Generic object-oriented models for the dynamic reconfiguration of protocol stacks in wireless 3G/4G mobile networks

This thesis studies research problems related to the efficient modeling, description and representation of the dynamic reconfiguration options pertaining to the communication subsystem of mobile devices and the associated access standards and protocol stacks enclosed therein. To this end, we introduce a generic object-oriented model that allows the description of all valid reconfiguration options in a technology-independent manner and supports querying these descriptions for particular properties. This is achieved by explicitly recording dependency and provision relationships between individual protocol layers as well as between entire protocol stacks in the communication subsystem. To select the most appropriate representation formats for the introduced information model, we identify and evaluate the related global standards. Furthermore, we validate the practicability of our model's design and representation format by applying them in the case of standardized protocol stacks for the GPRS, UMTS and IMS components of 3rd generation cellular systems. We also assess the complexity of our information model by developing a pair of algorithms that process relevant data (i.e., data whose structural organization complies with that of our model) to produce the set of all valid protocol stacks and access standards for a particular communication subsystem. As they differ in terms of their logical structure and information processing steps, we analyze these algorithms to devise mathematical formulas of the temporal complexity associated with such information discovery tasks over our information model. Finally, we develop prototype implementations of these algorithms which we subject to artificially generated load with particular statistical properties to measure their completion time and to assess their performance impact in a technologically realistic setting. We conclude the thesis with a summary of our findings and lessons learnt and provide directions for future work.Σε αυτή την διατριβή μελετάμε ερευνητικά προβλήματα μοντελοποίησης και περιγραφής των δυνατοτήτων δυναμικής αναδιαμόρφωσης των προτύπων πρόσβασης και των σχετικών με αυτά στοιβών πρωτοκόλλων μιας τηλεπικοινωνιακής συσκευής. Ως προς την δυναμική αναδιαμόρφωση των στοιβών πρωτοκόλλων μιας τηλεπικοινωνιακής συσκευής παρουσιάζουμε ένα γενικευμένο αντικειμενοστρεφές μοντέλο πληροφορίας κατάλληλο για την αποτύπωση των δυνατοτήτων δυναμικής αναδιαμόρφωσης των προτύπων πρόσβασης και των έγκυρων τρόπων συνδυασμού των επιμέρους στοιβών και στρωμάτων πρωτοκόλλων που περιλαμβάνονται σε αυτά. Ως βασική καινοτομία του, το μοντέλο αυτό εισάγει και επιστρατεύει συσχετίσεις παροχής και εξάρτησης μεταξύ των επιμέρους συστατικών μιας στοίβας πρωτοκόλλων προκειμένου να εγγυηθεί την επιθυμητή λειτουργικότητα. Προς την εξυπηρέτηση της καλύτερης αναπαράστασης και διακίνησης πληροφορίας σύμφωνης με το παρουσιαζόμενο μοντέλο πληροφορίας, αξιολογούμε τα υπάρχοντα διεθνή πρότυπα για γλώσσες περιγραφής της πληροφορίας, επιλέγουμε το καταλληλότερο από αυτά και προβαίνουμε στην πρακτική εφαρμογή του μοντέλου πληροφορίας για τα πρότυπα ασύρματης πρόσβασης GPRS, UMTS και IMS. Προκειμένου δε να αξιολογήσουμε την πολυπλοκότητα του μοντέλου πληροφορίας, αναπτύσσουμε (εκ του μηδενός) δύο νέους αλγόριθμους οι οποίοι, επεξεργαζόμενοι τις παραπάνω περιγραφές, παράγουν το σύνολο με τις έγκυρες στοίβες πρωτοκόλλων και τα πρότυπα πρόσβασης στα οποία και είναι δυνατό να αναδιαμορφωθεί το σχετικό τηλεπικοινωνιακό σύστημα. Αφού αναλύσουμε και εκφράσουμε πλήρως την χρονική πολυπλοκότητα των αλγορίθμων αυτών, προβαίνουμε σε μια πειραματική διαδικασία μέτρησης και καταγραφής της απόδοσης τους σε ένα περιβάλλον εκτέλεσης κατά το δυνατό πλησιέστερο με αυτό των ασύρματων τηλεπικοινωνιακών συσκευών 3ης και 4ης γενιάς. Ολοκληρώνοντας, αξιολογούμε τα αποτελέσματα της πειραματικής διαδικασίας προκειμένου να διατυπώσουμε συμπεράσματα ως προς την πρακτική εφαρμογή του μοντέλου πληροφορίας σε εγκατεστημένες δικτυακές υποδομές

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