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Chapter 15

WirelessLANs

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15.1 IEEE 802.1115.1 IEEE 802.11

Architecture

Physical Layer

MAC Layer

Addressing Mechanism

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Figure 15.1 BSSs

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Figure 15.2 ESS

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Figure 15.3 Physical layer specifications

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Figure 15.4 FHSS

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Figure 15.5 DSSS

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Figure 15.6 MAC layers in IEEE 802.11 standard

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Figure 15.7 CSMA/CA flowchart

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Figure 15.8 CSMA/CA and NAV

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Figure 15.9 Frame format

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Table 15.1 Subfields in FC fieldTable 15.1 Subfields in FC field

Field Explanation

VersionVersion The current version is 0.The current version is 0.

TypeType Type of information: management (00), control (01), or data (10).Type of information: management (00), control (01), or data (10).

SubtypeSubtype Defines the subtype of each type (see ).Defines the subtype of each type (see ).

To DSTo DS Defined later.Defined later.

From DSFrom DS Defined later.Defined later.

More flagMore flag When set to 1, means more fragments.When set to 1, means more fragments.

RetryRetry When set to 1, means retransmitted frame.When set to 1, means retransmitted frame.

Pwr mgtPwr mgt When set to 1, means station is in power management mode.When set to 1, means station is in power management mode.

More dataMore data When set to 1, means station has more data to send.When set to 1, means station has more data to send.

WEPWEPWired equivalent privacy. When set to 1, means encryption Wired equivalent privacy. When set to 1, means encryption implemented. implemented.

RsvdRsvd Reserved.Reserved.

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Figure 15.10 Control frames

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Table 14.2 Values of subfields in control framesTable 14.2 Values of subfields in control frames

Subtype Meaning

1011 Request to send (RTS)Request to send (RTS)

1100 Clear to send (CTS)Clear to send (CTS)

1101 Acknowledgment (ACK)Acknowledgment (ACK)

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Table 15.1 Subfields in FC fieldTable 15.1 Subfields in FC field

ToToDSDS

FromFromDSDS

AddressAddress11

AddressAddress22

AddressAddress33

AddressAddress44

00 00DestinationDestinationstationstation

SourceSourcestationstation

BSS IDBSS ID N/AN/A

00 11DestinationDestinationstationstation

SendingSendingAPAP

SourceSourcestationstation

N/AN/A

11 00ReceivingReceivingAPAP

SourceSourcestationstation

DestinationDestinationstationstation

N/AN/A

11 11ReceivingReceivingAPAP

SendingSendingAPAP

DestinationDestinationstationstation

SourceSourcestationstation

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Figure 15.11 Addressing mechanism: case 1

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Figure 15.12 Addressing mechanism: case 2

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Figure 15.13 Addressing mechanism: case 3

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Figure 15.14 Addressing mechanism: case 4

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15.2 Bluetooth15.2 Bluetooth

Architecture

Radio Layer

Baseband Layer

Other Upper Layers

L2CAP Layer

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Figure 15.15 Piconet

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Figure 15.16 Scatternet

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Figure 15.17 Bluetooth layers

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Figure 15.18 Single-slave communication

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Figure 15.19 Multiple-slave communication

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Figure 15.20 Frame format types

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Figure 15.21 L2CAP data packet format