White Space Devices Research Articles

On the Study of Interference Scenario on TV Broadcast and Wireless Systems for Emergency Communication Networks in TVWS

This paper investigated frequency sharing between primary TV systems (channels 32 and 49) and Emergency Communication Networks (ECNs). The networks to be implemented in the Osogbo axis of Osun State function on a secondary geographical basis, creating no harm to the original licensed primary TV viewers. A minimum separation distance of 41 dB was suggested as the protected contour for the UHF spectrum to oversee the protection of primary TV users for the UHF bands under consideration. The effects of changing the secondary systems' transmitting power, transmission frequency, and antenna height on the service coverage distance were also explored. The performance of the UHF band was evaluated when it was utilized for secondary transmission at both low and high transmitting powers, with the performance criterion being percentage coverage distance. This work complies with the International Telecommunication Union-Radio sector (ITU-R) recommendations of 16 dB for signal-to-noise ratio and 41 dB for signal strength. It can also be deduced from the result that when the transmission power of ECN devices is raised from 40 mW to 4 W, Effective Isotropic Radiated Power (EIRP) is used; it caused a 76.19% reduction in the coverage spacing for TV channels of ECN Network secondary devices. For the White Space Device (WSD) to operate in Temporal mode, the maximum allowable power (4 W) used in spatial mode should be replaced by a 76.19 per cent reduction. Additional sensing margins of 3.76 dB and 4.04 dB for channels 33 and 43 must be added to the FCC threshold limit of -114 dBm criterion for TV white spaces to assure ECN deployment without causing severe interference to TV customers.

Field Measurement Test on Protection Ratio For DVB-T2 Interfered By TV White Space Devices

TV white space (TVWS) refers to the unused UHF and VHF spectrum owned by primary users, such as TV (DVB-T2) broadcasters in a certain location. The protection of primary users' interference from white space devices has been the major implementation issue. Protection ratio setting is commonly used to limit the amount of transmission power that white space devices can permit. In the present study, the simulation and experiment for the proposed protection ratio values are compared. Simulation using Monte Carlo has been conducted. Field measurements were implemented to see whether the protection ratio value could be used to assist the government in implementing TVWS. The outcomes showed that the simulation-based protection ratio was 1 dB greater than the field test result. The results indicate that the simulation model can be used as a reference for the government to estimate the value of the protection ratio and facilitate better efficient implementation

Joint sub-Nyquist wideband spectrum sensing and reliable data transmission for cognitive radio networks over white space

The emerging cognitive radio technology resolves the spectrum scarcity problem by exploiting the unutilised licenced spectrum on an opportunistic basis. Meanwhile, future cognitive devices require advanced sensing techniques for rapid and active identification of spectrum holes over a wideband. Incorporation of prior information from the geolocation database enhances the sensing performance, reduces the computation complexity and maximizes the spectrum utilisation by white space devices. However, unlike the TV white space database, other wideband spectrum databases are not yet available. Therefore for dynamic and fragile cognitive networks, the geolocation database cannot assist the spectrum sensing process, which necessitated database-independent real-time spectrum sensing. Constant interference from primary users is yet another major challenge with cognitive radio networks which makes reliable communication extremely difficult for secondary users. Forward error correction codes ensure the reliability of transmitted data, among which low-density parity check codes are the most appropriate. Lengthy low-density parity check codes, however, have certain drawbacks specifically high encoding and decoding complexity. Parallel concatenated Gallager code addresses these issues. This paper presents a reliable data transmission scheme for secondary users using the proposed non-zero syndrome parallel concatenated Gallager codes with interleaver for cognitive radio networks performing real-time spectrum sensing over white space. The joint sensing scheme along with prior knowledge from the geolocation database improves the spectrum sensing performance with reduced complexity and is more suitable for low-power cognitive devices. Further, simulation results affirm that proposed PCGC outperform a dedicated LDPC in terms of coding gain and bit-error rate.

Priority based health data monitoring with IEEE 802.11af technology in wireless medical sensor networks.

In this work, the IEEE 802.11af technology-based wireless sensor network for health data monitoring with priority classes is proposed. In IEEE 802.11af technology, a White Space Device (WSD), a Station (STA), and an Access Point (AP) communicate through television white spectrum opportunistically without causing any harmful interference to licensed` services. In the proposed network; WSDs, STA, and AP employ Frequency Division Multiple Access (FDMA) technique with the aim of communicating through the white space spectrum determined by White Space Map (WSM). WSD collects health data such as body temperature and blood pressure from an implant or on-body sensors. The priority class is determined according to the emergency of a patient as red, yellow, and green. After obtaining the analytical model of the proposed network, the simulation model is carried out using Riverbed Modeler. The graphical results prove the validity and applicability of the proposed network in terms of delay (0.17 s) and energy consumption (4.7 mJ/s) without any spectrum cost for priority-based health data monitoring. Graphical abstract Cognitive radio based IEEE 802.11af environment for priority based health data monitoring.

Aggregate interference from white space devices into digital terrestrial television receivers

The cognitive radio devices operating in the digital terrestrial television (DTT) frequency band, known as white space devices (WSDs), use the free DTT channels under the condition that they do not cause interference above the limit set by the regulator. In 2015, the UK regulatory authority, Office of Communications (Ofcom), published the first European regulation allowing WSD systems to operate in the DTT band. It defines a methodology to calculate the maximum WSD transmission power based on single-entry interference. It does not guarantee, however, that the co-channel aggregate interference produced by the WSDs operating in the same region satisfies the intersystem interference limit. In addition, to define the maximum intersystem interference, the Ofcom methodology does not use the same criterion as that used in DTT system planning for the intrasystem interference. This work develops a new methodology for calculating the WSD transmission powers that solve the problems identified in the Ofcom regulation. Based on this methodology, a new WSD admission procedure that guarantees the protection of the DTT receivers from the WSD aggregate interference is proposed. It is compared to two other admission procedures based on the Ofcom regulation and Electronic Communications Committee report 186, respectively.

Operating white space devices in the DTV service area

Abstract White space devices (WSDs) that operate in the underutilized TV bands (TV white space) must not interfere with the incumbent digital TV (DTV) reception. We identify the conditions for harmonious coexistence between WSD and three different DTV services: Advanced Television Systems Committee, Integrated Services Digital Broadcasting - Terrestrial, and Digital Video Broadcasting - Terrestrial. We find that a WSD can operate within all three regions provided that (1) its radiated power is smaller than 13 dBm, (2) it keeps a minimum distance of 50 m from a DTV receiver, (3) it operates in the adjacent channels except the closest one.

Design of a Multimode UWB Antenna Using Characteristic Mode Analysis

In this communication, a low-profile ultrawide band (UWB) antenna is designed, fabricated, and measured for TV white space devices (TVWSDs). Starting from a simple annular ring, the proposed design procedure is guided by the characteristic mode analysis. First, a closed-form estimation to the resonant frequencies of the first two characteristic modes for the annular ring structure is provided. Then, the annular ring is modified to introduce more characteristic modes resonating within the interested spectrum. To excite these modes and to achieve a wideband antenna covering the whole ultrahigh frequency (UHF) TV spectrum, the feeding structure is also carefully designed and refined. Finally, a prototype is fabricated and measured to verify its UWB performance, and radiation patterns at different frequencies are presented to prove the switching of dominating resonating modes. The analyses and performance evaluation show that the proposed antenna is a strong contender to be used for TVWSDs. Furthermore, thanks to the simplicity of tuning and controlling modal resonant frequencies, this procedure can be flexibly applied to various antenna designs.

Joint Sub-Nyquist Spectrum Sensing Scheme With Geolocation Database Over TV White Space

To maximize spectrum access opportunities for white space devices, incorporating real-time spectrum sensing with geolocation database is a promising approach to enhance detection resolution with reduced computation complexity. Advanced spectrum sensing techniques are needed to quickly and accurately identify spectrum occupancy over a wide frequency range. However, the stringent requirements from wideband signal acquisition and processing pose a major implementation challenge in compact devices with limited energy storage and computation capabilities. In this paper, a hybrid scheme of sub-Nyquist wideband spectrum sensing with geolocation database is proposed to achieve accurate detection of the surrounding spectrum with reduced number of required measurements and computation complexity. Two iterative algorithms are modified to incorporate a priori information from geolocation database, therefore enabling spectrum sensing to be performed only on a limited number of potentially vacant channels over TV white space. Theoretical analyses and simulation results show that the proposed joint scheme speeds up the sensing process with enhanced detection performance and smaller required sampling rate, whereas the updated channel information from wideband spectrum sensing reduces the risk of interferences to the dynamic incumbent users.

Optimal Allocation of TV White Spaces to White Space Devices using Genetic Algorithm and Fuzzy Rule based Technique

Optimal Allocation of TV White Spaces to White Space Devices using Genetic Algorithm and Fuzzy Rule based Technique

Prototype of IEEE 802.11af-Based Baseband IC Enabling Compact Device for Wireless Local Area Network Systems in TV White-Spaces

In this paper, we present the world’s first prototype of the IEEE 802.11af-based baseband (BB) integrated circuit (IC) enabling compact, low power consumption and even low cost TV white-space (TVWS) devices. Although it has been already over three years since the IEEE 802.11af was standardized in December 2013 as a wireless local area network (WLAN) system utilizing the TVWS, the IEEE 802.11af-based system has not been commercially deployed yet due to difficulties in downsizing, power saving, cost reduction, etc. As well as conventional WLAN systems, an integration of the BB signal processing circuits is one of the promising technologies that can resolve these concerns. The prototype BB IC incorporates IEEE 802.11af physical layer and low-medium access control functions, buffer memories, and interface circuits, thus enabling easy installation, and easy control by connection to a host device via the universal serial bus interface. In addition, we also develop the compact radio frequency (RF) front-end circuit with variable circuits and filters based on the direct conversion scheme by using an off-the-shelf RF IC. By incorporating the prototype BB IC and the RF front-end circuit, we successfully prototype compact card-type TVWS devices in all-in-one package including an antenna. The practicality of the prototype BB IC is demonstrated by characterizing the card-type TVWS devices in respect to transmission and reception performance and throughput.

Compact low‐profile UWB antenna with characteristic mode analysis for UHF TV white space devices

A compact ultra-high frequency (UHF) ultra-wideband (UWB) antenna for Television TV white space (TVWS) applications is presented in this study. The proposed radiating body is transformed from a rectangular plate following physical essence revealed by characteristic mode analysis. Modal current distributions and their contributions to the total radiation are further analysed after printing the radiating body onto a thin substrate. It is proved that the structure achieves efficient radiation over a wide range of frequencies by exciting multiple modes. In addition, effects of significant parameters on the antenna performance are discussed, and according to which the geometry is optimised. A prototype is fabricated and measured to verify its ultra-wide impedance bandwidth and monopole-like radiation pattern. Realised gain and radiation efficiency over the UHF TV spectrum are also measured. The bandwidth efficiency product against antenna electrical size are analysed and compared with theoretical limit and products of existing designs.

Comprehensive evaluation of an antenna for TV white space devices

In this study, an ultra-high frequency antenna for TV white space devices (TVWSDs) is designed, fabricated and systematically tested. In addition to its radiation efficiency validation using a novel measurement approach, system performance of the antenna is comprehensively studied by integrating it onto different platforms, including a wideband spectrum monitor and a wireless communication client, and testing under realistic scenarios. The performance comparison with a commercial antenna is also performed to demonstrate the effectiveness and robustness of the in house-developed antenna. Overall practical and real-time performance evaluations show that the in-house developed antenna is a strong contender for TVWSDs.

Multilevel Protection to Broadcaster Contour and Its Impact on TV White Space Availability

In light of recent regulations from the Federal Communications Commission (FCC) governing the very-high-frequency/ultrahigh-frequency band sharing, we consider the database as a tool to plan the utilization of this spectrum by unlicensed wireless devices. Our approach, however, differs from that adopted by the FCC in the sense that it exploits the ability that white space (WS) devices have in controlling their effective isotropic radiated power through the transmit power control technique when concomitantly operating in a cochannel or in an adjacent channel to a TV station. We derive equations for the expected interference level generated by WS devices with antenna heights ranging from a few meters (portable devices) up to a 1000 m (fixed devices) based on very recent TV white space (TVWS) propagation literature and regulatory requirements. Additionally, we also provide exact and numerical methods to calculate the critical distance that prevents interference to primary contours, thus enabling fast identification of regions where operation is harmless to incumbents in the presence of shadowing and multipath fading. These equations reveal the intrinsic relationship between system design parameters, environmental parameters, and country regulations with TVWS availability. Finally, we provide an analysis that indicates notable enhancements in the expected TVWS availability through the use of a multilevel method while obtaining the same desirable degree of protection required by the current FCC regulation based on the single-level methodology. The analysis is divided in two parts: theoretical evaluations to obtain insights into the potential of multilevel protection in recovering TVWS-less regions from a single exclusion zone and extensive computations to obtain the expected TVWS availability yielded by both protection methodologies and primary-contour determination techniques across the Japanese territory. Specifically, multilevel protection is found to have the effect of doubling the TVWS bandwidth, as compared with single-level protection. On the other hand, diffraction methods used to determine the primary contour nearly triples the bandwidth, as compared with the height above average terrain (HAAT) technique. The combined effect of multilevel protection and diffraction-based primary contours is TVWS availability on 98.76% of the Japanese territory with a bandwidth expansion six times of that inherent to single-level protection and HAAT-based contours.

Systematic Analysis of Geo-Location and Spectrum Sensing as Access Methods to TV White Space

Access to the television white space by white space devices comes with a major technical challenge: white space devices can interfere with existing television signals. Two methods have been suggested in the literature to help white space devices identify unused channels in theTVfrequency band so that they can avoid causing harmful interference to primary users; geo-location spectrum database and spectrum sensing. Discussions in the literature have placed much emphasis on the limitations of the spectrum sensing approach mainly from the perspective of the developed world environment in which its drawbacks are significant. Little attention has been placed to the limitations of the geo-location database approach when applied in a developing regions. This paper considers a broader analysis of the approaches by looking at factors that can affect their performance and how the presence or absence of these factors in a developed region or developing region can affect their applicability. In so doing, the paper highlights the need to conduct more research on the performance of spectrum sensing in developing regions where there are much less TV broadcasting stations and therefore, white spaces are more abundant.

A Low Complexity Sub-Optimal Approach to Dynamic Spectrum Allocation for White Space Devices With Heterogeneous Bandwidth Requirements

This letter considers the decision-making method of dynamic spectrum allocation by a spectrum manager in a centralized white space cognitive radio communication network with various available frequency fragments and heterogeneous bandwidth requests. To achieve low complexity practical solution to this problem, we propose a hybrid sub-optimal dynamic programming-based algorithm. The performance of the proposed solution is compared with the optimal one and other alternative solutions. The numeric results show that the proposed solution achieves spectrum efficiency close to the optimal one and the complexity is considerably reduced to ${O((n+\lambda -1)!/(n!(\lambda -1)!))}$ as compared with that of the optimal solution ${O\left({\prod _{i=1}^{n}B_{0}^{(i)}}\right)}$ .

FROM OPPORTUNISTIC NETWORKS to 3GPP NETWORK-INDEPENDENT DEVICE-TO-DEVICE COMMUNICATION

Broadband access constitutes the "oxygen" for the Internet Era, to which end, the issue of spectrum management is foundational. In this position paper, we present an overview of FCC's pioneering work framing TV white space rules that allows unlicensed access by secondary users while protecting licensed primary users. The core contribution of this paper is an in-depth analysis of FCC's TV white space regulations (often treated as a global template). We argue that FCC's current white space regulations does not achieve the desired balance between effectively promoting unlicensed secondary access and providing adequate protection of the primary. As more countries around the world look at framing white space regulations, we argue for incorporating a more flexible design that can catalyze a white space device ecosystem to flourish, similar to Wi-Fi.

Location-Probability-Based Transmission Strategy for White Space Devices With Multiple Antennas in TV White Space

In the TV white space, geolocation database techniques are utilized to manage white space devices (WSDs) or secondary users' operations over the digital terrestrial TV (DTT) receiver protection, in which the location-specific maximum power of WSDs is calculated based on location probability . The multiple antennas can also be utilized for WSDs to protect the DTT receivers and simultaneously increase the WSDs' system performance. However, due to the lack of channel information at the transmitter, conventional multiple-antenna-based cognitive radio (CR) techniques cannot be applied to WSD transceivers. In this paper, we develop the transmission strategies for multiple-antenna-based WSDs operating on the geolocation database framework. We analyze the achievable throughput when the WSD receiver exploits zero-forcing (ZF) linear processing under imperfect channel estimation and, based on the analytic results, propose a dynamic WSD transmission strategy in which the number of active transmit antennas and the associated antenna indexes are determined according to the WSD operational parameters obtained from the geolocation database.

A Critique of FCC'S TV White Space Regulations

Broadband access constitutes the "oxygen" for the Internet Era, to which end, the issue of spectrum management is foundational. In this position paper, we present an overview of FCC's pioneering work framing TV white space rules that allows unlicensed access by secondary users while protecting licensed primary users. The core contribution of this paper is an in-depth analysis of FCC's TV white space regulations (often treated as a global template). We argue that FCC's current white space regulations does not achieve the desired balance between effectively promoting unlicensed secondary access and providing adequate protection of the primary. As more countries around the world look at framing white space regulations, we argue for incorporating a more flexible design that can catalyze a white space device ecosystem to flourish, similar to Wi-Fi.

Changing availability of TV white space in the UK

The UK regulator Ofcom has held a Pilot of TV white space (TVWS) technology in the UK. On the basis of the results of this Pilot, Ofcom has varied its calculations of allowed white space device equivalent isotropically radiated powers (EIRP). Further, the World Radiocommunication Conference (WRC) 2015 has assigned 694-790 MHz to mobile broadband on a co-primary basis, in International Telecommunication Union (ITU) Region 1 (which includes the UK/EU). Fundamental observations on the effects of these changes on TVWS availability in the UK are provided.

위치확률 기반의 하이브리드 WSD 무선자원 할당 방안 연구

국내 TV 화이트 스페이스(TVWS) 기술기준에 따르면 디지털 TV(DTV) 서비스영역 내에서 고정 전력을 사용하는 휴대용 TV 화이트 스페이스 기기(WSD)의 경우, DTV 서비스 영역 경계 부분에서 전파환경이 변화하면 간섭이 발생할 수 있다. 이러한 문제점을 해결하기 위하여 본 논문에서는 TVWS geo-location 데이터베이스 기반의 고정 전력할당 방안에 더하여 스펙트럼 센싱을 수행하는 하이브리드 WSD의 무선자원 할당 방안을 제안한다. 하이브리드 WSD의 현재 위치에서 DTV의 수신전력을 센싱하고, 위치확률을 계산하여 허용가능 실효 등방향 방사전력을 산출한다. 이러한 높은 정확도의 WSD 무선자원 할당 방안을 통해 WSD가 국내 기술기준을 만족하면서 주변 픽셀로의 유해한 간섭을 제거하고 주파수 효율을 향상시켰다. portable white space device(WSD) obeying the Korean regulations of TV white space(TVWS) can cause harmful interference to a digital TV receiver residing at the same pixel around the edge of the digital TV service coverage for the case with a changed propagation environment. In order to solve this problem, we propose a method to allocate the resource of a hybrid WSD based on TVWS geo-location DB with spectrum sensing. Using the received power of digital TV signal through the spectrum sensing, a hybrid WSD can calculate the maximum permitted EIRP based on location probability. Based on the accurate allocation method proposed in this paper, it is possible to satisfy the Korean TVWS regulations and to eliminate the harmful interference to TV receivers nearby the hybrid WSD.