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Because of its simplicity, amplify-and-forward (AF) is one of the most popular cooperative relaying technique. Relays are used in cooperative communication to improve reliability, coverage or spectral efficiency of cell-edge users. However, relays tend to increase the interferences seen by users of adjacent cells, particularly by the cell-edge users, when used in multi-cell systems. In this paper,...
We consider joint design of source and relay pre-coders in a cognitive multiuser two-way relay system, which supports simultaneous transmission of multiple secondary users concurrently with primary network with the help of a relay node. The design criterion is to minimize the sum mean square error (MSE) of all users under a transmit power constraint for each transmitting node while causing no interference...
Most nonlinear transceiver designs in amplify-and-forward (AF) multiple-input-multiple-output (MIMO) relay systems assume that instantaneous perfect channel state informations (CSIs) are available. Transceiver design with imperfect CSIs have rarely been addressed. In this paper, we consider an AF MIMO system in which a Tomlinson-Harashima precoder (THP) is used at the source, a linear precoder at...
In this paper, we consider the robust transceiver design with Tomlinson-Harashima precoding (THP) for multi-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relaying systems. THP is adopted at the source to mitigate the spatial inter-symbol interference and then a joint Bayesian robust design of THP at source, linear forwarding matrices at relays and linear equalizer at destination...
Distributed antenna system (DAS) can provide high speed data services for mobile terminals (MTs) within multi-floor buildings by reducing the radio transmission distance between the transmitter and the receiver. In this paper, the uplink spectral efficiency of an in-building DAS with frequency reuse is studied, where remote antenna units (RAUs) are deployed on each floor throughout the building and...
Incremental opportunistic relaying (IOR) has been proposed to increase the spectral efficiency of the two-phase cooperative transmissions by exploiting limited feedback from the destination node. Specifically, the relaying process is activated only if the source-destination channel is of insufficient quality. In this case, the feedback instructs the best relay to forward the source message to the...
In this work we compare full-duplex (FD) and half-duplex (HD) relaying in terms of outage probability and throughput. We consider a practical FD relay model where the loop interference between transmitted and received signals is taken into account. We analyze two modes for FD transmission, block Markov encoding and multi-hop transmission without interference cancellation, and two different modes for...
In this paper, single amplify and forward (AF) relay is placed between the source and the destination in space shift keying (SSK) multiple-input single output (MISO) system. In SSK, transmit-antenna indices form a spatial constellation diagram where each group of base two logarithm of the input data bits are mapped to one spatial constellation point. Hence, at each time instant, only single transmit...
In this paper, we investigate maximum mutual information design for multi-hop amplify-and-forward (AF) multiple-input multiple-out (MIMO) relaying systems with imperfect channel state information, i.e., Gaussian distributed channel estimation errors. The robust design is formulated as a matrix-variate optimization problem. Exploiting the elegant properties of Majorization theory and matrix-variate...
In this paper a new and accurate performance analysis of the Bartlett method-based spectrum sensor is presented for the application of cognitive radios. To do this, first the attributes of the quadratic form representation of Bartlett power spectrum estimator are studied, and then a closed form for the cumulative distribution function (CDF) is derived and exploited to obtain the probabilities of false...
Wireless Local Area Networks (WLAN) and Wireless Personal Area Networks (WPAN) such as the Bluetooth are designed to operate in 2.4 GHz ISM band. Since both IEEE 802.15 based Bluetooth and IEEE 802.11 WLAN devices, among various others, use the same frequency band, interference may lead to significant performance degradation. Hence, Cognitive Radio (CR) technology has been considered for coordinating...
Spectrum sensing is a fundamental feature of cognitive radio technologies facilitating detection and localization of spectrum opportunities. Combined with centralized database storage, it fosters reliable spatial spectrum measurements and Radio Environmental Maps (REMs) construction that can provide an accurate insight in the spectrum utilization over time, space and frequency. The spectrum sensing...
We consider a random access primary network. At the beginning of each time slot, a number of secondary users sense the channel and make an access decision based on the spectrum sensing outcome and the channel state information (CSI). Specifically, the channel is accessed by a secondary transmitter with a probability that depends on both the sensing metric and the gain or signal-to-noise-ratio (SNR)...
This paper presents a machine learning approach for link adaptation in orthogonal frequency-division multiplexing systems through adaptive modulation and coding. Although machine learning techniques have attracted attention for link adaptation, most of the the schemes proposed so far are based on off-line training algorithms, which make them not well suited for real time operation. The proposed solution,...
Internet of Things (IOT) is a wireless ad-hoc network of everyday objects collaborating and cooperating with one other in order to accomplish some shared objectives. The envisioned high degrees of association of humans with IOT nodes require equally high degrees of reliability of the network. In order to render this reliability to IOT networks, it is necessary to make them tolerant to faults. In this...
As energy saving and environmental protection become an inevitable trend, researchers need to shift their focus to “green” oriented architecture design. Recent advances in the area of cognitive radio (CR) have significant potential towards “green” communications. One of the critical challenges for operating CRs in a wireless mesh network is how to efficiently allocate transmission powers and frequency...
In this paper, we propose a high throughput and hardware efficient Fast Fourier Transform (FFT) architecture for Long Term Evolution (LTE) application. The proposed enhancement delay element matrix (EDEM) which contains the mixed radix unit supports 25, 16, 9, 8, 5, 4, 3 and 2-point FFTs. The reuse technology is also applied into EDEM to reduce the hardware resource. The EDEM reduces the computation...
It is known that in cellular systems, the users in cell edge suffer from the interference from interfering cells. In LTE-A, coordinated multi-point (CoMP) processing was proposed to solve the problem. In CoMP, the transmitted/received signals of the users in neighbor cells can be jointly processed such that interference can be either avoided or estimated as desired signals. In the current CoMP operations,...
The exponential increase in data traffic demand has focused attention on two layer network deployment strategies where low-power pico base-stations are placed within a macro cell coverage area targeting specific capacity demands. Two aspects of such a network are different from a macro-only deployment and are studied in this paper — (i) the choice of antenna geometry and polarization for a non-sectorized...
Most of the recent wireless communication systems are interference limited rather than noise limited. In the case of a very strong interferer the conventional assumption of the interference as Gaussian is extremely suboptimal. However optimal (capacity achieving) receivers utilize some prior knowledge about the interference to reach optimality. The link abstraction for such receiver structures is...
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