Software radio and reconfiguration management

Abstract

The Wireless World Research Forum (WWRF) work area on Emerging Technologies pursues the identification of technologies furthering the evolution of future wireless communication systems. Within this exercise, the progression of telecommunications in the next decade is characterised as the convergence towards an IP-based core network providing ubiquitous seamless wireless access in an hierarchical and hybrid self-organising network environment. Whereby, the various radio access systems and the IP based core network will handle interworking, mobility management, and roaming. The key to facilitate this convergence on the access side are Reconfigurable Software Defined Radio (SDR) equipments. Subscribers and users will greatly benefit from this federated telecommunication environment, but only, if they are equipped with a single integrated reconfigurable multi-mode multi-band terminal. Such terminals have to operate in either several or even all the different access environments available and they have to support the whole range of applications that are usually accessible on devices specific for the single access technology in the heterogeneous network environment.

This article outlines and describes the SDR Research issues identified in workarea 3 of WWRF (New Communication Environment and Heterogeneous Networks), it focuses and describes the three major research directions followed: High Level System Requirements, SDR Hardware Architecture and System and Software Architectures for Reconfigurable communication systems.

Introduction

Migration from today's rigidly defined and non-integrated communication networks towards an integrated communication and service environment, connected via an IP-based core network and providing ubiquitous seamless wireless access via any available radio access technology (2G, 3G, wireless broadband, broadcast, etc.) is one of the visions outlined in the most recent edition of the Wireless World Research Forum (WWRF) Book of Visions for the Wireless World [1]. A hierarchical and hybrid self-organising network environment is foreseen to facilitate interworking, mobility management, and roaming in such a heterogeneous environment. This structure will integrate the various medium access systems and the IP based core network.

Subscribers and users will greatly benefit from this federated telecommunication environment, but only, if they are equipped with a single integrated reconfigurable multi-mode multi-band terminal. Such terminals have to operate in either several or potentially all different access environments available and these terminals have to support a whole range of applications that are usually accessible only on devices specific for a single access technology in the heterogeneous network environment.

Reconfigurability and Software Defined Radio (SDR) equipments are seen as key technologies to facilitate, on the access side, the provision of such a communication and service environment.

Reconfigurability challenges a number of areas ranging from user, business and regulatory aspects to radio resource/spectrum management and system level interactions. While awareness towards the implications of reconfigurable equipments needs to be raised amongst operators and regulatory bodies (value chain and business models, spectrum allocation, security, material conformance, etc.), the technological challenges are not only on the enabling technologies necessary for the development of reconfigurable terminals and base stations but also on network and equipments architectures (HW/SW) supporting reconfiguration, on interactions between terminals and networks, on mode switching negotiation and vertical handovers, on (re)configuration management, etc. The research on SDR has to embrace design and architectural development aspects on all system levels.

Early research into SDR Technology had been initiated by military and moved only later towards civil [2] and finally commercial applications [1]. In 1996, a non-profit organisation called SDR Forum (previously, MMITS Forum: Modular Multifunction Information Transfer System) was founded with the aim to develop a set of technical specifications and to define the requirements and eventually standards for the realisation of SDRs [3]. Moving from the initial military background, all branches of the wireless industry ranging from defence, commercial wireless, civil government to regulatory bodies and academia are represented in this forum. The activities of the SDR Forum have helped raising the awareness of this emerging technology and are influencing the regulatory framework for reconfigurable SDR Terminals.

Other research efforts, namely those of the European Commission, provide significant advances in both hardware and software technologies, the research frameworks ACTS (Advanced Communications Technologies and Services) [4] and ESPRIT (the EU information technologies programme) [5] initiated projects including FIRST (Flexible Integrated Radio Systems Technology), SORT (Software Radio Technology), and SLATS (Software Libraries for Advanced Terminal Solutions). While the current fifth framework projects include TRUST (Transparently Reconfigurable UbiquitouS Terminal), CAST (Configurable radio with Advanced Software Technology), MOBIVAS (downloadable MOBIle Value Added Services through software radio and switching integrated platforms), SODERA (reconfigurable radio for SOftware DEfined RAdio for third generation mobile terminals), and PASTORAL (Platform And Software for Terminals Operationally ReconfigurAbLe) [6]. Other initiatives include UKs Mobile VCEs Soft-Terminal research with its Reconfiguration Management Architecture [7] as well as many ongoing projects in the industry.

Despite such a wide range of activities, and due to the complexity of the problem area there is still a wide area of uncharted territory for fundamental research into reconfigurability and the various levels of SDR technology. Successful development of SDR equipments will still require a huge amount of efforts in the next 5–10 years. The majority of papers published on SDR until the late 1990s have focused on aspects related to the RF and digital front-ends and on functionalities of the radio interface. Spotlight has been extended to the overall SDR problematic for 2–3 years, embracing the complete set of issues to be solved, from the enabling technologies to the system aspects, passing through the building of the federated user/operator/regulator vision. This imbalance is due to the technological problems still unsolved and the not-yet-availability of sufficiently powerful digital devices. Therefore, the future proliferation of SDR equipments does require both a powerful HW architecture and also the means to facilitate co-operation of SDR equipments within the supporting networks and the means to control reconfigurability.

This article presents the approach proposed inside WWRF SDR workarea to tackle the various research issues of reconfigurable communication equipment. The main section of the paper initially describes the high-level system requirements and therein defines the boundaries for research into the hardware and system/software requirements and architectures of SDR based reconfigurable wireless communication equipment. The final section summarises, based on the system and architectural requirements, the different research issues to be solved on the hardware, software and reconfiguration control aspects.