TV White Space Channels Research Articles

대한민국 남해상(부산-제주도)에서의 TVWS 가용채널 이용에 관한 연구

This paper describes the first study in Korea on the use of available TV white space (TVWS) channels that can be used in the South Sea for terrestrial digital television (DTV) broadcasting bands. Focusing on the Busan-Jeju route in the Soutn Sea of Korea, the possibility of using TVWS frequencies of DTV broadcast signals (channels 14-51 and 470∼698 MHz) was studied. Through the characteristic analysis of domestic DTV channels and other unusual measurement data, the DTV spillover signals of Japan are confirmed, and it is deduced that the available TVWS channels that could be used in the South Sea are affected. The analysis confirmed that channel No. 39 (623 MHz) can be used as an available channel for TVWS without interference from existing DTV channels in all seas between Busan Port and Jeju Port. Additionally, two channels, channel 45 (659 MHz) and 47 (671 MHz), were found to be available for the TVWS frequencies on the Busan-Jeju Island route section, excluding Busan Port and Jeju Port.

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.

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.

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.

Dynamic spectrum access for M2M-WANs: the African regulator's spectrum policy reform conundrum

This paper presents work that has been done to address the network capacity demands for internet of things (IoT) and machine-to-machine (M2M) communications, based on efficient management and utilisation of radio spectrum resources. IoT/M2M applications are predicted to exponentially grow and cause a massive up-surge in network traffic increase. We argue that existing mobile network architectures are not optimised to handle billions of small intermittent transactions generated by M2M connections, therefore, a technology based on dynamic spectrum access (DSA)-enabled low-power M2M-wide area networks (WANs) is proposed. Subsequently, the article presents a use-case scenario demonstrating a possible deployment of a smart metering M2M-WAN using TV white-space (TVWS) channels and geo-location spectrum database technique. The simulated experimental M2M-WAN showed that with only four TVWS channels an entire metropolitan city can be covered to provide smart-metering services. Furthermore, the article suggests changes in existing spectrum management policies and technical regulations to accommodate the new DSA-based technologies. Hence a cost-effective techno-regulatory-policy model is suggested to promote DSA-enabled low-power M2M-WANs.

Cognitive Communications for Commercial Networked Earth Observing Fractionated Small Satellites

Low cost fractionated small satellites have emerged as suitable infrastructure for future earth observations. They enable private operators to interactively deliver commercial earth observation services. Private operators have own meteorological networks (MetNets). These MetNets comprise ground and space segment infrastructure. MetNets are also expected to be robust and have enhanced quality of service. They require new communications systems to meet these requirements. This paper presents two mechanisms that meet these requirements. These mechanisms are incorporated in the space and ground segments of a future generation MetNet model. This model is called the cognitive earth observation network model (COEN). COEN comprises hybrid meteorological ground stations (HMGS) and fractionated small satellites in the ground and space segment respectively. The HMGS is hybrid and functions in primary mode using TV white space channels (TVWS) and in hybrid mode when it bonds channels of other networks that are predicted to be idle with own TVWS channels. The performance of COEN is evaluated using channel prediction accuracy, data availability, throughput and latency. The throughput, data availability and latency of COEN is compared with that of an existing network model. Results show that COEN outperforms existing model.

Throughput-Efficient Channel Allocation Algorithms in Multi-Channel Cognitive Vehicular Networks

Many studies show that the dedicated short range communication band allocated to vehicular communications is insufficient to carry the wireless traffic generated by emerging vehicular applications. A promising bandwidth expansion possibility presents itself through the release of large TV band spectra (i.e., the TV white space spectrum) by the Federal Communications Commission for cognitive access. One primary challenge of the so-called TV white space (TVWS) spectrum access in vehicular networks is the design of efficient channel allocation mechanisms in face of spatial-temporal variations of TVWS channels. In this paper, we address the channel allocation problem for multi-channel cognitive vehicular networks with the objective of system-wide throughput maximization. We show that the problem is an NP-hard non-linear integer programming problem, to which we present three efficient algorithms. We first propose a probabilistic polynomial-time (1-1/e)-approximation algorithm based on linear programming. Next, we prove that the objective function can be written as a submodular set function, based on which we develop a deterministic constant-factor approximation algorithm with a more favorable time complexity. Then, we further modify the second algorithm to improve its approximation ratio without increasing its time complexity. Finally, we show the efficacy of our algorithms through numerical examples.

Some Are Born With White Space, <italic>Some Achieve White Space</italic>, and Some Have White Space Thrust Upon Them

A few steps from Shakespeare's spiritual home The Globe Theatre in London, the U.K. regulator Ofcom is formulating its own well-crafted play based on TV white spaces (TVWSs). Such work comfortably fits into the Shakespearean analogy of “some achieve white space” through implementation of clever twists to make white space available while not causing harmful interference to incumbents, noting that the U.K. is extremely busy in terms of spectrum usage. This paper reports on some of the work of by our trial within the Ofcom TVWS Pilot, building key observations on beneficial usage scenarios for TVWS through link testing examples. It also particularly investigates performance of TVWS in terms of availability and capacity, through these scenarios and more generally, strongly focusing on aggregation of TVWS resources. A number of key observations result from this paper, some of which we highlight here. First, in the U.K., and in Europe in general where local DTT deployment characteristics and landscapes are similar to the U.K., TVWS has most benefit potential in below-rooftop receiver and indoor deployments. This is even more so if local white space device (WSD) deployment is extensive. Given this, we define and assess key baseline scenarios that we term as “mobile broadband downlink” and “indoor broadband provisioning” (akin to Wi-Fi or small cells in TVWS). We also argue comparison with other scenarios/topologies through parameter changes, and we further demonstrate the strength of TVWS for the indoor case through link performance tests. A second key observation is that good TVWS availability is achieved through the sophisticated regulatory approach of Ofcom, noting that the same approach to TVWS is harmonized across Europe through the ETSI EN 301 598 standard. However, this is affected by scenario: high power, high transmitter (e.g., 30 m above ground level) scenarios have a particularly reduced and variable availability. Further, high capacities are achieved by aggregating TVWS channels, especially if non-contiguous aggregation is supported; and moreover, profound implications for WSD RF design are derived based on such results, particularly under contiguous aggregation or channel bonding. A third key observation is that TVWS yields significant future potential, despite headwinds such as the WRC 2015 decision to allocate 694-790 MHz to mobile broadband on a co-primary basis in ITU region 1.

Dynamic Deployment of Small Cells in TV White Spaces

The operation of small cells in TV white spaces (TVWSs) represents a coexistence challenge due to their unplanned deployment, their heterogeneous transmission technologies, and the scarcity of TVWS channels in crowded cities. Whenever a new small cell is switched on, a spectrum reassignment of already-deployed small cells can be used to avoid high interference and enable coexistence. However, as users may turn on and off their small cells at times, these reassignments may lead to frequent reconfigurations of already-deployed small cells. For this reason, a solution named small-cell dynamic deployment (SCDD) is designed to reassign TVWS channels only to the small cells in the neighborhood of the new cell. A channel allocation is proposed for SCDD formulated as an exact potential game. Its exact potential function is the sum of the average capacity of the small cells considered in the game. Results show that SCDD requires a few channel reconfigurations of already-deployed small cells because the channel assignment outside the neighborhood of the new cell remains unchanged. However, SCDD performs similarly to the case in which the allocation may modify the channels of all small cells already deployed.

Pricing Model for TV White Spaces Channels With Different Priorities

A new type of TV white space (TVWS) channel called the high priority channel (HPC) has been proposed by the regulator of Singapore. The HPCs are TVWS channels that will always be available to unlicensed white space devices (WSDs) although a white space database (WSDB) provider may impose fees to WSDs for using HPCs. The HPC is of interest to WSDB providers since it creates a new business opportunity for them. In this letter, we investigate the optimal fee for using HPCs such that the WSDB provider achieves the maximum revenue. The solution of the optimal fee is provided in this letter. From this study, it is observed that WSDB provider should not always increase the fee when the total number of WSDs increases as our results show that sometimes lowering the fee to attract more WSDs to use HPCs actually increases the revenue.

Interplay Between TVWS and DSRC: Optimal Strategy for Safety Message Dissemination in VANET

In vehicular safety systems, two types of safety messages are required: Emergency Safety Message (ESM) and Periodic Beacon Message (PBM). The ESM has to be disseminated within a specified area with stringent delay and delivery ratio requirements, while the PBM does not need to meet these requirements. For exchanging the safety messages in Vehicular Ad-hoc NETwork (VANET), Inter-Vehicle Communication (IVC) is necessary whose de facto standard is Dedicated Short-Range Communications (DSRC). However, the effective transmission range in the DSRC-based IVC is short since a signal can be attenuated due to blocking by obstacles. In order to cover a large dissemination area in the DSRC-based IVC, multi-hop dissemination is required, which however causes channel collision and network congestion. Moreover, the coexistence with PBMs aggravates the collision and the congestion, which make it hard to satisfy the requirements of the ESM dissemination. To overcome the limitation of the DSRC, we utilize an extra TV White Space (TVWS) band that has a large communication range for ESM disseminations, and exploit a DSRC band for 1) the exchange of control data and 2) the compensation of ESM reception errors. In this paper, we propose and analyze a distributed channel usage framework that exploits advantages of DSRC and TVWS bands for ESM dissemination under the existence of PBMs. Our scheme employs TVWS Channel Rendezvous Algorithm (TCRA), ensuring that vehicles within a dissemination area select the same channel with the ESM sender. To compensate ESM reception failures in a TVWS band, our scheme adopts Two-Way Recovery Algorithm (TWRA) that uses DSRC and TVWS bands for ESM retransmission. Further, we establish an analytical delivery ratio model that considers a delay bound of an ESM for optimal parameter selections. To the best of our knowledge, this is the first attempt to propose a distributed channel usage scheme that leverages the strengths of TVWS and DSRC bands for safety message dissemination. Through an in-depth simulation study, we show that the proposed scheme satisfies ESM requirements for latency and packet delivery ratio, and outperforms previous approaches in various vehicular scenarios.

Field tests and indoor emulation of distributed autonomous multi-hop vehicle-to-vehicle communications over TV white space

Vehicular networking has significant potential to enable diverse range of applications, including safety and convenience. As the number of vehicles and applications using the specially designated wireless spectrum grow, one can expect substantial increase in the bandwidth requirements. In this paper and demonstration, we advocate that dynamic spectrum access techniques facilitating the utilization of white spaces for vehicles will be the first step towards solving the expected spectrum shortage. In the demonstration, we will introduce field tests of a multi-hop inter-vehicle communication system with distributed and autonomous TV white space channel selection, performed in Japan from January to February 2012. Furthermore, in addition to the field test videos, we will show an indoor emulation of the entire system used during the field tests in the vehicles.