Television White Space (TVWS) Geo-Location Database Access by Personal Portable Device
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Television White Spaces (TVWS) coupled with Dynamic Spectrum Access and Cognitive Radio (DSA-CR) technologies are increasingly viewed as key enablers to the bridging of the digital divide in rural areas. However, in order to realize maximum benefits of TVWS, spectrum regulators need to implement reforms to their archaic static spectrum management approaches to allow dynamic spectrum sharing among different players. In this context, this paper investigates the emerging regulatory, standardization, and technological trends necessary to the exploitation of TVWS for the provisioning of wireless broadband in rural areas, particularly in the developing regions. In such scenarios, we show that the incumbent (in this case TV broadcaster) could be better protected from potential harmful interference of the secondary users through the use of regulator controlled spatial-temporal databases. Simultaneously, the delivery of low-cost service(s) to the end-user(s) could be achieved by the telecommunication operator through the use of bridged TVWS/WiFi Access Points (APs).
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Due to the transition to digital TV (DTV); recently, many countries allow TV white spaces to be used by unlicensed devices. TV White Spaces is considered as an important step towards providing broadband access to millions of digital dividend household around the world and enabling a wide range of innovative wireless devices and services. The key challenge of TV white space systems is to have capabilities to avoid causing harmful interference to licensed services in the TV band as well as unlicensed devices. This requires that TV band devices (TVBDs) must be aware of the presence of each other and with incumbent devices in TV band. Specifically, TVBDs should have the ability to determine whether a TV channel or frequency band is unused before it could transmit. Due to the difficulties associated with sensing and to ensure high protection to broadcaster devices, geo-location database has been proposed recently, where each devices before transmit need to contact the database -at least once per day- and get the idle frequency carrier.
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Recent FCC regulations on TV white spaces allow geo-location databases to be the sole source of spectrum information for white space devices. Geo-location databases protect TV band incumbents by keeping track of TV transmitters and their protected service areas, based on each transmitter location and transmission parameters using sophisticated propagation models. In this article, we show that keeping track of both TV transmitters and TV receivers (i.e., TV sets) can achieve significant improvement in the availability of white spaces. We first identify temporal and spatial wasted spectrum opportunities due to the current approach to white space detection. We then propose our DynaWhite architecture, which is responsible for orchestrating the detection and dissemination of highly dynamic, real-time, and fine-grained TV white space information, based on both TV transmitter and receiver information. DynaWhite proposes the development of a new generation of geo-location databases that combine conventional geo-location databases with novel unconventional sensing approaches based on the detection of passive TV receivers using standard cell phones. We present a quantitative evaluation of the potential gains, reaching 24 extra 6 MHz channels in some cases, in white space availability for potential deployments of DynaWhite. We finally identify research challenges associated with the adoption of our DynaWhite architecture.
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Locally underutilized TV broadcasting spectrum is regarded as white space. Part of the TV frequency band, which is usually referred as 700MHz band, is excellent for radio communications due to its favorable radio propagation characteristic. This spectrum can be used to provide mobile broadband for the rural and mountainous areas effectively. Currently, this 700 MHz band is used exclusively for TV broadcasting. To open up the opportunity to other services, especially mobile broadband service, it is important that the new system should not cause harmful interference to the TV service areas. Strict requirements in terms of interference should be met. This paper evaluated the TV White Space (TVWS) in channel 43 in the Northern Part of Viet Nam by using the detailed terrain data and active TV stations database. Calculation results confirm that it is possible to allow TVWS devices (TWD) to operate in certain areas. The paper also suggested necessary regulation measures to ensure the coexistence of both services.
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Frequency allocation
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This paper is based on deployment of white spaces which are free or unused frequency space. This term related with Television frequency broadcast range is known as TV White Space (TVWS). So the transition of analog TV signals into digital TV signals results in creation of some more free frequency spectrum that also adds up to more TV white Spaces, since earlier TV channels which were being transmitted were allotted a certain UHF/VHF frequency channel bands. Now these TV channels are encoded digitally in a slightly different band and then transmitted. With this, the availability of White Space Spectrum has increased and so, many wireless solution providers are getting attracted to develop and deploy as opportunistic spectrum access in Wi-Fi like systems working on TV White Spaces. In time domain (TDMA) these white spaces can be referred as free or unused time slots. And are selected for transmission of messages using message generator, here selection and detection is done at transmitter section.
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This research is focused on evaluating the amount of television white space (TVWS) in the UHF band in Nigeria. The work takes a new perspective called the Geo-spatial approach in quantifying the available TVWS. Spectrum sharing model was developed from the protection viewpoint where the secondary users (SUs) are only allowed to reuse the spectrum outside the keep-out distance from the broadcast transmission grade B contour of the primary users. The spatial data used include the administrative map of Nigeria showing the states' boundary delineation and parameters for all the TV transmitters, including their coordinates. The broadcast range of transmission and protection contour of each UHF transmitter in Nigeria was obtained using the developed models. To show the broadcast range, the transmitter position, represented by a point, was subjected to GIS Buffering operation using the Analysis Tools extension within the ArcGIS ArcToolbox. Results obtained show that the proposed method recovers more white spaces when compared with the traditional command-and-control spectrum model. The work also provides the channel occupancy distribution of Nigeria, United Kingdom and the USA for the purpose of comparison.
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본 논문에서는 TV 유휴대역에서 가능한 응용서비스중 하나로서, UHF 대역(470~806 MHz)에서 동작하는 무선 영상전송 시스템을 구현하였다. 이 시스템은 RF 송수신기 모듈, 디지털 모뎀, 카메라, 스크린으로 구성된다. RF 송수신기와 디지털 모뎀을 연동하여 VGA급 화질의 카메라 영상을 2.6 인치 LCD 스크린에 표시하는 방식이다. RF 송수신기 구조는 크기와 비용을 줄이기 위해 직접변환 방식을 채택하였다. 성능지표인 Image Leakage를 향상시키기 위하여 PLL의 출력에 3차 하모닉 제거필터를 사용하였으며, DC offset 문제 해결을 위해 DAC 출력노드에 Current steering technique을 이용하여 공통모드 전압을 조절하게 하였다. 또한, 채널대역폭은 국가별 표준을 맞게 6, 7, 8 MHz 중 선택이 가능하다. 출력 파워와 수신감도는 각각 +10 dBm, -82 dBm이다. 디지털모뎀은 Kintex-7급 FPGA에서 구현하였다. QPSK와 512ch OFDM 변조를 기반으로 전송속도는 약 9 Mbps이다. 개발된 송수신 모듈을 이용하여 VGA급 화질을 무선으로 송수신하는데 성공하였다. In this paper, a wireless video streaming system is designed and implemented for TV white space applications. It consists of a RF transceiver module, a digital modem, a camera, and a LCD screen. A VGA resolution video is captured by a camera, modulated by modem, and transmitted by RF transceiver module, and finally displayed at a destination 2.6-inch LCD screen. The RF transceiver is based on direct-conversion architecture. Image leakage is improved by low pass filtering LO, which successfully covers the TVWS. Also, DC offset problem is solved by current steering techniques which control common mode level at DAC output node. The output power of the transmitter and the minimum sensitivity of the receiver is +10 dBm and -82 dBm, respectively. The channel bandwidth is tunable among 6, 7 and 8 MHz according to regulations and standards. Digital modem is realized in Kintex-7 FPGA. Data rate is 9 Mbps based on QPSK and 512ch OFDM. A VGA video is successfully streamed through the air by using the developed TV white-space RF communication module.
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Transceiver
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