Impulse Radio Systems Research Articles

Group waveform-coded biorthogonal pulse position modulation with level cutting for ultra-wideband impulse radio communications

A new modulation scheme termed as group waveform-coded biorthogonal pulse position modulation (GWC-BPPM) is proposed for an ultrawideband (UWB) impulse radio communication system. The group waveform-coded signal, generated using several orthogonal waveform codes to transmit data simultaneously, is converted to pulse position and polarity to improve data rate and obtain processing gain in reception. In addition, the authors also suggest greatly boosting the data rate of the proposed scheme by introducing the level cutting concept. By restricting the maximum level of the group waveform-coded signal, the authors can boost the data rate without any degradation in error performance. To guarantee the benefit and the validity of the proposed scheme, the authors focus on the achievable data rate as a performance measure and analyse it theoretically. Simulations show that the achievable data rate of the proposed systems can be increased by GWC-BPPM and can be boosted via level cutting compared with other schemes such as M-ary BPPM and MBOK.

Performance of Multi Pulse Position Amplitude Modulation for TH IR-UWB Communication Systems

The multi pulse position amplitude modulation scheme for time-hopping multiple access impulse radio ultrawideband communication systems has been presented in this paper. Multi pulse position amplitude modulation is a hybrid modulation technique, which combines multi pulse position modulation and pulse amplitude modulation. It is shown that multi pulse position amplitude modulation significantly outperforms pulse position modulation with respect to bandwidth efficiency. The multi pulse position amplitude modulation error probability over IEEE 802.15.3a multipath fading channels in multiuser environment is derived. The system analysis shows that the proper selection of modulation parameters can improve the system performance at the cost of hardware complexity (and vice versa).

Simplified structure of weighted energy detector for UWB-IR systems

Proposed is a simplified weighted energy detector (WED) receiver structure for ultra-wideband impulse radio (UWB-IR) systems. The performance improvement of the WED comes with the cost of increased hardware complexity when performing linear combination over the fractional energies. In this proposed scheme, multiplication for the combination process is replaced with a register-shifting operation based on simplified weighting coefficients. Simulations show that the proposed WED structure achieves the same BER performance as a multiplier-using WED structure with much lower hardware complexity.

Comparison of Kurtosis and Fourth Power Detectors with Applications to IR-UWB OOK Systems

On-off keying (OOK) is one of the modulation schemes for non-coherent impulse radio Ultra-wideband systems. In this paper, the utilization of the kurtosis detector (KD) and fourth power detector (FD) receivers for OOK signaling is introduced. We investigate the effect of integration interval and the optimum threshold on the performance of energy detector (ED), KD and FD receivers. The semi analytic expression of BER is obtained by using generalized extreme value distribution function for KD and FD receivers. From performance point of view, the simulation results show that FD receiver outperforms KD and ED receivers. In contrast, the sensitivity to the optimum threshold is greatly reduced in KD receiver compared to ED and FD receivers.

Training-Based Synchronization and Demodulation With Low Complexity for UWB Signals

In this paper, we propose a low-complexity data-aided (DA) synchronization and efficient demodulation technique for an ultrawideband (UWB) impulse radio system. Depending on the autocorrelation property of a judiciously chosen training sequence, a redundance-included demodulation template (RDT) can be extracted from the received signal by separating, shifting, and realigning two connected portions in the observation window. After constructing the RDT, two receiver designs are available. One approach is to demodulate transmitted symbols by correlating the RDT in a straightforward manner, which does not require the explicit timing acquisition and, thus, considerably reduces the complexity of the receiver. An alternative approach is accomplished with the assistance of a non-RDT (NRDT). The NRDT-based receiver is able to remove the redundant noisy component of the RDT by acquiring timing offset via a simple synchronization scheme, therefore achieving a better bit error rate (BER) performance. Both the schemes can counteract the effects of interframe interference (IFI) and unknown multipath channels. Furthermore, analytical performance evaluations of the RDT- and NRDT-based receivers are provided. Simulations verify the realistic performance of the proposed receivers in the presence of multiuser interference (MUI) and timing errors.

IR-UWB-Over-Fiber Systems Compatible With WDM-PON Networks

Integrating an ultrawideband-over-fiber (UWBoF) system into a wavelength division multiplexing passive optical network (WDM-PON) is of great interest due to the high potential to provide high data-rate and flexible wired and wireless services with a favorable cost. In this paper, we perform a comprehensive study on an impulse radio UWBoF system compatible with the WDM-PON architecture implemented based on a photonic microwave bandpass filter. The bandpass filter is a two-tap delay-line filter implemented using either a polarization modulator (PolM) or a phase modulator (PM), which is used to simultaneously shape an electrical Gaussian-like pulse to an optical UWB pulse and reduce the out-band noise and interference. The features of the photonic microwave bandpass filters are theoretically studied. The photonic microwave bandpass filter based on a PolM would produce a chirp-free UWB signal, while the one based on a PM would generate a UWB signal that is insensitive to fiber dispersion. A single-channel UWBoF system with ON-OFF keying, biphase modulation, and pulse-position modulation without and with time hopping are experimentally studied. The experimental results agree well with the theoretical predictions. A four-channel UWBoF broadcasting network as well as a hybrid WDM-PON network to provide both wireless and wired services is also experimentally investigated. Results show that a conventional WDM-PON network could be easily upgraded to provide UWB services by incorporating the proposed photonic microwave bandpass filter.

Novel signaling and detection schemes for ultra-wideband transmitted-reference systems

Ultra-Wideband (UWB) impulse radio systems apply sub-nanosecond pulses and are able to resolve multipath due to their fine time-resolution capability. To take full advantage of the available signal energy, a Rake receiver with high hardware complexity is required. To remedy this difficulty, an improved scheme called the transmitted reference (TR) systems is proposed. TR systems do not require the complex task of channel estimation and render a simple receiver structure. However, the low-complexity detection in the conventional TR scheme is achieved at the cost of 50% energy/bandwidth disadvantage. This disadvantage has become the popular research focus of UWB TR systems. In this paper a performance-enhanced signal and detection scheme, namely the dual averaging N-bit differential transmitted reference/balanced transmitted reference (A2NDTR/BTR) system, is proposed to increase the data rate while still maintain the overall system performance. Numerical results suggest that this proposed scheme is able to achieve superior data rate while maintain the same or better bit error performance as compared with others.

Co-design of ESD protection and UWB RF front-end ICs

This paper discusses critical aspects for co-design of ultra wideband (UWB) system-on-chip (SoC) and on-chip electrostatic discharge (ESD) protection, which are beyond the considerations on data rate and bandwidth. Impulse radio UWB system architecture has been defined with critical building blocks proposed and verified, including pulse generator, transmitter, low noise amplifier (LNA) and multiplier based correlator. ESD protection is well considered for each related block. Design examples have been implemented in a commercial RFCMOS processes to demonstrate the working principles for key UWB transmitter and receiver circuit blocks. UWB-ESD co-design techniques, simulation and measurement results for these UWB RF modules are presented in detail.

Performance Analysis and Optimization of $\hbox{T}_{\rm c}$-DTR IR-UWB Receivers Over Multipath Fading Channels With Tone Interference

In this paper, we analyze the performance of a particular class of transmitted-reference receivers for impulse radio ultrawideband communication systems, which is called chip-time differential transmitted-reference ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{T}_{\rm c}$</tex></formula> -DTR). The analysis aims at investigating the robustness of this receiver to single-tone and multitone narrowband interference (NBI) and comparing its performance with other noncoherent receivers that are proposed in the literature. It is shown that the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{T}_{\rm c}$</tex></formula> -DTR scheme provides more degrees of freedom for performance optimization and that it is inherently more robust to NBI than other noncoherent receivers. More specifically, it is analytically proved that the performance improvement is due to the chip-time-level differential encoding/decoding of the direct sequence (DS) code and to an adequate design of DS code and average pulse repetition time. The analysis encompasses performance metrics that are useful for both data detection (i.e., average bit error probability) and timing acquisition (i.e., false-alarm probability <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{P}_{\rm fa}$</tex></formula> and detection probability <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{P}_{\rm d}$</tex></formula> ). Moving from the proposed semianalytical framework, the optimal code design and system parameters are derived, and it is highlighted that the same optimization criteria can be applied to all the performance metrics considered in this paper. In addition, analytical frameworks and theoretical findings are substantiated through Monte Carlo simulations.

Direct Sequence and Time-Hopping Sequence Designs for Narrowband Interference Mitigation in Impulse Radio UWB Systems

Direct sequence and time-hopping sequence designs are proposed for impulse radio ultra-wide bandwidth systems to suppress the mutual interference between ultra-wide bandwidth wireless and coexisting narrowband services. Notch frequencies are created in the ultra-wide bandwidth signal spectrum at bands where narrowband services operate. The direct sequence and the time-hopping sequence designs have low computational complexities and can be easily implemented in practical systems. When combined with the cognitive radio technique, these designs can adapt to channel conditions according to the spectral occupancy information provided by cognitive radio. Numerical results are provided to show that these designs can significantly suppress the mutual interference between ultra-wide bandwidth and narrowband services. Therefore, the integrity of both ultra-wide bandwidth and narrowband systems can be highly enhanced.

Reduce-complexity fuzzy-inference-based iterative multiuser detection for wireless communication systems

In recent years, combining multiuser detection and intelligence computer scheme have received considerable attention. In this paper, adaptive fuzzy-inference multistage matrix wiener filtering (FI-MMWF) techniques, based on the minimum mean-square error criterion, are proposed for ultra-wideband (UWB) impulse radio communication systems. These FI-MMWF-based algorithms employ a time-varying fuzzy-inference-controlled filter stage. Consequently, the proposed approaches accomplish a substantial saving in complexity without trading off the system performance and dynamic-tracking characteristic. In addition, the fuzzy-logic-controlled matrix conjugate gradient algorithm is adopted to reduce the system complexity without trading off the bit-error-rate (BER). Simulations are conducted to evaluate the convergence and tracking behavior of the proposed MMWF algorithm, and the BER of the time-hopping-UWB system in a realistic UWB channel is investigated. Copyright © 2011 John Wiley & Sons, Ltd.

Waveform distortion performance evaluation using practical antennas in deterministic multipath impulse radio channels

As a potential future technology, impulse radio is a promising new reliable data transmission method for time-sensitive applications. However, owing to the complex nature of ultra-wideband (UWB) channels used in practice, there are many design problems that remain to be resolved. This study looks into some UWB channels classified as waveform distortion for which the authors present an implementation-oriented analysis to investigate the performance of impulse radio systems using antennas for a special class of deterministic multipath channels. This study analyses the waveform distortion along signal path to identify the effect of non-idealities in the system and evaluates overall performance of system in terms of bit error ratio observing the waveforms received at the correlator. Through simulation results practical aspects of the impulse-radio transceivers are discussed. From some of the results, the authors provide an antenna selection strategy for some propagation environments.

Sphere Decoding Based Multiple Symbol Detection for Differential Space-Time Block Coded Ultra-Wideband Systems

In this letter, a sphere decoding (SD) based noncoherent multiple symbol detection (MSD) scheme is proposed for differential space-time block coded (DSTBC) ultra-wideband (UWB) impulse radio systems. Exhaustive search based maximum likelihood (ML) MSD is impractical in DSTBC-UWB systems since its complexity exponentially increases with observation window size. To decrease the computational complexity, the original MSD metric is transformed into another equivalent form which can be implemented by SD for DSTBC-UWB systems.

A 1 Gb/s 3.8 pJ/bit Differential Input BPSK Detection Scheme for UWB-IR Communication Using 180 nm CMOS Technology

A CMOS detection procedure for ultra-wideband impulse radio (UWB-IR) communication system, employing Bi-Phase Shift Keying (BPSK) modulation scheme, is presented here. The chip was designed and fabricated in a 180nm CMOS process and it requires a supply voltage of 1.8V, with a die area of 0.01mm2. A train of Gaussian Monocycle Pulses (GMP), modulated by a random data sequence of 1Gb/s, has been detected successfully by the detector. Ability to process differential data without using conventional blocks like mixer, correlator etc. while consuming a very low power (3.8pJ/bit for a data rate of 1Gb/s) is the novelty of this work. The detection scheme employing a simple architecture with a noncoherent detection mechanism is well suited for UWB-IR communication system.

EXIT chart aided design of near-capacity UWB impulse radio using self-concatenated codes

A near-capacity Time Hopping (TH) Pulse Position Modulation (PPM) based Ultra Wide Band (UWB) Impulse Radio (IR) system is proposed, which invokes iteratively detected Self-Concatenated Convolutional Codes (SeCCC) employing Extrinsic Information Transfer (EXIT) charts. The TH-PPM-UWB-IR-SeCCC system configuration is capable of operating within about 0.9dB of the information-theoretic limits.

Orthogonal Exponential Spline Pulses with Application to Impulse Radio

With application to the impulse radio communications in mind, a time-limited and zero-mean pulse which is orthogonal to its shifts by integers is sought among the exponential splines having the knot interval 12. For the existence of real or complex-valued pulses, a necessary and sufficient condition is given in terms of the parameters of the dynamical system that shapes the exponential splines. The one for the existence of real-valued pulses is left as an open problem. Nonetheless, a real-valued example pulse is obtained that complies with the regulation imposed by the US Federal Communications Commission. This pulse will potentially enable an impulse radio communications system as fast as 6 giga pulses per second.

On-Body Area UWB Channel Modeling Including Reflection from Surroundings

This study aims how to contain the environment reflection in a dynamic on-body ultra wideband (UWB) channel model. Based on a measurement approach, it is demonstrated that a complete body area channel model can be regarded as a combination of the on-body propagation characteristic and additional components from the environment. Based on such a channel model, the effect of environment reflection on the average bit error rate performance was investigated for a typical impulse radio UWB system.

Transmission Performance of an In-Body to Off-Body UWB Communication Link

The objective of this study is to investigate the feasibility of an ultra wideband (UWB) impulse radio system for in-body to off-body wireless communication for biomedical applications. At first, a UWB antenna is designed in the UWB low band for implant use in the chest. Then the channel model is extracted and established based on the finite difference time domain (FDTD) simulation with an anatomical human body model. The established channel model consists of a small set of parameters for generating discrete time impulse responses. The generated model shows good agreement with the FDTD-calculated result in terms of key communication metrics. For effective communication over the multipath-affected channel, the pulse position modulation is employed and a 2-finger RAKE structure with a constant temporal delay is proposed in the receiver. The bit error rate performance has shown the validity of the system in the in-body to off-body chest channel.

Optimal Relay Antenna Location in Indoor Environment Using Particle Swarm Optimizer and Genetic Algorithm

An optimization procedure for the location of the relay transceiver in ultra-wideband wireless communication system is presented. The impulse responses of different transceiver locations are computed by shooting and bouncing ray/image (SBR/Image) techniques and inverse fast Fourier transform (IFFT). By using the impulse responses of these multi-path channels, the bit error rate (BER) performance for binary pulse amplitude modulation (BPAM) impulse radio UWB communication system are calculated. Based on the BER performance, the outage probability for any given relay location of the transceiver can be computed. The optimal relay antenna location for minimizing the outage probability is searched by genetic algorithm (GA) and particle swarm optimizer (PSO). The transmitter is in the center of the whole indoor environment and the receivers are uniform distributed with 1.5 meter intervals in the whole indoor environment. Two cases are considered as following: (I) Two relay transceivers with two different cases are employed. First, the whole space is divided into two areas and one relay transceiver is used in each area. The optimal relay antenna locations are searched in each area respectively. Second, the two optimal relay locations are searched in the whole space directly without any prior division. (II) Four relay transceivers with two different cases are employed. First, the whole space is divided into four areas and one relay transceiver is used in each area. The optimal relay antenna locations are searched in each area respectively. Second, the four optimal relay locations are searched in the whole space directly without any prior division. Numerical results have shown that our proposed method is effective for finding the optimal location for relay antenna to reduce BER and outage probability.

A 800 Mb/s CMOS detection scheme for UWB impulse-radio communication

A CMOS detection procedure for ultra-wideband impulse radio (UWB-IR) communication system, employing Bi-Phase Shift Keying (BPSK) modulation scheme, is presented here. The chip, designed and fabricated in a 0.18 μ m CMOS process, requires a supply voltage of 1.8 V and occupies a die area of 0.01 mm 2. A train of Gaussian monocycle pulses (GMP), modulated by a random data sequence of 800 Mb/s, is detected successfully by the detector. The detection scheme employing a very simple architecture with a power consumption of 3 mW is well suited for non-coherent wireless communication system.