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The following topics are dealt with: acquisition-synchronization; coding-modulation; UWB-impulse radio; signal generation; transceiver design; channel modeling; OFDM; transmitted reference; antennas; energy and bandwidth in wideband systems; networks and applications; diversity; circuits; positioning-localization
The satisfactory performance of classical tracking circuits presumes that acquisition (coarse synchronization) has provided a good estimate of the correct symbol or frame timing (typically within a fraction of the chip duration). This might not be a reasonable assumption for pilot-assisted UWB receivers in dense multipath, where initial acquisition of the LOS component is highly problematic, and coarse...
This paper addresses the problem of coarse synchronization of ultra wideband (UWB) signals in the dense multipath channel. We propose a very simple search strategy, based on successive constant integer jumps, which practically achieves minimum mean acquisition time (MAT) without using any channel knowledge. There is a parallelism between the popular bit reversal search, which is valid when the size...
We consider initial timing acquisition, frame synchronization and code acquisition for asynchronous DS-UWB transmissions in a distributed network topology, i.e., no common timing reference and neither synchronization among terminals are provided. Thus, when an arbitrary terminal in active mode needs to establish communication with reachable terminals, it listens for a common synchronization signal...
This paper is concerned with timing acquisition for ultra-wideband (UWB) communication systems operating in a dense multipath environment with a modest clock frequency offset (CFO). A low complexity maximum likelihood acquisition scheme based on a practical energy detector is considered in this paper where the dwell time for observing the signal at a given trial offset is fixed. This dwell time interval...
A two stage acquisition scheme for IR-UWB has been proposed to reduce the acquisition time of the spreading sequence. It has been shown that the performance of this scheme is better than that of the conventional scheme on AWGN channel. In this paper, the proposed scheme is investigated on the channel models of IEEE 802.15.4a. It is shown through the computer simulation that the proposed scheme can...
In this paper, we present an analog Viterbi decoder structure suitable for direct sequence UWB applications. Since the UWB receiver has data rates of several hundreds of megabits per second, the elimination of the power consuming A/D converter makes an analog Viterbi decoder a promising alternative to conventional digital decoders. Moreover, the high-speed implementation of the Viterbi decoder is...
Ultra wideband (UWB) communication systems are generally applied to short-range wireless communications. In order to achieve higher rates or to support multiple access capabilities, direct sequence spread spectrum (DSSS) techniques have been introduced to UWB systems. Furthermore, the concept of M-ary code shift keying (M-CSK) was introduced into DSSS systems to achieve higher rates. In this work,...
In the context of low data-rate UWB (ultra-wideband) networks, relying upon impulse radio-based devices, it has emerged the need of devising coding/modulation schemes amenable of both coherent and non-coherent detection. The rationale being the potential coexistence of different classes of devices characterized by different complexity/performances. In this work, we consider several orthogonal convolutional...
As a high-rate alternative of impulse radio (IR) ultra-wideband (UWB) communications, analog and digital multi-carrier UWB radios with coherent detection have been introduced. In this paper, we investigate digital multi-carrier differential (MCD) modulation and demodulation schemes for UWB. In our approach, the differential encoding and decoding are carried out across multiple digital carriers in...
Interleaved coding-modulation (ICM) is a recently proposed method for ultra-wideband impulse radio (UWB-IR) systems. ICM exploits the concept of chip interleaving, allowing to alleviate the problem of inter-symbol and inter-pulse interference commonly present in high data rate UWB-IR systems. In this paper, previous work on ICM is extended to scarcely populated multi-user scenarios. A novel design...
In this paper we propose a framework for analyzing the performance of ultra wide band (UWB) receiver architectures in sparse multipath channels with intra-pulse interference. In particular, we develop an analytical method based on approximating the moment generating function (MGF) of the received signal-to-noise ratio (SNR) via Pade expansion. We derive closed-form expressions for the average bit...
Time hopping-biorthogonal pulse position modulation (TH-BPPM) performance is characterized using a modified Saleh-Valenzuela (S-V) ultra wideband (UWB) channel model as adopted by the IEEE for personal area networks (PANs). TH-BPPM performance is characterized for single and multiple user scenarios using up to 20 multipath signals from each of 10 users operating for both synchronous and asynchronous...
Ultra-wideband (UWB) impulse radio systems based on non-coherent on-off keying (OOK) energy detection are relatively simpler to implement than their coherent counterparts, because the strict synchronization requirements are relaxed. However, the design challenge is to set a hard decision threshold value after energy detection because the detected energy may vary due to multipath fading and inter-pulse...
The purpose of this study is to analyze and improve performance of pre-post-RAKE combining in UWB-IR system. In UWB-IR system, it is easy and effective to improve communication quality by means of the path-diversity techniques such as RAKE combining. However, combining many paths requires large amount of calculations and this leads to the increase of the hardware complexity. This complexity may spoil...
In this paper, we develop an algorithm to extract the parameters of a multipath model of an UWB channel from measurement-simulated data. To this end, we cast the parameter estimation problem into a standard model selection problem and apply the well known minimum description length principle to solve the model selection problem. Numerical results obtained based on the CM1 and CM2 models suggest that...
Power efficient UWB pulse generation techniques have been introduced. A simple, compact, and efficient RF pulse compression technique based on a switched resonator concept is used for the pulse generation. It utilizes different charging/discharging speeds of the circuit resonator by varying the resonator's Q factor and can be applied to any other microwave resonators. The approach compresses the duration...
In this paper, a template generator circuit for impulse-radio (IR) ultra wide-band (UWB) receivers is presented. The circuit is implemented in a 0.18 mum CMOS process. It is capable of generating a differential template signal having a four cycles long square waveform for both rising and falling edges of the input triggering signal. The template waveform cycle time is 125 ps. This allows the detection...
This paper presents an experimental study on the generation of the ultra-wideband (UWB) pulses with full FCC's frequency band for UWB radio system by using UWB bandpass filters developed recently. This work includes, 1) generation of the full UWB (3.1-10.6 GHz) pulse using various UWB bandpass filters, 2) investigation of the time response (impulse response) of UWB bandpass filters, and 3) analysis...
A tunable ultra-wideband (UWB) pulse generator is designed and simulated with standard 0.18 mum CMOS technology. By using a voltage controlled delay line (VCDL) technique, the proposed UWB pulse generator can adjust the pulse width, adding flexibility for use with different UWB applications. Moreover, each peak of the proposed UWB pulse is separately controlled so that it complies with the FCC regulation...
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