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In this paper we consider the design of multi-stream demodulators for multiple-input multiple-output (MIMO) systems. Our proposed MIMO demodulator is based on the stack tree-search strategy and provides soft-outputs in the form of exact max-log log-likelihood ratios (max-log LLRs). We prove that our proposed demodulator is optimally efficient in that it visits the least number of nodes among all optimal...
To enable reliable data transfer in next generation Multiple-Input Multiple-Output (MIMO) communication systems, terminals must be able to react to fluctuating channel conditions by having flexible modulation schemes and antenna configurations. This creates a challenging real-time implementation problem: to provide the high performance required of cutting edge MIMO standards, such as 802.11n, with...
This paper focuses on the feedback scheme for downlink Multi-User Multiple-Input Multiple-Output (MU-MIMO) transmission with linear precoding. When the maximum transmission rank per user is limited to one, the multiple-antenna receiver uses a weight vector to transform MIMO channel matrix into an equivalent Multiple-Input Single-Output (MISO) channel vector. Then a Channel Directional Index (CDI)...
Network MIMO (multiple-input multiple output), also known as Coordinated Multipoint (CoMP), is a key enabling technology of future cellular systems. A unified framework and a novel generalized iterative approach (GIA) is proposed for the minimum mean square error (MMSE) transceiver design of general MTMR (multiple-transmitter multiple-receiver) MIMO systems with different CoMP configurations (including...
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...
The mobile satellite broadcasting arena is witnessing a constant increase in demand for improved transmission quality and higher number of services in order to remain on par with the corresponding terrestrial counterparts. A promising way forward in this regard is the migration from the conventional single polarization per beam to an advanced dual polarization per beam architecture for effective spectrum...
In this paper, RFSD (Robust Fixed-complexity Sphere Decoder) based on a new preprocessing algorithm is proposed for MIMO (Multiple Input Multiple Output) detection. Unlike the original FSD (Fixed-complexity Sphere Decoder) ordering which determines the FE (Full expansion) stage by choosing the signal component with greatest post-processing noise amplification on itself, the proposed RFSD determines...
In this work, we study the MIMO Gaussian bidirectional broadcast channel (BBC) with common message and characterize the capacity region. Moreover, we show that the transmit covariance matrix optimization problem has the same structure as the corresponding optimization problem of the BBC without common message which leads to the comfortable position to transfer results from one scenario to the other...
In this paper, the performance limit of lattice sequential decoder for coded M× N MIMO channel is analysed. We determine the rates achievable by lattice coding and sequential decoding applied to such channel. The diversity-multiplexing trade- off under lattice sequential decoding is derived as a function of its parameter---the bias term. Such parameter is critical for controlling the amount of computations...
Multiple-antenna systems, also known as multiple input-multiple output (MIMO) radio, improve the capacity and reliability of radio communication systems. Of considerable concern however is the huge complexity involved in the implementation of such systems. Therefore, the design of low complexity, low cost, MIMO systems that keep most of the advantages and benefits of the full-complexity system has...
TCH (Tomlinson, Cercas and Hughes) sequences have been studied for code-spreading and channel coding, but their true purpose is for synchronization and channel estimation. This is due to their property of being (virtually) orthogonal to all of their sequences obtained via circular shifts, and the use of the FFT (Fast Fourier Transform) for decoding. This property is extremely useful for time-offset...
Two numerical approaches, the Robust-Generalized Iterative Approach (R-GIA) and the Robust-Transmit Covariance Optimization Approach (R-TCOA), are proposed for jointly designing the minimum mean square error (MMSE) precoders and decoders of uplink multiuser multiple-input-multiple-output (MIMO) systems with arbitrary linear equality power constraints and possibly imperfect channel state information...
The optimal diversity-multiplexing-delay tradeoff for the multi- input multi-output (MIMO) automatic repeat request (ARQ) channel can be achieved using an incremental redundancy lattice space- time codes. The optimal tradeoff has been shown in to be achieved using a list lattice decoder for joint detection and decoding. However, such decoder suffers from high computational complexity for low-to-moderate...
This paper proposes a dimension reduction maximum likelihood (ML) soft demodulator for multiple-input multiple-output (MIMO) system. The proposed dimension reduction soft demodulator reduces the dimension of the search space for minimum Euclidean distance calculation by exploiting ML hard detection algorithms and can achieve significantly lower complexity than existing optimal soft demodulators based...
The use of hybrid automatic-repeat-request (HARQ) with multi-antenna systems (MIMO) promises high throughput with high reliability in broadband wireless communication systems. One of the combining methods in MIMO-HARQ is by directly optimizing the log-likelihood ratio (LLR) values instead of compensating the multiple signal-to-interference-and noise power ratios (SINRs) as in conventional combining...
In this paper, a new search strategy based on a derived cumulative distribution function (cdf) is proposed. It is shown that incorporating detection ordering into the conventional K-Best sphere decoding algorithm (SDA) offers a systematic method for determining the numbers of required ML search layers. With the features, applying the proposed search strategy to conventional complex K-Best SDA, the...
The maximum likelihood (ML) detection for multiple-input multiple-output (MIMO) system achieves the optimal performances at the cost of high computational complexities, while the linear detectors attain low complexities with degraded performances. In this paper, we propose two low-complexity detection schemes based on the minimum-mean-square-error (MMSE) detection for MIMO systems. Using on the MMSE-detected...
This paper presents a prototype of a high-throughput 4 × 4 64-QAM MIMO receiver consisting of a channel matrix QR decomposition, a soft-output K-Best MIMO detector and a Convolutional Turbo Code decoder. The proposed MIMO receiver provides low processing latency and a pipelined architecture scalable to a larger number of antennas and constellation order. Therefore, it is suitable for LTE-Advanced...
The LTE standard supports a maximum throughput of 300MBit/s using 4×4 MIMO and a channel bandwidth of 20 MHz. At the same time the latest HSDPA technology supports 82MBit/s using 2×2 MIMO and Dual Cell techniques. While LTE uses a conflict-free interleaver, which allows highly efficient implementation of parallel decoders for such throughputs, HSDPA uses the UMTS interleaver that causes memory access...
In modern Wireless Local Area Network (WLAN), both the transmitting data throughput and the connecting stability are very important. For the IEEE802.11n protocol specification, it is made of a multi-input multi-output (MIMO) system and an Orthogonal Frequency Division Multiplexing (OFDM) system. In order to decrease the decoding error rate at the receiving end and to fully restore the original transmitting...
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