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In this paper, performance of Transmit Antenna Selection / Maximal Ratio Combining (TAS / MRC) in two hop Amplify-and-Forward (AF) relay system is analyzed over frequency non-selective and slowly Rayleigh fading channel. In the system, all nodes are equipped with multiple antennas; TAS is employed at the source and relay for transmission, MRC is employed at the relay and destination for reception...
We analyze the performance of amplify-and-forward (AF) multiple-input multiple-output (MIMO) cooperative networks over independent but not identically distributed Nakagami-m fading channels. Specifically, we consider an AF MIMO relay network where the source deploys the transmit antenna selection scheme to communicate with the destination through the help of a relay. We derive analytical expressions...
In this article, we present options for energy-efficiency in adaptive bit and power loading algorithm in practical OFDM systems with imperfect Channel State Information (CSI) and pilot-aided channel estimation. We consider rate-adaptive and margin-adaptive schemes always treating energy-efficiency as the key paradigm. The studies presented aim at lowering the energy-wastage related to pilot symbols...
In wireless networks, designing transmission schemes adapting to time varying channel conditions is key to achieve better spectral efficiency. The design of such schemes for multi-hop wireless networks requires coordination among nodes in the network, which is achieved through feedback between nodes. Spectral efficiency can be improved for such networks by designing transmission schemes with limited...
In this paper, multiple-input multiple-output (MIMO) transmit beamforming (TB) systems under the consideration of nonlinear high-power amplifiers (HPAs) are investigated. The optimal beamforming scheme, with the optimal beamforming weight vector and combining vector, is proposed for MIMO systems with HPA nonlinearity. The performance of the proposed MIMO beamforming scheme in the presence of HPA nonlinearity...
Over the last decade high data rate wireless transmission has gained considerable attention in hot spot areas, including high buildings. It has been demonstrated that distributed antenna systems (DASs) improve the performance of the indoor environment by providing spatial diversity and covering dead spots. In this paper, indoor wireless communications have been studied together with a femtocell based...
A new partial transmit sequence (PTS) technique for orthogonal frequency division multiplexing (OFDM) signals which does not require side information, is proposed. In the proposed method, the transmitter applies PTS to reduce the peak-to-average power ratio (PAPR) and does not send the side information on the PTS phase factors to the receiver. Based on the OFDM symbol structure having pilot subcarriers,...
This paper proposes a precoding scheme for downlink multiuser MIMO-OFDM systems. The proposed precoding employs the minimum bit error rate (BER) criterion and estimates precoding matrices to minimize total BER of mobile stations by the steepest descent algorithm. As the cost function of the proposed scheme, an upper bound of the total BER is derived from the pairwise error probability (PEP) and is...
Vandermonde-subspace frequency division multiplexing (VFDM) is a technique for interference cancellation in overlay networks that allows a secondary network to operate simultaneously with a primary network, on the same frequency band. VFDM can be applied to block transmission systems with a guard time (or cyclic prefix) over frequency selective channels. It achieves zero interference towards the primary...
In this work, an efficient interleaving process is proposed for orthogonal frequency division multiplexing (OFDM) systems over impulsive noise channels. Unlike the conventional OFDM systems where the interleaving process is implemented before the inverse discrete Fourier transform (IDFT), the proposed scheme is based on performing the interleaving process post the IDFT. The aim of this process is...
This paper proposes an analytic model to study queuing effect on the handoff performance of Mobile IPv6 (MIPv6), which has not been particularly investigated in previous literature. The presented model regards handoff process as tandem service system, and adopts a simple two-moment approximation throughout the theoretic modeling. Without other specific assumptions, the model presents a generic approach...
This paper addresses the problem of theoretical characterization of the joint effect of a transmitter I/Q imbalance and nonlinear amplification on OFDM. We prove a theorem about a linear representation of the distorted signal and apply it to error rate analysis. In view of the structure of the distorted signal, the proven theorem can be referred to as an extension of Bussgang's theorem.
We consider a point-to-point, correlated and block fading multiple antenna channel where the receiver has a noisy channel estimation and the transmitter has the statistics of the channel. Although very high rates are promised when the receiver knows the channel perfectly, the capacity is not known when the receiver has a noisy channel estimation. In this paper, we will derive an upper bound to the...
Cooperative decoding is powerful technique for establishing good quality TV broadcasting. In cooperative decoding, some TV receivers, nodes, are cooperated, each other. These share the received information signal and thus obtain good quality information signal. Incremental-Maximum Ratio Combining (I-MRC) is one of the cooperative decoding methods. In I-MRC, the best condition's node and second one...
In this paper, a new type of collaboration in wireless sensor networks (WSN) is suggested that exploits array processing algorithms to improve the reception of a signal. For receive collaboration, the transmission power during intra-cluster transmissions decreases at the expense of increasing the inter-cluster communications. It is shown that, as a result of using receive collaboration, the destination...
An exact form of symbol error rate (SER) is derived for zero-forcing decision feedback equalization (ZF-DFE) on fast fading channels. We present an error propagation framework in ZF-DFE, which is dependent on the length of multipath and the size of M-ary quadrature amplitude modulation (M-QAM). By applying the concepts of “error event” and “state” on this framework, we can evaluate the error probability...
In a downlink transmission, users can benefit from the high capacity gain achieved by transmitting independent data streams from multiple antennas to multiple users sharing the same physical time-frequency resources. This technique is known as multiuser MIMO (MU-MIMO). However, performance of MU-MIMO is sensitive towards propagation imperfections, such as time dispersion and inter-stream interference...
In orthogonal frequency division multiplexing (OFDM) based cellular systems, co-channel interference (CCI) from adjacent interfering base stations (BSs) would greatly degrade the bit error rate (BER) performance of cell-border users. In the previous work, a blind single antenna interference cancellation (SAIC) algorithm named least mean square-blind joint maximum likelihood sequence estimation (LMS-BJMLSE)...
The main targets for the next generation of mobile communication systems, with LTE as a main candidate, are increased data rates and improved spectrum efficiency. The transmission scheme for the LTE downlink is OFDM which enables the design of low complexity and high performance receivers, if the channel is time-invariant. However in high-mobility scenarios, where the channel is time-variant, the...
In this paper, we propose a 2 × 2 cooperative multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) scheme based on Alamouti space-time coding. In this scheme, the the relay and the destination antennas receive the transmitted symbols from the source during the first stage. Then, both the relay and the destination generate their own decision variables using an Alamouti...
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