The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, we derive the maximum likelihood (ML) channel estimate in the presence of phase noise (PHN) and I/Q imbalance for OFDM systems. Since it is estimated jointly with I/Q and PHN, the channel estimate is more robust to these RF impairments compared to the conventional schemes. The complexity of the joint estimator is reduced using an approximate cost functions for both PHN and I/Q imbalance...
This paper proposes the distributed space-time block code (D-STBC) over frequency selective fading channel that achieves both spatial diversity gain and low decoding complexity with decoupling property in amplify-and-forward (AF) relay networks. These two goals are simultaneously achieved by our proposed code design, where the source permutates and conjugates the transmitted data before sending to...
A novel distribution referred to as N*generalized K, constructed as the product of N statistically independent, but not necessarily identically distributed, generalized K random variables (RVs) is introduced. Statistical characterization of the proposed distribution is carried out via the derivation of closed-form expressions for its moment generating, probability density, cumulative distribution...
Relays can improve wireless links by providing an extra path to the direct path which together form a virtual multiple antenna system. Network Coded-Distributive Antenna System (NC-DAS) and Plain-Distributive Antenna System (PDAS) are examples of realizations of such scenario. Although the asymptotic diversity gain for both the schemes is comparable, the network coded scheme can further take advantage...
Self-encoded spread spectrum (SESS) employs non-deterministic spreading codes that have been generated from the random information source and provide unique advantages over traditional pseudo-random codes. In previous work we have shown that the memory in SESS-modulated signals not only can deliver a 3dB gain in AWGN channels, but also can be exploited to achieve time diversity and robust bit-error...
Underwater acoustic sensor networks are quite different from terrestrial wireless sensor networks. Localization for underwater applications is different due to the bandwidth limited acoustic communication, sparsely distributed network deployment, and more expensive and powerful sensor nodes. In this paper, we propose a new scheme to achieve better localization accuracy for underwater acoustic sensor...
This paper develops a joint maximum a posteriori (MAP) spatial filtering receiver by employing a joint parameter estimation approach for multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) modulation systems, which can achieve promising bit-error-rate (BER) performance in the presence of co-channel interference (CCI). For a MAP receiver to suppress the CCI, conventionally,...
Frequency-domain equalization (FDE) has been studied for suppressing inter-symbol interference (ISI) due to frequency selective fading in single carrier systems. When a highmobility terminal is assumed in the system, channel transition within an FFT block cannot be ignored. Then, the ISI reduction performance of FDE degrades since cyclicity of the channel matrix is lost. To solve this problem, we...
A new method for detecting packet-based OFDM signals in the presence of phase noise is presented. The scattered pilots in each data OFDM symbol are used to non-iteratively estimate and mitigate the phase noise induced inter-carrier interference (ICI). A significant improvement in the bit error rate (BER) is achieved using this technique, especially for systems suffering from high phase noise.
We develop an efficient hard-detector for multiple-input multiple-output (MIMO) channels, which adaptively combines maximum-likelihood detection (MLD) and minimum-mean-square-error (MMSE) with a successive interference canceler (SIC) together. Unlike the conventional joint combination scheme which may suffer from considerable degradation in bit-error-rate (BER) performance over correlated channels...
Although current research focused on sensor deployment to balance the energy consumption among the sensor nodes for prolonging the lifetime of wireless sensor networks, sensor nodes with larger communication radius have to consume more energy to overcome wireless channel fading and path loss. Cooperative transmission allows nodes with single-antenna to cooperate on information transmission and/or...
This work presents a theoretical framework for determining the optimal clipping level for a multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) system. We start by modeling of the clipping noise, and propose a maximum likelihood (ML) receiver for the resulting signal. The bit error rate (BER) for this ML receiver is then derived for MIMO spatial multiplexing, space...
Modern state-of-the-art I/O links today rely exclusively upon a high SNR channel and an equalization-based inner transceiver to achieve a BER of 10-15. The equalizer typically consists of a transmit pre-emphasis driver for pre-cursor equalization and a receive DFE for post-cursor cancellation. Recently, forward error-correction (FEC) coding has been proposed to improve the BER and reduce power in...
In relay networks, partial channel state information at the transmitter due to feedback delay can severely degrade the beamforming performance. In this paper, the decremental effect of transmit beamforming with feedback delay on the downlink performance of a two hop Amplify-and-Forward (AF) relay network over Rayleigh fading channels is investigated. The source is equipped with multiple antennas while...
We consider power allocation (PA) and relay positioning in a dual-hop decode-and-forward relaying system over Nakagami-m fading channels. We investigate adaptive power allocation (PA) with fixed relay location, optimal relay location with fixed power allocation and joint optimization of the PA and relay location under transmit power constraint in order to minimize outage probability and average error...
Cooperative-diversity networks have recently been proposed as an effective technique to form virtual antenna arrays without using collocated multiple antennas. In this paper, we consider the adaptive decode-and-forward (DF) cooperative-diversity system with the Nth best-relay selection scheme. In the best-relay selection scheme, from the set of M relays the best relay only forwards the source signal...
We propose a novel equalizer for ultra wideband (UWB) multiple-input multiple-output (MIMO) channels characterized by severe delay spreads. The proposed equalizer is based on reactive tabu search (RTS), which is a heuristic originally designed to obtain approximate solutions to combinatorial optimization problems. The proposed RTS equalizer is shown to perform increasingly better for increasing number...
An adaptive power control scheme for cognitive radio system (CRS) in Rayleigh fading channel is proposed. The transmit power of a secondary user (SU) is adjusted in Rayleigh fading to maximize the constant output signal-to-noise ratio (SNR) at an SU receiver while keeping the interference to a primary user (PU) under given constraints. To calculate the maximum constant output SNR at the SU receiver...
In the new generation of mobile communication systems, high data transmission rate and low bit error rate has been common requirements. However the issue of signal fading in a multi-path environment still stands as a major problem. Using antenna diversity techniques can overcome the problem. In this paper, we thoroughly study the antenna diversity performance on a mobile terminal through theoretical...
This paper studies the tradeoff between channel coding and ARQ (automatic repeat request) in Rayleigh block-fading channels. A heavily coded system corresponds to a low transmission rate with few ARQ retransmissions, whereas lighter coding corresponds to a higher transmitted rate but more retransmissions. The optimum error probability, where optimum refers to the operating point that maximizes the...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.