fundamentals of modulation...

5/8/2006 CS-CMPE-5710: Mobile Wireless Networks 1

Fundamentals of Modulation Techniques

What is a baseband and passband signal?What is a baseband and passband signal?Analog vs. Digital modulationAnalog vs. Digital modulationModulation principal is the same in both cases, the Modulation principal is the same in both cases, the user signal format is differentuser signal format is differentRepresentation of the signalsRepresentation of the signals

Time domainTime domainFrequency domainFrequency domainOrthogonal signal spaceOrthogonal signal space

What is orthogonal signal space?What is orthogonal signal space?


Fundamentals of Modulation Techniques

Why modulate?Why modulate?To allow for efficient spectrum useTo allow for efficient spectrum usemultiple user support on a shared mediummultiple user support on a shared medium

How do we modulate?How do we modulate?Use a carrier to translate the spectrum of the userUse a carrier to translate the spectrum of the useruse different carriers to separate them in frequencyuse different carriers to separate them in frequency

Where does the information reside in a modulated Where does the information reside in a modulated signal?signal?

There are three parameters associated with a sinusoidal There are three parameters associated with a sinusoidal carrier signalcarrier signal

AmplitudeAmplitudefrequencyfrequencyphasephase

Use one of them to carry the users information bearing Use one of them to carry the users information bearing signalsignal


Digital Modulation

Desirable modulation method Desirable modulation method provides low BER at low SNRprovides low BER at low SNRPerforms well in multipath and fading environmentPerforms well in multipath and fading environmentOccupies least amount of bandwidth/symbolOccupies least amount of bandwidth/symbolEasy and cost effective to implementEasy and cost effective to implement

Generally they are two categoriesGenerally they are two categoriesPower efficient Power efficient –– FSK, Spread spectrumFSK, Spread spectrum

At low SNR provide acceptable BERAt low SNR provide acceptable BERBandwidth efficient Bandwidth efficient –– PSK, QAM and its variantsPSK, QAM and its variants

At fixed bandwidth provide acceptable BERAt fixed bandwidth provide acceptable BERBandwidth efficiency (BE)= R/BBandwidth efficiency (BE)= R/BBE =C/B= log2(1+SNR)BE =C/B= log2(1+SNR)


Digital Modulation – Shannon’s Capacity for an AWGN Channel

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Digital Modulation – Bandwidth and PSD of Signals


Digital Modulation – Line coding and Pulse Shaping


Digital Modulation – Pulse Shaping Nyquist Criteria for Zero ISI

Pulse passing through a band limited multipath channel experiencPulse passing through a band limited multipath channel experience smearing or time e smearing or time spreadingspreadingNyquist suggested that if the overall response of the system couNyquist suggested that if the overall response of the system could be such that at the ld be such that at the sampling instant only the desired signal has non zero value, i.esampling instant only the desired signal has non zero value, i.e.,.,


Digital Modulation

Any filter of the following kind also satisfies Nyquist criterioAny filter of the following kind also satisfies Nyquist criterion; where n; where Z(fZ(f)=Z()=Z(--f) and Z(f)=0 for mag.(f)>fo>1/2Tsf) and Z(f)=0 for mag.(f)>fo>1/2Ts


Digital Modulation – Raised Cosine Rolloff Filters

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Digital Modulation – Geometrical Representation of Signals

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Digital Modulation - BPSK


Digital Modulation - QPSK



Convert the bit sequence from unipolar to bipolar NRZConvert the bit sequence from unipolar to bipolar NRZSplit the input bit stream into even and odd streamsSplit the input bit stream into even and odd streamsModulate the two streams separately on quadrature carriersModulate the two streams separately on quadrature carriersSum them together to form the QPSK signalSum them together to form the QPSK signalPass it through the BPF to confine the signal in the desired Pass it through the BPF to confine the signal in the desired bandband


Digital Modulation – Offset QPSK

Amplitude of the QPSK is constant Amplitude of the QPSK is constant Because of pulse shaping, they loose the constant Because of pulse shaping, they loose the constant envelope propertyenvelope propertyThe 180 phase shift can cause the envelope to pass The 180 phase shift can cause the envelope to pass through the zero for just an instant that causes the through the zero for just an instant that causes the filtered side lobes to reappear because of nonlinear filtered side lobes to reappear because of nonlinear amplifiers that do not linearly amplify the small amplifiers that do not linearly amplify the small voltagesvoltagesThis requires the use of less power efficient linear This requires the use of less power efficient linear amplifiersamplifiersOQPSK is less susceptible to this effectOQPSK is less susceptible to this effect


Digital Modulation – Offset QPSK

In OQPSK the even and odd bit steam are staggered by one bit In OQPSK the even and odd bit steam are staggered by one bit period resulting in at the most 90 degree phase transitionsperiod resulting in at the most 90 degree phase transitions


Digital Modulation – Pi/4 QPSK

It is compromise between QPSK and OQPSK. Maximum phase It is compromise between QPSK and OQPSK. Maximum phase transition is +transition is +--135 degrees135 degreesConstant envelope property is better than QPSK and worse than Constant envelope property is better than QPSK and worse than OQPSKOQPSKThere is at least a pi/4 phase shift There is at least a pi/4 phase shift

every symbolevery symbolGood for timing recoveryGood for timing recovery


Digital Modulation: Minimum Shift Keying – MSK

MSK is a special case of the continuous phase MSK is a special case of the continuous phase frequency shift keying wherein peak frequency frequency shift keying wherein peak frequency deviation is equal to deviation is equal to ¼¼ the bit rate:the bit rate:When When moduolationmoduolation index is 0.5 the two FSK signals index is 0.5 the two FSK signals are coherently orthogonal.are coherently orthogonal.As it is the minimum frequency spacing for two As it is the minimum frequency spacing for two signals to be orthogonal, it is the reason for the signals to be orthogonal, it is the reason for the name Minimum Shift Keyingname Minimum Shift KeyingMSK is special form of OQPSK where base band MSK is special form of OQPSK where base band rectangular pulses are replaced by half rectangular pulses are replaced by half sinusoidal pulsessinusoidal pulses


Digital Modulation: Minimum Shift Keying – MSK


Digital Modulation: Gaussian Minimum Shift Keying – GMSK

It is passing the MSK signal with a Gaussian pulse It is passing the MSK signal with a Gaussian pulse shaping filter, further shaping filter, further smothingsmothing the instantaneous the instantaneous phase and thus the phase and thus the sidelobessidelobes of the transmitted of the transmitted signal.signal.


Spread Spectrum Techniques

What is it?What is it?Why spread?Why spread?

Interference rejectionInterference rejectionInherent securityInherent security

Types of Spread Spectrum techniquesTypes of Spread Spectrum techniquesDirect SequenceDirect SequenceFrequency HoppedFrequency Hopped

How spread spectrum signal rejects interferenceHow spread spectrum signal rejects interferenceProcessing gainProcessing gain

Pg=Tx. Signal bandwidth/Pg=Tx. Signal bandwidth/appliactionappliaction data ratedata ratethe interference rejection is directly proportional to the the interference rejection is directly proportional to the processing gain and the crossprocessing gain and the cross--correlation properties of the correlation properties of the spreading codespreading code


The ISI & ACI problem - design of the appropriate Transmitted Pulse-shape

The transmitted pulse should be such that it The transmitted pulse should be such that it eliminates ISI and reduces the Adjacent Channel eliminates ISI and reduces the Adjacent Channel Interference (ACI) as much as possible. Interference (ACI) as much as possible. The Sinc pulse eliminates ISI but is not physically The Sinc pulse eliminates ISI but is not physically realizable. Its roll off as a function of frequency is realizable. Its roll off as a function of frequency is slowslowRaised cosine pulse is suitable for most practical Raised cosine pulse is suitable for most practical purposespurposesIn FDM systems, ACI is important as it deteriorates In FDM systems, ACI is important as it deteriorates signal quality in the adjacent bandsignal quality in the adjacent bandUse Guassian filter to increase the roll off rate.Use Guassian filter to increase the roll off rate.


The Typical Transmitter

digitalsourcedata

FEC encoder

bit/blockinterleaver

modulatortransmit

filter

up-converter

poweramplifier duplexer

D/Aconverter

Digital

Discrete

Analog


The Typical Receiver

demod.Rx

filter

Discrete

low noiseamplifier

widebandfilter

signalcombiner

downconverter

Analog

digitaldatasink

FEC decoder

bit/block deinterleaver

Digital

A/Dconverter

detector

equalizer


Main Tx./Rx. components

Why FEC coding?Why FEC coding?To provide error correction capability and reduce the desired To provide error correction capability and reduce the desired SNRSNR

Why interleaving?Why interleaving?To reduce the amount of burst errors due to deep fades or To reduce the amount of burst errors due to deep fades or impulsive noiseimpulsive noise

Why receive filter?Why receive filter?To reject undesired signalsTo reject undesired signals

Why amplification?Why amplification?To combat signal attenuationTo combat signal attenuation

Why equalizer?Why equalizer?To remove ISITo remove ISI

Why diversity?Why diversity?To combat the effects of signal fading To combat the effects of signal fading


About Equalizers

What actually equalizers do?What actually equalizers do?Channel inversionChannel inversionEqualizer frequency responseEqualizer frequency response

Equalizer structuresEqualizer structuresTransversal filtersTransversal filtersLinear vs. nonLinear vs. non--linearlinear

Equalizer training and adaptationEqualizer training and adaptationAdaptation algorithmsAdaptation algorithms

LMS algorithmLMS algorithm


About FEC coding and Interleaving

What is FEC coding?What is FEC coding?Types of FEC codingTypes of FEC coding

Block vs. convolutional codingBlock vs. convolutional coding

How coding works?How coding works?RedundancyRedundancyError detection and correctionError detection and correctionCode efficiencyCode efficiencyCoding gainCoding gain

How interleaving works?How interleaving works?Interleaving introduces delayInterleaving introduces delay

How it impacts applicationsHow it impacts applicationsvoice voice -- compressed or noncompressed or non--compressed compressed datadata


About Diversity

What is diversity?What is diversity?How does it work?How does it work?

Correlation in multipath signalsCorrelation in multipath signals

Types of diversity techniquesTypes of diversity techniquesspace, time, frequency, polarizationspace, time, frequency, polarization

Diversity combiningDiversity combiningselection, equal gain, maximal ratioselection, equal gain, maximal ratio

Commonly used techniquesCommonly used techniquesWhen and where to use?When and where to use?

Base station vs. mobileBase station vs. mobilepower of mobile vs. base station transmitterspower of mobile vs. base station transmitters


Multiple Access in Mobile Networks

Multiple access is not just multiplexing.Multiple access is not just multiplexing.It allows sharing of finite resource among more users on a It allows sharing of finite resource among more users on a dynamic basisdynamic basis

Design of a mobile cellular systemDesign of a mobile cellular systemavailable resource is allocated bandwidth and maximum available resource is allocated bandwidth and maximum power limitspower limitsChallenge is to design a system that maximizes the number Challenge is to design a system that maximizes the number of users that can be simultaneously supported in a cell while of users that can be simultaneously supported in a cell while reducing the number of cells in a given service area.reducing the number of cells in a given service area.

This is the system capacity problemThis is the system capacity problemMultiple access schemes have a role in the system capacity Multiple access schemes have a role in the system capacity calculationcalculation

What options are availableWhat options are availableFDMA FDMA -- TDMA TDMA -- CDMACDMA


Frequency Division Multiple Access-FDMABand of frequencies is divided into segments.Band of frequencies is divided into segments.

Each segment is available to a user during a callEach segment is available to a user during a callEach user has to contend for the access to the bandwidth Each user has to contend for the access to the bandwidth resource through a admission control mechanismresource through a admission control mechanismChannels are assigned as pair of frequenciesChannels are assigned as pair of frequenciesChannels are generally narrow, guard band is neededChannels are generally narrow, guard band is needed

Amplifier nonAmplifier non--linearity causes intermodulation linearity causes intermodulation frequencies infrequencies in--band and out of bandband and out of band

Downlink Uplink

890 915 935 960 - EuropeMHz

824 849 869 894 - US


Time Division Multiple Access - TDMA

Users share the bandwidth in timeUsers share the bandwidth in timeuse the same frequency band but not all the timeuse the same frequency band but not all the timeN users use the system 1/N time eachN users use the system 1/N time eachadmission control is needed for each calladmission control is needed for each callresource is reserved on per call basisresource is reserved on per call basis

TDMA is practical with digital signalsTDMA is practical with digital signalsTDMA is a store and burst systemTDMA is a store and burst system

Typical TDMA frame formatTypical TDMA frame formatNeed stringent synchronizationNeed stringent synchronizationDelay is an issue; user close to base station and at the cell Delay is an issue; user close to base station and at the cell edge have different propagation delay edge have different propagation delay -- guard time is guard time is needed to protect against thisneeded to protect against this-- it is adaptive frame it is adaptive frame alignmentalignment


TDMA vs FDMA

TDMA permits much more capacity than FDMATDMA permits much more capacity than FDMANegligible Intermodulation products in TDMA as only Negligible Intermodulation products in TDMA as only one carrier is used and has less bandwidth than the one carrier is used and has less bandwidth than the total FDMA systemtotal FDMA systemTDMA systems have overhead TDMA systems have overhead Control information can be sent without interruption Control information can be sent without interruption of speechof speechMay assist in hand over by monitoring an idle slotMay assist in hand over by monitoring an idle slotDynamic channel assignment is easily possible for the Dynamic channel assignment is easily possible for the case that channel conditions worsen; similar to some case that channel conditions worsen; similar to some cordless phones.cordless phones.Increased system flexibilityIncreased system flexibility


Code Division Multiple Access - CDMA

In CDMA, all users use the same frequency band In CDMA, all users use the same frequency band separation is in code domainseparation is in code domain

Main advantages are?Main advantages are?lower transmit power at the base and mobile station. Why?lower transmit power at the base and mobile station. Why?Soft handoffSoft handoffSome level of securitySome level of securityMore capacity than FDMAMore capacity than FDMA

Main disadvantagesMain disadvantagesnear far problemnear far problempower controlpower controlvery complex handoff managementvery complex handoff management


Source Data - Coding & Compression

Compression of the source signals increases system Compression of the source signals increases system capacity proportionallycapacity proportionallyThere are two coding approachesThere are two coding approaches

Waveform based codingWaveform based codingVocoders Vocoders -- use a parametric model of the sourceuse a parametric model of the source

Waveform based coding techniques are source type Waveform based coding techniques are source type independent so can be used in variety of situationindependent so can be used in variety of situation

They are robust in noisy environment and yield less degree They are robust in noisy environment and yield less degree of compressionof compressionPCM, DPCM, ADPCM, DM, APCPCM, DPCM, ADPCM, DM, APC

Vocoders achieve high compression but are more Vocoders achieve high compression but are more complexcomplex

They are also signal specific as they use a specific They are also signal specific as they use a specific parametric model of the sourceparametric model of the source


Characteristics of the Speech Signal

Amplitude of the speech signal is nonAmplitude of the speech signal is non--unifromlyunifromlydistributeddistributedsuccessive speech samples have nonsuccessive speech samples have non--zero correlationzero correlationSpeech spectra is not flatSpeech spectra is not flatSpeech spectra is band limitedSpeech spectra is band limitedSpeech signal has voice and nonSpeech signal has voice and non--voice partvoice partquasiquasi--periodicity of the speech signalsperiodicity of the speech signalsPDF of voice is a two sided Laplacian distribution PDF of voice is a two sided Laplacian distribution (7.1)(7.1)


Waveform Coding

Sampling, Quantization and CodingSampling, Quantization and CodingQuantizationQuantization

what is itwhat is itQuantization noiseQuantization noiseSignal to Quantization noise ratioSignal to Quantization noise ratioUniform vs NonUniform vs Non--uniform uniform MuMu and A law and A law compandingcompanding

PCM encodingPCM encoding


PCM Encoding example


Delta Modulation

Quite Different in principal to PCMQuite Different in principal to PCMCoding is simple, one bit at a timeCoding is simple, one bit at a timesampling rate should be much higher, it determines the sampling rate should be much higher, it determines the quantization noise floor.quantization noise floor.Delta modulation, modulates the slope of the signal, Delta modulation, modulates the slope of the signal, negative (0)or positive (1).negative (0)or positive (1).Does not capture the instantaneous valueDoes not capture the instantaneous value

+- +

Integrator Pulse Generator

0

Input + 11 Output

0- 0IntegratorPulse

Generator1


ADPCM

Mix of both PCM and DMMix of both PCM and DMExploits correlation in adjacent samplesExploits correlation in adjacent samples

removes redundancy in the voice signalremoves redundancy in the voice signalvariance of the successive speech signals is much less than variance of the successive speech signals is much less than the variance of the speech signal itself.the variance of the speech signal itself.

Implemented using signal prediction techniquesImplemented using signal prediction techniquesA predictor predicts the current sampleA predictor predicts the current sampledifference between the predicted and actual sample is the difference between the predicted and actual sample is the prediction errorprediction errorprediction error is encoded using PCM and then transmitted prediction error is encoded using PCM and then transmitted decoder is essentially an integrator as in DM. decoder is essentially an integrator as in DM.

Speech Coding for 32 kbpsSpeech Coding for 32 kbps


Frequency Domain Coding

Two kindsTwo kindsSub band codingSub band codingBlock transform codingBlock transform coding

Sub band codingSub band codingControls and distributes quantization noise in different Controls and distributes quantization noise in different spectrum bands based on perceptibilityspectrum bands based on perceptibilityPerceptual quality Perceptual quality -- some bands of frequencies are more some bands of frequencies are more perceptible than otherperceptible than otheruse more bit to code those that are more perceptible to use more bit to code those that are more perceptible to human earhuman earUse 4 to 8 bandsUse 4 to 8 bandsUse octave band splitting as human ear has decreasing Use octave band splitting as human ear has decreasing sensitivity to frequencysensitivity to frequency

Speech Coding from 9.6Speech Coding from 9.6--32 kbps: Typical 16 kbps32 kbps: Typical 16 kbps


Sub Band Coding

LP Translator

LP Translator

Decimator

Decimator

Encoder

Encoder MU

LTIP

LEX

OR

s(t)

BP Translator

BP Translator

Decoder

Decoder

Interpolator

Interpolator

+

DEM

ULT

IPLE

XO

R

s’(t)


Adaptive Transform Coding

Take a block of input speech samples and then take Take a block of input speech samples and then take a transforma transformSeparately send each transform coefficients after Separately send each transform coefficients after quantization and encodingquantization and encodingInverse transform the quantized transform Inverse transform the quantized transform coefficients to find the approximated speech samples coefficients to find the approximated speech samples Most commonly used transform technique is Discrete Most commonly used transform technique is Discrete Cosine Transform (DCT) (Eq. 7.11 and 7.22)Cosine Transform (DCT) (Eq. 7.11 and 7.22)Transforms are computationally extensiveTransforms are computationally extensive

Fast algorithms are available Fast algorithms are available

Speech Coding from 9.6Speech Coding from 9.6--20 kbps:20 kbps:


ATC (DCT) Implementation

The frame of N samples to be transformed or inverse The frame of N samples to be transformed or inverse transformed are stored in a buffertransformed are stored in a bufferEach coefficient has a particular number of bits associated withEach coefficient has a particular number of bits associated witheach coefficient of a frameeach coefficient of a framebit allocation changes from frame to frame with total number of bit allocation changes from frame to frame with total number of bits/frame staying the samebits/frame staying the sameDynamic bit allocation is controlled by time varying statistics Dynamic bit allocation is controlled by time varying statistics that are transmitted as side/overhead information.that are transmitted as side/overhead information.In practical systems, overhead information is the log energy In practical systems, overhead information is the log energy spectrum that may be obtained from transform coefficients by spectrum that may be obtained from transform coefficients by averaging over a number of framesaveraging over a number of framesNumber of bits for each transform coefficient is proportional toNumber of bits for each transform coefficient is proportional tothe the corresponding spectral energy valuethe the corresponding spectral energy value


Vocoders

The parametric model of SpeechThe parametric model of SpeechSpeech generation modelSpeech generation modelSpeech I voiced and unvoicedSpeech I voiced and unvoicedSound generating mechanism and Vocal Tract Filter Sound generating mechanism and Vocal Tract Filter forms the systemforms the systemVoiced sounds are a result of quasiperiodic vibrations Voiced sounds are a result of quasiperiodic vibrations of the vocal cordof the vocal cord\\Unvoiced sounds are turbulent air flows through a Unvoiced sounds are turbulent air flows through a constrictionconstrictionThree parameters are Three parameters are

pitch frequencypitch frequencypole frequencies of the modulating filterpole frequencies of the modulating filteramplitude parameters (loudness)amplitude parameters (loudness)


Vocoders - Linear Predictive Coders (LPC)

Time domain class of vocodersTime domain class of vocodersLPC model vocal tract as an all pole linear filter with the tranLPC model vocal tract as an all pole linear filter with the transfer sfer function in 7.13function in 7.13The filter is excited by either a pulse at the pitch frequency oThe filter is excited by either a pulse at the pitch frequency or r random white noiserandom white noisefilter coefficients are obtained in time domain by the linear filter coefficients are obtained in time domain by the linear prediction techniques. The principal is same as ADPCMprediction techniques. The principal is same as ADPCMLPC systems send only selected characteristics of the error LPC systems send only selected characteristics of the error signal;signal;

the gain factorthe gain factorpitch informationpitch informationvoiced/unvoiced decision informationvoiced/unvoiced decision information

error signal info is the excitation for the synthesis filter.error signal info is the excitation for the synthesis filter.


LPC Coding System

LPC Filter

Pitch Analysis

Encoder

Encoder

Decoder

Decoder SYN

THES

IZERs(t)

Voice/UnvoicedDecision

Encoder Decoder

CH

AN

NEL

Estimate parameters over 15Estimate parameters over 15--30 ms; 30 ms; Typical 2.4 Typical 2.4 --4.8 kbps4.8 kbpsTradeoff is in rate vs latencyTradeoff is in rate vs latencyCELP CELP -- Code Excited Linear predictionCode Excited Linear prediction

Excitation

Voice/Unvoiced

Buffer


Factors in Speech Codec Decision

Compatibility with existing standards Compatibility with existing standards Perceived quality of the voicePerceived quality of the voiceEncoding delayEncoding delayAlgorithmic complexity of the CodecAlgorithmic complexity of the CodecDC power requirementDC power requirementRobustness to transmission errorsRobustness to transmission errors

64 PCM and 40 ADM show similar robustness for same BER64 PCM and 40 ADM show similar robustness for same BERVocoders have different importance to different bits. So Vocoders have different importance to different bits. So error protection should be accordingly providederror protection should be accordingly provided

GSM Codec is RPEGSM Codec is RPE--LTP (Regular Pulse Excited LTP (Regular Pulse Excited -- Long Long Term Prediction) 13 kbpsTerm Prediction) 13 kbpsTable 7.1, Example 7.4Table 7.1, Example 7.4


What is Network Management (NM)?

Effective NM Effective NM optimizesoptimizes a networka network’’s operational s operational capabilities capabilities

Primary/Key functionsPrimary/Key functionspeak network performancepeak network performanceforecasting performance deteriorationforecasting performance deteriorationfix the causes of deteriorationfix the causes of deteriorationfix the consequences of deteriorationfix the consequences of deteriorationnetwork survivabilitynetwork survivability

Secondary functionsSecondary functionsnetwork performance information in quasinetwork performance information in quasi--real timereal timemaintenance and enforcement of network securitymaintenance and enforcement of network securitydata on network usagedata on network usage

configuration managementconfiguration managementadministrative managementadministrative management


Network Management

Traditional breakout by taskTraditional breakout by taskFault ManagementFault Management

provide information on the status of all network elementsprovide information on the status of all network elementsdisplay faults and their locationdisplay faults and their locationdisplay deterioration in performance (e.g., congestion) and display deterioration in performance (e.g., congestion) and suggest solutionsuggest solutionRate of information should be high to ensure correlation of Rate of information should be high to ensure correlation of events before faultevents before fault

Configuration ManagementConfiguration ManagementInventory of the resourcesInventory of the resourcesHelps resource provisioning (deployment of network equipment Helps resource provisioning (deployment of network equipment to keep up with the demand or vice versa) to keep up with the demand or vice versa) and user provisioning (provides data for end user service and user provisioning (provides data for end user service provisioning such as initiation termination and management of provisioning such as initiation termination and management of services)services)


Network Management

Performance ManagementPerformance Managementensure specified network performanceensure specified network performancegrowth managementgrowth management

Security ManagementSecurity Managementcontrol access; no unauthorized usecontrol access; no unauthorized useprotect the network against intentional and accidental abuseprotect the network against intentional and accidental abuseprotect communication lossprotect communication losslink encryption, key and passwords management,user link encryption, key and passwords management,user authentication authentication

Accounting ManagementAccounting Managementservice and utilization records managementservice and utilization records managementcustomer billing reportscustomer billing reportscosts and service charge analysis and reportscosts and service charge analysis and reports

Network Survivability; It is the brainNetwork Survivability; It is the brainNM center is not operational because of flood, earth quake, NM center is not operational because of flood, earth quake, terrorism, All network is dead. terrorism, All network is dead.


Network Management System - NMS

What are NMS?What are NMS?Provide automatic means of remotely monitoring a network for Provide automatic means of remotely monitoring a network for

levels of performancelevels of performanceequipment failures, outagesequipment failures, outageslevels of traffic, network usagelevels of traffic, network usage

Network Management System use distributed processingNetwork Management System use distributed processingTypically require a communication link to monitor and control Typically require a communication link to monitor and control the networkthe network

It is the same link that is used for rest of the traffic. It is the same link that is used for rest of the traffic. It shares the link bandwidthIt shares the link bandwidthTypical approach is multiplexingTypical approach is multiplexingWhile resources for the user may be shared and not guaranteed, While resources for the user may be shared and not guaranteed, Network resources may be permanently availableNetwork resources may be permanently available


Network Management Protocols

There are two main protocols. Rest are their variations.There are two main protocols. Rest are their variations.SNMP SNMP -- Simple Network Management Protocol (TCP/IP World)Simple Network Management Protocol (TCP/IP World)CMIP CMIP -- Common Management Information Protocol (OSI World)Common Management Information Protocol (OSI World)

SNMPSNMPThree componentsThree components

The protocolThe protocolThe MIB (Management of Information Base)The MIB (Management of Information Base)The SMI (Structure of Management Information)The SMI (Structure of Management Information)

ClientClient--Server ModelServer Model

MIBSMI

NOC MIBSMI

Agent

Managing System - Client Managed System - Server

ManagementProtocol

Request Execute


SNMP

SMI SMI the set of Rules that define MIB objectsthe set of Rules that define MIB objectsgeneric types used to define management informationgeneric types used to define management information

Abstract Syntax Notation One Abstract Syntax Notation One -- ASN.1 (ITUASN.1 (ITU--T X.400)T X.400)high level abstract language high level abstract language

organizes MIB objects into an upside down treeorganizes MIB objects into an upside down tree

MIBMIBSet of managed objects or variablesSet of managed objects or variablesEach object has a unique name and identifier for Each object has a unique name and identifier for management purposesmanagement purposesMIBs are defined for each management element or nodeMIBs are defined for each management element or nodeComplete definition of a MIB element includesComplete definition of a MIB element includes

name, syntax, definition, access method, status (req., optional)name, syntax, definition, access method, status (req., optional)


SNMP Architecture and Messages

SNMP ArchitectureSNMP Architectureone or few managers and a number of agents scattered one or few managers and a number of agents scattered throughout the networkthroughout the networkagents use the local MIB to provide data to the NMS for agents use the local MIB to provide data to the NMS for manipulationmanipulationMessagesMessages

GetRequestGetRequestGetNextRequestGetNextRequestGetResponseGetResponseSetRequestSetRequestTrapTrap

Connectionless protocolConnectionless protocolSNMP/UDP/IP/SNMP/UDP/IP/……High overheadHigh overhead

MIB View

Agent

MIB View

Agent

GetRequest Trap SetRequest

MIB View

Agent

Mobile Station Router Workstation


SNMP Message Encapsulation

SNMP message encapsulated in the UDP (User SNMP message encapsulated in the UDP (User datagram Protocol) Datagramdatagram Protocol) DatagramUDP datagram encapsulated in IP datagramUDP datagram encapsulated in IP datagramIP packet encapsulated in the local network frameIP packet encapsulated in the local network frame

e.g., Ethernet, then local network frame is Ethernet framee.g., Ethernet, then local network frame is Ethernet frameif IP packet is too big, it will be in multiple Ethernet frameif IP packet is too big, it will be in multiple Ethernet frame

Local Network frame

IP Datagram

UDP Datagram

SNMP Message Local NetworkTrailer

Local NetworkHeader

UDP HeaderIP header


SNMP Messages Structure

Version No. to ensure same version used by all parties Version No. to ensure same version used by all parties Community name; a security mech. to authorize the registered useCommunity name; a security mech. to authorize the registered usersrsSNMP PDU is one of the five standard messagesSNMP PDU is one of the five standard messagesTRAP PDU structure is different from the otherTRAP PDU structure is different from the otherPDU Type field identifies one of the five message type, Table 18PDU Type field identifies one of the five message type, Table 18.1.1Request ID correlates request with responseRequest ID correlates request with response

Version GetRequest, SetRequest, GetNextRequest, GetResponse PDUCommunity

PDU Type Request ID Error Status Error Index Object 1, Value 1 Object 2, Value 2 ...

SNMP Message

Variable Binding


SNMP Messages Structure

Error Status field identifies errors or no errorsError Status field identifies errors or no errorsError Index filed identifies the error type if Error Status fileError Index filed identifies the error type if Error Status filed d indicated an error Table 18.2 p. 965indicated an error Table 18.2 p. 965A variable binding field pairs a variable name with its value A variable binding field pairs a variable name with its value e.g. a MIB element name and its valuee.g. a MIB element name and its value

Version GetRequest, SetRequest, GetNextRequest, GetResponse PDUCommunity

PDU Type Request ID Error Status Error Index Object 1, Value 1 Object 2, Value 2 ...

SNMP Message

Variable Binding


SNMP Trap Messages Structure

Trap is an unsolicited packet from an agent to a manger on a Trap is an unsolicited packet from an agent to a manger on a prescribed conditionprescribed condition

coldStart, warmStart, linkDown, linkUp, authenticationFailure, coldStart, warmStart, linkDown, linkUp, authenticationFailure, egpNeighbourloss, enterpriseSpecificegpNeighbourloss, enterpriseSpecific

Trap uses a different UDP port (162 instead of 161)Trap uses a different UDP port (162 instead of 161)PDU Type is set to 4. Why?PDU Type is set to 4. Why?Enterprise field; identifies the management enterprise Enterprise field; identifies the management enterprise authorityauthorityAgent Address: agents IP addressAgent Address: agents IP address

Version Trap PDUCommunity

SNMP Message

PDU Type

Enterprise Agent Address

Generic TrapType

Object 1, Value 1 Object 2, Value 2 ...Specific TrapType

Timestamp


SNMP Trap Messages Structure

Generic and Specific Trap Types; More specific information on Generic and Specific Trap Types; More specific information on the particular trap type; Table 18.3the particular trap type; Table 18.3Timestamp; value of the sysUpTimeobject. Amount of time Timestamp; value of the sysUpTimeobject. Amount of time elapsed between last reinitialization and the regeneration of elapsed between last reinitialization and the regeneration of the trap.the trap.

Version Trap PDUCommunity

PDU Type

Enterprise Agent Address

Generic TrapType

Object 1, Value 1 Object 2, Value 2 ...Specific TrapType

Timestamp

SNMP Message


Remote Monitoring - RMON

Distributed networksDistributed networksGeographicalGeographicalLogicalLogical

Remote MonitoringRemote Monitoringput remote management devices on remote segments of the put remote management devices on remote segments of the network, called probesnetwork, called probesprobes are sensors of the NMSprobes are sensors of the NMS

MIB for these probes is called RMON MIBMIB for these probes is called RMON MIBentries of this MIB may be exchanged between elements of entries of this MIB may be exchanged between elements of the network management systemthe network management system


SNMP V2Builds on the experience of SNMPBuilds on the experience of SNMPseparates the management protocol from the transport separates the management protocol from the transport mechanismmechanism

may be used in different protocol environmentmay be used in different protocol environmentincreases reliability of the SNMP increases reliability of the SNMP UDP is not as reliable a protocol as TCPUDP is not as reliable a protocol as TCPtrap messages are of significance but there is no confirmation trap messages are of significance but there is no confirmation mechanism for them in SNMPmechanism for them in SNMPif a trap message is lost, neither agent nor manager would if a trap message is lost, neither agent nor manager would know that a trap message is lostknow that a trap message is lostSNMP v2 eliminates trap primitive with GETSNMP v2 eliminates trap primitive with GET--RESPONSE frame RESPONSE frame generated by agent and meant for port 162 of the managergenerated by agent and meant for port 162 of the managerA trap MIB has been added to help trap event handlingA trap MIB has been added to help trap event handlingSNMP is inefficient from Bandwidth perspectiveSNMP is inefficient from Bandwidth perspectiveGetBulkRequest helps efficiency and removes the need of GetBulkRequest helps efficiency and removes the need of repeated request. repeated request. Allows manager to manager communications Allows manager to manager communications

stations can act as agent or managerstations can act as agent or manager


CMIP

Considerably more complex than SNMPConsiderably more complex than SNMPuses different terminology than SNMPuses different terminology than SNMPDatabase is MIT (Management Information Tree) not MIBDatabase is MIT (Management Information Tree) not MIBPlatforms and devices are MOs (Managed Objects)Platforms and devices are MOs (Managed Objects)CMIP is used by a platform to change, create, retrieve or CMIP is used by a platform to change, create, retrieve or delete MOs in an MITdelete MOs in an MITCMIP uses connection oriented communication vs CMIP uses connection oriented communication vs connectionless for SNMPconnectionless for SNMPCommunications are generally acknowledgedCommunications are generally acknowledged

Network Management in ATM NetworksNetwork Management in ATM NetworksInterim Local Management Interface (ILMI)Interim Local Management Interface (ILMI)It is SNMP without UDP and IP and an ATM UNI MIBIt is SNMP without UDP and IP and an ATM UNI MIBManagement channel is a wellManagement channel is a well--known VPI and VCI addressknown VPI and VCI address


Link Layer Protocol

Basic Protocol Functions:Basic Protocol Functions:Segmentation and reassemblySegmentation and reassembly

Breaking the data in blocks (PDU) and reassembling themBreaking the data in blocks (PDU) and reassembling them

EncapsulationEncapsulationAddition of control information (header). Address, sequence numbAddition of control information (header). Address, sequence number er and error control fields are typical examplesand error control fields are typical examples

Connection ControlConnection ControlConnection establishment, data transfer and connection terminatiConnection establishment, data transfer and connection terminationon

Ordered DeliveryOrdered DeliveryFor connectionless packet data, it ensures that all packets are For connectionless packet data, it ensures that all packets are in order in order

Error ControlError ControlThis helps recover lost or errored PDUs (e.g. TCP)This helps recover lost or errored PDUs (e.g. TCP)

Flow ControlFlow ControlMakes sure that buffers do not fill up causing erasures of PDUsMakes sure that buffers do not fill up causing erasures of PDUsWorks in several layersWorks in several layers


Link Layer Protocol

MultiplexingMultiplexingincreases efficiencyincreases efficiencymultiple higher layer functions should be multiplexed at the multiple higher layer functions should be multiplexed at the lower layer to increases transmission efficiency.lower layer to increases transmission efficiency.

Mapping of PDUs in Adjacent Layers Mapping of PDUs in Adjacent Layers PDU PDU -- Protocol Data UnitProtocol Data UnitSDU SDU -- Service Data UnitService Data UnitPCI PCI -- Protocol Control InformationProtocol Control Information

(N) PDU

(N-1) SDU

(N-1) PDU

(N-1) PCI

(N) layer

(N-1) layer


Link Layer Protocol

DataData--Link LayerLink LayerProvide reliable interchange of data across a link established Provide reliable interchange of data across a link established by the physical layerby the physical layerPhysical layer also tries to provide reliable transmission. ThisPhysical layer also tries to provide reliable transmission. Thislayer provides additional capabilitieslayer provides additional capabilitiesConsider the case of multiple physical links with disparate Consider the case of multiple physical links with disparate qualities. DLL will ensure parity on a peer basis. qualities. DLL will ensure parity on a peer basis.

HDLC: the mother of others (LAPBHDLC: the mother of others (LAPB--LAPD etc.)LAPD etc.)TerminologyTerminology

Primary Station Primary Station -- master; sends commandsmaster; sends commandsSecondary Station Secondary Station -- slave, sends responsesslave, sends responsesCombined Station Combined Station -- equal; does both commands and responsesequal; does both commands and responsesUnbalanced Configuration Unbalanced Configuration -- Masters and slaveMasters and slaveBalanced Configuration Balanced Configuration -- EqualsEquals


High-level Data-Link Control - HDLC

Combined CombinedCommands

Responses

Secondary Secondary

PrimaryCommands

Responses

Modes of OperationsNormal response mode

unbalanced configuration - respond only when polled

Asynchronous response modeunbalanced configuration - slave may initiate transmission

Asynchronous balanced modebalanced configuration - any of the combined stations may initiate data transmission and provide error recovery



HDLC Frame FormatHDLC Frame Format

Flag Flag -- 01111110 delimits frame boundary01111110 delimits frame boundaryAddress Field Address Field --

individual or group individual or group addresseaddresseaddress field in extendable address field in extendable --

if LSB is 0 next octet is address fieldif LSB is 0 next octet is address field

F A C I FCS F

OpeningFlag

Address Field Control Field Information Field Frame CheckSequence

ClosingFlag

8 bits 8 bitsexpandable

in 8 bitincrements

8 bitsexpandable

in 8 bitincrements

8 bits(32 bits optional)

8 bits



Control Field Control Field -- three kinds three kinds Information frameInformation frameSupervisory frameSupervisory frameUnnumbered frameUnnumbered frame

I field I field -- Carries informationCarries informationlength is variablelength is variable

fundamentals of modulation...

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