TV White Space Systems Research Articles

Toward the Coexistence of Cognitive Networks for Vehicular Communications on TVWS for IEEE Std. 802.22

The IEEE 802.22 is a standard for wireless regional area networks to opportunistically operate in TV bands; however, sharing TV White Space (TVWS) spectrum creates a problem of coexistence because no mechanism is defined for coordinating channel usage among secondary networks. We propose a White Space Resource Sharing mechanism (WSRS) for fixed secondary and mobile IEEE 802.22 networks to improve network coexistence and spectrum efficiency. Based on power control and channel allocation, our mechanism allows the TVWS system to serve vehicular networks in scenarios where there are active secondary fixed networks and no more TVWS channels available for opportunistic usage. Unlike state-of-the-art mechanisms for coexistence in TVWS spectrum, our mechanism allocates resources to vehicles even when the density of fixed nodes and the transmission power of the fixed network cause high interference to the vehicular network. Our results show the offered channel capacity increases up to 50% using the proposed WSRS mechanism compared to the recent IEEE 802.22 standard that does not have a defined TVWS channel sharing mechanism. Furthermore, our WSRS mechanism implements a strategy to protect the fixed secondary network from interference caused by vehicular transmissions while promoting fair usage for both secondary networks.

Realistic Channel Estimation of IEEE 802.11af Systems in TV White Space

This work investigates the realistic performance of IEEE 802.11af systems released for the efficient spectrum utilization of TV white space (TVWS). These systems are operated over many contiguous or non-contiguous channels based on the TVWS frequency band availability. Accordingly, we consider realistic channel estimation for TVWS system and analyze the corresponding system performance of linear minimum mean square error (LMMSE) and orthogonal matching pursuit (OMP) algorithms. While LMMSE estimates channel path gains assuming perfectly known tap delay locations, OMP estimates both channel path gains and delays. Owing to the realistic implementation and estimating the full channel state information (CSI) of sparse channels, we mainly assess the OMP performance together with the LMMSE estimation for comparison in terms of channel reconstruction and symbol detection errors. To address the channel estimation performance, Bayesian Cramer-Rao bound is derived theoretically for both perfect and imperfect CSI, and confirmed with the simulations. Simulation results demonstrate that the realistic OMP-based symbol detection performance is found to be only 1–2 dB inferior compared to the near-optimal LMMSE-based estimation with known delays in low and medium signal-to-noise-ratio regions, where communication mainly occurs in practice. In addition, the effects of channel multipath number, channel resolution and operation modes on the system performance are studied for different scenarios. The results of this work are important for the practical implementation of IEEE 802.11af-based systems.

Paper: Propagation Loss Model in Short Range LoS Environment for TV White Space Systems using Low Antenna Height Base Station

Paper: Propagation Loss Model in Short Range LoS Environment for TV White Space Systems using Low Antenna Height Base Station

WATCH: WiFi in Active TV Channels

The “white space” model allows TV channels not being used regionally by a TV broadcaster to be re-purposed for secondary access. Unfortunately, populated areas have few unused channels. Nonetheless, Nielsen data show severe <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">under-utilization</i> with vast regions in range of TV transmitters having <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">no active TV receivers</i> even at peak TV viewing time. In this paper, we present the design, implementation, and evaluation of WiFi in active TV channels (WATCH), the first system to enable secondary WiFi transmission in the presence of kilowatt-scale TV transmitters. To protect active TV receivers, WATCH includes a smartphone-based TV remote controller or an Internet-connected TV to inform WATCH controller of TV receivers’ spatial-spectral requirements. To enable WiFi transmission in UHF bands, we design WATCH-interference cancellation and constructive addition transmission to 1) exploit the unique environment of asynchronous WiFi transmission in the presence of a strong streaming interferer, and 2) require no coordination with legacy TV transmitters. With FCC permission to test our implementation, we show that WATCH can provide at least six times the total achievable rate to 4 watt secondary devices compared to current TV white space systems, while limiting the increase in TV channel switching time to less than 5%.

Coexistence of DTV and TV white space systems

SummaryIt is foreseeable that in near future, heterogeneous TV white space (TVWS) systems will operate in underused TV bands. Potential interference between TVWS systems and digital TV (DTV) broadcast system is a major concern. These TVWS systems need to maintain from the DTV service boundary some keep‐out distances dk, which vary depending on circumstances. This work provides a comprehensive analysis on dk for different TVWS devices that operate on co‐ and adjacent channels, based on 2 different protection criteria for DTV service, using 4 different propagation models (each suits different propagation environment) for estimating dk. In brief, this article contributes to the mathematical technique of determining dk under different circumstances. On the basis of the conditions chosen for the analysis, we come up with some recommendations for dk. Moreover, we share our opinions on some regulatory requirements for dk. The strictness of the regulatory requirement in this matter is important because when it is appropriately set, it can actually promote further development and expansion of TVWS technologies.

An efficient channel selection and power allocation scheme for TVWS based on interference analysis in smart metering infrastructure

Nowadays, smart meter (SM) technology is widely effectively used. In addition, power allocation (PA) and channel selection (CS) are considered problems with many proposed approaches. In this paper, we will suggest a specific scenario for an SM configuration system and show how to solve the optimization problem for transmission between SMs and the data concentrator unit (DCU), the center that collects the data from several SMs, via simulation. An efficient CS with PA scheme is proposed in the TV white space system, which uses the TV band spectrum. On the basic of the optimal configuration requirements, SMs can have a transmission schedule and channel selection to obtain the optimal efficiency of using spectrum resources when transmitting data to the DCU. The optimal goals discussed in this paper are the maximum capacity or maximum channel efficiency and the maximum allowable power of the SMs used to satisfy the quality of service without harm to another wireless system. In addition, minimization of the interference to the digital television system and other SMs is also important and needs to be considered when the solving coexistence scenario. Further, we propose a process that performs an interference analysis scheme by using the spectrum engineering advanced Monte Carlo analysis tool (SEAMCAT), which is an integrated software tool based on a Monte-Carlo simulation method. Briefly, the process is as follows: The optimization process implemented by genetic evolution optimization engines, i.e., a genetic algorithm, will calculate the best configuration for the SM system on the basis of the interference limitation for each SM by SEAMCAT in a specific configuration, which reaches the solution with the best defined optimal goal satisfaction.

テレビホワイトスペースシステムのための低アンテナ高基地局による短距離見通し環境の伝搬損失モデル

テレビホワイトスペースシステムのための低アンテナ高基地局による短距離見通し環境の伝搬損失モデル