Feasibility of Dynamic Spectrum Access in Underutilized Television Bands (original) (raw)
Related papers
The potential of VHF/UHF band as a candidate for secondary spectrum access, so called "TV white spaces", has been intensively investigated in recent years. However, the impact of the accumulated interference from multiple secondary users on different adjacent channels has not been well studied thus far, let alone the effect of combined interference from both co-channel and adjacent channels. This paper presents a framework for assessing secondary spectrum reuse opportunities for portable and mobile devices that comply with geo-location database concepts. The opportunity is evaluated in terms of the maximal number of secondary users that can access the "TV white space" simultaneously. Particular emphasis is given to the protection of TV receiver from harmful aggregate interference originated from not only the secondary users outside the TV coverage on the same channel but also those close to the TV receivers operating on different adjacent TV channels. An optimization problem is solved to maximize the number of secondary users admitted to the available TV channels at different locations. Through in-depth analysis of the interference characteristics of the optimal solution, it is identified that the cumulative effect of adjacent channel interferences has the dominant impact on TV reception, particularly for the case of secondary devices with limited transmit power. This suggests the possibility to achieve near-optimal exploitation of TV-bands for secondary reuse without explicit coordination of co-channel interference from the secondary users deployed over a wide geographical area.
Observations of Adjacent Channel Use by TV Band Secondary Devices
2007
This report presents observations from an ongoing study of the potential effects of unlicensed use of unoccupied television spectrum. These observations strongly suggest that secondary users could operate "White Space Devices" (WSD) in unoccupied channel bandwidth directly adjacent to a desired digital television (DTV) channel, with no observable adverse impact upon the reception of the desired channel content.
Measurements and Analysis of Secondary User Device Effects on Digital Television Receivers
EURASIP Journal on Advances in Signal Processing, 2009
This article presents results from a study of the potential effects of secondary users operating in unoccupied television spectrum. Television spectrum is known within the wireless communications community as being underutilized, making it a prime candidate for dynamic spectrum access. The proposed use of this open spectrum has prompted questions concerning the quantity of available channel space that could be used without negative impact on consumers who view digital television broadcasts and the viability of secondary use of open channels immediately adjacent to a digital television broadcast channel. In this work, we investigate secondary device operation in the channels directly adjacent to a desired television channel, and the effects upon a selection of consumer digital television (DTV) receivers. Our observations strongly suggest that secondary users could operate "White Space Devices" (WSDs) in unoccupied channel bandwidth directly adjacent to a desired digital television (DTV) channel, with no observable adverse impact upon the reception of the desired channel content.
Spectrum sensing for dynamic spectrum access of TV bands
… Wireless Networks and …, 2007
In this paper we address the issue of spectrum sensing in cognitive radio based wireless networks. Spectrum sensing is the key enabler for dynamic spectrum access as it can allow secondary networks to reuse spectrum without causing harmful interference to primary users. Here we propose a set of integrated medium access control (MAC) and physical layer (PHY) spectrum sensing techniques that provide reliable access to television (TV) bands. At the MAC level, we propose a two-stage spectrum sensing that guarantees timely detection of incumbents while meeting the quality of service (QoS) requirements of secondary users. At the PHY level, we introduce FFT-based pilot energy and location detection schemes that can detect a TV signal on a TV channel at levels as low as -116 dBm. We have evaluated these schemes through simulation and prototyping and show their effectiveness, reliability, and efficiency. These mechanisms are also part of the current IEEE 802.22 draft standard which is based on cognitive radio technology.
On the permissible transmit power for secondary user in TV white spaces
2012
Secondary spectrum access to TV white spaces is considered as a promising solution to relieve the spectrum shortage. In Europe, SE43 working group in CEPT is leading the discussion on the technical requirements for exploiting TV white spaces through the recent ECC report 159. Its analytical approach for determining the maximum permissible power for the secondary user, however, overestimates the power level, and leads to significant violation of the interference limit for TV reception. In this letter, we address the problem by proposing a new approach for determining the secondary user transmit power based on the framework established in ECC report 159. Monte Carlo simulation shows that our method keeps the interference close to the target.
Spectral occupation of TV broadcast bands: Measurement and analysis
Measurement, 2016
The findings of a TV broadcast spectrum measurement campaign, performed at six different locations on the Hatfield campus of the University of Pretoria, are presented. Since the use of television white spaces (TVWS) could help to alleviate the impending spectrum crunch, the motivation for the study was to identify possibly unused bands for use by emerging technologies, such as cognitive radio, and also to address the hidden node problem associated with spectrum sensing (SS). This was achieved by comparing measured data to both actual TV channel allocations and a geo-location database (GLDB) for the Tshwane metropolitan area (city of Pretoria). Localised measurements indicated that a number of TVWS opportunities existed, with between 216 and 376 MHz of spectrum found to be potentially available for secondary usage. However, a comparison with TV channel allocations (256 MHz free) and the GLDB (96 MHz free) highlighted the effect of the hidden node problem.
International Journal of Digital Multimedia Broadcasting, 2015
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 socalled 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.