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Chapter 5

The Medium Access Sublayer

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Chapter 5 The Medium Access Layer

• 5.1 The Channel Allocation problem - Static and dynamic channel allocation in LANs & MANs

• 5.2 Multiple Access Protocols - ALOHA, CSMA, CSMA/CD, Collision-free protocols, Limited-

contention protocols, Wireless LAN protocols

• 5.3 Ethernet - Cabling, MAC sublayer protocol, Backoff algorithm, Performance,

Gigabit Ethernet, 802.2 Logical Link Control

• 5.4 Wireless LANs - 802.11 protocol stack, physical layer, MAC sublayer protocol,

frame structure

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• 5.5 Broadband Wireless - Comparison of 802.11 with 802.16, protocol stack, frame

structure

• 5.6 Bluetooth - Bluetooth architecture, Application, Protocol stack, Frame

structure

• 5.7 Data Link Layer Switching - Bridges from 802.x to 802.y, Local internetworking, Spanning

tree bridges, Remote bridges

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5.1 The Channel Allocation problem5.1.1 Static channel Allocation in LANs and WANs

Frequency Division Multiplexing (FDM)

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5.1.2 Dynamic Channel Allocation in LANs and WANs

Assumptions1. Station Model. The model consists of N

independent stations, each generates the frame with probability in an interval . Once a frame is generated, the station is blocked.

2. Single Channel Assumption. A single channel is available for all communication.

3. Collision Assumption. If two frames are transmitted simultaneously, they are destroyed and must be retransmitted again later. There are no other errors.

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4a. Continuous Time. Frame transmission can begin at any instant.

4b. Slotted Time. Time is divided into slots. Frame transmission always begin at the start of a slot.

5a. Carrier Sense. Stations can tell if the channel is in use before trying to use it.

5b. No Carrier Sense. Stations cannot sense the channel before trying to use it.

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5.2 Multiple Access Protocols5.2.1 ALOHA

5-1.

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5-2.

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5-3.

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5.2.2 Carrier Sense Multiple Access Protocols

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5-4.

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5-5.