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The 802.11 Physical Layer
IEEE 802.11 standard, popularly known as WiFi, lays down the architecture and specifications of wireless LANs (WLANs). WiFi or WLAN uses high frequency radio waves instead of cables for connecting the devices in LAN. Users connected by WLANs can move around within the area of network coverage.
IEEE 802.11 Architecture
The physical layer architecture of IEEE 802.11 has the following components −
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Stations (STA) − Stations comprise all devices and equipment that are connected to the wireless LAN. A station can be of two types −
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Wireless Access Point (WAP) − WAPs or simply access points (AP) are generally wireless routers that form the base stations or access points for the network.
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Client − Clients are workstations, computers, laptops, printers, smartphones, etc.
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Each station has a wireless network interface controller.
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Basic Service Set (BSS) − A basic service set is a group of stations communicating at physical layer level. BSS can be of two categories depending upon mode of operation −
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Infrastructure BSS − Here, the devices communicate with other devices through access points.
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Independent BSS (IBSS) − Here, the devices communicate in peer-to-peer basis in an ad hoc manner without access points.
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Extended Service Set (ESS) − It is a set of all connected BSSs that appear as a single network to the upper layers.
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Distribution System (DS) − It connects access points in ESS and provides communication between different BSSs.
Types of Network Topologies
| Topology Type | Description | Key Features |
|---|---|---|
| Infrastructure BSS | Centralized network with Access Point | All communication through AP, managed access, better security |
| Independent BSS | Peer-to-peer ad-hoc network | Direct communication, no AP required, temporary networks |
| Extended Service Set | Multiple interconnected BSSs | Seamless roaming, larger coverage area, unified network |
Key Features
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Mobility − Stations can move within the coverage area while maintaining connectivity.
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Flexibility − Supports both infrastructure and ad-hoc network configurations.
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Scalability − ESS allows expansion by connecting multiple BSSs through distribution systems.
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Interoperability − Standardized protocols ensure compatibility between different vendors' equipment.
Conclusion
The IEEE 802.11 physical layer architecture provides a flexible framework for wireless networking through various service sets and station types. The architecture supports both centralized infrastructure networks and decentralized ad-hoc communications, enabling diverse wireless networking scenarios.
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