Kamelia Nikolova

High accuracy Hilbert transformer realization for multicarrier communications

The basic motivation for this work is to investigate how Hilbert transformer (HT) design optimization can influence the Bit Error Ratio (BER) performance of a multicarrier wireless system. The implementation of a novel digital allpass based HT is proposed. The HT realization is based on worst-case phase-sensitivity minimization of each individual allpass section used. This design procedure allows to improve the accuracy of the HT phase deviation even in the cases of severe wordlength limitations and fixed point arithmetic applications. A multicarrier wireless system is simulated and it is experimentally demonstrated that the low sensitivity HT design procedure can improve the BER performance. AWGN and Rayleigh wireless channels are considered.

High accuracy design and realization of fixed and variable allpass-based fractional delay digital filters

In this paper new methods for low-sensitivity design of allpass-based fixed and variable fractional delay filters are proposed. They are based on a sensitivity minimization of each individual first- and second-order allpass section in the cascade realization depending on their transfer function pole positions. Thus a higher accuracy of implementation and tuning, shorter wordlength and efficient multiplierless realizations are achieved.

A Case of Service Interaction in M2M Device Management

The explosion of diverse Machine to Machine (M2M) services and applications may lead to undesired service interaction. While the service interaction problem is thoroughly studied for telecommunication services, there is a lack of knowledge about the manifest of service interaction in M2M communications. The paper presents a model of connectivity management of M2M devices and formal definition of value added services related to device connectivity. An approach to detect service interaction is proposed based on standard reasoning on description logic.

2-bit word length Hilbert transformers for multicarrier communications

This work illustrates how the Hilbert transformer design method and the word length used can influence the Bit Error Ratio (BER) performance of multicarrier systems. The implementation of new digital even order allpass based Hilbert transformers is proposed. The Hilbert transformer realization is developed using worst case phase sensitivity minimization of each individual first order allpass sections. This design procedure improves the accuracy of the Hilbert transformer phase deviation even for severe word length limitations and fixed point arithmetic applications. The operation of a multicarrier system is simulated and the experimental results demonstrate that a good BER performance can be achieved using 2-bit even order allpass based Hilbert transformers.

Investigating the sensitivity of first-order recursive DSP networks

In addition to diverse applications as separate digital systems, first-order DSP networks provide a basic design framework for cascade and other efficient filter architectures. The use of very low-sensitivity digital structures is a key approach to reducing the negative impact of quantisation on digital signal processing (DSP) system implementation. This publication presents the experimental results of an investigation into sensitivity at all possible placements of poles for some of the most commonly-used recursive first-order digital networks.

Modeling M2M device registration status

Capability to control and manage device in remote manner is essential in the world of Machine-to-Machine communications. Device management is a challenging task due to the increased number of diverse devices, services importance, regulation compliance and performance issues. Lightweight M2M (LWM2M) is device management framework defined by Open Mobile Alliance. In this paper, we propose device registration models with extended functionality based on LWM2M and present an approach to formal verification of models which may facilitate the process of engineering of device management platforms.

Accuracy improvement of real-poles allpass-based digital Hilbert transformers

In this work a very efficient approach to extend the frequency range over which the real-poles allpass-based digital Hilbert transformers (HT) phase difference is kept near constant and to reduce the deviation of the phase from 90o in a limited word-length environment is proposed. This approach is based on minimisation of the phase sensitivity of each individual first- and second-order allpass section in the cascade realisation of the two branches of the structure used, depending on their transfer function pole positions, including replacements of second-order-sections by two first-order low-sensitivity allpass sections. The effectiveness of the proposed design is experimentally verified and the HTs so obtained are very suitable for different telecommunication applications.

A Novel Approach to Design a Scalable Air Quality Monitoring System

The research presents a novel approach to carbon dioxide (CO2) emissions monitoring and access to local air quality data. The approach applies the advanced Internet of things technology to design a mobile telemetry system for CO2 data collection and processing in order to be presented as a value-added application to mobile users. Based on requirements analysis, functional architecture for mobile telemetry system is proposed. The design aspects of mobile telemetry application layer protocol are studied. An approach to formal verification of protocol behavior is suggested. An information model that captures the basic concepts related to CO2 monitoring is proposed. Examples of ubiquitous access to CO2 measurements are described.