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Cognitive users (CUs) are allowed to access licensed bands without causing harmful interference to primary users (PUs). However, the quality of service (QoS) of CUs can not be guaranteed when CUs experience bad channel conditions in direct transmission between the cognitive source and its destination. In this paper, we consider the problem of cooperative transmission in cognitive radio networks. The...
In this paper, we propose a new interference alignment (IA) scheme designing jointly the linear transmitter and receiver for the 2 user MIMO X channel system, using minimum total mean square error criterion, subject to each transmitter power constraint. Considering the channel estimation errors, we further propose a robust design for the IA. Iterative method is used to obtain the optimal solutions...
In this paper, a covariance-based algorithm with multiple antennas is proposed to eliminate the follower jamming for frequency hopping systems (FH) by finding the interference-blocking filter over quasi-static flat fading channels. The system uses the auto-covariance matrix of the received signal and M-array receive antennas. The simulation results show that the proposed approach can estimate the...
This paper examines the challenging carrier frequency offset (CFO) estimation problem in the tile-based orthogonal frequency division multiple access (OFDMA) uplink systems. The existing solutions to this problem are either restricted to less flexible subcarrier assignments or too complex to implement in practice. This paper proposes simple iterative solutions with extremely low computational load,...
In this paper, a practical downlink multiuser multiple-input multiple-output (MU-MIMO) scheme with low-rate feedback channel is considered. Firstly, we propose a preferred-beam feedback method, which effectively conveys information of user channel and inter-user interference. Secondly, we propose a new low-complexity method to compute unitary preprocessing matrix based on the feedback method. The...
In this work, we propose two high-rate quasi-orthogonal space-time coding (STC) schemes which are designed in conjunction with the successive interference cancellation (SIC) based receiver. The symbols of the proposed STC are of judiciously designed diversity order which can be effectively exploited by the SIC based receiver to cancel interference as well as to obtain diversity gain. The proposed...
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