Leveraging on the Cognitive Radio Channel Aggregation Strategy for Next Generation Utility Networks

Spectrum scarcity demands for additional bandwidth where new services can be deployed on. However, today's spectrum allocation leaves almost no bands unallocated. Thus, Cognitive Radio has been studied to bring relief to the lack of spectrum, moving towards a more efficient and dynamic spectrum access. In this domain TV White Space have been proposed as a possible solution to bring new, valuable spectrum for opportunistic services. However, their availability is quite low in highly populated areas, and thus their viability is limited. This is mainly because the availability of TV White Space is typically considered at the rooftop, through two-dimensional propagation models which do not account for possible spectrum re-utilization policies within a building, or in a small-scale area. In this paper, we show that much more communication opportunities can be found when we consider also the third-dimension, i.e. the height from the terrain, and novel per-floor allocation policies. We propose three main contributions in this paper. First, we describe an analytical model through which we derive the number of available spectrum resources for indoor secondary networks, considering PU protection policies in the same building, and in surrounding buildings. Second, we estimate the number of TV Gray Space (TVGS) over realistic scenarios in candidate cities, considering realistic street topology and buildings locations, and we show that this value can be much higher than what reported in the spectrum database. Finally, we investigate co-existence of secondary networks on TVWS, when novel per-floor spectrum sharing models are used.

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.

OF THE THESIS Design Methodology for Backhaul and Distribution Networks Using TV White Spaces by Cyrus Gerami Thesis Directors: Narayan Mandayam and Larry Greenstein Since the FCCs approval of unlicensed use of TV white spaces, the issue of how to use these white spaces has led to innovative technologies such as cognitive radios as well as a variety of spectrum policy proposals. There have been proposals to devise alternate rules for spectrum usage citing the overly conservative restrictions on secondary transmissions to protect incumbents. In this thesis, instead, we propose to utilize white spaces for a backhaul network for internet traffic based on existing restrictions. Using the available white spaces and backhaul traffic demands in New Jersey as a case study, we evaluate the feasibility of such backhauling and present a methodology that can be used for other areas as well. Using a basic design involving fixed towers and directional antennas, our results show that the TV white spaces can be an effective medium for radio backhaul as an alternative to the costly laying of optical fiber. Although the most recent FCC ruling does not mandate protection of wireless microphones, we show that meeting the more stringent earlier FCC requirements on sensing and avoiding harm to wireless microphones would have only a minor impact on capacity. Finally, we study the aggregating of multiple data traffic flows at the nodes and show that, with proper engineering, multiple flows have but a slight effect on the need for optical fiber.

Cognitive Radio (CR) technology is one of the promising technology to efficiently utilize the unused radio spectrum. Recently, the Federal Communications Commission (FCC) allowed TV white space (TVWS) to be used for data communications provided the licensed user operations should be protected. The FCC made the rules and regulation for using the TVWS. Till now there is no real deployment of any communication system that operates on TVWS. As the first step towards the deployment of a communication system that operates on TVWS, we developed a UHF band CR test-bed based on ECMA-392 international standard. ECMA-392 standard defines the MAC and PHY for operation in TVWS for communication between portable devices. In this paper, we present the design and implementation of our test-bed system in detail. We also verified that the test-bed system operates in lines with the FCC rules.

We consider a non-cooperative Opportunistic Spectrum Access (OSA) where Secondary Users (SUs) access opportunistically the spectrum licensed for Primary Users (PUs) in TV white spaces (TVWS). As sensing licensed channels is time and energy consuming, we consider a hierarchical Cognitive Radio (CR) architecture, where CR base stations sense a subset of the spectrum in order to locate some free frequencies. Thereafter, a SU that needs to communicate through TVWS sends a request to a CR base station for a free channel. We model the problem using a Partially Observable Stochastic Game (POSG), and we take into consideration the energy consumption of CR base stations and the Quality of Services (QoS) of SUs. Since solving POSG optimally may require a significant amount of time and computational complexity, we model the OSA problem using a game theoretical approach, and we propose a symmetric Nash equilibrium solution concept. Finally, we provide some simulations that validate our theoretical findings.

The regulatory framework for secondary utilization of TV white spaces (TVWS) is well underway in the United Kingdom, while important steps in this direction are taken within the European Union and elsewhere. Mobile network operators are interested in the use of TVWS for cellular extension and rural access, where TVWS is seen as a significant new opportunity for operators to provide new wireless services. The government's plan to close the digital divide between the urban and rural communities has motivated the efforts to develop Wi-Fi like operation in TVWS for better coverage in rural areas. The IEEE currently has a working group developing 802.11af amendment which will allow for WLAN operations in the TVWS. This paper presents a quantitative analysis of downlink throughput performance of IEEE802.11af, also known as White-Fi in a rural environment while taking into account realistic modelling of TV channel availability, wireless channel, AP density, and the effect of co-channel interference caused by secondary APs and DVB-T transmitters. The paper shows that the low operating frequency of White-Fi offers a wide coverage in a rural environment, where there is limited cellular coverage due to the cost-inefficiency of base stations deployment. The presented results also show that there are more available TVWS channels and less co-channel interferers in a rural environment, resulting in a significant throughput performance even in high mobility if suitable channel estimation is considered, making it ideal for vehicular communications with White-Fi.

Cognitive Radio has now become a realistic option for the solution of the spectrum scarcity problem in wireless communication. TV channels (the primary user) can be protected from secondary-user interference by accurate prediction of TV White Spaces (TVWS) by using appropriate propagation modelling. In this paper we address two related aspects of channel occupancy prediction for cognitive radio. Firstly we investigate the best combination of empirical propagation model and spatial resolution of terrain data for predicting TVWS by examining the performance of three propagation models (Extended-Hata, Davidson-Hata and Egli) in the TV band 470 to 790 MHz along with terrain data resolutions of 1000, 100 and 30 m, when compared with a comprehensive set of propagation measurements taken in randomly-selected locations around Hull, UK. Secondly we describe how such models can be integrated into a database-driven tool for cognitive radio channel selection within the TVWS environment.

Preview studies have shown the current spectrum management is not efficient in which a lot of portions of the licensed spectrums are underutilized. TV White Spaces (TVWS) is one of the licensed spectrums that has many unused portions (white spaces) which can be utilized for many wireless broadband services such as WLAN (Wireless Local Area Networks), mobile phone services, and smart grid applications. Consequently there will be a need for more frequency resources in order to satisfy the rising demands for high capacity wireless systems as well as broadband in future. The cognitive radio is deemed a promising paradigm which uses idle spectrum portions in opportunistic manner resulting in increasing the overall spectral efficiency especially in the UHF TV broadcasting band. In this study, the spectrum occupancy measurements is performed in the UHF TV Band which has total (470 to 798) MHz in an indoor environment in a commercial city area of Kuala Lumpur, Malaysia. The analysis of the measurements and the identification of spectrum holes are conducted for two threshold values (-92.97dB and-88.97). The results have shown that the threshold value of -92.97 is better in the term of the accuracy in determining the spectrum occupancy. The results. also show that the average Duty Cycle which refers to the rate of utilized spectrum is (27.89%) which means a lot of portion of spectrum is available for employment of cognitive radio systems as well as TV White Spaces (TVWS) in the UHF TV broadcasting band.

Monitoring and sensing of spectrum are becoming more and more important, as the subject of using underused TV White Spaces (TVWS) spectrum by software defined radios (SDR) and cognitive radios is advanced forward towards practical applications. Correctly identifying available TVWS bands is critical for success of TVWS based broadband communications, not causing interference to reception of TV broadcast by TV receivers. This paper discusses side effects encountered with a popular design of a wire discone antenna. AntennaCraft model ST4 is exampled as an inexpensive candidate for spectrum monitoring and sensing in UHF frequency band. The study was done by both simulation and measurements, with well matching results. The candidate antenna was found to introduce notch banded loss in the system sensitivity. The influence of a potential mechanical damage onto the sensitivity of the antenna system has also been considered, and was found to be relatively small, under 3 dB.

In this paper, how to aggregate and allocate idle TVWS (TV White Space) bands for CR (Cognitive Radio) enabled TD-LTE (Time Division Long Term Evolution) system is investigated. Considering the limited spectrum aggregation capability of TD-LTE terminals, a Spectrum Aggregation algorithm with Minimum Spectrum Switch (SAMSS) is proposed to utilize the relatively wide and dynamic TVWS. Based on the theories of semi-Markov process and alternating renewal process, channel usage states of TVWS are constructed as an ON-OFF alternating model. Then, transition probabilities of the channel usage states are calculated and switching probability of the aggregation region is estimated by asymptotic analysis. The proposed algorithm finally selects the aggregation region with the smallest switching probability for UEs to minimize the number of spectrum switches during multiple sensing and transmitting periods. Numerical results show that the proposed algorithm outperforms the traditional methods by effectively reducing the number of spectrum switches in a long span of time, whilst guaranteeing favorable system access performance such as the total number of working UEs.Keywordsspectrum aggregationcognitive radioTD-LTEspectrum accessspectrum switchswitching probability

This paper introduces the use of the cognitive radio in the cellular system. Cognitive radio Approach aims to manage the traffic flow in dynamic systems. The cognitive radio is a self-aware communication system that efficiently uses spectrum in an intelligent way. The cognitive radio scheme offers several features like autonomy, negotiation and sensing. The use of cognitive radio gives greater autonomy to the base stations. This autonomy allows an increase in flexibility to deal with new situations in the traffic load. The negotiation is used to avoid conflict in the resource allocation. The proposed algorithm is very successful for two reasons. The cognitive radio handles the handoff problem that reduces the handoff blocking rate. The reduction of the call blocking rate in cellular networks will increase the accuracy and the reliability of the forecast model. A number of spectrum sensing techniques have been proposed. A spectrum scheme uses received signals to detect channel states. To improve the performance of spectrum sensing scheme new technique will be added to spectrum scheme. The new technique is channel states forecasting based on quality of experience.

The interest on Cognitive Radio (CR) technology is increased to efficiently utilize the unused spectrum. To investigate the feasibility of the CR system operating in TV white space, we have developed a CR test-bed which is based on the Ecma-392 standard. This paper presents the modem algorithms and implementation of physical layer module within the CR test-bed.

Recently, tremendous utilization of wireless networks has led to sever scarcity of radio spectrum resources. TV White Spaces (TVWSs) as novel bands enabling Cognitive Radio (CR) technology to improve spectrum resources utilization, have attracted significant standardisation efforts such as IEEE 802.11af, IEEE 802.16h and 802.22. As these heterogeneous networks may operate on the same channels of TVWSs, network coexistence problem cannot be avoided and is particularly challenging given the heterogeneous MAC/PHY layer protocols and operation parameters (e.g., tx power) employed in coexisting networks. In this paper, we develop a coexistence mechanism called ecological Species Competition based HEterogeneous networks coexistence MEchanism (SCHEME). Inspired by ecology based species competition model, SCHEME uses an ecological spectrum allocation method to assign available spectrums. Through both theoretical and simulation analysis, we demonstrate that SCHEME can achieve stable and fair spectrum allocation among coexisting networks.

In order to avoid the undesired interference with the activities of the primary users in cognitive radio networks, the secondary users are required to be able to predict the behavior of the primary users so as to leave the channel before the arrival of such licensed owner of the spectrum. While a number of existing literatures on cognitive radio spectrum prediction employ the use of propagation curves for predicting the spectrum holes otherwise known as TV white space, these models are built based on measurements conducted in regions that are different from Nigeria, suitability in terms of usage may therefore vary due to environmental factors and terrain profile. This work evaluates the efficacy of the developed model in predicting the cognitive spectrum availability in Nigeria. Models capable of predicting spectrum occupancy in the time domain using discrete-time two-state Markov chain with an appropriate Duty Cycle (DC) model and also a modified m-bell shaped exponential equation were formulated. The result obtained in all cases considered shows that the formulated models are appropriate to be used in any environment if the parameters were carefully extracted from the data. This work has also demonstrated that the accuracy of Markov chain models depends on the level of usage of a spectrum under consideration and may therefore not give desirable results when employed in some other spectrum.

Spectrum crunch is a severe issue for below 6GHz wireless communications. Cognitive radio and Dynamic Spectrum access (DSA) based on geographic database are promising techniques to cope with this spectrum shortage. TV White Space (TVWS) usage relies on unlicensed secondary DSA under the principle on a non-harmful interference with incumbent users, allowing to use UHF channels whose availability is changing over time and space. In order to do so, a well-designed physical layer is required in order to reach accurate frequency localization while being highly flexible. We describe field-test experiments done with an implementation of the BF-OFDM (Block-Filtered OFDM) physical layer on versatile and portable hardware prototyping boards. Field-trials results confirm the potential of BF-OFDM for fragmented spectrum access and spectrum sharing usage.