US Robotics USR2410 Manual de usuario descargar pdf (Pagina 20)

request containing the IP address of the desired system. The destination system will recognize

the request, and send a reply to the requesting system with its MAC address. The requesting

system can then send other packets directly to the destination system by encapsulating them in an

Ethernet header containing the destination system’s MAC address. [1]

2.6

Wireless 802.11 Standard

The 802.11 Wireless Networking Protocol defines how Ethernet packets are sent between 802.11

devices. It operates at the network interface layer and includes three main standards. The

standards commonly in use are: 802.11a, 802.11b and 802.11g and are shown in Table 2-1.

Table 2-1: 802.11 Standards

Standard

Center

Frequency

Non-

Overlapping

Channels

Max.

Transmission

Rate

802.11a 5 Ghz 11 54 Mb

802.11

2.4 Ghz 3 54 Mb

802.11b 2.4 Ghz 3 11 Mb

802.11a operates in the 5 GHz range and has eleven non-overlapping channels so that adjacent

networks do not interfere with one another. The high operating frequency limits the range and

penetration of the network’s signals, but the network avoids interference with devices operating

in the 2.4 GHz range. 802.11a networks can send data at a maximum rate of 54 Mbps.

The 802.11b and 802.11g networks both operate at the 2.4 GHz frequency. They differ in how

they modulate the data in the wireless medium. 802.11b networks use Direct Sequence Spread

Spectrum modulation, and can send data at a maximum rate of 11 Mbps. 802.11g networks use

orthogonal frequency division multiplexing, and can send data at a maximum rate of 54 Mbps.

Due to the lower operating frequency of these two standards, the range and penetration of the

network signals are greater than 802.11a. [2]

2.7

Atheros Chipset for Wireless Devices

These chip sets are commonly found in networking devices that support the 802.11a and 802.11g

modes, including models from D-Link, Linksys and Netgear. Because of their popularity among

wireless card manufactures we determined that devices using these chipsets would work well for

the project.

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