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IEEE 802.11 (WiFi) in Wireless Networks: Principles & Practice by Bhaskaran Raman, Slides of Wireless Networking

Indian Institute of Technology Wireless Networking

A part of the cs698t course notes at iit kanpur, focusing on ieee 802.11 (wifi) in wireless networks. It covers topics such as the role of ieee 802.11 in wireless networks, its phy and mac sub-layers, data rates, channels, service sets, mac classification, csma/ca, backoff procedure, and various problems and solutions. The document also includes diagrams and examples.

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Jan-Apr 2007 CS698T: “Wireless Networks: Principles & Practice”, Bhaskaran Raman, Dept. of CSE, IIT Kanpur Topic 16

CS698T

Wireless Networks:

Principles and Practice

Topic 16

IEEE 802.11 (WLAN/WiFi)

Bhaskaran Raman,

Department of CSE, IIT Kanpur

http://www.cse.iitk.ac.in/users/braman/courses/wless-spring2007/

Discover Slides of Wireless Networking Indian Institute of Technology

Partial preview of the text

Download IEEE 802.11 (WiFi) in Wireless Networks: Principles & Practice by Bhaskaran Raman and more Slides Wireless Networking in PDF only on Docsity!

CS698T

Wireless Networks:

Principles and Practice

Topic 16

IEEE 802.11 (WLAN/WiFi)

Bhaskaran Raman,

Department of CSE, IIT Kanpur

http://www.cse.iitk.ac.in/users/braman/courses/wless-spring2007/

IEEE 802.11 (WiFi)

Part of 802.x series

– 802.3 is Ethernet

802.11a, 802.11b, 802.11g specify three

different PHY layers

– MAC is the same

802.11a: 5.2 to 5.7GHz

802.11b/g: 2.4 to 2.4835GHz

802.11: What does it Specify?

PHY sub-layer

– 802.11a, 802.11b, 802.11g

MAC sub-layer

– Independent of the PHY

– DCF (Distributed Coodrination Function)

●

CSMA/CA

– PCF (Point Coordination Function)

MAC management

802.11 PHY

802.11b data-rates (modulation schemes):

– 1Mbps (BPSK), 2Mbps (QPSK), 5.5Mbps (CCK),

11Mbps (CCK)

802.11a and 802.11g data-rates:

– 6, 9, 12, 18, 24, 36, 48, 54 Mbps

– OFDM + BPSK/QPSK/16QAM/64QAM

– 802.11g also supports 802.11b data-rates and

modulations (backwards compatible)

802.11a Channels

Each channel

is 20MHz wide

As of now,

band is not

free in India

for outdoor

use

Source: Cisco

presentation

802.11 Service Sets

IBSS: Independent

Basic Service Set

Infrastructure Basic

Service Set

Basic Service Set: set of

STAs in a region

MAC Classification

Based on what dimension is used for multiplexing:

– SDMA, TDMA, FDMA, CDMA

Based on how control is achieved:

– Central

●

(+) Easy to design/implement

●

(-) Single point of failure, bottleneck

– Distributed

●

(+) Natural when there is no central information

802.11 specifies DCF (Distributed Coordination

Function), PCF (Point Coordination Function)

– PCF uses central control

Ethernet CSMA/CD: Prelude to

802.11 CSMA/CA

CSMA/CD: Carrier-Sense Multiple Access with

Collision Detection

– Listen before transmit (CS)

– Tx when (as soon as) medium is free (1-persistent)

– Collision Detection (CD)

– Backoff (exponential) on collision

The Backoff Procedure

data

A

B

C

data

DIFS

Slot-time Contention window:

Num slots=Random[0, CW)

CW = 32, 64, 128, 256, 512, 1024

Double CW on collision

Question: Why DIFS?

CSMA/CA + ACK

data

A

B

C

data

DIFS Slot-time SIFS ACK DIFS

IEEE 802.11 (WiFi) in Wireless Networks: Principles & Practice by Bhaskaran Raman, Slides of Wireless Networking

Related documents

Partial preview of the text

Download IEEE 802.11 (WiFi) in Wireless Networks: Principles & Practice by Bhaskaran Raman and more Slides Wireless Networking in PDF only on Docsity!

CS698T

Wireless Networks:

Principles and Practice

Topic 16

IEEE 802.11 (WLAN/WiFi)

Bhaskaran Raman,

Department of CSE, IIT Kanpur

http://www.cse.iitk.ac.in/users/braman/courses/wless-spring2007/

IEEE 802.11 (WiFi)

Part of 802.x series

– 802.3 is Ethernet

802.11a, 802.11b, 802.11g specify three

different PHY layers

– MAC is the same

802.11a: 5.2 to 5.7GHz

802.11b/g: 2.4 to 2.4835GHz

802.11: What does it Specify?

PHY sub-layer

– 802.11a, 802.11b, 802.11g

MAC sub-layer

– Independent of the PHY

– DCF (Distributed Coodrination Function)

CSMA/CA

– PCF (Point Coordination Function)

MAC management

802.11 PHY

802.11b data-rates (modulation schemes):

– 1Mbps (BPSK), 2Mbps (QPSK), 5.5Mbps (CCK),

11Mbps (CCK)

802.11a and 802.11g data-rates:

– 6, 9, 12, 18, 24, 36, 48, 54 Mbps

– OFDM + BPSK/QPSK/16QAM/64QAM

– 802.11g also supports 802.11b data-rates and

modulations (backwards compatible)

802.11a Channels

Each channel

is 20MHz wide

As of now,

band is not

free in India

for outdoor

use

Source: Cisco

presentation

802.11 Service Sets

IBSS: Independent

Basic Service Set

Infrastructure Basic

Service Set

Basic Service Set: set of

STAs in a region

MAC Classification

Based on what dimension is used for multiplexing:

– SDMA, TDMA, FDMA, CDMA

Based on how control is achieved:

– Central

(+) Easy to design/implement

(-) Single point of failure, bottleneck

– Distributed

(+) Natural when there is no central information

802.11 specifies DCF (Distributed Coordination

Function), PCF (Point Coordination Function)

– PCF uses central control

Ethernet CSMA/CD: Prelude to

802.11 CSMA/CA

CSMA/CD: Carrier-Sense Multiple Access with

Collision Detection

– Listen before transmit (CS)

– Tx when (as soon as) medium is free (1-persistent)

– Collision Detection (CD)

– Backoff (exponential) on collision

The Backoff Procedure

data

A

B

C