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14.1

Chapter 14

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Wireless LANs

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14.2

14-1 IEEE 802.11

IEEE has defined the specifications for a wireless LAN, called IEEE 802.11, which covers the physical and data link layers.

Architecture�MAC Sublayer

Physical Layer

Topics discussed in this section:

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14.3

A BSS without an AP is called an ad hoc network;

a BSS with an AP is called an infrastructure network.

Note

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14.4

Figure 14.1 Basic service sets (BSSs)

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14.5

Figure 14.2 Extended service sets (ESSs)

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14.6

Figure 14.3 MAC layers in IEEE 802.11 standard

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14.7

Figure 14.4 CSMA/CA flowchart

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14.8

Figure 14.5 CSMA/CA and NAV

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14.9

Figure 14.6 Example of repetition interval

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14.10

Figure 14.7 Frame format

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14.11

Table 14.1 Subfields in FC field

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14.12

Figure 14.8 Control frames

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14.13

Table 14.2 Values of subfields in control frames

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14.14

Table 14.3 Addresses

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14.15

Figure 14.9 Addressing mechanisms

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14.16

Figure 14.10 Hidden station problem

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14.17

The CTS frame in CSMA/CA handshake can prevent collision from �a hidden station.

Note

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14.18

Figure 14.11 Use of handshaking to prevent hidden station problem

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14.19

Figure 14.12 Exposed station problem

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14.20

Figure 14.13 Use of handshaking in exposed station problem

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14.21

Table 14.4 Physical layers

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14.22

Figure 14.14 Industrial, scientific, and medical (ISM) band

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14.23

Figure 14.15 Physical layer of IEEE 802.11 FHSS

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14.24

Figure 14.16 Physical layer of IEEE 802.11 DSSS

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14.25

Figure 14.17 Physical layer of IEEE 802.11 infrared

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14.26

Figure 14.18 Physical layer of IEEE 802.11b

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14.27

14-2 BLUETOOTH

Bluetooth is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers, coffee makers, and so on. A Bluetooth LAN is an ad hoc network, which means that the network is formed spontaneously.

Architecture�Bluetooth Layers�Baseband Layer

L2CAP

Topics discussed in this section:

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14.28

Figure 14.19 Piconet

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14.29

Figure 14.20 Scatternet

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14.30

Figure 14.21 Bluetooth layers

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14.31

Figure 14.22 Single-secondary communication

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14.32

Figure 14.23 Multiple-secondary communication

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14.33

Figure 14.24 Frame format types

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14.34

Figure 14.25 L2CAP data packet format