A Low-Power Baseband ASIC for an Energy-Collection IR-UWB Receiver

This paper reports on the realization and the characterization of an application-specific integrated circuit (ASIC) intended for the processing of impulse radio ultra-wideband (IR-UWB) baseband signals. The incoming baseband signals result from the direct down-conversion of IR-UWB radio-frequency pulses, which are modulated by a binary frequency-shift keying (BFSK) scheme. The realized mixed-signal integrated circuit features an analog demodulation based on the quadricorrelation method, a non-coherent pulse detector using an integrate-and-dump operation and a bit-level synchronization digital circuit. An novel acquisition algorithm intended for low duty-cycled IR-UWB signals enabling a signal-to-noise ratio (SNR) estimate is proposed. The baseband ASIC is able to demodulate, acquire and decode BFSK IR-UWB signals. It requires 13 mW of supply power during the initial acquisition and 6.5 mW during the signal tracking phase at a pulse repetition rate (PRR) of 5 MHz. The circuit is fabricated in a 0.18-$mu{hbox {m}}$ CMOS technology.      

A Low-Cost and Low-Power CMOS Receiver Front-End for MB-OFDM Ultra-Wideband Systems

This paper presents an RF receiver front-end for MB-OFDM-based ultra-wideband (UWB) systems. The receiver occupies only 0.35 mm² in a 0.18 mum CMOS process and consists of a low-noise amplifier, downconverter and a bandpass filter. There are no on-chip inductors and the receiver requires no off-chip matching components. The measured receiver gain is 21 dB, noise figure is less than 6.6 dB, input IIP₃ is -5.6 dBm, and the receiver consumes 19.5 mA from a 2.3 V supply. The receiver covers all the MB-OFDM bands from 3.1 to 8 GHz     

时空编码WCDMA下行链路MMSE接收机

ＷＣＤＭＡ下行链路的性能受到信道衰落和多址干扰的影响。本文提出一种带时空编码的ＷＣＤＭＡ下行链路ＭＭＳＥ接收机,可以在减小信道衰落的同时达到抑制多址干扰的目的。应用高斯近似法对接收机性能进行了分析。仿真结果表明,该接收机能使系统性能得以较大提高。     

Low-Power VLSI Implementation of the Inner Receiver for OFDM-Based WLAN Systems

In this paper, we propose low-power designs for the synchronizer and channel estimator units of the Inner Receiver in wireless local area network systems. The objective of the work is the optimization, with respect to power, area, and latency, of both the signal processing algorithms themselves and their implementation. Novel circuit design strategies have been employed to realize optimal hardware and power efficient architectures for the fast Fourier transform, arc tangent computation unit, numerically controlled oscillator, and the decimation filters. The use of multiple clock domains and clock gating reduces the power consumption further. These blocks have been integrated into an experimental digital baseband processor for the IEEE 802.11a standard implemented in the 0.25mum- 5-metal layer BiCMOS technology from Institute for High Performance Microelectronics.     

Downlink Specific Linear Equalization for Frequency Selective CDMA Cellular Systems

We derive and compare several linear equalizers for the CDMA downlink under frequency selective multipath conditions: minimum mean-square error (MMSE), zero-forcing (ZF), and RAKE. MMSE and ZF equalizers are designed based on perfect knowledge of the channel. The downlink specific structure involves first inverting the multipath channel to restore the synchronous multi-user signal transmitted from the base-station at the chip-rate, and then correlating with the product of the desired user's channel code times the base-station specific scrambling code once per symbol to decode the symbols. ZF equalization restores orthogonality of the Walsh-Hadamard channel codes on the downlink but often suffers from noise gain because certain channel conditions (no common zeros) are not met; MMSE restores orthogonality only approximately but avoids excessive noise gain. We compare MMSE and ZF to the traditional matched filter (also known as the RAKE receiver). Our formulation generalizes for the multi-channel case as might be derived from multiple antennas and/or over-sampling with respect to the chip-rate. The optimal symbol-level MMSE equalizer is derived and slightly out-performs the chip-level but at greater computational cost. An MMSE soft hand-off receiver is derived and simulated. Average BER for a class of multi-path channels is presented under varying operating conditions of single-cell and edge-of-cell, coded and un-coded BPSK data symbols, and uncoded 16-QAM. These simulations indicate large performance gains compared to the RAKE receiver, especially when the cell is fully loaded with users. Bit error rate (BER) performance for the chip-level equalizers is well predicted by approximate SINR expressions and a Gaussian interference assumption.     

A Neural Network-Based Blind Multiuser Receiver for DS-CDMA Communication Systems

The Universal Mobile Telecommunications System (UMTS) which is based on Wideband-Code Division Multiple Access (W-CDMA) techniques is one of the most important broadband wireless communication systems. Adaptive Blind Multiuser Detection was widely considered for mobile receivers. The main drawback of this approach is that it achieves the optimum solution after a certain number of bit times. This paper deals with a new neural network approach in order to reduce the convergence time in different application environments. In particular, a modified Kennedy-Chua neural network, based on the Hopfield model is proposed. The neural network stability was investigated by means of a suitable analytical approach, while the performance of the proposed receiver scheme was derived by means of computer simulations. The numerical results shown in this paper highlight a fast convergence behavior of the proposed scheme, in particular under multipath-fading conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bit Error Probability for Baseband and Subcarrier Optical Communication Systems

Digital baseband and digital subcarrier noncoherent optical communication systems are considered in this paper. Expressions are developed for the bit error probability of optical subcarrier systems which use a nonliner polarization modulator and either a one-detector or a two-detector receiver, The expressions are evaluated numerically, and the results are used to compare the one- and two-detector subcarrier systems with the corresponding one- and two-detector baseband systems for a fLxed bit error probability.     

CSI-Based Resource Allocation for OFDM Downlink Broadband Multimedia Services in Cellular Systems

Using channel state information (CSI) in resource allocation in Orthogonal Frequency Division Multiplexing (OFDM) wireless cellular systems has been recently considered to improve the overall throughput. This paper presents an analytical framework to compare the performance of two resource allocation schemes, using CSI-based and random sub-carrier selection, in terms of their user outage probability and throughput in relation to the system load in frequency-selective fading and interference-limited environments. Analytical and simulation results are in good agreement and indicate that a proper use of CSI can achieve substantially better performance in interference limited cellular systems as compared to the blind approach and thus show the benefits of multi-user diversity.     

卫星通信中的数字基带预失真技术研究

数字基带预失真技术是克服高功率放大器非线性失真最有效的方法之一。早期对预失真技术的研究大多局限与无记忆非线性，但对于宽带和多载波应用。记忆非线性失真将不能再被忽略，无记忆预失真非线性补偿机制可能失效。文中研究了卫星通信系统中大功率记忆非线性功放的自适应基带预失真线性化技术，提出了一种基于记忆多项式的非直接学习结构的自适应基带预失真方案，给出了自适应算法。仿真结果表明，该方案能有效抑制带外频谱扩散，减小带内失真，降低误比特率，实现有记忆非线性大功率放大器的自适应预失真。     

Differentiated TCP User Perception over Downlink Packet Data Cellular Systems

Current downlink scheduling algorithms in the (enhanced) third-generation (3G) cellular packet systems exploit instantaneous channel status of multiple users, but most of them are blind to traffic information. To improve TCP users' perception of quality-of-services (QoSs), characterized by response delay, goodput, and always-on connectivity, we propose a cross-layer hierarchical scheduler with traffic awareness and channel dependence to properly prioritize buffer and radio resource allocation among different TCP classes. The scheduler has two tiers: at the IP layer, an intrauser scheduler enhances a common practice, i.e., the DiffServ-based buffer management, by dequeuing same-user TCP packets according to per-class specified and measured responsiveness; at the MAC layer, an interuser scheduler transmits the dequeued packets by considering the opportunistic channel states, mean throughput, and class ID of all users. Both tiers consider the online measured throughput, a cross-layer metric, to achieve resource and performance fairness and TCP classification. Experiments show that, compared with (variations of) proportional fairness (PF) and other schemes, our scheduler can notably speed up time-critical interactive TCP services (HTTP and TELNET) or TCP slow-starts with minor cost to bulk file transfer (FTP) or long-lived flows. It offers scalable and low-cost TCP performance enhancement over the emerging cellular systems     

未来移动通信系统中的小区间干扰协调技术

在未来移动通信系统中,小区间干扰成了主要干扰源,因此小区间干扰减少技术已成为人们的研究重点.本文结合3GPP相关提案,从静态和半静态两方面,对小区间干扰减少技术中的主流技术--小区间干扰协调技术进行了综述,并对该技术的未来研究方向进行了一些探讨.     

一种用于低功耗低成本的IEEE802.15.4接收器的新颖解调算法

提出了一种基于低中频、适用于ISM2.4 GHz频段ZigBee接收机的新型解调算法,满足IEEE802.15.4标准.作为数字相位解调,本算法采用相位差分、频率补偿和符号恢复,不用分别恢复出I路和Q路的码序列,而直接提取出相位斜率码,恢复出符号,从而简化了解调结构、降低了功耗和成本.通过与零中频过零检测算法的比较,本算法具有更低复杂度,更好的误符号率和误包率,完全满足IEEE802.15.4/ZigBeeTM标准的要求.     

一种基于射频电子标签的超低电压低功耗基带处理器

设计了一款应用于超高频段射频识别系统中电子标签的超低电压低功耗基带处理器.该基带处理器兼容协议,并满足无源标签的超低功耗要求.在设计上有针对性地提出了一种适合于门控时钟电源管理机制的体系结构,以及简单有效的随机数发生机制和分布式译码电路;并灵活运用了流水线结构、降低逻辑深度等低功耗技术.实现了解码/编码、CRC校验、指令解析、防碰撞机制和权限认证,以及对EEPROM的读写操作等功能.芯片采用Chartered 0.35μm 1P3M CMOS标准工艺实现,正常工作的最低电压仅为1.5V,平均电流2.1μA,功耗3.15μW,面积1.1mm×0.8mm.     

无源UHF RFID芯片中低功耗基带处理器的设计

对UHF RFID标签芯片的数字基带处理器结构及工作原理进行了分析。该基带处理器兼容ISO18000-6C协议。采用一系列先进的低功耗技术,如门控时钟技术、减小工作电压、降低时钟频率等,以降低无源射频识别标签的功耗。整个标签芯片采用TSMC 0.18μm 1P5M嵌入式EEPROM混合CMOS工艺实现。测试结果表明,该芯片正常工作的最低电压仅为1 V,平均电流为6.8μA,功耗为6.8μW,面积仅为150μm×690μm。     

Reconfigurable Antenna for Future Wireless Communication Systems

This paper deals with the processing techniques which are known as reconfigurable antennas: these methods are foreseen to be a booster for the future high rate wireless communications, both for the benefits in terms of performance and for the capacity gains. In particular, adaptive digital signal processing can provide improved performance for the desired signal in terms of error probability or signal-to-noise ratio while the bandwidth efficiency can be increased linearly with the number of transmitting and receiving antennas. In this article, the main antenna processing techniques are reviewed and described, aiming at highlighting performance/complexity trade-offs and how they could be implemented in the future systems. The coexistence of all these different technologies in a wireless environment requires high efficiency and flexibility of the transceiver. Future transceiver implementations which are based on the Software Defined Radio technology are also reviewed and described.     

一种多进制扩频通信基带接收的实现方法

为了在不增加带宽和不减小灵敏度的情况下增加扩频通信的数据传输速率,采用了多进制扩频通信的方法,该方法利用不同的扩频码来代表并传输信息,而不是用一种扩频码对信息源进行频谱扩展,不同的扩频码之间互相关性小且自相关性强,针对多进制扩频通信的设计思想,介绍了FPGA实现方法,详细描述了多进制扩频通信中数字下变频、伪码捕获和跟踪、载波捕获和跟踪的理论推导和技术实现途径。利用多进制扩频通信可以提高数据传输速率,在工程应用中,多进制扩频通信是一个可靠且有效的数据传输方法。     

小功率无线远程控制发射机和接收机

本文简述260～470MHz频段OOK(开关键控)发射机和接收机低成本方案。所设计的接收机用于跟踪和锁定SAW(表面声波)谐振器的载波或晶控PLL发射机。ASK(幅移键控)最简单形式是OOK，在OOK中由PCM(脉冲码调制)波形简单地开关载波。通常，低成本OOK发射机由SAW谐振器和用做Colpitts振荡器的晶体管组成。频率稳定性是令人满意的，可与晶控源相比。时间和温度会影响频率稳定性，300MHz SAW谐振器振荡器一般漂移为±150KHz。所设计的标准OOK接收机具有宽带响应，以便锁定位偏移的发射机，这是以灵敏度和选择性为代价的。本文所给出的…     

一种基于射频电子标签的超低电压低功耗基带处理器

设计了一款应用于超高频段射频识别系统中电子标签的超低电压低功耗基带处理器.该基带处理器兼容协议,并满足无源标签的超低功耗要求.在设计上有针对性地提出了一种适合于门控时钟电源管理机制的体系结构,以及简单有效的随机数发生机制和分布式译码电路;并灵活运用了流水线结构、降低逻辑深度等低功耗技术.实现了解码/编码、CRC校验、指令解析、防碰撞机制和权限认证,以及对EEPROM的读写操作等功能.芯片采用Chartered 0.35μm 1P3M CMOS标准工艺实现,正常工作的最低电压仅为1.5V,平均电流2.1μA,功耗3.15μW,面积1.1mm×0.8mm.