Seeing the Unobservable: Channel Learning for Wireless Communication Networks

Wireless communication networks rely heavily on channel state information (CSI) to make informed decision for signal processing and network operations. However, the traditional CSI acquisition methods is facing many difficulties: pilot-aided channel training consumes a great deal of channel resources and reduces the opportunities for energy saving, while location-aided channel estimation suffers from inaccurate and insufficient location information. In this paper, we propose a novel channel learning framework, which can tackle these difficulties by inferring unobservable CSI from the observable one. We formulate this framework theoretically and illustrate a special case in which the learnability of the unobservable CSI can be guaranteed. Possible applications of channel learning are then described, including cell selection in multi-tier networks, device discovery for device-to-device (D2D) communications, as well as end-to-end user association for load balancing. We also propose a neuron-network-based algorithm for the cell selection problem in multi-tier networks. The performance of this algorithm is evaluated using geometry-based stochastic channel model (GSCM). In settings with 5 small cells, the average cell-selection accuracy is 73% - only a 3.9% loss compared with a location-aided algorithm which requires genuine location information.Comment: 6 pages, 4 figures, accepted by GlobeCom'1

Structural design options for the new 34 meter beam waveguide antenna

In addition to the successful network of 34 m High Efficiency antennas recently built by JPL, the Deep Space Network (DSN) is embarking on the construction of a 34 m high performance, research and development antenna with beam waveguide optics at the Venus site. The construction of this antenna presents many engineering challenges in the area of structural, mechanical, RF, and pointing system design. A set of functional and structural design requirements is outlined to guide analysts in the final configuration selection. Five design concepts are presented covering both the conventional center-fed beam optics as well as the nonconventional, by-pass beam configuration. The merits of each concept are discussed with an emphasis on obtaining a homologous design. The preliminary results of structural optimization efforts, currently in progress, are promising, indicating the feasibility of meeting, as a minimum, all X-band (8.4 GHz) requirements, with a goal towards meeting Ka-band (32 GHz) quality performance, at the present budget constraints

Optically transparent UWB antenna for wireless application & energy harvesting

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Transparent UWB antennas have been the focus of this PhD research. The use of transparent UWB antennas for stealth and energy harvesting has been the underlying applications that have given impetus to this research. Such transparent antennas being built on materials that are discreet, flexible, conformal, conductive and having the ability to provide good antenna performance on glass to serve as the ‘last mile’ link in subsequent generation communications after 4G have been the basis for this contention. UWB in this regard is able to provide the transmission and reception of high data rates and fast video transmission that is an elementary demand of even a 4G wireless communications system. The integration of UWB antennas with photovoltaic to provide integral energy harvesting solutions that will further enhance the value of the UWB system in terms of cost effectiveness and performance are thus the basis of this work. This work hence starts with the study of a transparent conductive oxide polymer, AgHT and its properties, and culminates in the development of a transparent UWB antenna, which can be integrated with photovoltaic for window glass applications on homes and buildings. Other applications such transparent antennas can find use for like on-body wireless communications in healthcare monitoring was also analysed and presented. The radar absorbing material (RAM) property of the AgHT was investigated and highlighted using CST simulation software, as no measurement facilities were available. The transparent UWB antenna in lieu of the inherent absorbent property of the AgHT material is thus able to exhibit stealth characteristics, a feature that would be much desired in military communications. Introduction of a novel method of connecting the co-axial connector to the feed of the antenna to improve gain and efficiency of transparent polymer based antennas and the development of a UWB antenna that maintains its Omni-directional characteristic instead of becoming directional on an amorphous silicon solar cell are presented as some of the contributions for this research work. Some preliminary analysis on the impact of glass on UWB antennas for video transmission and how to improve transmission is presented. The ability of the conductive part of the antenna radiator to be used as a RF and microwave harvester and how it can further add value to a transparent UWB antenna is presented by way of experimental data. Finally yet importantly, this thesis presents some insight into how transparent antennas may be used in Green Technology Buildings to provide an integrated solution for both wireless communications and energy harvesting as part of the future work. Improvement to the aesthetics of the external appearance of residential buildings through the integration of transparent satellite dish onto solar panels on rooftops is also discussed and illustrated as part of this future work

Wi-PoS : a low-cost, open source ultra-wideband (UWB) hardware platform with long range sub-GHz backbone

Ultra-wideband (UWB) localization is one of the most promising approaches for indoor localization due to its accurate positioning capabilities, immunity against multipath fading, and excellent resilience against narrowband interference. However, UWB researchers are currently limited by the small amount of feasible open source hardware that is publicly available. We developed a new open source hardware platform, Wi-PoS, for precise UWB localization based on Decawave’s DW1000 UWB transceiver with several unique features: support of both long-range sub-GHz and 2.4 GHz back-end communication between nodes, flexible interfacing with external UWB antennas, and an easy implementation of the MAC layer with the Time-Annotated Instruction Set Computer (TAISC) framework. Both hardware and software are open source and all parameters of the UWB ranging can be adjusted, calibrated, and analyzed. This paper explains the main specifications of the hardware platform, illustrates design decisions, and evaluates the performance of the board in terms of range, accuracy, and energy consumption. The accuracy of the ranging system was below 10 cm in an indoor lab environment at distances up to 5 m, and accuracy smaller than 5 cm was obtained at 50 and 75 m in an outdoor environment. A theoretical model was derived for predicting the path loss and the influence of the most important ground reflection. At the same time, the average energy consumption of the hardware was very low with only 81 mA for a tag node and 63 mA for the active anchor nodes, permitting the system to run for several days on a mobile battery pack and allowing easy and fast deployment on sites without an accessible power supply or backbone network. The UWB hardware platform demonstrated flexibility, easy installation, and low power consumption

Large deployable antenna program. Phase 1: Technology assessment and mission architecture

The program was initiated to investigate the availability of critical large deployable antenna technologies which would enable microwave remote sensing missions from geostationary orbits as required for Mission to Planet Earth. Program goals for the large antenna were: 40-meter diameter, offset-fed paraboloid, and surface precision of 0.1 mm rms. Phase 1 goals were: to review the state-of-the-art for large, precise, wide-scanning radiometers up to 60 GHz; to assess critical technologies necessary for selected concepts; to develop mission architecture for these concepts; and to evaluate generic technologies to support the large deployable reflectors necessary for these missions. Selected results of the study show that deployable reflectors using furlable segments are limited by surface precision goals to 12 meters in diameter, current launch vehicles can place in geostationary only a 20-meter class antenna, and conceptual designs using stiff reflectors are possible with areal densities of 2.4 deg/sq m

Delay line based passive radio frequency identification tags

This work describes the concept, design, fabrication, and characterization of delay-based radio frequency identification (RFID) tags and RFID-based sensor tags, representing a novel RFID technology. The presented delay-based RFID concept is based on the LC-delay-line and transmission-delay-line based approaches. The proposed concept allows the realization of RFIDs and RFID-based sensor tags at any allowed radio frequency, with the limitation of realizing delay elements capable of producing required delays. The RFID configurations presented in this work are for operation at 915 MHz. Simulations are used to design and optimize components and devices that constitute the tags, and to integrate them to realize tags of different configuration. A set of fabrication processes has been developed for the realization of the tag. Characterization and field testing of these tags show that delay-based RFID approach can be used to make passive tags at ultra high frequency (UHF) and other allowed frequencies. Delay-based tags have the advantages of time domain operation, and the feasibility of complying with FCC regulations. However, size, need of isolators and circulator, and design constraints in producing higher number of bits are some of the concerns that need to be further addressed. In summary, this dissertation work presents a viable alternative RFID approach based on the delay line concept. The results obtained show great promise for further development and optimization of this approach for a wide range of commercial applications

Design and development of triangular, spiral, and fractal antennas for radio frequency identification tags

This dissertation reports on the design and development of three compact, non-meandered microstrip patch antennas for ultra high frequency (UHF) radio frequency identification (RFID) applications. The monopole antennas considered in this work are an inset-fed triangular antenna, one arm Archimedes spiral antenna and a Half-Sierpinski fractal antenna. These antennas with small length to width ratios (\u3c 2/1), can be the preferred choice, in the tagging of small size consumer end products, over the ubiquitous meandered dipole antenna (length/width \u3e 5/1), which is often the antenna of choice, due to its high gain for UHF RFID applications. The lengths and widths of all three antennas are less than 5.5 cm. Earlier reports of planar antennas for RFID applications in the UHF range have lengths larger than 9 cm on one side or are developed on a rigid substrate. All three antennas have a surface area of about 30 cm2 and are designed for a flexible polyimide substrate. The new antennas satisfy the requirement of a voltage standing wave ratio (VSWR) \u3c 2 and exhibit a gain close to or greater than 0 dBi at the operation frequency of 915 MHz. All three antennas have a return-loss less than -10 dB at 915 MHz and a -10 dB bandwidth greater than 12 MHz. While the triangular and spiral antennas display peak gains of over 2 dBi, the fractal antenna has a gain close to 0 dBi (-0.64 dBi). The effect of ground geometry on the radiation performance of the antennas has been analyzed using ANSOFT Designer software. Slots, aligned to the top patch were introduced in the antenna ground plane to increase the gain of the antennas. The fabricated and tested antennas were then employed in the transmission-delay-line-based passive radio-frequency identification tag. The location of the antenna with respect to the transmission line on the tag was found to affect the radiation pattern of the antenna. A circular disc monopole antenna having a gain of 8.88 dBi and having a -10 dB bandwidth greater than 300 MHz was employed to transmit and receive the interrogating and back-scattered signals, respectively. The generation of bits, employing On-Off Keying (OOK) modulation technique was successfully demonstrated. The tag, fabricated with the triangular antenna is found to perform the best