Examinando por Autor "Cano, Alfonso"

Mostrando 1 - 3 de 3

Direct Link Aware Cooperative Relaying
(Wireless Communication Systems, 2006. ISWCS '06. 3rd International Symposium on, 2006-09-06) Figuera Pozuelo, Carlos; Morgado, Eduardo; Caamaño, Antonio J.; Cano, Alfonso
Cooperative relaying strategies enable spatial diversity gains. Using a proper forwarding strategy, these techniques can achieve diversity order as high as the number of diverse paths. We derive a strategy named Direct Link-Aware Relaying (DLA), which uses the source-destination link status as a condition to forward or not the signal at the relay. DLA is shown to achieve full diversity and to save energy compared to decodeand-forward strategies. Compared to selective-forwarding, DLA overcomes the use of error detection codes. Extension to the Multi-Branch case is developed. Simulations corroborate our analytical claims.
Distributed Double-Differential Modulation for Cooperative Communications Under CFO
(Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE, 2007-11-26) Cano, Alfonso; Morgado, Eduardo; Caamaño, Antonio J.; Ramos, Javier
When a terminal is recruited to cooperate with other neighboring terminals, its channel state and carrier frequency offset (CFO) may be unknown to the destination. Under these circumstances, this paper considers the use of distributed double-differential (DD) modulation, which simplifies receiver implementation because it by-passes channel and CFO estimation. Two double-differential codecs are proposed transmitting: i) across orthogonal channels using time-division multiplexing, achieving rate and error performance similar to that of co-located multi-antenna DD systems; or ii) simultaneously, benefiting from the distinct CFOs across terminals and bypassing the need of ordering protocols. Both (i)-(ii) approaches are considered in adaptive- and selective-relaying cooperation protocols demonstrating that maximum spatial diversity is achievable. Simulations corroborate the theoretical error performance claims.
Patrones Eficientes de Pilotos en Sistemas OFDM para Canales Inalámbricos Selectivos en Tiempo y Frecuencia
(2005-07-01T07:45:41Z) Garcia Marques, Antonio; Morgado, Eduardo; Cano, Alfonso; Caamaño, Antonio J.; Ramos, Javier
In coherent systems, when the channel is not known at the receiver, pilot-assisted techniques are needed to estimate the channel. Using OFDM, this paper overcomes the problem of designing such optimum pilot patterns that efficiently estimate doubly selective (in time and frequency)fading channels. We show that,decoupling time- and frequency- selectivity, the challenging process of estimating such channels can be seen as a two-dimensional sampling problem. We further propose efficient sampling patterns depending on the spreading (multipath and Doppler) function of the channel.