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Optimal Lattice-Reduction Aided Successive Interference Cancellation for MIMO Systems
Kyungchun Lee, K.,Joohwan Chun, J.,Hanzo, L. IEEE 2007 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.6 No.7
<P>In this letter, we investigated the optimal minimum-mean-squared-error (MMSE) based successive interference cancellation (SIC) strategy designed for lattice-reduction aided multiple-input multiple-output (MIMO) detectors. For the sake of generating the MMSE-based MIMO symbol estimate at each SIC detection stage, we model the so-called effective symbols generated with the aid of lattice-reduction as joint Gaussian distributed random variables. However, after lattice-reduction, the effective symbols become correlated and exhibit a non-zero mean. Hence, we derive the optimal MMSE SIC detector, which updates the mean and variance of the effective symbols at each SIC detection stage. As a result, the proposed detector achieves a better performance compared to its counterpart dispensing with updating the mean and variance, and performs close to the maximum likelihood detector.</P>
Resource-efficient wireless relaying protocols
Kyungchun Lee,Hanzo, Lajos IEEE 2010 IEEE wireless communications Vol.17 No.2
<P>Relay-aided communication is considered one of the key techniques to achieve high throughput at low cost in future wireless systems. However, when transmitting signals via a relay, additional time slots, antennas, or frequency slots are required, which may erode the potential gain of relay-aided systems. In this article various approaches to creating relay-aided systems are reviewed. The advantages and disadvantages of various relaying schemes are compared in terms of their slot efficiency, error rate performance, and feasibility. Our detailed comparisons and the numerical results indicate that the specific family of network coding aided relaying protocols constitutes one of the most promising solutions. We conclude this article by listing a number of open problems.</P>
ML Symbol Detection Based on the Shortest Path Algorithm for MIMO Systems
Lee, Kyungchun,Chun, Joohwan Institute of Electrical and Electronics Engineers 2007 IEEE transactions on signal processing Vol.55 No.11
<P> This paper presents a new maximum likelihood (ML) symbol detection algorithm for multiple-input multiple-output (MIMO) systems. To achieve the ML performance with low complexity, we search the integer points corresponding to symbol vectors in increasing order of the distance from the unconstrained least-squares solution. For each integer point, we test if it is the ML solution, and continue the integer point search until one of searched points is determined to be the ML solution. We present an efficient iterative search strategy, which is based on the shortest path algorithm for a graph. The simulation results show that the proposed algorithm has the lower complexity compared to the sphere decoding for channel matrices having low condition numbers. For further complexity reduction, we propose to use scaling, lattice-reduction, and regularization techniques. By applying these techniques, the computational complexity of proposed algorithm is reduced significantly when the channel matrix has a high condition number. </P>
Uplink Interference Alignment for Two-Cell MIMO Interference Channels
IEEE 2013 IEEE Transactions on Vehicular Technology VT Vol.62 No.4
<P>In this paper, we present uplink interference alignment (IA) schemes for two-cell multiple-input-multiple-output (MIMO) channels. Assuming that each cell has <I>K</I> interfering users, we propose an IA scheme for the full interference channel (FIC) and derive the achievable degrees of freedom (DOFs). The proposed scheme is extended to a two-cell Z-interference channel (ZIC), where only one of the two cells is subject to interference. The achievable DOF for the two-cell ZIC channel is also derived, and it is compared with that of the FIC with the IA and that of the conventional orthogonal scheme based on numerical results.</P>
Doubly Ordered Sphere Decoding for Spatial Modulation
IEEE 2015 IEEE communications letters Vol.19 No.5
<P>In this study, novel ordering algorithms of sphere decoding (SD) for spatial modulation (SM) are proposed to reduce the computational complexity. In the receive-ordering (Rx-ordering) scheme, the signals encountered at receive antennas are ordered to increase the probability of early termination during the search process. In contrast, the transmit-antenna indices and the constellation points in the transmit-ordering (Tx-ordering) scheme are ordered on the basis of a suboptimal solution, which is obtained from a subset of the received signals. To further reduce the computational complexity, the combined scheme of Rx-ordering and Tx-ordering is also presented. Simulation results show that SD aided by the proposed ordering schemes provides a substantial reduction in the computational complexity compared to existing SD algorithms in various environments while achieving near-optimal decoding performance.</P>