Performance Evaluation of 802.15.4 UWB PHY for High Speed Data Rate under IEEE Channel Mode

In modern day society the increase of data generation and transfer has been an issue that researchers are working on. This generated and shared data might have a different purpose but one thing is certain, the reception. This communication can cover continents, countries, cities or even just a few meters. For the purpose of the later, personal area networks (PAN) have been created with a main focus to lower the energy consumption. The protocol that is created under IEEE is 802.15.4 and it has multiple applications in the context of next generation sensor networks. This thesis investigates the performance IEEE 802.15.4 UWB PHY for high data rates over IEEE multipath fading channels and introduces receivers aiming to diversity and to mitigate the intersymbol interference (ISI) that might appear. We simulate the protocols highest mandatory data rate over slow, block faded, realistic IEEE channel models such as, residential, office, outdoor and industrial. The simulation includes Reed Solomon (RS) channel coding, optimal successive erasure decoding (SED), and coherent RAKE receivers. We verify that the selective RAKE (sRAKE) perform better than the nonselective RAKE (n-sRAKE) in all environments and also the increase of fingers is mandatory in order to improve performance. In cases with low number of fingers the ISI mitigation techniques like Maximum-Likehood Sequence Estimator (MLSE) & RAKE combination or Maximum Ration Combining (MRC) ISI cancellation receivers, can provide some gain in large delay spread environments. In cases with high number of ingers the MRC received employs its full diversity since the received power is arger than before. Overall the apply of optimal errors and erasures decoding can urther improve the system performance by adding a small gain, lowering existing it Error Probability (BEP) even more.A huge percentage of data has been generated in the last two years and it will grow more, as every one of us is constantly producing and releasing data. The latest years has been an extensive research on capacity maximization, bit rate increment and power optimization. That research lead to the development of various protocols for cellular and personal area networks (PAN), where they each utilizes the frequency spectrum differently. Even if cellular networks have the ability to cover large area, development of multiple personal area networks can be developed for the purpose to offload data from the cellular network. Keeping in mind the research needs, 802.15.4 UWH PHY is a solid candidate when it comes to data transfer in a small area. This protocol offers various mandatory transmission modes that can be selected depending the channel parameters and various data rate needs. Time hopping and spreading sequence offers the existence of multiuser environment where multiple transceivers can co-exist. Overall the complexity, cost and energy consumption for transmission and reception can be kept low, matching the research needs. The main issues regarding 802.15.4 UWH PHY and high speed data rates is first, the energy dispersion of the transmitted symbol to multiple bins and second, the appearance of Inter Symbol Interference (ISI) in high delay profile environments. The solution in the former problem is the necessary implementation of a RAKE receiver. Regarding the latter, literature offers multiple ways to mitigate the ISI but the aim should be to keep the lowest complexity possible regarding the implementation. In this thesis we evaluate the performance of 802.15.4 UWB PHY for high speed data rates under IEEE channel models. Various receivers has been build for the purpose of this thesis, Maximum Ratio Combining (MRC), MRC with Inter Symbol Interference and MLSE & RAKE combination receiver. The MRC is a simple RAKE receiver with maximum diversity, MRC with ISI cancellation is based on the MRC receiver with the ability to mitigate ISI, and MLSE & RAKE combination is an optimum ISI mitigation receiver without the diversity of the MRC

Ultra-wideband indoor communications using optical technology

La communication ultra large bande (UWB) a attiré une énorme quantité de recherches ces dernières années, surtout après la présentation du masque spectral de US Federal Communications Commission (FCC). Les impulsions ultra-courtes permettent de très hauts débits de faible puissance tout en éliminant les interférences avec les systèmes existants à bande étroite. La faible puissance, cependant, limite la portée de propagation des radios UWB à quelques mètres pour la transmission sans fil à l’intérieur d’une pièce. En outre, des signaux UWB reçu sont étendus dans le temps en raison de la propagation par trajet multiple qui résulte en beaucoup d’interférence inter-symbole (ISI) à haut débit. Le monocycle Gaussien, l’impulsion la plus commune dans UWB, a une mauvaise couverture sous le masque de la FCC. Dans cette thèse, nous démontrons des transmet- teurs qui sont capables de générer des impulsions UWB avec une efficacité de puissance élevée. Une impulsion efficace résulte dans un rapport de signal à bruit (SNR) supérieur au récepteur en utilisant plus de la puissance disponible sous le masque spectral de la FCC. On produit les impulsions dans le domaine optique et utilise la fibre optique pour les transporter sur plusieurs kilomètres pour la distribution dans un réseau optique pas- sif. La fibre optique est très fiable pour le transport des signaux radio avec une faible consommation de puissance. On utilise les éléments simples comme un modulateur Mach-Zehnder ou un résonateur en anneau pour générer des impulsions, ce qui permet l’intégration dans le silicium. Compatible avec la technologie CMOS, la photonique sur silicium a un potentiel énorme pour abaisser le coût et l’encombrement des systèmes optiques. La photodétection convertit les impulsions optiques en impulsions électriques avant la transmission sur l’antenne du côté de l’utilisateur. La réponse fréquentielle de l’antenne déforme la forme d’onde de l’impulsion UWB. Nous proposons une technique d’optimisation non-linéaire qui prend en compte la distorsion d’antenne pour trouver des impulsions qui maximisent la puissance transmise, en respectant le masque spectral de la FCC. Nous travaillons avec trois antennes et concevons une impulsion unique pour chacune d’entre elle. L’amélioration de l’énergie des impulsions UWB améliore directement la SNR au récepteur. Les résultats de simulation montrent que les impulsions optimisées améliorent considérablement le taux d’erreur (BER) par rapport au monocycle Gaussien sous propagation par trajet multiple. Notre autre contribution est l’évaluation d’un filtre adapté pour recevoir efficacement des impulsions UWB. Le filtre adapté est synthétisé et fabriqué en technologie microstrip, en collaboration avec l’Université McGill comme un dispositif de bande interdite électromagnétique. La réponse fréquentielle du filtre adapté montre une ex- cellente concordance avec le spectre ciblé de l’impulsion UWB. Les mesures de BER confirment la performance supérieure du filtre adapté par rapport à un récepteur à conversion directe. Le canal UWB est très riche en trajet multiple conduisant à l’ISI à haut débit. Notre dernière contribution est l’étude de performance des récepteurs en simulant un système avec des conditions de canaux réalistes. Les résultats de la simulation montrent que la performance d’un tel système se dégrade de façon significative pour les hauts débits. Afin de compenser la forte ISI dans les taux de transfert de données en Gb/s, nous étudions l’algorithme de Viterbi (VA) avec un nombre limité d’états et un égaliseur DFE (decision feedback equalizer). Nous examinons le nombre d’états requis dans le VA, et le nombre de coefficients du filtre dans le DFE pour une transmission fiable de UWB en Gb/s dans les canaux en ligne de vue. L’évaluation par simulation de BER confirme que l’égalisation améliore considérablement les performances par rapport à la détection de symbole. La DFE a une meilleure performance par rapport à la VA en utilisant une complexité comparable. La DFE peut couvrir une plus grande mémoire de canal avec un niveau de complexité relativement réduit.Ultra-wideband (UWB) communication has attracted an enormous amount of research in recent years, especially after the introduction of the US Federal Communications Commission (FCC) spectral mask. Ultra-short pulses allow for very high bit-rates while low power eliminates interference with existing narrowband systems. Low power, however, limits the propagation range of UWB radios to a few meters for indoors wireless transmission. Furthermore, received UWB signals are spread in time because of multipath propagation which results in high intersymbol interference at high data rates. Gaussian monocycle, the most commonly employed UWB pulse, has poor coverage under the FCC mask. In this thesis we demonstrate transmitters capable of generating UWB pulses with high power efficiency at Gb/s bit-rates. An efficient pulse results in higher signal-to-noise ratio (SNR) at the receiver by utilizing most of the available power under the FCC spectral mask. We generate the pulses in the optical domain and use optical fiber to transport the pulses over several kilometers for distribution in a passive optical network. Optical fiber is very reliable for transporting radio signals with low power consumption. We use simple elements such as a Mach Zehnder modulator or a ring resonator for pulse shaping, allowing for integration in silicon. Being compatible with CMOS technology, silicon photonics has huge potential for lowering the cost and bulkiness of optical systems. Photodetection converts the pulses to the electrical domain before antenna transmission at the user side. The frequency response of UWB antennas distorts the UWB waveforms. We pro- pose a nonlinear optimization technique which takes into account antenna distortion to find pulses that maximize the transmitted power, while respecting the FCC spectral mask. We consider three antennas and design a unique pulse for each. The energy improvement in UWB pulses directly improves the receiver SNR. Simulation results show that optimized pulses have a significant bit error rate (BER) performance improvement compared to the Gaussian monocycle under multipath propagation. Our other contribution is evaluating a matched filter to receive efficiently designed UWB pulses. The matched filter is synthesized and fabricated in microstrip technology in collaboration with McGill University as an electromagnetic bandgap device. The frequency response of the matched filter shows close agreement with the target UWB pulse spectrum. BER measurements confirm superior performance of the matched filter compared to a direct conversion receiver. The UWB channel is very rich in multipath leading to ISI at high bit rates. Our last contribution is investigating the performance of receivers by simulating a system employing realistic channel conditions. Simulation results show that the performance of such system degrades significantly for high data rates. To compensate the severe ISI at gigabit rates, we investigate the Viterbi algorithm (VA) with a limited number of states and the decision feedback equalizer (DFE). We examine the required number of states in the VA, and the number of taps in the DFE for reliable Gb/s UWB trans- mission for line-of-sight channels. Non-line-of-sight channels were also investigated at lower speeds. BER simulations confirm that equalization considerably improves the performance compared to symbol detection. The DFE results in better performance compared to the VA when using comparable complexity as the DFE can cover greater channel memory with a relatively low complexity level

Evaluation of ultra-wideband in vivo radio channel and its effects on system performance

This paper presents bit‐error‐rate (BER) performance analysis and improvement using equalizers for an in vivo radio channel at ultra‐wideband frequencies (3.1 GHz to 10.6 GHz). By conducting simulations using a bandwidth of 50 MHz, we observed that the in vivo radio channel is affected by small‐scale fading. This fading results in intersymbol interference affecting upcoming symbol transmission, causing delayed versions of the symbols to arrive at the receiver side and causes increase in BER. A 29‐taps channel was observed from the experimentally measured data using a human cadaver, and BER was calculated for the measured in vivo channel response along with the ideal additive white Gaussian noise and Rayleigh channel models. Linear and nonlinear adaptive equalizers, ie, decision feedback equalizer (DFE) and least mean square (LMS), were used to improve the BER performance of the in vivo radio channel. It is noticed that both the equalizers improve the BER but DFE has better BER compared to LMS and shows the 2‐dB and 4‐dB performance gains of DFE over the LMS at Eb/No = 12 dB and at Eb/No = 14 dB, respectively. The current findings will help guide future researchers and designers in enhancing systems performance of an ultra‐wideband in vivo wireless systems

Receiver design for nonlinearly distorted OFDM : signals applications in radio-over-fiber systems

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 201

Optimisation of Bluetooth wireless personal area networks

In recent years there has been a marked growth in the use of wireless cellular telephones, PCs and the Internet. This proliferation of information technology has hastened the advent of wireless networks which aim to increase the accessibility and reach of communications devices. Ambient Intelligence (Ami) is a vision of the future of computing in which all kinds of everyday objects will contain intelligence. To be effective, Ami requires Ubiquitous Computing and Communication, the latter being enabled by wireless networking. The IEEE's 802.11 task group has developed a series of radio based replacements for the familiar wired ethernet LAN. At the same time another IEEE standards task group, 802.15, together with a number of industry consortia, has introduced a new level of wireless networking based upon short range, ad-hoc connections. Currently, the most significant of these new Wireless Personal Area Network (WPAN) standards is Bluetooth, one of the first of the enabling technologies of Ami to be commercially available. Bluetooth operates in the internationally unlicensed Industrial, Scientific and Medical (ISM) band at 2.4 GHz. unfortunately, this spectrum is particularly crowded. It is also used by: WiFi (IEEE 802.11); a new WPAN standard called Zig- Bee; many types of simple devices such as garage door openers; and is polluted by unintentional radiators. The success of a radio specification for ubiquitous wireless communications is, therefore, dependant upon a robust tolerance to high levels of electromagnetic noise. This thesis addresses the optimisation of low power WPANs in this context, with particular reference to the physical layer radio specification of the Bluetooth system

Performance Enhancement of Ultra Wideband WPAN using Narrowband Interference Mitigation Techniques

A new promising technique adopted by 4G community is ultra-wideband technology, which offers a solution for high bandwidth, high data rate, low cost, low power consumption, position location capability etc. A conventional type of UWB communication is impulse radio, where very short transient pulses are transmitted rather than a modulated carrier. Consequently, the spectrum is spread over several GHz, complying with the definition of UWB. Currently, the Rake receiver used for spread spectrum is considered a very promising candidate for UWB reception, due to its capability of collecting multipath components. Since UWB signals occupy such a large bandwidth, they operate as an overlay system with other existing narrowband (NB) radio systems overlapping with their bands. In order to ensure a robust communication link, the issue of coexistence and interference of UWB systems with current indoor wireless systems must be considered. Ultra Wideband technology with its application, advantages and disadvantages are discussed in detail. Design of UWB short pulse and a detail study IEEE 802.15.3a UWB channel models statistical characteristics have been analyzed through simulation. Simulation studies are performed and improved techniques are suggested for interference reduction in both Impulse Radio based UWB and Transmitted Reference type of UWB system. Modified TR-UWB receiver with UWB pulse design at transmitter end and notch filtering at receiver’s front end proved to be more efficient in single NBI, multiple NBI and WBI suppression. Extensive simulation studies to support the efficacy of the proposed schemes are carried out in the MATLAB. Bit error rate (BER) performance study for different data rates over different UWB channel models are also analyzed using proposed receiver models. Performance improvement of TR-UWB system is noticed using the proposed techniques

An energy efficient sub-threshold baseband processor architecture for pulsed ultra-wideband communications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 79-83).Ultra-wideband (UWB) communications is currently being explored as a medium for high-data-rate last-meter wireless links. Accordingly, there has been much interest in integrating UWB radios onto battery-operated devices, creating a strong demand for energy efficient UWB systems. The objective of this work is to describe how operating the digital baseband processor in the sub-threshold region and increasing the degree of parallelism can translate into energy savings across the entire UWB receiver. While sub-threshold operation is traditionally used for low energy, low performance applications such as wrist-watches, this work examines how sub-threshold operation can be applied to low energy, high performance applications. Simulation results for a 100-Mbps UWB baseband processor using the digital logic cell library of a 90-nm process are presented.by Vivienne Sze.S.M