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We study practical, efficient codes for the Gaussian relay channel. It has been demonstrated that low-density lattice codes (LDLCs) can provide near-capacity performance for point-to-point Gaussian channels. We present an LDLC formulation that provides performance near the decode-and-forward inner bound of the relay channel capacity. We employ a superposition block Markov strategy tailored to LDLCs...
In this paper, we propose a novel opportunistic pair-wise transmission scheme in a multi-way relay channel (MWRC), in which multiple users exchange information via a common relay. We investigate pair-wise compute-and-forward for MWRCs by exploiting the multi-user fading channels. Conventionally, a pair-wise physical-layer network coding scheme with binary phase shift keying modulation was studied...
In this paper, the performance limits and the computational complexity of the lattice sequential decoder are analyzed for the unconstrained additive white Gaussian noise channel. The performance analysis available in the literature for such a channel has been studied only under the use of the minimum Euclidean distance decoder that is commonly referred to as the lattice decoder. Lattice decoders based...
Distributed storage systems have been receiving increasing attention lately due to the developments in cloud and grid computing. Furthermore, a major part of the stored information comprises of multimedia, whose content can be communicated even with a lossy reconstruction. In this context, Multiple Description Quantizers (MDQ) can be employed to encode such sources for distributed storage. However,...
The low-density parity-check (LDPC) lattices perform very well in high dimensions under generalized min-sum iterative decoding algorithm. In this work, we focus on 1-level LDPC lattices. We show that these lattices are the same as lattices constructed based on Construction A and low-density lattice-code (LDLC) lattices. In spite of having slightly lower coding gain, 1-level regular LDPC lattices have...
Recent years have witnessed the development of the Compute-and-Forward (CF) as a successful solution to perform noiseless linear Physical Layer Network Coding (PLNC). Research outcomes shed considerable light on the promising gain of this strategy from information-theoretic perspective. What misses is to design practical PLNC schemes based on the Compute-and-Forward and to evaluate their end-to-end...
To reduce the decoding complexity of linearly precoded MIMO systems, the sphere decoder is applied instead of maximum likelihood and the performance complexity trade-off is investigated. The max-dmin precoding criterion allows to enhance dramatically the Bit-Error-Rate (BER) of MIMO systems by maximizing the minimum Euclidean distance between the lattice points of received constellation. The maximum...
A Two-Way Relay Channel (TWRC) in which duplex transmission between two users via a relay station is considered. A physical layer network coding strategy based on compress-and-forward relaying scheme for the TWRC is proposed. In the underlying coding strategy, we use nested lattices for Wyner-Ziv coding and decoding. The relay uses the weaker side information available at the receivers from the first...
The Maximum Likelihood (ML) detector is a detection criteria which yields an optimal solution to Multiple-Input Multiple-Output (MIMO) systems but however, at the expense of its NP-hard complexity. Instead, the Sphere Decoder (SD) was proposed as an efficient algorithm for finding the solution to the ML detection problem in MIMO digital communication systems. Unlike the ML detector whose complexity...
In this paper, we investigate lattice network codes (LNCs) constructed from lattices over the ring of Eisenstein integers. Quantization and encoding algorithms over Eisenstein integers are first introduced. Then, a union bound estimation (UBE) of the decoding error probability is derived when the shaping region of the LNC is a product of regular hexagons. We show that the UBE is in the same form as...
We employ polar codes as the building blocks of Construction D to construct lattices for the additive white Gaussian noise (AWGN) channel. The construction of these component polar codes is based on the idea of Pedarsani et al. for binary-input memoryless symmetric (BMS) channels. Our lattice construction takes the advantage of the performance gain of polar codes over Reed-Muller codes. Simulation...
We describe a new family of integer lattices built from construction A and non-binary LDPC codes. An iterative message-passing algorithm suitable for decoding in high dimensions is proposed. This family of lattices, referred to as LDA lattices, follows the recent transition of Euclidean codes from their classical theory to their modern approach as announced by the pioneering work of Loeliger (1997),...
In this paper, lattice based coding is used over two-user Gaussian state-dependent multiple access channel with common message for two channel models. First, it is assumed that the additive channel interference is noncausally known at both encoders. Exploiting a lattice encoding and decoding scheme, the effect of the interference is completely removed and the capacity region is achieved. Then, the...
In this paper we consider the error performance analysis of lattice alignment for the many-to-one interference channel. An upper bound on the error probability for the first receiver when lattice codes are used is derived. More precisely, we consider the case of joint maximum-likelihood (ML) decoding of the desired signal and the sum of interfering signals, derive the union bound for the error probability...
We consider a two-way relay channel (TWRC) in which two terminals exchange messages with the help of a relay between them. The two terminals transmit messages to the relay through the Multiple Access Channel (MAC) and the relay transmits messages to the two terminals through the Broadcast Channel (BC). We assume that the MAC and the BC do not interfere with each other, and each terminal receives signals...
In this work, we consider an additive state-dependent Gaussian interference channel (ASD-GIC) where there is a common additive interference, known to both transmitters but not to the receivers. First, we obtain an outer bound on the sum-capacity for the asymptotic case where the interference is assumed to be Gaussian variable with unbounded variance. This asymptotic case has been referred to as the...
In this paper, the two-user interference relay channel (IRC) is studied. Transmission schemes for this network are compared. Namely, compress-and-forward (CF) and functional decode-and-forward (FDF) are presented. In CF, the relay establishes cooperation with the users by compressing its observation and forwarding it to the receivers. In FDF, the relay decodes a linear combination of the transmitted...
We propose a packet delayed lattice reduction aided MIMO detection for 802.1 1n system. Lattice reduction algorithms are iterative in nature that results in long latency. In high throughput systems like 802.11n, reduction of latency via parallelization causes high hardware complexity. Without parallelization, the receiver needs to buffer the incoming data until the lattice reduction finishes. Depending...
Recently, Delay-Tolerant Space-Time Codes (DT-STCs) have been designed for cooperative communications. They are optimal in synchronous transmission and preserve their full-diversity order for arbitrary delays in asynchronous case. In this paper, we investigate these DT-STCs in femtocell networks where Femtocell Access Points can assist Macrocell Base Stations to transmit data information to users...
This paper presents an efficient approach to spoken term detection (STD) from unstructured audio recordings using word lattices generated off-line from an automatic speech recognition (ASR) system. The approach facilitates open vocabulary STD and focuses specifically on reducing the difference between detection performance obtained for within-vocabulary (IV) and out-of-vocabulary (OOV) search terms...
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