Notes

Outline

S-72.423 Telecommunication Systems An Overview to Course Contents

Topics today Practicalities Table of course contents Networking paradigms: Determining networking trends Network evolvement Topology divided integrated mobile Telecommunication markets Review of course contents in selected topics The OSI-model Networking approaches: PSTN, ISDN, Mobile, Internet Future trends

Practicalities Lectures Timo Korhonen (timo.Korhonen@hut.Fi) Michael Hall (michael.Hall@hut.Fi) Tutorials Mika Nupponen (mika.nuppunen@hut.Fi) Lectures on Thursdays 10-12 in U358 Tutorials on Tuesdays 14-16 in E111 Textbooks: Ericsson, Telia: Understanding Telecommunications, Part II, ISBN 91-44-00214-9, W. Stallings: Data and Computer Communications, ISBN 0-13-571274-2 Homepage: http://www.comlab.hut.fi/opetus/423

Course contents Introduction Public Switched Telephone Network (PSTN) Exchange techniques Transmission Integrate Services Digital Network (ISDN) Functions Interfaces Automatic Transfer Mode (ATM) and Broadband-ISDN X.25, Frame relay Public land mobile networks GSM WCDMA Signaling networks: SS7 The Internet: Network topology, TCP/IP Suite, Services

Telecommunication networks have much in common Trunk and access parts Access part terminated by terminals Network nodes and links are optimized for certain assumed traffic patterns This model applies for both data and voice networks Due to these network similarities their analysis carriers common subtopics

Course contents: Networking subtopics User services and terminals Standards Routing and switching Transmission techniques Access and transport Server services Signaling Network management Interworking between networks Network planning

Paradigm shift

Network evolvement Most people observe that a telecommunications network is a system transmitting the messages… In this course we focus on analyzing that it consists of ...

Data and voice networks Nodes and links with well defined (standardized) interfaces Network nodes and links that are optimized for certain, assumed traffic Traditional assumption: Voice and  data services in different networks

Integrated Services Digital Network (ISDN)

Network/service adaptivity Services manifest themselves via various customer profiles (that differ within a short time period), and thus efficient adaptivity should be supported by network configurations Advanced networks have a tendency carry intelligence in terminals (and not in exchanges) Reduces signaling traffic Moves costs to end-users IN (Intelligent Network) solutions developed first for PSTN but a typical important part of most networks as in PLMNs Enables service flexibility in exchanges IN services designed in cooperation with terminal intelligence

Public Land Mobile Networks (PLMN) Mobility is required practically for all services in the very near future! In this course we will discuss especially the GSM (Global System for Mobile communications) (9.6 kbit/s) and WCDMA (Wideband Code Division Multiple Access) networks After 2002 WCDMA will be launched that will yield mobile data rates up to 3Mb/s. However, also the GSM network will be upgraded for higher rates thanks to GPRS (General Packet Switched Data), HSCSD (High Speed Circuit Switched Data) and EDGE (Enhanced Data Rates for GSM Evolution)

Telecomm market players Telecommunication network content and technology producers, operators and consumers form a hierarchy

Telecomm market players (example) End-users (individuals and companies) Information service providers (As a telephone catalog services designed by a company, giving telephone numbers when you give a name or an address) Service brokers sell dedicated service packages Network operators (as HPY, Telia, or Radiolinja) Content providers (as Paramount Pictures)

Telecom services categorized

The ISO-OSI Model

The OSI-functions

Practical networks usually melt OSI

Each OSI-layer has its standardized services

Practical network stratums OSI is seldom realized as itself but several layers are melted together into stratums In this example X.25 packet network operates on ATM  based SDH access stratums. ATM forms an efficient info pipe where no address checking or error correction is done but it is left for lower layers

The PSTN hierarchy Since ‘96 in Finland all the exchanges of PSTN have been digital However, there exists still analog phones Natural connection to the modern PSTN is the ISDN-interface

Example: PSTN Network operator in two towns

Telecommunications service requirements from the physical level Networking requirements: What services require from the network in respect of Bandwidth, Burstiness, Symmetry (uplink /downlink rates), Bit errors and blocking Delay Security These define QOS (Quality of Service)

Different services require different rates

Burstiness: video, voice, data Different services (telecomm. traffic) require different networking abilities Most real-life sources produce bursty traffic Modern networks can adapt into bursty service by allocation capacity very rapidly for other users

Speech and data communications Teletraffic can be forced to fixed rate or bandwidth as speech in PSTN or ATM traffic

Bit errors and blocking Real-time services for video and audio Can not tolerate delays clearly observable by human (in order 200 ms or larger) Can tolerate relatively large error rates Blocking probability depends on number of customers in a service area Fixed rate data services require much non-reusable capacity: Fixed delay demanding error rate limit High-latency data: Large flexibility in delay demanding error rate limit

Symmetry Cathegories: Symmetrical channel as in fixed line telephony Asymmetrical channel Most technical Internet realizations (As xDSL-techniques or data over DVB) are based on idea that downlink traffic is order of magnitude larger that uplink traffic Point-to-multipoint channel TV and Fax are point-to-multipoint distributive services Note, however that some new services in Internet (where your PC works as a server, as Napster) might require symmetrical traffic channel Also Internet is used for point-to-multipoint services as in Webcasting (as in Web-broadcasting or in the PointCast news service.) Therefore developing Internet services set stringent requirements for network planning!

Security and secrecy Services might require security, e. g. reliable, shielded transfer: rescue services police defence force some special applications as telesurgery Networks can provide this by using: fixed lines (PSTN) flexible routing (SS7) scrambling or encryption coding Often secrecy is reassured in several network levels

Public switched telephone network (PSTN) The oldest (1876) bearer network (other: ISDN, ATM, frame relay, The Internet) After 1960 has got many renovations: data, fax, processor exchanges, PCM, satellite communications, network intelligence Primary characteristics Analog access 300-3400 Hz Circuit switched connection Switched bandwidth 64 kbit/s (Digital exchanges) Immobility (or very limited mobility) Integrated nowadays especially with N-ISDN

The PSTN (cont.) The PSTN is optimized for statistically distributed, analog speech subscribers (by using the circuit switching technology that was available beginning of this century). Support for data traffic "artificially added" by modems ISDN (integrated into exchanges) xDSL (asynchronous digital subscriber line) However, PSTN is Easily congested when subscriber behavior changes unexpectedly (no graceful degradation as in CDMA-PLMN): resource wasting

The PSTN (cont.) Vulnerable: network paralyzed easily in exchange malfunctions Network intelligence in exchanges and dummy terminals Poor adaptivity However, an important backbone for other networks! The PSTN will be there for a long time and it seems that it can be used for modern day networking also on quite high data rates of order of several Mbytes by using various extension techniques Modern day networks are constructed thus that the required services can be supported: Thus

Integrated Services Data Network (ISDN) In N-ISDN (narrow band 2x64 kb/s +16 kb/s, extendable up to 30x64=1.92 Mb/s), B-ISDN (rates exceeding 100 Mb/s) and ATM (asynchronous transfer mode) networks all services are handled integrated, circuit switched way. Mobility enabled by DECT (Digital Enhanced Cordless Telecommunications ) Nowadays there exists many competitive techniques for ISDN as Cable modems, ISM -band (Industry, Science, Medicine) LANs (as the HiperLAN) Digital satellite networking by DVB (SAS Astra) WCDMA PSTN with 56 kbit/s (V.90) technology

Signaling networks Telecom nets require more and more processor capacity: More subscribers Setting up connection is getting increasingly complex Number of supplementary services increasing Thus the need to transmit signaling information (=interactive network telematic communication) is increasing

The Internet(working) The Internet carries “Everything over anything” (almost) Internet topics: TCP/IP: Frames and sessions Routing: Backbone connected subnets Network planning: Core - Regional nets - Access nets - Users Signaling: TCP client – server communications Services: http, ftp, email, irc, new, telnet …. Internetworking (!) for instance data over PSTN: PPP, SLIP

TCP/IP: Transmission Control Protocol             Internet Protocol The first Internet was ARPANET in 1969’s with four nodes Present TCP/IP version 4 has problems especially in lacking of address capacity security In 1997 ipV6 was initiated - However not too much used yet due to compatibility problems TCP/IP does not have any general advance (except that it is so widespread) when compared to IPX, AppleTalk, DECnet etc. Essential high level network functions routing management name servers network management protocols Network consists of hardware as workstations, networks, routers, bridges software as applications and protocols

TCP/IP Network tranmission TPC/IP tasks: end-to-end transmission, error correction, maintain packet order Internet is based on datagrams that address subnets via routers A simple routing could be accomplished by a lookup table between target IP and subnet IP

The playground of telecommunications markets

Future trends PSTN used to transfer more and more data traffic PSTN rates increase up to several Mb/s Also data networks (as the X.25) will be used for voice and there is a strong tendency to put everything over IP The fax service in PSTN will diminish and the respective messages are transmitted by e-mail (that is transferred via a packet networks (usually by TCP/IP)) Inter(net)working between networks increases Traditional voice service in PSTN transforms using packets and moves to Internet PLMNs and LANs develop very fast

Web resources xDSL: www.adsl.com 3:rd generation PLMN: www.w3.org, www.3gpp.org Telehallintokeskus: www.thk.fi IEEE standards: www.ieee.org Finnish standards: www.thk.fi/tele/suomi/standard.htm Network & terminal realization: www.nokia.com … and so many more!