Mobile Software Telecommunications
Gerhard Fettweis
1, Philippe Charas
2, Raymond Steele
31
) Dresden University of Technology, Mobile Communications Chair
D-01062 Dresden, Germany, [email protected]
http://www.ifn.et.tu-dresden.de/mks.htm
2
) Ericsson Radio Systems AB, Sweden, [email protected]
3) Multiple Access Communications Ltd., UK, [email protected]
Abstract - Telecommunications is shifting from
any-time, anywhere to anyany-time, anywhere, any way, any speed,
whatever. This requires a revolution in flexibility by
go-ing 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 servic-es on demand requirservic-es a new paradigm in network de-sign based on software radio systems in base stations and terminals. A minimum specification air interface is pro-posed as the backbone and operating system of future wireless networks. It allows for network access and con-nectivity, and a programming shell for setting up com-munications traffic channels. Its flexibility allows for the integration of existing wireless standards and systems as well as freely defining software programmed air inter-faces and services on demand.
Software telecommunications is the final step of para-digm shift from standards bodies and companies defin-ing 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 re-sult, but to present a vision on possible future mobile tele-communications developments.
Our primary objective is to move from the world of a cur-rent POTS related position in mobile communications to a
future network that facilitates mobile multimedia communi-cations 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
comput-ers, IT, communications and entertainment will not come about without considerable turbulence among service pro-viders, system suppliers, and confusion among the end us-ers.
The present constellation of regulators, operators, and system suppliers, are structured in a “closed” and “integrat-ed 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 commu-nications will result in a cultural transformation from inte-grated hierarchies, to open networks, from predominantly corporate environments to substantial ingredients of entre-preneurship.
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 encom-pass the chaotic migration to mobile multimedia communi-cations.
Visions of future wireless communications
• A plethora of multiple radio access standards will coex-ist alongside each other. No single standard will be able to provide all multimedia services and still provide suffi-ciently low network investment and operating costs. Terminals will be intelligent, being software reconfig-urable, will roam between networks and adapt to various network standards accordingly. Terminals will be config-ured with the bare minimum software, to make these able to adapt to various network and radio access require-ments. User centric/user defined radio communications
communica-tions platform similar to JAVA. Much of today’s hard-ware based radio functionality will be softhard-ware 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 serv-ices on demand by the user.
II. SOFTWARE TELECOMMUNICATIONS: MOTIVATION
A. What is the goal?
Currently communications networks and services are un-der a constant development, resulting in an increased com-plexity 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 intro-duced into the market is slowing down.
An Example for this kind of development is GSM. Mod-ifications and updates are becoming increasingly cumber-some 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
connectivi-ty, as well as the definition of classes of QoS for bit-stream transportation (as in ATM or IP). Furthermore a “program-ming language” (e.g. Java) is required as a platform for run-ning 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 plat-form, not the very details of the how and what of the services and links.
This results in a totally new concept for telecommunica-tions, i.e. the definition of services and links is freely soft-ware programmable and can be defined for each communications session individually by software. There-fore we use of the name “software telecommunications”.
For mobile communications this means a radical para-digm change compared to current activities. The software telecommunications platform must define the network ac-cess, 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 im-plementation 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/fre-quency interference and radiation masks (ISM band ap-proach).
This approach can finally lead to the integration of a vast variety of heterogeneous public (or private) communica-tions 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 ena-bler 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.
B. Context
Basic work on this topic has been emerging at many plac-es. 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 de-velopment of multimode phones and base stations on the way to software radios are clear signals for technology ena-blers. However, the system concept is just emerging. It is a clear new functionality step beyond anything available to-day.
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 domi-nated by today’s large players.
The subject as a system perspective is being examined in Germany in the ATMmobil project. A vast variety of specif-ic problems are being examined world-wide, as agents, soft-ware 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 im-portant 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 telecommu-nications 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 config-ured, so-called “software radios” [Steele], [Mitola].
D. Related Work and Results
There has been an increasing amount of research and de-velopment 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 de-mand for developing modems which can freely be pro-grammed to multiple standards. Software radio technology, as defined in [Mitola], leads to an attractive hardware plat-form 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 net-works[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 telecom-munications 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 inter-face to serve as a backbone of the software telecommunica-tions platform has been developed within the German ATMmobil project line IBMS [IBMS]. In this project a sep-arate signalling channel is being designed for only connect-ing 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 mo-bile networks will become sufficiently ubiquitous. High speed AD/DA conversion will provide the possibility of dig-itally 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 serv-ices will mainly be asymmetric, and only occasionally sym-metric, a dedicated network for symmetric broadband data services, using specific terminals could become prohibitive-ly 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 base-stations, could be a key element in providing the flexibility needed to provide symmetric and asymmetric high speed data services at a reasonable cost.
Nevertheless as Moore’s law drives down the cost for in-tegration, and as analogue to digital conversion becomes feasible at sufficient bandwidths and dynamic range, hard-ware will tend to be standardized, while softhard-ware will be ap-plication 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 mili-tary 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 telecommunica-tions 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 re-fer 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 re-quired 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 car-ried 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 pos-sibly 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 traf-fic.
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 specifica-tion is being carried out within the IBMS project. A partic-ular 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.
As mentioned above, the NACCH is observed in stand-by-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.
NACCH modem software radio modem SIM as e.g. GSM configuration application interface antenna(s)
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 net-work becomes a transparent bit transport infrastructure with the user having control over defining own services and ap-plications. 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 lobby-ing in standards bodies. Software telecommunications in mobile communications would revolutionize today’s tech-nology 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 play-ers. It therefore generates the equivalent market for commu-nications 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 operat-ing system (includoperat-ing NACCH), and thereafter leavoperat-ing space open for individual implementations in a time/fre-quency mask.
The NACCH/minimum specification air interface is the enabler for software telecommunications in wireless net-works, and hence it is the key for software telecommunica-tions to happen.
VI. CONCLUSIONS
Software telecommunications is in the final step of para-digm 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. It is the step communica-tions 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 telecommunica-tions 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. 29 - Oct. 2 1996.
[IBMS-2] M. Bronzel et al., “An integrated broadband mobile system IBMS,” accepted for ACTS mobile summit 1997, Aalborg, Denmark, Oc-tober 1997.
[Mitola] J. Mitola, ”Software Radio, “ IEEE
Commu-nications Magazine, May 1995.
[MMITS] http://www.mmitsforum.org/
[Steele] R. Steele, “Third generation PCN and the in-telligent multimode mobile portable,”
Elec-tronics & Communication Engineering Journal, pp. 147-156, June 1993.
[2005] “2005 - Ericsson entering the 21st century,” Ericsson annual report 1996.
(http://www.ericsson.se/annual_report/ 2005.html)