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—A multiuser dual-hop relaying system over mixed radio frequency/free-space optical (RF/FSO) links is investigated. Specifically, the system consists of m single-antenna sources, a relay node equipped with n ≥ m receive antennas and a single photo-aperture transmitter, and one destination equipped with a single photo-detector. RF links are used for the(More)
Power control is an important research topic for ad-hoc Wireless Sensor Networks (WSNs). In today's sophisticated and competitive wireless environment, the control of the energy consumption in a WSN for homecare e-health makes it possible to guarantee basic levels of system performance, such as connectivity, throughput, delay, QoS and survivability in the(More)
—The performance of the V-BLAST approach, which utilizes successive interference cancellation (SIC) with optimal ordering, over independent Nakagami-m fading channels is studied. Systems with two transmit and n receive antennas are employed whereas the potential erroneous decision of SIC is also considered. In particular, tight closed-form bound expressions(More)
Sensor grid deployments integrate wireless sensor networks (WSNs) and Grid Computing (GC) into a merged platform. A middleware architecture is a prerequisite for sensor grids in order to bridge the two heterogeneous technologies and efficiently support aggregated grid services available to a large number of grid users. On the other hand, the energy(More)
—The performance of a multiuser communication system with single-antenna transmitting terminals and a multi-antenna base-station receiver is analytically investigated. The system operates under independent and non-identically distributed rank-1 Rician fading channels with imperfect channel estimation and residual hardware impairments (compensation(More)
—In this letter, following a cross-layer design concept, we propose a novel subcarrier grouping technique for Orthogonal Frequency and Code Division Multiplexing (OFCDM) multiuser systems. We adopt a two dimensional (2D) spreading, so as to achieve both frequency-and time-domain channel gain. Furthermore , we enable a receiver-centric approach, where the(More)