TV White Space Research Articles

Correlation-Based Spectrum Sensing With Oversampling and Optimal Weights Selection for OFDM-Based Networks Coexistence in TVWS

Regulatory bodies recognize the possibility of an unlicensed and dynamic access to the TV-white spaces. As a consequence, it is expected that heterogeneous and independently operated networks will be interested in sharing the same bandwidth within the same service area. Along this direction, this article addresses the coexistence among multiple heterogeneous secondary networks (SNs) operating in the TV-white spaces by proposing a weighted autocorrelation-based spectrum sensing technique. This is designed for orthogonal frequency division multiplexing signals and is based on an efficient exploitation of the correlation properties of the received signal induced either by the cyclic prefix and by the potential oversampling at the receiver. In particular, the proposed approach enables the identification of concurrent SNs, belonging to a predefined set, suitably selecting the optimal autocorrelation weights. Furthermore, it is shown that the proposed scheme can operate in a blind mode to detect a potential unknown SN. A theoretical analysis is proposed in order to derive the false alarm probability of the proposed detector to prove that this is a Constant False Alarm Detector. Finally, performance comparisons with alternative schemes, by resorting to computer simulations, are presented to highlight the advantages of the proposed solution.

Primary User Protection Contour and No-Talk Zone Characterization for TV Whitespace Spectrum Reuse in Nigeria.

To encourage secondary spectrum access within the TV broadcast bands in Nigeria, the propagation properties of TV signals on the VHF and UHF frequency ranges were empirically studied through measurements carried from two TV stations. The Pathloss exponent for the VHF band was found to be 1.9 with a characterised Pathloss equation for VHF band computed as 𝑷𝑳 (𝒅𝑩)=𝟖𝟒.𝟎𝟒+𝟏𝟗.𝟎𝟑𝒍𝒐𝒈𝟏𝟎(𝒅), where (𝒅) is the distance from the transmitter to the receiver. The UHF band Pathloss exponent was computed to be 1.8 with a Pathloss equation characterised as 𝑷𝑳 (𝒅𝑩)=𝟓𝟕.𝟑𝟓+𝟏𝟕.𝟗𝟔𝒍𝒐𝒈𝟏𝟎(𝒅). The findings re-echoed the need for specific prediction model to accurately estimate the service coverage of TV stations and facilitate effective utilization of spatial TV white space as it was found that there were divergence in coverage prediction between the measured model and some of the conventional models. Using the protection view point, the protection contour in kilometers for TV signals propagating in the UHF band in Nigeria was characterized to be 𝒅𝒓𝒑= 𝟏𝟎[𝑷𝒕+𝟑𝟐.𝟔𝟓 𝟏𝟕.𝟗𝟔].. Where (𝒅𝒓𝒑) is the protection contour radius modeled as a function of the transmit power of the TV station in decibels with reference to one milliwatt (dBm) for co-channel and adjacent channel coverage. Similarly, the no-talk-zone in kilometers was characterized as a function of the transmit power of the secondary user device in dBm for co-channel usage to be 𝒅(𝒓𝒏−𝒓𝒑)=𝒂𝒏𝒕𝒊𝒍𝒐𝒈[𝑷𝒔−𝟖𝟗.𝟕𝟔𝟏𝟕.𝟗𝟔] modeled as a function of the secondary user transmit power 𝑷𝒔. The separation distance in kilometers from the TV station to the possible secondary user transmitter beyond which no interference exist was computed to have a relationship equal to 𝒂𝒏𝒕𝒊𝒍𝒐𝒈⟦𝑷𝒕+𝑷𝒔−𝟓𝟕.𝟏𝟏𝟏𝟕.𝟗𝟔⟧. This model will facilitate TVWS co-channel coexistence using the specified equation to determine the separation distances between television transmitters and secondary user transmitters.

A review of microstrip antenna designs for TV white space applications

<p><span>A review on prominent microstrip antennas fabricated for TV White Space applications is presented. This paper will delve into some of the most notable microstrip antenna designs in this frequency band that have come up in recent years. They will be analyzed to identify their strengths and weaknesses, and feedback is provided on their perceived usefulness. These antennas are designed with specific intentions, such as being placed in areas prone to harsh weather, or for long distance communications. One of the most recent antenna types to enter mainstream discussion is the microstrip patch antenna, which can easily be altered to fit various applications. Methods of connectivity such as TV White Space are enthusiastically used in various applications pertaining to connectivity and various microstrip antennas have been designed for this purpose. A conclusion was reached on the compact shorted printed monopole antenna being the most plausible choice from the antennas that have been considered and discussed.</span></p>

Delay-Minimized Edge Caching in Heterogeneous Vehicular Networks: A Matching-Based Approach

To enable ever-increasing vehicular applications, heterogeneous vehicular networks (HetVNets) are recently emerged to provide enhanced and cost-effective wireless network access. Meanwhile, edge caching is imperative to future vehicular content delivery to reduce the delivery delay and alleviate the unprecedented backhaul pressure. This work investigates content caching in HetVNets where Wi-Fi roadside units (RSUs), TV white space (TVWS) stations, and cellular base stations are considered to cache contents and provide content delivery. Particularly, to characterize the intermittent network connection provided by Wi-Fi RSUs and TVWS stations, we establish an on-off model with service interruptions to describe the content delivery process. Content coding then is leveraged to resist the impact of unstable network connections with optimized coding parameters. By jointly considering file characteristics and network conditions, we minimize the average delivery delay by optimizing the content placement, which is formulated as an integer linear programming (ILP) problem. Adopting the idea of student admission model, the ILP problem is then transformed into a many-to-one matching problem and solved by our proposed stable-matching-based caching scheme. Simulation results demonstrate that the proposed scheme can achieve near-optimal performances in terms of delivery delay and offloading ratio with low complexity.

TV white spaces exploration for cognitive radio: taxonomy and research issues

In order to implement the interweave cognitive radio solutions, the research for finding sparsely utilized spectrum bands has revealed the VHF and UHF television broadcast bands, known as television white spaces (TVWS) as the foremost candidate. The TVWS quantification and throughput analysis conducted via several measurement attempts and field trials uncover various facets of the TVWS spectrum measurement. Consequently, the conclusions obtained may be processed to get a statistical knowledge about spectrum availability in a particular geographic region and hence utilized for spectrum management. This paper explores inherent methodologies used for TVWS assessment and provides a comprehensive overview of the TVWS regulatory norms, results obtained by TVWS measurement campaigns and field trials conducted worldwide. In addition, research issues, implementation challenges and future directions for TVWS measurement procedure are highlighted.

Assessment of Error Bounds for Path Loss Prediction Models for TV White Space Usage in Ekiti State, Nigeria

Assessment of Error Bounds for Path Loss Prediction Models for TV White Space Usage in Ekiti State, Nigeria

Dynamic Interference Optimization in Cognitive Radio Networks for Rural and Suburban Areas

In this paper, we investigate the coexistence of cognitive radio networks on TV white spaces for rural and suburban connectivity. Although experimental models and laboratory measurements defined the maximum interference threshold for TV white space technologies for general use cases, our research found that in real wireless rural and suburban scenarios, severe interference to the broadcasting services might occur. This is particularly relevant when the traffic load of the telecom base stations (BSs) exceeds 80% of their maximum capacity. We propose a dynamic management algorithm for minimizing the interference, based on a centralized access control architecture for cognitive radio wireless networks. In an experimental emulation for assessing the impact of cognitive radio interference on the broadcasting service’s QoE, our method reduced the perceived video distortion by the broadcasting users by at least 50% and 27.5% in a rural and suburban scenario, respectively, while the spectrum usage is increased by just 8%.

Proposed Joint Propagation and Reinforcement Learning-based Television White Space Ledger

Proposed Joint Propagation and Reinforcement Learning-based Television White Space Ledger

Optimal crowd-augmented spectrum mapping via an iterative Bayesian decision framework

Recent spectrum measurements show that geo-location spectrum databases are inaccurate in Metropolitan areas by missing a large number of TV white spaces (TVWS). To counter this challenge, this paper introduces a crowd-augmented spectrum database, whose spatial resolution and accuracy are continuously and opportunistically augmented by the spectrum sensing data from the crowd of mobile users. To augment the accuracy of our database to a desired level, an iterative Bayesian decision framework is proposed, which coherently combines two major modules over multiple rounds, including (1) Bayesian spatial prediction for optimal prediction of the power spectrum density (PSD) values at different spatial locations under parameter uncertainty and (2) Bayesian experimental design for efficient selection of the locations with high utility for additional sampling. The proposed framework is implemented and verified within our university main campus. Abundant spectrum opportunities are discovered, compared with the traditional geo-location databases, e.g., Google spectrum database.

Streaming Delay-, Expenditure- and Quality-Balanced Video Over TV White Space

This paper develops a solution for video delivery over TV white space (TVWS) that can achieve a balanced tradeoff between expenditure, delay and quality. TVWS channels can be classified into two types, i.e., free TVWS channels (FTCs) and high-priority TVWS channels (HPCs). However, the development of this system encounters many challenges because of the time-varying TVWS available status, dynamic HPC spectrum leasing price, fluctuated data size of group of pictures, and diverse user requirements. To address the above issues, we first build a video data model and a TVWS model. Then, we formulate two optimization problems i) expenditure minimization subject to video quality requirement and target delay, and ii) delay minimization subject to video quality requirement and limited total budget, both of which are linear integer programming problems. Next, we develop online and offline algorithms for these two optimization problems. Finally, we implement a T VWS-based V ideo D elivery S ystem (TVDS) based on a cognitive wireless network, which can use FTCs or lease HPCs to provide point-to-point (P2P) video data delivery service. The proposed algorithms are implemented in the TVDS, and extensive simulations are presented to verify the effectiveness of the proposed algorithms under different conditions.

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.

Propagation curves and coverage areas of digital terrestrial television base stations in the tropical zone

This study investigated the propagation curves and coverage areas of some Digital Terrestrial Television Broadcast Stations (DTTBS) over four climatic zones of coastal (Lagos), tropical rain forest (Akure), Sudan Savannah (Kaduna) and Sahel Savannah (Katsina) cities of Nigeria. Measurement of the Received Signal Strength (RSS) was carried out along different routes with each of the DTTBS as reference points. Measurements of RSS were carried out using two specified antenna receiver heights of 1.5 and 3.0 m for each data point. The GPS receiver was used to measure the geographic coordinates, elevation and Line of Sight (LOS) of data points along the routes in a drive test. Measurement was done during dry and wet season months at 1 km interval up to about 20 km in each of the selected routes covering a period of three years (2016–2018). Mean data were obtained and used to generate the propagation curves and the coverage areas over the study locations. Generally, results revealed that RSS undulates with LOS separation distance from DTTBS in all routes irrespective of seasons and routes. Particularly, RSS reduces to about half of its base station's value at about 8 and 12 km LOS from the DTTBS in Akure and Katsina respectively while, it reduces to about half of its base station's value at about 6 km from the DTTBS in Lagos and Kaduna. The implication of this is that higher coverage areas were obtained in suburban compared to urban cities. In addition, radial maps showing coverage areas and their grades useful for networking purposes were generated. Television White Spaces (TVWS) for secondary users were also proposed. For networking purposes and spatial arrangements of DTTBS that will ensure optimum coverage over the study locations, DTTBS can be sited at 8.0 and 13.5 km (LOS) interval from each other in urban and sub urban cities respectively. The overall results will enable system engineers to know the appropriate distance(s) and locations to site additional DTTBS for networking purposes and prepare power budget for optimum coverage area and good quality of services for terrestrial digital channels.

Harmonious Coexistence of IEEE 802.11af Wireless LAN and Digital TV

ABSTRACT Congested Industrial, Scientific, and Medical (ISM) band stifles the growth of Wireless Local Area Network (WLAN). The recent switchover from analog to digital TV (DTV) broadcast frees from the conventional TV bands a sizeable amount of spectrum, which is commonly called TV white space (TVWS). TVWS is very attractive to many wireless technologies, including WLAN. IEEE came up with 802.11af, the standard for the WLAN technology that operates in TVWS. Nevertheless, it is unsure how best to guarantee its operation not causing harmful interference to DTV. In this paper, we present the conditions required for harmless coexistence of IEEE 802.11af WLAN and DTV. We make use of the standard prediction method based on radio propagation characteristics, i.e. the ITU-R P.1411-9 method which has been adopted in communication system planning. Based on our findings, we suggest the followings: (1) Operate IEEE 802.11af WLAN at any adjacent channel other than the first (i.e. except the closest neighbour channel). (2) The height of IEEE 802.11af installation does play a part when there is a relatively large separation distance between the WLAN and DTV (e.g. 50 m). (3) For outdoor operation, IEEE 802.11af WLAN should be installed at the second, third, or fourth channels adjacent to the DTV’s; fifth or sixth adjacent channel for indoor operation.

QoS aware distributed dynamic channel allocation for V2V communication in TVWS spectrum

Vehicles use Dedicated Short Range Communication (DSRC) standard for communicating among themselves. But, with the increased number of on-road vehicles, DSRC channels get congested. So, an alternative to DSRC needs to be introduced, to meet the diverse demand for various vehicular applications. Federal Communication Commission released TV White Space (TVWS) for dynamic spectrum access. These TVWS channels has the potential to be used for Vehicle-to-Vehicle (V2V) communication. However, the vehicles are highly mobile and communicate in an adhoc manner. Thus, employing TVWS in V2V communication requires efficient optimized channel allocation technique. In this work, a distributed joint channel and power allocation technique is devised, that considers both spatio-temporal change of TVWS availability and vehicular mobility. The channels are allocated based on user's transmission requirement with an adjusted power level such that significant interference is not caused to neighbouring primary users and other secondary users, transmitting in the same channel. Multiple vehicles are assigned a single channel using the proposed optimization technique to increase the system throughput. Vehicles are enabled with cognitive facility that allows them to sense the spectrum availability instead of relying on the geo-location TVWS database. The optimized channel and power allocation problem is a Mixed Integer Non-Linear Programming model which is solved using Lagrange's dual method. Simulation analysis shows that proposed optimization technique achieves high throughput while maintaining the network's QoS.

Integrating Low-Power Wide-Area Networks for Enhanced Scalability and Extended Coverage

Low-Power Wide-Area Networks (LPWANs) are evolving as an enabling technology for Internet-of-Things (IoT) due to their capability of communicating over long distances at very low transmission power. Existing LPWAN technologies, however, face limitations in meeting scalability and covering very wide areas which make their adoption challenging for future IoT applications, especially in infrastructure-limited rural areas. To address this limitation, in this paper, we consider achieving scal-ability and extended coverage by integrating multiple LPWANs. SNOW (Sensor Network Over White Spaces), a recently proposed LPWAN architecture over the TV white spaces, has demonstrated its advantages over existing LPWANs in performance and energy-efficiency. In this paper, we propose to scale up LPWANs through a seamless integration of multiple SNOWs which enables concurrent inter-SNOW and intra-SNOW communications. We then formulate the tradeoff between scalability and inter-SNOW interference as a constrained optimization problem whose objective is to maximize scalability by managing white space spectrum sharing across multiple SNOWs. We also prove the NP-hardness of this problem. To this extent, We propose an intuitive polynomial-time heuristic algorithm for solving the scalability optimization problem which is highly efficient in practice. For the sake of theoretical bound, we also propose a simple polynomial-time 1/2-approximation algorithm for the scalability optimization problem. Hardware experiments through deployment in an area of (25x15)sq. km as well as large scale simulations demonstrate the effectiveness of our algorithms and feasibility of achieving scalability through seamless integration of SNOWs with high reliability, low latency, and energy efficiency.

English

English

TV White Spaces Handover Scheme for Enabling Unattended Track Geometry Monitoring From In-Service Trains

Now more than ever, monitoring railway track geometry from in-service vehicles is an attractive proposition that ensures improved infrastructure performance without interrupting railway operations. Communicating the collected sensors-data to a central server has always been an issue due to the current GSM-R and LTE data-rate and spectrum limitations. The prospect of opportunistic access to an inefficiently utilised frequency spectrum, known as TV White Spaces (TVWS), is proposed to solve the spectrum scarcity problem that exploits desirable railway propagation characteristics. In order to provide full protection for the spectrum primary users, IEEE 802.22 standard sets strict policies on the mobile platforms. This research proposes a novel handover scheme that utilises a greedy algorithm to select the operational frequency channels. The scheme takes into account; the train's trajectory, including the possibility of train delays, and coexistence issues between the spectrum's secondary users. A case study of two trains reporting their collected maintenance data to 3 Access Points (APs) while travelling between Selly Oak and New Street Station, Birmingham, UK is presented. For high channels availability (≥40%), an average of 30 megabytes of extra track data can be transmitted using the new approach for an 8 min journey. In addition, a single channel can be used in the new approach for an average consecutive distance of 1.05 km compared with an average of 0.58 km for IEEE 802.22 standard. Both systems provide identical interference performance with more transmission power that can reach up to 42.2 dBm allowed under the new scheme.

A CDL-Based Channel Model With Dual-Polarized Antennas for 5G MIMO Systems in Rural Remote Areas

In the fifth-generation 5G mobile networks, it is expected that users experience high throughputs with an ultra-low-latency network, while a massive number of devices are connected to the network. However, in remote rural areas, there is still a large number of people that do not have access to broadband Internet. To overcome this issue, a possible strategy is to exploit the excellent propagation conditions of very high frequency (VHF) and ultra-high frequency (UHF) bands by allowing secondary spectrum reuse in the TV white space (TVWS) channels. But for that, a reliable channel model is required to perform valid coverage and data rate prediction studies. In this paper, a channel model is proposed that takes into account large and small scale fading effects, as well as the particularities of such remote rural areas. The proposed model makes use of measurements along with the clustered delay line CDL profiles from 3rd Generation Partnership Project (3GPP). It is a simple model to implement and can be used to provide fast link and system-level simulations. Numerical and analytical results are provided to validate the proposed model and a data rate evaluation is carried out for single-input single-output (SISO) and multipleinput multiple-output (MIMO) configurations, as well as for single-polarized (SP) and dual-polarized (DP) antennas.

AGRO-GAIN - AN ABSOLUTE AGRICULTURE BY SENSING AND DATA-DRIVEN THROUGH IOT PLATFORM

Abstract The Agro-gain provides an end-to-end lot platform for data-driven agriculture, that gives an seamless data collection from various sensor type like drones, cameras and sensors. Agro-gain can ensure the availability of system even when the power and internet outages caused by bad weather. First, to enable connectivity within the farm, Agro-gain leverages recent work in unlicensed TV White Spaces (TVWS) to setup a high band width link from the farmer’s home Internet connection to an IoT base station on the farm. Sensors, cameras and drones can connect to this base station over a Wi-Fi frontend. This ensures high bandwidth connectivity within the farm. However, due to the lack of power on the farm, the base station is powered by battery- backed solar power which suffers from power unreliability depending on weather conditions. As shown in past work, cloudy weather can reduce solar power output significantly and drain the batteries of the base station to shut it down. To solve this problem, Agro-gain uses a novel weather-aware IoT base station design. Specifically, it uses weather forecasts to appropriately duty cycle different components of the base station. To the best of our knowledge, this is the first weather-aware IoT base station design. Second, internet connection to the farm is typically weak and it is not sufficient to ship high bandwidth drone videos to the cloud. The Agro-gain uses a Gateway based design, where in a PC at the farmer’s home serves as a gateway for the farm data.

Hierarchical and Hybrid: Mobility-Compatible Database-Assisted Framework for Dynamic Spectrum Access

The protection of primary user activities plays a vital part in dynamic spectrum access. There are currently two types of schemes. One is based on spectrum sensing and the other one relies on spectrum database. There exist many works surrounding the subject of spectrum sensing, which requires high sensing accuracy, and thus poses extra time cost. Nevertheless, the database-based access scheme is receiving an increasing amount of devotion, e.g., IEEE 802.11af for TV white space. In comparison to spectrum sensing, nodes only need to look up the spectrum maps provided by the database. In this paper, we study the practical issues of the above two schemes, and propose a hierarchical framework, which enables the hybrid spectrum access scheme. In this framework, we build relatively reliable clusters, and have cluster heads connect to the spectrum database to assist nodes in their clusters. As a result, nodes with poor or no connections to the database can benefit from spectrum maps as well. The process of retrieving spectrum maps is formalized as a Markov Decision Process. Moreover, mobility compatibility is provided. We illustrate how the evolution of our hierarchical structure is affected by mobile nodes. We also propose a feasible algorithm to maximize the benefits that can be obtained from the database under the mobile environment. We model a virtual database and conduct simulations to reveal certain performances of our framework.