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An extension to decomposition based transmit beamforming is proposed for multiple input multiple output (MIMO) multiuser systems. In contrast to conventional beamforming which is constrained towards orthogonalizing the subchannels of the different users to yield groups of correlated antennas that belong to only one user, a more flexible orthogonalization approach is proposed which is targeted directly...
A new adaptive algorithm, called LLMS, which employs an array image factor, AI, sandwiched in between two Least Mean Square (LMS) sections, is proposed for different applications of array beamforming. The convergence of LLMS algorithm is analyzed, in terms of mean square error, in the presence of Additive White Gaussian Noise (AWGN) for two different modes of operation; namely with either an external...
Multiuser MIMO (MU-MIMO) system with limited feedback can be divided into two classes generally. One is zero-forcing beamforming (ZFBF), and the other is per user unitary rate control (PU2RC) which is an extended technique of random beamforming (RBF). However, in order to perform well, ZFBF requires many feedback bits, and PU2RC requires many users. These drawbacks of the existing MU-MIMO systems...
We investigate the use of lattices in phase quantizers and equal gain beamformers. We propose proper scaling methods so that the Voronoi regions of all lattice points are regular in the phase quantizers. As a result, existing fast algorithm for various lattices can be applied directly. In addition, we derive the number B of quantization bits with the proposed scaling. We found that the proposed scaling...
This paper investigates the user selection strategy in multiuser downlinks using zero-forcing beamforming (ZFBF) and finite-rate feedback (FRF). In order to mitigate the interference-limited effect, we propose an efficient user scheduling scheme combined with adaptive transmission mode selection to achieve a better diversity and multiplexing tradeoff in terms of the sum rate performance. In this scheme,...
In this paper an improved iterative algorithm is proposed for distributed transmit beamforming to achieve carrier phase alignment at the receiver. The transmitters adjust their phase offsets based on one-bit feedback from the receiver in each time slot. The proposed algorithm has an improvement in the convergence speed of phase alignment compared to a previously proposed algorithm in the literature...
In this paper, we introduce non-regenerative multi-group multi-way relaying. A half-duplex non-regenerative multi-antenna relay station (RS) assists multiple communication groups. In each group, there are multiple nodes that want to communicate with each other. Each node has a message and wants to decode the messages only from other nodes in its group. The required number of communication phases for...
Block diagonalization (BD) is a practically favorable precoding technique that eliminates the interuser interference in downlink multiuser multiple-input multiple-output (MIMO) systems. In this paper, we apply BD to the downlink transmission in a cooperative multi-cell system, where the signals from different base stations (BSs) to all the mobile stations (MSs) are jointly designed with the perfect...
Wireless amplify-and-forward relay networks in which the source communicates with the relays and destination in the first phase and the relays simultaneously forward signals to the destination in the second phase over uncorrelated Rayleigh fading channels are considered. We examine the scenario in which each relay only knows the perfect information of its source-relay channel while the destination...
We design binary weightbooks for multiple-input multiple-output (MIMO) beamforming systems using quantized feedback based on the Grassmannian beamforming criterion. We show that the Grassmannian criterion for binary weightbook design is to maximize the minimum Hamming distance of the corresponding block code. Thus, a block code that has a large minimum Hamming distance can be used for binary weightbook...
In this paper, we investigate transmission methods for a multi-user multiple-input multiple-output (MIMO) network that utilizes base stations (BS) cooperation. To eliminate the interference between users, iterative zero forcing- (ZF) and iterative Tomlinson Harashima precoding-based (THP) schemes are proposed. In the iterative ZF-based scheme, all interference is cancelled by using the transmit-receive...
Cognitive radio (CR) has been studied as a useful solution for efficient utilization of scarce radio spectrums. For it to succeed, two conflicting challenges are imposed on the secondary users: one is to ensure the quality of service (QoS) of the primary link, and the other is to maximize their own transmit throughput. To balance this tradeoff, beamforming and power control employing the multi-antenna...
In this paper, collaborative use of relays to form a beamforming system with the aid of perfect channel state information (CSI) and to provide communication in physical-layer security between a transmitter and two receivers is investigated. In particular, we describe decode-and-forward based null space beamforming schemes and optimize the relay weights jointly to obtain the largest secrecy rate region...
In the next generation cellular system, relay has been considered to increase coverage extension and cell-edge throughput. Cooperative relay can provide transmission diversity gain to improve outage probability, overall throughput and energy efficiency. Cooperative beamforming has been considered as one of the cooperative relay if the relay nodes can get the feedback information from the destination...
A MIMO-OFDM PHY Integrated (MOPI) scheme is proposed to provide confidentiality against eavesdroppers in wireless networks. The proposed MOPI scheme prevents any eavesdropper from learning the channel state information (CSI) of the wiretap channel and decoding the information being exchanged. This is achieved by the use of channel sounding combined with a novel physical-layer network coding (PNC)...
Base station cooperation is considered as a promising approach to increase the quality of service (QoS) in uplink. Base stations are connected via high-capacity backhaul links, which makes it possible to perform joint detection through information sharing among several base stations. Joint detection broadens the feasible signal to interference ratio (SIR) region, in which any SIR assignment for all...
We propose a multi-user medium access control (MAC) protocol to simultaneously support multi-packet transmission (MPT) and multi-packet reception (MPR) in wireless local area networks. By assuming perfect physical layer functions, we evaluate the maximum number of active stations that can be supported under different traffic arrival rates. Our analysis show that when the number of transmitting antennas...
This work considers the performance of multiple-input single-output (MISO) wireless systems employing beamforming over correlated wireless channels. More specifically, we examine the use of Random Vector Quantization (RVQ) as a limited feedback method of informing the transmitter of the appropriate beamforming vector. Using RVQ, we are able to derive the distribution functions of the beamforming gain...
This paper studies the downlink beamforming for a multi-cell system, where multiple base stations (BSs) each with multiple antennas cooperatively design their respective transmit beamforming vectors to optimize the overall system performance. It is assumed that all mobile stations (MSs) are equipped with a single antenna each, and there is one active MS in each cell at one time. Accordingly, the system...
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