Millimeter wave and UWB propagation for high throughput indoor communications

Millimeter-wave systems at 60 GHz and ultra-wideband (UWB) systems in the microwave range of 3-10 GHz have been received with great interest for their high data rate wireless communications. In design, test and optimization of future wireless systems, channel models featuring the relevant characteristics of radiowave propagation are required. Furthermore, detailed understanding of the propagation channel and its interaction with system, creates insights into possible solutions. In this work, both theoretical (ray-tracing) and statistical models of the 60 GHz and UWB channels are studied. Propagation characteristics of the 60 GHz and UWB indoor channels are also compared for providing useful information on design of radio systems. More specifically, based on real-time channel sounder measurements performed in the 60 GHz band, propagation mechanisms including person blocking effect are concluded. Ray-based models in LOS and NLOS indoor corridors are proposed. Multipath power distributions in the 60 GHz band are studied first time. Moreover, propagation interdependencies of path loss, shadowing, number of paths, Rice K-factor and cross polarization discrimination (XPD) with channel delay spread are established. In the UWB propagation channel, frequency- and bandwidth- dependencies are investigated. Multipath and clustering propagation characteristics are analyzed. A new cluster model is proposed and compared with the classical Saleh-Valenzuela model for gaining more understanding of channel general properties. Finally, the performance and capacities of the 60 GHz UWB and MIMO (multiple-in and multiple-out) systems are analyzed for providing reliable parameters for system design and useful information for standardization groups

Radio channel characterisation and system-level modelling for ultra wideband body-centric wireless communications

PhDThe next generation of wireless communication is evolving towards user-centric networks, where constant and reliable connectivity and services are essential. Bodycentric wireless network (BCWN) is the most exciting and emerging 4G technology for short (1-5 m) and very short (below 1 m) range communication systems. It has got numerous applications including healthcare, entertainment, surveillance, emergency, sports and military. The major difference between the BCWN and conventional wireless systems is the radio channel over which the communication takes place. The human body is a hostile medium from the radio propagation perspective and it is therefore important to understand and characterise the effect of the human body on the antenna elements, the radio propagation channel parameters and hence the system performance. In addition, fading is another concern that affects the reliability and quality of the wireless link, which needs to be taken into account for a low cost and reliable wireless communication system for body-centric networks. The complex nature of the BCWN requires operating wireless devices to provide low power requirements, less complexity, low cost and compactness in size. Apart from these characteristics, scalable data rates and robust performance in most fading conditions and jamming environment, even at low signal to noise ratio (SNR) is needed. Ultra-wideband (UWB) technology is one of the most promising candidate for BCWN as it tends to fulfill most of these requirements. The thesis focuses on the characterisation of ultra wideband body-centric radio propagation channel using single and multiple antenna techniques. Apart from channel characterisation, system level modelling of potential UWB radio transceivers for body-centric wireless network is also proposed. Channel models with respect to large scale and delay analysis are derived from measured parameters. Results and analyses highlight the consequences of static and dynamic environments in addition to the antenna positions on the performance of body-centric wireless communication channels. Extensive measurement i campaigns are performed to analyse the significance of antenna diversity to combat the channel fading in body-centric wireless networks. Various diversity combining techniques are considered in this process. Measurement data are also used to predict the performance of potential UWB systems in the body-centric wireless networks. The study supports the significance of single and multiple antenna channel characterisation and modelling in producing suitable wireless systems for ultra low power body-centric wireless networks.University of Engineering and Technology Lahore Pakista

Cross-Layer Design for Multi-Antenna Ultra-Wideband Systems

Ultra-wideband (UWB) is an emerging technology that offers great promises to satisfy the growing demand for low cost and high-speed digital wireless home networks. The enormous bandwidth available, the potential for high data rates, as well as the potential for small size and low processing power long with low implementation cost, all present a unique opportunity for UWB to become a widely adopted radio solution for future wireless home-networking technology. Nevertheless, in order for UWB devices to coexist with other existing wireless technology, the transmitted power level of UWB is strictly limited by the FCC spectral mask. Such limitation poses significant design challenges to any UWB system. This thesis introduces various means to cope with these design challenges. Advanced technologies including multiple-input multiple-output (MIMO) coding, cooperative communications, and cross-layer design are employed to enhance the performance and coverage range of UWB systems. First a MIMO-coding framework for multi-antenna UWB communication systems is developed. By a technique of band hopping in combination with jointly coding across spatial, temporal, and frequency domains, the proposed scheme is able to exploit all the available spatial and frequency diversity, richly inherent in UWB channels. Then, the UWB performance in realistic UWB channel environments is characterized. The proposed performance analysis successfully captures the unique multipath-rich property and random-clustering phenomenon of UWB channels. Next, a cross-layer channel allocation scheme for UWB multiband OFDM systems is proposed. The proposed scheme optimally allocates subbands, transmitted power, and data rates among users by taking into consideration the performance requirement, the power limitation, as well as the band hopping for users with different data rates. Also, an employment of cooperative communications in UWB systems is proposed to enhance the UWB performance and coverage by exploiting the broadcasting nature of wireless channels and the cooperation among UWB devices. Furthermore, an OFDM cooperative protocol is developed and then applied to enhance the performance of UWB systems. The proposed cooperative protocol not only achieves full diversity but also efficiently utilizes the available bandwidth

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

Improved Ultra Wideband Communication System through Adaptive Modulation and Spatial Diversity

PhDAdvances in Multimedia communications have shown the need for high data rate wireless links over short distances. This is to enhance flexibility, accessibility, portability and mobility of devices in home and enterprise environment thereby making users more productive. In 2004, the WiMedia group proposed the Multiband Orthogonal Frequency Division Multiplex Ultra Wideband (MB-OFDM UWB) system with a target of delivering data rate of 480Mbps over 3 metres. However, by now no existing commercial UWB product can meet this proposed specification. The project aims to investigate the reason why UWB technology has failed to realise its potential by carrying out detailed analysis and to seek ways of solving the technical problems. Detailed system analyses were carried out on the UWB technology using a commercial UWB product and a MB-OFDM UWB Evaluation kit. UWB channel measurements of different scenarios were carried out in order to characterise both time varying and time invariant channels. The scenarios are the realistic environments where UWB devices are operating with human subjects in various movement patterns. It gives insight into the effects of human object blocking on the MB-OFDM system performance and estimates an acceptable feedback rate in a UWB time varying channel when implementing an adaptive modulation. The adaptive modulation was proposed and implemented in the MB-OFDM system model to demonstrate the improved Bit Error Rate (BER) performance. Modulating bits are varied across the sub-channels depending on the signal to noise ratio (SNR). Sub-channels experiencing severe fading employ lower or no bit-loading while sub-channels with little or no fading utilise higher bit-loading to maintain a constant system data rate. Spatial diversity was employed to exploit different properties of the radio channel to improve performance. Good diversity gain of two receiving diversity systems using maximal ratio combining and antenna selection techniques is demonstrated in the measurements with the different antenna orientations. An antenna selection circuit is designed and implemented working together with AT90CAP9 UWB Evaluation kit, verifying an improved performance of the UWB system in an indoor environment. The maximal ratio combining technique is also implemented and demonstrated to give a better system performance on a test bed after post-processing

Baseband Implementation and Performance Analysis of the Multiband OFDM UWB System

In this thesis, we follow the standard proposal IEEE 802.12.3a to implement the MB-OFDM UWB system in C programming language. We also analyze the system performance in the multipath fading channel, the IEEE 802.15.3a channel standard. Four different conditions of frequency and timing synchronization are considered. Since the entire system consists of two subsystems: (a) the channel coding with the bit-interleaving and (b) OFDM modulation, the analysis is proceeded in two stages. First, we consider the performance of the only OFDM subsystem. Degradation ratio and average bit error probability are the two metrics used to evaluate the performance. Secondly, we provide the performance bound of the entire UWB system. The performance analysis provides a good understanding of the system behavior in the IEEE 802.15.3a channel standard under various synchronization conditions. The knowledge about the performance of the MB-OFDM UWB system defines our main contribution to the area of wireless communications

Ultra-Wideband Wireless Channels - Estimation, Modeling and Material Characterization

This licentiate thesis is focused on the characterization of ultra-wideband wireless channels. The thesis presents results on ultra-wideband communications as well as on the ultra-wideband characterization of materials. The communications related work consisted in the measurement and modeling of outdoor scenarios envisioned for infostation systems. By infostation, we mean a communication system covering a small area, i.e., ranging up to 20 m, where mobile users can pass by or stop while receiving large amounts of data in a short period of time. Considering the expected (but perhaps overly optimistic) 480 Mbps for UWB systems, it should be possible to download a complete DVD in roughly two minutes, which is something not realizable with any of the current wireless technologies. Channel models, commonly based on measurements, can be used to evaluate the performance of such systems. We therefore, we started by performing measurements at one of the scenarios where infostation systems can exist in the future, namely, petrol stations. The idealized model, was one that could correctly describe the continuous evolution of the channel impulse response for a moving user within the system’s range, and therefore it was deemed necessary to track the multipath components defining the impulse responses along a path of several meters. To solve this problem we designed a novel high-resolution scatterer detection method, which is described in Paper I, capable of tracking individual multipath components for a moving user by identifying the originating point scatterers in a two dimensional geometrical space. The same paper also gives insight on some properties of clusters of scatterers, such as their direction-selective radiated power. The scatterer detection method described in Paper I provided us with the required tools to create the channel model described in Paper II. The proposed channel model has a geometrical basis, i.e., each realization of the channel is based on a virtual map containing point scatterers that contribute to the impulse response by multipath components. Some of the particular characteristics of the model include non-stationary effects, such as shadowing and cluster’s visibility regions. At the end of Paper II, in a simple validation step, the output of the channel model showed a good match with the measured impulse responses. The second part of our work, documented in Paper III, consisted on the dielectric characterization of soil samples using microwave measurements. This project was made in cooperation with the Department of Physical Geography and Ecosystem Analysis at Lund University, which had been developing research work on methane emissions from the wetlands in Zackenberg, Greenland. In recent years, a lot of attention has been put into the understanding of the methane emissions from soils, since methane is a greenhouse gas 20 times stronger than carbon dioxide. However, whereas the methane emissions from natural soils are well documented, the reason behind this effect is an open issue. The usage of microwave measurements to monitor soil samples, aims to address this problem by capturing the sub-surface changes in the soil during gas emissions. An experiment consisting on the monitoring of a soil sample was performed, and a good correlation was found between the variations of the microwave signals and the methane emissions. In addition, the soil dielectric constant was calculated, and from that, the volumetric fractions of the soil constituents which provided useful data for the elaboration of models to describe the gas emission triggering mechanisms. Based on this laboratory experiment, a complete soil monitoring system was created and is at the time of writing running at Zackenberg, Greenland

Transceiver design and system optimization for ultra-wideband communications

This dissertation investigates the potential promises and proposes possible solutions to the challenges of designing transceivers and optimizing system parameters in ultra-wideband (UWB) systems. The goal is to provide guidelines for UWB transceiver implementations under constraints by regulation, existing interference, and channel estimation. New UWB pulse shapes are invented that satisfy the Federal Communications Commission spectral mask. Parameters are designed to possibly implement the proposed pulses. A link budget is quantified based on an accurate frequency-dependent path loss calculation to account for variations across the ultra-wide bandwidth of the signal. Achievable information rates are quantified as a function of transmission distance over additive white Gaussian noise and multipath channels under specific UWB constraints: limited power spectral density, specific modulation formats, and a highly dispersive channel. The effect of self-interference (SI) and inter-symbol interference (ISI) on channel capacity is determined, and modulation formats that mitigate against this effect is identified. Spreading gains of familiar UWB signaling formats are evaluated, and UWB signals are proved to be spread spectrum. Conditions are formulated for trading coding gain with spreading gain with only a small impact on performance. Numerical results are examined to demonstrate that over a frequency-selective channel, the spreading gain may be beneficial in reducing the SI and ISI resulting in higher information rates. A reduced-rank adaptive filtering technique is applied to the problem of interference suppression and optimum combining in UWB communications. The reduced-rank combining method, in particular the eigencanceler, is proposed and compared with a minimum mean square error Rake receiver. Simulation results are evaluated to show that the performance of the proposed method is superior to the minimum mean square error when the correlation matrix is estimated from limited data. Impact of channel estimation on UWB system performance is investigated when path delays and path amplitudes are jointly estimated. Cramér-Rao bound (CRB) expressions for the variance of path delay and amplitude estimates are formulated using maximum likelihood estimation. Using the errors obtained from the CRB, the effective signal-to-noise ratio for UWB Rake receivers employing maximum ratio combining (MRC) is devised in the presence of channel path delay and amplitude errors. An exact expression of the bit error rate (BER) for UWB Rake receivers with MRC is derived with imperfect estimates of channel path delays and amplitudes. Further, this analysis is applied to design optimal transceiver parameters. The BER is used as part of a binary symmetric channel and the achievable information rates are evaluated. The optimum power allocation and number of symbols allocated to the pilot are developed with respect to maximizing the information rate. The optimal signal bandwidth to be used for UWB communications is determined in the presence of imperfect channel state information. The number of multipath components to be collected by Rake receivers is designed to optimize performance with non-ideal channel estimation

Bayesian Compressive Sensing Approach For Ultra-wideband Channel Estimation

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Ultra geniş bant dürtü radyosu, kablosuz haberleşme için yeni gelişen bir teknolojidir. Amerika Birleşik Devletleri’nde haberleşme alanında düzenleyici kuruluş olan Federal Haberleşme Komisyonu (FCC) tarafından ultra geniş bant teknolojisiyle ilgili düzenlemeler yapıldıktan sonra öncelikle IEEE 802.15.3 standardı görev grubu, ultra geniş bant dürtü radyolarıyla yüksek hızlı kablosuz kişisel alan ağı uygulamaları için yeni bir fiziksel katman yapısı oluşturulması amacıyla 802.15.3a çalışma grubunu kurmuştur. Ultra geniş bant veri iletiminde iletim uzaklığındaki artış, veri hızında düşüşe neden olur. Bu doğrultuda IEEE 802.15.4 standardı görev grubu, ultra geniş bant dürtü radyolarıyla düşük hızlı fakat iletim uzaklığı daha büyük olan kablosuz kişisel alan ağı uygulamaları için yeni bir fiziksel katman yapısı oluşturulması amacıyla 802.15.4a çalışma grubunu kurmuştur. Bu çalışma grubu, özellikle ortalama bir veri hızı fakat düşük güç tüketimi, karmaşıklık ve maliyet gerektiren sensör ağı uygulamaları gibi uygulamalar üzerinde çalışmalarını yoğunlaştırmıştır. Bu çalışmada IEEE 802.15.4a bünyesindeki çeşitli ultra geniş bant kanal modellerinin kestirimi üzerine odaklanılmıştır. Düşük iletim gücü, düşük maliyetli basit yapı, düz sönümlemeye karşı bağışıklık ve çokyollu bileşenleri iyi bir zaman çözünürlüğüyle ayrı ayrı çözme yeteneği gibi ayırt edici özelliklere sahip olması dolayısıyla ultra geniş bant dürtü radyoları, konumlama, uzaklık belirleme ve düşük veri hızlı uygulamalar için belirlenen kablosuz kişisel alan ağı IEEE 802.15.4a standardının fiziksel katman yapısı olarak seçilmiştir. Ultra geniş bant dürtü radyolarının gerçekleştiriminde karşılaşılan temel zorluklardan biri de kanal kestirimidir. Kanal karakteristikleri hakkında doğru bir bilgiye sahip olmak, haberleşme açısından etkin bir veri iletimi gerçekleştirmek ve sistem performansını artırmak için oldukça önemlidir. Bu nedenle kanal dürtü yanıtı hakkında bilgi edinmek için kanal kestirimi gereklidir. Ultra geniş bant dürtü radyolarının bantgenişliğinin çok fazla olması dolayısıyla, kanal kestiriminde klasik en büyük olabilirlik kestirimcisinin kullanılmasının başlıca dezavantajı, hassas bir kanal kestirimi için Nyquist kriterine göre alıcıdaki örnekleme işleminde çok yüksek örnekleme oranlarına, bir başka ifadeyle çok yüksek hızlı analog-sayısal dönüştürücülere ihtiyaç duyulmasıdır. Bu durum alıcıda devre karmaşıklığının ve maliyetin artmasına neden olur. Yüksek örnekleme oranı gerektiren bu ultra geniş bant kanal kestirimi probleminin üstesinden gelmek için sıkıştırılmış algılama kullanılabilir. Sıkıştırılmış algılama yöntemi, Nyquist oranından önemli ölçüde daha düşük bir örnekleme oranıyla seyrek sinyallerin geri elde edilmesini mümkün kılmaktadır. Seyrek sinyal ifadesi en basit anlamda, bir çok bileşeni sıfır veya sıfıra yakın olan bir başka ifadeyle çok az bileşeni sıfırdan farklı olan sinyaller için kullanılan bir ifadedir. Alıcıda ard arda alınan ultra geniş bant sinyaller kayda değer bir zaman gecikmesiyle alıcıya ulaştığı ve alıcıda ayrı ayrı çözülebildiği için ultra geniş bant çokyollu kanallar için seyrek yapıya sahip olma varsayımı yaygın kabul görmüştür. Ultra geniş bant kanalların bu özelliği nedeniyle sıkıştırılmış algılama yöntemi, yüksek örnekleme oranı probleminin üstesinden gelmek için ultra geniş bant kanal kestiriminde kullanılabilir. Böylece sıkıştırılmış algılama ile alıcının yüksek maliyeti, karmaşıklığı ve güç tüketimi azaltılarak daha basit yapıda bir alıcı, ultra geniş bant sistemde kullanılabilir. Sıkıştırılmış algılama literatüründe, aynı zamanda basis pursuit (BP) olarak da bilinen ℓ1-norm enküçültme ve matching pursuit (MP) olmak üzere seyrek sinyal geri elde ediniminde kullanılan 2 temel algoritma vardır. Literatürde aynı zamanda bu algoritmaların basis pursuit de-noising (BPDN), orthogonal matching pursuit (OMP), stagewise orthogonal matching pursuit (StOMP) ve compressive sampling matching pursuit (CoSaMP) gibi çeşitli türevleri de bulunmaktadır. Son yıllarda Bayes yapının sıkıştırılmış algılama teorisine uygulanmasıyla birlikte, Bayes tabanlı çeşitli sıkıştırılmış algılama algoritmaları, sıkıştırılmış algılama literatürünün bir parçası olmaya başlamıştır. Bu tezde kullanılacak olan Bayes sıkıştırılmış algılama algoritması da bunlardan biridir. Sıkıştırılmış algılamanın bu çeşitli gerçekleştimlerinin arasında Bayes yapının katkısı, ilgili sinyalin istatistiksel özellikleri de göz önünde bulundurulduğundan sinyal geri elde ediniminin iyileştirilmesi açısından önemli bir potansiyel göstermiştir. Bu doğrultuda, Bayes sıkıştırılmış algılama yaklaşımının seyrek ultra geniş bant kanalların kestirimine uygulanması bu çalışma ile gerçekleştirilmiştir. Bu tezde gerçeğe uygun çeşitli ultra geniş bant kanal modelleri için Bayes sıkıştırılmış algılamanın kanal kestirim performansı incelenmiştir. Özellikle Bayes sıkıştırılmış algılama modelini doğrudan etkilediği için analiz açısından önemli olan (i) standartlaştırılmış IEEE 802.15.4a kanal modellerinin seyrek yapılarının, (ii) işaret-gürültü oranı seviyelerinin ve (iii) ölçüm sayısının çeşitli senaryolar için Bayes sıkıştırılmış algılama kanal kestirim performansı üzerindeki etkileri araştırılmış ve bu sonuçlar seyrek sinyal kestirimi için yaygın olarak kullanılan ℓ1-norm enküçültme tabanlı kestirim sonuçlarıyla karşılaştırılmıştır. Sıkıştırılmış algılama tabanlı ultra geniş bant kanal kestiriminde önemli rol oynayan ultra geniş bant kanalların seyrek yapıya sahip olma varsayımı, kanal ortamları incelenerek doğrulanmalıdır. Bu nedenle tezde, çeşitli kanal ortamlarını modelleyerek oluşturulmuş ve ultra geniş bant araştırma çalışmalarında yaygın olarak kullanılan IEEE 802.15.4a standardı bünyesindeki kanal modeli-1, kanal modeli-2, kanal modeli-5 ve kanal modeli-8 olmak üzere 4 farklı kanal modeli göz önünde bulundurulmuştur. Kısaca bu kanal modellerinin belirgin karakteristikleri özetlenecek olursa: Kanal modeli-1, alıcı verici arasında doğrudan görüşün (LOS) olduğu konut içi ortamı temsil eden ve IEEE 802.15.4a standardı bünyesindeki en seyrek yapıya sahip olan kanal modelidir. Kanal modeli-2, alıcı verici arasında doğrudan görüşün olmadığı (NLOS) konut içi ortamı temsil eden kanal modelidir. Kanal modeli-2 de kanal modeli-1 gibi seyrek yapıya sahiptir fakat kanal modeli-1’e kıyasla daha fazla çokyollu bileşene sahiptir. Kanal modeli-1 ve kanal modeli-2’nin temsil ettikleri ortam, kısa mesafedeki güvenlik ve ölçüm sensörlerinin bulunduğu ev ağları için oldukça önemlidir. Kanal modeli-5, alıcı verici arasında doğrudan görüşün olduğu kapalı olmayan (açık alan) ortamı temsil eden kanal modelidir. Kanal modeli-1 ve kanal modeli-2’ye gore oldukça düşük seyrekliğe sahiptir. Bu kanal modelinde çokyollu bileşenler genellikle birkaç küme halindedir. Kanal modeli-8, alıcı verici arasında doğrudan görüşün olmadığı endüstriyel ortamı temsil eden kanal modelidir. Ortam birçok metal yansıtıcılarla dolu geniş fabrika holleri tarafından karakterize edilir. Böylesi bir ortam çok yoğun şekilde çokyollu bileşenlerin oluşmasına neden olur. Bu sebeple kanal modeli-8, seyrek kanal modeli olarak tanımlanamaz. Dolayısıyla bu 4 kanal modeli içinde en az seyrek yapıya sahip kanal modelidir. Kestirim problemleri analizinde, olabilecek en iyi kestirimci hata performansını belirlemek, performans analizi için önemlidir. Performans alt sınırları da bu en iyi kestirimcinin hata performansını gösterdiği için gerçeklenen kestirimcinin hata performansının değerlendirilmesi açısından önemli bir değerlendirme ölçütüdür. Cramér-Rao alt sınırı yanlı olmayan (unbiased) kestirimciler için yaygın olarak kullanılan bir performans sınırıdır. Gerçekte Cramér-Rao alt sınırı, yanlı olmayan kestirimcilerin toplam varyansı üzerindeki bir alt sınırdır. Bununla birlikte yanlı olmayan kestirimciler için ortalama karesel hata varyansa eşit olduğu için, Cramér-Rao alt sınırı aynı zamanda kestirim hatası üzerindeki bir alt sınırdır. Ancak, bu çalışmada ultra geniş bant kanal kestirimi için önerilen Bayes sıkıştırılmış algılama kestirimcisi, Bayes bir kestirimci olmasının yanı sıra aynı zamanda yanlı (biased) bir kestirimcidir. Dolayısıyla kestirim hatası üzerinde değerlendirme ölçütü olarak bir performans alt sınırı belirlemek, Bayes sıkıştırılmış algılama kestirimcisinin performans analizi açısından önemlidir. Literatürde var olan sonsal (Posterior) Cramér-Rao alt sınırı veya Bayes Cramér-Rao alt sınırı, yanlı olmayan Bayes kestirimcilerin kestirim hatası değil de varyansları üzerindeki bir alt sınırdır. Cramér-Rao alt sınırına ek olarak sonsal Cramér-Rao alt sınırı için Bayes yapıdan dolayı kestirilecek parametre vektörüne ilişkin önsel (prior) olasılık dağılımı da göz önünde bulundurulur. Bu nedenle, bu çalışmada doğrusal yanlılık vektörlerine sahip yanlı Bayes kestirimciler için parameter vektörüne ilişkin önsel olasılık dağılımına ek olarak yanlılık terimi de göz önünde bulundurularak ortalama karesel hata üzerinde bir alt sınır sağlanmış ve bu ortalama karesel hata alt sınırı, gerçeklenen Bayes sıkıştırılmış algılama kestirimcisinin kanal kestirim performansıyla karşılaştırılmıştır. Dahası Bayes sıkıştırılmış algılama ve ℓ1-norm enküçültme yöntemlerinin işlemsel verimliliği büyük-O notasyonundan faydalanılarak işlem sürelerine göre incelenmiştir. Çalışma sonucunda, Bayes sıkıştırılmış algılamanın yüksek işaret-gürültü oranı seviyelerinde yeterli sayıda ölçüm ve seyrek kanal modelleri (kanal modeli-1 ve kanal modeli-2) için ℓ1-norm enküçültme yöntemine kıyasla üstün bir performans sergilediği görülmüştür. Ayrıca ℓ1-norm enküçültme yöntemiyle karşılaştırıldığında, Bayes sıkıştırılmış algılama yönteminin işlemsel olarak daha verimli olduğu sonucu çıkarılmıştır. Bu tezin sonuçları göz önünde bulundurulduğunda, farklı sistem gerçekleştirim durumları için Bayes sıkıştırılmış algılama yöntemi veya ℓ1-norm enküçültme yöntemi diğerinin yerine tercih edilebilir.Ultra-Wideband (UWB) impulse radio (IR) is an emerging technology for wireless communications. Owing to distinguishing properties such as having low transmit power, low-cost simple structure, immunity to flat fading and capability of resolving multipath components individually with good time resolution, UWB-IRs have been selected as the physical layer structure of Wireless Personal Area Network (WPAN) standard IEEE 802.15.4a for location and ranging, and low data rate applications. In the implementation of UWB-IRs, one of the main challenges is the channel estimation. Due to ultra-wide bandwidth of UWB-IRs, the main disadvantage of implementing the conventional maximum likelihood (ML) channel estimator is that very high sampling rates, i.e., very high speed analog-to-digital (A/D) converters are required for precise channel estimation. Reconstruction of sparse signals with a sampling rate significantly lower than Nyquist rate is possible with compressive sensing (CS). Due to the sparse structure of UWB channels, compressive sensing can be used for UWB channel estimation in order to overcome the high-rate sampling problem. Among various implementations of CS, the inclusion of Bayesian framework has shown potential to improve signal recovery as statistical information related to signal parameters is considered. Accordingly, the application of Bayesian CS (BCS) approach to the estimation of sparse UWB channels is considered in this study. In this thesis, the channel estimation performance of BCS is studied for various UWB channel models and noise conditions. Specifically, the effects of (i) sparse structure of standardized IEEE 802.15.4a channel models, (ii) signal-to-noise ratio (SNR) regions, and (iii) number of measurements on the BCS channel estimation performance are investigated, and they are compared to the results of ℓ1-norm minimization based estimation, which is widely used for sparse channel estimation. Furthermore, a lower bound on mean-square error (MSE) is provided for the biased BCS estimator and it is compared with the MSE performance of implemented BCS estimator. Moreover, the computation efficiencies of BCS and ℓ1-norm minimization are investigated in terms of computation time by making use of the big-O notation. The study shows that BCS exhibits superior performance at higher SNR regions for adequate number of measurements and sparser channel models (e.g., CM-1 and CM-2). Furthermore, BCS is found to be computationally more efficient compared to ℓ1-norm minimization. Based on the results of this thesis, the BCS method or the ℓ1-norm minimization method can be preferred over the other one for different system implementation conditions.Yüksek LisansM.Sc