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Communication Security: Wireless • Chapter 4 181

802.11b may still prove problematic because of interference in the widely used 2.4
GHz band. Because of this, it is unclear whether 802.11g will be a popular alterna-
tive to 802.11a for achieving higher rates of transmission on wireless networks.
See Table 4.1 for a comparison of 802.11 standards.

Table 4.1 Comparison of 802.11 Standards

802.11 Standard Frequency Speed Modulation Range (indoor)

802.11b 2.4 GHz. 11 Mbps. DSSS 100 Feet
802.11a 5 GHz. 54 Mbps. OFDM 100 Feet
802.11g 2.4 GHz. 54 Mbps. OFDM and QPSK 100 Feet

Ad-Hoc and Infrastructure Network Configuration

The 802.11 standard provides for two modes for ad-hoc and infrastructure wireless
clients to communicate.The ad-hoc mode is geared for a network of stations
within communication range of each other.Ad-hoc networks are created sponta-
neously between the network participants. In infrastructure mode,APs provide
more permanent structure for the network.An infrastructure consists of one or
more APs as well as a distribution system (that is, a wired network) behind the APs
that tie the wireless network to the wired network. Figures 4.3 and 4.4 show an
ad-hoc network and an infrastructure network, respectively.

Figure 4.3 Ad-Hoc Network Configuration

Laptop Laptop

Laptop

Workstation

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