Adaptive space-time processing for digital mobile radio communication systems

The performance of digital mobile radio communication systems is primarily limited by cochannel interference and multipath fading. Antenna arrays, with optimum combining (OC), have been shown to combat multipath fading of the desired signal and are capable of reducing the power of interfering signals at the receiver through spatial filtering. With OC, the signals received by several antenna elements are weighted and combined to maximize the output signal-to-interference-plus-noise ratio (SLNR). We derive new closed-form expressions for (1) the probability density function (PDF) of the SINR at the output of the optimum combiner, (2) the average probability of bit error rate (BER) and its upper bound, and (3) the outage probability in a Rayleigh fading environment with multiple cochannel interferers. The study covers both the case when the number of antenna elements exceeds the number of interferers and vice versa. We consider independent fading at each antenna element, as well as the effect of fading correlation. The analysis is also extended to processing using maximal ratio combining (MRC). The performance of the optimum combiner is compared to that of the maximal ratio combiner and results show that OC performs significantly better than MRC. We investigate the performance of OC in a microcellular environment where the desired signal and the cochannel interference can have different statistical characteristics. The desired signal is assumed to have Rician statistics implying that a dominant multipath reflection or a line-of-sight (LOS) propagation exists within-cell transmission. Interfering signals from cochannel cells are assumed to be subject to Rayleigh fading due to the absence of LOS propagation. This is the so called Rician/Rayleigh model. We also study OC for a special case of the Rician/Rayleigh model, the Nonfading/Rayleigh model. We derive expressions for the PDF of the SJNR, the BER and the outage probability for both Rician/Rayleigh and Nonfading/Rayleigh models. Similar expressions are derived with MRC. Another area in which space-time processing may provide significant benefits is when wideband signals (such as code division multiple access (CDMA) signals) are overlaid on existing narrowband user signals. The conventional approach of rejecting narrowband interference in direct-sequence (DS) CDMA systems has been to sample the received signal at the chip interval, and to exploit the high correlation between the interference samples prior to spread spectrum demodulation. A different approach is space-time processing. We study two space-time receiver architectures, referred to as cascade and joint, respectively, and evaluate the performance of a DS-CDMA signal overlaying a narrowband signal for personal communication systems (PCS). We define aild evaluate the asymptotic efficiency of each configuration. We develop new closed-form expressions for the PDF of the SINR at the array output, the BER and its upper bound, for both cascade and joint configurations. We also analyze the performance of this system in the presence of multiple access interference (MAJ)

Terahertz data processing for standoff detection of improvised explosive devices

Improvised Explosive Devices (IEDs) are homemade, non-conventional explosive devices, which are used to destruct and incapacitate individuals and property. IEDs are becoming a popular weapon of attack among terrorists and insurgents due to their easy of making and capability to cause major damage. Hence, is has become necessary to develop efficient systems for detecting and disarming these devices. The Terahertz technology which uses electromagnetic radiations between 0.3 THz to 10 THz for imaging is one of the most recently developed detection techniques and is ideally suitable for detection of IEDs and similar devices. Although a lot of work has been done for developing a standoff detection system for detecting IEDs using Terahertz imaging, it is still needed to develop advanced techniques for processing of the THz data. In this thesis, efficient signal processing techniques are developed for standoff, real time and wide area detection of IEDs. The signal processing algorithm is a two stage algorithm where the first stage is a preprocessing stage. In this stage, THz data from a large field is given to the correlation filters which detect hotspots in the field where an IED could be present. This stage avoids the computational burden of processing data from the entire field in the second stage. In the second stage, THz data from the hotspots of stage one are unmixed to find the individual explosive materials in each data point/pixel. The unmixing is done using a variant of the Independent Component Analysis algorithm which separates only the required component. Once the components are separated, they are analyzed to see if any of them matches an explosive. Thus, the presence of an IED or explosive can be accurately determined within the field --Abstract, page iii

Grothendieck groups of dd-exangulated categories and a modified Caldero-Chapoton map

A strong connection between cluster algebras and representation theory was established by the cluster category. Cluster characters, like the original Caldero-Chapoton (CC) map, are maps from certain triangulated categories to cluster algebras and they have generated much interest. Holm and J{\o}rgensen constructed a modified CC map from a sufficiently nice triangulated category to a commutative ring, which is a generalised frieze under some conditions. In their construction, a quotient $K_{0}^{sp}(\mathcal{T})/M$ of a Grothendieck group of a cluster tilting subcategory $\mathcal{T}$ is used. In this article, we show that this quotient is the Grothendieck group of a certain extriangulated category, thereby exposing the significance of it and the relevance of extriangulated structures. We use this to define another modified CC map that recovers the one of Holm--J{\o}rgensen. We prove our results in a higher homological context. Suppose $\mathcal{S}$ is a $(d+2)$-angulated category with subcategories $\mathcal{X}\subseteq\mathcal{T}\subseteq\mathcal{S}$, where $\mathcal{X}$ is functorially finite and $\mathcal{T}$ is $2d$-cluster tilting, satisfying some mild conditions. We show there is an isomorphism between the Grothendieck group $K_{0}(\mathcal{S},\mathbb{E}_{\mathcal{X}},\mathfrak{s}_{\mathcal{X}})$ of the category $\mathcal{S}$, equipped with the $d$-exangulated structure induced by $\mathcal{X}$, and the quotient $K_{0}^{sp}(\mathcal{T})/N$, where $N$ is the higher analogue of $M$ above. When $\mathcal{X}=\mathcal{T}$ the isomorphism is induced by the higher index with respect to $\mathcal{T}$ introduced recently by J{\o}rgensen. Thus, in the general case, we can understand the map taking an object in $\mathcal{S}$ to its $K_{0}$-class in $K_{0}(\mathcal{S},\mathbb{E}_{\mathcal{X}},\mathfrak{s}_{\mathcal{X}})$ as a higher index with respect to the rigid subcategory $\mathcal{X}$.Comment: V1: 28 pages. V2: Changes made following a review. There was an error in Remark 2.13 that has now been correcte

The index with respect to a rigid subcategory of a triangulated category

Palu defined the index with respect to a cluster tilting object in a suitable triangulated category, in order to better understand the Caldero-Chapoton map that exhibits the connection between cluster algebras and representation theory. We push this further by proposing an index with respect to a contravariantly finite, rigid subcategory, and we show this index behaves similarly to the classical index. Let $\mathcal{C}$ be a skeletally small triangulated category with split idempotents, which is thus an extriangulated category $(\mathcal{C},\mathbb{E},\mathfrak{s})$. Suppose $\mathcal{X}$ is a contravariantly finite, rigid subcategory in $\mathcal{C}$. We define the index $\mathrm{ind}_{\mathcal{X}}(C)$ of an object $C\in\mathcal{C}$ with respect to $\mathcal{X}$ as the $K_{0}$-class $[C]_{\mathcal{X}}$ in Grothendieck group $K_{0}(\mathcal{C},\mathbb{E}_{\mathcal{X}},\mathfrak{s}_{\mathcal{X}})$ of the relative extriangulated category $(\mathcal{C},\mathbb{E}_{\mathcal{X}},\mathfrak{s}_{\mathcal{X}})$. By analogy to the classical case, we give an additivity formula with error term for $\mathrm{ind}_{\mathcal{X}}$ on triangles in $\mathcal{C}$. In case $\mathcal{X}$ is contained in another suitable subcategory $\mathcal{T}$ of $\mathcal{C}$, there is a surjection $Q\colon K_{0}(\mathcal{C},\mathbb{E}_{\mathcal{T}},\mathfrak{s}_{\mathcal{T}}) \twoheadrightarrow K_{0}(\mathcal{C},\mathbb{E}_{\mathcal{X}},\mathfrak{s}_{\mathcal{X}})$. Thus, in order to describe $K_{0}(\mathcal{C},\mathbb{E}_{\mathcal{X}},\mathfrak{s}_{\mathcal{X}})$, it suffices to determine $K_{0}(\mathcal{C},\mathbb{E}_{\mathcal{T}},\mathfrak{s}_{\mathcal{T}})$ and $\operatorname{Ker} Q$. We do this under certain assumptions.Comment: V1: 26 pages. V2: 26 pages, minor title change, added to Remark 4.13. V3: Several changes made following a review. We now use the notation add(X*Y) for the extension subcategory previously denoted X*

InfoHarness: Managing Distributed, Heterogeneous Information

Today, important information is scattered in so many places, formats, and media, that getting the right information at the right time and place is an extremely difficult task. Developing a single software product, for example, includes the creation of documents ranging from the requirements specification and project schedules to marketing presentations, multimedia tutorials, and more. Each document may be created by a different person using a different tool, and each may be stored in a different place. InfoHarness is an information integration system, platform, and tool set that addresses these problems, managing huge amounts of heterogeneous information in a distributed environment. Through a powerful, consistent user interface, InfoHarness provides rapid search of and access to information assets including documents and parts of documents, mail messages, images, code files, video clips, Web pages with URLs, InfoHarness queries, and views of relational tables. The system makes all these artifacts available without relocating, restructuring, or reformatting the data

Television Advertising and Child Consumer: Different Strategies for U.S. and Japanese Marketers

This paper examines the consumer socialization of Japanese and American children from a socio-cultural and economic perspective. It presents the cultural differences between the two countries, and how these differences influence the marketing strategies in each country. Taking into consideration the television viewing habits and routine advertising strategies in Japan and USA, the paper offers the implications for Global Marketing Managers. Finally, the need for future research is addressed

Accounting Differences on Value Relevance in Asian Markets: Predictions and Business Implications

While East Asia has faced tremendous economic growth in recent years, research that systematically examines the value relevance of accounting information throughout the region is sparse. This study compares the accounting measurement rules in seven Asian countries and discusses the impact of accounting differences on value relevance of accounting information. The theoretical predictions have important implications for financial analysts, investors, stock exchanges, standard-setters, and regulators