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In opportunistic networks (Oppnets), nodes rely on contact opportunities between them to exchange information with each other. Routing and forwarding in Oppnets remains a challenging task because of the limited energy and bandwidth constraints. Various routing protocols for Oppnets have been proposed in the literature, but only few of them have explicitly investigated the energy issue. In this paper, some improvements in the already existing history-based prediction for routing protocol for infrastructure-less Oppnets (so-called HBPR) is suggested so as to make it energy efficient. The proposed energy-efficient HBPR protocol (EHBPR) addresses the energy constraints in HBPR and reduces the number of packets transferred in the network, which in turn results to a reduction in the nodes' energy consumption. Through simulations, the performance of EHBPR in terms of energy consumption is compared against the HBPR and the energy-efficient n-epidemic routing protocol. The results show that (1) EHBPR consumes 14.66% less energy than HBPR (respectively 13.14% less energy than n-epidemic); (2) EHBPR generates 67.4% less dead nodes compared with HBPR (resp. 66.33% less dead nodes compared to n-epidemic); and (3) EHBPR yields 77.86% less overhead ratio compared with HBPR (resp. 84.49% less overhead ratio compared with n-epidemic). Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Network switches and routers scale in rate by distributing the packet read/write operations across multiple memory banks. Rate scaling is achieved so long as sufficiently many packets can be written and read in parallel. However, due to the non-determinism of the read process, parallel pending read requests may contend on memory banks, and thus significantly lower the switching rate. In this paper, we provide a constructive study of codes that guarantee fully parallel data reconstruction without contention. We call these codes “switch codes,” and construct three optimal switch-code families with different parameters. All the constructions use only simple XOR-based encoding and decoding operations, an important advantage when operated in ultra-high speeds. Switch codes achieve their good performance by spanning simultaneous disjoint local-decoding sets for all their information symbols. Switch codes may be regarded as an extreme version of the previously studied batch codes, where the switch version requires parallel reconstruction of all the information symbols. [ABSTRACT FROM PUBLISHER]

The paper presents a study of key aspects in the design of a flexible unified data plane capable of integrating both fronthaul and backhaul transport in future 5G systems. In this study, we first review candidate access and multiplexing technologies from the state of the art and assess their capability to support legacy and new fronthaul and backhaul traffic. We then propose a new design framework for the targeted flexible unified data plane, featuring a primary packet-switching path supported by an auxiliary circuit-switching for extreme low latency scenarios. This comprises a summary of the first results achieved in the 5G-Crosshaul EU project since its kick-off in July 2015. [ABSTRACT FROM AUTHOR]

In recent years, optical label switching (OLS) gains lots of attentions due to its intrinsic advantages to implement protocol, bit-rate, granularity and data format transparency packet switching. In this paper, we propose a novel scheme to realize flexible-rate optical packet switching for OLS networks. At the transmitter node, flexible-rate packet is generated by parallel modulating different combinations of optical carriers generated from the optical multi-carrier generator (OMCG), among which the low-speed optical label occupies one carrier. At the switching node, label is extracted and re-generated in label processing unit (LPU). The payloads are switched based on routing information and new label is added after switching. At the receiver node, another OMCG serves as local oscillators (LOs) for optical payloads coherent detection. The proposed scheme offers good flexibility for dynamic optical packet switching by adjusting the payload bandwidth and could also effectively reduce the number of lasers, modulators and receivers for packet generation/detection. We present proof-of-concept demonstrations of flexible-rate packet generation/detection and label swapping in 12.5 GHz grid. The influence of crosstalk for cascaded label swapping is also investigated. [ABSTRACT FROM AUTHOR]

Packet collision is a well-known severe impairment in ALOHA-based networks and, more generally, in any random access network. As a consequence, several methodologies have been considered with the aim of lowering the resulting performance degradation. A novel multiuser detection scheme exploiting channel diversity to separate collided signals is proposed here to enable multiple packet reception capability in random access schemes. The performance of this approach is analytically derived and optimized in terms of network throughput, and compared with that of different alternatives. The overall performance in terms of throughput shows the effectiveness of the proposed scheme in different operating conditions. [ABSTRACT FROM AUTHOR]

The existing study shows that safety applications supported by vehicle-to-vehicle (V2V) communications have the potential to address 80% of all road crash issues. IEEE 802.11p is a key enabling technology to support V2V safety applications. To meet the stringent delay and reliability requirements of these applications, rate adaptation (RA) approaches have been proposed to determine the optimal data transmission rate, according to the channel conditions such as packet losses. However, existing RA solutions cannot be directly applied to V2V safety communications in highway scenarios, which exhibit lots of dynamics and severe packet losses. Moreover, physical (PHY)-layer channel fading and medium-access-control (MAC)-layer interference contribute differently to the packet losses and, thus, should be treated separately. To address these issues, in this paper, we propose a LOss differentiation RA (LORA) scheme. LORA can estimate the average packet loss rate (PLR) for each sender and differentiate the fading losses from the interference losses. Extensive evaluation results demonstrate that LORA can provide reliability guarantees for V2V safety applications, as well as a response to environment changes in a real-time manner. [ABSTRACT FROM PUBLISHER]

This paper addresses the distributed fusion filtering problem for discrete-time random signals from measured outputs perturbed by random parameter matrices and correlated additive noises. These measurements are obtained by a sensor network with a given topology, where random packet dropouts occur during the data transmission through the different network communication channels. The distributed fusion estimation is accomplished in two phases. Firstly, by an innovation approach and using the last observation that successfully arrived if a packet is lost, a preliminary distributed least-squares estimator is designed at each sensor node using its own measurements and those from its neighbors. Secondly, every sensor collects the preliminary filters that are successfully received from its neighbors and fuses this information with its own one to generate the least-squares linear matrix-weighted distributed fusion estimator. The accuracy of the proposed estimators, which is measured by the estimation error covariances, is examined by a numerical simulation example. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the performance of transmit antenna selection in multiple-input multiple-output (MIMO) systems with N Stop and Wait (N-SAW) at the data link layer. The impact of packet size, number of SAW processes and the stalling of packets inside the receiver reordering buffer, due to N-SAW, on transmit antenna selection is investigated. Antenna selection is implemented as a signal processing technique that enhances the performance of the MIMO system; two schemes, throughput and capacity based transmit antenna selection are considered. Results show that under similar conditions, throughput maximization outperforms capacity maximization in terms of throughput, transmission latency and dropped packets when stall avoidance is implemented. The results further show that throughput and dropped packets increase with increase in SAW processes and decrease with increase in packet size. Transmission latency increases with increase in packet size and remains unchanged with increase in number of SAW processes. [ABSTRACT FROM AUTHOR]

The deployment of Internet of Things (IoT) devices and services is accelerating, aided by ubiquitous wireless connectivity, declining communication costs, and the emergence of cloud platforms. Most major mobile network operators view machine-to-machine (M2M) communication networks for supporting IoT as a significant source of new revenue. In this article, we discuss the need for wide-area M2M wireless networks, especially for short data packet communication to support a very large number of IoT devices. We first present a brief overview of current and emerging technologies for supporting wide area M2M, and then using communication theory principles, discuss the fundamental challenges and potential solutions for these networks, highlighting tradeoffs and strategies for random and scheduled access. We conclude with recommendations for how future 5G networks should be designed for efficient wide-area M2M communications. [ABSTRACT FROM AUTHOR]

The problem of fault detection for switched systems with quantisation effects and packet dropout is presented in this study. A dynamic quantiser is introduced, which is composed of a dynamic scaling and a static quantiser. Since a novel switched system is modelled according to packet dropout, a switching strategy which combines average dwell time switching with event-driven switching is proposed. The systems performance and the relationship between the switching signal and the packet dropout rate are simultaneously developed. Furthermore, sufficient conditions for the existence of fault detection filters are given in the framework of linear matrix inequality, and the filter gains and the quantiser range are derived by a convex optimised method. Finally, two illustrative examples demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

We study error correction codes for multimedia streaming applications where a stream of source packets must be transmitted in real-time, with in-order decoding, and strict delay constraints. In our setup, the encoder observes a stream of source packets in a sequential fashion, and $M$ channel packets must be transmitted between the arrival of successive source packets. Each channel packet can depend on all the source packets observed up to and including that time, but not on any future source packets. The decoder must reconstruct the source stream with a delay of $T$ packets. We consider a class of packet erasure channels with burst and isolated erasures, where the erasure patterns are locally constrained. Our proposed model provides a tractable approximation to statistical models, such as the Gilbert–Elliott channel, for capacity analysis. When $M=1$ , i.e., when the source-packet arrival and channel-packet transmission rates are equal, we establish upper and lower bounds on the capacity, that are within one unit of the decoding delay $T$ . We also establish necessary and sufficient conditions on the column distance and column span of a convolutional code to be feasible, and in turn establish a fundamental tradeoff between these. Our proposed codes—maximum distance and span codes—achieve a near-optimal tradeoff between the column distance and column span, and involve a layered construction. When $M>1$ , we establish the capacity for the burst-erasure channel and an achievable rate in the general case. Extensive numerical simulations over Gilbert–Elliott and Fritchman channel models suggest that our codes also achieve significant gains in the residual loss probability over statistical channel models. [ABSTRACT FROM PUBLISHER]

Future digital optical communication cannot develop without all-optical high-speed optical devices, especially in the field of high speed large capacity optical transmission, all-optical packet switching and optical computing, and thus optical logic devices are becoming a hotter spot of research. Based on the cross-gain modulation (XGM), a novel scheme of all-optical logic XNOR gate using linear optical amplifier (LOA) is presented in this paper. LOA results show a good gain characteristic, which can get better output logic operation than traditional semiconductor optical amplifier (SOA). Choosing suitable injection current, wavelength scope of the input signal and CW power can achieve better logic operation effect. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of robust exponential stabilization for sampled-data systems with variable sampling and packet dropouts. It is assumed that the system parameter uncertainties are norm-bounded and appear in both the state and input matrices. An input delay approach is adopted to model the sample-and-hold behavior with a time-varying delayed control input, and a switched system approach is proposed to model the data-missing phenomenon. On this basis, the sampled-data control system with variable sampling and packet dropouts is modeled as a switched system with time-varying delay. The objective is to design a sampled-data controller to guarantee the robust exponential stability of the resulting closed-loop system. Based on a new piecewise time-dependent Lyapunov functional, novel sufficient conditions are derived for the existence of robustly exponentially stabilizing sampled-data controllers. It is shown that the controller gains can be obtained by solving a set of linear matrix inequalities. Two simulation examples are given to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In pocket switched networks (PSNs), devices carried by humans form a network environment, which utilizes both human mobility and occasional connectivity to deliver messages among mobile devices. Mobile phones are widely used in our daily lives. Therefore, the PSN composed of human-carried mobile phones will soon become an ubiquitous network environment. In this paper, we propose a communication strategy that applies the WiFi hotspot mode of a mobile phone in the PSN to realize the device-to-device communications. However, due to the lack of energy supply, a phone in hotspot mode could rapidly consume energy and shorten its battery lifetime significantly. To maximize the message dissemination scope within the limited energy constraint of each phone in PSNs, an Energy-efficient Phone-to-phone Communication method based on WiFi Hotspot (EPCWH) is presented to schedule the phone's switching between hotspot mode and client mode. Simulations based on the synthetic random-waypoint mobility pattern and real traces are conducted in an opportunistic network environment; the results show that EPCWH achieves the best performance in terms of message dissemination and energy consumption among different switching strategies. [ABSTRACT FROM PUBLISHER]

Reports on the celebration of the ARPANET 50th Anniversary that was recognized at the AAAS Annual Meeting. [ABSTRACT FROM AUTHOR]

Throughput imbalances among contending flows are known to occur when any carrier sense multiple access (CSMA)-based protocol is employed in multi-hop wireless networks. These imbalances may vary from slight difference in throughput to complete starvation in which some flows are unable to acquire channel accesses. The root cause of such imbalances is the lack of coordination when CSMA medium access control (MAC) protocols are employed in multi-hop wireless networks. In this paper, we accurately predict per-flow throughput in general multi-hop wireless networks while addressing CSMA's coordination problem. Unlike the previous work, our analytical throughput prediction model can clearly differentiate between links interfering from transmission range and carrier sensing range. Modeling of conditional packet loss probability and busy time sensed by each station is critical for per-flow throughput prediction in arbitrary networks. The calculation of both these parameters largely depends on MAC behavior due to geometrical configuration of interfering stations; we accurately compute conditional packet loss probability and busy time based on geometrical configuration of the interfering stations and predicted per-flow throughput. Our analytical results demonstrate improved accuracy, indicate throughput imbalances, and provide better understanding of CSMA-based protocol behavior in multi-hop wireless networks that can be used to design fair, scalable, and efficient MAC layer protocols. [ABSTRACT FROM AUTHOR]

In this paper, an all-optical reservoir computing (RC) setup is proposed for identifying the types of optical packet headers in optical packet switching (OPS) network. The numerical simulation identification results of 3 bits and 32 bits optical headers with the bit rate of 10 Gbps are as low as 0.625% and 2.25%, respectively. The identification errors with the variation of the feedback strength and feedback delay are presented separately. Hence, the optimal feedback parameters are obtained. The all-optical feedback RC setup is robust to the white Gaussian noise. The recognition error is acceptable when the signal-to-noise ratio (SNR) is greater than 15 dB. [ABSTRACT FROM AUTHOR]

Interrupt affinitization of multi-queue network interface cards is a fundamental composition that defines how packets from individual queue are processed by which CPU-cores on multi-core platforms. In this paper, we propose qcAffin to attain an optimal queue-to-core affinitization for packet processing systems based on a numerical cost model derived from hardware topology and runtime system workloads. Static architectural characteristics comprising the memory hierarchy and topology of hardware components are first analyzed to calculate static interrupt affinitization costs. Then we attempt dynamic interrupt affinitization to balance workloads on CPU-cores and improve overall performance. Classical networking applications ranging from bridging, routing, access control list (ACL) matching to deep packet inspection (DPI) with different frame sizes are extensively experimented to compare the performance of the proposed scheme and other existing approaches. As demonstrated in the comparison result, qcAffin achieves the similar performance of the best affinitization approach and outperforms the Linux default affinitizer by averages of 102, 278, 248 and 131 percent on 1G NICs for the four applications. On 10G NICs, dramatic boosts of 1,424 and 1,343 percent are measured for the bridging and routing applications, respectively. Moreover, the effectiveness of dynamic interrupt balancing is justified by a maximum of 150 percent higher system utilization and 1.2 Mpps more throughput compared to the fixed affinitization approach in a simulated setup of unbalanced traffic load. [ABSTRACT FROM PUBLISHER]

We consider a communication system in which status updates arrive at a source node, and should be transmitted through a network to the intended destination node. The status updates are samples of a random process under observation, transmitted as packets, which also contain the time stamp to identify when the sample was generated. The age of the information available to the destination node is the time elapsed, since the last received update was generated. In this paper, we model the source-destination link using the queuing theory, and we assume that the time it takes to successfully transmit a packet to the destination is an exponentially distributed service time. We analyze the age of information in the case that the source node has the capability to manage the arriving samples, possibly discarding packets in order to avoid wasting network resources with the transmission of stale information. In addition to characterizing the average age, we propose a new metric, called peak age, which provides information about the maximum value of the age, achieved immediately before receiving an update. [ABSTRACT FROM AUTHOR]

Industrial cyber-physical systems (ICPS) bridge the physical factory floor and the cyber computational space by leveraging the emerging techniques, such as wireless sensor networks for ubiquitous connection and perception, where sensors are deployed to monitor and collect industrial data according to different timeliness requirements. Priority-aware schemes are often used to tackle the differentiated data packet collection. However, it is challenging to coordinate the multichannel access while meeting the priority-aware transmission requirement in ICPS. In this paper, we propose a separate design principle (SDP) for priority-aware packet collection. In SDP, the transmission of each priority class of sensors is separately scheduled by a multichannel superframe which fully uses the available channels. As a result, each time slot on each channel is repeatedly scheduled to sensors of different priorities by different superframes. Then, a priority-aware transmission mechanism is devised to coordinate the transmissions of different sensors in the predefined priority order. Simulation results show that for four priorities, SDP achieves as low as 16, 18, 23, and 36 % of the mean packet transmission delay of non-overlap TDMA scheduling for each priority class, respectively. Moreover, SDP greatly outperforms IEEE 802.15.4e protocol for packet collection with two priorities. We also demonstrate the feasibility of SDP based on the implementation of software-defined radios. [ABSTRACT FROM AUTHOR]

As a benefit of their inherent rateless nature, fountain codes constitute a favorable choice for protecting packet-based transmissions in the physical layer for wireless channels having varying quality. However, previous research has revealed that the performance of fountain codes substantially degrades as their block length is reduced. Three structural phenomena of the Tanner graph were identified by Mackay in the hard decoding of fountain codes on binary erasure channels (BECs), which may be referred to as having “no degree-one check nodes (CNs),” “no emerging degree-one CNs,” and “uncovered variable nodes (VNs).” In this paper, we explicitly analyzed how these structural phenomena influence their soft decoding algorithm. Furthermore, these phenomena are shown to be responsible for the high error floors when fountain codes are transmitted over noisy fading channels, particularly for the transmissions of short blocks. To eliminate the influence of these structural phenomena, we conceived a technique of generating a few specifically encoded bits with the aid of the associated Tanner graph. Simulation results have demonstrated that our improved Raptor (IRaptor) codes significantly reduce the packet loss ratio (PLR) of conventional fountain codes, despite imposing reduced low complexity. Finally, we conceive a novel adaptive hybrid automatic repeat request (HARQ) scheme based on a lookup table (LUT)-aided technique, which may adapt its coding rate for each transmission. Our simulation results demonstrated that the proposed IRaptor HARQ achieves a similar performance to the Long-Term Evolution (LTE) turbo-coded HARQ scheme or even outperforms the LTE arrangement for block length in excess of 1000 bits. [ABSTRACT FROM PUBLISHER]

The Third Generation Partnership Project (3GPP) has developed a new cellular standard based packet switching allowing high data rate, 100 Mbps in Downlink and 50 Mbps in Uplink, and having the flexibility to be used in different bandwidths ranging from 1.4 MHz up to 20 MHz, this standard is termed LTE (Long Term Evolution). Radio Resource Management (RRM) procedure is one of the key design roles for improving LTE system performance, Packet scheduling is one of the RRM mechanisms and it is responsible for radio resources allocation, However, Scheduling algorithms are not defined in 3GPP specifications. Therefore, it gets a track interests for researchers. In this paper we proposed a new LTE scheduling algorithm and we compared its performances with other well known algorithms such as Proportional Fairness (PF), Modified Largest Weighted Delay First (MLWDF), and Exponential Proportional Fairness (EXPPF) in downlink direction. The simulation results shows that the proposed scheduler satisfies the quality of service (QoS) requirements of the real-time traffic in terms of packet loss ratio (PLR), average throughput and packet delay. This paper also discusses the key issues of scheduling algorithms to be considered in future traffic requirements. [ABSTRACT FROM AUTHOR]

As a kernel function in network routers, packet classification requires the incoming packet headers to be checked against a set of predefined rules. There are two trends for packet classification: (1) to examine a large number of packet header fields, and (2) to use software-based solutions on multi-core general purpose processors and virtual machines. Although packet classification has been widely studied, most existing solutions on multi-core systems target the classic 5-field packet classification; it is not easy to scale up their performance with respect to the number of packet header fields. In this work, we present a decomposition-based packet classification approach; it supports large rule sets consisting of a large number of packet header fields. In our approach, range-tree and hashing are used to search the fields of the input packet header in parallel. The partial results from all the fields are represented in rule ID sets; they are merged efficiently to produce the final match result. We implement our approach and evaluate its performance with respect to overall throughput and processing latency for rule set size varying from 1 to 32 K. Experimental results on state-of-the-art 16-core platforms show that, an overall throughput of 48 million packets per second and a processing latency of 2,000 ns per packet can be achieved for a 32 K rule set. [ABSTRACT FROM AUTHOR]

All-optical logic is the key to future high speed and large capacity optical transmission, the realization of optical packet switching and optical computing, and it has a very profound influence on the development of future optical communication. A linear optical amplifier as a new type of semiconductor optical amplifier, which has a good gain characteristic, has better signal performance than a traditional semiconductor optical amplifier in the wavelength conversion. This article presents a numerical simulation model of all-optical logic XOR gate and its logic operation based on cross- -gain modulation of linear optical amplifier, and has also completed some of the basic logic operations, including AND, OR, NOT operations. [ABSTRACT FROM AUTHOR]

Geographic routing protocols greatly reduce the requirements of topology storage and provide flexibility in the accommodation of the dynamic behavior of mobile ad hoc networks. This paper presents performance evaluations and comparisons of two geographic routing protocols and the popular AODV protocol. The tradeoffs among the average path reliabilities, average conditional delays, average conditional numbers of hops, and area spectral efficiencies and the effects of various parameters are illustrated for finite ad hoc networks with randomly placed mobiles. This paper uses a dual method of closed-form analysis and simple simulation that is applicable to most routing protocols and provides a much more realistic performance evaluation than has previously been possible. Some features included in the new analysis are shadowing, exclusion and guard zones, distance-dependent fading, and interference correlation. [ABSTRACT FROM PUBLISHER]

This paper studies fundamental throughput and delay tradeoffs in cognitive radio systems with cooperative secondary users. We focus on randomized cooperative policies, whereby the secondary user (SU) serves either its own queue or the primary users (PU) relayed packets queue with certain service probability. The proposed policy opens room for trading the PU delay for enhanced SU delay, and vice versa, depending on the application QoS requirements. Towards this objective, the system's stable throughput region is characterized. Furthermore, the moment generating function approach is employed and generalized for our system to derive closed-form expressions for the average packet delay for both users. The accuracy of these expressions is validated through simulations. Analytical and simulation results reveal that the service probability can steer the system into prioritizing PU's traffic at the expense of SU's QoS, or vice versa, independently from the admission probability. Alternatively, the ability of the admission probability to control the throughput and delay at the PU or the SU depends on the selected value for the service probability as well as the channel conditions. Finally, it is shown how the service and admission probabilities could be used to achieve the desired QoS level to both PU and SU. [ABSTRACT FROM AUTHOR]

The recently proposed optical cut-through (OpCut) switch holds a great potential in achieving high energy efficiency, as it allows optical packets to cut through the switch in optical domain whenever possible, which avoids power-hungry O/E/O conversion. In the OpCut switch, to ensure in-order transmission, only optical Head-of-Line (HOL) packet of a switch flow, i.e., the stream of packets sharing the same input and output port, is allowed to cut-through the switch, and optical HOL packets are always prioritized over buffered HOL packets to achieve high cut-through ratio, which is measured by the portion of packets cutting through the switch optically. However, under such priority rule, switch flows with buffered packets are at the risk of starvation, and the OpCut switch fails to achieve 100 percent throughput for all admissible i.i.d. traffics due to the unfairness in packet scheduling. To address this two issues, in this paper we propose a delay threshold rule for packet scheduling, in which buffered packets with delays exceeding a preset delay threshold are prioritized over optical packets. In the meanwhile, the cut-through ratio is very low under heavily congested traffic due to maintaining packet order, whereas the Internet is designed to accommodate a certain degree of packet reorder, which is very common in practice due to path multiplicity. In this paper, we design a bounded-reorder packet scheduling algorithm that significantly increases the cut-through ratio of the OpCut switch while allowing a small degree of out-of-order transmission. Our extensive simulation results show that the energy efficiency of OpCut switch can be significantly improved with only a very small degree of packet reordering, which has little adverse impact on the network application performance. [ABSTRACT FROM PUBLISHER]

This study presents novel joint scheduling and link adaptation schemes (JSL) to maximise a weighted sum of throughputs of wireless links, while their possibly different minimum required throughputs and packet error rate (PER), average power and delay constraints are provisioned. Weights are assigned based on the importance and requirements of the links. Notable features of the proposed scheme in comparison with the previously presented utility based scheduling schemes are: (a) in the designed scheme a statistical bound is presented for the delay instead of average delay constraint or long term queuing delay behaviour, (b) designed transmission scheme utilises adaptive modulation and coding provisioning PER constraint and may be integrated with H automatic repeat request in data link layer to provide error free communication, (c) the presented schemes are designed based on imperfect signal-to-noise ratio (SNR) estimate of the links. In addition to an analytical approach, a JSL scheme based on sub-gradient projection (JSL-SP) is presented in which there is no need to have SNRs probability density functions. Numerical results demonstrate how the proposed JSL schemes outperforms the benchmark schemes and effectively meets various user's requirements. [ABSTRACT FROM AUTHOR]

A stabilization problem in a networked control system with packet dropouts is studied and dynamic output-feedback control is constructed. Predictive control approach is employed for obtaining plant state estimates at each step k. This eliminates the need for considering explicitly plant state switching when a packet dropout occurs. [ABSTRACT FROM AUTHOR]

The IEEE 1588 protocol has received recent interest as a means of delivering sub-microsecond level clock phase synchronization over packet-switched mobile backhaul networks. Due to the randomness of the end-to-end delays in packet networks, the recovery of clock phase from packet timestamps in IEEE 1588 must be treated as a statistical estimation problem. A number of estimators for this problem have been suggested in the literature, but little is known about the best achievable performance. In this paper, we describe new minimax estimators for this problem, that are optimum in terms of minimizing the maximum mean squared error over all possible values of the unknown parameters. Minimax estimators that utilize information from past timestamps to improve accuracy are also introduced. Simulation results indicate that significant performance gains over conventional estimators can be obtained via such optimum processing techniques. These minimax estimators also provide fundamental limits on the performance of phase offset estimation schemes. [ABSTRACT FROM AUTHOR]

Wireless sensor-actor networks (WSANs) are applicable in versatile domains ranging from very common to those which demand reliable actions in the event area. The unique characteristics of WSANs and the resource-constrained nature of the constituent sensor nodes give rise to design energy and delay efficient routing protocols. Many researchers have made considerable efforts to meet these challenges by designing energy and delay efficient protocols. In this paper, a comprehensive survey is presented on existing routing protocols for WSAN to analyze and list out their merits and demerits. The study broadly segregates the existing routing protocols into two categories i.e., cluster based and non-cluster based protocols. The cluster based protocols structure the physical network into virtual groups, whereas the non-cluster based protocols either use flooding or broadcasting mechanisms for communication. All the routing protocols under consideration have been simulated in a common simulation platform. Their performances are analyzed with respect to average end-to-end delay, packet delivery ratio, and average energy dissipation in the network individually. In addition, the best protocols among both the categories are compared to derive an overall conclusion. [ABSTRACT FROM AUTHOR]

Modeling and analysis of communication link duration in vehicular ad hoc networks (VANETs) is crucial as it directly affects many performance metrics such as packet delivery ratio, throughput and end-to-end delay. In this paper, we investigate the properties of communication link duration in one-dimensional VANETs for different fading channel conditions. We employ a stochastic microscopic mobility model that takes into account time dependence of the inter-vehicle distance. A discrete-time finite-state Markov chain with state dependent transition probabilities is used to model the inter-vehicle distance. The presence of fading channel conditions will introduce fluctuations in the received signal power. Even when the inter-vehicle distance between a given pair of vehicles is less than their transmission range, poor channel conditions may result in link failure. A modified distance transition probability matrix is derived to describe the combined effects of relative velocity among a pair of vehicles, link failure due to outage, and inter-vehicle distance. The probability distribution of the communication link duration is derived from the modified distance transition probability matrix. The analytical results obtained from the model are validated by extensive simulation results. [ABSTRACT FROM AUTHOR]

Despite the growing importance of packet switching systems, there is still a shortage of thorough analyses of VoIP transmission effect on speech and speaker recognition performance. Voice over IP transmission systems use packet switching. There is no guarantee of delivery. The main disadvantage of VoIP is a packet loss which has a major impact on the performance experienced by the users of the network. There are several techniques to mask the effects of a packet loss, referred to as packet loss concealment. In this study, the effect of voice transmission over IP on automatic speaker verification system performance was investigated. The analyzed system was based on MAP-EM-GMM modelling methods. Four various speech codecs of H.323 standard were investigated with special emphasis placed on the packet loss phenomenon and various packet loss concealment techniques. [ABSTRACT FROM AUTHOR]

We present a new data acquisition system under development for the next upgrade of the LHCb experiment at CERN. We focus in particular on the design of a new common readout board, the PCIe40, and on the viability of PCI-Express as an interconnect technology for high speed readout. We describe a new high-performance DMA controller for data acquisition, implemented on an FPGA, coupled with a custom software module for the Linux kernel. Lastly, we describe how these components can be leveraged to achieve a throughput of 100 Gbit/s per readout board. [ABSTRACT FROM AUTHOR]

Reducing the NoC power is critical for scaling up the number of nodes in future many-core systems. Most NoC designs adopt packet-switching to benefit from its high throughput and excellent scalability. These benefits, however, come at the price of the power consumption and latency overheads of routers. Circuit-switching, on the other hand, enjoys a significant reduction in power and latency of communication by directing data over pre-established circuits, but the relatively large circuit setup time and low resource utilization of this switching mechanism is often prohibitive. In this paper, we address one of the major problems of circuit-switching, i.e. the circuit setup time overhead, by an efficient and fast algorithm based on the time-division multiplexing scheme. We then further improve the performance by reserving circuits for anticipated messages, and hence completely hide circuit setup time. To address the low resource utilization problem, we integrate the proposed circuit-switching into a packet-switched NoC and use unused circuit resources to transfer packet-switched data. Evaluation results show considerable reduction in NoC power consumption and packet latency. [ABSTRACT FROM AUTHOR]

Tail-biting codes are efficient for short data packets by eliminating the rate loss in conventional known-tail codes. The existing maximum-likelihood (ML) decoding algorithms, such as the Viterbi heuristic ML decoder (VH ML decoder) and the trap detection-based ML decoder (TD-ML decoder), have to visit each state of the tail-biting trellis at least once. The decoding efficiency of these decoding algorithms can be improved further. In this paper, we propose an ML decoder for tail-biting trellises with bounded searches (BSs). We first perform a unidirectional bounded searching algorithm to estimate the lower bound of path metric of tail-biting paths on each sub-tail-biting trellis and exclude impossible candidates of starting states. In the second phase, a bidirectional searching algorithm is applied to find the ML tail-biting (MLTB) path on the survivor sub-tail-biting trellises. The proposed algorithm exhibits lower decoding complexity floor than other existing algorithms on tail-biting trellis. Simulation results for the (24, 12, 8) Golay codes and Eb/N0=\5\ \dB show that, for the proposed ML decoder, the average number of visited states per decoded bit is less than 2, whereas the average number of visited states per decoded bit is more than 12 for the VH ML decoder. [ABSTRACT FROM PUBLISHER]

We consider a server serving a time-slotted queued system of multiple packet-based flows, where not more than one flow can be serviced in a single time slot. The flows have exogenous packet arrivals and time-varying service rates. At each time, the server can observe instantaneous service rates for only a subset of flows (selected from a fixed collection of observable subsets) before scheduling a flow in the subset for service. We are interested in queue length aware scheduling to keep the queues short. The limited availability of instantaneous service rate information requires the scheduler to make a careful choice of which subset of service rates to sample. We develop scheduling algorithms that use only partial service rate information from subsets of channels, and that minimize the likelihood of queue overflow in the system. Specifically, we present a new joint subset-sampling and scheduling algorithm called Max-Exp that uses only the current queue lengths to pick a subset of flows, and subsequently schedules a flow using the Exponential rule. When the collection of observable subsets is disjoint, we show that Max-Exp achieves the best exponential decay rate, among all scheduling algorithms that base their decision on the current (or any finite past history of) system state, of the tail of the longest queue. To accomplish this, we employ novel analytical techniques for studying the performance of scheduling algorithms using partial state, which may be of independent interest. These include new sample-path large deviations results for processes obtained by non-random, predictable sampling of sequences of independent and identically distributed random variables. A consequence of these results is that scheduling with partial state information yields a rate function significantly different from scheduling with full channel information. In the special case when the observable subsets are singleton flows, i.e., when there is effectively no a priori channel state information, Max-Exp reduces to simply serving the flow with the longest queue; thus, our results show that to always serve the longest queue in the absence of any channel state information is large deviations optimal. [ABSTRACT FROM AUTHOR]

The article discusses the development of a Packet Transport Multiplexer (PTM) link system by Nippon Telegraph and Telephone Corporation (NTT) Network Service Systems Laboratories. Topics explored include the integration of signal degradation detection technology in the PTM, the possible use of this system for addressing Internet Protocol (IP) and public switched telephone network (PSTN)-related traffic, and the energy consumption expected from the PTM.

Rate adaptation technologies aim at establishing a linear relationship between power consumption and traffic load in packet networks. They rely on power profiles of network elements, which map system configurations and traffic loads onto power consumption levels, for the selection of network resources to place into low-power states and to identify new system designs with high power-saving yields. We introduce a methodology for profiling the power consumption of network systems that reconciles modeling accuracy with cost containment and rapidity in the preparation and execution of power measurements. We apply the methodology to network systems from multiple vendors and find it capable of delivering a clear message: the power savings enabled by protocol and system software upgrades that support demandtimescale rate adaptation are worthwhile, but also largely inferior to those attainable with a new generation of hardware platforms that pervasively deploy packet-timescale rate adaptation. [ABSTRACT FROM PUBLISHER]

A new link layer protocol, quality of service hybrid multi channel protocol (QoS-HMCP), that takes into account the need for QoS support in multi-channel multi-interface wireless mesh networks (MCMI-WMNs) is proposed in this paper. QoS-HMCP protocol retains most properties of enhanced distributed channel access (EDCA) mechanism, defined by the 802.11 standard, as well as the basic mechanisms of HMCP protocol. To achieve good network performances with QoS-HMCP protocol in MCMI network, it was necessary to precisely define the channel coordination and procedure for the medium competition of EDCA functions (EDCAFs) after the expiration of interval of time within which a particular EDCAF has the right to initiate data exchange sequences onto the wireless medium-transmission opportunity. Taking into consideration the previously defined conditions, four versions of QoS-HMCP protocol are proposed in this paper. These versions were compared with each other and with basic HMCP with regard to the throughput of user data and delay through the network. The four versions of the QoS-HMCP protocol, multi channel routing (MCR) protocol and chosen metric were implemented in Glomosim simulator. The results have shown that implementation of QoS-HMCP protocol in MCMI-WMN resulted in a very small delay for voice and video traffic, while low-priority traffic categories (best effort and background) were still able to access the media. [ABSTRACT FROM AUTHOR]

In this paper, we propose E-STAR for establishing stable and reliable routes in heterogeneous multihop wireless networks. E-STAR combines payment and trust systems with a trust-based and energy-aware routing protocol. The payment system rewards the nodes that relay others’ packets and charges those that send packets. The trust system evaluates the nodes’ competence and reliability in relaying packets in terms of multi-dimensional trust values. The trust values are attached to the nodes’ public-key certificates to be used in making routing decisions. We develop two routing protocols to direct traffic through those highly-trusted nodes having sufficient energy to minimize the probability of breaking the route. By this way, E-STAR can stimulate the nodes not only to relay packets, but also to maintain route stability and report correct battery energy capability. This is because any loss of trust will result in loss of future earnings. Moreover, for the efficient implementation of the trust system, the trust values are computed by processing the payment receipts. Analytical results demonstrate that E-STAR can secure the payment and trust calculation without false accusations. Simulation results demonstrate that our routing protocols can improve the packet delivery ratio and route stability. [ABSTRACT FROM AUTHOR]

Maximising the tag reading rate of a reader is one of the most important design objectives in radio frequency identification (RFID) systems as it is inversely proportional to the time required to completely read all the tags within the reader's radio field. To this end, numerous techniques have been independently suggested so far and they can be broadly categorised into pure advancements in the link-layer tag anti-collision protocols and pure advancements in the physical-layer RF signal reception model. This study shows by rigorous mathematical analysis and Monte-Carlo simulations that how those two independent approaches can be coupled to maximise the tag reading efficiency in an RFID system, considering a slotted Aloha-based dynamic link-layer anti-collision protocol at tags and a multi-packet reception capable RF reception model at the reader. [ABSTRACT FROM AUTHOR]

This paper proposes a real-time data compression and adapted protocol technique for wide-area measurement systems (WAMS). The compression algorithm combines exception compression (EC) with swing door trending (SDT) compression. The compression logic is designed to perform this algorithm in real time. Selection of compression parameters and data reconstruction are presented. An adapted protocol is introduced by improving the format of data frames defined by IEEE standard C37.118 for compressed data packets. The proposed compression technique and protocol were applied to the phasor measurement units (PMUs) of a hydropower plant in Guizhou Power Grid in Southwest China. A low-frequency oscillation incident was recorded by this technique. The raw, compressed and reconstructed data were analyzed to verify the compression and determine the accuracy of the proposed technique. Also, the wavelet-based data compression, the standalone EC and SDT are compared with the proposed compression technique. Our results demonstrated that this compression can reach the compression ratios in the range of 6 to 11. Also, this compression and adapted protocol technique can reduce the size of data packets by approximately 75% with high accuracy in both dynamic and steady states. [ABSTRACT FROM PUBLISHER]

In this contribution, we propose and study a bufferaided opportunistic routing (BOR) scheme, which combines the benefits of both opportunistic routing and multihop diversity (MHD) aided transmissions. It was conceived for a buffer-aided three-node network (B3NN) composed of a source node (SN), a buffer-aided relay node (RN) and a destination node (DN). In this network, there are three channels namely the SN-RN, RN-DN and SN-DN channels. The key motivation is that we are aiming for activating the specific channels requiring a recuded energy dissipation. In order to study this problem, a three-dimensional (3D) transmission activation probability space (TAPS) is proposed, which is divided into four regions representing each of the three channels plus an outage region. In a specific time slot (TS), the instantaneous channel fading values may be directly mapped to a specific point in this 3D channel space. The BOR scheme then relies on the position of this point to select the most appropriate channel for its transmission. Both the energy dissipation and the outage probability (OP) are investigated for transmission in this network. The results show that when the system is operated at a normalized throughput of 0.4 packet/TS, the energy dissipation was reduced by 24.8% to 77.6% compared to three different benchmark schemes. Alternatively, our technique is capable of reducing the OP by 89.6% when compared to conventional opportunistic routing. As in all buffer-aided system, the performance improved with the cost of higher packet delay, which is also studied. [ABSTRACT FROM PUBLISHER]