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

Effect of Interfering Users on the Modulation Order and Code Rate for UWB Impulse-Radio Bit-Interleaved Coded M-ary PPM

We consider the impact of multi-user interference on a bit-interleaved coded-modulation system with M-ary PPM (BIC M-ary PPM) in an impulse-radio ultra-wideband physical layer. In a realistic scenario such as an ad hoc network, the interference is inherently variable. This justifies the need for a physical layer that can optimally adapt its transmission parameters to the interference level. We use puncturing on the channel code so that we can not only change the modulation order $M$ but also the channel code rate. We study by simulation how the optimal combination of modulation order $M$ and channel code rate behaves with various degrees of interference. The results show that BIC M-ary PPM can be successfully adapted to various levels of interference conditions. It also shows the benefit of both rate and modulation adaptation, especially in the presence of multi-user interference

Performance Evaluation of Adaptive Continuous Wavelet Transform based Rake Receiver for UWB Systems

This paper proposes an adaptive continuous wavelet transform (ACWT) based Rake receiver to mitigate interference for high speed ultra wideband (UWB) transmission. The major parts of the receiver are least mean square (LMS) adaptive equalizer and N-selective maximum ratio combiner (MRC). The main advantage of using continuous wavelet rake receiver is that it utilizes the maximum bandwidth (7.5GHz) of the UWB transmitted signal, as announced by the Federal Communication Commission (FCC). In the proposed ACWT Rake receiver, the weights and the finger positions are updated depending upon the convergence error over a period in which training data is transmitted. Line of sight (LOS) channel model (CM1 from 0 to 4 meters) and the Non line of sight (NLOS) channel models (CM, CM3 and CM4) are the indoor channel models selected for investigating in this research . The performance of the proposed adaptive system   is evaluated by comparing with conventional rake and continuous wavelet transform (CWT) based rake. It showed an improved performance in all the different UWB channels (CM1 to CM4) for rake fingers of 2, 4 and 8. Simulations showed that for 8 rake fingers, the proposed adaptive CWT rake receiver has shown an SNR improvement of 2dB, 3dB, 10dB and 2dB respectively over CWT rake receiver in different UWB channels CM1, CM2, CM3 and CM4

Timing Recovery for Ultra Wideband Systems

This paper examines the problems of symbol timing estimation and timing recovery for ultra wideband impulse radio signals. Two different approaches based onthe maximum likelihood technique are investigated. The first approach is based on derivative matched filter and the second one takes advantage of the early-late technique. Furthermore, two non-coherent timing recovery circuits are proposed and discussed. The first circuit is a digital delay-locked loop (DDLL) and the second circuit is based on early-late technique. Finally, performance analysis of the proposed techniques for IEEE 802.15.3a channel models in terms of the minimum squared error (MSE) is provided

Comparison of Bit Error Rate and Power Spectral Density on the Ultra Wideband Impulse Radio Systems

Ultra-Wideband (UWB) is defined as a wireless transmission scheme that occupies a bandwidth of more than 25% of its center frequency. UWB Impulse Radio (UWB-IR) is a popular implementation of the UWB technology. In UWB-IR, information is encoded in baseband without any carrier modulation. Pulse shaping and baseband modulation scheme are two of the determinants on the performance of the UWB-IR. In this thesis, both temporal and spectral characteristics of the UWB-IR are examined because all radio signals exist in both the time and frequency domains. Firstly, the bit error rate (BER) performance of the UWB-IR is investigated via simulation using three modulation schemes: Pulse position modulation (PPM), on-off shift keying (OOK), and binary phase shift keying (BPSK). The results are verified for three different pulse shaping named Gaussian first derivative, Gaussian second derivative, and return-to-zero (RZ) Manchester. Secondly, the effects of the UWB-IR parameters on the power spectral density (PSD) are investigated because PSD provides information on how the power is distributed over the radio frequency (RF) spectrum and determines the interference of UWB-IR and the existing systems to each other in the spectrum. The investigated UWB-IR parameters include pulse duration, pulse repetition rate, modulation scheme, and pseudorandom codes

Exact modeling of multiple access interference, ber derivation and a method to improve the performance of UWB communication systems

Master'sMASTER OF ENGINEERIN

The Trade-off between Processing Gains of an Impulse Radio UWB System in the Presence of Timing Jitter

In time hopping impulse radio, $N_f$ pulses of duration $T_c$ are transmitted for each information symbol. This gives rise to two types of processing gain: (i) pulse combining gain, which is a factor $N_f$, and (ii) pulse spreading gain, which is $N_c=T_f/T_c$, where $T_f$ is the mean interval between two subsequent pulses. This paper investigates the trade-off between these two types of processing gain in the presence of timing jitter. First, an additive white Gaussian noise (AWGN) channel is considered and approximate closed form expressions for bit error probability are derived for impulse radio systems with and without pulse-based polarity randomization. Both symbol-synchronous and chip-synchronous scenarios are considered. The effects of multiple-access interference and timing jitter on the selection of optimal system parameters are explained through theoretical analysis. Finally, a multipath scenario is considered and the trade-off between processing gains of a synchronous impulse radio system with pulse-based polarity randomization is analyzed. The effects of the timing jitter, multiple-access interference and inter-frame interference are investigated. Simulation studies support the theoretical results.Comment: To appear in the IEEE Transactions on Communication

Contribution to the Rapid Acquisition of Signals for UWB Communication Systems

Ultra Wide-band is a promising technology for future short-range wireless communications with high data rate. In generally, one of the biggest difficult tasks for researchers today is the acquisition task of signals, where they are looking through different tools for getting a good quality of transmission; the phenomenon of multipath always stands up in the front as the first problem to be faced. When we talk about the Ultra Wide Band (UWB) signals, the problem becomes more complicated due to ultrashort impulses duration used by this kind of signals that causes the generation of paths by huge numbers. In this thesis, to address the task mentioned above, the study is subdivided into two aspects. The first one is the UWB channel estimation that we have done to have information about the amplitudes and the delays of the paths. For this purpose, a maximum likelihood method is used to find the amplitudes and the delays estimate using two estimation contexts: Data Aided (DA) and Non-Data-Aided (NDA). In the second aspect, various parameters affecting the acquisition of signals are evaluated. Furthermore, several contributions in the framework of a new strategy based on an Intelligent Controlling System (ICS) are done and detailed in this thesis for the first once. This system is characterised by its flexibility through two techniques, one that allows to users to communicate even with different M-ary PPM levels at the same time. Another technique that gives the flexibility for dealing with the phenomenon of multipath, where this latter is combated through manipulating the modulation’s levels via the ICS to achieve a rapid acquisition of UWB signals