Non-coherent UWB Research Articles

System Level Simulation of Energy-Detection Based UWB Receivers

The performance of a non-coherent UWB receiver with Binary pulse position modulation is simulated with MATLAB; taking into account the effect of non-linearity, noise, pulse shape and channel effects. This simulation examines the minimum requirements for LNA, AGC, squarer, and operational transconductance amplifier in analog front-end for sensor network application with 100Kb/s data rate and 10-3 BER. The linearity requirement in OTA is achieved using Gilbert cell OTA with the technique of multiple gated transistors. For sensor network applications, analog front-end modules must have 4dB NF (Noise figure), -12dBm IIP3, 50dB gain and -75dBm sensitivity for 100Kb/s data rates. The transceiver power consumption is assumed to be below 50mW. The performance of energy detection non-coherent receiver is simulated in Simulink of MATLAB, it shows that BER of Gaussian pulse is lower than doublet and 4th Gaussian pulse. By increasing the number of transmitted pulse per bit and IIP3, the performance of receiver is improved.

Joint Multiple Symbol Differential Detection and Channel Decoding for Noncoherent UWB Impulse Radio by Belief Propagation

This paper proposes a belief propagation (BP) message passing algorithm-based joint multiple symbol differential detection (MSDD) and channel decoding scheme for noncoherent differential ultra-wideband impulse radio (UWB-IR) systems. MSDD is an effective means to improving the performance of noncoherent differential UWB-IR systems. To optimize the overall detection and decoding performance, this paper proposes a novel soft-in soft-out (SISO) MSDD scheme for noncoherent differential UWB-IR. We first propose a new sampling mechanism for the noncoherent auto-correlation receiver to sample the received UWB-IR signal. The proposed sampling mechanism can exploit the dependences (imposed by the differential modulation) among data symbols throughout the whole packet. The signal probabilistic model has a hidden Markov chain structure. We use a factor graph to represent this hidden Markov chain. Then, we apply BP message passing algorithm on the factor graph to develop an SISO MSDD scheme, which is easy to integrate with SISO channel decoding to form a joint MSDD and channel decoding scheme. Performance results of bit error rate simulations and EXIT chart analyses indicate the performance advantages of our scheme over the previous MSDD scheme.

초광대역 임펄스 라디오을 위한 변형된 블록 구조를 이용한 블록부호 변조 방식

무선광대역통신 시스템에서 채널 추정과 채널 동기를 얻기 위하여 복잡한 하드웨어 비용이 요구되는 동기 방식에 비하여, 구현이 용이한 비동기 방식이 다양하게 연구되고 있다. 본 논문에서는 비동기 방식중에서 성능이 우수한 블록부호 변조방식의 성능을 개선하는 방법을 제안한다. 블록부호 변조방식은 일반적으로 하나의 심볼을 N개의 펄스로 이루어진 블록으로 구성하고, 각각의 펄스의 간격은 일정한 길이를 유지한다. 펄스의 간격을 작게 하면 전송속도는 증가하지만, 펄스간의 간섭도 증가하여 비트오율이 커지게 된다. 제안하는 방식은 전송속도를 결정하는 펄스 간의 간격을 조정하여, 기존의 방식과 동일한 전송속도 하에서 비트오율을 낮추는 방법을 제안한다. 모의실험을 통하여, 제안된 방법은 전송속도 혹은 비트오율 측면에서 기존의 방식에 비하여 우수한 성능을 나타낸다. Non-coherent UWB receivers are promising due to the low hardware complexity while the coherent receiver such as the rake receiver requires the complex hardware to estimate channel characteristics and get the synchronization. In this letter, the block coded modulation scheme as one of the most promising method is enhanced in terms of the performance. The performance enhancement is carried out by the modification of the block structure with unequal frame length for each pulse. Simulation results show that the proposed method has the performance enhancement by the transmission rate or bit error rate.

CMOS energy detector based on complementary squarer circuit for non-coherent UWB receiver

CMOS energy detector based on complementary squarer circuit for non-coherent UWB receiver

Improved Noncoherent UWB Receiver for Implantable Biomedical Devices.

The purpose of this paper is to describe a novel noncoherent receiver architecture to improve the error performance of impulse-radio ultrawideband (IR-UWB) in bioimplanted devices. IR-UWB receivers based on energy detection are popular in biomedical applications owing to the low implementation cost/complexity and the high data rates that UWB can potentially support. Implanted devices suffer from severe frequency-dependent attenuation due to human blood and tissues, while most receivers in the literature are designed based on commonly used indoor wireless channel models. We propose a novel receiver design that is based on judiciously combining the energies in different bands of the signal spectrum with a weighted linear combiner. We derive the optimum coefficients of the combiner. The receiver retains almost all of the advantages of a conventional noncoherent detector, but can also compensate for attenuation properties of blood/tissue. The receiver design can be adapted to different implantation depths by simply varying the combiner weights. The receiver can also be considered to be a simple form of equalizer for noncoherent reception. Our simulations show about 2-dB improvement over other commonly used receivers. This receiver design is significant in that it can enhance critical battery life of implanted transmitters.

Particle Swarm Optimization Based Noncoherent Detector for Ultra-Wideband Radio in Intensive Multipath Environments

Given the dense multipath propagation in typical ultra-wideband channels, traditional coherent receivers may become computationally complex and impractical. Recently, noncoherent UWB architectures have been motivated with simple implementations. Nevertheless, the rudimentary statistical assumption and practical information uncertainty inevitably results in a hardly optimistic receiving performance. Inspired by the nature processes, in this paper we suggest a noncoherent UWB demodulator based on the particle swarm intelligence which can be realized in two steps. Firstly, a characteristic spectrum is developed from the received samples. From a novel pattern recognition perspective, four distinguishing features are extracted from this characteristic waveform to thoroughly reveal the discriminant properties of UWB multipath signals and channel noise. Subsequently, this established multidimensional feature space is compressed to a two-dimension plane by the optimal features combination technique, and UWB signal detection is consequently formulated to assign these pattern points into two classes at the minimum errors criterion. The optimal combination coefficients and the decision bound are then numerically derived by using the particle swarm optimization. Our biological noncoherent UWB receiver is independent of any explicit channel parameters, and hence is essentially robust to noise uncertainty. Numerical simulations further validate the advantages of our algorithm over the other noncoherent techniques.

An Energy-Detector for Noncoherent Impulse-Radio UWB Receivers

This study proposes an energy detector for a noncoherent impulse-radio UWB receiver, designed in a 0.18-mum CMOS technology. The squaring functionality is realized exploiting the quadratic characteristic of MOS transistors, and the deviation from such a characteristic due to short channel effects and device mismatch is carefully considered in the paper. The squared signal is integrated using a Gm-C integrator that is interfaced with the squarer using a flipped voltage follower current sensor as a current to voltage converter. The proposed circuit dissipates 5.4 mW for a receiver sensitivity at the antenna of -89 dBm. Synchronization is demonstrated at the system level and some considerations on robustness to narrowband interferers are presented.

An improved conditional maximum-likelihood detector for noncoherent UWB communication

A noncoherent UWB demodulation and detection algorithm has been proposed that circumvents the problems of timing synchronization and channel estimation for impulse based UWB systems. Originally two detection algorithms were offered, a maximum-likelihood sequence detector and a reduced complexity conditional ML detector. We offer an improvement to the conditional ML detector based on the observation that for this algorithm it does not matter whether or not the bursts are detected in forward or reverse order. Our algorithm improves performance by roughly 0.8 dB over the previous conditional ML detector.

A highly linear gilbert cell OTA with multiple gated transistors for non-coherent UWB receivers

A highly linear gilbert cell OTA with multiple gated transistors for non-coherent UWB receivers

Non-Coherent UWB Communications

Early UWB concepts for communications have almost exclusively relied on impulse radio, where the whole available bandwidth, i.e., up to 7.5 GHz, is covered at once by means of very short pulses which are generated with a low duty cycle. Meanwhile, a bandwidth of 7.5 GHz is only available in the US [1, 3]. In Europe, the spectrum which is available with the same transmit power spectral density of -41.3 dBm/MHz ranges only from 6.0 to 8.5 GHz [4], if no detect and avoid techniques are applied1. A potential UWB system has therefore to be able to ’live’ with a mean transmit power of less than -7.3 dBm.

A Multiple-Mask Operation Compatible with IEEE 802.15.4a Non-coherent UWB Ranging Systems

During the execution of precise ranging in the time domain, the most important fact to consider is how to achieve an accurate estimate of the time corresponding to first arrival of the transmitter. However, it is difficult to extract an estimate of the time-of-arrival (TOA) through use of a simple correlator due to degradation on correlation, and in the case where the pulse repetition interval (PRI) is less than the maximum excess delay (MED). In order to enhance the correlation capability, this paper proposes a TOA estimation method that obeys a threshold predetermined in a non-coherent system using multiple-mask operation (MMO). The performance of the proposed scheme is verified by conducting simulations under two different types of channel situations. The simulation results show that the proposed scheme performs well even in a dense indoor multipath environment and with the existence of multiple simultaneously operating piconets (SOPs).

A Novel Ranging Method using Energy Window Bank in Non-coherent UWB Systems

This paper proposes a novel UWB ranging scheme employing 1-bit ADCs and analog window bank for energy collection. For an appropriate 1-bit ADC process DC offset is exploited and removed via performing analog low pass filter. To improve ranging accuracy in presence of ambiguity, dual overlapped window banks designated as primary and auxiliary windows are utilized. Corresponding to the proposed ranging scheme, its performance is verified by conducting simulations in two types of channel conditions. The simulation results show that the proposed ranging scheme performs well even in condensed multipath environment and low SNR situation.

Comparison between Coherent and Noncoherent Receivers for UWB Communications

We present a comparison between coherent and noncoherent UWB receivers, under a realistic propagation environment, that takes into account also the effect of path-dependent pulse distortion. As far as coherent receivers are concerned, both maximal ratio combining (MRC) and equal gain combining (EGC) techniques are analyzed, considering a limited number of estimated paths. Furthermore, two classical noncoherent schemes, a differential detector, and a transmitted-reference receiver, together with two iterative solutions, recently proposed in the literature, are considered. Finally, we extend the multisymbol approach to the UWB case and we propose a decision-feedback receiver that reduces the complexity of the previous strategy, thus still maintaining good performance. While traditional noncoherent receivers exhibit performance loss, if compared to coherent detectors, the iterative and the decision-feedback ones are able to guarantee error probability close to the one obtained employing an ideal RAKE, without requiring channel estimation, in the presence of static indoor channel and limited multiuser interference.

A new noncoherent UWB impulse radio receiver

This letter analyzes the implementation issues related to coherent receivers for UWB impulse radio with a special emphasis on timing and jitter problems. We propose a new jitter tolerant receiver design that is easy to implement. Analytical BER analysis and simulations verify that the performance of the proposed receiver is comparable to that of a correlator-based receiver that includes jitter. The new design is a promising candidate for low-cost low-power UWB IR receiver implementations.