5G: Service Continuity in Heterogeneous Environments - Springer Link

Wireless Pers Commun (2011) 57:413–429 DOI 10.1007/s11277-010-0077-6

5G: Service Continuity in Heterogeneous Environments Josef Noll · Mohammad M. R. Chowdhury

Published online: 31 July 2010 © Springer Science+Business Media, LLC. 2010

Abstract This paper introduces service continuity as the main driver for 5G systems. It addresses user- and service-aspects in recently opened LTE networks, and identifies the system challenges. The main challenges are related to radio coverage, especially for the provision of high data rates for indoor users. The paper covers also network-, user- and service-authentication as well as user and society requirements. 5G is addressed as a system of systems in order to provide service continuity. It addresses both technology challenges, user related issues and operator revenue. Collaborative radio and a system availability beacon are discussed to cope with heterogeneity in 5G. As the SIM card has evolved towards a third-party offering for storage, authentication and payment, functionality of this future SIM is elaborated providing SIM-based service examples. The paper finally addresses service optimization based on light-weight semantic reasoning. Keywords Semantics

Mobile · Wireless · 5G · Collaborative radio · Authentication · SIM card ·

1 Introduction While mobile telephony serves more than 4.1 Billion people worldwide in 2009,1 representation of the services is still performed using access technology terms. Naming follows the evolution from analogue to digital systems identified as generations. An examples of a 1G system is the Nordic Mobile Telephony (NMT), examples of 2G are IS-95 and GSM, while

1 ITU Media kit, http://www.itu.int/newsroom/media-kit/story9.html.

J. Noll (B) Center for Wireless Innovation Norway, University of Oslo, Oslo, Norway e-mail: [email protected] M. M. R. Chowdhury University of Oslo/UNIK, Kjeller, Norway e-mail: [email protected]

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an example of 3G is wideband CDMA. The naming of technologies refers to the requirements set by ITU-R.2 When wideband CDMA was developed discussions started on “what is the next generation”. ITU-R continues the naming of 4G as the fourth generation of cellular wireless standards, called IMT Advanced. The IMT Advanced suggest target peak rates of 100 Mbit/s for high mobility and up to approximately 1 Gbit/s for low mobility [1]. This naming convention is followed by radio researchers, while system engineers pointed already back in 2000 to systems covering multiple access scenarios [2]. Network operators such as Netcom3 have recognized the marketing value of the “4G” naming and opened in December 2010 the LTE “4G” network. Long Term Evolution (LTE) does not fully comply with the ITU-R recommendations for 4G, and is therefore regarded as a pre-4G standard. The IT industry predicts that technology development will continue at the same speed as today until at least 2025 [3], providing advanced access speed for mobile and wireless devices. Together with increases in antenna system technology such as MIMO the recommended 4G access data rates might be achieved by advanced LTE systems. The increase in access speed will enable new applications. Kellerer et al. pointed out that from an operator’s point of view, a system beyond 3G (B3G) has to deal with various aspects like user preferences, system requirements, network architecture, business model, security, and standardization [4]. Thus he moved away from radio access when talking about 4G and 5G, and rather opens for a user- or service-centric view on the evolution of mobile systems. Discussions in this paper take up the user-centric (I-centric) view as introduced by van der Meer et al. [5] and extend it by a service-centric aspect. In Sect. 2 the user perspectives of a 5G system are discussed, and Sect. 3 deals with the challenges. These challenges will cover technological aspects such as radio access and authentication, but will mainly focus on the service aspects such as applications, device considerations, economics and society aspects. Section 4 will then provide details on the postulation of 5G as a system of systems, addressing radio-on-demand, collaborative radio, the role of the SIM and service optimization. The conclusions in Sect. 5 will summarize the findings and provide areas of future work.

2 User Perspective for 5G This chapter describes the user- and service-perspective of 5G systems, as sketched in Fig. 1. Technology-wise it takes almost 10 years for a system to be developed, as indicated by the arrows left in the time-diagram. Mobile telephony was the first telecom communication service in the analog systems. One of the main reasons for introducing GSM was mobile telephony service provision in European countries, including SMS and data services. 3G was introduced to provide roaming on a world-wide base, and compatible standards such as UMTS currently provide multimedia communication in the whole world. 2.1 System and Service Aspects Systems beyond 3G, as introduced by the Eurescom P1145 project, were supposed to provide personalized wireless broadband access [6]. Currently access systems such as LTE provide 2 ITU-R, http://www.itu.int/ITU-R/. 3 4G launch Dec 2010, http://accelerati.blogspot.com/2009/06/netcom-with-worlds-first-4g-connection.

html.

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5G: Service Continuity in Heterogeneous Environments

415

Seamless heterogeneity

5G?

Personalised broadband wireless services

B3G:

3G:

Multimedia communication

Mobile telephony, SMS, FAX, Data

2G:

1G: Mobile telephony

1970

1980

1990

2000

2010

2020

Fig. 1 Generations of mobile communications—a user perspective on services

wireless broadband with a typical user bit-rate of 10–20 Mbit/s, but will on the longer run suffer from reduced user satisfaction when being indoor. Further details on these radio topics are provided in Sect. 3.1. Mobile broadband is the fastest growing access technology. The total number of mobile broadband subscribers in key European markets will rise from about 22 million at the end of 2009 to over 43 million in 2011.4 As compared to traditional mobile telephony, only about 2% of this mobile traffic comes from mobile phones. The dominating part comes from Notebooks with inbuilt or USB-modems.5 These customers expect a similar service experience as known from the fixed network, including other types of services. The main changes in user expectations towards 5G systems are: Handsets: The traditional handsets are extended by other form factors such as notebooks, mobile TVs, music players and video recorders. Applications and operating systems: While more and more applications are web-centric, the total variety of application types is just increasing, covering all types of applets and widgets as well as specific streaming and gaming applications. A variety of operating systems has to be supported such as OS X, Android, S60, and Linux. Security: Solutions for access authentications such as EAP-SIM, -AKA, Diameter and password-based need to be supported, as well as session encryptions and various endto-end application encryptions. Users will expect that these security mechanisms work seamless even in a handover situation. Network Technologies: From a network technology point of view not only mobile technologies such as GSM, UMTS and LTE++ need to be supported, but also extensions of wireless systems such as 802.11 and 802.16. Communication between devices through e.g. wireless USB will need support, as well as M2M communication towards sensors. 4 http://www.gsmworld.com/newsroom/press-releases/2010/4549.htm. 5 Vegard Kjenner, NetCom, Norwegian UMTS Forum, Feb 2010, http://umts.no/index.aspx?pid=30&

docid=63.

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All this communication is happening in a wide range of frequencies, spanning from the “digital dividend” bands below 850 MHz towards 5.8 GHz bands for high-speed wireless. Our expectation is that context-independent service continuity in heterogeneous environments is the main challenge for 5G systems. 2.2 Context-Independent Service Continuity The service continuity refers to the continuity of the same service session without any disruption or with least possible interruption. Users want uninterrupted service experience though due to mobility there are frequent changes of locations, networks, and devices. Thus service continuity should have the goal of being context-independent. Nowadays a user expects a continuous good quality video streaming though he moves from outdoor to indoor. Users change to locations which may offer better networks and devices. Due to the dynamic nature of ubiquitous environments continuous service access is one of the main factors restricting the deployment of services [7]. This requires continuous monitoring of surroundings and a proactive handover scheme, both limiting the time of operation of the mobile device. A mobile agent based platform or middleware as suggested in [8,9] may address aspects of service continuity across networks, but complexities involved for deriving the decisions may hinder real-time service deliveries. With the advent of mobile devices the service continuity also needs to be ensured across heterogeneous devices. A change of location may provide the user with higher processing capabilities or lower the cost of service usage. For example, a user moving from outdoor to indoor may want to transfer his video streaming from the mobile phone towards a pad-reader without or with least possible interruption. Jorstad et. al [10] introduced a service continuity layer responsible for managing the service continuity. Realizing service continuity across heterogeneous devices does not only require information relevant to application layers but also needs to know about the network resources because the devices may not be connected to the same network.

3 System Aspects of 5G This section will address the challenges for mobile communications in a 5G system. In Sect. 1 we postulated that the ITU-R requirements for 4G systems might be met by advanced LTE. A user- and service-centric view as introduced in Sect. 2 and concludes with the statement of a a context-independent service continuity. Our postulation is that only collaborative radio can satisfy these requirements, which will be further outlined by discussing the main components of 5G systems. 3.1 Radio and Wave Propagation Claude E. Shannon defined the capacity C of a system as being proportional to the bandwidth B P C = Blog2 1 + , (1) N0 B with B the bandwidth of the carrier, P the signal power and N0 the noise level of the system. For a given bandwidth B, the maximum range Rmax is a log-function of the signal to noise ratio

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Table 1 Cellular technologies for urban scenario Frequency

Cellular technology

Allocated frequency (MHz)

Number of operators

Bandwidth/operator (MHz)

Available LTE bandwidth (MHz)

900

GSM, LTE

30

2

15

1,800

HSPA, LTE

65

4

10, 15, 20

2,100

LTE

45

3

15

15

2,600

LTE

50

3

15, 20

20

5 10

Fig. 2 Simulation of relative capacity in an outdoor to indoor scenario

P Rmax = log2 1 + . N0

(2)

Propagation attenuation (free space loss) is proportional to the carrier frequency, thus carriers such as WiFi have shorter ranges than GSM, but provide higher throughput. These indications support the usage of specific access networks for applications, e.g. broadcast for video, WiFi for email and ftp services, GSM for short messages, UMTS for voice and mobile services, and LTE for high-bandwidth services. The experienced increase in air capacity is due to increased bandwidth B of the communication channel, from BGSM = 200 kHz in GSM to BUMTS = 3.8 MHz in UMTS, and B802.11 = 25 MHz for 802.11b and BLTE = 5, . . . , 20 MHz for different operational modes of LTE. Equations 1 and 2 are valid for free space propagation. We computed the capacity increase of typical LTE systems at different mobile frequencies, both for free space and for indoor usage with a single concrete wall between the transmitter and the receiver. In order to simplify the calculations we assume that the SNR of LTE 900 MHz system having 5 MHz bandwidth is 10 dB. To derive the indoor communication capacity, the attenuation of a concrete wall at the specific carrier frequency has been taken into consideration. Table 1 presents our assumption for a typical distribution of cellular technologies in an urban scenario citing available bandwidth for LTE at each frequency spectrum. Figure 2 shows the result of the capacity calculation of LTE systems at different frequencies compared to LTE 900 system. The calculations suggest that higher frequencies provide

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Fig. 3 Radio coverage simulation of the inner Oslo area as a function of transmit power

less capacity to indoor users despite the increase of bandwidth. As a result, providing high capacity services such as video streaming to indoor users from an outdoor base station is a challenging task for a network operator, especially for frequencies higher than 2 GHz. Radio coverage simulations for 1,800 MHz as shown in Fig. 3 for the inner Oslo area were performed by H. Dommarsnes from Telenor. The simulations provide an estimation of indoor signal strengths, being 10–20 dB lower than the equivalent outdoor coverage. To cope with the additional path loss suggests to provide higher Tx power, indicated the Tx = 35 dBm level in Fig. 3. However such an over-provisioning will decrease the overall network capacity due to interference. Mobile operators have to cope with this radio dilemma, suggesting to use “as much bandwidth” as possible at low frequencies to provide high-capacity indoor service. Bandwidth in these lower bands is limited, only 24 MHz are available in the 900 MHz frequency range for standard GSM operation (see Table 1). Assuming a minimum of two operators in this band will limit the capabilities to provide LTE to 10 MHz bandwidth. Another access challenge for mobile operators is the service selection of users. Offering high-capacity networks will shift the service usage towards streaming instead of downloading content. Typical examples are music streaming, e.g. Spotify and video streaming from Web-TV or YouTube. However, the higher capacity demand does not increase the willingness to pay. Customers pay for mobility, i.e. having access independent of location, but not for high-bandwidth services. The outdoor to indoor challenge limits effectively the capacity that can be provided in mobile networks, as further outlined in Sect. 4.1. A second aspect of radio is related to the complexity of the radio interface in the handset. Figure 4 provides simulation results for high-speed download packet access (HSDPA) as compared to the Shannon limit [11]. As can be seen from the High Speed Data Packet Access (HSDPA) link adaptation curve, there is still some 10–20% improvement possible to provide higher data rates. Such advances are the goal of the HSPA+ developments. Similar evaluations for LTE were performed by Mogensen et. al [12] and are presented in Fig. 5. Both system simulations and link results

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Fig. 4 Capacity of UMTS HSDPA as compared to the Shannon bounds [11]

Fig. 5 Capacity of LTE as compared to Shannon [12]

have practically reached the Shannon limit. A further development of the radio interface has only minimum room for advances in data rates, especially taking into account the natural variation of the radio channel and the outdoor to indoor dilemma. 3.2 Authentication Authentication is formally spoken the process of verifying the authenticity of the claims made by a subject. In telecommunication authentication is used to verify user devices towards the network and the network towards the user devices. The former also requires that a user is authenticated towards his device. Authentication is only a part of the overall security framework of a telecommunication network with the SIM card being the digital representation of the user. EAP protocols (e.g. EAP-SIM and EAP-AKA) are used for authentication in 2G and 3G. EAP can be exclusively used for tunneled authentication where authentication is achieved through encrypted tunnel between the client and authentication server. But such

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authentication methods can be subject to active and passive attacks revealing for example IMSI in EAP-AKA. The protocol should have provision for mutual authentication to prevent such attacks. This has been included in 4G networks, but heterogeneity with seamless interoperability has not been achieved yet. From an authentication point of view the seamless interworking is critical because each network follows different authentication mechanisms. Thus seamless but secure authentication will be a crucial challenge in 5G networks. 3.3 Form Factors of Devices A mobile phone is an always-on device evolving towards an always-on computing device. The currently hand-held small form factor device turns into an embedded computing device requiring pervasive wireless connectivity. In order to deal with everyday tasks on the Web, it needs to provide a reasonable screen with good resolution, powerful processing unit, memory, keyboard, speaker and other extensions. It will have integrated capabilities such as digital signal processing or high definition audio and video. The first and the foremost challenge is to ensure adequate power supply to all these sophisticated units. Longer battery life, heat dissipation, and power management are some of the critical issues for these small form factor but high performance devices. In the network side, equipments such as base stations are also getting smaller (e.g. mini BTS, femtocell). Small form factors here brings advantages such as low energy requirements, low heat dissipation, convenient relocation and easy installation. 3.4 User and Society A constantly changing environment creates demands for a good understanding of user needs and preferences. The user’s contextual information may tailor the services to be delivered. The user should have full control on the decision and disclosure process. From a privacy point of view, it is very important for the user to decide which information can be disclosed to the provider. A user-centric control of information is crucial already today, but is absolutely essential for a upcoming SIM with multiple identity storage capabilities. One of the results of a multi-identity on the SIM might result in a bandwidth brokering system, where users can select the economically best connectivity for the selected application. An item of increased concern is the total energy consumption of mobile networks. Current network optimization is done towards coverage and data rates, not towards minimum energy consumption or minimum total radiation. Even though there is very little indication of electromagnetic impact from mobile networks on human beings, regulators might decide that the overall electromagnetic radiation has to be minimized. Such a decision would need another optimization of the radio interface. And it would also force mobile and fixed network operators to work together. 4 Evolution Towards Collaborative Radio Systems The previous section has provided challenges for 5G systems, pointing out the radio dilemma being of fundamental importance for service delivery to indoor users. This section outlines a strategy, suggesting collaborative radio systems to provide a good Quality of Experience (QoE) for indoor users. The section first indicates that LTE is already seen as an incorporation of a collaborative system, adding instead of replacing new access technologies. Collaboration

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Table 2 Requirements for 5G, a collaborative mobile system Generation Frequency

Radio

Authentication

Devices

Applications

1G

450, 900 MHz

Analog

Credential

Handset

Voice

2Ga

900, 1,800 MHz

TDMA

SIM, EAP-SIM

Handset

“1G” & SMS (data)

3Ga

WD-CDMA

“2G” & multimedia

“3G” & inbuilt

“3G” & broadband

5G

450–5,800 MHz

USIM, ISIM, EAP-AKA UMTS-AKA & FutureSIMb Service continuity “B3G” & Diameter++

“2G” & modem

B3G/4G

2,100 MHz (1,800 MHz) 450–2,700 MHz

“B3G” & mobile TV, others

Service continuity

OFDMA, SC-FDMA Collaborative radio

a Description of 2G and 3G are based on European standards b Further details on future SIM are found in Sect. 4.3

between existing 2G and 3G systems will dominate the rollout, supporting our postulation for an application—and context-specific radio interface. Collaboration in such a system of systems is of fundamental importance, and should be supported through an indication of available radio interfaces through a system beacon (see Sect. 4.2) as well as seamless authentication (see Sect. 4.3). Handling authentication, providing security and protecting private data is the challenge addressed in this section, where we suggest that these aspects can be handled in upcoming SIM cards. The last Sect. 4.4 deals with service integration and optimization, focussing on semantic technologies for context-aware and personalized service provisioning. 4.1 Application Specific Radio Interface Having to provide high data rates in indoor environments is a challenge which to our understanding can only be solved by an application specific radio interface. Current technologies such as 3G and LTE move towards this approach, providing operations in the frequency range 450–2,700 MHz. Table 2 summarizes these trends, indicating in gray areas of collaboration. Application specific radio concerns the selection of radio interfaces on demand. The following are the drivers to introduce the notion of radio on demand: 1. Reducing the number of active radio interfaces will minimize the interferences and thus improves the performance of the network. 2. There are concerns regarding the health effects of radio frequency and microwave radiations. Reducing the number of active radios also contributes in lowering such health hazards. 3. Cost of service provisioning varies with technology, e.g. voice over 3G is cheaper to produce than voice over 2G. 4. Different types of services require different communication bandwidth. For example, a low bandwidth network is enough for voice communication. For such services, switching the device to low energy radio may still satisfy the requirements but consumes less energy. In 4G we can have data-only LTE service where the device will only connect to 2G/3G circuit-switched network during voice communication. Collaborative radio can be an instance of radio on demand and an extension of the mobile network. To explain collaborative radio, we need to introduce a scenario which is illustrated in Fig. 6. Numbers in this scenario were provided by Telenor in the Norwegian UMTS forum

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(a)

(b) Fig. 6 (a) Cell capacity and user bit-rate with low usage and (b) high usage with indoor consumers

meeting in 2010 [13]. Let us assume a mobile cell with a cell capacity of 10 Mbit/s. Users will only experience this data rate close to the center of the cell. Moving further to the edge of the cell will reduce the user data rate to 0.5 Mbit/s (Fig. 6a). If the traffic in the cell increases the overall cell capacity will be reduced to 2.5 Mbit/s, and users at the edge of the cell might only experience 0.05 Mbit/s. Let us assume that mobile users require high data rates indoor. Penetration losses through the building walls will have a similar effect as moving towards the edge of the network (see simulations in Fig. 3). Both cell capacity, here: 2.5 Mbit/s and user data rate will be reduced (Fig. 6b). Providing indoor coverage reduces the cell capacity of the mobile operator, in the given example to 1/4 of the original cell data rate. Customers will experience a reduced user bandwidth. For an operator this scenario might lead to reduced customer satisfaction as well as reduced revenue. A collaborative radio with handover to an indoor operator will provide the end user with high data rates and release network load of the mobile operator by enhancing the overall available cell capacity. Such a collaborative scenario demands a service-handover of the connection to an indoor operator. In a collaborative business model both mobile and indoor

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Fig. 7 The collaborative business model in NFC, creating a Trusted Service Manager (adopted from [14])

operators have agreements to share the revenue. The handover happened because a demand is created either from the current operator or from the user himself. The following reasons prompt the mobile operator to perform a handover: – reduced cell capacity, – reduced customer satisfaction, and – declined revenue. From the user side, the demand is created as the user experiences much lower data rates when moving to an indoor location. Collaborative business models are known from network infrastructure sharing, where multiple operators use the same infrastructure. Collaborative business has also been introduced in mobile service provisioning, i.e. Near Field Communication (NFC)6 for payment and access. Fig. 7 outlines the collaborative business, where mobile operators and banks have introduced a Trusted Service Manager (TSM) [14]. A similar business model is proposed for customer-owned access infrastructure and will overcome the radio dilemma, with increased revenue for operators and enhanced QoE of the customer. 4.2 System Availability Beacon (SAB) While a collaborative business model between the operator and the customer will solve the radio dilemma in indoor communications, it will not ease the access network selection. The challenge for multi-network terminals is how to select an appropriate network, without the need of scanning through all available frequencies and standards. In GSM the network availability is signaled through the Broadcast Control CHannel (BCCH), which provides both availability as well as network quality parameters such as Mobile Network Code (MNC), Location Area Code (LAC), Routing Area Code (RAC) and BCCH Allocation (BA) list. Assuming co-existence of n generations (e.g. 2G, 3G and 4G systems) in m frequency bands (e.g. 450, 800, 900, 1800, 2100 and 2700 MHz) requires a n × m availability checks. For the selected example this means 18 checks of broadcast control channels, not including any potential channels of wireless networks. In order to overcome this cumbersome search we suggest a common system availability beacon—SAB, providing a common pilot channel for all infrastructure-based wireless systems in the “digital dividend” spectrum. Such a SAB signal should be only available in the coverage area of the network, thus a statistical model for frequency scaling is suggested. The SAB signal shall further include system information such as capacity, QoS parameters and network authentication information to ease the handover to this system. 6 NFC Forum, http://www.nfc-forum.org.

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The European E3 project7 suggests in a paper by Tian and Feng [15] a Cognitive Pilot Channel (CPC) to send necessary network information to the terminals. The projects suggests using a public downlink channel to deliver the networks information in order to assist the network selection for reconfigurable terminals. The CPC is the combinational application of an out-of-band and in-band signal, where the out-band CPC is used to transmit vital information such as operators information, and the in-band CPC transmits detailed information about the network. As most of the frequency bands are already regulated, this paper suggests to standardize a pilot channel in the “digital dividend” band from 790 to 862 MHz. This band is reserved for future mobile broadband applications by the European Union and other regions, but as of May 2010 no spectrum has been licensed yet. Thus a part of this band could be reserved for a system available beacon. Having introduced access issues like indoor radio access and access availability, the seamless access to services and service optimization are remaining challenges for service continuity in 5G systems. 4.3 Seamless Authentication Seamless access to heterogeneous wireless networks needs to make the physical change transparent to the mobile users and thus preserve the ongoing connection in application level. During the vertical handover, an authentication process is performed to ensure the security of the mobile terminal. As the authentication procedures are different in wireless networks, the associated delay can be an important factor in quality of service of many application. For example, in 3G-WLAN handover the authentication process can take up to hundreds of milliseconds which is not acceptable in delay-sensitive applications such as video streaming, VoIP or interactive gaming [16]. 3GPP provided a specific security architecture (3GPP TS 33.234 [17]) for 3G-WLAN interworking which is based on the EAP-AKA authentication procedure. But the authentication overhead is high due to double execution of the EAP-AKA protocol. Researchers proposed modified security architectures in 3G-WLAN interworking reducing such overheads but those may compromise security [18]. A simultaneous network connection as suggested in [19] reduces switching time without reducing security. A short overview over authentication protocols used for 3G and LTE shows already the variety of protocols being used to allow seamless service access. The Diameter protocol has been adopted as primary signaling protocol in the IP Multimedia Subsystem (IMS) for AAA and mobility management. It is a protocol for AAA (Authentication, Authorization and Accounting) which is a successor of RADIUS. Authentication and key agreement in LTE are based on UMTS AKA, providing strong mutual authentication. Because of the extended key hierarchy in LTE, the intra-LTE handovers are fast. The interoperability with non-3GPP networks is based on EAP-AKA. However, the latency due to the key management and mutual authentication can be significant. Efficient interworking between UMTS AKA and EAP-AKA can be achieved by avoiding the signaling with the home domain which may serve 3GPPs seamlessness requirement [20]. Though seamless authentication is a critical issue in the operation of heterogeneous networks, it can be solved through the combination of existing authentication methods. Keys used in the cryptographic algorithms and security in key management is an important issue. But the security solution should not add undue delay and thus impede the mobility and heterogeneity of the devices. Secure but fast key management is necessary in interworking between 7 E3 (End-to-End Efficiency) Project, http://www.ict-e3.eu/.

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Fig. 8 Capabilities of an upcoming SIM with USB and NFC interfaces

networks. This paper suggest to handle key management through the SIM card, which has evolved to become a standardised element in all mobile communications. Lately SIM-card standardization has succeeded in letting the SIM card become a Universal Integrated Circuit Card (UICC) card, including both communication and service provisioning capabilities. Figure 8 provides an overview over the new functionality, which can be summarized as follows: – Increased communication capabilities through USB and NFC interfaces, – Compatibility to advanced applications through adopting JavaCard specifications, – Applications support on the UICC including finance, transactions, physical and logical access, and – Third-party offerings for storage, authentication and payment. Communicating capabilities have been improved from the 9.6 kbit/s rate of current cards to around 8–12 Mbit/s using the USB protocol. This is actually one of the driving factors for the development of higher bandwidth protocols in the SIM, such as the SCWS and the implementation of native TCP/IP. Besides the advances in the physical communication, recent releases from SIM card producers such as Samsung and SanDisk have managed to deploy smart cards with powerful 32-bit processors and more than 1GB of memory. Such an enhanced SIM card will have the capability to handle multiple-operator accounts, and provide sufficient authentication security for operations in collaborative radio systems. There are several examples of applications and projects using the SIM card as a trusted element. Some examples are digital rights management (DRM), mobile-banking, one-time password (OTP) solutions, biometric verification, and unified authentication. Some of these applications make use of the Near-Field Communication (NFC) capabilities of the SIM as standardised in [21,22]. The current potential of the SIM towards a local identity manager is further discussed in [23]. This identity management is especially improved with the new hardware changes in the SIM, and it has triggered the specification of an Identity Management (IdM) framework by GSMA [24]. This IdM framework is capable of handling authentication protocols necessary for a seamless authentication in collaborative networks. Vilarinho et. al [25] provide an example of evidence-based trust modeling based on a mobile device. The work suggests that

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the SIM might become a harmonized infrastructure for secure network and service access, as well as protecting the privacy of the users. The following section addresses service integration and optimization and identifies the role of semantic technologies for mobile service provisioning. 4.4 Service Integration and Optimization Service integration has two different aspects: network service integration and integration of functionalities or services. Integration of indoor and outdoor network run by different operators is beneficial not only from a business point of view but also from service continuity aspects. An example of service integration is voice and data services in LTE. Several options are defined: Data-only LTE and Voice over LTE Generic Access (VoLGA). VoLGA is a combination of circuit-switched and packet switched approach supporting voice and data simultaneously. Voice can be carried over LTE through VoIP. Unfortunately there is no single method in LTE for integrating data, voice and SMS services. This rather simple example receives a much higher degree of complexity when integrating personalized and context-aware services to a mobile device. A user wants to prioritize relevant information and services depending on situation, mood, interests, preferences and ´ interest for services for examindividual privacy setting. Economy can also drive userbds ple user may prefer VoIP than GSM call when connected to a WiFi network. Contextual information is getting increasingly important when users are traceable in a wireless network. Visibility and location-aware service offerings may depend on context appropriate security measures. For example, an automatic encryption can be turned on while delivering sensitive information. Limited battery life is a main driver behind the device optimization where devices can sense the context and use the optimum capability for applications. From a service point of view, service requirements can trigger best-suited applications and appropriate network parameters. Most of these aspects require a multi-parameter optimization. Currently, the process of reaching optimum values are rule-based. This approach is too difficult to manage and maintain. The goal of a 5G system is to achieve an automatic optimization, e.g. through reasoning based on semantic technologies. Current semantics and automated reasoning have too much overhead and are not applicable to mobile devices with limited battery and CPU capacity. Light-weight semantics and event-based reasoning may address these problems. An example of such a light-weight semantic is the adding of machine readable tags to social information in web pages. Event-based reasoning can populate the decision results in advance and they are disclosed for interpretation only when results are queried. An example of such a light-weight implementation was performed in the ITEA-WellCom project,8 where user vicinity to a set-top box was used to trigger the event-based reasoning [26]. The resulting rule-set is then populated to the set-top box to perform content-matching of user preferences with the electronic service guide (ESG). While this scenario addressed user preferences and content match, the more generic 5G system needs to provide personalized and context-aware services.

8 ITEA WellCom project, http://itea-wellcom.org.

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5 Conclusions and Future Work This paper introduces a user- and service-perspective on the “generation”-term used in the developments of mobile systems. While technological parameters are defined by ITU-R, the mobile customers have set their own requirements. In the first available “4G” networks only about 2% of the traffic originates from mobile phones, the majority comes from mobile computers. Only 20–30% of mobile broadband services are generated outdoor, service usage is predominantly indoor and follows the trends from fixed broadband access, with a high amount of bandwidth-intensive applications such as streaming. Expectations for 5G systems see the need for integration of heterogeneity in handsets, applications, operating systems, security and network technologies. The main driver for system aspects in 5G is the radio dilemma, showing that an outdoor to indoor operation will decrease the cell capacity of the mobile cell to less than 30% of a cell with limited traffic. Likewise will the user data rate inside a building drop, leading to reduced customer satisfaction and reduced revenue of the mobile operator. The paper suggests collaborative radio for 5G systems, where users provide their own home network. Users in such a heterogeneous environment ask for service continuity, requiring trust-based relationships between the mobile and the fixed networks. Such a collaborative business model was lately introduced for Near-Field Communication (NFC), and will provide both increased user data rates for customers and increased revenues for operators. The paper further suggests a common system availability beacon—SAB, providing a common pilot channel for all infrastructure-based wireless systems in the “digital dividend” spectrum. Such a SAB will include coverage, capacity and system information and ease the handover to other systems. Further research is recommended for seamless authentication, required for service continuity. As the SIM card has evolved to a “system within a system”, the SIM might become the harmonized infrastructure for secure network and service access, carrying user- and 3rdparty information. Users require service offers tailored towards their specific situation. Such service optimization is based on user-, context-, device- and service-aspects. As reasoning based on semantic technologies is too resource intensive, the paper suggests light-weight semantics through event-based reasoning and rule execution.

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Author Biographies Josef Noll is professor at the University of Oslo in the area of Mobile Services. His group ConnectedLife concentrates on the working areas mobile-based trust and authentication, personalised and context-aware service provisioning, and service continuation in 5G systems. He is also Chief Technologist in Movation, Norway’s open innovation company for mobile services. He is co-founder and steering board member of the Center for Wireless Innovation Norway and Mobile Monday Norway, the Norway section of the worldwide community for nerds and professionals in mobile services. Previously he was Senior Advisor at Telenor R&I in the Products and Markets group, and project leader of Eurescom’s ‘Broadband services in the Intelligent Home’ and use-case leader in the EU FP6 ‘Adaptive Services Grid (ASG)’ projects, and has initiated a.o. the EU’s 6th FP ePerSpace and several Eurescom projects. In 2008 he received the IARIA fellow award. He is editorial board member of four International Journals, as well as reviewer and evaluator for several national and European projects and programs.

Mohammad M. R. Chowdhury received the Ph.D. degree from the Department of Informatics, University of Oslo in 2009. He received the M.Sc. degree in Telecommunication Engineering from Helsinki University of Technology (HUT). His current research interests include next generation networks and services, access control, identity management, personalized service access, and Internet of Things. He is currently working as postdoctoral fellow at UNIK-University Graduate Center, Kjeller, Norway. He was involved in research projects funded by the Norwegian Research Council and the European Union. Dr. Chowdhury has published more than 30 scientific articles in journals, books and international academic conferences. He contributed in several international conferences as technical program committee member, session chair and reviewer. Dr. Chowdhury is a member of IEEE Communication Society.

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