Chapter 4 Wireless Technology
167
Figure 4-19.
A laptop equipped
with a wireless
network adapter
listens for network
traffic. If all is clear,
it sends a request to
send (RTS) signal to
the Wireless Access
Point (WAP). The
WAP returns a clear
to send (CTS) or a
busy signal to the
laptop. This process
is repeated until the
laptop is cleared to
send the data. After
the data is sent to the
WAP, the WAP sends
an acknowledge
(AWK) signal to the
laptop.
CSMA/CA Process
1. Request to send (RTS)
2. Busy or clear to send (CTS)
3. Sends data after clear to send (CTS)
4. Acknowledge (ACK)
Laptop with
wireless adapter
Wireless Access Point (WAP)
Figure 4-20.
In an 802.3 network,
which uses the
CSMA/CD access
method, all
computers are wired
to each other and
each computer can
hear traffic on the
network. There is no
need for a computer
to send a signal
notifying the other
computers it is about
to transmit data. In an
802.11 network, which
uses the CSMA/
CA access method,
computers with
wireless network
interface cards
communicate within
an overlap area. A
Wireless Access
Point (WAP) controls
all communication
giving permission to
the individual devices
to communicate in an
organized fashion.
CSMA/CA Access Method
CSMA/CD Access Method
Radio signal
overlap area