Tim Farnham

Architecture and enablers for optimized radio resource usage in heterogeneous wireless access networks: The IEEE 1900.4 Working Group

Over the past decade or so, the wireless industry has undergone many significant changes. Radio systems have moved toward forming heterogeneous wireless networks: collaborations of multiple radio access networks, which in some cases operate different radio access technologies, such as second- and third-generation cellular RATs, IEEE 802.x wireless standards, and so on. On the other hand, multimode reconfigurable user devices with the ability to choose among various supported RATs have become a reality, and devices and networks with dynamic spectrum access capabilities, allowing real-time sharing of spectrum resource usage among different systems, are expected to be a part of the future radio eco-space. As a result of these changes, there is a need to develop a standard that addresses the requirements and leverages the opportunities posed by such a versatile radio environment. To this end, IEEE 1900.4 aims to standardize the overall system architecture and information exchange between the network and mobile devices, which will allow these elements to optimally choose from available radio resources. In other words, the standard facilitates the distributed dynamic optimization of the usage of spectrum offered by the heterogeneous wireless network, relying on a collaborative information exchange between networks and mobile devices, thereby acting as a common means to improve overall composite capacity and quality of service for the served networks. This article provides a snapshot of IEEE P1900.4 in its current form, covering the scope and purpose of the standard, reference use cases for which the standard is applicable, its system and functional architectures, and finally, the information model for its main interfaces.

Radio resource management considerations for LTE Femto cells

Femtocell access points (FAPs), also popularly known as Home Base Stations, are small base stations for use within indoor environments to improve coverage and capacity. FAPs have a limited range (e.g. limited to a home or office area) but offer immense capacity improvements for the network due to the ability to reuse a frequency more often as a result of smaller coverage areas. Because there may be thousands of these devices and since the nature of deployment is adhoc, it may not be possible to carry out elaborate frequency planning like that in the traditional cellular network. This paper aims to outline the radio resource management considerations within the context of femto cells, the broader objective being to initiate a discussion and encourage research in the areas highlighted.

Terminal-centric view of software. reconfigurable system architecture and enabling components and technologies

Reconfigurable radio in Europe is rapidly gaining momentum and becoming a key enabler for realizing the vision of being optimally connected anywhere, anytime. At the center of this exciting technology is the reconfigurable terminal that will move across different radio access networks, adapting at every instant to an optimum mode of operation. This will require coordinated reconfiguration management support from both the terminal and the network, but the terminal will inherit a significant part of this intelligence. This article focuses on a novel reconfigurable terminal architecture that advances the state of the art and encompasses the overall protocol stack from the physical to application layer in IP-based radio access networks. The proposed architecture is composed of a terminal reconfiguration management part and enabling middleware technologies like the complementary Distributed Processing Environment and agent platforms, flexible protocol stacks that can flexibly be interchanged to support different wireless technologies and associated mechanisms, and finally, object-oriented reconfigurable RF and baseband components. The work presented in this article is conducted in the context of the IST projects SCOUT (www.ist-scout.org) and TRUST (www4.in.tum.de/-scout/trust webpage/spl I.bar/src/ trust frameset.html) of the European 5th Framework Program.

Unified Link Layer API: A generic and open API to manage wireless media access

We present the Unified Link Layer API (ULLA) framework: an open and extensible API framework that incorporates a number of requirements related to a wide range of applications, including multi-mode and cross-layer optimisation scenarios. This work has been mainly motivated by the complexity and interoperability problems related to the large number of wireless APIs available today. ULLA provides database and object oriented service abstractions to applications through a generic query mechanism, a method to setup asynchronous notifications and a command interface. It encapsulates link level heterogeneity by defining a unified model for link technologies. We describe design details, various implementation options and discuss how the proposed ULLA design provides an extensible, scalable and platform independent framework, enabling seamless link access and control in various types of device platforms. Application programming using ULLA is illustrated using code examples. Numerous usage scenarios for ULLA are presented, highlighting unified access to heterogeneous link standards while encouraging application innovation.

Using cognitive radio principles for wireless resource management in home networking

The demand for higher data rates, capacity and better quality-of-service is constantly growing for home networks. Therefore, there is a pressing need for efficient use of wireless network resources. In this context, the application of cognitive radio principles that enable network nodes to characterize their environment and control their resources based on the acquired knowledge, is the prominent solution for next generation home networks. In this paper we present an architecture and a prototype implementation based on these principles. The proposed system is able to autonomously optimize the performance of network nodes in a dynamic environment according to the goals, restrictions and policy regulations formulated by network stakeholders. The obtained results show the momentous and suitability of the cognitive framework for home networking.

Reconfigurable mobile communications: compelling needs and technologies to support reconfigurable terminals

To date, research into reconfigurable mobile communications has predominantly focussed on the software radio concept, and specifically on the hardware technologies required to move physical layer processing into a programmable environment. Although an interesting and necessary challenge, this only represents a fraction of the overall support and technology required to realise the potential of the concept. Other necessary developments include network/terminal cooperation for seamless inter-standard handoff, QoS management, a secure software download mechanism, terminal software architecture supporting reconfiguration, configuration management, capability negotiation. Summarising results from early IST-TRUST (Transparently Reconfigurable Ubiquitous terminal) project deliverables, this paper describes the likely overall system environment, and the key technical challenges to be researched in TRUST for realising a reconfigurable terminal to meet the needs of users within that environment.

Enhancing multimedia streaming over existing wireless LAN technology using the unified link layer API

This paper examines how multimedia streaming scenarios can be enhanced by cross-layer interaction, and in particular link performance information and configuration options provided by the recently developed Unified Link Layer API (ULLA). It provides results of an experimental implementation developed for this purpose in a wireless LAN (WLAN) environment. Multimedia streaming is an application that is gaining in popularity for mobile devices and in particular mobile Internet-based content broadcasting is rapidly emerging as a key feature on mobile devices. In these scenarios, the wireless link (last hop) is normally the performance bottleneck due to the dynamic and limited capacity of the wireless medium. The use of ULLA in this context can provide the ability to tailor the video transmission to the wireless link performance and also to configure the links in response to performance problems or environmental changes. For this purpose the focus of multimedia streaming has been on WLAN link technology and dynamic adaptation (i.e., dynamic channel selection and video transcoding) using a dynamic resource reservation overlay protocol.

Cognitive Radio for Home Networking

Cognitive Radios have emerged as one the most promising methods to increase wireless system efficiency through dynamic spectrum access combined with other cross-layer optimization methods. Most of the research prototypes and demonstrations have so far focused on either general platforms or scenarios that are predominantly taken from military or emergency communications domain. In this demonstration we show the prototype environment that is build around realistic home networking scenarios. The demonstration has two purposes. First, it demonstrates how a set of different implemented and integrated components can achieve local area optimization both in frequency allocation and other domains. Second, it shows the viability and attractiveness of cognitive radio methods for future commercial home networking devices. The demonstration showcases dynamic spectrum allocation and policy based behavioral changes in a home environment, where several multimedia stream and data communication connections are competing against each other.

IEEE P1900.4 System Overview on Architecture and Enablers for Optimised Radio and Spectrum Resource Usage

The field of application of the IEEE P1900.4 standard is radio systems forming a composite radio access network, i.e. with multi-radio access networks (RAN) using different radio access technologies (RAT). The end-user terminals are multimode terminals, supporting several RATs, with multi-radio link capabilities and having cognitive radio capabilities, such as operating flexibly on different frequency bands. The composite radio access network is assumed to be operated by either a single or several operators. Within this field of application, the standard provides common means to improve overall composite capacity and quality of service through distributed optimization of the usage of spectrum and radio resources offered by the composite radio access network. Basically, the optimization relies on a collaborative information exchange between the composite network and terminals. For this purpose, two entities are identified to facilitate this collaboration: network reconfiguration manager (NRM) and terminal reconfiguration manager (TRM), whilst the communication between NRM and TRM is ensured via a logical communication channel, the radio enabler (RE). Accordingly, this paper provides an overview of the IEEE P1900.4 scope and purpose, the reference usage cases wherein the standard would be applicable, including system requirements, architecture, and its reference model with main interfaces linked to the information model that is currently being developed.

Self-organizing home networking based on cognitive radio technologies

The increasing complexity of the future wireless networks leads to the requirement for self-organization. This is true especially in home networking where users are typically not networking professionals and cannot be expected to perform complex optimization and management tasks. In this context, cognitive radio concept combining cross-layer optimization and learning mechanisms is a promising solution. We demonstrate a cognitive home networking prototype, which addresses practical problems users face with the present-day wireless networks at home. The prototype shows how nodes using IEEE 802.11 radios and WARP boards operate under the Cognitive Resource Manager (CRM). The nodes achieve the desired performance by handling network dynamics and controlling parameters taking independent or cooperative decisions and operating in different layers of the protocol stack. This is done using multiple control loops which are supported by the CRM architecture. We demonstrate the use of machine learning for online estimation of network activity patterns to enable more efficient Dynamic Spectrum Access (DSA) using Hidden Semi-Markov Models (HSMM). The demonstration showcases dynamic spectrum allocation and policy-based behavioral changes in a home environment, where several multimedia streams and data communication flows are competing against each other and against external, also primary, interferers.