wireless technology and network convergence 1224574383734501 8

8/3/2019 Wireless Technology and Network Convergence 1224574383734501 8

1/60


2/60

A Brief History

Wireless communications originated withthe demonstration by Tesla in 1893,followed by the invention of wirelesstelegraph by Marconi in 1896

Advances in wireless communicationshave led to radio, television, mobiletelephones, and communication satellites

Development of wireless networks: LAN,

MAN, and WAN Trend continues: Voice Data

Broadband Need to support mobility


3/60

Trends

Revenue for wireless communicationindustry has surpassed that of wiredtelephony industry

Wireless applications span both local areaand wide area for: voice-oriented services, and

data-oriented services

Global cellular networks are providing veryconvenient communication infrastructure

Broadband wireless networks areevolving: Wireless LANs are very popular


4/60

Licensed and Unlicensed Bands

Licensed: Cellular/PCS

Expensive (PCS bands in US were sold for around $20B)

Time consuming to deploy new applications rapidly at

low costs Unlicensed:

Industrial, Medical, and Scientific (ISM) Bands

Free, component costs are also low

New applications such as WLAN, Bluetooth are easily

developed With the increase in frequency and data rate, the

hardware cost increases, and the ability topenetrate walls also decreases


5/60

Duplexing

Duplexing facilitates communications inboth directions simultaneously: basestation to mobile and mobile to basestation

Duplexing is done either using frequencyor time domain techniques: Frequency division duplexing (FDD)

Time division duplexing (TDD) FDD is suitable for radio communication

systems, whereas TDD is more suitable forfixed wireless systems


6/60

Multiple Access Techniques

Frequency Division Multiple Access

Time Division Multiple Access

Spread Spectrum Multiple Access Space Division Multiple Access

Packet Radio


7/60

Frequency Division Multiple Access(FDMA)

The frequency spectrum is divided intounique frequency bands or channels

These channels are assigned to users on

demand Multiple users cannot share a channel

Users are assigned a channel as a pair of

frequencies (forward and reversechannels)

FDMA requires tight RF filtering to reduceadjacent channel interference


8/60

Channel-1

Channel-6

Channel-5

Channel-7

Channel-8

Channel-9

FDMA

TIME

FREQUENCY

Channel-2

Channel-3

Channel-6

Channel-4

Channel-5

Channel-7

Channel-8

Channel-9


9/60

Time Division Multiple Access-TDMA

TDMA systems divides the radio spectruminto time slots, and in each time slot onlyone use is allowed to either transmit orreceive

Transmission for any user is non-continuous

In each TDMA frame, the preamblecontains the address and synchronization

information TDMA shares a single carrier frequency

with several users

TDMA could allocate varied number of

time slots per frame to different users


10/60

TDMA

TIME

FREQUENC

Y

Channel-7

Channel-10

Channel-8

Channel-9

Channel-6

Channel-5

Channel-4

Channel-3

Channel-2

Channel-1


11/60

Spread Spectrum Multiple Access(SSMA)

SSMA uses signals that have atransmission bandwidth several orders ofmagnitude greater than the minimumrequired RF bandwidth

SSMA provides immunity to multipathinterference and robust multiple accesscapability

SSMA is bandwidth efficient in multi-user

environment SSMA techniques:

Frequency hopped (FH) multiple access Direct sequence (DS) multiple access

Also known as code division multiple access (CDMA)


12/60

FHMA

Carrier frequencies of individual users are variedin a pseudorandom fashion within a widebandchannel

Data of each user is broken into uniform size

bursts that are transmitted on different channelsat different time instants based on their pseudo-noise (PN) code sequence

In the FH receiver, a locally generated PN code isused to synchronize the receivers instantaneous

frequency with that of the transmitter FHMA provides inherent security, and guard

against erasures through error control coding andinterleaving

Use: Bluetooth and HomeRF


13/60

CDMA The narrowband message signal is multiplied by a very

large bandwidth signal called spreading signal The spreading signal has a pseudo-noise code sequence

that has a chip rate which is orders of magnitudes greaterthan the data rates of the message

All users use the same carrier frequency and can transmitsimultaneously

Each use has its own pseudorandom codeword that isorthogonal to the others

The receivers need to know the codeword of thecorresponding sender

Power control is used to combat the near-far problem Near-far problem:

When many mobile users share the same channel, thestrongest received mobile signal will capture thedemodulator at a base station. Thus a nearby subscribercould overpower the base-station receiver by drowningout the signals of far away subscribers.


14/60

CDMA Features

Many users of CDMA share the same frequency either TDD or FDD may be used

CDMA has soft capacity limit systemperformance is inversely proportional to the

number of users Multipath fading is reduced because of the signal

spread

Channel data rates are very high

Prone to self-jamming and near-far problem Self-jamming: when the spreading sequences ofdifferent users are not exactly orthogonal

Near-far problem occurs at a CDMA receiver if anundesired user has a high detected power

compared to the desired user


15/60

Space Division Multiple Access(SDMA)

SDMA controls the radiated energy foreach user and serves different users byusing spot beam antennas

Different areas covered by antenna beammay be served by same or differentfrequencies

Reverse links present difficulty:

Transmitted power from each subscriber mustbe controlled to prevent any single user fromdriving up the interference level

Transmit power is limited by batteryconsumption at the subscriber unit


16/60

Packet Radio

In Packet Radio (PR) access techniques,many subscribers attempt to access asingle channel in an uncoordinatedmanner

Collisions from simultaneoustransmissions from multiple transmittersare detected at the base station receiver,in which case an ACK or NACK signal isbroadcasted by the base station to alertthe user

PR subscribers use a contention techniqueto transmit on a common channel


17/60

Carrier Sense Multiple AccessProtocols (CSMA)

In CSMA protocols, each terminal onthe network is able to monitor thestatus of the channel before

transmitting information

Variations:

1-persistent CSMA

non-persistent CSMA

p-persistent CSMA

CSMA/CD


18/60

Convergence of Public Network

Carriers now use converged technologyprimarily in core, backbone portion of theirnetworks to carry customer traffic moreefficiently

Although carriers increasingly add IPequipment when they replace their voiceswitches, the majority of voice traffic isstill carried in circuit switched networks

A circuit is a physical path for thetransmission of voice, image or data.


19/60

ITU defines circuit switching as :

The switching of circuits for the exclusiveuse of the connection for the duration of acall

When a person or modem dials a call, the

network sets up a path between the callerand the dialed party Circuit switching is an example of a

connection-oriented system

The path is maintained exclusively for theduration of the call and not shared This causes wasteful utilization of network

capacity


20/60


21/60

Other Switching Technique-Message Switching

Message switching transfers arbitrarysized messages from a source to adestination using one or more

message switches Each switch stores the complete

message before forwarding it

Normally messages are stored foronly a short time, but they may bestored for days in some cases


22/60

A message being sent using oneintermediate message switch.


23/60

The telex network is an example of amessage switched network

Since the messages are stored in eachmessage switch, message switching is

suitable for the transfer of electronic mailand is used to send email to isolated partsof the world using connections providedby modems over the telephone network

Since there is no direct connectionbetween the sender and the recipient, it isnot possible to use message switching tologin to a remote computer


24/60

Rationale for Convergence

The Internet Protocol (IP) does not have thislimitation The Internet is a connection-less packet-switched

network. Packets from other sources fill pauses in one

conversation Eg. when a call is on hold, network capacity is

used for other traffic Moreover, technical advances have improved the

quality of voice and video carried on packet

networks In addition, costs for routers, hard drives and

fiber optics have decreased The capability to deploy and maintain a single

network for voice, data and video


25/60

As VoIP protocols becomeincreasingly standardised, custominterfaces between switches and

applications will increasingly becomeunnecessary


26/60


27/60

Softswitches

Process calls (issue commands onsetting up and ending calls)

Communicate with billing systems

Acts as an overall network controlpoint


28/60

Media Gateways

Switch calls and translate protocolsbetween different networks andbetween public network trunks such

as T-1 and T-3 trunks and IPnetworks


29/60

Media Servers

Generate touch-tone

Play announcements

Generate voice over IP packets from

voice mail application Convert voice mail messages to

digital IP packet and vice versa

Record voice mail messages Generate ring tones, busy signals,

dial tone


30/60

Application Servers

Contain complex applications

Eg.

unified messaging (capability to receivevoice mail, e-mail, and fax messages onpersonal computers)

Large audio conferencing systems


31/60

Peer-to-Peer Services

P2P services operate in adecentralised mode withoutsoftswitches to control signaling and

communication Napster, Gnutella, KaZaA enable

sharing of free music over theInternet

Skype introduced P2P architecturefor VoIP without central servers


32/60

Calling 911-VoIP vs Circuit switched

The Wireless Communication and Public SafetyAct (1999) establishes 911 as the emergencynumber throughout the US.

The first emergency number was 999 used inLondon

The act mandated all carriers to connect 911 callto appropriate local emergency dispatch centre

It also mandated FCC to develop a plan forwireless providers to transition to enhanced 911(E911)

Under E911, the agent who answer 911 calls isable to receive the callers phone number andlocation


33/60

Mobile Services

Competition between mobile networkoperators, and the desire for morerobust networks have led to the

implementation of third generationdigital networks by major mobileoperators


34/60

Evolution from 1G, 2G, 2.5G to 3G

The 1st G of cellular service usedanalog equipment in the early 1980s

The 1st service in US is AMPS

The 2nd G started in 1990s whencarriers upgrade their analog todigital networks to gain more

capacity These include GSM, CDMA, TDMA

and iDEN (Motorola)


35/60

2.5 G

Provides transition to WCDMA Most GSM operators implemented GPRS

and EDGE before WCDMA for the followingreasons:

WCDMA equipment was not stable until 2004 Small, lightweight 3G handset were not widely

available prior to 2004 Installing GPRS and EDGE delayed the large

expenses to upgrade to WCDMA

Handset for GPRS and EDGE were readilyavailable

GPRS and EDGE operate on the samefrequencies as GSM


36/60

3G

Transition from 2G CDMA TO 3GCDMA2000 is less costly and complex thantransition from GSM networks to WCDMA

The major incentive for upgarding is theincreased voice capacity as well as thedesire for a network capable of handlingadvanced application

Because it is easier to implement,CDMA2000 has more subscriberscompared to WCDMA


37/60


38/60

CDMA2000 1xEV-DO (dataoptimised- high data rate)

Network providers already have the1st stage CDMA2000 can upgrade tohigher data speeds by adding

software and channel cards to theirbase stations for high data rate

HDR service is a data-onlyenhancement with higher downlinkspeeds

No capacity is gained for voice traffic


39/60

WCDMA

Release FeaturesWCDMA(Release 4)

Enables operators to prioritisedata services per customer

subscriptionWCDMA(Release 5)

HSDPA (high speed downlinkpacket access)

IP voice and data

WCDMA(Release 6)

HASUPA (high speed uplinkpacket access)

Doubles the uplink speed


40/60

MobileFi

802.20: IP Mobile Broadband Wireless Access

In 2002, the IEEE stated its intention to providemobility in vehicles such as trains traveling up to150mph or 250kmph, and to support higher data

rates and more users than currently available Flarion uses a form of orthogonal FDM (OFDM) in

equipment called FLASH-OFDM.

Flash is short for Fast, Low-latency Access withSeamless Handoff

FLASH-OFDM spreads signals over a widerfrequencies and at faster rate than OFDM


41/60

Flarion service includes handoffs betweenWi-Fi and FLASH-OFDM networks so thatusers use Wi-Fi when it is availabale andFlarion when it is not

Flarion supports VoIP and able to prioritisetraffic It is not expected to be available until

2008

T-Mobile, Vodafone and TIME dotCOM (inMalaysia) are conducting trials of Flarionequipment


42/60

Wi-Fi, Wireless broadband, SensorNetworks and PANs

Wi-Fi IEEE 802.11

Wireless broadband - WiMax

Zigbee and IEEE 802.15 PANs


43/60

Evolution of Wireless LAN

Early experiences (1970-72): IBM, HP, Motorola Abandoned due to limited performance and

unavailability of frequency bands

Early challenges: Complexity and cost

Bandwidth Coverage Interference Frequency administration

Emergence of unlicensed bands

Release of Industrial, Scientific and Medical (ISM) bandsin 1985

Applications: military, home and enterprisenetworks, mobile networks, teetherless access


44/60

Wi-Fi is based on 802.11 technology

It is originally intended tio provide wirelesscomputing for staffs within businesses andcommercial organisations

However, residential customers adopted Wi-Fifaster than enterprises because of its simplicity,fewer concerns about security and the benefit ofavoiding the expenses for cabling

Its advantage is low equipment cost and easierinstallation

Benefits were also immediately noticed forhealthcare, education, retailing and warehousing


45/60


46/60

Logical link control

Point coordination function(PCF)

Distributed coordination function (DCF)

2.4-Ghz

frequency-hoppingspread

spectrum1Mbps2Mbps

2.4-Ghz

directsequence

spreadspectrum1Mbps2Mbps

Infrared

1Mbps2Mbps

5-Ghz

orthogonalFDM 6, 9.12. 18, 24,36, 48, 54

Mbps

2.4-Ghz

directsequence

spreadspectrum5.5 Mbps11 Mbps

Contention-free service

Contentionservice

MAClayer

IEEE 802.11 Protocol Architecture

IEEE 802.11 IEEE 802.11a IEEE 802.11b

802 11 hi h d ll


47/60

802.11a higher speeds, smallercoverage, more channels

Wi-Fi is also sold to hotspot operators particularlyhotel, convention centres, cafes, airports

Hotspots offer higher-speed Internet access thanmost cellular networks data offering and costless to build than cellular base station

802.11 wireless standards are based on Ethernetprotocols

802.11a is the only 802.11 standard thatoperates at 5 GHz

The use of 5 GHz band avoids interference frommicrowave ovens, Bluetooth equipments andcordless phones that operate at 2.4 GHz

Disadvantage is the signal fade faster


48/60

802.11b

When they were first available,802.11 equipments were equippedwith only 802.11b chips

Now most use b and g which aredesigned to interoperate

Because home broadband

connections are slower than 802.11networks, no advantage is gained


49/60

802.11g

Support higher data rates than802.11b

Use 2.4 gHz bands

The higher speeds and capacity of gand a are required to support voiceover IP on WLANs


50/60

802.11n

Backward compatibility with a, b andg

Improve coverage by overcoming a

certain amount of interference

Increase speeds and supports moreusers per access point


51/60

Broadband wireless access

Wimax and universal mobile telecommunicationsystem time division duplex (UMTS TDD) may inthe future provide mobile wireless broadbandservice for pedestrian, people in moving vehiclesand within buildings

However, most current implementations are forless complex wireless service between fixedlocations or for wireless service with Internetaccess and portability within a service providers

coverage area Currently no portability is provided within

buildings (therefore, Wi-Fi is still needed)

Wimax is based on 802.16

WCDMA M difi d f Wi l


52/60

WCDMA Modified for WirelessLocal Loop

SOMA Networks provide a packetized wirelesslocal loop service to replace broadband cable andDSL service

The service is designed for circuit-switched voice,fax and high-speed data

The equipments operate in the 1.9, 2.3 and 2.6GHz licensed frequency bands SOMA is used in developing countries where

cabling to residential or rural areas is rare SOMA modified 3G WCDMA to provide end-to-end

QOS and multimegabit data speed SOMA is not portable or mobile However, it is rolling out integrated Wi-Fi handset

for portable voice within home Jaring uses SOMA equipments


53/60

Sensor Networks An emerging technology to monitor condition in

buildings, control manufacturing systems, etc Until recently, large-scale sensor networks are

expensive because sensors require wiredconnection to each other and the LAN

The new sensor network is able to send infowirelessly

2 topology can be deployed Full-mesh: each sensor is connected to every

other device

Partial-mesh: some nodes are connected to eachother, others only to the nodes they exchangethe info most

Based on 802.15.4 which is slow speed (20-250kbps), non line-of-sight (LOS)


54/60

IEEE 802.15.4 and ZigBee

Home Applications

Internet connectivity, multi-PC connectivity,audio/video networking

[broadband, always-on, relatively expensive] Home automation, security, devicemanagement

[low-throughput, power-constraint, low-cost]

IEEE 802.11 and Bluetooth do not satisfythe requirements of the second set

Evolution of IEEE 802.15.4 and ZigBee in2000


55/60

ZigBee

Based on 802.15.4 standard, developed byZigBee Alliance

Defined higher-level protocols that will operateover network using 802.15.4

ZigBee 1.0 was announced in Dec 2004 It is a lightweight routing protocol for mesh

network that adds security and additional meshnetworking function to 802.15.4

It has potential to control alarms, monitorelectricity, provide status from smoke detectors,thermostat, and hot water tanks in commercial orresidential buildings


56/60

Protocol Stack

APPLICATIONS

APPLICATION FRAMEWORK

NETWORK/SECURITY LAYERS

MAC LAYER

PHY LAYER

User Defined

ZigBee Alliance

IEEE 802.15.4


57/60

It can monitor windows to determineif they are closed or not

Its target application include remote

controls (now using infrared thatrequires LOS)

However, it receives competitionfrom companies providing alarmservices like ADT

Has potential for future use


58/60

PANs Bluetooth- widely used (not discussed here) Ultra-Wideband (802.15.3a) Is high-speed, short range wireless tech that

works by transmitting low-power signals over awide range of frequencies

Does not require spectrum license It is designed not to interfere with conventional

radio It can penetrate walls and do not drain batteries

quickly

It is faster than Bluetooth and Wi-Fi Can be used to link electronics for home

entertainment network and asset tracking However, lack of uniform standard is holding its

sales


59/60

RFID

A non-LOS wireless tech used to control,detect and tract objects

RFID system is made up of Interrogator readers

Transponder with integrated antenna on chips Active transponder has battery, larger in

size, more costly than passive one.However can be read at further distance

from reader Passive one has no battery, size of a 5cent coin, are woken up by magneticinduction from reader, also known as tag


60/60

A middleware is required to reformatinformation gathered by readers to makeit compatible with database

RFID tags have electronic product codes(EPC)

Super RFID can be used for sensornetwork requires intelligent tags andreaders that record conditions beingmonitored and set off alarms if thethresholds are exceeded

Operates in low frequency (30-500KHz)- shorter range High frequency (850-950KHz/2.4-2.5GHz)

range up to 90 feet- may interfere with Bluetooth and Wi-Fi gear

wireless technology and network convergence 1224574383734501 8

Documents