Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and non-technical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e., (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions.

Survey of Spectrum Sharing for Inter-Technology Coexistence

In practical unlicensed communications in TV band, radio devices have to identify, at first, the transmission opportunities, that is, the portion of the spectrum licensed for broadcasting services unoccupied in a certain region at certain time, that is, the so-called TV white space. In this paper the outcome of field measurements in the UHF TV band (470–860 MHz) conducted in EU is presented. To obtain empirical values for the parameters upon which unlicensed radio devices are able to distinguish in a real scenario between empty and occupied TV channels, signal power measurements have been performed in Italy, Spain, and Romania on rural, suburban, and urban sites, at different heights over the ground by using different analysis bandwidths. The aim of this work is to provide a set of practical parameters upon which harmless unlicensed communication in the UHF TV white space is feasible. The results have been analyzed with respect to the hidden node margin problem, spectrum sensing bandwidth, and occupancy threshold.

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On the Feasibility of Unlicensed Communications in the TV White Space: Field Measurements in the UHF Band

In this paper we present results from a week long measurement campaign on spectrum use in London (UK). The measurements were conducted in order to understand the characteristics and especially the variability in spectrum use over different types of areas in a major metropolitan area. Three spectrum analyzers were used in the measurement campaign, one used for long-term measurements at a single location in a given area, with the other two used to sample spectrum use around the stationary measurement point. This measurement approach yields much more detailed information about spectrum use than the typical single-location campaigns reported in the literature. We give a detailed description of the measurement campaign, including the equipment setup and rationale for the choice of areas in which the measurements were conducted. We also present results from the first exploratory data analysis of the obtained data, and study in detail the correlation structures and dynamics in spectrum use in temporal, spatial and frequency domains.

Measurements of spectrum use in London: Exploratory data analysis and study of temporal, spatial and frequency-domain dynamics

In this paper a comparative study of two
measurement campaigns carried out in Barcelona, Spain, and
Pozna, Poland, to identify spectrum occupancy in different
bands, is presented In both cases the measurement setup was
harmonized to obtain comparable results The problem of
efficient noise floor estimation was also considered and a
pragmatic approach that takes into account both internal and
ambient noise has been proposed Obtained results show
significant amount of unused spectrum, with similar results for
both sites when analyzed globally (average spectrum occupancy
of 27% in Pozna? and 22% in Barcelona) On the contrary, when
going to the detailed analysis of some specific bands, more
relevant differences are obtained These differences have been
observed mainly in the Terrestrial TRunked RAdio (TETRA)
bands that in Poland are also used by Code Division Multiple
Access (CDMA) 450, as well as in the bands of theGlobal System
for Mobile communications (GSM) due to the effects of Universal
Mobile Telecommunications System (UMTS) refarming in the
900 MHz band

Spectrum occupancy in big cities - comparative study - Measurement campaigns in Barcelona and Poznan

Spectrum sharing based on the dedicated databases, particularly in the context of TV band, is widely considered as a promising tool for better spectrum utilization in the future wireless networks. Practical realization of this paradigm entails the need for the true protection of the incumbent system, and at the same time the guarantee of the quality of the services offered to the secondary users. In this respect, this paper discusses the results achieved in numerous measurement campaigns performed for last years in two European cities, i.e., Poznan, Poland, and Barcelona, Spain. Both indoor and outdoor measurements of the TV band have been compared with the main purpose of true identification of key practical considerations for spectrum sharing in the TV white spaces. As such, this paper constitutes a concise summary of various analyses and provides pragmatic guidelines for deployment of radio-environment maps (REM)-based systems. Based on the conducted measurements and achieved results, the set of practical conclusions for REMs has been deduced, and the prospective procedure of deployment of such a network has been proposed.

Application of Radio Environment Maps for Dynamic Broadband Access in TV Bands in Urban Areas

In this paper we report on spectrum use measurements carried out synchronously over the period of 48+ hours in seven European cities. Special care has been placed on harmonizing the measurement settings and equipment so as to obtain as comparable data as possible. We describe in detail the measurement setup, including the coordinated preparation activities carried out across the different measurement sites. We present preliminary analysis of the obtained data set, and particularly highlight similarities and differences in spectrum use between selected measurement locations. We plan to release later the full data set for research community for the further research.

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Two days of spectrum use in Europe

We report initial results from 48 hour spectrum occupancy measurement campaign that was done in time-correlated fashion in seven different European locations. We give a description of the measurement campaign and provide results from our preliminary analysis of overall duty cycle in the frequency range 110-3000 MHz. The paper particularly focuses on traffic and duty cycle patterns in GSM 900 and GSM 1800 bands. For the sake of completeness, we also discuss ISMband utilization in two of our measurement sites. We show that spectrum utilization is generally low, but that variance between frequency bands and locations is significant, which means that any statistical claims on occupancy statistics need to be done carefully before regulatory claims are made.

Peter. Scheele

Papers

Two days of spectrum use in Europe

Two days of European spectrum: Preliminary analysis of concurrent spectrum use in seven European sites in GSM and ISM bands