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By employing the regularized block diagonalization (RBD) preprocessing technique, the multi-user multi-input multi-output (MU-MIMO) broadcast channel is decomposed into multiple parallel independent single user multi-input multi-output (SU-MIMO) channels and achieves the maximum diversity order at high data rates. The computational complexity of RBD, however, is relatively high due to two singular...
This paper presents a category of detection schemes for Multiple-Input Multiple-Output (MIMO) system called Parallel Sphere Decoder (PSD). Compared to the conventional depth-first sphere decoder with Schnorr-Euchner enumeration (SE-SD), the proposed PSD algorithms use parallel computations and achieve approximately 50% searching time reductions under the same amount of computations. Namely, in hardware...
This paper considers the resources allocation problem in decode-and-forward (DF) relayed OFDM based cognitive radio (CR) system. The subcarrier matching and power allocation are optimized jointly under the individual power constraints in source and relay so that the sum rate is maximized while the interference induced to the primary system is kept below a pre-specified interference temperature limit...
Because of its simplicity, amplify-and-forward (AF) is one of the most popular cooperative relaying technique. Relays are used in cooperative communication to improve reliability, coverage or spectral efficiency of cell-edge users. However, relays tend to increase the interferences seen by users of adjacent cells, particularly by the cell-edge users, when used in multi-cell systems. In this paper,...
It is known that in cellular systems, the users in cell edge suffer from the interference from interfering cells. In LTE-A, coordinated multi-point (CoMP) processing was proposed to solve the problem. In CoMP, the transmitted/received signals of the users in neighbor cells can be jointly processed such that interference can be either avoided or estimated as desired signals. In the current CoMP operations,...
It has been well known that channel aware systems (closed-loop) have better performance than channel unknown systems (open-loop). In order to know channel in the transmitter, receivers should send own channel information the transmitter through reverse channel. However, the channel information should be fed back in Frequency Division Duplexing (FDD) additionally since forward link channel and reverse...
In this paper, a MIMO detection scheme is proposed based on a combination of Monte Carlo technique and list detection. Specifically, a list of Gaussian samples are first generated to determine the search range of constellation points in which the transmitted symbol is most likely to locate. Linear equalizations are then applied to equalize the effect caused by the channel mixing, and a list detector...
This paper deals with the problem of spectrum sensing in cognitive radio. We consider a stochastic system model where the Primary User (PU) transmits a periodic signal over fading channels. The effect of frequency offsets due to oscillator mismatch, and Doppler offset is studied. We show that for this case the Likelihood Ratio Test (LRT) cannot be evaluated pointwise. We present a novel approach to...
An OFDM based cognitive radio (CR) network is considered in this paper. The goal is to maximize the total sum rate of the CR system while ensuring that no excessive interference is induced to the primary system. The optimal scheme adopts the dual decomposition technique and in order to reduce the computational complexity of the optimal scheme, a greedy suboptimal algorithm is proposed. Selected numerical...
This paper proposes the separate-SMDP approximation technique to solve the dimensionality problem of the semi-Markov decision process (SMDP) model for radio resource management (RRM). The proposed separate-SMDP model approximates the original complex SMDP linear programming (LP) problem by building a series of simple SMDP LP problems. The estimated policy results are obtained by solving these LP problems...
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