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Mobile Ad hoc Network (MANET) is a type of Ad hoc network. General properties of MANET open the network to various security threats. Network layer-based Active attacks are widespread and destructive. Available security solutions contain complex calculations. Therefore, the objective of this research is to propose a lightweight security mechanism to enhance the security of data communications between source and destination nodes in a MANET from network layer-based active attack. Blackhole is used as a network layer-based Active attack. The network performance is evaluated using Packet Delivery Ratio (PDR), Average End-to-End Delay (AEED), Throughput, and Simulation Processing Time at Intermediate Nodes (SPTIN). The controller network was used to compare the performance of each network. During the experiment due to the impact of the blackhole attack, compared to the controller network, the PDR was found to be 0.28%, AEED was infinity and Throughput was 0.33%. The performance of the proposed security mechanism was compared with that of the controller network, and the values of PDR, AEED, Throughput, and SPTIN were found to be 98.0825%, 100.9346%, 99.9988%, and 96.5660%, respectively. The data packet delivery ratio was 100.00% compared to that of the controller network. The network that was affected by a blackhole attack showed a higher amount of ADDR than the controller network and the lowest amount of PDR. The network that was affected by the blackhole showed underperformance compared to the controller network. The proposed security mechanism performs well in PDR, AEED, and Throughput compared to the controller network. The AEED and SPTIN values prove that the proposed solution is free from complex calculations. The scope of the solution can be expanded into a lightweight Intruder Detection System to handle different types of security attacks in MANETs. [ABSTRACT FROM AUTHOR]

Internet of Things (IoT) is the new research paradigm which has gained a great significance due to its widespread applicability in diverse fields. Due to the open nature of communication and control, the IoT network is more susceptible to several security threats. Hence the IoT network requires a trust aware mechanism which can identify and isolate the malicious nodes. Trust Sensing has been playing a significant role in dealing with security issue in IoT. A novel a Light Weight Clustered Trust Sensing (LWCTS) model is developed which ensures a secured and qualitative data transmission in the IoT network. Simulation experiments are conducted over the proposed model and the performance is compared with existing models. The obtained results prove the effectiveness when compared with existing approaches. [ABSTRACT FROM AUTHOR]

We present nonasymptotic upper and lower bounds on the maximum coding rate achievable when transmitting short packets over a Rician memoryless block-fading channel for a given requirement on the packet error probability. We focus on the practically relevant scenario in which there is no a priori channel state information available at the transmitter or at the receiver. An upper bound built upon the min–max converse is compared with two lower bounds: the first one relies on a noncoherent transmission strategy in which the fading channel is not estimated explicitly at the receiver and the second one employs pilot-assisted transmission (PAT) followed by maximum-likelihood channel estimation and scaled mismatched nearest-neighbor decoding at the receiver. Our bounds are tight enough to unveil the optimum number of diversity branches that a packet should span so that the energy per bit required to achieve a target packet error probability is minimized, for a given constraint on the code rate and the packet size. Furthermore, the bounds reveal that noncoherent transmission is more energy efficient than PAT, even when the number of pilot symbols and their power is optimized. For example, in Rayleigh fading, for the case when a coded packet of 168 symbols is transmitted using a channel code of rate 0.48-bits/channel use, over a block-fading channel with block size equal to eight symbols, PAT requires an additional 1.2 dB of energy per information bit to achieve a packet error probability of 10−3 compared with a suitably designed noncoherent transmission scheme. Finally, we devise a PAT scheme based on punctured tail-biting quasi-cyclic codes and ordered-statistics decoding, whose performance is close (1-dB gap at 10−3 packet error probability) to the ones predicted by our PAT lower bound. This shows that the PAT lower bound provides useful guidelines on the design of actual PAT schemes. [ABSTRACT FROM AUTHOR]

This paper is concerned with information fusion estimation problems for multi-sensor networked systems with random packet losses. Based on a recent developed compensation strategy of packet losses that the predictor of lost observation is used as the observation when a packet is lost, centralized fusion estimators (CFEs), including the filter, predictor and smoother, in the linear unbiased minimum variance (LUMV) sense are first designed by completing square method. Then, local optimal estimators are designed for each sensor subsystem. Estimation error cross-covariance matrices between any two local estimators are derived. Based on local estimators and cross-covariance matrices, distributed fusion estimators (DFEs) are presented by using the matrix-weighted fusion estimation algorithm in the LUMV sense. Compared with the existing results with zero-input and hold-input compensations, the proposed algorithms with prediction compensations can obviously improve the estimation accuracy. Two simulation examples show their effectiveness. [ABSTRACT FROM AUTHOR]

This paper focuses on the past, present, and future of the Internet. It briefly overviews the first 40‐year development of the Internet, including the four‐node packet switched net, the packet radio program, the stanford research institute packet radio van, ARPANET, transmission control protocol/internet protocol, and National Science Foundation Network. It then elaborates the next 40‐year development of the Internet, discussing its unfinished business in seven major aspects of technology development (e.g., establishing various standards and developing reliable and updateable software) and five aspects of technology consequences (e.g., Internet of things and artificial intelligence/machine learning, and misinformation, disinformation). It concludes with four key messages, stressing that the Internet will continue to evolve as an open technology environment. [ABSTRACT FROM AUTHOR]

In this work, we consider the optimal sensory data scheduling of multiple process. A remote estimator is deployed to monitor S independent linear time-invariant processes. Each process is measured by a sensor, which is capable of computing a local estimate and sending its local state estimate wrapped up in packets to the remote estimator. The lengths of the packets are different due to different dynamics of each process. Consequently, it takes different time durations for the sensors to send the local estimates. In addition, only a portion of all the sensors are allowed to transmit at each time due to bandwidth limitation. We are interested in minimizing the sum of the average estimation error covariance of each process at the remote estimator under such packet transmission and bandwidth constraints. We formulate the problem as an average cost Markov decision process (MDP) over an infinite horizon. We first study the special case when S = 1 and find that the optimal scheduling policy always aims to complete transmitting the current estimate. We also derive a sufficient condition for boundedness of the average remote estimation error. We then study the case for general S . We establish the existence of a deterministic and stationary policy for the optimal scheduling problem. We find that the optimal policy has a consistent property among the sensors and a switching type structure. A stochastic algorithm is designed to utilize the structure of the policy to reduce computation complexity. Numerical examples are provided to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

This paper investigates simultaneous wireless information and power transfer (SWIPT) in the ad hoc network, where access points (APs) with multiple antennas can transfer energy as well as information using a common spectrum resource. The receiving nodes decode the incoming information data (information decoding, ID) and/or harvest the RF energy (energy harvesting, EH), where two different receiving node architectures—time switching (TS) and power splitting (PS)—are considered. By using a stochastic geometry approach, we aim to analyze the transmission capacity and the harvested energy per unit area as performance measures of the SWIPT in the ad hoc network. From the analytical results, we can derive the optimal node densities of ID nodes and EH nodes for TS architectures and, furthermore, optimize the power splitting ratio jointly with the node density for the PS architectures such that the harvested energy per unit area is maximized when the target transmission capacity is given. The proposed node density optimization gives us a useful insight into the design of SWIPT-based ad hoc network, where we can show how densely the APs/nodes can be deployed in a given area and furthermore, find that the ad hoc network with PS receiving nodes outperforms that with TS receiving nodes for a large target transmission capacity, and vice versa. [ABSTRACT FROM AUTHOR]

User distribution in ultradense networks (UDNs) plays a crucial role in affecting the performance of UDNs due to the essential coupling between the traffic and the service provided by the networks. Existing studies are mostly based on the assumption that users are uniformly distributed in space. The nonuniform user distribution has not been widely considered despite that it is much closer to the real scenario. In this paper, radiation and absorbing model (R&A model) is first adopted to analyze the impact of the nonuniformly distributed users on the performance of 5G UDNs. Based on the R&A model and queueing network theory, the stationary user density in each hot area is investigated. Furthermore, the coverage probability, network throughput, and energy efficiency are derived based on the proposed theoretical model. Compared with the uniformly distributed assumption, it is shown that nonuniform user distribution has a significant impact on the performance of UDNs. [ABSTRACT FROM AUTHOR]

Simultaneous wireless information and power transfer (SWIPT) is a promising technique to transfer information and energy signals at the same time and frequency utilizing the multi-input multi-output (MIMO) beamforming. In this correspondence, the SWIPT MIMO technique is realized in the multicell cooperative transmission environment, namely, network-MIMO where the signals from different base-stations (BSs) to all the mobile users can be jointly designed based on the perfect knowledge of the downlink channels and transmit messages. To develop an efficient precoding matrix, we adopt the weighted minimum mean squared error criterion that can be generally applied to the sum-utility maximization of each receiver's information rate. In the SWIPT network-MIMO, a number of constraints arise including the power constraint at each BS, namely, the per-BS power constraints and the energy constraint at the energy harvesting users, which makes the problem challenging. A main contribution of the paper is to propose a simple bisection-based algorithm that finds a solution. The efficiency of the proposed algorithm is verified via computer simulation results. [ABSTRACT FROM AUTHOR]

Absract Cognitive Radio Sensor Network (CRSN) is a promising solution to overcome spectrum under-utilization and spectrum scarcity in a resource-constrained Wireless Sensor Network (WSN). In CRSN, TCP has to cope with a new type of packet loss due to the Primary Users (PUs) arrival, known here as the secondary user blocking loss (SBL). In this paper the SBL is modelled by a discrete-time Markov Chain (DTMC). A new congestion control algorithm, known here as T-CRSN is proposed based on this model that differentiates the packet loss due to the PU activity from the congestion loss. The numerical evaluation of the model is verified using the COGNS, a NS2 simulation based framework for cognitive radio sensor networks. Furthermore, the proposed algorithm is compared with some of the recently proposed transport protocols, i.e. TCP Friendly Rate Control for cognitive radio (TFRC-CR), Opportunistic Hybrid Transport Protocol (OHTP) and TCP Reno to comparatively demonstrate the efficiency of our proposed algorithm. [ABSTRACT FROM AUTHOR]

The characterization of the performance of wireless devices plays a significant role in developing radio products that meet the demands of the latest standards and deliver a satisfying user experience. With current standard total isotropic sensitivity (TIS) measurement, the transmitters are set to work at their maximum transmission power level. However, the standard TIS test procedure is unable to accurately reflect a receiver's performance because in actual usage transmitters are rarely working at their maximum power level. In measurements, different kinds of devices hold different maximum power levels. The measured radio sensitivity depends on the instantaneous local temperature of the radio, and the local temperature depends on the heat generation (power levels), the heat dissipation, and time. So the power levels and the thermal conditions could affect their radio sensitivity and, hence, the TIS. With standard TIS methods, the maximum power level and the radio's thermal condition cause ambiguity in the measurements. However, this paper proposes a new objective TIS method. With this new TIS method, the measured TIS is a function of the transmitter power level at its thermally stable condition. The proposed method resolves the ambiguity of the TIS measurement. [ABSTRACT FROM PUBLISHER]

There is an urgent need for substantially enhancing random access schemes to be able to support native massive machine-to-machine communications in the next generation wireless systems. Lately, contention resolution diversity slotted ALOHA (CRDSA) and its variants have contributed to a drastic improvement in throughput compared with the traditional slotted ALOHA protocols. In this paper, we further enhance the CRDSA flexibility and performance along different physical layer dimensions. Based on simulation results, we show that there is still room for improvement in terms of throughput and, using heuristic methods, we find an optimized distribution of the packets power that is entering the demodulator for an additive white Gaussian noise channel. Applying this power distribution, which is easy to implement at the terminal in open loop and in a decentralized manner, is shown to achieve significantly enhanced performance. By introducing multi-frequency CRDSA, a drastic reduction in the terminal’s peak power requirement is attained. Furthermore, we investigate spread spectrum CRDSA, which improves the robustness of the scheme against irresolvable packet collisions allowing for enhanced energy efficiency. To support the work presented herein, we have developed a computationally efficient yet accurate methodology for estimating CRDSA performance, a novel approximate centrally coordinated CRDSA achievable sum rate analysis accounting for modulation and forward error correction constraints, as well as a more accurate loop probability analysis. [ABSTRACT FROM PUBLISHER]

Scatter radio, i.e., communication by means of reflection, has been recently proposed as a promising technology for low-power wireless sensor networks (WSNs). Specifically, this paper offers noncoherent receivers in scatter radio frequency-shift keying, for either channel-coded or uncoded scatter radio reception, in order to eliminate the need for training bits of coherent schemes (for channel estimation) at the packet preamble. Noncoherent symbol-by-symbol and sequence detectors based on hybrid composite hypothesis test (HCHT) and generalized likelihood-ratio test, for the uncoded case and noncoherent decoders based on HCHT, for small block-length channel codes, are derived. Performance comparison under Rician, Rayleigh, or no fading, taking into account fixed energy budget per packet is presented. It is shown that the performance gap between coherent and noncoherent reception depends on whether channel codes are employed, the fading conditions (e.g., Rayleigh versus Rician versus no fading), as well as the utilized coding interleaving depth; the choice of one coding scheme over the other depends on the wireless fading parameters and the design choice for extra diversity versus extra power gain. Finally, experimental outdoor results at 13-dBm transmission power corroborate the practicality of the proposed noncoherent detection and decoding techniques for scatter radio WSNs. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate a coding strategy devised to increase the throughput in hybrid ARQ (HARQ) transmission over a block fading channel. In our approach, the transmitter jointly encodes a variable number of bits for the each round of HARQ. The parameters (rates) of this joint coding can vary and may be based on the negative acknowledgment provided by the receiver or, on the past (outdated) information about the channel states. These new degrees of freedom allow us to improve the match between the codebook and the channel states experienced by the receiver. The results indicate that gains obtained using the proposed cross-packet coding strategy are particularly notable for the large values of the throughput. In this region, the conventional HARQ fails to offer throughput improvement even if the number of transmission rounds is increased. We implement the proposed cross-packet HARQ using turbo codes, where we show that the theoretically predicted throughput gains materialize in practice; the implementation challenges are also discussed. [ABSTRACT FROM PUBLISHER]

Fountain coding is a valuable tool for multicast transmissions in half-duplex packet radio networks if it is supported by an adaptive transmission protocol that compensates for fluctuations in the propagation losses on the radio links. Our goal is to devise low-complexity packet-by-packet adaptive modulation and channel coding protocols that provide high throughput for a broad range of multicast channels and operate with limited feedback and no knowledge of the fade levels or even the probability distribution for the fading on the radio links. The only control information for the protocols is derived from simple receiver statistics that are obtained by the demodulators and channel decoders in the receiving radios. Performance results are presented for practical fountain coding with low-complexity adaptive modulation and channel coding. Results on ideal fountain coding with adaptive transmission based on hypothetical perfect channel-state information are employed as performance benchmarks. [ABSTRACT FROM AUTHOR]

Spectrum sensing (SS) is one of the key tasks in cognitive radio networks that is performed to get awareness about the usage of electromagnetic spectrum. It enables the secondary user (SU) to detect the presence/absence of primary user (PU) and plan its transmission strategy accordingly. The aim of SS is to detect the presence or absence of PU in a certain frequency band and allow or prevent the SU's transmission on the basis of sensing result. In this paper, a review on different SS techniques is presented in the context of PU detection. We mainly focus on non-cooperative SS methods used for the PU detection. PU is the incumbent user in cognitive radio networks, and its transmission should not be interrupted. Moreover, it can start its transmission at any time, so the SU has to sense a channel before starting its transmission and monitor the arrival of PU continuously as long as it utilizes the channel to avoid any interference. The PU detection techniques are further divided into five main categories i.e. energy, covariance matrix, cyclostationary feature, matched filter, and wavelet-based detection. We investigated different algorithms based on each of these categories from PU detection perspective and discussed its various issues and challenges. Moreover, a detail comparison of the approaches is provided in terms of detection mechanism, parameters used, advantages, limitations, and comments on each scheme. Similarly, the comparison of the approaches is studied in context of detection over different levels of signal-to-noise ratio. Finally, detail findings from the study are provided for future enhancement of the PU detection mechanisms. [ABSTRACT FROM AUTHOR]

Device-to-device (D2D) communications bring significant improvements of spectral efficiency by underlaying cellular networks. However, they also lead to a more deteriorative interference environment for cellular users, especially the users in severely deep fading or shadowing. In this paper, we investigate a relay-based communication scheme in cellular systems, where the D2D communications are exploited to aid the cellular downlink transmissions by acting as relay nodes with underlaying cellular networks. We modeled two-antenna infrastructure relays employed for D2D relay. The D2D transmitter is able to transmit and receive signals simultaneously over the same frequency band. Then we proposed an efficient power allocation algorithm for the base station (BS) and D2D relay to reduce the loopback interference which is inherent due to the two-antenna infrastructure in full-duplex (FD) mode. We derived the optimal power allocation problem in closed form under the independent power constraint. Simulation results show that the algorithm reduces the power consumption of D2D relay to the greatest extent and also guarantees cellular users' minimum transmit rate. Moreover, it also outperforms the existing half-duplex (HD) relay mode in terms of achievable rate of D2D. [ABSTRACT FROM AUTHOR]

Analytical methods are provided for use in performance evaluations, tradeoff studies, and preliminary designs of adaptive modulation and coding protocols that obtain their control information from practical sources. Our approach employs capacity limits and Markov chain models of fading to give analytical results on the throughput achieved by adaptive transmission in packet radio systems. The analytical methods replace simulations of the modem, iterative decoder, and time-varying fading channel. The amount of processor time required for protocol performance evaluations is decreased by several orders of magnitude. [ABSTRACT FROM PUBLISHER]

We propose a power-efficient transmission scheme for wireless sensor networks. In this scheme, the sensor nodes compress their corresponding source-relay channel state information (CSI) and transmit this compressed CSI sequence along with a selected subset of their received bits from the source, which we refer to as the good bits. We assume slowly varying fading channels between source and relays and analytically derive the compression rate of the CSI sequence. We then study the relay-fusion centre link and find an optimal threshold for our proposed scheme, based on the target bit error rate and the packet delivery ratio of the network. Combining the threshold optimization and the reliable bit transmission schemes, we study the total number of transmitted bits for our proposed system. We show that for slowly varying fading channels, our proposed scheme considerably reduces the number of transmitted bits, and consequently the transmission power of the relay nodes compared with a conventional scheme where all bits are transmitted to the fusion center. We also compare the performance of our proposed scheme with a special decode and forward (SDF) scheme previously introduced in the literature. In order to have a fair comparison, we modify the SDF scheme, such that the modified scheme includes the originally proposed SDF scheme as a special case. We provide detailed comparisons and discussions on the achieved bit error rate, energy efficiency, and feasibility of the proposed and the modified SDF schemes. [ABSTRACT FROM AUTHOR]

This paper tackles the classical problem of transmission rate allocation in satellite networks where fading may negatively impact communications. Within the framework of multiobjective programming (MOP), this paper introduces a transmission rate allocation criterion among Earth stations (ESs) called L_p-problem-based rate allocation (L_{p}RA). The allocations provided by L_{p}RA are representative of a compromise among the need of different performance metrics such as packet loss and transmission power (TP). This paper determines the condition for the existence and the value of a LpRA transmission rate allocation bound R^{\mathrm{bound}}, to which the transmission rate globally allocated by LpRA converges when the overall available transmission rate R\mathrm{TOT} tends to infinity. The performance analysis, which is carried out through simulations under different satellite channel conditions, is aimed at investigating LpRA features, at showing the existence of the rate bound and the advantages concerning the rate allocation given by using LpRA, and at comparing LpRA with two other schemes in the literature concerning allocated rate, packet loss rate, transmit power, and execution time. [ABSTRACT FROM AUTHOR]

A novel air-to-ground (ATG) communication system, which is based on adaptive modulation and beamforming enabled by automatic dependent surveillance—broadcast (ADS-B) and multilateration techniques, is presented in this paper. From an aircraft geolocation perspective, the proposed multilateration technique uses the time-difference-of-arrival (TDOA), angle-of-arrival (AOA), and frequency-difference-of-arrival (FDOA) features within the ADS-B signal to implement the hybrid geolocation mechanism. Moreover, this hybrid mechanism aims for the optimal selection of multilateration sensors to provide a precise aircraft geolocation estimate by minimizing the geometric dilution-of-precision (GDOP) metric and imparts significant resilience to the current ADS-B-based geolocation framework to withstand any form of attack involving aircraft impersonation and ADS-B message infringement. From an ATG communication perspective, the ground base stations can use this hybrid aircraft geolocation estimate to dynamically adapt their modulation parameters and transmission beampattern in an effort to provide a high-data-rate secure ATG communication link. Additionally, we develop a hardware prototype that is highly accurate in estimating AOA data and facilitating TDOA and FDOA extraction associated with the received ADS-B signal. This hardware setup for the ADS-B-based ATG system is analytically established and validated with commercially available universal software-defined radio peripheral units. This hardware setup displays 1.5° AOA estimation accuracy, whereas the simulated geolocation accuracy is approximately 30 m over 100 nautical miles for a typical aircraft trajectory. The adaptive modulation and beamforming approach assisted by the proposed GDOP-minimization-based multilateration strategy achieves significant enhancement in throughput and reduction in packet error rate. [ABSTRACT FROM AUTHOR]

We study the repair problem in distributed storage systems where storage nodes are connected through packet erasure channels and some nodes are dedicated to repair [termed as dedicated-for-repair (DR) storage nodes]. We first investigate the minimum required repair-bandwidth in an asymptotic setup, in which the stored file is assumed to have an infinite size. The result shows that the asymptotic repair-bandwidth over packet erasure channels with a fixed erasure probability has a closed-form relation to the repair-bandwidth in lossless networks. Next, we show the benefits of DR storage nodes in reducing the repair bandwidth, and then we derive the necessary minimal storage space of DR storage nodes. Finally, we study the repair in a nonasymptotic setup, where the stored file size is finite. We study the minimum practical-repair-bandwidth, i.e., the repair-bandwidth for achieving a given probability of successful repair. A combinatorial optimization problem is formulated to provide the optimal practical-repair-bandwidth for a given packet erasure probability. We show the gain of our proposed approaches in reducing the repair-bandwidth. [ABSTRACT FROM AUTHOR]

In this paper, we study the data exchange problem, where a set of users is interested in gaining access to a common file, but where each has only partial knowledge about it as side-information. Assuming that the file is broken into packets, the side-information considered is in the form of linear combinations of the file packets. Given that the collective information of all the users is sufficient to allow recovery of the entire file, the goal is for each user to gain access to the file, while minimizing some communication cost. We assume that the users can communicate over a noiseless broadcast channel, and that the communication cost is a sum of each user’s cost function over the number of bits it transmits. For instance, the communication cost could simply be the total number of bits that needs to be transmitted. In the most general case studied in this paper, each user can have any arbitrary convex cost function. We provide deterministic, polynomial-time algorithms (in the number of users and packets), which find an optimal communication scheme that minimizes the communication cost. To further lower the complexity, we also propose a simple randomized algorithm inspired by our deterministic algorithm, which is based on a random linear network-coding scheme. [ABSTRACT FROM AUTHOR]

To keep up with the rapid development of railway and meet the high demand for communication business in China, Global System for Mobile Communications-Railway (GSM-R) based on General Packet Radio Service (GPRS) ahead of Europe has been developed. However, the current data communication mode of GPRS using TCP/IP has some disadvantages, such as poor mobility, lack of security etc. For this reason, there are some problems for GSM-R, like handover, which makes communication service quality undesirable. Named Data Networking focuses on named data, adopts data-facing communication mode, and does not care where the contents are stored but the contents themselves. It can effectively solve the problems caused by TCP/IP. In this paper, a new high-speed railway communication system with Named Data Networking (NDN) named NDN-GSM-R is proposed. Two simulations, called transmission interference time and end-to-end transmission delay of NDN-GSM-R, have been conducted. The simulation results show that NDN-GSM-R has better performance in high-speed mobile communication environment and can make up the insufficiency of the current GSM-R based on TCP/IP framework. [ABSTRACT FROM AUTHOR]

This paper proposes an approach to improving the efficiency of packet data transmission in computer radio networks on the basis of implementation of a complex of algorithms for operative compact data encoding and protection. The algorithms are implemented by subscribers of a network and provide the encryption and noise protection of binary sequences in noisy channels and formation and adaptive transmission of highly informative and noise-immune data packets consisting of interval code-signal sequences with a variable base. [ABSTRACT FROM AUTHOR]

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]

We examine the integration of adaptive modulation and channel coding protocols with fountain coding in a packet radio system. We present three modes of operation for the adaptive transmission system, each of which adapts the channel code in a way that accommodates the fixed-length packets produced by the fountain encoder. Each mode works with the fountain coding system to mitigate the effects of time-varying fading on the radio links and provide high throughput. [ABSTRACT FROM PUBLISHER]

In this article, we discuss full duplex for heterogenous networks that accommodate the coexistence of device-to-device communications. The short link distance and lower transmit power of device-to-device communications make them excellent candidates to exploit full duplex inband transmission. By incorporating power allocation for self-interference cancellation based on antenna isolation, analog cancellation, and digital cancellation, full-duplex device-to-device, FD-D2D, nodes can potentially improve spectrum efficiency in HetNets. We provide a comprehensive overview on FD-D2D communications in Het-Nets. Additionally, we identify several challenges, provide potential solutions to interference mitigation based on power control, beamforming, and resource scheduling, and further discuss applications of FD in 5G networks. [ABSTRACT FROM PUBLISHER]

Network information broadcasting in narrow band self-organizing networks is bounded by the low data transmission rate in such networks. Frequent broadcasting of network information leads to losing it due to collisions, which increases the station notification time about changes in the network. Rare broadcasting of network information reduces the probability of packet collisions but station notification time about changes also increases. For a given message broadcasting period the collision probability may be reduced if stations send out only changes in the network information. In this work, we introduce an original criterion for the efficiency of network information broadcasting that takes into account its relevance and propose a method to analytically estimate this criterion. With the introduced criterion, we perform efficient tuning of parameters for network information broadcasting parameters and perform a comparative analysis of two approaches: broadcasting complete network information and broadcasting incremental changes in the network information. [ABSTRACT FROM AUTHOR]

Reducing electricity consumption and integrating renewable power generation sources represent two of the main drivers of the so-called Smart Grid. Machine-to-Machine (M2M) communications will play a key role on making such a Smart Grid a reality, since they will enable the required bidirectional real-time bulk information exchange. However, communications for the Smart Grid present specific requirements from both technical and economic perspectives, so it is crucial to evaluate how existing communication architectures and technologies meet them before undertaking the important investments needed to deploy this kind of infrastructure on a large scale. The main goal of this paper is to evaluate, from different perspectives, the core M2M communications infrastructure of a platform designed to reduce electricity consumption and integrate renewable generation at residential level. Such a communications infrastructure is fully based on widely deployed wireless communications technologies such as IEEE 802.11 and General Packet Radio Service (GPRS). Notably, the paper assesses the operational costs of using different security solutions in the GPRS segment and the performance of the selected communications technologies based on different metrics (goodput, in the case of IEEE 802.11, and transmission time, in the case of GPRS). [ABSTRACT FROM AUTHOR]

This paper studies how to select a path with the minimum expected end-to-end delay (EED) in a multiradio multichannel (MR-MC) wireless mesh network. While the existing studies mainly focus on the packet transmission delay due to medium access control (MAC), our new EED metric further takes into account the queuing delay at the MAC layer. In particular, in the MR-MC context, we develop a generic iterative approach to compute the multiradio achievable bandwidth (MRAB) for a path, taking the impact of inter-/intraflow interference and space/channel diversity into consideration. The MRAB is then combined with the EED to form the metric weighted end-to-end delay (WEED). As a byproduct of MRAB, a channel diversity coefficient is defined to quantitatively represent the channel diversity for a given path. Moreover, we design and implement a distributed WEED-based routing protocol for MR-MC wireless networks by extending the well-known AODV protocol. Extensive simulation results are presented to demonstrate the performance of EED/WEED-based routing, with comparison to some existing well-known routing metrics. [ABSTRACT FROM AUTHOR]

Our protocol adapts the error-control code and spreading factor on the links of a direct-sequence (DS) spread-spectrum packet radio network. The radios employ half-duplex transmission, and they operate with fixed power and bandwidth. There are no base stations, access points, or other infrastructure, and the protocol requires no power measurements or channel estimates. We compare the protocol with hypothetical ideal protocols that have perfect channel state information and maximize the throughput for each packet transmission. [ABSTRACT FROM AUTHOR]

A low-complexity protocol is described and evaluated for adaptation of the modulation and coding for multicast transmission in half-duplex packet radio networks. The adaptive multicast transmission protocol is designed to compensate for changes in propagation conditions that occur from packet to packet during a session with one sender and multiple receivers. The protocol relies on simple receiver statistics to obtain the control information for adapting the modulation and coding, and it also provides scheduling to avoid collisions among acknowledgments from the receivers. The throughput provided by the protocol is compared with performance results for hypothetical ideal adaptive multicast transmission protocols that are given perfect channel state information. We illustrate the importance of adaptive modulation and channel coding in systems that employ fountain coding for packet erasure correction. [ABSTRACT FROM AUTHOR]

The reader-to-reader collision problem represents a research topic of great recent interest for the radio frequency identification (RFID) technology. Among the state-of-the-art anticollision protocols, the ones that provide high throughput often have special requirements, such as extra hardware. This study investigates new high throughput solutions for static RFID networks without additional requirements. In this paper, two contributions are presented: a new configuration, called Killer, and a new protocol, called distributed color noncooperative selection (DCNS). The proposed configuration generates selfish behavior, thereby increasing channel utilization and throughput. DCNS fully exploits the Killer configuration and provides new features, such as dynamic priority management, which modifies the performance of the RFID readers when it is requested. Simulations have been conducted in order to analyze the effects of the innovations proposed. The proposed approach is especially suitable for low-cost applications with a priority not uniformly distributed among readers. The experimental analysis has shown that DCNS provides a greater throughput than the state-of-the-art protocols, even those with additional requirements (e.g., 16 percent better than NFRA). [ABSTRACT FROM AUTHOR]

The resources especially energy in wireless sensor networks (WSNs) are quite limited. Since sensor nodes are usually much dense, data sampled by sensor nodes have much redundancy, data aggregation becomes an effective method to eliminate redundancy, minimize the number of transmission, and then to save energy. Many applications can be deployed in WSNs and various sensors are embedded in nodes, the packets generated by heterogenous sensors or different applications have different attributes. The packets from different applications cannot be aggregated. Otherwise, most data aggregation schemes employ static routing protocols, which cannot dynamically or intentionally forward packets according to network state or packet types. The spatial isolation caused by static routing protocol is unfavorable to data aggregation. To make data aggregation more efficient, in this paper, we introduce the concept of packet attribute, defined as the identifier of the data sampled by different kinds of sensors or applications, and then propose an attribute-aware data aggregation (ADA) scheme consisting of a packet-driven timing algorithm and a special dynamic routing protocol. Inspired by the concept of potential in physics and pheromone in ant colony, a potential-based dynamic routing is elaborated to support an ADA strategy. The performance evaluation results in series of scenarios verify that the ADA scheme can make the packets with the same attribute spatially convergent as much as possible and therefore improve the efficiency of data aggregation. Furthermore, the ADA scheme also offers other properties, such as scalable with respect to network size and adaptable for tracking mobile events. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient packet selection algorithm, called Weight Pick, for improving the efficiency of a network coding based multicast retransmission protocol in mobile communication networks. Unlike existing packet selection algorithms, Weight Pick introduces the concept of a dynamic combination number in performing network coding. Based on this concept, a base station dynamically determines the number of packets combined or encoded in a retransmission packet based on the current packet receiving status of users and the combination number for each retransmission packet can be different. In packet selection, Weight Pick attempts to find an encoding combination whose weight is not less than ( C − 1) for every user, where C is the combination number of that retransmission packet. Simulation results show that Weight Pick can significantly improve the retransmission performance as compared with existing packet selection algorithms in terms of both packet loss ratio and packet transmission delay. [ABSTRACT FROM AUTHOR]

Real-time monitoring allows the determination of the line state and the calculation of the actual rating value. The real-time monitoring systems measure sag, conductor tension, conductor temperature, or weather-related magnitudes. In this paper, a new ampacity monitoring system for overhead lines, based on the conductor tension, the ambient temperature, the solar radiation, and the current intensity is presented. The measurements are transmitted via general-packet radio service to a control center where a software program calculates the ampacity value. The system takes the creep deformation experienced by the conductors during their lifetime into account and calibrates the tension-temperature reference and the maximum-allowable temperature in order to obtain the ampacity. The system includes hardware implementation and remote-control software. [ABSTRACT FROM AUTHOR]

Abstract: This paper analyzes the performance of cooperative diversity wireless networks using amplify-and-forward relaying over independent, non-identical, Nakagami-m fading channels. We present a queuing model for performance analysis of go-back-N automatic repeat request (GBN-ARQ) protocols in wireless networks using dynamic radio link adaptation. Link adaptation technique allows multi-rate transmission which is assumed to be achieved through adaptive modulation and coding. We propose a Markov-based model, which encompasses the following aspects: (1) the transmission using amplify-and-forward cooperative diversity at the physical layer; (2) a flow control protocol, infinite transmitting buffers, and an ARQ-based error recovery mechanism at the radio link layer. The randomly changed feedback delay in cooperative diversity wireless networks is analyzed. The queuing problem is formulated as a GI/M/1 Markov chain where the exact queue length and delay statistics for the GBN-ARQ protocol can be obtained by using matrix geometric methods under random feedback delay values. We validate the analysis by simulation. The delay statistics obtained in this paper enables us to design wireless systems under statistical delay constraints and would be useful to predict the higher layer protocol performance. [Copyright &y& Elsevier]

This paper presents a novel approach to optimizing network packet transfer scheme through introducing a new method for on-demand chaotic noise injection strategy for the Broadcast Scheduling Problem (BSP). Packet radio networks have many applications, while finding an optimized scheduling to transmit data is proven to be a NP-hard problem. The objective of the proposed method is to find an optimal time division multiple access (TDMA) frame, based on maximizing the channel utilization. The proposed method benefits from an on-demand noise injection policy, which injects noise based on the status of neuron and its neighborhoods. The method is superior to other Noise Chaotic Neural Networks (NCNN) that suffer from blind injection policy. The experimental result shows that, in most cases, the proposed on-demand noise injection algorithm finds the best solution with minimal average time delay and maximum channel utilization. [ABSTRACT FROM AUTHOR]

SUMMARY A major challenge in packet-based optical networks is packet contention, which occurs when two or more packets are heading to the same output at the same time. To resolve contention in the optical domain, a fundamental approach is fiber delay-line (FDL) buffering, in which packets can be delayed for a fixed amount of time. In the literature, the performance of FDL buffering has been studied extensively. However, most existing works are based on an assumption that there is only one fiber per link in the network. In this paper, we address the architecture and performance of FDL buffers in packet-based asynchronous multifiber optical networks (PAMFONET), in which each link in the network may consist of multiple optical fibers. We propose a framework for FDL buffers in PAMFONET, in which we provide three essential architectures and corresponding packet scheduling policies. Extensive simulation results show that, with appropriate settings, the same number of FDLs can lead to better performance in multifiber networks than in single-fiber networks. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Rate control algorithms for commercial 802.11 devices strongly rely on packet losses for their adaptation. As a result, they give poor performance in dense networks because they are not able to distinguish packet losses related to channel error from packet losses due to collision. In this paper, we evaluate automatic rate adaptation algorithms in IEEE 802.11 dense networks. A certain number of works in the literature address this problem, but they demand modifications of the IEEE standard, or depend on some special feature not available in off-the-shelf devices. In this context, we propose a new automatic rate control algorithm which is simple, easy to implement, standards-compliant, and well-suited for crowded 802.11 networks. Our approach consists of measuring the contention level, inferring the collision probability, and choosing transmission rates which maximize throughput. Results from simulation and real experiments show throughput improvement of up to 100% from our mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Packet radio networks have attracted many applications due to their flexible structure and ability to provide high-speed wireless communication between nodes distributed over a large region. Broadcast scheduling is commonly used to find a collision-free time division multiple access protocol frame that schedule transmissions for all nodes in a minimal number of timeslots with maximum number of transmissions. In this paper, we propose a Harmony Search (HS) based algorithm for the broadcast scheduling problem. The HS-based algorithm explores the search space effectively and efficiently by exploiting the search rules of randomness, experience, and variation of experience. The effectiveness and robustness of our proposed algorithm is demonstrated through solving a set of benchmark problems and comparing the results with previously proposed techniques. Experimental results show the efficiency of the proposed algorithm in terms of quality of the solutions as well as computational time. [Copyright &y& Elsevier]

The mobile WiMAX standard was approved in late 2007 as the sixth IMT-2000 3G telecommunications standard by ITU. Although the core parts of the mobile WiMAX system have been finalized, a scheduling method to serve various traffic types efficiently is open for alternative implementations. Therefore, effective scheduling for UGS, rtPS, nrtPS, and BE-four service types of mobile WiMAX, requiring different QoS levels-needs to be developed to increase the efficiency of radio channels. In this study, we propose a MAC layer packet scheduling method that can effectively satisfy the QoS level for four different types of services in the mobile WiMAX system. The suggested scheduling method is based on the channel condition to increase the transmission rate for packets and the utilization level of radio channels. Numerical results are suggested for the mean delay of packet transmission for each mobile terminal, the transmission rate of data, and the final uplink capacity. The results of this study can be used as basic data to determine the capacity of highly portable Internet systems. [ABSTRACT FROM AUTHOR]

We address the problem of primary user detection in Cognitive Radio from a wideband signal comprising multiple primary channels, exploiting a priori knowledge about the primary network: channelization and spectral shape of primary transmissions. Using this second-order statistical information, a multichannel Gaussian model is formulated. In order to obtain a generalized likelihood ratio test, we first address maximum likelihood (ML) estimation of the power levels at the different channels, as well as of the noise variance. The ML conditions suggest a suboptimal closed-form estimate, which takes the form of a constrained least squares estimator whose asymptotic efficiency is shown for flat bandpass spectra in white noise, a case of practical importance. The resulting detectors exploit those frequency bins corresponding to guard bands and to primary channels perceived as weak to improve noise variance estimation. Analytical expressions for the probabilities of detection and false alarm are presented. Performance is evaluated via simulations in the setting of a terrestrial TV primary network with realistic channelization parameters. [ABSTRACT FROM AUTHOR]

The throughput of multicell systems is inherently limited by interference and the available communication resources. Coordinated resource allocation is the key to efficient performance, but the demand on backhaul signaling and computational resources grows rapidly with number of cells, terminals, and subcarriers. To handle this, we propose a novel multicell framework with dynamic cooperation clusters where each terminal is jointly served by a small set of base stations. Each base station coordinates interference to neighboring terminals only, thus limiting backhaul signalling and making the framework scalable. This framework can describe anything from interference channels to ideal joint multicell transmission. The resource allocation (i.e., precoding and scheduling) is formulated as an optimization problem (P1) with performance described by arbitrary monotonic functions of the signal-to-interference-and-noise ratios (SINRs) and arbitrary linear power constraints. Although (P1) is nonconvex and difficult to solve optimally, we are able to prove: 1) optimality of single-stream beamforming; 2) conditions for full power usage; and 3) a precoding parametrization based on a few parameters between zero and one. These optimality properties are used to propose low-complexity strategies: both a centralized scheme and a distributed version that only requires local channel knowledge and processing. We evaluate the performance on measured multicell channels and observe that the proposed strategies achieve close-to-optimal performance among centralized and distributed solutions, respectively. In addition, we show that multicell interference coordination can give substantial improvements in sum performance, but that joint transmission is very sensitive to synchronization errors and that some terminals can experience performance degradations. [ABSTRACT FROM AUTHOR]

Flooding is the simplest and most effective way to disseminate a packet to all nodes in a wireless sensor network (WSN). However, basic flooding makes all nodes transmit the packet at least once, resulting in the broadcast storm problem in a worst case, and in turn, network resources are severely wasted. Particularly, power is the most valuable resource of WSNs as nodes are powered by batteries, then the waste of energy by the basic flooding lessens the lifetime of WSNs. In order to solve the broadcast storm problem, this paper proposes a dynamic probabilistic flooding that utilizes the neighbor information like the numbers of child and sibling nodes. In general, the more sibling nodes there are, the higher is the probability that a broadcast packet may be sent by one of the sibling nodes. The packet is not retransmitted by itself, though. Meanwhile, if a node has many child nodes its retransmission probability should be high to achieve the high packet delivery ratio. Therefore, these two terms-the numbers of child and sibling nodes-are adopted in the proposed method in order to attain more reliable flooding. The proposed method also adopts the back-off delay scheme to avoid collisions between close neighbors. Simulation results prove that the proposed method outperforms previous flooding methods in respect of the number of duplicate packets and packet delivery ratio. [ABSTRACT FROM AUTHOR]

In this study, the authors consider a cognitive radio scenario and focus on the spectrum efficiency of sensing-transmission protocols for a secondary dual-hop relay system. A straightforward dedicated sensing protocol is first considered as a benchmark, where sensing is performed in dedicated sensing periods at both the source (S) and the relay (R) before their respective transmissions. This, however, leads to a substantial loss in spectrum efficiency for the secondary system. In view of the spectrum efficiency loss in the dedicated sensing protocol, the authors propose an alternative approach, namely simultaneous sensing protocol. In this protocol, sensing is only performed at S, during the period when R transmits to destination (D), by cancelling out the self-interference component that is known a priori. The authors derive the closed-form expression of the average probability of detection for the proposed simultaneous sensing protocol. Furthermore, by deriving the average collision time and average utilisation time for both the dedicated and simultaneous sensing protocols, the authors show that the simultaneous sensing protocol significantly improves the spectrum efficiency for the secondary system and also achieves a higher overall spectrum utilisation of the spectrum band, compared to the dedicated sensing protocol. [ABSTRACT FROM AUTHOR]

We formulate the problem of network-coding (NC)-based scheduling for media transmission to multiple users over a wireless-local-area-network-like or WiMAX-like network as a Markov decision process (MDP). NC is used to minimize the packet losses that resulted from unreliable wireless channel conditions, whereas the MDP is employed to find the optimal policy for transmissions of unequally important media packets. Based on this, a dynamic programming technique is used to give an optimal transmission policy. However, this dynamic programming technique quickly leads to computational intractability, even for scenarios with a moderate number of receivers. To address this problem, we further propose a simulation-based dynamic programming algorithm that has a much lower run time yet empirically converges quickly to the optimal solution. [ABSTRACT FROM PUBLISHER]