A low-cost time-hopping impulse radio system for high data rate transmission

We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are: (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110Mbit/s at 7-10m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special Issue on UWB - State of the Art

Wireless Alliance for Testing Experiment and Research (WALTER) Experts Workshop

The purpose of the publication is to describe the WALTER experts workshop and related results and findings. The workshop was conducted in Ispra, Varese, Italy from the 2nd to the 3rd of July 2008 at the European Commission JRC facilities. The workshop was organized as part of the FP7 WALTER project, which has the objective of define a networked test bed laboratory to evaluate UltraWideBand (UWB) technology and equipment. The purpose of WALTER workshop was to present and discuss the current regulatory, standardization and research status of UltraWideBand (UWB) technology with special focus on the definition of requirements, methodologies and tools for UWB measurements and testing. The WALTER workshop had the following main objectives: - Identify the main regulatory and standardization challenges for the adoption of UWB in Europe and the world. Support the identification and resolution of conflicting requirements. - Identify the main challenges in the UWB testing and measurements. Describe how the current industrial and research activity could support the resolution of these challenges. - Discuss the future developments like UWB at 60 GHz and innovative interference and mitigation techniques including Detect And Avoid (DAA). A number of international experts in the UltraWideBand field have been invited to participate to this workshop, to encourage bi-directional communication: in one direction to disseminate the information on WALTER project and its activities, in the other direction to collect the input and feedback on the regulatory and standardization work, industrial activity and research studies.JRC.G.6-Sensors, radar technologies and cybersecurit

Communication in a Poisson Field of Interferers -- Part I: Interference Distribution and Error Probability

We present a mathematical model for communication subject to both network interference and noise. We introduce a framework where the interferers are scattered according to a spatial Poisson process, and are operating asynchronously in a wireless environment subject to path loss, shadowing, and multipath fading. We consider both cases of slow and fast-varying interferer positions. The paper is comprised of two separate parts. In Part I, we determine the distribution of the aggregate network interference at the output of a linear receiver. We characterize the error performance of the link, in terms of average and outage probabilities. The proposed model is valid for any linear modulation scheme (e.g., M-ary phase shift keying or M-ary quadrature amplitude modulation), and captures all the essential physical parameters that affect network interference. Our work generalizes the conventional analysis of communication in the presence of additive white Gaussian noise and fast fading, allowing the traditional results to be extended to include the effect of network interference. In Part II of the paper, we derive the capacity of the link when subject to network interference and noise, and characterize the spectrum of the aggregate interference.Comment: To appear in IEEE Transactions on Wireless Communication

Spectrum control and iterative coding for high capacity multiband OFDM

The emergence of Multiband Orthogonal Frequency Division Modulation (MB-OFDM) as an ultra-wideband (UWB) technology injected new optimism in the market through realistic commercial implementation, while keeping promise of high data rates intact. However, it has also brought with it host of issues, some of which are addressed in this thesis. The thesis primarily focuses on the two issues of spectrum control and user capacity for the system currently proposed by the Multiband OFDM Alliance (MBOA). By showing that line spectra are still an issue for new modulation scheme (MB-OFDM), it proposes a mechanism of scrambling the data with an increased length linear feedback shift register (compared to the current proposal), a new set of seeds, and random phase reversion for the removal of line spectra. Following this, the thesis considers a technique for increasing the user capacity of the current MB-OFDM system to meet the needs of future wireless systems, through an adaptive multiuser synchronous coded transmission scheme. This involves real time iterative generation of user codes, which are generated over time and frequency leading to increased capacity. With the assumption of complete channel state information (CSI) at the receiver, an iterative MMSE algorithm is used which involves replacement of each users s signature with its normalized MMSE filter function allowing the overall Total Squared Correlation (TSC) of the system to decrease until the algorithm converges to a fixed set of signature vectors. This allows the system to be overloaded and user\u27s codes to be quasi-orthogonal. Simulation results show that for code of length nine (spread over three frequency bands and three time slots), ten users can be accommodated for a given QoS and with addition of single frequency sub-band which allows the code length to increase from nine to twelve (four frequency sub-bands and three time slots), fourteen users with nearly same QoS can be accommodated in the system. This communication is overlooked by a central controller with necessary functionalities to facilitate the process. The thesis essentially considers the uplink from transmitting devices to this central controller. Furthermore, analysis of this coded transmission in presence of interference is carried to display the robustness of this scheme through its adaptation by incorporating knowledge of existing Narrowband (NB) Interference for computing the codes. This allows operation of sub-band coexisting with NB interference without substantial degradation given reasonable interference energy (SIR=-l0dB and -5dB considered). Finally, the thesis looks at design implementation and convergence issues related to code vector generation whereby, use of Lanczos algorithm is considered for simpler design and faster convergence. The algorithm can be either used to simplify design implementation by providing simplified solution to Weiner Hopf equation (without requiring inverse of correlation matrix) over Krylov subspace or can be used to expedite convergence by updating the signature sequence with eigenvector corresponding to the least eigenvalue of the signature correlation matrix through reduced rank eigen subspace search

Energy-Efficient Power Control in Impulse Radio UWB Wireless Networks

In this paper, a game-theoretic model for studying power control for wireless data networks in frequency-selective multipath environments is analyzed. The uplink of an impulse-radio ultrawideband system is considered. The effects of self-interference and multiple-access interference on the performance of generic Rake receivers are investigated for synchronous systems. Focusing on energy efficiency, a noncooperative game is proposed in which users in the network are allowed to choose their transmit powers to maximize their own utilities, and the Nash equilibrium for the proposed game is derived. It is shown that, due to the frequency selective multipath, the noncooperative solution is achieved at different signal-to-interference-plus-noise ratios, depending on the channel realization and the type of Rake receiver employed. A large-system analysis is performed to derive explicit expressions for the achieved utilities. The Pareto-optimal (cooperative) solution is also discussed and compared with the noncooperative approach.Comment: Submitted to the IEEE Journal on Selected Topics in Signal Processing - Special issue on Performance Limits of Ultra-Wideband System

A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals

Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility