Telecommunications and Data Networks Final Paper Page 1 13 June 2005 What I have is only borrowed from God so that I may serve others. H Anthony Chan The

Telecommunications and Data NetworksFinal Paper Page 1 13 June 2005

What I have is only borrowed from God so that I may serve others. H Anthony Chan

The more I learn, the more I find out how little I know of the world around me. Never mind the universe.

EEE402F Telecommunications andData Networks

Final Examination: Monday 13 June 2005 09:00 at DO 2Duration: 3 hrs 00 min

Module A

Examiners: H Anthony Chan and

Mqhele Dlodlo

Department of Electrical Engineering

University of Cape Town




Instructions

Answer ALL the Questions. Organize your thoughts properly in the answer.

Your answer should include all the relevant points, and yet not be flooded with irrelevant or repetitive points.

For each question, answer in concise statements, if verbal, or else show your steps clearly in calculations.

Freely use relevant, clearly labelled illustrations. You should rarely need to use additional paper.




Grading

Module A – Wireless Networks incorporates EEE525Z material

Module B – Convergent Telecommunication Networks incorporates EEE526Z material

Each question carries 10 marks. The answer will earn 0 to 10 marks inclusive, depending on the degree of completeness.

Answers longer than the available PowerPoint slides including diagrams will attract -5 points per excess PowerPoint slide or equivalent sheet of paper.




Module A: Write Me FirstPlease don’t forget!

Name (Underline last name):

Student Number:

E-mail address:

Course Code (underline which): EEE402F-a/EEE525Z




Module A – Wireless Networks

Answer ALL 15 questions in this module. There are extra blank slides at the end of the

module in case of longer answers. If you use the extra slides be sure to

NUMBER your ANSWER according to the question concerned.

You have 1 hr 30 min for this module.




Question A1

The diagram on the next page shows the relations among the following components of a GSM/GPRS cellular network: Authentication centre Base Station Subsystem Gateway GPRS support node Gateway mobile switching centre Home location register Mobile switching center Packet Control Unit Serving GPRS support node Short message service server Visitor location register

Describe how the network facilitates an incoming call from the PSTN to invoke a response from the user of the MS.

Concisely explain the functions of the GGSN. [2 marks]




Other PLMN

Diagram for Question A1

MS

Um

MSC/VLRA

SMS-GMSCE

HLR/AUC

CEIR

DFPLMN

PSTN

ISDNBSS with PCU

SGSNGb

GGSNGnPDN

GsGd

GcGf

Gr

SGSNGn

GGSN

Gp TE

Gi




Answer to Question A1 – Interest is in how the student will invoke which functions to set up the called MS

1. Authentication centre – stores lists of valid terminals in the EIR, uses list along with unique user ID and handset ID to prevent re-use of stolen handsets

2. Base Station Subsystem – physically provides radio coverage to cells through the control function (BSC) and the transmit function (BTS); BTS contains the TRAU in full-rate GSM systems without compression.




Answer to Question A1 – Roles of each unit 2 marks, except GMSC and BSS each earn 1 mark

3. Gateway mobile switching centre – receives incoming call in the NSS, finds correct HLR for GSM subscriber and queries it, collects location information and routes call to visited MSC for provision of services, interfaces with external networks and with SS7 network of NSS entities.

4. Visitor location register – dynamically stores subscriber information while user is roaming in coverage area




Answer to Question A1 – The list of these 9 function sets is merely a database or reference

5. Home location register – unit for managing mobile subscribers, stores the International Mobile Subscriber Identity, MS ISDN number, VLR address and subscriber data such as supplementary services

6. Mobile switching centre – gives switching functions to mobiles in its area: mobility management (location registration/ handover), interworking, call routing and control, echo control




Answer to Question A1 – A good process description will earn 8 marks

7. Packet Control Unit – manages the operations of the Packet Broadcast CCH, Packet Common CCH, Packet Data TCH and Packet Associated CCH.

8. Serving GPRS support node – interfaces BSC to Gateway GPRS support node through which the MS reaches the packet switching network using a number of protocols.




Answer to Question A1 – Award 2 marks on GGSN

9. Short message service server – caters for paging services on GSM/GPRS whereby short text messages are managed through the SMS Message Centre: options include prioritising, delayed delivery time, acknowledgements, predefined messaging, voice/audio messaging

Gateway GPRS support node – receives information from the serving GPRS support node and relays it to the packet switching network (outside of GSM network).




Question A2

Use the figure below to illustrate the use of the IEEE802.16 in a network environment

BSC or

RNC

MS

TS

TS

TS

BTS or Node B

BTS or Node B

BTS or Node B




Answer to Question A2

The IEEE802.16 in the diagram is providing backhaul services, where:BSC = Base station controllerBTS = Base transceiver stationMS = Master stationTS = Terminal station

Brief explanations of functions of components as well as what backhaul services are earns full marks (2 X 5 = 10)




Question A3Diagram of the UMTS Network Architecture

3G-SGSN 3G-GGSN

BSS MSCA

Gb

UTRAN Iu

IuW-CDMA

GSM/EDGE

Circuit Switching Domain

Packet Switching Domain

G-MSC

PSTN

ISDN

IP Net




Question A3: From the diagram above

Discuss the case of a message being transmitted from the BSS to the ISDN.

Discuss the case of a message being transmitted from the UTRAN to the PSTN.

Discuss the case of the case of a signal transmission from the BSS to the IP network.




Answer Tips to Question A3

MS: is the physical subscriber equipment for access to the PLMN, including a MT, various TE, combinations of TE and TA functions, where TA acts as a gateway between the TE and the MT.

BSS: physical equipment that provides cellular radio coverage, consists of multiple BTSs to transmit over several cells and control function done by the BSC. The TRAU can be in the BTS for full rate or in the MSC for half rate transmission.





NSS: incorporates the main switching functions of the network with subscriber databases and mobility management, manages internetworking between GSM and other subscribers, consists of the MSC, HLR, VLR and GMSC.

OMSS: handles the system security for validating identities of different telecommunications entities through the AuC and EIR; also monitor remote operation and maintenance through NMCs.





Operational Part: interactions – external networks with NSS with BSS with MS

with subscriber [1 mark]

Control Part:OMSS interacting with service provider [1 mark]




Question A4

The three types of mobility specified in IMT2000 are personal, terminal and service profile mobility. The chief architectural engineer of a Cape Town based architectural firm visits the client’s premises in Zurich to finalise the working drawings. In the hotel room the night before the meeting she realises that the updates to requested changes to the building in question that she had sent ahead to the client had been corrupted en route.

Decide with explanations regarding the type of mobility that would assist her to be able to correct this anomaly in time for the morning meeting. Clearly state any assumptions and the scenario they would be suitable for.




Answer Tip to Question A4

First we must realise that:Personal mobility: Subscriber may access service from

any anywhere using any terminalTerminal mobility

• Subscriber terminal may be used anywhere (roaming)• Terminal continues to be functional while in motion (handoff)

Service Profile mobility: Subscriber may access the service profile from anywhere.

The assumptions made by the student must take these three types of mobility into consideration. A good answer gives a scenario suitable for each type, and the assumptions fit.




Question A5

In view of what you have learnt thus far about technological advances towards convergence, mobility and system miniaturisation, what technical observations can you make about any of the following technologies:Hard disk drives,Removable storage drives/devicesRechargeable battery packsMobile stations (cell phones)Capture/Storage of handwritten notes with drawings.




Answer Guide to Question A5: Any other verifiably accurate statement accepted

Hard disk drives: We have come to the point where the minimum user expectations are for at least 40 GB on a laptop personal computer hard disk.

Removable storage: The technologies of choice here include digital video disks (DVD), compact disk recordable/re-writable (CD R/RW) (700 MB), USB flash memory stick (128 kB – 4 GB)

Rechargeable battery packs: Lithium ion technology has led to long mobile phone and laptop battery life. Rechargeable alkaline batteries are filling the gap left by the carcinogenic nickel cadmium types

Mobile stations: The state-of-the-art cellular phone offers call registers, a phonebook, applications (such as Java, MP3 player, voice recorder, world time, alarm, calculator, currency converter, timer, stop watch, news, weather, sports, entertainment and location services), a browser, messages (SMS, MMS, voice mail, broadcast, email), fun box (images, videos, music, sounds, memory status), organiser (day/week/month view, schedule, anniversary, things to do, missed alarm events, memo), camera (photo, video, video clips), settings (time & date, phone, display, network services, connectivity, security, reset), many access security codes, and an emergency call facility.

Handwriting/free-hand drawing: Once on the decline with advances in word processing and computer-aided drawing, mobility requirements has seen a resurgence through mobile note-taking technology, which captures script written on plain paper with a special pen onto a personal computer.




Diagram for Question A6

3G-SGSN

3G-GGSN

MSC/VLR

Iu

Iu

CS Domain

PS Domain

G-MSC

IP Service Network

Service Network

UTRANUEUu

AAAAAA

E-mailE-mailSIPSIP

WebWeb

Core Network Service NetworkRadioNetwork

PSTNPSTNISDNISDN

SCPHLR

STP




Question A6

Name the system shown in the diagram. State the technological generation it belongs

to. Outline the system functionalities found in

the:Radio networkCore networkService network.

Name and briefly describe the air interface standard of the system.





Universal Mobile Telecommunications System

3G Functionalities:

Radio network: the access function to the coreCore network: the switching partServices network: the service manager

W-CDMA provides the air interface between the mobile terminal and the base station antenna through wideband CDMA.




Question A7

Describe forward error correction (FEC) as an open loop error-control strategy.

Describe an error control strategy that depends on feedback.





FEC uses redundant bits for each code word to both detect and pinpoint the position of an inverted bit without asking the source to re-transmit, hence it is an open-loop method.

ARQ uses a simpler code to detect errors and discard the corrupted code words at which point the decoder sends a NACK signal back to the source to re-transit. It is thus a closed-loop error control method.




Question A8

Your company has been asked to provide a wireless solution with the following features:Backhaul for Hotspots, GSM, Fixed Business

AccessHigh spectral efficienciesDSL for SOHO and Residential UsersLarge numbers of active MAN usersPotable and Nomadic AccessSustained user data rates

Would you supply WiMAX, IEEE802.20 or both? Justify your choice.




Answer to Question A8: Both, since:

WiMAX for:Backhaul for Hotspots, GSM, Fixed Business

AccessDSL for SOHO and Residential UsersPotable and Nomadic Access

IEEE 802.20 for:High spectral efficienciesSustained user data ratesLarge numbers of active MAN users




Question A9

Briefly explain the operation of a Bluetooth piconet.

Explain the difference between a piconet and a scatternet

Since both Bluetooth and Wi-Fi operate in the 2.45 GHz band, how do they differ?

What is the status of the operating band of Bluetooth and Wi-Fi?

Do you think Bluetooth can offer Voice over IP services? Explain your opinion based on its current capability and trends.




Answer Guide to Question A9

See the notes pages for the answers.




Question A10

The IEEE802 family of standards use Medium Access Control. Explain briefly:what it iswhere it fits in the OSI model, and how it works.
















Question A11

Data Bits Packets Frames Segments

Physical Layer Applications Layer Data-link Layer Session Layer Network Layer Session Layer Transport Layer

a. Set up the OSI model matching the data types on the left with the correct layer (1 – 7).

b. For each layer, state the major function in SIX or less words





OSI modelFrom Wikipedia, the free

encyclopaedia.a. The right hand side

states the functionalities. b. We know that each layer

interacts only with its neighbours above and

below.Up to 18 marks at 2 marks per point are possible. Give

them a break and count the first 10 for everyone.








Question A12

All electronic voice communication systems, both wireless and wire-line, transport information from a sending user to a receiving user. For voice quality digital communications, we must control the bandwidth requirements of the natural voice, increase the distance that the voice can travel, protect it from hazards in its path, and ensure that the right user receives the sent information.

Using functional block diagrams and lines, model an elementary communication system that achieves these goals.





Source Encoder

Channel Encoder

Modulator

Channel

DemodulatorChannel Decoder

Source Decoder

Transmitter

Receiver




Question A13

List at least FIVE services that 3G systems must support.





(1) Global roaming (2) Standardized interfaces (3) Packet data services (4) Circuit-switched services (5) Multimedia services




Question A14

Given the network to the right, explain the relationships it depicts.

Transport Hardware

Soft Switch Call Control

Services, Application, Features.

APIs

Protocols

Soft Switched








Question A15

Intelligent Networks were designed in the early 1990s as closed systems for delivering value added services in circuit switched telephony networks. The combination of the rise of the Internet and deregulation has made third-party control of the Intelligent Network necessary. OSA and Parlay have evolved from Intelligent Networks as an answer to this problem, and are seen by many as their natural successor.

Parlay and OSA specify the interfaces that allow third party applications to control network functions and respond to network events. These interfaces are open, language and platform independent, and include security features.

In the space of a single slide, describe the OSA-Parlay interface specifications.





OSA-Parlay standardise two types of interface: the framework interfaces provide non specific access functions like authentication, service discovery, and monitoring. The service interfaces give access to specific network functions, like call completion, messaging, mobile user location, or charging.

Figure 1 shows the OSA-Parlay architecture. The OSA-Parlay service interfaces provide access to service capability features, units of high level network functionality. The service capability features encapsulate lower level network functions that are not normally accessible from outside the network, like determining a user's location or setting up a voice circuit. These service capability features run on service capability servers, and there is a special server that offers the framework services.

Third party applications run in application servers and can make use of service capability features through the OSA-Parlay interface. These application services can be anything from a large enterprise server to a PC in a garage based start-up company, and can connect to the OSA-Parlay interfaces through standard TCP/IP connections using CORBA, SOAP or any other distributed applications technology.




Answer to Question B15




Answer to Question B15 – Table in Notes Pages




EEE402F Telecommunications and Data Networks

Final ExaminationEnd of Module A

Go on to Module B




EEE402F Telecommunications andData Networks

Final Examination: Monday 13 June 2005 09:00 at DO 2Duration: 3 hrs 00 min

Module B

Examiners: H Anthony Chan and

Mqhele E. Dlodlo

Department of Electrical Engineering

University of Cape Town




Module B: Write Me FirstPlease don’t forget!

Name (Underline last name):

Student Number:

E-mail address:

Course Code (underline which): EEE402F-b/EEE526Z




Module B – Convergent Telecommunications Networks

Answer ALL 15 questions in this module. There are extra blank slides at the end of the

module in case of longer answers. If you use the extra slides be sure to

NUMBER your ANSWER according to the question concerned.

You have 1 hr 30 min for this module.




Question B1

If by broadband we mean the use of multiple channels on the same physical medium to increase the effective transmission rate, do we need optical broadband access all the way to the user terminal in order to handle multimedia content?

Explain why or why not.





No, not exactly in practice. DSL technology is proving that we certainly need some sort of wider bandwidth but not the optical sort of broadband as originally envisioned by the telephone industry for video.

The ADSL modem uses analogue techniques to support bandwidth in the local loop of up to 1.1 MHz. This bandwidth has proved adequate for consumer requirements without re-wiring the local loop. See the notes pages for details.




Question B2

State and describe THREE (3) types of signalling network modes found in common use, where mode means the association between the signal path and the signalling relation. [6 marks]

Enumerate FOUR (4) of the many advantages of using SS7. [4 marks]




Answer to Question B2 (slide a)

Associated mode: the messages that correspond to a signalling relation between two points travel over a set of links directly connecting the source and destination signalling points together.

Non-associated mode: here the messages may follow a path or paths through two or more sets of links in tandem via two or more other signalling points between the source and the destination.

Quasi-associated mode: a version of the non-associated mode with a pre-determined and fixed path.




Answer Guide to Question B2 (slide b)

SS7 uses common-channel signalling. The Common Channel Signalling (CCS) network uses Out-of-Band signalling to signal between Stored Program Control (SPC) switching systems. These systems include: Class 4 SwitchesClass 5 SwitchesOperator Service Provisioning System (OSPS) Independent Company switching systems




Answer to Question B2 (slide c)

SS7 uses Non-Associated CCS, which is performed over an entirely different facility, or even network.

Reduced Toll Fraud, More efficient network utilization, Reduced signaling cost, Improved equipment utilization, Improved signaling reliability, Utilization of full potential of Electronic Switching

Systems, Provisions for new/improved services, Compatible with International Standards.




Question B3

Distinguish between synchronous digital hierarchy (SDH) and pleisiochronous digital hierarchy (PDH).

Describe wave division multiplexing (WDM). Describe time division duplex (TDD). Explain inter-symbol interference (ISI) in time

division multiple access (TDMA)





SDH – a group of fibre-optic technologies whose transmission rates that can transport digital signals with

different capacities. PDH –

a precursor to SDH/SONET used to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems. SONET differs from PDH in that the exact rates that are used to transport the data are tightly synchronized to network based clocks. Thus the entire network operates synchronously. SDH was made possible by the existence of atomic clocks.

WDM – an optical version of FDM where separate channels are assigned to different carrier wavelengths

or colours of laser light TDD -

use of time division multiplexing to transmit signals in the uplink and downlink using the same carrier. TDM allows switches to create channels, also known as tributaries, within a transmission stream. A standard voice signal has a bandwidth of 64 kbit/s, determined using Nyquist’s Sampling Criterion. TDM takes frames of the voice signals and multiplexes them into a TDM frame which runs at a higher bandwidth. So if the TDM frame consists of n voice frames, the bandwidth will be n*64 kbit/s.

ISI – distortion of the received signal, which distortion is manifested in the temporal spreading and

consequent overlap of individual pulses to the degree that the receiver cannot reliably distinguish between changes of state, i.e., between individual signal elements.

the disturbance caused by extraneous energy from the signal in one or more keying intervals that interferes with the reception of the signal in another keying interval.




Question B4

Define the following PSTN functions: Signalling Multiplexing Switching Routing




Answer Guide to Question B4 (slide a)

Signalling The use of signals for controlling communications. In a telecommunications network, the information exchange concerning

the establishment and control of a connection and the management of the network, in contrast to user information transfer.

The sending of a signal from the transmitting end of a circuit to inform a user at the receiving end that a message is to be sent.

Source: from Federal Standard 1037C and from MIL-STD-188

Multiplexing In telecommunications, multiplexing (also muxing or MUXing) is the

combining of two or more information channels onto a common transmission medium using hardware called a multiplexer or (MUX). The reverse of this is known as inverse multiplexing, demultiplexing, or demuxing.

When encoding video, multiplexing often refers to the process of interleaving audio and video into one coherent stream.

Retrieved from "http://en.wikipedia.org/wiki/Signaling_%28telecommunication%29"




Answer to Question B4 (slide b)

Switching is the function in an exchange that routes signals and user traffic between sources and destinations or end users. In particular, a telephone switch is the brains of an exchange. It is a device for routing calls from one telephone to another, generally as part of the public switched telephone network. They work by connecting two or more digital virtual circuits together, according to a dialled telephone number. Calls are setup between switches using the ISUP protocol, or one of its variants.

Routing in the PSTN is the process of selecting routes for telephone calls around the public switched telephone network using routing tables. Telephone exchanges are connected together with trunks. Each call that is to be routed contains a destination number that has two parts, a prefix which generally identifies the geographical location of the destination telephone, and a number unique within that prefix that determines the precise destination equipment.




Question B5

Select FIVE (5) protocols from the list, place each at either layer 4 or layer 7 and write its name or description in full: FTP HTTP SPX SMTP Telnet DNS UDP SCTP SSH IMAP RTP DICT





Layer 4 protocols are labelled as such, the rest belong in layer 7: FTP File Transfer Protocol HTTP HyperText Transport Protocol, used in the World Wide

Web SPX Sequenced Packet Exchange – Layer 4 SMTP Simple Mail Transfer Protocol Telnet, a remote terminal access protocol DNS Domain Name Service UDP User Datagram Protocol – Layer 4 SCTP Stream Control Transmission Protocol – Layer 4 SSH Secure SHell IMAP Internet Message Access Protocol RTP Real-time Transport Protocol DICT Dictionary protocol




Question B6

What is a Softswitch? Briefly explain how a softswitch works in

telecommunication networks.




Answer Guide to Question B6

Softswitch is a telecom voice and/or data switch in which the call processing function and the physical switching function are separate and are connected via a standard protocol. It is software-based rather than hardware-based switching.

It has a client server architecture. It consists of a virtual switch matrix and its network intelligence is

distributed. A Softswitch is typically used to control connections at the junction point

between circuit and packet networks. A single device containing both the switching logic and the switching

fabric can be used for this purpose; however, modern technology has led to a preference for decomposing this device into a Softswitch (containing the logic used to correctly connect incoming and outgoing ports in order to make end-to-end connections) a Media Gateway (that actually contains the incoming/outgoing ports and the switch fabric in between them).

Well known manufacturers of Softswitches include Lucent, Nortel, Siemens, Sonus, Alcatel, Santera, and Cisco.




Question B7

Refer to the Diagram for Question B7 below. Briefly explain the major role of the following:

Applications layerAny ONE of these (TCAP, SCCP, ISUP, BISUP,

TUP)MTP3 layerMTP2 layerMTP1 layer




Diagram for Question B7 SS7 Protocol Stack

MTP1 Physical layer

BISUP TUP

SCCP

TCAP

Applications

MTP2 Signaling Link layer

MTP3 Network layer

ISUP




Answer Guide to Question B7: Message Transfer Part MTP1

MTP1 defines the physical, electrical, and functional characteristics of the digital signaling link





Physical interfaces:E-1 (2048 kb/s; 32 64 kb/s channels),DS-1 (1544 kb/s; 24 64kb/s channels),V.35 (64 kb/s),DS-0 (64 kb/s), andDS-0A (56 kb/s).

c.f. the OSI Physical Layer is responsible for converting digital stream into bit stream over the network





MTP2 ensures accurate end-to-end transmission of message signaling units (MSUs) across a signaling link. It implements flow control, message sequence validation, and error checking.

The probability of undetectable errors in MTP2 messages is Pu_error < 10–10 in SS7 specification. When an error occurs on a signaling link, the message (or set of messages) is retransmitted.





c.f. the OSI Data Link Layer provides reliable communications between two devices





MTP3 provides message routing between signaling points in the SS7 network.

MTP3 re-routes traffic away from failed links and signaling points and controls traffic when congestion occurs.Route Management: Routing traffic around

nodes that have failedTraffic Management: Flow control mechanism





MTP3 is equivalent to the OSI Network Layer.




Answer Guide to Question B7: ISDN User Part ISUP

The ISDN User Part (ISUP) defines the protocol used to set-up, manage, and release trunk circuits that carry voice and data between terminating line exchanges (e.g., between a calling party and a called party)

ISUP is used for both ISDN and non-ISDN calls. However, calls that originate and terminate at the same switch do not use ISUP signaling.




Answer Guide to Question B7: Telephone User Part TUP

Telephone User Part (TUP) handles analog circuits only and is used In some parts of the world to support basic call setup and tear-down

ISUP has replaced TUP for call management TUP in many countries




Answer Guide to Question B7: Signaling Connection Control Part SCCP

SCCP provides connectionless and connection-oriented network services and global title translation (GTT) capabilities above MTP3

A global title is an address (e.g., a dialed 800 number, calling card number, or mobile subscriber identification number) which is translated by SCCP into a destination point code and subsystem number.

A subsystem number uniquely identifies an application at the destination signaling point.




Answer Guide to Question B7: Transaction Capabilities Applications Part (TCAP)

TCAP enables the deployment of advanced intelligent network services (8xx, calling card) by supporting the exchange of non-circuit related data between applications across the SS7 network using the SCCP connectionless service. Queries and responses sent between SSPs and SCPs are carried in TCAP messages.




Answer Guide to Question B7: Transaction Capabilities Applications Part (TCAP)

TCAP carries Mobile Application Part (MAP) messages in ANSI-41 and GSM mobile networks sent between mobile switches and databases to support user authentication, equipment identification, and roaming.




Question B8

Describe the essential characteristics of the Next Generation Network (NGN) architecture as currently conceived.

Explain why NGN is not replacing but complimenting existing networks.




Answer to Question B8: (slide a) See H. A. Chan for PPt

See notes pages below this slide and slide 4 (page 3) of eee526-4-600.pdf [8 marks]





Too much is already invested in large networks in the developed world, necessitating coexistence and upward compatibility. Replacement will be gradual. [2 marks]




Question B9

Use ANY TWO [6 marks] of the following formats to show how multiplexing differs from routing [4 marks]:

Frequency division multiplexing Time division multiplexing Code division multiplexing, and Wavelength division multiplexing, and Video encoder interleaving




Answer Guide to Question B9 (slide a)

Frequency division multiplexing divides channels into distinct frequency bands with guard bands in-between to avoid adjacent channel interference; uses the bands fulltime

Time division multiplexing divides the time among the various users of a single bandwidth by assigning time slots with clocking to avoid intersymbol interference

Code division multiplexing uses a broad range of frequencies fulltime for all users but assigns each user a unique pseudo-noise (PN) code such that all user channels are orthogonal to each other; it can be used to select a mobile station, a cell or a service area, each of which requires different PN code types




Answer Guide to Question B9 (slide b)

Wavelength division multiplexing assigns different wavelengths of the light waves to the separate channels in the same way that FDM confines RF energy to separate bandwidths

Video encoder interleaving breaks the video stream into coded clumps of picture elements and rearranges them in such a way that no neighbouring pixels will be found close to each other




Answer Guide to Question B9 (slide c)

Routing in the PSTN is the process by which telephone calls are routed around the public switched telephone network. Telephone exchanges are connected together with trunks. Each call that is to be routed contains a destination number that has two parts, a prefix which generally identifies the geographical location of the destination telephone, and a number unique within that prefix that determines the precise destination.

See the notes pages below the slide as well.




Question B10

Compare Multi-protocol Label Switching and Asynchronous Transfer Mode to show how boundaries between circuit switching and packet switching are becoming blurred.





It is in the flexibility of MPLS that we see this. See the notes page of this slide.




Question B11

Complete the table below to contrast today’s Class 5 local exchange switch with an NGN switch as envisioned. [8 marks]

Explain with informed reasons how you think broadcasting might feature in the converged Next Generation Network. [2 marks]




Answer to Question B11 (slide a)

Traditional Class-5 Switch

Next-Generation Switch

Start-up Costs R10’s million start-up R100,000’s start-up

Switching topology Hub and spoke switching

Distributed switching

Switching Architecture Remote Switching Modules (RSMs) and Digital Loop Carriers (DLCs)

ATM and/or IP core switching and backbones

Access to Services Adjunct boxes for enhanced services

Class-5 access device with integrated enhanced and data services





The dawn of ADSL-wired homes worldwide, and the widespread use of Internet-based entertainment from video clips, audio clips on to full scale movies has set the stage for a boom in IP-based TV and IP-based radio broadcasts. Devices with Internet access become the centre of telecommunications and entertainment for the home user. [Any other view based on fact is acceptable. The mark out of 2 depends on the degree of instructor-perceived plausibility.]




Question B12

Vodacom in South Africa has incorporated 4G network architecture. Discuss how this possibly inter-works with the existing PSTN.





4G is a wireless access network technology coming after 3G, also wireless. It can be configured with appropriate interfaces to Wi-Fi, UMTS, EDGE or any other emerging technology in the intelligent edge network, without directly affecting the core PSTN network.




Question B13

The the air interface forming the Generic Radio Access Network (GRAN) in UMTS permits dual UMTS/GSM cellular phones to roam between the two networks, but does not globally enable existing GSM cell phones to do the same. Explain why.





At the moment, only individual operators enable roaming between UMTS and GSM for existing GSM phone users, but there is no general interoperability for those without the dual UMTS/GSM phones. [See the notes pages for more details.]




Question B14

If the V.32 modem and ISDN failed to turn the local loop into a broadband link, how is the digital subscriber loop doing it?





The use of V.32 and ISDN to deliver at 1 Mb/s or higher rates to the home user premises required replacing twisted pair copper wires with optical access technology, an expensive option.

ADSL has been able to deliver interactive multimedia content to the home by utilising the existing spare capacity of 64 kb/s wide ISDN channels without changing the local loop hardware. It does this by keeping ADSL and voice channels separate.




Question B15

Briefly describe the operation, application and features of the Signalling System Number 7.





Applications and Features of SS7:Basic call setup, management, and tear down Wireless services, roaming, and mobile subscriber

authentication Local number portability (LNP)Toll-free (0800/0860) and toll (900) wire-line services Enhanced call features:

• call forwarding,• calling party name/number display,• three-way calling

Efficient and secure worldwide telecommunications





End of Module B

Du Umhloliso





End of Examination

Engineering innovation begins with curiosity. I wish you heightened

curiosity as you pursue your careers.

© MED 2005

Documents

Telecommunications and Data Networks Final Paper Page 1 13 June 2005 What I have is only borrowed from God so that I may serve others. H Anthony Chan The