Space-Time Block Coding for Wireless Communications

A comprehensive review on coordinated multi-point operation for LTE-A

Medical data sheet in safe havens - A tri-layer cryptic solution

Cellular networks are a central part of today's communication infrastructure. The global roll-out of 4G long-term evolution is underway, ideally enabling ubiquitous broadband Internet access. Mobile network operators, however, are currently facing an exponentially increasing demand for network capacity, necessitating densification of cellular base stations (keywords: small cells and heterogeneous networks) and causing a strongly deteriorated interference environment. Coordination among transmitters and receivers to mitigate and/or exploit interference is hence seen as a main path toward 5G mobile networks. We provide an overview of existing coordinated beamforming strategies for interference mitigation in broadcast and interference channels. To gain insight into their ergodic behavior in terms of signal to interference and noise ratio as well as achievable transmission rate, we focus on a simplified but representative scenario with two transmitters that serve two users. This analysis provides guidelines for selecting the best performing method depending on the particular transmission situation.

Exploring Coordinated Multipoint Beamforming Strategies for 5G Cellular

This paper proposes a new power allocation algorithm with precoding in cooperative small cell networks (SCNs). A power allocation algorithm based on cooperative water-filling (CoopWF) is proposed and block diagonalization (BD) precoding is adopted to cancel the inter-user interferences. The proposed scheme is easily implementable to SCNs such as femto-cell, metro-cell, and pico-cell. Simulation results show that the proposed CoopWF algorithm provides better mean capacity compared to the existing power allocation algorithm.

Cooperative water filling (CoopWF) algorithm for small cell networks

In this paper, based on the block (element)-wise inverse Jacket matrix, a unified fast hybrid diagonal block-wise transform (FHDBT) algorithm is proposed. A new fast diagonal block matrix decomposition is made by the matrix product of successively lower order diagonal Jacket matrix and Hadamard matrix. Using a common lower order matrix in the form of [111-1], a fast recursive structure can be developed in the FHDBT, which is able to convert a newly developed discrete cosine transform (DCT)-II, discrete sine transform (DST)-II, discrete Fourier transform (DFT), and Haar-based wavelet transform (HWT). Since these DCT-II, DST-II, DFT, and HWT are widely used in different areas of applications, the proposed FHDBT can be applied to the heterogeneous system requiring several transforms simultaneously. Comparing with pre-existing DCT-II, DST-II, DFT, and HWT, it is shown that the proposed FHDBT exhibits less the complexity as its matrix size gets larger. The proposed algorithm is also well matched to circulant channel matrix. From the numerical experiments, it is shown that a better performance can be achieved by the use of DCT/DST-II compression scheme compared with the DCT-II only compression method.

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A fast hybrid Jacket-Hadamard matrix based diagonal block-wise transform

Coordinated Multi-Point (CoMP) transmission is a technology targeted for Long Term Evolution Advanced (LTE-A). The Joint Processing (JP) technique for CoMP can maximize system performance, which is achieved mainly with channel information-based beamforming algorithms. Precoding methods perform differently in various CoMP scenarios. In this paper, we propose a joint processing scheme in downlink CoMP transmission system. We apply block diagonal beamforming to downlink transmission, and assume perfect knowledge of downlink channels and transmit messages at each transmit point.

Zero-forcing beamforming with block diagonalization scheme for Coordinated Multi-Point transmission

Multi-input multi-output (MIMO) precoding is developed for time division duplex (TDD) systems with block diagonalization (BD) relies on the channel state information (CSI) at the transmitter. Multi-cell BD algorithm is used to coordinate the transmissions across multiple evolved base stations (BSs) for downlink. In this paper, we apply BD to the downlink transmission in a cooperative multi-cell system, where the signals from different BSs to all the mobile stations (MSs) are jointly designed with the perfect knowledge of the downlink channels and transmit messages. The optimal form of BD with per-antenna power constraints and sum rate capacity are derived. Based on convex optimization techniques, this paper designs an efficient algorithm to solve this problem, and derives the structure of the corresponding optimal BD precoding matrix. The numerical results show that the proposed scheme is better performance than conventional scheme.

Multi-Cell block diagonalization precoding for multiuser MIMO broadcast channel

Coordinated Multi-Point transmission and reception (CoMP) technique is a new promising scheme which has been adopted in LTE-Advanced. CoMP is mostly required to reduce the inter-cell interference (ICI). It also increases the cell edge user throughput and improves the coverage. For downlink CoMP, most research work mainly focuses on joint processing/transmission (CoMP-JP) mode. The Joint Processing technique for CoMP can maximize system performance, which is achieved mainly with zero-forcing beamforming algorithms. In this paper, we study the performance of multiuser beamforming for differently in various CoMP scenarios. The simulation results indicate that the proposed scheme offers much higher performance gain compared with the CoMP-JP mode.

Zero-forcing based multiuser beamforming for coordinated Multi-Point transmission

Orthogonal space---time codes (OSTCs) have recently captivated considerable attention due to their properties of full diversity and low implementation complexity. Quasi-orthogonal space---time codes (QOSTCs) provide full diversity and rate one, which enables simple pair wise decoding to be performed as well as better results to be obtained. In this paper, we derive effective OSTCs and QOSTCs for multi-input multi-output systems, which enable us to calculate coding gain of the OSTC. In addition, the fast maximum-likelihood (ML) decoding at the receiver can be performed separately. Since the QOSTC has a fast ML decoding, the symbol pairs can be decoded independently. With the constellation rotation of the symbol, rotated version of QOSTC is generated. OSTCs are designed to achieve the maximum diversity order for a given number of transmit and receive antennas subject to the constraint of having a simple decoding algorithm. This goal is achieved by properly choosing the signal constellations and comparing bit-error-rate (BER) to signal-to-noise ratio (SNR) for different quadrature pulse shift keying and quadrature-amplitude modulation techniques. The simulation results show that the QOSTC outperforms the OSTC at low SNR whereas it has higher complexity than the OSTC. From simulation result, we also compare the STC and space frequency code at BER versus SNR.

Md. Hashem Ali Khan

Papers

A fast hybrid Jacket-Hadamard matrix based diagonal block-wise transform

Zero-forcing beamforming with block diagonalization scheme for Coordinated Multi-Point transmission

Multi-Cell block diagonalization precoding for multiuser MIMO broadcast channel

Zero-forcing based multiuser beamforming for coordinated Multi-Point transmission

Signal Constellations of Quasi-Orthogonal Space---Time Codes for MIMO Systems