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We propose a new type of ultimate-Shannon-limit-approaching codes called spatially coupled protograph-based low-density parity-check Hadamard convolutional codes (SC-PLDPCH-CCs), which are constructed by spatially coupling PLDPC-Hadamard block codes. We develop an efficient decoding algorithm that combines pipeline decoding and layered scheduling for the decoding of SC-PLDPCH-CCs, and analyze the latency and complexity of the decoder. To estimate the decoding thresholds of SC-PLDPCH-CCs, we first propose a layered protograph extrinsic information transfer (PEXIT) algorithm to evaluate the thresholds of spatially coupled PLDPC-Hadamard terminated codes (SC-PLDPCH-TDCs) with a moderate coupling length. With the use of the proposed layered PEXIT method, we develop a genetic algorithm to find good SC-PLDPCH-TDCs in a systematic way. Then we extend the coupling length of these SC-PLDPCH-TDCs to form good SC-PLDPCH-CCs. Results show that our constructed SC-PLDPCH-CCs can achieve comparable thresholds to the block code counterparts. Simulations illustrate the superiority of the SC-PLDPCH-CCs over the block code counterparts and other state-of-the-art low-rate codes in terms of error performance. For the rate-0.00295 SC-PLDPCH-CC, a bit error rate of 10−5 is achieved at $E_{b}/N_{0} = -1.465$ dB, which is only 0.125 dB from the ultimate Shannon limit. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new method to design low-density parity-check Hadamard (LDPC-Hadamard) codes — a type of ultimate-Shannon-limit approaching channel codes. The technique is based on applying Hadamard constraints to the check nodes in a generalized protograph-based LDPC code, followed by lifting the generalized protograph. We name the codes formed protograph-based LDPC Hadamard (PLDPC-Hadamard) codes. We also propose a modified Protograph Extrinsic Information Transfer (PEXIT) algorithm for analyzing and optimizing PLDPC-Hadamard code designs. The proposed algorithm further allows the analysis of PLDPC-Hadamard codes with degree- 1 and/or punctured nodes. We find codes with decoding thresholds ranging from −1.53 dB to −1.42 dB. At a BER of 10−5, the gaps of our codes to the ultimate-Shannon-limit range from 0.40 dB (for rate = 0.0494) to 0.16 dB (for rate = 0.003). Moreover, the error performance of our codes is comparable to that of the traditional LDPC-Hadamard codes. Finally, the BER performances of our codes after puncturing are simulated and compared. [ABSTRACT FROM AUTHOR]

In a joint source-channel coding (JSCC) system, excessive source compression can cause an error floor. In the original JSCC scheme based on double protograph LDPC (DP-LDPC) codes, only connections exist between check nodes (CNs) of the source protograph and variable nodes (VNs) of the channel protograph, and error floors are observed. In this paper, we investigate the joint protograph that forms the basis of a DP-LDPC code. The joint protograph consists of a source protograph, a channel protograph, and connections between the two protographs. Our main focus is on the complete-source-variable-linking (CSVL) protomatrix of the joint protograph, which determines the error floor of the DP-LDPC code. We propose a generalized source protograph extrinsic information transfer (GSP-EXIT) algorithm for evaluating the source decoding thresholds of the CSVL protomatrix. Based on the proposed algorithm, we analyze CSVL protomatrices with regular or irregular source protographs. We present design criteria for connections between VNs of the source protograph and CNs of the channel protograph. Such design rules will result in a higher source decoding threshold, which implies a lower error floor. We also propose a differential evolution algorithm for optimizing the source protograph. We present/compare analytical results and/with simulation results, and conclude that they are consistent. [ABSTRACT FROM AUTHOR]

A typical shuffle operation randomly partitions data on many computers, generating possibly a significant amount of network traffic which often dominates a job's completion time. This traffic is particularly pronounced in iterative distributed operations where each iteration invokes a shuffle operation. We observe that data of different iterations are related according to the transformation logic of distributed operations. If data generated by the current iteration are partitioned to the computers where they will be processed in the next iteration, unnecessary shuffle network traffic between the two iterations can be prevented. We model general iterative distributed operations as the transform-and-shuffle primitive and define a powerful notion named Confluence key dependency to precisely capture the data relations in the primitive. We further find that by binding key partitions between different iterations based on the Confluence key dependency, the shuffle network traffic can always be reduced by a predictable percentage. We implemented the Confluence system. Confluence provides a simple interface for programmers to express the Confluence key dependency, based on which Confluence automatically generates efficient key partitioning schemes. Evaluation results on diverse real-life applications show that Confluence greatly reduces the shuffle network traffic, resulting in as much as 23 percent job completion time reduction. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a max–min weighted signal-to-interference-plus-noise-ratio (SINR) problem in a full-duplex multiuser multiple-input-multiple-output system, where a full-duplex-capable base station (BS) equipped with multiple antennas communicates with multiple half-duplex downlink and uplink users under the same system resources. Specifically, we consider a practical scenario where the downlink minimum weighted SINR is maximized under specific SINR constraints for uplink users. Moreover, the optimization is conducted by jointly considering the BS transmit power, the transmit power of uplink users, and BS transmit and receive beamforming. This optimization problem is, therefore, subject to multiple uplink SINR constraints and multiple transmit power constraints. Due to the SINR constraints, negative matrix components arise and hence the optimization problem cannot be directly solved by the standard approach, i.e., Perron–Frobenius theory. We have provided an explicit iterative scheme to solve this joint optimization problem with a strict proof. The proposed algorithm is proved to converge to Karush–Kuhn–Tucker points. Simulation results show that our proposed algorithm has a fast convergence rate and leads to a better performance compared with other optimization techniques that do not jointly consider all parameters. [ABSTRACT FROM PUBLISHER]

Cloud computing increasingly leverages SMP virtual machines (VMs) to host multi-threaded applications. Interrupt balancing as a problem becomes more challenging because VMs are subject to the hypervisor's scheduling. Since the scheduling delays are typically tens of milliseconds, when they are added to one VM's interrupt delivery, they can seriously degrade the VM's I/O performance. Traditional balancing techniques are designed for dedicated environments, which cannot work well in virtualized environments because VMs are disallowed to directly control the hardware in many cases. In this paper, we present hBalance, a very simple approach to offload interrupt load balancing from SMP-VMs to the hypervisor. To accelerate the interrupt processing, our approach does not require shortening the hypervisor's scheduling time slice, but dynamically redirects interrupts from preempted virtual CPUs to running ones in a balanced manner. hBalance supports both Fully Virtualiized (FV) guests and Para-Virtualized (PV) guests, and exhibits high portability among various hypervisors. With our prototype implementation in Xen, the experimental results with both micro-level and application-level benchmarks show that hBalance significantly improves SMP-VMs’ I/O performance while introduces moderate overhead. [ABSTRACT FROM AUTHOR]

Resource allocation is an important strategy to optimize system performance in multiuser cooperative orthogonal frequency-division multiple-access (OFDMA) systems. In this paper, we jointly consider three different transmission modes in cooperative OFDMA systems, i.e., direct transmission (DT) mode, half-duplex (HD) relay cooperative transmission (HDRCT) mode, and full-duplex (FD) relay transmission (FDRT) mode. The joint optimization problem of transmission mode selection, subcarrier assignment, relay selection, subcarrier pairing, and power allocation (PA) is investigated. In this paper, we transform the binary assignment problem into a maximum-weighted bipartite matching problem, which can be solved by the classical Hungarian method. Based on the dual method, we solve the joint PA and binary assignment problem iteratively. Specifically, since the direct link is considered interference in the FD relay transmission mode, the PA problem in FD relay transmission mode is nontrivial. Thus, we provide a novel hierarchical dual method to solve the PA problem in FD relay transmission mode. In addition, in HDRCT mode, the joint transmission of both the source and relay is taken into account, and we provide a simple and insightful PA scheme. Simulation results show that the proposed algorithms can significantly enhance the overall system throughput, compared with previous works. [ABSTRACT FROM AUTHOR]

In this paper, we propose a dual particle swarm optimization (PSO) algorithm for parameter identification of chaotic systems. We also consider altering the search range of individual particles adaptively according to their objective function value. We consider both noiseless and noisy channels between the original system and the estimation system. Finally, we verify the effectiveness of the proposed dual PSO method by estimating the parameters of the Lorenz system using two different data acquisition schemes. Simulation results show that the proposed method always outperforms the traditional PSO algorithm. [ABSTRACT FROM AUTHOR]

Given the same number of encoded symbols, a Luby Transform (LT) decoder is more likely to decode successfully when there is little redundancy among the symbols. With the use of a Tanner graph, we describe two kinds of redundancy appearing in LT codes in this paper. We further propose an encoding algorithm called Low Redundancy (LR) algorithm used in the formation of the encoded symbols. The algorithm aims to reduce the redundancy of LT codes and to improve the decoder performance under the same complexity. Simulation results show various LT codes improve in terms of average overhead factor and probability of successful decoding when the codes are encoded using the proposed LR algorithm. Moreover, the encoding complexity remains unchanged. [ABSTRACT FROM AUTHOR]

This paper reports the characteristics and performance of a new type of Luby Transform codes, namely scale-free Luby Transform (SF-LT) codes. In the SF-LT codes, the degree of the encoded symbol follows a modified power-law distribution. Moreover, the complexity and decoding performance of SF-LT codes are compared with LT codes based on robust soliton degree distribution and LT codes based on suboptimal degree distribution. The results show that SF-LT codes outperform other LT codes in terms of the probability of successful decoding over an ideal channel and a binary erasure channel. Moreover, the encoding/decoding complexity for the SF-LT codes is superior. [ABSTRACT FROM AUTHOR]

Network coding has been shown to be an effective coding technique to improve the throughput of a multicast session in a communication network. In general, an undirected network can be used to model a communication network in which nodes at both ends of a link can exchange messages. For a single multicast session in an undirected network with network coding, the maximum throughput can be estimated based on the minimum maxflow between the source node and the destination nodes. In this letter, we evaluate the impact of the network topology on the maximum multicast throughput of a network-coded communication network. In particular, the scalefree network, which represents the topology of most man-made networks including the Internet, will be compared with the random network. The maximum throughputs of the multicast sessions are evaluated for different choices of source and destination nodes. It is found that network coding can achieve better throughput of a scalefree network only if the source and destination nodes are chosen from high-degree nodes. [ABSTRACT FROM AUTHOR]

Analytically studying the outage performance of channel-state-information (CSI)-assisted amplify-and-forward (AF) cooperative networks with maximal ratio combining (MRC) receivers at the destination has always been a difficult task. In this paper, we will derive upper and lower performance bounds--including outage probability, ergodic achievable rate, and average symbol error rate--for such a network that selects the "best relay" out of multiple relays to carry out the relay transmission. Our results show that the derived analytical bounds are able to accurately predict the simulated performance. The analytical technique used here can further be applied to investigate multiple-relay systems under dissimilar fading channel conditions. [ABSTRACT FROM AUTHOR]

In this paper, we extend the characteristic-function approach to derive an exact symbol error rate expression for the M-ary time-hopping orthogonal pulse position modulation (TH- PPM) ultra-wideband (UWB) system under the interference from multiple users. Monte Carlo simulations are then used to validate the analytical solutions. The results are found to be valid even when that the chip width is greater than the pulse duration. Moreover, the analytical results are compared to those found by Gaussian approximation and the Gaussian Quadrature Rule method. We further show that compared to a binary system, M-ary systems can produce better error rate performance. [ABSTRACT FROM AUTHOR]

The use of low-density-parity-check (LDPC) codes in coding digital messages has aroused much research interest because of their excellent bit-error performance. The behavior of the iterative LDPC decoders of finite length, however, has not been fully evaluated under different signal-to-noise conditions. By considering the finite-length LDPC decoders as high-dimensional nonlinear dynamical systems, we attempt to investigate their dynamical behavior and bifurcation phenomena for a range of signal-to-noise ratios (SNRs). Extensive simulations have been performed on both regular and irregular LDPC codes. Moreover, we derive the Jacobian of the system and calculate the corresponding eigenvalues. Results show that bifurcations, including fold, flip and Neimark–Sacker bifurcations, are exhibited by the LDPC decoder. Results are useful for optimizing the choice of parameters that may enhance the effectiveness of the decoding algorithm and improve the convergence rates. [ABSTRACT FROM AUTHOR]

In this Letter, we apply combined linear detector/parallel interference cancellation (PIC) detectors to jointly decode symbols in a multiple access chaotic-sequence spread-spectrum communication system. In particular, three different types of linear detectors, namely single-user detector, decorrelating detector and minimum mean-square-error detector, are used to estimate the transmitted symbols at the first stage of the PIC detector. The technique for deriving the approximate bit error rate (BER) is described and computer simulations are performed to verify the analytical BERs. [ABSTRACT FROM AUTHOR]

Recently, the demand for an accurate design on the distribution of the antennas in shopping malls is growing rapidly. To provide a guaranteed coverage inside the shopping malls, mobile operators may have installed a lot more antennas than that is really needed. This over-engineering design has increased the installation and operation cost. Therefore, the need to have a relatively more accurate indoor design is the most requesting goal in the telecommunication industry. The purpose of this paper is to derive an indoor design template, which can facilitate mobile operators to evaluate efficiently the optimized number of antennas and their locations within a premises. A tunnel propagation model is used to represent the propagation loss in an indoor environment. Measurements are also taken to derive the losses of various media. Field tests are finally performed to verify the accuracy of the distribution of RF signal strength predicted by the design template. [ABSTRACT FROM AUTHOR]

In a multiple access spread-spectrum communication system, the bit error performance is usually limited by the mutual interference between users. The use of multi-user detection is an effective method to reduce such interference. In this paper, we consider two linear multi-user detectors, namely, decorrelating detector and minimum mean-square-error detector, applied to a multiple access chaotic-sequence spread-spectrum communication system. An approach to calculate the bit error rate (BER) for such systems is presented. The calculated BERs are compared with those obtained using brute-force computer simulations which give the true system performance. [ABSTRACT FROM AUTHOR]

Studies the performance of selected chaos-based systems which share their frequency bands with conventional spread-spectrum systems. Factors responsible for creating such scenario; Highlights of chaos-based systems used in this investigation; Analysis of bit-error performance; Overview of the performance of the chaos-based digital communication system under the influence of a direct-sequence spread-spectrum signal under the computer simulation; Features of the non-coherent differential chaos-shift-keying system used in this evaluation.

Recently, an optimal noncoherent detection technique for chaos-shift-keying digital communication system has been proposed. It has been stated that computational intensity showed increases that were exponential with the spreading factor. In this Letter, we show that the implementation of the optimal detector can be made independent of the chaotic maps used, and that the computational intensity will increase almost linearly with the spreading factor. In particular, we use a tent map as an example to illustrate the decoding algorithm. The bit error performance of the system is then evaluated by computer simulations for a range of spreading factors. Further, we extend the optimal decoding algorithm for maps of higher dimension. The bit error performance for the case of simple 2-D maps are compared with that obtained using the tent map. Finally, the effect of increasing spreading factor on the bit error performance is studied for the case of 2-D maps. [ABSTRACT FROM AUTHOR]

Recently, an optimal noncoherent detection technique for chaos-shift-keying digital communication system has been proposed. The computational intensity required, however, increases exponentially with the spreading factor. In this Letter, we propose an approximate-optimal detection technique, whose computational effort increases only linearly with the spreading factor. In particular, we use the chaotic sequences generated by a skew tent map as an example to illustrate the approximate-optimal detection method. The bit error performance of the proposed detector is evaluated by computer simulations and the results are compared with those obtained using the optimal detector. [ABSTRACT FROM AUTHOR]

Chaos-based communications can be applied advantageously if the property of chaotic systems is suitably exploited. In this Letter a simple noncoherent detection method for chaos-shift-keying (CSK) modulation is proposed, exploiting some distinguishable property of chaotic maps for recovering the digital message. Specifically, the proposed method exploits the difference in the return maps of the signals representing the digital symbols. The determining parameter of the return maps is estimated using a simple regression algorithm. If the parameter strongly characterizes the chaotic map, the detection can achieve very good accuracy. This strong parametric characterization can be achieved by defining the regression model with only one parameter. Using the tent maps as chaos generators, the bit-error-rate under additive white Gaussian noise is studied by computer simulations. [ABSTRACT FROM AUTHOR]

In a chaos-shift-keying (CSK) digital communication system, correlators followed by a comparator are typically used for coherent detection of the signal. Such a detection method, however, does not take the temporal variation of the bit energy into consideration. In this paper, an optimum detection for a binary CSK system is derived, taking into account the temporal variation of the bit energy for minimizing the error rates. Simulations are carried out to compare the performance between the optimum receiver and a typical receiver. The results provide theoretical performance benchmarks of coherent CSK systems for future references. [ABSTRACT FROM AUTHOR]

By combining bit‐shift and exclusive‐or operations, a weighted zigzag decodable fountain code is proposed to achieve an unequal error protection property. In the proposed scheme, the input symbols of different importance levels are first pre‐coded into variable nodes using low‐density parity‐check codes. Then, bit‐shift operations prior to exclusive‐or are performed on the non‐uniformly selected variable nodes to generate encoded symbols. An analysis of the erasure probabilities based on the and‐or tree is further introduced. Simulation results show that by appropriately choosing the maximum bit‐shift amount, the proposed weighted zigzag decodable fountain codes can successfully recover the more important input symbols prior to the less important ones. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a general model for the analysis of forward-link capacity of a code-division multiple access cellular system with power control. Calculation geometry of interference model; Analysis of forward-link power control schemes; Effects of power control error and dynamic range of transmission; Numerical results; Conclusions.

We study the problem of adaptive polling in undirected general networks. Polling, also known as broadcast-confirm, consists of a propagation round and a feedback round. In adaptive polling, a spanning tree of unknown topology is built dynamically during the propagation round, and feedback messages are free to choose their paths in order to adapt to traffic and fault situations. We study three adaptive polling algorithms and analyze their worst-case communication bit complexities in the propagation round. Then, we prove a lower bound on the worst-case communication bit complexity of &om;(e + n log n) in the propagation round for all algorithms of the same kind as the three algorithms we study, where n is the number of nodes, and e the number of edges. We conclude that the cost introduced into the network due to the running of an adaptive polling algorithm is mild. [ABSTRACT FROM AUTHOR]

Presents information on a study which proposed a lower bound on the number of labels per edge for achieving routing optimality. Definition of properties which concern the interval labels; Details on the lower bounds; Theorems and proofs.

Presents a paper which proposes ways to layout rectangular midimew networks on a 2D grid for computer networks. How midimew networks are derived; Better than the most common topologies; What is proven in the paper; Rows and columns moved as a whole in the process.

Device-to-device (D2D) communication is a promising technology which can improve the spectrum efficiency of cellular networks. Despite abundant research on resource allocation and interference cancellation for D2D communication, few works discuss how D2D is realized within cellular communication. In this paper, we propose a symmetric cooperative communication architecture combining security and energy efficiency, in which the users in 5G cellular networks can adaptively select the communication mode among cellular, direct D2D, and relay-assisted D2D communication according to the energy-consumption requirement. Considering the security aspect, we propose a novel relay selection strategy based on the asymmetry of social networks for the architecture. Firstly, we reduce the number of candidate relay devices based on energy consumption, the devices' battery status, and the devices' state. Then, an appropriate relay device is selected according to the proposed criteria, combining energy consumption, wireless channel quality, proximity prestige, and spreading ability. Simulation results reveal that, compared with conventional cellular communication and D2D communication, the proposed architecture can increase the number of users accessing the cellular networks simultaneously, improving the throughput and the security of data transmission. It can also significantly reduce the energy consumption as well as outage probability. [ABSTRACT FROM AUTHOR]

A joint carrier-code index modulation aided M-ary differential chaos shift keying (JCCIM-MDCSK) system is proposed in this paper. In the proposed JCCIM-MDCSK system, the carrier and code indices are used to transmit extra carrier and code index bits, respectively. Moreover, the modulating bits are input to multiple M-ary DCSK modulators, and the resultant signals are transmitted by the selected spreading codes and loaded into the active carriers. The benefit of the joint carrier-code index modulation is fully exploited so that the data rate and bit-error-rate (BER) performance of the JCCIM-MDCSK system are enhanced in contrast to its competitors. In order to estimate the carrier and code index bits successfully, an effective joint carrier-code index detection algorithm is proposed for the JCCIM-MDCSK system. In addition, the theoretical BER expressions of the JCCIM-MDCSK system are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Finally, the BER performance of the JCCIM-MDCSK system is compared to other state-of-the-art IM-based noncoherent chaotic communication systems. It is shown that the JCCIM-MDCSK system can achieve better BER performance than its competitors. [ABSTRACT FROM AUTHOR]

Double protograph low-density parity-check code has been shown to be a good solution for joint source-channel coding. Moreover, the source code and channel code (as one code pair) can be jointly optimized to achieve a good bit error rate (BER) performance. In this paper, first, an optimal design criterion of this code pair based on an extended curve-fitting algorithm is proposed. Second, a joint optimization procedure which searches for both the optimal decoding threshold and the optimal code pair is presented. In addition, for short-to-moderate-length codewords, the finite-length effect cannot be ignored and the procedure has to be modified with a new notion named length-N decoding threshold. The protograph extrinsic information transfer analysis and the BER simulation have shown that our optimized code pairs acquire lower decoding thresholds than conventional code pairs. Moreover, the optimized code pairs with short-to-moderate-length codewords can mitigate the finite-length effect and obtain low length-N decoding thresholds. [ABSTRACT FROM AUTHOR]

Energy usage and data rate of differential chaos shift keying (DCSK) are both inefficient since half of the symbol duration is used to transmit reference. To improve the energy efficiency and data rate, we propose a new chaos modulation scheme which combines DCSK with code index modulation (CIM) referred to as CIM-DCSK. In the proposed scheme, a short reference signal is transmitted first. Then $P$ repeated reference signals, which serve as information-bearing signals, are simultaneously modulated by an information bit and a Walsh code with a specific index which is determined by an extra information symbol. The analytical bit error rate (BER) performance of the proposed scheme is derived and verified by simulations. Further, we improve the performance of the proposed system by applying noise-reduction and optimizing power coefficients on the reference and the information-bearing signals of CIM-DCSK. Simulation and analytical results show that these optimization methods significantly boost the BER performances of the proposed schemes. Finally, the BER performances of the proposed systems are compared with that of the conventional DCSK system and the short reference DCSK (SR-DCSK) system. Numerical results show that the proposed schemes outperform both DCSK and SR-DCSK. [ABSTRACT FROM PUBLISHER]

Trapping sets (TSs) are known to cause error floors in regular and irregular low-density parity-check (LDPC) codes. By avoiding major error-contributing TSs during the code construction process, codes with low error floors can effectively be built. In [14], it has been shown that TSs labeled as [w;u] are considered as being equivalent under the automorphism of the graph and are therefore contributing equally to the error floor. However, TSs with the same label [w;u] are not identical in general, particularly for the case of irregular LDPC codes. In this paper, we introduce a parameter e that can identify the number of "distinguishable" cycles in the connected subgraph induced by an elementary trapping set. Further, we propose a code construction algorithm, namely the Progressive-Edge-Growth Approximate-minimum-Cycle-Set-Extrinsic-message-degree (PEG-ACSE) method, that aims to avoid small elementary trapping sets (ETSs), particularly detrimental ETSs. We also develop theorems evaluating the minimum possible ETSs formed by PEG construction algorithms in general. We compare the characteristics of the codes built using the proposed method and those built using PEG-only or PEG-Approximate-minimum-Cycle-Extrinsic-message-degree (PEG-ACE) methods. Results from simulations show that the codes constructed using the proposed PEG-ACSE method produce lower error rates, particularly at the high signal-to-noise (SNR) region, compared with codes constructed using other PEG-based algorithms. [ABSTRACT FROM PUBLISHER]

Combining powerful error-correction codes (ECCs) with multipulse pulse-position modulation (MPPM) has great potential to realize high-throughput and high-reliability transmissions in free-space optical (FSO) communication systems. This paper conducts an insightful investigation on protograph low-density parity-check (PLDPC)-coded MPPM systems over Poisson channels. To be specific, we first put forward a novel type of constellations, referred to as irregular pulse-distribution (IPD) constellations, for MPPM. We also conceive a bit-level rate-adaptive (RA) scheme, which can exploit the structural property of the IPD constellations to significantly improve the convergence performance at the price of transmission-rate loss. Furthermore, with the aid of a modified protograph extrinsic information transfer (PEXIT) algorithm, we construct three enhanced PLDPC codes with code rates $1/2, 2/3$ and $3/4$ that exhibit excellent decoding thresholds over Poisson channels. The proposed PLDPC-coded MPPM systems with the use of the IPD constellations, RA scheme, and enhanced PLDPC codes are superior to the state-of-the-art counterparts. [ABSTRACT FROM AUTHOR]

We consider the scenario of a cognitive radio network overlaying on top of a legacy primary network by overhearing feedback signals over primary channels. The considered problem can be cast into a restless multiarmed bandit (RMAB) problem that is of fundamental importance in decision theory. It is well known that the optimal policy of the RMAB problem is PSPACE-hard to obtain due to its exponential computation complexity. A natural alternative is to consider an easily implementable myopic policy that maximizes immediate reward but ignores the impact of the current strategy on future reward. In this paper, we perform an analytical study on the structure, optimality, and performance of the myopic policy for the considered RMAB problem. The myopic policy is shown to have a simple queue structure, and then, its optimality is established for accessing N - \1 of N channels and conjectured for the general case. The performance of the myopic policy is analyzed, which, based on the structure of the myopic policy and the domination theory, characterizes the lower and upper bounds of the throughput of a multichannel opportunistic communication system. [ABSTRACT FROM AUTHOR]

Wireless sensor networks are widely adopted in target tracking applications. Wireless sensor nodes are battery-powered devices. These low-cost communication devices have high failure rates and are vulnerable to attacks. To maintain network connectivity and to ensure large network coverage, excessive wireless sensor nodes are usually deployed to provide redundancy. However, these extra wireless sensor nodes would dissipate more power. This problem can be relieved by proper scheduling and putting unnecessary sensor nodes into sleep mode. In this paper, an energy-aware scheduling scheme for wireless sensor networks is proposed. The proposed scheme is a kind of an adaptive/periodic on–off scheduling scheme in which sensor nodes use only local information to make scheduling decisions. The scheme is evaluated in terms of target hit rate, detection delay, and energy consumption per successful target detection. Simulation results show that when comparing with other generic scheduling schemes, the proposed scheme can significantly reduce energy consumption. [ABSTRACT FROM PUBLISHER]

Multipath performance is an important consideration for chaos-based communication systems. In this letter, the performance of the FM-DCSK communication system over multipath fading channels is evaluated by computer simulations. Both Rayleigh fading and Ricean fading are considered, and the low-pass equivalent model of the FM-DCSK system is used in the simulation. Based on this model, we analyze the bit error performance of the system and the effects of system parameters on the bit-error performance. [ABSTRACT FROM AUTHOR]

A number of schemes have been proposed for communication using chinos over the past years. Regardless of the exact modulation method used. the transmitted signal must go through a physical channel which undesirable introduces distortion to the signal and adds noise to it. The problem is particularly serious when coherent-based demodulation is used because the necessary process of chaos synchronization is difficult to implement in practice. This paper addresses the channel distortion problem and proposes a technique for channel equalization in chaos-based communication systems, The proposed equalization is realized by a modified recurrent neural network (RNN) incorporating a specific training (equalizing) algorithm. Computer simulations are used to demonstrate the performance of the proposed equalizer in chaos-based communication systems. The Henon map and Chua's circuit arc used to generate chaotic signals. It is shown that the proposed RNN-based equalizer outperforms conventional equalizers as well as those based on feedforward neural networks for noisy, distorted linear and non-linear channels. [ABSTRACT FROM AUTHOR]

As a typical example of bandwidth-efficient techniques, bit-interleaved coded modulation with iterative decoding (BICM-ID) provides desirable spectral efficiencies in various wireless communication scenarios. In this paper, we carry out a comprehensive investigation on tail-biting (TB) spatially coupled protograph (SC-P) low-density parity-check (LDPC) codes in BICM-ID systems. Specifically, we first develop a two-step design method to formulate a novel type of constellation mappers, referred to as labeling-bit-partial-match (LBPM) constellation mappers, for SC-P-based BICM-ID systems. The LBPM constellation mappers can be seamlessly combined with high-order modulations, such as $M$ -ary phase-shift keying (PSK) and $M$ -ary quadrature amplitude modulation (QAM). Furthermore, we conceive a new bit-level interleaving scheme, referred to as variable node matched mapping (VNMM) scheme, which can substantially exploit the structure feature of SC-P codes and the unequal protection-degree property of labeling bits to trigger the wave-like convergence for TB-SC-P codes. In addition, we propose a hierarchical extrinsic information transfer (EXIT) algorithm to predict the convergence performance (i.e., decoding thresholds) of the proposed SC-P-based BICM-ID systems. Theoretical analyses and simulation results illustrate that the LBPM-mapped SC-P-based BICM-ID systems are remarkably superior to the state-of-the-art mapped counterparts. Moreover, the proposed SC-P-based BICM-ID systems can achieve even better error performance with the aid of the VNMM scheme. As a consequence, the proposed LBPM constellation mappers and VNMM scheme make the SC-P-based BICM-ID systems a favorable choice for the future-generation wireless communication systems. [ABSTRACT FROM AUTHOR]

As a bandwidth-efficient technique, bit-interleaved coded modulation with iterative demapping and decoding (BICM-ID) has attracted much research attention in the field of wireless communication. In this paper, we put forth a joint design of root-protograph (RP) low-density parity-check (LDPC) codes and BICM-ID, referred to as RP-based BICM-ID (RP-BICM-ID), over block-fading (BF) channels so as to boost the throughput under limited bandwidth. To preserve the full-diversity property of RP codes, we propose an efficient modulation strategy for the RP-BICM-ID system by taking the fading-block length into consideration. We also analyze the outage-probability limit of the RP-BICM-ID systems to establish the fundamental lower-limit on their word-error-rate (WER) performance. Moreover, we conceive a multi-level protograph extrinsic information transfer (ML-PEXIT) algorithm to derive the asymptotic WER and bit error rate (BER) of the RP-BICM-ID systems over BF channels. As a further insight, we develop a novel unequal-error-protection (UEP) bit-to-symbol (B2S) mapping scheme for the RP-BICM-ID systems, which gives rise to an additional performance improvement. Analyses and simulations show that the proposed RP-BICM-ID systems can not only realize desirable spectral efficiency, but also obtain near-outage-limit performance over BF channels. Therefore, the proposed RP-BICM-ID systems are very promising in achieving high-reliability and high-rate transmissions under slow-fading wireless-communication environments. [ABSTRACT FROM AUTHOR]

Mobile sensor networks (MSNs) are utilized in many sensing applications that require both target seeking and tracking capabilities. Dynamics of mobile agents and the interactions among them introduce new challenges in designing robust cooperative control mechanisms. In this paper, a distributed semiflocking algorithm inspired by Temnothorax albipennis migration model is proposed to address the above issues. Mobile agents under the control of the proposed semiflocking algorithm are capable of detecting targets faster and tracking them with lower energy consumption when compared with existing MSN motion control algorithms. Furthermore, the proposed semiflocking algorithm can operate energy-efficiently on both flat and uneven terrains. Simulation results demonstrate that the proposed semiflocking algorithm can provide promising performances in target seeking and tracking applications of MSNs. [ABSTRACT FROM AUTHOR]