Intelligent hybrid cheapest cost and mobility optimization RAT selection approaches for heterogeneous wireless networks

The evolution of wireless networks has led to the deployment of different Radio Access Technologies (RATs) such as UMTS Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE), Wireless Local Area Network (WLAN) and Mobile Worldwide Interoperability for Microwave Access (WiMAX) which are integrated through a common platform. Common Radio Resource Management (CRRM) was proposed to manage radio resource utilization in heterogeneous wireless networks and to provide the required Quality of Service (QoS) for allocated calls. RAT selection algorithms are an integral part of the CRRM algorithms. Their role is to decide, when a new or Vertical Handover (VHO) call is requested, which of the available RATs is most suitable to fit the need of the incoming call and when to admit them. This paper extends our earlier work on the proposed intelligent mobility optimization and proposes an intelligent hybrid cheapest cost RAT selection approach which aims to increase users' satisfaction by allocation users that are looking for cheapest cost connections to a RAT that offers the cheapest cost of service. A comparison for the performance of centralized load-balancing, proposed and distributed cheapest cost and mobility optimization algorithms is presented. Simulation results show that the proposed intelligent algorithms perform better than the centralized load-balancing and the distributed algorithms. © 2014 Academy Publisher

Order-4 Quasi-Orthogonal Cooperative Communication in STFC MB-OFDM UWB

Recently, cooperative communication and Space-Time-Frequency-Codes (STFCs) have been introduced into the Multiband OFDM Ultra-Wideband (MB-OFDM UWB) to improve the reliability, data rate and system capacity. This paper proposes a cooperative communication scheme for a four source node MB-OFDM UWB system using Quasi-Orthogonal STFCs, which is referred to as order-4 Quasi-Orthogonal Cooperative Communication Scheme (4-QOCCS). Simulation results show that the proposed 4-QOCCS provides significantly better error performance over the conventional MB-OFDM UWB and our order-2 Orthogonal Cooperative Communication Scheme (2-OCCS) using the Alamouti STFCs, and even better than the order-4 Orthogonal Cooperative Communication Scheme (4-OCCS), which we have been recently proposed, in the high spectral efficiency cases

Adaptive relaying protocol multiple-input multiple-output orthogonal frequency division multiplexing systems

In wireless broadband communications, orthogonal frequency division multiplexing (OFDM) has been adopted as a promising technique to mitigate multi-path fading and provide high spectral efficiency. In addition, cooperative communication can explore spatial diversity where several users or nodes share their resources and cooperate through distributed transmission. The concatenation of the OFDM technique with relaying systems can enhance the overall performance in terms of spectral efficiency and improve robustness against the detrimental effects of fading. Hybrid relay selection is proposed to overcome the drawbacks of conventional forwarding schemes. However, exciting hybrid relay protocols may suffer some limitations when used for transmission over frequency-selective channels. The combination of cooperative protocols with OFDM systems has been extensively utilized in current wireless networks, and have become a promising solution for future high data rate broadband communication systems including 3D video transmission. This thesis covers two areas of high data rate networks. In the first part, several techniques using cooperative OFDM systems are presented including relay selection, space time block codes, resource allocation and adaptive bit and power allocation to introduce diversity. Four (4) selective OFDM relaying schemes are studied over wireless networks; selective OFDM; selective OFDMA; selective block OFDM and selective unequal block OFDM. The closed-form expression of these schemes is derived. By exploiting the broadcast nature, it is demonstrated that spatial diversity can be improved. The upper bound of outage probability for the protocols is derived. A new strategy for hybrid relay selection is proposed to improve the system performance by removing the sub-carriers that experience deep fading. The per subcarrier basis selection is considered with respect to the predefined threshold signal-to-noise ratio. The closed-form expressions of the proposed protocol in terms of bit error probability and outage probability are derived and compared with conventional hybrid relay selection. Adaptive bit and power allocation is also discussed to improve the system performance. Distributed space frequency coding applied to hybrid relay selection to obtain full spatial and full data rate transmission is explored. Two strategies, single cluster and multiple clusters, are considered for the Alamouti code at the destination by using a hybrid relay protocol. The power allocation with and without sub-carrier pairing is also investigated to mitigate the effect of multipath error propagation in frequency-selective channels. The second part of this thesis investigates the application of cooperative OFDM systems to high data rate transmission. Recently, there has been growing attention paid to 3D video transmission over broadband wireless channels. Two strategies for relay selection hybrid relay selection and first best second best are proposed to implement unequal error protection in the physical layer over error prone channels. The closed-form expressions of bit error probability and outage probability for both strategies are examined. The peak signal-to-noise ratio is presented to show the quality of reconstruction of the left and right views

sistemi di interazione vocale per la domotica

Una delle questioni aperte nell’ambito dell’home automation è la realizzazione di interfacce uomo-macchina che siano non solo efficaci per il controllo di un sistema, ma anche facilmente accessibili. La voce è il mezzo naturale per comunicare richieste e comandi, quindi l’interfaccia vocale presenta notevoli vantaggi rispetto alle soluzioni touch-screen, interruttori ecc. Il lavoro di tesi proposto è finalizzato alla realizzazione di un sistema di interazione vocale per l’home automation, in grado non solo di riconoscere singoli comandi veicolati da segnali vocali, ma anche di personalizzare i servizi richiesti tramite il riconoscimento del parlatore e di interagire mediante il parlato sintetizzato. Per ciascuna tipologia di interazione vocale, verranno proposte soluzioni volte a superare i limiti dell’approccio classico in letteratura. In prima analisi, verrà presentato un sistema di riconoscimento vocale distribuito (DSR) per il controllo delle luci, che implementa ottimizzazioni ad-hoc per operare nell’ambiente in modo non invasivo e risolvere le problematiche di uno scenario reale. Nel sistema DSR sarà integrato un algoritmo di identificazione del parlatore per ottenere un sistema in grado di personalizzare i comandi sulla base dell’utente riconosciuto. Un sistema di identificazione vocale deve essere in grado di classificare l’utente con frasi della durata inferiore a 5 s. A tal fine verrà proposto un algoritmo basato su truncated Karhunen-Loève transform con performance, su brevi sequenze di speech (< 3.5 s), migliori della convenzionale tecnica basata su Mel-Cepstral coefficients. Verrà infine proposto un framework di sintesi vocale Hidden Markov Model/unit-selection basato su Modified Discrete Cosine Transform, che garantisce la perfetta ricostruibilità del segnale e supera i limiti imposti dalla tecnica Mel-cepstral. Gli algoritmi ed il sistema proposto saranno applicati a segnali acquisiti in condizioni realistiche, al fine di verificarne l’adeguatezza.One of the open questions in home automation is the realization of human-machine interfaces that are not only effective for the control of the available functions, but also easily accessible. The voice is the natural way to communicate requests and commands, in this way speech interface offers considerable advantages over solutions such as touch-screen, switches etc. The proposed thesis is aimed at studying and realizing a speech interaction system for home automation to be able not only to recognize individual commands conveyed by voice signals, but also to customize the services requested through a speaker recognizer and to interact by means of synthesized speech. For each speech interaction mechanism, solutions are suggested to overcome the traditional limitations of previous work. In the first analysis, it is offered a speech distributed recognition system (DSR), for the voice control of a lighting system, that implements strategies and ad-hoc optimizations and is able to solve the typical problems of a real scenario. The DSR system can also be integrated with a speaker identification algorithm in order to obtain a system able to customize the spoken commands on the user specific settings. In the home automation, a speaker identification system must be able to classify the user with sequences of speech frames of a duration less than 5 s. To this goal, an algorithm based on truncated Karhunen-Loève transform able to produce results, with short sequences of speech frames (< 3.5 s), better than those achieved with the Mel-Cepstral coefficients, is suggested. Moreover, this work presents a novel Hidden Markov Models/unit-selection speech synthesis framework based on Modified Discrete Cosine Transform, which guarantees the perfect reconstruction of the speech signal and overcomes the main lacks of Mel-cepstral technique. The algorithms and the proposed system will be applied to signals acquired under realistic conditions, in order to verify its adequacy