A Spectrum Aggregation Algorithm with Minimum Spectrum Switch for CR Enabled TD-LTE on TVWS

A novel 802.11ah transmitter for TV white space (TVWS) band devices is presented. To realize the transmitter meeting the stringent FCC and ETSI TVWS device emission limits for the adjacent channels and FCC restricted bands, a low noise and high linear class- AB voltage- to-current converter (V2I) as the mixer driver and a 2nd -order harmonic notch filter with the frequency tracking capability on the power amplifier (PA) load are newly proposed. The designed transmitter is implemented in a 40nm CMOS process as a part of the TVWS band 802.11ah connectivity System-on-Chip (SoC), and the measured results with the 802.11ah CBW4 signal show −55dBr and −58dBr Adjacent Channel Leakage Ratio (ACLR) at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 3\mathbf{MHz}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 20\mathbf{MHz}$</tex> frequency offset, respectively, and 60dB 2nd harmonic rejection for 470MHz ~ 790MHz TVWS bands. This transmitter is the first SoC level transmitter meeting the FCC and ETSI ACLR requirements.

TV White Space (TVWS) refers to frequency band reserved only for licensed terrestrial TV broadcasting and is opened to unlicensed use under regulatory conditions. While regulations protect licensed systems from interference, interference among unlicensed systems is left mainly to manufacturers. Consequently, there is a need to develop new coexistence approaches between TVWS networks. Busy tone broadcasting is a coexistence method, which can be used by TVWS networks to announce the selected frequency band is occupied. In this paper, a busy tone based coexistence algorithm is proposed for IEEE 802.11af and IEEE 802.22 networks and analyzed by considering different client distributions experiencing log-normal shadowing, where the exact interfering packet rate and successful packet transmission rate expressions are obtained and validated by simulations for different scenarios. The results show that with the proposed coexistence approach, a WLAN can reliably detect the busy tone signal to change its frequency band and can reduce interference to WRAN. Even if there is no available frequency band for the WLAN, the WRAN still maintains its enhanced successful packet transmission performance. The deployment of the proposed algorithm is important for successful coexistence between cognitive wireless networks, where interference is not regulated, such as in TVWS bands.

In Time Division Long Term Evolution(TD-LTE) system, decreasing the cross time slot interference is very important to improve the system throughput. Accordingly, we will propose a multi-cells Orthogonal Frequency Division Multiplexing(OFDM) resource allocation model for TD-LTE system in this paper, which considers the cross time slot interference and the fairness. Subsequently, a TD-LTE resource allocation evolutionary algorithm based on adaptive fairness threshold is proposed to solve this model through introducing adaptive fairness threshold. Empirical studies show that the proposed model and algorithm can effectively decrease the cross time slot interference and improve the transmit rate of OFDM system under the same fairness.KeywordsTD-LTEEvolutionary AlgorithmCross SlotAdaptive Fairness Threshold

Integrating cognitive radio into the current power grid is designed to enable smart communication and decisions within the grid. Communication within the grid is not feasible without channel(s) and most studies have emphasized the use of cellular spectrum. This study proposes a strategy that enables the use of television white space (TVWS) within the grid. To be specific, we propose using a next-generation utility network (Next-GUN), which leverages on the cognitive radio (CR) channel aggregation capability. This strategy enables the aggregation of idle TVWS into a usable channel, thus making the Next-GUN different from the traditional power network. Next-GUN differs in terms of security, reliability, self-awareness, and cross-layer compatibility to the interface, and conveys different traffic classes, thereby making it a hybrid system. It has no dedicated channel assigned to it, and hence, utilizes the idle TVWS opportunistically to transmit data. The proposed scheme was modelled as a Markovian process and analyzed using a continuous time Markov chain (CTMC). Extensive system simulations were performed to evaluate this proposed model and the corresponding comparison with the literature was done to see the improvement. The result of our comparisons shows that when channels are aggregated, more data/information are transmitted. In addition, the use of cognitive radios on a power network enables smart transaction because idle TVWS is utilized instead of congesting the GSM spectrum. Lastly, the power utility establishment can save the cost of paying for a licensed spectrum.

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.

With the large-scale construction of TD-LTE (Time Division Long Term Evolution) networks, the long-distance co-channel interference phenomenon of mobile communication has become a hot spot. In this paper, the over-the-horizon propagation characteristics of radio wave are used to study the propagation characteristics of electromagnetic waves above irregular terrain in the non-uniform distribution of atmospheric structure. In the tropospheric propagation, electromagnetic waves are affected by complex geography, tropospheric ducts, and atmospheric turbulence. Terrain occlusion may intercept radio wave propagation. In addition, the atmospheric duct environment forms over-the-horizon propagation, resulting in long-distance co-channel interference in mobile communications, affecting the normal operation of the system. Therefore, it is of great practical significance to study the propagation characteristics of radio waves in a complex atmosphere above a non-uniform surface. This paper studies the phenomenon of co-channel interference in the characteristics of over-the-horizon propagation from the perspective of non-uniform surface and complex atmospheric environment.

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.

Utilization of the TV white-spaces (TVWS), which are spatially or temporally unused frequency in TV bands, is promising technology to alleviate spectrum resource shortage. Services using the TVWS have been already started in the U.S.A., and the TVWS pilot program has been performed and test operation of qualified white-spaces database (WSDB) has been started by the Ofcom in the U.K. Authors have developed TVWS LTE (Long Term Evolution) system with white-space devices (WSDs) licensed by the Ofcom and WSDB qualified by also the Ofcom, and participated in the pilot program performed in the U.K. In this paper, developed TVWS LTE system is summarized and field experiment of throughput measurement is performed in the London urban area is described. As a result of the field experiment, maximum downlink throughput of 45.4 Mbps in the FDD mode and 19.5 Mbps in the TDD mode were obtained under the condition of SISO with a signal bandwidth of 20 MHz. This is the first report on the field experiment of the TVWS LTE system aiming for practical use.

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.

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.

Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) are two major technologies toward next-generation mobile broadband standards, which are both expected to provide higher throughput and lower transmission latency for mobile users. This article measures and compares the latency and the throughput of Time Division - Long Term Evolution (TD-LTE), WiMAX, and third-generation (3G) systems based on several technical trials. Our quantitative measures and comparisons provide guidelines for the operators to deploy their future networks.

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.

Wireless Local Area Network (WLAN) is currently used in the train-ground communication for the urban rail transit systems. Due to the high speed and frequency band limitations, WLAN is unable to meet the demand of future city and intercity rail transit. Time Division-Long Term Evolution (TD-LTE) technology allows to construct a flexible service environment compared with current WLAN based system. In this paper, a TD-LTE based train-ground communication system for the urban rail transit system is given. It integrates all the applications in urban rail transit system. An outdoor testing environment is set up to test the performance of the integrated TD-LTE based train-ground communication system. The packet loss rate, response time, throughput of the TD-LTE system are analyzed. Extensive testing results show that the Quality of Service (QoS) of the integrated TD-LTE based train-ground communication system satisfies the requirements of urban rail transit system.