Wireless Basics

How CCNA Wireless Airwaves candidate should understand how RF signals to send data about employees.

Fundamentals CCNA Wireless.

The wireless LAN IEEE has created a work on a specification that defines how to use the same frequency of half-duplex transmit and receive in addition to a. The specification known as 802.11.

To use the frequencies specified by the IEEE 802.11 standard does not require approval by the userprovided that you shall follow the established rules of the IEEE.

Country or region has a regulatory authority (the FCC in North America and Europe ETSI), which governs the frequencies that can be used each can be used together with the amount of power that the wireless device can be operated and transfer of technology types .

(ETSI is a non-profit Journal. ETSI is responsible for levels of performance standards and frequencies in Europe)

In 1986,North America is the FCC allowed the use of a technology called "spread spectrum" in the commercial market in a band called industrial frequency bands scientific and medical (ISM).

Bandwidth and data rate

The world in which we have data is used to refer to past the word "gang" the amount of data measured on a fixed point in bits per second, kilobits, megabits and Gigabit Ethernet. These use the range limit is not technically correct. The correct term would be"Data Rate".

When talking about bandwidth, we refer to the number of vibrations per second. A cycle is in Hertz. A Hertz measures how many cycles per second. Some examples are to be used in FM radio and TV is about 175kHz 4500Khz would.

electromagnetic spectrum

At extremely low frequency (ELF) 3 Hz to 30 Hz
Super Low Frequency (SLF) 30Hz to 300Hz
Ultra Low Frequency (ULF) 300Hz to 3kHz
Very low frequency (VLF) 3KHz to 30kHz
Low frequency (LF) 30 kHz to 300 kHz
Medium Frequency (MF) 300kHz to 3MHz
High frequency (HF) 3 MHz to 30 MHz
High frequency (VHF) 30 MHz to 300 MHz
Ultra High Frequency (UHF) 300MHz to 3GHz
Super high frequency (SHF) 3GHz to 30GHz
Extremely high frequency (EHF) to 30 GHz 300 GHz

Which frequencies can be used depends on the country you are in Europe, allows the use of 2.4 GHz and 5 GHz, these areas as Cipta A, B, C, bands are known.

2.4Ghz

CEPT A =5,15-5.25 GHz
CEPT B = 5.25 5.35Ghz
C = 5.47 CEPT 5.725Ghz

North America uses Unlicensed National Information Infrastructure (UNII) bands.

900Mhz

2.4 GHz ISM

UNII-1 GHz = 5,15-5.25
5,25-5.35 GHz UNII-2 =
Extended GHz UNII-2 = 5.47 to 5725

900Mhz

Range: 900MHz - 928MHz to 902Mhz Start

For phones without core

2.4Ghz

Use of 802.11, 802.11b, 802.11g, 802.11g and 802.11n

The 2.4 GHz channel is divided intoSub-channels. The number of sub-channels used depends on the country:

Northern = 11 channels, each 22MHz wide channel
ETSI (Europe) = 13 channels, each channel is 22MHz wide
Japan = 14 channels, each 22MHz wide channel

Many of the channels overlap and it is recommended that non-overlapping channels, the three non-overlapping channels are used 1, 6 and 11

5GHz

Used by 802.11a and 802.11n.

For the 802.11a data rates from 6 Mbps to 54 Mbps

The802.11

802.11b specification

= 2.4 GHz frequency spectrum
The technology used HF = DSSS (Direct Sequence Spread Spectrum)
Non-overlapping channels = 1, 6 and 11
DBPSK and DQPSK modulation =
Data rate = 1, 2, 5.5 and 11 Mbit / s
= 11 Barker coding and CCK (Complementary Code Keying)

802.11b is an improvement over the simple, that alone could reach 802.11 data rates of 1 or 2 Mbps 802.11b is designed to be compatible with 802.11 Barker11-encoding where it is necessary, and CCK, when not needed, compatible with 802.11.

802.11b allows customers to dynamically transfer data rates, such as the access point and gain speed as they move closer to the transition to the access point.

802.11g Specification

= 2.4 GHz frequency spectrum
The RF technology used = OFDM (Orthogonal Frequency Division Multiplexing) and DSSS nonoverlapping
Channels = 1, 6 and 11
DBPSK and DQPSK modulation =
Data Rates= 1, 2, 5.5 and 11 Mbps DSSS and 6, 9, 12, 18, 24, 36, 48, 54 Mbps OFDM
= 11 Barker coding and CCK (Complementary Code Keying)

The 802.11g specification allows additional 8 data transfer rate up to 54Mbps more like 802.11a.

802.11g is compatible with 802.11b with identical coding and modulation, but it's only 802.11b, 802.11g and return to negotiate prices if access to the medium after it was broadcast 802.11g data rates of early

You should alwaysKeep in mind that still uses the 2.4 GHz and as such are only three non-overlapping channels 1, 6 and 11

802.11a specification

= 5Ghz frequency spectrum

The RF technology used = OFDM (Orthogonal Frequency Division Multiplexing) and DSSS

Non-overlapping channels = 4 non-overlapping channels per band, the middle eight channels with 52 sub-carriers used on each channel

DBPSK and DQPSK modulation =

Data rate = 1, 2, 5.5 and 11 Mbps DSSS and 6, 9, 12,18, 24, 36, 48, 54 Mbps OFDM

UNII-1 is designed for indoor use, for outdoor use with external antenna and UNII UNII-3 is designed for outdoor decks and external antennas designed.

Four non-overlapping channels per frequency band (each band is or UNII-1 = low, 2 = medium-UNII, UNII-3 = high). Consumers generally use the middle and lower bands. With four not on the lapping channels per band. Each channel of each book series has 52 sub-carriers on each channel

Low-and middle-Channels in a total of eight channels each 20Mhz, 20Mhz each of these channels are divided and then divided into 52 sub-carriers of 300kHz.

ETSI allows the use of 19 channels with support for dynamic control of frequency to avoid interfering with radar, which also takes the same bandwidth.

802.11a also encourage the use of Transmit Power Control as not to disturb even the radar.