Querying spectrum databases and improved sensing for vehicular cognitive radio networks

A Spectrum Handoff Scheme for Optimal Network Selection in NEMO based Cognitive Radio Vehicular Networks: A Cost Function MADM Method based on Grey Theory based Approach

In this paper, a novel spectrally efficient half-duplex cooperative transmission protocol is proposed for cooperative multiple-access channels in wireless vehicular networks, where multiple sources (vehicles) deliver messages to a common destination (roadside base station or roadside infrastructure) with the help of multiple decode-and-forward relays (roadside stations). The basic idea is to apply superposition coding at each transmitter in order to achieve the full diversity gain, where the linear zero-forcing detection is used at each relay to combat inter-relay interference. Compared to existing uplink cooperative protocols, the proposed scheme can exploit the cooperation involving both the relays and the sources. An achievable diversity-multiplexing trade-off is developed for the proposed transmission protocol. Even with strong inter-relay interference which has been ignored by many existing works, the proposed scheme can still approach the optimal multiple-input single-output upper bound. Numerical results have also been provided to demonstrate the performance of the proposed protocol.

Vehicular plays an important role in day-to-day world in the field of automobiles. VANETs are the subclass of mobile ad-hoc Networks which have no central infrastructure. Nodes are highly mobile in VANET. VANET is distinguished from MANET by their features, design and applications. A Vehicular Ad-Hoc Network or VANET is a sub form of Mobile Ad-Hoc Network or MANET that provides communication between vehicles and between vehicles and road-side base stations with an aim of providing efficient and safe transportation. A vehicle in VANET is considered to be an intelligent mobile node capable of communicating with its neighbors and other vehicles in the network. VANET introduces more challenges aspects as compare to MANET because of high mobility of nodes and fast topology changes in VANET. In this paper, VANET basics structure, its architecture, challenges, applications are discussed. Data dissemination is a challenging task because by utilizing limited bandwidth, maximum data has to disseminate over the vehicular network. Many researchers have provided several techniques to disseminate data so that the data can be accessed more efficiently. Major stress is given to this topic where data dissemination types and its protocols are compared.

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.

Cognitive radio vehicular ad-hoc networks (CR-VANETs) allow the vehicles to exploit the unused channels in their vicinity to fulfil the bandwidth demands of infotainment applications. Existing CR-VANET approaches aim at incorporating spectrum sensing and reporting to the widely used IEEE 802.11p standard developed for VANETs. However, all such approaches were developed for CR-VANETs with low vehicular traffic densities. Applying such approaches at high traffic densities results in long sensing periods, long contention periods with frequent collisions and unnecessary transmissions of sensing information, and variable delays that depend on the vehicular density. In this study, the authors present the single-channel slotted contention ( ( SC ) 2 ) protocol designed for highways with highly dense vehicular traffic. The ( SC ) 2 protocol counters the deficiencies of typical CR-VANETs in high-density networks using three components: random single-channel sensing, slotted contention, and implicit-OR aggregation. The proposed protocol can be easily incorporated with the IEEE 802.11p. Analytic and simulation results show that the proposed protocol increases the CR-VANET throughput and the overall spectrum utilisation while significantly decreasing the radio environment map time in high densities when compared to the conventional IEEE 802.11p protocols.

Vehicular communication networking is one of the most important building blocks of Intelligent Transportation System (ITS). The vehicular communication network is a wireless communication system enabling vehicles to communicate with each other as well as with roadside base stations. Mobility management of vehicles which move at high speeds and occasionally make a long journey is an interesting research area of vehicular communication networks. Recently, The Proxy Mobile IPv6 (PMIPv6) protocol is proposed for network-based mobility management to reduce the overhead of mobile nodes. PMIPv6 shifts the burden of the mobility management from mobile nodes to network agents to decrease the overhead and latency for the mobility management. In this paper, we derive the scenario of deploying PMIPv6 in vehicular communication networks and propose a new LMA handover mechanism for realizing the scenario. By carrying out the ns-2 based simulations, we verify the operability of the proposed mechanism.

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.

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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.

On efficient neighbor sensing in vehicular networks

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.

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.

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.

Information-centric networking (ICN) technology is becoming a popular research topic in vehicular networks due to the connectionless and lightweight characteristics of this networking paradigm. Caching plays an essential role in information-centric networks, but current caching techniques for ICN are not ideal for the dynamic and wireless vehicular networks. This paper presents a caching approach for ICN-based vehicular networks that takes into account both the dynamicity of vehicular networks and the popularity of the information being distributed. We introduce an interval metric for selective caching. With this metric and estimates of information popularity and vehicle density, cooperative caching can be realized without exchanging cache management information among the vehicular nodes. Simulation results show that the proposed approach can increase the storage space utilization and has low data response time for vehicular networks.

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.