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A modified sphere decoding (SD) scheme is proposed for multiple-input multiple-output (MIMO) communication systems in this paper. The conventional SD goes from the lower dimension to the higher dimension to examine whether a lattice point lies inside the sphere of some radius, which remains fixed for all dimensions. Since the sphere radius directly affects the search range and thus the complexity,...
In this paper a novel detection algorithm for spatial modulation (SM) based on sphere decoder (SD) tree search idea is proposed. The aim is to reduce the receiver complexity of the existing optimal decoder while maintaining an optimum performance. The algorithm performs a maximum likelihood (ML) search, only over those points that lie inside a sphere, centered at the received signal, of given radius...
In the paper, a modified Log-MAP algorithm based on a novel approximation of the max* operator derived from the Jensen inequality is proposed. In this approach, the max* operation is performed on n≥2 arguments, thus the recursive calculations are avoided and significant reduction in the number of operations performed per decoding step, as compared with the conventional Log-MAP, is achieved. Simulation...
We consider a time division duplex multiple-input multiple-output (nt × nr MIMO). Using channel state information (CSI) at the transmitter, singular value decomposition (SVD) of the channel matrix is performed. This transforms the MIMO channel into parallel subchannels, but has a low overall diversity order. Hence, we propose X-Codes which achieve a higher diversity order by pairing the subchannels,...
In this paper, a new family of linear dispersion codes (LDCs) that can be decoded using a fast sphere decoding (SD) algorithm in MIMO systems is proposed. The basic principle of this structure is to make the LDC to have as many as possible the rows orthogonal in the dispersion matrices. Monte Carlo simulation results show that the optimum LDCs with this orthogonal structure have nearly identical bit-error-rate...
A new decoding algorithm that consists of two decoding stages to reduce the complexity of the maximum likelihood decoding for parallel combinatory high-compaction multi-carrier modulation is presented. The first decoding stage is in charge of a preliminary decision that coarsely searches the candidates using the QRD-M algorithm, and the second decoding stage is responsible for the final decision that...
Recently, the turbo-detected sphere packing (SP) aided space-time block-coding (STBC) STBC-SP scheme was demonstrated to provide useful performance improvements over conventionally-modulated orthogonal design based STBC schemes in the context of single-user multiple-input multiple-output (SU-MIMO) systems. Hence, in this treatise we extend its employment to the multi-user MIMO (MU-MIMO) scenario....
MIMO systems (with multiple transmit and receive antennas) are becoming increasingly popular, and many next-generation systems such as WiMAX, 3-GPP LTE and IEEE802.11 n wireless LANs rely on the increased throughput of MIMO systems with up to four antennas at receiver and transmitter. High throughput implementation of the detection unit for MIMO systems is a significant challenge. This challenge becomes...
This paper provides a performance comparison of multiple-input multiple-output (MIMO) demodulators for bit-interleaved coded modulation (BICM) systems with non-iterative demodulation and decoding. We propose to use the capacity of an equivalent ldquomodulationrdquo channel as a performance measure that has the advantage of not depending on the outer error correcting code. Based on this approach, we...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
Unequal error protection is the key to future transport of multimedia data. The paper presents an overview of some new approaches realizing UEP properties in physical transport, especially multicarrier modulation, or with LDPC and turbo codes. For multicarrier modulation, a UEP bit-loading method is described allowing for an arbitrary number of classes, arbitrary SNR margins between the classes and...
In this paper, a novel approach using frame-based iterative channel fading parameters estimation technique from the received data sequence exploiting orthogonal property of the space-time block (STB) code is proposed. For practical implementation of STB code, the receiver requires to estimate these parameters. Regarding this type of estimation, the inherent orthogonal nature of STB code can be exploited...
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