UWB Modulation Research Articles

Performance Evaluation of High Data Rate M-OAM UWB Physical Layer for Intelligent Transportation Systems

In this paper, a high data rate modulation scheme for impulse radio ultra-wideband (IR-UWB) communication system using orthogonal waveforms is presented. The proposed M-state Orthogonal Amplitude Modulation (M-OAM) is evaluated under additive White Gaussian noise and indoor multipath channels IEEE.802.15. The simulation results show that the proposed system performance, in term of bit error rate (BER), is of the same order as that of the traditional UWB modulation. In addition, the M-OAM modulations provide a high data rate for short range wireless applications. Nevertheless, the multipath effect reduces the quality of transmission. Thus, the performances of three receiver architectures, that employ different pulse combining schemes, are investigated. Namely, a conventional matched filter receiver, a RAKE receiver and a minimum mean square error equalizer are considered. This study shows that the proposed M-OAM communication system offers good performances in term of quality of services, channel capacity and BER.

Constrained pre-equalization accounting for multi-path fading emulated using large RC networks: applications to wireless and photonics communications

Multi-path propagation is modelled assuming a multi-layer RC network with randomly allocated resistors and capacitors to represent the transmission medium. Due to frequency-selective attenuation, the waveforms associated with each propagation path incur path-dependent distortion. A pre-equalization procedure that takes into account the capabilities of the transmission source as well as the transmission properties of the medium is developed. The problem is cast within a Mixed Integer Linear Programming optimization framework that uses the developed nominal RC network model, with the excitation waveform customized to optimize signal fidelity from the transmitter to the receiver. The objective is to match a Gaussian pulse input accounting for frequency regions where there would be pronounced fading. Simulations are carried out with different network realizations in order to evaluate the sensitivity of the solution with respect to changes in the transmission medium mimicking the multi-path propagation. The proposed approach is of relevance where equalization techniques are difficult to implement. Applications are discussed within the context of emergent communication modalities across the EM spectrum such as light percolation as well as emergent indoor communications assuming various modulation protocols or UWB schemes as well as within the context of space division multiplexing.

A New Optical UWB Modulation Technique for 250Mbps Wireless Link in Implantable Biotelemetry Systems

We propose an optical UWB modulation based on a new pulsed coding technique for wireless implantable biotelemetry. The solution employs sub-nanosecond laser pulses allowing for both high data rates and reduction of the power consumption compared to the state-of-the-art. Thus, the proposed approach is suitable for upcoming biomedical systems like autonomous implantable neural devices. The developed architecture consists of a transmitter and a receiver employing a pulsed semiconductor laser and a small sensitive area photodiode, respectively, and includes coding and decoding digital systems, biasing and driving analogue circuits for laser pulse generation and photodiode signal conditioning. Experimental findings, obtained by employing discrete components prototype PCBs and FPGA implementations, validate the novel technique showing the capabilities to achieve a BER less than 10-9 with data rates up to 250Mbps and an estimated power consumption lower than 5mW. These results enable, for example, the transmission of a 1000-channel neural recording system sampled at 16 kHz with 16-bit resolution.

IEEE 다중경로 채널에서 다중접속 M진 변조 초광대역 시스템을 위한 개선된 Rake 수신기

본 논문에서는 다중사용자 간섭이 존재하는 M-ary TH-PPM 시스템에서 확률분포 모델에 기반하는 개선된 초광대역 Rake 수신기법이 연구되었다. Rake 수신기의 성능 향상을 위해서 다중사용자 간섭과 잡음의 혼합 분포를 유연하게 근사할 수 있는 확률모델이 필요하며, 본 연구에서는 라플라스분포와 첨두치 정합(kurtosis matching) 기법이 적용된 일반화된 정규 라플라스모델이 고려되었다. 각 확률분포에 기반하는 Rake 수신기의 성능이 IEEE 다중 경로 페이딩 채널에서 평가되었고 종래의 Rake 수신기와 비교 되었다. 제안된 접근법은 종래의 Rake 수신기보다 더 우수한 BER 성능을 보인다.

Transmission Performance Investigation of IR-UWB Signals over Existing optical fiber Transmission link

Recently there is increasing interest in using optical fiber links to distribute impulse radio-ultrawideband (IR-UWB) signals in order to increase the coverage area. This paper investigates the transmission performance of these signals over existing fiber links and addresses the possibility of increasing the coverage area beyond 30 km.The transmission link consists of a single- mode fiber, dispersion compensating fiber (DCF) and, optical amplifiers. Simulation results are presented using Optisystem (version 13.0) software package for both Gaussian monocycle and 5th-order derivative Gaussian systems, each operating with ON-OFF keying (OOK) and biphase modulation (BPM) formats. The results reveal that extending the coverage area for 625 Mb/s UWB signal toward 100 km is possible for the UWB signals and modulation formats adopted in this study.

Signal Design for Improved Multiple Access Capacity in DS-UWB Communication

The paper addresses the signal design and performance analysis of direct-sequence ultra-wideband (DS-UWB) multiuser communication employing offset quadrature-spread phase shit keying (OQPSK) modulation with novel chip waveforms. Analytical bit error rate (BER) performance analysis is derived for different receiver structures, emphasizing the impact of the chip mean-squared auto-correlation function (MS-ACF) on BER performance in multiuser and multipath environments. A low-complexity flexible algorithm for designing chip pulses that maximize multiuser system capacity by minimizing the chip MS-ACF is proposed. The optimized waveforms are based on the use of prolate spheroidal wave function (PSWF) expansions. The proposed schemes also provide increased spectrum placement flexibility and minimized phase jumps compared to carrier-less pulse amplitude modulation (PAM) UWB schemes. Several design examples and numerical results are presented to illustrate the relative performance of the novel pulses compared to UWB schemes employing Gaussian monocycle derivatives and modified Hermite polynomials, and it is shown that a clear improvement in multiple access capacity can be achieved by the proposed PSWF-based pulses, particularly with maximum ratio combining receivers.

A Reconfigurable FM-UWB Transceiver for Short-Range Wireless Communications

A 3.7-4.3 GHz frequency modulated ultra wideband (FM-UWB) transceiver with digitally reconfigurable subcarrier modulation index, UWB bandwidth and RF frequency band is fabricated in 0.18 μm CMOS. Considering short-range low-data-rate applications for wireless body area networks, RF front ends, consisting of an output amplifier with -14 dBm power level, an FM demodulator with -35 dBm sensitivity, and a preamplifier with 25 dB gain, 6 dB noise figure, are designed. The presented implementation including UWB bowtie antennas achieves a bit error rate (BER) of 10-6 at a data rate of 12.5 kb/s with a wireless communication distance of 60 cm and the power dissipation of 21 mW.

All-optical UWB generation and modulation using SOA-XPM effect and DWDM-based multi-channel frequency discrimination

An all-optical UWB pulses generation and modulation scheme using cross phase modulation (XPM) effect of semiconductor optical amplifier (SOA) and DWDM-based multi-channel frequency discrimination is proposed and demonstrated, which has potential application in multiuser UWB-Over-Fiber communication systems. When a Gaussian pulse light and a wavelength-tunable CW probe light are together injected into the SOA, the probe light out from the SOA will have a temporal chirp due to SOA-XPM effect. When the chirped probe light is tuned to the slopes of single DWDM channel transmittance curve, the optical phase modulation to intensity modulation conversion is achieved at DWDM that serves as a multi-channel frequency discriminator, the inverted polarity Gaussian monocycle and doublet pulse is detected by a photodetector, respectively. If the probe lights are simultaneously aimed to different slopes of several DWDM channels, multi-channel or binary-phase-coded UWB signal generation can be acquired. Using proposed scheme, pulse amplitude modulation (PAM), pulse polarity modulation (PPM) and pulse shape modulation (PSM) to UWB pulses also can be conveniently realized.

Cyclic Prefix Signaling for Pulse Shape Modulation UWB RAKE Receivers

Combining transmission of ultra wideband pulses, organized in blocks, with the inclusion of cyclic prefixing pulses yields a pulsewidth periodic signal at the receiver. Although unknown, this signal fits perfectly the diversity exploitive architecture of a RAKE receiver. Aiming to profit from this signal arrangement, we propose a pulse shape modulation system employing a RAKE receiver that estimates this periodic signal during a training interval and uses the estimated values for detection of data symbols. Our proposal relies on the invariability of the multipath propagation channel during the transmission of a UWB packet, the adequate application of the cyclic prefix, and the fact that different transmitted pulses result in different periodic signals at the receiver. This system is equivalent to transforming the multipath nature of the UWB propagation channel into a multichannel digital communications affected solely by additive noise. Our proposal is important because it ameliorates the performance of a pulse shape modulation RAKE receiver. On the other hand, the cost of our proposed system resides in the inefficiencies product of the cyclic prefix inclusion.

Optically tunable multiband UWB pulse generation

A novel tunable multiband ultra-wide band (MB-UWB) pulses generation method using synchronously-apodized polarization modulation and birefringence time delay is proposed and demonstrated in this letter. Proper apodization profile is used to get MB-UWB pulses with spectra sidelobes suppression over 20dB. Five bands of MB-UWB pulses are generated by tuning the modulation frequency and transmitted over wireless channel. The central frequencies are from 4GHz to 6GHz and bandwidths larger than 500MHz. This method can be used in multiband modulation UWB over fiber systems.

Exact bit error rate analysis of direct sequence ultra-wide band multiple access systems in lognormal multipath fading channels

Exact BER analysis is carried out using the characteristic function (CF) method for direct sequence ultra-wide band (DS-UWB) systems in lognormal multipath fading channels. Unlike the Gaussian approximation (GA) method, the CF method deals with exact probability density function (PDF) of the total noise [including multiple access interference, self interference and additive white gaussian noise (AWGN)] instead of making approximation on PDF of the total noise. Exact bit error rate (BER) formula is derived and verified by simulation results. It is shown that the CF method is more accurate than the GA method in BER calculation when SNR is large. Based on the BER formula, the performance of the DS pulse amplitude modulation UWB and DS pulse position modulation UWB systems is accurately compared. Discussions based on CFs provide further insight into the numerical results.

Performance Analysis of TH-BPPM and TH-BPAM UWB System and the Applications in Data and Image Transmission

In this paper, we mainly analyze the performance of two ultra wideband communication systems, the classical Time Hopping Binary Pulse Position Modulation (TH-BPPM) UWB system and the Time Hopping Bipolar Pulse Amplitude Modulation (TH-BPAM) UWB system. The performance of TH-BPPM and TH-BPAM is analyzed in detail under an ideal AWGN channel and a correlation receiver. We use the power spectral density function to get the expression of BER of these two UWB systems. It yields simple and exact formulas relating the performance to the system parameters. The analysis shows that TH-BPPM suffers performance degradation with respect to TH-BPAM. Furthermore, we give the computer simulation of both data and image transmission and our simulation results also prove our theoretical analysis.

Ultra-wideband for multiple access communications

Ultra-wideband wireless communications techniques have many merits, including an extremely simple radio that inherently leads to low-cost design, large processing gain for robust operations in the presence of narrowband interference, covert operations, and fine time resolution for accurate position sensing. However, there are a number of challenges in UWB receiver design, such as capturing multipath energy, intersymbol interference especially in a non-line-of-sight environment, and the need for high-sampling-rate analog-to-digital converters. In this article, we provide a comprehensive review of UWB multiple access and modulation schemes, and their comparison with narrowband radios. We also outline the issues with UWB signal reception and detection, and explore various suboptimal low-complexity receiving schemes.

Software approach to access UWB interference on GPS receivers

Ever since the FCC approved the use of UWB devices in commercial and federal bands, various agencies whose operations and/or products rely on the integrity of signals within certain restricted radio frequency bands have voiced concerns over the potential impact of the UWB interference. GPS signals are among these restricted bands. Several groups in the GPS community have conducted experimental studies concerning the impact of UWB interference on the performance of various grades of commercial and aviation GPS receivers. In this paper, we present a software approach to simulate and evaluate UWB interference on GPS receivers. The software approach provides greater flexibility in the design of testing scenarios, such as the inclusion of a large number of aggregated UWB devices, the generation of new UWB signals and modulation schemes, and the possibility of extending the study to new GPS signals. The paper discusses a general framework for developing algorithms to evaluate UWB and GPS interference under a wide variety of hardware and software conditions. This framework consists of three classes of components: input, processing, and analysis. The input components are responsible for the generation of UWB signal waveforms and modulation schemes, and GPS signals. The processing components include a simulated model of GPS RF front end and software implementation of GPS processing blocks, such as acquisition, tracking, and post-processing. The analysis components focus on the study of specific receiver processing component outputs. Both real and simulated UWB signals can be used in the study. The real UWB signals are primarily used to validate the simulation procedure, whereas the simulated UWB signals are used to allow the immediate incorporation of new UWB waveforms and modulations in the evaluations. This paper presents details of the software components developed and the preliminary results achieved