As for 2.4GHz, there are 14 channels. Each has 22MHz bandwidth, which is shown in Figure 1-3. Evidently, only channel 1,6,11 are the channels which are not intertwined each other.
Figure 1-3 wireless channel
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Wi-Fi architecture
Figure 1-4 Infra networks
Wi-Fi has two main modes: Infra and Adhoc networks
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Infra networks
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Minimum element: BSS (Basic Service Set), shown in Figure 1-4.
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One or more radio hosts;
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AP: Access Point, i.e., BS (Base Station)
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Radio hosts communicate with the outside by AP
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Inter-connection among APs by the inter-connection with Hub/Switch /Router
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SSID (Service Set Identification)
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Manager assigns a SSID less than 32 bytes for an AP;
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A BSS can exist lonely. It can also be connected to another BSS by the connection with DS (Distribution System) for the constitution of ESS.
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ESS (Extension Service Set)
ESS is composed of several APs and DS. All of the APs share an ESSID, and an ESS can include several BSS, as shown in Figure 1-5.
Figure 1-5 ESS
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DS (Distribution System)
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Distribution System, which is used to the logical connection BSS, and provide the roam distribution system for the wireless APs.
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When DS is used, then all of the BSSes seem like a BSS in a BSS.
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DS is usually denoted by Ethernet, point-to-point link or other wireless networks.
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Adhoc networks
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No AP center control
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Generally no connection to the outside networks
Figure 1-6 Adhoc networks