A SURVEY AND QUALITATIVE ANALYSIS OF MAC
-
Upload
arjun-bedi -
Category
Documents
-
view
218 -
download
0
Transcript of A SURVEY AND QUALITATIVE ANALYSIS OF MAC
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
1/26
HAMID MENOUAR AND FETHI FILALI, EURECOM
MASSIMILIANO LENARDI, HITACHI EUROPE
Arjun BediPEC , Chandigarh
IEEE Wireless Communications
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
2/26
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.
2
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
3/26
3
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
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
4/26
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
4
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
5/26
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.
5
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
6/26
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
6
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
7/26
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
7
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
8/26
Driver-Information (safety-related) applications
Emergency braking
Accident information Passing assistance
Security distance warning
8
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
9/26
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
9
FRAME 1
FRAME
FRAME 3
TIME
Venerable time
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
10/26
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
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
11/26
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.
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
12/26
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.
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
13/26
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.
3
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
14/26
14
A and B are hidden to each other
MACA Protocol
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
15/26
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.
15
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
16/26
16
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
17/26
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.
17
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
18/26
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.
18
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
19/26
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.
19
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
20/26
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.
0
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
21/26
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
21
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
22/26
R-ALOHA Continue
A slot successfully captured is periodically reserved (every N
slots) till released.
22
Needs a centralized radio
environment (full broadcast)so that all terminals see
the same slot status: busy,free, collided.
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
23/26
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.
23
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
24/26
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.
24
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
25/26
25
-
8/7/2019 A SURVEY AND QUALITATIVE ANALYSIS OF MAC
26/26
Inter-vehicular networks offers
interesting research opportunities ... in the meanwhile
26