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est_320_Lect_5_Networking_wireless 2_28_08

est_320_Lect_5_Networking_wireless 2_28_08 - Lecture 5...

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Lecture 5 Wireless Networks
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Wide Area Wireless Networks Wireless networks connect devices without wires. Wireless networks use radio signals to transfer data. These radio signals are subject to interference. Transmission quality varies depending on the environment.
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Wide Area Wireless Networks IEEE 802.11, 802.11a, 802.11b and 802.11g are the standards for wireless LANs along with two new standards, 802.11e and 802.11n 802.11a provides data speeds of up to 54MBps in a 5HGz band. 802.11b was the first to gain popularity and provides data speeds of up to 11 Mbps in the 2.4GHz band. 802.11g provides data speeds of up to 20Mbps in the 2.4 GHz band. 802.11e is similar to a & b with support VOIP quality of service 802.11n the IEEE is working on this standard and when finished, bandwidth is expected to reach up to 100Mbps.
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Wide Area Wireless Networks 802.11 defines the Basic Service Set (BSS) and is the basic building blocks of a wireless LAN. BSS consist of stationary or mobile wireless stations and a central base. This central base is called an Access Point (AP). No AP means that the BSS is a stand-alone network. Access Points are needed to connect and send data to other BSSs.
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Basic Service Set BSS without an AP Stations without an access point can find each other an agree to form a BSS network without the use of an access point. This type architecture is call and ad hoc architecture . Station Station Station Station
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Basic Service Set BSS with an AP Wired Network ACCESS POINT AP Stations A Stations B Stations A and B communicate with the access point but do not communicate with each other.
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Wide Area Wireless Networks Extended service set consists of two or more BSSs with APs. APs connect to a distribution system which is usually a wired LAN. IEEE 802.11 standards does not limit the type of LAN. The distribution System can be an Ethernet LAN.
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Extended service set Server Distribution System BBS BBS BBS
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Extended service set In an extender service set, as long as they are in reach of each other, stations can communicate without an AP. However, if a station in one BSS wishes to communicate with a station in another BSS, then communication occurs via the AP.
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Wide Area Wireless Networks Infrastructure network allows for BSSs within reach of each other to connect without an AP, however, communication between BSSs not within reach requires the use of an AP.
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IEEE 802.11 Physical Layer The IEEE 802.11 protocol defines ways in which wireless LANs can convert bits to a signal in the physical layer. Remember, the physical layer is responsible for changing data into an electromagnetic signal and sending it across a wire.
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