The issue of timing signal ghimbav path and the collision with obstacles and reflect changes. Early

802.11b standard IEEE 802.11b standard or short .11 b with the establishment in 1999, the Association of Electrical and Electronics Engineers substantial change in the current decision and Ethernet-based network presented. The standard substrate medium access protocol CSMA / CA profit. Three techniques ghimbav used in the physical layer of radio standards are as follows: - using DSSS radio in the 2.4 GHz frequency ghimbav band and modulation of CCK - using the Bandfrkansy 2.4 GHz FHSS radio with modulation of CCK - waves The original 802.11 standard infrared radio data rates of 1 and 2 Mbps. While the standard 802.11 b using CCK and QPSK sharing data transmission rate to 5.5 Mbps DSSS technique to increase the data transmission rate is 11 Mbps. DSSS and FHSS technology traditionally uses of this Standard. Both the above methods 1 and 2 Mbps data rates are useful ghimbav
In the United States, the Federal Telecommunications Commission, or FCC, transmit and receive radio frequency controls. The Commission has a specific frequency band of 2.4 GHz to 2.4835 GHz, known as the ISM within the IEEE 802.11b standard for radio technologies are allocated.
Distance from the transmitter on the performance and throughput of wireless networks has considerable influence. At the current 802.11 standard data transmission rate varies according to the specific bandwidth of 11 Mbps bandwidth from 30 to 45 m and 5.5 Mbps, 40 to 45 meters and the bandwidth of 2 Mbps, 75 to 107 m is. It should be noted that the distance by other factors ghimbav such as the quality and signal strength, location of the transmitter and receiver, and the physical and environmental conditions change. Depending on the standard 802.11 b protocol that requires the recipient to send a packet acknowledges (see section 2.4 Media Access). Note that the authentication mechanism in addition to the authentication mechanisms used in the transport layer (TCP protocol, such as what happens) acts. If the packet is not acknowledged within ghimbav a specified period from the receiver to the sender, the sender assumes that the package is missing from the package and send again. If this situation continues, it reduces the data transmission rate (Fall Back) to finally reach a value of 1 Mpbs. If the rate at which the sender does not receive packets acknowledged at the right time, and other communication receiver package to cut the recipient is considered for nothing more. So far an important role in the efficiency (the efficiency of the network) and throughput (number of unique packets sent per time unit) plays. On the contrary, many experts bridge between networked computer networks, bridges Bridging the network or are not covered in the standard ghimbav 802.11 b. The bridge allows the network connection point (or a point-to-multipoint) to connect to a local area network ghimbav provided by one or more other local networks. This is particularly applicable in cases where we want without spending cabling (fiber or copper) local networks to connect the two buildings are very attractive and are needed. Although the standard 802.11 b This application does not cover, but many companies have proprietary implementations of wireless bridge to extend the standard 802.11 b have provided. Wireless ghimbav bridges are controlled by FCC rules and the effective ghimbav permittivity or otherwise be emitted effectively convergent (EIRP) of the equipment shall not be more than 4 watts. Signals ghimbav emitted by FCC regulations LANs should not exceed 1 watt.
The issue of timing signal ghimbav path and the collision with obstacles and reflect changes. Early implementations of the standard 802.11 ghimbav b FHSS technique used at the physical layer. The striking features of this technique is its remarkable resistance against ghimbav multi-path phenomenon. The technique of multiple channels (79 channels) with a relatively small bandwidth and frequency transceiver to change their frequency channel. The channel change occurs every 400 milliseconds, so the problem of multi-path to be dropped dramatically. ghimbav For the receiver, the original ghimbav signal (which was faster than the others and is free from interference) ghimbav receive and change their frequency channel signals reflecting the receiver when the receiver reaches its previous frequency channel ghimbav change and thus felt by the recipient and not received.
Standard 802.11 a, a new radio band for wireless networks and broadband wireless networks uses up to 54 Mbps increases. The significant increase in bandwidth ghimbav due to the modulation technique is known as OFDM. Data rates in IEEE 802.11a standard include: 6,9,12,18,24,36,48,54 Mbps based on the standard, supporting ghimbav speeds 6,12,24 Mbps is required. Some experts ghimbav in wireless networks, IEEE 802.11a standard is considered the next generation ghimbav IEEE 802.11 networks are even some products such as chips, Atheros Vkarthay PCMCIA / Cardbus product Card Access Inc. Standard