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The spectrum sharing has recently passed into a mainstream Cognitive Radio (CR) strategy. We investigate the core issue in this strategy: interference mitigation at Primary Receiver (PR).We propose a linear precoder design which aims at alleviating the interference caused by Secondary User (SU) from the source for Orthogonal Space-Time Block Coding (OSTBC) based CR. We resort to Minimum Variance (MV)...
In this paper, a two-stage detector is proposed for signals transmitted using multiple antenna configurations over frequency-selective channels. For the first stage, a frequency domain equalizer applying the minimum mean-squared error criterion is used to mitigate the intersymbol interference introduced by the channel's non-flat frequency response. Following, the output of this frequency domain equalizer,...
In the context of Long Term Evolution (LTE)-Advanced, the transmission points responsible for Coordinated Multi-Point (CoMP) transmission can be arranged in a distributed way and each one can be equipped with multiple antennas. In such scenario, efficient Radio Resource Allocation (RRA) strategies are required to exploit the available spatial degrees of freedom, coordinate the resources usage and...
Energy consumption in mobile networks, e.g. 3G networks, may be a substantial part of an operator's expenses. A large part of the total energy of the network is consumed by the radio access network. Today operators are saving energy by turning off carriers or cells during periods with low traffic by manually configuring on-off periods. At the same time, operators are seeking to increase cost efficiency...
In this paper we investigate the optimal relay location in the sense of maximizing suitably defined coverage region for MIMO relay channel. We consider the general Rayleigh fading case and assume that the channel state information is only available at the receivers (CSIR), which is an important practical case in applications such as cooperative vehicular communications. In order to overcome the mathematical...
The Alamouti scheme is a well known coding form for providing transmit diversity in wireless communication scenarios and is, for example, used in the 3G standard. The generalization of this technique using quaternions, allowing to use e.g. polarization as another signal attribute for diversity, has been discussed in several publications. However, there is still the open question how to design such...
Large-scale multiple-input multiple-output (MIMO) systems use a large array of nodes to offer high communication performance to multiple mobile users. For such systems to be economically practical, each node participating in the large-scale link likely has limited transmit power capability, and therefore properly limiting the per-node transmit power must be incorporated into the signal processing...
Beamforming techniques offer array gain and spatial multiplexing gain in multiple input multiple output (MIMO) systems. Wireless systems with massive numbers of transmit antennas (Massive MIMO) are attractive to increase the channel capacity and/or energy efficiency. However, the downlink channel state information (CSI) estimation sequence suffers increased loss in terms of lower MAC efficiency and...
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