Reduced-Complexity Maximum-Likelihood Detection in Multiple-Antenna-Aided Multicarrier Systems

In this contribution we explore a novel Optimized Hierarchy Reduced Search Algorithm (OHRSA)-aided space-time processing method, which may be regarded as an advanced extension of the Complex Sphere Decoder (CSD) method. The algorithm proposed extends the potential application range of the CSD method, as well as reduces the associated computational complexity

Decision Directed Channel Estimation Aided OFDM Employing Sample-Spaced and Fractionally-Spaced CIR Estimators

Abstract—In this letter we characterize the substantial difference between two channel estimation approaches, namely the sample-spaced (SS) and the fractionally-spaced (FS) channel impulse response (CIR) estimators. The achievable performance of decision-directed channel estimation (DDCE) methods employing both the SS- and the FS-CIR estimators is analyzed in the context of an OFDM system. The performance of the two estimation methods is compared and it is shown that the DDCE scheme employing the Projection Approximation Subspace Tracking (PAST)-aided FS-CIR estimator outperforms its SS-CIR estimator-based counterpart. Index Terms—Multiuser OFDM, decision directed channel estimation, impulse response estimation SDMA

Heterogeneous Networking: An Enabling Paradigm for Ubiquitous Wireless Communications

In this paper we explore the principle of heterogeneous wireless networking and discuss the potential avenues towards the realization of the ubiquitous wireless communications. Specifically, we demonstrate that the heterogeneous network architecture, constituted by the fusion of the classic cellular and the ad hoc network topologies, inherits the vital complementary characteristics of both architectures, and thus has the potential of attaining the levels of performance and efficiency required by the future wireless communications

Soft-Information Assisted Near-Optimum Nonlinear Detection for BLAST-type Space Division Multiplexing OFDM Systems

In this contribution, a nonlinear hybrid detection scheme based on a novel soft-information assisted Genetic Algorithm (GA) is proposed for a Turbo Convolutional (TC) coded Space Division Multiplexing (SDM) aided Orthogonal Frequency Division Multiplexing (OFDM) system. Our numerical results show that the performance of the currently known GA-assisted system can be improved by about 2dB with the aid of the GA’s population-based soft solution, approaching the optimum performance of the soft-information assisted Maximum Likelihood (ML) detection, while exhibiting a lower complexity, especially in high-throughput scenarios. Furthermore, the proposed scheme is capable of achieving a good performance even in the so-called overloaded systems, where the number of transmit antennas is higher than the number of receiver antennas. Index Terms—Genetic algorithm, orthogonal frequency division multiplexing, soft information, space division multiplexing

Iterative joint channel and data estimation for rank-deficient MIMO-OFDM

In this paper we propose a turbo-detected multi-antenna-multi-carrier receiver scheme. Following the philosophy of the turbo processing, our turbo MIMO-OFDM receiver comprises a succession of detection modules, namely the channel estimator, the space-time detector and the decoder, which iteratively exchange soft bit-related information and thus facilitate a substantial improvement of the overall system performance. In this paper we analyze the achievable performance of the iterative system proposed with the aim of documenting the various design trade-offs, such as the achievable error-rate performance, the attainable data-rate as well as the associated computational complexity. Specifically, we report a virtually error-free performance for a rate-1/2 turbo-coded 8x8-QPSK-OFDM system, exhibiting an effective throughput of 8*2/2=8 bits/sec/Hz and having a pilot overhead of only 10%, at SNR of 7.5dB and normalized Doppler frequency of 0.003, which corresponds to a mobile terminal speed of about 65 km/h

Channel Impulse Response Tap Prediction for Time-Varying Wireless Channels

Abstract—In this paper, we perform a comparative study of both the achievable performance and the associated computational complexity of two major time-domain prediction strategies proposed for employment in wireless mobile communication systems. Specifically, we investigate the intrinsic design tradeoffs of the so-called stationary robust predictor and the adaptive Recursive-Least-Squares (RLS) predictor. We demonstrate that the RLS predictor outperforms its robust counterpart at a cost of slightly higher computational complexity, and hence, the RLS predictor constitutes a better alternative for employment in wireless transceivers. Index Terms—Channel prediction of time-varying channels, minimum mean square error (MMSE) channel prediction, orthogonal-frequencydivision-multiplexing (OFDM), recursive least squares

Power Versus Bandwidth Efficiency in Wireless Communication: The Economic Perspective

We carry out a comprehensive analysis of a range of wireless network efficiency considerations. Firstly, we explore the properties and the implications of the power- versus bandwidth-efficiency criteria. Secondly, we perform a detailed top-down analysis of a typical commercial wireless network, which emphasizes the inherent differences between the aforementioned two efficiency metrics, while demonstrating that the appropriate choice of the network optimization criterion can have a profound effect on the overall network performance. Finally, we address the issue of resource management and its impact on the definition of the overall system efficiency

Low-Complexity Channel Estimation for OFDM and MC-CDMA

A low complexity decision-directed channel estimation method is proposed, which is suitable for a wide range of multi-carrier modulation schemes such as OFDM and MC-CDMA. The method exploits the a priori knowledge available concerning the nature of the wireless channel and exploits both the time- and frequency-domain correlation of the channel parameters, yet it is shown to be robust to the channel model mismatch routinely encountered in practical propagation environments. The performance of the OFDM system using the channel estimation scheme proposed in the scenario of encountering multipath Rayleigh-fading channel conditions is shown to be close to that of the idealistic system assuming perfect channel knowledge

Closed-Form Approximation of MIMO Capacity

A closed-form expression is provided for the calculation of the minimum SNR required to achieve a target data-rate using a generic MIMO-aided $M$-QAM transceiver. The computationally efficient technique proposed facilitates the convenient characterization of MIMO-assisted wireless systems

Smart Antenna-Aided Multicarrier Transceivers for Mobile Communications

EThOS - Electronic Theses Online ServiceGBUnited Kingdo