Code-Multiplexing-Based One-Way Detect-and-Forward Relaying Schemes for Multiuser UWB MIMO Systems

In this paper, we consider decode-and-forward (DF) one-way relaying schemes for multiuser impulse-radio ultrawideband (UWB) communications. We assume low-complexity terminals with limited processing capabilities and a central transceiver unit (i.e., the relay) with a higher computational capacity. All nodes have a single antenna differently from the relay in which multiple antennas may be installed. In order to keep the complexity as low as possible, we concentrate on noncoherent transceiver architectures based on multiuser code-multiplexing transmitted-reference schemes. We propose various relaying systems with different computational complexity and different levels of required channel knowledge. The proposed schemes largely outperform systems without relay in terms of both bit error rate (BER) performance and coverage

Initial synchronisation of wideband and UWB direct sequence systems: single- and multiple-antenna aided solutions

This survey guides the reader through the open literature on the principle of initial synchronisation in single-antenna-assisted single- and multi-carrier Code Division Multiple Access (CDMA) as well as Direct Sequence-Ultra WideBand (DS-UWB) systems, with special emphasis on the DownLink (DL). There is a paucity of up-to-date surveys and review articles on initial synchronization solutions for MIMO-aided and cooperative systems - even though there is a plethora of papers on both MIMOs and on cooperative systems, which assume perfect synchronization. Hence this paper aims to ?ll the related gap in the literature

Analysis, Modeling and Testing of a Multi-Receiver Wireless System for Telemetry Applications

This thesis investigates the potential value of multiple co-located receiver units for telemetry applications. In this thesis, a test board based on the NRF24L01 RF chip produced by Nordic Semiconductor was tested. Testing consisted of sending pseudo-random test data over a link between two test boards at progressive distances. Packet loss rate was identified as the dominant failure mode of the chip, and was used to determine performance increase. A parametric model of the chip performance was developed based on coherent and noncoherent FSK detectors and curve fit to the experimental data to model the performance of a single GFSK receiver with unknown parameters. The chip exhibited an estimated 10 fold improvement in bit error performance at short range, with the performance improvement dropping off as distance increased. This result implies that there may be significant utility to using multiple receiver systems when traditional methods of improving performance such as amplifiers and antennas do not provide the necessary benefit

Amplify-and-Forward Cooperative Diversity for Green UWB-Based WBSNs

This paper proposes a novel green cooperative diversity technique based on suboptimal template-based ultra-wideband (UWB) wireless body sensor networks (WBSNs) using amplify-and-forward (AF) relays. In addition, it analyzes the bit-error-rate (BER) performance of the proposed nodes. The analysis is based on the moment-generating function (MGF) of the total signal-to-noise ratio (SNR) at the destination. It also provides an approximate value for the total SNR. The analysis studies the performance of equally correlated binary pulse position modulation (EC-BPPM) assuming the sinusoidal and square suboptimal template pulses. Numerical results are provided for the performance evaluation of optimal and suboptimal template-based nodes with and without relay cooperation. Results show that one relay node provides ~23 dB performance enhancement at BER, which mitigates the effect of the nondesirable non-line-of-sight (NLOS) links in WBSNs

A low complexity distributed differential scheme based on orthogonal space time block coding for decode-and-forward wireless relay networks

This work proposes a new differential cooperative diversity scheme with high data rate and low decoding complexity using the decode-and-forward protocol. The proposed model does not require either differential encoding or channel state information at the source node, relay nodes, or destination node where the data sequence is directly transmitted and the differential detection method is applied at the relay nodes and the destination node. The proposed technique enjoys a low encoding and decoding complexity at the source node, the relay nodes, and the destination node. Furthermore, the performance of the proposed strategy is analyzed by computer simulations in quasi-static Rayleigh fading channel and using the decode-and-forward protocol. The simulation results show that the proposed differential technique outperforms the corresponding reference strategies

Efficient approaches to robust and cooperative wireless network design

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 181-200).In wireless networks, relaying and user cooperation offer several attractive benefits such as higher throughput, better power efficiency, and larger coverage. As a result, cooperative networks are regarded as one of the most promising enabling technologies able to meet the increasingly high rate demands and quality of service requirements in wireless networks. In this dissertation, we investigate the efficient design of cooperative wireless networks from the perspectives of robust resource allocation, wideband communications, and energy efficiency. Given that the primary resource to be allocated is the relay node's transmission power, we propose robust and efficient relay power allocation algorithms when the global channel state information is subject to uncertainty. In addition, we propose practical algorithms that do not require frequent tracking of the global channel state information. This work reveals that ignoring global channel state information uncertainties and solving the relay power optimization problems often lead to poor performance, highlighting the importance of robust algorithm designs in practical wireless networks. Wideband cooperative networks allow for both higher data rate and higher resistance to interference. Since the gains achieved by using cooperation come at the cost of higher node complexity and substantial coordination overhead, it is important to study practical low-complexity signaling and receiver schemes suitable for wideband networks. In particular, we consider transmitted-reference signaling schemes and provide a unified performance analysis in terms of bit error rate. Since wideband networks are expected to coexist with many existing narrowband systems, it is important to characterize the effect of narrowband interference. We further extend the performance analysis of transmitted-reference signaling schemes to include the effect of narrowband interference..(cont) Finally, we conclude by studying the benefits of cooperation in a wireless sensor network, which aims at detecting the presence or absence of a certain physical phenomenon of interest using geographically dispersed sensor nodes. We propose a consensus flooding protocol and analyze its average energy consumption. We investigate the tradeoff between the detection reliability and the energy efficiency when nodes are allowed to cooperate. By addressing the above design challenges, this dissertation will be useful for obtaining insight into the theory and application of cooperative networks in future communication systemsby Tony Q.S. Quek.Ph.D

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