Characterization of Mobile Services

in Heterogeneous Communication Environments

Nataliya Kohvakko

Department of Mathematical Information Technology,

University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland

Abstract. The term “service” is quite overused in the telecommunications

research area. This paper continues previous research by the author toward a

better understanding of the service concept. The term service in this paper

means the “something” that a human user receives from the computing

environment that includes mobile and fixed devices, various kinds of

interconnected networks forming a larger whole, and a variety of existing

software. The main concern of this paper is to derive a set of essential

properties of services within heterogeneous networks. It also defines the

relationships among established properties and references each of them to a

certain functional layer within a service conceptual model. Finally, this paper

represents an example of “service content value”-based classification and the

service characterization framework using an ontological representation

1 Introduction

There is no doubt that the communication world is evolving into a so-called pervasive

computing environment, meaning that computers and electronic devices are so

intrinsic in everyday life that people no longer realize how much they use these

technologies. Of course, this also means that everything is interconnected, so users

can be recognized regardless of their locations or the devices they are using. This

concept results from the variety of application services and electronic devices

available and the options provided by networks, interoperability, seamless roaming,

context awareness and personalization.

The convergence of fixed and mobile networks brings us to interoperability

solutions regarding the first stages of the networks’ confluence and a new age of the

Internet with a shared core but heterogeneous access networks along the edge. The

achievement of these goals presumes an extended evolution in both technological

areas. Nevertheless, the mobile and fixed networks remain distinct. For example, the

“Wireless Internet” does not exist globally yet and requires the wider spread of

UMTS; but even when these tasks are completed, the wireless Internet still will be

different from the traditional Internet.

The diversity of networks is, however, a challenge because modern technologies

that deal with network content can be implemented much easier in a new network

than through upgrading the existing one. It is clear that, for small-sized mobile

devices, the current Internet content is to be updated and huge amount of new content

Kohvakko N. (2004).

Characterization of Mobile Services in Heterogeneous Communication Environments.

In Proceedings of the 1st International Workshop on Ubiquitous Computing, pages 3-10

DOI: 10.5220/0002665100030010

 SciTePress

needs to be provided. However, one essential goal of current research is to decrease

the necessity of the updating of content as much as possible, so “essential generic

functionality for mobile applications should be implemented in the infrastructure” [1].

One of the very important concepts to be understood is the notion of service in the

context of a heterogeneous communication environment [2] note that this term is

quite “overloaded” and that it is important to understand its complex meaning. In the

area of wireless mobile communications little research has been devoted to the

question of service characterization and categorization [3], [4] yet and even these

researchers consider service from some particular point of view.

The main purpose of this paper is to define the set of essential characteristics of

services provided in heterogeneous networks, and parts which can be represented by

any networking standard. The characteristics of services should be defined in abstract

way and represent fundamental properties, but not existing instances labeled by some

standard. It is also important correlate the properties and to define their

interrelationships based on some structural model of the network or service.

This paper seeks to use a complex approach to categorize services by their

essential properties, and to link the categories to each other and to existing instances

of suggested concepts. In preparing this work, it was studied a wide range of papers

and websites that describe current services and some still under research and

development [5], [6-12]. The categorization given within this paper can be

understood as an ontology of a service in its most conceptual sense within the

computer networks domain and is intended to be used by telecommunication

networks to further improve their functional separation and openness.

3 Characterization Basis

When discussing the variety of services in future communication networks, it is

appropriate to divide services into two major categories – vertical and horizontal.

This division is presented in [13], where it is recommended to pass from vertical

services like the SMS, cableTV and PSTN to horizontal ones, which would represent

parts of network functionality (access, transport, service network, etc.). Such

transition is a common trend in the telecommunication world and represents a high

degree of flexibility compared to the current situation.

The vertical service (complex service) is a functional complex that works in

communication network and has value and content intended for the human user.

Vertical service is usually quite complex and consists of all constituents of the

communication network functionality (transmission, routing, representation, etc.).

Horizontal service is a set of service primitives all working on the same layer of

abstraction (functional layer) and providing the network with similar or

complementary functions (see Fig.1).

The conceptual idea presented in the figure 1 has its practical implementation in

the existing Internet, where layers of OSI reference model are fixed and clearly

defined as well as each of service primitives. However, the existing division does not

meet the needs of mobile and wireless communications, nor does it take into account

many recent scientific and industrial developments. Therefore a need exists for

reconsidering the current understanding of computing networks with respect to the

emerging technologies, such as mobile and wireless networks.

In this paper, the model described in [2] and represented on the figure 2 is used as

a basis for characterization. In principle, any kind of reference model can be utilized,

but the chosen one is particularly suitable from the service provisioning point of view.

It introduces a conceptual view on the service and consists of the horizontal services,

shown as model layers briefly described below.

The network layer is needed to provide communication capability between two

network nodes – perform mobility, scalability, routing, handover, format

transformation, load balancing, medium access control and other functions concerned

with the transmission of traffic node-by-node from the source to the destination. The

transport layer of the reference model represents the transport service in a

mobile/fixed heterogeneous network in an end-to-end macroscopic scale. The

principal idea of the middleware layer is to provide the functionality that will allow

applications to avoid a majority of the problems that arise within the heterogeneity of

the communication environment. According to [2], the middleware scale provides

service portability, device and user mobility, and make them seamless for end-service

applications. The application layer provides and represents service content to the end-

user. Another aspect of the application layer functionality concerns the AAA issues

that are specific for the concrete service. The content of service is what the user

actually receives. In other words, content is the service value. The metacontent

describes the service in terms of metadata for easy machine retrieval, analysis and

use.

The research results described in the following section establish a set of essential

properties of a complex service provided in a heterogeneous network. The collection

must allow for the classification of all, or a majority of, the existing complex services

and distinguish the services from each other according to their characteristics. In

addition, the set of properties should be essential and allow for the exclusive

classification of services.

Vertical Service 1

Vertical Service 2

service

primitives

functional

layers

(horizontal

services)

Content

Application

Middleware

Transport

etwor

Metacontent

Fig.

Commun

icatio

service reference model

Fig.

1 .

Assembling the vertical service

3 Complex Service Essential Properties Derivation

3.1 Mobility

One of the most crucial properties of service in modern networks is mobility, which is

well described in [14]. There are three types of mobility: service mobility (the

movement of the same service from one network/device/user to another), device

mobility (the same device is moving across different networks), and user mobility

(the same user moves across different devices).

Device mobility support requires additional functionality (roaming, device mobility

tracking), mainly in the network part of the complex service functionality. Service

can be such that it is provided for mobile user(s), stationary user(s) or in an ad hoc

manner. Since device mobility is the most popular and widely used type of mobility,

let’s use this corresponding property as simply mobility.

Service mobility and user mobility can be characterized by the two properties of a

complex service: network and consumer, which are addressed on the middleware

layer of service provision. The following separation: can be done with respect to the

network: local network services, cross-network services, multi-network services.

Local network service is service that is provided only in the home network and

cannot be transported to any other network, due to a technical or advisability reason.

Cross-network services are those that can be provided in the home network as well as

in a host network; the latter can represent another telecommunication standard. Multi-

network services always engage two or more telecommunication networks standards.

The consumer property accomplishes a set of service properties describing

mobility issues and represents the addressee of the service. The classification of

services based on a consumer property is to be used in the provision of the AAA

functionality on the middleware layer – internetworking and co-operation issues:

human-addressed services, terminal-addressed services, unaddressed services.

A human-addresses service means that the service is to be provided to the actual

human(s), regardless of the terminal he/she is using (e-mail, reservation services,

etc.). A terminal-addressed service is to be provided to the concrete terminal(s)

without taking into account the user’s personality (speech call, remote diagnostics,

location-based services, etc.). Unaddressed services can be provided in an

unauthorized way to every entity in the network (advertising, emergency, news, etc.).

3.2 Network Architecture

When considering the service provision in heterogeneous environments, it is

necessary to distinguish the networks from an architectural point of view. Despite the

fact that networks are interconnected, service is usually targeted to one or another

type of network architecture or a certain set of them.

Based on the current variety of computer network standards, we would derive the

following groups of general network architectures: Cellular, Satellite, Wireless LAN,

Wireless PAN, Broadcast, Fixed. The given set represents the modern network

architectures domain and with respect to the architecture property of vertical service

belonging to network layer of complex service reference model.

3.3 Traffic Flow Shape

Each complex service considered in this paper includes an information exchange

between network nodes participating in a service provision, consuming or

communication process. The corresponding functional layer, which is responsible for

handling data traffic on a logical level, is a transport service. Structure and behavior

describe, from a traffic point of view, the properties of the transport service.

Behavior represents the dynamics of the service. The following general types of

traffic behavior are seen: static, dynamic, real-time.

Structure of the traffic flow reflects the “relationship” between its sources and

destinations (the transport session architecture). The following structures of

macroscopic traffic flows can be considered in fixed and mobile network domains:

one-to-one (unidirectional, bidirectional), one-to-many (multicast), one-to-all

(broadcast), many-to-many (conferencing).

3.4 Application Properties

A complex service, when meant for the human user, always has an application(s) that

performs actions that particularly conclude this concrete service and provide a user

interface. There are many characteristics of applications from various points of view.

Let us derive two essential properties of a complex service with respect to its

application(s), specifically describing it in a mobile heterogeneous network

environment: context and execution.

The context property describes the common situations in which the service is used or

which influence its execution. With respect to a service application context, the

following types of services could be established: location-based services, mobility-

dependent, disconnection-sensitive, user terminal/class specific, and network specific.

Another important characteristic of the service application(s) is its execution

pattern, which we define as an execution property of the service application layer.

With respect to the application execution pattern, complex services can be: client-

server, peer-to-peer, distributed, third-party, download.

The client-service type of execution supposes that the principal part of the

computational efforts is executed on a server; peer-to-peer service means that two

network users communicate directly without a coordination unit; distributed service is

executed in several parts in various places in the network; third-party type of

execution assumes the participation of three parties: the service consumer, the

service provider, and the telecommunications operator, which provides the

accessibility to service; download service means that all components of the service

are first downloaded to the user’s terminal and then the service is executed locally.

3.5 Service Content

The content of a complex service is the only horizontal layer of the reference model

[2] that does not introduce any physical entities into the network, unlike the

applications, hardware, or middleware procedures. While it is abstract, it remains a

very important property of a complex service. Actually, the target of the entire service

provisioning process is precisely the provision of content to the user. Consideration of

services from content point of view is very important in marketing issues, AAA

schemes planning, business models design, etc. Many classifications of services in

communication environments are based on the content that sometimes places

technologically the same services into completely different categories. In some cases

it is reasonable, in other cases it is not. However, content as a characteristic of service

should be always taken into account. Two properties of content considered essential

are user and value.

Depending on the intended user group, application developers should design a user

interface and serving capabilities of communication service. That is why it is

important to separate such property of communication service content as user. The

following general categories can be distinguished: private customer, collective user,

service provider, communication device manufacturer, telecommunication operator.

The collective user means that a service is addressed to several persons considered

as one and paying as one, for example, business users, family members, etc. The

communication device manufacturer has produced the device through which the user

is served by the service provider. The telecommunication operator normally

maintains the communication line between the service provider and the user, although

sometimes it may perform the functions of the service provider as well.

Content value is what the user actually receives by the service. It can be

information, data, communication or control capability, or any combination of these.

Based on the list of functioning and emerging services provided by various networks,

we derived this set of service content types: communication, information, assistance,

remote control

News Advertising

Information

retreival

Location-

based

infoservices

Information

collectin

Environment

monitoring

information

Resource

download

Resource

retreival

Resource

storage

Information

resource

management

resource

management

Electronic

payments

Electronic

purchase

Electronic

banking

transaction

Teaching

learning

Reservation

services

Navigation

assistance

Personal

assistance

Speech

call

Mail

Messaging

Teleconference

Video,

radio

Emergency

communication

Interactive

games

Content

value

Remote

diagnostics

Remote

control

Technical

support

Residental

security

Local

games

Organizer

Calendar

Alarm

clock

terminal

Fig. 3. Content value-based service classification

transaction, remote control, resource management, terminal. Figure 3 classifies the

selected set of existing services with respect to the content value viewpoint.

Communication means that two or more network users exchange some piece of data;

the information type reflects the situation in which the user retrieves some

information from the network; assistance is a challenging type of content that implies

the existence of some entity that guides the user within some period of time, type of

activity or until some goal is achieved (navigation assistance, e-learning, personal

assistant); commerce represents services with a high level of security and a

transactional type of functionality; remote control refers situations when the user

controls the physical or logical devices through the communication network in real

time or off-line; resource management is concerned with applications representing,

usually, the user interface to network resources and allows users to create, modify or

destroy network information resources, such as databases, files, information storage,

etc; terminal type of content value represents applications that are executed on the

user’s terminal and do not interact with a network while execution.

All presented characteristics of complex service to be provided in heterogeneous

computer network are visualized (relatively to the selected reference model) on the

figure 4.

5 Conclusions

The service that a user receives by being connected to a heterogeneous networking

environment via a communication device can be understood in many different ways,

depending on the point of view. This paper presents a conceptual study of service,

and describes its essential properties and the interrelationship of these properties. The

defined set of properties is correlated with a chosen service reference model in order

to place each service property on the general map in telecommunications area.

Network

Transport

Middleware Application

Content

Service

Mobility

Architecture

Behavior

Structure

Consumer

Network

Context

Execution

Value

User

WPAN

WLAN fixed

satellite

broadcastcellular

Ad-Hoc

stationary

mobile

distributed

peer-to-peer

client-server

download

third party

disconnection-

sensitive

location-based

user terminal

specific

network

specific

mobility-

dependent

information

recource

management

remote

control

terminal

transaction

communication

assistance

collective

user

private

customer

telecom operator

communication

device manufacturer

service

provider

unaddressed

Human-addressed

Terminal-addressed

Multi-

network

Cross-

network

Local

real-time

dynamic

static

many-to-many

one-to-all

one-to-many

one-to-one

Fig. 4. Characteristics of service in heterogeneous communication environments

The proposed characterization framework can be used, first of all, in service

classification efforts. One of such classification examples is represented in figure 4

and is based on a service content value property.

The key goal of this work was a comprehensive overview of existing and emerging

services within heterogeneous environments. Such an overview is very useful for

extracting knowledge about a service from the service itself and from service

provisioning mechanisms. It is also valuable when needing to satisfy one or all of the

requirements of service provisioning, such as ubiquitous access – the capability of a

terminal to access diverse communication networks; cross-network mobility – the

seamless roaming among diverse access networks; service portability – the adaptation

and reusability of existing services across multiple communication systems; context

awareness – the dynamic service adaptability to changing user and network

conditions; and independent service creation – the separation of service creation from

the specifics of service delivery in every communication network.

The primary value of this work is seen in taken the service characterization

approach and categorization from various viewpoints rather than in assigning labels

for concrete entities (properties and types of services).

The results obtained in this work are still subject to further improvements.

However, even now they can be used as one of the inputs in areas such as context

utilization, service portability provision, middleware development, heterogeneous

network integration, and adaptive services support, among others.

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