Cooperative Impulse Radio Ultra-Wideband Communication Using Coherent and Non-Coherent Detectors: A Review

Ultra-wideband (UWB) is a booming technology in the field of wireless communication. This paper presents a brief idea related to the various coherent and non-coherent IR-UWB detectors. Due to the limitation in transmit power spectral density of UWB system, the major challenges faced by UWB system includes, achieving Quality of Service, system performance and coverage area. So, the combination of UWB system with cooperative communication will not only improve the system performance, but also help in expanding coverage area of signals. A brief review of the work done by various researchers in the field of cooperative impulse radio (IR) UWB communication is also presented in this paper. The working principle and performance analysis of the various coherent and non-coherent IR-UWB detectors using cooperative relay strategies are also discussed at large in this paper. The various fixed cooperative relay strategies used for cooperative UWB communication is Amplify and Forward, Decode and Forward and Detect and Forward. From the simulation results it can be inferred that, even though IR-UWB DTR receiver gives a much better BER performance than IR-UWB ED receiver using both cooperative and non-cooperative strategies, yet ED receiver is preferred because of its less complexity and low power consumption. Future prospects in the field of cooperative IR-UWB communication have also been discussed in this paper.     

Non-Coherent Fourth-Order Detector for Impulse Radio Ultra Wideband Systems: Empirical Evaluation Using Channel Measurements

Low-complex and low-power non-coherent energy detectors (EDs) are interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems, but suffer from a loss in performance compared to coherent receivers. The performance of an ED also strongly depends on the integration interval (window size) of the integrator and the window position. This paper presents a non-coherent fourth-order detector (FD) which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. The performance of the detectors is evaluated using realistic channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed FD receiver is slightly better than the ED in low signal-to-noise ratio (SNR) region and its performance improves as the SNR increases. In addition, BER of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.     

基于高速ADC和FPGA的IR-UWB相干接收机设计

为了探索超宽带(UWB)技术的空间应用,设计了一款脉冲无线超宽带(IR-UWB)的全数字化相干接收机。本系统利用高速采样芯片ADC08D1000对IR-UWB信号进行双通道交织采样,接下来利用Xilinx FPGA对采样数据进行降速处理。按照二分搜索、相干捕获、脉冲跟踪的方案进行接收系统设计,并对该接收机进行了实际测试。最终实现了1 ns脉宽的IR-UWB信号的正确接收和1 Mb/s码速率的OOK编码通信。     

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.     

Data-aided efficient synchronization for UWB signals based on minimum average error probability

One of the biggest challenges in ultra-wideband （UWB） radio is the accurate timing acquisition for the receiver. In this article, we develop a novel data-aided synchronization algorithm for pulses amplitude modulation （PAM） UWB systems Pilot and information symbols are transmitted simultaneously by an orthogonal code division multiplexing （OCDM） scheme. In the receiver, an algorithm based on the minimum average error probability （MAEP） of coherent detector is applied to estimate the timing offset. The multipath interference （MI） problem for timing offset estimation is considered. The mean-square-error （MSE） and the bit-error-rate（BER） performances of our proposed scheme are simulated. The results show that our algorithm outperforms the algorithm based on the maximum correlator output （MCO） in multipath channels.     

A continuous-time IR-UWB RAKE receiver for coherent symbol detection

The ultra-wide bandwidth released for unlicensed use by FCC a decade ago has initiated significant research efforts. The large ultra-wide bandwidth is attractive not only for increased data transfer speed but may also be exploited for added functionality like high-precision ranging in wireless sensor networks. RAKE based receivers are preferred for ultra-wideband (UWB) technology due to wide bandwidth. However, designing RAKE based correlating receivers remains quite challenging. Correlating receivers are also power consuming due to high-speed DSPs, ADC and matched filter. Timing synchronization is another issue associated with correlating receivers. In this paper a impulse radio ultra-wideband (IR-UWB) RAKE receiver is presented utilizing a continuous-time binary value coding scheme for power-efficiency and coherent symbol detection without the need for synchronization to achieve precise ranging using time-of-flight technique. A working prototype of the IR ranging transceiver which uses the IR-UWB RAKE receiver is presented with measured high-precision ranging towards 1.4 cm.     

IR-UWB数字相干接收机的硬件电路设计

在超宽带信号的接收中,相干接收比非相干接收拥有更高的分辨率,能充分发挥超宽带信号定位精度高等优点.相干接收机对UWB信号进行高速采样后再处理,采样的速度和精度是限制UWB相干接收机测距精度的主要因素.本文设计并实现了IR-UWB的数字相干接收机,接收机采用高速采样芯片ADC08D1000对脉冲超宽带（IR-UWB）信号进行双通道交织采样,然后使用FPGA对采样数据进行降速处理.测试结果证明,本文设计的接收机能准确捕获到脉宽为1 ns的UWB信号.     

Performance analysis of non-coherent UWB receivers at different synchronization levels

Non-coherent ultra-wideband (UWB) receivers require no channel state information for demodulating the received signal. The primary non-coherent receiver in the UWB literature is the autocorrelation receiver, which autocorrelates the received signal at specific time lags, circumventing problems of template signal design and multipath energy combining. A unique advantage of the UWB autocorrelation receiver is its robustness to synchronization errors, which has not been explored yet to date. This paper investigates two major UWB schemes employing autocorrelation receivers: the transmitted reference (TR) scheme (R. Hoctor and H. Tomlinson, 2002) and the differential (DF) scheme (M. Ho et al., 2002). Performance is analyzed for TR and DF receivers at different synchronization accuracy levels, their robustness to synchronization errors is shown, and the existence of a tradeoff between performance and synchronization complexity for non-coherent UWB receivers is revealed. As a result of our analysis, comparisons of TR and DF schemes are also made in the presence of synchronization errors, which have not been addressed before. Simulations corroborate our findings.     

A self-duty-cycled 7.2–8.5 GHz IR-UWB receiver for low power and low data rate applications

A self-duty-cycled non-coherent impulse radio-ultra wideband receiver targeted at low-power and low-data-rate applications is presented. The receiver is implemented in a 130 nm CMOS technology and works in the 7.2–8.5 GHz UWB band, which covers the IEEE 802.15.4a and 802.15.6 mandatories high-band channels. The receiver architecture is based on a non-coherent RF front-end (high gain LNA and pulse detector) followed by a synchronizer block (clock and data recovery or CDR function and window generation block), which enables to shut down the power-hungry LNA between pulses to strongly reduce the receiver power consumption. The main functions of the receiver, i.e. the RF front-end and the CDR block, were measured stand-alone. A maximum gain of 40 dB at 7.2 GHz is measured for the LNA. The RF front-end achieves a very low turn-on time (<1 ns) and an average sensitivity of ?92 dBm for a 10^?3 BER at a 1 Mbps data rate. A root-mean-square (RMS) jitter of 7.9 ns is measured for the CDR for a power consumption of 54 µW. Simulation results of the fully integrated self-duty-cycled 7.2–8.5 GHz IR-UWB receiver (that includes the measured main functions) confirm the expected performances. The synchronizer block consumes only 125 µW and the power consumption of the whole receiver is 1.8 mW for a 3% power duty-cycle (on-window of 30 ns).     

Performance of UWB Receivers with Partial CSI Using a Simple Body Area Network Channel Model

Ultra wideband (UWB) communication is a very promising candidate for the use in wireless body area networks (BAN). The high UWB peak data rate allows for medium average data rates in combination with a very low duty cycle, which is the key for a very low power consumption. Devices in a wireless BAN require low complexity. Hence, mainly non-coherent receivers such as energy detector and transmitted-reference receiver are suited. In this paper, the symbol-wise maximum-likelihood (ML) detectors for pulse position modulation (PPM) and transmitted reference pulse amplitude modulation (TR PAM) are derived assuming partial channel state information (CSI) at the receiver. Additionally, also the ML detectors for a combination of PPM and TR PAM are presented. The performance of the derived receiver structures is evaluated using a novel BAN channel model not distinguishing line-of-sight and non line-of-sight situations. This simple channel model is based on 1100 channel measurements in the frequency range between 2 and 8 GHz, which were measured in an anechoic chamber. Using the BAN channel model, performance of the derived receiver structures is evaluated showing that the knowledge of the average power delay profile (APDP) at the receiver improves performance substantially. Requiring only slightly more complexity such receivers are a well suited alternative to non-coherent receivers for the use in a BAN.     

60 GHz芯片间无线互连系统中的Rake接收性能

在60 GHz芯片间无线互连信道中存在着多径干扰问题,采用Rake接收是提高系统性能的重要手段。针对脉冲超宽带( IR-UWB)的芯片间无线互连系统,分析了多径信道下Rake接收机的误码性能。在IEEE 802.15.3 c信道模型基础上,对不同分支数以及不同合并方案下的选择Rake ( S-Rake)和部分Rake(P-Rake)接收机误码性能进行了研究。仿真结果表明采用支路数为2的P-Rake在数据速率为10 Gb/s时仍具有良好的抗多径性能,这为芯片间无线互连系统的Rake接收方案提供了技术参考。     

An energy detection receiver for non-coherent IR-UWB

A non-coherent receiver for impulse radio ultra-wide band(IR-UWB)is presented.The proposed receiver front-end consists of a high gain LNA,a high frequency detector and an intermediate frequency(IF)amplifier to amplify the recovered signal and drive an external test instrument.To meet the requirements of high gain and a low noise figure(NF)under moderate power consumption for the LNA,capacitor cross coupled(CCC)and current reuse techniques were adopted.The detector consists of a squarer and an integrator.The overall circuit consumes 41.2mA current with a supply voltage of 1.8 V at a 400 MHz pulse rate.The resulting energy efficiency is 0.19 nJ/pulse.A chip prototype is implemented in 0.18-μm CMOS.The die area is 2.1×1.4 mm~2 and the active area is 1.7×0.98 mm~2.     

Simple non-coherent equaliser for the DECT system

A non-coherent equaliser structure suitable for DECT-type systems is introduced which performs equalisation at the output of a differential detector. It employs a two-state Viterbi algorithm using a simple channel estimation process. Performance assessments are presented which suggest that the new receiver can yield significant improvements with respect to standard non-coherent receivers in dispersive channels. At the same time, unlike coherent equaliser structures, it remains largely unaffected by both modulation index drifts and frequency offsets     

一种软件无线电GMSK非相干接收机

本文给出了一种适用于软件无线电的突发模式非相干GMSK接收机。该接收机可以在很短的前导字序列内完成载波和符号同步，采用线性近似的非相干检测算法来对非线性的GMSK。信号实现解调。该接收机采用前馈结构实现快速同步，同时具有较低的计算复杂度和相对优越的性能，适合于在线性软件无线电接收机平台上实现。通过仿真给出了该接收机与几种典型GMSK。接收机的性能比较，并且在实际软件无线电平台上得到验证。     

超宽带系统在窄带干扰条件下的性能研究

超宽带（Ultra Wide-Band，UWB）系统发射信号的带宽在一个非常大的频段范围内，易与已存在的窄带无线通信系统的带宽形成重叠。因此，有必要研究UWB系统在频段重合范围内的抗干扰能力。文中首先分析了直接扩频超宽带系统在最小均方误差准则检测方式下，RAKE接收机的比特误码率（Bit Error Rate，BERl，然后研究了普通窄带系统的功率谱密度，最后做出了仿真分析。结果表明，在CM1信道传播下，窄带干扰对UWB系统不会造成很大影响，而在CM2信道传播下会照成一定影响，必须通过其他通信手段如信道编码来降低BER，实现通信的可靠性。     

Performance Analysis of Time Reversal UWB Communication with Non-coherent Energy Detector

Non-coherent receivers, such as energy detectors (ED), are the simplest and the most practical alternatives to coherent receivers for low-rate and low-complexity applications in ultra-wideband (UWB) systems. However, these advantages are achieved at the expense of non-negligible performance degradation. One solution to improve the performance is to make use of time reversal (TR) technique. In this study, the performance of TR technique with non-coherent ED is analyzed in UWB systems. First, we derive an approximate analytical formula for the error probability of TR-ED which is based on tapped-delay line (TDL) channel model. Next, we theoretically and by simulations analyze the optimum integration interval which maximizes the performance of TR-ED. The results show that TR technique, by reducing the integration interval, considerably improves the performance compared to the conventional ED scheme.     

低功耗IR-UWB接收机和LNA设计研究

在分析各种超宽带(UWB)接收机系统结构的基础上,提出了一种低功耗IR-UWB接收机结构.该结构基于非相干通信机制,使用自混频技术和脉冲宽度调制方式(PPM).在该结构中,低噪声放大器(LNA)的低功耗优化是系统低功耗实现的关键.综合分析各种宽带LNA结构,提出了一种低功耗LNA设计.该LNA采用65 nmCMOS标准...     

Performance analyses of adaptive noncoherent receivers for MC‐CDMA communications

In this paper, we propose differential phase‐shift keying (DPSK) noncoherent receivers for multicarrier code division multiple access systems in multipath channels. The noncoherent receivers are composed of a linear equalizer and a decision‐feedback differential detector to detect DPSK signals. The performances of the proposed noncoherent receivers can be improved by increasing the number of feedback symbols. For an infinite number of feedback symbols, the optimum weight can be derived analytically, and the performances of the proposed noncoherent receivers approach that of the conventional coherent receiver. For adaptation of the equalizer coefficients, modified least mean square and recursive least squares algorithms are proposed. Furthermore, the reduced‐rank schemes are proposed to simplify the system complexities. Some simulation examples are given to show the system performances of the four proposed receivers. Copyright © 2014 John Wiley & Sons, Ltd.     

On the performance of a rapid synchronization algorithm for IR‐UWB receivers

Because of the very low signal duty cycles, synchronization is the most critical issue in ultra wideband (UWB) impulse radio (IR) systems. Some effective synchronization schemes like a symbol‐differential (SD) IR‐UWB receiver have been proposed to synchronize received signals rapidly. Yet, SD IR‐UWB receiver is unsuitable for operation in multi‐user environment because of multiple access interference (MAI). By taking advantage of frame‐differential IR‐UWB receivers, we propose a parallel frame‐differential (PFD) IR‐UWB receiver to do so. Our proposed PFD IR‐UWB receiver manifests better immunity against message passing interface and MAI than the SD IR‐UWB. Based on this PFD IR‐UWB receiver, uncertain (search) regions are limited to one frame duration without any symbol‐level synchronization process. Performance of PFD and SD receivers are compared by computer simulations, showing that the proposed PFD receiver not only achieves significant bit error rate performance but also better and more robust results than the SD receiver in this literature. Copyright © 2012 John Wiley & Sons, Ltd.     

Non‐Data‐Aided Weighted Non‐Coherent Receiver for IR‐UWB PPM Signals

This letter proposes an energy‐detection‐based non‐data‐aided weighted non‐coherent receiver (NDA‐WNCR) scheme for impulse radio ultra‐wideband (IR‐UWB) pulse‐position modulated signals. Compared to the conventional WNCR, the optimal weights of the proposed NDA‐WNCR are tremendously simplified as the maximum eigenvector of the IR‐UWB signal energy sample autocorrelation matrix. The NDA‐WNCR serves to blindly obtain the optimal weights and entirely circumvent the transmission of training symbols or channel estimation in practice. Analysis and simulation results verify that the bit error rate (BER) performance of the NDA‐WNCR closely approaches the ideal BER of the conventional WNCRs.