unit 4 -wireless communication & mobile programming

Wireless Communication & Mobile ProgrammingUNIT- 4 – WIRELESS APPLICATION PROTOCOL(WAP), MMS, GPRS APPLICATION CDMA & 3G

A C A D E M I C Y E A R : 2 0 1 3 - 1 4 @ S C E T, S U R AT

VINTESH PATEL, SCET 1

Reference Book

“Mobile Computing” By Asoke K Telukder, Roopa R Yavagal, TMH

Chapters – PART I(9, 10), PART II (17, 20)


UNIT 4 – PART I Chapter – 9 – CDMA & 3G

Chapter – 10 – Wireless LAN


Topic Timeline• Introduction

• Spread Spectrum Technology

• CDMA vs GSM (will be covered after completion of GSM)

• Wireless Data


Introduction

First Generation Wireless Comm. – Analogue FDMA

• FDMA

• TDMA

• FDD/TDD

• CDMA


Second Generation Wireless Comm. – Digital TDMA


Introduction• FDMA

• TDMA

• FDD/TDD

• CDMA

FDMA + TDMA = FDD/TDD



• TDMA

• FDD/TDD

• CDMA

Third Generation Wireless Comm. – CDMA



• TDMA

• FDD/TDD

• CDMA




• Wireless Data


Spread SpectrumMain Idea of evolution of Spread Spectrum

- Strength against Signal/Frequency Jamming

- Uses total Spectrum instead of Specific Freq./Freq. Range

- Spread Transmission Power over complete band


Different Techniques of Spread SpectrumDirect Sequence SS

- Typically used to transmit Digital Information

- Mix Specific/Pseudo Random Code with Digital Information

- Commonly called CDMA – Code Division Multiplexing

Frequency Hopping SS

- Center frequency of Conventional carrier is altered within a fixed time period in accordance with pseudo random list of channels


Different Techniques of Spread SpectrumChrip

- Carrier that swap over the range of frequencies

- Used in ranging and radar systems

Time Hopping

- Carrier is ON-OFF keyed by Pseudo Noise sequence resulting in very low duty cycle.

- The Speed of keying decides the amount of signal spreading


Different Techniques of Spread SpectrumHybrid System

- Combination of any two systems of earlier SS techniques

- Obviously, performance of this system will be more than can be applied any single SS technique for the same cost

- Generally, FHSS & DSSS is commonly used


Direct Sequence Spread Spectrum/DSSS- Example

Party A & B communicating in any X language. Now n people in a room with A & B are communicating simultaneously with different –different language, then other than Language X, all other is noise for them.

- Key to DSSSExtract desired signal/s & reject all other as noise


Direct Sequence Spread Spectrum/DSSS- Key Elements

1. Signal occupies the bandwidth much larger than what is necessary to send the information.

2. Bandwidth is spread by the means of the code, which is independent of the data.

3. The receiver is synchronizes to the code to recover data. The use of independent code and synchronous reception allows multiple users to access the same frequency band at the same time.

- To protect the signal, code used is pseudo random, which appears random while being actually deterministic i.e. Rx is enable to retrieve on its side.

- This pseudo random code is called pseudo random noise.

- DSSS allows each station to transmit over entire range of frequency all the time.


Direct Sequence Spread Spectrum/DSSS- DSSS – commonly called CMDA

- Each station is assigned a unique m-bit code called CDMA chip sequence

- To transmit 1, Tx sends its chip sequence & for 0, it sends complement chip sequence- E.g. suppose A station have chip sequence is “00011011”

- It transmit 1 by sending – 00011011 & 0 by – 11100100

- In Bipolar Notation, 0 is +1 & 1 is -1,

- so A transmits bit 0 by sending (-1,-1,-1,+1,+1,-1,+1,+1) & 1 by sending (+1,+1,+1,-1,-1,+1,-1-1)


Direct Sequence Spread Spectrum/DSSS- For manipulation of bits, we XOR the input bits, whereas In Bipolar Notations we multiply to get the desired result, i.e.

-XOR => Bipolar

-0 XOR 0 = 0 => +1 x +1 = +1

-1 XOR 1 = 0 => -1 x -1 = +1

-1 XOR 0 = 1 => -1 x +1 = -1

-0 XOR 1 = 1 => +1 x -1 = -1


Direct Sequence Spread Spectrum/DSSS


Direct Sequence Spread Spectrum/DSSS- Each station is having unique chip sequence. Say S indicates the m-chip vector for station S, & S’ is its negation.

- Note that All chip sequence are pairwise orthogonal, i.e. two different chip sequences S & T, the product S.T = 0 & S.T’ = 0 & S.S = 1 & S.S’ = -1


Direct Sequence Spread Spectrum/DSSSWhy Orthogonally Require?

- When two or more stations transmits simultaneously, their bipolar signal add linearity.

- Understand working of CDMA & BPSK - QPSK ….


DSSS – How it works? Encoding

A: 00011011B: 00101110C: 01011100D: 01000010

A: (-1, -1, -1, +1, +1, -1, +1, -1)B: DIYC: DIYD: DIY

– – 1 –– 1 1 –1 0 – –1 0 1 –1 1 1 11 1 0 1

CB + CA + B’A + B’ + CA + B + C + DA + B + C’ + D

S1 = (-1, +1, -1, +1, +1, +1, -1, -1)S2 = (-2, 0, 0, 0, +2, +2, 0, -2)S3 = DIYS4 = DIYS5 = DIYS6 = DIY


DSSS – How it works? Decoding

S1 . C = (+1+1+1+1+1+1+1+1) / 8 = 1S2 . C = (+2+0+0+0+2+2+0+2) / 8 = 1S3 . C = (+0+0+2+2+0-2+0-2) / 8 = 0S4 . C = DIYS5 . C = DIYS6 . C = DIY


For Station C,




• Wireless Data


Wireless Data- Typically raw channel data error rates for cellular X’mission are 10-2 i.e. every 100 bits have a Error. This error rate is very high & even it can detect by the human ear also.

- The acceptable BER/bit error rate is 10-2 i.e. one bit in million bits can be tolerate as an error.

- It requires effective ECC/Error correction code & ARQ/Automatic Repeat Request.

- CDMA Protocol Stack have following layers,


Wireless DataApplication Interface Layer

- Interface between MS & Transport Layer

- Functions: Modem Control, AT- Attention, Command Processing, Data compression

Transport Layer

- Transport layer for CDMA asynch. Data & Fax is based on TCP. TCP has been modified for IS-95

Network Layer

- Network layer for CDMA asynch. Data & Fax is based on IP. IP has been modified for IS-95


Wireless DataSub-network Dependent Convergence Function

- Performs harder compression on the header of X’port & N/w Layers

- Accepts the network layer datagram packets from n/w layer, performs header compression & passes that datagram to PPP/Point-to-Point Protocol layer. In reverse process, it receives n/w layer datagram & passes with compresses header from PPP layer and passes it to n/w layer.

Data Link Layer

- uses PPP.

- The PPP Link Control Protocol(LCP) is used for initial link establishment and for negotiation of optional links establishment.


Wireless DataInternet Protocol Control Protocol Sublayer

- Supports negotiation of IP Address & IP compression protocol parameters.

- Generally, MS is not having the permanent/static IP address. Therefore it needs to be negotiated and obtained from the network.

- This assigned IP address is discarded when the connection is closed like DHCP in LAN.

Radio Link Protocol Layer

- Responsible for reducing Error Rate over F/w & Reverse Channels.


CDMA – Protocol Stack


SMS - Wireless Data - 160 alphanumeric characters

- uses Control Channels of GSM, also works in ongoing call

- working is same in GSM/IS-95

- administration features includes Storage, Profiling, Verification of receipt & status enquiries.





• Wireless Data

• 3rd Generation Networks


Third Generation NetworksWhy telecommunication services are important?

- The mobile devices will be used as an integral part of our lives.

- Data/Non-Voice usage of 3G will become important and different from the traditional voice business.

- Mobile communications will be similar in its social positioning.

- CDMA is proffered approach for third generation network and systems.

- In North America – CDMA2000 is version of 3G

- In Europe/Asia/Austrailia/many other, 3G has been accepted as UMTS/Universal Mobile Telecommunication System and WCDMA/Wideband CDMA


Third Generation NetworksMain Goals of UMTS is to offer much attractive & richer set of services to the users like,

Universal Roaming – Any User will able to move across the world and access the network

Higher Bit Rate – More Speed would open the path to wards RICH Multimedia Applications.

Mobile Fixed Convergence – to Offer Cross domain services, Virtual Home Environment

Flexible Service Architecture – By standardizing not the services themselves but the building blocks that make up services.


Third Generation NetworksInternational Mobile Telecommunication - 2000 The 2G network – mainly for digital voice

Then comes 2.5G in which GPRS is introduced – step towards packet data in evolution of 3G

GPRS offers moderate data bandwidth that was sufficient for services like WAP/Wireless Application Protocol, MMS, low bandwidth Internet Access.

GPRS n/ws evolved into – Enhanced Data rates for GSM evolution/EDGE networks that offered high bandwidth packet data capable of multimedia video. It falls under 2.75G & almost in the 3G.

IMT-2000 is the worldwide standard for 3G wireless communications, defined by ITU.


Third Generation NetworksIMT 2k & 3G capabilities


Third Generation NetworksInternational Mobile Telecommunication - 2000 3rd Generation standards includes EDGE, CDMA 2000, UMTS, DECT and WiMax. These standards are both revolutionary & evolutionary. i.e. they are backward compatible to work with 2G systems as well as they are revolutionary as they require – new networks & frequency allocation techniques.


Third Generation NetworksCDMA - 2000 Third version of IS-95/CDMA-One(cdmaOne radio transmission technology is spread spectrum, wideband radio interface)

Uses CDMA modulation technique

Meets specification of ITU & IMT – 2000

Ranges: Indoor/Outdoor picocell(<50 meters e.g. one office floor) Indoor/Outdoor microcell(upto 1km e.g. shopping mall)Outdoor macrocell(1-35km radius)Outdoor megacell(>35 kms radius)Wireless Local Loop(WiLL)


Third Generation NetworksUMTS/WCDMA UMTS/Universal Mobile Telecommunication System – some of the encoding techniques are patented by Qualcomm & to avoid that Europe & Japan have different flavor of CDMA i.e. WCDMA/Wideband CDMA

WCDMA is also known as UTRAN/UMTS Terresterial Radio Access Network, uses FDD/Frequency Division Duplex.

Physical layer of UMTS/WCDMA uses DSSS/Direct Sequence SS with chip rate of 3.84 Mcps => Channel bandwidth is 5MHz

Data Rate Supported is few kbps to 2 Mbps

Two Mode of operation : FDD & TDD


Third Generation NetworksOperational mode TDD/FDD of UMTS/WCDMA FDD carries UPLINK – MS to BS & DOWNLINK – BS to MS on separate frequencies of 5MHz each. Both transmissions are of equal size.

FDD used for large outdoor n/ws as it can support large no of users.

FDD works well when carrying voice traffic.

In TDD, X’mission shares the same frequency band by sending the UPLINK & DOWNLINK channels during different timeslots.

TDD doesn’t support as many users as FDD, so works well in smaller cells.

TDD more suitable for carrying asymmetric data traffic like Internet.

In TDD UPLINK & DOWNLINK can be modified by assigning more/fewer time slots to each link when ever necessary.





• Wireless Data


• Wireless LAN


Wireless LAN WLAN/Wireless Local Area Network – users can be a part of network by staying mobile.

AdvantagesMobility: productivity increases when users have access of network at any

location. Wire-free within operating range of WLAN

Low Cost Implementation: Easy to setup, relocate, change & manage. Can operate in the regions where wiring may be impractical

Installation Speed & Simplicity: Installing WLAN is easy & fast & eliminate the cabling structures.

Network Expansion: Easy expansion - very limited Infrastructure need to be setup.


Wireless LANAdvantagesReduce Cost of Ownership: Initial setup require cost more than Wired LAN but

after that it is one can look for Long term benefits.

Reliability

Scalability

Usage of ISM Bands: 2.40 GHz, 2.484 GHz, 5.725 GHz, 5.850 GHz – Unlicensed Band, anyone can use that for free use. 5.7 is C band satellite link & yet to be unlicensed.


Wireless LAN - Applications Office/Campus Environment

Factory/Mall Floor

Home Networks

Workgroup Environment

Public Places like Air-Ports, Railway Stations

War/Defense Sites





• Wireless Data


• Wireless LAN

• IEEE 802.11 Standards


IEEE 802.11 Standards Complete list is there in the book of different standards. Do it yourself.





• Wireless Data


• Wireless LAN


• WLAN Architecture


Wireless LAN Architecture -Types of Wireless LAN 802.11 Initial specifications of Wireless LAN by IEEE

Uses 2.4 GHz Band @Data Rate of 1Mbps & 2Mbps

This standard evolves in many flavors like 802.11b/g/n/a

Up to 54 Mpbs (in 802.11a) – latest MacAir – for personalized Routers

HyperLAN Began in Europe

Current version i.e. HyperLAN works @5GHz

Next version of HyperLAN/2 will provide 54Mbps with QoS Support


Wireless LAN Architecture -Types of Wireless LAN HomeRF For interoperability between PC & other consumer devices within home.

Uses FHSS & provide 1Mbps to 2Mbps @2.4Ghz

Bluetooth Promoted by IBM, Sony, Microsoft, Motorola, Nokia & Other Giants

It is WPAN/Wireless Personal Area Network @2.4Ghz

Offers 1Mbps using FHSS in <10 meters

MANET Is working group within IETF to investigate & develop the standard for Mobile Adhoc

Networks.


Wireless LAN Architecture –Adhoc vs. Infrastructure Mode

Two basic types of (topologically),

Infrastructure based Networks

In Infrastructure based networks, the MS/s are associated with the AP-Access Point/BS-Base Stations like in the STAR topology.

In Infrastructure based networks, the area covered by one AP/BS forms BSS/Basic Service Set & combination of more than one BSS forms ESS/Extened Service Set

Adhoc Networks

In ad-hoc networks, there is no AP/BS. A number of MS forms a cluster to make the network for communication.


Wireless LAN Architecture –Adhoc vs. Infrastructure Mode


Wireless LAN Architecture –Infrastructure based Networks


Wireless LAN Architecture –Adhoc Networks





• Wireless Data


• Wireless LAN



• Mobility in Wireless LAN


Mobility in Wireless LAN When station wants to access BSS, the station needs to get synch information from AP/from other station in the case of ad hoc networks.

Two means by which stations can get this information

Passive Scanning

Station waits to receive BEACON Frame from AP(AP continuously broadcasts it’s beacon frame to indicate its presence)

Active Scanning

Station tries to locate AP by transmitting PROBE REQUEST Frame & PROBE RESPONSE from the AP


Mobility in Wireless LANThe Authentication Process

Once station has located an AP & decides to join its’ BSS, it goes through the authentication process. This is interchange of authentication infon betn the AP and MS, where WLAN device proves its identity.

The Association Process

After authentication, the information exchange about the MS & BSS starts, which allows DSS-set of Aps to know about the current position of the station. MS can start Tx/Rx once the association process completes.


Mobility in Wireless LANRoaming

• Process of moving from one cell(here BSS) to another without losing the connection.

• Similar to the cellular phone’s handover, with 2 differences,• On packet-based LAN system, the transition from once cell to another be performed between packet

transmission, while in telephony where the transition occur during a phone conversation

• On voice system, a temporary disconnection during H/O-Handoff doesn’t affect the conversation. However, in packet-based environment it significantly reduces the performance as transmission performed by the upper layer protocols.

• The 802.11 standard doesn’t define how roaming should be performed, but defines the basic tools – that includes active/passive scanning & re-association process, where station that roaming from one AP to another becomes associated with the new AP. The IAPP/Inter Access Point Protocol specification addresses the common roaming protocols enabling wirelss station to move across multivendor APs.


Mobility in Wireless LANRoaming

• IAPP = Announce Protocol + Handover Protocol

• The Announce Protocol – provides coordination information between AP. This information relates to network wide configuration information about active APs.

• The Handover Protocol - allows APs to coordinate with each other & determine the status of a station to a new AP. The new AP updates the necessary table/data in the MAC layer. This type of roaming is called HORIZONTAL roaming.

• MobileIP is another protocol that is used to allow application layer roaming.



Mobility in Wireless LAN (Handoff in 802.11 networks)




• Wireless Data


• Wireless LAN




• Deploying Wireless LAN


Deploying Wireless LANNetwork Design

Basic Steps

- Identify the areas that need to be covered

- Identify the number of users that need to be serve

- Form above 2 steps identify the APs need to be placed

- Goal: Provide RF/network coverage to every user

- Obstacles: environments objects – walls & other impediments

- Based on that also Multipath & RF Inference(caused by another 2.4Ghz signals that are present) need to be taken into account


Deploying Wireless LANChannel Selection

Within 2.4Ghz band, IEEE 802.11 standard define 13 ‘center frequency channel’ Channel 1 – 2.412 GHz

Channel 6 – 2.437 GHz

Channel 11 - 2.462 GHz

Fig shows a three-store building serviced by Nine Aps configured with 3 channels.


Deploying Wireless LANScaling Capability and BandwidthUses “Aggregate bandwidth” in localized coverage area helps to service more dense population of wireless clients to increase bandwidth available to each users.


Fig (a) shows one AP provides the bandwidth of 11Mbps & Fig (b) shows at the same time 3 APs can provides 33Mbps of bandwidth for a user.

Deploying Wireless LANConfiguring the Wireless LAN Includes configurations of AP as well as MS

Includes – Assign IP Address to MS

The WEP/Wired Equivalent Privacy security – shared key between AP & MS

IP Address to MS can also possible by DHCP

Advance configurations can include SSID, Beacon Interval, Channel Selection etc.


Deploying Wireless LANManaging 802.11 N/ws Managing Access Point

Task of managing AP can be broken down in 2 parts Management tools – Typically provided by AP

Monitoring & Reporting – Provide real time monitoring & alerting





• Wireless Data


• Wireless LAN





• Mobile Adhoc N/w & Wireless sensor N/w


Mobile Adhoc N/w(MANET) & Wireless sensor N/wMobile Adhoc N/w


MANET & Wireless sensor N/wMobile Adhoc N/w MANET is autonomous system of mobile stations connected by wireless links from a network.

Peer to Peer, Multi-hop Routing of data packets from source to destination via intermediate stations(which work as routers).

Challenges in setting up the Adhoc network

1. Dynamic TopologyNodes are allowed to move in arbitrary fashion. No predefined fix topology. On Demand

network configurations.

2. Limited Security

More vulnerable to attack as any node can join/leave at anytime. This requires higher openness & flexibility.


MANET & Wireless sensor N/wMobile Adhoc N/w

3. Bandwidth LimitationWireless networks are generally bandwidth limited. It is more limited in adhoc networks

as no Backbone to handle higher bandwidth.

Que: Why wired network can provide more bandwidth?

4. Routing

The Routing in Adhoc networks is more complex. Depends on many factors like, routing path, topology, protocol, selection of routes etc.


MANET & Wireless sensor N/wWireless Sensor Networks / WSN Special class of wireless Adhoc networks.

“A wireless sensor network (WSN) consists of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location.”

- Wikipedia

Nodes/Motes in WSN are mostly of type use & throw. So efficient design required in all terms like routing, energy consumptions, sensing etc.





• Wireless Data


• Wireless LAN WLAN Architecture




• Wireless LAN Security

• 3G vs WiFi


Wireless LAN Security


In Wired Networks, one have to physically connected to the network in order to Tx & Rx data.

In contrast, in wireless n/ws, the radio Tx & Rx is used. Any one in the range can see the communications, so Security is necessary.

SSID/Service Set Identifier According to 802.11 standard, MS connects to AP by providing SSID of the network. i.e. ID of the Basic Service Set/BSS covered by one AP.

MS must know SSID of the AP/network or else it’s packets are rejected by AP.

Advice: one have to change default/factory set SSID provided.

Wireless LAN SecurityLimiting RF Transmission

It is important to control RF transmission by AP/Access Point.

Proper selection of Antenna used can improve the coverage of network as well as power transmitted can also be optimized.

Omni direction antenna, have 360 degree coverage.

Directional Antenna, have one proper angular coverage of the area.


Wireless LAN SecurityMAC Address Access Control

Many AP are configured using MAC Filtering.

List of the MAC Address representing the MSs are allowed/blocked (depends on the configurations of AP) to use the service.

Idea behind MAC Filtering: Every Network Card contains Unique MAC Address.


Wireless LAN SecurityAuthentication Modes Two types of Authentication are defined in 802.11, Open System Authentication – NO Authentication at all

Shared Key Authentication – based on Symmetric Encryption

It is assumed key is transmitted to both end through some secure channel.

The authenticated station receives the challenge text packet from AP & it send that packet by applying some transformation/modification as response – This completes the One Way Authentication.

To achieve Two Way Authentication, this process is repeated on both the side.


Wireless LAN SecurityWEP/Wired Equipment Privacy

WEP is designed to provide these services, Reasonable Strong Encryption:

It relies on the difficulty to find out the secrete key through brute force attack.

It increases as the key length increases.

Self Synchronization: Each packet contains the information & required to decrypt.

There is no need to deal with packet lost.

Efficient: It can be implement in software with reasonable efficiency.

Exportable: Limiting Key length leads to greater possibility of export beyond US

WEP algorithm is RC4 cryptographic algorithm from RSA Data Security.

RC4 –> Stream Cipher & Symmetric Cryptographic Algorithm.



WEP/Wired Equipment Privacy - Algorithm

Wireless LAN SecurityPossible Attacks


Wireless LAN Security802.1X Authentication 802.1X requires 3 entities, The Supplicant – resides on the wireless LAN client.

The Authenticator – resides on AP.

The Authenticator Server – resides on server authenticating client (e.g. KERBEROS / Other Authenticator Server)


Wireless LAN Security802.1X Authentication The authenticator creates one logical port per client, based on clients’ association ID.

The logical port has two data parts – Uncontrolled data path – allows n/w traffic

through the n/w.

Controlled data path – requires successful authentication to allow n/w traffic.

Complete association with an AP involves 3 states – Unauthenticated & Unassociated

Authenticated & Unassociated

Authenticated & Associated





• Wireless Data


• Wireless LAN WLAN Architecture




• Wireless LAN Security

• 3G vs WiFi


3G vs WiFi


UNIT 4 – PART II Chapter 17 – Voice Over Internet Protocol & Convergence

Chapter 20 – Information Security


Topic Timeline• Voice Over Internet Protocol – VoIP - Introduction


Voice Over Internet Protocol - VoIP Traditionally, circuit switch technologies were used in voice communications. Uses FDMA/TDMA.

Provides good QoS & digitized voice or analog voice.

In 1995, hobbyists in Israel made attempt to send voice over/though IP n/w

Then comes Internet Phone Software by VocalTec & era of VoIP begins


Topic Timeline• Voice Over Internet Protocol – VoIP

• H.323 Framework for VoIP


H.323 Framework for VoIP It’s a standard that provides foundation for multipoint conferencing audio, video and data over IP n/ws – Standardize by ITU.

It is a part of the ITU-T H.32x series of protocols, which also address multimedia communications over ISDN, the PSTN or SS7, and 3G mobile networks.


H.323 Protocol Stack


H.323 Framework for VoIP In H.323 implementations, Along with end user devices three additional logical entities are required, they are also known as endpoints Gateways

Gatekeepers

Multipoint Control Units

Gateway Purpose: to do media & signal translations from IP to ckt n/w & vice-versa

Translation between audio/video/call setup/clearing

Primary Application:

Establishing links along PSTN terminals

Establishing links with remote H.320 – complaint terminals over Integrated Service Digital Network/ISDN n/w

Establishing links with remote H.324 – complaint terminals over PSTN n/w


H.323 Framework for VoIP Gatekeeper Works as central point of control for all calls

within its zone for all registered endpoints.

Terminals must use the service provided by Gatekeepers.

Performs functions like Bandwidth management & address translation.

Plays a major role in multipoint connections by redirecting the H.245 Control Channel to multipoint controller.

GateWAY can use GateKEEPER to translate incoming E.164 address to IP Address.


H.323 Framework for VoIP Multipoint Control Unit Provides conference between three or more end points.

MCU consists of MicroController.




• SIP/Session Initiation Protocol


SIP/Session Initiation ProtocolArchitecture

• Protocol to control Telephone over IP

• Designed specially for Internet

• SIP supports Five Points for establishing & terminating multimedia communication: • User Location

• User Capabilities

• User Availability

• Call Setup

• Call Handling

• Call Teardown


SIP/Session Initiation ProtocolSupports Five Facts User Location: Determines the location & end system to be used for communication

User Capabilities: Determination of media & media parameters to be used

User Availability: Determining the called parties’ willingness to engage in communication

Call Setup: “ringing” establishing call parameters at both parties

Call Handling: manage the transfer of Data/Voice

Call Teardown: at the end of the call, terminate call & release all resources


SIP/Session Initiation ProtocolEntities in Effect

1. Proxy Server

2. Registrar Server

3. Redirect Server

4. Location Server

5. Gateways


SIP/Session Initiation ProtocolEntities in Effect Proxy Server:

SIP Proxies functions are similar to Routers and routing decisions & modifying the request before forwarding it to the next network element. But more capabilities then regular routers.


SIP/Session Initiation ProtocolEntities in Effect Registrar Server:• Can be defined as the Server Maintaining the whereabouts of domain.

• Accepts the REGISTER request from nodes in VoIP network.

• REGISTER requests are generated by clients in order to create/remove mapping with their externally known SIP address & IP address they wish to be connect at.

• Uses location service in order to store & retrieve location information.

Redirect Server• Does same function like in case of forwarding the call in PSTN / cellular networks.

• It receives REQUEST & RESPONSE with redirection response.

• The alternate address is returned as contact headers in the response of SIP message.


SIP/Session Initiation ProtocolEntities in Effect Presence Server:• Allows the calling party to know ability & willingness of the other party to participate

in the call.

• Users interested in getting information of the other party’s precense can subscribe & will receive the notifications of the Users’ Presence.

• This is achieved through the Event Server.

SAP(Session Announcement Protocol)/SDP(Session Description Protocol):• SAP – used by Session Directory Clients

• SAP announcer periodically multicasts an announcement packet to known multicast port & address

• The scope is same as the session it is announcing.


SIP/Session Initiation ProtocolEntities in Effect SAP(Session Announcement Protocol)/SDP(Session Description Protocol):• SDP describes multimedia session for purpose of session announcement, session

invitation and other types of multimedia session initiation.

• Many SDP messages are sent using SAP.

• Message can also be sent using Email/WWW.

QoS & Security• In Internet Applications, RSVP/Resource ReSerVation Protocol is designed for Quality

Integrated Services. RSVP is used by the host to provide particular QoS.

• COPS/Common Open Policy Service protocol is used for simple REQ & RES that can be used to exchange policy information between policy SERVER (PDP/Policy Decision Point) and policy CLIENT(PEP/Policy Enforcement Point)





• SIP vs H.323



H.323 vs SIP




• H.323 vs SIP

• Real Time Protocols


Real Time Protocols Good QoS is required to support real time communication

RTTP/Real Time Transport Protocols RTP is both IEFT & ITU standard/H.255

It defines the packet format for multimedia data

Is used by many protocols, such as Realtime Streaming H.232 & SIP

RTCP/Real Time Control Protocols Is based on periodic transmission of control protocol packets to all participants in session

RTSP/Real Time Streaming Protocols Is a client server protocol, designed to address video streaming efficiency





• H.323 vs SIP


• Convergence Technologies


Convergence Technologies To make convergence & interworking between PSTN & IP network possible, three functional elements are defined, Media Gateway – Packetization of voice & other traffic

Signaling Gateway – Responsible for interfacing of SS#7 network & Forwarding signal to IP Network

Media Gateway Controller – Plays role of mediator to enable & control access & resource usage between IP & PSTN network


Convergence Technologies SCP – Service Control

Point (more detail on Chapter-11 in Reference Book – 1)

SCP addressable from SS#7 Networks


Convergence TechnologiesMedia Gateway


MG/Media Gateway allows various type of media(i.e. Fax, Voice, Video etc) from one type of n/w to another. These media must be transportable for IP networks as well as digital/analog ckt s/w networks.

Integrity or Quality is controlled by encoding, echo cancelling, decoding etc.

MG function provides bi-directional interface between ckt s/w networks and media related elements in IP networks.

Example: High scalable MG are implemented by High Speed Time Domain Multiplexing(TDM) trunk interface, which are commonly used between s/wing elements in ckt s/w networks. (Trunk – Line/Link)

Convergence TechnologiesMedia Gateway Controller


Key responsibility: Data flow related information & provide associated instructions on interconnecting of 2 or more IP elements so that they can exchange information.

Maintains the information of all current data flow.

Instructs MG that how to setup, maintain and terminate the data flow.

Exchanges ISUP(ISDN/Integrated Services Digital Network User Part) messages with Central Office via SG/Signaling Gateway

In H.323 these functions are performed by Gatekeepers

Sometimes, AKA SoftSwitch

Convergence TechnologiesSignaling Gateway


SG implements interface between an SS7 network and other call oriented elements in IP network.

Key Responsibility: Repack SS#7 packets into format understood by elements in each network & to present actual view of elements in IP network to SS#7 network.

SG needs to implement SS#7 messaging that obeys all rules of SS#7 network, while also accommodate variety of behavior in IP network.

It is necessary that SG understand all the messages & protocols of SS#7 network to perform it functionality.

It should also provide protection against the undesirable traffic & malicious instructions.

Convergence TechnologiesMegaco/H.248 - Media Gateway Control Protocol


Defined in RFC 3015 & Adapted by ITU

Two basic components 1. Termination & 2. Contexts

Terminations represents stream entering/leaving MG. Examples – analog telephone lines, ATM Stream, MPEG stream. They should be placed in Contexts, which are defined as two or more termination stream are mixed & connected together.

Context are created by adding the first termination, & removing last terminations.

There is a special context called NULL CONTEXT – it contains terminations that are not connected to other terminations.

Media Gateway Control Protocol


SIGTRAN/Signaling Transport & SCTP/Stream Control Transmission Signaling Transport (SIGTRAN) refers to a protocol stack for the transport of Switched Circuit Network (SCN) signaling protocols (SS7/C7) over an IP network.

SIGTRAN is the evolution of SS7, which defines adaptors and a core transport capabilities that blend SS7 and packet protocols to provide users with the best both technologies have to offer.

Applications of SIGTRAN include: Internet dial-up remote access, IP telephony interworking with PSTN and other services as identified.

Source: http://www.javvin.com/protocolSIGTRAN.html


http://www.javvin.com/protocolSIGTRAN.html

SIGTRAN/Signaling Transport & SCTP/Stream Control Transmission SIGTRAN defines the protocol architecture through RFC2719 and SCTP/Stream Control Transmission protocol through RFC2960

A RFC/Request for Comments is a publication of the IETF/Internet Engineering Task Force and the Internet Society, the principal technical development and standards-setting bodies for the Internet. i.e. Set of protocol suits

SCTP is end-to-end, connection oriented that transport in independent sequenced stream.

SCTP was designed to provide general purpose transport protocol for message-oriented application, as in need for the transportation of signaling data.

In TCP/IP layer stack, SCTP resides in the Transport layer, along with TCP/UDP.


SIGTRAN/Signaling Transport & SCTP/Stream Control Transmission Difference between TCP & SCTP Multihoming – SCTP supports multi-homed nodes, i.e. one node can be accessed by

Several IP Address which is not the case in TCP which allows the use of alternate route for a particular node when there is the network failure. This make the node fault tolerant.

In TCP if packet is lost, communication stops & waits leads to retransmission. This phenomenon where packets are blocked by packet in front which has been lost is known as Head- of -Line Blocking.

MultiStreaming – effective way of limiting Head- of -Line Blocking. The advantage of multi streaming is that if one stream is failed then can work with another stream & communication can be continued w/o interruption.





• H.323 vs SIP



• Call Routing


Call Routing Four Groups:1. IP to IP

2. IP to PSTN

3. PSTN to IP

4. PSTN to PSTN via IP


Call RoutingSIP to SIP Call Flow Say communicating parties are A & B.

Two SPI proxies are there for A & B in the system to facilitate session establishment.

A calls B using B’s SIP URI/Uniform Resource Identifier, similar to email address, typically containing Username & Hostname. E.g. sip:[email protected] where xyz.com is domain name of B’s SPI provider. Say A has SIP URI – sip:[email protected]

It can be sips:[email protected] to indicate secured URI.

Transaction begins with A’s sending an INVITE request addressed to B’s SIP URI. The format of INVITE is shown in next figure.


sip:[email protected]

sip:[email protected]

sips:[email protected]

Call RoutingSIP to SIP Call Flow – INVITE format


B’s SIP URI SIP Version No.SIP MessageType

Call Routing

SIP Session SetupRPT = Resource Path Testing

Each Message starts with F & the following number to Fshows the message serial number in transaction sequence.


Call Routing

SIP Session SetupSource: http://www.tutorial-reports.com/internet/telephony/voip/sip/sip-voip.php


http://www.tutorial-reports.com/internet/telephony/voip/sip/sip-voip.php

Call RoutingSIP to PSTN Call Flow


Take the case where Party-A calls Party-B from IP Phone with IP address to PSTN phone with valid Phone number.

When A calls B by using user agent(i.e. Skype like software) to B’s Phone Number(i.e. say 011-12312123) then first B’s phone number is get converted to the E.164 format (i.e. say +23121231110). In which last 3 digits specifies the SIP server to be reached to route the message to(i.e. here in this case which is 1.1.0), which is SIP Proxy Server.

Before starting routing SIP Proxy make Query to the local database for the location of B. That is equivalent to HLR system. The proxy finds out whether the user have capability for calling the person or not.

The SIP Server on receiving this request, queries its database and finds out the number belongs to the PSTN. Then SIP Server triggers CA/Calling Agent or MGC.

Call Routing

SIP to PSTN Call Flow…..

Here SG is responsible for Message conversion from SIP to PSTN format & vice-versa.

CA/MGC contacts MG/Media Gateway using MGCP/Media Gateway Control Protocol for establishing the RTP path and coded conversion.


Call RoutingPSTN to SIP Call Flow


When Party B(PSTN) calls Party A(IP), assume that Party A have number to be dialed from normal telephone.

Now as idea is to have maximum traffic is to be transferred to IP network, the SSP to which party is linked/associated.

Every SSP should be having a MG/SG linked to itself, which is not practical so in option to that SSP handles those messages to some SSP which has MG/SG.

If number dialed by a person is XXX-XX-XXX then at the first Signaling Gateway, SIP proxy would know that destination SIP proxy is in place ABC, then normal SIP package routes through the IP network, this message also routes till reaches the SIP proxy @ABC.

Call Routing

PSTN to SIP Call Flow





• H.323 vs SIP



• Call Routing

• Applications of VoIP – DIY

• IMS – IP Multimedia SubSystem


IMS/IP Multimedia Subsystem IMS – emerging standard, which looks at total convergence of voice and multimedia.

Sometimes referred as All IP network, was specified by 3GPP/3rd Generation Partnership Project.

REQUIREMENTS:-


IMS/IP Multimedia Subsystem


CONVERGED SERVICES:-

IMS/IP Multimedia SubsystemArchitectureThree Layers:

1. Service/Application Layer

2. Session Control Layer

3. Communication Layer

CSCF provides registration & routing of SIP signaling to application server.

Session Control Layer includes HSS/Home Subscriber Server database that maintain unique profile for each end user which includes – IP Address, Roaming Info, Telephony Services, Voice Mail Services





• H.323 vs SIP



• Call Routing

• Applications of VoIP – DIY

• IMS – IP Multimedia SubSystem

• Mobile VoIP


Mobile VoIP

H.323 & Magaco have not addressed mobility for VoIP.

User mobility is defined as the ability to communicate of mobile users irrespective of the terminal & user mobility/location.

In VoIP context, roaming referred to connectivity between endpoints are assured while they both/any one is moving. Such reachability can be continuous or discrete.


Topic Timeline Security Issues in Mobile Computing


Aspect of Information Security

Security Attack

Security Mechanism

Security Service


Security AttackAny action that compromises the security of information owned by an organization

Security MechanismA mechanism that is designed to detect, prevent, or recover from a security attack.

Security Services◦ It is something that enhances the security of the data processing

systems and the information transfers of an organization

◦ Intended to counter security attacks

◦ Makes the use of one or more security mechanisms to provide the service

Information Security

To build information security system, we need to know answers of questions like,

- Who is enemy?

- Vulnerabilities?

- Weak leaks in system?

- What need special protection?

- Possible effects of vulnerabilities after attack?

- How much security system costs, in terms of Money, Resource & Time?

- Strategy to recover from loss due to attacks?

- When to deploy system? VINTESH PATEL, SCET 136

Information Security

Classification of Attacks based on Assets,

• Attacks on Dynamic Assets• Interception

• Modification

• Fabrication

• Interruption

• Attacks on Static Assets• Virus & Worms

• DoS

• Intrusion

• Replay Attacks

• Buffer overflow Attacks

• Trapdoor Attacks


Components of Information SecurityInformation Security = Secrecy of Information/Message etc.

• Confidentiality

• Availability

• Integrity

• Non-Repudiation

• Authorization

• Trust

• Accounting


Confidentiality

Ensured by Encryption/Decryption of Data

Terms:

PT/Plain Text, CT/Cipher Text

Key-space: The range of possible key values .

Cryptography | Cryptographers | Cryptanalyst | Cryptanalysis

Steganography?


• Confidentiality

• Integrity

• Authorization

• Availability

• Non-Repudiation

• Trust

• Accounting


Integrity

Ensured by adding additional information like Checksum

Message Diagest

MAC/HASH

Ensures the no alternation of message @RX party

Authorization

It deals with privileges/rights.

Transactions involves 2 parties: Subject/User & Object/Data

The privilege to an object is defined through ACL/Access Control List.

e.g. Database Users with different rights/privileges have access according to their rights only.


• Confidentiality

• Integrity

• Authorization

• Availability

• Non-Repudiation

• Trust

• Accounting


Availability

Media Mgt. is not under the scope of Security Protocols & Algorithms

Media Mgt. is needed to ensure Availability of Service

Example: Providing service to e-commerce webapp against the threat(which targets the webapp to goes down due to too many request – situation like GTU’s Exam Result Servers on first hour – DoS attacks) which servers a purpose of making someone out from the competition during particular season like Blackfriday.

Sometime against the terrorist organizations – area called Censorship-Resistant Publishing through document entanglement.

Non-Repudiation

Authentication & non-repudiation have some overlapping properties.

Authentication: You are the one who you claim to be.

Non-Repudiation: We identify the identity of party beyond any point of doubt. i.e. Authentication with formal record – which have some binding like signature in cheque.


• Confidentiality

• Integrity

• Authorization

• Availability

• Non-Repudiation

• Trust

• Accounting


Trust

Mobile users expect to access resources & service anytime & anywhere. This leads to security risks & access control problem.

To handle such dynamic ever-changing context, trust based authentication system is necessary.

Trust involves developing a security policy, assigning cardinalities to entities, verifying that the cardinalities fulfill the policy.

Accounting

For any Service, The provider need to be paid, irrespective to the service type whether it is of kind Content Service or Network Service. So Accounting & Billing is very critical aspect in mobile computing.

Accounting is the process by which the usage of service is metered. Based on the usage, the service provider collects the fees directly from the user.

Security Techniques & Algorithms• Stream & Block Cipher

• Symmetric Key Cryptography• DES

• 3-DES/Triple DES

• AES

• Public Key Cryptography• Deffie Hellman

• RSA

• ECC

• Hashing Algorithm• MD5

• SHA

• MAC

• Security Protocols • SSL

• TSL

• WTSL

• Multifactor Security

• Digital Watermarking

• Key RecoveryVINTESH PATEL, SCET 142

Strem & Block Cipher

In Stream Ciphers, a bit/byte is taken at a time & processed(i.e. Encrypted/Decrypted).

Wireless LAN uses the Stream Cipher.

In this scenario, Key should be unique for every encryption.

While in Block Cipher, the blocks/chunks(like 64 Bits/128 Bits etc.) of PT/Plain Text is processed.

Majority of Cryptosystems uses the Block Cipher.




• AES

• Public Key Cryptography• Deffie Hellman

• RSA

• ECC


• SHA

• MAC


• TSL

• WTSL




Symmetric Key Cryptography

Same key is used for Encryption & Decryption at Sender & Receiver side respectively.

PlainText

Message

Encryption

Algorithm

Secret

Key

Plaintext

Message

Decryption

Algorithm

Secret

Key

Transmitted CT/Cipher Text




• AES

• Public Key Cryptography• Deffie-Hellman Key Exchange

• RSA

• ECC


• SHA

• MAC


• TSL

• WTSL




Public/ASymmetric Key Cryptography

Different keys are used for Encryption & Decryption at Sender & Receiver side respectively.




• AES


• RSA

• ECC


• SHA

• MAC


• TSL

• WTSL




Hashing Algorithm

Authentication Functions HASH

MAC

Message Encryption itself is providing Authentication

HASH vs MAC HASH(Message) = Fixed Length of HaSh value i.e. Authenticator

MAC(Message, Key) = Fixed Length of HaSh value i.e. Authenticator

Why Hash? Provides Authenticity of Message. Remember we are not hiding the

message but ensuring that the message has not been altered in-between & came from legal Party.

Different Methods for Hashing – MD5

SHA

MAC




• AES


• RSA

• ECC


• SHA

• MAC


• TSL

• WTSL




Security

Protocols SSL

TSL

WTSL

Multifactor

Security

Digital

Watermarking

Key Recovery

Security Frameworks for Mobile Environment.

• 3GPP

• Mobile Virtual Private Network


• Smartcard Security

• RFID Security

• Mutual & Spatial Authentication

• Mobile Agent Security

• Mobile Worm & Virus


Overview

DIY

References “Mobile Computing” By Asoke K Telukder, Roopa R Yavagal, TMH

“Principle of Wireless Networks” By Pahlavan & Prashant – Highly recommended for

Specific Questions(& For Better Grades Specially in GTU)


unit 4 -wireless communication & mobile programming

Education

diy vintesh patel

noisevintesh patel

usedvintesh patel

spectrumdsssvintesh

wireless lanvintesh

cdma chip sequence

station s

signal spreadingvintesh