Evanny Obregon

A Model for Aggregate Adjacent Channel Interference in TV White Space

The presence of white spaces and spectrum holes in the TV bands represents potential opportunities for alleviating the apparent spectrum scarcity. Opportunistic spectrum access (OSA) has been proposed for the secondary users operation and the main concern is the harmful interference that secondary systems could cause to the primary receivers. Existing studies have focused on establishing the limits for co-channel and adjacent channel interference when only one adjacent channel is used by a single secondary user. This paper presents a characterization of the aggregate adjacent channel interference (AACI) when different adjacent channels are simultaneously accessed by multiple secondary users or white space devices (WSDs). An analytical expression is proposed to approximate the limits of the tolerable AACI. Our model states that not only the interference received in each adjacent channel should stay below the corresponding threshold for that particular channel, but also the weighted sum of the total adjacent channel interference power should be kept below a certain threshold. Measurement campaigns show the cumulative effect of the adjacent channel interference (ACI) when multiple WSDs access multiple adjacent channels at the same time. The proposed analytical expression for AACI closely matches the measurement results.

On the requirements of secondary access to 960–1215 MHz aeronautical spectrum

In this paper, we investigate the spectrum sharing requirements of secondary access to 960–1215 MHz band which is primarily allocated to aeronautical usage. Primary system of interest is distance measuring equipments (DME) aiding navigation of airplanes. We consider a scenario where indoor femtocells share the spectrum as secondary users. For the protection of the primary system, each secondary user decides whether to transmit or not depending on an interference threshold established by a central network. We provide a simple mathematical framework for analyzing the aggregate interference generated by multiple secondary users spreading in a large area. Requirement for the secondary access is established in terms of the size of exclusion region depending on the density of secondary users. Numerical results suggest the use of adjacent DME channel is required for a dense deployment of the secondary users. We discuss the challenges and implementation issues of practical secondary access, and suggest the directions of further research.

Experimental verification of indoor TV White Space opportunity prediction model

Recent work has demonstrated that the underutilized spectrum in the Digital Television Bands, commonly referred to as TV White Space (TVWS), is a prime candidate for opportunistic spectrum access (OSA). However, a systematic assessment of the availability of this spectrum for secondary transmission was, until very recently, lacking. In a TVWS opportunity prediction model to estimate indoor secondary usage probability was proposed. In this paper we aim at verifying this model by means of measurement campaigns in both laboratory and real indoor environments. The match between the predictions from the simulation models in and measurement results suggest that the model provides a realistic evaluation of the opportunities in TVWS for low power indoor secondary usage.

On the sharing opportunities for ultra-dense networks in the radar bands

Finding additional spectrum for indoor networks with very high capacity (ultra-dense networks, UDN) is a prime concern on the road to 5G wireless systems. Spectrum below or around 10 GHz has attractive propagation properties and previous work has indicated that vertical spectrum sharing between indoor users and outdoor wide-area services is feasible. In this paper, we focus on spectrum sharing between UDNs and radar systems. We propose and evaluate regulatory policies that improve sharing conditions/opportunities in areas with large demand (i.e. hot-spots and urban areas). We consider three regulatory policies: area power regulation, deployment location regulation and the combination of these. We address the scenario where secondary users can reliably exploit time and space domain sharing opportunities in the S- and Ku-Bands by means of geo-location databases and spectrum sensing. We evaluate these opportunities in terms of the required time-averaged separation distance between the radar system and the UDN that both protects the radar system as well as guarantees a minimum secondary transmission probability. Our results show that there are ample adjacent channel sharing opportunities for indoor usage in both the S- and Ku-Bands. In the Ku-Band, even outdoor hot-spot use is feasible with very relaxed restrictions. Co-channel usage in the S-band requires large separation distances that makes it practically unfeasible in cities with nearby radar sites. Overall, deployment location regulation seems to be the most effective means to limit interference to the radar system and improve sharing opportunities.

CellTV—On the Benefit of TV Distribution Over Cellular Networks: A Case Study

As mobile IP-access is becoming the dominant technology for providing wireless services, the demand for more spectrum for this type of access is increasing rapidly. Since IP-access can be used for all types of services, instead of a plethora of dedicated, single-service systems, there is a significant potential to make spectrum use more efficient. In this paper, the feasibility and potential benefit of replacing the current terrestrial UHF TV broadcasting system with a mobile, cellular data (IP-) network are analyzed. In the cellular network, TV content would be provided as one of the services (CellTV). In the investigation, we consider typical Swedish rural and urban environments. We use different models for TV viewing patterns and cellular technologies as expected in the year 2020. Results of the quantitative analysis indicate that CellTV distribution can be beneficial if the TV consumption trend goes toward more specialized programming, more local contents, and more on-demand requests. Mobile cellular systems, with their flexible unicast capabilities, will be an ideal platform to provide these services. However, the results also demonstrate that CellTV is not a spectrum-efficient replacement for terrestrial TV broadcasting with current viewing patterns (i.e., a moderate number of channels with each a high numbers of viewers). In this case, it is doubtful whether the expected spectrum savings can motivate the necessary investments in upgrading cellular sites and developing advanced TV receiver required for the success of CellTV distribution.

On the feasibility of indoor broadband secondary access to 960–1215 MHz aeronautical spectrum

The avalanche in mobile data consumption represents a big challenge for mobile networks operators and national regulators. This thesis focuses on finding additional spectrum to meet this demand in a cost-efficient way by considering shared spectrum access. Our studies aim at identifying key factors in achieving large-scale business success,quantifying the spectrum availability and identifying suitable regulatory/sharing polices for large-scale secondary access in the aeronautical and radar bands. This thesis proposes a research methodology, that considers business, technical and regulatory aspects involved in assessing commercial viability of large-scale deployment of wireless networks, employing vertical spectrum sharing in the aeronautical and radar bands. We pinpoint the following criteria which are critical in ensuring business success:spectrum availability, radio technology availability, low-cost end-userdevices, system scalability and quality of service. Our investigation centers on the technical aspects of these criteria, and thus deals mainly with the assessment of spectrum availability. The availability of spectrum opportunities is found to be ample for adjacent channel usage despite the strict requirements of the radar receiver. However, it is alsovery location-dependent and mostly non-contiguous.Finally, with regard to the regulatory aspects, our results show thatapplying regulatory policies, especially to the deployment of secondary users, can boost availability in cities or urban areas where the capacity demand is high. In addition, Licensed Shared Access (LSA) is identified as a suitable regulatory framework to meet tough protection criteria ofthe radar receivers and to apply the selected regulatory policies to improve exploitation of sharing opportunities. Based on our results and analysis, we conclude that there is a significant amount of spectrum opportunities for large-scale secondary access in the aeronautical and radar bands from the technical point of view. However, the commercial viability of secondary spectrum access is still undetermined giventhe remaining uncertainties regarding its total cost and the exact time needed for relevant technology to become available. Moreover, thereis no single answer to the commercial viability since it will most likelydepend on the country or region in question, which affects the spectrum availability, which in turn is a key criterion for business success. Futurework should therefore strive to clarify these uncertainties and to identify new responsibilities for all the entities involved in the LSA framework. Moreover, a quantitative evaluation would be needed to obtain more explicit conclusions on the business viability.

Availability assessment of secondary usage in aeronautical spectrum

In this paper, we provide a quantitative assessment of the available spectrum for massive indoor broadband secondary access in the 960-1215 MHz band, primarily allocated to the distance measuring equipment (DME) systems. We employ a practical sharing scheme where the secondary users share the DME spectrum via geo-location database and spectrum sensing. Since the DME system performs a safety-of-life functionality, protection from harmful interference becomes extremely critical. A DME channel is considered available in a certain time and location if the secondary users, under the applied sharing scheme, are able to successfully access the channel without violating the primary protection criteria. We analyze the impact of the secondary system parameters and the potential uncertainties in the applied sharing mechanism on the availability in the DME band. Numerical results show that at least 30% of the total DME band (57 MHz out of 190 MHz) can be available for a dense low-power indoor secondary network, even if conservative primary system protection criteria and high levels of uncertainty are considered.