As a CCNA wireless candidate you are expected to understand how RF signals are employed to send data over the airwave. Basics of CCNA Wireless. The IEEE worked on a created a specification which defines how to use the same frequency in half duplex to send and receive over a wireless LAN. The Specification is known as 802.11. To use the frequencies specified by the IEEE 802.11 standards do not require any licensing on the part of the user provided the user adheres to the rules laid down by the IEEE. Each country or region has a regulatory body (FCC in North America and ETSI in Europe) which regulates the frequencies that can be used along with the amount of power which the Wireless device can operate at and the types of transmission technologies which may be employed. (ETSI is an official non-profit organisation. ETSI is responsible for standardises power levels and frequencies in Europe) In 1986 the in North America the FCC allowed the use of a technology called “Spread Spectrum” within the commercial market in a frequency band referred to as the Industry, Scientific and Medical (ISM) frequency bands. Bandwidth and Datarate In the data world we are used to using the term “bandwidth” to refer to the amount of data passing a fixed point per second measured in bits, kilobits, megabits and gigabits. These use of the term bandwidth is not technically correct. The correct term would be “datarate”. When we speak of bandwidth we refer to the number of cycles per second. One cycle is on Hertz. A hertz is measures how many cycles per second. Some examples are FM radio would use 175Khz and Television is around 4500Khz. Electromagnetic Spectrum Extremely low Frequency (ELF) 3Hz to 30Hz Super Low Frequency (SLF) 30Hz to 300Hz Ultra Low Frequency (ULF) 300Hz to 3Khz Very Low Frequency (VLF) 3Khz to 30Khz Low Frequency (LF) 30Khz to 300Khz Medium Frequency (MF) 300Khz to 3Mhz High Frequency (HF) 3Mhz to 30Mhz Very High Frequency (VHF) 30Mhz to 300Mhz Ultra High Frequency (UHF) 300Mhz to 3Ghz Super High Frequency (SHF) 3Ghz to 30Ghz Extremely High Frequency (EHF) 30Ghz to 300Ghz Which frequencies can be used depends on the country that you happen to be in. Europe allows the use of the 2.4Ghz and 5Ghz ranges, these ranges are known as the CIPT A, B, C bands. 2.4Ghz CEPT A = 5.15-5.25Ghz CEPT B = 5.25-5.35Ghz CEPT C = 5.47-5.725Ghz North America uses Unlicensed National Informational Infrastructure (UNII) bands. 900Mhz 2.4Ghz ISM UNII-1 = 5.15-5.25Ghz UNII-2 = 5.25-5.35Ghz UNII-2 Extended = 5.47-5.725Ghz 900Mhz Range: 900Mhz

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