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The local area technologies as 1-WLAN(Wireless Local Area Network) with moderate bandwidth. And WiMax 2.The large area technologies as GSM, GPRSor UMTS, LTEwhich have much higher bandwidth.
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1Eng: Mohammed Hussein
Wireless Technology
Eng: Mohammed Hussein2
Wireless Technology can make the businesses more flexible and
cheaper for sending and receiving data in short time.
Increasing efficiency in the companies, and makes efficient and is
almost very economical.
Users have access easier at their offices.
Now at home, the users don't need to use cables to have internet
access.
Reduced the costs due to cheaper cost of install and maintains.
Mobility is very high for users, they can move inside the network
without sitting at one place. Avoiding LAN restrictions
Wireless Technology Classifications
1. The local area technologies as WLAN
(Wireless Local Area Network) with
moderate bandwidth. And WiMax
2. The large area technologies as GSM,
GPRS or UMTS, LTE which have
much higher bandwidth.
3Eng: Mohammed Hussein
Data transmission
Eng: Mohammed Hussein4
SMS
FAX
Internet
Multimedia
114 kb/s
Voice +SMS +MM
IP
9.6 kb/s
Voice +SMS
Circuit-Switching
TimePacket-Switching
MB
IEEE 802.11 (WLAN) Architecture
ESS
BSS BSSIBSS
APAP
AP: Access point, BSS : Basic Set service, ESS : Extented Set Service, IBSS Independent BSS.
5 Eng: Mohammed Hussein
GSM network ?
BSC
BSC
MSC
MS
MS
MSBTS
BTS
BTS
GMSC
PSTNISDNPSDN
EIRAUC
HLR
VLR
6Eng: Mohammed Hussein
General Packet Radio Service (GPRS) ?
Eng: Mohammed Hussein7
Scope
Enhanced algorithms
Fairness and QoSover wireless
to Satisfy Applications requirements
8 Eng: Mohammed Hussein
WLAN?
Access Port Switch
Ma
in C
orp
ora
te B
ac
kb
on
e
Server
Server
Server
iPaq
Notebook
PalmPilot
Mobile Phone
Notebook
9 Eng: Mohammed Hussein
IEEE 802.11
Frequency : band 2,4 GHz;
Infrastructure or Ad-hoc
IEEE 802.11 is Cellular
10Eng: Mohammed Hussein
802.11 WLANs required centralized access points to mediate the wireless connection.
nodes are limited in power, computational capacities and memory.
IEEE 802.11
802.11
DSSS
FHSS
IR
802.11b 802.11g 802.11a
802.11 – 802.11e – 802.11i
802.11fMAC Layer
Physical Layer
LLC 802.2
11 Eng: Mohammed Hussein
WLAN
1990 : WLAN Project
IEEE (Institute of Electrical and Electronics
Engineers) :
IEEE 802.11 WiFi
IEEE 802.15
IEEE 802.16 WiMAX
Hiperlan (High Performance Local Area Network)
HiperLAN
12Eng: Mohammed Hussein
3 Network
IP Routing Protocols
AODV , DSR , DSDV,…
2
Data Link
1 Physical (PHY)
LLC 802.2
MAC 802
4 Transport
5 Session
6 Presentation
7 Application
Figure :OSI layers with MAC and PHY details
802.3
CSMA/CD
802.4
Token Bus
802.5
Token Ring
802.11
Wireless
LAN
Logical Link Control
Network layers
Eng: Mohammed Hussein13
SME/MLME = MAC Control / Management
Coordination Function
(DCF, PCF , HCF, ..) CSMA/CA
802.11 Media Access Control (MAC)
802.11 Physical Layer (PHY)
802.11a5
4 Mbps
/5
GHz
802.11b
11 Mbps
/2.4
GHz
PLME
Packet Transfer Function
802.11g
54 Mbps
/2.4
GHz
802.11e – Quality of Service
Sync, power
save, Beacon
Segmentation & Reassembly
802.11
legacy
2 Mbps
/2.4
GHz
FHSS
S-Band ISM
DSSS
S-Band ISM
OFDM
C-Band ISM
OFDM
S-Band ISM
802.11n
54-600
Mbps
/2.4 or
5 GHz
OFDM
MIMO14
Eng: Mohammed Hussein
Media Access Control (MAC)
Eng: Mohammed Hussein15
The MAC is the way to transfer the data safely when there is more
than one node accessing a channel simultaneously .
The MAC have some techniques such as:
Distributed Coordination Function (DCF) used by both methods Ad-
Hoc mode or Infrastructure mode. With asynchronous transmission
data service.
Point Coordination Function (PCF) used only by Infrastructure mode.
With both asynchronous and time-bounded service
Access Method
MAC layer:
DCF (Distributed Coordination Function) :
based on CSMA/CA
PCF (Point Coordination Function) :
based on polling
16Eng: Mohammed Hussein
The Medium Elements
Next FrameFrame
DIFS
PIFS
SIFS
DIFS
Time
Defer Access
Contention
Window
Backoff Slot time
Medium is available
17
DCF inter-frame spacing (DIFS) : between the end of one transmission and another next
round cycle transmission in Ad-Hoc mode
Short inter-frame spacing (SIFS) : has a high priority and comes after frames such as
(RTS, CTS, ACK).
PCF inter-frame spacing (PIFS) : between the end of one transmission and another next round
cycle transmission in Infrastructure mode
Medium is Busy
Eng: Mohammed Hussein
Wireless Problems
18 Eng: Mohammed Hussein
Hidden Terminal Problem
Eng: Mohammed Hussein19
BA C
The transmissions from node A and node C collide at the
receiver node B . (in the same time)
Exposed Terminal Problem
Eng: Mohammed Hussein20
BA C D
Wait the
medium is busy
The node C senses the medium is busy, therefore node C waits unnecessarily
time before it begins transmitting to node D.
So the waiting here is not required and node C is exposed to node B.
CSMA/CA PROTOCOL
Eng: Mohammed Hussein21
The nodes throughputs are measured in the CSMA/CA by a collisions and idle slots resulting from Backoff algorithm for each CW period.
The CSMA/CA is algorithm for IEEE 802.11 DCF, simply listen-before-talk scheme.
N+1-th Packet
TransmissionCollision
DIFSSIFS DIFS
N-th Packet
Transmission ACK ACKCollision
Idle Backoff Slots
(at each contention period)
Virtual Transmission Time
SIFS DIFSCollision
Node 1
Node 2
Node 3
Node 4
Time
DIFS
DCF (NAV , RTS, CTS, ACK )DIFS
Node 5
Data
Data General data frameBackoff slot time
ACK
RTS
CTSSIFS
SIFS
SIFS
Defer Access
Node 4 increase
2 slot more
SIFS
Data
ACK
CTS
RTS ACKRequest To Send Frame
NAV (RTS)
NAV (CTS)
NAV (data)
Remaining Backoff
Clear To Send FrameClear To Send Frame
Backoff
NAV NAV timer
NAV
updates
22Eng: Mohammed Hussein
(PCF) infrastructure mode
The idea of this access method is that the access point pools
its mobile nodes corresponding to a list.
For avoiding problems with the two DCF access methods
the PCF-IFS (PIFS) are used.
They grant an access point priority access to the medium
23 Eng: Mohammed Hussein
Beacon in infrastructure mode
Synchronization in infrastructure mode is very easy.
The Access Point (AP) regularly sends out a synchronization packet
(beacon).
If the medium is busy the AP just waits for a free PIFS frame
24 Eng: Mohammed Hussein
Server(internet)
802.11 frame
2Bytes 2 6 6 6 2 6 0-2312 4
Frame
Control
Duration / ID
Address 1
Address 2
Address 3
Sequence
Control
Payload
(Frame Body)
CRC
Address 4
MAC Header
25Eng: Mohammed Hussein
frame
controlduration
address
1
address
2
address
4
address
3payload CRC
2 2 6 6 6 2 6 0 - 2312 4
seq
control
802.11 frame: addressing
Address 2: MAC addressof wireless host or AP transmitting this frame
Address 1: MAC addressof wireless host or AP to receive this frame
Address 3: MAC addressof router interface to which AP is attached
Address 3: used only in ad hoc mode
26Eng: Mohammed Hussein
BSS1
BSS2
DS ( Distribution System)
STA 2
SS STA 3
DSS
DSS
802.X LAN
internet
DSS
ESS
STA 1
STA 4
802.11 MAC/PHY
802.11 MAC/PHY
SS :Station services
SS
STA :Station
DSS: Distribution System services
ESS: Extended Service Set
BSS: Basic Service Set
Portal
27Eng: Mohammed Hussein
Infrastructure network
28 Eng: Mohammed Hussein
Handover between APs
29 Eng: Mohammed Hussein
Ad-Hoc Network
IBSS (Independent Basic Service Set)
30 Eng: Mohammed Hussein
Ad-Hoc Network
Eng: Mohammed Hussein31
Ad Hoc classification
32 Eng: Mohammed Hussein
33 Eng: Mohammed Hussein
Sensor node
Internet
Manager Nodeuser
Sink Node
The environment Sensors field
Target
Wireless Sensor Network
34Eng: Mohammed Hussein
Sensor Node
Eng: Mohammed Hussein35
WiMax Scenario
Eng: Mohammed Hussein36
Scenarios for integrated
WiFi and WiMAX networks
Eng: Mohammed Hussein37
Summary of QoS
Eng: Mohammed Hussein38
COMNET III
COMNET III is a commercial off-the-shelf
application whose function is to allow users to
estimate the performance characteristics of
computer based networks.
A network description is created graphically using a
window interface, and no actual programming is
required of the user.
The application was formulated primarily for the
modeling of both Wide Area Networks (WANs) and
Local Area Networks (LANs). 39
Eng: Mohammed Hussein
COMNET III
The COMNET III application was written in the
programming language MODSIM II using an
object-oriented design.
1. RUNNING A SIMULATION
2. STATISTICAL DISTRIBUTIONS AND TABLES
3. REPORTS
4. PLOTS AND PERCENTILES
COMNET III uses a discrete event simulation
methodology when running the simulation of a
network model.
40Eng: Mohammed Hussein
References
Eng: Mohammed Hussein41
Some Books : Second Generation Mobile And Wireless Technologies; Black, Uyless Prentice Hall; 09/1998; Wireless Personal Communications; A Systems Approach; Goodman,
David J. Addison Wesley; 09/1997; Principles of Mobile
Communication; Stuber, Gordon L. Kluwer Academic Publishing; 6/96.
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