Wireless IEEE 802 .11 A B

             The standard 802 .11A is used for extended wireless network that uses a frequency of 5 GHz UNII. These network speeds faster than standard 802.11 and 802 .11b standards on transfer rate up to 54 Mbps. Speed can be faster if using the right technology.

              To use the standard 802 .11A, computer devices (devices) is only need support communication speeds of 6 Mbps, 12 Mbps, and 24 Mbps. 802 .11A Standard also operates the channel/Channel 4 (four) times more than can be done by standard 802.11 and 802 .11b. Although the standard 802 .11A standard has similarities with 802 .11b at the Media Access Control Layer (MAC), it still isn't compatible with standard 802.11 or 802 .11b 802 .11A standard because in using radio frequency 5 GHz 802 .11b standards while using a frequency of 2.4 GHz.

              The advantages of the standard 802 .11A is because it operates on the 5 GHz radio frequency so that it need not compete with wireless communications devices (cordless) such as a cordless phone (cordless phone) commonly use a frequency of 2.4 GHz.

The other main difference between the standard 802 .11A standard with 802 .11A and 802 .11b are 802 .11A standards that use this type of additional modulation is called Orthogonal Frequency Division Multiplexing (on) on the physical layer in the OSI model.

               Although the standard 802 .11A is not compatible with the 802 .11b standard, some vendor/device Access Point manufacturer attempting to get around this by making a kind of bridge (bridge) that can connect between the standard 802 .11A and 802 .11b access point device on their BREW. The access point made in such a way so that it can be used on 2 (two) types of standards, namely on the standard 802 .11A and 802 .11b standard without mutually affect each other.

              The standard 802 .11A is a very expensive option when implemented. It inidisebabkan because this standard requires more Access points to reach speed communication. The cause is due to the fact that frequency waves has a weakness in the 5 GHz range.

               Wireless (IEEE 802 .11b)

               802 .11b standard is a standard that is most widely used in the 802.11 standard class. This standard is the development of the standard 802.11 physical layer for high speed. Aiming to increase the speed of up to 3.4 Mb/s or 11 Mb/s but still use a frequency of 2.45 GHz. Also known as IEEE 802.11 HR.

               A transmission method that uses 802 .11b DSSS. is used to define a wireless network for direct-sequence spread spectrum (DSSS) which uses wave frequency indusrial, scientific, medicine (ISM) 2.4 GHz and communicate at speeds up to 11 Mbps. It's faster than the speed of 1 Mbos or 2 Mbps offered by standard 802 .11A. 802 .11b standard is also compatible with all devices that operate on DSSS 802.11 standards.

               In practice, the maximum speed that can be achieved by IEEE 802 .11b reached 5.9 Mb/s on the TCP protocol, and 7.2 Mb/s on UDP protocol. The standard was accepted by the user in the world and still endures today. But the system b works on a fairly chaotic band, such as Cordless disturbance frequency and Microwave can interfere with each other for the power range. Standard 802.11 b only has the ability transmission standard with 11Mbps or average 5 MB bit/s the perceived slow, downloading double (turbo mode) wireless capability in addition to the more expensive but still not able to rival the capabilities of type a and g.

                The standard 802 .11b only concentrate only at the physical layer and Media Access Control (MAC). This standard uses only one type of frame that has a maximum width of 2.346 bytes. However, it can be further divided into 1,277 byte if in connect are cross (cross) with the access point so that it can also communicate with the Ethernet-based networks (cable-based).

The standard 802 .11b only emphasize on the operation of the DSSS devices only. This standard provides a method for those devices to search (discover), associations, and authenticate each other. It also provides a Standard method to handle collisions (collision) and fragmentation and enable WEP encryption method through protocols (wired equivalent protocol).

                  802 .11b standard is currently the most widely used one. Offering the maximum of 11Mbps through put (6 Mbps in practice) and range up to 300 meters in an open environment. It use 2.4 GHz frequency range, with 3 radio channels available. Frequency 2.4 Ghz frequency is probably the most widely used in the WLAN. 2.4 Ghz used by 802.11, 802 .11b, 802.11 g, and 802 .11n IEEE standard. 2.4 Ghz frequency that can be used by WLAN is split for became channel which ranges from 2.4000 to 2.4835 Ghz. In US has 11 Channels, and each channel has a bandwidth 22 Mhz. Multiple Channel overlap/overlap with each other and cause interference. For this reason, Channel 1, 6, and 11 are frequently used channel because the signal cannot overlap.

                  At a frequency of 2.4 Ghz modulation modulation is used for Direct Sequence Spread Spectrum (DSSS). The data transmission speed is 1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps. 5 Ghz Frequency While used by the standard 802 .11A and 802 .11n draft standard. In the standard 802 .11A, speed data transmission range between 6 Mbps up to 54 Mbps. 802 .11A Equipment can not be found in the market after 2001, therefore the market penetration for equipment standard 802 .11A is not as much as the standard 802 .11b equipment. 5 GHz frequency is also divided into several channels, each 20 Mhz wide channels Total Channel non-overlap is 23 5 GHz frequency channel.

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