Chaos-based TOA estimator for DS-UWB ranging systems in multiuser environment

International audienceIn this paper, we present a chaos-based decoupled multiuser ranging (DEMR) estimator for multiuser DS-UWB ranging system. In the DEMR estimator, users are decoupled by the knowledge of all the users' limited number of data bits. Then, the ranging performance of each user mainly depends on the non-cyclic autocorrelation property of the spreading code. Based on this property, we improve DEMR estimator by using the selected binary chaotic sequences instead of the Gold sequences in order to increase the system capacity and to improve the ranging accuracy. Simulations in CM1 channel show that the chaos-based DEMR estimator is quite near-far resistant and achieves a noticeable ranging accuracy even in a heavily loaded system. Compared with using Gold sequences, chaos-based DEMR not only works with more users than full load of Gold sequences but also improves the ranging accuracy especially under low SNR condition

WUB-IP : a high-precision UWB positioning scheme for indoor multi-user applications

High-precision positioning scheme, an important part of the indoor navigation system, can be implemented using an ultra-wide band (UWB) based ranging system. Recently, solutions for precise positioning in dense multi-path and non-line-of-sight (NLOS) conditions have attracted a lot of attention in literature. On the other hand, it is expected that Waveform Division Multiple Access (WDMA) technology for multi-user UWB positioning application will be indispensable in the near future. In this regard, a WDMA-UWB based positioning scheme is investigated in this paper, for enhancing the performance of positioning accuracy in multi-user applications. In accordance with practical requirements of indoor positioning, we propose a new indoor positioning scheme, termed as WUB-IP. This scheme adopts WDMA for multiple access, and utilizes an entropy-based approach for the Time of Arrival (TOA) estimation. Moreover, a transfer learning approach is used for ranging error mitigation in NLOS conditions, in order to improve the positioning accuracy in NLOS conditions. System-level simulations demonstrate that the proposed scheme enhances the performance of indoor positioning for multi-user applications

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

Interference mitigation and awareness for improved reliability

Wireless systems are commonly affected by interference from various sources. For example, a number of users that operate in the same wireless network can result in multiple-access interference (MAI). In addition, for ultrawideband (UWB) systems, which operate at very low power spectral densities, strong narrowband interference (NBI) can have significant effects on the communications reliability. Therefore, interference mitigation and awareness are crucial in order to realize reliable communications systems. In this chapter, pulse-based UWB systems are considered, and the mitigation of MAI is investigated first. Then, NBI avoidance and cancelation are studied for UWB systems. Finally, interference awareness is discussed for short-rate communications, next-generation wireless networks, and cognitive radios.Mitigation of multiple-access interference (MAI)In an impulse radio ultrawideband (IR-UWB) communications system, pulses with very short durations, commonly less than one nanosecond, are transmitted with a low-duty cycle, and information is carried by the positions or the polarities of pulses [1-5]. Each pulse resides in an interval called frame, and the positions of pulses within frames are determined according to time-hopping (TH) sequences specific to each user. The low-duty cycle structure together with TH sequences provide a multiple-access capability for IR-UWB systems [6].Although IR-UWB systems can theoretically accommodate a large number of users in a multiple-access environment [2, 4], advanced signal processing techniques are necessary in practice in order to mitigate the effects of interfering users on the detection of information symbols efficiently [6]. © Cambridge University Press 2011

Performance Analysis and Optimization of Tc-DTR IR-UWB Receivers over Multipath Fading Channels with Tone Interference

International audienceIn this paper, we analyze the performance of a particular class of transmitted-reference receivers for impulse radio ultra wideband communication systems, which is called chip-time differential transmitted-reference (Tc-DTR). The analysis aims at investigating the robustness of this receiver to single-tone and multi-tone narrowband interference (NBI) and comparing its performance with other non-coherent receivers that are proposed in the literature. It is shown that the Tc-DTR scheme provides more degrees of freedom for performance optimization and that it is inherently more robust to NBI than other non-coherent receivers. More specifically, it is analytically proved that the performance improvement is due to the chip-time-level differential encoding/decoding of the direct sequence (DS) code and to an adequate design of DS code and average pulse repetition time. The analysis encompasses performance metrics that are useful for both data detection (i.e., average bit error probability) and timing acquisition (i.e., false-alarm probability Pfa and detection probability Pd). Moving from the proposed sem-analytical framework, the optimal code design and system parameters are derived, and it is highlighted that the same optimization criteria can be applied to all the performance metrics considered in this paper. In addition, analytical frameworks and theoretical findings are substantiated through Monte Carlo simulations