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McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004 IEEE 802.11 Architecture Physical Layer MAC Layer Addressing Mechanism... Figure 15.3 Physical layer specifications... McGraw-Hill ©The

McGraw-Hill ©The McGraw-Hill Companies, Inc., 2004

IEEE 802.11

Architecture Physical Layer MAC Layer

Addressing Mechanism

Figure 15.1 BSSs

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Figure 15.2 ESS

Figure 15.3 Physical layer specifications

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Figure 15.6 MAC layers in IEEE 802.11 standard

Figure 15.8 CSMA/CA and NAV

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Figure 15.9 Frame format

Table 15.1 Subfields in FC field

Version The current version i s 0

Type Type of informati on: management (0 0 ), control (0 1), or data (10 ). Subtype Defines the s ubtype of each type (se e ).

To DS Defined later.

From DS Defined later.

More flag When set to 1, means more fragments

Retry When set to 1, means retrans mitted frame.

Pwr mgt When set to 1, means station is in power manage me nt mode More data When set to 1, means station has more data to send.

WEP Wired equivalent privacy When s et to 1, means enc ryption implemente d

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Control Frame

Control frames

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Table 14.2 Values of subfields in control frames

10 11 Request to send (RTS)

110 0 Clear to send (CTS)

110 1 Acknowledgment (ACK)

Management Frame

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Data Frame

Table 15.1 Subfields in FC field

To

DS

From DS

A ddress 1

A ddress 2

A ddress 3

A ddress 4

0 0 Des tination station Source station BS S ID N/A

0 1 Des tination station Sending AP Source station N/A

1 0 Receiving AP Source station Destinatio n

station

N/A

1 1 Receiving AP Sending AP

Destinatio n

station

Source station

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Figure 15.11 Addressing mechanism: case 1

To DS =0, From DS = 0

Figure 15.12 Addressing mechanism: case 2

To DS =0, From DS = 1

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Figure 15.13 Addressing mechanism: case 3

To DS =1, From DS = 0

Figure 15.14 Addressing mechanism: case 4

To DS =1, From DS = 0