Mobile Software Telecommunications

Transcription

1 Mobile Software Telecommunications Gerhard Fettweis 1, Philippe Charas 2, Raymond Steele 3 1 ) Dresden University of Technology, Mobile Communications Chair D Dresden, Germany, fettweis@ifn.et.tu-dresden.de 2 ) Ericsson Radio Systems AB, Sweden, philippe.charas@era-t.ericsson.se 3 ) Multiple Access Communications Ltd., UK, rs@macltd.demon.co.uk Abstract - Telecommunications is shifting from anytime, anywhere to anytime, anywhere, any way, any speed, whatever. This requires a revolution in flexibility by going from today s pre-defined networks and services to a new user-centric software-based creation of wireless communications and services. This creation of wireless communications and services on demand requires a new paradigm in network design based on software radio systems in base stations and terminals. A minimum specification air interface is proposed as the backbone and operating system of future wireless networks. It allows for network access and connectivity, and a programming shell for setting up communications traffic channels. Its flexibility allows for the integration of existing wireless standards and systems as well as freely defining software programmed air interfaces and services on demand. Software telecommunications is the final step of paradigm shift from standards bodies and companies defining what consumers/customers supposedly need, to a customer-centric approach by giving the customer all the means to create what he really wants/needs. I. INTRODUCTION This paper is not intended to present a novel technical result, but to present a vision on possible future mobile telecommunications developments. Our primary objective is to move from the world of a current POTS related position in mobile communications to a future network that facilitates mobile multimedia communications from anywhere, at any time, and at any speed. The migration of mobile communications, from the POTS related regulatory driven world to a deregulated and open environment, dominated by the confluence of computers, IT, communications and entertainment will not come about without considerable turbulence among service providers, system suppliers, and confusion among the end users. The present constellation of regulators, operators, and system suppliers, are structured in a closed and integrated hierarchical fashion. This in contrast to the network and open oriented culture predominant in the IT world. It is our view that the migration to mobile multimedia communications will result in a cultural transformation from integrated hierarchies, to open networks, from predominantly corporate environments to substantial ingredients of entrepreneurship. The linkage of content providers with service providers, system providers and end users, with inventors of innovative services, technologies and standards will not mainly take place under the auspices of standardization hierarchies, large corporations or public broadcasting corporations. The emergence of computer networking, open standards, the Internet, JAVA etc., is a good indication of the emerging fractal like pattern of hi tech evolution, that also will encompass the chaotic migration to mobile multimedia communications. Visions of future wireless communications A plethora of multiple radio access standards will coexist alongside each other. No single standard will be able to provide all multimedia services and still provide sufficiently low network investment and operating costs. Terminals will be intelligent, being software reconfigurable, will roam between networks and adapt to various network standards accordingly. Terminals will be configured with the bare minimum software, to make these able to adapt to various network and radio access requirements. User centric/user defined radio communications and services will be enabled, running on a communica-

2 tions platform similar to JAVA. Much of today s hardware based radio functionality will be software based. A new dominant hardware/software (Wintel) combination could emerge. Dynamic resource allocation in the radio access network will be common place permitting effective sharing of available spectrum. A combination of system centric and mobile centric decision making will be used, depending on the type of network and mix of services. Asymmetric resource allocation will be possible by asymmetric timesharing, or flexibility in using different modulation techniques. Terminals and infrastructure will permit up and down link asymmetry. Enabling technologies, such as powerful Digital Signal Processors, new signal processing algorithms, fast A to D and D to A converters, all will enable the physical implementation of multi-standard radios. New software languages and software platforms, equivalent to JAVA or further modifications thereof, but for the radio world, will enable software radio roaming in multiple standard networks with the creation of communications and services on demand by the user. II. SOFTWARE TELECOMMUNICATIONS: MOTIVATION A. What is the goal? Currently communications networks and services are under a constant development, resulting in an increased complexity of offerings, i.e. capabilities are becoming more and more complex, and due to the globalization of markets more and more players are (and want to be) involved. Hence, standardization is becoming more difficult, which results in the fact that the speed of new technology being introduced into the market is slowing down. An Example for this kind of development is GSM. Modifications and updates are becoming increasingly cumbersome procedures, whereas a new technology development (as UMTS) has been showing a dramatically slow pace. The key for future success therefore has to be in defining a new communications technology basis which inherently is open for modifications, allowing for customizing of services and applications by individual subscribers and not by large standardization bodies. Hence, we need a communications operating system for basic network access and connectivity, as well as the definition of classes of QoS for bit-stream transportation (as in ATM or IP). Furthermore a programming language (e.g. Java) is required as a platform for running the desired communications session, which is to be used for defining both, physical links and services. This can be utilized e.g. during call set-up to define the (proprietary) speech coder, the modulation technique, the encryption scheme to be used, as well as service specific features (IN). Furthermore it can be employed for defining service specific protocols, negotiating the bandwidth with the network (e.g. via agents) etc. Hence, the standardization only needs to concentrate on the definition of the communications platform, not the very details of the how and what of the services and links. This results in a totally new concept for telecommunications, i.e. the definition of services and links is freely software programmable and can be defined for each communications session individually by software. Therefore we use of the name software telecommunications. For mobile communications this means a radical paradigm change compared to current activities. The software telecommunications platform must define the network access, the mobility management, in particular for standby mode, paging, call set-up and call negotiation protocols, as well as the physical layer only for this network access part of communications. This should be geared towards the implementation of simple modems with a long standby time. The data transport can be left undefined, allowing the use of specific implementations (e.g. GSM) but leaving the space open for quasi standards to develop. Only coarse parameters for the physical link have to be specified, as e.g. the time/frequency interference and radiation masks (ISM band approach). This approach can finally lead to the integration of a vast variety of heterogeneous public (or private) communications systems as particular instances in one backbone. It therefore can be viewed as the enabler of mobile multimedia (the integration of heterogeneous communications into one system). Enabling technology for software telecommunications is being developed within the following activities: Software radio/multimode terminals, which are the enabler on the terminal equipment side. ATM and/or IP technology for QoS definition of bit streams IN for the user definition of services, and more recently and more important the work on Telescript and Java.

3 B. Context Basic work on this topic has been emerging at many places. The introduction of Telescript and Java as well as ETSI projects as CAMEL are clear indicators for the move in the direction of developing technology enablers for a software telecommunications platform. On the hardware side the development of multimode phones and base stations on the way to software radios are clear signals for technology enablers. However, the system concept is just emerging. It is a clear new functionality step beyond anything available today. Embedding this platform concept within the Internet would lead to an ideal situation for globalization of this technology. Software telecommunications in mobile communications would revolutionize today s technology and would allow for a great market potential to be filled by a large number of new small medium enterprises by removing the standardization grid-lock enforced onto the technology development dominated by today s large players. The subject as a system perspective is being examined in Germany in the ATMmobil project. A vast variety of specific problems are being examined world-wide, as agents, software radio, Java, ATM, IN, etc. C. What needs to be done? The two main problems that need to be addressed are: Minimum specification air interface, and software radios. To understand what needs to be standardized for network access and connectivity to the network, the whole problem of network access and mobility must be analyzed. It is important that call setup, paging, and other basic features of enabling network access are standardized. This minimum set needs to be defined. To enable software telecommunications, the telecommunications hardware must be designed to allow for software defined flexibility. To enable this for network infrastructure is a challenge. But the bigger challenge lies in the design of radio terminals and base stations which can be freely configured, so-called software radios [Steele], [Mitola]. D. Related Work and Results There has been an increasing amount of research and development on multimode modems for either base stations or mobile terminals. The heterogeneity of the current cellular world, in particularly pressing in the U.S. commercial world as well as for military (Speakeasy project), has led to the demand for developing modems which can freely be programmed to multiple standards. Software radio technology, as defined in [Mitola], leads to an attractive hardware platform for solving the problem. In addition, to allow free roaming between multiple networks based on different standards has led to the activities of the MMITS Forum, which is defining a common signalling interface to be used to interface and handoff between different networks[mmits]. However, Mitola went much farther than this by pointing out that the modem could not only obey to fixed standards but also vary the air interface according to the user demand and the radio channel. Software telecommunications goes yet another step farther by demanding full software configuration of all parts of the communications traffic/services network. A first step in defining a minimum specification air interface to serve as a backbone of the software telecommunications platform has been developed within the German ATMmobil project line IBMS [IBMS]. In this project a separate signalling channel is being designed for only connecting to the network and for mobility management. It serves as the base for a free choice of the air interface. III. SOFTWARE RADIO SYSTEM ARCHITECTURES FOR TERMINALS AND BASE-STATIONS Economies of scale from the point of view of terminal and base-station hardware implementation and production, as well as optimal usage of the available resources in the transport network, will determine to what extent future mobile networks will become sufficiently ubiquitous. High speed AD/DA conversion will provide the possibility of digitally converting radio signals. On one hand end users will want a plethora of mobile services. On the other hand the cost for using these mobile services must be reasonable. Thirdly, since broadband services will mainly be asymmetric, and only occasionally symmetric, a dedicated network for symmetric broadband data services, using specific terminals could become prohibitively expensive. Also the data rate needs to be adapted to the radio frequency and propagation limitations of the channel. The introduction of multi-standard terminals and basestations, could be a key element in providing the flexibility needed to provide symmetric and asymmetric high speed data services at a reasonable cost.

4 Nevertheless as Moore s law drives down the cost for integration, and as analogue to digital conversion becomes feasible at sufficient bandwidths and dynamic range, hardware will tend to be standardized, while software will be application specific. The door can open for a new radio INTEL/Microsoft (Wintel) combination, that will create global radio software/hardware standard. There is research going on in both the US and Japan. Software radio architectures, originally developed for military applications, are now becoming viable from the cost/ performance point of view. The action of Moore s Law will probably drive the cost of software radio down at a greater rate than other competitive technologies. IV. MINIMUM SPECIFICATION AIR INTERFACE A. The NACCH To achieve full flexibility of software telecommunications in the mobile world, not everything can be left to be software definable on demand, but a minimum standard on the air interface side needs to be defined. This minimum standard has to serve for enabling the basic connectivity to the network of a mobile terminal, i.e. to serve for network access, mobility management, paging, etc. We therefore refer to this as the NACCH: network access and connectivity channel. It basically provides the equivalent of an RJ11- plug plus a BIOS and a kernel. It clearly does not include any traffic channels except possibly for paging. The NACCH also must allow for mobiles to setup the required grade of service on demand. Independent of the number of traffic channels and services which a mobile is currently using, mobility management should only be carried out once. Hence, the NACCH includes mobility management (location management): The NACCH needs to be available for all user centric location management and location update. The mobility of a user must be managed in an network only once, independent of service channels currently in use by that users. All service/traffic channels are connected to the same mobility server. authentication and registration: Authentication and registration into a ubiquitous mobile network needs only to be executed once. It enables the user to create as many traffic channels and use as many services in parallel as he wishes. call paging and call setup signalling: Similar to an operating system where you have logged onto, the centrally controlled mobility, registration and authentication have enabled the user to be located and accessible. The first step towards setting-up a traffic channel is paging. It therefore also needs to be provided by the NACCH, including the additional information necessary for knowing which service to fire-up (and possibly download the software). an operating interface to define/program traffic channels and services, either user defined or off a list of existing solutions via software. In particular the NACCH must also enable to serve as a communications channel for negotiating the data transfer (i.e. the rate, modulation, etc.) for carrying the payload traffic. The idea of defining the NACCH functionality separately from the traffic channel air interfaces is fairly new, and therefore no larger research effort is known which addresses this topic. Related work of defining a minimum specification is being carried out within the IBMS project. A particular emphasis is being made on defining the NACCH to enable long standby times, low power consumption, high mobility, good coverage, etc., to allow terminals to have a maximum reliability in keeping connectivity to the network. B. The Hand-Set: Possible Scenario One possibility for a mobile terminal architecture for software telecommunications is depicted in Fig. 1. antenna(s) NACCH modem configuration software radio modem SIM as e.g. GSM application interface Fig. 1 Possible mobile terminal architecture As mentioned above, the NACCH is observed in standby-mode e.g. for registering with the network and location update. It furthermore boots the software radio modem into its desired mode of operation for transmission of traffic data.

5 Note, in case the NACCH modem and the software radio modem are realized as two distinct different hardware units, it enables the hand-set to power-down everything except the NACCH modem during standby mode. During traffic mode however, the NACCH modem can be used for searching other channels for the availability of a NACCH of another base station or another network, and initiate the hand-off procedure. C. Network In the context of software telecommunications the network becomes a transparent bit transport infrastructure with the user having control over defining own services and applications. However, the network operator must provide the NACCH infrastructure and its intelligence, to process and respond to the customer s need. In addition, the network operator will be able to provide the users with a data-base server, from which new releases and services as well as modems, speech coders etc. can be downloaded. The service providers riding on the network will be able to provide own services as well as means of accessing and managing the software definable resource efficiently. A summary on 3 possible scenarios is given in [2005]. V. DISCUSSION Software Telecommunications is an enabling technology for allowing innovation and competition to be introduced into the communications market, without being strangled by network limitation and standardization delay burdens. It is therefore key for small innovative companies to be able to develop new technology and see ROI (return on investment) by being able to market technology directly, without lobbying in standards bodies. Software telecommunications in mobile communications would revolutionize today s technology and would allow for a great market potential to be filled by a large number of new small medium enterprises by removing the standardization grid-lock enforced onto the technology development dominated by today s large players. It therefore generates the equivalent market for communications as it is known today in the PC and PC-software market. Hence, it will generate a boom in communications beyond what can be foreseen by current developments. The impact on standards bodies and regulatory agencies is great, since it would change their mode of operations from caring about every bit transmitted and defining its handling to applying this level of standardization only to the operating system (including NACCH), and thereafter leaving space open for individual implementations in a time/frequency mask. The NACCH/minimum specification air interface is the enabler for software telecommunications in wireless networks, and hence it is the key for software telecommunications to happen. VI. CONCLUSIONS Software telecommunications is in the final step of paradigm shift from standards bodies and companies defining what consumers/customers supposedly need, to a customercentric approach by giving the customer all the means to create what he really wants/needs. It is the step communications industry has to take to follow the step which has been dominating the success of computer industry. The minimum specification air interface/nacch and software radios are enablers for a software telecommunications future in new wireless networks. VII. REFERENCES [IBMS-1] G. Fettweis et al., A closed solution for an integrated broadband mobile system IBMS, in Proceedings IEEE ICUPC 1996, Boston, MA, Sept Oct [IBMS-2] M. Bronzel et al., An integrated broadband mobile system IBMS, accepted for ACTS mobile summit 1997, Aalborg, Denmark, October [Mitola] J. Mitola, Software Radio, IEEE Communications Magazine, May [MMITS] [Steele] R. Steele, Third generation PCN and the intelligent multimode mobile portable, Electronics & Communication Engineering Journal, pp , June [2005] Ericsson entering the 21st century, Ericsson annual report ( html)