from RF signals, it is necessary to send signals in the form of electrical signals using certain types of transmitting methods. In 1986, the FCC agreed to allow the use of spread spectrum technology in the general ISM (Industry, Scientific, And Medical) bands in the commercial market. In order to load data into the RF signal, modulation techniques are used. Modulation is the attachment of data to the carrier signal. Perhaps you are already familiar with this technique. Music, news, or speeches can be sent over the radio waves using either FM ( Frequency Modulation) or AM ( Amplitude Modulation) technology. When you sit in your car and listen to the radio, you are actually using this technology.1. Using unlicensed bands in a WLANThe more information that is put into a signal, the more spectrum it takes up, or the wider the bandwidth it takes up. When it comes to bandwidth, you are probably already familiar with the terms bit, kilobit, megabit, and gigabit. In wireless networks, the term bandwidth can mean two different things, one meaning the data rate and the other meaning the RF channel bandwidth.Note: This book uses the term bandwidth to denote RF channel bandwidth rather than data rate.When referring to bandwidth in wireless networks, the standard unit of measure is Hertz (Hz). Hertz is used to measure the number of cycles per second. One hertz is one cycle per second. In radio technology, the quality of radio broadcasts from civil band (CB, Citizens, Band) stations is very low. This band uses a bandwidth of about 3 kHz. fm radio broadcasts are generally of higher quality and use a bandwidth of about 175 kHz. receiving this TV signal requires nearly as much bandwidth as a TV signal that sends both sound and video over the radio.6 Chapter 1 Introduction to Wireless Networking Concepts 4500 kHz of bandwidth.1.2 Basic themes 7The entire electromagnetic spectrum is shown in Figure 1-1. Note that the range of frequencies used in CB radio, FM radio, and TV broadcasting is only a small portion of the entire spectrum. Most of the spectrum is managed by an agency like the FCC. This means that the same frequencies as FM radio frequencies cannot be used in your wireless LAN.