Wireless Hosts, Access Points, and Wireless Links

802.11 Networks consist of wireless hosts, Access Points (APs), and wireless links.

Diagram adapted from "Computer Networking: A Top Down Approach 5th Ed." ©1996-2012 J.F. Kurose and K.W. Ross, All Rights Reserved

Wireless Hosts

  • Laptops, tablets, IP phones, embedded PIC® MCUs
  • Run applications
  • May be stationary or mobile

Wireless does not always mean mobility.

802.11 does not provide IP address mobility
Your application must monitor association status and re-associate with the same AP or another, if necessary!

Access Points (APs)

  • Typically connected to a wired network
  • Relay - responsible for sending packets between the wired network and wireless host(s) in its area

In a typical home access network, the AP function is combined with switch and router functionality in a single device, such as the Linksys E1200.

Wireless Links

  • Typically used to connect mobile(s) to access point
  • CSMA/CA multiple access protocol coordinates link access
  • Various data rates, transmission distances

Wireless Link Characteristics

  • Decreased signal strength: radio signal attenuates as it propagates through matter (path loss).
  • Interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as well.
  • Multipath propagation: radio signal reflects off objects ground, arriving at the destination at slightly different times.

These characteristics can lead to a variable latency of data transfer, directly impacting the performance of the application.

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