Architettura per il controllo del traffico nel sistema radiomobile Umts

Introduzione 
15 
Oltre ai normali servizi offerti ora dal GSM sar� possibile scambiare dati ad alta velocit�, 
mandare messaggi di posta elettronica, consultare pagine web, acquisire e memorizzare delle 
immagini e cosi via dicendo. Il tutto ad un grado di qualit� paragonabile a quello che ora 
offrono le reti fisse. 
  
Il successo avuto in questi anni dal sistema GSM e da Internet � un ottimo trampolino di 
lancio per il progetto del nuovo sistema che mira ad essere un�ambiziosa sintesi, almeno sul 
piano dei servizi offerti, di queste due storie evolutive che rappresentano il mercato delle 
telecomunicazioni di questi anni. 
In quest�ottica si pone il progetto VIRTUOUS, che vuole contribuire a consolidare la 
posizione dell�Europa in questo mercato, in continua espansione ed evoluzione, che offre 
altissimi margini di sviluppo. 
L�obiettivo fondamentale di VIRTUOUS � contribuire alla realizzazione di un sistema 
integrato UMTS e GPRS, che utilizza differenti tecniche d�accesso (terrestre e satellitare). 
In particolare il progetto vuole cooperare con gli enti di standardizzazione per partecipare 
attivamente alla definizione del sistema UMTS, in particolare per la parte satellitare. 
Infatti, fino ad ora l�ETSI e il 3GPP si sono dedicati solo alla parte terrestre definendo quasi 
tutte le specifiche del T-UMTS (Terrestial UMTS). 
Per quanto riguarda S-UMTS (Satellite UMTS) nulla � stato definito e sono molti i punti 
oscuri. VIRTUOUS ha intenzione di realizzare un simulatore che contenga anche un 
segmento satellitare e, in particolare, si propone di implementare e testare il modello 
d�accesso W-CDMA (Wideband Code Division Multiple Access) proposto dall�ESA 
(European Space Agency). 
Il passaggio verso l�UMTS sar� graduale perci� bisogner� garantire un interlavoro tra la rete 
GSM e quella UMTS. 
Alla luce di questi aspetti nell�ambito del progetto si realizzeranno: 
 
• Le principali funzioni dell�URAN (UMTS Radio Access Network) sia per la parte 
indipendente dall�accesso radio (RTI) che, quindi sar� in comune tra la parte terrestre 
e quella satellitare, sia per le parti specificatamente dipendenti dall�accesso radio 
(RTD). 
• Le principali funzioni del GPRS (General Packet Radio Service) che rappresenta 
l�evoluzione del GSM in modo da poter realizzare e controllare l�interazione tra i due 
sistemi. A tale scopo si realizzeranno delle opportune unit� d�interlavoro 
(Interworking Units). 
• Dei terminali cosiddetti �three-mode� in modo da consentire l�utilizzo del normale 
sistema GSM/GPRS e dei segmenti terrestri e satellitari dell�UMTS 
 
Introduzione 
16 
Il risultato sar� un simulatore �hardware� che dovr� testare il modo di funzionare del sistema 
complessivo. 
In particolare il progetto VIRTUOUS andr� a realizzare tre esperimenti: 
• Esperimento di mobilit� tra i vari segmenti  
• Esperimento di gestione della Qualit� del Servizio  
• Esperimento di gestione dei servizi da estremo ad estremo  
  
Questa tesi si occuper� solo dell�esperimento sulla Qualit� del Servizio perch� l�Universit� di 
Roma �La Sapienza�, nell�ambito del progetto, ha il compito di fornire le basi teoriche e 
implementative di questo esperimento. 
L�obiettivo fondamentale � di realizzare un sistema che sia in grado di garantire un servizio 
adeguato a tutte le connessioni instaurate dagli utenti, in base alle caratteristiche del tipo di 
traffico. In altre parole il sistema dovr� assicurare agli utenti una ben definita Qualit� del 
Servizio nel rispetto del Virtual Home Enviroment (VHE). Il VHE � un ambiente virtuale che 
UMTS definisce per garantire all�utente l�accesso ai servizi sottoscritti, nel modo da lui 
impostato, a prescindere da terminale e rete. 
Garantire un certo grado di servizio implica il rispetto di vincoli sulla perdita dei pacchetti e 
sul ritardo di trasferimento, che sono gli elementi essenziali che distinguono le varie tipologie 
di traffico. 
Nel progetto VIRTUOUS si fa riferimento a tre classi di servizio: 
 
• Una prima classe molto sensibile al ritardo di trasferimento e alla sua variabilit�, poco 
sensibile alla perdita dei dati. Nell�ambito di questa classe sar� considerato il traffico 
voce.  
• Una seconda classe molto sensibile alla perdita dei dati e con una certa sensibilit� al 
ritardo di trasferimento. Tipica applicazione � il �Web Browsing� ovvero la 
consultazione di pagine Web.  
• Una terza classe anch�essa molto sensibile alla perdita dei dati, ma con minori vincoli 
sul ritardo di trasferimento. Le applicazioni tipiche sono il trasferimento di files (FTP 
File Transfer Protocol) e la posta elettronica.  
  
Nello scenario generale ogni utente � in grado di avere un certo numero di connessioni attive, 
appartenenti alle tre classi di servizio. All�instaurazione d�ogni connessione avviene la 
negoziazione dei parametri di traffico tra utente e rete. In particolare l�utente fa le sue 
richieste e la rete deve stabilire, sulla base della sua capacit�, se ammettere o meno la nuova 
connessione. In caso positivo la chiamata � ammessa ed � stabilito il contratto di QoS che la 
rete avr� cura di rispettare. L�organo che provvede all�ammissione delle connessioni prende il 
nome di CAC (Connection Admission Control). Per garantire, invece, il rispetto dei parametri 
negoziati � necessario realizzare un sistema che effettui il controllo del traffico; ovvero cerchi 
Introduzione 
17 
di prevenire eventuali situazioni di congestione che potrebbero portare ad una riduzione della 
qualit� del servizio. In questa tesi vengono presentate delle architetture funzionali per il 
controllo del traffico evidenziandone i pregi e i difetti. In particolare si considerer� una 
soluzione, implementata poi con il programma OPNET, che prevede l�utilizzo di tre Dual 
Leaky Buckets (DLBs) e tre code, una per ogni tipologia di traffico. Per ogni coda sono 
effettuate delle misure, in particolare il numero di pacchetti presenti all�interno. I risultati 
arrivano ad un organo di controllo chiamato Congestion Control Handler (CCH) che, in 
conformit� a queste misure, ordina ai DLBs di aumentare o diminuire il traffico che arriva 
dentro ciascuna coda. I DLBs sono, in pratica, gli esecutori dell�algoritmo di controllo e 
variano il traffico proveniente dalle sorgenti sulla base degli ordini del CCH.  
Ad esempio se in una coda ci sono troppi pacchetti il CCH fa in modo che il DLB, che fa 
riferimento a quella coda, riduca il traffico entrante. In questo modo i pacchetti in coda 
possono essere smaltiti senza grossi problemi di ritardo. 
Un altro elemento fondamentale dell�architettura presentata � lo scheduler che, utilizzando la 
disciplina Earliest Deadline First (EDF), preleva i pacchetti dalle tre code e li spedisce sulla 
base della loro priorit� temporale. 
In questo modo si garantisce, se le sorgenti rispettano il contratto di traffico, la trasmissione 
dei pacchetti entro un prefissato istante, rispettando rigorosamente i requisiti di ritardo delle 
applicazioni specificate. Se, invece, le sorgenti non rispettano il contratto e producono un 
surplus di traffico che � chiamato �non-conforme� allora il sistema pu� comportarsi nei modi 
seguenti:  
• Se la rete pu� accettare il traffico non-conforme, perch� ad esempio � abbastanza 
scarica, allora il traffico � accettato ed � trattato allo stesso modo di quello conforme. 
• Se la rete non � in grado di accettare altro traffico, allora il non-conforme � scartato 
dai DLBs e ci� non influisce sul ritardo di trasferimento del traffico conforme. 
 
Nella simulazione si vedr�, comunque, che anche quando il sistema accetta il traffico non 
conforme, grazie all�azione congiunta dello scheduler EDF e del controllo di congestione, i 
pacchetti ammessi nel sistema non subiscono un ritardo maggiore di quello massimo tollerato. 
Lo svantaggio di quest�architettura � che non � possibile ottenere un trattamento differenziato 
per ogni singola connessione, ma solo per ogni classe di servizio. 
Ci� � dovuto alla presenza di un solo DLB, che controlla il traffico proveniente da tutte le 
sorgenti di una classe, e una sola coda per ogni tipologia di servizio, che rende impossibile 
discriminare i pacchetti di connessioni diverse. Questo �, tuttavia, il prezzo da pagare per 
avere un�architettura semplice, scalabile e facilmente adattabile com�� quella che abbiamo 
implementato. 
Dal punto di vista dell�efficienza, la soluzione migliore prevede l�uso di un DLB e di una 
coda per ogni connessione e non per classe. In questo modo si pu� controllare il traffico in 
maniera completa avendo per� un modello molto complesso e poco scalabile. 
Introduzione 
18 
Nella scelta finale dell�architettura, si tratter�, come sempre, di trovare un compromesso tra i 
costi, la fattiva realizzabilit� e le prestazioni. 
  
In questa introduzione � stato fatto un quadro riassuntivo in italiano di tutti gli argomenti 
trattati pi� ampiamente e dettagliatamente nella tesi in lingua inglese. 
Nel capitolo 1 ci sar� un�introduzione al progetto VIRTUOUS che evidenzia gli obiettivi e gli 
intendimenti.   
 Nel capitolo 2 saranno discussi gli aspetti pi� importanti dell�UMTS; sar� posta l�attenzione 
sui servizi offerti e sulla architettura della rete; saranno evidenziate anche le differenze con il 
GPRS. Sar� dato spazio anche alle caratteristiche e ai requisiti del Satellite UMTS. 
Nel capitolo 3 saranno trattati gli aspetti peculiari degli strati RRC e RLC dell�architettura 
protocollare dell�UMTS e messo in risalto tutto ci� che riguarda la Qualit� del Servizio e la 
sua gestione. 
Nel capitolo 4 sar� presentato il dimostratore VIRTUOUS.  
Nel capitolo 5 sar� descritto dettagliatamente l�esperimento di Qualit� del Servizio illustrando 
l�architettura per il controllo del traffico.   
Nel sesto e ultimo capitolo sar� definita la simulazione dell�architettura in OPNET e saranno 
discussi i risultati ottenuti. 
 
 
 
Chapter 1 � VIRTUOUS Project 
19 
 
 
CHAPTER 1 - VIRTUOUS Project 
 
 
 
 
1.1 Introduction 
 
The VIRTUOUS project belongs to the Information Society and Technology (IST) project 
group funded by European Commission. The consortium has started on 1/1/2000 and will end 
on 1/7/2002.  
The project would directly contribute to maintain the European strategical competitive 
position in the sector of the future development of phase 2 Terrestrial UMTS and Satellite 
UMTS starting from the present second-generation systems (GSM and GPRS). The success of 
this policy would guarantee, for the European countries, to maintain a real presence in the 
telecommunication market that represents one of the highest growing sectors of the economy 
in Europe. 
Therefore, the contribution that the leading mobile terrestrial and satellite mobile services 
could bring to the market are of the outmost strategy if compared to a general situation where 
European market suffers of general structural rigidity in product, services and labour 
organisation.  
Products and processes like mobile telecommunications, with the take-off of new market for 
multimedia and added value services, are the most important opportunities for stimulating 
demand growth and industry development. 
The growth of the telecommunication software and services industry is creating employment 
opportunity and new jobs. The diffusion of Internet and linked communication services is 
demonstrating that there is a strong potential for further expansion in the service and mass 
electronic product markets.  
The S-UMTS and T-UMTS developments, promoted by VIRTUOUS, will provide important 
benefits for the mobile users in terms of more efficient use of the telecommunication 
resources, new useful services and better quality of the services. 
Moreover the network operators will avail of remarkable benefits as well, since they will 
manage more flexible networks and will be able to provide more standardized services. 
 
The project team is composed of the different type of companies (manufacturers, operators, 
research bodies, engineering companies, universities): 
 
Chapter 1 � VIRTUOUS Project 
20 
Italy   Telespazio 
Italy   Space Engineering 
Austria  Siemens Austria 
France  Thomson 
Italy   University of Rome �La Sapienza� 
Germany  Aachen University of Technology 
Switzerland  Ascom 
Italy   European Business Associates 
Spain  Telefonica 
Italy   CSELT 
 
Through the cooperation among the entire companies VIRTUOUS project should try to give 
an important contribution to Standards. 
Standardization activities will start by identifying European and international bodies 
potentially interacting with the project team. The purpose of this activity is twofold: to 
identify the standards the VIRTUOUS system has to comply with, and to identify the 
standardization activities that may benefit from VIRTUOUS outputs.  
Cooperation with organizations that are more traditionally involved in satellite 
communications (e.g. the European Space Agency) will be also considered, and actions will 
be started soon. 
Therefore, in the area of standardization, the VIRTUOUS team will carry out the following 
activities: 
- dissemination of project results within the European and international organizations; 
- direct participation in the activities of Working Groups involved on UMTS matters; 
- interaction with other IST projects to create synergies which can yield stronger impacts 
on the standardization bodies. 
 
 
1.2 Project Objectives 
 
VIRTUOUS Project primarily addresses the following topics of the IST framework [40]: 
Network integration, interoperability and internetworking: VIRTUOUS is expected to 
provide contributions to this action, since one of the key objectives of the VIRTUOUS project 
is to develop interworking procedures among 2
nd
 generation (GPRS) and 3
rd
 generation 
(Terrestrial-Satellite- (T-S)-UMTS) Access and Core Networks and interworking among T-
UMTS and S-UMTS networks. The developed and experimented procedures will carry into 
effect the VHE (Virtual Home Environment) concept. 
Engineering of intelligent services: VIRTUOUS will address the problem of providing 
services across heterogeneous networks (i.e. 2
nd
 and 3
rd
 generation terrestrial and satellite 
Chapter 1 � VIRTUOUS Project 
21 
networks). In this respect, service negotiation, quality assurance and management in a 
heterogeneous network will be key issues. 
Terrestrial wireless system and networks: VIRTUOUS is expected to provide major 
contributions to this key action, since it is expected to develop and experiment (i) meaningful 
functions of the RTI (Radio Technology Independent) and RTD (Radio Technology 
Dependent) parts of the URAN (UMTS Radio Access Networks), (ii) appropriate Inter 
Working Units (IWUs). The equipment to be used will deal with fundamental wireless system 
procedures such as resource management, flow control, signalling, QoS adaptation, intelligent 
mobility (roaming), etc� 
Integrated satellite systems and services: VIRTUOUS will contribute to the development 
and experimentation of the S-UMTS standard proposed by the European Space Agency 
(ESA). Moreover, VIRTUOUS will integrate the S-UMTS in the URAN; this means that a 
common RTI part between S-UMTS and T-UMTS will be developed. Finally, VIRTUOUS 
will cope with the problem of interworking a satellite system with the terrestrial networks 
(inter-segment mobility procedures, inter-segment QoS adaptation, etc.). 
Resuming VIRTUOUS will facilitate the introduction of Terrestrial/Satellite UMTS by:  
 
• drawing and demonstrating a viable migration path from second to third generation 
systems, 
• introducing UMTS functions in a modular, flexible and scalable way, 
• sponsoring and demonstrating the S-UMTS standard sponsored by ESA, 
• designing and demonstrating interworking procedures among second-third, terrestrial-
satellite, Access-Core Networks, 
• experimenting attractive UMTS services. 
 
Main VIRTUOUS project objective is to design, develop and implement a test-bed where 
specific functionalities of GPRS, T-UMTS and S-UMTS are integrated. 
As components of this test-bed, a Radio Technology Indipendent (RTI) and separated Radio 
Technology Dependent (RTD) parts of a URAN, are to be designed, developed and 
implemented, having as result a hardware emulator representative of satellite and terrestrial 
UMTS protocol layers. This separation is made in terms of decoupling control and transport 
functions. As part of the test-bed, GPRS segment elements are provided. Additionally, IWUs 
necessary to complete the architecture will be designed and developed. 
The integration of the test-bed will be done in terms of identifying, designing and 
demonstrating a feasible, pragmatic and smooth migration path towards T-S-UMTS. The 
migration path is being identified taking into account current standardization activities and 
other UMTS related projects.  
In a fist migration step, an URAN is being gradually introduced providing real UMTS access. 
The RTI and RTD URAN functionalities and features are still limited. Under these 
Chapter 1 � VIRTUOUS Project 
22 
restrictions, the URAN is used to enhance second-generation capacity and to provide 3
rd
 
generation mobile users higher bit rate access and a limited set of services. In order to 
guarantee the interworking between UMTS and GPRS, an IWU is placed on the terminal side. 
The VIRTUOUS project test-bed is built from the conclusions reached during this fist step 
and consequently will serve to trial a limited set of UMTS features. 
In a second migration step, the URAN RTI and RTD parts will be upgraded in order to 
encompass the whole set of UMTS functions and features. This will allow the deployment of 
the full set of UMTS services. In all the situations, however, the trials will be performed to 
assess fundamental UMTS concepts such as: 
 
• the Virtual Home Environment (VHE). This concept refers to portability of 
personalized services across network boundaries and between terminals. Users are 
consistently presented with the same personalized features, user interface, 
customization and services in whatever network and whatever terminal, wherever 
they are roaming; of course, this is possible only within the range of the terminal 
and network capabilities. So, in principle, a user traveling through a 
heterogeneous service area has the same look and feel as if he/she was roaming in 
its home network. 
• the QoS adaptation. This concept is strictly related to the previous one and refers 
to the network ability to perform the best possible fitting between the required 
service features and the service capabilities offered by the available access 
network(s);  
• the IP layer implemented as a high layer of the UMTS network. In this 
respect, several concepts including media gateway control protocols will be 
developed in order to test in a multi-segment UMTS environment the Internet 
telephony service;  
• the inter-segment mobility issue (in the proposed demonstrator there are three 
segments, namely the GPRS, the S-UMTS and the T-UMTS segments). In this 
respect, the inter-segment roaming will be designed and experimented; inter-
segment roaming refers to the network ability to reach a called user regardless of 
the access network (either second or third generation, either terrestrial or satellite) 
which is presently serving the user. In this respect, the relationships and the 
mappings between IP addressing and UMTS addressing will be coped with. 
 
Each study or activity carried out under VIRTUOUS project is being done following 
standardization bodies� publications, as we saw before, in such a way that the test-bed and 
trials will support standards activity results. Within the project lifetime neither a satellite 
constellation offering wideband support capabilities nor a real terrestrial UMTS network, 
would be available. The emulation was proposed as an available recourse to provide both 
Chapter 1 � VIRTUOUS Project 
23 
satellite and terrestrial RTD access parts. An adaptation of a physical layer emulator based 
upon Satellite W-CDMA proposed by ESA as S-UMTS standard and the development of a 
unit able to support Terrestrial W-CDMA was proposed as VIRTUOUS RTD access part. 
With the trials to be performed within the project, conclusions to evaluate the feasibility of 
ESA proposal will be laid out [40]. 
 
In the following we will explain the most important aspects of the UMTS putting into 
evidence all the characteristics implemented in the VIRTUOUS Demonstrator. 
 
Chapter 2 � UMTS Overview 
24 
 
 
CHAPTER 2 - UMTS Overview 
 
 
 
 
2.1 Introduction 
 
The Universal Mobile Telecommunications System (UMTS) is the European Union proposal 
for a third generation of mobile systems, successor to the Global System for Mobile 
Communications and General Packet Radio Service (GSM/GPRS). 
UMTS will give users up to 2 Mb/s bit rate and support multimedia services efficiently, for 
example file transfer. It is expected to provide worldwide access and global roaming for a 
range of services combined with seamless operation across a variety of environments, and 
quality comparable to that of fixed networks. 
All the issues and the definitions regarding the UMTS emerge from the standardization bodies 
like the 3GPP (Third Generation Partnership Project), ETSI (European Telecommunication 
Standards Institutes) and the European Union ACTS (Advanced Communication Technology 
and Services) programs. 
Standardizations bodies are well on the way to harmonizing views on a range of key and 
interrelated issues. These include architecture of the radio interface and fixed network, system 
evolution and backward compatibility, accommodation of user migration and global roaming, 
and phased introduction of mobile services and capabilities for terminal mobility support. 
 
The standardization process develops through the drafting of specifics and technical reports 
regarding various aspects such as: 
- radio access network 
- core network 
- terminals 
- services and systems 
 
The UMTS introduction will be gradual and it will concern the period 2002-2005. 
The development has been modeled in four phases: 
- GSM Capacity extension: development and introduction of GPRS 
(end of 2000-2001) 
Chapter 2 � UMTS Overview 
25 
- Pre UMTS Trial Phase: in Italy the operators (Omnitel, Tim in 
cooperation with CSELT and Ericsson) are testing, in laboratory, 
the new terminals and the UMTS network. 
- Develop phase: it will begin in 2002 with the introduction of only 
some UMTS services. 
- Commercial phase: in the period 2003-2005 with the introduction 
of all the UMTS services. 
 
In the following paragraphs we will deal about the main technical aspects of UMTS putting 
our attention on the offered services (paragraph 2.2), on the network and protocol 
architecture of UMTS and GPRS and their differences (paragraphs 2.3 and 2.4), on the main 
characteristics of Satellite UMTS (paragraph 2.5). 
 
 
2.2 UMTS Services 
 
Basic telecommunication services are divided in two categories: bearer services and 
teleservices. 
 
Bearer services are telecommunication services that are capable to transmit signals between 
access points. The connection may contain a terminating network, a transit network and a 
PLMN. The different networks between the access points use means for bearer control that 
may be also different. The terminating point related to this service occurs at the reference 
point between the Terminal Adaptation Function (TAF) and the Mobile Termination (MT).  
 
Teleservices are telecommunication services providing the complete capability, including 
terminal equipment functions for communication between users according to the introduced 
protocols. As shown in Figure 2.1 the teleservices also include the TAF. 
 
Chapter 2 � UMTS Overview 
26 
TE
MT
PLMN
possible
transit
network
Terminating
network
Bearer services
Teleservices
UE
UE:  User Equipment
MT:  Mobile Termination
TE:   Terminal Equipment
TAF: Teminal Adaptation Function
TETAF
 
Figure 2.1: Basic telecommunication service 
 
2.2.1 Bearer Services  
 
Bearer services enable the information transfer between access points and involve only low 
layer functions. The user may choose any set of higher layer protocols for the communication 
transmission. The communication link may overlap different networks such as Internet, 
Intranets, LANs, and ATM based networks and therefore network specific means for bearer 
control exist. These control mechanisms are in general different. Hence the bearer services are 
translated at the network interfaces within the communication link to obtain an end-to-end 
bearer service. Bearer services are determined by a set of end-to-end characteristics with 
requirements on QoS.  
The requirements on bearer services contain requirements related to the information transfer 
and characteristics according to information quality. The former describes the network 
transfer capabilities such as the traffic type and the traffic characteristics and the latter 
describes the quality of user information. 
 
It shall be possible to define the traffic requirements to the network for one application by 
requesting a bearer service which includes the traffic type, the traffic characteristics, 
maximum transfer delay, delay variation, bit error ratios and data rates [4]. 
 
Traffic type  
A bearer service makes the transmission of different traffic types available. It is possible to 
transfer data with a guaranteed and constant bit rate, with a non-guaranteed and dynamically 
variable bit rate and real time dynamically variable bit rate with a minimum guaranteed bit 
rate. Furthermore real time and non real time applications are also performed.  
 
Chapter 2 � UMTS Overview 
27 
Traffic characteristics  
There are several configurations related to the bearer services that are requested by an 
application. 
 
Point-to-Point: Uni-Directional 
   Bi-Directional (symmetric, asymmetric) 
 
Point-to-Multipoint (Uni-Directional) 
   Multicast 
   Broadcast 
 
Bit Rates 
up to 144 kbit/s in satellite radio environment 
up to 144 kbit/s in rural outdoor radio environment 
up to 384 kbit/s in urban/suburban outdoor radio environment 
up to 2048 kbit/s in indoor/low range outdoor radio environment 
 
QoS 
It is possible to request a bearer service regarding to an application which specifies the used 
QoS requirements  
 
2.2.2 Teleservices 
 
Teleservices supply the full capabilities for communication, which contain the terminal 
equipment and also network functions. The realization of teleservices demands the association 
of terminals and network capabilities. The network uses lower layer capabilities and the 
terminals use lower and upper layer capabilities. A teleservice is a set of upper layer 
capabilities that apply the lower layer capabilities [2, 4].  
Speech 
The speech service should be supported and therefore a default speech codec shall be 
specified.  
 
The GSM and UMTS standards define currently six different Codec Types: GSM Full Rate, 
GSM Half Rate, GSM Enhanced Full Rate, GSM Full Rate Adaptive Multi-Rate, GSM Half 
Rate Adaptive Multi-Rate and UMTS Adaptive Multi-Rate. 
 
Recently the Wideband AMR codec was proposed. 
Chapter 2 � UMTS Overview 
28 
 
UMTS does support the UMTS Adaptive Muli-Rate (UMTS AMR), Full Rate Adaptive 
Multi-Rate (FR AMR) and the Half Rate Adaptive Multi-Rate (HR AMR) and may support 
also the GSM Enhanced Full Rate (GSM_EFR) codec[ 
Emergency Calls 
This teleservice is used to establish a speech connection from a mobile station to an 
Emergency Center, allocated to the location where the call is originated. Emergency calls are 
routed to the Emergency Center in agreement with the national regulations. The mobile 
subscriber initiates the service by dialling the standardised emergency code 112. In addition to 
this the operator shall specify preferred emergency call MMI(s) (e.g. 911 for US citizens or  
110, 118 and 119 for Japanese citizens) for use in any (i.e. home or visited) PLMN. This 
action can be carried out without a SIM/USIM inserted in the handset The network operator 
may either allow or reject emergency calls that are originated by a mobile station without a 
SIM/USIM card.  
Short Message Service Point to Point (SMS-PP) 
The SMS-PP enables the transfer of short text messages to and from mobile stations. The 
short messages are transmitted with the use of the SMS Service Center. It is possible to 
perform a Short Message Mobile Terminated and a Short Message Mobile Originated Service. 
The short text messages contain up to 140 octets. 
Short Message Service Cell Broadcast (SMS-CB) 
This service is used to transmit Cell Broadcast Service (CBS) messages to all subscribers 
within an individual region. This region is a defined geographical area known as cell 
broadcast areas. These areas may include one or more cells or may include the entire PLMN. 
 
2.2.3 Supplementary Services 
 
Supplementary services are only offered together with a basic telecommunication service and 
hence modify or supplement a basic telecommunication service. The use of supplementary 
services without the basic telecommunication services is not possible. A supplementary 
service is available for a number of telecommunication services. It shall be possible to carry 
out multiple supplementary services within a call. A simultaneous use of supplementary 
services involves a prioritization of these services. Hence, certain services may override or 
deactivate other services [4]. 
Call Forwarding (CF) 
This set of services is applicable for mobile terminated calls. There are several different 
possibilities to carry out this service.