NEW NETWORK AND SERVICE CAPABILITIES USING SOFTWARE DEFINED RADIO TECHNOLOGY Milan Janković, Borislav Odadžić Community of Yugoslav PTT, Belgrade, Yugoslavia, E-mail:
[email protected] 1. INTRODUCTION In 2000 the telecommunications industry, network operators and service providers are navigating its way through a maze of technological crossroads that will ultimately determine what kind of networks the world will use in the 21st century. An important crossroad still to be passed related to the question of how intelligent, open, smart (growing middleware) or proprietary the future fixed and mobile networks will be. From this point of view the resource space needs to be considered to its entirety from endpoint devices to service operating centers. Its overall use can be considered as enabling the creation, provisioning and management of services. Someone creates a service using the functions of their local resources, and the network provides service functionality, provisions it and offers it to users to subscribe and use. The network can greatly offset the overhead required for managing subscribers and resources. To this end, exist substantial benefits in pushing some common service capabilities to the network (however that is implemented). The telecommunications industry, network operators and service providers has to differentiate between application resources, network service resources and the physical network resources, agree on the mandatory services vs. voluntary services the network must guarantee and develop a service platform that hides much of the service support complexity [8]. The industrial competition between Asia, Europe, and America promises a very difficult path toward the definition of a unique standard for future mobile systems, although market analyses underline the trading benefits of a common worldwide standard. It is therefore in this field that the Software Defined Radio SDR concept is emerging as a potential pragmatic solution: a software implementation of the user terminal able to dynamically adapt to the radio environment in which it is, time by time, located. In fact, the term (SDR) stands for radio functionality defined by software, meaning the possibility to define by software the typical functionality of a radio interface, usually implemented in TX and RX equipment by dedicated hardware. The presence of the software defining the radio interface necessarily implies the use of Digital Signal Processors (DSP) to replace dedicated hardware, to execute, in real time, the necessary software. SDR is considered as a promising technology for the next generation of mobile systems The requirements for the advanced services foreseen with the advent of UMTS (Universal Mobile Telecommunication
System) and SDR technologies are quite demanding (see Figure 1). 2. SOFTWARE DEFINED RADIO OBJECTIVES Exact definition of the SDR concept does not yet exist, even though the need to precisely clarify what is intended for SDR has been proclaimed by many. Some definitions often found in the literature are [7]: • Flexible TX/RX architecture, controlled and programmable by software • Signal processing able to replace, as much as possible, radio functionality’s • “Air interface downloadability”: radio equipment dynamically reconfigurable by downloadable software at every level of the protocol stack • SDR realization of terminals “multiple mode/standard” • Transceiver where the following can be defined by software: − Frequency band and radio channel bandwidth − Modulation and coding scheme − Radio resource and mobility management protocols − User applications These parameters can be adapted and changed by the network operator, the service provider, or the final user. The flexibility of an SDR radio system consists in its capability to operate in multiservice environments, without being constrained to a particular standard, but able to offer, in theory, services of any already standardized systems or future ones on any radio frequency band. The compatibility of an SDR system with any defined radio mobile is guaranteed by its reconfigurability, that is, by DSP engine reprogrammability, which, in real time, implement radio interface and upper layer protocols. The development of an SDR system implies, above all, the achievement of two main goals: •
•
To move, in TX and RX, the border between the analog and digital worlds as much as possible toward radio frequency (RF), by adopting analog-digital (A/D) and digital-analog (D/A) wideband conversion as near as possible to the antenna To replace Application-Specific Integrated Circuits (ASICs) with DSPs for baseband signal processing
Voice
Information Society Demands
Multi-Media Text
Video
Compression Technology
Cost of Spectrum
Cost of Deployment (Cell Size)
Broadband Data
Bandwidth on Demand Technology
Graphics
Emulation Technology
Air Interface
UMTS User Service Requirements, Bit Rate
Different Cell Sizes
Figure 1: Requirements for the advanced services foreseen with the advent of UMTS and SDR technologies As stated before, an SDR system should be able to adapt itself to a large variety of cellular systems, already standardized or developed in the future, by means of a common hardware platform, adaptable to any radio interface by simply changing the software running on it. 3. SERVICE DEPLOYMENT Over the past few years several major efforts have been undergone towards the directions in many fields into a telecommunications sector: • • • • • •
The introduction of the basic UMTS protocols and functionality’s, The evolution of IN (Intelligent Network) towards UMTS, The efforts for the migration of 2nd and 3rd generation mobile systems, The efforts for provision of global roaming The introduction of Common Object Request Broker Architecture (CORBA) for the support of open architectures The formation of the Telecommunication Information Networking Architecture Consortium (TINA-C) to cooperatively define a common architecture to capitalize on the latest advances in computers and telecommunications technologies to rationalize
organization of complex software for services and network management. TINA was developed as a CORBA-based system supported by a single Distributed Processing Environment (DPE) • The use of JAVA. More recently Sun Microsystems has presented the Java-language-based Java Advanced Intelligent Network (JAIN) solution for building and deploying state of the art telecom services blending IN and Internet technologies. • Very recently, an industry working group (the PARLAY Group) formed by several telecom and software companies started to create the open Application Programming Interface (API) specification to enable a new generation of dynamic telecommunications applications to be created and maintained by the networks’ customers themselves, using their own private data. • The introduction of the Wireless Application Protocol (WAP). WAP is the result of the WAP Forum’s attempts to promote specifications of protocols for the development of applications and services in the wireless telecommunications domain. WAP specifies an application framework and network protocols for wireless data services such as mobile/cellular phones and pagers. For the support of SDR services, the Access Network (AN) capabilities will have to integrate advanced solutions in the protocol and software based on the aforementioned cases.
Radio dependent/independent functions
Radio Independent Functions Radio Independent Functions
Radio Dependent Functions
Radio Independent Functions
Radio Dependent Functions
Radio Physical Layer
Radio Physical Layer
Mobile Terminal
Radio Access System
Fixed Network Subsystem
Figure 2: Categorization of software/service download functions
To this end, the introduction of intelligent Base Stations (BS) is required, incorporating part of the intelligence of the rest of the network. The AN will have to be able to cope with various types of BS, mobile terminals, protocol and service demands. Terminal classification will become an important issue for service provision and adaptation (if possible). Various service providers may be offering services to mobile users via one or several operators. According to the user profile, mobile terminal and BS capabilities, a differentiated list of possible services may be provided by the AN. Another important issue is the handover between heterogeneous BS, networks and operators. Issues regarding Accounting/billing become crucial. In order to cope with the protocol and service complexity the simplest case will be the evolution of BS intelligence to cope with various protocols, terminal classification, handling of service components, interworking with other types of BS and downloading issues. 3.1 Service download issues The old philosophy, where new technologies were developed for the support of new services, is now replaced by a novel approach that addresses the provision of service spanning multiple, existing as well as forthcoming network technologies. Rather they will provide seamless access to services that reside in any network (fixed or mobile) and empower customers with advanced control and management capabilities. In recent years a service centric vision of platform architectures has been promoted. The service and network elements are treated as service platform elements that can be tuned to meet the requirements of each specific service and communication environment. The provision of a service is the result of interaction among service components that reside on service platform elements (e.g. user terminals,
network nodes etc.) The integration of IN and UMTS has enforced the introduced functional model as a powerful potential for the implementation of future SDR services. Therefore, it is an inspiring concept for the provision of future services. Software download is the process of introducing new program code to a mobile terminal to modify or enhance its operation or performance. With the introduction of software download features, the mobile terminals potentially offer reconfigurability of their functions and flexible introduction of new services. This of great benefit to manufacturers, operators, service providers / third-party software developers and subscribers. The software download capability enables the ongoing convergence of personal computing and personal communications, applications and services and the enhancement of bearer capabilities. Downloaded software and services may be categorized as (see Figure 2): • Radio independent: High-level communications and software applications/services parts, independent of the underlying air interfaces • Radio dependent: Protocol entities and middleware for the modification of the interface or bearer capabilities, dependent of the underlying communication physical layer processing. Potential areas of application that will benefit from the introduction of software and service download are: • •
Download of mobile Value Added Services to mobile users Download of new user interface
• • • •
Adaptation of various protocols Adaptation of air interface to implement different features Download of software component enhancements Download of activation licenses
The SDR access may be used to allow a flexible/smooth upgrade from current 2G systems (e.g. GSM) to 2.5G (EDGE) or 3G systems (UMTS). In some cases the indoor environment may be upgraded than the outdoor cells.
Various methods for software download can be foreseen: • • • • • •
Distribution via Subscriber Identification Module (SIM)card or other removable media Software downloading via fixed network Software downloading from a handheld device Software downloading from CD-ROM or Internet/Intranet via a PC Software downloading from a Point of Sale terminal in a service center Software downloading over the air
The SDR Forum and other organizations with wide activity in the area of SDR have proposed basic protocols and API designs for software and service download, as well as architectures to cope with the software download issues. The hardware design is carried out in parallel with the software design. First, this requires the choice of proper software architecture (likely object-oriented), with its development environment and programming language. The final goal is the design of software libraries that implement the considered radio interface. Therefore, SDR represents a means to make a radio interface independent of the hardware platform 4. CONCLUSION At present, several standards exist and most of them are incompatible in them way of providing services to user. This situations is not friendly and needs to be improved. Current standardization activities on UMTS and other systems are addressing this issue. In order to achieve roaming between each domain and seamless service provision, new techniques are necessary (e.g. SDR). SDR techniques can provide a flexible framework for the support of various radio and application protocols. Pioneering the path of SDR, the WAP protocol is introduced for the support of wireless applications. All these considerations can be resolved in an adaptable to every environment and protocol scheme manner with the downloading of protocol components. A rough identification of the functional components of the SDRbased architecture for protocol component download are protocol identification and classification entity, protocol component triggering entity and protocol component download entity.
REFERENCES [1] EURESCOM: Project P816, Implementation Frameworks for Integrated Wireless Optical Access Networks, Del. 1, April 1999. [2] Tuttlebee W.: Software Radio Technology: A Communication European Perspective, IEEE Magazine, Vol.37, No.2, February 1999. [3] Carselo R. and al.: IMT-2000 Standards: Radio Aspects, IEEE Personal Communication, Vol.4, No.4, August 1997. [4] Mitola J.: Technical Challenges in the IEEE Globalization of Software Radio, Communication Magazine, Vol.37, No.2, February 1999. [5] Jankovic M., Odadzic B., Siltanen A., Hoegland K.: The Potential Services for Hybrid Fiber Radio Access Systems, Proc. of ICT '99, Cheju Korea, June 1999. [6] Efstathion D et al.: Recent Developments in Enabling Technologies for Software Defined Radio, IEEE Communication magazine Vol. 37 No8, August 1999. [7] Buracchini E.; The Software Radio Concept, IEEE Communication magazine, September 2000. [8] EURESCOM: Project P921-PF, DEL-1, Low cost radio independent access with SDR and HFR, June 2000. [9] Jankovic M., Odadzic B.: Software Defined Radio implementation in Hybrid Fiber Radio Systems, TELFOR99, Belgrade, November 1999. Abstract: This paper deals with the technologies used for the development for the SDR systems. Some architectures, service deployment scenarios and download issues dealing with the above systems are analyzed. Lastly SDR is considered as a promising technology for the future fixed and mobile networks. NEW NETWORK AND SERVICE CAPABILITIES USING SOFTWARE DEFINED RADIO TECHNOLOGY Milan Janković, Borislav Odadžić
