First on the menu is the 802.11b standard. It was the most widely deployed wireless standard, and it operates in the 2.4GHz unlicensed radio band that delivers a maximum data rate of 11Mbps.
The 802.11b standard has been widely adopted by both vendors and customers who found that its 11Mbps data rate worked pretty well for most applications. But now that 802.11b has a big brother (802.11g), no one goes out and just buys an 802.11b card or access point anymore because why would you buy a 10Mbps Ethernet card when you can score a 10/100 Ethernet card for the same price?
An interesting thing about all Cisco 802.11 WLAN products is that they have the ability to data-rate-shift while moving. This allows the person operating at 11Mbps to shift to 5.5Mbps, 2Mbps, and finally still communicate farthest from the access point at 1Mbps. And furthermore, this rate shifting happens without losing connection and with no interaction from the user. Rate shifting also occurs on a transmission-by-transmission basis. This is important because it means that the access point can support multiple clients at varying speeds depending upon the location of each client.
The problem with 802.11b lies in how the Data Link layer is dealt with. In order to solve problems in the RF spectrum, a type of Ethernet collision detection was created called CSMA/CA, or Carrier Sense Multiple Access with Collision Avoidance. Check this out in Figure 1.
CSMA/CA is also called a Request To Send, Clear To Send (RTS/CTS) because of the way that hosts must communicate to the access point (AP). For every packet sent, an RTS/CTS and acknowledgment must be received, and because of this rather cumbersome process, it’s kind of hard to believe it all actually works!
Figure 1:802.11b CSMA/CA
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The 802.11b standard has been widely adopted by both vendors and customers who found that its 11Mbps data rate worked pretty well for most applications. But now that 802.11b has a big brother (802.11g), no one goes out and just buys an 802.11b card or access point anymore because why would you buy a 10Mbps Ethernet card when you can score a 10/100 Ethernet card for the same price?
An interesting thing about all Cisco 802.11 WLAN products is that they have the ability to data-rate-shift while moving. This allows the person operating at 11Mbps to shift to 5.5Mbps, 2Mbps, and finally still communicate farthest from the access point at 1Mbps. And furthermore, this rate shifting happens without losing connection and with no interaction from the user. Rate shifting also occurs on a transmission-by-transmission basis. This is important because it means that the access point can support multiple clients at varying speeds depending upon the location of each client.
The problem with 802.11b lies in how the Data Link layer is dealt with. In order to solve problems in the RF spectrum, a type of Ethernet collision detection was created called CSMA/CA, or Carrier Sense Multiple Access with Collision Avoidance. Check this out in Figure 1.
CSMA/CA is also called a Request To Send, Clear To Send (RTS/CTS) because of the way that hosts must communicate to the access point (AP). For every packet sent, an RTS/CTS and acknowledgment must be received, and because of this rather cumbersome process, it’s kind of hard to believe it all actually works!
Figure 1:802.11b CSMA/CA
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