Cluster-based cooperative subcarrier sensing using antenna diversity-based weighted data fusion

Cooperative spectrum sensing (CSS) is used in cognitive radio (CR) networks to improve the spectrum sensing performance in shadow fading environments. Moreover, clustering in CR networks is used to reduce reporting time and bandwidth overhead during CSS. Thus, cluster-based cooperative spectrum sensing (CBCSS) has manifested satisfactory spectrum sensing results in harsh environments under processing constraints. On the other hand, the antenna diversity of multiple input multiple output CR systems can be exploited to further improve the spectrum sensing performance. This paper presents the CBCSS performance in a CR network which is comprised of single- as well as multiple-antenna CR systems. We give theoretical analysis of CBCSS for orthogonal frequency division multiplexing signal sensing and propose a novel fusion scheme at the fusion center which takes into account the receiver antenna diversity of the CRs present in the network. We introduce the concept of weighted data fusion in which the sensing results of different CRs are weighted proportional to the number of receiving antennas they are equipped with. Thus, the receiver diversity is used to the advantage of improving spectrum sensing performance in a CR cluster. Simulation results show that the proposed scheme outperforms the conventional CBCSS scheme

Self-concatenated coding for wireless communication systems

In this thesis, we have explored self-concatenated coding schemes that are designed for transmission over Additive White Gaussian Noise (AWGN) and uncorrelated Rayleigh fading channels. We designed both the symbol-based Self-ConcatenatedCodes considered using Trellis Coded Modulation (SECTCM) and bit-based Self- Concatenated Convolutional Codes (SECCC) using a Recursive Systematic Convolutional (RSC) encoder as constituent codes, respectively. The design of these codes was carried out with the aid of Extrinsic Information Transfer (EXIT) charts. The EXIT chart based design has been found an efficient tool in finding the decoding convergence threshold of the constituent codes. Additionally, in order to recover the information loss imposed by employing binary rather than non-binary schemes, a soft decision demapper was introduced in order to exchange extrinsic information withthe SECCC decoder. To analyse this information exchange 3D-EXIT chart analysis was invoked for visualizing the extrinsic information exchange between the proposed Iteratively Decoding aided SECCC and soft-decision demapper (SECCC-ID). Some of the proposed SECTCM, SECCC and SECCC-ID schemes perform within about 1 dB from the AWGN and Rayleigh fading channels’ capacity. A union bound analysis of SECCC codes was carried out to find the corresponding Bit Error Ratio (BER) floors. The union bound of SECCCs was derived for communications over both AWGN and uncorrelated Rayleigh fading channels, based on a novel interleaver concept.Application of SECCCs in both UltraWideBand (UWB) and state-of-the-art video-telephone schemes demonstrated its practical benefits.In order to further exploit the benefits of the low complexity design offered by SECCCs we explored their application in a distributed coding scheme designed for cooperative communications, where iterative detection is employed by exchanging extrinsic information between the decoders of SECCC and RSC at the destination. In the first transmission period of cooperation, the relay receives the potentially erroneous data and attempts to recover the information. The recovered information is then re-encoded at the relay using an RSC encoder. In the second transmission period this information is then retransmitted to the destination. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel-concatenated encoder. At the destination a Distributed Binary Self-Concatenated Coding scheme using Iterative Decoding (DSECCC-ID) was employed, where the two decoders (SECCC and RSC) exchange their extrinsic information. It was shown that the DSECCC-ID is a low-complexity scheme, yet capable of approaching the Discrete-input Continuous-output Memoryless Channels’s (DCMC) capacity.Finally, we considered coding schemes designed for two nodes communicating with each other with the aid of a relay node, where the relay receives information from the two nodes in the first transmission period. At the relay node we combine a powerful Superposition Coding (SPC) scheme with SECCC. It is assumed that decoding errors may be encountered at the relay node. The relay node then broadcasts this information in the second transmission period after re-encoding it, again, using a SECCC encoder. At the destination, the amalgamated block of Successive Interference Cancellation (SIC) scheme combined with SECCC then detects and decodes the signal either with or without the aid of a priori information. Our simulation results demonstrate that the proposed scheme is capable of reliably operating at a low BER for transmission over both AWGN and uncorrelated Rayleigh fading channels. We compare the proposed scheme’s performance to a direct transmission link between the two sources having the same throughput

Time-Hopping Multicarrier Code-Division Multiple-Access

A time-hopping multicarrier code-division multiple-access (TH/MC-CDMA) scheme is proposed and investigated. In the proposed TH/MC-CDMA each information symbol is transmitted by a number of time-domain pulses with each time-domain pulse modulating a subcarrier. The transmitted information at the receiver is extracted from one of the, say $M$, possible time-slot positions, i.e., assuming that $M$-ary pulse position modulation is employed. Specifically, in this contribution we concentrate on the scenarios such as system design, power spectral density (PSD) and single-user based signal detection. The error performance of the TH/MC-CDMA system is investigated, when each subcarrier signal experiences flat Nakagami-$m$ fading in addition to additive white Gaussian noise (AWGN). According to our analysis and results, it can be shown that the TH/MC-CDMA signal is capable of providing a near ideal PSD, which is flat over the system bandwidth available, while decreases rapidly beyond that bandwidth. Explicitly, signals having this type of PSD is beneficial to both broadband and ultra-wide bandwidth (UWB) communications. Furthermore, our results show that, when optimum user address codes are employed, the single-user detector considered is near-far resistant, provided that the number of users supported by the system is lower than the number of subcarriers used for conveying an information symbol

Detection of PPM-UWB random signals

This paper focuses on the symbol detection problem of random pulse-position modulation (PPM) ultrawideband (UWB) signals in the absence of interframe interference. Particular attention is devoted to severely time-varying channels where optimal detectors are proposed for both uncorrelated and correlated scattering scenarios. This is done by assuming the received waveforms to be unknown parameters. In UWB communication systems, the assumption of unknown random waveforms is consistent with the fact that the received waveform has very little resemblance with the original transmitted pulse. In order to circumvent this limitation, a conditional approach is presented herein by compressing the likelihood ratio test with the information regarding the second-order moments of the end-to-end channel response. Both full-rank and rank-one detectors are derived. For the reduced complexity rank-one detector, an iterative procedure is presented that maximizes the J-divergence between the hypotheses to be tested. Finally, simulation results are provided to compare the performance of the proposed detectors in different propagation environments.Peer Reviewe

High-performance wireless interface for implant-to-air communications

Nous élaborons une interface cerveau-machine (ICM) entièrement sans fil afin de fournir un système de liaison directe entre le cerveau et les périphériques externes, permettant l’enregistrement et la stimulation du cerveau pour une utilisation permanente. Au cours de cette thèse, nous explorons la modélisation de canal, les antennes implantées et portables en tant que propagateurs appropriés pour cette application, la conception du nouveau système d’un émetteur-récepteur UWB implantable, la conception niveau système du circuit et sa mise en oeuvre par un procédé CMOS TSMC 0.18 um. En plus, en collaboration avec Université McGill, nous avons conçu un réseau de seize antennes pour une détection du cancer du sein à l’aide d’hyperfréquences. Notre première contribution calcule la caractérisation de canal de liaison sans fil UWB d’implant à l’air, l’absorption spécifique moyennée (ASAR), et les lignes directrices de la FCC sur la densité spectrale de puissance UWB transmis. La connaissance du comportement du canal est nécessaire pour déterminer la puissance maximale permise à 1) respecter les lignes directrices ANSI pour éviter des dommages aux tissus et 2) respecter les lignes directrices de la FCC sur les transmissions non autorisées. Nous avons recours à un modèle réaliste du canal biologique afin de concevoir les antennes pour l’émetteur implanté et le récepteur externe. Le placement des antennes est examiné avec deux scénarios contrastés ayant des contraintés de puissance. La performance du système au sein des tissus biologiques est examinée par l’intermédiaire des simulations et des expériences. Notre deuxième contribution est dédiée à la conception des antennes simples et à double polarisation pour les systèmes d’enregistrement neural sans fil à bande ultra-large en utilisant un modèle multicouches inhomogène de la tête humaine. Les antennes fabriquées à partir de matériaux flexibles sont plus facilement adaptées à l’implantation ; nous étudions des matériaux à la fois flexibles et rigides et examinons des compromis de performance. Les antennes proposées sont conçues pour fonctionner dans une plage de fréquence de 2-11 GHz (ayant S11-dessous de -10 dB) couvrant à la fois la bande 2.45 GHz (ISM) et la bande UWB 3.1-10.6 GHz. Des mesures confirment les résultats de simulation et montrent que les antennes flexibles ont peu de dégradation des performances en raison des effets de flexion (en termes de correspondance d’impédance). Finalement, une comparaison est réalisée entre quatre antennes implantables, couvrant la gamme 2-11 GHz : 1) une rigide, à la polarisation simple, 2) une rigide, à double polarisation, 3) une flexible, à simple polarisation et 4) une flexible, à double polarisation. Dans tous les cas une antenne rigide est utilisée à l’extérieur du corps, avec une polarisation appropriée. Plusieurs avantages ont été confirmés pour les antennes à la polarisation double : 1) une taille plus petite, 2) la sensibilité plus faible aux désalignements angulaires, et 3) une plus grande fidélité. Notre troisième contribution fournit la conception niveau système de l’architecture de communication sans fil pour les systèmes implantés qui stimulent simultanément les neurones et enregistrent les réponses de neurones. Cette architecture prend en charge un grand nombre d’électrodes (> 500), fournissant 100 Mb/s pour des signaux de stimulation de liaison descendante, et Gb/s pour les enregistrements de neurones de liaison montante. Nous proposons une architecture d’émetteur-récepteur qui partage une antenne ultra large bande, un émetteur-récepteur simplifié, travaillant en duplex intégral sur les deux bandes, et un nouveau formeur d’impulsions pour la liaison montante du Gb/s soutenant plusieurs formats de modulation. Nous présentons une démonstration expérimentale d’ex vivo de l’architecture en utilisant des composants discrets pour la réalisation les taux Gb/s en liaison montante. Une bonne performance de taux d’erreur de bit sur un canal biologique à 0,5, 1 et 2 Gb/s des débits de données pour la télémétrie de liaison montante (UWB) et 100 Mb/s pour la télémétrie en liaison descendante (bande 2.45 GHz) est atteinte. Notre quatrième contribution présente la conception au niveau du circuit d’un dispositif d’émission en duplex total qui est présentée dans notre troisième contribution. Ce dispositif d’émission en duplex total soutient les applications d’interfaçage neural multimodal et en haute densité (les canaux de stimulant et d’enregistrement) avec des débits de données asymétriques. L’émetteur (TX) et le récepteur (RX) partagent une seule antenne pour réduire la taille de l’implant. Le TX utilise impulse radio ultra-wide band (IR-UWB) basé sur une approche alliant des bords, et le RX utilise un nouveau 2.4 GHz récepteur on-off keying (OOK).Une bonne isolation (> 20 dB) entre le trajet TX et RX est mis en oeuvre 1) par mise en forme des impulsions transmises pour tomber dans le spectre UWB non réglementé (3.1-7 GHz), et 2) par un filtrage espace-efficace du spectre de liaison descendante OOK dans un amplificateur à faible bruit RX. L’émetteur UWB 3.1-7 GHz peut utiliser soit OOK soit la modulation numérique binaire à déplacement de phase (BPSK). Le FDT proposé offre une double bande avec un taux de données de liaison montante de 500 Mbps TX et un taux de données de liaison descendante de 100 Mb/s RX, et il est entièrement en conformité avec les standards TSMC 0.18 um CMOS dans un volume total de 0,8 mm2. Ainsi, la mesure de consommation d’énergie totale en mode full duplex est de 10,4 mW (5 mW à 100 Mb/s pour RX, et de 5,4 mW à 500 Mb/s ou 10,8 PJ / bits pour TX). Notre cinquième contribution est une collaboration avec l’Université McGill dans laquelle nous concevons des antennes simples et à double polarisation pour les systèmes de détection du cancer du sein à l’aide d’hyperfréquences sans fil en utilisant un modèle multi-couche et inhomogène du sein humain. Les antennes fabriquées à partir de matériaux flexibles sont plus facilement adaptées à des applications portables. Les antennes flexibles miniaturisées monopôles et spirales sur un 50 um Kapton polyimide sont conçus, en utilisant high frequency structure simulator (HFSS), à être en contact avec des tissus biologiques du sein. Les antennes proposées sont conçues pour fonctionner dans une gamme de fréquences de 2 à 4 GHz. Les mesures montrent que les antennes flexibles ont une bonne adaptation d’impédance dans les différentes positions sur le sein. De Plus, deux antennes à bande ultralarge flexibles 4 × 4 (simple et à double polarisation), dans un format similaire à celui d’un soutien-gorge, ont été développés pour un système de détection du cancer du sein basé sur le radar.We are working on a fully wireless brain-machine-interface to provide a communication link between the brain and external devices, enabling recording and stimulating the brain for permanent usage. In this thesis we explore channel modeling, implanted and wearable antennas as suitable propagators for this application, system level design of an implantable UWB transceiver, and circuit level design and implementing it by TSMC 0.18 um CMOS process. Also, in a collaboration project with McGill University, we designed a flexible sixteen antenna array for microwave breast cancer detection. Our first contribution calculates channel characteristics of implant-to-air UWB wireless link, average specific absorption rate (ASAR), and FCC guidelines on transmitted UWB power spectral density. Knowledge of channel behavior is required to determine the maximum allowable power to 1) respect ANSI guidelines for avoiding tissue damage and 2) respect FCC guidelines on unlicensed transmissions. We utilize a realistic model of the biological channel to inform the design of antennas for the implanted transmitter and the external receiver. Antennas placement is examined under two scenarios having contrasting power constraints. Performance of the system within the biological tissues is examined via simulations and experiments. Our second contribution deals with designing single and dual-polarization antennas for wireless ultra-wideband neural recording systems using an inhomogeneous multi-layer model of the human head. Antennas made from flexible materials are more easily adapted to implantation; we investigate both flexible and rigid materials and examine performance trade-offs. The proposed antennas are designed to operate in a frequency range of 2–11 GHz (having S11 below -10 dB) covering both the 2.45 GHz (ISM) band and the 3.1–10.6 GHz UWB band. Measurements confirm simulation results showing flexible antennas have little performance degradation due to bending effects (in terms of impedance matching). Finally, a comparison is made of four implantable antennas covering the 2-11 GHz range: 1) rigid, single polarization, 2) rigid, dual polarization, 3) flexible, single polarization and 4) flexible, dual polarization. In all cases a rigid antenna is used outside the body, with an appropriate polarization. Several advantages were confirmed for dual polarization antennas: 1) smaller size, 2) lower sensitivity to angular misalignments, and 3) higher fidelity. Our third contribution provides system level design of wireless communication architecture for implanted systems that simultaneously stimulate neurons and record neural responses. This architecture supports large numbers of electrodes (> 500), providing 100 Mb/s for the downlink of stimulation signals, and Gb/s for the uplink neural recordings. We propose a transceiver architecture that shares one ultra-wideband antenna, a streamlined transceiver working at full-duplex on both bands, and a novel pulse shaper for the Gb/s uplink supporting several modulation formats. We present an ex-vivo experimental demonstration of the architecture using discrete components achieving Gb/s uplink rates. Good bit error rate performance over a biological channel at 0.5, 1, and 2 Gbps data rates for uplink telemetry (UWB) and 100 Mbps for downlink telemetry (2.45 GHz band) is achieved. Our fourth contribution presents circuit level design of the novel full-duplex transceiver (FDT) which is presented in our third contribution. This full-duplex transceiver supports high-density and multimodal neural interfacing applications (high-channel count stimulating and recording) with asymmetric data rates. The transmitter (TX) and receiver (RX) share a single antenna to reduce implant size. The TX uses impulse radio ultra-wide band (IR-UWB) based on an edge combining approach, and the RX uses a novel 2.4-GHz on-off keying (OOK) receiver. Proper isolation (> 20 dB) between the TX and RX path is implemented 1) by shaping the transmitted pulses to fall within the unregulated UWB spectrum (3.1-7 GHz), and 2) by spaceefficient filtering (avoiding a circulator or diplexer) of the downlink OOK spectrum in the RX low-noise amplifier. The UWB 3.1-7 GHz transmitter can use either OOK or binary phase shift keying (BPSK) modulation schemes. The proposed FDT provides dual band 500-Mbps TX uplink data rate and 100 Mbps RX downlink data rate, and it is fully integrated into standard TSMC 0.18 um CMOS within a total size of 0.8 mm2. The total measured power consumption is 10.4 mW in full duplex mode (5 mW at 100 Mbps for RX, and 5.4 mW at 500 Mbps or 10.8 pJ/bit for TX). Our fifth contribution is a collaboration project with McGill University which we design single and dual-polarization antennas for wireless ultra-wideband breast cancer detection systems using an inhomogeneous multi-layer model of the human breast. Antennas made from flexible materials are more easily adapted to wearable applications. Miniaturized flexible monopole and spiral antennas on a 50 um Kapton polyimide are designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues. The proposed antennas are designed to operate in a frequency range of 2–4 GHz (with reflection coefficient (S11) below -10 dB). Measurements show that the flexible antennas have good impedance matching while in different positions with different curvature around the breast. Furthermore, two flexible conformal 4×4 ultra-wideband antenna arrays (single and dual polarization), in a format similar to that of a bra, were developed for a radar-based breast cancer detection system