We investigate an optimized blind SeLected Mapping (SLM) algorithm to reduce the Peak-to-Average Power Ratio (PAPR) for Orthogonal Frequency Division Multiplexing (OFDM) systems with Signal Space Diversity (SSD). Several phase sequences based on two Rotated and Cyclically Q-Delayed (RCQD) constellations are used at the transmitter to considerably reduce the PAPR. The pair of RCQD constellations is selected so as to achieve the highest average mutual information for both the Coded Modulation (CM) and the Bit-Interleaved Coded Modulation (BICM) schemes. These constellations also allow, along with Hadamarad sequences, good blind detection performances with no spectral spoilage. Simulations totally confirm our theoretical results.

In this paper, we derive the analytical expression of the Bayesian Cramer-Rao Bound (BCRB) for the joint estimation of random time delay and channel gains. The BCRB is evaluated for the Rayleigh fading channel for both Data-Aided (DA) and Non-Data-Aided (NDA) processing modes. Simulation results make a comparison, over various channels, between several synchronization modes. In particular, we show that a better performance can be achieved by using DA and off-line estimation techniques, where all the received signal samples are used at any time of the estimation process.

This paper presents an off-line algorithm for dynamical time delay recovery for which the whole observation block is used. The time offset varies over the observation interval following a random walk model. The proposed synchronizer applies to data-aided (DA), non-data-aided (NDA), and code-aided (CA) modes. Theoretical performance of the off-line technique is derived and compared with simulation results. The Bayesian Cramer-Rao Bound (BCRB) is also evaluated for DA, NDA, and CA modes and for both the off-line and on-line scenarios. Simulation results show the improvement brought by the off-line and the CA schemes. The presented algorithm outperforms the conventional on-line estimator, which only considers the current and previous observations, and its mean square error approaches the BCRB.

We propose to derive the analytical expression of the Hybrid Cramer-Rao Bound HCRB for the joint time delay and channel fading estimation. The time delay is considered as a deterministic parameter and the channel is considered as a complex gaussian random variable. The HCRB expression is computed for both the data-aided (DA) and the non data-aided (NDA) modes. The obtained result allows us to assess the performance of on-line and offline dynamical Rayleigh channel gains estimation. It also evaluates timing recovery techniques under a time varying fading channel.

Spin-torque transfer magnetic random access memory (STT-MRAM) has emerged as a promising nonvolatile memory technology, with advantages, such as scalability, speed, endurance, and power consumption. This paper presents an STT-MRAM cell operation channel model with write and read operations for information theorists and error correction code designers. This model considers the effects of process variations and thermal fluctuations and considers all principle flaws during the fabrication and operation processes. With this model, evaluations are not only made for the write channel, the read channel, but also the write and read channel with metrics, such as operation failure rate, bit error rate, channel ergodic capacity, and channel outage probability at certain outage capacity. Moreover, it is proved that the distributions of written-in bit states are not uniformly distributed and are proportional to their respective write success probabilities. Finally, simulation results show that practical code rates and code block lengths can guarantee reliable performances only if the operation success rate difference between state 1 and state 0 is small enough.

In this paper, we propose a maximum likelihood based Code-Aided (CA) timing recovery algorithm for square-QAM modulated signals. We also theoretically derive the analytical expression of the CA Crammaximum likelihood based Code-Aided (CA) timing recovery algorithmer-Rao Bound for time delay estimation. Our simulations show that the proposed CA approach realizes a performance equivalent to the Data-Aided (DA) approach over a large interval of signal to noise ratio (SNR) values.

DVB-T2 was the first industrial standard deploying rotated and cyclic Q delayed (RCQD) modulation to improve performance over fading channels. This enables important gains compared to conventional quadrature amplitude modulations (QAM) under severe channel conditions. However, the corresponding demodulation complexity still prevents its use for wider applications. This paper proposes several rotation angles for different QAM constellations and a corresponding low-complexity detection method. Results show that the proposed solution simplifies both the transmitter and the receiver with often better performance than the proposed angles in DVB-T2. Compared with the lowest complexity demappers currently used in DVB-T2, the proposed solution achieves an additional reduction by more than 60%.

In this paper, we consider a dual-hop Multiple Input Multiple Output (MIMO) wireless multi-relay network, in which a source-destination pair both equipped with multiple antennas communicates through multiple half-duplex amplify-and-forward (AF) relay terminals which are also with multiple antennas. Imperfect channel estimations for all nodes are considered. We propose a novel robust linear beamforming at the relays, based on the QR decomposition filter at the destination node which performs successive interference cancellation (SIC). Using Law of Large Number, we obtain the asymptotic rate, upon which the proposed relay beamforming is optimized. Simulation results show that the asymptotic rate matches with the ergodic rate well. Analysis and simulation results demonstrate that the proposed beamforming outperforms the conventional beamforming schemes.

In this paper we design novel decoders for non-binary low density parity check (LDPC) codes. For a non-binary LDPC code C over the field Fqof size q for some q > 0, we propose two novel cooperative decoders, each composed of a binary component decoder and a q-ary component decoder in a concatenated manner, to obtain excellent decoding performance. Specifically to reduce the complexity of the cooperative decoders, we design a hybrid q-ary component decoder. Then, we propose an algorithm to construct the parity check matrix to eliminate the bit-level cycles. Simulations show that the decoding performance of the proposed algorithm approaches the capacity limit within 0.2dB at BER= 10−4.

In this work, we study the quality-delay tradeoff for video streaming over mobile ad hoc network by utilizing a class of scheduling schemes. We show that node spatial mobility indeed impacts on the performance of wireless video transmission under the assumption that all the nodes can identically and uniformly visit the entire network. To describe a practical mobile scenario, we consider a random walk mobility model in which each node can randomly and independently choose its mobility direction at each time-slot. The contributions of this work are twofold: 1) It investigates the optimal node velocity for the mobile video network which helps to identify the impact of mobility on the video performance; 2) It derives the achievable quality-delay tradeoff range for any node mobility velocity, and thus it is helpful to design appropriate quality and delay requirements. These results provide insights on network design and fundamental guidelines on establishing an efficient mobile wireless video transmission system.

Distributed scheduling for hybrid media flows over wireless body sensor network faces three technical challenges: constrained communication channel, random node placement and strict transmission latency. In this work, we study this problem by jointly considering the above three challenges to achieve the minimum media distortion and optimal network resource utilization. At first, we construct a general flow transmission model according to network's transmission mechanism, as well as media-aware flow's characteristics. Then, a distributed scheduling scheme is proposed based on dynamic network resource update. It is proved that the proposed scheme can achieve the optimal scheduling solution with an exponential convergence rate, and an explicit form of the asymptotic convergence rate is provided. Furthermore, the realization of the distributed scheduling scheme through the collaboration between the network and the sources is the highlight of this paper. Extensive simulation results are provided to demonstrate the effectiveness of our proposed scheme.

The integrated computing system optical network has been viewed as a promising platform to support real-time distributed computing applications. For such a system involving so many heterogeneous computing and network resources, faults seem to be inevitable. Therefore, a fault-tolerant scheme is necessary to improve the availability of the integrated system. However, existing joint task scheduling schemes for real-time distributed computing applications generally do not consider the application availability issues when making scheduling decisions. In this paper, we develop an availability-aware joint task scheduling (AAJTS) scheme, by both taking into account availability improvement and timing requirements. The proposed scheme iteratively enhances the application availability under deadline constraint to protect data communication tasks from network link failures. Extensive simulations demonstrate the effectiveness and the feasibility of the proposed scheme.

An important issue of supporting multi-user video streaming over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resources while, at the same time, to meet each video's Quality of Service (QoS) requirement. In this work, we study the problem of video streaming over multi-channel multi-radio multihop wireless networks, and develop fully distributed scheduling schemes with the goals of minimizing the video distortion and achieving certain fairness. We first construct a general distortion model according to the network¿s transmission mechanism, as well as the rate distortion characteristics of the video. Then, we formulate the scheduling as a convex optimization problem, and propose a distributed solution by jointly considering channel assignment, rate allocation, and routing. Specifically, each stream strikes a balance between the selfish motivation of minimizing video distortion and the global performance of minimizing network congestions. Furthermore, we extend the proposed scheduling scheme by addressing the fairness problem. Unlike prior works that target at users' bandwidth or demand fairness, we propose a media-aware distortion-fairness strategy which is aware of the characteristics of video frames and ensures max-min distortion-fairness sharing among multiple video streams. We provide extensive simulation results which demonstrate the effectiveness of our proposed schemes.

An important issue of supporting multi-user video streaming over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resources while, at the same time, to meet each video's QoS (quality of service) requirement. In this work, we study the problem of video scheduling over multi-channel multi-radio multi-hop networks with the goals of minimizing the video distortion. At first, we construct a general distortion model according to the network's transmission mechanism, as well as video's rate-distortion characteristics. Then, by joint considering the channel assignment, rate allocation and routing, we develop a fully distributed scheduling scheme to get an optimal QoS performance. Furthermore, the realization of the distributed scheduling scheme through cooperation among the channel, link and source is the highlight of this paper. Extensive simulation results are provided which demonstrate the effectiveness of our proposed scheme.

In this paper, we study Bayesian and hybrid Cramer-Rao bounds for the dynamical phase estimation of QAM modulated signals. We present the analytical expressions for the various CRBs. This avoids the calculation of any matrix inversion and thus greatly reduces the computation complexity. Through simulations, we also illustrate the behaviors of the BCRB and of the HCRB with the signal-to-noise ratio.

This paper presents a near-optimum, low-complexity, fixed-interval smoothing algorithm that approaches the performance of an optimal smoother for the price of two low-complexity sequential estimators (two PLLs). The proposed Smoothing PLL (S-PLL) algorithm is easy to implement and fits the Cramer-Rao bounds over a wide range of signal-to-noise ratios. Moreover we show that, compared to the conventional forward loop, the proposed scheme allows to have a large gain of several dBs and is able to track frequency offsets.

In this paper, we study Bayesian and hybrid Cramer-Rao bounds (BCRB and HCRB) for the code-aided (CA) dynamical phase estimation of QAM modulated signals. In order to avoid the calculus of the inverse of the Bayesian information matrix and of the hybrid information matrix, we present some analytical expressions for the various CRBs, which greatly reduce the computation complexity.

The support for multiple high-definition video streams in wireless home networks requires appropriate routing and rate control measures, ascertaining the reasonable links for transmitting each stream and the rate of the video to be delivered over the chosen links. In this paper, we invest the combination of the routing and rate control in a united convex optimization formulation and propose a distributed joint solution based on cross-layer design. We first develop a distortion model which captures both the impact of encoder quantization and packet loss due to network congestion on the overall video quality. Then, the optimal joint rate control and routing scheme is realized by adapting its rate to the time-varying traffic and minimizing the overall network congestion. Furthermore, simulation results are provided, which demonstrate the effectiveness of our proposed joint routing and rate control scheme in the context of wireless home networks.

An important issue for supporting multimedia applications in multiple heterogeneous networks, a typical pervasive computing environment, is how to optimize the rate allocation by intelligently utilizing the available network resources while, at the same time, to meet each application's QoS (Quality of Service) requirement. In this work, we develop and evaluate a rate allocation scheme in terms of audio and video applications based on a cross-layer design framework. At first, we construct a general distortion model according to the observed parameters in each network, as well as each application's rate-distortion characteristic. Then, the rate allocation is formulated as a convex optimization problem that minimizes the sum of the expected distortion of all applications. Furthermore, the realization of the distributed rate allocation algorithm for achieving an optimal or close-to-optimal end-to-end QoS under the overall limited resource budget is the highlight of this paper. Simulation results are provided which demonstrate the effectiveness of our proposed distributed rate allocation scheme.

Mobile IP allows a mobile node to maintain a continuous connectivity to the Internet when moving from one access point to another. However, due to the link switching delay and to the Mobile IP handover operations, packets designated to mobile nodes can be delayed or lost during the handover period. This paper presents a new control function called Extended Handover Control Function (E-HCF) in order to improve the handover performance in the context of Mobile IPv6 over wireless networks. With an analytical model and some OPNET simulations, we show in this paper that our solution allows to provide low latency, low packet loss to the standard handover of Mobile IPv6.

This letter deals with the CramrRao bound for the estimation of a hybrid vector with both random and deterministic parameters. We point out the specificity of the case when the deterministic and the random vectors of parameters are statistically dependent. The relevance of this expression is illustrated by studying a practical phase estimation problem in a non-data-aided communication context.

In this letter we present a low-complexity architecture designed for the decoding of block turbo codes. In particular we simplify the implementation of Pyndiah's algorithm by not storing any of the concurrent codewords generated by the list decoder.

This paper is concerned with the design of block turbo codes for very high bit rate applications. We first introduce an original low-complexity architecture designed for the iterative decoding of product codes. The implementation of the Chase-Pyndiah algorithm is simplified by not memorizing any of the list decoding concurrent code words. We then illustrate that such block turbo codes allow some bit rate improvement in the context of local loop transmission

This paper describes several power mask designs for local loop multi-carrier transmission. The proposed algorithms exploit the signal to noise and interference ratio knowledge at the transmitter in order to maximize the overall bit rate. This design prevents from the multiple large constellations soft-demapping burden by using a single mid-size Quadrature Amplitude Modulation (QAM). We illustrate the algorithms performance by giving results for Very high bit rate Digital Suscriber Line (VDSL) systems.

This letter presents an original phase synchronization scheme designed for block turbo coded systems. This is a low-complexity scheme. It copes with low signal-to-noise ratios, taking complete advantage of the turbo coding possibilities. We display various results, showing that the proposed algorithm is able to process blocks of a few hundreds bits and that it tackles the case of large quadrature amplitude modulation constellations very well and with no phase ambiguity.

This paper concerns a new synchronizing scheme designed for block turbo coded system. The phase estimation relies on the feedback of the extrinsic information. A near optimum version of the algorithm based on the block turbo decoder devised by Pyndiah allows easy implementation. We display various results showing that the proposed algorithm is able to track frequency shifts and that it works very well in the case of general Quadrature Amplitude Modulation (QAM) constellations. We also show that this turbo synchronizer works at low Signal to Noise Ratios (SNR) taking completely advantage of the turbo coding possibilities.

This paper concerns the equalization problem of an underwater high rate transmission system. As the channel delay spread is large compared with the data duration, we have developed an equalizer in order to minimize the calculus burden. Test on real data is also made.