Goodput-Based Link Resource Adaptation for Reliable Packet Transmissions in BIC-OFDM Cognitive Radio Networks

Cognitive radio (CR) stands out as a potential cornerstone to break the spectrum gridlock through enabling the coexistence of licensed (primary) and unlicensed (secondary) users in the same bandwidth. This paper deals with a novel link resource adaptation (LRA) strategy to be applied in CR scenarios for reliable packet transmissions based on bit interleaved coded orthogonal frequency division multiplexing (BIC-OFDM). We first formulate the power allocation (PA) problem constrained by both the available power at the secondary transmitter (ST) and the interference tolerable at the primary receivers, aimed at maximizing the offered layer 3 data rate, i.e., the goodput (GP) metric. Then, we derive the optimal PA strategy resorting to the customary Lagrangian dual decomposition (LDD) technique, which, however, like many other conventional numerical methods, exhibits several drawbacks, such as slow convergence and need for parameter tuning. These restrictions are circumvented through the development of a novel iterative yet simple PA algorithm, referred to as successive set reduction (SSR) approach, whose optimality conditions are analytically demonstrated by resorting to the Quasi Variational Inequality (QVI) framework. Based on this PA algorithm, an adaptive modulation and coding (AMC) scheme at the ST is eventually derived. Simulation results over a realistic scenario corroborate the effectiveness of the proposed SSR-based AMC algorithm, highlighting the GP improvements over non-adaptive LRA techniques, besides a remarkable complexity reduction w.r.t. conventional numerical methods

Resource Allocation and Path Selection Strategies for Cognitive Radio Multihop Networks

The next-generation cellular wireless networks will support high data rates and provide quality of service (QoS) for multimedia applications with increased network capacity. Under limited frequency resources, the conventional approach to increase network capacity is to install more base stations (BSs) to exploit spatial reuse. This solution is not very efficient because the cost of the BS transceiver is quite high. An alterna- tive approach is to employ relay stations (RSs) as intermediate nodes to establish multihop communication paths between mobile hosts and their corresponding BSs. Multihop cellular networks (MCN) can potentially enhance coverage, data rates, QoS performance in terms of call block- ing probability, bit error rate, as well as QoS fairness for different users. A number of different architectures, protocols, and analytical models for MCNs have been proposed in the literature where different system aspects were investigated. This thesis aims to present strategies of re- source allocation (RA) and path selection (PS) for cognitive radio (CR) multi-hop communications over a packet-oriented and bit-interleaved- coded OFDM transmission, employing practical modulation and coding schemes. As a promising technology, cognitive radio can be leveraged by the cellular network to increase the overall spectral efciency by allowing additional users in an already crowded spectrum. Here, we assume that a secondary transmitter (ST) adapt his parameters for transmitting to a secondary receiver (SR) or to a relay, over sections of spectrum owned by licensed or primary users (PUs), without harming the quality of service of the latter. This approach is known as underlay. The performance of the system are evaluated in terms of goodput (GP), which is defined as the number of information bits delivered in error free packets per unit of time. It is able to quantify the trade-off between data rate and link reliability, and it is a more suitable metric to quantify the actual perfor- mance of packet-oriented systems, employing practical modulation and coding schemes, respect to the capacity for example. A generic trans- mitter of the network is able to optimize the GP by a proper selection of the transmission parameters, if the channel state information (CSI) are perfect. In most wireless networks, because of channel estimation errors and channel feedback delay, this CSI will not be perfect there- fore any transmitting node only has outdated and imperfect CSI and the channel prediction and as a consequence, a predicted GP (PGP), will be optimized. GP depends on PER that is not easy to calculate for a multi-carrier system and so will be use kESM technique. From here a Local-RA (L-RA) technique and a Sub-Optimal PS (Sub-PS) strategies are formulated for non-cooperative CR multi-hop communications, ex- ploiting xed decode-and-forward (DF) relay nodes (RNs). With these strategies we are able to reduce the signaling over the feedback channel and the computational complexity, compared to the Optimal-RA with Optimal-PS method, paying a very little reduction of GP. Finally we will evaluate whether the increase of the number of relays corresponds to a performance increase

D13.2 Techniques and performance analysis on energy- and bandwidth-efficient communications and networking

Deliverable D13.2 del projecte europeu NEWCOM#The report presents the status of the research work of the various Joint Research Activities (JRA) in WP1.3 and the results that were developed up to the second year of the project. For each activity there is a description, an illustration of the adherence to and relevance with the identified fundamental open issues, a short presentation of the main results, and a roadmap for the future joint research. In the Annex, for each JRA, the main technical details on specific scientific activities are described in detail.Peer ReviewedPostprint (published version

Adaptive Techniques for Packet-Oriented Transmissions in Future Multicarrier Wireless Systems

I sistemi wireless dei prossimi anni sono tenuti a fornire trasmissioni caratterizzate da data rate e affidabilità sempre maggiori per sostenere la sempre più crescente richiesta di applicazioni e servizi eterogenei. Inoltre, tali requisiti devono essere soddisfatti nel difficile ambiente di propagazione rappresentato dal canale wireless, e devono far fronte alla scarsità dello spettro radio disponibile. Per tali sistemi, la tecnica di modulazione multiportante nota come orthogonal frequency division multiplexing (OFDM) è emersa come tecnologia chiave a livello fisico grazie alla sua elevata efficienza spettrale, struttura di ricetrasmissione piuttosto semplice e robustezza al fenomeno di multipath fading. In tale contesto, questa tesi indaga nuove tecniche adattative in cui le risorse e parametri di trasmissione sono adattati in base alle informazioni sullo stato di canale al fine di fornire una consegna affidabile ed efficiente di pacchetti dati su canali selettivi in frequenza. Queste tecniche, note in letteratura come link resource adaptation (LRA) e resource allocation (RA), sono proposte in combinazione con un numero di funzionalità avanzate come l'efficiente tecnica di codifica di canale chiamata bit interleaved coded modulation (BICM) e meccanismi di hybrid automatic repeat request (HARQ). Diversamente dalla maggior parte dei problemi di LRA e RA considerati nella letteratura, questa tesi si basa sul goodput come figura di merito, definito come il numero di bit di informazione consegnati in pacchetti senza errori per unità di tempo. Quest'ultimo rappresenta, infatti, una metrica adeguata per dare un quadro attendibile delle effettive prestazioni del collegamento caratterizzato da modulazione e codifici pratici, trasmissioni a pacchetto e meccanismi di HARQ. In dettaglio, i contributi principali della tesi sono: la derivazione di una strategia di LRA che assegna modulazione, tasso di codifica e potenza ad un sistema BIC-OFDM cognitivo; un nuovo metodo di predizione delle prestazioni, che sfrutta la metodologia di effective signal-to-noise ratio (SNR), per sistemi BIC-OFDM impieganti protocolli di HARQ con packet combining; un algoritmo di LRA che seleziona la migliore distribuzione dei bit e tasso di codifica per sistemi BIC-OFDM; uno schema equo di RA che assegna potenza, ordine di modulazione, tasso di codifica e sottoportanti agli utenti sul downlink di un sistema BIC orthogonal frequency division multiple access (OFDMA) col fine di ottimizzare le prestazioni dell'utente avente il valore più basso di goodput

D13.3 Overall assessment of selected techniques on energy- and bandwidth-efficient communications

Deliverable D13.3 del projecte europeu NEWCOM#The report presents the outcome of the Joint Research Activities (JRA) of WP1.3 in the last year of the Newcom# project. The activities focus on the investigation of bandwidth and energy efficient techniques for current and emerging wireless systems. The JRAs are categorized in three Tasks: (i) the first deals with techniques for power efficiency and minimization at the transceiver and network level; (ii) the second deals with the handling of interference by appropriate low interference transmission techniques; (iii) the third is concentrated on Radio Resource Management (RRM) and Interference Management (IM) in selected scenarios, including HetNets and multi-tier networks.Peer ReviewedPostprint (published version

D13.1 Fundamental issues on energy- and bandwidth-efficient communications and networking

Deliverable D13.1 del projecte europeu NEWCOM#The report presents the current status in the research area of energy- and bandwidth-efficient communications and networking and highlights the fundamental issues still open for further investigation. Furthermore, the report presents the Joint Research Activities (JRAs) which will be performed within WP1.3. For each activity there is the description, the identification of the adherence with the identified fundamental open issues, a presentation of the initial results, and a roadmap for the planned joint research work in each topic.Preprin