White Space Network Management: Spectrum Quanti cation, Spectrum Allocation and Network Design

Philosophiae Doctor - PhD (Computer Science)The unused spectrum in the television broadcasting frequency bands (so-called TV white spaces) can alleviate the spectrum crunch, and have potential to provide broadband connection to rural areas of countries in the developing world. Current research on TV white spaces focuses on how to detect them accurately, and how they can be shared or allocated to secondary devices. Therefore, the focus of this research is three-fold: to investigate a novel distributed framework, which does not use propagation models in detecting TV white spaces, and suitable for use in countries of the developing world; to investigate a suitable spectrum sharing mechanism for short-time leasing of the TV white spaces to secondary devices; and extend the research to investigate the design of a TV white space-ware network in TV white space frequencies

Distributed spectrum leasing via cooperation

“Cognitive radio” networks enable the coexistence of primary (licensed) and secondary (unlicensed) terminals. Conventional frameworks, namely commons and property-rights models, while being promising in certain aspects, appear to have significant drawbacks for implementation of large-scale distributed cognitive radio networks, due to the technological and theoretical limits on the ability of secondary activity to perform effective spectrum sensing and on the stringent constraints on protocols and architectures. To address the problems highlighted above, the framework of distributed spectrum leasing via cross-layer cooperation (DiSC) has been recently proposed as a basic mechanism to guide the design of decentralized cognitive radio networks. According to this framework, each primary terminal can ”lease” a transmission opportunity to a local secondary terminal in exchange for cooperation (relaying) as long as secondary quality-of-service (QoS) requirements are satisfied. The dissertation starts by investigating the performance bounds from an information-theoretical standpoint by focusing on the scenario of a single primary user and multiple secondary users with private messages. Achievable rate regions are derived for discrete memoryless and Gaussian models by considering Decode-and-Forward (DF), with both standard and parity-forwarding techniques, and Compress-and-Forward (CF), along with superposition coding at the secondary nodes. Then a framework is proposed that extends the analysis to multiple primary users and multiple secondary users by leveraging the concept of Generalized Nash Equilibrium. Accordingly, multiple primary users, each owning its own spectral resource, compete for the cooperation of the available secondary users under a shared constraint on all spectrum leasing decisions set by the secondary QoS requirements. A general formulation of the problem is given and solutions are proposed with different signaling requirements among the primary users. The novel idea of interference forwarding as a mechanism to enable DiSC is proposed, whereby primary users lease part of their spectrum to the secondary users if the latter assist by forwarding information about the interference to enable interference mitigation at the primary receivers. Finally, an application of DiSC in multi-tier wireless networks such as femtocells overlaid by macrocells whereby the femtocell base station acts as a relay for the macrocell users is presented. The performance advantages of the proposed application are evaluated by studying the transmission reliability of macro and femto users for a quasi-static fading channel in terms of outage probability and diversity-multiplexing trade-off for uplink and, more briefly, for downlink

Options for affordable rural broadband connectivity: a focus on TV White Space technology

There appears to be a coordinated effort the world over to achieve digital switch over (DSO) from analogue based to digital technology. Ghana signed the Geneva agreement which set 17th June 2015 as the deadline for the DSO. This switch over will create new spectrum opportunities for many wireless technologies due to the abundance of radio spectrum the switch over provides. This paper focuses on the opportunity for using White Spaces (TV frequencies allocated to a broadcasting service but not used locally) for internet connectivity in the rural and underserved areas of Ghana, using TV White Spaces in Koforidua as a case study. The paper investigates the challenges associated with lack of internet connectivity in rural Ghana and determines if the infrastructure necessary for the implementation of White Space technology in the rural areas was present and adequate. It also documents the user experience of Africa’s first commercial TV White Space network services in Koforidua, Ghana. A combination of qualitative and quantitative data collection approaches was used. Purposive and simple random sampling techniques were used in selection and administering of questionnaires. Lack of internet in the rural areas was found to be mainly due to perceived risk by the commercial network operators because of value for money considerations of existing technology options. Negative incentives for the common ISP to go rural included technical and geographic/landscape challenges. The relevant infrastructure necessary is still undeveloped in Ghana but various infrastructural projects are being undertaken by the Ghana Investment Fund for Electronic Communication (GIFEC) to bridge the infrastructure gap in these areas. Lastly, the user experience of Africa’s first commercial service network using TV White Spaces in Koforidua, Ghana were described and documented. Keywords: TV White Space, Digital switch over (DSO), Internet connectivity and Ghana Investment Fund for Electronic Communication (GIFEC) JEL classifications: O1, O32, O34, O38, O14, O1

Modelling and Design of Resilient Networks under Challenges

Communication networks, in particular the Internet, face a variety of challenges that can disrupt our daily lives resulting in the loss of human lives and significant financial costs in the worst cases. We define challenges as external events that trigger faults that eventually result in service failures. Understanding these challenges accordingly is essential for improvement of the current networks and for designing Future Internet architectures. This dissertation presents a taxonomy of challenges that can help evaluate design choices for the current and Future Internet. Graph models to analyse critical infrastructures are examined and a multilevel graph model is developed to study interdependencies between different networks. Furthermore, graph-theoretic heuristic optimisation algorithms are developed. These heuristic algorithms add links to increase the resilience of networks in the least costly manner and they are computationally less expensive than an exhaustive search algorithm. The performance of networks under random failures, targeted attacks, and correlated area-based challenges are evaluated by the challenge simulation module that we developed. The GpENI Future Internet testbed is used to conduct experiments to evaluate the performance of the heuristic algorithms developed

Application-aware Cognitive Multi-hop Wireless Networking Testbed and Experiments

In this thesis, we present a new architecture for application-aware cognitive multihop wireless networks (AC-MWN) with testbed implementations and experiments. Cognitive radio is a technique to adaptively use the spectrum so that the resource can be used more efficiently in a low cost way. Multihop wireless networks can be deployed quickly and flexibly without a fixed infrastructure. In presented new architecture, we study backbone routing schemes with network cognition, routing scheme with network coding and spectrum adaptation. A testbed is implemented to test the schemes for AC-MWN. In addition to basic measurements, we implement a video streaming application based on the AC-MWN architecture using cognitive radios. The Testbed consists of three cognitive radios and three Linux laptops equipped with GNU Radio and GStreamer, open source software development toolkit and multimedia framework respectively. Resulting experiments include a range from basic half duplex data to full duplex voice communications and audio/video streaming with spectrum sensing. This testbed is a foundation for a scalable multipurpose testbed that can be used to test such networks as AC-MWN, adhoc, MANET, VANET, and wireless sensor networks. Experiment results demonstrate that the AC-MWN is applicable and valuable for future low-cost and flexible communication networks. Adviser: Yi Qia

Design and optimisation of a low cost Cognitive Mesh Network

Wireless Mesh Networks (WMNs) have been touted as the most promising wireless technology in providing high-bandwidth Internet access to rural, remote and under-served areas, with relatively lower investment cost as compared to traditional access networks. WMNs structurally comprise of mesh routers and mesh clients. Furthermore, WMNs have an envisaged ability to provide a heterogeneous network system that integrates wireless technologies such as IEEE 802.22 WRAN, IEEE 802.16 WiMAX, IEEE 802.11 Wi-Fi, Blue-tooth etc. The recent proliferation of new devices on the market such as smart phones and, tablets, and the growing number of resource hungry applications has placed a serious strain on spectrum availability which gives rise to the spectrum scarcity problem. The spectrum scarcity problem essentially results in increased spectrum prices that hamper the growth and efficient performance of WMNs as well as subsequent transformation of WMN into the envisaged next generation networks. Recent developments in TV white space communications technology and the emergence of Cognitive radio devices that facilitate Dynamic Spectrum Access (DSA) have provided an opportunity to mitigate the spectrum scarcity problem. To solve the scarcity problem, this thesis reconsiders the classical Network Engineering (NE) and Traffic Engineering (TE) problems to objectively design a low cost Cognitive Mesh network that promotes efficient resources utilization and thereby achieve better Quality of Service (QoS) levels

Channel Access and Reliability Performance in Cognitive Radio Networks:Modeling and Performance Analysis

Doktorgradsavhandling ved Institutt for Informasjons- og kommunikasjonsteknologi, Universitetet i AgderAccording to the facts and figures published by the international telecommunication union (ITU) regarding information and communication technology (ICT) industry, it is estimated that over 3.2 billion people have access to the Internet in 2015 [1]. Since 2000, this number has been octupled. Meanwhile, by the end of 2015, there were more than 7 billion mobile cellular subscriptions in the world, corresponding to a penetration rate of 97%. As the most dynamic segment in ICT, mobile communication is providing Internet services and consequently the mobile broadband penetration rate has reached 47% globally. Accordingly, capacity, throughput, reliability, service quality and resource availability of wireless services become essential factors for future mobile and wireless communications. Essentially, all these wireless technologies, standards, services and allocation policies rely on one common natural resource, i.e., radio spectrum. Radio spectrum spans over the electromagnetic frequencies between 3 kHz and 300 GHz. Existing radio spectrum access techniques are based on the fixed allocation of radio resources. These methods with fixed assigned bandwidth for exclusive usage of licensed users are often not efficient since most of the spectrum bands are under-utilized, either/both in the space domain or/and in the time domain. In reality, it is observed that many spectrum bands are largely un-occupied in many places [2], [3]. For instance, the spectrum bands which are exclusively allocated for TV broadcasting services in USA remain un-occupied from midnight to early morning according to the real-life measurement performed in [4]. In addition to the wastage of radio resources, spectrum under-utilization constraints spectrum availability for other intended users. Furthermore, legacy fixed spectrum allocation techniques are not capable of adapting to the changes and interactions in the system, leading to degraded network performance. Unlike in the static spectrum allocation, a fraction of the radio spectrum is allocated for open access as license-free bands, e.g., the industrial, scientific and medical (ISM) bands (902-928, 2400-2483.5, 5725-5850 MHz). In 1985, the federal communications commission (FCC) permitted to use the ISM bands for private and unlicensed occupancy, however, under certain restrictions on transmission power [5]. Consequently, standards like IEEE 802.11 for wireless local area networks (WLANs) and IEEE 802.15 for wireless personal area networks (WPAN) have grown rapidly with open access spectrum policies in the 2.4 GHz and 5 GHz ISM bands. With the co-existence of both similar and dissimilar radio technologies, 802.11 networks face challenges for providing satisfactory quality of service (QoS). This and the above mentioned spectrum under-utilization issues motivate the spectrum regulatory bodies to rethink about more flexible spectrum access for licenseexempt users or more efficient radio spectrum management. Cognitive radio (CR) is probably the most promising technology for achieving efficient spectrum utilization in future wireless networks

ACUTA Journal of Telecommunications in Higher Education

In This Issue 5G\u27s Promise: 1,000 x Capacity, 1,000 x Challenges Higher-Speed WLANs About to Emerge State of the Residential Network 2013 LTE: The Next Wave of Wireless Evolution The 10 Most Costly Pitfalls of DAS Deployment and How to Avoid Them DAS on Campus: Solutions for Wireless Service Decision Criteria for Selecting a Wireless lntrusion Prevention System lnstitutional Excellence Award President\u27s Message From the CE

An investigation of nanoscale materials and their incorporation in patch antenna for high frequency applications

The rapid development in the polymer-based electronic contribute a strong determination for using these materials as substitute to the high-cost materials commonly used as medium substrate in the fabrication of Microstrip Patch Antenna (MPA). Antenna technology can strongly gain from the utilisation of low-cost, flexible, light weight with suitable fabrication techniques. The uniqueness of this work is the use of variety of common but unexplored different polymer materials such as Polyethylene (PE), Polypropylene (PP), Polyvinyl chloride, (PVC) Polystyrene (PS), Polystyrene fibre (PSF) as the substrates for the design and fabrication of different MPAs for communication and sensing applications in millimetre wave (MMW)region. Electrospinning (ES) technique is used to reconstruct PS and produced PSF material of low dielectric constant. A co-solvent vehicle(comprising 50:50 ratio) of Dichloromethane (DCM) and acetone was utilised with processing condition of solution infusion flow-rate of 60μL/min and an applied voltage of 12± kV yielded rigid PSF substrates. The PSF Produced has complex permittivity of 1.36±5% and a loss tangent of 2.4E-04±4.8E-04 which was measured using Spilt-Post Dielectric Resonators (SPDR) technique at National Physics Laboratory, Teddington, London. A diamond-shaped MPAs on RT Duriod material were simulated and fabricated using photo-lithography for different inner lengths to work in the frequencies range from (1-10 GHz). The resonant frequency is approximated as a function of inner length L1 in the form of a polynomial equation. The fabricated diamond-shaped MPA more compact (physical geometry) as compared with a traditional monopole antenna. This MPAs experimentally measured and have a good agreement with the simulated results. The coplanar waveguide (CPW) diamond-shaped MPA working in the MMW region was designed and fabricated with polymer materials as substrates using thermal evaporation technique and the RF measurement was carried out using Vector Network Analyser (VNA). The resonant frequencies of the CPW diamond shaped MPAs for (PE, PP, PVC, PS and PSF) were found to be 67.5 GHz, 72.36 GHz, 62.41 GHz, 63.25 GHz and 80.58 GHz, respectively. The antenna fabricated on PSF were resonating at higher frequency when compared to the other polymers materials. In adding an air-bridge to the CPW diamond-shaped MPA the resonating frequency increased from ≈55 GHz to≈ 62 GHz. Three different shaped nano-patch antennas (Diamond shaped, diamond shaped array and T-shaped) have been designed, simulated and fabricated on Silicon substrate with DLC deposition using focused Ion Beam (FIB) technique, these antennas were found to resonate at 1.42 THz with (-19 dB return loss), 2.42 THz with (-14 dB return loss) and 1.3 THz with (-45 dB return loss) respectively

Potential markets for advanced satellite communications

This report identifies trends in the volume and type of traffic offered to the U.S. domestic communications infrastructure and extrapolates these trends through the year 2011. To describe how telecommunications service providers are adapting to the identified trends, this report assesses the status, plans, and capacity of the domestic communications infrastructure. Cable, satellite, and radio components of the infrastructure are examined separately. The report also assesses the following major applications making use of the infrastructure: (1) Broadband services, including Broadband Integrated Services Digital Network (BISDN), Switched Multimegabit Data Service (SMDS), and frame relay; (2) mobile services, including voice, location, and paging; (3) Very Small Aperture Terminals (VSAT), including mesh VSAT; and (4) Direct Broadcast Satellite (DBS) for audio and video. The report associates satellite implementation of specific applications with market segments appropriate to their features and capabilities. The volume and dollar value of these market segments are estimated. For the satellite applications able to address the needs of significant market segments, the report also examines the potential of each satellite-based application to capture business from alternative technologies