This thesis aims to establish methods for identifying and training the knowledge and skills of operating a novel automated system still undergoing final design and construction. The absence of operating experience requires the characteristics of the system to be examined so that the future tasks of supervisors can be anticipated in order to address human factors design. This work is carried out in the context of an 'Integrated Mail Processor' (IMP)—a highly automated letter sorting machine being developed by Royal Mail.

In this thesis, we study channel estimation in time-varying cooperative network. Since channels vary with time, we insert training blocks periodically to trace channel variation. In this work, we adopt Kalman filter to trace channel variation due to its low complexity. By storing previous channel estimate, Kalman filter simply requires to process next received vectors to update current channel estimate. We use all past observations to estimate current channel state to avoid wasting information. In content of cooperation, we directly estimate effective channel from source through relay to the destination. The reason is that, we separately estimate the source-relay and relay-destination links, relays need extra efforts to estimate the channel and feedback estimates to the destination. It will increase the computational loading on relays, and the feedback channel may suffer channel fading, resulting in more distortion of estimates. Therefore, the destination directly estimate effective channel, using Kalman filter to trace variation. Furthermore, we design pre-coding scheme on relays for forwarding training symbols in order to reduce channel estimation errors and obtain more accurate channel information. To detect data symbols, we need to channel state information over each data block as well. Therefore, estimates over previous training blocks are interpolated to estimate channel over data blocks based on LMMSE criterion. Since estimates over training blocks are obtained from Kalman filter, it consequently improves estimation quality of the channel over the data blocks. The main contributions of the thesis are optimal training design to reduce the estimation error, the estimation based on Kalman filter, and linearly combing the estimates to provide more accurate estimates of the channels over data blocks.

No description available.

The client-therapist relationship has long been recognized as an important element in psychotherapy, and research has demonstrated its robust association with positive outcomes. This study examined the feasibility and preliminary efficacy of training therapists in strategies for improving therapeutic relationships with clients. The strategies were compiled from the empirical literature, drawing on the work of Hilsenroth and Cromer (2007), Castonguay (1996), and Safran and Muran (2000). The study employed a manipulated training design that has the benefit of addressing naturalistic effectiveness questions, while adhering to the rigorous scientific standards of controlled efficacy research (Hayes, 2002). Participants were 57 therapists working at five community mental health clinics who were randomly assigned to the brief alliance training workshop (in which they participated prior to starting treatment with a new client) or to a delayed-training control condition. Outcomes assessed included therapists' self-reported use of alliance strategies in session 1, therapist-rated alliance quality after session 1, and early client engagement. Engagement was operationalized in several ways: number of sessions attended in the first four weeks, planned session frequency (e.g., weekly, monthly), attendance rate (i.e., percent of scheduled sessions attended), and treatment status at the end of four weeks (e.g., therapist and client had next session scheduled, client had terminated unilaterally). Counter to hypotheses, one-way ANOVAs and chi-square analyses revealed no statistically significant differences between the training and the delayed-training conditions on the primary outcomes. However, effect size estimates suggested that clinicians in the training condition reported better alliances with their clients than clinicians who had yet to receive the training (d = 0.40, 95% CI [-0.13, 0.93], small to medium effect). Furthermore, therapists' use of alliance strategies taught in the workshop was significantly correlated with alliance quality. In addition to the preliminary efficacy findings, the study generated important information about the feasibility of conducting psychotherapy research in naturalistic settings, as well as recommendations for future studies. The manipulated training design holds promise for collaborations between researchers and clinicians seeking to bridge science and practice.

The aim of this study is to investigate the effectiveness of the ”accelerated” development training programme by using two specifically compiled in-basket exercises equivalent in complexity. A pre- and post-evaluation were performed to determine whether learning transfer actually took place-that is, whether competencies developed. The research focused on the following competencies: action orientation; planning and organising; analysis and problem solving; teamness; and impact. From the statistical analysis conducted, significant differences were obtained for three competencies, impact, action orientation and problem solving. The separation of variables proved to be problematic and the results could not be attributed directly to the training programme. The results are explained, the design of the evaluation critically reviewed and recommendations made to improve the design of the evaluation. The value of the study is discussed and directions for possible future research provided. / Industrial and Organisational Psychology / M. A.(Industrial and Organisational Psychology)

The demand for sophisticated wireless applications capable of conveying information content represented in various forms such as voice, data, audio and video is ever increasing. In order to support such applications, either additional wireless spectrum is needed or advanced signal processing techniques must be employed by the next-generation wireless communication systems. An immediate observation that can be made regarding the first option is that radio frequency spectrum is a limited natural resource. Moreover, since existing spectrum allocation policies of several national regulatory agencies such as the Federal Communications Commission (FCC) restrict spectrum access to licensed entities only, it has been identified that most of the licensed spectrum across time and frequency is inefficiently utilized. To facilitate greater spectral efficiency, many national regulatory agencies are considering a paradigm shift towards spectrum allocation by allowing unlicensed users to temporarily borrow unused spectral resources. This concept is referred to a dynamic spectrum access (DSA). Although, several spectrum measurement campaigns have been reported in the published literature for quantitatively assessing the available vacant spectrum, there are certain aspects of spectrum utilization that need a deeper understanding. First, we examine two complementary approaches to the problem of characterizing the usage of licensed bands. In the first approach, a linear mixed-effects based regression model is proposed, where the variations in percentage spectrum occupancy and activity period of the licensed user are described as a function of certain independent regressor variables. The second approach is based on the creation of a geo-location database consisting of the licensed transmitters in a specific geographical region and identifying the coverage areas that affect the available secondary channels. Both of these approaches are based on the energy spectral density data-samples collected across numerous frequency bands in several locations in the United States. We then study the mutual interference effects in a coexistence scenario consisting of licensed and unclicensed users. We numerically evaluate the impact of interference as a function of certain receiver characteristics. Specifically, we consider the unlicensed user to utilize OFDM or NOFDM symbols since the appropriate subcarriers can be turned off to facilitate non- contiguous spectrum utilization. Finally, it has been demonstrated that multiple-input and multiple-output (MIMO) antennas yield significant throughput while requiring no increase in transmit power or required bandwidth. However, the separation of spectrally overlapping signals is a challenging task that involves the estimation of the channel. We provide results concerning channel and symbol estimation in the scenario described above. In particular, we focus on the MIMO-OFDM transmission scheme and derive capacity lower bounds due to imperfect channel estimation.

The aim of this study is to investigate the effectiveness of the ”accelerated” development training programme by using two specifically compiled in-basket exercises equivalent in complexity. A pre- and post-evaluation were performed to determine whether learning transfer actually took place-that is, whether competencies developed. The research focused on the following competencies: action orientation; planning and organising; analysis and problem solving; teamness; and impact. From the statistical analysis conducted, significant differences were obtained for three competencies, impact, action orientation and problem solving. The separation of variables proved to be problematic and the results could not be attributed directly to the training programme. The results are explained, the design of the evaluation critically reviewed and recommendations made to improve the design of the evaluation. The value of the study is discussed and directions for possible future research provided. / Industrial and Organisational Psychology / M. A.(Industrial and Organisational Psychology)

Τα σύγχρονα τηλεπικοινωνιακά συστήματα, καθώς επίσης και οι επόμενες γενιές τους, πρέπει να προσαρμόζονται για να υποστηρίζουν ένα μεγάλο αριθμό από υπηρεσίες με διαφορετικές απαιτήσεις ποιότητας. Για παράδειγμα, στα κυψελικά συστήματα, οι κυψέλες μικραίνουν σε μέγεθος και αυξάνονται σε πλήθος για να υποστηρίζουν ένα συνεχώς αυξανόμενο πλήθος χρηστών. Επίσης, σε μια άλλη κατεύθυνση, τα δίκτυα αισθητήρων αποτελούνται από μικρές συσκευές που εισάγουν περιορισμούς μεγέϑους, ενέργειας και επεξεργαστικής ισχύος. Αυτά τα δυο παραδείγματα επιδεικνύου τόσο την αυξανόμενη πολυπλοκότητα των τηλεπικοινωνιακών συστημάτων όσο και τις ιδιαίτερες απαιτήσεις που υπάρχουν στους μεμονωμένους κόμβους τους. Τα τηλεπικοινωνιακά συστήματα πολλαπλών εισόδων και εξόδων έχουν την δυνατότητα να προσφέρουν αυξημένη χωρητικότητα και αξιοπιστία στην μετάδοση δεδομένων μέσω της έννοιας της χωρικής ποικιλομορφίας (space diversity). Συγκεκριμένα, αυτό επιτυγχάνεται με την μετάδοση της ζητούμενης πληροφορίας μέσω ενός αριθμού από διαφορετικά χωρικά μονοπάτια τα οποία δημιουργούνται από την ύπαρξη πολλαπλών κεραιών στον πομπό ή/και στον δέκτη. Ωστόσο, η προαναφερόμενη πολυπλοκότητα στα τηλεπικοινωνιακά συστήματα και οι ιδιαίτερες απαιτήσεις των κόμβων έχουν ως αποτέλεσμα να μην επαρκούν οι τεχνικές που έχουν αναπτυχθεί. Μια πιθανή διέξοδο έρχεται να δώσει η ιδέα της συνεργασίας. Η έννοια της συνεργασίας έχει διάφορες οπτικές γωνίες σε ένα τηλεπικοινωνιακό σύστημα. Πρώτον, αν οι συσκευές δεν μπορούν να υποστηρίξουν πολλαπλές κεραίες (π.χ. λόγω μεγέϑους όπως στα δίκτυα αισθητήρων και στα κινητά τηλέφωνα), σίγουρα μπορούν να συνεργαστούν ώστε με έναν κατανεμημένο τρόπο να προσφέρουν σε επίπεδο συστήματος τα απαραίτητα διαφορετικά χωρικά μονοπάτια. Δεύτερον, ακόμη και αν είναι δυνατή η χρήση πολλαπλών κεραιών σε κάποιον κόμβο ενός δικτύου, π.χ. σε σταθμούς ϐάσης κυψελικών συστημάτων, ο αριθμός τους μπορεί απλώς να μην αρκεί λόγω της αυξημένης πολυπλοκότητας και του μεγέθους του δικτύου. Η κατάλληλη χρήση συνεργατικών κόμβων μπορεί να δώσει επίσης λύση στον εν λόγω περιορισμό.Η παρούσα διδακτορική διατριβή ϑα ϐασιστεί πάνω σε συνεργατικά συστήματα υπό την πρώτη οπτική γωνία που παρουσιάστηκε παραπάνω. Συγκεκριμένα, ϑα ϑεωϱηθεί ένα συνεργατικό δίκτυο με τρεις κόμβους, δηλαδή μια πηγή, έναν αναμεταδότη και έναν προορισμό. ϑα μελετηθούν τεχνικές εκτίμησης των καναλιών που συμμετέχουν στην μετάδοση της πληροφορίας αναδεικνύοντας τα ϐασικά χαρακτηριστικά που εισάγει η έννοια της συνεργασίας στις εν λόγω τεχνικές. Επίσης, ϑα παρουσιαστούν υλοποιήσεις διαφόρων συνεργατικών πρωτοκόλλων μετάδοσης σε ένα πραγματικό τηλεπικοινωνιακό σύστημα προσφέροντας έτσι την απαραίτητη πρακτική διαίσθηση πίσω από αυτά τα συστήματα. Συγκεκριμένα, αφού παρουσιαστούν κάποιες ϐασικές έννοιες για τις συνεργατικές επικοινωνίες και την λειτουργία της εκτίμησης καναλιών, ϑα μελετηθεί το πρόβλημα εκτίμησης με μερική επίβλεψη σε σχέση με το μοντέλο του συνεργατικού συστήματος που ϑεωρήθηκε. Προτείνονται εναλλακτικά σχήματα για την υλοποίηση του εκτιμητή καθώς επίσης και ένας απλός σχεδιασμός της ακολουθίας συμβόλων που υποβοηθάει το εφαρμοζόμενο κριτήριο ετεροσυσχέτισης. ΄Ολες οι έννοιες που παρουσιάζονται σε αυτό το κεφάλαιο υποστηρίζονται με πειραματικά και ημιαναλυτικά επιχειρήματα. Στην συνέχεια, παρουσιάζεται το πρόβλημα σχεδιασμού της κατανομής ενέργειας σε σύμβολα εκμάθησης για την εκτίμηση συσχετισμένων καναλιών. Αφού περιγραφεί το προς μελέτη πρόβλημα, ϑα επικεντρωθούμε στο κριτήριο ελαχίστων τετραγώνων για το οποίο παρουσιάζονται η ϐέλτιστη και τρεις υποβέλτιστες λύσεις που συνοδεύονται από χρήσιμα συμπεράσματα και παρατηρήσεις. ΄Επειτα, μελετάται το κριτήριο ελάχιστου μέσου τετραγωνικού σφάλματος για δυο περιπτώσεις. Στην πρώτη, παρουσιάζεται μια ανάλυση χειρότερης περίπτωσης και γίνεται η σύνδεση των λύσεων του προβλήματος με τις λύσεις του προηγούμενου κριτηρίου. Επίσης, υπό την υπόθεση των καναλιών χωρίς συσχέτιση, παρουσιάζεται η ϐέλτιστη λύση για τον σχεδιασμό της ακολουθίας των συμβόλων εκμάθησης. Στην τρίτη κατεύθυνση, ϑα παρουσιαστεί αρχικά το σύστημα στο οποίο ϑα υλοποιηθούν και εκτελεστούν τα πρωτόκολλα συνεργατικής επικοινωνίας. Στην συνέχεια, παρουσιάζονται τα εν λόγω σχήματα και το κεφάλαιο καταλήγει με την πειραματική διαδικασία, την παρουσίαση και αξιολόγηση των αποτελεσμάτων καθώς και την εξαγωγή χρήσιμων συμπερασμάτων. Στο τέλος της διατριβής περιγράφονται συνοπτικά τα ϐασικά συμπεράσματα που έχουν προκύψει και παρουσιάζονται κάποιες ενδιαφέρουσες νέες κατευθύνσεις. / Contemporary communication systems, as well as their next generations, are expected to adapt to a rapidly increasing number of desired applications and quality of service levels. For example, in cellular systems, the cells are getting smaller in size and larger in numbers in order to support the increasing number of users. Also, towards another direction, wireless sensor network consist of small devices that comply with stringent constraints such as size, consumed energy and computational power. These examples demonstrate both the high complexity of communication networks and the specific requirements that exist in individual communication nodes. Multiple input multiple output systems are capable of offering high capacity and reliable data communications utilizing the notion of spatial diversity. This is achieved by transmitting the desired information through different spatial paths that are created because of multiple antennas at the transmitter and/or the receiver side. However, the aforementioned complexity of communication networks and the specific requirements of the nodes have as a result that currently proposed techniques, for such systems, are inadequate. A possible solution to this dead end is the idea of cooperation. Cooperation has several aspects in a communication system. Firstly, if the nodes cannot support multiple antennas (e.g. due to size restriction as in sensor networks and mobile phones), they can cooperate in order to provide, in a distributed manner, the desired spatial paths. Secondly, even if multiple antennas can be used, as in base stations, their number might not be good enough because of the increased complexity and size of the network. The appropriate use of cooperative nodes can provide a solution to this problem, too. This dissertation has been focused on cooperative systems that are viewed according to the first aspect. Specifically, it has been assumed that the cooperative network consists of three nodes, a source, a relay and a destination. On this network, channel estimation techniques have been studied pointing out the main characteristics that are inherent to cooperation. Moreover, test-bed implementations have been provided for several well known cooperative schemes and protocols pointing out the practical aspects of such systems. In more detail, after the presentation of some introductory notions on cooperation and channel estimation, a semi-blind technique has been studied that is based on the so called cross-relation criterion. Two alternative schemes for constructing the channel estimator have been proposed as well as a simple training design procedure for improving the estimation performance has been devised. The results that have been produced are supported by semi analytic arguments and computer simulations. Then, a training design problem has been studied for a training based channel estimator. The design has been focused on the energy allocation of training symbols under the assumption that channel taps are correlated. After the description of the problem, the least squares criterion has been utilized and the optimal solution, along with three suboptimal ones, has been presented and useful conclusions have been drawn. Also, the problem has been studied under the minimum mean square error criterion for two cases. In the first one, a worst case analysis has been presented. There, a connection to the least squares solution was provided. In the second case, relaxing the assumption of correlated channel taps, the optimal solution has been presented. In the third direction, a number of well known protocols have been implemented in a test-bed system. A measurement campaign has been conducted to acquire the bit error performance and the computational complexity of the protocols. The protocols have been compared according to three different metrics and useful insights have been identified. The dissertation is concluded with a brief presentation of the main points that have been raised in the aforementioned directions. Moreover, new interesting research directions have been provided.