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When fast and accurate channel state information (CSI) at the transmitter is available, opportunistic power control (OPC) is an attractive alternative to signal-to-interference-and-noise ratio (SINR) target following approaches, because it maximizes throughput by taking advantage of fast channel variations. On the other hand, in multiple-input multiple-output (MIMO) systems, open loop schemes such...
Recently, the LTE (Long Term Evolution) and LTE-Advanced systems, developed by the 3GPP (Third Generation Partnership Project), has been proposed as the candidate for the 4G systems (forth mobile communication systems). The combination of OFDM (orthogonal frequency division multiplexing) and MIMO (multiple-input multiple-output) transmission technologies has been introduced into LTE systems for achieving...
The problem of MIMO communications with imperfect channel knowledge at the receiver is considered. Imperfect channel knowledge results from errors due to noise and errors due to time variations which cause the channel estimates to become outdated. A receiver structure named the Unified Generalized Likelihood Ratio Detector (UGLRD) is presented. The UGLRD is based on joint symbol-channel estimation,...
In this paper, we propose a robust transceiver design for the K-pair quasi-static MIMO interference channel. Each transmitter is equipped with M antennas, each receiver is equipped with N antennas, and the kth transmitter sends Lk independent data streams to the desired receiver. In the literature, there exist a variety of theoretically promising transceiver designs for the interference channel such...
We propose a practical MIMO precoding strategy for the multiple-access phase of the two-way relay channel with network coding and M-QAM modulation. The proposed scheme is a hybrid between three classes of constrained precoders, namely subspace alignment, subspace separation and maximum ratio transmission. The optimal solution within each class can be computed efficiently, and switching between the...
We study a multi-antenna wiretap channel, where the transmitter does not have perfect knowledge about the channels to the eavesdropper. The transmitter only knows that the logical location of the eavesdropper is drawn from a certain set. We characterize the worst-case secrecy rate in this scenario for given transmit strategies and derive an upper and a lower bound for the worst-case secrecy rate that...
A Gaussian multiple-input single-output (MISO) wiretap channel model is considered, where there exists a transmitter equipped with multiple antennas, a legitimate receiver and an eavesdropper each equipped with a single antenna. We study the problem of finding the optimal input covariance that maximizes the ergodic secrecy rate subject to a power constraint, where the full information on the legitimate...
In this work, we investigate the Gaussian MIMO bidirectional broadcast wiretap channel, from the vantage point of optimal transmit strategy design, to fulfill a certain secrecy constraint. An achievable secrecy rate region is computed and the gap to the capacity region of the same channel without the secrecy constraint is upper-bounded. Moreover, for the case of single receive antennas at all terminals,...
In this paper we analyze the distribution of effective Signal-to-Interference-plus-Noise-Ratio (SINR) in multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with application to 3GPP Long Term Evolution (LTE) Downlink. The asymptotic distribution of effective SINR in case of correlated post-processed SINR is established analytically to obey normal distribution...
In this paper, the performance of various ultra-wideband (UWB) multiple-input multiple-output (MIMO) relay systems is evaluated for the first time based on UWB channel measurements. In particular, the measurement results for UWB relay channels in line-of-sight as well as non-line-of-sight indoor environments are presented. The average bit error rates of dual-hop MIMO relay systems and cooperative...
Multiple-input multiple-output (MIMO) Beamforming (BF) performance is analyzed for amplify-and-forward (AF) fixed two-hop relay networks in independent and identically distributed (i.i.d.) Rayleigh fading channels. A novel performance bound using a new symbol-error-rate (SER) approximation is presented for AF relay networks equipped with multiple antennas at the source, relay, and destination when...
Distributed antenna system (DAS) or distributed multiple-input multiple-output (MIMO) can enhance the cellular throughput performance, thanks to the largely separated multiple remote antenna units (RAU) which can experience the different large scale fading and the small scale fading. So far, much research work has been published in the DAS. However, to the authors' best knowledge, there is no research...
By using frequency-domain oversampling at the receiver, we propose a novel blind channel estimation scheme for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Specifically, a subspace blind channel estimation approach is developed, based only on second-order statistics of the received signal. The estimated MIMO channel is nicely determined by Nt minimum...
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...
In this paper, we first introduce a simple two-cell multiple-input multiple-output (MIMO) solution where each base station has only its own data message. The algorithm is based on limited feedback from the mobile station (MS). We assume there is no base station (BS) cooperation through backbone; therefore cooperation among BSs is not a requirement. This renders the concept of the proposed solution...
Linear receivers are often used in multiple-antenna systems due to ease of implementation. However, traditional linear receivers such as the Decorrelator and the linear minimum-mean squared error (MMSE) receiver often have a significant performance loss compared to the optimal joint maximum likelihood (ML) receiver. In previous work, we proposed the Integer-Forcing linear receiver, which bridges the...
We investigate the performance of MIMO beamforming with quantized feedback in ad hoc networks. The primary findings are that a moderate number of feedback bits are sufficient to obtain significant transmission capacity gains compared to non-feedback schemes, whilst also achieving a high percentage of the transmission capacity obtained with unlimited feedback. We demonstrate that this achievable percentage...
In this paper, the optimal spectral efficiency (data rate divided by the message bandwidth) that minimizes the probability of causing disruptive interference for ad hoc wireless networks or cognitive radios is investigated. Two basic problem constraints are considered: a given message size, or fixed data rate. Implicitly, the trade being optimized is between longer transmit duration and wider bandwidth...
In this paper we are concerned with a scenario in which multiple messages (K) are concurrently flooding a dense wireless network. Rather than using standard packet switching we assume that the nodes relay cooperatively the messages, if they are able to decode them. Our objective is to propose and analyze a scheme that exploits the alignment of interference that opportunistically arises in the relay...
We study the impact of higher-order sectorization (up to 12 sectors per cell site) in cellular networks with low angle spread and a high density of users. Under ideal sector patterns (with no intersector interference), the mean throughput per site scales directly with S, the number of sectors per site. Fixing the number of antennas per site to be 12, higher-order sectorization with S = 12 and single-antenna...
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