Cognitive radio (CR) is still an emerging and disruptive communication technology which is expected to improve the overall efficiency of the spectrum use. It is envisaged that cognitive radio systems (CRS) could impact many aspects of communications and in particular could facilitate accommodation of the increasing amount of services and applications in wireless networks. Intensive research on CR aims at maximising the utilisation of the limited radio spectrum resource. There have been many advances in CR regarding the technology development aspects; however supplementary research on regulation, policy and market structure reforms in relation with application specific deployment is still required before any CR-based spectrum access could be implemented for specific broadband mobile applications. Indeed, mobile community is still at an early stage of understanding and development of CR capabilities and it is premature to envisage wide deployment of CRS without careful consideration of regulatory and business issues. Therefore, this paper gives a classification of CR-based network and application scenarios, and investigates the feasibility of them from a regulatory perspective at a global level (ITU-R). Main part of this paper presents the wireless network operator's approach to CRS specific for International Mobile Telecommunications (IMT) systems and proposes the radio environment map (REM) concept as a cognitive tool that increases environmental awareness in wireless network operator's networks. Studies, which the authors performed internally and within the framework of a collaborative European project as well as within ITU-R yield the conclusion that, at shorter term, only intra-operator based CRS maximises the possibility for CR capabilities to be implemented.

This paper presents the Cognitive Pilot Channel (CPC) solution as a mechanism allowing the terminal to be aware of the communication means available at a given time and place in a flexible spectrum management scenario. The different aspects to be considered in the CPC deployment are highlighted, together with the different implementation options. As a result, a CPC dimensioning methodology is formulated, identifying the main parameters involved in the process and the corresponding design trade-offs.

For cognitive radio one of the most challenging issue is how to get the intelligence necessary to make the best possible allocation decision. Techniques such as sensing to get the information on the occupancy of the radio environment are being discussed. And designing terminals with scanning/sensing capabilities is a vibrant research topic; such terminals, and the sensing principles, can be very helpful when limited parts of spectrum are to be scanned. But in cases where there is no knowledge about the amount of spectrum to be scanned, this can result in time-and power-consuming operations. An alternative approach, described in this paper, consists of a "Cognition supporting Pilot Channel" (CPC) which directly provides relevant information to the terminal. This paper looks at the concept of this CPC, it initially describes the expected functionality and discusses the regulatory implications such a cognition supporting pilot channel, in the context of flexible spectrum management faces.

Future wireless communications will benefit from cognitive functionalities, operated by reconfigurable networks and terminals. In a context where any parameter could be adapted dynamically in an "always best connected" perspective, the spectrum allocation flexibility would be a powerful feature. In this paper, we study the technical feasibility of dynamic spectrum allocation in a multi-technology and multi-operator context. Firstly, the generic technical approach will be described; secondly, an algorithm, inspired by the cognitive radio cycle will then be proposed. An example of DSA simulation with legacy systems will be presented, in order to underline the algorithm validity.

This contribution presents spectrum occupancy measurements which have been performed during the 2006 Football World Cup in Germany, in the cities of Kaiserslautern and Dortmund. The measurements investigate the time-variation of powers in 2G bands (900 MHz and 1800 MHz), a spectrum bandwidth including 3G bands and an ISM band (2000- 2600 MHz), and a global band (400-2600 MHz), on the day prior to a match, the day of the match, and during the match. The first intention is to study changes in power levels and subsequently relate this to specific events, such as (i) the start of the match, (ii) half-time, and (Hi) the end of the match. A next intention is to investigate the autocorrelation structure of changes in power levels, and relate this to the ease with which dynamic spectrum allocation might be performed. The results that ensue are used to inspire a discussion as to how dynamic spectrum allocation and short-range localized solutions such as IEEE 802.11 basestations might be leveraged to bolster capacity at large-scale events.

An important emerging capability is for mobile terminals to be dynamically reconfigured. Through ongoing advances in technology such as software defined radio, reconfiguration of mobile terminals will in the near future be achievable across all layers of the protocol stack. However, along with the capability for such wide-ranging reconfiguration comes the need to manage reconfiguration procedures. This is necessary to coordinate reconfigurations, to ensure that there are no negative effects (e.g. interference to other RATs) as a result of reconfigurations, and to leverage maximal potential benefits of reconfiguration and ensuing technologies such as those involving dynamic spectrum access. The IEEE P1900.4 working group is therefore defining three building blocks for reconfiguration management: network reconfiguration management (NRM), terminal reconfiguration management (TRM), and a radio enabler to provide connectivity between the NRM and TRMs. In this paper we concentrate on aspects of the radio enabler, highlighting its relevance in heterogeneous radio access scenarios, its advantages, and some aspects of its technical realization.

The global beyond 3G system consists of several coexisting and cooperating access technologies. One of the key concepts of this global technology is the reconfigurability, that allows different network elements to dynamically adapt their configuration to the new conditions encountered in specific service areas and time. Reconfigurability may comprise dynamic spectrum allocation: a technique that varies spectrum allocation of different systems in order to meet changing demands. In this context of multiple access techniques and changing spectrum allocation, when a mobile is switched on, it has no information about the available systems in its area nor on the current spectrum allocation to these systems. In order to avoid the scanning of all the spectrum range and to facilitate the initial connection to the network, this paper proposes that the mobile listens first to a broadcast radio channel containing the necessary information to initiate its connection. The paper defines the content of this broadcast channel, denoted common pilot channel, and proposes a technical implementation

ZigBee is a standard optimised for radio networks used in applications such as interconnecting sensors, monitoring and automating home, medical, industrial, and agricultural systems where low levels of data throughput and low-power consumption are needed. The physical (PHY) and medium access control (MAC) layers of ZigBee are defined by the IEEE 802.15.4 standard. One of the operational frequency bands of ZigBee is the unlicensed 2.4 GHz Industrial, Scientific and Medical (ISM) band which is also used by WiFi. Several ZigBee and WiFi devices may operate in the same environment, which may result in the two systems performance degradation. Before transmitting, WiFi and ZigBee devices perform the clear channel assessment (CCA) according to three different modes defined in the standards. In this paper, ZigBee throughput is obtained for the different CCA modes used by both ZigBee and WiFi systems operating in the same environment. Simulation results show that, ZigBee performance can be optimised by choosing the suitable CCA mode with respect to the interference level at the receiver