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The LLL algorithm developed by Lenstra, Lenstra, and Lovász has been widely studied to improve the conditioning of linear systems of equations that arise in multi-input multi-output (MIMO) antenna systems. In the first part of this correspondence, we show how a certain class of matrices can be transformed so that the LLL algorithm can be carried out efficiently, without compromising its performance...
This paper addresses the optimization of resource allocation based on Decode and Forward (DF) or Amplify and Forward (AF) relaying techniques for packet access Orthogonal Frequency Division Multiple Access (OFDMA) networks. A power allocation quasi-optimal solution with a low complexity has been proposed for the two forwarding techniques. To illustrate theirs performances, a selection of numerical...
Based on wavelet transform (WT), this paper proposed an approach to extract ICESat/GLAS full waveform characteristics. Through wavelet decomposition of the full waveform data, setting the threshold function and reconstructing signal, the filtered waveforms were achieved. All comparisons were performed on simulated LiDAR full waveform signals with typical back scattering noise. In the simulation and...
Block diagonalization is a linear precoding technique which eliminates the multi-user interference at the transmitter side by creating parallel orthogonal single user links. In this technique, the transmit diversity order is fixed for each user and only power can be controlled to satisfy SINR requirements. This restricts the degrees of freedom available for resource allocation and limits the energy...
We are motivated to exploit the broadcast nature of a radio medium in combating its unreliable and time-varying characteristics. This leads to cooperative transmission where a neighbor node keeps a copy of an overheard packet and helps in retransmitting the overheard packet to its intended destination when the original transmission fails. Cooperative transmission improve wireless network performance...
In this paper, serial distributed detection under node failure for wireless sensor networks is studied. All previously suggested distributed detection algorithms for wireless sensor networks assume sensor nodes are completely functional. However, sensor nodes are vulnerable to failure for variety of reasons. Hence, node failure tolerant algorithm design is crucial to provide robustness to system under...
Spectrum occupancy modeling in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) constitutes a rather unexplored research area that still requires much more effort. This paper addresses the problem of modeling spectrum occupancy in the spatial domain by proposing a novel theoretical approach that enables modeling the occupancy level perceived at any geographical location based on the...
We consider a power allocation problem for three-node cooperative diversity systems using a relay node. Specifically, we focus on an amplify-and-forward (AF) protocol due to the simple operation at the relay node which makes the mathematical analysis tractable. This protocol consists of two phases. The source transmits the signal to both relay and destination in the first phase. In the second phase,...
Alamouti code with differential encoding has been recently proposed for OFDM systems. It allows full-rate and full-diversity communication and can be decoded with a linear complexity when using two transmit and one receive antennas. However, these advantages assume no interbloc interference (IBI) and no intersymbol interference (ISI) which occur only if the Guard Interval (GI) size is larger than...
We consider two different users sharing the same spectrum resource, interfering with each other, under outage performance requirements for both the users. We derive a practical condition to enable the spectrum-sharing under simultaneous outage performance. Furthermore, when the condition is fulfilled, we provide equations to define the two-dimensional region of allocated powers (P1, P2), for the two...
Estimation of the variance of AWGN is important to the initialization of iterative decoder, such as turbo code and LDPC code. Hence this paper puts forward a low-complexity and effective blind Gaussian variance estimator for MPSK and MQAM. The algorithm is derived from empirical characteristic function and provides a good un-biased estimation despite the knowledge of modulation type, as is proved...
We study the performance of distributed analog linear coding of multiple correlated multivariate Gaussian sources over the multiple access channel. Assuming the correlation structure is known both at the encoder and the decoder, optimal linear encoding and decoding is introduced. A general performance analysis is presented for both random and optimal linear encoders and compared to a lower bound on...
Interference alignment has proven to be a powerful tool in characterizing the high SNR behavior of wireless networks. Using this technique, Cadambe and Jafar showed that the sum degrees-of-freedom for the K-user interference channel is K/2 rather than 1 as was originally expected. In recent work, we showed that these gains are not limited to the high SNR regime. In fact, for the interference channel,...
The In0.53Ga0.47As interdigitated lateral p-i-n photodiode (ILPP) is a a cheap and affordable device to meet growing demands of optical communication networks operating at speeds below 10 Gbps. A ILPP model utilizing In0.53Ga0.47As as the absorbing layer was developed and optimized statistically using fractional factorial design (FFD) methodology. Seven model factors were investigated and a new analytical...
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