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New robust iterative minimum mean squared error-based interference alignment al...
Teodoro, Sara; Silva, Adão; Castanheira, Daniel; Dinis, Rui; Gameiro, AtílioInterference alignment (IA) is a promising technique for multiple input multiple output interference channels based systems, achieving the theoretical bound on degrees of freedom. However, these gains are reduced in the presence of imperfect channel state informa- tion (CSI), because of quantisation or channel estimation errors. In this Letter, the authors propose a new robust iterative IA minimum mean squared ...
Low-bit rate feedback strategies for iterative IA-precoded MIMO-OFDM-based systems
Teodoro, Sara; Silva, Adão; Dinis, Rui; Gameiro, AtílioInterference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the oth...
Data-precoded algorithm for multiple-relay-assisted systems
Teodoro, Sara; Silva, Adão; Gil, João M.; Gameiro, AtílioA data-precoded relay-assisted (RA) scheme is proposed for a system cooperating with multiple relay nodes (RNs), each equipped with either a single-antenna or a two-antenna array. The classical RA systems using distributed space-time/frequency coding algorithms, because of the half-duplex constraint at the relays, require the use of a higher order constellation than in the case of a continuous link transmission...
Distributed coding for systems with cooperative diversity
Teodoro, Sara Helena MarquesO presente trabalho propõe-se a divulgar as mais significativas técnicas de esquemas cooperativos, de forma a ultrapassar alguns dos problemas dos sistemas móveis sem fios da próxima geração, estendendo a área de cobertura destes sistemas, assim como a sua capacidade e fiabilidade. O estudo de diversos esquemas cooperativos é efetuado em termos de capacidade e de taxa de erros, fazendo variar o número de relays...
Single and multiple antenna relay-assisted techniques for uplink and downlink O...
Moço, Andreia; Teodoro, Sara; Silva, Adão; Lima, Hugo; Gameiro, AtílioIn this paper we propose and assess the performance of relay-assisted schemes designed for both the uplink and downlink OFDM based systems, using efficient distributed space-frequency block coding protocols. We consider the use of an antenna array at the base station and a single antenna at the user terminal. At the relay node we consider either single antenna or an antenna array. We assume that some of the use...
Novel precoded relay-assisted algorithm for cellular systems
Teodoro, Sara; Silva, Adão; Gil, João M.; Gameiro, AtílioCooperative schemes are promising solutions for cellular wireless systems to improve system fairness, extend coverage and increase capacity. The use of relays is of significant interest to allow radio access in situations where a direct path is not available or has poor quality. A data precoded relay-assisted scheme is proposed for a system cooperating with 2 relays, each equipped with either a single antenna o...
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