Transmitted Reference UWB 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.

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.

Reference-Modulated PI-DCSK: A New Efficient Chaotic Permutation Index Modulation Scheme

In this paper, we propose a reference-modulated permutation index differential chaos shift keying (RM-PI-DCSK) over multipath fading channels. Due to quasi-orthogonal property between different permutated chaotic signals, the proposed scheme can remarkably suppress the inter-sequence interference to recover the desired information. Moreover, the proposed RM-PI-DCSK has one more modulation bit in the reference segment than the conventional permutation index differential chaos shift keying (PI-DCSK). Both the reference signal in the first time-slot and a permuted replica of the reference in the second time-slot are modulated for efficient transmission. The theoretical bit-error-rate (BER) performance and the highly consistent simulation results demonstrate that the proposed RM-PI-DCSK can achieve a performance gain 3 dB over the conventional PI-DCSK at a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-4}$</tex-math></inline-formula> , and this gain becomes larger in a high-delay-spread channel. In particular, the performance superiority of the RM-PI-DCSK is further demonstrated in a typical ultra-wideband (UWB) channel with narrow-band interference. Therefore, this proposed scheme can be deemed as an efficient transmission alternative for chaotic-based wireless communications, such as in wireless local area network (WLAN) applications and indoor applications of the transmitted-reference UWB.

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

&lt;p&gt;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 &lt;em&gt;x&lt;/em&gt;-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 &lt;em&gt;x&lt;/em&gt;, 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 &lt;em&gt;x&lt;/em&gt; 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.&lt;/p&gt;

Differential Permutation Index DCSK Modulation for Chaotic Communication System

This letter proposes a differential permutation index differential chaos shift keying (DPI-DCSK) modulation for wireless communications. The conventional PI-DCSK has the disadvantage of wasting transmission energy and the loss of system performance. In $M$ -ary DPI-DCSK, one chaotic sequence to be sent represents current modulated ${M}$ -ary symbol as well as the reference of next modulation symbol in a data frame, which can fully utilize the transmission energy with the same hardware implementation as PI-DCSK. The bit error performance of the proposed DPI-DCSK over the multipath Rayleigh fading channel is theoretically analyzed. The simulation results show that the proposed DPI-DCSK achieves a performance gain of more than 3 dB over PI-DCSK, especially in high-delay multipath fading channels. The performance advantage of the proposed scheme is also illustrated in practical ultra-wideband (UWB) channels. Thus, DPI-DCSK is an efficient alternative transmission scheme for chaos-based wireless communication, such as indoor applications of transmitted-reference UWB communications.

Transmitted reference UWB wireless receiver based on FFT technique

Transmitted reference UWB wireless receiver based on FFT technique

An Efficient Transmission Scheme for DCSK Cooperative Communication Over Multipath Fading Channels

Differential-chaos-shift-keying cooperative communication (DCSK-CC) has attracted a great deal of attention in the past five years, because it can overcome the negative effect of wireless multipath fading. However, the conventional DCSK-CC system suffers from a major disadvantage of low data rate due to the resource consumption in cooperation. To address the issue, this paper proposes an efficient cooperative scheme, called partial-sequence CC (PS-CC) scheme , for the DCSK-CC system. In the PS-CC framework, the source and relays only transmit a partial chaotic sequence corresponding to one bit to the destination, while consuming the same transmission energy as DCSK-CC. To validate the feasibility of the DCSK PS-CC system, this paper carries out the error performance, diversity order, and data rate analyses under different cooperative conditions over multipath fading channels. Both numerical and simulated results show that the proposed PS-CC system outperforms the DCSK-based non-cooperative system and DCSK-CC systems over the range of signal-to-noise ratio under study. Moreover, the proposed system can enhance data rate and reduce the computational overhead of the relays as compared with the DCSK-CC system. In addition, it will be demonstrated that the DCSK PS-CC system preserves its advantages in typical ultra-wideband (UWB) channels. Overall, the PS-CC appears to be a desirable cooperative scheme for those applications featured by high-data-rate, low-power, and low-complexity, such as wireless sensor networks using the transmitted reference UWB technique.

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

Coded M-ary Pulse Position Modulation for Transmitted Reference UWB Communication System

In this paper, a coded M-ary pulse position modulation (PPM) scheme for transmitted reference ultra-wideband (TR-UWB) systems is proposed. In conventional M-ary PPM TR-UWB scheme, modulation level M is defined only with a number of possible pulse positions Z. So, Z radio frequency (RF) wideband delay lines are required in order to map data bits into the proper pulse position, which makes such system very impractical to implement when the current CMOS technology is used. In the proposed scheme the number of required delay lines is reduced by mapping data bits in both, pulse position and K different orthogonal codes on frame level of the signal, producing a modulation level of M = KZ. To evaluate the performances of the proposed coded M-ary PPM scheme, the analytical model for realistic IEEE standard UWB channel models is developed. The performances of the proposed scheme are compared with these of the conventional M-ary PPM scheme for the same modulation level M. The results show that the proposed coded M-ary PPM scheme achieves approximately the same bit error probability (BEP), higher data rate and higher bandwidth efficiency, while the hardware complexity is lower in terms of number of required RF delay lines. However, by increasing the number of used orthogonal codes the minimum number of frames per one information symbol rises and consequently the maximum achievable data rate is limited. Thus the trade-off between the number of orthogonal codes and target data rate should be made. DOI: http://dx.doi.org/10.5755/j01.eee.20.10.6797

A Differential Transmitted Reference UWB Receiver Using Time Reversal Technique

A Differential Transmitted Reference (DTR) system is analyzed for Ultra Wideband (UWB) communications in a multipath propagation environment with single user transmitted. In order to improve the data rate, The Time-Reversal technology is proposed for the DTR receiver in the paper, which can also resist the influence of Inter/intra Symbol Interference (ISI). Computer simulation is conducted in the presence of an IEEE802.15.3a CM2 channel with Scholtz’s pulse. Analysis and simulation are both shown that the TiR-DTR receiver can improve the data rate of UWB system.

CLOSED-FORM PDF FOR MULTIUSER TR-UWB SYSTEMS UNDER GAUSSIAN NOISE AND IMPULSIVE INTERFERENCE

In most existing transmitted-reference ultra-wideband (TR-UWB) communication systems, receivers use the standard Gaussian approximation (SGA) for multiuser interference (MUI). It is an assumption used in most conventional multiuser systems, where the MUI tends to a Gaussian process by the central limit theorem, and convergence is relatively fast with respect to the number of users. However, for TR-UWB systems which are developed for short-range applications, we have a small number of active users. In this case, significant performance degradation is found in TR-UWB receivers due to the impreciseness of SGA. In this paper, we show that the Middleton class-A model is a more appropriate statistical model for MUI modeling in TR-UWB systems than the often used SGA. A closed-form expression for the probability density function (PDF) of the TR-UWB system under MUI, Gaussian noise and impulsive alpha-stable interference is developed. All these analytical results are confirmed by numerical simulations. (17 References).

A window detection technique with adjustable threshold for transmitted reference receivers

Abstract This paper presents a threshold decision circuit with an adjustable detection window designed in a 90-nm IBM CMOS technology. Together with an RF mixer, the decision Section realizes the circuit implementation of the back-end of a transmitted reference ultra wideband receiver, which is yet to be reported in literature. The proposed circuit is built on a differential amplifier core and avoids the use of integrator and sampling blocks, which reduces the device burden necessary for the architecture. Moreover, the detection window threshold of the design can be regulated by three independent factors defined by the circuit elements. The circuit is tested at an input data rate of 0.1∼2.0 Gbps and the core decision section consumes 9.14 mW from a 1.2-V bias supply (with a maximum capacity/Pdc ratio of 218.8 GHz/W). When compared against other reported decision blocks, the proposed detection circuit shows improved performance in terms of capacity and power requirement.

Wavelet Pulse를 이용한 다중 사용자 환경에서의 TR-UWB 시스템의 성능 비교

Abstract In this paper, the performance comparison of the TR-UWB System using Wavelet Pulse, DPSS pulse, and second Gaussian pulse in multi-user environment is analyzed. The data signal and the reference signal is sent with some time intervals in TR-UWB system. At this time the two signals are through the same channel. In the receiver the reference signal is used as a template. This advantage results in demodulation without channel estimation and low complexity of it. However the conventional TR-UWB system based on a Gaussian signal in a multi-user environment has the disadvantage of poor performance due to the interferences between the users. To overcome this disadvantage, DPSS (Discrete Prolate Shperoidal Sequence) is used to reduce the interferences between the users. We propose the system with multiresolution function of orthogonal wavelet reducing the interferences, which has a better performance in multi-user environment when they are sent in transmission side. Key Words : Wavelet, Discrete Prolate Shperoidal Sequence, Transmitted Reference Ultra Wide Band, Multiresolution

DDCSK-Walsh Coding: A Reliable Chaotic Modulation-Based Transmission Technique

To overcome the performance loss of noncoherent detectors of differential chaos-shift keying (DCSK), some improved versions of DCSK have been proposed. However, little has been done to improve the multiuser DCSK system based on Walsh codes (WCs), i.e., referred to as DCSK-WC, although it is considered more feasible in practice among the existing multiuser DCSK systems. This brief introduces a novel differentially DCSK (DDCSK) technique into such a multiuser system so as to build the desirable DDCSK-WC, obtaining significant performance gain, as compared with the conventional DCSK-WC, while retaining its hardware complexity unchanged. Moreover, the proposed system can greatly enhance the robustness against intersymbol interference in a wireless multipath fading channel. Therefore, the new system is deemed to provide a good alternative transmission scheme for wireless communication based on chaotic modulation, in such as indoor applications of the transmitted-reference ultrawideband. The theoretical analysis and simulated noise performances of the proposed system demonstrate their high consistence.

Improved low-complexity transmitted reference pulse cluster for ultra-wideband communications

Transmitted reference pulse cluster (TRPC) signalling was recently proposed for robust low-rate ultra-wideband (UWB) communications. TRPC provides significant performance gains over conventional transmitted reference (TR) UWB, and overcomes the critical long delay line problem associated with TR UWB. Thus, it is suited for practical implementation of a UWB communication system. The compact spacing of the pulses in TRPC leads to inter-pulse interference (IPI). In this study, the authors show that there exists an asymmetry between the two conditional distributions of the autocorrelation decision variable because of this IPI. This implies that the conventional zero decision threshold (ZDT) is not optimal for a TRPC autocorrelation receiver, and hence the authors derive the optimal maximum likelihood decision threshold. The authors propose two practical techniques for threshold determination. The first technique employs a training sequence whereas the other simply uses the decision variables of the received data signals to estimate the threshold. Simulation results show that in terms of the bit error rate (BER) performance, both the training-assisted adaptive decision threshold (TA-ADT) and the data-assisted ADT (DA-ADT) can achieve significant gains over the conventional ZDT-based detection for TRPC.

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.

A modified code domain transmitted reference UWB system

Based on the research on time domain and frequency domain transmitted reference Impulse Radio Ultra-WideBand (IR-UWB) system, this paper studies the optimization design for code domain transmitted reference IR-UWB system, and proposes a modified code domain transmitted reference IR-UWB system. The Bit Error Rate (BER) expressions for the modified system model in the condition of Additive White Gaussian Noise (AWGN) and multipath fading are deduced respectively. In addition, the performances of the modified system and the other three transmitted reference IR-UWB systems are simulated and compared. Theoretical analysis and simulation results show that the performance of the modified system is superior to the other three systems.

Performance of Non-Polarized Noise Modulated Communications System in the Presence of Interference

The noise modulated non-polarized communication system, developed by us recently, is an ultra-wideband transmitted-reference system designed for secure interferencefree communications. By using ultra-wideband random noise to spread the signal and by using polarization diversity for transmitting the spread message and the reference signal, we make the transmitted signal appear totally featureless and noise-like. However, the system may encounter intentional and non-intentional interference since its operating bandwidth is very large. This paper derives analytical models to characterize system performance in partial-band jamming channels and channels containing narrowband interference. Models compare very well with simulations and results validate successful system operation under low signal-to-interference ratio conditions. Research also reveals that the center frequency of transmitted signal must be suitably protected to prevent link outage due to the presence of cross-interference terms. Since multipath acts as self-interference for communication systems, a new method which can improve system performance in multipath environments is also introduced in this paper.

IR-UWB Transmitted-Reference Systems With Partial Channel Knowledge: A Receiver Design Based on the Statistical Invariance Principle

This paper deals with detection algorithms for impulse-radio ultrawideband transmitted-reference systems. For binary modulation schemes, we propose a novel detector that operates on the partial autocorrelations of the received signal as computed over time intervals (bins) of size less than the symbol period. Assuming that the receiver has knowledge of the partial autocorrelations of the channel response over those bins, we derive the minimum error probability detector (MEPD). In doing so, we exploit some invariance properties of the detection problem under consideration. It turns out that the receiver adopting such a strategy is superior to a conventional TR system, the more so the smaller the bin size is. Also, we address the problem of estimating the partial autocorrelations of the channel response and propose a simple solution by exploiting a training sequence. The impact of the estimation errors on the receiver performance is shown to be marginal.