Transmitted Reference Research Articles

Analysis and Design of Low Complexity Receiver for UWB Transmitted Reference Based on Wavelets Transform

The Rake receiver has become very popular in wireless communication in recent years, but it has a number of drawbacks, including complexity, high noise, poor performance, and a slow transmission rate. As a result, a system with high performance, low complexity, low noise, and high efficiency is required. In this article, the idea of a new discrete wavelet transform (DWT)-based system is called Low Complexity (LC) Transmitted Reference (TR) Ultra Wideband (UWB) that achieves high performance, low complexity, higher transmission rate, and lower noise than previous discrete wavelet transform systems. High frequencies that caused noise in the system were cut off using DWT. To remove these frequencies, DWT uses two types of FIR filters. To get a better result, use three levels in this system. The simulation results show that when three levels of noise reduction are used, the effect is to remove high frequencies that cause noise in the TR UWB received signal.

An Energy Efficient On-Off Keying Transmitted Reference Pulse Cluster System for UWB Communications

In order to overcome the long wideband delay line issue of conventional transmitted reference (TR) ultra-wideband (UWB) systems, a transmitted reference pulse cluster (TRPC) structure was proposed and many related studies have been done. This paper presents a new on-off keying TRPC (OOK-TRPC) structure which can save half of the transmitting energy of the original TRPC scheme. Based on this new structure, an energy detector (ED) is applied and estimating methods for its symbol decision threshold are designed under different signal-to-noise ratio conditions. Analytical and simulation results show the energy efficiency of the proposed OOK-TRPC ED scheme. Therefore, from a practical point of view, the designed OOK-TRPC ED, which also can be applied to some previous TRPC related studies, is considered as a highly recommended practice, particularly in wireless sensor networks, internet of things, and wireless body area networks etc, where energy-saving has been becoming increasingly crucial.

A Solution to the Non-Ideal Delay Line Problem in Transmitted Reference Pulse Cluster Schemes for UWB Communications

The conventional transmitted reference (TR) technique in ultra wide-band (UWB) communications has provided a springboard for a lot of studies, and a TR pulse cluster (TRPC) structure was proved to have robust performance. Most of TR and TRPC related studies hitherto are based on the assumption that the delay lines (DLs) in their schemes are ideal. However, the group delay ripple (GDR) of nonideal DLs triggered by practical imperfect factors at implementation causes an unexpected distortion in both TR and TRPC UWB systems, and there are few studies so far. In this article, we first analyze the impact of the GDR of nonideal DLs on the performance of TR and TRPC UWB systems. Then a new design solution for both TR and TRPC transceivers is proposed, where the GDR information of the nonideal DL at the receiver side is introduced into transmitter side. The performance of the new design solution is analyzed and simulation results prove the robustness and efficiency of this new design method in reducing the impaction caused by nonideal DLs. Moreover, the proposed design solution can also greatly relieve the high design requirement of DLs in both the transmitter and receiver side and therefore offer valuable insight for the practical transceiver design in both TR and TRPC related UWB systems.

X-law detection scheme for monobit transmitted-reference ultra wideband receivers

<p>In ultra-wideband (UWB) communications, monobit receivers offer a low complexity implementation but at the same time exhibit a great performance loss. In this paper, a novel detection scheme, denoted as <em>x</em>-law detection (XLD), is proposed to diminish the performance loss caused by employing monobit analog-to-digital converters in transmitted-reference (TR) UWB receivers. Simulation results show that if the optimal value is employed for <em>x</em>, the XLD-based monobit weighted TR (MWTR) receiver can achieve 14.2~15.5 dB and 8~9.2 dB performance gain over the conventional MWTR receiver in LOS and NLOS scenarios, respectively. Moreover, the XLD-based MWTR receiver performance with the optimal value of <em>x</em> is only 1.6~3 dB away from the optimum MWTR receiver performance in intra-vehicle UWB channels. Additionally, the XLD-based MWTR receiver is not sensitive to the summation interval. This feature decreases the receiver complexity and guarantees a robust performance over different multipath channels. The significant performance improvement of the XLD scheme comes at a limited complexity increase. Thus, the XLD approach is a good candidate for TR-based and other training-based monobit receivers requiring low complexity, high performance, and low power consumption.</p>

Improved coded/uncoded monobit receiver for transmit-reference UWB communication systems: Performance evaluation and digital circuit design

In transmit-reference (TR) receivers, noise in the reference (pilot) pulse causes a noise × noise term in the decision statistic. This term severely degrades receiver performance. We propose a detection algorithm to decrease the noise in the reference pulse in TR receivers. Computer simulations show that at BER = 10−5, the proposed algorithm outperforms the existing algorithm by about 0.8 dB in both coded and uncoded scenarios. In high-rate applications, inter-symbol interference (ISI) drastically impairs the received signal. Monobit quantization intensifies the ISI and hence dramatically degrades the receiver performance. At first glance, channel coding increases ISI and seems useless to combat ISI. However, we propose to employ channel coding to overcome the severe performance loss caused by ISI. Simulation results show that in high SNR values, channel coding tackles the ISI problem especially when convolutional coding is used. Moreover, simulations reveal that convolutional coding is more robust to ISI compared to block coding schemes. Furthermore, the digital circuit design of coded/uncoded traditional and proposed monobit TR receivers is done in 0.18 µm CMOS technology at 2 V supply voltage. Simulations confirm the numerical results obtained in MATLAB. Finally, the power consumption of each receiver is reported.

Analysis of UWB Systems for Synchronization and Fine Timing

Ultra-Wide Band (UWB) technology due to its high speed, data rate and multipath immune characteristics is one of the promising solutions for communication systems. There have been awesome studies efforts to apply extremely-huge bandwidth using Ultra Wide band (UWB) technology to the military and government sectors. In UWB technology challenging task is synchronization and fine timing performance for the specified application. This paper explores the different types of UWB receivers which are Transmitted Reference (TR) UWB Receivers and Frequency Shifted Reference (FSR) UWB Receiver focusing on the synchronization and timing performance of the specified application. In order to identify these issues, the existing researches carried out in the domain of synchronization and timing performance of UWB from existing literatures. Through the review of existing literatures certain research gap are identified which are all stated in the research gap.

Biorthogonal PPM for Transmitted Reference IR-UWB Communication Systems

Research of impulse radio ultra-wideband (IR- UWB) systems has been extensively increasing in recent years due to their high power efficiency, high data rates and low hardware complexity. The choice of the modulation scheme used in an IR-UWB system has a great impact on its overall performances. In this paper, the biorthogonal pulse position modulation (BPPM) scheme for the application in transmitted reference (TR) IR-UWB communication systems is proposed. Performances of the BPPM scheme over two different IEEE 805.15.3a channel models in a multi-user environment are analyzed and compared to the performances of the pulse position modulation (PPM) scheme. The results show that the BPPM scheme outperforms the PPM scheme in terms of bit error rate (BER), data rate and hardware complexity. Additionally, the influence of different system parameters on the BPPM performances in TR IR-UWB systems is analyzed and possible trade-offs are proposed.

Design and Analysis of Passband Transmitted Reference Pulse Cluster UWB Systems in the Presence of Phase Noise

Transmitted reference pulse cluster (TRPC) signaling was recently proposed and developed for noncoherent ultra-wideband (UWB) communications. In this paper, a practical passband TRPC-UWB system is designed and analyzed to deal with the carrier frequency offset, phase offset and phase noise inherent in voltage-controlled oscillators (VCO) of the transmitter and the receiver. Based on a general model of noisy VCO and employing some reasonable assumptions, an equivalent linear time-invariant (LTI) analytical model is obtained to facilitate the bit error rate (BER) analysis. Our analysis shows that the constant carrier frequency offset and the phase offset can be removed by employing the passband transmitter and the noncoherent receiver. Furthermore, a semi-analytical BER expression is derived to show the impact of phase noise on the system error performance. Simulation results validate the semi-analytical expressions and both of them indicate that TRPC is more robust to the effect of phase noise than conventional transmitted reference (TR) and coherent UWB Rake receivers.

Low-density parity-check codes for noncoherent UWB communication systems

In order to guarantee reliable data transmission, powerful channel coding techniques are usually required in noncoherent ultra- wideband (UWB) communication systems. Accordingly, several forward error correction (FEC) codes, such as Reed-Solomon and convolutional codes have been used in noncoherent UWB systems to improve the bit error rate (BER) performance. In this paper, low-density parity-check (LDPC) codes are further studied as more powerful FEC candidates for noncoherent UWB systems. Two LDPC codes and the corresponding decoding procedures are presented for noncoherent UWB systems. Moreover, performance comparison between the LDPC codes and other FEC codes are provided for three major noncoherent UWB communication systems, namely, noncoherent pulse position modulation (NC-PPM), transmitted reference (TR) and transmitted reference pulse cluster (TRPC). Both theoretical analysis and simulation results show that the two investigated LDPC codes outperform other existing FEC codes with limited penalty in terms of complexity and therefore they are promising FEC candidates for noncoherent UWB systems with low- cost and low-power consumption.

A Transmitted Reference Pulse Cluster Averaging UWB Receiver

The transmitted reference pulse cluster (TRPC) structure for ultrawideband communications enables a more robust autocorrelation receiver (AcR) than a conventional transmitted reference (TR) scheme. In this paper, to further improve the performance of TRPC AcR, we propose a TRPC averaging (TRPC-A) AcR by using a TRPC-A method, which is similar but different from the pulse averaging method used in a conventional TR scheme. The proposed receiver structure is designed in both analog and digital methods, and their implementation complexities are explored. Our analytical and simulation results show that the proposed receiver can greatly improve the performance over the original TRPC receiver. What is more, the required additional implementation complexity of the proposed TRPC-A receiver added to the original TRPC AcR is much less than that of the averaging TR AcR added to conventional TR AcR due to the TRPC signaling characteristics. Therefore, from a practical point of view, the designed TRPC-A AcR is considered as a highly recommended practice, particularly in multiuser access environments.

Spectral-Efficient Green Wireless Communications via Cognitive UWB Signal Model

This paper focuses on spectral lines suppression for non-coherent impulse-radio ultra-wideband (IR-UWB) signals in the presence of pulse attenuation and timing jitter. Particular attention is devoted to severely unbalanced (i.e. non-uniform distributed) data sources where a unified spectral analysis is considered for both uncorrelated and correlated M-ary biorthogonal data-stream scenarios. Indeed, the specific novelty insights of this paper are as follows: i) Proposal of a new spectral-efficient signal model as a modified version of transmitted-reference (TR) approach, where each transmitted symbol is represented by a preamble Data-based Statistical Reference (DSR) followed by a set of transmitted data pulses and within this context, the preamble signal is designed to eliminate spectral lines via an adaptive monitoring of data-stream statistics as the optimal spectral policy; ii) Performance analysis in order to derive optimal signal parameters; iii) Evaluation of the system capabilities over different predefined operational modes.

Spectral-Efficient Green Wireless Communications via Cognitive UWB Signal Model

This paper focuses on spectral lines suppression for non-coherent impulse-radio ultra-wideband (IR-UWB) signals in the presence of pulse attenuation and timing jitter. Particular attention is devoted to severely unbalanced (i.e. non-uniform distributed) data sources where a unified spectral analysis is considered for both uncorrelated and correlated M-ary biorthogonal data-stream scenarios. Indeed, the specific novelty insights of this paper are as follows: i) Proposal of a new spectral-efficient signal model as a modified version of transmitted-reference (TR) approach, where each transmitted symbol is represented by a preamble Data-based Statistical Reference (DSR) followed by a set of transmitted data pulses and within this context, the preamble signal is designed to eliminate spectral lines via an adaptive monitoring of data-stream statistics as the optimal spectral policy; ii) Performance analysis in order to derive optimal signal parameters; iii) Evaluation of the system capabilities over different predefined operational modes.

무선광대역 시스템을 위한 블록 부호화 상관기 기반의 효율적인 수신기 설계 기법

Noncoherent receivers are favored for block-code-modulated ultrawideband impulse radio (UWB-IR) systems because of their low implementation complexity compared with coherent rake receivers. However, existing noncoherent schemes, such as transmitted reference (TR) systems and averaged differential receivers (ADR), suffer from performance degradation and energy efficiency loss. Codeword matching and signal aggregation (CMSA) is a low complexity noncoherent receiver for UWB-IR. As the frame/symbol duration is shortened to boost data rate, interframe interference (IFI) or intersymbol interference (ISI) occurs and degrades the detection performance of CMSA. In this paper, block coded correlator which consists of the delay components and the reference signal is proposed to improve the performance of the receiver. Simulation results show that the proposed system leads to the better performance compared to the conventional CMSA receiver.

Method for Bandwidth Efficiency Increasing of M-ary PPM Transmitted-Reference UWB Communication Systems

One of the main drawbacks of conventional transmitted reference (TR) ultra-wideband systems is the fact that time delay between the reference and the data pulse has to be at least equal to channel delay spread, in order to avoid inter-pulse interference (IPI). This requirement drastically limits the achievable data rate of conventional TR systems based on M-ary pulse position modulation (PPM). In this paper, the new method for M-ary TR PPM scheme bandwidth efficiency increasing is proposed. In the proposed method the orthogonal codes are used such that only the pulses which can cause IPI are coded. Usage of such type of coding allows the reduction of time delay between the reference and the data pulse, whereas IPI is avoided. The proposed method achieves higher bandwidth efficiency than the conventional TR PPM method for the similar BEP performance level. Furthermore, the results show that an additional increase in bandwidth efficiency can be achieved by using higher modulation levels. Additionally, the analysis on tradeoffs between the BEP performance, bandwidth reduction and system costs is given in this paper.

Optimal Receiver Scheme for Transmitted-Reference Ultra-Wideband System in Coal Mine

An average Transmitted-Reference (TR) receiver scheme based on orthogonal codes is proposed for improving the bit error rate (BER) performance and the transmitting rate of Ultra-wideband (UWB) TR receiver systems in coal mine. Orthogonal codes are used for modulating the reference pulses and the data pulses in each frame of every bit. Since the orthogonality of the two codes, the inter-pulse interference (IPI) is greatly reduced. Then the decoding reference pulses and the data pulses are averaged in a frame, which decreases the noise in the reference pulses and the data pulses. Finally, I demonstrate this optimal receiver scheme by the simulation in the coal mine roadway ultra-wideband channel model. Detailed simulation experiments are presented to validate the effectiveness of this proposed method. The experimental results show that this method can not only efficiently reduce the noise interference in receiving signals, but also can provide higher transmission rate, which make UWB signal receiving in coal mines more accurately. Index Terms—Coal mine, Ultra-wideband, Transmitted- Reference receiver, bit error rate

Performance of a Multi-hop UWB Transmitted Reference System using Decode-and-Forward Relays

In this paper, end-to-end average bit error rate (ABER) of a multi-hop decode-and-forward relay system is evaluated using ultra-wideband transmitted reference (TR) receiver over a multi-path fading channel. Distribution of individual hop signal to noise ratio (SNR) is approximated by a log-normal distribution and corresponding ABER is evaluated by Gauss-Hermite Quadrature rule. These individual hop ABERs are then used to find the end-to-end ABER performance analytically which is faster than the simulation method available in the literatures. Performances of three variants of non-coherent TR receivers: simple transmitted reference, average transmitted reference and differential transmitted reference (DTR) receivers are compared assuming same total transmit power for a fixed end-to-end distance in line-of-sight (LOS) and non line-of-sight (NLOS) channel model. It is observed that the end-to-end ABER performance using DTR receivers is the best and multi-hop relaying is also most effective using these receivers to improve the performance. It is also found that the laws of diminishing returns hold for performance gain in average transmit SNR per bit at a particular ABER in LOS channel i.e. performance improvement in terms of transmit SNR is not equal as the number of hop increases. It decreases with increase in hop number but the reverse trend can be found in NLOS channel.

Polarity-Invariant Square Law Technology for Monobit Impulse Radio Ultra Wideband Receivers

In this paper, a novel nonlinear signal processing technology, which is denoted as the polarity-invariant square law (PISL) algorithm, is proposed to compensate nonlinear distortions caused by monobit digitization and to mitigate the performance degradation of impulse radio ultra wideband (IR-UWB) receivers employing monobit analog-to-digital converters (ADCs). An analytical framework based on characteristic functions has been developed to evaluate bit error rates of monobit transmitted-reference (TR) receivers and performance improvement offered by the PISL algorithm. Both theoretical analysis and simulations show that by employing the PISL algorithm, the monobit weighted TR (MWTR) receivers can achieve a bit-error-rate performance that is more than 10 dB over the direct-reference algorithm and is less than 1.5 dB away from the performance bound of the MWTR receivers in intravehicle UWB channels. Furthermore, the MWTR receiver employing the PISL algorithm is insensitive to a correlation interval; this feature not only reduces complexity of the receiver design but also ensures performance robustness over various multipath channels. Therefore, the PISL algorithm can be considered an enabling technology for the monobit IR-UWB receivers that demand high performance, lower power consumption, and low complexity.

A passive-matched 22 GHz 2.6-dB-NF CMOS front-end with a 70-800 ps delay block

This paper presents a power-efficient RF differential receiver front-end supporting transmitted-reference (TR) communication in a 90 nm CMOS technology. Particularly, it addresses the issues of designing the frontend amplifier with low-noise and passive matching circuits on a silicon process and integrating a low-power delay unit in the front-end with wideband characteristics. The proposed architecture includes a differential high simulated gain (11 dB) amplifier which is centered at 21.6 GHz (in the K-Band) with a 6.2 GHz bandwidth (18.1~24.3 GHz). The input and output reflection parameters have centered values around -26 and -18 dB, respectively. With noise matching, the amplifier achieves 2.6~2.9 dB bandwidth noise-figure and 2 dBm input power limit for linear coverage. To interface the amplifier with a following RF mixer, a submicron delay-block (DB) is proposed with provision of adjusting number of stages in the delay chain. The branched DB architecture achieves monotonic delays covering a range of 70-800 ps (including group-dispersion). Tweaking of delay is possible through four design parameters and the set-up is analyzed by extending the number of cascaded stages up to eight. Driven from a 1.2 V supply, the amplifier and the DB consume 13.9 and 8.52- 10.61 mW power, respectively, and realize the circuits for the TR front-end. When compared with simulated results of reported CMOS receivers, the proposed design delivers higher performance in terms of a microwave figure-of-merit.

블럭부호변조 기반의 Transmitted Reference 광대역 통신 시스템

In the noncoherent methods for UWB-IR (ultra-wideband impulse radio), block coded modulation (BCM) is better than the transmitted reference (TR) systems in terms of the energy efficiency and data rate. However, even BCM suffers from the performance degradation in the presence of strong inter-frame interference and inter symbol interference. We propose the transmitted reference based on the BCM (TR-BCM) which is the hybrid system of TR and BCM. Performance evaluation shows that the performance of TR-BCM is better than that of BCM in the high SNR range.

A novel 7 Gbps low-power CMOS ultra-wideband pulse generator

In this study, a novel low-power high data rate ultra-wideband (UWB) pulse generator circuit is presented, which can be fully integrated in complementary metal oxide semiconductor (CMOS) process. The basic part of the circuit generates a UWB Gaussian monocycle pulse using the triangular pulse generation technique. A new bipolar phase shift keying pulse modulator is designed to control the polarity of the output pulses. The design includes additional functionality to make the pulse generator also applicable for transmitted reference (TR) signalling system. The circuit can generate pulses at a maximum rate of 7 giga pulse per second (Gpps) without TR pulse (TRP) and 3.5 Gpps with TRP. The generated pulses are symmetrical, each having a width of 142 ps and a peak-to-peak swing of 500 mV. The −3 dB bandwidth of the pulse spectrum is 9 GHz. The pulse generator consumes only 1.13 pJ per pulse from 1.2 V supply. The circuit is designed and simulated in 90 nm CMOS technology.