A SURVEY AND QUALITATIVE ANALYSIS OF MAC

8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC

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HAMID MENOUAR AND FETHI FILALI, EURECOM

MASSIMILIANO LENARDI, HITACHI EUROPE

Arjun BediPEC , Chandigarh

IEEE Wireless Communications


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Mobile Ad Hoc Networks (MANETs)

As the term states, MANETs have mobile

devices as nodes and are connected bywireless links.

MANETs are self-configuring and do not

use a centralized administration.

Because the network nodes are mobilenetwork topology changes often over

time.

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MANET nodes use radio frequencies

which are also called transmission channels, each

one considered as a common medium over which

two neighboring terminals cannot transmitsimultaneously

because a transmission collision occurs.

in order to efficiently share the medium,

medium access control (MAC) protocols are

proposed


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ALOHA , S-ALOHACSMA / CA - Hidden Node Problem

CSMAW - Exposed Node Problem

BTMA - Busy Tone Multiple Excess

DBTMA Dual Busy Tone Multiple Excess

TDMA , FDMA , CDMA

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Vehicular Ad Hoc Networks (VANETs) are a

specific instance of MANETs, network nodes

are represented by vehicles.

Goal is to provide distributed real timecommunication between nearby vehicles and

between vehicles and the road-side

The network nodes have restricted mobility:

cars can move only on roads and highways. Another advantage is that storage and power

are not an issue, thus longer lifetimes are

possible.

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Road safety is today one of the major

problems of modern societies

The European Commission is pushing for a

new research effort in this area in order toreach the goal of reducing the car accidents

of 0% by 010

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Unregulated traffic generates

congestion, queues, danger situations,

etc.

Traffic control system allows toimprove traffic routing on the roads

Flow/congestion control

Load balancing

Interaction

with navigation systems to suggestalternative routes

With dynamic traffic regulator devices

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Driver-Information (safety-related) applications

Emergency braking

Accident information Passing assistance

Security distance warning

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ALOHA (hello in Hawaiian)

first MAC protocol proposed for packet radio

networks

when a node wants to use a common channel,

first it transmits on it, then, if a transmissioncollision occurs, it waits for a random time

before retransmitting again.

throughput of this protocol is 1 . percent of

Channel Capacity

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FRAME 1

FRAME

FRAME 3

TIME

Venerable time


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Slotted ALOHA

This protocol divides the medium into several

time slots and a sender attempts to transmitat the beginning of a time slot.

Compared to ALOHA, in S-ALOHA the

vulnerable period of a transmission is halved,

thus doubling the efficiency

Slotted ALOHA vulnerable time = Tfr


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Carrier Sense Multiple Access (CSMA)

In CSMA a node that has data to send senses the

common channel at first: if it is idle, it transmits;otherwise, it attempts again after a random time.

Collision detection (CSMA/CD) was then added in

order to detect collisions during transmissions,

stopping them, and allowing another attempt later.


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CSMA /CD is not useful in Wireless for following reasons

I. For collision detection a station must be able to send data andreceive collision signals at the same time. This can meancostly stations and increased bandwidth requirements.

. Collision may not be detected because of the hidden stationproblem.

3. The distance between stations can be great. Signal fadingcould prevent a station at one end from hearing a collision atthe other end.


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The first protocol to overcome the hiddenterminal.

This protocol uses request to send (RTS) and

clear to send (CTS) packets to initiate ahandshake between the sender and thereceiver.

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A and B are hidden to each other

MACA Protocol


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To let the exposed terminals be aware about the

transmission duration time in its neighborhood,MACA Wireless (MACAW) proposes to add data

sending (DS) and acknowledgment (ACK) packets

with regard to RTS and CTS packets.

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Busy Tone Multiple Access

proposed a new way to overcome the hiddenterminal problem

By splitting into channels: Data and Control.

In BTM

A, when a node wants to transmit, it sensesthe control channel; if the busy tone is free, it

transmits the busy tone signal on the channel

control and then starts the data transmission on

the data channel. All neighbors which sense the

busy tone signal transmit it as well. In this way,

all two-hop neighbors of the sender are not

allowed to transmit, which avoids collisions.

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Dual Busy Tone Multiple Access (DBTMA)

extends BTMA by using two busy tones (control

channels) and one Data channel.

The first is used by the sender to inform its

neighbors that it is transmitting, and the

second is used by the receiver to inform itsneighbors that it is receiving data packets.

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Time Division Multiple Access: way to split themedium is to divide it into several fixed framesin time

Frequency Division Multiple Access: the mediumis slotted, but in terms of frequencies, so severalnodes can transmit

simultaneously.

Code Division Multiple Access: several orthogonalcodes are available, and each node uses onecode to encrypt messages before transmittingthem.

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WAVE (IEEE 802.11p) An IEEE working group isinvestigating a new PHY/MAC for VANETs, referredas Wireless Access in Vehicular Environments. At thePHY layer, 0 .11p should work in the

. 0 . GHz spectrum in North America

The main Aim is High reliability and low latency.

For example, the Vehicle Infrastructure Integration (VII)initiative in the United States proposes that theinformation about an accident should be communicatedthrough VANET within half a second to all equippedvehicles in a 00 m range.

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Based on Reliable Reservation-ALOHA (RR-

ALOHA) scheme.

RR-ALOHA is extended version of R-ALOHA.

R-ALOHAIn R-ALOHA each active vehicle needs to

select for itself one basic channel (BCH),

which is one time slot periodically repeated

in successive frames.

Furthermore, each vehicle has to have a

global view of the transmissions

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R-ALOHA Continue

A slot successfully captured is periodically reserved (every N

slots) till released.

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Needs a centralized radio

environment (full broadcast)so that all terminals see

the same slot status: busy,free, collided.


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Reliable Reservation ALOHA

In RR-ALOHA each vehicle sends on its BCH its frameinformation (FI), which is a vector with N entries that

indicate how were sensed the status of the previous N time

slots in the previous frame.

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With a directional antenna, terminals can transmit ina specific direction. Generally, when using thattechnology, the transmission space around a terminalis divided into N transmission angles of (3 0/N)degrees.

The main advantage when using this approach isreducing transmission collisions, as well as increasingthe channel reuse possibility.

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Inter-vehicular networks offers

interesting research opportunities ... in the meanwhile

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A SURVEY AND QUALITATIVE ANALYSIS OF MAC